Optical filter

Abstract

The present invention relates to an optical filter comprising: a near infrared ray absorbing glass; dielectric multilayer films respectively stacked on both principal surfaces of the near infrared ray absorbing glass; and an absorption layer stacked on a front surface of at least one of the dielectric multilayer films and having a maximum absorption wavelength in a near infrared light region. The optical filter satisfies all of specific spectral characteristics (i-1) to (i-5).

Description

[Technical Field]

[0001] This invention relates to an optical filter that selectively transmits light in the visible light region and a specific near-infrared light region, while blocking light outside these regions. [Background technology]

[0002] Imaging devices using solid-state image sensors have expanded their applications to include surveillance cameras and in-vehicle cameras, which capture images day and night. Such devices require the acquisition of both visible light-based (color) images and infrared-based (black and white) images.

[0003] Therefore, the use of optical filters that have a near-infrared cut filter function to transmit visible light and faithfully reproduce images based on that visible light, as well as a function to selectively transmit specific near-infrared light, so-called dual-bandpass filters, is being considered.

[0004] Patent Document 1 describes an optical filter that combines a dielectric multilayer film and a resin substrate containing a near-infrared absorbing dye, which transmits visible light and near-infrared light around 800 nm and blocks other light. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent No. 5884953 [Overview of the initiative] [Problems that the invention aims to solve]

[0006] However, the optical filter described in Patent Document 1 does not have sufficient shielding ability for near-infrared light in the 1000-1200 nm range. In recent years, in order to reduce the number of imaging devices used in ARVR devices and to save space, there has been consideration of incorporating imaging devices that can simultaneously acquire images based on visible light and infrared light. ARVR devices require higher image quality than in-vehicle cameras or surveillance cameras. Since image sensors are sensitive to wavelengths of 1000nm to 1200nm, if the shielding of near-infrared light in the 1000nm to 1200nm range is insufficient, the acquired visible light and infrared images will suffer from image quality degradation due to unwanted light, such as flare and ghosting, making them unsuitable for use in ARVR devices. From this perspective, there is a need for optical filters that can sufficiently block the 1000 to 1200nm range.

[0007] Furthermore, from a performance standpoint, optical filters are desirable to be able to correct the image sensor's light-receiving sensitivity curve to approximate the human visual sensitivity curve, and also to have weather resistance even under high temperature and high humidity conditions.

[0008] The present invention aims to provide an optical filter that exhibits excellent transmittance of visible light and specific near-infrared light, can sufficiently shield other near-infrared light, particularly in the wavelength range of 1000 to 1200 nm, and further exhibits excellent visual sensitivity correction in the visible region and high reliability in terms of weather resistance. [Means for solving the problem]

[0009] The present invention provides an optical filter having the following configuration. [1] Near-infrared absorbing glass, A dielectric multilayer film laminated on both main surfaces of the near-infrared absorbing glass, An optical filter comprising: an absorption layer laminated on the surface of at least one of the dielectric multilayer films and having a maximum absorption wavelength in the near-infrared region, The optical filter is an optical filter that satisfies all of the following spectral characteristics (i-1) to (i-5). (i-1) In the spectral transmittance curve at wavelengths of 450 nm to 600 nm and an incident angle of 0 degrees, the average transmittance T 450-600(0deg)AVE over 60% In the spectral transmittance curve at a wavelength of 700 nm to 750 nm and an incident angle of 0 degrees, the average transmittance T 700-750(0deg)AVE is 5% or less In the spectral transmittance curve at a wavelength of 1050 nm to 1200 nm and an incident angle of 0 degrees, the maximum transmittance T 1050-1200(0deg)MAX is 7% or less In the spectral transmittance curve at a wavelength of 800 nm to 1000 nm and an incident angle of 0 degrees, the maximum transmittance T 800-1000(0deg)MAX is 20% or more When the maximum transmittance in the spectral transmittance curve at a wavelength of 450 nm to 600 nm and an incident angle of 0 degrees is T 450-600(0deg)MAX then In the spectral transmittance curve at an incident angle of 0 degrees, the wavelength λ 450-600(0deg)MAX at which the transmittance becomes 70% of the above T (70%) and the wavelength λ 450-600(0deg)MAX at which the transmittance becomes 30% of the above T (30%) are included in the range of 600 nm to 700 nm, For the wavelength λ (70%) let the transmittance be T (70%) and for the wavelength λ (30%) let the transmittance be T (30%) then the following relational expression is satisfied -2 ≤ [T (30%) - T (70%) / [λ (30%) - λ (70%) ≤ -0.75

Advantages of the Invention

[0010] According to the present invention, an optical filter can be provided that has excellent transmittance for visible light and specific near-infrared light, particularly in the wavelength range of 800 to 900 nm, excellent shielding properties for other near-infrared light, particularly in the wavelength range of 1000 to 1200 nm, excellent visual sensitivity correction in the visible region, and high reliability regarding weather resistance.

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1 is a cross-sectional view schematically showing an example of an optical filter according to an embodiment. [Figure 2]Figure 2 is a schematic cross-sectional view showing another example of an optical filter according to one embodiment. [Figure 3] Figure 3 shows the spectral transmittance curve of near-infrared absorbing glass. [Figure 4] Figure 4 shows the spectral transmittance curves of the absorption layers for Example 1-1 and Example 1-2. [Figure 5] Figure 5 shows the spectral transmittance curve of the optical filter in Example 2-1. [Figure 6] Figure 6 shows the spectral transmittance curve of the optical filter in Example 2-2. [Figure 7] Figure 7 shows the spectral transmittance curve of the optical filter in Example 2-3. [Figure 8] Figure 8 shows the spectral transmittance curve of the optical filter in Example 2-5. [Figure 9] Figure 9 shows the spectral transmittance curve of the optical filter in Example 2-6. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below. In this specification, near-infrared absorbing dyes may be abbreviated as "NIR dyes," and ultraviolet absorbing dyes may be abbreviated as "UV dyes." In this specification, the 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, the group represented by formula (I) is also referred to as group (I), and the same applies to groups represented by other formulas.

[0013] In this specification, internal transmittance is defined by the formula {measured transmittance / (100-reflectance)}×100, which is the transmittance obtained by subtracting the effect of interfacial reflection from the measured transmittance. In this specification, absorbance is -log 10 It is calculated from the (internal) transmittance using the formula ((internal) transmittance / 100). In this specification, the spectral transmission of a substrate and the transmission of an absorption layer, including cases where the dye is contained in the resin, are all referred to as "internal transmission" even when the term "transmission" is used. On the other hand, the transmission measured by dissolving the dye in a solvent such as dichloromethane, the transmission of a dielectric multilayer film, and the transmission of an optical filter having a dielectric multilayer film are measured transmissions.

[0014] In this specification, for a particular wavelength range, a transmittance of, for example, 90% or more means that the transmittance does not fall below 90% across the entire wavelength range, i.e., the minimum transmittance in that wavelength range is 90% or more. Similarly, for a particular wavelength range, a transmittance of, for example, 1% or less means that the transmittance does not exceed 1% across the entire wavelength range, i.e., the maximum transmittance in that wavelength range is 1% or less. The same applies to internal transmittance. The average transmittance and average internal transmittance in a particular wavelength range are the arithmetic mean of the transmittance and internal transmittance for every 1 nm in that wavelength range. The spectral characteristics can be measured using a UV-Vis spectrophotometer. In this specification, the symbol "~" used to indicate a numerical range includes both upper and lower limits.

[0015] <Optical filters> An optical filter according to one embodiment of the present invention (hereinafter also referred to as "this filter") comprises a near-infrared absorbing glass, a dielectric multilayer film laminated on both main surfaces of the near-infrared absorbing glass, and an absorbing layer laminated on the surface of at least one of the dielectric multilayer films, having a maximum absorption wavelength in the near-infrared region. The reflective properties of the dielectric multilayer film, combined with the absorption properties of the near-infrared absorbing glass and absorption layer, enable the overall optical filter to achieve excellent transmittance in the visible light region and specific near-infrared light regions, as well as excellent shielding in other near-infrared light regions.

[0016] An example of the configuration of this filter will be explained using the drawings. Figures 1 and 2 are schematic cross-sectional views showing an example of an optical filter according to one embodiment.

[0017] The optical filter 1A shown in Figure 1 is an example that comprises a near-infrared absorbing glass 10, a dielectric multilayer film 21 laminated on one main surface of the near-infrared absorbing glass 10, and a dielectric multilayer film 22 laminated on the other main surface, and further comprises an absorption layer 30 on the surface of the dielectric multilayer film 22. Here, it is preferable that the dielectric multilayer films 21 and 22 are laminated in contact with the main surface of the near-infrared absorbing glass 10. As the near-infrared absorbing glass, phosphate glass or fluorine phosphate glass containing copper or iron to absorb near-infrared rays is often used, but components such as P2O5 contained in the glass tend to dissolve easily into water in the environment. Since the dielectric multilayer film is usually composed of inorganic materials, by being laminated directly onto both main surfaces of the near-infrared absorbing glass, it also functions as a barrier layer that prevents contact between the glass and water. As a result, the degradation of the near-infrared absorbing glass is suppressed, and a highly reliable optical filter can be obtained.

[0018] The optical filter 1B shown in Figure 2 is an example in which a dielectric multilayer film 23 is further provided on the surface of the absorption layer 30.

