JPWO2018021222A1 - Optical glass and near infrared cut filter - Google Patents

Abstract

Providing optical glass and near-infrared cut filters that reliably cut near-ultraviolet light and have high transmittance of light in the visible region (especially blue light). An optical glass which absorbs infrared rays and ultraviolet rays, and the optical glass has a wavelength and a transmittance which are calculated in a wavelength range of 3 nm before and after the wavelength where light transmittance is 50% in a wavelength band of 300 nm to 450 nm. It is characterized in that the slope of the approximate straight line of is 3 or more.

Description

  The present invention relates to an optical glass and a near-infrared cut filter which are used for color correction filters (near-infrared cut filters) of digital still cameras and color video cameras, and in particular, have excellent light transmittance 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 around 1200 nm. Therefore, since good color reproducibility can not be obtained as it is, the visibility is corrected using a near infrared cut filter glass to which a specific substance that absorbs infrared light is added. As this near infrared cut filter glass, an optical glass in which CuO is added to fluorophosphate glass, or an optical glass in which CuO is added to phosphate glass is developed and used.

With the increase in sensitivity and definition of solid-state imaging devices, near-infrared cut filter glass is required to have near-ultraviolet cut characteristics and high transmittance of light in the visible region.
An example of a near infrared cut filter glass having near ultraviolet cut characteristics is described in Patent Document 1.
Moreover, as a near infrared cut filter glass provided with the high transmittance | permeability of the light of a visible region, there exists a thing of patent document 2. FIG.

JP, 2008-1544, A International Publication No. 2015/156163

The near-infrared cut filter glass described in Patent Document 1 has a cut characteristic of ultraviolet light by containing Ce ⁴⁺ which shows absorption near a wavelength of 350 nm in the glass. However, rare earth elements such as Ce and transition metal elements show absorption characteristics with a certain wavelength width from the central wavelength showing 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. Thereby, the transmittance of visible light may be reduced. Further, this near infrared cut filter glass is not provided with a steep near ultraviolet absorption characteristic, and part of the transmitted near ultraviolet light is purple flare (purple extending in the longitudinal direction from the long square at the center of the photographed image) It may cause a haze.

  The near-infrared cut filter glass described in Patent Document 2 is an optical that has high transmittance of light in the visible region and low transmittance of light in the near-infrared region by strictly controlling the valence of the Cu component in the glass. Characteristics are obtained. However, in this near infrared cut filter glass, an optical multilayer film is provided on glass, and near ultraviolet rays are cut by the reflection action of the optical multilayer film. The optical multilayer film changes its reflection characteristics depending on the incident angle of light, so that even if the light has a wavelength of 0 for light incident perpendicularly to the film formation surface, it is completely for light incident obliquely. There is a case where it can not be reflected but transmitted. For this reason, there is a concern that false colors, ghosts, flares, and the like may be exerted in the peripheral portion of the image where the amount of light obliquely incident on the solid-state imaging device increases. In addition, when light reflected by the optical multilayer film becomes stray light in the optical system and obliquely enters the optical multilayer film again, it reaches the photoelectric conversion surface of the solid-state imaging device and disturbs the color of the photographed image such as false color It becomes a cause.

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

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

  According to the present invention, an optical glass and a near-infrared cut filter having high transmittance of light in the visible region (especially blue light) are provided by reliably cutting near-ultraviolet rays to suppress generation of false color and flare. can do.

  Hereinafter, embodiments of the present invention will be described. The optical glass of the present invention is mainly composed of glass, and it is essential to contain crystals in the glass. Moreover, the optical characteristic of the optical glass in this specification shall have surface reflection resulting from the difference in the refractive index of 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 imaging device. Near-infrared cut filter glass is disposed between the imaging optical system (lens group) and the solid-state imaging device (sensor) in the solid-state imaging device, or on the object side of the imaging optical system (opposite side of the solid-state imaging device) Ru.

  The optical glass of the present invention has optical properties of transmitting light in the visible region and absorbing ultraviolet and infrared light. The optical glass of the present invention is an optical glass that absorbs infrared rays and ultraviolet rays, and is calculated in the wavelength range of 3 nm before and after the wavelength at which light transmittance is 50% in the wavelength band of 300 nm to 450 nm. The slope of the approximate straight line between the wavelength and the transmittance has an optical characteristic of 3 or more. Hereinafter, “Slope (S)” of “the slope of the approximate straight line between the wavelength and the transmittance, which is calculated in the range of the wavelength of 3 nm before and after the wavelength where light transmittance is 50% in the wavelength band of 300 nm to 450 nm” It may also be said.

  By providing such an optical characteristic, it is possible to reliably cut near-ultraviolet light and to suppress the occurrence of false color, flare and the like. In addition, since the near ultraviolet rays are cut by the absorption of the optical glass, not by the reflection by the optical multilayer film, the change of the optical characteristics accompanying the oblique incidence of light is extremely small, and the near ultraviolet rays caused by the stray light in the solid-state imaging device Even when oblique incident light is incident on the optical glass, near-ultraviolet light can be reliably cut.

  In the optical glass, if the inclination (S) is less than 3, generation of a false color, flare, or the like may occur due to the transmission of part of near-ultraviolet light. The optical glass of the present invention has a slope (S) of 3 or more. The slope (S) is preferably 3.5 or more, and more preferably 4 or more. In addition, if the inclination (S) is more than 20, adjustment of the glass composition of the optical glass is extremely difficult, which is not preferable because the manufacturing cost becomes high. The inclination (S) is preferably 20 or less, and more preferably 15 or less.

