Optical filter

Abstract

The present invention relates to an optical filter comprising: phosphate glass having near-infrared absorption capability and a thickness of 0.3 mm or less; a dielectric multilayer film 1 and a dielectric multilayer film 2 provided on both surfaces of the phosphate glass; a barrier film 1 provided between the phosphate glass and the dielectric multilayer film 1; a barrier film 2 provided between the phosphate glass and the dielectric multilayer film 2; and a light absorption layer provided on the dielectric multilayer film 2 and containing a near-infrared absorption dye. The barrier film 1 and the barrier film 2 each independently contain one or more selected from TiO2, Nb2O5, Ta2O5, and HfO2, and the optical filter satisfies all of specific spectral characteristics (i-1) to (i-5).

Description

Optical Filters

[0001] The present invention relates to an optical filter that transmits visible light and blocks near-infrared light.

[0002] In order to reproduce color tones well and obtain clear images, imaging devices using solid-state imaging elements use optical filters that transmit light in the visible wavelength range (hereinafter also referred to as "visible light") and block light in the near-infrared wavelength range (hereinafter also referred to as "near-infrared light").

[0003] Examples of such optical filters include various types, such as a reflective filter in which dielectric thin films with different refractive indices are alternately stacked on one or both sides of a transparent substrate (dielectric multilayer film) and the filter reflects light to be blocked by utilizing optical interference, an absorptive filter in which glass or a dye that absorbs light in a specific wavelength range is used to absorb light to be blocked, and a filter that combines a reflective type and an absorptive type.

[0004] Phosphate glass is known as a type of glass that absorbs light, but it is susceptible to the effects of moisture in the environment, and phosphoric acid may leach out and decompose other constituent materials of the optical filter. Therefore, technologies to prevent the leaching of phosphoric acid have been investigated. Patent Document 1 describes phosphate glass whose surface is coated with alumina to form a protective film for improved moisture resistance. Patent Document 2 describes an infrared cut filter in which infrared absorbing glass such as phosphate glass is bonded to a cover glass via an adhesive to improve moisture resistance.

[0005] Furthermore, Patent Document 3 describes an infrared cut filter using fluorophosphate glass.

[0006] Japanese Patent Application Publication No. 4-139035 Japanese Patent Application Publication No. 2016-18092 International Publication No. 2019 / 151348

[0007] However, with the technology described in Patent Document 1, the phosphate glass surface covered with an alumina protective film is less susceptible to moisture and moisture resistance is improved, but it is not possible to prevent the reaction of moisture with the glass end face that is not covered with the protective film.Furthermore, there is a risk that phosphoric acid eluted from the glass end face will react with the alumina protective film, resulting in a decrease in adhesion and causing film peeling.Also, with the technology described in Patent Document 2, the adhesive is an organic material, so moisture is likely to penetrate from near the end face.As a result, there is a risk that phosphoric acid eluted from the glass will deteriorate the adhesive and reduce adhesion.

[0008] Furthermore, optical filters having a dielectric multilayer film have a problem in that the optical film thickness of the dielectric multilayer film changes depending on the angle of incidence of light, resulting in a change in the spectral transmittance curve depending on the angle of incidence. In particular, with the recent trend toward thinner camera modules, the overall thickness of optical filters is required to be thinner, and since use under high angle of incidence is expected, optical filters that are less susceptible to the effects of the angle of incidence are required. The fluorophosphate glass described in Patent Document 3 has excellent moisture resistance, but its near-infrared light absorption ability is low, so to compensate for this, it is necessary to enhance the reflective properties of the dielectric multilayer film. However, dielectric multilayer films with strong reflective properties are easily affected by the angle of incidence, which may result in a decrease in visible light transmittance.

[0009] An object of the present invention is to provide an optical filter that is excellent in moisture resistance, can be made thin, and has excellent transmittance in the visible light region and excellent blocking in the near-infrared light region even at a high incident angle.

[0010] The present invention provides an optical filter or the like having the following configuration: an optical filter comprising phosphate glass, a dielectric multilayer film 1 and a dielectric multilayer film 2 provided on both sides of the phosphate glass, a barrier film 1 provided between the phosphate glass and the dielectric multilayer film 1, a barrier film 2 provided between the phosphate glass and the dielectric multilayer film 2, and a light absorbing layer provided on the dielectric multilayer film 2, wherein the phosphate glass has near-infrared absorbing properties, contains substantially no fluorine atoms, and has a thickness of 0.3 mm or less, the light absorbing layer contains a near-infrared absorbing dye, and the barrier films 1 and 2 each independently contain TiO ２ , Nb ２ O５ , Ta ２ O ５ , and HfO ２ An optical filter comprising one or more selected from the group consisting of: (i) an optical filter that satisfies all of the following spectral characteristics (i-1) to (i-5): (i-1) an average transmittance of wavelengths from 440 to 500 nm is 75% or more at an incident angle of 0 degrees and 60% or more at an incident angle of 60 degrees; (i-2) an average transmittance of wavelengths from 750 to 1000 nm is 2% or less at an incident angle of 0 degrees and 2% or less at an incident angle of 60 degrees; and (i-3) a wavelength IR10 at which the transmittance is 10% in the spectral transmittance curve at an incident angle of 0 degrees. （０ｄｅｇ） (i-4) In the spectral transmittance curve at an incident angle of 0 degrees, the wavelength IR10 at which the transmittance is 10% in the range of 600 to 700 nm （０ｄｅｇ） and the wavelength IR10 where the transmittance is 10% in the range of 600 to 700 nm in the spectral transmittance curve at an incident angle of 60 degrees. （６０ｄｅｇ） (i-5) The transmittance at a wavelength of 1100 nm is 5% or less at an incident angle of 0 degrees and 5% or less at an incident angle of 60 degrees.

[0011] According to the present invention, it is possible to provide an optical filter that is excellent in moisture resistance, can be made thin, and has excellent transmittance in the visible light region and excellent blocking in the near-infrared light region even at a high incident angle.

[0012] FIG. 1 is a cross-sectional view schematically showing an example of an optical filter according to an embodiment. FIG. 2 is a cross-sectional view schematically showing another example of an optical filter according to an embodiment. FIG. 3 is a diagram showing the spectral transmittance curve of glass 4. FIG. 4 is a diagram showing the spectral transmittance curve of a light absorbing layer. FIG. 5 is a diagram showing the spectral reflectance curves of a dielectric multilayer film 1A and a barrier film 1. FIG. 6 is a diagram showing the spectral reflectance curves of a dielectric multilayer film 1B and a barrier film 1. FIG. 7 is a diagram showing the spectral transmittance curve of an optical filter according to Example 2-8. FIG. 8 is a diagram showing the spectral reflectance curve (light absorbing layer side) of the optical filter according to Example 2-8. FIG. 9 is a diagram showing the spectral reflectance curve (dielectric multilayer film 1 side) of the optical filter according to Example 2-8.

[0013] Hereinafter, embodiments of the present invention will be described. In this specification, a near-infrared absorbing dye may be abbreviated as "NIR dye" and an ultraviolet absorbing dye may be abbreviated as "UV dye". In this specification, a compound represented by formula (I) is referred to as compound (I). The same applies to compounds represented by other formulas. A dye consisting of compound (I) is also referred to as dye (I), and the same applies to other dyes. Furthermore, a group represented by formula (I) is also referred to as group (I), and the same applies to groups represented by other formulas.

[0014] In this specification, the transmittance of glass, the light-absorbing layer including those in which a dye is contained in a resin, the transmittance measured by dissolving a dye in a solvent such as dichloromethane, the transmittance of a dielectric multilayer film, and the transmittance spectrum of an optical filter having a dielectric multilayer film are all "external (measured) transmittance" including reflection losses on the front and back surfaces, even when they are described as "transmittance."

[0015] In this specification, a transmittance of, for example, 90% or more in a specific wavelength range means that the transmittance is not below 90% across the entire wavelength range, i.e., the minimum transmittance is 90% or more across the wavelength range. Similarly, a transmittance of, for example, 1% or less in a specific wavelength range means that the transmittance is not more than 1% across the entire wavelength range, i.e., the maximum transmittance is 1% or less across the wavelength range. The average transmittance in a specific wavelength range is the arithmetic mean of the transmittance per 1 nm in the wavelength range. Spectral characteristics can be measured using a UV-Vis spectrophotometer. In this specification, the term "to" indicating a numerical range includes the upper and lower limits.

[0016] <Optical Filter> An optical filter according to one embodiment of the present invention (hereinafter also referred to as "this filter") comprises phosphate glass, dielectric multilayer film 1 and dielectric multilayer film 2 provided on both sides of the phosphate glass, and a light-absorbing layer provided on dielectric multilayer film 2. This filter further comprises barrier film 1 between the phosphate glass and dielectric multilayer film 1, and barrier film 2 between the phosphate glass and dielectric multilayer film 2. Barrier films 1 and 2 contain specific materials, as described below. Such barrier films prevent the phosphate glass from reacting with moisture in the environment, resulting in an optical filter with excellent moisture resistance. Furthermore, since the thickness of the phosphate glass is 0.3 mm or less, it is possible to reduce the thickness of the optical filter.

