Optical glass, optical elements, optical systems, cemented lenses, interchangeable lenses for cameras, objective lenses for microscopes, and optical devices

Abstract

An optical glass wherein: in mass%, the SiO2 content is 33-60%; the TiO2 content is 10-35%; the Na2O content is 15-40%; and the refractive index nd at d-line is not more than 1.71.

Description

Technical Field

[0001] The present invention relates to optical glass, optical elements, optical systems, cemented lenses, interchangeable lenses for cameras, objective lenses for microscopes, and optical devices. The present invention claims the priority of Japanese Patent Application No. 2021-095258 filed on June 7, 2021, and for designated countries where incorporation by reference is recognized, the contents described in that application are incorporated herein by reference.

Background Art

[0002] As optical glass that can be used for optical elements used in optical devices such as cameras, for example, Patent Document 1 discloses SiO2-B2O3-Nb2O5-based optical glass.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The first aspect according to the present invention is, in mass%, SiO2 content: 33 % or more 60% or less TiO2 content: 10 % or more 35% or less Na2O content: 15 % or more 40% or less, Total content of SiO2, TiO2, and Na2O (SiO2 + TiO2 + Na2O): 95.00% or more and 99% or less , SiO 2 and Na 2 O and TiO 2 The ratio of the Na 2 O content to the total content of (SiO 2 + TiO 2 + Na 2 O) (Na 2 O / (SiO 2 + TiO 2 + Na 2 O)): 0.25 or more and 0.40 or less That is, it is optical glass. Further, in mass%, SiO2 content: 33 % or more 60%or less , TiO₂ content: 10 % or more 35% or less , Na₂O content: 15 % or more 40% or less, S Total content of iO₂ and Na₂O (SiO₂ + Na₂O): 76.67% or more 85% or less, Na 2 The ratio of the TiO 2 content to the Na 2 O content (TiO 2 / Na It is an optical glass. Also, in mass%, SiO₂ content: 33 O): 0.77 or more and 1.6 or less 60% % or more , TiO₂ content: 10 or less 32% % or more , Na₂O content: 15 or less 40% % or more , Total content of SiO₂, TiO₂ and Na₂O (SiO₂ + TiO₂ + Na₂O): 93.49% or more and 99% or less or less, SiO 2 and Na 2 O and TiO 2 The ratio of the Na 2 O content to the total content of (SiO 2 + TiO 2 + Na 2 O) (Na 2 O / (SiO 2 + TiO 2 + Na 2 O)): 0.25 or more and 0.40 or less It is an optical glass.

[0005] The second aspect according to the present invention is an optical element using the above optical glass.

[0006] The third aspect according to the present invention is an optical system including the above optical element.

[0007] The fourth aspect according to the present invention is an interchangeable lens for a camera including an optical system including the above optical element.

[0008] The fifth aspect according to the present invention is an objective lens for a microscope including an optical system including the above optical element.

[0009] The sixth aspect according to the present invention is an optical device including an optical system including the above optical element.

[0010] The seventh aspect of the present invention is a cemented lens having a first lens element and a second lens element, wherein at least one of the first lens element and the second lens element is the above-described optical glass.

[0011] The eighth aspect of the present invention is an optical system including the above-described cemented lens.

[0012] The ninth aspect of the present invention is an objective lens for a microscope including an optical system including the above-described cemented lens.

[0013] The tenth aspect of the present invention is an interchangeable lens for a camera including an optical system including the above-described cemented lens.

[0014] The eleventh aspect of the present invention is an optical device including an optical system including the above-described cemented lens.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

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Figure 6

Modes for Carrying Out the Invention

[0016] Hereinafter, embodiments according to the present invention (hereinafter referred to as "the present embodiment") will be described. The following present embodiment is an exemplification for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be appropriately modified and implemented within the scope of its gist.

[0017] In this specification, unless otherwise specified, the content ratio of each component is assumed to be mass% (mass percentage) with respect to the total weight of the glass in terms of oxide conversion composition. Here, the oxide conversion composition means a composition in which oxides, composite salts, etc. used as raw materials for the glass constituent components of the present embodiment are all decomposed into oxides when melted and changed, and the total mass of the oxides is set to 100 mass%, and each component contained in the glass is expressed.

[0018] In addition, the expression "0 to N%" for the Q content ratio includes the case where the Q component is not contained and the case where the Q component exceeds 0% and is N% or less.

[0019] In addition, the expression "devitrification resistance stability" means the resistance of the glass to devitrification. Here, "devitrification" means a phenomenon in which the transparency of the glass is lost due to crystallization or phase separation that occurs when the glass is heated above the glass transition temperature or when the melt is cooled below the liquidus temperature.

[0020] The optical glass according to the present embodiment has, in mass%, a SiO2 content ratio of 33 to 60%, a TiO2 content ratio of 10 to 35%, and a Na2O content ratio of 15 to 40%, and the refractive index n at the d line dIt is an optical glass with a refractive index nd at the d-line of 1.71 or less. Further, the optical glass according to the present embodiment has, by mass%, an SiO2 content of 33 to 60%, a TiO2 content of 10 to 35%, a Na2O content of 15 to 40%, and an Sb2O3 content of more than 0% to 1%, and is an optical glass with a refractive index nd at the d-line of 1.71 or less. Further, the optical glass according to the present embodiment has, by mass%, an SiO2 content of 33 to 60%, a TiO2 content of 10 to 35%, a Na2O content of 15 to 40%, a total content of SiO2, TiO2, and Na2O (SiO2 + TiO2 + Na2O) of 75% or more, a total content of SiO2 and Na2O (SiO2 + Na2O) of 55 to 85%, and a ratio of TiO2 content to Na2O content (TiO2 / Na2O) of 0.3 to 1.6, and is an optical glass.

[0021] In order to increase the degree of freedom in the design of optical systems such as optical devices, an optical glass having a high dispersion and a small value of ΔP, which is a value indicating anomalous dispersion, g,F is required. ΔP g,F In order to produce an optical glass with a small ΔP, a composition containing a large amount of generally expensive Nb2O5 component is generally required. By containing a large amount of Nb2O5 component, while keeping the refractive index (n d ) with respect to the d-line at a small value, it was difficult to reduce the Abbe number (ν d ).

