Optical glass, optical element, and preform

Abstract

To provide an optical glass that has an optical property of a high refractive index and low dispersion and in which devitrification can be further reduced and can be obtained stably, and to provide a preform and an optical element using the optical glass.SOLUTION: An optical glass contains, in cation % (mole %) representation, P5+ by 17.0% or more and 42.0% or less, Al3+ by 7.0% or more and 30.0% or less, Mg2+ by more than 0% and 22.0% or less, and Ca2+ by more than 0% and 25.0% or less, Sr2+ by more than 0% and 30.0% or less, and Ba2+ by more than 0% and 35.0% or less, and in which, in anion % (mole %) representation, a content of F- is 37.0 to 64.0%, a content of O2- is 36.0 to 63.0%, a refractive index (nd) is 1.48 or more and 1.58 or less, an Abbe number (νd) is 70 or more and 88 or less, and a liquidus temperature is 800°C or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to optical glass, optical elements, and preforms.

Background Art

[0002] In recent years, the digitalization and high definition of devices using optical systems have been rapidly progressing. In the fields of various optical devices such as imaging devices like digital cameras and video cameras, and image reproduction (projection) devices like projectors and projection TVs, there is an increasing demand to reduce the number of optical elements such as lenses and prisms used in the optical system, and to lighten and miniaturize the entire optical system.

[0003] As a material for optical elements constituting an optical system, there is a very high demand for high refractive index and low dispersion glass having a refractive index (n d ) of 1.48 or more and 1.58 or less and an Abbe number (ν d ) of 70 or more and 88 or less. As such high refractive index and low dispersion glass, for example, glass compositions represented by Patent Documents 1 to 3 are known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, fluorophosphate-based glass as described in Patent Documents 1 and 2 has a concern of devitrification, especially when producing glass or performing heat forming of glass. Therefore, a high refractive index and low dispersion glass capable of further reducing devitrification and stably obtaining it is desired.

[0006] The present invention has been made in view of the above problems, and an object thereof is to provide an optical glass having optical properties of high refractive index and low dispersion, and capable of more reducing devitrification and stably obtaining the same, a preform using the same, and an optical element.

Means for Solving the Problems

[0007] In order to solve the above problems, the present inventors have conducted intensive tests and studies. As a result, as a cation component, P 5+ , Al 3+ , Mg 2+ , Ca 2+ and Ba 2+ are contained in the glass, and by adjusting the content of each component, it has been found that a stable glass having a low liquidus temperature can be obtained while having a desired refractive index and Abbe number, and the present invention has been completed. Specifically, the present invention provides the following.

[0008] (1) In terms of cation% (mol%), P 5+ is 17.0% or more and 42.0% or less, Al 3+ is 7.0% or more and 30.0% or less, Mg 2+ is more than 0% and 22.0% or less, Ca 2+ is more than 0% and 25.0% or less, Sr 2+ is more than 0% and 30.0% or less, Ba 2+ is more than 0% and 35.0% or less contained, In terms of anion% (mol%), F - the content rate is 37.0 to 64.0%, O 2- the content rate is 36.0 to 63.0% and, the refractive index (nd) is 1.48 or more and 1.58 or less, and has an Abbe number (νd) of 70 or more and 88 or less, An optical glass having a liquidus temperature of 800 ° C or lower.

[0009] (2) Mg 2+ 、Ca 2+ 、Sr 2+ and Ba 2+ The total content rate (R 2+ : cation %) of one or more selected from the group consisting of is 37.0 to 63.0% for the optical glass described in (1).

[0010] (3) In terms of cation % (mol %), The content rate of La 3+ is 0 to 10.0%, The content rate of Gd 3+ is 0 to 12.0%, The content rate of Y 3+ is 0 to 12.0%, The content rate of Yb 3+ is 0 to 10.0%, The content rate of Lu 3+ is 0 to 10.0% for the optical glass described in (1) or (2).

[0011] (4) La 3+ 、Gd 3+ 、Y 3+ 、Yb 3+ and Lu 3+ The total content rate (Ln 3+ : cation %) of one or more selected from the group consisting of is 13.0% or less for the optical glass described in any one of (1) to (3).

[0012] (5) In terms of cation % (mol %), The content rate of Li + is 0 to 10.0%, The content rate of Na + is 0 to 10.0%, The content rate of K + is 0 to 10.0% for the optical glass described in any one of (1) to (4).

[0013] (6) Li + 、Na + and K + The total content rate (Rn +: The optical glass according to any one of (1) to (5) wherein the cation % is 10.0% or less.

