Optical glass, near-infrared cut filter, glass element for press molding, optical element blank, and optical elements

Abstract

Provided are: an optical glass comprising a near-infrared absorption function while maintaining flatness and high transmittance in the visible light range, having excellent oblique incidence characteristics, and having excellent durability, heat resistance, and weather resistance; a near-infrared cut filter comprising the optical glass; glass elements for press molding; optical element blank; and optical elements.　This optical glass has a glass composition as a base and contains at least Yb2O3 and B2O3 as essential components. The optical glass is characterized in that the content of Yb2O3 is 5-60 mass%, the content of B2O3 is 10-50 mass%, and when the thickness of the optical glass is 2.5 mm, the average transmittance in the wavelength range of 925-955 nm is 0-70%, and the average transmittance in the wavelength range of 965-985 nm is 0-50%.

Description

Optical glass, near-infrared cut filters, glass elements for press molding, optical element blanks, and optical elements

[0001] The present invention relates to an optical glass that has excellent light transmittance in the visible region and excellent light absorption in the near-infrared region, and to a near-infrared cut filter, a glass element for press molding, an optical element blank, and an optical element that include the optical glass.

[0002] In recent years, autonomous driving technology for automobiles has been advancing rapidly. This autonomous driving technology requires accurate recognition and distance measurement of fast-moving objects over a wide area around the vehicle, and therefore uses a Light Detection and Ranging (LiDAR) system.

[0003] A LiDAR system is a type of optical remote sensing technology that irradiates a target with a pulsed laser and measures the scattered light to analyze the distance to a distant target and its characteristics. Such LiDAR systems typically use lasers in the 900 nm wavelength band (e.g., 905 nm, 940 nm, 970 nm) because they are less susceptible to ambient light and direct sunlight. Furthermore, autonomous driving of automobiles requires the ability to safely navigate highways and public roads. To ensure sensing redundancy in the system, imaging devices incorporating solid-state imaging elements such as charge-coupled devices (CCDs) and complementary metal oxide semiconductors (CMOSs) are often used in conjunction with LiDAR systems. However, because the solid-state imaging elements in such imaging devices have spectral sensitivity ranging from the near-ultraviolet to near-infrared ranges, using them with a LiDAR system can result in poor color reproduction due to the influence of the LiDAR system's laser light. For this reason, imaging devices have been proposed that include a near-infrared cut filter (optical filter) to block the laser light of the LiDAR system.

[0004] As such near-infrared cut filters, those having a configuration in which a dielectric multilayer film is formed on a glass substrate and light of a predetermined wavelength (near-infrared) is reflected by the dielectric multilayer film (for example, Patent Document 1), and those having a configuration in which an absorption layer that absorbs near-infrared light is formed on a glass substrate and light of a predetermined wavelength (near-infrared) is absorbed by the absorption layer (for example, Patent Document 2) are in practical use.

[0005] Patent No. 6194384 International Publication No. 2019 / 151344

[0006] According to the configuration described in Patent Document 1, light of a specific wavelength (near-infrared) incident on the near-infrared cut filter is reflected by the dielectric multilayer film, while only light of the desired wavelength (visible light) is transmitted. Therefore, a solid-state imaging device that receives the transmitted light can produce an image with excellent color reproducibility. However, when a LiDAR system and an imaging device are used simultaneously, the laser light (near-infrared) of the LiDAR system is reflected by the dielectric multilayer film of the near-infrared cut filter. This reflected light becomes noise in the LiDAR system and affects the measurement accuracy of the LiDAR system. Furthermore, when light is incident obliquely on the dielectric multilayer film, the optical path length increases, causing a phase shift, which can shift the spectral transmittance curve toward shorter wavelengths or cause ripples in the spectral transmittance curve. Furthermore, wavelength shifts in the spectral transmittance curve can reduce the color reproducibility of the solid-state imaging device, and ripples in the spectral transmittance curve can result in a type of ghost image being observed on the solid-state imaging device.

[0007] Furthermore, according to the configuration described in Patent Document 2, light of a predetermined wavelength (near-infrared light) among light incident on the near-infrared cut filter is absorbed by the absorption layer, and only light of a desired wavelength (visible light) is transmitted, thereby enabling a solid-state imaging element that receives the transmitted light to obtain an image with excellent color reproducibility. However, the absorption layer described in Patent Document 2 contains a near-infrared absorbing dye and a transparent resin, and has problems such as poor durability, heat resistance, and weather resistance. Furthermore, particularly in vehicle-mounted LiDAR systems, high reliability is required from the standpoint of outdoor use and safety, and therefore near-infrared cut filters used in LiDAR systems are also required to have far greater durability, heat resistance, and weather resistance than conventional ones.

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical glass with a near-infrared absorbing function, which has excellent oblique incidence characteristics (i.e., extremely little incidence angle dependency) while maintaining a flat and high transmittance in the visible light range, and which also has excellent durability, heat resistance, and weather resistance, as well as a near-infrared cut filter, a glass element for press molding, an optical element blank, and an optical element each including the optical glass.

[0009] As a result of extensive research conducted by the present inventors to achieve the above object, they have focused on the absorption of Yb (ytterbium) in the 900 nm band and found that by increasing the amount of Yb added, it is possible to produce optical glass that selectively absorbs near-infrared light in the 900 nm band while maintaining a flat and high transmittance in the visible light range, without using the dielectric multilayer film or absorption layer that are used in conventional near-infrared cut filters. The present invention was made based on this finding.

