TW202113397A - Optical glass and optical element in which the optical glass has a desired optical constant and excellent stability upon reheating - Google Patents

Abstract

The present invention provides an optical glass having a desired optical constant and excellent stability upon reheating, and an optical element made of the aforementioned optical glass. The refractive index nd of the optical glass is 1.60~1.72, the Abbe number [nu]d is 22~36, the content of P2O5 is 20~55 mass%, the content of Nb2O5 is 0~45 mass%, the content of K2O is greater than 0 mass% and less than 13 mass%, the content of WO3 is less than 5 mass%, the content of ZnO is less than 15 mass%, the content of Al2O3 is less than 5 mass%, the total content of TiO2, Nb2O5, WO3, Bi2O3 and Ta2O5 is 15~45 mass%, the mass ratio of the total content of P2O5, B2O3 and SiO2 to the total content of Li2O, Na2O, K2O and Cs2O is 1.0~2.0, the mass ratio of the content of B2O3 to the content of P2O5 is 0.39 or less, the mass ratio of the content of Na2O to the content of K2O is 1.0 or more, the total content of MgO, CaO, SrO, and BaO is 8.0 mass% or less, and the mass ratio of the total content of TiO2, Nb2O5, WO3, Bi2O3, and Ta2O5 to the total content of P2O5, B2O3, SiO2, Li2O, Na2O, K2O, and Cs2O is 0.75 or less.

Description

Optical glass and optical components

The present invention relates to optical glass and optical elements.

Glass softens when heated to a temperature higher than the glass transition temperature Tg. As a method for molding optical elements using this property, the following press molding method (reheat pressing) is known: the glass material obtained by heating, melting and molding the glass material is reheated, softened, and pressurized And molded into the desired shape. At this time, by reheating the glass, the glass may crystallize and the glass may devitrify. In particular, phosphate-based high-dispersion optical glasses tend to have insufficient devitrification resistance.

In addition, in the design of the optical system, among the optical glasses having the same degree of refractive index nd, the glass with a lower Abbe number νd has high utility value in correcting chromatic aberration, and making the optical system more functional and compact.

Patent Document 1 discloses an optical glass having a low Abbe number νd. However, it is known that the glass of Patent Document 1 does not satisfy the required devitrification resistance. Prior art literature Patent literature

Patent Document 1: Japanese Patent Application Publication No. 2019-1697

The problem to be solved by the invention

Glass with excellent stability during reheating can suppress devitrification caused by reheating. Therefore, an object of the present invention is to provide an optical glass having a desired optical constant and further excellent stability during reheating, and an optical element made of the above-mentioned optical glass. way of solving the problem

The gist of the present invention is as follows.

(1) An optical glass, the refractive index nd is 1.60~1.72, the Abbe number νd is 22~36, _{the content of P 2} O ₅ is 20~55 mass%, and _{the content of Nb 2} O ₅ is 0~45 mass% , _{The content of K 2} O is greater than 0% by mass and _{less than 13% by mass, the content of WO 3} is less than 5% by mass, the content of ZnO is less than 15% by mass, the content of Al ₂ O ₃ is less than 5% by mass, TiO ₂ , Nb ₂ The total content of O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O _{5 [TiO 2} ＋Nb ₂ O ₅ ＋WO ₃ ＋Bi ₂ O ₃ ＋Ta ₂ O ₅ ] is 15-45% by mass, P ₂ O ₅ , B ₂ The mass ratio of the total content of O ₃ and SiO _{2 to} the total content of Li ₂ O, Na ₂ O, K ₂ O, and Cs _{2 O [(P 2} O ₅ ＋B ₂ O ₃ ＋SiO ₂ )/(Li ₂ O＋Na ₂ O＋K ₂ O＋Cs ₂ O)] is 1.0~2.0, the mass ratio of the content of _{B 2} O _{3 to} the content of P ₂ O _{5 [B 2} O ₃ /P ₂ O ₅ ] is 0.39 or less, and the content of _{Na 2 O is relatively} The mass ratio [Na ₂ O/K ₂ O] of the K ₂ O content is 1.0 or more, the total content of MgO, CaO, SrO, and BaO [MgO + CaO + SrO + BaO] is 8.0 mass% or less, TiO ₂ , Nb ₂ O ₅ , WO _3. Mass ratio of the total content of Bi ₂ O ₃ and Ta ₂ O _{5 to} the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ , Li ₂ O, Na ₂ O, K ₂ O, and Cs _{2 O} [(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ )/(P ₂ O ₅ +B ₂ O ₃ +SiO ₂ +Li ₂ O+Na ₂ O+K ₂ O+Cs ₂ O)] is 0.75 or less.

(2) The optical glass described in (1) above, wherein the mass ratio [B ₂ O ₃ /P ₂ O _{5 ] of the content of B 2} O _{3 to} the content of P ₂ O ₅ is greater than zero.

(3) (1) or (2) described in the above optical glass, wherein, Na ₂ O with respect to the content of K ₂ O content mass ratio of _{[Na 2 O / K 2 O} ] is 5.0 or less.

(4) The optical glass according to any one of (1) to (3) above, wherein the total content of _{TiO 2} , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O _{5 is relative to P 2} The mass ratio of the total content of O ₅ , B ₂ O ₃ , SiO ₂ , Li ₂ O, Na ₂ O, K ₂ O, and Cs _{2 O [(TiO 2} ＋Nb ₂ O ₅ ＋WO ₃ ＋Bi ₂ O ₃ ＋Ta ₂ O ₅ )/(P ₂ O ₅ +B ₂ O ₃ +SiO ₂ +Li ₂ O+Na ₂ O+K ₂ O+Cs ₂ O)] is 0.15 or more.

