WO2021090589A1 - Optical glass, preform, and optical element - Google Patents

Abstract

The present invention provides optical glass that has high devitrification resistance and good reheat press moldability while having a partial dispersion ratio (θg, F) within a desired range. The optical glass contains, in mass% in terms of oxides, 10.0-35.0% of SiO₂ components, 10.0-40.0% of Nb₂O₅ components, 1.0-15.0% of ZrO₂ components, 1.0-15.0% of Li₂O components, and 1.0-20.0% of Ln₂O₃ components (where Ln is at least one selected from the group consisting of La, Y, Gd, and Yb), wherein the mass ratio (Li₂O+La₂O₃)/SiO₂ is 0.35 or higher, the mass ratio Li₂O/(Li₂O+Na₂O+K₂O) is 0.50 or higher, and the partial dispersion ratio (θg, F) and the Abbe number (ν_d) satisfy the following relation: (-0.00162×ν_d+0.624)≤(θg, F)≤(-0.00162×ν_d+0.654).

Description

Optical glass, preforms and optics

The present invention relates to optical glass and optical elements.

Optical systems such as digital cameras and video cameras, although they are large and small, contain bleeding called aberrations. This aberration is classified into monochromatic aberration and chromatic aberration, and in particular, chromatic aberration strongly depends on the material characteristics of the lens used in the optical system.

Generally, chromatic aberration is corrected by combining a low-dispersion convex lens and a high-dispersion concave lens, but this combination can only correct aberrations in the red region and the green region, and aberrations in the blue region remain. This aberration in the blue region that cannot be completely removed is called a quadratic spectrum. In order to correct the secondary spectrum, it is necessary to carry out an optical design that takes into account the trend of the g-line (435.835 nm) in the blue region. At this time, the partial dispersion ratio (θg, F) is used as an index of the optical characteristics attracting attention in the optical design. In the optical system combining the above-mentioned low-dispersion lens and high-dispersion lens, an optical material having a large partial dispersion ratio (θg, F) is used for the low-dispersion side lens, and a partial dispersion ratio (partial dispersion ratio) is used for the high-dispersion side lens. By using an optical material having a small θg, F), the secondary spectrum is satisfactorily corrected.
In recent years, in optical design, there is an increasing need for glass having a small partial dispersion ratio (θg, F).

The partial dispersion ratio (θg, F) is expressed by the following equation (1).
_{θg, F = (n g -n} F) / (n F -n C) ······ (1)

In optical glass, there is a substantially linear relationship between the partial dispersion ratio (θg, F) and the Abbe number (ν _{d), which represent the partial dispersibility in the short wavelength region.} The straight line representing this relationship is a plot of the partial dispersion ratio and Abbe number of NSL7 and PBM2 on Cartesian coordinates with the partial dispersion ratio (θg, F) on the vertical axis and the Abbe number (ν _{d) on the horizontal axis.} It is represented by a straight line connecting two points and is called a normal line. The normal glass, which is the standard of the normal line, differs depending on the optical glass manufacturer, but each company defines it with almost the same inclination and section (NSL7 and PBM2 are optical glasses manufactured by O'Hara Co., Ltd., and Abbe of PBM2. The number (ν _d ) is 36.3, the partial dispersion ratio (θg, F) is 0.5828, the Abbe number (ν _d ) of NSL7 is 60.5, and the partial dispersion ratio (θg, F) is 0.5436. .).

Examples of a method for producing an optical element from optical glass include a method of obtaining a shape of an optical element by grinding and polishing a gob or a glass block formed of the optical glass, and a gob or glass formed of the optical glass. A method of grinding and polishing a glass molded body obtained by reheating a block and molding (reheat press molding), and molding a preform material obtained from a gob or a glass block with an ultra-precision machined mold. A method of obtaining the shape of an optical element by (precision mold press molding) is known. Regardless of the method, it is required that stable glass can be obtained when forming a gob or a glass block from a molten glass raw material. Here, when the stability (devitrification resistance) of the glass constituting the obtained gob or glass block against devitrification is lowered and crystals are generated inside the glass, it is possible to obtain a glass suitable as an optical element. Can not.

Japanese Unexamined Patent Publication No. 2006-248897 Japanese Unexamined Patent Publication No. 2012-240909

With the glass of Patent Document 1, it is difficult to obtain a glass having a small partial dispersion ratio (θg, F), and the devitrification property tends to deteriorate.
Although the glass of Patent Document 2 has a common problem of reducing the partial dispersion ratio (θg, F), it contains the Ta ₂ O ₅ component as an essential component, so that the manufacturing cost is high and the glass is melted. The moldability is not good due to the poor property.

The present invention has been made in view of the above problems, and an object of the present invention is that the partial dispersion ratio (θg, F) is within a desired range, the devitrification resistance is high, and reheat press molding is performed. The purpose is to obtain optical glass having good properties.

More specifically, when the partial dispersion ratio (θg, F) is with the Abbe number (ν _d ), (−0.00162 × ν _d + 0.624 ≦ (θg, F) ≦ (−0.00162 ×). Ν _d +0.654) is satisfied, the liquidus temperature is 1150 ° C. or lower, and an optical glass having good reheat press moldability is obtained.

As a result of intensive test and research to solve the above problems, the present inventor has a relationship between the contents of the Ln ₂ O ₃ component and the Li _{O 2 component in the glass containing the SiO 2} component and the Nb ₂ O _{5 component.} By adjusting the above, it has been found that an optical glass having a low partial dispersion ratio, high devitrification resistance, and good reheat press characteristics can be produced, and the present invention has been completed.

