JP2018002520A - Optical glass, optical element blank and optical element - Google Patents

Abstract

An object of the present invention is to provide a high-refractive-index, high-dispersion optical glass excellent in moldability and devitrification resistance. The total content of P2O5, B2O3, SiO2 and Al2O3 is 26% by mass or more based on oxides, and the mass ratio of the content of B2O3 to the total content of P2O5, B2O3, SiO2 and Al2O3 is is 0.11 or more and 0.24 or less, and the mass ratio of the total content of LiO, NaO and KO to the total content of PO, B2O3, SiO2 and Al2O3 is 0.35 or more and 0.56 or less, and TiO2 and the total content of TiO2, Nb2O5, WO3 and Bi2O3 is 0.12 or more and 0.32 or less, the refractive index nd is more than 1.85 and less than 1.90, and Abbe Optical glass having a number νd of 15 or more and 25 or less. [Selection drawing] Fig. 1

Description

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

  In designing an optical system, an optical glass with a high refractive index and a high dispersion having a high refractive index nd and a low Abbe number νd is highly useful in correcting chromatic aberration and making the optical system highly functional and compact.

As an optical glass having a high refractive index and high dispersion, for example, phosphate glass mainly containing P ₂ O ₅ is known (see Patent Documents 1 to 12).

JP 2010-260746 A JP-A-6-345481 JP-A-8-104537 JP-A-9-188540 Japanese Patent Laid-Open No. 2003-300751 JP 2010-222236 A JP 2010-260740 A JP 2010-260742 A JP 2011-195369 A JP 2012-17261 A Japanese Patent Laying-Open No. 2015-063460 Japanese Patent Laying-Open No. 2015-096468

  By the way, phosphate-based high-refractive-high-dispersion optical glass needs to maintain a high temperature when melting a glass raw material. Therefore, the viscosity of the molten glass is excessively lowered and the moldability of the molten glass tends to be poor.

Moreover, for manufacturing an optical element, a method in which optical glass is reheated and molded as in a reheat press may be used. At this time, in the high refractive index and high dispersion glass as described above, crystals may precipitate, and the devitrification resistance tends to be poor.
Therefore, there has been a demand for a phosphate-based high refractive index, high dispersion optical glass excellent in moldability and devitrification resistance of molten glass.

  This invention is made | formed in view of such an actual condition, The one aspect | mode aims at providing the high refractive index high dispersion optical glass excellent in moldability and devitrification resistance.

  As a result of intensive studies to achieve the above object, the present inventor can achieve the object by adjusting the content ratio of various glass constituent components (hereinafter referred to as glass components) constituting the glass. The present invention has been completed based on this finding.

That is, one aspect of the present invention is as follows.
In the oxide-based glass composition,
The total content [P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ ] of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ is 26% by mass or more,
And the content of _{B 2 O 3, P 2 O} 5, B 2 O 3, the mass ratio of the total content of SiO ₂ and _{Al 2 O 3 [B 2 O} 3 / (P 2 O 5 + B 2 O 3 + SiO ₂ + Al ₂ O ₃ )] is 0.11 or more and 0.24 or less,
Mass ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O and the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ [(Li ₂ O + Na ₂ O + K ₂ O) / (P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ )] is 0.35 or more and 0.56 or less,
And the content of _{TiO 2, TiO 2, Nb 2} O 5, WO 3 and _Bi 2 mass ratio of the total content of _{O 3 [TiO 2 / (TiO} 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3)] is 0.12 or more and 0.32 or less,
An optical glass having a refractive index nd of more than 1.85 and less than 1.90, and an Abbe number νd of 15 or more and 25 or less.

  According to one embodiment of the present invention, it is possible to provide a high refractive index, high dispersion optical glass excellent in moldability and devitrification resistance. Moreover, according to 1 aspect of this invention, the optical element blank and optical element which consist of such optical glass can be provided.

This shows the relationship between the refractive index nd of glass and the crystal melting peak temperature Tl obtained in this embodiment. It is an example of a DSC chart.

  Hereinafter, modes for carrying out the present invention (hereinafter simply referred to as “embodiments”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented with appropriate modifications within the scope of the gist thereof. Further, the description of the overlapping parts may be omitted as appropriate, but the gist of the invention is not limited. In the present specification, “optical glass” is a glass composition containing a plurality of types of glass constituent components (glass components), and unless otherwise specified, forms (lumps, plates, spheres, etc.) It is used as a general term regardless of application (optical element blank, optical element, etc.) and size. That is, there is no restriction | limiting in the form of an optical glass, a use, and a magnitude | size, The optical glass of any form, the optical glass of any use, and the optical glass of any magnitude | size are contained in the optical glass in this invention. In the present specification, the optical glass may be simply referred to as “glass”.

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

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

  In this specification, a glass composition is displayed based on content of each glass component in the mass% display. Unless otherwise specified, the% indication in each content means mass%.

