Optical glass and optical element

Abstract

To provide a fluorophosphate glass having a low thermal expansion coefficient.SOLUTION: There is provided an optical glass which contains O ions, F ions, Al ions, P ions, Mg ions, Ca ions, Sr ions and Ba ions as essential components, wherein in the glass composition represented by atomic percentage, the ratio (O / P) of the content of O ions to the content of P ions is 3.30 or more and 4.50 or less, the ratio (Al / P) of the content of Al ions to the content of P ions is 1.50 or less and the ratio (F / Al) of the content of F ions to Al ions is 6.00 or less, and in the glass composition represented by cation percentage, the total content (Mg+Ca+Sr+Ba) of Mg ions, Ca ions, Sr ions and Ba ions is 40.00 cation % or more and the cation ratio ((Mg+Ca) / (Mg+Ca+Sr+Ba)) of the total content of Mg ions and Ca ions to the total content of Mg ions, Ca ions, Sr ions and Ba ions is 0.40 or more.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] Phosphate glass is generally an optical glass having low dispersibility and is used as a material for various optical elements (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One of the physical properties desired for optical glass is a low coefficient of thermal expansion. For example, an optical glass with a small coefficient of thermal expansion can suppress the occurrence of cracks and fractures in the glass during press molding.

[0005] One aspect of the present invention aims to provide phosphate glass having a low coefficient of thermal expansion.

Means for Solving the Problems

[0006] As a result of intensive studies, the present inventors have newly found that phosphate glass having the following glass composition can exhibit a low coefficient of thermal expansion.

[0007] One aspect of the present invention is as follows. [1] Including O ions, F ions, Al ions, P ions, Mg ions, Ca ions, Sr ions, and Ba ions as essential components, In the glass composition expressed in atomic%, The ratio of the content of O ions to the content of P ions (O / P) (hereinafter, also referred to as "O / P ratio" or "O / P") is 3.30 or more and 4.50 or less, The ratio of the content of Al ions to the content of P ions (Al / P) (hereinafter, also referred to as "Al / P ratio" or "Al / P") is 1.50 or less, The ratio of the content of F ions to the content of Al ions (F / Al) (hereinafter, also referred to as "F / Al ratio" or "F / Al") is 6.00 or less, In the glass composition expressed in cation %, The total content of Mg ions, Ca ions, Sr ions and Ba ions (Mg + Ca + Sr + Ba) is 40.00 cation % or more, and The cation ratio of the total content of Mg ions and Ca ions to the total content of Mg ions, Ca ions, Sr ions and Ba ions ((Mg + Ca) / (Mg + Ca + Sr + Ba)) is 0.40 or more, An optical glass (hereinafter, also simply referred to as "glass"). [2] The total content of Li ions, Na ions and K ions (Li + Na + K) in the optical glass described in [1] is 20.00 cation % or less. [3] The cation ratio of the content of Mg ions to the content of Ba ions (Mg / Ba) in the optical glass described in [1] or [2] is 0.05 or more and 5.00 or less. [4] The total content of Mg ions and Ca ions (Mg + Ca) in the optical glass described in any one of [1] to [3] is 1.00 cation % or more and 50.00 cation % or less. [5] The total content of Y ions, La ions, Gd ions and Yb ions (Y + La + Gd + Yb) in the optical glass described in any one of [1] to [4] is 0.10 cation % or more and 5.00 cation % or less. [6] The total content of Si ions and B ions (Si + B) in the optical glass described in any one of [1] to [5] is 10.00 cation % or less. [7] The average linear expansion coefficient α at 100 °C to 300 °C is less than 155×10 -7 / K in the optical glass described in any one of [1] to [6]. [8] The total content of Li ions, Na ions and K ions (Li + Na + K) is 20.00 cation % or less, The cation ratio (Mg / Ba) of the content of Mg ions to the content of Ba ions is 0.05 or more and 5.00 or less, The total content of Mg ions and Ca ions (Mg + Ca) is 1.00 cation % or more and 50.00 cation % or less, The total content of Y ions, La ions, Gd ions and Yb ions (Y + La + Gd + Yb) is 0.10 cation % or more and 5.00 cation % or less, The total content of Si ions and B ions (Si + B) is 10.00 cation % or less, and The average linear expansion coefficient α at 100°C to 300°C is less than 155×10 -7 / K, the optical glass according to any one of [1] to [7]. [9] An optical element made of the optical glass according to any one of [1] to [8]. [Advantages of the Invention]

[0008] According to one aspect of the present invention, an optical glass which is a fluorophosphate glass having a low thermal expansion coefficient, and an optical element made of this optical glass can be provided. [Embodiments for Carrying Out the Invention]

[0009] [Optical Glass] [Glass Composition] [Analysis Method] Regarding various components constituting the glass, the content (mass % of the element) of the elements contained in the glass can be quantified by known methods, for example, inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), etc. Regarding the anion component, the anion component contained in the glass can be identified and quantified by known analysis methods, for example, ion chromatography, non-dispersive infrared absorption method (ND-IR), etc. In the present invention and this specification, when the content of a component is 0%, 0.0%, 0.00%, not contained, or not introduced, it means that this component is substantially not contained, and it is allowed that this component is contained at an unavoidable impurity level.

