Fluorophosphate glass, near-infrared cutoff filter, and optical device

Abstract

A fluorophosphate glass which essentially contains P, Al, K, Cu, F, and R (R is one or more elements selected from among Li, Na, Rb, and Cs), has an Al < 3 + > content of 2-20% by mass, and has an expected value of an ion radius of an alkali metal component containing K and R of 80 picometers or more and less than 133 picometers.

Description

Technical Field

[0001] This invention relates to fluorophosphate glass, particularly with excellent light transmittance in the visible light region and light absorption in the near-infrared region, and good weather resistance, for color correction filters used in digital cameras, color video cameras, etc.; near-infrared cut-off filters and optical devices incorporating the glass. Background Technology

[0002] Solid-state imaging elements such as CCDs and CMOS sensors used in PCs, digital cameras, etc., have spectral sensitivity ranging from the visible light region to the near-infrared region around 1200nm. Therefore, solid-state imaging elements cannot directly achieve good color reproduction, so near-infrared cutoff filter glass with added substances that absorb infrared light is used to correct visual sensitivity.

[0003] The optical properties and weather resistance of near-infrared cut-off filter glass are two important characteristics.

[0004] The optical properties of near-infrared cutoff filter glass require strong absorption in the near-infrared region (800nm~1200nm) and high transmittance in the visible light region to the red light region (400nm~600nm). In particular, a sharper absorption shape (hereinafter also referred to as sharp cutoff) is required in terms of the shape of the transmittance curve from the red light transmission region to the near-infrared shielding region.

[0005] Furthermore, regarding near-infrared cutoff filter glass, in order to obtain the aforementioned optical properties, optical glass with Cu added to fluorine-free phosphate glass (hereinafter also referred to as copper phosphate glass) has been developed. However, copper phosphate glass has issues with weather resistance. Therefore, in order to achieve high weather resistance, optical glass with Cu added to fluorophosphate glass (fluorine-containing phosphate glass) has been developed (hereinafter also referred to as copper fluorophosphate glass, Cu-containing fluorophosphate glass, or fluorophosphate glass). The composition of these glasses is disclosed in Patent Documents 1 to 4.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2016-60671

[0009] Patent Document 2: Japanese Patent Application Publication No. 2004-83290

[0010] Patent Document 3: WO2022 / 009558

[0011] Patent Document 4: CN114455836A Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] The near-infrared cutoff filter glass described in the patent literature is difficult to combine optical properties and weather resistance at a high level.

[0014] In other words, as mentioned above, copper phosphate glass has high absorption capacity and excellent sharp cutoff in the near-infrared region, but its weather resistance is problematic. On the other hand, while copper fluorophosphate glass has high weather resistance, its absorption capacity and sharp cutoff in the near-infrared region are also problematic.

[0015] For example, as described in Patent Document 4, in copper fluorophosphate glass, increasing the P content in the glass is effective in improving the absorption capacity and sharp cutoff of the near-infrared region, but on the other hand, it may lead to a decrease in weather resistance.

[0016] The purpose of this invention is to provide a fluorophosphate glass that combines high transmittance in the visible light to red light regions, high absorption capacity in the near-infrared region, high sharp cutoff in the near-infrared region, and high weather resistance, as well as a near-infrared cutoff filter, filter, and optical device incorporating the glass.

[0017] means for solving problems

[0018] Through repeated and in-depth research, the inventors discovered that by adjusting the content of Al and the ratio of alkali metal components to specified ranges in Cu-containing fluorophosphate glass, glass with good weather resistance and desired optical properties can be obtained.

[0019] That is, the present invention is as follows.

[0020] A fluorophosphate glass, wherein the fluorophosphate glass must contain components of P, Al, K, Cu, F, and R (R being one or more selected from Li, Na, Rb, and Cs), in the following mass percentages: Al 3+ The content is 2% to 20%, and the expected value of the ionic radius of the alkali metal components containing K and R is greater than or equal to 80 picometers and less than 133 picometers.

[0021] Invention Effects

[0022] According to the present invention, it is possible to provide a fluorophosphate glass with both excellent optical properties and high weather resistance, a near-infrared cutoff filter having the glass, and filters and optical devices. Attached Figure Description

[0023] Figure 1A graph showing the transmittance of light with wavelengths from 300 nm to 1200 nm for the fluorophosphate glasses of Example 5 (Example) and Example 10 (Comparative Example). Detailed Implementation

[0024] The following describes in detail the methods for implementing the present invention. It should be noted that the present invention is not limited to the embodiments and mechanisms described below.

[0025] In this specification, unless otherwise stated, the content and total content of each component are expressed as "mass %". Here, mass % as used in this specification represents the percentage of the mass of each ion when the total mass of the cationic components is set to 100. In this specification, "α~β" indicating a range means "α or more and β or less". "α~less than β" means "greater than or equal to α and less than β". Furthermore, the transmittance of the glass in this embodiment includes the reflective properties of the glass surface (i.e., not the internal transmittance of the glass).

[0026] <Fluorophosphate glass>

[0027] The fluorophosphate glass of the present invention (hereinafter also referred to as the fluorophosphate glass of this embodiment, or simply as fluorophosphate glass or glass) is characterized in that it must contain each of the components P, Al, K, Cu, F and R (R being one or more selected from Li, Na, Rb and Cs), Al 3+ The content is 2% to 20%, and the expected value of the ionic radius of the alkali metal components containing K and R is greater than or equal to 80 pm (picometer) and less than 133 pm (picometer).

[0028] The glass of this invention is a copper fluorophosphate glass with P, Al, K, Cu, F, and R (R being one or more selected from Li, Na, Rb, and Cs) as essential components. Glass with P as the main component has the effect of improving absorption capacity and sharp cutoff in the near-infrared region. Furthermore, by containing F and Al in the glass, weather resistance can be improved. Moreover, by adjusting the desired ionic radius of the alkali metal components containing K and R to greater than or equal to 80 pm and less than 133 pm, absorption capacity and sharp cutoff in the near-infrared region can be improved, and weather resistance can be improved by including K and R.

[0029] Alkali metal composition refers to K + Li + Na + 、Rb + and Cs + The expected values ​​of the ionic radii of the components are defined as follows.

[0030] The ionic radii of each alkali metal component are as follows. Li+ ionic radius r Li For 60pm, Na + ionic radius r Na At 95pm, K + ionic radius r K It was 1:33 pm, Rb + ionic radius r Rb At 148pm, Cs + ionic radius r Cs The value is 169 pm. These ionic radii are based on values ​​from L. Pauling (1931-1933) and *The Nature of the Chemical Bond* (1963, translated by Masao Koizumi, "The Nature of the Chemical Bond"), Kyoritsu Publishing. "Cation%" refers to the mole percentage of each cation component when the total content of all cations in the glass is set at 100 mol%.