[0014] (7) In terms of cation % (mol %), Si 4+ the content is 0 to 10.0%, B 3+ the content is 0 to 10.0%, Zn 2+ the content is 0 to 10.0%, Ti 4+ the content is 0 to 10.0%, Nb 5+ the content is 0 to 10.0%, W 6+ the content is 0 to 10.0%, Zr 4+ the content is 0 to 10.0%, Ta 5+ the content is 0 to 10.0%, Ge 4+ the content is 0 to 10.0%, Bi 3+ the content is 0 to 10.0%, Te 4+ the content is 0 to 10.0% is the optical glass according to any one of (1) to (6).

[0015] (8) An optical element made of the optical glass according to any one of (1) to (7).

[0016] (9) A preform for polishing and / or precision mold press forming made of the optical glass according to any one of (1) to (7).

Advantages of the Invention

[0017] According to the present invention, an optical glass having high refractive index and low dispersion optical characteristics and being difficult to devitrify and stably obtainable, and a preform and an optical element using the same can be obtained.

Modes for Carrying Out the Invention

[0018] The optical glass of the present invention is expressed in cation % (mol %), and P 5+ is 17.0% or more and 42.0% or less, Al 3+ is 7.0% or more and 30.0% or less, Mg 2+ is more than 0% and 22.0% or less, Ca 2+ is more than 0% and 25.0% or less, Sr 2+ is more than 0% and 30.0% or less, Ba 2+ is more than 0% and 35.0% or less, and in terms of anion % (mol %), the content of F - is 37.0 to 64.0%, and the content of O 2- is 36.0 to 63.0%. The refractive index (nd) is 1.48 or more and 1.58 or less, and it has an Abbe number (νd) of 70 or more and 88 or less, and the liquidus temperature is 800 °C or lower. As the cation components, P 5+ , Al 3+ , Mg 2+ , Ca 2+ and Ba 2+ are contained in the glass, and by adjusting the content of each component, an optical glass having high refractive index and low dispersion optical properties and a low liquidus temperature can be obtained, so that an optical glass that is difficult to devitrify and can be stably obtained can be obtained.

[0019] Hereinafter, embodiments of the optical glass of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. Note that, for parts where the description overlaps, the description may be omitted as appropriate, but it does not limit the gist of the invention.

[0020] <Glass components> Each component constituting the optical glass of the present invention will be described. In this specification, unless otherwise specified, the content of each component is expressed as cation % or anion % based on the molar ratio. Here, "cation %" and "anion %" (hereinafter, may be referred to as "cation % (mol%)" and "anion % (mol%)") are compositions in which the glass constituent components of the optical glass of the present invention are separated into cation components and anion components, and the total ratio in each is set to 100 mol%, and the content of each component contained in the glass is described. Note that since the ionic valence of each component is merely using a representative value for convenience, it is not to distinguish from those of other ionic valences. The ionic valence of each component present in the optical glass may be other than the representative value. For example, P is usually present in the glass in a state with an ionic valence of 5, so in this specification, "P 5+ " is represented, but it may be present in other ionic valence states. Thus, even if it is strictly present in other ionic valence states, in this specification, each component is treated as being present in the glass with the ionic valence of the representative value.

[0021] [Regarding the cation component] P 5+ is a glass-forming component, has the property of lowering the liquidus temperature of the glass to reduce devitrification, and increasing the refractive index. Therefore, the content of P 5+ is preferably 17.0% or more, more preferably more than 20.0%, still more preferably more than 23.0%, still more preferably more than 26.0%, and still more preferably 28.0% or more. On the other hand, by reducing the content of P 5+ within the range of 42.0% or less, the Abbe number can be increased. Therefore, the content of P 5+ is preferably capped at 42.0%, more preferably less than 39.0%, still more preferably less than 36.0%, and still more preferably less than 33.0%.

[0022] Al 3+ is a component that lowers the liquidus temperature of the glass to reduce devitrification, increases the Abbe number, and has the property of lowering the abrasion degree. Therefore, Al 3+The content rate is preferably 7.0% or more, more preferably more than 10.0%, still more preferably more than 13.0%, and even more preferably more than 15.0%. On the other hand, by reducing the content rate of Al 3+ within the range of 30.0% or less, the refractive index can be increased. Therefore, the content rate of Al 3+ is preferably capped at 30.0%, more preferably less than 27.0%, still more preferably less than 25.0%, even more preferably less than 23.0%, and even more preferably less than 21.0%.

[0023] Mg 2+ has the property of lowering the liquidus temperature of the glass to reduce devitrification and lowering the abrasion degree. Therefore, the lower limit of the content rate of Mg 2+ is preferably more than 0%, more preferably more than 1.0%, still more preferably more than 3.0%, even more preferably more than 5.0%, and even more preferably 5.7% or more. On the other hand, by reducing the content rate of Mg 2+ within the range of 22.0% or less, devitrification due to excessive content can be reduced, and it becomes easier to obtain a desired high refractive index. Therefore, the content rate of Mg 2+ is preferably capped at 22.0%, more preferably less than 20.0%, still more preferably less than 17.0%, even more preferably less than 15.0%, and even more preferably less than 13.0%.