[0010] That is, the optical glass of the present invention contains at least Yb ２ O ３ and B ２ O ３ An optical glass based on a glass composition containing as an essential component Yb ２ O ３ The content of B is 5 to 60 mass %. ２ O ３The optical glass is characterized in that the content of the compound (II) is 10 to 50 mass %, and when the thickness of the optical glass is 2.5 mm, the average transmittance in the wavelength range of 925 to 955 nm is 0 to 70%, and the average transmittance in the wavelength range of 965 to 985 nm is 0 to 50%.

[0011] According to this configuration, since it does not have a conventional dielectric multilayer film or an absorption layer, it is possible to obtain an optical glass that has excellent oblique incidence characteristics (i.e., extremely little incidence angle dependency), as well as excellent durability, heat resistance, and weather resistance, maintains a flat and high transmittance in the visible light range, and has a near-infrared absorbing function.

[0012] Furthermore, it is desirable that the average transmittance in the wavelength range of 400 to 800 nm is 80 to 92%.

[0013] In addition, in the transmittance curve of the optical glass, it is desirable that the first wavelength when the transmittance decreases to 50% is 860 to 940 nm, and the second wavelength when the transmittance increases to 50% is 970 to 1040 nm.

[0014] The thickness of the optical glass is preferably 0.5 to 5.0 mm.

[0015] It is also desirable that the liquidus temperature of the optical glass is 1350° C. or lower.

[0016] Furthermore, it is desirable that the water resistance of the optical glass be of grade 1, 2 or 3 as determined by the powder method.

[0017] The glass composition contains, in mass %, SiO ２ : 0 to 30%, Al ２ O ３ : 0-15%, MgO: 0-10%, CaO: 0-20%, SrO: 0-10%, BaO: 0-25%, ZnO: 0-25%, TiO ２ : 0 to 15%, Nb ２ O ５ : 0 to 15%, Ta ２ O ５ : 0-7%, WO ３ :0~10%, ZrO ２ : 0 to 10%, La ２ O ３ : 0 to 30%, Y ２ O３ : 0-30%, Gd ２ O ３ : 0 to 30%, Sb ２ O ３ :0~0.05%, SO ３ : It is desirable to contain 0 to 0.3%.

[0018] Also, Li ２ O, Na ２ O and K ２ It is desirable that at least one of Yb and O is further contained in a total content range of more than 0 to 10 mass %. ２ O ３ It is desirable that the content of is 30 mass % or more.

[0019] Also, Ln ２ O ３ Yb to the sum of components (Ln is one or more selected from the group consisting of Yb, La, Y, and Gd) ２ O ３ It is desirable that the content of is in the range of 0.6 to 1.0.

[0020] From another viewpoint, the near-infrared cut filter of the present invention is characterized by comprising any one of the optical glasses described above.

[0021] From another viewpoint, the press-molding glass element of the present invention is characterized by comprising any one of the optical glasses described above.

[0022] From another viewpoint, the optical element blank of the present invention is characterized by comprising any one of the optical glasses described above.

[0023] From another viewpoint, the optical element of the present invention is characterized by comprising any one of the optical glasses described above.

[0024] As described above, the present invention provides an optical glass that does not have a conventional dielectric multilayer film or absorption layer, and therefore has excellent oblique incidence characteristics (i.e., extremely little incidence angle dependency), as well as excellent durability, heat resistance, and weather resistance, maintains flatness and high transmittance in the visible light range, and has near-infrared absorbing properties. It is also possible to provide a near-infrared cut filter, a glass element for press molding, an optical element blank, and an optical element that include such an optical glass.

[0025] FIG. 1 is a graph showing the spectral transmittance curve of an optical glass according to an embodiment (Example 1) of the present invention. FIG. 2 is a graph showing the spectral transmittance curve of an optical glass according to an embodiment (Example 2) of the present invention. FIG. 3 is a graph showing the spectral transmittance curve of an optical glass according to an embodiment (Example 3) of the present invention. FIG. 4 is a graph showing the spectral transmittance curve of an optical glass according to an embodiment (Example 4) of the present invention. FIG. 5 is a graph showing the spectral transmittance curve of an optical glass according to an embodiment (Example 5) of the present invention. FIG. 6 is a graph showing the spectral transmittance curve of an optical glass according to an embodiment (Example 6) of the present invention. FIG. 7 is a graph showing the spectral transmittance curve of an optical glass according to an embodiment (Example 7) of the present invention. FIG. 8 is a graph showing the spectral transmittance curve of an optical glass according to an embodiment (Example 8) of the present invention. FIG. 9 is a graph showing the spectral transmittance curve of an optical glass according to an embodiment (Example 9) of the present invention. FIG. 10 is a graph showing the spectral transmittance curve of an optical glass according to an embodiment (Example 10) of the present invention. FIG. 11 is a graph showing the spectral transmittance curve of an optical glass according to an embodiment (Example 11) of the present invention. FIG. 12 is a graph showing the spectral transmittance curve of an optical glass according to an embodiment (Example 12) of the present invention. Fig. 13 is a diagram showing the spectral transmittance curve of an optical glass according to an embodiment (Example 13) of the present invention. Fig. 14 is a diagram showing the spectral transmittance curve of an optical glass according to an embodiment (Example 14) of the present invention. Fig. 15 is a diagram showing the spectral transmittance curve of an optical glass according to a comparative example (Comparative Example 1) of the present invention.

[0026] The optical glass according to the embodiment of the present invention contains at least Yb ２ O ３The glass is based on a glass composition containing the above as an essential component, and has a near-infrared absorbing function (i.e., a band-stop filter function) that selectively absorbs near-infrared light in the 900 nm band of incident light.