[0010] (Notation of glass composition based on oxides) Based on the results obtained from the above analysis, the content (unit: mol%) of each component in the glass composition based on oxides can be calculated. The specific method is as follows. The content of element i (element mass % P i ) obtained by the above analysis method is divided by the atomic weight M i of element i to obtain the number of moles n i = P i / M i of each element. When the above element i is the cation component A i , the number of moles n i of the element obtained above is replaced with the number of moles n' i of the corresponding oxide. Specifically, when the composition formula of the oxide of the cation component A i corresponding to element i is represented by A i xOy, n' i = n i / x. When the above element i is an anion component B i other than O ions, the number of moles n i of the corresponding above element is hereinafter denoted as m i . In the glass composition based on oxides, the content PA i of the oxide A i xOy of the cation component A i (mol%) is PA i = n' i / (Σn' i + Σm i ) × 100 and is represented by. The content in the glass composition based on oxides can also be called the oxide-based fraction.

[0011] In the glass composition based on oxides, the anion component B other than O ions i The oxide-based fraction PB i (mol%) is PB i = m i / (Σn’ i + Σm i ) × 100 and is represented by

[0012] Here, Σn’ i is the total number of moles of the oxide A i xOy of the cation component contained in the glass. However, depending on the significant figures of the content, even if trace components are ignored, it does not affect the calculation result.

[0013] (cation%, anion%) In the present invention and this specification, unless otherwise specified, the content and total content of the cation component are expressed in cation%, and the content and total content of the anion component are expressed in anion%. Here, "cation%" is the content in the glass composition based on oxides (expressed in mol%), and is a value calculated by "(the number of cations of interest / the total number of cations of the glass components) × 100", and means the molar percentage of the amount of the cation component of interest with respect to the total amount of the cation component. The molar ratio (cation ratio) of the contents of the cation components is equal to the ratio of the contents in terms of cation% of the cation components of interest. "Anion%" is the content in the glass composition based on oxides (expressed in mol%), and is a value calculated by "(the number of anions of interest / the total number of anions of the glass components) × 100", and means the molar percentage of the amount of the anion component of interest with respect to the total amount of the anion component. Based on the above description of the notation of the glass composition based on oxides, the anion% of O ions is The composition formula of the oxide of the cation component A i corresponding to the element i is A i xOy, and the number of O contained in the oxide of the cation component A i is the number of cations of the cation component A iOxide reference fraction PA i (mol%) is used for O i = PA i × y, and for the anion component B k when the valence is N k it can be calculated as (ΣO i - Σ(N k / 2)B k ) / (ΣO i - Σ(N k / 2)B k + ΣB k ) × 100 Here, ΣO is the sum of the number of moles of O ions in the glass composition based on oxides, and Σ(N i / 2)B k represents the number of moles of O ions replaced by the anion component B k . The numerator of the formula (ΣO k - Σ(N i / 2)B k / 2)B k ) becomes the number of moles of O ions contained in the glass. On the other hand, in the present invention and this specification, regarding the oxygen content, when no anion component other than oxygen is detected by analysis by a known method, it is assumed that all (i.e., 100 anion%) in the anion component are O ions.

[0014] (Cation component, anion component) Regarding the valence of the cation component, the formal valence of each cation is used. The formal valence is the valence required for the oxide of the cation of interest to maintain electrical neutrality when the valence of the O ions constituting the oxide is -2, and it can be uniquely determined from the chemical formula of the oxide. For example, for P ions, in the chemical formula of the oxide P2O5, the valence of P to maintain electrical neutrality with O 2- is +2 × 5 / 2 = +5. Generalizing this, the formal valence of the cation Ai contained in the oxide AixOy is “+2y / x”. Therefore, when analyzing the glass composition, it is not necessary to analyze the valence of the cation up to that point. Also, regarding the valence of anions (e.g., the valence of O ions is -2), it is the formal valence based on the idea that O ions accept two electrons and adopt a closed-shell structure. Therefore, when analyzing the glass composition, it is not necessary to analyze the valence of anions. Also, a part of Cu 2+ can become Cu + during melting, but usually, the amount is small, so the valence of Cu can all be regarded as +2 without problem.

[0015] (Various ratios in the glass composition expressed in atomic percentages) In the glass composition expressed in atomic percentages, the ratio of the cation content to the anion content is the ratio of the contents (expressed in atomic percentages) of the components of interest when the total amount of all cation components and all anion components is 100 atomic %. Therefore, the ratio of the O ion content to the P ion content (O / P) is the ratio of the O ion content (expressed in atomic percentages) to the P ion content (expressed in atomic percentages) when the total amount of all cation components and all anion components is 100 atomic %. The ratio of the Al ion content to the P ion content (Al / P) is the ratio of the Al ion content (expressed in atomic percentages) to the P ion content (expressed in atomic percentages) when the total amount of all cation components and all anion components is 100 atomic %. The ratio of the F ion content to the Al ion content (F / Al) is the ratio of the F ion content (expressed in atomic percentages) to the Al ion content (expressed in atomic percentages) when the total amount of all cation components and all anion components is 100 atomic %.

[0016] Hereinafter, the glass composition of the above optical glass will be described.

[0017] The above optical glass contains, as essential components, O ions, F ions, Al ions, P ions, Mg ions, Ca ions, Sr ions, and Ba ions. The content of each of the above ions of the essential components is more than 0.00 atomic % in atomic percentage representation, more than 0.00 anion % for the anion component, and more than 0.00 cation % for the cation component.

