JP2014214082A - Optical glass, preform and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide optical glass having a refractive index (n) and an Abbe number (ν) within a desired range and capable of improving work environment during manufacturing although preferably used for correction of chromatic aberration, and a lens preform using the same.SOLUTION: The optical glass contains a BOcomponent of 5.0 mass% or more and 35.0 mass% or less, a LaOcomponent of 10.0-60.0 mass% and a F component of more than 0 mass% and 30.0 mass% or less in terms of outer percentage. A mass ratio BO/SiOis 5.000 or less. A lens preform is formed of the optical glass.

Description

  The present invention relates to an optical glass, a preform, and an optical element.

  Optical systems such as digital cameras and video cameras, although large and small, contain blurs called aberrations. This aberration is classified into monochromatic aberration and chromatic aberration. In particular, the chromatic aberration is strongly dependent on the material characteristics of the lens used in the optical system.

  In general, chromatic aberration is corrected by combining a low-dispersion convex lens and a high-dispersion concave lens. However, this combination can only correct aberrations in the red region and the green region, and remains in the blue region. This blue region aberration that cannot be removed is called a secondary spectrum. In order to correct the secondary spectrum, it is necessary to perform an optical design in consideration of the trend of the g-line (435.835 nm) in the blue region. At this time, the partial dispersion ratio (θg, F) is used as an index of the optical characteristics to be noticed in the optical design. In the optical system combining the low dispersion lens and the high dispersion lens, an optical material having a large partial dispersion ratio (θg, F) is used for the low dispersion side lens, and the partial dispersion ratio ( By using an optical material having a small θg, F), the secondary spectrum is corrected well.

The partial dispersion ratio (θg, F) is expressed by the following equation (1).
θg, F = (n _g −n _F ) / (n _F −n _C ) (1)

In optical glass, there is an approximately linear relationship between a partial dispersion ratio (θg, F) representing partial dispersion in a short wavelength region and an Abbe number (ν _d ). The straight line representing this relationship plots the partial dispersion ratio and Abbe number of NSL7 and PBM2 on the Cartesian coordinates employing the partial dispersion ratio (θg, F) on the vertical axis and the Abbe number (ν _d ) on the horizontal axis. It is represented by a straight line connecting two points and is called a normal line (see FIG. 1). Normal glass, which is the standard for normal lines, differs depending on the optical glass manufacturer, but each company defines it with almost the same slope and intercept. (NSL7 and PBM2 are optical glasses manufactured by OHARA, Inc., and the Abbe number (ν _d ) of PBM2 is 36.3, the partial dispersion ratio (θg, F) is 0.5828, and the Abbe number (ν _d ) of NSL7. Is 60.5, and the partial dispersion ratio (θg, F) is 0.5436.)

Here, as a glass having a high refractive index (n _d ) of 1.70 or more and a high Abbe number (ν _d ) of 40 or more and 55 or less, for example, optical glasses as shown in Patent Documents 1 and 2 are used. Are known.

JP 2012-046410 A JP 2013-063888 A

  However, in the conventional optical glass as described in Patent Documents 1 and 2, white smoke is generated due to volatilization of various components including the F component when the glass raw material is melted. This white smoke contains substances harmful to the human body and the environment, and it is necessary to provide a device for detoxifying the exhaust from the melting vessel in the glass raw material melting device. That is, it is desired to develop an optical glass that can improve the working environment at the time of manufacture without providing such an apparatus.

The present invention has been made in view of the above problems, and its object is that the refractive index (n _d ) and the Abbe number (ν _d ) are within the desired ranges, which is preferable for correcting chromatic aberration. It is to obtain an optical glass that can improve the working environment at the time of manufacture while being used, and a preform and an optical element using the optical glass.

In order to solve the above-mentioned problems, the present inventors have conducted intensive test studies, and as a result, the mass ratio B ₂ O _{3 with} respect to the glass that uses the F component in combination with the B ₂ O ₃ component and the La ₂ O ₃ component. By making / SiO ₂ within a predetermined range, it was found that the volatilization of various components including the F component during melting of the glass raw material was reduced, and the present invention was completed.
Specifically, the present invention provides the following.

(1)% by weight _B 2 _{O 3} component 35.0% 5.0% or more of the following, a _La 2 _{O 3} component containing 10.0 to 60.0 percent, the F component in terms of% by mass on the outer split 0 % Optical glass having a mass ratio B ₂ O ₃ / SiO ₂ of 5.000 or less.

(2) The optical glass according to (1), which contains, by mass%, a SiO ₂ component of more than 0% and 30.0% or less.

(3) In mass%,
Y ₂ O ₃ component More than 0% and 30.0% or less WO ₃ component More than 0% and 20.0% or less The optical glass according to (1) or (2).

(4) The optical glass according to any one of (1) to (3), containing, by mass%, an Al ₂ O ₃ component of more than 0% and 15.0% or less.

(5) Ln ₂ O ₃ component (wherein Ln is at least one selected from the group consisting of La, Gd, Y, Yb, and Lu) in terms of mass%, 20.0% or more and 70.0% by mass. % Or less of the optical glass according to any one of (1) to (4).

(6) In mass%,
Gd ₂ O ₃ component 0 to less than 25.0% Yb ₂ O ₃ component 0 to less than 20.0% Lu ₂ O ₃ component 0 to less than 10.0% (1) to (5) Optical glass.

(7) By mass%
SrO component 0 to less than 20.0% ZrO ₂ component 0 to less than 15.0% Optical glass according to any one of (1) to (6).

(8) The optical glass according to any one of (1) to (7), wherein the mass sum (SrO + ZrO ₂ ) is less than 20.0%.

(9) By mass%
TiO ₂ component 0 to less than 15.0% Nb ₂ O ₅ component 0 to less than 20.0% Bi ₂ O ₃ component 0 to less than 10.0% Optical glass according to any one of (1) to (8) .

(10) The optical glass according to any one of (1) to (9), wherein a mass sum (TiO ₂ + Nb ₂ O ₅ + Bi ₂ O ₃ + WO ₃ ) is 1.0% or more and less than 20.0%.

(11) In mass%,
MgO component 0 to less than 10.0% CaO component 0 to less than 20.0% BaO component 0 to less than 25.0% The optical glass according to any one of (1) to (10).

  (12) Any of (1) to (11), wherein the mass sum of the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is less than 30.0% The optical glass described.

(13) The optical glass according to any one of (1) to (12), wherein the Li ₂ O component content is less than 5.0% by mass.

