Optical glass, optical element using optical glass, optical system, interchangeable lens, optical device, and method for manufacturing optical glass

Abstract

To provide an optical glass that features high diepersion and small abnormal dispersion ΔPg,F.SOLUTION: An optical glass contains, in mass%, SiO2 component: 17-35%, B2O3 component: 0-13%, ZrO2 component: 0-10%, Nb2O5 component: 34-52%, Na2O component: 0-10%, MgO component: 0-10% (excluding 0%), Li2O component: 0-10% (excluding 0%), WO3 component: 0-3%. Based on mass percentage, the ratio of SiO2 to MgO (SiO2 / MgO) is 5-27.5.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical glass, an optical element, an optical system, an interchangeable lens, an optical device, and a method for manufacturing the optical glass, which use the optical glass. [Background technology]

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

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-169157 Summary of the Invention

[0004] The first aspect of the present invention is a composition containing, in mass%, SiO2 Content rate :17 % or more 35% below , B2O3 Content rate :0 % or more 13% below , ZrO2 Content rate :0 % or more 10% below , Nb2O5 Content rate :34 % or more 52% below , Na2O Content rate :0 % or more 10% below , MgO Content rate :0 Greater than % 10% below, LiO Content rate :0 Greater than % 10% below , WO3 Content rate :0 % or more 3% below , La 2 O 3 and Gd 2 O 3 and Y 2 O 3 and Lu 2O 3 Total content of La 2 O 3 +Gd 2 O 3 +Y 2 O 3 +Lu 2 O 3 ) is 0% or more and 2% or less, Li relative to MgO 2 O ratio (Li 2 O / MgO) is 0.1 or more and 3.7 or less, and SiO to MgO 2 and B 2 O 3 The ratio of the sum of (SiO 2 +B 2 O 3 ) / MgO) is 8 or more and 39 or less, That is, optical glass.

[0005] A second aspect of the present invention is an optical element using the optical glass described above.

[0006] A third aspect of the present invention is an optical system including the optical element described above.

[0007] A fourth aspect of the present invention is an interchangeable lens comprising the optical system described above.

[0008] A fifth aspect of the present invention is an optical device comprising the optical system described above.

[0009] A sixth aspect of the present invention is a method for producing an optical glass, comprising the steps of: 50g 1340 ℃ or higher 1400℃ The time it takes to melt when heated at the following temperature Less than 15 minutes a melting step of melting the raw materials at a temperature of 1100°C or higher and 1500°C or lower; and a molding step of molding the molten raw materials, and the optical glass has a glass transition temperature (T g ) is 560 ° C or less, and SiO 2 Content rate: 17% or more and 35% or less, B 2 O 3 Content rate: 0% or more and 13% or less, ZrO 2 Content: 0% or more and 10% or less, Nb 2 O 5 Content: 34% to 50%, Na 2 O content: 0% to 10%, Li 2 O content: greater than 0% and less than 10%, K 2 O content: greater than 0% and less than 7%, WO 3 Content rate: 0% or more and 3% or less, La 2 O 3 and Gd 2 O 3 and Y 2 O 3 and Lu 2 O 3 Total content of La 2 O 3 +Gd2 O 3 +Y 2 O 3 +Lu 2 O 3 ): 0% or more and 3% or less, This is a method for manufacturing optical glass. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view of an imaging device equipped with an optical element using the optical glass according to this embodiment. [Figure 2] FIG. 2 is a front view of another example of an imaging device equipped with an optical element using the optical glass according to this embodiment. [Figure 3] FIG. 3 is a rear view of the imaging device of FIG. [Figure 4] FIG. 4 is a block diagram showing an example of the configuration of a multiphoton microscope equipped with an optical element using the optical glass according to this embodiment. [Figure 5] FIG. 5 is a graph showing the relationship between the partial dispersion ratio (Pg,F) and the Abbe number (νd) of the optical glass of this example. DETAILED DESCRIPTION OF THE INVENTION

[0011] An embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described below. The present embodiment is an example for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be practiced with appropriate modifications within the scope of its gist.

[0012] In this specification, unless otherwise specified, the content of each component is expressed as mass % of the total weight of the glass in terms of oxide composition. Note that the oxide composition referred to here is a composition in which each component contained in the glass is expressed, assuming that the oxides, composite salts, etc. used as raw materials for the glass constituent components of this embodiment are all decomposed and converted to oxides during melting, and the total mass of the oxides is taken as 100 mass %.

[0013] The optical glass according to this embodiment contains, in mass %, an SiO2 component: 17 to 35%, a B2O3 component: 0 to 13%, a ZrO2 component: 0 to 10%, an Nb2O5 component: 34 to 52%, a Na2O component: 0 to 10%, an MgO component: more than 0 to 10%, a Li2O component: more than 0 to 10%, and a WO3 component: 0 to 3%, and the ratio of SiO2 to MgO (SiO2 / MgO), in mass %, is 5 to 27.5.