[0022] Further, the optical glass according to the present embodiment can also be a low specific gravity optical glass with a specific gravity of 3.10 or less.

[0023] Hereinafter, the components of the optical glass according to the present embodiment will be described.

[0024] SiO2 forms a glass skeleton and keeps the refractive index at a small value while keeping ΔP g,FIt is a component that reduces the SiO2 content. If this content is too low, the devitrification resistance stability of the glass will be insufficient. If this content is too high, the meltability of the glass will decrease and the viscosity of the glass itself will increase, making molding difficult. From these points of view, the SiO2 content is 33 to 60%. The lower limit of this content is preferably 34%, more preferably 36%, even more preferably 47.3%, and even more preferably 47.5%. The upper limit of this content is preferably 58%, more preferably 55%, and even more preferably 54%.

[0025] TiO2 is a component that increases the refractive index of glass and makes it highly dispersive. However, if its content is too high, d and ΔP g,F It is a component that significantly increases the transmittance and also deteriorates the transmittance. From this viewpoint, the TiO2 content is 10 to 35%. The lower limit of this content is preferably 11%, more preferably 14%, and even more preferably 20%. The upper limit of this content is preferably 34%, more preferably 32%, and even more preferably 29%.

[0026] Na2O improves the melting property of the raw material, and reduces ΔP while maintaining a low refractive index and high dispersion. g,F If the NaO content is too high, chemical durability and devitrification resistance stability will decrease. From this viewpoint, the NaO content is 15 to 40%. The lower limit of this content is preferably 17%, more preferably 19%, and even more preferably 21%. The upper limit of this content is preferably 38%, more preferably 37%, and even more preferably 36%.

[0027] The optical glass according to this embodiment may further contain, as an optional component, one or more components selected from the group consisting of B2O3, La2O3, Gd2O3, Y2O3, ZrO2, Nb2O5, MgO, Ta2O5, ZnO, BaO, CaO, SrO, Al2O3, WO3, Li2O, K2O, and Sb2O3.

[0028] Furthermore, for each of the above-described components, more preferable combinations are as follows: B2O3 content: 0 to 10%, La2O3 content: 0 to 5%, Gd2O3 content: 0 to 5%, Y2O3 content: 0 to 5%, ZrO2 content: 0 to 20%, Nb2O5 content: 0 to 25%, MgO content: 0 to 5%, Ta2O5 content: 0 to 10%, ZnO content: 0 to 25%, BaO content: 0 to 5%, CaO content: 0 to 5%, SrO content: 0 to 5%, Al2O3 content: 0 to 5%, WO3 content: 0 to 5%, Li2O content: 0 to 5%, K2O content: 0 to 10%, Sb2O3 content: 0 to 1%.

[0029] B2O3 is a component that forms a glass skeleton and improves chemical durability. If the content of this component is too high, it will highly disperse and ΔP g,F will increase. From such a perspective, the content of B2O3 is 0 to 10%. And the lower limit of this content is preferably more than 0%, more preferably 1%, and still more preferably 3%. Also, the upper limit of this content is preferably less than 10%, more preferably 8%, and still more preferably 7%.

[0030] La2O3 is a component effective for adjusting the constants of the glass. From such a perspective, as a preferable embodiment, the content of La2O3 may be 0 to 5%. And the lower limit of this content is more preferably more than 0%, and still more preferably 0.5%. Also, the upper limit of this content is more preferably 4%, and still more preferably 3%.

[0031] Gd2O3 is a component effective for adjusting the constants of the glass. From such a perspective, as a preferable embodiment, the content of Gd2O3 may be 0 to 5%. And the lower limit of this content is more preferably more than 0%, and still more preferably 0.5%. Also, the upper limit of this content is more preferably 4%, and still more preferably 3%.

[0032] Y2O3 is a component effective for adjusting the constants of the glass. From this perspective, as a preferred embodiment, the content of Y2O3 may be 0 to 5%. And the lower limit of this content is more preferably more than 0%, and still more preferably 0.5%. Also, the upper limit of this content is more preferably 4%, and still more preferably 3%.

[0033] ZrO2 is a component that increases the refractive index of the glass and achieves high dispersion while suppressing the increase of ΔP g,F If the content of ZrO2 is too high, the fusibility of the glass raw material and the devitrification resistance stability will decrease. From this perspective, the content of ZrO2 is 0 to 20%. And the lower limit of this content is preferably more than 0%, more preferably 4%, still more preferably 8%, and even more preferably 10%. Also, the upper limit of this content is preferably 16%, more preferably 14%, still more preferably 12%. ZrO2 can be mutually substituted with SiO2. When substituting SiO2 to increase the content of ZrO2, the glass can be made to have a higher refractive index and higher dispersion while suppressing the increase of ΔP g ,F

[0034] Nb2O5 is a component that increases the refractive index of the glass and achieves high dispersion while suppressing the increase of ΔP g,F If the content of Nb2O5 is too high, the refractive index will increase. Also, from the perspective of further improving the devitrification resistance stability and the perspective of raw material cost, the content of Nb2O5 is 0 to 25%. And the lower limit of this content is preferably more than 0%, more preferably 5%, still more preferably 8%. Also, the upper limit of this content is preferably less than 25%, more preferably 23%, still more preferably 20%, and even more preferably less than 20%.

[0035] MgO is a component effective for adjusting the constants of the glass. From this perspective, the content of MgO is preferably 0 to 5%. And the lower limit of this content is more preferably more than 0%, and still more preferably 0.5%. Also, the upper limit of this content is more preferably 4%, and still more preferably 3%.​

[0036] Ta2O5 is a component that increases the refractive index of the glass and achieves high dispersion while suppressing the increase in ΔP g,F From the viewpoints of further improving the devitrification resistance stability and the raw material cost, the content of Ta2O5 is preferably 0 to 10%. And the lower limit of this content is more preferably more than 0%, still more preferably 0.5%, and even more preferably 2%. Also, the upper limit of this content is more preferably 8%, still more preferably 7%, and even more preferably 6%. Since Ta2O5 has a similar effect to ZrO2, it can be mutually substituted with ZrO2.

