U.S. patent application number 15/404609 was filed with the patent office on 2017-05-11 for cover glass.
This patent application is currently assigned to ASAHI GLASS COMPANY, LIMITED. The applicant listed for this patent is ASAHI GLASS COMPANY, LIMITED. Invention is credited to Kensuke FUJII, Shinji KOBUNE, Hitoshi MISHIRO, Minoru TAMADA.
Application Number | 20170129806 15/404609 |
Document ID | / |
Family ID | 55078499 |
Filed Date | 2017-05-11 |
United States Patent
Application |
20170129806 |
Kind Code |
A1 |
FUJII; Kensuke ; et
al. |
May 11, 2017 |
COVER GLASS
Abstract
A cover glass includes: a glass substrate having a convex and
concave shape formed on at least one of surfaces thereof by an
antiglare treatment; and an antireflection film disposed on the
surface of the glass substrate, the surface having the convex and
concave shape. In the cover glass, a difference .DELTA.a* in a*
value between any two points within a surface of the cover glass on
the side where the antireflection film is present and a difference
.DELTA.b* in b* value between any two points within the surface of
the cover glass on the side where the antireflection film is
present satisfy the following expression:
{(.DELTA.a*).sup.2+(.DELTA.b*).sup.2}.ltoreq.4.
Inventors: |
FUJII; Kensuke; (Tokyo,
JP) ; KOBUNE; Shinji; (Tokyo, JP) ; TAMADA;
Minoru; (Tokyo, JP) ; MISHIRO; Hitoshi;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ASAHI GLASS COMPANY, LIMITED |
Chiyoda-ku |
|
JP |
|
|
Assignee: |
ASAHI GLASS COMPANY,
LIMITED
Chiyoda-ku
JP
|
Family ID: |
55078499 |
Appl. No.: |
15/404609 |
Filed: |
January 12, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2015/070084 |
Jul 13, 2015 |
|
|
|
15404609 |
|
|
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C03C 3/087 20130101;
C03C 4/18 20130101; C03C 2218/154 20130101; C03C 21/002 20130101;
C03C 2217/218 20130101; C03C 2204/00 20130101; C03C 2218/31
20130101; C09D 1/00 20130101; C09D 5/006 20130101; C03C 3/085
20130101; C03C 2217/734 20130101; G02B 1/115 20130101; C03C 3/083
20130101; C03C 17/42 20130101; C09D 5/1675 20130101; G02B 27/0006
20130101; G02B 5/0268 20130101; C03C 17/3417 20130101 |
International
Class: |
C03C 17/34 20060101
C03C017/34; C03C 3/085 20060101 C03C003/085; C03C 3/087 20060101
C03C003/087; C03C 21/00 20060101 C03C021/00; C09D 1/00 20060101
C09D001/00; C09D 5/00 20060101 C09D005/00; C09D 5/16 20060101
C09D005/16; C03C 3/083 20060101 C03C003/083; C03C 4/18 20060101
C03C004/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 16, 2014 |
JP |
2014-146264 |
Jul 16, 2014 |
JP |
2014-146265 |
Claims
1. A cover glass comprising: a glass substrate having a convex and
concave shape formed on at least one of surfaces thereof by an
antiglare treatment; and an antireflection film disposed on the
surface of the glass substrate, the surface having the convex and
concave shape, wherein a difference .DELTA.a* in a* value between
any two points within a surface of the cover glass on the side
where the antireflection film is present and a difference .DELTA.b*
in b* value between any two points within the surface of the cover
glass on the side where the antireflection film is present satisfy
the following expression (1).
{(.DELTA.a*).sup.2+(.DELTA.b*).sup.2}.ltoreq.4 (1)
2. The cover glass according to claim 1, wherein the .DELTA.a* and
the .DELTA.b* are determined by selecting any square portion of 10
cm.sup.2 as a measuring range from the glass substrate, dividing
the measuring range into 11.times.11 equal portions, examining all
100 intersections of equally dividing lines for a* values and b*
values, determining a maximum value a*.sub.max of the a* values, a
minimum value a*.sub.min of the a* values, a maximum value
b*.sub.max of the b* values, and a minimum value b*.sub.min of the
b* values, from the a* values and b* values, and taking a
difference (a*.sub.max-a*.sub.min) between the a*.sub.max and the
a*.sub.min as the .DELTA.a* and a difference
(b*.sub.max-b*.sub.min) between the b*.sub.max and the b*.sub.min
as the .DELTA.b*.
3. The cover glass according to claim 1, wherein the glass
substrate has a microcrack(s) having a maximum depth of less than 3
.mu.m on the surface thereof, the surface having the convex and
concave shape.
4. The cover glass according to claim 1, wherein the surface of the
cover glass, which has the convex and concave shape, has a degree
of ion exchange of 1% or more and 25% or less.
5. The cover glass according to claim 4, wherein the degree of ion
exchange is a degree of ion exchange determined using aluminum as
an index.
6. The cover glass according to claim 1, which has a haze of 1% to
35%.
7. The cover glass according to claim 1, wherein the antireflection
film is a laminate comprising one or more layers containing niobium
and one or more layers containing silicon.
8. The cover glass according to claim 1, which has a luminous
reflectance of 2% or less.
9. The cover glass according to claim 1, further comprising an
antifouling film disposed on the antireflection film, wherein a
contact angle of water on a surface of the cover glass on the side
where the antifouling film is present is 90.degree. or larger.
Description
TECHNICAL FIELD
[0001] The present invention relates to a cover glass.
BACKGROUND ART
[0002] In recent years, image display devices are coming to be
increasingly used in various appliances, e.g., navigation systems
and speedometers, to be mounted on vehicles, etc. The properties
required of the cover glasses of such image display devices include
diminishing the reflection of external light and preventing
external light from being reflected in the screen and thereby
rendering the images less visible, from the standpoints of safety
and appearance improvement.
[0003] As a means for preventing light or images from being
reflected by or in surfaces of transparent substrates such as
glasses, a glass substrate surface is subjected to an antiglare
treatment (AG treatment). For example, as a known method, a glass
substrate surface is subjected to a chemical or physical surface
treatment to form irregularities and this surface is then etched
with, for example, hydrofluoric acid in order to arrange the
surface shape (Patent Document 1).
[0004] Also known as a means for preventing light or images from
being reflected by or in a glass surface is a technique for
reflection prevention which reduces surface reflection. Having been
proposed as a technique for reflection prevention is one in which
several layers each having appropriate values of refractive index
and optical film thickness are laminated as optical interference
layers to thereby reduce light reflection occurring at the
interface between the laminate and air (Patent Document 2).
PRIOR ART DOCUMENTS
Patent Documents
[0005] Patent Document 1: JP-A-S61-36140 [0006] Patent Document 2:
JP-A-2003-215309
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0007] It is thought that in cases where an antiglare treatment and
the formation of an antireflection film are both performed, the
reflection by or in the glass surface can be more effectively
prevented. However, there is a possibility that the methods
described above might have a problem in that the color tone of the
glass is uneven and varies, that is, unevenness in color results.
This problem is thought to arise due to the following.
[0008] In the course of the antiglare treatment, there are cases
where an extremely thin layer which is deficient in cationic
components of the glass and which is called a leach-out layer is
unevenly formed in the surface of the glass substrate. The
leach-out layer differs from the glass substrate in refractive
index. Consequently, in cases where an antireflection film is
further formed thereon, the leach-out layer behaves as if this
layer is a low-refractive-index layer unevenly interposed between
the antireflection film and the glass substrate. The unevenness in
color is thought to thus result.
[0009] An object of the present invention is to provide a cover
glass which is less apt to suffer color tone unevenness even when
produced through both an antiglare treatment and formation of an
antireflection film.
Means for Solving the Problems
[0010] The present inventors have found that the above problem(s)
could be solved by the cover glass having no leach-out layer. That
is, the present invention relates to the following cover glass.
[0011] [1] A cover glass comprising: a glass substrate having a
convex and concave shape formed on at least one of surfaces thereof
by an antiglare treatment; and an antireflection film disposed on
the surface of the glass substrate, the surface having the convex
and concave shape, wherein
[0012] a difference .DELTA.a* in a* value between any two points
within a surface of the cover glass on the side where the
antireflection film is present and a difference .DELTA.b* in
between any two points within the surface of the cover glass on the
side where the antireflection film is present satisfy the following
expression (1).
(.DELTA.a*).sup.2+(.DELTA.b*).sup.2).ltoreq.4 (1)
[0013] [2] The cover glass according to [1], wherein the .DELTA.a*
and the .DELTA.b* are determined by selecting any square portion of
10 cm.sup.2 as a measuring range from the glass substrate, dividing
the measuring range into 11.times.11 equal portions, examining all
100 intersections of equally dividing lines for a* values and b*
values, determining a maximum value a*.sub.max of the a* values, a
minimum value a*.sub.min of the a* values, a maximum value
b*.sub.max of the b* values, and a minimum value b*.sub.min of the
b* values, from the a* values and b* values, and taking a
difference (a*.sub.max-a*.sub.min) between the a*.sub.max and the
a*.sub.min as the .DELTA.a* and a difference
(b*.sub.max-b*.sub.min) between the b*.sub.max and the b*.sub.min
as the .DELTA.b*.
[0014] [3] The cover glass according to [1] or [2], wherein the
glass substrate has a microcrack(s) having a maximum depth of less
than 3 .mu.m on the surface thereof, the surface having the convex
and concave shape.