[0027] The glass composition contains Yb as an essential component. ２ O ３ and B ２ O ３ and optionally, SiO ２ , Al ２ O ３ , Li ２ O, Na ２ O.K. ２ O, MgO, CaO, SrO, BaO, ZnO, TiO ２ , Nb ２ O ５ , Ta ２ O ５ , W.O. ３ , ZrO ２ , La ２ O ３ , Y ２ O ３ , Gd ２ O ３ The desirable composition ranges of the components constituting the glass composition are as follows: Yb ２ O ３ : 5 to 60%, B ２ O ３ :10~50%, SiO ２ :0~30%, Al ２ O ３ :0~15%, Li ２ O: 0-10%, Na ２ O: 0-10%, K ２ O: 0-10%, MgO: 0-10%, CaO: 0-20%, SrO: 0-10%, BaO: 0-25%, ZnO: 0-25%, TiO ２ :0~15%, Nb ２ O ５ :0~15%, Ta ２ O ５ : 0-7%, WO ３ :0~10%, ZrO ２:0~10%, La ２ O ３ : 0 to 30%, Y ２ O ３ :0~30%, Gd ２ O ３ :0~30%, Sb ２ O ３ :0~0.05%, SO ３ : 0 to 0.3%, Yb ２ O ３ When the content is 25% or more, Al ２ O ３ and SiO ２ It is desirable to contain as an essential component, and in this case, Al ２ O ３ and SiO ２ It is desirable that the total content of Yb is more than 0% and not more than 32%. ２ O ３ When the content is 30% or more, Al ２ O ３ and SiO ２ In addition, alkali metals (Li ２ O, Na ２ O.K. ２ O) as an essential component, and in this case, Li ２ O, Na ２ O and K ２ It is desirable to contain at least one of rare earth elements Ln and O so that the total content is 10% or less. ２ O ３ component (wherein Ln is one or more selected from the group consisting of Yb, La, Y, and Gd) ２ O ３ The content of each component is preferably in the range of 0.6 to 1.0. The content of each component is expressed as mass % relative to the total mass of the glass in terms of oxide. Here, the oxide-equivalent composition is a composition in which each component contained in the glass is expressed, assuming that the oxides, composite salts, metal fluorides, etc. used as raw materials for the glass constituent components of the present invention are all decomposed and converted to oxides during melting, with the total mass of the oxides produced being 100 mass %.

[0028] The glass composition in the present invention can be quantified by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). The analytical value obtained by ICP-AES may include a measurement error of about ±5% of the analytical value. Furthermore, in this specification and the present invention, the content of a constituent component being 0%, or not being contained or not being incorporated means that the constituent component is substantially not contained, and indicates that the content of the constituent component is at or below the impurity level.

[0029] Hereinafter, with regard to numerical ranges, (more) preferred lower limits and (more) preferred upper limits may be shown in a table. In the table, the lower the numerical value, the more preferred, and the numerical value listed furthest down is the most preferred. Furthermore, unless otherwise specified, a (more) preferred lower limit means that it is (more) preferred to be equal to or greater than the value listed, and a (more) preferred upper limit means that it is (more) preferred to be equal to or less than the value listed. A numerical range can be defined by any combination of the numerical value listed in the (more) preferred lower limit column and the numerical value listed in the (more) preferred upper limit column in the table.

[0030] Yb ２ O ３ , La ２ O ３ , Y ２ O ３ , Gd ２ O ３ improves the chemical durability and weather resistance of the glass and increases the glass transition temperature. ２ O ３ , La ２ O ３ , Y ２ O ３ , Gd ２ O ３ Among them, Yb ２ O ３ is a rare earth element that absorbs near-infrared light with wavelengths of 860 to 1030 nm. ２ O ３When the content of Yb is less than 5%, the near-infrared absorbing function is significantly reduced, but when the content is 5% or more, the near-infrared absorbing function according to the content is obtained, and it becomes possible to produce glass having the above-mentioned optical properties. ２ O ３ If the content of Yb exceeds 60%, the tendency to devitrify increases, but if it is 60% or less, the thermal stability can be improved, so that crystallization during glass production can be suppressed and unmelted raw materials can be reduced when melting the glass. ２ O ３ is preferably in the range of 5 to 60%, more preferably 10 to 57%, even more preferably 13 to 55%, even more preferably 16 to 53%, even more preferably 18 to 51%, and even more preferably 20 to 50%. ２ O ３ component (wherein Ln is one or more selected from the group consisting of Yb, La, Y, and Gd) ２ O ３ The content is adjusted to be in the range of 0.6 to 1.0.

[0031] B ２ O ３ is a component that improves the thermal stability and meltability of glass. ２ O ３ When the content of B is large, the viscosity of the molten glass when it is molded tends to decrease. ２ O ３ The preferred range is 10 to 50%, more preferably 12 to 48%, and even more preferably 14 to 46%.

[0032] SiO ２ is a component that improves the thermal stability and chemical durability of glass and is effective in adjusting the viscosity when molding molten glass. ２When the content of SiO is large, the glass raw material tends to remain unmelted during melting, that is, the meltability of the glass also tends to decrease. ２ is preferably in the range of 0 to 30%, more preferably in the range of 0 to 28%, and even more preferably in the range of 0 to 25%, and SiO ２ The content can also be set to 0%.

[0033] Al ２ O ３ is a component that can function to improve the thermal stability and chemical durability of glass. In order to improve the thermal stability and chemical durability of glass and to prevent an increase in the liquidus temperature and a decrease in devitrification resistance, Al is ２ O ３ The preferred range of Al is 0 to 15%, more preferably 0 to 13%, and even more preferably 0 to 11%. ２ O ３ The content can also be set to 0%.

