JP6808555B2 - Glass, press-molded glass materials, optic blanks, and optics - Google Patents

Description

The present invention relates to glass, glass materials for press molding, optical element blanks, and optical elements.

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

Japanese Unexamined Patent Publication No. 2007-063071 JP-A-2007-230835 JP-A-2007-249112 Japanese Unexamined Patent Publication No. 2007-261826 Japanese Unexamined Patent Publication No. 2003-267748 Japanese Unexamined Patent Publication No. 2009-203083 Japanese Unexamined Patent Publication No. 2011-230992 Japanese Unexamined Patent Publication No. 2012-205638 JP-A-54-090218 Japanese Unexamined Patent Publication No. 56-160340 Japanese Unexamined Patent Publication No. 2001-348244 Japanese Unexamined Patent Publication No. 2008-001551 Special Table 2013-536791 WO10 / 053214 Japanese Unexamined Patent Publication No. 2012-180278 Japanese Unexamined Patent Publication No. 2012-236754 Japanese Unexamined Patent Publication No. 2014-0843235 JP-A-2014-062025 JP-A-2014-062026 Japanese Unexamined Patent Publication No. 2011-93780

For glass for optical elements, an optical property map (also called an Abbe chart) is widely used to show the distribution of optical properties. The optical characteristic map has the Abbe number νd on the horizontal axis and the refractive index nd on the vertical axis, the Abbe number νd increases from the right side to the left side of the horizontal axis, and the refractive index increases from the bottom to the top of the vertical axis. Created to increase accordingly. In the following, unless otherwise specified, the refractive index and the Abbe number refer to the refractive index nd for the d-line of helium (wavelength 587.56 nm) and the Abbe number νd for the d-line of helium (wavelength 587.56 nm).

In the optical characteristic map, the optical characteristics of high refractive index low dispersion glass (high nd high νd glass) increase the refractive index as the Abbe number decreases, and decrease as the Abbe number increases, so-called upward slope. The distribution is generally shown. This is considered to be due to the following reasons.
Many high-refractive-index, low-dispersion glasses contain rare earth oxides such as boron oxide and lanthanum 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, if the content of the rare earth oxide is increased in the conventional high refractive index low dispersion glass, the thermal stability of the glass is lowered and the glass tends to be devitrified in the process of producing the glass. Therefore, in the conventional high-refractive-index low-dispersion glass, it is difficult to increase both the Abbe number and the refractive index while suppressing the devitrification of the glass for use as an optical element material. This point is considered to be the reason why the conventional high refractive index low dispersion glass shows the above distribution in the optical characteristic map.

On the other hand, in the design of optical systems, glass with a high refractive index and a large Abbe number (low dispersion) is an extremely effective material for optical elements for correcting chromatic aberration, improving the functionality of the optical system, and making it compact. is there. Therefore, it is very significant to set a straight line that rises to the right on the optical characteristic map and provide glass that has a higher refractive index than this straight line and the straight line (located in the region on the left side of the straight line on the map). Is big.
From the above points, the Abbe number νd is 39.5 to 41.5, and the refractive index nd is equal to or greater than the value obtained by 2.0927-0.0058 × νd with respect to this Abbe number, that is, nd ≧ 2. The glass satisfying the relationship of .0927-0.0058 × νd is a high refractive index low dispersion glass useful in an optical system.

By the way, it is desirable to reduce the weight of the optical elements constituting the projection optical system such as the imaging optical system and the projector. This is because reducing the weight of the optical element leads to weight reduction of the imaging optical system and the projection optical system incorporating this optical element. For example, if a heavy optical element is incorporated in an autofocus type camera, the power consumption when driving the autofocus increases, and the battery is consumed quickly. On the other hand, if the optical element is made lighter, the power consumption when driving the autofocus can be reduced and the battery life can be extended.
However, in the glass described in Patent Documents 1 to 20, the present inventor has an Abbe number νd in the range of 39.5 to 41.5 and a relationship of nd ≧ 2.0927-0.0058 × νd. It is considered that the optical element manufactured by using the high refractive index low dispersion glass satisfying the above conditions tends to be heavy. This is because the composition adjustment for high refractive index and low dispersion described in Patent Documents 1 to 20 tends to increase the specific gravity of the glass.

One aspect of the present invention provides a glass having an Abbe number νd of 39.5 to 41.5, satisfying the relationship of nd ≧ 2.0927-0.0058 × νd, and capable of contributing to weight reduction of the optical element. The purpose is to do.

One aspect of the present invention is
In cation% display, 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+ have} a total content of 90% or more.
The Abbe number νd is in the range of 39.5-41.5.
The following equation (1): When the refractive index nd is the Abbe number νd:
nd ≧ 2.0927-0.0058 × νd ・ ・ ・ (1)
The total D of the values obtained by multiplying the content of each cation component by the coefficient shown in Table 1 with respect to the cation components shown in Table 1 shown below is the following formula (B) with respect to the refractive index nd:
D ≦ 6.242 × nd-8.8042 ・ ・ ・ (B)
Glass, which is an oxide glass that meets the requirements
Regarding.

The above glass has 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 in% cation display. The total content of ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ , and Bi ³⁺ (hereinafter referred to as “major cation components”) is 90% or more. The present inventor has focused on the fact that the effects of the main cation components on the specific gravity of glass are different in the diligent studies to achieve the above object. Then, as a result of repeated trial and error, the coefficients shown in Table 1 were determined for each of the main cation components. By adjusting the composition so that the total D calculated using these coefficients satisfies the equation (B), nd ≧ 2.0927-0.0058 × in the range where the Abbe number νd is 39.5 to 41.5. It is possible to provide a glass that can contribute to a reduction in the specific gravity of a high refractive index low dispersion glass that satisfies the relationship of νd, that is, a weight reduction of an optical element.

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

In FIG. 1, the horizontal axis is the specific gravity of each glass of Example 1 and each glass of Comparative Examples 1 to 4, and the vertical axis is the total D of the values obtained by multiplying the content of each cation component by the coefficient shown in Table 1. It is a graph taken in. FIG. 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 taken on the horizontal axis, and the value A calculated by the formula (A) described later is taken on the vertical axis. ..

[Glass]
The glass according to one aspect of the present invention has B ³⁺ , Si ⁴⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ , W ⁶⁺ , Zr ⁴⁺ , Zn in ^{terms of} cation%. The total content of ²⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ , and Bi ³⁺ is 90% or more, and the Abbe number νd is 39.5 to 41. For the cation components in the range of 5, the refractive index nd satisfies the above equation (1) with respect to the Abbe number νd, and the cation components shown in Table 1 shown below, the coefficients shown in Table 1 are included in the content of each cation component. The total D of the values multiplied by is the oxide glass satisfying the above equation (B) with respect to the refractive index nd.

The details of the glass will be described below.

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. Further, in the present specification and the present invention, when the content of the constituent component is 0% or not contained or introduced, it means that the constituent component is substantially not contained, and the content of the constituent component is at the impurity level. It means that it is below the degree.

