Optical filter glass and optical filters

Abstract

To provide glass for optical filters and an optical filter with which it is possible to maintain transmittance of light in a short wavelength infrared region high while suppressing transmittance of light in a near-infrared region low.SOLUTION: Glass for optical filters and the optical filter according to the present invention are as follows. [1] Glass for optical filters, of which transmittance in a wavelength 1550 nm is 25% or greater and average transmittance in wavelengths 700-1200 nm is 5% or less. [2] Glass for optical filters stated in [1] above, which is phosphate glass containing Cu, and of which average transmittance in wavelengths 430-550 nm is 80% or greater, average transmittance in wavelengths 800-950 nm is 2% or less, and average transmittance in wavelengths 1000-1200 nm is 3% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to glass for optical filters, which are used in color correction filters for solid-state imaging devices such as digital still cameras and color video cameras, and which have excellent light transmittance in the short-wavelength infrared region and excellent light absorption in the near-infrared region, and to optical filters. [Background technology]

[0002] In recent years, with the advancement of autonomous driving technology, sensing cameras installed in automobiles have become more multifunctional. For example, in addition to conventional image sensing using light in the visible light range, a sensing technology called LiDAR (Light detection and ranging) that uses light in the short-wavelength infrared range is also being used. In particular, the wavelength range of over 1200nm to 1600nm in the short-wavelength infrared range is known as an eye-safe wavelength range that causes less damage to the eyes, and light with a wavelength of 1550nm in particular is becoming increasingly important.

[0003] The sensing camera uses a solid-state imaging element that can capture images from the visible light range to the non-visible light range including the short-wavelength infrared range, making it possible to perform optical sensing using both visible light and short-wavelength infrared light with the same element. However, because such a solid-state imaging element also has absorption sensitivity in the near-infrared range, it is not possible to obtain good color reproducibility in images in the visible light range as is. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-202127 [Patent Document 2] Japanese Patent Publication No. 2010-8908 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional optical filters use glass that transmits visible light to short-wavelength infrared light, and a dielectric multilayer film that reflects near-infrared light to block it. However, these optical filters have incident angle dependency in their spectral transmittance, which can cause ghosts and flares that affect image quality and can degrade sensing accuracy in the visible and long-wavelength infrared regions. Such optical filters are disclosed in Patent Document 1.

[0006] The copper (Cu)-doped glass described in Patent Document 2 can cut near-infrared light (wavelengths of 700 nm to 1200 nm) through the absorption of copper ions, which have absorption around a wavelength of 900 nm. However, the optical properties of the glass focus only on the wavelength range used in solid-state imaging devices for digital cameras, and no consideration is given to the short-wavelength infrared range (wavelengths of over 1200 nm to 1600 nm).

[0007] The present invention has been made against this background, and an object of the present invention is to provide a glass for optical filters and an optical filter that can maintain a high transmittance of light in the short-wavelength infrared region while suppressing the transmittance of light in the near-infrared region to a low level. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that, by providing specific optical properties, it is possible to obtain glass for optical filters and optical filters that can maintain a high transmittance of light in the short-wavelength infrared region while suppressing the transmittance of light in the near-infrared region to a low level compared to conventional optical filters.

[0009] The glass for optical filters and the optical filters of the present invention are as follows. [1] Transmittance of 25% or more at wavelength 1550nm, Average transmittance of 5% or less for wavelengths between 700 and 1200 nm This is glass for optical filters. [2] It is a phosphate glass containing Cu, Average transmittance of 80% or more for wavelengths between 430 and 550 nm Average transmittance of 2% or less for wavelengths between 800 and 950 nm Average transmittance of 1000-1200nm wavelength is less than 3%. The glass for optical filters according to [1] above, wherein [3] The glass for optical filters according to [1] or [2] above, wherein the wavelength at which the glass exhibits a transmittance of 50% in the wavelength range of 600-800 nm is 615 nm or more. [4] In terms of oxide mass%, P2O5: 50-80%, Al2O3: 5-20% ΣR2O: 0.5 to 20% (R2O is one or more components selected from Li2O, Na2O, K2O, Rb2O, and Cs2O, and ΣR2O is the total amount of R2O), ΣR′O: 0 to 15% (R′O is one or more components selected from CaO, MgO, BaO, SrO, and ZnO, and ΣR′O is the total amount of R′O), CuO: 4-20%, The glass for optical filters according to any one of the above [1] to [3], comprising: [5] The glass for optical filters according to any one of [1] to [4] above, which contains more than 7% CuO in terms of mass % on an oxide basis. [6] The glass for optical filters according to any one of [1] to [5] above, which contains 60 to 75% of P2O5 in mass % on an oxide basis. [7] The glass for optical filters according to any one of [1] to [6] above, which contains 9 to 16.5% of Al2O3 in mass % on an oxide basis. [8] The glass for optical filters according to any one of the above [1] to [7], which is substantially free of BaO. [9] The glass for optical filters according to any one of [1] to [8] above, which is substantially free of divalent cations other than Cu.

