JPS6344693B2 - - Google Patents

Description

Detailed Description of the Invention The present invention has optical constants in the range of a refractive index (nd) of about 1.69 to 1.85, an Atsube number (νd) of about 23 to 31, and has good chemical durability and spectral transparency. and a novel optical glass with excellent meltability.

Conventionally, as glasses having the above optical constants,
SiO ₂ -PbO-R ₂ O (R is an alkali metal element) glass containing a large amount of PbO is known, but while this glass has the advantage of high meltability, it has a high PbO content, so It has poor chemical durability, and during the process of polishing the lens or using it for a long period of time, the lens surface tends to be chemically eroded, causing so-called "staining", and the spectral transmittance is poor, resulting in a large degree of discoloration. Therefore, in order to improve these drawbacks, a part of PbO was replaced with Al ₂ O ₃ which has high chemical durability, and in order to obtain high dispersibility while avoiding coloration, Bi ₂ O ₃ , WO ₃ , PbO− containing all or part of each component of ZrO ₂ and ZnO
Al ₂ O ₃ −(Bi ₂ O ₃ +WO ₃ +ZrO ₂ +ZnO) type glasses have been proposed. However, since this glass must contain a relatively large amount of Al ₂ O ₃ and the R ₂ O component is excluded to prevent coloring, it has extremely poor meltability and is difficult to manufacture. Difficult to put into practical use. Therefore, the reality is that it is difficult to obtain an optical glass that has optical constants within the above range and also comprehensively solves the above drawbacks.

An object of the present invention is to comprehensively improve the various drawbacks found in the above-mentioned conventional glasses. As a result of extensive testing and research to achieve the above object, the present inventors focused on the fact that Nb ₂ O ₅ and metal fluoride components have a positive and negative relationship in their effects on the optical constants of glass, Both of these ingredients are essential
We have found that by coexisting SiO ₂ −PbO−R ₂ O-based glass with additives, it is possible to improve chemical durability and spectral transmittance while maintaining desired optical constants and good meltability. However, the present invention has been accomplished.

The characteristics of the composition of the optical glass of the present invention that achieves the above object are as described in the claims.
In weight%, _SiO2 24-40%, PbO40-72%,
_Nb2O5 1~12% _{, Na2O} and/or _K2O0.5 ~
7%, and a total of 0.1 to 1.5% of each component as _F2 of one or more fluorides of the above metal elements. Therefore, an important feature of the present invention is that a fluoride component in which part of the oxygen of an oxide of Si, Pb, Nb, Na, K, etc. is replaced with F.
This is due to the essential coexistence of Nb ₂ O ₅ .

The reason for limiting the composition range of each of the above components is as follows. That is, in the glass of the present invention, the amount of SiO ₂ , which is the main glass-forming oxide, is
When it is less than 24%, the chemical durability of the glass decreases, and the tendency for devitrification increases. Moreover, if the amount exceeds 40%, the optical constants targeted by the present invention cannot be maintained. PbO is a necessary component to prevent the tendency of the glass to devitrify and maintain the desired optical constants. If the amount of PbO is less than 40%, desired optical constants cannot be maintained, and if it exceeds 72%, chemical durability decreases and the degree of coloring increases. In the present invention, both Nb ₂ O ₅ and metal fluoride components are SiO ₂ −PbO−
By coexisting in Na ₂ O glass,
While maintaining predetermined optical constants and good meltability,
It is an important combination component that has been found to be able to improve chemical durability and spectral transparency all at once.
However, if only Nb ₂ O ₅ is added to this type of glass, the coloring and melting properties of the glass will deteriorate, and if only metal fluoride components are added, it will be difficult to adjust the optical constants, and the chemical durability will deteriorate. It doesn't improve sex either. Among the above components, Nb ₂ O ₅ has the effect of increasing the refractive index of the glass, reducing the Atsbe's number, and improving the chemical durability, but it has the effect of increasing the Atsbe's number, but it has the effect of increasing the Atsbe's number. By coexistence, it is possible to introduce a larger amount of Nb ₂ O ₅ into the glass while adjusting the optical constant to a predetermined value, and at the same time
Since the content of PbO can be reduced, the chemical durability of the glass can be further improved. but,
If the amount of Nb ₂ O ₅ is less than 1%, the effect is not sufficient, and if it exceeds 12%, the glass tends to devitrify. In addition, Na ₂ O and/or K ₂ O have the effect of increasing the melting properties and devitrification resistance of glass, but if the amount is less than 0.5%, these effects are insufficient, and if it exceeds 7%, the chemical durability is reduced. The metal fluoride is a fluoride of one or more of the above-mentioned metal elements,
For example, fluorine can be introduced into glass in the form of PbF ₂ , NaF, KF, K ₂ SiF ₆ , etc., and it is thought that during glass melting, fluorine is ionized and coordinates to an unspecified number of cationic metals. The metal fluoride has the effect of improving the spectral transmittance of the glass of the present invention, significantly reducing the degree of coloring, and promoting the melting of the SiO ₂ raw material to improve the meltability of the glass. However, the total amount of these fluoride components as _F2 is
If it is less than 0.1%, these effects are not sufficient,
Moreover, if it exceeds 1.5%, the tendency to devitrify increases or it becomes impossible to maintain desired optical constants.