[0024] Ca 2+ has the property of lowering the liquidus temperature of the glass to reduce devitrification, suppressing the decrease in refractive index, and lowering the abrasion degree. Therefore, the lower limit of the content rate of Ca 2+ is preferably more than 0%, more preferably more than 1.0%, still more preferably more than 3.0%, and even more preferably more than 5.0%. On the other hand, by reducing the content rate of Ca 2+ within the range of 25.0% or less, devitrification due to excessive content can be reduced, and it becomes easier to obtain a desired high refractive index. Therefore, the content rate of Ca 2+The content rate preferably has an upper limit of 25.0%, more preferably less than 22.0%, still more preferably less than 20.0%, and even more preferably less than 17.0%.

[0025] Sr 2+ When the content exceeds 0%, it has the property of lowering the liquidus temperature of the glass to reduce devitrification and suppressing the decrease in refractive index. Therefore, Sr 2+ The content rate is preferably more than 0%, more preferably more than 1.0%, still more preferably more than 3.0%, and even more preferably more than 5.0%. On the other hand, by reducing the content rate of Sr 2+ within the range of 30.0% or less, devitrification due to excessive content can be reduced, and a desired high refractive index can be easily obtained. Therefore, Sr 2+ The content rate preferably has an upper limit of 30.0%, more preferably less than 27.0%, still more preferably less than 24.0%, and even more preferably less than 21.0%.

[0026] Ba 2+ has the property of enhancing the devitrification resistance of the glass, maintaining low dispersibility, and increasing the refractive index. Therefore, Ba 2+ The content rate is preferably more than 0%, more preferably more than 1.0%, still more preferably more than 3.0%, even more preferably more than 5.0%, and even more preferably more than 8.0%. On the other hand, by reducing the content rate of Ba 2+ within the range of 35.0% or less, the devitrification resistance of the glass can be enhanced and the specific gravity can be reduced. Therefore, Ba 2+ The content rate preferably has an upper limit of 35.0%, more preferably less than 32.0%, still more preferably less than 30.0%, even more preferably less than 27.0%, and even more preferably less than 25.0%.

[0027] R 2+ is one or more selected from the group consisting of Mg 2+ Ca 2+ Sr 2+ and Ba 2+ In addition, the total content rate of R 2+ is Mg 2+ Ca2+ 、Sr 2+ and Ba 2+ is one or more selected from the group consisting of in total. Here, by setting the total content rate of R 2+ within the range of 37.0 to 63.0%, a glass with a lower liquid phase temperature and higher devitrification resistance can be obtained. Therefore, the lower limit of the total content rate of R 2+ is preferably 37.0% or more, more preferably more than 40.0%, still more preferably more than 43.0%, and still more preferably more than 46.0%. Also, the upper limit of the total content rate of R 2+ is preferably 63.0% or less, more preferably less than 60.0%, still more preferably less than 57.0%, and still more preferably less than 54.0%.

[0028] The optical glass of the present invention has a ratio (R 3+ total content rate (cation%) of R to the Al 2+ content rate (cation%)) (R 2+ / Al 3+ ) preferably in the range of 1.50 or more and 6.00 or less. In particular, by setting this ratio (R 2+ / Al 3+ ) to 1.50 or more, the refractive index of the glass can be increased. Therefore, this (R 2+ / Al 3+ ) ratio preferably has a lower limit of 1.50, more preferably 1.80, still more preferably 2.10, and still more preferably 2.40. On the other hand, by setting this ratio (R 2+ / Al 3+ ) to 6.00 or less, an excessive increase in the refractive index can be suppressed and the Abbe number can be increased. Therefore, this (R 2+ / Al 3+ ) ratio preferably has an upper limit of 6.00, more preferably 5.40, still more preferably 4.80, still more preferably 4.20, still more preferably 3.70, and still more preferably 3.30.

[0029] Also, the optical glass of the present invention has a ratio of Ba to the Al 3+ content rate (cation%)2+ Ratio of content (cation%) (Ba 2+ / Al 3+ ) is preferably 2.50 or less. 2+ / Al 3+ By reducing this (Ba), it is possible to suppress an unnecessary increase in the refractive index. 2+ / Al 3+ ) ratio is preferably upper limit 2.50, more preferably 2.00, even more preferably 1.80, even more preferably 1.50, even more preferably 1.30. On the other hand, (Ba 2+ / Al 3+ The lower limit of the ratio may be preferably greater than 0, more preferably greater than 0.20, and even more preferably greater than 0.40.

