U.S. patent application number 15/243144 was filed with the patent office on 2016-12-08 for method for sparkle control and articles thereof.
The applicant listed for this patent is Corning Incorporated. Invention is credited to Charles Warren Lander, Kelvin Nguyen, Alan Thomas Stephens, II.
Application Number | 20160355689 15/243144 |
Document ID | / |
Family ID | 47226432 |
Filed Date | 2016-12-08 |
United States Patent
Application |
20160355689 |
Kind Code |
A1 |
Lander; Charles Warren ; et
al. |
December 8, 2016 |
METHOD FOR SPARKLE CONTROL AND ARTICLES THEREOF
Abstract
A glass article including: at least one anti-glare surface
having haze, distinctness-of-image, surface roughness, uniformity
properties and sparkle properties, as defined herein. A method of
making the glass article includes, for example, slot coating a
suspension of particles on at least one surface of the article to
provide a particulated mask covering from about 40 to 92% of the
coated surface area; contacting the at least one surface of the
article having the particulated mask and an etchant to form the
anti-glare surface, and optionally continuously polishing the
suspension of particles just prior to slot coating. A display
system that incorporates the glass article, as defined herein, is
also disclosed.
Inventors: |
Lander; Charles Warren;
(Wayland, NY) ; Nguyen; Kelvin; (Wilmington,
NC) ; Stephens, II; Alan Thomas; (Beaver Dams,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Corning Incorporated |
Corning |
NY |
US |
|
|
Family ID: |
47226432 |
Appl. No.: |
15/243144 |
Filed: |
August 22, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13662789 |
Oct 29, 2012 |
9446979 |
|
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15243144 |
|
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|
61554609 |
Nov 2, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09D 125/06 20130101;
C03C 3/087 20130101; C09D 5/006 20130101; C03C 2218/34 20130101;
G02B 5/0278 20130101; C09D 133/12 20130101; G02B 5/0268 20130101;
G02B 5/0221 20130101; G02B 5/0226 20130101; C03C 3/093 20130101;
C03C 15/00 20130101 |
International
Class: |
C09D 5/00 20060101
C09D005/00; G02B 5/02 20060101 G02B005/02; C09D 133/12 20060101
C09D133/12; C03C 15/00 20060101 C03C015/00; C03C 3/087 20060101
C03C003/087; C09D 125/06 20060101 C09D125/06 |
Claims
1.-13. (canceled)
14. A glass article prepared by the method comprising: slot coating
a suspension of particles on at least one surface of the article to
provide a particulated mask covering from about 40 to 92% of the
coated surface area; and contacting the at least one surface of the
article having the particulated mask and an etchant to form the
anti-glare surface comprising: at least one anti-glare surface
having: a haze of from about 0.1 to about 30; a
distinctness-of-image (DOI 20.degree.) of from about 25 to about
85; a surface roughness (Ra) of from about 50 to about 500 nm; low
sparkle of from about 1 to about less than or equal to 7 as
measured by PPD at 0.degree. and 90.degree.; and an average
roughness peak-to-valley difference profile of from about 0.1 to
about 10 micrometers.
15. The glass article of claim 14 wherein the anti-glare surface
comprises a distribution of topographic features having an average
diameter of about 1 to about 100 micrometers.
16. The glass article of claim 14 wherein the article is a
protective cover glass for a display device.
17. The glass article of claim 14 wherein the haze is from about
0.1 to about 30.
18. The glass article of claim 14 wherein the haze is from about
0.1 to about 5.
19. A slot coater comprising: a slot die; a source of a particle
suspension; and a polisher situated between the source of the
particle suspension and the slot die, wherein the polisher
continuously polishes the particle suspension during slot coating.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority under 35
U.S.C. .sctn.119 of U.S. Provisional Application Ser. No.
61/554,609, filed Nov. 2, 2011, the content of which is relied upon
and incorporated herein by reference in its entirety.
BACKGROUND
[0002] The disclosure relates generally to methods of and apparatus
for making and using an anti-glare surface and articles thereof
having controlled sparkle properties.
SUMMARY
[0003] The disclosure provides a method of and apparatus for making
an anti-glare surface having controlled sparkle properties,
articles made by the method, and a display system incorporating the
article having the anti-glare surface having reduced or controlled
sparkle properties. The method of making includes controllably
depositing a suspension of sacrificial particles on at least one
surface of an article in limited amounts, such as from about 40 to
92% surface coverage of the total area contacted, that is less than
a monolayer of closely packed particles, and contacting the
particle treated surface (particulated surface) with an etchant to
form the anti-glare surface.
BRIEF DESCRIPTION OF THE DRAWING(S)
[0004] In embodiments of the disclosure:
[0005] FIG. 1 schematically shows the steps in the process of
creating an anti-glare layer on, for example, a GORILLA.RTM. glass
surface.
[0006] FIG. 2 shows a micrograph of a Gorilla.RTM. glass coated
(particulated) sample that is ready for etching.
[0007] FIGS. 3a and 3b show, respectively, before analysis (3a) and
after (3b) applying the image analysis to determine the percent
coverage for 3 micrometer particle deposition for an exemplary slot
coated sample at 100.times. magnification at 100% and 60%
coverage.
[0008] FIGS. 4a and 4b show, respectively, the exact same image
location captured in FIGS. 3a and 3b but at 500.times.
magnification.
[0009] FIGS. 5a and 5b show another slot sample having a different
area coverage of 74% at 500.times. magnification.
[0010] FIGS. 6a and 6b show another slot coated sample having a
different area coverage of 83% at 500.times. magnification.
[0011] FIGS. 7a and 7b show another slot coated sample having a
particle surface area coverage of 92% at 500.times.
magnification.
[0012] FIGS. 8a and 8b show still another slot coated sample of a
mixed particle formulation having a mixed particle surface area
coverage of 61% at 100.times. magnification.
[0013] FIGS. 9a and 9b show another slot coated sample having a
coated particle surface area coverage of 43% at 500.times.
magnification.
[0014] FIGS. 10a and 10b show another slot coated sample having a
coated particle surface area coverage of 52% at 500.times.
magnification.
[0015] FIGS. 11a and 11b show the roughness of a 3 micron
polystyrene (only) particle formulation coated at 74% (140 nm RMS)
and 83% (224 nm RMS) area coverage, respectively.
[0016] FIG. 12 shows a slot coater apparatus (1200) including an
in-line polishing device.
[0017] FIGS. 13A to 13D show micrographs of Gorilla.RTM. glass
coated with un-polished dispersions.
[0018] FIGS. 14A to 14D show micrographs of Gorilla.RTM. glass
coated with polished dispersions.
[0019] FIG. 15 shows a graph of optical data for un-polished
dispersion coatings (left side) and for dispersions coatings (right
side) that were polished for 30 minutes prior to slot coating.
[0020] FIGS. 16A to 16C show micrographs of Gorilla.RTM. glass
coated with particle dispersions that included a surfactant
additive.
DETAILED DESCRIPTION
[0021] Various embodiments of the disclosure will be described in
detail with reference to drawings, if any. Reference to various
embodiments does not limit the scope of the invention, which is
limited only by the scope of the claims attached hereto.
Additionally, any examples set forth in this specification are not
limiting and merely set forth some of the many possible embodiments
of the claimed invention.
DEFINITIONS
[0022] "Anti-glare" or like terms refer to a physical
transformation of light contacting the treated surface of an
article, such as a display, of the disclosure that changes, or to
the property of changing light reflected from the surface of an
article, into a diffuse reflection rather than a specular
reflection. In embodiments, the surface treatment can be produced
by mechanical or chemical etching. Anti-glare does not reduce the
amount of light reflected from the surface, but only changes the
characteristics of the reflected light. An image reflected by an
anti-glare surface has no sharp boundaries. In contrast to an
anti-glare surface, an anti-reflective surface is typically a
thin-film coating that reduces the reflection of light from a
surface via the use of refractive-index variation and, in some
instances, destructive interference techniques.
[0023] "Contacting" or like terms refer to a close physical
touching that can result in a physical change, a chemical change,
or both, to at least one touched entity. In the present disclosure
various particulate deposition or contacting techniques, such as
slot coating, spray coating, dip coating, and like techniques, can
provide a particulated surface when contacted as illustrated and
demonstrated herein. Additionally or alternatively, various
chemical treatments of the particulated surface, such as spray,
immersion, and like techniques, or combinations thereof, as
illustrated and demonstrated herein, can provide an etched surface
when contacted with one or more etchant compositions.
[0024] "Distinctness-of-reflected image," "distinctness-of-image,"
"DOI" or like term is defined by method A of ASTM procedure D5767
(ASTM 5767), entitled "Standard Test Methods for Instrumental
Measurements of Distinctness-of-Image Gloss of Coating Surfaces."
In accordance with method A of ASTM 5767, glass reflectance factor
measurements are made on the at least one roughened surface of the
glass article at the specular viewing angle and at an angle
slightly off the specular viewing angle. The values obtained from
these measurements are combined to provide a DOI value. In
particular, DOI is calculated according to equation (1):
DOI = [ 1 - Ros Rs ] .times. 100 ( 1 ) ##EQU00001##
where Rs is the relative amplitude of reflectance in the specular
direction and Ros is the relative amplitude of reflectance in an
off-specular direction. As described herein, Ros, unless otherwise
specified, is calculated by averaging the reflectance over an
angular range from 0.2.degree. to 0.4.degree. away from the
specular direction. Rs can be calculated by averaging the
reflectance over an angular range of .+-.0.05.degree. centered on
the specular direction. Both Rs and Ros were measured using a
goniophotometer (Novo-gloss IQ, Rhopoint Instruments) that is
calibrated to a certified black glass standard, as specified in
ASTM procedures D523 and D5767. The Novo-gloss instrument uses a
detector array in which the specular angle is centered about the
highest value in the detector array. DOI was also evaluated using
1-side (black absorber coupled to rear of glass) and 2-side
(reflections allowed from both glass surfaces, nothing coupled to
glass) methods. The 1-side measurement allows the gloss,
reflectance, and DOI to be determined for a single surface (e.g., a
single roughened surface) of the glass article, whereas the 2-side
measurement enables gloss, reflectance, and DOI to be determined
for the glass article as a whole. The Ros/Rs ratio can be
calculated from the average values obtained for Rs and Ros as
described above. "20.degree. DOI," or "DOI 20.degree." refers to
DOI measurements in which the light is incident on the sample at
20.degree. off the normal to the glass surface, as described in
ASTM D5767. The measurement of either DOI or common gloss using the
2-side method can best be performed in a dark room or enclosure so
that the measured value of these properties is zero when the sample
is absent.