  The slope (slope (S)) of the approximate straight line between the wavelength and the transmittance calculated in the range of the wavelength of 3 nm before and after the wavelength at which the light transmittance is 50% in the above 300 nm to 450 nm wavelength band. 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 light transmittance in the wavelength band of 300 nm to 450 nm is 50% is specified. Here, when the wavelength obtained from the curve indicating the spectral transmittance does not become an integer value, the closest integer value is regarded as the wavelength at which the transmittance is 50%. Then, from the λ _{50 (300-450)} to the short wavelength side and the long wavelength side, centering on the wavelength at which the transmittance is 50% (hereinafter sometimes referred to as “λ _{50 (300-450)} ” ₎ Seven points of transmittance data for each 1 nm are determined up to a wavelength 3 nm apart. For example, when the wavelength at which the transmittance is 50% is 380 nm, data (total 7 points) of wavelengths and transmittance 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 seven 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 taken as the slope (S). .

  The optical glass of the present invention preferably has an average transmittance of 80% or more for light with a wavelength of 450 nm to 480 nm. By providing such characteristics, when the optical glass of the present invention is used in, for example, a solid-state imaging device, it is possible to obtain a captured image having high blue light transmittance in the visible region and excellent color reproducibility. it can. In addition, conventionally, the sensitivity of the sensor has been adjusted to balance the color with other wavelength components in the visible region in accordance with the transmittance of blue light. Therefore, by using the optical glass of the present invention, it is possible to perform high-sensitivity imaging that makes the best use of the light reception sensitivity capability that the sensor originally has.

  In addition, 81% or more is more preferable, and, as for the above-mentioned average transmittance | permeability, 82% or more is further more preferable. Moreover, adjustment of the glass composition of optical glass as it is very difficult that the above-mentioned average transmittance | permeability is more than 92% is unpreferable in order to become expensive for manufacturing cost. 92% or less is preferable and 91% or less of the above-mentioned average transmittance | permeability is more preferable.

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

The optical glass of the present invention has an average absorptivity at a wavelength of 700 nm to 850 nm (hereinafter, an “ε ₍₇₀₀ ) to an average absorptivity at a wavelength of 450 nm to 480 nm (hereinafter sometimes referred to as“ ε _(450-480) ”). ratio of _-850) "and sometimes referred _{to.), ε (700-850) /} ε (450-480) is preferably not more than 33. By providing such a characteristic, when the optical glass of the present invention is used in, for example, a solid-state imaging device, the transmittance of blue light in the visible region is reliably cut while reliably removing near-infrared light unnecessary for a captured image. Since the height can be increased, a captured image with high sensitivity and excellent color reproducibility can be obtained.

In addition, 34 or more are preferable and, as for the ratio ( _{(epsilon) (700-850)} / _{(epsilon) (450-480)} ) of an average absorption coefficient, 35 or more are more preferable. In addition, if the ratio of the average light absorption coefficient (ε _(700-850) / ε _(450-480) ) is more than 80, adjustment of the glass composition of the optical glass is extremely difficult, and the production cost becomes high. 80 or less is preferable and, as for the ratio ( _{(epsilon) (700-850)} / _{(epsilon) (450-480)} ) of an average transmittance _| permeability, 70 or less is more preferable.

  In the near infrared cut filter glass, it is desirable to simultaneously improve the transmittance of light with a wavelength of 450 nm to 480 nm and reduce the transmittance of light with a wavelength of 700 nm to 850 nm. In the conventional near infrared cut filter glass, there is a method to lower the Cu concentration in the glass in order to increase the transmittance of light with a wavelength of 450 nm to 480 nm. In this case, the transmittance of light with a wavelength of 700 nm to 850 nm is There is a bad effect of getting higher. Further, there is a method of increasing the Cu concentration in order to lower the transmittance of light having a wavelength of 700 nm to 850 nm, but in this case, there is a disadvantage 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 originally difficult to simultaneously achieve increasing the transmittance of light with a wavelength of 450 nm to 480 nm and decreasing the transmittance of light with a wavelength of 700 nm to 850 nm. The choice was either to compromise one or the other or to balance the two.

The optical glass of the present invention, which will be described in detail later, has a wavelength of 450 nm to 480 nm for the Cu component in the optical glass related to both the transmittance of light of wavelength 450 nm to 480 nm and the transmittance of light of wavelength 700 nm to 850 nm. The above optical characteristics are obtained by precipitating as crystals in the glass as Cu ⁺ ions that lower the transmittance of the metal as halides and reducing the amount of Cu ⁺ ions present in the amorphous (glass) portion as much as possible. It is found that it can be obtained.

In the case where Cu ⁺ ions are precipitated as crystals in the glass as halides, there is almost no influence on the Cu 2 ⁺ ions of the amorphous part which lowers the transmittance of light with a wavelength of 700 nm to 850 nm. The light transmittance of the light having a wavelength of 450 nm to 480 nm can be increased while maintaining the preferable optical property that the light transmittance of the light emitting element is low. Moreover, since the halide of Cu precipitated as crystals in glass has a steep absorption characteristic in the ultraviolet region, the optical glass of the present invention can also cut near ultraviolet light unnecessary for a captured image.

  The optical glass of the present invention essentially contains P and Cu as a cation component, contains at least one selected from Cl, Br and I as an anion component, and the content of Cu is 0.5 to 0.5 in cation%. 25% and contains crystals. That is, the optical glass of the present invention comprises glass and crystals. Glass is an amorphous component and is a main component of the optical glass of the present invention. The crystal is preferably a crystal in which the component contained in the glass is precipitated in the glass as a crystal. In the present specification, the content of each component indicates the content in the optical glass. Moreover, in the following description, when only calling it "glass", it means the glass as an amorphous component in optical glass.