[0030] The optical glass of the present invention further comprises Mg 2+ Ba content (cation %) 2+ Ratio of content (cation%) (Ba 2+ / Mg 2+ ) is preferably 5.00 or less. This allows for a glass with a low liquidus temperature and high resistance to devitrification. 2+ / Mg 2+ ) ratio is preferably upper limit 5.00, more preferably 4.50, even more preferably 4.00, even more preferably 3.80, even more preferably 3.50, even more preferably 3.20, even more preferably 3.00. In addition, (Ba 2+ / Mg 2+ The lower limit of the ratio may be preferably greater than 0, more preferably greater than 0.50, even more preferably greater than 0.70, and even more preferably greater than 0.90.

[0031] La 3+ , Gd 3+ , Y 3+ , Yb 3+ and Lu 3+ are optional components that, when contained in an amount exceeding 0%, maintain low dispersion (high Abbe number), increase the refractive index, and further increase resistance to devitrification. In particular, Gd 3+ and Y3+ The content rate of one or both of them may preferably be more than 0%, more preferably more than 0.5%, and still more preferably more than 1.0%. On the other hand, La 3+ , Yb 3+ and Lu 3+ Among them, the content rate of at least any one of them is reduced to within the range of 10.0% or less, or the content rate of one or both of Gd 3+ and Y 3+ is reduced to within the range of 12.0% or less, so that devitrification due to excessive content of these components can be reduced. Therefore, the content rates of La 3+ , Yb 3+ and Lu 3+ are each preferably capped at 10.0%, more preferably less than 5.0%, and still more preferably less than 3.0%. Also, the content rate of one or both of Gd 3+ and Y 3+ is preferably capped at 12.0%, more preferably less than 10.0%, still more preferably less than 7.0%, still more preferably less than 4.0%, still more preferably less than 2.0%, and still more preferably less than 1.5%.

[0032] Ln 3+ is one or more selected from the group consisting of Y 3+ , La 3+ , Gd 3+ , Yb 3+ and Lu 3+ . Also, the total content rate of Ln 3+ is the total of one or more selected from the group consisting of Y 3+ , La 3+ , Gd 3+ , Yb 3+ and Lu 3+ . Here, by reducing the total content rate of Ln 3+ to within the range of 13.0% or less, the glass can be made difficult to devitrify. Therefore, the total content rate of Ln 3+ is preferably capped at 13.0%, more preferably less than 10.0%, still more preferably less than 7.0%, still more preferably less than 4.0%, and still more preferably less than 2.0%. On the other hand, Ln3+ The lower limit of the total content may preferably be more than 0%, more preferably more than 0.5%, and even more preferably more than 1.0% from the viewpoint of further increasing the refractive index and Abbe number.

[0033] Li + , Na + and K + are optional components having the property of lowering the glass transition point (Tg) while maintaining the devitrification resistance during glass formation when at least any one of them is contained at more than 0%. On the other hand, by reducing the content of at least any one of Li + , Na + and K + within the range of 10.0% or less, the abrasion degree of the glass can be reduced and the chemical durability can be enhanced. Therefore, the content of Li + , Na + and K + is preferably set with an upper limit of 10.0% each, more preferably less than 5.0%, even more preferably less than 3.0%, even more preferably less than 2.0%, even more preferably less than 1.0%, and even more preferably 0.3% or less. Also, at least any one of Li + , Na + and K + may not be contained.

[0034] Rn + is one or more selected from the group consisting of Li + , Na + and K + . Also, the total content of Rn + is the total of one or more selected from the group consisting of Li + , Na + and K + . Here, by reducing the total content of Rn + within the range of 10.0% or less, the abrasion degree of the glass can be reduced and the chemical durability can be enhanced. Therefore, Rn +The total content ratio preferably has an upper limit of 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%, and most preferably 0.3% or less.

[0035] Si 4+ When it contains more than 0%, it is an optional component having the properties of enhancing the devitrification resistance of the glass, increasing the refractive index, and reducing the abrasion degree. On the other hand, by reducing the content ratio of Si 4+ within the range of 10.0% or less, devitrification of the glass due to excessive content of Si 4+ can be reduced. Therefore, the content ratio of Si 4+ preferably has an upper limit of 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%, and most preferably does not contain.

[0036] B 3+ When it contains more than 0%, it is an optional component having the properties of enhancing the devitrification resistance of the glass, increasing the refractive index, and reducing the abrasion degree. On the other hand, by reducing the content ratio of B 3+ within the range of 10.0% or less, the chemical durability of the glass can be enhanced. Therefore, the content ratio of B 3+ preferably has an upper limit of 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%, and most preferably does not contain.

[0037] The optical glass of the present invention preferably has a total content (cation%) of P 5+ , Si 4+ and B 3+ in the range of 17.0% or more and 42.0% or less. Here, by setting the total content of P 5+ , Si 4+ and B 3+ to 17.0% or more, the refractive index of the glass can be increased. Therefore, the sum of these content ratios (P 5+ +Si 4+ +B 3+) is preferably at least 17.0%, more preferably at least 20.0%, still more preferably at least 23.0%, and even more preferably at least 26.0%. Also, P 5+ , Si 4+ and B 3+ By setting the total content of these to 42.0% or less, the Abbe number of the glass can be increased. Therefore, the sum of these contents (P 5+ +Si 4+ +B 3+ ) is preferably at most 42.0%, more preferably at most 40.0%, still more preferably at most 37.0%, and even more preferably at most 33.0%.