[0031] The expected value of the ionic radius of the alkali metal component is calculated by the following formula.

[0032] The expected value of the ionic radius = [ionic radius of each alkali metal component × total amount of cations of each component] / [total amount of cations of all alkali metal components]. The specific details are as follows.

[0033] [Ionic radius of each alkali metal component × total amount of cations of each component] = ionic radius r Li ×Li cation content + ionic radius r Na ×Na cation mass + ionic radius r K ×K cation content + ionic radius r Rb ×Rb cation content + ionic radius r Cs The amount of ×Cs cations, [The sum of the cations of all alkali metal components] = Cation amount of Li + Cation amount of Na + Cation amount of K + Cation amount of Rb + Cation amount of Cs By using alkali metal components (Li + Na + K + 、Rb + Cs + By adjusting the desired ionic radius of the ion to 80 pm or higher, the glass of the present invention can maintain a high transmittance in the red light region and retain a sharp absorption shape that enhances absorption in the near-infrared region. The reason for this is speculated as follows.

[0034] Non-bridging oxygen and Cu in glass 2+Coordination forms a regular octahedron. When it interacts with Cu... 2+ When the symmetry of coordinated non-bridging oxygen atoms is high, they exhibit sharp absorption peaks in the near-infrared region. However, when the symmetry of these non-bridging oxygen atoms decreases for reasons described later, Cu... 2+ The absorption peak shifts, and the shape of the glass's transmittance curve changes from a sharp absorption shape to a broad absorption shape. For transition metals containing Cu, the absorption spectrum is easily affected by changes in the coordination environment within the glass, as reported in "Konno Hirai (2009), Optical Properties of Glass II, NEW GLASS, Vol. 24, No. 2".

[0035] With Cu in glass 2+ Coordinated, unbridged oxygen atoms are attracted by the surrounding, more electronegative components, thus reducing symmetry. Electronegativity is a property representing the strength of the force that attracts surrounding electrons to the atomic nucleus. Additionally, the ionic radius is a value representing the distance from the atomic nucleus to the outermost electron shell. Within the same group of atoms, atoms farther from their bound electron pairs have lower electronegativity; therefore, in other words, components with larger ionic radii have lower electronegativity.

[0036] Therefore, by including components with large ionic radii among the alkali metals in the glass, and combining them with Cu... 2+ The symmetry of the coordinated non-bridging oxygen is not reduced, enabling high absorption capacity and high sharp cutoff in the near-infrared region.

[0037] On the other hand, by using alkali metal components (Li + Na + K + 、Rb + Cs + The desired value of the ionic radius of the sample was adjusted to be above 133 pm, out of concern for reduced weather resistance. The reasons for this are speculated as follows.

[0038] Weather resistance is evaluated by assessing the degree of surface deterioration of glass caused by prolonged exposure to high temperature and humidity. Under high temperature and humidity, the H₂ present on the glass surface... + The H3PO4 penetrates the glass interior, attacking the -OPO- structure and causing hydrolysis. As a result, the H3PO4 detached from the glass surface becomes liquid and remains there, subsequently reacting with the glass to precipitate foreign matter, thus degrading the glass surface. When the glass contains a large amount of alkali metal components with large ionic radii, the force attracting non-bridging oxygen in the glass weakens, and the strength of the glass structure decreases. Therefore, when the glass is left to stand for a long time under high temperature and humidity, the H3PO4 present on the glass surface... + It can easily penetrate into the glass, thus promoting the aforementioned hydrolysis reaction and reducing the glass's weather resistance.

[0039] Based on the above, the desired ionic radius of the alkali metal component is preferably greater than or equal to 80 pm and less than 133 pm. If it is greater than or equal to 80 pm, the high absorption capacity and improved sharp cutoff in the near-infrared region can be fully obtained. If it is less than 133 pm, problems such as reduced weather resistance are less likely to occur. Therefore, it is more preferably 85 pm or more, further preferably 90 pm or more, even more preferably 95 pm or more, most preferably 100 pm or more, and even more preferably 130 pm or less, further preferably 128 pm or less, even more preferably 125 pm or less, and most preferably 120 pm or less.

[0040] The glass in embodiments of the present invention must contain an alkali metal component comprising both K and R. By including two or more alkali metal components in the glass, weather resistance can be improved. The reason for this is speculated as follows.

[0041] For glass with low weather resistance, surface degradation occurs under high temperature and high pressure conditions, resulting in the observation of precipitates and the dissolution of liquids. Possible reasons for this include: the presence of alkali metals and hydrogen. + Ion exchange reaction. When glass is left to stand for a long time under high temperature and high humidity, H+ present on the glass surface... + An ion exchange reaction occurs between the alkali metal ions and the glass surface. Specifically, through the ion exchange reaction, the alkali metal component dissolves into the glass surface, H... + It is easy to enter the interior of the glass. H enters the interior of the glass. + The effects on glass are as described above. Alkali metal components have a higher ion diffusion coefficient than other components, resulting in higher ion mobility and a greater susceptibility to H+ ion diffusion. + The ion exchange reaction reduces the weather resistance of the glass.

[0042] It is known that by combining two or more alkali metal components in a glass, the ion mobility of each alkali metal component decreases due to the mixed alkali effect. This effect can suppress H₂ present on the glass surface. + It reacts with alkali metal components through ion exchange, inhibiting the decrease in weather resistance.

[0043] Hereinafter, the components of the glass that can constitute an embodiment of the present invention and their preferred contents will be described.

[0044] In the glass of the embodiments of the present invention, P (phosphorus) is used as P 5+ The form contains. P 5+ It is a major component in the formation of fluorophosphate glass and an essential component for improving sharp cutoff in the near-infrared region. 5+ The preferred content is 20%–70%. If P 5+ If the content is above 20%, its full effect can be obtained. If P5+ When the content of P is below 70%, problems such as glass instability and reduced weather resistance are less likely to occur. Therefore, P 5+ The content of [agent] is more preferably 25% or more, further preferably 30% or more, even more preferably 33% or more, and even more preferably 60% or less, further preferably 55% or less, even more preferably 50% or less, and most preferably 45% or less. It should be noted that regarding P... 5+ From the perspective of inhibiting the corrosion of platinum crucibles and suppressing the volatilization of components, phosphate or its salts are preferred as raw materials.

[0045] In the glass of the embodiments of the present invention, F (fluorine) is used as F - The form contains. F - It is an essential component used to stabilize glass and improve its weather resistance. In this specification, when the total amount of all cationic elements contained in the glass is set at 100% by mass, the amount of F in the glass is expressed as an external addition ratio. - The content of F. In addition to the proportion of other additives, F - The preferred content is 3% to 60%.

