CN114763293A

CN114763293A - Optical glass and optical element

Info

Publication number: CN114763293A
Application number: CN202210021089.4A
Authority: CN
Inventors: 桑谷俊伍
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2021-01-13
Filing date: 2022-01-10
Publication date: 2022-07-19
Also published as: JP2022108395A; TW202231592A

Abstract

The present invention provides an optical glass having a refractive index nd in the range of 1.55 to 1.68 and high dispersion, and an optical element formed of the optical glass. An optical glass comprising B₂O₃And K₂O as a glass component, P₂O₅Is 35.0 to 60.0 mass%, B₂O₃Content of (A) and P₂O₅Mass ratio of contents of [ B ]₂O₃/P₂O₅]Less than 0.39, Na₂The content of O is 5.0-40.0 mass%, the content of BaO is 15.0 mass% or less, and the total content of MgO, CaO, SrO and BaO [ MgO + CaO + SrO + BaO ]]Is 18.0 mass% or lessZnO content of 15.0 mass% or less, Nb₂O₅Content of (b) 25.0 mass% or less, WO₃Is 5.0 mass% or less, Bi₂O₃TiO in an amount of 10.0 mass% or less₂、Nb₂O₅、WO₃、Bi₂O₃And Ta₂O₅Total content of [ TiO ]₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅]3.0 to 30.0 mass% of TiO₂、Nb₂O₅、WO₃、Bi₂O₃、Ta₂O₅And the total content of ZnO [ TiO₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅+ZnO]3.0 to 33.0 mass%.

Description

Optical glass and optical element

Technical Field

The present invention relates to an optical glass and an optical element.

Background

In the design of an optical system, the optical glass with the refractive index nd in the range of 1.55-1.68 and high dispersion has high use value in the aspects of correcting chromatic aberration, enabling the optical system to have high performance and miniaturization.

Patent documents 1 to 3 disclose optical glasses having a low abbe number ν d. However, the optical glasses of patent documents 1 to 3 have a large refractive index nd. Further, the optical glass disclosed in patent document 4 was measured for optical constants, and as a result, it was found that the refractive index nd was high although the abbe number ν d was relatively low. That is, patent documents 1 to 4 do not propose optical glass having a refractive index nd in the range of 1.55 to 1.68 and high dispersion.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-.

Patent document 2: japanese patent laid-open publication No. 2018-70414.

Patent document 3: international publication No. 2013/031385.

Patent document 4: japanese patent application laid-open No. 2020-505311.

Disclosure of Invention

Problems to be solved by the invention

Accordingly, an object of the present invention is to provide an optical glass having a refractive index nd in the range of 1.55 to 1.68 and high dispersion, and an optical element formed of the optical glass.

Means for solving the problems

The gist of the present invention is as follows.

(1) An optical glass comprising B₂O₃And K₂O is used as a glass component, and the glass composition,

P₂O₅the content of (B) is 35.0 to 60.0 mass%,

B₂O₃content of (A) and P₂O₅The quality ofQuantitative ratio [ B₂O₃/P₂O₅]The content of the compound is less than 0.39,

Na₂the content of O is 5.0 to 40.0 mass%,

the content of BaO is 15.0 mass% or less,

the total content of MgO, CaO, SrO and BaO [ MgO + CaO + SrO + BaO ] is 18.0 mass% or less,

the content of ZnO is 15.0 mass% or less,

Nb₂O₅the content of (B) is 25.0 mass% or less,

WO₃the content of (B) is 5.0 mass% or less,

Bi₂O₃the content of (B) is 10.0 mass% or less,

TiO₂、Nb₂O₅、WO₃、Bi₂O₃and Ta₂O₅Total content of [ TiO ]₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅]3.0 to 30.0% by mass,

TiO₂、Nb₂O₅、WO₃、Bi₂O₃、Ta₂O₅and the total content of ZnO [ TiO₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅+ZnO]3.0 to 33.0 mass%.

(2) An optical element formed of the optical glass according to the above (1).

Effects of the invention

According to the present invention, it is possible to provide an optical glass having a refractive index nd in the range of 1.55 to 1.68 and high dispersion, and an optical element formed of the optical glass.

Detailed Description

In the present invention and the present specification, unless otherwise specified, the glass composition of an optical glass is represented on an oxide basis. The "oxide-based glass composition" means a glass composition obtained by decomposing all glass raw materials at the time of melting and converting the glass raw materials into glass components present in the form of oxides in the optical glass,the formulation of the individual glass components follows the convention, recorded as SiO₂、TiO₂And the like. Unless otherwise specified, "%" means "% by mass" with the contents of glass components and the total content being based on mass.

The content of the glass component can be quantified by a known method such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), and the like. Further, in the present specification and the present invention, the content of the constituent component of 0% means that the constituent component is not substantially contained, allowing the component to be present in an inevitable impurity level.

In addition, in this specification, unless otherwise specified, the refractive index refers to a refractive index nd at the d line (wavelength 587.56nm) of helium.

The abbe number ν d is a value indicating a property related to chromatic dispersion, and is represented by the following formula. Here, nF is the refractive index at the F line (wavelength 486.13nm) of blue hydrogen, and nC is the refractive index at the C line (656.27nm) of red hydrogen.

vd＝(nd-1)/(nF-nC) …(1)

The optical glass of the present embodiment will be described in detail.

The optical glass of the present embodiment contains B₂O₃As a glass component. B is₂O₃The lower limit of the content of (b) is preferably 0.3%, and more preferably 0.6%, 0.8%, and 1.0% in this order. In addition, B₂O₃The upper limit of the content of (b) is preferably 15%, and more preferably 13.0%, 11.0%, and 10.0% in this order.