[0038] Zn 2+ When contained in an amount exceeding 0%, it has the properties of reducing the linear expansion coefficient of the glass, lowering the glass transition point, and enhancing the devitrification resistance and acid resistance of the glass. On the other hand, by reducing the content of Zn 2+ within the range of 10.0% or less, it becomes easier to obtain a desired low Abbe number. Therefore, the content of Zn 2+ is preferably capped at 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, even more preferably less than 1.0%, and most preferably not contained.

[0039] Ti 4+ , Nb 5 and W 6+ are optional components that have the property of increasing the refractive index of the glass when at least any one of them is contained in an amount exceeding 0%. In addition, Nb 5+ has the property of enhancing chemical durability, and W 6+ is also a component that has the property of lowering the glass transition point. On the other hand, by reducing the content of at least any one of Ti 4+ , Nb 5 and W 6+ within the range of 10.0% or less, it becomes easier to obtain a desired high Abbe number. In addition, by reducing the content of Ti 4+ and W 6+ within these ranges, the coloring of the glass can be reduced. Therefore, Ti4+ , Nb 5 and W 6+ The content ratios of each are preferably up to 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, and even more preferably less than 1.0%.

[0040] Zr 4+ When Zr contains more than 0%, it is an optional component having the property of increasing the refractive index of the glass. On the other hand, by reducing the content ratio of Zr within the range of 10.0% or less, the veining due to the volatilization of components in the glass can be reduced. Therefore, the content ratio of Zr 4+ is preferably up to 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, and even more preferably less than 1.0%. 4+

[0041] Ta 5+ When Ta contains more than 0%, it is an optional component having the property of increasing the refractive index of the glass. On the other hand, by reducing the content ratio of Ta within the range of 10.0% or less, the devitrification of the glass can be reduced. Therefore, the content ratio of Ta 5+ is preferably up to 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, and even more preferably less than 1.0%. 5+

[0042] Ge 4+ When Ge contains more than 0%, it is an optional component having the properties of increasing the refractive index of the glass and enhancing the devitrification resistance. On the other hand, by reducing the content ratio of Ge within the range of 10.0% or less, the material cost of the glass can be reduced. Therefore, the content ratio of Ge 4+ is preferably up to 10.0%, more preferably less than 5.0%, still more preferably less than 3.0%, and even more preferably less than 1.0%. 4+

[0043] Bi 3+ and Te 4+ ​​​is an optional component that, when contained in an amount exceeding 0%, has the property of increasing the refractive index of the glass and lowering the glass transition point. On the other hand, by reducing the content of at least one of 3+ Bi 4 and 3+ Te 4 to within a range of 10.0% or less, coloring and devitrification of the glass can be reduced. Therefore, the content of

[0044] [Regarding the anion component] F - has the property of increasing the anomalous dispersibility and Abbe number of the glass, lowering the glass transition point, and making the glass difficult to devitrify. Therefore, the content of - F is preferably 37.0% or more, more preferably more than 40.0%, still more preferably more than 43.0%, and still more preferably more than 46.0%. - On the other hand, when the content of - F

[0045] is large, it has the property of excessively increasing the Abbe number of the glass, decreasing the refractive index, decreasing the liquidus temperature, and decreasing the abrasion degree. Therefore, the content of 2- F 2- is preferably 64.0% or less, more preferably less than 60.0%, still more preferably less than 57.0%, and still more preferably less than 53.0%. 2- O

[0046] has the property of suppressing devitrification of the glass and suppressing an increase in the abrasion degree. Therefore, the content of O 2- is preferably 36.0% or more, more preferably more than 40.0%, still more preferably more than 43.0%, and still more preferably more than 47.0%. On the other hand, in order to easily obtain the effects of other anion components, the content of 2- O

[0046] 2- is preferably 63.0% or less, more preferably less than 60.0%, still more preferably less than 57.0%, and still more preferably less than 54.0%.

[0046] Also, from the viewpoint of suppressing devitrification of the glass, the total content of O 2- and F - is preferably 98.0% or more, more preferably 99.0% or more, and even more preferably 100% as the lower limit. That is, the total content of anions other than O 2- and F - , for example, Cl - or Br - , I - selected from the group consisting of is preferably 2.0% or less, more preferably 1.0% or less, and most preferably 0% as the upper limit.

