JP6664826B2 - Optical glass and optical element - Google Patents

Description

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

  2. Description of the Related Art In recent years, digitalization and high-definition of devices using optical systems have been rapidly progressing, and various optical devices such as photographing devices such as digital cameras and video cameras, and image reproducing (projection) devices such as projectors and projection televisions. In the field of, there is an increasing demand to reduce the number of optical elements such as lenses and prisms used in the optical system, and to reduce the weight and size of the entire optical system.

Among optical glasses for producing an optical element, in particular, it has a refractive index ( _nd ) of 1.75 or more and 2.00 or less and 23 or more and 45 or less, which can reduce the weight and size of the entire optical system. Demand for a high-refractive-index, low-dispersion glass having an Abbe number (ν _d ) is extremely increasing. As such a high-refractive-index low-dispersion glass, a glass composition represented by Patent Documents 1 and 2 is known.

JP 2006-016293 A JP 2011-144069 A

  Examples of a method of manufacturing an optical element from optical glass include, for example, a method of performing grinding and polishing on a gob or a glass block formed of optical glass to obtain a shape of the optical element, a gob or glass formed of optical glass. A method of grinding and polishing a glass molded body obtained by reheating and molding a block (reheat press molding), and molding a preform material obtained from a gob or a glass block with a mold that has been subjected to ultraprecision processing. A method of obtaining the shape of an optical element by performing (precision mold press molding) is known. In any method, when forming a gob or a glass block from a molten glass raw material, it is required that a stable glass be obtained. Here, when the stability of the glass constituting the obtained gob or glass block to devitrification (resistance to devitrification) is reduced and crystals are generated inside the glass, it is possible to obtain glass suitable as an optical element. Can not.

  Further, in order to reduce the material cost of the optical glass, it is desired that the raw material costs of the components constituting the optical glass be as low as possible. However, it is difficult to say that the glasses described in Patent Documents 1 and 2 sufficiently satisfy such requirements.

  Further, the glasses described in Patent Documents 1 and 2 have a problem that the specific gravity of the glass is large and the mass of the optical element is large. That is, when these glasses are used for an optical device such as a camera or a projector, there is a problem that the mass of the entire optical device tends to increase.

  The present invention has been made in view of the above problems, and an object thereof is to provide a stable glass having a refractive index and an Abbe number within a desired range and capable of contributing to weight reduction of an optical device. Is to be obtained at a lower cost.

Means for Solving the Problems The present inventors have conducted intensive studies and researches to solve the above-mentioned problems. As a result, the glass containing the B ₂ O ₃ component and the La ₂ O ₃ component as essential components has a ZrO ₂ component and a Nb ₂ O ₅ component. By containing the components, Ta ₂ O ₅ component and WO ₃ component in predetermined amounts, a stable glass having a desired high refractive index and high Abbe number can be obtained, but the material cost of the glass is reduced, and The inventors have found that the specific gravity is small, and have completed the present invention. Specifically, the present invention provides the following.

(1) In terms of mass% of oxide equivalent composition, B ₂ O ₃ contains 5.0 to 30.0%, La ₂ O ₃ contains 30.0 to 60.0%, and mass sum based on oxide. (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ + WO ₃ ) is 20.0% or less, has a refractive index (nd) of 1.85 or more, has an Abbe number (νd) of 30 or more, and has a specific gravity of 5.00. An optical glass that is:

(2) In mass% of oxide equivalent composition,
Y ₂ O ₃ component from 0 to 20.0%,
Gd ₂ O ₃ component 0 to 10.0%,
Yb ₂ O ₃ component 0 to 15.0%
The optical glass according to (1), wherein

(3) In mass% of oxide equivalent composition,
SiO ₂ component 0 to 15.0%,
TiO ₂ component 0-30.0%,
ZrO ₂ component 0 to 15.0%,
WO ₃ ingredients 0-10.0%,
ZnO component 0-20.0%,
MgO component 0-10.0%,
CaO component 0-15.0%,
SrO component 0-15.0%,
BaO component 0-15.0%,
Li ₂ O component 0 to 10.0%
Na ₂ O component 0 to 10.0%,
K ₂ O component 0 to 10.0%,
Ta ₂ O ₅ component 0 to 10.0%,
Nb ₂ O ₅ component 0 to 10.0%,
ZrO ₂ component 0 to 15.0%,
P ₂ O ₅ component 0 to 10.0%,
GeO ₂ component 0-10.0%,
Al ₂ O ₃ component 0 to 10.0%,
Ga ₂ O ₃ component 0 to 10.0%,
Bi ₂ O ₃ component 0 to 10.0%,
TeO ₂ components 0 to 5.0%, and SnO ₂ component from 0 to 1.0% of the content by _Sb 2 _{O 3} component from 0 to 1.0% by mass% of the outer split
The optical glass according to (1) or (2), wherein

(4) The mass sum of the Ln ₂ O ₃ components (where Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) is 45.0% to 70% by mass based on the oxide. 0.0%, the mass sum of the Rn ₂ O component (where Rn is at least one selected from the group consisting of Li, Na, and K) is 0 to 15.0% or less, and the RO component (where R is The optical glass according to any one of (1) to (3), wherein the mass sum of at least one selected from the group consisting of Mg, Ca, Sr, and Ba) is 0 to 25.0%.