[0015] [4] The cover glass according to any one of [1] to [3],
wherein the surface of the cover glass, which has the convex and
concave shape, has a degree of ion exchange of 1% or more and 25%
or less.
[0016] [5] The cover glass according to [4], wherein the degree of
ion exchange is a degree of ion exchange determined using aluminum
as an index.
[0017] [6] The cover glass according to any one of [1] to [5],
which has a haze of 1% to 35%.
[0018] [7] The cover glass according to any one of [1] to [6],
wherein the antireflection film is a laminate comprising one or
more layers containing niobium and one or more layers containing
silicon.
[0019] [8] The cover glass according to any one of [1] to [7],
which has a luminous reflectance of 2% or less.
[0020] [9] The cover glass according to any one of [1] to [8],
further comprising an antifouling film disposed on the
antireflection film, wherein a contact angle of water on a surface
of the cover glass on the side where the antifouling film is
present is 90.degree. or larger.
Effects of the Invention
[0021] According to the present invention, a cover glass in which
reflection by or in the glass surface is little and which is
reduced in color tone unevenness is provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1A to FIG. 1D are a flowchart which shows steps of one
embodiment of the production process in the present invention.
[0023] FIG. 2A to FIG. 2F are a flowchart which shows steps of
another embodiment of the production process in the present
invention.
MODES FOR CARRYING OUT THE INVENTION
[0024] The cover glass of the present invention includes: a glass
substrate having a convex and concave shape formed on at least one
of surfaces thereof by an antiglare treatment; and an
antireflection film disposed on the surface of the glass substrate,
the surface having the convex and concave shape, and in the cover
glass, a difference .DELTA.a* in a* value between any two points
within a surface of the glass on the side where the antireflection
film is present and a difference .DELTA.b* in b* value between any
two points within the surface of the glass on the side where the
antireflection film is present satisfy the following expression
(1).
{(.DELTA.a*).sup.2+(.DELTA.b*).sup.2}.ltoreq.4 (1)
[0025] Expression (1) is an index to a color distribution in the
glass surface. In cases where the left side of the expression is 4
or less, this means that differences in the color distribution in
the glass surface are small, that is, the color tone variation is
narrow. Expression (1) is preferably 3 or less, more preferably 2
or less.
[0026] The .DELTA.a* in expression (1) can be determined by
selecting any two points within the glass surface of the cover
glass on the side where the antireflection film is present and
calculating the difference between measured two a* values for the
points. The .DELTA.b* can be calculated in the same manner. a* and
b* are luminous reflectances obtained from spectral reflectances
measured by examining, with a spectrophotometric colorimeter, the
surface of the substrate which has undergone an antiglare treatment
and an antireflection treatment (JIS Z 8729 (2004)).
[0027] Specifically, it is preferable that the .DELTA.a* and the
.DELTA.b* should be determined by selecting any square portion of
10 cm.sup.2 as a measuring range from the glass substrate, dividing
the measuring range into 11 x11 equal portions, examining all 100
intersections of equally dividing lines for a* values and b*
values, determining a maximum value a*.sub.max of the a* values, a
minimum value a*.sub.min of the a* values, a maximum value
b*.sub.max of the b* values, and a minimum value b*.sub.min of the
b* values, from the a* values and b* values, and taking the
difference (a*.sub.max-a*.sub.min) between the a*.sub.max and the
a*.sub.min as the .DELTA.a* and the difference
(b*.sub.max-b*.sub.min) between the b*.sub.max and the b*.sub.min
as the .DELTA.b*.
[0028] The shape of the measuring range is not limited to square,
so long as the measuring range has an area of 10 cm.sup.2. In the
case of a measuring range which is not square, 100 measuring points
may be suitably selected so that distributions of luminous
reflectances a* and b* in the measuring range can be
recognized.
[0029] The cover glass of the present invention can satisfy the
expression (1) because no leach-out layer is present on the glass
substrate. The term "leach-out" means a phenomenon in which when a
glass surface is treated with a strong acid or the like, cations
present in a surface layer part of the glass undergo an exchange
reaction with H.sup.+ ions of the acid and the surface layer part
of the glass thus comes to differ in composition from the bulk. The
extremely thin layer thus formed in the surface and having a
different composition is called a leach-out layer. Examples of
methods for avoiding the presence of a leach-out layer include a
method of removing the leach-out layer formed by an antiglare
treatment, a method of conducting an antiglare treatment which is
less apt to result in formation of a leach-out layer, and the
like.
[0030] The cover glass of the present invention has a degree of ion
exchange of desirably 25% or less, preferably 23% or less, more
preferably 20% or less, even more preferably 15% or less,
especially preferably 10% or less. The degree of ion exchange
thereof is preferably 1% or higher. The degree of ion exchange is
defined as a value obtained by dividing the content of cations of
any kind in the extremely thin surface region of the glass by the
content of cations of the same kind in the bulk part of the glass,
and is an index to the degree of deficiency of cations in the
glass.
[0031] Examples of the cation component include sodium, potassium,
and aluminum. The term "extremely thin surface region of the glass"
means a region ranging from the glass surface to 5 nm. The term
"bulk part" means a region extending inward from a depth of 30 nm
from the glass surface. In the case where the glass is soda-lime
glass, it is preferred to use sodium for the index. In the case of
aluminosilicate glass, it is preferred to use aluminum or potassium
for the index. In this application, aluminum was used for the index
in the case of aluminosilicate glass. So long as the degree of ion
exchange is within that range, the difference in refractive index
between the bulk part and the extremely thin surface region is
sufficiently negligible and deposition of an antireflection film
thereon exerts a negligible influence on the spectrum.
[0032] The glass composition of the extremely thin surface region
can be determined, for example, by X-ray photoelectron spectroscopy
(XPS). The glass composition of the bulk part can be determined,
for example, by XPS, X-ray fluorescence analysis (XRF), etc.
[0033] The thickness of the ion-exchange layer before the removal,
i.e., the leach-out layer, as measured from the outermost surface
of the glass substrate is preferably 10 nm or less, more preferably
8 nm or less, even more preferably 6 nm or less. It is also
preferable that the thickness of the ion-exchange layer before the
removal, i.e., the leach-out layer, should be larger than 1 nm. So
long as the thickness of the leach-out layer before the removal is
10 nm or less, not only this leach-out layer can be efficiently
removed, but also a suitable antiglare effect and even reflection
properties can be finally obtained. So long as the thickness of the
leach-out layer before the removal is larger than 1 nm, the minimum
necessary antiglare effect and even reflection properties can be
obtained. Such leach-out layer thicknesses are hence preferred.
<Glass Substrate>
[0034] As the glass substrate in the present invention, any of
glasses having various compositions can be utilized.
[0035] For example, it is preferable that the glass to be used in
the present invention should contain sodium and have a composition
which renders the glass formable and capable of being strengthened
by a chemical strengthening treatment. Specific examples thereof
include aluminosilicate glass, soda-lime glass, borosilicate glass,
lead glass, alkali-barium glasses, and aluminoborosilicate
glass.
[0036] The composition of the glass in the present invention is not
particularly limited, but examples thereof include the following
glass compositions.
(i) A glass including, in terms of % by mole, from 50% to 80% of
SiO.sub.2, from 2% to 25% of Al.sub.2O.sub.3, from 0% to 10% of
Li.sub.2O, from 0% to 18% of Na.sub.2O, from 0% to 10% of K.sub.2O,
from 0% to 15% of MgO, from 0% to 5% of CaO, and from 0% to 5% of
ZrO.sub.2 (ii) A glass which includes, in terms of % by mole, from
50% to 74% of SiO.sub.2, from 1% to 10% of Al.sub.2O.sub.3, from 6%
to 14% of Na.sub.2O, from 3% to 11% of K.sub.2O, from 2% to 15% of
MgO, from 0% to 6% of CaO, and from 0% to 5% of ZrO.sub.2, and in
which a total content of SiO.sub.2 and Al.sub.2O.sub.3 is 75% or
less, a total content of Na.sub.2O and K.sub.2O is 12% to 25%, and
a total content of MgO and CaO is 7% to 15% (iii) A glass
including, in terms of % by mole, from 68% to 80% of SiO.sub.2,
from 4% to 10% of Al.sub.2O.sub.3, from 5% to 15% of Na.sub.2O,
from 0% to 1% of K.sub.2O, from 4% to 15% of MgO, and from 0% to 1%
of ZrO.sub.2 (iv) A glass which includes, in terms of % by mole,
from 67% to 75% of SiO.sub.2, from 0% to 4% of Al.sub.2O.sub.3,
from 7% to 15% of Na.sub.2O, from 1% to 9% of K.sub.2O, from 6% to
14% of MgO, and from 0% to 1.5% of ZrO.sub.2 and in which a total
content of SiO.sub.2 and Al.sub.2O.sub.3 is 71% to 75%, a total
content of Na.sub.2O and K.sub.2O is 12% to 20%, and the content of
CaO, if it is contained, is less than 1%
[0037] Processes for producing the glass are not particularly
limited. The glass can be produced by introducing desired raw
materials for glass into a continuous melting furnace, heating and
melting the raw materials for glass preferably at 1,500.degree. C.
to 1,600.degree. C., clarifying the melt, feeding the clarified
melt to a forming device to form the molten glass into a plate
shape, and gradually cooling the formed glass.
[0038] Various methods can be employed for forming the glass.
