JP2019210156A - Optical glass and optical element - Google Patents

Abstract

To provide an optical glass having a desired optical constant, a relatively small specific gravity, a small partial dispersion ratio Pg,F and excellent stability when re-heated, and an optical element made of the optical glass.SOLUTION: The optical glass has an Abbe number νd of 26.0 or more and contains SiOby over 0 mass% and less than 40 mass%, TiOby 0 to 15 mass%, NbOby 25 to 45 mass%, and ZrOby over 0 mass%.SELECTED DRAWING: None

Description

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

  An optical element mounted on an autofocus optical system is required to be light in weight in order to reduce power consumption when driving an autofocus function. If the specific gravity of glass can be reduced, the weight of optical elements such as lenses can be reduced. In addition, the partial dispersion ratios Pg and F are required to be small in order to correct chromatic aberration.

  Moreover, as a manufacturing method of such optical glass used by an optical system, the reheat press manufacturing method which re-heats and shape | molds glass is mentioned. In this manufacturing method, devitrification at the time of reheating is observed in the silicate-based high refractive index and high dispersibility optical glass. Furthermore, a high degree of stability is required such that the inside of the glass is not easily devitrified during reheating of the glass.

Patent Documents 1 to 3 disclose optical glasses having a predetermined optical constant and an object of reducing the partial dispersion ratio. However, the optical glasses disclosed in Patent Documents 1 to 3 have a large specific gravity.
In Patent Document 4, it is an object to obtain an optical glass having a small partial dispersion ratio at low cost. However, the optical glass disclosed in Patent Document 4 is a relatively low-dispersion glass and does not have the optical constant desired by the present invention.

Japanese Patent Laying-Open No. 2015-193515 JP2015-193516A Japanese Patent Laid-Open No. 2006-88759 JP 2017-105702 A

  The present invention comprises an optical glass having a desired optical constant, a relatively small specific gravity, a small partial dispersion ratio Pg, F with respect to the Abbe number νd, and excellent stability during reheating, and the optical glass. An object is to provide an optical element.

The gist of the present invention is as follows.
(1) Abbe number νd is 26.0 or more,
The content of SiO ₂ is more than 0% by mass and less than 40% by mass,
The content of TiO ₂ is 0 to 15% by mass,
The content of Nb ₂ O ₅ is 25 to 45% by mass,
The content of ZrO ₂ exceeds 0% by mass,
The mass ratio of the content of _B 2 _{O 3} to the content of _{SiO 2 [B 2 O 3 /} SiO 2] is at 0.800 or less,
The mass ratio of the total content of SiO ₂ and B ₂ O _{3 to} the total content of Nb ₂ O ₅ and TiO ₂ [(SiO ₂ + B ₂ O ₃ ) / (Nb ₂ O ₅ + TiO ₂ )] is 0.950 or less And
The total content [Li ₂ O + Na ₂ O + K ₂ O] of Li ₂ O, Na ₂ O and K ₂ O is 10 to 25% by mass,
The mass ratio of the content of Na ₂ O to the total content of Li ₂ O, Na ₂ O and K ₂ O [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is 0.330 or more,
The mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of Li ₂ O, Na ₂ O and K ₂ O [(MgO + CaO + SrO + BaO + ZnO) / (Li ₂ O + Na ₂ O + K ₂ O)] is 0. 480 or less,
The mass ratio of the content of TiO ₂ to the content of _{Nb 2 O 5 [TiO 2 /} Nb 2 O 5] is at 0.340 or less,
Mass ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O to the total content of TiO ₂ and Nb ₂ O ₅ [(Li ₂ O + Na ₂ O + K ₂ O) / (TiO ₂ + Nb ₂ O ₅ )] Is 0.700 or less,
_{SiO 2, B 2 O 3,} P 2 O 5, Al 2 O 3, Li 2 O, Na 2 O, K 2 O, MgO, CaO, ZnO, La 2 O 3, Y 2 O 3, Gd 2 O 3 , ZrO ₂ , TiO ₂ and Nb ₂ O _{5 have} a total content of 96.0% by mass or more,
PbO, the content of CdO and _As 2 _{O 3} is 0.01 mass% or less, optical glass.

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

  According to the present invention, an optical glass having a desired optical constant, a relatively small specific gravity, a small partial dispersion ratio Pg, F with respect to the Abbe number νd, and excellent stability during reheating, and the optical glass The optical element which consists of can be provided.

Hereinafter, embodiments of the present invention will be described. In addition, in this invention and this specification, the glass composition of optical glass is displayed on an oxide basis unless otherwise specified. Here, “oxide-based glass composition” refers to a glass composition obtained by converting all glass raw materials to be decomposed at the time of melting and existing as oxides in the optical glass, and the notation of each glass component is According to custom, it is described as SiO ₂ , TiO ₂ or the like. The content of glass components and the total content are based on mass unless otherwise specified, and “%” means “mass%”.

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

  Further, in this specification, the refractive index refers to the refractive index nd in the helium d-line (wavelength 587.56 nm) unless otherwise specified.

The Abbe number νd is used as a value representing a property relating to dispersion, and is represented by the following equation. Here, nF is the refractive index of blue hydrogen on the F line (wavelength 486.13 nm), and nC is the refractive index of red hydrogen on the C line (656.27 nm).
νd = (nd−1) / (nF−nC)

The partial dispersion ratios Pg and F are expressed as follows using the respective refractive indexes ng, nF and nC in the g-line, F-line and c-line.
Pg, F = (ng-nF) / (nF-nC)
In the plane in which the horizontal axis is Abbe number νd and the vertical axis is the partial dispersion ratio Pg, F, the normal line in this embodiment is expressed by the following equation.
Pg, F (0) ′ = 0.688900−0.00286 × νd
Further, deviations ΔPg, F ′ of the partial dispersion ratios Pg, F from the normal line are expressed as follows.
ΔPg, F ′ = Pg, F−Pg, F (0) ′

The optical glass according to this embodiment is
Abbe number νd is 26.0 or more,
The content of SiO ₂ is more than 0% and less than 40%,
The content of TiO ₂ is 0 to 15%,
The content of Nb ₂ O ₅ is 25 to 45%,
The content of ZrO ₂ exceeds 0%,
The mass ratio of the content of _B 2 _{O 3} to the content of _{SiO 2 [B 2 O 3 /} SiO 2] is at 0.800 or less,
The mass ratio of the total content of SiO ₂ and B ₂ O _{3 to} the total content of Nb ₂ O ₅ and TiO ₂ [(SiO ₂ + B ₂ O ₃ ) / (Nb ₂ O ₅ + TiO ₂ )] is 0.950 or less And
The total content of Li ₂ O, Na ₂ O and K ₂ O [Li ₂ O + Na ₂ O + K ₂ O] is 10-25%,
The mass ratio of the content of Na ₂ O to the total content of Li ₂ O, Na ₂ O and K ₂ O [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is 0.330 or more,
The mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of Li ₂ O, Na ₂ O and K ₂ O [(MgO + CaO + SrO + BaO + ZnO) / (Li ₂ O + Na ₂ O + K ₂ O)] is 0. 480 or less,
The mass ratio of the content of TiO ₂ to the content of _{Nb 2 O 5 [TiO 2 /} Nb 2 O 5] is at 0.340 or less,
Mass ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O to the total content of TiO ₂ and Nb ₂ O ₅ [(Li ₂ O + Na ₂ O + K ₂ O) / (TiO ₂ + Nb ₂ O ₅ )] Is 0.700 or less,
_{SiO 2, B 2 O 3,} P 2 O 5, Al 2 O 3, Li 2 O, Na 2 O, K 2 O, MgO, CaO, ZnO, La 2 O 3, Y 2 O 3, Gd 2 O 3 , ZrO ₂ , TiO ₂ and Nb ₂ O _{5 have} a total content of 96.0% or more,
The contents of PbO, CdO and As ₂ O ₃ are each 0.01% or less.