(5) The optical glass according to any one of (1) to (4), wherein the wavelength (λ ₇₀ ) at which the spectral transmittance indicates 70% is 480 nm or less.

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

(7) A preform for polishing and / or precision press molding comprising the optical glass according to any one of (1) to (5).

(8) An optical element obtained by precision pressing the preform according to (7).

  ADVANTAGE OF THE INVENTION According to this invention, the refractive index and Abbe number are in a desired range, and the stable glass which can contribute to the weight reduction of an optical device can be obtained more cheaply.

The optical glass of the present invention, in mass% with respect to the glass the total weight of the oxide basis the _composition, B 2 _{O 3} component from 5.0 to 30.0% and content _{of La} 2 _{O 3} component from 30.0 to 60.0% When the mass sum (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ + WO ₃ ) on the oxide basis is 20.0% or less, rare earth elements which are expensive and often increase the specific gravity of the glass, In particular, even if Gd ₂ O ₃ or Yb ₂ O ₃ is reduced, a high refractive index and Abbe number can be obtained, and a rise in liquidus temperature can be suppressed. Therefore, while having a refractive index of 1.85 or more and an Abbe number of 30 or more and 50 or less, the specific glass having a small specific gravity of 5.00 or less and capable of contributing to the weight reduction of an optical device has a high devitrification-resistant optical glass. , Can be obtained at a lower cost.

  Hereinafter, embodiments of the optical glass of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and is implemented with appropriate modifications within the scope of the present invention. be able to. In addition, although the description may be omitted as appropriate for portions where the description is duplicated, the purpose of the invention is not limited.

[Glass component]
The composition range of each component constituting the optical glass of the present invention will be described below. In the present specification, unless otherwise specified, the contents of the respective components are all represented by mass% with respect to the total mass of the glass in terms of oxide. Here, the `` composition in terms of oxides '' refers to oxides, composite salts, metal fluorides, and the like used as raw materials of the glass constituent components of the present invention, assuming that they are all decomposed at the time of melting and change to oxides. The composition is a composition in which each component contained in the glass is described, with the total mass of the generated oxide being 100% by mass.

<About essential and optional components>
The B ₂ O ₃ component is an essential component indispensable as a glass-forming oxide.
In particular, by containing the B ₂ O ₃ component at 5.0% or more, the devitrification resistance of the glass can be increased and the dispersion of the glass can be reduced. Therefore, the lower limit of the content of the B ₂ O ₃ component is preferably 5.0%, more preferably 5.0%, further preferably 8.5%, and still more preferably 10.5%.
On the other hand, by setting the content of the B ₂ O ₃ component to 30.0% or less, a higher refractive index can be easily obtained, and deterioration of chemical durability can be suppressed. Therefore, the upper limit of the content of the B ₂ O ₃ component is preferably 30.0%, 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.

The La ₂ O ₃ component is a component that increases the refractive index of the glass and reduces the dispersion (increases the Abbe number). In particular, by containing the La ₂ O ₃ component at 30.0% or more, a desired high refractive index can be obtained. Therefore, the lower limit of the content of the La ₂ O ₃ component is preferably 30.0%, more preferably 35.0%, further preferably 37.0%, and still more preferably 40.0%.
On the other hand, by setting the content of the La ₂ O ₃ component to 60.0% or less, the devitrification resistance of the glass can be increased. Therefore, the upper limit of the content of the La ₂ O ₃ component is preferably 60.0%, more preferably 55.0%, and even 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.

In the optical glass of the present invention, the sum (mass sum) of the contents of the ZrO ₂ component, the Nb ₂ O ₅ component, the Ta ₂ O ₅ component, and the WO ₃ component is preferably 20.0% or less. Thereby, while maintaining a high refractive index and a high Abbe number, specific gravity can be reduced and visible light transmittance can be suppressed. Accordingly, the upper limit of the mass sum (ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ + WO ₃ ) is preferably 20.0%, more preferably 10.0%, and further preferably 7.0%.

The Y ₂ O ₃ component is an optional component that, when contained in more than 0%, can maintain a high refractive index and a high Abbe number, can suppress the material cost of glass, and can reduce the specific gravity. This Y ₂ O ₃ component is useful for the optical glass of the present invention because the material cost is low among the rare earth elements and the specific gravity is easily reduced as compared with other rare earth elements. Therefore, the content of the Y ₂ O ₃ component may be preferably more than 0%, more preferably more than 1.0%, further preferably more than 3.0%, and still more preferably more than 5.0%.
On the other hand, when the content of the Y ₂ O ₃ component is 20.0% or less, a decrease in the refractive index of the glass can be suppressed, and the devitrification resistance of the glass can be increased. Therefore, the upper limit of the content of the Y ₂ O ₃ component is preferably 20.0%, more preferably 15.0%, still more preferably 13.0%, and most preferably 10.0%.
As the Y ₂ O ₃ component, Y ₂ O ₃ , YF ₃ or the like can be used as a raw material.

