CN112551893A

CN112551893A - Optical glass and optical element

Info

Publication number: CN112551893A
Application number: CN202010939733.7A
Authority: CN
Inventors: 桑谷俊伍
Original assignee: Hoya Corp
Current assignee: Hoya Corp
Priority date: 2019-09-26
Filing date: 2020-09-09
Publication date: 2021-03-26
Also published as: TW202113397A; JP2021050125A; JP7401236B2

Abstract

The present invention provides an optical glass having desired optical constants and excellent stability in reheating, and an optical element made of the optical glass. The refractive index nd of the optical glass is 1.60-1.72, the Abbe number vd is 22-36, and the optical glass has a specific content range of components.

Description

Optical glass and optical element

Technical Field

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

Background

The glass softens when heated to a temperature above the glass transition temperature Tg. As a method for molding an optical element utilizing such properties, the following press molding method (reheat press) is known: a glass material obtained by heating, melting and molding a glass material is reheated, softened, and pressed to be molded into a desired shape. At this time, the glass may be crystallized and devitrified by reheating the glass. In particular, in phosphate-based highly dispersible optical glasses, devitrification resistance tends to be insufficient.

In designing an optical system, a glass having a lower abbe number ν d among optical glasses having similar refractive indexes nd is highly valuable in correcting chromatic aberration, and making the optical system highly functional and compact.

Patent document 1 discloses an optical glass having a low abbe number ν d. However, it is known that the glass of patent document 1 does not satisfy the required resistance to devitrification.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2019-1697

Disclosure of Invention

Problems to be solved by the invention

The glass excellent in stability upon reheating can suppress devitrification due to reheating. Accordingly, an object of the present invention is to provide an optical glass having desired optical constants and excellent stability in reheating, and an optical element made of the optical glass.

Means for solving the problems

The gist of the present invention is as follows.

(1) An optical glass having a refractive index nd of 1.60 to 1.72,

the Abbe number vd is 22-36,

P₂O₅the content of (B) is 20 to 55 mass%,

Nb₂O₅the content of (B) is 0 to 45% by mass,

K₂the content of O is more than 0 mass% and 13 mass% or less,

WO₃the content of (a) is less than 5 mass%,

the content of ZnO is less than 15 mass%,

Al₂O₃the content of (a) is less than 5 mass%,

TiO₂、Nb₂O₅、WO₃、Bi₂O₃and Ta₂O₅Total content of [ TiO ]₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅]15 to 45 mass% of the binder,

P₂O₅、B₂O₃and SiO₂The total content of (A) to Li₂O、Na₂O、K₂O and Cs₂Mass ratio of total O content [ (P)₂O₅+B₂O₃+SiO₂)/(Li₂O+Na₂O+K₂O+Cs₂O)]Is 1.0 to 2.0,

B₂O₃relative to P₂O₅Mass ratio of contents of [ B ]₂O₃/P₂O₅]The content of the compound is less than 0.39,

Na₂the content of O relative to K₂Mass ratio of O content [ Na ]₂O/K₂O]Is a mixture of a water-soluble polymer and a water-soluble polymer, wherein the water-soluble polymer is at least 1.0,

the total content of MgO, CaO, SrO and BaO [ MgO + CaO + SrO + BaO ] is 8.0 mass% or less,

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)]Is 0.75 or less.

(2) The optical glass according to the above (1), wherein,

B₂O₃relative to P₂O₅Mass ratio of contents of [ B ]₂O₃/P₂O₅]Greater than 0.

(3) The optical glass according to the above (1) or (2), wherein,

Na₂the content of O relative to K₂Mass ratio of O content [ Na ]₂O/K₂O]Is 5.0 or less.

(4) The optical glass according to any one of (1) to (3) above, wherein,

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)]Is 0.15 or more.

(5) The optical glass according to any one of (1) to (4) above, wherein,

TiO₂in relation to TiO₂、Nb₂O₅、WO₃、Bi₂O₃And Ta₂O₅In total content of [ TiO ]₂/(TiO₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅)]Is 0.10 or more.

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

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide an optical glass having a desired optical constant and further excellent in stability at the time of reheating, and an optical element made of the optical glass.