[0017] An example of the configuration of this filter will be described with reference to the drawings. Figures 1 and 2 are cross-sectional views that schematically show an example of an optical filter according to an embodiment.

[0018] The optical filter 1A shown in Figure 1 is an example that includes phosphate glass 10, a dielectric multilayer film 21 provided on one main surface of the phosphate glass 10, a dielectric multilayer film 22 provided on the other main surface of the phosphate glass 10, a light absorbing layer 30 provided on the dielectric multilayer film 22, a barrier film 11 provided between the phosphate glass 10 and the dielectric multilayer film 21, and a barrier film 12 provided between the phosphate glass 10 and the dielectric multilayer film 22.

[0019] The optical filter 1B shown in FIG. 2 is an example further including a dielectric multilayer film 23 laminated on the surface of the light absorbing layer 30.

[0020] The optical filter according to the embodiment of the present invention satisfies all of the following spectral characteristics (i-1) to (i-5): (i-1) the average transmittance for wavelengths from 440 to 500 nm is 75% or more at an incident angle of 0 degrees and 60% or more at an incident angle of 60 degrees; (i-2) the average transmittance for wavelengths from 750 to 1000 nm is 2% or less at an incident angle of 0 degrees and 2% or less at an incident angle of 60 degrees; (i-3) the wavelength IR10 at which the transmittance is 10% in the spectral transmittance curve at an incident angle of 0 degrees （０ｄｅｇ） (i-4) In the spectral transmittance curve at an incident angle of 0 degrees, the wavelength IR10 at which the transmittance is 10% in the range of 600 to 700 nm（０ｄｅｇ） and the wavelength IR10 where the transmittance is 10% in the range of 600 to 700 nm in the spectral transmittance curve at an incident angle of 60 degrees. （６０ｄｅｇ） (i-5) The transmittance at a wavelength of 1100 nm is 5% or less at an incident angle of 0 degrees and 5% or less at an incident angle of 60 degrees.

[0021] This filter, which satisfies all of the spectral characteristics (i-1) to (i-5), is an optical filter that has excellent visible light transmittance, as shown in characteristic (i-1), excellent near-infrared light blocking properties with wavelengths of 750 to 1000 nm, as shown in characteristic (i-2), and particularly excellent near-infrared light blocking properties with a wavelength of 1100 nm, as shown in characteristic (i-5), and is resistant to transmittance shift even at high angles of incidence, as shown in characteristic (i-4).

[0022] Satisfying the spectral characteristic (i-1) means that the transmittance in the visible light region of 440 to 500 nm is excellent even at a high incident angle. The average transmittance in the wavelength region of 440 to 500 nm is preferably 80% or more, more preferably 85% or more, at an incident angle of 0 degrees, and preferably 75% or more, more preferably 80% or more, at an incident angle of 60 degrees. In addition, in order to satisfy the spectral characteristic (i-1), for example, a dielectric multilayer film, phosphate glass, or near-infrared light absorbing dye, which has excellent transmittance in the visible light region, may be used.

[0023] Satisfying the spectral characteristic (i-2) means that the film has excellent shielding properties for near-infrared light in the 750 to 1000 nm region, even at high angles of incidence. The average transmittance for wavelengths of 750 to 1000 nm is preferably 1.5% or less, more preferably 1% or less, and even more preferably 0.5% or less at an angle of incidence of 0 degrees, and is preferably 1% or less, more preferably 0.5% or less, and even more preferably 0.4% or less at an angle of incidence of 60 degrees. In addition, in order to satisfy the spectral characteristic (i-2), for example, light shielding can be achieved by the absorption ability of phosphate glass or a near-infrared light-absorbing dye.

[0024] Satisfying the spectral characteristic (i-3) means that the wavelength region of 600 to 700 nm is a region in which the spectral transmittance curve rises from the near-infrared blocking region to the visible light transmitting region. （０ｄｅｇ）is preferably in the range of 610 to 695 nm, more preferably in the range of 620 to 690 nm.

[0025] Satisfying the spectral characteristic (i-4) means that the spectral transmittance curve is unlikely to shift in the wavelength region of 600 to 700 nm even at a high incident angle. （０ｄｅｇ） and wavelength IR10 （６０ｄｅｇ） The absolute value of the difference between the wavelengths is preferably 14 nm or less, and more preferably 13 nm or less. In addition, in order to satisfy the spectral characteristic (i-4), for example, light in the wavelength region of 600 to 700 nm can be shielded by phosphate glass or the absorption ability of a near-infrared light absorbing dye, which is not affected by the angle of incidence.

[0026] Satisfying the spectral characteristic (i-5) means that the glass has excellent shielding properties in the near-infrared region of 1100 nm even at a high angle of incidence. The transmittance at a wavelength of 1100 nm is preferably 4% or less, more preferably 3% or less, even more preferably 2% or less, even more preferably 1% or less, and most preferably 0.7% or less at an angle of incidence of 0 degrees, and is preferably 4% or less, more preferably 3% or less, even more preferably 2% or less, even more preferably 1% or less, and most preferably 0.4% or less at an angle of incidence of 60 degrees. In addition, in order to satisfy the spectral characteristic (i-5), for example, light blocking can be achieved by utilizing the absorption ability of phosphate glass.

[0027] The optical filter according to this embodiment preferably satisfies the following spectral characteristic (i-6). (i-6) The maximum transmittance at wavelengths of 750 to 1000 nm is 2% or less at an incident angle of 0 degrees and 2% or less at an incident angle of 60 degrees. Satisfying the spectral characteristic (i-6) means that the filter has excellent shielding properties for the near-infrared light region of 750 to 1000 nm, even at high incident angles. The maximum transmittance at wavelengths of 750 to 1000 nm is preferably 1.5% or less, more preferably 1.0% or less, at an incident angle of 0 degrees, and preferably 1.0% or less, more preferably 0.5% or less at an incident angle of 60 degrees. In addition, in order to satisfy the spectral characteristic (i-6), for example, light shielding can be achieved by the absorption ability of phosphate glass or a near-infrared light-absorbing dye.

[0028] The optical filter according to this embodiment preferably satisfies the following spectral characteristic (i-8). (i-8) When the light-absorbing layer side is the incident direction, the maximum reflectance at wavelengths of 450 to 950 nm is 35% or less at an incident angle of 5 degrees and 35% or less at an incident angle of 60 degrees. Satisfying the spectral characteristic (i-8) means that the reflectance characteristics at wavelengths of 450 to 950 nm are suppressed in the incident direction of external light. This is preferable in that it can suppress the phenomenon of light being emitted outside the originally intended optical path, so-called stray light. The maximum reflectance at wavelengths of 450 to 950 nm is preferably 15% or less, more preferably 10% or less, at an incident angle of 5 degrees, and preferably 25% or less, more preferably 20% or less at an incident angle of 60 degrees. To satisfy the spectral characteristic (i-8), for example, an anti-reflection film may be laminated on the light-absorbing layer.

[0029] The optical filter according to this embodiment preferably satisfies the following spectral characteristic (i-9). (i-9) When the dielectric multilayer film 1 side is the incident direction, the maximum reflectance at wavelengths of 450 to 950 nm is 20% or less at an incident angle of 5 degrees and 20% or less at an incident angle of 60 degrees. Satisfying the spectral characteristic (i-9) means that the reflectance at wavelengths of 450 to 950 nm is suppressed in the incident direction on the sensor side. This is preferable in that it can suppress so-called stray light, a phenomenon in which light reflected from the sensor surface is re-reflected on the dielectric multilayer film 1 surface and incident, causing light to be emitted outside the originally intended optical path. The maximum reflectance at wavelengths of 450 to 950 nm is preferably 15% or less, more preferably 10% or less, at an incident angle of 5 degrees, and preferably 15% or less, more preferably 10% or less, at an incident angle of 60 degrees. To satisfy the spectral characteristic (i-9), for example, a dielectric multilayer film 1 with low reflectance at wavelengths of 450 to 950 nm can be used.

[0030] The optical filter according to this embodiment preferably satisfies the following spectral characteristic (i-10): (i-10) The absolute value of the difference between the average transmittance at an incident angle of 0 degrees and the average transmittance at an incident angle of 60 degrees, for wavelengths of 440 to 500 nm, is 15% or less. Satisfying the spectral characteristic (i-10) means that the change in transmittance (ripple) of visible light is small even at high incident angles. The above absolute value is more preferably 10% or less. In order to satisfy the spectral characteristic (i-10), it is possible to use a dielectric multilayer film that has a small change in transmittance (ripple) of visible light even at high incident angles.

[0031] The optical filter according to this embodiment preferably satisfies the following spectral characteristic (i-11): (i-11) Average transmittance for wavelengths of 900 to 1000 nm is 1% or less at an incident angle of 0 degrees Satisfying the spectral characteristic (i-11) means that the filter has excellent shielding properties for near-infrared light with wavelengths of 900 to 1000 nm. The average transmittance for wavelengths of 900 to 1000 nm is more preferably 0.5% or less at an incident angle of 0 degrees. In order to satisfy the spectral characteristic (i-11), for example, the absorption ability of the phosphate glass and the reflection characteristics of the dielectric multilayer film can be combined to shield the relevant region.