[0025] For anti-glare surfaces, it is generally desirable that DOI
be relatively low and the reflectance ratio (Ros/Rs) of eq. (1) be
relatively high. This results in visual perception of a blurred or
indistinct reflected image. In embodiments, the at least one
roughened surface of the glass article has a Ros/Rs greater than
about 0.1, greater than about 0.4, and, greater than about 0.8,
when measured at an angle of 20.degree. from the specular direction
using the 1-side method measurement. Using the 2-side method, the
Ros/Rs of the glass article at a 20.degree. angle from the specular
direction is greater than about 0.05. In embodiments, the Ros/Rs
measured by the 2-side method for the glass article is greater than
about 0.2, and greater than about 0.4. Common gloss, as measured by
ASTM D523, is insufficient to distinguish surfaces with a strong
specular reflection component (distinct reflected image) from those
with a weak specular component (blurred reflected image). This can
be attributable to the small-angle scattering effects that are not
measurable using common gloss meters designed according to ASTM
D523.
[0026] "Transmission haze," "haze," or like terms refer to a
particular surface light scatter characteristic related to surface
roughness. Haze measurement is specified in greater detail
below.
[0027] "Roughness," "surface roughness (Ra)," or like terms refer
to, on a microscopic level or below, an uneven or irregular surface
condition, such as an average root mean squared (RMS) roughness or
RMS roughness described below.
[0028] "Gloss," "gloss level," or like terms refer to, for example,
surface luster, brightness, or shine, and more particularly to the
measurement of specular reflectance calibrated to a standard (such
as, for example, a certified black glass standard) in accordance
with ASTM procedure D523, the contents of which are incorporated
herein by reference in their entirety. Common gloss measurements
are typically performed at incident light angles of 20.degree.,
60.degree., and 85.degree., with the most commonly used gloss
measurement being performed at 60.degree.. Due to the wide
acceptance angle of this measurement, however, common gloss often
cannot distinguish between surfaces having high and low
distinctness-of-reflected-image (DOI) values. The anti-glare
surface of the glass article has a gloss (i.e.; the amount of light
that is specularly reflected from sample relative to a standard at
a specific angle) of up to 90 SGU (standard gloss units), as
measured according to ASTM standard D523, and, in one embodiment,
has a gloss in a range from about 60 SGU up to about 80 SGU. See
also the DOI definition above.
[0029] "ALF" or "average characteristic largest feature size" or
like terms refer to a measure of surface feature variation in the
x- and y-directions, i.e., in the plane of the substrate, as
discussed further below.
[0030] "Sparkle," "display sparkle," or like terms refer to the
relationship between the size of features on the at least one
roughened glass surface and pixel pitch, particularly the smallest
pixel pitch, is of interest. Display "sparkle" is commonly
evaluated by human visual inspection of a material that is placed
adjacent to a pixelated display. ALF and its relationship to
display "sparkle" has been found to be a valid metric for different
materials having different surface morphologies, including glasses
of varying composition and particle-coated polymer materials. A
strong correlation between average largest characteristic feature
size (ALF) and visual ranking of display sparkle severity exists
across multiple different sample materials and surface
morphologies. In embodiments, the glass article can be a glass
panel that forms a portion of a display system. The display system
can include a pixelated image display panel that is disposed
adjacent to the glass panel. The smallest pixel pitch of the
display panel can be greater than ALF.
[0031] "Include," "includes," or like terms means encompassing but
not limited to, that is, inclusive and not exclusive.
[0032] "About" modifying, for example, the quantity of an
ingredient in a composition, concentrations, volumes, process
temperature, process time, yields, flow rates, pressures, and like
values, and ranges thereof, employed in describing the embodiments
of the disclosure, refers to variation in the numerical quantity
that can occur, for example: through typical measuring and handling
procedures used for preparing materials, compositions, composites,
concentrates, or use formulations; through inadvertent error in
these procedures; through differences in the manufacture, source,
or purity of starting materials or ingredients used to carry out
the methods; and like considerations. The term "about" also
encompasses amounts that differ due to aging of a composition or
formulation with a particular initial concentration or mixture, and
amounts that differ due to mixing or processing a composition or
formulation with a particular initial concentration or mixture. The
claims appended hereto include equivalents of these "about"
quantities.
[0033] "Consisting essentially of" in embodiments can refer to, for
example:
[0034] a method of making a glass article by depositing sacrificial
particles on a surface of the article, such as by slot coating a
suspension of particles on at least one surface of the article to
provide a particulated mask covering from about 40 to 92% of the
coated surface area; and contacting the particulated surface with
an etchant;
[0035] a glass article having an anti-glare surface having low
sparkle from about 1 to about less than or equal to 7 as measured
by PPD at 0.degree. and 90.degree., haze, distinctness-of-image,
surface roughness, and uniformity properties, as defined
herein;
[0036] a slot coating apparatus including an in-line particle
polishing device or module; or
[0037] a display system that incorporates the glass article, as
defined herein.
[0038] The method of making, the article, the display system,
compositions, formulations, or any apparatus of the disclosure, can
include the components or steps listed in the claim, plus other
components or steps that do not materially affect the basic and
novel properties of the compositions, articles, apparatus, or
methods of making and use of the disclosure, such as particular
reactants, particular additives or ingredients, a particular agent,
a particular surface modifier or condition, or like structure,
material, or process variable selected. Items that may materially
affect the basic properties of the components or steps of the
disclosure or that may impart undesirable characteristics to the
present disclosure include, for example, a surface having
objectionable high glare or high gloss properties, for example,
having a sparkle, a haze, a distinctness-of-image, a surface
roughness, a uniformity, or a combination thereof, that are beyond
the values, including intermediate values and ranges, defined and
specified herein.
[0039] The indefinite article "a" or "an" and its corresponding
definite article "the" as used herein means at least one, or one or
more, unless specified otherwise.
[0040] Abbreviations, which are well known to one of ordinary skill
in the art, may be used (e.g., "h" or "hr" for hour or hours, "g"
or "gm" for gram(s), "mL" for milliliters, and "rt" for room
temperature, "nm" for nanometers, and like abbreviations).
[0041] Specific and preferred values disclosed for components,
ingredients, additives, and like aspects, and ranges thereof, are
for illustration only; they do not exclude other defined values or
other values within defined ranges. The compositions, apparatus,
and methods of the disclosure can include any value or any
combination of the values, specific values, more specific values,
and preferred values described herein.
[0042] Chemically strengthened glass is used in many handheld and
touch-sensitive devices where resistance to mechanical damage is
important to the visual appearance and functionality of the
product. During chemical strengthening, larger alkali ions in a
molten salt bath are exchanged for smaller mobile alkali ions
located within a certain distance from the glass surface. This ion
exchange process places the surface of the glass in compression,
allowing it to become more resistant to any mechanical damage it is
commonly subjected to during use.
[0043] Reduction in the specular reflection (a significant factor
in glare) from these display surfaces is often desired, especially
by manufacturers whose products are designed for outdoor use where
glare can be exacerbated by sunlight.
[0044] One way to reduce the intensity of the specular reflection,
quantified as gloss, is to roughen the glass surface or cover it
with a textured film. The dimensions of the roughness or texture
should be large enough to scatter visible light, producing a
slightly hazy or matte surface, but not too large as to
significantly affect the transparency of the glass. Textured or
particle-containing polymer films can be used if maintaining the
properties of the glass substrate (e.g., scratch resistance) are
not important. While these films maybe cheap and easy to apply,
they are easily subject to abrasion which reduces the functionality
of the device.
[0045] Another approach to roughening the glass surface is chemical
etching. U.S. Pat. Nos. 4,921,626, 6,807,824, 5,989,450, and
WO2002053508, mention glass etching compositions and methods of
etching glass with the compositions. Wet etching is a method of
generating an anti-glare surface on the glass while preserving its
inherent mechanical surface properties. During this process, the
glass surface is selectively exposed to chemicals which degrade the
surface to the correct roughness dimensions for the scattering of
visible light. When micro-structural regions having differential
solubility are present, such as in soda lime silicate glasses, a
roughened surface can be formed by placing the glass in a
(typically fluorine-containing) mineral acid solution. Such
selective leaching or etching is generally ineffective at
generating a uniform, anti-glare surface on other display glasses
lacking such differentially soluble micro-structural regions, such
as alkaline earth aluminosilicates and mixed alkali borosilicates,
and for alkali and mixed alkali aluminosilicates containing
lithium, sodium, potassium, or a combination thereof.
[0046] One result of roughening a glass surface is to create
"sparkle," which is perceived as a grainy appearance. Sparkle is
manifested by the appearance of bright and dark or colored spots at
approximately the pixel-level size scale. The presence of sparkle
reduces the view-ability of pixilated displays, particularly under
high ambient lighting conditions.
[0047] In embodiments, the disclosure provides a wet etch method
for generating an anti-glare surface on the glass while preserving
its inherent mechanical surface properties. During this process, a
particulated glass surface is exposed to chemicals which can
degrade the surface to alter the surface roughness dimensions that
are responsible for scattering visible light. When significant
quantities of mobile alkali ions are present in the glass, such as
in soda lime silicate glasses, a roughened surface can be formed
by, for example, contacting the glass surface in an acid etchant
solution, such as a solution containing fluoride ion.
[0048] In embodiments, the disclosure provides a process to form a
nano- to micro-scale textured surface on silicate glasses with
improved optical properties. The process involves 1) a partial
coverage of particles on the glass surface, 2) allowing the solvent
to dry off, which is sufficient to promote adhesion of the
particles onto the glass surface and without additional or external
heating. The process can be followed by 3) etching in an HF bath,
or multi-component acid solution. The HF solution creates
preferential etching around particles on the glass surface to form
an AG roughened surface layer.
[0049] One process to produce anti-glare layer on the Gorilla.RTM.
glass surface is to apply 100% coverage of small polymer beads
followed by the drying and etching steps. When coating 100%
coverage, sample quality often suffers with respect to increased
sparkle. Low sparkle is a "must" requirement by certain display
glass customers and high material coverage (100%) rarely yields low
sparkle results. The present disclosure provides partial etch mask
coverage that has substantial benefits compared to 100% coverage.