[0019] The optical filter of the present invention satisfies all of the following spectral characteristics (i-1) to (i-5). (i-1) In the spectral transmittance curve at wavelengths of 450 nm to 600 nm and an incident angle of 0 degrees, the average transmittance T 450-600(0deg)AVE over 60% (i-2) In the spectral transmittance curve at wavelengths of 700 nm to 750 nm and an incident angle of 0 degrees, the average transmittance T 700-750(0deg)AVE less than 5% (i-3) In the spectral transmittance curve at wavelengths of 1050 nm to 1200 nm and an incident angle of 0 degrees, the maximum transmittance T 1050-1200(0deg)MAX less than 7% (i-4) In the spectral transmittance curve at wavelengths of 800 nm to 1000 nm and an incident angle of 0 degrees, the maximum transmittance T 800-1000(0deg)MAX over 20% (i-5) The maximum transmittance in the spectral transmittance curve at wavelengths of 450 nm to 600 nm and an incident angle of 0 degrees is T 450-600(0deg)MAX In that case, In the spectral transmittance curve at an incident angle of 0 degrees, the transmittance is the T 450-600(0deg)MAXThe wavelength λ is 70% of (70%) and the T 450-600(0deg)MAX The wavelength λ is 30% of that. (30%) However, it falls within the range of 600nm to 700nm. The wavelength λ (70%) Transmittance in T (70%) And the wavelength λ (30%) Transmittance in T (30%) When this is the case, the following relation is satisfied -2≦[T (30%) -T (70%) ] / [λ (30%) -λ (70%) ]≦-0.75

[0020] This filter, which satisfies all of the spectral characteristics (i-1) to (i-5), is a dual-passband filter that excels in the transmittance of visible light as shown in characteristic (i-1), the transmittance of specific near-infrared light as shown in characteristic (i-4), the shielding of other near-infrared light as shown in characteristics (i-2) and (i-3), and the luminous efficiency correction in the visible region as shown in characteristic (i-5).

[0021] Satisfying spectral characteristics (i-1) means that the material exhibits excellent transmittance in the visible light region of 450-600 nm. T 450-600(0deg)AVE Preferably, it is 80% or more, more preferably 88% or more. Furthermore, in order to satisfy the spectral characteristics (i-1), for example, a dielectric multilayer film, absorption layer, or glass with excellent transmittance in the visible light region can be used.

[0022] Satisfying spectral characteristics (i-2) means that the material exhibits excellent shielding properties in the near-infrared region of 700-750 nm. T 700-750(0deg)AVE Preferably, it is 2% or less, more preferably 1% or less. Furthermore, in order to satisfy the spectral characteristics (i-2), for example, an absorption layer containing a near-infrared absorbing dye can be used, and light can be blocked by the absorption capacity of the dye.

[0023] Satisfying the spectral characteristics (i-3) means that it has excellent shielding properties in the near-infrared light region of 1000-1200 nm. T 1050-1200(0deg)MAX Preferably, it is 3% or less, and more preferably 1% or less. Furthermore, in order to satisfy the spectral characteristics (i-3), for example, glass that absorbs near-infrared light beyond 1000 nm can be used.

[0024] Satisfying the spectral characteristics (i-4) means that it has excellent transmittance in the near-infrared light region of 800-1000 nm. T 800-1000(0deg)MAX The percentage is preferably 40% or more, and more preferably 60% or more. Furthermore, in order to satisfy the spectral characteristics (i-4), for example, a dielectric multilayer film with excellent transmittance in the near-infrared light region of 800 to 1000 nm can be used.

[0025] Relational equation in spectral characteristics (i-5) [T (30%) -T (70%) ] / [λ (30%) -λ (70%) This refers to the degree of decrease in the spectral transmittance curve (the slope of the visible band cutoff) in the 600nm to 700nm wavelength range, where the light switches from the visible light to be transmitted to the near-infrared light to be blocked. From the perspective of efficiently capturing light, a steeper spectral curve at the boundary between the transmission and blocking regions is ideal. However, from a performance perspective, correcting the spectral curve to approximate the light-receiving sensitivity to the luminous efficiency curve brings it closer to what the human eye perceives. A relationship (slope) of -2 or greater and -0.75 or less in the spectral characteristics (i-5) means that the luminous efficiency correction in the visible region is excellent. The above relational expression (slope) in the spectral characteristics (i-5) is preferably -1.5 or higher, and also preferably -0.8 or lower. To satisfy the spectral characteristics (i-5), for example, an absorption layer containing a near-infrared absorbing dye can be used, and light can be blocked by the absorption capacity of the dye.

[0026] The optical filter of the present invention preferably further satisfies the following spectral characteristics (i-6). (i-6) The spectral transmittance curve at an incident angle of 0 degrees is T (0deg) Let (λ) be the spectral transmittance curve at an incident angle of 35°, and T be the spectral transmittance curve at an incident angle of 35°. (35deg) When (λ) is denoted as such, the following relationship is satisfied in the wavelength range of 450 nm ≤ λ ≤ 600 nm. |T (0deg) (λ)-T (35deg) (λ)|≦10%

[0027] The relationship in characteristic (i-6) means that the visible light transmittance in the 450-600 nm range does not change significantly even at high incidence angles, i.e., ripple is suppressed. |T (0deg) (λ)-T (35deg) (λ)| is preferably 7% or less, more preferably 4% or less. Ripple occurs when the transmittance in the visible light region changes due to interference caused by reflected light at each layer interface, depending on the number of layers of the multilayer film used to reflect the near-infrared region, and the ripple is larger with higher incidence. To satisfy characteristic (i-6), for example, a dielectric multilayer film in which ripple is suppressed by controlling the number of layers can be used, and infrared absorbing glass can be used to compensate for the light shielding properties in the near-infrared region.

[0028] The optical filter of the present invention preferably further satisfies the following spectral characteristics (i-7). (i-7) The maximum transmittance in the spectral transmittance curve at wavelengths of 450 nm to 600 nm and an incident angle of 0 degrees is T 450-600(0deg)MAX In that case, At an incidence angle of 0 degrees, the T 450-600(0deg)MAX The wavelength λ at which it becomes 50% VIS(0deg)(50%) , and the T at an incident angle of 35 degrees 450-600(0deg)MAX The wavelength λ at which it becomes 50% VIS(35deg)(50%) It is included in the range of 600nm to 700nm, and The following relationship is satisfied |λ VIS(0deg)(50%) -λ VIS(35deg)(50%) |≦10nm

[0029] Satisfying spectral characteristics (i-7) means that the spectral curve in the 600-700 nm region is less likely to shift even at high incidence angles. |λ VIS(0deg)(50%) -λ VIS(35deg)(50%) The | is preferably 7 nm or less, more preferably 5 nm or less. To satisfy the spectral characteristics (i-7), for example, an absorption layer containing a near-infrared absorbing dye can be used, and light can be blocked by the absorption capacity of the dye.

[0030] The optical filter of the present invention preferably further satisfies the following spectral characteristics (i-8). (i-8) In the spectral transmittance curve at wavelengths of 800 nm to 1000 nm and an incident angle of 0 degrees, the maximum transmittance is T 800-1000(0deg)MAX The wavelength at which the maximum transmittance is obtained is λ 800-1000(0deg)MAX In that case, 750nm~λ 800-1000(0deg)MAX In the spectral transmittance curve in the nm range and at an incident angle of 0 degrees, the transmittance is T 800-1000(0deg)MAX The wavelength λ is 50% of IRS(0deg)(50%) and, 750nm~λ 800-1000(0deg)MAX In the spectral transmittance curve in the nm range and at an incident angle of 35 degrees, the transmittance is T 800-1000(0deg)MAX The wavelength λ is 50% of IRS(35deg)(50%) However, satisfying the following relationship |λ IRS(0deg)(50%) -λ IRS(35deg)(50%) | ≤ 30nm

[0031] By satisfying the spectral characteristics (i-8), the spectrum is visible from 750 nm to λ even at high incidence angles. 800-1000(0deg)MAX This means that the spectral curve in the nm region is less likely to shift. |λ IRS(0deg)(50%) -λ IRS(35deg)(50%) The | is preferably 20 nm or less, more preferably 10 nm or less. To satisfy the spectral characteristics (i-8), for example, an absorption layer containing a near-infrared absorbing dye can be used, and light can be blocked by the absorption capacity of the dye.

[0032] The optical filter of the present invention preferably further satisfies the following spectral characteristics (i-9). (i-9) In the spectral transmittance curve at wavelengths of 800 nm to 1000 nm and an incident angle of 0 degrees, the maximum transmittance is T 800-1000(0deg)MAX The wavelength at which the maximum transmittance is obtained is λ 800-1000(0deg)MAX In that case, λ 800-1000(0deg)MAX In the spectral transmittance curve in the range of nm to 1050 nm and at an incident angle of 0 degrees, the transmittance is T 800-1000(0deg)MAX The wavelength λ is 50% of IRL(0deg)(50%) and, λ 800-1000(0deg)MAX In the spectral transmittance curve in the range of nm to 1050 nm and at an incident angle of 35 degrees, the transmittance is T 800-1000(0deg)MAX The wavelength λ is 50% of IRL(35deg)(50%) However, satisfying the following relationship |λ IRL(0deg)(50%) -λ IRL(35deg)(50%) | ≤ 60nm

[0033] By satisfying the spectral characteristics (i-9), λ is also available at high incidence angles. 800-1000(0deg)MAX This means that the spectral curve in the region from nm to 1050 nm is less likely to shift. |λ IRL(0deg)(50%) -λ IRL(35deg)(50%) The | is preferably 55 nm or less, more preferably 50 nm or less. To satisfy the spectral characteristics (i-8), for example, an absorption layer containing a near-infrared absorbing dye can be used, and light can be blocked by the absorption capacity of the dye.