(1) By mass% of oxide equivalent composition,
10.0 to 35.0% of SiO _{2 component}
Nb ₂ O ₅ component 10.0-40.0%
The ZrO ₂ component from 1.0 to 15.0%,
Li ₂ O component 1.0 to 15.0%
It _{contains 1.0 to 20.0% of Ln 2} O ₃ component (in the formula, Ln is one or more selected from the group consisting of La, Y, Gd, and Yb).
The mass ratio (Li ₂ O + La ₂ O ₃ ) / SiO ₂ is 0.35 or more, and
The mass ratio Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) is 0.50 or more, and
The partial dispersion ratio (θg, F) is _{between the Abbe number (ν d} ) and (-0.00162 x ν _d +0.624) ≤ (θg, F) ≤ (-0.00162 x ν _d +0.654). ) Satisfying the relationship.

(2) By mass% of oxide equivalent composition,
B ₂ O ₃ component 0-20.0%,
La ₂ O ₃ component 0-20.0%
CaO component 0-20.0%,
SrO component 0-20.0%,
BaO component 0-20.0%,
Na ₂ O component 0 to 10.0%,
The optical glass according to (1) contained.

(3) Containing more _{SiO 2} component than B ₂ O _{3 component,}
The mass ratio (ZnO + TiO ₂ + P ₂ O ₅ ) / (ZrO ₂ + La ₂ O ₃ + LiO ₂ ) is less than 0.15.
The sum of mass BaO + CaO + SrO is 5.0 to 20.0%.
The optical glass according to either (1) or (2).

(4) refractive index _{(n d)} is from 1.70000 to 1.80000, the optical glass according the Abbe number ([nu _d) is from 30.00 to 40.00 (1) to (3).

(5) The optical glass according to (1) to (4), wherein the liquidus temperature is 1150 ° C. or lower.

(6) An optical element made of the optical glass according to any one of (1) to (5).

(7) A preform for polishing and / or precision press molding made of the optical glass according to any one of (1) to (5).

(8) An optical device including the optical element according to any one of (6) and (7).

According to the present invention, it is possible to obtain an optical glass having a low partial dispersion ratio (θg, F), a low liquidus temperature, and good reheat press moldability.

It is a figure which shows the relationship between the partial dispersion ratio (θg, F) and the Abbe number (ν _{d) about the glass of the Example of this application.}

The embodiment of the optical glass of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be carried out with appropriate modifications within the scope of the object of the present invention. It should be noted that the description may be omitted as appropriate for the parts where the explanations are duplicated, but the gist of the invention is not limited.

[Glass component]
The composition range of each component constituting the optical glass of the present invention is described below. Unless otherwise specified in the present specification, the content of each component shall be expressed as a mass% of the total mass of the glass in the oxide conversion composition. Here, the "oxide-equivalent composition" is based on the assumption that the oxides, composite salts, metal fluorides, etc. used as raw materials for the glass constituents of the present invention are all decomposed at the time of melting and changed to oxides. It is a composition which describes each component contained in a glass, assuming that the total mass of the produced oxide is 100 mass%.

<About essential ingredients and optional ingredients>
The SiO ₂ component is an essential component that promotes stable glass formation and reduces devitrification (generation of crystals) that is unfavorable for optical glass.
In particular, by _{setting the content of the SiO 2} component to 10.0% or more, a glass having excellent devitrification resistance can be obtained without significantly increasing the partial dispersion ratio. Moreover, the liquidus temperature can be reduced. Therefore, _{the content of the SiO 2} component is preferably 10.0% or more, more preferably 13.0% or more, still more preferably 15.0% or more, still more preferably 18.0% or more, and most preferably 20. The lower limit is 0% or more.
On the other hand, _{by reducing the content of the SiO 2} component to 35.0% or less, an increase in the partial dispersion ratio can be suppressed. Therefore, _{the content of the SiO 2} component is preferably 35.0% or less, more preferably 33.0% or less, and most preferably 31.0% or less.

The Nb ₂ O ₅ component is an essential component capable of increasing the refractive index and decreasing the Abbe number.
In particular, the refractive index can be increased by setting the content of _{the Nb 2} O _{5 component to 10.0% or more.} Therefore, _{the content of the Nb 2} O ₅ component is preferably 10.0% or more, more preferably 12.0% or more, still more preferably 15.0% or more, still more preferably 20.0% or more, most preferably. The lower limit is 23.0% or more.
On the other hand, by _{setting the content of the Nb 2} O ₅ component to 40.0% or less, thermal stability can be obtained and the material cost of the glass can be reduced. Further, the devitrification of the glass can be reduced. Therefore, _{the content of the Nb 2} O ₅ component is preferably 40.0% or less, more preferably 38.0% or less, still more preferably 36.0% or less, and most preferably 34.0% or less. ..

ZrO ₂ component increases the refractive index of the glass and the Abbe number, which is an essential component that can reduce the partial dispersion ratio.
In particular, by setting the content of the ZrO ₂ component above 1.0%, while lowering the partial dispersion ratio, it is possible to obtain a stable glass. Therefore, the content of the ZrO ₂ component is preferably 1.0% or more, more preferably 2.0% or more, more preferably 3.0% or more, more preferably 5.0% or more, and most preferably 6. The lower limit may be 0% or more.
On the other hand, by the content of the ZrO ₂ component below 15.0%, it is possible to reduce the devitrification and can be easy to obtain a more homogeneous glass. Therefore, the content of the ZrO ₂ component is preferably 15.0% or less, more preferably 12.0 percent or less, 11.0% and more preferably less, more preferably 10.0% or less, and most preferably 9. The upper limit is 0% or less.

