Optical filter

Abstract

The present invention relates to an optical filter having a dielectric multilayer film (1), a light absorption layer, a glass substrate, and a dielectric multilayer film (2) in this order, in which the thickness of the dielectric multilayer film (1) is 1500 nm or more, the light absorption layer contains a near-infrared absorbing dye and a resin having a glass transition temperature of 200 DEG C or more, and the optical filter satisfies spectral characteristics (i-1) and (i-2).

Description

Technical Field

[0001] The present invention relates to a filter. Background Art

[0002] For imaging devices using solid-state imaging elements, their applications are extended to devices such as surveillance cameras and in-vehicle cameras that perform imaging day and night. In such devices, it is necessary to separately obtain (color) images based on visible light and (black-and-white) images based on infrared light.

[0003] Therefore, research is being conducted on filters that, in addition to having the function of a near-infrared cut-off filter that allows visible light to pass through and faithfully reproduces an image based on the visible light, also have the function of selectively allowing specific near-infrared light to pass through, so-called dual-bandpass filters.

[0004] Patent Document 1 describes a filter obtained by combining a dielectric multilayer film and a resin substrate containing a near-infrared absorbing pigment, which allows visible light and near-infrared light around 850 nm to pass through and shields light other than this.

[0005] Patent Document 2 describes a filter obtained by combining a dielectric multilayer film and a resin substrate containing a near-infrared absorbing pigment, which allows visible light and near-infrared light around 940 nm to pass through and shields light other than this.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: International Publication No. 2017 / 030174

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2016-200771 Summary of the Invention

[0010] Problems to be Solved by the Invention

[0011] In recent years, with the diversification of the sensing regions in the imaging field, the above Patent Document 1 and Patent Document 2 use lasers in a part of the near-infrared light region of 1000 nm or more with different wavelength ranges. Therefore, there is a demand for a filter that can allow near-infrared light in this sensing region to pass through and can shield other near-infrared light that becomes noise.

[0012] In addition, for a filter having a dielectric multilayer film, the optical film thickness of the dielectric multilayer film varies according to the incident angle of light. Therefore, the change in the spectral transmittance curve caused by the incident angle becomes a problem. For example, when the incident angle of light becomes larger, the reflection characteristic shifts toward the short wavelength side. As a result, the reflection characteristic may decrease in a region where shielding is originally desired. The larger the incident angle, the more likely this phenomenon is to occur significantly. When such a filter is used, the spectral sensitivity of the solid-state imaging device may be affected by the incident angle. With the recent trend of reducing the height of camera modules, it is envisioned to be used under high incident angle conditions. Therefore, a filter that is not easily affected by the incident angle is required.

[0013] An object of the present invention is to provide a filter that has excellent transmittance for visible light and specific near-infrared light even at a high incident angle and also has excellent shielding properties for other near-infrared light.

[0014] Means for Solving the Problem

[0015] The present invention provides a filter having the following configuration.

[0016] A filter that sequentially has a dielectric multilayer film (1), a light absorption layer, a glass substrate, and a dielectric multilayer film (2), wherein

[0017] the thickness of the dielectric multilayer film (1) is 1500 nm or more,

[0018] the light absorption layer contains a near-infrared absorbing dye and a resin having a glass transition temperature of 200°C or more,

[0019] the filter satisfies the following spectral characteristics (i-1) and (i-2):

[0020] (i-1) When the sum of the transmittances of light having wavelengths of 450 nm to 700 nm at an incident angle of 0° is set as S1 （0） 、the sum of the transmittances of light having wavelengths of 700 nm to 1000 nm is set as S2 （0） 、the sum of the transmittances of light having wavelengths of 1000 nm to 1300 nm is set as S3 （0） 、then

[0021] S1 （0） / S2 （0） ≥40, and S3 （0） / S2 （0） ≥40;

[0022] (i-2)When the sum of the transmittances of light having wavelengths of 450 nm to 700 nm at an incident angle of 30° is set as S1 （30） 、the sum of the transmittances of light having wavelengths of 700 nm to 1000 nm is set as S2 （30）Let the sum of the transmittances of light with wavelengths from 1000 nm to 1300 nm be S3 （30） When

[0023] S1 （30） / S2 （30） ≥40, and S3 （30） / S2 （30） ≥40.