[0046] If F - If the content of F is above 3% (excluding the added proportion), the weather resistance effect can be fully obtained. - If the content of [specific ingredient] is less than 60%, it is less likely to cause problems such as reduced transmittance in the visible light region, reduced absorption capacity in the near-infrared region, reduced sharpness, or reduced mechanical properties such as strength, hardness, and elastic modulus, or increased ultraviolet transmittance. - The content of [the substance] is more preferably 4% or more, further preferably 6% or more, even more preferably 8% or more, most preferably 10% or more, and even more preferably 50% or less, further preferably 40% or less, even more preferably 30% or less, and most preferably 20% or less.

[0047] In the glass of the embodiments of the present invention, Cu (copper) is used as Cu + or Cu 2+ The form contains, but is described in this application specification entirely in Cu 2+ The content when it exists in the form of .

[0048] Cu 2+ It is an essential component for improving absorption in the near-infrared region. Additionally, Cu... 2+Cu has the property of attracting phosphate chains in glass to form bridging structures, thus enhancing the glass structure, weather resistance, and strength. 2+ The preferred content of Cu is 1% to 20%. 2+ When the content of Cu is less than 1%, the absorption capacity of the glass in the near-infrared region may decrease. 2+ The content of Cu is preferably 2% or more, more preferably 3% or more, further preferably 4% or more, and even more preferably 5% or more. Additionally, when Cu... 2+ When the content of Cu exceeds 20%, the glass becomes unstable, and the risk of devitrification increases. 2+ The content is preferably 18% or less, more preferably 16% or less, even more preferably 15.2% or less, and even more preferably 14% or less.

[0049] Furthermore, the total Cu content is the total amount of Cu expressed as a percentage by mass, including monovalent, divalent, and other existing valences. This refers to the content of all components of the glass in this embodiment (excluding F). - When the Cu content is set to 100%, the preferred range for the total Cu content in this glass is 1% to 20%. When the total Cu content is 1% or more, sufficient absorption capacity in the near-infrared region can be obtained; conversely, when the total Cu content is 20% or less, the decrease in transmittance in the visible light region can be suppressed. It should be noted that Cu... + The content, expressed as a percentage, can be found in (Cu). + The percentage of total Cu (%) × 100 is determined within the range of 0.01% to 4.0%.

[0050] In the glass of the embodiments of the present invention, Al (aluminum) is used as Al 3+ The form contains. Al 3+ Al is a component that forms glass and is essential for improving its strength and weather resistance. 3+ If the content is above 2%, its full effect can be obtained. If Al 3+ If the content is below 20%, it is less likely to cause problems such as glass instability, reduced absorption capacity in the near-infrared region, or decreased sharpness. 3+ The content is preferably 2% to 20%. More preferably 3.5% or more, further preferably 4% or more, even more preferably 4.5% or more, most preferably 5% or more, and even more preferably 19% or less, further preferably 18% or less, even more preferably 15% or less, and most preferably 13% or less.

[0051] It should be noted that, as an AI 3+The raw materials can include AlF3, Al2O3, Al(OH)3, etc., among which, it is less likely to cause an increase in melting temperature, the formation of unmelted material, and F - Considering issues such as reduced input volume leading to glass instability, AlF3 is the preferred choice.

[0052] Lithium (Li) is used to lower the melting temperature of glass, lower the liquidus temperature of glass, improve the weather resistance of glass, and stabilize glass. + The content of [Li] is preferably 0% to 30%. If Li + When the content of alkali metal is below 30%, the glass is less likely to become unstable. When Li is present, the absorption capacity and sharp cutoff in the near-infrared region decrease; therefore, it is more preferable to be below 28%, further preferably below 25%, even more preferably below 20%, and most preferably below 10%. When the alkali metal component is only Li... + While weather resistance improves, absorption capacity and sharp cutoff in the near-infrared region decrease. Therefore, it is necessary to contain one or more ionic radicals with a radius greater than that of Li. + Large alkali metal content.

[0053] Sodium (Na) is used to lower the melting temperature of glass, lower the liquidus temperature of glass, and stabilize glass. + The preferred content of Na is 0% to 40%. + When the content of alkali metal is below 40%, the glass is less likely to become unstable. More preferably, it is below 30%, further preferably below 25%, even more preferably below 20%, and most preferably below 10%. When the alkali metal content is only Na... + At the same time, one can obtain either improved weather resistance or improved absorption capacity and sharp cutoff in the near-infrared region, depending on the composition of the system. However, it is difficult to achieve improvements in both properties simultaneously. Therefore, to improve weather resistance, it is necessary to contain more than one of the following: Na. + In addition to alkali metals, to improve absorption and sharp cutoff in the near-infrared region, it is necessary to contain ionic radii larger than Na. + Large alkali metal content.

[0054] In the glass of the embodiments of the present invention, K (potassium) is used as K + The form contains. K + It is an essential component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, improves absorption capacity in the near-infrared region, and enhances sharp cutoff. As K... + The content of K is preferably 1% to 40%. +A content of less than 40% makes the glass less prone to instability, therefore it is preferred. More preferably, it is 2% or more; further preferably, 5% or more; even more preferably, 8% or more; and most preferably, 10% or more. Additionally, when it contains K... + At this point, weather resistance decreases, therefore it is preferable to have a content of 30% or less, more preferably 25% or less, even more preferably 20% or less, and most preferably 14% or less. When the alkali metal content is only K... + At this time, the absorption capacity and sharp cutoff in the near-infrared region increase, but the weather resistance decreases. Therefore, in order to improve weather resistance through the alkali mixing effect, it is necessary to contain more than one substance other than K. + Other than alkali metal components.

[0055] Rubidium (Rb) is a component that lowers the melting temperature and liquidus temperature of glass, enhances absorption in the near-infrared region, and provides sharp cutoff. As Rb... + The content of Rb is preferably 0% to 20%. + If the content of Rb is below 20%, the glass is less likely to become unstable, therefore it is preferred. + At this point, weather resistance decreases, therefore it is more preferable to be 15% or less, further preferably 10% or less, and even more preferably 5% or less. When the alkali metal content is only Rb... + At this time, the absorption capacity and sharp cutoff in the near-infrared region increase, but the weather resistance decreases. Therefore, in order to improve weather resistance through the alkali mixing effect, it is necessary to contain more than one substance other than Rb. + Other than alkali metal components.