[0034] The optical filter of the present invention preferably further satisfies the following spectral characteristics (i-10) to (i-11). (i-10) In the spectral reflectance curve at an incident angle of 5 degrees for at least one of the surfaces, the average reflectance R in the wavelength range of 450 nm to 600 nm. 450-600(5deg)AVE less than 15% (i-11) In the spectral reflectance curve at an incident angle of 5 degrees for at least one of the surfaces, the average reflectance R at wavelengths of 1050 to 1200 nm 1050-1200(5deg)AVE over 40% Spectroscopic characteristics (i-10) and (i-11) mean that at least one of the dielectric multilayer films is a multilayer film having reflective properties in the near-infrared region. R450-600(5deg)AVE is preferably 5% or less, more preferably 3% or less. R 1050-1200(5deg)AVE is preferably 80% or more, more preferably 90% or more.

[0035] <Near-infrared absorbing glass> This filter has a near-infrared absorbing glass. By blocking the near-infrared light region by the absorption ability of the glass, the light-shielding property of the dielectric multilayer film can be supplemented. The near-infrared absorbing glass preferably satisfies all of the following spectral characteristics (iii-1) to (iii-3). (iii-1) The average internal transmittance T in the spectral transmittance curve at wavelengths of 450 to 600 nm G_450-600AVE is 80% or more (iii-2) The average internal transmittance T in the spectral transmittance curve at wavelengths of 1050 to 1200 nm G_1050-1200AVE is less than the average internal transmittance T G_450-600AVE (iii-3) The internal transmittance T at wavelengths of 800 to 1000 nm G_800-1000 decreases monotonically

[0036] Characteristic (iii-1) means excellent transmittance in the visible light region with wavelengths of 450 to 600 nm. T G_450-600AVE is preferably 90% or more, more preferably 95% or more.

[0037] Characteristic (iii-2) means excellent light-shielding property in the near-infrared light region with wavelengths of 1050 to 1200 nm. T G_1050-1200AVE is preferably 30% or less, more preferably 20% or less.

[0038] By satisfying characteristic (iii-3), it means that the absorption band becomes a wavelength region of 1000 nm or more and the region can be sufficiently absorbed. Here, the monotonic decrease preferably means the internal transmittance T at a wavelength of 800 nm G_800 , the internal transmittance T at a wavelength of 900 nm G_900 , the internal transmittance T at a wavelength of 1000 nm G_1000However, this means that the following relationship is satisfied. T G_800 >T G_900 >T G_1000 Also, T G_800 Preferably 55% or more, T G_1000 Preferably, it is 40% or less.

[0039] In particular, as shown in characteristic (iii-2), by blocking light in the wavelength range of 1050 to 1200 nm due to the absorption capacity of the glass, it is possible to sufficiently block light in this wavelength range, which was an area where there was room for improvement in conventional optical filters.

[0040] The near-infrared absorbing glass is not limited as long as it is a glass that can obtain the above spectral characteristics. For example, phthalic acid glass or phosphate glass containing iron or copper is preferably used, and among these, phthalic acid glass or phosphate glass containing iron is more preferred from the viewpoint of easily obtaining the above spectral characteristics, and phosphate glass containing iron is particularly preferred.

[0041] Examples of iron-containing phosphated glass (iron phosphated glass) include glass having any of the following compositions. (1) Glass containing P2O5, Al2O3, R'O (where R'O represents one or more selected from MgO, CaO, SrO, BaO, and ZnO) and Fe2O3 as essential components, expressed in mole percent based on oxides, and substantially free of F (fluorine component), with Fe2O3 content of 0.1% to 35%. (2) Glass containing, in molar percentages based on oxides, P2O5: 40%~75%, Al2O3: 5%~22%, R2O: 0%~20% (where R2O represents the combined amount of Li2O, Na2O, and K2O), R''O: 0.1%~35% (where R''O represents the combined amount of MgO, CaO, SrO, BaO, and ZnO), and Fe2O3: 5%~35%. (3) Glass containing, in molar percentages based on oxides, P2O5: 25%~75%, Al2O3: 2.5%~22%, R2O: 0%~35% (where R2O represents the combined amount of Li2O, Na2O, and K2O), R''O: 0.1%~35% (where R''O represents the combined amount of MgO, CaO, SrO, BaO, and ZnO), and Fe2O3: 0.1%~5% (where 5% is not included). (4) Glass containing, in molar percentages based on oxides, P2O5: 40%~75%, Al2O3: 5%~22%, R2O: 0.1%~20% (where R2O represents the total amount of Li2O, Na2O, and K2O), R''O: 0.1%~25% (where R''O represents the total amount of MgO, CaO, SrO, BaO, and ZnO), and Fe2O3: 0.1%~5% (where 5% is not included).

[0042] Furthermore, in the glass having the compositions of (1) to (4) above, it is preferable that it contains 0.1% to 20% ZnO in mole percent based on oxide. In the glass with the above compositions (1) to (4), the divalent iron (Fe) in the total iron (total Fe amount) converted to Fe2O3 2+ ) Mass ratio ((Fe 2+ It is preferable that the ratio of (total Fe content) × 100[%]) is between 25% and 99%.

[0043] As the near-infrared absorbing glass, commercially available products may be used, or they can be manufactured by known methods. For example, iron phosphate glass described in International Publication No. 2020 / 262296 can be used.

[0044] Furthermore, as near-infrared absorbing glass, chemically strengthened glass obtained by exchanging alkali metal ions with small ionic radii (e.g., Li ions, Na ions) present on the main surface of the glass plate with alkali ions with larger ionic radii (e.g., Na ions or K ions for Li ions, and K ions for Na ions) by ion exchange at a temperature below the glass transition temperature may be used.

[0045] From the viewpoint of reducing the height of the camera module, the near-infrared absorbing glass preferably has a thickness of 0.5 mm or less, more preferably 0.3 mm or less, and from the viewpoint of element strength, preferably 0.15 mm or more.

[0046] <Dielectric multilayer film> In this filter, the dielectric multilayer film is laminated on both sides of the near-infrared absorbing glass. This suppresses the intrusion of water, which causes degradation of the near-infrared absorbing glass, resulting in an optical filter with excellent weather resistance.

[0047] In this filter, it is preferable that at least one of the dielectric multilayer films is designed as a near-infrared reflective layer (hereinafter also referred to as the NIR reflective layer). The other dielectric multilayer film is preferably designed as an NIR reflective layer, a reflective layer having a reflection region other than the near-infrared region, or an anti-reflective layer.

[0048] The NIR reflective layer in this filter has wavelength selectivity, for example, to transmit visible light and specific near-infrared light, and to primarily reflect light other than the transmission region of the absorption layer and the specific near-infrared light. The reflective region of the NIR reflective layer may also include the light-shielding region in the near-infrared region of the absorption layer. The NIR reflective layer may be designed to further block light in wavelengths other than the near-infrared region, such as the near-ultraviolet region, not limited to NIR reflection characteristics.

[0049] When designed as an NIR reflective layer, the dielectric multilayer film is preferably one that satisfies the following spectral characteristics. (iv-1) Average reflectance R in the spectral reflectance curve at wavelengths of 450-600 nm D_450-600AVE less than 2% (iv-2) Average reflectance R in the spectral reflectance curve at wavelengths of 1000-1200 nm D_1000-1200AVE over 40% A certain degree of transmittance is necessary in the near-infrared light region of 700-1000 nm. By considering the reflective properties of the dielectric multilayer film and the absorption properties of the near-infrared absorbing dye, the reflective properties of the dielectric multilayer film can be appropriately designed to achieve the desired transmittance for the optical filter as a whole.

[0050] The NIR reflective layer is composed of a dielectric multilayer film made by stacking two or more of the following: a low refractive index dielectric film, a medium refractive index dielectric film, and a high refractive index dielectric film. The high refractive index film preferably has a refractive index of 1.6 or higher, and more preferably 2.2 to 2.5. Examples of materials for the high refractive index film include Ta2O5, TiO2, TiO2, TiO, and Nb2O5. Other commercially available products include OS50 (Ti3O5), OS10 (Ti4O7), OA500 (a mixture of Ta2O5 and ZrO2), and OA600 (a mixture of Ta2O5 and TiO2), all manufactured by Canon Optron. Of these, TiO2 is preferred in terms of film formation properties, reproducibility in refractive index, and stability.

[0051] The medium refractive index film preferably has a refractive index of 1.6 or higher and less than 2.2. Examples of materials for the medium refractive index film include ZrO2, Nb2O5, Al2O3, HfO2, and OM-4, OM-6 (a mixture of Al2O3 and ZrO2) and OA-100 sold by Canon Optron, as well as H4 and M2 (alumina antania) sold by Merck. Of these, Al2O3-based compounds and mixtures of Al2O3 and ZrO2 are preferred in terms of film formation properties, reproducibility in refractive index, and stability.