B₂O₃Is a network forming component of the glass and has the function of improving the thermal stability of the glass. By making B₂O₃Is in the above range, so that the thermal stability and devitrification resistance of the glass can be improved. On the other hand, when B₂O₃When the content of (b) is too large, the thermal stability and devitrification resistance of the glass tend to be lowered.

The optical glass of the present embodiment contains K₂O as a glass component. K₂The lower limit of the O content is preferably 3.0%, and more preferably 5.0%, 7.0%, 8.5%, in this order,9.00 percent and 9.20 percent. Furthermore, K₂The upper limit of the content of O is preferably 20.0%, and more preferably 17.0%, 15.0%, and 14.0% in this order.

K₂O has the effect of improving the thermal stability and solubility of the glass. By making K₂When the content of O is in the above range, an optical glass having excellent thermal stability and solubility can be obtained. On the other hand, when K₂When the content of O is too small, thermal stability and solubility may be deteriorated. In addition, when K is₂When the content of O is too large, thermal stability may be lowered.

In the optical glass of the present embodiment, P₂O₅The content of (B) is 35.0-60.0%. P₂O₅The lower limit of the content of (b) is preferably 40.0%, and more preferably 41.0%, 42.0%, 43.0%, 43.5%, and 45.5% in this order. Furthermore, P₂O₅The upper limit of the content of (b) is preferably 60.0%, and more preferably 58.0%, 56.0%, and 55.0% in this order.

P₂O₅The network-forming component for the glass is a component necessary for containing a high dispersion component in the glass more. By making P₂O₅When the content of (b) is in the above range, an optical glass having excellent thermal stability and desired optical constants can be obtained. On the other hand, when P₂O₅When the content of (b) is too small, there is a possibility that an optical glass having desired optical constants cannot be obtained. In addition, when P is₂O₅When the content of (A) is too large, the thermal stability of the glass may be deteriorated.

In the optical glass of the present embodiment, B₂O₃Content of (A) and P₂O₅Mass ratio of contents of [ B ]₂O₃/P₂O₅]Is 0.39 or less. The upper limit of the mass ratio is preferably 0.34, and more preferably 0.30, 0.27, and 0.25 in this order. The lower limit of the mass ratio is preferably 0.005, and more preferably 0.01, 0.015, and 0.02 in this order.

By making the mass ratio [ B ]₂O₃/P₂O₅]Within the above range, an optical glass having excellent thermal stability can be obtained. Another one isOn the other hand, when the mass ratio is too large, the thermal stability of the glass may deteriorate.

In the optical glass of the present embodiment, Na₂The content of O is 5.0-40.0%. Na (Na)₂The lower limit of the content of O is preferably 10%, and more preferably 12.0%, 13.5%, 15.0%, 16.5%, 17.5%, 18.0% in this order. Further, Na₂The upper limit of the content of O is preferably 30.0%, and more preferably 27.0%, 25.0%, and 23.0% in this order.

Na₂O has the effect of improving the thermal stability and solubility of the glass. By reacting Na₂When the content of O is in the above range, an optical glass having excellent thermal stability and solubility can be obtained. On the other hand, when Na₂When the content of O is too small, thermal stability and solubility may be deteriorated. Furthermore, when Na₂When the content of O is too large, thermal stability may be lowered.

In the optical glass of the present embodiment, the content of BaO is 15.0% or less. The upper limit of the content of BaO is preferably 13.0%, and more preferably 11.0%, 9.0%, and 7.0% in this order. Further, the content of BaO is preferably small, and the lower limit thereof is preferably 0%, and more preferably as small as 1.0%, 2.0%, 3.0% in this order. The content of BaO may be 0%.

BaO is also a glass component having an effect of improving the thermal stability and resistance to devitrification of the glass. By setting the content of BaO in the above range, an optical glass excellent in thermal stability and devitrification resistance can be obtained. On the other hand, when the content of BaO is too large, the high dispersion property of the glass is impaired, and the thermal stability and the devitrification resistance of the glass may be lowered.

In the optical glass of the present embodiment, the total content [ MgO + CaO + SrO + BaO ] of MgO, CaO, SrO and BaO is 18.0% or less. The upper limit of the total content is preferably 16.0%, and more preferably 14.0%, 12.0%, and 10.0% in this order. The total content is preferably small, and the lower limit thereof is preferably 0%, and more preferably as small as 1.0%, 2.0%, and 3.0% in this order. The total content may be 0%.

By setting the total content [ MgO + CaO + SrO + BaO ] in the above range, thermal stability and devitrification resistance can be maintained without hindering high dispersion. On the other hand, if the total content is too large, the high dispersion property of the glass may be impaired, and the thermal stability and the devitrification resistance of the glass may be lowered.

In the optical glass of the present embodiment, the content of ZnO is 15.0% or less. The upper limit of the ZnO content is preferably 13.0%, and more preferably 11.0%, 9.0%, and 7.0% in this order. Further, the content of ZnO is preferably small, and the lower limit thereof is preferably 0%, and more preferably as small as 1.0%, 2.0%, 3.0% in this order. The content of ZnO may be 0%.

When the content of ZnO is in the above range, the thermal stability of the glass can be improved and the increase in specific gravity of the glass can be suppressed. Further, an optical glass having desired optical constants can be obtained.

In the optical glass of the present embodiment, Nb₂O₅The content of (B) is less than 25.0%. Nb₂O₅The upper limit of the content of (b) is preferably 20.0%, and more preferably 15.0%, 10.0%, 7.0%, and 5.0% in this order. Further, Nb₂O₅The content of (b) is preferably small, and the lower limit thereof is preferably 0%, and more preferably at least 1.0%, 2.0%, and 3.0% in this order. Nb₂O₅The content of (B) may be 0%.

