Optical glass, optical elements, optical systems, cemented lenses, microscope objective lenses, camera interchangeable lenses, and optical devices.

Abstract

An optical glass in which La3+ content: 5 to 35%, Si4+ content: 5 to 25%, Nb5+ content: 5 to 35%, Al3+ content: 5 to 35%, and total content of Ti4+, Zr4+, Nb5+, Ta5+, and Al3+ (Ti4++Zr4++Nb5++Ta5++al3+): 45 to 80%, expressed in mol% of cation.

Description

[Technical Field]

[0001] The present invention relates to optical glass, an optical element, an optical system, a cemented lens, a microscope objective lens, an interchangeable lens for a camera, and an optical device. The present invention claims priority from Japanese Patent Application No. 2022-158015 filed on September 30, 2022, and for designated countries where incorporation by reference of documents is permitted, the content described in that application is incorporated into the present application by reference. [Background Art]

[0002] Optical glass is used in various optical elements and optical devices. For example, Patent Document 1 discloses a halide glass used in the ultraviolet to infrared region. In order to expand the degree of freedom in designing optical systems used in optical devices, development of optical glass having a high refractive index is demanded. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. Hei 07-081973 [Summary of the Invention]

[0004] One aspect according to the present invention provides an optical glass, wherein in terms of cation content expressed in mol%, La 3+ content: 5 to 35%, Si 4+ content: 5 to 25%, Nb 5+ content: 5 to 35%, Al 3+ content: 5 to 35%, Ti 4+ , Zr 4+ , Nb 5+ , Ta 5+ and Al 3+ have a total content (Ti 4+ +Zr 4+ +Nb 5+ +Ta 5+ +Al 3+ ): 45 to 80%.

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

[0006] Another aspect of the present invention is an optical system including the optical elements described above.

[0007] Another aspect of the present invention is a microscope objective lens including an optical system that includes the optical elements described above.

[0008] Another aspect of the present invention is a camera interchangeable lens that includes an optical system containing the above-described optical elements.

[0009] Another aspect of the present invention is an optical device including an optical system that includes the optical elements described above.

[0010] Another 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 optical glass described above.

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

[0012] Another aspect of the present invention is a microscope objective lens that includes an optical system including the cemented lens described above.

[0013] Another aspect of the present invention is a camera interchangeable lens that includes an optical system including the cemented lens described above.

[0014] Another aspect of the present invention is an optical device that includes an optical system including the cemented lens described above. [Brief explanation of the drawing]

[0015] [Figure 1] This is a perspective view showing an example in which the optical device according to this embodiment is used as an imaging device. [Figure 2] This is a schematic diagram showing another example in which the optical device according to this embodiment is used as an imaging device, and is a front view of the imaging device. [Figure 3]This is a schematic diagram showing another example in which the optical device according to this embodiment is used as an imaging device, and is a rear view of the imaging device. [Figure 4] This is a block diagram showing an example of the configuration of a multiphoton microscope according to this embodiment. [Figure 5] This is a schematic diagram showing an example of a cemented lens according to this embodiment. [Figure 6] This is a schematic diagram of the overall configuration of the gas jet type floating furnace according to this embodiment. [Figure 7] This is an enlarged schematic diagram of the base on the stage of the gas jet type floating furnace according to this embodiment. [Figure 8] This graph plots the optical constant values ​​(νd-Pg,F) for each example. [Figure 9] This graph plots the optical constant values ​​(νd-nd) for each embodiment. [Modes for carrying out the invention]

[0016] The following describes embodiments of the present invention (hereinafter referred to as "these embodiments"). These embodiments are illustrative examples for explaining the present invention and are not intended to limit the present invention to the following content. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0017] Furthermore, the expression "0-N%" for the Q content includes cases where the Q component is not present, as well as cases where the Q component is greater than 0% but less than or equal to N%.

[0018] Furthermore, the expression "Q component-free" means that this Q component is substantially absent, and that the content of this component is below the level of an impurity. Below the level of an impurity means, for example, less than 0.01%.

[0019] The term "devitrification resistance" refers to the glass's resistance to devitrification. Here, "devitrification" refers to the phenomenon in which the transparency of glass is lost due to crystallization or phase separation that occurs when the glass is heated above its glass transition temperature or when it is cooled from a molten state to below its liquidus temperature.

[0020] <Optical Glass> The optical glass according to this embodiment is expressed in mol% cations, La 3+ Content: 5~35%, Si 4+ Content: 5~25%, Nb 5+ Content: 5~35%, Al 3+ Content: 5~35%, Ti 4+ , Zr 4+ Nb 5+ Ta 5+ and Al 3+ Total content (Ti 4+ +Zr 4+ +Nb 5+ +Ta 5+ +Al 3+ It is optical glass with a viscosity of 45-80%.