[0052] The low refractive index film preferably has a refractive index of less than 1.6, and more preferably 1.45 or more and less than 1.55. Examples of materials for the low refractive index film include SiO2 and SiO2. x N y、 Examples include MgF2. Other commercially available products include S4F and S5F (a mixture of SiO2 and AlO2) manufactured by Canon Optron. Of these, SiO2 is preferred in terms of reproducibility, stability, and cost-effectiveness in film formation.

[0053] For an NIR reflective layer to transmit visible light and specific near-infrared light, it is necessary to combine several dielectric multilayer films with different spectral characteristics to transmit and select the desired wavelength band. For example, this can be adjusted by the materials that make up the film, the film thickness of each layer, and the number of layers.

[0054] From the viewpoint of controlling the wavelength bands of transmission and light blocking, the total number of layers of dielectric multilayer films constituting the NIR reflective layer is preferably 20 or more, more preferably 25 or more, and from the viewpoint of suppressing ripple, it is preferably 50 or less.

[0055] Furthermore, the thickness of the dielectric multilayer film is preferably 600 nm or more, more preferably 1 μm or more, from the viewpoint of suppressing degradation of the near-infrared absorbing glass, and preferably 5 μm or less from the viewpoint of productivity and suppression of reflection ripple in the visible light region.

[0056] Furthermore, for the formation of dielectric multilayer films, vacuum deposition processes such as CVD, sputtering, and vacuum evaporation, as well as wet deposition processes such as spraying and dipping, can be used.

[0057] The NIR reflective layer may provide predetermined optical properties with a single layer (a group of dielectric multilayer films) or with two layers. If there are two or more layers, each reflective layer may have the same or different configuration. When there are two or more reflective layers, they are usually composed of multiple reflective layers with different reflection bands. When two reflective layers are provided, one may be a near-infrared reflective layer that shields light in the short-wavelength band of the near-infrared region, and the other may be a near-infrared / near-ultraviolet reflective layer that shields light in both the long-wavelength band of the near-infrared region and the near-ultraviolet region.

[0058] Examples of anti-reflective layers include dielectric multilayer films, intermediate refractive index media, and moth-eye structures with gradually changing refractive indices. Among these, dielectric multilayer films are preferred from the viewpoint of optical efficiency and productivity. The anti-reflective layer is obtained by alternately stacking dielectric films with high refractive indices and dielectric films with low refractive indices, similar to the reflective layer.

[0059] <Absorbing layer> This filter includes an absorption layer having a maximum absorption wavelength in the near-infrared region on at least one surface of the dielectric multilayer film. This allows for efficient shielding of the near-infrared region. Furthermore, since the absorption layer is laminated via the dielectric multilayer film without contacting the near-infrared absorbing glass, water penetration into the glass can be prevented.

[0060] The absorption layer preferably satisfies all of the following spectral characteristics (ii-1) to (ii-2). (ii-1) In the spectral transmittance curve for wavelengths of 650-720 nm, the shortest wavelength at which the internal transmittance is 30% is λ A_VIS(30%) The shortest wavelength at which the internal transmittance is 30% in the spectral transmittance curve for wavelengths of 720-1000 nm is defined as λ. A_IR(30%) When this is the case, the following relation is satisfied |λ A_IR(30%) -λ A_VIS(30%) |≧100nm (ii-2) The absorbance at a wavelength of 450 nm is A A_450 And the absorbance at a wavelength of 720 nm is A A_720 When this is the case, the following relation is satisfied A A_720 ―A A_450 ≥1

[0061] |λ in characteristic (ii-1) A_IR(30%) -λ A_VIS(30%) The | symbol is an indicator of the near-infrared light absorption band centered at 720 nm, and a value of 100 nm or more indicates that the absorption layer broadly absorbs light in that region. |λ A_IR(30%) -λ A_VIS(30%) The wavelength is more preferably 120 nm or greater. Furthermore, since it becomes more difficult to maintain high transmittance in the visible light region as the maximum absorption wavelength of the dye is in the longer wavelength region, it is preferably 150 nm or less. To satisfy characteristic (ii-1), for example, two near-infrared absorbing dyes with different maximum absorption wavelengths in the 680-800 nm range can be combined, preferably a dye with a maximum absorption wavelength of 680-740 nm and a dye with a maximum absorption wavelength of 740-800 nm. In addition, from the viewpoint of achieving a wide absorption range with a small amount of additive, squarylium dyes can be used.

[0062] Characteristic (ii-2) means that the absorption layer achieves both high visible light transmittance at 450 nm and high near-infrared light shielding at 720 nm. A A_720 -A A_450 Preferably, it is 1.5 or higher, more preferably 2 or higher. To satisfy characteristic (ii-2), for example, a symmetrical squarylium dye can be used as a near-infrared absorbing dye that strongly absorbs around 720 nm while maintaining high transmittance in the visible light region.

[0063] The absorption layer preferably contains a dye (NIR dye) having a maximum absorption wavelength of 680-800 nm in dichloromethane. By including such a dye, the absorption layer can broadly absorb near-infrared light absorption band centered on 720 nm, as shown in the above characteristics (ii-1) and (ii-2), and it is easy to achieve both visible light transmittance at 450 nm and near-infrared light shielding at 720 nm. As a result, the near-infrared light region around 720 nm, where the shielding effect is somewhat weak in infrared absorbing glass, can be shielded by the absorption characteristics of the dye. From the viewpoint of being able to absorb a wide range of near-infrared regions, it is preferable to combine two dyes that have different maximum absorption wavelengths and are in the 680-800 nm range, preferably a dye with a maximum absorption wavelength of 680-740 nm and a dye with a maximum absorption wavelength of 740-800 nm. The absorbent layer is preferably a resin film containing the dye and resin.

[0064] Examples of NIR dyes include squarylium compounds and cyanine compounds. Among these, squarylium compounds are preferred from the viewpoint of the absorption layer easily satisfying the above characteristics (ii-1) and (ii-2), the region of maximum absorption wavelength, transmittance in the visible light range, solubility in resin, and durability.

[0065] The NIR dye, a squarylium compound, is preferably the compound represented by formula (I) below or the compound represented by formula (II) below. Furthermore, if two or more identical symbols exist in a squarylium compound, these symbols may be identical or different. The same applies to cyanine compounds.

[0066] <Squallium compound (I)>

[0067] [ka]

[0068] However, the symbols in the above formula are as follows: R 24 and R 26 Each of these independently consists of a hydrogen atom, a halogen atom, a hydroxyl group, a C1-C20 alkyl or alkoxy group, a C1-C10 acyloxy group, a C6-C11 aryl group, a C7-C18 alaryl group which may have substituents and may have oxygen atoms between carbon atoms, and -NR 27 R 28 (R 27 and R 28 These are, independently, a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, and -C(=O)-R 29 (R 29 (This may include hydrogen atoms, halogen atoms, hydroxyl groups, hydrocarbon groups having 1 to 25 carbon atoms that may have substituents, unsaturated bonds between carbon atoms, oxygen atoms, or saturated or unsaturated ring structures), -NHR 30 , or -SO2-R 30 (R 30(R) represents a hydrocarbon group having 1 to 25 carbon atoms, in which each hydrogen atom may be substituted with a halogen atom, hydroxyl group, carboxyl group, sulfo group, or cyano group, and which may contain unsaturated bonds, oxygen atoms, or saturated or unsaturated ring structures between carbon atoms. ) or a group represented by the following formula (S) (R) 41 , R 42 k independently represents a hydrogen atom, a halogen atom, or an alkyl or alkoxy group having 1 to 10 carbon atoms. k is 2 or 3.

[0069] [ka]

[0070] R 21 and R 22 , R 22 and R 25 , and R 21 and R 23 These may be linked together to form heterocycles A, B, and C, respectively, with nitrogen atoms, each having a membership of 5 or 6. R when a heteroalgebra A is formed 21 and R 22 This represents an alkylene group or alkylene oxy group in which the hydrogen atom may be substituted with an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an acyloxy group having 1 to 10 carbon atoms that may have substituents, as the divalent group -Q- to which these are bonded. R when a heteroalgebra B is formed 22 and R 25 , and R when a heterocyclic ring C is formed 21 and R 23 These are the divalent groups -X to which they are bonded. 1 -Y 1 -and -X 2 -Y 2 -(The side that bonds to nitrogen is X) 1 and X 2 ) as X 1 and X 2 These are the groups represented by the following formulas (1x) or (2x), and Y 1 and Y 2Each of these is a group represented by one of the following formulas (1y) to (5y). 1 and X 2 However, in the case of the base represented by the following formula (2x), Y 1 and Y 2 Each of these may be a single bond, in which case there may be an oxygen atom between the carbon atoms.

[0071] [ka]

[0072] In formula (1x), the four Zs are each independently a hydrogen atom, a hydroxyl group, an alkyl or alkoxy group having 1 to 6 carbon atoms, or -NR 38 R 39 (R 38 and R 39 Each of these independently represents either a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. 31 ~R 36 Each independently comprises a hydrogen atom, a C1-C6 alkyl group, or a C6-C10 aryl group, R 37 This represents an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms. R 27 , R 28 , R 29 , R 31 ~R 37 , R when it does not form a heteroalgebra 21 ~R 23 , and R 25 These may bond with any of the others to form a five-membered ring or a six-membered ring. 31 and R 36 , R 31 and R 37 They may be directly joined. When R does not form a heteroalgebra, 21 , R 22 , R 23 and R 25Each of these independently represents a hydrogen atom, a halogen atom, a hydroxyl group, a C1-C20 alkyl or alkoxy group, a C1-C10 acyloxy group, a C6-C11 aryl group, or a C7-C18 alaryl group which may have substituents or oxygen atoms between carbon atoms.