Nb₂O₅Are components that contribute to high refractive index and high dispersion. Therefore, by making Nb₂O₅The content of (b) is in the above range, whereby an optical glass having desired optical constants can be obtained. On the other hand, when Nb₂O₅When the content of (b) is too large, the thermal stability of the glass may be lowered and the coloring of the glass may be enhanced.

In the optical glass of the present embodiment, WO₃The content of (B) is 5.0% or less. WO₃The upper limit of the content of (b) is preferably 4.5%, and more preferably 4.0%, 3.5%, and 3.0% in this order. Furthermore, WO₃The lower limit of the content (c) is preferably 0%, and successively more preferably at least 0.5%, 1.0%, 1.5%. WO₃The content of (b) may be 0%.

By reacting WO₃Is composed ofWhen the amount is in the above range, the transmittance of the glass can be improved and the increase in specific gravity of the glass can be suppressed.

In the optical glass of the present embodiment, Bi₂O₃The content of (B) is 10.0% or less. Bi₂O₃The upper limit of the content of (b) is preferably 8.0%, and more preferably 7.0%, 6.0%, and 5.0% in this order. In addition, Bi₂O₃The content of (b) is preferably small, and the lower limit thereof is preferably 0%, and more preferably in the order of at least 1.0%, 1.5%, 2.0%. Bi₂O₃The content of (b) may be 0%.

By reacting Bi₂O₃The content of (b) is in the above range, so that the thermal stability of the glass can be improved and the increase of the specific gravity of the glass can be suppressed. On the other hand, when Bi₂O₃When the content of (b) is too large, the specific gravity may increase and the coloring of the glass may increase.

In the optical glass of the present embodiment, TiO₂、Nb₂O₅、WO₃、Bi₂O₃And Ta₂O₅Total content of [ TiO ]₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅]3.0 to 30.0%. The lower limit of the total content is preferably 6.0%, and more preferably 8.0%, 10.0%, and 12.0% in this order. The upper limit of the total content is preferably 29.0%, and more preferably 27.0%, 25.0%, 22.0%, 20.0%, and 18.0% in this order.

TiO₂、Nb₂O₅、WO₃、Bi₂O₃And Ta₂O₅Are components that contribute to the high dispersion of the glass. Therefore, by making the total content [ TiO ]₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅]Within the above range, an optical glass having desired optical constants can be obtained. In addition, the thermal stability of the glass can be improved. On the other hand, when the total content is too large, there is a possibility that an optical glass having desired optical constants cannot be obtained and that the glass is thermally stableThe quality may be lowered and the coloring of the glass may be enhanced.

In the optical glass of the present embodiment, TiO₂、Nb₂O₅、WO₃、Bi₂O₃、Ta₂O₅And the total content of ZnO [ TiO₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅+ZnO]3.0 to 33.0%. The lower limit of the total content is preferably 6.0%, and more preferably 8.0%, 10.0%, and 12.0% in this order. The upper limit of the total content is preferably 29.0%, and more preferably 27.0%, 25.0%, 22.0%, 20.0%, and 18.0% in this order.

By making the total content of [ TiO ]₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅+ZnO]Within the above range, an optical glass having desired optical constants can be obtained. In addition, the thermal stability of the glass can be improved. On the other hand, if the total content is too large, there is a possibility that an optical glass having desired optical constants cannot be obtained, and that the thermal stability of the glass is lowered and the coloring of the glass is enhanced.

The contents and ratios of glass components other than those described above in the optical glass of the present embodiment are given below as non-limiting examples.

TiO₂、Nb₂O₅、WO₃、Bi₂O₃And Ta₂O₅Total content of (2) and P₂O₅、B₂O₃、SiO₂、Li₂O、Na₂O、K₂O and Cs₂Mass ratio of total O content [ (TiO)₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅)/(P₂O₅+B₂O₃+SiO₂+Li₂O+Na₂O+K₂O+Cs₂O)]The upper limit of (d) is preferably 0.45, and more preferably 0.43, 0.40, 0.37, 0.35, and 0.33 in this order. The lower limit of the mass ratio is preferably 0.10, andless preferably 0.12, 0.14, 0.15.

The mass ratio [ TiO ] is preferable from the viewpoint of obtaining an optical glass having desired optical constants₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅)/(P₂O₅+B₂O₃+SiO₂+Li₂O+Na₂O+K₂O+Cs₂O)]Within the above range.

In the optical glass of the present embodiment, TiO is used₂Content of (A) and P₂O₅And B₂O₃Mass ratio of the total content of [ TiO ]₂/(P₂O₅+B₂O₃)]The lower limit of (b) is preferably 0.10, and more preferably 0.16, 0.21, and 0.24 in this order. The upper limit of the mass ratio is preferably 0.40, and more preferably 0.37, 0.35, and 0.33 in this order.

TiO₂The component having a particularly large effect of high dispersion among the high-refractive-index high-dispersion components. However, when TiO is used₂If the content of (b) is too large, thermal stability and devitrification resistance may be deteriorated. Therefore, the mass ratio [ TiO ] is preferred from the viewpoint of obtaining an optical glass having high dispersion, excellent thermal stability and excellent devitrification resistance₂/(P₂O₅+B₂O₃)]Within the above range.