[0037] ZnO is a component that increases the refractive index of the glass and achieves high dispersion. If the content of ZnO is too high, the refractive index will increase. Also, from the viewpoint of further improving the devitrification resistance stability, the content of ZnO is preferably 0 to 25%. And the lower limit of this content is more preferably more than 0%, still more preferably 5%, and even more preferably 10%. Also, the upper limit of this content is more preferably 23%, still more preferably 19%.

[0038] BaO is a component effective for adjusting the constants of the glass. From such a viewpoint, the content of BaO is preferably 0 to 5%. And the lower limit of this content is more preferably more than 0%, still more preferably 0.5%. Also, the upper limit of this content is more preferably 4%.

[0039] CaO is a component effective for adjusting the constants of the glass. From such a viewpoint, the content of CaO is preferably 0 to 5%. And the lower limit of this content is more preferably more than 0%, still more preferably 0.5%. Also, the upper limit of this content is more preferably 4%.

[0040] SrO is a component effective for adjusting the constants of the glass. From this perspective, the content of SrO is preferably 0 to 5%. And the lower limit of this content is more preferably more than 0%, and still more preferably 0.5%. Also, the upper limit of this content is more preferably 4%.

[0041] Al2O3 is a component effective for adjusting the constants of the glass. From this perspective, the content of Al2O3 is preferably 0 to 5%. And the lower limit of this content is more preferably more than 0%, and still more preferably 0.5%. Also, the upper limit of this content is more preferably 4%.

[0042] WO3 is a component effective for adjusting the constants of the glass. From this perspective, the content of WO3 is preferably 0 to 5%. And the lower limit of this content is more preferably more than 0%, and still more preferably 0.5%. Also, the upper limit of this content is more preferably 4%.

[0043] Li2O is a component that increases the refractive index of the glass and improves the meltability of the glass raw materials. If the content is too high, the devitrification resistance stability decreases and ΔP g,F increases. From this perspective, the content of Li2O is 0 to 5%. And the lower limit of this content is preferably more than 0%, more preferably 0.3%, and still more preferably 0.5%. Also, the upper limit of this content is preferably 3.4%, more preferably 2.4%, and still more preferably 1.4%.

[0044] K2O increases the meltability of the raw materials and keeps the low refractive index and high dispersion while ΔP g,FAlthough it is a component that reduces [the relevant property], if its content rate is too high, it will result in low dispersion and also reduce chemical durability. From this perspective, the content rate of K2O is preferably 0 to 10%. And the lower limit of this content rate is more preferably more than 0%, still more preferably 0.5%, and even more preferably 0.8%. Also, the upper limit of this content rate is preferably 5%, more preferably 4%, still more preferably 3%, and even more preferably 2%. Note that K2O can be mutually substituted with Na2O.

[0045] Sb2O3 is a component that functions as a defoaming agent for clarifying glass, but if its content rate is too high, it will reduce the transmittance. From this perspective, the content rate of Sb2O3 is preferably 0 to 1%. And the lower limit of this content rate is more preferably more than 0%, still more preferably 0.02%, and even more preferably 0.03%. Also, the upper limit of this content rate is more preferably 0.5%, still more preferably 0.2%, and even more preferably 0.1%. Sb2O3 may be mutually substituted with at least one of SiO2, Na2O, and TiO2. If it is within the above preferred range, it will not significantly change the optical constant.

[0046] From the perspective of reducing the refractive index, part or all of the above one or more oxides may be substituted with fluorides. Fluorine (F) contained in the fluoride reduces the refractive index of the glass and also causes low dispersion, and ΔP g,FIt is increased. Therefore, the content rate of the mass of F (fluorine) divided by the total mass of the glass in terms of oxide composition is 0 to 15%. In the present specification, the content rate of the mass of F (fluorine) divided by the total mass of the glass in terms of oxide composition means the mass percentage of the mass of fluorine (F) with respect to the sum of the mass of the oxide composition, the mass of the oxide conversion of the cation component of the fluoride, and the mass of fluorine (F): mass of fluorine (F) / (mass of oxide composition + mass of oxide conversion of cation component of fluoride + mass of fluorine (F)). In other words, when the total content rate of the mass of the oxide conversion of all components other than fluorine (F) is 100%, it represents the mass of fluorine (F) with respect to the sum of the mass of the oxide conversion of all components other than fluorine (F) and the mass of fluorine (F) in mass %. The lower limit of this content rate is preferably more than 0%, more preferably 4%, and still more preferably 8%. Also, the upper limit of this content rate is preferably 13%, more preferably 10%, and still more preferably 9%. As fluoride, for example, K2SiF6, Na2SiF6, ZrF4, AlF3, NaF, CaF2, LaF3, etc. can be used as raw materials to contain fluorine in the glass. Also, the mass of the oxide conversion of the cation component of the fluoride means, for example, when K2SiF6 is used as the raw material, since the cation components of K2SiF6 are K and Si, it refers to the amount obtained by converting the masses of these two into K2O and SiO2.

[0047] On the other hand, the optical glass according to this embodiment can achieve a desired optical constant without containing elements with a large environmental load such as As, Pb, and Cd. From such a viewpoint, it is preferable that the optical glass according to this embodiment does not substantially contain each of the elements As, Pb, and Cd.

[0048] The optical glass according to this embodiment is required to have good transmittance and not emit fluorescence. Elements that cause coloring and fluorescence, such as Fe, Ni, Cr, Mn, Ag, Cu, Mo, Eu, Au, etc., are preferably not intentionally added from the stage of preparing the raw materials, and more preferably do not substantially contain them.

[0049] In this specification, "substantially free of" means that the component is not contained as a constituent component that affects the properties of the glass composition beyond the concentration at which it is inevitably contained as an impurity. Since the allowable ratio as an impurity varies depending on the raw material, for example, if the content is less than 40 ppm, preferably less than 30 ppm, more preferably less than 10 ppm, and even more preferably less than 8 ppm, it is considered to be substantially free of.

[0050] In addition, optional components may be added to the optical glass according to the present embodiment so as to satisfy the following conditions.

[0051] ΔP g,F From the viewpoint of not increasing ΔP, the ratio of the total content of B2O3, K2O, and Al2O3 to the Na2O content ((B2O3 + K2O + Al2O3) / Na2O)) is preferably 0 to 0.5. The lower limit of this ratio is more preferably greater than 0, still more preferably 0.10, and even more preferably 0.15. The upper limit of this ratio is more preferably 0.34, still more preferably 0.22, and even more preferably 0.20.