[10] The glass for optical filters according to any one of the above [1] to [9], wherein ΣR2O is more than 7% and 18% or less (R2O is one or more components selected from Li2O, Na2O, K2O, Rb2O, and Cs2O, and ΣR2O is the total amount of R2O).

[11] The glass for optical filters according to any one of [1] to

[10] above, which contains two or more components selected from Li2O, Na2O, K2O, Rb2O, and Cs2O.

[12] The glass for optical filters according to any one of [1] to

[11] above, which is substantially free of Li2O.

[13] The glass for optical filters according to any one of [1] to

[12] above, which is substantially free of B2O3.

[14] The glass for optical filters according to any one of the above [1] to

[13] , which is substantially free of F.

[15] An optical filter comprising the glass for optical filters according to any one of [1] to

[14] above. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide glass for optical filters and optical filters that can maintain a high transmittance of light in the short-wavelength infrared region while suppressing the transmittance of light in the near-infrared region to a low level. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a graph showing the transmittance of light having a wavelength of 300 to 2500 nm in Example 26 (Example) and Example 144 (Comparative Example). DETAILED DESCRIPTION OF THE INVENTION

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes in detail the embodiments of the present invention, but the present invention is not limited to the embodiments described below. In addition, in the present specification, the range "A to B" means "A or more and B or less."

[0013] Glass for optical filters (hereinafter also simply referred to as "glass") according to an embodiment of the present invention has a transmittance of 25% or more at a wavelength of 1550 nm, and an average transmittance of 5% or less at wavelengths of 700-1200 nm, measured when light is incident on the principal surface from the normal direction. The glass of this embodiment has such optical properties, making it possible to obtain glass suitable for use as an optical filter that can maintain a high transmittance of light in the short-wavelength infrared region while suppressing the transmittance of light in the near-infrared region. Specifically, for example, when imaging and sensing are performed using the same image sensor, it is possible to obtain glass suitable for use as an optical filter that can obtain images with good color reproducibility in the visible light region while also enabling sensing using infrared light with a wavelength of 1550 nm.

[0014] Here, the short-wavelength infrared range is called the eye-safe wavelength range that causes less damage to the eyes, and in this embodiment refers to the range of wavelengths from 1200 nm to 1600 nm. In particular, high transmittance around a wavelength of 1550 nm is particularly excellent from the perspective of improving sensing accuracy. In this embodiment, the near-infrared region refers to a wavelength region of 700 to 1200 nm.

[0015] The glass of this embodiment has a transmittance at a wavelength of 1550 nm of preferably 26% or more, more preferably 27% or more, and even more preferably 28% or more, and is usually 92% or less.

[0016] The glass of this embodiment has an average transmittance in the wavelength range of 700 to 1200 nm of preferably 4% or less, more preferably 3% or less, even more preferably 2% or less, particularly preferably 1.8% or less, and usually 0.0001% or more.

[0017] The glass of this embodiment is preferably a phosphate glass containing Cu, and preferably has an average transmittance of 80% or more for wavelengths of 430 to 550 nm, an average transmittance of 2% or less for wavelengths of 800 to 950 nm, and an average transmittance of 3% or less for wavelengths of 1000 to 1200 nm, measured when light is incident on the main surface from the normal direction. Such optical properties of glass make it possible to obtain images with better color reproducibility in the visible light range, for example, when imaging and sensing are performed using the same image sensor.