In addition, in the glass of the present invention, As ₂ O ₃ and/or Sb ₂ O ₃ are effective as defoaming and clarifying agents during glass melting, and may be added arbitrarily, but the amount thereof must be 1% or less. It is enough. In addition, in order to adjust the optical constants, as necessary, within the range that does not impair the meltability, devitrification resistance, coloring properties, etc. of the glass,
Divalent metal oxides such as MgO, CaO, BaO, ZnO,
One or more components such as TiO ₂ , WO ₃ and ZrO ₂ may be added in a total amount of about 5%. however,
It is better not to add Al ₂ O ₃ because it makes the glass devitrified.

Next, an example of the composition of the optical glass of the present invention (No.
1 to No. 16) as the optical constants (nd,
Table 1 shows the measurement test results for νd) and chemical durability (RW, RA). Table 1 also shows SiO ₂ -PbO-R ₂ O glass Nos. having optical constants equivalent to those of Example Nos. 1, 2 and 3, respectively;
and are shown as comparative composition examples. Furthermore, FIGS. 1, 2, and 3 show glasses of practical composition examples of the present invention and comparative examples, that is, No. 1 and No. 3, respectively.
Comparative diagrams of spectral transmittance curves of samples No. 2 and No. 3, and samples No. 3 and No. (all 10 mm thick) are shown.

In Table 1, RW represents water resistance and RA represents acid resistance, and these values are:
The crushed sample, which was measured in accordance with the Japan Optical Glass Industry Association standards and remains within the standard sieve size of 420 to 590 μm, is placed in distilled water (PH6.5 to 7.5) for RW.
In the case of RA, the weight loss is expressed as a percentage after being placed in a 0.01N nitric acid solution and treated in a boiling water bath for 60 minutes.

As shown in Table 1, the glasses of Example Nos. 1, 2, and 3 are the same as the glasses of Comparative Composition Example No. 1, 2, and 3, respectively.
It can be seen that the chemical durability values (RW, RA) are all much better than that of , and, and the glasses of other examples are also excellent. In addition, as seen in Figures 1 to 3, Example No.
Glasses Nos. 1, 2, and 3 are all superior to the glass of the comparative composition example in that they have a higher spectral transmittance and are therefore much less colored. The glasses of other examples of the present invention also have high spectral transmittances, similar to the glasses of Examples Nos. 1 to 3.

Furthermore, the glass of the above embodiment of the present invention is produced by mixing optical compounding raw materials such as carbonates, nitrates, oxides, and fluorides, and then using a platinum crucible etc.
It is obtained by melting and defoaming at 1350℃ for about 1 to 4 hours, homogenizing by stirring, and then casting into a mold and slowly cooling. However, since both contain R ₂ O and fluoride components, the same melting 50~ compared to the conventional improved glass with equivalent optical constants.
It can be defoamed and clarified at a low temperature of 150℃.

As mentioned above, the glass of the present invention has optical constants in the range of a refractive index (nd) of about 1.69 to 1.85 and an Abbe number (νd) of about 23 to 31, and unlike conventional glasses,
It has excellent chemical durability, spectral transparency, and meltability. Further, the glass of the present invention is useful because it has a small tendency to devitrify during melting, is easily homogenized, and can be mass-produced.

[Brief explanation of drawings]

FIG. 1, FIG. 2, and FIG. 3 show the glasses of Example of the present invention and Comparative example, namely, No. 1 and No. 3, respectively.
A comparison diagram of spectral transmittance curves of glass samples No. 2 and No. 3, and No. 3 and No.

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Claims (1)

[Claims] 1% by weight, _SiO2 24-40%, PbO40-72%,
_Nb2O5 1~12% _{, Na2O} and/or _K2O0.5 ~
7%, and one or more fluorides of each of the above metal elements in a total range of 0.1 to 1.5% as _F2 .