TW201733942A - Glass, glass raw material for press molding, optical element blank, and optical element - Google Patents

Abstract

There is provided glass which is oxide glass having, by cation%, total content of B3+, Si4+, La3+, Y3+, Gd3+, Yb3+, Nb5+, Ti4+, Ta5+, W6+, Zr4+, Zn2+, Mg2+, Ca2+, Sr2+, Ba2+, Li+, Na+, K+, Al3+ and Bi3+ of 90% or more, the Abbe number [nu]d in a range of 39.5 to 41.5, a refractive index nd satisfying a relation of (nd ≥ 2.0927-0.0058*[nu]d) to the Abbe number [nu]d and total D of values obtained by multiplying the contents of the cation components by specific factor of 0.032 to 0.090 respectively satisfying (D ≤ 6.242*nd-6.8042).

Description

Glass, glass materials for press molding, optical component blanks and optical components

The present invention relates to a glass, a glass material for press molding, an optical element blank, and an optical element.

By combining a lens formed of a high refractive index low-dispersion glass with a lens formed of ultra-low dispersion glass or the like to form a cemented lens, it is possible to correct chromatic aberration and to make the optical system compact. Therefore, the high refractive index low dispersion glass occupies a very important position as an optical element constituting a projection optical system such as an imaging optical system or a projector. Such high refractive index low dispersion glass is described, for example, in Patent Documents 1 to 20.

[Previous Technical Literature]

[Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. 2007-063071.

Patent Document 2: Japanese Laid-Open Patent Publication No. 2007-230835.

Patent Document 3: Japanese Laid-Open Patent Publication No. 2007-249112.

Patent Document 4: Japanese Laid-Open Patent Publication No. 2007-261826.

Patent Document 5: Japanese Laid-Open Patent Publication No. 2003-267748.

Patent Document 6: Japanese Laid-Open Patent Publication No. 2009-203083.

Patent Document 7: Japanese Laid-Open Patent Publication No. 2011-230992.

Patent Document 8: Japanese Laid-Open Patent Publication No. 2012-025638.

Patent Document 9: Japanese Laid-Open Patent Publication No. SHO 54-090218.

Patent Document 10: Japanese Laid-Open Patent Publication No. SHO 56-160340.

Patent Document 11: Japanese Laid-Open Patent Publication No. 2001-348244.

Patent Document 12: Japanese Laid-Open Patent Publication No. 2008-001551.

Patent Document 13: Japanese Laid-Open Patent Publication No. 2013-536791.

Patent Document 14: WO10/053214.

Patent Document 15: Japanese Laid-Open Patent Publication No. 2012-180278.

Patent Document 16: Japanese Laid-Open Patent Publication No. 2012-236754.

Patent Document 17: Japanese Laid-Open Patent Publication No. 2014-084235.

Patent Document 18: Japanese Laid-Open Patent Publication No. 2014-062025.

Patent Document 19: Japanese Laid-Open Patent Publication No. 2014-062026.

Patent Document 20: Japanese Laid-Open Patent Publication No. 2011-93780.

For the glass for optical elements, an optical characteristic map (or also referred to as an Abbe chart) is widely used in order to show the distribution of optical characteristics. The optical characteristic map takes the Abbe number (νd) on the horizontal axis, the refractive index (nd) on the vertical axis, and increases the Abbe number (νd) from the right side of the horizontal axis to the left side, and the refractive index self-vertical. A method in which the lower direction of the shaft is sequentially increased is sequentially formed. In addition, unless otherwise indicated, the refractive index and Abbe number refer to the refractive index (nd) of the d line (wavelength 587.56 nm) of 氦, and the d line (wavelength of 587.56 nm) of 氦. Bay number (νd).

In the optical characteristic diagram, the optical characteristics of high refractive index low dispersion glass (high nd high νd glass) generally show an increase in refractive index when the Abbe number becomes smaller, when The so-called rightward rising distribution of the refractive index decreases as the Abbe number increases. This can be considered for the following reasons.

High refractive index low dispersion glass mostly contains rare earth oxides such as boron oxide and cerium oxide. In such a glass, in order to increase the refractive index without reducing the Abbe number, the content of the rare earth oxide is increased. However, in the prior art high refractive index low dispersion glass, when the content of the rare earth oxide is increased, the thermal stability of the glass is lowered, and the glass tends to exhibit devitrification during the process of producing the glass. Therefore, in the prior art high refractive index low dispersion glass, it is difficult to increase the Abbe number and the refractive index together while suppressing the devitrification of the glass which is intended to be used as the optical element material. This is considered to be the reason why the prior art high refractive index low dispersion glass exhibits such a distribution in the optical property map.

On the other hand, in the design of an optical system, a glass having a high refractive index and a large Abbe number (low dispersion) is an optical element which is extremely effective for correcting chromatic aberration, high function of an optical system, and compactness. material. Therefore, setting a straight line rising to the right on the optical characteristic map provides a very large meaning on the straight line and the glass having a higher refractive index than the straight line (the area on the left side of the line on the drawing).

From the above aspects, the Abbe number (νd) is 39.5 to 41.5, and the glass having a value equal to or higher than the Abbe number and the refractive index (nd) of 2.0927 to 0.0058 × νd satisfies nd. A glass having a relationship of 2.0927-0.0058 x νd is a high refractive index low dispersion glass useful in an optical system.

Further, an optical element constituting a projection optical system such as an imaging optical system or a projector is expected to be lighter. This is because the optical element is lightweight and related to the weight reduction of the imaging optical system and the projection optical system in which the optical element is mounted. For example, when a heavy optical component is mounted in an auto-focus camera, the drive The power consumption consumed during autofocus increases and the battery is quickly consumed. On the other hand, if the optical element is made lighter, the power consumption when driving the autofocus is lowered, and the life of the battery can be extended.

However, the inventors of the present invention considered that the range of the Abbe number (νd) used in the glass described in Patent Documents 1 to 20 is 39.5 to 41.5, which satisfies nd. An optical element produced by a high refractive index low dispersion glass having a relationship of 2.0927 to 0.0058 x νd tends to become heavy. This is because, in the composition adjustment for high refractive index and low dispersion described in Patent Documents 1 to 20, the specific gravity of the glass tends to increase.

An object of one aspect of the present invention is to provide an Abbe number (νd) of 39.5 to 41.5, satisfying nd A glass having a relationship of 2.0927-0.0058 × νd and contributing to weight reduction of an optical element.

One aspect of the present invention relates to a glass which is an oxide glass represented by a cation %, B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Ti ^{4 +} , Ta ⁵⁺ , W ⁶⁺ , Zr ⁴⁺ , Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ and Bi ³⁺ The total content is 90% or more, and the Abbe number (νd) is in the range of 39.5 to 41.5. The refractive index (nd) satisfies the following formula (1) with respect to the Abbe number (νd):

With respect to the cation component described in Table 1 below, the total D of the content of each cation component multiplied by the coefficient described in Table 1 with respect to the refractive index (nd) satisfies the following formula (B):

In the above glass, represented by cation %, B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ , W ⁶⁺ , Zr ⁴⁺ , Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ and Bi ³⁺ (hereinafter, these cation components are referred to as "mainly The total content of the cationic component ") is 90% or more. In order to achieve the above object, the inventors of the present invention have focused on the effects of the specific gravity of the above-mentioned main cationic component on the glass. Moreover, a considerable number of tests were repeated, and as a result, the coefficients shown in Table 1 were determined for each of the main cation components. By adjusting the composition in such a manner that the total D calculated using these coefficients satisfies the formula (B), it is possible to provide nd which can contribute to the range of the Abbe number (νd) of 39.5 to 41.5. The low specific gravity of the high refractive index low-dispersion glass in the relationship of 2.0927-0.0058 × νd is a lightweight glass of an optical element.

