U.S. patent application number 11/273621 was filed with the patent office on 2006-05-18 for optical glass, precision press-molding preform, process for producing the preform, optical element and process for producing the element.
This patent application is currently assigned to HOYA CORPORATION. Invention is credited to Yoshiko Kasuga, Xuelu Zou.
Application Number | 20060105900 11/273621 |
Document ID | / |
Family ID | 36387145 |
Filed Date | 2006-05-18 |
United States Patent
Application |
20060105900 |
Kind Code |
A1 |
Kasuga; Yoshiko ; et
al. |
May 18, 2006 |
Optical glass, precision press-molding preform, process for
producing the preform, optical element and process for producing
the element
Abstract
An optical glass having high refractivity and a low sag
temperature and having a low-temperature softening property that
enables precision press-molding is provided, and the optical glass
contains, by mol %, 5 to 50% of B.sub.2O.sub.3, 3 to 50% of
SiO.sub.2, 5 to 40% of TiO.sub.2, 1 to 40% of ZnO, 5 to 20% of
La.sub.2O.sub.3, 0 to 10% of Gd.sub.2O.sub.3, 0 to 15% of
Nb.sub.2O.sub.5, 0 to 10% of ZrO.sub.2, 0 to 5% of Ta.sub.2O.sub.5,
0 to 10% of Bi.sub.2O.sub.3, 0 to 10% of MgO, 0 to 8% of CaO, 0 to
10% of SrO, 0 to 10% of BaO, provided that the total content of
MgO, CaO, SrO and BaO is 15% or less, 0 to 20% of Li.sub.2O, and 0
to 5% of Na.sub.2O, optionally containing Sb.sub.2O.sub.3 as a
refining agent, and having a refractive index (nd) of 1.8 or more
and an Abbe's number (vd) of 35 or less.
Inventors: |
Kasuga; Yoshiko; (Tokyo,
JP) ; Zou; Xuelu; (Tokyo, JP) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
HOYA CORPORATION
Tokyo
JP
|
Family ID: |
36387145 |
Appl. No.: |
11/273621 |
Filed: |
November 15, 2005 |
Current U.S.
Class: |
501/78 ;
501/64 |
Current CPC
Class: |
C03B 11/08 20130101;
C03C 3/068 20130101 |
Class at
Publication: |
501/078 ;
501/064 |
International
Class: |
C03C 3/095 20060101
C03C003/095; C03C 3/068 20060101 C03C003/068 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 2004 |
JP |
2004-330047 |
Claims
1. An optical glass comprising, by mol %, 5 to 50% of
B.sub.2O.sub.3, 3 to 50% of SiO.sub.2, 5 to 40% of TiO.sub.2, 1 to
40% of ZnO, 5 to 20% of La.sub.2O.sub.3, 0 to 10% of
Gd.sub.2O.sub.3, 0 to 15% of Nb.sub.2O.sub.5, 0 to 10% of
ZrO.sub.2, 0 to 5% of Ta.sub.2O.sub.5, 0 to 10% of Bi.sub.2O.sub.3,
0 to 10% of MgO, 0 to 8% of CaO, 0 to 10% of SrO, 0 to 10% of BaO
provided that the total content of MgO, CaO, SrO and BaO is 15% or
less, 0 to 20% of Li.sub.2O, and 0 to 5% of Na.sub.2O, optionally
containing Sb.sub.2O.sub.3 as a refining agent, and having a
refractive index (nd) of 1.8 or more and an Abbe's number (vd) of
35 or less.
2. An optical glass comprising, by mol %, 5 to 50% of
B.sub.2O.sub.3, 3 to 50% of SiO.sub.2, 5 to 40% of TiO.sub.2, 1 to
40% of ZnO, 5 to 20% of La.sub.2O.sub.3, 0 to 10% of
Gd.sub.2O.sub.3, 0 to 15% of Nb.sub.2O.sub.5, 0 to 10% of
ZrO.sub.2, 0 to 5% of Ta.sub.2O.sub.5, 0 to 10% of Bi.sub.2O.sub.3,
0 to 10% of MgO, 0 to 8% of CaO, 0 to 10% of SrO, 0 to 10% of BaO,
the content of BaO being less than 13% by weight, provided that the
total content of MgO, CaO, SrO and BaO is 15% by weight or less, 0
to 20% of Li.sub.2O, 0 to 5% of Na.sub.2O, 0 to 1% of
Sb.sub.2O.sub.3, and having a refractive index (nd) of over 1.88
and an Abbe's number (vd) of 35 or less.
3. An optical glass comprising, by mol %, to 50% of B.sub.2O.sub.3,
3 to 50% Of SiO.sub.2, 5 to 40% of TiO.sub.2, 1 to 40% of ZnO, 5 to
20% of La.sub.2O.sub.3, 0 to 10% of Gd.sub.2O.sub.3, 0 to 15% of
Nb.sub.2O.sub.5, 0 to 10% of ZrO.sub.2, 0 to 5% of Ta.sub.2O.sub.5,
0 to 10% of Bi.sub.2O.sub.3, 0 to 10% of MgO, 0 to 8% of CaO, 0 to
10% of SrO, 0 to 10% of BaO, provided that the total content of
MgO, CaO, SrO and BaO is less than 6% by weight, 0 to 20% of
Li.sub.2O, 0 to 5% of Na.sub.2O, and 0 to 1% of Sb.sub.2O.sub.3,
the amount of Sb.sub.2O.sub.3 being 1% by weight or less, and
having a refractive index of 1.8 or more and an Abbe's number (vd)
of 35 or less.
4. An optical glass comprising, by mol %, 25 to 50% of
B.sub.2O.sub.3, the content of B.sub.2O.sub.3 being over 15% by
weight, 3 to 50% Of SiO.sub.2, 5 to 40% of TiO.sub.2, 1 to 40% of
ZnO, 5 to 20% of La.sub.2O.sub.3, 0 to 10% of Gd.sub.2O.sub.3, 0 to
15% of Nb.sub.2O.sub.5, 0 to 10% of ZrO.sub.2, 0 to 5% of
Ta.sub.2O.sub.5, 0 to 10% of Bi.sub.2O.sub.3, 0 to 10% of MgO, 0 to
8% of CaO, 0 to 10% of SrO, 0 to 10% of BaO, the content of BaO
being less than 13% by weight, provided that the total content of
MgO, CaO, SrO and BaO is less than 15% by weight, 0 to 20% of
Li.sub.2O, 0 to 5% of Na.sub.2O, and 0 to 1% of Sb.sub.2O.sub.3,
the amount of Sb.sub.2O.sub.3 being 1% by weight or less, and
having a refractive index (nd) of 1.8 or more and an Abbe's number
(vd) of 35 or less.
5. An optical glass comprising, by mol %, 5 to 50% of
B.sub.2O.sub.3, 3 to 50% of SiO.sub.2, 5 to 40% of TiO.sub.2, 1 to
40% of ZnO, 5 to 20% of La.sub.2O.sub.3, 0 to 10% of
Gd.sub.2O.sub.3, 0 to 15% of Nb.sub.2O.sub.5, 0 to 10% of
ZrO.sub.2, 0 to 5% of Ta.sub.2O.sub.5, 0 to 10% of Bi.sub.2O.sub.3,
0 to 10% of MgO, 0 to 8% of CaO, 0 to 10% of SrO, 0 to 10% of BaO,
the content of BaO being less than 13% by weight, provided that the
total content of MgO, CaO, SrO and BaO is less than 15% by weight,
2 to 20% of Li.sub.2O, the content of Li.sub.2O being over 2% by
weight, 0 to 5% of Na.sub.2O, and 0 to 1% of Sb.sub.2O.sub.3, the
amount of Sb.sub.2O.sub.3 being 1% by weight or less, and having a
refractive index (nd) of 1.8 or more and an Abbe's number (vd) of
35 or less.
6. An optical glass comprising, by mol %, 25 to 50% of
B.sub.2O.sub.3, the content of B.sub.2O.sub.3 being over 17% by
weight, 3 to 50% Of SiO.sub.2, 5 to 40% of TiO.sub.2, 1 to 40% of
ZnO, 5 to 20% of La.sub.2O.sub.3, 0 to 10% of Gd.sub.2O.sub.3, 0 to
15% of Nb.sub.2O.sub.5, 0 to 10% of ZrO.sub.2, 0 to 5% of
Ta.sub.2O.sub.5, 0 to 10% of Bi.sub.2O.sub.3, 0 to 10% of MgO, 0 to
8% of CaO, 0 to 10% of SrO, 0 to 10% of BaO, the content of BaO
being less than 13% by weight, 2 to 20% of Li.sub.2O, the content
of Li.sub.2O being over 2% by weight, 0 to 5% of Na.sub.2O, and 0
to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3 being 1% by
weight or less, and having a refractive index (nd) of 1.8 or more
and an Abbe's number (vd) of 35 or less.
7. An optical glass comprising, by mol %, 5 to 50% of
B.sub.2O.sub.3, 3 to 50% of SiO.sub.2, 12 to 40% of TiO.sub.2, the
content of TiO.sub.2 being over 12% by weight but not more than 30%
by weight, 1 to 40% of ZnO, 5 to 20% of La.sub.2O.sub.3, 0 to 10%
of Gd.sub.2O.sub.3, 0 to 15% of Nb.sub.2O.sub.5, 0 to 10% of
ZrO.sub.2, 0 to 5% of Ta.sub.2O.sub.5, 0 to 10% of Bi.sub.2O.sub.3,
0 to 10% of MgO, 0 to 8% of CaO, 0 to 10% of SrO, 0 to 10% of BaO,
the content of BaO being less than 13% by weight, provided that the
total content of MgO, CaO, SrO and BaO is less than 6% by weight, 0
to 20% of Li.sub.2O, 0 to 5% of Na.sub.2O, and 0 to 1% of
Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3 being less than 1%
by weight, and having a refractive index (nd) of 1.8 or more and an
Abbe's number (vd) of 35 or less.
8. An optical glass comprising, by mol %, 5 to 50% of
B.sub.2O.sub.3, 3 to 20% of SiO.sub.2, the content of SiO.sub.2
being less than 8% by weight, 5 to 40% of TiO.sub.2, 1 to 40% of
ZnO, 5 to 20% of La.sub.2O.sub.3, 0 to 10% of Gd.sub.2O.sub.3, 0 to
15% of Nb.sub.2O.sub.5, 0 to 10% of ZrO.sub.2, 0 to 5% of
Ta.sub.2O.sub.5, 0 to 10% of Bi.sub.2O.sub.3, 0 to 10% of MgO, 0 to
8% of CaO, 0 to 10% of SrO, 0 to 10% of BaO, the content of BaO
being less than 13% by weight, 2 to 20% of Li.sub.2O, the content
of Li.sub.2O being over 2% by weight, 0 to 5% of Na.sub.2O, and 0
to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3 being 1% by
weight or less, and having a refractive index (nd) of 1.8 or more
and an Abbe's number (vd) of 35 or less.
9. An optical glass comprising, by mol %, 5 to 50% of
B.sub.2O.sub.3, 3 to 20% of SiO.sub.2, the content of SiO.sub.2
being less than 8% by weight, 5 to 40% of TiO.sub.2, 1 to 40% of
ZnO, 5 to 20% of La.sub.2O.sub.3, 0 to 10% of Gd.sub.2O.sub.3, 0 to
15% of Nb.sub.2O.sub.5, 0 to 10% of ZrO.sub.2, 0 to 5% of
Ta.sub.2O.sub.5, 0 to 10% of Bi.sub.2O.sub.3, 0 to 10% of MgO, 0 to
8% of CaO, 0 to 10% of SrO, 0 to 10% of BaO, the content of BaO
being less than 13% by weight, 0 to 20% of Li.sub.2O, 0 to 5% of
Na.sub.2O, and 0 to 1% of Sb.sub.2O.sub.3, and having a refractive
index (nd) of over 1.88 and an Abbe's number (vd) of 35 or
less.
10. The optical glass of claim 1, which contains 1 to 20 mol % of
Li.sub.2O.
11. The optical glass of claim 1, which contains over 27% by weight
of La.sub.2O.sub.3.
12. The optical glass of claim 1, which contains 16% by weight or
less of TiO.sub.2.
13. The optical glass of claim 1, which contains over 27% by weight
of La.sub.2O.sub.3 and 1 to 20 mol % of Li.sub.2O.
14. The optical glass of claim 1, wherein the content of CaO is
less than 5% by weight.