[0047] The optical glass of the present invention preferably has a ratio (F 5+ content (anion %) to P - content (cation %)) (F - / P 5+ ) of 1.00 or more. By increasing this ratio (F - / P 5+ ), the Abbe number of the glass can be increased. Therefore, this (F - / P 5+ ) ratio may preferably have a lower limit of 1.00, more preferably 1.20, and even more preferably 1.40. On the other hand, from the viewpoint of increasing the liquidus temperature of the glass to reduce devitrification, the upper limit of the (F - / P 5+ ) ratio is preferably 3.00 or less, more preferably less than 2.50, even more preferably less than 2.20, even more preferably 2.05 or less, and even more preferably 1.95 or less.

[0048] The optical glass of the present invention preferably has a total content (Ba 2+ content (cation %) and F - content (anion %)) (Ba 2+ +F - ) of 87.0% or less. Thereby, the liquidus temperature of the glass can be increased to reduce devitrification. Therefore, the sum of the content of Ba 2+ and the content of F - (Ba 2+ +F -) is preferably capped at 87.0%, more preferably 85.0%, still more preferably 82.0%, still more preferably 80.0%, and still more preferably 77.7%. Incidentally, Ba 2+ content and F - content sum (Ba 2+ + F - ) may have a lower limit of preferably more than 37.0%, more preferably more than 45.0%, still more preferably more than 50.0%, still more preferably more than 55.0%, and still more preferably more than 58.0%.

[0049] [Regarding other components] In the optical glass of the present invention, other components can be added as necessary within a range that does not impair the characteristics of the glass of the present application.

[0050] [Regarding components that should not be contained] Next, components that should not be contained in the optical glass of the present invention and components that are preferably not contained will be described.

[0051] Cations of transition metals such as Cu, Nd, V, Cr, Mn, Fe, Co, Ni, Ag, and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, cause the glass to be colored and absorb at specific wavelengths in the visible region even when contained in small amounts alone or in combination. Therefore, in optical glass that uses wavelengths in the visible region, it is preferably substantially free of them.

[0052] Cations of Pb, As, Th, Cd, Tl, Os, Be, and Se tend to be avoided in recent years as harmful chemicals, and environmental measures are required not only in the glass manufacturing process but also in the processing process and disposal after productization. Also, the cation of S (sulfur) can also generate harmful chemicals (SO x etc.). Therefore, when emphasizing environmental impacts, the content of one or more of these is preferably less than 1.0%, more preferably less than 0.5%, and most preferably, one or more of these are substantially not contained.

[0053] In addition, "substantially free of" in this specification preferably means that the content is less than 0.1%, and more preferably it contains nothing except for those contained as inevitable impurities.

[0054] Although cations of Sb and Ce are useful as defoaming agents, in recent years, there has been a tendency not to include them in optical glass as components that are disadvantageous to the environment. Therefore, in the optical glass of the present invention, it is preferable that Sb and Ce are also substantially free of such points.

[0055] [Manufacturing Method] The manufacturing method of the optical glass of the present invention is not particularly limited. For example, the above raw materials are uniformly mixed so that each component is within a predetermined content rate range, and the prepared mixture is put into a quartz crucible, an alumina crucible, or a platinum crucible and roughly melted, and then put into a platinum crucible, a platinum alloy crucible, or an iridium crucible and melted in a temperature range of 900 to 1200 °C for 2 to 10 hours, stirred and homogenized to remove bubbles, etc., and then cooled to a temperature of 850 °C or lower and then finish stirring to remove veins, and cast into a mold and slowly cooled to manufacture.

[0056] [Physical Properties] The optical glass of the present invention can be obtained more stably with reduced devitrification. In particular, the liquidus temperature in the optical glass of the present invention preferably has 800 °C as the upper limit, and more preferably any one of 780 °C, 760 °C, 740 °C, 720 °C, 700 °C, and 680 °C as the upper limit. Thereby, when obtaining glass or when heat-molding the obtained glass, since the glass is less likely to devitrify, a transparent optical glass having desired optical properties can be stably obtained. The liquidus temperature in the present invention is the lowest temperature at which no crystals are observed when a 25 cc carat-shaped glass sample is put into a platinum crucible with a capacity of 50 ml, covered with an alumina lid, completely melted at 950 °C, cooled to any temperature set at 10 °C intervals from 900 °C to 600 °C, held for 4 hours, taken out of the furnace and cooled, and then immediately observing the presence or absence of crystals on the glass surface and in the glass. Note that the lower limit of the liquidus temperature of the optical glass of the present invention is not particularly limited, and even if the glass sample in a molten state is cooled to 600 ° C, those in which no crystal is observed (that is, those having a liquidus temperature of 600 ° C or lower) may be included in the optical glass of the present invention. Further, 620 ° C or 650 ° C may be used as the lower limit of the liquidus temperature.