[0018] The average transmittance of the glass of this embodiment in the wavelength range of 430 to 550 nm is more preferably 81% or more, even more preferably 82% or more, even more preferably 83% or more, and most preferably 84% or more. The average transmittance of the glass of this embodiment in the wavelength range of 800 to 950 nm is more preferably 1.75% or less, even more preferably 1.5% or less, even more preferably 1.25% or less, and most preferably 1% or less. The average transmittance of the glass of this embodiment in the wavelength range of 1000 to 1200 nm is more preferably 2.75% or less, even more preferably 2.5% or less, even more preferably 2.25% or less, and most preferably 2% or less.

[0019] The glass of this embodiment preferably has a wavelength (IR50) of 615 nm or more at which transmittance is 50% in the wavelength range of 600-800 nm measured when light is incident on the main surface from the normal direction. Because the glass of this embodiment has such optical properties, when imaging and sensing are performed using the same image sensor, for example, the amount of red transmitted becomes equal to or greater than a certain level, making it possible to obtain images with better color reproducibility. The wavelength at which the transmittance is 50% is more preferably 617 nm or more, even more preferably 619 nm or more, even more preferably 621 nm or more, and most preferably 623 nm or more. From the viewpoint of near-infrared shielding, the wavelength at which the transmittance is 50% is preferably 650 nm or less, and more preferably 640 nm or less.

[0020] Furthermore, the transmittance described above for the glass of this embodiment is not a value converted to a specific plate thickness. This is because glass for optical filters is used, for example, in color correction filters for solid-state imaging devices or in the light receiving parts of infrared sensors, and transmittance from the visible light region to the infrared region is important, so glass is not used at a specific plate thickness. Therefore, even glasses with the same composition may or may not satisfy the above transmittance depending on the plate thickness.

[0021] When the glass of this embodiment is used as a color correction filter for a solid-state imaging device, for example, it is often used with a thickness of 2 mm or less. From the viewpoint of reducing the weight of the component, it is preferably used with a thickness of 1 mm or less, more preferably 0.5 mm or less, even more preferably 0.3 mm or less, and even more preferably 0.2 mm or less. Furthermore, from the viewpoint of ensuring the strength of the glass, it is preferably 0.05 mm or more.

[0022] When the glass of this embodiment is used in the light receiving portion of an infrared sensor, for example, it is usually used in a thickness of 3 mm or less. From the viewpoint of reducing the weight of the part, it is preferably used in a thickness of 2 mm or less, more preferably 1 mm or less, even more preferably 0.5 mm or less, and even more preferably 0.3 mm or less. Furthermore, from the viewpoint of ensuring the strength of the glass, it is preferably 0.05 mm or more.

[0023] Each component that can constitute the glass of this embodiment and its suitable content (expressed as mass% on an oxide basis) are described below. In this specification, unless otherwise specified, the content of each component and the total content are expressed as mass% on an oxide basis.

[0024] P2O5 is the main component that forms glass and is a component that enhances near-infrared blocking properties. If the P2O5 content is 50% or more, this effect is sufficiently obtained, and if it is 80% or less, problems such as glass instability and reduced weather resistance are unlikely to occur. Therefore, the content is preferably 50 to 80%, more preferably 52 to 78%, even more preferably 54 to 77%, even more preferably 56 to 76%, and most preferably 60 to 75%.

[0025] Al2O3 is the main component that forms glass and is a component that increases the strength of the glass, etc. If the Al2O3 content is 5% or more, this effect is sufficiently obtained, and if it is 20% or less, problems such as glass instability and reduced near-infrared blocking properties are unlikely to occur. Therefore, the content is preferably 5 to 20%, more preferably 6 to 18%, even more preferably 7 to 17%, still more preferably 8 to 17%, and most preferably 9 to 16.5%. If the Al2O3 content is 9% or more, the weather resistance of the glass can be improved.

[0026] R2O (where R2O is one or more components selected from Li2O, Na2O, K2O, Rb2O, and Cs2O) is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, stabilizes glass, and so on. If the total amount of R2O (ΣR2O) is 0.5% or more, these effects are sufficiently obtained, and if it is 20% or less, the glass is less likely to become unstable, which is preferable. Therefore, the content is preferably 0.5 to 20%, more preferably 1 to 20%, even more preferably 2 to 20%, still more preferably 3 to 20%, and most preferably 4 to 20%.