[0032] <Phosphate Glass> The optical filter according to this embodiment includes phosphate glass. In this specification, phosphate glass is defined as a glass containing phosphate in mole percent (mol%) based on oxides. ２ O ５ The term "substantially free of fluorine atoms" refers to glass containing 40% or more of fluorine atoms and substantially free of fluorine atoms. Here, "substantially free of fluorine atoms" means that, when the content of component elements other than fluorine atoms contained in the glass is taken as 100% by mass and the content of fluorine atoms contained in the glass is expressed as an exclusive percentage, the content of fluorine atoms is less than 3% by mass. Phosphate glass has near-infrared absorbing properties and also functions as a support for optical filters. Furthermore, because it blocks light due to its absorption properties, its light blocking properties are less susceptible to the influence of the angle of incidence, unlike dielectric multilayer films.

[0033] The phosphate glass preferably has, in terms of a plate thickness of 0.25 mm, an average transmittance of 70% or more at wavelengths of 440 to 500 nm, a transmittance of 5.5% or less at wavelengths of 1200 nm, a transmittance of 1.0% or less at wavelengths of 1000 nm, and a transmittance of 1.5% or less at wavelengths of 800 nm. Phosphate glass that satisfies these spectral characteristics is preferable because it has sufficient transmittance of visible light and excellent near-infrared light absorption ability. The average transmittance of 440 to 500 nm is more preferably 80% or more. The transmittance of 1200 nm is more preferably 5% or less. The transmittance of 1000 nm is more preferably 0.5% or less. The transmittance of 800 nm is more preferably 1.0% or less.

[0034] The components that can constitute phosphate glass and their suitable contents are described below. In this specification, unless otherwise specified, the content of each component and the total content are expressed in mole percent based on the oxide.

[0035] The phosphate glass contains substantially no fluorine atoms and contains, in mole percent on an oxide basis, ２ O ５ 40%~75%, Al ２ O ３ 10% to 30%, ΣR ２ O 0.1% to 30% (However, R ２ O is Li ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ and one or more components selected from ΣR ２ O is R ２ and ΣR′O 0% to 30% (wherein R′O is one or more components selected from CaO, MgO, BaO, SrO, and ZnO, and ΣR′O represents the total content of R′O), and CuO 2 to 30%.

[0036] P ２ O ５ is the main component that forms glass and is a component that enhances the near-infrared ray blocking properties. ２ O ５If the content is 40% or more, the effect is sufficiently obtained, and if it is 75% or less, problems such as glass instability and reduced weather resistance are unlikely to occur. Therefore, the content is preferably 40% to 75%, more preferably 45 to 75%, even more preferably 50 to 70%, still more preferably 52 to 65%, particularly preferably 54 to 65%, and most preferably 55 to 60%.

[0037] Al ２ O ３ is the main component that forms glass, and is a component that increases the strength and weather resistance of glass. ２ O ３ If the content of Al is 10% or more, the effect is sufficiently obtained, and if it is 30% or less, problems such as glass instability and reduced near-infrared cutoff are unlikely to occur. Therefore, the content is preferably 10 to 30%, more preferably 11 to 27%, even more preferably 12 to 26%, still more preferably 12.5 to 25%, and most preferably 13 to 24.5%. ２ O ３ If the content is 13% or more, the weather resistance of the glass can be particularly improved.

[0038] R ２ O (However, R ２ O is Li ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ O) are components for lowering the melting temperature of the glass, lowering the liquidus temperature of the glass, stabilizing the glass, etc. ２ The total amount of O (ΣR ２ If O) is 0.1% or more, the effect is sufficiently obtained, and if it is 30% or less, the glass is less likely to become unstable, which is preferable. Therefore, it is preferably 1 to 25%, more preferably 2 to 20%, even more preferably 3 to 18%, still more preferably 4 to 17%, and most preferably 5 to 18%.

[0039] Li ２O is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass, etc. ２ The content of O is preferably 0 to 20%. ２ If the O content is 20% or less, problems such as glass instability and a decrease in near-infrared blocking properties are unlikely to occur, which is preferable. The O content is more preferably 0 to 15%, even more preferably 0 to 10%, still more preferably 0 to 5%, and most preferably Li ２ It should be noted that, in the present invention, "substantially free of O" means that a specific component is not intentionally added, and does not exclude the inclusion of a component that is unavoidably mixed in from raw materials or the like and that does not affect the desired properties.

[0040] Na ２ O is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, and stabilizes the glass. ２ The content of O is preferably 0 to 25%. ２ If the O content is 25% or less, the glass is less likely to become unstable, which is preferable, and the O content is more preferably 0.5 to 20%, even more preferably 1 to 15%, and even more preferably 2 to 10%.

[0041] K ２ O is a component that has the effect of lowering the melting temperature of the glass and the liquidus temperature of the glass. ２ The O content is preferably 0 to 25%. ２ If the O content is 25% or less, the glass is less likely to become unstable, which is preferable, and the O content is more preferably 0.5 to 20%, even more preferably 1 to 15%, and even more preferably 2 to 13%.

[0042] Rb ２ O is a component that has the effects of lowering the melting temperature of the glass and lowering the liquidus temperature of the glass. ２ The content of O is preferably 0 to 25%. ２If the O content is 25% or less, the glass is less likely to become unstable, which is preferable, and the O content is more preferably 0.5 to 20%, even more preferably 1 to 15%, and even more preferably 2 to 10%.

[0043] Cs ２ O is a component that has the effect of lowering the melting temperature of the glass and the liquidus temperature of the glass. ２ The content of O is preferably 0 to 25%. ２ If the O content is 25% or less, the glass is less likely to become unstable, which is preferable, and the O content is more preferably 0.5 to 20%, even more preferably 1 to 15%, and even more preferably 2 to 10%.

[0044] In addition, the above R ２ The alkali metal components represented by O produce a mixed alkali effect in the glass by adding two or more of each component at the same time, and R ＋ The mobility of ions is reduced, so that when the glass comes into contact with water, the H ＋ Ions and R in glass ＋ The hydration reaction caused by the ion exchange of ions is inhibited, and the weather resistance of the glass is improved. ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ In this case, it is preferable that the compound contains two or more components selected from R ２ O (However, R ２ O is Li ２ O, Na ２ O.K. ２ O, Rb ２ O, and Cs ２ The total amount (ΣR ２ O) is preferably 6 to 18% (but not including 7%). ２ If the total amount of O is 6% or more, the effect can be sufficiently obtained, and if it is 18% or less, problems such as instability of the glass, deterioration of the near-infrared cutoff property, and deterioration of the strength of the glass are unlikely to occur, which is preferable. ２O is preferably 7 to 18%, more preferably 8 to 18%, even more preferably 9 to 18%, still more preferably 10 to 18%, and most preferably 10.5 to 18%.

[0045] R'O (where R'O is one or more components selected from CaO, MgO, BaO, SrO, and ZnO) is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass, and increases the strength of the glass. The total amount of R'O (ΣR'O) is preferably 0 to 30%. A total amount of R'O of 30% or less is preferred because problems such as glass instability, reduced near-infrared blocking ability, reduced short-wavelength infrared transmittance, and reduced glass strength are less likely to occur. The amount is more preferably 0 to 25%, and even more preferably 0 to 20%. The amount is even more preferably 0 to 15%, and even more preferably 0 to 10%.

[0046] The glass of this embodiment preferably does not substantially contain divalent cations other than Cu. The reason for this is as follows. When the glass of this embodiment contains CuO, Cu ２＋ Light absorption in the near-infrared region is cut off by ions. ２－ Cu split by the electric field of ions ２＋ This occurs due to electron transitions between the d orbitals of the ions. The splitting of the d orbitals occurs in Cu ２＋ O present around the ion ２－ This is promoted by reducing the symmetry of the ion. For example, O ２－ When positive ions are present around an ion, the electric field of the positive ions causes the ２－ Ions are attracted and O ２－ The symmetry of the ions decreases. As a result, the splitting of d orbitals is promoted, and light absorption occurs due to electronic transitions between the split d orbitals, weakening the light absorption ability in the near-infrared region and strengthening the light absorption ability in the short-wavelength infrared region. Since the strength of the electric field of a cation increases with the valence of the ion, adding an oxide containing a divalent cation other than Cu to glass may reduce the near-infrared blocking ability and reduce the transmittance of short-wavelength infrared light.

[0047] CaO is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, stabilizes glass, and increases the strength of glass. The CaO content is preferably 0 to 20%. A CaO content of 20% or less is preferred because it is less likely to cause problems such as glass instability, reduced near-infrared blocking properties, and reduced transmittance of short-wavelength infrared rays. The CaO content is more preferably 0 to 15%, even more preferably 0 to 10%, and even more preferably 0 to 5%. Most preferably, the glass contains substantially no CaO.