[0034] Li ２ O has the function of improving the meltability and formability of the glass. ２ If the content of O is too high, the thermal stability of the glass may be reduced. ２ The O content is preferably in the range of 0 to 10%, more preferably 0 to 8%, even more preferably 0 to 6%, and still more preferably 0 to 5%.

[0035] Na ２ O has the function of improving the meltability and formability of the glass. ２ If the O content is too high, the thermal stability of the glass may decrease. ２ The O content is preferably in the range of 0 to 10%, more preferably 0 to 8%, even more preferably 0 to 6%, and still more preferably 0 to 5%.

[0036] K ２ O has the function of improving the melting property of glass. ２ If the O content is too high, the thermal stability of the glass may decrease.２ The O content is preferably in the range of 0 to 10%, more preferably 0 to 8%, even more preferably 0 to 6%, and still more preferably 0 to 5%.

[0037] MgO is a component that functions to improve the meltability of glass. On the other hand, as the MgO content increases, glass stability tends to decrease. Therefore, the MgO content is preferably in the range of 0 to 10%, more preferably 0 to 9%, and even more preferably 0 to 8%, and the MgO content can be 0%.

[0038] CaO is a component that functions to improve the meltability of glass. On the other hand, as the CaO content increases, glass stability tends to decrease. Therefore, the CaO content is preferably in the range of 0 to 20%, more preferably 0 to 18%, and even more preferably 0 to 15%, and the CaO content can be 0%.

[0039] SrO is a component that functions to improve the meltability of glass. On the other hand, as the SrO content increases, glass stability tends to decrease. Therefore, the SrO content is preferably in the range of 0 to 10%, more preferably 0 to 9%, and even more preferably 0 to 8%, and the SrO content can be 0%.

[0040] BaO is a component that functions to improve the meltability of glass. On the other hand, as the BaO content increases, glass stability tends to decrease. Therefore, the BaO content is preferably in the range of 0 to 25%, more preferably 0 to 22%, and even more preferably 0 to 19%, and the BaO content can be 0%.

[0041] ZnO is a component that functions to improve the meltability of glass raw materials when melting glass and improves mechanical workability. On the other hand, as the ZnO content increases, the viscosity of the molten glass when it is molded tends to decrease. Therefore, the ZnO content is preferably in the range of 0 to 25%, more preferably 0 to 22%, and even more preferably 0 to 19%, and the ZnO content can be 0%.

[0042] TiO２ is a component that has the function of improving the thermal stability of glass. ２ When the content of TiO increases, the light absorption edge on the short wavelength side of the spectral transmittance shifts to the long wavelength side. As a result, the light absorption edge on the short wavelength side shifts to the long wavelength side. ２ The content of is preferably in the range of 0 to 15%, more preferably in the range of 0 to 13%, and even more preferably in the range of 0 to 11%. ２ The content can also be set to 0%.

[0043] Nb ２ O ５ is a component that has the function of improving the thermal stability of glass, and TiO ２ YaWO ３ Compared with Nb, Nb is a component that is less likely to shift the optical absorption edge on the short wavelength side of the glass to a longer wavelength. ２ O ５ The content of Nb is preferably in the range of 0 to 15%, more preferably in the range of 0 to 13%, and even more preferably in the range of 0 to 11%. ２ O ５ The content can also be set to 0%.

[0044] Ta ２ O ５ is an expensive component and acts to increase the specific gravity of the glass. Therefore, by reducing the production cost of the glass, it is possible to provide the glass more stably and to suppress the increase in the specific gravity, so that Ta is used. ２ O ５ The content of Ta is preferably in the range of 0 to 15%, more preferably in the range of 0 to 13%, and even more preferably in the range of 0 to 11%. ２ O ５ The content can also be set to 0%.

[0045] WO ３ is a component that has the function of improving the thermal stability of glass. ３ When the content of WO increases, the light absorption edge on the short wavelength side of the spectral transmittance shifts to the long wavelength side. As a result, the light absorption edge on the short wavelength side shifts to the long wavelength side. ３The content of WO is preferably in the range of 0 to 10%, more preferably in the range of 0 to 8%, and even more preferably in the range of 0 to 6%. ３ The content can also be set to 0%.

[0046] ZrO ２ is a component that has the function of improving the thermal stability of glass. It also has the function of making the glass less susceptible to breakage during mechanical processing by increasing the glass transition point. ２ If the amount of ZrO added is too large, crystallization or unmelted residue occurs during glass production. ２ The content of ZrO is preferably in the range of 0 to 10%, more preferably in the range of 0 to 9%, and even more preferably in the range of 0 to 8%. ２ The content can also be set to 0%.

[0047] La ２ O ３ Is Y ２ O ３ , Gd ２ O ３ , Yb ２ O ３ Compared with Yb, it is a component that is less likely to lose thermal stability even if its content is increased. ２ O ３ It is also a rare earth component that does not absorb near-infrared light with a wavelength of 860 to 1030 nm. ２ O ３ The content of La is preferably in the range of 0 to 30%, more preferably in the range of 0 to 27%, even more preferably in the range of 0 to 25%, and still more preferably in the range of 0 to 23%. ２ O ３ The content can also be set to 0%.

[0048] Y ２ O ３ is a component that has the function of improving the thermal stability of the glass. ２ O ３ It is also a rare earth component that does not absorb near-infrared light in the wavelength range of 860 to 1030 nm. ２ O ３The content of Y is preferably in the range of 0 to 30%, more preferably in the range of 0 to 27%, even more preferably in the range of 0 to 25%, and still more preferably in the range of 0 to 23%. ２ O ３ The content can also be set to 0%.

