Optical filter

Abstract

The present invention relates to an optical filter provided with a dielectric multilayer film (1), a resin film, a phosphate glass, and a dielectric multilayer film (2) in this order, the resin film comprising a resin and a near-infrared absorbing dye in the resin, the near-infrared absorbing dye having a maximum absorption wavelength at 690-800 nm, the thickness of the resin film being 10 [mu] m or less, and the thickness of the phosphate glass being 10 [mu] m or less. The optical filter satisfies all specific spectral characteristics (i-1) to (i-5).

Description

Technical Field

[0001] The invention relates to an optical filter which transmits visible light and cuts off near infrared light. Background Art

[0002] In an imaging device using a solid-state imaging element, an optical filter is used that transmits light in the visible region (hereinafter also referred to as "visible light") and cuts off light in the near-infrared wavelength region (hereinafter also referred to as "near-infrared light") in order to reproduce color tones well and obtain a clear image.

[0003] As such optical filters, for example, there are various types of filters, 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 films), a filter that uses interference of light to reflect the light to be shielded, an absorptive filter that uses glass or pigments that absorb light in a specific wavelength region to absorb the light to be shielded, and a filter that combines reflective and absorptive types.

[0004] Patent Documents 1 and 2 describe optical filters having a dielectric multilayer film and an absorption layer containing a dye.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2019 / 151348

[0008] Patent Document 2: International Publication No. 2018 / 043564 Summary of the invention

[0009] Since the optical film thickness of the dielectric multilayer film of the optical filter changes according to the incident angle of light, the change of the spectral transmittance curve caused by the incident angle becomes a problem. For example, due to the interference caused by the reflected light at the interface of each layer corresponding to the number of stacked layers of the multilayer film, a sharp change in the transmittance in the visible light region, the so-called ripple, is generated more strongly as the incident angle of light increases. If such a filter is used, the spectral sensitivity of the solid-state imaging element may be affected by the incident angle. In particular, with the recent reduction in the height of camera modules, it is envisaged that they will be used under high incident angle conditions, so an optical filter that is not easily affected by the incident angle is needed.

[0010] In addition, when using an infrared sensor and an image sensor together, infrared light may be captured by the image sensor unintentionally, which may adversely affect the image. To avoid this, an optical filter that can block the 900-1000nm wavelength region in the near-infrared region is required.

[0011] An object of the present invention is to provide an optical filter having excellent transmittance in the visible light region, little change in transmittance in the visible light region at high incident angles, and excellent shielding properties in the near-infrared region, particularly shielding properties in the range of 900 to 1000 nm.

[0012] The present invention provides an optical filter and the like having the following configurations.

[0013] [1] An optical filter comprising, in order, a dielectric multilayer film 1, a resin film, phosphate glass, and a dielectric multilayer film 2,

[0014] The resin film comprises a resin and a near infrared absorbing pigment in the resin, wherein the near infrared absorbing pigment has a maximum absorption wavelength in the range of 690 to 800 nm.

[0015] The thickness of the resin film is 10 μm or less.

[0016] The above optical filter satisfies all of the following spectral characteristics (i-1) to (i-5).

[0017] (i-1) Average transmittance T at wavelength 430-550nm and incident angle 0 degrees 430－550(0deg)AVE More than 80%,

[0018] (i-2) Average transmittance T at wavelength 430 to 550 nm and incident angle 60 degrees 430－550(60deg)AVE More than 80%,

[0019] (i-3) In the wavelength range of 500 to 700 nm, the wavelength IR with a transmittance of 50% at an incident angle of 0 degrees 50(0deg) In the wavelength region of 600 to 660 nm,

[0020] (i-4) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 0 degrees and at intervals of 1 nm. n(0deg) (n: any integer), the above transmittance T n(0deg) There are 20 or more n with a content of 0.04% or less.

[0021] (i-5) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 40 degrees and at intervals of 1 nm. n(40deg) (n: any integer), the above transmittance T n(40deg) There are 20 or more n's that are 0.04% or less.

[0022] According to the present invention, an optical filter can be provided which has excellent transmittance in the visible light region, little change in transmittance in the visible light region at high incident angles, and excellent shielding properties in the near infrared region, particularly 900 to 1000 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a cross-sectional view schematically showing an example of an optical filter according to an embodiment.

[0024] Figure 2 : is a graph showing the spectral transmittance curve of phosphoric acid glass.

[0025] Figure 3 This is a graph showing the spectral transmittance curve of the resin film of Example 1-1.

[0026] Figure 4 This is a graph showing a spectral transmittance curve of the optical filter of Example 2-1.

[0027] Figure 5 This is a graph showing a spectral reflectance curve of the optical filter of Example 2-1.

[0028] Figure 6 This is a diagram showing a spectral transmittance curve of the optical filter of Example 2-3.

[0029] Figure 7 This is a diagram showing a spectral reflectance curve of the optical filter of Example 2-3.

[0030] Figure 8 This is a graph showing a spectral transmittance curve of the optical filter of Example 2-5.

[0031] Fig. 9 This is a graph showing a spectral reflectance curve of the optical filter of Example 2-5. DETAILED DESCRIPTION

[0032] Hereinafter, embodiments of the present invention will be described.

[0033] 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”.

[0034] In this specification, the compound represented by formula (I) is referred to as compound (I). The same applies to compounds represented by other formulas. The pigment composed of compound (I) is also referred to as pigment (I), and the same applies to other pigments. In addition, the group represented by formula (I) is also referred to as group (I), and the same applies to groups represented by other formulas.

[0035] In this specification, the internal transmittance refers to the transmittance obtained by subtracting the influence of interface reflection from the measured transmittance, which is represented by the formula {measured transmittance (incident angle 0 degrees) / (100-reflectivity (incident angle 5 degrees))}×100.

[0036] In this specification, the transmittance for a specific wavelength region, for example, 90% or more, means that the transmittance in the entire wavelength region is not less than 90%, that is, the minimum transmittance in the wavelength region is 90% or more. Similarly, the transmittance for a specific wavelength region, for example, 1% or less, means that the transmittance in the entire wavelength region does not exceed 1%, that is, the maximum transmittance in the wavelength region is less than 1%. The same applies to internal transmittance. The average transmittance and average internal transmittance in a specific wavelength region are the arithmetic mean values ​​of the transmittance and internal transmittance per 1nm in the wavelength region.

[0037] The spectral characteristics can be measured using a UV-visible spectrophotometer.

[0038] <Optical filter>

[0039] In the present specification, "to" indicating a numerical range includes both upper and lower limits.

[0040] The optical filter of the present embodiment includes a dielectric multilayer film 1 , a resin film, phosphate glass, and a dielectric multilayer film 2 in this order.

[0041] Here, the resin film includes a resin and a near infrared absorbing pigment in the resin, the near infrared absorbing pigment having a maximum absorption wavelength in the range of 690 to 800 nm, and the thickness of the resin film is 10 μm or less.

[0042] Due to the reflection characteristics of the dielectric multilayer film and the absorption characteristics of the phosphate glass and the near-infrared absorbing pigment as near-infrared absorbing glass, the optical filter as a whole can achieve excellent transmittance in the visible light region and excellent shielding properties in the near-infrared light region.

[0043] A configuration example of the optical filter according to the present embodiment will be described using the drawings. Figure 1 This is a cross-sectional view schematically showing an example of an optical filter according to an embodiment.

[0044] Figure 1 The optical filter 1 shown includes a dielectric multilayer film A1 , a resin film 12 , a phosphate glass 11 , and a dielectric multilayer film A2 in this order.

[0045] The optical filter of the present embodiment satisfies all of the following spectral characteristics (i-1) to (i-5).

[0046] (i-1) Average transmittance T at wavelength 430-550nm and incident angle 0 degrees 430－550(0deg)AVE More than 80%,

[0047] (i-2) Average transmittance T at wavelength 430 to 550 nm and incident angle 60 degrees 430－550(60deg)AVE More than 80%,

[0048] (i-3) In the wavelength range of 500 to 700 nm, the wavelength IR with a transmittance of 50% at an incident angle of 0 degrees 50(0deg) In the wavelength region of 600 to 660 nm,

[0049] (i-4) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 0 degrees and at intervals of 1 nm. n(0deg) (n: any integer), the above transmittance T n(0deg) There are 20 or more n with a content of 0.04% or less.

[0050] (i-5) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 40 degrees and at intervals of 1 nm. n(40deg) (n: any integer), the above transmittance T n(40deg) There are 20 or more n's that are 0.04% or less.

[0051] The optical filter of this embodiment that satisfies all spectral characteristics (i-1) to (i-5) has, in particular, high transmittance of visible light as shown in characteristic (i-1), and high shielding of near-infrared light with a wavelength of 900 to 1000 nm as shown in characteristics (i-4) to (i-5). In addition, as shown in characteristics (i-1) and (i-2), the transmittance in the visible light region does not decrease even at high incident angles, and the ripples in the visible light region are suppressed.

[0052] Satisfying the spectral characteristic (i-1) means that the transmittance in the visible light region of 430 to 550 nm is excellent.

[0053] Satisfying the spectral characteristic (i-2) means that the transmittance in the visible light region of 430 to 550 nm is excellent even at a high incident angle.

[0054] Average transmittance T 430－550(0deg)AVE It is preferably 85% or more, and more preferably 90% or more.

[0055] Average transmittance T 430－550(60deg)AVE It is preferably 81% or more, and more preferably 83% or more.

