Optical glass, optical element, optical system, cemented lens, objective lens for microscope, interchangeable lens for camera, and optical device

Abstract

In the optical glass, the content of La < 3 + > is 5-35%, the content of Si < 4 + > is 5-25%, the content of Nb < 5 + > is 5-35%, the content of Al < 3 + > is 5-35%, and the total content of Ti < 4 + >, Zr < 4 + >, Nb < 5 + >, Ta < 5 + > and Al < 3 + > (Ti < 4 + > + Zr < 4 + > + Nb < 5 + > + Ta < 5 + > + Al < 3 + >) is 45-80%.

Description

Technical Field

[0001] The present invention relates to optical glass, optical elements, optical systems, cemented lenses, microscope objective lenses, camera interchangeable lenses, and optical devices. The present invention claims priority to Japanese Patent Application No. 2022-158015 filed on September 30, 2022, and the contents described in the application are incorporated into the present application by reference for designated countries that recognize the introduction of contents by reference. Background Art

[0002] Optical glass is used in various optical elements, optical devices, etc. For example, halide glass used in the ultraviolet to infrared region is disclosed in Patent Document 1. In order to expand the design freedom of optical systems used in optical devices, it is required to develop optical glass having a high refractive index.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 07-081973 Summary of the invention

[0006] One embodiment of the present invention is an optical glass, wherein, expressed in terms of mol% of cations, La 3+ The content is 5% to 35%, Si 4+ The content is 5% to 25%, Nb 5+ The content is 5% to 35%, Al 3+ The content is 5% to 35%, Ti 4+ 、Zr 4+ , Nb 5 + 、 5+ and Al 3+ The total content (Ti 4+ +Zr 4+ +Nb 5+ +Ta 5+ +Al 3+ ) is 45% to 80%.

[0007] Another aspect of the present invention is an optical element using the above-mentioned optical glass.

[0008] Another aspect of the present invention is an optical system including the above-mentioned optical element.

[0009] Another aspect of the present invention is a microscope objective lens including an optical system including the above-mentioned optical element.

[0010] Another aspect of the present invention is an interchangeable lens for a camera, comprising: an optical system including the above-mentioned optical element.

[0011] Another aspect of the present invention is an optical device including an optical system including the above-mentioned optical element.

[0012] Another aspect of the present invention is a cemented lens including 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-mentioned optical glass.

[0013] Another aspect of the present invention is an optical system including the above-mentioned cemented lens.

[0014] Another aspect of the present invention is a microscope objective lens including an optical system including the above-mentioned cemented lens.

[0015] Another aspect of the present invention is an interchangeable lens for a camera, comprising: an optical system including the above-mentioned cemented lens.

[0016] Another aspect of the present invention is an optical device including an optical system including the above-mentioned cemented lens. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a perspective view showing an example in which the optical device according to the present embodiment is used as an imaging device.

[0018] Figure 2 This is a schematic diagram showing another example in which the optical device according to the present embodiment is used as an imaging device, and is a front view of the imaging device.

[0019] Figure 3 This is a schematic diagram showing another example of using the optical device of this embodiment as an imaging device, and is a rear view of the imaging device.

[0020] Figure 4 This is a block diagram showing an example of the configuration of the multiphoton microscope according to the present embodiment.

[0021] Figure 5 This is a schematic diagram showing an example of a cemented lens according to the present embodiment.

[0022] Figure 6 It is a schematic diagram of the overall structure of the gas injection type suspension furnace of this embodiment.

[0023] Figure 7 It is an enlarged schematic diagram of a base on a stage of the gas jet type suspension furnace according to the present embodiment.

[0024] Figure 8 is the optical constant value (ν d -Pg，F ) to obtain the graph.

[0025] Fig. 9 is the optical constant value (ν d -n d ) to obtain the graph. DETAILED DESCRIPTION

[0026] Hereinafter, an embodiment of the present invention (hereinafter referred to as "this embodiment") is described. The following this embodiment is an example for describing the present invention, and does not mean that the present invention is limited to the following content. The present invention can be implemented by appropriately deforming within the scope of the purpose of the invention.

[0027] In addition, the expression "0 to N%" of the Q content includes a case where the Q component is not contained and a case where the Q component exceeds 0% and is N% or less.

[0028] The expression “does not contain the Q component” means that the Q component is not substantially contained and the content of the constituent component is below the impurity level. Below the impurity level means, for example, less than 0.01%.

[0029] The term "devitrification resistance" refers to the resistance of glass to devitrification. Here, "devitrification" refers to the phenomenon of loss of transparency of glass due to crystallization or phase separation when the temperature of glass is raised to above the glass transition temperature or when the temperature of glass is lowered from a molten state to below the liquidus temperature.