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

Moreover, Cu is an essential component for near-infrared cutting. Cu is contained in the glass, for example, as Cu ²⁺ , Cu ⁺ . If the content of Cu in the optical glass is less than 0.5%, the effect is not sufficiently obtained when the thickness of the optical glass is reduced, and if it exceeds 25%, the visible light transmittance is reduced, which is preferable. Absent. The content of Cu is preferably 0.5 to 19%, more preferably 0.6 to 18%, and still more preferably 0.7 to 17%. In addition, content of Cu means the total amount of Cu ^{< 2+ >} in a glass, Cu ^<+> , and the Cu component in a crystal | crystallization.

The optical glass of the present invention contains at least one selected from Cl, Br and I as an anion component. Cl, Br and I may be contained in combination of two or more. 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 total of anion%. If the content of Cl, Br and I is less than 0.01%, it is difficult to precipitate crystals, and if it exceeds 20%, the volatility becomes high and the striae in the glass may increase, which is not preferable. The total content of Cl, Br and I in the optical glass is more preferably 0.01 to 15%, further 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. These components make it possible to cut light in the near ultraviolet region sharply in the obtained optical glass. Cl ^-, Br ^-, I ^- to fit the wavelength to be cut sharply the light in the near ultraviolet range can be appropriately selected.

  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 be precipitated as crystals. Since at least one selected from CuCl, CuBr and CuI is precipitated in a crystalline state, the sharp cuttability of light in the ultraviolet region can be enhanced.

  The optical glass of the present invention preferably contains Ag as a cationic component. Ag combines with 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 action 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 can not be obtained sufficiently. On the other hand, if it exceeds 5%, an Ag colloid is formed and the transmittance of visible light is unfavorably reduced.

  Further, a component to be a crystal nucleus other than silver halide may be precipitated or introduced into the optical glass to precipitate at least one crystal selected from CuCl, CuBr and CuI.

  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 a crystal nucleus or other crystal nucleus in which at least one selected from Ag and Cl, Br and I is bonded. May be included.

  Next, the optical glass of the present invention will be described by taking the optical glass of the two embodiments, that is, the optical glass of Embodiment 1 consisting of phosphate glass and crystals and the optical glass of Embodiment 2 consisting of fluorophosphate glass and crystals. Do.

The optical glass of Embodiment 1 of the present invention has P ₂ O ₅ : 35 to 75% in terms of mass% on an oxide basis.
Al ₂ O ₃ : 5 to 15%
R ₂ O: 3 to 30% (provided that R ₂ O represents the total amount of Li ₂ O, Na ₂ O and K ₂ O)
R'O: 3 to 35% (wherein R'O represents the total amount of MgO, CaO, SrO, BaO, and ZnO)
CuO: 0.5 to 20%
Contains

  The optical glass of Embodiment 1 contains at least one selected from Cl, Br and I. The content and the form of at least one selected from Cl, Br and I in the optical glass of Embodiment 1 are as described above. The reason for limiting the content of each component constituting the optical glass of Embodiment 1 of the present invention as described above will be described below. In the following description, the content “%” of the components of the optical glass of Embodiment 1 is mass% based on oxide unless otherwise specified.

P ₂ O ₅ is a main component (glass-forming oxide) that forms glass, and is an essential component for enhancing the cuttability of the near-infrared region of optical glass, but with less than 35%, the effect is sufficiently obtained When the content exceeds 75%, the glass becomes unstable, the weatherability decreases, and the residual amount of at least one selected from Cl, Br and I in the optical glass decreases, and the crystals do not precipitate sufficiently. Unfavorable. 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 the weather resistance etc. However, if it is less than 5%, the effect is not sufficiently obtained, and 15% When it is exceeded, the glass becomes unstable, and the near infrared cuttability of the optical glass is lowered, 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 total amount 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, stabilizes the glass If it is less than 3%, its effect can not be sufficiently obtained, and if it exceeds 30%, the glass becomes unstable. The content of R ₂ O is preferably 5 to 28%, more preferably 6 to 25%. 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. R ₂ O is one or more selected from Li ₂ O, Na ₂ O and K ₂ O, and in the case of two or more, 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 it contains Li ₂ O, it is not preferable because the glass becomes unstable if it exceeds 15%. 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 the glass, lowering the liquidus temperature of the glass, stabilizing the glass, and the like. When it contains Na ₂ O, if it exceeds 25%, the glass becomes unstable. 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 the glass, lowering the liquidus temperature of the glass, and the like. When it contains K ₂ O, if it exceeds 25%, the glass becomes unstable, and the thermal expansion coefficient becomes extremely large, which is not preferable. The content of K ₂ O is preferably 0 to 20%, more preferably 0 to 15%.

  R'O (where R'O represents the total amount of MgO, CaO, SrO, BaO, and ZnO) lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass It is an essential component for improving the strength of the glass, etc. If it is less than 3%, the effect can not be obtained sufficiently, and if it exceeds 35%, the glass becomes unstable, the near infrared cuttability of the optical glass is lowered, the strength of the glass is lowered, and so on. The content of R′O is preferably 3.5 to 32%, more preferably 4 to 30%. R'O is the total of MgO, CaO, SrO, BaO and ZnO, that is, R'O is MgO + CaO + SrO + BaO + ZnO. R'O is one or more selected from MgO, CaO, SrO, BaO and ZnO, and in the case of two or more, any combination may be used.

  MgO is a component for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, increasing the strength of the glass, and the like. However, MgO tends to destabilize the glass and tends to devitrify, and it is preferable not to contain it especially when the content of Cu needs to be set high. When it contains MgO, if it exceeds 5%, the glass becomes extremely unstable and the near infrared cuttability of the optical glass is unfavorably reduced. The content of MgO is preferably 0 to 3%, more preferably 0 to 2%.

