JP2003252646A - Optical glass - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical glass high in refractive index and dispersion, lightweight, low in a glass transition temperature (Tg), and suitable for precision press. <P>SOLUTION: The optical glass contains glass components consisting of, by wt.%, 15.0-25.0% of SiO<SB>2</SB>, 0.5-7.0% of B<SB>2</SB>O<SB>3</SB>, 0.5-4.0% of LiO<SB>2</SB>, 0-30.0% of Na<SB>2</SB>O, 0-30.0% of K<SB>2</SB>O (provided 15.0-30.0% of Na<SB>2</SB>O+K<SB>2</SB>O), 16.0-46.0% of TiO<SB>2</SB>, 1.0-30.0% of Nb<SB>2</SB>O<SB>5</SB>, and 0.1-3.0% of WO<SB>3</SB>. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical glass,
More specifically, the present invention relates to an optical glass having a relatively high refractive index, a small specific gravity, a low glass transition temperature and suitable for precision press molding.

[0002]

2. Description of the Related Art Molding of glass by precision press molding has become widespread in recent years because polishing and cutting processes are not required and cost can be reduced. When glass is molded by precision press molding, it is necessary to bring the press die to a temperature near or above the glass transition temperature (hereinafter sometimes abbreviated as “Tg”) or higher. At this time, if the press die is repeatedly used at 500 ° C. or higher, surface oxidation or change in metal composition occurs in the press die, the surface of the die deteriorates severely, and it becomes difficult to maintain the surface accuracy. Will not be obtained. As a measure for suppressing the mold deterioration, controlling the molding atmosphere to an inert atmosphere such as nitrogen can be considered, but this causes an increase in production cost.
Therefore, Tg is 50 when using the precision press molding method.
Optical glass below 0 ° C is desirable.

Further, in recent years, as lenses made by precision press molding have become larger (diameter of about 10 mm to 30 mm).
To 50 mm), a glass having a smaller specific gravity is required.

[0004]

However, in an optical glass having a relatively high refractive index (n _d : 1.76 to 1.85), Tg is less than 500 ° C. and specific gravity is 3.3.
Up to now, there has been no one satisfying 0 g / cm ³ or less. For example, Japanese Patent Laid-Open No. 2001-58845 and Japanese Laid-Open Patent Publication No. 10-316448 proposed as optical glass for precision press,
Those described in JP-A-9-142872, JP-A-9-71435, and JP-A-7-97234 include Bi ₂ O ₃ and Te.
Since it contained a large amount of O ₂ and WO ₃ , it had a large specific gravity.
Further, the optical glass described in JP-A-8-175841 and JP-A-8-157231 had a Tg of 500 ° C. or higher.

The present invention has been made in view of such a conventional problem, and its object is to obtain a refractive index (n
_d ) is an optical glass having an optical constant of 1.76 to 1.85 and a dispersion (ν _d ) of 22 to 27, and a specific gravity of 3.30.
g / cm ³ or less and glass transition temperature (Tg) of 500
An object of the present invention is to provide an optical glass having a temperature of less than ° C, that is, an optical glass having a high refractive index and a high dispersion, which is lightweight and has a low Tg and which is suitable for precision press molding.

[0006]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventor has found that SiO ₂ , B ₂ O ₃ , L
The inventors have found that the desired object can be achieved by setting the respective glass components of i ₂ O, Na ₂ O, K ₂ O, TiO ₂ , Nb ₂ O ₅ , and WO ₃ in specific ranges, and have completed the present invention. That is, the optical glass of the present invention contains SiO ₂ : 1 at wt%.
_{5.0~25.0%, B 2 O 3:} 0.5~7.0%, Li
₂ O: 0.5 to 4.0%, Na ₂ O: 0 to 30.0%, K
₂ O: 0 to 30.0%, provided that Na ₂ O + K ₂ O: 15.
_{0~30.0%, TiO 2: 16.0~46.0%} , N
_{b 2 O 5: 1.0~30.0%,} WO 3: 0.1~3.0
% Glass component. In the present specification, the following “%” means “wt%” unless otherwise specified.

From the viewpoint of adjusting the refractive index of glass, SrO: 2.0% or less, BaO: 2.0% or less, Z
One or two or more glass components of nO: 3.0% or less and Bi ₂ O ₃ : 3.0% or less may be further contained.

From the viewpoint of refining when melting the glass, A is added to 100 parts by weight of the total amount of each glass component.
s ₂ O ₃ : 0.5 parts by weight or less, Sb ₂ O ₃ : 0.5 parts by weight or less, SnO ₂ : 0.5 parts by weight or less, one or more glass components may be further contained. .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The reason why each component of the optical glass of the present invention is limited as described above will be described below. First S
iO ₂ is the main component forming the optical glass. If the SiO ₂ content is less than 15.0%, the glass becomes unstable, while if the SiO ₂ content exceeds 25.0%, it is difficult to obtain the desired optical constant. Therefore, the content of SiO ₂ is set to 15.0.
The range was set to 25.0%. More preferable content is 1
It is in the range of 7.0 to 21.0%.

