TWI765099B - Optical Glass, Preforms, and Optical Components - Google Patents

Abstract

(θ_g，F)

(-0.00162×ν_d+0.657)之關係，相對折射率(589.29nm)之溫度係數(40℃至60℃)在+6.0×10^-6(℃^-1)至-5.0×10^-6(℃^-1)之範圍內。 The subject of the present invention is to obtain an optical glass, a preform, and an optical element, the refractive index (n _d ) and the Abbe number (ν _d ) of the optical glass are within expected ranges, and the partial dispersion ratio (θ _g , F) is smaller. The optical glass contains 20.0% to 45.0% of SiO ₂ component, 25.0% to 60.0% of Nb ₂ O ₅ component, 0% to 5.0% of TiO ₂ component in mass %, and a mass ratio (Li ₂ O/Na ₂ O+K ₂ O) is 0.40 to 1.00, the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) satisfy (-0.00162×ν _d +0.620)

(θ _g , F)

(-0.00162×ν _d +0.657), the temperature coefficient (40°C to 60°C) of the relative refractive index (589.29nm) ranges from +6.0×10 ^-6 (°C ^-1 ) to -5.0×10 ^-6 (°C ^-1 ) within the range.

Description

Optical Glass, Preforms, and Optical Components

The present invention relates to an optical glass, a preform and an optical element.

Optical systems such as digital cameras or video cameras contain more or less color bleeding called aberrations. The aberrations are classified into monochromatic aberrations and chromatic aberrations, and chromatic aberrations in particular depend largely on the material properties of the lenses used in the optical system.

Generally speaking, chromatic aberration is corrected by a combination of a low-dispersion convex lens and a high-dispersion concave lens. However, this combination can only correct the aberrations in the red and green areas, and the aberrations in the blue area still exist. This aberration that cannot remove the clean blue region is called the secondary spectrum. When correcting the secondary spectrum, it is necessary to carry out an optical design that takes into account the g-line (435.835nm) movement in the blue region. At this time, the partial dispersion ratio (θ _g , F) is used as an optical characteristic index that is important in optical design. In the optical system composed of the above-mentioned low-dispersion lens and high-dispersion lens, the lens on the low-dispersion side uses an optical material with a larger partial dispersion ratio (θ _g , F), and the lens on the high-dispersion side uses partial dispersion For optical materials smaller than (θ _g , F), the secondary spectrum will be well corrected.

The partial dispersion ratio (θ _g , F) can be represented by the following formula (1).

θ _g , F=(n _g -n _F )/(n _F -n _C )‧‧‧‧‧‧(1)

In optical glass, there is a nearly linear relationship between the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ), which represent the partial dispersion in the short wavelength region. The straight line representing this relationship is drawn on the rectangular coordinates with the partial dispersion ratio (θ _g , F) as the vertical axis and the Abbe number (ν _d ) as the horizontal axis. A straight line connecting two points is represented, and this straight line is called a normal line (see FIG. 1 ). Although the standard glass that is a regular line standard varies with optical glass manufacturers, almost all manufacturers define it with the same inclination and intercept. (NSL7 and PBM2 are optical glasses manufactured by Ohara Co., Ltd. PBM2 has an Abbe number (ν _d ) of 36.3, a partial dispersion ratio (θ _g , F) of 0.5828, and NSL7 has an Abbe number (ν _d ) of 60.5 and a partial dispersion ratio (ν d ) of 0.5828. The dispersion ratio (θ _g , F) is 0.5436.)

In recent years, glass having an Abbe number (ν _d ) of 25 or more and 40 or less has been used as an optical material with a small partial dispersion ratio (θ _g , F) due to the needs of optical design.

In addition, in recent years, optical elements assembled in automotive optical instruments such as car cameras, or optical elements assembled in optical instruments such as projectors, photocopiers, laser printers, and playback machines that generate a lot of heat have been used in more Conditions in high temperature environments continue to increase. In such a high temperature environment, the temperature of the optical elements constituting the optical system is likely to fluctuate greatly during use, and it often occurs that the temperature reaches 100°C or higher. In this case, the adverse effects on the imaging characteristics of the optical system due to temperature fluctuations are too great to be ignored. Therefore, it is desirable to configure an optical system that is less likely to affect imaging characteristics and the like even if temperature fluctuations occur.

When configuring an optical system that is unlikely to be affected by temperature fluctuations on imaging characteristics, etc., an optical element composed of glass whose refractive index decreases as the temperature rises and has a negative temperature coefficient of the relative refractive index, is different from an optical element made of glass whose temperature increases as the temperature increases. When the refractive index is high and the temperature coefficient of the relative refractive index is used together with an optical element made of glass, it is preferable to compensate for the influence of the temperature change on the imaging characteristics and the like.

On the other hand, in an optical material with a small partial dispersion ratio (θ _g , F), components (such as Nb ₂ O ₅ component, La ₂ O ₃ component, etc.) are contained in order to obtain various excellent optical properties. , the temperature coefficient of the relative refractive index tends to increase. As such an optical glass, the glass composition shown in patent document 1 is known, for example.

In particular, in-vehicle lenses and interchangeable lenses, which have been used in recent years, are increasingly used in various environments. Therefore, there is a need for a lens with a small partial dispersion ratio (θ _g , F) and a relatively small temperature coefficient of refractive index. Optical glass.

[Prior Art Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 58-125637.

However, the glass disclosed in Patent Document 1 has a small content of the Nb ₂ O ₅ component and a large amount of TiO ₂ , which reduces the partial dispersion ratio, so it is not sufficient for use as a lens for correcting the secondary spectrum. Furthermore, it cannot be said that the smaller the content of the alkali metal, the smaller the temperature coefficient of the relative refractive index.

The present invention is made in view of the above-mentioned problems, and its object is to obtain an optical glass whose refractive index (n _d ) and Abbe number (ν _d ) are within expected ranges, and a partial dispersion ratio (θ) of the optical glass is obtained. _g , F) are small, and the temperature coefficient of the relative refractive index is small.

In order to solve the above-mentioned problems, the present inventors have concentrated on the results of accumulation experiments and found that, in glass containing SiO ₂ components and Nb ₂ O ₅ components, by limiting the amount of TiO ₂ components to 5.0% or less, it is possible to obtain products having The present invention has been completed by an optical glass having a high refractive index and Abbe number (high dispersion) within the expected range, a low partial dispersion ratio, and a relatively small temperature coefficient of the relative refractive index.

