Optical glass for near-infrared light absorption, optical device, and imaging device

Abstract

The present invention relates to an optical glass for near-infrared light absorption, wherein the optical glass contains, as mass% on an oxide basis, 10-50% Yb2O3 and has a maximum refractive index (nIR) of 1.50-1.70 for light with a wavelength of 900-1000 nm.

Description

Optical glass for near-infrared light absorption, optical devices, and imaging devices

[0001] The present invention relates to optical glass for near-infrared light absorption, optical devices, and imaging devices.

[0002] Imaging devices using solid-state image sensors have expanded their applications to include surveillance cameras and in-vehicle cameras, which capture images day and night. In recent years, near-infrared (IR) light sensing technologies such as LiDAR (Light detection and ranging) have advanced, and for example, Patent Document 1 describes a sensor that uses light with a wavelength of 900 nm to 1000 nm. In such sensing technologies, light emitted from the sensor is reflected by the object, and the distance to the object and its properties are analyzed by measuring this reflected light with an imaging device. However, when a sensor is placed near an imaging device, light with a wavelength of 900 nm to 1000 nm can become stray light and enter the imaging device, causing unexpected malfunctions (such as adverse effects on the color of the captured image) when it enters the camera sensor of the imaging device.

[0003] Using IR light absorbing glass, particularly Cu-containing phosphate glass, as an optical filter in front of the camera sensor allows for efficient absorption of light with wavelengths of 900 nm to 1000 nm (Patent Document 2). However, Cu-containing phosphate glass alone has weak IR light absorption and cannot adequately shield against IR light. On the other hand, shielding with a reflective film may generate further stray light due to reflection.

[0004] Therefore, one method is to install an optical filter in front of the camera sensor, and then install another IR light absorbing glass in front of the optical filter to compensate for the IR light absorption capacity. Patent Document 3 describes using an IR light absorbing lens containing Cu to compensate for the IR light absorption capacity. In addition, glass containing Yb is known as a glass that can absorb light with wavelengths of 900 nm to 1000 nm (Patent Document 4).

[0005] Japanese Patent Publication No. 2014-525091, Japanese Patent Publication No. 2010-8908, Japanese Patent Publication No. 2007-101585, Japanese Patent Publication No. 2015-151321

[0006] However, as described in Patent Documents 2 and 3, when using Cu-containing glass, a decrease in visible light transmittance is unavoidable. Also, as described in Patent Document 4, Yb ２ O ３ Yb is known as a component that increases the refractive index, and in glass containing Yb, although the transmittance of visible light is maintained, the refractive index of the glass and the reflectivity become high, which may further generate stray light of IR light.

[0007] The present invention aims to provide an optical glass for near-infrared light absorption that exhibits excellent absorption characteristics for near-infrared light, particularly light with wavelengths of 900 nm to 1000 nm, and suppresses near-infrared light reflection characteristics.

[0008] This invention relates to a glass having the following configuration: Yb, expressed as a mass percentage based on oxide. ２ O ３ Optical glass for near-infrared light absorption, containing 10% to 50% of [a specific substance], and having a maximum refractive index (nIR) of 1.50 to 1.70 for light with wavelengths of 900 nm to 1000 nm.

[0009] According to the present invention, it is possible to provide an optical glass for absorbing near-infrared light that has excellent absorption characteristics for near-infrared light, particularly light with wavelengths of 900 nm to 1000 nm, and suppresses the reflection characteristics of near-infrared light.

[0010] Figure 1 shows the spectral transmittance curve of the near-infrared light absorbing optical glass of Example 1.

[0011] <Optical Glass for Near-Infrared Light Absorption> The optical glass for near-infrared light absorption according to an embodiment of the present invention (hereinafter also referred to as "the glass of this embodiment") has a composition of Yb, expressed in mass % on an oxide basis. ２ O ３is contained in an amount of 10% to 50%, and the maximum refractive index (nIR) for light with a wavelength of 900 nm to 1000 nm is 1.50 to 1.70. By containing ytterbium (Yb) in the glass composition, the glass exhibits excellent absorption characteristics for near-infrared light, particularly light with a wavelength of 900 nm to 1000 nm. Furthermore, since the change in spectral characteristics in the wavelength region transitioning from the absorption band to the transmission band is steep, the transmittance in regions other than the maximum absorption wavelength region can be maintained at a high level, and the transmittance in the visible light region is excellent. In addition, since light is cut off by the absorption characteristics, the influence of the incident angle on the spectral characteristics can be reduced, unlike light shielding that utilizes the reflection characteristics of a reflective film. Further, by setting the maximum refractive index (nIR) for light with a wavelength of 900 nm to 1000 nm to 1.50 to 1.70, the reflection characteristics for near-infrared light, particularly light with a wavelength of 900 nm to 1000 nm, are suppressed, and as a result, the generation of stray light due to reflection can be inhibited.

[0012] The respective components that can constitute the glass of the present embodiment and their preferable contents (expressed in mass% on an oxide basis) are described below. In the present specification, unless otherwise specified, the content of each component and the total content are expressed in mass% on an oxide basis.

[0013] Yb ２ O ３ is an essential component for efficiently absorbing light in the vicinity of a wavelength of 900 nm to 1000 nm. In the glass of the present embodiment, Yb ２ O ３ has a content of 10% to 50%. When the content of Yb ２ O ３ is 10% or more, sufficient absorption performance can be obtained, and when it is 50% or less, problems such as deterioration of the devitrification property of the glass, deterioration of meltability, and generation of stray light due to fluorescence are less likely to occur. The content of Yb ２ O ３ is preferably 11% to 50%, more preferably 15% to 50%, even more preferably 20% to 50%, still more preferably 25% to 50%, particularly preferably 30% to 50%, and most preferably 35% to 50%.

