TW201733943A - Glass, glass raw material for press molding, optical element blank, and optical element - Google Patents

Abstract

To provide glass having the Abbe number [nu]d of 39.5 to 41.5, satisfying a relation of nd ≥ 2.0927-0.0058*[nu]d, capable of stably supplying and contributing to weight saving of an optical element. There is provided glass which is an oxide glass having, by cation%, total content of B ion+Si ion of 43 to 65%, total content of La ion, Y ion, Gd ion and Yb ion of 25 to 50%, total content of Nb ion, Ti ion, Ta ion and W ion of 3 to 12%, content of Zr ion of 2 to 8%, each cation ratio in a predetermined range and the Abbe number [nu]d in a range of 39.5 to 41.5 and refractive index nd satisfying the above-mentioned relation to the Abbe number [nu]d.

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 a high refractive index low dispersion glass is described in, for example, 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 may also be referred to as an Abbe chart) is widely used in order to show the distribution of optical characteristics. The optical characteristic map is prepared in such a manner that the Abbe number (νd) is on the horizontal axis, the refractive index (nd) is on the vertical axis, and the Abbe number (νd) is increased from the right side to the left side of the horizontal axis. The vertical direction of the vertical axis increases. 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 the high refractive index low dispersion glass (high nd high νd glass) generally show that when the Abbe number becomes smaller, the refractive index increases, and when The so-called rightward rising distribution of the refractive index decreases as the number of bayons 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 exhibits a tendency to devitrify during the process of producing the glass. Therefore, in the prior art high refractive index low dispersion glass, it is difficult to suppress the Abbe number and the refractive index together while suppressing the devitrification of the glass used as the material of the optical element. This is considered to be the reason why the prior art high refractive index low dispersion glass shows the above distribution in the optical characteristic diagram.

On the other hand, in the design of the optical system, the glass having a high refractive index and a large Abbe number (low dispersion) is an optical element material which is extremely effective for correcting chromatic aberration, high function of an optical system, and compactness. . 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.

On the other hand, in the glass described in Patent Documents 1 to 20, the Abbe number (νd) ranges from 39.5 to 41.5, and satisfies nd. The high refractive index low dispersion glass having a relationship of 2.0927 to 0.0058 x νd contains any of strontium (Gd) and strontium (Ta). However, although both Gd and Ta are rare and expensive elements, demand in various industrial fields is increasing in recent years, and thus supply is insufficient relative to market demand. Therefore, from the viewpoint of stable supply of high refractive index low dispersion glass, it is desirable to reduce the content of Gd and Ta in the high refractive index low dispersion glass.

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-focusing camera, power consumption when driving autofocus increases, and the battery is quickly consumed. On the other hand, if the optical element is made lighter, the power consumption at the time of driving the autofocus can be reduced, and the life of the battery can be prolonged.

However, the present inventors believe that the range of the Abbe number (νd) used in the glasses 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 relationship between 2.0927 and 0.0058 × νd, a glass that can be stably supplied and contributes 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 %, and a total content of B ³⁺ and Si ⁴⁺ is 43 to 65%; La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ The total content is 25~50%; the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is 3~12%; Zr ⁴⁺ content is 2~8%; B ³⁺ and Si ⁴⁺ The ratio of the total amount of cations to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is {(B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ + Yb ³⁺ )} is 0.70 to 1.42; the ratio of the total content of B ³⁺ and Si ^{4+ to} the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is {(B ³⁺ +Si) ⁴⁺ )/(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is 5.80 to 7.70; the total content of W ^{6+ is} relative to Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ The content of the cation ratio {W ⁶⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is 0.50 or less; the Zn ²⁺ content is relative to La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ cations total content ratio ^{{Zn 2+ / (La 3+ +} Y 3+ + Gd 3+ + Yb 3+)} is 0.17 or less; the content of La ³⁺ content with respect to the La ^3+, Y ^3+, The cation ratio of the total content of Gd ³⁺ and Yb ³⁺ is {La ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is 0.50-0.95; the content of Y ^{3+ is} relative to La ³⁺ The cation ratio of the total content of Y ³⁺ , Gd ³⁺ and Yb ³⁺ is {Y ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is 0.10~0.50; Gd ³⁺ content The cation ratio {Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} with respect to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is 0.10 or less; Cation ratio of Ta ⁵⁺ content relative to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ {Ta ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} It is 0.2 or less; the Abbe number (νd) ranges from 39.5 to 41.5, and the refractive index (nd) satisfies the following formula (1) with respect to the Abbe number (νd): nd 2.0927-0.0058×νd.