15. The optical glass of claim 1, which has a sag temperature of
670.degree. C. or lower.
16. The optical glass of claim 1, which is for use in precision
press-molding.
17. A precision press-molding preform formed of the optical glass
recited in claim 15.
18. A process for producing a precision press-molding preform
formed of a glass, which comprises separating a molten glass from a
flowing glass and shaping the molten glass into a preform during
cooling of the molten glass, wherein said glass is the optical
glass recited in claim 15.
19. An optical element formed of the optical glass recited in claim
1.
20. A process for producing an optical element, which comprises
heating a precision press-molding preform formed of a glass and
precision press-molding the preform with a press mold, wherein the
preform recited in claim 17 is used as the precision press-molding
preform.
21. A process for producing an optical element, which comprises
heating a precision press-molding preform formed of a glass and
precision press-molding the preform with a press mold, wherein a
preform produced by the process recited in claim 18 is used as the
precision press-molding preform.
22. The process for producing an optical element as recited in
claim 20, wherein the press mold and the preform are heated
together to precision press-mold the preform with the press
mold.
23. The process for producing an optical element as recited in
claim 20, wherein the press mold is pre-heated, and the preform is
pre-heated separately from the press mold and introduced into the
pre-heated press mold to precision press-mold the preform with the
press mold.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an optical glass, a
precision press-molding preform formed of the above optical glass,
a process for producing the preform, an optical element formed of
the above optical glass and a process for producing the
element.
TECHNICAL BACKGROUND
[0002] A high-refractivity low-dispersion glass is briskly in high
demand as a material for optical elements such as various lenses.
As a glass having such optical properties, there are known a heavy
tantalum flint glass TaSF17, and the like, which are described in
"Glass Composition Handbook" written by Hiroshi OGAWA and Shinei
OGAWA and issued by Japan Glass Product Society, 1991, page
106.
DISCLOSURE OF THE INVENTION
[0003] In recent years, with rapid widespread use of digital
cameras, video cameras and the like, glass lenses as parts therefor
are much in demand. On the other hand, with an increase in the
pixels of the cameras, optical elements such as glass lenses are
required to have high performances, and it is required to produce
optical elements formed of a glass having high form accuracy highly
productively.
[0004] A precision press-molding method is known as a method for
highly productively producing optical elements formed of a glass
having high form accuracy. Any one of conventional glasses such as
TaSF17 has a high glass transition temperature, and they are hence
not suitable for precision press-molding.
[0005] Overcoming the problems of the above conventional glasses,
the first object of the present invention is to provide an optical
glass that has a high refractive index and that has a low sag
temperature and a low-temperature softening property enabling
precision press-molding.
[0006] Further, the second and third objects of the present
invention are to provide a precision press-molding formed of the
optical glass that achieves the above object and to provide a
process for producing such a precision press-molding preform.
[0007] Furthermore, the fourth and fifth objects of the present
invention are to provide an optical element formed of the optical
glass that achieves the above object and a process for producing
such an optical element.
[0008] The present inventors have made diligent studies and as a
result have found that the above objects can be achieved by an
optical glass comprising B.sub.2O.sub.3, SiO.sub.2, TiO.sub.2, ZnO
and La.sub.2O.sub.3 which are co-present as essential components
and having contents of these essential components and other
optional components in predetermined ranges, and the present
invention has been accordingly completed.
[0009] That is, the present invention provides
[0010] (1) an optical glass comprising, by mol %,
[0011] 5 to 50% of B.sub.2O.sub.3,
[0012] 3 to 50% of SiO.sub.2,
[0013] 5 to 40% of TiO.sub.2,
[0014] 1 to 40% of ZnO,
[0015] 5 to 20% of La.sub.2O.sub.3,
[0016] 0 to 10% of Gd.sub.2O.sub.3,
[0017] 0 to 15% of Nb.sub.2O.sub.5,
[0018] 0 to 10% of ZrO.sub.2,
[0019] 0 to 5% of Ta.sub.2O.sub.5,
[0020] 0 to 10% of Bi.sub.2O.sub.3,
[0021] 0 to 10% of MgO,
[0022] 0 to 8% of CaO,
[0023] 0 to 10% of SrO,
[0024] 0 to 10% of BaO
[0025] provided that the total content of MgO, CaO, SrO and BaO is
15% or less,
[0026] 0 to 20% of Li.sub.2O, and
[0027] 0 to 5% of Na.sub.2O,
optionally containing Sb.sub.2O.sub.3 as a refining agent, and
having a refractive index (nd) of 1.8 or more and an Abbe's number
(vd) of 35 or less (to be referred to as "glass I"
hereinafter),
[0028] (2) an optical glass comprising, by mol %,
[0029] 5 to 50% of B.sub.2O.sub.3,
[0030] 3 to 50% of SiO.sub.2,
[0031] 5 to 40. % of TiO.sub.2,
[0032] 1 to 40% of ZnO,
[0033] 5 to 20% of La.sub.2O.sub.3,
[0034] 0 to 10% of Gd.sub.2O.sub.3,
[0035] 0 to 15% of Nb.sub.2O.sub.5,
[0036] 0 to 10% of ZrO.sub.2,
[0037] 0 to 5% of Ta.sub.2O.sub.5,
[0038] 0 to 10% of Bi.sub.2O.sub.3,
[0039] 0 to 10% of MgO,
[0040] 0 to 8% of CaO,
[0041] 0 to 10% of SrO,
[0042] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0043] provided that the total content of MgO, CaO, SrO and BaO is
15% by weight or less,
[0044] 0 to 20% of Li.sub.2O,
[0045] 0 to 5% of Na.sub.2O,
[0046] 0 to 1% of Sb.sub.2O.sub.3,
and having a refractive index (nd) of over 1.88 and an Abbe's
number (vd) of 35 or less (to be referred to as "glass 2"
hereinafter),
[0047] (3) an optical glass comprising, by mol %,
[0048] 5 to 50% of B.sub.2O.sub.3,
[0049] 3 to 50% of SiO.sub.2,
[0050] 5 to 40% of TiO.sub.2,
[0051] 1 to 40% of ZnO,
[0052] 5 to 20% of La.sub.2O.sub.3,
[0053] 0 to 10% of Gd.sub.2O.sub.3,
[0054] 0 to 15% of Nb.sub.2O.sub.5,
[0055] 0 to 10% of ZrO.sub.2,
[0056] 0 to 5% of Ta.sub.2O.sub.5,
[0057] 0 to 10% of Bi.sub.2O.sub.3,
[0058] 0 to 10% of MgO,
[0059] 0 to 8% of CaO,
[0060] 0 to 10% of SrO,
[0061] 0 to 10% of BaO,
[0062] provided that the total content of MgO, CaO, SrO and BaO is
less than 6% by weight,
[0063] 0 to 20% of Li.sub.2O,
[0064] 0 to 5% of Na.sub.2O, and
[0065] 0 to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3
being 1% by weight or less,
and having a refractive index of 1.8 or more and an Abbe's number
(vd) of 35 or less (to be referred to as hereinafter),
[0066] (4) an optical glass comprising, by mol %,
[0067] 25 to 50% of B.sub.2O.sub.3, the content of B.sub.2O.sub.3
being over 15% by weight,
[0068] 3 to 50% of SiO.sub.2,
[0069] 5 to 40% of TiO.sub.2,
[0070] 1 to 40% of ZnO,
[0071] 5 to 20% of La.sub.2O.sub.3,
[0072] 0 to 10% of Gd.sub.2O.sub.3,
[0073] 0 to 15% of Nb.sub.2O.sub.5,
[0074] 0 to 10% of ZrO.sub.2,
[0075] 0 to 5% of Ta.sub.2O.sub.5,
[0076] 0 to 10% of Bi.sub.2O.sub.3,
[0077] 0 to 10% of MgO,
[0078] 0 to 8% of CaO,
[0079] 0 to 10% of SrO,
[0080] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0081] provided that the total content of MgO, CaO, SrO and BaO is
less than 15% by weight,
[0082] 0 to 20% of Li.sub.2O,
[0083] 0 to 5% of Na.sub.2O, and
[0084] 0 to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3
being 1% by weight or less,
and having a refractive index (nd) of 1.8 or more and an Abbe's
number (vd) of 35 or less (to be referred to as "glass 4"
hereinafter),
[0085] (5) an optical glass comprising, by mol %,
[0086] 5 to 50% of B.sub.2O.sub.3,
[0087] 3 to 50% of SiO.sub.2,
[0088] 5 to 40% of TiO.sub.2,
[0089] 1 to 40% of ZnO,
[0090] 5 to 20% of La.sub.2O.sub.3,
[0091] 0 to 10% of Gd.sub.2O.sub.3,
[0092] 0 to 15% of Nb.sub.2O.sub.5,
[0093] 0 to 10% of ZrO.sub.2,
[0094] 0 to 5% of Ta.sub.2O.sub.5,
[0095] 0 to 10% of Bi.sub.2O.sub.3,
[0096] 0 to 10% of MgO,
[0097] 0 to 8% of CaO,
[0098] 0 to 10% of SrO,
[0099] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0100] provided that the total content of MgO, CaO, SrO and BaO is
less than 15% by weight,
[0101] 2 to 20% of Li.sub.2O, the content of Li.sub.2O being over
2% by weight,
[0102] 0 to 5% of Na.sub.2O, and
[0103] 0 to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3
being 1% by weight or less,
and having a refractive index (nd) of 1.8 or more and an Abbe's
number (vd) of 35 or less (to be referred to as "glass 5"
hereinafter),
[0104] (6) an optical glass comprising, by mol %,
[0105] 25 to 50% of B.sub.2O.sub.3, the content of B.sub.2O.sub.3
being over 17% by weight,
[0106] 3 to 50% of SiO.sub.2,
[0107] 5 to 40% of TiO.sub.2,
[0108] 1 to 40% of ZnO,
[0109] 5 to 20% of La.sub.2O.sub.3,
[0110] 0 to 10% of Gd.sub.2O.sub.3,
[0111] 0 to 15% of Nb.sub.2O.sub.5,
[0112] 0 to 10% of ZrO.sub.2,
[0113] 0 to 5% of Ta.sub.2O.sub.5,
[0114] 0 to 10% of Bi.sub.2O.sub.3,
[0115] 0 to 10% of MgO,
[0116] 0 to 8% of CaO,
[0117] 0 to 10% of SrO,
[0118] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0119] 2 to 20% of Li.sub.2O, the content of Li.sub.2O being over
2% by weight,
[0120] 0 to 5% of Na.sub.2O, and
[0121] 0 to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3
being 1% by weight or less,
and having a refractive index (nd) of 1.8 or more and an Abbe's
number (vd) of 35 or less (to be referred to as "glass 6"
hereinafter),
[0122] (7) an optical glass comprising, by mol %,
[0123] 5 to 50% of B.sub.2O.sub.3,
[0124] 3 to 50% of SiO.sub.2,
[0125] 12 to 40% of TiO.sub.2, the content of TiO.sub.2 being over
12% by weight but not more than 30% by weight,
[0126] 1 to 40% of ZnO,
[0127] 5 to 20% of La.sub.2O.sub.3,
[0128] 0 to 10% of Gd.sub.2O.sub.3,
[0129] 0 to 15% of Nb.sub.2O.sub.5,
[0130] 0 to 10% of ZrO.sub.2,
[0131] 0 to 5% of Ta.sub.2O.sub.5,
[0132] 0 to 10% of Bi.sub.2O.sub.3,
[0133] 0 to 10% of MgO,
[0134] 0 to 8% of CaO,
[0135] 0 to 10% of SrO,
[0136] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0137] provided that the total content of MgO, CaO, SrO and BaO is
less than 6% by weight,
[0138] 0 to 20% of Li.sub.2O,
[0139] 0 to 5% of Na.sub.2O, and
[0140] 0 to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3
being less than 1% by weight,
and having a refractive index (nd) of 1.8 or more and an Abbe's
number (vd) of 35 or less (to be referred to as "glass 7"
hereinafter),
[0141] (8) an optical glass comprising, by mol %,
[0142] 5 to 50% of B.sub.2O.sub.3,
[0143] 3 to 20% of SiO.sub.2, the content of SiO.sub.2 being less
than 8% by weight,
[0144] 5 to 40% of TiO.sub.2,
[0145] 1 to 40% of ZnO,
[0146] 5 to 20% of La.sub.2O.sub.3,
[0147] 0 to 10% of Gd.sub.2O.sub.3,
[0148] 0 to 15% of Nb.sub.2O.sub.5,
[0149] 0 to 10% of ZrO.sub.2,
[0150] 0 to 5% of Ta.sub.2O.sub.5,
[0151] 0 to 10% of Bi.sub.2O.sub.3,
[0152] 0 to 10% of MgO,
[0153] 0 to 8% of CaO,
[0154] 0 to 10% of SrO,
[0155] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0156] 2 to 20% of Li.sub.2O, the content of Li.sub.2O being over
2% by weight,
[0157] 0 to 5% of Na.sub.2O, and
[0158] 0 to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3
being 1% by weight or less,
and having a refractive index (nd) of 1.8 or more and an Abbe's
number (vd) of 35 or less (to be referred to as "glass 8"
hereinafter),
[0159] (9) an optical glass comprising, by mol %,
[0160] 5 to 50% of B.sub.2O.sub.3,
[0161] 3 to 20% of SiO.sub.2, the content of SiO.sub.2 being less
than 8% by weight,
[0162] 5 to 40% of TiO.sub.2,
[0163] 1 to 40% of ZnO,
[0164] 5 to 20% of La.sub.2O.sub.3,
[0165] 0 to 10% of Gd.sub.2O.sub.3,