[0073] Examples of compound (I) include compounds represented by any of formulas (I-1) to (I-3), and from the viewpoint of solubility in the resin, heat resistance and light resistance in the resin, and visible light transmittance of the resin layer containing it, the compound represented by formula (I-1) is particularly preferred.

[0074] [ka]

[0075] The symbols in formulas (I-1) to (I-3) are the same as those specified for the same symbols in formula (I), and the preferred embodiments are also the same.

[0076] In compound (I-1), X 1 As for the base, (2x) is preferred, Y 1 A single bond or group (1y) is preferred. In this case, R 31 ~R 36 Preferably, it is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and more preferably a hydrogen atom or a methyl group. 1 -X 1 Specifically, examples include the divalent organic groups shown in formulas (11-1) to (12-3).

[0077] -C(CH3)2-CH(CH3)- …(11-1) -C(CH3)2-CH2- …(11-2) -C(CH3)2-CH(C2H5)- …(11-3) -C(CH3)2-C(CH3)(nC3H7)- …(11-4) -C(CH3)2-CH2-CH2- …(12-1) -C(CH3)2-CH2-CH(CH3)- …(12-2) -C(CH3)2-CH(CH3)-CH2- …(12-3)

[0078] Furthermore, in compound (I-1), R 21 From the viewpoint of solubility, heat resistance, and the steepness of the change near the boundary between the visible and near-infrared regions in the spectral transmittance curve, the group represented by formula (4-1) or (4-2) is independently preferred.

[0079] [ka]

[0080] In equations (4-1) and (4-2), R 71 ~R 75 This independently represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 4 carbon atoms.

[0081] In compound (I-1), R 24 -NR 27 R 28 Preferably. -NR 27 R 28 From the perspective of solubility in resins and coating solvents, -NH-C(=O)-R 29 or -NH-SO2-R 30 It is preferable.

[0082] In compound (I-1), R 24 ga-NH-SO2-R 30 The compound is shown in formula (I-12).

[0083] [ka]

[0084] R 23 and R 26 These are preferably, independently, a hydrogen atom, a halogen atom, or an alkyl or alkoxy group having 1 to 6 carbon atoms, with a hydrogen atom being more preferred in any case.

[0085] R 30 From the viewpoint of light resistance, it is preferable to have a branched alkyl or alkoxy group having 1 to 12 carbon atoms, or a hydrocarbon group having 6 to 16 carbon atoms with an unsaturated ring structure. Examples of unsaturated ring structures include benzene, toluene, xylene, furan, and benzofuran. 30 Independently, a branched alkyl or alkoxy group having 1 to 12 carbon atoms is more preferable. 30 In each of the groups exhibiting this characteristic, some or all of the hydrogen atoms may be substituted with halogen atoms, particularly fluorine atoms.

[0086] More specifically, compounds (I-12) include those listed in the table below. Furthermore, in the compounds listed in the table below, the meaning of each symbol is the same on both the left and right sides of the squarylium skeleton.

[0087] [Table 1]

[0088] Among these compounds (I-12), (I-12-1), (I-12-6), (I-12-11), (I-12-16), (I-12-21), and (I-12-26) are preferred from the viewpoint of visible light transmittance, solubility in resin, heat resistance, and light resistance, and (I-12-11) and (I-12-26) are more preferred from the viewpoint of heat resistance and light resistance.

[0089] <Squallium compound (II)>

[0090] [ka]

[0091] However, the symbols in the above formula are as follows: Each ring Z is independently a 5-membered or 6-membered ring having 0 to 3 heteroatoms in the ring, and the hydrogen atoms in ring Z may be substituted. R1 and R 2 , R 2 and R 3 , and R 1 The carbon atoms or heteroatoms constituting ring Z may be linked to each other and form heterorings A1, B1, and C1, respectively, together with the nitrogen atom, in which case the hydrogen atoms in heterorings A1, B1, and C1 may be substituted. 1 and R 2 Each of these independently represents a hydrocarbon group which may contain an unsaturated bond, heteroatom, saturated or unsaturated ring structure between a hydrogen atom, a halogen atom, or carbon atoms, and which may have substituents. 4 and R when it does not form a heterocycle 3 Each of these independently represents an alkyl or alkoxy group which may contain a hydrogen atom, a halogen atom, or a heteroatom between carbon atoms, and which may have substituents.

[0092] Examples of compound (II) include compounds represented by any of formulas (II-1) to (II-3), and from the viewpoint of solubility in the resin and visible light transmittance in the resin, the compound represented by formula (II-3) is particularly preferred.

[0093] [ka]

[0094] In formula (II-1) and formula (II-2), R 1 and R 2 Each independently represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 15 carbon atoms which may have substituents, and R 3 ~R 6 Each of these independently represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 10 carbon atoms, which may have substituents.

[0095] In formula (II-3), R 1 , R 4 , and R 9 ~R12 Each independently represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 15 carbon atoms which may have substituents, and R 7 and R 8 Each of these independently represents a hydrogen atom, a halogen atom, or a C1-C5 alkyl group which may have substituents.

[0096] R in compound (II-1) and compound (II-2) 1 and R 2 From the viewpoint of solubility in resin, visible light transmittance, etc., an alkyl group having 1 to 15 carbon atoms is preferred, and an alkyl group having 7 to 15 carbon atoms is more preferred, R 1 and R 2 At least one of them is more preferably an alkyl group having a branched chain with 7 to 15 carbon atoms, R 1 and R 2 Alkyl groups having branched chains with 8 to 15 carbon atoms are particularly preferred for both.

[0097] R in compound (II-3) 1 From the viewpoint of solubility in transparent resins and visible light transmittance, alkyl groups having 1 to 15 carbon atoms are preferred, alkyl groups having 1 to 10 carbon atoms are more preferred, and ethyl groups and isopropyl groups are particularly preferred.

[0098] R 4 From the viewpoint of visible light transmittance and ease of synthesis, hydrogen atoms and halogen atoms are preferred, with hydrogen atoms being particularly preferred. R 7 and R 8 The following are preferred independently: a hydrogen atom, a halogen atom, and a C1-C5 alkyl group which may be substituted with a halogen atom; a hydrogen atom, a halogen atom, and a methyl group are more preferred.

[0099] R 9 ~R 12 The following are preferred independently: a hydrogen atom, a halogen atom, and a C1-C5 alkyl group which may be substituted with a halogen atom. -CR 9 R 10 -CR 11 R12 -Examples include the divalent organic groups represented by the following groups (13-1) to (13-5). -CH(CH3)-C(CH3)2- …(13-1) -C(CH3)2-CH(CH3)- …(13-2) -C(CH3)2-CH2- …(13-3) -C(CH3)2-CH(C2H5)- …(13-4) -CH(CH3)-C(CH3)(CH2-CH(CH3)2)-…(13-5)

[0100] More specifically, compounds (II-3) include those shown in the table below. Furthermore, in the compounds shown in the table below, the meaning of each symbol is the same on both the left and right sides of the squarylium skeleton.

[0101] [Table 2]

[0102] Compounds (I) and (II) can each be prepared by known methods. Compound (I) can be prepared by the methods described in U.S. Patent No. 5,543,086, U.S. Patent Publication No. 2014 / 0061505, and International Publication No. 2014 / 088063. Compound (II) can be prepared by the methods described in International Publication No. 2017 / 135359.

[0103] The content of the NIR dye in the absorption 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 resin. When two or more compounds are combined, the above content is the sum of the individual compounds.

[0104] The absorption layer may contain other dyes besides the NIR dyes mentioned above. Preferred other dyes are those having a maximum absorption wavelength of 370-440 nm in the resin (UV dyes). This allows for efficient shielding of the near-ultraviolet light region.

[0105] 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. One type may be used alone, or two or more types may be used in combination.

[0106] <Resin> The resin used in the absorbent layer is not limited to transparent resins, and one or more transparent resins selected from polyester resin, acrylic resin, epoxy resin, ene-thiol resin, polycarbonate resin, polyether resin, polyarylate resin, polysulfone resin, polyethersulfone resin, polyparaphenylene resin, polyarylene ether phosphine oxide resin, polyamide resin, polyimide resin, polyamide-imide resin, polyolefin resin, cyclic olefin resin, polyurethane resin, and polystyrene resin can be used. These resins may be used individually or in combination of two or more. From the viewpoint of the spectral characteristics of the absorption layer, glass transition temperature (Tg), and adhesion, one or more resins selected from polyimide resin, polycarbonate resin, polyester resin, and acrylic resin are preferred.

[0107] When multiple compounds are used as NIR dyes or other dyes, they may be contained in the same absorption layer, or they may each be contained in a separate absorption layer.

[0108] The absorbent layer can be formed by preparing a coating solution by dissolving or dispersing a dye, a resin or resin raw material component, and each component as needed in a solvent, coating this solution onto a dielectric multilayer film, drying it, and further curing it as needed. Alternatively, the absorbent layer may be formed separately by coating a releaseable support with the coating solution. The solvent can be any dispersion medium or solvent that can stably disperse or dissolve the components.