(5) The optical glass according to any one of (1) to (4) above, wherein _{the content of TiO 2} is relative to that of TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O ₅ The mass ratio of the total content [TiO ₂ /(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ )] is 0.10 or more.

(6) An optical element made of the optical glass described in any one of (1) to (5) above. The effect of the invention

According to the present invention, it is possible to provide an optical glass having a desired optical constant and further excellent stability during reheating, and an optical element made of the above-mentioned optical glass.

In the present invention and this specification, unless otherwise stated, the glass composition of the optical glass is expressed on an oxide basis. Here, the "oxide-based glass composition" refers to the glass composition obtained by converting the glass raw materials into the form of oxides in the optical glass when the glass raw materials are completely decomposed during melting. The expression of each glass component is in accordance with customary It is described as SiO ₂ , TiO ₂ and the like. Unless otherwise stated, the content of the glass components and the total content are based on mass, and "%" means "% by mass".

The content of the glass component can be quantified by a known method, for example, inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), and the like. In addition, in this specification and the present invention, the content of a constituent component being 0% means that the constituent component is not substantially contained, and it is allowed to contain the component to the extent of unavoidable impurities.

In this specification, the thermal stability and devitrification resistance of glass both refer to the difficulty of crystal precipitation in the glass. In particular, thermal stability refers to the ease with which crystals precipitate when glass in a molten state is solidified, and the devitrification resistance refers to the ease with which crystals precipitate when the solidified glass is reheated at the time of reheating and pressing.

In addition, in this specification, unless otherwise stated, the refractive index means the refractive index nd under the d-ray (wavelength of 587.56 nm) of helium.

In addition, the Abbe number νd is used as a value representing properties related to dispersion, and is expressed by the following mathematical formula. Among them, nF is the refractive index under the F-ray (wavelength: 486.13 nm) of blue hydrogen, and nC is the refractive index under the C-ray (656.27 nm) of red hydrogen. Νd=(nd-1)/nF-nC　...(1)

The optical glass of this embodiment is demonstrated 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 adjusted to a desired value by appropriately adjusting the content of each glass component. The components having the effect of relatively increasing the refractive index nd (high refractive index components) are Nb ₂ O ₅ , TiO ₂ , WO ₃ , Bi ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , La ₂ O ₃ and the like. On the other hand, the components (low-refractive-index components) having the effect of relatively lowering the refractive index nd are P ₂ O ₅ , SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, and the like. Therefore, it is possible to increase the total content of _{TiO 2} , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O _{5 relative to P 2} O ₅ , B ₂ O ₃ , SiO ₂ , Li ₂ O, Na ₂ O , The mass ratio of the total content of _{K 2} O and Cs _{2 O [(TiO 2} ＋Nb ₂ O ₅ ＋WO ₃ ＋Bi ₂ O ₃ ＋Ta ₂ O ₅ )/(P ₂ O ₅ ＋B ₂ O ₃ ＋SiO ₂ ＋Li ₂ O＋Na ₂ O＋K ₂ O+Cs ₂ O)] to increase the refractive index nd, and the refractive index nd can be lowered by reducing the mass ratio.

In the optical glass of this embodiment, the Abbe number νd is 22-36. The lower limit of the Abbe number νd can be 24, 25, or 26, and the upper limit of the Abbe number νd can be 34, 32, or 30.

The Abbe number νd can be adjusted to a desired value by appropriately adjusting the content of each glass component. Components with a relatively low Abbe number νd, that is, highly dispersed components, are Nb ₂ O ₅ , TiO ₂ , WO ₃ , Bi ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ and the like. On the other hand, components with relatively high Abbe number νd, that is, low-dispersion components, are P ₂ O ₅ , SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, La ₂ O ₃ , BaO, CaO, SrO, etc.

In the optical glass of this embodiment, _{the content of P 2} O ₅ is 20 to 55%. The lower limit of the content of P ₂ O ₅ is preferably 23%, and more preferably in the order of 25%, 27%, and 29%. In addition, _{the upper limit of the content of P 2} O ₅ is preferably 51%, and more preferably in the order of 49%, 48%, and 47%.

P ₂ O ₅ is a network-forming component of glass, and is a component necessary for the glass to contain a large amount of highly dispersed components. By setting _{the content of P 2} O ₅ in the above range, thermal stability can be improved.

In the optical glass of this embodiment, _{the content of Nb 2} O ₅ is 0 to 45%. The lower limit of the Nb ₂ O ₅ content is preferably 4%, and more preferably in the order of 7%, 9%, and 10%. In addition, _{the upper limit of the Nb 2} O ₅ content is preferably 41%, and more preferably in the order of 39%, 37%, and 36%.

Nb ₂ O ₅ is a component that contributes to high refractive index and high dispersion. Therefore, by setting _{the content of Nb 2} O ₅ in the above range, an optical glass having a desired optical constant can be obtained. On the other hand, _{when the content of Nb 2} O ₅ is too large, the thermal stability of the glass may decrease and the coloring of the glass may increase.

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

By setting _{the content of K 2} O in the above range, the thermal stability of the glass can be improved.

In the optical glass of this embodiment, _{the content of WO 3} is less than 5%. The upper limit of the WO ₃ content is preferably 4%, and more preferably in the order of 3%, 2%, and 1%. It is preferable _{that the content of WO 3} is small, and the lower limit is preferably 0%. The content of WO ₃ may also be 0%.

By setting _{the content of WO 3} in the above-mentioned range, the transmittance can be improved, and an increase in the specific gravity of the glass can be suppressed.