[0024] Advantages of the Invention

[0025] According to the present invention, it is possible to provide a filter that has excellent transmittance of visible light and specific near-infrared light even at a high incident angle, and also has excellent shielding of other near-infrared light. The filter of the present invention is a filter that has excellent transmittance in the near-infrared light region of 1000 nm to 1300 nm including the sensing wavelength range even at a high incident angle and is not easily affected by the incident angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a cross-sectional view schematically showing an example of a filter of an embodiment.

[0027] Figure 2 is a cross-sectional view schematically showing another example of a filter of an embodiment.

[0028] Figure 3 is a graph showing the spectral transmittance curve of glass.

[0029] Figure 4 is a graph showing the spectral transmittance curve of the light absorption layer.

[0030] Figure 5 is a graph showing the spectral transmittance curve of the filter of Example 3.

[0031] Figure 6 is a graph showing the spectral reflectance curve of the filter of Example 3.

[0032] Figure 7 is a graph showing the spectral transmittance curve of the filter of Example 5.

[0033] Figure 8 is a graph showing the spectral reflectance curve of the filter of Example 5.

[0034] Reference Signs

[0035] 1 Dielectric multilayer film

[0036] 2 Dielectric multilayer film

[0037] 3 Dielectric multilayer film

[0038] 4 Light absorption layer

[0039] 5 Glass substrate

[0040] 10 Filter Detailed implementation mode

[0041] Hereinafter, the implementation modes of the present invention will be described.

[0042] In this specification, the near-infrared absorbing pigment is sometimes abbreviated as "NIR pigment", and the ultraviolet absorbing pigment is sometimes abbreviated as "UV pigment".

[0043] 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 containing 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 described as group (I), and the same applies to groups represented by other formulas.

[0044] In this specification, the transmittance of glass, the transmittance of the light absorption layer including the case where the pigment is contained in the resin, the transmittance measured by dissolving the pigment in a solvent such as dichloromethane, the transmittance of the dielectric multilayer film, and the transmittance of the filter having the dielectric multilayer film are all "external (measured) transmittance" including the reflection loss on the front and back surfaces when described as "transmittance".

[0045] In this specification, the transmittance in a specific wavelength range being 90% or more means that the transmittance is not less than 90% in the entire wavelength range, that is, the minimum transmittance in the wavelength range is 90% or more. Similarly, the transmittance in a specific wavelength range being 1% or less means that the transmittance does not exceed 1% in the entire wavelength range, that is, the maximum transmittance in the wavelength range is 1% or less. The average transmittance in a specific wavelength range is the arithmetic average of the transmittances per 1 nm in the wavelength range.

[0046] The spectral characteristics can be measured using an ultraviolet-visible spectrophotometer.

[0047] In this specification, "~" representing a numerical range includes the upper and lower limits.

[0048] <Filter>

[0049] A filter according to an embodiment of the present invention (hereinafter, also referred to as "this filter") sequentially has a dielectric multilayer film (1), a light absorption layer, a glass substrate, and a dielectric multilayer film (2). The thickness of the dielectric multilayer film (1) is 1500 nm or more, and the light absorption layer contains a near-infrared absorbing pigment and a resin having a glass transition temperature of 200 °C or more.

[0050] Utilizing the reflection characteristics of the dielectric multilayer film and the absorption characteristics of the light absorption layer, the overall filter can achieve excellent transmittance in the visible light region and a specific near-infrared light region, as well as excellent shielding in the remaining near-infrared light regions.

[0051] The structure example of this filter is described using the attached drawings. Figures 1 to 2 It is a cross-sectional view schematically showing an example of the filter of one embodiment.

[0052] Figure 1 The filter 10 shown is an example having a dielectric multilayer film 1, a light absorption layer 4, a glass substrate 5, and a dielectric multilayer film 2 in sequence.

[0053] Figure 2 The filter 10 shown is an example having a dielectric multilayer film 1, a light absorption layer 4, a dielectric multilayer film 3, a glass substrate 5, and a dielectric multilayer film 2 in sequence.

[0054] This filter satisfies the following spectral characteristics (i-1) and (i-2).