  CaO is a component for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, stabilizing the glass, enhancing the strength of the glass, and the like. When it contains CaO, if it exceeds 10%, the glass becomes unstable and it tends to be devitrified, which is not preferable because the near infrared cuttability of the optical glass is lowered. The content of CaO is preferably 0 to 7%, more preferably 0 to 5%.

  SrO 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 the content of SrO is more than 15%, it is not preferable because the glass becomes unstable and devitrification tends to occur and the near infrared cuttability of the optical glass is lowered. 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 the glass, lowering the liquidus temperature of the glass, stabilizing the glass, and the like. When the content of BaO is more than 30%, it is not preferable because the glass becomes unstable and devitrification tends to occur and the near-infrared cuttability of the optical glass is lowered. The content of BaO 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 the glass, lowering the liquidus temperature of the glass, and enhancing the chemical durability of the glass. When it contains ZnO, if it exceeds 10%, the glass tends to be unstable, and the solubility of the glass is deteriorated. The content of ZnO is preferably 0 to 8%, more preferably 0 to 5%.

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

  In addition, content in the cation% of Cu in the optical glass of Embodiment 1 is 0.5 to 25% as above-mentioned, and preferable content is also as above-mentioned. When Cl, Br, and I respectively form CuCl, CuBr, and CuI, the cation% of Cu in the optical glass is the total content of the Cu component and other Cu components in the halogenated copper. It is.

The optical glass of Embodiment 1 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 the effect of enhancing the visible region transmittance of the optical glass. When Sb ₂ O ₃ is contained, it is not preferable because the stability of the glass decreases if it exceeds 3%. The content of Sb ₂ O ₃ is preferably 0 to 2.5%, more preferably 0 to 2%.

The optical glass of Embodiment 1 can further contain, as an optional component, other components usually contained in phosphate glass such as SiO ₂ , SO ₃ , B ₂ O _{3 and the} like within the range that does not impair the effect of the present invention. The total content of these components is preferably 3% or less.

  The optical glass of Embodiment 1 contains crystals as described above, and preferably contains at least one crystal selected from CuCl, CuBr and CuI.

  The optical glass of Embodiment 1 may further contain Ag as an optional component. The content and the form of Ag in the optical glass of Embodiment 1 are as described above.

Optical Glass of Embodiment 2
The optical glass of Embodiment 2 has a cation% P 5 ⁺ : 20 to 50%
Al ³⁺ : 5 to 20%
R ⁺ : 15 to 40% (provided that R ⁺ represents the total amount of Li ⁺ , Na ⁺ and K ⁺ )
R ′ ²⁺ : 5 to 30% (provided that R ′ ²⁺ represents the total amount of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ )
Total content of Cu ²⁺ and Cu ⁺ : 0.5 to 25%
F ^{− at} 10% of anions: 10 to 70%
It is characterized by containing.

  In the present specification, "cation%" and "anion%" are units as follows. First, the components of the optical glass are divided into a cationic component and an anionic component. And "cation%" is a unit which represented content of each cation component in percentage, when sum total content of all the cation components contained in optical glass is set to 100 mol%. The “anion%” is a unit in which the content of each anion component is expressed in percentage, when the total content of all the anion components contained in the optical glass is 100 mol%.

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

  The reason for limiting the content (in cation%, anion%) of each component constituting the optical glass of Embodiment 2 of the present invention as described above will be described below. In the following description, the content “%” of the components of the optical glass of Embodiment 2 is cation% for the cation component and anion% for the anion component unless otherwise noted.

(Cation component)
P ⁵⁺ is a main component (glass forming oxide) that forms glass, and is an essential component for enhancing the cuttability of the near infrared region of optical glass, but if it is less than 20%, the effect can not be obtained sufficiently When 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%, and 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 the weather resistance etc. However, if it is less than 5%, the effect is not sufficiently obtained, and if it exceeds 20% It is not preferable because the glass becomes unstable and the near infrared cuttability of the optical glass is lowered. The content of Al ³⁺ is preferably 6 to 18%, more preferably 6.5 to 15%, and still more preferably 7 to 13%.

R ⁺ (where R ⁺ represents the total amount of Li ⁺ , Na ⁺ and K ⁺ ) for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, for stabilizing the glass, etc. Although it is an essential component, if it is less than 15%, its effect can not be sufficiently obtained, and if it exceeds 40%, the glass becomes unstable. The content of R ⁺ is preferably 15 to 38%, more preferably 16 to 37%, and still more preferably 17 to 36%. R ⁺ refers to the total amount of Li ⁺ , Na ⁺ , and K ⁺ , that is, Li ⁺ + Na ⁺ + K ⁺ . R ⁺ is one or more selected from Li ⁺ , Na ⁺ and K ⁺ , and in the case of two or more, any combination may be used.

Li ⁺ is an essential component for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, stabilizing the glass, and the like. If it is less than 5%, the effect can not be obtained sufficiently, and if it exceeds 40%, the glass becomes unstable. The content of Li ⁺ is preferably 8 to 38%, more preferably 10 to 35%, and 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 it contains Na ⁺ , its effect can not be sufficiently obtained if it is less than 5%, and the glass becomes unstable if it exceeds 40%, which is not preferable. The content of Na ⁺ 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, if it is less than 0.1%, the effect is not sufficiently obtained, 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+ (provided that, R' ^{2+ is, Mg 2+, Ca 2+, Sr} 2+, Ba 2+, and represent the total amount of ^{Zn 2+)} lowers the melting temperature of the glass, lower the liquidus temperature of the glass It is an essential component for stabilizing the glass, enhancing the strength of the glass, and the like. If it is less than 5%, the effect can not be obtained sufficiently, and if it exceeds 30%, the glass becomes unstable, the near infrared cuttability of the optical glass is lowered, the strength of the glass is lowered, and so on. The content of R ′ ²⁺ is preferably 5 to 28%, more preferably 7 to 25%, and still more preferably 9 to 23%. R ' ²⁺ refers to 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 or more selected from Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ , and in the case of two or more, any combination may be used.