[0014] In order to increase the degree of freedom in designing optical systems such as optical devices, ΔP is a value that indicates anomalous dispersion while maintaining high dispersion. g,F While optical glass with a small Abbe number (ν d ) becomes smaller, ΔP g,F tends to be large, and small ΔP g,F In this regard, the optical glass according to this embodiment has a small ΔP while having high dispersion. g,F This solves the problem. The optical glass according to this embodiment also has excellent resistance to devitrification.

[0015] Furthermore, the optical glass according to this embodiment can have a composition that reduces volatile loss during melting. This reduces adhesion of volatile components to the melting furnace during production, thereby achieving excellent productivity. Furthermore, because the glass has a low glass transition temperature, it can also be made into an optical glass that is excellent in press formability and mold formability and has a low specific gravity.

[0016] The components of the optical glass according to this embodiment will be described below.

[0017] SiO2 forms a glass skeleton, and ΔP g,FIt is a component that reduces the refractive index. If the content is too low, the devitrification resistance of the glass will be insufficient. If the content is too high, it will be difficult to give the glass a high refractive index, and the viscosity of the glass itself will increase, making molding difficult. From these perspectives, the SiO2 content is 17 to 35%. The lower limit of this content is preferably 18%, more preferably 19%. The upper limit of this content is preferably 34%, more preferably 33%.

[0018] B2O3 forms a glassy framework, and ΔP g,F If the B2O3 content is too high, it becomes difficult to achieve a high refractive index of the glass, and the viscosity decreases, resulting in poor devitrification resistance. From this perspective, the B2O3 content is 0 to 13%. The lower limit of this content is preferably more than 0%, more preferably 3%, and even more preferably 5%. The upper limit of this content is preferably 12%, more preferably 10%, and even more preferably 9%.

[0019] ZrO2 is a component that increases the refractive index of the glass and provides high dispersion, as well as ΔP g,F If the content is too high, the meltability and devitrification resistance of the glass raw materials will decrease. From this viewpoint, the content of ZrO2 is 0 to 10%. The lower limit of this content is preferably more than 0%, more preferably 2%, and even more preferably 3%. The upper limit of this content is preferably 9%, more preferably 8.5%, and even more preferably 8%.

[0020] Nb2O5 is a component that increases the refractive index and makes the glass highly dispersible. If the content is too low, it becomes difficult to achieve a high refractive index and high dispersion. If the content is too high, devitrification resistance decreases. From this viewpoint, the Nb2O5 content is 34 to 52%. The lower limit of this content is preferably 35%, more preferably 36%, and even more preferably 37%. The upper limit of this content is preferably 51%, more preferably 50%, and even more preferably 49%.

[0021] Na2O increases the melting property of the raw material and g,F If the content is too high, it becomes difficult to achieve a high refractive index, and devitrification resistance also decreases. From this viewpoint, the content of Na2O is 0 to 10%. The lower limit of this content is preferably 4%, more preferably 4.5%, and even more preferably 5.5%. The upper limit of this content is preferably 8%, more preferably 7%, and even more preferably 6.5%.

[0022] MgO has a ΔP g,F It is a component that has the effect of increasing the devitrification resistance of the glass without increasing the refractive index. If MgO is not contained, the devitrification resistance of the glass decreases, making it difficult to achieve a high refractive index. If the content is too high, it becomes difficult to achieve high dispersion in the glass. From this perspective, the MgO content is more than 0 to 10%. The lower limit of this content is preferably 1.5%, more preferably 2.5%. The upper limit of this content is preferably 6%, more preferably 4%.

[0023] Li2O is a component that increases the refractive index of glass and improves the meltability of glass raw materials. If this content is too high, devitrification resistance decreases. From this perspective, the Li2O content is more than 0 to 10%. The lower limit of this content is preferably 0.5%, more preferably 1.0%, and even more preferably 1.5%. The upper limit of this content is preferably 8%, more preferably 7%, and even more preferably 6%.

[0024] WO3 is a component that increases the refractive index of the glass, provides high dispersion, and further improves devitrification resistance. From this perspective, the WO3 content is 0 to 3%. The lower limit of this content is preferably more than 0%, and more preferably 0.5%. The upper limit of this content is preferably 2.5%.

[0025] From the viewpoint of improving the meltability and devitrification resistance of the glass raw materials and achieving high dispersion, the mass ratio of SiO2 to MgO (SiO2 / MgO) is 5 to 27.5. The lower limit of this ratio is preferably 6, more preferably 6.5, and even more preferably 7. The upper limit of this ratio is preferably 27, more preferably 26, and even more preferably 25.