[0055] (i-1) When the sum of the transmittances of light with wavelengths from 450 nm to 700 nm at an incident angle of 0 degrees is set as S1 （0） , the sum of the transmittances of light with wavelengths from 700 nm to 1000 nm is set as S2 （0） , and the sum of the transmittances of light with wavelengths from 1000 nm to 1300 nm is set as S3 （0） , then

[0056] S1 （0） / S2 （0） ≥40, and S3 （0） / S2 （0） ≥40.

[0057] (i-2) When the sum of the transmittances of light with wavelengths from 450 nm to 700 nm at an incident angle of 30 degrees is set as S1 （30） , the sum of the transmittances of light with wavelengths from 700 nm to 1000 nm is set as S2 （30） , and the sum of the transmittances of light with wavelengths from 1000 nm to 1300 nm is set as S3 （30） , then

[0058] S1 （30） / S2 （30） ≥40, and S3 （30） / S2 （30） ≥40.

[0059] S1 （0） and S1 （30） respectively correspond to the visible light transmittance amounts at incident angles of 0 degrees and 30 degrees.

[0060] S2 （0） and S2 （30） respectively correspond to the light transmittance of light with wavelengths from 700 nm to 1000 nm at incident angles of 0 degrees and 30 degrees.

[0061] S3 （0） and S3 （30） respectively correspond to the light transmittance of light with wavelengths from 1000 nm to 1300 nm at incident angles of 0 degrees and 30 degrees.

[0062] S1 is the wavelength region of the camera module, and S3 is the sensing region. In both regions, the greater the light transmittance, the greater the amount of light obtained, and higher sensing can be performed.

[0063] On the other hand, S2 is a light shielding region. Therefore, from the viewpoint of reducing noise that causes a decrease in sensor sensitivity, the smaller S2 is, the more preferable it is.

[0064] The present filter that satisfies spectral characteristics (i-1) to (i-2) is a dual-bandpass filter with excellent balance between the transmission region and the light shielding region even at high incident angles.

[0065] The sum of the transmittances of S1 to S3 can be obtained by adding the transmittances (%) for each 1 nm wavelength.

[0066] Preferably, S1 （0） / S2 （0） ≥100, and S3 （0） / S2 （0） ≥100.

[0067] Preferably, S1 （30） / S2 （30） ≥200, and S3 （30） / S2 （30） ≥200.

[0068] In order to satisfy spectral characteristics (i-1) to (i-2), for example, it can be cited: using the absorption characteristics of near-infrared absorbing pigments or light-absorbing glass whose spectral characteristics are not affected by the incident angle to shield the light in the light shielding region of S2.

[0069] The present filter preferably satisfies the following spectral characteristic (i-3).

[0070] (i-3) The absolute value of the difference between the wavelength at which the transmittance of light with wavelengths from 550 nm to 750 nm is 50% at an incident angle of 0 degrees and the wavelength at which the transmittance of light with wavelengths from 950 nm to 1150 nm is 50% at an incident angle of 0 degrees is 300 nm or more.

[0071] The absolute value of the difference in the above wavelengths corresponds to the distance between the visible light transmission region S1 and the near-infrared light transmission region S3. The absolute value is more preferably 350 nm or more.

[0072] In order to satisfy the spectral characteristic (i-3), and particularly to sufficiently separate the position of the near-infrared light transmission region S3 from the visible light transmission region S1, for example, the following can be cited: combining the reflection characteristics of both the dielectric multilayer film 1 and the dielectric multilayer film 2, combining near-infrared absorbing pigments having different maximum absorption wavelengths, using light-absorbing glass, etc., and combining multiple characteristics to perform wide-range light shielding.

[0073] This filter preferably satisfies the following spectral characteristics (i-4) and (i-5).

[0074] (i-4) The absolute value of the difference between the above S1 （0） / S2 （0） and the above S1 （30） / S2 （30） is 200 or less.

[0075] (i-5) The absolute value of the difference between the above S3 （0） / S2 （0） and the above S3 （30） / S2 （30） is 200 or less.

[0076] Satisfying the spectral characteristic (i-4) means that even when the incident angle increases, the transmission amount of visible light and the transmission amount of the near-infrared light shielding region do not change.