In the optical glass according to the present embodiment, the Abbe number νd is 26.0 or more. The lower limit of the Abbe number νd is preferably 26.5, and further 27.0, 27.2, 27.4, 27.6, 27.8, 28.0, 28.2, 28.4, 28 .6, 28.8, 29.0 in order. The upper limit of the Abbe number νd is preferably in the order of 31.0, 30.8, 30.6, 30.4, 30.2, 30.0. Components that relatively lower the Abbe number νd are Nb ₂ O ₅ , TiO ₂ , ZrO ₂ , and Ta ₂ O ₅ . Components that relatively increase the Abbe number νd are SiO ₂ , P ₂ O ₅ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, La ₂ O ₃ , BaO, CaO, and SrO. The Abbe number νd can be controlled by appropriately adjusting the contents of these components.

In the optical glass according to the present embodiment, the content of SiO ₂ is more than 0% and less than 40%. The lower limit of the content of SiO ₂ is preferably 10%, and more preferably in the order of 15%, 17%, 19%, 21%, 23%, 25%, 26%, 27%, 28%. Further, the upper limit of the content of SiO ₂ is preferably 39%, and more preferably in the order of 38%, 37%, 36%, 35%, 34%, 33%.
SiO ₂ is a glass network forming component. When the content of SiO ₂ is too small, the network forming effect of the glass is lowered, stability at the time of re-heating of the glass may be reduced. When the content of SiO ₂ is too large, there is a possibility that desired optical constants can not be obtained.

In the optical glass according to the present embodiment, the content of TiO ₂ is 0 to 15%. The upper limit of the content of TiO ₂ is preferably 14%, and more preferably in the order of 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%. The lower limit of the content of TiO ₂ is preferably 0.05%, and further 0.10%, 0.15%, 0.20%, 0.25%, 0.30%, 0.35%. More preferred in order.
TiO ₂ is a component for highly dispersing glass. When the content of TiO ₂ is too large, the partial dispersion ratio Pg, F is likely to increase. When the content of TiO ₂ is too small, the desired optical constants can not be obtained. Moreover, there exists a possibility that the network formation effect | action of glass may fall and stability at the time of reheating of glass may fall.

In the optical glass according to the present embodiment, the content of Nb ₂ O ₅ is 25 to 45%. The lower limit of the content of Nb ₂ O ₅ is preferably 27%, and more preferably 28%, 29%, 30%, 31%, 32%, 33%, 34%, and 35% in this order. Further, the upper limit of the content of Nb ₂ O ₅ is preferably 44.5%, and further 44.0%, 43.5%, 43.2%, 43.0%, 42.7%, 42 More preferable in order of 5%.
Nb ₂ O ₅ is a component that makes the glass highly dispersed and reduces the partial dispersion ratios Pg and F. When the content of Nb ₂ O ₅ is too large, it decreases the thermal stability of the glass, and there is a possibility that the raw material cost is increased. If the content of Nb ₂ O ₅ is too small, the partial dispersion ratio Pg, F increases, and the desired optical constant may not be obtained.

In the optical glass according to the present embodiment, the content of ZrO ₂ exceeds 0%. The lower limit of the content of ZrO ₂ is preferably 1%, and more preferably in the order of 2%, 3%, 4%, 5%, 6%, 7%, 8%. The upper limit of the content of ZrO ₂ is preferably 15%, and further 14%, 13.5%, 13.2%, 13.0%, 12.8%, 12.6%, 12. 4% order is more preferable.
ZrO ₂ is a component that makes glass highly dispersed and reduces the partial dispersion ratios Pg and F. When the content of ZrO ₂ is too large, the network forming effect of the glass is lowered, stability at the time of re-heating of the glass may be reduced. If the content of ZrO ₂ is too small, the partial dispersion ratios Pg and F increase, and the desired optical constant may not be obtained.

In the optical glass according to the present embodiment, the mass ratio of the content of _B 2 _{O 3} to the content of _{SiO 2 [B 2 O 3 /} SiO 2] is 0.800 or less. The upper limit of the mass ratio [B ₂ O ₃ / SiO ₂ ] is preferably 0.700, and further 0.600, 0.550, 0.500, 0.450, 0.350, 0.300, 0 .250, 0.200 in order. The mass ratio [B ₂ O ₃ / SiO ₂ ] may be zero.
When the mass ratio [B ₂ O ₃ / SiO ₂ ] is too large, the specific gravity increases, and the coloring of the glass may increase.

In the optical glass according to the present embodiment, the mass ratio of the total content of SiO ₂ and B ₂ O _{3 to} the total content of Nb ₂ O ₅ and TiO ₂ [(SiO ₂ + B ₂ O ₃ ) / (Nb ₂ O ₅ + TiO ₂ )] is 0.950 or less. The upper limit of the mass ratio [(SiO ₂ + B ₂ O ₃ ) / (Nb ₂ O ₅ + TiO ₂ )] is preferably 0.930, more preferably 0.920, 0.910, 0.900, 0.890. 0.880, 0.870, 0.860, 0.850, 0.840, 0.830, 0.820, 0.810, 0.800, 0.790, 0.780 in this order. Further, the lower limit of the mass ratio [(SiO ₂ + B ₂ O ₃ ) / (Nb ₂ O ₅ + TiO ₂ )] is preferably 0.300, and further 0.350, 0.400, 0.450, 0 .500, 0.550, 0.600, 0.630, 0.650, 0.670, 0.680, 0.690 in order.
If the mass ratio [(SiO ₂ + B ₂ O ₃ ) / (Nb ₂ O ₅ + TiO ₂ )] is too large, a desired optical constant may not be obtained. When the mass ratio [(SiO ₂ + B ₂ O ₃ ) / (Nb ₂ O ₅ + TiO ₂ )] is too small, the network forming action of the glass is lowered, and the stability during reheating of the glass may be lowered.

In the optical glass according to the present embodiment, the total content [Li ₂ O + Na ₂ O + K ₂ O] of Li ₂ O, Na ₂ O and K ₂ O is 10 to 25%. The lower limit of the total content [Li ₂ O + Na ₂ O + K ₂ O] is preferably 11.0%, and further 12.0%, 12.5%, 13.0%, 13.5%, 13.7 %, 13.9%, 14.1%, 14.3%, 14.5% in this order. Further, the upper limit of the total content [Li ₂ O + Na ₂ O + K ₂ O] is preferably 23%, and further 22%, 21.5%, 21.0%, 20.5%, 20.0%, It is more preferable in the order of 19.5% and 19.0%.
When the total content _{[Li 2 O + Na 2 O} + K 2 O] is too large, the network forming effect of the glass is lowered, stability at the time of re-heating of the glass may be reduced. Moreover, there exists a possibility of shortening the lifetime of refractories, such as a glass kiln. When the total content _{[Li 2 O + Na 2 O} + K 2 O] is too small, the melting properties of the glass decreases.

In the optical glass according to the present embodiment, the mass ratio of the content of Na ₂ O to the total content of Li ₂ O, Na ₂ O and K ₂ O [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is It is 0.330 or more. The lower limit of the mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is preferably 0.380, and further 0.420, 0.440, 0.460, 0.480, 0.500. 0.520, 0.540, 0.560, 0.580, 0.600 in this order. Further, the upper limit of the mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is preferably 1.000, and further 0.950, 0.900, 0.880, 0.860, 0 .840, 0.820, 0.800, 0.780, 0.760, 0.740, 0.720, 0.700 in this order.
If the mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is too large, the thermal stability of the glass may be reduced. If the mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is too small, the specific gravity increases, the thermal stability may decrease, and the raw material cost may increase.

