TWI756192B - Glass, glass materials for press molding, optical element blanks and optical elements - Google Patents

Abstract

2.0927-0.0058×νd，且對於表1中記載的陽離子成分，各陽離子成分的含量乘以表1記載的係數的值的合計D相對於折射率(nd)滿足下述(B)式。 The present invention provides a glass, which is oxide glass, expressed in cation %, B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Ta Total content of ⁵⁺ , 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, and the refractive index (nd) satisfies the following relationship with respect to the Abbe number (νd): nd

2.0927-0.0058×νd, and for the cation components described in Table 1, the total D of the values obtained by multiplying the content of each cation component by the coefficient described in Table 1 satisfies the following formula (B) with respect to the refractive index (nd).

Description

Glass, glass materials for press molding, optical element blanks and optical elements

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 high-refractive-index, low-dispersion glass, and a lens formed of ultra-low-dispersion glass to form a cemented lens, chromatic aberration can be corrected and the optical system can be made 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 and a projector. Such a high-refractive-index, low-dispersion glass is described in, for example, Patent Documents 1 to 20.

[Prior Art Literature]

[Patent Literature]

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

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

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

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

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

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

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

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

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

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

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

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

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

Patent Document 14: WO10/053214.

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

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

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

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

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

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

For glass for optical elements, in order to show the distribution of optical properties, an optical property diagram (or also referred to as an Abbe diagram) is widely used. In the optical characteristic diagram, the Abbe number (νd) is taken on the horizontal axis, and the refractive index (nd) is taken on the vertical axis. The shaft is made so that it increases in order from the bottom to the top. It should be noted that, unless otherwise specified, the refractive index and Abbe number refer to the refractive index (nd) for helium d-line (wavelength 587.56 nm) and the d-line (wavelength 587.56 nm) for helium. Shell number (νd).

The optical properties of high-refractive-index, low-dispersion glass (high nd and high νd glass) generally show that when the Abbe number decreases, the refractive index increases, and when the Abbe number decreases, A so-called rightward-rising profile in which the refractive index decreases as the Abbe number increases. This is considered to be due to the following reasons.

Most of the high-refractive-index and low-dispersion glasses contain rare earth oxides such as boron oxide and lanthanum oxide. In such glass, in order to increase the refractive index without reducing the Abbe number, the content of the rare earth oxide must be increased. However, in the high-refractive-index, low-dispersion glass of the prior art, when the content of rare earth oxide is increased, the thermal stability of the glass decreases, and the glass tends to devitrify in the process of manufacturing the glass. Therefore, in the high-refractive-index, low-dispersion glass of the prior art, it is difficult to increase both the Abbe number and the refractive index while suppressing devitrification of the glass intended to be used as an optical element material. This is considered to be the reason why the high-refractive-index, low-dispersion glass of the prior art exhibits such a distribution in the optical characteristic diagram.

On the other hand, in the design of an optical system, glass with a high refractive index and a large Abbe number (low dispersion) is used as an optical element that is extremely effective for chromatic aberration correction, functionalization and compactness of the optical system. Material. Therefore, it is very meaningful to set a straight line rising to the right on the optical characteristic graph, and to provide a glass with a higher refractive index than the straight line (the area on the left side of the straight line on the graph).

2.0927-0.0058×νd的關係的玻璃是在光學系統中有用的高折射率低色散玻璃。 From the above point of view, a glass having an Abbe number (νd) of 39.5 to 41.5 and a refractive index (nd) of 2.0927-0.0058×νd or more with respect to the Abbe number satisfies nd

Glass having a relationship of 2.0927-0.0058×νd is a high-refractive-index, low-dispersion glass useful in optical systems.

In addition, it is desired to reduce the weight of optical elements constituting projection optical systems such as imaging optical systems and projectors. This is because reducing the weight of the optical element is related to the weight reduction of the imaging optical system and the projection optical system to which the optical element is mounted. For example, when mounting heavy optics in an autofocus camera, driving The power consumption during autofocusing increases and the battery drains quickly. On the other hand, if the weight of the optical element is reduced, the power consumption when driving the autofocus is reduced, and the life of the battery can be extended.

2.0927-0.0058×νd的關係的高折射率低色散玻璃而製作的光學元件有變重的傾向。這是因為，在專利文獻1~20中記載的用於高折射率低色散化的組成調整中，有玻璃的比重增大的傾向。 However, the present inventors considered that the range of Abbe's number (νd) used in the glasses described in Patent Documents 1 to 20 is 39.5 to 41.5, which satisfies nd

The optical element produced by the high-refractive-index, low-dispersion glass having the relationship of 2.0927-0.0058×νd tends to be 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.

2.0927-0.0058×νd的關係、且可有助於光學元件的輕量化的玻璃。 One aspect of the present invention aims to provide an Abbe number (νd) of 39.5 to 41.5 that satisfies nd

A glass that has a relationship of 2.0927-0.0058×νd and can contribute to the weight reduction of optical elements.

One aspect of the present invention relates to a glass, which is an oxide glass, expressed in % of cations, 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 MgO is 90% or more, the Abbe number (νd) is in the range of 39.5 to 41.5, and the refractive index (nd) relative to the Abbe number (νd) satisfies the following formula (1):

Regarding the cationic components described in Table 1 shown below, with respect to the refractive index (nd), the total D of the values obtained by multiplying the content of each cationic component by the coefficient described in Table 1 satisfies the following formula (B):

2.0927-0.0058×νd的關係的高折射率低分散玻璃的低比重化即光學元件的輕量化的玻璃。 In the above glasses, expressed in % of cations, 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 cationic components are referred to as “main The total content of cationic components") is 90% or more. In order to achieve the above-mentioned object, the inventors of the present invention have paid attention to the difference in the influence of the specific gravity of the glass given by the above-mentioned main cationic components. Furthermore, the experiment was repeated a considerable number of times, and as a result, the coefficients shown in Table 1 were determined for each main cationic component. By adjusting the composition so that the total D calculated by using these coefficients satisfies the formula (B), it is possible to provide a value that contributes to satisfying nd in the range of Abbe number (νd) of 39.5 to 41.5.

The low specific gravity of the high-refractive-index, low-dispersion glass with the relationship of 2.0927-0.0058×νd is the glass that reduces the weight of the optical element.