[0166] 0 to 15% of Nb.sub.2O.sub.5,
[0167] 0 to 10% of ZrO.sub.2,
[0168] 0 to 5% of Ta.sub.2O.sub.5,
[0169] 0 to 10% of Bi.sub.2O.sub.3,
[0170] 0 to 10% of MgO,
[0171] 0 to 8% of CaO,
[0172] 0 to 10% of SrO,
[0173] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0174] 0 to 20% of Li.sub.2O,
[0175] 0 to 5% of Na.sub.2O, and
[0176] 0 to 1% of Sb.sub.2O.sub.3,
and having a refractive index (nd) of over 1.88 and an Abbe's
number (vd) of 35 or less (to be referred to as "glass 9"
hereinafter),
[0177] (10) the optical glass of any one of the above (1), (2),
(3), (4), (7) and (9), which contains 1 to 20 mol % of
Li.sub.2O,
[0178] (11) the optical glass of any one of the above (1), (3),
(4), (5), (6), (7) and (8), which contains over 27% by weight of
La.sub.2O.sub.3,
[0179] (12) the optical glass of any one of the above (1), (3),
(4), (5), (6), (7) and (8), which contains 16% by weight or less of
TiO.sub.2,
[0180] (13) the optical glass of any one of the above (1), (3), (4)
and (7), which contains over 27% by weight of La.sub.2O.sub.3 and 1
to 20 mol % of Li.sub.2O,
[0181] (14) the optical glass of any one of the above (1) to (12),
wherein the content of CaO is less than 5% by weight,
[0182] (15) the optical glass of any one of the above (1) to (13),
which has a sag temperature of 670.degree. C. or lower,
[0183] (16) the optical glass of any one of the above (1) to (14),
which is for use in precision press-molding,
[0184] (17) a precision press-molding preform formed of the optical
glass of the above (15),
[0185] (18) a process for producing a precision press-molding
preform formed of a glass, which comprises separating a molten
glass from a flowing glass and shaping the molten glass into a
preform during cooling of the molten glass,
[0186] wherein said glass is the optical glass of the above
(15),
[0187] (19) an optical element formed of the optical glass of any
one of the above (1) to (15),
[0188] (20) a process for producing an optical element, which
comprises heating a precision press-molding preform formed of a
glass and precision press-molding the preform with a press
mold,
[0189] wherein the preform of the above (17) is used as the
precision press-molding preform,
[0190] (21) a process for producing an optical element, which
comprises heating a precision press-molding preform formed of a
glass and precision press-molding the preform with a press
mold,
[0191] wherein a preform produced by the process of the above (18)
is used as the precision press-molding preform,
[0192] (22) the process for producing an optical element as recited
in the above (20) or (21), wherein the press mold and the preform
are heated together to precision press-mold the preform with the
press mold, and
[0193] (23) the process for producing an optical element as recited
in the above (20) or (21), wherein the press mold is pre-heated,
and the preform is pre-heated separately from the press mold and
introduced into the pre-heated press mold to precision press-mold
the preform with the press mold.
EFFECT OF THE INVENTION
[0194] According to the present invention, there can be obtained an
optical glass having a high refractive index and a low sag
temperature and having a low-temperature softening property that
enables precision press-molding, and there can be obtained a
precision press-molding preform formed of the above optical glass
and an optical element formed of the above optical glass.
BRIEF DESCRIPTION OF DRAWINGS
[0195] FIG. 1 is a schematic drawing of a precision press-molding
apparatus used in Example.
PREFERRED EMBODIMENTS OF THE INVENTION
[Optical Glass]
[0196] The optical glass of the present invention will be explained
first.
[0197] The optical glass of the present invention is a
high-refractivity glass having a refractive index (nd) of 1.8 or
more and an Abbe's number (vd) of 35 or less, and has a
low-temperature softening property suitable for precision
press-molding. Further, when a glass preform for precision
press-molding is shaped directly from a molten glass thereof, the
optical glass of the present invention does not easily undergo
crystallization and has excellent glass stability.
[0198] For realizing the above various properties, the optical
glass of the present invention contains B.sub.2O.sub.3 and
SiO.sub.2 as essential components for forming a glass network,
contains TiO.sub.2 and La.sub.2O.sub.3 as essential components for
increasing the refractive index and contains ZnO as an essential
component for imparting the optical glass with the low-temperature
softening property while maintaining the high refractivity. The
optical glass of the present invention has the above
B.sub.2O.sub.3--SiO.sub.2--TiO.sub.2--ZnO--La.sub.2O.sub.3
composition system, in which the contents of alkaline earth metal
oxides such as MgO, CaO, SrO and BaO are limited and the contents
of divalent components (MgO, CaO, SrO, BaO, ZnO, etc.) are arranged
to be occupied by the content of ZnO, and are preferably arranged
to be occupied by the contents of ZnO and Li.sub.2O.
[0199] Glass components for constituting the glasses 1 to 9
included in the optical glass of the present invention will be
explained in detail below. Percents (%) for the content of each
component and each of total contents thereof will stand for mol %
unless otherwise specified.
[0200] B.sub.2O.sub.3 is an essential component for the glass
network of the optical glass. When it is introduced to excess, the
refractive index (nd) is decreased. Therefore, in the glasses 1 to
3, 5 and 7 to 9, the content of B.sub.2O.sub.3 is 5 to 50%,
preferably 10 to 40%, more preferably 10 to 38%. In the glasses 4
and 6, the content of B.sub.2O.sub.3 is 25 to 50% (however, the
content thereof in the glass 4 is adjusted such that it is over 15%
by weight, and the content thereof in the glass 6 is adjusted such
that it is over 17% by weight).
[0201] SiO.sub.2 is an essential component that works to improve
the optical glass in stability. When it is introduced to excess,
the refractive index is decreased, and the sag temperature is
increased. Therefore, the content of SiO.sub.2 in the glasses 1 to
7 is 3 to 50%, preferably 5 to 20%, more preferably 5 to 18%, and
the content of SiO.sub.2 in the glasses 8 and 9 is 3 to 20%
(however, the content thereof is adjusted such that it is less than
8% by weight).
[0202] In addition, one of the objects of the optical glass of the
present invention is to have a low-temperature softening property
suitable for precision press-molding, and the effect of
B.sub.2O.sub.3 is superior to the effect of SiO.sub.2 in this
regard, so that it is preferred to adjust the contents of
B.sub.2O.sub.3 and SiO.sub.2 by weight ratio such that the content
of B.sub.2O.sub.3 is larger than the content of SiO.sub.2. It is
more preferred to adjust the weight ratio of the B.sub.2O.sub.3
content/SiO.sub.2 content to 1.2 or more, and it is still more
preferred to adjust the above weight ratio to 1.3 or more. The
above property is common to the glasses 1 to 9 included in the
optical glass of the present invention. B.sub.2O.sub.3 and
SiO.sub.2 are introduced so as to satisfy the above relationship,
and in this case, there can be also obtained a glass that is less
colored and that has high light transmissivity in the visible light
region.
[0203] TiO.sub.2 is an essential component for increasing the
refractive index. When it is introduced to excess, however, the
optical glass is degraded in stability and is colored. Therefore,
the content of TiO.sub.2 in the glasses 1 to 6, 8 and 9 is 5 to
40%, preferably 10 to 40%, more preferably 10 to 35%, still more
preferably 10 to 32%. The content of TiO.sub.2 in the glass 7 is 12
to 40% (however, the content thereof is adjusted such that it is
over 12% by weight but not more than 30% by weight). Further, the
content of TiO.sub.2 in the glasses 1 and 3 to 8 is preferably 16%
by weight or less.
[0204] ZnO is introduced such that the content thereof is 1% or
more, for imparting the optical glass with the low-temperature
softening property while maintaining the high refractivity. When it
is introduced to excess, the optical glass is degraded in
stability, so that the content of ZnO is limited to 40% or less.
The content of ZnO is preferably 3 to 35%, more preferably 5 to
32%.
[0205] La.sub.2O.sub.3 is introduced such that the content thereof
is 5% or more, for imparting the optical glass with the
high-refractivity and low-dispersion properties. When it is
introduced to excess, the optical glass is degraded in stability,
so that the content of La.sub.2O.sub.3 is limited to 20% or less.
The content of La.sub.2O.sub.3 is preferably 5 to 18%, more
preferably 5 to 17%. La.sub.2O.sub.3 is relatively a component that
increases the refractive index without coloring the optical glass.
For obtaining an optical glass having a refractive index (nd) of
1.8 or more, or the glasses 1 and 3 to 8 in particular, therefore,
the content thereof is preferably adjusted such that it is over 27%
by weight, and it is more preferably adjusted to 30% by weight or
more.
[0206] Gd.sub.2O.sub.3 is an optional component for imparting the
optical glass with high-refractivity low-dispersion properties.
When it is introduced to excess, the optical glass is degraded in
stability, so that the content of Gd.sub.2O.sub.3 is limited to 0
to 10%. The content of Gd.sub.2O.sub.3 is preferably 0 to 8%, more
preferably 0.5 to 5%.
[0207] Nb.sub.2O.sub.5 is an optional component for increasing the
refractive index. When it is introduced to excess, the optical
glass is degraded in stability, and the liquidus temperature is
increased, so that the content of Nb.sub.2O.sub.5 is limited to 0
to 15%. The content of Nb.sub.2O.sub.5 is preferably 1 to 10%, more
preferably 1 to 8%.
[0208] ZrO.sub.2 is an optional component that works to increase
the refractive index. However, when it is introduced to excess, the
optical glass is degraded in stability, and the liquidus
temperature is increased, so that the content of ZrO.sub.2 is
limited to 0 to 10%. The content of ZrO.sub.2 is preferably 1 to
8%, more preferably 1 to 5%.
[0209] Ta.sub.2O.sub.5 is an optional component that increases the
refractive index. However, when it is introduced to excess, the
optical glass is degraded in stability, so that the content of
Ta.sub.2O.sub.5 is limited to 0 to 5%. The content of
Ta.sub.2O.sub.5 is preferably 0 to 4%, more preferably 0 to 3%.
[0210] Bi.sub.2O.sub.3 is an optional component that increases the
refractive index and improves the optical glass in stability.
However, when it is introduced to excess, the optical glass is
colored, so that the content of Bi.sub.2O.sub.3 is limited to 0 to
10%. The content of Bi.sub.2O.sub.3 is preferably 0 to 6%, more
preferably 0 to 4%.
[0211] MgO is an optional component that works to improve the glass
in meltability. However, when it is introduced to excess, the glass
is degraded in refractivity and stability, so that the content of
MgO is limited to 0 to 10%. The content of MgO is preferably 0 to
8%, more preferably 0 to 6%.
[0212] CaO works to improve the glass in meltability and is an
optional component for adjusting optical constants. However, when
it is introduced to excess, the optical glass is degraded in
refractivity and stability, so that the content of CaO is limited
to 0 to 8%. The content of CaO is preferably less than 5% by
weight, more preferably 4% by weight or less, still more preferably
0 to 6%.
[0213] SrO is an optional component that works to improve the
optical glass in meltability. However, when it is introduced to
excess, the optical glass is degraded in refractivity and
stability, so that the content of SrO is limited to 0 to 10%. The
content of SrO is preferably 0 to 8%, more preferably 0 to 6%.