The Gd ₂ O ₃ component is an optional component that can increase the refractive index of the glass and increase the Abbe number when contained more than 0%.
On the other hand, by reducing the particularly expensive Gd ₂ O ₃ component among the rare earth elements to 10.0% or less, the material cost of the glass is reduced, so that a cheaper optical glass can be manufactured. In addition, this can suppress an unnecessary increase in the Abbe number of the glass. Therefore, the upper limit of the content of the Gd ₂ O ₃ component is preferably 10.0%, more preferably 9.0%, and still more preferably 8.0%.
In particular, setting the content of the Gd ₂ O ₃ component to 3.0% or less can contribute to lower cost and lower specific gravity. Therefore, when it is desired to further reduce the material cost, the upper limit of the content of the Gd ₂ O ₃ component is preferably 3.0%, more preferably less than 1.0%.
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 is an optional component that can increase the refractive index of the glass and reduce the dispersion when containing more than 0%.
On the other hand, by setting the content of the Yb ₂ O ₃ component to 10.0% or less, the devitrification resistance of the glass can be increased. Therefore, the upper limit of the content of the Yb ₂ O ₃ component is preferably 9.0%, more preferably 8.0%.
In particular, setting the content of the Yb ₂ O ₃ component to 3.0% or less can contribute to lower cost and lower specific gravity. Therefore, in order to further reduce the material cost, the upper limit of the content of the Yb ₂ O ₃ component is preferably 3.0%, and more preferably less than 1.0%.
As the Yb ₂ O ₃ component, Yb ₂ O ₃ or the like can be used as a raw material.

The sum (mass sum) of the contents of Ln ₂ O ₃ components (where Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) is 45.0% or more and 70.0% or less. Is preferred.
In particular, by making this sum 45.0% or more, the dispersion of glass can be reduced. Therefore, the lower limit of the mass sum of the Ln ₂ O ₃ component is preferably 45.0%, more preferably 48.0%, further preferably 50.0%, and still more preferably 54.0%.
On the other hand, by setting the sum to 70.0% or less, the liquidus temperature of the glass is lowered, so that the devitrification resistance can be improved. Therefore, the upper limit of the mass sum of the Ln ₂ O ₃ component is preferably 70.0%, more preferably 65.0%, and further preferably 60.0%.

The Ta ₂ O ₅ component is an optional component that, when contained in more than 0%, can increase the refractive index of the glass and increase the devitrification resistance.
On the other hand, by reducing the expensive Ta ₂ O ₅ component to 10.0% or less, the material cost of the glass is reduced, so that a cheaper optical glass can be manufactured. Further, since the melting temperature of the raw material is lowered and the energy required for melting the raw material is reduced, the production cost of the optical glass can be reduced. Therefore, the upper limit of the content of the Ta ₂ O ₅ component is preferably 10.0%, more preferably 9.0%, and still more preferably 8.0%. In particular, from the viewpoint of producing an optical glass having a lower specific gravity and a lower cost, the upper limit of the content of the Ta ₂ O ₅ component is preferably 5.0%, more preferably 4.0%, and further preferably 1. Less than 0%, most preferably not contained.
As the Ta ₂ O ₅ component, Ta ₂ O ₅ or the like can be used as a raw material.

WO ₃ component, when 0% super-containing, refractive index increasing while reducing the coloration of the glass due to other high refractive index component, and is an optional component that enhances devitrification resistance of the glass. Therefore, the content of WO ₃ ingredient is preferably 0 percent, more preferably 0.1%, more preferably may be a lower limit of 0.5%.
On the other hand, when the content of the WO ₃ component is set to 10.0% or less, the coloring of the glass by the WO ₃ component is reduced, the visible light transmittance is increased, and the cost and the specific gravity can be reduced. . Therefore, the content of WO ₃ component is preferably 10.0%, more preferably 5.0%, more preferably the upper limit of 3.0%.
As the WO ₃ component, WO ₃ or the like can be used as a raw material.

The Nb ₂ O ₅ component is an optional component that, when contained in more than 0%, can increase the refractive index of the glass and increase the devitrification resistance. Further, since the specific gravity is reduced and the material cost of the glass is reduced, a cheaper optical glass can be manufactured.
On the other hand, by reducing the content of the Nb ₂ O ₅ component to 10.0% or less, a decrease in the devitrification resistance of the glass and a decrease in the transmittance of visible light due to an excessive content of the Nb ₂ O ₅ component are prevented. Can be suppressed. Therefore, the upper limit of the content of the Nb ₂ O ₅ component is preferably 10.0%, more preferably 8.0%, and still more preferably 5.0%.
As the Nb ₂ O ₅ component, Nb ₂ O ₅ or the like can be used as a raw material.

The TiO ₂ component is an optional component that, when contained in more than 0%, can increase the refractive index of the glass, adjust the Abbe number to be low, and increase the devitrification resistance. Therefore, the lower limit of the content of the TiO ₂ component is preferably more than 0%, more preferably 3.0%, and even more preferably 5.0%.
On the other hand, by setting the content of TiO ₂ to 30.0% or less, the coloring of the glass is reduced, the visible light transmittance is increased, and the Abbe number of the glass is prevented from being reduced more than necessary. In addition, devitrification due to excessive inclusion of the TiO ₂ component can be suppressed. Therefore, the content of the TiO ₂ component is preferably 30.0%, more preferably 20.0%, further preferably 15.0%, and more preferably less than 13.0%.
As the TiO ₂ component, TiO ₂ or the like can be used as a raw material.