Usable examples of various forming methods includes downdraw
processes (e.g., overflow downdraw process, slot-down process, and
redraw process), float process, rolling-out process, and
pressing.
[0039] The thickness of the glass is not particularly limited.
However, in the case of performing a chemical strengthening
treatment, the thickness of the glass is usually preferably 5 mm or
less, more preferably 3 mm or less, from the standpoint of
effectively conducting the treatment.
[0040] It is preferable that the glass substrate should have been
chemically strengthened from the standpoint of enhancing the
strength of the cover glass. The chemical strengthening is
conducted after an antiglare treatment and before the formation of
an antireflection film. A specific method therefor will be
described later in the section of process for production.
<Antiglare Treatment>
[0041] In the cover glass of the present invention, at least one of
the surfaces of the glass substrate has undergone an antiglare
treatment (referred to also as "AG treatment"). Methods for the
antiglare processing are not particularly limited, and usable
examples thereof include a method in which a main surface of the
glass is subjected to a surface treatment to form desired
irregularities.
[0042] Specifically, examples of the method include a method in
which a first main surface of the glass substrate is subjected to a
chemical treatment, e.g., a frosting treatment. The frosting
treatment can be conducted, for example, by immersing the glass
substrate, as an object to be treated, in a mixed solution of
hydrogen fluoride and ammonium fluoride to chemically treat the
surface immersed therein.
[0043] Usable examples of besides methods based on such a chemical
treatment include methods based on a physical treatment such as,
for example, the so-called sand blasting in which a crystalline
silicon dioxide powder, silicon carbide powder, or the like is
blown against the surface of the glass substrate by compressed air
or grinding with a brush equipped with bristles which have a
crystalline silicon dioxide powder, silicon carbide powder, or the
like adhered thereto and which have been moistened with water.
[0044] Especially in the method in which a frosting treatment is
given to chemically treat the glass substrate surface with a liquid
chemical such as, for example, hydrogen fluoride, microcracks are
less apt to be formed in the surface of the object being treated
and a decrease in mechanical strength is less apt to occur. This
method can hence be advantageously used as a method for treating
the glass substrate surface. That surface of the glass substrate on
which irregularities have been formed by the antiglare treatment
may have microcracks having a maximum depth of less than 3 .mu.m.
This is because microcracks of such a size are less apt to cause a
decrease in mechanical strength.
[0045] After irregularities are thus formed by a chemical surface
treatment (frosting treatment) or a physical surface treatment, the
glass surface is generally etched chemically in order to arrange
the surface shape. By this etching, the haze can be regulated to a
desired value in accordance with the etching amount and the cracks
formed by the sand blasting or the like can be eliminated.
Furthermore, glittering can be reduced.
[0046] Examples of preferred methods for the etching include a
method of immersing the glass substrate, as an object to be
treated, in a solution which includes hydrogen fluoride as a main
component. This solution may contain an acid such as hydrochloric
acid, nitric acid, or citric acid as a component other than
hydrogen fluoride. Due to the inclusion of the acid, cationic
components contained in the glass can be inhibited from reacting
with the hydrogen fluoride and thereby locally causing a
precipitation reaction, and the etching can hence be allowed to
proceed evenly throughout the surface.
[0047] With respect to the surface shape after the AG treatment,
the surface roughness (RMS) is preferably 0.01 .mu.m to 0.5 .mu.m,
more preferably 0.01 .mu.m to 0.3 .mu.m, even more preferably 0.01
.mu.m to 0.2 .mu.m.
[0048] The RMS can be determined in accordance with the method as
provided for in JIS B 0601 (2001). Specifically, a laser microscope
(trade name VK-9700, manufactured by Keyence Corp.) was used to
examine a measuring surface of a specimen with respect to a field
of view having an area set at 300 .mu.m.times.200 .mu.m to acquire
height information on the substrate, and a value of RMS was
determined by subjecting the acquired data to a cut-off correction
and calculating a root mean square of the heights obtained. When
conducting this measurement, it is preferred to use 0.08 mm as a
cut-off value. It is preferable that circular holes having a size
of 10 .mu.m or less should be observed in the specimen surface.
When the size of the circular holes is within such a range, it is
possible to attain both prevention of glittering and antiglare
properties.
[0049] It is thought that a leach-out layer is formed in this
etching step. In particular, it is thought that the presence of an
acid causes cationic components present in the glass surface to
selectively dissolve away and thereby renders a leach-out layer
prone to be formed in the glass surface. It is therefore preferable
that especially in the case where the process includes a step in
which etching is performed using a solution containing an acid, the
leach-out layer should be removed after the step as will be
described later.
<Antireflection Film>
[0050] The cover glass of the present invention has an
antireflection film disposed on the antiglare-treated surface of
the glass substrate by performing an antireflection film treatment
(referred to also as "AR treatment").
[0051] The material of the antireflection film is not particularly
limited, and any of various materials capable of inhibiting the
reflection of light can be utilized. For example, the
antireflection film may have a configuration composed of laminated
layers including a high-refractive-index layer and a
low-refractive-index layer. The high-refractive-index layer herein
is a layer having a refractive index at a wavelength of 550 nm of
1.9 or higher, while the low-refractive-index layer is a layer
having a refractive index at a wavelength of 550 nm of 1.6 or
less.
[0052] The antireflection film may include one
high-refractive-index layer and one low-refractive-index layer, or
may have a configuration including two or more
high-refractive-index layers and two or more low-refractive-index
layers. In the case where the antireflection film includes two or
more high-refractive-index layers and two or more
low-refractive-index layers, it is preferable that this
antireflection film should be one in which the
high-refractive-index layers and the low-refractive-index layers
have been alternately laminated.
[0053] Especially from the standpoint of enhancing the
antireflection performance, it is preferable that the
antireflection film should be a laminate formed by laminating a
plurality of layers. For example, the laminate is preferably
composed of two to six laminated layers in total, and more
preferably is composed of two to four laminated layers in total.
This laminate is preferably a laminate composed of laminated layers
including one or more high-refractive-index layers and one or more
low-refractive-index layers as described above, and it is
preferable that the total number of the high-refractive-index
layers and the low-refractive-index layers should be within that
range.
[0054] The materials of each high-refractive-index layer and each
low-refractive-index layer are not particularly limited, and can be
selected while taking account of the required degree of reflection
prevention, production efficiency, etc. As the material which
constitutes the high-refractive-index layer, a material containing
one or more elements selected from niobium, titanium, zirconium,
tantalum, and silicon can, for example, be advantageously utilized.
Specific examples thereof include niobium oxide (Nb.sub.2O.sub.5),
titanium oxide (TiO.sub.2), zirconium oxide (ZrO.sub.2), tantalum
oxide (Ta.sub.2O.sub.5), and silicon nitride. As the material which
constitutes the low-refractive-index layer, a material containing
silicon can, for example, be advantageously utilized. Specific
examples thereof include silicon oxide (SiO.sub.2), a material
including a mixed oxide of Si and Sn, a material including a mixed
oxide of Si and Zr, and a material including a mixed oxide of Si
and Al.
[0055] From the standpoints of production efficiency and the degree
of refractive index, it is more preferable that the
high-refractive-index layer should be a layer selected from a
niobium-containing layer and a tantalum-containing layer, and the
low-refractive-index layer should be a silicon-containing layer,
and it is even more preferable that the high-refractive-index layer
should be constituted of a niobium-containing layer. Namely, it is
preferable that the antireflection film should be a laminate
including one or more niobium-containing layers and one or more
silicon-containing layers.
[0056] In the cover glass of the present invention, the antiglare
treatment and the formation of an antireflection film on at least
one of the main surfaces of the glass substrate suffice. However,
the cover glass may have a configuration in which antiglare
irregularities and an antireflection film are disposed on each of
both main surfaces of the glass substrate as needed.
[0057] Methods for forming the antireflection film will be
described in detail in the section of process for production.
<Antifouling Film>
[0058] The cover glass of the present invention may have an
antifouling film (referred to also as "anti finger print (AFP)
film") on the antireflection film, from the standpoint of
protecting the glass surface. The antifouling film can be
constituted, for example, of a fluorine-containing organosilicon
compound. Fluorine-containing organosilicon compounds which impart
antifouling properties, water repellency, and oil repellency can be
used without particular limitations. Examples thereof include
fluorine-containing organosilicon compounds having one or more
groups selected from the group consisting of polyfluoropolyether
groups, polyfluoroalkylene groups, and polyfluoroalkyl groups. The
term "polyfluoropolyether group" means a divalent group having a
structure in which a polyfluoroalkylene group and an etheric oxygen
atom have been alternately bonded.
[0059] Specific examples of the fluorine-containing organosilicon
compounds having one or more groups selected from the group
consisting of polyfluoropolyether groups, polyfluoroalkylene
groups, and polyfluoroalkyl groups include compounds represented by
the following general formulae (I) to (V).
##STR00001##
[0060] In the formula, Rf is a linear polyfluoroalkyl group having
1 to 16 carbon atoms (examples of the alkyl group include methyl,
ethyl, n-propyl, isopropyl, and n-butyl); X is a hydrogen atom or a
lower alkyl group having 1 to 5 carbon atoms (e.g., methyl, ethyl,
n-propyl, isopropyl, n-butyl, etc.); R1 is a hydrolyzable group
(e.g., amino, an alkoxy, etc.) or a halogen atom (e.g., fluorine,
chlorine, bromine, iodine, etc.); m is an integer of 1 to 50,
preferably 1 to 30; n is an integer of 0 to 2, preferably 1 or 2;
and p is an integer of 1 to 10, preferably 1 to 8.