Mg ²⁺ is a component for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, enhancing the strength of the glass, and the like. However, Mg ²⁺ tends to destabilize the glass and tends to devitrify, and when it contains Mg ²⁺ , its effect can not be sufficiently obtained if it is less than 1%, and the glass is extremely unstable if it exceeds 30%. 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 the glass, lowering the liquidus temperature of the glass, stabilizing the glass, enhancing the strength of the glass, and the like. When it contains Ca ²⁺ , its effect can not be sufficiently obtained if it is less than 1%, and the glass becomes unstable and it tends to be devitrified if it exceeds 30%, which is not preferable. The content of Ca ²⁺ is preferably 1 to 25%, more preferably 1 to 20%.

Although not essential components, Sr ²⁺ 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 it contains Sr ²⁺ , its effect can not be obtained sufficiently if it is less than 1%, and if it exceeds 30%, the glass becomes unstable and devitrification tends to occur, which is not preferable because the strength of the glass decreases. 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 the glass, lowering the liquidus temperature of the glass, stabilizing the glass, and the like. When it contains Ba ²⁺ , its effect can not be obtained sufficiently if it is less than 0.1%, and if it exceeds 30%, the glass becomes unstable and devitrification tends to occur, which is not preferable because the strength of the glass is lowered. 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 the glass, lowering the liquidus temperature of the glass, and enhancing the chemical durability of the glass. When it contains Zn ²⁺ , its effect can not be obtained sufficiently if it is less than 1%, and if it exceeds 30%, the glass becomes unstable and devitrification tends to occur, which is not preferable because the solubility of the glass is deteriorated. 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 Embodiment 2, that is, the total content of Cu ²⁺ and Cu ^{+ is} the total amount of the Cu component and the other Cu component in the copper halide. Specifically, the content of Cu is 0.5 to 25% as described above, and the preferable content is also as described above.

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

Cu ⁺ reacts with Cl, Br, and I, and precipitates as a copper halide crystal, whereby the effect of sharp cutting ultraviolet light can be imparted to the optical glass. The content of Cu ⁺ is preferably 0.1 to 15%. If the content is less than 0.1%, the effect is not sufficiently obtained, and if it exceeds 15%, the blue intensity of the optical glass is undesirably reduced. The content of Cu ⁺ is preferably 0.2 to 13%, more preferably 0.3 to 12%, and still more preferably 0.4 to 11%.

The optical glass of Embodiment 2 may contain 0 to 1% of Sb ³⁺ as an optional cationic component. Although Sb ³⁺ is not an essential component, it has the effect of enhancing the visible region transmittance. When Sb ³⁺ is contained, it is not preferable because the stability of the glass is reduced if it exceeds 1%. The content of Sb ³⁺ is preferably 0.01 to 0.8%, more preferably 0.05 to 0.5%, and still more preferably 0.1 to 0.3%.

  The optical glass of Embodiment 2 can further contain, as an optional cationic component, other components usually contained by fluorophosphate glass, such as Si and B, in a range that does not impair the effect of the present invention. The total content of these components is preferably 5% or less.

(Anion component)
O ²⁻ is an essential component for reducing the ultraviolet light transmittance, in order to stabilize the glass, to increase the visible region transmittance of the optical glass, and to enhance the mechanical characteristics 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 can not 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 to improve the weatherability in order to stabilize the glass, but if it is less than 10%, the effect is not sufficiently obtained, and if it exceeds 70%, the visible region transmittance of the optical glass And mechanical properties such as strength, hardness and elastic modulus are lowered, and volatility is increased to increase striae. The content of F ⁻ is preferably 10 to 50%, more preferably 15 to 40%.

  The optical glass of Embodiment 2 of the present invention is excellent in weatherability because it contains the F component. Specifically, it is possible to suppress the deterioration of the optical glass surface and the reduction of the transmittance due to the reaction with the moisture in the atmosphere. The evaluation of the weather resistance is, for example, using a high temperature and high humidity tank, and holding the optically polished optical glass sample in a high temperature and high humidity tank at 65 ° C. and 90% relative temperature for 1000 hours. Then, the burnt state of the optical glass surface can be visually observed and evaluated. In addition, the transmittance of the optical glass before being charged into the high temperature and high humidity tank can be evaluated by comparing the transmittance of the optical glass after being held in the high temperature and high humidity tank for 1000 hours.

  The optical glass of Embodiment 2 can further contain, as an optional anion component, other components which fluorophosphate glass such as S usually contains, 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.

  The optical glass of Embodiment 2 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 Embodiment 2 is preferably in the same range as above as the degree of crystallinity of the filter glass.

  The optical glass of Embodiment 2 may further contain Ag as an optional cationic component. The content and the form of Ag in the optical glass of Embodiment 2 are as described above.

  Next, the contents of other components which are optional components other than the above-described components, which are common to the optical glass of Embodiment 1 of the present invention and the optical glass of Embodiment 2, will be described. In the present specification, "does not substantially contain" means that it is not intended to be used as a raw material, and it is considered that the raw material component and the unavoidable impurities mixed from the manufacturing process are not contained.