In the present invention, the glass composition is expressed in% cation with respect to the cation component. As is well known, the cation% is a percentage with the total content of all cation components contained in the glass as 100%.
Hereinafter, unless otherwise specified, the content of the cation component and the total content of the plurality of cation components (total content) are indicated by cation%. Further, in the cation% display, the ratio of the contents of the cation components (including the total content of a plurality of cation components) is referred to as a cation ratio.
In the following, a (more) preferred lower limit and a (more) preferred upper limit may be listed in a table with respect to the numerical range. In the table, the numerical values listed below are preferable, and the numerical values listed at the bottom are most preferable. Unless otherwise specified, the (more) preferable lower limit means that it is (more) preferable that it is equal to or more than the stated value, and the (more) preferable upper limit is that it is equal to or less than the stated value. It means (more) preferable. A numerical range can be defined by arbitrarily combining the numerical values listed in the (more) preferred lower limit column and the numerical values listed in the (more) preferred upper limit column in the table.

<Glass composition>
The above glasses are 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⁺ . The total content of ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ , and Bi ³⁺ (major cation component) is 90% or more. The glass may contain only the main cation component (that is, the total content of the main cation component is 100%), and contains one or more of other cation components in addition to the main cation component. May be good. The preferred lower limit of the total content of the major cation components is as shown in the table below.

In the glass composition of the glass, the total D of the values obtained by multiplying the content of each cation component by the coefficient shown in Table 1 for various cation components of the main cation components is the following formula (B) with respect to the refractive index nd. :
D ≦ 6.242 × nd-8.8042 ・ ・ ・ (B)
It is adjusted to meet. Thereby, the weight of the high refractive index low dispersion glass satisfying the above equation (1) is achieved with respect to the Abbe number νd in the range of 39.5 to 41.5 and the refractive index nd of the Abbe number νd. Can be done. This point was newly discovered as a result of diligent studies by the present inventor. The total D is as follows in detail. The unit of the following content is cation%.
D = B ³⁺ content x 0.032
+ Si ^{4 +} content x 0.029
+ La ^{3 +} content x 0.066
+ Y ^{3 +} content x 0.053
+ Gd ^{3 +} content x 0.093
+ Yb ^{3 +} content x 0.094
+ Nb ⁵ + content x 0.049
+ Ti ^{4 +} content x 0.045
+ Ta ⁵ + content x 0.104
+ W ⁶ + content x 0.111
+ Zr ^{4 +} content x 0.080
+ Zn 2 ⁺ content x 0.051
+ Mg ²⁺ content x 0.030
+ Ca ²⁺ content x 0.024
+ Sr 2 ⁺ content x 0.043
+ Ba 2 ⁺ content x 0.055
+ Li ⁺ content x 0.031
+ Na ⁺ content x 0.021
+ K ⁺ content x 0.012
+ Al ^{3 +} content x 0.034
+ Bi ^{3 +} content x 0.090

The above formula (B) is preferably the following formula (B-1), more preferably the following formula (B-2), further preferably the following formula (B-3), and further preferably the following formula (B-3). It is the formula B-4), more preferably the following formula (B-5), even more preferably the following formula (B-6), and even more preferably the following formula (B-7). , Even more preferably the following formula (B-8), and even more preferably the following formula (B-9).
D ≦ 6.242 × nd-6.8142 ・ ・ ・ (B-1)
D ≦ 6.242 × nd-6.8242 ・ ・ ・ (B-2)
D ≦ 6.242 × nd-6.8342 ・ ・ ・ (B-3)
D ≦ 6.242 × nd-6.8442 ... (B-4)
D ≦ 6.242 × nd-6.8542 ・ ・ ・ (B-5)
D ≦ 6.242 × nd-6.8642 ・ ・ ・ (B-6)
D ≦ 6.242 × nd-6.8742 ・ ・ ・ (B-7)
D ≦ 6.242 × nd-6.8842 ... (B-8)
D ≦ 6.242 × nd-6.8942 ・ ・ ・ (B-9)

The glass composition of the glass may be such that the total content of the main cation components is 90% or more and satisfies the formula (B), and the main cation components are not included in the glass ( That is, the content may be 0%) and there may be a cation component. The preferable range of the content of each cation component will be described later. However, the present invention is not limited to the following preferable range.

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 is 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, a decrease in the refractive index nd can be suppressed, which is preferable in producing a glass having the above-mentioned optical characteristics. Therefore, the total content of B ³⁺ and Si ⁴⁺ in the glass is preferably in the range of 43 to 65%. The more preferable lower limit and the more preferable upper limit of the total content of B ³⁺ and Si ⁴⁺ are as shown in the table below.

La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ are components having a function of increasing the refractive index while suppressing a decrease in the Abbe number νd. In addition, these components also have a function of improving the chemical durability and weather resistance of the glass and increasing the glass transition temperature.
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 decrease in the refractive index nd can be suppressed. It is preferable for producing a glass having. Furthermore, it is possible to suppress a decrease in the chemical durability and weather resistance of the glass. When the glass transition temperature decreases, the glass is easily broken (decreased in machinability) when the glass is mechanically processed (cutting, cutting, grinding, polishing, etc.), but La ³⁺ , Y ³⁺ , and Gd. ^When the total content of 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, if 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 enhanced, so that the crystallization during the production of the glass It is also possible to suppress and reduce the unmelted residue of the raw material when melting the glass. It is also preferable for suppressing an increase in specific gravity. Therefore, in the above glass, the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is preferably in the range of 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 the table below.

Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ are components having a function of increasing the refractive index, and also have a function of improving the thermal stability of glass by containing an appropriate amount. If 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, it is possible to realize the above optical characteristics while maintaining thermal stability. preferable. 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 glass, the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is preferably in the range of 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 the table below.

Zr ⁴⁺ is a component having a function of increasing the refractive index, and also has a function of improving the thermal stability of glass by containing an appropriate amount. In addition, Zr ⁴⁺ also has a function of making the glass less likely to break during mechanical processing by raising the glass transition temperature. In order to obtain these effects well, it is preferable that the content of Zr ⁴⁺ in the above glass is 2% or more. On the other hand, when the content of Zr ⁴⁺ is 8% or less, the thermal stability of the glass can be improved, so that crystallization during glass production and generation of unmelted residue during glass melting can be suppressed. .. Therefore, the Zr ⁴⁺ content in the glass is preferably in the range of 2-8%. The more preferable lower limit and the more preferable upper limit of the Zr ⁴⁺ content are shown in the table below.

In order to realize optical characteristics 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 equation (1), Nb ⁵⁺ , Ti ⁴⁺ , and Ta ⁵⁺ are used in the glass. And the cation ratio of Zr ⁴⁺ content to the total content of W ⁶⁺ {Zr ⁴⁺ content / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is preferably in the range of 0.48 to 2.20. The cation ratio in the range of 0.48 to 2.20 is also preferable from the viewpoint of suppressing a decrease in the glass transition temperature (improving machinability by this). Further, it is preferable that the cation ratio is 0.48 or more from the viewpoint of improving the thermal stability and reducing the dispersion of the glass. On the other hand, the cation ratio of 2.20 or less is preferable from the viewpoint of improving the meltability and suppressing crystallization. The more preferable lower limit and the more preferable upper limit of the cation ratio {Zr ⁴⁺ content / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} are shown in the table below.