[0057] The optical glass of the present invention has a high refractive index (n d ) and has low dispersibility (high Abbe number). The optical glass of the present invention preferably has a refractive index (n d ) of 1.48 or more and 1.58 or less. More specifically, the lower limit of the refractive index of the optical glass of the present invention is preferably 1.48, more preferably 1.50, and even more preferably 1.52. On the other hand, the upper limit of the refractive index (n d ) of the optical glass of the present invention is preferably 1.58, more preferably 1.56, and even more preferably 1.54 or less. The optical glass of the present invention preferably has an Abbe number (ν d ) of 70 or more and 88 or less. More specifically, the lower limit of the Abbe number (ν d ) of the optical glass of the present invention is preferably 70, more preferably 73, and even more preferably 75. On the other hand, the upper limit of the Abbe number (ν d ) of the optical glass of the present invention is preferably 88, more preferably 85, even more preferably 82, and even more preferably 79. By having such a high refractive index, a large amount of light refraction can be obtained even when the optical element is thinned. Further, by having such low dispersion, when used as a single lens, the deviation of the focal point (chromatic aberration) due to the wavelength of light can be reduced. Therefore, for example, when an optical system is configured in combination with an optical element having high dispersion (low Abbe number), the aberration of the entire optical system can be reduced and high imaging characteristics and the like can be achieved. As described above, the optical glass of the present invention is useful in optical design, and particularly when an optical system is configured, it is possible to reduce the size of the optical system while achieving high imaging characteristics and the like, and to expand the degree of freedom in optical design.

[0058] [Preform and Optical Element] From the produced optical glass, a glass molded body can be produced using, for example, means of grinding or means of heat forming such as reheat press molding or precision mold press molding. That is, a glass molded body can be produced by performing machining such as grinding and polishing on the optical glass, or a preform for mold press molding can be produced from the optical glass, and after performing reheat press molding on this preform, polishing is performed to produce a glass molded body, or a preform produced by polishing or a preform molded by known floating molding or the like is subjected to precision mold press molding to produce a glass molded body. Note that the means for producing the glass molded body is not limited to these means.

[0059] As described above, the optical glass of the present invention is useful for various optical elements and optical designs. Among them, in particular, it is preferable to form a preform from the optical glass of the present invention and perform reheat press molding, precision mold press molding, etc. using this preform to produce optical elements such as lenses and prisms. Thereby, since it becomes possible to form a preform with a large diameter, while increasing the size of the optical element, high-definition and high-precision imaging characteristics and projection characteristics can be realized when used in an optical device.

[0060] The glass molded body made of the optical glass of the present invention can be used for applications of optical elements such as lenses, prisms, and mirrors, and typically can be used for devices that tend to become hot, such as in-vehicle optical devices, projectors, and copy machines.

Examples

[0061] The compositions of the glasses of Examples (No. 1 to No. 31) and Comparative Example (No. A) which are the optical glasses of the present invention (shown in mol% in terms of cation% or anion%), refractive index (n d ), Abbe number (ν d ), and the results of the liquidus temperature are shown in Tables 1 to 4. Note that the following examples are for illustrative purposes only and are not limited to only these examples.

[0062] In each of the examples and comparative examples, high-purity raw materials such as the corresponding oxides, carbonates, nitrates, fluorides, metaphosphate compounds, etc., which are usually used in phosphate glasses, were selected as raw materials for each component, weighed to obtain the composition of each example shown in the table, and uniformly mixed. Then, they were put into a platinum crucible, the crucible was covered, and heated at 950 °C for 2 hours using an electric furnace to dissolve the raw materials, stir and homogenize them to remove bubbles, etc. After that, the temperature was lowered to 700 °C or lower and then cast into a mold and slowly cooled to produce glass. For the obtained glass, elemental analysis was performed by ICP emission spectrometry to determine the composition (cation %) of the cation components in the glass composition. On the other hand, for the composition of the anion components, the content of F - was measured by ion chromatography, and the content of O 2- was measured by infrared absorption method, respectively. The content of F - and O 2- relative to the total of these was determined (anion %). The composition (analytical composition) of the obtained glass was as shown in the table.

[0063] The refractive index (n d ) and Abbe number (ν d ) of the glasses in the examples and comparative examples were measured according to the V-block method specified in JIS B 7071-2:2018. Here, the refractive index (n d ) was shown as the measured value for the d-line (587.56 nm) of a helium lamp. Also, the Abbe number (ν d ) was calculated from the formula of Abbe number (ν d ) = [(n d - 1) / (n F - n C )] using the refractive index for the d-line of a helium lamp and the refractive indices (n F ) for the F-line (486.13 nm) of a hydrogen lamp and (n C ) for the C-line (656.27 nm). These refractive index (n d ) and Abbe number (ν d ) were determined by measuring the glass obtained with a slow cooling rate of -25 °C / hr.

