JP7024711B2 - Optical glass and near infrared cut filter - Google Patents

Description

The present invention relates to an optical glass and a near-infrared cut filter that are used in a color correction filter (near-infrared cut filter) such as a digital still camera and a color video camera, and have particularly excellent light transmission in the visible region.

Solid-state imaging devices such as CCDs and CMOSs used in digital still cameras and the like have spectral sensitivities ranging from the visible region to the near-infrared region near 1200 nm. Therefore, since good color reproducibility cannot be obtained as it is, the visibility is corrected by using a near-infrared cut filter glass to which a specific substance that absorbs infrared rays is added. As the near-infrared cut filter glass, an optical glass in which CuO is added to a phosphate-based glass or an optical glass in which CuO is added to a phosphate-based glass has been developed and used.

With the increase in sensitivity and definition of solid-state image sensors, near-infrared cut filter glass is required to have near-ultraviolet ray-cutting characteristics and high light transmittance in the visible region.
As a near-infrared cut filter glass having near-ultraviolet ray-cutting characteristics, there is one described in Patent Document 1.
Further, as a near-infrared cut filter glass having a high transmittance of light in the visible region, there is one described in Patent Document 2.

Japanese Unexamined Patent Publication No. 2008-1544 International Publication No. 2015/156163

The near-infrared cut filter glass described in Patent Document 1 has a UV-cutting property by containing Ce ⁴⁺ , which exhibits absorption in the vicinity of a wavelength of 350 nm, in the glass. However, rare earth elements such as Ce and transition metal elements exhibit absorption characteristics having a certain wavelength width from the central wavelength showing the absorption peak in glass. For example, since Ce ⁴⁺ does not have a steep near-ultraviolet absorption characteristic, it also absorbs blue light in the visible region adjacent to the near-ultraviolet light. This may reduce the transmittance of visible light. In addition, this near-infrared cut filter glass does not have steep near-ultraviolet absorption characteristics, so some of the transmitted near-ultraviolet light is purple flare (purple that extends vertically from the long square in the center of the captured image). May cause haze).

The near-infrared cut filter glass described in Patent Document 2 has high light transmittance in the visible region and low light transmittance in the near-infrared region by strictly controlling the valence of the Cu component in the glass. The characteristics are obtained. However, in this near-infrared cut filter glass, an optical multilayer film is provided on the glass, and near-ultraviolet rays are cut by the reflective action of the optical multilayer film. Since the reflection characteristics of the optical multilayer film change depending on the incident angle of the light, even if the light has a wavelength of 0 for the light beam perpendicularly incident on the film forming surface, it is completely for the light incident at an angle. It may not be able to be reflected and may be transmitted. Therefore, there is a concern that false colors, ghosts, flares, etc. may occur in the peripheral portion of the image where the amount of light obliquely incident on the solid-state image sensor increases. Further, when the light reflected by the optical multilayer film becomes stray light in the optical system and is obliquely incident on the optical multilayer film again, it reaches the photoelectric conversion surface of the solid-state image sensor and disturbs the color of the captured image such as false color. It causes.

An object of the present invention is to provide an optical glass and a near-infrared cut filter that reliably cuts near-ultraviolet rays and has high transmittance of light in the visible region (particularly blue light).

The optical glass according to the present invention is an optical glass that absorbs infrared rays and ultraviolet rays, and the optical glass has a wavelength range of 3 nm before and after the wavelength at which the light transmittance is 50% in the wavelength band of 300 nm to 450 nm. It is characterized in that the slope of the calculated approximate straight line between the wavelength and the transmittance is 3 or more.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided an optical glass and a near-infrared cut filter that suppress the generation of false colors and flares by reliably cutting near-ultraviolet rays and have high transmittance of light in the visible region (particularly blue light). can do.

Hereinafter, embodiments of the present invention will be described. The optical glass of the present invention is mainly made of glass, and it is essential that the glass contains crystals. Further, it is assumed that the optical characteristics of the optical glass in the present specification have surface reflection due to the difference in the refractive index between the optical glass and air.

The optical glass of the present invention can be suitably used as a near-infrared cut filter glass in a solid-state image pickup device. The near-infrared cut filter glass is arranged between the image pickup optical system (lens group) and the solid-state image sensor (sensor) in the solid-state image sensor, or on the subject side (opposite side of the solid-state image sensor) of the image pickup optical system. To.

The optical glass of the present invention has optical properties of transmitting light in the visible region and absorbing ultraviolet rays and infrared rays. The optical glass of the present invention is an optical glass that absorbs infrared rays and ultraviolet rays, and is calculated in a wavelength range of 3 nm before and after the wavelength at which the light transmittance is 50% in the wavelength band of 300 nm to 450 nm. It has optical characteristics with an inclination of an approximate straight line between wavelength and transmittance of 3 or more. Hereinafter, "the slope of the approximate straight line between the wavelength and the transmittance calculated in the wavelength range of 3 nm before and after the wavelength at which the light transmittance is 50% in the wavelength band of 300 nm to 450 nm" is referred to as "slope (S)". Sometimes that is the case.

By having such optical characteristics, it is possible to reliably block near-ultraviolet rays and suppress the occurrence of false colors and flares. In addition, because the near-ultraviolet rays are cut by the absorption action of the optical glass instead of the reflection action by the optical multilayer film, the change in the optical characteristics due to the oblique incident of light is extremely small, and the near-ultraviolet rays caused by the stray light in the solid-state image pickup device Even when obliquely incident light is incident on the optical glass, it is possible to reliably block near-ultraviolet rays.

When the inclination (S) of the optical glass is less than 3, there is a concern that false color, flare, etc. may occur due to the transmission of a part of near-ultraviolet rays. The optical glass of the present invention has an inclination (S) of 3 or more. The inclination (S) is preferably 3.5 or more, and more preferably 4 or more. Further, if the inclination (S) is more than 20, it is extremely difficult to adjust the glass composition of the optical glass, and the manufacturing cost is high, which is not preferable. The inclination (S) is preferably 20 or less, more preferably 15 or less.

The slope (slope (S)) of the approximate straight line between the wavelength and the transmittance calculated in the wavelength range of 3 nm before and after the wavelength at which the light transmittance is 50% in the wavelength band of 300 nm to 450 nm described above. Is determined in detail by the following method.

First, the spectral transmittance of the optical glass is measured. Next, a wavelength (integer value) at which the transmittance of light in the wavelength band of 300 nm to 450 nm becomes 50% is specified. Here, if the wavelength obtained from the curve showing the spectral transmittance is not an integer value, the closest integer value is regarded as the wavelength at which the transmittance is 50%. Then, centering on the wavelength at which the transmittance is 50% (hereinafter, may be referred to as "λ _{50 (300-450)} "), from λ _{50 (300-450)} to the short wavelength side and the long wavelength side. 7 points of transmittance data for each 1 nm are determined up to wavelengths separated by 3 nm. For example, when the wavelength at which the transmittance is 50% is 380 nm, the wavelength and transmittance data (7 points in total) at 377 nm, 378 nm, 379 nm, 380 nm, 381 nm, 382 nm, and 383 nm are determined. Then, an approximate straight line is created from the data of these 7 points with the wavelength [nm] as the X-axis and the transmittance [%] as the Y-axis, and the slope [% / nm] of the obtained approximate straight line is set as the slope (S). ..