[0021] In this specification, unless otherwise specified, the content of each component shall be expressed in mole percent of cations. Mole percent of cations refers to the ratio of the number of moles of the cation in question to the total number of moles of cations contained in the optical glass. More specifically, in the case of SiO2 50 mol% and Na2O 50 mol%, the mole percent of cations would be Si 4+ is 33.3%, Na + This amounts to 66.7%. Furthermore, the form of each cation is not particularly limited, but for example, it can be contained in optical glass in the form of an oxide.

[0022] The optical glass according to this embodiment is a novel optical glass that achieves high refractive index and high transmittance by having a composition system mainly composed of La2O3 and Nb2O5. This composition system does not vitrify in crucible melting and can be obtained by the floating melting method. However, by achieving both low specific gravity and high devitrification resistance stability, the glass can be easily floated, and glass gobs with a diameter of 10 mm or more can be stably produced even by the floating melting method.

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

[0024] La 3+ For example, in terms of oxide composition, it is a component that is included as La2O3. 3+ It has the effect of increasing refractive index and transmittance. However, as the content of this substance increases, the specific gravity tends to increase. From this perspective, La 3+ The content is 5-35%. The lower limit of this content is preferably 8%, more preferably 12%, and even more preferably 15%. The upper limit of this content is preferably 32%, more preferably 29%, and even more preferably 26%.

[0025] Si 4+ For example, Si is a component that is included as SiO2 in the oxide-based composition. 4+ This component can enhance devitrification resistance stability while maintaining a low specific gravity. However, as the content of this component increases, the refractive index tends to decrease. From this perspective, Si 4+ The content is 5-25%. The lower limit of this content is preferably 6%, more preferably 8%, and even more preferably 10%. The upper limit of this content is preferably 24%, more preferably 22%, and even more preferably 20%.

[0026] Nb 5+ For example, in oxide-based composition, it is a component that is included as Nb2O5. It has the effect of increasing refractive index and transmittance. However, as the content of this component increases, it tends to increase the specific gravity. From this viewpoint, Nb5+ The content is 5-35%. The lower limit of this content is preferably 8%, more preferably 12%, and even more preferably 16%. The upper limit of this content is preferably 32%, more preferably 29%, and even more preferably 26%.

[0027] Al 3+ For example, Al is a component that is included as Al2O3 in terms of oxide composition. 3+ Al is a component that can enhance devitrification resistance stability while maintaining a low specific gravity. However, as the content of this component increases, the refractive index tends to decrease. From this perspective, 3+ The content is 5-35%. The lower limit of this content is preferably 8%, more preferably 12%, and even more preferably 14%. The upper limit of this content is preferably 32%, more preferably 29%, and even more preferably 26%.

[0028] Zr 4+ For example, Zr is a component that is included as ZrO2 in terms of oxide composition. 4+ It has the effect of improving devitrification resistance and refractive index. From this viewpoint, Zr 4+ The content is 0-15%. The lower limit of this content is preferably 2%, more preferably 4%, and even more preferably 6%. The upper limit of this content is preferably 14%, more preferably 12%, and even more preferably 10%.

[0029] Ti 4+ For example, Ti is a component that is included as TiO2 in terms of oxide composition. 4+ It has the effect of increasing the refractive index while maintaining a low specific gravity. However, as the content of this substance increases, the transmittance tends to decrease. From this perspective, Ti 4+ The content is 0-20%. The lower limit of this content is preferably 2%, more preferably 4%, and even more preferably 6%. The upper limit of this content is preferably 20%, more preferably 16%, and even more preferably 10%.

[0030] Ta 5+ For example, in terms of oxide composition, it is a component that is included as Ta2O5. 5+ It has the effect of improving devitrification resistance stability while maintaining low dispersibility. However, as the content of this substance increases, the specific gravity tends to increase. From this perspective, Ta 5+ The content is 0-15%. The lower limit of this content is preferably 2%, more preferably 3%, and even more preferably 5%. The upper limit of this content is preferably 12%, more preferably 10%, and even more preferably 8%.

[0031] Ti 4+ and Zr 4+ and Nb 5+ and Ta 5+ and Al 3+ Total content (Ti 4+ +Zr 4+ +Nb 5+ +Ta 5+ +Al 3+ (Ti 4+ +Zr 4+ +Nb 5+ +Ta 5+ +Al 3+ By setting the range to match, it is possible to achieve both high refractive index and high transmittance while maintaining devitrification resistance stability during melting.