In the optical glass of the present embodiment, P₂O₅、B₂O₃And SiO₂Total content of (2) and Li₂O、Na₂O、K₂O and Cs₂Mass ratio of total O content [ (P)₂O₅+B₂O₃+SiO₂)/(Li₂O+Na₂O+K₂O+Cs₂O)]The lower limit of (b) is preferably 0.80, and more preferably 1.00, 1.20, and 1.30 in this order. The upper limit of the mass ratio is preferably 2.60, and more preferably 2.40, 2.20, and 2.10 in this order.

From the viewpoint of obtaining an optical glass having excellent thermal stability, the mass ratio [ (P)₂O₅+B₂O₃+SiO₂)/(Li₂O+Na₂O+K₂O+Cs₂O)]Within the above range.

In the optical glass of the present embodiment, TiO is used₂In relation to TiO₂、Nb₂O₅、WO₃、Bi₂O₃And Ta₂O₅In total content of [ TiO ]₂/(TiO₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅)]The lower limit of (b) is preferably 0.20, and more preferably 0.30, 0.40, and 0.50 in this order. The upper limit of the mass ratio is preferably 0.90, and more preferably 0.80, 0.70, and 0.60 in this order. The mass ratio may be 1.00.

TiO₂The component having a particularly large effect of high dispersion among the high-refractive-index and high-dispersion components. Therefore, the mass ratio [ TiO ] is preferred from the viewpoint of obtaining an optical glass having desired optical constants and excellent thermal stability and devitrification resistance₂/(TiO₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅)]Within the above range.

In the optical glass of the present embodiment, Na₂Content of O and K₂Mass ratio of O content [ Na ]₂O/K₂O]The lower limit of (b) is preferably 0.80, and more preferably 1.00, 1.20, and 1.30 in this order. The upper limit of the mass ratio is preferably 2.70, and more preferably 2.50, 2.30, and 2.20 in this order.

From the viewpoint of improving the thermal stability and resistance to devitrification of the glass, the mass ratio [ Na ] is preferred₂O/K₂O]Within the above range. In particular, from the viewpoint of suppressing an excessive decrease in refractive index and a decrease in chemical durability, the lower limit of the mass ratio is preferably in the above range.

In the optical glass of the present embodiment, Al₂O₃The upper limit of the content of (b) is preferably 15.0%, and more preferably 11.0%, 8.0%, and 6.0% in this order. Further, Al₂O₃The lower limit of the content of (b) is preferably 0%, and more preferably 0.5%, 1.0%, and 1.5% in this order. Al (Al)₂O₃May also be containedIs 0%.

From the viewpoint of suppressing deterioration of devitrification resistance of the glass, Al is preferable₂O₃The content of (b) is within the above range.

In the optical glass of the present embodiment, SiO₂The upper limit of the content of (b) is preferably 5.0%, and more preferably 4.0%, 3.0%, and 2.0% in this order. SiO 2₂The lower limit of the content of (b) is preferably 0%. SiO 2₂The content of (B) may be 0%.

SiO₂Is a network-forming component of glass, and has the effects of improving the thermal stability, chemical durability, weather resistance of glass, increasing the viscosity of molten glass, and facilitating the shaping of the molten glass. On the other hand, when SiO₂When the amount of (B) is large, the devitrification resistance of the glass tends to be low. Therefore, from the viewpoint of improving the thermal stability, resistance to devitrification, and the like of the glass, SiO is preferable₂The upper limit of the content of (B) is the above range.

In melting glass, a melting tool made of quartz glass, such as a crucible made of quartz glass, is sometimes used. In this case, a small amount of SiO is dissolved into the glass melt from the melting vessel₂Therefore, even if the glass raw material does not contain SiO₂The produced glass will also contain a small amount of SiO₂. SiO mixed into glass from melting vessel made of quartz glass₂The amount of (b) is also dependent on the melting conditions, but is, for example, about 0.5 to 1 mass% relative to the total content of all glass components. SiO 2₂SiO in the case where the content ratio of the other glass components is kept constant₂The amount of the (B) is increased by about 0.5 to 1 mass%. The amount is increased or decreased depending on the melting conditions. Due to SiO₂Since optical properties such as refractive index and Abbe number are changed, the content of (2) is adjusted to SiO₂The content of the other glass components is finely adjusted to obtain an optical glass having desired optical characteristics.

In the optical glass of the present embodiment, TiO₂The lower limit of the content of (b) is preferably 0%, and more preferably 5.0%, 9.0%, and 12.0% in this order. TiO 2₂The content of (B) may be 0%. Furthermore, TiO₂The upper limit of the content of (B) is preferablyIs 30.0%, and more preferably 25.0%, 21.0%, and 18.0% in this order.

TiO₂Greatly contributing to high dispersion. On the other hand, TiO₂It is easier to increase the coloration of the glass. In addition, TiO is used in the process of forming and gradually cooling molten glass to obtain optical glass₂The crystal formation in the glass is promoted, and the transparency of the glass is lowered (cloudiness). Therefore, TiO is preferred₂The content of (B) is in the above range.

In the optical glass of the present embodiment, Ta₂O₅The upper limit of the content of (b) is preferably 10.0%, and more preferably 5.0%, 3.0%, and 1.0% in this order. Ta₂O₅The lower limit of the content of (b) is preferably 0%. Ta₂O₅The content of (b) may be 0%.

Ta₂O₅A glass component having an effect of improving the thermal stability and resistance to devitrification of the glass. On the other hand, Ta₂O₅The refractive index is increased and the dispersion of the glass is increased. In addition, when Ta₂O₅When the amount of (b) is large, the thermal stability of the glass is lowered, and the glass raw material is likely to be melted and left when the glass is melted. Therefore, Ta is preferred₂O₅The content of (B) is in the above range. Further, Ta is compared with other glass components₂O₅For very expensive components, when Ta₂O₅When the content of (A) is increased, the production cost of the glass is increased. Further, since Ta is compared with other glass components₂O₅Since the molecular weight of (2) is large, the specific gravity of the glass may be increased, and as a result, the weight of the optical element may be increased.

