Fluorophosphate glass and near-infrared cut filter

Abstract

This invention relates to a fluorophosphate glass containing P, F, and O as essential components, with Cu as a cation percentage. 2+ It is 5-14%, (Ca 2+ Ba content 2+ (content) / ΣR 2+ (ΣR 2+ It refers to Ba 2+ 、Sr 2+ Ca 2+ Mg 2+ The total amount (total) is 0.75–1.0, Li + Content / ΣR' + (ΣR' + It refers to Li + Na + The total amount of the substance is 0.75 to 1.0 (excluding 1.0), and its Young's modulus is above 70 GPa.

Description

Technical Field

[0001] This invention relates to fluorophosphate glass used in color correction filters for digital cameras or color video cameras, and near-infrared cutoff filters made therefrom. Background Technology

[0002] Solid-state imaging elements such as CCDs or CMOS sensors used in digital cameras and other devices have spectral sensitivity ranging from the visible light region to the near-infrared region around 1200 nm. Therefore, good color reproduction cannot be obtained if used directly, so near-infrared cut-off filter glass with added specific substances that absorb infrared radiation is used to correct visual sensitivity. To enable this near-infrared cut-off filter glass to selectively absorb wavelengths in the near-infrared region and possess high weather resistance, optical glasses made by adding copper to fluorophosphate glass have been developed and are used. The composition of these glasses is disclosed in Patent Document 1.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-182586 Summary of the Invention

[0006] The technical problem that the invention aims to solve

[0007] Cameras and other devices using solid-state imaging elements are becoming increasingly thinner. At the same time, there is also a demand for thinner imaging equipment and its peripheral components. When producing thin sheets of near-infrared cut-off filter glass made by adding copper to fluorophosphate glass, it is known that magnesium can be added, for example, to increase the hardness of the glass (see Patent Document 1). However, if these components are added, devitrification may occur during glass forming.

[0008] The purpose of this invention is to provide a fluorophosphate glass with high strength and suppressed devitrification that is conducive to thinning, and a near-infrared cutoff filter made therefrom.

[0009] Technical solutions adopted to solve technical problems

[0010] After careful research, the inventors discovered that for fluorophosphate glass, by ensuring that the proportions of alkali metal and alkaline earth metal components are within specified ranges, glass with high strength and low devitrification can be obtained, thus achieving the desired optical properties.

[0011] A fluorophosphate glass according to one embodiment of the present invention is characterized in that it contains P, F, and O as essential components, and Cu in the cation percentage is [missing information]. 2+ It is 5-14%, (Ca 2+ Ba content2+ (content) / ΣR 2+ (ΣR 2+ It refers to Ba 2+ 、Sr 2+ Ca 2+ Mg 2+ The total amount (total) is 0.75–1.0, Li + Content / ΣR' + (ΣR' + It refers to Li + Na + The total amount of the substance is 0.75 to 1.0 (excluding 1.0), and its Young's modulus is above 70 GPa.

[0012] Invention Effects

[0013] According to one embodiment of the present invention, it is possible to obtain fluorophosphate glass with desired optical properties that is less prone to devitrification and thus allows for low-temperature melting of glass raw materials, and near-infrared cutoff filters made therefrom. Furthermore, according to the present invention, due to the high strength of the glass, the risk of cracking during thinning can be reduced. Attached Figure Description

[0014] Figure 1 The figures show the transmittance in the embodiments and comparative examples of the present invention. Detailed Implementation

[0015] One embodiment of the fluorophosphate glass (hereinafter also referred to as "glass") of the present invention contains P, F, and O as essential components, and Cu in the cation percentage 2+ It is 5-14%, (Ca 2+ Ba content 2+ (content) / ΣR 2+ (ΣR 2+ It refers to Ba 2+ 、Sr 2+ Ca 2+ Mg 2+ The total amount (total) is 0.75–1.0, Li + Content / ΣR' + (ΣR' + It refers to Li + Na + The total amount of the substance is 0.75 to 1.0 (excluding 1.0), and its Young's modulus is above 70 GPa.