[0032] The glass composition according to this embodiment includes, as an additional optional component, Y 3+ B 3+ It may further contain any one of the following.

[0033] Y 3+ For example, Y is a component that is included as Y2O3 in the oxide-based composition. 3+This is a component that can increase refractive index and transmittance without impairing low dispersion. From this perspective, Y 3+ The content is 0-15%. The lower limit of this content is preferably 2%, more preferably 4%, and even more preferably 6%. The upper limit of this content is preferably 12%, more preferably 10%, and even more preferably 8%. 3+ and Y 3+ It is preferable that both are included.

[0034] B 3+ For example, in terms of oxide composition, it is included as B2O3 and is a component that constitutes network-forming oxides. 3+ Because it is a highly volatile component, if introduced in excess, it can cause changes in the composition of the glass during manufacturing, making striations apparent. From this perspective, B 3+ It is preferable that it substantially does not contain B. 3+ If it contains, the upper limit of this content is preferably 10%, more preferably 5%, and even more preferably 2%.

[0035] Furthermore, as needed, appropriate amounts of known clarifying agents, colorants, defoaming agents, fluorine compounds, and other components can be added to the glass composition for purposes such as clarification, coloring, decolorization, and fine-tuning of optical constants. In addition, other components can be added, not limited to those mentioned above, as long as the effects of the optical glass according to this embodiment can be obtained.

[0036] It is preferable to use high-purity raw materials with a low impurity content. High-purity materials are those containing 99.85% by mass or more of the relevant component. Using high-purity materials tends to result in a lower amount of impurities, which in turn tends to increase the internal transmittance of the optical glass.

[0037] Next, the physical properties of the optical glass in this embodiment will be described.

[0038] From the viewpoint of visible light transmittance of the optical system, it is preferable that the optical glass according to this embodiment has high internal transmittance. Given this, the wavelength (λ80) at which the internal transmittance per 10 mm of the optical glass according to this embodiment is 420 nm or less. The upper limit of the wavelength at which λ80 occurs is preferably 405 nm, more preferably 400 nm, and even more preferably 395 nm.

[0039] From the viewpoint of making the lens thinner, the optical glass according to this embodiment has a high refractive index (refractive index (n d A large refractive index (n) is desirable. However, generally speaking, d The higher the refractive index (n) of the optical glass according to this embodiment, the lower the transmittance tends to be. d The refractive index (n) is in the range of 1.95 to 2.15. d The lower limit of the refractive index (n) is preferably 1.96, more preferably 1.97, and even more preferably 1.99. d The upper limit of ) is preferably 2.12, more preferably 2.08, and even more preferably 2.05.

[0040] The Abbe number (ν) of the optical glass according to this embodiment d ) is in the range of 20 to 35. And the Abbe number (ν d The lower limit of the Abbe number (ν) is preferably 22, more preferably 24, and even more preferably 25. d The upper limit of ) is preferably 32, more preferably 30, and even more preferably 29.

[0041] From the viewpoint of correcting lens aberrations, the partial dispersion ratio (P) of the optical glass according to this embodiment is g , F The partial variance ratio (P) is 0.55 to 0.65. g , F The lower limit of the partial variance ratio (P) is preferably 0.56, more preferably 0.57, and even more preferably 0.58. g ,F The upper limit of ) is preferably 0.64, more preferably 0.62, and still more preferably 0.61. Further, the partial dispersion ratio (P g , F ) satisfies the following formula -0.00403×ν d +0.704 < P g,F < -0.00403×ν d +0.717 ···(1) It is preferable that the above formula is satisfied. Note that the partial dispersion ratio (P g , F ) is a value calculated based on the refractive index measured by the V-block method.

[0042] The optical glass according to the present embodiment has a length in the major axis direction of 10 mm or more. The length in the major axis direction is preferably 11 mm or more, more preferably 12 mm or more, and still more preferably 13 mm or more. The "length in the major axis direction" as used herein refers to the maximum value in the diameter direction of a glass gob, and in the case of a substantially spherical shape, refers to the diameter value thereof.

[0043] The optical glass according to the present embodiment preferably has a thickness (T) of 4 mm or more, more preferably 5 mm or more, and still more preferably 5.5 mm or more. The "thickness" as used herein refers to the height in a direction perpendicular to the maximum diameter (diameter (D)) of the glass gob, and in the case of a substantially spherical shape, refers to the diameter value thereof.

[0044] The optical glass according to the present embodiment preferably has a weight of 1.5 g or more, more preferably 2.0 g or more, and still more preferably 2.5 g or more.