Detailed Description

In the present invention and the present specification, unless otherwise specified, the glass composition of the optical glass is expressed on an oxide basis. Here, the "oxide-based glass composition" refers to a glass composition obtained by converting all glass raw materials into substances existing in the form of oxides in optical glass through decomposition at the time of melting, and the expression of each glass component is conventionally described as SiO₂、TiO₂And the like. Unless otherwise specified, "%" means "% by mass" with respect to the content and total content of glass components.

The content of the glass component can be determined by a known method, for example, inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), or the like. 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, and the content of the constituent component is allowed to be at an inevitable impurity level.

In the present specification, both the thermal stability and the devitrification resistance of a glass mean the degree of difficulty in crystal precipitation in the glass. In particular, the thermal stability refers to the degree of difficulty of crystal precipitation when the glass in a molten state is solidified, and the devitrification resistance refers to the degree of difficulty of crystal precipitation when the solidified glass is reheated such as in reheat pressing.

In the present specification, unless otherwise specified, the refractive index "nd" refers to a refractive index "nd" of helium d-ray (wavelength 587.56 nm).

The abbe number ν d is used as a value representing a property related to dispersion, and is represented by the following numerical expression. Where nF is the refractive index of blue hydrogen at F-ray (486.13 nm) and nC is the refractive index of red hydrogen at C-ray (656.27 nm).

Νd＝(nd－1)/nF－nC···(1)

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

In the optical glass of the present embodiment, the refractive index nd is 1.60 to 1.72. The lower limit of the refractive index nd may be 1.62, 1.64 or 1.66 and the upper limit of the refractive index nd may be 1.71, 1.70 or 1.695.

The refractive index nd can be set to a desired value by appropriately adjusting the content of each glass component. The component having the effect of relatively increasing the refractive index nd (high refractive index component) is Nb₂O₅、TiO₂、WO₃、Bi₂O₃、Ta₂O₅、ZrO₂、La₂O₃And the like. On the other hand, the component having the action of relatively lowering the refractive index nd (low refractive index component) is P₂O₅、SiO₂、B₂O₃、Li₂O、Na₂O、K₂O, and the like. Thus, it is possible to increase the amount of TiO by adding₂、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)]To increase the refractive index nd, the refractive index nd can be decreased by decreasing the mass ratio.

In the optical glass of the present embodiment, Abbe number vd is 22 to 36. The lower limit of the abbe number ν d may be 24, 25, or 26, and the upper limit of the abbe number ν d may be 34, 32, or 30.

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

In the optical glass of the present embodiment, P₂O₅The content of (A) is 20-55%. P₂O₅The lower limit of the content of (b) is preferably 23%, and more preferably 25%, 27%, and 29% in this order. In addition, P₂O₅The upper limit of the content of (b) is preferably 51%, and more preferably 49%, 48%, and 47% in this order.

P₂O₅Is a network-forming component of glass, and is a component necessary for containing a large amount of a highly dispersed component in glass. By adding P₂O₅When the content of (b) is in the above range, thermal stability can be improved.

In the optical glass of the present embodiment, Nb₂O₅The content of (A) is 0-45%. Nb₂O₅The lower limit of the content of (b) is preferably 4%, and more preferably 7%, 9%, and 10% in this order. In addition, Nb₂O₅The upper limit of the content of (b) is preferably 41%, and more preferably 39%, 37%, and 36%, in this order.

Nb₂O₅Is a component contributing to increase in refractive index and dispersion. Therefore, by adding Nb₂O₅When the content of (b) is in the above range, an optical glass having desired optical constants can be obtained. On the other hand, Nb₂O₅If the content of (b) is too large, the thermal stability of the glass may be lowered and the coloring of the glass may be increased.

In the optical glass of the present embodiment, K₂The content of O is more than 0% and 13% or less. K₂The lower limit of the content of O is preferably 1%, and more preferably 2%, 3%, and 4% in this order. In addition, K₂The upper limit of the content of O is preferably 12%, and more preferably 11%, 10.5%, and 10% in this order.

By mixing K₂When the content of O is in the above range, the thermal stability of the glass can be improved.

In the optical glass of the present embodiment, WO₃The content of (A) is less than 5%. WO₃The upper limit of the content of (b) is preferably 4%, and more preferably 3%, 2%, and 1% in this order. Preference is given to WO₃When the content of (3) is small, the lower limit is preferably 0%. WO₃The content of (B) may be 0%.