C.sub.qF.sub.2q+1CH.sub.2CH.sub.2Si(NH.sub.2).sub.3 (II)
[0061] In the formula, q is an integer of 1 or larger, preferably 2
to 20.
[0062] Examples of the compounds represented by general formula
(II) include n-trifluoro(1,1,2,2-tetrahydro)propylsilazane
(n-CF.sub.3CH.sub.2CH.sub.2Si(NH.sub.2).sub.3) and
n-heptafluoro(1,1,2,2-tetrahydro)pentylsilazane
(n-C.sub.3F.sub.7CH.sub.2CH.sub.2Si(NH.sub.2).sub.3).
C.sub.q'F.sub.2q'+1CH.sub.2CH.sub.2Si(OCH.sub.3).sub.3 (III)
[0063] In the formula, q' is an integer of 1 or larger, preferably
1 to 20.
[0064] Examples of the compounds represented by general formula
(III) include 2-(perfluorooctyl)ethyltrimethoxysilane
(n-C.sub.8F.sub.17CH.sub.2CH.sub.2Si(OCH.sub.3).sub.3).
##STR00002##
[0065] In the formula (IV), R.sup.f2 is a divalent linear
polyfluoropolyether group represented by
--(OC.sub.3F.sub.6).sub.s--(OC.sub.2F.sub.4).sub.t--(OCF.sub.2).sub.u--
(s, t, and u are each independently an integer of 0 to 200), and
R.sup.2 and R.sup.3 are each independently a monovalent hydrocarbon
group having 1 to 8 carbon atoms (e.g., methyl, ethyl, n-propyl,
isopropyl, n-butyl, etc.). X.sub.2 and X.sub.3 are each
independently a hydrolyzable group (e.g., an amino, alkoxy,
acyloxy, alkenyloxy, or isocyanate group, etc.) or a halogen atom
(e.g., a fluorine, chlorine, bromine, or iodine atom, etc.); d and
e are each independently an integer of 1 or 2; c and f are each
independently an integer of 1 to 5 (preferably 1 or 2); and a and b
are each independently 2 or 3.
[0066] In R.sup.f2 possessed by compound (IV), s+t+u is preferably
20 to 300, more preferably 25 to 100. It is more preferable that
R.sup.2 and R.sup.3 should be methyl, ethyl, or butyl. The
hydrolyzable groups represented by X.sup.2 and X.sup.3 are more
preferably alkoxy groups having 1 to 6 carbon atoms, and especially
preferably methoxy or ethoxy. Furthermore, it is preferable that a
and b each should be 3.
[Chem. 3]
F--(CF.sub.2).sub.v--(OC.sub.3F.sub.6).sub.w--(OC.sub.2F.sub.4).sub.y--(-
OCF.sub.2).sub.z(CH.sub.2).sub.i--Si(X.sup.4).sub.3-k(R.sup.4).sub.k
(V)
[0067] In the formula (V), v is an integer of 1 to 3; w, y, and z
are each independently an integer of 0 to 200; h is 1 or 2; i is an
integer of 2 to 20; X.sup.4 is a hydrolyzable group; R.sup.4 is a
linear or branched hydrocarbon group having 1 to 22 carbon atoms;
and k is an integer of 0 to 2. The value of w+y+z is preferably 20
to 300, more preferably 25 to 100. It is more preferable that i
should be 2 to 10. X.sup.4 is preferably an alkoxy group having 1
to 6 carbon atoms, more preferably methoxy or ethoxy. R.sup.4 is
more preferably an alkyl group having 1 to 10 carbon atoms.
[0068] Commercial products of the fluorine-containing organosilicon
compounds having one or more groups selected from the group
consisting of polyfluoropolyether groups, polyfluoroalkylene
groups, and polyfluoroalkyl groups include KP-801 (trade name;
manufactured by Shin-Etsu Chemical Co., Ltd.), KY178 (trade name;
manufactured by Shin-Etsu Chemical Co., Ltd.), KY-130 (trade name;
manufactured by Shin-Etsu Chemical Co., Ltd.), KY-185 (trade name;
manufactured by Shin-Etsu Chemical Co., Ltd.), and Optool
(registered trademark) DSX and Optool AES (both being trade names;
manufactured by Daikin Industries, Ltd.). These commercial products
can be advantageously used.
[0069] The antifouling film is laminated on the antireflection
film. In the case where an antireflection film has been deposited
on each of both main surfaces of the glass substrate, the
antifouling film can be formed on each of both antireflection
films. However, a configuration in which the antifouling film is
laminated on only either of the two antireflection films may be
used. This is because the formation of an antifouling film at least
on the portion where contact with human fingers, etc. is possible
suffices. The formation can be selected in accordance with the
intended use, etc.
<Contact Angle>
[0070] It is preferable that the cover glass of the present
invention should have a contact angle of water of 90.degree. or
larger. Thus, the cover glass surface has water repellency and oil
repellency, and this cover glass is less apt to suffer adhesion of
fouling substances thereto. Examples of means for regulating the
contact angle thereof to 90.degree. or larger include disposing the
antifouling film.
<Haze>
[0071] The haze of the cover glass of the present invention is
preferably 1% to 35%, more preferably 2% to 35%, even more
preferably 2% to 25%. So long as the haze is within that range, a
cover glass which has the desired antiglare properties and, despite
this, exerts little influence on the resolution of the display
object can be obtained. The haze is provided for in JIS K 7136.
[0072] The haze can be controlled by regulating the etching period
in the AG treatment.
<Reflectance>
[0073] It is preferable that the cover glass of the present
invention should have a luminous reflectance of 2% or less. So long
as the luminous reflectance thereof is within that range,
reflection in the cover glass surface can be sufficiently
prevented. The luminous reflectance is provided for in JIS Z8701.
As the illuminant, illuminant D65 was used.
<Process for Production of the Cover Glass>
[0074] The cover glass of the present invention can be produced,
for example, by the following steps, but usable production
processes are not limited thereto. Step 1, antiglare treatment;
step 2, chemical strengthening; step 3, leach-out layer removal;
step 4, antireflection film formation; step 5, antifouling film
formation.
[0075] The chemical strengthening as step 2, the leach-out layer
removal as step 3, and the antifouling film formation as step 5
each can be conducted according to need. A printing treatment can
also be performed according to need.
[0076] It is preferable that the chemical strengthening treatment
as step 2 should be conducted between the antiglare treatment as
step 1 and the antireflection film formation as step 4. The
chemical strengthening as step 2 and the leach-out layer removal as
step 3 may be conducted in the reverse order. However, from the
standpoint of minimizing substances adherent to the glass substrate
which is to be subjected to the antireflection film formation, it
is preferred to conduct the leach-out layer removal just before the
antireflection film formation.
[0077] The printing treatment is a treatment in which, when the
cover glass is required to be decorated, a pattern according to
intended uses or applications, as in, for example, frame printing
or logo printing, is printed in suitably selected color(s).
Although any of known printing methods is applicable, screen
printing, for example, is suitable.
[0078] It is preferable that the printing treatment should be
conducted between the antiglare treatment as step 1 and the
antireflection film formation as step 4 and after the leach-out
layer removal as step 3, in order to prevent the printed portion
from being affected by the etching or other treatment for the
leach-out layer removal.
[0079] In the case where a chemical strengthening treatment and a
printing treatment are both performed, it is preferred to conduct
the chemical strengthening treatment, leach-out layer removal, and
printing treatment in this order.
[0080] It is preferable that the antifouling film formation should
be conducted after the final step, that is, after the
antireflection film formation, because the antifouling film is a
film formed in order to protect the glass surface.
[0081] In FIG. 1A to FIG. 1D show a flowchart of steps which shows
one embodiment of the production process in the present invention.
Of the main surfaces 10a and 10b of a glass substrate 10, the main
surface 10a is subjected to an antiglare treatment (FIG. 1A). The
glass surface 10a which has undergone the antiglare treatment not
only has irregularities formed therein (not shown) but also is in
such a state that cations contained in the glass have been replaced
with ions contained in the acid, thereby forming a leach-out layer
10R in a surface layer part (FIG. 1B). This leach-out layer 10R is
removed by at least one method selected from between etching and
grinding (FIG. 1C). This treatment for removing the leach-out layer
does not result in elimination of the irregularities formed by the
antiglare treatment. An antireflection film 20 is further formed on
the glass main surface 10a from which the leach-out layer has been
removed (FIG. 1D).
[0082] In FIG. 2A to FIG. 2F shows a flowchart of steps which shows
another embodiment of the production process in the present
invention. An antiglare treatment is given to a main surface 10a of
a glass substrate 10, and the glass surface 10a which has undergone
the antiglare treatment has irregularities formed therein (not
shown) and has a leach-out layer 10R formed therein (FIG. 2A and
FIG. 2B). Subsequently, this glass substrate is chemically
strengthened to thereby form a compressive stress layer 10E as a
surface layer in the glass substrate (FIG. 2C). The compressive
stress layer 10E is formed to an extent of a larger depth than the
leach-out layer 10R. Thereafter, the leach-out layer 10R is removed
(FIG. 2D), and an antireflection film 20 is formed on the surface
which has undergone the antiglare treatment (FIG. 2E). Furthermore,
an antifouling film 30 is formed on the antireflection film 20
(FIG. 2F).
[0083] Each step is explained below.
