JP7126341B2 - Optical glass, preforms and optical elements - Google Patents

Description

The present invention relates to optical glass and optical elements.

The optical systems of digital cameras, video cameras, and the like, regardless of their size, contain blurring called aberration. This aberration is classified into monochromatic aberration and chromatic aberration, and chromatic aberration in particular strongly depends on the material properties of the lenses used in the optical system.

Chromatic aberration is generally corrected by combining a low-dispersion convex lens and a high-dispersion concave lens, but this combination can only correct aberrations in the red and green regions, leaving aberrations in the blue region. This unremovable aberration in the blue region is called a secondary spectrum. In order to correct the secondary spectrum, it is necessary to perform an optical design that takes into consideration 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 optical characteristics that is of interest in optical design. In the above-described optical system that combines a low-dispersion lens and a high-dispersion lens, an optical material with a large partial dispersion ratio (θg, F) is used for the lens on the low-dispersion side, and the partial dispersion ratio ( By using an optical material with small θg,F), the secondary spectrum is well corrected.

The partial dispersion ratio (θg, F) is given by the following formula (1).
θg, F=(n _g −n _F )/(n _F −n _C ) (1)

In optical glass, there is an approximately linear relationship between the partial dispersion ratio (θg, F) representing partial dispersion in the short wavelength region and the Abbe number (ν _d ). The straight line representing this relationship plots the partial dispersion ratios and Abbe numbers of NSL7 and PBM2 on orthogonal coordinates with the partial dispersion ratio (θ g, F) on the vertical axis and the Abbe number (ν _d ) on the horizontal axis. A straight line connecting two points is called a normal line (see FIG. 1). The normal glass used as the standard of the normal line differs depending on the optical glass manufacturer, but each company defines it with almost the same slope and intercept. (NSL7 and PBM2 are optical glasses manufactured by Ohara Co., Ltd., the Abbe number (ν _d ) of PBM2 is 36.3, the partial dispersion ratio (θg, F) is 0.5828, and the Abbe number (ν _d ) of NSL7 is 36.3. is 60.5, and the partial dispersion ratio (θg, F) is 0.5436.)

In recent years, due to needs in optical design, glass having an Abbe number (ν _d ) of 30 or more and 45 or less is often used as an optical material with a small partial dispersion ratio (θg, F).

In recent years, optical elements incorporated in in-vehicle optical devices such as in-vehicle cameras, and optical devices that generate a lot of heat such as projectors, copiers, laser printers, and broadcasting equipment, are becoming more Use in high temperature environments is increasing. In such a high-temperature environment, the temperature of the optical elements constituting the optical system tends to fluctuate greatly during use, and the temperature often reaches 100° C. or higher. At this time, the adverse effect of temperature fluctuations on the imaging characteristics of the optical system becomes unignorable. Therefore, there is a demand for an optical system that is less likely to be affected by temperature fluctuations.

In order to construct an optical system that is less likely to be affected by temperature fluctuations on imaging characteristics, etc., an optical element made of glass whose refractive index decreases when the temperature rises and the temperature coefficient of the relative refractive index becomes negative. The refractive index increases when the temperature rises, and the use of an optical element made of glass whose relative refractive index has a positive temperature coefficient compensates for the effects of temperature changes on imaging characteristics. It is preferable in that it can be done.

On the other hand, in optical materials with a small partial dispersion ratio (θg, F), components contained to obtain various excellent optical properties (for example, Nb ₂ O ₅ components, La ₂ O ₃ components, etc.), A low alkali metal content tends to increase the temperature coefficient of the relative refractive index. Glass compositions disclosed in Patent Documents 1 and 2 are known as such optical glasses.
Furthermore, since it is often used in various environments such as in-vehicle lenses and interchangeable lenses that are used in recent years, optical glasses with a small partial dispersion ratio (θg, F) and a small temperature coefficient of relative refractive index are required. It has been demanded.

JP 2013-245140 A Showa 58-125637 publication

However, the glass disclosed in Patent Document ₁ has a large content of the BaO component that increases the partial dispersion ratio and a small content of the Nb ₂ O component that decreases the partial dispersion ratio, resulting in a large partial dispersion ratio. and is not sufficient for use as a lens for correcting the secondary spectrum. In addition, since the transmittance of visible light deteriorates, it cannot be said that sufficient optical characteristics are obtained. Further, the glass disclosed in Patent Document 2 has a large content of La ₂ O ₃ component, but a small content of Nb ₂ O ₅ , so that the partial dispersion ratio becomes large and the content of alkali metal is small. It cannot be said that the temperature coefficient of the relative refractive index is small.

The present invention has been made in view of the above problems, and its object is to maintain the refractive index (n _d ) and Abbe number (ν _d ) within desired ranges while maintaining the partial dispersion ratio ( An object of the present invention is to obtain an optical glass having a small θg, F) and a small temperature coefficient of relative refractive index.

As a result of intensive testing and research in order to solve the above-mentioned problems, the inventors of the present invention have found that by including a Na ₂ O component in a glass containing SiO ₂ component and Nb ₂ O ₅ component, the desired range of The inventors have found that an optical glass having a high refractive index, an Abbe number (high dispersion), a low partial dispersion ratio, and a small temperature coefficient of relative refractive index can be obtained, leading to the completion of the present invention.