By mixing WO₃When the content (b) is in the above range, the transmittance can be improved and the increase in the specific gravity of the glass can be suppressed.

In the optical glass of the present embodiment, the content of ZnO is less than 15%. The upper limit of the content of ZnO is preferably 10%, and more preferably 7%, 5%, and 3% in this order. The content of ZnO is preferably small, and the lower limit is preferably 0%. The content of ZnO may be 0%.

By setting the content of ZnO to 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, Al₂O₃The content of (A) is less than 5%. Al (Al)₂O₃The upper limit of the content of (b) is preferably 4%, and more preferably 3%, 2%, and 1% in this order. Preferably Al₂O₃Content (wt.)In a case where the content is small, the lower limit is preferably 0%. Al (Al)₂O₃The content of (B) may be 0%.

By mixing Al₂O₃The content of (b) is in the above range, and thus deterioration of devitrification resistance of the glass can be suppressed.

In the optical glass of the present embodiment, TiO₂、Nb₂O₅、WO₃、Bi₂O₃And Ta₂O₅Total content of [ TiO ]₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅]15 to 45 percent. The lower limit of the total content is preferably 17%, and more preferably 19%, 21%, and 23% in this order. The upper limit of the total content is preferably 44%, and more preferably 43%, 42%, and 41% in this order.

TiO₂、Nb₂O₅、WO₃、Bi₂O₃And Ta₂O₅Is a component contributing to high dispersion of the glass. Therefore, by adding the total amount of [ TiO ]₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅]With the above range, an optical glass having desired optical constants can be obtained. In addition, the thermal stability of the glass can also be improved. On the other hand, if the total content is too large, an optical glass having desired optical constants may not be obtained, and thermal stability of the glass may be lowered and coloring of the glass may be increased.

In the optical glass of the present embodiment, P₂O₅、B₂O₃And SiO₂The total content of (A) to Li₂O、Na₂O、K₂O and Cs₂Mass ratio of total O content [ (P)₂O₅+B₂O₃+SiO₂)/(Li₂O+Na₂O+K₂O+Cs₂O)]Is 1.0 to 2.0. The lower limit of the mass ratio is preferably 1.10, and more preferably 1.20, 1.30, and 1.40 in this order. The upper limit of the mass ratio is preferably 1.95, and more preferably 1.90, 1.85, and 1.80 in this order。

By mixing the mass ratios of [ (P)₂O₅+B₂O₃+SiO₂)/(Li₂O+Na₂O+K₂O+Cs₂O)]With the above range, an optical glass having excellent thermal stability can be obtained.

In the optical glass of the present embodiment, B₂O₃Relative to P₂O₅Mass ratio of contents of [ B ]₂O₃/P₂O₅]Is 0.39 or less. The upper limit of the mass ratio is preferably 0.30, and more preferably 0.20, 0.15, and 0.13 in this order. The mass ratio is preferably greater than 0, and the lower limit thereof is more preferably 0.005, 0.01, and 0.015 in this order.

By mixing the mass ratio [ B₂O₃/P₂O₅]With the above range, an optical glass having excellent thermal stability can be obtained.

In the optical glass of the present embodiment, Na₂The content of O relative to K₂Mass ratio of O content [ Na ]₂O/K₂O]Is 1.0 or more. The lower limit of the mass ratio is preferably 1.2, and more preferably 1.4, 1.5, and 1.6 in this order. The upper limit of the mass ratio is preferably 5.0, and more preferably 4.5, 4.0, and 3.7 in this order.

By mixing the mass ratio of [ Na ]₂O/K₂O]When the amount is within the above range, the glass can be improved in thermal stability and resistance to devitrification. In addition, the mass ratio of [ Na ] is adjusted₂O/K₂O]The lower limit of (b) is in the above range, and excessive decrease in refractive index and decrease in chemical durability can be suppressed.

In the optical glass of the present embodiment, the total content [ MgO + CaO + SrO + BaO ] of MgO, CaO, SrO and BaO is 8.0% or less. The upper limit of the total content is preferably 6.0%, and more preferably 4.0%, 3.0%, and 2.0% in this order. The lower limit of the total content is preferably 0%.