The optical glass of the present invention preferably has an average transmittance of 80% or more for light having a wavelength of 450 nm to 480 nm. By having such characteristics, when the optical glass of the present invention is used in, for example, a solid-state image pickup device, it is possible to obtain an image taken with high transmittance of blue light in the visible region and excellent color reproducibility. can. Conventionally, the sensitivity of the sensor has been adjusted in order to balance the color with other wavelength components in the visible region according to the transmittance of blue light. Therefore, by using the optical glass of the present invention, it is possible to perform high-sensitivity imaging by making the best use of the light-receiving sensitivity ability inherent in the sensor.

The above-mentioned average transmittance is more preferably 81% or more, further preferably 82% or more. Further, if the above-mentioned average transmittance is more than 92%, it is extremely difficult to adjust the glass composition of the optical glass and the manufacturing cost is high, which is not preferable. The above-mentioned average transmittance is preferably 92% or less, more preferably 91% or less.

The optical glass of the present invention has a wavelength of 500 nm to 50% in the wavelength band of 600 nm to 700 nm (hereinafter, may be referred to as “λ _{50 (600-700)} ”) to 300 nm to 450 nm. The value obtained by subtracting the wavelength (λ _{50 (300-450)} ) at which the light transmittance in the wavelength band of λ 50 (300-450) is 50%, λ _{50 (600-700)} -λ _{50 (300-450)} is 200 nm to 300 nm. It is preferably in the range. By having such characteristics, it is possible to obtain a captured image having high light transmittance in the visible region, high sensitivity, and excellent color reproducibility. The wavelength width (λ _{50 (600-700)} -λ _{50 (300-450)} ) described above is preferably 220 nm to 290 nm, more preferably 230 nm to 280 nm.

The optical glass of the present invention has an average absorption coefficient with a wavelength of 700 nm to 850 nm (hereinafter, "ε ₍₇₀₀ )" with respect to an average absorption coefficient with a wavelength of 450 nm to 480 nm (hereinafter, may be referred to as "ε _(450-480) "). _-850) ”), ε _(700-850) / ε _(450-480) is preferably 33 or more. By having such characteristics, when the optical glass of the present invention is used, for example, in a solid-state imaging device, the transmittance of blue light in the visible region can be reduced while reliably cutting near infrared rays unnecessary for the captured image. Since the height can be increased, it is possible to obtain a captured image with high sensitivity and excellent color reproducibility.

The ratio of the average extinction coefficient (ε _(700-850) / ε _(450-480) ) is preferably 34 or more, and more preferably 35 or more. Further, when the ratio of the average extinction coefficient (ε _(700-850) / ε _(450-480) ) is more than 80, it is extremely difficult to adjust the glass composition of the optical glass and the manufacturing cost is high, which is not preferable. The ratio of the average transmittance (ε _(700-850) / ε _(450-480) ) is preferably 80 or less, more preferably 70 or less.

In the near-infrared cut filter glass, it is desirable to achieve both high transmittance of light having a wavelength of 450 nm to 480 nm and low transmittance of light having a wavelength of 700 nm to 850 nm. In the conventional near-infrared cut filter glass, there is a method of lowering the Cu concentration in the glass in order to increase the transmittance of light having a wavelength of 450 nm to 480 nm, but in this case, the transmittance of light having a wavelength of 700 nm to 850 nm is high. There is a harmful effect that it becomes expensive. Further, there is a method of increasing the Cu concentration in order to reduce the transmittance of light having a wavelength of 700 nm to 850 nm, but in this case, there is an adverse effect that the transmittance of light having a wavelength of 450 nm to 480 nm is lowered. That is, in the conventional near-infrared cut filter glass, it is difficult to achieve both high transmittance of light having a wavelength of 450 nm to 480 nm and low transmittance of light having a wavelength of 700 nm to 850 nm. , I had to either compromise one of the characteristics or make a balance between the two.

The optical glass of the present invention will be described in detail later, but the Cu component in the optical glass related to both the transmittance of light having a wavelength of 450 nm to 480 nm and the transmittance of light having a wavelength of 700 nm to 850 nm has a wavelength of 450 nm to 480 nm. Cu ⁺ ions that reduce the transmittance of the glass are precipitated as crystals in the glass as halides, and the abundance of Cu ⁺ ions in the amorphous (glass) portion is reduced as much as possible to obtain the above-mentioned optical characteristics. It was found that it could be obtained.

When Cu ⁺ ions are precipitated as crystals in glass as a halide, the amorphous portion that reduces the transmittance of light having a wavelength of 700 nm to 850 nm has almost no effect on Cu 2 ⁺ ions, so the wavelength is 700 nm to 850 nm. It is possible to increase the transmittance of light having a wavelength of 450 nm to 480 nm while maintaining the preferable optical property of low light transmittance. Further, since the Cu halide precipitated as crystals in the glass has a steep absorption characteristic in the ultraviolet region, the optical glass of the present invention can also cut near ultraviolet rays unnecessary for the captured image.

The optical glass of the present invention contains P and Cu as cation components indispensably, and at least one selected from Cl, Br and I as an anion components, and the content of Cu is 0.5 to 0.5% in cation%. It is 25% and contains crystals. That is, the optical glass of the present invention is composed of glass and crystals. Glass is an amorphous component and is a main component of the optical glass of the present invention. Further, the crystal is preferably a crystal in which the components contained in the glass are precipitated in the glass as crystals. In the present specification, the content of each component indicates the content in the optical glass. Further, in the following description, the term "glass" simply means glass as an amorphous component in optical glass.

P is a main component (glass-forming oxide) that forms glass, and is an essential component for enhancing the cuttability of the optical glass in the near-infrared region. P is contained in the glass, for example, as P ⁵⁺ .

Further, Cu is an essential component for cutting near infrared rays. Cu is contained in the glass as, for example, Cu ²⁺ and Cu ⁺ . If the Cu content in the optical glass is less than 0.5%, the effect cannot be sufficiently obtained when the wall thickness of the optical glass is reduced, and if it exceeds 25%, the visible transmittance is lowered, which is preferable. do not have. The Cu content is preferably 0.5 to 19%, more preferably 0.6 to 18%, still more preferably 0.7 to 17%. The Cu content refers to the total amount of Cu ²⁺ , Cu ⁺ in the glass, and the Cu component in the crystal.