<Step 1: Antiglare Treatment>
[0084] A specific method for antiglare treatment is as described
above in detail in the explanation of the cover glass. Namely, at
least one of the surfaces of a glass substrate is subjected to a
chemical surface treatment or a physical surface treatment to
thereby form irregularities and then etched with either a hydrogen
fluoride solution or a solution containing both hydrogen fluoride
and an acid, thereby performing an antiglare treatment.
[0085] It is preferable that shaping according to applications,
e.g., machining such as cutting, edge surface machining, and
drilling, should be performed before the glass substrate is
subjected to the chemical strengthening described below.
<Step 2: Chemical Strengthening>
[0086] For the chemical strengthening, conventional methods can be
utilized. For example, chemical strengthening by so-called ion
exchange is possible, in which metal ions having a small ionic
radius (e.g., Na ions) contained in the glass are replaced by metal
ions having a larger ionic radius (e.g., K ions) to thereby yield a
compressive stress layer in the glass surface and thus improve the
strength of the glass.
[0087] Specifically, the glass substrate which has undergone the
antiglare treatment is immersed in one or more molten salts to form
a compressive stress layer in the surfaces of the glass. Examples
of the molten salts include inorganic potassium slats. The
inorganic potassium salts preferably are ones which are in a molten
state at temperatures not higher than the strain point (usually
500.degree. C. to 600.degree. C.) of the glass to be chemically
strengthened. For example, it is preferable that the molten salts
should include potassium nitrate (melting point, 330.degree. C.).
Inorganic potassium salts other than potassium nitrate may be
contained as molten slats. Examples thereof include combinations
with one or more salts selected from alkali sulfates and alkali
chlorides, such as potassium sulfate and potassium chloride, and
potassium carbonate and the like.
[0088] The temperature at which the glass is preheated depends on
the temperature at which the chemical strengthening treatment is to
be conducted (temperature of the slat bath). However, the
preheating temperature is generally preferably 100.degree. C. or
higher.
[0089] It is preferable that the temperature for the chemical
strengthening treatment of the glass should be not higher than the
strain point (usually 500.degree. C. to 600.degree. C.) of the
glass to be strengthened. From the standpoint of obtaining a larger
compressive-stress depth (depth of layer; DOL), the chemical
strengthening temperature is preferably 350.degree. C. or
higher.
[0090] The immersion period during which the glass is immersed in
the molten salts is preferably 10 minutes to 12 hours, more
preferably 30 minutes to 10 hours. So long as the immersion period
is within that range, a chemically strengthened glass having an
excellent balance between strength and the depth of the compressive
stress layer can be obtained.
[0091] As a chemical-strengthening tank for conducting the chemical
strengthening treatment therein, metals, quartz, ceramics, and the
like can be used. Of these, metallic materials are preferred from
the standpoint of durability. From the standpoint of corrosion
resistance, stainless steel (SUS) materials are preferred.
<Step 3: Leach-Out Layer Removal>
[0092] In the case where the antiglare treatment has resulted in
the formation of a leach-out layer on the glass surface, this
leach-out layer is removed. Specifically, examples of methods
therefor include a chemical method in which the glass surface is,
for example, etched with a liquid chemical and a physical method in
which the glass surface is, for example, ground with an abrasive
material.
[0093] Examples of methods for the etching include a method in
which the glass substrate is subjected to an acid treatment, a
method in which the glass substrate is subjected to an alkali
treatment, or a method in which the glass substrate is subjected to
an acid treatment and then an alkali treatment.
[0094] The acid treatment is conducted by immersing the glass
substrate in an acidic solution.
[0095] The acidic solution is not particularly limited so long as
the pH thereof is lower than 7, and either a weak acid or a strong
acid may be used. Specifically, preferred acids are hydrofluoric
acid, hydrochloric acid, nitric acid, sulfuric acid, phosphoric
acid, acetic acid, oxalic acid, carbonic acid, citric acid, and the
like. These acids may be used alone or in combination of two or
more thereof. It is preferable that the acid treatment should be
conducted at a temperature of 100.degree. C. or lower, although the
temperature varies depending on the kind and concentration of the
acid used and on the period.
[0096] The period of the acid treatment varies depending on the
kind and concentration of the acid used and on the temperature.
However, the period thereof is preferably 10 seconds to 5 hours
from the standpoint of production efficiency, and is more
preferably 1 minute to 2 hours.
[0097] The concentration of the solution with which the acid
treatment is performed varies depending on the kind of the acid
used, period, and temperature, but preferably is such a
concentration that there is no possibility of corroding the vessel.
Specifically, concentrations of 1 wt % to 20 wt % are
preferred.
[0098] In the acid treatment step, the leach-out described above
also occurs simultaneously. A relationship with etching rate is
hence important. Specifically, it is preferred to use concentration
and temperature conditions under which the etching rate is at least
1.5 times the rate of leach-out layer formation. The etching rate
is more preferably at least 2 times, even more preferably at least
2.5 times, the rate of leach-out layer formation.
[0099] The alkali treatment is conducted by immersing the glass
substrate in an alkaline solution.
[0100] The alkaline solution is not particularly limited so long as
the pH thereof exceeds 7, and either a weak base or a strong base
may be used. Specifically, preferred bases are sodium hydroxide,
potassium hydroxide, potassium carbonate, sodium carbonate, and the
like. These bases may be used alone or in combination of two or
more thereof.
[0101] The temperature at which the alkali treatment is to be
conducted varies depending on the kind and concentration of the
base used and on the period, but is preferably 0.degree. C. to
100.degree. C., more preferably 10.degree. C. to 80.degree. C.,
especially preferably 20.degree. C. to 60.degree. C. Such
temperature range is preferred since there is no possibility of
corroding the glass.
[0102] The period of the alkali treatment varies depending on the
kind and concentration of the base used and on the temperature.
However, the period thereof is preferably 10 seconds to 20 hours
from the standpoint of production efficiency, and is more
preferably 1 minute to 12 hours, even more preferably 10 minutes to
5 hours.
[0103] The concentration of the solution with which the alkali
treatment is performed varies depending on the kind of the base
used, period, and temperature, but preferably is 1 wt % to 20 wt %
from the standpoint of glass surface removal.
[0104] In the case where an alkali treatment is conducted after an
acid treatment, the glass substrate which has undergone the acid
treatment described above is successively subjected to an alkali
treatment. The acid treatment and the alkali treatment may be
conducted under the same conditions as shown above.
[0105] Although any of the methods described above may be selected
as the chemical removal method, the method in which an alkali
treatment is conducted after an acid treatment is preferred from
the standpoint of ease of removal of the leach-out layer.
[0106] Examples of methods for grinding with an abrasive material
include a method in which a grinding fluid containing an abrasive
material selected from calcium carbonate, cerium oxide, colloidal
silica, and the like is used to grind the surface of the glass
substrate.
[0107] When the leach-out layer is removed by the chemical removal
method, it is preferred to remove a glass substrate surface layer
down to a depth of 3 nm or larger, preferably 5 nm or larger, more
preferably 10 nm or larger. In the case of the physical removal
method, it is preferred to remove a glass substrate surface layer
down to a depth of 5 nm or larger, preferably 10 nm or larger, more
preferably 30 nm or larger. So long as a surface layer is removed
in such amount, the leach-out layer can be sufficiently removed.
However, from the standpoint that the surface shape formed by the
antiglare treatment is kept substantially unchanged, a preferred
upper limit of removal amount is 2 .mu.m.
[0108] Either the chemical removal method or the physical removal
method may be selected. However, the chemical removal method is
preferred because the chemical removal method does not form cracks
or the like in the glass surface and is free from the possibility
that an abrasive material residue might foul the glass surface. The
chemical removal method and the physical removal method may be
conducted in combination.
<Step 4: Antireflection Film Formation>
[0109] Methods for depositing an antireflection film are not
particularly limited, and any of various deposition methods can be
utilized. It is especially preferred to deposit the film by a
method such as pulse sputtering, AC sputtering, digital sputtering,
or the like. By these methods, a dense antireflection film can be
formed and durability can be ensured.
[0110] When the deposition is conducted, for example, by pulse
sputtering, an antireflection film can be deposited on the glass
substrate by disposing the glass substrate in a chamber filled with
a mixed gas atmosphere constituted of a mixture of an inert gas and
oxygen gas and by using targets suitably selected so as to result
in desired compositions.
[0111] In this step, the kind of the inert gas in the chamber is
not particularly limited, and any of various inert gases including
argon and helium can be used.
[0112] The pressure of the inert gas/oxygen mixed gas in the
chamber is not particularly limited. However, it is preferred to
regulate the pressure thereof so as to be 0.5 Pa or lower, since
such a pressure makes it easy to yield an antireflection film
having surface roughness within a preferred range. The reason for
this is thought to be as follows. In cases where the pressure of
the inert gas/oxygen mixed gas in the chamber is 0.5 Pa or lower,
an average free path of film-forming molecules is ensured and the
film-forming molecules carrying a larger amount of energy arrive at
the substrate. Because of this, rearrangement of film-forming
molecules is accelerated and a relatively dense film having a
smooth surface is formed. There is no particular lower limit on the
pressure of the inert gas/oxygen mixed gas within the chamber, but
the pressure thereof is, for example, preferably 0.1 Pa or
higher.
