WO2018021222A1

WO2018021222A1 - Optical glass and near-infrared cut filter

Info

Publication number: WO2018021222A1
Application number: PCT/JP2017/026640
Authority: WO
Inventors: 信夫犬塚; 貴尋坂上
Original assignee: 旭硝子株式会社
Priority date: 2016-07-29
Filing date: 2017-07-24
Publication date: 2018-02-01
Also published as: CN109562981A; JPWO2018021222A1; JP7024711B2; TWI725213B; TW201806895A

Abstract

The present invention provides an optical glass and a near-infrared cut filter that reliably cut near-ultraviolet rays and have a high transmittance of light in the visible range (in particular, blue light). This optical glass absorbs infrared and ultraviolet rays, and is characterized in that an approximate straight line that represents the relationship between wavelength and transmittance and that is calculated in a wavelength range between 3 nm lower and 3 nm higher than a wavelength at which light transmittance is 50% in a wavelength band of 300-450 nm, has an inclination of 3 or more.

Description

Optical glass and near-infrared cut filter

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

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

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

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

The near-infrared cut filter glass described in Patent Document 1 has ultraviolet cut characteristics by containing Ce ⁴⁺ that 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 at which absorption peaks in glass. For example, Ce ⁴⁺ does not have steep near-ultraviolet absorption characteristics, and therefore absorbs blue light in the visible region adjacent to near-ultraviolet. Thereby, there exists a possibility that the transmittance | permeability of visible light may fall. In addition, this near-infrared cut filter glass does not have a steep near-ultraviolet absorption characteristic, so that part of the transmitted near-ultraviolet light is purple flare (purple that extends vertically from the long square at the center of the captured image). There is a risk of causing a haze).

The near-infrared cut filter glass described in Patent Document 2 is an optical that has high transmittance in the visible region and low transmittance 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 the glass, and near-ultraviolet rays are cut by the reflection action of the optical multilayer film. The optical multilayer film has a reflection characteristic that changes depending on the incident angle of light. Therefore, even for light having a wavelength of 0 with respect to light incident perpendicularly to the film formation surface, the optical multilayer film is completely resistant to obliquely incident light. In some cases, the light cannot be reflected and is transmitted. For this reason, there is a concern about the influence of false color, ghost, flare, etc. on the periphery of the image where light incident obliquely on the solid-state imaging device increases. In addition, when the light reflected by the optical multilayer film becomes stray light in the optical system and enters the optical multilayer film obliquely again, it reaches the photoelectric conversion surface of the solid-state image sensor and disturbs the color of the photographed image such as false color. Cause.

An object of the present invention is to provide an optical glass and a near-infrared cut filter that reliably cut near ultraviolet rays and have a 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. The calculated slope of the approximate line of wavelength and transmittance is 3 or more.

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 for 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 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) or on the subject side of the imaging optical system (on the opposite side of the solid-state imaging device) in the solid-state imaging device. The

The optical glass of the present invention has optical properties that transmit light in the visible region and absorb 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. The optical characteristic has an inclination of an approximate straight line between the wavelength and the 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 it is.

By providing such optical characteristics, it is possible to reliably cut near ultraviolet rays and suppress the occurrence of false colors, flares, and the like. In addition, because the near-ultraviolet ray is cut by the absorption action of the optical glass, not by the reflection action by the optical multilayer film, the change in the optical characteristics due to the oblique incidence of light is extremely small, and the near-ultraviolet ray caused by stray light in the solid-state imaging device Even when obliquely incident light is incident on the optical glass, near-ultraviolet rays can be reliably cut.

In the optical glass, if the inclination (S) is less than 3, a part of near ultraviolet rays are transmitted, and there is a concern about generation of false color or flare. The optical glass of the present invention has an inclination (S) of 3 or more. The slope (S) is preferably 3.5 or more, and more preferably 4 or more. Further, if the slope (S) is more than 20, it is not preferable because adjustment of the glass composition of the optical glass is extremely difficult and the production cost is increased. The slope (S) is preferably 20 or less, and more preferably 15 or less.

