JP2019210157A - Optical glass and optical element - Google Patents

Abstract

To provide an optical glass having a desired optical constant, a specific gravity as small as possible, a small partial dispersion ratio Pg,F and excellent stability when re-heated, and high homogeneity, and an optical element made of the optical glass.SOLUTION: The optical glass has such properties that: a mass ratio [SiO/(NbO+TiO)] of the content of SiOwith respect to the total content of NbOand TiOis greater than 0.80; a mass ratio [SiO/NaO] of the content of SiOwith respect to the content of NaO is 2.5 to 8.5; and a mass ratio [(SiO+BO+PO)/(LiO+NaO+KO)] of the total content of SiO, BOand POwith respect to the total content of LiO, NaO and KO is 1.45 to 4.55.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. Furthermore, the partial dispersion ratios Pg and F are required to be small for correcting 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 is likely to occur during reheating in a silicate-based high refractive index and high dispersibility optical glass. Therefore, a high degree of stability is required such that the inside of the glass is not easily devitrified when the glass is reheated.

  Patent Document 1 discloses an optical glass having a refractive index nd of 1.673 or more and an Abbe number νd of 30.2 or more. However, the optical glass described in Patent Document 1 has low homogeneity, and devitrification during reheating is observed. Furthermore, the conditions of low specific gravity and low Pg, F are not satisfied. Therefore, an optical glass having higher performance while having a desired optical constant is desired.

JP 2017-105702 A

  The present invention provides an optical glass having a desired optical constant, a specific gravity as small as possible, a small partial dispersion ratio Pg, F, excellent stability during reheating and high homogeneity, and the optical glass. It aims at providing the optical element which becomes.

The gist of the present invention is as follows.
(1) The mass ratio of the content of SiO ₂ to the total content of Nb ₂ O ₅ and TiO ₂ [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] is greater than 0.80,
Na ₂ O weight ratio of the content of SiO ₂ to the content of _[SiO 2 / _Na 2 O] is 2.5 to 8.5,
Mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O _{5 to} the total content of Li ₂ O, Na ₂ O and K ₂ O [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / ( _{li 2 O + Na 2 O +} K 2 O)] is 1.45 to 4.55,
The mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] of the Na ₂ O content to the total content of Li ₂ O, Na ₂ O and K ₂ O is 0.45 or more,
The total content of SiO ₂ and _{Nb 2 O 5 [SiO 2 +} Nb 2 O 5] is a 62-84 wt%, the optical glass.

(2) The mass ratio of the content of SiO ₂ to the total content of Nb ₂ O ₅ and TiO ₂ [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] is greater than 0.80,
The mass ratio of the total content of TiO ₂ and Nb ₂ O _{5 to} the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is from 0.7 big,
Mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O _{5 to} the total content of Li ₂ O, Na ₂ O and K ₂ O [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / ( _{li 2 O + Na 2 O +} K 2 O)] is 1.45 to 4.55,
The mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] of the Na ₂ O content to the total content of Li ₂ O, Na ₂ O and K ₂ O is 0.45 or more,
The total content of SiO ₂ and _{Nb 2 O 5 [SiO 2 +} Nb 2 O 5] is a 62-84 wt%, the optical glass.

(3) Abbe number νd is 30 to 36,
Specific gravity is 3.4 or less,
An optical glass having a partial dispersion ratio Pg, F deviation ΔPg, F of 0.0030 or less.

(4) An optical element comprising the optical glass according to any one of (1) to (3) above.

  According to the present invention, an optical glass having a desired optical constant, a specific gravity as small as possible, a small partial dispersion ratio Pg, F, excellent stability during reheating and high homogeneity, and the optical An optical element made of glass 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 a plane with the Abbe number νd on the horizontal axis and the partial dispersion ratios Pg, F on the vertical axis, the normal line is expressed by the following equation.
Pg, F (0) = 0.6483- (0.0018 × νd)
Further, the 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)

  Below, the optical glass of this invention is demonstrated as 1st Embodiment, 2nd Embodiment, and 3rd Embodiment. In addition, the effect | action and effect of each glass component in 2nd, 3rd embodiment are the same as the effect | action and effect of each glass component in 1st Embodiment. Accordingly, in the second and third embodiments, matters overlapping with the description regarding the first embodiment are omitted as appropriate.

First Embodiment The optical glass according to the first embodiment is
The mass ratio of the content of SiO ₂ to the total content of Nb ₂ O ₅ and TiO ₂ [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] is greater than 0.80,
Na ₂ O weight ratio of the content of SiO ₂ to the content of _[SiO 2 / _Na 2 O] is 2.5 to 8.5,
Mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O _{5 to} the total content of Li ₂ O, Na ₂ O and K ₂ O [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / ( _{li 2 O + Na 2 O +} K 2 O)] is 1.45 to 4.55,
The mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] of the Na ₂ O content to the total content of Li ₂ O, Na ₂ O and K ₂ O is 0.45 or more,
The total content [SiO ₂ + Nb ₂ O ₅ ] of SiO ₂ and Nb ₂ O ₅ is 62 to 84%.