[0027] Li2O is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass, and so on. The Li2O content is preferably 0 to 15%. A Li2O content of 15% or less is preferred because it is less likely to cause problems such as glass instability and reduced near-infrared blocking properties. The Li2O content is more preferably 0 to 8%, even more preferably 0 to 7%, even more preferably 0 to 6%, and most preferably substantially no Li2O is contained.

[0028] In the present invention, "substantially free of a specific component" means that the component is not intentionally added, and does not exclude the component being unavoidably mixed in from raw materials, etc., to the extent that it does not affect the desired properties.

[0029] Na2O is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, and stabilizes glass. The Na2O content is preferably 0 to 15%. If the Na2O content is 15% or less, the glass is less likely to become unstable, which is preferable. The Na2O content is more preferably 0.5 to 14%, even more preferably 1 to 13%, and even more preferably 2 to 13%.

[0030] K2O is a component that has the effect of lowering the melting temperature of glass, lowering the liquidus temperature of glass, etc. The K2O content is preferably 0 to 15%. If the K2O content is 15% or less, the glass is less likely to become unstable, which is preferable. The K2O content is more preferably 0.5 to 14%, even more preferably 1 to 13%, and even more preferably 2 to 13%.

[0031] RbO is a component that has the effects of lowering the melting temperature of glass, lowering the liquidus temperature of glass, etc. The RbO content is preferably 0 to 15%. If the RbO content is 15% or less, the glass is less likely to become unstable, which is preferable. The RbO content is more preferably 0.5 to 14%, even more preferably 1 to 13%, and even more preferably 2 to 13%.

[0032] CsO is a component that has the effect of lowering the melting temperature of glass, lowering the liquidus temperature of glass, etc. The CsO content is preferably 0 to 15%. If the CsO content is 15% or less, the glass is less likely to become unstable, which is preferable. The CsO content is more preferably 0.5 to 14%, even more preferably 1 to 13%, and even more preferably 2 to 13%.

[0033] In addition, when two or more types of alkali metal components represented by R2O are added simultaneously, a mixed alkali effect occurs in the glass, and R + The mobility of ions is reduced, so that when the glass comes into contact with water, the H + Ions and R in glass + This inhibits the hydration reaction caused by ion exchange, improving the weather resistance of the glass. Therefore, the glass of this embodiment preferably contains two or more components selected from Li2O, Na2O, K2O, Rb2O, and Cs2O. In this case, the total amount (ΣR2O) of R2O (where R2O includes Li2O, Na2O, K2O, Rb2O, and Cs2O) is preferably 7 to 18% (but not including 7%). If the total amount of R2O exceeds 7%, its effects are sufficiently obtained, and if it is 18% or less, problems such as glass instability, reduced near-infrared blocking properties, and reduced glass strength are unlikely to occur, which is preferable. Therefore, ΣR2O is preferably more than 7% and 18% or less, more preferably 7.5 to 17%, even more preferably 8 to 16%, even more preferably 8.5% to 15%, and most preferably 9 to 14%.

[0034] R'O (where R'O is one or more components selected from CaO, MgO, BaO, SrO, and ZnO) is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, stabilizes glass, and increases the strength of glass. The total amount of R'O (ΣR'O) is preferably 0 to 15%. If the total amount of R'O is 15% or less, problems such as glass instability, reduced near-infrared blocking ability, reduced short-wavelength infrared transmittance, and reduced glass strength are unlikely to occur, which is preferable. The amount is more preferably 0 to 13%, and even more preferably 0 to 11%. The amount is even more preferably 0 to 9%, and even more preferably 0 to 8%.

[0035] The glass of this embodiment preferably contains substantially no divalent cations other than Cu, for the reasons described below.

[0036] When the glass of this embodiment contains CuO, Cu 2+ Light in the near-infrared region is cut off by the light absorption of ions. 2- Cu split by the electric field of ions 2+ This occurs due to electron transitions between the d orbitals of the ions. The splitting of the d orbitals occurs in Cu 2+ O around the ion 2- This is promoted by reducing the symmetry of the ion. For example, O 2- When positive ions are present around an ion, the electric field of the positive ions causes the 2- Ions are attracted, and O 2- The symmetry of the ions decreases. As a result, the splitting of d orbitals is promoted, and light absorption occurs due to electronic transitions between the split d orbitals, weakening the light absorption ability in the near-infrared region and strengthening the light absorption ability in the short-wavelength infrared region. Since the strength of the electric field of cations increases with the valence of the ions, adding oxides containing divalent cations other than Cu to glass may reduce the near-infrared blocking ability and reduce the transmittance of short-wavelength infrared light.