Note that 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. Is determined in detail by the following method.

First, the spectral transmittance of the optical glass is measured. Next, the 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, centering on the wavelength at which the transmittance is 50% (hereinafter sometimes referred to as “λ _{50 (300-450)} ” _), from λ _{50 (300-450)} to the short wavelength side and the long wavelength side. Seven points of transmittance data for each 1 nm are determined up to a wavelength of 3 nm. For example, when the wavelength at which the transmittance is 50% is 380 nm, the wavelength and transmittance data (total of 7 points) at 377 nm, 378 nm, 379 nm, 380 nm, 381 nm, 382 nm, and 383 nm are determined. Then, an approximate straight line with the wavelength [nm] as the X axis and the transmittance [%] as the Y axis is created from the data of these seven points, and the slope [% / nm] of the obtained approximate straight line is defined as the slope (S). .

The optical glass of the present invention preferably has an average transmittance of light having a wavelength of 450 nm to 480 nm of 80% or more. By having such characteristics, when the optical glass of the present invention is used in, for example, a solid-state imaging device, a captured image having high visible light blue light transmittance and excellent color reproducibility can be obtained. it can. Conventionally, the sensitivity of the sensor has been adjusted so as to achieve a color balance 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 receiving sensitivity capability inherent to the sensor.

Note that the above-described average transmittance is more preferably 81% or more, and further preferably 82% or more. Further, if the above-mentioned average transmittance is more than 92%, it is not preferable because it is very difficult to adjust the glass composition of the optical glass and the production cost is increased. The average transmittance is preferably 92% or less, and more preferably 91% or less.

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

The optical glass of the present invention has an average extinction coefficient at a wavelength of 700 nm to 850 nm (hereinafter referred to as “ε _{(700 (700} ₎ ”) with respect to an average extinction coefficient at a wavelength of 450 nm to 480 nm (hereinafter also 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 having such characteristics, when the optical glass of the present invention is used in, for example, a solid-state imaging device, the near-infrared ray unnecessary for the captured image is reliably cut, and the transmittance of blue light in the visible region is increased. Since the height can be increased, a captured image with high sensitivity and excellent color reproducibility can be obtained.

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, if the ratio of the average extinction coefficient (ε _(700-850) / ε _(450-480) ) is more than 80, it is not preferable because adjustment of the glass composition of the optical glass is extremely difficult and the production cost is increased. The average transmittance ratio (ε _(700-850) / ε _(450-480) ) is preferably 80 or less, and more preferably 70 or less.

In the near-infrared cut filter glass, it is desirable to increase both the light transmittance of wavelengths 450 nm to 480 nm and the light transmittance of wavelengths 700 nm to 850 nm. In the conventional near-infrared cut filter glass, there is a method of reducing 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 reduced. There is a harmful effect of becoming higher. In order to reduce the transmittance of light having a wavelength of 700 nm to 850 nm, there is a method of increasing the Cu concentration. However, in this case, 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 in the first place to increase both the light transmittance of wavelengths 450 nm to 480 nm and the light transmittance of wavelengths 700 nm to 850 nm. , One of the means of compromising one of the characteristics or making it a characteristic that balances the two had to be taken.

Although the optical glass of the present invention will be described in detail later, the Cu component in the optical glass related to both the transmittance of light with a wavelength of 450 nm to 480 nm and the transmittance of light with a wavelength of 700 nm to 850 nm will be described. By precipitating Cu ⁺ ions, which reduce the transmittance, as crystals in the glass as halides, and reducing the amount of Cu ⁺ ions present in the amorphous (glass) portion as much as possible, the above-mentioned optical characteristics can be achieved. It has been found that it can be obtained.

When Cu ⁺ ions are precipitated as crystals in glass as halides, there is almost no influence on Cu ²⁺ ions in the amorphous portion that reduces the transmittance of light with a wavelength of 700 nm to 850 nm. The transmittance of light having a wavelength of 450 nm to 480 nm can be increased while maintaining the preferable optical characteristic that the transmittance of light is low. Moreover, 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 cut near-ultraviolet rays unnecessary for the captured image.

