JP2707010B2 - Optical glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a refraction index ( Nd) of 1.6.
3 to 1.75, Abbe number (νd) 45 to 57
And the refractive index (Nd) -abbe number (νd) right angle
On coordinates, refractive index (Nd) = 1.63, Abbe number
(Νd) = 60.5 point and refractive index (Nd) = 1.75;
A straight line connecting the point of Abbe number (νd) = 53.5
Optical constants in the range where the value of the number (νd) is small and 555-6
Yield point in the range of 40 ° C. (At) about excellent _{B 2 O 3 -La 2 O 3} -ZrO 2 and / or _{Ta 2 O 5 -SrO-Li 2} O system optical glass chemical durability with.

[0002]

2. Description of the Related Art Heretofore, glass having the above-mentioned optical constant has been typically of a lanthanum borate composition, for example, Japanese Patent Publication Nos. 31-4686, 48-61517 and 54-54. Various glasses are disclosed as disclosed in Japanese Patent Publication No. 3115 and the like. However, since these glasses generally have a high yield point and exceed 650 ° C., they are unsuitable as glasses which are recently required and have excellent mold pressability for directly molding optical elements. Therefore, various types of glasses have been developed for the purpose of providing low softening properties while maintaining the optical constant. For example, JP-A-59-146
No. 952 discloses B ₂ O _3- containing fluorine (F).
La ₂ O ₃ —BaO—R ′ ₂ O (R ′ is an alkali metal element) glass is disclosed. However, this glass is liable to be volatilized by a fluorine (F) component in the melting step, and it is difficult to obtain high homogeneity. Further, Japanese Patent Application Laid-Open No. 1-286934
In the publication, B ₂ O ₃ —SiO ₂ —La ₂ O ₃ —CaO
And / or BaO-Li ₂ O-based glass is disclosed, but this glass has poor chemical durability and is hardly practical.

[0003]

SUMMARY OF THE INVENTION The present invention improves the above-mentioned drawbacks of the conventional glass and improves the refractive index (Nd) of the glass .
63 to 1.75, in the range of Abbe number ([nu] d) 45-57
Yes, and the refractive index (Nd) minus the Abbe number (νd)
On angular coordinates, refractive index (Nd) = 1.63, Abbe
Point of number (νd) = 60.5 and refractive index (Nd) = 1.7
5. From the straight line connecting the point of Abbe number (νd) = 53.5
An object of the present invention is to provide an optical glass having further excellent chemical durability and homogeneity while maintaining an optical constant in a range where the Abbe number (νd) is small and a yield point (At) suitable for a mold press. And

[0004]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have made B ₂ O ₃ -La ₂ O _3- having low softening properties.
Based on a Li ₂ O-based glass and conducting various tests and studies on components to be added thereto, the glass composition was changed to B
_{2 O 3 -La 2 O 3 -ZrO} 2 and / or Ta
_{By using the 2} O ₅ —SrO—Li ₂ O system, the chemical durability of the glass can be further improved while maintaining a predetermined optical constant and low softening characteristics suitable for a mold press, that is, a low yield point. Thus, the present invention has been accomplished.

The characteristics of the optical glass according to the present invention are as follows: B ₂ O ₃ 15 to 45%, SiO ₂ 0 to 30%, but B ₂ O ₃ + SiO ₂ 35 to 55%, La ₂ O ₃ 21
_{~35%, Gd 2 O 3 0~10} %, ZrO 2 0~10
%, Ta ₂ O ₅ 0 to 10%, provided that ZrO ₂ + Ta ₂ O
_{5 0.5~10%, Al 2 O 3} 0~ 1%, SrO 0.
5-25%, MgO 0-10%, CaO 0-15
%, BaO 0 to 20%, ZnO 0 to 10%, provided that MgO + CaO + BaO + ZnO 0 to 30% and SrO 15.5 to 25%, BaO 0 to 5%
_{Less, Li 2 O 2.5~8%, Na} 2 O 0~10
%, K ₂ O 0 to 10%, provided that Li ₂ O + Na ₂ O +
K ₂ O is composed of each component in the range of 2.5 to 15% , and has a refractive index (Nd) of 1.63 to 1.75 and an Abbe number (ν).
d) It is in the range of 45 to 57 and the refractive index (N
d)-refractive index on Abbe number (νd) rectangular coordinates
(Nd) = 1.63, Abbe number (νd) = 60.5
And refractive index (Nd) = 1.75, Abbe number (νd) = 5
The value of Abbe number (νd) is smaller than the straight line connecting the point of 3.5.
It has an optical constant in the range and a yield point (At) in the range of 555 to 640 ° C.

Next, the reasons for limiting the content of each component as described above will be described. That is, the B ₂ O ₃ component is a glass forming component that is advantageous for imparting low softening properties to glass, but its amount is in the range of 15 to 45% for maintaining the devitrification resistance and chemical durability of the glass. Is appropriate. SiO ₂
Components can be added in a range where low softening property can be maintained, that is, up to 30%, for improving chemical durability. However, B ₂ O
The total amount of the ₃ and SiO ₂ components should be in the range of 35-55% to maintain the devitrification resistance of the glass and to maintain the desired optical constant.

The La ₂ O ₃ component needs to be contained in an amount of 21% or more in order to make the refractive index of the glass a target value.
If the amount exceeds 35%, the glass tends to be devitrified.
The Gd ₂ O ₃ component can be added to adjust the optical constant of the glass, but up to 10% is sufficient.

In the present invention, the ZrO ₂ and / or Ta ₂ O ₅ components are contained in the glass together with the SrO component to be described later, thereby maintaining the predetermined yield point and greatly improving the chemical durability. It is an important ingredient found. The amounts of these components should each be limited to 10% to maintain devitrification resistance. Also,
The total amount of these components is required to be 0.5% or more in order to exert the above effect, and 1% for maintaining devitrification resistance.
It should be limited to 0%.