[0030] <Optical Glass>

[0031] The optical glass of the present embodiment is an optical glass in which, expressed in terms of mol% of cations, La 3+ The content is 5% to 35%, Si 4+ The content is 5% to 25%, Nb 5+ The content is 5% to 35%, Al 3+ The content is 5% to 35%, Ti 4+ 、Zr 4 + , Nb 5+ 、 5+ and Al 3+ The total content (Ti 4+ +Zr 4+ +Nb 5+ +Ta 5+ +Al 3+ ) is 45% to 80%.

[0032] It should be noted that, in this specification, unless otherwise stated, the content of each component is expressed in mole % of cations. Mole % of cations refers to the ratio of the mole number of cations of the object to the total mole number of cations contained in the optical glass. More specifically, in SiO 2 50mol and Na 2 In the case of 50 mol of O, it is expressed as the molar % of the cation, then Si 4+ is 33.3%, Na + The form of each cation is not particularly limited, and for example, the cation may be contained in the optical glass in the form of an oxide or the like.

[0033] The optical glass of this embodiment is: 2 O 3 and Nb 2 O 5 This is a new type of optical glass with a high refractive index and high transmittance, which is a composition system with a main component. This composition system does not vitrify when melted in a crucible, but can be obtained by the suspension melting method. The glass easily floats due to its low specific gravity and high resistance to devitrification. The suspension melting method can also stably produce glass droplets with a diameter of more than 10 mm.

[0034] First, each component of the optical glass according to the present embodiment will be described.

[0035] La 3+ For example, La is used as the oxide conversion composition. 2 O 3 The ingredients contained in the form of 3+ It has the effect of increasing the refractive index and transmittance. However, as the content increases, the specific gravity tends to increase. 3+ The content of is 5 to 35%. The lower limit of the content is preferably 8%, more preferably 12%, and further preferably 15%. The upper limit of the content is preferably 32%, more preferably 29%, and further preferably 26%.

[0036] Si 4+ For example, in the composition calculated by oxide conversion, SiO 2 The ingredients contained in the form of Si 4+ It is a component that can improve the stability against devitrification while maintaining a low specific gravity. However, if the content increases, the refractive index tends to decrease. 4+ The content of is 5 to 25%. The lower limit of the content is preferably 6%, more preferably 8%, and further preferably 10%. In addition, the upper limit of the content is preferably 24%, more preferably 22%, and further preferably 20%.

[0037] Nb 5+ For example, in the composition calculated as oxide, Nb 2 O 5 It is a component contained in the form of. It has the effect of increasing the refractive index and transmittance. However, if the content increases, it is easy to increase the specific gravity. From this point of view, Nb 5+ The content of is 5 to 35%. The lower limit of the content is preferably 8%, more preferably 12%, and further preferably 16%. The upper limit of the content is preferably 32%, more preferably 29%, and further preferably 26%.

[0038] Al 3+ For example, in the composition calculated as oxide, Al 2 O 3 The ingredients contained in the form of Al 3+ It is a component that can improve the stability against devitrification while maintaining a low specific gravity. However, if the content increases, the refractive index will tend to decrease. 3+ The content of is 5 to 35%. The lower limit of the content is preferably 8%, more preferably 12%, and further preferably 14%. The upper limit of the content is preferably 32%, more preferably 29%, and further preferably 26%.

[0039] Zr 4+ For example, in the composition calculated as oxide, ZrO 2 The ingredients contained in the form of Zr 4+ It has the effect of improving the devitrification stability and refractive index. 4+ The content of is 0 to 15%. The lower limit of the content is preferably 2%, more preferably 4%, and further preferably 6%. The upper limit of the content is preferably 14%, more preferably 12%, and further preferably 10%.

[0040] Ti 4+ For example, in the composition calculated by oxide conversion, TiO 2 The ingredients contained in the form of Ti 4+ It has the effect of increasing the refractive index while maintaining a low specific gravity. However, as the content increases, the transmittance tends to decrease. 4+ The content of is 0 to 20%. The lower limit of the content is preferably 2%, more preferably 4%, and further preferably 6%. The upper limit of the content is preferably 20%, more preferably 16%, and further preferably 10%.

[0041] Ta 5+ For example, in the composition calculated by oxide conversion, Ta 2 O 5The ingredients contained in the form of 5+ It has the effect of improving the stability against devitrification while maintaining low dispersion. However, as the content increases, the specific gravity tends to increase. 5+ The content of is 0 to 15%. The lower limit of the content is preferably 2%, more preferably 3%, and further preferably 5%. The upper limit of the content is preferably 12%, more preferably 10%, and further preferably 8%.