In order to realize optical characteristics 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 equation (1) while improving the thermal stability of the glass, the above In 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 preferably 0.70 to 1.75. 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 the devitrification of the glass is suppressed. can do. It is also preferable for suppressing an increase in the specific gravity of glass. On the other hand, it is preferable that the cation ratio {(B ³⁺ + Si ⁴⁺ ) / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )} is 1.75 or less in order to realize the above optical characteristics. The more preferable lower limit and the more preferable upper limit of the cation ratio {(B ³⁺ + Si ⁴⁺ ) / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )} are shown in the table below.

In order to improve the thermal stability of the glass, suppress the decrease in the refractive index nd, and realize the above-mentioned optical characteristics, in the above-mentioned glass, B with respect to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ^6+. The cation ratio of the total content of ³⁺ and Si ⁴⁺ {(B ³⁺ + Si ⁴⁺ ) / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is preferably 9.00 or less.
Set the cation ratio {(B ³⁺ + Si ⁴⁺ ) / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} to 5.00 or more in order to improve the thermal stability of the glass while suppressing the decrease in the Abbe number νd. Is preferable. Further, it is preferable to set the cation ratio {(B ³⁺ + Si ⁴⁺ ) / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} to 5.00 or more from the viewpoint of low specific gravity.
The more preferable lower limit and the more preferable upper limit of the cation ratio {(B ³⁺ + Si ⁴⁺ ) / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} are shown in the table below.

From the viewpoint of improving the thermal stability of the glass and suppressing the crystallization of the glass while lowering the specific gravity of the glass, the cation of the W ⁶⁺ content with respect to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ^6+. The ratio {W ⁶⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is preferably 0.50 or less. Further, it is preferable that the cation ratio {W ⁶⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is 0.50 or less from the viewpoint of increasing the refractive index of the glass and reducing the coloring. The more preferable lower limit and the more preferable upper limit of the cation ratio {W ⁶⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} are shown in the table below.

In order to realize the above-mentioned optical characteristics while improving the thermal stability of the glass and suppressing the crystallization of the glass, the above-mentioned glass has Zn with respect to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ^3+. The cation ratio of the ²⁺ content {Zn ²⁺ / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )} is preferably less than 0.20. In addition, the cation ratio {Zn ²⁺ / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )} is less than 0.20, which suppresses the decrease in the glass transition temperature (improves machinability) and improves chemical durability. It is also preferable from the viewpoint of. The cation ratio {Zn ²⁺ / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )} is preferably 0% or more, and more preferably more than 0%, from the viewpoint of improving the meltability. The preferred lower and upper limits of the cation ratio {Zn ²⁺ / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )} are shown in the table below.

Among the rare earth elements La, Y, Gd and Yb, Gd belongs to the heavy rare earth element and is a component required to reduce the content in the glass from the viewpoint of stable supply of glass. In addition, Gd has a large atomic weight and is also a component that increases the specific gravity of glass.
Yb also belongs to heavy rare earth elements and has a large atomic weight. In addition, Yb has absorption in the near infrared region. On the other hand, it is desirable that interchangeable lenses for single-lens reflex cameras and lenses for surveillance cameras have high light transmittance in the near infrared region. Therefore, it is desirable to reduce the Yb content in order to obtain glass useful for producing these lenses.
On the other hand, La and Y do not adversely affect the light transmittance in the near infrared region, and by allocating an appropriate amount to the total content of rare earth elements, the specific gravity is improved while improving the thermal stability. It is a useful component for suppressing an increase in the amount of light and providing a glass having a high refractive index and low dispersion.

Therefore, in the glass, the ^{La 3+ is,} La ^3+, Y 3+, the ^{La 3+} content of the cation ratio to the total content of ^{Gd 3+} and ^{Yb 3+ {La 3+ / (La} 3+ + Y 3+ + Gd 3+ + Yb 3+)}, It is preferably in the range of 0.50 to 0.95. The more preferable lower limit and the more preferable upper limit of the cation ratio {La ³⁺ / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )} are shown in the table below.

^Also, the ^{Y 3+,} La ^3+, Y 3+, the content of the cation ratio of ^{Y 3+} to the total content of ^{Gd 3+} and ^{Yb 3+} a ^{{Y 3+ / (La 3+ +} Y 3+ + Gd 3+ + Yb 3+)} 0.10 It is preferably in the range of ~ 0.50. The more preferable lower limit and the more preferable upper limit of the cation ratio {Y ³⁺ / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )} are shown in the table below.

As described above, Gd ³⁺ is a component whose content in glass should be reduced from the viewpoint of stable supply of glass. In the above glass, in order to stably supply the high refractive index low dispersion glass having the above optical characteristics, the cation ratio of the content of Gd ³⁺ to the total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ {Gd ³⁺ / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )} is preferably 0.10 or less. Satisfying the above cation ratio can also contribute to lowering the specific gravity of glass. The more preferable lower limit and the more preferable upper limit of the cation ratio {Gd ³⁺ / (La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ )} are shown in the table below.

The total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ , and the cation ratio of La ³⁺ content, Y ³⁺ content and Gd ³⁺ content to this total content are as described above. The following table shows the preferable lower limit and the preferable upper limit of the content of each component of La ³⁺ , Y ³⁺ , Gd ³⁺ , and Yb ³⁺ . Regarding the Y ³⁺ content, the lower limit shown in the table below is preferable from the viewpoint of improving the thermal stability and meltability of the glass.

Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ serve to increase the refractive index and improve the thermal stability of the glass by containing an appropriate amount. However, although Ta ⁵⁺ has a function of increasing the refractive index, it is an extremely expensive component. Therefore, from the viewpoint of stable supply of glass, it is not preferable to positively use Ta ⁵⁺ . Further, if the content of Ta ⁵⁺ is large, the raw material tends to remain unmelted when the glass is melted. In addition, the specific gravity of glass increases. As described above, Ta ⁵⁺ is a component whose content should be reduced. Therefore, it is not preferable to positively use Ta ⁵⁺ . For ta ^5+, while improving the thermal stability of the glass, in order to reduce the amount of high refractive index and low dispersion of the ^{Ta, Nb 5+, Ti 4+,} Ta 5+ to the total content of ^{Ta 5+} and ^{W 6+} The cation ratio of the content of {Ta ⁵⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is preferably 0.2 or less. The preferred lower limit and more preferred upper limit of the cation ratio {Ta ⁵⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} are shown in the table below.

