JP2795334B2 - Optical glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a refractive index (Nd) of 1.6.
SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —La ₂ having optical constants in the range of 5 to less than 1.78 and Abbe number (νd) of 35 to 50, and excellent chemical durability and low softening property. O ₃ -Ti
The present invention relates to an O ₂ —BaO—Li ₂ O-based optical glass.

[0002]

Heretofore, glass showing the optical constants of said ones of _{SiO 2 -B 2 O 3 -La 2} O 3 -BaO systems are typically, for example JP-49-72311, JP Kosho 5
Various glasses are disclosed as disclosed in JP-A-6-40092. However, since these glasses generally have a high yield point (At) and exceed 650 ° C., they are unsuitable as glass which has been recently required and has excellent mold pressability for directly molding optical elements. Therefore, for the purpose of providing low-temperature softening properties while maintaining the above optical constant, R ′ ₂ O
Glasses in which (R 'is an alkali metal) are introduced. For example, Japanese Patent Laid-Open No. _{1-286934, B 2 O 3 -SiO 2} -La 2 O 3 but -CaO and / or BaO-Li ₂ O system glass is disclosed, the glass of B ₂ O ₃ Poor chemical durability due to high content. Further, JP-A-58-194755 discloses SiO2.
Although _{2 -B 2 O 3 -La 2 O} 3 -ZrO 2 -BaO-Li 2 O system glass is disclosed, those sag of 650 ° C. or less hardly practically usable poor durability. Japanese Patent Application Laid-Open No. 2-263
No. 728 discloses that SiO ₂ —B ₂ O ₃ —Nb ₂ O ₅ —ZnO
Although a system-based glass is disclosed, ZnO is useful for providing low-temperature softening properties, but has a problem in that the environment is polluted by glass chips, sludge, and the like discharged during processing.

[0003]

DISCLOSURE OF THE INVENTION The present invention has the above-mentioned predetermined optical constants, comprehensively improves the drawbacks of the prior art, and contains a ZnO component which is environmentally problematic. An object of the present invention is to provide an optical glass having a further excellent chemical durability while maintaining a yield point (At) suitable for a mold press with low-temperature softening property.

[0004]

Means for Solving the Problems In order to achieve the above object, the present inventors have made intensive studies and studied and found that a specific range of SiO ₂ -B ₂ O which is not specifically disclosed in the prior art.
_3- Al ₂ O ₃ —La ₂ O ₃ —TiO ₂ —BaO—Li ₂ O-based glass having the above-mentioned predetermined optical constant, containing no harmful components and containing low-temperature softening suitable for a mold press The inventors have found that an optical glass having properties, that is, a low yield point and excellent chemical durability can be obtained, and the present invention has been accomplished.

The optical glass according to the present invention is characterized in that, by weight%, 15 to 35% of SiO ₂ , _{3 to} 20% of B ₂ O ₃ ,
Al ₂ O ₃ 0.5 to 10%, La ₂ O ₃ 6 to 16%
_{Mitsuru, TiO 2 6~15%, ZrO 2} 0~10%, Ta
₂ O ₅ 0-5%, WO ₃ 0-5%, MgO 0-5
%, CaO 0~ 14%, SrO 0~20%, BaO
18-44%, but MgO + CaO + SrO + BaO
_{18~44%, Li 2 O 0.5~10%} , Na 2 O
_{0~6%, K 2 O 0~8%} , provided that Li ₂ O + Na ₂ O
+ K ₂ contain O 0.5 to 15% and Sb ₂ O ₃ 0~1% of each ingredient in the range, free of ZnO and Nb ₂ O ₅
The refractive index (Nd) is less than 1.65 to 1.78 and the Abbe number (νd) has an optical constant in the range of 35 to 50.

The reasons for limiting the composition range of each component as described above are as follows. That is, if the amount of the SiO ₂ component is less than 15%, the chemical durability of the glass is reduced, and if the amount exceeds 35%, the low-temperature softening property cannot be maintained, and the optical target of the present invention is not obtained. The constant cannot be maintained. The B ₂ O ₃ component is an effective component for imparting low-temperature softening properties to glass. However, if the amount is less than 3%, the meltability and devitrification resistance deteriorate, and if it exceeds 20%, the chemical durability becomes poor. Getting worse. The Al ₂ O ₃ component is an important component that has been found to have an effect of significantly improving chemical durability while maintaining low softening properties by being contained in glass together with a TiO ₂ component described below. 0.
5% or more is required, and 10% to maintain devitrification resistance
Should be limited.

[0007] La ₂ O ₃ component is required to be contained 6% or more to the value of the target refractive index of the glass, but 16% or less
Above the glass tends to devitrify. The TiO ₂ component increases the value of the optical constant of the glass and, as described above, Al ₂ O ₃
The chemical durability is remarkably improved by being contained together with the components, but if the amount is less than 6%, the above effect is not sufficient, and if it exceeds 15%, the devitrification resistance and light transmittance of the glass deteriorate. ZrO ₂ , Ta ₂ O ₅ and WO ₃
Can be added as needed to increase the refractive index and improve the chemical durability, but their amounts are 10% and 5%, respectively.
% And 5% or less is sufficient.