In the optical glass according to the present embodiment, the mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of Li ₂ O, Na ₂ O and K ₂ O [(MgO + CaO + SrO + BaO + ZnO) / (Li ₂ O + Na ₂ O _{+ K 2} O)] is 0.480 or less. The upper limit of the mass ratio [(MgO + CaO + SrO + BaO + ZnO) / (Li ₂ O + Na ₂ O + K ₂ O)] is preferably 0.400, and further 0.350, 0.300, 0.250, 0.200, 0.150. , 0.100 in order. The mass ratio [(MgO + CaO + SrO + BaO + ZnO) / (Li ₂ O + Na ₂ O + K ₂ O)] may be zero.
If the mass ratio [(MgO + CaO + SrO + BaO + ZnO) / (Li ₂ O + Na ₂ O + K ₂ O)] is too large, the specific gravity may increase and the thermal stability may decrease. If the mass ratio [(MgO + CaO + SrO + BaO + ZnO) / (Li ₂ O + Na ₂ O + K ₂ O)] is too small, the refractive index nd may decrease.

In the optical glass according to the present embodiment, the mass ratio of the content of TiO ₂ to the content of _{Nb 2 O 5 [TiO 2 /} Nb 2 O 5] is 0.340 or less. The upper limit of the mass ratio [TiO ₂ / Nb ₂ O ₅ ] is preferably 0.300, and further in the order of 0.280, 0.260, 0.240, 0.220, 0.200, 0.180. Is more preferable. The lower limit of the mass ratio [TiO ₂ / Nb ₂ O ₅ ] is preferably 0, and more preferably in the order of 0.001, 0.002, 0.003, 0.004, and 0.005.
If the mass ratio [TiO ₂ / Nb ₂ O ₅ ] is too large, the partial dispersion ratios Pg and F may increase. When the mass ratio [TiO ₂ / Nb ₂ O ₅ ] is too small, the network forming action of the glass is lowered, the stability during reheating of the glass may be lowered, and the specific gravity may be increased.

In the optical glass according to the present embodiment, the mass ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O to the total content of TiO ₂ and Nb ₂ O ₅ [(Li ₂ O + Na ₂ O + K ₂ O) / (TiO ₂ + Nb ₂ O ₅ )] is 0.700 or less. The upper limit of the mass ratio [(Li ₂ O + Na ₂ O + K ₂ O) / (TiO ₂ + Nb ₂ O ₅ )] is preferably 0.650, and further 0.600, 0.570, 0.550,. 530, 0.510, 0.500, 0.490, 0.480, 0.470, 0.460, 0.450 are more preferable in this order. The lower limit of the mass ratio [(Li ₂ O + Na ₂ O + K ₂ O) / (TiO ₂ + Nb ₂ O ₅ )] is preferably 0.100, and further 0.150, 0.200, 0.250, 0.00. 270, 0.290, 0.300, 0.310, 0.320, 0.330, and 0.340 are more preferable in this order.
If the mass ratio [(Li ₂ O + Na ₂ O + K ₂ O) / (TiO ₂ + Nb ₂ O ₅ )] is too large, the desired optical constant may not be obtained. If the mass ratio _{[(Li 2 O + Na 2} O + K 2 O) / (TiO 2 + Nb 2 O 5)] is too small, there is a possibility that melting of the glass decreases.

In the optical glass according to the present _{embodiment, SiO 2, B 2 O 3} , P 2 O 5, Al 2 O 3, Li 2 O, Na 2 O, K 2 O, MgO, CaO, ZnO, La 2 O 3, The total content of Y ₂ O ₃ , Gd ₂ O ₃ , ZrO ₂ , TiO ₂ and Nb ₂ O ₅ is 96.0% or more. The lower limit of the total content is preferably 96.5%, and further 97.0%, 97.5%, 98.0%, 98.2%, 98.4%, 98.6%, 98 .8%, 99.0% in order. The total content may be 100%.
If the total content is too small, the desired optical constant may not be obtained. Moreover, the network forming action of the glass may be reduced, the stability during reheating of the glass may be reduced, the specific gravity may be increased, and the partial dispersion ratio may be increased.

In the optical glass according to the present embodiment, the contents of PbO, CdO, and As ₂ O ₃ are each 0.01% or less. The upper limit of the content of PbO, CdO and As ₂ O ₃ is preferably 0.005%, and more preferably in the order of 0.003%, 0.002% and 0.001%. The content of PbO, CdO and As ₂ O ₃ is preferably small, and may be 0%. These components are components that are concerned about environmental impact, and are preferably not substantially contained.

  The contents and ratios of glass components other than those described above in the optical glass according to this embodiment will be described in detail below.

In the optical glass according to the present embodiment, the upper limit of the content of B ₂ O ₃ is preferably 20%, and further 18%, 16%, 14%, 12%, 10%, 8%, 6%, 5%, 4%, 3%, 2%, and 1% are more preferable in this order. Further, the content of B ₂ O ₃ is preferably small, and the content of B ₂ O ₃ may be 0%.
By setting the content of B ₂ O _{3 in} the above range, the specific gravity of the glass is reduced, and the thermal stability of the glass can be improved.

In the optical glass according to the present embodiment, the upper limit of the content of P ₂ O ₅ is preferably 2.50%, and further 2.00%, 1.00%, 0.90%, 0.80%. 0.70%, 0.60%, 0.50% in this order. Further, the lower limit of the content of P ₂ O ₅ is preferably 0%, and further 0.05%, 0.10%, 0.12%, 0.14%, 0.16%, 0.18 %, 0.20% in order. The content of P ₂ O ₅ may be 0%. Since P ₂ O ₅ is a glass network former, by the content satisfies the lower limit described above, it is possible to improve the thermal stability of the glass. On the other hand, P ₂ O ₅ is a component that lowers the dispersion and relatively increases ΔPg, F ′. Therefore, when the content satisfies the above upper limit, the lower dispersion is suppressed, and the thermal stability of the glass. Can retain sex.

In the optical glass according to the present embodiment, the upper limit of the content of Al ₂ O ₃ is preferably 20%, and further 15%, 13%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, and 3% are more preferable in this order. The content of Al ₂ O ₃ may be 0%. The content of Al ₂ O ₃ within the above range can hold devitrification resistance and thermal stability of the glass.

In the optical glass according to the present embodiment, the upper limit of the total content [SiO ₂ + P ₂ O ₅ ] of SiO ₂ and P ₂ O ₅ is preferably 40%, and further 39%, 38%, 37%, It is more preferable in the order of 36%, 35%, and 34%. The lower limit of the total content [SiO ₂ + P ₂ O ₅ ] is preferably 10%, and more preferably in the order of 15%, 20%, 22%, 24%, 26%, 28%, 30%. . The total content of _{[SiO 2 + P 2 O 5} ] in the above range, and suppress the partial dispersion ratio Pg, F is increased, it can be maintained the thermal stability of the glass.

Further, in the optical glass according to the present embodiment, the upper limit of the total content [SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ] of SiO ₂ , P ₂ O ₅ and B ₂ O ₃ is preferably 40%, Furthermore, 39%, 38%, 37%, 36%, 35%, and 34% are more preferable in this order. Further, the lower limit of the total content [SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ] is preferably 10%, and further 15%, 20%, 22%, 24%, 26%, 28%, 30%. Is more preferable.