[0037] CaO is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, stabilizes glass, and increases the strength of glass. The CaO content is preferably 0 to 10%. A CaO content of 10% or less is preferred because it is less likely to cause problems such as glass instability, reduced near-infrared blocking properties, and reduced transmittance of short-wavelength infrared rays. The CaO content is more preferably 0 to 8%, even more preferably 0 to 6%, and even more preferably 0 to 5%. Most preferably, the glass contains substantially no CaO.

[0038] MgO is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, stabilizes glass, and increases the strength of glass. The MgO content is preferably 0 to 15%. An MgO content of 15% or less is preferred because it is less likely to cause problems such as glass instability, reduced near-infrared blocking properties, and reduced transmittance of short-wavelength infrared rays. The content is more preferably 0 to 13%, even more preferably 0 to 10%, and even more preferably 0 to 9%. Most preferably, the glass is substantially free of MgO.

[0039] BaO is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, stabilizes glass, and so on. The BaO content is preferably 0 to 10%. A BaO content of 10% or less is preferred because it is less likely to cause problems such as glass instability, reduced near-infrared blocking properties, and reduced transmittance of short-wavelength infrared rays. The BaO content is more preferably 0 to 8%, even more preferably 0 to 6%, and even more preferably 0 to 5%. The BaO content may be 0.1% or more. Most preferably, BaO is substantially not contained.

[0040] SrO is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, stabilizes glass, etc. The SrO content is preferably 0 to 10%. If the SrO content is 10% or less, problems such as glass instability, reduced near-infrared blocking properties, and reduced transmittance of short-wavelength infrared rays are unlikely to occur, which is preferable. The content is more preferably 0 to 8%, and even more preferably 0 to 7%. Most preferably, SrO is substantially not contained.

[0041] ZnO has the effect of lowering the melting temperature of glass, lowering the liquidus temperature of glass, etc. The ZnO content is preferably 0 to 15%. If the ZnO content is 15% or less, problems such as deterioration of the melting point of the glass, deterioration of the near-infrared blocking ability, and deterioration of the transmittance of short-wavelength infrared rays are unlikely to occur, which is preferable. The ZnO content is more preferably 0 to 13%, even more preferably 0 to 10%, and even more preferably 0 to 9%. Most preferably, ZnO is substantially not contained.

[0042] CuO is a component for blocking near-infrared rays. If the CuO content is 4% or more, this effect is sufficiently obtained, and if it is 20% or less, problems such as a decrease in transmittance in the visible light region and a decrease in transmittance in the short-wavelength infrared region are unlikely to occur, so this is preferable. The CuO content is more preferably 4 to 19.5%, even more preferably 5 to 19%, and even more preferably 6 to 18.5%. Furthermore, it is even more preferably more than 7%. In particular, when the glass does not substantially contain divalent cations other than Cu, a CuO content of more than 7% can further improve the near-infrared blocking properties and the short-wavelength infrared transmittance. The CuO content is most preferably 7 to 18% (but excluding 7%).

[0043] B2O3 may be contained in a range of 10% or less to stabilize the glass. A B2O3 content of 10% or less is preferable because problems such as a deterioration in the weather resistance of the glass, a decrease in the near-infrared blocking ability, and a decrease in the transmittance of short-wavelength infrared rays are unlikely to occur. The B2O3 content is preferably 9% or less, more preferably 8% or less, even more preferably 7% or less, even more preferably 6% or less, and most preferably substantially no B2O3 is contained.

[0044] In the glass of this embodiment, F is an effective component for improving weather resistance, but it is an environmentally hazardous substance and there is a risk of reducing the near-infrared blocking properties. Therefore, it is preferable that F is substantially not contained.

[0045] In the glass of this embodiment, SiO2, GeO2, ZrO2, SnO2, TiO2, CeO2, WO3, Y2O3, La2O3, Gd2O3, Yb2O3, and Nb2O5 may be contained in a range of 5% or less to improve the weather resistance of the glass. A content of these components of 5% or less is preferable because problems such as a decrease in near-infrared blocking ability and a decrease in short-wavelength infrared transmittance are unlikely to occur. The content is preferably 4% or less, more preferably 3% or less, even more preferably 2% or less, and even more preferably 1% or less.

