JP2020132471A - Optical glass, method for producing optical glass, optical element, optical device, and imaging device - Google Patents

Abstract

To solve the problem in which: it is difficult to obtain an optical glass that has low glass transition temperature and prevents crystal deposition in a glass mold making step, and has high refractive index and high dispersion.SOLUTION: Provided is an optical glass, wherein, with the sum of cations constituting glass being 100 cat%, it satisfies 15 cat%≤RE≤25 cat% (RE denotes La alone, or denotes one with La substituted with at least one element selected from Gd, Y, Lu and Yb), 20 cat%≤Nb≤50 cat%, 10 cat%≤Zn≤30 cat%, 5 cat%≤Ta≤20 cat%, 0 cat%≤Ti≤20 cat%, 0 cat%≤Al≤5 cat%, 0 cat%≤Ca≤5 cat%.SELECTED DRAWING: Figure 2

Description

The present invention relates to an optical glass containing La ₂ O ₃ , Nb ₂ O ₅ , ZnO and Ta ₂ O ₅ as essential components, and a method for producing the same. Further, the present invention relates to an optical element made of the optical glass, an optical device using the optical element, and an imaging device.

In recent years, with the increasing functionality of optical instruments, optical elements such as lenses used in optical instruments are required to have high optical characteristics. Therefore, the optical glass used for the lens is required to have a high refractive index and a high dispersion.

Optical glass generally contains a network-forming oxide that forms the skeleton of glass such as SiO ₂ , B ₂ O ₃ , and P ₂ O ₅ , a network-modified oxide that cuts the network and enters the gap, and an intermediate oxide. contains. As the network-modified oxide, Nb ₂ O ₅ and TiO ₂ having an absorption edge existing in the visible light region (wavelength 380 to 730 nm) are known. When a glass having a high refractive index and a high dispersion is to be obtained, the network-forming oxide is replaced with Nb ₂ O ₅ or TiO ₂ to increase the proportion of the network-modified oxide and the intermediate oxide in the glass. It has been known. For example, Patent Document 1 discloses TiO _2- La ₂ O _3- Ta ₂ O ₅ type glass. Further, Patent Document 2 discloses TiO _2- La ₂ O _3- Nb ₂ O ₅ type glass.

Japanese Unexamined Patent Publication No. 2016-199408 Japanese Unexamined Patent Publication No. 2016-147775

The glass disclosed in Patent Document 1 is based on TiO _2- La ₂ O _3- Ta ₂ O ₅ , and contains a large amount of TiO ₂ in order to achieve a high refractive index and high dispersion. When a large amount of TiO ₂ functioning as a network-modified oxide or an intermediate oxide is contained, the glass transition temperature (Tg) rises. Therefore, the glass mold manufacturing process (GMo process) for molding glass using a mold must be performed at a high temperature. When the temperature is high, the reactivity of TiO ₂ increases in the glass, and there is a problem that a large amount of gas such as oxygen is easily generated.

Further, the glass disclosed in Patent Document 2 uses TiO _2- La ₂ O _3- Nb ₂ O ₅ as a base material. With this composition, it is difficult to make large glass because the conditions under which glass can be stably produced are narrow. Further, there is a problem that crystals are easily precipitated in the glass mold manufacturing process.

That is, it has been difficult to obtain optical glass having a low glass transition temperature and a high refractive index and high dispersion in which crystals are less likely to precipitate in the glass mold manufacturing process.

In the optical glass of the present invention, the sum of the cations constituting the glass is 100 cat%, and 15 cat% ≤ RE ^{3 +} ≤ 25 cat% (RE is La only, or La is selected from Gd, Y, Lu, and Yb at least one. 20cat% ≤Nb ⁵⁺ ≤50cat%, 10cat% ≤Zn ²⁺ ≤30cat%, 5cat% ≤Ta ⁵⁺ ≤20cat%, 0cat% ≤Ti ⁴⁺ ≤20cat%, 0cat% ≤ It is characterized by satisfying Al ³⁺ ≤5cat% and 0cat% ≤Ca ²⁺ ≤5cat%.

