JPH0692674A - Optical glass - Google Patents

Abstract

PURPOSE:To provide an optical glass free from PbO and having a refractive index (Nd) of about 1.51-1.60 and an Abbe number (nud) of about 38-52 as optical constants and improved devitrification resistance and light-transmittance. CONSTITUTION:The optical glass contains 40-62wt.% of SiO2, 0-5wt.% of B2O3, 0-8wt.% of Al2O3, 0.5-15wt.% of P2O5, 2-20wt.% of TiO2+Nb2O5 (wherein TiO2 is 0-20wt.% and Nb2O5 is 0-15wt.%), 0-5wt.% of WO3, 12.5-40wt.% of Na2O+K2O (wherein Na2O is 12.5-35wt.% and K2O is 0-27.5wt.%), 0-4wt.% of ZrO2, 0-5wt.% of MgO+CaO+SrO+BaO and 0-5wt.% (in terms of F in total) of the fluoride of one or more kinds of the metals of the above metal oxides.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention has a refractive index (Nd) of about 1.51 to 1.60 and an Abbe number (νd) of about 38.
S showing an optical constant in the range of up to 52, having excellent devitrification resistance and light transmittance, and containing no harmful PbO component.
iO ₂ -P ₂ O ₅ -TiO ₂ and / or _Nb 2 _{O 5}
-Na ₂ O-based optical glass.

[0002]

2. Description of the Related Art Conventionally, PbO-containing silicate glass is well known as a glass having the above optical constants. However, in order to deal with the pollution problem in the glass manufacturing process, various TiO ₂ -containing glasses containing no harmful PbO component have been studied, but they are not often used because of their poor light transmission properties and devitrification resistance. Not not. For example, German Patent No. 973,350 discloses TiO.
_2. Fluorine-containing silicate glass has been disclosed, but it has poor light transmission properties and devitrification resistance, and is liable to cause quality deterioration due to volatilization of fluorine components during glass melting. Further, in JP-A-54-105,119, SiO ₂ —TiO ₂ is disclosed.
₂ -K ₂ O-BPO ₄ and / or Al _{(PO 3)} 3
Although a system glass is disclosed, this glass also has insufficient light transmittance and devitrification resistance.

[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 the drawbacks found in the above-mentioned conventional glasses.

[0004]

In order to achieve the above-mentioned object, the inventors of the present invention have conducted intensive studies and studies, and as a result, have found that SiO ₂
P ₂ O ₅ -TiO ₂ and / or _{Nb 2 O} 5 -Na 2
In the O-based glass, it has been found that the desired optical constant can be maintained, the devitrification resistance and the light transmittance are improved, and a desired glass that can be mass-produced can be obtained, and the present invention has been completed. .

The characteristics of the optical glass according to the present invention are, in weight%, 40 to 62% of SiO ₂ , 0 to 5% of B ₂ O ₃₀ ,
_{Al 2 O 3 0~8%, P} 2 O 5 0.5~15%, T
iO ₂ + Nb ₂ O ₅ 2 to 20%, provided that TiO ₂ 0
_{~20%, Nb 2 O 5 0~15} %, WO 3 0~5
%, Na ₂ O + K ₂ O 12.5-40%, but Na
₂ O 12.5 to 35%, K ₂ O 0 to 27.5%, Z
rO ₂ 0 to 4%, MgO + CaO + SrO + BaO
0 to 5% and a total amount of 0 to 5%, as F, of fluorides of one or more metals of the above metal oxides.

The reason for limiting the composition range of each of the above components is as follows.
It is as follows. That is, if the amount of the SiO ₂ component that is a glass-forming oxide is less than 40%, the light transmittance and chemical durability of the glass deteriorate, and if it exceeds 62%, it becomes difficult to melt the glass. The B ₂ O ₃ component is effective in improving the meltability and stability of glass,
If the amount exceeds 5%, deterioration of chemical durability and coloration are likely to occur. The Al ₂ O ₃ component is effective in improving the devitrification resistance and the chemical durability of the glass, but if the amount exceeds 8%, the viscosity becomes high and the devitrification resistance also deteriorates.
The P ₂ O ₅ component is an important component that makes the glass highly dispersible while maintaining the glass stability, and its amount is 0.5%.
If less than 15%, it is difficult to obtain the effect, and if more than 15%, the stability of glass deteriorates. Each component of TiO ₂ and Nb ₂ O ₅ is an effective component for imparting high dispersibility to glass.
However, if the total amount of one or two of them is less than 2%, it is difficult to obtain the required optical constant, and the total amount of them is 2%.
If it exceeds 0%, the glass is significantly colored or the devitrification tendency is increased. However, the proper amounts of the TiO ₂ and Nb ₂ O ₅ components are 20% and 15%, respectively, for the same reason.
Up to%. The WO ₃ component can be added up to 5% for the same reason.