[0016] In this specification, "cation%" and "anion%" refer to the following units. First, the constituent components of the glass are divided into cationic components and anionic components. "Cat%" refers to the mole percentage of each cationic component when the total content of all cationic components in the glass is 100 mol%. "Anion%" refers to the mole percentage of each anionic component when the total content of all anionic components in the glass is 100 mol%. In the following description, unless otherwise specified, the content "%" of the components in the glass of the present invention is cation% for cationic components and anion% for anionic components.

[0017] The glass of this embodiment is a copper fluorophosphate glass with P, F, and O as essential components. Glass with P as the main component has the effect of improving cutoff in the near-infrared region. Furthermore, the presence of F in the glass improves weather resistance.

[0018] The glass in this embodiment contains 5-14% Cu, a component that imparts near-infrared cutoff and enhances weather resistance. 2+ Furthermore, due to Cu 2+ It possesses the property of attracting phosphate chains in glass to form cross-linked structures, thus strengthening the glass structure and increasing Young's modulus. If Cu 2+ If the absorption rate is less than 5%, near-infrared absorption may decrease during glass thinning. Cu 2+ Preferably, it is 6% or more, more preferably 8% or more. Furthermore, if Cu 2+ If the value is greater than 14%, the glass becomes unstable, increasing the risk of devitrification. Cu 2+ Preferably below 12%, more preferably below 10%.

[0019] In the glass of this embodiment, the cation percentage (Ca) 2+ Ba content 2+ (content) / ΣR 2+ (ΣR 2+ It refers to Ba 2 + 、Sr 2+ Ca 2+ Mg 2+ The total amount (total) is 0.75 to 1.0.

[0020] Contains R 2+ (R 2+ It refers to Ba 2+ 、Sr 2+ Ca 2+ Mg 2+ It has the effect of stabilizing glass, increasing Young's modulus, and improving weather resistance. Specifically, due to R... 2+It possesses the property of attracting phosphate chains in glass to form a cross-linked structure, thereby strengthening the glass structure and increasing Young's modulus. Preferably, it contains 1-20% ΣR. 2+ If ΣR 2+ At concentrations above 1%, sufficient glass stabilization can be achieved. ΣR 2+ Preferably, it is 3% or more, more preferably 5% or more. Furthermore, if ΣR 2+ Below 20%, it can effectively suppress the deterioration of depermeability, etc. ΣR 2+ Preferably below 15%, more preferably below 10%.

[0021] The inventors have carried out a process including Ba 2+ 、Sr 2+ Ca 2+ The glass underwent melting tests, and impurities identified in the glass were analyzed, revealing crystalline substances containing P, O, Cu, Ba, Sr, and Ca. Subsequently, three glass samples were prepared from the glass containing these crystalline substances: one showing only Ba reduction, one showing only Sr reduction, and one showing only Ca reduction. Melting tests were then conducted on these samples, confirming that the glass showing only Sr reduction exhibited good melting properties and reduced Sr content. 2+ It is effective in improving solubility.

[0022] Furthermore, the inventors implemented a method containing Ba 2+ Ca 2+ Mg 2+ Glass containing only Mg 2+ The melting properties of glass (containing the same proportions of other components) were tested. The results showed that glass containing Mg... 2+ The glass has poor solubility and contains only Mg. 2+ The glass exhibits good solubility. This confirms the effectiveness of reducing Mg. 2+ It is effective in improving solubility.

[0023] The above results show that in order to improve the solubility of glass and reduce ΣR 2+ Sr 2+ and Mg 2+ The content of [specific ingredient] is beneficial for suppressing the risk of devitrification in glass.

[0024] If (Ca) 2+ Ba content 2+ (content) / ΣR 2+ (ΣR 2+ It refers to Ba 2+ 、Sr 2+ Ca 2+ Mg 2+ If the total concentration (Ca) is less than 0.75, the risk of devitrification may increase. 2+ Ba content2+ (content) / ΣR 2+ Preferably, it is 0.8 or higher, more preferably 0.86 or higher, even more preferably 0.95 or higher, and still more preferably 1.0.

[0025] In the glass of this embodiment, the cation percentage of Li + Content / ΣR' + (ΣR' + It refers to Li + Na + The total amount is 0.75 to 1.0 (excluding 1.0).