The above glass satisfies nd in the range of Abbe number (νd) of 39.5 to 41.5. a glass having a relationship of 2.0927-0.0058×νd, comprising a total content of various components of Gd ³⁺ (ie, La ³⁺ , Y ³⁺ , Gd ³⁺ , and Yb ³⁺ ) and various components including Ta ⁵⁺ (ie, The total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ , and W ⁶⁺ ) is in the above range, and satisfies the above cation ratio including Gd ³⁺ and Ta ⁵⁺ in the denominator or the molecule. Therefore, in the glass composition, the ratio of Gd and Ta is lowered. By adjusting the composition satisfying the above-described content, total content, and cation ratio in a composition satisfying such a total content and a cation ratio, the glass can achieve high thermal stability (difficult to devitrify property) and low specific gravity. . The optical element formed of the glass can be made lighter by the glass having a low specific gravity.

According to an aspect of the present invention, it is possible to provide a glass which has optical characteristics useful in an optical system, can be stably supplied, and contributes 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 photograph of a glass evaluated in Comparative Example 6.

2 is a graph in which the Abbe number (νd) of each of the glass of Example 1 and each of Comparative Examples 1 to 4 is taken on the horizontal axis, and the value A calculated according to 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 having the above glass composition, the Abbe number (νd) is in the range of 39.5 to 41.5, and the refractive index (nd) satisfies the above with respect to the Abbe number (νd) (1) )formula.

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

The glass composition in the present invention can be, for example, ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) or the like. The method is quantified. The analysis value obtained by ICP-AES sometimes includes a measurement error of about ±5% of the analysis value. Further, 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. As is well known, the cation % is a percentage in which the total content of all the cation components contained in the glass is 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, with respect to the numerical range, the (better) preferred lower limit and (better) preferred upper limit are sometimes shown in the table. In the table, the numerical value described below is better, and the numerical value described at the bottom is the best. 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>

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, so that the glass having the above optical characteristics can be produced. Therefore, the range of the total content of B ³⁺ and Si ⁴⁺ in the above glass is set to 43 to 65%. A preferred lower limit and a preferred upper limit of the total content of B ³⁺ and Si ⁴⁺ are shown in Table 1 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 possible to produce 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 (Tg) is lowered, the glass is easily broken (machineability is lowered) when the glass is machined (cut, cut, polished, polished, etc.), but when La ^{3 When} the total content of ⁺ , Y ³⁺ , 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 each component of La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ is 50% or less, the thermal stability of the glass can be improved, and therefore, the crystallization at the time of glass production can be suppressed. And the melting residue of the raw material when the molten glass is lowered. In addition, it is also possible to suppress 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 set to 25 to 50%. A preferred lower limit and a preferred upper limit of the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ are shown in Table 2 below.

Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ are components having an effect of increasing the refractive index, and by containing them in an appropriate amount, they also have an effect of improving the thermal stability of the glass. 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, thermal stability can be maintained and the above can be achieved. Optical properties. 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} in the range of 3 to 12%. A preferred lower limit and a preferred upper limit of the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ are shown in Table 3 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. Further, Zr ⁴⁺ also has an effect of making the glass less susceptible to breakage during mechanical processing by increasing the glass transition temperature. In order to obtain these effects favorably, the content of Zr ⁴⁺ is set to 2% or more in the above glass. On the other hand, when the content of Zr ⁴⁺ is 8% or less, the thermal stability of the glass can be improved. Therefore, it is possible to suppress the occurrence of crystallization during the production of the glass and the occurrence of the melt residue during the glass melting. Therefore, the range of the Zr ⁴⁺ content in the above glass is set to 2 to 8%. The preferred lower limit and preferred upper limit of the Zr ⁴⁺ content are shown in Table 4 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 5 below.

In order to achieve an improvement in the thermal stability of the glass and an Abbe's 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), 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 0.70~1.42. When the cation ratio ((B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ ))) is 0.70 or more, the thermal stability of the glass can be improved, and thus the glass can be suppressed. Destruction. Further, it is also possible to suppress an increase in the specific gravity of the glass. On the other hand, when the cation ratio ((B ³⁺ + Si ⁴⁺ ) / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ ))) is 1.42 or less, the above optical characteristics can be achieved. A preferred lower limit and a preferred upper limit of the cation ratio {(B ³⁺ + Si ⁴⁺ ) / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )} are shown in Table 6 below.