[0048] MgO is a component that lowers the melting temperature of glass, lowers the liquidus temperature of glass, stabilizes glass, and increases the strength of glass. The MgO content is preferably 0 to 20%. An MgO content of 20% or less is preferred because it is less likely to cause problems such as glass instability, reduced near-infrared blocking properties, and reduced transmittance of short-wavelength infrared rays. The content is more preferably 0 to 15%, even more preferably 0 to 10%, and even more preferably 0 to 5%. Most preferably, the glass is substantially free of MgO.

[0049] BaO is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass, and so on. The BaO content is preferably 0 to 20%. A BaO content of 20% or less is preferable because it is less likely to cause problems such as glass instability, reduced near-infrared blocking properties, and reduced transmittance of short-wavelength infrared rays. The BaO content is more preferably 0 to 15%, even more preferably 0 to 10%, and even more preferably 0 to 5%. The BaO content may be 0.1% or more. Most preferably, BaO is substantially not contained.

[0050] SrO is a component that lowers the melting temperature of the glass, lowers the liquidus temperature of the glass, stabilizes the glass, and so on. The SrO content is preferably 0 to 20%. If the SrO content is 20% or less, problems such as glass instability, reduced near-infrared blocking properties, and reduced transmittance of short-wavelength infrared rays are unlikely to occur, which is preferable. The SrO content is more preferably 0 to 15%, and even more preferably 0 to 10%. Most preferably, the glass is substantially free of SrO.

[0051] ZnO has the effect of lowering the melting temperature of glass, lowering the liquidus temperature of glass, etc. The ZnO content is preferably 0 to 20%. A ZnO content of 20% or less is preferable because problems such as deterioration of the melting point of the glass, deterioration of the near-infrared blocking ability, and deterioration of the transmittance of short-wavelength infrared rays are unlikely to occur. The ZnO content is more preferably 0 to 15%, even more preferably 0 to 10%, and even more preferably 0 to 5%. Most preferably, ZnO is substantially not contained.

[0052] CuO is a component for blocking near-infrared rays. The CuO content is preferably 2 to 30%. A CuO content of 2% or more provides sufficient effects, while a CuO content of 30% or less is preferable because problems such as reduced transmittance in the visible light region and reduced transmittance in the short-wavelength infrared region are unlikely to occur. It is more preferably 5 to 25%, even more preferably 8 to 20%, and even more preferably 11 to 18%. Furthermore, it is even more preferably 12% or more. In particular, when the glass is substantially free of divalent cations other than Cu, a CuO content of 12% or more can further enhance the near-infrared blocking properties and the short-wavelength infrared transmittance. It is most preferably 13 to 18%.

[0053] B ２ O ３ may be contained in an amount of 15% or less to stabilize the glass. ２ O ３If the content of B is 15% or less, problems such as deterioration of the weather resistance of the glass, deterioration of the near-infrared cutoff property, and deterioration of the transmittance of short-wavelength infrared rays are unlikely to occur, and therefore it is preferable. It is preferably 13% or less, more preferably 11% or less, even more preferably 9% or less, still more preferably 7% or less, and most preferably B ２ O ３ It is substantially free of

[0054] MoO ３ is a component for increasing the transmittance of light in the visible region of the glass. ３ If the content is 0.1% or more, the effect of increasing the transmittance of light in the visible region of the glass is sufficient, and if it is 5% or less, problems such as a decrease in the near-infrared blocking ability and the occurrence of devitrification in the glass are unlikely to occur, so this is preferable. The content is more preferably 0.1 to 4.5%, even more preferably 0.1 to 4%, even more preferably 0.1 to 3.5%, and most preferably 0.1 to 3%.

[0055] In the glass of this embodiment, F (fluorine atom) is an effective component for improving weather resistance, but since it is an environmentally hazardous substance and there is a risk of reducing the near-infrared blocking ability, the glass does not substantially contain F. Here, "substantially not containing F" means that, when the content of component elements other than F contained in the glass is taken as 100 mass %, and the content of F contained in the glass is expressed as an exclusive percentage, the content of F is less than 3 mass % as an exclusive percentage.

[0056] In the glass of this embodiment, SiO ２ , GeO ２ , ZrO ２ , SnO ２ , TiO ２ , CeO ２ , W.O. ３ , Y ２ O ３ , La ２ O ３ , Gd ２ O ３ , Yb ２ O ３ , Nb ２ O ５may be contained in a range of 5% or less to improve the weather resistance of the glass. If the content of these components is 5% or less, problems such as a decrease in near-infrared blocking ability and a decrease in transmittance of short-wavelength infrared rays are unlikely to occur, which is preferable. The content is preferably 4% or less, more preferably 3% or less, even more preferably 2% or less, and even more preferably 1% or less.

[0057] The thickness of the phosphate glass is 0.3 mm or less, preferably 0.25 mm or less, from the viewpoint of ease of optical design when incorporating it into a camera module, and is preferably 0.05 mm or more, more preferably 0.1 mm or more, from the viewpoint of element strength and the need to obtain desired optical properties. The glass of this embodiment has excellent near-infrared absorption properties, so that even a thin glass can impart sufficient near-infrared light-blocking properties to an optical filter.

[0058] <Barrier Film> The optical filter according to this embodiment has barrier films 1 and 2 on both main surfaces of the phosphate glass. These barrier films are each independently made of TiO ２ , Nb ２ O ５ , Ta ２ O ５ , and HfO ２ The material contains one or more selected from the group consisting of TiO ２ , Nb ２ O ５ , Ta ２ O ５ , and HfO ２ Both of these have high resistance to moisture, and the presence of a barrier film having such a configuration between the phosphate glass and the dielectric multilayer film can prevent the phosphate glass from dissolving due to moisture. Furthermore, from the viewpoint of excellent adhesion to the phosphate glass, it is preferable that the barrier film satisfy such a configuration. For example, resin materials are not preferable as materials for barrier film 1 and barrier film 2 because they have lower moisture penetration resistance than inorganic materials.

[0059] The barrier film is TiO ２ , Nb ２ O ５ , Ta ２ O ５ , and HfO ２Preferably, the barrier film contains one or more selected from the group consisting of TiO 2 and TiO 3 in a total content of 80 mol % or more, more preferably 90 mol % or more, even more preferably 95 mol % or more, and particularly preferably 100 mol %. ２ , Nb ２ O ５ , Ta ２ O ５ , and HfO ２ The barrier film may contain 80 mol % or more of one or more materials selected from the group consisting of TiO and TiO 2 , or may contain 80 mol % or more of two or more materials in total, as long as the resistance to moisture is not impaired. ２ , Nb ２ O ５ , Ta ２ O ５ , and HfO ２ For example, from the viewpoint of adjusting the refractive index of the barrier film, SiO ２ and Al ２ O ３ It may contain TiO ２ , Nb ２ O ５ , Ta ２ O ５ , and HfO ２ When materials other than these are contained, it is preferable that the total content is 20 mol% or less. On the other hand, since a layer containing silicon (Si) may reduce adhesion to the glass substrate, it is preferable that it is not contained as much as possible. Furthermore, from the viewpoint of improving the water resistance of the optical filter, it is preferable that it is not contained with materials other than oxides of metals such as aluminum (Al), titanium (Ti), niobium (Nb), tantalum (Ta), and hafnium (Hf).

[0060] Furthermore, it is preferable that the physical thickness of the barrier film 2 and the dielectric multilayer film 2 positioned in the direction of incidence of external light satisfy a specific condition. That is, when a film consisting of the barrier film 2 and the dielectric multilayer film 2 is defined as the laminated film 2, X represented by the following formula (1) is preferably 35% or more.

[0061] X (%) = {A / (B-C)} x 100 (1) In formula (1), A (nm) is the total physical film thickness of the laminate film 2 that has a QWOT of less than 2 and a refractive index of 1.9 or less in the laminate film 2. B (nm) is the overall thickness of the laminate film 2 (total physical film thickness), and C (nm) is the total thickness of the layers in the laminate film 2 that have a QWOT of 2 or more. Here, QWOT (Quarter Wave Optical Thickness) is the optical film thickness at a wavelength of λ / 4, and is calculated by the following formula (2): QWOT = (physical film thickness nm / 550 nm) x 4 x (refractive index at 550 nm) (2) By controlling X, it is possible to suppress the reflection behavior caused by the provision of a barrier film, and to obtain an optical filter with better spectral characteristics. If X is 35% or more, for example, the maximum reflectance for wavelengths of 450 to 950 nm when the light-absorbing layer side is the incident direction, as shown in the spectral characteristics (i-5) of the optical filter, tends to fall within the desired range, which is preferable. As described above, by suppressing the maximum reflectance when the light-absorbing layer side is the incident direction, it is possible to suppress the intrusion of unnecessary light into the sensor. In other words, by providing a barrier film 2 and a dielectric multilayer film 2 in which X satisfies 35% or more, it is possible to control the reflectance on the light-absorbing layer side. X is more preferably 50% or more, and particularly preferably 70% or more.