[0026] The optical glass according to this embodiment preferably further contains, as an optional component, one or more components selected from the group consisting of a La2O3 component, a Ta2O5 component, a ZnO component, a BaO component, an Al2O3 component, a K2O component, a TiO2 component, and a Sb2O3 component.

[0027] Furthermore, a more preferred combination of the above-mentioned components is Ta2O5 component: 0-6%, ZnO component: 0-8%, BaO component: 0-3%, Al2O3 component: 0-2%, K2O component: 0-7%, TiO2 component: 0-10%, and Sb2O3 component: 0-1%.

[0028] La2O3 is a component effective for adjusting the constants of glass and for improving devitrification resistance. From this viewpoint, in a preferred embodiment, the La2O3 content may be 0 to 3%. The lower limit of this content is more preferably more than 0%, and even more preferably 0.5%. The upper limit of this content is more preferably 1%.

[0029] Ta2O5 increases the refractive index of the glass, provides high dispersion, and increases ΔP g,FIt is a component that reduces the Ta2O5 content. From the viewpoint of further improving devitrification resistance and from the viewpoint of raw material costs, the Ta2O5 content is preferably 0 to 6%. The upper limit of this content is more preferably 3%, even more preferably 1.5%, and still more preferably 1%. The lower limit of this content is more preferably more than 0%, and even more preferably 0.5%.

[0030] On the other hand, the optical glass according to this embodiment has a high refractive index, high dispersion, and a small ΔP g,F From this perspective, when it is desired to further reduce the cost of the optical glass according to this embodiment, it is preferable that Ta2O5 is not substantially contained.

[0031] In this specification, the term "substantially free" means that the component is not contained as a constituent component that affects the properties of the glass composition at a concentration exceeding the concentration that is inevitably contained as an impurity. For example, a content of about 100 ppm is considered to be substantially free.

[0032] ZnO is a component that increases the refractive index of the glass and further improves devitrification resistance. From this perspective, the ZnO content is preferably 0 to 8%. The upper limit of this content is more preferably 7%, and even more preferably 6%. The lower limit of this content is more preferably greater than 0%, and even more preferably 0.3%, and even more preferably 0.4%.

[0033] BaO is a component that increases the refractive index of glass, but if its content is too high, ΔP g,F From this viewpoint, the BaO content is preferably 0 to 3%. The upper limit of this content is more preferably 1%. The lower limit of this content is more preferably more than 0%, and even more preferably 0.5%.

[0034] Al2O3 is a component that disperses glass and improves chemical durability, but if its content is too high, ΔPg,F From this viewpoint, the content of Al2O3 is preferably 0 to 2%. The upper limit of this content is more preferably 1.5%, and even more preferably 1%. The lower limit of this content is more preferably more than 0%, and even more preferably 0.5%.

[0035] K2O is a component that increases the refractive index of glass and improves the melting properties of glass raw materials. However, if the content is too high, ΔP g,F From this viewpoint, the content of K2O is preferably 0 to 7%. The upper limit of this content is more preferably 6%, even more preferably 5%, and even more preferably 4.5%. The lower limit of this content is more preferably more than 0%, even more preferably 0.5%, and even more preferably 1%.

[0036] TiO2 is a component that increases the refractive index of glass and makes it highly dispersible, but if its content is too high, ΔP g,F It is a component that significantly increases the transmittance and also deteriorates the transmittance. From this viewpoint, the content of TiO2 is preferably 0 to 10%. The upper limit of this content is more preferably 9%, even more preferably 8%, and still more preferably 7%. The lower limit of this content is more preferably greater than 0%, even more preferably 0.5%, and still more preferably 3%.

[0037] Sb2O3 is a component that functions as a defoaming agent for clarifying glass, but if its content is too high, it reduces transmittance. From this perspective, the Sb2O3 content is preferably 0 to 1%. The upper limit of this content is more preferably 0.5%. The lower limit of this content is more preferably more than 0%, and even more preferably 0.03%.

[0038] Furthermore, in addition to the components described above, the optical glass according to this embodiment may contain further optional components so as to satisfy the following conditions.

[0039] From the viewpoint of further improving the meltability and devitrification resistance of the glass raw materials and achieving high dispersion, the mass ratio of B2O3 to MgO (B2O3 / MgO) is preferably 0 to 5. The upper limit of this ratio is more preferably 4.5, even more preferably 4, and still more preferably 3.5. The lower limit of this ratio is more preferably greater than 0, even more preferably 1.0, and still more preferably 1.5.

[0040] From the viewpoint of further improving the meltability and devitrification resistance of the glass raw materials and achieving high dispersion, the mass ratio of the sum of SiO2 and B2O3 to MgO ((SiO2 + B2O3) / MgO) is preferably 8 to 39. The upper limit of this ratio is more preferably 30, even more preferably 25, and still more preferably 20. The lower limit of this ratio is more preferably 9, even more preferably 10, and still more preferably 11.