[0214] BaO is an optional component that works to increase the
refractive index. However, when it is introduced to excess, the
optical glass is degraded in stability, so that the content of BaO
is limited to 0 to 10%. The content of BaO is preferably 1 to 8%,
more preferably 1 to 6%. In the glasses 2 and 4 to 9, the content
of BaO is limited to less than 13% by weight.
[0215] The total content of MgO, CaO, SrO and BaO in the glass 1 is
limited to 15% or less, the above total content in each of the
glasses 2, 4 and 5 is limited to less than 15% by weight, and the
above total content in each of the glasses 3 and 7 is limited to
less than 6% by weight. These conditions are imposed on the optical
glass for the following reason. The total content to divalent
components such as the above alkaline earth metal oxides and ZnO is
limited, and of these divalent components, ZnO alone works to
decrease the sag temperature of the optical glass. Although the
total content is limited, therefore, a necessary amount of ZnO is
to be secured for maintaining or improving the stability of the
optical glass. In addition, in the glasses 1, 6, 8 and 9, the total
content of MgO, CaO, SrO and BaO is also preferably limited to less
than 15% by weight, more preferably, to 14% by weight or less.
[0216] Li.sub.2O is a component that highly effectively decreases
the glass transition temperature. However, when it is introduced to
excess, not only the refractive index is decreased, but also the
optical glass is degraded in stability. Therefore, the content of
Li.sub.2O in each of the glasses 1 to 4, 7 and 9 is limited to 0 to
20%, preferably, to 1 to 20%, more preferably, to 2 to 20%, still
more preferably 4 to 15%, and the content in each of the glasses 5,
6 and 8 is limited to 2 to 20% (however, the content of Li.sub.2O
is adjusted such that it is over 2% by weight). Further, in the
glasses 1, 3, 4 and 7, preferably, the content of La.sub.2O.sub.3
is adjusted such that it is over 27% by weight, and the content of
Li.sub.2O is adjusted to 1 to 20%.
[0217] Na.sub.2O is a component that works to improve the optical
glass in meltability. However, when it is introduced to excess, the
optical glass is degraded in refractivity and stability, so that
the content of Na.sub.2O is limited to 0 to 5%. The content of
Na.sub.2O is preferably 0 to 4%, more preferably 0 to 3%.
[0218] Alkali metal oxides such as Li.sub.2O, Na.sub.2O, K.sub.2O,
etc., all work to improve the optical glass in meltability.
However, Li.sub.2O, Na.sub.2O and K.sub.2O greatly differ in the
effect on the decreasing of the glass transition temperature, and
the above effect is the greatest when Li.sub.2O is introduced. In
addition to these, ZnO is also a component that has an effect on
the decreasing of the glass transition temperature as well. Both
ZnO and Li.sub.2O improve the low-temperature softening property
without decreasing the refractive index. In the optical glass of
the present invention, therefore, the method of introducing ZnO and
the alkali metal oxides can be largely classified into two
types.
[0219] In the first type, a decrease in the glass transition
temperature is attained mainly by ZnO, and the total content of
Li.sub.2O, Na.sub.2O and K.sub.2O is suppressed. The above total
content (Li.sub.2O+Na.sub.2O+K.sub.2O) is preferably less than 1.5%
by weight, more preferably 1% by weight or less. It can be said
that the first type constitutes preferred embodiments of the
glasses 1, 2, 3, 4, 7 and 9.
[0220] In the second type, ZnO is used as an essential component
and the content of Li.sub.2O is adjusted such that it is the
largest among the alkali metal oxides. An optical glass in which
the content of Li.sub.2O is greater than each of the content of
Na.sub.2O and the content of K.sub.2O in terms of weight ratio is
preferred, and an optical glass in which the content of Li.sub.2O
is greater than the total content of Na.sub.2O and K.sub.2O in
terms of weight ratio is more preferred. It can be said that the
second type constitutes preferred embodiments of the glasses 1, 2,
3, 4, 7 and 9 that contain Li.sub.2O (those in which the content of
Li.sub.2O is over 0% in terms of both weight percent and mol %) and
the glasses 5, 6 and 8.
[0221] Sb.sub.2O.sub.3 is a refining agent that can be added as
required. In the glasses 2 to 9, the amount of Sb.sub.2O.sub.3 is 0
to 1%. In the glasses 3 to 8, the amount of Sb.sub.2O.sub.3 is
limited to 1% by weight or less for preventing damage caused on the
molding surface of a press mold by oxidation during precision
press-molding. In the glasses 1, 2 and 9, it is as well preferred
to limit the amount of Sb.sub.2O.sub.3 to 1% by weight or less.
[0222] For attaining more preferable properties with regard to
various properties of the above optical glass, it is preferred to
adjust the total amount of the total content of the above glass
components and the amount of Sb.sub.2O.sub.3 to at least 98%, it is
more preferred to adjust the above total amount such that it is
over 99%, and it is still more preferred to adjust the above total
amount to 100%.
[0223] In the optical glass of the present invention, WO.sub.3 is
one of components whose introduction is undesirable. That is
because it is considered that the introduction of WO.sub.3 degrades
the optical glass in stability.
[0224] Further, it is also desirable not to introduce components
that cause environmentally detrimental effects such as PbO and
As.sub.2O.sub.3 into the optical glass of the present invention.
These components are also undesirable for precision press-molding.
In a glass containing PbO, PbO on the glass surface is reduced in a
non-oxidizing atmosphere (particularly, a reducing atmosphere
containing a reducing gas such as hydrogen, or the like) during
precision press-molding to be precipitated on the glass surface,
and the precipitate adheres to a press mold to cause the surface
accuracy of a precision press-molded product to decrease.
As.sub.2O.sub.3 oxidizes the molding surface of a press mold to
cause the molding surface to be damaged.
[0225] Further, except for a case where the optical glass is
imparted with the function to absorb light in a specific wavelength
region by coloring it, it is desirable not to introduce components
such as Cu, Fe, Cd, Cr, Ni, Co, and the like.
[0226] F can be introduced so long as its amount is small. However,
when a precision press-molding is shaped directly from a molten
glass, F is volatilized from the glass surface to cause defects
such as striae, etc., or to cause a variation in optical properties
such as a refractive index, etc., in some cases so that
non-introduction of F is preferred.
[0227] Compositions of the glasses 1 to 9 included in the optical
glass of the present invention will be explained below.
[0228] (Glass 1)
[0229] The glass 1 is an optical glass comprising, by mol %,
[0230] 5 to 50% of B.sub.2O.sub.3,
[0231] 3 to 50% of SiO.sub.2,
[0232] 5 to 40% of TiO.sub.2,
[0233] 1 to 40% of ZnO,
[0234] 5 to 20% of La.sub.2O.sub.3,
[0235] 0 to 10% of Gd.sub.2O.sub.3,
[0236] 0 to 15% of Nb.sub.2O.sub.5,
[0237] 0 to 10% of ZrO.sub.2,
[0238] 0 to 5% of Ta.sub.2O.sub.5,
[0239] 0 to 10% of Bi.sub.2O.sub.3,
[0240] 0 to 10% of MgO,
[0241] 0 to 8% of CaO,
[0242] 0 to 10% of SrO,
[0243] 0 to 10% of BaO
[0244] provided that the total content of MgO, CaO, SrO and BaO is
15% or less,
[0245] 0 to 20% of Li.sub.2O, and
[0246] 0 to 5% of Na.sub.2O,
optionally containing Sb.sub.2O.sub.3 as a refining agent, and
having a refractive index (nd) of 1.8 or more and an Abbe's number
(vd) of 35 or less.
[0247] In the glass 1, the contents of divalent components such as
MgO, CaO, SrO, BaO and ZnO are brought to ranges where the glass
stability is maintained, and the contents of the divalent
components are arranged to be occupied mainly by ZnO that greatly
contributes to an improvement in the low-temperature softening
property. Therefore, the total content of MgO, CaO, SrO and BaO is
limited to 15% or less, preferably, to 13% or less, and the
contents of MgO and CaO which do not contribute to high
refractivity among the alkaline earth metal oxides are limited to
10% or less and 8% or less, respectively. A proper amount of
Sb.sub.2O.sub.3 is incorporated into the above glass composition
not as a glass component but as a refining agent. The amount of
Sb.sub.2O.sub.3 can be 1% or less as a standard amount, and the
amount of Sb.sub.2O.sub.3 is preferably 0 to 1% by weight.
[0248] (Glass 2)
[0249] The glass 2 is an optical glass comprising, by mol %,
[0250] 5 to 50% of B.sub.2O.sub.3,
[0251] 3 to 50% of SiO.sub.2,
[0252] 5 to 40% of TiO.sub.2,
[0253] 1 to 40% of ZnO,
[0254] 5 to 20% of La.sub.2O.sub.3,
[0255] 0 to 10% of Gd.sub.2O.sub.3,
[0256] 0 to 15% of Nb.sub.2O.sub.5,
[0257] 0 to 10% of ZrO.sub.2,
[0258] 0 to 5% of Ta.sub.2O.sub.5,
[0259] 0 to 10% of Bi.sub.2O.sub.3,
[0260] 0 to 10% of MgO,
[0261] 0 to 8% of CaO,
[0262] 0 to 10% of SrO,
[0263] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0264] provided that the total content of MgO, CaO, SrO and BaO is
15% by weight or less,
[0265] 0 to 20% of Li.sub.2O,
[0266] 0 to 5% of Na.sub.2O,
[0267] 0 to 1% of Sb.sub.2O.sub.3,
and having a refractive index (nd) of over 1.88 and an Abbe's
number (vd) of 35 or less.
[0268] In the glass 2, the total content of MgO, CaO, SrO and BaO
is as well limited to less than 15% by weight, preferably to 14% by
weight or less, and the contents of MgO and CaO are limited to 10%
or less and 8% or less, respectively, for realizing a
high-refractivity glass having a refractive index (nd) of over
1.88, preferably 1.89 or more, while maintaining the glass
stability and imparting the glass with the low-temperature
softening property. BaO is a component that contributes to higher
refractivity among the alkaline earth metal oxides. However, for
realizing the low-temperature softening property while maintaining
the glass stability, the content of BaO is limited to less than 13%
by weight, and the content of BaO is preferably 12.5% by weight or
less, more preferably 12% by weight or less.
[0269] (Glass 3)
[0270] The glass 3 is an optical glass comprising, by mol %,
[0271] 5 to 50% of B.sub.2O.sub.3,
[0272] 3 to 50% of SiO.sub.2,
[0273] 5 to 40% of TiO.sub.2,
[0274] 1 to 40% of ZnO,
[0275] 5 to 20% of La.sub.2O.sub.3,
[0276] 0 to 10% of Gd.sub.2O.sub.3,
[0277] 0 to 15% of Nb.sub.2O.sub.5,
[0278] 0 to 10% of ZrO.sub.2,
[0279] 0 to 5% of Ta.sub.2O.sub.5,
[0280] 0 to 10% of Bi.sub.2O.sub.3,
[0281] 0 to 10% of MgO,
[0282] 0 to 8% of CaO,
[0283] 0 to 10% of SrO,
[0284] 0 to 10% of BaO,
[0285] provided that the total content of MgO, CaO, SrO and BaO is
less than 6% by weight,
[0286] 0 to 20% of Li.sub.2O,
[0287] 0 to 5% of Na.sub.2O, and
[0288] 0 to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3
being 1% by weight or less,
and having a refractive index of 1.8 or more and an Abbe's number
(vd) of 35 or less.
[0289] In the glass 3, the total content of MgO, CaO, SrO and BaO
is as well limited to less than 6% by weight, preferably to 5% by
weight or less, and the contents of MgO and CaO are also limited to
10% or less and 8% or less, respectively, for realizing a
high-refractivity glass having a refractive index (nd) of 1.8 or
more while maintaining the glass stability and imparting the glass
with the low-temperature softening property. Further, the amount of
Sb.sub.2O.sub.3 which is optionally added as a refining agent is
limited to 1% by weight or less for preventing damage on the
molding surface of a press mold by oxidation during precision
press-molding.