According to the present invention, it is possible to provide an optical glass having a high refractive index and a high dispersion, a low glass transition temperature, and less likely to precipitate crystals in a glass mold manufacturing process.

It is the schematic which shows one Embodiment of the image pickup apparatus of this invention. It is the schematic which shows the gas jet levitation device which can be used in the manufacturing method of the optical glass of this invention.

Hereinafter, the present invention will be described in detail.

(Optical glass)
The optical glass of the present invention is a glass having a high refractive index and high dispersion and a low glass transition temperature (Tg). Further, the optical glass of the present invention is a glass having a high content ratio of rare earth ions (La ³⁺ , Gd ³⁺ , Y ³⁺ , Lu ³⁺ , Yb ³⁺ ), Nb ⁵⁺ , Zn ²⁺ and Ta ⁵⁺ .

The optical glass of the present invention satisfies 15cat% ≤ RE ³⁺ ≤25cat% when the sum of the cations constituting the glass is 100cat% (expressed as cation%). Here, RE represents only La or La replaced with at least one rare earth element selected from Gd, Y, Lu and Yb.

La ³⁺ plays a role similar to the network-forming component in glass. If the content of rare earth ions containing La ³⁺ is less than 15 cat%, it is difficult to obtain glass, and if it is more than 25 cat%, the glass transition temperature rises, so a high temperature is required for molding. La ³⁺ can be replaced with at least one rare earth ion selected from Gd ³⁺ , Y ³⁺ , Lu ³⁺ and Yb ³⁺ . Y ³⁺ , Lu ³⁺ and Yb ³⁺ can replace La ³⁺ in the range of 10 cat% or less. Gd ³⁺ can replace La ³⁺ in the range of 15 cat% or less. Within these ranges, the role of a network-forming component can be exerted.

The optical glass of the present invention satisfies 20 cat% ≤ Nb 5 ⁺ ≤ 50 cat%. A part of Nb ⁵⁺ plays a role of a network forming component in the glass, and imparts a high refractive index and a high dispersion. If the content of Nb ⁵⁺ is less than 20 cat%, the refractive index does not increase. If it exceeds 50 cat%, the glass will crystallize and devitrify.

The optical glass of the present invention satisfies 10 cat% ≤ Zn ²⁺ ≤ 30 cat%. Zn ²⁺ has the effect of lowering the glass transition temperature. It also suppresses the decrease in refractive index. If the content of Zn ²⁺ is less than 10 cat%, it will not be vitrified, and if it exceeds 30 cat%, volatilization will increase when the glass is melted. Further, when RE ³⁺ is 25 cat% or less, Nb ⁵⁺ is 50 cat% or less, and Ta ⁵⁺ is 20 cat% or less, if the Zn ²⁺ content exceeds 30 cat%, devitrification occurs under the temperature conditions of the GMo process. It ends up. Here, the temperature condition of the GMo step is, for example, a condition of holding at a temperature 50 ° C. higher than the glass transition temperature (Tg + 50 ° C. temperature) for 5 minutes.

The optical glass of the present invention satisfies 5cat% ≤ Ta ⁵⁺ ≤ 20cat%. Ta ⁵⁺ is an ion necessary for stably producing a large glass, and especially in this range, Ta ⁵⁺ has an effect of remarkably reducing the glass transition temperature. Further, in this range, the decrease in the refractive index is suppressed. If the content of Ta ⁵⁺ is less than 5 cat%, devitrification occurs under the condition that the temperature of Tg + 50 ° C. described above is maintained for 5 minutes. If the content of Ta ⁵⁺ exceeds 20 cat%, the glass transition temperature will increase. In addition, a large amount of volatilization occurs when the glass is melted, making it difficult to obtain a glass having a stable refractive index.

The optical glass of the present invention satisfies 0cat% ≤ Ti ⁴⁺ ≤ 20cat%. Ti ⁴⁺ has the effect of imparting a high refractive index and high dispersion, and in this range, a high refractive index can be obtained. However, if the content of Ti ⁴⁺ is more than 20 cat%, it will crystallize and devitrify.

