Fluorophosphate glass and near infrared ray cut filter

Abstract

To provide a fluorophosphate glass having high strength and suppressed devitrification, which is suitable for thinning, and a near-infrared cut filter made using the same.SOLUTION: The present invention relates to a fluorophosphate glass which comprises P, F, and O as essential components, and has 5-14 cation% of Cu2+, 20-50% of ΣR'+ (where ΣR'+ represents the total amount of Li+ and Na+), a ((content of Ca2+)+(content of Ba2+)) / ΣR2+ value (where ΣR2+ represents the total amount of Ba2+, Sr2+, Ca2+, and Mg2+) of 0.75-1.0, and 5-37.2 anion% of F-.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fluorophosphate glass used in a color correction filter for a digital still camera, a color video camera, etc., and a near-infrared cut filter using the same. [Background technology]

[0002] Solid-state imaging devices such as CCDs and CMOSs ​​used in digital still cameras have spectral sensitivity ranging from the visible range to the near-infrared range around 1200 nm. Therefore, good color reproducibility cannot be achieved using these devices alone, so luminosity is corrected using near-infrared cut filter glass doped with a specific infrared-absorbing substance. Optical glass made by doping copper with fluorophosphate glass has been developed and is used as this near-infrared cut filter glass, which selectively absorbs wavelengths in the near-infrared range and has high weather resistance. The compositions of these glasses are disclosed in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2006-182586 Summary of the Invention [Problem to be solved by the invention]

[0004] Cameras and the like using solid-state imaging elements are becoming thinner. Accordingly, imaging devices and their peripheral components are also required to be thinner. When thinning a near-infrared cut filter glass in which a copper component is added to a fluorophosphate glass, it is known that the hardness of the glass can be increased by adding, for example, a magnesium component (see Patent Document 1). However, the addition of these components may cause devitrification when the glass is formed.

[0005] An object of the present invention is to provide a fluorophosphate glass that has high strength, is suppressed from devitrifying, and is suitable for thinning, and a near-infrared cut filter using the same. [Means for solving the problem]

[0006] As a result of extensive research, the inventors have found that by setting the content ratios of the alkali metal component and the alkaline earth metal component in a fluorophosphate glass within respective predetermined ranges, it is possible to obtain glass that is high in strength, is less susceptible to devitrification, and has desired optical properties.

[0007] The fluorophosphate glass of one embodiment of the present invention contains P, F, and O as essential components, and Cu in cation %. 2+ is 5-14%, ΣR' + (ΣR' + Li + , Na + (The total amount of Ca 2+ Content of +Ba 2+ content) / ΣR 2+ (ΣR 2+ Ba 2+ , Sr 2+ , Ca 2+ , Mg 2+ The total amount of anions is 0.75 to 1.0, and the anion percentage is F - is 5 to 37.2%. [Effects of the Invention]

[0008] According to one embodiment of the present invention, since devitrification is unlikely to occur, the glass raw materials can be melted at low temperatures, and it is possible to obtain fluorophosphate glass with desired optical properties and a near-infrared cut filter using the same. Furthermore, since the strength of the glass is high according to the present invention, the risk of cracking when it is made into a thin plate can be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 shows a graph of transmittance in examples of the present invention and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0010] The fluorophosphate glass (hereinafter also simply referred to as "glass") according to one embodiment of the present invention contains P, F, and O as essential components, and Cu in cation %. 2+ 5-14%, (Ca 2+ Content of +Ba 2+ content) / ΣR 2+ (ΣR 2+ Ba 2+ , Sr 2+ , Ca 2+ , Mg 2+ The total amount of + Content of / ΣR' + (ΣR' + Li + , Na + (meaning the total amount of) is 0.75 to 1.0 (but does not include 1.0), and the Young's modulus is 70 GPa or more.

[0011] In this specification, "cation %" and "anion %" are units as follows. First, the constituent components of glass are divided into cationic components and anionic components. Then, "cation %" is a unit expressing the content of each cationic component as a molar percentage when the total content of all cationic components contained in the glass is taken as 100 mol %. "anion %" is a unit expressing the content of each anionic component as a molar percentage when the total content of all anionic components contained in the glass is taken as 100 mol %. In the following description, unless otherwise specified, the "%" of the content of components contained in the glass of the present invention is cation % for cationic components and anion % for anionic components.