(1) in mass %,
SiO ₂ component 15.0-45.0%
Nb ₂ O ₅ components 10.0-40.0%
Na ₂ O component more than 0 to 20.0%
mass sum (ZrO ₂ +Li ₂ O) of 5.0 to 20.0%,
Containing a mass ratio (BaO / MgO + CaO + SrO + BaO) of 0.90 or less,
Between the partial dispersion ratio (θg, F) and the Abbe number (ν _d ),
(−0.00162×ν _d +0.620)≦(θg, F)≦(−0.00162×ν _d +0.657), and the temperature coefficient of the relative refractive index (589.29 nm) (40 to 60° C.) is in the range of +6.0×10 ⁻⁶ to −5.0×10 ⁻⁶ (° C. ⁻¹ ).

(2) The optical glass according to (1), wherein the mass ratio (Li ₂ O/Li ₂ O+Na ₂ O+K ₂ O) is 1.00 or less.

(3) Refractive index (n _d ) and Abbe number (ν _d ) satisfy the relationship of (−0.01×ν _d +2.01)≦n _d ≦(−0.01×ν _d +2.12) The optical glass according to (1) or (2).

(4) A preform material made of the optical glass according to any one of (1) to (3).

(5) An optical element made of the optical glass described in any one of (1) to (3).

(6) An optical instrument comprising the optical element according to (5).

According to the present invention, it is possible to obtain an optical glass having a low partial dispersion ratio and a small temperature coefficient of relative refractive index while having a refractive index (n _d ) and an Abbe number (ν _d ) within desired ranges. can be done.

FIG. 10 is a diagram showing a normal line represented on an orthogonal coordinate system in which the partial dispersion ratio (θg, F) is on the vertical axis and the Abbe number (ν _d ) is on the horizontal axis. It is a figure which shows the relationship between partial dispersion ratio ((theta)g, F) and Abbe's number ((nu) _d ) about the Example of this application. FIG. 4 is a diagram showing the relationship between refractive index (n _d ) and Abbe number (ν _d ) for Examples of the present application.

The optical glass of the present invention contains 15.0 to 45.0% by mass of SiO ₂ component, 10.0 to 40.0% by 10.0 to 40.0% of Nb ₂ O ₅ component, and 0 Na ₂ O component in terms of mass % of oxide conversion composition. contains more than 20.0%, and the partial dispersion ratio (θg, F) is between the Abbe number (ν _d ), (-0.00162 × ν _d + 0.620) ≤ (θg, F) ≤ ( −0.00162×ν _d +0.657) and has a small temperature coefficient of relative refractive index.
An optical glass containing predetermined amounts of SiO ₂ component and Nb ₂ O ₅ component and containing Na ₂ O and having a high refractive index and Abbe number (high dispersion) within desired ranges and a low partial dispersion ratio. In particular, by containing more than 0 to 20.0% of Na ₂ O, it is possible to reduce the temperature coefficient of the relative refractive index while keeping the partial dispersion ratio (θg, F) small.
Therefore, while having the desired high refractive index (n _d ) and low Abbe number (ν _d ), the partial dispersion ratio (θg, F) is small, which is useful for reducing chromatic aberration of the optical system, and the relative refractive index An optical glass having a small temperature coefficient of is obtained.

Hereinafter, embodiments of the optical glass of the present invention will be described in detail, but the present invention is not limited to the following embodiments at all, and can be carried out with appropriate modifications within the scope of the object of the present invention. . It should be noted that descriptions of overlapping descriptions may be omitted as appropriate, 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 this specification, the content of each component is expressed in % by mass with respect to the total mass of the glass in terms of oxide composition. Here, the term "composition converted to oxide" means that, when it is assumed that oxides, composite salts, metal fluorides, etc. used as raw materials for the constituent components of the glass of the present invention are all decomposed and changed into oxides when melted, It is a composition in which each component contained in the glass is expressed with the total mass of the produced oxide being 100% by mass.

<Regarding essential ingredients and optional ingredients>
The _SiO2 component promotes stable glass formation and can lower the liquidus temperature, so it is an essential component for reducing devitrification (generation of crystals), which is undesirable as optical glass.
In particular, by setting the content of the _SiO2 component to 15.0% or more, a glass having excellent devitrification resistance can be obtained without greatly increasing the partial dispersion ratio. Moreover, devitrification and coloring can be reduced. Therefore, the lower limit of the content of the _SiO2 component is preferably 15.0% or more, more preferably 18.0% or more, more preferably 20.0% or more, still more preferably 25.0% or more.
On the other hand, by setting the content of the SiO ₂ component to 45.0% or less, the refractive index is less likely to decrease, making it easier to obtain a desired high refractive index and suppressing an increase in the partial dispersion ratio. Moreover, this suppresses the deterioration of the meltability of the glass raw material. Therefore, the upper limit of the content of the _SiO2 component is preferably 45.0% or less, more preferably 43.0% or less, still more preferably 41.5% or less, and most preferably 40.0% or less.
_SiO2 component can use _SiO2 , _K2SiF6 , _{Na2SiF6 etc.} as a _raw material.

The Nb ₂ O ₅ component is an essential component capable of increasing the refractive index, lowering the Abbe's number and partial dispersion ratio, and enhancing the resistance to devitrification.
In particular, by increasing the content of the Nb ₂ O ₅ component to 10.0% or more, the refractive index is increased to the target optical constant, and the anomalous dispersion is reduced by adjusting the component within the range of the present invention. can do. Therefore, the lower limit of the content of the Nb ₂ O ₅ component is preferably 10.0% or more, more preferably 12.0% or more, and still more preferably 15.0% or more.
On the other hand, by setting the content of the Nb ₂ O ₅ component to 40.0% or less, the material cost of the glass can be reduced. In addition, it is possible to suppress an increase in the melting temperature during glass production and to reduce devitrification due to an excessive content of the Nb ₂ O ₅ component. Furthermore, deterioration of chemical durability of glass can be improved. Therefore, the upper limit of the content of the Nb ₂ O ₅ component is preferably 40.0%, more preferably 38.0% or less, and still more preferably 35.0% or less.
_{Nb2O5 etc.} can be used as a raw material for the _{Nb2O5 component} .