In the optical glass according to the present embodiment, the upper limit of the mass ratio of the content of _P 2 _{O 5} to the total content of SiO ₂ and _{P 2 O 5 [P 2 O} 5 / (SiO 2 + P 2 O 5)] , the It is preferably 0.200, and more preferably in the order of 0.100, 0.050, 0.030, 0.020, 0.018, 0.015. The mass ratio [P ₂ O ₅ / (SiO ₂ + P ₂ O ₅ )] may be zero.
Mass ratio _{[P 2 O 5 / (SiO} 2 + P 2 O 5)] in the above range, it is possible to suppress the partial dispersion ratio Pg, F is increased.

In the optical glass according to the present embodiment, the mass ratio of the content of P ₂ O ₅ to the total content of SiO ₂ , P ₂ O ₅ and B ₂ O ₃ [P ₂ O ₅ / (SiO ₂ + B ₂ O ₃ + P ₂ O ₅ )] is preferably 0.200, more preferably 0.100, 0.050, 0.030, 0.020, 0.018, 0.015 in this order. The mass ratio [P ₂ O ₅ / (SiO ₂ + B ₂ O ₃ + P ₂ O ₅ )] may be zero.

Furthermore, in the optical glass according to the present embodiment, the mass ratio of the content of SiO ₂ to the total content of SiO ₂ , P ₂ O ₅ and B ₂ O ₃ [SiO ₂ / (SiO ₂ + B ₂ O ₃ + P ₂ O The upper limit of ₅ )] is preferably 1. Further, the lower limit of the mass ratio [SiO ₂ / (SiO ₂ + B ₂ O ₃ + P ₂ O ₅ )] is preferably 0.900, and further 0.905, 0.910, 0.915, 0.920. It is more preferable in this order.

In the optical glass according to the present embodiment, the lower limit of the total content [Nb ₂ O ₅ + TiO ₂ ] of Nb ₂ O ₅ and TiO ₂ is preferably 30%, and further 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, and 40% are more preferable in this order. Moreover, the upper limit of the total content [Nb ₂ O ₅ + TiO ₂ ] content is preferably 55%, and further 53%, 51%, 49%, 47%, 45%, 44% and 43%. More preferred in order. By setting the total content [Nb ₂ O ₅ + TiO ₂ ] in the above range, a desired optical constant can be realized.

In the optical glass according to the present embodiment, the upper limit of the mass ratio of the content _{[P 2 O 5 / Nb 2} O 5] of _P 2 _{O 5} with respect to the content of _Nb 2 _{O 5} is preferably 0.200, Furthermore, 0.100, 0.050, 0.020, 0.018, 0.015, 0.014, 0.013, and 0.012 are more preferable in this order. The mass ratio [P ₂ O ₅ / Nb ₂ O ₅ ] may be zero. Mass ratio _{[P 2 O 5 / Nb 2} O 5] in the above range,? Pg, the increase of F 'can be suppressed.

In the optical glass according to the present embodiment, the upper limit of the mass ratio [P ₂ O ₅ / (Nb ₂ O ₅ + TiO ₂ )] of the content of P ₂ O ₅ to the total content of Nb ₂ O ₅ and TiO ₂ is Preferably it is 0.200, and further 0.100, 0.050, 0.020, 0.018, 0.015, 0.014, 0.013, 0.012, 0.011, 0.010. More preferred in order. The mass ratio [P ₂ O ₅ / (Nb ₂ O ₅ + TiO ₂ )] may be zero. Mass ratio _{[P 2 O 5 / (Nb} 2 O 5 + TiO 2)] in the above range,? Pg, the increase of F 'can be suppressed.

In the optical glass according to the present embodiment, the upper limit of the content of WO ₃ is preferably 5.0%, and further 4.0%, 3.0%, 2.0%, 1.5%, 1 0.0%, 0.5%, 0.3% and 0.1% are more preferable in this order. Further, the lower limit of the content of WO ₃ is preferably 0%. The content of WO ₃ may be 0%. By setting the upper limit of the content of WO ₃ within the above range, the transmittance can be increased, and the partial dispersion ratios Pg, F and specific gravity can be reduced.

In the optical glass according to the present embodiment, the upper limit of the Bi ₂ O ₃ content is 5.0%, and further 4.0%, 3.0%, 2.0%, 1.5%, 1% 0.0%, 0.5%, 0.3% and 0.1% are more preferable in this order. Moreover, the lower limit of the content of Bi ₂ O ₃ is preferably 0%. The content of Bi ₂ O ₃ may be 0%. By making the content of Bi ₂ O _{3 in} the above range, the thermal stability of the glass can be improved, and the partial dispersion ratios Pg, F and specific gravity can be reduced.

In the optical glass according to the present embodiment, the lower limit of the total content [Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ ] of Nb ₂ O ₅ , TiO ₂ , WO ₃ and Bi ₂ O ₃ is preferably 30%. Furthermore, 32%, 34%, 36%, 38%, 39%, and 40% are more preferable in this order. The upper limit of the total content [Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ ] is preferably 55%, and further 53%, 51%, 50%, 49%, 48%, 47%, More preferable in the order of 46%, 45%, 44%, 43%. By setting the total content [Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ ] in the above range, a desired optical constant can be realized.

In the optical glass according to this _embodiment, Nb ₂ O 5, the mass ratio of the content of _TiO 2, WO ₃ and _{Bi Nb} 2 _{O 5} to the total content of _{2 O 3 [Nb 2 O 5} / (Nb 2 O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )]] is preferably 0.500, more preferably 0.5500, 0.600, 0.650, 0.700, 0.750, 0.800, It is more preferable in the order of 0.820, 0.840, and 0.850. The upper limit of the mass ratio is preferably 1.000, and more preferably in the order of 0.999, 0.998, 0.997, 0.996, and 0.995.

Furthermore, in the optical glass according to the present embodiment, the mass ratio of the content of ZrO ₂ to the total content of Nb ₂ O ₅ , TiO ₂ , WO ₃ and Bi ₂ O ₃ [ZrO ₂ / (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )] is preferably 0.05, and more preferably 0.07, 0.09, 0.11, 0.13, 0.15, 0.17, 0.18. More preferred in order. The upper limit of the mass ratio is preferably 0.40, and further 0.39, 0.38, 0.37, 0.36, 0.35, 0.34, 0.33, 0.32 It is more preferable in this order. By setting the mass ratio within the above range, the Abbe number νd and the partial dispersion ratios Pg and F can be controlled.

Then, the optical glass according to this _{embodiment, Nb 2 O 5, TiO 2} , WO 3 and the total content mass ratio of the _{Bi SiO} 2 to the total content of 2 _{O 3,} P 2 _{O 5} and _B 2 _{O 3} The lower limit of [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )] is preferably 0.400, and further 0.450, 0.500. 0.550, 0.600, 0.650, 0.670, 0.680, 0.690, 0.700 in this order. The upper limit of the mass ratio is preferably 1.000, and further 0.980, 0.960, 0.940, 0.920, 0.900, 0.890, 0.880, 0.870. , 0.860, 0.850, 0.840 in this order. By setting the mass ratio within the above range, the Abbe number νd and the partial dispersion ratios Pg and F can be controlled.

In the optical glass according to the present embodiment, the upper limit of the content of Li ₂ O is preferably 10%, and more preferably 9%, 8%, 7%, and 6%. The lower limit of the content of Li ₂ O is preferably 0%, and further 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4% More preferable in the order of 0.0%. By setting the content of Li ₂ O in the above range, an increase in the partial dispersion ratios Pg and F can be suppressed, and chemical durability, weather resistance, and stability during reheating can be maintained.