[0041] From the viewpoint of further improving devitrification resistance and achieving high dispersion, the mass ratio of Li2O to MgO (Li2O / MgO) is preferably 0.1 to 3.7. The upper limit of this ratio is more preferably 3, even more preferably 2.5, and still more preferably 2.2. The lower limit of this ratio is more preferably 0.2, even more preferably 0.4, and still more preferably 0.8.

[0042] Improved devitrification resistance, ΔP g,F From the viewpoint of reducing the mass ratio of MgO to the sum of MgO, BaO, SrO, and CaO (MgO / (MgO+BaO+SrO+CaO)) is preferably 0.35 to 1.0. The lower limit of this ratio is more preferably 0.4, even more preferably 0.5, and still more preferably 0.8.

[0043] From the viewpoint of improving devitrification resistance, the mass ratio of the sum of Nb2O5 and TiO2 to MgO ((Nb2O5 + TiO2) / MgO) is preferably 5 to 60. The upper limit of this ratio is more preferably 40, even more preferably 35, and still more preferably 30. The lower limit of this ratio is more preferably 6, even more preferably 8, and still more preferably 9.

[0044] Improved devitrification resistance, ΔP g,F From the viewpoint of reducing the content, the sum of La2O3, Gd2O3, Y2O3, and Lu2O3 (La2O3 + Gd2O3 + Y2O3 + Lu2O3) is preferably 0 to 3%. The upper limit of this sum is more preferably less than 3%, even more preferably 2%, and even more preferably 1%.

[0045] ΔP g,F From the viewpoint of reducing the content and achieving high dispersion, the value obtained by subtracting MgO from the sum of CaO, SrO, and BaO ((CaO+SrO+BaO)-MgO) is preferably 1% or less, more preferably less than 1%, even more preferably 0.6% or less, and still more preferably 0.3% or less. Note that even when this value ((CaO+SrO+BaO)-MgO) is a negative value, it falls under the above-mentioned "1% or less" and the like.

[0046] In addition to the components described above, the optical glass according to this embodiment may contain appropriate amounts of known fining agents, colorants, defoamers, fluorine compounds, phosphoric acid, and other components added to the glass composition for the purpose of clarifying, coloring, decoloring, adjusting optical constants, etc. Furthermore, other components may be added in addition to the components described above, as long as the effects of this embodiment can be obtained.

[0047] For each of the above-mentioned components, it is preferable to use high-purity products with 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. The use of high-purity products reduces the amount of impurities, which tends to increase the internal transmittance of light with a wavelength of 400 nm or less, for example.

[0048] Next, the physical properties of the optical glass according to this embodiment will be described.

[0049] The refractive index (n d ) is preferably in the range of 1.71 to 1.90, with a lower limit of 1.71 and an upper limit of 1.90. The upper limit of the refractive index is more preferably 1.89, and even more preferably 1.88. The lower limit of the refractive index is more preferably 1.72, and even more preferably 1.73.

[0050] In addition, the Abbe number (ν d ) is preferably in the range of 24 to 34, with a lower limit of 24 and an upper limit of 34. The upper limit of the Abbe number is more preferably 33.5, and even more preferably 33. The lower limit of the Abbe number is more preferably 24.5, and even more preferably 25.

[0051] Furthermore, the value indicating the anomalous dispersion of the optical glass according to this embodiment (ΔP g,F ) is preferably 0.0100 or less, more preferably 0.0090 or less, even more preferably 0.0080 or less, and still more preferably 0 or less.

[0052] Furthermore, the optical glass according to this embodiment has a refractive index (n d ) is 1.71 to 1.90, and the Abbe number (ν d ) is 24 to 34, and the value indicating anomalous dispersion (ΔP g,F) is 0.0100 or less.

[0053] Furthermore, the partial dispersion ratio (P g,F ) is preferably 0.613 or less, more preferably 0.610 or less, and even more preferably 0.590 or less.

[0054] The refractive index, Abbe number, anomalous dispersion value, and partial dispersion ratio can be measured in accordance with the method described in the examples below.

[0055] As described above, the optical glass according to this embodiment has a high refractive index (refractive index (n d )), high dispersion (large Abbe number (ν d ) is small), while the value indicating anomalous dispersion (ΔP g,F ) can be reduced. Furthermore, the partial dispersion ratio can be reduced. By using such optical glass, it is possible to reduce the thickness of optical elements such as optical lenses, and to design optical systems in which chromatic aberration and other aberrations are well corrected.

[0056] The specific gravity (S g ) is preferably 3.75 or less, more preferably 3.5 or less, even more preferably 3.4 or less, and even more preferably 3.35 or less. The optical glass according to this embodiment can be made to have such a low specific gravity, and therefore can be suitably used as a material for lightweight optical elements, etc.