According to one aspect of the present invention, it is possible to provide a glass that has optical properties useful in an optical system and can contribute to the weight reduction of optical elements. Furthermore, according to one aspect of this invention, the glass material for press molding, the optical element blank, and the optical element which consist of the said glass can be provided.

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

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

[grass]

The glass of one aspect of the present invention is an oxide glass, that is, B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , in terms of cation %, 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, the Abbe number (νd) is in the range of 39.5 to 41.5, and the refractive index (nd) with respect to the Abbe number (νd) satisfies the above formula (1), and for the following For the cationic components described in Table 1, the total D of the values obtained by multiplying the content of each cationic component 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-mentioned 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 analytical value obtained by ICP-AES may include a measurement error of about ±5% of the analytical value. It should be noted that, in the present specification and the present invention, the content of a constituent component is 0%, and no inclusion or introduction means that the constituent component is not substantially contained, and it means that the content of the constituent component is equal to or less than the impurity level.

In the present invention, the glass composition is represented by cation % with respect to the cationic component. It is well known that the cation % is a percentage based on the total content of all the cationic components contained in the glass as 100%.

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

Hereinafter, about the numerical range, the (more preferable) lower limit and the (more preferable) preferable upper limit may be shown in a table|surface. The numerical value described at the bottom in the table is better, and the numerical value written at the bottom is the best. In addition, unless otherwise specified, the (preferable) lower limit refers to a value greater than or equal to the stated value (more preferred), and the (more preferred) upper limit refers to a value below the stated value (more preferred) good. The numerical range can be defined by arbitrarily combining the numerical values described in the column of the (preferable) lower limit and the numerical value described in the column of the (more preferred) upper limit in the table.

<Glass composition>

For the above glasses, 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 cationic components) is 90% or more. The above-mentioned glass may contain only the main cationic components (that is, the total content of the main cationic components is 100%), or may contain one or more other cationic components in addition to the main cationic components. The preferable lower limit of the total content of the main cationic components is shown in Table 2 below.

In the glass composition of the above-mentioned glass, for each cationic component as the main cationic component, the total D of the value obtained by multiplying the content of each cationic component with respect to the refractive index (nd) by the coefficient described in Table 1 satisfies the following formula (B) :

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

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 × 0.012 + 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), still more preferably the following formula (B-3), and still more preferably the following ( B-4) formula, Still more preferably the following formula (B-5), still more preferably the following (B-6) formula, still more preferably the following (B-7) formula, and further still further The following formula (B-8) is preferable, and the following formula (B-9) is still more preferable.

In the glass composition of the above-mentioned glass, as long as the total content of the main cationic components is 90% or more and satisfies the formula (B), the main cationic components may be not contained in the above-mentioned glass (that is, the content is 0%). cationic components. The preferable range etc. of content of each cation component will be described further later. However, the present invention is not limited to the following preferable ranges.

B ³⁺ and Si ⁴⁺ are network-forming components of glass. When the total content of B ³⁺ and Si ⁴⁺ (B ³⁺ +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 total content of B ³⁺ and Si ⁴⁺ is 65% or less, the decrease in the refractive index (nd) can be suppressed, which is preferable from the viewpoint of producing glass having the above-mentioned optical properties. Therefore, the range of the total content of B ³⁺ and Si ⁴⁺ in the glass is preferably 43 to 65%. A more preferable lower limit and a more preferable 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 that have the effect of suppressing the decrease in Abbe's number (νd) and increasing the refractive index. In addition, these components also have the 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 Therefore, it is preferable from the viewpoint of producing glass having the above-mentioned optical properties. Furthermore, the chemical durability and weather resistance of glass can also be suppressed from falling. In addition, when the glass transition temperature is lowered, when the glass is subjected to mechanical processing (cutting, cutting, grinding, polishing, etc.), the glass becomes prone to breakage (reduction in machinability), and 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 also 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, the crystallization during glass production can also be suppressed and the reduction The melting of the raw material at the time of melting glass remains. Moreover, it is also preferable from the viewpoint of suppressing the rise of a specific gravity. Therefore, in the above-mentioned glass, the range of the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is preferably 25 to 50%. The more preferable lower limit and the more preferable 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 that have the effect of increasing the refractive index, and also have the effect of improving the thermal stability of the glass by including 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-mentioned It is better to consider the optical properties. On the other hand, when the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is 12% or less, the decrease in thermal stability and the decrease in Abbe number (νd) can be suppressed. Therefore, in the above-mentioned glass, it is preferable to set the range of the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ to 3 to 12%. The more preferable lower limit and the more preferable 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 which has the effect of increasing the refractive index, and by containing an appropriate amount thereof, also has the effect of improving the thermal stability of the glass. In addition, Zr ⁴⁺ has the effect of making glass difficult to break during machining by increasing the glass transition temperature. In order to obtain these effects favorably, the content of Zr ⁴⁺ in the above-mentioned glass is preferably 2% or more. On the other hand, when the content of Zr ⁴⁺ is 8% or less, since the thermal stability of the glass can be improved, the crystallization during glass production and the occurrence of melting residue during glass melting can be suppressed. Therefore, the range of the content of Zr ⁴⁺ in the above-mentioned glass is preferably 2 to 8%. A better lower limit and a better upper limit of the Zr ⁴⁺ content are shown in Table 6 below.

In order to realize optical properties 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 preferable that the Zr ⁴⁺ content in the above-mentioned glass be The range of the cation ratio {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⁺ was set to 0.48 ~2.20. It is also preferable that the range of the said cation ratio is 0.48-2.20 from a viewpoint of suppressing the fall of glass transition temperature (thereby improving machinability). In addition, from the viewpoint of improvement of thermal stability and low dispersion of glass, it is also preferable that the above-mentioned cation ratio is 0.48 or more. On the other hand, from the viewpoints of improvement in solubility and suppression of crystallization, the cation ratio is preferably 2.20 or less. A better lower limit and a better 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 improve the thermal stability of the glass and achieve optical properties in which the Abbe number (νd) is 39.5 to 41.5, and the refractive index (nd) and the Abbe number (νd) satisfy the relationship of the above-mentioned formula (1), it is preferable in the above-mentioned 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, it is possible to suppress the glass loss of clarity. In addition, it is also preferable from the viewpoint of suppressing an increase in the specific gravity of the glass. On the other hand, a 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-mentioned optical properties. A better lower limit and a better 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-mentioned optical properties of improving the thermal stability of the glass and suppressing the decrease in the refractive index (nd), it is preferable that the total content of B ³⁺ and Si ⁴⁺ in the above-mentioned glass is relative to Nb ⁵⁺ , Ti ⁴⁺ , 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 Abbe number (νd) and improve the thermal stability of the glass, it is preferable to set the cation ratio {(B ³⁺ +Si ⁴⁺ )/(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is set to 5.00 or more. Furthermore, from the viewpoint of lowering the specific gravity, the cation ratio {(B ³⁺ +Si ⁴⁺ )/(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is preferably 5.00 or more.