In the optical glass according to the first embodiment, the mass ratio [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] of the content of SiO ₂ to the total content of Nb ₂ O ₅ and TiO ₂ is greater than 0.80. The lower limit of the mass ratio [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] is preferably 0.83, and more preferably in the order of 0.85, 0.86, 0.87, and 0.88. The upper limit of the mass ratio [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] is preferably 1.50, and more preferably in the order of 1.40, 1.30, and 1.20. By setting the mass ratio [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] within the above range, crystallization of the glass is suppressed, and an optical glass excellent in homogeneity and stability during reheating is obtained.

In the optical glass according to the first embodiment, the mass ratio of the content of SiO ₂ to the content of _{Na 2 O [SiO 2 / Na} 2 O] is 2.5 to 8.5. The lower limit of the mass ratio [SiO ₂ / Na ₂ O] is preferably 2.6, and more preferably in the order of 2.65, 2.70, and 2.75. Further, the upper limit of the mass ratio [SiO ₂ / Na ₂ O] is more preferably 8.2, and further preferably 8.0, 7.8, and 7.6. By setting the mass ratio [SiO ₂ / Na ₂ O] within the above range, an optical glass excellent in homogeneity and stability during reheating can be obtained.

In the optical glass according to the first embodiment, the mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O _{5 to} the total content of Li ₂ O, Na ₂ O and K ₂ O [(SiO ₂ + B _{2 O 3 + P 2 O 5} ) / (Li 2 O + Na 2 O + K 2 O)] is 1.45 to 4.55. The lower limit of the mass ratio [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / (Li ₂ O + Na ₂ O + K ₂ O)] is preferably 1.70, and further 1.72, 1.74, 1. 76 is more preferred. Further, the upper limit of the mass ratio [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / (Li ₂ O + Na ₂ O + K ₂ O)] is preferably 4.20, and more preferably 4.0, 3.95, 3. Order of 90 is more preferable. By setting the mass ratio [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / (Li ₂ O + Na ₂ O + K ₂ O)] in the above range, crystallization of the glass can be suppressed.

In the optical glass according to the first embodiment, the mass ratio of Na ₂ O content 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 0.45 or more. The lower limit of the mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is preferably 0.46, and more preferably in the order of 0.47, 0.48, and 0.49. The upper limit of the mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is preferably 0.97, and further 0.96, 0.90, 0.85, 0.80, 0 .75, 0.70 in order. Mass ratio _{[Na 2 O / (Li 2} O + Na 2 O + K 2 O)] in the above range, lowering the liquidus temperature, it can improve the thermal stability of the glass. Moreover, crystallization of the glass is suppressed, and an optical glass excellent in homogeneity and stability during reheating can be obtained.

In the optical glass according to the first embodiment, the total content [SiO ₂ + Nb ₂ O ₅ ] of SiO ₂ and Nb ₂ O ₅ is 62 to 84%. The lower limit of the total content [SiO ₂ + Nb ₂ O ₅ ] is preferably 63.0%, and more preferably in the order of 63.5%, 64.0%, and 64.5%. The upper limit of the total content [SiO ₂ + Nb ₂ O ₅ ] is preferably 83%, and more preferably in the order of 82.7%, 82.3%, and 82.1%. The total content _{[SiO 2 + Nb 2 O 5} ] in the above range, lowering the liquidus temperature, can improve the thermal stability of the glass. Moreover, crystallization of glass can be suppressed.

In the optical glass according to the first embodiment, the mass ratio of the total content of TiO ₂ and Nb ₂ O _{5 to} the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably greater than 0.7. The lower limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is more preferably 0.73, and further in the order of 0.75, 0.77, and 0.79. preferable. Further, the upper limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably 1.15, and further in the order of 1.13, 1.11 and 1.09. Is more preferable. By setting the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] in the above range, the liquidus temperature can be lowered and the thermal stability of the glass can be improved.

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

In the optical glass according to the first embodiment, the lower limit of the content of SiO ₂ is preferably 33.0%, and more preferably 33.5%, 34.0%, and 34.5%. The upper limit of the content of SiO ₂ is preferably 44.0%, and more preferably 43.5%, 43.0%, and 42.5%. By setting the content of SiO _{2 in} the above range, the specific gravity of the glass is reduced, and stability improvement during reheating of the glass and a desired optical constant can be obtained.