[0109] Furthermore, the coating solution may contain surfactants to improve voids caused by minute bubbles, indentations caused by the adhesion of foreign matter, and repelling during the drying process. Additionally, methods such as immersion coating, cast coating, or spin coating can be used for applying the coating solution. If the coating solution contains raw material components of a transparent resin, further curing treatments such as thermosetting or photocuring are performed.

[0110] Furthermore, the absorption layer can also be manufactured in film form by extrusion molding. The filter can be manufactured by laminating the obtained film-like absorption layer onto a dielectric multilayer film and integrating them by thermocompression bonding or the like.

[0111] The absorption layer may be one layer or two or more layers within the optical filter. If there are two or more layers, each layer may have the same configuration or different configurations, and they may be formed on the surface of each dielectric multilayer film or two or more layers may be stacked on the surface of one of the dielectric multilayer films.

[0112] The thickness of the absorption layer is preferably 10 μm or less, more preferably 5 μm or less, from the viewpoint of in-plane film thickness distribution within the substrate after coating and appearance quality, and preferably 0.5 μm or more from the viewpoint of exhibiting desired spectral characteristics with an appropriate dye concentration. If the optical filter has two or more absorption layers, it is preferable that the total thickness of each absorption layer is within the above range.

[0113] This filter may also include other components, such as a component (layer) that provides absorption by inorganic nanoparticles that control the transmission and absorption of light in a specific wavelength range. Specific examples of inorganic nanoparticles include ITO (Indium Tin Oxides), ATO (Antimony-doped Tin Oxides), cesium tungstate, and lanthanum boride. ITO nanoparticles and cesium tungstate nanoparticles have high transmittance of visible light and light absorption over a wide range in the infrared wavelength region exceeding 1200 nm, and can therefore be used when shielding against such infrared light is required.

[0114] Based on the above, this specification discloses the following optical filters, etc. [1] Near-infrared absorbing glass, A dielectric multilayer film laminated on both main surfaces of the near-infrared absorbing glass, An optical filter comprising: an absorption layer laminated on the surface of at least one of the dielectric multilayer films and having a maximum absorption wavelength in the near-infrared region, The optical filter is an optical filter that satisfies all of the following spectral characteristics (i-1) to (i-5). (i-1) In the spectral transmittance curve at wavelengths of 450 nm to 600 nm and an incident angle of 0 degrees, the average transmittance T 450-600(0deg)AVE over 60% (i-2) In the spectral transmittance curve at wavelengths of 700 nm to 750 nm and an incident angle of 0 degrees, the average transmittance T 700-750(0deg)AVE less than 5% (i-3) In the spectral transmittance curve at wavelengths of 1050 nm to 1200 nm and an incident angle of 0 degrees, the maximum transmittance T 1050-1200(0deg)MAX less than 7% (i-4) In the spectral transmittance curve at wavelengths of 800 nm to 1000 nm and an incident angle of 0 degrees, the maximum transmittance T 800-1000(0deg)MAX over 20% (i-5) The maximum transmittance in the spectral transmittance curve at wavelengths of 450 nm to 600 nm and an incident angle of 0 degrees is T 450-600(0deg)MAX In that case, In the spectral transmittance curve at an incident angle of 0 degrees, the transmittance is the T 450-600(0deg)MAX The wavelength λ is 70% of (70%) and the T 450-600(0deg)MAX The wavelength λ is 30% of that. (30%) However, it falls within the range of 600nm to 700nm. The wavelength λ (70%) Transmittance in T (70%) And the wavelength λ (30%) Transmittance in T (30%) When this is the case, the following relation is satisfied -2≦[T (30%) -T (70%) ] / [λ (30%) -λ (70%) ]≦-0.75 [2] The optical filter according to [1], wherein the optical filter further satisfies the following spectral characteristics (i-6). (i-6) The spectral transmittance curve at an incident angle of 0 degrees is T(0deg) Let (λ) be the spectral transmittance curve at an incident angle of 35°, and T be the spectral transmittance curve at an incident angle of 35°. (35deg) When (λ) is denoted as such, the following relationship is satisfied in the wavelength range of 450 nm ≤ λ ≤ 600 nm. |T (0deg) (λ)-T (35deg) (λ)|≦10% [3] The optical filter according to [1] or [2], wherein the optical filter further satisfies the following spectral characteristics (i-7). (i-7) The maximum transmittance in the spectral transmittance curve at wavelengths of 450 nm to 600 nm and an incident angle of 0 degrees is T 450-600(0deg)MAX In that case, At an incidence angle of 0 degrees, the T 450-600(0deg)MAX The wavelength λ at which it becomes 50% VIS(0deg)(50%) , and the T at an incident angle of 35 degrees 450-600(0deg)MAX The wavelength λ at which it becomes 50% VIS(35deg)(50%) It is included in the range of 600nm to 700nm, and The following relationship is satisfied |λ VIS(0deg)(50%) -λ VIS(35deg)(50%) |≦10nm [4] The optical filter according to any one of [1] to [3], wherein the optical filter further satisfies the following spectral characteristics (i-8). (i-8) In the spectral transmittance curve at wavelengths of 800 nm to 1000 nm and an incident angle of 0 degrees, the maximum transmittance is T 800-1000(0deg)MAX The wavelength at which the maximum transmittance is obtained is λ 800-1000(0deg)MAX In that case, 750nm~λ 800-1000(0deg)MAX In the spectral transmittance curve in the nm range and at an incident angle of 0 degrees, the transmittance is T 800-1000(0deg)MAX The wavelength λ is 50% of IRS(0deg)(50%) and, 750nm~λ 800-1000(0deg)MAX In the spectral transmittance curve in the nm range and at an incident angle of 35 degrees, the transmittance is T 800-1000(0deg)MAX The wavelength λ is 50% of IRS(35deg)(50%) However, satisfying the following relationship |λ IRS(0deg)(50%) -λ IRS(35deg)(50%) | ≤ 30nm [5] The optical filter according to any one of [1] to [4], wherein the optical filter further satisfies the following spectral characteristics (i-9). (i-9) In the spectral transmittance curve at wavelengths of 800 nm to 1000 nm and an incident angle of 0 degrees, the maximum transmittance is T 800-1000(0deg)MAX The wavelength at which the maximum transmittance is obtained is λ 800-1000(0deg)MAX In that case, λ 800-1000(0deg)MAX In the spectral transmittance curve in the range of nm to 1050 nm and at an incident angle of 0 degrees, the transmittance is T 800-1000(0deg)MAX The wavelength λ is 50% of IRL(0deg)(50%) and, λ 800-1000(0deg)MAX In the spectral transmittance curve in the range of nm to 1050 nm and at an incident angle of 35 degrees, the transmittance is T 800-1000(0deg)MAX The wavelength λ is 50% of IRL(35deg)(50%) However, satisfying the following relationship |λ IRL(0deg)(50%) -λ IRL(35deg)(50%) | ≤ 60nm [6] The optical filter according to any one of [1] to [5], wherein the thickness of the dielectric multilayer film laminated on both main surfaces of the near-infrared absorbing glass is 600 nm or more. [7] The optical filter according to any one of [1] to [6], wherein the near-infrared absorbing glass is phthalic acid glass or phosphate glass containing iron or copper. [8] An optical filter according to any of [1] to [7], wherein the near-infrared absorbing glass satisfies all of the following spectral characteristics (iii-1) to (iii-3). (iii-1) Average internal transmittance T in the spectral transmittance curve at wavelengths of 450-600 nm G_450-600AVE over 80% (iii-2) Average internal transmittance T in the spectral transmittance curve at wavelengths of 1050-1200 nm G_1050-1200AVE is the average internal transmittance T G_450-600AVE Less than (iii-3) Internal transmittance T at wavelengths of 800-1000 nm G_800-1000 It decreases monotonically. [9] The optical filter according to any one of [1] to [8], wherein the absorption layer contains a dye having a maximum absorption wavelength of 680 to 800 nm in dichloromethane. 〔10〕The optical filter according to any one of 〔1〕~〔9〕, wherein the optical filter further satisfies the following spectral characteristics (i-10)~(i-11). (i-10) In the spectral reflectance curve at an incident angle of 5 degrees on at least one surface, the average reflectance R at wavelengths of 450 nm to 600 nm 450-600(5deg)AVE is 15% or less (i-11) In the spectral reflectance curve at an incident angle of 5 degrees on at least one surface, the average reflectance R at wavelengths of 1050 to 1200 nm 1050-1200(5deg)AVE is 40% or more 〔11〕The optical filter according to any one of 〔1〕~〔10〕, wherein the absorption layer satisfies all of the following spectral characteristics (ii-1)~(ii-2). (ii-1) Let the shortest wavelength at which the internal transmittance becomes 30% in the spectral transmittance curve of wavelengths 650 to 720 nm be λ A_VIS(30%) and the shortest wavelength at which the internal transmittance becomes 30% in the spectral transmittance curve of wavelengths 720 to 1000 nm be λ A_IR(30%) When this is the case, the following relational expression is satisfied |λ A_IR(30%) - λ A_VIS(30%) |≧100 nm (ii-2) Let the absorbance at a wavelength of 450 nm be A A_450 and the absorbance at a wavelength of 720 nm be A A_720 When this is the case, the following relational expression is satisfied A A_720 - A A_450 ≧1 〔12〕An imaging device including the optical filter according to any one of 〔1〕~〔11〕. <000090​​​​​​​​​​​​​ Compound 1 (squallium compound): Synthesized according to U.S. Patent No. 5,543,086, U.S. Patent Application Publication No. 2014 / 0061505, and International Publication No. 2014 / 088063. Compound 2 (squallium compound): Synthesized according to International Publication No. 2017 / 135359. Compound 3 (merocyanine compound): Synthesized according to German Patent Publication No. 10109243. Compound 4 (merocyanine compound): Synthesized according to German Patent Publication No. 10109243. Compounds 1 and 2 are near-infrared absorbing dyes (NIR dyes), while compounds 3 and 4 are near-ultraviolet absorbing dyes (UV dyes).