In the optical glass of the present embodiment, Li₂The upper limit of the content of O is preferably 5%, and more preferably 3%, 2%, and 1% in this order. Li₂The lower limit of the content of O is preferably 0%. Li₂The content of O may be 0%.

Li₂O has the effect of lowering the glass transition temperature Tg. On the other hand, when Li₂When the content of O increases, the acid resistance decreases. Therefore, Li is preferable₂The content of O is in the above range.

In the optical glass of the present embodiment, Li₂O、Na₂O and K₂Total content of O [ Li₂O+Na₂O+K₂O]The upper limit of (d) is preferably 45.0%, and more preferably 42.0%, 39.0%, and 37.0% in this order. The lower limit of the total content is preferably 10.0%, and more preferably 15.0%, 19.0%, and 22.0% in this order.

Li₂O、Na₂O and K₂O has an effect of improving the thermal stability of the glass. However, when their content is increased, chemical durability and weather resistance are lowered. Therefore, Li is preferable₂O、Na₂O and K₂Total content of O [ Li₂O+Na₂O+K₂O]The above range.

In the optical glass of the present embodiment, Cs₂The upper limit of the content of O is preferably 5%, and more preferably 3%, 2%, and 1% in this order. In addition, Cs₂The lower limit of the content of O is preferably 0%. Cs₂The content of O may be 0%.

Although Cs₂O has an effect of improving the thermal stability of the glass, but when the content is increased, the thermal stability, chemical durability, weather resistance of the glass are decreased. Therefore, Cs is preferred₂The content of O is in the above range.

In the optical glass of the present embodiment, the upper limit of the content of MgO is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5.0% in this order. The lower limit of the content of MgO is preferably 0%. The MgO content may be 0%.

In the optical glass of the present embodiment, the upper limit of the content of CaO is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5% in this order. The lower limit of the CaO content is preferably 0%. The content of CaO may be 0%.

In the optical glass of the present embodiment, the upper limit of the SrO content is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5.0% in this order. The lower limit of the SrO content is preferably 0%. The SrO content may be 0%.

MgO, CaO, SrO, BaO are glass components having an effect of improving thermal stability and resistance to devitrification of the glass. However, when the content of these glass components is increased, high dispersion properties are impaired, and thermal stability and devitrification resistance of the glass are lowered. Therefore, it is preferable that the respective contents of these glass components are in the above ranges, respectively.

In the optical glass of the present embodiment, ZrO₂The upper limit of the content of (b) is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5.0% in this order. Furthermore, ZrO₂The lower limit of the content of (b) is preferably 0%. ZrO (ZrO)₂The content of (b) may be 0%.

ZrO₂A glass component having an effect of improving the thermal stability and resistance to devitrification of the glass. However, when ZrO₂When the content of (b) is too large, thermal stability tends to be lowered. Therefore, ZrO is preferable from the viewpoint of maintaining thermal stability and devitrification resistance of the glass well₂The content of (B) is in the above range.

In the optical glass of the present embodiment, Sc₂O₃The upper limit of the content of (b) is preferably 2%. Further, Sc₂O₃The lower limit of the content of (b) is preferably 0%.

In the optical glass of the present embodiment, HfO₂The upper limit of the content of (b) is preferably 2%. Further, HfO₂The lower limit of the content of (b) is preferably 0%.

Sc₂O₃、HfO₂All the components have the function of improving the refractive index nd and are high in price. Therefore, Sc is preferable₂O₃、HfO₂The respective contents of (a) and (b) are within the above ranges.

In the optical glass of the present embodiment, Lu₂O₃The upper limit of the content of (b) is preferably 2%. Furthermore, Lu₂O₃The lower limit of the content of (b) is preferably 0%.

Lu₂O₃Has the function of improving the refractive index nd. In addition, because of the large molecular weight, it is also a glass component that increases the specific gravity of the glass. Therefore, Lu is preferred₂O₃The content of (B) is in the above range.

In the bookIn the optical glass of embodiment, GeO₂The upper limit of the content of (b) is preferably 2%. Furthermore, GeO₂The lower limit of the content of (b) is preferably 0%.

GeO₂Is a component which has an effect of increasing the refractive index nd and is extremely expensive among glass components which are generally used. Accordingly, GeO is preferred from the viewpoint of reducing the production cost of the glass₂The content of (B) is in the above range.

In the optical glass of the present embodiment, La₂O₃The upper limit of the content of (b) is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5.0% in this order. Further, La₂O₃The lower limit of the content of (b) is preferably 0%. La₂O₃The content of (B) may be 0%.

When La₂O₃When the content (c) is increased, the thermal stability and devitrification resistance of the glass are lowered, and the glass is easily devitrified during production. Therefore, La is preferable from the viewpoint of suppressing a decrease in thermal stability and resistance to devitrification₂O₃The content of (B) is in the above range.

In the optical glass of the present embodiment, Gd₂O₃The upper limit of the content of (b) is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5.0% in this order. In addition, Gd₂O₃The lower limit of the content of (b) is preferably 0%.

When Gd is present₂O₃When the content of (b) is too large, the thermal stability and devitrification resistance of the glass are lowered, and the glass is easily devitrified during production. In addition, when Gd is present₂O₃When the content of (b) is too large, the specific gravity of the glass increases, which is not preferable. Therefore, Gd is preferred from the viewpoint of keeping the thermal stability and devitrification resistance of the glass well and suppressing the increase in specific gravity₂O₃The content of (B) is in the above range.