In the optical glass according to the first embodiment, the upper limit of the content of B ₂ O ₃ is preferably 5.0%, and more preferably in the order of 4.5%, 4.0%, and 3.5%. . Further, the lower limit of the content of B ₂ O ₃ is preferably 0%, and more preferably in the order of 0.1%, 0.2%, and 0.3%. 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 first embodiment, the upper limit of the content of P ₂ O ₅ is preferably 1.5%, and more preferably in the order of 1.4%, 1.3%, and 1.2%. . Further, the lower limit of the content of P ₂ O ₅ is preferably 0%, and more preferably in the order of 0.2%, 0.4%, and 0.6%. The content of P ₂ O ₅ may be 0%. The content of P ₂ O ₅ in the above range, the partial dispersion ratio Pg, the increase in F is suppressed, can hold the thermal stability of the glass.

In the glass according to the first embodiment, the upper limit of the content of Al ₂ O ₃ is preferably 5%, more preferably 4%, 3%, and 2%. 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 first embodiment, the upper limit of the total content [SiO ₂ + B ₂ O ₃ ] of SiO ₂ and B ₂ O ₃ is preferably 48.0%, and further 47.0%, 46 0.0%, 45.0%, and 44.5% are more preferable in this order. Further, the lower limit of the total content [SiO ₂ + B ₂ O ₃ ] is preferably 32.0%, and further 33.0%, 34.0%, 35.0%, 35.5%. Is more preferable. By setting the total content [SiO ₂ + B ₂ O ₃ ] in the above range, the specific gravity of the glass is reduced, the thermal stability of the glass is improved, and a desired optical constant can be obtained.

In the optical glass according to the first embodiment, the upper limit of the total content [SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ] of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ is preferably 48.0%. Furthermore, 47.0%, 46.0%, 45.0%, and 44.5% are more preferable in this order. Further, the lower limit of the content of the total content [SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ] is preferably 33.0%, and further 34.0%, 35.0%, 36.0%, More preferred in the order of 36.5%. By setting the total content [SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ] in the above range, the specific gravity of the glass is reduced, the thermal stability of the glass is improved, and a desired optical constant can be obtained. it can.

In the optical glass according to the first embodiment, the upper limit of the content of TiO ₂ is preferably 10%, and more preferably in the order of 9.5%, 9%, and 8.5%. The lower limit of the content of TiO ₂ is preferably 0%, more preferably 1%, 2%, and 3%. The content of TiO ₂ may be 0%. By setting the content of TiO _{2 in} the above range, a desired optical constant can be realized and the raw material cost of glass can be reduced.

In the optical glass according to the first embodiment, the lower limit of the Nb ₂ O ₅ content is preferably 45%, and more preferably in the order of 44%, 43%, and 42%. Moreover, the upper limit of the content of Nb ₂ O ₅ is preferably 24%, and more preferably in the order of 25%, 26%, and 27%. By setting the content of Nb ₂ O _{5 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 first embodiment, the lower limit of the total content [TiO ₂ + Nb ₂ O ₅ ] of TiO ₂ and Nb ₂ O ₅ is preferably 28%, and further 29%, 30%, and 31%. Is more preferable. The upper limit of the total content [TiO ₂ + Nb ₂ O ₅ ] is preferably 45%, and more preferably in the order of 44%, 43%, and 42%. By setting the total content [TiO ₂ + Nb ₂ O ₅ ] in the above range, a desired optical constant can be realized.

In the glass according to the first embodiment, the upper limit of the content of WO ₃ is preferably 5%, and more preferably 4%, 3%, and 2%. 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 first embodiment, the upper limit of the Bi ₂ O ₃ content is preferably 5%, and more preferably 4%, 3%, and 2%. 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 glass according to the first embodiment, the lower limit of the content of ZrO ₂ is preferably 0%, and more preferably 1%, 2%, and 3%. Moreover, the upper limit of the content of ZrO ₂ is preferably 12.5%, and more preferably in the order of 12.2%, 11.8%, and 11.4%. The content of ZrO ₂ may be 0%. By setting the content of ZrO _{2 in} the above range, a desired optical constant can be realized and the partial dispersion ratios Pg and F can be reduced.

In the glass according to the first embodiment, the upper limit of the content of Li ₂ O is preferably 10%, and more preferably 9%, 8%, and 7%. The lower limit of the content of Li ₂ O is preferably 0%, and more preferably in the order of 1%, 2%, and 3%. The content of Li ₂ O may be 0%. By setting the content of Li ₂ O in the above range, a desired optical constant can be realized, and chemical durability, weather resistance, and stability during reheating can be maintained.

In the glass according to the first embodiment, the upper limit of the content of Na ₂ O is preferably 15%, and more preferably in the order of 14%, 13.5%, and 13%. The lower limit of the Na ₂ O content is preferably 4%, more preferably 4.5%, 5%, and 5.5%. By setting the content of Na ₂ O in the above range, the partial dispersion ratios Pg and F can be reduced.

In the glass according to the first embodiment, the upper limit of the content of K ₂ O is preferably 5%, and more preferably 4.5%, 4%, and 3.5% in this order. The lower limit of the content of K ₂ O is preferably 0%, and more preferably in the order of 0.1%, 0.2%, and 0.3%. The content of K ₂ O may be 0%. By setting the content of K ₂ O in the above range, the thermal stability of the glass can be improved.

