U.S. patent application number 17/006199 was filed with the patent office on 2021-03-04 for optical glass.
This patent application is currently assigned to AGC Inc.. The applicant listed for this patent is AGC Inc.. Invention is credited to Shinichi AMMA, Akira SHIBATA.
Application Number | 20210061703 17/006199 |
Document ID | / |
Family ID | 1000005093087 |
Filed Date | 2021-03-04 |
United States Patent
Application |
20210061703 |
Kind Code |
A1 |
SHIBATA; Akira ; et
al. |
March 4, 2021 |
OPTICAL GLASS
Abstract
Provided is an optical glass having a high refractive index and
high light transmittance. The optical glass contains, in terms of
mol % based on oxides, SiO.sub.2: 9.0% to 11.0%, B.sub.2O.sub.3:
22.0% to 24.0%, La.sub.2O.sub.3: 18.0% to 20.0%, and TiO.sub.2:
30.0% to 31.0%.
Inventors: |
SHIBATA; Akira; (Tokyo,
JP) ; AMMA; Shinichi; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AGC Inc. |
Tokyo |
|
JP |
|
|
Assignee: |
AGC Inc.
Tokyo
JP
|
Family ID: |
1000005093087 |
Appl. No.: |
17/006199 |
Filed: |
August 28, 2020 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2019/033347 |
Aug 26, 2019 |
|
|
|
17006199 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C03C 3/068 20130101 |
International
Class: |
C03C 3/068 20060101
C03C003/068 |
Claims
1. An optical glass comprising, in terms of mol % based on oxides:
SiO.sub.2: 9.0% to 11.0%; B.sub.2O.sub.3: 22.0% to 24.0%;
La.sub.2O.sub.3: 18.0% to 20.0%; and TiO.sub.2: 30.0% to 31.0%.
2. The optical glass according to claim 1, further comprising, in
terms of mol % based on oxides: Y.sub.2O.sub.3: 3.0% to 5.0%;
WO.sub.3: 0.1% to 0.4%; Nb.sub.2O.sub.5: 2.5% to 4.0%; ZrO.sub.2:
5.0% to 8.0%; and Gd.sub.2O.sub.3: 3.0% to 5.0%.
3. The optical glass according to claim 2, satisfying, in terms of
mol % based on oxides: SiO.sub.2: 9.0% to 10.0%; B.sub.2O.sub.3:
22.5% to 23.5%; Y.sub.2O.sub.3: 3.5% to 4.5%; TiO.sub.2: 30.3% to
30.7%; WO.sub.3: 0.2% to 0.3%; Nb.sub.2O.sub.5: 3.0% to 3.5%;
La.sub.2O.sub.3: 18.5% to 19.5%; ZrO.sub.2: 6.0% to 7.0%; and
Gd.sub.2O.sub.3: 3.5% to 4.5%.
4. The optical glass according to claim 1, having a composition in
a range of
99.5%.ltoreq.(SiO.sub.2+B.sub.2O.sub.3+Y.sub.2O.sub.3+TiO.sub.2+-
WO.sub.3+Nb.sub.2O.sub.5+La.sub.2O.sub.3+ZrO.sub.2+Gd.sub.2O.sub.3).ltoreq-
.100.0%, in terms of mol % based on oxides.
5. The optical glass according to claim 1, having a refractive
index in a range of 1.90 to 2.10.
6. The optical glass according to claim 1, having an internal
transmittance at 450 nm of 88.0% or higher.
7. The optical glass according to claim 1, having a devitrification
temperature T in a range of T<1,170.degree. C.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a continuation of International
Application No. PCT/JP2019/033347, filed on Aug. 26, 2019, the
entire contents of which are incorporated herein by reference.
FIELD
[0002] The present invention relates to an optical glass, and in
particular relates to an optical glass to be used for a light guide
plate.
BACKGROUND
[0003] In recent years, head mounted displays (HMD) compatible
with, for example, augmented reality (AR), virtual reality (VR),
and mixed reality (MR) have been a topic of interest. As a light
guide plate for this optical device, it is known to use a glass
having a high refractive index. For a light guide plate for HMD,
the thickness of the light guide plate and a refractive index,
which greatly affects flexibility in the total design of HMD, are
particularly important. For example, Patent Literature 1 discloses
a high-refractive-index glass for HMD, the glass having a
refractive index of approximately 2.0.