[0052] From the viewpoint of further improving the meltability and devitrification resistance stability of the glass raw material and achieving high dispersion, the total content of K2O and Al2O3 (K2O + Al2O3) is preferably 0 to 10%. The lower limit of this total content is more preferably greater than 0%, still more preferably 0.10%, and even more preferably 0.15%. The upper limit of this total content is preferably 5%, more preferably 4.1%, still more preferably 2.8%, and even more preferably 1.8%.

[0053] From the perspective of further improving the fusibility and devitrification resistance stability of the glass raw materials and achieving high dispersion, the total content rate of MgO, CaO, SrO, and BaO (MgO + CaO + SrO + BaO) is preferably 0 to 10%. And the lower limit of this total content rate is more preferably more than 0%, still more preferably 1%, and even more preferably 1.4%. Also, the upper limit of this total content rate is preferably 5%, more preferably 3.5%, still more preferably 2%, and even more preferably less than 1.5%.

[0054] From the perspective of further improving the fusibility and devitrification resistance of the glass raw materials and achieving high dispersion, the total content rate of La2O3, Gd2O3, and Y2O3 (La2O3 + Gd2O3 + Y2O3) is preferably 0 to 10%. And the lower limit of this total content rate is more preferably more than 0%, still more preferably 1%, and even more preferably 1.5%. Also, the upper limit of this total content rate is preferably 5%, more preferably 4%, still more preferably 3%, and even more preferably 2%.

[0055] From the perspective of further improving the fusibility and devitrification resistance stability of the glass raw materials and achieving high dispersion, the total content rate of Li2O, Na2O, and K2O (Li2O + Na2O + K2O) is preferably 15 to 40%. And the lower limit of this total content rate is more preferably 15%, still more preferably 17%, and even more preferably 19%. Also, the upper limit of this total content rate is more preferably 35%, still more preferably 32%, and even more preferably 30%.

[0056] To improve the devitrification resistance stability and reduce ΔP g,F From the perspective of making it smaller, the ratio of the B2O3 content rate to the SiO2 content rate (B2O3 / SiO2) is preferably 0 to 0.15. And the lower limit of this ratio is more preferably more than 0, still more preferably 0.03, and even more preferably 0.05. Also, the upper limit of this ratio is more preferably 0.14, still more preferably 0.13, and even more preferably 0.12.

[0057] While achieving a low refractive index, high dispersion, and a small ΔP g,F From the perspective of reducing ΔP while achieving high dispersion, the total content rate of SiO2, TiO2, and Na2O (SiO2 + TiO2 + Na2O) is 75% or more. And the lower limit of this total content rate is preferably 84%, more preferably 90%, still more preferably 94%. Also, the upper limit of this total content rate is preferably 99%, more preferably 98%, still more preferably 96%.

[0058] While achieving high dispersion and a small ΔP g,F From the perspective of reducing ΔP while achieving high dispersion, the total content rate of SiO2 and Na2O (SiO2 + Na2O) is 55% - 85%. And the lower limit of this total content rate is preferably 76%, more preferably 76.5%, still more preferably 77%. Also, the upper limit of this total content rate is preferably 80%, more preferably 79.5%, still more preferably 79%.

[0059] While achieving high dispersion and a small ΔP g,F From the perspective of reducing ΔP while achieving high dispersion, the ratio of TiO2 to Na2O (TiO2 / Na2O) is 0.3 - 1.6. And the lower limit of this ratio is preferably 0.40, more preferably 0.77, still more preferably 0.80. Also, the upper limit of this ratio is preferably 1.0, more preferably 0.97, still more preferably 0.96, even more preferably 0.94.

[0060] While achieving a low refractive index, high dispersion, and a small ΔP g,F From the perspective of reducing ΔP while achieving high dispersion, the ratio of the Na2O content rate to the total content rate of SiO2, TiO2, and Na2O (Na2O / (SiO2 + TiO2 + Na2O)) is preferably 0.18 - 0.40. The lower limit of this ratio is preferably 0.19, more preferably 0.21, still more preferably 0.23, even more preferably 0.25. The upper limit of this ratio is preferably 0.39, more preferably 0.37, still more preferably 0.35, even more preferably 0.27.

[0061] If necessary, for the purpose of clarification, coloring, decoloring, or fine adjustment of optical constant values, etc., known clarifying agents, coloring agents, and defoaming agents can be added in appropriate amounts to the glass composition, with an upper limit of 0.5% by external addition. Here, external addition means, for example, in the case of a clarifying agent, when the total content rate of the oxides of all glass components excluding the clarifying agent is taken as 100%, the mass of the clarifying agent relative to the sum of the mass of the oxides of all glass components excluding the clarifying agent and the mass of the clarifying agent (mass of clarifying agent / (mass of oxides of all glass components excluding the clarifying agent + mass of clarifying agent)), expressed as mass%. The definition of external addition for coloring agents and defoaming agents is the same. Specifically, tin oxide (SnO2) is used as the defoaming agent. Also, not limited to the above components, other components can be added within the range where the effects of the optical glass according to this embodiment can be obtained.

[0062] Regarding each of the above-described components, it is preferable to use high-purity products with a low impurity content as raw materials. For example, it is preferable to use high-purity products for one or more of the SiO2 raw material and the B2O3 raw material. A high-purity product is one that contains 99.85 mass% or more of the component. By using high-purity products, the impurity content is reduced, and as a result, for example, the internal transmittance of light with a wavelength of 400 nm or less tends to be higher.

[0063] Next, the physical properties, etc. of the optical glass according to this embodiment will be described.

[0064] Regarding the refractive index (n d ) of the optical glass according to this embodiment with respect to the d-line, as a preferred example, it is in the range of 1.58 to 1.71, with a lower limit of 1.58 and an upper limit of 1.71. The lower limit of the refractive index is more preferably 1.60, even more preferably 1.605, and even more preferably 1.61. Also, the upper limit of the refractive index is more preferably 1.705, even more preferably 1.70, and even more preferably 1.634.

