JPH06107427A - Optical glass - Google Patents

Abstract

PURPOSE:To obtain optical glass not contg. a component harmful to the environment and excellent in devitrification resistance and light transmittance by imparting a specified compsn. of SiO2-B2O3-TiO2-Na2O and regulating refractive index and Abbe's number. CONSTITUTION:This optical glass contains, by weight, 40-70% SiO2, 20.5%, in total, of 0-5% B2O3 and 0-15% Al2O3, 2-20% TiO2, 0-5% ZrO2, 0-4% Nb2O5, 0-5% WO3, 15-40% Na2O+K2O and 0-10% MgO+CaO+SrO+BaO+ZnO and has such optical constants as about 1.5-1.65 refractive index and about 35-55 Abbe's number. Since this optical glass does not contain a component harmful to the environment, e.g. PbO, the environment is not polluted by glass scraps, etc., discharged at the time of working this optical glass. This optical glass is also excellent in mass productivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a refractive index (Nd) of about 1.
PbO having an optical constant in the range of 50 to 1.65 and an Abbe number (νd) of about 35 to 55 and having excellent devitrification resistance.
Free _SiO 2 _-B 2 _{O 3} and / or _Al 2 _{O 3}
-TiO ₂ -Na ₂ O and / or K ₂ O-based optical glass.

[0002]

2. Description of the Related Art PbO-containing silicate glass is well known as a glass having the above optical constant.
However, in order to deal with pollution problems in the glass manufacturing process, etc., it does not contain harmful PbO component,
Various glasses containing O ₂ have been studied. For example, German Patent No. 973350 discloses TiO ₂ ,
Fluorine-containing silicate glass is disclosed, and JP-A-54-105119 discloses SiO ₂ —TiO ₂ —.
K 2 _{O-BPO 4} and / or Al (PO ₃₎ is ₃ based glass is disclosed, these glasses is insufficient stability and light transmittance with respect to devitrification both, also the former glass During melting, it is difficult to homogenize due to volatilization of the fluorine component.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical glass having the above-mentioned predetermined optical constant and comprehensively eliminating various drawbacks found in the prior art.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies in order to achieve the above object, and as a result, have found that SiO ₂ -B ₂ O ₃ and / or Al ₂ O ₃
In TiO ₂ —Na ₂ O and / or K ₂ O based glass, it is possible to obtain a desired mass-producible glass having improved devitrification resistance and light transmittance while maintaining the optical constant. The present invention has been completed.

The characteristics of the optical glass according to the present invention are as follows: SiO ₂ 40-70% B ₂ O ₃₀ 0-5%, A
l ₂ O _{3 0 to} 15%, provided that B ₂ O ₃ + Al ₂ O ₃
0.5% or _{more, TiO 2 2~20%, ZrO 2} 0~
_{5%, Nb 2 O 5 0~4} %, WO 3 0~5%, Na
₂ O + K ₂ O 15-40% and MgO + CaO + S
rO + BaO + ZnO Contains each component in the range of 0 to 10%, and has an optical constant in the range of refractive index (Nd) of about 1.50 to 1.65 and Abbe number (νd) of about 35 to 55. .

The reason for limiting the composition range of each of the above components is as follows.
That is, SiO ₂ is effective as a glass-forming component, but if the amount is less than 40%, the light transmittance and chemical durability of the glass deteriorate, and if it exceeds 70%. It becomes difficult to melt the glass. The B ₂ O ₃ component is effective in improving the meltability and devitrification resistance of glass and adjusting the optical constant, but if the amount exceeds 5%, the chemical durability is likely to deteriorate or coloring occurs. The Al ₂ O ₃ component is effective in improving the devitrification resistance and chemical durability of the glass and adjusting the optical constant, but if the amount exceeds 15%, the melting property and the devitrification resistance of the glass are reduced. become worse. However, the total amount of one or two of B ₂ O ₃ and Al ₂ O ₃ components is required to be 0.5% or more in order to improve the devitrification resistance of the glass. The TiO ₂ component is an effective component for imparting high dispersibility to glass. But T
When the amount of iO ₂ is less than 2%, it is difficult to obtain the required optical constant,
On the other hand, if it exceeds 20%, the glass is markedly colored or the devitrification tendency is increased. The ZrO ₂ component can be added up to a range of 5% so as not to deteriorate the meltability in order to improve the chemical durability of the glass. The Nb ₂ O ₅ component is effective in improving devitrification resistance and light transmittance, but if the amount exceeds 4%, it becomes difficult to obtain a desired optical constant. The WO ₃ component is an effective component for imparting a glass with high dispersibility, but if it exceeds 5%, the devitrification tendency increases.