[0046] Fe2O3, Cr2O3, Bi2O3, NiO, V2O5, MoO3, MnO2, and CoO are all components that, when present in glass, reduce transmittance of near-ultraviolet light. Therefore, adding these components in excess can reduce transmittance of visible light from the ultraviolet region. Therefore, it is preferable that these components are substantially not contained in the glass.

[0047] The glass of this embodiment has an average thermal expansion coefficient of 60×10 in the range of 30°C to 300°C. -7 / ℃~180×10 -7 / °C is preferred.

[0048] When the glass of this embodiment is used as a color correction filter for a solid-state imaging device, it may be directly bonded to a packaging material because it also functions as a cover glass for hermetically sealing the solid-state imaging device. In this case, if there is a large difference in the thermal expansion coefficients between the glass and the packaging material, peeling or breakage may occur at the joint, making it impossible to maintain an airtight state.

[0049] Generally, materials such as glass, crystallized glass, ceramics, and alumina are used as packaging materials in consideration of heat resistance, and it is preferable to reduce the difference in thermal expansion coefficient between these packaging materials and the glass. Therefore, it is preferable that the thermal expansion coefficient of the glass of this embodiment is within the above range in the temperature range of 30°C to 300°C. If the thermal expansion coefficient of the glass of this embodiment is outside the above range, the difference with the thermal expansion coefficient of the packaging material will be large, and there is a risk that the airtight state will not be maintained due to peeling or breakage. A more preferable range for the thermal expansion coefficient is 65×10 -7 / ℃~175×10 -7 / °C, and a more preferable range is 70 × 10 -7 / ℃~170×10 -7 / ℃.

[0050] The glass of this embodiment can be produced, for example, as follows. First, the raw materials are weighed and mixed so that the composition falls within the above range (mixing process). This raw material mixture is placed in a platinum crucible and heated and melted in an electric furnace at a temperature of 700-1300°C (melting process). After thorough stirring and clarification, the mixture is poured into a mold, cut, polished, and formed into a plate of the specified thickness (forming process).

[0051] In the melting step of the above-mentioned manufacturing method, the highest temperature of the glass during melting is preferably 1300°C or lower. If the highest temperature of the glass during melting is below this temperature, problems such as deterioration of transmittance characteristics and accelerated fluorine volatilization, making the glass unstable, etc. are unlikely to occur. The above temperature is more preferably 1250°C or lower, even more preferably 1200°C or lower, and even more preferably 1150°C or lower.

[0052] 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 may occur, so the temperature is preferably 750°C or higher, more preferably 800°C or higher.

[0053] 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 obtain an optical filter comprising the above-described glass for optical filters. 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.

[0054] An adhesion-strengthening film may be provided between the glass and the optical multilayer film of this embodiment. The provision of an adhesion-strengthening film improves adhesion between the glass and the optical multilayer film, preventing 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-containing 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.

[0055] The optical filter of this embodiment may include an absorption layer containing a near-infrared absorbing material having a maximum absorption wavelength in the near-infrared region on at least one main surface of the glass of this embodiment. By adopting such a configuration, an optical filter with a lower transmittance of light in the near-infrared region can be obtained.

[0056] The optical filter of this embodiment is preferably made of a transparent resin selected from acrylic resin, epoxy resin, ene-thiol resin, polycarbonate resin, polyether resin, polyarylate resin, polysulfone resin, polyethersulfone resin, polyparaphenylene resin, polyarylene ether phosphine oxide resin, polyimide resin, polyamideimide resin, polyolefin resin, cyclic olefin resin, and polyester resin, and is preferably made of one of these resins alone or a mixture of two or more of these resins, to which a near-infrared absorbing dye has been added and which is contained in the absorption layer. As the near-infrared absorbing dye, it is preferable to use a near-infrared absorbing material made of at least one selected from the group consisting of squarylium dyes, phthalocyanine dyes, cyanine dyes and diimmonium dyes. [Example]

[0057] Examples will be described below, but the present invention is not limited to these examples. Examples and comparative examples of the glass for optical filters of the present invention are shown in Tables 1 to 11. Examples 1 to 143 and 146 to 156 are examples, and Examples 144 and 145 are comparative examples.