According to an aspect of the present invention, it is possible to provide a glass having optical characteristics useful in an optical system and contributing to weight reduction of an optical element. Further, according to one aspect of the present invention, it is possible to provide a glass material for press molding, an optical element blank, and an optical element which are formed of the above glass.

1 is a total of D in which the specific gravity of each glass of Example 1 and each of Comparative Examples 1 to 4 is plotted on the horizontal axis, and the content of each cationic component is multiplied by the coefficient described in Table 1 on the vertical axis. chart.

2 is a graph in which the Abbe number (νd) of each of the glasses of Example 1 and each of Comparative Examples 1 to 4 is taken on the horizontal axis, and the value A calculated based on the formula (A) described later is taken on the vertical axis.

[glass]

The glass of one embodiment of the present invention is an oxide glass which is represented by a cation %, B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ , W ⁶⁺ , Zr ⁴⁺ , Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ and Bi The total content of ³⁺ is 90% or more, and the Abbe number (νd) is in the range of 39.5 to 41.5. The refractive index (nd) satisfies the above formula (1) with respect to the Abbe number (νd), and is as follows. The total content D of the cation component described in Table 1 and the content of each cation component multiplied by the coefficient described in Table 1 with respect to the refractive index (nd) satisfies the above formula (B).

Hereinafter, the details of the above glass will be described.

The glass composition in the present invention can be quantified by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). The analysis value obtained by ICP-AES sometimes includes a measurement error of about ±5% of the analysis value. In the present specification and the present invention, the content of the constituent component is 0%, and the inclusion or non-introduction means that the constituent component is substantially not contained, and the content of the constituent component is not more than the impurity level.

In the present invention, the glass component is represented by the cationic component % of the cationic component. The cation % is known as a percentage of the total content of all the cationic components contained in the glass to 100%.

Hereinafter, the total content (total content) of the content of the cationic component and the content of the plurality of cationic components is represented by the cationic % unless otherwise specified. Further, in the cation % expression, the ratio of the content of the cation components (including the total content of the plurality of cation components) is referred to as a cation ratio.

Hereinafter, for the numerical range, the (better) preferred lower limit and (better) preferred upper limit are sometimes shown in the table. The higher the numerical value described below in the table, the better the numerical value described at the bottom. Further, unless otherwise specified, the (better) preferred lower limit means that the value above the value (better) is better, and the (better) preferred upper limit means the value below the value (better). good. The numerical value range can be arbitrarily combined with the numerical values described in the column of the (better) preferred lower limit in the table and the numerical values described in the column of the (better) preferred upper limit.

<glass composition>

For the above glass, B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ , W ⁶⁺ , Zr ⁴⁺ , Zn ^{2 The total content of +} , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ and Bi ³⁺ (main cation component) is 90% or more. The cation component contained in the glass may be only the main cation component (that is, the total content of the main cation component is 100%), and may contain one or more other cation components in addition to the main cation component. A preferred lower limit of the total content of the main cationic components is shown in Table 2 below.

In the glass composition of the glass, the total of the values of the respective cationic components of the main cation component multiplied by the content of each cationic component in the refractive index (nd) by the coefficient described in Table 1 satisfies the following formula (B). :

The way to adjust. Thereby, the range of the Abbe's number (νd) is 39.5 to 41.5, and the refractive index (nd) satisfies the weight reduction of the high refractive index low-dispersion glass of the above formula (1) with respect to the Abbe number (νd). This point was newly discovered by the inventors after intensive research. It should be noted that the details of the above total D are as follows, The unit of the content is the cationic %.

D = B ^{3 +} content × 0.032 + Si ^{4 +} content × 0.029 + La ^{3 +} content × 0.066 + Y ^{3 +} content × 0.053 + Gd ^{3 +} content × 0.093 + Yb ^{3 +} content × 0.094 + Nb ^{5 +} content × 0.049 +Ti ⁴⁺ content × 0.045 + Ta ^{5 +} content × 0.104 + W ^{6 +} content × 0.111 + Zr ^{4 +} content × 0.080 + Zn ²⁺ content × 0.051 + Mg ²⁺ content × 0.030 + Ca ²⁺ content × 0.024 + Sr ²⁺ content × 0.043 + Ba ²⁺ content × 0.055 + Li ⁺ content × 0.031 + Na ⁺ content × 0.021 + K ⁺ content × 0.01 2 + Al ^{3 +} content × 0.034 + Bi ^{3 +} content × 0.090

The above formula (B) is preferably the following formula (B-1), more preferably the following formula (B-2), further preferably the following formula (B-3), and still more preferably the following ( B-4), Further, it is more preferably the following formula (B-5), and still more preferably the following formula (B-6), and still more preferably the following formula (B-7), and furthermore The following formula (B-8) is preferable, and the following formula (B-9) is still more preferable.

In the glass composition of the glass, the total content of the main cationic component is 90% or more and the formula (B) is satisfied, and the main cationic component may be contained in the glass (that is, the content is 0%). Cation component. A preferred range of the content of each cationic component will be further described later. However, the invention is not limited to the preferred ranges described below.

B ³⁺ and Si ⁴⁺ are network forming components of glass. When the total content (B ³⁺ + Si ⁴⁺ ) of B ³⁺ and Si ⁴⁺ is 43% or more, the thermal stability of the glass can be improved, and the crystallization of the glass during production can be suppressed. On the other hand, when the content of B ³⁺ and the total content of Si ⁴⁺ are 65% or less, the decrease in the refractive index (nd) can be suppressed, and therefore it is preferable from the viewpoint of producing a glass having the above optical characteristics. Therefore, the range of the total content of B ³⁺ and Si ⁴⁺ in the above glass is preferably set to 43 to 65%. A more preferred lower limit and a higher upper limit of the total content of B ³⁺ and Si ⁴⁺ are shown in Table 3 below.

La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ are components having an effect of suppressing a decrease in the Abbe number (νd) and increasing the refractive index. Further, these components also have an effect of improving the chemical durability, weather resistance, and glass transition temperature of the glass.

When the total content of La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ ) is 25% or more, the refractive index (nd) can be suppressed. Since it is lowered, it is preferable from the viewpoint of producing a glass having the above optical characteristics. Further, it is also possible to suppress chemical durability and deterioration of weather resistance of the glass. In addition, when the glass transition temperature is lowered, when the glass is machined (cut, cut, polished, polished, etc.), the glass becomes easily broken (deterioration of machinability) when La ³⁺ , Y ³⁺ When the total content of Gd ³⁺ and Yb ³⁺ is 25% or more, the decrease in the glass transition temperature can be suppressed, so that the machinability can be improved. On the other hand, when the total content of La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ is 50% or less, since the thermal stability of the glass can be improved, crystallization at the time of glass production can be suppressed and the crystallization can be suppressed. The melting of the raw material at the time of melting the glass remains. In addition, it is also preferable from the viewpoint of suppressing an increase in the specific gravity. Therefore, in the above glass, the range of the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is preferably 25 to 50%. A more preferred lower limit and a higher upper limit of the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ are shown in Table 4 below.