[0012] The glass of this embodiment is a copper-containing fluorophosphate glass containing P, F, and O as essential components. Glass containing P as the main component has the effect of improving the ability to cut near-infrared light. Furthermore, the inclusion of F in the glass can improve weather resistance.

[0013] The glass of this embodiment contains Cu, which is a component that imparts near-infrared blocking properties and improves weather resistance. 2+ It contains 5 to 14% of Cu. 2+ Cu has the property of attracting phosphate chains in the glass together to form a cross-linked structure, which strengthens the glass structure and improves the Young's modulus. 2+ If Cu is less than 5%, the near-infrared absorption may decrease when the glass is made into a thin plate. 2+ is preferably 6% or more, more preferably 8% or more. 2+ If Cu exceeds 14%, the glass becomes unstable and the risk of devitrification increases. 2+ is preferably 12% or less, more preferably 10% or less.

[0014] The glass of this embodiment has a cation percentage of (Ca 2+ Content of +Ba 2+ content) / ΣR 2+ (ΣR 2+ Ba 2+ , Sr 2+ , Ca 2+ , Mg 2+ The total amount of (meaning the total amount of) is 0.75 to 1.0.

[0015] R 2+ (R 2+ Ba 2+ , Sr 2+ , Ca 2+ , Mg 2+ The inclusion of R has the effect of stabilizing the glass, increasing the Young's modulus, and improving weather resistance. 2+ has the property of attracting phosphate chains in the glass together to form a cross-linked structure, strengthening the glass structure and improving the Young's modulus. 2+ The content of ΣR is preferably 1 to 20%. 2+ When the content of ΣR is 1% or more, the effect of stabilizing the glass can be sufficiently obtained. 2+ is preferably 3% or more, more preferably 5% or more. 2+ When ΣR is 20% or less, deterioration of devitrification and the like can be sufficiently suppressed. 2+is preferably 15% or less, more preferably 10% or less.

[0016] The present inventors have 2+ , Sr 2+ , Ca 2+ A solubility test was conducted on a glass containing P, O, Cu, Ba, Sr, and Ca, and the foreign matter found in the glass was analyzed, revealing that crystals containing P, O, Cu, Ba, Sr, and Ca were detected. Furthermore, from the glass in which the above crystals were detected, three glasses were prepared: one with Ba content reduced, one with Sr content reduced, and one with Ca content reduced. The solubility test showed that the glass with Sr content reduced had good solubility, and that the solubility could be improved by reducing Sr. 2+ It was confirmed that reducing

[0017] In addition, the present inventors have 2+ , Ca 2+ , Mg 2+ Glass containing Mg 2+ The solubility test was carried out on the glass that did not contain only Mg (the content ratio of other components was the same). 2+ Glass containing Mg has poor solubility. 2+ The melting property of the glass containing only Mg was good. 2+ It was confirmed that reducing

[0018] From the above results, it is clear that in order to improve the melting property of glass, ΣR 2+ in Sr 2+ and Mg 2+ It has been found that reducing the content of is desirable in order to suppress the risk of devitrification of the glass.

[0019] (Ca 2+ Content of +Ba 2+ content) / ΣR 2+ (ΣR 2+ Ba 2+ , Sr 2+ , Ca 2+ , Mg 2+ If the Ca content is less than 0.75, the risk of devitrification may increase. 2+ Content of +Ba2+ content) / ΣR 2+ is preferably 0.8 or more, more preferably 0.86 or more, even more preferably 0.95 or more, and even more preferably 1.0.

[0020] The glass of this embodiment contains Li in cation %. + Content of / ΣR' + (ΣR' + Li + , Na + The total amount of the above (meaning the total amount of the above) is 0.75 to 1.0 (but does not include 1.0).