The optical glass of the present invention contains at least one selected from Cl, Br and I as an anion component. Two or more kinds of Cl, Br and I may be contained in combination. Cl, Br ^and I are contained in the glass as ^Cl- , Br- and I- ^, respectively. The content of Cl, Br and I in the optical glass is preferably 0.01 to 20% in terms of the total amount of anion%. If the content of Cl, Br and I is less than 0.01%, crystals are difficult to precipitate, and if it exceeds 20%, the volatility becomes high and the veins in the glass may increase, which is not preferable. The total content of Cl, Br and I in the optical glass is preferably 0.01 to 15%, more preferably 0.02 to 10%.

Cl ⁻ , Br ⁻ , and I ⁻ react with Cu ⁺ in the glass, Cl ⁻ forms CuCl, Br ⁻ forms CuBr, and I ⁻ forms CuI. With these components, it becomes possible to sharply cut the light in the near-ultraviolet region in the obtained optical glass. ^Cl- , Br- ^, and I ^- can be appropriately selected according to the wavelength at which light in the near-ultraviolet region is desired to be sharply cut.

The crystal contained in the optical glass of the present invention preferably contains at least one crystal selected from CuCl, CuBr and CuI. That is, it is preferable that CuCl, CuBr, and CuI contained in the optical glass are precipitated as crystals. Since at least one selected from CuCl, CuBr and CuI is precipitated in the crystalline state, the sharp cut property of light in the ultraviolet region can be enhanced.

The optical glass of the present invention preferably contains Ag as a cationic component. Ag binds to at least one selected from Cl, Br and I to precipitate silver halide (eg AgCl). In this case, AgCl acts as a crystal nucleus and has an effect of facilitating the precipitation of CuCl crystals. The content of Ag in the optical glass is preferably 0.01 to 5% as% cation. If it is less than 0.01%, the effect of precipitating crystals cannot be sufficiently obtained. On the other hand, if it exceeds 5%, Ag colloid is formed and the transmittance of visible light is lowered, which is not preferable.

Further, at least one crystal selected from CuCl, CuBr and CuI may be deposited by precipitating or introducing a component that becomes a crystal nucleus other than silver halide into the optical glass.

The crystal component in the optical glass of the present invention is mainly composed of at least one selected from CuCl, CuBr and CuI, and crystal nuclei in which at least one selected from Ag and Cl, Br and I are bonded or other crystal nuclei. It may be included.

Next, the optical glass of the present invention will be described by taking as an example the optical glass of the two embodiments, that is, the optical glass of the first embodiment composed of the phosphoric acid glass and the crystal and the optical glass of the second embodiment composed of the futhuric acid glass and the crystal. do.

The optical glass according to the first embodiment of the present invention has P2 O ₅ : 35 to 75% in _terms of mass% based on oxides.
Al ₂ O ₃ : 5 to 15%
R ₂ O: 3 to 30% (However, R ₂ O represents the total amount of Li ₂ O, Na ₂ O and K ₂ O).
R'O: 3 to 35% (However, R'O represents the total amount of MgO, CaO, SrO, BaO, and ZnO).
CuO: 0.5-20%
Contains.

The optical glass of the first embodiment contains at least one selected from Cl, Br and I. The content and the content form of at least one selected from Cl, Br and I in the optical glass of the first embodiment are as described above. The reason why the content of each component constituting the optical glass of the first embodiment of the present invention is limited as described above will be described below. In the following description, the content "%" of the component contained in the optical glass of the first embodiment is the mass% based on the oxide unless otherwise specified.

P ₂ O ₅ is a main component (glass-forming oxide) that forms glass and is an essential component for improving the cuttability in the near-infrared region of optical glass, but if it is less than 35%, the effect is sufficiently obtained. If it exceeds 75%, the glass becomes unstable, the weather resistance is lowered, and the residual amount of at least one selected from Cl, Br and I in the optical glass is lowered, and the crystals are not sufficiently precipitated. Therefore, it is not preferable. The content of P ₂ O ₅ is preferably 38 to 73%, more preferably 40 to 72%.

Al ₂ O ₃ is a main component (glass-forming oxide) that forms glass and is an essential component for enhancing weather resistance, but if it is less than 5%, its effect cannot be sufficiently obtained, and 15% is used. If it exceeds the limit, the glass becomes unstable and the near-infrared cut property of the optical glass deteriorates, which is not preferable. The content of Al ₂ O ₃ is preferably 5.5 to 12%, more preferably 6 to 10%.

R ₂ O (where R ₂ O represents the sum of Li ₂ O, Na ₂ O and K ₂ O) lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, and stabilizes the glass. It is a component for making it into a substance, but if it is less than 3%, the effect cannot be sufficiently obtained, and if it exceeds 30%, the glass becomes unstable, which is not preferable. The content of R2O is preferably ₅ to 28%, more preferably 6 to 25%. It should be noted that R ₂ O means the total amount of Li ₂ O, Na ₂ O and K ₂ O, that is, Li ₂ O + Na ₂ O + K ₂ O. Further, R ₂ O is one kind or two or more kinds selected from Li ₂ O, Na ₂ O and K ₂ O, and in the case of two or more kinds, any combination may be used.

Li ₂ O is a component for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, stabilizing the glass, and the like. When Li ₂ O is contained, if it exceeds 15%, the glass becomes unstable, which is not preferable. The content of Li ₂ O is preferably 0 to 10%, more preferably 0 to 8%.

Na ₂ O is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, stabilizing the glass, and the like. When Na ₂ O is contained, if it exceeds 25%, the glass becomes unstable, which is not preferable. The content of Na ₂ O is preferably 0 to 22%, more preferably 0 to 20%.

K ₂ O is not an essential component, but is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, and the like. When K ₂ O is contained, if it exceeds 25%, the glass becomes unstable and the thermal expansion rate becomes remarkably large, which is not preferable. The content of K2O is preferably ₀ to 20%, more preferably 0 to 15%.

R'O (where R'O represents the sum of MgO, CaO, SrO, BaO, and ZnO) lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, and stabilizes the glass. It is an essential ingredient for making glass and increasing the strength of glass. If it is less than 3%, the effect cannot be sufficiently obtained, and if it exceeds 35%, the glass becomes unstable, the near-infrared ray cutting property of the optical glass is lowered, the strength of the glass is lowered, and so on, which is not preferable. The content of R'O is preferably 3.5 to 32%, more preferably 4 to 30%. In addition, R'O means the total amount of MgO, CaO, SrO, BaO, and ZnO, that is, R'O means MgO + CaO + SrO + BaO + ZnO. Further, R'O is one kind or two or more kinds selected from MgO, CaO, SrO, BaO and ZnO, and in the case of two or more kinds, any combination may be used.

MgO is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, increasing the strength of glass, and the like. However, MgO tends to make the glass unstable and easily devitrified, and it is preferable not to contain MgO especially when it is necessary to set a high Cu content. When MgO is contained, if it exceeds 5%, the glass becomes extremely unstable, and the near-infrared cut property of the optical glass is deteriorated, which is not preferable. The content of MgO is preferably 0 to 3%, more preferably 0 to 2%.