[0056] Spectral characteristics (i-1) and spectral characteristics (i-2) can be achieved, for example, by using a dielectric multilayer film with low reflectivity in the visible light region, and using a near-infrared absorbing dye and phosphate glass with high transmittance in the visible light region.

[0057] Satisfying the spectral characteristic (i-3) means shielding light in the near-infrared region and effectively introducing visible transmission light.

[0058] Wavelength IR 50(0deg)It is preferably 610 to 650 nm, more preferably 615 to 640 nm.

[0059] Satisfying the spectral characteristic (i-4) means that the light shielding property in the near-infrared region of 900 to 1000 nm is excellent.

[0060] Satisfying the spectral characteristic (i-5) means that the light shielding property in the near-infrared region of 900 to 1000 nm is excellent even at a high incident angle.

[0061] Transmittance T n(0deg) The number of n which is 0.04% or less is preferably 30 or more, and more preferably 40 or more.

[0062] Transmittance T n(40deg) The number of n which is 0.04% or less is preferably 30 or more, and more preferably 40 or more.

[0063] The spectral characteristics (i-4) and (i-5) can be realized by using, for example, a dielectric multilayer film having a reflection characteristic at a wavelength of 900 to 1000 nm.

[0064] The optical filter of the present embodiment preferably further satisfies the following spectral characteristics (i-6) to (i-7).

[0065] (i-6) Average transmittance T at wavelength 750-1200 nm and incident angle 0 degrees 750－1200(0deg)AVE Less than 2%.

[0066] (i-7) Average transmittance T at wavelength 750 to 1200 nm and incident angle 40 degrees 750－1200(40deg)AVE Less than 2%.

[0067] Satisfying the spectral characteristic (i-6) means that the light shielding property in the near-infrared region of 750 to 1200 nm is excellent.

[0068] Satisfying the spectral characteristic (i-7) means that the light shielding property is excellent also in the near-infrared light region of 750 to 1200 nm at a high incident angle.

[0069] Average transmittance T 750－1200(0deg)AVE It is more preferably 1.5% or less, and still more preferably 0.8% or less.

[0070] Average transmittance T 750－1200(40deg)AVE It is more preferably 1% or less, and even more preferably 0.5% or less.

[0071] Spectral characteristics (i-6) and spectral characteristics (i-7) can be realized by combining the absorption characteristics of near-infrared absorbing pigments and phosphate glass and the reflection characteristics of a dielectric multilayer film that reflects near-infrared light to block light over a wide range.

[0072] The optical filter of the present embodiment preferably further satisfies the following spectral characteristics (i-8) to (i-9).

[0073] (i-8) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 0 degrees and at intervals of 1 nm. n(0deg) (n: any integer), the above transmittance T n(0deg) There are 20 or more n's that are 0.01% or less.

[0074] (i-9) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 40 degrees and at intervals of 1 nm. n(40deg) (n: any integer), the above transmittance T n(40deg) There are 20 or more n's that are 0.01% or less.

[0075] Satisfying the spectral characteristic (i-8) means that the light shielding property in the near-infrared light region of 900 to 1000 nm is excellent.

[0076] Satisfying the spectral characteristic (i-9) means that the light shielding property is excellent also in the near-infrared light region of 900 to 1000 nm at a high incident angle.

[0077] Transmittance T n(0deg) The number of n which is 0.01% or less is preferably 30 or more, and more preferably 40 or more.

[0078] Transmittance T n(40deg) The number of n which is 0.01% or less is preferably 25 or more, and more preferably 30 or more.

[0079] The spectral characteristics (i-8) and (i-9) can be realized by using, for example, a dielectric multilayer film having a reflection characteristic at a wavelength of 900 to 1000 nm.

[0080] The optical filter of the present embodiment preferably further satisfies the following spectral characteristics (i-10) to (i-11).

[0081] (i-10) The above average transmittance T 430－550(0deg)AVE With the above average transmittance T 430－550(60deg)AVE The absolute value of the difference is less than 10%.

[0082] (i-11) Maximum transmittance T at wavelength 430-550nm and incident angle 0 degrees 430－550(0deg)MAX The maximum transmittance T at an incident angle of 60 degrees 430－550(60deg)MAX The absolute value of the difference is less than 10%.

[0083] Satisfying the spectral characteristics (i-10) and (i-11) means that the change in visible light transmittance is small at high incident angles, and the moire is reduced.

[0084] Average transmittance T 430－550(0deg)AVE With the average transmittance T 430－550(60deg)AVE The absolute value of the difference is more preferably 9% or less, and further preferably 8% or less.

[0085] Maximum transmittance T 430－550(0deg)MAX With the maximum transmittance T 430－550(60deg)MAX The absolute value of the difference is more preferably 9% or less, and further preferably 8% or less.

[0086] Spectral characteristics (i-10) and spectral characteristics (i-11) can be achieved, for example, by using a dielectric multilayer film with low reflectivity in the visible light region, and using a near-infrared absorbing dye and phosphate glass with high transmittance in the visible light region.

[0087] The optical filter of the present embodiment preferably further satisfies the following spectral characteristics (i-12) to (i-17).

[0088] (i-12) When the dielectric multilayer film 2 side is the incident direction, the average reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 5 degrees 430－550(5deg)AVE Less than 10%.

[0089] (i-13) When the dielectric multilayer film 2 side is the incident direction, the average reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 60 degrees 430－550(60deg)AVE Less than 10%.

[0090] (i-14) When the dielectric multilayer film 2 side is the incident direction, the maximum reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 5 degrees 430－550(5deg)MAX Less than 15%.

[0091] (i-15) When the dielectric multilayer film 2 side is the incident direction, the maximum reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 60 degrees 430－550(60deg)MAX Less than 15%.

[0092] (i-16) When the dielectric multilayer film 2 side is the incident direction, the reflectivity R2 of each wavelength is read from a wavelength of 900 nm to a wavelength of 1000 nm at an incident angle of 5 degrees and at intervals of 1 nm. n(5deg) (n: any integer), the above reflectivity R2 n(5deg) There are 30 or more n's that are 95% or more.

[0093] (i-17) When the dielectric multilayer film 2 side is the incident direction, the reflectivity R2 of each wavelength is read from a wavelength of 900 nm to a wavelength of 1000 nm at an incident angle of 40 degrees and at intervals of 1 nm. n(40deg) (n: any integer), the above reflectivity R2 n(40deg) There are 25 or more n's that are 95% or more.

[0094] Satisfying the spectral characteristics (i-12) to (i-15) means that the reflectance in the visible light region is small even at a high incident angle, and the reflection ripple is also small.

[0095] Average reflectivity R2 430－550(5deg)AVE It is more preferably 5% or less, and even more preferably 3% or less.

[0096] Average reflectivity R2 430－550(60deg)AVE It is more preferably 9.5% or less, and even more preferably 9% or less.

[0097] Maximum reflectivity R2 430－550(5deg)MAX It is more preferably 10% or less, and even more preferably 5% or less.

[0098] Maximum reflectivity R2 430－550(60deg)MAX It is more preferably 13% or less, and even more preferably 10% or less.

[0099] Spectral characteristics (i-12) to (i-15) can be realized by using a dielectric multilayer film 2 having a low reflectance in the visible light region, for example.

[0100] Satisfying the spectral characteristics (i-16) and (i-17) means that the near-infrared light region with a wavelength of 900 to 1000 nm is shielded by the reflection characteristics.

[0101] Reflectivity R2 n(5deg) The number n which is 95% or more is more preferably 40 or more, and further preferably 50 or more.

[0102] Reflectivity R2 n(40deg) The number n which is 95% or more is more preferably 30 or more, and further preferably 40 or more.

[0103] The spectral characteristics (i-16) and (i-17) can be realized by using, for example, a dielectric multilayer film 2 having a high reflectivity at a wavelength of 900 to 1000 nm.

[0104] The optical filter of the present embodiment preferably further satisfies the following spectral characteristics (i-18) to (i-19).

[0105] (i-18) When the dielectric multilayer film 2 side is the incident direction, the average reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 5 degrees 430－550(5deg)AVE Average reflectivity R2 at an incident angle of 60 degrees 430－550(60deg)AVE The absolute value of the difference is less than 10%.

[0106] (i-19) When the dielectric multilayer film 2 side is the incident direction, the maximum reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 5 degrees 430－550(5deg)MAX Maximum reflectivity R2 at an incident angle of 60 degrees 430－550(60deg)MAX The absolute value of the difference is less than 10%

[0107] Satisfying the spectral characteristics (i-18) and (i-19) means that the reflectivity change in the visible light region at a high incident angle is small and the reflection ripple is small.

[0108] Average reflectivity R2 430－550(5deg)AVE With the average reflectivity R2 430－550(60deg)AVE The absolute value of the difference is more preferably 9% or less, and further preferably 8% or less.

[0109] Maximum reflectivity R2 430－550(5deg)MAX With maximum reflectivity R2 430－550(60deg)MAX The absolute value of the difference is more preferably 9% or less, and further preferably 8% or less.

[0110] The spectral characteristics (i-18) and (i-19) can be realized by using a dielectric multilayer film 2 having a low reflectivity in the visible light region, for example.

[0111] The optical filter of the present embodiment preferably further satisfies the following spectral characteristic (i-20).

[0112] (i-20) When the dielectric multilayer film 2 side is the incident direction, the reflectivity R2 of each wavelength is read from a wavelength of 900 nm to a wavelength of 1000 nm at an incident angle of 5 degrees and at intervals of 1 nm. n(5deg) (n: any integer), the above reflectivity R2 n(5deg) There are 30 or more n's that are 98% or more.