In order to achieve the above optical characteristics for improving the thermal stability of the glass and suppressing the decrease in the refractive index (nd), in the above glass, the total content of B ³⁺ and Si ⁴⁺ is relative to Nb ⁵⁺ , Ti ⁴⁺ , Ta The cation ratio {(B ³⁺ + Si ⁴⁺ ) / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} of the total content of ⁵⁺ and W ⁶⁺ is set to 7.70 or less.

In order to suppress the decrease in the Abbe number (νd) and improve the thermal stability of the glass, the cation ratio {(B ³⁺ + Si ⁴⁺ ) / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} Set to 5.80 or more. 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 5.80 or less.

A preferred lower limit and a preferred upper limit of the cation ratio {(B ³⁺ + Si ⁴⁺ ) / (Nb ⁵ + + Ti ⁴ + + Ta ⁵ + + W ⁶⁺ )} are shown in Table 7 below.

In order to improve the thermal stability of the glass to suppress the crystallization of the glass and the glass of a low specific gravity, the W ⁶⁺ content of the Nb ^5+, the total cation content of Ti ^4+, Ta ^5+, and W ⁶⁺ 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 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 8 below.

In order to improve the thermal stability of the glass to suppress the crystallization of the glass and achieve the above optical characteristics, in the above glass, the content of Zn ^{2+ is} relative to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ . The cation ratio {Zn ²⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is set to 0.17 or less. 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 0.17 or less. 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 9 below.

Among lanthanum (La), yttrium (Y), yttrium (Gd), and yttrium (Yb) which are rare earth elements, Gd is a heavy rare earth element, and from the viewpoint of stable supply of glass, A component that requires a reduction in the content of the 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 has absorption in the near-infrared region. On the other hand, the interchangeable lens for a single-lens reflex camera and the lens of the surveillance camera are expected to have high light transmittance in the near-infrared region. Therefore, in order to become a glass useful for the production of these lenses, it is desirable to reduce the content of Yb.

On the other hand, La and Y have no adverse effect on the light transmittance of the near-infrared region, and are appropriately distributed with respect to the total content of the rare earth elements, thereby improving thermal stability and suppressing an increase in specific gravity, in order to provide a high refractive index. A useful component of low dispersion 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 preferred lower limit and a preferred upper limit of the cation ratio {La ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} are shown in Table 10 below.

In addition, Y ^3+, the content of Y ³⁺ cations with respect to the total content of La ^3+, Y ^3+, Gd ³⁺ and Yb ³⁺ ratio ^{{Y 3+ / (La 3+ +} Y 3+ + The range of Gd ³⁺ + Yb ³⁺ )} is set to 0.10 to 0.50. A preferred lower limit and a preferred upper limit of the cation ratio {Y ³⁺ /(La ³ ++Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} are shown in Table 11 below.

As described above, Gd ³⁺ is a component which should be reduced in the amount of glass from the viewpoint of stable supply of glass. In the glass, by the content of Gd ³⁺ is La ^3+, Y ^3+, and the total content of Gd ³⁺ and Yb ^{3+ 3+} content with respect to the total content of Gd is determined. From the viewpoint of stably supplying the high refractive index low dispersion glass having the above optical characteristics, the content of Gd ³⁺ in the above glass is relative to the total content of La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ . 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 also contributes to the low specific gravity of the glass. The preferred lower limit and preferred upper limit of the cation ratio {Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} are shown in Table 12 below.

The cation ratio of the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ and the La ³⁺ content, the Y ³⁺ content, and the Gd ³⁺ content to the total content is as described above. The preferred 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 13 to 16 below. Further, the Y ³⁺ content is preferably a lower limit shown in Table 14 below from the viewpoint of improving the thermal stability and the meltability of the glass.

For Nb ⁵⁺ , Ti ⁴⁺ , Ta ^{5+ ,} and W ⁶⁺ , by appropriately containing them, the refractive index is improved and the thermal stability of the glass is improved. 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. Therefore, 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 to reduce the amount of Ta used, for Ta ⁵⁺ , the content of Ta ⁵⁺ is relative to Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ^{6+ .} The cation ratio {Ta ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} of the total content is set to 0.2 or less. A preferred lower limit and a preferred upper limit of the cation ratio {Ta ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} are shown in Table 17 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 preferred to increase the cation ratio {Nb ⁵⁺ /(Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )}. The lower limit and the preferred upper limit of the cation ratio {Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} are shown in Table 18 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 19 below.