In the optical glass according to the present embodiment, the upper limit of the content of Na ₂ O is preferably 30%, and further in the order of 25%, 23%, 21%, 19%, 17%, 15%, 13%. Is more preferable. The lower limit of the Na ₂ O content is preferably 0%, and more preferably in the order of 1%, 2%, 3%, 4%, 5%, 6%, 7%, and 8%. By setting the content of Na ₂ O in the above range, the partial dispersion ratios Pg and F can be reduced.

In the optical glass according to the present embodiment, the upper limit of the content of K ₂ O is preferably 30%, and further 25%, 20%, 15%, 10%, 8%, 6%, 4%, 2% % Order is more preferable. The lower limit of the content of K ₂ O is preferably 0%, and more preferably in the order of 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%. 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 according to the present embodiment, the upper limit of the content of Cs ₂ O is preferably 10%, and further in the order of 8%, 6%, 5%, 4%, 3%, 2%, 1%. Is more preferable. The lower limit of the content of Cs ₂ O is preferably 0%. The content of Cs ₂ O may be 0%.
Cs ₂ O has a function of improving the thermal stability of the glass. However, when the content thereof increases, chemical durability and weather resistance deteriorate. In addition, the specific gravity may increase. Therefore, each content of Cs ₂ O is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the total content [Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O] of Li ₂ O, Na ₂ O, K ₂ O and Cs ₂ O is preferably 40%, Furthermore, 35%, 30%, 28%, 26%, 24%, 22%, 21%, 20%, and 19% are more preferable in this order. The lower limit of the total content [Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O] is preferably 3%, and further 5%, 7%, 9%, 10%, 11%, 12%, 13%, 14% Is more preferable. The total content _{[Li 2 O + Na 2 O} + K 2 O + Cs 2 O] to within the above range, improved meltability and thermal stability of the glass, can decrease the liquidus temperature.

In the optical glass according to the present _embodiment, the weight ratio of the total content of SiO _2, P 2 _{O 5} and _B 2 _{O 3 Li} 2 _O to the total content _of, Na _{2 O, K} 2 O and Cs ₂ O The upper limit of [(Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O) / (SiO ₂ + B ₂ O ₃ + P ₂ O ₅ )] is preferably 5.000, and further 3.000, 2.000, 1. 500, 1.300, 1.100, 1.000, 0.900, 0.800, 0.780, 0.760, 0.740, 0.720, 0.700, 0.680, 0.660, More preferable in the order of 0.640, 0.620, and 0.600. Further, the lower limit of the mass ratio is preferably 0.100, and further 0.200, 0.300, 0.350, 0.400, 0.420, 0.440, 0.460, 0.480. Is more preferable. If the mass ratio is too low, the meltability is deteriorated and the partial dispersion ratios Pg and F may be increased. If the mass ratio is too high, the glass stability may be decreased.

Further, the optical glass according to this _embodiment, Nb ₂ O 5, the total content of _TiO 2, WO ₃ and _Bi 2 _{O 3 Li} 2 _O to the total content _of, Na _{2 O, K} 2 O and Cs ₂ O The upper limit of the mass ratio [(Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O) / (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )] is preferably 4.000, and further 3.000, 2 .000, 1.000, 0.900, 0.800, 0.750, 0.700, 0.650, 0.600, 0.550, 0.520, 0.500, 0.490, 0.480 , 0.470 in order. Further, the lower limit of the mass ratio is preferably 0.100, and further 0.150, 0.200, 0.240, 0.260, 0.280, 0.300, 0.310, 0.320. , 0.330 is more preferable. If the mass ratio is too low, the partial dispersion ratios Pg and F may increase and the transmittance may deteriorate, and if it is too high, the glass stability may decrease.

Then, the optical glass according to the present _{embodiment, Li 2 O, Na 2 O} , the mass ratio of the content of _P 2 _{O 5} to the total content of _{K 2} O and _{Nb 2 O 5 [P 2 O} 5 / (Li ₂ O + Na ₂ O + K ₂ O + Nb ₂ O ₅ )]] is preferably 0.500, more preferably 0.300, 0.100, 0.090, 0.080, 0.050, 0.030. 0.020, 0.015, 0.013, 0.011, 0.010, 0.009, 0.008 in this order. The mass ratio [P ₂ O ₅ / (Li ₂ O + Na ₂ O + K ₂ O + Nb ₂ O ₅ )] may be zero. By setting the mass ratio within the above range, an increase in ΔPg, F ′ can be suppressed.

In the optical glass according to the present embodiment, P ₂ O ₅ with respect to the total content of Li ₂ O, Na ₂ O, K ₂ O, Cs ₂ O, Nb ₂ O ₅ , TiO ₂ , WO ₃ and Bi ₂ O ₃ . The upper limit of the mass ratio of the content [P ₂ O ₅ / (Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O + Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )] is preferably 0.500, and further 0.300, 0.100, 0.090, 0.080, 0.050, 0.030, 0.020, 0.015, 0.013, 0.011, 0.010, 0.009, 0. 008 is more preferable. The mass ratio may be zero. By setting the mass ratio within the above range, an increase in ΔPg, F ′ can be suppressed.

  In the optical glass according to the present embodiment, the upper limit of the content of MgO is preferably 20%, and further 15%, 10%, 8%, 7%, 6%, 5%, 4%, 3%, 2% is more preferable. Further, the lower limit of the content of MgO is preferably 0%. The content of MgO may be 0%.

  In the optical glass according to the present embodiment, the upper limit of the CaO content is preferably 20%, and further 15%, 10%, 8%, 7%, 6%, 5%, 4%, 3%, 2% is more preferable. Moreover, the lower limit of the CaO content is preferably 0%. The content of CaO may be 0%.

  In the optical glass according to the present embodiment, the upper limit of the SrO content is preferably 20%, and further 15%, 10%, 8%, 7%, 6%, 5%, 4%, 3%, 2% is more preferable. Moreover, the lower limit of the SrO content is preferably 0%. The SrO content may be 0%.

  In the optical glass according to the present embodiment, the upper limit of the content of BaO is preferably 20%, and further 15%, 10%, 8%, 7%, 6%, 5%, 4%, 3%, 2% is more preferable. Further, it is preferable that the content of BaO is small, and the content of BaO may be 0%.

  MgO, CaO, SrO, and BaO are all glass components that have a function of improving the thermal stability and devitrification resistance of glass. However, when the content of these glass components increases, the specific gravity increases, the high dispersibility is impaired, and the thermal stability and devitrification resistance of the glass decrease. Therefore, it is preferable that each content of these glass components is the said range, respectively.

  In the optical glass according to the present embodiment, the upper limit of the total content [MgO + CaO] of MgO and CaO is preferably 20%, and further 15%, 10%, 8%, 7%, 6%, 5%, 4%, 3% and 2% are more preferable in this order. Moreover, the lower limit of the total content [MgO + CaO] is preferably 0%. The total content [MgO + CaO] may be 0%. By making total content [MgO + CaO] into the said range, thermal stability can be maintained, without preventing high dispersion.

In the optical glass according to the present embodiment, the upper limit of the ZnO content is preferably 20%, and further 15%, 10%, 8%, 7%, 6%, 5%, 4%, 3%, 2% is more preferable. Moreover, the lower limit of the ZnO content is preferably 0%. The content of ZnO may be 0%.
ZnO is a glass component having a function of improving the thermal stability of glass. However, when the content of ZnO is too large, the specific gravity increases. Therefore, from the viewpoint of improving the thermal stability of the glass and maintaining the desired optical constant, the ZnO content is preferably in the above range.