The BaO component increases the optical constant of the glass and is superior in devitrification resistance and low softening characteristics to other divalent metal oxide components, but its content is 18 to 44%. Is valid. Mg, another divalent metal oxide component
O, CaO and SrO components can be added for adjusting the optical constants, but if the amounts of these components exceed 5%, 14 % and 20%, respectively, the stability of the glass tends to be impaired. However, the total amount of one or more of BaO, MgO, CaO and SrO components should be in the range of 18 to 44% for maintaining the target optical constant and devitrification resistance. The Li ₂ O component is an important component because it has a particularly large effect of imparting low softening properties to the glass. However, in order to exert the effect while maintaining the devitrification resistance of the glass, the amount is 0.5 to 0.5%. It should be in the range of 10%.

The Na ₂ O and K ₂ O components can be added as needed, but their amounts should be less than 6% and 8%, respectively, to maintain devitrification resistance and chemical durability. However the total amount of one or a Li ₂ O component of Na ₂ O and K ₂ O is 0.5 to 15% of the range for the same reason. The Sb ₂ O ₃ component can be arbitrarily added as a fining agent when the glass is melted, but an amount of 1% or less is sufficient. In addition, components other than the above, for example, Rb ₂ O, C
s ₂ O, SnO ₂ , Gd ₂ O ₃ , Bi ₂ O ₃ and F (fluorine)
Such components as described above may be added as needed up to a total of about 2% for adjusting the optical constants and improving the melting property and devitrification resistance of the glass.

[0010]

EXAMPLES Next, the refractive index (N) of each of the obtained glasses was determined for each of the composition examples (No. 1 to No. 8 ) of the optical glass of the present invention and the comparative composition example of the conventional optical glass.
The results are shown in Table 1 together with the measurement results of d), Abbe number (νd), yield point (At, ° C), and chemical durability. In the chemical durability test, each glass sample (about 30 × 30 × 5 m / m) having a broken surface and a polished surface was subjected to a 3N-nitric acid aqueous solution (25 ° C.).
After immersion for 1 hour, the degree of erosion on both surfaces was observed, and those with no change in either surface condition and transparency were indicated by ○, and both surfaces were roughened and the transparency was improved. A method of displaying those that are clearly damaged with a cross is adopted. In addition, these glass samples are prepared by weighing and mixing ordinary optical materials such as oxides, carbonates, nitrates, and hydroxides at a predetermined ratio, and then throwing the mixture into a platinum crucible, depending on the degree of melting difficulty depending on the composition. It can be easily obtained by melting at a temperature of 1100 to 1350 ° C. for about 2 to 4 hours, homogenizing with stirring, and casting it into a mold or the like and gradually cooling.

[0011]

[Table 1]

As can be seen from Table 1, all the glasses of the embodiments of the present invention have a desired optical constant and a low yield point (At).
And the chemical durability is further improved as compared with the conventionally known comparative glass. In addition, all of these glasses are excellent in devitrification resistance and are easily homogenized. For this reason, the glass of the above embodiment is easy to manufacture and is suitable as a material for mold press.

[0013]

As mentioned above, according to the present invention, the optical glass of the present _{invention, SiO 2 -B 2 O 3 -Al} 2 O 3 -La 2 O 3 -TiO 2
Since it has a characteristic composition of —BaO—Li ₂ O system, the refractive index (Nd) is less than 1.65 to less than 1.78 , and the Abbe number (νd) is in the range of 35 to 50, which is an optical constant and low yielding. It has a point (At), does not contain the harmful components described above, and is much more excellent in chemical durability than conventional glass. Further, it is easy to manufacture, easy to homogenize, and suitable for a mold press.

Claims (1)

(57) [Claims] 1. A method according to claim 1, wherein 15 to 35% of SiO ₂ and B ₂
O ₃ 3-20%, Al ₂ O ₃ 0.5-10%, La ₂ O
₃ 6 than _{16%, TiO 2 6~15%,} ZrO 2
_{0~10%, Ta 2 O 5 0~5} %, WO 3 0~5%,
0~5% MgO, CaO 0~ 14% , SrO 0~
20%, BaO 18-44%, but MgO + CaO
+ SrO + BaO 18-44%, Li ₂ O 0.5-
_{10%, Na 2 O 0~6%} , K 2 O 0~8%, provided that _{Li 2 O + Na 2 O +} K 2 O 0.5~15% and Sb ₂
Containing the components of O ₃ 0 to 1% range, ZnO and
It does not contain Nb ₂ O _5, and the refractive index (Nd) 1.65~
Less than 1.78 and Abbe number (νd) 35-50
An optical glass having an optical constant of