Nb ⁵⁺ , Ti ⁴⁺ , Ta ^{5+ ,} and W ⁶⁺ are components having an effect of increasing the refractive index, and have an effect of improving the thermal stability of the glass by being contained in an appropriate amount. When the total content of Ti ⁴⁺ , Nb ⁵⁺ , Ta ^{5+ ,} and W ⁶⁺ (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ ) is 3% or more, the thermal stability is maintained and the above is achieved. The optical characteristics are better considered. On the other hand, when the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is 12% or less, it is possible to suppress a decrease in thermal stability and a decrease in Abbe number (νd). Therefore, in the above glass, the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is preferably in the range of 3 to 12%. A more preferred lower limit and a higher upper limit of the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ are shown in Table 5 below.

Zr ⁴⁺ is a component having an effect of increasing the refractive index, and has an effect of improving the thermal stability of the glass by containing it in an appropriate amount. In addition, Zr ⁴⁺ also has an effect of making the glass difficult to break during machining by increasing the glass transition temperature. In order to obtain these effects satisfactorily, it is preferred to set the content of Zr ⁴⁺ to 2% or more in the above glass. On the other hand, when the content of Zr ⁴⁺ is 8% or less, since the thermal stability of the glass can be improved, it is possible to suppress the occurrence of crystallization during the production of the glass and the occurrence of the melt residue at the time of glass melting. Therefore, the content of Zr ⁴⁺ in the above glass is preferably in the range of 2 to 8%. A more preferred lower limit and a higher upper limit of the Zr ⁴⁺ content are shown in Table 6 below.

In order to achieve an optical property in which the Abbe number (νd) is 39.5 to 41.5, the refractive index (nd), and the Abbe number (νd) satisfy the relationship of the above formula (1), it is preferred to compare the Zr ⁴⁺ content in the above glass. The ratio of the cation ratio of {Zr ⁴⁺ content/(Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} of the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ^{5+ ,} and W ⁶⁺ is set to 0.48. ~2.20. From the viewpoint of suppressing a decrease in the glass transition temperature (and thereby improving machinability), the range of the above cation ratio is preferably 0.48 to 2.20. Further, from the viewpoint of improvement in thermal stability and low dispersion of glass, the cation ratio is preferably 0.48 or more. On the other hand, from the viewpoint of improvement in meltability and suppression of crystallization, the cation ratio is preferably 2.20 or less. A more preferred lower limit and a higher upper limit of the cation ratio {Zr ⁴⁺ content / (Nb ⁵ + + Ti ⁴ + + Ta ⁵ + + W ⁶⁺ )} are shown in Table 7 below.

In order to achieve an improvement in the thermal stability of the glass and an Abbe number (νd) of 39.5 to 41.5, a refractive index (nd) and an Abbe number (νd) satisfying the optical characteristics of the above relationship (1), it is preferably in the above glass. The cation ratio of the total content of B ³⁺ and Si ^{4+ to} the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ {B ³⁺ +Si ⁴⁺ /(La ³⁺ +Y ^{3 +} +Gd ³⁺ +Yb ³⁺ )} is set to 0.70~1.75. When the cation ratio ((B ³⁺ + Si ⁴⁺ ) / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )) is 0.70 or more, since the thermal stability of the glass can be improved, the glass can be suppressed Destruction. Further, it is also preferable from the viewpoint of suppressing an increase in the specific gravity of the glass. On the other hand, the cation ratio ((B ³⁺ + Si ⁴⁺ ) / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ ))) of 1.75 or less is preferable from the viewpoint of achieving the above optical characteristics. A more preferred lower limit and a higher upper limit of the cation ratio {(B ³⁺ + Si ⁴⁺ ) / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )} are shown in Table 8 below.

In order to achieve the above-described optical characteristics of improving the thermal stability of the glass and suppressing the decrease in the refractive index (nd), it is preferred to compare the total content of B ³⁺ and Si ⁴⁺ with respect to Nb ⁵⁺ and Ti ⁴⁺ in the above glass. The cation ratio {(B ³⁺ + Si ⁴⁺ ) / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} of the total content of Ta ⁵⁺ and W ⁶⁺ is set to 9.00 or less.

In order to suppress the decrease in the Abbe number (νd) and improve the thermal stability of the glass, it is preferred to have a cation ratio of {(B ³⁺ +Si ⁴⁺ )/(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} Set to 5.00 or higher. Further, from the viewpoint of low specific gravity, the cation ratio {(B ³⁺ + Si ⁴⁺ ) / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is preferably 5.00 or more.

A more preferred lower limit and a higher upper limit of the cation ratio {(B ³⁺ + Si ⁴⁺ ) / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} are shown in Table 9 below.

From the viewpoint of improving the thermal stability of the glass, suppressing the crystallization of the glass, and lowering the specific gravity of the glass, the W ⁶⁺ content is preferably compared with the total contents of Nb ⁵⁺ , Ti ⁴⁺ , Ta ^{5+ ,} and W ⁶⁺ . The cation ratio {W ⁶⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is set to 0.50 or less. Further, from the viewpoint of high refractive index and coloration of the glass, the cation ratio {W ⁶⁺ /(Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is preferably 0.50 or less. A more preferred lower limit and a higher upper limit of the cation ratio {W ⁶⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} are shown in Table 10 below.

In order to improve the thermal stability of the glass, suppress the crystallization of the glass, and achieve the above optical characteristics, it is preferred to add the Zn ²⁺ content to the total of La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ in the above glass. The content of the cation ratio {Zn ²⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is set to be less than 0.2. Further, from the viewpoint of suppressing a decrease in glass transition temperature (thus improving machinability) and improving chemical durability, a preferred cation ratio {Zn ²⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ + ) is also preferable. Yb ³⁺ )} is less than 0.20. From the viewpoint of improving the meltability, the cation ratio {Zn ²⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is preferably 0% or more, more preferably more than 0%. A preferred lower limit and a preferred upper limit of the cation ratio {Zn ²⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} are shown in Table 11 below.

Among the rare earth elements La, Y, Gd, and Yb, Gd is a heavy rare earth element, and is a component that is required to lower the content in the glass from the viewpoint of stable supply of glass. Further, Gd is also a component having a large atomic weight and increasing the specific gravity of the glass.

Yb is also a heavy rare earth element and has a large atomic weight. In addition, Yb absorbs in the near-infrared region. On the other hand, the exchange lens for the SLR camera, surveillance camera The lens of the camera is expected to have a high light transmittance in the near-infrared region. Therefore, it is desirable to reduce the content of Yb in the glass which is useful for the production of these lenses.

On the other hand, La and Y do not adversely affect the light transmittance of the near-infrared region, and are improved in thermal stability and suppress the increase in specific gravity by appropriately distributing the total content of the rare earth elements. Consider the useful ingredients in terms of dispersive glass.

Therefore, in the glass, it is preferable for La ^3+, La ³⁺ content relative to the total content of cations La ^3+, Y ^3+, Gd ³⁺ and Yb ³⁺ ratio {La ³⁺ / (La ^{3 The range of +} +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is set to 0.50 to 0.95. A more preferred lower limit and a higher upper limit of the cation ratio {La ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} are shown in Table 12 below.

In addition, Y ^3+, preferably the content of Y ³⁺ La ³⁺ cations respect, Y ^3+, Gd ³⁺ and the total content ratio of Yb ^{3+ {Y 3+ / (La 3+ +} Y 3 ^{The range of +} +Gd ³⁺ +Yb ³⁺ )} is set to 0.10 to 0.50. A more preferred lower limit and a higher upper limit of the cation ratio {Y ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} are shown in Table 13 below.