[0065] Also, the Abbe number (ν dRegarding , as a preferred example, it is in the range of 25 to 42 with 25 as the lower limit and 42 as the upper limit. The lower limit of the Abbe number is preferably 28, more preferably 28.5, and even more preferably 29. Also, the upper limit of the Abbe number is more preferably 41, and even more preferably 40.

[0066] In addition, the refractive index (n d ) with respect to the d-line of the optical glass according to the present embodiment and the Abbe number (ν d ) are the values measured by the V-block method or the minimum deviation method.

[0067] Furthermore, the value (ΔP g,F ) indicating the anomalous dispersibility of the optical glass according to the present embodiment is preferably 0.0060 or less, more preferably 0.0040 or less, and even more preferably 0.0020 or less.

[0068] Furthermore, as the optical glass according to the present embodiment, the refractive index (n d ) is 1.58 to 1.71, the Abbe number (ν d ) is 25 to 42, and it is preferable to have each physical property such that the value (ΔP g,F ) indicating the anomalous dispersibility is 0.0060 or less.

[0069] Moreover, the partial dispersion ratio (P g,F ) of the optical glass according to the present embodiment is preferably 0.603 or less, more preferably 0.600 or less, even more preferably 0.590 or less, and still more preferably 0.585 or less.

[0070] Note that the refractive index, Abbe number, value indicating anomalous dispersibility, and partial dispersion ratio can be measured in accordance with the methods described in the examples below.

[0071] As described above, the optical glass according to the present embodiment has a low refractive index (the refractive index (n d ) is small), a high dispersion (the Abbe number (ν d ) is small), and yet the value (ΔP g,F) can be made smaller. Furthermore, by using such optical glass, for example, an optical system with good correction of chromatic aberration and other aberrations can be designed. In addition, the optical glass according to this embodiment does not contain a large amount of Nb2O5, and since the raw material cost is low, it can be supplied at low cost.

[0072] The specific gravity (S g ) of the optical glass according to this embodiment is preferably 3.10 or less, more preferably 3.08 or less, still more preferably 3.06 or less, and even more preferably 3.00 or less. Since the optical glass according to this embodiment can also have such a low specific gravity, it can be suitably used as a material for lightweight optical elements and the like.

[0073] The manufacturing method of the optical glass according to this embodiment is not particularly limited, and a known method can be adopted. Also, the manufacturing conditions can be appropriately selected as suitable conditions. For example, oxides, hydroxides, phosphate compounds (phosphates, orthophosphoric acid, etc.), carbonates, sulfates, nitrates, and fluorides corresponding to the above-mentioned respective raw materials are formulated to achieve the target composition, and preferably melted at 1100 to 1500 °C, more preferably 1340 to 1400 °C, homogenized by stirring, degassed, and then a manufacturing method such as casting into a mold can be adopted. The optical glass thus obtained can be processed into a desired shape by performing a reheat press or the like as necessary and polished or the like to obtain a desired optical element.

[0074] And from the same viewpoint, the manufacturing method of the optical glass according to this embodiment includes at least a step of heating the raw material of the optical glass at 1340 to 1400 °C, and preferably the time until 50 g of the raw material of the optical glass melts when heated at a temperature of 1340 to 1400 °C is less than 15 minutes. By heating at 1340 to 1400 °C using such a raw material with a melting time, the remaining glass raw material during the heating process is not mixed into the glass, and high-quality optical glass can be produced with good yield.

[0075] From the above viewpoints, the optical glass according to the present embodiment can be suitably used, for example, as an optical element included in an optical device. Such optical elements include mirrors, lenses, prisms, filters, and the like. Examples of the optical system in which the above optical element is used include an objective lens, a condenser lens, an imaging lens, an interchangeable lens for a camera, and the like. These optical systems can be suitably used in various optical devices such as an imaging device such as an interchangeable-lens camera or a fixed-lens camera, and a microscope device such as a fluorescence microscope or a multiphoton microscope. Such optical devices are not limited to the above-described imaging devices and microscopes, and include, but are not limited to, telescopes, binoculars, laser rangefinders, projectors, and the like. An example of each of these will be described below.

[0076] <Imaging device> FIG. 1 is a perspective view showing an example in which the optical device according to the present embodiment is an imaging device. The imaging device 1 is a so-called digital single-lens reflex camera (interchangeable-lens camera), and the photographing lens 103 (optical system) includes an optical element having the optical glass according to the present embodiment as a base material. A lens barrel 102 is detachably attached to a lens mount (not shown) of the camera body 101. Then, the light passing through the lens 103 of the lens barrel 102 is imaged on a sensor chip (solid-state imaging device) 104 of a multi-chip module 106 disposed on the back side of the camera body 101. The sensor chip 104 is a bare chip such as a so-called CMOS image sensor, and the multi-chip module 106 is, for example, a COG (Chip On Glass) type module in which the sensor chip 104 is mounted as a bare chip on a glass substrate 105.

[0077] FIGS. 2 and 3 are schematic views showing other examples in which the optical device according to the present embodiment is an imaging device. FIG. 2 shows a front view of the imaging device CAM, and FIG. 3 shows a rear view of the imaging device CAM. The imaging device CAM is a so-called digital still camera (fixed-lens camera), and the photographing lens WL (optical system) includes an optical element having the optical glass according to the present embodiment as a base material.

[0078] When the imaging device CAM presses the power button (not shown), the shutter (not shown) of the photographing lens WL opens, light from the subject (object) is collected by the photographing lens WL, and an image is formed on the imaging element arranged on the image plane. The subject image formed on the imaging element is displayed on the liquid crystal monitor M arranged behind the imaging device CAM. After determining the composition of the subject image while looking at the liquid crystal monitor M, the photographer presses the release button B1 to image the subject image with the imaging element and records and stores it in the memory (not shown).

[0079] The imaging device CAM is provided with an auxiliary light emitting unit EF that emits auxiliary light when the subject is dark, a function button B2, etc. used for various condition settings of the imaging device CAM, etc.