(14) In mass%,
The optical glass according to any one of Na is less than ₂ O component from 0 to 10.0% less than _{K 2} O component from 0 to 10.0% (1) to (13).

(15) Any of (1) to (14), wherein the mass sum of the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is less than 10.0% The optical glass described.

(16) In mass%,
P ₂ O less than ₅ components than 0 to 10.0% less than GeO ₂ component from 0 to 10.0% _Ta 2 _{O 5} component from 0 to 10.0% less than ZnO component 0~25.0% _Ga 2 _{O 3} component 0 Less than 10.0% TeO ₂ component 0 to less than 10.0% SnO ₂ component 0-5.0 less than% less than _Sb 2 _{O 3} component from 0 to 3.0% (1) to (15) or wherein the optical glass.

(17) The optical glass according to any one of (1) to (16), which has a refractive index (n _d ) of 1.70 or more and an Abbe number (ν _d ) of 40 or more and 55 or less.

  (18) The optical glass according to any one of (1) to (17), wherein the specific gravity is 5.00 or less.

  (19) A coordinate system in which the Abbe number (νd) is the x axis and the partial dispersion ratio (θg, F) is the y axis, and (x, y) = (36.3, 0.5828) and (60.5, The optical component according to any one of (1) to (18), wherein the magnitude of deviation in the θg, F direction (anomalous dispersion Δθg, F) from the straight line connecting two points of 0.5436) is −0.0150 or more. Glass.

  (20) A preform comprising the optical glass according to any one of (1) to (19).

  (21) An optical element produced by press-molding the preform according to (20).

  (22) An optical element having the optical glass according to any one of (1) to (19) as a base material.

  (23) An optical apparatus comprising the optical element according to any one of (21) and (22).

According to the present invention, the refractive index (n _d ) and Abbe number (ν _d ) are within the desired ranges, and the optical system capable of improving the working environment at the time of manufacture while being preferably used for correcting chromatic aberration. Glass, a preform using the glass, and an optical element can be obtained.

It is a figure which shows the normal line by which partial dispersion ratio ((theta) g, F) is represented on the orthogonal coordinate of a vertical axis | shaft and Abbe number ((nu) _d ) on a horizontal axis.

The optical glass of the present invention, _B 2 _{O 3} ingredient 35.0% 5.0% inclusive by mass%, a _La 2 _{O 3} component containing 10.0 to 60.0%, of the outer split the F component More than 0% and 30.0% or less by mass%, and the mass ratio B ₂ O ₃ / SiO ₂ is 5.000 or less. By containing the B ₂ O ₃ component and the La ₂ O ₃ component in a predetermined content range, the refractive index of the glass is increased, dispersion is reduced, and transparency to visible light is increased. By setting the mass ratio B ₂ O ₃ / SiO ₂ within a predetermined range, volatilization of various components including the F component when the glass raw material is melted is reduced. Further, B ₂ O ₃ in component and La ₂ O ₃ be used in combination F component to component, also contain a strong La ₂ O ₃ rare earth element component ingredients such as the effect of lowering the partial dispersion ratio, the partial dispersion ratio (Θg, F) is increased. For this reason, an optical glass capable of improving the working environment at the time of manufacture while having a refractive index (n _d ) and an Abbe number (ν _d ) within desired ranges and preferably used for correcting chromatic aberration, A preform and an optical element using the same can be obtained.

  Hereinafter, embodiments of the optical glass of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, although description may be suitably abbreviate | omitted about the location where description overlaps, the meaning of invention is not limited.

[Glass component]
The composition range of each component constituting the optical glass of the present invention is described below. In this specification, unless there is particular notice, content of each component shall be displayed by the mass% with respect to the glass total mass of an oxide conversion composition. Here, the “oxide equivalent composition” is assumed when the oxide, composite salt, metal fluoride, etc. used as a raw material of the glass constituent of the present invention are all decomposed and changed into oxides when melted. It is the composition which described each component contained in glass by making the total mass of the said oxide into 100 mass%.

<About essential and optional components>
The B ₂ O ₃ component is an essential component that makes it difficult to devitrify the glass because it contains 5.0% or more to form a network structure inside the glass. Therefore, the content of the B ₂ O ₃ component is preferably 5.0%, more preferably 10.0%, still more preferably 13.0%, and further preferably 15.0%.
On the other _hand, by making the content of B 2 _{O 3} component below 35.0%, suppressed the decrease in the refractive index. Moreover, generation | occurrence | production of the white smoke originating in F component from a molten glass, etc. can be reduced, and the striae at the time of glass forming can be reduced. Therefore, the content of the B ₂ O ₃ component is preferably 35.0%, more preferably 25.0%, and still more preferably 20.0%.
As the B ₂ O ₃ component, H ₃ BO ₃ , Na ₂ B ₄ O ₇ , Na ₂ B ₄ O ₇ .10H ₂ O, BPO ₄ or the like can be used as a raw material.

By containing 10.0% or more of the La ₂ O ₃ component, it is possible to increase the refractive index of the glass and reduce the dispersion, and to easily obtain a glass having a high visible light transmittance. Accordingly, the content of the La ₂ O ₃ component is preferably 10.0%, more preferably 20.0%, still more preferably 25.0%, still more preferably 30.0%, and even more preferably 36.0%. More preferably, the lower limit is 42.0%.
On the other hand, by making the content of the La ₂ O ₃ component 60.0% or less, the glass can be made hard to devitrify, and an increase in the specific gravity of the glass can be suppressed. Accordingly, the content of the La ₂ O ₃ component is preferably 60.0%, more preferably 55.0%, and still more preferably 50.0%.
As the La ₂ O ₃ component, La ₂ O ₃ , La (NO ₃ ) ₃ .XH ₂ O (X is an arbitrary integer) or the like can be used as a raw material.

The F component is contained in an amount exceeding 0%, so that the partial dispersion ratio of the glass can be increased, the glass transition point can be lowered, the melting temperature of the glass can be lowered, and the visible light transmittance on the short wavelength side can be increased. It is an ingredient. Therefore, the content of the F component in an external ratio with respect to the total mass of the oxide basis is preferably more than 0%, more preferably more than 1.0%, still more preferably more than 2.0%, still more preferably 3.0%. More than%.
On the other hand, when the content of the F component is 30.0% or less, striae during glass molding can be reduced, and white smoke from the molten glass can be reduced. In addition, this can suppress an increase in the specific gravity of the glass and makes it difficult to devitrify the glass. In the optical glass of the present invention, even if the content of the F component is suppressed, a desired partial dispersion ratio can be obtained and the melting temperature can be lowered by adjusting the content of other components. Therefore, the content of the F component on an external basis with respect to the mass based on the oxide is preferably 30.0% or less, more preferably 15.0% or less, still more preferably 7.5% or less, and even more preferably 6. Less than 0%.
As the F component, ZrF ₄ , AlF ₃ , NaF, CaF ₂ , LaF ₃ or the like can be used as a raw material.