In the optical glass of the present embodiment, Y is₂O₃The upper limit of the content of (b) is preferably 10.0%, and more preferably 8.0%, 7.0%, 6.0%, and 5.0% in this order. Furthermore, Y₂O₃The lower limit of the content of (b) is preferably 0%. Y is₂O₃The content of (B) may be 0%.

On the other hand, when Y₂O₃When the content of (A) is too large, the thermal stability and devitrification resistance of the glass are lowered. Therefore, from the viewpoint of suppressing the decrease in thermal stability and resistance to devitrification, Y is preferable₂O₃The content of (B) is in the above range.

In the optical glass of the present embodiment, Yb₂O₃The upper limit of the content of (b) is preferably 2%. In addition, Yb₂O₃The lower limit of the content of (b) is preferably 0%.

Because of Yb₂O₃And La₂O₃、Gd₂O₃、Y₂O₃The specific gravity of the glass is increased because of the large molecular weight. When the specific gravity of the glass increases, the mass of the optical element increases. When, for example, a lens having a large mass is incorporated into an auto focus type image pickup lens, power required for driving the lens at the time of auto focus increases, and battery consumption increases. Therefore, it is desired to reduce Yb₂O₃The content of (b), the increase of the specific gravity of the glass is suppressed.

In addition, when Yb₂O₃When the content of (A) is too large, the thermal stability and devitrification resistance of the glass are lowered. From the viewpoint of preventing the thermal stability of the glass from decreasing and suppressing the increase in specific gravity, Yb is preferable₂O₃The content of (B) is in the above range.

The optical glass of the present embodiment is preferably composed mainly of the above-mentioned glass components, i.e., contains B₂O₃、K₂O、P₂O₅、Na₂O as an essential component, ZnO, Nb₂O₅、WO₃、Bi₂O₃、Al₂O₃、SiO₂、TiO₂、Ta₂O₅、Li₂O、Cs₂O、MgO、CaO、SrO、BaO、ZrO₂、Sc₂O₃、HfO₂、Lu₂O₃、GeO₂、La₂O₃、Gd₂O₃、Y₂O₃And Yb₂O₃The total content of the above glass components is preferably 95% as optional componentsThe content is more preferably 98% or more, still more preferably 99% or more, and still more preferably 99.5% or more.

In the optical glass of the present embodiment, TeO₂The upper limit of the content of (b) is preferably 2%. Furthermore, TeO₂The lower limit of the content of (b) is preferably 0%.

Because of TeO₂Has toxicity, so TeO reduction is preferable₂The content of (b). Therefore, TeO is preferable₂The content of (b) is within the above range.

The optical glass of the present embodiment is preferably composed substantially of the above glass components, but may contain other components within a range not affecting the action and effect of the present invention. In the present invention, the inclusion of inevitable impurities is not excluded.

< composition of other Components >

Pb, As, Cd, Tl, Be, Se are toxic. Therefore, the optical glass of the present embodiment preferably does not contain these elements as a glass component.

U, Th and Ra are radioactive elements. Therefore, the optical glass of the present embodiment preferably does not contain these elements as a glass component.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm increase the coloration of glass and can be a source of fluorescence. Therefore, the optical glass of the present embodiment preferably does not contain these elements as a glass component.

Sb(Sb₂O₃)、Sn(SnO₂)、Ce(CeO₂) An element that can be added arbitrarily and functions as a clarifying agent. Wherein Sb (Sb)₂O₃) The clarifying agent has a large clarifying effect. However, Sb (Sb)₂O₃) Has strong oxidizing property when Sb (Sb)₂O₃) When the amount of (B) is large, Sb (Sb) contained in the glass at the time of precision press molding₂O₃) The molding surface of the press molding die is oxidized. Therefore, the molding surface is significantly deteriorated with repetition of the precision press molding, and the precision press molding cannot be performed. Also, the surface quality of the molded optical element is degraded. In addition, with Sb (Sb)₂O₃) In contrast, Sn (SnO)₂)、Ce(CeO₂) Has a small clarification effect. Further, when Ce (CeO) is added₂) When the amount of (B) is large, the coloring of the glass becomes strong. Therefore, in the case of adding a clarifier, attention is paid to the amount added, and Sb (Sb) is preferably added₂O₃)。

The contents of the following clarifying agents are shown in terms of oxides.

Sb₂O₃The content of (D) is represented by an addition rate. Namely, mixing Sb₂O₃、SnO₂And CeO₂Sb content of all glass components except for 100 mass%₂O₃The content of (b) is preferably 1% by mass or less, and more preferably 0.2% by mass or less, 0.05% by mass or less, 0.02% by mass or less, and 0.01% by mass or less in this order. Sb₂O₃The content of (b) may be 0 mass%.

SnO₂The content of (B) is also expressed by an addition rate. Namely, SnO₂、Sb₂O₃And CeO₂SnO when total content of all other glass components is 100% by mass₂The content of (b) is preferably 1% by mass or less, more preferably 0.2% by mass or less, and further preferably 0.02% by mass or less. SnO₂The content of (b) may be 0% by mass, and preferably substantially no SnO is contained₂. By reacting SnO₂The content of (b) is within the above range, and the clarity of the glass can be improved.