  In addition, in this specification, the mass% display of a glass composition is about each glass component when the total content of all the glass components is 100 mass% about each glass component represented by an oxide or fluoride. This means displaying the content by mass percentage.

  In the present embodiment, the glass composition can be quantified by ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). The analysis value obtained by ICP-AES may include a measurement error of about ± 5% of the analysis value, for example. Further, in the present specification and this embodiment, the content of the constituent component of the glass being 0% or not means that the constituent component is substantially not included, and the content of the constituent component is the impurity level. It means less than or equal to.

As will be described later, Sb ₂ O ₃ and CeO ₂ may be added to the glass in small amounts as a fining agent. However, in the mass percentage of the specification, it does not include the content of Sb ₂ O ₃ and CeO ₂ in the total content of all glass components. That is, each content at _Sb 2 _O 3, of CeO ₂ weight percentages of the glass components, in the case where the total content of all glass components other than _Sb 2 _{O 3} and CeO ₂ is 100 mass% Sb It is displayed as each content of ₂ O ₃ and CeO ₂ . In this specification, such a notation is referred to as extra division.

  A total content means the total amount of content (including the case where content is 0%) of multiple types of glass component. Moreover, mass ratio means the ratio (ratio) of glass component content (a total content of multiple types of components is also included) in the mass% display.

  As used herein, the moldability of molten glass is sometimes simply referred to as “formability”. Moreover, in this specification, the thermal stability and devitrification resistance of glass both refer to the difficulty of crystal precipitation in glass. In particular, thermal stability refers to the difficulty of crystal precipitation when the molten glass solidifies, and devitrification resistance refers to crystal precipitation when the solidified glass is reheated as in reheat press. It shall refer to nigakusa.

  In the optical glass according to the present embodiment, the refractive index nd is greater than 1.85 and less than 1.90, and the Abbe number νd is 15 or more and 25 or less. Hereinafter, the optical glass according to the present embodiment will be described in detail.

In the optical glass according to the present embodiment, the total content [P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ ] of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ is 26%. That's it. The total content [P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ ] is preferably 26.5% or more, more preferably 27% or more, 27.5% or more, and 28% or more in this order. . The total content [P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ ] is preferably 45% or less, and more preferably 40% or less, 37% or less, and 35% or less in this order.

P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ are known as glass network forming components. These glass networking components improve devitrification resistance. Moreover, it has the function which suppresses that the viscosity of a molten glass falls excessively and makes a molten glass easy to shape | mold. Therefore, in the embodiment of the present invention, by making the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O _{3 in} the above range, an optical glass excellent in moldability and devitrification resistance Is obtained.

In the optical glass according to the present _embodiment, B and content _{2 O 3, P 2 O 5} , B 2 O 3, the mass ratio of the total content of SiO ₂ and _{Al 2 O 3 [B 2 O} 3 / ( _{P 2 O 5 + B 2 O} 3 + SiO 2 + Al 2 O 3)] is 0.11 or more 0.24 or less. The mass ratio [B ₂ O ₃ / (P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ )] is preferably 0.13 or more, more preferably 0.15 or more, 0.16 or more, and 0.0. More preferred is an order of 17 or more. Further, the mass ratio [B ₂ O ₃ / (P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ )] is preferably 0.22 or less, and further 0.21 or less, 0.20 or less, More preferable in order of 0.19 or less.

B ₂ O ₃ has a function of improving moldability among glass network forming components. On the other hand, if the content of B ₂ O ₃ is large, devitrification is likely to deteriorate. In the embodiment of the present invention, an optical glass excellent in moldability and devitrification resistance can be obtained by setting the content ratio of B ₂ O ₃ in the network forming component in the above range.

In the optical glass according to the present embodiment, the total content of Li ₂ O, Na ₂ O and K ₂ O [Li ₂ O + Na ₂ O + K ₂ O], P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O weight ratio of the total content of _{3 [(Li 2 O + Na} 2 O + K 2 O) / (P 2 O 5 + B 2 O 3 + SiO 2 + Al 2 O 3)] is 0.35 or more 0.56 or less . The mass ratio [(Li ₂ O + Na ₂ O + K ₂ O) / (P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ )] is preferably 0.40 or more, more preferably 0.45 or more, and 0.0. It is more preferable in the order of 48 or more and 0.50 or more. Further, the mass ratio [(Li ₂ O + Na ₂ O + K ₂ O) / (P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ )] is preferably 0.55 or less, more preferably 0.54 or less. More preferable in the order of 0.53 or less.

Li ₂ O, Na ₂ O, and K ₂ O all have a function of improving the meltability, but when these contents increase, the devitrification resistance decreases. In the embodiment of the present invention, by setting the content ratio of Li ₂ O, Na ₂ O and K ₂ O to the network forming component in the above range, an optical glass excellent in moldability and devitrification resistance can be obtained.