(θ_g，F)

(-0.00162×ν_d+0.657)之關係，相對折射率(589.29nm)的溫度係數(40℃至60℃)在+6.0×10^-6(℃^-1)至-5.0×10^-6(℃^-1)的範圍內。 (1): An optical glass containing, in mass %, 20.0% to 45.0% of SiO ₂ component, 25.0% to 60.0% of Nb ₂ O ₅ component, 0% to 5.0% of TiO ₂ component, and a mass ratio (Li ₂ O/ Na ₂ O+K ₂ O) is 0.40 to 1.00, and the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) satisfy (−0.00162×ν _d +0.620)

(θ _g , F)

(-0.00162×ν _d +0.657), the temperature coefficient (40°C to 60°C) of the relative refractive index (589.29nm) ranges from +6.0×10 ^-6 (°C ^-1 ) to -5.0×10 ^-6 (°C ^-1 ) range.

(2): The optical glass according to (1), wherein the mass ratio (Rn ₂ O/Nb ₂ O ₅ ) is 0.50 or less, and Rn in the formula is one selected from the group consisting of Li, Na, and K. above.

n_d

(-0.01×ν_d+2.13)之關係。 (3): The optical glass described in (1) or (2), the refractive index (n _d ) and the Abbe number (ν _d ) satisfy (-0.01×ν _d +2.03)

n _d

(-0.01×ν _d +2.13).

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

(5): An optical element comprising the optical glass according to any one of (1) to (3).

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

According to the present invention, it is possible to obtain an optical glass whose refractive index (n _d ) and Abbe number (ν _d ) are within the expected ranges, the partial dispersion is relatively low, and the temperature coefficient of the relative refractive index is relatively small .

1 is a schematic diagram of a normal line represented by a rectangular coordinate with the partial dispersion ratio (θ _g , F) as the vertical axis and the Abbe number (ν _d ) as the horizontal axis; FIG. 2 shows the partial dispersion ratio of an embodiment of the present invention A schematic diagram of the relationship between (θ _g , F) and the Abbe number (ν _d ); FIG. 3 is a schematic diagram showing the relationship between the refractive index (n _d ) and the Abbe number (ν _d ) of the embodiment of the present invention.

(θ_g，F)

(-0.00162×ν_d+0.657)之關係，相對折射率的溫度係數較小。 The optical glass of the present invention is characterized by containing 20.0% to 45.0% of SiO ₂ component, 25.0% to 60.0% of Nb ₂ O ₅ component, 0% to 5.0% of TiO ₂ component, in terms of mass % of oxide conversion composition, The mass ratio (Li ₂ O/Na ₂ O+K ₂ O) is 0.40 to 1.00, and the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) satisfy (-0.00162×ν _d +0.620)

(θ _g , F)

(-0.00162×ν _d +0.657), the temperature coefficient of the relative refractive index is small.

Optical glass containing a predetermined amount of SiO ₂ component, Nb ₂ O ₅ component and 5.0% or less of TiO ₂ component can obtain a high refractive index and Abbe number (high dispersion) within the expected range, and a low partial dispersion ratio. Glass. In particular, by keeping the content of TiO ₂ at 5.0% or less, the temperature coefficient of the relative refractive index can be reduced while the partial dispersion ratio (θ _g , F) is kept small.

Therefore, it is possible to obtain the desired high refractive index (n _d ) and low Abbe number (ν _d ), and at the same time, the partial dispersion ratio (θ _g , F) is small, which is beneficial to reduce the chromatic aberration of the optical system, And optical glass with a relatively small temperature coefficient of refractive index.

Hereinafter, 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 implemented with appropriate changes within the scope of the object of the present invention. In addition, although the description of the part which repeated description may be abbreviate|omitted suitably, it does not limit the meaning of invention by this.

[glass composition]

The composition range of each component which comprises the optical glass of this invention is as follows. In this specification, unless otherwise specified, the content of each component is represented by mass % with respect to the total mass of the glass of the oxide-converted composition. Here, the "composition in terms of oxides" means that when all the oxides, complex salts, metal fluorides, etc. used as the raw materials for the glass constituents of the present invention are decomposed into oxides at the time of melting, the resulting oxidation The composition of the various components contained in the glass is represented by the total mass of the material as 100% by mass.

<About essential ingredients and optional ingredients>

The _SiO2 component is an essential component that promotes stability of glass formation, lowers the liquidus temperature, and reduces undesired devitrification (generation of crystals) in optical glass.

In particular, by setting the content of the SiO ₂ component to be 20.0% or more, a glass excellent in devitrification resistance can be obtained without greatly increasing the partial dispersion ratio. In addition, devitrification and coloring can be reduced. Therefore, the content of the SiO ₂ component is preferably 20.0% or more, preferably 23.0% or more, and more preferably 25.0% or more.

On the other hand, by setting the content of the SiO ₂ component to be 45.0% or less, the refractive index is less likely to be lowered, the desired high refractive index can be easily obtained, and an increase in the partial dispersion ratio can be suppressed. Moreover, the fall of the meltability of glass raw material can also be suppressed by this. Therefore, the content of the SiO ₂ component is preferably 45.0% or less, preferably 43.0% or less, more preferably 41.5% or less, and most preferably 40.0% or less.

For the SiO ₂ component system, SiO ₂ , K ₂ SiF ₆ , Na ₂ SiF ₆ or the like can be used as raw materials.

The Nb ₂ O ₅ component is an essential component, which can increase the refractive index, reduce the Abbe number and the partial dispersion ratio, and can improve the devitrification resistance.

In particular, anomalous dispersion can be reduced by adjusting the content of the Nb ₂ O ₅ component to 25.0% or more and adjusting within the range of the present invention to increase the refractive index until the target optical constant is reached. Therefore, the content of the Nb ₂ O ₅ component is preferably 25.0% or more, preferably 30.0% or more, and more preferably 35.5% or more.

_On the other hand, by making content of a _Nb2O5 component 60.0% or less, the cost of a glass material can be reduced. In addition, it is possible to suppress a rise in melting temperature during glass production, and to reduce devitrification due to excessive Nb ₂ O ₅ content. In addition, the deterioration of chemical durability of the glass can also be improved. Therefore, the content of the Nb ₂ O ₅ component is preferably 60.0% or less, preferably 55.0% or less, more preferably 50.0% or less, and more preferably 48.0% or less.