In the glass according to the first embodiment, the upper limit of the total content [Li ₂ O + Na ₂ O + K ₂ O] of Li ₂ O, Na ₂ O and K ₂ O is preferably 22%, and further 21%, 20 More preferable in the order of 5% and 20%. The lower limit of the total content is preferably 11%, and more preferably in the order of 11.1%, 11.2%, and 11.3%. By making this total content into the said range, the meltability and thermal stability of glass can be improved, and liquidus temperature can be lowered | hung.

In the glass according to the first embodiment, the upper limit of the content of Cs ₂ O is preferably 5%, and more preferably in the order of 3%, 1%, and 0.5%. The lower limit of the content of Cs ₂ O is preferably 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. Therefore, each content of Cs ₂ O is preferably in the above range.

  In the glass according to the first embodiment, the upper limit of the content of MgO is preferably 10%, and more preferably in the order of 8%, 6%, 4%, and 2%. Further, the lower limit of the content of MgO is preferably 0%. The content of MgO may be 0%.

  In the glass according to the first embodiment, the upper limit of the content of CaO is preferably 10%, and more preferably in the order of 8%, 6%, 4%, and 2%. Moreover, the lower limit of the CaO content is preferably 0%. The content of CaO may be 0%.

  In the glass according to the first embodiment, the upper limit of the SrO content is preferably 10%, and more preferably in the order of 8%, 6%, 4%, and 2%. Moreover, the lower limit of the SrO content is preferably 0%. The SrO content may be 0%.

  In the optical glass according to the first embodiment, the upper limit of the BaO content is preferably 10%, and more preferably in the order of 8%, 6%, 4%, and 2%. The lower limit of the content of BaO is preferably 0%. The content of BaO may be 0%. By setting the content of BaO within the above range, an increase in specific gravity can be suppressed.

  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 glass according to the first embodiment, the upper limit of the total content [MgO + CaO + SrO + BaO] of MgO, CaO, SrO and BaO is preferably 10%, and more preferably in the order of 7%, 6% and 5%. 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 glass according to the first embodiment, the upper limit of the content of ZnO is preferably 10%, and more preferably in the order of 5%, 4%, and 3%. 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 first embodiment, the upper limit of the content of La ₂ O ₃ is preferably 5%, and more preferably 4%, 3%, and 2%. Moreover, the lower limit of the content of La ₂ O ₃ is preferably 0%. 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 glass according to the first embodiment, the upper limit of the content of Y ₂ O ₃ is preferably 5%, more preferably 4%, 3%, and 2%. Moreover, the lower limit of the content of Y ₂ O ₃ is preferably 0%. The content of Y ₂ O ₃ may be 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 glass according to the first embodiment, the upper limit of the content of Ta ₂ O ₅ is preferably 5%, and more preferably 4%, 3%, and 2%. Further, the lower limit of the content of Ta ₂ O ₅ is preferably 0%. The content of Ta ₂ O ₅ may be 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. Therefore, the content of Ta ₂ O ₅ is preferably in the above range.

In the glass according to the first 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 glass according to the first 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 glass according to the first 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 glass according to the first 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 glass according to the first 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. 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 glass according to the first 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. As the specific gravity of the glass increases, the mass of the optical element increases. For example, if a lens with a large mass is incorporated into an autofocus imaging lens, the power required to drive the lens during autofocus increases, and battery consumption becomes severe. 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 glass according to the first embodiment is mainly composed of the glass components described above, that is, SiO ₂ and Na ₂ O as essential components, and B ₂ O ₃ , P ₂ O ₅ , Al ₂ O ₃ , TiO ₂ and Nb ₂ as optional components. _{O 5, WO 3, Bi 2} O 3, ZrO 2, Li 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 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)
In addition to the above components, the optical glass may 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%.

Pb, Cd, As, Th, and the like are components that are concerned about environmental impact. Therefore, the contents of PbO, CdO, and ThO ₂ are each preferably 0 to 0.1%, more preferably 0 to 0.05%, and 0 to 0.01%. Is more preferable, and it is particularly preferable that PbO, CdO, and ThO ₂ are not substantially contained.

The content of As ₂ O ₃ is preferably 0 to 0.1%, more preferably 0 to 0.05%, still more preferably 0 to 0.01%, and As ₂ O It is particularly preferred that ₃ is not substantially contained.

  Furthermore, 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 first embodiment, the refractive index nd is preferably 1.690 to 1.760. The refractive index nd may be 1.695 to 1.755, or 1.700 to 1.750. 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.

<Abbe number νd>
In the optical glass according to the first embodiment, the Abbe number νd is preferably 30 to 36. The Abbe number νd can be 30.5 to 35.8, or 31 to 35.5. 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 , 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.