The optical glass of the present invention satisfies 0cat% ≤ Al ³⁺ ≤ 5cat%. Al ³⁺ increases the viscosity when the glass is melted and makes it easier to prevent devitrification. However, if the content of Al ³⁺ is more than 5 cat%, it will crystallize and devitrify.

The optical glass of the present invention satisfies 0cat% ≤ Ca ²⁺ ≤ 5cat%. Ca ²⁺ has the effect of reducing the glass transition temperature. It also has the effect of promoting vitrification. However, if the Ca ²⁺ content is more than 5 cat%, crystallization will be promoted.

The total content of RE ³⁺ , Nb ⁵⁺ , Zn ²⁺ , Ta ⁵⁺ and Ti ⁴⁺ contained in the optical glass of the present invention is 90 cat% or more when the sum of the cations constituting the glass is 100 cat%. It is preferable to have. This is because glass can be easily obtained without crystallization. It is more preferably 95 cat%, and even more preferably 100 cat%.

The optical glass of the present invention preferably has a content of at least one cation selected from Si ⁴⁺ , B ³⁺ and P ⁵⁺ of 100 ppm or less. These cations are unavoidable impurities contained in the raw material powders of RE ³⁺ , Nb ⁵⁺ , Zn ²⁺ and Ta ⁵⁺ , which are essential components of the optical glass of the present invention. Since Si ⁴⁺ , B ³⁺ and P ⁵⁺ function as network forming components, they are stable as glass. However, if the content of each cation exceeds 100 ppm, the refractive index (nd) on the d-line decreases and the Abbe number (νd) on the d-line increases. That is, the refractive index becomes low and the dispersion becomes low.

The optical glass of the present invention can contain ions other than the above-mentioned cations as long as it has a high refractive index, high dispersion, a low glass transition temperature, and can maintain the colorless and transparent characteristics. The ions that can be contained are, for example, Zr ⁴⁺ , Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Sr ²⁺ , Ba ²⁺ , F ⁻ and S ^2- .

On the other hand, it is desirable that the optical glass of the present invention does not contain the following ions.

W ⁶⁺ gives a high refractive index and high dispersion, and has an effect of lowering the glass transition point. However, since it is easily reduced, it reacts with the molding mold during the GMo process, and gas is easily generated. Therefore, it is desirable that the lens is not contained because defects are likely to occur as a lens.

Bi ³⁺ , Pb ²⁺ and Te ⁴⁺ give the effect of high refractive index and high dispersion, but there is a region in the visible light region where electronic transitions are absorbed. Therefore, when at least one of these ions is contained, the glass becomes yellowish. Further, since it is easy to reduce, it reacts with the molding die during the GMo process to generate gas and these ions are precipitated as a metal, so it is desirable not to contain it.

The optical glass of the present invention has a high refractive index and high dispersion. Specifically, it is preferable that the refractive index (nd) on the d-line is 2.17 or more and 2.25 or less, and the Abbe number (νd) on the d-line is 18 or more and 23 or less. More preferably, the refractive index is 2.19 or more and 2.24 or less, and the Abbe number is 19 or more and 22 or less.

The optical glass of the present invention preferably has a glass transition temperature (Tg) of 720 ° C. or lower. This is because when the Tg is high, the temperature at which the glass is molded rises, so that the reaction between the glass and the molding die is promoted, and bubbles are likely to be generated. It is more preferably 710 ° C., and even more preferably 705 ° C. or lower.

(Manufacturing method of optical glass)
The method for producing the optical glass of the present invention is described below.

As the raw material powder constituting the optical glass of the present invention, for example, La ₂ O ₃ , Nb ₂ O ₅ , ZnO, and Ta ₂ O ₅ are used as essential components, and Gd ₂ O ₃ , Y ₂ O ₃ , and Lu ₂ O _{3 are used.} , Yb ₂ O ₃ , TiO ₂ , Al ₂ O ₃ , and CaO can be used as optional components.

Further, the raw material powder constituting the optical glass of the present invention is not limited to the above-mentioned oxides, but is known materials such as the above-mentioned ion-containing hydroxides, carbonates, nitrates, sulfates, sulfides and fluorides. You can choose from.