[0014] Silicon (Si) is the main component that forms glass, and is a component that increases the devitrification resistance and viscosity with respect to liquidus temperature of glass, and also adjusts the nIR, so the glass of this embodiment may contain silicon. ２ A content of 0.1% or more is preferable because it is less likely to cause problems such as glass instability, reduced weather resistance, and the formation of striations in the glass. ２ If the content is 50% or less, problems such as deterioration of glass meltability are less likely to occur. ２ The content is preferably 0.1% to 50%, more preferably 5% to 50%, even more preferably 10% to 50%, even more preferably 15% to 50%, particularly preferably 15% to 40%, and most preferably 15% or more and less than 30%.

[0015] Boron (B) is the main component that forms the glass, and is a component that increases the devitrification resistance and viscosity with respect to liquidus temperature of the glass, and also adjusts the nIR, so the glass of this embodiment may contain boron. In the glass of this embodiment, B ２ O ３ If the content is 1% or more, problems such as glass instability are less likely to occur. ２ O ３ If the content is 20% or less, problems such as a decrease in the weather resistance of the glass and the formation of striations in the glass are less likely to occur. Therefore, B ２ O ３ The content is preferably 1% to 20%, more preferably 3% to 20%, even more preferably 5% to 20%, even more preferably 6% to 20%, particularly preferably 7% to 19%, extremely preferably 8% to 18%, and most preferably 9% to 15%.

[0016] The glass of this embodiment preferably contains at least one of silicon and boron, from the viewpoint of obtaining stable glass and facilitating adjustment of nIR. ２ and B ２ O ３The total content of SiO is preferably 2% or more from the viewpoint of minimizing problems such as glass instability, and preferably 60% or less from the viewpoint of minimizing problems such as deterioration of glass meltability. ２ and B ２ O ３ The total content is more preferably 10% to 60%, even more preferably 15% to 57%, even more preferably 20% to 55%, particularly preferably 25% to 55%, and most preferably 30% to 50%.

[0017] P ２ O ５ P is a component for improving the meltability and stability of the glass and for adjusting the nIR. In the glass of this embodiment, P ２ O ５ The content is preferably 0% to 54%. ２ O ５ If the content is 54% or less, problems such as deterioration of the glass's weather resistance, phase separation of the glass, and the formation of striations within the glass are less likely to occur. ２ O ５ The content is more preferably 1% to 54%, even more preferably 2% to 40%, even more preferably 3% to 30%, and most preferably 4% to 20%.

[0018] GeO ２ This is a component for adjusting nIR, which increases the devitrification resistance and viscosity with respect to liquidus temperature of the glass. In the glass of this embodiment, GeO ２ The content is preferably 0% to 15%. ２ If the content is 15% or less, problems such as deterioration of glass meltability are less likely to occur. ２ The content is more preferably 0% to 13%, even more preferably 0% to 11%, even more preferably 0% to 9%, and most preferably 0% to 7%.

[0019] Ga ２ O ３ This is a component for increasing the Young's modulus of the glass, improving its meltability and stability, and adjusting its nIR. In the glass of this embodiment, Ga２ O ３ The content is preferably 0% to 30%. Ga ２ O ３ If the content is 30% or less, problems such as deterioration of the devitrification of the glass, increased reflectivity, and stray light due to reflected light are less likely to occur. ２ O ３ The content of is more preferably 0.5% to 28%, even more preferably 1% to 26%, even more preferably 2% to 24%, and most preferably 3% to 22%.

[0020] ZrO ２ ZrO is a component that increases the Young's modulus of the glass and increases the viscosity of the glass at the liquidus temperature. In the glass of this embodiment, ZrO ２ The content is preferably 0% to 7%. ZrO ２ If the content is 7% or less, problems such as deterioration of glass devitrification and deterioration of meltability are less likely to occur. ２ The content of is more preferably 0% to 6%, even more preferably 0% to 5%, even more preferably 0% to 4%, and most preferably 0% to 3%.

[0021] La ２ O ３ La is a component that increases the Young's modulus of the glass and improves its meltability. In the glass of this embodiment, La ２ O ３ The content is preferably 0% or more and less than 20%. ２ O ３ If the content is less than 20%, problems such as deterioration of glass devitrification, nIR exceeding 1.70, increased reflectivity, and stray light due to reflected light are less likely to occur. ２ O ３ The content is more preferably 0% to 15%, even more preferably 0% to 10%, even more preferably 0% to 5%, and most preferably 0% to 2.5%.

[0022] Al ２ O ３Al is a component that increases the Young's modulus of the glass, adjusts the nIR of the glass, and improves the chemical resistance of the glass. In the glass of this embodiment, Al ２ O ３ The content is preferably 0.1% to 20%. ２ O ３ If the content is 0.1% or more, the effect is sufficiently obtained, and if it is 20% or less, problems such as phase separation and crystallization of the glass causing deterioration of devitrification, increased reflectivity, and stray light due to reflected light are less likely to occur. ２ O ３ The content is more preferably 0.1% to 18%, even more preferably 0.1% to 15%, even more preferably 0.1% to 9%, even more preferably 0.1% to 4.5%, even more preferably 0.1% to 4.0%, particularly preferably 0.1% to 3.7%, extremely preferably 0.1% to 3.0%, even more extremely preferably 0.1% to 2.0%, even more extremely preferably 0.1% to 1.7%, and most preferably 0.1% to 1.6%. ２ O ３ If the content is between 0.1% and 1.6%, problems such as phase separation and crystallization of the glass, which worsen devitrification, are particularly unlikely to occur.