[0026] Li + Na + The ion diffusion coefficient of Li is larger than that of other components, but by combining both and incorporating them into the glass, it exhibits a smaller ion diffusion coefficient than its individual components due to the mixed alkali effect. Specifically, due to Li... + Na + Because their ionic radii differ, the ions are less mobile when mixed in glass compared to when they exist alone. That is, due to the decreased mobility of each ion, the ion diffusion coefficient becomes smaller. In particular, Li... + Relative to ΣR' + The higher the proportion of [agent], the more stable the glass is, and the less likely it is to undergo structural mitigation, thus increasing the Young's modulus.

[0027] If Li + Content / ΣR' + (ΣR' + It refers to Li + Na + If the sum of its components (e.g., 0.75) is less than 0.75, then Young's modulus may decrease. + Content / ΣR' + Preferably, the concentration is 0.78 or higher, more preferably 0.8 or higher. Furthermore, if Li... + Content / ΣR' + A value of 1.0 could lead to a decrease in Young's modulus. Li + Content / ΣR' + Preferably, it is below 0.95, and more preferably below 0.9.

[0028] ΣR' + It has the effects of stabilizing glass and lowering the melting temperature of glass, and is preferably contained in 20-50%. If ΣR' + At a concentration above 20%, its full effect can be achieved. ΣR' + Preferably, it is 25% or more, more preferably 30% or more. Furthermore, if ΣR' +Below 50%, it can effectively suppress the decrease in depermeability, etc. + Preferably below 45%, more preferably below 40%.

[0029] The reasons for limiting the content of each component (expressed as cation % and anion %) of the glass constituting this embodiment will be explained below.

[0030] (Catonic component)

[0031] P 5+ It is the main component that forms glass (glass-forming oxides) and is an essential component for improving the stability of glass. P 5+ The preferred content of P is 30-60%. 5+ When the content is above 30%, its effect can be fully achieved, while if it is below 60%, it can effectively inhibit the glass from becoming unstable and also effectively inhibit the decline in weather resistance. 5+ The content of [the substance] is more preferably 40-60%, and even more preferably 40-50%.

[0032] Al 3+ It can be a major component of glass (glass-forming oxide), which combines with non-crosslinked oxygen in the glass to form a dense glass network to improve Young's modulus, weather resistance, and chemical durability. 3+ The preferred content of Al is 4-20%. 3+ A content of 4% or higher is sufficient to achieve its full effect, while a content below 20% can significantly reduce the risk of devitrification. 3+ The content of [the substance] is more preferably 6-15%, and even more preferably 6-12%.

[0033] Li + It is a component that stabilizes glass and increases its Young's modulus. In glass containing Li... + In the case of Li + The preferred content of Li is 15-40%. + A content of 15% or higher is sufficient to achieve this effect, while a content below 40% is sufficient to suppress glass instability. Li + The preferred content is 20-40%.

[0034] Na + It is a component that stabilizes glass. In glass containing Na... + In the case of Na + The preferred content is 0.1% to 15%. If Na... + When the content of Na is above 0.1%, its effect can be fully obtained, while when it is below 15%, the decrease in Young's modulus can be effectively suppressed. +The content is preferably 0.1-10%, more preferably 0.1-6%.

[0035] K + It is not an essential component, but it is used to lower the melting temperature and liquidus temperature of glass. However, in the presence of K... + In such cases, the strength may decrease, so it is preferable to not contain it.

[0036] Ca 2+ It is a component that increases the Young's modulus of glass, improves its weather resistance, and stabilizes it. In glass containing Ca... 2+ In the case of Ca 2+ The upper limit of the content of [certain substances] is preferably below 10%. If Ca... 2+ When the content of Ca is below 10%, it can effectively suppress glass instability and, moreover, effectively suppress the deterioration of devitrification. 2+ The preferred content is 0-6%.

[0037] Ba 2+ It is a component that increases the Young's modulus of glass, improves its weather resistance, and stabilizes it. In glass containing Ba... 2+ In the case of Ba 2+ The upper limit of its content is preferably below 10%. If Ba... 2+ When the content of Ba is below 10%, it can effectively suppress glass instability and, moreover, effectively suppress the deterioration of devitrification. 2+ The preferred content is 0-6%.