The optical glass of the present invention can be produced by a container-free solidification method. The container-free solidification method is a method in which a material is heated and melted without using a container such as a Pt alloy (Pt or platinum alloy, for example, Pt-Au, Pt-Au-Rh, etc.) or C-based (C, SiC, etc.). After that, it is a method of obtaining glass by cooling and solidifying.

The containerless solidification method has two characteristics. One is that since a container is not used, non-uniform nucleation does not occur at the interface between the melt and the container, and a deep cooling degree can be obtained. The other is that since a container is not used, a sample having a melting point equal to or higher than the melting point of the container itself (for example, 1768 ° C. in the case of Pt) can be heated and melted.

The main steps of the containerless solidification method are a step of heating and melting the glass raw material powder, a step of floating the melt, and a step of cutting the heating source and cooling and solidifying.

In the step of heating and melting the glass raw material powder, a sintered body obtained by pre-sintering the glass raw material powder can be used. As the heating source, for example, a laser heating source typified by a carbon dioxide gas laser, a high frequency heating source, a microwave heating source, or an image furnace by condensing a halogen lamp can be used.

In the process of levitating the melt, for example, magnetic levitation, electrostatic levitation, sonic levitation, gas jet levitation and their combinations (for example, sonic levitation and gas jet levitation), and under microgravity (for example, falling or outer space). Can be used. Above all, gas jet levitation that ejects a gas fluid from a nozzle is preferable because the apparatus configuration is simple. As the gas type of the gas fluid, an inert gas typified by air, nitrogen, oxygen, argon or the like can be used according to the application. The gas flow rate is, for example, discharged at a rate of 200 to 5000 ml / min according to the floating of the melt.

In the step of cooling the melt while the melt is levitated, spherical transparent glass can be obtained by cooling and solidifying at a cooling rate at which crystals are not formed from the melt.

(Optical element)
The optical element of the present invention can be obtained by molding the above optical glass. In the present specification, the optical element means an element constituting an optical system in an optical device such as a lens, a prism, a reflecting mirror, and a diffraction grating.

(Imaging device)
FIG. 1 shows the configuration of a single-lens reflex digital camera, which is an example of a preferred embodiment of the imaging device of the present invention. In FIG. 1, the camera body 602 and the lens barrel 601 which is an optical device are coupled, and the lens barrel 601 is a so-called interchangeable lens that can be attached to and detached from the camera body 602.

The light from the subject passes through an optical system including a plurality of lenses 603, 605 and the like arranged on the optical axis of the photographing optical system in the housing 620 of the lens barrel 601 and is received by the image sensor. The optical element of the present invention can be used, for example, in lenses 603 and 605.

Here, the lens 605 is supported by the inner cylinder 604 and is movably supported with respect to the outer cylinder of the lens barrel 601 for focusing and zooming.

During the observation period before shooting, the light from the subject is reflected by the main mirror 607 in the housing 621 of the camera body, passes through the prism 611, and then the shot image is projected to the photographer through the finder lens 612. The main mirror 607 is, for example, a half mirror, and the light transmitted through the main mirror is reflected by the sub mirror 608 in the direction of the AF (autofocus) unit 613. For example, this reflected light is used for distance measurement. Further, the main mirror 607 is attached and supported on the main mirror holder 640 by adhesion or the like. At the time of photographing, the main mirror 607 and the sub mirror 608 are moved out of the optical path via a drive mechanism (not shown), the shutter 609 is opened, and the image pickup element 610 is imaged with a photographed light image incident on the lens barrel 601. Further, the aperture 606 is configured so that the brightness and the depth of focus at the time of shooting can be changed by changing the aperture area.

Hereinafter, the present invention will be described with reference to examples. The evaluation method of the optical glass in the examples was carried out by the following procedure.

[Evaluation method]
(composition)
The composition of the produced optical glass was measured by inductively coupled plasma (ICP) emission analysis using an ICP emission spectrometer (Spectro, CIROS-120EOP).

(Judgment of vitrification)
The produced transparent spherical sample was observed with an optical microscope (100 times) to determine the presence or absence of crystals. A was assigned to those in which no crystals were observed, and B was assigned to those in which crystals were observed.