CeO₂The content of (D) is also expressed by the addition rate. Namely, CeO is added₂、Sb₂O₃、SnO₂CeO where the total content of all other glass components is set to 100 mass%₂The content of (b) is preferably 1% by mass or less, more preferably 0.2% by mass or less, and further preferably 0.02% by mass or less. CeO (CeO)₂The content of (B) may be 0 mass%, and preferably, CeO is not substantially contained₂. By making CeO₂The content of (b) is in the above range, and the glass can be improved in the fining property.

(glass Properties)

< refractive index nd >

In the optical glass of the present embodiment, the refractive index nd is preferably in the range of 1.55 to 1.68, more preferably 1.55 to 1.65 or 1.57 to 1.64.

By appropriately adjusting the content of each glass component, the refractive index nd can be made to a desired value. The component having the effect of relatively increasing the refractive index nd (high refractive index-increasing component) is Nb₂O₅、TiO₂、WO₃、Bi₂O₃、Ta₂O₅、ZrO₂、La₂O₃And the like. On the other hand, the component having the effect of relatively lowering the refractive index nd (low refractive index-lowering component) is P₂O₅、SiO₂、B₂O₃、Li₂O、Na₂O、K₂O, and the like. Thus, by making TiO₂、Nb₂O₅、WO₃、Bi₂O₃And Ta₂O₅Relative to the total content of P₂O₅、B₂O₃、SiO₂、Li₂O、Na₂O、K₂O and Cs₂Mass ratio of total O content [ TiO ]₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅)/(P₂O₅+B₂O₃+SiO₂+Li₂O+Na₂O+K₂O+Cs₂O)]The refractive index nd can be increased by increasing the mass ratio, and the refractive index nd can be decreased by decreasing the mass ratio.

< Abbe number ν d >

In the optical glass of the present embodiment, the abbe number ν d is preferably 25 to 50, more preferably 28 to 45.

The abbe number ν d can be made a desired value by appropriately adjusting the contents of the respective glass components. A component having a relatively low Abbe number ν d, i.e., a high dispersion component of Nb₂O₅、TiO₂、WO₃、Bi₂O₃、Ta₂O₅、ZrO₂And so on. On the other hand, a component having a relatively high Abbe number ν d, that is, a low-dispersion component is P₂O₅、SiO₂、B₂O₃、Li₂O、Na₂O、K₂O、La₂O₃BaO, CaO, SrO, etc.

< specific gravity of glass >

In the optical glass of the present embodiment, the specific gravity is preferably 3.20 or less, and more preferably 3.10 or less and 2.95 or less in this order. The lower limit of the specific gravity is not particularly limited, but is usually 2.50. If the specific gravity of the glass can be reduced, the weight of the lens can be reduced. As a result, the power consumption for driving the auto-focus of the imaging lens having the lens mounted thereon can be reduced.

< glass transition temperature Tg >

The glass transition temperature Tg of the optical glass of the present embodiment is preferably 520 ℃ or lower, and more preferably 500 ℃ or lower, 480 ℃ or lower, and 470 ℃ or lower in this order. The lower limit of the glass transition temperature Tg is generally 300 ℃ and preferably 350 ℃.

When the upper limit of the glass transition temperature Tg satisfies the above range, the increase of the forming temperature and the annealing temperature of the glass can be suppressed, and the thermal damage to the press-forming equipment and the annealing equipment can be reduced. Further, when the lower limit of the glass transition temperature Tg satisfies the above range, the desired abbe number and refractive index can be maintained, and the thermal stability of the glass can be easily maintained.

< light transmittance of glass >

The light transmittance of the optical glass of the present embodiment can be evaluated by the coloring degree λ 5.

Spectral transmittance was measured at a wavelength of 200 to 700nm for a glass sample having a thickness of 10.0 mm. + -. 0.1mm, and λ 5 was defined as a wavelength at which the external transmittance is 5%.

The λ 5 of the optical glass of the present embodiment is preferably 390nm or less, more preferably 380nm or less, and further preferably 375nm or less.

By using optical glass with a wavelength of λ 5 shortened, an optical element capable of performing appropriate color reduction can be provided.

In the optical glass of the present embodiment, the average linear expansion coefficient α is 100 to 300 DEG C_100-300The lower limit of (B) is preferably 100X 10^-7℃^-1And still more preferably 120 × 10 in this order^-7℃^-1、130×10^-7℃^-1、140×10^-7℃^-1. Further, from the viewpoint of maintaining the stability of the glass and obtaining desired optical characteristics, the average linear expansion coefficient α_100-300Can be exemplified by an upper limit of (2) 210 × 10^-7℃^-1Preferably 205X 10^-7℃^-1Further, more preferably 200 × 10 in this order^-7℃^-1、195×10^-7℃^-1、190×10^-7℃^-1。

JOGIS 08-2019-based standard measurement average linear expansion coefficient alpha_100-300. The test sample is a round bar with the length of 20mm +/-0.5 mm and the diameter of 5mm +/-0.5 mm. Heating was performed with a load of 98mN applied to the sample at a constant rate of 4 ℃ per minute, and the temperature and the elongation of the sample were measured every 1 second. Average linear expansion coefficient alpha_100-300The average value of the linear expansion coefficient of 100-300 ℃.

In addition, in this specification, the unit "DEG C" is used^-1"denotes the average linear expansion coefficient α, however," K "is used^-1"the average linear expansion coefficient α is the same in value as the unit.

(production of optical glass)

The optical glass according to the embodiment of the present invention may be produced by a known glass production method using a glass raw material prepared to have the above-described predetermined composition. For example, a plurality of compounds are prepared, mixed well to form a batch raw material, and the batch raw material is put into a quartz crucible or a platinum crucible to be roughly melted (rough melt). The melt obtained by the coarse melting is quenched and pulverized to obtain cullet. Further, the cullet is charged into a platinum crucible, heated and remelted (remelt) to form molten glass, and the molten glass is further clarified and homogenized, and then molded and slowly cooled to obtain optical glass. The molten glass may be formed and gradually cooled by any known method.

