JPH08119666A - Optical glass - Google Patents

Abstract

PURPOSE: To obtain optical glass having a refractive index and an Abbe's number each in a prescribed range and excellent in chemical durability by imparting a specified compsn. contg. SiO2 , B2 O3 , Al2 O3 , ZrO2 , ZnO, BaO and Li2 O. CONSTITUTION: This optical glass consists of, by weight, 25-45% SiO2 , 8-20% B2 O3 , 2-8% Al2 O3 , 0-3% TiO2 , 0.5-8% ZnO, 0-3% MgO, 0-2% CaO, 37-55% BaO, 0.3-8%, in total, of 0.3-5% Li2 O, Na2 O and K2 O and 0-0.5% Sb2 O3 and has a refractive index of 1.6-1.65 and an Abbe's number of 55-62 as optical constants. This optical glass is easily produced as follows; starting materials for optical glass such as carbonates, nitrates or oxides are weighed and mixed, this mixture is melted and homogenized at about 1,200-1,400 deg.C for about 2-5hr and the resultant melt is poured into a metal mold and slowly cooled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to SiO ₂ --B ₂ O ₃ --A
1 ₂ O ₃ —ZrO ₂ —ZnO—BaO—Li ₂ O system composition, optical constant with refractive index (Nd) of 1.60 to 1.65 and Abbe number (νd) of 55 to 62. And a novel optical glass having excellent chemical durability.

[0002]

_2. Description of the Related Art Conventionally, a glass having the above optical constant is SiO ₂ --B ₂ O containing a large amount of BaO component.
_3- BaO-based glass is known, and ZnO, PbO and TiO ₂ components are used for adjusting optical constants. For example, "Glass Composition Data Book 1991
In {{issued by Japan Glass Products Manufacturers Association}}, SiO ₂ −
_{B 2 O 3 -Al 2 O 3} -TiO 2 -ZnO-CaO-BaO
Although the glass of the system is described, it cannot be said that the chemical durability is good. Generally, the glass having the present optical constant region is
Conventionally, the occurrence of burns tends to be a problem, and improvement in chemical durability has been demanded. In recent years, glass with a low transition temperature has been demanded as a material for mold press molding,
Further, there has been a problem that the chemical durability is deteriorated.

[0003]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The present invention comprehensively improves the various drawbacks of the above-mentioned conventional glass, and improves the refractive index (N
d) is 1.60 to 1.65, Abbe number (νd) is 55 to
It is an object of the present invention to provide an optical glass having an optical constant in the range of 62 and excellent chemical durability.

[0004]

In order to achieve the above object, the present inventor has conducted extensive studies and studies, and as a result, SiO ₂ -B ₂ O ₃
In _{Al 2 O 3 -ZrO 2 -ZnO-} BaO-Li 2 O -based glass, glass having excellent chemical durability while maintaining the number of the optical constants is predicated on this finding discovered the present invention can be obtained .

The characteristics of the optical glass according to the present invention are% by weight.
, SiO ₂ 25-45%, B ₂ O ₃ 8-20%, A
1 ₂ O ₃ 2-8%, TiO ₂ 0-3%, ZrO ₂ 0.
5-8%, ZnO 0.2-8%, MgO 0-3%,
CaO 0-2%, BaO 37-55%, Li ₂ O + N
a ₂ O + K ₂ O 0.3-8%, provided that Li ₂ O 0.
3 to 5%, Sb ₂ O ₃ consisting of each component in the range of 0 to 0.5%, an optical index (Nd) of 1.60 to 1.65, Abbe number (νd) of 55 to 62 To have a constant.

The reason for limiting the composition range of each of the above components is as follows.
It is as follows. That is, the amount of SiO ₂ component is 25
If it is less than 40%, the chemical durability of the glass decreases, and if it exceeds 45%, the melting property of the glass deteriorates, and the optical constants targeted by the present invention cannot be maintained.
When the amount of the B ₂ O ₃ component is less than 8%, the viscosity at the time of melting the glass is increased and it is difficult to obtain a homogeneous glass, and when the amount exceeds 20%, the chemical durability of the glass is deteriorated. To do. The Al ₂ O ₃ component is a particularly effective component for improving chemical durability, but if the amount is less than 2%, it is difficult to obtain the effect, and if it exceeds 8%, the melting property and devitrification resistance of glass deteriorate. To do.