[0113] Satisfying the spectral characteristic (i-20) means that the near-infrared light region with a wavelength of 900 to 1000 nm is shielded by the reflection characteristic.

[0114] Reflectivity R2 n(5deg) The number n which is 98% or more is more preferably 40 or more, and further preferably 50 or more.

[0115] The spectral characteristic (i-20) can be realized by using, for example, a dielectric multilayer film 2 having a high reflectivity at a wavelength of 900 to 1000 nm.

[0116] <Dielectric multilayer film>

[0117] In the optical filter of the present embodiment, the dielectric multilayer film 1 is stacked on the resin film side, and the dielectric multilayer film 2 is stacked on the phosphate glass side.

[0118] As shown in the spectral characteristics (i-16), spectral characteristics (i-17) and spectral characteristics (i-20) of the above optical filter, the near-infrared light region with a wavelength of 900 to 1000 nm is preferably shielded by the reflection characteristics of the dielectric multilayer film 2. In addition, since the dielectric multilayer film designed to reflect a wide range of near-infrared light is easily affected by the angle of incidence, the near-infrared light region that improves the reflection characteristics is preferably specified as a wavelength of 900 to 1000 nm. By combining the reflection characteristics of the above-mentioned specific wavelength region with the absorption characteristics of the near-infrared absorption pigment having a maximum absorption wavelength at 690 to 800 nm and the absorption characteristics of the phosphate glass, light in the near-infrared light region with a wavelength of 750 to 1200 nm can be shielded over a wide range.

[0119] On the other hand, as shown in the spectral characteristics (i-12) to (i-15) of the above optical filter, the dielectric multilayer film 2 preferably has a smaller reflective characteristic in the visible light region. Thus, an optical filter is obtained in which the spectral characteristic in the visible light region is not easily changed by the incident angle and the ripple is reduced.

[0120] In summary, the dielectric multilayer film 2 is preferably designed as a reflective layer that reflects near-infrared light of 900 to 1000 nm.

[0121] The dielectric multilayer film 1 is preferably designed as an antireflection layer.

[0122] The dielectric multilayer film 1 and the dielectric multilayer film 2 are composed of, for example, dielectric multilayer films formed by stacking dielectric films having different refractive indices. More specifically, dielectric films having a low refractive index (low refractive index film), dielectric films having a medium refractive index (medium refractive index film), and dielectric films having a high refractive index (high refractive index film) can be cited, and the dielectric multilayer film is composed of a dielectric multilayer film formed by stacking two or more of them.

[0123] The refractive index of the high refractive index film at a wavelength of 500nm is preferably 1.6 or more, more preferably 1.8 to 2.5, and particularly preferably 2.2 to 2.5. As materials for the high refractive index film, for example, Ta2O5, TiO2, TiO, and Nb2O5 can be cited. In addition, as commercial products, OS50 (Ti3O5), OS10 (Ti4O7), OA500 (a mixture of Ta2O5 and ZrO2), and OA600 (a mixture of Ta2O5 and TiO2) manufactured by Canon Optron can be cited. Among them, TiO2 is preferred from the aspects of film-forming properties, reproducibility of refractive index, stability, etc.

[0124] The medium refractive index film preferably has a refractive index of 1.6 or more and less than 2.2 at a wavelength of 500 nm. As the material of the medium refractive index film, for example, ZrO2, Nb2O5, Al2O3, HfO2, OM-4 and OM-6 (a mixture of Al2O3 and ZrO2) sold by Canon Optron, OA-100, H4 and M2 (aluminum oxide lanthanum oxide) sold by Merck, etc. can be cited. Among them, from the aspects of film forming properties, reproducibility of refractive index, stability, etc., Al2O3-based compounds and mixtures of Al2O3 and ZrO2 are preferred.

[0125] The refractive index of the low refractive index film at a wavelength of 500 nm is preferably less than 1.6, more preferably 1.38 to 1.5. Examples of the material of the low refractive index film include SiO2, SiO x N y , MgF2, etc. In addition, commercial products include S4F and S5F (a mixture of SiO2 and Al2O3) manufactured by Canon Optron. Among them, SiO2 is preferred from the aspects of reproducibility, stability, and economy of film forming properties.

[0126] The ratio of [the sum of QWOT of dielectric films with relatively high refractive index T(H)] / [the sum of QWOT of dielectric films with relatively low refractive index T(L)] of at least one of the dielectric multilayer film 1 and the dielectric multilayer film 2 is preferably 1.6 or more. This makes it easy to obtain a dielectric multilayer film that satisfies the above spectral characteristics, reflects near-infrared light with a wavelength of 900 to 1000 nm, and suppresses visible light reflection. In addition, it is preferred that at least the dielectric multilayer film 2 satisfies the above ratio relationship.

[0127] It should be noted that, here, QWOT (Quarter Wave Optical Thickness) refers to an optical film thickness at a wavelength of λ / 4, and is calculated from a physical film thickness according to the following formula.

[0128] QWOT = physical film thickness / center wavelength (500nm) × 4 × refractive index at a wavelength of 500nm

[0129] When the dielectric multilayer film is a stack of low refractive index films and high refractive index films, the total QWOT T(H) is the total QWOT of the high refractive index films, and the total QWOT T(L) is the total QWOT of the low refractive index films.

[0130] When the dielectric multilayer film is a stack of a low refractive index film and a medium refractive index film, the total QWOT T(H) is the total QWOT of the medium refractive index film, and the total QWOT T(L) is the total QWOT of the low refractive index film.

[0131] When the dielectric multilayer film is a stack of medium refractive index films and high refractive index films, the total QWOT T(H) is the total QWOT of the high refractive index films, and the total QWOT T(L) is the total QWOT of the medium refractive index films.

[0132] In addition, at least one of the dielectric multilayer film 1 and the above-mentioned dielectric multilayer film 2 is preferably a multilayer film in which H2 layers and M2 layers defined below are alternately stacked in 10 or more layers.

[0133] H2 layer: a single layer with a refractive index of 1.8 to 2.5 and a QWOT of 1.1 to 3.5

[0134] M2 layer: a single layer or multiple layers existing between two H2 layers with a total QWOT of 1.2 to 1.8

[0135] The specific stacked structure is a structure in which a single layer (H2 layer) with a large refractive index and optical film thickness and a layer (M2 layer) with a total optical film thickness within a specified range are alternately stacked for more than 10 layers. With the above structure, it is easy to obtain a dielectric multilayer film that reflects near-infrared light with a wavelength of 900 to 1000 nm and has a low reflectivity for visible light.

[0136] It should be noted that if the M2 layer satisfies the prescribed optical film thickness, it may be a single layer or a multilayer. From the viewpoint of obtaining a smoother spectral characteristic, it is preferably composed of a plurality of layers. In addition, the minimum film thickness of the single layer is preferably 5 nm or more, and more preferably 10 nm or more. In addition, the refractive index of the dielectric film constituting the M2 layer is preferably the same as the refractive index of the H2 layer, or lower than the refractive index of the H2 layer.

[0137] The film having the above-mentioned specific stacked structure is preferably at least the dielectric multilayer film 2 .

[0138] When the dielectric multilayer film 2 has the above-mentioned stacked structure, the layer closest to the phosphate glass between the H2 layer and the M2 layer is preferably the H2 layer. The H2 layer closest to the phosphate glass may be directly stacked on the phosphate glass, or another layer that is neither equivalent to the H2 layer nor the M2 layer may exist between the H2 layer closest to the phosphate glass and the phosphate glass.

[0139] As the dielectric multilayer film 2, the total number of laminated dielectric multilayer films is preferably 10 layers or more, more preferably 20 layers or more, and further preferably 30 layers or more. However, if the total number of laminated dielectric layers increases, warping and the like will occur, and the film thickness will increase, so the total number of laminated dielectric layers is preferably 110 layers or less, more preferably 80 layers or less, and further preferably 60 layers or less.

[0140] In addition, the overall film thickness (physical film thickness) of the dielectric multilayer film 2 is preferably 1 to 6 μm.

[0141] When the optical filter is mounted on an imaging device, the dielectric multilayer film 1 is usually designed as an antireflection layer so that the dielectric multilayer film 1 is on the sensor side. The total number of stacked layers of the dielectric multilayer film 1 is preferably 40 layers or less, more preferably 30 layers or less, further preferably 20 layers or less, and preferably 6 layers or more.

[0142] In addition, the overall film thickness (physical film thickness) of the dielectric multilayer film 1 is preferably 0.2 to 1.0 μm.

[0143] The dielectric multilayer film can be formed by using, for example, a vacuum film forming process such as a CVD method, a sputtering method, or a vacuum evaporation method, or a wet film forming process such as a spray method or a dipping method.

[0144] When the dielectric multilayer film is a reflective layer or an anti-reflective layer, the prescribed optical properties can be imparted by one layer (one set of dielectric multilayer films), or by two or more layers. When there are two or more layers, each dielectric multilayer film can have the same structure or different structures.

[0145] When the optical filter is mounted on an imaging device, usually, the dielectric multilayer film 2 laminated on the glass surface is on the lens side, and the dielectric multilayer film 1 laminated on the resin film surface is on the sensor side.

[0146] <Phosphoric acid glass>

[0147] The phosphate glass in the optical filter of the present invention functions as infrared absorbing glass.

[0148] Phosphoric acid glass preferably satisfies all of the following spectral characteristics (ii-1) to (ii-5).