Unlike other alkali metals, the Li ₂ O component is an essential component capable of reducing the partial dispersion ratio.
In particular, by _{setting the content of the Li 2} O component to 1.0% or more, the meltability of the glass can be increased and the partial dispersion ratio can be reduced. Therefore, _{the content of the Li 2} O component may be preferably 1.0% or more, more preferably 1.5% or more, further preferably 2.0% or more, and most preferably 2.5% or more as the lower limit. ..
On the other hand, _{by reducing the content of the Li 2} O component to 15.0% or less, devitrification due to excessive content can be reduced, and devitrification of the reheat press can also be reduced.
Therefore, _{the content of the Li 2} O component is preferably 15.0% or less, more preferably 12.0% or less, still more preferably 10.0% or less, still more preferably 9.0% or less, and most preferably 8. The upper limit is 0.0% or less.

The B ₂ O ₃ component is an optional component that promotes stable glass formation, can lower the liquidus temperature, enhances devitrification resistance, and enhances the meltability of the glass raw material.
In particular, by _{setting the content of the B 2} O ₃ component to 0% or more, it is possible to suppress an increase in the liquidus temperature. Therefore, _{the content of the B 2} O ₃ component is preferably 0% or more, more preferably more than 0%, more preferably 0.1% or more, still more preferably 0.2% or more, and most preferably 0.3%. The above may be the lower limit.
On the other hand, by _{setting the content of the B 2} O ₃ component to 20.0% or less, the decrease in the refractive index can be suppressed and the increase in the partial dispersion ratio can be suppressed. Therefore, _{the content of the B 2} O ₃ component is preferably 20.0% or less, more preferably 18.0% or less, more preferably 16.0% or less, more preferably 14.0% or less, still more preferably. The upper limit is 12.0% or less, most preferably 11.0% or less.

The SiO ₂ component is preferably contained in a larger amount than the _{B 2} O _{3 component.} If the B ₂ O ₃ component is _{larger than the SiO 2} component, the partial dispersion ratio will increase. _{Therefore, by containing the SiO 2} component more than the B ₂ O ₃ component, the partial dispersion ratio is lowered while stabilizing the glass. be able to.

The La ₂ O ₃ component is a component that can reduce the partial dispersion ratio while reducing devitrification, and when it is contained, it has an effect different from that of other rare earths that are easily devitrified.
In particular, by _{setting the content of the La 2} O ₃ component to 0% or more, the refractive index can be increased, and by adjusting within the range of the components of the present invention, the anomalous dispersibility can be reduced. Therefore, _{the content of the La 2} O ₃ component is preferably 0% or more, more preferably 1.0% or more, more preferably 2.0% or more, still more preferably 3.0% or more, still more preferably 4. The lower limit is 0% or more, most preferably 5.0% or more.
On the other hand, by _{setting the content of the La 2} O ₃ component to 20.0% or less, an increase in the Abbe number can be suppressed, devitrification can be reduced, and coloring can be reduced. Therefore, _{the content of the La 2} O ₃ component is preferably 20.0% or less, more preferably 19.0% or less, further preferably 17.0% or less, and most preferably 16.0% or less. ..

The Gd ₂ O ₃ component, the Y ₂ O ₃ component, and the Yb ₂ O ₃ component are optional components that can increase the refractive index and reduce the partial dispersion ratio by containing at least any one of more than 0%.
On the other hand, if _{a large amount of Gd 2} O ₃ component, Y ₂ O ₃ component and Yb ₂ O ₃ component is contained, the liquidus temperature drops and the glass is devitrified.
In particular, by _{setting the content of each of the Gd 2} O ₃ component, the Y ₂ O ₃ component, and the Yb ₂ O ₃ component to 10.0% or less, devitrification can be reduced and coloring can be reduced. Therefore, _{the content of each of the Gd 2} O ₃ component, the Y ₂ O ₃ component, and the Yb ₂ O ₃ component is preferably 10.0% or less, more preferably 8.0% or less, still more preferably 5.0%. Hereinafter, the upper limit is most preferably 3.0% or less.

The Na ₂ O component and the K ₂ O component are optional components that increase the meltability of the glass raw material and reduce the coloring when the content exceeds 0%.
On the other hand, if _{a large amount of Na 2} O component and K ₂ O component is contained, the stability of the glass is deteriorated and the devitrification resistance is lowered.
On the other hand, devitrification can be reduced by reducing the contents _{of the Na 2} O component and the K _{2 O component to 10.0% or less.} Therefore, _{the contents of the Na 2} O component and the K ₂ O component are preferably 10.0% or less, more preferably 8.0% or less, still more preferably 7.0% or less, still more preferably 6.0% or less. Most preferably, the upper limit is 5.0% or less.

The MgO component is an optional component that can improve the meltability and lower the liquidus temperature, but if it is contained in a large amount, the glass will be devitrified.
On the other hand, devitrification can be reduced by reducing the content of the MgO component to 10.0% or less. Therefore, the content of the MgO component is preferably 10.0% or less, more preferably 8.0% or less, still more preferably 5.0% or less, still more preferably 3.0% or less, and most preferably 2.0. The upper limit is%.