A better lower limit and a better 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 reducing the specific gravity of the glass, it is preferable to set the W ⁶⁺ content to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ The cation ratio of {W ⁶⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is set to 0.50 or less. Also, from the viewpoint of increasing the refractive index of the glass and reducing the coloration, the cation ratio {W ⁶⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is preferably 0.50 or less. A better lower limit and a better 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 realize the above-mentioned optical properties, the content of Zn ²⁺ in the above-mentioned glass is preferably adjusted relative to the sum of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ The content cation ratio {Zn ²⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is set to be less than 0.2. Furthermore, from the viewpoints of suppressing a decrease in glass transition temperature (thereby improving machinability) and improving chemical durability, a 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 meltability, the cation ratio {Zn ²⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is preferably 0% or more, more preferably 0% or more. The preferable lower limit and preferable upper limit of the cation ratio {Zn ²⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} are shown in Table 11 below.

Among rare earth elements La, Y, Gd, and Yb, Gd is a heavy rare earth element, and is a component required to be reduced in content in glass from the viewpoint of stable supply of glass. Moreover, Gd is also a component which has a large atomic weight and increases the specific gravity of 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, interchangeable lenses for single-lens reflex cameras, surveillance cameras The lens of the camera is expected to have high light transmittance in the near-infrared region. Therefore, it is desired to reduce the content of Yb in order to be a useful glass for the production of these lenses.

On the other hand, La and Y do not adversely affect the light transmittance in the near-infrared region, and by distributing an appropriate amount relative to the total content of rare earth elements, the thermal stability is improved and the increase in specific gravity is suppressed. Aspects of dispersive glass consider useful components.

Therefore, in the above-mentioned glass, it is preferable for La ³⁺ to set the cation ratio of La ³⁺ content to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ {La ³⁺ /(La ³⁺ The range of ⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is set to 0.50~0.95. A better lower limit and a better upper limit of the cation ratio {La ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} are shown in Table 12 below.

Further, for Y ³⁺ , it is preferable to set the cation ratio of the content of Y ³⁺ to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ {Y ³⁺ /(La ³⁺ +Y ³ The range of ⁺ +Gd ³⁺ +Yb ³⁺ )} is set to 0.10~0.50. A better lower limit and a better 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 whose content in glass should be reduced from the viewpoint of stable supply of glass. From the viewpoint of stably supplying high-refractive-index, low-dispersion glass having the above-mentioned optical properties, it is preferable that the content of Gd ³⁺ in the above-mentioned glass be adjusted to the sum of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ The content of the cation ratio {Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} is made 0.10 or less. Satisfying the above-mentioned cation ratio also contributes to lowering the specific gravity of the glass. A better lower limit and a better 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 ratios of La ³⁺ content, Y ³⁺ content, and Gd ³⁺ content to the total content are as described above. The preferable lower limit and preferable 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. In addition, the lower limit shown in Tables 15 to 18 below is also preferable from the viewpoint of improving the thermal stability and meltability of the glass for the content of Y ³⁺ .

When Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ are contained in an appropriate amount, the refractive index is increased and the thermal stability of the glass is improved. However, Ta ⁵⁺ is an extremely expensive component although it has the effect of increasing the refractive index. Therefore, from the viewpoint of stable supply of glass, it is not preferable to actively use Ta ⁵⁺ . In addition, when the content of Ta ⁵⁺ is large, the raw material tends to be melted and remain when the glass is melted. In addition, the specific gravity of glass increases. In conclusion, Ta ⁵⁺ is the component whose content should be reduced. Therefore, Ta ⁵⁺ is not preferably used actively. In order to improve the thermal stability of the glass, achieve high refractive index and low dispersion, and reduce 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 . The cation ratio {Ta ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ^{5+ +} W ⁶⁺ )} of the total content of + is set to 0.2 or less. The preferable lower limit and the more preferable upper limit of the cation ratio {Ta ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} are shown in Table 19 below.

In addition, for Nb ⁵⁺ , in order to supply glass stably, the contents of Gd ³⁺ and Ta ⁵⁺ are reduced, and it is preferable to reduce the content of Yb ³⁺ together with Gd ³⁺ and Ta ⁵⁺ , and it is excellent in thermal stability. For low-dispersion glass with refractive index, considering the above-mentioned effects of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ , and W ⁶⁺ , it is preferable to set the content of Nb ⁵⁺ relative to that of 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. In addition, Nb ⁵⁺ is a component that tends to increase the refractive index without increasing the specific gravity compared to Ta ⁵⁺ and W ⁶⁺ . Therefore, in order to suppress the increase in specific gravity, the preferable cation ratio {Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is increased. The preferable lower limit and preferable upper limit of the cation ratio {Nb ⁵⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} are shown in Table 20 below.

Furthermore, from the viewpoint of preventing high dispersion and coloring, the cation ratio of the Ti ⁴⁺ content to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is preferably {Ti ⁴⁺ / (Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is set to 0.6 or less. A preferable lower limit and a better 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 preferable 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 preferable lower limit value 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 preferable 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 a preferable upper limit value shown in Table 22 below.

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

The total content and the like of B ³⁺ and Si ⁴⁺ which are network-forming components of glass are as described above. Regarding B ³⁺ and Si ⁴⁺ , B ³⁺ is superior to Si ⁴⁺ in improving the meltability, but it tends to be exhibited during melting. On the other hand, Si ⁴⁺ has the effect of improving the chemical durability, weather resistance, and machinability of the glass, or improving the viscosity of the glass at the time of melting.