The TiO ₂ component is an optional component that increases the refractive index, lowers the Abbe number, and increases devitrification resistance when it is contained in an amount exceeding 0%. Therefore, the content of the TiO ₂ component is preferably more than 0%, more preferably more than 1.0%, even more preferably 2.5%.
On the other hand, when the content exceeds 20.0%, it is a component that increases the partial dispersion ratio. Therefore, by setting the content of the TiO ₂ component to 20.0% or less, the coloration of the glass can be reduced and the internal transmittance can be increased. Further, this makes it difficult for the partial dispersion ratio to increase, so that a desired low partial dispersion ratio close to a normal line can be easily obtained. Therefore, the upper limit of the content of the TiO ₂ component is preferably 20.0% or less, more preferably 15.0% or less, more preferably 12.0% or less, and still more preferably less than 10.0%.
The _TiO2 component can use _TiO2 or the like as a raw material.

The K ₂ O component is an optional component that increases the coefficient of thermal expansion and decreases the temperature coefficient of the relative refractive index.
Therefore, the lower limit of the K ₂ O component content is preferably more than 0%, more preferably more than 0.3%, and still more preferably more than 0.5%.
On the other hand, by setting the content of the K ₂ O component to 10.0% or less, an increase in the partial dispersion ratio can be suppressed, and devitrification can be reduced. Therefore, the upper limit of the K ₂ O component content is preferably 10.0% or less, more preferably less than 8.0%, and even more preferably less than 5.0%.
_K2O component can use _{K2CO3 , KNO3} , KF, _{KHF2 , K2SiF6} etc. as a raw material.

When the B ₂ O ₃ component is contained at more than 0%, it can promote stable glass formation and lower the liquidus temperature, so that the devitrification resistance can be improved and the meltability of the glass raw material can be improved. Optional. Therefore, the content of the B ₂ O ₃ component is preferably more than 0%, more preferably more than 0.5%, more preferably more than 1.0%, and even more preferably more than 1.5%. .
On the other hand, by setting the content of the B ₂ O ₃ component to 15.0% or less, it is possible to suppress a decrease in the refractive index and an increase in the partial dispersion ratio. Furthermore, deterioration of the chemical durability of the glass can be improved. Therefore, the upper limit of the content of the B ₂ O ₃ component is preferably 15.0% or less, more preferably 14.0% or less, and still more preferably 12.0% or less.
For the B ₂ O ₃ component, H ₃ BO ₃ , Na ₂ B ₄ O ₇ , Na ₂ B ₄ O _{7.10H 2} O, BPO ₄ and the like can be used as raw materials.

The Li ₂ O component is an optional component that can lower the partial dispersion ratio, improve the transmittance, lower the liquidus temperature, and enhance the meltability of the glass raw material when it is contained in an amount exceeding 0%. Therefore, the lower limit of the content of the Li ₂ O component may be preferably more than 0%, more preferably more than 0.5%, more preferably more than 1.0%, and even more preferably more than 1.5%.
On the other hand, by setting the content of the Li ₂ O component to 15.0% or less, the decrease in refractive index can be suppressed, and devitrification due to excessive content can be reduced.
Therefore, the content of the Li ₂ O component is preferably 15.0% or less, more preferably 10.0% or less, still more preferably less than 8.0%.
Li ₂ CO ₃ , LiNO ₃ , LiF or the like can be used as raw materials for the Li ₂ O component.

The Na ₂ O component is an optional component that can reduce the partial dispersion ratio, increase the coefficient of thermal expansion, and decrease the temperature coefficient of the relative refractive index when the content exceeds 0%. Therefore, the lower limit of the content of the Na ₂ O component may be preferably more than 0%, more preferably more than 0.5%, and even more preferably more than 1.0%.
On the other hand, by setting the content of the Na ₂ O component to 20.0% or less, the decrease in refractive index can be suppressed and devitrification due to excessive content can be reduced.
Therefore, the content of the Na ₂ O component is preferably 20.0% or less, more preferably 19.0% or less, still more preferably less than 18.0%.
_Na2O component can use _{Na2CO3 , NaNO3} , _NaF , _Na2SiF6 etc. as a raw material.

The sum (mass sum) of the content (sum of mass) of the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is the temperature coefficient of the relative refractive index when it contains more than 0 is an optional component that can reduce Therefore, the sum of the Rn ₂ O components is preferably more than 0%, more preferably more than 3.0%, and still more preferably more than 5.0% as the lower limit.
On the other hand, by setting the sum of the contents of the Rn ₂ O components to 30.0% or less, it is possible to increase the viscosity in the glass and improve the formability. Therefore, the upper limit is preferably 30.0% or less, more preferably 28.0% or less, and still more preferably 26.0% or less.