[0018] In the glass composition expressed in atomic %, the O / P ratio (O / P) is 3.30 or more from the viewpoint of lowering the thermal expansion coefficient of the glass, preferably 3.33 or more, and more preferably 3.35 or more, 3.38 or more, 3.40 or more, 3.42 or more, 3.44 or more, 3.46 or more, 3.48 or more, 3.50 or more in this order. From the viewpoint of maintaining the thermal stability of the glass, the O / P ratio is 4.50 or less, preferably 4.40 or less, and more preferably 4.30 or less, 4.20 or less, 4.10 or less, 4.00 or less in this order.

[0019] The Al / P ratio (Al / P) is 1.50 or less from the viewpoint of maintaining the thermal stability of the glass, preferably 1.40 or less, and more preferably 1.30 or less, 1.20 or less, 1.15 or less, 1.13 or less, 1.10 or less in this order. From the viewpoint of maintaining the high refractive index of the glass, the Al / P ratio (Al / P) is preferably 0.20 or more, and more preferably 0.30 or more, 0.40 or more, 0.50 or more, 0.60 or more, 0.70 or more, 0.80 or more in this order.

[0020] The F / Al ratio (F / Al) is 6.00 or less from the viewpoint of lowering the thermal expansion coefficient of the glass, preferably 5.95 or less, and more preferably 5.90 or less, 5.85 or less, 5.80 or less, 5.75 or less, 5.70 or less, 5.65 or less, 5.60 or less, 5.55 or less, 5.50 or less in this order. From the viewpoint of maintaining the low dispersibility of the glass, the F / Al ratio (F / Al) is preferably 3.00 or more, and more preferably 3.20 or more, 3.40 or more, 3.60 or more, 3.80 or more, 4.00 or more, 4.10 or more, 4.20 or more, 4.30 or more, 4.40 or more, 4.50 or more in this order.

[0021] Regarding the O ion content, from the viewpoints of the thermal stability of the glass and maintaining a high refractive index, it is preferably 20.00 anion% or more, more preferably 22.00 anion% or more, 24.00 anion% or more, 26.00 anion% or more, 28.00 anion% or more, and still more preferably 30.00 anion% or more in this order. From the viewpoint of maintaining the low dispersibility of the glass, the O ion content is preferably 80.00 anion% or less, more preferably 75.00 anion% or less, 70.00 anion% or less, 65.00 anion% or less, 60.00 anion% or less, 58.00 anion% or less, 56.00 anion% or less, 54.00 anion% or less, 52.00 anion% or less, and still more preferably 50.00 anion% or less in this order.

[0022] Regarding the F ion content, from the viewpoint of maintaining the low dispersibility of the glass, it is preferably 20.00 anion% or more, more preferably 25.00 anion% or more, 30.00 anion% or more, 35.00 anion% or more, 40.00 anion% or more, 42.00 anion% or more, 44.00 anion% or more, 46.00 anion% or more, 48.00 anion% or more, and still more preferably 50.00 anion% or more in this order. From the viewpoint of maintaining the high refractive index of the glass, the F ion content is preferably 80.00 anion% or less, more preferably 78.00 anion% or less, 76.00 anion% or less, 74.00 anion% or less, 72.00 anion% or less, and still more preferably 70.00 anion% or less in this order.

[0023] Regarding the Al ion content, from the viewpoints of the thermal stability, chemical stability, and maintaining a high refractive index of the glass, it is preferably 5.00 cation% or more, more preferably 8.00 cation% or more, 10.00 cation% or more, 12.00 cation% or more, 14.00 cation% or more, 15.00 cation% or more, 16.00 cation% or more, 17.00 cation% or more, 18.00 cation% or more, 19.00 cation% or more, and still more preferably 20.00 cation% or more in this order. From the viewpoint of suppressing the increase in the liquid-phase temperature, the Al ion content is preferably 40.00 cation % or less, more preferably 38.00 cation % or less, 36.00 cation % or less, 35.00 cation % or less, 34.00 cation % or less, 33.00 cation % or less, 32.00 cation % or less, 31.00 cation % or less, 30.00 cation % or less in this order.

[0024] Regarding the P ion content, from the viewpoints of maintaining the thermal stability and low dispersibility of the glass, it is preferably 1.00 cation % or more, more preferably 3.00 cation % or more, 5.00 cation % or more, 7.00 cation % or more, 10.00 cation % or more, 12.00 cation % or more, 14.00 cation % or more, 16.00 cation % or more, 18.00 cation % or more, 20.00 cation % or more in this order. From the viewpoint of maintaining the chemical durability of the glass, the P ion content is preferably 50.00 cation % or less, more preferably 48.00 cation % or less, 46.00 cation % or less, 44.00 cation % or less, 42.00 cation % or less, 40.00 cation % or less, 38.00 cation % or less, 36.00 cation % or less, 35.00 cation % or less, 34.00 cation % or less, 33.00 cation % or less, 32.00 cation % or less, 31.00 cation % or less, 30.00 cation % or less in this order.

[0025] Regarding the Mg ion content, from the viewpoints of maintaining the thermal stability of the glass and lowering the thermal expansion coefficient, it is preferably 0.10 cation % or more, more preferably 0.50 cation % or more, 0.70 cation % or more, 1.00 cation % or more, 2.00 cation % or more, 3.00 cation % or more, 4.00 cation % or more, 5.00 cation % or more in this order. From the viewpoint of suppressing the decrease in the thermal stability of the glass, the Mg ion content is preferably 30.00 cation % or less, more preferably 25.00 cation % or less, 20.00 cation % or less, 18.00 cation % or less, 16.00 cation % or less, 15.00 cation % or less, 14.00 cation % or less, 13.00 cation % or less, 12.00 cation % or less, 11.00 cation % or less, 10.00 cation % or less in this order.