In the optical glass according to the present embodiment, the content of _{TiO 2, TiO 2, Nb 2} O 5, the mass ratio of the total content of WO ₃ and _{Bi 2 O 3 [TiO 2 /} (TiO 2 + Nb 2 O 5 + WO ₃ + Bi ₂ O ₃ )] is 0.12 or more and 0.32 or less. The mass ratio [TiO ₂ / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )] is preferably 0.15 or more, more preferably 0.18 or more, 0.20 or more, and 0.21 or more. Is more preferable. The mass ratio [TiO ₂ / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )] is preferably 0.30 or less, more preferably 0.28 or less, 0.26 or less, or 0.24 or less. Is more preferable.

TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ are all glass components that contribute to high dispersion, but also cause increased coloring. In particular, TiO ₂ greatly contributes to high dispersion as compared with Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ , but tends to increase the coloring of the glass. Further, TiO ₂ has a function of facilitating crystal formation in the glass in the process of forming and gradually cooling the molten glass and lowering the transparency (white turbidity) of the glass. Therefore, in the embodiment of the present invention, by setting the content ratio of TiO ₂ in TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ within the above range, an optical glass having high dispersion and excellent transmittance can be obtained. It is done.

(Glass component)
The glass component of the optical glass according to the present embodiment will be described in detail below.

In the optical glass according to the present embodiment, the content of P ₂ O ₅ is preferably 18% or more, and more preferably 20% or more, 21% or more, and 22% or more. The content of P ₂ O ₅ is preferably 32% or less, and more preferably 28% or less, 26% or less, and 25% or less.

P ₂ O ₅ is an essential component for containing many highly dispersed components in the glass. On the other hand, if P ₂ O ₅ is excessively contained, the thermal stability is deteriorated. Therefore, the content of P ₂ O ₅ is preferably in the above range.

In the optical glass according to the present embodiment, the content of B ₂ O ₃ is preferably 0.1% or more, and more preferably 2% or more and 3% or more. Further, the content of B ₂ O ₃ is preferably 12% or less, and more preferably 9% or less, 7% or less, and 6% or less in this order.

B ₂ O ₃ is a glass network-forming component and has a function of improving the thermal stability of the glass. On the other hand, if the content of B ₂ O ₃ is large, preventing the highly dispersed, also tend to devitrification resistance is decreased. Therefore, from the viewpoint of improving the thermal stability and devitrification resistance of the glass, the content of B ₂ O ₃ is preferably in the above range.

In the optical glass according to the present embodiment, the content of SiO ₂ is preferably 3% or less, more preferably 2% or less and 1.5% or less in this order. The content of SiO ₂ may be 0%.

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

In the optical glass according to the present embodiment, the content of Al ₂ O ₃ is preferably 3% or less, and more preferably 2% or less and 1% or less. The content of Al ₂ O ₃ may be 0%.

Al ₂ O ₃ is a glass component having a function of improving the chemical durability and weather resistance of glass, and can be considered as a network forming component. On the other hand, when the content of Al ₂ O ₃ increases, the devitrification resistance of the glass decreases. In addition, problems such as an increase in the glass transition temperature Tg and a decrease in thermal stability are likely to occur. From the viewpoint of avoiding such a problem, the upper limit of the content of Al ₂ O ₃ is preferably within the above range.

In the optical glass according to the present embodiment, the content of TiO ₂ is preferably 3% or more, and more preferably 5% or more, 8% or more, and 10% or more. Further, the content of TiO ₂ is preferably 20% or less, and more preferably in the order of 18% or less, 16% or less, and 14% or less.

TiO ₂ greatly contributes to high dispersion. On the other hand, TiO ₂ is relatively easy to increase the coloration of the glass. In addition, TiO ₂ promotes crystal formation in the glass and lowers the transparency of the glass (white turbidity) in the process of forming an optical glass by forming and gradually cooling the molten glass. Therefore, the content of TiO ₂ is preferably in the above range.

In the optical glass according to the present embodiment, the content of Nb ₂ O ₅ is preferably 35% or more, and more preferably 38% or more, 40% or more, and 42% or more. The content of Nb ₂ O ₅ is preferably 56% or less, and more preferably 50% or less, 48% or less, and 46% or less.

Nb ₂ O ₅ is a component that contributes to high dispersion. It is also a glass component that improves the thermal stability and chemical durability of the glass. On the other hand, if the content of Nb ₂ O ₅ is too large, the thermal stability of the glass tends to decrease and the glass tends to become more colored. Therefore, in the optical glass according to the present embodiment, the Nb ₂ O ₅ content is preferably in the above range.

In the optical glass according to the present embodiment, the lower limit of the content of WO ₃ is preferably 0%. Further, the content of WO ₃ is preferably 5% or less, and more preferably 3% or less and 1% or less.