[0057] The glass transition temperature (T g ) is preferably 560°C or lower, more preferably 555°C or lower. The optical glass according to this embodiment can have a low glass transition temperature, which further improves formability during reheat pressing. It also improves mold formability. The glass transition temperature can be measured in accordance with the method described in the Examples below.

[0058] When 50 mg of raw materials for optical glass (glass raw materials) are heated from 700°C to 1300°C at a heating rate of 20°C / min, the volatilization loss between 1000 and 1300°C is preferably 0.51 mg or less, more preferably 0.46 mg or less, and even more preferably 0.40 mg or less. When 50 mg of raw materials for optical glass (glass raw materials) are heated from 700°C to 1300°C at a heating rate of 20°C / min, the volatilization loss between 1200 and 1300°C is preferably 0.43 mg or less, more preferably 0.38 mg or less, and even more preferably 0.32 mg or less. Glass raw materials with such a small volatilization loss suppress adhesion of volatile components to a melting furnace during glass melting, thereby preventing the inclusion of bubbles and foreign matter caused by volatilization dropping into molten glass and enabling the production of high-quality glass with a high yield.

[0059] The method for producing the optical glass according to this embodiment is not particularly limited, and known methods can be employed. Furthermore, suitable production conditions can be selected as appropriate. For example, oxides, hydroxides, phosphate compounds (phosphates, orthophosphates, etc.), carbonates, sulfates, nitrates, fluorides, etc. corresponding to the above-mentioned raw materials are mixed to achieve the target composition, melted preferably at 1100 to 1500°C, more preferably 1340 to 1400°C, stirred to homogenize, and then allowed to defoam, and then poured into a mold for molding. The optical glass thus obtained can be processed into the desired shape by reheat pressing, etc., as needed, and polished to form the desired optical element.

[0060] When 50 g of raw materials (glass frits) for optical glass are heated at a temperature of 1340 to 1400°C, the time required for the raw materials to melt (melting time) is preferably less than 15 minutes. If the glass frits do not melt within a short time in the temperature range of 1340 to 1400°C, the remaining glass frits may become mixed into the glass. Furthermore, if the glass frits are heated at a higher temperature or maintained at a higher temperature for a longer period in an attempt to melt the remaining glass frits, this may result in a decrease in glass production efficiency and a deterioration in transmittance. From this perspective, if the melting time for the raw materials (glass frits) for optical glass is less than 15 minutes, it is possible to effectively prevent the remaining glass frits from becoming mixed into the glass, as well as a decrease in glass production efficiency and a decrease in transmittance.

[0061] From the same viewpoint, the method for producing optical glass according to this embodiment preferably includes at least a step of heating raw materials for the optical glass at 1340 to 1400° C., and the time it takes for 50 g of raw materials for the optical glass to melt when heated at a temperature of 1340 to 1400° C. is less than 15 minutes. By using raw materials with such a melting time and heating at 1340 to 1400° C., residual glass raw materials remaining during the heating step do not get mixed into the glass, and high-quality optical glass can be produced with a good yield.

[0062] The optical glass according to this embodiment is suitable as an optical element, such as a lens, for use in optical devices such as cameras and microscopes. Examples of such optical elements include mirrors, lenses, prisms, and filters. Examples of optical systems that include these optical elements include objective lenses, condenser lenses, imaging lenses, and interchangeable camera lenses. These can be used in imaging devices such as interchangeable-lens cameras and non-interchangeable-lens cameras, and microscopes such as multiphoton microscopes. Optical devices are not limited to the imaging devices and microscopes described above, but also include video cameras, teleconverters, telescopes, binoculars, monoculars, laser rangefinders, projectors, and the like. Examples of these devices are described below.

[0063] <Imaging device> FIG. 1 is a perspective view of an imaging device equipped with an optical element using the optical glass according to this embodiment.

[0064] The imaging device 1 is a so-called digital single-lens reflex camera (interchangeable lens camera), and the taking lens 103 (optical system) is equipped with an optical element whose base material is the optical glass according to this embodiment. A lens barrel 102 is detachably attached to a lens mount (not shown) of a camera body 101. Light passing through a lens 103 of the lens barrel 102 forms an image on a sensor chip (solid-state image sensor) 104 of a multi-chip module 106 disposed on the rear side of the camera body 101. This 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 bare-chip mounted on a glass substrate 105.

[0065] FIG. 2 is a front view of another example of an imaging device equipped with an optical element using the optical glass according to this embodiment, and FIG. 3 is a rear view of the imaging device of FIG.

[0066] This imaging device CAM is a so-called digital still camera (lens non-interchangeable camera), and the taking lens WL (optical system) is equipped with an optical element whose base material is the optical glass according to this embodiment.