In order to maintain the thermal stability of the glass and suppress the decrease in the Abbe number (νd), the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is preferably (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 set to a value of a preferred lower limit shown in Table 20 below.

On the other hand, in order to suppress the refractive index reduction and maintain the thermal stability of the glass, it is preferred to have a cation ratio {(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )/(Nb ⁵⁺ +Ti ⁴⁺ + The upper limit of Ta ⁵⁺ + W ⁶⁺ )} is set to a value of a preferred upper limit shown in Table 20 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 more excellent than Si ^{4+ in} improving the meltability, but is easily volatilized during melting. On the other hand, Si ⁴⁺ has an effect of improving chemical durability, weather resistance, and machinability of glass, and has an effect of improving the viscosity of glass at the time of melting.

For 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 generally low. However, when the viscosity of the glass at the time of melting is low, it becomes easy to crystallize. The crystallization at the time of glass production is more stable than the state of crystallization in an amorphous state (amorphous state), which is formed by arranging crystal ions in the glass to have a crystal structure. . 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 crystal 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 21 below. From the viewpoint of improving the meltability of the glass, it is also preferably set to a lower limit or more as shown in the following table. Further, from the viewpoint of improving the viscosity of the glass at the time of melting, it is preferably set to be equal to or less than the upper limit shown in the following table. Further, in order to reduce fluctuations in the glass composition due to volatilization during melting and variations in optical characteristics caused thereby, it is also improved from one or more of chemical durability, weather resistance, and machinability of the glass. It is set below the upper limit shown in the table below.

From the viewpoint of improving the devitrification resistance, the meltability, the moldability, the chemical durability, the weather resistance, the machinability, and the like of the glass, a preferred lower limit and a preferable ^{ratio of the} B ³⁺ content and the Si ⁴⁺ content are preferable. The upper limit is shown in Tables 22~23 below.

Zn ²⁺ has an effect of promoting melting of the glass raw material when the glass is molten, that is, an effect of improving the meltability. Further, it also has an effect of adjusting the refractive index (nd) and the Abbe number (νd) to lower 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 may or may not contain optional components in the glass, the cation ratio {Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )} is preferably 0 or more, but in order to improve the meltability, It is easy to produce a homogeneous glass, and it is more preferable that the glass contains Zn and the cation ratio {Zn ³⁺ /(B ³⁺ +Si ⁴⁺ )} is set to be larger than zero. A lower limit and a higher upper limit of the cation ratio {Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )} are shown in Table 24 below.

The lower limit and the preferred upper limit of the Zn ²⁺ content are as shown in Table 25 from the viewpoint of improving the meltability, heat stability, moldability, and machinability of the glass to achieve the above optical characteristics.

From the viewpoint of further improving the thermal stability of the glass, suppressing the decrease in the glass transition temperature (thus improving the machinability), and improving the chemical durability, the Zn ²⁺ content is preferably relative to Nb ⁵⁺ , Ti ⁴⁺ , The cation ratio {Zn ²⁺ /(Ti ⁴⁺ +Nb ⁵⁺ +Ta ⁵⁺ +W ⁶⁺ )} of the total content of Ta 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 26 below.

For Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ , and W ⁶⁺ , the contents of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ , and W ⁶⁺ are compared based on the above effects and effects. The preferred range is shown in Tables 27~30 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. Moreover, the tendency of chemical durability and weather resistance to fall is also shown. Therefore, it is preferable to set the Li ⁺ content to 5% or less. A preferred lower limit and a higher upper limit of the content of Li ⁺ are shown in Table 31 below. The content of Li ⁺ may also be 0%.

Na ⁺ , K ⁺ , Rb ⁺ , and Cs ⁺ all have an effect of improving the meltability of the glass. However, when the content of these increases, the thermal stability, chemical durability, weather resistance, and machinability of the glass tend to decrease. . Therefore, the lower limit and the upper limit of the respective contents of Na ⁺ , K ⁺ , Rb ⁺ and Cs ⁺ are preferably as shown in Tables 32 to 35 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 36 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 set to be equal to or higher than the lower limit and lower limit shown in the following Tables 37 to 40, respectively.

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 and the upper limit or less shown in Table 41 below.

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 Al ³⁺ content is preferably set to be equal to or higher than the lower limit and lower than the upper limit shown in Table 42 below.