[0042] Ti 4+ 、Zr 4+ , Nb 5+ 、 5+ and Al 3+ The total content (Ti 4+ +Zr 4+ +Nb 5+ +Ta 5+ +Al 3+ ) is 45 to 80%. The lower limit of the total content is preferably 50%, more preferably 54%, and further preferably 56%. The upper limit of the total content is preferably 76%, more preferably 73%, and further preferably 70%. By making (Ti 4+ +Zr 4+ +Nb 5+ +Ta 5+ +Al 3+ ) content within such a range can achieve both a high refractive index and a high transmittance while maintaining the stability against devitrification during melting.

[0043] The optical glass composition of this embodiment may further contain Y 3+ and B 3+ Any one of .

[0044] Y 3+ For example, in the composition calculated as oxide, Y 2 O 3 The ingredients contained in the form of 3+ It is a component that can increase the refractive index and transmittance without damaging the low dispersion. 3+ The content of La is 0 to 15%. The lower limit of the content is preferably 2%, more preferably 4%, and further preferably 6%. In addition, the upper limit of the content is preferably 12%, more preferably 10%, and further preferably 8%. In addition, La is preferably contained at the same time. 3+ and Y 3+ .

[0045] B 3+ For example, in the composition calculated as oxide, B 2 O 3The components contained in the form of are the components that constitute the mesh-forming oxides. 3+ Since B is a highly volatile component, if it is introduced in excessive amounts, it may cause the composition of the glass to change during production, making the wave lines obvious. From this aspect, it is preferred that B is substantially not contained. 3+ In addition, in the presence of B 3+ In the case of , the upper limit of the content is preferably 10%, more preferably 5%, and further preferably 2%.

[0046] In addition, known clarifiers, colorants, degassing agents, fluorine compounds and other components can be added to the glass composition in appropriate amounts for the purpose of clarification, coloring, decolorization, fine adjustment of optical constant values, etc. In addition, it is not limited to the above components, and other components can also be added within the scope of the effect of the optical glass of this embodiment.

[0047] The raw material preferably uses a high-purity product with a small amount of impurities. A high-purity product means that the component contains 99.85% by mass or more. By using a high-purity product, the amount of impurities is reduced, and as a result, there is a tendency to be able to improve the internal transmittance of the optical glass.

[0048] Next, the physical property values ​​of the optical glass according to the present embodiment will be described.

[0049] From the perspective of visible light transmittance of the optical system, the optical glass of this embodiment preferably has a high internal transmittance. According to this actual situation, the optical glass of this embodiment has an internal transmittance of 80% of the wavelength (λ 80 ) is less than 420nm. And, 80 The upper limit of the wavelength is preferably 405 nm, more preferably 400 nm, further preferably 395 nm.

[0050] From the perspective of reducing the thickness of the lens, the optical glass of this embodiment preferably has a high refractive index (refractive index (n d ) is large). However, the general tendency is that the refractive index (n d ) is higher, the transmittance is lower. Based on this actual situation, the refractive index (n) of the optical glass of this embodiment for d line is d ) is in the range of 1.95 to 2.15. d The lower limit of ) is preferably 1.96, more preferably 1.97, and further preferably 1.99. d ) is preferably 2.12, more preferably 2.08, and further preferably 2.05.

[0051] The Abbe number (ν d ) is in the range of 20 to 35. Also, the Abbe number (ν dThe lower limit of ) is preferably 22, more preferably 24, and further preferably 25. The Abbe number (ν d ) is preferably 32, more preferably 30, and further preferably 29.

[0052] From the perspective of lens aberration correction, the partial dispersion ratio (P g，F ) is 0.55 to 0.65. In addition, the partial dispersion ratio (P g，F The lower limit of the partial dispersion ratio (P g，F The upper limit of ) is preferably 0.64, more preferably 0.62, and further preferably 0.61. g，F ) preferably satisfies the following formula. It should be noted that the partial dispersion ratio (P g，F ) is a value calculated based on the refractive index measured by the V-block method.

[0053] -0.00403×ν d +0.704<P g，F <-0.00403×ν d +0.717…(1)

[0054] The length of the optical glass of this embodiment in the long axis direction is 10 mm or more. The length in the long axis direction is preferably 11 mm or more, more preferably 12 mm or more, and further preferably 13 mm or more. The "length in the long axis direction" mentioned here refers to the maximum value in the diameter direction of the glass drop, and in the case of a nearly spherical shape, refers to its diameter value.

[0055] The thickness (T) of the optical glass of this embodiment is preferably 4 mm or more, more preferably 5 mm or more, and further preferably 5.5 mm or more. The "thickness" mentioned here refers to the height in the vertical direction relative to the maximum value (diameter (D)) of the diameter of the glass drop, and in the case of a nearly spherical shape, refers to its diameter value.