As described above, Gd ³⁺ is a component which should lower the content in the glass from the viewpoint of stable supply of glass. From the viewpoint of stably supplying the high refractive index low dispersion glass having the above optical characteristics, it is preferred to ^add the content of Gd ^{3+ to} the total of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ in the above glass. The content of the cation ratio {Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is set to 0.10 or less. Satisfying the above cation ratio can also contribute to the low specific gravity of the glass. A more preferred lower limit and a higher upper limit of the cation ratio {Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} are shown in Table 14 below.

The total content of La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ , and the cation ratio of the La ³⁺ content, the Y ³⁺ content, and the Gd ³⁺ content to the total content are as described above. The lower limit and the preferred upper limit of the content of each component of La ³⁺ , Y ³⁺ , Gd ³⁺ , and Yb ³⁺ are shown in Tables 15 to 18 below. Further, as for the content of Y ³⁺ , from the viewpoint of improving the thermal stability and the meltability of the glass, the lower limits shown in the following Tables 15 to 18 are also preferable.

Nb ⁵⁺ , Ti ⁴⁺ , Ta ^{5+ ,} and W ^{6+ are} contained in an appropriate amount to exhibit an effect of increasing the refractive index and improving the thermal stability of the glass. However, although Ta ⁵⁺ has an effect of increasing the refractive index, it is an extremely expensive component. Therefore, from the viewpoint of stable supply of glass, Ta ⁵⁺ is not preferably used actively. Further, when the content of Ta ^{5+ is} large, the raw material becomes easily melted and remains when the glass is molten. In addition, the specific gravity of the glass increases. In summary, Ta ⁵⁺ is a component that should be reduced in content. Therefore, Ta ⁵⁺ is not preferably used actively. In order to improve the thermal stability of the glass and to achieve high refractive index and low dispersion and reduction in the amount of Ta used, for Ta ⁵⁺ , the content of Ta ⁵⁺ is preferably relative to Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ^{6 . +} cation total content ratio ^{{Ta 5+ / (Nb 5+ +} Ti 4+ + Ta 5+ + W 6+)} is set to 0.2 or less. A preferred lower limit and a higher upper limit of the cation ratio {Ta ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} are shown in Table 19 below.

Further, in order to provide Nb ⁵⁺ , it is preferable to reduce the content of Gd ³⁺ and Ta ⁵⁺ in order to stably supply the glass, and it is preferable to reduce the content of Yb ³⁺ together with Gd ³⁺ and Ta ^{5+ and} to have high thermal stability. refractive index of low-dispersion glass, in consideration of the above-described effect of ^{Nb 5+, Ti 4+, Ta 5+} , W 6+ is based on the content of Nb ⁵⁺ preferred with respect to Nb ^5+, Ti ^4+, Ta ⁵ The cation ratio {Nb ⁵⁺ /(Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} of the total content of ⁺ and W ⁶⁺ is set to 0.2 or more. Further, Nb ⁵⁺ is a component having a tendency to increase the refractive index without increasing the specific gravity as compared with Ta ⁵ and W ⁶⁺ . Therefore, in order to suppress an increase in specific gravity, it is preferable that the cation ratio {Nb ⁵⁺ /(Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is increased. A more preferred lower limit and a preferred upper limit of the cation ratio {Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} are shown in Table 20 below.

Further, from the viewpoint of preventing the high dispersion and coloring of view, the preferred content of Ti ⁴⁺ with respect Nb ^5+, Ti ⁴⁺ cations, the total content of Ta ^5+, and W ⁶⁺ ratio {Ti ⁴⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is set to 0.6 or less. A preferred lower limit and a higher upper limit of the cation ratio {{Ti ⁴⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} are shown in Table 21 below.

In order to maintain the thermal stability of the glass and suppress the decrease in the Abbe number (νd), it is preferred to make the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ (La ³⁺ +Y ³⁺ +Gd ^{3 +} +Yb ³⁺ ) relative to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ ) cation ratio {(La ³ The lower limit of ⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )/(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is a value of a preferred lower limit shown in the following table.

On the other hand, in order to suppress the decrease in the refractive index and maintain the thermal stability of the glass, it is preferred to make the cation ratio {(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )/(Nb ⁵⁺ +Ti ⁴⁺ The upper limit of +Ta ⁵⁺ +W ⁶⁺ )} is the value of the preferred upper limit shown in Table 22 below.

The glass composition of the above glass will be further described below.

The total content of B ³⁺ and Si ⁴⁺ as a network forming component of glass is as described above. For B ³⁺ and Si ⁴⁺ , B ^{3+ is} superior to Si ^{4+ in} improving the meltability, but it is easy to exhibit during melting. On the other hand, Si ⁴⁺ has an effect of improving the chemical durability, weather resistance, machinability of the glass, or improving the viscosity of the glass at the time of melting.

Generally, in a high refractive index low dispersion glass containing a rare earth element such as B ³⁺ and La ³⁺ , the viscosity of the glass at the time of melting is low. However, when the viscosity of the glass at the time of melting is low, it becomes easy to crystallize. In the crystallization of glass production, the state of crystallization is more stable than the amorphous state (amorphous state), which is arranged in such a manner as to have a crystal structure by the ions constituting the glass moving in the glass. produce. Therefore, by adjusting the ratio of the content of each component of B ³⁺ and Si ⁴ so as to increase the viscosity at the time of melting, it is difficult to arrange the ions so as to have a crystal structure, and it is possible to further suppress the crystallization of the glass. Further improve the resistance to devitrification of the glass.

From the above viewpoint, the content of B ³⁺ and B ³⁺ cations with respect to the total content of Si ⁴⁺ preferred lower limit of the ratio of ^{{B 3+ / (B 3+ +} Si 4+)} and preferred The upper limit is shown in Table 23 below. The lower limit or more shown in the table below is also preferable from the viewpoint of improving the meltability of the glass. Further, it is also preferable to set the upper limit or less shown in the following Table 23 from the viewpoint of improving the viscosity of the glass at the time of melting. Furthermore, in order to reduce fluctuations in the glass composition due to volatilization during melting and variations in optical characteristics, it is also required to improve the chemical durability, weather resistance, and machinability of the glass. The upper limit shown in Table 23 is also preferred below.

From the viewpoints of improving the devitrification resistance, the meltability, the moldability, the chemical durability, the weather resistance, the machinability, and the like of the glass, each of the B ³⁺ content and the Si ⁴⁺ content has a preferred lower limit and a preferred upper limit. See Table 24~25 below.

Zn ²⁺ has an effect of promoting the melting of the glass raw material at the time of melting the glass, that is, improving the meltability. Further, it also has an effect of adjusting the refractive index (nd) and the Abbe number (νd) and lowering the glass transition temperature. From the viewpoint of suppressing the decrease in the Abbe number (νd), improving the thermal stability of the glass, suppressing the decrease in the glass transition temperature (the mechanical workability), and the low specific gravity of the glass, it is preferred to use Zn ²⁺ . The value of the content divided by the total content of B ³⁺ and Si ⁴⁺ , that is, the cation ratio {Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )} is set to 0.15 or less. Further, since Zn in the glass may or may not contain an optional component, the cation ratio {Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )} is preferably 0 or more, but it is easy to improve the meltability. A homogeneous glass is produced, preferably containing Zn such that the cation ratio {Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )} is greater than zero. The lower limit and the higher upper limit of the cation ratio {Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )} are shown in Table 26 below.

From the viewpoint of improving the meltability, heat stability, moldability, machinability, and the like of the glass to achieve the above optical characteristics, a preferred lower limit and a preferred upper limit of the Zn ²⁺ content are shown in Table 27 below.