The CaO component is an optional component that can improve the stability of the glass.
In particular, the meltability can be enhanced by setting the content of the CaO component to 0% or more. Therefore, the content of the CaO component is preferably 0% or more, more preferably 0.1% or more, still more preferably 0.5% or more, still more preferably 1.0% or more, and most preferably 2.0% or more. Is the lower limit.
On the other hand, by setting the content of the CaO component to 20.0% or less, the press moldability is improved and the increase in the partial dispersion ratio can be suppressed. Therefore, the content of the CaO component is preferably 20.0% or less, more preferably 17.0% or less, still more preferably 14.0% or less, still more preferably 12.0% or less, and most preferably 10.0%. The upper limit is% or less.

The SrO component is an optional component that can improve the stability of the glass.
On the other hand, by setting the content of the SrO component to 20.0% or less, the press moldability is improved and the increase in the partial dispersion ratio can be suppressed. Therefore, the content of the SrO component is preferably 20.0% or less, more preferably 17.0% or less, still more preferably 14.0% or less, still more preferably 12.0% or less, and most preferably 10.0%. The upper limit is% or less.

The BaO component is an optional component that can improve the stability of the glass.
On the other hand, by setting the content of the BaO component to 20.0% or less, the press moldability is improved and the increase in the partial dispersion ratio can be suppressed. Therefore, the content of the BaO component is preferably 20.0% or less, more preferably 17.0% or less, still more preferably 14.0% or less, still more preferably 12.0% or less, and most preferably 10.0%. The upper limit is% or less.

The TiO ₂ component is an optional component that increases the refractive index and decreases the Abbe number. On the other hand, when the TiO ₂ component is contained in a large amount, the partial dispersion ratio becomes large.
In particular, by _{setting the content of the TiO 2} component to 10.0% or less, it is possible to reduce the Abbe number while suppressing an increase in the partial dispersion ratio. Therefore, _{the content of the TiO 2} component is preferably 10.0% or less, more preferably 5.0% or less, further preferably 3.0% or less, and most preferably 2.0% or less.

The ZnO component is an optional component that is inexpensive and can be adjusted to the high dispersion side. On the other hand, when the ZnO component is contained in a large amount, the partial dispersion ratio becomes large.
In particular, by reducing the content of the ZnO component to 10.0% or less, devitrification and coloring can be reduced. Therefore, the content of the ZnO component is preferably 10.0% or less, more preferably 5.0% or less, further preferably less than 3.0%, and most preferably 1.0% or less.

The Ta ₂ O ₅ component is an optional component capable of increasing the refractive index, lowering the Abbe number and the partial dispersion ratio, and increasing the devitrification resistance.
In particular, _{by reducing the content of the Ta 2} O ₅ component to 10.0% or less, the amount of the Ta ₂ O ₅ component, which is a rare mineral resource, is reduced, and the glass is easily melted at a lower temperature. Production cost can be reduced. Further, this can reduce the devitrification of the glass due to the excessive content _{of the Ta 2} O _{5 component.} Therefore, _{the content of the Ta 2} O ₅ component is preferably 10.0% or less, more preferably 5.0% or less, further preferably 3.0% or less, and most preferably 1.0% or less. .. In particular, from the viewpoint of reducing the material cost of glass, it is not necessary to contain the _{Ta 2} O _{5 component.}

The WO ₃ component is an optional component that can increase the refractive index, reduce the Abbe number, and enhance the meltability of the glass raw material. By _{setting the content of the WO 3} component to 10.0% or less, it is possible to make it difficult to increase the partial dispersion ratio of the glass, and it is possible to reduce the coloring of the glass and increase the internal transmittance. Therefore, _{the content of the WO 3} component is preferably 10.0% or less, more preferably 5.0% or less, further preferably 3.0% or less, and most preferably 1.0% or less.

The P ₂ O ₅ component is an optional component that can enhance the stability of the glass.
On the other hand, by _{setting the content of the P 2} O ₅ component to 10.0% or less, the increase in the partial dispersion ratio due to the excessive content _{of the P 2} O _{5 component can be reduced.} Therefore, _{the content of the P 2} O ₅ component is preferably 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less, still more preferably less than 2.0%, and most preferably. The upper limit is 1.0% or less.

The GeO ₂ component is an optional component that can increase the refractive index and reduce devitrification. By _{reducing the content of the GeO 2} component to 10.0% or less, the amount of the expensive GeO ₂ component used can be reduced, so that the material cost of the glass can be reduced. Therefore, _{the content of the GeO 2} component is preferably 10.0% or less, more preferably 5.0% or less, further preferably 3.0% or less, and most preferably 1.0% or less.

The Al ₂ O ₃ component is an optional component capable of increasing the refractive index and improving the devitrification resistance.
On the other hand, by the content of the _Al 2 _{O 3} component to 10.0% or less, it can be reduced devitrification due to excessive content of _Al 2 _{O 3} component. Therefore, _{the content of the Al 2} O ₃ component is preferably 10.0% or less, more preferably 5.0% or less, further preferably 3.0% or less, and most preferably 1.0% or less. ..

The Ga ₂ O ₃ component is an optional component capable of increasing the refractive index and improving the devitrification resistance.
On the other hand, by the content of _Ga 2 _{O 3} component to 10.0% or less, it can be reduced devitrification due to excessive content of _Ga 2 _{O 3} component. Therefore, _{the content of the Ga 2} O ₃ component is preferably 10.0% or less, more preferably 5.0% or less, further preferably 3.0% or less, and most preferably 1.0% or less. ..