Some benefits that have been achieved in embodiments of the present
disclosure include, for example:
[0050] low sparkle, in the 5 to 6 range (note that 100% particle
coverage typically results in sparkle in the 8 to 12 range);
[0051] low sparkle, with low haze, and low DOI;
[0052] low sparkle, with low haze, and medium DOI;
[0053] low sparkle with a variety of optical combinations (e.g.,
high haze/low DOI; low haze/medium DOI, etc.);
[0054] with partial mask coverage, multiple optical targets could
be achieved by simply changing the acid etch concentration;
[0055] easy to control the mask coverage by changing the coating
thickness, bead loading, or both;
[0056] samples can be etched in horizontal, vertical, or both
configurations;
[0057] cost saving by having less mask material consumption since
less surface coverage is needed; and
[0058] different mask deposition processes (e.g., slot coating and
spray coating) can obtain similar optical results when samples have
partial coverage.
[0059] Optical modeling suggests that to achieve low sparkle, the
lateral spacing between particles should be less than about 20
microns. That means the particle size distributions must be very
carefully controlled. With partial mask coverage, one can have
larger unmasked space between particles so that an inexpensive,
broad particle size distribution can be selected.
[0060] In embodiments, the disclosure provides a method of making
an article having an anti-glare surface, comprising:
[0061] slot coating a suspension of particles on at least one
surface of the article to provide a particulated mask covering from
about 40 to 92% of the coated surface area; and
[0062] contacting the at least one surface of the article having
the slot coated particles and an etchant to form the anti-glare
surface.
[0063] In embodiments, the at least one surface of the article can
be, for example, a glass, a composite, a ceramic, a plastic or
resin based material, and like materials, or combinations thereof.
In embodiments, the deposited particles can be, for example, a
glass, a composite, a ceramic, a plastic or resin based material, a
wax, a metal, a salt, a clay, a polymer, a copolymer,
nano-particles, cross-linked polymer particles, UV cured particles,
and like materials, or combinations thereof. In embodiments, the
etchant can be comprised of at least one acid suitable for etching
the surface beneath the deposited particles.
[0064] In embodiments, the glass surface and the glass particles
when selected can be independently selected from, for example, at
least one aluminosilicate, aluminoborosilicate, soda lime,
borosilicate, silica, and like glasses, or a combination thereof,
and the etchant can comprise at least one acid selected from HF,
H.sub.2SO.sub.4, HNO.sub.3, HCl, CH.sub.3CO.sub.2H,
H.sub.3PO.sub.4, and like acids, or a combination thereof.
[0065] Additionally or alternatively, the contacting the at least
one surface with particles can be accomplished with a concentrated
particle suspension, or a particle suspension of intermediate
concentration. The particle-surface contacting or particle
depositing can be accomplished using any suitable method, for
example, slot-coating, spin-coating, spray-coating, roll-coating,
laminating, brushing, dipping, and like application methods, or a
combination thereof. The deposited particles can have, for example,
a D.sub.50 diameter of from about 0.1 to about 10 micrometers, from
about 1 to about 10 micrometers, and from about 1 to about 5
micrometers, including intermediate values and ranges. In
embodiments, the particle size range can be, for example, from
about 0.1 to about 50 micrometers, 1 to about 30 micrometers, and
like particle diameters including intermediate values and
ranges.
[0066] In embodiments, the contacting of the particulated surface
with an etchant can be accomplished by, for example, exposing the
surface having the deposited particles to the etchant, for example,
for from about 1 second to about 30 minutes, including intermediate
values and ranges.
[0067] In embodiments, the preparative method can optionally
further include, for example, washing the resulting etched
anti-glare surface, chemically strengthening the anti-glare
surface, applying a functional coating or film (e.g., a light
sensitive or polarizing film) or protective surface coating or
film, and like coatings or films, or a combination thereof.
[0068] In embodiments, when a single-side acid-etch, or like
modification is desired on a sheet of glass, one side of the glass
can be protected from the etching solution. Protection can be
achieved, for example, by applying an insoluble non-porous coating
such as an acrylic wax, or a laminate film having an adhesive
layer, for example, an acrylic, a silicone, and like adhesives
materials, or combinations thereof. Protective coating application
methods can include, for example, brushing, rolling, spraying,
laminating, and like methods. The acid-etch exposed insoluble
non-porous protective coating survives the etching process and can
be readily removed after the etching. Removing the protective film
from the surface of the article can be accomplished using any
suitable method, such as contacting the protective film with a
dissolving liquid, heating the film to liquefy and drain, and like
methods and materials, or a combination thereof. Thus, the
preparative method can optionally further include, prior to
etching, contacting at least another surface, e.g., a second
surface such as the backside of a glass sheet, of the article with
an optionally removable, etch-resistant protective layer.
[0069] In embodiments, the disclosure provides an article prepared
by any of the preparative processes disclosed herein, such as a
glass article prepared by the above mentioned particle deposition
and etching process.
[0070] In embodiments, the at least one surface of the article can
be a glass, the deposited particles can be a polymer, a wax, or
mixtures or combinations thereof, and the etchant can be at least
one acid.
[0071] In embodiments, the disclosure provides a glass article
comprising:
at least one anti-glare surface having:
[0072] a haze of, for example, from about 0.1 to about 30, such as
from about 0.1 to about 25, from about 0.1 to about 20, from about
0.1 to about 10, and from about 1 to about 10, and low haze, such
as from about 0.1 to about 5, and from about 1 to about 5,
including intermediate values and ranges;
[0073] a distinctness-of-image (DOI 20.degree.) of, for example,
from about 25 to about 85, from about 40 to about 80, from about 45
to about 75, and from about 50 to about 70, including intermediate
values and ranges;
[0074] a surface roughness (Ra) of, for example, from about 50 to
about 500 nm, and from about 100 to about 300 nm, including
intermediate values and ranges;
[0075] an average roughness peak-to-valley profile of from about
0.1 to about 10 micrometers, including intermediate values and
ranges; and
[0076] low sparkle from about less than or equal to 7 as measured
by PPD at 0.degree. and 90.degree..
[0077] In embodiments, the glass article having the anti-glare
surface of the disclosure can comprise a distribution of
topographic features having an average diameter of about 1 to about
100 micrometers, about 1 to about 50 micrometers, including
intermediate values and ranges.
[0078] In embodiments, the disclosure provides a display system
including, for example:
[0079] a glass panel having at least one roughened anti-glare
surface having:
[0080] a haze of from about 0.1 to less than about 30 including
intermediate values and ranges;
[0081] a distinctness-of-image (DOI 20.degree.) of from about 40 to
about 80, including intermediate values and ranges;
[0082] a surface roughness (Ra) of from about 100 to about 300 nm,
including intermediate values and ranges; and
[0083] an average roughness peak-to-valley difference profile of
from about 0.1 to about 10 micrometers, including intermediate
values and ranges;
[0084] low sparkle from about less than or equal to 7 as measured
by PPD at 0.degree. and 90.degree.; and
[0085] an optional pixelated image-display panel adjacent to the
glass panel.
[0086] In embodiments, the disclosure provides a method of creating
an anti-glare glass surface having low sparkle properties,
including, for example:
[0087] contacting a glass surface with a liquid suspension of
suitable particles, the contacting can be accomplished by slot
coating with the liquid suspension to provide a particle-coated
glass surface with a surface area coverage of about 40 to about
92%, of about 50 to about 91%, or of about 60 to about 90%, of the
coated area; and
[0088] contacting the resulting particulated glass surface and an
etchant to form the anti-glare surface, where the resulting an
anti-glare surface has low sparkle from about 1 to about less than
or equal to 7 as measured by PPD at 0.degree. and 90.degree..
[0089] In embodiments, the disclosure provides a wet etch process
to form a uniform, nano- to micro-scale textured surface on most
silicate glasses and without having a significant impact on
chemical strengthening capability of the glass. The process
includes depositing or otherwise coating suitable particles, such
as glass, polymer, or composite particles, on the glass surface,
followed by acid etching, such as in an HF, or multi-component acid
solution. In embodiments, the HF solution can preferentially etch
around the particles deposited on the glass surface, then
subsequently erodes the particles from the etched surface, and can
also reduce the surface roughness.
[0090] In embodiments, the desired reduced gloss or glare levels
can be obtained, for example, by adjusting at least one or more of
the following parameters: the viscosity of the particulate
suspension, the binder level in the suspension, the level or
concentration of the glass or like particles in the suspension, the
concentration of the acid etchant, etchant types, the amount of
particles deposited on the surface, the particle size distribution
(PDS) of the particles used, and the exposure interval or the time
that the particle-bearing surface of the glass sample is in contact
with the acid etchant.
[0091] In embodiments, an anti-glare glass article is provided. The
glass article can be ion-exchangeable and can have at least one
roughened surface. The roughened surface has a
distinctness-of-reflected image (DOI) of less than 90 when measured
at an incidence angle of 20.degree. (DOI at 20.degree.). A
pixelated display system that includes the anti-glare glass article
is also provided. The glass article can be, for example, a planar
sheet or panel having two major surfaces joined on the periphery by
at least one edge, although the glass article can be formed into
other shapes such as, for example, a three-dimensional shape. At
least one of the surfaces is a roughened surface including, for
example, topological or morphological features, such as,
projections, protrusions, depressions, pits, closed or open cell
structures, particles, islands, lands, trenches, fissures,
crevices, and like geometries and features, or combinations
thereof.
[0092] In embodiments, the disclosure provides an aluminosilicate
glass article. The aluminosilicate glass article can include, for
example, at least 2 mol % Al.sub.2O.sub.3, can be ion-exchangeable,
and can have at least one roughened surface. The aluminosilicate
glass article can have at least one roughened surface comprising a
plurality of topographical features. The plurality of topographical
features can have an average characteristic largest feature size
(ALF) of from about 1 micrometer to about 50 micrometers.
[0093] In embodiments, the disclosure provides a display system.