By setting the total content [ MgO + CaO + SrO + BaO ] in the above range, thermal stability and resistance to devitrification can be maintained without hindering high dispersion.

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)]Is 0.75 or less. The upper limit of the mass ratio is preferably 0.70, and more preferably 0.67, 0.65, and 0.63 in this order. The lower limit of the mass ratio is preferably 0.15, and more preferably 0.25, 0.30, and 0.35 in this order.

By mixing the mass ratio of [ (TiO)₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅)/(P₂O₅+B₂O₃+SiO₂+Li₂O+Na₂O+K₂O+Cs₂O)]With the above range, an optical glass having desired optical constants can be obtained.

In the optical glass of the present embodiment, TiO₂In relation to TiO₂、Nb₂O₅、WO₃、Bi₂O₃And Ta₂O₅In total content of [ TiO ]₂/(TiO₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅)]The lower limit of (b) is preferably 0.00, and more preferably 0.10, 0.13, 0.15, and 0.16 in this order. The upper limit of the mass ratio is preferably 1.00, and more preferably 0.90, 0.80, 0.70, and 0.65 in this order.

TiO₂The component having a high refractive index and a high dispersion property is particularly effective in high dispersion. Thus, by mixing the mass ratio [ TiO ]₂/(TiO₂+Nb₂O₅+WO₃+Bi₂O₃+Ta₂O₅)]Within the above range, canTo obtain an optical glass having a desired optical constant, high thermal stability and excellent devitrification resistance.

In the optical glass of the present embodiment, TiO₂Relative to P₂O₅、B₂O₃、SiO₂In total content of [ TiO ]₂/(P₂O₅+B₂O₃+SiO₂)]The lower limit of (b) is preferably 0.00, and more preferably 0.05, 0.08, 0.10 or 0.12. The upper limit of the mass ratio is preferably 0.60, and more preferably 0.55, 0.52, and 0.50.

TiO₂The component having a high refractive index and a high dispersion property is particularly effective in high dispersion. However, if TiO is contained in a large amount₂If the amount is larger than the above range, the thermal stability and the devitrification resistance are deteriorated. By mixing the mass ratio of [ TiO ]₂/(P₂O₅+B₂O₃+SiO₂)]Within the above range, an optical glass having high dispersion, high thermal stability and high devitrification resistance can be obtained.

(glass component)

The content and ratio of the glass components other than those described above in the optical glass of the present embodiment are not limited to the following examples.

In the optical glass of the present embodiment, B₂O₃The upper limit of the content of (b) is preferably 10%, and more preferably 8%, 7%, and 6% in this order. In addition, B₂O₃The lower limit of the content of (b) is preferably 0.2%, and more preferably 0.3%, 0.4%, and 0.5% in this order.

B₂O₃Is a network forming component of the glass, and has the function of improving the thermal stability of the glass. On the other hand, B₂O₃When the amount of (b) is large, the devitrification resistance tends to be low. Therefore, from the viewpoint of improving the thermal stability and devitrification resistance of the glass, B₂O₃The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, SiO₂The upper limit of the content of (b) is preferably 5%, and further, cis-form of 3%, 2% or 1%The sequence is more preferred. 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 and weather resistance of glass, increasing the viscosity of molten glass, and easily molding the molten glass. On the other hand, 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, SiO₂The upper limit of the content of (b) is preferably the above range.

A melting tool made of quartz glass, such as a crucible made of quartz glass, may be used for melting glass. In this case, a small amount of SiO₂The glass melt is melted by the melting vessel, and therefore, 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 apparatus made of quartz glass₂The amount of (b) depends on the melting conditions, and is, for example, about 0.5 to 1 mass% based on the total content of all glass components. SiO removal₂The content ratio of the other glass components is kept constant, SiO₂The amount of the compound (B) is increased by about 0.5 to 1 mass%. The amount is increased or decreased depending on the melting conditions. Optical properties such as refractive index and Abbe number are determined by SiO₂Is varied, and thus, SiO is removed₂The 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 1%, 2%, 3%, and 4% in this order. TiO 2₂The content of (B) may be 0%. In addition, TiO₂The upper limit of the content of (b) is preferably 30%, and more preferably 28%, 26%, 24%, and 22% in this order.