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

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

In the optical glass of this embodiment, _{the content of Al 2} O ₃ is less than 5%. The upper limit of the content of Al ₂ O ₃ is preferably 4%, and more preferably in the order of 3%, 2%, and 1%. It is preferable that the _{content of Al 2} O _{3 is} small, and the lower limit is preferably 0%. The content of Al ₂ O ₃ may also be 0%.

By setting _{the content of Al 2} O ₃ in the above range, it is possible to suppress the decrease in the devitrification resistance of the glass.

In the optical glass of the present embodiment, the total content of _{TiO 2} , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O _{5 [TiO 2} ＋Nb ₂ O ₅ ＋WO ₃ ＋Bi ₂ O ₃ ＋Ta ₂ O ₅ ] It is 15~45%. The lower limit of the total content is preferably 17%, and more preferably in the order of 19%, 21%, and 23%. In addition, the upper limit of the total content is preferably 44%, and more preferably in the order of 43%, 42%, and 41%.

TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O ₅ are components that contribute to the high dispersion of glass. Therefore, by setting the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ ] in the above range, an optical glass having a desired optical constant can be obtained. In addition, the thermal stability of the glass can also be improved. On the other hand, when the total content is too large, there is a possibility that an optical glass having a desired optical constant may not be obtained, and there is also a possibility that the thermal stability of the glass decreases and the coloration of the glass increases.

In the optical glass of this embodiment, the mass ratio of the total content of _{P 2} O ₅ , B ₂ O ₃ and SiO _{2 to} the total content of Li ₂ O, Na ₂ O, K ₂ O, and Cs _{2 O [(P 2} O ₅ +B ₂ O ₃ ＋SiO ₂ )/(Li ₂ O＋Na ₂ O＋K ₂ O＋Cs ₂ O)] is 1.0 to 2.0. The lower limit of the mass ratio is preferably 1.10, and more preferably in the order of 1.20, 1.30, and 1.40. In addition, the upper limit of the mass ratio is preferably 1.95, and more preferably in the order of 1.90, 1.85, and 1.80.

By setting the mass ratio [(P ₂ O ₅ +B ₂ O ₃ +SiO ₂ )/(Li ₂ O+Na ₂ O+K ₂ O+Cs ₂ O)] in the above range, an optical glass with excellent thermal stability can be obtained.

In the optical glass of the present embodiment, the mass ratio of the content of _{B 2} O _{3 to} the content of P ₂ O _{5 [B 2} O ₃ /P ₂ O ₅ ] is 0.39 or less. The upper limit of the mass ratio is preferably 0.30, and more preferably in the order of 0.20, 0.15, and 0.13. In addition, the mass ratio is preferably greater than 0, and the lower limit thereof is more preferably in the order of 0.005, 0.01, and 0.015.

By setting the mass ratio [B ₂ O ₃ /P ₂ O ₅ ] to the above range, an optical glass excellent in thermal stability can be obtained.

In the optical glass of the present embodiment, Na ₂ O with respect to the content of K ₂ O content mass ratio of _{[Na 2 O / K 2 O} ] is 1.0 or more. The lower limit of the mass ratio is preferably 1.2, and more preferably in the order of 1.4, 1.5, and 1.6. In addition, the upper limit of the mass ratio is preferably 5.0, and more preferably in the order of 4.5, 4.0, and 3.7.

By setting the mass ratio [Na ₂ O/K ₂ O] to the above range, the thermal stability and devitrification resistance of the glass can be improved. In addition, by setting _{the lower limit of the mass ratio [Na 2} O/K ₂ O] to the above range, it is possible to suppress an excessive decrease in the refractive index and a decrease in chemical durability.

In the optical glass of this embodiment, the total content of MgO, CaO, SrO, and BaO [MgO+CaO+SrO+BaO] is 8.0% or less. The upper limit of the total content is preferably 6.0%, and more preferably in the order of 4.0%, 3.0%, and 2.0%. In addition, 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 devitrification resistance can be maintained without hindering high dispersion.

The total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O _{5 is relative to P 2} O ₅ , B ₂ O ₃ , SiO ₂ , Li ₂ O, Na ₂ O, K ₂ O and The mass ratio of the total content of Cs _{2 O [(TiO 2} ＋Nb ₂ O ₅ ＋WO ₃ ＋Bi ₂ O ₃ ＋Ta ₂ O ₅ )/(P ₂ O ₅ ＋B ₂ O ₃ ＋SiO ₂ ＋Li ₂ O＋Na ₂ O＋K ₂ O＋Cs ₂ O) ] Is 0.75 or less. The upper limit of the mass ratio is preferably 0.70, and more preferably in the order of 0.67, 0.65, and 0.63. In addition, the lower limit of the mass ratio is preferably 0.15, and more preferably in the order of 0.25, 0.30, and 0.35.

By setting the mass ratio [(TiO ₂ ＋Nb ₂ O ₅ ＋WO ₃ ＋Bi ₂ O ₃ ＋Ta ₂ O ₅ )/(P ₂ O ₅ ＋B ₂ O ₃ ＋SiO ₂ ＋Li ₂ O＋Na ₂ O＋K ₂ O＋Cs ₂ O)] to the above range , Can obtain the optical glass with the desired optical constant.

In the optical glass of the present embodiment, TiO ₂ content with respect to _{TiO 2, Nb 2 O 5,} 3 mass ₂ O ₃ and the total content of Ta ₂ O ₅ is Bi WO, than _{[TiO 2 / (TiO 2 +} Nb 2 The lower limit of O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ )] is preferably 0.00, and more preferably in the order of 0.10, 0.13, 0.15, and 0.16. In addition, the upper limit of the mass ratio is preferably 1.00, and more preferably in the order of 0.90, 0.80, 0.70, and 0.65.