[0026] Regarding the Ca ion content, from the viewpoints of maintaining the thermal stability of the glass and lowering the coefficient of thermal expansion, it is preferably 0.10 cation % or more, more preferably 0.50 cation % or more, 0.70 cation % or more, 1.00 cation % or more, 3.00 cation % or more, 5.00 cation % or more, 7.00 cation % or more, 10.00 cation % or more, 11.00 cation % or more, 12.00 cation % or more, 13.00 cation % or more, 14.00 cation % or more, 15.00 cation % or more in this order. From the viewpoint of suppressing the decrease in the thermal stability of the glass, the Ca ion content is preferably 40.00 cation % or less, more preferably 35.00 cation % or less, 33.00 cation % or less, 30.00 cation % or less, 29.00 cation % or less, 28.00 cation % or less, 27.00 cation % or less, 26.00 cation % or less, 25.00 cation % or less in this order.

[0027] Regarding the Sr ion content, from the viewpoints of maintaining the thermal stability of the glass and maintaining a high refractive index, it is preferably 0.10 cation % or more, more preferably 0.50 cation % or more, 0.70 cation % or more, 1.00 cation % or more, 3.00 cation % or more, 5.00 cation % or more, 7.00 cation % or more, 10.00 cation % or more, 11.00 cation % or more, 12.00 cation % or more, 13.00 cation % or more, 14.00 cation % or more, 15.00 cation % or more in this order. From the viewpoints of reducing the coefficient of thermal expansion and suppressing the decrease in thermal stability, the Sr ion content is preferably 40.00 cation% or less, more preferably 35.00 cation% or less, 33.00 cation% or less, 30.00 cation% or less, 27.00 cation% or less, 25.00 cation% or less, 24.00 cation% or less, 23.00 cation% or less, 22.00 cation% or less, 21.00 cation% or less, 20.00 cation% or less in this order.

[0028] Regarding Ba ions, from the viewpoints of maintaining the thermal stability and high refractive index of the glass, it is preferably 0.10 cation% or more, more preferably 0.50 cation% or more, 0.70 cation% or more, 1.00 cation% or more, 2.00 cation% or more, 3.00 cation% or more, 4.00 cation% or more, 5.00 cation% or more in this order. From the viewpoints of reducing the coefficient of thermal expansion, suppressing the increase in specific gravity, and suppressing the decrease in thermal stability, the Ba ion content is preferably 30.00 cation% or less, more preferably 25.00 cation% or less, 20.00 cation% or less, 18.00 cation% or less, 15.00 cation% or less, 14.00 cation% or less, 13.00 cation% or less, 12.00 cation% or less, 11.00 cation% or less, 10.00 cation% or less in this order.

[0029] From the viewpoint of maintaining the thermal stability of the glass, the total content of Mg ions, Ca ions, Sr ions, and Ba ions (Mg + Ca + Sr + Ba) is 40.00 cation% or more, preferably 41.00 cation% or more, more preferably 42.00 cation% or more, 43.00 cation% or more, 44.00 cation% or more, 45.00 cation% or more in this order. From the viewpoint of suppressing the decrease in the thermal stability of the glass, the total content of Mg ions, Ca ions, Sr ions, and Ba ions (Mg + Ca + Sr + Ba) is preferably 70.00 cation% or less, more preferably 65.00 cation% or less, 63.00 cation% or less, 60.00 cation% or less, 57.00 cation% or less, 55.00 cation% or less in this order.

[0030] The cation ratio ((Mg + Ca) / (Mg + Ca + Sr + Ba)) of the total content of Mg ions, Ca ions, Sr ions and Ba ions to the total content of Mg ions and Ca ions is 0.40 or more from the viewpoints of maintaining the thermal stability of the glass and lowering the coefficient of thermal expansion, preferably 0.41 or more, more preferably 0.42 or more, 0.43 or more, 0.44 or more, and 0.45 or more in this order. From the viewpoint of maintaining the high refractive index of the glass, the cation ratio ((Mg + Ca) / (Mg + Ca + Sr + Ba)) of the total content of Mg ions, Ca ions, Sr ions and Ba ions to the total content of Mg ions and Ca ions is preferably 0.70 or less, more preferably 0.65 or less, 0.63 or less, 0.60 or less, 0.59 or less, 0.58 or less, 0.57 or less, 0.56 or less, and 0.55 or less in this order.

[0031] The cation ratio (Mg / Ba) of the content of Mg ions to the content of Ba ions is preferably 0.05 or more, more preferably 0.08 or more, 0.10 or more, 0.13 or more, 0.15 or more, 0.18 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, and 0.60 or more in this order from the viewpoints of maintaining the thermal stability of the glass and lowering the coefficient of thermal expansion. From the viewpoint of maintaining the high refractive index of the glass, the above cation ratio (Mg / Ba) is preferably 5.00 or less, more preferably 4.00 or less, 3.00 or less, 2.80 or less, 2.60 or less, 2.40 or less, 2.20 or less, 2.00 or less, 1.80 or less, 1.50 or less, 1.40 or less, 1.30 or less, 1.20 or less, 1.10 or less, and 1.00 or less in this order.