[0062] The total physical film thickness of the laminated film 2 is determined by adding together the physical film thickness of the barrier film 2 and the physical film thickness of the dielectric multilayer film 2. The total physical film thickness of the laminated film 2 having a QWOT of 2 or more is determined by adding together the physical film thicknesses of the barrier film 2 and the films contained in the dielectric multilayer film 2 having a QWOT of 2 or more. The total physical film thickness of the laminated film 2 having a QWOT of less than 2 and a refractive index of 1.9 or less is determined by adding together the physical film thicknesses of the barrier film 2 and the films contained in the dielectric multilayer film 2 having a QWOT of less than 2 and a refractive index of 1.9 or less.

[0063] The thickness of the barrier film 1 is preferably 10 nm or more, more preferably 20 nm or more, from the viewpoint of improving the moisture resistance and reliability of the optical filter. The thickness of the barrier film 2 is preferably 10 nm or more, more preferably 20 nm or more, from the viewpoint of improving the moisture resistance and reliability of the optical filter.

[0064] The total physical thickness of the barrier film 1 and the dielectric multilayer film 1 is preferably 150 nm or more, more preferably 180 nm or more, even more preferably 200 nm or more, and particularly preferably 300 nm or more. This range is preferable from the viewpoint of improving the water resistance of the optical filter and preventing film deformation when the glass surface is altered. On the other hand, from the viewpoint of relieving stress and suppressing peeling from the glass, the total physical thickness of the barrier film 1 and the dielectric multilayer film 1 is preferably 5 μm or less, more preferably 3 μm or less. The total physical thickness of the barrier film 1 and the dielectric multilayer film 1 can be selected according to the desired characteristics of the optical filter. The total physical thickness of the barrier film 2 and the dielectric multilayer film 2 is preferably 150 nm or more, more preferably 180 nm or more, even more preferably 200 nm or more, and particularly preferably 300 nm or more. This range is preferable from the viewpoint of improving the water resistance of the optical filter and preventing film deformation when the glass surface is altered. On the other hand, from the viewpoint of alleviating stress and suppressing peeling from the glass, the total physical thickness of the barrier film 2 and the dielectric multilayer film 2 is preferably 5 μm or less, and more preferably 3 μm or less. The total physical thickness of the barrier film 2 and the dielectric multilayer film 2 can be selected according to the desired characteristics of the optical filter.

[0065] The barrier film can be formed by, for example, a vacuum film-forming process such as CVD, sputtering, or vacuum deposition, or a wet film-forming process such as spraying or dipping.

[0066] The laminated film 2 is SiO ２ In the case where the laminated film 2 has a layer made of SiO, X' represented by the following formula (3) may be 35% or more. X' (%) is more preferably 50% or more, and even more preferably 70% or more: X' (%) = {A' / (B'-C')} x 100 (3) In formula (3), A' (nm) represents the percentage of SiO in the laminated film 2 having a thickness of 180 nm or less. ２ B' (nm) is the total thickness of the stacked film 2; C' (nm) is the thickness of the SiO 2 layer having a thickness greater than 180 nm in the stacked film 2; ２ is the total thickness of the layers.

[0067] <Dielectric Multilayer Film> The optical filter according to this embodiment has a dielectric multilayer film 1 on the barrier film 1 side and a dielectric multilayer film 2 on the barrier film 2 side. As will be described in detail later, when a film consisting of the barrier film 1 and the dielectric multilayer film 1 is stacked film 1, and when a film consisting of the barrier film 2 and the dielectric multilayer film 2 is stacked film 2, stacked film 1 and stacked film 2 are preferably designed as a reflective film that reflects a portion of near-infrared light (hereinafter also referred to as an "NIR reflective film") or a near-infrared anti-reflective film (hereinafter also referred to as an "NIR anti-reflective film"). The optical filter according to this embodiment preferably includes phosphate glass, which has excellent near-infrared absorption properties. In this case, even when stacked film 1 and stacked film 2 are designed as NIR reflective films, the optical filter as a whole has excellent near-infrared light blocking properties without increasing the reflectivity in the near-infrared light region. By designing these stacked films to suppress the reflectivity in the near-infrared light region, a decrease in transmittance in the visible light region can be avoided and a shift in spectral characteristics depending on the incident angle is less likely to occur.

[0068] The NIR reflective film preferably has wavelength selectivity that transmits visible light and primarily reflects near-infrared light, for example. Specifically, it is preferably configured to have a wavelength band with a width of 100 nm or more, in which the reflectance at an incident angle of 5 degrees is 80% or more for light with a wavelength between 750 nm and 1200 nm. The NIR reflective film may also be appropriately designed to reflect light in wavelength ranges other than near-infrared light, for example, near-ultraviolet light. As an NIR anti-reflection film, in order to suppress reflection of visible light even when the incident angle changes, a film with low reflectance over the entire wavelength band is preferred, rather than a film that reflects a specific wavelength.

[0069] A dielectric multilayer film is a laminate of dielectric films with different refractive indices. More specifically, examples include a low-refractive index dielectric film (low-refractive index film), a medium-refractive index dielectric film (medium-refractive index film), and a high-refractive index dielectric film (high-refractive index film), and the dielectric multilayer film is composed of two or more of these laminated films. When transmitting or selecting a desired wavelength band, the reflection characteristics can be adjusted by combining several types of dielectric films with different spectral characteristics.

[0070] The high refractive index material preferably has a refractive index of 1.9 or more and 3.0 or less, more preferably 1.9 or more and 2.8 or less, and even more preferably 1.9 or more and 2.6 or less at a wavelength of 500 nm. ２ O ５ , TiO ２ , TiO, Nb ２ O ５ Other commercially available products include OS50 (Ti) manufactured by Canon Optron Co., Ltd. ３ O ５ ), OS10 (Ti ４ O ７ ), OA500 (Ta ２ O ５ and ZrO ２ a mixture of OA600 (Ta ２ O ５ and TiO ２ Among these, TiO is preferred in terms of film-forming property, reproducibility in refractive index, stability, etc. ２ is preferred.

[0071] The medium refractive index material is a material having a relatively lower refractive index than the high refractive index material, and the refractive index at a wavelength of 500 nm is preferably 1.5 or more and 2.0 or less, more preferably 1.5 or more and 1.95 or less, and even more preferably 1.5 or more and 1.9 or less. ２ , Nb ２ O ５ , Al ２ O ３ , HfO ２ and OM-4 and OM-6 (Al) sold by Canon Optron. ２ O ３ and ZrO ２ Among these, Al is preferred in terms of film-forming properties, reproducibility in refractive index, stability, etc. ２ O ３ Al-based compounds ２ O ３ and ZrO ２ A mixture of is preferred.

[0072] The low refractive index material is a material that has a relatively lower refractive index than the medium refractive index material, and the refractive index at a wavelength of 500 nm is preferably 1.3 or more and 1.7 or less, more preferably 1.3 or more and 1.65 or less, and even more preferably 1.3 or more and 1.6 or less. Examples of low refractive index materials include SiO ２ , SiO ｘ N ｙ、 MgF ２ Other commercially available products include S4F and S5F (SiO ２ and AlO ２ Among these, SiO is preferred from the viewpoints of reproducibility, stability, economy, etc. in film formation. ２ is preferred.

[0073] When the dielectric multilayer film 1 is formed into a laminate film 1 consisting of a barrier film 1 and a dielectric multilayer film 1, the laminate film 1 is preferably designed as a reflective film that reflects a portion of near-infrared light, and more preferably as a reflective film that gently blocks light in the near-infrared region. Designing a dielectric multilayer film to enhance the reflectivity in the near-infrared region makes it more likely that ripples will occur in the visible light region when light is incident at a high angle of incidence, resulting in a decrease in visible light transmittance. Designing the laminate film 1 so that it does not strongly block light in the near-infrared region results in an optical filter that is less susceptible to the effects of the angle of incidence. The light blocking properties in the near-infrared region that cannot be completely blocked by the reflectivity properties of the laminate film 1 are complemented by the absorption properties of the phosphate glass described above and the near-infrared absorbing dye described below, thereby providing excellent near-infrared light blocking properties as a whole for the optical filter of the present invention. Specifically, the average reflectivity in the wavelength range from 800 nm to 1200 nm at an incident angle of 5° is preferably 50% to 90%.

[0074] The thickness (physical thickness) of the dielectric multilayer film 1 is preferably 100 nm or more, more preferably 300 nm or more, from the viewpoint of suppressing deterioration of the material, and is preferably 5 μm or less from the viewpoint of productivity and suppressing reflection ripples in the visible light region.

[0075] The total number of layers in the dielectric multilayer film 1 is preferably 15 or more, more preferably 30 or more, and even more preferably 35 or more. However, since a larger total number of layers may cause warping or an increase in film thickness, the total number of layers is preferably 100 or less, more preferably 75 or less, and even more preferably 60 or less.

[0076] The thickness (physical thickness) of the dielectric multilayer film 2 is preferably 100 nm or more, more preferably 300 nm or more, from the viewpoint of suppressing deterioration of the material, and is preferably 5 μm or less from the viewpoint of productivity and suppressing reflection ripples in the visible light region.