[0056] The weight of the optical glass of the present embodiment is preferably 1.5 g or more, more preferably 2.0 g or more, and further preferably 2.5 g or more.

[0057] When the optical glass of the present invention is manufactured using a suspension furnace, its specific gravity is preferably 6.0 or less. g ) is 4.6 to 5.6. The lower limit of the specific gravity is preferably 4.7, more preferably 4.8, and further preferably 4.9. The upper limit of the specific gravity is preferably 5.5, more preferably 5.3, and further preferably 5.1.

[0058] The glass transition temperature (T g ) and the crystallization start temperature (T x ) temperature difference (ΔT = T x -T g ) is larger, the higher the devitrification resistance is. According to this actual situation, the glass transition temperature (T g ) and the crystallization start temperature (T x ) temperature difference (ΔT = T x -T g ) is 80°C to 200°C. Furthermore, the lower limit of the difference is preferably 100°C, more preferably 130°C, and further preferably 160°C. Furthermore, the upper limit of the difference is preferably 190°C, more preferably 180°C, and further preferably 170°C. ΔT can be used as an indicator of devitrification resistance stability. Generally speaking, a high ΔT means that the glass has a high devitrification resistance stability. Furthermore, in the present embodiment, the glass transition temperature (T g ) and the crystallization start temperature (T x ) can be measured by differential thermal analysis.

[0059] From the above viewpoint, the optical glass of the present embodiment can be suitable for use as an optical element, for example, an optical device. Such optical elements include reflectors, lenses, prisms, filters, etc. In addition, as optical systems using the above optical elements, for example, objective lenses, focusing lenses, imaging lenses, interchangeable lenses for cameras, etc. can be cited. Moreover, these optical systems can be suitable for use in various optical devices: imaging devices such as lens interchangeable cameras and lens non-interchangeable cameras, and microscope devices such as fluorescence microscopes and multiphoton microscopes. As optical devices, it is not limited to the above imaging devices and microscopes, but also includes but is not limited to telescopes, binoculars, laser rangefinders, projectors, etc. An example thereof is described below.

[0060] <Camera>

[0061] Figure 11 is a stereoscopic diagram showing an example of an optical device of the present embodiment 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) has an optical element whose base material is the optical glass of the present embodiment. The lens barrel 102 is detachably mounted on a lens mount (not shown) of a camera body 101. In addition, light from the lens 103 that has passed through the lens barrel 102 is imaged on a sensor chip (solid-state imaging element) 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 a COG (Chip On Glass) type module in which, for example, the sensor chip 104 is mounted on a glass substrate 105 in a bare chip manner.

[0062] Figure 2 and Figure 3 This is a schematic diagram showing another example of the optical device of this embodiment as an imaging device. Figure 2 A front view of the camera device CAM is shown, Figure 3 The rear view of the imaging device CAM is shown. The imaging device CAM is a so-called digital still camera (non-interchangeable lens camera), and the taking lens WL (optical system) includes an optical element using the optical glass of the present embodiment as a base material.

[0063] In the camera device CAM, if the power button (not shown) is pressed, the shutter (not shown) of the photographic lens WL is opened, and the light from the subject (object) is condensed by the photographic lens WL and formed on the imaging element arranged on the image plane. The subject image formed on the imaging element is displayed on the liquid crystal display M1 arranged on the back of the camera device CAM. The photographer determines the composition of the subject image while observing the liquid crystal display M1, and then presses the release button B1, and the subject image is photographed by the imaging element and recorded and stored in the memory (not shown).

[0064] The imaging device CAM is provided with an auxiliary light emitting unit EF for emitting auxiliary light when the subject is dark, a function button B2 for setting various conditions of the imaging device CAM, and the like.

[0065] Optical systems used in such digital cameras and the like are required to have higher resolution, lower chromatic aberration, and smaller size. In order to achieve these functions, it is effective to use glasses with different dispersion characteristics in the optical system. In particular, glasses with low dispersion and a higher partial dispersion ratio (P g，F) is in high demand. From this aspect, the optical glass of this embodiment is suitable as a component of the optical device. It should be noted that the optical device applicable to this embodiment is not limited to the above-mentioned camera device, and a projector, etc., can also be cited. The optical element is not limited to the lens, and a prism, etc., can also be cited.

[0066] <Microscope>

[0067] Figure 4 1 is a block diagram showing an example of the structure of the multiphoton microscope 2 of the present embodiment. The multiphoton microscope 2 includes an objective lens 206, a converging lens 208, and an imaging lens 210. At least one of the objective lens 206, the converging lens 208, and the imaging lens 210 includes an optical element using the optical glass of the present embodiment as a base material. The following description will focus on the optical system of the multiphoton microscope 2.