[0049] Gd ２ O ３ is a component that improves the thermal stability of the glass. On the other hand, it is a component that increases the specific gravity of the glass. ２ O ３ It is a rare earth component that does not absorb near-infrared light in the wavelength range of 860 to 1030 nm. ２ O ３ The content of is preferably in the range of 0 to 30%, more preferably 0 to 27%, even more preferably 0 to 25%, and still more preferably 0 to 23%. ２ O ３ The content can also be set to 0%.

[0050] Pb, As, Cd, Tl, Be, and Se are each toxic. Therefore, it is preferable to avoid the inclusion of these elements, i.e., not incorporate these elements into the glass as glass components. U, Th, and Ra are all radioactive elements. Therefore, it is preferable to avoid the inclusion of these elements, i.e., not incorporate these elements into the glass as glass components. V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Ce increase the coloration of the glass or are sources of fluorescence, making them undesirable elements to be contained in glass for optical elements. Therefore, it is preferable to avoid the inclusion of these elements, i.e., not incorporate these elements into the glass as glass components.

[0051] Sb ２ O ３ is a component that can be added as a clarifier. Addition of a small amount can suppress the decrease in light transmittance caused by the inclusion of impurities such as Fe. ２ O ３ When the amount of Sb added is increased, the coloring of the glass tends to increase. ２ O３ The content of Sb is preferably in the range of 0 to 0.5%, more preferably in the range of 0 to 0.4%, and even more preferably in the range of 0 to 0.3%. ２ O ３ The content can also be set to 0%.

[0052] S is a component that can be added as a fining agent. On the other hand, if the amount of S added is large, the likelihood of overflow of molten glass and coloring of the glass tends to increase. Therefore, the amount of S is ３ The content of S is preferably in the range of 0 to 0.3%, more preferably 0 to 0.2%, and even more preferably 0 to 0.1% in terms of S. The S content can be set to 0%. In addition to S, small amounts of Ce oxide, Sn oxide, nitrate, chloride, or fluoride can also be added as a fining agent.

[0053] Thus, the optical glass according to some embodiments of the present invention contains at least Yb ２ O ３ , B ２ O ３ The glass composition is based on a glass composition containing as an essential component, and contains the above-mentioned other components as optional components. ２ O ３ When the content of Al is large (for example, when it is 25% or more), there is a problem that the tendency to devitrify increases. ２ O ３ and SiO ２ By reducing the total content of Yb ２ O ３ Specifically, the content of Al is increased. ２ O ３ and SiO ２ By making the total content of Yb exceed 0%, the thermal stability of the glass is improved. ２ O ３ Based on the knowledge that the content of Yb can be increased, ２ O ３ When the content of Al is 25% or more, ２ O ３ and SiO ２ The total content of (i.e., Al ２ O ３Content and SiO ２ The total content of Al and Al is 32% or less. This can improve the thermal stability of the glass and prevent the glass from being easily devitrified during glass production. ２ O ３ and SiO ２ The total content of Yb is preferably in the range of from more than 0% to 32%, more preferably from more than 2% to 30%, and even more preferably from more than 4% to 25%. ２ O ３ , B ２ O ３ , Al ２ O ３ and SiO ２ The glass composition is based on a glass composition containing as an essential component, and contains the above-mentioned other components as optional components. ２ O ３ When the content of Li is increased (for example, when it is 30% or more), there is a problem that the tendency to devitrify is further increased. Therefore, in some embodiments of the present invention, ２ O.K. ２ O, Na ２ By adding Yb ２ O ３ Specifically, the content of Li ２ O, Na ２ O and K ２ By making the total content of O exceed 0%, the meltability of the glass is improved, and Yb ２ O ３ Based on the knowledge that the content of Yb can be increased, ２ O ３ When the content is 30% or more, Li ２ O, Na ２ O and K ２ O as an essential component, and ２ O, Na ２ O and K ２ The total content of O (i.e., Li ２ O content and Na ２O content and K content ２ The total content of Li and O is 10% or less. This improves the thermal stability of the glass, and prevents the glass from easily devitrifying during glass production. ２ O, Na ２ O and K ２ The total content of O is preferably in the range of from 0 to 10%, more preferably from 0 to 9%, even more preferably from 0 to 8%, and still more preferably from 0 to 5%. ２ O ３ By allocating an appropriate amount of Yb to the total content of rare earth elements, it is an effective component for improving thermal stability and providing a glass having a near-infrared absorbing function. ２ O ３ For Yb ２ O ３ , La ２ O ３ , Y ２ O ３ , and Gd ２ O ３ Yb relative to the total content ２ O ３ Mass ratio of content {Yb ２ O ３ / (Yb ２ O ３ , La ２ O ３ , Y ２ O ３ and Gd ２ O ３ )} is preferably in the range of 0.35 to 1%, more preferably 0.5 to 1%, even more preferably 0.60 to 1%, and even more preferably 0.7 to 1%.

[0054] The light incident on the optical glass of this embodiment is absorbed by a rare earth element (Yb ２ O ３ ), and only near-infrared light in the 900 nm band is attenuated and emitted. Therefore, the spectral transmittance characteristics of optical glass can be explained by the so-called Lambert-Beer law. ２ O ３That is, the optical glass of this embodiment is determined by the concentration of a rare earth element (Yb) that absorbs near-infrared rays so as to maintain a flat and high transmittance in the visible range and to have spectral transmittance characteristics that rapidly attenuate in the 900 nm band. ２ O ３ ) concentration was adjusted.