TiO ₂ is a component that has a particularly large effect on high dispersion among components with high refractive index and high dispersion. Therefore, by setting the mass ratio [TiO ₂ /(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ )] to the above range, it is possible to obtain desired optical constants, high thermal stability, and resistance to loss. Optical glass with good permeability.

In the optical glass of the present embodiment, TiO ₂ content relative to the _{P 2 O 5, B 2 O} 3, by mass of SiO total content ₂ ratio _{[TiO 2 / (P 2 O} 5 + B 2 O 3 + SiO 2)] The lower limit of is preferably 0.00, and more preferably in the order of 0.05, 0.08, 0.10, and 0.12. In addition, the upper limit of the mass ratio is preferably 0.60, and more preferably in the order of 0.55, 0.52, and 0.50.

TiO ₂ is a component that has a particularly large effect on high dispersion among components with high refractive index and high dispersion. However, if the amount of TiO ₂ is contained in a large amount, thermal stability and resistance to devitrification deteriorate. By setting the mass ratio [TiO ₂ /(P ₂ O ₅ +B ₂ O ₃ +SiO ₂ )] in the above range, an optical glass with high dispersion, high thermal stability, and high devitrification resistance can be obtained. (Glass composition)

Regarding the content and ratio of glass components other than the above in the optical glass of the present embodiment, non-limiting examples are shown below.

In the optical glass of the present embodiment, _{the upper limit of the content of B 2} O ₃ is preferably 10%, and more preferably in the order of 8%, 7%, and 6%. In addition, _{the lower limit of the content of B 2} O ₃ is preferably 0.2%, and more preferably in the order of 0.3%, 0.4%, and 0.5%.

B ₂ O ₃ is a network forming component of glass and has the effect of improving the thermal stability of glass. On the other hand, when _{the content of B 2} O _{3 is} large, the devitrification resistance tends to decrease. Therefore, from the viewpoint of improving the thermal stability and devitrification resistance of the glass, _{the content of B 2} O ₃ is preferably within the above-mentioned range.

In the optical glass of the present embodiment, _{the upper limit of the content of SiO 2} is preferably 5%, and more preferably in the order of 3%, 2%, and 1%. The content of SiO ₂ may also be 0%.

SiO ₂ is a network-forming component of glass, which has the function of improving the thermal stability, chemical durability, and weather resistance of glass, increasing the viscosity of molten glass, and facilitating molding of molten glass. On the other hand, when _{the content of SiO 2 is} large, the devitrification resistance of the glass tends to decrease. Therefore, from the viewpoint of improving the thermal stability and devitrification resistance of the glass, the upper limit of the content of _{SiO 2 is preferably the above range.}

It should be noted that a melting utensil made of quartz glass such as a crucible made of quartz glass may be used for melting of glass. In this case, a small amount of SiO ₂ will be melted into the glass melt from the melting tool. Therefore, even if the glass raw material does not contain SiO ₂ , the produced glass will contain a small amount of SiO ₂ . _{The amount of SiO 2} mixed into the glass from the melting tool made of quartz glass depends on the melting conditions, for example, the total content of all glass components is about 0.5 to 1% by mass. The content ratio of glass components other than SiO _{2 is kept constant, and the amount of SiO 2} is increased by about 0.5 to 1% by mass. It should be noted that the above-mentioned amount is increased or decreased according to the melting conditions. The optical properties of refractive index, Abbe number and the like vary depending on the content of SiO _2, therefore, the content of glass component other than SiO ₂ is finely adjusted to obtain an optical glass having desired optical properties.

In the optical glass of the present embodiment, _{the lower limit of the content of TiO 2} is preferably 0%, and more preferably in the order of 1%, 2%, 3%, and 4%. The content of TiO ₂ may also be 0%. In addition, _{the upper limit of the content of TiO 2} is preferably 30%, and more preferably in the order of 28%, 26%, 24%, and 22%.

TiO ₂ significantly contributes to high dispersion. On the other hand, TiO ₂ is easier to increase the coloration of glass. In addition, TiO ₂ promotes the formation of crystals in the glass and reduces the transparency (white turbidity) of the glass during the process of molding the molten glass and slowly cooling it to obtain the optical glass. Therefore, _{the content of TiO 2} is preferably within the above-mentioned range.

In this embodiment, _{the upper limit of the content of Bi 2} O ₃ is preferably 15%, and more preferably in the order of 10%, 7%, 5%, and 3%. In addition, the lower limit of the content of _{Bi 2} O _{3 is preferably 0%.}

By containing Bi ₂ O ₃ in an appropriate amount, it has the effect of improving the thermal stability of the glass. On the other hand, if _{the content of Bi 2} O ₃ is increased, the coloration of the glass increases. Therefore, _{the content of Bi 2} O ₃ is preferably within the above-mentioned range.

In the optical glass of this embodiment, the lower limit of the total content of _{TiO 2} , Nb ₂ O ₅ , WO ₃ and Bi ₂ O _{3 [TiO 2} ＋Nb ₂ O ₅ ＋WO ₃ ＋Bi ₂ O ₃ ] is preferably 15%, and further The order of 17%, 19%, 21% is more preferable. In addition, the upper limit of the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ] is preferably 45%, and more preferably in the order of 44%, 43%, and 42%.

TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ contribute to the high dispersion of the glass, and if contained in an appropriate amount, it also has the effect of improving the thermal stability of the glass. On the other hand, it is also a component that increases the coloring of the glass. Therefore, the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ] is preferably in the above-mentioned range.

In the optical glass of the present embodiment, _{the upper limit of the content of Ta 2} O ₅ is preferably 10%, and more preferably in the order of 7%, 5%, and 3%. In addition, the lower limit of the content of _{Ta 2} O _{5 is preferably 0%.} The content of Ta ₂ O ₅ may also be 0%.