[0021] Li + , Na + Although the ion diffusion coefficient of Li is larger than that of other components, when the two are combined and contained in glass, the mixed alkali effect makes the ion diffusion coefficient smaller than that of each component. + , Na + Since the ionic radii of each ion are different, when they are mixed in glass, each ion is less likely to move than when they are present alone in glass. In other words, the mobility of each ion decreases, resulting in a smaller ion diffusion coefficient. In particular, ΣR' + Li against + When the content ratio of is high, the glass becomes stable and structural relaxation is less likely to occur, thereby improving the Young's modulus.

[0022] Li + Content of / ΣR' + (ΣR' + Li + , Na + If the total amount of Li is less than 0.75, the Young's modulus may decrease. + Content of / ΣR' + is preferably 0.78 or more, more preferably 0.8 or more. + Content of / ΣR' + If the value is 1.0, there is a risk that the Young's modulus will decrease. + Content of / ΣR' + is preferably 0.95 or less, more preferably 0.9 or less.

[0023] ΣR' + has the effects of stabilizing the glass and lowering the melting temperature of the glass, and is preferably contained in an amount of 20 to 50%. + When ΣR' is 20% or more, the effect can be sufficiently obtained. + is preferably 25% or more, more preferably 30% or more. + When ΣR' is 50% or less, the deterioration of devitrification resistance can be sufficiently suppressed. + is preferably 45% or less, more preferably 40% or less.

[0024] The reasons for limiting the content (indicated as cation % and anion %) of each component constituting the glass of this embodiment will be explained below.

[0025] (cationic component) P 5+ is the main component that forms glass (glass-forming oxide) and is an essential component for improving the stability of glass. 5+ The content of P is preferably 30 to 60%. 5+ When the content is 30% or more, the effect can be sufficiently obtained, and when it is 60% or less, the glass can be sufficiently prevented from becoming unstable and the deterioration of weather resistance can be sufficiently prevented. 5+ The content is more preferably 40 to 60%, and even more preferably 40 to 50%.

[0026] Al 3+ Al may be the main component that forms glass (glass-forming oxide), and is a component that increases Young's modulus, weather resistance, and chemical durability by bonding with non-bridging oxygen in the glass and forming a dense glass network. 3+ The content of Al is preferably 4 to 20%. 3+ When the content of Al is 4% or more, the effect can be sufficiently obtained, and when it is 20% or less, the risk of devitrification can be sufficiently reduced. 3+ The content is more preferably 6 to 15%, and even more preferably 6 to 12%.

[0027] Li + is a component that stabilizes the glass and improves the Young's modulus. + If it contains Li + The content of Li is preferably 15 to 40%. + When the content of Li is 15% or more, the effect can be sufficiently obtained, and when it is 40% or less, the glass can be sufficiently prevented from becoming unstable. + The content is more preferably 20 to 40%.

[0028] Na + is a component for stabilizing the glass. + If it contains Na + The content of Na is preferably 0.1 to 15%. + When the content of Na is 0.1% or more, the effect can be sufficiently obtained, and when it is 15% or less, the decrease in Young's modulus can be sufficiently suppressed. + The content is preferably 0.1 to 10%, more preferably 0.1 to 6%.

[0029] K + Although K is not an essential component, it is a component that lowers the melting temperature of glass and the liquidus temperature of glass. + When it is contained, there is a risk of the strength decreasing, so it is preferable not to contain it.

[0030] Ca 2+ Ca is a component that increases the Young's modulus of glass, improves weather resistance, and stabilizes glass. 2+ If it contains Ca 2+ The upper limit of the Ca content is preferably 10% or less. 2+ When the Ca content is 10% or less, it is possible to sufficiently prevent the glass from becoming unstable and also to sufficiently prevent the devitrification tendency from worsening. 2+ The content is more preferably 0 to 6%.

[0031] Ba 2+is a component that increases the Young's modulus of glass, improves weather resistance, and stabilizes glass. 2+ If it contains Ba 2+ The upper limit of the Ba content is preferably 10% or less. 2+ When the Ba content is 10% or less, it is possible to sufficiently prevent the glass from becoming unstable and also to sufficiently prevent the devitrification tendency from worsening. 2+ The content is more preferably 0 to 6%.

