JPH06144868A - Optical glass - Google Patents

Abstract

PURPOSE:To obtain optical glass having excellent chemical durability while maintaining low-temperature softening properties and a yield point suitable to a mold press by limiting a component composition, especially adding a specific amount of SiO2, B2O3, Al2O3, La2O, TiO2 and BaO. CONSTITUTION:Optical glass comprises 15-35wt.% SiO2, 3-20wt.% B2O3, 0 5-10wt.% Al2O3, 6-19wt.% La2O3, 6-15wt.% TiO2 and 0-10wt.% ZrO2, 0-5wt.% Ta2O5, 0-5wt.% WO3, 0-5wt.% MgO, 0-20wt.% CaO, 0-20wt.% SrO, 8-44wt.% BaO with the proviso that 18-44wt.% MgO+CaO+SrO+BaO, 0.5-10wt.% Li2O, 0-6wt.% Na2O, 0-8wt.% K2O with the proviso that 0.5-15wt.% Li2O+Na2O+K2O and 0-1wt.% Sb2O3. This optical glass has 1.65-1.80 refractive index (Nd), an optical constant of 35-50 Abbe's number (nud) and a low yield point (At) and contains no harmful components.

Description

Detailed Description of the Invention

[0001]

The present invention has a refractive index (Nd) of 1.6.
SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —La ₂ O having an optical constant in the range of 5 to 1.80 and an Abbe number (νd) of 35 to 50, and excellent chemical durability and low softening property. ₃ -TiO ₂ -
It relates to an optical glass of the BaO-Li ₂ O system.

[0002]

2. Description of the Related Art Conventionally, a glass showing the above optical constants
Is SiO₂-B₂O₃-La₂O₃-Representative of BaO type
For example, JP-A-49-72311 and JP-B-5
Various glasses as seen in the publication of 6-40092
Is disclosed. However, these glasses are generally
Since the yield point (At) is high and exceeds 650 ° C, it has recently been requested.
Excellent mold pressability for direct molding of optical elements
Unsuitable as a frosted glass. Therefore, the optical constant
R ′ for the purpose of imparting low temperature softening property while maintaining₂O
Proposal for a glass with (R 'is an alkali metal) introduced
Has been done. For example, in Japanese Patent Laid-Open No. 1-286934.
Is B₂O₃-SiO₂-La₂O₃-CaO and / or
Is BaO-Li₂O-based glass is disclosed.
Glass is B₂O ₃Has a high chemical content, resulting in poor chemical durability.
Yes. Further, JP-A-58-194755 discloses SiO.
₂-B₂O₃-La₂O₃-ZrO₂-BaO-Li₂O system moth
Lath is disclosed, but the yield point is 650 ° C or less
Has poor durability and is difficult to put into practical use. In addition, JP-A-2-263
No. 728 discloses SiO.₂-B₂O₃-Nb₂O_Five-ZnO
Although glass of the system is disclosed, ZnO has low temperature softening property.
Glass scraps that are useful for feeding but are discharged during processing
There is a problem of polluting the environment with sludge and the like.

[0003]

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

[0004]

In order to achieve the above-mentioned object, the inventors of the present invention have conducted diligent tests and studies, and as a result, have 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, which has the above-mentioned predetermined optical constant and does not contain the above-mentioned harmful components and is suitable for mold press at low temperature softening. It was found that an optical glass having characteristics, that is, a low yield point and excellent chemical durability can be obtained, and the present invention has been completed.

The characteristics of the optical glass according to the present invention are, in weight%, SiO ₂ 15 to 35%, B ₂ O _{3 3 to} 20%,
_{Al 2 O 3 0.5~10%, La} 2 O 3 6~19%, T
_{iO 2 6~15%, ZrO 2 0~10} %, Ta 2 O 5 0
_{~5%, WO 3 0~5%,} 0~5% MgO, CaO
0-20%, SrO 0-20%, BaO 18-4
4%, MgO + CaO + SrO + BaO 18-44
%, Li ₂ O 0.5 to 10%, Na ₂ O 0 to 6%, K
₂ O 0 to 8%, provided that Li ₂ O + Na ₂ O + K ₂ O 0.
5 to 15% and Sb ₂ O ₃ containing each component in the range of 0 to 1%, and an optical constant in the range of refractive index (Nd) 1.65 to 1.80 and Abbe number (νd) 35 to 50. Is where you have.