[0032] The total content of Mg ions and Ca ions (Mg + Ca) is preferably 1.00 cation % or more, more preferably 3.00 cation % or more, 5.00 cation % or more, 7.00 cation % or more, 10.00 cation % or more, 12.00 cation % or more, 10.00 cation % or more, 12.00 cation % or more, 14.00 cation % or more, 16.00 cation % or more, 18.00 cation % or more, 20.00 cation % or more, from the viewpoints of maintaining the thermal stability of the glass and reducing the coefficient of thermal expansion. From the viewpoint of maintaining the high refractive index of the glass, the total content of Mg ions and Ca ions (Mg + Ca) is preferably 50.00 cation % or less, more preferably 45.00 cation % or less, 40.00 cation % or less, 38.00 cation % or less, 36.00 cation % or less, 34.00 cation % or less, 32.00 cation % or less, 30.00 cation % or less, 29.00 cation % or less, 28.00 cation % or less, 27.00 cation % or less, 26.00 cation % or less, 25.00 cation % or less.

[0033] The total content of Li ions, Na ions and K ions (Li + Na + K) can be 0.00 cation %, 0.00 cation % or more, more than 0.00 cation % or 0.10 cation % or more. From the viewpoint of reducing the coefficient of thermal expansion of the glass, the total content of Li ions, Na ions and K ions (Li + Na + K) is preferably 20.00 cation % or less, more preferably 18.00 cation % or less, 15.00 cation % or less, 13.00 cation % or less, 10.00 cation % or less, 9.00 cation % or less, 8.00 cation % or less, 7.00 cation % or less, 6.00 cation % or less, 5.00 cation % or less.

[0034] The content of each of Li ions, Na ions and K ions can be 0.00 cation %, 0.00 cation % or more, more than 0.00 cation % or 0.10 cation % or more. From the perspective of reducing the thermal expansion coefficient of the glass, the content of each of Li ions, Na ions, and K ions is preferably 20.00 cation% or less, more preferably 18.00 cation% or less, 15.00 cation% or less, 13.00 cation% or less, 10.00 cation% or less, 9.00 cation% or less, 8.00 cation% or less, 7.00 cation% or less, 6.00 cation% or less, and 5.00 cation% or less in that order.

[0035] The total content (Y + La + Gd + Yb) of Y ions, La ions, Gd ions, and Yb ions can be 0.00 cation%, 0.00 cation% or more, or more than 0.00 cation%. From the perspective of maintaining the high refractive index of the glass, it is preferably 0.10 cation% or more, more preferably 0.20 cation% or more, 0.30 cation% or more, 0.40 cation% or more, and 0.50 cation% or more in that order. From the perspective of suppressing the increase in the liquidus temperature of the glass and maintaining thermal stability, the total content (Y + La + Gd + Yb) of Y ions, La ions, Gd ions, and Yb ions is preferably 5.00 cation% or less, more preferably 4.50 cation% or less, 4.00 cation% or less, 3.80 cation% or less, 3.60 cation% or less, 3.40 cation% or less, 3.20 cation% or less, and 3.00 cation% or less in that order.

[0036] The content of each of Y ions, La ions, Gd ions, Yb ions, and Lu ions can be 0.00 cation%, 0.00 cation% or more, or more than 0.00 cation%. From the perspective of suppressing the increase in the liquidus temperature while maintaining the high refractive index of the glass and maintaining thermal stability, the content of each of Y ions, La ions, Gd ions, Yb ions, and Lu ions is preferably 5.00 cation% or less, more preferably 4.00 cation% or less, and 3.00 cation% or less in that order.

[0037] The total content of Si ions and B ions (Si + B) can be 0.00 cation%, 0.00 cation% or more, or more than 0.00 cation%. From the viewpoint of suppressing volatilization during glass melting and maintaining a high refractive index of the glass, the total content of Si ions and B ions (Si + B) is preferably 10.00 cation% or less, and more preferably 7.00 cation% or less, 5.00 cation% or less, 3.00 cation% or less, 1.00 cation% or less, 0.50 cation% or less in this order.

[0038] The Si ion content can be 0.00 cation%, 0.00 cation% or more, or more than 0.00 cation%. From the viewpoint of suppressing volatilization during glass melting and maintaining a high refractive index of the glass, the Si ion content is preferably 10.00 cation% or less, and more preferably 7.00 cation% or less, 5.00 cation% or less, 3.00 cation% or less, 1.00 cation% or less, 0.50 cation% or less in this order.

[0039] The B ion content can be 0.00 cation%, 0.00 cation% or more, or more than 0.00 cation%. From the viewpoint of suppressing volatilization during glass melting and maintaining a high refractive index of the glass, the B ion content is preferably 10.00 cation% or less, and more preferably 7.00 cation% or less, 5.00 cation% or less, 3.00 cation% or less, 1.00 cation% or less, 0.50 cation% or less in this order.

[0040] The Zn ion content can be 0.00 cation%, 0.00 cation% or more, or more than 0.00 cation%. From the viewpoint of maintaining low dispersibility of the glass, the Zn ion content is preferably 10.00 cation% or less, and more preferably 8.00 cation% or less, 5.00 cation% or less, 3.00 cation% or less, 1.00 cation% or less in this order.

[0041] The Zr ion content can be 0.00 cation %, 0.00 cation % or more, or more than 0.00 cation %. From the viewpoints of suppressing the increase in the liquidus temperature of the glass and maintaining low dispersibility, the Zr ion content is preferably 5.00 cation % or less, more preferably 3.00 cation % or less, still more preferably 1.00 cation % or less, and even more preferably 0.50 cation % or less.