Ta ₂ O ₅ is a glass component that has the effect of improving the thermal stability and devitrification resistance of glass. On the other hand, Ta ₂ O ₅ increases the refractive index and makes the glass highly dispersed. In addition, when _{the content of Ta 2} O ₅ increases, the thermal stability of the glass decreases, and when the glass is melted, a molten residue of the glass raw material is likely to be generated. Therefore, _{the content of Ta 2} O ₅ is preferably within the above-mentioned range. In addition, Ta ₂ O ₅ is a very expensive component compared to other glass components, and when the content of Ta ₂ O ₅ increases, the production cost of the glass increases. In addition, Ta ₂ O ₅ has a higher molecular weight than other glass components, and therefore increases the specific gravity of the glass, and as a result, increases the weight of the optical element.

In the optical glass of the present embodiment, _{the upper limit of the content of Li 2} O is preferably 5%, and more preferably in the order of 3%, 2%, and 1%. The lower limit of the content of Li _{2 O is preferably 0%.} The content of Li ₂ O may also be 0%.

Li ₂ O has the effect of lowering the glass transition temperature Tg. On the other hand, when _{the content of Li 2} O increases, the acid resistance decreases. Therefore, _{the content of Li 2} O is preferably within the above-mentioned range.

In the optical glass of the present embodiment, _{the lower limit of the content of Na 2} O is preferably 6%, and more preferably in the order of 8%, 9%, and 10%. In addition, _{the upper limit of the content of Na 2} O is preferably 30%, and more preferably in the order of 28%, 26%, and 25%.

Na ₂ O has the effect of improving the thermal stability of the glass, but when the content increases, the refractive index, thermal stability, and acid resistance decrease. Therefore, _{the content of Na 2} O is preferably within the above-mentioned range.

In the optical glass of the present embodiment, the upper limit of the total content of _{Li 2} O, Na ₂ O, and K _{2 O [Li 2} O+Na ₂ O+K ₂ O] is preferably 40%, and more preferably 35%, 34% The order of 33% is more preferable. In addition, the lower limit of the total content is preferably 10%, and more preferably in the order of 12%, 13%, and 14%.

Li ₂ O, Na ₂ O, and K ₂ O all have the effect of improving the thermal stability of glass. However, when their content increases, the chemical durability and weather resistance decrease. Therefore, it is preferable that the total content of _{Li 2} O, Na ₂ O, and K _{2 O [Li 2} O+Na ₂ O+K ₂ O] is in the above-mentioned range.

In the optical glass of the present embodiment, _{the upper limit of the content of Cs 2} O is preferably 5%, and more preferably in the order of 3%, 2%, and 1%. In addition, the lower limit of the content of _{Cs 2 O is preferably 0%.} The content of Cs ₂ O may also be 0%.

Cs ₂ O has the effect of improving the thermal stability of the glass, but when its content increases, the thermal stability, chemical durability, and weather resistance of the glass decrease. Therefore, _{the content of Cs 2} O is preferably within the above-mentioned range.

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

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

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

MgO, CaO, SrO, and BaO are all glass components that improve the thermal stability and devitrification resistance of glass. However, when the content of these glass components increases, high dispersibility is impaired, and the thermal stability and devitrification resistance of the glass decrease. Therefore, each content of these glass components is each preferably in the above-mentioned range.

In the optical glass of the present embodiment, _{the content of ZrO 2} is preferably 5% or less, and more preferably 3% or less and 1% or less in this order. In addition, the lower limit of the content of _{ZrO 2 is preferably 0%.}

ZrO ₂ is a glass component that has the effect of improving the thermal stability and devitrification resistance of glass. However, _{when the content of ZrO 2} is too large, the thermal stability tends to decrease. Therefore, from the viewpoint of maintaining the thermal stability and devitrification resistance of the glass well, _{the content of ZrO 2} is preferably within the above-mentioned range.

In the optical glass of this embodiment, the upper limit of the content of _{Sc 2} O _{3 is preferably 2%.} In addition, the lower limit of the content of _{Sc 2} O _{3 is preferably 0%.}

In the optical glass of this embodiment, the upper limit of the content of _{HfO 2 is preferably 2%.} In addition, the lower limit of the content of _{HfO 2 is preferably 0%.}

Both Sc ₂ O ₃ and HfO ₂ have the effect of increasing the refractive index nd, and are expensive components. Therefore, _{the respective contents of Sc 2} O ₃ and HfO ₂ are preferably within the above-mentioned ranges.

In the optical glass of the present embodiment, the upper limit of the content of _{Lu 2} O _{3 is preferably 2%.} In addition, the lower limit of the content of _{Lu 2} O _{3 is preferably 0%.}

Lu ₂ O ₃ has the effect of increasing the refractive index nd. In addition, since its molecular weight is large, it is also a glass component that increases the specific gravity of glass. Therefore, _{the content of Lu 2} O ₃ is preferably within the above-mentioned range.

In the optical glass of this embodiment, the upper limit of the content of _{GeO 2 is preferably 2%.} In addition, the lower limit of the content of _{GeO 2 is preferably 0%.}

GeO ₂ has the effect of increasing the refractive index nd, and is a prominently expensive component among glass components that are commonly used. Therefore, from the viewpoint of reducing the production cost of glass, _{the content of GeO 2} is preferably within the above-mentioned range.

In the optical glass of this embodiment, the upper limit of the content of _{La 2} O _{3 is preferably 2%.} In addition, the lower limit of the content of _{La 2} O _{3 is preferably 0%.} The content of La ₂ O ₃ may also be 0%.