For the Nb ₂ O ₅ component system, Nb ₂ O ₅ or the like can be used as a raw material.

The TiO ₂ component is an arbitrary component, and when the content thereof exceeds 0%, the refractive index can be increased, the Abbe number can be decreased, and the devitrification resistance can be improved. On the other hand, if the content is too large, the partial dispersion ratio becomes large.

Therefore, by making content of a _TiO2 component 5.0 % or less, the coloring of glass can be reduced and internal transmittance can be improved. In addition, this makes it difficult to increase the partial dispersion ratio, and it is easy to obtain a low partial dispersion ratio close to the normal line, that is, as expected. Therefore, the content of the TiO ₂ component is preferably 5.0% or less, preferably 4.8% or less, and more preferably less than 4.5%.

_TiO2 component system can use _TiO2 etc. as a raw material.

The K ₂ O component is an arbitrary component, and when the content thereof exceeds 0%, the thermal expansion coefficient can be increased, and the temperature coefficient of the relative refractive index can be decreased.

Therefore, the content of the K ₂ O component is preferably more than 0%, preferably more than 0.3%, and most preferably more than 0.5%.

On the other hand, by setting the content of the K ₂ O component to 10.0% or less, it is possible to suppress an increase in the partial dispersion ratio and reduce devitrification. Therefore, the content of the K ₂ O component is preferably 10.0% or less, preferably less than 8.0%, more preferably less than 5.0%.

As a K ₂ O component, K ₂ CO ₃ , KNO ₃ , KF, KHF ₂ , K ₂ SiF ₆ or the like can be used as a raw material.

The B ₂ O ₃ component is an optional component, and when the content thereof exceeds 0%, stability of glass formation is promoted, and the liquidus temperature can be lowered, so that the devitrification resistance can be improved, and the meltability of the glass raw material can be improved. Therefore, the content of the B ₂ O ₃ component may be preferably more than 0%, preferably more than 0.3%, and more preferably more than 0.5%.

On the other hand, by setting the content of the B ₂ O ₃ component to 7.0% or less, the decrease in the refractive index can be suppressed, the increase in the partial dispersion ratio can be suppressed, and the deterioration of the chemical durability of the glass can be improved. Therefore, the content of the B ₂ O ₃ component is preferably 7.0% or less, preferably 6.0% or less, and more preferably 5.0% or less.

For the B ₂ O ₃ component system, H ₃ BO ₃ , Na ₂ B ₄ O ₇ , and Na ₂ B ₄ O ₇ can be used. 10H ₂ O, BPO ₄ , etc. as raw materials.

The Li ₂ O component is an arbitrary component, and when the content thereof exceeds 0%, the partial dispersion ratio can be lowered, the transmittance can be improved, the liquidus temperature can be lowered, and the solubility of the glass raw material can be improved. Therefore, the content of the Li ₂ O component is preferably more than 0%, preferably more than 1.0%, more preferably more than 3.0%.

On the other hand, by setting the content of the Li ₂ O component to be 15.0% or less, a decrease in the 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, preferably 10.0% or less, and more preferably less than 7.0%.

For the Li ₂ O component system, Li ₂ CO ₃ , LiNO ₃ , LiF or the like can be used as raw materials.

The Na ₂ O component is an arbitrary component, and when the content thereof exceeds 0%, the partial dispersion ratio can be reduced, the thermal expansion coefficient can be increased, and the temperature coefficient of the relative refractive index can be reduced. Therefore, the content of the Na ₂ O component may be preferably more than 0%, preferably more than 1.0%, and more preferably more than 3.0%.

_On the other hand, by making content of a Na2O component 15.0 % or less, a refractive index fall can be suppressed, and devitrification by the excess content can be reduced.

Therefore, the content of the Na ₂ O component is preferably 15.0% or less, preferably 10.0% or less, and more preferably less than 8.0%.

For the Na ₂ O component system, Na ₂ CO ₃ , NaNO ₃ , NaF, Na ₂ SiF ₆ or the like can be used as raw materials.

The Rn ₂ O component (in the formula, Rn is one or more selected from the group consisting of Li, Na, and K) is an arbitrary component, and when the sum (mass sum) of the content is greater than 0%, the temperature at which the relative refractive index can be increased coefficient becomes smaller. Therefore, the sum of the Rn ₂ O components is preferably more than 0%, preferably more than 3.0%, preferably more than 5.0%, more preferably more than 8.0%.

On the other hand, by setting the sum (mass sum) of the content of the Rn ₂ O component (in the formula, Rn is at least one selected from the group consisting of Li, Na, and K) to 20.0% or less, glass can be strengthened. The viscosity in the medium improves the formability. Therefore, 20.0% or less is preferable, 19.0% or less is preferable, and 18.0% or less is more preferable.

The ZrO ₂ component is an arbitrary component, and when the content thereof exceeds 0%, the refractive index and Abbe number of the glass can be increased, the partial dispersion ratio can be reduced, and the devitrification resistance can be improved. In addition, devitrification and coloring can be reduced. Therefore, the content of the ZrO ₂ component is preferably greater than 0%, preferably greater than 1.0%, preferably greater than 3.0%.

_On the other hand, by making content of a ZrO2 component 15.0 % or less, devitrification can be reduced, and it becomes easy to obtain a homogeneous glass. Therefore, the upper limit of the content of the ZrO ₂ component is preferably 15.0% or less, preferably 10.0% or less, and more preferably 8.0% or less.

For the ZrO ₂ component system, ZrO ₂ , ZrF ₄ and the like can be used as raw materials.

The MgO component is an arbitrary component, and when the content thereof exceeds 0%, the melting temperature of the glass can be lowered.

On the other hand, by setting the content of the MgO component to be 10.0% or less, devitrification can be reduced while suppressing a decrease in the refractive index. Therefore, the content of the MgO component is preferably 10.0% or less, preferably less than 5.0%, more preferably less than 3.0%.

As the MgO component system, MgO, MgCO ₃ , MgF ₂ or the like can be used as a raw material.

The CaO component is an arbitrary component, and when the content thereof exceeds 0%, the Abbe number and devitrification can be reduced while the cost of the glass material can be reduced, and the solubility of the glass raw material can be improved.