The SiO ₂ component is an optional component that, when contained in more than 0%, can increase the viscosity of the molten glass, reduce the coloring of the glass, and increase the devitrification resistance. Therefore, the lower limit of the content of the SiO ₂ component may be preferably more than 0%, more preferably 3.0%, and even more preferably 5.0%.
On the other hand, by setting the content of the SiO ₂ component to 15.0% or less, it is possible to suppress an increase in the glass transition point and a decrease in the refractive index. Therefore, the upper limit of the content of the SiO ₂ component is preferably 15.0%, more preferably 13.0%, further preferably 10.0%, and still more preferably 8.0%.
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.

Further, the content ratio (mass ratio) of the SiO ₂ component to the B ₂ O ₃ component is preferably 0.40 or more and 0.80 or less.
In particular, by setting this ratio to 0.40 or more, the devitrification resistance of the glass can be increased. Therefore, the mass ratio (SiO ₂ ) / (B ₂ O ₃ ) preferably has a lower limit of preferably 0.40, more preferably 0.50, and still more preferably 0.55.
On the other hand, by setting this ratio to 0.80 or less, a higher refractive index can be easily obtained. Accordingly, the upper limit of the mass ratio (SiO ₂ ) / (B ₂ O ₃ ) is preferably 0.80, more preferably 0.75, and even more preferably 0.70.

The ratio (mass ratio) of the Y ₂ O ₃ component, the TiO ₂ component, and the ZnO component to the La ₂ O ₃ component, the Gd ₂ O ₃ component, and the Y ₂ O ₃ component is 0.40 or more. 00 or less is preferable.
In particular, by setting this ratio to 0.40 or more, the specific gravity can be reduced. Therefore, the mass ratio (Y ₂ O ₃ + TiO ₂ + ZnO) / (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ ) is preferably 0.30, more preferably 0.35, and still more preferably 0.40. Lower limit.
On the other hand, by setting the ratio to 0.80 or less, it is possible to suppress coloring and reduction in viscosity due to excessive content, and to suppress the occurrence of striae. Therefore, the mass ratio (Y ₂ O ₃ + TiO ₂ + ZnO) / (La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ ) is preferably 0.80, more preferably 0.70, and still more preferably 0.60. Upper limit.

Further, TiO ₂ component, ZrO ₂ component, _Nb 2 _{O 5} component, for _Ta 2 _{O 5} component, and WO ₃ components, the ratio of the content of WO ₃ components (mass ratio), 0.03 or 0.22 or less preferable.
In particular, by setting this ratio to 0.03 or more, the devitrification resistance of the glass can be increased. Therefore, the mass ratio (WO ₃ ) / (TiO ₂ + ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ + WO ₃ ) preferably has a lower limit of 0.03, more preferably 0.035, and still more preferably 0.04. .
On the other hand, by setting the ratio to 0.22 or less, it is possible to suppress coloring of the glass due to excess of the high refractive index component. Therefore, the mass ratio (WO ₃ ) / (TiO ₂ + ZrO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ + WO ₃ ) is preferably 0.22, more preferably 0.20, even more preferably 0.10, and most preferably. Has an upper limit of 0.08.

The MgO component, the CaO component, the SrO component and the BaO component are optional components that, when contained in more than 0%, can enhance the melting property of the glass raw material and the devitrification resistance of the glass.
On the other hand, by reducing the content of each of the BaO component, the CaO component and the SrO component to 15.0% or less and / or the content of the MgO component to 10.0% or less, A decrease in the refractive index and a decrease in the devitrification resistance due to excessive content can be suppressed. Therefore, the content of each of the BaO, CaO, and SrO components is preferably 15.0%, more preferably 10.0%, and even more preferably 5.0%. Further, the upper limit of the content of the MgO component is preferably 10.0%, more preferably 5.0%, and still more preferably 3.0%.
The MgO component, the CaO component, the SrO component, and the BaO component include MgCO ₃ , MgF ₂ , CaCO ₃ , CaF ₂ , Sr (NO ₃ ) ₂ , SrF ₂ , BaCO ₃ , Ba (NO ₃ ) ₂ , and BaF ₂ as raw materials. Can be used.

  The total content (mass sum) of the RO components (where R is at least one selected from the group consisting of Mg, Ca, Sr, and Ba) is preferably 25.0% or less. Thereby, a decrease in the refractive index and a decrease in the devitrification resistance of the glass due to the excessive content of the RO component can be suppressed. Therefore, the upper limit of the mass sum of the RO component is preferably 25.0%, more preferably 15.0%, further preferably 10.0%, and still more preferably 5.0%.