When _{the content of La 2} O ₃ increases, the thermal stability and devitrification resistance of the glass decrease, and the glass tends to become devitrified during production. _{Therefore, the content of La 2} O ₃ is preferably in the above-mentioned range from the viewpoint of suppressing a decrease in thermal stability and resistance to devitrification.

In the optical glass of this embodiment, the upper limit of the content of _{Gd 2} O _{3 is preferably 2%.} In addition, the lower limit of the content of _{Gd 2} O _{3 is preferably 0%.}

When _{the content of Gd 2} O ₃ is too large, the thermal stability and devitrification resistance of the glass decrease, and the glass tends to become devitrified during production. In addition, _{when the content of Gd 2} O ₃ is too large, the specific gravity of the glass increases, which is not preferable. Therefore, from the viewpoint of maintaining the thermal stability and devitrification resistance of the glass while suppressing an increase in specific gravity, _{the content of Gd 2} O ₃ is preferably within the above-mentioned range.

In the optical glass of this embodiment, the upper limit of the content of _{Y 2} O _{3 is preferably 2%.} In addition, the lower limit of the content of _{Y 2} O _{3 is preferably 0%.} The content of Y ₂ O ₃ may also be 0%.

When _{the content of Y 2} O ₃ is too large, the thermal stability and devitrification resistance of the glass decrease. _{Therefore, the content of Y 2} O ₃ is preferably within the above-mentioned range from the viewpoint of suppressing a decrease in thermal stability and resistance to devitrification.

In the optical glass of this embodiment, the upper limit of the content of _{Yb 2} O _{3 is preferably 2%.} In addition, the lower limit of the content of _{Yb 2} O _{3 is preferably 0%.}

Yb ₂ O ₃ has a _{larger molecular weight than La 2} O ₃ , Gd ₂ O ₃ , and Y ₂ O ₃ and therefore increases the specific gravity of glass. As the specific gravity of the glass increases, the quality of the optical element increases. For example, if a high-quality lens is introduced into an auto-focusing type imaging lens, the power required for driving the lens increases during auto-focusing, and the battery consumption becomes serious. Therefore, it is desirable to reduce _{the content of Yb 2} O ₃ and suppress an increase in the specific gravity of the glass.

In addition, _{when the content of Yb 2} O ₃ is too large, the thermal stability and devitrification resistance of the glass decrease. From the viewpoints of preventing a decrease in the thermal stability of the glass and suppressing an increase in specific gravity, _{the content of Yb 2} O ₃ is preferably within the above-mentioned range.

It is preferable that the optical glass of this embodiment mainly consists of the above-mentioned glass components, namely P ₂ O ₅ , K ₂ O, Na _{2 O as essential components, and Nb 2} O ₅ , WO ₃ , ZnO, Al ₂ O ₃ as optional components. , B ₂ O ₃ , SiO ₂ , TiO ₂ , Bi ₂ O ₃ , Ta ₂ O ₅ , Li ₂ O, Cs ₂ O, MgO, CaO, SrO, BaO, ZrO ₂ , Sc ₂ O ₃ , HfO ₂ , Lu ₂ O ₃ , GeO ₂ , La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ , the total content of the above-mentioned glass components is preferably 95% or more, more preferably 98% or more, and still more preferably It is 99% or more, more preferably 99.5% or more.

In the optical glass of the present embodiment, _{the upper limit of the TeO 2} content is preferably 2%. In addition, _{the lower limit of the TeO 2} content is preferably 0%.

Since TeO ₂ is toxic, it is preferable to reduce the content of _{TeO 2.} Therefore, _{the content of TeO 2} is preferably within the above-mentioned range.

It should be noted that the optical glass of the present embodiment is basically composed of the above-mentioned glass components, but may contain other components within a range that does not hinder the effects of the present invention. In addition, in the present invention, the inclusion of unavoidable impurities is not excluded. ＜Other component composition＞

Pb, As, Cd, Tl, Be, and Se are all toxic. Therefore, it is preferable that the optical glass of this embodiment does not contain these elements as a glass component.

U, Th, and Ra are all radioactive elements. Therefore, it is preferable that the optical glass of this embodiment 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 can increase the coloring of glass and become a source of fluorescence. Therefore, it is preferable that the optical glass of this embodiment does not contain these elements as a glass component.

Sb(Sb ₂ O ₃ ) and Ce(CeO ₂ ) are arbitrarily added elements that function as fining agents. Among them, Sb (Sb ₂ O ₃ ) is a clarifying agent with a large clarifying effect. However, Sb (Sb ₂ O ₃ ) is highly oxidizing, and if the addition amount of Sb (Sb ₂ O ₃ ) is increased, the coloration of the glass increases due to light absorption by Sb ions, which is not preferable. In addition, when the glass is melted, if Sb is present in the melt, the elution of the platinum constituting the glass melting crucible into the melt is promoted, and the platinum concentration in the glass becomes higher. In glass, when platinum exists in the form of ions, the color of the glass increases due to the absorption of light. In addition, when platinum exists in the form of a solid substance in glass, it becomes a scattering source of light and reduces the quality of the glass. Ce(CeO ₂ ) has a smaller clarifying effect than Sb(Sb ₂ O _{3 ). If Ce(CeO 2} ) is added in a large amount, the coloring of the glass is enhanced. Therefore, when adding a clarifying agent, it is preferable to add Sb (Sb ₂ O ₃ ) while paying attention to the addition amount.

The content of Sb ₂ O ₃ is expressed as an additional ratio. That is, when the total content of all glass components other _{than Sb 2} O ₃ and CeO _{2 is set to 100% by mass, the content of Sb 2} O ₃ is preferably less than 1% by mass, more preferably less than 0.1% by mass, and further less than 0.05% by mass. The order of %, less than 0.03% by mass, and less than 0.02% by mass is preferable. The content of Sb ₂ O ₃ may be 0% by mass.