On the other hand, by setting the content of the CaO component to be 10.0% or less, the decrease in refractive index, the increase in the Abbe number, and the increase in the partial dispersion ratio can be suppressed, and devitrification can be reduced. Therefore, the content of the CaO component is preferably 10.0% or less, preferably less than 7.0%, more preferably less than 5.0%.

For the CaO component system, CaCO ₃ , CaF ₂ or the like can be used as a raw material.

The SrO component is an arbitrary component, and when the content thereof exceeds 0%, the refractive index can be increased and the devitrification resistance can be improved.

In particular, by setting the content of the SrO component to be 10.0% or less, deterioration of chemical durability can be suppressed. Therefore, the content of the SrO component is preferably 10.0% or less, preferably less than 8.0%, more preferably less than 6.0%, more preferably less than 5.0%.

For the SrO component system, Sr(NO ₃ ) ₂ , SrF ₂ or the like can be used as a raw material.

The BaO component is an arbitrary component, and when its content is more than 0%, the refractive index can be increased to and devitrification resistance, and the thermal expansion coefficient is increased, and the temperature coefficient of the relative refractive index is decreased.

In particular, by setting the content of the BaO component to be 5.0% or less, the decrease in refractive index, the increase in the Abbe number, and the increase in the partial dispersion ratio can be suppressed, and devitrification can be reduced. Therefore, the content of the BaO component is preferably 5.0% or less, preferably less than 4.0%, more preferably less than 3.0%, more preferably less than 1.0%.

For the BaO component system, BaCO ₃ , Ba(NO ₃ ) ₂ and the like can be used as raw materials.

The ZnO component is an arbitrary component, and when the content thereof exceeds 0%, the glass becomes inexpensive, the devitrification resistance can be improved, and the glass transition temperature can be lowered. Therefore, the content of the ZnO component may be preferably more than 0%, preferably more than 0.1%, more preferably more than 0.3%.

On the other hand, by making content of a ZnO component 10.0 % or less, devitrification and coloring can be reduced. Therefore, the content of the ZnO component is preferably 10.0% or less, preferably 8.0% or less, and preferably less than 6.0%.

The La ₂ O ₃ component, the Gd ₂ O ₃ component, the Y ₂ O ₃ component and the Yb ₂ O ₃ component are optional components, and when the content of at least one of these components exceeds 0%, the refractive index can be increased and the partial dispersion ratio can be reduced.

In particular, by setting the respective contents of the La ₂ O ₃ component, the Gd ₂ O ₃ component, the Y ₂ O ₃ component, and the Yb ₂ O ₃ component to be 10.0% or less, the increase in Abbe number can be suppressed and devitrification can be reduced, and reduce material costs. Therefore, the respective contents of the La ₂ O ₃ component, the Gd ₂ O ₃ component, the Y ₂ O ₃ component and the Yb ₂ O ₃ component are preferably 10.0% or less, more preferably 7.0% or less, and more preferably less than 5.0%.

La ₂ O ₃ and La(NO ₃ ) ₃ can be used for La ₂ O ₃ component, Gd ₂ O ₃ component, Y ₂ O ₃ component and Yb ₂ O ₃ component. XH ₂ O (X is an arbitrary integer), Y ₂ O ₃ , YF ₃ , Gd ₂ O ₃ , GdF ₃ , Yb ₂ O ₃ and the like are used as raw materials.

The Ta ₂ O ₅ component is an arbitrary component, and when the content thereof exceeds 0%, the refractive index can be increased, the Abbe number and the partial dispersion ratio can be reduced, and the devitrification resistance can be improved.

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 used as a rare mineral resource can be reduced, and the glass can be more easily melted at low temperature, so that the production of the glass can be reduced. cost. Moreover, by this, the devitrification of the glass due to the excessive content of the Ta ₂ O ₅ component can be reduced. Therefore, the content of the Ta ₂ O ₅ component is preferably 10.0% or less, preferably less than 5.0%, more preferably less than 3.0%, more preferably less than 1.0%. In particular, from the viewpoint of reducing the material cost of glass, the Ta ₂ O ₅ component may not be contained.

_Ta2O5 component system can use _{Ta2O5 etc.} as a _raw material.

The WO ₃ component is an arbitrary component, and when the content thereof exceeds 0%, the refractive index can be increased, the Abbe number can be decreased, the devitrification resistance can be improved, and the meltability of the glass raw material can be improved.

On the other hand, by making content _of WO3 component 10.0% or less, it becomes difficult to raise the partial dispersion ratio of glass, and the coloring of glass can be reduced and internal transmittance can be improved. Therefore, the content of the WO ₃ component is preferably 10.0% or less, preferably less than 5.0%, more preferably less than 3.0%, more preferably less than 1.0%.

_WO3 component, _WO3 etc. can be used as a raw material.

The P ₂ O ₅ component is an arbitrary component, and when the content thereof exceeds 0%, the stability of the glass can be improved.

_On the other hand, by making content of a _P2O5 component 10.0 % or less, _{devitrification} by excess content of a _P2O5 component can be reduced. Therefore, the content of the P ₂ O ₅ component is preferably 10.0% or less, preferably less than 5.0%, more preferably less than 3.0%.

As the P ₂ O ₅ component, Al(PO ₃ ) ₃ , Ca(PO ₃ ) ₂ , Ba(PO ₃ ) ₂ , BPO ₄ , H ₃ PO ₄ and the like can be used as raw materials.

The GeO ₂ component is an arbitrary component, and when the content thereof exceeds 0%, the refractive index can be increased and devitrification can be reduced.

On the other hand, by setting the content of the GeO ₂ component to be 10.0% or less, the usage amount of the expensive GeO ₂ component 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, preferably less than 5.0%, more preferably less than 3.0%.

For the GeO ₂ component, GeO ₂ or the like can be used as a raw material.

The Al ₂ O ₃ component and the Ga ₂ O ₃ component are optional components, and when the content of at least any one of the components exceeds 0%, the refractive index can be increased, and the devitrification resistance can be improved.

On the other hand, by setting the content of the Al ₂ O ₃ component and the Ga ₂ O ₃ component to be 10.0% or less, devitrification due to excessive content of the Al ₂ O ₃ component or the Ga ₂ O ₃ component can be reduced. 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, preferably less than 5.0%, and more preferably less than 3.0%.

For the Al ₂ O ₃ component and the Ga ₂ O ₃ component, Al ₂ O ₃ , Al(OH) ₃ , AlF ₃ , Ga ₂ O ₃ , Ga(OH) ₃ and the like can be used as raw materials.