[0064] As the liquidus temperature of the glasses of the examples and comparative examples, 25 cc of a cullet-shaped glass sample was placed in a platinum crucible with a capacity of 50 ml, covered with an alumina lid, completely melted at 950 °C, cooled to any temperature set at 10 °C intervals from 900 °C to 600 °C, held for 4 hours, taken out of the furnace and cooled, and then the lowest temperature at which no crystals were observed when observing the presence or absence of crystals on the glass surface and in the glass was determined.

[0065] [Table 1]

[0066] [Table 2]

[0067] [Table 3]

[0068] [Table 4]

[0069] As shown in the table, all of the optical glasses of the examples of the present invention had a liquidus temperature of 800 °C or lower, which was within the desired range. On the other hand, the optical glasses of the comparative examples had a liquidus temperature exceeding 800 °C. For this reason, it became clear that the optical glasses of the examples of the present invention had a lower liquidus temperature than the glasses of the comparative examples.

[0070] In addition, all of the optical glasses of the examples of the present invention had a refractive index of 1.48 or higher, more specifically 1.52 or higher, which was within the desired range. Also, all of the optical glasses of the examples of the present invention had an Abbe number of 70 or higher, more specifically 75 or higher, which was within the desired range.

[0071] Therefore, it has been clarified that the optical glass of the embodiment of the present invention has a refractive index and an Abbe number within a desired range and a low liquidus temperature. From this, it is presumed that the optical glass of the embodiment of the present invention is less likely to devitrify and can be obtained more stably.

[0072] Furthermore, after forming a preform for polishing using the optical glass of the embodiment of the present invention, grinding and polishing were performed to process it into the shapes of lenses and prisms. Also, using the optical glass of the embodiment of the present invention, a preform for precision mold pressing was formed, and this preform was precision mold pressed into the shapes of lenses and prisms. In both cases, it was possible to process into various lens and prism shapes.

[0073] As described above, the present invention has been described in detail for illustrative purposes. However, it should be understood that these embodiments are for illustrative purposes only, and those skilled in the art can make many modifications without departing from the spirit and scope of the present invention.

Claims

1. Cationic % (mol %): P 5+ More than 20.0% and 42.0% or less, A 3+ More than 15.0% and 30.0% or less, Mg 2+ More than 0% and 22.0% or less, Ca 2+ 10.42% or more and 25.0% or less, Sr 2+ More than 0% and 30.0% or less, Ba 2+ More than 0% and 35.0% or less Contains Anion % (mol %): F - The content is 37.0 to 64.0%, O 2- The content is 36.0 to 63.0% and P 5+ F vs. content (cation %) - Ratio of content (anion%) (F - / P 5+ ) is 1.20 or more and 1.95 or less, A 3+ Ba content (cation %) 2+ Ratio of content (cation%) (Ba 2+ / Al 3+ ) is greater than 0 and less than or equal to 1.30 and Refractive index (n ｄ ) is 1.48 or more and less than 1.54, and the Abbe number (ν ｄ ) An optical glass having a liquidus temperature of 800° C. or less.

2. Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ The total content (R 2+ 2. The optical glass according to claim 1, wherein the content of C(cation) is 37.0 to 63.0%.

3. In terms of cation% (mol%), the content of La 3+ is 0 to 10.0%, the content of Gd 3+ is 0 to 12.0%, the content of Y 3+ is 0 to 12.0%, the content of Yb 3+ is 0 to 10.0%, the content of Lu 3+ is 0 to 10.0% The optical glass according to claim 1 or 2.

4. La 3+ , Gd 3+ , Y 3+ , Yb 3+ and Lu 3+ The total content of one or more selected from the group consisting of (Ln 3+ : cation%) is 13.0% or less. The optical glass according to any one of claims 1 to 3.

5. In terms of cation% (mol%), the content of Li + is 0 to 10.0%, the content of Na + is 0 to 10.0%, the content of K + is 0 to 10.0% The optical glass according to any one of claims 1 to 4.

6. Li ＋ , Na ＋ and K ＋ The total content of one or more selected from the group consisting of (Rn ＋ : cation%) is 10.0% or less. The optical glass according to any one of claims 1 to 5.

7. In terms of cation% (mol%), the content of Si 4+ is 0 to 10.0%, the content of B 3+ is 0 to 10.0%, the content of Zn 2+ is 0 to 10.0%, Ti 4+ has a content of 0 to 10.0%, Nb 5+ has a content of 0 to 10.0%, W 6+ has a content of 0 to 10.0%, Zr 4+ has a content of 0 to 10.0%, Ta 5+ has a content of 0 to 10.0%, Ge 4+ has a content of 0 to 10.0%, Bi 3+ has a content of 0 to 10.0%, Te 4+ has a content of 0 to 10.0% The optical glass according to any one of claims 1 to 6.

8. An optical element made of the optical glass according to any one of claims 1 to 7.

9. A preform for polishing and / or precision press forming made of the optical glass according to any one of claims 1 to 7.

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