The content of CeO ₂ is also expressed as an additional ratio. That is, when the total content of all glass components _{except CeO 2} and Sb ₂ O _{3 is 100% by mass, the content of CeO 2} is preferably less than 2% by mass, more preferably less than 1% by mass, and still more preferably less than 0.5% by mass. More preferably, the range is less than 0.1% by mass. The content of CeO ₂ may also be 0% by mass. By setting _{the content of CeO 2} in the above range, the clarity of the glass can be improved. (Glass characteristics) <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, it is possible to reduce the power consumption of the autofocus drive of the lens-mounted camera lens. ＜Glass transition temperature Tg＞

The glass transition temperature Tg of the optical glass of the present embodiment is preferably 560°C or lower, and more preferably in the order of 550°C or lower, 540°C or lower, and 530°C or lower.

When the upper limit of the glass transition temperature Tg satisfies the above range, it is possible to suppress the increase in the molding temperature and annealing temperature of the glass, and it is possible to reduce the damage of heat to the press forming equipment and the annealing equipment. In addition, by making the lower limit of the glass transition temperature Tg satisfy the above range, it is easy to maintain the thermal stability of the glass while maintaining the desired Abbe number and refractive index. ＜Transmittance of glass＞

The light transmittance of the optical glass of this embodiment can be evaluated by the coloring degree λ5.

For a glass sample with a thickness of 10.0 mm±0.1 mm, the spectral transmittance is measured in a wavelength range of 200 to 700 nm, and the wavelength at which the external transmittance becomes 5% is set to λ5.

The λ5 of the optical glass of the present embodiment is preferably 400 nm or less, more preferably 390 nm or less, and even more preferably 380 nm or less.

By using an optical glass whose wavelength has been shortened to λ5, it is possible to provide an optical element capable of realizing suitable color reproduction. (Manufacturing of optical glass)

The optical glass of the embodiment of the present invention may be prepared by blending glass raw materials so as to achieve the above-mentioned predetermined composition, and using the blended glass raw materials according to a known glass manufacturing method. For example, a variety of compounds are prepared and mixed thoroughly to form batch materials, and the batch materials are put into a quartz crucible or a platinum crucible for rough melt. The melt obtained by the rough melting is quenched and crushed to produce cullet. Furthermore, the cullet was put into a platinum crucible and heated and remelt (remelt) to prepare a molten glass. After further clarification and homogenization, the molten glass was molded and slowly cooled to obtain an optical glass. A known method may be used for molding and slow cooling of molten glass.

It should be noted that as long as the desired glass component can be introduced into the glass and the desired content is achieved, there are no particular limitations on the compound used when preparing batch materials. Examples of such compounds include oxides and carbonates. , Nitrate, hydroxide, fluoride, etc. (Manufacturing of optical components, etc.)

When an optical element is produced using the optical glass of the embodiment of the present invention, a known method may be used. For example, a glass raw material is melted to make molten glass, and the molten glass is poured into a mold to shape it into a plate shape to produce a glass material made of the optical glass of the present invention. The obtained glass material is appropriately cut, ground, and ground to produce fragments of a size and shape suitable for press molding. The fragments are heated and softened, and are press-formed (re-hot-pressed) by a known method to produce an optical element blank having a shape similar to the optical element. The optical element blank is annealed, ground and polished by a known method to produce an optical element.

According to the purpose of use, an anti-reflection film, a total reflection film, etc. may be coated on the optically functional surface of the manufactured optical element.

As the optical element, various lenses such as spherical lenses, prisms, diffraction gratings, and the like can be exemplified.

Hereinafter, the present invention will be explained more specifically through examples, but the present invention is not limited to the following examples. Example [Production of glass samples]

The compound raw materials corresponding to each component, that is, raw materials such as phosphates, carbonates, oxides, etc., are weighed and mixed thoroughly so as to become glass with the composition of sample Nos. 1 to 50 shown in Tables 1 to 8. Made the blended raw materials. The prepared raw material was put into a platinum crucible, heated to 900 to 1350°C in an air atmosphere, melted, homogenized by stirring, and clarified to obtain molten glass. This molten glass was cast into a molding die, molded and slowly cooled, to obtain a bulk glass sample.

It should be noted that the prepared raw materials can be put into a crucible made of quartz glass, melted, transferred to a crucible made of platinum, further heated, melted, homogenized by stirring, clarified, and the obtained molten glass is cast into a forming mold , Carry out molding and slow cooling. [Evaluation of glass samples]

For the obtained glass sample, the glass composition, specific gravity, refractive index nd, Abbe number νd, λ5, and glass transition temperature Tg were measured by the methods shown below, and the devitrification resistance was evaluated. The results are shown in Tables 1, 3, 5, and 7. 〔1〕Glass composition

For the obtained glass sample, the content of each glass component was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). 〔2〕Proportion

Measured based on JOGIS-05 standard of Japan Optical Glass Industry Association. [3] Refractive index nd and Abbe number νd

Measured based on the standard JOGIS-01 of the Japan Optical Glass Industry Association. 〔4〕Glass transition temperature Tg

The glass transition temperature Tg is determined based on a DSC chart when the glass in a solid state is heated up using a differential scanning calorimeter DSC3300SA (NETZSCH JAPAN Co., Ltd.). 〔5〕λ5

The glass sample was processed into a thickness of 10 mm and had planes that were parallel to each other and optically polished, and the spectral transmittance in the wavelength region of 280 nm to 700 nm was measured. The intensity of light incident perpendicular to one of the optically polished planes was defined as intensity A, and the intensity of light emitted from the other plane was defined as intensity B, and the spectral transmittance B/A was calculated. Let λ5 be the wavelength at which the spectral transmittance is 5%. It should be noted that the spectral transmittance also includes the reflection loss of light on the surface of the sample. 〔6〕Softening test (devitrification resistance)