CITATION LIST
Patent Literature
[0004] Patent Literature 1: Japanese Laid-open Patent Publication
No. 2019-20723
SUMMARY
Technical Problem
[0005] However, in recent years, higher performance has been
required for products, and accordingly, higher light transmittance
of glass has been required. The optical glass described in Patent
Literature 1 has an insufficient internal transmittance, that is,
approximately 0.6 in the blue wavelength range.
[0006] Under such circumstances, an optical glass having a high
refractive index and high light transmittance has been desired.
Solution to Problem
[0007] An optical glass of the present invention comprises, in
terms of mol % based on oxides:
[0008] SiO.sub.2: 9.0% to 11.0%;
[0009] B.sub.2O.sub.3: 22.0% to 24.0%;
[0010] La.sub.2O.sub.3: 18.0% to 20.0%; and
[0011] TiO.sub.2: 30.0% to 31.0%.
Advantageous Effects of Invention
[0012] According to the present invention, an optical glass having
a high refractive index and high light transmittance can be
industrially produced. In particular, the present invention is
suitable for continuous production.
DESCRIPTION OF EMBODIMENTS
[0013] Descriptions are given of an optical glass of the present
invention. The shape of the optical glass is not particularly
limited. For example, the optical glass may be shaped like a
plate.
[0014] [Component of Optical Glass]
[0015] The optical glass of the present invention includes a
combination of essential components and optional components. The
essential components are essentially contained in the optical glass
and offer important functions in performance. The optional
components are used if needed. Unless there is a specific
description in the present specification, % means mol % based on
oxides. A numerical range includes a rounded-of range. A numerical
range "A to B" means "A or more and B or less".
[0016] [Essential Component]
[0017] <SiO.sub.2>
[0018] SiO.sub.2 is a component that forms glass, gives strength
and cracking resistance to glass, and enhances the stability and
chemical durability of glass. The optical glass of the present
embodiment has a SiO.sub.2 content of 9.0% to 11.0%, and preferably
9.0% to 10.0%. The optical glass having a SiO.sub.2 content within
the above-mentioned range can acquire both high strength and a high
refractive index.
[0019] <B.sub.2O.sub.3>
[0020] B.sub.2O.sub.3 is a component that provides a low glass
transition temperature (Tg) and enhances mechanical properties such
as the strength and the crack resistance of glass. The optical
glass of the present embodiment has a B.sub.2O.sub.3 content of
22.0% to 24.0%, and preferably 22.5% to 23.5%. The optical glass
having a B.sub.2O.sub.3 content within the above-mentioned range
can acquire both high strength and a high refractive index.
[0021] <La.sub.2O.sub.3>
[0022] La.sub.2O.sub.3 is a component that contributes to
increasing the refractive index of the present optical glass and
lowering the devitrification temperature of the present optical
glass. The optical glass of the present embodiment has a
La.sub.2O.sub.3 content of 18.0% to 20.0%, and preferably 18.5% to
19.5%. The optical glass having a La.sub.2O.sub.3 content within
the above-mentioned range can acquire both a high refractive index
and a low devitrification temperature.
[0023] <TiO.sub.2>
[0024] TiO.sub.2 is a component that, typically, increases the
refractive index of glass and enlarges the dispersion of glass, in
the present optical glass, TiO.sub.2 is a component that
contributes to, in particular, the devitrification temperature and
light transmittance of the optical glass. The optical glass of the
present embodiment has a TiO.sub.2 content of 30.0% to 31.0%, and
preferably 30.3% to 30.7%. The optical glass having a TiO.sub.2
content within the above-mentioned range can acquire both a high
transmittance and a low devitrification temperature.
[0025] [Optional Component]
[0026] <Y.sub.2O.sub.3>
[0027] The optical glass of the present embodiment preferably
contains Y.sub.2O.sub.3. Y.sub.2O.sub.3 is a component that
contributes to increasing the refractive index of the present
optical glass and lowering the devitrification temperature of the
present optical glass. In the case where the optical glass of the
present embodiment contains Y.sub.2O.sub.3, the Y.sub.2O.sub.3
content of the optical glass is preferably 3.0% to 5.0%, and
particularly preferably 3.5% to 4.5%. The optical glass having a
Y.sub.2O.sub.3 content within the above-mentioned range can acquire
both a high refractive index and a low devitrification
temperature.
[0028] <WO.sub.3>
[0029] The optical glass of the present embodiment preferably
contains WO.sub.3. WO.sub.3 is a component that inhibits the
devitrification of glass and contributes to the coloring of glass.