[0149] (ii-1) Internal transmittance T at a wavelength of 450 nm 450 It is more than 92%.

[0150] (ii-2) Average internal transmittance T at wavelengths of 450 to 600 nm 450－600AVE More than 90%.

[0151] (ii-3) IR50, where the internal transmittance is 50%, is in the wavelength range of 625 to 650 nm.

[0152] (ii-4) Average internal transmittance T at wavelengths of 750 to 1000 nm 750－1000AVE It is less than 2.5%.

[0153] (ii-5) Average internal transmittance T at wavelengths of 1000 to 1200 nm 1000－1200AVE Less than 7%.

[0154] Satisfying the spectral characteristic (ii-1) means that the transmittance in the blue light region is excellent, and satisfying the spectral characteristic (ii-2) means that the transmittance in the visible light region of 450 to 600 nm is excellent.

[0155] Internal transmittance T 450 It is more preferably 93% or more, and even more preferably 95% or more.

[0156] Average internal transmittance T 450－600AVE It is more preferably 94% or more, and even more preferably 95% or more.

[0157] Satisfying the spectral characteristic (ii-3) means shielding light in the near-infrared region and efficiently acquiring visible transmitted light.

[0158] IR50 is more preferably in the range of 625 to 645 nm, and even more preferably in the range of 625 to 640 nm.

[0159] Satisfying the spectral characteristic (ii-4) means that the light shielding property in the near-infrared region of 750 to 1000 nm is excellent.

[0160] Average internal transmittance T 750－1000AVE It is more preferably 2% or less, and even more preferably 1.2% or less.

[0161] Satisfying the spectral characteristic (ii-5) means that the light shielding property in the infrared region of 1000 to 1200 nm is excellent.

[0162] Average internal transmittance T 1000－1200AVE It is more preferably 2.3% or less, and still more preferably 2.2% or less.

[0163] Phosphate glass preferably absorbs near-infrared light starting from the 625-650 nm region as shown in the above characteristic (ii-3), and exhibits high light-shielding properties after 750 nm as shown in the above characteristic (ii-4). This can compensate for the light-shielding properties of the dielectric multilayer film.

[0164] In the present invention, the phosphate glass preferably contains copper ions. By containing copper ions that absorb light with a wavelength near 900 nm, near-infrared light of 700 to 1200 nm can be cut off. It should be noted that the phosphate glass also includes phosphosilicate glass in which a part of the glass skeleton is composed of SiO2.

[0165] For example, the phosphate glass preferably contains the following glass-constituting components. In addition, the content ratio of each of the following glass-constituting components is represented by mass % converted into oxides.

[0166] P2O5 is the main component of glass and is an essential component for improving near-infrared cutoff. If the content of P2O5 is 40% or more, its effect can be fully obtained. If it is 80% or less, it is not easy to cause problems such as glass becoming unstable and weather resistance being reduced. Therefore, it is preferably 40 to 80%, more preferably 52 to 78%, further preferably 54 to 77%, further preferably 56 to 76%, and most preferably 60 to 75%.

[0167] Al2O3 is the main component of glass and is used to improve the strength and weather resistance of glass. If the content of Al2O3 is 0.5% or more, its effect can be fully obtained. If it is less than 20%, it is not easy to cause problems such as glass becoming unstable and near-infrared cutoff properties being reduced. Therefore, it is preferably 0.5 to 20%, more preferably 1.0 to 20%, further preferably 2.0 to 18%, further preferably 3.0 to 17%, particularly preferably 4.0 to 16%, and most preferably 5.0 to 15.5%.

[0168] R2O (wherein R2O is one or more components selected from Li2O, Na2O, K2O, Rb2O and Cs2O) is a component used to lower the melting temperature of glass, lower the liquidus temperature of glass, stabilize glass, etc. If the total amount of R2O (ΣR2O) is 0.5% or more, its effect can be fully obtained, and if it is 20% or less, the glass is less likely to become unstable, so it is preferred. Therefore, it is preferably 0.5 to 20%, more preferably 1 to 19%, further preferably 1.5 to 18%, further preferably 2.0 to 17%, particularly preferably 2.5 to 16%, and most preferably 3.0 to 15.5%.

[0169] Li2O is a component used to lower the melting temperature of glass, lower the liquidus temperature of glass, stabilize glass, etc. The content of Li2O is preferably 0 to 15%. If the content of Li2O is 15% or less, it is less likely to cause problems such as glass becoming unstable and near-infrared cutoff properties being reduced, so it is preferred. It is more preferably 0 to 8%, further preferably 0 to 7%, further preferably 0 to 6%, and most preferably 0 to 5%.

[0170] Na2O is a component used to lower the melting temperature of glass, lower the liquidus temperature of glass, stabilize glass, etc. The content of Na2O is preferably 0 to 15%. If the content of Na2O is 15% or less, the glass is less likely to become unstable, which is preferred. It is more preferably 0.5 to 14%, further preferably 1 to 13%, further preferably 2 to 13%, and most preferably 3 to 13%.

[0171] K2O is a component that has the effect of lowering the melting temperature of glass and the liquidus temperature of glass. The content of K2O is preferably 0 to 20%. If the content of K2O is 20% or less, the glass is less likely to become unstable, which is preferred. It is more preferably 0.5 to 19%, further preferably 1 to 18%, further preferably 2 to 17%, and most preferably 3 to 16%.

[0172] Rb2O is a component that has the effect of lowering the melting temperature of glass and the liquidus temperature of glass. The content of Rb2O is preferably 0 to 15%. If the content of Rb2O is 15% or less, the glass is less likely to become unstable, which is preferred. It is more preferably 0.5 to 14%, further preferably 1 to 13%, further preferably 2 to 13%, and most preferably 3 to 13%.

[0173] Cs2O is a component that has the effect of lowering the melting temperature of glass and the liquidus temperature of glass. The content of Cs2O is preferably 0 to 15%. If the content of Cs2O is 15% or less, the glass is less likely to become unstable, which is preferred. It is more preferably 0.5 to 14%, further preferably 1 to 13%, further preferably 2 to 13%, and most preferably 3 to 13%.

[0174] In addition, for the alkali metal component represented by R2O, a mixed alkali effect is produced in the glass by adding two or more components at the same time. + The mobility of ions is reduced. As a result, when the glass comes into contact with water, the H + Ions and R in Glass + The hydration reaction produced by the ion exchange of ions improves the weather resistance of the glass. Therefore, the glass of this embodiment preferably contains two or more components selected from Li2O, Na2O, K2O, Rb2O and Cs2O. In this case, the total amount (ΣR2O) of R2O (wherein R2O is Li2O, Na2O, K2O, Rb2O and Cs2O) is preferably 7 to 18% (excluding 7%). If the total amount of R2O exceeds 7%, its effect can be fully obtained. If it is less than 18%, it is not easy to cause problems such as the glass becoming unstable, the near-infrared cutoff property being reduced, and the strength of the glass being reduced, so it is preferred. Therefore, ΣR2O is preferably more than 7% and less than 18%, more preferably 7.5 to 17%, further preferably 8 to 16%, further preferably 8.5% to 15%, and most preferably 9 to 14%.

[0175] R'O (wherein R'O is one or more components selected from CaO, MgO, BaO, SrO and ZnO) is a component used to lower the melting temperature of glass, lower the liquidus temperature of glass, stabilize glass, increase the strength of glass, etc. The total amount of R'O (ΣR'O) is preferably 0 to 40%. If the total amount of R'O is 40% or less, it is less likely to cause problems such as glass becoming unstable, near-infrared cutoff properties being reduced, and glass strength being reduced, so it is preferred. It is more preferably 0 to 35%, further preferably 0 to 30%, further preferably 0 to 25%, particularly preferably 0 to 20%, and most preferably 0 to 15%.

[0176] CaO is a component used to lower the melting temperature of glass, lower the liquidus temperature of glass, stabilize glass, and increase the strength of glass. The content of CaO is preferably 0 to 10%. If the content of CaO is 10% or less, it is less likely to cause problems such as glass becoming unstable and near-infrared cutoff properties being reduced, so it is preferred. It is more preferably 0 to 8%, further preferably 0 to 6%, further preferably 0 to 5%, and most preferably 0 to 4%.

[0177] MgO is a component used to lower the melting temperature of glass, lower the liquidus temperature of glass, stabilize glass, and improve the strength of glass. The content of MgO is preferably 0 to 15%. If the content of MgO is 15% or less, it is less likely to cause problems such as glass instability and reduced near-infrared cutoff properties, so it is preferred. It is more preferably 0 to 13%, more preferably 0 to 10%, more preferably 0 to 9%, and most preferably 0 to 8%.

[0178] BaO is a component used to lower the melting temperature of glass, lower the liquidus temperature of glass, stabilize glass, etc. The BaO content is preferably 0 to 40%. If the BaO content is 40% or less, it is less likely to cause problems such as glass becoming unstable and near-infrared cutoff properties being reduced, so it is preferred. It is more preferably 0 to 30%, further preferably 0 to 20%, further preferably 0 to 10%, and most preferably 0 to 5%.

[0179] SrO is a component used to lower the melting temperature of glass, lower the liquidus temperature of glass, stabilize glass, etc. The content of SrO is preferably 0 to 10%. If the content of SrO is 10% or less, it is less likely to cause problems such as glass becoming unstable and near-infrared cutoff properties being reduced, so it is preferred. It is more preferably 0 to 8%, further preferably 0 to 7%, and most preferably 0 to 6%.