TiO₂Significantly contributing to high dispersion. On the other hand, TiO₂It is relatively easy to increase the coloration of the glass. In addition, TiO₂In the process of obtaining optical glass by molding molten glass and slowly cooling the glass, the crystal generation in the glass is promoted, and the transparency of the glass is reducedSex (white turbidity). Thus, TiO₂The content of (b) is preferably in the above range.

In this embodiment, Bi₂O₃The upper limit of the content of (b) is preferably 15%, and more preferably 10%, 7%, 5%, and 3% in this order. In addition, Bi₂O₃The lower limit of the content of (b) is preferably 0%.

By containing Bi in a proper amount₂O₃It has the function of improving the thermal stability of the glass. On the other hand, if Bi is increased₂O₃The coloring of the glass increases. Thus, Bi₂O₃The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, TiO₂、Nb₂O₅、WO₃And Bi₂O₃Total content of [ TiO ]₂+Nb₂O₅+WO₃+Bi₂O₃]The lower limit of (b) is preferably 15%, and more preferably 17%, 19%, 21% in this order. Further, the total content [ TiO₂+Nb₂O₅+WO₃+Bi₂O₃]The upper limit of (b) is preferably 45%, and more preferably 44%, 43%, and 42% in this order.

TiO₂、Nb₂O₅、WO₃And Bi₂O₃The glass can be dispersed more easily, and the thermal stability of the glass can be improved by adding the glass in a proper amount. On the other hand, it is also a component for increasing the coloring of glass. Therefore, the total content thereof [ TiO₂+Nb₂O₅+WO₃+Bi₂O₃]Preferably within the above range.

In the optical glass of the present embodiment, Ta₂O₅The upper limit of the content of (b) is preferably 10%, and more preferably 7%, 5%, and 3% in this order. In addition, Ta₂O₅The lower limit of the content of (b) is preferably 0%. Ta₂O₅The content of (B) may be 0%.

Ta₂O₅The glass component has the function of improving the thermal stability and devitrification resistance of the glass. On the other hand, Ta₂O₅The refractive index is improved, and the glass is highly dispersed. In addition, Ta₂O₅When the content (b) is increased, the thermal stability of the glass is lowered, and when the glass is melted, a molten residue of the glass raw material is likely to be generated. Thus, Ta₂O₅The content of (b) is preferably in the above range. Further, Ta₂O₅Ta, a very expensive component compared to other glass components₂O₅When the content (c) is increased, the production cost of the glass increases. Further, Ta₂O₅Since the glass has a larger molecular weight than other glass components, the specific gravity of the glass increases, and as a result, the weight of the optical element increases.

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, Li₂When the content of O is increased, acid resistance is lowered. Thus, Li₂The content of O is preferably in the above range.

In the optical glass of the present embodiment, Na₂The lower limit of the content of O is preferably 6%, and more preferably 8%, 9%, and 10% in this order. In addition, Na₂The upper limit of the content of O is preferably 30%, and more preferably 28%, 26%, and 25% in this order.

Na₂O has an effect of improving the thermal stability of the glass, but when the content is increased, the refractive index, thermal stability, and acid resistance are lowered. Thus, Na₂The content of O is preferably 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 (b) is preferably 40%, and more preferably 35%, 34%, and 33% in this order. The lower limit of the total content is preferably 10%, and more preferably 12%, 13%, and 14% in this order.

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

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

In the optical glass of the present embodiment, the content of MgO is preferably 5% or less, and more preferably 3% or less and 1% or less 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 content of CaO is preferably 5% or less, and more preferably 3% or less and 1% or less 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 SrO content is preferably 5% or less, and more preferably 3% or less and 1% or less in this order. The lower limit of the SrO content is preferably 0%.

In the optical glass of the present embodiment, the content of BaO is preferably 8% or less, and more preferably 5% or less, 3% or less, and 1% or less in this order. The lower limit of the BaO content is preferably 0%.

MgO, CaO, SrO and BaO are glass components having an effect of improving the thermal stability and devitrification resistance of the glass. However, when the content of these glass components is increased, high dispersibility is impaired, and thermal stability and devitrification resistance of the glass are lowered. Therefore, the content of each of these glass components is preferably within the above range.