[0038] Sr 2+ It is not an essential component, but it is used to increase the Young's modulus of glass and improve its weather resistance. In glass containing Sr... 2+ In the case of Sr 2+ The upper limit of its content is preferably below 5%. If Sr... 2+ When the content of Sr is below 5%, it can effectively suppress glass instability and, moreover, effectively suppress the deterioration of devitrification. 2+ The content of [the substance] is more preferably 0-2%, and even more preferably none.

[0039] Mg 2+ It is not an essential component, but it is used to increase the Young's modulus of glass and improve its weather resistance. In glass containing Mg... 2+ In the case of Mg 2+ The upper limit of Mg content is preferably below 5%. 2+ When the content of Mg is below 5%, it can effectively suppress glass instability and, moreover, effectively suppress the deterioration of devitrification. 2+ The content of [the substance] is more preferably 0-2%, and even more preferably none.

[0040] Zn2+ It is not an essential component, but it is used to increase the Young's modulus of glass and improve its weather resistance. (In glass containing Zn...) 2+ In the case of Zn 2+ The upper limit of Zn content is preferably below 10%. 2+ When the content of Zn is below 10%, it can effectively suppress glass instability and, moreover, effectively suppress the deterioration of devitrification. 2+ The content of [the substance] is more preferably 0-5%, and even more preferably 0-2%.

[0041] The glass in this embodiment may contain 0-1% Sb as an optional cation component. 3+ Sb 3+ It is not an essential component, but it has the effect of improving transmittance in the visible light region. In the presence of Sb... 3+ In cases where its concentration is below 1%, the decrease in glass stability can be sufficiently suppressed. 3+ The content is preferably 0.01-0.8%, more preferably 0.05-0.5%, and even more preferably 0.1-0.3%.

[0042] The glass of this embodiment may further contain other components typically found in fluorophosphate glasses, such as S, Si, and B, as optional cationic components, without impairing the effects of the present invention. The combined content of these components is preferably 5% or less.

[0043] (Anionic component)

[0044] O 2- This component, essential for stabilizing glass, improving visible light transmittance, enhancing mechanical properties such as strength, hardness, or elastic modulus, and reducing ultraviolet transmittance, preferably contains 40-95% of the required amount. If O 2- When the content is above 40%, its effect can be fully obtained, while if it is below 95%, it can fully inhibit the glass from becoming unstable, and can also fully inhibit the decline in weather resistance.

[0045] To increase the Young's modulus of glass, O 2- The content of [O] is preferably 80-95% (but not exceeding 80%). In this case, O 2- The content of [substance name] is more preferably 82-93%, and even more preferably 85-92%.

[0046] To improve the weather resistance of the glass, O 2- The preferred content is 40-80%. In this case, O 2- The content of [the substance] is more preferably 50-70%, and even more preferably 50-60%.

[0047] F - An essential component for stabilizing glass. F- The preferred content is 5-60%. If F... - A content of 5% or higher can effectively suppress the formation of unmelted material during the melting of glass raw materials. If F - When the content is below 60%, the increase in volatility and the increase in glass fiber can be effectively suppressed.

[0048] To increase the Young's modulus of glass, F - The preferred content is 5-20% (but not exceeding 20%). In this case, F - The content of [the substance] is more preferably 7-18%, and even more preferably 8-15%.

[0049] To improve the weather resistance of glass, F - The preferred content is 20-60%. In this case, F - The content of [the substance] is more preferably 30-50%, and even more preferably 40-50%.

[0050] The glass of this embodiment may further contain, without impairing the effects of the present invention, other components typically found in fluorophosphate glasses, such as Cl, Br, and I, as optional anionic components. The combined content of these components is preferably 5% or less.

[0051] Next, the content of other components besides the aforementioned components will be described in this embodiment. Furthermore, in this specification, "substantially free of" means not intended for use as a raw material; unavoidable impurities introduced from the raw material components or manufacturing process are considered to be free of these components.