[0180] ZnO has the effect of lowering the melting temperature of glass and the liquidus temperature of glass. The content of ZnO is preferably 0 to 15%. If the content of ZnO is 15% or less, it is less likely to cause problems such as glass instability, deterioration of glass solubility, and reduction of near-infrared cutoff properties, so it is preferred. It is more preferably 0 to 13%, further preferably 0 to 10%, further preferably 0 to 9%, and most preferably 0 to 8%.

[0181] CuO is a component for cutting off near infrared rays. If the content of CuO is 0.5% or more, its effect and the effect of improving the transmittance of light in the visible region of the glass obtained when MoO3 described later is contained are fully obtained. In addition, if it is 40% or less, it is not easy to produce devitrified foreign matter in the glass, and the transmittance of light in the visible region is reduced, so it is preferred. It is more preferably 1.0 to 35%, more preferably 1.5 to 30%, more preferably 2.0 to 25%, and most preferably 2.5 to 20%.

[0182] MoO3 is a component for improving the transmittance of light in the visible region of glass, and is preferably contained together with CuO. The inventors prepared a phosphate glass containing Cu (which does not contain a fluorine component) and a phosphate glass containing only Mo added to the glass, and confirmed their optical properties. As a result, it was confirmed that the transmittance of light with a wavelength of 400nm to 540nm in the latter glass was greatly increased compared with the former glass. Although this phenomenon is only hypothetical, it is believed that the reason is as follows.

[0183] It is known that Mo exists in glass as MO 6+ However, if Mo and Cu are added together in phosphate glass, the Cu in the glass + It releases electrons (e － ) becomes Cu 2+ (Cu + →Cu 2+ +e － ), MO 6+ Will receive Cu + The released electrons become MO 5+ (5 price)(MO 6+ +e － →MO 5+ ). Thus, Cu, which has absorption characteristics near the wavelength of 300nm to 600nm, + The presence ratio of (monovalent) decreases, and the transmittance of light with a wavelength of 400nm to 540nm increases. 5+ Since it has the property of absorbing light with a wavelength of about 400 nm, it is believed that the transmittance of light with a wavelength of about 400 nm does not increase. Phosphate glass containing Cu and Mo has not been known before, and the above is believed to be a new finding found by the inventors of the present application.

[0184] If the content of MoO3 is 0.01% or more, the effect of improving the transmittance of light in the visible region of the glass can be sufficiently obtained, and if it is 10% or less, problems such as reduction in near infrared cutoff and generation of devitrified foreign matter in the glass are less likely to occur, and thus it is preferred. It is more preferably 0.02 to 9%, further preferably 0.03 to 8%, further preferably 0.04 to 7%, and most preferably 0.05 to 6%.

[0185] The phosphoric acid glass of the optical filter of the present embodiment may contain F in a range of 10% or less in order to improve weather resistance. If the F content is 10% or less, it is less likely to cause problems such as reduced near-infrared cutoff properties and generation of devitrified foreign matter in the glass, and therefore it is preferred. It is more preferably 9% or less, further preferably 8% or less, further preferably 7% or less, particularly preferably 6% or less, and most preferably 5% or less.

[0186] B2O3 may be contained in a range of 10% or less in order to stabilize the glass. If the content of B2O3 is 10% or less, it is not easy to cause problems such as deterioration of the weather resistance of the glass and reduction of the near-infrared cutoff property, so it is preferred. It is preferably 9% or less, more preferably 8% or less, further preferably 7% or less, further preferably 6% or less, and most preferably 5% or less.

[0187] Among the above components, SiO2, GeO2, ZrO2, SnO2, TiO2, CeO2, WO3, Y2O3, La2O3, Gd2O3, Yb2O3, and Nb2O5 may be contained in a range of 5% or less in order to improve the weather resistance of the glass. If the content of these components is 5% or less, it is not easy to cause problems such as devitrification foreign matter in the glass and reduction of near-infrared cutoff properties, so it is preferred. It is more preferably 4% or less, further preferably 3% or less, particularly preferably 2% or less, and further preferably 1% or less.

[0188] Fe2O3, Cr2O3, Bi2O3, NiO, V2O5, MnO2, and CoO are all components that reduce the transmittance of light in the visible region by existing in the glass. Therefore, it is preferred that these components are not substantially contained in the glass.

[0189] In the present invention, “substantially containing no specific component” means that the specific component is not intentionally added, and does not exclude the inclusion of the specific component to the extent that the specific component is inevitably mixed from raw materials and the like and does not affect the desired properties.

[0190] From the viewpoint of reducing the height of the camera module, the thickness of the phosphate glass is preferably 0.5 mm or less, more preferably 0.3 mm or less, and from the viewpoint of maintaining the strength of the device, it is preferably 0.10 mm or more, more preferably 0.15 mm or more.

[0191] Phosphoric acid glass can be produced, for example, as follows.

[0192] First, the raw materials are weighed and mixed in such a manner as to achieve the above-mentioned composition range (mixing step). The raw material mixture is placed in a platinum crucible and heated and melted at a temperature of 700 to 1400° C. in an electric furnace (melting step). After being fully stirred and clarified, it is cast into a mold, cut and ground to form a flat plate with a specified wall thickness (forming step).

[0193] In the melting step of the manufacturing method, the maximum temperature of the glass during the glass melting is preferably set to 1400° C. or less. If the maximum temperature of the glass during the glass melting exceeds the above temperature, the transmittance characteristics may deteriorate. The above temperature is more preferably 1350° C. or less, further preferably 1300° C. or less, and further preferably 1250° C. or less.

[0194] If the temperature of the melting step is too low, problems such as devitrification during melting and melting taking time may occur, so the temperature is preferably 700° C. or higher, more preferably 800° C. or higher.

[0195] <Resin film>

[0196] The resin film in the optical filter of the present invention comprises a resin and a near infrared absorbing pigment in the resin, wherein the near infrared absorbing pigment has a maximum absorption wavelength in the range of 690 to 800 nm. Here, the resin refers to a resin constituting the resin film.

[0197] The resin film preferably satisfies all of the following spectral characteristics (iii-1) to (iii-3).

[0198] (iii-1) Internal transmittance T at a wavelength of 450 nm 450 More than 85%.

[0199] (iii-2) Average internal transmittance T at wavelengths of 450 to 600 nm 450－600AVE More than 90%.

[0200] (iii-3) The wavelength IR50 at which the internal transmittance is 50% is in the range of 620 to 750 nm.

[0201] Satisfying the spectral characteristic (iii-1) means that the transmittance in the blue light region is excellent.

[0202] Internal transmittance T 450 It is more preferably 95% or more, and even more preferably 98% or more.

[0203] Satisfying the spectral characteristic (iii-2) means that the transmittance in the visible light region of 450 to 600 nm is excellent.

[0204] Average internal transmittance T 450－600AVE It is more preferably 92% or more, and even more preferably 94% or more.

[0205] Satisfying the spectral characteristic (iii-3) means shielding light in the near-infrared region and efficiently obtaining visible transmitted light.

[0206] The wavelength IR50 is more preferably in the range of 625 to 645 nm, and even more preferably in the range of 625 to 640 nm.

[0207] The resin film of the present invention contains a pigment having a maximum absorption wavelength of 690 to 800 nm, and can shield light in the near-infrared region of around 700 nm, which has a slightly weaker light-shielding property, by utilizing the absorption characteristics of the pigment in the phosphate glass.

[0208] As near infrared absorbing pigment, for example, at least one selected from cyanine pigment, phthalocyanine pigment, squarylium pigment, naphthalocyanine pigment and diimine pigment can be enumerated, and can be used alone or in a mixed manner. Among them, from the viewpoint of easily bringing into play the effect of the present invention, preferred squarylium pigment and cyanine pigment are considered.

[0209] The content of the near infrared absorbing pigment in the resin film is preferably 0.1 to 30 parts by mass, more preferably 0.1 to 20 parts by mass, based on 100 parts by mass of the resin. When two or more compounds are combined, the above content is the total of the compounds.

[0210] The resin film may contain other pigments, for example, ultraviolet light absorbing pigments, within a range not impairing the effects of the present invention.

[0211] Examples of ultraviolet light absorbing pigments include Azoles, merocyanines, anthocyanines, naphthalene diimide pigments, Oxadiazole pigments, Azine pigment, Oxazolidine pigment, naphthalene dicarboxylic acid pigment, styryl pigment, anthracene pigment, cyclic carbonyl pigment, triazole pigment, etc. Among them, merocyanine pigment is particularly preferred. In addition, one kind can be used alone, or two or more kinds can be used in combination.

[0212] As the resin, there is no restriction 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, polyarylether phosphine oxide resins, polyamide resins, polyimide resins, polyamideimide resins, polyolefin resins, cyclic olefin resins, polyurethane resins, and polystyrene resins can be used. One of these resins can be used alone, or two or more of them can be mixed and used.

[0213] From the viewpoint of the spectral characteristics, glass transition temperature (Tg) and adhesion of the resin film, at least one resin selected from the group consisting of polyimide resins, polycarbonate resins, polyester resins and acrylic resins is preferred.

[0214] When a plurality of dyes are used, they may be contained in the same resin film or may be contained in different resin films.

[0215] Resin film can be prepared by dissolving or being dispersed in the solvent the raw material composition of pigment, resin or resin and each component coordinated as required and being applied to the support body and being dried, and then being solidified and formed as required. The support body at this moment can be the phosphoric acid glass used in the filter, and can also be the strippable support body used only when forming resin film. In addition, the solvent can be a dispersion medium or a soluble solvent that can be stably dispersed.