[0056] Cesium (Cs) is a component that lowers the melting temperature and liquidus temperature of glass, enhances its absorption capacity in the near-infrared region, and provides sharp cutoff. As a component of Cs... + The content of Cs is preferably 0% to 20%. + When the content of Cs is below 20%, the glass is less likely to become unstable, therefore it is preferred. + At this point, weather resistance decreases, therefore, it is more preferable to be 15% or less, further preferably 10% or less, and even more preferably 5% or less. When the alkali metal content is only Cs... + At this time, the absorption capacity and sharp cutoff in the near-infrared region increase, but the weather resistance decreases. Therefore, in order to improve weather resistance through the alkali mixing effect, it is necessary to contain more than one substance other than Cs. + Other than alkali metal components.

[0057] K + and R + (R) + Selected from Li + Na + 、Rb +and Cs + One or more of these components are necessary for lowering the melting temperature of glass, lowering the liquidus temperature of glass, and stabilizing glass. If R... + and K + The total quantity, i.e., Li + Na + K + 、Rb + and Cs + The total quantity (ΣR) + +K + If ΣR is above 14%, its full effect can be achieved. + +K + When the content is below 42%, the glass is less likely to become unstable, therefore it is preferred. Therefore, ΣR + +K + The preferred content is 14% to 42%. + +K + The content is more preferably 14.5% or more, further preferably 15% or more, even more preferably 17% or more, and most preferably 18% or more. Additionally, ΣR + +K + The content of [the substance] is more preferably 35% or less, further preferably 30% or less, even more preferably 28% or less, and most preferably 25% or less.

[0058] Magnesium (Mg) is used to lower the melting temperature of glass, lower the liquidus temperature of glass, stabilize glass, increase the strength of glass, and improve the weather resistance of glass. As Mg... 2+ The content of Mg is preferably 0% to 20%. 2+ When the content of Mg is below 20%, problems such as glass instability and reduced near-infrared cutoff are less likely to occur. 2+ The content of [the substance] is more preferably 15% or less, more preferably 10% or less, and even more preferably 5% or less.

[0059] Ca (calcium) is a component used to lower the melting temperature of glass, lower the liquidus temperature of glass, stabilize glass, increase the strength of glass, and improve the weather resistance of glass. As Ca... 2+ The content of [certain substances] is preferably 0% to 20%. If Ca [is present]... 2+ If the content is below 20%, problems such as glass instability and reduced near-infrared cutoff are less likely to occur. 2+ The content of [the substance] is more preferably 1% or more, further preferably 2% or more, and even more preferably 18% or less, further preferably 15% or less, even more preferably 10% or less, and most preferably 7% or less.

[0060] Sr (strontium) is a component used to lower the melting temperature of glass, lower the liquidus temperature of glass, stabilize glass, increase the strength of glass, and improve the weather resistance of glass. As Sr... 2+ The content of Sr is preferably 0% to 30%. 2+ When the content is below 30%, problems such as glass instability and reduced near-infrared cutoff are less likely to occur. 2+ The content of [the substance] is more preferably 1% or more, further preferably 2% or more, even more preferably 4% or more, most preferably 5% or more, and even more preferably 25% or less, further preferably 20% or less, even more preferably 16% or less, and most preferably 14% or less.

[0061] Barium (Ba) is used to lower the melting temperature of glass, lower the liquidus temperature of glass, stabilize glass, improve the absorption capacity of light in the near-infrared region, and improve the sharpness of the near-infrared region. As a component of Ba... 2+ The content of [specific component] is preferably 0% to 40%. If Ba [specific component]... 2+ If the content is below 40%, problems such as glass instability are less likely to occur. 2+ The content of [the substance] is more preferably 1% or more, further preferably 5% or more, even more preferably 10% or more, most preferably 13% or more, and even more preferably 35% or less, further preferably 30% or less, even more preferably 22% or less, and most preferably 19% or less.

[0062] R” 2+ (R) 2+ Selected from Mg 2+ Ca 2+ 、Sr 2+ and Ba 2+ One or more of the components (R) are used to lower the melting temperature of glass, lower the liquidus temperature of glass, and stabilize glass. 2+ The total amount, i.e., Mg 2+ Ca 2+ 、Sr 2+ and Ba 2+ The total quantity (∑R”) 2+ If the percentage is above 14.5%, then its full effect can be achieved; if ∑R” 2+ When the content of [agent] is below 35%, the glass is less likely to become unstable. Therefore, ∑R” 2+ The content is preferably 14.5% to 35%. More preferably 16.5% or more, further preferably 18% or more, even more preferably 20% or more, most preferably 22% or more, and even more preferably 34% or less, further preferably 32.5% or less, even more preferably 30% or less, and most preferably 28% or less.

[0063] Zinc (Zn) has the effect of lowering the melting temperature and liquidus temperature of glass. 2+ The preferred content of Zn is 0% to 20%. 2+ With a zinc content of 20% or less, problems such as glass instability, reduced meltability, or decreased near-infrared cutoff are less likely to occur. More preferably, the zinc content is 15% or less, further preferably 10% or less, and even more preferably 5% or less. Most preferably, it contains no zinc.

[0064] P 5+ The content of ∑R' (R' is selected from Al) 3+ Mg 2+ and Li + The content of one or more components (where ∑R' is the total amount of R') is preferably 3.0 to 7.7.

[0065] P 5+ It is a component that improves the sharpness of the near-infrared region, but it also reduces weather resistance. Additionally, Al... 3+ Li + Mg + Each component has the effect of improving weather resistance.

[0066] Therefore, by P 5+ By adjusting the content of P relative to ΣR' to below 7.7, the weather resistance of the glass can be improved. Additionally, by adjusting the content of P... 5+ By adjusting the content of P relative to ΣR' to a ratio of 3.0 or higher, the sharp cutoff in the near-infrared region of the glass can be maintained at a high level. 5+ The content of P relative to ΣR' is more preferably 3.2 or more, further preferably 3.5 or more, more preferably 4.0 or more, and most preferably 4.5 or more. Additionally, P 5+ The content of is more preferably 7.5 or less relative to ΣR', even more preferably 7.0 or less, even more preferably 6.3 or less, and most preferably 5.5 or less.

[0067] To stabilize the glass, it can contain boron (B) in the range of up to 20%. If B... 3+ If the content is below 20%, problems such as decreased weather resistance or reduced near-infrared cutoff of the glass are less likely to occur. 3+ The content of [the substance] is more preferably 15% or less, further preferably 10% or less, even more preferably 8% or less, and most preferably 5% or less.

[0068] In the glass of the embodiments of the present invention, in order to improve the weather resistance of the glass, SiO2, GeO2, ZrO2, SnO2, TiO2, CeO2, WO3, Y2O3, La2O3, Gd2O3, Yb2O3, and Nb2O5 may be contained in the range of 10% or less. If the content of these components is 10% or less, problems such as the formation of devitrifying foreign matter in the glass or a reduction in near-infrared cutoff are less likely to occur. The content of these components is preferably 4% or less, more preferably 3% or less, further preferably 2% or less, and even more preferably 1% or less.