[0068] The pulse laser device 201 emits, for example, ultrashort pulse light of near-infrared wavelength (about 1000 nm) and pulse width in femtoseconds (e.g., 100 femtoseconds). The ultrashort pulse light immediately after being emitted from the pulse laser device 201 generally forms linearly polarized light polarized in a predetermined direction.

[0069] The pulse splitting device 202 splits the ultrashort pulse light, increases the repetition frequency of the ultrashort pulse light, and then emits the split pulse light.

[0070] The beam adjustment unit 203 has the following functions: a function of adjusting the beam diameter of the ultrashort pulse light incident from the pulse splitting device 202 in accordance with the pupil diameter of the objective lens 206; a function of adjusting the convergence and divergence angles of the ultrashort pulse light in order to correct the axial chromatic aberration (focal difference) between the wavelength of the light emitted from the sample S and the wavelength of the ultrashort pulse light; a function of pre-chirping the ultrashort pulse light with an opposite group velocity dispersion (group velocity dispersion compensation function) in order to correct the situation in which the pulse width of the ultrashort pulse light becomes wider due to group velocity dispersion while passing through the optical system, etc.

[0071] The ultrashort pulse light emitted from the pulse laser device 201 increases its repetition frequency under the action of the pulse splitting device 202, and the above adjustment is performed by the beam adjusting unit 203. In addition, the ultrashort pulse light emitted from the beam adjusting unit 203 is reflected in the direction of the dichroic mirror 204, passes through the dichroic mirror 205, and is converged by the objective lens 206 to irradiate the sample S. At this time, the ultrashort pulse light can be scanned on the observation surface of the sample S by using a scanning device (not shown).

[0072] For example, when performing fluorescence observation on sample S, in the area where sample S is irradiated with ultrashort pulse light and its vicinity, the fluorescent pigment that dyes sample S is subjected to multi-photon excitation and emits fluorescence having a wavelength shorter than the infrared wavelength of the ultrashort pulse light (hereinafter referred to as "observation light").

[0073] The observation light emitted from the sample S toward the objective lens 206 is collimated by the objective lens 206 , and is reflected by the dichroic mirror 205 or passes through the dichroic mirror 205 according to its wavelength.

[0074] 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 blocking 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 light quantity. In addition, the fluorescence detection unit 207 detects the observation light on the observation surface of the sample S in coordination with the scanning of the ultrashort pulse light on the observation surface of the sample S.

[0075] It should be noted that the fluorescence detection unit 211 can also detect all observation light emitted from the sample S in the direction of the objective lens 206 by removing the dichroic mirror 205 from the optical path. In this case, the observation light is descanned by a scanning device (not shown), passes through the dichroic mirror 204, is converged by the convergent lens 208, passes through the pinhole 209 set 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.

[0076] The fluorescence detection unit 211 is composed of, for example, a blocking filter, a PMT, etc., receives the observation light formed by the imaging lens 210 on the light receiving surface of the fluorescence detection unit 211, and outputs an electrical signal corresponding to the light quantity. In addition, the fluorescence detection unit 211 detects the observation light on the observation surface of the sample S by scanning the ultrashort pulse light on the observation surface of the sample S.

[0077] It should be noted that the dichroic mirror 205 may be removed from the optical path so that 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 .

[0078] 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 blocking filter, a PMT, etc., receives the observation light reflected by the dichroic mirror 212, and outputs an electrical signal corresponding to the light amount. In addition, the fluorescence detection unit 213 detects the observation light on the observation surface of the sample S in coordination with the scanning of the ultrashort pulse light on the observation surface of the sample S.

[0079] The electrical signals outputted from the fluorescence detection units 207 , 211 , and 213 are inputted into, 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 observation image data.

[0080] <Joint lens>

[0081] Figure 5 Schematic diagram showing an example of a joined lens of the present embodiment. The joined 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 uses the optical glass of the present embodiment. The first lens element and the second lens element are joined by a joining component 303. As the joining component 303, a known adhesive or the like can be used. It should be noted that the so-called "lens element" refers to each lens constituting a single lens or a joined lens.

[0082] The joint lens of the present embodiment is useful in the aspect of chromatic aberration correction, and can be suitable for the above-mentioned optical element, optical system, optical device, etc. In addition, the optical system including the joint lens is particularly suitable for camera interchangeable lenses, optical devices, etc. It should be noted that in the above-mentioned manner, the joint lens using two lens elements is described, but it is not limited to this, and it can also be a joint lens using more than three lens elements. In the case of making a joint lens using more than three lens elements, at least one of the more than three lens elements can be formed using the optical glass of the present embodiment.