[0067] When the power button (not shown) of the imaging device CAM is pressed, the shutter (not shown) of the taking lens WL is opened, and light from the subject (object) is collected by the taking lens WL and formed into an image on an imaging element arranged on the image plane. The subject image formed on the imaging element is displayed on an LCD monitor LM arranged behind the imaging device CAM. After the photographer decides the composition of the subject image while looking at the LCD monitor LM, he or she presses the release button B1 to capture the subject image with the imaging element, which is then recorded and saved in memory (not shown).

[0068] The image pickup device CAM is provided with an auxiliary light emitting section EF that emits auxiliary light when the subject is dark, a function button B2 used to set various conditions for the image pickup device CAM, and the like.

[0069] The optical systems used in digital cameras and other devices require higher resolution, lighter weight, and smaller size. To achieve these, it is effective to use glass with a high refractive index. In particular, glass with a high refractive index and a low specific gravity (S g ) and has excellent press-formability and mold-formability, there is a great demand for glass. From this perspective, the optical glass according to this embodiment is suitable as a component of such optical equipment. Note that optical equipment to which this embodiment can be applied is not limited to the imaging device described above, but also includes, for example, projectors. The optical element is also not limited to a lens, but also includes, for example, a prism.

[0070] <Multiphoton microscope> FIG. 4 is a block diagram showing an example of the configuration of a multiphoton microscope 2 equipped with an optical element using optical glass according to this embodiment.

[0071] 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 whose base material is the optical glass according to this embodiment. The following description will focus on the optical system of the multiphoton microscope 2.

[0072] The pulsed laser device 201 emits ultrashort pulsed light, for example, with a near-infrared wavelength (approximately 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 in a predetermined direction.

[0073] The pulse splitting device 202 splits the ultrashort pulsed light, increases the repetition frequency of the ultrashort pulsed light, and emits it.

[0074] The beam adjusting unit 203 has functions such as a function to adjust the beam diameter of the ultrashort pulsed light incident from the pulse splitter 202 to match the pupil diameter of the objective lens 206, a function to adjust the focusing and divergence angles of the ultrashort pulsed light in order to correct the axial chromatic aberration (focus difference) between the wavelength of the multiphoton excitation light emitted from the sample S and the wavelength of the ultrashort pulsed light, and a pre-chirp function (group velocity dispersion compensation function) to impart an inverse group velocity dispersion to the ultrashort pulsed light in order to correct the pulse width of the ultrashort pulsed light being widened by group velocity dispersion while passing through the optical system.

[0075] The repetition frequency of the ultrashort pulsed light emitted from the pulsed laser device 201 is increased by the pulse dividing device 202, and the above-mentioned adjustment is performed by the beam adjusting unit 203. Then, the ultrashort pulsed light emitted from the beam adjusting unit 203 is reflected by the dichroic mirror 204 in the direction of the dichroic mirror 205, passes through the dichroic mirror 205, and is collected by the objective lens 206 to be irradiated onto the sample S. At this time, the ultrashort pulsed light may be scanned over the observation surface of the sample S by using a scanning means (not shown).

[0076] For example, when observing the fluorescence of a sample S, the fluorescent dye with which the sample S is stained undergoes multiphoton excitation in the area of ​​the sample S irradiated with the ultrashort pulsed light and in its vicinity, emitting fluorescence (hereinafter referred to as "observation light") with a wavelength shorter than that of the ultrashort pulsed light, which is an infrared wavelength.

[0077] Observation light emitted from the sample S in the direction of the objective lens 206 is collimated by the objective lens 206 and is either reflected by or transmitted through the dichroic mirror 205 depending on its wavelength.

[0078] The observation light reflected by the dichroic mirror 205 enters the fluorescence detection unit 207. The fluorescence detection unit 207 is configured with, for example, a barrier filter, a PMT (photomultiplier tube), etc., receives the observation light reflected by the dichroic mirror 205, and outputs an electrical signal according to the amount of light. Furthermore, the fluorescence detection unit 207 detects the observation light across the observation surface of the sample S as the ultrashort pulsed light scans the observation surface of the sample S.

[0079] On the other hand, the observation light that has passed through the dichroic mirror 205 is descanned by a scanning means (not shown), passes through the dichroic mirror 204, is focused by the focusing lens 208, passes through a pinhole 209 located at a position approximately conjugate with the focal position of the objective lens 206, passes through an imaging lens 210, and enters the fluorescence detection unit 211.

[0080] The fluorescence detection unit 211 is configured with, 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 according to the amount of light. Furthermore, the fluorescence detection unit 211 detects the observation light across the observation surface of the sample S as the ultrashort pulsed light scans the observation surface of the sample S.