The display system can include, for example, at least one glass
panel and a pixelated image-display panel adjacent to the glass
panel. The image-display panel can have a minimum native pixel
pitch dimension. The average characteristic largest feature size
(ALF) of the glass panel can be less than the minimum native pixel
pitch dimension of the display panel. The pixelated image display
panel can be, for example, one of an LCD display, an OLED display,
or like display devices. The display system can also include
touch-sensitive elements or surfaces. The glass can be, for
example, any of the aforementioned glasses, such as an
aluminosilicate ion-exchanged glass that has at least one roughened
surface including a plurality of features having an ALF, and the
image-displaying panel has a minimum native pixel pitch. The
minimum native pixel pitch can be, for example, greater than the
ALF of the roughened surface of the glass panel.
[0094] ALF is measured in the plane of (i.e., parallel to) the
roughened glass surface, and is therefore independent of roughness.
ALF is a measurement of feature variation in the x- and
y-directions, i.e., in the plane of the roughened glass surface.
Selecting the largest characteristic features is a useful
distinction from other methods that determine a more global average
feature size. The largest features are most easily seen by the
human eye and are therefore most important in determining visual
acceptance of the glass article. In embodiments, the topological or
morphological features of the at least one roughened surface has an
average characteristic largest feature (ALF) size of from about 1
micrometer to about 50 micrometers, of from about 5 micrometers to
about 40 micrometers; of from about 10 micrometers to about 30
micrometers; and from about 14 micrometers to about 28 micrometers,
including intermediate values and ranges. The average
characteristic largest feature size is the average cross-sectional
linear dimension of the twenty largest repeating features within a
viewing field on a roughened surface. A standard calibrated optical
light microscope can typically be used to measure feature size. The
viewing field is proportional to the feature size, and typically
has an area of approximately 30(ALF).times.30(ALF). If, for
example, the ALF is approximately 10 micrometers, then the viewing
field from which the twenty largest features are selected is
approximately 300 micrometers.times.300 micrometers. Small changes
in the size of the viewing field do not significantly affect ALF.
The standard deviation of the twenty largest features that are used
to determine ALF should generally be less than about 40% of the
average value, i.e., major outliers should be ignored since these
are not considered "characteristic" features.
[0095] The topography of the anti-glare surface can include, for
example, features such as protrusions or projections, depressions,
and like features having a maximum dimension of less than about 400
nm. In embodiments, these topographical features can be separated
from each other or spaced apart at a mean distance of from about 10
nm up to about 200 nm. The resulting anti-glare surface can have an
average roughness, as measured by the peak-to-valley difference
(PV) measure on the surface. In embodiments, the anti-glare surface
can have a RMS roughness of about 800 nm, of about 500 nm, and
about 100 nm.
[0096] The features used to calculate ALF are "characteristic;"
i.e., at least twenty similar features can be located in the
proportional viewing field. Different morphologies or surface
structures can be characterized using ALF. For example, one surface
structure may appear to be closed-cell repeating structures,
another may appear to be small pits separated by large plateaus,
and a third may appear to be a field of small particles punctuated
by intermittent large smooth regions. In each instance, the ALF is
determined by measuring the twenty largest repeating surface
regions that are substantially optically smooth. In the instance of
the repeating closed cell surface structure, the features to be
measured are the largest of the cells in the closed-cell matrix.
For the surface structure comprising small pits separated by large
plateaus, the large plateaus between pits are to be measured. For
the surface comprising a field of small particles punctuated by
intermittent large smooth regions, the intermittent large smooth
regions are to be measured. All surfaces with substantially varying
morphologies can thus be characterized using ALF.
[0097] In embodiments, the at least one roughened surface of the
glass article has an average RMS roughness can be from about 10 nm
to about 800 nm, from about 40 nm to about 500 nm, and from about
40 nm to about 300 nm. In embodiments, the average RMS roughness
can be greater than about 10 nm and less than about 10% of the ALF,
greater than about 10 nm and less than about 5% of ALF, and greater
than about 10 nm and less than about 3% of ALF.
[0098] The specification of low DOI and high Ros/Rs provide
constraints on the characteristic feature size and ALF. For a given
roughness level, it has been found that larger feature sizes result
in lower DOI and higher Ros/Rs. Therefore, to balance the display
sparkle and the DOI target, in embodiments, it can be desirable to
create anti-glare surfaces having an intermediate characteristic
feature size that is neither too small nor too large. It is also
desirable to minimize reflected or transmitted haze when the
transmitted haze is scattering into very high angles that can cause
a milky white appearance of a roughened article under ambient
lighting.
[0099] "Transmission haze," "haze," or like terms refer to the
percentage of transmitted light scattered outside an angular cone
of .+-.4.0.degree. according to ASTM D1003. For an optically smooth
surface, the transmission haze is generally close to zero.
Transmission haze of a glass sheet roughened on two sides
(Haze.sub.2-side) can be related to the transmission haze of a
glass sheet having an equivalent surface that is roughened on only
one side (Haze.sub.1-side), according to the approximation of eq.
(2):
Haze.sub.2-side.apprxeq.[(1-Haze.sub.1-side)Haze.sub.1-side]+Haze.sub.1--
side (2).
[0100] Haze values are usually reported in terms of percent haze.
The value of Haze.sub.2-side from eq. (2) must be multiplied by
100. In embodiments, the disclosed glass article can have a
transmission haze of less than about 50% and even less than about
30%.
[0101] A multistep surface treatment process has been used to form
the roughened glass surface. An example of a multistep etch process
is disclosed in commonly owned copending U.S. Provisional Patent
Appln 61/165,154, filed Mar. 31, 2009, to Carlson, et al., entitled
"Glass Having Anti-Glare Surface and Method of Making," where a
glass surface is treated with a first etchant to form crystals on
the surface, then etching a region of the surface adjacent to each
of the crystals to a desired roughness, followed by removing the
crystals from the glass surface, and reducing the roughness of the
surface of the glass article to provide the surface with a desired
haze and gloss.
[0102] Other related commonly owned applications include, for
example, U.S. Ser. No. 13/090,561 (SP10-112), U.S. Ser. No.
13/090,522 (SP10-114), U.S. Ser. No. 61/417,674 (SP10-318P), US
provisional application U.S. Ser. No. 61/165,154 (SP09-087P), and
US provisional application U.S. Ser. No. 61/242,529 (SP09-271P),
which disclosures are incorporated herein in their entirety.
[0103] In embodiments, various performance enhancing additives can
be included in the particle suspension, the etch solution, or both,
including for example, a surfactant, a co-solvent, a diluent, a
lubricant, a gelation agent, a viscosity improver, and like
additives, or combinations thereof.
[0104] The contacting with etchant can involve, for example,
selective partial or complete dipping, spaying, immersion, and like
treatments, or a combination of treatments, with an acidic etch
solution including, for example, 2 to 10 wt % hydrofluoric acid and
2 to 30 wt % of a mineral acid, such as hydrochloric acid, sulfuric
acid, nitric acid, phosphoric acid, and like acids, or combinations
thereof. The glass surface can be etched in the solution for
periods of from about 1 to about 10 minutes, with longer times
generally leading to a greater reduction in the surface roughness.
The disclosed concentrations and etch times are representative of
suitable examples. Concentrations and etch times outside the
disclosed ranges can also be used to obtain the roughened surface
of the glass article albeit potentially less efficiently.
[0105] In chemical strengthening, larger alkali metal ions are
exchanged for smaller mobile alkali ions near the glass surface.
This ion-exchange process places the surface of the glass in
compression, allowing it to be more resistant to any mechanical
damage. In embodiments, the outer surface of the glass article can
optionally be ion-exchanged where smaller metal ions are replaced
or exchanged by larger metal ions having the same valence as the
smaller ions. For example, sodium ions in the glass can be replaced
with larger potassium ions by immersing the glass in a molten salt
bath containing potassium ions. The replacement of smaller ions
with larger ions creates a compressive stress within the layer. In
embodiments, the larger ions near the outer surface of the glass
can be replaced by smaller ions, for example, by heating the glass
to a temperature above the strain point of the glass. Upon cooling
to a temperature below the strain point, a compressive stress is
created in an outer layer of the glass. Chemical strengthening of
the glass can optionally be performed after the surface roughening
treatment, with little negative effect on the ion-exchange behavior
or the strength of the glass article.
[0106] In embodiments, the disclosure provides a method for making
an anti-glare surface including, for example, "particulating"
(i.e., populating) the surface with particles, such as with a
liquid suspension or a soot gun, etching the particulated surface
with a suitable etchant, ion-exchanging the etched surface, and
optionally accomplishing further processing to reduce objectionable
surface flaws (i.e., flaw reduction). Alternatively or
additionally, the surface can be ion-exchanged, particulated with
particles, etched with an etchant, and optionally flaw reduction
processing.
[0107] Referring to the figures, FIG. 1 schematically shows the
steps in the process of creating an anti-glare layer on, for
example, a GORILLA.RTM. glass surface. Particles having an average
size, such as less than about 10 micrometers, are suspended in a
suitable liquid, and the resulting suspension can be selectively
deposited (100), for example, slot coated onto a glass substrate,
and the solvent removed to leave a residual layer of particles
(105) adhered on the glass substrate (110). The sample can then be
etched, such as by being dipped into or immersed in an acid etch
(120) bath. The HF/H.sub.2SO.sub.4 etchant attacks the area around
the particles and eventually under-cuts the area covered by
individual particles. The glass particles are liberated from the
substrate surface during the etch (120), during rinsing, or both,
and thus create a textured surface (130) on the glass substrate
having anti-glare properties.
[0108] FIG. 2 shows a micrograph of a Gorilla.RTM. glass coated
(particulated) sample that is ready for etching. The sample has
100% particle coverage that was obtained by applying the particles
by spray. No opening between the particles can be seen. The coated
layer is also relatively very thick (120 micron).
[0109] FIGS. 3a and 3b show, respectively, before analysis (3a) and
after applying the image analysis (3b) to determine the percent
coverage for 3 micrometer particle deposition for an exemplary slot
coated sample at 100.times. magnification. FIG. 3b has 60% area
coverage.
[0110] FIGS. 4a and 4b show, respectively, the exact same image
location captured in FIGS. 3a and 3b but at 500.times.
magnification. FIG. 4b has 61% area coverage. A 3 micron
polystyrene bead (only) particle suspension was used.
[0111] FIGS. 5a and 5b show another slot sample having a different
area coverage of 74% at 500.times. magnification. A 3 micron
polystyrene bead (only) particle suspension was used.