[0023] The glass of this embodiment is Li to the extent that it does not impair the purpose of the present invention. ２ O, Na ２ O, K ２ Alkali metal oxides such as O, alkaline earth metal oxides such as MgO, CaO, SrO, BaO, ZnO, Nb ２ O ５ It may also contain Cl, F, and other components.

[0024] Li ２ O is a component that enhances the meltability of the glass and adjusts the nIR. In the glass of this embodiment, Li ２ The O content is preferably 0% to 20%. ２ If the O content is 20% or less, problems such as deterioration of the devitrification of the glass, increased reflectivity, and stray light due to reflected light are less likely to occur. ２The O content is more preferably 0.5% to 15%, even more preferably 0.5% to 10%, even more preferably 0.5% to 8%, and most preferably 0.5% to 6%.

[0025] Na ２ O is a component that enhances the meltability of the glass and adjusts the nIR. In the glass of this embodiment, Na ２ The O content is preferably 0% to 20%. ２ If the O content is 20% or less, problems such as deterioration of glass devitrification, increased reflectivity, and stray light due to reflected light are less likely to occur. ２ The O content is more preferably 0.5% to 18%, even more preferably 0.5% to 16%, even more preferably 0.5% to 14%, and most preferably 0.5% to 12%.

[0026] K ２ O is a component that enhances the meltability of the glass and adjusts the nIR. In the glass of this embodiment, K ２ The O content is preferably 0% to 25%. ２ If the O content is 25% or less, problems such as deterioration of glass devitrification, increased reflectivity, and stray light due to reflected light are less likely to occur. ２ The O content is more preferably 0.5% to 20%, even more preferably 0.5% to 17%, even more preferably 0.5% to 15%, and most preferably 0.5% to 10%.

[0027] MgO is a component used to improve the weather resistance of glass, lower the devitrification temperature, improve the meltability of glass, and adjust the nIR. In the glass of this embodiment, the MgO content is preferably 0% to 15%. If the MgO content is 15% or less, problems such as deterioration of the devitrification properties of the glass, increased reflectivity, and stray light due to reflected light are less likely to occur. The MgO content is more preferably 0.1% to 15%, even more preferably 0.5% to 15%, even more preferably 1% to 15%, and most preferably 2% to 10%.

[0028] SrO is a component that enhances the weather resistance of glass, lowers the devitrification temperature, improves the meltability of glass, and adjusts the nIR. In the glass of this embodiment, the SrO content is preferably 0% to 15%. If the SrO content is 15% or less, problems such as deterioration of the devitrification of glass, increased reflectivity, and stray light due to reflected light are less likely to occur. The SrO content is more preferably 0.1% to 13%, even more preferably 0.1% to 11%, even more preferably 0.1% to 9%, and most preferably 0.1% to 7%.

[0029] CaO is a component used to improve the weather resistance of glass, lower the devitrification temperature, improve the meltability of glass, and adjust the nIR. In the glass of this embodiment, the CaO content is preferably 0% to 15%. If the CaO content is 15% or less, problems such as deterioration of the devitrification properties of the glass, increased reflectivity, and stray light due to reflected light are less likely to occur. The CaO content is more preferably 0.1% to 13%, even more preferably 0.1% to 11%, even more preferably 0.1% to 9%, and most preferably 0.1% to 7%.

[0030] BaO is a component used to improve the weather resistance of glass, lower the devitrification temperature, improve the meltability of glass, and adjust the nIR. In the glass of this embodiment, the BaO content is preferably 0% to 35%. If the BaO content is 35% or less, problems such as deterioration of the devitrification of glass, increased reflectivity, and stray light due to reflected light are less likely to occur. The BaO content is more preferably 0.1% to 30%, even more preferably 0.1% to 25%, even more preferably 0.1% to 20%, and most preferably 0.1% to 15%.

[0031] ZnO is a component for enhancing the weather resistance of glass, lowering the devitrification temperature, improving the meltability of glass, and adjusting nIR. In the glass of the present embodiment, the content of ZnO is preferably 0% to 10%. When the content of ZnO is 10% or less, problems such as deterioration of the devitrification property of glass, an increase in reflectance, and generation of stray light due to reflected light are less likely to occur. The content of ZnO is more preferably 0% to 8%, further preferably 0% to 6%, still more preferably 0% to 4%, and most preferably 0% to 2%.

[0032] Nb ２ O ５ is a component for enhancing the meltability of glass and adjusting nIR. In the glass of the present embodiment, Nb ２ O ５ content is preferably 0% to 20%. When the Nb ２ O ５ content is 20% or less, problems such as deterioration of the devitrification property of glass, an increase in reflectance, and generation of stray light due to reflected light are less likely to occur. Nb ２ O ５ content is more preferably 0.5% to 15%, further preferably 0.5% to 13%, still more preferably 0.5% to 12%, and most preferably 0.5% to 9%.

[0033] Cl is a component for enhancing the meltability of glass and adjusting nIR. In the glass of the present embodiment, the content of Cl is preferably 0% to 10%. When the content of Cl is 10% or less, problems such as deterioration of the devitrification property of glass and deterioration of the homogeneity of glass are less likely to occur. The content of Cl is more preferably 0.5% to 10%, further preferably 0.5% to 9%, still more preferably 0.5% to 8%, and most preferably 0.5% to 6%.