Regarding Nb ⁵⁺ , the content of Gd ³⁺ and Ta ⁵⁺ is reduced in order to enable a stable supply of glass, and preferably the content of Yb ³⁺ together with Gd ³⁺ and Ta ⁵⁺ is reduced while being thermally. to provide a high-refractivity low-dispersion glass having excellent ^{stability, Nb 5+, Ti 4+, Ta} 5+, in consideration of the above effects of ^{W 6+, Nb 5+, Ti 4+} , total content of ^{Ta 5+} and ^{W 6+} The cation ratio of the content of Nb ^{5+ to} the amount {Nb ⁵⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is preferably 0.2 or more. Further, Nb ⁵⁺ is a component that tends to increase the refractive index without increasing the specific gravity as compared with Ta ⁵ and W ⁶⁺ . Therefore, in order to suppress the increase in specific gravity, it is preferable to increase the cation ratio {Nb ⁵⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )}. The more preferable lower limit and preferable upper limit of the cation ratio {Nb ⁵⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} are shown in the table below.

Furthermore, from the viewpoint of preventing high dispersion and coloring, the cation ratio of Ti ⁴⁺ content to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ {Ti ⁴⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} Is preferably 0.6 or less. The preferred lower limit and more preferred upper limit of the cation ratio {Ti ⁴⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} are shown in the table below.

La ³⁺ with respect to the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ ) in order to suppress the decrease in Abbe number νd while maintaining the thermal stability of the glass. Y ^3+, the lower limit of the total content of ^{Gd 3+} and ^{Yb 3+ (La 3+ + Y 3+} + Gd 3+ + Yb 3+) cation ratio of ^{{(La 3+ + Y 3+ +} Gd 3+ + Yb 3+) / (Nb 5+ + Ti 4+ + Ta 5+ + W 6+)} Is preferably set to a preferable lower limit value shown in the table below.
On the other hand, in order to maintain the thermal stability of the glass while suppressing the decrease in the refractive index, the upper limit of the cation ratio {(La ³⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ ) / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is set. , It is preferable to set a preferable upper limit value shown in the table below.

The glass composition of the above 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⁺ has a better function of improving ^meltability than Si ⁴⁺ , but it easily volatilizes during melting. On the other hand, Si ⁴⁺ has a function of improving the chemical durability, weather resistance and machinability of glass, and increasing the viscosity of glass at the time of melting.
Generally, in high refractive index 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, if the viscosity of the glass at the time of melting is low, it tends to crystallize. Crystallization during glass production is more stable when crystallized than in an amorphous state (amorphous state), and occurs when the ions constituting the glass move in the glass and are arranged so as to have a crystal structure. Therefore, by adjusting the ratio of the contents 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 above ions so as to have a crystal structure, and the glass can be crystallized. It can be further suppressed and the devitrification resistance of the glass can be further improved.
From the above viewpoint, the preferable lower limit and preferable upper limit of the cation ratio of B ³⁺ content to the total content of B ³⁺ and Si ⁴⁺ {B ³⁺ / (B ³⁺ + Si ⁴⁺ )} are as shown in the table below. It is preferable that the temperature is equal to or higher than the lower limit shown in the table below from the viewpoint of improving the meltability of the glass. Further, it is preferable that the value is not more than the upper limit shown in the table below in order to increase the viscosity of the glass at the time of melting. Furthermore, the value below the upper limit shown in the table below is to reduce fluctuations in the glass composition due to volatilization during melting and fluctuations in optical properties due to this, and to reduce the chemical durability, weather resistance and machinability of the glass. It is also preferable from the viewpoint of one or more improvements.

For each of the B ³⁺ content and the Si ⁴⁺ content, the preferable lower limit and the preferable upper limit are set from the viewpoint of improving the devitrification resistance, meltability, moldability, chemical durability, weather resistance, machinability, etc. of the glass. It is shown in the table below.

Zn ²⁺ has a function of promoting the melting of the glass raw material when melting the glass, that is, a function of improving the meltability. It also has the function of adjusting the refractive index nd and Abbe number νd and lowering the glass transition temperature. The value obtained by dividing the Zn ²⁺ content by the total content of B ³⁺ and Si ⁴⁺ , that is, the cation ratio {Zn ²⁺ / (B ³⁺ + Si ⁴⁺ )} suppresses the decrease in the Abbe number νd and the thermal of the glass. From the viewpoint of improving stability, suppressing a decrease in glass transition temperature (improving machineability by this), and reducing the specific gravity of glass, it is preferably 0.15 or less. Since Zn is an optional component that may or may not be contained in the above glass, the cation ratio {Zn ²⁺ / (B ³⁺ + Si ⁴⁺ )} is preferably 0 or more, but the meltability It is more preferable that Zn is contained and the cation ratio {Zn ²⁺ / (B ³⁺ + Si ⁴⁺ )} is more than 0 in order to improve the above and easily produce a homogeneous glass. The more preferable lower limit and the more preferable upper limit of the cation ratio {Zn ²⁺ / (B ³⁺ + Si ⁴⁺ )} are shown in the table below.

The preferable lower limit and the preferable upper limit of the Zn ²⁺ content are as shown in the table below in order to improve the meltability, thermal stability, moldability, machinability, etc. of the glass and realize the above-mentioned optical characteristics. ..

The total of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ from the viewpoints of further improvement of thermal stability of glass, suppression of decrease in glass transition temperature (improvement of machinability by this), and improvement of chemical durability. The cation ratio of Zn ²⁺ content to the content {Zn ²⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )} is preferably 1.0 or less. On the other hand, since Zn is an arbitrary component, the lower limit of the cation ratio {Zn ²⁺ / (Nb ⁵⁺ + Ti ⁴⁺ + Ta ⁵⁺ + W ⁶⁺ )} is preferably 0, but it is more preferable to set it to more than 0 from the viewpoint of improving meltability. preferable. In consideration of the above points, the more preferable lower limit and the more preferable upper limit of the cation ratio {Zn ²⁺ / (Ti ⁴⁺ + Nb ⁵⁺ + Ta ⁵⁺ + W ⁶⁺ )} are as shown in the table below.

^{Nb 5+, Ti 4+, Ta 5+} , the ^{W 6+,} in consideration of the above-described action and ^{effect, Nb 5+, Ti 4+, Ta} 5+, the preferred range of the content of each component of ^{W 6+,} shown in the following Table.

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

Since Li ⁺ has a strong effect of lowering the glass transition temperature, the machinability tends to decrease as the content of Li ⁺ increases. In addition, chemical durability and weather resistance also tend to decrease. Therefore, the Li ⁺ content is preferably 5% or less. The preferred lower limit and the more preferable upper limit of the Li ⁺ content are shown in the table below. The Li ⁺ content may be 0%.

Na ⁺ , K ⁺ , Rb ⁺ , and Cs ⁺ all have the function of improving the meltability of glass, but when the content of these is increased, the thermal stability, chemical durability, and weather resistance of the glass are increased. , Machinability tends to decrease. Therefore, it is preferable that the lower and upper limits of the contents of Na ⁺ , K ⁺ , Rb ⁺ , and Cs ⁺ are as shown in the table below.