[0081] It is also possible to remove the dichroic mirror 205 from the optical path so that all of the observation light emitted from the sample S in the direction of the objective lens 206 is detected by the fluorescence detection unit 211 .

[0082] Furthermore, 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 213 is configured, for example, with a barrier filter, a PMT, etc., and receives the observation light reflected by the dichroic mirror 212 and outputs an electrical signal according to the amount of light. Furthermore, the fluorescence detection unit 213 detects the observation light across the observation surface of the sample S as the ultrashort pulsed light scans the observation surface of the sample S.

[0083] The electrical signals output from the fluorescence detection units 207, 211, and 213 are input, for example, to a computer (not shown), which can generate an observation image based on the input electrical signals, display the generated observation image, and store the data of the observation image. [Example]

[0084] Examples and comparative examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0085] Each table shows the chemical composition of each component in terms of mass % based on the oxide, the refractive index (n d ), Abbe number (ν d ), glass transition temperature (T g ), specific gravity (S g ), partial dispersion ratio (P g,F ), the value indicating anomalous dispersion (ΔP g,F ) and the observation of the devitrification resistance of the prepared glass, and the volatilization loss of the prepared glass are shown together with the results of the experiment.

[0086] <Production of optical glass> The optical glasses according to each example and comparative example were produced by the following procedure. First, glass raw materials such as oxides, carbonates, and nitrates were weighed out to a total weight of 100 g so as to obtain the chemical composition (mass %) shown in each table. Next, the weighed raw materials were mixed and placed in a platinum crucible with a capacity of approximately 100 mL, and melted and stirred for approximately 70 minutes at a temperature of 1340 to 1400°C to homogenize. After fining, the mixture was poured into a mold or the like, slowly cooled, and molded to obtain each sample.

[0087] <Optical glass measurement> Refractive index (n d ) and Abbe number (ν d ) The refractive index (n d ) and Abbe number (ν d The Abbe number (ν) was measured and calculated using a refractive index measuring instrument (Shimadzu Device Manufacturing Co., Ltd.: KPR-2000).d ) was calculated based on the following formula (1). The refractive index value was rounded to six decimal places. ν d =(n d -1) / (n F -n C )····(1) n d : Refractive index of glass for light with a wavelength of 587.562 nm n F : Refractive index of glass for light with a wavelength of 486.133 nm n C : Refractive index of glass for light with a wavelength of 656.273 nm

[0088] Glass transition temperature (T g ) The glass transition temperature (T g ) was determined from a differential thermal analysis (DTA) curve measured at a heating rate of 4°C / min.

[0089] ·Specific gravity (S g ) The specific gravity (S g ) was measured by the Archimedes method as the mass ratio to the same volume of pure water at 4°C.

[0090] Volatile loss The volatilization loss of each sample was determined by thermogravimetry (TG), measuring the weight change between 1000 and 1300°C and the weight change between 1200 and 1300°C when the temperature was raised from 700°C to 1300°C at a rate of 20°C / min. The sample weight was 50 mg, and measurements were taken using a cylindrical, lidless platinum cell with an opening diameter of 5 mm and a height of 5 mm. After the measurements, visual inspection was performed to ensure that the glass did not overflow from the platinum cell and that the glass in the platinum cell did not devitrify.

[0091] -Melting time of glass raw materials The melting time of the glass raw materials means the time required for the glass raw materials to melt when 50 g of the glass raw materials are thoroughly mixed and placed in a platinum crucible, and heated and maintained at a temperature of 1340 to 1400° C. In this example, it was determined that the glass raw materials were melted when no remaining melted glass raw materials could be visually confirmed in the platinum crucible.

[0092] ·Devitrification resistance The devitrification resistance of each sample was evaluated by polishing the prepared glass and visually inspecting it for the presence or absence of devitrification. In each table, "Devitrification present" means that devitrification was observed in the sample, and "No devitrification present" means that no devitrification was observed in the sample.

[0093] ·Partial dispersion ratio (P g,F ) The partial variance ratio (P g,F ) was calculated based on the following formula (2). The partial dispersion ratio value was rounded to four decimal places. P g,F =(n g -n F ) / (n F -n C )····(2) n F : Refractive index of glass for light with a wavelength of 486.133 nm n C : Refractive index of glass for light with a wavelength of 656.273 nm n g : Refractive index of glass for light with a wavelength of 435.835 nm

[0094] Anomalous dispersion value (ΔP g,F ) The value indicating the anomalous dispersion of each sample (ΔP g,F ) was determined in accordance with the method shown below.