[0077] Satisfying the spectral characteristic (i-5) means that even when the incident angle increases, the transmission amount of light with wavelengths of 1000 nm to 1300 nm and the transmission amount of the near-infrared light shielding region do not change.

[0078] That is, it means that the function as a dual-bandpass filter is not easily affected by the incident angle.

[0079] The absolute value of the difference in the spectral characteristic (i-4) is more preferably 130 or less, and further preferably 120 or less.

[0080] The absolute value of the difference in the spectral characteristic (i-5) is more preferably 130 or less, and further preferably 120 or less.

[0081] In order to satisfy the spectral characteristics (i-4) and (i-5), for example, the following can be cited: using both the dielectric multilayer film 1 and the dielectric multilayer film 2 to undertake the light shielding property based on the reflection characteristic in the near-infrared light shielding region; providing the dielectric multilayer film 3 described later between the light absorption layer and the glass substrate; using light-absorbing glass as the glass substrate.

[0082] This filter preferably satisfies all of the following spectral characteristics (i-6) to (i-8).

[0083] (i-6) When the medium multilayer film (1) side is taken as the incident direction, the wavelength IR at which the reflectance of light at an incident angle of 5 degrees is 50%. 50S is in the range of 650 nm to 830 nm.

[0084] (i-7) When the medium multilayer film (1) side is taken as the incident direction, the wavelength IR at which the reflectance of light at an incident angle of 5 degrees is 50%. 50L is in the range of 950 nm to 1200 nm.

[0085] (i-8) The above wavelength IR 50S and the above wavelength IR 50L The absolute value of the difference is 230 nm or more.

[0086] The spectral characteristics (i-6) to (i-8) essentially mean the reflection characteristics of the medium multilayer film (1) on the light absorption layer side, meaning that the medium multilayer film (1) has reflection characteristics between the visible light region of 650 nm to 830 nm and the near-infrared light region of 950 nm to 1200 nm.

[0087] Wavelength IR 50S is more preferably in the range of 700 nm to 780 nm, and wavelength IR 50L is more preferably in the range of 970 nm to 1150 nm, and the wavelength IR 50S and the wavelength IR 50L The absolute value of the difference is more preferably 240 nm or more.

[0088] In order to satisfy the spectral characteristics (i-6) to (i-8), for example, it can be cited: having a medium multilayer film 1 designed in a manner that satisfies the above reflection characteristics.

[0089] This filter preferably satisfies all of the following spectral characteristics (i-9) to (i-10).

[0090] (i-9) When the medium multilayer film (1) side is taken as the incident direction, the average reflectance of light with a wavelength of 450 nm to 600 nm at an incident angle of 5 degrees is 5% or less.

[0091] (i-10) When the medium multilayer film (2) side is taken as the incident direction, the average reflectance of light with a wavelength of 450 nm to 600 nm at an incident angle of 5 degrees is 5% or less.

[0092] The spectral characteristic (i-9) substantially means the reflection characteristic in the visible light region of the dielectric multilayer film (1), and the spectral characteristic (i-10) substantially means the reflection characteristic in the visible light region of the dielectric multilayer film (2). Both the spectral characteristic (i-9) and the spectral characteristic (i-10) mean that the reflection characteristic for visible light is small.

[0093] The average reflectance in the spectral characteristic (i-9) is more preferably 4.8% or less.

[0094] The average reflectance in the spectral characteristic (i-10) is more preferably 4.8% or less.

[0095] In order to satisfy the spectral characteristics (i-9) to (i-10), for example, it can be cited that: there are provided a dielectric multilayer film 1 and a dielectric multilayer film 2 designed in such a manner as to satisfy the above reflection characteristics.

[0096] This filter preferably satisfies the following spectral characteristic (i-11).

[0097] (i-11) When the incident direction is the side of the dielectric multilayer film (1), the absolute value of the difference between the average reflectance of light with a wavelength of 450 nm to 600 nm at an incident angle of 5 degrees and the average reflectance of light with a wavelength of 450 nm to 600 nm at an incident angle of 5 degrees when the incident direction is the side of the dielectric multilayer film 2 is 0.5% or less.

[0098] The spectral characteristic (i-11) corresponds to the difference in the reflection characteristics in the visible light region between the dielectric multilayer film (1) and the dielectric multilayer film (2). By satisfying the above range, it means that the reflection characteristics are of the same degree.