  In the optical glass according to the present embodiment, the upper limit of the total content [MgO + CaO + SrO + BaO + ZnO] of MgO, CaO, SrO, BaO and ZnO is preferably 20%, and further 15%, 10%, 8%, 7%, 6%, 5%, 4%, 3% and 2% are more preferable in this order. Moreover, the lower limit of the total content is preferably 0%. The total content may be 0%. By setting the total content in the above range, an increase in specific gravity can be suppressed, and thermal stability can be maintained without hindering high dispersion.

In the optical glass according to the present embodiment, the mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of Li ₂ O, Na ₂ O, K ₂ O and Cs ₂ O [(MgO + CaO + SrO + BaO + ZnO) / The upper limit of (Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O)] is preferably 20.000, and further 15,000, 10.000, 7.000, 5.000, 3.000, 2.000, 1.000, 0.900, 0.800, 0.700, 0.600, 0.500, 0.400, 0.300, 0.200, 0.100, 0.050, 0.030 preferable. Further, the lower limit of the mass ratio is preferably 0. The mass ratio may be zero.

In the optical glass according to the present embodiment, the upper limit of the content of La ₂ O ₃ is preferably 20%, and further 15%, 12%, 10%, 8%, 7%, 6%, 5%, 4%, 3% and 2% are more preferable in this order. Further, the lower limit of the content of La ₂ O ₃ is preferably 0%, and the content of La ₂ O ₃ may be 0%. By setting the content of La ₂ O _{3 in} the above range, a desired optical constant can be realized, an increase in specific gravity can be suppressed, and the partial dispersion ratios Pg and F can be reduced.

In the optical glass according to the present embodiment, the upper limit of the content of Y ₂ O ₃ is preferably 20%, and further 18%, 16%, 15%, 14%, 13%, 12%, 10%, It is more preferable in the order of 9% and 8%. Moreover, the lower limit of the content of Y ₂ O ₃ is preferably 0%.
When the content of Y ₂ O ₃ is too large, the thermal stability of the glass is lowered, and the glass tends to be devitrified during production. Therefore, from the viewpoint of suppressing a decrease in the thermal stability of the glass, the content of Y ₂ O ₃ is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of Ta ₂ O ₅ is preferably 20%, and further 15%, 12%, 10%, 8%, 7%, 6%, 5%, 4%, 3% and 2% are more preferable in this order. Further, the lower limit of the content of Ta ₂ O ₅ is preferably 0%.
Ta ₂ O ₅ is a glass component that has a function of improving the thermal stability of the glass, and is a component that lowers the partial dispersion ratios Pg and F. On the other hand, when the content of Ta ₂ O ₅ is increased, the thermal stability of the glass is lowered, and when the glass is melted, unmelted glass raw material tends to be generated. Also, the specific gravity increases. In addition, the raw material cost increases. Therefore, the content of Ta ₂ O ₅ is preferably in the above range.

In the optical glass according to the present embodiment, the content of Sc ₂ O ₃ is preferably 2% or less. Moreover, the lower limit of the content of Sc ₂ O ₃ is preferably 0%.

In the optical glass according to the present embodiment, the content of HfO ₂ is preferably 2% or less. Moreover, the lower limit of the content of HfO ₂ is preferably 0%, and more preferably in the order of 0.05% and 0.1%.

Sc ₂ O ₃ and HfO ₂ have a function of enhancing the high dispersibility of the glass, but are expensive components. Therefore, each content of Sc ₂ O ₃ and HfO ₂ is preferably in the above range.

In the optical glass according to the present embodiment, the content of Lu ₂ O ₃ is preferably 2% or less. Moreover, the lower limit of the content of Lu ₂ O ₃ is preferably 0%.

Lu ₂ O ₃ has a function of enhancing the high dispersibility of the glass, but is also a glass component that increases the specific gravity of the glass because of its large molecular weight. Therefore, the content of Lu ₂ O ₃ is preferably in the above range.

In the optical glass according to the present embodiment, the GeO ₂ content is preferably 2% or less. Moreover, the lower limit of the GeO ₂ content is preferably 0%.

GeO ₂ has a function of enhancing the high dispersibility of the glass, but is a prominently expensive component among commonly used glass components. Therefore, from the viewpoint of reducing the manufacturing cost of glass, the GeO ₂ content is preferably in the above range.

In the optical glass according to the present embodiment, the content of Gd ₂ O ₃ is preferably 2% or less. Moreover, 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 of the glass is lowered. On the other hand, if the content of Gd ₂ O ₃ is too large, the specific gravity of the glass increases. In addition, the raw material cost increases. Therefore, the content of Gd ₂ O ₃ is preferably in the above range from the viewpoint of suppressing the increase in specific gravity while maintaining the thermal stability of the glass well.

In the optical glass according to the present embodiment, the content of Yb ₂ O ₃ is preferably 2% or less. Moreover, the lower limit of the content of Yb ₂ O ₃ is preferably 0%.
Since Yb ₂ O ₃ has a higher molecular weight than La ₂ O ₃ , Gd ₂ O ₃ , and Y ₂ O ₃ , it increases the specific gravity of the glass. Therefore, it is desirable to reduce the content of Yb ₂ O ₃ to suppress an increase in the specific gravity of the glass.
The thermal stability of the glass decreases the content of Yb ₂ O ₃ is too large. From the viewpoint 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 in the above range.

The optical glass according to the present embodiment is mainly composed of the above glass components, that is, SiO ₂ , Nb ₂ O ₅ , ZrO ₂ as essential components, B ₂ O ₃ , P ₂ O ₅ , Al ₂ O ₃ , TiO as optional components. ₂ , WO ₃ , Bi ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, Cs ₂ O, MgO, CaO, SrO, BaO, ZnO, La ₂ O ₃ , Y ₂ O ₃ , Ta ₂ O ₅ , Sc ₂ O ₃ , HfO ₂ , Lu ₂ O ₃ , GeO ₂ , Gd ₂ O ₃ and Yb ₂ O ₃ , and the total content of the above glass components is more than 95% Preferably more than 98%, more preferably more than 99%, and still more preferably more than 99.5%.

  In addition, although it is preferable that the optical glass which concerns on this embodiment is fundamentally comprised by the said glass component, in the range which does not prevent the effect of this invention, it is also possible to contain another component. In the present invention, the inclusion of inevitable impurities is not excluded.

(Other ingredients)
The optical glass according to the present embodiment can also contain a small amount of _{Sb 2 O} 3, CeO 2 or the like as a fining agent. The total amount of the refining agent (external addition amount) is preferably 0% or more and less than 1%, and more preferably 0% or more and 0.5% or less.

  The extra addition amount is the weight percentage of the amount of fining agent added when the total content of all glass components excluding the fining agent is 100%.

  The optical glass has a high transmittance over a wide range in the visible region. In order to take advantage of these features, it is preferable not to include a coloring element. Examples of coloring elements include Cu, Co, Ni, Fe, Cr, Eu, Nd, Er, V, and the like. Any element is preferably less than 100 ppm by mass, more preferably 0 to 80 ppm by mass, still more preferably 0 to 50 ppm by mass, and particularly preferably substantially not contained.

Ga, Te, Tb, etc. are components that do not need to be introduced and are also expensive components. Therefore, the ranges of the contents of Ga ₂ O ₃ , TeO ₂ , and TbO ₂ by mass% are all preferably 0 to 0.1%, more preferably 0 to 0.05%. Preferably, it is 0 to 0.01%, more preferably 0 to 0.005%, still more preferably 0 to 0.001%, and it is not substantially contained. Particularly preferred.