[0058] [Glass production] These glasses were prepared by weighing and mixing the raw materials to obtain the compositions (oxide mass%) shown in Tables 1 to 11, placing them in a crucible with an internal volume of approximately 400 cc, and melting them in an air atmosphere for 2 hours. The mixture was then refined and stirred, and poured into a rectangular mold measuring 100 mm long x 80 mm wide x 20 mm high that had been preheated to approximately 300°C to 500°C. It was then slowly cooled at a rate of approximately 1°C / min to obtain glass samples in the form of plates measuring 40 mm long x 30 mm wide x 0.3 mm thick or 40 mm long x 30 mm wide x 0.4 mm thick, with both sides optically polished.

[0059] The raw materials for each glass were, in the case of P2O5, one or more of H3PO4, Al(PO3)3, Mg(PO3)2, Zn(PO3)2, LiPO3, NaPO3, and KPO3. In the case of Al2O3, Al(PO3)3 was used. In the case of Li2O, one or more of LiPO3, LiNO3, and Li2CO3 were used. In the case of Na2O, one or more of NaPO3, NaNO3, and Na2CO3 were used. In the case of K2O, one or more of KPO3, KNO3, and K2CO3 were used. In the case of Rb2O, one or more of RbPO3, RbNO3, and Rb2CO3 were used. In the case of Cs2O, one or more of CsPO3, CsNO3, and Cs2CO3 were used. In the case of B2O3, one or more of PBO4, H3BO3, and BN were used. In the case of CaO, one or more of Ca(PO3)2 and CaCO3 was used. In the case of SrO, one or more of SrCO3, SrSO4, and Sr(NO3)2 were used. In the case of MgO, one or more of MgO and Mg(PO3)2 was used. In the case of BaO, one or more of Ba(NO3)2, Ba(PO3)2, and BaCO3 was used. In the case of ZnO, at least one of oxide and Zn(PO3)2 was used. In the case of SnO2, one or more of oxide and SnSO4 was used. In the case of TiO2, one or more of oxide and TiCl2 were used. In the case of WO3, one or more of oxides and CaWO4 were used. In the case of Y2O3, the oxide was used. In the case of La2O3, the oxide was used. In the case of Nb2O5, the oxide was used. In the case of CeO2, the oxide was used. In the case of CuO, one or more of oxide, Cu(PO3)2, and CuSO4 were used. In the case of Ga2O3, the oxide was used. In the case of F, one or more of AlF3, YF3, LaF3, MgF3, CaF2, SrF2, BaF2, LiF, NaF, KF, RbF and CsF were used. The raw materials for the glass are not limited to those mentioned above, and known materials can be used.

[0060] [evaluation] For the glass samples prepared as described above, the transmittance was measured using a spectrophotometer (JASCO Corporation, V-570) at wavelengths of 300-2500 nm, and for the glasses of Examples 1 to 156 (excluding Examples 11, 13, and 22), the transmittance was converted to a value for a wall thickness of 0.3 mm. For the glasses of Examples 11, 13, and 22, the transmittance at wavelengths of 300-2500 nm was converted to a value for a wall thickness of 0.4 mm. From the converted transmittances, the transmittance for light with a wavelength of 1550 nm, the average transmittance for light with wavelengths of 700-1200 nm, the average transmittance for light with wavelengths of 430-550 nm, the average transmittance for light with wavelengths of 800-950 nm, the average transmittance for light with wavelengths of 1000-1200 nm, the transmittance for light with a wavelength of 430 nm, and the transmittance for light with a wavelength of 1000 nm were obtained. Furthermore, from the transmittance measured above, the wavelength (IR50) showing a transmittance of 50% in the near-infrared region was calculated. The results are shown in Tables 1 to 11. The transmittance of light with wavelengths of 300 to 2500 nm in Example 26 (Example) and Example 144 (Comparative Example) is shown in FIG.