[0032] Sr 2+ Although not an essential component, Sr is a component that increases the Young's modulus of glass and improves weather resistance. 2+ If it contains Sr 2+ The upper limit of the Sr content is preferably 5% or less. 2+ When the Sr content is 5% or less, it is possible to sufficiently prevent the glass from becoming unstable and also to sufficiently prevent the devitrification tendency from worsening. 2+ The content is more preferably 0 to 2%, and even more preferably none is contained.

[0033] Mg 2+ Although not an essential component, Mg is a component that increases the Young's modulus of glass and improves weather resistance. 2+ If it contains Mg 2+ The upper limit of the Mg content is preferably 5% or less. 2+ When the content of Mg is 5% or less, the glass can be sufficiently prevented from becoming unstable and the devitrification tendency can be sufficiently prevented. 2+ The content is more preferably 0 to 2%, and even more preferably none is contained.

[0034] Zn 2+ Although not an essential component, Zn is a component that increases the Young's modulus of glass and improves weather resistance. 2+ If it contains Zn 2+ The upper limit of the Zn content is preferably 10% or less. 2+ When the content of Zn is 10% or less, it is possible to sufficiently prevent the glass from becoming unstable and also to sufficiently prevent the devitrification tendency from worsening.2+ The content is more preferably 0 to 5%, and further preferably 0 to 2%.

[0035] The glass of this embodiment contains Sb as an optional cation component. 3+ May contain 0 to 1% of Sb 3+ Although Sb is not an essential component, it has the effect of increasing the transmittance in the visible range. 3+ When Sb is contained, the content of Sb is 1% or less, so that the deterioration of the stability of the glass can be sufficiently suppressed. 3+ The content is preferably 0.01 to 0.8%, more preferably 0.05 to 0.5%, and even more preferably 0.1 to 0.3%.

[0036] The glass of this embodiment may further contain other components typically contained in fluorophosphate glass, such as S, Si, and B, as optional cationic components, within a range that does not impair the effects of the present invention. The total content of these components is preferably 5% or less.

[0037] (anionic component) O 2- is an essential component for stabilizing the glass, increasing the visible transmittance, improving mechanical properties such as strength, hardness, and elastic modulus, and reducing the ultraviolet transmittance, and its content is preferably 40 to 95%. 2- When the content is 40% or more, the effect can be sufficiently obtained, and when it is 95% or less, the glass can be sufficiently prevented from becoming unstable and the deterioration of weather resistance can be sufficiently prevented.

[0038] In order to improve the Young's modulus of glass, O 2- The content of O is preferably 80 to 95% (but excluding 80%). 2- The content is more preferably 82 to 93%, and even more preferably 85 to 92%.

[0039] To improve the weather resistance of glass, 2- The content of O is preferably 40 to 80%. 2-The content is more preferably 50 to 70%, and even more preferably 50 to 60%.

[0040] F - is an essential component for stabilizing glass. - The content of F is preferably 5 to 60%. - When the content of F is 5% or more, the occurrence of unmelted material when melting glass raw materials can be sufficiently suppressed. - When the content is 60% or less, it is possible to sufficiently prevent the volatility from becoming high and the formation of striae from increasing.

[0041] To improve the Young's modulus of glass, F - The content of F is preferably 5 to 20% (but not including 20%). - The content is more preferably 7 to 18%, and further preferably 8 to 15%.

[0042] To improve the weather resistance of glass, F - The content of F is preferably 20 to 60%. - The content is more preferably 30 to 50%, and further preferably 40 to 50%.

[0043] The glass of this embodiment may further contain other optional anion components that are normally contained in fluorophosphate glass, such as Cl, Br, and I, within a range that does not impair the effects of the present invention. The total content of these components is preferably 5% or less.

[0044] Next, the contents of other optional components other than the above components of this embodiment will be described. In this specification, "substantially not containing" means that the component is not intentionally used as a raw material, and it is assumed that the component is not contained in the raw material components or inevitable impurities that are mixed in during the manufacturing process.