[0034] F is a component that enhances the meltability of the glass and adjusts the nIR. In the glass of this embodiment, the F content is preferably 0% to 10%. If the F content is 10% or less, problems such as deterioration of the devitrification of the glass and deterioration of the homogeneity of the glass are less likely to occur. The F content is more preferably 0.5% to 10%, even more preferably 0.5% to 9%, even more preferably 0.5% to 8%, and most preferably 0.5% to 6%.

[0035] The glass of this embodiment may inevitably contain small amounts of Zr, Gd, W, Nd, Ti, Y, Hf, Ta, Te, and Bi, but it is preferable that it is substantially free of them, from the viewpoint of making it easier to adjust the nIR to 1.50 to 1.70. The content of Zr, Gd, W, Nd, Ti, Y, Hf, Ta, Te, and Bi in the glass of this embodiment is preferably 5% or less if it is inevitably present in small amounts, and preferably 0.5% or less if it is substantially free of them. Here, Zr, Gd, W, Nd, Ti, Y, Hf, Ta, Te, and Bi do not refer only to the elemental metals of Zr, Gd, W, Nd, Ti, Y, Hf, Ta, Te, and Bi contained in the glass, but may also include elemental metals and compounds of Zr, Gd, W, Nd, Ti, Y, Hf, Ta, Te, and Bi.

[0036] In this embodiment, from the viewpoint of increasing visible light transmittance, the total content of Fe, Cr, and Ni is preferably 5.0 ppm or less, more preferably 4.5 ppm or less, even more preferably 4.0 ppm or less, even more preferably 3.5 ppm or less, particularly preferably 3.0 ppm or less, and most preferably 2.5 ppm or less. The lower limit is not particularly limited, but the lower limit of the total content of Fe, Cr, and Ni is, for example, 1.0 ppm or more. Here, Fe, Cr, and Ni refer not only to the elemental metals of Fe, Cr, and Ni contained in the glass, but may also include elemental metals of Fe, Cr, and Ni and compounds. That is, the total content of Fe, Cr, and Ni can be said to include the content of elemental metals of Fe, Cr, and Ni and the content of Fe, Cr, and Ni ions in compounds. By keeping the total content of the coloring transition metals Fe, Cr, and Ni within this range, it is possible to suppress a decrease in the visible light transmittance of the glass. The total content of Fe, Cr, and Ni can be measured by ICP mass spectrometry. For example, the Agilent 8800 from Agilent Technologies can be used as a measuring instrument.

[0037] In this embodiment, from the viewpoint of increasing visible light transmittance, the Pt content of the glass is preferably 1.5 ppm or less, more preferably 1.2 ppm or less, even more preferably 1.0 ppm or less, even more preferably 0.70 ppm or less, particularly preferably 0.50 ppm or less, and most preferably 0.40 ppm or less. The lower limit is not particularly limited, but the lower limit of the Pt content is, for example, 0.10 ppm or more.

[0038] The glass of this embodiment preferably has an Au content of 1.0 ppm or less, more preferably 0.50 ppm or less, even more preferably 0.25 ppm or less, even more preferably 0.15 ppm or less, particularly preferably 0.10 ppm or less, and most preferably 0.05 ppm or less. The lower limit is not particularly limited, but the lower limit of the Au content is, for example, 0.01 ppm or more.

[0039] By having such low Pt and Au content, the visible light transmittance can be improved. Here, Pt and Au refer not only to the elemental metals of Pt and Au contained in the glass, but may also include elemental metals of Pt and Au and compounds. In other words, the total Pt and Au content can be said to include the content of elemental metals of Pt and Au and the content of Pt and Au ions in compounds. The Pt and Au content can be measured by ICP mass spectrometry. As a measuring instrument, for example, the Agilent 8800 manufactured by Agilent Technologies can be used.

[0040] The glass of this embodiment containing the above components has a maximum refractive index (nIR) of 1.50 to 1.70 for light with a wavelength of 900 nm to 1000 nm. This suppresses the reflection characteristics of light with a wavelength of 900 nm to 1000 nm, even in glass containing Yb, thereby suppressing the generation of stray light. The nIR is preferably 1.50 to 1.68, more preferably 1.50 to 1.65, even more preferably 1.50 to 1.63, and even more preferably 1.50 to 1.61. The maximum refractive index (nIR) for light with a wavelength of 900 nm to 1000 nm refers to the maximum value of the refractive index in the wavelength band of 900 nm to 1000 nm. In order to achieve the above range for nIR, the type and content of the above-mentioned glass components can be adjusted. In this specification, the refractive index of glass can be measured using the V-block method or ellipsometry, but is not limited to these methods.

[0041] The glass of this embodiment preferably has a refractive index (nd) of 1.50 to 1.70 for visible light, particularly light with a wavelength of 587.5618 nm. This suppresses the reflectance of visible light and reduces reflected stray light. More preferably, nd is 1.50 to 1.68, and even more preferably 1.50 to 1.65. To achieve nd within the above range, the type and content of the glass components described above can be adjusted.

[0042] In the glass of the present embodiment, the ratio (nIR / nd) of the maximum refractive index (nIR) for light at a wavelength of 900 nm to 1000 nm to the refractive index (nd) for visible light is preferably 0.800 to 1.100. It is preferable that nIR / nd falls within such a range, since the change in refractive index between visible light and IR light is small. nIR / nd is more preferably 0.850 to 1.050.