[0112] FIGS. 6a and 6b show another slot coated sample with a
different area coverage of 83% at 500.times. magnification. A 3
micron polystyrene bead (only) particle suspension was used.
[0113] FIGS. 7a and 7b show another slot coated sample having a
particle surface area coverage of 92% at 500.times. magnification.
A 3 micron polystyrene bead (only) particle suspension was
used.
[0114] FIGS. 8a and 8b show still another slot coated sample of a
mixed particle formulation having a mixed particle surface area
coverage of 61% at 100.times. magnification. The formulation used
was a particle suspension of a mixture of polymer beads (PMMA; 8
microns) and wax (6 microns) particles, i.e., gross mixture of
polymer and wax particles and not particles comprised of and
intimate physical mixture or blend of polymer and wax.
[0115] FIGS. 9a and 9b show another slot coated sample having a
coated particle surface area coverage of 43% at 500.times.
magnification. A 5 micron polystyrene (only) particle suspension
formulation was used.
[0116] FIGS. 10a and 10b show another slot coated sample having a
coated particle surface area coverage of 52% at 500.times.
magnification. A particle suspension having 5 micron
polymethylmethacrylate (PMMA) particles suspended in a suitable
liquid, such as the first three entries in Table 2, was used.
[0117] FIGS. 11a and 11b show the roughness of a 3 micron
polystyrene (only) particle formulation coated at 74% and 83% area
coverage, respectively. Both images were captured with a 20.times.
objective, and 2.times. image zoom.
[0118] In embodiments, the disclosed method and article can provide
at least one or more of the following advantages. The disclosed
etch method can be accomplished quickly, for example, in from about
1 to about 10 minutes, in from about 1 to about 5 minutes, such as
in from about 2 to about 4 minutes, to create an anti-glare layer
on a glass surface. A conventional multi-bath method can take about
60 minutes or more. The disclosed etch method can use a single
chemical etchant bath (e.g., HF+H.sub.2SO.sub.4) instead of three
or more baths used in conventional processes.
[0119] In embodiments, the disclosed method can etch away, for
example, from about 1 to about 50 micrometers of the substrate
being etched (i.e., into the plane of the substrate or the
z-direction), from about 1 to about 30 micrometers of the
substrate, from about 1 to about 20 micrometers of the substrate,
from about 1 to about 10 micrometers of the substrate, including
intermediate values and ranges, to create a desired anti-glare
layer. In contrast, a conventional etch process can typically
remove about 100 to about 200 micrometers of the glass surface.
[0120] Samples prepared with the disclosed process show similar
optical properties (e.g., haze, gloss, and distinctness of image
(DOI)) when compared with samples etched with a conventional
process, but the present method and samples are advantaged by
having substantial reductions in process time, material
consumption, and costs. The disclosed process is readily scaled-up
for large parts, such as a one square meter glass sheet, and above,
while a conventional dip process is less readily scalable for
larger units.
[0121] With a proper design selection, the disclosed process does
not need backside protection to make single-sided samples.
Single-sided samples can be prepared using for example, single-side
dip, spray, slot die coating, or spin coating methods. A multi-bath
conventional process needs backside protection film, which can
further increase manufacturing costs.
[0122] In embodiments, the method of making can further comprise an
optional particle formulation polishing step, where the suspension
of particles are, for example, ball milled, and more preferably the
suspension of particles are milled in close proximity in time and
place to the slot die coater head, just prior to slot coating the
particle formulation on at least one surface with a slot die
coater. In embodiments, the method of making includes polishing the
particle formulation just prior to slot die coating. In
embodiments, the method of making includes polishing the particle
formulation in a polishing mill just prior to slot die. In
embodiments, the method of making can include use of an apparatus
having a polishing mill disposed just prior to slot die coating
head.
[0123] In embodiments, the coating method as illustrated in FIG. 1
can be further improved by incorporating a so-called particle
"polishing" step of the particle dispersion prior to a slot coating
of the dispersion. Particles having an average size less than about
10 micrometers can be suspended in a suitable liquid. The
dispersion can then be polished to homogenize it as a uniform
dispersion (i.e., no settling), then the resulting suspension can
be deposited, for example, by slot coating onto a glass substrate,
and the solvent can be removed by, for example, evaporation or
other methods, such as vacuum or drying, to leave a residual
partial layer of particles adhered on the glass substrate. The
sample can then be dipped into or immersed in an acid etch bath.
The HF/H.sub.2SO.sub.4 etchant attacks the area around the
particles and eventually under-cuts the area covered by individual
particles. The particles, if any remain on the substrate surface
after etching, can be removed from the substrate surface with a
rinsing step. The resulting glass substrate has anti-glare
properties.
[0124] In embodiments, the disclosure provides a slot coater
apparatus and system (1200) as illustrated in FIG. 12,
comprising:
[0125] a slot die (1201);
[0126] a source of a particle suspension (1202), the source of the
particle suspension can be driven by any suitable pump (1203) or
like propellant device or force such as gravity; and
[0127] a polisher (1204) situated between the source of the
particle suspension and the slot die, wherein the polisher
continuously polishes the particle suspension during slot coating
and feeds the polished particles to the slot die head for
coating.
[0128] The polisher (1204) can include, for example, a motor (1205)
for driving the polisher, and a screen (1206) or like filter member
to retain, for example, large milling media, such as ball bearings
or shot. In embodiments, the polisher can be, for example, a high
speed mixer or an opposed microfluidic stream mixing chamber.
[0129] The continuously polished particle stream is delivered to
the slot die (1201) and controllably deposited on a glass substrate
(1207) in desired thicknesses. The slot die (1201) and the glass
substrate (1207) are preferably in relative motion (1208) to
promote deposition of uniformly thick particle masks.
[0130] In embodiments, the suspension of particles for the particle
mask formulation can further include an anionic surfactant in the
formulation.
[0131] In embodiments, the disclosure provides a method for
obtaining anti-glare surfaces having low haze properties. The
method includes a process to form a nano- to micro-scale textured
surface on, for example, a silicate glass having haze reduction
(e.g., having haze less than 5%) while maintaining other optical
properties. The method involves coating particles on a glass
surface, allowing the solvent to escape, such as evaporation or
heat-drying, which escape method is sufficient to promote adhesion
of the deposited particles onto the glass surface. This process is
followed by etching in, for example, an HF etchant bath, or
multi-component acid solution. The etchant preferentially etches
around the particles on the glass surface to form an AG roughened
surface layer.
[0132] Haze becomes an important optical characteristic when device
contrast is an issue. This disclosure provides a method of making
AG samples by adding a surfactant into the formulation to make low
haze while maintaining others optical attributes in an acceptable
range. Other advantages include, for example:
[0133] Haze of less than about 5% can be achieved with low sparkle
and acceptable DOI.
[0134] Use of a surfactant facilitates achieving desired optical
properties, and also facilitates achieving desired coating
uniformity properties. The results are highly repeatable.
[0135] The use of a selected surfactant in the particle dispersion
formulation permits one to achieve a wide range of AG optical
properties.
[0136] The use of a selected surfactant in the particle dispersion
formulation also permits cost saving by using less material in the
particle mask. For comparative formulations free of surfactant, the
mask can be coated to a 45 microns wet thickness to obtain a
sparkle lower than 7 and a haze of about 8. Addition of a
surfactant into the particle mask coating formulation can be coated
to a wet thickness of 35 microns and the measured haze is less than
5%. The particle mask formulation material consumption can be
reduced, for example, by about 22%.
[0137] Generally, a surfactant can be used to improve the wetting
of the substrate surface. However, in the present methods inclusion
of a surfactant in the particle mask formulation appears to assist
in lubrication of the mask particles, and the milling beads if
present, such as in the polisher, and in releasing the mask
particles from the substrate surface during the etching step. These
events help to achieve low haze while maintaining other desired
optical attributes for AG.
[0138] A workable anionic surfactant concentration range can be,
for example, from 0.1% to 2% wt based on the total weight of the
particulate dispersion prior to slot die coating.
[0139] Suitable anionic surfactants can be, for example, Silwet
Hydrostable 212 (available from Momentive Performance Materials),
Q2-5211 Super wetter (available from Dow Corning), Novec-FC4430
(available from 3M), Surfynol 104 (available from Air Products),
and Dodecylbenzenesulfonic acid, sodium salt (available from
Aldrich).