[0055] (Method of Manufacturing Glass (Near-Infrared Cut Filter Glass)) The above glass can be obtained by weighing, blending, and thoroughly mixing raw materials such as oxides, carbonates, sulfates, nitrates, and hydroxides so as to obtain the desired glass composition, heating and melting the mixture in a melting vessel, degassing, and stirring to produce a homogeneous, bubble-free glass melt, and then shaping the resulting mixture. Specifically, the glass can be produced using a known melting method. The above glass is a near-infrared cut filter glass having the above optical properties, yet has excellent thermal stability, and therefore can be produced stably using known melting and shaping methods.

[0056] (Glass Material for Press Molding, Optical Element Blank, and Manufacturing Methods Thereof) The above-mentioned glasses can also be applied to glass materials for press molding and optical element blanks.

[0057] The press-molding glass material can be obtained by molding the above-mentioned glass into a press-molding glass material. Furthermore, the optical element blank can be obtained by press-molding the above-mentioned press-molding glass material using a press mold. Furthermore, the optical element blank can also be obtained by molding the above-mentioned glass into an optical element blank.

[0058] An optical element blank is an optical element base material that approximates the shape of the desired optical element, with polishing allowances (surface layers to be removed by polishing) and, if necessary, grinding allowances (surface layers to be removed by grinding) added to the shape of the optical element. The optical element is finished by grinding and polishing the surface of the optical element blank. In one embodiment, the optical element blank can be produced by a method (called a direct press method) in which a molten glass obtained by melting an appropriate amount of the above glass is press-molded. In another embodiment, the optical element blank can also be produced by solidifying a molten glass obtained by melting an appropriate amount of the above glass.

[0059] Press molding of a glass material for press molding can be carried out by a known method in which a glass material for press molding in a heated and softened state is pressed in a press mold. Both heating and press molding can be carried out in the atmosphere. After press molding, the glass is annealed to reduce internal strain, thereby obtaining a homogeneous optical element blank.

[0060] Glass materials for press molding include not only glass gobs for press molding that are used for press molding in their original state to produce optical element blanks, but also glass gobs for press molding that are machined by cutting, grinding, polishing, or other processes and then used for press molding. Cutting methods include forming a groove in the area of ​​the surface of the glass plate to be cut by a method called scribing, applying local pressure to the grooved area from the back side of the surface where the groove was formed, and breaking the glass plate at the grooved area, or cutting the glass plate with a cutting blade. Grinding and polishing methods include barrel polishing.

[0061] A glass material for press molding can be produced, for example, by casting molten glass into a mold to form a glass plate, and then cutting this glass plate into a plurality of glass pieces. Alternatively, a suitable amount of molten glass can be molded to produce a glass gob for press molding. An optical element blank can also be produced by reheating, softening, and press-molding a glass gob for press molding. The method of producing an optical element blank by reheating, softening, and press-molding glass is called a reheat press method, as opposed to a direct press method.

[0062] (Optical elements and manufacturing methods thereof) The above-mentioned glass can also be used in optical elements. Optical elements can be obtained, for example, by grinding and / or polishing the above-mentioned optical element blank. Known methods can be used for grinding and polishing, and optical elements with high internal and surface quality can be obtained by thoroughly cleaning and drying the surface of the optical element after processing. Examples of optical elements include various lenses such as spherical lenses, aspherical lenses, and microlenses, as well as prisms.

[0063] The optical glass of this embodiment will be further described below with reference to examples (Examples 1 to 14) and comparative examples (Comparative Examples 1 to 3), but the present invention is not limited to these examples.

[0064] (Method of Producing Optical Glass) Silica powder, boric acid, oxides, hydroxides, carbonates, nitrates, sulfates, etc. were used as raw materials. These raw materials were weighed for each example and comparative example, and thoroughly mixed to prepare a blended raw material so that the glass composition shown in Tables 1 to 3 was obtained. The obtained blended raw material was placed in a platinum crucible and heated to approximately 1300 to 1450°C, melted, refined, and stirred for 2 to 3 hours to obtain a homogenized molten glass. The molten glass was poured into a preheated mold and rapidly cooled, held at a temperature near the glass transition temperature for 2 hours, and then lowered at a rate of -30°C / hour to prepare optical glass samples for Examples 1 to 8, 10 to 14, and Comparative Examples 1 and 3. Note that Example 9 used Yb ２ O ３This is an example of a glass composition in which the content of Yb is 45%, and is used to simulate the spectral transmittance characteristics described later. ２ O ３ The simulated composition is when the content of Yb is 50%. ２ O ３ / Ln ２ O ３ " indicates the amount of rare earth Ln ２ O ３ component (wherein Ln is one or more selected from the group consisting of Yb, La, Y, and Gd) ２ O ３ The content of

[0065]

[0066]

[0067]

[0068] (Evaluation of Spectral Transmittance of Optical Glass) The spectral transmittance was evaluated for the optical glasses of Examples 1 to 14 and Comparative Example 1. For Comparative Example 3, the sample was devitrified, so the spectral transmittance was not evaluated. For Comparative Example 2, the sample was devitrified in the simulation, so the spectral transmittance was not evaluated. FIGS. 1 to 14 show the spectral transmittance curves of the optical glasses of Examples 1 to 14 at a thickness of 2.5 mm. FIG. 15 shows the spectral transmittance curve of the optical glass of Comparative Example 1 at a thickness of 2.5 mm. The vertical axis of FIGS. 1 to 15 represents transmittance (%), and the horizontal axis represents wavelength (nm). For the measurements of FIGS. 1 to 15 , both surfaces of each of the optical glasses of Examples 1 to 14 and Comparative Example 1 were optically polished to a thickness of 2.5±0.1 mm. A spectrophotometer was used to apply light with an intensity Iin perpendicular to the polished surfaces, and the intensity Iout of the light transmitted through each sample was measured, and the spectral transmittance Iout / Iin was calculated. 1 to 15, "L_λ50" indicates the half-value wavelength (first wavelength) at which the transmittance decreases to 50% in the spectral transmittance curves of the optical glasses of Examples 1 to 14 and Comparative Example 1, and "H_λ50" indicates the half-value wavelength (second wavelength) at which the transmittance increases to 50% in the spectral transmittance curves of the optical glasses of Examples 1 to 14 and Comparative Example 1.