From the viewpoint of further improving the thermal stability of the glass, suppressing the decrease in the glass transition temperature (thereby improving the machinability), and improving the chemical durability, the Zn ²⁺ content is preferably relative to Nb ⁵⁺ , Ti ⁴⁺ , Ta. The cation ratio {Zn ²⁺ /(Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )} of the total content of ⁵⁺ and W ⁶⁺ is 1.0 or less. On the other hand, since Zn is an optional component, the lower limit of the preferred cation ratio {Zn ²⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is 0, but from the viewpoint of improving the meltability From the point of view, it is better than 0. In view of the above aspects, a lower limit and a higher upper limit of the cation ratio {Zn ²⁺ /(Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )} are shown in Table 28 below.

Based on the above effects and effects, the contents of the respective components of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ , W ⁶⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ , and W ⁶⁺ are compared. The preferred range is shown in Tables 29 to 32 below.

Next, optional components other than the components described above will be described.

Since Li ⁺ has a strong effect of lowering the glass transition temperature, when the content thereof is increased, the mechanical workability tends to be lowered. Further, chemical durability and weather resistance also tend to decrease. Therefore, it is preferable to set the Li ⁺ content to 5% or less. The preferred lower limit and the better upper limit of the Li ⁺ content are shown in Table 33 below. The content of Li ⁺ may also be 0%.

Each of Na ⁺ , K ⁺ , Rb ⁺ , and Cs ⁺ has an effect of improving the meltability of the glass. However, when these contents are increased, the thermal stability, chemical durability, weather resistance, and machinability of the glass tend to be lowered. Therefore, the lower limit and the upper limit of the respective contents of Na ⁺ , K ⁺ , Rb ⁺ and Cs ⁺ are preferably as shown in Tables 34 to 37 below.

The total content of Li ⁺ , Na ⁺ and K ⁺ (Li ⁺ +Na ⁺ +K ⁺ ) is maintained from the viewpoint of maintaining thermal stability, chemical durability, weather resistance, machinability, and improvement of glass meltability of the glass. The preferred lower limit and preferred upper limit are shown in Table 38 below.

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ are all components having an effect of improving the meltability of the glass. However, when the content of these components is increased, the thermal stability of the glass is lowered, showing a tendency to devitrification. Therefore, the content of each of these components is preferably equal to or lower than the lower limit shown in the following Tables 39 to 42, and preferably equal to or less than the upper limit.

Further, from the viewpoint of maintaining the thermal stability of the glass, the total content of Mg ²⁺ , Ca ²⁺ , Sr ^{2+ ,} and Ba ²⁺ is preferably (Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ ). It is set to the lower limit or more shown in Table 43 below, and is preferably set to the upper limit or less.

Al ³⁺ is a component having an effect of improving the chemical durability and weather resistance of the glass. However, when the content of Al ³⁺ is increased, the refractive index (nd) tends to decrease, the thermal stability of the glass tends to decrease, and the meltability tends to decrease. In view of the above, the content of Al ³⁺ is preferably at least the lower limit shown in Table 44 below, and preferably at most the upper limit.

Ga ³⁺ , In ³⁺ , Sc ³⁺ , and Hf ⁴⁺ all have an effect of increasing the refractive index (nd). However, these components are expensive, and are not essential components from the viewpoint of obtaining the above optical glass. Therefore, the content of each of Ga ³⁺ , In ³⁺ , Sc ³⁺ , and Hf ⁴⁺ is preferably equal to or lower than the lower limit shown in the following Tables 45 to 48, and preferably equal to or less than the upper limit.

Lu ³⁺ has an effect of increasing the refractive index (nd), but is also a component that increases the specific gravity of the glass. Further, Lu, like Gd and Yb, is a heavy rare earth element, and therefore it is preferable to reduce the content of Lu. From the above aspects, the preferred lower limit and the preferred upper limit of the content of Lu ³⁺ are shown in Table 49 below.

Ge ⁴⁺ has an effect of increasing the refractive index (nd), but is an extremely expensive component among commonly used glass components. From the viewpoint of lowering the production cost of the glass, a preferred lower limit and a preferred upper limit of the content of Ge ⁴⁺ are shown in Table 50 below.

Bi ³⁺ is a component that increases the refractive index (nd) and lowers the Abbe number (νd). Further, it is also a component which is easy to increase the specific gravity and coloration. In order to produce a glass having the above optical characteristics and having less coloration and a lower specific gravity, a preferred lower limit and a preferred upper limit of the Bi ³⁺ content are shown in Table 51 below.

In order to satisfactorily obtain the various actions and effects described above, the total content (total content) of each of the cationic components described above is preferably more than 95%, more preferably more than 98%, still more preferably more than 99%, still more preferably more than 99.5%.

In the cation component other than the cation component described above, P ⁵⁺ is a component which lowers the refractive index (nd) and is a component which lowers the thermal stability of the glass. However, when a very small amount is introduced, the glass may be used. Increased thermal stability. In order to produce a glass having the above optical characteristics and excellent thermal stability, a preferred lower limit and a preferred upper limit of the P ⁵⁺ content are shown in Table 52 below.

Te ⁴⁺ is a component that increases the refractive index (nd), but since it is a toxic component, it is preferable to reduce the content of Te ⁴⁺ . A preferred lower limit and a preferred upper limit of the content of Te ⁴⁺ are shown in Table 53 below.

In addition, in the above-mentioned respective tables, it is described that the (better) preferred lower limit or 0% component is also preferably 0%. The same is true for the total content of various components.

The inventors of the present invention have conducted repeated studies to examine the influence of the dispersion (Abbe number) imparted to each glass by the respective cationic components. Furthermore, the inventors of the present invention have further studied and determined that the coefficient for which the influence of the chromatic dispersion of the glass is given to each of the cation components is adjusted so that the value A calculated by the following formula (A) is in the range of 8.5000 to 11.000. It is preferable to achieve an optical property of the relationship (1) in which the Abbe number (νd) is 39.5 to 41.5, the refractive index (nd), and the Abbe number (νd) satisfy the above formula (1).

(A) Formula A = 0.01 × Si ^{4 +} content + 0.01 × B ^{3 +} content + 0.05 × La ^{3 +} content + 0.07 × Y ^{3 +} content + 0.07 × Yb ^{3 +} content + 0.085 × Zn ²⁺ content + 0.3 × Zr ⁴⁺ content +0.5×Ta ⁵⁺ content+0.8×Nb ⁵⁺ content+0.9×W ⁵⁺ content+0.95×Ti ⁴⁺ content

A more preferable lower limit and a higher upper limit of the value A calculated by the above formula (A) are shown in Table 54 below.

Further, among the various cationic components described above, for Nb ⁵⁺ , Ti ⁴⁺ and Gd ³⁺ , Nb ⁵⁺ and Ti ⁴⁺ are components having an effect of increasing the refractive index, and compared with Gd ³⁺ A component that has a small effect on the increase in specific gravity. Therefore, in order to suppress an increase in specific gravity and increase the refractive index, it is preferred to balance the total content of Nb ⁵⁺ and Ti ⁴⁺ with the content of Gd ³⁺ . From the above, in the glass composition represented by the cation %, the value C calculated by the following formula (C) is preferably -1.000 or more. Further, from the viewpoint of high dispersion and low dispersion, the value C calculated by the following formula (C) is preferably 6.720 or less.

(C) Formula C = 0.567 × (Nb ^{5 +} content + Ti ^{4 +} content) - 1.000 × Gd ^{3 +} content

A more preferable lower limit and a higher upper limit of the value C calculated by the formula (C) are shown in Table 55 below.