[0043] The glass of the present embodiment preferably has an internal transmittance of 80% or more for light at a wavelength of 400 nm when converted to a thickness of 10 mm. Thereby, an optical glass for near-infrared light absorption having excellent visible light transmittance can be obtained. The internal transmittance for light at a wavelength of 400 nm is more preferably 85% or more, further preferably 87% or more, still more preferably 89% or more, particularly preferably 91% or more, and most preferably 93% or more.

[0044] The glass of the present embodiment preferably has a maximum absorbance of 0.25 or more for light at a wavelength of 900 nm to 1000 nm when converted to a thickness of 1 mm. Thereby, an optical glass for near-infrared light absorption having excellent absorption characteristics for light at a wavelength of 900 nm to 1000 nm can be obtained. The maximum absorbance is more preferably 0.30 or more, further preferably 0.40 or more, still more preferably 0.60 or more, and particularly preferably 1.0 or more. There is no particular upper limit, and a higher value is more preferable. The absorbance is calculated by the following formula using the internal transmittance (%). Absorbance = -log １０ (Internal transmittance / 100)

[0045] In the glass of the present embodiment, the average reflectance (at an incident angle of 5 degrees) for light at a wavelength of 900 nm to 1000 nm is preferably 6.8% or less, more preferably 6.5% or less, further preferably 6.0% or less, and still more preferably 5.5% or less. In the glass of the present embodiment, since the maximum refractive index (nIR) for light at a wavelength of 900 nm to 1000 nm falls within the above specific range, the reflection characteristics for light at a wavelength of 900 nm to 1000 nm are suppressed.

[0046] The glass in this embodiment preferably has an Abbe number of 45 or higher. This is preferable because it reduces chromatic aberration. More preferably, the Abbe number is 46 or higher, even more preferably 48 or higher, and particularly preferably 50 or higher. From the viewpoint of cost reduction, it is preferably 65 or lower, more preferably 60 or lower, and even more preferably 55 or lower. The Abbe number ν can be calculated from the refractive index of the glass at a wavelength of 486.1327 nm (nF), the refractive index of light at a wavelength of 656.2725 nm (nC), and the visible light refractive index (nd) described above, using the following formula: ν = (nd - 1) / (nF - nC)

[0047] The glass in this embodiment preferably has a specific gravity of 4.5 or less. This reduces the weight of optical devices and imaging devices. The specific gravity is more preferably 4.3 or less, even more preferably 4.1 or less, and particularly preferably 3.9 or less. Furthermore, from the viewpoint of cost reduction, it is preferably 3.8 or less, more preferably 3.7 or less, and even more preferably 3.6 or less. The specific gravity can be measured by the Archimedes method, but is not limited to this method.

[0048] The glass in this embodiment preferably has a Young's modulus of 120 GPa or less. This results in a lower elastic modulus, which reduces stress concentration and makes it easier to suppress cracking in the usage environment, thus making it easier to obtain high-strength glass. The Young's modulus is more preferably 115 GPa or less, even more preferably 110 GPa or less, and particularly preferably 105 GPa or less. Also, from the viewpoint of reducing processing costs, it is preferably 100 GPa or less. The Young's modulus can be measured by ultrasonic pulse testing or tensile testing, but is not limited to these methods.

[0049] The glass of this embodiment preferably has a water resistance of grade 1 to 5 as measured by JOGIS 06:2019 Method for measuring the chemical durability of optical glass (powder method). This makes the glass less likely to deteriorate even under high humidity conditions. More preferably, it is grade 1 to 4, even more preferably grade 1 to 3, particularly preferably grade 1 to 2, and most preferably grade 1.

[0050] The glass of this embodiment preferably has an acid resistance of grade 1 to 5 as measured by JOGIS 06:2019 Method for measuring the chemical durability of optical glass (powder method). This allows the optical performance of the glass to be maintained for a long period of time. More preferably grades 1 to 4, even more preferably grades 1 to 3, particularly preferably grades 1 to 2, and most preferably grade 1.

[0051] The glass of this embodiment can be manufactured, for example, as follows: First, the raw materials are weighed and mixed to achieve the above composition range (mixing step). This raw material mixture is placed in a platinum crucible and heated and melted in an electric furnace at a temperature of 1200°C to 1650°C (melting step). After thorough stirring and clarification, it is cast into a mold, cut and polished to form a flat plate of a predetermined thickness (forming step).

[0052] In the melting step of the above manufacturing method, it is preferable to keep the highest temperature of the glass during melting below 1650°C. If the highest temperature of the glass during melting is below this temperature, problems such as crystallization of the glass and generation of unmelted foreign matter in the glass are less likely to occur. The above temperature is more preferably 1625°C or lower, even more preferably 1600°C or lower, even more preferably 1500°C or lower, and particularly preferably 1450°C or lower.

[0053] Furthermore, if the temperature in the above dissolution process is too low, problems such as devitrification occurring during dissolution and a long time for complete dissolution may occur. Therefore, the temperature is preferably 1200°C or higher, more preferably 1225°C or higher, and even more preferably 1250°C or higher.