The ZrO ₂ component is an optional component that can increase the refractive index and Abbe number of the glass, decrease the partial dispersion ratio, and increase the devitrification resistance when it is contained in an amount exceeding 0%. Moreover, devitrification and coloring can be reduced. Therefore, the lower limit of the content of the ZrO ₂ component may be preferably more than 0%, more preferably more than 1.0%, more preferably more than 3.0%.
On the other hand, by setting the content of the ZrO ₂ component to 10.0% or less, devitrification can be reduced and more homogeneous glass can be easily obtained. Therefore, the upper limit of the content of the ZrO ₂ component is preferably 10.0% or less, more preferably 9.0% or less, and more preferably 8.5% or less.
For the ZrO ₂ component, ZrO ₂ , ZrF ₄ and the like can be used as raw materials.

The MgO component is an optional component that can lower the melting temperature of the glass when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the MgO component to 10.0% or less, devitrification can be reduced while suppressing a decrease in refractive index. Therefore, the lower limit of the MgO component content is preferably 10.0% or less, more preferably less than 5.0%, and still more preferably less than 3.0%.
For the MgO component, MgO, MgCO ₃ , MgF ₂ or the like can be used as raw materials.

The CaO component is an optional component that can lower the Abbe number, reduce devitrification, and improve the meltability of the glass raw material while reducing the material cost of the glass when it is contained in an amount of more than 0%. Therefore, the lower limit of the CaO component content is preferably more than 0%, more preferably more than 0.3%, and even more preferably more than 0.5%.
On the other hand, by setting the content of the CaO component to 10.0% or less, it is possible to suppress a decrease in refractive index, an increase in Abbe's number, and an increase in partial dispersion ratio, and to reduce devitrification. Therefore, the upper limit of the content of the CaO component is preferably 10.0% or less _{, more} preferably less than 8.0%, and still more preferably less than 6.0%. can be used.

The SrO component is an optional component that can increase the refractive index and the devitrification resistance when contained in an amount exceeding 0%.
In particular, by setting the content of the SrO component to 10.0% or less, deterioration of chemical durability can be suppressed. Therefore, the upper limit of the content of the SrO component is preferably 10.0% or less, more preferably less than 8.0%, still more preferably less than 6.0%, and even more preferably less than 5.0%.
SrO component can use Sr( _NO3 ) ₂ , _SrF2 , etc. as a raw material.

The BaO component is an optional component that increases the refractive index, increases the devitrification resistance, increases the coefficient of thermal expansion, and decreases the temperature coefficient of the relative refractive index when it is contained in an amount of more than 0%. Therefore, the lower limit of the BaO component content is preferably more than 0%, more preferably more than 0.3%, and still more preferably more than 0.5%.
In particular, by setting the content of the BaO component to 10.0% or less, it is possible to suppress a decrease in the refractive index, an increase in the Abbe's number, and an increase in the partial dispersion ratio, and to reduce devitrification. Therefore, the upper limit of the BaO component content is preferably 10.0% or less, more preferably less than 9.0%, more preferably less than 8.5%, and even more preferably less than 8.0%.
BaCO ₃ , Ba(NO ₃ ) ₂ and the like can be used as raw materials for the BaO component.

The ZnO component is an optional component that is inexpensive, can improve devitrification resistance, and lowers the glass transition point when contained in an amount exceeding 0%. Therefore, the content of the ZnO component may be preferably more than 0%, more preferably more than 0.3%, even more preferably more than 0.5%.
On the other hand, by setting the content of the ZnO component to 10.0% or less, devitrification and coloring can be reduced. Therefore, the upper limit of the content of the ZnO component is preferably 10.0% or less, more preferably 8.0% or less, and more preferably less than 5.5%.

At least one of La ₂ O ₃ component, Gd ₂ O ₃ component, Y ₂ O ₃ component and Yb ₂ O ₃ component contains more than 0% to increase the refractive index and reduce the partial dispersion ratio. is an ingredient.
In particular, by setting the content of each of the _three La ₂ O components, the _three Gd ₂ O components, the _three Y ₂ O components, and the _three Yb ₂ O components to 10.0% or less, an increase in the Abbe number can be suppressed, Permeation can be reduced, and material costs can be reduced. Therefore, the content of each of the _three La ₂ O components, the _three Gd ₂ O components, the _three Y ₂ O components and the _three Yb ₂ O components is preferably 10.0% or less, more preferably 8.0% or less, and further preferably The upper limit is preferably less than 7.0%.
La ₂ O ₃ component, Gd ₂ O ₃ component, Y ₂ O ₃ component and Yb ₂ O ₃ component are La ₂ O ₃ , La(NO ₃ ) ₃ ·XH ₂ O (X is an arbitrary integer) as raw materials, Y ₂ O ₃ , YF ₃ , Gd ₂ O ₃ , GdF ₃ , Yb ₂ O ₃ and the like can be used.

The Ta ₂ O ₅ component is an optional component that can increase the refractive index, decrease the Abbe number and the partial dispersion ratio, and increase the devitrification resistance when it is contained in an amount exceeding 0%.
On the other hand, by setting 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, can be reduced and the glass can be easily melted at a lower temperature. The production cost of glass can be reduced. In addition, devitrification of the glass due to the excessive content of the Ta ₂ O ₅ component can thereby be reduced. Therefore, the content of the Ta ₂ O ₅ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, and still more preferably less than 1.0%. . Especially from the viewpoint of reducing the material cost of the glass, the Ta ₂ O ₅ component may not be contained.
For the Ta ₂ O ₅ component, Ta ₂ O ₅ or the like can be used as a raw material.