[0077] The total number of layers in the dielectric multilayer film 2 is preferably 1 or more, more preferably 2 or more. However, if the total number of layers is too large, warping or the like may occur or the film thickness may increase, so the total number of layers is preferably 100 or less, more preferably 75 or less, even more preferably 50 or less, still more preferably 25 or less, and most preferably 10 or less.

[0078] The filter may have at least one outermost surface, preferably on the surface of the light absorbing layer, a dielectric multilayer film 3. From the viewpoint of reducing ripples in the visible light region, the dielectric multilayer film 3 is preferably designed as a near-infrared anti-reflection film (NIR anti-reflection film), for example.

[0079] The total number of laminated layers in the dielectric multilayer film 3 is preferably 25 or less, more preferably 20 or less, even more preferably 17 or less, and is preferably 3 or more. In order to suppress reflection in the visible wavelength range even when the angle of incidence changes, a film with low reflectance over the entire wavelength range is preferred, rather than a film that reflects only specific wavelengths. The overall thickness (physical thickness) of the dielectric multilayer film 3 is preferably 200 to 600 nm.

[0080] The dielectric multilayer film can be formed by, for example, a vacuum film-forming process such as CVD, sputtering, or vacuum deposition, or a wet film-forming process such as spraying or dipping.

[0081] <Light Absorption Layer> The optical filter according to this embodiment includes a light absorption layer provided on the dielectric multilayer film 2. The light absorption layer contains a near-infrared absorbing dye, and can compensate for the wavelength region that is not blocked by the reflection characteristics of the dielectric multilayer film by absorbing light. The near-infrared absorbing dye preferably has a maximum absorption wavelength in the range of 680 to 800 nm. From the viewpoint of being able to absorb light over a wide range in the near-infrared region and suppressing a decrease in visible light transmittance, it is preferable to combine two or more near-infrared absorbing dyes that have different maximum absorption wavelengths in the range of 680 to 800 nm, and it is more preferable to combine one or more near-infrared absorbing dyes whose maximum absorption wavelength is 700 nm or more but less than 740 nm with one or more near-infrared absorbing dyes whose maximum absorption wavelength is 740 to 800 nm.

[0082] The near-infrared absorbing dye is preferably at least one selected from the group consisting of squarylium dyes, cyanine dyes, phthalocyanine dyes, naphthalocyanine dyes, dithiol metal complex dyes, azo dyes, polymethine dyes, phthalide dyes, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, pyrylium dyes, thiopyrylium dyes, croconium dyes, tetradehydrocoline dyes, triphenylmethane dyes, aminium dyes, and diimmonium dyes.

[0083] The near-infrared absorbing dye preferably contains at least one dye selected from a squarylium dye, a phthalocyanine dye, and a cyanine dye. Among these dyes, squarylium dyes and cyanine dyes are preferred from the viewpoint of spectral properties, and phthalocyanine dyes are preferred from the viewpoint of durability.

[0084] The light-absorbing layer is preferably a resin film containing the dye and a resin. The content of the near-infrared absorbing dye in the light-absorbing layer is preferably 0.1 to 25 parts by mass, more preferably 0.3 to 15 parts by mass, per 100 parts by mass of the resin. When two or more compounds are combined, the above content is the total of the respective compounds.

[0085] The light absorbing layer may contain other dyes in addition to the near-infrared absorbing dye. The other dyes are preferably dyes (UV dyes) that have a maximum absorption wavelength in the resin of 370 to 440 nm. This allows for efficient blocking of the near-ultraviolet light region.

[0086] Examples of UV dyes include oxazole dyes, merocyanine dyes, cyanine dyes, naphthalimide dyes, oxadiazole dyes, oxazine dyes, oxazolidine dyes, naphthalic acid dyes, styryl dyes, anthracene dyes, cyclic carbonyl dyes, and triazole dyes. Among these, merocyanine dyes are particularly preferred. Furthermore, one type may be used alone, or two or more types may be used in combination.

[0087] The resin in the light-absorbing layer is not limited as long as it is a transparent resin, and one or more transparent resins selected from polyester resins, acrylic resins, epoxy resins, ene-thiol resins, polycarbonate resins, polyether resins, polyarylate resins, polysulfone resins, polyethersulfone resins, polyparaphenylene resins, polyarylene ether phosphine oxide resins, polyamide resins, polyimide resins, polyamideimide resins, polyolefin resins, cyclic olefin resins, polyurethane resins, and polystyrene resins are used. These resins may be used alone or in combination of two or more. From the viewpoints of the spectral characteristics, glass transition temperature (Tg), and adhesion of the light-absorbing layer, one or more resins selected from polyimide resins, polycarbonate resins, polyester resins, and acrylic resins are preferred.

[0088] When a plurality of compounds are used as the near-infrared absorbing dye or other dyes, they may be contained in the same light absorbing layer, or may be contained in separate light absorbing layers.

[0089] The light absorbing layer can be formed by preparing a coating liquid by dissolving or dispersing the dye, the resin or raw material components of the resin, and other components that are blended as necessary in a solvent, applying this onto the dielectric multilayer film 2, drying it, and further curing it as necessary. Alternatively, the coating liquid may be applied to a peelable support that is used only when forming the light absorbing layer, and the light absorbing layer may then be laminated on the dielectric multilayer film 2. The solvent may be any dispersion medium that allows stable dispersion or dissolution.

[0090] The coating liquid may also contain a surfactant to prevent voids caused by minute bubbles, depressions caused by the adhesion of foreign matter, and repellency during the drying process. For application of the coating liquid, methods such as dip coating, cast coating, and spin coating can be used. When the coating liquid contains raw materials for a transparent resin, it is further subjected to a curing treatment such as heat curing or photocuring.

[0091] The light absorbing layer can also be manufactured in the form of a film by extrusion molding. The obtained film-shaped absorbing layer can be laminated on the dielectric multilayer film 2 and integrated by thermocompression bonding or the like to manufacture the present filter.

[0092] The optical filter may have one light absorbing layer or two or more light absorbing layers. When two or more light absorbing layers are included, the layers may have the same or different configurations, and may be formed on each of the dielectric multilayer films, or two or more layers may be stacked on one of the dielectric multilayer films.

[0093] The thickness of the light-absorbing layer is 10 μm or less, preferably 5 μm or less, from the viewpoint of the in-plane film thickness distribution within the substrate after coating and the appearance quality, and is preferably 0.5 μm or more, from the viewpoint of expressing desired spectral characteristics at an appropriate dye concentration. When the optical filter has two or more light-absorbing layers, it is preferable that the total thickness of the light-absorbing layers is within the above range.

[0094] The optical filter according to this embodiment may also include, as other components, a component (layer) that provides absorption by inorganic fine particles that control the transmission and absorption of light in a specific wavelength range. Specific examples of inorganic fine particles include ITO (indium tin oxide), ATO (antimony-doped tin oxide), cesium tungstate, lanthanum boride, and the like. ITO fine particles and cesium tungstate fine particles have high transmittance for visible light and have light absorption properties over a wide range of infrared wavelengths exceeding 1200 nm, and therefore can be used when such infrared light blocking properties are required.

[0095] <Imaging Device> An imaging device according to an embodiment of the present invention preferably includes the optical filter according to the embodiment of the present invention. The imaging device preferably further includes a solid-state imaging element and an imaging lens. The optical filter according to this embodiment can be used, for example, by being disposed between the imaging lens and the solid-state imaging element, or by being directly attached to the solid-state imaging element, imaging lens, etc. of the imaging device via an adhesive layer. By including this filter, which has excellent visible light transmittance, specific near-infrared light blocking properties, and is less likely to shift in its spectral curve even at high angles of incidence, an imaging device can be obtained that has excellent color reproducibility even for light at high angles of incidence.

[0096] When mounting an optical filter on an imaging device, it is usually preferable to place the dielectric multilayer film 1 on the lens side (external light incident side) and the dielectric multilayer film 2 on the sensor side.