[0045] When the optical glass according to the present invention is produced using a floating furnace, the specific gravity thereof is desirably 6.0 or less. In view of such circumstances, the optical glass according to the present embodiment has a specific gravity (S gThe specific gravity is between 4.6 and 5.6. The lower limit of the specific gravity is preferably 4.7, more preferably 4.8, and even more preferably 4.9. The upper limit of the specific gravity is preferably 5.5, more preferably 5.3, and even more preferably 5.1.

[0046] The optical glass according to this embodiment has a glass transition temperature (T g ) and crystallization initiation temperature (T x ) temperature difference (ΔT=T x -T g The larger the value, the higher the devitrification resistance stability. Considering this situation, the glass transition temperature (T) of the optical glass according to this embodiment is g ) and crystallization initiation temperature (T x ) temperature difference (ΔT=T x -T g The glass transition temperature (T) is 80°C to 200°C. The lower limit of this difference is preferably 100°C, more preferably 130°C, and even more preferably 160°C. The upper limit of this difference is preferably 190°C, more preferably 180°C, and even more preferably 170°C. ΔT can be used as an indicator of devitrification resistance stability. Generally, a high ΔT means that the glass has high devitrification resistance stability. In this embodiment, the glass transition temperature (T) is g ) and crystallization initiation temperature (T x ) can all be measured by differential thermal analysis.

[0047] From the above-mentioned perspective, the optical glass according to this embodiment can be suitably used, for example, as an optical element in an optical instrument. Such optical elements include mirrors, lenses, prisms, filters, etc. Examples of optical systems in which the above optical elements are used include objective lenses, focusing lenses, imaging lenses, interchangeable lenses for cameras, etc. These optical systems can be suitably used in various optical devices of imaging devices such as interchangeable-lens cameras and non-interchangeable-lens cameras, and microscopes such as fluorescence microscopes and multiphoton microscopes. Such optical devices are not limited to the imaging devices and microscopes mentioned above, but also include, but are not limited to, telescopes, binoculars, laser rangefinders, projectors, etc. An example of these will be described below.

[0048] <Imaging device> Figure 1 is a perspective view showing an example of an optical device according to this embodiment used as an imaging device. The imaging device 1 is a so-called digital single-lens reflex camera (interchangeable lens camera), and the photographic lens 103 (optical system) is equipped with an optical element made of optical glass according to this embodiment. A lens barrel 102 is detachably attached to the lens mount (not shown) of the camera body 101. The light passing through the lens 103 of the lens barrel 102 is then imaged onto the sensor chip (solid-state image sensor) 104 of a multi-chip module 106 located on the back 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 a COG (Chip On Glass) type module in which the sensor chip 104 is bare-chip mounted on a glass substrate 105.

[0049] Figures 2 and 3 are schematic diagrams showing other examples in which the optical device according to this embodiment is used as an imaging device. Figure 2 shows a front view of the imaging device CAM, and Figure 3 shows a rear view of the imaging device CAM. The imaging device CAM is a so-called digital still camera (a camera with a non-interchangeable lens), and the photographic lens WL (optical system) is equipped with optical elements made of optical glass according to this embodiment.

[0050] When the power button (not shown) of the imaging device CAM is pressed, the shutter (not shown) of the photographic lens WL is opened, and light from the subject (object) is collected by the photographic lens WL and formed on the image sensor located on the image plane. The image of the subject formed on the image sensor is displayed on the LCD monitor M1 located behind the imaging device CAM. The photographer determines the composition of the subject image while looking at the LCD monitor M1, then presses down the release button B1 to capture the subject image with the image sensor and record it in memory (not shown).

[0051] The imaging device CAM is equipped with an auxiliary light emitter EF that emits auxiliary light when the subject is dark, and a function button B2 used for setting various conditions of the imaging device CAM, etc.

[0052] Optical systems used in digital cameras and similar devices require higher resolution, lower chromatic aberration, and miniaturization. To achieve these, it is effective to use glasses with different dispersion characteristics in the optical system. In particular, low dispersion while maintaining a high partial dispersion ratio (P) is desirable. g , F There is high demand for glass having the properties described above. From this viewpoint, the optical glass according to this embodiment is suitable as a component of such optical equipment. The optical equipment applicable to this embodiment is not limited to the imaging device described above, but also includes, for example, a projector. The optical elements are not limited to lenses, but also include, for example, prisms.