[0069] (Evaluation of Optical Glass Stability) For the optical glasses of Examples 1 to 14 and Comparative Example 1, the "liquidus temperature (LT): °C" was used as an index of stability to evaluate each optical glass. Specifically, 10 cc (10 ml) of sample (the optical glass sample of Examples 1 to 14 and Comparative Example 1) was placed in a platinum crucible and melted at 1250°C to 1350°C for 20 to 30 minutes, after which it was cooled to below the glass transition temperature Tg. The sample, together with the platinum crucible, was placed in a melting furnace at a predetermined temperature and held there for two hours. The holding temperature was 1000°C or higher in increments of 20°C or 30°C, and the lowest temperature at which no crystals precipitated after two hours of holding was defined as the "liquidus temperature (LT): °C." If the liquidus temperature is too high, devitrification is likely to occur during production, so the liquidus temperature is preferably 1350°C or lower, more preferably 1200°C or lower, and most preferably 1100°C or lower.

[0070] (Evaluation of Chemical Durability of Optical Glass) The optical glasses of Examples 1 to 14 and Comparative Examples 1 to 3 were evaluated using the "powder method water resistance (Dw): grade" as an index of chemical durability. The "powder method water resistance (Dw): grade" is specified in the Japan Optical Glass Industry Association standard: JOGIS06-1999. Specifically, a powder sample (optical glass samples of Examples 1 to 14 and Comparative Example 1: particle size 425 to 600 μm) with a mass equivalent to the specific gravity was placed in a platinum cage, immersed in a quartz glass round-bottom flask containing 80 ml of pure water (pH = 6.5 to 7.5), and treated in a boiling water bath for 60 minutes. The weight loss (%) was then classified into six grades: Grade 1 (<0.05%), Grade 2 (≧0.05 to <0.10%), Grade 3 (≧0.10 to <0.25%), Grade 4 (≧0.25 to <0.60%), Grade 5 (≧0.60 to <1.10%), and Grade 6 (≧1.10%). If the chemical durability is too poor, it will be difficult to use the glass as optical glass. In particular, when considering the application of the optical glass of the present invention to an in-vehicle LiDAR system, the "powder method water resistance (Dw): grade" is preferably grade 1 to 3, more preferably grade 1 to 2, and most preferably grade 1.

[0071] (Evaluation Results and Discussion) Tables 4 to 6 show the average transmittance (%) in the wavelength range of 925 to 955 nm, the average transmittance (%) in the wavelength range of 965 to 985 nm, the average transmittance (%) in the wavelength range of 400 to 800 nm, the half-value wavelength ("L_λ50": nm) at which the transmittance decreases to 50% on the spectral transmittance curve, and the half-value wavelength ("H_λ50": nm) at which the transmittance increases to 50%, as well as the "liquidus temperature (LT): ° C." and "powder method water resistance (Dw): grade" for each of Examples 1 to 14 and Comparative Examples 1 to 3 shown in FIGS.

[0072]

[0073]

[0074]

[0075] As shown in Tables 4 and 5, the optical glasses of Examples 1 to 14 had average transmittances (%) in the wavelength range of 925 to 955 nm of 0.6 to 50.2%, and average transmittances (%) in the wavelength range of 965 to 985 nm of 0.3 to 30.4%, and the optical glasses of Examples 1 to 14 had a near-infrared absorption function (i.e., a band-stop filter function) that selectively absorbs near-infrared light in the 900 nm band. Furthermore, the optical glass of Comparative Example 1 (Table 6) had an average transmittance (%) in the wavelength range of 925 to 955 nm of 87.7%, and an average transmittance (%) in the wavelength range of 965 to 985 nm of 88.0%, which is comparable to the optical glass of Comparative Example 1 (i.e., Yb ２ O ３ The glass with a Yb content of 0% does not have a near-infrared absorption function (i.e., a band-stop filter function). ２ O ３ It can be seen that it is preferable to set the lower limit of the content of 5% (Example 6). ２ O ３ In the glass containing 50% Yb, devitrification occurs. ２ O ３ It can be seen that the upper limit of the content of Yb is preferably set to 45% (Example 9). ２ O ３ It has been found that by adjusting the contents of these and other components, the average transmittance in the wavelength range of 925 to 955 nm can be adjusted within a range of 0 to 70%, and the average transmittance in the wavelength range of 965 to 985 nm can be adjusted within a range of 0 to 50%.

[0076] Furthermore, as shown in Tables 4 and 5, the optical glasses of Examples 1 to 14 had average transmittances (%) in the wavelength range of 400 to 800 nm ranging from 87.4 to 88.9%, demonstrating that extremely high transmittances were maintained at a flat level across the visible range. Experiments by the inventors have shown that by adjusting the content of each component in Examples 1 to 14, the average transmittance (%) in the wavelength range of 400 to 800 nm can be adjusted to fall within the range of 80 to 92%.