Generally, in the high refractive index and low dispersion glass containing rare earth elements 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 molten glass is low, it becomes easy to crystallize. For crystallization during glass production, the crystallization state is more stable than the amorphous state (amorphous state), and the ions constituting the glass move in the glass and are arranged to have a crystalline structure. produce. Therefore, by adjusting the content ratio of each component of B ³⁺ and Si ⁴ so that the viscosity during melting increases, it becomes difficult for the above-mentioned ions to arrange so as to have a crystal structure, and the crystallization of the glass can be further suppressed, Further improve the devitrification resistance of glass.

From the above viewpoints, the preferable lower limit and preferable cation ratio {B ³⁺ /(B ³⁺ +Si ⁴⁺ )} of the content of B ³⁺ to the total content of B ³⁺ and Si ⁴⁺ The upper limit is shown in Table 23 below. It is also preferable to make it more than the lower limit shown in the following table from a viewpoint of improving the meltability of glass. Moreover, it is also preferable to make it below the upper limit shown in Table 23 below from the viewpoint of improving the viscosity of the glass at the time of melting. Furthermore, in order to reduce the fluctuation of glass composition due to volatilization during melting and the fluctuation of optical properties caused by it, and from the viewpoint of improving one or more of the chemical durability, weather resistance, and machinability of the glass, the following It is also preferable that it is below the upper limit shown in Table 23.

From the viewpoints of improving the devitrification resistance, meltability, formability, chemical durability, weather resistance, machinability, etc. of the glass, the B ³⁺ content and the Si ⁴⁺ content each have a preferable lower limit and a preferable upper limit. As shown in Tables 24~25 below.

Zn ²⁺ has the effect of promoting the melting of the glass raw material when the glass is melted, that is, the effect of improving the meltability. In addition, it also has the effect of adjusting the refractive index (nd) and the Abbe number (νd) and lowering the glass transition temperature. From the viewpoints of suppressing the decrease in Abbe's number (νd), improving the thermal stability of the glass, suppressing the decrease in the glass transition temperature (thereby improving the machinability), and reducing the specific gravity of the glass, the Zn ²⁺ The cation ratio {Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )}, which is a value obtained by dividing the content by the total content of B ³⁺ and Si ⁴⁺ , is set to 0.15 or less. In addition, since Zn is an optional component which may or may not be contained in the above-mentioned glass, it is preferable that the cation ratio {Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )} is 0 or more, but in order to improve the meltability and ease the In order to produce a homogeneous glass, it is more preferable to contain Zn so that the cation ratio {Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )} is greater than 0. A better lower limit and a better 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, thermal stability, formability, machinability, etc. of the glass and realizing the above-mentioned optical properties, the preferable lower limit and preferable upper limit of the Zn ²⁺ content are shown in Table 27 below.

From the viewpoints of further improving the thermal stability of the glass, suppressing the decrease in glass transition temperature (thereby improving the machinability), and improving the chemical durability, the content of Zn ²⁺ is preferable 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 preferable cation ratio {Zn ²⁺ /(Nb ⁵⁺ +Ti ⁴⁺ +Ta ⁵⁺ +W ⁶⁺ )} is 0, but it is not possible to improve the meltability. From a viewpoint, it is better to be greater than 0. Taking the above aspects into consideration, a better lower limit and a better upper limit of the cation ratio {Zn ²⁺ /(Ti ⁴⁺ +Nb ⁵⁺ +Ta ⁵⁺ +W ⁶⁺ )} are shown in Table 28 below.

On the basis of considering the above functions and effects, for Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ , W ⁶⁺ , the content of each component of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ , and W ⁶⁺ is compared The optimum 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 increases, the machinability tends to decrease. In addition, chemical durability and weather resistance also showed a tendency to decrease. Therefore, the Li ⁺ content is preferably 5% or less. A preferable lower limit and a more preferable upper limit of the content of Li ⁺ are shown in Table 33 below. The content of Li ⁺ may also be 0%.

Na ⁺ , K ⁺ , Rb ⁺ , and Cs ⁺ all have the effect of improving the meltability of glass, but when these contents increase, the thermal stability, chemical durability, weather resistance, and machinability of the glass tend to decrease. Therefore, the preferred lower and upper limits of the respective contents of Na ⁺ , K ⁺ , Rb ⁺ , and Cs ⁺ are shown in Tables 34 to 37 below, respectively.

From the viewpoint of maintaining the thermal stability, chemical durability, weather resistance, and machinability of the glass and improving the meltability of the glass, the total content of Li ⁺ , Na ⁺ and K ⁺ (Li ⁺ +Na ⁺ +K ⁺ ) is The preferred lower limit and the 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 glass. However, when the content of these components increases, the thermal stability of the glass decreases, and the devitrification tends to be exhibited. Therefore, the content of each of these components is preferably equal to or more than the lower limit shown in Tables 39 to 42 below, and preferably equal to or less than the upper limit.

In addition, from the viewpoint of maintaining the thermal stability of the glass, the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ (Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ ) is preferable It is set to be more than the lower limit shown in Table 43 below, and it is preferable to set it as below the upper limit.

Al ³⁺ is a component having the effect of improving chemical durability and weather resistance of glass. However, when the content of Al ³⁺ increases, the refractive index (nd) tends to decrease, the thermal stability of the glass tends to decrease, and the meltability tends to decrease. Considering the above aspects, the content of Al ³⁺ is preferably equal to or more than the lower limit shown in Table 44 below, and preferably equal to or less than the upper limit.

Ga ³⁺ , In ³⁺ , Sc ³⁺ , and Hf ⁴⁺ all have the effect of increasing the refractive index (nd). However, these components are expensive, and are not essential components from the viewpoint of obtaining the above-mentioned optical glass. Therefore, the respective contents of Ga ³⁺ , In ³⁺ , Sc ³⁺ , and Hf ⁴⁺ are preferably set to be equal to or more than the lower limit shown in Tables 45 to 48 below, and preferably equal to or less than the upper limit.