[0053] <Microscope> Figure 4 is a block diagram showing an example of the configuration of the multiphoton microscope 2 according to this embodiment. The multiphoton microscope 2 comprises an objective lens 206, a focusing lens 208, and an imaging lens 210. At least one of the objective lens 206, focusing lens 208, and imaging lens 210 is equipped with an optical element made of optical glass according to this embodiment. The optical system of the multiphoton microscope 2 will be described below.

[0054] The pulsed laser device 201 emits ultrashort pulsed light, for example, with a near-infrared wavelength (approximately 1000 nm) and a pulse width in the femtosecond range (for example, 100 femtoseconds). The ultrashort pulsed light immediately after being emitted from the pulsed laser device 201 is generally linearly polarized and polarized in a predetermined direction.

[0055] The pulse splitting device 202 splits the ultrashort pulse light and emits it with a higher repetition frequency.

[0056] The beam adjustment unit 203 has functions such as adjusting the beam diameter of the ultrashort pulse light incident from the pulse splitting device 202 to match the pupil diameter of the objective lens 206, adjusting the focusing and divergence angles of the ultrashort pulse light to correct axial chromatic aberration (focus difference) between the wavelength of light emitted from the sample S and the wavelength of the ultrashort pulse light, and a pre-chirp function (group velocity dispersion compensation function) that applies the opposite group velocity dispersion to the ultrashort pulse light to correct the widening of the pulse width of the ultrashort pulse light due to group velocity dispersion as it passes through the optical system.

[0057] The ultrashort pulse light emitted from the pulse laser device 201 has its repetition frequency increased by the pulse splitting device 202, and the beam adjustment unit 203 performs the adjustments described above. The ultrashort pulse light emitted from the beam adjustment unit 203 is reflected in the direction of the dichroic mirror 204 by the dichroic mirror 204, passes through the dichroic mirror 205, is focused by the objective lens 206, and irradiates the sample S. At this time, a scanning means (not shown) may be used to scan the ultrashort pulse light on the observation surface of the sample S.

[0058] For example, when observing a sample S using fluorescence, the fluorescent dye staining the sample S is multiphoton-excited in the area of ​​the sample S irradiated with ultrashort pulse light and its vicinity, and fluorescence with a wavelength shorter than the ultrashort pulse light, which is in the infrared range (hereinafter referred to as "observation light") is emitted.

[0059] Observation light emitted from sample S towards objective lens 206 is collimated by objective lens 206 and, depending on its wavelength, is either reflected by dichroic mirror 205 or transmitted through dichroic mirror 205.

[0060] 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 (photomultiplier tube), and receives the observation light reflected by the dichroic mirror 205 and outputs an electrical signal corresponding to the amount of light. The fluorescence detection unit 207 also detects the observation light across the observation surface of the sample S as the ultrashort pulse light is scanned across the observation surface of the sample S.

[0061] Alternatively, by removing the dichroic mirror 205 from the optical path, all observation light emitted from the sample S toward the objective lens 206 may be detected by the fluorescence detection unit 211. In this case, the observation light 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 to the focal point of the objective lens 206, passes through the imaging lens 210, and enters the fluorescence detection unit 211.

[0062] The fluorescence detection unit 211 is composed of, for example, a barrier filter, a PMT, etc., and 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 light. The fluorescence detection unit 211 also detects the observation light across the observation surface of the sample S as the ultrashort pulse light is scanned across the observation surface of the sample S.

[0063] Alternatively, by removing the dichroic mirror 205 from the optical path, all observation light emitted from the sample S in the direction of the objective lens 206 may be detected by the fluorescence detection unit 211.

[0064] Furthermore, observation light emitted from the sample S in the opposite direction to the objective lens 206 is reflected by the dichroic mirror 212 and incident on the fluorescence detection unit 213. The fluorescence detection unit 113 is composed of, for example, a barrier filter, a PMT, etc., and receives the observation light reflected by the dichroic mirror 212 and outputs an electrical signal corresponding to the amount of light. The fluorescence detection unit 213 also detects the observation light across the observation surface of the sample S as the ultrashort pulse light is scanned across the observation surface of the sample S.

[0065] The electrical signals output from the fluorescence detection units 207, 211, and 213 are input to, for example, a computer (not shown), which can generate an observation image based on the input electrical signals, display the generated observation image, or store the data of the observation image.

[0066] <Bonded Lens> Figure 5 is a schematic diagram showing an example of a bonded lens according to this embodiment. The bonded lens 3 is a composite 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 is made of optical glass according to this embodiment. The first lens element and the second lens element are joined together via a joining member 303. A known adhesive or the like can be used as the joining member 303. Note that "lens element" refers to each lens that constitutes a single lens or a bonded lens.