[0052] The glass in this embodiment preferably contains substantially none of PbO, As2O3, V2O5, YbF3, and GdF3. PbO is a component that reduces the viscosity of the glass and improves manufacturing operability. As2O3 is a component that acts as an excellent clarifying agent, generating clarifying gases over a wide temperature range. However, PbO and As2O3 are environmentally hazardous substances, so they are preferably excluded as much as possible. V2O5 absorbs in the visible light region, so it is preferable to exclude it as much as possible for near-infrared cutoff filter glass for solid-state imaging elements that require high transmittance in the visible light region. Although YbF3 and GdF3 are components that stabilize the glass, their raw materials are relatively expensive, which increases costs, so they are preferably excluded as much as possible.

[0053] For these components, "substantially not contained" means that they are not intentionally used as raw materials, implying that the content of each component in the near-infrared cutoff filter glass is below 0.1%.

[0054] In the glass of this embodiment, nitrate or sulfate compounds containing glass-forming cations can be added as oxidizing agents or clarifying agents. Oxidizing agents increase the total Cu content in the glass. 2+ The ratio of ions is used to improve the transmittance in the visible light region and enhance the cutoff of near-infrared rays.

[0055] In the case of nitrate or sulfate compounds, the amount added is preferably 0.5 to 15% by mass relative to the raw material mixture. If the amount of nitrate or sulfate compound added is 0.5% by mass or more, the effect of improved transmittance is easily observed, while if it is below 15% by mass, difficulties in glass formation can be sufficiently suppressed. The amount of nitrate or sulfate compound added is more preferably 1 to 10% by mass, and even more preferably 3 to 8% by mass.

[0056] As nitrate compounds, they include Al(NO3)3, LiNO3, NaNO3, KNO3, Ca(NO3)2, Sr(NO3)2, Ba(NO3)2, Zn(NO3)2, Cu(NO3)2, etc. As sulfate compounds, they include Al2(SO4)3·16H2O, Li2SO4, Na2SO4, K2SO4, CaSO4, SrSO4, BaSO4, ZnSO4, CuSO4, etc.

[0057] The Young's modulus of the glass in this embodiment must be above 70 GPa. The fracture toughness of the glass (K... 1C The relationship between the glass's strength (r) and fracture energy (r) and Young's modulus (E) is as shown in the following equation. Therefore, increasing the Young's modulus of glass is effective in improving its strength.

[0058]

Mathematical Formula 1

[0059]

[0060] If the Young's modulus is less than 70 GPa, problems such as easy cracking during glass thinning and easy damage during the grinding process will occur. When the glass is used in imaging equipment, it may break. It is preferable to have a modulus of 75 GPa or higher.

[0061] Furthermore, in the glass of this embodiment, with a plate thickness of 0.1 mm, the average transmittance of light with wavelengths of 450 to 600 nm is preferably 80% or higher. If this average transmittance is 80% or higher, light in the visible light region can be sufficiently transmitted, enabling the display of a clear image when used in an imaging device.

[0062] Furthermore, the glass in this embodiment preferably has a transmittance of 50% within the wavelength range of 600-670 nm when the plate thickness is 0.1 mm. Meeting this condition requires a thin sensor capable of achieving the desired optical characteristics. Additionally, with a plate thickness of 0.1 mm, if the transmittance of light with a wavelength of 400 nm is 85% or more and the transmittance of light with a wavelength of 1200 nm is 40% or less, it becomes a thin near-infrared cutoff filter with excellent optical properties.

[0063] The transmittance value is converted to the value assuming a plate thickness of 0.1 mm. The transmittance conversion is performed using the following formula 1. T i1 This refers to the measurement of the internal transmittance of the sample (data after removing reflection loss from the back side of the surface), t1 refers to the thickness of the sample plate (e.g., 0.15–0.3 mm), T i2 t1 refers to the converted transmittance, and t2 refers to the converted plate thickness (0.1 mm in the case of this invention).

[0064]

Mathematical Formula 2

[0065]

[0066] Because the near-infrared cutoff filter glass of this embodiment can accommodate the miniaturization and thinning of imaging equipment and its peripheral components, good spectral characteristics can be obtained even when the glass thickness is relatively thin. The glass 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. Furthermore, the lower limit of the glass thickness is not particularly limited, but considering the strength to prevent breakage during manufacturing or handling when mounted on the imaging equipment, it is preferably 0.03 mm or more, more preferably 0.05 mm or more.