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

Ge ⁴⁺ has the effect of increasing the refractive index (nd), but is an extremely expensive component among commonly used glass components. From the viewpoint of reducing the manufacturing cost of glass, the preferable lower limit and preferable 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). In addition, it is also a component that tends to increase specific gravity and coloration. In order to produce glass with the above-mentioned optical properties, less coloration, and low specific gravity, the preferable lower limit and preferable upper limit of the Bi ³⁺ content are shown in Table 51 below.

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

Among the cationic components other than the cationic components described above, P ⁵⁺ is a component that lowers the refractive index (nd) and is also a component that lowers the thermal stability of the glass. Thermal stability is improved. In order to produce glass having the above-mentioned optical properties and excellent thermal stability, the preferable lower limit and preferable 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⁺ . The preferable lower limit and preferable upper limit of the content of Te ⁴⁺ are shown in Table 53 below.

It should be noted that the content of the components described as (more preferable) as the lower limit or 0% in each of the above-mentioned tables is also preferably 0%. The same applies to the total content of a plurality of components.

Regarding the various cationic components described above, the inventors of the present invention have studied repeatedly, and have paid attention to considering that each cationic component has a different influence on the dispersion (Abbé number) of the glass. Furthermore, the inventors of the present invention have conducted further studies and, as a result, considered that the composition is adjusted so that the value A calculated from the following formula (A) falls within the range of 8.5000 to 11.000, for each cationic component, the coefficient that takes into account the influence of dispersion on the glass is defined, It is preferable to realize optical properties in which the Abbe number (νd) is 39.5 to 41.5, and the refractive index (nd) and the Abbe number (νd) satisfy the relationship of 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 more preferable upper limit of the value A calculated from the above formula (A) are shown in Table 54 below.

In addition, among the various cationic components described above, among Nb ⁵⁺ , Ti ⁴⁺ and Gd ³⁺ , Nb ⁵⁺ and Ti ⁴⁺ are components that have the effect of increasing the refractive index, and are more effective than Gd ³⁺ . A component with a small effect of increasing the specific gravity. Therefore, in order to suppress the increase in specific gravity and increase the refractive index, it is preferable to balance the total content of Nb ⁵⁺ and Ti ⁴⁺ with the content of Gd ³⁺ . From this point of view, it is preferable that the value C calculated by the following formula (C) is -1.000 or more in the glass composition represented by the cation %. In addition, from the viewpoint of high refractive index and low dispersion, the value C calculated from 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 more preferable upper limit of the value C calculated from the formula (C) are shown in Table 55 below.

Pb, As, Cd, Tl, Be, and Se each have toxicity. Therefore, it is preferable not to contain these elements, that is, not to introduce these elements into the glass as glass components.

U, Th, and Ra are all radioactive elements. Therefore, it is preferable not to contain these elements, that is, not to introduce these elemental components into glass as glass.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Ce can increase the coloring of glass or become a source of fluorescence , which is not preferable as an element contained in glass for optical elements. Therefore, it is preferable not to contain these elements, that is, not to introduce these elements into the glass as glass components.

Sb and Sn are elements that can be arbitrarily added and function as clarifying agents.

The addition amount of Sb is converted into Sb ₂ O ₃ , and when the total content of the glass components other than Sb ₂ O ₃ is 100 mass %, the preferable range is 0 to 0.11 mass %, and the more preferable range is 0.01-0.08 mass %, and a more preferable range is 0.02-0.05 mass %.

The amount of Sn added is converted into SnO ₂ , and when the total content of the glass components other than SnO ₂ is 100 mass %, the preferred range is 0 to 0.5 mass %, and the more preferred range is 0 to 0.2 mass % %, and a more preferable range is 0 mass %.

The cationic component has been described above. Next, the anion component is demonstrated.

Since the said glass is an oxide glass, it contains ^O2- as an anion component. The preferable lower limit of the content of O ^2- is shown in Table 56 below.

F ^- , Cl ^- , Br ^- , and I ^- can be exemplified as anion components other than O ^2- . However, F ^- , Cl ^- , Br ^- , and I ^- are all easily exerted in the melting of glass. Due to the volatilization of these components, there is a tendency that the characteristics of the glass fluctuate, the homogeneity of the glass decreases, and the consumption of the melting equipment becomes significant. Therefore, it is preferable to control the total content of F ^- , Cl ^- , Br ^- and I ^- to an amount that subtracts the content of O ^2- from 100 anion %.

In addition, it is well known that the anion % means the percentage when the total content of all the anion components contained in glass is 100%.

<Glass Properties>

(optical properties of glass)

The above-mentioned glass is a glass whose Abbe number (νd) is in the range of 39.5 to 41.5, and whose refractive index (nd) satisfies the following formula (1) with respect to the Abbe number (νd).

Glass having an Abbe number (νd) of 39.5 or more is effective in correcting chromatic aberration as a material for an optical element. On the other hand, when the Abbe number (νd) is larger than 41.5, unless the refractive index is lowered, the thermal stability of the glass is remarkably lowered, and devitrification tends to be easy in the process of producing the glass. The preferable lower limit and preferable upper limit of Abbe number (νd) are shown in Table 57 below.

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

The upper limit of the refractive index (nd) is naturally determined by the glass composition. In order to obtain a glass with improved thermal stability and less devitrification, it is preferable that the refractive index (nd) satisfies the following formula (2).

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

In addition, the refractive index (nd) is preferably equal to or more than the lower limit shown in Table 59 below, and is also preferably equal to or less than the upper limit.

(Partial Dispersion Characteristics)

From the viewpoint of correcting chromatic aberration, it is preferable that the above-mentioned glass is a glass having a small relative partial dispersion when the Abbe number (νd) is fixed.

Here, the partial dispersion ratio (Pg, F) is expressed as (ng-nF)/ (nF-nc).

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

(glass transition temperature)

Although the glass transition temperature of the said glass is not specifically limited, It is preferable that it is 640 degreeC or more. By making glass transition temperature (glass transition temperature, Tg) 640 degreeC or more, when glass is subjected to mechanical processing such as cutting, cutting, grinding, and polishing, glass can be made difficult to break. In addition, since components such as Li and Zn, which have a strong effect of lowering the glass transition temperature, need not be contained in large amounts, even if Gd and Ta are contained in a small amount, and Yb is contained in a further small amount, thermal stability can be easily improved.