<Specific gravity of glass>
The specific gravity of the optical glass according to the first embodiment is preferably 3.40 or less, and more preferably 3.35 or less, 3.30 or less, 3.25 or less in this order. The specific gravity is preferably as small as possible, and the lower limit is not particularly limited, but is generally about 3.10. 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.

<Partial dispersion ratio Pg, F>
The upper limit of the partial dispersion ratio Pg, F of the optical glass according to the first embodiment is preferably 0.5980, and more preferably 0.5970, 0.5960, 0.5950, 0.5940. Further, the partial dispersion ratio Pg, F is preferably low, and the lower limit thereof is preferably 0.5780, and can also be 0.5800, 0.5820, 0.5840, 0.5860. 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. The partial dispersion ratios Pg and F can be controlled by adjusting the contents of SiO ₂ , B ₂ O ₃ , TiO ₂ , Nb ₂ O _{5 and the} like.

  Further, the upper limit of the deviation ΔPg, F of the partial dispersion ratios Pg, F of the optical glass according to the first embodiment is preferably 0.0030, and further in the order of 0.0025, 0.0020, 0.0015. preferable. Further, the deviation ΔPg, F is preferably low, and the lower limit thereof is preferably −0.0060, and may be −0.0050, −0.0040, −0.0030, and −0.0020. it can.

<Liquid phase temperature>
The liquidus temperature LT of the optical glass according to the first embodiment is preferably 1200 ° C. or lower, and more preferably in the order of 1190 ° C. or lower, 1180 ° C. or lower, and 1170 ° C. or lower. By setting the liquidus temperature in the above range, the melting and forming temperature of the glass can be lowered, and as a result, the erosion of the glass melting apparatus (for example, crucible, molten glass stirring apparatus, etc.) in the melting process can be reduced. . The lower limit of the liquidus temperature LT is not particularly limited, but is generally about 1000 ° C. The liquidus temperature LT is determined by the balance of the contents of all glass components. Among these, the influence of the content of SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, etc. is large on the liquidus temperature LT.

  The liquidus temperature is determined as follows. 10 cc (10 ml) of glass is put into a platinum crucible and melted at 1250 ° C. to 1400 ° C. for 15 to 30 minutes, then cooled to a glass transition temperature Tg or lower, and the glass is put together with the platinum crucible in a melting furnace at a predetermined temperature and held for 2 hours. To do. The holding temperature is 1000 ° C. or higher, in increments of 5 ° C. or 10 ° C., held for 2 hours, cooled, and the presence of crystals inside the glass is observed with a 100 × optical microscope. The lowest temperature at which no crystals are deposited is defined as the liquidus temperature.

<Glass transition temperature Tg>
The upper limit of the glass transition temperature Tg of the optical glass according to the first embodiment is preferably 670 ° C, and more preferably in the order of 650 ° C, 630 ° C, and 610 ° C. Further, the lower limit of the glass transition temperature Tg is preferably 510 ° C, and more preferably in the order of 520 ° C, 525 ° C, and 530 ° 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.

<Stability during reheating>
In the optical glass according to the first embodiment, the number of crystals observed per 1 g when heated at a glass transition temperature Tg for 10 minutes and further heated at a temperature 140 to 220 ° C. higher than the Tg is preferably Is 20 or less, more preferably 10 or less.

  The stability during reheating is measured as follows. A glass sample having a size of 1 cm × 1 cm × 0.8 cm is heated for 10 minutes in a first test furnace set to the glass transition temperature Tg of the glass sample, and further 140 to 220 ° C. higher than the glass transition temperature Tg. After heating for 10 minutes in the second test furnace set to the temperature, the presence or absence of crystals is confirmed with an optical microscope (observation magnification: 10 to 100 times). Then, the number of crystals per gram is measured. Moreover, the presence or absence of cloudiness of glass is confirmed visually.

(Manufacture of optical glass)
The optical glass according to the first embodiment may be prepared according to a known glass manufacturing method by preparing glass raw materials so as to have the above-mentioned 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 first 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.

Second Embodiment The optical glass according to the second embodiment is
The mass ratio of the content of SiO ₂ to the total content of Nb ₂ O ₅ and TiO ₂ [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] is greater than 0.80,
The mass ratio of the total content of TiO ₂ and Nb ₂ O _{5 to} the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is from 0.7 big,
Mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O _{5 to} the total content of Li ₂ O, Na ₂ O and K ₂ O [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / ( _{li 2 O + Na 2 O +} K 2 O)] is 1.45 to 4.55,
The mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] of the Na ₂ O content to the total content of Li ₂ O, Na ₂ O and K ₂ O is 0.45 or more,
The total content [SiO ₂ + Nb ₂ O ₅ ] of SiO ₂ and Nb ₂ O ₅ is 62 to 84%.