The WO ₃ component is an optional component that can increase the refractive index, lower the Abbe's number, improve devitrification resistance, and improve the meltability of the glass raw material when contained in an amount exceeding 0%.
_On the other hand, by setting the content of the WO3 component to 10.0% or less, it is possible to make it difficult to increase the partial dispersion ratio of the glass, and to reduce the coloration of the glass to increase the internal transmittance. Therefore, the upper limit of the content of the _three WO components is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, and even more preferably less than 1.0%.
_WO3 etc. can be used as a raw material for the _WO3 component.

The P ₂ O ₅ component is an optional component that can improve the stability of the glass when it is contained in an amount exceeding 0%.
On the other hand, by setting the content of the P ₂ O ₅ component to 10.0% or less, it is possible to reduce devitrification due to an excessive content of the P ₂ O ₅ component. Therefore, the content of the P ₂ O ₅ component is preferably 10.0% or less, more preferably less than 5.0%, even more preferably less than 3.0%.
Al(PO3) ₃ , Ca _{( PO3)2, Ba(PO3)2 , BPO4 , H3PO4 , etc. can be} used as raw materials for the P2O5 component.

The GeO ₂ component is an optional component that can increase the refractive index and reduce devitrification when the content exceeds 0%.
On the other hand, by setting the content of the GeO ₂ component to 10.0% or less, the usage amount of the expensive GeO ₂ component is 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 less than 5.0%, and even more preferably less than 3.0%.
The _GeO2 component can use _GeO2 or the like as a raw material.

The Al ₂ O ₃ component and the Ga ₂ O ₃ component are optional components capable of increasing the refractive index and improving the devitrification resistance when at least one of them is contained in an amount exceeding 0%.
On the other hand, by setting the content of each of the Al ₂ O ₃ component and the Ga ₂ O ₃ component to 10.0% or less, the devitrification due to the excessive content of the Al ₂ O ₃ component and the Ga ₂ O ₃ component is reduced. can. Therefore, the content of each of the Al ₂ O ₃ component and the Ga ₂ O ₃ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%.
_{Al2O3 ,} Al ₍ OH) ₃ , _{AlF3 , Ga2O3} , Ga ₍ OH) _{3 ,} etc. can be used as raw materials for the _Al2O3 component and the Ga2O3 component.

The Bi ₂ O ₃ component is an optional component that can increase the refractive index, lower the Abbe number, and lower the glass transition point when contained in an amount exceeding 0%.
On the other hand, 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 to reduce the coloration of the glass to increase the internal transmittance. Therefore, the content of the Bi ₂ O ₃ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, and even more preferably less than 1.0%.
_{Bi2O3 etc.} can be used as a _raw material for the _Bi2O3 component.

The TeO ₂ component is an optional component that can increase the refractive index, lower the partial dispersion ratio, and lower the glass transition point when contained in an amount exceeding 0%.
On the other hand, by setting the content of the TeO ₂ component to 5.0% or less, it is possible to reduce the coloration of the glass and increase the internal transmittance. Also, by reducing the use of the expensive TeO ₂ component, it is possible to obtain a glass with a lower material cost. Therefore, the content of the TeO ₂ component is preferably 5.0% or less, more preferably less than 3.0%, further preferably less than 1.0%.
_The TeO2 component can use _TeO2 or the like as a raw material.

The SnO ₂ component is an optional component capable of refining (defoaming) the molten glass and increasing the visible light transmittance of the glass when it is contained in an amount exceeding 0%.
On the other hand, by setting the SnO ₂ component content to 1.0% or less, it is possible to make it difficult for the glass to be colored due to reduction of the molten glass and devitrification of the glass to occur. In addition, since alloying of SnO ₂ components and melting equipment (especially precious metals such as Pt) is reduced, the service life of the melting equipment can be extended. Therefore, the SnO ₂ component content is preferably 1.0% or less, more preferably less than 0.5%, and even more preferably less than 0.1%.
SnO ₂ component can use SnO, SnO ₂ , SnF ₂ , SnF ₄ etc. as raw materials.

The Sb ₂ O ₃ component is a component that promotes defoaming of the glass and clarifies the glass when it is contained in an amount exceeding 0%, 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 with respect to the total mass of the glass, it is possible to make it difficult for excessive foaming to occur during glass melting, and the Sb ₂ O ₃ component is used in the melting equipment (especially Pt (e.g., noble metals) can be made difficult to alloy with. Therefore, the upper limit of the content of the Sb ₂ O ₃ component with respect to the total mass of the glass in terms of oxide composition is preferably 1.0% or less, more preferably 0.8% or less, and still more preferably 0.6% or less. .
For the Sb ₂ O ₃ component, Sb ₂ O ₃ , Sb ₂ O ₅ , Na ₂ H _{2 Sb 2} O _7.5 H ₂ O, etc. can be used as raw materials.

The component for refining and defoaming the glass is not limited to the above Sb ₂ O ₃ component, and a known refining agent or defoaming agent in the field of glass production, or a combination thereof can be used. .

The mass sum of ZrO ₂ and Li ₂ O is preferably 5.0% or more. Thereby, a glass with a small partial dispersion ratio can be obtained. Therefore, the lower limit of the mass sum (ZrO ₂ +Li ₂ O) is 5.0% or more, preferably 7.0% or more, and still more preferably 8.0% or more.
On the other hand, the mass sum (ZrO ₂ +Li ₂ O) is preferably 20.0% or less. Thereby, devitrification due to excessive content can be reduced, and devitrification during reheat press can be suppressed. Therefore, it is preferably 20.0% or less, more preferably 18.0% or less, still more preferably 16.0% or less.