[0067] The glass of this embodiment can be formed into a near-infrared cut-off filter by forming an optical multilayer film on at least one side of the glass after it has been shaped into a predetermined shape. Examples of optical multilayer films include IR cut-off films (films that reflect near-infrared rays), UV / IR cut-off films (films that reflect ultraviolet and near-infrared rays), UV cut-off films (films that reflect ultraviolet rays), and anti-reflective films. These optical films can be formed by known methods such as vapor deposition or sputtering.

[0068] An adhesion strengthening film can be provided between the glass and the optical multilayer film. By providing this film, the adhesion between the glass and the optical multilayer film can be improved, and film peeling can be suppressed. Examples of adhesion strengthening 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 silicon fluoride. Substances containing fluorine or oxygen exhibit even higher adhesion, particularly magnesium fluoride and / or titanium dioxide, which improve adhesion to the glass or film, making them preferred as adhesion strengthening films. The adhesion strengthening film can be a single layer or two or more layers. In the case of two or more layers, multiple substances can be combined.

[0069] The near-infrared cutoff filter glass of this embodiment can be prepared as follows: Weigh and mix the raw materials to achieve the above-mentioned composition range (mixing step). Place the raw material mixture in a platinum crucible and heat it in an electric furnace at a temperature of 700-900°C to melt it (melting step). After thorough stirring and clarification, pour it into a mold, cut and grind it to form a flat plate of a specified thickness (forming step).

[0070] In the melting process of the above-described manufacturing method, the highest temperature of the glass during melting is preferably below 900°C. This is because if the highest temperature of the glass during melting exceeds this temperature, the transmittance characteristics deteriorate, and the diffusion of fluorine is promoted, making the glass unstable. More preferably, the temperature is below 880°C, even more preferably below 850°C, and still more preferably below 820°C.

[0071] Furthermore, if the temperature in the above melting process is too low, problems such as devitrification and excessive melting time may occur. Therefore, it is preferable to use a temperature of 750°C or higher, and more preferably 800°C or higher.

[0072] Example

[0073] Embodiments and comparative examples of the present invention are shown in Tables 1 to 3. Examples 1 to 10 and 20 to 22 are embodiments of the present invention, and Examples 11 to 19 are comparative examples of the present invention.

[0074] [Glass Preparation]

[0075] For these glasses, the raw materials were weighed and mixed to achieve the glass composition shown in Tables 1-3 (cation % and anion %). The mixture was placed in a platinum crucible with an internal volume of approximately 1 L and melted, clarified, and stirred at 800-900°C for 2 hours. The mixture was then poured into a rectangular mold (100 mm long × 80 mm wide × 20 mm high) preheated to approximately 50-500°C. The mold was then slowly cooled to 360-440°C at a rate of approximately 1°C / min to obtain the sample. Next, the back surface was optically ground to obtain glass with a thickness of 0.15-0.3 mm.

[0076] In addition, the raw materials for each type of glass use the following substance, namely P 5+ In the case of Al, it is selected from H3PO4 and Al(PO3)3. 3+ In the case of Li, it is selected from AlF3, Al(PO3)3, and Al2O3. + In the case of Sr, it is selected from one of LiF, LiNO3, Li2CO3 and LiPO3. 2+ In the case of Ba, it is selected from SrF2, SrCO3, and Sr(PO3)2. 2+ In the case of Na, it is selected from BaF2, BaCO3, and Ba(PO3)2. + K is selected from NaCl, NaBr, NaI, NaF, and Na(PO3). + Ca 2+ In the case of Cu, it is selected from fluorides, carbonates, and metaphosphates. 2+ Cu + In this case, it is CuO.