[0042] The content of each of the Ti ion, Nb ion, W ion and Bi ion can be 0.00 cation %, 0.00 cation % or more, or more than 0.00 cation %. From the viewpoints of maintaining the thermal stability of the glass and maintaining low dispersibility, the content of each of the Ti ion, Nb ion, W ion and Bi ion is preferably 5.00 cation % or less, more preferably 3.00 cation % or less, still more preferably 1.00 cation % or less, and even more preferably 0.50 cation % or less.

[0043] The Cl ion content can be 0.00 anion %, 0.00 anion % or more, or more than 0.00 anion %. From the viewpoint of suppressing the deterioration of the glass quality due to creep by suppressing the creep of the glass to the outer periphery of the pipe when the molten glass flows out of the pipe, the Cl ion content is preferably 1.00 anion % or less, more preferably 0.50 anion % or less, and still more preferably 0.30 anion % or less.

[0044] The content of each of the Sb ion and Ce ion can be 0.00 cation %, 0.00 cation % or more, or more than 0.00 cation %. By adding Sb and / or Ce, a clarification effect can be obtained. The content of each of the Sb ion and Ce ion is preferably 1.00 cation % or less, more preferably 0.50 cation % or less, and still more preferably 0.30 % or less.

[0045] Since there are concerns about the environmental impact of Pb, Cd, As, and Th, it is preferable that the above optical glass does not contain these elements. That is, the above optical glass is preferably a glass that does not contain Pb, Cd, As, and Th in the glass composition expressed in cation% and in the glass expressed in atomic%.

[0046] Cu, Co, Ni, Fe, Cr, Eu, Nd, and Er are elements that cause coloring. Therefore, it is preferable that the above optical glass does not contain these elements. The content in the glass composition expressed in atomic% of each of the above elements is preferably 100 ppm or less, more preferably 80 ppm or less, and even more preferably 50 ppm or less. The above optical glass is preferably a glass that does not contain Cu, Co, Ni, Fe, Cr, Eu, Nd, and Er in the glass composition expressed in cation% and in the glass expressed in atomic%.

[0047] Since Hf, Ga, Ge, Te, and Tb are expensive components, it is preferable that the above optical glass does not contain these elements. That is, the above optical glass is preferably a glass that does not contain Hf, Ga, Ge, Te, and Tb in the glass composition expressed in cation% and in the glass expressed in atomic%.

[0048] <Glass physical properties> (Coefficient of thermal expansion) By having the glass composition described above, the above optical glass can exhibit a low coefficient of thermal expansion. As an index of the coefficient of thermal expansion, the average linear expansion coefficient α at 100 °C to 300 °C can be cited. Hereinafter, the average linear expansion coefficient α at 100 °C to 300 °C will also be referred to as "α(100 - 300)". The α(100 - 300) of the above optical glass is -7 less than 155×10 -7 / K, preferably -7 154×10 -7 / K or less, more preferably -7 153×10 -7 / K or less, still more preferably -7 152×10 -7 / K or less, yet more preferably / K or less, 147×10 -7 / K or less, 146×10 -7 / K or less, 145×10 -7 / K or less in this order is more preferable. α(100 - 300) is, for example, 130×10 -7 / K or more or 132×10 -7 / K or more, but it can also be less than the values exemplified herein. The average linear expansion coefficient α at 100°C to 300°C is measured by the method defined in the Japan Optical Glass Industry Association Standard JOGIS 08 - 1975 "Method for Measuring Thermal Expansion of Optical Glass". The measurement can be carried out, for example, by preparing a cylindrical glass sample with a diameter of 5 mm and a length of 20 mm and using a thermomechanical analyzer TMA4000s manufactured by BRUKER axs.

[0049] (Abbe number νd) The above optical glass can exhibit low dispersibility by having the above glass composition. The Abbe number νd, which is an index of dispersibility, is expressed as νd=(nd - 1) / (nF - nC) using the refractive indices nd, nF, and nC at the d - line, F - line, and C - line. From the viewpoint of the usefulness as a material for optical elements, the Abbe number νd of the above optical glass is preferably more than 76.50, more preferably in the order of 77.00 or more, 77.50 or more, 77.70 or more, 78.00 or more. Also, the Abbe number νd of the above optical glass can be, for example, 90.00 or less or 85.00 or less, but it may also exceed the values exemplified herein.

[0050] (Refractive index nd) The refractive index nd of the above optical glass can be, for example, 1.45000 or more, 1.46000 or more, 1.47000 or more, 1.48000 or more, 1.49000 or more, 1.50000 or more from the viewpoint of the usefulness as a material for optical elements, and can also be, for example, 1.55000 or less or 1.54000 or less. In the present invention and this specification, "refractive index" means "refractive index nd". The refractive index nd is the refractive index at a wavelength of 587.56 nm.

[0051] (Glass transition temperature Tg) By having the above glass composition, the optical glass can exhibit a glass transition temperature Tg of, for example, 550 °C or lower, 540 °C or lower, 530 °C or lower, 520 °C or lower, 510 °C or lower, or 500 °C or lower. Further, the glass transition temperature Tg of the optical glass can be, for example, 300 °C or higher or 400 °C or higher, but can also be lower than the values exemplified herein. The glass transition temperature Tg is determined by the method described below.

[0052] (Specific gravity) A low specific gravity of the optical glass is preferable from the viewpoint of reducing the weight of the optical element. The specific gravity of the optical glass can be, for example, 4.00 g / cc or lower, 3.90 g / cc or lower, 3.85 g / cc or lower, 3.80 g / cc or lower, or 3.75 g / cc or lower. Further, the specific gravity of the optical glass can be, for example, 3.00 g / cc or higher. However, since a lower specific gravity is more preferable, the lower limit is not particularly limited. The specific gravity is determined by the Archimedes' method.