[0099] The absolute value of the difference in the spectral characteristic (i-11) is more preferably 0.4% or less.

[0100] In order to satisfy the spectral characteristic (i-11), for example, it can be cited that: there are provided a dielectric multilayer film 1 and a dielectric multilayer film 2 designed in such a manner as to satisfy the above reflection characteristics.

[0101] <Glass substrate>

[0102] This filter has a glass substrate. Since this filter has at least two dielectric multilayer films, as a base material, a material with high rigidity like glass is preferred rather than a resin film. Thus, warping during film formation can be reduced.

[0103] As the glass substrate, it can be a transparent glass substrate or a light-absorbing glass substrate, but a light-absorbing glass substrate is preferred. Regarding the reflection characteristics of the dielectric multilayer film, the light shielding region shifts according to the incident angle of light. In contrast, regarding the absorption characteristics of the light-absorbing glass substrate, the shift of the light shielding region caused by the incident angle of light is small, and high light shielding performance can be exhibited even at a high incident angle.

[0104] As a light-absorbing glass, a glass containing ytterbium is preferred. The glass containing ytterbium has the property of absorbing light in the near-infrared light region with a wavelength of 900 nm to 1000 nm. Moreover, the waveform of the absorption band is steep, so the transmittance in the region other than the maximum absorption wavelength region is excellent. Therefore, the transmittance in the visible light region, from visible light to a wavelength of about 800 nm, and the near-infrared light region on the long-wavelength side of a wavelength of 1000 nm is excellent.

[0105] Hereinafter, each component that can constitute the glass and its suitable content (in mol% based on oxide basis) will be described. In this specification, unless otherwise specified, the content and total content of each component are in mol% based on oxide basis.

[0106] Yb 2 O 3 is a component for effectively absorbing light near a wavelength of 900 nm to 1000 nm, particularly light with a wavelength of 940 nm, and reducing the transmittance. In the glass of the present embodiment, if the content of Yb 2 O 3 is 20% or more, its effect can be sufficiently obtained. If the content of Yb 2 O 3 is 60% or less, problems such as deterioration of the devitrification resistance of the glass, deterioration of the meltability, and generation of stray light caused by fluorescence are not likely to occur.

[0107] Therefore, the content of Yb 2 O 3 is preferably 20% to 60%, more preferably 25% to 60%, further preferably 30% to 60%, still further preferably 35% to 60%, particularly preferably greater than 40% and less than or equal to 60%, and most preferably 45% to 60%.

[0108] SiO 2 is a main component for forming the glass and is a component for improving the devitrification resistance of the glass and the viscosity at the liquidus temperature. In the glass of the present embodiment, if the content of SiO 2 is 0.1% or more, problems such as the glass becoming unstable, deterioration of the weather resistance, and generation of striae in the glass are not likely to occur. If the content of SiO 2 is 50% or less, problems such as deterioration of the meltability of the glass are not likely to occur.

[0109] Therefore, the content of SiO 2 is preferably 0.1% to 50%, more preferably 0.1% to 40%, further preferably 0.1% to 30%, still further preferably 0.1% to 20%, particularly preferably 0.1% to 10%, and most preferably 0.1% to 9%.

[0110] B 2 O 3 is a main component for forming glass and is a component for improving the devitrification resistance and viscosity at the liquidus temperature of the glass. In the glass of the present embodiment, if the content of B 2 O 3 is 15% or more, problems such as the glass becoming unstable are less likely to occur. If the content of B 2 O 3 is 40% or less, problems such as a decrease in the weather resistance of the glass and the generation of striae in the glass are less likely to occur.

[0111] Therefore, the content of B 2 O 3 is preferably 15% to 40%, more preferably 15% to 38%, further preferably 15% to 36%, still further preferably 15% to 34%, particularly preferably 15% to 32%, and most preferably 15% to 30%.

[0112] As the light-absorbing glass, from the viewpoint of obtaining a stable glass, it preferably contains at least one of SiO 2 and B 2 O 3 . From the viewpoint of less likely to occur problems such as the glass becoming unstable, the total content of the above components is preferably greater than 65%. In addition, from the viewpoint of less likely to occur problems such as the meltability of the glass becoming poor, the total content of the above components is preferably 80% or less.