[0290] (Glass 4)
[0291] The glass 4 is an optical glass comprising, by mol %,
[0292] 25 to 50% of B.sub.2O.sub.3, the content of B.sub.2O.sub.3
being over 15% by weight,
[0293] 3 to 50% of SiO.sub.2,
[0294] 5 to 40% of TiO.sub.2,
[0295] 1 to 40% of ZnO,
[0296] 5 to 20% of La.sub.2O.sub.3,
[0297] 0 to 10% of Gd.sub.2O.sub.3,
[0298] 0 to 15% of Nb.sub.2O.sub.5,
[0299] 0 to 10% of ZrO.sub.2,
[0300] 0 to 5% of Ta.sub.2O.sub.5,
[0301] 0 to 10% of Bi.sub.2O.sub.3,
[0302] 0 to 10% of MgO,
[0303] 0 to 8% of CaO,
[0304] 0 to 10% of SrO,
[0305] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0306] provided that the total content of MgO, CaO, SrO and BaO is
less than 15% by weight,
[0307] 0 to 20% of Li.sub.2O,
[0308] 0 to 5% of Na.sub.2O, and
[0309] 0 to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3
being 1% by weight or less,
and having a refractive index (nd) of 1.8 or more and an Abbe's
number (vd) of 35 or less.
[0310] In the glass 4, the content of B.sub.2O.sub.3 as a
network-forming component is limited to 25 to 50% (however, the
content thereof is over 15% by weight) for improving the glass in
stability. The content of B.sub.2O.sub.3 is preferably 28 to 50%
(however, the content thereof is 15.5% by weight or more), more
preferably 30 to 47% (however, the content thereof is 16% by weight
or more). The upper limit of the content of B.sub.2O.sub.3 is
particularly preferably 40%. Further, for realizing a
high-refractivity glass maintaining glass stability, having the
low-temperature softening property and a refractive index (nd) of
1.8 or more, the total content of MgO, CaO, SrO and BaO is limited
to less than 15% by weight, preferably to 14% by weight of less,
the content of MgO is limited to 10% or less, the content of CaO is
limited to 8% or less, and Zno is used as an essential component.
BaO is a component that contributes to higher refractivity among
the alkaline earth metal oxides. However, for realizing the
low-temperature softening property while maintaining the glass
stability, the content of BaO is limited to less than 13% by
weight, and the content of BaO is preferably 12.5% by weight or
less, more preferably 12% by weight or less. Further, the amount of
Sb.sub.2O.sub.3 which is optionally added as a refining agent is
limited to 1% by weight or less for preventing damage on the
molding surface of a press mold by oxidation during precision
press-molding.
[0311] (Glass 5)
[0312] The glass 5 is an optical glass comprising, by mol %,
[0313] 5 to 50% of B.sub.2O.sub.3,
[0314] 3 to 50% of SiO.sub.2,
[0315] 5 to 40% of TiO.sub.2,
[0316] 1 to 40% of ZnO,
[0317] 5 to 20% of La.sub.2O.sub.3,
[0318] 0 to 10% of Gd.sub.2O.sub.3,
[0319] 0 to 15% of Nb.sub.2O.sub.5,
[0320] 0 to 10% of ZrO.sub.2,
[0321] 0 to 5% of Ta.sub.2O.sub.5,
[0322] 0 to 10% of Bi.sub.2O.sub.3,
[0323] 0 to 10% of MgO,
[0324] 0 to 8% of CaO,
[0325] 0 to 10% of SrO,
[0326] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0327] provided that the total content of MgO, CaO, SrO and BaO is
less than 15% by weight,
[0328] 2 to 20% of Li.sub.2O, the content of Li.sub.2O being over
2% by weight,
[0329] 0 to 5% of Na.sub.2O, and
[0330] 0 to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3
being 1% by weight or less,
and having a refractive index (nd) of 1.8 or more and an Abbe's
number (vd) of 35 or less.
[0331] In the glass 5, for realizing a high-refractivity glass
maintaining glass stability, having the low-temperature softening
property and a refractive index (nd) of 1.8 or more, the total
content of MgO, CaO, SrO and BaO is as well limited to less than
15% by weight, preferably to 14% by weight or less, and the
contents of MgO and CaO are limited to 10% or less and 8% or less,
respectively. BaO is a component that contributes to higher
refractivity among the alkaline earth metal oxides. However, for
realizing the low-temperature softening property while maintaining
the glass stability, the content of BaO is limited to less than 13%
by weight, and the content of BaO is preferably 12.5% by weight or
less, more preferably 12% by weight or less. In the glass 5, 2 to
20% (however, over 2% by weight) of Li.sub.2O is introduced from
the point of view of realizing a glass more suitable for precision
press-molding by decreasing the sag temperature of the glass while
maintaining high refractivity. Further, the amount of
Sb.sub.2O.sub.3 which is optionally added as a refining agent is
limited to 1% by weight or less for preventing damage on the
molding surface of a press mold by oxidation during precision
press-molding.
[0332] (Glass 6)
[0333] The glass 6 is an optical glass comprising, by mol %,
[0334] 25 to 50% of B.sub.2O.sub.3, the content of B.sub.2O.sub.3
being over 17 % by weight,
[0335] 3 to 50% of SiO.sub.2,
[0336] 5 to 40% of TiO.sub.2,
[0337] 1 to 40% of ZnO,
[0338] 5 to 20% of La.sub.2O.sub.3,
[0339] 0 to 10% of Gd.sub.2O.sub.3,
[0340] 0 to 15% of Nb.sub.2O.sub.5,
[0341] 0 to 10% of ZrO.sub.2,
[0342] 0 to 5% of Ta.sub.2O.sub.5,
[0343] 0 to 10% of Bi.sub.2O.sub.3,
[0344] 0 to 10% of MgO,
[0345] 0 to 8% of CaO,
[0346] 0 to 10% of SrO,
[0347] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0348] 2 to 20% of Li.sub.2O, the content of Li.sub.2O being over
2% by weight,
[0349] 0 to 5% of Na.sub.2O, and
[0350] 0 to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3
being 1% by weight or less,
and having a refractive index (nd) of 1.8 or more and an Abbe's
number (vd) of 35 or less.
[0351] In the glass 6, the content of B.sub.2O.sub.3 as a
network-forming component is limited to 25 to 50% (however, over
17% by weight) for improving the glass in stability. The content of
B.sub.2O.sub.3 is preferably 28 to 50% (however, the content
thereof of is 17.5% by weight or more), more preferably 30 to 50%
(however, the content thereof is 18% by weight or more). The upper
limit of the content of B.sub.2O.sub.3 is particularly preferably
40%. Further, for realizing a high-refractivity glass having a
refractive index (nd) of 1.8 or more while maintaining the glass
stability and imparting the glass with the low-temperature
softening property, the contents of MgO and CaO are limited to 10%
or less and 8% or less, respectively, and ZnO is used as an
essential component. BaO is a component that contributes to higher
refractivity among the alkaline earth metal oxides. However, for
realizing the low-temperature softening property while maintaining
the glass stability, the content of BaO is limited to less than 13%
by weight, and the content of BaO is preferably 12.5% by weight or
less, more preferably 12% by weight or less. From the point of view
of realizing a glass more suitable for precision press-molding by
decreasing the sag temperature of the glass while maintaining high
refractivity, 2 to 20% (however, over 2% by weight) of Li.sub.2O is
introduced, and preferably, 2.5% by weight or more of Li.sub.2O is
introduced. Further, the amount of Sb.sub.2O.sub.3 which is
optionally added as a refining agent is limited to 1% by weight or
less for preventing damage on the molding surface of a press mold
by oxidation during precision press-molding.
[0352] (Glass 7)
[0353] The glass 7 is an optical glass comprising, by mol %,
[0354] 5 to 50% of B.sub.2O.sub.3,
[0355] 3 to 50% of SiO.sub.2,
[0356] 12 to 40% of TiO.sub.2, the content of TiO.sub.2 being over
12% by weight but not more than 30% by weight,
[0357] 1 to 40% of ZnO,
[0358] 5 to 20% of La.sub.2O.sub.3,
[0359] 0 to 10% of Gd.sub.2O.sub.3,
[0360] 0 to 15% of Nb.sub.2O.sub.5,
[0361] 0 to 10% of ZrO.sub.2,
[0362] 0 to 5% of Ta.sub.2O.sub.5,
[0363] 0 to 10% of Bi.sub.2O.sub.3,
[0364] 0 to 10% of MgO,
[0365] 0 to 8% of Cao,
[0366] 0 to 10% of SrO,
[0367] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0368] provided that the total content of MgO, CaO, SrO and BaO is
less than 6% by weight,
[0369] 0 to 20% of Li.sub.2O,
[0370] 0 to 5% of Na.sub.2O, and
[0371] 0 to 1% of Sb.sub.2O.sub.3, the amount of Sb.sub.2O.sub.3
being less than 1% by weight,
and having a refractive index (nd) of 1.8 or more and an Abbe's
number (vd) of 35 or less.
[0372] In the glass 7, the content of TiO.sub.2 as a component for
increasing the refractive index is limited to 12 to 40% (however,
the content thereof is limited to over 12% by weight but not more
than 30% by weight), preferably, to 12.5% by weight or more but not
more than 30% by weight, more preferably, to 13% by weight or more
but not more than 30% by weight. The lower limit of the content of
TiO.sub.2 by mol % is preferably 12%. Further, for realizing a
high-refractivity glass having a refractive index (nd) of 1.8 or
more while maintaining the glass stability and imparting the glass
with the low-temperature softening property, the total content of
MgO, CaO, SrO and BaO is limited to less than 6% by weight,
preferably, to 5.5% by weight or less, the contents of MgO and CaO
are limited to 10% or less and 8% or less, respectively, and ZnO is
used as an essential component. BaO is a component that contributes
to higher refractivity among the alkaline earth metal oxides.
However, for realizing the low-temperature softening property while
maintaining the glass stability, the content of BaO is limited to
less than 13% by weight, and the content of BaO is preferably 12.5%
by weight or less, more preferably 12% by weight or less. From the
point of view of realizing a glass more suitable for precision
press-molding by decreasing the sag temperature of the glass while
maintaining high refractivity, 2 to 20% (however, over 2 % by
weight) of Li.sub.2O is introduced. Further, the amount of
Sb.sub.2O.sub.3 which is optionally added as a refining agent is
limited to 1% by weight or less for preventing damage on the
molding surface of a press mold by oxidation during precision
press-molding.
[0373] [Glass 8]
[0374] The glass 8 is an optical glass comprising, by mol %,
[0375] 5 to 50% of B.sub.2O.sub.3,
[0376] 3 to 20% of SiO.sub.2, the content of SiO.sub.2 being less
than 8% by weight,
[0377] 5 to 40% of TiO.sub.2,
[0378] 1 to 40% of ZnO,
[0379] 5 to 20% of La.sub.2O.sub.3,
[0380] 0 to 10% of Gd.sub.2O.sub.3,
[0381] 0 to 15% of Nb.sub.2O.sub.5,
[0382] 0 to 10% of ZrO.sub.2,
[0383] 0 to 5% of Ta.sub.2O.sub.5,
[0384] 0 to 10% of Bi.sub.2O.sub.3,
[0385] 0 to 10% of MgO,
[0386] 0 to 8% of CaO,
[0387] 0 to 10% of SrO,
[0388] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0389] 2 to 20% of Li.sub.2O, the content of Li.sub.2O being over
2% by weight,
[0390] 0 to 5% of Na.sub.2O, and
[0391] 0 to 1% of Sb.sub.2O.sub.3, the content of Sb.sub.2O.sub.3
being 1% by weight or less,
and having a refractive index (nd) of 1.8 or more and an Abbe's
number (vd) of 35 or less.
[0392] In the glass 8, the content of SiO.sub.2 is adjusted to 3 to
20% (however, the content thereof is less than 8% by weight) for
increasing the refractive index. However, the content of SiO.sub.2
is preferably 3 to 18% (however, the content thereof is 7.5% by
weight or less), more preferably 5 to 16% (however, the content
thereof is 7% by weight or less). Further, for realizing a
high-refractivity glass having a refractive index (nd) of 1.8 or
more while maintaining the glass stability and imparting the glass
with the low-temperature softening property, the contents of MgO
and CaO are limited to 10% or less and 8% or less, respectively,
and ZnO is used as an essential component. BaO is a component that
contributes to higher refractivity among the alkaline earth metal
oxides. However, for realizing the low-temperature softening
property while maintaining the glass stability, the content of BaO
is limited to less than 13% by weight, and the content of BaO is
preferably 12.5% by weight or less, more preferably 12% by weight
or less. From the point of view of realizing a glass more suitable
for precision press-molding by decreasing the sag temperature of
the glass while maintaining high refractivity, 2 to 20% (however,
over 2% by weight) of Li.sub.2O is introduced. Further, the amount
of Sb.sub.2O.sub.3 which is optionally added as a refining agent is
limited to 1% by weight or less for preventing damage on the
molding surface of a press mold by oxidation during precision
press-molding.