(Measurement of glass transition temperature and ΔTx)
The produced transparent spherical sample is crushed in an agate mortar, packed in a platinum pan having an outer diameter of 5 mm and a height of 2.5 mm, and then 10 ° C./min with a differential scanning calorimeter (DSC) manufactured by Rigaku. The temperature was raised to 1200 ° C., and the glass transition temperature (Tg) was detected. Further, the difference ΔTx (Tx−Tg = ΔTx) between the crystal start temperature Tx and the glass transition point Tg was determined.

(Refractive index measurement)
The refractive index and Abbe number were measured by polishing the obtained sample to prepare two planes orthogonal to each other and using a precision refractometer (KPR-2000 manufactured by Shimadzu Corporation). When the sample was small, the obtained transparent spherical sample was polished into a hemisphere and then measured with an ellipsometer (M-2000F manufactured by JA Woollam Co. Inc.).

(Heating test)
In the heating test, a gostone-shaped glass block having an outer diameter of 4 to 6.5 mm was placed in an electric furnace under an atmospheric atmosphere set to a temperature 50 ° C. higher than the glass transition temperature. In addition, the gostone-shaped glass block was placed on a plate made of aluminum oxide in the electric furnace. After holding at the above temperature for 5 minutes, it was taken out from an electric furnace and allowed to cool. The cooled sample was observed with an optical microscope (100 times) to determine the presence or absence of crystals.

[Manufacturing of optical glass and optical elements]
The glass raw material powder was weighed so that the composition of the cations in the glass was the composition shown in Tables 1 and 2 and the total amount was 10 g. Glass raw material powders include Al ₂ O ₃ (Al (OH) ₃ ), La ₂ O ₃ (LaF ₃ , La ₂ S ₃ ), Gd ₂ O ₃ , Y ₂ O ₃ , ZnO, Nb ₂ O ₅ , Ta. ₂ O ₅ , TiO ₂ and CaCO ₃ were used. The compositions of Examples 1 to 23 are summarized in Table 1, and the compositions of Comparative Examples 1 to 22 are summarized in Table 2.

Then, the mixture was mixed for 15 minutes using an agate mortar so that the raw material powder became uniform. In order to remove the water content in the obtained mixture, it was fired in an electric furnace at 600 ° C. for 7 hours. The calcined powder was filled in a pressurized rubber mold and held at 20 kN for 1 minute by a cold isotropic pressurization method to obtain a rod-shaped powder (compact powder). The obtained rod-shaped powder was fired in an electric furnace at 1200 ° C. for 7 hours to obtain a sintered body 1. However, if it is not necessary to pay particular attention to the water content in the mixture, the green compact may be obtained simply by pressing the powder.

This sintered body 1 is set on the nozzle 3 of the gas jet floating device shown in FIG. 2, and the laser beam 5 of carbon dioxide gas is irradiated from above while flowing the oxygen gas 4 from the nozzle hole at a flow rate of 500 ml / min. It was heated. Here, the oxygen gas 4 may be dry air or nitrogen as long as the sample 2 can be floated. Further, the amount of gas can be appropriately adjusted between 0.5 and 6 L / min according to the size of the sintered body 1.

The sintered body 1 set on the nozzle 3 of the gas jet floating device is heated to be in a completely melted state, and after confirming the floating by oxygen gas, the laser output is cut off and the sintered body 1 is rapidly cooled to obtain the present invention. A transparent spherical sample of optical glass was obtained.

Subsequently, the obtained spherical sample was introduced into a molding mold consisting of an upper mold, a lower mold, and a body mold for accommodating them on the same axis, and the optical element was molded. The upper mold is connected to the press shaft, and the glass material installed in the lower mold can be press-formed by moving the press shaft up and down. In addition, a heater is built in the body type, and the temperature of the upper and lower types can be controlled.

A cemented carbide containing tungsten carbide as the main component was selected as the mold material. The molding surface of the upper mold was processed into a convex shape, the molding surface of the lower mold was processed into a concave shape, and an optical element having a convex meniscus shape was formed. A carbon film was formed on the molding surfaces of the upper and lower molds. Here, the film formed on the molded surface is not limited to the carbon film, and a noble metal-based film may be used.