[0069] Fe2O3, Cr2O3, Bi2O3, NiO, V2O5, MnO2, and CoO are all components that reduce the transmittance of light in the visible light region by virtue of their presence in glass. Therefore, it is preferable that the glass is substantially free of these components. Here, "substantially free of" means that the glass is free of these components except for unavoidable impurities, and that these components are not actively added. Specifically, it means that the content of each of these components in the glass is approximately 100 ppm by mass or less.

[0070] From the viewpoint of ensuring the strength of the glass, the Young's modulus of the glass in the embodiments of the present invention is preferably 48 GPa or more, more preferably 50 GPa or more, even more preferably 55 GPa or more, and even more preferably 60 GPa or more.

[0071] The average coefficient of thermal expansion of the glass in the embodiments of the present invention is preferably 60 × 10⁻⁶ in the range of 30°C to 300°C. -7 / ℃~180×10 -7 / ℃, more preferably 65×10 -7 / ℃~165×10 -7 / ℃, further preferably 70×10 -7 / ℃~157×10 -7 / ℃, further preferably 70×10 -7 / ℃~150×10 -7 / ℃, the optimal value is 70×10 -7 / ℃~143×10 -7 / ℃.

[0072] In embodiments of the present invention, the glass, when used as a color correction filter (near-infrared cut-off filter glass) for a solid-state imaging element, also functions as a protective glass for hermetically sealing the solid-state imaging element, and therefore is sometimes directly bonded to the encapsulation material. In this case, when the difference in thermal expansion coefficients between the near-infrared cut-off filter glass and the encapsulation material is large, peeling or breakage may occur at the bonding point, making it impossible to maintain an hermetically tight seal.

[0073] Typically, materials such as glass, crystal glass, ceramics, and alumina are used as encapsulation materials to ensure heat resistance, and it is preferable to minimize the difference in thermal expansion coefficients between these encapsulation materials and the near-infrared cutoff filter glass. Therefore, the glass in this embodiment preferably has an average thermal expansion coefficient adjusted to within the aforementioned range over a temperature range of 30°C to 300°C.

[0074] The glass of the embodiments of the present invention preferably has a spectral transmittance of 22% or less at a wavelength of 1200 nm when the thickness is converted using a wavelength (hereinafter referred to as IR half-value) of 630 nm with a transmittance of 50% in the near-infrared region. This allows for the production of glass with low transmittance in the near-infrared region. More preferably, the spectral transmittance is 21% or less, even more preferably 20% or less, and still more preferably 19% or less. The spectral transmittance can be measured using the method described in the examples.

[0075] The glass of the embodiments of the present invention preferably has a spectral transmittance of 60% or more at a wavelength of 600 nm when the plate thickness is converted with an IR half-value of 630 nm. This allows for the production of glass with high sharp cutoff in the near-infrared region. More preferably, the spectral transmittance is 62% or more, further preferably 64% or more, and even more preferably 66% or more. The spectral transmittance can be measured using the method described in the examples.

[0076] The glass of the embodiments of the present invention preferably has a spectral transmittance of 4.0% or less at a wavelength of 800 nm when the plate thickness is converted with an IR half-value of 630 nm. This allows for the production of glass with low transmittance in the near-infrared region. More preferably, the spectral transmittance is 3.8% or less, even more preferably 3.6% or less, and still more preferably 3.4% or less. The spectral transmittance can be measured using the method described in the examples.

[0077] The glass of the embodiments of the present invention preferably has a spectral transmittance of 75% or more at a wavelength of 420 nm when the plate thickness is converted using an IR half-value of 630 nm. This allows for the production of glass with high transmittance in the visible light region. More preferably, the spectral transmittance is 78% or more; even more preferably, 80% or more; and particularly preferably, 82% or more. The spectral transmittance can be measured using the method described in the examples.

[0078] In embodiments of the present invention, the glass preferably has a spectral transmittance ratio of 600 nm to 800 nm (spectral transmittance at 600 nm / spectral transmittance at 800 nm) of 20 or more when the plate thickness is converted using an IR half-value of 630 nm. This results in a glass with high sharp cutoff in the near-infrared region. More preferably, this spectral transmittance ratio is 21 or more, even more preferably 21.5 or more, and particularly preferably 22 or more. The spectral transmittance can be measured using the method described in the examples.

[0079] The conversion formula (T) for the thickness of the glass with an IR half-value of 630 nm in the embodiments of the present invention is used. i2 =T i1 (t2 / t1) (To be continued.) i1 T refers to the internal transmittance of the object glass at a wavelength of 630nm (excluding reflection losses from the surface and back), t1 refers to the thickness of the object glass, and T i2 t1 refers to the converted transmittance value, and t2 refers to the plate thickness to be converted (plate thickness with an IR half-value of 630 nm). It should be noted that in the conversion from transmittance to internal transmittance, the reflection loss Ref of the glass surface and back side is assumed to be 0.0454 respectively, and the following formula is used.

[0080] Internal transmittance = transmittance / {100 × (1 - Ref)} 2}

[0081] The glass used in embodiments of the present invention, for example, when used as a color correction filter for a solid-state imaging element, is often 0.4 mm or less. When converting the plate thickness to an IR half-value of 630 nm, the plate thickness is preferably 0.4 mm or less, more preferably 0.3 mm or less, even more preferably 0.25 mm or less, and even more preferably 0.23 mm or less. Furthermore, from the viewpoint of ensuring the strength of the glass, a thickness of 0.05 mm or more is preferred.

[0082] The glass of the embodiments of the present invention can be manufactured, for example, as follows.

[0083] First, the raw materials are weighed and mixed in a manner that falls within the above composition range (mixing process). The raw material mixture is placed in a platinum crucible and heated and melted in an electric furnace at a temperature of 750°C to 1000°C (melting process). After thorough stirring and clarification, the mixture is poured into a mold, cut, and ground to form a flat plate of a specified thickness (forming process).

[0084] In the melting process of the above manufacturing method, it is preferable to adjust the maximum temperature of the glass during melting to below 1000°C. If the maximum temperature of the glass during melting is higher than the above temperature, the transmittance characteristics may deteriorate. More preferably, the temperature is below 950°C, further preferably below 930°C, and even more preferably below 900°C.

[0085] In addition, if the temperature in the above melting process is too low, problems such as devitrification during melting and time wasted in complete melting may occur. Therefore, it is preferable to have a temperature of 800°C or higher, and more preferably 820°C or higher.