[0097] As described above, this specification discloses the following optical filters, etc. [1] An optical filter comprising phosphate glass, a dielectric multilayer film 1 and a dielectric multilayer film 2 provided on both sides of the phosphate glass, a barrier film 1 provided between the phosphate glass and the dielectric multilayer film 1, a barrier film 2 provided between the phosphate glass and the dielectric multilayer film 2, and a light absorbing layer provided on the dielectric multilayer film 2, wherein the phosphate glass has near-infrared absorbing properties, contains substantially no fluorine atoms, and has a thickness of 0.3 mm or less, the light absorbing layer contains a near-infrared absorbing dye, and the barrier film 1 and the barrier film 2 each independently contain TiO ２ , Nb２ O ５ , Ta ２ O ５ , and HfO ２ An optical filter comprising one or more selected from the group consisting of: (i) an optical filter that satisfies all of the following spectral characteristics (i-1) to (i-5): (i-1) an average transmittance of wavelengths from 440 to 500 nm is 75% or more at an incident angle of 0 degrees and 60% or more at an incident angle of 60 degrees; (i-2) an average transmittance of wavelengths from 750 to 1000 nm is 2% or less at an incident angle of 0 degrees and 2% or less at an incident angle of 60 degrees; and (i-3) a wavelength IR10 at which the transmittance is 10% in the spectral transmittance curve at an incident angle of 0 degrees. （０ｄｅｇ） (i-4) In the spectral transmittance curve at an incident angle of 0 degrees, the wavelength IR10 at which the transmittance is 10% in the range of 600 to 700 nm （０ｄｅｇ） and the wavelength IR10 where the transmittance is 10% in the range of 600 to 700 nm in the spectral transmittance curve at an incident angle of 60 degrees. （６０ｄｅｇ） (i-5) The transmittance at a wavelength of 1100 nm is 5% or less at an incident angle of 0 degrees and 5% or less at an incident angle of 60 degrees. [2] The optical filter according to [1], wherein the optical filter satisfies the following spectral characteristic (i-6): (i-6) The maximum transmittance at wavelengths of 750 to 1000 nm is 2% or less at an incident angle of 0 degrees and 2% or less at an incident angle of 60 degrees. [3] The optical filter according to [1] or [2], wherein the thickness of the phosphate glass is 0.25 mm or less, and the optical filter satisfies the following spectral characteristic (i-7): (i-7) The transmittance at a wavelength of 1100 nm is 2% or less at an incident angle of 0 degrees. [4] The optical filter according to any one of [1] to [3], wherein the phosphate glass contains 12% or more CuO in mole % on an oxide basis. [5] The phosphate glass contains 10% or more Al in mole % on an oxide basis. ２ O ３ [6] The optical filter according to [4], wherein the phosphate glass contains 13% or more of MoO in mole percent on an oxide basis. ３[7] The optical filter according to any one of [1] to [6], wherein the phosphate glass has, in terms of a plate thickness of 0.25 mm, an average transmittance of 70% or more at wavelengths of 440 to 500 nm, a transmittance of 5.5% or less at a wavelength of 1200 nm, a transmittance of 1.0% or less at a wavelength of 1000 nm, and a transmittance of 1.5% or less at a wavelength of 800 nm. [8] The barrier film 1 and the barrier film 2 are each made of TiO ２ [9] The optical filter according to any one of [1] to [7], comprising:

[0022] a first barrier film 1 and a second barrier film 2 each having a thickness of 10 nm or more;

[0023] the first dielectric multilayer film 1 having a thickness of 1.0 μm or more;

[0024] the light absorbing layer comprising one or more near-infrared absorbing dyes having a maximum absorption wavelength of 700 nm or more and less than 740 nm; and

[0025] one or more near-infrared absorbing dyes having a maximum absorption wavelength of 740 nm or more and 800 nm or less;

[0026] an imaging device comprising the optical filter according to any one of [1] to

[11] .

[0098] Next, the present invention will be described in more detail with reference to examples. Each spectral characteristic was measured using an ultraviolet-visible spectrophotometer (UH-4150, manufactured by Hitachi High-Technologies Corporation). Unless otherwise specified, the spectral characteristics are values ​​measured at an incident angle of 0 degrees (perpendicular to the main surface of the optical filter).

[0099] The dyes used in each example are as follows. Compound 1 (cyanine compound): Synthesized based on Dyes and Pigments 73 (2007) 344-352. Compound 2 (merocyanine compound): Synthesized based on German Patent Publication No. 10109243. Compound 3 (squarylium compound): Synthesized based on International Publication No. 2017 / 135359. Compound 4 (squarylium compound): Synthesized based on International Publication Nos. 2014 / 088063 and 2016 / 133099.

[0100]

[0101] Compounds 1, 3, and 4 are near-infrared absorbing dyes (NIR dyes), and Compound 2 is a near-ultraviolet absorbing dye (UV dye). The maximum absorption wavelength of each dye is shown in Table 5 below.

[0102] <Spectral Properties of Glass> The following glasses were prepared. Raw materials for phosphate glass or fluorophosphate glass were weighed and mixed to have the contents shown in Table 5, expressed in mol% on an oxide basis. The mixture was placed in a crucible with an internal volume of approximately 400 mL and melted for 2 hours. The mixture was then refined and stirred, and poured into a rectangular mold measuring 100 mm in length, 80 mm in width, and 20 mm in height that had been preheated to approximately 300°C to 500°C. The mixture was then slowly cooled at a rate of approximately 1°C / min, and a plate-shaped glass sample was obtained with both sides optically polished to a thickness of 0.25 mm.

[0103] The spectral characteristics of each glass are shown in Table 1. The spectral transmittance curve of Glass 4 is shown in FIG.

[0104]

[0105] From the above results, it can be seen that the near-infrared absorption properties of Glasses 1 to 6 can be improved by containing 12% or more of CuO. ３ By including the above, it was possible to increase the visible light transmittance.

[0106] <Glass Reliability Test 1> A test piece measuring 5 mm in length, 5 mm in width, and with the thickness shown in Table 2 was prepared from any of the glasses 4 to 7 produced above. A barrier film was formed by depositing the materials shown in Table 2 on both main surfaces by vapor deposition. The barrier film-coated glass substrate was subjected to a high-temperature, high-humidity test under the following conditions. The barrier film-coated glass substrate was left in an environment of 85°C temperature and 85% relative humidity for the period shown in Table 2, and then the edge was observed from the main surface side using a metallurgical microscope at 200x magnification to evaluate the degree of deterioration. The distance from the edge to the point with the most advanced deterioration was measured and evaluated based on the following criteria. A grade of C or higher was considered acceptable. A: Edge deterioration was less than 100 μm. B: Edge deterioration was 100 μm or more but less than 150 μm. C: Edge deterioration was 150 μm or more but less than 200 μm. D: Edge deterioration was 200 μm or more. The evaluation results are shown in Table 2 below. Examples 1-1 to 1-5 are reference examples, and Examples 1-6 to 1-10 are reference comparative examples.

[0107]

[0108] The above results show that the barrier films made of titania or tantalum have excellent durability, with titania being particularly preferable. On the other hand, the barrier films made of alumina and silica showed degradation of the end faces and did not achieve durability.

[0109] <Glass Reliability Test 2> Test pieces of Glasses 1 to 7 manufactured above, each measuring 5 mm in length, 5 mm in width, and 0.3 mm in thickness, were prepared, and TiO ２ The barrier films were formed by laminating the above by vapor deposition. ２ and TiO ２ These were alternately laminated by vapor deposition to form dielectric multilayer films A or B having the configurations shown in Table 4. Film number 1 is the layer in contact with the barrier film. The obtained test specimens were evaluated for the degree of deterioration of the end faces using the same method and criteria as in Glass Reliability Test 1. The evaluation results are shown in Table 3 below. Examples 1-11 to 1-18 are reference examples.

[0110]

[0111]

[0112] The results of Examples 1-11 to 1-18 above confirmed that the barrier film had good durability in all phosphate glasses. Furthermore, a comparison between Examples 1-17 and 1-18 confirmed that the greater the total thickness of the barrier film and the dielectric multilayer film, the higher the durability.

[0113] <Spectral Characteristics of Light-Absorbing Layer 1> The dyes of Compounds 1 to 4 were dissolved in polyimide resin C-3G30G manufactured by Mitsubishi Gas Chemical Company, Inc., and mixed at the concentrations shown in Table 5 below. The mixture was stirred and dissolved at 50°C for 2 hours to obtain a coating liquid. The obtained coating liquid was applied to alkali glass (D263 glass manufactured by SCHOTT, thickness 0.2 mm) by spin coating to form a light-absorbing layer with a film thickness of 1.0 μm. The spectral transmittance curve and spectral reflectance curve of the obtained light-absorbing layer in the wavelength range of 350 to 1200 nm were measured using a UV-visible spectrophotometer. The results are shown in Table 5 below. The spectral transmittance curve of the light-absorbing layer is also shown in FIG. 4.

[0114]

[0115] Example 2-1: Spectral characteristics of optical filter A TiO 2 film having the same composition as in Example 1-1 was applied to both main surfaces of a 0.3 mm thick glass 1 (phosphate glass). ２ The barrier film 1 and the barrier film 2 were formed by depositing the SiO ２ and TiO ２ The dielectric multilayer film 1A having the structure shown in Table 6 was formed by alternately laminating these layers by vapor deposition. The film number 1 is the layer in contact with the light absorbing layer. ２ and TiO ２ By alternately laminating these layers by vapor deposition, a dielectric multilayer film 2A having the configuration shown in Table 6 was formed. Film number 1 is the layer in contact with the light absorbing layer. A resin solution having the same composition as the light absorbing layer 1 was applied to the surface of the barrier film 2, and the solution was heated sufficiently to remove the organic solvent, thereby forming a light absorbing layer having a thickness of 1.0 μm. SiO ２ and TiO ２ These were alternately stacked by vapor deposition to form a dielectric multilayer film 3A (anti-reflection film). In this way, an optical filter 2-1 was manufactured.

[0116] Example 2-2 Optical filter 2-2 was produced in the same manner as in Example 2-1, except that glass 4 (phosphate glass) was used instead of glass 1.

[0117] Example 2-3 An optical filter 2-3 was produced in the same manner as in Example 2-2, except that a dielectric multilayer film 1B having the configuration shown in Table 6 was formed instead of the dielectric multilayer film 1A.