Ga ³⁺ , In ³⁺ , Sc ³⁺ , and Hf ⁴⁺ are components each having an effect of increasing the refractive index (nd). However, these components are expensive and are not essential components in view of obtaining the above optical glass. Therefore, the respective contents of Ga ³⁺ , In ³⁺ , Sc ³⁺ , and Hf ⁴⁺ are preferably set to be equal to or higher than the lower limit and lower limit shown in the following Tables 43 to 46.

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 is a heavy rare earth element like Gd and Yb, 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 Lu ³⁺ content are shown in Table 47 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 manufacturing cost of the glass, a preferred lower limit and a preferred upper limit of the Ge ⁴⁺ content are shown in Table 48 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 low specific gravity, a preferred lower limit and a preferred upper limit of the Bi ³⁺ content are shown in Table 49 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, if a small amount is introduced, the heat of the glass may be caused. Increased 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 50 below.

Te ⁴⁺ is a component that raises the refractive index (nd), but is also a toxic component, so it is preferable to reduce the content of Te ⁴⁺ . A preferred lower limit and a preferred upper limit of the Te ⁴⁺ content are shown in Table 51 below.

Further, in each of the above tables, a (better) preferred lower limit or a 0% component is also preferably present in an amount of 0%. The same is true for the total content of various components.

The present inventors have conducted a number of studies on various cationic components described above, and have focused on the effects of the dispersion (Abbe number) imparted to each glass by the respective cationic components. Furthermore, the present inventors have further studied and determined that the coefficient of the influence of the dispersion of the glass is given to each of the cation components so that the range of the value A calculated by the following formula (A) is 8.5000 to 11.000. It is preferable to adjust the optical characteristics for satisfying the relationship of the above formula (1) such that the Abbe number (νd) is 39.5 to 41.5, the refractive index (nd), and the Abbe number (νd).

(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 52 below.

Further, among the various cationic components described above, Gd ³⁺ exerts a function of increasing the refractive index but has a large effect of increasing the specific gravity. On the other hand, among the components exhibiting an effect of increasing the refractive index, Nb ⁵⁺ and Ti ⁴⁺ are components having a particularly large effect. Further, Nb ⁵⁺ and Ti ^{4+ are} not only capable of greatly increasing the refractive index but also a component having a small effect of increasing the specific gravity. In order to suppress an increase in the specific gravity and to increase the refractive index, the glass preferably has a value B of -1.000 or more calculated from the following formula (B) in the glass composition represented by the cation %. Further, from the viewpoint of high refractive index and low dispersion, the value B calculated by the following formula (B) is preferably 6.720 or less.

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

A more preferable lower limit and a more preferable upper limit of the value B calculated by the formula (B) are shown in Table 53 below.

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

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 not to contain these elements, that is, these elements are not introduced into the glass as a glass component.

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

When the amount of addition of Sb 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 amount of Sb added is preferably in the range of 0 to 0.11% by mass, more preferably The range is from 0.01 to 0.08% by mass, and a further preferred range is from 0.02 to 0.05% by 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 amount of Sn added is preferably in the range of 0 to 0.5% by mass, and more preferably in the range of 0 to 0.5% by mass. 0.2% by mass, and a further preferred range is 0% by mass.

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

The glass is an oxide glass, so as an anionic component comprising O ^2-. A preferred lower limit of the O ^2- content is shown in Table 54 below.

Examples of the anion component other than O ²⁻ are F ⁻ , Cl ⁻ , Br ⁻ , and I ⁻ . However, F ^- , Cl ^- , Br ^- , and I ^- are all easily volatilized 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, as a well-known thing, an anion % is a percentage which makes the total content of all the anion components contained in glass into 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).

Nd 2.0927-0.0058×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 55 below.

The refractive index (nd) of the above glass 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 not easily devitrified, the refractive index (nd) preferably satisfies the following formula (2).

(2) Formula nd 2.1270-0.0058×νd

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 56 below.

Further, the refractive index (nd) is also preferably a lower limit or more and an upper limit or less as shown in the following Table 57.

(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 relative partial dispersion (Pg, F) uses each refractive index (ng), refractive index (nF), and refractive index (nc) in the g-line, the F-line, and the c-line, and (ng-nF)/( nF-nc) indicates.

From the viewpoint of providing 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 58 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 to 640 ° C or higher, it is possible to make the glass less likely to be broken when the glass is subjected to mechanical processing such as cutting, cutting, polishing, and polishing. Further, since a component such as Li or Zn having a strong effect of lowering the glass transition temperature is not contained in a large amount, even if the content of Gd or Ta is reduced, the content of Yb is further reduced, and the thermal stability is easily 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 mold at a high temperature. 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 59 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 (incidence and exit surface of the light to be controlled) of the lens. When the curvature of the optical functional surface is to be increased, the thickness of the lens also increases. As a result, the lens becomes heavy. 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 effect of the refractive index (nd) on the refractive power, 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.