[0086] The glass of the embodiments of the present invention can have an optical multilayer film formed on at least one side of the glass after being formed into a predetermined shape. Examples of optical multilayer films include: IR cut-off films (films that reflect near-infrared light), UV / IR cut-off films (films that reflect ultraviolet and near-infrared light), UV cut-off films (films that reflect ultraviolet light), anti-reflection films, etc. These optical films can be formed by known methods such as vapor deposition or sputtering.

[0087] An adhesion enhancement film can be provided between the glass in the embodiments of the present invention and the aforementioned optical multilayer film. By providing the adhesion enhancement film, the adhesion between the glass and the optical multilayer film is improved, and film peeling can be suppressed. Examples of adhesion enhancement films include: silicon dioxide (SiO2), titanium dioxide (TiO2), lanthanum titanate (La2Ti2O7), aluminum oxide (Al2O3), mixtures of aluminum oxide and zirconium oxide (ZrO2), magnesium fluoride (MgF2), calcium fluoride (CaF2), strontium fluoride (SrF2), and fluorinated organosilicones. If the material contains fluorine or oxygen, the adhesion is even higher, especially magnesium fluoride and / or titanium dioxide, which have higher adhesion to the glass or film, and are therefore preferred as adhesion enhancement films. The adhesion enhancement film can be a single layer or two or more layers. In the case of two or more layers, multiple materials can be combined.

[0088] Near-infrared cutoff filter

[0089] The near-infrared cutoff filter of the present invention includes the glass described in the embodiments of the present invention. Therefore, a near-infrared cutoff filter can be obtained that maintains high transmittance of light in the visible light region (especially blue light) and low transmittance of light in the near-infrared region. In addition to including the glass of the embodiments of the present invention, the near-infrared cutoff filter of the present invention may also have the following configuration.

[0090] The near-infrared cutoff filter of the present invention may have an absorption layer on at least one main surface of the glass of the present invention, the absorption layer comprising a near-infrared absorbing material having a maximum absorption wavelength in the near-infrared region. By adopting such a configuration, a near-infrared cutoff filter with lower transmittance in the near-infrared region can be obtained.

[0091] In the near-infrared cutoff filter of the present invention, it is preferable to add a near-infrared absorbing pigment to a transparent resin so that it is contained in the absorption layer. The transparent resin is selected from acrylic resins, epoxy resins, olefin-thiol resins, polycarbonate resins, polyether resins, polyaryl ester resins, polysulfone resins, polyethersulfone resins, poly(p-phenylene) resins, polyaryl ether phosphine oxide resins, polyimide resins, polyamide-imide resins, polyolefin resins, cyclic olefin resins, and polyester resins, and is formed by using one or more of them alone or by mixing two or more.

[0092] In addition, as a near-infrared absorbing pigment, it is preferable to use a pigment containing selected succinic acid. Near-infrared absorbing material of at least one pigment from the group consisting of salt pigment, phthalocyanine pigment, anthocyanin pigment and diamine pigment.

[0093] <Optical Devices>

[0094] The glass of the embodiments of the present invention can be applied to optical devices. Optical devices are devices that use light to record and transmit information. Examples of optical devices include the imaging device of a digital camera and a light sensor that detects light and converts it into an electrical signal. By applying the glass of the embodiments of the present invention to optical devices, its excellent absorption characteristics, particularly in the near-infrared region, offer advantages that contribute to the miniaturization and height reduction of optical devices.

[0095] When the glass of the embodiments of the present invention is applied to optical devices, it can be used in conjunction with a filter having different light absorption characteristics than the glass of the embodiments of the present invention. Examples of light absorption characteristics of the filter include: the ability to absorb light in a wavelength region different from that of the glass of the embodiments of the present invention, and the ability to absorb light in a different wavelength region within the same near-infrared wavelength region as the glass of the embodiments of the present invention. By using the glass of the embodiments of the present invention in conjunction with a filter having different light absorption characteristics in an optical device, optical properties that are difficult to obtain using a single glass can be achieved. Examples of filters include: an infrared cut-off filter disposed near the imaging element of an imaging device, a protective glass covering the opening on the subject side of the optical device, and a lens disposed inside the optical device. Furthermore, the glass and filter of the embodiments of the present invention can also be used in a stacked manner.

[0096] As stated above, the following matters are disclosed in this specification.

[0097] [1] A fluorophosphate glass, wherein the fluorophosphate glass must contain components of P, Al, K, Cu, F and R (R being one or more selected from Li, Na, Rb and Cs), In terms of mass%, Al 3+ The content is 2% to 20%. The expected ionic radius of alkali metal components containing K and R is greater than or equal to 80 picometers and less than 133 picometers.

[0098] [2] According to the fluorophosphate glass described in [1], wherein, by mass%, ∑R + (R) + Selected from Li + Na + 、Rb + and Cs + One or more components in ∑R + For R + (total measurement) and K + The total concentration is 14%–42%. ∑R” 2+ (R) 2+ Selected from Ba 2+ 、Sr 2+ Ca 2+ and Mg 2+ One or more components in ∑R” 2+ For R” 2+ The total percentage (of the total amount) is 14.5% to 35%.

[0099] [3] According to the fluorophosphate glass described in [1] or [2], wherein, by mass%, K + The content is 1% to 40%.

[0100] [4] The fluorophosphate glass according to any one of [1] to [3], wherein, by mass%, Al 3+ The content is 3.5% to 20%.

[0101] [5] The fluorophosphate glass according to any one of [1] to [4], wherein, by mass%, the fluorophosphate glass contains: P 5+ 20%~70% Al 3+ 3.5%~20% K + 1%~40% Li +0%~30% Na + 0%~40% Rb + 0%~20% Cs + 0%~20% Mg 2+ 0%~20% Ca 2+ 0%~20% Sr 2+ 0%~30% Ba 2+ 0%~40% Cu 2+ 1%~20% Zn 2+ 0% to 20%, and The fluorophosphate glass contains 3% to 60% F, based on the proportion of added fluorine. - .

[0102] [6] The fluorophosphate glass according to any one of [1] to [5], wherein P 5+ The content of / ΣR' (R' is selected from Al) 3+ Mg 2+ and Li + The content of one or more components (ΣR' is the total amount of R') is 3.0 to 7.7.

[0103] [7] The fluorophosphate glass according to any one of [1] to [4], wherein when the plate thickness is calculated in such a way that the wavelength (IR half value) when the transmittance in the near-infrared region is 50% is 630 nm, the plate thickness is 0.4 mm or less, the spectral transmittance at a wavelength of 1200 nm is 22% or less, and the spectral transmittance at a wavelength of 600 nm is 60% or more.