[0216] In addition, the coating liquid may contain a surfactant to improve the gaps caused by microbubbles, the depressions caused by the attachment of foreign matter, the shrinkage in the drying process, etc. In addition, in the coating of the coating liquid, for example, a dip coating method, a cast coating method or a spin coating method, etc. can be used. After the above-mentioned coating liquid is applied to the support, it is dried to form a resin film. In addition, when the coating liquid contains a raw material component of a transparent resin, a curing treatment such as heat curing or light curing is further performed.

[0217] The resin film can also be produced in a film shape by extrusion molding. The obtained film-shaped resin film can be laminated on phosphate glass and integrated by heat pressing or the like to produce a substrate.

[0218] The resin film may have one layer in the optical filter, or may have two or more layers. When having two or more layers, the respective layers may have the same structure or different structures.

[0219] From the perspective of the in-plane film thickness distribution and appearance quality of the coated substrate, the thickness of the resin film is 10 μm or less, preferably 5 μm or less, and from the perspective of reflecting the desired spectral characteristics with an appropriate pigment concentration, it is preferably 0.5 μm or more. It should be noted that when the optical filter has two or more layers of resin films, the total thickness of each resin film is preferably within the above range.

[0220] The optical filter of this embodiment may also have other components such as components (layers) that provide absorption using inorganic particles, etc., for controlling the transmission and absorption of light in a specific wavelength region. Specific examples of inorganic particles include ITO (Indium Tin Oxides), ATO (Antimony-doped Tin Oxides), cesium tungstate, lanthanum boride, etc. ITO particles and cesium tungstate particles have high transmittance of visible light and light absorption in a wide range of infrared wavelength regions exceeding 1200nm, so they can be used when the above-mentioned infrared light shielding is required.

[0221] The optical filter of this embodiment can provide an imaging device with excellent color reproducibility when used in an imaging device such as a digital camera, for example. The imaging device comprises a solid imaging element, a shooting lens, and the optical filter of this embodiment. The optical filter of this embodiment can be arranged between the shooting lens and the solid imaging element, or can be directly attached to the solid imaging element, the shooting lens, etc. of the imaging device via an adhesive layer for use.

[0222] As described above, this specification discloses the following optical filters and the like.

[0223] [1] An optical filter comprising: a dielectric multilayer film 1, a resin film, phosphate glass, and a dielectric multilayer film 2, in this order;

[0224] The resin film comprises a resin and a near infrared absorbing pigment in the resin, wherein the near infrared absorbing pigment has a maximum absorption wavelength in the range of 690 to 800 nm.

[0225] The thickness of the resin film is 10 μm or less.

[0226] The above optical filter satisfies all of the following spectral characteristics (i-1) to (i-5).

[0227] (i-1) Average transmittance T at wavelength 430-550nm and incident angle 0 degrees 430－550(0deg)AVE More than 80%.

[0228] (i-2) Average transmittance T at wavelength 430 to 550 nm and incident angle 60 degrees 430－550(60deg)AVE More than 80%.

[0229] (i-3) In the wavelength range of 500 to 700 nm, the wavelength IR with a transmittance of 50% at an incident angle of 0 degrees 50(0deg) In the wavelength region of 600 to 660 nm.

[0230] (i-4) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 0 degrees and at intervals of 1 nm. n(0deg) (n: any integer), the above transmittance T n(0deg) There are 20 or more n's that are 0.04% or less.

[0231] (i-5) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 40 degrees and at intervals of 1 nm. n(40deg) (n: any integer), the above transmittance T n(40deg) There are 20 or more n's that are 0.04% or less.

[0232] [2] The optical filter according to [1], further satisfying the following spectral characteristics (i-6) to (i-7).

[0233] (i-6) Average transmittance T at wavelength 750-1200 nm and incident angle 0 degrees 750－1200(0deg)AVE Less than 2%.

[0234] (i-7) Average transmittance T at wavelength 750 to 1200 nm and incident angle 40 degrees 750－1200(40deg)AVE Less than 2%.

[0235] [3] The optical filter according to [1] or [2], further satisfying the following spectral characteristics (i-8) to (i-9).

[0236] (i-8) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 0 degrees and at intervals of 1 nm. n(0deg) (n: any integer), the above transmittance T n(0deg) There are 20 or more n's that are 0.01% or less.

[0237] (i-9) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 40 degrees and at intervals of 1 nm. n(40deg) (n: any integer), the above transmittance T n(40deg) There are 20 or more n's that are 0.01% or less.

[0238] [4] The optical filter according to any one of [1] to [3], further satisfying the following spectral characteristics (i-10) to (i-11).

[0239] (i-10) The above average transmittance T 430－550(0deg)AVE With the above average transmittance T 430－550(60deg)AVE The absolute value of the difference is less than 10%.

[0240] (i-11) Maximum transmittance T at wavelength 430-550nm and incident angle 0 degrees 430－550(0deg)MAX The maximum transmittance T at an incident angle of 60 degrees 430－550(60deg)MAX The absolute value of the difference is less than 10%.

[0241] [5] The optical filter according to any one of [1] to [4], further satisfying the following spectral characteristics (i-12) to (i-17).

[0242] (i-12) When the dielectric multilayer film 2 side is the incident direction, the average reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 5 degrees 430－550(5deg)AVE Less than 10%.

[0243] (i-13) When the dielectric multilayer film 2 side is the incident direction, the average reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 60 degrees 430－550(60deg)AVE Less than 10%.

[0244] (i-14) When the dielectric multilayer film 2 side is the incident direction, the maximum reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 5 degrees 430－550(5deg)MAX Less than 15%.

[0245] (i-15) When the dielectric multilayer film 2 side is the incident direction, the maximum reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 60 degrees 430－550(60deg)MAX Less than 15%.

[0246] (i-16) When the dielectric multilayer film 2 side is the incident direction, the reflectivity R2 of each wavelength is read from a wavelength of 900 nm to a wavelength of 1000 nm at an incident angle of 5 degrees and at intervals of 1 nm. n(5deg) (n: any integer), the above reflectivity R2 n(5deg) There are 30 or more n's that are 95% or more.

[0247] (i-17) When the dielectric multilayer film 2 side is the incident direction, the reflectivity R2 of each wavelength is read from a wavelength of 900 nm to a wavelength of 1000 nm at an incident angle of 40 degrees and at intervals of 1 nm. n(40deg) (n: any integer), the above reflectivity R2 n(40deg) There are 25 or more n's that are 95% or more.

[0248] [6] The optical filter according to any one of [1] to [5], further satisfying the following spectral characteristics (i-18) to (i-19).

[0249] (i-18) When the dielectric multilayer film 2 side is the incident direction, the average reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 5 degrees 430－550(5deg)AVE Average reflectivity R2 at an incident angle of 60 degrees 430－550(60deg)AVE The absolute value of the difference is less than 10%.

[0250] (i-19) When the dielectric multilayer film 2 side is the incident direction, the maximum reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 5 degrees 430－550(5deg)MAX Maximum reflectivity R2 at an incident angle of 60 degrees 430－550(60deg)MAX The absolute value of the difference is less than 10%.

[0251] [7] The optical filter according to any one of [1] to [6], further satisfying the following spectral characteristic (i-20).

[0252] (i-20) When the dielectric multilayer film 2 side is the incident direction, the reflectivity R2 of each wavelength is read from a wavelength of 900 nm to a wavelength of 1000 nm at an incident angle of 5 degrees and at intervals of 1 nm. n(5deg) (n: any integer), the above reflectivity R2 n(5deg) There are 30 or more n's that are 98% or more.

[0253] [8] An optical filter according to any one of [1] to [7], wherein at least one of the above-mentioned dielectric multilayer film 1 and the above-mentioned dielectric multilayer film 2 is a stack of dielectric films with different refractive indices, and [the sum of the QWOT of dielectric films with relatively high refractive indices] / [the sum of the QWOT of dielectric films with relatively low refractive indices] is greater than 1.6.

[0254] [9] An optical filter according to any one of [1] to [8], wherein at least one of the dielectric multilayer film 1 and the dielectric multilayer film 2 is a multilayer film in which 10 or more H2 layers and 10 or more M2 layers defined below are alternately stacked.

[0255] H2 layer: a single layer with a refractive index of 1.8 to 2.5 and a QWOT of 1.1 to 3.5.

[0256] M2 layer: A single layer or multiple layers existing between two H2 layers, with the sum of QWOT being 1.2 to 1.8.

[0257]

[10] The optical filter according to any one of [1] to [9], wherein the phosphate glass satisfies all of the following spectral characteristics (ii-1) to (ii-5).

[0258] (ii-1) Internal transmittance T at a wavelength of 450 nm 450 It is more than 92%.

[0259] (ii-2) Average internal transmittance T at wavelengths of 450 to 600 nm 450－600AVE More than 90%.

[0260] (ii-3) IR50, where the internal transmittance is 50%, is in the wavelength range of 625 to 650 nm.

[0261] (ii-4) Average internal transmittance T at wavelengths of 750 to 1000 nm 750－1000AVE It is less than 2.5%.

[0262] (ii-5) Average internal transmittance T at wavelengths of 1000 to 1200 nm 1000－1200AVE Less than 7%.