In the glass, the ratio of the Gd and Ta which are increased in specific gravity is small, and the ratio of the occupation of Yb can be reduced. Therefore, the glass is high in refractive index and low in dispersion, and can be made low in specific gravity. Therefore, the d/(nd-1) of the above glass can be, for example, 5.70 or less. However, when d/(nd-1) is excessively reduced, the thermal stability of the glass shows a tendency to decrease. Therefore, it is preferable to set d/(nd-1) to 5.00 or more. A more preferred lower limit and a more preferred upper limit of d/(nd-1) are shown in Table 60 below.

Further, a preferred lower limit and a preferred upper limit of the specific gravity (d) of the above glass are shown in Table 61 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 61 below. Further, in order to further improve the thermal stability of the glass, it is preferred to set the specific gravity to be equal to or higher than the lower limit shown in the following Table 61.

(liquidus temperature)

The liquidus temperature is one of the indicators of the thermal stability of the glass. In order to suppress crystallization and 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 still more preferably 1250 ° C or lower. The lower limit of the liquidus temperature (LT) is, for example, 1100 ° C or more, but is preferably a lower temperature, and is not particularly 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 above, it is also possible to homogenize the glass and reduce the specific gravity. Therefore, the above glass is suitable as an optical glass for forming a lighter weight optical element.

<Method of Manufacturing Glass>

The above glass can be obtained by: obtaining a target glass group The method is to weigh and mix oxides, carbonates, sulfates, nitrates, hydroxides, etc. as raw materials, and mix them thoroughly to form a mixed batch, which is heated and melted in a melting vessel to perform defoaming and stirring. A homogeneous, foam-free molten glass is produced and molded. Specifically, it can be produced by a known melting method. Since the glass is a high refractive index 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 the following.

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 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.

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.

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 shape of the optical element (the surface layer removed by polishing), and the polishing allowance is increased as needed (removed by grinding) The surface layer of the optical element base material. By grinding and polishing the surface of the optical element blank The optical component was completed. 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 by 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 supplied to the glass material for press molding, which is called a glass gob for press molding, which is used for press forming of an optical element blank, in the same manner, and includes cutting, grinding, polishing, and the like. The glass material for press molding is supplied to a press-molding glass material by mechanical processing and through a glass gob 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, and a portion of the groove is cut. A method of cutting a glass sheet; a method of cutting a glass sheet with a cutting blade, and the like. Further, as the polishing and polishing method, barrel polishing or the like can be mentioned.

The glass material for press molding can be formed into a glass plate by, for example, casting molten glass into a mold, and the glass plate is cut into a plurality of glass sheets. And making. 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 press-molding the glass gob for press molding by reheating and softening. The method of producing an optical element blank by reheating, softening, and press-molding the glass is referred to as a reheat pressing method with respect to the 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, there is provided a method of manufacturing an optical element having a step of producing an optical element by polishing and/or polishing the above-described optical element blank.

In the method for producing an optical element, it is only necessary to apply a known method for polishing and polishing, and an optical element having high internal quality and surface quality can be obtained by sufficiently washing the surface of the optical element after processing, drying it, or the like. In this way, 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 also suitable as a lens constituting a cemented 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, a glued optical element can be fabricated by reversing the glued surface of the glued two optical elements. The shape is precisely processed (for example, spherical polishing), and the ultraviolet-curable adhesive used for bonding the cemented lens is applied, and after bonding, the lens is irradiated with ultraviolet rays to cure the adhesive. In order to produce such a glued optical element, the above glass is preferred. By arranging a plurality of glued optical elements by using a plurality of glasses having different Abbe numbers (νd), and bonding them together, it is possible to form an element suitable for correction of chromatic aberration.

As a result of 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 represented by mass% in terms of oxides can be converted into a composition represented by cation % and anion % according to, for example, 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 . Here, 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 atom 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 rounding off the fourth decimal place and expressing the value to the third decimal place. It should be noted that the molecular weights expressed by the oxide standard for some glass components and additives are as follows: 62 said.

Example

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 immediately placed in the annealing furnace together with the molding die. Then, annealing was performed for about 1 hour near the glass transition temperature. After annealing, it was placed in an annealing furnace and cooled to room temperature.