[0045] The glass of this embodiment preferably contains substantially no PbO, As2O3, V2O5, YbF3, or GdF3. PbO is a component that reduces the viscosity of the glass and improves manufacturing workability. Furthermore, As2O3 is a component that acts as an excellent fining agent, capable of generating clarified gas over a wide temperature range. However, since PbO and As2O3 are environmentally hazardous substances, it is preferable to avoid their inclusion as much as possible. Since V2O5 has absorption in the visible range, it is preferable to avoid its inclusion as much as possible in near-infrared cut filter glasses for solid-state imaging devices, which require high visible transmittance. Although YbF3 and GdF3 are components that stabilize the glass, their raw materials are relatively expensive, which leads to increased costs, so it is preferable to avoid their inclusion as much as possible.

[0046] With regard to these components, "substantially not containing" means that they are not intentionally used as raw materials, and the content of each component in the near-infrared cut filter glass is 0.1% or less.

[0047] The glass of this embodiment can be added with a nitrate compound or a sulfate compound having a glass-forming cation as an oxidizing agent or a fining agent. The oxidizing agent is a compound that occupies 10% of the total amount of Cu in the glass. 2+ Increasing the proportion of ions has the effect of improving the visible light transmittance and the ability to block near-infrared light.

[0048] When a nitrate compound or a sulfate compound is contained, the amount added is preferably 0.5 to 15 mass% based on the raw material mixture. When the amount of the nitrate compound or sulfate compound added is 0.5 mass% or more, the effect of improving transmittance is easily achieved, and when it is 15 mass% or less, difficulties in glass formation can be sufficiently suppressed. The amount of the nitrate compound or sulfate compound added is more preferably 1 to 10 mass%, and even more preferably 3 to 8 mass%.

[0049] Nitrate compounds include Al(NO3)3, LiNO3, NaNO3, KNO3, Ca(NO3)2, Sr(NO3)2, Ba(NO3)2, Zn(NO3)2, Cu(NO3)2, etc. Sulfate compounds include Al2(SO4)3·16H2O, Li2SO4, Na2SO4, K2SO4, CaSO4, SrSO4, BaSO4, ZnSO4, CuSO4, etc.

[0050] The glass of this embodiment must have a Young's modulus of 70 GPa or more. 1C There is a correlation between the fracture energy (r) and Young's modulus (E), as shown in the formula below. Therefore, improving the Young's modulus of glass is an effective way to increase the strength of glass.

[0051]

number

[0052] If the Young's modulus is less than 70 GPa, problems will arise such as the glass being more likely to break when made into a thin plate or being more likely to be scratched during the polishing process, which may result in breakage when the glass is used in an imaging device, etc. Preferably, the Young's modulus is 75 GPa or more.

[0053] Furthermore, the glass of this embodiment preferably has an average transmittance of 80% or more for light with a wavelength of 450 to 600 nm when the glass has a plate thickness of 0.1 mm. By ensuring that the average transmittance is 80% or more, light in the visible range can be sufficiently transmitted, making it possible to display clear images when used in an imaging device.

[0054] Furthermore, when the glass of this embodiment has a plate thickness of 0.1 mm, the wavelength at which the transmittance is 50% is preferably in the range of 600 to 670 nm. By satisfying these conditions, it becomes possible to achieve the desired optical characteristics in sensors that require a thin profile. Furthermore, when the plate thickness is 0.1 mm, by ensuring that the transmittance for light with a wavelength of 400 nm is 85% or more and the transmittance for light with a wavelength of 1200 nm is 40% or less, a near-infrared cut filter with excellent optical characteristics can be obtained in a thin plate.

[0055] The transmittance value was converted to the value for a plate thickness of 0.1 mm. The transmittance was converted using the following formula 1. i1 is the internal transmittance of the measurement sample (data excluding reflection loss on the front and back surfaces), t1 is the plate thickness of the measurement sample (for example, 0.15 to 0.3 mm), T i2 indicates the converted transmittance, and t2 indicates the converted plate thickness (0.1 mm in the present invention).