[0117] [ka]

[0118] <Spectral properties of pigments> The above dyes (compounds 1-4) are shown, and the maximum absorption wavelength in the absorption spectrum measured after dissolving each in dichloromethane is indicated.

[0119] [Table 3]

[0120] <Spectral characteristics of near-infrared absorbing glass> As a near-infrared absorbing glass, iron phosphate glass with the composition shown in the table below was manufactured, referring to International Publication No. 2020 / 262296. For near-infrared absorbing glass, spectral transmittance curves were measured in the wavelength range of 350 to 1200 nm using a UV-Vis spectrophotometer. The results are shown in the table below. Note that the spectral characteristics shown in the table below were evaluated using internal transmittance to avoid the influence of reflection at the air interface and glass interface. Internal transmittance (%) = {Measured transmittance} (0deg) / (100-reflectance (5deg))}×100 The spectral transmittance curve of the near-infrared absorbing glass (iron phosphate glass with a thickness of 0.21 mm) is shown in Fig. 3.

[0121]

Table 4

[0122] <Examples 1-1 to 1-2: Spectral characteristics of the absorption layer> Any of the dyes of Compounds 1 to 4 was mixed into the polyimide resin solution prepared in the same manner as when calculating the spectral characteristics of the above compounds at the concentrations described in the following table, and stirred and dissolved at 50 °C for 2 hours to obtain a coating solution. The obtained coating solution was applied to an alkali glass (D263 glass manufactured by SCHOTT, thickness 0.2 mm) by the spin coating method to form an absorption layer with the film thickness shown in the following table. For the obtained absorption layer, the spectral transmittance curve in the wavelength range of 350 to 1200 nm was measured using an ultraviolet-visible spectrophotometer. The results of adjusting the transmittance at the maximum absorption wavelength to 10% are shown in the following table. <省 Regarding the spectral characteristics shown in the following table, in order to avoid the influence of reflection at the air interface and the glass interface, it was evaluated by the internal transmittance. Internal transmittance (%) = {Measured transmittance (0deg) / (100 - Reflectance (5deg) )}×100 The absorbance indicates the value converted from the internal transmittance according to the following formula. Absorbance = -log 10 (Internal transmittance / 100) The spectral transmittance curves of the absorption layers of Examples 1-1 and 1-2 are shown in Fig. 4. Examples 1-1 to 1-2 are reference examples.

[0123]

Table 5

[0124] <Example 2-1: Spectral characteristics of the optical filter> A first dielectric multilayer film (reflective film) was formed on one side of an infrared-absorbing glass (iron phosphate glass) by alternately depositing 28 layers of SiO2 and TiO2 by vapor deposition. A second dielectric multilayer film (reflective film) was formed on the other side of the infrared-absorbing glass (iron phosphate glass) by alternately depositing 41 layers of SiO2 and TiO2 by vapor deposition. Using the same composition as the absorption layer in Example 1-1, a resin solution was coated onto the surface of a second dielectric multilayer film, and the organic solvent was removed by heating to a thickness of 1 μm to form an absorption layer. A third dielectric multilayer film (anti-reflective film) was formed by alternately stacking nine layers of SiO2 and TiO2 on the surface of the absorption layer by vapor deposition. Based on the above, optical filter 2-1 was manufactured.

[0125] <Example 2-2> An optical filter was manufactured in the same manner as in Example 2-1, except that the infrared-absorbing glass (iron phosphate glass) was replaced with non-absorbing glass (alkali glass, manufactured by SCHOTT, D263).

[0126] <Example 2-3> An optical filter was manufactured in the same manner as in Example 2-1, except that a first dielectric multilayer film (reflective film) was formed on one side of an infrared absorbing glass (iron phosphate glass) by alternately depositing 40 layers of SiO2 and TiO2 by vapor deposition, and a second dielectric multilayer film (anti-reflective film) was formed on the other side by alternately depositing 19 layers of SiO2 and TiO2 by vapor deposition.

[0127] <Example 2-4> An optical filter was manufactured in the same manner as in Example 2-1, except that a first dielectric multilayer film (reflective film) was formed by alternately depositing 66 layers of SiO2 and TiO2 onto one surface of infrared absorbing glass (iron phosphate glass) by vapor deposition, and a second dielectric multilayer film was not formed.

[0128] <Example 2-5> An optical filter was manufactured in the same manner as in Example 2-1, except that the number of layers of the first dielectric multilayer film (reflective film) was set to 50, the number of layers of the second dielectric multilayer film (reflective film) was set to 39, and the composition of the absorption layer was the same as in Example 1-2.

[0129] <Example 2-6> An optical filter was manufactured in the same manner as in Example 2-1, except that the number of layers of the first dielectric multilayer film (reflective film) was set to 82, the number of layers of the second dielectric multilayer film (reflective film) was set to 76, and no absorption layer or third dielectric multilayer film was formed.

[0130] <Example 2-7> An optical filter was manufactured in the same manner as in Example 2-1, except that the infrared-absorbing glass (iron phosphate glass) was replaced with non-absorbing glass (alkali glass, manufactured by SCHOTT, D263), the number of layers of the first dielectric multilayer film (reflective film) was set to 50, and the second dielectric multilayer film was not formed.

[0131] The reflectances of the first and second dielectric multilayer films in each of the above optical filters are shown in the table below. When the dielectric multilayer film is the outermost layer, the reflectance is estimated as that of alkali glass. When the dielectric multilayer film is not the outermost layer, the reflectance is estimated as that of alkali glass and polyimide resin (the resin used in the absorption layer) on both sides.

[0132] For each optical filter obtained as described above, spectral transmittance curves at incident angles of 0 and 35 degrees in the wavelength range of 350 to 1200 nm, and spectral reflectance curves at an incident angle of 5 degrees were measured using an ultraviolet-visible spectrophotometer. The reflectance characteristics were measured from either the first dielectric multilayer film side or the third (or second) dielectric multilayer film side. From the obtained spectral characteristics data, the following characteristics were calculated as shown in the table below. Furthermore, the spectral transmittance curves for the optical filters in Examples 2-1, 2-2, 2-3, 2-5, and 2-6 are shown in Figures 5-9, respectively. The solid line represents the result at an incident angle of 0°, and the dashed line represents the result at an incident angle of 35°.

[0133] Examples 2-1, 2-3, and 2-5 are examples, while examples 2-2, 2-4, 2-6, and 2-7 are comparative examples.

[0134] [Table 6]

[0135] From the above results, it can be seen that the optical filters of Examples 2-1, 2-3, and 2-5 exhibit excellent transmittance of visible light and near-infrared light in the 800-900 nm range, excellent shielding of other near-infrared light, especially in the 1000-1200 nm wavelength range, and furthermore, excellent luminous sensitivity correction in the visible range, making them highly reliable optical filters in terms of weather resistance. Furthermore, the optical filters of Examples 2-1 and 2-3, which use two types of NIR dyes, |λ IRS(0deg)(50%) -λ IRS(35deg)(50%) Since | is less than 30 nm, even at high incidence angles, 750 nm ~ λ 800-1000(0deg)MAX This optical filter is less prone to shifting the spectral curve in the nm range.

[0136] The optical filters in Examples 2-2 and 2-7, which do not use near-infrared absorbing glass, have a maximum transmittance T 1050-1200(0deg)MAX The percentage exceeded 7%, resulting in poor light shielding performance in the 1050nm to 1200nm range. The optical filter in Example 2-4, in which an absorption layer is laminated on one main surface of the near-infrared absorbing glass and no multilayer film is laminated on both sides of the glass, is presumed to be an optical filter with low reliability due to the glass's susceptibility to degradation, as can be seen from the reliability test results in Examples 3-1 to 3-3 described later. The optical filters in Example 2-6, which do not have an absorption layer, are [T (30%) -T (70%) ] / [λ (30%) -λ (70%) The value was less than -2, indicating poor luminous efficiency correction in the visible region.

[0137] <Examples 3-1 to 3-3: Reliability Testing> The relationship between the film thickness and reliability of a dielectric multilayer film formed on near-infrared absorbing glass was evaluated. A dielectric multilayer film was formed on one side of an infrared-absorbing glass (iron phosphate glass) by alternately depositing SiO2 and TiO2 by vapor deposition. The number of layers of each dielectric multilayer film is shown in the table below. Glass substrates with dielectric multilayer films were left standing for 250 hours in an atmosphere of 85°C and 85% relative humidity, and their appearance was observed. In addition, a tape (adhesive strength 3.9 N / 10 mm, equivalent to Nichiban Cellotape® No. 405) was adhered to the surface of the dielectric multilayer film, and the tape was peeled off in a vertical direction to perform a peel test. The results are shown in the table below. Examples 3-1 to 3-3 are for reference only.