  The content of the F component in this specification is based on the assumption that all of the cation components constituting the glass are made of oxides combined with oxygen that balances the charge, and the total mass of the glass made of these oxides is 100. % Represents the mass of the F component in mass% (externally divided mass% with respect to the oxide-based mass).

The ratio (mass ratio) of the B ₂ O ₃ component to the SiO ₂ component is set to 5.000 or less. Thereby, generation | occurrence | production of the white smoke derived from F component etc. from a molten glass can be reduced, and the striae at the time of glass forming can be reduced. Therefore, the mass ratio B ₂ O ₃ / SiO ₂ is preferably 5.000, more preferably 4.800, still more preferably 4.200, still more preferably 3.600, and still more preferably 3.250. .
On the other hand, the mass ratio B ₂ O ₃ / SiO ₂ is preferably more than 0, more preferably 1.000, and still more preferably 1.500, from the viewpoint that a stable glass can be formed even if it contains a large amount of rare earth elements. Also good.

By containing more than 0% of SiO ₂ component, it is possible to promote the formation of stable glass and suppress devitrification (generation of crystal), and to reduce the generation of white smoke originating from F component etc. from molten glass And it is an arbitrary component which can reduce the striae at the time of glass forming. Accordingly, the content of the SiO ₂ component is preferably more than 0%, more preferably 1.0%, still more preferably 2.0%, still more preferably 3.5%, still more preferably 4.5%, even more preferably. May have a lower limit of 5.6%.
On the other hand, by setting the content of the SiO ₂ component to 30.0% or less, the SiO ₂ component can be easily dissolved in the molten glass, and the melting temperature of the glass can be lowered. The content of the SiO ₂ component is preferably 30.0%, more preferably 20.0%, and still more preferably 10.0%.
As the SiO ₂ component, SiO ₂ , K ₂ SiF ₆ , Na ₂ SiF ₆ or the like can be used as a raw material.

B ₂ O ₃ component, the sum of _La 2 _{O 3} component and the content of SiO ₂ component (wt sum) is preferably more than 40.0%. Since the B ₂ O ₃ component and the SiO ₂ component form a network structure inside the glass, it is difficult to devitrify the glass. In addition, the La ₂ O ₃ component can increase the refractive index of the glass. Therefore, by making these mass sums 50.0% or more, the desired high refractive index and Abbe number can be easily obtained by their synergistic effect, visible light transmittance can be increased, and the glass is devitrified. Can be reduced. Therefore, the mass sum (B ₂ O ₃ + La ₂ O ₃ + SiO ₂ ) is preferably 40.0%, more preferably 50.0%, still more preferably 60.0%, and even more preferably 70.0%. And On the other hand, the upper limit of the mass sum (B ₂ O ₃ + La ₂ O ₃ + SiO ₂ ) is preferably 90.0%, more preferably 85.0% in order to reduce devitrification due to excessive inclusion of these components. More preferably, it may be 80.0%.

The ratio (mass ratio) of the content of the B ₂ O ₃ component to the sum of the contents of the B ₂ O ₃ component, the La ₂ O ₃ component, and the SiO ₂ component is preferably 0.50 or less. Thereby, generation | occurrence | production of the white smoke derived from F component from molten glass can be reduced, and the striae at the time of glass forming can be reduced. Therefore, the mass ratio B ₂ O ₃ / (B ₂ O ₃ + La ₂ O ₃ + SiO ₂ ) is preferably 0.50, more preferably 0.40, still more preferably 0.30, and still more preferably 0.27. The upper limit.

The Y ₂ O ₃ component is an optional component that can increase the refractive index and Abbe number, reduce the specific gravity, and reduce the material cost of the glass by containing more than 0%. Therefore, the content of the Y ₂ O ₃ component is preferably more than 0%, more preferably 1.0%, still more preferably 3.0%, still more preferably 6.0%, still more preferably 9.0%, More preferably, 13.0% may be the lower limit.
On the other hand, it is possible to make the glass difficult to devitrify by setting the content of the Y ₂ O ₃ component to 30.0% or less. Therefore, the content of the Y ₂ O ₃ component is preferably 30.0%, more preferably 25.0%, still more preferably 20.0%, and even more preferably 17.0%.
As the Y ₂ O ₃ component, Y ₂ O ₃ , YF ₃ or the like can be used as a raw material.

The WO ₃ component is an optional component that contains more than 0%, thereby increasing the partial dispersion ratio of the glass, increasing the refractive index of the glass, lowering the Abbe number, and increasing the chemical durability of the glass. Moreover, it is a component which reduces the material cost of glass. Therefore, the content of the WO ₃ component is preferably more than 0%, more preferably more than 1.0%, still more preferably 2.3% or more, and even more preferably 5.0% or more.
On the other hand, by making the content of the WO ₃ component 20.0% or less, a desired high Abbe number can be easily obtained, and the light transmittance at a visible short wavelength (500 nm or less) is hardly deteriorated. it can. Therefore, the upper limit of the content of the WO ₃ component is preferably 20.0%, more preferably 15.0%, still more preferably 12.0%, and still more preferably 10.0%.
As the WO ₃ component, WO ₃ or the like can be used as a raw material.

The Al ₂ O ₃ component is an optional component that can easily form a stable glass and can reduce the material cost of the glass by containing more than 0%. Accordingly, the content of the Al ₂ O ₃ component is preferably more than 0%, more preferably 0.5%, still more preferably 1.0%, still more preferably 2.0%, still more preferably 3.0%. It is good also as a minimum.
On the other hand, by making the content of the _Al 2 _{O 3} component below 15.0%, it is possible to suppress the deterioration of the Abbe number of the glass. Accordingly, the upper limit of the content of the Al ₂ O ₃ component is preferably 15.0%, more preferably 10.0%, and still more preferably 8.0%.
As the Al ₂ O ₃ component, Al ₂ O ₃ , Al (OH) ₃ , AlF ₃ or the like can be used as a raw material.