CaO is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, stabilizing the glass, increasing the strength of the glass, and the like. When CaO is contained, if it exceeds 10%, the glass becomes unstable and easily devitrified, and the near-infrared cut property of the optical glass is lowered, which is not preferable. The CaO content is preferably 0 to 7%, more preferably 0 to 5%.

SrO is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, stabilizing the glass, and the like. When SrO is contained, if it exceeds 15%, the glass becomes unstable and easily devitrified, and the near-infrared cut property of the optical glass is lowered, which is not preferable. The content of SrO is preferably 0 to 12%, more preferably 0 to 10%.

Although BaO is not an essential component, it is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, stabilizing the glass, and the like. When BaO is contained, if it exceeds 30%, the glass becomes unstable and easily devitrified, and the near-infrared cut property of the optical glass is lowered, which is not preferable. The BaO content is preferably 0 to 27%, more preferably 0 to 25%.

Although ZnO is not an essential component, it has effects such as lowering the melting temperature of glass, lowering the liquidus temperature of glass, and increasing the chemical durability of glass. When ZnO is contained, if it exceeds 10%, the glass tends to become unstable, and the solubility of the glass deteriorates, which is not preferable. The ZnO content is preferably 0 to 8%, more preferably 0 to 5%.

CuO is an essential component for cutting near infrared rays. If the content of CuO in the optical glass is less than 0.5%, the effect cannot be sufficiently obtained when the wall thickness of the optical glass is reduced, and if it exceeds 20%, the visible transmittance is lowered, which is preferable. do not have. The content of CuO is preferably 0.8 to 19%, more preferably 1.0 to 18%.

The content of Cu in the cation% of the optical glass of the first embodiment is 0.5 to 25% as described above, and the preferable content is also as described above. When the above Cl, Br, and I form CuCl, CuBr, and CuI, respectively, the cation% of Cu in the optical glass is the total content of the Cu component and other Cu components in the copper halide. Is.

The optical glass of the first embodiment may contain 0 to 3% of Sb ₂ O ₃ as an optional component. Although Sb ₂ O ₃ is not an essential component, it has an effect of increasing the visible region transmittance of the optical glass. When Sb ₂ O ₃ is contained, if it exceeds 3%, the stability of the glass is lowered, which is not preferable. The content of Sb ₂ O ₃ is preferably 0 to 2.5%, more preferably 0 to 2%.

The optical glass of the first embodiment can further contain other components normally contained in the phosphoric acid glass such as SiO ₂ , SO ₃ , B ₂ O ₃ as optional components within a range that does not impair the effects of the present invention. The total content of these components is preferably 3% or less.

Further, the optical glass of the first embodiment contains crystals as described above, and preferably contains at least one crystal selected from CuCl, CuBr and CuI.

The optical glass of the first embodiment may further contain Ag as an optional component. The Ag content and the content form in the optical glass of the first embodiment are as described above.

<Optical glass of Embodiment 2>
The optical glass of the second embodiment has ^{P5 +} : 20 to 50% in% cation.
Al ³⁺ : 5 to 20%
R ⁺ : 15-40% (However, R ⁺ represents the total amount of Li ⁺ , Na ⁺ and K ⁺ )
^R'2+ : 5 to 30% (However, R'2 ^{+ represents the total amount of Mg 2+ ,} Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ ).
Total amount of Cu ²⁺ and Cu ⁺ : 0.5-25%
F- ^: 10-70% with anion%
It is characterized by containing.

In the present specification, "cation%" and "anion%" are the following units. First, the constituent components of the optical glass are divided into a cation component and an anion component. The "cation%" is a unit in which the content of each cation component is expressed as a percentage when the total content of all cation components contained in the optical glass is 100 mol%. The "anion%" is a unit in which the content of each anion component is expressed as a percentage when the total content of all anion components contained in the optical glass is 100 mol%.

The optical glass of the second embodiment contains ^O2- as an anion component in addition to F- ^, and contains at least one selected from ^Cl- , Br- ^{, and} I-. The content of O ^2- in the optical glass of the second embodiment is as described later, and the content and the content form of at least one selected from Cl ⁻ , Br ⁻ and I ⁻ are as described above.

The reason why the content (displayed in% cation and% anion) of each component constituting the optical glass of the second embodiment of the present invention is limited as described above will be described below. In the following description, the content "%" of the component contained in the optical glass of the second embodiment is cation% for the cation component and anion% for the anion component unless otherwise specified.

(Cation component)
P ⁵⁺ is a main component (glass-forming oxide) that forms glass, and is an essential component for improving the cuttability in the near-infrared region of optical glass, but if it is less than 20%, the effect cannot be sufficiently obtained. If it exceeds 50%, the glass becomes unstable and the weather resistance is lowered, which is not preferable. The content of P ⁵⁺ is preferably 20 to 48%, more preferably 21 to 46%, still more preferably 22 to 44%.

Al ³⁺ is a main component (glass-forming oxide) that forms glass and is an essential component for enhancing weather resistance, but if it is less than 5%, its effect cannot be sufficiently obtained, and if it exceeds 20%, the effect cannot be sufficiently obtained. It is not preferable because the glass becomes unstable and the near-infrared ray cutting property of the optical glass is deteriorated. The content of Al ³⁺ is preferably 6 to 18%, more preferably 6.5 to 15%, still more preferably 7 to 13%.

R ⁺ (where R ⁺ represents the sum of Li ⁺ , Na ⁺ and K ⁺ ) is used to lower the melting temperature of the glass, lower the liquidus temperature of the glass, stabilize the glass, etc. Although it is an essential component, if it is less than 15%, the effect cannot be sufficiently obtained, and if it exceeds 40%, the glass becomes unstable, which is not preferable. The content of R ⁺ is preferably 15 to 38%, more preferably 16 to 37%, still more preferably 17 to 36%. Note that R ⁺ means the total amount of Li ⁺ , Na ⁺ , and K ⁺ , that is, Li ⁺ + Na ⁺ + K ⁺ . Further, R ⁺ is one kind or two or more kinds selected from Li ⁺ , Na ⁺ and K ⁺ , and in the case of two or more kinds, any combination may be used.

Li ⁺ is an essential component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, stabilizing the glass, and the like. If it is less than 5%, the effect cannot be sufficiently obtained, and if it exceeds 40%, the glass becomes unstable, which is not preferable. The Li ⁺ content is preferably 8 to 38%, more preferably 10 to 35%, still more preferably 15 to 30%.

Na ⁺ is not an essential component, but is a component for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, stabilizing the glass, and the like. When Na ⁺ is contained, the effect is not sufficiently obtained if it is less than 5%, and if it exceeds 40%, the glass becomes unstable, which is not preferable. The Na ⁺ content is preferably 5 to 35%, more preferably 6 to 30%.

K ⁺ is not an essential component, but is a component for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, and the like. When K ⁺ is contained, the effect is not sufficiently obtained if it is less than 0.1%, and if it exceeds 30%, the glass becomes unstable, which is not preferable. The content of K ⁺ is preferably 0.5 to 25%, more preferably 0.5 to 20%.