[0083] <Method for producing optical glass>

[0084] The optical glass of this embodiment can be manufactured using a suspension furnace, for example. Suspension furnaces include electrostatic, electromagnetic, sonic, magnetic, and gas jet types, etc., and are not particularly limited. It is preferred to use a gas jet type suspension furnace for suspension melting (melting) of oxides. Below, a manufacturing method using a gas jet type suspension furnace is described as an example.

[0085] Figure 6 A schematic diagram showing the overall structure of a gas jet type suspension furnace, Figure 7 It is an enlarged schematic diagram of the base on the carrier of the gas jet type suspension furnace.

[0086] In the gas jet type suspension furnace 4, the raw material M is arranged on a base 402 on a stage 401. Then, the laser light L emitted from the laser light source 403 is irradiated onto the raw material M via the reflector 404 and the reflector 405. The temperature of the raw material M heated by the irradiation of the laser light L is monitored by the 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 the computer 407. In addition, the state of the raw material M is photographed by the CCD camera 408 and output to the monitor 409 (refer to FIG. 4 ). Figure 5 ) It should be noted that, as the laser light source, for example, a carbon dioxide laser can be used.

[0087] In the gas jet type suspension furnace 4, the raw material M is suspended by the gas fed into the base (see Figure 7 ). The flow rate of the gas fed into the base is controlled by the gas flow regulator 410. For example, the gas may be ejected from a nozzle having a conical hole, and non-contact heating may be performed using the laser L while the raw material M is suspended. When the raw material M is melted, it forms a spherical or ellipsoidal shape due to its own surface tension and is suspended in this state.

[0088] Afterwards, when the laser L is cut off, the raw material in the molten state is cooled to obtain transparent glass. It should be noted that the type of gas is not particularly limited, and known gases can be appropriately used, such as oxygen, nitrogen, carbon dioxide, argon, air, etc. In addition, the shape of the nozzle and the heating method are not particularly limited, and known methods can be appropriately used.

[0089] Conventionally, when optical glass is manufactured using a container such as a crucible, it is necessary to contain a large amount of SiO 2 , B 2 O 3 , P 2 O 5 ,GeO 2 The glass forming ability is improved by adding mesh-forming oxides such as 2-(4-nitrogen)-2-oxide to the glass composition. Therefore, when the glass composition contains a large amount of materials that are not mesh-forming oxides and the content of the mesh-forming oxides is small, there are cases where crystallization (heterogeneous nucleation) often occurs starting from the container-melt interface and vitrification cannot be achieved. In addition, glass droplets are sometimes used as materials for optical lenses of various optical devices. As such glass droplets, it is desired to be able to stably produce large glass droplets.

[0090] In this regard, in the present embodiment, for example, when manufacturing optical glass by using the above-mentioned suspension furnace method, since the container is not in contact with the melt, heterogeneous nucleation can be suppressed to the greatest extent. As a result, the glass formation of the melt is greatly promoted, and even a composition that cannot be manufactured by crucible melting and has a small content of mesh-forming oxides or does not contain mesh-forming oxides at all can be vitrified. By adopting this manufacturing method, optical glass of the composition system of the present embodiment that could not be vitrified in the past can be manufactured. Furthermore, the above-mentioned large glass droplets can also be made. In addition, the optical glass of the present embodiment has a high refractive index and a high Abbe number. The optical glass of the present embodiment has many such advantages, and can therefore be used as a high-refractive and low-dispersion glass material or a wide-band transmission material.

[0091] Example

[0092] Next, examples and comparative examples of the present invention will be described. However, the present invention is not limited to these examples.

[0093] <Production of optical glass>

[0094] use Figure 6 and Figure 7 The gas jet type suspension furnace 4 shown in the figure is used to produce the optical glass of each embodiment and each comparative example according to the following steps. First, the glass raw materials selected from oxides are weighed in such a way as to obtain the composition (mol% of cations) recorded in each table. In addition, the glass raw materials can also be selected from hydroxides, carbonates, nitrates, sulfates, etc. Next, the weighed raw materials are mixed in an alumina mortar. The raw materials are unidirectionally pressurized at 20 MPa and formed into cylindrical pellets. The obtained pellets are fired in an electric furnace at 1000°C to 1300°C in the atmosphere for 3 hours to 6 hours to produce a sintered body. The obtained sintered body is coarsely crushed, and 50 mg to 4000 mg are taken and placed in the nozzle of the base. Then, the raw materials are melted by irradiating with carbon dioxide laser from above while spraying air. The molten raw materials become spherical or ellipsoidal due to their own surface tension and become suspended under the pressure of the gas. The laser output is cut off when the raw materials are completely melted, thereby cooling the raw materials. Furthermore, annealing was performed at 760°C to 810°C for 10 hours to obtain glass droplets (glass balls) with diameters of 10.30 mm to 14.55 mm and thicknesses of 5.20 mm to 6.04 mm. No visible volatilization, bubbles or devitrification was observed during melting of the glass of each example.