The total content (mass) of the Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) is 20.0% or more and 70.0% The following is preferred.
By making this mass sum 20.0% or more, a desired high refractive index and Abbe number can be easily obtained, the visible light transmittance can be increased, and the photoelastic constant can be reduced. In particular, in the optical glass of the present invention, even if a large amount of rare earth is contained, the partial dispersion ratio does not easily decrease, so that it is easy to achieve both a desired high partial dispersion ratio, a high refractive index, and an Abbe number. Therefore, the total content of the Ln ₂ O ₃ components is preferably 20.0%, more preferably 30.0%, still more preferably 42.0%, and even more preferably 50.0%.
On the other hand, devitrification at the time of producing glass can be reduced by making this mass sum 70.0% or less. Therefore, the total content of the Ln ₂ O ₃ components is preferably 70.0%, more preferably 67.0%, and still more preferably 65.0%.

The ratio (mass ratio) of the content of the Y ₂ O ₃ component to the total content of the Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) ) Is preferably 0.40 or less. Thus, also contain a large amount of Ln ₂ O ₃ component, while reducing the devitrification of making the glass, can easily obtain desired high refractive index and Abbe number, and enhanced visible light transmittance. Therefore, the mass ratio Y ₂ O ₃ / Ln ₂ O ₃ is preferably 0.40, more preferably 0.30, and still more preferably 0.25.

The Gd ₂ O ₃ component is an optional component that can increase the refractive index and Abbe number of the glass by containing more than 0%.
On the other hand, by making the content of the Gd ₂ O ₃ component less than 25.0%, it is possible to suppress an increase in the specific gravity of the glass and a decrease in the partial dispersion ratio, and it is difficult to devitrify the glass. Moreover, this can reduce the material cost of glass. Therefore, the content of the Gd ₂ O ₃ component is preferably less than 25.0%, more preferably less than 18.0%, still more preferably less than 10.0%, and even more preferably less than 4.0%.
As the Gd ₂ O ₃ component, Gd ₂ O ₃ , GdF ₃ or the like can be used as a raw material.

The Yb ₂ O ₃ component and the Lu ₂ O ₃ component are optional components that can increase the refractive index and the Abbe number of the glass by containing more than 0%.
On the other hand, it is possible to make the glass difficult to devitrify by setting the content of the Yb ₂ O ₃ component to less than 20.0% or the content of the Lu ₂ O ₃ component to less than 10.0%. In particular, by reducing the content of the Yb ₂ O ₃ component, it becomes difficult for absorption to occur on the long wavelength side of the glass (near the wavelength of 1000 nm). Therefore, the content of the Yb ₂ O ₃ component is preferably less than 20.0%, more preferably less than 10.0%, still more preferably less than 8.0%, and even more preferably less than 5.0%. Further, the content of the Lu ₂ O ₃ component is preferably less than 10.0%, more preferably less than 8.0%, and still more preferably less than 5.0%.
For the Yb ₂ O ₃ component and the Lu ₂ O ₃ component, Yb ₂ O ₃ , Lu ₂ O ₃ or the like can be used as a raw material.

The SrO component is an optional component that improves the meltability of the glass and enhances the devitrification resistance by containing more than 0%.
On the other hand, by making the content of the SrO component less than 20.0%, it is possible to suppress a reduction in the partial dispersion ratio of the glass, to make it difficult to lower the refractive index, and to reduce the devitrification of the glass. Therefore, the content of the SrO component is preferably less than 20.0%, more preferably less than 10.0%, still more preferably less than 8.0%, and even more preferably less than 5.0%.
As the SrO component, Sr (NO ₃ ) ₂ , SrF ₂ or the like can be used as a raw material.

The ZrO ₂ component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance by containing more than 0%.
On the other hand, by making the content of the ZrO ₂ component less than 15.0%, a decrease in the partial dispersion ratio of the glass can be suppressed. Moreover, this suppresses a decrease in the Abbe number of the glass and suppresses an increase in the melting temperature of the glass. Therefore, the content of the ZrO ₂ component is preferably less than 15.0%, more preferably less than 10.0%, even more preferably less than 8.0%, still more preferably 5.0% or less, and even more preferably 2. 5% or less, more preferably less than 2.0%.
As the ZrO ₂ component, ZrO ₂ , ZrF ₄ or the like can be used as a raw material.

The total content (mass sum) of the SrO component and the ZrO ₂ component is preferably less than 20.0%. Thereby, the fall of a partial dispersion ratio can be suppressed. Therefore, the mass sum (SrO + ZrO ₂ ) is preferably less than 20.0%, more preferably less than 10.0%, still more preferably 8.0% or less, still more preferably 5.0% or less, and even more preferably 3. 0% or less.

The TiO ₂ component is an optional component that can contain more than 0% to increase the partial dispersion ratio and refractive index of the glass, adjust the Abbe number low, and reduce the specific gravity of the glass.
On the other hand, by making the content of the TiO ₂ component less than 15.0%, a desired high Abbe number can be easily obtained, and the light transmittance at a visible short wavelength (500 nm or less) can be made difficult to deteriorate. it can. Accordingly, the content of the TiO ₂ component is preferably less than 15.0%, more preferably less than 10.0%, even more preferably less than 8.0%, still more preferably less than 5.0%, and even more preferably 2. Less than 0%.
As the TiO ₂ component, TiO ₂ or the like can be used as a raw material.

The Nb ₂ O ₅ component is an optional component that, by containing more than 0%, can increase the partial dispersion ratio and refractive index of the glass, adjust the Abbe number low, and reduce the specific gravity of the glass.
On the other hand, by making the content of the Nb ₂ O ₅ component less than 20.0%, a desired high Abbe number can be easily obtained. Accordingly, the content of the Nb ₂ O ₅ component is preferably less than 20.0%, more preferably less than 10.0%, even more preferably less than 8.0%, even more preferably less than 5.0%, and still more preferably. Less than 2.0%.
As the Nb ₂ O ₅ component, Nb ₂ O ₅ or the like can be used as a raw material.

The Bi ₂ O ₃ component is an optional component that can contain more than 0% to increase the partial dispersion ratio and refractive index of the glass, adjust the Abbe number to a low level, and reduce the specific gravity of the glass.
On the other hand, by the content of _Bi 2 _{O 3} component to less than 10.0%, it is difficult to deteriorate the light transmittance of the visible short wavelength (500 nm or less). Therefore, the content of the Bi ₂ O ₃ component is preferably less than 10.0%, more preferably less than 8.0%, and even more preferably less than 5.0%.
As the Bi ₂ O ₃ component, Bi ₂ O ₃ or the like can be used as a raw material.