The optical glass of the present invention essentially contains P and Cu as the cation component, and contains at least one selected from Cl, Br and I as the anion component, and the Cu content is from 0.5 to 0.5 in terms of cation%. 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 the 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. 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 improving the near-infrared cut property of optical glass. P is contained, for example, as P ⁵⁺ in the glass.

Cu is an essential component for cutting near infrared rays. Cu is contained in the glass, for example, as Cu ²⁺ or Cu ⁺ . When the content of Cu in the optical glass is less than 0.5%, the effect cannot be sufficiently obtained when the thickness of the optical glass is reduced, and when it exceeds 25%, the visible region transmittance is decreased, which is preferable. Absent. The Cu content is preferably 0.5 to 19%, more preferably 0.6 to 18%, and still more preferably 0.7 to 17%. In addition, Cu content means the total amount of Cu ^< ²⁺ ^{> in} 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 anionic 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 contents of Cl, Br and I in the optical glass are preferably 0.01 to 20% in terms of the total amount of anions. If the content of Cl, Br and I is less than 0.01%, crystals are difficult to precipitate, and if it exceeds 20%, volatility increases and the striae in the glass may increase, such being undesirable. 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. These components make it possible to sharply cut near-ultraviolet light 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 cut sharply.

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. When at least one selected from CuCl, CuBr, and CuI is precipitated in a 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 cation component. Ag is combined with at least one selected from Cl, Br and I, and silver halide (eg, AgCl) is precipitated. In this case, AgCl acts as a crystal nucleus and has an effect of facilitating 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 obtained sufficiently. On the other hand, if it exceeds 5%, Ag colloid is formed and the visible light transmittance is lowered, which is not preferable.

In addition, at least one crystal selected from CuCl, CuBr, and CuI may be precipitated 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 includes crystal nuclei in which at least one selected from Ag and Cl, Br and I is bonded, and other crystal nuclei. 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 the first embodiment composed of phosphate glass and crystals and the optical glass of Embodiment 2 composed of fluorophosphate glass and crystals as examples. To do.

The optical glass of Embodiment 1 of the present invention has a P ₂ O ₅ ratio of 35 to 75% in terms of mass% based on oxide.
Al ₂ O ₃ : 5 to 15%
R ₂ O: 3 to 30% (where R ₂ O represents the total amount of Li ₂ O, Na ₂ O and K ₂ O)
R′O: 3 to 35% (where R′O represents the total amount of MgO, CaO, SrO, BaO, and ZnO)
CuO: 0.5-20%
Containing.

The optical glass of Embodiment 1 contains at least one selected from Cl, Br, and I. The content and 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 contained in 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 improving the near-infrared cut property of optical glass. However, if it is less than 35%, the effect is sufficiently obtained. If it exceeds 75%, the glass becomes unstable, the weather resistance decreases, and the residual amount of at least one selected from Cl, Br and I in the optical glass decreases, and crystals do not sufficiently precipitate. 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. However, if it is less than 5%, the effect cannot be sufficiently obtained, and 15% If it exceeds, the glass becomes unstable, and the near-infrared cutting property 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 However, 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 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. Further, _{R 2} O _is, Li 2 O, is one or more selected from Na ₂ O and _{K 2} O, when two or more kinds may be any combination.

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 containing Li ₂ O, it is not preferable because the glass may become unstable when more than 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 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 the glass, lowering the liquidus temperature of the glass, and the like. When K ₂ O is contained, if it exceeds 25%, the glass becomes unstable and the coefficient of thermal expansion becomes remarkably 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 ingredient for increasing the strength of the 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 cutting property of the optical glass is lowered, and the strength of the glass is not preferred. The content of R′O is preferably 3.5 to 32%, more preferably 4 to 30%. Note that R′O is the total amount 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 any combination of two or more 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 make it easy to devitrify, and it is preferable not to include it particularly when the Cu content needs to be set high. When MgO is contained, if it exceeds 5%, the glass becomes extremely unstable, and the near-infrared cutting property of the optical glass is lowered, 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 the glass, lowering the liquidus temperature of the 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 tends to be devitrified. The CaO content 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 it contains SrO, if it exceeds 15%, the glass becomes unstable and easily devitrified. The SrO content 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 it contains BaO, if it exceeds 30%, the glass becomes unstable and tends to be devitrified. The content of BaO is preferably 0 to 27%, more preferably 0 to 25%.