[0393] (Glass 9)
[0394] The glass 9 is an optical glass comprising, by mol %,
[0395] 5 to 50% of B.sub.2O.sub.3,
[0396] 3 to 20% of SiO.sub.2, the content of SiO.sub.2 being less
than 8% by weight,
[0397] 5 to 40% of TiO.sub.2,
[0398] 1 to 40% of ZnO,
[0399] 5 to 20% of La.sub.2O.sub.3,
[0400] 0 to 10% of Gd.sub.2O.sub.3,
[0401] 0 to 15% of Nb.sub.2O.sub.5,
[0402] 0 to 10% of ZrO.sub.2,
[0403] 0 to 5% of Ta.sub.2O.sub.5,
[0404] 0 to 10% of Bi.sub.2O.sub.3,
[0405] 0 to 10% of MgO,
[0406] 0 to 8% of CaO,
[0407] 0 to 10% of SrO,
[0408] 0 to 10% of BaO, the content of BaO being less than 13% by
weight,
[0409] 0 to 20% of Li.sub.2O,
[0410] 0 to 5% of Na.sub.2O, and
[0411] 0 to 1% of Sb.sub.2O.sub.3,
and having a refractive index (nd) of over 1.88 and an Abbe's
number (vd) of 35 or less.
[0412] In the glass 9, for realizing a high-refractivity glass
having a refractive index (nd) of over 1.88, preferably 1.89 or
more, the content of SiO.sub.2 is adjusted to 3 to 20% (however,
the content thereof is less than 8% by weight), and the content of
SiO.sub.2 is preferably 3 to 18% (however, the content thereof is
7.5% by weight or less), more preferably 5 to 16%. The lower limit
of the content of SiO.sub.2 is preferably 5%. Further, for
maintaining the glass stability and imparting the glass with the
low-temperature softening property, the contents of MgO and CaO are
limited to 10% or less and 8% or less, respectively. BaO is a
component that contributes to higher refractivity among the
alkaline earth metal oxides. However, for realizing the
low-temperature softening property while maintaining the glass
stability, the content of BaO is limited to less than 13% by
weight, and the content of BaO is preferably 12.5% by weight or
less, more preferably 12% by weight or less.
[0413] In the glasses 1 to 4, 7 and 9 in which Li.sub.2O is an
optional component, preferably, Li.sub.2O is caused to be
co-present with the other essential components for further
decreasing the sag temperature and more improving the
low-temperature softening property. In this case, the content of
Li.sub.2O is preferably 1 to 20%, more preferably 2 to 20%.
[0414] The glasses 1 to 9 will be explained with regard to their
properties.
[0415] The glasses 1 and 3 to 8 have a refractive index (nd) of 1.8
or more, preferably 1.82 or more, more preferably over 1.88, and
the glasses 2 and 9 have a refractive index (nd) of over 1.88. The
glasses 1 to 9 still more preferably have a refractive index (nd)
in the range of 1.89 and more, more preferably in the range of 1.9
and more. The upper limit of the refractive index (nd) is not
specially limited. However, when the refractive index (nd) is
increased to excess, other properties may be impaired, so that it
is preferred to use a refractive index (nd) of 2.2 or less as a
standard value of the upper limit for preparing each glass
composition.
[0416] The glasses 1 to 9 have the above refractive index (nd) and
also exhibit dispersion properties represented by an Abbe's number
(vd) of 35 or less, preferably less than 35, more preferably 34 or
less. The lower limit of the Abbe's number (vd) is not specially
limited. However, when the Abbe's number (vd) is decreased to
excess, other properties may be impaired, so that it is preferred
to use an Abbe's number (vd) of 23 or more as a standard value of
the lower limit for preparing each glass composition.
[0417] The above glasses 1 to 9 have a low-temperature softening
property suitable for precision press-molding, which is represented
by a sag temperature (Ts) of 670.degree. C. or lower, preferably
650.degree. C. or lower. Each glass has a glass transition
temperature (Tg) of 620.degree. C. or lower, preferably 600.degree.
C. or lower. The lower limit of each of the sag temperature (Ts)
and the glass transition temperature (Tg) is not specially limited.
However, these temperatures are decreased to excess, other
properties may be impaired, so that it is preferred to use a sag
temperature (Ts) of 450.degree. C. or higher and a glass transition
temperature (Tg) of 400.degree. C. or higher as a standard value of
the lower limit for preparing each glass composition.
[0418] The optical glass of the present invention can be produced
by preparing oxides, hydroxides, carbonates, nitrates, etc., which
correspond to glass components, as glass raw materials, weighing
the raw materials so as to obtain an intended glass composition,
fully mixing the raw materials, then, heating, melting, refining
and homogenizing the raw materials in a melting vessel such as a
platinum vessel, or the like, to obtain a molten glass and causing
the molten glass to flow out and shaping it. Each of the above
procedures can be carried out in atmosphere, and the method for
producing the optical glass can be selected from known methods.
[Precision Press-Molding Preform and Process for Producing the
Preform]
[0419] The precision press-molding preform of the present invention
will be explained below.
[0420] The precision press-molding preform (to be referred to as
"preform" hereinafter) of the present invention is
characteristically formed of the optical glass of the present
invention.
[0421] The preform is a glass shaped material having a weight
equivalent to the weight of a precision press-molded product. The
preform is shaped in a proper form depending upon the precision
press-molded product, and examples of the form include the form of
a sphere, the form of a spheroid, and the like. The preform is
heated so as to have a viscosity enabling press-molding before its
press-molding.
[0422] The form of the preform including the above form of a
spheroid is preferably a form having one rotational-symmetry axis.
The above form having one rotational-symmetry axis includes a form
having a smooth contour free of a corner and a dent in a cross
section including the above rotational-symmetry axis, such as a
form whose contour is an ellipse whose minor axis is aligned with
the rotational-symmetry axis in the above cross section. Further,
the following form is preferred. When one of angles formed by a
line connecting any point on the contour of a preform in the above
cross section to the center of the gravity of the preform on the
axis of revolution symmetry and a tangent line contacting the
contour on the above point on the contour is taken as .theta., and
when the above point starts at the axis of revolution symmetry and
moves along the contour, the angle .theta. monotonously increases
from 90.degree., then decreases monotonously and then increases
monotonously to come to be 90.degree. at the other point where the
contour crosses the axis of revolution symmetry.
[0423] The above preform may have a thin film such as a mold
release film on its surface as required. Examples of the mold
release film include a carbon-containing film, a self-organizing
film, and the like. The above preform can provide an optical
element having predetermined optical constants by
press-molding.
[0424] The process for producing a preform, provided by the present
invention, will be explained below.
[0425] The process for producing a preform, provided by the present
invention, is a process for producing a precision press-molding
preform formed of a glass, which comprises separating a molten
glass from a flowing glass and shaping the molten glass into a
preform during cooling of the molten glass,
[0426] wherein said glass is the optical glass of the present
invention.
[0427] In the above production process, the preform is shaped in a
step where the glass in a molten state is cooled, and the glass can
be brought into a state where a shaped glass can be used as a
preform without machining after solidification of the glass, so
that the above production process has an advantage that machining
processes such as cutting, grinding, polishing, etc., are not
required. In the process for producing a preform, provided by the
present invention, further, a preform having a smooth surface can
be shaped, and the entire surface of the preform is a surface
formed by solidification of the glass in a molten state, so that
the surface is smooth and free of fine scratches caused by grinding
or latent scratches. On the other hand, in the process for
producing a preform, provided by the present invention, a preform
free of defects such as devitrification, etc., is shaped directly
from a molten glass. The glass used in the process is therefore
required to have such particularly excellent stability that the
glass does not undergo crystallization from a step in which the
glass is caused to flow out to a step in which the glass is shaped
into the preform. Having the above excellent stability, the optical
glass of the present invention can be suitably used in the process
for producing a preform, provided by the present invention.
[0428] Desirably, the preform is free of a cutting mark called a
shear mark on its surface. The shear mark occurs when a molten
glass that is flowing out is cut with a cutting blade. When the
shear mark remains in a stage where the preform has been molded
into a precision press-molded product, a portion of such a shear
mark constitutes a defect. It is therefore preferred to preclude
the shear mark in a preform stage. The method for separating a
molten glass using no cutting blade so as not to cause any shear
mark includes a method in which a molten glass is caused to drop
from a flow pipe and a method in which the forward end of a molten
glass flow flowing out of a flow pipe is supported and the support
is removed at a time when a molten glass gob having a predetermined
weight can be separated (to be referred to as "descent cutting
method" hereinafter). In the descent cutting method, a glass is
separated at a narrow portion generated between the forward end
side and the flow pipe side of the molten glass flow, whereby a
molten glass gob having a predetermined weight can be obtained.
[0429] Then, the thus-obtained molten glass gob is shaped into a
form suitable for press molding while it is in a softened state,
whereby a preform can be obtained. As a method for shaping the
above molten glass gob into a preform, it is preferred to employ a
method in which the preform is shaped while the separated glass gob
having a predetermined weight is caused to float, or caused to
float mostly so as to decrease its contact to a shaping mold, by
applying a gas pressure to the molten glass gob (to be referred to
as "float shaping." hereinafter). The floating shaping can decrease
a contact of the glass having a high temperature to the shaping
mold, so that the cracking of a preform can be prevented. Further,
a preform of which the entire surface is formed of a free surface
can be shaped.
[0430] In addition to the above method, a preform can be produced
by a method in which a glass block is formed from a molten glass
and then processed. A preform formed of the optical glass of the
present invention can be also produced by this method. In the above
method, there may be employed a constitution in which a glass block
formed of the optical glass of the present invention is formed by
casting a molten glass into a frame and the glass block is machined
to obtain a preform having a predetermined weight. Before the
machining, preferably, strain-removing treatment is fully carried
out by annealing the glass for preventing cracking of the
glass.
[0431] In any one of the above methods, high quality preforms free
of defects such as devitrification, striae, scratches, a cracking,
etc., can be shaped by the use of the optical glass of the present
invention in a molten state, since the optical glass of the present
invention has high stability.
[Optical Element and Process for Producing the Same]
[0432] The optical element of the present invention will be
explained below.
[0433] The optical element of the present invention is
characteristically formed of the above optical glass of the present
invention. Due to the optical properties that the optical glass of
the present invention has, various optical elements can be obtained
as optical elements of the present invention. Examples of the
optical elements include various lenses such as a spherical lens,
an aspherical lens, a microlens, etc., a diffraction grating, a
lens with a diffraction grating, a lens array, a prism, and the
like.
[0434] The optical element of the present invention may be provided
with optical thin films such as an anti-reflection film, a total
reflection film, a partial reflection film, a film having spectral
characteristics, and the like.
[0435] The process for producing an optical element, provided by
the present invention, will be explained below.
[0436] The process for producing an optical element, provided by
the present invention, comprises heating a precision press-molding
preform formed of a glass and precision press-molding the preform
with a press mold,
[0437] wherein the above preform is used as the precision
press-molding preform.
[0438] The process for producing an optical element, provided by
the present invention, comprises heating a precision press-molding
preform formed of a glass and precision press-molding the preform
with a press mold,
[0439] wherein a preform produced by the above production process
is used as the precision press-molding preform.
[0440] The above precision press-molding is also called mold optics
molding and is known in the filed of art of the present invention.
In an optical element, a surface that transmits, refracts,
diffracts or reflects light is referred to as an optical-function
surface (for example, the lens surface of a lens, such as the
aspherical surface of an aspherical lens or the spherical surface
of a spherical lens corresponds to the optical-function surface).
According to the precision press-molding, the form of molding
surface of a press mold is precisely transferred to a glass, so
that the optical-function surface can be formed by press molding,
and it is no longer required to apply machine processes such as
grinding, polishing, etc., for finishing the optical-function
surface.
[0441] Therefore, the process for producing an optical element,
provided by the present invention, is suitable for producing
optical elements such as a lens, a lens array, a diffraction
grating, a prism, and the like, and is particularly suitable as a
process for highly productively producing aspherical lenses.
[0442] According to the process for producing an optical element,
provided by the present invention, all of the above optical
elements having the above optical properties can be produced.