(Glass properties)
<Refractive index nd>
In the optical glass according to the present embodiment, the refractive index nd is preferably 1.70 to 1.90. The refractive index nd may be 1.72 to 1.85, or 1.73 to 1.83. Components that relatively increase the refractive index nd are Nb ₂ O ₅ , TiO ₂ , ZrO ₂ , Ta ₂ O ₅ , and La ₂ O ₃ . Components that lower the refractive index nd relatively are SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, and K ₂ O. The refractive index nd can be controlled by appropriately adjusting the contents of these components.

<Partial dispersion ratio Pg, F>
The upper limit of the partial dispersion ratio Pg, F of the optical glass according to this embodiment is preferably 0.6500, and further 0.6400, 0.6300, 0.6200, 0.6100, 0.6050,. 6040, 0.6030, 0.6020, 0.6010, 0.6000 are more preferable in this order. The partial dispersion ratio Pg, F is preferably as low as possible, and the lower limit thereof is preferably 0.5500, and further 0.5600, 0.5700, 0.5800, 0.5840, 0.5850, 0.5870. , 0.5890, 0.5900, 0.5910, 0.5920, 0.5930, 0.5940.
By setting the partial dispersion ratios Pg and F in the above ranges, an optical glass suitable for high-order chromatic aberration correction can be obtained. Components that relatively increase the partial dispersion ratios Pg and F are Nb ₂ O ₅ , TiO ₂ , ZrO ₂ , and Ta ₂ O ₅ . Components that lower the partial dispersion ratios Pg, F relatively are SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O. The partial dispersion ratios Pg and F can be controlled by appropriately adjusting the contents of these components.

In the optical glass according to the present embodiment, the partial dispersion ratio Pg, F is preferably the following formula (1), more preferably the following formula (2), still more preferably the following formula (3), particularly preferably the following formula (4). Is satisfied. When the partial dispersion ratios Pg and F satisfy the following expression, an optical glass suitable for secondary chromatic aberration correction can be provided.
Pg, F ≦ −0.00286 × νd + 0.68900 (1)
Pg, F ≦ −0.00286 × νd + 0.68800 (2)
Pg, F ≦ −0.00286 × νd + 0.68600 (3)
Pg, F ≦ −0.00286 × νd + 0.68400 (4)

Further, the upper limit of ΔPg, F ′ of the optical glass according to the present embodiment is preferably 0.0000, and further −0.0010, −0.0020, −0.0030, −0.0040, −0. .0050, -0.0060 in order. Further, ΔPg, F ′ is preferably as low as possible, and the lower limit thereof is preferably −0.0200, and further −0.0180, −0.0160, −0.0140, −0.0130, and −0.0120. It can also be. Components that relatively increase ΔPg, F ′ are P ₂ O ₅ , B ₂ O ₃ , and TiO ₂ . Components that relatively lower ΔPg, F ′ are Nb ₂ O ₅ , La ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , Li ₂ O, Na ₂ O, K ₂ O. ΔPg, F ′ can be controlled by appropriately adjusting the contents of these components.

<Specific gravity of glass>
The specific gravity of the optical glass according to the present embodiment is preferably 3.60 or less, and further 3.55 or less, 3.50 or less, 3.48 or less, 3.46 or less, 3.45 or less, 3.44 or less. Hereinafter, 3.43 or less, 3.42 or less, 3.41 or less, and 3.40 or less are more preferable in this order. The specific gravity is preferably as small as possible, and the lower limit is not particularly limited, but is generally about 3.00. Components that relatively increase the specific gravity include BaO, La ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ and the like. Components that lower the specific gravity relatively include SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, and the like. The specific gravity can be controlled by adjusting the content of these components.

<Glass transition temperature Tg>
The upper limit of the glass transition temperature Tg of the optical glass according to this embodiment is preferably 700 ° C, and more preferably in the order of 670 ° C, 650 ° C, 630 ° C, 620 ° C, 610 ° C, 600 ° C, and 590 ° C. Moreover, the lower limit of the glass transition temperature Tg is preferably 450 ° C, and more preferably in the order of 470 ° C, 500 ° C, 510 ° C, 520 ° C, 530 ° C, and 540 ° C. Components that lower the glass transition temperature Tg relatively include Li ₂ O, Na ₂ O, K ₂ O, and the like. Components that relatively increase the glass transition temperature Tg are La ₂ O ₃ , ZrO ₂ , Nb ₂ O ₅ and the like. The glass transition temperature Tg can be controlled by appropriately adjusting the contents of these components.

<Light transmittance of glass>
The light transmittance of the optical glass according to the present embodiment can be evaluated by the coloring degrees λ70 and λ5.
The spectral transmittance of a glass sample having a thickness of 10.0 mm ± 0.1 mm is measured in the wavelength range of 200 to 700 nm. The wavelength at which the external transmittance is 70% is λ70, and the wavelength at which the external transmittance is 5% is λ5. And

Λ70 of the optical glass according to the present embodiment is preferably 500 nm or less, more preferably 470 nm or less, still more preferably 450 nm or less, and still more preferably 430 nm or less. Further, λ5 is preferably 400 nm or less, more preferably 380 nm or less, and further preferably 370 nm or less. The coloring degrees λ70 and λ5 can be controlled by adjusting the contents of ZrO ₂ , Nb ₂ O ₅ , TiO ₂ , SiO ₂ , and B ₂ O ₃ .

<Stability during reheating>
The optical glass according to the present embodiment preferably does not become cloudy when heated for 5 minutes in a test furnace set to a temperature 200 to 220 ° C. higher than the glass transition temperature Tg. More preferably, the number of crystals precipitated by the heating is 100 or less per sample. The stability during reheating can be controlled by adjusting the contents of Nb ₂ O ₅ , TiO ₂ , SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, and P ₂ O _5. .

  The stability during reheating is measured as follows. A glass sample having a size of 10 mm × 10 mm × 7.5 mm was heated for 5 minutes in a test furnace set to a temperature 200 to 220 ° C. higher than the glass transition temperature Tg of the glass sample, and then an optical microscope (observation magnification: 40 to 200 times), the number of crystals per sample is measured. Moreover, the presence or absence of cloudiness of glass is confirmed visually.

(Manufacture of optical glass)
The optical glass according to the present embodiment may be prepared according to a known glass manufacturing method by preparing glass raw materials so as to have the predetermined composition and using the prepared glass raw materials. For example, a plurality of types of compounds are prepared and mixed sufficiently to obtain a batch raw material, and the batch raw material is placed in a quartz crucible or a platinum crucible and roughly melted (rough melt). The melt obtained by rough melting is rapidly cooled and pulverized to produce cullet. Further, the cullet is placed in a platinum crucible and heated and re-melted (remelted) to obtain a molten glass. After further clarification and homogenization, the molten glass is formed and slowly cooled to obtain an optical glass. A publicly known method may be applied to forming molten glass and slow cooling.

  In addition, as long as a desired glass component can be introduced into the glass so as to have a desired content, the compound used when preparing the batch raw material is not particularly limited. Examples include salts, nitrates, hydroxides, fluorides, and the like.

(Manufacture of optical elements, etc.)
In order to produce an optical element using the optical glass according to the present embodiment, a known method may be applied. For example, in the production of the optical glass, molten glass is poured into a mold and formed into a plate shape to produce a glass material made of the optical glass according to the present invention. The obtained glass material is appropriately cut, ground and polished to produce a cut piece having a size and shape suitable for press molding. The cut piece is heated and softened, and press-molded (reheat press) by a known method to produce an optical element blank that approximates the shape of the optical element. The optical element blank is annealed and ground and polished by a known method to produce an optical element.

  The optical functional surface of the manufactured optical element may be coated with an antireflection film, a total reflection film, or the like according to the purpose of use.