[0140] In embodiments, the glass article can comprise, consist
essentially of, or consist of one of a soda lime silicate glass, an
alkaline earth aluminosilicate glass, an alkali aluminosilicate
glass, an alkali borosilicate glass, and combinations thereof. In
embodiments, the glass article can be, for example, an alkali
aluminosilicate glass having the composition: 60-72 mol %
SiO.sub.2; 9-16 mol % Al.sub.2O.sub.3; 5-12 mol % B.sub.2O.sub.3;
8-16 mol % Na.sub.2O; and 0-4 mol % K.sub.2O, wherein the ratio
Al 2 O 3 ( mol % ) + B 2 O 3 ( mol % ) alkali metal modifiers ( mol
% ) > 1 , ##EQU00002##
where the alkali metal modifiers are alkali metal oxides. In
embodiments, the alkali aluminosilicate glass substrate can be, for
example: 61-75 mol % SiO.sub.2; 7-15 mol % Al.sub.2O.sub.3; 0-12
mol % B.sub.2O.sub.3; 9-21 mol % Na.sub.2O; 0-4 mol % K.sub.2O; 0-7
mol % MgO; and 0-3 mol % CaO. In embodiments, the alkali
aluminosilicate glass substrate can be, for example: 60-70 mol %
SiO.sub.2; 6-14 mol % Al.sub.2O.sub.3; 0-15 mol % B.sub.2O.sub.3;
0-15 mol % Li.sub.2O; 0-20 mol % Na.sub.2O; 0-10 mol % K.sub.2O;
0-8 mol % MgO; 0-10 mol % CaO; 0-5 mol % ZrO.sub.2; 0-1 mol %
SnO.sub.2; 0-1 mol % CeO.sub.2; less than 50 ppm As.sub.2O.sub.3;
and less than 50 ppm Sb.sub.2O.sub.3; wherein 12 mol
%.ltoreq.Li.sub.2O+Na.sub.2O+K.sub.2O.ltoreq.20 mol % and 0 mol
%.ltoreq.MgO+CaO.ltoreq.10 mol %. In embodiments, the alkali
aluminosilicate glass substrate can be, for example: 64-68 mol %
SiO.sub.2; 12-16 mol % Na.sub.2O; 8-12 mol % Al.sub.2O.sub.3; 0-3
mol % B.sub.2O.sub.3; 2-5 mol % K.sub.2O; 4-6 mol % MgO; and 0-5
mol % CaO, wherein: 66 mol
%.ltoreq.SiO.sub.2+B.sub.2O.sub.3+CaO.ltoreq.69 mol %;
Na.sub.2O+K.sub.2O+B.sub.2O.sub.3+MgO+CaO+SrO>10 mol %; 5 mol
%.ltoreq.MgO+CaO+SrO.ltoreq.8 mol %;
(Na.sub.2O+B.sub.2O.sub.3)--Al.sub.2O.sub.3.ltoreq.2 mol %; 2 mol
%.ltoreq.Na.sub.2O--Al.sub.2O.sub.3.ltoreq.6 mol %; and 4 mol
%.ltoreq.(Na.sub.2O+K.sub.2O)--Al.sub.2O.sub.3.ltoreq.10 mol %. In
embodiments, the alkali aluminosilicate glass can be, for example:
50-80 wt % SiO.sub.2; 2-20 wt % Al.sub.2O.sub.3; 0-15 wt %
B.sub.2O.sub.3; 1-20 wt % Na.sub.2O; 0-10 wt % Li.sub.2O; 0-10 wt %
K.sub.2O; and 0-5 wt % (MgO+CaO+SrO+BaO); 0-3 wt % (SrO+BaO); and
0-5 wt % (ZrO.sub.2+TiO.sub.2), wherein
0.ltoreq.(Li.sub.2O+K.sub.2O)/Na.sub.2O.ltoreq.0.5. In embodiments,
the alkali aluminosilicate glass can be, for example, substantially
free of lithium. In embodiments, the alkali aluminosilicate glass
can be, for example, substantially free of at least one of arsenic,
antimony, barium, or combinations thereof. In embodiments, the
glass can optionally be batched with 0 to 2 mol % of at least one
fining agent, such as Na.sub.2SO.sub.4, NaCl, NaF, NaBr,
K.sub.2SO.sub.4, KCl, KF, KBr, SnO.sub.2, at like substances, or
combinations thereof.
[0141] In embodiments, the selected glass can be, for example, down
drawable, i.e., formable by methods such as slot draw or fusion
draw processes that are known in the art. In these instances, the
glass can have a liquidus viscosity of at least 130 kpoise.
Examples of alkali aluminosilicate glasses are described in
commonly owned and assigned U.S. patent application Ser. No.
11/888,213, to Ellison, et al., entitled "Down-Drawable, Chemically
Strengthened Glass for Cover Plate," filed Jul. 31, 2007, which
claims priority from U.S. Provisional Application 60/930,808, filed
May 22, 2007; U.S. patent application Ser. No. 12/277,573, to
Dejneka, et al., entitled "Glasses Having Improved Toughness and
Scratch Resistance," filed Nov. 25, 2008, which claims priority
from U.S. Provisional Application 61/004,677, filed Nov. 29, 2007;
U.S. patent application Ser. No. 12/392,577, to Dejneka, et al.,
entitled "Fining Agents for Silicate Glasses," filed Feb. 25, 2009,
which claims priority from U.S. Provisional Application No.
61/067,130, filed Feb. 26, 2008; U.S. patent application Ser. No.
12/393,241, to Dejneka, et al., entitled "Ion-Exchanged, Fast
Cooled Glasses," filed Feb. 26, 2009, which claims priority to U.S.
Provisional Application No. 61/067,732, filed Feb. 29, 2008; U.S.
patent application Ser. No. 12/537,393, to Barefoot, et al.,
entitled "Strengthened Glass Articles and Methods of Making," filed
Aug. 7, 2009, which claims priority to U.S. Provisional Application
No. 61/087,324, entitled "Chemically Tempered Cover Glass," filed
Aug. 8, 2008; U.S. Provisional Patent Application No. 61/235,767,
to Barefoot, et al., entitled "Crack and Scratch Resistant Glass
and Enclosures Made Therefrom," filed Aug. 21, 2009; and U.S.
Provisional Patent Application No. 61/235,762, to Dejneka, et al.,
entitled "Zircon Compatible Glasses for Down Draw," filed Aug. 21,
2009.
[0142] The glass surfaces and sheets described in the following
example(s) can use any suitable particle-coatable and etchable
glass substrate or like substrates, and can include, for example, a
glass composition 1 through 11, or a combination thereof, listed in
Table 1. Table 1 provides representative glass substrate
compositions.
TABLE-US-00001 TABLE 1 Representative glass substrate compositions.
Oxides Glass (mol %) 1 2 3 4 5 6 7 8 9 10 11 SiO.sub.2 66.16 69.49
63.06 64.89 63.28 67.64 66.58 64.49 66.53 67.19 70.62
Al.sub.2O.sub.3 10.29 8.45 8.45 5.79 7.93 10.63 11.03 8.72 8.68
3.29 0.86 TiO.sub.2 0 -- -- 0.64 0.66 0.056 0.004 -- 0.089
Na.sub.2O 14 14.01 15.39 11.48 15.51 12.29 13.28 15.63 10.76 13.84
13.22 K.sub.2O 2.45 1.16 3.44 4.09 3.46 2.66 2.5 3.32 0.007 1.21
0.013 B.sub.2O.sub.3 0.6 1.93 -- 1.9 -- -- 0.82 -- 2.57 --
SnO.sub.2 0.21 0.185 -- -- 0.127 -- -- 0.028 -- -- -- BaO 0 -- --
-- -- -- -- 0.021 0.01 0.009 -- As.sub.2O.sub.3 0 -- -- -- -- 0.24
0.27 -- 0.02 -- Sb.sub.2O.sub.3 -- -- 0.07 -- 0.015 -- 0.038 0.127
0.08 0.04 0.013 CaO 0.58 0.507 2.41 0.29 2.48 0.094 0.07 2.31 0.05
7.05 7.74 MgO 5.7 6.2 3.2 11.01 3.2 5.8 5.56 2.63 0.014 4.73 7.43
ZrO.sub.2 0.0105 0.01 2.05 2.4 2.09 -- -- 1.82 2.54 0.03 0.014
Li.sub.2O 0 -- -- -- -- -- -- -- 11.32 -- -- Fe.sub.2O.sub.3 0.0081
0.008 0.0083 0.008 0.0083 0.0099 0.0082 0.0062 0.0035 0.0042 0.0048
SrO -- -- -- 0.029 -- -- -- -- -- -- --
EXAMPLES
[0143] The following examples serve to more fully describe the
manner of using the above-described disclosure, and to further set
forth the best modes contemplated for carrying out various aspects
of the disclosure. It is understood that these examples do not
limit the scope of this disclosure, but rather are presented for
illustrative purposes. The working examples further describe how to
prepare the articles of the disclosure.
[0144] The following generally summarizes the steps of how the
particle mask suspension was prepared, coated, and then etched.
Corning 2318 glass (6''.times.10'') specimens were washed in a Big
Dipper automatic dish washer using about 4% semi-clean KG detergent
in DI water. Glass sheets were then laminated on one side with
backside protection film. Then the particle coat formulation was
prepared by weighing out each component listed in Table 2. The
binder was mixed in ethanol until completely dissolved. Butanol and
particles or beads were then added. The particle concentrate
contained in roller bottles was placed on rollers to keep the
particles well suspended. The formulation was then spray coated or
slot coated on the glass surface. The samples were then etched
either vertically or horizontally with an acid solution having a
specific concentration (e.g., 5.5 M HF/6.5M H.sub.2SO.sub.4) for a
specific time (e.g., 30 seconds); the etched sample was then
removed and then rinsed; and Haze, sparkle, and DOI of the etched
samples were measured.
Preparation of Particulated Surfaces
Example 1
Preparation of Particle Suspensions
[0145] Particle suspension masks were prepared by dispersing the
particles as described above. Table 2 lists a representative
polystyrene polymer particle suspension formulation.
TABLE-US-00002 TABLE 2 Components Wt. % 2 propyl methylcellulose
(J).sup.1 3.27 Ethanol 78.53 Butanol 13.2 Polystyrene XOI 3
microns.sup.2 5 Total 100
[0146] 1. 2-propyl methylcellulose (J)--average molecular weight
140,000, from Ashland Chemicals. [0147] 2. Polystyrene XOI are 3
micron polystyrene beads from Sekisui, Japan.
Example 2
Slot Coating of Particle Suspensions
[0148] Different methods for applying the particles can be
selected. For example, the particle formulation can be spray
coated, curtain-coated, screen printed, dip coated, spin coated,
applied with a roller onto the glass surface, and like other known
methods, or combinations thereof. A slot die is particularly
advantaged in embodiments of the disclosure. One advantage of the
slot die coating technique is that the coating thickness can be
controlled precisely. This is directly related to how much coverage
one wishes to achieve on the glass surface. After coating, a very
thin layer of particles remained on the surface, such as a
monolayer or less than a complete monolayer. This very thin layer
of particles improves the ability of the acid to infiltrate the
spaces in the coating mask, resulting in, for example, more
efficient etching, less acid consumption, and less particle
consumption. In embodiments, the interaction between the particles
and the glass surface can be further improved by adjusting, for
example, the glass or particle chemistry, the particle
concentration, the surface charge, and like aspects, or combination
thereof. Examples of coating conditions using the spray and slot
technologies are listed in Tables 3 and 4.
Etching Particulated Surfaces
Example 3
Immersion Etch of Particulated Surfaces
[0149] Glass sheets having particulated glass surfaces prepared by
spray or slot coating conditions were etched using various acid
formulations with controlled variation in etch time and temperature
according to Example 1 were etched using various acid formulations
with controlled variation in etch time and temperature, for
example, an etch time of 0.5 minute, acids concentration of 6 M HF
and 7 M H.sub.2SO.sub.4, at ambient (25.degree. C.) temperature,
and like conditions. Table 3 provides an exemplary set of the spray
conditions.