Each of the components Na ₂ O and K ₂ O improves the meltability of the glass, but unexpectedly maintains the devitrification resistance by containing a relatively large amount and has a desired optical constant. It is a component found to be obtainable, and the total amount of one or two of them is required to be 15% or more.
However, if the total amount of those components exceeds 40%, the chemical durability of the glass deteriorates. MgO, CaO, Sr
Each component of O, BaO and ZnO may be added for improving the devitrification resistance, but the total amount of one or more of these components is up to 10% in order to maintain a desired optical constant. . Further, in the glass of the present invention, if necessary, other components such as As ₂ O ₃ and Sb ₂ O ₃ are used as fining agents up to about 1%, Li ₂ O up to about 5%, R 2
It is possible to add one or two kinds of b ₂ O and Cs ₂ O up to about 10% and SnO up to about 2%.

[0008]

EXAMPLES Next, examples of the optical glass of the present invention will be described. Table 1 shows the example compositions (No. 1 to No. 12) of the optical glass of the present invention and the comparative composition examples (No. A and No. B) of the conventional glass, and the refractive index (Nd) of these glasses. , Abbe number (νd), liquidus temperature (° C) measurement test result and 80% light transmission wavelength (T80 (n
m)).

[0009]

[Table 1]

The glass described above was prepared by mixing and mixing using ordinary optical glass raw materials, melting it using a platinum crucible, homogenizing with stirring, shaping it into a block shape and gradually cooling. In Table 1, the liquidus temperature measurement test results are as follows: the glass sample obtained by the above method was crushed and then placed on a platinum plate,
It was obtained by observing the devitrification condition by observing it with a microscope while holding it in a temperature gradient furnace for 30 minutes. The 80% light transmission wavelength was measured by a spectrophotometer using a glass sample polished on both sides to a thickness of 10 m / m. As seen in Table 1 which is the measured value,
Conventional glass comparative example No. A and No. B has a high liquidus temperature, whereas all the glasses of the examples have a low liquidus temperature and have improved devitrification resistance. In addition, Comparative Example No. Compared with the glass of A, this Example No. showing an optical constant almost equal to this. In the glass of Nos. 1 to 3, the 80% transmission wavelength is shifted to the short wavelength side, and the comparative example No. Compared with the glass of B, the glass No. of this example showing an optical constant almost equal to this. Similar shifts were observed in Nos. 4 to 7, and the coloring property was improved. Further, the coloring properties of the other glasses of this example are similarly improved.

[0011]

As described above, the optical glass of the present invention has a specific composition range of SiO ₂ —B ₂ O ₃ and / or Al ₂ O ₃ —TiO ₂ —Na ₂ O and / or K ₂ O.
Since it is a system glass, the refractive index (Nd) is about 1.50 to
It has an optical constant of 1.65 and an Abbe number (νd) of about 35 to 55, does not contain harmful PbO components, and is superior in devitrification resistance and light transmittance as compared with conventional glass, It also excels in mass productivity.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C03C 3/093 3/097

Claims (1)

[Claims] 1. SiO ₂ 40-70%, B _{2 by} weight%.
_{O 3 0~5%, Al 2 O} 3 0~15%, provided that _{B 2
O 3 + Al 2 O 3 0.5} % or _more, TiO 2 2 to 20
_{%, ZrO 2 0~5%, Nb} 2 O 5 0~4%, WO
_{30 to} 5%, Na ₂ O + K ₂ O 15 to 40% and MgO + CaO + SrO + BaO + ZnO 0-10%
Of each component and having a refractive index (Nd) of about 1.
An optical glass having an optical constant in the range of 50 to 1.65 and Abbe number (νd) of about 35 to 55.