In the optical glass of the present embodiment, ZrO₂The content of (b) is preferably 5% or less, more preferably 3% or less and 1% or less in this order. In addition, ZrO₂The lower limit of the content of (b) is preferably 0%.

ZrO₂The glass component has the function of improving the thermal stability and devitrification resistance of the glass. However, ZrO₂When the content of (b) is too large, thermal stability tends to be lowered. Therefore, ZrO can be used from the viewpoint of maintaining the thermal stability and devitrification resistance of the glass well₂The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, Sc₂O₃The upper limit of the content of (b) is preferably 2%. In addition, 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、HfO₂Have the effect of increasing the refractive index nd and are expensive components. Thus, Sc₂O₃、HfO₂The respective contents of (a) are preferably within the above ranges.

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

Lu₂O₃Has the function of improving the refractive index nd. In addition, since it has a large molecular weight, it is also a glass component that increases the specific gravity of the glass. Thus, Lu₂O₃The content of (b) is preferably in the above range.

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

GeO₂Has an effect of increasing the refractive index nd, and is a component which is remarkably expensive among glass components which are generally used. Therefore, from the viewpoint of reducing the production cost of glass, GeO₂The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, La₂O₃The upper limit of the content of (b) is preferably 2%. In addition, La₂O₃The lower limit of the content of (b) is preferably 0%. La₂O₃The content of (B) may be 0%.

La₂O₃When the content (b) is increased, the thermal stability and devitrification resistance of the glass are lowered, and the glass is easily devitrified during production. Therefore, from the viewpoint of suppressing the decrease in thermal stability and resistance to devitrification, La₂O₃The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, Gd₂O₃The upper limit of the content of (b) is preferably 2%. In addition, Gd₂O₃The lower limit of the content of (b) is preferably 0%.

Gd₂O₃When 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, Gd₂O₃When the content of (b) is too large, the specific gravity of the glass increases, which is not preferable. Therefore, Gd is considered to suppress an increase in specific gravity while maintaining good thermal stability and devitrification resistance of the glass₂O₃The content of (b) is preferably in the above range.

In the optical glass of the present embodiment, Y is₂O₃The upper limit of the content of (b) is preferably 2%. In addition, Y₂O₃The lower limit of the content of (b) is preferably 0%. Y is₂O₃The content of (B) may be 0%.

Y₂O₃When the content of (b) 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, Y₂O₃The content of (b) is preferably 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%.

Yb₂O₃And La₂O₃、Gd₂O₃、Y₂O₃In contrast, the molecular weight is large, and therefore, the specific gravity of the glass is increased. When the specific gravity of the glass increases, the mass of the optical element increases. For example, if a lens having a large mass is introduced into an autofocus type image pickup lens, power required for driving the lens increases during autofocus, and battery consumption becomes serious. Therefore, it is desired to reduce Yb₂O₃The content (c) of (a) inhibits an increase in the specific gravity of the glass.

In addition, Yb₂O₃When the content of (b) is too large, the thermal stability and devitrification resistance of the glass are lowered. Yb is considered to prevent the thermal stability of the glass from decreasing and to suppress the increase in specific gravity₂O₃The content of (b) is preferably in the above range.

The optical glass of the present embodiment preferably mainly contains the above-mentioned glass component, i.e., P as an essential component₂O₅、K₂O、Na₂O, Nb as an optional component₂O₅、WO₃、ZnO、Al₂O₃、B₂O₃、SiO₂、TiO₂、Bi₂O₃、Ta₂O₅、Li₂O、Cs₂O、MgO、CaO、SrO、BaO、ZrO₂、Sc₂O₃、HfO₂、Lu₂O₃、GeO₂、La₂O₃、Gd₂O₃、Y₂O₃And Yb₂O₃The total content of the glass components is preferably 95% or more, 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%. In addition, TeO₂The lower limit of the content of (b) is preferably 0%.

Due to TeO₂Has toxicity, therefore, it is preferable to reduce TeO₂The content of (a). Thus, TeO₂The content of (b) is preferably in the above range.

The optical glass of the present embodiment is basically composed of the above glass components, but may contain other components within a range not to impair the operational effects of the present invention. In the present invention, the inclusion of inevitable impurities is not excluded.