[0263]

[11] The optical filter according to any one of [1] to

[10] , wherein the phosphate glass contains, expressed in mass % based on oxides:

[0264] 40-80% P2O5,

[0265] 0.5~20% Al2O3,

[0266] 0.5 to 20% of ΣR2O (wherein R2O is one or more components selected from Li2O, Na2O, K2O, Rb2O, and Cs2O, and ΣR2O is the total amount of R2O),

[0267] 0 to 40% of ΣR'O (wherein R'O is one or more components selected from CaO, MgO, BaO, SrO and ZnO, and ΣR'O is the total amount of R'O),

[0268] 0.5~40% CuO.

[0269]

[12] The optical filter according to any one of [1] to

[11] , wherein the near-infrared absorbing pigment comprises a squarylium pigment,

[0270] The above-mentioned resin film satisfies all of the following spectral characteristics (iii-1) to (iii-3).

[0271] (iii-1) Internal transmittance T at a wavelength of 450 nm 450 More than 85%.

[0272] (iii-2) Average internal transmittance T at wavelengths of 450 to 600 nm 450－600AVE More than 90%.

[0273] (iii-3) The wavelength IR50 at which the internal transmittance is 50% is in the range of 620 to 750 nm.

[0274]

[13] An imaging device comprising the optical filter according to any one of [1] to

[12] .

[0275] Example

[0276] Next, the present invention will be described in more detail based on examples.

[0277] Each spectral characteristic was measured using an ultraviolet-visible spectrophotometer (UH-4150, manufactured by Hitachi High-Technologies Corporation).

[0278] In addition, when the incident angle is not particularly clearly stated, the spectral characteristics are values ​​measured at an incident angle of 0° (a direction perpendicular to the main surface of the optical filter).

[0279] The dyes used in each example are as follows.

[0280] Compound 1 (squarylium compound): synthesized based on International Publication No. 2017 / 135359.

[0281] Compound 2 (cyanine compound): synthesized according to the method described in Dyes and Pigments, 73, 344-352 (2007).

[0282] Compound 3 (merocyanine compound): synthesized based on the specification of German Patent Publication No. 10109243.

[0283]

[0284] <Spectral characteristics of pigments in resin>

[0285] A polyimide resin ("C3G30G" (trade name) manufactured by Mitsubishi Gas Chemical Co., Ltd., refractive index 1.59) was dissolved in γ-butyrolactone (GBL):cyclohexanone=1:1 (mass ratio) to prepare a polyimide resin solution having a resin concentration of 8.5 mass %.

[0286] Each pigment of each of the above compounds 1 to 3 was added to the above resin solution at a concentration of 7.5 parts by mass relative to 100 parts by mass of the resin, and stirred and dissolved at 50° C. for 2 hours to obtain a coating liquid. The obtained coating liquid was applied to an alkali glass (manufactured by SCHOTT, D263 glass, thickness 0.2 mm) by spin coating to form a coating film with a film thickness of about 1.0 μm.

[0287] The spectral transmittance curve of the obtained coating film in the wavelength range of 350 to 1200 nm was measured using an ultraviolet-visible spectrophotometer.

[0288] The spectral characteristics of each of the above compounds 1 to 3 in the polyimide resin are shown in the following Table 1. In addition, the spectral characteristics shown in the following table were evaluated by internal transmittance in order to avoid the influence of reflection at the air interface and the glass interface.

[0289] [Table 1]

[0290] Pigment number Maximum absorption wavelength in resin Compound 1 752nm Compound 2 773nm Compound 3 400nm

[0291] <Spectral characteristics of glass>

[0292] As the near-infrared absorbing glass, phosphate glass and fluorophosphate glass having the compositions shown in the following table were prepared.

[0293] The raw materials were weighed and mixed in such a manner as to have the composition (mass % of oxides) shown in Table 2 below, placed in a crucible with an internal volume of about 400 cc, and melted for 2 hours in an air atmosphere. Then, the mixture was clarified and stirred, and cast into a rectangular mold of 100 mm in length, 80 mm in width, and 20 mm in height preheated to about 300° C. to 500° C., and then slowly cooled at about 1° C. / min to obtain a glass plate of 40 mm in length, 30 mm in width, and a predetermined thickness (mm) with both sides optically polished.

[0294] [Table 2]

[0295] (quality%) Phosphoric acid glass Fluorophosphate glass <![CDATA[P2O5]]> 68.53 41.45 <![CDATA[Al2O3]]> 11.32 6.27 <![CDATA[Li2O]]> 0.00 4.87 <![CDATA[Na2O]]> 3.15 0.00 <![CDATA[K2O]]> 9.04 0.00 CaO 0.00 3.37 SrO 0.00 7.75 BaO 0.00 11.91 <![CDATA[MoO3]]> 0.30 0.00 CuO 7.66 3.08 F 0.00 21.28 total 100 100

[0296] The spectral transmittance curve of each glass in the wavelength range of 350 to 1200 nm was measured using an ultraviolet-visible spectrophotometer.

[0297] The obtained spectral characteristics are shown in the following Table 3. In addition, the spectral characteristics shown in the following table were evaluated by internal transmittance in order to avoid the influence of reflection at the air interface and the glass interface.

[0298] In addition, the spectral transmittance curve of phosphate glass is shown in Figure 2 .

[0299] [Table 3]

[0300]

[0301] As described above, it is understood that the phosphoric acid glass used has a higher transmittance in the visible light region and is excellent in light shielding properties in the near infrared region than the fluorophosphate glass.

[0302] <Example 1-1 to Example 1-3: Spectral Characteristics of Resin Film>

[0303] The pigments of Compounds 1 to 3 were mixed in the polyimide resin solution prepared in the same manner as when calculating the spectral characteristics of the above compounds at the concentrations listed in Table 4 below, stirred and dissolved at 50° C. for 2 hours to obtain a coating solution. The obtained coating solution was applied to an alkali glass (manufactured by SCHOTT, D263 glass, thickness 0.2 mm) by spin coating to form a resin film with a film thickness of 3.0 μm.

[0304] The spectral transmittance curve of the obtained resin film in the wavelength range of 350 to 1200 nm was measured using an ultraviolet-visible spectrophotometer.

[0305] The obtained spectral characteristics are shown in the following Table 4. In addition, the spectral characteristics shown in the following table were evaluated by internal transmittance in order to avoid the influence of reflection at the air interface and the glass interface.

[0306] In addition, the spectral transmittance curve of the resin film of Example 1-1 is shown in Figure 3 .

[0307] It should be noted that Examples 1-1 to 1-3 are reference examples.

[0308] [Table 4]

[0309]

[0310] <Example 2-1: Spectral characteristics of optical filters>

[0311] A resin film was formed on one main surface of the phosphate glass by the same method as in Example 1-1. TiO2 (refractive index at a wavelength of 500 nm: 2.47) and SiO2 (refractive index at a wavelength of 500 nm: 1.48) were deposited on the surface of the resin film in the order and film thickness (nm) shown in Table 5 below to form a dielectric multilayer film 1. In addition, TiO2 and SiO2 were deposited on the other main surface of the phosphate glass in the order and film thickness (nm) shown in Table 5 below to form a dielectric multilayer film 2.

[0312] In this way, an optical filter having a structure of dielectric multilayer film 2 (surface close to the front) / phosphate glass / resin film / dielectric multilayer film 1 (surface close to the rear) is produced.

[0313] <Examples 2-2 to 2-4: Spectral characteristics of optical filters>

[0314] An optical filter was produced in the same manner as in Example 2-1 except that the dielectric multilayer film 1 and the dielectric multilayer film 2 were changed to the configurations shown in Table 5 or Table 6 below.

[0315] <Examples 2-5 and 2-6: Spectral characteristics of optical filters>

[0316] An optical filter was produced in the same manner as in Example 2-1 except that phosphate glass was changed to fluorophosphate glass 1 or fluorophosphate glass 2, and the resin film, dielectric multilayer film 1, and dielectric multilayer film 2 were changed to the configurations shown in Table 6 below.

[0317] [Table 5]

[0318]

[0319] [Table 6]

[0320]

[0321] For each optical filter, a spectral transmittance curve at incident angles of 0 and 60 degrees and a spectral reflectance curve at an incident angle of 5 degrees were measured in a wavelength range of 350 to 1200 nm using an ultraviolet-visible spectrophotometer.

[0322] The results are shown in Table 7 below.

[0323] In addition, the spectral transmittance curve of the optical filter of Example 2-1 is shown in Figure 4 , the spectral reflectance curve is shown in Figure 5 The spectral transmittance curve of the optical filter of Example 2-3 is shown in Figure 6 , the spectral reflectance curve is shown in Figure 7 The spectral transmittance curve of the optical filter of Example 2-5 is shown in Figure 8 , the spectral reflectance curve is shown in Fig. 9 .

[0324] It should be noted that Examples 2-1 to 2-3 are examples, and Examples 2-4 to 2-6 are comparative examples.

[0325] [Table 7]

[0326]

[0327] The above results show that the optical filters of Examples 2-1 to 2-3 have high transmittance in the visible light region and high shielding properties in the near-infrared light region, and have small changes in visible light transmittance at high incident angles, thereby suppressing the generation of moire.

[0328] The results of the optical filter of Example 2-4 are as follows: the number of wavelengths with a transmittance of 0.04% or less in the wavelength range of 900 to 1000 nm is 0 at both the incident angles of 0 and 40 degrees, and the shielding property in the near-infrared region is low. It is believed that this is because the dielectric multilayer films of Example 2-4 are all designed as anti-reflection layers, and the absorption characteristics of phosphate glass and near-infrared absorbing pigments alone cannot fully shield the near-infrared region, especially the wavelength range of 900 to 1000 nm.