The mold for molding was heated by a heater in a state where the upper mold was sufficiently pulled up by moving the press shaft, and press molding was performed at a temperature of Tg + 50 ° C. or less of the upper and lower molds to obtain a glass mold lens.

Table 1 shows the evaluation results of the obtained optical glasses and optical elements of Examples 1 to 23. Table 2 shows the evaluation results of the optical glass and the optical element of Comparative Examples 1 to 22.

For all the optical glasses of Examples 1 to 23, a transparent spherical sample could be obtained. In addition, no crystals were observed in any of the optical glasses of Examples 1 to 23 by observation with an optical microscope. Further, in all of the optical glasses of Examples 1 to 23, glass transition was confirmed by measurement with a differential scanning calorimeter, and the glass transition temperature was less than 705 ° C. In Example 8, a glass sample of Φ6.5 was subjected to a heating test at 720 ° C. (Tg + 50 ° C.), but no crystals were confirmed even after the heating test.

In all of the optical glasses of Examples 1 to 23, the total of RE ³⁺ is 15 cat% or more and 25 cat% or less, Nb ⁵⁺ is 20 cat% or more and 50 cat% or less, Zn ²⁺ is 10 cat% or more and 30 cat% or less, and Ta ⁵⁺ is 5 cat% or more. The composition was 20 cat% or less. Further, the composition was such that Ti ⁴⁺ was 20 cat% or less, Al ³⁺ was 5 cat% or less, and Ca ²⁺ was 5 cat% or less.

Further, all of the optical glasses of Examples 1 to 23 had a refractive index of 2.19 or more at the d line (587.56 nm) and an Abbe number (νd) of 22 or less. In addition, none of the pressed glass molded lenses had any appearance defects such as cracking, chipping, and cloudiness.

In Comparative Examples 1 to ^{3 and 5 to 8, since} the content of Al ³⁺ was more than 5 cat%, they crystallized and devitrified. That is, no glass was obtained. Comparative Examples 1 to 3 and 5 to 8 did not contain Ta ⁵⁺ .

In Comparative Examples 4, 9 to 11, since the content of Ca ²⁺ was more than 5 cat%, they crystallized and devitrified. That is, no glass was obtained. In addition, Comparative Examples 4, 9 to 11 did not contain Ta ⁵⁺ .

Comparative Examples 12 and 13 did not contain Ta ⁵⁺ . Therefore, a transparent glass body was obtained, but when a glass sample of Φ6.5 was placed in an electric furnace at 712 ° C and 727 ° C for 5 minutes, taken out and left to stand, and observed with an optical microscope (100 times), crystals were found. confirmed.

In Comparative Examples 14 and 15, the content of Ta ⁵⁺ was more than 20 cat%. Therefore, a transparent glass body was obtained, but the glass transition temperature was higher than the high temperature of 705 ° C. In Comparative Examples 14 and 15, high temperature was required when molding into a lens, and bubbles were likely to enter.

Comparative Example 16 had a La ³⁺ content of more than 25 cat%. Therefore, a transparent glass body was obtained, but the glass transition roll was higher than 705 ° C. Therefore, a high temperature is required when molding the lens, and bubbles are likely to enter.

In Comparative Example 17, since the content of La ³⁺ was less than 15 cat%, it crystallized and devitrified. That is, no glass was obtained.

In Comparative Example 18, the content of Zn ²⁺ was more than 30 cat%. Therefore, a transparent glass body was obtained, but volatilization during glass production was remarkable. Further, a glass sample of Φ6.5 was placed in an electric furnace at 717 ° C. for 5 minutes, taken out and left to stand, and observed with an optical microscope (100 times). Crystals were confirmed.

In Comparative Example 19, since the content of La ³⁺ was less than 15 cat% and the content of Zn ²⁺ was less than 10 cat%, it crystallized and was devitrified. That is, no glass was obtained.

In Comparative Example 20, since the content of La ³⁺ was less than 15 cat% and the content of Nb ⁵⁺ was more than 50 cat%, it crystallized and devitrified. That is, no glass was obtained.