The compound used in preparing the batch raw materials is not particularly limited as long as a desired glass component is introduced into the glass so as to have a desired content, and examples of such a compound include oxides, carbonates, nitrates, hydroxides, fluorides, and the like.

(production of optical element, etc.)

For producing an optical element using the optical glass of the embodiment of the present invention, a known method may be used. For example, a glass material made of the optical glass of the present invention is produced by melting a glass raw material to form a molten glass, pouring the molten glass into a mold, and molding the molten glass into a plate shape. The obtained glass material is appropriately cut, ground and polished to prepare a cut piece having a size and a shape suitable for press molding. The cut pieces were heated and softened, and press-molded (re-pressed) by a known method to produce an optical element blank having a shape similar to that of the optical element. The optical element blank is annealed, polished and polished by a known method to produce an optical element.

The optically functional surface of the produced optical element may be coated with an antireflection film, a total reflection film, or the like depending on the purpose of use.

Examples of the optical element include various lenses such as a spherical lens, a prism, and a grating.

The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

(examples)

[ preparation of glass sample ]

Raw materials such as phosphates, carbonates, and oxides, which are compound raw materials corresponding to the respective components, were weighed so as to form glasses having compositions of sample nos. 1 to 32 shown in tables 1(1) and (2), and sufficiently mixed to obtain formulated raw materials. The prepared raw materials are put into a platinum crucible, heated and melted at 900 to 1350 ℃ in an atmospheric atmosphere, and homogenized and clarified by stirring to obtain molten glass. The molten glass was poured into a mold for molding, and slowly cooled to obtain a block-shaped glass sample.

Alternatively, the blending raw material may be put into a quartz glass crucible, melted, moved to a platinum crucible, further heated and melted, homogenized and clarified by stirring to obtain molten glass, and the obtained molten glass may be poured into a molding die to be molded and slowly cooled.

[ evaluation of glass sample ]

With respect to the obtained glass samples, the glass composition, specific gravity, refractive index nd, Abbe number ν d, λ 5, glass transition temperature Tg, and average linear expansion coefficient α were measured by the methods shown below_100-300And, resistance to devitrification was evaluated. The results are shown in tables 2(1) and (2).

{1} glass composition

With respect to the obtained glass sample, the content of each glass component was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES).

Specific gravity of {2}

The measurement was performed based on the Japan optical glass industry Association standard JOGIS-05.

{3} refractive index nd and Abbe number ν d

The measurement was performed based on the Japan optical glass industry Association standard JOGIS-01.

{4}λ5

The glass sample was processed so as to have a thickness of 10mm and planes parallel to each other and optically polished, and the spectral transmittance in a wavelength region of wavelengths from 280nm to 700nm was measured. The spectral transmittance B/a was calculated by setting the intensity of light perpendicularly incident on the plane on one side of the optical polishing as intensity a and the intensity of light exiting from the plane on the other side as intensity B. The wavelength at which the spectral transmittance is 5% is defined as λ 5. The spectral transmittance also includes reflection loss of light on the sample surface.

{5} glass transition temperature Tg

The glass transition temperature Tg was determined from a DSC chart obtained when a glass in a solid state was heated using a differential scanning calorimeter DSC3300SA (NETZSCH Japan K.K.).

{6} average Linear expansion coefficient α_100-300

For the resulting glass samples, the average linear expansion coefficient was measured with reference to the standard of JOGIS 08-2019. The average linear expansion coefficient was measured using a thermomechanical analyzer TMA4000SE (NETZSCH Japan). The sample is a round bar with the length of 20mm +/-0.5 mm and the diameter of 5mm +/-0.5 mm. In the measurement, the temperature and the elongation of the sample were measured every 1 second while heating the sample at a constant rate of 4 ℃ per minute with a load of 98mN applied. Taking the average value of the linear expansion coefficients of 100-300 ℃ as the average linear expansion coefficient alpha_100-300。

(7) resistance to devitrification

The presence or absence of crystals or cloudiness of the obtained glass sample was confirmed by an optical microscope. The observation magnification of the optical microscope is 10 to 100 times. The glass was judged to be "good" when no crystal or white turbidity was observed in the glass, and judged to be "poor" when at least one of the crystal and the white turbidity was observed. The samples No.1 to 32 of the examples were all judged to be "good". It was confirmed that sample Nos. 1 to 32 of the examples are glasses excellent in devitrification resistance.

[ TABLE 1(1) ]

[ TABLE 1(2) ]

[ TABLE 2(1) ]

[ TABLE 2(2) ]

(example 2)

The glass sample obtained in example 1 was cut and polished to prepare a cut piece. The cut pieces were press-molded by reheating pressing to produce optical element blanks. The optical element blank is subjected to precision annealing to precisely adjust the refractive index to a desired refractive index, and then, ground and polished by a known method to obtain various lenses such as a biconvex lens, a biconcave lens, a plano-convex lens, a plano-concave lens, a concave meniscus lens and a convex meniscus lens.

The embodiments disclosed herein are illustrative and not restrictive in all respects. The scope of the present invention is indicated by the scope of the claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.

For example, the optical glass according to one embodiment of the present invention can be produced by adjusting the composition of the glass composition exemplified above as described in the specification.

It is needless to say that two or more items described as examples or preferable ranges in the specification may be arbitrarily combined.

Claims

1. An optical glass comprising B₂O₃And K₂O is used as a glass component, and the glass composition,