[0095] <Physical Property Evaluation>

[0096] Figure 8 and Fig. 9 This is a graph in which the optical constant values ​​of each example are plotted.

[0097] Crystallization start temperature (T x ), glass transition temperature (T g ) and its temperature difference (ΔT)

[0098] Crystallization start temperature (T x ) and glass transition temperature (T g ) were measured by differential thermal analysis during the heating process (heating temperature 10°C / min), and T x -T g as the temperature difference (ΔT).

[0099] Specific gravity (S g )

[0100] The specific gravity of each sample (S g ) is measured by the Archimedean method. The specific gravity value is rounded to the third decimal place.

[0101] Diameter (D), Thickness (T)

[0102] The diameter (D) and thickness (T) of each sample were measured using an electronic vernier caliper.

[0103] Refractive index (n d ) and the Abbe number (ν d )

[0104] The samples of the examples were subjected to 90-degree prism processing, and the refractive index was measured by a V-block method using a refractometer (manufactured by Kalnew Optical Industries, Ltd., “KPR-3000”), and the Abbe number and partial dispersion ratio were calculated.

[0105] For the comparative example, a prism coupler (manufactured by Metricon, "2010 / M" model) was used to measure the refractive index and calculate the Abbe number by the prism coupling method. In the prism coupling method, the glass sample is ground so that the ground surface is in close contact with a single crystal rutile prism, and the total reflection angle when light of the measured wavelength is incident is measured to determine the refractive index. The three wavelengths of 473nm, 594.1nm, and 656nm were measured 5 times each, and the average value was taken as the measured value. Furthermore, for the obtained measured values, the following Drude-Voigt dispersion equation was used to perform a least squares fitting to calculate the refractive index and Abbe number (ν d ).

[0106] [Number 1]

[0107] Mathematical formula 1

[0108] (n: refractive index, m: electron mass, c: speed of light, e: elementary charge, N: number of molecules per unit volume, f: oscillator strength, λ 0 : inherent resonance wavelength, λ: wavelength)

[0109] n d Indicates the refractive index of glass for light at 587.562nm. d ) is obtained by the following formula (2). C 、n F Respectively, they represent the refractive index of glass for light with a wavelength of 656.273nm and 486.133nm. The refractive index value is rounded to the sixth decimal place.

[0110] ν d =(n d -1) / (n F -n C )…(2)

[0111] Partial dispersion ratio (P g，F )

[0112] The partial dispersion ratio (P g，F ) represents partial dispersion (n g -n F ) relative to the main dispersion (n F -n C ) is calculated by the following formula (3). g It indicates the refractive index of glass for light with a wavelength of 435.835nm. g，F ) is rounded to 4 decimal places.

[0113] P g，F =(n g -n F ) / (n F -n C )…(3)

[0114] Internal transmittance

[0115] The internal transmittance of each sample is measured using a spectrophotometer (manufactured by Hitachi High-Tech Science, "UV-Vis-Infrared Spectrophotometer UH4150") for a 4 mm to 9 mm thick parallel polished material at a wavelength of 300 nm to 700 nm, and the measured transmittance is corrected by excluding the contribution to the transmittance due to the reflectivity at each wavelength using the refractive index measurement data, and converted to a transmittance value of 10 mm thickness. The refractive index data of the V-block method based on the 10 bright lines (spectral lines) of the h line, g line, F' line, F line, e line, d line, C' line, C line, r line, and t line are fitted by the least squares method using the following dispersion curve equation.

[0116] [Number 2]

[0117] Mathematical formula 2

[0118] n (λ) =A 0 +A 1 λ 2 +A 2 λ 4 +A 3 λ -2 +A 4 λ -4 +A 5 λ -6 +A 6 λ -8 +A 7 λ -10 +A 8 λ -12

[0119] The refractive index value n at each wavelength λ calculated using the dispersion curve equation is used. λ , the surface reflectance R and transmittance T of each wavelength are calculated by the following formula th , transmittance T th It is the transmittance calculated by considering the multiple reflections of the incident light on the front and back surfaces, assuming that there is no internal absorption of light. exp and T th Calculate the internal transmittance T (tmm) .

[0120] [Number 3]

[0121] Mathematical formula 3

[0122]

[0123] The internal transmittance T when the thickness tmm calculated above is used (tmm), the transmittance value T of 10mm thickness is calculated by the following formula (10mm) .