[0080] Such optical systems used in digital cameras and the like are required to have higher resolution, lower chromatic aberration, and smaller size. To achieve these, it is effective to use glasses with different dispersion characteristics in the optical system. In particular, there is a high demand for glasses having a lower dispersion and a higher partial dispersion ratio (P g , F ) From this perspective, the optical glass according to the present embodiment is suitable as a member of such optical devices. Note that the optical devices applicable in the present embodiment are not limited to the above-described imaging devices, and examples include projectors and the like. Regarding optical elements, they are not limited to lenses, and examples include prisms and the like.

[0081] <Microscope> FIG. 4 is a block diagram showing an example of the configuration of the multiphoton microscope 2 according to the present embodiment. The multiphoton microscope 2 includes an objective lens 206, a condenser lens 208, and an imaging lens 210. At least one of the objective lens 206, the condenser lens 208, and the imaging lens 210 includes an optical element having the optical glass according to the present embodiment as a base material. Hereinafter, the optical system of the multiphoton microscope 2 will be mainly described.

[0082] The pulsed laser device 201 emits ultrashort pulsed light, for example, with a near-infrared wavelength (about 1000 nm) and a pulse width in femtosecond units (for example, 100 femtoseconds). The ultrashort pulsed light immediately after being emitted from the pulsed laser device 201 is generally linearly polarized light polarized in a predetermined direction.

[0083] The pulse splitting device 202 splits the ultrashort pulsed light and emits it with an increased repetition frequency of the ultrashort pulsed light.

[0084] The beam adjustment unit 203 has functions such as adjusting the beam diameter of the ultrashort pulsed light incident from the pulse splitting device 202 to match the pupil diameter of the objective lens 206, adjusting the converging and diverging angles of the ultrashort pulsed light to correct the axial chromatic aberration (focus difference) between the wavelength of the light emitted from the sample S and the wavelength of the ultrashort pulsed light, and a pre-chirp function (group velocity dispersion compensation function) that gives the ultrashort pulsed light an inverse group velocity dispersion to correct the broadening of the pulse width of the ultrashort pulsed light due to group velocity dispersion while passing through the optical system.

[0085] The ultrashort pulsed light emitted from the pulsed laser device 201 has its repetition frequency increased by the pulse splitting device 202, and the above-described adjustments are performed by the beam adjustment unit 203. Then, the ultrashort pulsed light emitted from the beam adjustment unit 203 is reflected by the dichroic mirror 204 in the direction of the dichroic mirror, passes through the dichroic mirror 205, and is converged by the objective lens 206 and irradiated onto the sample S. At this time, the ultrashort pulsed light may be scanned on the observation surface of the sample S by using scanning means (not shown).

[0086] For example, when observing fluorescence of the sample S, in the irradiated region of the ultrashort pulsed light on the sample S and its vicinity, the fluorescent dye with which the sample S is stained is multi-photon excited, and fluorescence (hereinafter referred to as "observation light") having a wavelength shorter than that of the ultrashort pulsed light with an infrared wavelength is emitted.

[0087] Observation light emitted from the sample S in the direction of the objective lens 206 is collimated by the objective lens 206 and, depending on its wavelength, is reflected by the dichroic mirror 205 or transmitted through the dichroic mirror 205.

[0088] The observation light reflected by the dichroic mirror 205 enters the fluorescence detection unit 207. The fluorescence detection unit 207 is composed of, for example, a barrier filter, a PMT (photo multiplier tube), etc., receives the observation light reflected by the dichroic mirror 205, and outputs an electrical signal corresponding to the amount of the light. Also, the fluorescence detection unit 207 detects the observation light over the observation surface of the sample S in accordance with the scanning of the ultrashort pulsed light over the observation surface of the sample S.

[0089] Note that by removing the dichroic mirror 205 from the optical path, all the observation light emitted from the sample S in the direction of the objective lens 206 may be detected by the fluorescence detection unit 211. In that case, after passing through the scanning means (not shown), the observation light passes through the dichroic mirror 204, is condensed by the condenser lens 208, passes through the pinhole 209 provided at a position substantially conjugate with the focal position of the objective lens 206, passes through the imaging lens 210, and enters the fluorescence detection unit 211.

[0090] The fluorescence detection unit 211 is composed of, for example, a barrier filter, a PMT, etc., receives the observation light imaged on the light receiving surface of the fluorescence detection unit 211 by the imaging lens 210, and outputs an electrical signal corresponding to the amount of the light. Also, the fluorescence detection unit 211 detects the observation light over the observation surface of the sample S in accordance with the scanning of the ultrashort pulsed light over the observation surface of the sample S.

[0091] Note that by removing the dichroic mirror 205 from the optical path, all the observation light emitted from the sample S in the direction of the objective lens 206 may be detected by the fluorescence detection unit 211.

[0092] In addition, the observation light emitted from the sample S in the direction opposite to the objective lens 206 is reflected by the dichroic mirror 212 and enters the fluorescence detection unit 213. The fluorescence detection unit 113 is composed of, for example, a barrier filter, a PMT, etc., receives the observation light reflected by the dichroic mirror 212, and outputs an electrical signal corresponding to the amount of the light. In addition, the fluorescence detection unit 213 detects the observation light over the observation surface of the sample S in accordance with the scanning of the ultrashort pulsed light over the observation surface of the sample S.

[0093] The electrical signals respectively output from the fluorescence detection units 207, 211, and 213 are input to, for example, a computer (not shown), and the computer can generate an observation image based on the input electrical signals, display the generated observation image, or store the data of the observation image.

[0094] <Bonding lens> FIG. 5 is a schematic diagram showing an example of the bonding lens according to the present embodiment. The bonding lens 3 is a compound lens having a first lens element 301 and a second lens element 302. At least one of the first lens element and the second lens element uses the optical glass according to the present embodiment. The first lens element and the second lens element are joined via a joining member 303. As the joining member 303, a known adhesive or the like can be used. Note that the "lens element" means each lens constituting a single lens or a bonding lens.

[0095] The bonding lens according to the present embodiment is useful from the viewpoint of chromatic aberration correction and can be suitably used for the above-described optical elements, optical systems, optical devices, etc. And the optical system including the bonding lens can be suitably used particularly for an interchangeable lens for a camera, an optical device, etc. In the above-described aspect, the bonding lens using two lens elements has been described, but the present invention is not limited thereto, and a bonding lens using three or more lens elements may be used. When a bonding lens using three or more lens elements is used, it is sufficient that at least one of the three or more lens elements is formed using the optical glass according to the present embodiment.