The Bi ₂ O ₃ component is an arbitrary component, and when the content thereof exceeds 0%, the refractive index can be increased, the Abbe number can be decreased, and the glass transition temperature can be decreased.

On the other hand, by setting the content of the Bi ₂ O ₃ component to be 10.0% or less, the partial dispersion ratio can be made difficult to increase, and the coloring of the glass can be reduced and the internal transmittance can be improved. Therefore, the content of the Bi ₂ O ₃ component is preferably 10.0% or less, preferably less than 5.0%, more preferably less than 3.0%, more preferably less than 1.0%.

For the Bi ₂ O ₃ component system, Bi ₂ O ₃ or the like can be used as a raw material.

The TeO ₂ component is an arbitrary component, and when the content thereof exceeds 0%, the refractive index can be increased, the partial dispersion ratio can be decreased, and the glass transition temperature can be decreased.

_On the other hand, by making content of a TeO2 component 5.0 % or less, the coloring of glass can be reduced and internal transmittance can be improved. In addition, by reducing the TeO ₂ component which is expensive to use, glass with low material cost can be obtained. Therefore, the content of the TeO ₂ component is preferably 5.0% or less, more preferably less than 3.0%, and more preferably less than 1.0%.

_TeO2 component system can use _TeO2 etc. as a raw material.

The SnO ₂ component is an arbitrary component, and when the content thereof exceeds 0%, the glass after melting can be made clear (defoaming), and the visible light transmittance of the glass can be improved.

On the other hand, by making content of a _SnO2 component 1.0 % or less, the coloring of glass by reduction of a molten glass, and the devitrification of glass can be made difficult to generate|occur|produce. In addition, since the alloying between the SnO ₂ composition and the melting equipment (particularly noble metals such as Pt) is reduced, it can be expected to prolong the service life of the melting equipment. Therefore, the content of the SnO ₂ component is preferably 1.0% or less, preferably less than 0.5%, more preferably less than 0.1%.

For the SnO ₂ component system, SnO, SnO ₂ , SnF ₂ , SnF ₄ and the like can be used as raw materials.

The Sb ₂ O ₃ component is an optional component in the optical glass of the present invention, and when the content thereof exceeds 0%, the defoaming of the glass is accelerated and the glass becomes clear. By setting the content of the Sb ₂ O ₃ component to 1.0% or less, excessive bubbles are less likely to be generated during glass melting, and alloying between the Sb ₂ O ₃ component and melting equipment (especially noble metals such as Pt) is difficult to occur. Therefore, the content of the Sb ₂ O ₃ component is preferably 1.0%, preferably 0.8%, and more preferably 0.6%.

Sb ₂ O ₃ , Sb ₂ O ₅ , Na ₂ H ₂ Sb ₂ O ₇ can be used for the Sb ₂ O ₃ component system. 5H ₂ O etc. as raw materials.

In addition, as a component for making glass clear and defoaming, it is not limited to the above-mentioned SnO ₂ component or Sb ₂ O ₃ component, and conventional clarifying agents, defoaming agents, or combinations thereof can be used in the field of glass manufacturing.

The mass ratio of Li ₂ O to Na ₂ O and K ₂ O is preferably 1.38 or less. Thereby, the deterioration of devitrification can be suppressed. Therefore, the mass ratio Li ₂ O/(Na ₂ O+K ₂ O) is preferably 1.38 or less, preferably 1.00 or less, more preferably 0.95 or less, more preferably 0.90 or less.

On the other hand, when the mass ratio Li ₂ O/(Na ₂ O+K ₂ O) is set to 0.40 or more, glass with relatively small partial dispersion can be obtained. Therefore, 0.40 or more is preferable, 0.45 or more is preferable, and 0.50 or more is more preferable.

The ratio of TiO ₂ to Li ₂ O is preferably 1.42 or less. Thereby, devitrification of the glass can be reduced. Therefore, the mass ratio of TiO ₂ /Li ₂ O is preferably 1.00 or less, preferably 0.95 or less, and more preferably 0.90 or less.

On the other hand, when the mass ratio TiO ₂ /Li ₂ O is larger than 0, the partial dispersion ratio can be reduced without deteriorating the transmittance. Therefore, more than 0 is preferable, preferably 0.20 or more, more preferably 0.25 or more, more preferably 0.30 or more.

The ratio of the Rn ₂ O component (in the formula, Rn is at least one selected from the group consisting of Li, Na, and K) and Nb ₂ O ₅ is preferably 0.50 or less. Thereby, a desired refractive index can be obtained, and the partial dispersion ratio can be reduced. Therefore, the mass ratio Rn ₂ O/Nb ₂ O ₅ is preferably 0.50 or less, preferably 0.48 or less, more preferably 0.45 or less.

On the other hand, by setting the mass ratio Rn ₂ O/Nb ₂ O ₅ to be 0.10 or more, the temperature coefficient of the relative refractive index can be reduced. Therefore, 0.10 or more is preferable, 0.20 or more is preferable, and 0.25 or more is more preferable.

The ratio of SiO ₂ to Nb ₂ O ₅ is preferably 0.50 or more. Thereby, the partial dispersion ratio can be reduced, and the stability of the glass can be improved. Therefore, the lower limit is preferably 0.50 or more, preferably 0.55 or more, and more preferably 0.60 or more.

On the other hand, the ratio of SiO ₂ to Nb ₂ O ₅ is preferably 1.00 or less. Therefore, the upper limit is preferably 1.00 or less, preferably 0.95 or less, and more preferably 0.90 or less. Thereby, a high refractive index and a desired Abbe number can be obtained.

The total content of TiO ₂ , Nb ₂ O ₅ , and ZrO ₂ is preferably 35.0% or more. Thereby, the partial dispersion ratio becomes small, and the refractive index and Abbe number are expected to be numerical values. Therefore, the mass sum (TiO ₂ +Nb ₂ O ₅ +ZrO ₂ ) is preferably 35.0% or more, preferably 38.0% or more, preferably 40.0% or more, and more preferably 45.0% or more.

On the other hand, the mass sum (TiO ₂ +Nb ₂ O ₅ +ZrO ₂ ) is preferably 70.0% or less. Thereby, the deterioration of devitrification property can be suppressed, and the transmittance|permeability becomes more favorable. 70.0% or less is preferable, preferably less than 65.0%, more preferably less than 60.0%, more preferably less than 58.0%.