Therefore, a too large amount of WO.sub.3 causes a decrease in
light transmittance. Hence, in the case where the optical glass of
the present embodiment contains WO.sub.3, the WO.sub.3 content of
the optical glass is preferably 0.1% to 0.4%, and particularly
preferably 0.2% to 0.3%. The optical glass having a WO.sub.3
content within the above-mentioned range can acquire both a high
transmittance and a low devitrification temperature.
[0030] <Nb.sub.2O.sub.5>
[0031] The optical glass of the present embodiment preferably
contains Nb.sub.2O.sub.5. Nb.sub.2O.sub.5 is a component that
contributes to increasing the refractive index of the present
optical glass and lowering the devitrification temperature of the
present optical glass. In the case where the optical glass of the
present embodiment contains Nb.sub.2O.sub.5, the Nb.sub.2O.sub.5
content of the optical glass is preferably 2.5% to 4.0%, and
particularly preferably 3.0% to 3.5%. The optical glass having a
Nb.sub.2O.sub.5 content within the above-mentioned range can
acquire both a high refractive index and a low devitrification
temperature.
[0032] <ZrO.sub.2>
[0033] The optical glass of the present embodiment preferably
contains ZrO.sub.2. ZrO.sub.2 is a component that increases the
refractive index of glass and enhances the chemical durability of
glass. In the case where the optical glass of the present
embodiment contains ZrO.sub.2, the ZrO.sub.2 content of the optical
glass is preferably 5.0% to 8.0%, and particularly preferably 6.0%
to 7.0%. The optical glass having a ZrO.sub.2 content within the
above-mentioned range can acquire both high durability and a high
refractive index.
[0034] <Gd.sub.2O.sub.3>
[0035] The optical glass of the present embodiment preferably
contains Gd.sub.2O.sub.3. Gd.sub.2O.sub.3 is a component that
contributes to increasing the refractive index of the present
optical glass and lowering the devitrification temperature of the
present optical glass. In the case where the optical glass of the
present embodiment contains Gd.sub.2O.sub.3, the Gd.sub.2O.sub.3
content of the optical glass is preferably 3.0% to 5.0%, and
particularly preferably 3.5% to 4.5%. The optical glass having a
Gd.sub.2O.sub.3 content within the above-mentioned range can
acquire both a high refractive index and a low devitrification
temperature.
[0036] <Other Optional Components>
[0037] Besides the above-mentioned components, the optical glass of
the present embodiment may include a minor component and an
additive that are typically used for the production of optical
glasses, without impairing the effects of the present
invention.
[0038] [Composition of Optical Glass]
[0039] The optical glass of the present embodiment contains the
following compounds in mol % based on oxides.
[0040] SiO.sub.2: 9.0% to 11.0%
[0041] B.sub.2O.sub.3: 22.0% to 24.0%
[0042] La.sub.2O.sub.3: 18.0% to 20.0%
[0043] TiO.sub.2: 30.0% to 31.0%
[0044] The optical glass of the present embodiment preferably
contains the following compounds in mol % based on oxides.
[0045] SiO.sub.2: 9.0% to 11.0%
[0046] B.sub.2O.sub.3: 22.0% to 24.0%
[0047] Y.sub.2O.sub.3: 3.0% to 5.0%
[0048] TiO.sub.2: 30.0% to 31.0%
[0049] WO.sub.3: 0.1% to 0.4%
[0050] Nb.sub.2O.sub.5: 2.5% to 4.0%
[0051] La.sub.2O.sub.3: 18.0% to 20.0%
[0052] ZrO.sub.2: 5.0% to 8.0%
[0053] Gd.sub.2O.sub.3: 3.0% to 5.0%
[0054] The optical glass of the present embodiment particularly
preferably contains the following compounds in mol % based on
oxides.