The total content of Li ⁺ , Na ⁺ and K ⁺ (Li ⁺ + Na ⁺⁾ to improve the meltability of the glass while maintaining the thermal stability, chemical durability, weather resistance and machinability of the glass. The preferred lower limit and preferred upper limit of + K ⁺ ) are as shown in the table below.

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ are all components having a function of improving the meltability of glass. However, when the content of these components is increased, the thermal stability of the glass is lowered and the glass tends to be devitrified. Therefore, the content of each of these components is preferably not more than the lower limit shown below, and more preferably not more than the upper limit.

In addition, in order to maintain 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⁺ ) shall be at least the lower limit shown in the table below. Is preferable, and the upper limit or less is preferable.

Al ³⁺ is a component having a function of improving the chemical durability and weather resistance of 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 consideration of the above points, the Al ³⁺ content is preferably not more than the lower limit shown in the table below, and more preferably not more than the upper limit.

Ga ³⁺ , In ³⁺ , Sc ³⁺ , and Hf ⁴⁺ all have a function of increasing the refractive index nd. However, these components are expensive and are not essential components for obtaining the above optical glass. Therefore, the contents of Ga ³⁺ , In ³⁺ , Sc ³⁺ , and Hf ⁴⁺ are preferably at least the lower limit shown in the table below, and preferably at least the upper limit.

Lu ³⁺ has a function of increasing the refractive index nd, but is also a component that increases the specific gravity of glass. Further, since Lu is a heavy rare earth element like Gd and Yb, it is preferable to reduce the content of Lu. From the above points, the preferable lower limit and the preferable upper limit of the Lu ³⁺ content are as shown in the table below.

Ge ⁴⁺ has a function of increasing the refractive index nd, but is a prominently expensive component among commonly used glass components. From the viewpoint of reducing the manufacturing cost of glass, the preferable lower limit and the preferable upper limit of the Ge ⁴⁺ content are as shown in the table below.

Bi ³⁺ is a component that increases the refractive index nd and decreases the Abbe number νd. It is also a component that easily increases specific gravity and coloring. The preferable lower limit and the preferable upper limit of the Bi ³⁺ content are as shown in the table below in order to produce a glass having the above-mentioned optical characteristics, less coloring and low specific gravity.

In order to obtain the various actions and effects described above satisfactorily, the total content (total content) of the above-mentioned cation components is preferably more than 95%, and more than 98%. More preferably, it is more preferably more than 99%, and even more preferably more than 99.5%.

Among the cation components other than the above-mentioned cation components, P ⁵⁺ is a component that lowers the refractive index nd and is also a component that lowers the thermal stability of the glass, but if a very small amount is introduced, the glass May improve thermal stability. The preferable lower limit and preferable upper limit of the P ⁵⁺ content in producing a glass having the above-mentioned optical characteristics and excellent thermal stability are as shown in the table 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 preferred lower and upper limits of the Te ⁴⁺ content are as shown in the table below.

It is also preferable that the content of the component for which a (more) preferable lower limit or 0% is described in each of the above tables is 0%. The same applies to the total content of the plurality of components.

As the present inventor repeated studies on the various cation components described above, he focused on the fact that the effects of each cation component on the dispersion (Abbe number) of the glass are considered to be different. Then, as a result of further studies, the present inventor defines a coefficient in consideration of the influence of each cation component on the dispersion of the glass, and the value A calculated by the following formula (A) is 8.5000 to 11.000. It is preferable to adjust the composition so as to be within the range in order to realize the optical characteristics 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 equation (1). I came to think that.
A = 0.01 x Si ^{4 +} content + 0.01 x B ^{3 +} content + 0.05 x La ^{3 +} content + 0.07 x Y ^{3 +} content + 0.07 x Yb ^{3 +} content + 0.085 x Zn 2 ⁺ content +0.3 x Zr ^{4 +} content + 0.5 x Ta ⁵ + content + 0.8 x Nb ⁵ + content + 0.9 x W ⁵ + content + 0.95 x Ti ^{4 +} content ... (A)

The more preferable lower limit and the more preferable upper limit of the value A calculated by the above formula (A) are as shown in the following table.

Further, among the various cation components described above, with respect to Nb ⁵⁺ , Ti ⁴⁺ and Gd ³⁺ , Nb ⁵⁺ and Ti ⁴⁺ have an action of increasing the refractive index and an action of increasing the specific gravity as compared with Gd ^3+. It is a small component. Therefore, it is preferable to balance the total content of Nb ⁵⁺ and Ti ⁴⁺ with the content of Gd ³⁺ in order to increase the refractive index while suppressing the increase in specific gravity. 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 cation%. Further, from the viewpoint of high refractive index and low dispersion, the value C calculated by the following formula (C) is preferably 6.720 or less.
C = 0.567 × (Nb ⁵ + content + Ti ^{4 +} content) -1.000 × Gd ^{3 +} content ... (C)

The more preferable lower limit and the more preferable upper limit of the value C calculated by the formula (C) are as shown in the following table.

Pb, As, Cd, Tl, Be and Se are toxic respectively. Therefore, it is preferable not to contain these elements, that is, not to introduce these elements into the glass as a glass component.
U, Th, and Ra are all radioactive elements. Therefore, it is preferable not to contain these elements, that is, not to introduce these elements 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 increase the coloring of glass and become a source of fluorescence. , It is not preferable as an element contained in glass for an optical element. Therefore, it is preferable not to contain these elements, that is, not to introduce these elements into the glass as a glass component.

Sb and Sn are arbitrarily addable elements that function as finings.
The addition amount of Sb is converted into _Sb 2 _{O 3,} when the total content of glass components other than _Sb 2 _{O 3} is 100 mass%, preferably in the range of 0 to 0.11 wt%, It is more preferably in the range of 0.01 to 0.08% by mass, and even more preferably in the range of 0.02 to 0.05% by mass.
The amount of Sn added is preferably in the range of 0 to 0.5% by mass when converted to SnO ₂ and the total content of glass components other than SnO ₂ is 100% by mass, and 0 to 0. It is more preferably in the range of 2% by mass, and further preferably in the range of 0% by mass.

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

The glass are the oxide glass, comprising the O ^2- as anionic components. The preferred lower limit of the O ^2- content is as shown in the table below.

The anionic component of O ^{2- except, F -, Cl -, Br} -, I - can be exemplified. However, F ⁻ , Cl ⁻ , Br ⁻ , and I ⁻ are all liable to volatilize during melting of glass. Volatilization of these components tends to fluctuate the characteristics of the glass, reduce the homogeneity of the glass, and significantly consume the melting equipment. Therefore, it is preferable to limit the total content of F ⁻ , Cl ⁻ , Br ⁻ and I ^{− to} the amount obtained by subtracting the content of O ^2- from 100 anion%.
As is well known, the anion% is a percentage with the total content of all anion components contained in the glass as 100%.