WO ₃ tends to cause coloring of the glass and deteriorates the transmittance. Therefore, the content of WO ₃ is preferably in the above range.

In the present embodiment, the content of Bi ₂ O ₃ is preferably 5% or less, and more preferably 3% or less and 2% or less. Moreover, the lower limit of the content of Bi ₂ O ₃ is preferably 0%.

Bi ₂ O ₃ has a function of improving the thermal stability of the glass by containing an appropriate amount. On the other hand, when the content of Bi ₂ O ₃ is increased, the coloring of the glass increases. Therefore, the content of Bi ₂ O ₃ is preferably in the above range.

In the optical glass according to the present embodiment, the total content [TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ ] of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ is preferably 45% or more. Furthermore, it is more preferable in the order of 50% or more, 52% or more, 54% or more. The total content [TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ ] is preferably 65% or less, more preferably 60% or less and 58% or less.

TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ contribute to high dispersion of the glass, and also have a function of improving the thermal stability of the glass by containing an appropriate amount. On the other hand, it is also a component that increases the coloration of the glass. Therefore, the total content [TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ ] is preferably in the above range.

In the optical glass according to the present embodiment, the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O _{3 and} the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ The mass ratio [(P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ ) / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )] preferably 0.40 or more and 0.60 or less It is. The mass ratio [(P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ ) / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )] is more preferably 0.42 or more, and further 0 .44 or more, 0.46 or more, and 0.48 or more in order. The mass ratio [(P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ ) / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )] is more preferably 0.58 or less, and Is more preferable in the order of 0.56 or less, 0.54 or less, and 0.52 or less.

TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ are all glass components that contribute to high dispersion. Therefore, the content ratio of these components and the network forming component is preferably in the above range.

In the optical glass according to this embodiment, the content of Li ₂ O is preferably 5% or less, and more preferably 3% or less and 1% or less. The lower limit of the content of Li ₂ O is preferably 0%.

In the optical glass according to the present embodiment, the content of Na ₂ O is preferably 12% or less, and more preferably 10% or less, 9% or less, and 8% or less in this order. The content of Na ₂ O is preferably 0% or more, and more preferably 3% or more, 5% or more, and 6% or more.

In the optical glass according to the present embodiment, the content of K ₂ O is preferably 12% or less, and more preferably 10% or less, 9% or less, and 8% or less. Further, the content of K ₂ O is preferably 0% or more, more preferably 3% or more, 5% or more, and 6% or more in order.

Li ₂ O, Na ₂ O and K ₂ O have a function of improving the thermal stability of the glass. However, when these contents increase, the thermal stability, chemical durability, and weather resistance decrease. . _Therefore, the content of Li 2 O, Na ₂ O and _{K 2} O is preferably each in the above range. In particular, Na ₂ O is preferably contained in order to improve thermal stability and devitrification resistance.

In the optical glass according to the present embodiment, the total content [Li ₂ O + Na ₂ O + K ₂ O] of Li ₂ O, Na ₂ O and K ₂ O is preferably 20% or less, more preferably 18% or less, 16 % Or less is preferable. The total content [Li ₂ O + Na ₂ O + K ₂ O] is preferably 8% or more, and more preferably 10% or more, 12% or more, and 13% or more.

Li ₂ O, Na ₂ O and K ₂ O all have a function of improving the thermal stability of the glass. However, when these contents increase, chemical durability and weather resistance are lowered. Therefore, the total content [Li ₂ O + Na ₂ O + K ₂ O] of Li ₂ O, Na ₂ O and K ₂ O is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of Cs ₂ O is preferably 2%. Moreover, the lower limit of the content of Cs ₂ O is preferably 0%.

Cs ₂ O has a function of improving the thermal stability of the glass, but when the content is increased, the thermal stability, chemical durability, and weather resistance of the glass are lowered. Therefore, each content of Cs ₂ O is preferably in the above range.

  In the optical glass according to this embodiment, the content of MgO is preferably 5% or less, and more preferably 3% or less and 1% or less. Further, the lower limit of the content of MgO is preferably 0%. The content of MgO may be 0%.

  In the optical glass according to the present embodiment, the CaO content is preferably 5% or less, and more preferably 3% or less and 1% or less. Moreover, the lower limit of the CaO content is preferably 0%. The content of CaO may be 0%.

  In the optical glass according to the present embodiment, the content of SrO is preferably 5% or less, and more preferably 3% or less and 1% or less. Moreover, the lower limit of the SrO content is preferably 0%.

  In the optical glass according to the present embodiment, the upper limit of the content of BaO is preferably 5%, and more preferably 3% or less and 1% or less. Moreover, the lower limit of the BaO content is preferably 0%.