The TiO ₂ component is an effective component for improving the chemical durability, but if the amount of the TiO ₂ component is increased, the light transmittance is deteriorated, so the content is preferably 3% or less. The ZrO ₂ component is a very effective component in the evaluation of chemical durability, particularly acid resistance by the surface method, but if its amount is less than 0.5%, its effect is small, and if it exceeds 8%. It deteriorates the devitrification resistance of glass. The ZnO component is an essential component for adjusting the optical constant and improving the water resistance of chemical durability, but if the amount thereof is 0.2% or less, it has no effect.
If it exceeds%, the devitrification resistance deteriorates. The MgO component is an effective component for adjusting the optical constant and improving the meltability, but if the amount exceeds 3%, the devitrification resistance deteriorates. Ca
The O component is an effective component for adjusting the optical constant and improving the melting property, but if its amount exceeds 2%, the acid resistance in the surface method of chemical durability is deteriorated.

The BaO component is an important component that maintains the desired optical constant and improves the devitrification resistance of the glass, but if its amount is 37% or less, its effect cannot be obtained, and it exceeds 55%. And the chemical durability of the glass deteriorates, the viscosity at the time of melting increases, and it becomes impossible to obtain a homogeneous glass. Li
_{The 2} O component is not only effective in improving the meltability, but also increases the amount of SiO ₂ and Al ₂ O ₃ which are components that improve the chemical durability when adjusting the optical constant. Has a positive effect. Therefore, although it is an R ₂ O component, it is an essential component that improves chemical durability. However, if the amount is 0.3% or less, there is no effect, and if it exceeds 5%, the chemical durability deteriorates. The Na ₂ O and K ₂ O components are effective in improving the meltability, but when the total amount of one or more of them, including Li ₂ O, is 0.3% or less, the effect is not obtained. If it exceeds 8%, the chemical durability is deteriorated and the desired optical constant cannot be maintained. The Sb ₂ O ₃ component is an effective component as a defoaming agent at the time of melting the glass, but its amount is preferably 0.5% or less.

[0009]

EXAMPLES Next, suitable composition examples (No. 1 to No. 4) of the optical glass of the present invention and conventional glass comparative examples (No. A and No. B) are shown as optical materials of these glasses. Table 1 shows the constants (Nd, νd) and the evaluation results of water resistance (class) and acid resistance (class) by the powder method.

[0010]

[Table 1]

[Table 1]

The evaluation results of the powder method in Table 1 are based on Japan Optical Glass Industry Association Standard 06-1975, and the smaller the numerical value indicating the grade, the better the chemical durability.

As can be seen in Table 1, the glass No. of the example of the present invention was used. 1 and No. Comparative Example Nos. 2 and 3 have almost the same optical constants. A and No. Compared with B, the evaluation results of the powder method were improved in all cases, and further excellent chemical durability was exhibited. The glasses of other composition examples of the present invention likewise show good evaluation results of the powder method. In addition, although not shown in Table 1, Example No.
The glass transition point of 3 is 550 to 580 ° C, which is suitable for mold pressing. In the glass of the above-mentioned embodiment of the present invention, ordinary raw materials for optical glass such as carbonates, nitrates and oxides are weighed and mixed, and this is mixed with a platinum crucible or the like at a temperature of about 1200 to 1400 ° C. for about 2 It can be easily obtained by melting and homogenizing for 5 hours, then casting in a mold and gradually cooling.

[0013]

As described above, according to the present _{invention, SiO 2 -B 2 O 3 -Al} 2 O of optical glass specified composition range of the present invention ₃ -ZrO ₂
A -ZnO-BaO-Li ₂ O-based glass, the refractive index (Nd) is from 1.60 to 1.65, an Abbe's number ([nu] d) 5
It has an optical constant in the range of 5 to 62, is more excellent in chemical durability than conventional glass, and is also excellent in meltability and excellent in mass productivity.

Claims (1)

[Claims] 1. By weight%, SiO ₂ 25-45%, B _{2
O 3 8~20%, Al 2 O} 3 2~8%, TiO 2 0~
3%, ZrO ₂ 0.5-8%, ZnO 0.2-8
%, MgO 0-3%, CaO 0-2%, BaO 3
_{7~55%, Li 2 O + Na} 2 O + K 2 O 0.3~8
%, But Li ₂ O 0.3-5%, Sb ₂ O ₃ 0-
An optical glass comprising each component in the range of 0.5% and having an optical constant in which the refractive index (Nd) is 1.60 to 1.65 and the Abbe number (νd) is 55 to 62. .