[0056]

number

[0057] The near-infrared cut filter glass of this embodiment is compatible with the miniaturization and thinning of imaging devices and their peripheral components, and therefore provides good spectral characteristics even when the glass plate is thin. The glass plate thickness is preferably 0.5 mm or less, more preferably 0.3 mm or less, even more preferably 0.2 mm or less, and most preferably 0.15 mm or less. There is no particular lower limit to the glass plate thickness, but in consideration of the strength required to resist breakage during glass manufacturing and transportation when incorporated into imaging devices, it is preferably 0.03 mm or more, more preferably 0.05 mm or more.

[0058] The glass of this embodiment may be formed into a predetermined shape, and then an optical multilayer film may be provided on at least one surface of the glass to form a near-infrared cut filter. Examples of optical multilayer films include IR cut films (films that reflect near-infrared rays), UV / IR cut films (films that reflect ultraviolet rays and near-infrared rays), UV cut films (films that reflect ultraviolet rays), and anti-reflection films. These optical thin films can be formed by known methods such as vapor deposition and sputtering.

[0059] An adhesion-strengthening film may be provided between the glass and the optical multilayer film. The provision of an adhesion-strengthening film improves adhesion between the glass and the optical multilayer film, making it possible to prevent film peeling. Examples of adhesion-strengthening films include silicon oxide (SiO2), titanium oxide (TiO2), lanthanum titanate (La2Ti2O7), aluminum oxide (Al2O3), a mixture of aluminum oxide and zirconium oxide (ZrO2), magnesium fluoride (MgF2), calcium fluoride (CaF2), strontium fluoride (SrF2), and fluorine silicone. Substances containing fluorine or oxygen have higher adhesion, and magnesium fluoride and / or titanium oxide are particularly preferred as adhesion-strengthening films because they enhance adhesion to the glass or film. The adhesion-strengthening film may be a single layer or two or more layers. In the case of two or more layers, multiple substances may be combined.

[0060] The near-infrared cut filter glass of this embodiment can be produced as follows: Raw materials are weighed and mixed so as to have the above-mentioned composition range (mixing step). This raw material mixture is placed in a platinum crucible and heated and melted at a temperature of 700 to 900°C in an electric furnace (melting step). After thorough stirring and clarification, the mixture is poured into a mold, cut, polished, and formed into a flat plate of a specified thickness (forming step).

[0061] In the melting step of the above-mentioned manufacturing method, the highest temperature of the glass during melting is preferably 900°C or lower. If the highest temperature of the glass during melting exceeds this temperature, the transmittance characteristics will deteriorate and the volatilization of fluorine will be promoted, making the glass unstable. The above temperature is more preferably 880°C or lower, even more preferably 850°C or lower, and even more preferably 820°C or lower.

[0062] Furthermore, if the temperature in the melting step is too low, problems such as devitrification occurring during melting and a long time required for melting through occur, so the temperature is preferably 750°C or higher, more preferably 800°C or higher. [Example]

[0063] Examples of the present invention and comparative examples are shown in Tables 1 to 3. Examples 1 to 10 and Examples 20 to 22 are examples of the present invention, and Examples 11 to 19 are comparative examples of the present invention.

[0064] [Glass production] These glasses were prepared by weighing and mixing raw materials so that the glass components would have the compositions (cation %, anion %) shown in Tables 1 to 3. The mixture was placed in a platinum crucible with an internal volume of approximately 1 L, melted at a temperature of 800 to 900°C for 2 hours, refined, and stirred. The mixture was then poured into a rectangular mold measuring 100 mm in length, 80 mm in width, and 20 mm in height that had been preheated to approximately 50 to 500°C, and gradually cooled to 360 to 440°C, decreasing the temperature at a rate of approximately 1°C / min to obtain a sample. The front and back surfaces were then optically polished to obtain glass plates with thicknesses of 0.15 to 0.3 mm.

[0065] The raw materials for each glass are P 5+ In the case of H3PO4 and Al(PO3)3, one selected from Al 3+ In the case of AlF3, Al(PO3)3 and Al2O3, one of them is used. + In the case of 2+ In the case of Ba, one selected from SrF2, SrCO3 and Sr(PO3)2 2+ In the case of BaF2, BaCO3 and Ba(PO3)2, Na + is one selected from NaCl, NaBr, NaI, NaF and Na(PO3), + , Ca 2+ In the case of , one selected from fluoride, carbonate and metaphosphate is added to Cu 2+ , Cu + In the case of , CuO was used.