The Li ₂ O component, the Na ₂ O component, the K ₂ O component, and the Cs ₂ O component are optional components that can improve the melting property of the glass and lower the glass transition point when containing more than 0%. Of these, the Na ₂ O component, the K ₂ O component and the Cs ₂ O component are also components that can enhance the devitrification resistance of glass. Here, by setting each content of the Li ₂ O component, the Na ₂ O component, the K ₂ O component, and the Cs ₂ O component to 10.0% or less, it becomes difficult to lower the refractive index of the glass, and Devitrification resistance can be increased. Therefore, the content of each of the Li ₂ O component, the Na ₂ O component, the K ₂ O component, and the Cs ₂ O component is preferably 10.0%, more preferably 8.0%, and still more preferably 5.0%. Is the upper limit.
In particular, by setting the content of the Li ₂ O component to 3.0% or less, the viscosity of the glass increases, and thus the striae of the glass can be reduced. Therefore, from the viewpoint of reducing the striae of the glass, the upper limit of the content of the Li ₂ O component is preferably 3.0%, more preferably 1.0%, and still more preferably 0.3%.
The Li ₂ O component, the Na ₂ O component, the K ₂ O component and the Cs ₂ O component are, as raw materials, Li ₂ CO ₃ , LiNO ₃ , Li ₂ CO ₃ , NaNO ₃ , NaF, Na ₂ SiF ₆ , K ₂ CO ₃ , KNO ₃ , KF, KHF ₂ , K ₂ SiF ₆ , Cs ₂ CO ₃ , CsNO _{3 and the} like can be used.

The total amount of the Rn ₂ O component (where Rn is at least one selected from the group consisting of Li, Na, K, and Cs) is preferably 15.0% or less. Thereby, a decrease in the refractive index of the glass can be suppressed, and the devitrification resistance can be increased. Therefore, the upper limit of the mass sum of the Rn ₂ O component is preferably 15.0%, more preferably 10.0%, and still more preferably 5.0%.

The P ₂ O ₅ component is an optional component that can enhance the devitrification resistance of the glass when it contains more than 0%. In particular, by setting the content of the P ₂ O ₅ component to 10.0% or less, it is possible to suppress a decrease in chemical durability, particularly, water resistance of the glass. Therefore, the upper limit of the content of the P ₂ O ₅ component is preferably 10.0%, more preferably 5.0%, and still more preferably 3.0%.
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 that, when contained in more than 0%, can increase the refractive index of glass and improve devitrification resistance. However, since the raw material price of GeO ₂ is high, if the amount is large, the material cost increases, and the effect of cost reduction by reducing the Gd ₂ O ₃ component and the Ta ₂ O ₅ component is diminished. Therefore, the content of the GeO ₂ component is preferably set to 10.0%, more preferably 5.0%, further preferably 1.0%, and most preferably not contained.
As the GeO ₂ component, GeO ₂ or the like can be used as a raw material.

When the ZrO ₂ component is contained in an amount exceeding 0%, it can contribute to increasing the refractive index and lowering the dispersion of the glass, and can enhance the devitrification resistance of the glass. Therefore, the lower limit of the content of the ZrO ₂ component is preferably more than 0%, more preferably 1.0%, and still more preferably 3.0%.
On the other hand, by reducing the ZrO ₂ component to 15.0% or less, a decrease in the devitrification resistance of the glass due to the excessive content of the ZrO ₂ component can be suppressed. Therefore, the upper limit of the content of the ZrO ₂ component is preferably 15.0%, more preferably 10.0%, and still more preferably 8.0%.
As the ZrO ₂ component, ZrO ₂ , ZrF ₄ or the like can be used as a raw material.

The ZnO component is an optional component that can maintain desired refractive index and Abbe number and enhance chemical durability when contained more than 0%. Further, since the material cost of the glass is reduced, a cheaper optical glass can be manufactured. Therefore, the lower limit of the content of the ZnO component is preferably more than 0%, more preferably 3.0%, further preferably 5.0%, and most preferably 6.5%.
On the other hand, by setting the content of the ZnO component to 20.0% or less, a decrease in the refractive index of the glass and a decrease in the devitrification resistance can be suppressed. In addition, since the viscosity of the molten glass is increased, the occurrence of striae on the glass can be reduced. Therefore, the upper limit of the content of the ZnO component is preferably 20.0%, more preferably 18.0%, still more preferably 15.0%, and still more preferably 10.0%.
As the ZnO component, ZnO, ZnF ₂ or the like can be used as a raw material.

The Al ₂ O ₃ component and the Ga ₂ O ₃ component are optional components that, when contained in more than 0%, can increase the chemical durability of the glass and increase the devitrification resistance of the glass.
On the other hand, by setting the content of each of the Al ₂ O ₃ component and the Ga ₂ O ₃ component to 10.0% or less, a decrease in the devitrification resistance of the glass due to an excessive content thereof can be suppressed. Therefore, the upper limit of the content of each of the Al ₂ O ₃ component and the Ga ₂ O ₃ component is preferably 10.0%, more preferably 5.0%, and still more preferably 3.0%.
As the Al ₂ O ₃ component and the Ga ₂ O ₃ component, Al ₂ O ₃ , Al (OH) ₃ , AlF ₃ , Ga ₂ O ₃ , Ga (OH) _{3 and the} like can be used as raw materials.