[0054] The glass of this embodiment is preferably used in optical elements. An optical element in this invention is a device that transmits and absorbs light of a specific wavelength, such as visible light, and refracts light to focus or diverge a beam of light. The shape of the optical element can be composed of a combination of spherical, aspherical, and planar surfaces for the light entry and exit surfaces, or an arrangement for focusing, diffusing, parallelizing, or homogenizing light. Various shapes are also possible, such as those that have refractive power in only one direction, or those that are divided into concentric regions with adjusted thickness. Specific examples include, but are not limited to, lens arrays, cylindrical lenses, Fresnel lenses, and plate filters.

[0055] In this embodiment, the glass preferably has a thickness in the optical axis direction of the optical element of 0.20 mm to 20 mm, more preferably 0.20 mm to 18 mm, even more preferably 0.20 mm to 14 mm, and most preferably 0.20 mm to 10 mm.

[0056] The glass of this embodiment may have a functional layer on at least one surface. By providing a functional film to the glass, desired optical properties, improved weather resistance, and other functions can be imparted. Examples of functional layers include dielectric films for imparting optical properties. Dielectric films include IR-cut films (films that reflect near-infrared light), UV / IR-cut films (films that reflect ultraviolet and near-infrared light), UV-cut films (films that reflect ultraviolet light), and anti-reflective films. These dielectric films can be single-layer or multi-layered and can be formed by known methods such as vapor deposition or sputtering. Other functional layers include light-absorbing layers for imparting optical properties. Light-absorbing layers consist of a resin containing an absorbent having the maximum absorption wavelength in the infrared or ultraviolet region. Absorbent materials include inorganic dyes such as copper complexes, and organic dyes such as squarylium dyes, phthalocyanine dyes, cyanine dyes, and diimmonium dyes. By using a transparent resin to which these absorbents are added and providing a light-absorbing layer on the glass surface, desired optical properties can be imparted to the glass. Transparent resins include acrylic resins, epoxy resins, ene-thiol resins, polycarbonate resins, polyether resins, polyarylate resins, polysulfone resins, polyethersulfone resins, polyparaphenylene resins, polyarylene ether phosphine oxide resins, polyimide resins, polyamide-imide resins, polyolefin resins, cyclic olefin resins, and polyester resins, which may be used individually or in mixtures of two or more. Other functional layers include dielectric films and resin coatings to improve the weather resistance of the glass. Another functional layer is a fine uneven structure, also known as a moth-eye structure, to suppress light reflection from the glass surface. By forming a fine uneven structure with appropriate period and height on the glass surface, light can be prevented from scattering, and high anti-reflective performance can be achieved over a wide wavelength range and angle of incidence. The uneven structure can be formed by known methods such as dry etching with an appropriate mask on the glass, or molding the resin using nanoimprint technology.

[0057] The above describes the glass of this embodiment, but the present invention is not limited to the above configuration, and various modifications are possible within the scope of the technical idea of ​​the present invention.

[0058] <Optical Devices> The glass of this embodiment can be applied to optical devices. An optical device is a device that uses light to record and transmit information. Examples of optical devices include the imaging device of a digital still camera and an optical sensor that detects light and converts it into an electrical signal. Applying the glass of this embodiment to optical devices has the advantage of being particularly excellent in absorption characteristics in the near-infrared region, and the generation of stray light is suppressed due to the low reflection characteristics in the near-infrared region, thus contributing to the miniaturization and reduction of the height of optical devices.

[0059] The glass of this embodiment can be used in combination with a near-infrared light cut filter when applied to an optical device. In this case, it is preferable that the near-infrared light cut filter has different light absorption characteristics than the glass of this embodiment. By applying the glass of this embodiment to an optical device in combination with an optical filter having different light absorption characteristics, optical characteristics that are difficult to obtain with a single glass can be obtained. Examples of light-shielding characteristics of the near-infrared light cut filter include characteristics that have absorption ability in a different wavelength range than the glass of this embodiment, and characteristics that have different absorption ability in the same near-infrared wavelength range as the glass of this embodiment.

[0060] Examples of near-infrared light cut filters include a near-infrared light cut filter provided near the image sensor of an imaging device, a cover glass that covers the aperture on the subject side of an optical device, and a lens provided inside an optical device. In addition, the glass and the near-infrared light cut filter of this embodiment may be used in a laminated form.

[0061] The near-infrared light cut filter preferably includes near-infrared light absorbing glass, and from the viewpoint of mutually complementing the near-infrared light absorption capabilities, it is preferable that the near-infrared light absorbing glass has absorption capabilities in a different wavelength range than the glass of this embodiment. Furthermore, it is preferable that the near-infrared light absorbing glass includes at least one selected from Cu, Fe, and Yb. Furthermore, from the viewpoint of efficiently absorbing infrared rays, phosphate glass and fluorine phosphate glass are preferred for the near-infrared light absorbing glass. "Phosphoric acid glass" refers to phosphate glass in molar percentage based on oxides. ２ O ５ This refers to glass in which the content of P is 40 mol% or more, and the content of fluorine atoms in the phosphate glass is less than 3 mass% of the total content of other elemental components in the phosphate glass (100 mass%). Furthermore, "phthalic acid glass" refers to glass in which P is present in phthalic acid glass. ５＋ The content of is 20% by mass or more, and F in phthalic acid glass － The amount of F contained in phthalic acid glass － This refers to glass in which the content of all other constituent elements is 3% by mass or more, relative to 100% by mass.