The sum (mass sum) of the contents of TiO ₂ component, Nb ₂ O ₅ component, Bi ₂ O ₃ component and WO ₃ is preferably 1.0% or more. Thereby, the partial dispersion ratio and refractive index of the glass can be increased, the Abbe number can be adjusted low, and the specific gravity of the glass can be reduced. Accordingly, the mass sum (TiO ₂ + Nb ₂ O ₅ + Bi ₂ O ₃ + WO ₃ ) is preferably 1.0%, more preferably 3.0%, still more preferably 5.0%, and even more preferably 6.0%. Is the lower limit.
On the other hand, devitrification of the glass due to excessive inclusion of these components can be suppressed by making the sum of these contents less than 20.0%. Accordingly, the mass sum (TiO ₂ + Nb ₂ O ₅ + Bi ₂ O ₃ + WO ₃ ) is preferably less than 20.0%, more preferably less than 10.0%, even more preferably less than 8.0%, and even more preferably 5 Less than 0%.

The MgO component, CaO component and BaO component are optional components that contain more than 0%, thereby improving the meltability of the glass and increasing the devitrification resistance.
On the other hand, the refractive index of the glass is lowered by making the content of the MgO component less than 10.0%, the content of the CaO component less than 20.0%, or the content of the BaO component less than 25.0%. It is possible to reduce the devitrification of the glass.
The content of the MgO component is preferably less than 10.0%, more preferably less than 8.0%, and still more preferably less than 5.0%.
The content of the CaO component is preferably less than 20.0%, more preferably less than 10.0%, still more preferably less than 8.0%, and even more preferably less than 5.0%.
The content of the BaO component is preferably less than 25.0%, more preferably less than 15.0%, more preferably less than 10.0%, still more preferably less than 8.0%, and even more preferably 5.0. %.
MgO 3, CaO component, SrO component and BaO component use MgCO ₃ , MgF ₂ , CaCO ₃ , CaF ₂ , Sr (NO ₃ ) ₂ , SrF ₂ , BaCO ₃ , Ba (NO ₃ ) _{2 and the} like as raw materials. Can do.

  The total content (mass sum) of RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is preferably less than 30.0%. Thereby, the devitrification of the glass due to excessive inclusion of the RO component can be reduced, and the refractive index of the glass can be hardly lowered. Therefore, the total content of RO components is preferably less than 30.0%, more preferably less than 20.0%, even more preferably less than 10.0%, still more preferably less than 8.0%, and even more preferably 5. Less than 0%.

Li 2 _O component, by ultra containing 0%, which is an optional component for improving the meltability of the glass.
On the other hand, by setting the content of the Li ₂ O component to less than 5.0%, it is possible to reduce devitrification and the like due to excessive inclusion of the Li ₂ O component while suppressing a decrease in the partial dispersion ratio and refractive index of the glass. . Therefore, the content of the Li ₂ O component is preferably less than 5.0%, more preferably less than 3.0%, further preferably less than 1.0%, and further preferably less than 0.5%. In particular, from the viewpoint of obtaining an optical glass having a high partial dispersion ratio, the Li ₂ O component may not be substantially contained.
For the Li ₂ O component, Li ₂ CO ₃ , LiNO ₃ , LiF, or the like can be used as a raw material.

Na 2 _O component, by ultra containing 0%, which is an optional component that can improve the meltability of the glass.
On the other hand, by making the content of the Na ₂ O component less than 10.0%, the refractive index of the glass is hardly lowered, the stability of the glass is increased, and devitrification and the like are hardly caused. Therefore, the content of the Na ₂ O component is preferably less than 10.0%, more preferably less than 8.0%, and still more preferably less than 5.0%.
As the Na ₂ O component, Na ₂ CO ₃ , NaNO ₃ , NaF, Na ₂ SiF ₆ or the like can be used as a raw material.

The K ₂ O component is an optional component that can further increase the partial dispersion ratio of the glass and improve the meltability of the glass by containing more than 0%.
On the other hand, by making the content of the K ₂ O component less than 10.0%, it is difficult to lower the refractive index of the glass, and it is possible to reduce the devitrification of the glass. Therefore, the content of the K ₂ O component is preferably less than 10.0%, more preferably less than 8.0%, and even more preferably less than 5.0%.
As the K ₂ O component, K ₂ CO ₃ , KNO ₃ , KF, KHF ₂ , K ₂ SiF ₆ or the like can be used as a raw material.

The total content (mass sum) of the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is less than 10.0%, whereby the refractive index of the glass Can be made difficult to decrease, and devitrification of the glass can be reduced. Therefore, the total content of the Rn ₂ O component is preferably less than 10.0%, more preferably less than 8.0%, and even more preferably less than 5.0%.

The P ₂ O ₅ component is an optional component that can contain more than 0% to lower the liquidus temperature of the glass and improve the devitrification resistance.
On the other hand, when the content of P ₂ O ₅ component to less than 10.0%, the chemical durability of the glass, in particular suppressing a decrease in water resistance. Therefore, the content of the P ₂ O ₅ component is preferably less than 10.0%, more preferably less than 8.0%, and still more preferably less than 5.0%.
As the P ₂ O ₅ component, Al (PO ₃ ) ₃ , Ca (PO ₃ ) ₂ , Ba (PO ₃ ) ₂ , BPO ₄ , H ₃ PO ₄ or the like can be used as a raw material.

The GeO ₂ component is an optional component having an effect of increasing the refractive index of glass and improving devitrification resistance by containing more than 0%.
However, since the raw material price of the GeO ₂ component is high, the material cost increases when the amount of the GeO ₂ component is large, and thus the obtained glass becomes impractical. Therefore, the content of the GeO ₂ component is preferably less than 10.0%, more preferably less than 8.0%, still more preferably less than 5.0%, and even more preferably less than 3.0%.
As the GeO ₂ component, GeO ₂ or the like can be used as a raw material.

The Ta ₂ O ₅ component is an optional component that can stabilize the glass while increasing the refractive index of the glass by containing more than 0%.
On the other hand, by making the content of the Ta ₂ O ₅ component less than 10.0%, a decrease in the partial dispersion ratio of the glass can be suppressed. In addition, this can reduce the material cost of the glass, and can avoid melting at high temperature to suppress an increase in production cost due to energy loss during glass production. Therefore, the content of the Ta ₂ O ₅ component is preferably less than 10.0%, more preferably less than 8.0%, even more preferably less than 5.0%, and even more preferably less than 3.0%.
As the Ta ₂ O ₅ component, Ta ₂ O ₅ or the like can be used as a raw material.