The Bi ₂ O ₃ component is an optional component that can increase the refractive index and lower the glass transition point when containing more than 0%.
On the other hand, by setting the content of the Bi ₂ O ₃ component to 10.0% or less, the devitrification resistance of the glass can be increased, and the coloring of the glass can be reduced to increase the visible light transmittance. Therefore, the upper limit of the content of the Bi ₂ O ₃ component is preferably 10.0%, more preferably 5.0%, and still more preferably 3.0%.
As the Bi ₂ O ₃ component, Bi ₂ O 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 when containing more than 0%.
However, there is a problem that TeO ₂ can be alloyed with platinum when a glass material is melted in a platinum crucible or in a melting tank in which a portion in contact with the molten glass is formed of platinum. Therefore, the content of the TeO ₂ component is preferably 5.0%, more preferably 3.0%, further preferably less than 1.0%, and further preferably not contained.
As the TeO ₂ component, TeO ₂ or the like can be used as a raw material.

The SnO ₂ component is an optional component that, when contained in more than 0%, can reduce the oxidization of the molten glass to clarify it and increase the visible light transmittance of the glass.
On the other hand, by setting the content of the SnO ₂ component to 1.0% or less, coloring of the glass due to reduction of the molten glass and devitrification of the glass can be reduced. Further, since the alloying of the SnO ₂ component and the melting equipment (particularly, a noble metal such as Pt) is reduced, the life of the melting equipment can be extended. Therefore, the upper limit of the content of the SnO ₂ component is preferably 1.0%, more preferably 0.7%, and still more preferably 0.5%.
As 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 capable of defoaming the molten glass when containing more than 0%. The Sb ₂ O ₃ component is defined as an external mass%.
On the other hand, if the amount of Sb ₂ O ₃ is too large, the transmittance in the short wavelength region of the visible light region becomes poor. Therefore, the upper limit of the content of the Sb ₂ O ₃ component is preferably 1.0%, more preferably 0.7%, and still more preferably 0.5%.
Sb ₂ O ₃ component can be used _{Sb 2 O 3, Sb 2 O} 5, Na 2 H 2 Sb 2 O 7 · 5H 2 O and the like as raw materials.

The component for clarifying and defoaming the glass is not limited to the above-mentioned Sb ₂ O ₃ component, and a known fining agent, defoaming agent or a combination thereof in the field of glass production can be used.

<Ingredients that should not be contained>
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.

  Other components can be added as needed as long as the properties of the glass of the present invention are not impaired. However, each of transition metal components such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, is used alone. Or, even when a small amount is contained in a complex, the glass is colored, and has a property of causing absorption at a specific wavelength in the visible region.In particular, in an optical glass using a wavelength in the visible region, it is preferable that the glass is not substantially contained. .

Further, lead compounds such as PbO and arsenic compounds such as As ₂ O ₃ are components that have a high environmental load, and therefore, should not substantially be contained, that is, should not be contained at all except for unavoidable contamination.

  Furthermore, each component of Th, Cd, Tl, Os, Be, and Se tends to refrain from using as harmful chemicals in recent years, and is used not only in the glass manufacturing process but also in the processing process and disposal after commercialization. Environmental measures are required to this extent. Therefore, when importance is placed on environmental influences, it is preferable that these are not substantially contained.

The glass composition of the present invention cannot be directly expressed in terms of mol% since its composition is expressed in terms of mass% with respect to the total mass of the glass in terms of oxide, but various properties required in the present invention. The composition in terms of mol% of each component present in the glass composition that satisfies the above generally takes the following values in terms of oxide composition.
B ₂ O ₃ component from 2.0 to 55.0 mol%, and _La 2 _{O 3} component from 5.0 to 30.0 mol%,
And _Y 2 _{O 3} component 0 to 20.0 mol%,
Gd ₂ O ₃ component 0 to 20.0 mol%,
Yb ₂ O ₃ component 0 to 10.0 mol%,
Ta ₂ O ₅ component 0 to 10.0 mol%,
WO ₃ components 0 to 20.0 mol%,
Nb ₂ O ₅ component from 0 to 15.0 mol%,
TiO ₂ component from 0 to 40.0 mol%,
SiO ₂ component 0 to 50.0 mol%,
MgO component 0-50.0 mol%,
CaO component 0 to 40.0 mol%,
SrO component 0-30.0 mol%,
BaO component 0 to 35.0 mol%,
Li ₂ O component 0 to 30.0 mol%,
Na ₂ O component 0 to 25.0 mol%,
K ₂ O component 0 to 20.0 mol%,
Cs ₂ O component 0 to 10.0 mol%,
P ₂ O ₅ component from 0 to 15.0 mol%,
GeO ₂ component 0 to 10.0 mol%,
ZrO ₂ component 0 to 20.0 mol%,
ZnO component 0 to 50.0 mol%,
Al ₂ O ₃ component 0 to 20.0 mol%,
Ga ₂ O ₃ component 0 to 10.0 mol%,
Bi ₂ O ₃ component 0 to 10.0 mol%,
TeO ₂ component 0 to 20.0 mol%,
SnO ₂ component 0 to 0.3 mol% or Sb ₂ O ₃ component 0 to 0.5 mol%

[Production method]
The optical glass of the present invention is produced, for example, as follows. That is, the above-mentioned raw materials are uniformly mixed so that each component falls within a predetermined content range, the prepared mixture is put into a platinum crucible, and is heated to 1100 to 1500 ° C. in an electric furnace according to the melting difficulty of the glass composition. Is melted in the temperature range of 2 to 5 hours, stirred and homogenized, lowered to an appropriate temperature, poured into a mold, and gradually cooled.