The ratio of ZrO ₂ to Nb ₂ O ₅ is preferably 0.01 or more. Thereby, the partial dispersion ratio becomes small, and the devitrification property is improved while having a high refractive index. Therefore, the mass ratio ZrO ₂ /Nb ₂ O ₅ is preferably 0.01 or more, preferably 0.05 or more, and more preferably 0.10 or more.

On the other hand, the mass ratio ZrO ₂ /Nb ₂ O ₅ is preferably 0.25 or less. Thereby, the stability of glass becomes more favorable, and the rise of Abbe's number can be suppressed. 0.25 or less is preferable, 0.22 or less is preferable, 0.20 or less is preferable, and 0.15 or less is more preferable.

The ratio of the Na ₂ O component to the Rn ₂ O component (in the formula, Rn is one or more selected from the group consisting of Li, Na, and K) is preferably 0.25 or more. Thereby, the temperature coefficient of the relative refractive index becomes small. Therefore, the mass ratio Na ₂ O/Rn ₂ O is preferably 0.25 or more, preferably 0.27 or more, and more preferably 0.30 or more.

On the other hand, the mass ratio Na ₂ O/Rn ₂ O is preferably 0.65 or less. Thereby, devitrification and a decrease in refractive index due to reheat press molding can be suppressed. 0.65 or less is preferable, 0.63 or less is preferable, and 0.60 or less is more preferable.

When the total content (mass sum) of RO components (where 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 content of the RO component is preferably more than 0%, preferably more than 0.5%, more preferably more than 1.5%.

On the other hand, it is preferable that the total content of RO components is less than 9.0%. Thereby, the fall of glass refractive index and the fall of devitrification resistance by excessive content of RO component can be suppressed. Therefore, the mass sum of the RO component is preferably less than 9.0%, preferably less than 7.0%, preferably 6.5% or less, more preferably 6.0% or less.

It is preferable that the total content (mass sum) of the Ln ₂ O ₃ component (in the formula, Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) is less than 5.0%. Thereby, the fall of the glass refractive index and the fall of devitrification resistance by excessive content of the Ln ₂ O ₃ component can be suppressed. Therefore, the mass sum of the Ln ₂ O ₃ component is preferably less than 5.0%, preferably 4.5% or less, more preferably 4.0% or less.

<About 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 suitable to be contained will be described.

Other components may be added as needed within the range that does not impair the properties of the glass of the present invention. However, in addition to Ti, Zr, Nb, W, La, Gd, Y, Yb, Lu, various transition metal components such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, Mo, etc. When it is contained in a compound form, even a small amount of it will cause the glass to be colored, and the property of absorbing light of a specific wavelength in the visible range will occur. is not substantially contained.

In addition, lead compounds such as PbO and arsenic compounds such as As ₂ O ₃ are components with a high environmental load, and it is desirable not to contain them substantially, that is, not to contain them at all except for unavoidable contamination.

Furthermore, the components of Th, Cd, Tl, Os, Be, and Se have been regarded as harmful chemical substances in recent years, and their use tends to be avoided, not only in the glass manufacturing step, but also in the processing step and after the productization. Before disposal, measures must be taken in response to environmental countermeasures. Therefore, from the viewpoint of emphasizing the influence on the environment, it is preferable that these components are not contained substantially.

[Manufacturing method]

The optical glass of the present invention can be produced, for example, as follows. That is, the above-mentioned 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 aluminum-oxygen crucible for preliminary melting, and then put into a gold crucible, platinum crucible, In platinum alloy crucible or iridium crucible, melt for 3 hours to 5 hours in the temperature range of 1000℃ to 1400℃, stir to make it uniform and carry out defoaming and other steps, cool down to the temperature of 900℃ to 1200℃, and then carry out the final process. Staged stirring to remove the texture, and then poured into the mold, slow cooling, so as to make.

<physical properties>

The optical glass system of the present invention has a high refractive index and an Abbe number in a predetermined range.

The lower limit of the refractive index (n _d ) system of the optical glass of the present invention is preferably 1.70 or more, preferably 1.72 or more, and more preferably 1.75 or more. The upper limit of the refractive index is preferably 1.90 or less, preferably 1.88 or less, more preferably 1.85 or less, and more preferably 1.83 or less.

The lower limit of the Abbe number (ν _d ) system of the optical glass of the present invention is preferably 25.0, more preferably 25.5, more preferably 26.0. On the other hand, the upper limit of the Abbe number ((nu) _d ) of the optical glass of the present invention is preferably 35.0, more preferably 34.0, more preferably 33.0.

Since the optical glass of the present invention has such a refractive index and Abbe number, it can be effective in optical design. In particular, while high imaging characteristics are desired, miniaturization of the optical system is also desired, and expansion is possible. Degrees of freedom in optical design.

n_d

(-0.01×ν_d+2.13)之關係為佳。本發明所特定的組成的玻璃，折射率(n_d)及阿貝數(ν_d)滿足該關係，能夠獲得穩定的玻璃。 Here, the optical glass-based refractive index (n _d ) and Abbe number (ν _d ) of the present invention satisfy (−0.01×ν _d +2.03)

n _d

The relationship of (-0.01×ν _d +2.13) is preferable. In the glass of the composition specified in the present invention, the refractive index (n _d ) and the Abbe number (ν _d ) satisfy this relationship, and a stable glass can be obtained.

(-0.01×ν_d+2.03)之關係為佳，較佳為滿足n_d

(-0.01×ν_d+2.05)之關係。 Therefore, the refractive index (n _d ) and the Abbe number (ν _d ) of the optical glass system of the present invention satisfy n _d

The relationship of (-0.01×ν _d +2.03) is preferable, and it is preferable to satisfy n _d

(-0.01×ν _d +2.05).

(-0.01×ν_d+2.13)之關係為佳，較佳為滿足n_d

(-0.01×ν_d+2.10)之關係。 On the other hand, the refractive index (n _d ) and the Abbe number (ν _d ) of the optical glass system of the present invention satisfy n _d

The relationship of (-0.01×ν _d +2.13) is preferable, and it is preferable to satisfy n _d

(-0.01×ν _d +2.10).

The optical glass system of the present invention has a low partial dispersion ratio (θ _g , F).