When the glass produced in this manner was observed, no precipitation of crystals, bubbles, streaks, 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 was weighed and sufficiently mixed to prepare a batch raw material, and the examples were used. 1 The same method was used to obtain glass.

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 were measured by the method shown below. 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)

Using a differential scanning calorimeter (DSC) at a rate of 10 ° C / min The degree was measured.

(3) Specific gravity

The measurement was carried out by 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 held 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.

(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.

(Comparative Example 6)

The cation ratio of {Zn ²⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} of the glass of one embodiment of the present invention is 0.17 or less.

On the other hand, the cation ratio of the glass of No. 6 shown in Table 1 of JP-A-2014-62026 is 0.578. In the glass composition of the glass of No. 6 shown in Table 1 of JP-A-2014-62026, it is shown that only the reduction of the cation ratio {Zn ²⁺ /(La ³⁺ +Y ³⁺ +Gd ^{3 ) is performed.} The composition adjustment of ⁺ +Yb ³⁺ )} is difficult to suppress the precipitation of crystals, and thus the glass described below was produced.

In the glass of No. 6 shown in Table 1 of JP-A-2014-62026, Zn ²⁺ is reduced, and the amount of reduction is distributed to other components so that the balance of the contents of other components is not largely changed. The composition adjustment shown in the following Table 64 was carried out, and two types of glass (composition adjustment 1, composition adjustment 2) were produced. The ratio of the glass components in Table 64 to each other is a cation ratio. Specifically, a glass raw material was prepared, and 170 g of a raw material was placed in a platinum crucible, and melted and clarified at 1400 ° C for 2 hours. After the molten glass was agitated and homogenized, the molten glass was cast into a preheated molding die, left to cool to near the glass transition temperature, and immediately placed in an annealing furnace together with the molding die. Then, annealing was performed for about 1 hour near the glass transition temperature. After annealing, it was placed in an annealing furnace and cooled to room temperature.

After that, the inside of the glass was observed.

1 is a photograph of a glass evaluated in Comparative Example 6. It can be clearly seen from Fig. 1 that a large amount of crystals are precipitated in the glass, which is cloudy and loses transparency.

On the other hand, in the glass of one embodiment of the present invention, the composition adjustment described in detail above, such as {Zn ²⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )}, is performed. Thereby, crystal precipitation can be suppressed.

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 for adjusting the Abbe number.

Finally, summarize the various ways mentioned above.

According to one embodiment, it is possible to provide a glass which is an oxide glass, the total content of B ³⁺ and Si ⁴⁺ is 43 to 65%, and the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is 25~50%, the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is 3~12%, Zr ⁴⁺ content is 2~8%, and the total content of B ³⁺ and Si ⁴⁺ is relative The ratio of cations to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is {(B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ ) } is a ratio of cations of 0.70 to 1.42, the total content of B ³⁺ and Si ^{4+ to} the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ {(B ³⁺ +Si ⁴⁺ )/ ^{(Nb 5+ + Ti 4+ + Ta} 5+ + W 6+)} is 5.80 ~ 7.70, W ⁶⁺ content of the Nb ^5+, the total cation content of Ti ^4+, Ta ^5+, and W ⁶⁺ ratio {W ⁶⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is 0.50 or less, and the total Zn ²⁺ content is relative to La ³⁺ , Y ³⁺ , Gd ^{3+ ,} and Yb ³⁺ . cation content ratio ^{{Zn 2+ / (La 3+ +} Y 3+ + Gd 3+ + Yb 3+)} is 0.17, La ³⁺ content relative to the content of La ^3+, Y ^3+, Gd ^3+, and The cation ratio of the total content of Yb ³⁺ is {La ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is 0.50-0.95, and the content of Y ^{3+ is} relative to La ³⁺ , Y ³⁺ , Gd ³⁺ The cation ratio of the total content of Yb ³⁺ to {Y ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is 0.10 to 0.50, and the Gd ³⁺ content is relative to La ³⁺ and Y ³ The cation ratio of the total content of ⁺ , Gd ³⁺ and Yb ³⁺ is {Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is 0.10 or less, and the content of Ta ^{5+ is} relative to Nb ⁵ The cation ratio of the total content of ⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is {Ta ⁵⁺ /(Nb ⁵⁺ + Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is 0.2 or less, and the Abbe number ( The range of νd) is 39.5 to 41.5, and the refractive index (nd) satisfies the above formula (1) with respect to the Abbe number (νd).