^R'2+ (where R'2 ^{+ represents the sum of Mg 2+ ,} Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ ) lowers the melting temperature of the glass, lowers the liquidus temperature of the glass. It is an essential ingredient for stabilizing glass and increasing the strength of glass. If it is less than 5%, the effect cannot be sufficiently obtained, and if it exceeds 30%, the glass becomes unstable, the near-infrared ray cutting property of the optical glass is lowered, the strength of the glass is lowered, and so on, which is not preferable. The content of ^R'2+ is preferably 5 to 28%, more preferably 7 to 25%, and even more preferably 9 to 23%. Note that R'2 ^{+ means the total amount of Mg 2+ ,} Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ , that is, Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Ba ²⁺ + Zn ²⁺ . Further, R'2 ^{+ is one kind or two or more kinds selected from Mg 2+ ,} Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ , and in the case of two or more kinds, any combination may be used.

Mg ²⁺ is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, increasing the strength of glass, and the like. However, Mg ²⁺ tends to destabilize the glass and make it easy to devitrify. When Mg ²⁺ is contained, the effect cannot be sufficiently obtained if it is less than 1%, and if it exceeds 30%, the glass is extremely unstable. It is not preferable because the melting temperature of the glass rises. The content of Mg ²⁺ is preferably 1 to 25%, more preferably 1 to 20%.

Although Ca ²⁺ is not an essential component, it is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, stabilizing the glass, increasing the strength of the glass, and the like. When Ca ²⁺ is contained, the effect is not sufficiently obtained if it is less than 1%, and if it exceeds 30%, the glass becomes unstable and easily devitrified, which is not preferable. The Ca ²⁺ content is preferably 1 to 25%, more preferably 1 to 20%.

Although Sr ²⁺ is not an essential component, it is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, stabilizing the glass, and the like. When Sr ²⁺ is contained, the effect is not sufficiently obtained if it is less than 1%, and if it exceeds 30%, the glass becomes unstable and easily devitrified, and the strength of the glass is lowered, which is not preferable. The content of Sr ²⁺ is preferably 1 to 25%, more preferably 1 to 20%.

Although Ba ²⁺ is not an essential component, it is a component for lowering the melting temperature of glass, lowering the liquidus temperature of glass, stabilizing the glass, and the like. When Ba ²⁺ is contained, the effect is not sufficiently obtained if it is less than 0.1%, and if it exceeds 30%, the glass becomes unstable and easily devitrified, which is not preferable because the strength of the glass decreases. The content of Ba ²⁺ is preferably 1 to 25%, more preferably 1 to 20%.

Although Zn ²⁺ is not an essential component, it has effects such as lowering the melting temperature of glass, lowering the liquidus temperature of glass, and increasing the chemical durability of glass. When Zn ²⁺ is contained, the effect is not sufficiently obtained if it is less than 1%, and if it exceeds 30%, the glass becomes unstable and easily devitrified, and the solubility of the glass deteriorates, which is not preferable. The content of Zn ²⁺ is preferably 1 to 25%, more preferably 1 to 20%.

The content of Cu as a cation component in the optical glass of the second embodiment, that is, the total content of Cu ²⁺ and Cu ⁺ is the total amount of the Cu component and other Cu components in the copper halide. Specifically, the Cu content is 0.5 to 25% as described above, and the preferable content is also as described above.

Cu ²⁺ is an essential component for cutting near infrared rays, and the content is preferably 0.1% or more and less than 25%. If the content is less than 0.1%, the effect cannot be sufficiently obtained when the wall thickness of the optical glass is reduced, and if it is 25% or more, the visible transmittance of the optical glass is lowered. It is not preferable because it cannot contain Cu ⁺ . The content of Cu ²⁺ is preferably 0.2 to 24%, more preferably 0.3 to 23%, still more preferably 0.4 to 22%.

Cu ⁺ reacts with Cl, Br, and I and precipitates as copper halide crystals, whereby the effect of sharply cutting ultraviolet rays can be imparted to the optical glass. The Cu ⁺ content is preferably 0.1 to 15%. If the content is less than 0.1%, the effect cannot be sufficiently obtained, and if it exceeds 15%, the intensity of the blue color of the optical glass is weakened, which is not preferable. The content of Cu ⁺ is preferably 0.2 to 13%, more preferably 0.3 to 12%, and even more preferably 0.4 to 11%.

The optical glass of the second embodiment may contain 0 to 1% of Sb ³⁺ as an arbitrary cationic component. Although Sb ³⁺ is not an essential component, it has the effect of increasing the visible region transmittance. When Sb ³⁺ is contained, if it exceeds 1%, the stability of the glass is lowered, which is not preferable. The content of Sb ³⁺ is preferably 0.01 to 0.8%, more preferably 0.05 to 0.5%, and even more preferably 0.1 to 0.3%.

The optical glass of the second embodiment can further contain, as an arbitrary cation component, other components such as Si and B normally contained in the borosilicate glass as long as the effects of the present invention are not impaired. The total content of these components is preferably 5% or less.

(Anion component)
^O2- is an essential component for reducing the ultraviolet transmittance in order to stabilize the glass, increase the visible region transmittance of the optical glass, enhance the mechanical properties such as strength, hardness and elastic modulus. The content is preferably 30 to 90%. If the content of O ^2- is less than 30%, the effect cannot be sufficiently obtained, and if it exceeds 90%, the glass becomes unstable and the weather resistance is lowered, which is not preferable. The content of O ^2- is more preferably 30 to 80%, still more preferably 30 to 75%.

F ^- is an essential component for improving weather resistance in order to stabilize the glass, but if it is less than 10%, the effect cannot be sufficiently obtained, and if it exceeds 70%, the visible region transmittance of the optical glass is obtained. It is not preferable because there is a risk that the mechanical properties such as strength, hardness and elastic modulus will decrease, and the volatility will increase and the pulse will increase. The content of F ⁻ is preferably 10 to 50%, more preferably 15 to 40%.

Since the optical glass of the second embodiment of the present invention contains the F component indispensably, it has excellent weather resistance. Specifically, it is possible to suppress the deterioration of the optical glass surface and the decrease in the transmittance due to the reaction with the moisture in the atmosphere. For the evaluation of weather resistance, for example, an optically polished optical glass sample is held in a high-temperature and high-humidity tank at 65 ° C. and a relative temperature of 90% for 1000 hours using a high-temperature and high-humidity tank. Then, the discolored state of the optical glass surface can be visually observed and evaluated. It is also possible to compare and evaluate the transmittance of the optical glass before it is put into the high-temperature and high-humidity tank and the transmittance of the optical glass after being held in the high-temperature and high-humidity tank for 1000 hours.

The optical glass of the second embodiment can further contain, as an arbitrary anion component, other components usually contained in borosilicate glass such as S, as long as the effects of the present invention are not impaired. The total content of these components is preferably 5% or less.