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

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

In addition, the content of Cu in the cation% in the optical glass of Embodiment 1 is 0.5 to 25% as described above, and the preferable content is also as described above. When 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. 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 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 Embodiment 1 can further contain other components normally contained in phosphate glass such as SiO ₂ , SO ₃ , and B ₂ O ₃ as optional components as long as the effects of the present invention are not impaired. The total content of these components is preferably 3% or less.

Further, 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 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% of P ⁵⁺ : 20 to 50%
Al ³⁺ : 5 to 20%
R ⁺ : 15 to 40% (where R ⁺ represents the total amount of Li ⁺ , Na ⁺ and K ⁺ )
R ′ ²⁺ : 5 to 30% (where R ′ ²⁺ represents the total amount of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ )
Cu ²⁺ and Cu ⁺ in total amount: 0.5 to 25%
Anion% F ⁻ : 10-70%
It is characterized by containing.

In this specification, “cation%” and “anion%” are units as follows. First, the constituent components of the optical glass are divided into a cation component and an anion component. “Cation%” is a unit in which the content of each cation component is expressed as a percentage when the total content of all the cation components contained in the optical glass is 100 mol%. “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 embodiment 2, F ^- as an anion component other ^than, contain ^{O 2-,} ^Cl ^-, Br - and I ^- contains at least one selected from. In the optical glass of Embodiment 2, the content of O ²⁻ is as described later, and the content and content of at least one selected from Cl ⁻ , Br ⁻ and I ⁻ are as described above.

The reason why the contents (cation% and anion% display) of the respective components constituting the optical glass of Embodiment 2 of the present invention are limited as described above will be described below. In the following description, the content “%” of the component contained in the optical glass of Embodiment 2 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 near-infrared cut property of optical glass. However, if it is less than 20%, the effect cannot be sufficiently obtained. If it exceeds 50%, the glass becomes unstable and the weather resistance decreases, 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 weather resistance. However, if it is less than 5%, the effect cannot be sufficiently obtained, and if it exceeds 20%. This is not preferable because the glass becomes unstable and the near-infrared cutting property 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 ⁺ ) 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%, and still more preferably 17 to 36%. Note that R ⁺ is 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 any combination of two or more 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 cannot be sufficiently obtained, and if it exceeds 40%, the glass becomes unstable, which is not preferable. 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 Na ⁺ is contained, if less than 5%, the effect cannot be sufficiently obtained, and if it exceeds 40%, the glass becomes unstable, 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 less than 0.1%, the effect cannot be 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⁺ (where R ′ ²⁺ represents the total amount of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ ) lowers the melting temperature of the glass and lowers the liquidus temperature of the glass. It is an essential component for stabilizing the glass and increasing the strength of the 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 cutting property of the optical glass is deteriorated, and the strength of the glass is not preferable. The content of R ′ ²⁺ is preferably 5 to 28%, more preferably 7 to 25%, and still more preferably 9 to 23%. Note that R ′ ²⁺ is 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⁺ . R ′ ²⁺ is one or more selected from Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ , and any combination may be used in the case of two or more.

Mg ²⁺ 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, Mg ²⁺ tends to make the glass unstable and easily devitrified. When Mg ²⁺ is contained, the effect cannot be obtained sufficiently if it is less than 1%, and if it exceeds 30%, the glass is extremely unstable. And the melting temperature of the glass is increased. The Mg ²⁺ content 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, increasing the strength of the glass, and the like. When containing Ca ^2+, its effect can not be obtained sufficiently less than 1% is not preferable because the glass exceeds 30% tends to be devitrified to become unstable. The content of Ca ²⁺ is preferably 1 to 25%, more preferably 1 to 20%.