In the optical glass according to the second embodiment, the mass ratio [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] of the content of SiO ₂ to the total content of Nb ₂ O ₅ and TiO ₂ is greater than 0.80. The lower limit of the mass ratio [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] is preferably 0.83, and more preferably in the order of 0.85, 0.86, 0.87, and 0.88. The upper limit of the mass ratio [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] is preferably 1.50, and more preferably in the order of 1.40, 1.30, and 1.20. By setting the mass ratio [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] within the above range, crystallization of the glass is suppressed, and an optical glass excellent in homogeneity and stability during reheating is obtained.

In the optical glass according to the second embodiment, the mass ratio of the total content of TiO ₂ and Nb ₂ O _{5 to} the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is greater than 0.7. The lower limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably 0.73, and more preferably in the order of 0.75, 0.77, and 0.79. . Further, the upper limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably 1.15, and further in the order of 1.13, 1.11 and 1.09. Is more preferable. By setting the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] in the above range, the liquidus temperature can be lowered and the thermal stability of the glass can be improved.

In the optical glass according to the second embodiment, the mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O _{5 to} the total content of Li ₂ O, Na ₂ O and K ₂ O [(SiO ₂ + B _{2 O 3 + P 2 O 5} ) / (Li 2 O + Na 2 O + K 2 O)] is 1.45 to 4.55. The lower limit of the mass ratio [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / (Li ₂ O + Na ₂ O + K ₂ O)] is preferably 1.70, and further 1.72, 1.74, 1. 76 is more preferred. Further, the upper limit of the mass ratio [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / (Li ₂ O + Na ₂ O + K ₂ O)] is preferably 4.2, and more preferably 4.0, 3.95, More preferable in the order of 3.9. By setting the mass ratio [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / (Li ₂ O + Na ₂ O + K ₂ O)] in the above range, crystallization of the glass can be suppressed.

In the optical glass according to the second embodiment, the mass ratio of Na ₂ O content 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 0.45 or more. The lower limit of the mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is preferably 0.46, and more preferably in the order of 0.47, 0.48, and 0.49. The upper limit of the mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is preferably 0.97, and further 0.96, 0.90, 0.85, 0.80, 0 .75, 0.70 in order. Mass ratio _{[Na 2 O / (Li 2} O + Na 2 O + K 2 O)] in the above range, lowering the liquidus temperature, it can improve the thermal stability of the glass. Moreover, crystallization of the glass is suppressed, and an optical glass excellent in homogeneity and stability during reheating can be obtained.

In the optical glass according to the second embodiment, the total content [SiO ₂ + Nb ₂ O ₅ ] of SiO ₂ and Nb ₂ O ₅ is 62 to 84%. The lower limit of the total content [SiO ₂ + Nb ₂ O ₅ ] is preferably 63.0%, and more preferably in the order of 63.5%, 64.0%, and 64.5%. The upper limit of the total content [SiO ₂ + Nb ₂ O ₅ ] is preferably 83%, and more preferably in the order of 82.7%, 82.4%, and 82.1%. The total content _{[SiO 2 + Nb 2 O 5} ] in the above range, lowering the liquidus temperature, can improve the thermal stability of the glass. Moreover, crystallization of glass can be suppressed.

In the optical glass according to the second embodiment, Na ₂ O weight ratio of the content of SiO ₂ to the content of _[SiO 2 / _Na 2 O] is preferably 2.5 to 8.5. The lower limit of the mass ratio [SiO ₂ / Na ₂ O] is more preferably 2.6, and further preferably in the order of 2.65, 2.7, and 2.75. Further, the upper limit of the mass ratio [SiO ₂ / Na ₂ O] is more preferably 8.2, and further preferably 8.0, 7.8, and 7.6. By setting the mass ratio [SiO ₂ / Na ₂ O] within the above range, an optical glass excellent in homogeneity and stability during reheating can be obtained.

  In the optical glass according to the second embodiment, the content and ratio of glass components other than those described above can be the same as those in the first embodiment. Further, the glass characteristics, the production of optical glass, and the production of optical elements and the like in the second embodiment can be the same as those in the first embodiment.

Third Embodiment The optical glass according to the third embodiment is
Abbe number νd is 30-36,
Specific gravity is 3.4 or less,
The deviations ΔPg, F of the partial dispersion ratios Pg, F are 0.0030 or less.

In the optical glass according to the third embodiment, the Abbe number νd is 30 to 36. The Abbe number νd can be 30.5 to 35.8, or 31 to 35.5. 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 , 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 third embodiment, the specific gravity is 3.4 or less. The specific gravity is preferably 3.35 or less, more preferably 3.30 or less and 3.25 or less. The specific gravity is preferably as small as possible, and the lower limit is not particularly limited, but is generally about 3.10.