[0077] [evaluate]

[0078] The transmittance of light with wavelengths from 350 to 1200 nm was measured using a spectrophotometer (V-570 manufactured by Nippon Spectrophotometer Co., Ltd.). The measurement results were converted to transmittance for a plate thickness of 0.1 mm using the method described above. Tables 1 to 3 show the transmittance of light with wavelengths of 400 nm, 420 nm, and 1200 nm converted to a plate thickness of 0.1 mm. Furthermore, the wavelengths at which the transmittance in the near-infrared region reaches 50% (IR half-peak) were calculated from the converted transmittance. In addition, transmittance measurements were not performed in Examples 13 to 18 due to devitrification (data is not recorded in Table 2).

[0079] Meltability is evaluated using the following steps. First, the glass is melted at 800–900°C for 2 hours. The presence of devitrification pits in the molten glass is then visually confirmed. Devitrification pits are marked as ×, and those not seen are marked as ○.

[0080] The Young's modulus of glass with a thickness of 0.15–0.3 mm was measured using an ultrasonic thickness gauge (Olympus Corporation 35DL) via the ultrasonic pulse method. The average values ​​of the results from two measurements are recorded in Tables 1–3.

[0081] [Table 1]

[0082]

[0083] [Table 2]

[0084]

[0085] [Table 3]

[0086]

[0087] Furthermore, for Examples 8 (Example) and 19 (Comparative Example), the transmittance converted to a plate thickness of 0.1 mm is shown below. Figure 1 .

[0088] In the various embodiments of the present invention (Examples 1 to 10, Examples 20 to 22), glass with good optical properties, no devitrification (good solubility) and a Young's modulus of 70 GPa or higher is obtained.

[0089] In contrast, in Example 12, which serves as a comparative example, because Li + Content / ΣR' + With a modulus less than 0.75, it is a glass with a low Young's modulus.

[0090] Furthermore, in Examples 13 to 18, due to (Ca) 2++ Ba 2+ ) / ΣR 2+ It is less than 0.75, therefore it causes devitrification.

[0091] The effect of Sr on solubility was confirmed by the following method. Glasses were prepared by subtracting certain amounts of Sr, Ca, and Ba from the glass of Example 15 (Examples 11 (Sr reduced by only 2% from Example 15), Example 16 (Ca reduced by only 2% from Example 15), and Example 17 (Ba reduced by only 2% from Example 15)). The solubility was then confirmed. The results showed that only Example 11 exhibited good solubility, indicating that reducing Sr contributes to improved solubility.

[0092] The effect of Mg on solubility was confirmed by the following method. A glass (Example 10) made from the glass of Example 18 without Mg was prepared, and its solubility was confirmed. The results showed that the glass of Example 10 had good solubility, indicating that reducing Mg helps improve solubility.

[0093] Furthermore, the effect of Al content on Young's modulus was confirmed by the following method. The Young's modulus of glasses from Examples 20 to 22, which were obtained by only changing the Al content (converting to ensure the total cation percentage of components other than Al reaches 100%), was compared. The results showed that as the Al content increased, the Young's modulus of the glass increased, indicating that increasing the Al content within a certain range helps to improve the Young's modulus.

[0094] Furthermore, embodiments of the present invention are shown in Table 4. Examples 23 to 29 are embodiments of the present invention.

[0095] [Glass Preparation]

[0096] For these glasses, the raw materials were weighed and mixed to achieve the composition (cation % and anion %) shown in Table 4 after molten forming. This mixture was placed in a platinum crucible with an internal volume of approximately 1 L and melted, clarified, and stirred at 800–900 °C for 1–4 hours. The mixture was then poured into a rectangular mold (100 mm long × 80 mm wide × 20 mm high) preheated to approximately 50–500 °C. The mold was then slowly cooled to 360–440 °C at a rate of approximately 1 °C / min to obtain the sample. Next, the back surface was optically ground to obtain glass with a thickness of 0.15–0.3 mm.

[0097] In addition, the raw materials used for each type of glass are those substances mentioned above. Furthermore, the evaluation methods for each item are those mentioned above.

[0098] [Table 4]

[0099]

[0100] In the various embodiments of the present invention (Examples 23 to 29), glass with good optical properties, no devitrification (good solubility) and a Young's modulus of 70 GPa or higher is obtained.