The mass sum of ZrO ₂ and Nb ₂ O ₅ is preferably 18.0% or more. Thereby, a glass having a small partial dispersion ratio and a high transmittance can be obtained. Therefore, the mass sum ZrO ₂ +Nb ₂ O ₅ is preferably 18.0% or more, more preferably 19.0% or more, and still more preferably 21.1% or more as the lower limit.
On the other hand, the mass sum of ZrO ₂ +Nb ₂ O ₅ is preferably 45.0% or less. Thereby, devitrification due to excessive content can be reduced, and devitrification during reheat press can be suppressed. Therefore, it is preferably 45.0% or less, more preferably 44.0% or less, more preferably 43.0% or less, and even more preferably 42.0% or less.

The desired refractive index and dispersion can be obtained when the ratio of BaO to the mass sum of MgO, CaO, SrO, BaO is greater than zero. Therefore, the mass ratio BaO/(MgO+CaO+SrO+BaO) is preferably greater than 0, more preferably 0.05 or more, and even more preferably 0.09 or more.
On the other hand, the mass ratio BaO/(MgO+CaO+SrO+BaO) is preferably 0.90 or less. Thereby, a glass having a small partial dispersion ratio and a light specific gravity can be obtained.
Therefore, it is preferably 0.90 or less, more preferably 0.85 or less, and still more preferably 0.80 or less.

The ratio of Li ₂ O to the mass sum of Li ₂ O, Na ₂ O and K ₂ O is preferably 0.01 or more. Thereby, a glass with a small partial dispersion ratio can be obtained. Therefore, the mass ratio Li ₂ O/(Li ₂ O+Na ₂ O+K ₂ O) is preferably 0.01 or more, more preferably 0.02 or more, still more preferably 0.03 or more.
On the other hand, the ratio of Li ₂ O to the mass sum of Li ₂ O, Na ₂ O and K ₂ O is preferably 1.00 or less. This makes it possible to obtain a glass that does not become too low in viscosity and that is easy to mold. Therefore, it is preferably 1.00 or less, more preferably 0.90 or less, still more preferably 0.70 or less.

If the total content (mass sum) of the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) exceeds 0%, the desired refractive index and dispersion can be adjusted. Therefore, the lower limit of the RO component content is preferably more than 0%, more preferably more than 0.5%, and even more preferably more than 1.5%.
On the other hand, the total content of RO components is preferably less than 15.0%. This suppresses a decrease in the refractive index of the glass and a decrease in devitrification resistance due to excessive inclusion of the RO component. Therefore, the upper limit of the mass sum of RO components is preferably less than 15.0%, more preferably 14.0% or less, and even more preferably 13.0% or less.

The total content (mass sum) of the _three Ln ₂ O components (wherein Ln is one or more selected from the group consisting of La, Gd, Y and Yb) is preferably less than 10.0%. As a result, it is possible to suppress the decrease in the refractive index and devitrification resistance of the glass due to the excessive content of the Ln ₂ O ₃ component. Therefore, the mass sum of the Ln ₂ O ₃ components is preferably less than 10.0%, more preferably 8.5% or less, and still more preferably 7.0% or less as the upper limit.

<Ingredients that should not be contained>
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 necessary within a range that does not impair the properties 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 Or even if it is combined and contained in a small amount, the glass is colored and has the property of causing absorption at a specific wavelength in the visible region. .

In addition, since lead compounds such as PbO and arsenic compounds such as As ₂ O ₃ are components with 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, Th, Cd, Tl, Os, Be, and Se components have recently tended to refrain from being used as harmful chemical substances, and are not only used in the glass manufacturing process, but also in the processing process and disposal after manufacturing. Environmental measures are required up to the present. Therefore, it is preferable not to contain these substantially when environmental influence is emphasized.

[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. , Put it in a platinum alloy crucible or an iridium crucible and melt it for 3 to 5 hours at a temperature range of 1000 to 1400 ° C. After homogenizing with stirring and removing bubbles, etc., lower the temperature to 900 to 1200 ° C. and finish stirring. to remove striae, cast in a mold, and slowly cool.

<Physical properties>
The optical glass of the present invention has a high refractive index and an Abbe number within a predetermined range.
The lower limit of the refractive index (n _d ) of the optical glass of the present invention is preferably 1.65 or more, more preferably 1.67 or more, and still more preferably 1.68 or more. The upper limit of the refractive index is preferably 1.80 or less, more preferably 1.79 or less, and more preferably 1.78 or less.
The lower limit of the Abbe number (ν _d ) of the optical glass of the present invention is preferably 25.0, more preferably 27.0, and still more preferably 29.0. On the other hand, the upper limit of the Abbe number (ν _d ) of the optical glass of the present invention is preferably 40.0, more preferably 39.0, and still more preferably 38.0.
The optical glass of the present invention having such a refractive index and Abbe number is useful in optical design. You can extend the degree.

Here, the optical glass of the present invention has a refractive index (n _d ) and an Abbe number (ν _d ) of (−0.01×ν _d +2.01)≦n _d ≦(−0.01×ν _d +2). .12) is preferably satisfied. Even if the refractive index (n _d ) and Abbe number (ν _d ) satisfy this relationship, the glass having the composition specified in the present invention can be obtained as a stable glass.
Therefore, in the optical glass of the present invention, the refractive index (n _d ) and Abbe number (ν _d ) preferably satisfy the relationship n _d ≧(−0.01×ν _d +2.01), and n _d ≧ More preferably, the relationship (−0.01×ν _d +2.03) is satisfied.
On the other hand, in the optical glass of the present invention, the refractive index (n) and the Abbe number (ν _d ) preferably satisfy the relationship n _d ≦ (−0.01×ν _d +2.12) _. It is more preferable to satisfy the relationship of (-0.01×ν _d +2.11).