(-0.00162×ν_d+0.657)之關係為佳。 More specifically, the partial dispersion ratio (θ _g , F) of the optical glass of the present invention and the Abbe number (ν _d ) satisfy (−0.00162×ν _d +0.620))(θ _g , F)

The relationship of (-0.00162×ν _d +0.657) is preferable.

(-0.00162×ν_d+0.620)之關係為佳，較佳為(θ_g，F)

(-0.00162×ν_d+0.630)之關係。 Therefore, the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) of the optical glass system of the present invention satisfy (θ _g , F)

The relationship of (-0.00162×ν _d +0.620) is better, preferably (θ _g , F)

(-0.00162×ν _d +0.630).

(-0.00162×ν_d+0.657)之關係為佳，較佳為滿足θ_g，F

(-0.00162×ν_d+0.650)之關係。 On the other hand, the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) of the optical glass system of the present invention satisfy θ _g , F

The relationship of (-0.00162×ν _d +0.657) is better, preferably satisfying θ _g , F

(-0.00162× _νd +0.650).

Thereby, an optical glass having a low partial dispersion ratio (θ _g , F) can be obtained, and the optical element formed of the optical glass can be effective in reducing chromatic aberration of an optical system.

In addition, especially in the region where the Abbe number (ν _d ) is small, the value of the partial dispersion ratio (θ _g , F) of the general glass is higher than that of the normal line, and the horizontal axis is taken as the Abbe number (ν _{d )} ), when the vertical axis is the partial dispersion ratio (θ _g , F), the relationship between the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) of general glass is shown by a curve with a greater inclination than the normal line . The above relationship between the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) shows that the partial dispersion ratio (θ _g , F) Glass smaller than ordinary glass.

Moreover, the temperature coefficient (dn/dT) of the relative refractive index of the optical glass system of the present invention takes a low value.

More specifically, the upper limit of the temperature coefficient system of the relative refractive index of the optical glass of the present invention is preferably +6.0×10 ^-6 °C ^-1 , preferably +5.5×10 ^-6 °C ^-1 , more preferably + 5.0×10 ^-6 °C ^-1 , and can take the upper limit value or a value lower (negative value side) than the upper limit value.

On the other hand, the lower limit value of the temperature coefficient of the relative refractive index of the optical glass of the present invention is preferably -5.0×10 ^-6 °C ^-1 , preferably -1.0×10 ^-6 °C ^-1 , more preferably -0.5 ×10 ^-6 °C ^-1 , and can take the lower limit value or a higher value (positive value side) than the lower limit value.

Among them, among glasses with a refractive index (n _d ) of 1.70 or more and an Abbe number (ν _d ) of 25 or more and 35 or less, glass with a relatively low temperature coefficient of the refractive index is rare, so that the temperature coefficient depends on the temperature. There are more options for compensating for situations such as image out-of-focus caused by changes, and the correction can be performed more easily. Therefore, by setting the temperature coefficient of the relative refractive index to the above-mentioned range, it is possible to contribute to the correction of image defocusing due to temperature changes.

The temperature coefficient of the relative refractive index of the optical glass of the present invention refers to the temperature coefficient of the refractive index (589.29 nm) of the optical glass in air at the same temperature. The corresponding change amount (°C ^-1 ) is expressed.

The average linear thermal expansion coefficient α at 100°C to 300°C of the optical glass of the present invention is preferably 80 (10 ^-7 °C ^-1 ) or more. That is, the lower limit of the average linear thermal expansion coefficient α system at 100°C to 300°C of the optical glass of the present invention is preferably 80 (10 ^-7 °C ^-1 ) or more, more preferably 85 (10 ^-7 °C ^-1 ) or more, Preferably it is 90 (10 ^-7 °C ^-1 ) or more.

In general, in glass processing, when the average linear thermal expansion coefficient α is large, cracks are likely to occur, so it is desirable that the average linear thermal expansion coefficient α is small. On the other hand, from the viewpoint of bonding with a glass material having a low temperature coefficient of relative refractive index and a large average coefficient of linear thermal expansion α, it is desirable that the value of the average coefficient of linear thermal expansion α is the same as that of the glass material or similar.

Among them, among glasses with a refractive index (n _d ) of 1.70 or more and an Abbe number (ν _d ) of 25 or more and 35 or less, there are few glass materials with a large average linear thermal expansion coefficient α, which are in contrast to low refractive index and low dispersion. When used in combination with different glass materials, the average linear thermal expansion coefficient α shown in the present invention is more useful.

The optical glass of the present invention desirably has a small specific gravity. More specifically, the specific gravity of the optical glass of the present invention is preferably 5.00 (g/cm ³ ) or less. Thereby, the mass of the optical element and the optical instrument using the optical element can be reduced, and it is possible to contribute to the weight reduction of the optical instrument.

Therefore, the upper limit of the specific gravity of the optical glass of the present invention is preferably 5.00, more preferably 4.70, and more preferably 4.50. Moreover, the specific gravity of the optical glass of this invention is about 2.80 or more in many cases, More specifically, it is 2.90 or more, More specifically, it is 3.00 or more.

The specific gravity of the optical glass of the present invention is measured in accordance with the Japan Optical Glass Industry Association standard JOGIS05-1975 "Method for measuring the specific gravity of optical glass".

[Preform and Optical Element]

A glass molded body can be produced from the optical glass produced by a press molding method such as reheat press molding, precision press molding, or the like. That is, a preform for press molding can be produced from optical glass, and the preform can be subjected to reheat press molding After that, grinding is performed to produce a glass molded body; or a preform produced by grinding is subjected to precision press molding to produce a glass molded body or the like. In addition, the method of producing a glass molded body is not limited to the above-mentioned methods.

The glass molded body produced as described above can be applied to various optical elements, and its use is particularly suitable for optical elements such as lenses and lenses. Thereby, color bleeding due to chromatic aberration can be reduced with respect to the transmitted light of the optical system provided with the optical element. Therefore, when the optical element is used in a viewing window, the photographed object can be more accurately represented, and when the optical element is used in a projector, a desired map can be projected with higher clarity.

[Example]

Compositions of Examples (No. 1 to No. 12) and Comparative Examples of the present invention, as well as refractive index (n _d ), Abbe number (ν _d ), partial dispersion ratio (θ _g , F), relative refractive index The results of the temperature coefficient (dn/dT), the average linear thermal expansion coefficient (100-300°C), and the specific gravity are shown in Tables 1 to 2. In addition, the following examples are for illustrative purposes only, and the present invention is not limited to these examples.