[0066] [evaluation] The transmittance of light with wavelengths of 350 to 1200 nm was measured using a spectrophotometer (JASCO Corporation, V-570). The measurement results were converted into transmittance for a plate thickness of 0.1 mm using the method described above. Tables 1 to 3 show the transmittance of light at wavelengths of 400 nm, 420 nm, and 1200 nm when converted into a plate thickness of 0.1 mm. In addition, from the converted transmittance, the wavelength at which the transmittance in the near-infrared region becomes 50% (IR half-value) was calculated. Note that in Examples 13 to 18, transmittance was not measured because devitrification occurred (listed as No Data in Table 2).

[0067] The meltability was evaluated by the following procedure: First, the glass was melted at 800 to 900°C for 2 hours, and the presence or absence of devitrification particles in the molten glass was visually confirmed. If devitrification particles were observed, it was marked with ×, and if no devitrification particles were observed, it was marked with ○.

[0068] The Young's modulus of glass having a thickness of 0.15 to 0.3 mm was measured by the ultrasonic pulse method using an ultrasonic thickness gauge (Olympus, 35DL). The average values ​​of the results of measurements at two points are shown in Tables 1 to 3.

[0069] [Table 1]

[0070] [Table 2]

[0071] [Table 3]

[0072] FIG. 1 shows the transmittance converted into a plate thickness of 0.1 mm for Example 8 (Example) and Example 19 (Comparative Example).

[0073] In each of the examples of the present invention (Examples 1 to 10, Examples 20 to 22), glasses were obtained that had good optical properties, did not suffer from devitrification (good solubility), and had a Young's modulus of 70 GPa or more. In contrast, in Example 12, which was used as a comparative example, Li + Content of / ΣR' + Since the Young's modulus was less than 0.75, the glass had a low Young's modulus.

[0074] In addition, in Examples 13 to 18, (Ca 2+ +Ba 2+ ) / ΣR 2+ Since the value was less than 0.75, devitrification occurred.

[0075] The effect of Sr on solubility was confirmed by the following method. Glasses in which the Sr, Ca, and Ba contents were reduced by a certain amount from the glass of Example 15 were prepared (Example 11 (only Sr reduced by 2% from Example 15), Example 16 (only Ca reduced by 2% from Example 15), and Example 17 (only Ba reduced by 2% from Example 15)), and the solubility was confirmed. As a result, only Example 11 had good solubility, suggesting that reducing the amount of Sr contributes to improving solubility.

[0076] The effect of Mg on solubility was confirmed by the following method. A glass (Example 10) was prepared from the glass of Example 18, but without Mg, and its solubility was confirmed. As a result, the glass of Example 10 had good solubility, suggesting that reducing the amount of Mg contributes to improving solubility.

[0077] The effect of Al content on Young's modulus was confirmed by the following method. Young's modulus was compared between glasses of Examples 20 to 22, in which only the Al content was changed (components other than Al were converted so that the total cation percentage was 100%). As a result, the Young's modulus of the glass increased as the Al content increased, suggesting that increasing the Al content within a certain range contributes to improving Young's modulus.

[0078] Further, examples of the present invention are shown in Table 4. Examples 23 to 29 are examples of the present invention.

[0079] [Glass production] These glasses were prepared by weighing and mixing the raw materials so that the glass components after melt molding would have the composition (cation %, anion %) shown in Table 4. The mixture was placed in a platinum crucible with an internal volume of approximately 1 L, melted at a temperature of 800-900°C for 1-4 hours, refined, and stirred. The mixture was then poured into a rectangular mold measuring 100 mm in length, 80 mm in width, and 20 mm in height that had been preheated to approximately 50-500°C, and gradually cooled to 360-440°C, decreasing the temperature at a rate of approximately 1°C / min to obtain a sample. The front and back surfaces were then optically polished to obtain glass plates with thicknesses of 0.15-0.3 mm.

[0080] The raw materials for each glass were as described above, and the evaluation methods for each item were as described above.