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

  In the optical glass according to this embodiment, the total content [MgO + CaO + SrO + BaO] of MgO, CaO, SrO and BaO is preferably 6% or less, and more preferably 4% or less and 2% or less. Moreover, the lower limit of the total content [MgO + CaO + SrO + BaO] is preferably 0%. From the viewpoint of maintaining thermal stability and devitrification resistance without hindering high dispersion, the total content [MgO + CaO + SrO + BaO] is preferably in the above range.

  In the optical glass according to this embodiment, the content of ZnO is preferably 5% or less, and more preferably 3% or less and 1% or less. Moreover, the lower limit of the ZnO content is preferably 0%.

  ZnO is a glass component having a function of improving the thermal stability of glass. However, when there is too much content of ZnO, the high dispersibility of glass will be impaired. Therefore, from the viewpoint of improving the thermal stability of the glass and maintaining desired optical properties, the content of ZnO is preferably in the above range.

In the optical glass according to the present embodiment, the content of ZrO ₂ is preferably 5% or less, more preferably 3% or less and 1% or less. Further, the lower limit of the content of ZrO ₂ is preferably 0%.

ZrO ₂ is a glass component that functions to improve the thermal stability and devitrification resistance of glass. However, if the content of ZrO ₂ is too large, the thermal stability tends to decrease. Therefore, the content of ZrO ₂ is preferably in the above range from the viewpoint of maintaining good thermal stability and devitrification resistance of the glass.

In the optical glass according to the present embodiment, the content of Ta ₂ O ₅ is preferably 5% or less, and more preferably 3% or less and 2% or less. Further, the lower limit of the content of Ta ₂ O ₅ is preferably 0%.

Ta ₂ O ₅ is a glass component having a function of improving the thermal stability and devitrification resistance of glass. On the other hand, Ta ₂ O ₅ increases the refractive index and lowers the dispersion of the glass. Further, when the content of Ta ₂ O ₅ is increased, the thermal stability of the glass is lowered, and when the glass is melted, unmelted glass raw material tends to be generated. Therefore, the content of Ta ₂ O ₅ is preferably in the above range. Furthermore, Ta ₂ O ₅ is an extremely expensive component compared to other glass components, and the production cost of glass increases as the content of Ta ₂ O ₅ increases. Furthermore, since Ta ₂ O ₅ has a higher molecular weight than other glass components, it increases the specific gravity of the glass and consequently increases the weight of the optical element.

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

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

Sc ₂ O ₃ and HfO ₂ both have a function of increasing the refractive index nd and are expensive components. Therefore, each content of Sc ₂ O ₃ and HfO ₂ is preferably in the above range.

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

Lu ₂ O ₃ has a function of increasing the refractive index nd. It is also a glass component that increases the specific gravity of glass because of its high molecular weight. Therefore, the content of Lu ₂ O ₃ is preferably in the above range.

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

GeO ₂ functions to increase the refractive index nd, and is a prominently expensive component among commonly used glass components. Therefore, from the viewpoint of reducing the manufacturing cost of glass, the GeO ₂ content is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of La ₂ O ₃ is preferably 2%. Moreover, the lower limit of the content of La ₂ O ₃ is preferably 0%. The content of La ₂ O ₃ may be 0%.

When the content of La ₂ O ₃ is increased, the thermal stability and devitrification resistance of the glass are lowered, and the glass is easily devitrified during production. Therefore, from the viewpoint of suppressing a decrease in thermal stability and devitrification resistance, the content of La ₂ O ₃ is preferably in the above range.

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

When the content of Gd ₂ O ₃ is too large, the thermal stability and devitrification resistance of the glass are lowered, and the glass is easily devitrified during production. On the other hand, if the content of Gd ₂ O ₃ is too large, the specific gravity of the glass increases, which is not preferable. Therefore, the content of Gd ₂ O ₃ is preferably in the above range from the viewpoint of suppressing an increase in specific gravity while maintaining the thermal stability and devitrification resistance of the glass well.

In the optical glass according to the present embodiment, the upper limit of the content of Y ₂ O ₃ is preferably 2%. Moreover, the lower limit of the content of Y ₂ O ₃ is preferably 0%. The content of Y ₂ O ₃ may be 0%.

When the content of Y ₂ O ₃ is too large, the thermal stability and devitrification resistance of the glass are lowered. Therefore, the content of Y ₂ O ₃ is preferably in the above range from the viewpoint of suppressing the decrease in thermal stability and devitrification resistance.

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

Since Yb ₂ O ₃ has a higher molecular weight than La ₂ O ₃ , Gd ₂ O ₃ , and Y ₂ O ₃ , it increases the specific gravity of the glass. As the specific gravity of the glass increases, the mass of the optical element increases. For example, if a lens with a large mass is incorporated into an autofocus imaging lens, the power required to drive the lens during autofocus increases, and battery consumption becomes severe. Therefore, it is desirable to reduce the content of Yb ₂ O ₃ to suppress an increase in the specific gravity of the glass.