By containing more than 0%, the ZnO component is an optional component that improves the meltability of the glass, lowers the glass transition point, and facilitates the formation of a stable glass.
On the other hand, by making the content of the ZnO component less than 25.0%, a decrease in the refractive index and partial dispersion ratio of the glass can be suppressed. In addition, since the photoelastic constant of the optical glass is kept low, the polarization characteristics of the transmitted light of the optical glass can be improved, and as a result, the color rendering properties of the projector and camera can be improved. Accordingly, the content of the ZnO component is preferably less than 25.0%, more preferably less than 15.0%, further preferably less than 8.0%, more preferably less than 5.0%, and still more preferably 3.0. %.
As the ZnO component, ZnO, ZnF ₂ or the like can be used as a raw material.

The Ga ₂ O ₃ component is an optional component that can easily form a stable glass by containing more than 0%.
On the other hand, by making the content of _Ga 2 _{O 3} component to less than 10.0%, it is possible to suppress the deterioration of the Abbe number of the glass. Therefore, the content of the Ga ₂ O ₃ component is preferably less than 10.0%, more preferably less than 8.0%, still more preferably less than 5.0%, and even more preferably less than 3.0%.
For the Ga ₂ O ₃ component, Ga ₂ O ₃ , Ga (OH) ₃ or the like can be used as a raw material.

The TeO ₂ component is an optional component that can increase the refractive index and lower the glass transition point by containing more than 0%.
On the other hand, TeO ₂ has a problem that it can be alloyed with platinum when melting a glass raw material in a crucible made of platinum or a melting tank in which a portion in contact with molten glass is formed of platinum. Accordingly, the TeO ₂ content is preferably less than 10.0%, more preferably less than 8.0%, even more preferably less than 5.0%, and even more preferably less than 3.0%.
TeO ₂ component can use TeO ₂ or the like as a raw material.

The SnO ₂ component is an optional component that, when contained in excess of 0%, can clarify the molten glass by reducing the oxidation of the molten glass and can hardly deteriorate the visible light transmittance of the glass.
On the other hand, when the content of the SnO ₂ component is less than 5.0%, the coloring of the glass due to the reduction of the molten glass and the devitrification of the glass can be hardly caused. Further, since the alloying of the SnO ₂ component and the melting equipment (especially a noble metal such as Pt) is reduced, the life of the melting equipment can be extended. Therefore, the content of the SnO ₂ component is preferably less than 5.0%, more preferably less than 3.0%, and even more preferably less than 1.0%.
For the SnO ₂ component, SnO, SnO ₂ , SnF ₂ , SnF ₄ or the like can be used as a raw material.

The Sb ₂ O ₃ component is an optional component that can degas the molten glass by containing more than 0%.
On the other hand, by making the content of the Sb ₂ O ₃ component less than 3.0%, excessive foaming at the time of glass melting can be suppressed, and the Sb ₂ O ₃ component and the melting equipment (especially noble metals such as Pt) Alloying can be suppressed. Therefore, the content of the Sb ₂ O ₃ component is preferably less than 3.0%, more preferably less than 2.0%, and even more preferably less than 1.0%.
As the Sb ₂ O ₃ component, Sb ₂ O ₃ , Sb ₂ O ₅ , Na ₂ H ₂ Sb ₂ O ₇ .5H ₂ O, or the like can be used as a raw material.

Incidentally, components defoamed fining glass is not limited to the above Sb ₂ O ₃ component, a known refining agents in the field of glass production, it is possible to use a defoamer or a combination thereof.

<About ingredients that should not be included>
Next, components that should not be contained in the optical glass of the present invention and components that are not preferably contained will be described.

If necessary, other components can be added to the optical glass of the present invention as long as the properties of the glass of the present invention are not impaired. However, it is preferable that the GeO ₂ component is not substantially contained since it increases the dispersibility of the glass.

  Moreover, each transition metal component such as Hf, V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, Even when a small amount is contained alone or in combination, the glass is colored and has the property of absorbing light of a specific wavelength in the visible range. It is preferable not to include.

Furthermore, lead compounds such as PbO, arsenic compounds such as As ₂ O ₃ , and components of Th, Cd, Tl, Os, Be, and Se have tended to refrain from being used as harmful chemical substances in recent years. Environmental measures are required not only in the manufacturing process but also in the processing process and disposal after commercialization. Therefore, when importance is placed on the environmental impact, it is preferable not to substantially contain them except for inevitable mixing. As a result, the optical glass is substantially free of substances that pollute the environment. Therefore, the optical glass can be manufactured, processed, and discarded without taking any special environmental measures.

The glass composition of the present invention cannot be expressed directly in the description of mol% because the composition is expressed by mass% with respect to the total mass of the glass of oxide conversion composition, but various properties required in the present invention. The composition expressed by mol% of each component present in the glass composition satisfying the above conditions generally takes the following values in terms of oxide conversion.
B ₂ O ₃ component from 10.0 to 50.0 mol%,
La ₂ O ₃ component from 10.0 to 25.0 mol%
And SiO ₂ component 0 to 50.0 mol%
Y ₂ O ₃ component from 0 to 25.0 mol%
WO ₃ components 0 to 15.0 mol%
Al ₂ O ₃ component 0 to 25.0 mol%
Gd ₂ O ₃ component 0 to 15.0 mol%
Yb ₂ O ₃ component 0 to 10.0 mol%
Lu ₂ O ₃ component 0-5.0 mol%
SrO component 0 to 30.0 mol%
ZrO ₂ component 0 to 15.0 mol%
TiO ₂ component 0 to 30.0 mol%
Nb ₂ O ₅ component 0 to 10.0 mol%
Bi ₂ O ₃ component 0-4.0 mol%
MgO component 0-35.0 mol%
CaO component 0-40.0 mol%
BaO component 0 to 25.0 mol%
Li ₂ O component 0 to 15.0 mol%
Na ₂ O component from 0 to 25.0 mol%
K ₂ O component from 0 to 15.0 mol%
P ₂ O ₅ component 0 to 10.0 mol%
GeO ₂ component 0 to 20.0 mol%
Ta ₂ O ₅ component 0-4.0 mol%
ZnO component 0 to 25.0 mol%
Ga ₂ O ₃ component from 0 to 8.0 mol%
TeO ₂ component 0-8.0 mol%
SnO ₂ component 0-5.0 mol%
Sb ₂ O ₃ component to 2.0 mole%
In addition, the total amount as F of the fluoride substituted with one or more oxides of one or more of the above metal elements as more than 0 mol% to 75.0 mol%