[0061] [Table 1]

[0062] [Table 2]

[0063] [Table 3]

[0064] [Table 4]

[0065] [Table 5]

[0066] [Table 6]

[0067] [Table 7]

[0068] [Table 8]

[0069] [Table 9]

[0070] [Table 10]

[0071] [Table 11]

[0072] Each of the examples of the present invention (Examples 1 to 143, Examples 146 to 156) had a transmittance of 25% or more at a wavelength of 1550 nm and an average transmittance of 5% or less at wavelengths of 700-1200 nm, and was able to maintain a high transmittance of light in the short-wavelength infrared region while keeping the transmittance of light in the near-infrared region low. On the other hand, in the comparative examples (Examples 144 to 145), the transmittance at a wavelength of 1550 nm was 25% or more, and the average transmittance at wavelengths of 700-1200 nm was over 5%, and the transmittance of light in the near-infrared region could not be kept low. 1, Example 26 can maintain a high transmittance of light in the visible light range (wavelength 430 to 550 nm) while suppressing the transmittance of light in the near-infrared range (wavelength 700-1200 nm) at a low level, and can also maintain a high transmittance of light in the short-wavelength infrared range (wavelengths over 1200 nm to 1600 nm). On the other hand, Example 144 cannot maintain a low transmittance of light in the near-infrared range (wavelength 700-1200 nm).

[0073] Next, the weather resistance of the glass of the examples was evaluated by determining whether or not there was any change in appearance after 100 hours under atmospheric conditions of a temperature of 85°C and a relative humidity of 85%. Specifically, glass samples showing only minor deterioration of the glass surface after the test were evaluated as "Good," while glass samples showing significant deterioration due to elution of glass components onto the surface and dripping were evaluated as "Poor."

[0074] As a result, the weather resistance of Example 4 of the present invention was rated as "×", while Examples 12, 15, 24, and 26 were rated as "◯". Examples 12, 15, 24, and 26 showed higher weather resistance than Example 4.

[0075] 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.

[0076] This application is based on a Japanese patent application (Patent Application No. 2022-056647) filed on March 30, 2022, the contents of which are incorporated herein by reference.

Claims

1. A phosphate glass containing Cu, In terms of mass % based on oxides, P2O5: 50-76%, Al2O3: 5-20%, CuO: 4-20%, ZnO: 0-4.82% Including, It is substantially free of SiO 2 , substantially free of GeO 2 ; Transmittance at wavelength 1550 nm is 25% or more, Average transmittance of wavelengths between 700 and 1200 nm is 5% or less. The wavelength showing a transmittance of 50% in the wavelength range of 600-800 nm is 617 nm or more, This is glass for optical filters.

2. An average transmittance of 80% or more for wavelengths of 430-550 nm, Average transmittance of 2% or less for wavelengths of 800-950 nm Average transmittance of 3% or less for wavelengths of 1000-1200 nm, 2. The glass for optical filters according to claim 1, wherein

3. In terms of mass % based on oxides, ΣR ２ O: 0.5-20% (R ２ O is Li ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ one or more components selected from O, ΣR ２ O is R ２ the total amount of O), ΣR′O: 0 to 15% (R′O is one or more components selected from CaO, MgO, BaO, SrO, and ZnO, and ΣR′O is the total amount of R′O), The glass for optical filters according to claim 1 , comprising:

4. 4. The glass for optical filters according to claim 3, containing more than 7% CuO in mass % on an oxide basis.

5. In terms of oxide mass%, P ２ O ５ 4. The glass for optical filters according to claim 3, wherein the glass contains 60 to 75% of the above.

6. Al, expressed as mass% on an oxide basis ２ O ３ 4. The glass for optical filters according to claim 3, containing 9 to 16.5% of

7. 4. The glass for optical filters according to claim 3, which is substantially free of BaO.

8. 4. The glass for optical filters according to claim 3, which is substantially free of divalent cations other than Cu.

9. ΣR ２ O contains more than 7% and not more than 18% (R ２ O is Li ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ one or more components selected from O, ΣR ２ O is R ２ 4. The glass for optical filters according to claim 3, wherein the total amount of O is 0.

10. Li ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ 4. The glass for optical filters according to claim 3, which contains two or more components selected from the group consisting of:

11. Li ２ 4. The glass for optical filters according to claim 3, which is substantially free of O.

12. B ２ O ３ 4. The glass for optical filters according to claim 3, which is substantially free of:

13. 4. The glass for optical filters according to claim 3, which is substantially free of F.

14. An optical filter comprising the glass for optical filters according to any one of claims 1 to 13.

15. A solid-state imaging device comprising the glass for optical filters according to any one of claims 1 to 13.

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