Sr ²⁺ 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 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 tends to be devitrified. The content of Sr ²⁺ is preferably 1 to 25%, more preferably 1 to 20%.

Ba ²⁺ 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. In the case of containing Ba ²⁺ , the effect is not sufficiently obtained if it is less than 0.1%, and if it exceeds 30%, the glass becomes unstable and tends to be devitrified. The Ba ²⁺ content is preferably 1 to 25%, more preferably 1 to 20%.

Zn ²⁺ is not an essential component, but has effects such as lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, and increasing the chemical durability of the glass. In the case of containing Zn ²⁺ , if less than 1%, the effect is not sufficiently obtained, and if it exceeds 30%, the glass becomes unstable and tends to be devitrified. The Zn ²⁺ content 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 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%. When the content is less than 0.1%, the effect cannot be sufficiently obtained when the thickness of the optical glass is reduced, and when it is 25% or more, the visible region transmittance of the optical glass is lowered. It is not preferable because Cu ⁺ cannot be contained. The Cu ²⁺ content 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, thereby giving the optical glass the effect of sharply cutting ultraviolet rays. 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 blue intensity 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 still more preferably 0.4 to 11%.

The optical glass of Embodiment 2 may contain 0 to 1% of Sb ³⁺ as an optional cation component. Sb ³⁺ is not an essential component, but has an 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 still more preferably 0.1 to 0.3%.

The optical glass of Embodiment 2 can further contain, as an optional cation component, other components that are normally contained in a fluorophosphate glass such as Si and B within a range not impairing the effects of the present invention. The total content of these components is preferably 5% or less.

(Anion component)
O ²⁻ is an essential component for stabilizing the glass, increasing the visible region transmittance of the optical glass, increasing mechanical properties such as strength, hardness and elastic modulus, and decreasing the ultraviolet transmittance. 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 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 the 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 not obtained. This is not preferred because there is a risk that mechanical properties such as strength, hardness and elastic modulus will decrease, volatility will increase and striae will increase. The content of F ⁻ is preferably 10 to 50%, more preferably 15 to 40%.

Since the optical glass of Embodiment 2 of the present invention contains the F component as an essential component, it has excellent weather resistance. Specifically, alteration of the optical glass surface and a decrease in transmittance due to reaction with moisture in the atmosphere can be suppressed. The weather resistance is evaluated by, for example, holding an optically polished optical glass sample in a high temperature and high humidity chamber at 65 ° C. and a relative temperature of 90% for 1000 hours using a high temperature and high humidity chamber. And the burnt state of the optical glass surface can be visually observed and evaluated. Moreover, the transmittance of the optical glass before being put into the high-temperature and high-humidity tank and the transmittance of the optical glass after being kept in the high-temperature and high-humidity tank for 1000 hours can also be compared and evaluated.

The optical glass of Embodiment 2 can further contain other components normally contained in a fluorophosphate glass such as S as an optional anion component within a range not impairing the effects of the present invention. 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. In addition, content of the crystal component in the optical glass of Embodiment 2 has the preferable range similar to the above as a crystallinity degree of filter glass.

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

Next, the content of other components, which are optional components other than the above-described components, common to the optical glass of Embodiment 1 and the optical glass of Embodiment 2 of the present invention will be described. In the present specification, “substantially not contained” means that it is not intended to be used as a raw material, and it is regarded as not containing a raw material component or an inevitable impurity mixed from a manufacturing process.

The optical glass of the present invention preferably contains substantially no PbO, As ₂ O ₃ , V ₂ O ₅ , YbF ₃ , or GdF ₃ . PbO is a component that lowers the viscosity of the glass and improves manufacturing workability. As ₂ O ₃ is a component that acts as an excellent clarifier that can generate a clarified 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 imaging device that is required to have high visible region transmittance. YbF ₃ and GdF ₃ are components that stabilize the glass, but since the raw materials are relatively expensive and lead to an increase in cost, it is desirable that YbF ₃ and GdF ₃ are not contained as much as possible.