Like SiO ₂ , B ₂ O ₃ is a main component for forming glass and has an effect of lowering Tg of glass.
If the B ₂ O ₃ content is less than 0.5%, such an effect cannot be obtained. On the other hand, if the content exceeds 7.0%, the glass becomes unstable. Therefore, the content is set in the range of 0.5 to 7.0%. More preferable content is 3.0 to 5.0%
Is the range.

Li ₂ O has the effect of effectively lowering the Tg of glass. If the content of Li ₂ O is less than 0.5%, the effect cannot be sufficiently obtained. On the other hand, the content is 4.0
If it exceeds%, the glass tends to devitrify rapidly. Therefore, the content is set in the range of 0.5 to 4.0%. A more preferable content is in the range of 1.0 to 3.0%.

Na ₂ O and K ₂ O stabilize the glass and Tg
Has the effect of lowering the If the total amount of these is less than 15.0%, the effect cannot be sufficiently obtained. On the other hand, if the total amount of these exceeds 30.0%, the glass becomes unstable.
Therefore, the total amount of these is defined as a range of 15.0 to 30.0%. A more preferable total amount is in the range of 18.0 to 26.0%. The content of each of Na ₂ O and K ₂ O is 3
It must be 0.0% or less. This is because if the content exceeds 30.0%, the chemical durability is significantly reduced, and the volatilization of these components becomes severe during melting.

TiO ₂ is an effective component for increasing the refractive index while keeping the specific gravity of glass small. TiO ₂
If the content of is less than 16.0%, it becomes difficult to obtain the desired refractive index. On the other hand, if the content exceeds 46.0%, the glass tends to devitrify. Therefore, the content is 16.0
The range was set to 46.0%. More preferable content is 1
It is in the range of 9.0 to 40.0%.

Nb₂O_FiveStabilizes the glass and bends
It has the effect of increasing the folding rate. Nb ₂O_FiveContent of 1.
If it is less than 0%, the effect cannot be sufficiently obtained. other
On the other hand, if the content exceeds 30.0%, the glass tends to devitrify.
Become Therefore, the content is determined to be in the range of 1.0-30.0%.
I have A more preferable content is in the range of 16.0 to 28.0%.
It is a fence.

WO ₃ has the effect of increasing the refractive index of glass and, at the same time, effectively lowering the Tg as compared with TiO ₂ and Nb ₂ O ₅ . If the content of WO ₃ is less than 0.1%, the effect cannot be sufficiently obtained. On the other hand, the content is 3.
If it exceeds 0%, the glass tends to be colored. Therefore, the content is set in the range of 0.1 to 3.0%. A more preferable content is in the range of 0.3 to 1.5%.

Further, in the optical glass of the present invention, SrO,
One or two of glass components of BaO, ZnO and Bi ₂ O ₃
You may further contain the specific amount of 1 or more types as needed.
The refractive index of glass can be adjusted within a desired range by SrO, BaO and ZnO, but the content is 2.0%,
If it exceeds 2.0% or 3.0%, the specific gravity of glass becomes large. Therefore, the content of SrO is 2.0% or less, and the content of B is
A range in which aO is 2.0% or less and ZnO is 3.0% or less is preferable.

Bi ₂ O ₃ has the effect of increasing the refractive index and lowering the Tg, but if the content thereof exceeds 3.0%, the coloring of the glass will be significantly deteriorated and the glass will be easily devitrified. Therefore, the content is preferably in the range of 3.0% or less.

As a fining agent, As ₂ O ₃ , Sb ₂ O ₃ ,
One type or two or more types of each glass component of SnO ₂ may be contained in a range of 0.5 parts by weight or less based on 100 parts by weight of the total amount of the glass components. The reason why the content is set to 0.5 parts by weight or less is that a sufficient fining action can be obtained by including 0.5 parts by weight.

Other known glass components and additives may be added, if desired, within a range that does not impair the effects of the present invention.

The optical glass of the present invention can be manufactured by a conventionally known manufacturing method, but precision press molding is preferable. As the precision press molding which can be used here, for example, it is more preferable to mold molten glass by dropping molten glass from a nozzle into a mold heated to a predetermined temperature. According to such a method, the polishing and grinding steps are unnecessary and the productivity is improved.

The optical glass of the present invention is used, for example, as a collimator lens for digital cameras and laser beam printers.

[0022]

EXAMPLES The present invention will be described more specifically below with reference to examples. The present invention is not limited to these examples.