Example

[0096] Next, examples and comparative examples of the present invention will be described. Note that the present invention is not limited thereto.

[0097] Each table shows the chemical composition, refractive index (n d ), Abbe number (ν d ), specific gravity (S g ), partial dispersion ratio (P g,F ), value indicating anomalous dispersion (ΔP g,F ), and devitrification resistance stability of the optical glass according to each example and each comparative example, based on the mass% of each component on an oxide basis.

[0098] <Fabrication of Optical Glass> The optical glass according to each example and each comparative example was fabricated by the following procedure. First, glass raw materials such as oxides, carbonates, and nitrates were weighed so that the weight of the oxide after melting would be 100 g to achieve the chemical composition (mass%) described in each table. Next, the weighed raw materials were mixed and put into a platinum crucible with an internal volume of about 100 mL, and melted at a temperature of 1250 - 1400 °C for about 70 minutes and stirred for homogenization. After clarification, it was cast into a mold or the like and slowly cooled and molded to obtain each sample. For Example 19, it was melted at 1300 °C for about 40 minutes and then dropped into water to produce frit, and the frit was melted at 1300 °C for 30 minutes and stirred for homogenization, and then cast into a mold or the like and slowly cooled and molded to obtain a sample.

[0099] <Physical Property Evaluation> Figure 6 is a graph plotting P g,F and ν d for each example and each comparative example.

[0100] Refractive index (n d ) and Abbe number (ν d ) The refractive index (n d ) and Abbe number (ν d ) of each sample were measured and calculated using the V-block method for Examples 1 - 4, 6, 8, and using the minimum deviation angle method for Examples 5, 7, 9 - 19. n dshows the refractive index of the glass with respect to light of 587.562 nm. ν d was determined from the following formula (1). n C , n F , respectively show the refractive indices of the glass with respect to light of wavelengths 656.273 nm and 486.133 nm. ν d =(n d - 1) / (n F - n C ) ··· (1) The refractive index values were up to the 6th decimal place.

[0101] Specific gravity (S g ) The specific gravity (S g ) of each sample was measured by the Archimedes method as the mass ratio to the same volume of pure water at 4°C.

[0102] Devitrification resistance stability The devitrification resistance stability of each sample was determined by polishing the prepared glass and visually checking for the presence or absence of devitrification. "Devitrification present" in each table means that devitrified parts were observed in the sample, and "no devitrification" means that no devitrified parts were observed in the sample.

[0103] Partial dispersion ratio (P g , F ) The partial dispersion ratio (P g , F ) of each sample indicates the ratio of the partial dispersion (n F - n C ) to the main dispersion (n g - n F ) and was determined from the following formula (2). n g indicates the refractive index of the glass with respect to light of wavelength 435.835 nm. The value of the partial dispersion ratio (P g , F ) was up to the 4th decimal place. P g , F =(n g - n F ) / (n F - n C ) ··· (2)

[0104] Abnormal dispersibility (ΔP g,F ) The abnormal dispersibility (ΔP g,F ) of each sample indicates the deviation from the partial dispersion ratio standard line based on two types of glasses, F2 and K7, as glasses with normal dispersibility. That is, on the coordinate system with the partial dispersion ratio (P g,F ) on the vertical axis and the Abbe number ν d on the horizontal axis, the difference in the vertical coordinate between the straight line connecting the two types of glasses and the value of the glass to be compared is the deviation of the partial dispersion ratio, that is, the abnormal dispersibility (ΔP g, F ). In the above coordinate system, when the value of the partial dispersion ratio is located above the straight line connecting the reference types of glasses, the glass shows positive abnormal dispersibility (+ΔP g,F ), and when it is located below, the glass shows negative abnormal dispersibility (-ΔP g,F ). The Abbe number νd and the partial dispersion ratio (P g,F ) of F2 and K7 are as follows. F2: Abbe number νd = 36.33, partial dispersion ratio (P g,F ) = 0.5834 K7: Abbe number νd = 60.47, partial dispersion ratio (P g,F ) = 0.5429 The value of the abnormal dispersibility (ΔP g , F ) is up to the fourth decimal place. ΔP g , F = P g , F -(-0.0016777×ν d +0.6443513)···(3)

[0105] For the optical glasses of each example and each comparative example, the composition by mass% based on the oxides of each component, the mass% of the external proportion of the F component, and the evaluation results of each physical property are shown in Tables 1 to 5.

[0106]

Table 1

[0107]

Table 2

[0108]

Table 3

[0109]

Table 4

[0110]

Table 5

[0111] In Comparative Example 1, since devitrification was confirmed in the produced glass, the measurement of the optical constants was not carried out.

[0112] As described above, the optical glass of this example has a low refractive index (n d ), a small Abbe number (ν d ), a small ΔP g,F value, and has been confirmed to have excellent devitrification resistance stability. Also, it has been confirmed to have a low specific gravity, which contributes to the weight reduction of the optical system.

Explanation of Signs

[0113] 1... Imaging device, 101... Camera body, 102... Lens barrel, 103... Lens, 104... Sensor chip, 105... Glass substrate, 106... Multi-chip module, CAM... Imaging device (lens non-interchangeable camera), WL... Photographing lens, M... Liquid crystal monitor, EF... Auxiliary light emitting unit, B1... Release button, B2... Function button, 2... Multiphoton microscope, 201... Pulse laser device, 202... Pulse splitting device, 203... Beam adjustment unit, 204, 205, 212... Dichroic mirror, 206... Objective lens, 207, 211, 213... Fluorescence detection unit, 208... Condensing lens, 209... Pinhole, 210... Imaging lens, S... Specimen, 3... Joining lens, 301... First lens element, 302... Second lens element, 303... Joining member

Claims

1. In mass %, SiO ２ Content ratio: 33% or more and 60% or less, TiO ２ Content: 10% or more and 35% or less, Na ２ O content: 15% or more and 40% or less, SiO ２ and TiO ２ and Na ２ The total content rate of O (SiO ２ + TiO ２ + Na ２ O): 95.00% or more and 99% or less, The ratio of the Na₂O content to the total content of SiO₂, Na₂O, and TiO₂ (Na₂O / (SiO₂ + TiO₂ + Na₂O)): 0.25 or more and 0.40 or less, an optical glass.