The Al ₂ O ₃ component is composed of ZrO ₂ or Ta
Unlike ₂ O ₅ , the glass is unexpectedly easily devitrified, so it is better not to use it positively. However, depending on the composition of the glass, it can be added up to 1% for adjusting the optical constant.

The SrO component increases the value of the optical constant of the glass, and is most generally advantageous over other divalent metal oxide components in terms of chemical durability, devitrification resistance and low softening characteristics. As described above, it is included together with the ZrO ₂ and / or Ta ₂ O ₅ components to significantly improve the chemical durability, but the amount is effective in the range of 0.5 to 25%. MgO, CaO, which are other divalent metal oxide components,
BaO and ZnO components can be added for adjusting the optical constants, but the amounts of these components are 10% and 15%, respectively.
%, 20% and 10%, the stability of the glass tends to be impaired. However, the total amount of one or more of these other divalent metal oxide components should be in the range of 0 to 30% in order to maintain a target optical constant and devitrification resistance. When the amount of the SrO component is 15.5 to 25%, the amount of the BaO component should be less than 5% in order to maintain the devitrification resistance of the glass.

The Li ₂ O component is an important component because it has a particularly large effect of imparting low softening characteristics to the glass. However, in order to exert the effect while maintaining the devitrification resistance of the glass, the amount thereof is required. It should be in the range of 2.5-8%. Na
_{The 2} O and K ₂ O components can be added as needed,
The amount should be up to 10% each to maintain devitrification resistance and chemical durability. However, Na ₂ O and K
The total amount of one or a Li ₂ O ingredient ₂ O is in the range of 2.5 to 15% for the same reason.

It is to be noted that Nb ₂ O ₅ , TiO ₂ , WO ₃ and
A PbO component may be added. Sb as a defoaming fining agent
_An appropriate amount of ₂ O ₃ and As ₂ O ₃ components can be added.

[0013]

EXAMPLES Next, examples of compositions (Nos. 1 to 8 ) of the optical glass of the present invention and comparative examples (Nos. A and B) of the conventional optical glass were obtained. Glass refractive index (Nd), Abbe number (ν
The results are shown in Table 1 together with the measurement test results of d), yield point (At, ° C) and chemical durability.

[0014]

[Table 1]

[Table 1]

In the chemical durability test, each glass sample (about 30 × 30 × 5 mm) having a broken surface and a polished surface was subjected to 3N-
Immerse in an aqueous nitric acid solution (25 ° C) for 1 hour to observe the degree of erosion on both surfaces. Indicate that there is no change in the surface condition and transparency is maintained, and both surfaces are rough. And a method in which transparency was clearly impaired was indicated by a cross. These glass samples were prepared by weighing and mixing optical materials such as oxides, carbonates, nitrates, and hydroxides at a predetermined ratio, and then charging the mixture into a platinum crucible. , 100 to 1,350 ° C, then homogenized, cast into a mold, and gradually cooled.

As can be seen from Table 1, the glasses of the examples of the present invention all show the target Nd value, vd value and At value, and the chemical durability is remarkably improved as compared with the glass of the comparative example. I have. Further, these glasses are all excellent in devitrification resistance and are easily homogenized. For this reason, the glass of the above embodiment is easy to manufacture, suitable for a mold press, and hardly changes its surface state.

[0017]

As mentioned above, according to the present invention, the optical glass of the present invention _has a specific composition of _{B 2 O 3 -La 2 O 3} -ZrO 2 and / or _{Ta 2 O 5 -SrO-Li 2} O component system Therefore, the refractive index (Nd) is 1.63 to 1.7.
5. Abbe number (νd) is in the range of 45 to 57.
The refractive index (Nd)-Abbe number (νd)
And the refractive index (Nd) = 1.63, the Abbe number (νd) =
Point 60.5, refractive index (Nd) = 1.75, Abbe number
Abbe number (ν) from the straight line connecting the point (νd) = 53.5
It has an optical constant in a range where the value of d) is small and a yield point (At) in a range of 555 to 640 ° C, and is further excellent in chemical durability. Further, it is easy to manufacture, easy to homogenize, and suitable for a mold press.

Claims (1)

(57) [Claims] (1) B ₂ O ₃ 15 to 45% by weight, SiO 2
₂ 0-30%, provided that _B 2 _O 3 ₊ SiO 2 _35~55
%, La ₂ O ₃ 21 to 35%, Gd ₂ O ₃ 0 to 10%,
ZrO ₂ 0 to 10%, Ta ₂ O ₅ 0 to 10%, provided that Z
rO ₂ + Ta ₂ O ₅ 0.5 to 10%, Al ₂ O _{30 to} 1
%, SrO 0.5-25%, MgO 0-10%, C
aO 0-15%, BaO 0-20%, ZnO 0
10%, provided that MgO + CaO + BaO + ZnO 0
場合 30% and SrO 15.5-25% Ba
O 0 to less than 5%, Li ₂ O 2.5 to 8%, Na ₂ O
_{0~10%, K 2 O 0~10%} , provided that _Li 2 O +
From each component of _{Na 2 O + K 2 O 2.5~15} % range
And the refractive index (Nd) is in the range of 1.63 to 1.75, the Abbe number (νd) is 45 to 57 , and the refractive index is
Rate (Nd)-Abbe number (νd)
Folding ratio (Nd) = 1.63, Abbe number (νd) = 60.5
And the refractive index (Nd) = 1.75, Abbe number (νd) =
The value of Abbe number (νd) is obtained from the straight line connecting the point of 53.5
An optical glass characterized by having an optical constant in a small range and a yield point (At) in a range of 555 to 640 ° C.