[0113] A preferred range of the surface roughness of the
antireflection film is approximately the same as the preferred
range for the surface shape obtained through the antiglare
treatment. This is because the thickness of the antireflection film
itself is as small as 100 nm to 300 nm at the most and, hence, the
size of the irregularities of the antireflection film itself is so
small as compared with the size of the irregularities formed by the
antiglare treatment, which are present beneath the antireflection
film layer, that the size thereof is negligible. Consequently, it
can be thought that the surface roughness of the antireflection
film on the substrate which has undergone the antiglare treatment
is determined substantially by the surface roughness of the
substrate which has undergone the antiglare treatment.
<Step 5: Antifouling Film Formation>
[0114] Methods for depositing an antifouling film in this
embodiment are not particularly limited. However, it is preferred
to deposit the film by vacuum deposition using any of the
fluorine-containing organosilicon compound materials mentioned
above.
[0115] In general, fluorine-containing organosilicon compounds are
stored in the form of a mixture with a solvent, such as a
fluorochemical solvent, for the purpose of, for example, inhibiting
the deterioration due to reaction with atmospheric moisture.
However, in cases where a fluorine-containing organosilicon
compound in the state of containing the solvent is subjected to a
deposition step, this organosilicon compound may adversely affect
the durability and other properties of the thin film obtained
therefrom.
[0116] It is therefore preferable that either a fluorine-containing
organosilicon compound which has undergone a solvent removal
treatment before being heated in a heating vessel or a
fluorine-containing organosilicon compound which has not been
diluted with a solvent (i.e., which contains no solvent added
thereto) should be used in this embodiment. For example, it is
preferred to use a fluorine-containing organosilicon compound
solution having a solvent concentration of preferably 1 mol % or
less, more preferably 0.2 mol % or less. It is especially preferred
to use a fluorine-containing organosilicon compound containing no
solvent.
[0117] Examples of the solvents usable for storing the
fluorine-containing organosilicon compound include perfluorohexane,
m-xylene hexafluoride (C.sub.6H.sub.4(CF.sub.3).sub.2),
hydrofluoropolyethers, and HFE 7200/7100 (trade names; manufactured
by Sumitomo 3M Ltd.; HFE 7200 is represented by
C.sub.4F.sub.9C.sub.2H.sub.5 and HFE 7100 is represented by
C.sub.4F.sub.9OCH.sub.3).
[0118] A treatment for removing the solvent from a solution of a
fluorine-containing organosilicon compound in a fluorochemical
solvent can be accomplished, for example, by evacuating a vessel
which contains the solution of a fluorine-containing organosilicon
compound.
[0119] The period during which the evacuation is conducted varies
depending on the evacuation ability of the evacuation line, vacuum
pump, etc., the amount of the solution, etc., and is hence not
limited. However, the period thereof may be, for example, about 10
hours or longer.
[0120] A treatment for removing the solvent can also be conducted
after the solution of a fluorine-containing organosilicon compound
is introduced into the heating vessel of a deposition device for
antifouling film deposition, by evacuating the heating vessel at
room temperature before the heating vessel is heated. It is also
possible to remove the solvent beforehand with an evaporator or the
like before introduction into the heating vessel.
[0121] It is, however, noted that fluorine-containing organosilicon
compounds having a low solvent content or containing no solvent are
prone to be deteriorated by contact with the air as compared with
ones containing a solvent, as stated above.
[0122] It is therefore preferable that the atmosphere inside the
storage container in which the fluorine-containing organosilicon
compound having a low solvent content (or containing no solvent) is
stored should be replaced with an inert gas, e.g., nitrogen, before
the container is closed. When this fluorine-containing
organosilicon compound is used and handled, it is preferred to
minimize the time period during which the compound is exposed to or
in contact with the air.
[0123] Specifically, it is preferable that after the storage
container is opened, the fluorine-containing organosilicon compound
should be immediately introduced into the heating vessel of the
deposition device for antifouling film deposition. It is preferable
that after the introduction, the inside of the heating vessel
should be made vacuum or replaced with an inert gas, e.g., nitrogen
or a rare gas, thereby removing the atmosphere (air) contained in
the heating vessel. It is more preferable that the storage
container and the heating vessel of the production device should
have been connected to each other by a valved pipeline so that the
compound can be introduced from the storage container into the
heating vessel without coming into with the air.
[0124] It is preferable that after the fluorine-containing silicon
compound is introduced into the heating vessel and the inside of
the heating vessel is thereafter made vacuum or replaced with an
inert gas, heating for deposition should be initiated
immediately.
[0125] In the method for antifouling film deposition described
above as an example in the explanation of this embodiment, a
fluorine-containing organosilicon compound in a solution state or
an undiluted state is used. However, methods for antifouling film
deposition are not limited thereto. Examples of the other methods
include, for example, a method in which use is made of commercial
vapor-deposition pellets obtained by impregnating beforehand a
porous metal (e.g., tin or copper) or a fibrous metal (e.g.,
stainless steel) with a certain amount of a fluorine-containing
organosilicon compound (an example of the pellets being Surfclear,
manufactured by Canon Optron Inc.). In this case, an antifouling
film can be easily deposited using, as a deposition source, the
pellets in an amount according to the capacity of the deposition
device and the necessary film thickness.
[0126] By the production process described above, the cover glass
of the present invention can be produced.
EXAMPLES
[0127] The present invention is explained below in detail by
reference to Examples, but the present invention should not be
construed as being limited to the following Examples.
Example 1
[0128] A cover glass was produced in the following manner.
[0129] As a glass substrate was used DRAGONTRAIL (registered
trademark), manufactured by Asahi Glass Co., Ltd.
(1) One of the surfaces of the glass substrate was subjected to an
antiglare treatment by frosting treatment in the following
manner.
[0130] First, an acid-resistant protective film (hereinafter also
referred to simply as "protective film") was applied to that
surface of the substrate which was not subjected to the antiglare
treatment. Subsequently, this substrate was immersed in a 3% by
weight solution of hydrogen fluoride for 3 minutes to etch the
substrate and thereby remove fouling substances adherent to the
surface. The substrate was then immersed for 3 minutes in a mixed
solution of 15% by weight hydrogen fluoride and 15% by weight
potassium fluoride to conduct a frosting treatment of the surface.
Finally, the substrate was immersed in a 10% solution of hydrogen
fluoride for 6 minutes to thereby regulate the haze value to 25%.
In the present invention, this time period during which the
substrate is finally immersed in the hydrogen fluoride solution to
regulate the haze value is referred to as etching period.
(2) Next, a chemical strengthening treatment was conducted in the
following manner.
[0131] The substrate from which the protective film had been
removed was immersed for 2 hours in potassium nitrate kept in a
molten state by heating at 450.degree. C. Thereafter, the substrate
was pulled out of the molten salt and gradually cooled to room
temperature over 1 hour, thereby obtaining a chemically
strengthened substrate.
(3) This substrate was subsequently immersed in an alkali solution
(SUN WASH TL-75, manufactured by Lion Corp.) for 4 hours to remove
a leach-out layer present in the surfaces. The amount of the
leach-out layer removed was calculated from the glass weights
respectively measured before and after the treatment for leach-out
layer removal and from the surface area and density of the glass.
(4) Next, an antireflection film was deposited on the surface which
had undergone the antiglare treatment, in the following manner.
[0132] First, in a vacuum chamber, pulse sputtering was conducted
using a niobium oxide target (trade name, NBO Target; manufactured
by AGC Ceramics Co., Ltd.) under the conditions of a pressure of
0.3 Pa, frequency of 20 kHz, power density of 3.8 W/cm.sup.2, and
inversion pulse width of 5 .mu.sec, while introducing thereinto a
mixed gas obtained by mixing argon gas with 10% by volume oxygen
gas, thereby forming a high-refractive-index layer made of niobium
oxide (niobia) and having a thickness of 13 nm on that surface of
the glass substrate which had undergone the antiglare
treatment.
[0133] Subsequently, pulse sputtering was conducted using a silicon
target under the conditions of a pressure of 0.3 Pa, frequency of
20 kHz, power density of 3.8 W/cm.sup.2, and inversion pulse width
of 5 .mu.sec, while introducing a mixed gas obtained by mixing
argon gas with 40% by volume oxygen gas, thereby forming a
low-refractive-index layer made of silicon oxide (silica) and
having a thickness of 35 nm on the high-refractive-index layer.
[0134] Next, pulse sputtering was conducted using a niobium oxide
target (trade name, NBO Target; manufactured by AGC Ceramics Co.,
Ltd.) under the conditions of a pressure of 0.3 Pa, frequency of 20
kHz, power density of 3.8 W/cm.sup.2, and inversion pulse width of
5 .mu.sec, while introducing a mixed gas obtained by mixing argon
gas with 10% by volume oxygen gas, thereby forming a
high-refractive-index layer made of niobium oxide (niobia) and
having a thickness of 115 nm on the low-refractive-index layer.
[0135] Subsequently, pulse sputtering was conducted using a silicon
target under the conditions of a pressure of 0.3 Pa, frequency of
20 kHz, power density of 3.8 W/cm.sup.2, and inversion pulse width
of 5 .mu.sec, while introducing a mixed gas obtained by mixing
argon gas with 40% by volume oxygen gas, thereby forming a
low-refractive-index layer made of silicon oxide (silica) and
having a thickness of 80 nm.
[0136] Thus, an antireflection film composed of a total of four
laminated layers of niobium oxide (niobia) and silicon oxide
(silica) was formed.