[0062] The above-mentioned near-infrared light cut filter may have a dielectric multilayer film and a near-infrared light absorbing dye from the viewpoint of light shielding. Examples of dielectric multilayer films include IR cut films (films that reflect near-infrared light), UV / IR cut films (films that reflect ultraviolet and near-infrared light), UV cut films (films that reflect ultraviolet light), and anti-reflective films. These dielectric multilayer films can be formed by stacking multiple dielectric films using known methods such as vapor deposition or sputtering. As the near-infrared light absorbing dye, it is preferable to use a near-infrared light absorbing dye consisting of at least one selected from the group consisting of squarylium dye, phthalocyanine dye, cyanine dye, and diimmonium dye. It is preferable that the near-infrared light absorbing dye is provided in the near-infrared light cut filter as an absorption layer containing the dye and a transparent resin such as polyimide resin.

[0063] As described above, this specification discloses the following optical glass for near-infrared light absorption: [1] Yb２ O ３ [2] Optical glass for near-infrared light absorption, containing 10% to 50% of and having a maximum refractive index (nIR) of 1.50 to 1.70 for light with wavelengths of 900 nm to 1000 nm. [2] A material containing at least one of boron and silicon, expressed in mass % on an oxide basis, Yb ２ O ３ The content is 11% to 50%, Al ２ O ３ The content of is 4.5% or less, La ２ O ３ [1] Optical glass for near-infrared light absorption, wherein the content of is less than 20%. [3] In mass % based on oxide, B ２ O ３ Optical glass for near-infrared light absorption as described in [1] or [2], wherein the content of is 20% or less. [4] In mass % based on oxide, P ２ O ５ Optical glass for near-infrared light absorption described in any one of [1] to [3], wherein the content of is 54% or less. [5] In mass % based on oxide, SiO ２[1] to [4], an optical glass for absorbing near-infrared light, wherein the content of is 30% or less. [6] An optical glass for absorbing near-infrared light, wherein it substantially does not contain Zr, Gd, W, Nd, Ti, Y, Hf, Ta, Te, and Bi, wherein it contains substantially no Zr, Gd, W, Nd, Ti, Y, Hf, Ta, Te, and Bi, wherein it contains substantially no Zr, Gd, Nd, Ti, Y, Hf, Ta, Te, and Bi, wherein it contains substantially no Zr, Nd, Ti, Y, Hf, Ta, Te, and Bi, wherein it contains substantially no Zr, Nd, Ti, Y, Hf, Ta, Te, and Bi, wherein it contains substantially no Zr, Nd, or Bi, wherein it contains substantially no Zr, Gd, Nd, Ti, Y, Hf, Ta, Te, and Bi, wherein it contains substantially no Zr, Nd, or Bi, wherein it contains substantially no Zr, Gd, Nd, Ti, T, Nd, Ti, T, Nd, Hf, Ta, Te, and Bi, wherein it contains substantially no Zr, Nd, or Nd, wherein it contains substantially no Zr, Gd, Nd, Ti, T, Nd, Ti Nd, Ti, Nd, Ti, T, Nd, Ta, Te, and Bi, wherein it contains substantially no Zr, Gd, Nd, Ti, Nd, Ti, Nd, Ti, Nd, Hf, Nd, Ta, Te, and Bi, wherein it contains substantially no Zr, Nd, or Nd, Ti, Nd, or Nd, Ti, Nd, T, N

[10] Near-infrared light absorbing optical glass according to any one of [1] to [9], wherein the internal transmittance of light with a wavelength of 400 nm is 80% or more when converted to a thickness of 10 mm.

[11] Near-infrared light absorbing optical glass according to any one of [1] to

[10] , wherein the maximum absorbance of light with a wavelength of 900 nm to 1000 nm is 0.25 or more when converted to a thickness of 1 mm.

[12] Optical device comprising near-infrared light absorbing optical glass according to any one of [1] to

[11] and a near-infrared light cut filter.

[13] Optical device according to

[12] , wherein the near-infrared light cut filter includes near-infrared light absorbing glass.

[14] Optical device according to

[12] or

[13] , wherein the near-infrared light cut filter includes a dielectric multilayer film and a near-infrared light absorbing dye.

[15] The optical device according to any one of

[12] to

[14] , wherein the near-infrared light cut filter includes near-infrared light absorbing glass containing at least one selected from Cu, Fe, and Yb.

[16] An imaging device comprising near-infrared light absorbing optical glass according to any one of [1] to

[11] and a near-infrared light cut filter.

[0064] The present invention will be described in more detail below using examples, but the present invention is not limited to these. The internal transmittance of the glass was calculated by determining the reflectance R of the glass surface based on the measured reflectance of a glass sample of a predetermined thickness at an incident angle of 5 degrees, and then converting it to the transmittance for thicknesses of 1 mm and 10 mm using the following formula (1). Converted transmittance (thickness 1 mm, 10 mm) = 100 × (1 - R) ２ × {Measured transmittance} （０ｄｅｇ） / (100×(1-R) ２ )} ((1 mm, 10 mm) / actual thickness) Formula (1)

[0065] <Examples 1 to 15> Examples 1 to 13 and 15 are examples, and Example 14 is a comparative example.

[0066] [Glass Preparation] The raw materials were weighed and mixed to achieve the composition shown in Table 1 (based on oxides, mass%), placed in a crucible with an internal volume of approximately 400 cc, and melted in an air atmosphere at the temperature shown in Table 1 (1300°C to 1600°C) for 2 hours. After that, the mixture was clarified and stirred, and then poured into a rectangular mold measuring 100 mm (length) x 50 mm (width) x 20 mm (height) that had been preheated to approximately 300°C to 500°C. The mixture was slowly cooled to room temperature at approximately -1°C / min, cut to a predetermined thickness in the range of 40 mm (length) x 30 mm (width) x 0.3 mm to 1.5 mm (thickness), and both sides were optically polished to obtain plate-like glass.