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 decreases, and if the amount exceeds 35%, the low temperature softening property cannot be maintained, and the optical target of the present invention is It becomes impossible to maintain a constant number. The B ₂ O ₃ component is an effective component for imparting low temperature softening properties to glass, but 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 the effect of significantly improving the chemical durability while maintaining low softening property by containing it in the glass together with the TiO ₂ component described below. 0 to show it.
5% or more is required and 10% to maintain devitrification resistance
Should be the limit.

The La ₂ O ₃ component must be contained in an amount of 6% or more in order to bring the refractive index of the glass to a target value, but if it exceeds 19%, the glass tends to devitrify. The TiO ₂ component raises the optical constant value of the glass, and as described above, Al ₂
Although the chemical durability is remarkably improved by containing it together with the O ₃ component, 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. To do. The components of ZrO ₂ , Ta ₂ O ₅ and WO ₃ may be added if necessary in order to increase the refractive index and improve the chemical durability, but the amount thereof is 10 respectively.
%, 5% and below 5% are sufficient.

The BaO component is superior to the other divalent metal oxide components in terms of increasing the optical constant of the glass, devitrification resistance and low softening property, but the amount thereof is 18 to 44%. The range is valid. Mg which is another divalent metal oxide component
O, CaO and SrO components can be added for optical constant adjustment and the like, but if the amounts of these components exceed 5%, 20% 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 giving the glass a low softening property, but in order to exert the effect while maintaining the devitrification resistance of the glass, the amount thereof is 0.5 to It should be in the range of 10%.

The Na ₂ O and K ₂ O components can be added if necessary, but their amounts should be 6% and 8% or less, respectively, in order 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 optionally added as a fining agent at the time of glass melting, but the amount is 1% or less. The glass of the present invention may contain components other than the above, such as Rb ₂ O and C.
s ₂ O, SnO, Gd ₂ O ₃ , Bi ₂ O ₃ and F (fluorine)
These components may be added up to a total of about 2%, if necessary, in order to adjust the optical constant and improve the melting property and devitrification resistance of the glass.

[0010]

EXAMPLES Next, with respect to the example compositions (No. 1 to No. 10) of the optical glass of the present invention and the comparative composition example of the conventional optical glass, the refractive index (Nd) and Abbe number of the obtained glass, respectively. It is shown in Table 1 together with the measurement results of (νd), yield point (At, ° C) and chemical durability. In the chemical durability test, each glass sample (about 30 × 30 × 5 m / m) having a fractured surface and a polished surface was treated with a 3N-nitric acid aqueous solution (25
℃) for 1 hour and observe the degree of erosion on both surfaces,
We adopted a method in which the transparency was maintained with no change in any surface state and marked with ○, and the transparency was clearly impaired on both surfaces and marked with ×. . Note that these glass samples include oxides, carbonates,
Ordinary optical raw materials such as nitrates and hydroxides are weighed and mixed at a predetermined ratio, and then charged into a platinum crucible and heated at a temperature of 1100 to 1350 ° C. for about 2 to 4 depending on the difficulty of melting depending on the composition.
It can be easily obtained by melting for a period of time, homogenizing by stirring, and then casting in a mold or the like and gradually cooling.

[0011]

[Table 1]

[Table 1]

[Table 1]

[Table 1]

As can be seen from Table 1, each of the glasses of the examples of the present invention has 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. Further, all of these glasses have excellent devitrification resistance and are easily homogenized. Therefore, the glass of the above example is easy to manufacture and is suitable as a material for mold pressing.

[0013]

As described above, the optical glass of the present invention is made of 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, it has a refractive index (Nd) of 1.65 to 1.80 and an Abbe number (ν
d) has an optical constant in the range of 35 to 50 and a low yield point (A
It has t), does not contain the harmful components, and is more excellent in chemical durability than conventional glass. In addition, it is easy to manufacture and homogenizes easily, and is suitable for mold pressing.

Claims (1)

[Claims] 1. By weight% SiO ₂ 15-35%, B _{2
O 3 3~20%, Al 2 O} 3 0.5~10%, La 2 O
_{3 6~19%, TiO 2 6~15%} , ZrO 2 0~
_{10%, Ta 2 O 5 0~5} %, WO 3 0~5%, Mg
O 0-5%, CaO 0-20%, SrO 0-20
%, BaO 18 to 44%, but MgO + CaO + S
_{rO + BaO 18~44%, Li 2} O 0.5~10
%, Na ₂ O 0 to 6%, K ₂ O 0 to 8%, but Li
₂ O + Na ₂ O + K ₂ O 0.5-15% and Sb ₂ O ₃
An optical glass containing each component in the range of 0 to 1%.