The Bi ₂ O ₃ component is an optional component that can increase the refractive index, reduce the Abbe number, and lower the glass transition point. By _{setting the content of the Bi 2} O ₃ component to 10.0% or less, it is possible to make it difficult to increase the partial dispersion ratio, and it is possible to reduce the coloring of the glass and increase the internal transmittance. Therefore, _{the content of the Bi 2} O ₃ component is preferably 10.0% or less, more preferably 5.0% or less, further preferably 3.0% or less, and most preferably 1.0% or less. ..

The TeO ₂ component is an optional component capable of increasing the refractive index, lowering the partial dispersion ratio, and lowering the glass transition point. By _{setting the content of the TeO 2} component to 10.0% or less, the coloring of the glass can be reduced and the internal transmittance can be increased. Further, by reducing the use of the expensive TeO ₂ component, a glass having a lower material cost can be obtained. Therefore, _{the content of the TeO 2} component is preferably 10.0% or less, more preferably 5.0% or less, still more preferably 3.0%, and most preferably 1.0% or less. In particular, from the viewpoint of reducing the material cost of glass, it is not necessary to contain _{the TeO 2 component.}

SnO ₂ is an optional component that can clarify (defoam) the molten glass and increase the visible light transmittance of the glass. By _{setting the SnO 2} content to 1.0% or less, it is possible to prevent the glass from being colored or devitrified by the reduction of the molten glass. Further, since _{the alloying of SnO 2} and the melting equipment (particularly noble metal such as Pt) is reduced, the life of the melting equipment can be extended. Therefore, the SnO ₂ content is preferably 1.0% or less, more preferably 0.5% or less, and further preferably 0.1% or less.

The Sb ₂ O ₃ component is a component that promotes defoaming of the glass and clarifies the glass, and is an optional component in the optical glass of the present invention. By _{setting the content of the Sb 2} O ₃ component to 1.0% or less of the total mass of the glass, it is possible to prevent excessive foaming during glass melting, and the Sb ₂ O ₃ component is a melting facility (particularly Pt). It can be made difficult to alloy with precious metals such as. _{Therefore, the content of the Sb 2} O ₃ component with respect to the total mass of the glass in the oxide conversion composition is preferably 1.0% or less, more preferably 0.5% or less, still more preferably 0.3% or less, and most preferably. The upper limit is 0.1% or less.

The component that clarifies and defoams the _{glass is not limited to the above Sb 2} O ₃ component, and a clarifying agent, a defoaming agent, or a combination thereof known in the field of glass production can be used. ..

The Ln ₂ O ₃ component (in the formula, Ln is one or more selected from the group consisting of La, Y, Gd, and Yb) is contained when the sum of the contents (mass sum) is 1.0% or more. , The partial dispersion ratio can be reduced while increasing the refractive index. Therefore, the _{lower limit of the sum of the Ln 2} O ₃ components is preferably 1.0% or more, more preferably 3.0% or more, still more preferably 5.0% or more, and most preferably 7.0% or more.
On the other hand, _{by setting the sum (mass sum) of the contents of the Ln 2} O ₃ components to 20.0% or less, devitrification due to excessive content can be reduced. Therefore, the upper limit is preferably 20.0% or less, more preferably 18.0% or less, further preferably 17.0% or less, and most preferably 16.0% or less.

The Rn ₂ O component (in the formula, Rn is one or more selected from the group consisting of Li, Na, and K) is contained in the glass when the sum of the contents (mass sum) is 1.0% or more. Stability can be improved. Therefore, the _{lower limit of the sum of the Rn 2} O components is preferably 1.0% or more, more preferably 2.5% or more, still more preferably 3.0% or more, and most preferably 3.5% or more.
On the other hand, when _{the sum of the contents (mass sum) of the Rn 2} O components is 15.0% or less, the decrease in the refractive index can be suppressed and the devitrification due to the excessive content can be reduced. Therefore, the upper limit is preferably 15.0% or less, more preferably 14.0% or less, further preferably 13.0% or less, and most preferably 12.0% or less.

When the sum of the contents of the RO component (in the formula, R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is 5.0% or more, the low temperature meltability is improved. Can be done. Therefore, the lower limit of the sum of the contents of the RO components is preferably 5.0%, more preferably 5.3% or more, further preferably 5.8% or more, and most preferably 6.0% or more.
On the other hand, the sum of the contents of the RO components is preferably 20.0% or less because the decrease in devitrification resistance due to the excessive content can be suppressed. Therefore, the mass sum of the RO components is preferably 20.0% or less, more preferably 19.0% or less, still more preferably 18.0% or less, and most preferably 16.0% or less.

When the mass sum BaO + CaO + SrO is 5.0% or more, the low temperature meltability can be improved. Therefore, the lower limit of the mass sum BaO + CaO + SrO is preferably 5.0% or more, more preferably 5.3% or more, further preferably 5.8% or more, and most preferably 6.0% or more.
On the other hand, if the sum of mass BaO + CaO + SrO is excessively contained, the refractive index and dispersion will be increased, it will be difficult to obtain desired optical characteristics, and the devitrification property will be deteriorated. The following is preferable. Therefore, the mass sum BaO + CaO + SrO is preferably 20.0% or less, more preferably 19.0% or less, still more preferably 18.0% or less, and most preferably 16.0% or less.

When the mass ratio (Li ₂ O + La ₂ O ₃ ) / SiO ₂ is 0.35 or more, the partial dispersion ratio can be lowered while stabilizing the glass. Therefore, the mass ratio (Li ₂ O + La ₂ O ₃ ) / SiO ₂ preferably has a lower limit of 0.35 or more, more preferably 0.36 or more, still more preferably 0.38 or more, and most preferably 0.40 or more. To do.
On the other hand, the mass ratio (Li ₂ O + La ₂ O ₃ ) / SiO ₂ is preferably 1.00 or less in order to suppress an increase in the liquidus temperature. Therefore, the mass ratio (Li ₂ O + La ₂ O ₃ ) / SiO ₂ is preferably 1.00 or less, more preferably 0.90 or less, still more preferably 0.88 or less, and most preferably 0.85 or less. To do.