Each of Pb, As, Cd, Tl, Be, and Se is toxic. Therefore, it is preferred that these elements are not contained, that is, these elements are not introduced into the glass as a glass component.

U, Th, and Ra are all radioactive elements. Therefore, it is preferred that these elements are not contained, that is, these elemental components are not introduced into the glass as glass.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Ce or increase the color of the glass, or become a source of fluorescence It is not preferable as an element contained in the glass for optical elements. Therefore, it is preferred that these elements are not contained, that is, these elements are not introduced into the glass as a glass component.

Sb and Sn are elements which can be arbitrarily added as a clarifying agent.

When the amount of Sb added is converted to Sb ₂ O ₃ and the total content of the glass components other than Sb ₂ O ₃ is 100% by mass, the preferred range is 0 to 0.11% by mass, and a more preferable range is From 0.01 to 0.08 mass%, a further preferred range is from 0.02 to 0.05 mass%.

When the amount of addition of Sn is converted to SnO ₂ and the total content of the glass components other than SnO ₂ is 100% by mass, the preferred range is 0 to 0.5% by mass, and more preferably 0 to 0.2% by mass. Further, a further preferred range is 0% by mass.

The cationic component has been described above. Next, the anion component will be described.

Since the glass is an oxide glass, it contains O ^2- as an anion component. A preferred lower limit of the content of O ^2- is as shown in Table 56 below.

Examples of the anion component other than O ²⁻ are F ⁻ , Cl ⁻ , Br ⁻ , and I ⁻ . However, F ^- , Cl ^- , Br ^- , and I ^- are easily exhibited in the melting of the glass. Due to the volatilization of these components, the characteristics of the glass fluctuate, the homogeneity of the glass is lowered, and the consumption of the melting equipment tends to be remarkable. Therefore, it is preferred to control the total content of F ^- , Cl ^- , Br ^- and I ^{- to} an amount obtained by subtracting the content of O ^2- from 100 anions %.

In addition, the anion% is a percentage which is a case where the total content of all the anion components contained in glass is 100%.

<glass characteristics>

(Optical properties of glass)

The glass is a glass having an Abbe number (νd) in the range of 39.5 to 41.5 and having a refractive index (nd) satisfying the following formula (1) with respect to the Abbe number (νd).

A glass having an Abbe number (νd) of 39.5 or more is effective as a material of an optical element in correcting chromatic aberration. On the other hand, when the Abbe number (νd) is more than 41.5, if the refractive index is not lowered, the thermal stability of the glass is remarkably lowered, and it becomes easy to devitrify during the process of producing glass. The preferred lower limit and preferred upper limit of the Abbe number (νd) are shown in Table 57 below.

In the above glass, the refractive index (nd) satisfies the formula (1) with respect to the Abbe number (νd). A glass having an Abbe number (νd) in the range of 39.5 to 41.5 and having a refractive index (nd) satisfying the formula (1) is a glass having high value in the design of an optical system.

The upper limit of the refractive index (nd) is naturally determined by the composition of the glass. In order to obtain a glass which is improved in thermal stability and is difficult to devitrify, the refractive index (nd) preferably satisfies the following formula (2).

a preferred lower limit and a better upper limit of the refractive index (nd) relative to the Abbe number (νd) The limits are shown in Table 58 below.

Further, the refractive index (nd) is preferably at least the lower limit shown in Table 59 below, and is preferably at most the upper limit.

(partial dispersion characteristics)

From the viewpoint of correcting chromatic aberration, the glass is preferably a glass having a relatively small partial dispersion when the Abbe number (νd) is fixed.

Here, the partial dispersion ratio (Pg, F) is a refractive index (ng), a refractive index (nF), and a refractive index (nc) in the g-line, the F-line, and the c-line, and is expressed as (ng-nF)/ (nF-nc).

In order to provide a glass suitable for high-order chromatic aberration correction, a preferred lower limit and a preferred upper limit of the relative partial dispersion (Pg, f) of the above glass are shown in Table 60 below.

(glass transition temperature)

The glass transition temperature of the above glass is not particularly limited, but is preferably 640 ° C or higher. By setting the glass transition temperature (Tg) to 640 ° C or higher, it is possible to make the glass hard to be broken when the glass is subjected to mechanical processing such as cutting, cutting, polishing, and polishing. In addition, since components such as Li and Zn which have a strong effect of lowering the glass transition temperature are not contained in a large amount, even if Gd and Ta are contained less and Yb is further contained less, thermal stability is likely to be improved.

On the other hand, when the glass transition temperature is too high, the glass must be annealed at a high temperature, and the annealing furnace is significantly consumed. Further, when molding glass, it is necessary to perform molding at a high temperature, and the consumption of the mold used for molding becomes remarkable.

From the viewpoint of improving the machinability and reducing the burden on the annealing furnace and the molding die, a preferred lower limit and a preferred upper limit of the glass transition temperature are shown in Table 61 below.

(specific gravity of glass)

In the optical element (lens) constituting the optical system, the refractive power is determined according to the refractive index of the glass constituting the lens and the curvature of the optical functional surface (light incident and exit surface to be controlled) of the lens. When the curvature of the optical functional surface is to be increased, the thickness of the lens is also increased. The result is that the lens will become heavier. On the other hand, if a glass having a high refractive index is used, a large refractive power can be obtained even if the curvature of the optical functional surface is not increased.

Thereby, as long as the increase in the specific gravity of the glass can be suppressed and the refractive index is increased, the optical element having a fixed refractive power can be made lighter.

Regarding the refractive power imparted to the refractive index (nd), by taking the ratio of the specific gravity (d) of the glass to the value (nd-1) of the refractive index (1) in the vacuum from the refractive index (nd) of the glass, It can be used as an indicator for reducing the weight of optical components. In other words, by using d/(nd-1) as an index for reducing the weight of the optical element, by reducing the value, it is possible to reduce the weight of the lens.

By satisfying the above formula (B) with respect to the refractive index (nd), the above-mentioned glass can be made to have a low specific gravity while being a high refractive index low dispersion glass. Therefore, the d/(nd-1) of the above glass can be, for example, 5.70 or less. However, when d/(nd-1) is excessively decreased, the thermal stability of the glass tends to be lowered. therefore, Preferably, d/(nd-1) is set to 5.00 or more. A preferred lower limit and a better upper limit of d/(nd-1) are shown in Table 62 below.

Further, a preferred lower limit and a preferred upper limit of the specific gravity (d) of the above glass are shown in Table 63 below. From the viewpoint of weight reduction of the optical element formed of the glass, the specific gravity (d) is preferably set to be equal to or less than the upper limit shown in Table 63 below. Further, in order to further improve the thermal stability of the glass, the specific gravity is preferably set to a lower limit or more as shown in the following Table 63.

(liquidus temperature)

The liquidus temperature is one of the indicators of the thermal stability of the glass. In order to suppress crystallization and suppress devitrification during glass production, the liquidus temperature (LT) is preferably 1350 ° C or lower, more preferably 1330 ° C or lower, further preferably 1300 ° C or lower, and even more preferably 1250 ° C or lower. . The lower limit of the liquidus temperature (LT) is 1100 ° C or more as an example, but the lower limit of the preferred liquidus temperature (LT) is low, and there is no particular Limited.

The glass of one embodiment of the present invention described above has a large refractive index (nd) and an Abbe number (νd), and is useful as a glass material for optical elements. Further, by performing the composition adjustment described earlier, it is also possible to homogenize the glass and reduce the specific gravity. Therefore, the above glass is suitable as an optical glass that imparts a lighter weight optical element.