[Physical properties]
The optical glass of the present invention preferably has a high refractive index and a high Abbe number (low dispersion). In particular, the lower limit of the refractive index ( _nd ) of the optical glass of the present invention is preferably 1.85, more preferably 1.87, and still more preferably 1.88. The upper limit of the refractive index may be preferably 2.20, more preferably 2.15, and even more preferably 2.10. The Abbe number (ν _d ) of the optical glass of the present invention is preferably 30, more preferably 32, further preferably 33, and still more preferably 34, preferably 50, more preferably 45, and still more preferably 40. , Most preferably less than 38.
By having such a high refractive index, a large amount of light refraction can be obtained even if the optical element is made thin. Further, by having such a low dispersion, even if a single lens is used, a focus shift (chromatic aberration) due to the wavelength of light is reduced. In addition, by having such a low dispersion, for example, when combined with an optical element having a high dispersion (low Abbe number), high imaging characteristics and the like can be achieved.
Therefore, the optical glass of the present invention is useful in optical design, and can achieve downsizing of the optical system and widen the degree of freedom in optical design while achieving particularly high imaging characteristics.

Further, the optical glass of the present invention preferably has a low specific gravity. More specifically, the specific gravity of the optical glass of the present invention is 5.00 [g / cm ³ ] or less. This reduces the mass of the optical element and the optical device using the same, which can contribute to the weight reduction of the optical device. Therefore, the upper limit of the specific gravity of the optical glass of the present invention is preferably 5.00, more preferably 4.95, and preferably 4.90. 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 of the present invention is measured based on JOGIS05-1975 “Method for measuring specific gravity of optical glass” specified by Japan Optical Glass Industrial Association.

It is preferable that the optical glass of the present invention has a high visible light transmittance, particularly a high transmittance of light on the short wavelength side of the visible light, and thereby has a small coloring.
In particular, in the optical glass of the present invention, the wavelength (λ ₈₀ ) at which the sample having a thickness of 10 mm exhibits a spectral transmittance of 80% is preferably 520 nm, more preferably 510 nm, and further preferably 500 nm.
The upper limit of the wavelength (λ ₇₀ ) at which the sample having a thickness of 10 mm in the optical glass of the present invention exhibits a spectral transmittance of 70% is preferably 480 nm, more preferably 450 nm, and still more preferably 430 nm.
The shortest wavelength (λ ₅ ) of the optical glass of the present invention having a spectral transmittance of 5% in a sample having a thickness of 10 mm is preferably 440 nm, more preferably 420 nm, further preferably 400 nm, and still more preferably 380 nm. I do.
As a result, the absorption edge of the glass is in the vicinity of the ultraviolet region, and the transparency of the glass to visible light is increased. Therefore, this optical glass can be preferably used for optical elements such as lenses that transmit light.

[Glass molded body and optical element]
From the produced optical glass, a glass molded body can be produced, for example, by means of polishing or by means of mold press molding such as reheat press molding or precision press molding. That is, the optical glass is subjected to mechanical processing such as grinding and polishing to produce a glass molded body, or the preform produced from the optical glass is subjected to reheat press molding and then polished to perform glass molding. It is possible to produce a molded glass body by performing precision press molding on a preform produced by forming a body, performing a polishing process, or a preform formed by known floating molding or the like. The means for producing the glass molded body is not limited to these means.

  As described above, the glass molded body formed from the optical glass of the present invention is useful for various optical elements and optical designs, and among them, it is particularly preferable to use it for optical elements such as lenses and prisms. As a result, it is possible to form a glass molded body having a large diameter. Therefore, while increasing the size of the optical element, when used in an optical device such as a camera or a projector, high-definition and high-precision imaging characteristics and projection are performed. Characteristics can be realized.

The composition of Example (No.1~No.31) and comparative examples of the present invention (No. A), and the refractive index of these glasses _(n d), Abbe number ([nu _d), the spectral transmittance of 5 Tables 1 to 4 show the results of wavelengths (λ ₅ , λ ₇₀ , λ ₈₀ ) indicating%, 70%, and 80% and specific gravity. The following embodiments are for illustrative purposes only, and are not limited to these embodiments.

  The glasses of Examples and Comparative Examples of the present invention are all ordinary optical glasses such as oxides, hydroxides, carbonates, nitrates, fluorides, hydroxides, metaphosphate compounds, etc., corresponding to the raw materials of the respective components. High-purity raw material used in the composition, weighed to the composition ratio of each example shown in the table, uniformly mixed, then put into a platinum crucible, according to the melting difficulty of the glass composition After melting in a temperature range of 1100 to 1500 ° C. for 2 to 5 hours in an electric furnace, the mixture was homogenized with stirring, cast into a mold or the like, and gradually cooled to produce glass.

  Here, the refractive indices and Abbe numbers of the glasses of the examples and comparative examples were measured based on the Japan Optical Glass Industrial Association standard JOGIS01-2003.