[0104] [8] The fluorophosphate glass according to any one of [1] to [7], wherein when the plate thickness is calculated in such a way that the wavelength (IR half value) when the transmittance in the near-infrared region is 50% is 630 nm, the plate thickness is 0.4 mm or less, the spectral transmittance at a wavelength of 800 nm is 4% or less, and the spectral transmittance at a wavelength of 420 nm is 75% or more.

[0105] [9] The fluorophosphate glass according to any one of [1] to [8], wherein when the thickness is calculated in such a way that the wavelength (IR half value) when the transmittance in the near-infrared region is 50% is 630 nm, the thickness is 0.4 mm or less, and the spectral transmittance ratio (A / B) when the spectral transmittance at a wavelength of 600 nm is set as A and the spectral transmittance at a wavelength of 800 nm is set as B is 20 or more.

[0106]

[10] A near-infrared cutoff filter, wherein the near-infrared cutoff filter comprises any one of [1] to [9] fluorophosphate glass.

[0107]

[11] An optical device, wherein the optical device has any one of the fluorophosphate glass described in [1] to

[10] .

[0108]

[12] An optical device, wherein the optical device has a fluorophosphate glass as described in any one of [1] to

[11] and a filter having light absorption properties different from those of the fluorophosphate glass.

[0109] Example

[0110] The following describes the embodiments, but the present invention is not limited to these embodiments.

[0111] Examples and comparative examples of the fluorophosphate glass of the present invention are shown in Tables 1 to 4. Examples 1 to 7 and Examples 19 to 32 are examples, and Examples 8 to 18 are comparative examples.

[0112] Example 10 shows the results of producing and evaluating a glass composition equivalent to that of Example 9 described in Patent Document 1.

[0113] [Glass making]

[0114] Regarding the glass from Examples 1 to 32, the composition of the molten glass is as shown in Tables 1 to 4 (mass %, F). - The raw materials were weighed and mixed according to the proportion of alkali metals and cations (%). The mixture was placed in a 1L platinum crucible and heated in an electric furnace at the melting temperatures specified in the tables for 1 to 100 hours. The mixture was then clarified, stirred, and cast into a rectangular mold (100mm x 65mm x 20mm) preheated to 50°C to 500°C. The mold was then held at 300°C to 500°C for at least 2 hours, followed by slow cooling at approximately 1°C / min. This yielded a plate-shaped sample of glass with optically ground surfaces, measuring 40mm x 40mm x 0.1mm to 0.5mm in thickness.

[0115] F -F has high volatility, therefore, before and after melting, F... - The content change. The F content in the raw materials before melting of the glasses from Examples 1 to 32 was compared. - The value obtained by converting the content is shown in "Conversion value of raw materials before melting F". - The glass samples from Examples 1-7, 11-13, 19, 21-27, and 30 were analyzed using XRF (manufactured by Rigaku, ZSX Primus II) to detect the F content in the molten glass. - The values ​​obtained by analyzing the content are shown in "Analytical Value F after Melting". - ".

[0116] Find the F value before and after melting of the glass in Examples 1-7, 11-13, 19, 21-27, and 30. - The content of "analytical value F after melting" - " / "Conversion value of raw materials before melting F - The average value of the raw materials before melting, F, is calculated based on the values ​​of Examples 8-10, 14-18, 20, 28, 29, 31, and 32. - The content of F, estimated to be present after melting. - The content. The calculated value is shown in "Estimated value F after melting". - ".

[0117] The following raw materials are used as raw materials for various types of glass.

[0118] In P 5+ In this case, use H3PO4.

[0119] In Al 3+ In such cases, use AlF3.

[0120] In Li + In such cases, use LiF or LiNO3.

[0121] In Na + In such cases, use NaF.

[0122] In K + In such cases, use KF.

[0123] In Mg 2+ In such cases, MgO is used.

[0124] In Ca 2+ In this case, use CaF2.

[0125] In Sr 2+ In this case, use SrF2.

[0126] In Ba2+ In this case, use BaF2.

[0127] In Cu 2+ In such cases, CuO is used.

[0128] In Zn 2+ In such cases, ZnO is used.

[0129] In F - In such cases, fluoride raw materials containing the above-mentioned components are used.

[0130] In addition to the components described in the examples and comparative examples, the glass also contains O 2- As an anion. O 2- The content depends on the high volatility of F - The content varies and therefore is not recorded, but all the glasses in the examples and comparative examples contained O. 2- .

[0131] It should be noted that the raw materials for glass are not limited to the substances mentioned above, and well-known raw materials can be used.

[0132] [Transmittance Evaluation]

[0133] Transmittance was evaluated using the following steps. For the optically polished glass, the transmittance of light with wavelengths from 300 nm to 1200 nm was measured per 1 nm using a spectrophotometer (Nippon Spectrophotometer Co., Ltd., V-570). The thickness was then converted using an IR half-value (the wavelength at which 50% transmittance in the near-infrared region, including reflection losses from the surface and back sides), set at 630 nm. In the conversion, the obtained transmittance was first converted to internal transmittance using the following formula.

[0134] T i2 =T i1 (t2 / t1)

[0135] ·T i1 Internal transmittance of the actual sample (before conversion)

[0136] ·t1: Actual plate thickness of the sample

[0137] ·T i2 : Converted internal transmittance

[0138] ·t2: Plate thickness to be converted

[0139] Based on the converted internal transmittance (T) i2The transmittance, including reflection losses from both the surface and back sides, is used to calculate the spectral transmittance at 1200 nm, 800 nm (B), 600 nm (A), and 420 nm. Furthermore, the transmittance ratio A / B is calculated based on the aforementioned transmittances A and B. It should be noted that in the conversion from transmittance to internal transmittance, the reflection losses Ref from the surface and back sides of the glass are assumed to be 0.0454, and the following formula is used: Internal transmittance = Transmittance / {100 × (1 - Ref)} 2}

[0140] [Weather Resistance Evaluation]

[0141] Weather resistance was evaluated using the following steps: The glass was left to stand for 100 hours in an atmosphere of 85°C and 85% humidity, and then visually observed under a high-brightness light source. A condition where no foreign matter was precipitated, no liquid was dissolved, and no deterioration was confirmed was rated as "0"; a condition where only foreign matter was precipitated or only liquid was dissolved was rated as "△"; and a condition where both foreign matter precipitation and liquid dissolution were confirmed was rated as "×".

[0142] [Meltability Evaluation]

[0143] Meltability was evaluated using the following steps: The glass was melted at 750°C to 1000°C, then held and cooled under the aforementioned conditions. The presence or absence of devitrification in the resulting glass was visually confirmed. The presence of devitrification was indicated by “×”, and the absence of devitrification was indicated by “○”.