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 and the Abbe number (ν _d ) satisfy (−0.00162×ν _d +0.620)≦(θg, F )≦(−0.00162×ν _d +0.657).
Therefore, in the optical glass of the present invention, the partial dispersion ratio (θg, F) and the Abbe number (ν _d ) preferably satisfy the relationship θg, F≧(−0.00162×ν _d +0.620). More preferably, the relationship θg,F≧(−0.00162×ν _d +0.630) is satisfied.
On the other hand, in the optical glass of the present invention, the partial dispersion ratio (θg, F) and the Abbe number (ν _d ) preferably satisfy the relationship θg, F≦(−0.00162×ν _d +0.657). , θg,F≦(−0.00162×ν _d +0.650).
As a result, an optical glass having a low partial dispersion ratio (θg, F) can be obtained, and an optical element formed from this optical glass can be used to reduce chromatic aberration in an optical system.

In a region where the Abbe number (ν _d ) is particularly small, the partial dispersion ratio (θg, F) of general glass is higher than that of the normal line _. When the partial dispersion ratio (θg, F) is taken, the relationship between the partial dispersion ratio (θg, F) of general glass and the Abbe number (ν _d ) is represented by a curve with a steeper slope than the normal line. . In the relational expressions of the partial dispersion ratio (θg, F) and the Abbe number (ν _d ) described above, a straight line with a larger slope than the normal line is used to define these relationships, so that the partial dispersion is greater than that of ordinary glass. This indicates that a glass with a small ratio (θg, F) can be obtained.

The optical glass of the present invention has a low temperature coefficient of relative refractive index (dn/dT).
More specifically, the temperature coefficient of the relative refractive index of the optical glass of the present invention is preferably +6.0×10 ⁻⁶ ° C. ⁻¹ , more preferably +5.5×10 ⁻⁶ ° C. ⁻¹ , further preferably +5.0×10 ⁻⁶ ° C. ⁻¹ is the upper limit, and this upper limit or lower (negative side) values can be taken.
On the other hand, the temperature coefficient of the relative refractive index of the optical glass of the present invention is preferably −2.0×10 ⁻⁶ ° C. ⁻¹ , more preferably −1.0×10 ⁻⁶ ° C. ⁻¹ , further preferably − The lower limit is set to 0.5×10 ⁻⁶ ° C. ⁻¹ , and this lower limit or higher (plus side) values can be taken.
Among these glasses, there are many glasses having a refractive index (n _d ) of 1.65 or more and an Abbe number (ν _d ) of 20 or more and 35 or less and having a low temperature coefficient of relative refractive index. However, the options for correction of image formation deviation due to temperature change can be expanded, and the correction can be made easier. Therefore, by setting the temperature coefficient of the relative refractive index within such a range, it is possible to contribute to the correction of image formation deviation due to temperature change.
The temperature coefficient of the relative refractive index of the optical glass of the present invention is the temperature coefficient of the refractive index (589.29 nm) in air at the same temperature as the optical glass. is expressed as the amount of change per 1°C (°C ^-1 ).

The optical glass of the present invention preferably has an average linear thermal expansion coefficient α of 75 (10 ^-7 ° C. ^-1 ) or more at 100 to 300°C. That is, the average linear thermal expansion coefficient α at 100 to 300° C. of the optical glass of the present invention is preferably 75 (10 ⁻⁷ ° C. ⁻¹ ) or more, more preferably 80 (10 ⁻⁷ ° C. ⁻¹ ) or more, and more preferably has a lower limit of 85 (10 ^-7 ° C. ^-1 ) or more.
In general, when the average coefficient of linear thermal expansion α is large, cracks are likely to occur during processing of the glass, so it is desirable that the average coefficient of linear thermal expansion α is small. On the other hand, from the viewpoint of bonding in combination with a glass material having a low temperature coefficient of relative refractive index and a large average linear thermal expansion coefficient α, the value of the average linear thermal expansion coefficient α is the same as or similar to that of the glass material. is desirable.
Among these, in glasses having a refractive index (n _d ) of 1.65 or more and an Abbe number (ν _d ) of 25 or more and 40 or less, there are few glass materials having a large average linear thermal expansion coefficient α, and a low refractive index When used in combination with a low-dispersion glass material, it is useful to have a large average linear thermal expansion coefficient α as in the present invention.

[Preform and optical element]
A molded glass body can be produced from the produced optical glass by means of mold press molding such as reheat press molding and precision press molding. That is, a preform for mold press molding is produced from optical glass, and the preform is subjected to reheat press molding and then polished to produce a glass molded body, or for example, produced by polishing. A glass molding can be produced by performing precision press molding on the preform obtained. In addition, 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, and it is particularly preferable to use it for optical elements such as lenses and prisms. This reduces color fringing due to chromatic aberration in the light transmitted through the optical system in which the optical element is provided. Therefore, when this optical element is used in a camera, the object to be photographed can be represented 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 to No. 13) of the present invention and comparative examples, refractive index (n _d ), Abbe number (ν _d ), partial dispersion ratio (θg, F), average linear thermal expansion coefficient (100-300° C.) and the temperature coefficient of the relative refractive index (dn/dT) of the glass are shown in Tables 1 and 2. It should be noted that the following examples are for the purpose of illustration only, and the present invention is not limited only to these examples.