[0095] (1) Creating a reference line First, as normal partial dispersion glass, the Abbe number (ν d ) and partial variance ratio (P g,FTwo glasses, "F2" and "K7", having the same refractive index, were selected as reference materials. For each glass, the horizontal axis represents the Abbe number, and the vertical axis represents the partial dispersion ratio (P g,F ) and the line connecting the two points corresponding to the two reference materials was used as the reference line. Characteristics of optical glass F2: ν d =36.33, P g,F =0.5834 Characteristics of optical glass K7: ν d =60.47, P g,F =0.5429

[0096] (2)ΔP g,F Calculation of Next, as shown in Figure 5, the horizontal axis represents the Abbe number (ν d ), and the vertical axis is the partial variance ratio (P g,F ), the values ​​corresponding to the optical glass of each example were plotted on a graph, and the Abbe number (ν d ) and the point on the reference line (solid line) corresponding to the vertical axis value (P g,F ) is the value indicating anomalous dispersion (ΔP g,F ) was calculated. The partial variance ratio (P g,F ) is above the reference line, ΔP g,F has a positive value, and the partial variance ratio (P g,F ) is below the reference line, ΔP g,F has a negative value.

[0097] [Table 1]

[0098] [Table 2]

[0099] [Table 3]

[0100] In Comparative Examples 1 to 4, devitrification was confirmed in the produced glasses, so measurements of optical constants and volatilization loss were not carried out.

[0101] As described above, the optical glass of this example has a high refractive index (n d ), small Abbe number (ν d ), small ΔP g,F It was confirmed that the optical glass of this example had excellent resistance to devitrification, and that it had a low volatile loss, which resulted in excellent production efficiency. g ) and specific gravity are also low. Furthermore, the melting time of the glass raw materials during glass production is short, which contributes to improved production efficiency. [Explanation of symbols]

[0102] 1...imaging device, 101...camera body, 102...lens barrel, 103...lens, 104...sensor chip, 105...glass substrate, 106...multichip module, 2...multiphoton microscope, 201...pulse laser device, 202...pulse splitter, 203...beam adjustment unit, 204, 205, 212...dichroic mirror, 206...objective lens, 207, 211, 213...fluorescence detection unit, 208...condenser lens, 209...pinhole, 210...imaging lens, S...sample, CAM...imaging device, WL...photographing lens, EF...fill-in light emitting unit, LM...liquid crystal monitor, B1...release button, B2...function button

Claims

1. In mass%, SiO ２ Content rate: 17% or more but less than 35%, B ２ O ３ Content rate: 0% or more but less than 13% ZrO ２ Content rate: 0% or more but less than 10% Nb ２ O ５ Content rate: 34% or more and 52% or less, Na ２ O content: 0% or more but less than 10% MgO content: greater than 0% and less than 10% Li ２ O content: greater than 0% and less than 10% WO ３ Content rate: 0% or more but less than 3% La ２ O ３ and G-d ２ O ３ and Y ２ O ３ and Lu ２ O ３ Total content (La ２ O ３ +Gd ２ O ３ +Y ２ O ３ +Lu ２ O ３ ) is between 0% and 2% Li relative to MgO ２ O ratio (Li ２ O / MgO) is 0.1 or more and 3.7 or less, SiO to MgO ２ and B ２ O ３ The ratio of the sum of (SiO ２ +B ２ O ３ ) / MgO) is 8 or more and 39 or less, That is, optical glass.

2. In mass%, Ta ２ O ５ Content rate: 0% or more but less than 6% ZnO content: 0% or more and 8% or less, BaO content: 0% or more and 3% or less, Al ２ O ３ Content rate: 0% or more but less than 2% K ２ O content: 0% or more but less than 7% TiO ２ Content rate: 0% or more but less than 10% Sb ２ O ３ 2. The optical glass according to claim 1, wherein the content is 0% or more and 1% or less.

3. SiO relative to MgO in mass % ２ Ratio of (SiO ２ 3. The optical glass according to claim 1, wherein the ratio of MgO to MgO is 5 or more and 27.5 or less.

4. In mass%, B to MgO ２ O ３ The ratio (B ２ O ３ 4. The optical glass according to claim 1, wherein the ratio of MgO to MgO is 0 or more and 5 or less.

5. In mass%, 5. The optical glass according to claim 1, wherein the ratio of MgO to the sum of MgO, BaO, SrO, and CaO (MgO / (MgO+BaO+SrO+CaO)) is 0.35 or more and 1.0 or less.

6. In mass%, Nb to MgO ２ O ５ and TiO ２ The ratio of the sum of (Nb ２ O ５ + TiO ２ 6. The optical glass according to claim 1, wherein the ratio of MgO to MgO is 5 or more and 60 or less.

7. In mass%, 7. The optical glass according to claim 1, wherein the value obtained by subtracting MgO from the sum of CaO, SrO, and BaO ((CaO+SrO+BaO)-MgO) is 1% or less.

8. The optical glass according to any one of claims 1 to 7, which is used as an optical element for an imaging device.

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