  According to one embodiment of the present invention, an optical element made of the optical glass can be provided. Examples of the types of optical elements include lenses such as spherical lenses and aspheric lenses, prisms, diffraction gratings, and the like. Examples of the shape of the lens include various shapes such as a biconvex lens, a plano-convex lens, a biconcave lens, a plano-concave lens, a convex meniscus lens, and a concave meniscus lens. The optical element can be manufactured by a method including a step of processing a glass molded body made of the optical glass. Examples of processing include cutting, cutting, rough grinding, precision grinding, polishing, and the like. When such processing is performed, the use of the glass can reduce breakage and stably supply high-quality optical elements.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, this invention is not limited to the aspect shown in the Example.

(Example 1)
Glass samples having the glass compositions shown in Tables 1 to 4 were prepared by the following procedures and subjected to various evaluations.

[Manufacture of optical glass]
First, oxides, hydroxides, carbonates, and nitrates corresponding to glass constituents are prepared as raw materials, and the above-mentioned raw materials are set so that the glass composition of the obtained optical glass has the compositions shown in Tables 1 to 4. Were weighed and blended to thoroughly mix the raw materials. The prepared raw material (batch raw material) thus obtained is put into a platinum crucible, heated at 1350 ° C. to 1450 ° C. for 2 to 5 hours to form molten glass, stirred to homogenize, clarified, and then molten glass. Was cast into a mold preheated to an appropriate temperature. The cast glass was heat-treated at a temperature 100 ° C. lower than the glass transition temperature Tg for 30 minutes, and allowed to cool to room temperature in a furnace to obtain a glass sample.

[Confirmation of glass component composition]
About the obtained glass sample, content of each glass component was measured by the inductively coupled plasma emission spectrometry (ICP-AES), and it was confirmed that it was as each composition shown in Tables 1-4.

[Measurement of optical properties]
The obtained glass sample was further annealed in the vicinity of the glass transition temperature Tg for about 30 minutes to about 2 hours, and then cooled to room temperature at a temperature drop rate of −30 ° C./hour in an oven to obtain an annealed sample. With respect to the obtained annealed sample, refractive indexes nd, ng, nF and nC, Abbe number νd, partial dispersion ratios Pg, F, specific gravity, glass transition temperature Tg, λ70 and λ5 were measured. The results are shown in Tables 1-4.
(I) Refractive index nd, ng, nF, nC and Abbe number νd
About the said annealing sample, refractive index nd, ng, nF, nC was measured by the refractive index measuring method of JIS specification JIS B70771, and Abbe number (nu) d was computed based on the following formula.
νd = (nd−1) / (nF−nC)

(Ii) Partial dispersion ratio Pg, F
The partial dispersion ratios Pg and F were calculated based on the following formula using the refractive indexes ng, nF, and nC for the g-line, F-line, and c-line.
Pg, F = (ng-nF) / (nF-nC)

(Iii) Deviation ΔPg, F ′ of partial dispersion ratios Pg, F
The partial dispersion ratio Pg, F and the Abbe number νd were used to calculate based on the following formula.
ΔPg, F ′ = Pg, F + (0.00286 × νd) −0.68900

(Iv) Specific gravity The specific gravity was measured by the Archimedes method.

(V) Glass transition temperature Tg
The glass transition temperature Tg was measured using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN at a heating rate of 10 ° C./min.

(Vi) λ70, λ5
The annealed sample was processed to have flat surfaces that were 10 mm in thickness and parallel to each other and optically polished, and the spectral transmittance in the wavelength range from 280 nm to 700 nm was measured. Spectral transmittance B / A was calculated by setting the intensity of light incident perpendicularly to one plane polished optically as intensity A and the intensity of light exiting from the other plane as intensity B. The wavelength at which the spectral transmittance becomes 70% was λ70, and the spectral transmittance B / A was calculated. The wavelength at which the spectral transmittance is 5% is λ5. The spectral transmittance includes a reflection loss of light rays on the sample surface.

[Stability during reheating]
The obtained glass sample was cut to obtain a cut piece having a size of 10 mm × 10 mm × 7.5 mm. The cut piece was heated for 5 minutes in a test furnace set to a temperature 200 to 220 ° C. higher than the glass transition temperature Tg of the glass sample. The number of crystals per cut piece was measured with an optical microscope (observation magnification: 40 to 200 times). The presence or absence of crystals was confirmed visually. The case where the number of crystals per cut piece was 100 or less was evaluated as A, the case where the number of crystals per cut piece exceeded 100, B, and the case where crystals were observed by visual inspection were evaluated as C. The results are shown in Tables 1-4.

(Example 2)
Using each optical glass produced in Example 1, a lens blank was produced by a known method, and the lens blank was processed by a known method such as polishing to produce various lenses.
The produced optical lenses are various lenses such as a biconvex lens, a biconcave lens, a planoconvex lens, a planoconcave lens, a concave meniscus lens, and a convex meniscus lens.
Various lenses were able to satisfactorily correct secondary chromatic aberration by combining with lenses made of other types of optical glass.

  In addition, since glass has a low specific gravity, each lens has a smaller weight than a lens having the same optical characteristics and size, and is suitable for various imaging devices, particularly for autofocus imaging devices due to the fact that energy can be saved. is there. Similarly, prisms were produced using the various optical glasses produced in Example 1.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

For example, the optical glass according to one embodiment of the present invention can be manufactured by performing the composition adjustment described in the specification on the glass composition exemplified above.
Of course, it is possible to arbitrarily combine two or more of the matters described as examples or preferred ranges in the specification.

Claims (2)

Abbe number νd is 26.0 or more,
The content of SiO ₂ is more than 0% by mass and less than 40% by mass,
The content of TiO ₂ is 0 to 15% by mass,
The content of Nb ₂ O ₅ is 25 to 45% by mass,
The content of ZrO ₂ exceeds 0% by mass,
The mass ratio of the content of _B 2 _{O 3} to the content of _{SiO 2 [B 2 O 3 /} SiO 2] is at 0.800 or less,
The mass ratio of the total content of SiO ₂ and B ₂ O _{3 to} the total content of Nb ₂ O ₅ and TiO ₂ [(SiO ₂ + B ₂ O ₃ ) / (Nb ₂ O ₅ + TiO ₂ )] is 0.950 or less And
The total content [Li ₂ O + Na ₂ O + K ₂ O] of Li ₂ O, Na ₂ O and K ₂ O is 10 to 25% by mass,
The mass ratio of the content of Na ₂ O to the total content of Li ₂ O, Na ₂ O and K ₂ O [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is 0.330 or more,
The mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of Li ₂ O, Na ₂ O and K ₂ O [(MgO + CaO + SrO + BaO + ZnO) / (Li ₂ O + Na ₂ O + K ₂ O)] is 0. 480 or less,
The mass ratio of the content of TiO ₂ to the content of _{Nb 2 O 5 [TiO 2 /} Nb 2 O 5] is at 0.340 or less,
Mass ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O to the total content of TiO ₂ and Nb ₂ O ₅ [(Li ₂ O + Na ₂ O + K ₂ O) / (TiO ₂ + Nb ₂ O ₅ )] Is 0.700 or less,
_{SiO 2, B 2 O 3,} P 2 O 5, Al 2 O 3, Li 2 O, Na 2 O, K 2 O, MgO, CaO, ZnO, La 2 O 3, Y 2 O 3, Gd 2 O 3 , ZrO ₂ , TiO ₂ and Nb ₂ O _{5 have} a total content of 96.0% by mass or more,
PbO, the content of CdO and _As 2 _{O 3} is 0.01 mass% or less, optical glass.   An optical element comprising the optical glass according to claim 1.