<Evaluation of the Glass>
(Luminous Reflectance)
[0137] The spectral reflectance of that surface of the glass
substrate which was on the side where the antiglare treatment and
the antireflection treatment had been performed was measured with a
spectrophotometric colorimeter (Type CM-2600d, manufactured by
Konica Minolta) in the SCI mode, and a luminous reflectance (value
of reflective stimulus Y as provided for in JIS Z8701) was
determined from the value of spectral reflectance. The back surface
of the glass to be subjected to this measurement was painted in
black in order to eliminate reflection from the back surface, which
had undergone neither the antiglare treatment nor the
antireflection treatment. The illuminant was regarded as illuminant
D65 when calculating the reflectance.
(Degree of Ion Exchange)
[0138] An X-ray photoelectron spectrometer (Type JPS-9200,
manufactured by JEOL Ltd.) was used to determine the degree of ion
exchange of the glass surface using aluminum as an index. With this
apparatus, the proportion of ions present can be examined along the
depth direction. First, the proportion of ions present at a
sufficiently large depth from the surface is calculated as a
reference. In this measurement, the proportion (A) of ions present
at a depth of 30 nm was taken as a reference. The proportion of
aluminum ions present at a depth of 5 nm was expressed by (B), and
the degree of ion exchange p was determined using the following
equation.
.rho.=B/A
(Color Distribution)
[0139] First, any 10 cm.sup.2-square portion within the glass
substrate was selected as a measuring range, and this measuring
range was divided into 11.times.11 equal portions. The 100
intersections in the resultant lattice pattern on the substrate
were examined for color in the following manner.
[0140] The spectral reflectance of that surface of the substrate
which was on the side where the antireflection treatment had been
performed was measured with a spectrophotometric colorimeter (Type
CM-2600d, manufactured by Konica Minolta) in the SCI mode, and a
luminous reflectance (color indexes a* and b* as provided for in
JIS Z8729) was determined form the value of spectral reflectance.
The back surface of the glass to be subjected to this measurement
was painted in black in order to eliminate reflection from the back
surface, which had undergone neither the antiglare treatment nor
the antireflection treatment.
[0141] From the maximum values and minimum values of a* and b*
(a*.sub.max, a*.sub.min, b*.sub.max, and b*.sub.min) among the
measured values for all the 100 points, the color distribution E
was determined using the following calculation formula (1-1).
E= {(a*.sub.max-a*.sub.min).sup.2+(b*.sub.max-b*.sub.min).sub.2}
(1-1)
[0142] Subsequently, the measuring range was changed, and the same
measurement as described above was repeatedly made three times in
total. With respect to each measurement, the value of E was
determined.
(Contact Angle with Water)
[0143] An about 1-.mu.L droplet of pure water was placed on that
surface of the glass substrate which was on the side where the
antiglare treatment and antireflection treatment had been
performed. Using a contact angle meter (device name, DM-51;
manufactured by Kyowa Interface Science Co., Ltd.), the contact
angle of water was measured.
Example 2
[0144] A cover glass was produced in the same manner as in Example
1, except that the period of immersion in the alkali solution in
the leach-out layer removal step (3) in Example 1 was changed to 8
hours and that the following antifouling film formation in Example
1 was conducted as step (5). (5) An antifouling film was deposited
on the antireflection film in the following manner.
[0145] First, an antifouling-film material (trade name, KY-185;
manufactured by Shin-Etsu Chemical Co., Ltd.) was introduced into a
heating vessel. Thereafter, the heating vessel was evacuated over
10 hours or longer with a vacuum pump to remove the solvent
contained in the solution, thereby obtaining a composition for
forming fluorine-containing organosilicon compound coating
film.
[0146] Subsequently, the heating vessel which contained the
composition for forming fluorine-containing organosilicon compound
film was heated to 270.degree. C. After the temperature of the
heating vessel had reached 270.degree. C., the heated state was
maintained for 10 minutes until the temperature became stable.
[0147] The composition for forming fluorine-containing
organosilicon compound film was fed, through a nozzle connected to
the heating vessel which contained the composition for forming
fluorine-containing organosilicon compound film, to the
antireflection film laminated on the transparent substrate disposed
in a vacuum chamber, thereby performing deposition.
[0148] The deposition was conducted while measuring the film
thickness with a quartz oscillator monitor disposed in the vacuum
chamber, until the thickness of the fluorine-containing
organosilicon compound film formed over the transparent substrate
reached 4 nm.
[0149] At the time when the thickness of the fluorine-containing
organosilicon compound film had reached 4 nm, the feeding of the
starting material through the nozzle was stopped. Thereafter, the
optical part produced was taken out of the vacuum chamber.
[0150] The optical part taken out was placed on a hot plate so that
the film surface faced upward, and was thus heat-treated at
150.degree. C. for 60 minutes in the air.
Example 3
[0151] A cover glass was produced in the same manner as in Example
1, except that the etching treatment period in the antiglare
treatment step (1) in Example 1 was changed to 20 minutes to
thereby regulate the haze to 4%, that the period of immersion in
the alkali solution in the leach-out layer removal step (3) in
Example 1 was changed to 8 hours, and that the antireflection film
formation step (4) in Example 1 was conducted by the following
method.
[0152] Antireflection Film Formation Step:
[0153] An antireflection film was deposited on the surface which
had undergone the antiglare treatment, in the following manner.
[0154] First, pulse sputtering was conducted using a niobium oxide
target (trade name, NBO Target; manufactured by AGC Ceramics Co.,
Ltd.) under the same deposition conditions as in Example 1, thereby
forming a high-refractive-index layer made of niobium oxide
(niobia) and having a thickness of 15 nm on that surface of the
glass substrate which had undergone the antiglare treatment.
[0155] Subsequently, pulse sputtering was conducted using a silicon
target under the same conditions as in Example 1, thereby forming a
low-refractive-index layer made of silicon oxide (silica) and
having a thickness of 30 nm on the high-refractive-index layer.
[0156] Next, pulse sputtering was conducted using a niobium oxide
target (trade name, NBO Target; manufactured by AGC Ceramics Co.,
Ltd.) under the same deposition conditions as in Example 1, thereby
forming a high-refractive-index layer made of niobium oxide
(niobia) and having a thickness of 110 nm on that side of the glass
substrate which had undergone the antiglare treatment.
[0157] Subsequently, pulse sputtering was conducted using a silicon
target under the same conditions as in Example 1, thereby forming a
low-refractive-index layer made of silicon oxide (silica) and
having a thickness of 90 nm on the high-refractive-index layer.
[0158] Thus, an antireflection film composed of a total of four
laminated layers of niobium oxide (niobia) and silicon oxide
(silica) was formed.
Example 4
[0159] A cover glass was produced in the same manner as in Example
1, except that the etching treatment period in the antiglare
treatment step (1) in Example 1 was changed to 10 minutes to
thereby regulate the haze to 10%, that the leach-out layer removal
step (3) in Example 1 was conducted by calcium carbonate washing
under the following conditions, and that the antireflection film
formation step (4) in Example 1 was conducted by the method used in
Example 3.
[0160] Calcium carbonate washing: A calcium-carbonate abrasive
material having an average particle diameter of 1.6 .mu.m (particle
size distribution, 0.1 .mu.m to 50 .mu.m) was used as an aqueous
solution (slurry) having a concentration of 20% by weight to grind
one surface of the substrate with a nylon brush at a grinding
pressure of 30 to 50 kPa and a conveying speed of 55 mm/sec, in an
amount of about 1 nm.
Example 5
[0161] A cover glass was produced in the same manner as in Example
1, except that the leach-out layer removal step (3) in Example 1
was conducted by cerium oxide washing under the following
conditions and that the antireflection film formation step (4) in
Example 1 was conducted under the following conditions.
[0162] Cerium oxide washing: A cerium-oxide abrasive material
having an average particle diameter of 1.2-1.8 .mu.m, an aqueous
solution (slurry) having a concentration of 4 Be, and a suede pad
were used to grind one surface of the substrate 20 times at a
grinding pressure of 0.113 MPa and a conveying speed of 20 mm/sec,
in an amount of about 1 .mu.m.
[0163] Antireflection Film Formation Step:
An antireflection film was deposited on the surface which had
undergone the antiglare treatment, in the following manner.
[0164] First, in a vacuum chamber, AC sputtering was conducted
using two niobium oxide targets (trade name, NBO Target;
manufactured by AGC Ceramics Co., Ltd.) at a pressure of 0.3 Pa,
frequency of 40 kHz, and power density of 3.8 W/cm.sup.2, while
introducing thereinto a mixed gas obtained by mixing argon gas with
10% by volume oxygen gas. Thus, a high-refractive-index layer made
of niobium oxide (niobia) and having a thickness of 11 nm was
formed on that surface of the glass substrate which had undergone
the antiglare treatment.
[0165] Subsequently, AC sputtering was conducted using two silicon
targets at a pressure of 0.3 Pa, frequency of 40 kHz, and power
density of 3.8 W/cm.sup.2, while introducing a mixed gas obtained
by mixing argon gas with 40% by volume oxygen gas, thereby forming
a low-refractive-index layer made of silicon oxide (silica) and
having a thickness of 40 nm on the high-refractive-index layer.
[0166] Next, AC sputtering was conducted using two niobium oxide
targets (trade name, NBO Target; manufactured by AGC Ceramics Co.,
Ltd.) at a pressure of 0.3 Pa, frequency of 40 kHz, and power
density of 3.8 W/cm.sup.2, while introducing a mixed gas obtained
by mixing argon gas with 10% by volume oxygen gas, thereby forming
a high-refractive-index layer made of niobium oxide (niobia) and
having a thickness of 120 nm on the low-refractive-index layer.
