JPH09249429A - Optical glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical glass satisfying both of chemical durability and moldability. SOLUTION: This glass possesses the following composition: SiO2 : 19-33wt.%, B2 O3 : 22-32wt.%, BaO: 29-40wt.%, Al2 O3 : 5-11wt.%, La2 O3 : 8-21wt.%, Na2 O+K2 O: 0-3wt.%, As2 O3 : 0-1wt.% and has a refractive index (nd) of 1.59-1.64 and an optical constant in a range of 57.5-61.0 on the Abbe's number (υd).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to SiO ₂ --B ₂ O ₃
-Al ₂ O ₃ -La ₂ O ₃ has a composition of -BaO based, refractive index (nd) of 1.59 to 1.64 and Abbe number ([nu] d)
Relates to an optical glass having an optical constant in the range of 57.5 to 61.0.

[0002]

2. Description of the Related Art Conventionally, the refractive index (nd) is 1.59-
1.64 and Abbe number (νd) is 57.5 to 61.0
Various optical glasses having optical constants in the range of are known, and, for example, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —BaO type glass has been widely manufactured. However, since the optical glass of this system contains a large amount of BaO, its chemical durability is very poor.

As an optical glass having enhanced chemical durability, US Pat. No. 3,248,238 discloses Si glass.
_{O 2 -B 2 O 3 -BaO-} La 2 O 3 system of the optical glass is disclosed. In addition, in Japanese Patent Laid-Open No. 55-80736,
_{SiO 2 -B 2 O 3 -BaO-} CaO-Al 2 O 3 -La 2 O
_Three types of optical glass are disclosed.

[0004]

The above optical glass is
For example, SiO ₂ —B ₂ O ₃ —BaO—La ₂ O ₃ -based optical glass has improved chemical durability as compared with conventional optical glass, but is not sufficient. In addition, SiO ₂ −
The B ₂ O ₃ —BaO—CaO—Al ₂ O ₃ —La ₂ O ₃ system optical glass has a problem in that it is inferior in moldability to conventional optical glass. An object of the present invention is to solve the above-mentioned drawbacks of conventional glass and to provide an optical glass having high chemical durability and good moldability.

[0005]

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
An optical glass composition containing ₃ , BaO, Al ₂ O ₃ , and La ₂ O ₃ as an essential component has a desired optical constant within a predetermined composition range, and further has high chemical durability and good moldability. It was found that glass could be obtained, and the present invention was accomplished. That is, in the present invention, the weight ratio (wt%) is SiO ₂ 19 to 33 wt% B ₂ O ₃ 22 to 32 wt% BaO 29 to 40 wt% Al ₂ O ₃ 5 to 11 wt% La ₂ O ₃ 8 to 21. It has a composition of wt% Na ₂ O + K ₂ O 0 to 3 wt% As ₂ O ₃ 0 to 1 wt% and has a refractive index (nd) of 1.59 to 1.64 and an Abbe number (νd) of 57.5. An optical glass having an optical constant in the range of ˜61.0 is provided.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The above composition range has been found experimentally and the reason for limiting the composition range is shown below. The SiO ₂ component is an essential component for forming glass, but if the amount is 19 wt% or less, the chemical durability of the glass deteriorates, and if it exceeds 33 wt%,
The meltability of glass deteriorates.

The B ₂ O ₃ component is an essential component for improving the meltability and stability of the glass, but its amount is 22 wt.
% Or less, the devitrification of the glass increases, and 32w
If it exceeds t%, the chemical durability of the glass deteriorates. B
The aO component is an effective component for preventing the devitrification tendency of the glass, but when it is 29 wt% or less, the devitrification property of the glass increases, and when it exceeds 40 wt%, the chemical durability of the glass deteriorates. To do.

The Al ₂ O ₃ component is an essential component for improving the chemical durability of glass, but its amount is 5 wt.
% Or less, the chemical durability of the glass deteriorates, and 11
When it exceeds wt%, the meltability of glass deteriorates. La ₂
The O ₃ component is an effective component for improving the chemical durability, but if its amount is 8 wt% or less, the chemical durability deteriorates, and if it exceeds 21 wt%, the meltability deteriorates.

The Na ₂ O and K ₂ O components improve the meltability of the glass and are effective in suppressing the devitrification tendency and coloring, but if the amount exceeds 3 wt%, the chemical durability deteriorates. . As
_{The 2} O ₃ component is effective as a defoaming accelerator, but the amount of 1 wt% is sufficient. The CaO component is effective for improving the chemical durability, but it is not preferable because it lowers the moldability.

[0010]

EXAMPLE The optical glass according to the present invention uses an oxide as a raw material of each component, and as the oxide, a corresponding carbonate or nitrate can be used. Raw materials for each of these components were weighed in desired ratios and sufficiently mixed to prepare a blended raw material. This was melted in a platinum crucible at a temperature of 1200 ° C to 1400 ° C, for example. The molten glass was homogenized with stirring, cast into an iron mold preheated to about 500 ° C., and after slowly cooling, the refractive index (nd) and Abbe number (νd) were measured.

Examples 1 to 12 of the optical glass according to the present invention
The composition (wt%), the refractive index (nd), and the dispersion (νd) of are shown in Tables 1 and 2.

[0012]

[Table 1]

[0013]

[Table 2]

[0014]

As described above, according to the present invention, SiO _{2
-B 2 O 3 -Al 2 O 3} -La 2 O 3 has a composition of -BaO based, refractive index (nd) of 1.59 to 1.64 and Abbe number ([nu] d) is from 57.5 to 61. A heavy crown optical glass having an optical constant in the range of 0, high chemical durability, and good moldability is provided.

Claims (5)

[Claims] 1. A weight ratio (hereinafter referred to as wt%) of SiO ₂ 19 to 33 wt% B ₂ O ₃ 22 to 32 wt% BaO 29 to 40 wt% Al ₂ O ₃ 5 to 11 wt% La ₂ O ₃ 8 21 wt% Na ₂ O + K ₂ O 0 to 3 wt% As ₂ O ₃ 0 to 1 wt% heavy crown optical glass. 2. The heavy crown optical glass according to claim 1, wherein the refractive index (nd) is 1.59 to 1.64 and the Abbe number (νd) is in the range of 57.5 to 61.0. Heavy crown optical glass with. 3. The heavy-crown optical glass according to claim 1, wherein the weight ratio of SiO ₂ is 21 to 30 wt%. 4. The heavy-crown optical glass according to claim 1, wherein B ₂ O ₃ is 22 to 28 wt% in weight ratio. 5. The heavy-crown optical glass according to claim 1, wherein the weight ratio of BaO is 30 to 36 wt%.