[0055] SiO.sub.2: 9.0% to 10.0%
[0056] B.sub.2O.sub.3: 22.5% to 23.5%
[0057] Y.sub.2O.sub.3: 3.5% to 4.5%
[0058] TiO.sub.2: 30.3% to 30.7%
[0059] WO.sub.3: 0.2% to 0.3%
[0060] Nb.sub.2O.sub.5: 3.0% to 3.5%
[0061] La.sub.2O.sub.3: 18.5% to 19.5%
[0062] ZrO.sub.2: 6.0% to 7.0%
[0063] Gd.sub.2O.sub.3: 3.5% to 4.5%
[0064] Furthermore, the composition of the optical glass of the
present embodiment is preferably in a range of
99.5%.ltoreq.(SiO.sub.2+B.sub.2O.sub.3+Y.sub.2O.sub.3+TiO.sub.2+WO.sub.3+-
Nb.sub.2O.sub.5+La.sub.2O.sub.3+ZrO.sub.2+Gd.sub.2O.sub.3).ltoreq.100.0%,
and particularly preferably
(SiO.sub.2+B.sub.2O.sub.3+Y.sub.2O.sub.3+TiO.sub.2+WO.sub.3+Nb.sub.2O.sub-
.5+La.sub.2O.sub.3+ZrO.sub.2+Gd.sub.2O.sub.3)=100.0%, in mol %
based on oxides (note that the inclusion of inevitable impurities
due to manufacture is allowed).
[0065] The optical glass having a composition within the
above-mentioned range can satisfy all of a high refractive index,
light transmittance, and a low devitrification temperature.
[0066] Furthermore, the optical glass of the present embodiment
preferably does not contain ZnO in an amount larger than the amount
of impurities inevitably contained due to manufacture. If
containing ZnO, the present optical glass is easily
devitrified.
[0067] Furthermore, the optical glass of the present embodiment
preferably does not contain alkali metal in an amount larger than
the amount of impurities inevitably contained due to manufacture.
If containing alkali metal, the present optical glass has lower
weather resistance and lower chemical resistance.
[0068] [Optical Glass]
[0069] The optical glass of the present embodiment has a refractive
index nd of preferably 1.90 to 2.10, and particularly preferably
1.95 to 2.05. In particular, in the case where the optical glass of
the present invention is used for a light guide plate, the optical
glass having a refractive index nd in the above-mentioned range
makes it possible to design a thinner light guide plate.
[0070] The optical glass of the present embodiment has an internal
transmittance at a wavelength of 450 nm of preferably 88.0% or
higher, and particularly preferably 90.0% or higher. The optical
glass having an internal transmittance in the above-mentioned range
can substantially prevent the attenuation of blue light in a light
guide plate, and can substantially prevent a picture projected on
HMD from looking yellow.
[0071] The optical glass of the present embodiment has a
devitrification temperature of preferably less than 1,170.degree.
C., and particularly preferably less than 1,150.degree. C. The
optical glass having a devitrification temperature in the
above-mentioned range reduces devitrification caused by crystal
formation during glass manufacture, and thereby makes glass
manufacture easier.
[0072] [Method for Producing Optical Glass]
[0073] A method for producing the optical glass of the present
embodiment is not limited to a particular method, and existing
methods for producing plate glasses can be applied. For example,
well-known methods, such as float method, fusion method, and
roll-out method, can be used.
EXAMPLES
[0074] Hereinafter, detailed descriptions will be given of Examples
and Comparative Examples of the present invention. As long as the
advantageous effects of the present invention are exhibited, the
embodiments may be suitably modified.
[0075] <Measurement Method>
[0076] [Devitrification Temperature]
[0077] A devitrification temperatures T of the optical glass of
each of Examples and Comparative Examples was measured on the
following conditions.
[0078] Raw materials of compositions listed in Table 1 were melted
in a platinum crucible at 1,250.degree. C. for 2 hours to form a
uniform molten glass. The molten glass was casted into a mold
(length.times.width.times.height=60 mm.times.50 mm.times.30 mm)
heated to 200.degree. C. to obtain a glass block. The glass block
was put into water of ordinary temperature to be pulverized, so
that cullet measuring approximately 2 mm per side was obtained.
From this cullet, 5 g of cullet was taken as an evaluation
sample.
[0079] The evaluation sample was put into a platinum plate, and
heated for 16 hours in an electric furnace set at a predetermined
temperature of 1,100.degree. C. to 1,200.degree. C. to melt the
sample. After a lapse of the 16 hours, the sample was taken out of
the electric furnace, and, while the sample was naturally allowed
to cool, whether the sample was precipitated as crystals was
observed by using an optical microscope. Conditions on which
crystals had been observed were recorded, and the highest
temperature among set temperatures of the electric furnace under
the conditions is regarded as a devitrification temperature T. For
the optical glasses of Examples and Comparative Examples,
devitrification temperatures T of evaluation samples are judged on
the following criteria, and it is determined that a devitrification
temperature T with a double circle or a circle is acceptable.