[0138] [Table 7]

[0139] From the results above, it can be seen that a larger film thickness of the dielectric multilayer film is preferable from the viewpoint of preventing degradation of near-infrared absorbing glass.

[0140] 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 invention. This application is based on Japanese Patent Application No. 2021-126030, filed on 30 July 2021, the contents of which are incorporated herein by reference. [Industrial applicability]

[0141] The optical filter of the present invention exhibits excellent transmittance of visible light and specific near-infrared light, while also having shielding properties for other near-infrared light. It is useful in applications such as information acquisition devices like cameras and sensors for transport aircraft, where performance has been steadily improving in recent years. [Explanation of symbols]

[0142] 1A, 1B... Optical filters 10…Near-infrared absorbing glass 21, 22, 23… Dielectric multilayer film 30… Absorption layer

Claims

1. Near-infrared absorbing glass, A dielectric multilayer film laminated on both main surfaces of the near-infrared absorbing glass, An optical filter comprising: an absorption layer laminated on the surface of at least one of the dielectric multilayer films and having a maximum absorption wavelength in the near-infrared region, The optical filter is an optical filter that satisfies all of the following spectral characteristics (i-1) to (i-5) and (i-8). (i-1) In the spectral transmittance curve at wavelengths of 450 nm to 600 nm and an incident angle of 0 degrees, the average transmittance T ４５０－６００（０ｄｅｇ）ＡＶＥ over 60% (i-2) In the spectral transmittance curve at wavelengths of 700 nm to 750 nm and an incident angle of 0 degrees, the average transmittance T ７００－７５０（０ｄｅｇ）ＡＶＥ less than 5% (i-3) In the spectral transmittance curve at wavelengths of 1050 nm to 1200 nm and an incident angle of 0 degrees, the maximum transmittance T １０５０－１２００（０ｄｅｇ）ＭＡＸ less than 7% (i-4) In the spectral transmittance curve at wavelengths of 800 nm to 1000 nm and an incident angle of 0 degrees, the maximum transmittance T ８００－１０００（０ｄｅｇ）ＭＡＸ over 20% (i-5) The maximum transmittance in the spectral transmittance curve at wavelengths of 450 nm to 600 nm and an incident angle of 0 degrees is T. ４５０－６００（０ｄｅｇ）ＭＡＸ In that case, In the spectral transmittance curve at an incident angle of 0 degrees, the wavelength λ at which the transmittance becomes 70% of the T ４５０－６００（０ｄｅｇ）ＭＡＸ and the wavelength λ at which the transmittance becomes 30% of the T （７０％） are included within the range of 600 nm to 700 nm, ４５０－６００（０ｄｅｇ）ＭＡＸ and the wavelength λ at which the transmittance becomes 30% of the T （３０％） is included within the range of 600 nm to 700 nm, The wavelength λ （７０％） Transmittance in T （７０％） And the wavelength λ （３０％） Transmittance in T （３０％） When this is the case, the following relation is satisfied -2≦[T （３０％） -D （７０％） ] / [l （３０％） -l （７０％） ]≦-0.75 (i-8) In the spectral transmittance curve at wavelengths of 800 nm to 1000 nm and an incident angle of 0 degrees, when the maximum transmittance is defined as T 800-1000 (0 deg) MAX and the wavelength at which the maximum transmittance occurs is defined as λ 800-1000 (0 deg) MAX, In the spectral transmittance curve in the range of 750 nm to λ 800-1000 (0 deg) MAX nm and at an incident angle of 0 degrees, the wavelength λ IRS (0 deg) (50%) at which the transmittance is 50% of T 800-1000 (0 deg) MAX is, In the spectral transmittance curve in the range of 750 nm to λ 800–1000 (0 deg) MAX nm and at an incident angle of 35 degrees, the wavelength λ IRS (35 deg) (50%) at which the transmittance is 50% of T 800–1000 (0 deg) MAX satisfies the following relationship. |λ IRS (0deg) (50%) -λ IRS (35deg) (50%) |≦30nm

2. The optical filter according to claim 1, wherein the optical filter further satisfies the following spectral characteristics (i-6). (i-6) The spectral transmittance curve at an incident angle of 0 degrees is T （０ｄｅｇ） Let (λ) be the spectral transmittance curve at an incident angle of 35°, and T （３５ｄｅｇ） When (λ) is denoted as such, the following relationship is satisfied in the wavelength range of 450 nm ≤ λ ≤ 600 nm. |T （０ｄｅｇ） (l)-T （３５ｄｅｇ） (λ)|≦10%

3. The optical filter according to claim 1, wherein the optical filter further satisfies the following spectral characteristics (i-7). (i-7) The maximum transmittance in the spectral transmittance curve at wavelengths of 450 nm to 600 nm and an incident angle of 0 degrees is T. ４５０－６００（０ｄｅｇ）ＭＡＸ In that case, At an incidence angle of 0 degrees, the T ４５０－６００（０ｄｅｇ）ＭＡＸ The wavelength λ at which it becomes 50% ＶＩＳ（０ｄｅｇ）（５０％） , and at an incident angle of 35 degrees, the T ４５０－６００（０ｄｅｇ）ＭＡＸ The wavelength λ at which it becomes 50% ＶＩＳ（３５ｄｅｇ）（５０％） It is included in the range of 600 nm to 700 nm, and The following relationship is satisfied |l ＶＩＳ（０ｄｅｇ）（５０％） -l ＶＩＳ（３５ｄｅｇ）（５０％） |≦10nm

4. The optical filter according to claim 1, wherein the optical filter further satisfies the following spectral characteristics (i-9). (i-9) In the spectral transmittance curve at wavelengths of 800 nm to 1000 nm and an incident angle of 0 degrees, the maximum transmittance is T ８００－１０００（０ｄｅｇ）ＭＡＸ The wavelength at which the maximum transmittance is obtained is λ ８００－１０００（０ｄｅｇ）ＭＡＸ In that case, λ ８００－１０００（０ｄｅｇ）ＭＡＸ In the spectral transmittance curve in the range of nm to 1050 nm and at an incident angle of 0 degrees, the transmittance is T ８００－１０００（０ｄｅｇ）ＭＡＸ The wavelength λ is 50% of ＩＲＬ（０ｄｅｇ）（５０％） and, λ ８００－１０００（０ｄｅｇ）ＭＡＸ In the spectral transmittance curve in the range of nm to 1050 nm and at an incident angle of 35 degrees, the transmittance is T ８００－１０００（０ｄｅｇ）ＭＡＸ The wavelength λ is 50% of ＩＲＬ（３５ｄｅｇ）（５０％） However, satisfying the following relationship |l ＩＲＬ（０ｄｅｇ）（５０％） -l ＩＲＬ（３５ｄｅｇ）（５０％） |≦60nm

5. The optical filter according to claim 1, wherein the thickness of the dielectric multilayer film laminated on both main surfaces of the near-infrared absorbing glass is 600 nm or more.

6. The optical filter according to claim 1, wherein the near-infrared absorbing glass is phthalic acid glass or phosphate glass containing iron or copper.

7. The optical filter according to claim 1, wherein the near-infrared absorbing glass satisfies all of the following spectral characteristics (iii-1) to (iii-3). (iii-1) Average internal transmittance T in the spectral transmittance curve at wavelengths of 450-600 nm Ｇ＿４５０－６００ＡＶＥ over 80% (iii-2) Average internal transmittance T in the spectral transmittance curve at wavelengths of 1050-1200 nm Ｇ＿１０５０－１２００ＡＶＥ is the average internal transmittance T Ｇ＿４５０－６００ＡＶＥ Less than (iii-3) Internal transmittance T at wavelengths of 800-1000 nm Ｇ＿８００－１０００ It decreases monotonically.

8. The optical filter according to claim 1, wherein the absorption layer contains a dye having a maximum absorption wavelength of 680 to 800 nm in dichloromethane.

9. The optical filter according to claim 1, wherein the optical filter further satisfies the following spectral characteristics (i-10) to (i-11). (i-10) In the spectral reflectance curve at an incident angle of 5 degrees for at least one of the surfaces, the average reflectance R in the wavelength range of 450 nm to 600 nm. ４５０－６００（５ｄｅｇ）ＡＶＥ less than 15% (i-11) In the spectral reflectance curve at an incident angle of 5 degrees for at least one of the surfaces, the average reflectance R at wavelengths of 1050 to 1200 nm. １０５０－１２００（５ｄｅｇ）ＡＶＥ over 40%

10. The optical filter according to claim 1, wherein the absorption layer satisfies all of the following spectral characteristics (ii-1) to (ii-2). (ii-1) In the spectral transmittance curve for wavelengths of 650-720 nm, the shortest wavelength at which the internal transmittance is 30% is λ Ａ＿ＶＩＳ（３０％） The shortest wavelength at which the internal transmittance is 30% in the spectral transmittance curve for wavelengths of 720 to 1000 nm is defined as λ. Ａ＿ＩＲ（３０％） When this is the case, the following relation is satisfied |l Ａ＿ＩＲ（３０％） -l Ａ＿ＶＩＳ（３０％） |≧100nm (ii-2) The absorbance at a wavelength of 450 nm is A Ａ＿４５０ And the absorbance at a wavelength of 720 nm is A Ａ＿７２０ When this is the case, the following relation is satisfied A Ａ＿７２０ -A Ａ＿４５０ ≧1

11. An imaging apparatus comprising an optical filter according to any one of claims 1 to 10.

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