  In the optical glass according to the third embodiment, the deviations ΔPg, F of the partial dispersion ratios Pg, F are 0.0030 or less. The upper limit of the deviation ΔPg, F is preferably 0.0025, and more preferably in the order of 0.0020 and 0.0015. Further, the deviation ΔPg, F is preferably low, and the lower limit thereof is preferably −0.0060, and may be −0.0050, −0.0040, −0.0030, and −0.0020. it can.

  In general, the partial dispersion ratios Pg and F tend to decrease as the Abbe number νd increases. Therefore, in the third embodiment, the partial dispersion ratios Pg, F are defined using ΔPg, F described above instead of the partial dispersion ratios Pg, F themselves. In the Abbe number νd, for example, ΔPg, F is set to 0.0030 or less when νd≈30, and ΔPg, F is set to 0.0010 or less when νd≈32, which is suitable for high-order chromatic aberration correction. Optical glass can be provided. Furthermore, when the specific gravity is 3.4 or less, more preferably 3.25 or less, the weight of the optical element can be reduced.

  Next, the preferable aspect of content and a ratio of a glass component in the optical glass which concerns on 3rd Embodiment is explained in full detail below.

In the optical glass according to the third embodiment, the mass ratio of the content of SiO ₂ to the total content of Nb ₂ O ₅ and TiO ₂ [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] is preferably 0.80. The lower limit is more preferable in the order of 0.83, 0.85, 0.86, 0.87, and 0.88. The upper limit of the mass ratio [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] is preferably 1.50, and more preferably in the order of 1.40, 1.30, and 1.20. By setting the mass ratio [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] within the above range, crystallization of the glass is suppressed, and an optical glass excellent in homogeneity and stability during reheating is obtained.

In the optical glass according to the third embodiment, Na ₂ O weight ratio of the content of SiO ₂ to the content of _[SiO 2 / _Na 2 O] is preferably 2.5 to 8.5. The lower limit of the mass ratio [SiO ₂ / Na ₂ O] is more preferably 2.6, and further preferably in the order of 2.65, 2.7, and 2.75. Further, the upper limit of the mass ratio [SiO ₂ / Na ₂ O] is more preferably 8.2, and further preferably 8.0, 7.8, and 7.6. By setting the mass ratio [SiO ₂ / Na ₂ O] within the above range, an optical glass excellent in homogeneity and stability during reheating can be obtained.

In the optical glass according to the third embodiment, the mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O _{5 to} the total content of Li ₂ O, Na ₂ O and K ₂ O [(SiO ₂ + B _{2 O 3 + P 2 O 5} ) / (Li 2 O + Na 2 O + K 2 O)] is preferably from 1.45 to 4.55. The lower limit of the mass ratio [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / (Li ₂ O + Na ₂ O + K ₂ O)] is more preferably 1.70, and further 1.72, 1.74, 1 .76 in order. The upper limit of the mass ratio [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / (Li ₂ O + Na ₂ O + K ₂ O)] is more preferably 4.2, and further 4.0 and 3.95. 3.9 is more preferable. By setting the mass ratio [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / (Li ₂ O + Na ₂ O + K ₂ O)] in the above range, crystallization of the glass can be suppressed.

In the optical glass according to the third embodiment, the mass ratio of the Na ₂ O content 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 , Preferably 0.45 or more. The lower limit of the mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is more preferably 0.46, and further preferably in the order of 0.47, 0.48, and 0.49. The upper limit of the mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] is preferably 0.97, and further 0.96, 0.90, 0.85, 0.80, 0 .75, 0.70 in order. Mass ratio _{[Na 2 O / (Li 2} O + Na 2 O + K 2 O)] in the above range, lowering the liquidus temperature, it can improve the thermal stability of the glass. In addition, it is possible to obtain an optical glass that suppresses the crystallization of the glass and is excellent in homogeneity and stability during reheating.

In the optical glass according to the third embodiment, the total content [SiO ₂ + Nb ₂ O ₅ ] of SiO ₂ and Nb ₂ O ₅ is preferably 62 to 84%. The lower limit of the total content [SiO ₂ + Nb ₂ O ₅ ] is more preferably 63.0%, and further preferably in the order of 63.5%, 64.0%, and 64.5%. Further, the upper limit of the total content [SiO ₂ + Nb ₂ O ₅ ] is more preferably 83%, and further preferably in the order of 82.7%, 82.4%, and 82.1%. The total content _{[SiO 2 + Nb 2 O 5} ] in the above range, lowering the liquidus temperature, can improve the thermal stability of the glass. Moreover, crystallization of glass can be suppressed.

In the optical glass according to the third embodiment, the mass ratio of the total content of TiO ₂ and Nb ₂ O _{5 to} the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably greater than 0.7. The lower limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is more preferably 0.73, and further in the order of 0.75, 0.77, and 0.79. preferable. Further, the upper limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is preferably 1.15, and further in the order of 1.13, 1.11 and 1.09. Is more preferable. By setting the mass ratio [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] in the above range, the liquidus temperature can be lowered and the thermal stability of the glass can be improved.