The above glass is a glass satisfying the formula (1) and is a high refractive index low dispersion glass useful in an optical system. Since the glass has a reduced ratio of Gd and Ta in the glass composition, the glass can be stably supplied, and by satisfying the above-described content, total content, and cation ratio, high thermal stability can be obtained, and the specific gravity can be reduced.

In one embodiment, in the glass composition represented by the cation %, the value A calculated by the above formula (A) is preferably 8.5000 to 11.0000.

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

In one ^embodiment , the cation ratio of the Zr ⁴⁺ content in the above glass to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is preferably {Zr ⁴⁺ content / (Nb ⁵⁺ + Ti) ^{The range of 4+} +Ta ⁵⁺ +W ⁶⁺ )} is 0.48~2.20.

In one embodiment, the specific gravity of the glass is 5.20 or less.

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

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

Further, according to another aspect, a method of manufacturing 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 can be provided.

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, it is also possible to provide a step of fabricating an optical element by grinding and/or polishing the above-mentioned optical element blank. A method of manufacturing an optical element.

It is to be understood that the embodiments disclosed herein are illustrative and not restrictive. The scope of the present invention is defined by the scope of the claims and 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 of course possible to arbitrarily combine two or more of the items described in the specification or as the items described in the preferred range.

[Industry Utilization]

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

Claims (12)

A glass, which is an oxide glass, wherein the total content of B ³⁺ and Si ⁴⁺ is 43 to 65%, and the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is 25 ~50%; the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is 3~12%; Zr ⁴⁺ content is 2~8%; the total content of B ³⁺ and Si ⁴⁺ is relative to The ratio of cations of the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ to {(B ³⁺ +Si ⁴⁺ )/(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} a ratio of cations of 0.70 to 1.42; total content of B ³⁺ and Si ^{4+ to} the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ {(B ³⁺ +Si ⁴⁺ )/( Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is 5.80 to 7.70; cation ratio of W ⁶⁺ content relative to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ W ⁶⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is 0.50 or less; the total content of Zn ²⁺ relative to La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ The cation ratio {Zn ²⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is 0.17 or less; the La ³⁺ content is relative to La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ cations total content ratio ^{{La 3+ / (La 3+ +} Y 3+ + Gd 3+ + Yb 3+)} is 0.50 ~ 0.95; Y ³⁺ content with respect to the La ^3+, Y ^3+, Gd ³⁺ and Yb ³⁺ The total cation ratio of {Y ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is 0.10-0.50; the Gd ³⁺ content is relative to La ³⁺ , Y ³⁺ , Gd ³ The cation ratio of the total content of ⁺ and Yb ³⁺ is {Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is 0.10 or less; the content of Ta ^{5+ is} relative to Nb ⁵⁺ , Ti ⁴ The cation ratio of the total content of ⁺ , Ta ⁵⁺ and W ⁶⁺ is {Ta ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is 0.2 or less; the range of Abbe number (νd) It is 39.5 to 41.5, and the refractive index nd satisfies the following formula (1) with respect to the Abbe number (νd): (1) Formula nd 2.0927-0.0058×νd. The glass according to claim 1, wherein in the glass composition represented by the cation %, the value A calculated by the following formula (A) ranges from 8.5000 to 11.0000: (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. The glass according to claim 1 or 2, wherein in the glass composition represented by the cation %, the value B calculated by the following formula (B) ranges from -1.000 to 6.720: (B) Formula B = 0.567 × (Ti ^{4 +} content + Nb ^{5 +} content) - 1.000 × Gd ^{3 +} content. The application of a glass or two of the scope of patent 1, wherein the Zr ⁴⁺ content relative to the total content of Nb ^5+, Ti ^4+, Ta ^5+, and W ⁶⁺ ratio {Zr ⁴⁺ cation content / (Nb ^{The range of 5+} + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is 0.48 to 2.20. The application of paragraph 3 of the glass patentable scope, wherein the content of Zr ⁴⁺ with respect to Nb ^5+, the total cation content of Ti ^4+, Ta ^5+, and W ⁶⁺ content ratio of Zr ⁴⁺ {/ (Nb ⁵⁺ The range of +Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is 0.48 to 2.20. The glass according to claim 1 or 2, wherein the specific gravity is 5.20 or less. The glass according to claim 3, wherein the specific gravity is 5.20 or less. The glass according to claim 4, wherein the specific gravity is 5.20 or less. The glass according to claim 5, wherein the specific gravity is 5.20 or less. 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.