On the other hand, when the glass transition temperature is too high, the glass must be annealed at a high temperature, which consumes the annealing furnace significantly. Moreover, when shaping|molding glass, it is necessary to shape|mold at a high temperature, and consumption of the mold used for shaping|molding becomes remarkable.

From the viewpoint of improving the machinability and reducing the burden on the annealing furnace and the molding die, the preferable lower limit and preferable 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 function surface of the lens (light incident and exit surfaces to be controlled). 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 becomes heavier. On the other hand, if glass with a high refractive index is used, a large refractive power can be obtained without increasing the curvature of the optical function surface.

Accordingly, as long as the refractive index can be increased while suppressing an increase in the specific gravity of the glass, the optical element having a fixed refractive power can be reduced in weight.

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) that subtracts the refractive index (1) in vacuum from the refractive index (nd) of the glass, It can be used as an indicator for reducing the weight of optical elements. That is, d/(nd-1) is used as an index for reducing the weight of the optical element, and by reducing this value, the weight of the lens can be reduced.

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

Moreover, the preferable lower limit and preferable upper limit of the specific gravity (d) of the said glass are shown in Table 63 below. From the viewpoint of weight reduction of the optical element formed of this glass, the specific gravity (d) is preferably equal to or less than the upper limit shown in Table 63 below. Moreover, in order to further improve the thermal stability of glass, it is preferable to make specific gravity more than the lower limit shown in Table 63 below.

(liquidus temperature)

The liquidus temperature is one of the indicators of the thermal stability of 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, still more preferably 1300°C or lower, still more preferably 1250°C or lower . As an example, the lower limit of the liquidus temperature (LT) is 1100° C. or higher, but the lower limit of the liquidus temperature (LT) is preferably low, and there is no particular limit.

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. Furthermore, by performing the composition adjustment described previously, it is also possible to homogenize and lower the specific gravity of the glass. Therefore, the above-mentioned glass is suitable as an optical glass for imparting a lighter-weight optical element.

<Manufacturing method of glass>

The above-mentioned glass can be obtained by weighing and mixing oxides, carbonates, sulfates, nitrates, hydroxides, etc. as raw materials so that the target glass composition can be obtained, and mixing them sufficiently The batches are mixed, heated and melted in a melting vessel, defoamed and stirred to produce a homogeneous and foam-free molten glass, which is then shaped. Specifically, it can be produced using a known melting method. Since the above-mentioned glass has the above-mentioned high-refractive-index and low-dispersion glass with the above-mentioned optical properties 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 their manufacturing method]

Another aspect of this invention relates to the glass material for press molding which consists of the above-mentioned glass.

An optical element blank formed from the above glass.

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

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

A kind of glass material with the above-mentioned press-molding glass material is pressed into A method of manufacturing an optical element blank in which a mold is press-molded to produce an optical element blank.

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

The optical element blank is similar to the shape of the optical element set as the target, and the polishing allowance (surface layer to be removed by polishing) is added to the optical element shape, and the grinding allowance (the surface layer that is removed by polishing) is added as required. the surface layer that will be removed) of the optical element base material. The optical element is completed by grinding and polishing the surface of the optical element blank. In one form, an optical element blank can be produced by a method of press-molding a molten glass obtained by melting an appropriate amount of the above-mentioned glass (referred to as a direct pressing method). In another form, an optical element blank can also be produced by solidifying a molten glass obtained by melting a suitable amount of the above-mentioned glass.

Moreover, in another form, the optical element blank can be produced by producing the glass material for press molding, and press-molding the produced glass material for press molding.

The press-molding of the glass material for press-molding can be performed by the well-known method of press-molding the glass material for press-molding in a softened state after heating with a press-molding die. Both heating and press molding can be performed in the atmosphere. The stress inside the glass can be reduced by annealing after press molding, thereby obtaining a homogeneous optical element blank.

The glass material for press molding is supplied in its original state to the glass material for press molding called a glass gob for press molding, which is used for press molding of optical element blanks, and also includes cutting, grinding, and polishing. The glass material for press-molding is supplied to the press-molding glass material through press-molding glass gobs, such as mechanical processing. As a cutting method, a groove is formed on a portion of the surface of the glass plate to be cut by a method called scribing, and local pressure is applied to the groove portion from the back surface of the formed groove surface, and the groove portion is A method of cutting a glass plate; a method of cutting a glass plate with a cutting blade, etc. Moreover, barrel polishing etc. are mentioned as a grinding|polishing and a polishing method.

The glass material for press molding can be produced by, for example, casting molten glass in a mold, molding it into a glass plate, and cutting the glass plate into a plurality of glass pieces. Alternatively, an appropriate amount of molten glass can be molded to produce a glass gob for press molding. An optical element blank can also be produced by reheating and softening the glass gob for press molding and press molding. The method of reheating glass, softening it, and press-molding it to produce an optical element blank is called a reheat pressing method as compared with the direct pressing method.

[Optical element and its manufacturing method]

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

The above-mentioned optical element is produced using the above-mentioned glass. In the above-mentioned optical element, for example, one or more coating films such as multilayer films such as antireflection films may be formed on the glass surface.

Furthermore, according to one aspect of the present invention, there can be provided a method for manufacturing an optical element including a step of producing an optical element by grinding and/or polishing the above-mentioned optical element blank.

In the above-mentioned manufacturing method of an optical element, a known method may be used for grinding and polishing, and the surface of the optical element can be sufficiently polished after the processing. Cleaning, drying, etc. to obtain an optical element with high internal quality and surface quality. In this way, an optical element formed of the above-mentioned glass can be obtained. As the optical element, various lenses such as spherical lenses, aspherical lenses, and microlenses, prisms, and the like can be exemplified.

Further, an optical element formed of the above-mentioned glass is preferable as a lens constituting a cemented optical element. As the cemented optical element, a cemented optical element (cemented lens) in which lenses are cemented together, a cemented optical element in which a lens and a prism are cemented, and the like can be exemplified. For example, a cemented optical element can be produced by performing precise processing (such as spherical polishing) on the cemented surfaces of the two optical elements to be cemented so that the shape is reversed, and applying a cemented lens for bonding The UV-curable adhesive used, after bonding, is irradiated with ultraviolet rays through the lens to harden the adhesive. In order to manufacture such a cemented optical element, the above-mentioned glass is preferable. By using a plurality of types of glass having different Abbe numbers (νd), a plurality of optical elements to be glued are respectively produced and glued, so that an element suitable for chromatic aberration correction can be obtained.