<Method of Manufacturing Glass>

The glass can be obtained by weighing and blending oxides, carbonates, sulfates, nitrates, hydroxides, and the like as raw materials in such a manner as to obtain a desired glass composition. The batch is mixed, heated and melted in a melting vessel, defoamed and stirred, and a homogeneous molten glass containing no foam is produced and molded. Specifically, it can be produced by a known melting method. Since the glass has high refractive index and low dispersion glass having the above optical characteristics and is excellent in thermal stability, it can be stably produced by a known melting method or molding method.

[Glass material for press molding, optical element blank, and method for producing the same]

Another aspect of the present invention relates to a glass material for press molding formed of the above glass.

An optical element blank formed from the above glass.

According to another aspect of the present invention, the following may also be provided.

A method for producing a glass material for press molding having a step of molding the above-described glass into a glass material for press molding.

One having a pressurization using the above-mentioned glass material for press molding A method of manufacturing an optical element blank in which a mold is subjected to press molding to produce an optical element blank.

A method of manufacturing an optical element blank having the step of molding the above-described glass into an optical element blank.

The optical element blank is similar to the shape of the target optical element, and the polishing allowance is added to the optical element shape (the surface layer removed by polishing), and the grinding allowance is increased as needed (by grinding) The optical element base material of the surface layer to be removed. The optical element is completed by polishing and polishing the surface of the optical element blank. In one embodiment, an optical element blank can be produced by a method of press molding a molten glass obtained by appropriately melting the glass (referred to as a direct pressing method). In another aspect, the optical element blank can also be produced by curing the molten glass obtained by appropriately melting the glass.

Further, in another embodiment, the glass material for press molding can be produced by press-forming the produced glass material for press molding to produce an optical element blank.

The press molding of the glass material for press molding can be carried out by a known method of pressing a glass material for press molding which is softened after heating with a press molding die. Both heating and press molding can be carried out in the atmosphere. The stress inside the glass can be reduced by annealing after press molding to obtain a homogeneous optical element blank.

The glass material for press molding is provided, in addition to the glass material for press molding, which is called press-molding glass gob for press molding for optical element blank production, and includes cutting, grinding, and polishing. After machining, the glass gob is subjected to press molding and supplied to a press-molded glass material for press molding. As a cutting method, a groove is formed in a portion to be cut on the surface of the glass sheet by a method called scribing, and a partial pressure is applied to a portion of the groove from the back surface of the surface of the formed groove, in the portion of the groove. A method of cutting a glass sheet; a method of cutting a glass sheet with a cutting blade, and the like. Further, examples of the polishing and polishing methods include barrel polishing and the like.

The glass material for press molding can be produced by, for example, casting molten glass into a mold to form a glass plate, and cutting the glass plate into a plurality of glass sheets. Alternatively, an appropriate amount of molten glass can be molded to produce a glass gob for press molding. It is also possible to produce an optical element blank by reheating and softening the glass gob for press molding and performing press molding. The method of reheating, softening, and press-forming a glass to produce an optical element blank is referred to as a reheat pressing method with respect to a direct pressing method.

[Optical element and its manufacturing method]

Another aspect of the invention relates to an optical element formed from the above-described glass.

The above optical element is produced using the above glass. In the above optical element, one or more coat films such as a multilayer film such as an antireflection film may be formed on the surface of the glass.

Further, according to an aspect of the present invention, a method of manufacturing an optical element having a step of fabricating an optical element by polishing and/or polishing the above-described optical element blank can be provided.

In the above method for producing an optical element, polishing and polishing may be performed by applying a known method, and the surface of the optical element can be sufficiently formed by processing. It is washed, dried, and the like to obtain an optical element having high internal quality and surface quality. Thus, an optical element formed of the above glass can be obtained. As the optical element, various lenses, prisms, and the like such as a spherical lens, an aspherical lens, and a microlens can be exemplified.

Further, an optical element formed of the above glass is preferable as a lens constituting the glued optical element. As the glue optical element, a glue optical element (glued lens) that bonds lenses to each other, a glue optical element that bonds a lens and a prism, and the like can be exemplified. For example, the glue optical element can be produced by precisely processing the glued surface of the two glued optical elements in such a manner that the shape is reversed (for example, spherical polishing), and bonding of the coated cemented lens. After the ultraviolet curable adhesive used is bonded, the ultraviolet rays are irradiated by the lens to harden the adhesive. In order to produce such a glued optical element, the above glass is preferred. By using a plurality of kinds of glass having different Abbe numbers (νd) to produce a plurality of glued optical elements and bonding them, it is possible to obtain an element suitable for chromatic aberration correction.

For the quantitative analysis of the glass composition, the glass component is represented by an oxide standard, and the content of the glass component is represented by mass%. The composition expressed in mass% in terms of the oxide standard can be converted into a composition represented by cation % and anion %, for example, by the following method.

When the glass contains N kinds of glass components, the glass composition of the kth type is represented by A(k) _m O _n . However, k is an arbitrary integer of 1 or more and N or less.

A(k) is a cation, O is oxygen, and m and n are integers determined by stoichiometry. For example, when the oxide standard is represented by B ₂ O ₃ , m=2 and n=3; when it is represented by SiO ₂ , m=1 and n=2.

Next, the content of A(k) _m O _n is represented by X(k) [% by mass]. Here, when the atomic weight of A(k) is P(k) and the atomic number of oxygen O is Q, the molecular weight R(k) of A(k) _m O _n is R(k)= P(k) × m + Q × n.

Further, when B=100/{Σ[m×X(k)/R(k)]}, the content (cation %) of the cationic component A(k) ^s+ is (X(k)/R(k)) × m × B (cation %). Here, Σ means the total of m × X (k) / R (K) from k = 1 to N. m varies according to k. s is 2n/m.

Further, the molecular weight R(k) may be calculated by using a value obtained by rounding off the fourth digit after the decimal point and three decimal places. Incidentally, the molecular weights expressed by the oxide standard for a plurality of glass components and additives are shown in Table 64 below.

[Examples]

Hereinafter, the present invention will be further described based on examples. However, the present invention is not limited to the embodiment shown in the embodiment.

(Example 1)

A compound such as an oxide or a boric acid as a raw material is weighed so that a glass having a composition shown in the following table can be obtained, and sufficiently mixed to prepare a batch raw material.

The batch of raw materials was placed in a platinum crucible and heated together with hydrazine to 1350 to 1450 ° C. After 2 to 3 hours, the glass was melted and clarified. After the molten glass was stirred and homogenized, the molten glass was cast into a preheated molding die, left to cool to near the glass transition temperature, and then immediately placed in the annealing furnace together with the molding die. Then, an annealing treatment was performed for about 1 hour in the vicinity of the glass transition temperature. After the annealing treatment, it was left to cool to room temperature in an annealing furnace.

When the glass thus produced was observed, no precipitation of crystals, bubbles, texture, and melting of the raw material were observed. Thereby, it is possible to produce a glass having high homogeneity.

(Comparative examples 1 to 4)

In the form of a glass having a composition of each of Comparative Examples 1 to 4 shown in the following table, a compound such as an oxide or a boric acid as a raw material is weighed and sufficiently mixed to prepare a bulk raw material, and The glass was obtained in the same manner as in Example 1.

The composition of Comparative Example 1 is a composition in which the composition of the glass No. 11 of Patent Document 20 is converted into a glass composition represented by a cationic %.

Comparative Example 2 is a composition in which the composition of the glass No. 25 of Patent Document 20 is converted into a glass composition represented by a cationic %.

In Comparative Example 3, the composition of the glass No. 45 of Patent Document 20 was converted into a composition of a glass composition represented by a cationic %.