[0080] Double Circle: T<1,150.degree. C.
[0081] Circle: 1,150.ltoreq.T<1,170.degree. C.
[0082] Cross: 1,170.degree. C..ltoreq.T
[0083] [Light Transmittance]
[0084] A light transmittance X was measured on the following
conditions.
[0085] Two types of glass plates were used, obtained in Examples
and the likes and having a size of length.times.width=30
mm.times.30 mm, one type of the glass plates having a plate
thickness of 10 mm and the other type of the glass plates having a
plate thickness of 1 mm. The light transmittance X at a wavelength
of 450 nm of a glass plate having a plate thickness of 10 mm was
measured by a spectrophotometer (U-4100, manufactured by Hitachi
High-Technologies Corporation) (the light transmittance in the
present embodiment means an internal transmittance except a
reflection loss in front and back faces). For the optical glasses
of Examples and Comparative Examples, the light transmittance X of
each of the evaluation samples is judged on the following criteria,
and it is determined that a light transmittance X marked with a
double circle or a circle is acceptable.
[0086] Double Circle: 90.0%.ltoreq.X
[0087] Circle: 88.0%.ltoreq.X<90.0%
[0088] Cross: 88.0<X
[0089] [Refractive Index]
[0090] The refractive index (nd) of each of the glass plates
obtained in Examples and the likes and having a size of
length.times.width.times.plate thickness=30 mm.times.30 mm.times.10
mm was measured by a refractometer (KPR-2000, manufactured by
Kalnew).
Example 1
[0091] A raw material of a composition listed in Table 1 was melted
in a platinum crucible at 1,250.degree. C. for 2 hours to obtain a
uniform molten glass. The molten glass was poured into a mold
(length.times.width.times.height=60 mm.times.50 mm.times.30 mm)
heated to 200.degree. C. to obtain a glass block.
[0092] Next, by the use of a cutting machine (a small-sized cutting
machine manufactured by Maruto Instrument Co., Ltd.), the glass
block was cut into pieces each having a size of
length.times.width=30 mm.times.30 mm, and the resulting pieces were
subjected to plate thickness adjustment and surface polishing by
the use of a grinding machine (SGM-6301, manufactured by SHUWA
Industry Company Limited) and an one-side polishing machine
(EJ-380IN, manufactured by Engis Japan Corporation) to produce
glass plates having a size of length.times.width=30 mm.times.30 mm
and a plate thickness of 10 mm or 1 mm. These glass plates were
subjected to various evaluations. Table 1 lists evaluation
results.
[0093] Grinding Condition: The glass plates were ground at 2.0
.mu.m/sec by the use of a #100 diamond wheel, and then ground at
1.0 .mu.m/sec by the use of a #1000 diamond wheel, and subsequently
ground at 0.5 .mu.m/sec by the use of a #2000 diamond wheel.
[0094] Polishing Condition: abrasive (cerium oxide), the number of
revolutions (80 rpm for 10 minutes)
Examples 2 to 3, Comparative Examples 1 to 2
[0095] The same operation as in Example 1 was performed, except
that the condition was changed to conditions listed in Table 1.
TABLE-US-00001 TABLE 1 Evaluation Devitrification Light Composition
(mol %) Temperature Transmittance SiO.sub.2 B.sub.2O.sub.3
Y.sub.2O.sub.3 TiO.sub.2 WO.sub.3 Nb.sub.2O.sub.5 La.sub.2O.sub.3
ZrO.sub.2 Gd.sub.2O.sub.3 nd .degree. C. Judgment % Judgment
Example 1 9.5 23.1 4.0 30.5 0.25 3.3 19.0 6.5 3.9 2.00 1138
.circleincircle. 92.2 .circleincircle. Example 2 9.8 23.1 3.7 31.0
0.25 3.2 19.0 6.4 3.7 2.00 1125 .circleincircle. 88.7 .largecircle.
Example 3 9.3 23.1 4.3 30.0 0.25 3.4 19.1 6.5 4.1 2.00 1155
.largecircle. 92.8 .circleincircle. Comparative 10.0 23.1 3.4 31.5
0.25 3.1 18.9 6.3 3.5 2.00 1113 .circleincircle. 87.0 X Example 1
Comparative 9.0 23.1 4.6 29.5 0.25 3.5 19.1 6.6 4.4 2.00 1175 X
92.3 .circleincircle. Example 2
* * * * *