[0081] [Table 4]

[0082] In each of the examples (Examples 23 to 29) of the present invention, glass was obtained that had good optical properties, did not suffer from devitrification (good solubility), and had a Young's modulus of 70 GPa or more.

[0083] The effect of the F content on Young's modulus was confirmed by the following method. The Young's modulus was compared between the glasses of Examples 27 to 29, in which the same amount of glass raw materials was used and the F content was changed by changing only the melting time. As a result, the Young's modulus of the glass increased as the F content decreased, suggesting that reducing the F content within a certain range contributes to improving the Young's modulus.

[0084] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0085] This application is based on a Japanese patent application (Patent Application No. 2020-217105) filed on December 25, 2020, the contents of which are incorporated herein by reference. [Industrial Applicability]

[0086] According to the present invention, the glass composition is resistant to devitrification even when the Cu content is high due to thinner plates, and since it can be melted at low temperatures, it has high transmittance in the visible range, making it extremely useful as a near-infrared cut filter for imaging devices that are becoming smaller and thinner.

Claims

1. Contains P, F, and O as essential components, and the cationic percentage Cổ ２＋ が5~11%、 ΣR' ＋ (ΣR' ＋ Li ＋ , Na ＋ The total amount of (Ca ２＋ Content of + Ba ２＋ Content of ) / ΣR ２＋ (ΣR ２＋ is Ba ２＋ , Sr ２＋ , Ca ２＋ , Mg ２＋ (referring to the total amount of) is 0.75 to 1.0, Anion % F － 5 to 37.2% Fluorophosphate glass characterized by:

2. in cation % Li ＋ Content of / ΣR' ＋ (ΣR' ＋ Li ＋ , Na ＋ (The total amount of) is 0.75 to 1.0 (but does not include 1.0), 2. The fluorophosphate glass according to claim 1, wherein

3. Young's modulus is 70 GPa or more 3. The fluorophosphate glass according to claim 1, wherein

4. Li ＋ Content of / ΣR' ＋ (ΣR' ＋ Li ＋ , Na ＋ 4. The fluorophosphate glass according to claim 1, wherein the total amount of (a) is 0.8 to 0.

9.

5. Cation % P ５＋ 30~60%、 Al ３＋ 4~20%、 ΣR' ＋ (ΣR' ＋ Li ＋ , Na ＋ (The total amount of) 20 to 50%, Li ＋ 15-40%, No ＋ 0.1 to 15%, ΣR ２＋ (ΣR ２＋ is Ba ２＋ , Sr ２＋ , Ca ２＋ , Mg ２＋ (The total amount of) 1 to 20%, Mg ２＋ 0~5%、 Ca ２＋ 0~10%, Sr ２＋ 0~5%、 No ２＋ 0~10%, Cổ ２＋ 5-14%, Anion % F － 20~37.2%、 O ２－ 62.8~80%、 The fluorophosphate glass according to any one of claims 1 to 4, comprising:

6. Cation % P ５＋ 30~60%、 Al ３＋ 4~20%、 ΣR' ＋ (ΣR' ＋ Li ＋ , Na ＋ (The total amount of) 20 to 50%, Li ＋ 15-40%, No ＋ 0.1 to 15%, ΣR ２＋ (ΣR ２＋ is Ba ２＋ , Sr ２＋ , Ca ２＋ , Mg ２＋ (The total amount of) 1 to 20%, Mg ２＋ 0~5%、 Ca ２＋ 0~10%, Sr ２＋ 0~5%、 No ２＋ 0~10%, Cổ ２＋ 5-14%, Anion % F － 5 to 20% (but not including 20%) O ２－ 80-95% (but not including 80%) The fluorophosphate glass according to any one of claims 1 to 4, comprising:

7. At a plate thickness of 0.1 mm, The wavelength at which the transmittance is 50% is within the range of 600 to 670 nm, The transmittance of light at a wavelength of 400 nm is 85% or more, Light transmittance at a wavelength of 1200 nm is 40% or less 7. The fluorophosphate glass according to claim 1, wherein

8. A near-infrared cut filter comprising the fluorophosphate glass according to any one of claims 1 to 7.

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