The Na ₂ O and K ₂ O components improve the meltability of the glass, but especially when a relatively large amount of Na ₂ O is added,
Surprisingly, it is an important component found that glass having good light transmittance can be obtained while maintaining a desired optical constant, and the total amount of one or two of them is 12.5%. The above is necessary, and if the total amount exceeds 40%, the chemical durability of the glass deteriorates. However, Na ₂ O
The amounts of K ₂ O and K ₂ O are 12.5 each for the above reasons.
It should be in the range of ~ 35% and 0-27.5%.
Further, the glass of the present invention contains 4% of ZrO ₂ if necessary.
And the total amount of one or more of MgO, CaO, SrO and BaO components up to 5%, and the total amount of one or more of the above metal oxides as fluoride as F. Up to 5% can be contained in order to adjust the optical constant of the glass and improve the chemical durability. Each component of As ₂ O ₃ and Sb ₂ O ₃ was used as a fining agent to about 1%, and Rb ₂ O and Cs were added.
_It does not matter if ₂ O is added to about 10% each, and Li ₂ O and SnO are added to about 0.5% each.

[0008]

EXAMPLES Next, examples of the optical glass of the present invention will be described. Table 1 shows the preferred composition examples (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 prior art, and the refractive index (Nd of these glasses. ), Abbe number (νd), devitrification test results and 80% light transmission wavelength (T80).

[0009]

[Table 1]

The glass samples of each composition shown in Table 1 were prepared and mixed by using a predetermined optical glass raw material which is usually used, melted using a platinum crucible, homogenized by stirring, and then molded into a block shape. It was then slowly cooled. The devitrification test results in Table 1 are obtained by placing the crushed pieces of glass obtained by the above method on a platinum plate and holding it in a temperature gradient furnace for 30 minutes, observing the devitrification condition with a microscope, and determining the liquidus temperature. The 80% light transmission wavelength is a value obtained by measuring a 10 m / m-thick double-side polished sample with a spectrophotometer.
As can be seen in Table 1, Comparative Example No. 1 of the conventional glass. A
And No. B shows a desired value in which the optical constant is almost the same as that of the glass of this example, but the liquidus temperature is high, and
No. B has an 80% transmission wavelength on the long wavelength side. On the other hand, the glass of this example has a low liquidus temperature and is 80%.
The transmission wavelength is shifted to the short wavelength side, the coloring property is improved, and the melting property is also excellent.

[0011]

As described above, the optical glass of the present invention has a novel specific composition range of SiO ₂ —P ₂ O ₅ —TiO _2.
2 and / or Nb ₂ O ₅ —Na ₂ O based glass, it has a refractive index (Nd) of about 1.51 to 1.60 and an Abbe number (νd) of about 38 to 52, and is harmful. Na P
It contains no bO component, and compared to conventional glass,
It has improved stability against devitrification, excellent light transmittance, and little coloring. It is also useful because it has good meltability and mass productivity.

Claims (1)

[Claims] 1. By weight%, SiO ₂ 40-62%, B ₂
O ₃ 0-5%, Al ₂ O ₃ 0-8%, P ₂ O ₅
0.5 to 15%, TiO ₂ + Nb ₂ O ₅ 2 to 20%,
However, TiO ₂ 0 to 20%, Nb ₂ O _{5 0 to} 15
%, WO _{30 to} 5%, Na ₂ O + K ₂ O 12.5 to
40%, provided that _{Na 2 O 12.5~35%, K 2} O0
_{~27.5%, ZrO 2 0~4%,} MgO + CaO +
SrO + BaO 0-5% and the total amount of fluoride of one or more metals of the above metal oxides as F 0-
An optical glass containing 5%.