[0167] Subsequently, AC sputtering was conducted using two silicon
targets at a pressure of 0.3 Pa, frequency of 20 kHz, and power
density of 3.8 W/cm.sup.2, while introducing a mixed gas obtained
by mixing argon gas with 40% by volume oxygen gas, thereby forming
a low-refractive-index layer made of silicon oxide (silica) and
having a thickness of 95 nm.
[0168] Thus, an antireflection film composed of a total of four
laminated layers of niobium oxide (niobia) and silicon oxide
(silica) was formed.
Example 6
[0169] A cover glass was produced in the same manner as in Example
1, except that the period of immersion in the alkali solution in
the leach-out layer removal step (3) in Example 1 was changed to 10
hours.
Example 7
[0170] A cover glass was produced in the same manner as in Example
1, except that the chemical strengthening step (2) in Example 1 was
omitted.
Example 8
[0171] A cover glass was produced in the same manner as in Example
1, except that the leach-out layer removal in Example 1 was
conducted by etching by immersing the substrate in 10% aqueous NaOH
solution for 12 hours.
Example 9
[0172] A cover glass was produced in the same manner as in Example
2, except that the leach-out layer removal in Example 2 was
conducted by immersing the substrate in 2% aqueous hydrofluoric
acid solution for 20 seconds.
Example 10
[0173] A cover glass was produced in the same manner as in Example
2, except that the leach-out layer removal in Example 2 was
conducted by immersing the substrate in a 13.4% by weight solution
of hydrochloric acid for 3 hours, rinsing this substrate with pure
water, and subsequently immersing the substrate in 10% aqueous NaOH
solution for 4 hours.
Example 11
[0174] A cover glass was produced in the same manner as in Example
8, except that the chemical strengthening treatment in Example 8
was omitted.
Example 12
[0175] A cover glass was produced in the same manner as in Example
8, except that in the leach-out layer removal, the period of
immersion in the NaOH solution in Example 8 was changed to 4
hours.
Comparative Example 1
[0176] A cover glass was produced in the same manner as in Example
1, except that the leach-out layer removal step (3) in Example 1
was replaced by pure-water cleaning conducted under the following
conditions.
[0177] Pure-water cleaning: Pure water was introduced into an
immersion tank, and the substrate was immersed therein. An
ultrasonic wave of 40 kHz was propagated thereto to clean the
substrate for 10 minutes. Thereafter, the substrate was immersed in
pure water heated at 60.degree. C., and was then pulled out
gradually and dried thereby.
Comparative Example 2
[0178] A cover glass was produced in the same manner as in Example
3, except that the leach-out layer removal step (3) in Example 3
was replaced by plasma cleaning conducted under the following
conditions.
[0179] Plasma cleaning: A plasma generated at the atmospheric
pressure was applied to the substrate for 40 seconds under the
conditions of a nitrogen (N.sub.2) flow rate of 250 liter/min,
clean dry air (CDA) flow rate of 0.5 liter/min, and accelerating
voltage of 10 kV.
Reference Example 1
[0180] A cover glass was produced in the same manner as in
Comparative Example 1, except that the antiglare treatment
(frosting treatment) in Example 1 was omitted.
Reference Example 2
[0181] A cover glass was produced in the same manner as in Example
1, except that the leach-out layer removal in Example 1 was omitted
and the antireflection film formation was omitted.
[0182] The results of evaluation of the cover glasses thus produced
are shown in Table 1 and Table 2.
TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4
Example 5 Example 6 Example 7 Example 8 Glass DT DT DT DT DT DT DT
(un- DT strengthened) Size (mm .times. mm) 150 .times. 250 150
.times. 250 400 .times. 600 150 .times. 250 150 .times. 250 150
.times. 250 150 .times. 250 150 .times. 250 Frosting treatment
conducted conducted conducted conducted conducted conducted
conducted conducted Haze 25% 25% 4% 10% 25% 25% 25% 25% Leach-out
layer alkali alkali alkali calcium cerium oxide alkali alkali NaOH
removal immersion immersion immersion carbonate washing immersion
immersion 4 hr 8 hr 8 hr washing 10 hr 4 hr 12 hr Removal amount 3
nm 6 nm 6 nm 1 nm 1 .mu.m 8 nm 3 nm 10 nm Low-reflection 4-layer
4-layer 4-layer 4-layer 4-layer 4-layer 4-layer 4-layer film AR1
AR1 AR2 AR2 AR3 AR1 AR1 AR1 AFP film none Shin-Etsu none none none
none none none Degree of ion 17% 14% 3% 23% 11% 7% 17% 7% exchange
Color distribution 3.6 2.3 1.5 3.3 2.2 1.9 3.2 2.3 E (first) Color
distribution 3.2 2 1.2 4 2 2.2 3.2 -- E (second) Color distribution
4 2.3 1.8 4 2.5 1.7 3.1 -- E (third) Contact angle 20.degree.
110.degree. 20.degree. 20.degree. 20.degree. 20.degree. 20.degree.
-- Luminous 0.80% 0.80% 1% 1% 0.70% 0.80% 0.80% 0.80% reflectance
(SCI)
TABLE-US-00002 TABLE 2 Comparative Comparative Reference Reference
Example 9 Example 10 Example 11 Example 12 Example 1 Example 2
Example 1 Example 2 Glass DT DT DT (un- DT (un- DT DT DT DT
strengthened) strengthened) Size (mm .times. mm) 150 .times. 250
150 .times. 250 150 .times. 250 150 .times. 250 150 .times. 250 400
.times. 600 150 .times. 250 150 .times. 250 Frosting treatment
conducted conducted conducted conducted conducted conducted not
conducted conducted Haze 25% 25% 25% 25% 25% 4% 25% 25% Leach-out
layer hydro- HCl 3 hr .fwdarw. NaOH NaOH pure water O.sub.2 plasma
pure water none removal fluoric acid NaOH 4 hr US cleaning US 20
sec 12 hr 4 hr Removal amount 1 .mu.m 8 nm 10 nm 3 nm -- -- -- --
Low-reflection 4-layer 4-layer 4-layer 4-layer 4-layer 4-layer
4-layer none film AR1 AR1 AR1 AR1 AR1 AR2 AR1 AFP film Shin-Etsu
Shin-Etsu none none none none none none Degree of ion 4% 7% 7% 17%
27% 32% 4% 27% exchange Color distribution 1.9 2.5 2.6 3.6 8.7 10.6
1.9 0.2 E (first) Color distribution -- -- -- -- 7.7 12 1.7 -- E
(second) Color distribution -- -- -- -- 8 9.8 1.5 -- E (third)
Contact angle 112.degree. 113.degree. -- -- 20.degree. 20.degree.
20.degree. -- Luminous 0.80% 0.80% 0.80% 0.80% 0.80% 0.80% 0.80%
4.0% reflectance (SCI)
[0183] In Reference Example 1, in which an antiglare treatment had
not been performed, the values of color distribution E were small
and this cover glass hence is less apt to have the problem wherein
the glass suffers color tone differences. The color distribution in
Reference Example 1 is mainly due to unevenness in the thickness of
each of the layers deposited in the deposition step, and indicates
that the color tone differences within 10 cm.sup.2 are sufficiently
small. However, it can be seen that in the case where an antiglare
treatment and formation of an antireflection film are both
performed without removing the leach-out layer, this results in
large values of color distribution E and large differences in color
tone, as shown in Comparative Example 1 and Comparative Example 2.
Thus, the differences in color tone due to the presence of a
leach-out layer are clearly distinguished from the color tone
unevenness due to a film thickness distribution attributable to the
deposition step.
[0184] In contrast, the cover glasses of the Examples each showed
reduced values of color distribution E, indicating that the
differences in color tone have been reduced. It can be seen that
this improvement is an effect of the removal of the leach-out
layer. Furthermore, since each of the three measurements of color
distribution in each Example satisfied E.ltoreq.4, it can be seen
that the glass has high in-plane evenness.
[0185] In Example 4, two of the three measurements gave E=4, which
is on the limit of the satisfactory range. This is thought to be
because grinding with calcium carbonate was conducted in this
Example and the amount of the leach-out layer removed was 1 nm,
which was smaller than in the other Examples. It is thus preferable
that the removal amount should be larger than 1 nm. Furthermore,
since calcium carbonate is abrasive grains which are not high in
grinding property among abrasive materials and which cannot bring
about a large removal amount, it is difficult for calcium carbonate
to give results in which the value of color distribution E stably
satisfies E.ltoreq.4. From the standpoint of attempting to remove
the leach-out layer by grinding, abrasive grains having sufficient
grinding properties, such as cerium oxide, are more preferred, as
in Example 5.
[0186] While the present invention has been described in detail and
with reference to specific embodiments thereof, it will be apparent
to one skilled in the art that various changes and modifications
can be made therein without departing from the spirit and scope
thereof. This application is based on a Japanese patent application
filed on Jul. 16, 2014 (Application No. 2014-146264) and a Japanese
patent application filed on Jul. 16, 2014 (Application No.
2014-146265), the entire contents thereof being incorporated herein
by reference.
DESCRIPTION OF REFERENCE NUMERALS AND SIGN
[0187] 10 Glass substrate [0188] 10R Leach-out layer [0189] 20
Antireflection film [0190] 30 Antifouling film
* * * * *