When the mass ratio Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) is 0.50 or more, the effect of the LiO ₂ component acting on the reduction of the partial dispersion ratio is most effectively exhibited, and the meltability is improved. It is possible to suppress devitrification while raising it. Therefore, the mass ratio Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) is preferably 0.50 or more, more preferably 0.52 or more, still more preferably 0.54 or more, and most preferably 0.55 or more. The lower limit.

When the mass ratio (SiO ₂ + B ₂ O ₃ + Ln ₂ O ₃ ) / Rn ₂ O is 3.50 or more, the liquidus temperature can be lowered while suppressing devitrification. Therefore, the mass ratio (SiO ₂ + B ₂ O ₃ + Ln ₂ O ₃ ) / Rn ₂ O is preferably 3.50 or more, more preferably 3.55 or more, still more preferably more than 3.58, and most preferably 3. The lower limit is 60 or more.
On the other hand, when the mass ratio (SiO ₂ + B ₂ O ₃ + Ln ₂ O ₃ ) / Rn ₂ O is 12.0 or less, the Abbe number (ν _d ) can be maintained. Therefore, the mass ratio (SiO ₂ + B ₂ O ₃ + Ln ₂ O ₃ ) / Rn ₂ O is preferably 12.0 or less, more preferably 11.80 or less, still more preferably 11.50 or less, and most preferably 11. The upper limit is 20 or less.

When the mass ratio (ZnO + TiO ₂ + P ₂ O ₅ ) / (ZrO ₂ + La ₂ O ₃ + LiO ₂ ) is less than 0.15, the partial dispersion ratio increases due _{to the ZnO component, TiO 2} component, and P ₂ O _{5 component.} Can be suppressed. Therefore, the mass ratio (ZnO + TiO ₂ + P ₂ O ₅ ) / (ZrO ₂ + La ₂ O ₃ + LiO ₂ ) is preferably less than 0.15, more preferably 0.12 or less, still more preferably 0.10 or less, most preferably 0.10 or less. The upper limit is 0.08 or less.

<Ingredients that should not be included>
Next, components that should not be contained in the optical glass of the present invention and components that are not preferable to be contained will be described.

Other components can be added as needed within a range that does not impair the characteristics of the glass of the present invention. However, each transition metal component such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb and Lu, is used alone. Alternatively, even if it is compounded and contained in a small amount, the glass is colored and has a property of causing absorption at a specific wavelength in the visible region. Therefore, it is preferable that the glass is substantially not contained, especially in optical glass using a wavelength in the visible region. ..

Further, since lead compounds such as PbO and _{arsenic compounds such as As 2} O ₃ are components having a high environmental load, it is desirable that they are not substantially contained, that is, they are not contained at all except for unavoidable contamination.

Furthermore, each component of Th, Cd, Tl, Os, Be, and Se has tended to refrain from being used as a harmful chemical substance in recent years, and is used not only in the glass manufacturing process but also in the processing process and disposal after commercialization. Up to this point, environmental measures are required. Therefore, when the environmental impact is important, it is preferable that these are not substantially contained.

[Production method]
The optical glass of the present invention is produced, for example, as follows. That is, the above raw materials are uniformly mixed so that each component is within a predetermined content range, and the prepared mixture is put into a platinum crucible, a quartz crucible or an alumina crucible and roughly melted, and then a gold crucible and a platinum crucible. , Platinum alloy crucible or iridium crucible, melt in a temperature range of 1000 to 1400 ° C for 2 to 5 hours, homogenize with stirring to break bubbles, etc., then lower to a temperature of 950 to 1250 ° C and then finish stirring. It is produced by removing the crucible, casting it into a mold, and slowly cooling it.

<Physical characteristics>
The optical glass of the present invention has a refractive index ( _nd ) and an Abbe number (ν _d ) in a predetermined range.
Refractive index of the optical glass of the present invention _{(n d)} is preferably 1.70000 or more, more preferably 1.73000 or more, more preferably the lower limit or more 1.75000. The upper limit of the refractive index is preferably 1.80000 or less, more preferably 1.79000 or less.
_{The Abbe number (ν d} ) of the optical glass of the present invention is preferably 30.00 or more, more preferably 32.00 or more, and further preferably 33.00 or more as the lower limit. On the other hand, the Abbe number (ν _d ) of the optical glass of the present invention is preferably 40.00 or less, more preferably 38.00 or less, still more preferably 37.00 or less.
The optical glass of the present invention having such a refractive index and Abbe number is useful in optical design, and the optical system can be miniaturized while achieving particularly high imaging characteristics, so that the optical design is free. You can increase the degree.

The optical glass of the present invention has a low partial dispersion ratio (θg, F).
More specifically, the partial dispersion ratio (θg, F) of the optical glass of the present invention is not particularly limited, but may be preferably 0.560 or more, more preferably 0.565 or more. On the other hand, the partial dispersion ratio (θg, F) of the optical glass of the present invention is preferably 0.600 or less, more preferably 0.595 or less, still more preferably 0.593 or less. Further, the partial dispersion ratio (θg, F) of the optical glass of the present invention is preferably (−0.00162 × ν _d +0.624) ≦ (θg, F) ≦ in _{relation to the Abbe number (ν d).} The relationship (-0.00162 x ν _d +0.654) is satisfied.
As described above, the optical glass of the present invention has a lower partial dispersion ratio (θg, F) than the conventionally known glass containing a large amount of _{SiO 2} component and Nb ₂ O _{5 component.} Therefore, the optical element formed from this optical glass can be preferably used for correcting chromatic aberration.