[0329] The optical filter of Example 2-5 has a small average transmittance at 60 degrees in the visible light region. In addition, the difference between the average transmittance at an incident angle of 0 degrees and the average transmittance at 60 degrees is large, that is, the visible light transmittance decreases at high incident angles. This is believed to be because the dielectric multilayer film 2 of Example 2-5 has a large reflective property in the near-infrared light region, so it is easy to generate ripples in the visible light region at high incident angles.

[0330] The results of the optical filter of Example 2-6 are as follows: the number of wavelengths with a transmittance of 0.04% or less in the wavelength range of 900 to 1000 nm is small at an incident angle of 40 degrees. This is probably because phosphate glass was not used in Example 2-6, and thus the near-infrared region could not be fully shielded.

[0331] The present invention has been described in detail with reference to specific embodiments, but it is obvious that those skilled in the art can add various changes and modifications without departing from the spirit and scope of the present invention. This application is based on the Japanese patent application (Japanese Patent Application No. 2022-138363) filed on August 31, 2022, and its contents are incorporated herein by reference.

[0332] Industrial Applicability

[0333] The optical filter of this embodiment has excellent transmittance of visible light, little change in transmittance in the visible light region at high incident angles, and excellent spectral characteristics of shielding in the near-infrared light region. In recent years, it is useful in applications such as conveyor cameras, sensors and other imaging devices that have been developed with high performance.

[0334] Explanation of symbols

[0335] 1 Optical filter

[0336] A1 Dielectric Multilayer

[0337] A2 Dielectric Multilayer

[0338] 11 Phosphoric acid glass

[0339] 12 Resin film

Claims

1. An optical filter comprising: a dielectric multilayer film 1, a resin film, phosphate glass, and a dielectric multilayer film 2, in this order; The resin film comprises a resin and a near infrared absorbing pigment in the resin, wherein the near infrared absorbing pigment has a maximum absorption wavelength in the range of 690 to 800 nm. The thickness of the resin film is 10 μm or less, The optical filter satisfies all of the following spectral characteristics (i-1) to (i-5), (i-1) Average transmittance T at wavelength 430-550nm and incident angle 0 degrees 430－550(0deg)AVE More than 80%, (i-2) Average transmittance T at wavelength 430 to 550 nm and incident angle 60 degrees 430－550(60deg)AVE More than 80%, (i-3) In the wavelength range of 500 to 700 nm, the wavelength IR with a transmittance of 50% at an incident angle of 0 degrees 50(0deg) In the wavelength region of 600 to 660 nm, (i-4) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 0 degrees and at intervals of 1 nm. n(0deg) When the transmittance T n(0deg) There are 20 or more n whose content is less than 0.04%, and n is an arbitrary integer. (i-5) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 40 degrees and at intervals of 1 nm. n(40deg) When the transmittance T n(40deg) There are 20 or more n whose content is 0.04% or less, and n is an arbitrary integer.

2. The optical filter according to claim 1, wherein Further satisfying the following spectral characteristics (i-6) to (i-7), (i-6) Average transmittance T at wavelength 750-1200 nm and incident angle 0 degrees 750－1200(0deg)AVE Less than 2%, (i-7) Average transmittance T at wavelength 750 to 1200 nm and incident angle 40 degrees 750－1200(40deg)AVE Less than 2%.

3. The optical filter according to claim 1, wherein Further satisfying the following spectral characteristics (i-8) to (i-9), (i-8) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 0 degrees and at intervals of 1 nm. n(0deg) When the transmittance T n(0deg) There are 20 or more n with a value of 0.01% or less, where n is an arbitrary integer. (i-9) Read the transmittance T of each wavelength from 900 nm to 1000 nm at an incident angle of 40 degrees and at intervals of 1 nm. n(40deg) When the transmittance T n(40deg) There are 20 or more n whose content is 0.01% or less, and n is an arbitrary integer.

4. The optical filter according to claim 1, wherein Further satisfying the following spectral characteristics (i-10) to (i-11), (i-10) The average transmittance T 430－550(0deg)AVE With the average transmittance T 430－550(60deg)AVE The absolute value of the difference is less than 10%. (i-11) Maximum transmittance T at wavelength 430-550nm and incident angle 0 degrees 430－550(0deg)MAX The maximum transmittance T at an incident angle of 60 degrees 430－550(60deg)MAX The absolute value of the difference is less than 10%.

5. The optical filter according to claim 1, wherein Further satisfying the following spectral characteristics (i-12) to (i-17), (i-12) When the dielectric multilayer film 2 side is the incident direction, the average reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 5 degrees 430－550(5deg)AVE Less than 10%, (i-13) When the dielectric multilayer film 2 side is the incident direction, the average reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 60 degrees 430－550(60deg)AVE Less than 10%, (i-14) When the dielectric multilayer film 2 side is the incident direction, the maximum reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 5 degrees 430－550(5deg)MAX Less than 15%, (i-15) When the dielectric multilayer film 2 side is the incident direction, the maximum reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 60 degrees 430－550(60deg)MAX Less than 15%, (i-16) When the dielectric multilayer film 2 side is the incident direction, the reflectivity R2 of each wavelength is read from a wavelength of 900 nm to a wavelength of 1000 nm at an incident angle of 5 degrees and at intervals of 1 nm. n(5deg) When the reflectivity R2 n(5deg) There are more than 30 n for which the probability of success is greater than 95%, where n is an arbitrary integer. (i-17) When the dielectric multilayer film 2 side is the incident direction, the reflectivity R2 of each wavelength is read from a wavelength of 900 nm to a wavelength of 1000 nm at an incident angle of 40 degrees and at intervals of 1 nm. n(40deg) When the reflectivity R2 n(40deg) There are 25 or more n where the percentage is 95% or more, and n is an arbitrary integer.

6. The optical filter according to claim 1, wherein Further satisfying the following spectral characteristics (i-18) to (i-19), (i-18) When the dielectric multilayer film 2 side is the incident direction, the average reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 5 degrees 430－550(5deg)AVE Average reflectivity R2 at an incident angle of 60 degrees 430－550(60deg)AVE The absolute value of the difference is less than 10%. (i-19) When the dielectric multilayer film 2 side is the incident direction, the maximum reflectivity R2 at a wavelength of 430 to 550 nm and an incident angle of 5 degrees 430－550(5deg)MAX Maximum reflectivity R2 at an incident angle of 60 degrees 430－550(60deg)MAX The absolute value of the difference is less than 10%.

7. The optical filter according to claim 1, wherein Further satisfying the following spectral characteristics (i-20), (i-20) When the dielectric multilayer film 2 side is the incident direction, the reflectivity R2 of each wavelength is read from a wavelength of 900 nm to a wavelength of 1000 nm at an incident angle of 5 degrees and at intervals of 1 nm. n(5deg) When the reflectivity R2 n(5deg) There are 30 or more n whose percentage is 98% or more, and n is an arbitrary integer.

8. The optical filter according to claim 1, wherein At least one of the dielectric multilayer film 1 and the dielectric multilayer film 2 is a stack of dielectric films having different refractive indices, and [sum of QWOT of dielectric films having relatively high refractive indices] / [sum of QWOT of dielectric films having relatively low refractive indices] is 1.6 or more.

9. The optical filter according to claim 1, wherein: At least one of the dielectric multilayer film 1 and the dielectric multilayer film 2 is a multilayer film in which 10 or more H2 layers and 10 or more M2 layers defined below are alternately stacked. H2 layer: a single layer with a refractive index of 1.8 to 2.5 and a QWOT of 1.1 to 3.

5. M2 layer: A single layer or multiple layers existing between two H2 layers, with the sum of QWOT being 1.2 to 1.

8.

10. The optical filter according to claim 1, wherein The phosphate glass satisfies all of the following spectral characteristics (ii-1) to (ii-5), (ii-1) Internal transmittance T at a wavelength of 450 nm 450 More than 92% (ii-2) Average internal transmittance T at wavelengths of 450 to 600 nm 450－600AVE More than 90%, (ii-3) IR50 with an internal transmittance of 50% is in the wavelength range of 625 to 650 nm, (ii-4) Average internal transmittance T at wavelengths of 750 to 1000 nm 750－1000AVE Below 2.5%, (ii-5) Average internal transmittance T at wavelengths of 1000 to 1200 nm 1000－1200AVE Less than 7%.

11. The optical filter according to claim 1, wherein The phosphate glass contains, expressed in terms of mass % based on oxides: 40-80% P2O5, 0.5~20% Al2O3, 0.5 to 20% of ΣR2O, wherein R2O is one or more components selected from Li2O, Na2O, K2O, Rb2O and Cs2O, and ΣR2O is the total amount of R2O, 0 to 40% of ΣR'O, wherein R'O is one or more components selected from CaO, MgO, BaO, SrO and ZnO, and ΣR'O is the total amount of R'O, 0.5~40% CuO.

12. The optical filter according to claim 1, wherein: The near infrared absorbing pigment comprises a squarylium pigment, The resin film satisfies all of the following spectral characteristics (iii-1) to (iii-3), (iii-1) Internal transmittance T at a wavelength of 450 nm 450 More than 85%, (iii-2) Average internal transmittance T at wavelengths of 450 to 600 nm 450－600AVE More than 90%, (iii-3) The wavelength IR50 at which the internal transmittance is 50% is in the range of 620 to 750 nm. 13 . An imaging device comprising the optical filter according to claim 1 .

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