TABLE-US-00003 TABLE 3 Particle formulation spray coat conditions
Spray Condition Setting Nozzle opening diameter (mm) 0.76 Flute
(degree) 10 Air assist (psi) 85 Fluid pressure (psi) 15 Dispense
height (inches) 3 Speed (inches/sec) 10 Stroke (mils) 5 Pass width
(in) 0.10 Number of Passes 1
[0150] Table 4 provides an exemplary set of the slot coating
conditions for a 3 micron polystyrene (only) particle
suspension.
TABLE-US-00004 TABLE 4 Particle formulation slot coating
conditions. Coater .sup.1Coating Wet Speed mL/ Gap Horiz Vert Liq
Sample (microns) (mm/sec) min (microns) Del.sup.2 Del.sup.3
Trig.sup.4 1 25 1.12 50 2 35 1.57 50 3 45 2.02 50 4 55 2.46 80 5 65
2.91 80 0.5 0.5 0.5 6 75 5 3.36 100 7 85 3.81 100 8 95 4.25 120 9
105 4.70 120 10 115 5.15 150
[0151] 1. Height of slot die head from substrate surface in microns
prior to depositing particles. [0152] 2. Horiz Del is the
horizontal delay, which is a programmable period of time for the
machine to delay moving the platen (coating) while the pump is
dispensing fluid out the lips. This delay allows sufficient time
for the distance between the die and the substrate (the gap) to be
filled with fluid. This is also referred to as "forming the bead".
[0153] 3. Vert Del is the Vertical Delay, which is a programmable
period of time for the machine to wait before moving from the start
gap position to the coating gap position. In all instances where an
AG surface is being prepared, it can be coated having the start gap
being equal to the coating gap, and the horizontal delay setting
becomes moot. [0154] 4. Liq Trig is the Liquid Trigger Stop, which
is a programmable period of time, towards the end of a coating,
where one can turn off the suspension formulation pump prior to
reaching the end of the substrate. The platen continues to move, as
it was pre programmed, to the stop position (generally the end of
the substrate), while the pump pressure subsides. This can be
useful for achieving cleaner stops where higher viscosity fluids
are being coated.
[0155] Table 5 provides examples of various percent coverages for 3
micron particles. The same acid and concentrations of 6M HF/7M
H.sub.2SO.sub.4 were used.
TABLE-US-00005 TABLE 5 Etch Wet coating Time (secs thickness, % for
each micron(s) Coverage sample) Haze DOI PPD-0 PPD-90 25 57 2.7
86.4 5.64 5.61 45 83 11.4 26 6.41 6.53 55 86 15.9 25.7 6.59 6.58 65
92 30 18.3 26.4 8.38 7.98 75 95 20.6 26.5 9.99 9.69 85 95 19 27
10.62 10.44 95 95 18.2 27 10.91 10.46 105 96 15.6 27.9 11.8
11.5
[0156] Table 6 provides examples of various percent coverages for 5
micron PMMA polymer particles. The same acid concentrations, 6M
HF/7M H.sub.2SO.sub.4, were used.
TABLE-US-00006 TABLE 6 % Area Wet Coverage coating of total Etching
thickness, Coated Time micron(s) Area (secs.) Haze DOI PPD-0 PPD-90
15 63.1 30 4.5 65 5.9 5.8 20 76.1 30 7 42 6 5.9 25 91 30 13 27 6 6
30 90.5 30 16 26 6.3 6.1 35 92.2 30 16 26 7.9 8.0 40 97.9 30 14 27
11 11.1 45 97.8 30 13 27 12.8 11.1 50 98.2 30 12 28 15.3 14.3
[0157] In general, as the coverage increased, more particles
deposited on the glass surface and became multi-layer, having fewer
or smaller openings between particles and the particles were
adhered strongly to the glass surface. The higher the particle
coverage, the more the particles clump together and have a negative
impact on the optical properties. This is clearly demonstrated when
the haze level increased and the DOI got lower as seen in Tables 3
and 4. The sparkle (or PPD) increased as the coverage increased as
well.
[0158] The data in Tables 5 and 6 also demonstrate a wide range of
haze that we can achieve by controlling the percent coverage.
[0159] The particles used were based on polymer beads (e.g., PMMA
and Polystyrene). A wide variety of other particles can be
selected. For low molecular weight materials, the annealing
temperatures were chosen to be roughly proportional to the Tg of
the particles. Examples of other particle materials include, for
example, polyesters, polyolefins, polyvinylchloride, polyvinyl
acetate, polyvinyl alcohol, polyacrylonitrile, silicone,
polyethylene, melamine, (meth)acrylate, polyethylene terephthalate,
and like polymers, and mixtures thereof. The particles can be
homopolymers, copolymers, terpolymers, and like polymers, and
mixtures thereof. The beads may be modified with a surface
treatment. They may be either crosslinked or un-crosslinked, and
any spherical or flattened fine particles comprised of a plastic
can be selected. Waxes are polymers that are considered
particularly useful in the disclosure. Classes of waxes can be, for
example, plant, mineral, or animal based, and petroleum derived and
synthetic waxes. Some example materials are erucamide, stearamide,
oleamide, Montan, oxidized polyethylene, copolymers containing
these combinations, and a core of one polymer and shell of a
different polymer, and others known in the art. These other
particles can be selected based on cost, ease of removal, or
robustness in acid solutions, and like practical reasons, or
combinations thereof.
[0160] The mask particle size is not particularly limited. For
anti-glare surfaces in display applications, a generally desirable
particle size range is from about 1 micron to about 50 microns.
Below this range, sub-wavelength effects can reduce the anti-glare
scattering, and above this range, unacceptable `display sparkle`
can become visible in some pixelated displays. However, the general
technique outlined here is still applicable using particle sizes
outside this range--in particular, the slot die coating method for
creating several layers of particles, the ability to tune glass
roughness through annealing of a particle mask before etching, or
combinations thereof. Particles larger than 50 microns may be
useful in non-display applications, such as in mouse pads or other
touch input devices, anti-glare surface for non-pixelated displays,
and like articles or devices. Particles less than 1 micron may be
useful for generating nano-structured surfaces, for example
gradient-index anti-reflection coatings or hydrophobic/oleophobic
structured surfaces. Other non-display applications that could
benefit from this method for creating light-scattering surfaces on
glass include photovoltaic panels for improved light
trapping/absorption, and aesthetic panels or covers for appliances
or architectural applications.
Post Etch Processing
Example 4
Optional Flaw Reduction
[0161] If desired the etched surface can optionally be further
processed to remove surface flaws or defects from the surface and
to further enhance the strength, toughness or scratch resistance,
and appearance properties of the surface (see for example, commonly
owned and assigned U.S. Provisional Patent Application 61/293,032,
filed Jan. 7, 2010, entitled "Impact-Damage-Resistant Glass
Sheet"). Thus, a glass sheet including at least one acid-etched
surface as disclosed herein, alone or in combination with a
tempering surface compression layer, is subjected to a combination
of a surface tempering treatment and then an additional acidic etch
treatment. The resulting glass sheet exhibits high strength (ball
drop) and is a useful component in damage-resistant consumer
display devices.
Example 5
Polymer Particle Formulations
[0162] Table 7 provides a summary of several exemplary polymer
particle formulations.
TABLE-US-00007 TABLE 7 Coating formulation Mixture of polymer and
Polystyrene PMMA wax particles.sup.2 particles.sup.3
particles.sup.4 Ingredients wt. % wt. % wt. % Medium 80 683 Solvent
20.66 -- -- Blend.sup.1 2 propyl methylcellulose (J) 0.92 3.24 3.27
Ethanol 54.61 78.37 77.47 Isopropanol 7.5 -- -- Butanol -- 13.20
14.26 Sekisui PMMA- 8 microns 13.81 -- -- Polystyrene - 3 microns
-- 5.19 -- Wax - Durex 8015 - 6 2.5 -- -- microns Sekisui PMMA- 5
microns -- -- 5 Total 100 100 100
[0163] Exemplary particle compositions used for particle suspension
and deposition were, for example, a copolymer of methyl
methacrylate and ethylene glycol dimethacrylate. Other polymer
particle sizes, particle compositions, mixing two or more particle
sizes with same or different compositions together, or glass
substrates may involve additional or further formulation
manipulation to produce finished substrates having the desired
roughness, haze level, and DOI properties in the finished
article.
Example 6
Particle Mask Formulations
[0164] FIGS. 13A to 13D show micrographs of Gorilla.RTM. glass
coated with un-polished dispersion. The wet coated layer
thicknesses were approximately 35 microns, 40 microns, 45 microns,
and 50 microns, respectively. It can be seen that the wet coated
layer on the surface is neither a mono-layer, nor less than a
mono-layer. The beads are piled up and distributed un-evenly on the
surface. In the macro-view, one can easily see the density bands on
the coated samples, which directly relates to the surface defect
discovered on the AG surface after etching.
[0165] FIGS. 14A to 14D show micrographs of Gorilla.RTM. glass
coated with a polished dispersion. The wet coated layer thicknesses
were approximately 35 microns, 40 microns, 45 microns, and 50
microns, respectively.
[0166] In contrast to the un-polished dispersion shown in FIG. 13,
the polished dispersion shown in FIG. 14, resulted in a
configuration having slightly less than mono-layer particle
coverage. Polishing the dispersion results in the dispersion being
homogenous and can flow from the slot die cavity uniformly disperse
and at a uniform rate. The coated polished and unpolished
dispersion samples look very different considering that both
dispersions were coated having the identical coating parameters
with the exception of the disclosed in-line polishing treatment.
Table 8 lists a representative particle formulation used in
embodiments of the disclosure.
TABLE-US-00008 TABLE 8 Particle formulation. Components Wt. % 2
propyl methylcellulose (J).sup.1 3.1 Ethanol 74.61 Butanol 12.54
Water 4.43 Polystyrene XOI 3 microns.sup.2 4.75 DODEC 0.57 Total
100
[0167] 1. & 2. See Table 2 footnotes above.
[0168] Table 9 shows examples of the slot conditions selected for
obtaining different wet thicknesses.