Here, the lower limit of the partial dispersion ratio (θg, F) in relation to _{the Abbe number (ν d} ) of the optical glass of the present invention _{is not particularly limited, but is preferably (−0.00162 × ν d} +0.624). As described above, it may be more preferably (−0.00162 × ν _d +0.627) or more, and even more preferably (−0.00162 × ν _d +0.630) or more. On the other hand, the upper limit of the partial dispersion ratio (θg, F) in relation to _{the Abbe number (ν d} ) of the optical glass of the present invention _{is preferably (−0.00162 × ν d} +0.654) or less, more preferably. It is (-0.00162 x ν _d +0.651) or less, more preferably (-0.00162 x ν _d +0.648) or less.

It is preferable that the optical glass of the present invention has a high visible light transmittance, particularly a light transmittance on the short wavelength side of visible light, and thus less coloring.
_{In particular, the optical glass of the present invention has a wavelength (λ 80} ) showing a spectral transmittance of 80% in a sample having a thickness of 10 mm, preferably 420 nm or less, more preferably 417 nm or less, still more preferably. The upper limit is 410 nm or less.
Further, in the optical glass of the present invention, the shortest wavelength (λ ₅ ) showing a spectral transmittance of 5% in a sample having a thickness of 10 mm is preferably 345 nm or less, more preferably 343 nm or less, still more preferably 342 nm or less. ..
As a result, the absorbing edge of the glass becomes near the ultraviolet region, and the transparency of the glass with respect to visible light is enhanced. Therefore, this optical glass can be preferably used for an optical element such as a lens that transmits light.

The optical glass of the present invention preferably has high devitrification resistance, and more specifically, has a low liquidus temperature.
That is, the liquidus temperature of the optical glass of the present invention is preferably 1150 ° C. or lower, more preferably 1148 ° C. or lower, and further preferably 1145 ° C. or lower. As a result, even if the molten glass flows out at a lower temperature, the crystallization of the produced glass is reduced, so that devitrification can be reduced especially when the glass is molded from the molten state, and the optical element using the glass. The effect on the optical characteristics of the glass can be reduced. Further, since the glass can be molded even if the melting temperature of the glass is lowered, the manufacturing cost of the glass can be reduced by suppressing the energy consumed during the molding of the glass.

[Preforms and optics]
From the produced optical glass, a glass molded body can be produced by using a mold press molding means such as reheat press molding or precision press molding. That is, a preform for mold press molding is produced from optical glass, and after reheat press molding is performed on this preform, polishing is performed to produce a glass molded product, or for example, polishing is performed to produce the preform. A glass molded body can be produced by performing precision press molding on the preform. The means for producing the glass molded body is not limited to these means.

The glass molded body produced in this way is useful for various optical elements, but it is particularly preferable to use it for applications of optical elements such as lenses and prisms. As a result, color bleeding due to chromatic aberration in the transmitted light of the optical system provided with the optical element is reduced. Therefore, when this optical element is used in a camera, an object to be photographed can be expressed more accurately, and when this optical element is used in a projector, a desired image can be projected with higher definition.

Compositions of Examples (No.1 ~ No.20) and Comparative Example A of the present invention, and a refractive index _(n d), Abbe number ([nu _d), the partial dispersion ratio ([theta] g, F), the liquidus temperature, The results of the transmittances λ ₅ and λ ₈₀ are shown in Tables 1 and 2. The following examples are for purposes of illustration only, and are not limited to these examples.

The glasses of Examples and Comparative Examples are of high purity, which are used for ordinary optical glass such as oxides, hydroxides, carbonates, nitrates, fluorides, metaphosphate compounds, etc., which correspond to each component as a raw material. After selecting the raw materials, weighing them so as to have the composition ratios of each of the examples and comparative examples shown in the table and mixing them uniformly, a stone crucible (depending on the meltability of the glass, a platinum crucible or an alumina crucible is used. It does not matter), and after melting in an electric furnace in a temperature range of 1100 to 1400 ° C. for 0.5 to 5 hours depending on the degree of difficulty of melting the glass composition, it is transferred to a platinum crucible and stirred to homogenize to break bubbles, etc. After that, the temperature was lowered to 1000 to 1200 ° C., the mixture was stirred and homogenized, cast into a mold, and slowly cooled to prepare glass.

The refractive index of the glass of the Examples and Comparative Examples _(n d), Abbe number ([nu _d) and partial dispersion ratio ([theta] g, F) is, JIS B 7071-2: Measured in accordance with V-block method specified in 2018 did. Here refractive index _{(n d)} is indicated by the measured value for the helium lamp d line (587.56 nm). The Abbe number ([nu _d) is the refractive index at the d-line of a helium lamp and _{(n d),} to the refractive index with respect to hydrogen lamp F line _{(486.13nm) (n F),} C line (656.27 nm) It was calculated from the formula of _{Abbe number (ν d} ) = [(n _d -1) / (n _{F −} n _C )] using the value of the refractive index (n _C). The partial dispersion ratio ([theta] g, F) is the refractive index for the g-line of Hg lamp and _{(n g),} the refractive index with respect to hydrogen lamp F line _{(486.13nm) (n F),} C line (656.27 nm ) With respect to the value of the refractive index (n _C ), it was calculated from the formula of partial dispersion ratio (θ _{g, F) = (ng −} n _F ) / (n _{F −} n _C). These refractive index (n _d), Abbe number ([nu _d) and partial dispersion ratio ([theta] g, F) is obtained by making measurements on glass obtained by the annealing cooling rate to -25 ° C. / hr ..