In the glasses of the examples and comparative examples of the present invention, the raw materials of each component are selected from the high-purity raw materials used in general optical glasses such as oxides, hydroxides, carbonates, nitrates, fluorides, metaphosphoric acid compounds and so on. Then, these raw materials are weighed so that the composition ratios of the respective Examples and Comparative Examples shown in the table are weighed, and after mixing uniformly, they are put into a quartz crucible (a platinum crucible or an alumina crucible can also be used depending on the melting property of the glass). and according to the melting difficulty of the glass composition, use an electric furnace in the temperature range of 1100 ° C to 1400 ° C, after melting for 0.5 to 5 hours, transfer it into a platinum crucible, stir it to make it uniform, and carry out steps such as defoaming, and then cool down. After the temperature reaches 1000°C to 1200°C, it is stirred again to make it uniform, then cast into a mold, and slowly cooled to make glass.

The refractive index (n _d ), Abbe number (ν _d ), and partial dispersion ratio (θ _g , 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 relative refractive index (dn/dT) of the glasses of the examples and comparative examples is based on the interference in the method described in the Japan Optical Glass Industry Association Standard JOGIS18-2008 "Method for Measuring the Temperature Coefficient of Refractive Index of Optical Glass" method to measure the value of the temperature coefficient of the relative refractive index of light with a wavelength of 589.29 nm at 40°C to 60°C.

In addition, the average coefficient of linear thermal expansion (100-300°C) of the glasses of the examples and comparative examples is in accordance with the Japan Optical Glass Industry Association standard JOGIS08-2003 "Measuring method of thermal expansion of optical glass", by measuring the temperature and the elongation of the sample The thermal expansion curve obtained by the relationship between the ratios was obtained.

The specific gravity of the glass of the Example and the comparative example was measured according to the Japan Optical Glass Industry Association standard JOGIS05-1975 "measurement method of the specific gravity of optical glass".

The optical glass-based refractive index (n _d ) of the examples of the present invention is 1.70 or more, more specifically, 1.72 or more, and the refractive index (n _d ) is 1.90 or less, more specifically, 1.88 or less, all of which are expected In the range.

In addition, the Abbe number (ν _d ) of the optical glass system of the examples of the present invention is 25 or more, more specifically, 26 or more, and the Abbe number (ν _d ) is 35 or less, all within the expected range.

(θ_g，F)

(-0.00162×ν_d+0.657)之關係，更詳細而言滿足(-0.00162×ν_d+0.630)

(θ_g，F)

(-0.00162×ν_d+0.650)之關係。亦即，關於本案實施例的玻璃的部分色散比(θ_g，F)與阿貝數(ν_d)之間之關係，結果如圖2所示。 As shown in the above tables, the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) of the optical glass system of the examples of the present invention satisfy (-0.00162×ν _d +0.620)

(θ _g , F)

(-0.00162×ν _d +0.657), more specifically (-0.00162×ν _d +0.630)

(θ _g , F)

(-0.00162× _νd +0.650). That is, regarding the relationship between the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) of the glass of the examples of the present application, the results are shown in FIG. 2 .

(θ_g，F)

(-0.00162×ν_d+0.657)之關係。 On the other hand, the optical glass system of the comparative example did not satisfy (-0.00162×ν _d +0.620)

(θ _g , F)

(-0.00162×ν _d +0.657).

n_d

(-0.01×ν_d+2.13)之關係，更詳細而言滿足(-0.01×ν_d+2.05)

n_d

(-0.01×ν_d+2.10)之關係。亦即，關於本申請實施例的玻璃的折射率(n_d)及阿貝數(ν_d)之間之關係，結果如圖3所示。 Furthermore, the refractive index (n _d ) and the Abbe number (ν _d ) of the optical glass system of the examples of the present invention satisfy (−0.01×ν _d +2.03)

n _d

(-0.01×ν _d +2.13), more specifically, (-0.01×ν _d +2.05)

n _d

(-0.01×ν _d +2.10). That is, regarding the relationship between the refractive index (n _d ) and the Abbe number (ν _d ) of the glasses of the examples of the present application, the results are shown in FIG. 3 .

As shown in the table, the temperature coefficients of the relative refractive indices of the optical glass systems of the examples are all within the range of +6.0×10 ^-6 (°C ^-1 ) to -0.5×10 ^-6 (°C ^-1 ), which are expected within the range.

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

Moreover, the specific gravity of the optical glass system of the Example of this invention is 5.00 or less. therefore, It can be clearly seen that the specific gravity of the optical glass of the embodiment of the present invention is relatively small.

Furthermore, a glass brick was formed using the optical glass of the example of the present invention, and the glass brick was ground and polished to be processed into a lens and a sapphire shape. As a result, various shapes of lenses and lenses can be processed stably.

Although the present invention has been described in detail for the purpose of illustration, the purpose of this embodiment is only for the purpose of illustration. Numerous modifications may be made to the present invention.

Claims (6)

An optical glass, in mass %, comprising: SiO ₂ composition 20.0% to 45.0%; Nb ₂ O ₅ composition 25.0% to 60.0%; TiO ₂ composition 0% to 5.0%; and a mass ratio (Li ₂ O/Na ₂ O+K ₂ O) is 0.40 to 1.00; mass sum (TiO ₂ +Nb ₂ O ₅ +ZrO ₂ ) is 45.0% to 70.0%; and refractive index (n _d ) is 1.75 or more; partial dispersion ratio (θ _g , F) and Abbe's number ν _d satisfy (-0.00162×ν _d +0.620)

(θ _g , F)

(-0.00162×ν _d +0.657), the temperature coefficient (40°C to 60°C) of the relative refractive index (589.29nm) is in the range of +6.0×10 ^-6 to -5.0×10 ^-6 (°C ^-1 ) Inside. The optical glass according to claim 1, wherein the mass ratio (Rn ₂ O/Nb ₂ O ₅ ) is 0.50 or less, and Rn in the formula is one or more selected from the group consisting of Li, Na, and K. The optical glass according to claim 1 or 2, wherein the refractive index n _d and the Abbe number ν _d satisfy (-0.01×ν _d +2.03)

n _d

(-0.01×ν _d +2.13). A preform comprising the optical glass as recited in claim 1 or 2. An optical element comprising the optical glass as recited in claim 1 or 2. An optical instrument provided with the optical element as described in claim 5.

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