<Glass characteristics>
(Optical characteristics of glass)
The glass is a glass in which the Abbe number νd is in the range of 39.5 to 41.5 and the refractive index nd satisfies the following equation (1) with respect to the Abbe number νd.
nd ≧ 2.0927-0.0058 × vd ・ ・ ・ (1)
Glass having an Abbe number νd of 39.5 or more is effective as a material for an optical element in correcting chromatic aberration. On the other hand, when the Abbe number νd is larger than 41.5, the thermal stability of the glass is remarkably lowered unless the refractive index is lowered, and the glass is easily devitrified in the process of manufacturing the glass. The preferred lower limit and the preferred upper limit of the Abbe number νd are shown in the table below.

The glass has a refractive index nd satisfying equation (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 a refractive index nd satisfying the equation (1) is a glass having high utility value in the design of an optical system.
The upper limit of the refractive index nd is naturally determined by the glass composition. In order to improve the thermal stability and obtain a glass that does not easily devitrify, it is preferable that the refractive index nd satisfies the following equation (2).
nd ≦ 2.1270-0.0058 × vd ・ ・ ・ (2)
The preferred lower limit and the more preferable upper limit of the refractive index nd with respect to the Abbe number νd are shown in the table below.

Further, the refractive index nd is preferably not more than the lower limit shown in the table below, and more preferably not more than the upper limit.

(Partial dispersion characteristics)
From the viewpoint of chromatic aberration correction, the glass is preferably a glass having a small partial dispersion ratio when the Abbe number νd is fixed.
Here, the partial dispersion ratios Pg and F are expressed as (ng-nF) / (nF-nc) using the refractive indexes ng, nF and nc of the g-line, F-line and c-line.
In order to provide a glass suitable for high-order chromatic aberration correction, the preferable lower limit and the preferable upper limit of the partial dispersion ratios Pg and f of the glass are as shown in the table below.

(Glass-transition temperature)
The glass transition temperature of the 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 prevent the glass from being damaged when the glass is mechanically processed such as cutting, cutting, grinding, and polishing. Further, since it is not necessary to contain a large amount of components such as Li and Zn, which have a strong function of lowering the glass transition temperature, even if the content of Gd and Ta is reduced, the content of Yb is also reduced. However, it is easy to improve the thermal stability.
On the other hand, if the glass transition temperature is set too high, the glass must be annealed at a high temperature, and the annealing furnace is significantly consumed. Further, when molding glass, the molding must be performed at a high temperature, and the mold used for molding is significantly consumed.
The preferable lower limit and the preferable upper limit of the glass transition temperature are as shown in the table below from the viewpoint of improving the machinability and reducing the burden on the annealing furnace and the molding die.

(Specific gravity of glass)
In an optical element (lens) that constitutes an optical system, the refractive power is determined by the refractive index of the glass that constitutes the lens and the curvature of the optical functional surface of the lens (the surface on which light rays to be controlled enter and exit). When the curvature of the optical functional surface is increased, the thickness of the lens also increases. As a result, the lens becomes heavy. On the other hand, if glass having a high refractive index is used, a large refractive power can be obtained without increasing the curvature of the optical functional surface.
From the above, if the refractive index can be increased while suppressing the increase in the specific gravity of the glass, the weight of the optical element having a constant refractive power can be reduced.
Regarding the contribution of the refractive index nd to the refractive power, the ratio of the specific gravity d of the glass to the value (nd-1) obtained by subtracting 1 which is the refractive index in vacuum from the refractive index nd of the glass is taken as optics. It can be used as an index when reducing the weight of the element. 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.
By satisfying the above formula (B) with respect to the refractive index nd, the glass can have a low specific gravity even though it is a high-refractive index, low-dispersion glass. Therefore, the d / (nd-1) of the glass can be, for example, 5.70 or less. However, when d / (nd-1) is excessively reduced, the thermal stability of the glass tends to decrease. Therefore, d / (nd-1) is preferably 5.00 or more. The more preferable lower limit and the more preferable upper limit of d / (nd-1) are shown in the table below.

Further, a preferable lower limit and a preferable upper limit of the specific gravity d of the glass are shown in the table below. It is preferable that the specific gravity d is not more than the upper limit shown in the table below from the viewpoint of weight reduction of the optical element made of glass. Further, it is preferable that the specific gravity is equal to or higher than the lower limit shown in the table below in order to further improve the thermal stability of the glass.

(Liquid phase temperature)
Liquid phase temperature is one of the indicators of thermal stability of glass. From the viewpoint of suppressing crystallization and devitrification during glass production, the liquid phase temperature LT is preferably 1350 ° C. or lower, more preferably 1330 ° C. or lower, further preferably 1300 ° C. or lower, and 1250 ° C. More preferably, it is below ° C. The lower limit of the liquidus temperature LT is, for example, 1100 ° C. or higher, but it is preferably low and is not particularly limited.

The glass according to one aspect of the present invention described above has a large refractive index nd and Abbe number νd, and is useful as a glass material for an optical element. Further, by adjusting the composition described above, it is possible to homogenize the glass and reduce the specific gravity. Therefore, the above glass is suitable as an optical glass that provides a lighter optical element.

<Glass manufacturing method>
In the above glass, raw materials such as oxides, carbonates, sulfates, nitrates, and hydroxides are weighed and mixed, and sufficiently mixed to form a mixing batch so that the desired glass composition can be obtained. It can be obtained by heating, melting, defoaming, and stirring the glass to produce a homogeneous and foam-free molten glass, which is then molded. Specifically, it can be produced by using a known melting method. Although the glass is a high-refractive index, low-dispersion glass having the above-mentioned optical characteristics, it has excellent thermal stability, and therefore, it can be stably produced by using a known melting method or molding method.

[Glass material for press molding, optical element blanks, and their manufacturing methods]
Another aspect of the present invention is
A glass material for press molding made of the above-mentioned glass;
The above-mentioned optical element blank made of glass,
Regarding.

According to another aspect of the invention
A method for producing a glass material for press molding, which comprises a step of molding the above-mentioned glass into a glass material for press molding;
A method for manufacturing an optical element blank, comprising a step of producing an optical element blank by press-molding the above-mentioned glass material for press molding using a press molding mold;
A method for manufacturing an optical element blank, which comprises a step of forming the above-mentioned glass into an optical element blank.
Is also provided.

The optical element blank is similar to the shape of the target optical element, and should be polished to the shape of the optical element (surface layer to be removed by polishing), and if necessary, ground (removed by grinding). It is an optical element base material to which a surface layer) is added. The optical element is finished by grinding and polishing the surface of the optical element blank. In one aspect, an optical element blank can be produced by a method of press-molding a molten glass obtained by melting an appropriate amount of the glass (referred to as a direct press method). In another aspect, the optical element blank can also be produced by solidifying the molten glass obtained by melting the above glass in an appropriate amount.

In another aspect, an optical element blank can be produced by producing a 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 a known method of pressing the glass material for press molding in a softened state by heating with a press molding mold. Both heating and press molding can be performed in the atmosphere. A homogeneous optical element blank can be obtained by annealing after press molding to reduce distortion inside the glass.