[Production method]
The optical glass of the present invention is produced, for example, as follows. That is, the above raw materials are uniformly mixed so that each component is within a predetermined content range, and the prepared mixture is put into a platinum crucible, a quartz crucible or an alumina crucible and roughly melted, then a gold crucible, a platinum crucible In a platinum alloy crucible or iridium crucible, melt in a temperature range of 900 to 1400 ° C. for 1 to 5 hours, stir to homogenize, blow out bubbles, etc., then lower the temperature to 1200 ° C. or lower and then stir to finish This is produced by removing the striae and molding using a mold. Here, as means for obtaining glass molded using a mold, means for drawing molten glass from the other end of the mold at the same time as flowing the molten glass to one end of the mold, or molten glass There is a means of slowly cooling by casting into a mold.

[Physical properties]
The optical glass of the present invention preferably has a high refractive index and low dispersion (high Abbe number).
More specifically, the refractive index (n _d ) of the optical glass of the present invention is preferably 1.70, more preferably 1.72, and still more preferably 1.74. On the other hand, the refractive index (n _d ) of the optical glass of the present invention is preferably 1.90, more preferably 1.85, and even more preferably 1.80.
Further, the Abbe number (ν _d ) of the optical glass of the present invention is preferably 40, more preferably 42, and still more preferably 45. On the other hand, the Abbe number (ν _d ) of the optical glass of the present invention is preferably 55, more preferably 52, and even more preferably 50.
As a result, the degree of freedom in optical design is increased, and a large amount of light refraction can be obtained even if the device is made thinner.

The optical glass of the present invention preferably has a small specific gravity.
More specifically, the specific gravity of the optical glass of the present invention is 5.00 [g / cm ³ ] or less. Thereby, since the mass of an optical element and an optical apparatus using the same is reduced, it can contribute to the weight reduction of an optical apparatus. Accordingly, the specific gravity of the optical glass of the present invention is preferably 5.00, more preferably 4.80, and preferably 4.70. The specific gravity of the optical glass of the present invention is generally about 3.00 or more, more specifically 3.50 or more, and more specifically 4.00 or more in many cases.

  The specific gravity of the optical glass can be measured based on Japan Optical Glass Industry Association Standard JOGIS05-1975 “Measurement Method of Specific Gravity of Optical Glass”.

The optical glass of the present invention has a high partial dispersion ratio (θg, F).
More specifically, the optical glass of the present invention is a coordinate system in which the Abbe number (νd) is the x axis and the partial dispersion ratio (θg, F) is the y axis, and (x, y) = (36.3, 0.5828) and (60.5, 0.5436) from the straight line connecting the two points θg, the magnitude of deviation in the F direction (anomalous dispersion Δθg, F) is −0.0150 or more, , −0.0150 or a larger value in the positive direction is preferable. As a result, the relationship between the typical Abbe number and the partial dispersion ratio of the conventionally known glass was expressed by two points (x, y) = (36.3, 0.5828) and (60.5, 0.5436). An optical glass having a higher partial dispersion ratio (θg, F) is obtained with respect to a straight line connecting the two, that is, a normal line. Therefore, chromatic aberration of an optical element formed from the optical glass can be reduced while achieving high refractive index and low dispersion of the glass. Here, the lower limit of the anomalous dispersion (Δθg, F) of the optical glass is preferably −0.0150 or more, more preferably −0.0140 or more, and further preferably −0.0130 or more.

  The partial dispersion ratio (θg, F) of the optical glass is measured based on Japan Optical Glass Industry Association Standard JOGIS01-2003. In addition, the glass used for this measurement uses what was processed in the slow cooling furnace by making slow cooling temperature-fall rate into -25 degrees C / hr.

The optical glass of the present invention is preferably less colored.
In particular, when the optical glass of the present invention is represented by the transmittance of the glass, the wavelength (λ ₇₀ ) showing a spectral transmittance of 80% in a sample having a thickness of 10 mm is 450 nm or less, more preferably 420 nm or less, and still more preferably. Is 400 nm or less. In the optical glass of the present invention, a wavelength (λ ₅ ) showing a spectral transmittance of 5% in a sample having a thickness of 10 mm is 400 nm or less, more preferably 380 nm or less, and further preferably 360 nm or less. Thereby, the absorption edge of the glass is positioned in the vicinity of the ultraviolet region, and the transparency of the glass in the visible region is enhanced. Therefore, this optical glass can be used as a material for an optical element such as a lens.

The transmittance of the optical glass is measured according to Japan Optical Glass Industry Association Standard JOGIS02. Specifically, a face parallel polished product having a thickness of 10 ± 0.1 mm was measured for a spectral transmittance of 200 to 800 nm in accordance with JISZ8722, and λ ₇₀ (wavelength at 70% transmittance) and λ ₅ (transmittance). Wavelength at 5%).

  The optical glass of the present invention preferably has high devitrification resistance during glass production (in the specification, it may be simply referred to as “devitrification resistance”). Thereby, since the fall of the transmittance | permeability by crystallization of the glass at the time of glass preparation etc. is suppressed, this optical glass can be used preferably for the optical element which permeate | transmits visible lights, such as a lens.

[Preforms and optical elements]
A glass molded body can be produced from the produced optical glass by means of mold press molding such as reheat press molding or precision press molding. That is, a preform for mold press molding is prepared from optical glass, and after performing reheat press molding on the preform, polishing is performed to prepare a glass molded body, or for example, polishing is performed. The preform can be precision press-molded to produce a glass molded body. In addition, the means for producing the glass molded body is not limited to these means.

  The glass molded body thus produced is useful for various optical elements, and among them, it is particularly preferable to use it for applications of optical elements such as lenses and prisms. As a result, color bleeding due to chromatic aberration in the transmitted light of the optical system provided with the optical element is reduced. Therefore, when this optical element is used in a camera, a photographing object can be expressed more accurately, and when this optical element is used in a projector, a desired image can be projected with higher definition.