Then, from the value of the obtained Abbe number obtained by measuring ([nu _d) and partial dispersion ratio ([theta] g, F), equation (θg, F) = - in _{a 2 × ν d + b 2} , gradient _{a 2} is 0. _{The intercept b 2} at the time of 00162 was obtained.

The transmittance of the glass of Examples and Comparative Examples was measured according to the Japan Optical Glass Industry Association standard JOBIS02-2003. In the present invention, the presence or absence and degree of coloring of the glass were determined by measuring the transmittance of the glass. Specifically, a face-to-face parallel polished product having a thickness of 10 ± 0.1 mm is measured for a spectral transmittance of 200 to 800 nm according to JISZ8722, and wavelengths (λ ₈₀ , λ) showing spectral transmittances of 80% and 5%. ₅ ) was requested.

For the liquidus temperature of the glass of Examples and Comparative Examples, crushed glass samples were placed on a platinum plate at 10 mm intervals, held in a furnace with a temperature gradient of 800 ° C. to 1200 ° C. for 30 minutes, and then taken out. After cooling, the presence or absence of crystals in the glass sample was measured by observing with a microscope at a magnification of 80 times. At this time, as a sample, optical glass was pulverized into granules having a diameter of about 2 mm.

 

As represented in the table, the optical glasses of Examples of the present invention are both refractive index _{(n d)} with at 1.70000 or more, were within the desired range is at 1.80000 or less.
In addition, the optical glasses of the examples of the present invention all had an Abbe number (ν _d ) of 30.00 or more and 40.00 or less, which were within a desired range.

As represented in the table, the optical glasses of Examples of the present invention, the Abbe number ([nu _d) and partial dispersion ratio ([theta] g, F) relationship of _{(-0.00162 × ν d +0.624) ≦} ( θg, F) ≦ (−0.00162 × ν _d +0.654) was satisfied.

As shown in the table, the optical glass of the embodiment of the present invention had a liquid phase temperature of 1150 ° C. or lower. Further, it is presumed that the optical glass of the embodiment of the present invention has high reheat press moldability because the liquidus temperature is low.

As shown in the table, all of the optical glasses of the examples have a wavelength (λ ₈₀ ) showing a spectral transmittance of 80% or less of 420 nm and a wavelength (λ ₅ ) showing a spectral transmittance of 5% of 345 nm. It was below.

_{Since the mass ratio (Li 2} O + La ₂ O ₃ ) / SiO ₂ of the glass of Comparative Example A was less than 0.35, the glass was severely devitrified and did not vitrify.

Although the present invention has been described in detail above for the purpose of exemplification, the present embodiment is merely for the purpose of exemplification, and many modifications can be made by those skilled in the art without departing from the idea and scope of the present invention. Will be understood.

All disclosures (including specifications, drawings, claims) of the documents described in this specification and the Japanese application specification which is the basis of the Paris priority of the present application are incorporated herein by reference.

Claims (8)

1. By mass% of oxide equivalent composition,
   SiO ₂ component 10.0 to 35.0%,
   Nb ₂ O ₅ component 10.0-40.0%,
   The ZrO ₂ component from 1.0 to 15.0%,
   Li ₂ O component 1.0 to 15.0%,
   Ln ₂ O ₃ component (in the formula, Ln is one or more selected from the group consisting of La, Y, Gd, Yb) is 1.0 to 20.0%.
   Contains,
   The mass ratio (Li ₂ O + La ₂ O ₃ ) / SiO ₂ is 0.35 or more, and
   The mass ratio Li ₂ O / (Li ₂ O + Na ₂ O + K ₂ O) is 0.50 or more, and
   Partial dispersion ratio ([theta] g, F) is between the Abbe number _{(ν d), (- 0.00162} × ν d + 0.624 ≦ (θg, F) ≦ (-0.00162 × ν d +0.654) Optical glass that satisfies the relationship.
2. By mass% of oxide equivalent composition,
   B ₂ O ₃ component 0-20.0%,
   La ₂ O ₃ component 0-20.0%,
   CaO component 0-20.0%,
   SrO component 0-20.0%,
   BaO component 0-20.0%,
   Na ₂ O component 0 to 10.0%,
   The optical glass according to claim 1.
3. Containing more SiO ₂ component _{than B 2} O _{3 component,}
   The mass ratio (ZnO + TiO ₂ + P ₂ O ₅ ) / (ZrO ₂ + La ₂ O ₃ + LiO ₂ ) is less than 0.15.
   The sum of mass BaO + CaO + SrO is 5.0 to 20.0%.
   The optical glass according to claim 1 or 2.
4. Refractive index _{(n d)} is from 1.70000 to 1.80000, an Abbe's number ([nu _d) is 30.00 to 40.00 in the optical glass according to claims 1 to 3.
5. The optical glass according to claims 1 to 4, wherein the liquidus temperature is 1150 ° C. or less.
6. An optical element made of the optical glass according to any one of claims 1 to 5.
7. A preform for polishing and / or precision press molding made of the optical glass according to any one of claims 1 to 5.
8. An optical device including the optical element according to any one of claims 6 or 7.

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