Further, the transmittances of the glasses of the examples and the comparative examples were measured according to the Japan Optical Glass Industrial Association standard JOGIS02. In the present invention, the presence or absence and the degree of coloring of the glass were determined by measuring the transmittance of the glass. Specifically, a face-to-face parallel polished product having a thickness of 10 ± 0.1 mm was measured for spectral transmittance from 200 to 800 nm according to JISZ8722, and λ ₅ (wavelength at a transmittance of 5%), λ ₇₀ (transmittance) (Wavelength at 70%) and λ ₈₀ (wavelength at a transmittance of 80%) were determined.

The specific gravities of the glasses of the examples and the comparative examples were measured based on JOGIS05-1975 "Method for measuring the specific gravity of optical glass" specified by Japan Optical Glass Industrial Association.

Each of the optical glasses of Examples of the present invention had a specific gravity of 5.00 or less. On the other hand, the glass of the comparative example has a specific gravity of more than 5.00.
Therefore, it became clear that the optical glass of the example of the present invention had a lower specific gravity than the glass of the comparative example.

Further, the optical glasses of the examples of the present invention each had a λ ₈₀ (wavelength at a transmittance of 80%) of 520 nm or less, more specifically 500 nm or less. Further, λ ₇₀ (wavelength at a transmittance of 70%) was 480 nm or less, and more specifically, 430 nm or less. Further, the optical glasses of the examples of the present invention each had λ ₅ (wavelength at a transmittance of 5%) of 440 nm or less, more specifically 380 nm or less.

The optical glasses of Examples of the present invention are both refractive index _{(n d)} of 1.85 or more, with more detail is 1.88 or more, the refractive index is 2.20 or less, more detail Was 2.00 or less, which was within a desired range.

Further, the optical glasses of the examples of the present invention each have an Abbe number (ν _d ) of 30 or more, more specifically 33 or more, and this Abbe number of 50 or less, more specifically 45 or less, It was within the desired range.

  Therefore, it is apparent that the optical glass of the example of the present invention can be manufactured at a low cost while having a refractive index and an Abbe number within a desired range, has high devitrification resistance, has little coloring, and has a small specific gravity. became.

  Further, a glass block was formed using the optical glass of the example of the present invention, and the glass block was ground and polished to be processed into the shape of a lens and a prism. As a result, it was possible to stably process into various lens and prism shapes.

  As described above, the present invention has been described in detail for the purpose of illustration. However, this embodiment is for the purpose of illustration only, 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 (7)

Terms of% by mass on the oxide composition in terms _of, B 2 _{O 3} of 5.0-30.0%, _La 2 _{O 3} of 30.0 to 60.0%, ZnO 3.0% or more, the _Gd 2 _{O 3} 3.0% or less, _Nb 2 _{O 5} 10.0% or less, and contains TiO ₂ 3.0% to 15.0% or less, _Ln 2 _{O 3} component (wherein, Ln is La, Gd, Y, The mass sum of one or more selected from the group consisting of Yb is 48.0 to 70.0%, and the Rn ₂ O component (where Rn is one selected from the group consisting of Li, Na, K, and Cs) 0 to 15.0% of the sum of the masses of the RO components (where R is at least one selected from the group consisting of Mg, Ca, Sr, and Ba) in the range of 0 to 25.0%. , the weight ratio _{(Y 2 O 3 + TiO 2} + ZnO) / (La 2 O 3 + Gd 2 O 3 + Y 2 O 3) is not less than 0.4, the oxide basis Ryowa _{(ZrO 2 + Nb 2 O 5} + Ta 2 O 5 + WO 3) is not more than 10.0%, refractive index _{(n d)} of 1.85 or more, an Abbe number ([nu _d) has more than 30, An optical glass having a specific gravity of 5.00 or less. In mass% of oxide equivalent composition,
Yb ₂ O ₃ component 0 to 15.0%
The optical glass according to claim 1, wherein In mass% of oxide equivalent composition,
SiO ₂ component 0 to 15.0%,
ZrO ₂ component 0 to 15.0%,
WO ₃ ingredients 0-10.0%,
MgO component 0-10.0%,
CaO component 0-15.0%,
SrO component 0-15.0%,
BaO component 0-15.0%,
Li ₂ O component 0 to 10.0%
Na ₂ O component 0 to 10.0%,
K ₂ O component 0 to 10.0%,
Ta ₂ O ₅ component 0 to 10.0%,
Nb ₂ O ₅ component 0 to 10.0%,
ZrO ₂ component 0 to 15.0%,
P ₂ O ₅ component 0 to 10.0%,
GeO ₂ component 0-10.0%,
Al ₂ O ₃ component 0 to 10.0%,
Ga ₂ O ₃ component 0 to 10.0%,
Bi ₂ O ₃ component 0 to 10.0%,
TeO ₂ components 0 to 5.0%, and SnO ₂ component from 0 to 1.0% of the content by _Sb 2 _{O 3} component from 0 to 1.0% by mass% of the outer split
The optical glass according to claim 1, wherein The optical glass according to any one of claims 1 to 3 , wherein the wavelength (λ ₇₀ ) at which the spectral transmittance indicates 70% is 480 nm or less. An optical element formed of the optical glass according to any of claims 1 to 4. Preform for polishing machining and / or precision press molding claims 1 consisting of four optical glass according to any one. An optical element obtained by precision-pressing the preform according to claim 6 .