[0077] Furthermore, as shown in Tables 4 and 5, the half-value wavelengths ("L_λ50": nm) at which the transmittance of the optical glasses of Examples 1 to 14 decreases to 50% are in the range of 882 to 935 nm, and the half-value wavelengths ("H_λ50": nm) at which the transmittance increases to 50% are in the range of 984 to 1026 nm, and it was found that near-infrared light in the 900 nm band can be accurately cut off (bandstopped). ２ O ３ It has been found that by adjusting the contents of the above and other components, the half-value wavelength ("L_λ50": nm) at which the transmittance decreases to 50% can be adjusted in the range of 860 to 940 nm, and the half-value wavelength ("H_λ50": nm) at which the transmittance increases to 50% can be adjusted in the range of 970 to 1040 nm.

[0078] Furthermore, when Example 8 is compared with Comparative Example 3, the optical glass of Comparative Example 3 (i.e., Li ２ In the case of a glass with a LiO content of 0%, devitrification occurs. ２ By adding 1% of O, Yb ２ O ３ It can be seen that the content of alkali metal (Li ２ O.K. ２ O, Na ２ O) content, Yb ２ O ３ It has been found that the content can be increased to 30% or more.

[0079] Furthermore, from the "Liquidus Temperature (LT): °C" in Tables 4 and 5, it can be seen that the "Liquidus Temperature (LT): °C" of the optical glasses of Examples 1 to 14 was all 1,350°C or lower (i.e., stable) and was unlikely to devitrify during production.

[0080] Furthermore, from the "Powder method water resistance (Dw): grade" in Tables 4 and 5, it is clear that the "Powder method water resistance (Dw): grade" of the optical glasses of Examples 1 to 14 is all Grade 3 or lower, which indicates that these optical glasses have sufficient chemical durability.

[0081] Thus, the optical glasses of Examples 1 to 14 contain at least Yb ２ O ３ and B ２ O ３ The optical glass of this embodiment (Examples 1 to 14) is based on a glass composition containing as an essential component, and has spectral transmission characteristics that maintain a flat and high transmittance in the wavelength range of 400 to 800 nm and sharply attenuate in the 900 nm band, while also having sufficient stability and chemical durability as an optical glass. Therefore, for example, when the optical glass of this embodiment (Examples 1 to 14) is applied to a near-infrared cut filter, it can be used as an optical filter (near-infrared cut filter) for blocking laser light in a LiDAR system. Furthermore, by applying the optical glass of this embodiment (Examples 1 to 14) to a press-molding glass element, an optical element blank, and an optical element, it is also possible to provide a press-molding glass element, an optical element blank, and an optical element for blocking laser light in a LiDAR system.

[0082] The above is a description of the embodiment and examples of the present invention, but the present invention is not limited to the above configurations, and various modifications are possible within the scope of the technical concept of the present invention.

[0083] Furthermore, the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

Claims

1. At least Yb ２ O ３ and B ２ O ３ An optical glass based on a glass composition containing as an essential component Yb ２ O ３ The content of is 5 to 60 mass %, ２ O ３ the content of is 10 to 50 mass %, and when the thickness of the optical glass is 2.5 mm, the average transmittance in the wavelength range of 925 to 955 nm is 0 to 70%, and the average transmittance in the wavelength range of 965 to 985 nm is 0 to 50%.

2. The optical glass according to claim 1, characterized in that the average transmittance in the wavelength range of 400 to 800 nm is 80 to 92%.

3. The optical glass according to claim 1, wherein, in the spectral transmittance curve of said optical glass, a first wavelength when the transmittance decreases to 50% is 860 to 940 nm, and a second wavelength when the transmittance increases to 50% is 970 to 1040 nm.

4. The optical glass according to claim 1, wherein the optical glass has a thickness of 0.5 to 5.0 mm.

5. The optical glass according to claim 1, wherein the liquidus temperature of said optical glass is 1350° C. or lower.

6. The optical glass according to claim 1, characterized in that the water resistance of said optical glass by the powder method is Class 1, Class 2 or Class 3.

7. The glass composition contains, in mass %, SiO ２ :1~30%, Al ２ O ３ : 0-15%, MgO: 0-10%, CaO: 0-20%, SrO: 0-10%, BaO: 0-25%, ZnO: 0-25%, TiO ２ :0~15%, Nb ２ O ５ :0~15%, Ta ２ O ５ :0~15%, WO ３ :0~10%, ZrO ２ :0~10%, La ２ O ３ : 0-30%, Y ２ O ３ :0~30%, Gd ２ O ３ :0~30%, Sb ２ O ３ :0~0.05%, SO ３ 2. The optical glass according to claim 1, further comprising: 0 to 0.3% of 8. Li ２ O, Na ２ O and K ２ 8. The optical glass according to claim 7, further comprising at least one kind of O in a total content range of more than 0 to 10 mass %.

9. Yb ２ O ３ 9. The optical glass according to claim 8, wherein the content of is 30 mass % or more.

10. Ln ２ O ３ The ratio of Yb to the sum of components (Ln is one or more selected from the group consisting of Yb, La, Y, and Gd) ２ O ３ 8. The optical glass according to claim 7, wherein the content of is in the range of 0.6 to 1.

0.

11. A near-infrared cut filter comprising the optical glass according to any one of claims 1 to 10.

12. A glass element for press molding comprising the optical glass according to any one of claims 1 to 10.

13. An optical element blank comprising an optical glass according to any one of claims 1 to 10.

14. An optical element comprising the optical glass according to any one of claims 1 to 10.