[0101] Furthermore, the effect of F content on Young's modulus was confirmed by the following method. The Young's modulus of glasses from Examples 27 to 29, obtained by varying the F content, was compared using the same amount of glass raw material but with only the melting time changed. The results showed that as the F content decreased, the Young's modulus of the glass increased, indicating that reducing the amount of F within a certain range helps to improve the Young's modulus.

[0102] Various embodiments have been described above with reference to the accompanying drawings, but the present invention is not limited to these examples. Those skilled in the art will obviously conceive of various modifications or variations within the scope of the claims, and it should be understood that these also fall within the technical scope of the present invention. Furthermore, the various constituent elements of the above embodiments can be arbitrarily combined without departing from the spirit of the invention.

[0103] Furthermore, this application is based on Japanese Patent Application No. 2020-217105, filed on December 25, 2020, the contents of which are incorporated herein by reference.

[0104] Industrial applications

[0105] According to the present invention, it is a composition that is not easily devitrified even when the content of Cu component is high during thinning. It can be melted at low temperature, thereby increasing the transmittance of light in the visible light region. Therefore, it is very useful for near-infrared cut-off filters in miniaturized and thin imaging devices.

Claims

1. A fluorophosphate glass, characterized in that, It contains P, F, and O as essential components, and the cation percentage is [missing information]. With 2+ for 5~14%, Li + is 25.7 to 40%, Na + 0.1~15%, Zn-free 2+ , (Ca 2+ Ba content 2+ (content) / ΣR 2+ It ranges from 0.86 to 1.0, where ΣR 2+ It refers to Ba 2+ 、Sr 2+ Ca 2+ Mg 2+ Total measurement, Li + Content / ΣR' + It is 0.75 to 1.0 but does not include 1.0, where ΣR' + It refers to Li + Na + Total measurement, Its Young's modulus is above 70 GPa. "Cation%" refers to the content of each cationic component as a mole percentage when the total content of all cationic components in the glass is 100 mol%.

2. The fluorophosphate glass as described in claim 1, characterized in that, It contains cation%: That + 5.1~15%.

3. The fluorophosphate glass as described in claim 1 or 2, characterized in that, Li + Content / ΣR' + It is 0.8 to 0.9, where ΣR' + It refers to Li + Na + Total measurement.

4. The fluorophosphate glass as described in claim 1, characterized in that, It contains cation%: P 5+ 30～60％、 Al 3+ 4～20％、 ΣR’ + 20~50%、 That + 25.7~40%, That + 0.1~15%, ΣR 2+ 1~20%、 Mg 2+ 0~5%、 That 2+ 0~10%, Sr 2+ 0～5％、 Not 2+ 0~10%, With 2+ 5~14%; Anions %: F - 20～60％、 O 2- 40～80％， Where ΣR' + It refers to Li + Na + The total quantity, ΣR 2+ It refers to Ba 2+ 、Sr 2+ Ca 2+ Mg 2+ The total measurement, "anion%", refers to the content of each anion component expressed as a mole percentage when the total content of all anion components contained in the glass is 100 mol%.

5. The fluorophosphate glass as described in claim 1, characterized in that, It contains cation%: P 5+ 30～60％、 Al 3+ 4～20％、 ΣR’ + 20~50%、 That + 25.7~40%, That + 0.1~15%, ΣR 2+ 1~20%、 Mg 2+ 0~5%、 That 2+ 0~10%, Sr 2+ 0～5％、 Not 2+ 0~10%, With 2+ 5~14%; Anions %: F - 5-20% but excluding 20%, O 2- 80-95% but not exceeding 80%, Where ΣR' + It refers to Li + Na + The total quantity, ΣR 2+ It refers to Ba 2+ 、Sr 2+ Ca 2+ Mg 2+ The total measurement, "anion%", refers to the content of each anion component expressed as a mole percentage when the total content of all anion components contained in the glass is 100 mol%.

6. The fluorophosphate glass as described in claim 1 or 2, characterized in that, With a plate thickness of 0.1mm, The wavelength range where transmittance reaches 50% is 600–670 nm. The transmittance of light with a wavelength of 400nm is over 85%. The transmittance of light with a wavelength of 1200nm is below 40%.

7. A near-infrared cutoff filter made of fluorophosphate glass according to any one of claims 1 to 6.

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