The softening test is an evaluation method used as an index of devitrification resistance in this embodiment. A 1 cm square glass sample was heated for 10 minutes in the first test furnace set to the glass transition temperature Tg of the glass, and further heated in the second test furnace set to a temperature 120 to 200°C higher than the Tg of the glass After 10 minutes, the presence or absence of crystals or white turbidity was confirmed by an optical microscope. Set the observation magnification of the optical microscope to 10 to 100 times. The case where crystals and white turbidity were not confirmed inside the glass was judged as "good", and the case where at least one of crystals and white turbidity was confirmed was judged as "bad". The samples Nos. 1 to 50 of the examples were all judged as "good", and it was confirmed that the samples Nos. 1 to 50 of the examples were glasses with excellent devitrification resistance. (Comparative example) (Production and evaluation of glass sample No.I)

The production and evaluation of the glass were performed by the same method as in Example Glass Nos. 1-50. The results are shown in Tables 5 and 6.

The glass of Comparative Example No. I was judged to be "bad" in the evaluation of the softening test. The glass of Comparative Example No. I is inferior in devitrification resistance compared with the glass of the example.

[Table 1]

[Table 2]

[table 3]

[Table 4]

[table 5]

[Table 6]

[Table 7]

(實施例2)[Table 8]

(Example 2)

The glass sample obtained in Example 1 was cut and ground to produce fragments. The fragments were press-formed by reheating and pressing, and an optical element blank was produced. The optical element blanks are precisely annealed, the refractive index is precisely adjusted so that the refractive index becomes the required refractive index, and then ground and polished by a known method to obtain biconvex lenses, biconcave lenses, plano-convex lenses, plano-concave lenses, Various lenses such as concave meniscus lens and convex meniscus lens.

It should be understood that the embodiments disclosed this time are all exemplary and do not constitute a limitation. The scope of the present invention is defined by the scope of the patent application rather than the above description, and is intended to include the meaning equivalent to the scope of the patent application and all modifications within the scope.

For example, by performing the composition adjustment described in the specification on the glass composition exemplified above, the optical glass of one embodiment of the present invention can be produced.

In addition, it is of course possible to arbitrarily combine two or more of the items exemplified in the specification or described as preferred ranges.

no

no.

Claims (6)

An optical glass, the refractive index nd is 1.60~1.72, the Abbe number νd is 22~36, _{the content of P 2} O ₅ is 20~55 mass%, _{the content of Nb 2} O ₅ is 0~45 mass%, and the K ₂ The content of O is greater than 0% by mass and _{less than 13% by mass, the content of WO 3} is less than 5% by mass, the content of ZnO is less than 15% by mass, the content of Al ₂ O ₃ is less than 5% by mass, TiO ₂ , Nb ₂ O ₅ , The total content of WO ₃ , Bi ₂ O ₃ and Ta ₂ O _{5 [TiO 2} ＋Nb ₂ O ₅ ＋WO ₃ ＋Bi ₂ O ₃ ＋Ta ₂ O ₅ ] is 15-45% by mass, and P ₂ O ₅ , B ₂ O ₃ and The mass ratio of the total content of SiO _{2 to} the total content of Li ₂ O, Na ₂ O, K ₂ O, and Cs _{2 O [(P 2} O ₅ ＋B ₂ O ₃ ＋SiO ₂ )/(Li ₂ O＋Na ₂ O＋K ₂ O＋Cs ₂ O)] of 1.0 to 2.0, the content of B ₂ O ₃ with respect to the content of P ₂ O ₅ mass ratio of [B ₂ O ₃ / P ₂ O _5] is 0.39 or less, ₂ O content of Na relative to K ₂ The mass ratio of O content [Na ₂ O/K ₂ O] is 1.0 or more, the total content of MgO, CaO, SrO, and BaO [MgO＋CaO＋SrO＋BaO] is 8.0 mass% or less, TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi The mass ratio of the total content of ₂ O ₃ and Ta ₂ O _{5 to} the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ , Li ₂ O, Na ₂ O, K ₂ O, and Cs _{2 O [(TiO 2} +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ )/(P ₂ O ₅ +B ₂ O ₃ +SiO ₂ +Li ₂ O+Na ₂ O+K ₂ O+Cs ₂ O)] is 0.75 or less. The optical glass according to claim 1, wherein the mass ratio of the content of _{B 2} O _{3 to} the content of P ₂ O _{5 [B 2} O ₃ /P ₂ O ₅ ] is greater than zero. The optical glass of the requested item 1 or 2, wherein, Na ₂ O with respect to the content of K ₂ O content mass ratio of _{[Na 2 O / K 2 O} ] is 5.0 or less. The optical glass according to any one of claims 1 to 3, wherein the total content of _{TiO 2} , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O _{5 is relative to P 2} O ₅ , B ₂ The mass ratio of the total content of O ₃ , SiO ₂ , Li ₂ O, Na ₂ O, K ₂ O, and Cs _{2 O [(TiO 2} ＋Nb ₂ O ₅ ＋WO ₃ ＋Bi ₂ O ₃ ＋Ta ₂ O ₅ )/(P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O)] is 0.15 or more. The optical glass according to any one of claims 1 to 4, wherein the mass ratio of the content of _{TiO 2 to} the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and Ta ₂ O ₅ [TiO ₂ /(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +Ta ₂ O ₅ )] is 0.10 or more. An optical element made of the optical glass described in any one of claims 1 to 5.