[0053] ><Manufacturing method of optical glass> The above optical glass can be obtained by weighing, formulating, and thoroughly mixing raw materials such as phosphates, fluorides, oxides, carbonates, sulfates, nitrates, hydroxides, etc. so as to obtain the target glass composition, heating and melting the mixture in a melting container, performing defoaming and stirring to produce a homogeneous and bubble-free molten glass, and then shaping this molten glass. Specifically, it can be produced using a known melting method.

[0054] [Glass material for press molding, optical element blank, and manufacturing methods thereof] Another aspect of the present invention is A glass material for press molding made of the above optical glass; An optical element blank made of the above optical glass; relates to.

[0055] According to another aspect of the present invention, A manufacturing method of a glass material for press molding, comprising a step of shaping the above optical glass into a glass material for press molding; A method for manufacturing an optical element blank, comprising a step of producing an optical element blank by press-molding the glass material for press-molding an optical glass using a press mold; A method for manufacturing an optical element blank, comprising a step of molding the optical glass into an optical element blank; is also provided.

[0056] An optical element blank is an optical element base material that approximates the shape of a target optical element and has a surface layer to be polished (a surface layer to be removed by polishing) and, if necessary, a surface layer to be ground (a surface layer to be removed by grinding) added to the shape of the optical element. By grinding and polishing the surface of the optical element blank, the optical element is finished. In one form, an optical element blank can be produced by a method of press-molding the molten glass obtained by melting an appropriate amount of the above glass (referred to as the direct press method). In another form, an optical element blank can also be produced by solidifying the molten glass obtained by melting an appropriate amount of the above glass.

[0057] Also, in another form, an optical element blank can be produced by producing a glass material for press-molding and press-molding the produced glass material for press-molding.

[0058] The press-molding of the glass material for press-molding can be performed by a known method of press-molding the glass material for press-molding in a softened state by heating using a press mold. Both heating and press-molding can be performed in the atmosphere. By annealing after press-molding to reduce the strain inside the glass, a homogeneous optical element blank can be obtained.

[0059] The glass material for press forming includes, in addition to what is called a glass gob for press forming that is directly used for press forming to produce an optical element blank in its original state, those that are subjected to machining such as cutting, grinding, and polishing and then used for press forming via the glass gob for press forming. As cutting methods, there are methods such as forming a groove in a portion to be cut on the surface of a glass plate by a method called scribing, applying local pressure to the groove portion from the back surface of the surface where the groove is formed to break the glass plate at the groove portion, and cutting the glass plate with a cutting blade. Also, as grinding and polishing methods, barrel polishing and the like can be mentioned.

[0060] The glass material for press forming can be produced, for example, by casting molten glass into a mold to form a glass plate and then cutting this glass plate into a plurality of glass pieces. Or, an appropriate amount of molten glass can be formed to produce a glass gob for press forming. An optical element blank can also be produced by reheating and softening the glass gob for press forming and then performing press forming. The method of reheating, softening, and press forming the glass to produce an optical element blank is called a reheat press method as opposed to the direct press method.

[0061] [Optical Element and Method for Manufacturing the Same] Another aspect of the present invention is an optical element made of the above optical glass and relates to. The above optical element is produced using the above optical glass. In the above optical element, one or more coatings such as a multilayer film such as an antireflection film may be formed on the glass surface.

[0062] Also, according to one aspect of the present invention, a method for manufacturing an optical element comprising a step of producing an optical element by grinding and / or polishing the above optical element blank, is also provided.

[0063] In the method for manufacturing the above optical element, machining such as grinding and polishing can be performed by applying known methods. By sufficiently cleaning and drying the surface of the optical element after machining, an optical element with high internal quality and surface quality can be obtained. In this way, an optical element made of the above optical glass can be obtained. Examples of the optical element include various lenses such as spherical lenses, aspherical lenses, and microlenses, and prisms.

[0064] In addition, the optical element made of the above optical glass is also suitable as a lens constituting a joined optical element. Examples of the joined optical element include those obtained by joining lenses together (joined lenses), those obtained by joining a lens and a prism, etc. For example, the joined optical element can be manufactured by precisely machining (e.g., spherical polishing) the joining surfaces of the two optical elements to be joined so that the shapes are inverted, applying an ultraviolet curable adhesive used for bonding the joined lenses, laminating them, and then irradiating ultraviolet light through the lenses to cure the adhesive. By manufacturing each of the plurality of optical elements to be joined using a plurality of types of glasses having different Abbe numbers νd and joining them, an element suitable for correcting chromatic aberration can be obtained.

Example

[0065] Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the embodiments shown in the examples.

[0066] [Example 1] <Sample No. 1 to 73> In order to obtain the glass compositions shown in the following table, corresponding phosphates, fluorides, nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. were used as raw materials for introducing each component. The raw materials were weighed and thoroughly mixed to prepare a blended raw material. This compounding raw material was placed in a platinum crucible and heated in a furnace set at 700 to 1100 °C for 90 minutes to melt. After stirring and homogenizing the molten glass, the molten glass was poured into a preheated mold, allowed to cool to near the glass transition temperature, and then immediately placed in an annealing furnace. After holding at a temperature around the glass transition temperature for about 30 minutes, it was gradually cooled at a rate of -30 °C / hour for 4 hours, and then allowed to cool to room temperature in the furnace, thereby obtaining each optical glass of Sample Nos. 1 to 73 shown in the following table.