[0144] [Young's Modulus Evaluation]

[0145] Young's modulus was evaluated using the following steps: Glass was processed into pieces measuring 30 mm × 30 mm × 10 mm and measured using the ultrasonic pulse method (JIS R 1602: Test method for elastic modulus of fine ceramics). The measured value is expressed in [GPa].

[0146] [Evaluation of Average Thermal Expansion Coefficient]

[0147] The average coefficient of thermal expansion was evaluated using the following steps. Glass was processed into a rod shape, and the average coefficient of thermal expansion in the range of 30°C to 300°C was determined using a thermal analysis apparatus (manufactured by Rigaku Co., Ltd., trade name: TMA8310) at a heating rate of 5°C / min via the thermal expansion method.

[0148] The results are shown in Tables 1 through 4.

[0149] [Table 1]

[0150] [Table 2]

[0151] [Table 3]

[0152] [Table 4]

[0153] Furthermore, regarding Examples 5 (Examples) and 10 (Comparative Examples), the transmittance calculated based on the plate thickness with an IR half-value of 630 nm is shown below. Figure 1 .

[0154] The various embodiments of the present invention yield glass with high absorption capacity in the near-infrared region, high sharp cutoff, no devitrification (good melting properties), and good weather resistance.

[0155] In contrast, the glass used as comparative examples 8 to 18 is described below.

[0156] In Example 8, the expected value of the ionic radius of the alkali metal component is less than 80 picometers, thus resulting in a glass with good weather resistance but low absorption capacity and sharp cutoff in the near-infrared region.

[0157] In Example 9, it contains only one alkali metal component, and P 5+ The content of ∑R' (R' is selected from Al) 3+ Mg 2+ and Li + If one or more of the components are present (∑R' is the total amount of R') and the content is greater than 7.5, it becomes a glass with high absorption capacity and sharp cutoff in the near-infrared region, but reduced weather resistance.

[0158] In Example 10, P 5+ The content of / ΣR' (R' is selected from Al) 3+ Mg 2+ and Li + With one or more components in the glass (ΣR' being the total amount of R') less than 3.0, it becomes a glass with good weather resistance but low absorption capacity and sharp cutoff in the near-infrared region.

[0159] In Examples 11 to 14, there is only one alkali metal component, and the expected value of the ionic radius of the alkali metal component is above 133 picometers. Therefore, it becomes a glass with high absorption capacity and sharp cutoff in the near-infrared region, but low weather resistance.

[0160] In Examples 15 and 16, there are two alkali metal components, but the expected value of the ionic radius of the alkali metal components is above 133 picometers. Therefore, they are glasses with high absorption capacity and sharp cutoff in the near-infrared region, but reduced weather resistance.

[0161] In Example 17, ΣR + Less than 14%, thus becoming a glass that is devitrified and has low melting point.

[0162] Based on Example 17, it is suggested that by ΣR + When the content is adjusted to the specified range, the melting properties are improved.

[0163] In Example 18, ΣR + Less than 14%, and ΣR” + With a content greater than 40%, it becomes a glass that is devitrified and has low melting point.

[0164] Based on Example 18, it is suggested that by ΣR + The content and ΣR” + When the content is adjusted to the specified range, the melting properties are improved.

[0165] This application claims priority to Japanese Patent Application No. 2023-109751, filed on July 4, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A fluorophosphate glass, wherein, The fluoro-phosphate glass must contain P, Al, K, Cu, F, and R (R is one or more selected from Li, Na, Rb, and Cs), Al 3+ 2% to 20%, The ionic radius of the alkali metal component including K and R is desirably equal to or greater than 80 picometers and less than 133 picometers.

2. The fluorophosphate glass of claim 1, wherein, in mass%, ∑R + (R + is one or more components selected from the group consisting of Li + , Na + , Rb + , and Cs + , and the total amount of R + is 14 to 42% of the total amount of R + and K + . ∑R" 2+ (R" 2+ is one or more selected from Ba 2+ , Sr 2+ , Ca 2+ and Mg 2+ , and ∑R" 2+ is the total amount of R" 2+ ) is 14.5% to 35%.

3. The fluorophosphate glass of claim 1, wherein, K + from 1% to 40% by mass.

4. The fluorophosphate glass of claim 1, wherein, Al 3+ from 3.5% to 20% in mass.

5. The fluorophosphate glass of claim 1, wherein, The fluoro-phosphate glass contains, in mass%: P 5+ ：20%～70%、 Al 3+ ：3.5%～20%、 K + ：1%～40%、 Li + : 0% to 30%, Na + : 0%~40%, Rb + : 0% to 20%, Cs + : 0% to 20%, Mg 2+ : 0% to 20%, Ca 2+ : 0% to 20%, Sr 2+ ：0%～30%、 Ba 2+ : 0% to 40%, Cu 2+ : 1 to 20%, Zn 2+ : 0 to 20%, and The fluorophosphate glass contains 3 to 60% of F in terms of the addition ratio - .

6. The fluorophosphate glass of claim 1, wherein, P 5+ the content of the component selected from one or more of Al 3+ , Mg 2+ , and Li + , ΣR' (ΣR' is the total amount of R') is 3.0 to 7.

7.

7. The fluorophosphate glass of claim 1, wherein, When the thickness is converted so that the wavelength at which the transmittance in the near-infrared region is 50% (IR half value) is 630 nm, the thickness is 0.4 mm or less, the spectral transmittance at a wavelength of 1200 nm is 22% or less, and the spectral transmittance at a wavelength of 600 nm is 60% or more.

8. The fluorophosphate glass of claim 1, wherein, When the thickness is converted so that the wavelength at which the transmittance in the near-infrared region is 50% (IR half value) is 630 nm, the thickness is 0.4 mm or less, the spectral transmittance at a wavelength of 800 nm is 4% or less, and the spectral transmittance at a wavelength of 420 nm is 75% or more.

9. The fluorophosphate glass of claim 1, wherein, When the thickness is converted so that the wavelength at which the transmittance in the near-infrared region is 50% (IR half value) is 630 nm, the thickness is 0.4 mm or less, and the spectral transmittance ratio (A / B) when the spectral transmittance at a wavelength of 600 nm is A and the spectral transmittance at a wavelength of 800 nm is B is 20 or more.

10. A near-infrared cut filter, wherein, The near-infrared cut filter has the fluoro-phosphate glass of claim 1.

11. An optical device, wherein, The optical device has the fluoro-phosphate glass of claim 1.

12. An optical device, wherein, The optical device has the fluoro-phosphate glass of claim 1 and a filter having a light absorption characteristic different from that of the fluoro-phosphate glass.

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