In the optical glass according to the third embodiment, the content and ratio of glass components other than those described above can be the same as those in the first embodiment. Further, the glass characteristics other than those described above in the third embodiment, the production of optical glass, the production of optical elements, and the like can be the same as those in the first embodiment.
In the third embodiment, any one of the configurations of the first or second embodiment may be adopted.

  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 3 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 glass transition temperature Tg ± 10 ° C. 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, deviation ΔPg, F, specific gravity, glass transition temperature Tg, λ80, λ70 and λ5 were measured. The results are shown in Tables 1-4. The glass samples obtained in Comparative Examples A and B were very inhomogeneous with remarkable striae, so that the refractive index nd, Abbe number νd, partial dispersion ratios Pg and F, and deviations ΔPg and F were It was not possible to measure.
(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 + (0.0018 × νd) −0.6483

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

(V) Liquidus temperature LT
The glass was placed in a furnace heated to a predetermined temperature and held for about 2 hours. After cooling, the inside of the glass was observed with an optical microscope of 40 to 100 times, and the liquidus temperature was determined from the presence or absence of crystals.

(Vi) 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.

(Vii) λ80, 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 80% was λ80, and the spectral transmittance B / A was calculated. The wavelength at which the spectral transmittance is 70% is λ70, and 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 is cut into a size of 1 cm × 1 cm × 0.8 cm, heated in the first test furnace set to the glass transition temperature Tg of the glass sample for 10 minutes, and further, the glass transition temperature Tg is exceeded. It heated for 10 minutes in the 2nd test furnace set to 140-220 degreeC high temperature. Thereafter, the presence or absence of crystals was confirmed with an optical microscope (observation magnification: 10 to 100 times). And the number of crystals per gram was measured. The presence or absence of cloudiness of the glass was confirmed visually. "Good" when the number of crystals per gram is 20 or less and no cloudiness is confirmed, "Yes" when the number of crystals per 1g is confirmed to be 21-60, "60", the number of crystals per gram is 60 It was judged as “impossible” when the amount was more than that or when white turbidity or crystals were confirmed visually.

[Evaluation of vitrification]
About the obtained glass sample, the presence or absence of the crystal | crystallization was confirmed visually or with the optical microscope (observation magnification: 40 times), and it was set as "impossible" if there was no crystal | crystallization, if it was not.
Each optical glass of the above examples was optically homogeneous and no striae were observed. On the other hand, the glasses of Comparative Examples A and B produced under the same conditions as in the Examples were very heterogeneous with marked striae. In Comparative Example C, crystals were confirmed visually.

(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 (4)

The mass ratio of the content of SiO ₂ to the total content of Nb ₂ O ₅ and TiO ₂ [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] is greater than 0.80,
Na ₂ O weight ratio of the content of SiO ₂ to the content of _[SiO 2 / _Na 2 O] is 2.5 to 8.5,
Mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O _{5 to} the total content of Li ₂ O, Na ₂ O and K ₂ O [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / ( _{li 2 O + Na 2 O +} K 2 O)] is 1.45 to 4.55,
The mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] of the Na ₂ O content to the total content of Li ₂ O, Na ₂ O and K ₂ O is 0.45 or more,
The total content of SiO ₂ and _{Nb 2 O 5 [SiO 2 +} Nb 2 O 5] is a 62-84 wt%, the optical glass. The mass ratio of the content of SiO ₂ to the total content of Nb ₂ O ₅ and TiO ₂ [SiO ₂ / (Nb ₂ O ₅ + TiO ₂ )] is greater than 0.80,
The mass ratio of the total content of TiO ₂ and Nb ₂ O _{5 to} the total content of SiO ₂ and B ₂ O ₃ [(TiO ₂ + Nb ₂ O ₅ ) / (SiO ₂ + B ₂ O ₃ )] is from 0.7 big,
Mass ratio of the total content of SiO ₂ , B ₂ O ₃ and P ₂ O _{5 to} the total content of Li ₂ O, Na ₂ O and K ₂ O [(SiO ₂ + B ₂ O ₃ + P ₂ O ₅ ) / ( _{li 2 O + Na 2 O +} K 2 O)] is 1.45 to 4.55,
The mass ratio [Na ₂ O / (Li ₂ O + Na ₂ O + K ₂ O)] of the Na ₂ O content to the total content of Li ₂ O, Na ₂ O and K ₂ O is 0.45 or more,
The total content of SiO ₂ and _{Nb 2 O 5 [SiO 2 +} Nb 2 O 5] is a 62-84 wt%, the optical glass. Abbe number νd is 30-36,
Specific gravity is 3.4 or less,
An optical glass having a partial dispersion ratio Pg, F deviation ΔPg, F of 0.0030 or less.   The optical element which consists of optical glass in any one of Claims 1-3.