2. In mass %, SiO ２ Content ratio: 33% or more and 60% or less, TiO ２ Content rate: 10% or more and 35% or less, Na ２ O content: 15% or more and 40% or less, SiO ２ and Na ２ O total content rate (SiO ２ + Na ２ O): 76.67% or more and 85% or less, The ratio of the TiO₂ content to the Na₂O content (TiO₂ / Na₂O): 0.77 or more and 1.6 or less, an optical glass.

3. In mass %, SiO ２ Content rate: 33% or more and 60% or less, TiO ２ Content: 10% or more and 32% or less, Na ２ O content: 15% or more and 40% or less, SiO ２ and TiO ２ and Na ２ The total content rate of O (SiO ２ + TiO ２ + Na ２ O): 93.49% or more and 99% or less, The ratio of the Na₂O content to the total content of SiO₂, Na₂O, and TiO₂ (Na₂O / (SiO₂ + TiO₂ + Na₂O)): 0.25 or more and 0.40 or less, an optical glass.

4. SiO ２ and Na ２ O total content rate (SiO ２ + Na ２ O): 55% or more and 85% or less, the optical glass according to claim 1 or 3.

5. In mass %, The content of F (fluorine) in terms of the mass fraction with respect to the total mass of the glass in terms of oxide composition: more than 0% and 15% or less, the optical glass according to any one of Claims 1 to 4.

6. In mass %, Sb ２ O ３ The optical glass according to any one of claims 1 to 5, having a content of 0% or more and 1% or less.

7. In mass %, B ２ O ３ Content ratio: 0% or more and 10% or less, La ２ O ３ Content ratio: 0% or more and 5% or less Gd ２ O ３ Content ratio: 0% or more and 5% or less Y ２ O ３ Content ratio: 0% or more and 5% or less ZrO ２ Content: 0% or more and 20% or less, Nb ２ O ５ Content by mass: 0% or more and 25% or less The MgO content: 0% or more and 5% or less, Ta ２ O ５ Content ratio: 0% or more and 10% or less, The ZnO content: 0% or more and 25% or less, The BaO content: 0% or more and 5% or less, The CaO content: 0% or more and 5% or less, The SrO content: 0% or more and 5% or less, Al ２ O ３ Content by mass: 0% or more and 5% or less WO ３ Content ratio: 0% or more and 5% or less, Li ２ O content: 0% or more and 5% or less, K ２ O content: 0% or more and less than 10%, The optical glass according to any one of Claims 1 to 6.

8. Na ２ The ratio of the content rate of TiO ２ to the content rate of O (TiO ２ / Na ２ O): is 0.3 or more and 1.6 or less, and the optical glass according to any one of claims 1 to 7.

9. Substantially free of each element of Pb and As, The optical glass according to any one of Claims 1 to 8.

10. Substantially free of each element of Cd, Fe, Ni, Cr, Mn, Ag, Cu, Mo, Eu, and Au, The optical glass according to any one of Claims 1 to 9.

11. The content of each element of Pb, As, Cd, Fe, Ni, Cr, Mn, Ag, Cu, Mo, Eu, and Au is less than 40 ppm, The optical glass according to any one of Claims 1 to 10.

12. Na ２ Ratio of the total content of B ２ O ３ and K ２ O and Al ２ O ３ to the Na ２ O ３ content ratio ((B ２ O + K ２ O + Al ３ O)) / Na ２ O): 0 or more and 0.5 or less, The optical glass according to any one of Claims 1 to 11.

13. K ２ O and Al ２ O ３ The total content rate of (K ２ O + Al ２ O ３ ): is 0% or more and 10% or less The optical glass according to any one of Claims 1 to 12.

14. The total content of MgO, CaO, SrO, and BaO (MgO + CaO + SrO + BaO): 0% or more and 10% or less, The optical glass according to any one of Claims 1 to 13.

15. La ２ O ３ and Gd ２ O ３ and Y ２ O ３ The total content rate of (La ２ O ３ + Gd ２ O ３ + Y ２ O ３ ): 0% or more and 10% or less The optical glass according to any one of Claims 1 to 14.

16. Li ２ O and Na ２ O and K ２ The total content ratio of O (Li ２ O + Na ２ O + K ２ O): 15% or more and 40% or less The optical glass according to any one of Claims 1 to 15.

17. SiO ２ Ratio of the content of B ２ O ３ to the content of SiO ２ O ３ / SiO ２ ): 0 or more and 0.15 or less The optical glass according to any one of Claims 1 to 16.

18. SiO ２ and Na ２ O and TiO ２ The ratio of the content of Na ２ O to the total content of (SiO ２ + TiO ２ + Na ２ O), (Na ２ O / (SiO ２ + TiO ２ + Na ２ O)): is 0.18 or more and 0.40 or less The optical glass according to any one of claims 1 to 17.

19. Refractive index (n ｄ ) with respect to the d-line is 1.58 or more and 1.71 or less, The optical glass according to any one of claims 1 to 18.

20. Abbe number (ν ｄ ) is 25 or more and 42 or less, The optical glass according to any one of claims 1 to 19.

21. Abnormal dispersibility (ΔP ｇ，Ｆ ) is 0.0060 or less, The optical glass according to any one of claims 1 to 20.

22. Partial dispersion ratio (P ｇ，Ｆ ) is 0.603 or less, The optical glass according to any one of claims 1 to 21.

23. Specific gravity (S ｇ ) is 3.10 or less, The optical glass according to any one of claims 1 to 22.

24. An optical element using the optical glass according to any one of claims 1 to 23.

25. An optical system including the optical element according to claim 24.

26. An interchangeable lens for a camera including the optical system according to claim 25.

27. An objective lens for a microscope including the optical system according to claim 25.

28. An optical device including the optical system according to claim 25.

29. Having a first lens element and a second lens element, A cemented lens, wherein at least one of the first lens element and the second lens element is the optical glass according to any one of claims 1 to 23.

30. An optical system including the cemented lens according to claim 29.

31. An objective lens for a microscope including the optical system according to claim 30.

32. An interchangeable lens for a camera including the optical system according to claim 30.

33. An optical device including the optical system according to claim 30.

Images