Examples 1 to 12 and Comparative Examples 1 to 4 Using general glass raw materials such as oxide raw materials, carbonates and sulfates, glass raw materials were prepared so as to have the target composition shown in Table 1. The powder was thoroughly mixed to prepare a raw material. This is put into a platinum crucible in an electric furnace heated to 1,000 to 1,300 ° C., melted and clarified, stirred and homogenized, cast into a preheated iron or carbon mold, and slowly cooled to each temperature. A sample was manufactured. D for each of these samples
The refractive index (n _d ) with respect to the line, the Abbe number (ν _d ), the specific gravity and the glass transition temperature (Tg) were measured. In addition, these measurements were performed according to the test method of Japan Optical Glass Industry Standard (JOGIS). The Tg is measured by DTA (Seiko I
nstruments Inc. “EXSTAR 6000 TG / DTA6300”) at 5 ° C./min under elevated temperature conditions. The measurement results are also shown in Table 1.

[0024]

[Table 1]

As can be seen from Table 1, Examples 1-12
The optical glass of has a high refractive index (1.761 to 1.848),
High dispersion (Abbe number: 22.6 to 26.3), light weight with specific gravity of 3.27 g / cm ³ or less, and glass transition temperature (Tg) of 498 ° C. or less, suitable for precision press molding. Met.

On the other hand, the optical glass of Comparative Example 1 containing no Li ₂ O had a high Tg of 523 ° C. and was not suitable for precision press molding. On the contrary, Li ₂ O is 5.2%
The optical glass of Comparative Example 2, which contained a large amount of, devitrified during melting. In addition, an optical glass of Comparative Example 3 containing no WO ₃ ,
The optical glasses of Comparative Example 4 containing neither B ₂ O ₃ nor WO ₃ had high Tg of 505 ° C. and 512 ° C., respectively, and were not suitable for press molding.

[0027]

The optical glass of the present invention is made of SiO.₂, B₂O
₃, Li₂O, Na₂O, K₂O, TiO ₂, Nb₂O_Five, W
O₃Since each glass component contains a specific amount, it has a high refractive index.
High dispersion (n_d: 1.76 to 1.85, ν_d: 22-27)
It has the optical constant of and is lightweight (specific gravity: 3.30 g / c
m³Precision press forming with low Tg (below 500 ° C)
Suitable for shape.

Further, since the optical glass of the present invention does not contain a fluorine raw material which is harmful to the human body, it is not necessary to newly install a facility for treating fluorine, and an expensive raw material unlike the phosphate optical glass. Since the raw materials are hardly used, the raw material cost is low, and the manufacturing cost can be reduced to less than half of the conventional one.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4G062 AA04 BB01 DA04 DB01 DC02                       DC03 DD01 DE01 DE02 DE03                       DF01 EA02 EA03 EB01 EB02                       EB03 EB04 EC01 EC02 EC03                       EC04 ED01 EE01 EF01 EF02                       EF03 EG01 EG02 EG03 FA01                       FB04 FB05 FC01 FD01 FE01                       FE02 FF01 FG03 FG04 FH01                       FJ01 FK01 FL01 GA01 GA02                       GA03 GB01 GC01 GD01 GE01                       HH01 HH03 HH05 HH07 HH09                       HH11 HH13 HH15 HH17 HH20                       JJ01 JJ03 JJ04 JJ05 JJ07                       JJ10 KK01 KK03 KK05 KK07                       KK10 MM02 NN01 NN02

Claims (4)

[Claims] 1. SiO ₂ at 1 wt%: 15.0 to 25.
_{0%, B 2 O 3:} 0.5~7.0%, Li 2 O: 0.5~
_{4.0%, Na 2 O: 0~30.0} %, K 2 O: 0~3
0.0%, but Na ₂ O + K ₂ O: 15.0-30.0
_{%, TiO 2: 16.0~46.0%,} Nb 2 O 5: 1.
An optical glass containing a glass component of 0 to 30.0% and WO ₃ : 0.1 to 3.0%. 2. Wt%, SrO: 2.0% or less, Ba
O: 2.0% or less, ZnO: 3.0% or less, Bi ₂ O ₃ :
The optical glass according to claim 1, further containing one or more glass components of 3.0% or less. 3. As ₂ O ₃ : 0.5 parts by weight or less, Sb ₂ O ₃ : 0.
The optical glass according to claim 1, further comprising 5 parts by weight or less, SnO ₂ : 0.5 parts by weight or less, and one or more glass components. 4. The refractive index (n _d ) is 1.76 to 1.85,
The optical glass according to any one of claims 1 to 3, which has a dispersion (ν _d ) of 22 to 27, a glass transition temperature (Tg) of less than 500 ° C, and a specific gravity of 3.30 g / cm ³ or less.