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 an effect of improving the near-infrared cutting property by increasing the ratio of Cu ²⁺ ions in the total amount of Cu in the optical glass. The addition amount of the nitrate compound or sulfate compound is preferably 0.5 to 10% by mass based on the external addition to the raw material mixture. If the addition amount is less than 0.5% by mass, the effect of improving the transmittance is difficult to be obtained, and if it exceeds 10% by mass, glass formation tends to be difficult. More preferably, it is 1 to 8% by mass, and still more preferably 3 to 6% by mass.

As 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. The sulfate _{_{_{_{compounds, Al 2 (SO 4) 3}}}} · 16H 2 O, Li 2 SO 4, Na 2 SO 4, K 2 SO 4, MgSO 4, CaSO 4, SrSO 4, BaSO 4, ZnSO 4, CuSO 4 Etc.

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

Further, when the optical glass of the present invention has a thickness of 0.03 to 0.3 mm, the wavelength at which the transmittance is 50% is preferably 600 to 650 nm. By satisfying 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 a near-infrared cut filter having optical characteristics with high transmittance of light in the visible region is obtained.

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

In addition, since the optical glass of the present invention can cope with the downsizing and thinning of the imaging device and the equipment on which it is mounted, good spectral characteristics can be obtained even when the optical glass is thin. 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. Further, the lower limit value of the thickness of the optical glass is not particularly limited. However, in view of the strength that is difficult to break during the manufacture of the optical glass or when it is incorporated into the imaging apparatus, it is preferably 0.03 mm or more, more preferably 0.00. 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 in that the optical glass alone has the above-mentioned optical characteristics, but for the purpose of further improving the optical characteristics and protecting the optical glass from moisture etc., an antireflection film or You may provide optical thin films, such as an infrared cut film, an ultraviolet-ray, and an infrared cut film. These optical thin films are composed 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. Similarly to the 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 optical characteristics and protecting the optical glass from moisture or the like.

The optical glass of the present invention can be produced as follows.
First, raw materials are weighed and mixed so that the obtained optical glass is in the above composition range (mixing step). This raw material mixture is placed in a platinum crucible and heated and melted at a temperature of 700 to 1300 ° C. in an electric furnace (melting step). After sufficiently stirring and clarifying, a step of casting into a mold and precipitating crystals (crystal precipitation step) is performed, followed by cutting and polishing to form a flat plate having a predetermined thickness (molding step).

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

In addition, if the temperature in the melting step becomes too low, problems such as devitrification occur during melting and it takes a long time to melt off are caused. Therefore, in a fluorophosphate glass, it is preferably 700 ° C. or higher, more preferably 750 ° C. That's it. In the phosphate glass, it is more preferably 800 ° C. or higher, and further 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 within the above range.

The crystal precipitation step performed subsequent to the dissolution step is preferably performed by slow cooling or by slow cooling and heat treatment. The slow cooling is preferably performed at a rate of 0.1 to 2 ° C./min until it reaches 200 to 250 ° C. for fluorophosphate glass. In the case of phosphate glass, it is preferably performed at a rate of 0.1 to 2 ° C./min until the temperature reaches 200 to 250 ° C.

In the case where the crystal precipitation step is performed by gradual cooling and heat treatment, after gradual cooling similar to the above-mentioned gradual cooling conditions, in the fluorophosphate glass, the temperature is increased from 400 to 600 ° C. from the temperature after gradual cooling. It is preferable to perform heat treatment. Similarly, it is preferable that the phosphate glass is subjected to a heat treatment in which the temperature is raised from 350 to 600 ° C. after the slow cooling under the same slow cooling conditions as described above.