In Comparative Example 21, since the content of La ³⁺ was more than 25 cat% and the content of Nb ⁵⁺ was less than 20 cat%, it crystallized and devitrified. That is, no glass was obtained.

In Comparative Example 22, since the content of Ti ⁴⁺ was more than 20 cat%, it crystallized and devitrified. That is, no glass was obtained.

For example, it can be used as a lens for cameras, digital cameras, surveillance cameras, etc., and as an optical pickup lens for VTRs, DVDs, etc.

1 Sintered body 2 Sample 3 Nozzle 4 Oxygen gas 5 Carbon dioxide laser 600 Camera 603, 605 Lens

Claims (10)

The sum of the cations that make up the glass is 100cat%.
15cat% ≤ RE ³⁺ ≤25cat% (RE represents only La or La replaced with at least one element selected from Gd, Y, Lu and Yb),
20cat% ≤ Nb ⁵⁺ ≤50cat%,
10cat% ≤ Zn ²⁺ ≤30cat%,
5cat% ≤ Ta ⁵⁺ ≤20cat%,
0cat% ≤ Ti ⁴⁺ ≤20cat%,
0cat% ≤ Al ³⁺ ≤5cat%,
0cat% ≤ Ca ²⁺ ≤ 5cat%
Optical glass characterized by satisfying. The sum of the cations that make up the glass is 100cat%.
The optical glass according to claim 1, wherein the content of La ³⁺ , Gd ³⁺ , Y ³⁺ , Lu ³⁺ , Yb ³⁺ , Nb ⁵⁺ , Zn ²⁺ , Ta ⁵⁺ and Ti ⁴⁺ is 90 cat% or more. The optical glass according to claim 1 or 2, wherein the content of at least one cation selected from Si ⁴⁺ , B ³⁺ , and P ⁵⁺ is 100 ppm or less. The optical glass according to any one of claims 1 to 3, wherein the refractive index on the d-line is 2.19 or more and 2.24 or less, and the Abbe number on the d-line is 19 or more and 22 or less. The optical glass according to any one of claims 1 to 4, wherein the glass transition temperature (Tg) is 705 ° C. or lower. The sum of the cations constituting the glass is 100 cat%, and 15 cat% ≤ RE ^{3 +} ≤ 30 cat% (RE is La only, or La is replaced with at least one element selected from Gd, Y, Lu, and Yb. ), 20cat% ≤Nb ⁵⁺ ≤50cat%, 10cat% ≤Zn ²⁺ ≤30cat%, 5cat% ≤Ta ⁵⁺ ≤20cat%, 0cat% ≤Ti ⁴⁺ ≤20cat%, 0cat% ≤Al ³⁺ ≤5cat%, 0cat A step of heating and melting a raw material powder satisfying% ≤ Ca ²⁺ ≤ 5 cat% to obtain a melt, and
The step of floating the melt with gas and
A step of cooling and solidifying the melt while the melt is floated, and
A method for manufacturing an optical glass, which comprises. The sum of the cations that make up the optical element is 100cat%.
15cat% ≤ RE ³⁺ ≤25cat% (RE represents only La or La replaced with at least one element selected from Gd, Y, Lu and Yb),
20cat% ≤ Nb ⁵⁺ ≤50cat%,
10cat% ≤ Zn ²⁺ ≤30cat%,
5cat% ≤ Ta ⁵⁺ ≤20cat%,
0cat% ≤ Ti ⁴⁺ ≤20cat%,
0cat% ≤ Al ³⁺ ≤5cat%,
0cat% ≤ Ca ²⁺ ≤ 5cat%
An optical element characterized by satisfying. An optical device including a housing and an optical system composed of a plurality of lenses in the housing.
An optical device according to claim 7, wherein the lens is the optical element. An image pickup apparatus comprising a housing, an optical system composed of a plurality of lenses in the housing, and an image pickup element that receives light that has passed through the optical system.
An image pickup apparatus in which the lens is the optical element according to claim 7. The imaging device according to claim 9, wherein the imaging device is a camera.

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