In the quantitative analysis of the glass composition, the glass component may be represented by an oxide basis, and the content of the glass component may be represented by mass %. Thus, the composition represented by mass % on the basis of oxide can be converted into the composition represented by cation % and anion % by the following method, for example.

When the glass contains N types of glass components, the k- _th glass composition is represented by A(k) _m On. However, k is an arbitrary integer of 1 or more and N or less.

A(k) is a cation, O is oxygen, m and n are stoichiometrically determined integers. For example, when expressed as B ₂ O ₃ on the basis of oxide, m=2 and n=3; when expressed as SiO ₂ , m=1 and n=2.

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

Furthermore, 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 sum of m×X(k)/R(K) from k=1 to N. m varies according to k. s is 2n/m.

In addition, the molecular weight R(k) may be calculated using a value that is rounded off to the fourth decimal place and represented to three decimal places. In addition, about some glass components and additives, the molecular weights based on oxide standards are shown in Table 64 below.

[Example]

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

(Example 1)

Compounds such as oxides and boric acid as raw materials are weighed so that glass having the composition shown in the following table can be obtained, and they are sufficiently mixed to prepare batch raw materials.

The batch of raw materials is put into a platinum crucible, and the crucible is heated to 1350-1450° C. for 2-3 hours to melt and clarify the glass. After stirring and homogenizing the molten glass, the molten glass is cast into a preheated molding die, left to cool to the vicinity of the glass transition temperature, and immediately placed into the annealing furnace together with the molding die. Then, annealing treatment is 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.

As a result of observing the glass produced in this way, precipitation of crystals, bubbles, texture, and melting residue of raw materials were not found. Thereby, glass with high homogeneity can be produced.

(Comparative Examples 1 to 4)

Compounds such as oxides and boric acid as raw materials were weighed so as to obtain glasses having the respective compositions of Comparative Examples 1 to 4 shown in the following table, and compounds such as boric acid were sufficiently mixed to prepare batch raw materials. Glass was obtained in the same manner as in Example 1.

The composition of Comparative Example 1 is a composition obtained by converting the composition of Glass No. 11 of Patent Document 20 into a glass composition expressed by cation %.

Comparative Example 2 is a composition obtained by converting the composition of Glass No. 25 of Patent Document 20 into a glass composition expressed by cation %.

Comparative Example 3 is a composition obtained by converting the composition of glass No. 45 of Patent Document 20 into a glass composition expressed by cation %.

Comparative Example 4 is a composition obtained by converting the composition of glass No. 49 of Patent Document 20 into a glass composition expressed in cation %.

The glass properties of the obtained glass were determined by the method shown below. Measured. 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)

For the glass obtained by cooling at a cooling rate of -30°C/hour, the refractive index (nd), the refractive index (nF), the refractive index (nc), the refractive index (nc), the refractive index (nc), and 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 performed at a temperature increase rate of 10°C/min using a differential scanning calorimeter (DSC).

(3) Specific gravity

Determined according to Archimedes' method.

(4) Relative partial dispersion (Pg, F)

Calculated from the values of nF, nc, and ng measured in the above (1).

(5) Liquidus temperature

The glass was placed in a furnace heated to a predetermined temperature, kept for 2 hours, and after cooling, the inside of the glass was observed with an optical microscope at a magnification of 100 times, and the liquidus temperature was determined based on the presence or absence of crystals.

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

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

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

As shown in FIG. 2 , the value A calculated from the above formula (A) shows a good correlation with the Abbe number. From this result, it can be 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, glass blocks (glass gobs) for press molding were produced. The glass block was heated in the atmosphere, softened, and press-molded with a press-molding die to produce a lens blank (optical element blank). The produced lens blanks were taken out from the press molding die, annealed, and subjected to machining including polishing to produce spherical lenses made of various glasses produced in Example 1.

(Example 3)

A desired amount of the molten glass produced in Example 1 was press-molded with a press-molding die to produce a lens blank (optical element blank). The produced lens blanks were taken out from the press molding die, annealed, and subjected to machining including polishing to produce spherical lenses made of various glasses produced in Example 1.

(Example 4)

The glass block (optical element blank) produced by solidifying the molten glass produced in Example 1 was annealed, and machining including polishing was performed to produce spherical lenses made of various glasses produced in Example 1.

(Example 5)

The spherical lenses produced in Examples 2 to 4 were bonded to spherical lenses formed of other types of glass to produce a cemented lens. The cemented surfaces of the spherical lenses produced in Examples 2 to 4 were convex surfaces, and the cemented surfaces of spherical lenses formed of other types of glass were concave surfaces. The above-mentioned two glued surfaces are produced so that the absolute values of the mutual radii of curvature are equal. Apply UV-curable adhesive for optical element bonding on the glued surface to bond the two lenses between the glued surfaces. Then, the adhesive agent coated on the bonding surface was irradiated with ultraviolet rays through the spherical lenses produced in Examples 2 to 4 to cure the adhesive agent.

A cemented lens was produced as described above. The cemented lens has a sufficiently high cement strength, and is a cemented lens with sufficiently high optical performance.

Finally, the above methods are summarized.

According to one embodiment, a glass can be provided, which is an oxide glass, expressed in % of cations, 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, the Abbe number (νd) is in the range of 39.5 to 41.5, the refractive index (nd) with respect to the Abbe number (νd) satisfies the above formula (1), and for the above-mentioned Table 1 The cationic components of , the total D of the values obtained by multiplying the content of each cationic component by the coefficient described in Table 1 with respect to the refractive index (nd) satisfies the above formula (B).

The above-mentioned glass is a glass whose Abbe number (νd) is in the range of 39.5 to 41.5, and satisfies the formula (1), and is a high-refractive-index, low-dispersion glass useful in optical systems. Furthermore, the said glass can contribute to weight reduction of an optical element.

In one embodiment, the glass preferably has a total content of B ³⁺ and Si ⁴⁺ in the range of 43 to 65 cation %.

In one embodiment, the glass preferably has a total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ in the range of 25 to 45%.