[0067] <Physical Property Evaluation> The various physical properties of each optical glass shown in the table below were measured by the following methods.

[0068] (1) Average linear expansion coefficient α at 100 °C to 300 °C For each optical glass, the average linear expansion coefficient α at 100 °C to 300 °C was measured by the method defined in the Japan Optical Glass Industry Association Standard JOGIS 08-1975 "Method for Measuring Thermal Expansion of Optical Glass". Specifically, a cylindrical glass sample with a diameter of 5 mm and a length of 20 mm was prepared, and the measurement was carried out using a thermomechanical analyzer TMA4000s manufactured by BRUKER axs.

[0069] (2) Refractive index nd and Abbe number νd For each optical glass, the refractive index nd and the Abbe number νd were measured by the refractive index measurement method of the Japan Optical Glass Industry Association Standard.

[0070] (3) Glass transition temperature Tg A sample obtained by thoroughly pulverizing the glass in a mortar was used as the sample, a platinum cell was used as the sample container, and the glass transition temperature Tg was measured using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN at a heating rate of 10 °C / min.

[0071] (4) Specific gravity The specific gravity was measured by the Archimedes method.

[0072] The above results are shown in the following table.

[0073]

Table 1-1

[0074]

Table 1-2

[0075]

Table 1-3

[0076]

Table 1-4

[0077]

Table 1-5

[0078]

Table 1-6

[0079]

Table 1-7

[0080]

Table 2-1

[0081]

Table 2-2

[0082]

Table 2-3

[0083]

Table 2-4

[0084]

Table 2-5

[0085]

Table 2-6

[0086]

Table 2-7

[0087] (Example 2) Using the various glasses obtained in Example 1, a glass block (glass gob) for press molding was produced. This glass block was heated and softened in the air and press molded in a press mold to produce a lens blank (optical element blank). The produced lens blank was taken out of the press mold, annealed, and machined including polishing to produce a spherical lens made of the various glasses produced in Example 1. As a result of visually observing the produced spherical lens, cracks and fractures were not confirmed.

[0088] (Example 3) A desired amount of the molten glass produced in Example 1 was press molded in a press mold to produce a lens blank (optical element blank). The produced lens blank was taken out of the press mold, annealed, and machined including polishing to produce a spherical lens made of the various glasses produced in Example 1. As a result of visually observing the produced spherical lens, cracks and fractures were not confirmed.

[0089] (Example 4) The glass block (optical element blank) produced by solidifying the molten glass produced in Example 1 was annealed and machined including polishing to produce a spherical lens made of the various glasses produced in Example 1.

[0090] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims be included. For example, with respect to the glass compositions exemplified above, by performing the composition adjustment described in the specification, an optical glass according to one aspect of the present invention can be obtained. In addition, it is of course possible to arbitrarily combine two or more of the matters exemplified or described as preferred ranges in the specification.

Claims

1. comprising O ions, F ions, Al ions, P ions, Mg ions, Ca ions, Sr ions and Ba ions as essential components, in the glass composition expressed in atomic %, the ratio (O / P) of the content of O ions to the content of P ions is 3.30 or more and 4.50 or less, the ratio (Al / P) of the content of Al ions to the content of P ions is 1.50 or less, the ratio (F / Al) of the content of F ions to the content of Al ions is 6.00 or less, in the glass composition expressed in cation %, the total content (Mg + Ca + Sr + Ba) of Mg ions, Ca ions, Sr ions and Ba ions is 40.00 cation % or more, and the cation ratio ((Mg + Ca) / (Mg + Ca + Sr + Ba)) of the total content of Mg ions and Ca ions to the total content of Mg ions, Ca ions, Sr ions and Ba ions is 0.40 or more, an optical glass.

2. The optical glass according to claim 1, wherein the total content (Li + Na + K) of Li ions, Na ions and K ions is 20.00 cation % or less.

3. The optical glass according to claim 1, wherein the cation ratio (Mg / Ba) of the content of Mg ions to the content of Ba ions is 0.05 or more and 5.00 or less.

4. The optical glass according to claim 1, wherein the total content (Mg + Ca) of Mg ions and Ca ions is 1.00 cation % or more and 50.00 cation % or less.

5. The optical glass according to claim 1, wherein the total content (Y + La + Gd + Yb) of Y ions, La ions, Gd ions and Yb ions is 0.10 cation % or more and 5.00 cation % or less.

6. The optical glass according to claim 1, wherein the total content (Si + B) of Si ions and B ions is 10.00 cation % or less.

7. The average linear expansion coefficient α at 100°C to 300°C is less than 155×10 －７ / K, and the optical glass according to claim 1.

8. the total content (Li + Na + K) of Li ions, Na ions and K ions is 20.00 cation % or less, the cation ratio (Mg / Ba) of the content of Mg ions to the content of Ba ions is 0.05 or more and 5.00 or less, the total content (Mg + Ca) of Mg ions and Ca ions is 1.00 cation % or more and 50.00 cation % or less, the total content (Y + La + Gd + Yb) of Y ions, La ions, Gd ions and Yb ions is 0.10 cation % or more and 5.00 cation % or less, The total content of Si ions and B ions (Si + B) is 10.00 cation% or less, and The average linear expansion coefficient α at 100°C to 300°C is less than 155×10 －７ / K, and the optical glass according to claim 1.

9. An optical element made of the optical glass according to any one of Claims 1 to 8.

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