< composition of other ingredients >

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

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

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

Sb(Sb₂O₃)、Ce(CeO₂) Is an element that can be added arbitrarily and functions as a clarifying agent. Wherein Sb (Sb)₂O₃) Is a clarifying agent with large clarifying effect. However, Sb (Sb)₂O₃) Has strong oxidizing property, if Sb (Sb) is added₂O₃) The amount of (3) is not preferable because the coloring of the glass is increased by light absorption by Sb ions. In addition, when the glass is melted, if Sb is present in the melt, elution of platinum constituting the glass melting crucible into the melt is promoted, and the concentration of platinum in the glass becomes high. In glass, when platinum is present in the form of ions, the coloration of the glass increases due to absorption of light. Further, in the glass, when platinum exists as a solid substance, it becomes a scattering source of light, and the quality of the glass is deteriorated. Ce (CeO)₂) And Sb (Sb)₂O₃) Compared with the prior art, the clarifying effect is small. If Ce (CeO) is added in a large amount₂) The coloring of the glass is enhanced. Therefore, when the clarifier is added, it is preferable to add Sb (Sb) while paying attention to the amount of addition₂O₃)。

Sb₂O₃The content of (b) is expressed as an external ratio. I.e. will remove Sb₂O₃And CeO₂All glass exceptSb is present in an amount of 100 mass% of the total glass component₂O₃The content of (b) is preferably less than 1% by mass, more preferably less than 0.1% by mass, and further preferably less than 0.05% by mass, less than 0.03% by mass, and less than 0.02% by mass in this order. Sb₂O₃The content of (b) may be 0 mass%.

Adding CeO₂The content of (b) is also expressed as an external ratio. That is, CeO will be removed₂、Sb₂O₃CeO when the total content of all other glass components is 100 mass%₂The content of (b) is preferably less than 2% by mass, more preferably less than 1% by mass, still more preferably less than 0.5% by mass, and still more preferably less than 0.1% by mass. CeO (CeO)₂The content of (b) may be 0 mass%. By mixing CeO₂When the content of (b) is in the above range, the glass can be improved in the fining property.

(glass Properties)

Specific gravity of glass

In the optical glass of the present embodiment, the specific gravity is preferably 3.60 or less, and more preferably 3.40 or less and 3.30 or less in this order. If the specific gravity of the glass can be reduced, the weight of the lens can be reduced. As a result, power consumption for autofocus driving of the camera 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 560 ℃ or lower, and more preferably 550 ℃ or lower, 540 ℃ or lower, and 530 ℃ or lower in this order.

When the upper limit of the glass transition temperature Tg satisfies the above range, the increase of the forming temperature and annealing temperature of the glass can be suppressed, and the damage of heat 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, it is easy to maintain the thermal stability of the glass well while maintaining a desired abbe number and refractive index.

< light transmittance of glass >

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

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

The λ 5 of the optical glass of the present embodiment is preferably 400nm or less, more preferably 390nm or less, and further preferably 380nm or less.

By using the optical glass having a wavelength of λ 5 shortened, an optical element capable of realizing appropriate color reproduction can be provided.

(production of optical glass)

The optical glass according to the embodiment of the present invention may be produced by blending glass raw materials so as to have the above-described predetermined composition and using the blended glass raw materials according to a known glass production method. For example, a plurality of compounds are prepared and mixed well to prepare a batch of raw materials, and the batch of raw materials 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 produce cullet. Further, the cullet was placed in a platinum crucible and heated and remelted (remelt) to prepare molten glass, and after further clarification and homogenization, the molten glass was molded and slowly cooled to obtain optical glass. The molten glass may be molded or slowly cooled by a known method.

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

(production of optical elements, etc.)

When an optical element is produced using the optical glass according to the embodiment of the present invention, a known method may be used. For example, a glass material comprising the optical glass of the present invention is produced by melting a glass raw material to produce a molten glass, and injecting the molten glass into a mold to mold the molten glass into a plate shape. The obtained glass material is appropriately cut, ground and polished to produce chips having a size and shape suitable for press molding. The chips are heated and softened, and press-formed (reheat-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, and then ground and polished by a known method to produce an optical element.