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 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 deposit at least one crystal selected from CuCl, CuBr, and CuI in the glass. By precipitating CuCl, CuBr, and CuI crystals, the amount of Cu ^{+ in} the amorphous (glass) portion excluding the crystal portion in the obtained optical glass can be reduced, and a sharp cut effect of ultraviolet rays can be provided. 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, etc. have been improved in sensitivity and definition, have good near-UV cut characteristics, and have a visible light transmittance (especially blue light transmittance). By using the high optical glass of the present invention as a near-infrared cut filter of a solid-state imaging device, it is possible to obtain a captured image in which color reproducibility is good and generation of noise components such as flare, false color, and ghost is suppressed. it can.

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

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

[Production of optical glass]
The raw materials are weighed and mixed so as to have the composition shown in Table 1 (expressed by mass% based on oxide) and the compositions shown in Table 2 and Table 3 (cation%, anion%), and put into a platinum crucible having an internal volume of about 400 cc. After melting, clarifying and stirring at a temperature of 800 to 1300 ° C. for 2 hours, it was cast into a rectangular mold having a length of 50 mm × width 50 mm × height 20 mm preheated to about 300 to 500 ° C.

For the examples of the present invention (Example 1-1, Example 1-2, Example 2-1, Example 2-4 to Example 2-8), after casting into a rectangular mold, slow cooling or slow cooling And heat treatment (Example 1-1 and Example 1-2: held at 460 ° C. for 1 hour, cooled to room temperature at 1 ° C./minute, then held at 480 ° C. for 1 hour, then cooled to room temperature at 1 ° C./minute, 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 to Example 2-8: Hold at 360 ° C. for 1 hour, then 1 ° C. / Cool to room temperature in minutes, then hold at 410 ° C. for 2 hours, then cool to room temperature at 1 ° C./minute, Example 2-5: Hold at 410 ° C. for 1 hour, then cool to room temperature at 1 ° C./minute) It was. For the comparative examples (Example 1-3, Example 2-2, and Example 2-3), slow cooling (Example 1-3: holding at 460 ° C. for 1 hour, then cooling to room temperature at 1 ° C./minute, Example 2- 2, Example 2-3: held at 360 ° C. for 1 hour and then cooled to room temperature at 1 ° C./minute). In each example, a block-shaped optical glass of 50 mm length × 50 mm width × 20 mm thickness was obtained. After this optical glass was ground, 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⁺ , and AlF ₃ , Al (PO ₃ ) ₃ and / or Al ₂ O _{3 in} the case of Al ^3+. the, in the case of Li ⁺ _LiF, a LiNO _{_3,} Li 2 _CO ₃ and / or LiPO ₃ a, in the case of ^{Mg 2+} MgF ₂ and / or MgO and / or Mg _(PO _{3) 2,} the case of ^{Sr 2+} is the SrF _2, SrCO ₃ and / or Sr _(PO _{3) 2,} a _BaF 2, BaCO ₃ and / or Ba _(PO _{3) 2} in the case of ^{Ba 2+,} Na ⁺ is NaCl and / or NaBr and / or NaI and / Or NaF and / or Na (PO ₃ ), fluorides, carbonates and / or metaphosphates in the case of K ⁺ , Ca ²⁺ , Zn ²⁺ , Sb in the case of Sb ³⁺ _{In the case of 2} O ₃ and 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 with 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 with an ultraviolet-visible near-infrared spectrophotometer (manufactured by JASCO Corporation, V570). For Examples 1-1 to 1-3, the transmittance (calculated with the surface reflection of the glass plate) converted to a thickness of 0.3 mm was obtained. For Examples 2-1 to 2-8, the transmittance (calculated with the surface reflection of the glass plate) converted to a 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.

(Slope of approximate straight line between wavelength and transmittance)
The method for determining the slope (S) is as follows.
The spectral transmittance of the optical glass is measured. Next, the 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 nearest integer value is set as a wavelength at which the transmittance is 50%. Then, seven points of transmittance data for each 1 nm are determined from λ _{50 (300-450)} as the center to a wavelength 3 nm away from λ _{50 (300-450)} on the short wavelength side and the long wavelength side. Then, an approximate straight line with 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 set as the slope of the approximate straight line between the wavelength and the transmittance.
Tables 4, 5, and 6 show the slopes (S) of Examples and Comparative Examples determined by this method.