[0067] [Evaluation: Spectroscopic Characteristics] For each glass plate prepared as described above, the transmittance (incident angle 0 degrees) at wavelengths of 300 nm to 1200 nm was measured using a spectrophotometer (JASCO Corporation, V-770), and this was converted to the transmittance for a thickness of 10 mm using the above formula (1). From the converted transmittance, the transmittance for light at a wavelength of 400 nm, the transmittance for light at a wavelength of 500 nm, and the maximum absorbance at wavelengths of 900 nm to 1000 nm were obtained. In addition, the reflectance (incident angle 5 degrees) at wavelengths of 300 nm to 1200 nm was measured, and the average reflectance at wavelengths of 900 nm to 1000 nm was obtained.

[0068] [Evaluation: Refractive Index, Abbe Number] For each glass plate prepared as described above, the refractive index at wavelength 587.5618 nm (nd), the refractive index at wavelength 486.1327 nm (nF), the refractive index at wavelength 656.2725 nm (nC), and the maximum refractive index (nIR) for light from wavelength 900 nm to 1000 nm were measured by performing data fitting calculations using Optichar from Optilayer GmbH, adjusting the Smooth to minimize the error function D to 0.1 or less. Specifically, the refractive indices at 587 nm and 588 nm for nd, 486 nm and 487 nm for nF, and 656 nm and 657 nm for nC were approximated by linear equations, and the refractive indices at the aforementioned wavelengths were calculated by fitting calculations. The refractive index ratio (nIR / nd) was calculated from each measured refractive index. Furthermore, the Abbe number (nd-1) / (nF-nC) was calculated from each measured refractive index.

[0069] The evaluation results are shown in Table 1. In Table 1, "-" indicates that measurement was not performed. Figure 1 shows the transmittance curves for light with wavelengths of 300 nm to 1200 nm in the glass of Example 1.

[0070]

[0071] From the results above, it can be seen that the average reflectivity of light with wavelengths of 900 nm to 1000 nm was kept low for all of the glasses in Examples 1 to 13 and 15. On the other hand, the glass in Example 14 had an nIR of over 1.70, resulting in a high average reflectivity of light with wavelengths of 900 nm to 1000 nm.

[0072] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. This application is based on Japanese Patent Application No. 2025-068158 filed on 17 April 2025, the contents of which are incorporated herein by reference.

[0073] The glass according to the embodiment of the present invention has excellent near-infrared light absorption characteristics. Such glass is useful in imaging devices such as cameras and sensors for transport aircraft, for example, as performance has been improving in recent years.

Claims

1. Expressed as mass % based on oxides, Yb ２ O ３ Optical glass for near-infrared light absorption, containing 10% to 50% of [a specific substance], and having a maximum refractive index (nIR) of 1.50 to 1.70 for light with wavelengths of 900 nm to 1000 nm.

2. Contains at least one of boron and silicon, and expressed as a mass % on an oxide basis, Yb ２ O ３ The content is 11% to 50%, Al ２ O ３ The content of is 4.5% or less, La ２ O ３ The near-infrared light absorbing optical glass according to claim 1, wherein the content of is less than 20%.

3. In mass% on an oxide basis, B ２ O ３ The near-infrared light absorbing optical glass according to claim 1, wherein the content thereof is 20% or less.

4. Expressed as mass % based on oxides, P ２ O ５ The near-infrared light absorbing optical glass according to claim 1, wherein the content of is 54% or less.

5. In terms of mass percentage based on oxides, SiO ２ The near-infrared light absorbing optical glass according to claim 1, wherein the content of is 30% or less.

6. The near-infrared light absorbing optical glass according to claim 1, which substantially does not contain Zr, Gd, W, Nd, Ti, Y, Hf, Ta, Te, and Bi.

7. The near-infrared light absorbing optical glass according to claim 1, wherein the Abbe number is 45 or greater.

8. The near-infrared light absorbing optical glass according to claim 1, wherein the refractive index (nd) of visible light is 1.50 to 1.

70.

9. The near-infrared light absorbing optical glass according to claim 1, wherein the ratio (nIR / nd) of the maximum refractive index (nIR) of light with a wavelength of 900 nm to 1000 nm to the refractive index (nd) of visible light is 0.800 to 1.

100.

10. The near-infrared light absorbing optical glass according to claim 1, wherein the internal transmittance of light with a wavelength of 400 nm is 80% or more when converted to a thickness of 10 mm.

11. The near-infrared light absorbing optical glass according to claim 1, wherein the maximum absorbance of light with wavelengths of 900 nm to 1000 nm is 0.25 or more when converted to a thickness of 1 mm.

12. An optical device comprising an optical glass for absorbing near-infrared light according to any one of claims 1 to 11 and a near-infrared light cut filter.

13. The optical device according to claim 12, wherein the near-infrared light cut filter includes near-infrared light absorbing glass.

14. The optical device according to claim 12, wherein the near-infrared light cut filter comprises a dielectric multilayer film and a near-infrared light absorbing dye.

15. The optical device according to claim 12, wherein the near-infrared light cut filter includes a near-infrared light absorbing glass containing at least one selected from Cu, Fe, and Yb.

16. An imaging device comprising an optical glass for absorbing near-infrared light according to any one of claims 1 to 11 and a near-infrared light cut filter.

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