[0067] The cemented lens according to this embodiment is useful in terms of chromatic aberration correction and can be suitably used in the optical elements, optical systems, and optical devices described above. Furthermore, the optical system including the cemented lens can be particularly suitably used in interchangeable lenses for cameras and optical devices. In the above embodiment, a cemented lens using two lens elements has been described, but the invention is not limited to this, and a cemented lens using three or more lens elements may also be used. In the case of a cemented lens using three or more lens elements, it is sufficient that at least one of the three or more lens elements is formed using the optical glass according to this embodiment.

[0068] <Manufacturing method for optical glass> The optical glass according to this embodiment can be manufactured, for example, using a levitation furnace. Levitation furnaces include electrostatic, electromagnetic, sonic, magnetic, and gas jet types, and are not particularly limited, but it is preferable to use a gas jet type levitation furnace for the levitation melting of oxides. A manufacturing method using a gas jet type levitation furnace will be described below as an example.

[0069] Figure 6 shows a schematic diagram of the overall configuration of a gas-jet type floating furnace, and Figure 7 is an enlarged schematic diagram of the base on the stage of the gas-jet type floating furnace.

[0070] In the gas-jet type levitation furnace 4, the raw material M is placed on a base 402 on a stage 401. Laser light L emitted from the laser light source 403 is irradiated onto the raw material M via mirrors 404 and 405. The temperature of the raw material M, which is heated by the irradiation of the laser light L, is monitored by a radiation thermometer 406. Based on the temperature information of the raw material M monitored by the radiation thermometer 406, the output of the laser light source 403 is controlled by a computer 407. The state of the raw material M is also imaged by a CCD camera 408 and output to a monitor 409 (see Figure 6). For example, a carbon dioxide laser can be used as the laser light source.

[0071] In the gas-jet type levitation furnace 4, the raw material M is suspended by the gas supplied to the base (see Figure 7). The flow rate of the gas supplied to the base is controlled by the gas flow regulator 410. For example, by injecting gas from a nozzle with a conical hole, non-contact heating with laser light L can be performed while the raw material M is suspended. When the raw material M melts, it becomes spherical or ellipsoidal due to its own surface tension and levitates in that state.

[0072] Subsequently, when the laser beam L is cut off, the molten raw material cools, and transparent glass is obtained. The type of gas is not particularly limited, and any known gas can be used as appropriate, such as oxygen, nitrogen, carbon dioxide, argon, or air. Furthermore, the shape of the nozzle and the heating method are not particularly limited, and any known methods can be used as appropriate.

[0073] Conventionally, when manufacturing optical glass using containers such as crucibles, it was necessary to include a large amount of network-forming oxides such as SiO2, B2O3, P2O5, and GeO2 to enhance the glass-forming ability. Therefore, when the glass composition contained a large amount of non-network-forming oxides and a small amount of the aforementioned network-forming oxides, crystallization (heterogeneous nucleation) often occurred at the container-melt interface, making vitrification impossible. Furthermore, glass gobs are sometimes used as materials for optical lenses in various optical instruments, and there is a need for the ability to stably manufacture large glass gobs.

[0074] In this embodiment, for example, when optical glass is manufactured using the floating furnace method described above, there is no contact between the container and the molten material, thus minimizing heterogeneous nucleation. As a result, glass formation in the molten material is greatly promoted, making it possible to vitrify even compositions with low or no network-forming oxide content, which are impossible to manufacture by crucible melting. By adopting this manufacturing method, it is possible to manufacture optical glass with compositions according to this embodiment that could not be vitrified conventionally. Furthermore, large glass gobs as described above can also be produced. In addition, the optical glass according to this embodiment has a high refractive index and a high Abbe number. Because the optical glass according to this embodiment has many such advantages, it can be applied as a high refractive index, low dispersion glass material and a broadband transmission material. [Examples]

[0075] Next, examples and comparative examples of the present invention will be described. However, the present invention is not limited to these examples.

[0076] <Fabrication of optical glass> The optical glass for each example and comparative example was manufactured using the gas-jet type levitation furnace 4 shown in Figures 6 and 7, following the procedure below. First, glass raw materials selected from oxides were weighed to achieve the composition (mol %) of cations listed in each table. Alternatively, the glass raw materials may be selected from hydroxides, carbonates, nitrates, and sulfates. Next, the weighed raw materials were mixed in an alumina mortar. This raw material was uniaxially pressed at 20 MPa to form cylindrical pellets. The obtained pellets were fired in an electric furnace at 1000-1300°C in air for 3-6 hours to produce a sintered body. The obtained sintered body was roughly crushed, and 50-4000 mg was taken and placed in the nozzle of the base. Then, the raw material was melted by irradiating it from above with a carbon dioxide laser while spraying air gas. The melted raw material became spherical or ellipsoidal due to its own surface tension and was suspended by the gas pressure. The raw material was cooled by shutting off the laser output when the raw material was completely melted. Furthermore, annealing was performed at a temperature of 760-810°C for 10 hours, and gobs (glass spheres) with a diameter of 10.30-14.55 mm and a thickness of 5.20-6.04 mm were obtained for each example. No visible volatilization was observed during melting of any of the glass samples in each example, and no bubbles or devitrification were observed.