Further, the optical glass of the second embodiment contains crystals as described above, and preferably contains at least one crystal selected from CuCl, CuBr and CuI. The content of the crystal component in the optical glass of the second embodiment is preferably in the same range as the above as the crystallinity of the filter glass.

The optical glass of the second embodiment may further contain Ag as an arbitrary cationic component. The Ag content and the content form in the optical glass of the second embodiment are as described above.

Next, the content of other components, which are optional components other than the above-mentioned components, common to the optical glass of the first embodiment and the optical glass of the second embodiment of the present invention will be described. In addition, in this specification, "substantially not contained" means that it is not intentionally used as a raw material, and it is considered that it does not contain raw material components or unavoidable impurities mixed from the manufacturing process.

It is preferable that the optical glass of the present invention contains substantially none of PbO, As ₂ O ₃ , V ₂ O ₅ , YbF ₃ , and GdF ₃ . PbO is a component that lowers the viscosity of glass and improves manufacturing workability. Further, As ₂ O ₃ is a component that acts as an excellent clarifying agent capable of generating a clarifying gas in a wide temperature range. However, since PbO and As ₂ O ₃ are environmentally hazardous substances, it is desirable not to contain them as much as possible. Since V ₂ O ₅ has absorption in the visible region, it is desirable that V 2 O 5 is not contained as much as possible in the near-infrared cut filter glass for a solid-state image sensor, which is required to have high visible region transmittance. Although YbF ₃ and GdF ₃ are components that stabilize glass, they are relatively expensive as raw materials and lead to cost increase, so it is desirable not to contain them as much as possible.

In the optical glass of the present invention, a nitrate compound or a sulfate compound having cations forming the glass can be added as an oxidizing agent or a clarifying agent. The oxidant has an effect of improving the cuttability of near infrared rays by increasing the ratio of Cu ²⁺ ions in the total amount of Cu in the optical glass. The amount of the nitrate compound or the sulfate compound added is preferably 0.5 to 10% by mass based on the external split addition with respect to the raw material mixture. If the amount added is less than 0.5% by mass, the effect of improving the transmittance is difficult to obtain, and if it exceeds 10% by mass, it tends to be difficult to form glass. It is more preferably 1 to 8% by mass, and even more preferably 3 to 6% by mass.

Examples of the nitrate compound include Al (NO ₃ ) ₃ , LiNO ₃ , NaNO ₃ , KNO ₃ , Mg (NO ₃ ) ₂ , Ca (NO ₃ ) ₂ , Sr (NO ₃ ) ₂ , Ba (NO ₃ ) ₂ , and Zn. There are (NO ₃ ) ₂ , Cu (NO ₃ ) ₂ , and the like. Examples of sulfate compounds include Al ₂ (SO ₄ ) _{3.16H 2} O, Li ₂ SO ₄ , Na ₂ SO ₄ , K ₂ SO ₄ , Л ₄ , CaSO ₄ , SrSO ₄ , BaSO ₄ , ZnSO ₄ , and CuSO ₄ . And so on.

Further, the optical glass of the present invention preferably has an average transmittance of light of 80% or more at a wavelength of 450 to 600 nm.

Further, when the optical glass of the present invention has a wall thickness of 0.03 to 0.3 mm, it is preferable that the wavelength at which the transmittance is 50% is 600 to 650 nm. Under such conditions, it is possible to realize desired optical characteristics in a sensor that is required to be thin. Further, when the wall thickness is 0.03 to 0.3 mm, the transmittance at a wavelength of 450 nm is 80% or more, so that the near-infrared cut filter has optical characteristics with high transmittance of light in the visible region.

The value of the transmittance was converted so as to be the value when the wall thickness was 0.03 to 0.3 mm. The conversion of the transmittance was performed using the following formula 1. _{Ti 1} is the internal transmittance of the measurement sample (data excluding the reflection loss on the front and back surfaces), t ₁ is the wall thickness (mm) of the measurement sample, _Ti 2 is the transmittance of the converted value, and t ₂ is. , Refers to the wall thickness to be converted (0.03 to 0.3 mm in the case of the present invention).

In addition, since the optical glass of the present invention corresponds to the miniaturization and thinning of the image pickup device and the equipment mounted on the image pickup device, good spectral characteristics can be obtained even when the wall thickness of the optical glass is thin. The wall thickness of the optical glass is preferably 1 mm or less, more preferably 0.8 mm or less, still more preferably 0.6 mm or less, and most preferably 0.4 mm or less. The lower limit of the wall thickness of the optical glass is not particularly limited, but is preferably 0.03 mm or more, more preferably 0. It is 05 mm or more, more preferably 0.07 mm or more, and most preferably 0.1 mm or more.

The optical glass of the present invention is characterized by having the above-mentioned optical characteristics as a single optical glass, but for the purpose of further improving the optical characteristics and protecting the optical glass from moisture and the like, an antireflection film or an antireflection film is provided on the surface of the optical glass. An optical thin film such as an infrared cut film, an ultraviolet ray, and an infrared cut film may be provided. These optical thin films are made of a single-layer film or a multilayer film, and can be formed by a known method such as a vapor deposition method or a sputtering method. Further, as described above, a resin film containing a dye component that absorbs infrared rays or ultraviolet rays may be provided on the surface of the optical glass for the purpose of improving the optical characteristics and protecting the optical glass from moisture and the like.

The optical glass of the present invention can be produced as follows.
First, the raw materials are weighed and mixed so that the obtained optical glass has the above composition range (mixing step). This raw material mixture is housed in a platinum crucible and melted by heating at a temperature of 700 to 1300 ° C. in an electric furnace (melting step). After being sufficiently stirred and clarified, it is cast in a mold to precipitate crystals (crystal precipitation step), and then cut and polished to form a flat plate having a predetermined wall thickness (molding step).

In the melting step of the above manufacturing method, in the optical glass composed of futhuric acid glass and crystals, for example, in the optical glass of the second embodiment, the highest temperature of the glass during glass melting is set to 950 ° C. or lower, and the optical glass composed of phosphoric acid glass and crystals is used. In the case of glass, for example, the optical glass of the first embodiment, the temperature is preferably 1280 ° C or lower. This is because when the highest temperature of the glass during glass melting exceeds the above temperature, the transmittance characteristics deteriorate, and in the borosilicate glass, the volatilization of fluorine is promoted and the glass becomes unstable. The temperature is more preferably 900 ° C. or lower, still more preferably 850 ° C. or lower in the borosilicate glass. In phosphoric acid glass, it is more preferably 1250 ° C. or lower, still more preferably 1200 ° C. or lower.

Further, if the temperature in the melting step becomes too low, problems such as devitrification during melting and a long time for melting will occur. Therefore, the temperature of borosilicate glass is preferably 700 ° C. or higher, more preferably 750 ° C. That is all. In phosphoric acid glass, it is more preferably 800 ° C. or higher, still more preferably 850 ° C. or higher. In the method for producing an optical glass of the present invention, it is preferable that the glass component does not crystallize before the following crystal precipitation step, and therefore the temperature in the melting step is preferably in the above range.