In the comparative example 4, the composition of the glass No. 49 of the patent document 20 is converted into the composition of the glass composition represented by the cationic %.

The glass characteristics of the obtained glass are obtained by the method shown below. The measurement was taken. The measurement results are shown in the table below.

(1) Refractive index (nd), refractive index (nF), refractive index (nc), refractive index (ng), Abbe number (νd)

The glass obtained by cooling at a temperature drop rate of -30 ° C / hour is subjected to refractive index (nd), refractive index (nF), refractive index (nc), and refractive index according to the refractive index measurement method of the Japan Optical Glass Industry Association standard. The rate (ng) was measured. The Abbe number (νd) was calculated using each measured value of the refractive index (nd), the refractive index (nF), and the refractive index (nc).

(2) Glass transition temperature (Tg)

The measurement was carried out at a temperature elevation rate of 10 ° C /min using a differential scanning calorimeter (DSC).

(3) Specific gravity

The measurement was carried out according to the Archimedes method.

(4) Relative partial dispersion (Pg, F)

It is calculated from the values of nF, nc, and ng measured by the above (1).

(5) liquidus temperature

The glass was placed in a furnace heated to a predetermined temperature and kept for 2 hours. After cooling, the inside of the glass was observed with a 100-fold optical microscope, and the liquidus temperature was determined depending on the presence or absence of crystals.

1 is a graph in which the specific gravity of each glass of Example 1 and each of Comparative Examples 1 to 4 is taken as a horizontal axis, and the content of each cationic component is multiplied by the coefficient described in Table 1 on the vertical axis. .

As shown in Fig. 1, the total D of the content of each cationic component multiplied by the coefficient described in Table 1 has a good correlation with the specific gravity. From this result, it was confirmed that the glass having a low specific gravity can be obtained by performing composition adjustment so as to satisfy the formula (B) based on the total D.

2 is a graph in which the Abbe number (νd) of each of the glasses of Example 1 and each of Comparative Examples 1 to 4 is taken on the horizontal axis, and the value A calculated by the above formula (A) is taken on the vertical axis.

As shown in FIG. 2, the value A calculated by the above formula (A) shows a good correlation with the Abbe number. From this result, it was confirmed that the composition adjustment based on the value A is preferable from the viewpoint of adjusting the Abbe number.

(Example 2)

Using the various glasses obtained in Example 1, a glass block for press molding (glass gob) was produced. The glass block was heated and softened in the atmosphere, and press-molded by a press molding die to prepare a lens blank (optical element blank). The produced lens blank was taken out from the press molding die, annealed, and subjected to polishing including polishing to prepare a spherical lens formed of various glasses produced in Example 1.

(Example 3)

The required amount of the molten glass produced in Example 1 was compression-molded by a press molding die to prepare a lens blank (optical element blank). The produced lens blank was taken out from the press molding die, annealed, and subjected to polishing including polishing to prepare a spherical lens formed of various glasses produced in Example 1.

(Example 4)

A glass block (optical element blank) obtained by curing the molten glass produced in Example 1 was annealed, and subjected to polishing including polishing to prepare a spherical lens formed of various glasses produced in Example 1.

(Example 5)

The spherical lenses produced in Examples 2 to 4 were bonded to a spherical lens formed of other kinds of glass to produce a cemented lens. The cemented surface of the spherical lens produced in Examples 2 to 4 was a convex surface, and the cemented surface of a spherical lens formed of other kinds of glass was a concave surface. The two cemented surfaces are produced such that the absolute values of the mutual curvature radii are equal. The ultraviolet curable adhesive for optical component bonding is applied to the bonding surface to bond the two lenses between the bonding surfaces. Thereafter, the adhesive coated on the bonding surface was irradiated with ultraviolet rays by the spherical lenses produced in Examples 2 to 4 to cure the adhesive.

A cemented lens was produced as described above. The cemented lens has a sufficiently high bonding strength and is a cemented lens having high optical properties.

Finally, summarize the above methods.

According to one embodiment, it is possible to provide a glass which is an oxide glass represented by a cation %, B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Ti ^{4 +} , Ta ⁵⁺ , W ⁶⁺ , Zr ⁴⁺ , Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ , and Bi ³ The total content of ⁺ is 90% or more, and the Abbe number (νd) is in the range of 39.5 to 41.5. The refractive index (nd) satisfies the above formula (1) with respect to the Abbe number (νd), and is described in the above Table 1. The total amount of the cation component, the content of each cation component multiplied by the coefficient described in Table 1, with respect to the refractive index (nd) satisfies the above formula (B).

The glass is a glass having an Abbe number (νd) in the range of 39.5 to 41.5 and satisfying the formula (1), and is a high refractive index low dispersion glass useful in an optical system. Further, the glass can contribute to weight reduction of the optical element.

In one embodiment, the glass preferably has a total content of B ³⁺ and Si ⁴⁺ ranging from 43 to 65 cationic %.

In one embodiment, the glass preferably has a total content of La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ ranging from 25 to 45%.

In one ^embodiment , the glass preferably has a total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ^{5+ ,} and W ⁶⁺ ranging from 3 to 12%.

In one embodiment, the glass preferably has a value C calculated by the above formula (C) in the glass composition represented by the cation % in the range of -1.000 to 6.720.

According to the glass described above, a glass member for press molding, an optical element blank, and an optical element can be produced. That is, according to another aspect, a glass material for press molding, an optical element blank, and an optical element formed of the above glass can also be provided.

Further, according to another aspect, a method of producing a glass material for press molding having the step of molding the glass into a glass material for press molding can be provided.

Further, according to another aspect, there is provided a method of producing an optical element blank having a step of producing an optical element blank by press-molding the above-mentioned glass material for press molding using a press molding die.

Further, according to another aspect, a method of manufacturing an optical element blank having the step of molding the above-described glass into an optical element blank can also be provided.

Further, according to another aspect, there is provided a method of manufacturing an optical element having the step of producing an optical element by polishing and/or polishing the optical element blank.

It is to be understood that the embodiments disclosed herein are illustrative in all aspects and are not limiting. The scope of the present invention is defined by the scope of the claims and the scope of the claims.

For example, the glass of one embodiment of the present invention can be obtained by performing the composition adjustment described in the specification for the glass composition exemplified above.

In addition, it is needless to say that two or more of the items described in the specification or as the items described in the preferred range can be arbitrarily combined.

(industrial use)

The invention is useful in the field of manufacture of various optical components.

Claims (8)

A glass, which is an oxide glass, wherein is represented by a cationic %, B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ The total content of W ⁶⁺ , Zr ⁴⁺ , Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ and Bi ³⁺ is 90 % or more; the Abbe number (νd) ranges from 39.5 to 41.5; the refractive index (nd) satisfies the following formula (1) with respect to the Abbe number (νd): With respect to the cationic component described in Table 1, the total D of the content of each cationic component multiplied by the coefficient described in Table 1 satisfies the following formula (B) with respect to the refractive index (nd): The glass according to claim 1, wherein the total content of B ³⁺ and Si ⁴⁺ ranges from 43 to 65 cationic %. The glass according to claim 1 or 2, wherein the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ ranges from 25 to 45%. The glass according to claim 1 or 2, wherein the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ ranges from 3 to 12%. The glass according to claim 3, wherein the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ ranges from 3 to 12%. A glass material for press molding, which is formed from the glass according to any one of claims 1 to 5. An optical element blank formed of the glass of any one of claims 1 to 5. An optical element formed from the glass of any one of claims 1 to 5.