[0077] <Evaluation of physical properties> Figures 8 and 9 are graphs plotting the optical constants for each embodiment.

[0078] Crystallization initiation temperature (T x ), glass transition temperature (T g ), measurement of the temperature difference (ΔT) Crystallization initiation temperature (T x ) and the glass transition temperature (T g ) were all measured by differential thermal analysis during the heating process (heating temperature 10°C / min), T x -T g This was defined as the temperature difference (ΔT).

[0079] Specific gravity (S g ) Specific gravity of each sample (S gThe specific gravity was measured by the Archimedes method. The specific gravity value was rounded to three decimal places.

[0080] Diameter (D), Thickness (T) The diameter (D) and thickness (T) of each sample were measured using electronic calipers.

[0081] Refractive index (n d ) and Abbe number (ν d ) The sample of the example was processed into a 90-degree prism, and the refractive index was measured using the V-block method with a refractive index meter (KPR-3000, manufactured by Carnew Optical Industries Co., Ltd.). The Abbe number and partial dispersion ratio were then calculated.

[0082] In the comparative example, the refractive index was measured and the Abbe number calculated using the prism coupling method with a prism coupler (Metricon, model "2010 / M"). In the prism coupling method, the glass sample was polished, the polished surface was placed in close contact with a single-crystal rutile prism, and the refractive index was determined by measuring the total reflection angle when light of the measurement wavelength was incident on it. Measurements were taken five times each at three wavelengths: 473 nm, 594.1 nm, and 656 nm, and the average value was used as the measured value. Furthermore, the obtained measured values ​​were fitted using the least squares method with the following Drude-Voigt dispersion formula to determine the refractive index at the d line (587.562 nm), F line (486.133 nm), and C line (656.273 nm), and the Abbe number (ν d ) was calculated.

[0083]

number

[0084] (n: refractive index, m: electron mass, c: speed of light, e: elementary charge, N: number of molecules per unit volume, f: oscillator intensity, λ0: intrinsic resonance wavelength, λ: wavelength)

[0085] n d This indicates the refractive index of the glass for light at 587.562 nm. Abbe number (ν d n was obtained from the following equation (2).C , n F These values ​​represent the refractive indices of the glass for light with wavelengths of 656.273 nm and 486.133 nm, respectively. ν d =(n d -1) / (n F -n C )···(2) The refractive index value was given to six decimal places.

[0086] Partial dispersion ratio (P g , F ) Partial variance ratio (P) of each sample g , F ) is the principal variance (n F -n C Partial variance (n) for ) g -n F The ratio of ) was shown and obtained from the following equation (3). n g This indicates the refractive index of the glass for light with a wavelength of 435.835 nm. Partial dispersion ratio (P) g , F The value of ) was rounded to four decimal places. P g , F =(n g -n F ) / (n F -n C )···(3)

[0087] internal transmittance The internal transmittance of each sample was measured using a spectrophotometer (Hitachi High-Tech Science Corporation; "Ultraviolet-Visible-Infrared Spectrophotometer UH4150") at wavelengths of 300-700 nm for parallel polished samples with a thickness of 4-9 mm. Further correction was performed by removing the contribution of reflectance to the transmittance at each wavelength using refractive index measurement data, and the value was converted to the transmittance of a 10 mm thickness. Fitting was performed using the least squares method with the following dispersion curve equation from the refractive index data of 10 emission lines in the V-block method for h, g, F', F, e, d, C', C, r, and t lines.

[0088]

number

[0089] The refractive index n at each wavelength λ calculated using the dispersion curve equation. λ Using this, the surface reflectance R for each wavelength and the transmittance T, calculated assuming no absorption of light inside, taking into account multiple reflections on the front and back surfaces of the incident light. th The external transmittance measurement T at a thickness of t mm was calculated using the following formula. exp and T th Using the internal transmittance T (tmm) The result was calculated.