The crystal precipitation step performed following the melting step is preferably carried out by slow cooling, slow cooling and heat treatment. For borosilicate glass, the slow cooling is preferably performed at a rate of 0.1 to 2 ° C./min until the temperature reaches 200 to 250 ° C. In the case of phosphoric acid glass, it is preferable to carry out the process at a rate of 0.1 to 2 ° C./min until the temperature reaches 200 to 250 ° C.

When the crystal precipitation step is carried out by slow cooling and heat treatment, after slow cooling similar to the above slow cooling conditions, the temperature of the borosilicate glass is raised from the temperature after slow cooling to 400 to 600 ° C. It is preferable to carry out a heat treatment to make the glass. Similarly, in the case of phosphoric acid glass, it is preferable to perform a slow cooling similar to the above-mentioned slow cooling conditions, and then perform a heat treatment for raising the temperature from the temperature after the slow cooling to 350 to 600 ° C.

In the method for producing optical glass of the present invention, crystals are deposited in the glass in such a crystal precipitation step. The obtained optical glass of the present invention is an optical glass composed of an amorphous (glass) portion and a crystalline portion. In the crystal precipitation step, it is preferable to precipitate at least one crystal selected from CuCl, CuBr and CuI in the glass. By precipitating crystals of CuCl, CuBr, and CuI, the amount of Cu ⁺ in the amorphous (glass) portion excluding the crystal portion can be reduced in the obtained optical glass, and the sharp cut effect of ultraviolet rays can be imparted. It is also preferable because it can be used.

The optical glass of the present invention can be suitably used as a near-infrared cut filter. Solid-state image sensors used in digital cameras and the like are becoming more sensitive and finer, have good near-ultraviolet ray cut characteristics, and have a high light transmission rate in the visible region (particularly blue light transmission rate). By using the high optical glass of the present invention as a near-infrared cut filter for a solid-state image sensor, it is possible to obtain an image taken with good color reproducibility and suppressed generation of noise components such as flare, false color, and ghost. can.

Examples and comparative examples of the present invention are shown below.

Examples and comparative examples of the present invention are shown in Tables 1 to 3. Examples 1-1 and 1-2 are examples of the optical glass of the present invention relating to a phosphoric acid glass, and Example 1-3 is a comparative example of the optical glass of the present invention relating to a phosphoric acid glass. Examples 2-1 and 2-4 to 2-8 are examples of the optical glass of the present invention relating to the borosilicate glass, and Examples 2-2 and 2-3 are the optics of the present invention relating to the borosilicate glass. This is a comparative example of glass.

[Making optical glass]
Weigh and mix the raw materials so that they have the composition shown in Table 1 (indicated by mass% based on oxide) and the composition shown in Tables 2 and 3 (cation%, anion%), and put them in a platinum crucible with an internal volume of about 400 cc. After melting, clarifying, and stirring at a temperature of 800 to 1300 ° C. for 2 hours, the product was cast into a rectangular mold having a length of 50 mm, a width of 50 mm, and a height of 20 mm, which was preheated to about 300 to 500 ° C.

Examples of the present invention (Example 1-1, Example 1-2, Example 2-1, Example 2-4 to Example 2-8) are cast into a rectangular mold and then slowly cooled or slowly cooled. And heat treatment (Example 1-1, Example 1-2: after holding at 460 ° C. for 1 hour, cooling to room temperature at 1 ° C./min, then holding at 480 ° C. for 1 hour, then cooling to room temperature at 1 ° C./min, Example 2-1: After holding at 360 ° C for 1 hour, cooling to room temperature at 1 ° C / min, Example 2-4, Example 2-6 to Example 2-8: After holding at 360 ° C for 1 hour, 1 ° C / Cool to room temperature in minutes, then hold at 410 ° C for 2 hours, then cool to room temperature at 1 ° C / min, Example 2-5: Hold at 410 ° C for 1 hour, then cool to room temperature at 1 ° C / min). rice field. For comparative examples (Example 1-3, Example 2-2, Example 2-3), slow cooling (Example 1-3: After holding at 460 ° C for 1 hour, cooling to room temperature at 1 ° C / min, Example 2- 2. Example 2-3: After holding at 360 ° C. for 1 hour, cooling to room temperature at 1 ° C./min). In each example, a block-shaped optical glass having a length of 50 mm, a width of 50 mm, and a thickness of 20 mm was obtained. After grinding this optical glass, a glass plate polished to a desired thickness was used for evaluation.

The raw materials for each optical glass are H ₃ PO ₄ and / or Al (PO ₃ ) ₃ in the case of P ⁵⁺ , Al F ₃ , Al (PO ₃ ) ₃ and / or Al ₂ O ₃ in the case of Al ³⁺ . LiF, LiNO ₃ , Li ₂ CO ₃ and / or LiPO ₃ for Li ⁺ , MgF ₂ and / or MgO and / or Mg (PO ₃ ) ₂ for Mg ²⁺ , and Sr ²⁺ . SrF ₂ , SrCO ₃ and / or Sr (PO ₃ ) ₂ , BaF ₂ , BaCO ₃ and / or Ba (PO ₃ ) ₂ for Ba ²⁺ , Na ⁺ NaCl and / or NaBr and / or NaI and / Or NaF and / or Na (PO ₃ ), fluoride, carbonate and / or metaphosphate for K ⁺ , Ca ²⁺ , Zn ²⁺ , Sb ₂ O ₃ for Sb ³⁺ , Cu ²⁺ In the case of Cu ⁺ , CuO, CuCl, and CuBr were used, respectively. In the case of Ag ⁺ , AgNO ₃ was used.

[evaluation]
With respect to the glass plates obtained in each example, the presence or absence of crystal precipitation can be confirmed by a transmission electron microscope (TEM: Transmission Electron Microscope) or the like. Further, the transmittance of light having a wavelength of 450 to 600 nm was measured by an ultraviolet-visible near-infrared spectrophotometer (manufactured by JASCO Corporation, V570). For Examples 1-1 to 1-3, the transmittance (calculated based on the surface reflection of the glass plate) converted to a wall thickness of 0.3 mm was obtained. For Examples 2-1 to 2-8, the transmittance (calculated based on the surface reflection of the glass plate) converted to a wall thickness of 0.05 mm was obtained. Tables 1, 2 and 3 show the presence or absence of crystals, the average transmittance of light having a wavelength of 450 to 600 nm, and the transmittance of light having a wavelength of 450 nm. Table 1 shows the content of Cu (total of Cu ²⁺ and Cu ⁺ ) in% cation and the content of Cl + Br + I in% anion.

The following items were evaluated for the optical characteristics of each optical glass produced as described above.