[0124] [Number 4]

[0125] Mathematical formula 4

[0126]

[0127] The compositions and physical property values ​​of each embodiment and each comparative example are shown in each table. It should be noted that, unless otherwise stated, the content of each component is based on the mole % of the cation. In addition, each physical property value is the physical property value of the glass in the unpressurized state.

[0128] [Table 1]

[0129]

[0130] [Table 2]

[0131]

[0132] [Table 3]

[0133]

[0134] [Table 4]

[0135]

[0136] From the above, it can be confirmed that the optical glass of each example can have high refractive index, high transmittance, low specific gravity and stability against devitrification at a high level, and can be enlarged to a diameter of 10 mm or more when produced by the suspension melting method.

[0137] Explanation of symbols

[0138] 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…photographic lens, M1…liquid crystal display, EF…auxiliary light emitting unit, B1…release button, B2…function button, 2…multiphoton microscope, 201…pulse laser device, 202…pulse splitting device, 203…light beam adjusting unit, 204, 205, 212…dichroic mirror, 206…objective lens , 207, 211, 213…fluorescence detection unit, 208…converging lens, 209…pinhole, 210…imaging lens, S…sample, 3…joined lens, 301…first lens element, 302…second lens element, 303…joined component, 4…gas levitation furnace, 401…stage, 402…base, 403…laser light source, 404, 405…reflecting mirror, 406…radiation thermometer, 407…computer, 408…CCD camera, 409…monitor, 410…gas flow regulator, L…laser, M…raw material.

Claims

1. An optical glass, wherein: Expressed as mole % of cation, La 3+ The content is 5% to 35%, Si 4+ The content is 5% to 25%, Nb 5+ The content is 5% to 35%, Al 3+ The content is 5% to 35%, Ti 4+ 、Zr 4+ , Nb 5+ 、 5+ and Al 3+ The total content (Ti 4+ +Zr 4+ +Nb 5+ +Ta 5+ +Al 3+ ) is 45% to 80%.

2. The optical glass according to claim 1, wherein: Expressed as mole % of cation, Ti 4+ The content is 0% to 20%.

3. An optical glass, wherein: Expressed as mole % of cation, La 3+ The content is 5% to 35%, Si 4+ The content is 5% to 25%, Nb 5+ The content is 5% to 35%, Ti 4+ The content is 0% to 20%, Ti 4+ 、Zr 4+ , Nb 5+ 、 5+ and Al 3+ The total content (Ti 4+ +Zr 4+ +Nb 5+ +Ta 5+ +Al 3+ ) is 45% to 80%.

4. The optical glass according to any one of claims 1 to 3, wherein Expressed as mole % of cation, Zr 4+ The content is 0%~15%.

5. The optical glass according to any one of claims 1 to 4, wherein Expressed as mole % of cation, Ta 5+ The content is 0%~15%.

6. The optical glass according to any one of claims 1 to 5, wherein Expressed as mole % of cation, Y 3+ The content is 0%~15%.

7. The optical glass according to any one of claims 1 to 6, wherein Contains virtually no B 3+ .

8. The optical glass according to any one of claims 1 to 7, wherein The internal transmittance of the optical glass per 10 mm is 80% of the wavelength λ 80 Below 420nm.

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

15.

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

11. The optical glass according to any one of claims 1 to 10, wherein The partial dispersion ratio P of the optical glass g,F Satisfies the following formula, -0.00403×ν d +0.704<P g,F <-0.00403×ν d +0.717…(1)。 12. The optical glass according to any one of claims 1 to 11, wherein The specific gravity S of the optical glass g It is 4.6 to 5.

6.

13. The optical glass according to any one of claims 1 to 12, wherein: The glass transition temperature T of the optical glass g and the crystallization start temperature T x The temperature difference (ΔT = T x -T g ) is 80℃~200℃.

14. The optical glass according to any one of claims 1 to 13, wherein The length of the optical glass in the long axis direction is 10 mm or more. 15 . An optical element using the optical glass according to claim 1 .

16. An optical system comprising the optical element according to claim 15.

17. An objective lens for a microscope, comprising the optical system according to claim 16.

18. An interchangeable lens for a camera, comprising the optical system according to claim 16.

19. An optical device comprising the optical system according to claim 16.

20. A cemented lens comprising a first lens element and a second lens element, 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 14. An optical system comprising the cemented lens according to claim 20 .

22. An objective lens for a microscope, comprising the optical system according to claim 21.

23. An interchangeable lens for a camera, comprising the optical system according to claim 21.

24. An optical device comprising the optical system according to claim 21.

Images