The glass material for press molding is a glass gob for press molding that is subjected to machining such as cutting, grinding, and polishing in addition to what is called a glass gob for press molding that is used as it is for press molding for manufacturing an optical element blank. Also includes those that are subjected to press molding through. As a cutting method, a groove is formed on the surface of the glass plate to be cut by a method called scribing, and local pressure is applied from the back surface of the grooved surface to the groove portion to apply glass to the groove portion. There are methods such as breaking the plate and cutting the glass plate with a cutting blade. Further, as a grinding and polishing method, barrel polishing and the like can be mentioned.

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

[Optical element and its manufacturing method]
Another aspect of the present invention is
The present invention relates to an optical element made of glass.
The optical element is manufactured using the glass described above. In the above optical element, one or more coatings such as a multilayer film such as an antireflection film may be formed on the glass surface.

Further, according to one aspect of the present invention.
A method for manufacturing an optical element, which comprises a step of manufacturing an optical element by grinding and / or polishing the above-mentioned optical element blank.
Is also provided.

In the above-mentioned manufacturing method of an optical element, a known method may be applied for grinding and polishing, and an optical element having high internal quality and surface quality can be obtained by sufficiently cleaning and drying the surface of the optical element after processing. it can. In this way, an optical element made of the above glass can be obtained. Examples of the optical element include various lenses such as a spherical lens, an aspherical lens, and a microlens, and a prism.

Further, the optical element made of glass is also suitable as a lens constituting a junction optical element. Examples of the bonding optical element include those in which lenses are bonded to each other (bonded lens) and those in which a lens and a prism are bonded. For example, a bonding optical element is an ultraviolet curable adhesive used for bonding a bonding lens by precisely processing the bonding surface of the two optical elements to be bonded so that the shape is inverted (for example, spherical polishing). Can be produced by applying, bonding, and then irradiating ultraviolet rays through a lens to cure the adhesive. The glass is preferable for producing the junction optical element in this way. A plurality of optical elements to be bonded can be manufactured by using a plurality of types of glasses having different Abbe numbers νd and bonded to obtain an element suitable for correcting chromatic aberration.

As a result of quantitative analysis of the glass composition, the glass component may be expressed on an oxide basis, and the content of the glass component may be displayed in mass%. The composition displayed in mass% based on the oxide as described above can be converted into the composition displayed in% cation and% anion by, for example, the following method.
If it contains N species of the glass component in the glass, a k-th of the glass component is denoted as A (k) _m O _n. However, k is an arbitrary integer of 1 or more and N or less.
A (k) is a cation, O is oxygen, and m and n are stoichiometrically determined integers. For example, when the notation based on the oxide standard is B ₂ O ₃ , m = 2 and n = 3, and when SiO ₂ is used, m = 1 and n = 2.
Next, the content of A _(k) m _{O n,} and X (k) [wt%]. Here, _assuming that 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) _mOn is
R (k) = P (k) × m + Q × n
Will be.
In addition
B = 100 / {Σ [m × X (k) / R (k)]}
Then, the content (cation%) of the cation 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 changes according to k. s is 2 n / m.
Further, the molecular weight R (k) may be calculated by rounding off the fourth digit after the decimal point and using the value displayed up to the third digit after the decimal point. Table 64 below shows the molecular weights of some glass components and additives in terms of oxide standards.

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

(Example 1)
Compounds such as oxides and boric acid were weighed as raw materials and sufficiently mixed to prepare a batch raw material so that a glass having the composition shown in the table below could be obtained.
This batch raw material was placed in a platinum crucible, heated to a temperature of 1350 to 1450 ° C. together with the crucible, and the glass was melted and clarified over 2 to 3 hours. After stirring and homogenizing the molten glass, the molten glass was cast into a preheated molding die, allowed to cool to near the glass transition temperature, and immediately put the glass together with the molding die into the annealing furnace. Then, it was annealed for about 1 hour near the glass transition temperature. After annealing, it was allowed to cool to room temperature in an annealing furnace.
When the glass produced in this manner was observed, no crystal precipitation, bubbles, veins, or undissolved raw material was observed. In this way, a glass with high homogeneity could be produced.

(Comparative Examples 1 to 4)
Except for the fact that compounds such as oxides and boric acid were weighed as raw materials and sufficiently mixed to prepare batch raw materials so that glasses having the respective compositions of Comparative Examples 1 to 4 shown in the table below could be obtained. Glass was obtained in the same manner as in Example 1.
The composition of Comparative Example 1 is the glass No. of Patent Document 20. A composition obtained by converting the composition of 11 into a glass composition displayed in% cation.
Comparative Example 2 shows the glass No. of Patent Document 20. A composition obtained by converting the composition of 25 into a glass composition displayed in% cation.
Comparative Example 3 shows the glass No. of Patent Document 20. A composition obtained by converting the composition of 45 into a glass composition displayed in% cation.
Comparative Example 4 shows the glass No. of Patent Document 20. A composition obtained by converting the composition of 49 into a glass composition displayed in% cation.
Is.

The glass properties of the obtained glass were measured by the methods shown below. The measurement results are shown in the table below.
(1) Refractive index nd, nF, nc, ng, Abbe number νd
The refractive indexes nd, nF, nc, and ng of the glass obtained by lowering the temperature at a temperature lowering rate of −30 ° C./hour were measured by the refractive index measuring method standardized by the Japan Optical Glass Industry Association. The Abbe number νd was calculated using the measured values of the refractive indexes nd, nF, and nc.
(2) Glass transition temperature Tg
Measurement was performed using a differential scanning calorimetry device (DSC) at a heating rate of 10 ° C./min.
(3) Specific gravity Measured by Archimedes method.
(4) Partial dispersion ratio Pg, F
It was calculated from the values of nF, nc, and ng measured in (1) above.
(5) Liquid phase 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 100x optical microscope, and the liquid phase temperature was determined from the presence or absence of crystals.

In FIG. 1, the horizontal axis is the specific gravity of each glass of Example 1 and each glass of Comparative Examples 1 to 4, and the vertical axis is the total D of the values obtained by multiplying the content of each cation component by the coefficient shown in Table 1. It is a graph taken in.
As shown in FIG. 1, the total D of the values obtained by multiplying the content of each cation component by the coefficient shown in Table 1 showed a good correlation with the specific gravity. From this result, it can be confirmed that a glass having a low specific gravity can be obtained by adjusting the composition so as to satisfy the formula (B) based on the total D.

FIG. 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 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 equation (A) showed a good correlation with the Abbe number. From this result, it can be confirmed that it is preferable to adjust the composition based on the value A in order to adjust the Abbe number.

(Example 2)
Using the various types of glass obtained in Example 1, a glass block (glass gob) for press molding was produced. This glass block was heated and softened in the air and press-molded with a press molding die to prepare a lens blank (optical element blank). The produced lens blank was taken out from the press molding mold, annealed, and subjected to machining including polishing to produce a spherical lens made of various glasses produced in Example 1.

(Example 3)
The molten glass produced in Example 1 was press-molded in a desired amount with a press molding mold to prepare a lens blank (optical element blank). The produced lens blank was taken out from the press molding mold, annealed, and subjected to machining including polishing to produce a spherical lens made of various glasses produced in Example 1.