Furthermore, the thermal stability and devitrification resistance of the glass when the content of Yb ₂ O ₃ is too large is reduced. From the viewpoint of preventing a decrease in the thermal stability of the glass and suppressing an increase in specific gravity, the content of Yb ₂ O ₃ is preferably in the above range.

The optical glass according to the present embodiment is mainly composed of the glass components described above, that is, P ₂ O ₅ , B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, Cs ₂ O, MgO, CaO, SrO, BaO, ZnO, ZrO ₂ , Ta ₂ O ₅ , Sc ₂ O ₃ , HfO ₂ , Lu ₂ O ₃ , GeO ₂ , la ₂ O _{3, Gd} 2 _{O 3,} Y 2 _{O 3,} and _Yb is preferably configured in 2 _{O 3,} the total content of the glass component described above is preferably larger than the 95%, 98 % Is more preferable, more than 99% is more preferable, and more than 99.5% is still more preferable.

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

Since TeO ₂ has toxicity, it is preferable to reduce the content of TeO ₂ . Therefore, the content of TeO ₂ is preferably in the above range.

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

<Other component composition>
Pb, As, Cd, Tl, Be and Se are all toxic. Therefore, it is preferable that the optical glass according to the present embodiment does not contain these elements as glass components.

  U, Th, and Ra are all radioactive elements. Therefore, it is preferable that the optical glass according to the present embodiment does not contain these elements as glass components.

  V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, and Tm can increase the coloration of the glass and become a source of fluorescence. Therefore, it is preferable that the optical glass according to the present embodiment does not contain these elements as glass components.

Sb (Sb ₂ O ₃ ) and Ce (CeO ₂ ) are arbitrarily addable elements that function as a fining agent. Among these, Sb (Sb ₂ O ₃ ) is a fining agent having a large fining effect. However, Sb (Sb ₂ O ₃ ) is highly oxidizable, and increasing the amount of Sb (Sb ₂ O ₃ ) is not preferable because the glass coloration increases due to light absorption by Sb ions. Further, when Sb is present in the melt when melting the glass, elution of platinum constituting the glass melt crucible into the melt is promoted, and the platinum concentration in the glass increases. In the glass, when platinum is present as ions, the coloration of the glass increases due to light absorption. Moreover, when platinum exists in glass as a solid substance, it will become a light-scattering source and will reduce the quality of glass. Ce (CeO ₂ ) has a smaller refining effect than Sb (Sb ₂ O ₃ ). When Ce (CeO ₂ ) is added in a large amount, the coloring of the glass is strengthened. Therefore, when adding a clarifier, it is preferable to add Sb (Sb ₂ O ₃ ) while paying attention to the amount added.

The content of Sb ₂ O ₃ is displayed on an external basis. That is, the content of Sb ₂ O ₃ when the total content of all glass components other than Sb ₂ O ₃ and CeO ₂ is 100% by mass is preferably less than 1% by mass, more preferably 0.5% by mass. Is less than. Furthermore, is preferable in the order of less than 0.1% by mass, less than 0.05% by mass, and less than 0.03% by mass. Content of Sb ₂ O ₃ may be 0 mass%.

The content of CeO ₂ is also displayed as an outside display. That is, when the total content of all glass components other than CeO ₂ and Sb ₂ O ₃ is 100% by mass, the content of CeO ₂ is preferably less than 2% by mass, more preferably less than 1% by mass, and even more preferably Is less than 0.5% by weight, more preferably less than 0.1% by weight. The CeO ₂ content may be 0% by mass. By setting the content of CeO _{2 in} the above range, the clarity of the glass can be improved.

(Glass properties)
In the optical glass according to the present embodiment, the refractive index nd is greater than 1.85 and less than 1.90. The refractive index nd is preferably 1.855 or more, more preferably 1.860 or more and 1.865 or more. The refractive index nd is preferably 1.890 or less, more preferably 1.885 or less, 1.880 or less, and 1.875 or less.

  In the optical glass according to the present embodiment, the Abbe number νd is 15 or more and 25 or less. The Abbe number νd is preferably 16 or more, and more preferably in the order of 17 or more, 18 or more, and 19 or more. The Abbe number νd is preferably 24 or less, and more preferably in the order of 23 or less, 22 or less, and 21 or less.

<Crystal melting peak temperature Tl>
The crystal melting peak temperature Tl is a temperature at which all pseudo crystals in the glass disappear, and correlates with the liquidus temperature. For example, when the crystal melting peak temperature Tl becomes high, the glass temperature at the time of molding needs to be kept high, so that the viscosity of the molten glass is excessively lowered and the formability deteriorates.