[0118] Example 2-4 An optical filter 2-4 was produced in the same manner as in Example 2-1, except that Glass 7 (phosphate glass) was used instead of Glass 1.

[0119] Example 2-5 An optical filter 2-5 was produced in the same manner as in Example 2-1, except that Glass 8 (fluorophosphate glass) was used instead of Glass 1.

[0120] Example 2-6 Optical filter 2-6 was produced in the same manner as in Example 2-1, except that Glass 1 (phosphate glass) having a plate thickness of 0.25 mm was used instead of Glass 1 (phosphate glass) having a plate thickness of 0.3 mm.

[0121] Example 2-7 Optical filter 2-7 was produced in the same manner as in Example 2-2, except that Glass 4 (phosphate glass) having a plate thickness of 0.25 mm was used instead of Glass 4 (phosphate glass) having a plate thickness of 0.3 mm.

[0122] Example 2-8 An optical filter 2-8 was produced in the same manner as in Example 2-3, except that Glass 4 (phosphate glass) having a plate thickness of 0.25 mm was used instead of Glass 4 (phosphate glass) having a plate thickness of 0.3 mm.

[0123] Example 2-9 Optical filter 2-9 was produced in the same manner as in Example 2-4, except that Glass 7 (phosphate glass) having a plate thickness of 0.25 mm was used instead of Glass 7 (phosphate glass) having a plate thickness of 0.3 mm.

[0124] Example 2-10 An optical filter 2-10 was produced in the same manner as in Example 2-5, except that Glass 8 (fluorophosphate glass) having a plate thickness of 0.25 mm was used instead of Glass 8 (fluorophosphate glass) having a plate thickness of 0.3 mm.

[0125]

[0126] The spectral reflectance curve of a laminated film consisting of dielectric multilayer film 1A and barrier film 1 is shown in Figure 5. The spectral reflectance curve of a laminated film consisting of dielectric multilayer film 1B and barrier film 1 is shown in Figure 6. The reflection characteristics of the laminated film mainly indicate the reflection characteristics of dielectric multilayer film 1A or dielectric multilayer film 1B. From this, it can be seen that both dielectric multilayer film 1A and dielectric multilayer film 1B are designed to have low reflectance in the visible light region.

[0127] For each optical filter obtained above, a UV-visible spectrophotometer was used to measure the spectral transmittance curves at incident angles of 0 degrees and 60 degrees, and the spectral reflectance curves at incident angles of 5 degrees and 60 degrees in the wavelength range of 350 to 1200 nm. The degree of deterioration of the end faces was also evaluated using the same method and criteria as in Glass Reliability Test 1. From the obtained spectral characteristic data, the properties shown in Tables 7 and 8 below were calculated.

[0128] The method of calculating X in the laminated film 2 will be specifically shown by taking the laminated film 2 consisting of the dielectric multilayer film 2A and the barrier film 2 as an example. ２ The refractive index of TiO is 1.9 or less. ２ The total physical thickness of the laminated film 2 having a QWOT of less than 2 and a refractive index of 1.9 or less is 1.0 times the total thickness of the SiO ２ Physical thickness of the film and SiO ２ The total physical thickness of the laminated film 2 can be calculated from the sum of the physical thickness of the entire dielectric multilayer film 2A and the physical thickness of the barrier film 2. The total physical thickness of the laminated film 2 having a QWOT of 2 or more can be calculated from the sum of the physical thickness of the SiO ２ The physical thickness of the film corresponds to this. From the above, X was calculated.

[0129] The spectral transmittance curve of the optical filter of Example 2-8 is shown in FIG. 7, the spectral reflectance curve (light absorbing layer side) is shown in FIG. 8, and the spectral reflectance curve (multilayer film 1 side) is shown in FIG.

[0130] Examples 2-1 to 2-4 and 2-6 to 2-9 are working examples, and Examples 2-5 and 2-10 are comparative examples.

[0131]

[0132]

[0133] From the above results, it can be seen that the optical filters of Examples 2-1 to 2-4 and 2-6 to 2-9 have excellent visible light transmittance even at high angles of incidence, excellent shielding properties for near-infrared light in the 750 to 1000 nm range, particularly infrared light at 1000 nm, and small shifts in the spectral curve even at high angles of incidence. Comparing Examples 2-4 and 2-9, it can be seen that when the phosphate glass had a low CuO content, Example 2-9, which was thinned to a thickness of 0.25 mm, exhibited transmittance at a wavelength of 1100 nm exceeding 2%, resulting in reduced shielding properties. Therefore, it can be seen that a CuO content of 12 mol% or more in the phosphate glass is preferable. The optical filters of Examples 2-5 and 2-10 exhibited poor shielding properties for near-infrared light in the 750 to 1000 nm range and near-infrared light at 1000 nm. This is thought to be due to the low absorption characteristics in these regions caused by the use of fluorophosphate glass.

[0134] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2023-135694) filed on August 23, 2023, the contents of which are incorporated herein by reference.

[0135] The optical filter of the present invention has excellent visible light transmittance and near-infrared light blocking properties, and is useful for applications in information acquisition devices such as cameras and sensors for transport aircraft, which have become increasingly sophisticated in recent years.

[0136] 1A, 1B Optical filter 10 Phosphate glass 11, 12 Barrier film 21, 22, 23 Dielectric multilayer film 30 Light absorption layer

Claims

1. An optical filter comprising phosphate glass, a dielectric multilayer film 1 and a dielectric multilayer film 2 provided on both sides of the phosphate glass, a barrier film 1 provided between the phosphate glass and the dielectric multilayer film 1, a barrier film 2 provided between the phosphate glass and the dielectric multilayer film 2, and a light absorbing layer provided on the dielectric multilayer film 2, wherein the phosphate glass has near-infrared absorbing properties, contains substantially no fluorine atoms, and has a thickness of 0.3 mm or less, the light absorbing layer contains a near-infrared absorbing dye, and the barrier film 1 and the barrier film 2 are each independently formed of TiO ２ , Nb ２ O ５ , Ta ２ O ５ , and HfO ２ An optical filter comprising one or more selected from the group consisting of: (i-1) an average transmittance of 75% or more at wavelengths of 440 to 500 nm at an incident angle of 0 degrees and 60% or more at an incident angle of 60 degrees; (i-2) an average transmittance of 2% or less at wavelengths of 750 to 1000 nm at an incident angle of 0 degrees and 2% or less at an incident angle of 60 degrees; (i-3) an average transmittance of 10% at a wavelength IR10 at which the transmittance is 10% in the spectral transmittance curve at an incident angle of 0 degrees; （０ｄｅｇ） (i-4) In the spectral transmittance curve at an incident angle of 0 degrees, the wavelength IR10 at which the transmittance is 10% in the range of 600 to 700 nm is （０ｄｅｇ） and the wavelength IR10 at which the transmittance is 10% in the range of 600 to 700 nm in the spectral transmittance curve at an incident angle of 60 degrees. （６０ｄｅｇ） (i-5) The transmittance at a wavelength of 1100 nm is 5% or less at an incident angle of 0 degrees and 5% or less at an incident angle of 60 degrees.

2. The optical filter according to claim 1, which satisfies the following spectral characteristic (i-6): (i-6) the maximum transmittance in the wavelength range of 750 to 1000 nm is 2% or less at an incident angle of 0 degrees and 2% or less at an incident angle of 60 degrees.

3. The optical filter according to claim 1, wherein the thickness of the phosphate glass is 0.25 mm or less, and the optical filter satisfies the following spectral characteristic (i-7): (i-7) transmittance at a wavelength of 1100 nm is 2% or less at an incident angle of 0 degrees.

4. The optical filter according to claim 1, wherein said phosphate glass contains 12% or more of CuO, expressed as mole percent on an oxide basis.

5. The phosphate glass contains Al in mole percent on an oxide basis. ２ O ３ 5. The optical filter according to claim 4, wherein the content is 13% or more.

6. The phosphate glass is MoO ３ 5. The optical filter according to claim 4, containing 0.1 to 5% of 7. The optical filter according to claim 1, wherein the phosphate glass has, converted into a plate thickness of 0.25 mm, an average transmittance of 70% or more at wavelengths of 440 to 500 nm, a transmittance of 5.5% or less at a wavelength of 1200 nm, a transmittance of 1.0% or less at a wavelength of 1000 nm, and a transmittance of 1.5% or less at a wavelength of 800 nm.

8. The barrier film 1 and the barrier film 2 are TiO ２ The optical filter of claim 1 , comprising:

9. The optical filter according to claim 1, wherein the thickness of said barrier film 1 and said barrier film 2 is 10 nm or more.

10. The optical filter according to claim 1, wherein the thickness of said dielectric multilayer film 1 is 1.0 μm or more.

11. The optical filter according to claim 1, wherein the light absorbing layer contains one or more near infrared absorbing dyes having a maximum absorption wavelength in the range of 700 nm or more and less than 740 nm, and one or more near infrared absorbing dyes having a maximum absorption wavelength in the range of 740 nm or more and 800 nm or less.

12. An imaging device comprising an optical filter according to any one of claims 1 to 11.

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