TABLE-US-00009 TABLE 9 Example slot coating conditions selected for
different wet thicknesses. Wet Sample Thickness S-gap C-gap Horiz
Vert Lig material (microns) mm/sec mL/min (microns) (microns) Del
Del Trig 52 35 10 3.13 60 60 0.5 0.5 5 40 3.58 90 90 45 4.03 50
4.48
[0169] The "polished" particle dispersions were prepared as
mentioned above and polished as follows. When the dispersion
formulations were ready to coat, 1.5 mm high density zirconium
oxide beads, known as Zirmil-Y, available from Glen Mills Inc., New
Jersey, are added into the formulation (e.g., in a 1:1 ratio), and
rolled for 30 minutes on a roller at 60 rpm or similarly processed
using the in-line polisher as illustrated in FIG. 12. The larger
oxide milling beads were then filtered out or retained by the
in-line mill. The resulting dispersion was homogenous and ready to
be coated with the slot die coater. The coated samples were etched
vertically in an acid solution at a specific concentration, for
example, 5.5M HF/6.5M H.sub.2SO.sub.4, for a specific time, for
example, 30 seconds. The etched sample was then removed from the
bath for rinsing and removal of the backside protection film. The
etched sample was then measured for Haze, sparkle, and DOI
properties.
[0170] Different methods for applying the particles can be
contemplated. For example, a formulation could be sprayed,
curtain-coated, screen printed, dip coated, spin coated, applied
with a roller, and like methods, or combinations thereof, onto the
glass surface. Slot die was a particularly useful coating method in
this disclosure. One particular advantage of the slot die coating
approach is that the coating thickness can be controlled very
precisely. This control is useful in obtaining desired particle
surface coverage on the glass surface. After coating, a very thin
layer of particles remained on the surface. The interaction between
the particles and the glass surface can be further improved, for
example, by adjusting the glass or particle chemistry, particle
concentration, the surface charge, and like aspects, or
combinations thereof. In embodiments, a wet coating method can be
further improved by, for example, applying only from about 1 to 2
layers of particles. In embodiments, the wet coating method can be
further improved by, for example, applying less than a monolayer.
Table 10 below shows the optical data for samples with and without
polished dispersions at the same thickness. The results make
evident that DOI values increase and sparkle values decrease for
the polished dispersion samples compared to the "unpolished"
dispersion control samples.
TABLE-US-00010 TABLE 10 Optical data for samples with and without
polished dispersions having the same layer thickness. Wet Thickness
Haze DOI Sparkle (microns) (9 meas) (3 meas) (6 meas) Un-polished
Dispersion 35 4 46 7.3 4 51 7.3 4 55 7.0 4 46 7.3 30 minute
Polished Dispersion 35 4 70 6.6 4 74 7.0 4 75 6.2 4 74 6.2 4 72 6.2
4 73 6.3 4 75 6.3 4 70 6.5
[0171] The wet thickness is the same for both instances but the
optical values for the dispersion without polishing shows
unacceptable sparkle. Sparkle is the most important attribute for
AG properties and sparkle is preferably less than 7. When sparkle
is greater than 7, users or observers will usually report
"non-uniformity" in the display due to AG features that are not
small enough.
[0172] FIG. 15 shows a graph of the data listed in Table 10.
Optical data for samples 1 to 4 (left side) are from un-polished
dispersion coatings. Data for samples 8 to 15 (right side) were for
polishing the dispersion for 30 minutes prior to slot coating. The
formulation is preferably homogenized by polishing in a bead mill
or in-line bead mill prior to coating.
[0173] The polishing step can be an excellent method to obtain
superior uniform particle coating quality and good optical
properties of the resulting etched surfaces. We have demonstrated
that this is also a preferred method for scale-up to coat larger
sized substrates. The disclosed coating method including a particle
polishing step is particularly advantaged by, for example, avoiding
density bands and poor coating quality in the resulting coated
substrate.
Example 7
Particle Mask Formulations Including an Anionic Surfactant
[0174] Table 11 shows examples of optical properties of parts
coated with a particle mask formulation without a surfactant.
TABLE-US-00011 TABLE 11 Optical property results for etching of
surfactant-free mask formulations. Wet Thickness (microns) Haze %
DOI P-0 P-90 35 5 43 7.4 7.2 5 46 7.5 7.3 5 47 7.5 7.3 40 8 27 6.9
6.9 7 29 7.1 7.0 7 31 7.5 7.6 45 10 26 6.6 6.4 10 27 6.8 6.8 9 27
7.0 6.9 50 13 26 6.4 6.4 11 26 6.6 6.6 12 26 6.7 6.4 55 13 26 7.2
7.1 12 26 7.2 7.0 15 26 6.8 6.6
[0175] Columns P-0 and P-90 are the sparkle measurements on AG
sample in the 0 and 90 degree orientation. The sparkle is
preferably less than 7 than selected applications. At 35 microns
wet thickness, haze is about 5% but the sparkle is unacceptable.
Only a wet thickness of 45 microns and 50 microns show the sparkle
less than 7. However, the haze is very high and will decrease the
device contrast. One goal is to have haze less than 5% while still
have PPD less than 5. A particle mask formulation without a
surfactant cannot achieve this targeted specification. Table 12
shows examples of parts coated using a formulation having added
surfactant (0.6 wt % DODEC).
TABLE-US-00012 TABLE 12 Impact of added surfactant in the particle
mask coating formulation on optical properties resulting after 30
second acid etching with 6M HF/7M H.sub.2SO.sub.4. Wet thickness
(microns) Haze % DOI P-0 P-90 35 5 67 5.5 5.5 5 58 5.8 5.5 5 60 5.6
5.5 5 60 5.6 5.5 45 7 35 6.4 5.9 6 39 6.2 6.1 50 8 35 6.7 6.7 7 36
6.6 6.6 7 41 6.9 6.7 6 40 7.2 7.3 7 38 6.9 6.7 8 34 6.8 6.5 8 38
6.8 6.7 7 36 7.0 6.8
[0176] Several points are notable in the Table 12. First, at 35
microns wet thickness and the same acid concentration and the same
etching time, it was possible to make samples having sparkle less
than 7 when using a formulation having added surfactant (vs. data
in Table 11). Also, the sparkle is about 1 point reduced for 35
microns (vs. Table 11). Additionally, the haze at 50 microns
thickness was reduced from 13% for a formulation free of surfactant
to about 7% when a surfactant was added (vs. Table 11). Table 13
shows examples of parts coated using a formulation having added
surfactant (0.6 wt % DODEC).
TABLE-US-00013 TABLE 13 Optical results for acid (5.5M HF/6.5M
H.sub.2SO.sub.4) etching of parts coated at a wet thickness of 35
microns with a mask formulation having added surfactant. Etching
time (seconds) Haze % DOI P-0 P-90 20 3 69 6.2 6.2 3 71 6.1 6.1 3
67 6.1 6.2 3 69 6.4 6.3 3 69 6.2 6.2 3 71 6.2 6.1 3 68 6.4 6.1 3 70
6.5 6.4 3 66 6.4 6.2 3 69 6.4 6.2 3 68 6.3 6.3 3 71 6.4 6.4 3 65
6.5 6.4 3 64 6.7 6.5 3 64 6.5 6.2 3 68 6.5 6.4 3 71 6.5 6.2 3 70
6.4 6.5 3 67 6.6 6.4 3 67 6.7 6.6 3 66 6.6 6.4
[0177] The 35 microns wet thickness results in Table 13 are similar
to 35 microns wet thickness results in Table 12 data except that
the acid concentration was lower and the etch time was shorter.
Reducing the acid concentration and time allows one to achieve even
lower haze and while maintaining sparkle less than 7. Without the
added surfactant, the desired optical properties on Gorilla glass
could not be achieved. The surfactant apparently helped the
particles release from the glass surface at about the same time
during the acid etching step in repeated experiments and thus
produced very reproducible results.
[0178] Although not limited by theory, a specific surfactant (i.e.,
dodecylbenzenesulfonic acid, sodium salt, DODEC) selected may form
a mono-molecular layer surrounding each polymer particle, creating
lubrication conducive to achieving the proper spacing of particles
after drying. This surfactant layer also acts to release the
polymer particle from the glass surface during the etching process.
The release timing can be significant in achieving the proper AG
optical characteristics. Another material, classically defined as a
silyated organic surfactant blend or coating aide, Silwet.RTM.
Hydrostable 212 surfactant, available from Momentive Performance
Materials, Columbus, Ohio.
[0179] A surfactant is desired so as to have the formulation obtain
good AG optical properties. It was found that not all surfactants
work the same. Data in tables demonstrates a wide range of haze
that can be achieved while still maintaining other optical
attributes, and reproduced very well when surfactant is
present.
[0180] Commonly owned and assigned U.S. Ser. No. 13/090,522
mentions use of surfactant to improve the optical properties,
especially to achieve low haze while maintaining the sparkle and
DOI in an acceptable range.
[0181] FIGS. 16A to 16C show micrographs of Gorilla.RTM. glass
coated having particle dispersions that include a surfactant
additive. FIG. 16A has a coating of 35 micron particles having a
wet thickness including a surfactant. FIG. 16B has a coating of 45
micron particles having a wet thickness including a surfactant.
FIG. 16C has a coating of 55 micron particles having a wet
thickness including a surfactant. Table 14 shows examples of the
slot die conditions for two different wet thickness using a 3
micron particle suspension to a glass substrate.
TABLE-US-00014 TABLE 14 Unpolished Particle formulation and
Polished Particle formulation slot coating conditions. Wet Coater
Dispense Formulation Thickness Speed rate S-Gap C-Gap Horiz Vert
Liq Sample (microns) (mm/sec) (mL/min) (microns) (microns)
Del.sup.2 Del.sup.3 Trig.sup.4 unpolished 35 15 4.70 70 70 0.5 0.5
5 polished 50 10 4.48 100 100 0.5 0.5 5
[0182] 1., 2., 3., and 4. see Table 4 above.
[0183] Table 15 lists a particle formulation A having added
surfactant and a comparative formulation B free of added
surfactant.
TABLE-US-00015 TABLE 15 Particle formulation having surfactant
("A") and a comparative formulation ("B") free of surfactant. A B
Components (Wt. %) (Wt. %) 2 propyl methylcellulose (J).sup.1 3.1
3.27 Ethanol 74.61 78.53 Butanol 12.54 13.2 Water 4.43 --
Polystyrene XOI 3 microns.sup.2 4.75 5 DODEC surfactant 0.57 --
(Dodecylbenzenesulfonic acid, sodium salt) Total 100 100
[0184] 1. and 2., see Table 2 footnotes above.
[0185] The disclosure has been described with reference to various
specific embodiments and techniques. However, it should be
understood that many variations and modifications are possible
while remaining within the scope of the disclosure.
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