The glasses of Examples and Comparative Examples each contain oxides, hydroxides, carbonates, nitrates, fluorides, metaphosphoric acid compounds, etc., of high purity used in ordinary optical glasses as raw materials for each component. Raw materials were selected, weighed so that the composition ratio of each example and comparative example shown in the table was obtained, and mixed uniformly. ), melt in an electric furnace at a temperature range of 1100 to 1400 ° C for 0.5 to 5 hours depending on the melting difficulty of the glass composition, transfer to a platinum crucible, stir and homogenize to remove bubbles, etc. After the temperature was lowered to 1000 to 1200° C., the mixture was stirred and homogenized, cast into a mold, and slowly cooled to produce glass.

The refractive index (n _d ), Abbe number (ν _d ) and partial dispersion ratio (θg, F) of the glasses of Examples and Comparative Examples were measured according to the Japan Optical Glass Industry Association Standard JOGIS01-2003.

The temperature coefficient of the relative refractive index (dn/dT) of the glass of Examples and Comparative Examples was determined by the method described in the Japan Optical Glass Industry Association Standard JOGIS18-2008 "Method for measuring temperature coefficient of refractive index of optical glass". The value of the temperature coefficient of relative refractive index was measured at 40-60° C. for light with a wavelength of 589.29 nm by interferometry.

In addition, the average linear thermal expansion coefficient (100-300°C) of the glasses of Examples and Comparative Examples was measured according to the temperature and elongation of the sample according to the Japan Optical Glass Industry Standard JOGIS08-2003 "Method for measuring thermal expansion of optical glass". It was obtained from the thermal expansion curve obtained by measuring the relationship between

The optical glasses of Examples of the present invention all have a refractive index (n _d ) of 1.65 or more, more specifically 1.67 or more, and this refractive index (n _d ) of 1.80 or less. , was within the desired range.
Further, the optical glasses of the examples of the present invention all have an Abbe number (ν _d ) of 25 or more, more specifically 29 or more, and this Abbe number (ν _d ) is 40 or less, which is within a desired range. was inside.

As shown in these tables, the optical glasses of the examples of the present invention have a partial dispersion ratio (θg, F) and an Abbe number (ν _d ) of (−0.00162×ν _d +0.620)≦(θg, F )≦(−0.00162×ν _d +0.657), more specifically, (−0.00162×νd+0.650)≦(θg, F)≦(−0.00162×ν _d +0.630). That is, the relationship between the partial dispersion ratio (θg, F) and the Abbe number (ν _d ) for the glasses of the examples of the present application is shown in FIG.
On the other hand, the optical glass of the comparative example did not satisfy the relationship of (−0.00162×ν _d +0.620)≦(θg, F)≦(−0.00162×ν _d +0.657).

In addition, the optical glass of the example of the present invention has a refractive index (n _d ) and an Abbe number (ν _d ) of (−0.01×ν _d +2.01)≦n _d ≦(−0.01× ν _d +2.12), more specifically, (−0.01×ν _d +2.03)≦n _d ≦(−0.01×ν _d +2.11). rice field. That is, the relationship between the refractive index (n _d ) and the Abbe number (ν _d ) for the glasses of the examples of the present application is shown in FIG.

As shown in the table, all the optical glasses of Examples have a temperature coefficient of relative refractive index within the range of +6.0×10 ⁻⁶ to −0.5×10 ⁻⁶ (° C. ⁻¹ ). , was within the desired range.

In addition, the optical glass of the present invention had an average linear thermal expansion coefficient α of 80 (10 ^-7 ° C. ^-1 ) or more at 100 to 300 °C.

Furthermore, using the optical glass of the example of the present invention, a glass block was formed, and this glass block was ground and polished to be processed into the shapes of lenses and prisms. As a result, it was possible to stably process various lens and prism shapes.

Although the invention has been described in detail for purposes of illustration, the examples are for illustration only and many modifications may be made by those skilled in the art without departing from the spirit and scope of the invention. be understood.

Claims (6)

in % by mass,
_SiO2 component 20.0-43.0 %
Nb ₂ O ₅ component 10.0-38.0 %
Na ₂ O component more than 0 to 20.0%
Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na and K)
The sum of the contents (mass sum) of 20.79 % or more,
Mass sum (ZrO ₂ +Li ₂ O) of 5.0 to 10.34 % (however, the ZrO ₂ component contains more than 0%)
Containing a mass ratio (BaO / MgO + CaO + SrO + BaO) of 0.90 or less,
Between the partial dispersion ratio (θg, F) and the Abbe number (ν _d ),
(−0.00162×ν _d +0.620)≦(θg, F)≦(−0.00162×ν _d +0.657), and the temperature coefficient of the relative refractive index (589.29 nm) (40 to 60° C.) is in the range of +6.0×10 ⁻⁶ to −5.0×10 ⁻⁶ (° C. ⁻¹ ). _2. The optical glass according to claim 1, wherein the mass ratio (Li2O/Li2O _{+ Na2O +} K2O) is 1.00 or less. 1. The refractive index (n _d ) and the Abbe number (ν _d ) satisfy the relationship of (−0.01×ν _d +2.01)≦n _d ≦(−0.01×ν _d +2.12). 3. The optical glass according to 2 above. A preform material comprising the optical glass according to any one of claims 1 to 3. An optical element comprising the optical glass according to any one of claims 1 to 3. An optical instrument comprising the optical element according to claim 5 .

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