(Example 4)
A 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 a spherical lens made of various glasses produced in Example 1.

(Example 5)
The spherical lens produced in Examples 2 to 4 was bonded to a spherical lens made of another type of glass to produce a bonded lens. The joint surface of the spherical lens produced in Examples 2 to 4 was a convex surface, and the joint surface of a spherical lens made of another type of optical glass was a concave surface. The above two joint surfaces were prepared so that the absolute values of the radii of curvature were equal to each other. An ultraviolet curable adhesive for joining optical elements was applied to the joint surfaces, and the two lenses were bonded to each other. Then, the adhesive applied to the joint surface was irradiated with ultraviolet rays through the spherical lenses produced in Examples 2 to 4 to solidify the adhesive.
A bonded lens was produced as described above. The bonding strength of the bonded lens was sufficiently high, and the optical performance was also at a sufficient level.

Finally, each of the above aspects will be summarized.

According to one aspect, 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+ are} displayed in% cation. , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , Li ⁺ , Na ⁺ , K ⁺ , Al ³⁺ , and Bi ^{3+ have} a total content of 90% or more, and the Abbe number νd is in the range of 39.5 to 41.5. Yes, the refractive index nd satisfies the above equation (1) for the Abbe number νd, and for the cation components listed in Table 1, the sum of the values obtained by multiplying the content of each cation component by the coefficient shown in Table 1. It is possible to provide a glass in which D is an oxide glass satisfying the above equation (B) with respect to the refractive index nd.

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

In one aspect, the glass preferably has a total content of B ³⁺ and Si ^{4+ in} the range of 43-65 cation%.

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

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

In one aspect, it is preferable that the value C calculated by the above formula (C) is in the range of -1,000 to 6.720 in the glass composition represented by% cation.

From the glass described above, a glass material for press molding, an optical element blank, and an optical element can be produced. That is, according to another aspect, a press-molded glass material made of the above glass, an optical element blank, and an optical element are provided.

Further, according to another aspect, there is also provided a method for producing a glass material for press molding, which comprises a step of molding the glass into a glass material for press molding.

According to still another aspect, there is also provided a method for producing an optical element blank, which comprises a step of producing an optical element blank by press-molding the press-molded glass material using a press-molding mold.

According to still another aspect, there is also provided a method for manufacturing an optical element blank, which comprises a step of forming the glass into an optical element blank.

According to still another aspect, there is also provided a method for manufacturing an optical element, which comprises a step of manufacturing the optical element by grinding and / or polishing the optical element blank.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.
For example, the glass according to one aspect of the present invention can be obtained by adjusting the composition described in the specification with respect to the above-exemplified glass composition.
In addition, it is of course possible to arbitrarily combine two or more of the items described in the specification as an example or a preferable range.

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

Claims (9)

In cation% display, 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+ have} a total content of 90% or more.
The total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is in the range of 28-45%.
Y ³⁺ content is in the range of 1-20%
The Abbe number νd is in the range of 39.5-41.5.
The following equation (1): When the refractive index nd is the Abbe number νd:
nd ≧ 2.0927-0.0058 × νd ・ ・ ・ (1)
The filling,
Equation (A) below:
A = 0.01 x Si ⁴⁺ content
+0.01 x B ³⁺ content
+0.05 x La ³⁺ content
+0.07 x Y ³⁺ content
+0.07 x Yb ³⁺ content
+0.085 x Zn ²⁺ content
+0.3 x Zr ⁴⁺ content
^+0.5 x Ta ⁵⁺ content
+0.8 × Nb ⁵⁺ content
+0.9 x W ⁵⁺ content
+0.95 x Ti ^{4 +} content ... (A)
The value A calculated by is in the range of 8.5000 to 11.000.
Equation (C) below:
C = 0.567 x (Nb ⁵ + content + Ti ^{4 +} content) -1.000 x Gd ^{3 +} content ... (C)
The value C calculated by is in the range of -1,000 to 6.720.
Further, for the cation components shown in Table 1, the total D of the values obtained by multiplying the content of each cation component by the coefficient shown in Table 1 is the following formula (B) with respect to the refractive index nd:
D ≦ 6.242 × nd-8.8042 ・ ・ ・ (B)
Glass that is an oxide glass that meets the requirements.
In cation% display, 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+ have} a total content of 90% or more.
The total content of La ³⁺ , Y ³⁺ , Gd ³⁺ and Yb ³⁺ is in the range of 28-45%.
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⁺ + Y ³⁺ + Gd ³⁺ + Yb ³⁺ ) is in the range of 0.50 to 0.95.
The Abbe number νd is in the range of 39.5-41.5.
The following equation (1): When the refractive index nd is the Abbe number νd:
nd ≧ 2.0927-0.0058 × νd ・ ・ ・ (1)
The filling,
Equation (A) below:
A = 0.01 x Si ⁴⁺ content
+0.01 x B ³⁺ content
+0.05 x La ³⁺ content
+0.07 x Y ³⁺ content
+0.07 x Yb ³⁺ content
+0.085 x Zn ²⁺ content
+0.3 x Zr ⁴⁺ content
^+0.5 x Ta ⁵⁺ content
+0.8 × Nb ⁵⁺ content
+0.9 x W ⁵⁺ content
+0.95 x Ti ^{4 +} content ... (A)
The value A calculated by is in the range of 8.5000 to 11.000.
Equation (C) below:
C = 0.567 x (Nb ⁵ + content + Ti ^{4 +} content) -1.000 x Gd ^{3 +} content ... (C)
The value C calculated by is in the range of -1,000 to 6.720.
Further, for the cation components shown in Table 1, the total D of the values obtained by multiplying the content of each cation component by the coefficient shown in Table 1 is the following formula (B) with respect to the refractive index nd:
D ≦ 6.242 × nd-8.8042 ・ ・ ・ (B)
Glass that is an oxide glass that meets the requirements.
Gd ³⁺ Content is 3 cation% or less,
Yb ³⁺ Content is 2.0 cation% or less,
The glass according to claim 1 or 2. Si ⁴⁺ Content is 3 to 20 cation%,
B ³⁺ Content is 20-55 cation%,
Nb ⁵⁺ Content is 12 cation% or less,
Zr ⁴⁺ Content is 8 cation% or less,
Zn ²⁺ Content is 10.00 cation% or less,
The glass according to any one of claims 1 to 3. The glass according to any one of claims 1 to ⁴ , wherein the total content of B ³⁺ and Si ⁴⁺ is in the range of 43 to 65 cation%. The glass according to any one of claims 1 to 5 , wherein the total content of Nb ⁵⁺ , Ti ⁴⁺ , Ta ⁵⁺ and W ⁶⁺ is in the range of 3 to 12 cation %. A glass material for press molding made of the glass according to any one of claims 1 to 6 . The optical element blank made of glass according to any one of claims 1 to 6 . The optical element made of glass according to any one of claims 1 to 6 .