The crystal melting peak temperature Tl varies depending on the components contained in the glass. In the present embodiment, in order to increase the refractive index nd of the glass, it is necessary to contain a large amount of a high refractive index component such as Nb ₂ O ₅ or TiO _2. It is also a component that increases Tl. Furthermore, in order to stably contain these components in the glass, it is necessary to simultaneously increase the content of network forming components such as P ₂ O ₅ and B ₂ O ₃ . Here, a network formation component has the effect | action which suppresses the viscosity fall of molten glass. That is, as the refractive index nd of the glass increases, the crystal melting peak temperature Tl apparently increases, but a decrease in viscosity of the molten glass, that is, deterioration of formability may be suppressed.

FIG. 1 shows the relationship between the refractive index nd of glass and the crystal melting peak temperature Tl (° C.) obtained in this embodiment. In FIG. 1, the glass with good formability is shown as an example (diamond plot), and the glass other than the example is shown as a comparative example (square plot). Thus, it can be seen that the preferred crystal melting peak temperature Tl tends to increase as the refractive index nd of the glass increases. From FIG. 1, the preferable crystal melting peak temperature Tl with respect to the refractive index nd of the glass is expressed by the following formula (2).
Tl <1000nd-790 (2)
A more preferable crystal melting peak temperature Tl is represented by the following formula (3).
Tl <1300nd-1364 (3)

  The crystal melting peak temperature Tl can be determined by differential scanning calorimetry (DSC (Differential Scanning Calorimetry)). FIG. 2 is an example of a DSC chart. The vertical axis represents the differential scanning calorific value (DSC), and the horizontal axis represents the sample temperature (T). The DSC chart has regions that exhibit glass transition, crystallization, and crystal melting. The crystal melting peak temperature Tl is a temperature at which DSC shows a peak in the crystal melting region of FIG. Note that the crystal melting start temperature in FIG. 2 is a temperature at which DSC starts to rise in the crystal melting region. By DSC, the crystal melting peak temperature Tl that is an index of the liquidus temperature can be obtained with high accuracy and relatively easily.

<Glass transition temperature Tg>
The glass transition temperature Tg of the optical glass according to this embodiment is preferably 750 ° C. or lower, and more preferably in the order of 730 ° C. or lower and 710 ° C. or lower. The glass transition temperature Tg is preferably 520 ° C. or higher, and more preferably 560 ° C. or higher and 600 ° C. or higher.

  When the upper limit of the glass transition temperature Tg satisfies the above range, an increase in the annealing temperature of the glass can be suppressed, and thermal damage of annealing equipment such as continuous annealing called a layer or batch annealing furnace can be reduced. .

  When the lower limit of the glass transition temperature Tg satisfies the above range, the thermal stability of the glass can be easily maintained well while maintaining the desired Abbe number and refractive index.

<Light transmittance of glass>
In the present embodiment, the light transmittance can be evaluated by the coloring degree λ5.
Using glass with two planes parallel to each other and optically polished (thickness 10.0 mm ± 0.1 mm), light is incident perpendicularly to this plane from one of the two planes. Let Then, the ratio (Iout / Iin) of the intensity Iout of the transmitted light emitted from the other plane and the intensity Iin of the incident light, that is, the external transmittance is calculated. A spectral transmittance curve is obtained by measuring the external transmittance using a spectrophotometer while scanning the wavelength of incident light in the range of, for example, 280 to 700 nm.

  The external transmittance increases as the wavelength of incident light goes from the absorption edge on the short wavelength side of the glass toward the long wavelength side, and shows a high value.

  λ5 is a wavelength at which the external transmittance is 5%. In the wavelength range of 280 to 700 nm, the external transmittance of the glass on the longer wavelength side than λ5 is greater than 5%.

  By using optical glass having a shorter wavelength of λ5, an optical element capable of suitable color reproduction can be provided.

  For these reasons, the range of λ5 is preferably 400 nm or less, and more preferably 390 nm or less. The lower limit of λ5 is, for example, 360 nm.

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

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

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

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

  Examples of the optical element include various lenses such as a spherical lens, a prism, a diffraction grating, and the like.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the following examples.

(Example)
[Production of glass samples]
Example No. shown in Tables 1 and 2 Compound raw materials corresponding to the respective components, that is, raw materials such as phosphates, carbonates, oxides, and the like were weighed and mixed sufficiently so as to obtain a glass having a composition of 1 to 32, thereby preparing a mixed raw material. The prepared raw material was put into a platinum crucible, heated to 1000 to 1350 ° C. in an atmospheric atmosphere to melt, and homogenized and refined by stirring to obtain a molten glass. The molten glass was cast into a mold and molded, followed by slow cooling to obtain a block-shaped glass sample.

[Evaluation of glass sample]
With respect to the obtained glass sample, the glass composition, specific gravity, refractive index nd, Abbe number νd, λ5, glass transition temperature Tg and crystal melting peak temperature Tl were measured by the following methods. The permeability was evaluated.