(Inclination of the approximate straight line of wavelength and transmittance)
The method for determining the inclination (S) is as follows.
Measure the spectral transmittance of optical glass. Next, a wavelength (integer value, λ _{50 (300-450)} ) at which the transmittance of light in the wavelength band of 300 nm to 450 nm is 50% is specified. Here, when the wavelength obtained from the curve showing the spectral transmittance is not an integer value, the closest integer value is set as the wavelength at which the transmittance is 50%. Then, seven points of transmittance data for each 1 nm are determined from λ 50 ₍ 300-450) to wavelengths separated from λ _{50 (300-450)} by 3 nm on the short wavelength side and the long wavelength side, respectively. Then, an approximate straight line having the wavelength as the X axis and the transmittance as the Y axis is created from the data of these seven points, and the slope of the obtained approximate straight line is defined as the slope of the approximate straight line between the wavelength and the transmittance described above.
The slopes (S) of Examples and Comparative Examples determined by this method are shown in Tables 4, 5, and 6.

(Average transmittance of light in the wavelength band of 450 nm to 480 nm)
Measure the spectral transmittance of optical glass. Then, the average transmittance of light in the wavelength band of 450 nm to 480 nm is calculated from the obtained spectral transmittance.
The average transmittances of Examples and Comparative Examples obtained by this method are shown in Tables 4, 5 and 6.

(Difference between the wavelength with a transmittance of 50% on the ultraviolet side and the wavelength with a transmittance of 50% on the infrared side)
Let λ _{50 (300-450)} obtained above be a wavelength having a transmittance of 50% on the ultraviolet side. Similarly, a wavelength (integer value, λ _{50 (600-700)} ) at which the transmittance of light in the wavelength band of 600 nm to 700 nm is 50% is specified. Then, the wavelength difference (λ _{50 (600-700)} -λ _{50 (300-450)} ) is calculated from the difference between the two data.
The wavelength differences between Examples and Comparative Examples obtained by this method are shown in Tables 4, 5, and 6.

(Ratio of average extinction coefficient)
The method for determining the ratio of the average extinction coefficient of the optical glass is as follows.
Measure the spectral transmittance of optical glass. Then, from the obtained spectral transmittance, the average extinction coefficient (ε (450-480)) in the wavelength band of 450 nm to 480 nm and the average extinction coefficient (ε _{( 700-850)} ) in the wavelength band of 700 nm to 850 nm are obtained. Calculate each. Then, the ratio of the average extinction coefficient (ε _(700-850) / ε _(450-480) ) is obtained by dividing the average extinction coefficient in the wavelength band of 700 nm to 850 nm by the average extinction coefficient in the wavelength band of 450 nm to 480 nm. To determine.
The ratios of the average extinction coefficients of Examples and Comparative Examples obtained by this method are shown in Tables 4, 5 and 6.

From Tables 4, 5 and 6, each optical glass of the embodiment of the present invention has a steep cut characteristic of near-ultraviolet rays (a steep slope (S)) with respect to each optical glass of the comparative example. As a result, the transmittance of unnecessary near-ultraviolet rays can be made extremely low, and the occurrence of flares, false colors, ghosts, etc. in the captured image can be suppressed.

Each optical glass of the embodiment of the present invention has a particularly high transmittance of blue light in the visible region with respect to each optical glass of the comparative example. This makes it possible to obtain a captured image with good color reproducibility.
Each optical glass of the embodiment of the present invention has a wide wavelength band in the visible region (λ _{50 (600-700)} -λ _{50 (300-450)} ). This makes it possible to obtain a captured image with good color reproducibility.

Each optical glass of the embodiment of the present invention has a high ratio of the average extinction coefficient (ε _(700-850) / ε _(450-480) ) to each optical glass of the comparative example. That is, each optical glass of the embodiment of the present invention has a high transmittance of blue light in the visible region to be transmitted while surely blocking the near-infrared light to be shielded. As described above, since it has sharp optical characteristics, it is possible to obtain an image taken with good color reproducibility.

According to the present invention, it is possible to obtain an optical glass that suppresses the generation of false colors and flares by reliably cutting near ultraviolet rays and has a high transmission rate of light in the visible region (particularly blue light), and thus has high sensitivity. When used for the near-infrared cut filter glass of a solid-state image pickup device with higher definition and higher definition, the transmittance of blue light is particularly high and the color reproducibility is good. In addition, since it has a high cut characteristic of near-ultraviolet rays, it is possible to suppress the generation of noise such as flare, false color, and ghost in the captured image.

Claims (9)

Optical glass that absorbs infrared rays and ultraviolet rays
The optical glass has an inclination of an approximate straight line between the wavelength and the transmittance of 3 or more, which is calculated in the wavelength range of 3 nm before and after the wavelength at which the light transmittance is 50% in the wavelength band of 300 nm to 450 nm.
Essentially contains P and Cu as cation components,
Containing at least one selected from Cl, Br and I as an anion component,
The content of P is 35 to 75% as P ₂ O ₅ in terms of mass% based on oxides .
The Cu content is 0.5 to 25% in terms of cation% and contains crystals.
The crystal is characterized by containing at least one crystal selected from CuCl, CuBr and CuI.
Optical glass. The optical glass according to claim 1, wherein the average transmittance of light having a wavelength of 450 nm to 480 nm is 80% or more. The value obtained by subtracting the wavelength at which the light transmittance in the wavelength band of 300 nm to 450 nm is 50% from the wavelength at which the light transmittance in the wavelength band of 600 nm to 700 nm is 50% is in the range of 200 nm to 300 nm. The optical glass according to claim 1 or 2, characterized in that there is. The optical glass according to any one of claims 1 to 3, wherein the ratio of the average extinction coefficient having a wavelength of 700 nm to 850 nm to the average extinction coefficient having a wavelength of 450 nm to 480 nm is 33 or more. The optical glass according to any one of claims 1 to 4, wherein the content of at least one selected from Cl, Br and I is 0.01 to 20% in% anion. .. Contains Ag as a cation component,
The optical glass according to any one of claims 1 to 5, wherein the content of Ag is 0.01 to 5% in terms of cation%. P ₂ O ₅ : 35-75% in terms of mass% based on oxides
Al ₂ O ₃ : 5 to 15%
R ₂ O: 3 to 30% (However, R ₂ O represents the total amount of Li ₂ O, Na ₂ O and K ₂ O).
R'O: 3 to 35% (However, R'O represents the total amount of MgO, CaO, SrO, BaO, and ZnO).
CuO: 0.5-20%
The optical glass according to any one of claims 1 to 6, wherein the optical glass contains. Cation% P ⁵⁺ : 20-50%
Al ³⁺ : 5 to 20%
R ⁺ : 15-40% (However, R ⁺ represents the total amount of Li ⁺ , Na ⁺ , and K ⁺ )
^R'2+ : 5 to 30% (however, R'2 ^{+ represents the total amount of Mg 2+ ,} Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ ).
Total amount of Cu ²⁺ and Cu ⁺ : 0.5-25%
F- ^: 10-70% with anion%
The optical glass according to any one of claims 1 to 6, wherein the optical glass contains. A near-infrared cut filter comprising the optical glass according to any one of claims 1 to 8.