The optical glass of the present invention preferably 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. In addition, As ₂ O ₃ is a component that acts as an excellent fining agent capable of generating a fining gas in a wide temperature range. However, since PbO and As ₂ O ₃ are environmentally harmful 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 not to contain as much as possible in the near infrared cut filter glass for solid-state imaging device, which is required to have a high visible region transmittance. Although YbF ₃ and GdF ₃ are components for stabilizing the glass, it is desirable not to contain as much as possible because the raw materials are relatively expensive and cost increases.

In the optical glass of the present invention, a nitrate compound or a sulfate compound having a cation forming glass can be added as an oxidizing agent or a clarifying agent. The oxidizing agent has the effect of improving the near-infrared cuttability by increasing the proportion of Cu ²⁺ ions in the total amount of Cu in the optical glass. As for the addition amount of a nitrate compound and a sulfate compound, 0.5-10 mass% is preferable by external addition addition with respect to a raw material mixture. If the addition amount is less than 0.5% by mass, it is difficult to obtain the effect of improving the transmittance, and if it exceeds 10% by mass, the formation of glass tends to be difficult. More preferably, it is 1-8 mass%, More preferably, it is 3-6 mass%.

The nitrate _{compounds, 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, Zn (NO ₃ ) ₂ , Cu (NO ₃ ) _{2 and the} like. As a sulfate compound, Al ₂ (SO ₄ ) ₃ .16H ₂ O, Li ₂ SO ₄ , Na ₂ SO ₄ , Na ₂ SO ₄ , K ₂ SO ₄ , MgSO ₄ , CaSO ₄ , SrSO ₄ , BaSO ₄ , ZnSO ₄ , CuSO ₄ Etc.

  Moreover, it is preferable that the average transmittance | permeability of the light in wavelength 450-600 nm of the optical glass of this invention is 80% or more.

  Moreover, when the optical glass of this invention is made into 0.03-0.3 mm in thickness, it is preferable that the wavelength used as 50% of the transmittance | permeability is 600-650 nm. Under such conditions, it is possible to realize desired optical characteristics in a sensor that is required to be thin. Furthermore, when the thickness is 0.03 to 0.3 mm, by setting the transmittance at a wavelength of 450 nm to be 80% or more, a near infrared cut filter having optical characteristics with high transmittance of light in the visible region is obtained.

The value of the transmittance was converted so as to be a value in the case of a thickness of 0.03 to 0.3 mm. The conversion of the transmittance was performed using the following equation 1. Note that T _i1 is the internal transmittance of the measurement sample (data excluding reflection loss on the front and back surfaces), t ₁ is the thickness of the measurement sample (mm), T _i2 is the transmittance of the conversion value, and t ₂ is , The thickness to be converted (in the case of the present invention, 0.03 to 0.3 mm).

  In addition, since the optical glass of this invention respond | corresponds to size reduction and thickness reduction of an imaging device and its mounting apparatus, even if it is a state with thin thickness of optical glass, a favorable spectral characteristic is acquired. The 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 thickness of the optical glass is not particularly limited, but preferably 0.03 mm or more, more preferably 0. 3 mm or more, in consideration of the strength which is not easily damaged in the transportation at the time of manufacturing the optical glass or incorporating in the imaging device. It is at least 05 mm, more preferably at least 0.07 mm, and most preferably at least 0.1 mm.

  The optical glass of the present invention is characterized in that the optical glass alone is provided with the above-mentioned optical characteristics, but for the purpose of further improving the optical characteristics and protecting the optical glass from moisture etc. Optical thin films such as infrared cut films, ultraviolet light and infrared cut films may be provided. These optical thin films are formed 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, in the same manner 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, raw materials are weighed and mixed such that the resulting optical glass has the above composition range (mixing step). This raw material mixture is accommodated in a platinum crucible, and is heated and melted in an electric furnace at a temperature of 700 to 1300 ° C. (melting step). After sufficiently stirring and clarifying, casting is performed in a mold to carry out a step of crystal precipitation (crystal precipitation step), followed by cutting and polishing to form a flat plate having a predetermined thickness (forming step).

  In the melting step of the above manufacturing method, in the optical glass comprising fluorophosphate glass and crystals, for example, in the optical glass of Embodiment 2, the highest temperature of the glass being melted is an optical glass comprising phosphate glass and crystals at 950 ° C. or less In the glass, for example, the optical glass of Embodiment 1, the temperature is preferably 1280 ° C. or less. When the highest temperature of the glass during glass melting exceeds the above temperature, the transmittance characteristics deteriorate, and in fluoric acid glass, the volatilization of fluorine is promoted and the glass becomes unstable. The temperature is more preferably 900 ° C. or less, still more preferably 850 ° C. or less in fluorophosphate glass. In phosphate glass, it is more preferably 1250 ° C. or less, still more preferably 1200 ° C. or less.

  Also, if the temperature in the melting step becomes too low, problems such as devitrification during melting and long time to burn out will occur, so in fluoric acid glass preferably 700 ° C. or higher, more preferably 750 ° C. It is above. The phosphate glass is more preferably 800 ° C. or more, still more preferably 850 ° C. or more. In the method for producing an optical glass of the present invention, it is preferable that the glass component is not crystallized prior to the following crystal precipitation step, so that the temperature in the melting step is preferably in the above range.

  The crystal precipitation step performed subsequently to the melting step is preferably performed by slow cooling or slow cooling and heat treatment. Slow cooling is preferably performed at a rate of 0.1 to 2 ° C./minute in fluorophosphate glass until it reaches 200 to 250 ° C. In phosphate glass, it is preferable to carry out at a rate of 0.1 to 2 ° C./minute up to 200 to 250 ° C.

In addition, when the crystal precipitation step is performed by gradual cooling and heat treatment, after performing slow cooling similar to the above-described slow cooling conditions, temperature rise after slow cooling in fluorophosphate glass is from 400 to 600 ° C. It is preferable to carry out heat treatment. Similarly, after performing slow cooling similar to the conditions of the above-mentioned slow cooling in phosphoric acid glass, it is preferable to perform heat treatment to raise the temperature from the temperature after slow cooling to 350 to 600 ° C.