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

(Difference between the wavelength of 50% transmittance on the ultraviolet side and the wavelength of 50% transmittance on the infrared side)
Obtained above lambda ₅₀ an _(300-450) and 50% transmittance of wavelengths of ultraviolet light side. Similarly, the 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, a wavelength difference (λ _{50 (600−700)} −λ _{50 (300−450)} ) is calculated from the difference between the two data.
Table 4, Table 5, and Table 6 show the wavelength differences of Examples and Comparative Examples obtained by this method.

(Average extinction coefficient ratio)
The method for determining the ratio of the average extinction coefficient of the optical glass is as follows.
The spectral transmittance of the optical glass is measured. Then, from the obtained spectral transmittance, the average extinction coefficient in the wavelength band of the wavelength _{450nm ~ 480nm (ε (450-480)} ) and the average absorption coefficient in the wavelength band of the wavelength _{700nm ~ 850nm (ε (700-850)} ) 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 range of 700 nm to 850 nm by the average extinction coefficient of the wavelength range of 450 nm to 480 nm. To 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 examples of the present invention has a steep near-ultraviolet cut characteristic (slope (S) is steep) with respect to each optical glass of the comparative example. Thereby, since the transmittance of unnecessary near ultraviolet rays can be extremely reduced, the occurrence of flare, false color, ghost, and the like in the captured image can be suppressed.

Each optical glass of the Example of this invention has especially high transmittance | permeability of the blue light of a 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 in the visible region (λ _{50 (600-700)} −λ _{50 (300-450)} ). Thereby, a captured image with good color reproducibility can be obtained.

Each optical glass of the example of the present invention has a higher ratio of average extinction coefficient (ε _(700-850) / ε _(450-480) ) than that of the 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 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, the near-ultraviolet rays are surely cut to suppress generation of false colors and flares, and an optical glass having a high transmittance of light in the visible region (particularly blue light) can be obtained. When used in near-infrared cut filter glass of a solid-state imaging device that is becoming higher in definition, the blue light transmittance is particularly high and the color reproducibility is good. In addition, since the near-ultraviolet cut characteristic is high, it is possible to suppress the occurrence of noise such as flare, false color, and ghost in the captured image.

Claims

An optical glass that absorbs infrared rays and ultraviolet rays,
In the optical glass, 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 3 or more. Optical glass characterized by
2. The optical glass according to claim 1, wherein an 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, wherein the optical glass is provided.
4. The optical glass according to claim 1, wherein a ratio of an average extinction coefficient at a wavelength of 700 nm to 850 nm to an average extinction coefficient at a wavelength of 450 nm to 480 nm is 33 or more.
Containing P and Cu as a cation component,
Containing at least one selected from Cl, Br and I as an anionic component;
The optical glass according to any one of claims 1 to 4, wherein the Cu content is 0.5 to 25% in terms of cation%, and contains crystals.
6. 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 includes at least one crystal selected from CuCl, CuBr, and CuI.
Containing Ag as a cation component,
8. The optical glass according to claim 5, wherein the Ag content is 0.01 to 5% in terms of cation%.
P 2 O 5 : 35 to 75% in terms of mass% based on oxide
Al 2 O 3 : 5 to 15%
R 2 O: 3 to 30% (where R 2 O represents the total amount of Li 2 O, Na 2 O and K 2 O)
R′O: 3 to 35% (where R′O represents the total amount of MgO, CaO, SrO, BaO, and ZnO)
CuO: 0.5-20%
The optical glass according to claim 5, further comprising:
P 5+ in cation%: 20-50 %
Al 3+: 5 ~ 20%
R + : 15 to 40% (where R + represents the total amount of Li + , Na + , and K + )
R ′ 2+ : 5 to 30% (where 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%
Anion% F − : 10-70%
The optical glass according to claim 5, further comprising:
A near-infrared cut filter comprising the optical glass according to any one of claims 1 to 10.