In one embodiment, the glass preferably has a total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ in the range of 3 to 12%.

In one form, it is preferable that the range of the value C calculated by the said (C) formula in the glass composition represented by the cation % is -1.000-6.720.

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

Moreover, according to another aspect, the manufacturing method of the glass material for press molding which has the process of shaping|molding the said glass into the glass material for press molding can also be provided.

Furthermore, according to another aspect, it is also possible to provide a method for producing an optical element blank including a step of producing an optical element blank by press-molding the above-mentioned glass material for press-molding using a press-molding die.

Furthermore, according to another aspect, the manufacturing method of the optical element blank which has the process of shaping|molding the said glass into an optical element blank can also be provided.

Furthermore, according to another aspect, it is also possible to provide a method of manufacturing an optical element including a step of grinding and/or polishing the above-mentioned optical element blank to produce an optical element.

It should be understood that the embodiments disclosed this time are illustrative and not restrictive in all respects. The scope of the present invention is indicated not by the above description but by the scope of the claims, and is intended to include the meaning equivalent to the scope of the claims and all modifications within the scope.

For example, the glass of one embodiment of the present invention can be obtained by adjusting the composition described in the specification with respect to the glass composition exemplified above.

In addition, it is needless to say that two or more of the matters exemplified in the specification or described as preferable ranges can be arbitrarily combined.

(industrial applicability)

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

Claims (8)

A glass, which is an oxide glass, wherein, expressed in cation molar %, B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Ta Total content of ⁵⁺ , W ⁶⁺ , Zr ⁴⁺ , Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ and Bi ³⁺ 90% or more; the total content of B ³⁺ and Si ⁴⁺ ranges from 43 to 57%; the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ ranges from 25 to 50%; Nb The range of the total content of ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is 3~12%; the range of the content of Zr ⁴⁺ is 2~8%; the range of the content of Zn ²⁺ is 0~10.00% ; The range of the cation ratio {Zn ²⁺ /(B ³⁺ +Si ⁴⁺ )} of the Zn ²⁺ content to the total content of B ³⁺ and Si ⁴⁺ is 0.073 or less; the range of the Abbe number (νd) is 39.5~41.5; the refractive index (nd) satisfies the following formula (1) relative to the Abbe number (νd):

The specific gravity (d) relative to the value of [refractive index (nd)-1] (d/(nd-1)) is 5.7 or less; and for the cationic components described in Table 1, the content of each cationic component is multiplied by the value in Table 1 The total D of the values of the stated coefficients satisfies the following formula (B) with respect to the refractive index (nd):

[Table 1]

. A glass, which is an oxide glass, wherein, expressed in cation molar %, B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Ta Total content of ⁵⁺ , W ⁶⁺ , Zr ⁴⁺ , Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ and Bi ³⁺ 90% or more; the total content of B ³⁺ and Si ⁴⁺ ranges from 43 to 57%; the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ ranges from 25 to 50%; Nb The range of the total content of ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is 3~12%; the range of the content of Zr ⁴⁺ is 2~8%; the range of the content of Zn ²⁺ is 0~10.00% ; Abbe's number (νd) ranges from 39.5 to 41.5; Refractive index (nd) satisfies the following formula (1) relative to Abbe's number (νd):

The specific gravity (d) relative to the value of [refractive index (nd)-1] (d/(nd-1)) is 5.7 or less; and for the cationic components described in Table 1, the content of each cationic component is multiplied by the The total D of the values of the stated coefficients satisfies the following formula (B) with respect to the refractive index (nd):

; The value C calculated from the following formula (C) is −1.000 or more: (C) formula C=0.567×(content of Nb ^{5+ +} content of Ti ⁴⁺ )−1.000×content of Gd ³⁺ . A glass, which is an oxide glass, wherein, expressed in cation molar %, B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Ta Total content of ⁵⁺ , W ⁶⁺ , Zr ⁴⁺ , Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ and Bi ³⁺ 90% or more; the total content of B ³⁺ and Si ⁴⁺ ranges from 43 to 57%; the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ ranges from 25 to 50%; Nb The range of the total content of ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is 3~12%; the range of the content of Zr ⁴⁺ is 2~8%; the range of the content of Zn ²⁺ is 0~10.00% The range of the content of Gd ³⁺ is below 3%; the range of Abbe number (νd) is 39.5~41.5; the refractive index (nd) satisfies the following formula (1) relative to the Abbe number (νd):

The specific gravity (d) relative to the value of [refractive index (nd)-1] (d/(nd-1)) is 5.7 or less; and for the cationic components described in Table 1, the content of each cationic component is multiplied by the value in Table 1 The total D of the values of the stated coefficients satisfies the following formula (B) with respect to the refractive index (nd):

[Table 1]

. A glass, which is an oxide glass, wherein, expressed in cation molar %, B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Ta Total content of ⁵⁺ , W ⁶⁺ , Zr ⁴⁺ , Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ and Bi ³⁺ 90% or more; the total content of B ³⁺ and Si ⁴⁺ ranges from 43 to 57%; the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ ranges from 25 to 50%; Nb The range of the total content of ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is 3~12%; the range of the content of Zr ⁴⁺ is 2~8%; the range of the content of Zn ²⁺ is 0~10.00% ; Cation ratio of Gd ³⁺ content to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ {Gd ³⁺ /(La ³⁺ +Y ³⁺ +Gd ³⁺ +Yb ³⁺ )} in the range of 0.10 or less; the Abbe number (νd) in the range of 39.5 to 41.5; the refractive index (nd) relative to the Abbe number (νd) satisfies the following formula (1):

The specific gravity (d) relative to the value of [refractive index (nd)-1] (d/(nd-1)) is 5.7 or less; and for the cationic components described in Table 1, the content of each cationic component is multiplied by the The total D of the values of the stated coefficients satisfies the following formula (B) with respect to the refractive index (nd):

. The glass according to any one of Claims 1 to 4, wherein the glass transition temperature Tg is 702°C or higher. A glass material for press molding, which is formed from the glass described in any one of claims 1 to 5 of the patent application scope. An optical element blank formed of the glass described in any one of claims 1 to 5 of the patent application scope. An optical element formed of the glass described in any one of claims 1 to 5 of the application scope.

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