In the method for producing an optical glass of the present invention, crystals are precipitated in the glass in such a crystal precipitation step. The resulting optical glass of the present invention is an optical glass comprising 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 depositing 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 light is imparted. It is preferable because it can also be used.

  The optical glass of the present invention can be suitably used as a near infrared cut filter. Solid-state imaging devices used in digital cameras and the like have advanced in sensitivity and resolution, are excellent in near-ultraviolet cut characteristics, and have transmittance of light in the visible region (in particular, transmittance of blue light). By using the high optical glass of the present invention as a near-infrared cut filter of a solid-state image pickup device, it is possible to obtain a pickup image having good color reproducibility and suppressing generation of noise components such as flare, false color and ghost. it can.

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

  Tables 1 to 3 show examples of the present invention and comparative examples. Examples 1-1 and 1-2 are examples of the optical glass of the present invention according to phosphate glass, and example 1-3 is a comparative example of the optical glass of the present invention according to phosphate glass. Example 2-1, Example 2-4 to Example 2-8 is an example of the optical glass of the present invention according to fluorophosphate glass, and Example 2-2, Example 2-3 is the optical according to the present invention according to fluorophosphate glass It is a comparative example regarding glass.

[Preparation of optical glass]
Raw materials are weighed and mixed so as to obtain the compositions shown in Table 1 (mass% based on oxides) and the compositions shown in Table 2 and Table 3 (cation%, anion%), and put in a platinum crucible having an internal volume of about 400 cc. Then, it was melted at a temperature of 800 to 1300 ° C. for 2 hours, clarified and stirred, and then cast in a rectangular mold of 50 mm × 50 mm × 20 mm high preheated to about 300 to 500 ° C.

  About the example (Example 1-1, Example 1-2, Example 2-1, Example 2-4-Example 2-8) of this invention, after casting in a rectangular mold, it is annealed or annealed And heat treatment (Example 1-1 and Example 1-2: after holding at 460 ° C. for 1 hour, cool to room temperature at 1 ° C./min, then hold at 480 ° C. for 1 hour, then cool to room temperature at 1 ° C./min, Example 2-1: Hold at 360 ° C. for 1 hour, then cool to room temperature at 1 ° C./min, Example 2-4, Example 2-6, Example 2-8: After hold at 360 ° C. for 1 hour, 1 ° C./minute After cooling to room temperature in 1 minute and then holding at 410 ° C. for 2 hours, cooling at 1 ° C./minute to room temperature, Example 2-5: holding at 410 ° C. for 1 hour, then cooling to 1 ° C./minute to room temperature) The For Comparative Examples (Examples 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./minute, Example 2- 2. Example 2-3: After holding at 360 ° C. for 1 hour, it was cooled to room temperature at 1 ° C./minute). In each example, a block-shaped optical glass of 50 mm long × 50 mm wide × 20 mm thick was obtained. After grinding this optical glass, a glass plate polished to a desired thickness was used for evaluation.

The starting of the optical ^glass, the case of ^{P 5+} _H 3 PO ₄ and / or Al _{(PO 3)} 3, in the case of _{^{Al 3+ AlF 3, Al (PO}} 3) 3 and / or _Al 2 _{O 3} In the case of Li ⁺ LiF, LiNO ₃ , Li ₂ CO ₃ and / or LiPO ₃ , in the case of Mg ²⁺ MgF ₂ and / or MgO and / or Mg (PO ₃ ) ₂ , in the case Sr ²⁺ SrF ₂ , SrCO ₃ and / or Sr (PO ₃ ) ₂ , in the case of Ba ²⁺ , BaF ₂ , BaCO ₃ and / or Ba (PO ₃ ) ₂ , Na ⁺ is NaCl and / or NaBr and / or NaI and / or NaI and And / or NaF and / or Na (PO ₃ ), K ⁺ , Ca ²⁺ , fluoride in the case of Zn ²⁺ , carbonate and / or metaphosphate, Sb ^{3 in} the case of Sb ³⁺ ₂ O ₃ was used, and in the case of Cu ²⁺ and Cu ⁺ , CuO, CuCl and CuBr were used respectively. In the case of Ag ⁺ , AgNO ₃ was used.

[Evaluation]
About the glass plate 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. Furthermore, the transmittance | permeability of the light of wavelength 450-600 nm was measured with the ultraviolet visible near-infrared spectrophotometer (made by JASCO Corporation V570). About Example 1-1 to Example 1-3, the transmittance | permeability (calculated by surface reflection of a glass plate) converted into 0.3 mm in thickness was obtained. About Example 2-1 to Example 2-8, the transmittance | permeability (calculated by surface reflection of a glass plate) converted into thickness of 0.05 mm was obtained. Tables 1, 2 and 3 show the presence or absence of a crystal, 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 also 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 about the optical characteristic of each optical glass produced as mentioned above.

(Slope of approximate straight line of wavelength and transmittance)
The method of determining the slope (S) is as follows.
The spectral transmittance of the optical glass is measured. 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 indicating the spectral transmittance does not become an integer value, the closest integer value is taken as the wavelength at which the transmittance becomes 50%. Then, lambda ₅₀ centered at _{(300-450), λ 50 (300-450} ) to determine the transmittance data 7 points per 1nm to wavelength apart 3nm respectively to the short wavelength side and the long wavelength side from. Then, an approximate straight line is created from the data of these seven points with the wavelength as the X axis and the transmittance as the Y axis, and the slope of the approximate straight line obtained is taken as the slope of the approximate straight line between the wavelength and the transmittance.
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)
The spectral transmittance of the optical glass is measured. And the average transmittance | permeability of the light of a wavelength zone | band of wavelength 450nm-480nm is calculated from the obtained spectral transmission factor.
The average transmittances of Examples and Comparative Examples obtained by this method are shown in Tables 4, 5 and 6.