Composition of Examples (No. 1 to No. 22) and Comparative Example (No. A) of the present invention, refractive index (n _d ) and Abbe number (ν _d ), partial dispersion ratio (θg) of these glasses , F), anomalous dispersion (Δθg, F), wavelengths (λ ₇₀ , λ ₅ ) at which the spectral transmittances are 70% and 5%, and specific gravity values are shown in Tables 1 to 3. The following examples are merely for illustrative purposes, and are not limited to these examples.

  The glasses of Examples and Comparative Examples are used as ordinary optical glasses such as oxides, hydroxides, carbonates, nitrates, fluorides, hydroxides, metaphosphate compounds, etc., as raw materials for the respective components. High-purity raw materials are selected, weighed so as to have the composition ratios of the examples and comparative examples shown in the table, mixed uniformly, and then put into a platinum crucible, depending on the melting difficulty of the glass composition. After melting for 1 to 6 hours in a temperature range of 1000 to 1400 ° C. in an electric furnace, stirring and homogenizing to remove bubbles, etc., lowering the temperature to 1200 ° C. or lower and stirring and homogenizing, then casting into a mold and slow cooling It was produced by doing.

The refractive index of the glass of the Examples and Comparative Examples _(n d), Abbe number ([nu _d) and partial dispersion ratio ([theta] g, F) were measured according to Japan Optical Glass Industry Society Standard JOGIS01-2003. The obtained Abbe number (ν _d ) and partial dispersion ratio (θg, F) values are expressed in a coordinate system with the Abbe number (νd) as the x axis and the partial dispersion ratio (θg, F) as the y axis. (X, y) = (36.3, 0.5828) and (60.5, 0.5436) from the straight line connecting the two points θg, magnitude of deviation in the F direction (anomalous dispersion Δθg, F) Asked. In addition, the glass used for this measurement used what was processed in the slow cooling furnace by making slow cooling temperature-fall rate into -25 degrees C / hr.

Visible light transmittances of the glasses of Examples and Comparative Examples were measured according to Japan Optical Glass Industry Association Standard JOGIS02. In addition, in this invention, the presence or absence and the grade of coloring of glass were calculated | required by measuring the visible light transmittance | permeability of glass. More specifically, a face parallel polished product having a thickness of 10 ± 0.1 mm is measured for a spectral transmittance of 200 to 800 nm in accordance with JISZ8722, and λ ₅ (wavelength when the transmittance is 5%) and λ ₇₀ (transmittance). Wavelength at 70%).

  The specific gravity of the glass of an Example and a comparative example was measured based on Japan Optical Glass Industry Association standard JOGIS05-1975 "measurement method of specific gravity of optical glass".

In each of the examples (No. 1 to No. 22), white smoke was little generated when the glass raw material was melted. On the other hand, in the comparative example (No. A), a large amount of white smoke was generated. The reason for the difference in the amount of white smoke generated is presumed to be that the mass ratio B ₂ O ₃ / SiO _{2 of} Examples (No. 1 to No. 22) was 5.000 or less. The Therefore, in the optical glass of the example of the present invention, the volatilization of each component including the F component at the time of melting is higher than that of the comparative glass having a mass ratio B ₂ O ₃ / SiO ₂ larger than 5.000. It became clear that there were few.

Further, the optical glass of the example had an anomalous dispersibility (Δθg, F) of −0.0150 or more, more specifically −0.0120 or more. Therefore, the optical glass of the example of the present invention has a large partial dispersion ratio (θg, F) in the relational expression with the Abbe number (ν _d ), and it has been clarified that the chromatic aberration when the optical element is formed can be reduced. .

The optical glasses of the examples all have a refractive index (n _d ) of 1.70 or more, more specifically 1.75 or more, and the refractive index (n _d ) of 1.90 or less, more details. Was 1.78 or less, which was within the desired range.
The optical glasses of the examples all have an Abbe number (ν _d ) of 40 or more, more specifically 47 or more, and this Abbe number (ν _d ) is 55 or less, more specifically 49 or less. Yes and within the desired range.

  In addition, the optical glasses of the examples all had a specific gravity of 5.00 or less, more specifically 4.70 or less, and more specifically 4.61 or less, and were within a desired range.

Therefore, the optical glass of the example has a refractive index (n _d ) and an Abbe number (ν _d ) within desired ranges, anomalous dispersion is large in the positive direction, a specific gravity is small, and a working environment at the time of manufacture. It became clear that it was possible to improve.

  Furthermore, using the optical glass obtained in the example, after performing reheat press molding, grinding and polishing were performed to process into the shape of a lens and a prism. Further, a precision press molding preform was formed using the optical glass of the example of the present invention, and this precision press molding preform was precision press molded. In either case, the glass after heat softening did not cause problems such as opacification and devitrification, and could be stably processed into various lens and prism shapes.

  Although the present invention has been described in detail for the purpose of illustration, this embodiment is only for the purpose of illustration, and many modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention. Will be understood.

Claims (12)

% By mass _B 2 _{O 3} component 35.0% 5.0% or more of the following, a _La 2 _{O 3} component containing 10.0 to 60.0%, 0% and the F component in terms of% by mass on the outer split 30 Optical glass containing 0.0% or less and having a mass ratio B ₂ O ₃ / SiO ₂ of 5.000 or less. % By mass
Y ₂ O ₃ component 0% and 30.0% or less WO ₃ ingredient 0% and 20.0% or less containing to claim 1 of the optical glass. % By mass, _Al 2 _{O 3} according to claim 1 or 2, wherein the optical glass components containing less 0% and 15.0%. Contains 20.0% to 70.0% by mass of Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y, Yb, and Lu) The optical glass according to any one of claims 1 to 3. The optical glass according to any one of claims 1 to 4, wherein the content of the Li ₂ O component is less than 5.0% by mass. The optical glass according to claim 1, which has a refractive index (n _d ) of 1.70 or more and an Abbe number (ν _d ) of 40 or more and 55 or less.   The optical glass according to any one of claims 1 to 6, having a specific gravity of 5.00 or less.   A coordinate system in which the Abbe number (νd) is the x axis and the partial dispersion ratio (θg, F) is the y axis, (x, y) = (36.3, 0.5828) and (60.5, 0.5436). 8) The optical glass according to any one of claims 1 to 7, wherein the magnitude of deviation in the θg, F direction from the straight line connecting the two points (anomalous dispersion Δθg, F) is −0.0150 or more.   A preform comprising the optical glass according to claim 1.   An optical element produced by press-molding the preform according to claim 9.   The optical element which uses the optical glass in any one of Claim 1 to 8 as a base material.   An optical apparatus comprising the optical element according to claim 10.

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