Further, since the optical glass has a low glass transition
temperature (Tg), the press molding temperature can be decreased,
so that damage on the molding surface of a press mold can be
decreased, and the lifetime of the press mold can be hence
increased. Further, since the optical glass constituting the
preform has high stability, the devitrification of the optical
glass can be effectively prevented in the re-heating and pressing
steps. Further, a series of steps beginning with the melting of the
optical glass and ending with the obtainment of a final product can
be highly productively carried out.
[0443] As a press mold for the precision press-molding, there can
be used a known press mold, such as a press mold formed from a
refractory ceramic mold material such as silicon carbide, zirconia,
alumina, or the like and provided with a mold release film on the
molding surface of the mold material. Above all, a press mold
formed from silicon carbide is preferred, and a carbon-containing
film or the like can be used as a mold release film. A carbon film
is particularly preferred from the viewpoint of durability and a
cost.
[0444] In the precision press-molding, desirably, a non-oxidizing
atmosphere is employed as an atmosphere during the precision
press-molding for maintaining the molding surface of the press mold
under good conditions. As a non-oxidizing gas, nitrogen, a mixture
of nitrogen with hydrogen, or the like is preferred.
[0445] The precision press-molding for use in the process for
producing an optical element, provided by the present invention,
includes the following two embodiments, precision press-molding 1
and precision press-molding 2.
[0446] (Precision Press-Molding 1)
[0447] The precision press-molding 1 is a method in which the press
mold and the preform are heated together and the preform is
precision press-molded with the press mold.
[0448] In the precision press-molding 1, preferably, the precision
press-molding is carried out by heating the press mold and the
above preform together to a temperature at which the glass
constituting the preform exhibits a viscosity of 10.sup.6 to
10.sup.12 dPas.
[0449] Further, desirably, a precision press-molded product are
taken out of the press mold after they are cooled to a temperature
at which the above glass exhibits a viscosity of 10.sup.12 dPas or
higher, more preferably 10.sup.14 dPas or higher, still more
preferably 10.sup.16 dPas or higher.
[0450] Under the above conditions, not only the form of the molding
surface of the press mold can be more precisely transferred to the
glass, but also the precision press-molded product can be taken out
without causing any deformation.
[0451] (Precision Press-Molding 2)
[0452] The precision press-molding 2 is a method in which the
preform that has been pre-heated separately from the press mold is
introduced into the press mold that has been pre-heated and the
preform is precision press-molded.
[0453] In the precision press-molding 2, the above preform is
heated before its introduction into the press mold, so that the
cycle time can be decreased, and at the same time there can be
produced an optical element that is free of surface defects and has
an excellent surface accuracy.
[0454] Preferably, the temperature for pre-heating the press mold
is set at a temperature lower than the temperature for pre-heating
the preform. The temperature for pre-heating the press mold is set
at a lower temperature in this manner, so that the abrasion of the
press mold can be decreased.
[0455] In the precision press-molding 2, preferably, the above
preform is pre-heated to a temperature at which the glass
constituting the preform exhibits a viscosity of 10.sup.9 dPas or
less.
[0456] Further, it is preferred to pre-heat the above preform while
it is caused to float. Further, the above preform is preferably
pre-heated to a temperature at which the glass constituting the
preform exhibits a viscosity of 10.sup.5.5 to 10.sup.9 dPas, more
preferably, a viscosity of 10.sup.5.5 dPas or higher but lower than
10.sup.9 dPas.
[0457] Preferably, the cooling of the glass is initiated
simultaneously with the initiation of the pressing or during the
pressing.
[0458] The temperature of the press mold is set at a temperature
lower than the temperature for pre-heating the above preform, and a
temperature at which the above glass exhibits a viscosity of
10.sup.9 to 10.sup.12 dPas can be used as a standard value.
[0459] In the above method, preferably, the precision press-molded
product is taken out of the mold after it is cooled to a
temperature at which the above glass exhibits a viscosity of
10.sup.12 dPas or more.
[0460] An optical element obtained by the precision press-molding
is taken out of the press mold, and it is gradually cooled as
required. When the molded product is an optical element such as a
lens, or the like, the surface of the optical element may be coated
with an optical thin film as required.
EXAMPLES
[0461] The present invention will be more specifically explained
with reference to Examples hereinafter. The present invention shall
not be limited by these Examples.
[0462] Oxides, hydroxides, carbonates, nitrates, etc., which
corresponded to glass components were used as glass raw materials,
the glass raw materials were weighed so as to obtain each of
compositions shown in Tables 1-1 to 1-5 and fully mixed, and each
of mixtures was separately from the others placed in a platinum
crucible and melted under heat at a temperature in the range of
1,200 to 1,250.degree. C. in an electric furnace with stirring in
atmosphere for 2 to 4 hours. Each homogenized and refined glass
melt was separately cast into a 40.times.70.times.15 mm mold made
from carbon and allowed to cool gradually to its glass transition
temperature. Immediately thereafter, each glass was placed in an
annealing furnace and annealed around the glass transition
temperature for 1 hour. In the furnace, then, each glass was
allowed to cool gradually to room temperature, to give optical
glasses Nos. 1 to 34 shown in Tables 1-1 to 1-5.
[0463] When each of the obtained glasses was observed by enlarging
it through a microscope, no precipitation of a crystal was found,
nor was a non-melt remainder found.
[0464] Each of the thus-obtained glasses was measured for a
refractive index (nd), an Abbe's number (vd), a transition
temperature (Tg) and a sag temperature (Ts) as follows, and Table 2
shows the results.
[0465] (1) Refractive Index (nd) and Abbe's number (vd)
[0466] Optical glasses obtained by setting the gradually cooling
temperature at -30.degree. C./hour were measured.
[0467] (2) Glass Transition Temperature (Tg) and sag Temperature
(Ts)
[0468] Measured with an apparatus for thermomechanical analysis
supplied by Rigaku Corporation at a temperature elevation rate of
4.degree. C./minute.
[0469] As shown in Table 2, all of the glasses had desired
refractive indexes, Abbe's numbers (vd) and sag temperatures and
exhibited excellent low-temperature softening properties and
meltability, so that they were suitable as an optical glass for
precision press-molding.
[0470] Each of refined and homogenized molten glasses having
compositions Nos. 1 to 34 shown in Tables 1-1 to 1-5 was separately
caused to flow at a constant rate out of a pipe formed of a
platinum alloy which was temperature-adjusted to a temperature
region in which the glass was stably flowable without undergoing
devitrification, and molten glass gobs each having a weight of a
preform as an end product were separated by a dropping method or a
descent-cutting method. Each of the molten glass gobs was
separately received with a receiving mold having a gas-ejecting
port in its bottom, and each glass gob was shaped into a
press-molding preform while the glass gobs were caused to float by
ejecting a gas from the gas-ejecting port. The preforms were shaped
in the form of a sphere or a flattened sphere by adjusting and
setting the timing of separation of molten glass. The weights of
the thus-obtained preforms were precisely in agreement with the
corresponding set values, and all of the preforms had smooth
surfaces.
[0471] Separately, each of the molten glasses was cast into a frame
to form plate-shaped glasses, and the plate-shaped glasses were
annealed and then cut to obtain glass blocks. The surface of each
block was ground and polished to give preforms whose entire
surfaces were smooth.
[0472] The thus-obtained preforms whose entire surfaces were formed
by solidification of glasses in a molten state and the preforms
obtained by grinding and polishing the surfaces of the glass blocks
were precision press-molded with a press machine shown in FIG. 1,
to give aspherical lenses. Specifically, a preform 4 was placed
between a lower mold member 2 and an upper mold member 1 which
constituted a press mold together with a sleeve member 3, then, a
nitrogen atmosphere was introduced into a quartz tube 11, and a
heater 12 is electrically powered to heat an inside the quartz tube
11. The temperature in the press mold was set at a temperature at
which a glass to be molded exhibited a viscosity of 10.sup.8 to
10.sup.10 dPas, and while this temperature was maintained, the
upper mold member 1 was pressed by moving a pressing rod 13
downward to press the preform set in the press mold. The pressing
was carried out under a pressure of 8 MPa for 30 seconds. After the
pressing, the pressing pressure was removed, the glass molded
product was gradually cooled to a temperature at which the above
glass exhibited a viscosity of 10.sup.12 dPas or higher in a state
where the lower mold member and the upper mold member were in
contact with each other. Then, the glass molded product was rapidly
cooled to room temperature and then taken out of the press mold to
give an aspherical lens. The aspherical lenses obtained in the
above manner had remarkably high surface accuracy.
[0473] The aspherical lenses obtained by the above precision
press-molding were provided each with an anti-reflection film as
required.
[0474] Then, the same preforms as the above preforms were precision
press-molded by other method. In this method, while a preform was
caused to float, the preform was pre-heated to a temperature at
which a glass constituting the preform exhibited a viscosity of
10.sup.8 dPas. Separately, a press mold having an upper mold
member, a lower mold member and a sleeve member was heated up to a
temperature at which the above glass exhibited a viscosity of
10.sup.9 to 10.sup.12 dPas, and the above pre-heated preform was
introduced into the cavity of the press mold to carry out precision
press-molding of the preform at a pressure of 10 MPa. Upon the
initiation of the pressing, the cooling of the glass and the press
mold together was initiated, and the cooling was continued until
the molded glass had a viscosity of at least 10.sup.12 dPas, and
then the molded product was taken out of the mold to give an
aspherical lens. The aspherical lenses obtained in the above manner
were lenses having remarkably high surface accuracy.
[0475] The aspherical lenses obtained by the precision
press-molding were provided each with an anti-reflection film as
required.
[0476] In the above manner, optical elements formed of the glasses
having high internal quality were highly productively and highly
precisely obtained. TABLE-US-00001 TABLE 1-1 Table 1-1 No. 1 2 3 4
5 6 Corresponding glass Glasses Glasses Glasses Glasses Glasses
Glasses 1, 2, 9 1, 2, 9 1.about.3, 7, 9 1.about.3, 7, 9 1.about.3,
7, 9 1.about.3, 7, 9 B2O3 mol % 23.94 23.94 23.94 23.94 23.94 23.94
wt % 13.45 13.68 13.91 14.15 14.08 13.91 SiO2 mol % 14.08 14.08
14.08 14.08 14.08 14.08 wt % 6.83 6.94 7.06 7.18 7.15 7.06 TiO2 mol
% 19.73 19.73 19.73 19.73 19.72 19.72 wt % 12.71 12.92 13.14 13.37
13.32 13.15 ZnO mol % 9.86 12.68 15.49 18.31 18.31 18.31 wt % 6.48
8.46 10.52 12.65 12.59 12.44 La2O3 mol % 14.08 14.08 14.08 14.08
12.68 12.68 wt % 37.03 37.65 38.28 38.94 34.89 34.47 Gd2O3 mol %
0.00 0.00 0.00 0.00 1.41 0.00 wt % 0.00 0.00 0.00 0.00 4.31 0.00
Nb2O5 mol % 2.82 2.82 2.82 2.82 2.82 2.82 wt % 6.04 6.14 6.25 6.35
6.33 6.25 ZrO2 mol % 7.04 7.04 7.04 7.04 7.04 7.04 wt % 7.00 7.12
7.24 7.36 7.33 7.24 Ta2O5 mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt %
0.00 0.00 0.00 0.00 0.00 0.00 Bi2O3 mol % 0.00 0.00 0.00 0.00 0.00
1.41 wt % 0.00 0.00 0.00 0.00 0.00 5.48 MgO mol % 0.00 0.00 0.00
0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 CaO mol % 0.00
0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 SrO mol
% 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00
BaO mol % 8.45 5.63 2.82 0.00 0.00 0.00 wt % 10.46 7.09 3.60 0.00
0.00 0.00 RO mol % 8.45 5.63 2.82 0.00 0.00 0.00 wt % 10.46 7.09
3.60 0.00 0.00 0.00 Li2O mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt %
0.00 0.00 0.00 0.00 0.00 0.00 Na2O mol % 0.00 0.00 0.00 0.00 0.00
0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 Sb2O3 mol % 0.00 0.00 0.00
0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 Total mol %
100.00 100.00 100.00 100.00 100.00 100.00 wt % 100.00 100.00 100.00
100.00 100.00 100.00 (Note) RO represents a total content of MgO,
CaO, SrO and BaO.