(The difference between the wavelength of 50% transmittance on the ultraviolet side and the wavelength of 50% on the infrared side)
Let λ _{50 (300-450)} obtained above be a wavelength of 50% transmittance 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. And the difference ((lambda _{) 50 (600-700)} -(lambda _{) 50 (300-450)} ) of a wavelength is calculated from the difference of both data.
Tables 4, 5, and 6 show the differences in wavelength of the examples and comparative examples obtained by this method.

(Ratio of average extinction coefficient)
The method of determining the ratio of the average absorption coefficient of the optical glass is as follows.
The spectral transmittance of the optical glass is measured. Then, based on the obtained spectral transmittance, the average absorption coefficient (ε _(450-480) ) of the wavelength band of wavelength 450 nm-480 nm and the average absorption coefficient (ε _(700-850) ) of the wavelength band of wavelength 700 nm-850 nm Calculate each. And the ratio of the average absorption coefficient (ε _(700-850) / ε _(450-480) ) by dividing the average absorption coefficient of the wavelength band of 700 nm to 850 nm by the average absorption coefficient of the wavelength band of 450 nm to 480 nm Decide.
Tables 4, 5, and 6 show the ratios of the average extinction coefficients of Examples and Comparative Examples obtained by this method.

  From Table 4, Table 5, and Table 6, each optical glass of the Example of this invention is steep in the cut characteristic of near-ultraviolet light with respect to each optical glass of a comparative example (slope (s) is steep). As a result, the transmittance of unnecessary near-ultraviolet light can be extremely reduced, and the occurrence of flare, false color, ghost, and the like in a captured image can be suppressed.

Each optical glass of the Example of this invention has the especially high transmittance | permeability of blue light of visible region with respect to each optical glass of a comparative example. Thereby, a captured image with good color reproducibility can be obtained.
Each optical glass of the embodiment of the present invention has a wide wavelength band ([lambda] _{50 (600-700)} -[lambda] _{50 (300-450)} ) in the visible region. Thereby, a captured image with good color reproducibility can be obtained.

Each optical glass of the Example of this invention has a high ratio ( _{(epsilon) (700-850)} / _{(epsilon) (450-480)} ) of an average absorption coefficient with respect to each optical glass of a comparative example. That is, each optical glass of the embodiment of the present invention has high transmittance of blue light in the visible region to be transmitted while reliably cutting near infrared light to be shielded. As described above, since the optical characteristics are sharp, it is possible to obtain a captured image with good color reproducibility.

  According to the present invention, it is possible to suppress the generation of false color, flare and the like by reliably cutting near-ultraviolet light, and to obtain optical glass having high transmittance of light in the visible region (especially blue light). When it is used for near-infrared cut filter glass of a solid-state imaging device to realize high definition and high resolution, in particular, the transmittance of blue light is high and the color reproducibility is good. In addition, since the near-ultraviolet cut characteristics are high, it is possible to suppress the occurrence of noise such as flare, false color, and ghost in a captured image.

Claims (11)

An optical glass that absorbs infrared and ultraviolet light,
In the optical glass, the slope of the approximate straight line between the wavelength and the transmittance is 3 or more, which is calculated in the range of the wavelength of 3 nm before and after the wavelength where light transmittance is 50% in the wavelength band of 300 nm to 450 nm. Optical glass characterized by   The optical glass according to claim 1, wherein the average transmittance of light with 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 becomes 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   The optical glass according to any one of claims 1 to 3, wherein a ratio of an average absorption coefficient at a wavelength of 700 nm to 850 nm to an average absorption coefficient at a wavelength of 450 nm to 480 nm is 33 or more. Essentially containing P and Cu as cationic components,
Containing at least one selected from Cl, Br and I as an anion component,
The optical glass according to any one of claims 1 to 4, wherein the content of Cu is 0.5 to 25% in cation%, and contains a crystal.   The optical glass according to claim 5, wherein the content of at least one selected from Cl, Br and I is 0.01 to 20% in terms of anion%.   The optical glass according to claim 5 or 6, wherein the crystal contains at least one crystal selected from CuCl, CuBr and CuI. Contains Ag as a cation component,
The optical glass according to any one of claims 5 to 7, wherein the content of Ag is 0.01 to 5% in terms of cation%. P ₂ O ₅ : 35 to 75% in mass% display based on oxide
Al ₂ O ₃ : 5 to 15%
R ₂ O: 3 to 30% (provided that R ₂ O represents the total amount of Li ₂ O, Na ₂ O and K ₂ O)
R'O: 3 to 35% (wherein R'O represents the total amount of MgO, CaO, SrO, BaO, and ZnO)
CuO: 0.5 to 20%
The optical glass according to any one of claims 5 to 8, characterized in that P ^{5+ in} cation%: 20 to 50%
Al ³⁺ : 5 to 20%
R ⁺ : 15 to 40% (wherein R ⁺ represents the total amount of Li ⁺ , Na ⁺ , and K ⁺ )
R ′ ²⁺ : 5 to 30% (wherein R ′ ²⁺ represents the total amount of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ )
Total content of Cu ²⁺ and Cu ⁺ : 0.5 to 25%
F ^{− at} 10% of anions: 10 to 70%
The optical glass according to any one of claims 5 to 8, characterized in that   A near infrared cut filter comprising the optical glass according to any one of claims 1 to 10.