[1] Glass composition An appropriate amount of the glass sample obtained as described above was collected, treated with an acid and an alkali, and the content of the glass component was measured by ICP-AES. The results are shown in Tables 1 and 2.

[2] Specific gravity Measured based on Japan Optical Glass Industry Association Standard JOGIS-05. The results are shown in Tables 4 and 5.

[3] Refractive index nd and Abbe number νd
It measured based on Japan Optical Glass Industry Association standard JOGIS-01. The results are shown in Tables 4 and 5.

[4] Glass transition temperature Tg, crystal melting peak temperature Tl
The glass transition temperature Tg and the crystal melting peak temperature Tl were determined based on the DSC chart when the glass in the solid state was heated using a differential scanning calorimeter DSC3300SA (NETZSCH Japan). The results are shown in Tables 4 and 5.

[5] λ5
The glass sample was processed to have a plane that was 10 mm in thickness and parallel to each other and optically polished, and the spectral transmittance in a wavelength range from 280 nm to 700 nm was measured. Spectral transmittance B / A was calculated by setting the intensity of light incident perpendicularly to one plane polished optically as intensity A and the intensity of light exiting from the other plane as intensity B. The wavelength at which the spectral transmittance is 5% is λ5. The spectral transmittance includes a reflection loss of light rays on the sample surface. The results are shown in Tables 4 and 5.

[6] Formability In this embodiment, the formability of the molten glass was evaluated based on whether or not the crystal melting peak temperature Tl satisfies the following formula (2). When the crystal melting peak temperature Tl calculated | required by said [4] satisfy | fills Formula (2), it determined with (circle), and when not satisfy | filling following formula (2), it determined with x. The results are shown in Tables 4 and 5.
Tl <1000nd-790 (2)
Glass No. of an Example. 1 to 32 were all judged as “good”. Glass No. of an Example. 1 to 32 were confirmed to be glasses excellent in moldability of molten glass.

[7] Softening test (devitrification resistance)
The softening test is an evaluation method that serves as an index of devitrification resistance in the present embodiment. A 1 cm square glass sample was heated for 10 minutes in a first test furnace set to the glass transition temperature Tg of the glass, and further to a second test furnace set to a temperature 120 to 200 ° C. higher than the Tg of the glass. After heating for 10 minutes, the presence or absence of crystals or cloudiness was confirmed with an optical microscope. The observation magnification of the optical microscope was 10 to 100 times. When neither crystal nor white turbidity was confirmed, it was judged as “good”, and when at least one of crystal and white turbidity was confirmed, it was judged as “poor”. The results are shown in Tables 4 and 5. Glass No. of an Example. 1 to 32 were all judged as “good”. Glass No. of an Example. 1 to 32 were confirmed to be glasses having excellent devitrification resistance.

(Comparative example)
(Production and evaluation of glass sample No. 33-41)
The production and evaluation of the glass were carried out in accordance with Example Glass No. It carried out by the method similar to 1-32. The results are shown in Tables 3 and 6.

  Comparative Example Glass No. The glasses Nos. 33 to 41 are evaluated as x in the evaluation of formability or softening test. The comparative glass was inferior in thermal stability or devitrification resistance as compared with the glass of the example.

(Production of optical element blank)
No. shown in Tables 1 and 2. A glass sample having a composition of 1 to 32 was annealed, cut, and ground to produce a cut piece.
The cut piece was press-molded by reheat press to produce an optical element blank.

  The optical element blank was precisely annealed and the refractive index was adjusted precisely to obtain the required refractive index, and then ground and polished by a known method to obtain an optical element.

Claims (5)

In the oxide-based glass composition,
The total content [P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ ] of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ is 26% by mass or more,
And the content of _{B 2 O 3, P 2 O} 5, B 2 O 3, the mass ratio of the total content of SiO ₂ and _{Al 2 O 3 [B 2 O} 3 / (P 2 O 5 + B 2 O 3 + SiO ₂ + Al ₂ O ₃ )] is 0.11 or more and 0.24 or less,
Mass ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O and the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ [(Li ₂ O + Na ₂ O + K ₂ O) / (P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ )] is 0.35 or more and 0.56 or less,
And the content of _{TiO 2, TiO 2, Nb 2} O 5, WO 3 and _Bi 2 mass ratio of the total content of _{O 3 [TiO 2 / (TiO} 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3)] is 0.12 or more and 0.32 or less,
An optical glass having a refractive index nd of more than 1.85 and less than 1.90, and an Abbe number νd of 15 or more and 25 or less. The optical glass according to claim 1, wherein the content of Bi ₂ O ₃ is less than 5% by mass. Mass ratio of the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O _{3 and} the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ [(P ₂ The optical device according to claim 1, wherein O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ ) / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )] is 0.40 or more and 0.60 or less. Glass.   An optical element blank made of the optical glass according to claim 1.   The optical element which consists of optical glass in any one of Claims 1-3.

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