[0090]

number

[0091] The internal transmittance T at a thickness t mm is calculated above. (tmm) Using this method, the transmittance value T for a 10mm thickness is obtained. (10mm) This was calculated using the following formula.

[0092]

number

[0093] Each table shows the composition and physical properties of each example and comparative example. Unless otherwise specified, the content of each component is based on mol% of cations. Furthermore, each physical property value is for glass in its unpressed state.

[0094] [Table 1]

[0095] [Table 2]

[0096] [Table 3]

[0097] [Table 4]

[0098] Based on the above, it was confirmed that the optical glass of each embodiment possesses high refractive index, high transmittance, low specific gravity, and devitrification resistance at a high level, and that it can be enlarged to a diameter of 10 mm or more when manufactured by the floating melting method. [Explanation of Symbols]

[0099] 1...Imaging device, 101...Camera body, 102...Lens barrel, 103...Lens, 104...Sensor chip, 105...Glass substrate, 106...Multi-chip module, CAM...Imaging device (non-interchangeable lens camera), WL...Photography lens, M1...LCD monitor, EF...Auxiliary light emission 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...Focusing lens, 209...Pinhole, 210...Imaging lens, S...Sample, 3...Conging lens, 301...First lens element, 302...Second lens element, 303...Jointing member, 4...Gas levitation furnace, 401...Stage, 402...Base, 403...Laser light source, 404, 405...Mirror, 406...Infrared thermometer, 407...Computer, 408...CCD camera, 409...Monitor, 410...Gas flow regulator, L...Laser light, M...Raw material

Claims

1. An oxide glass, wherein the cation is expressed in mole percent, La ３＋ Content: 5-35% Si ４＋ Content rate: 5-25% Nb ５＋ Content: 5-35% Al ３＋ Content: 5-35% Ti ４＋ , Zr ４＋ , Nb ５＋ , Ta ５＋ and Al ３＋ total content (Ti ４＋ +Zr ４＋ +Nb ５＋ +Ta ５＋ +Al ３＋ ): 45 to 80%, which is an optical glass.

2. In terms of cation molar percentage, Ti ４＋ The optical glass according to claim 1, wherein the content is 0 to 20%.

3. In terms of cation molar percentage, Zr ４＋ The optical glass according to any one of claims 1 to 2, wherein the content is 0 to 15%.

4. In terms of cation molar percentage, Ta ５＋ The optical glass according to any one of claims 1 to 2, wherein the content is 0 to 15%.

5. In terms of cations expressed in mole percent, Y ３＋ The optical glass according to any one of claims 1 to 2, wherein the content is 0 to 15%.

6. B ３＋ An optical glass according to any one of claims 1 to 2, which substantially does not contain.

7. The optical glass according to any one of claims 1 to 2, wherein the wavelength (λ80) at which the internal transmittance per 10 mm of the optical glass is 80% is 420 nm or less.

8. The optical glass according to any one of claims 1 to 2, wherein the refractive index of the optical glass with respect to the d line is 1.95 to 2.

15.

9. The optical glass according to any one of claims 1 to 2, wherein the Abbe number of the optical glass is 20 to 35.

10. The partial dispersion ratio (P) of the optical glass ｇ , Ｆ ) is expressed as follows: -0.00403×ν ｄ +0.704<P ｇ,Ｆ <-0.00403×ν ｄ +0.717・・・(1) An optical glass according to any one of claims 1 to 2 that satisfies the requirements.

11. The specific gravity (S) of the optical glass ｇ The optical glass according to any one of claims 1 to 2, wherein the ratio is 4.6 to 5.

6.

12. The glass transition temperature (T) of the optical glass ｇ ) and crystallization initiation temperature (T ｘ ) temperature difference (ΔT = T ｘ -T ｇ The optical glass according to any one of claims 1 to 2, wherein the temperature is 80 to 200°C.

13. The optical glass according to any one of claims 1 to 2, wherein the length of the optical glass in the longitudinal direction is 10 mm or more.

14. An optical element using optical glass as described in any one of claims 1 to 2.

15. An optical system including the optical element described in claim 14.

16. A microscope objective lens comprising the optical system described in claim 15.

17. A camera interchangeable lens comprising the optical system described in claim 15.

18. An optical apparatus including the optical system described in claim 15.

19. It has a first lens element and a second lens element, A cemented lens in which at least one of the first lens element and the second lens element is the optical glass described in any one of claims 1 to 2.

20. An optical system including the cemented lens described in claim 19.

21. A microscope objective lens comprising the optical system described in claim 20.

22. A camera interchangeable lens comprising the optical system described in claim 20.

23. An optical apparatus comprising the optical system described in claim 20.

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