[0477] TABLE-US-00002 TABLE 1-2 Table 1-2 No. 7 8 9 10 11 12
Corresponding glass Glasses Glasses Glasses Glasses Glasses Glasses
1.about.3, 7, 9 1.about.3, 7, 9 1.about.3, 7, 9 1.about.3, 7, 9
1.about.3, 7, 9 1.about.3, 7, 9 B2O3 mol % 23.94 22.22 24.29 21.38
19.73 24.46 wt % 14.29 13.30 14.52 12.81 11.85 14.64 SiO2 mol %
14.08 13.89 14.29 13.79 13.61 14.39 wt % 7.25 7.17 7.37 7.13 7.06
7.43 TiO2 mol % 19.72 19.44 19.98 19.31 19.04 20.13 wt % 13.50
13.35 13.72 13.29 13.13 13.84 ZnO mol % 21.13 23.61 18.57 24.83
27.21 17.27 wt % 14.74 16.52 12.98 17.39 19.12 12.08 La2O3 mol %
14.08 13.89 14.29 13.79 13.61 14.39 wt % 39.34 38.90 39.98 38.68
38.26 40.31 Gd2O3 mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00
0.00 0.00 0.00 0.00 0.00 Nb2O5 mol % 2.82 2.78 2.86 2.76 2.72 2.88
wt % 6.42 6.35 6.52 6.31 6.24 6.58 ZrO2 mol % 4.23 4.17 4.29 4.14
4.08 4.32 wt % 4.46 4.41 4.54 4.39 4.34 4.57 Ta2O5 mol % 0.00 0.00
0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 Bi2O3 mol %
0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00
MgO mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00
0.00 0.00 CaO mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00
0.00 0.00 0.00 0.00 SrO mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt %
0.00 0.00 0.00 0.00 0.00 0.00 BaO mol % 0.00 0.00 0.00 0.00 0.00
0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 RO mol % 0.00 0.00 0.00
0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 Li2O mol % 0.00
0.00 1.43 0.00 0.00 2.16 wt % 0.00 0.00 0.37 0.00 0.00 0.55 Na2O
mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00
0.00 Sb2O3 mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00
0.00 0.00 0.00 Total mol % 100.00 100.00 100.00 100.00 100.00
100.00 wt % 100.00 100.00 100.00 100.00 100.00 100.00 (Note) RO
represents a total content of MgO, CaO, SrO and BaO.
[0478] TABLE-US-00003 TABLE 1-3 Table 1-3 No. 13 14 15 16 17 18
Corresponding glass Glasses Glasses Glasses Glasses Glasses Glasses
1.about.3, 7, 9 1.about.3, 7, 9 1.about.4, 7, 9 1.about.4, 7, 9
1.about.5, 7 1.about.3, 7, 9 B2O3 mol % 24.82 23.94 25.00 25.37
26.15 23.53 wt % 14.89 14.43 15.01 15.27 15.81 14.20 SiO2 mol %
14.60 14.08 14.71 14.93 15.38 14.71 wt % 7.56 7.33 7.62 7.75 8.03
7.66 TiO2 mol % 20.43 19.73 20.58 20.88 21.54 20.58 wt % 14.05
13.64 14.19 14.43 14.93 14.26 ZnO mol % 14.60 23.94 13.24 10.45
4.62 13.24 wt % 10.24 16.88 9.29 7.35 3.26 9.34 La2O3 mol % 14.60
14.08 14.71 14.93 15.38 14.71 wt % 40.98 39.74 41.32 42.03 43.53
41.53 Gd2O3 mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00
0.00 0.00 0.00 Nb2O5 mol % 2.92 2.82 2.94 2.99 3.08 2.94 wt % 6.69
6.48 6.74 6.86 7.10 6.78 ZrO2 mol % 4.38 1.41 4.41 4.48 4.62 4.41
wt % 4.65 1.50 4.69 4.77 4.94 4.71 Ta2O5 mol % 0.00 0.00 0.00 0.00
0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 Bi2O3 mol % 0.00 0.00
0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 MgO mol %
0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00
CaO mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00
0.00 0.00 SrO mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00
0.00 0.00 0.00 0.00 BaO mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt %
0.00 0.00 0.00 0.00 0.00 0.00 RO mol % 0.00 0.00 0.00 0.00 0.00
0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 Li2O mol % 3.65 0.00 4.41
5.97 9.23 5.88 wt % 0.94 0.00 1.14 1.54 2.40 1.52 Na2O mol % 0.00
0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 Sb2O3
mol % 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00
0.00 Total mol % 100.00 100.00 100.00 100.00 100.00 100.00 wt %
100.00 100.00 100.00 100.00 100.00 100.00 (Note) RO represents a
total content of MgO, CaO, SrO and BaO.
[0479] TABLE-US-00004 TABLE 1-4 Table 1-4 No. 19 20 21 22 23 24 25
Corresponding glass Glasses Glasses Glasses Glasses Glasses Glasses
Glasses 1.about.3, 7, 9 1.about.3, 7, 9 1.about.3, 7, 9 1.about.3,
7, 9 1.about.3, 7, 9 1.about.3, 7, 9 1.about.3, 7 B2O3 mol % 21.74
20.00 22.63 22.63 22.63 22.30 21.99 wt % 13.16 12.14 13.68 13.79
13.90 14.06 14.46 SiO2 mol % 14.49 14.29 14.60 14.60 14.60 14.39
14.18 wt % 7.57 7.48 7.61 7.68 7.74 7.83 8.05 TiO2 mol % 20.29
19.99 20.44 20.43 20.43 20.13 19.86 wt % 14.07 13.92 14.17 14.28
14.40 14.57 14.99 ZnO mol % 15.94 18.57 14.60 10.95 7.30 14.39
14.18 wt % 11.28 13.18 10.31 7.80 5.24 10.60 10.90 La2O3 mol %
14.49 14.29 14.60 14.60 14.60 12.95 11.35 wt % 41.05 40.57 41.29
41.62 41.96 38.19 34.92 Gd2O3 mol % 0.00 0.00 0.00 0.00 0.00 0.00
0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Nb2O5 mol % 2.90 2.86
2.92 2.92 2.92 2.88 2.84 wt % 6.70 6.62 6.74 6.79 6.85 6.92 7.12
ZrO2 mol % 4.35 4.29 4.38 4.38 4.38 4.32 4.26 wt % 4.66 4.60 4.68
4.72 4.76 4.81 4.95 Ta2O5 mol % 0.00 0.00 0.00 0.00 0.00 0.00 0.00
wt % 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Bi2O3 mol % 0.00 0.00 0.00
0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 0.00 MgO mol
% 0.00 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00
0.00 0.00 CaO mol % 0.00 0.00 0.00 3.65 7.30 2.88 5.67 wt % 0.00
0.00 0.00 1.79 3.61 1.46 3.01 SrO mol % 0.00 0.00 0.00 0.00 0.00
0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 0.00 BaO mol % 0.00
0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00
0.00 RO mol % 0.00 0.00 0.00 3.65 7.30 2.88 5.67 wt % 0.00 0.00
0.00 1.79 3.61 1.46 3.01 Li2O mol % 5.80 5.71 5.84 5.84 5.84 5.76
5.67 wt % 1.51 1.49 1.51 1.53 1.54 1.56 1.60 Na2O mol % 0.00 0.00
0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 0.00
Sb2O3 mol % 0.00 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00
0.00 0.00 0.00 0.00 Total mol % 100.00 100.00 100.00 100.00 100.00
100.00 100.00 wt % 100.00 100.00 100.00 100.00 100.00 100.00 100.00
(Note) RO represents a total content of MgO, CaO, SrO and BaO.
[0480] TABLE-US-00005 TABLE 1-5 Table 1-5 No. 26 27 28 29 30 31 32
33 34 Corresponding glass Glasses Glasses Glasses Glasses Glasses
Glasses Glasses Glasses Glasses 1, 3.about.7 1.about.9 1, 3.about.7
1.about.9 1.about.3, 7, 9 1, 2, 9 1.about.3, 7, 9 1.about.5, 7, 9
1.about.3, 7, 9 B2O3 mol % 27.01 26.15 29.69 29.69 22.63 22.63
22.30 26.15 20.00 wt % 18.87 15.72 18.45 18.32 13.37 13.08 13.88
15.81 12.14 SiO2 mol % 14.60 12.31 15.63 9.38 14.60 14.60 14.39
15.38 14.29 wt % 8.80 6.38 8.38 4.99 7.44 7.28 7.73 8.03 7.48 TiO2
mol % 20.43 21.54 18.74 21.86 20.43 20.43 20.13 21.54 19.99 wt %
16.37 14.86 13.37 15.48 13.86 13.56 14.38 14.93 13.92 ZnO mol %
14.60 7.69 4.69 7.81 10.95 7.30 14.39 4.62 18.57 wt % 11.92 5.41
3.41 5.64 7.56 4.93 10.47 3.26 13.18 La2O3 mol % 8.76 15.38 14.84
14.06 14.60 14.60 12.95 15.38 14.29 wt % 28.64 43.28 43.17 40.61
40.37 39.49 37.73 43.53 40.57 Gd2O3 mol % 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 Nb2O5 mol % 2.92 3.08 2.34 3.13 2.92 2.92 2.88 3.08 2.86 wt %
7.79 7.06 5.56 7.36 6.59 6.44 6.84 7.10 6.62 ZrO2 mol % 4.38 4.62
4.69 4.69 4.38 4.38 4.32 4.62 4.29 wt % 5.42 4.91 5.16 5.12 4.58
4.48 4.76 4.94 4.60 Ta2O5 mol % 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Bi2O3
mol % 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 MgO mol % 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.00 CaO mol % 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 wt
% 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 SrO mol % 0.00 0.00
0.00 0.00 0.00 0.00 2.88 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00
0.00 2.67 0.00 0.00 BaO mol % 0.00 0.00 0.00 0.00 3.65 7.30 0.00
0.00 0.00 wt % 0.00 0.00 0.00 0.00 4.75 9.29 0.00 0.00 0.00 RO mol
% 0.00 0.00 0.00 0.00 3.65 7.30 2.88 0.00 0.00 wt % 0.00 0.00 0.00
0.00 4.75 9.29 2.67 0.00 0.00 Li2O mol % 7.30 9.23 9.38 9.38 5.84
5.84 5.76 9.23 5.71 wt % 2.19 2.38 2.50 2.48 1.48 1.45 1.54 2.40
1.49 Na2O mol % 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 wt %
0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Sb2O3 mol % 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 wt % 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 Total mol % 100.00 100.00 100.00 100.00 100.00
100.00 100.00 100.00 100.00 wt % 100.00 100.00 100.00 100.00 100.00
100.00 100.00 100.00 100.00 (Note) RO represents a total content of
MgO, CaO, SrO and BaO.
[0481] TABLE-US-00006 TABLE 2 Glass transition Sag Refractive
Abbe's number temperature (Tg) temperature No. index (nd) (.nu.d)
[.degree. C.] (TS) [.degree. C.] 1 1.90996 31.39 628 678 2 1.91491
30.55 624 674 3 1.91870 30.35 618 668 4 1.92306 30.00 615 664 5
1.92181 29.99 616 664 6 1.93390 28.51 606 654 7 1.91623 30.13 606
655 8 1.92175 30.01 605 654 9 1.91507 30.13 593 644 10 1.92393
29.98 602 651 11 1.92937 29.88 600 651 12 1.91394 30.22 590 640 13
1.91224 30.27 583 634 14 1.90840 30.22 600 647 15 1.91131 30.23 579
634 16 1.90866 30.12 575 627 17 1.90336 30.34 571 624 18 1.91418
30.07 566 622 19 1.91949 30.01 564 619 20 1.92439 29.92 561 617 21
1.91646 29.97 568 622 22 1.91795 30.10 573 626 23 1.91944 30.40 578
631 24 1.90521 30.60 561 615 25 1.89323 31.40 552 608 26 1.87618
29.13 544 595 27 1.91261 29.54 556 612 28 1.87167 32.22 569 619 29
1.90800 29.72 553 604 30 1.91119 30.36 572 627 31 1.90548 30.78 576
631 32 1.90829 30.06 565 618 33 1.90336 30.34 571 624 34 1.92439
29.92 561 617
INDUSTRIAL UTILITY
[0482] According to the present invention, there can be obtained an
optical glass having a high refractive index and a low sag
temperature and having a low-temperature softening property
enabling precision press-molding, and precision press-molding
preforms and optical elements such as various lenses, etc., can be
produced from the above optical glass.
* * * * *