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

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

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

Examples

[ preparation of glass sample ]

Compound raw materials corresponding to the respective components, i.e., raw materials such as phosphates, carbonates, and oxides were weighed so as to obtain glasses having compositions of sample nos. 1 to 50 shown in tables 1 to 8, and sufficiently mixed to prepare formulated raw materials. The prepared raw materials are put into a platinum crucible, heated to 900-1350 ℃ in an atmosphere, melted, homogenized by stirring, and clarified to obtain molten glass. The molten glass was cast into a mold, molded and slowly cooled to obtain a bulk glass sample.

The raw materials for preparation may be put into a crucible made of quartz glass, and the crucible is transferred to a crucible made of platinum after melting, and further heated to melt, homogenized by stirring, clarified, and cast into a mold to mold and slowly cool the molten glass.

[ 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, and glass transition temperature Tg were measured by the methods shown below, and devitrification resistance was evaluated. The results are shown in tables 1, 3, 5 and 7.

[ 1] glass composition

With respect to the obtained glass samples, the contents of the respective glass components were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES).

Specific gravity of [ 2]

The measurement was carried out based on the Japan optical Nitri Industrial Association Standard JOGIS-05.

[ 3] refractive index nd and Abbe number ν d

The measurement was carried out based on the Japan optical Nitri Industrial Association Standard JOGIS-01.

[ 4] glass transition temperature Tg

The glass transition temperature Tg was determined based on a DSC chart when the temperature of a glass in a solid state was raised using a differential scanning calorimeter DSC3300SA (NETZSCH JAPAN co., ltd.).

〔5〕λ5

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

[ 6] softening test (resistance to devitrification)

The softening test is an evaluation method which becomes an index of resistance to devitrification in the present embodiment. A1 cm square glass sample was heated in a 1 st test furnace set to the glass transition temperature Tg of the glass for 10 minutes, and further heated in a 2 nd test furnace set to a temperature 120 to 200 ℃ higher than the Tg of the glass for 10 minutes, and then the presence or absence of crystal or haze was confirmed by an optical microscope. The observation magnification of the optical microscope is set to 10 to 100 times. The case where no crystal or white turbidity was observed in the glass was judged as "good", and the case where at least one of the crystal and white turbidity was observed was judged as "poor". The samples No.1 to 50 of the examples were all judged to be "good", and it was confirmed that the samples No.1 to 50 of the examples are glasses excellent in devitrification resistance.

Comparative example

(production and evaluation of glass sample No. I)

The production and evaluation of the glass were carried out by the same methods as in the glass Nos. 1 to 50 of examples. The results are shown in tables 5 and 6.

The glass of comparative example No. i was judged to be "poor" in the evaluation of the softening test. The glass of comparative example No. i was inferior to the glass of example in devitrification resistance.

[ Table 1]

[ Table 2]

[ Table 3]

[ Table 4]

[ Table 5]

[ Table 6]

[ Table 7]

[ Table 8]

(example 2)

The glass sample obtained in example 1 was cut and ground to prepare a chip. The chips were press-molded by reheat pressing to prepare an optical element blank. 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 can be obtained by precisely annealing an optical element blank to precisely adjust the refractive index so as to obtain a desired refractive index, and then grinding and polishing the optical element blank by a known method.

It should be understood that the embodiments disclosed herein are all exemplary and not limiting. The scope of the invention is indicated by the appended claims, rather than 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 described in the description of the glass composition exemplified above.

It is needless to say that 2 or more of the items exemplified in the description or described as the preferable ranges may be arbitrarily combined.

Claims

1. An optical glass having a refractive index nd of 1.60 to 1.72,

the Abbe number vd is 22-36,

P₂O₅the content of (B) is 20 to 55 mass%,

Nb₂O₅the content of (B) is 0 to 45% by mass,

K₂the content of O is more than 0 mass% and 13 mass% or less,

WO₃the content of (a) is less than 5 mass%,

the content of ZnO is less than 15 mass%,

Al₂O₃the content of (a) is less than 5 mass%,

2. The optical glass according to claim 1,

3. The optical glass according to claim 1 or 2,

4. The optical glass according to any one of claims 1 to 3,

5. The optical glass according to any one of claims 1 to 4,

6. An optical element made of the optical glass as defined in any one of claims 1 to 5.