[0113] Therefore, it is more preferably greater than 65% and less than or equal to 79%, further preferably greater than 65% and less than or equal to 78%, still further preferably greater than 65% and less than or equal to 77%, particularly preferably greater than 65% and less than or equal to 76%, and most preferably greater than 65% and less than or equal to 75%.

[0114] P 2 O 5 is a component for improving the meltability and stability of the glass. In the glass of the present embodiment, the content of P 2 O 5 is preferably 0% to 15%. If the content of P 2 O 5 is 15% or less, problems such as a decrease in the weather resistance of the glass, phase separation of the glass, and the generation of striae in the glass are less likely to occur.

[0115] P 2 O 5 The content is more preferably 1% to 13%, further preferably 2% to 12%, still further preferably 3% to 11%, and most preferably 4% to 10%.

[0116] GeO 2is a component for improving the devitrification resistance of glass and the viscosity at the liquidus temperature. In the glass of the present embodiment, GeO 2 The content of is preferably 0% to 15%. If GeO 2 The content of is 15% or less, problems such as deterioration of the meltability of the glass are less likely to occur.

[0117] GeO 2 The content of is more preferably 0% to 13%, further preferably 0% to 11%, still further preferably 0% to 9%, and most preferably 0% to 7%.

[0118] Ga 2 O 3 is a component for improving the Young's modulus of glass and improving meltability and stability. In the glass of the present embodiment, Ga 2 O 3 The content of is preferably 0% to 30%. If Ga 2 O 3 The content of is 30% or less, problems such as deterioration of the devitrification resistance of the glass, increase in reflectivity, and generation of stray light caused by reflected light are less likely to occur.

[0119] Ga 2 O 3 The content of is more preferably 0.5% to 28%, further preferably 1% to 26%, still further preferably 2% to 24%, and most preferably 3% to 22%.

[0120] ZrO 2 is a component for improving the Young's modulus of glass and increasing the viscosity at the liquidus temperature of glass. In the glass of the present embodiment, ZrO 2 The content of is preferably 0% to 7%. If ZrO 2 The content of is 7% or less, problems such as deterioration of the devitrification resistance of the glass and deterioration of meltability are less likely to occur.

[0121] ZrO 2 The content of is more preferably 0% to 6%, further preferably 0% to 5%, still further preferably 0% to 4%, and most preferably 0% to 3%.

[0122] La 2 O 3 is a component for improving the Young's modulus of glass and improving meltability. In the glass of the present embodiment, La 2 O 3 The content of is preferably 0.1% to 20%. If La 2 O 3 The content of is 0.1% or more, its effect can be fully obtained. If La 2 O 3If the content is 20% or less, problems such as deterioration of the devitrification resistance of the glass, increase in the reflectivity, and generation of stray light caused by reflected light are less likely to occur.

[0123] La 2 O 3 The content is more preferably 0.5% to 19%, further preferably 1% to 18%, still further preferably 2% to 17%, and most preferably 2% to 16%.

[0124] Al 2 O 3 is a component for increasing the Young's modulus of the glass and reducing the refractive index of the glass. In the glass of the present embodiment, Al 2 O 3 The content is preferably 0.1% to 20%. If the content of Al 2 O 3 is 0.1% or more, its effect can be sufficiently obtained. If the content of Al 2 O 3 is 20% or less, problems such as deterioration of the devitrification resistance of the glass, increase in the reflectivity, and generation of stray light caused by reflected light are less likely to occur.

[0125] Al 2 O 3 The content is more preferably 0.1% to 18%, further preferably 0.1% to 15%, still further preferably 0.1% to 13%, and most preferably 0.1% to 11%.

[0126] From the viewpoint of vitrifying the glass containing the Yb component without devitrification, the total content of the components of Al 2 O 3 , GeO 2 , Ga 2 O 3 and P 2 O 5 and the total content of the components of SiO 2 and B 2 O 3 , that is, (the total content of Al 2 O 3 , GeO 2 , Ga 2 O 3 and P 2 O 5 ) / (the total content of SiO 2 and B 2 O 3 ) is preferably less than 0.1.

[0127] As the light-absorbing glass, it may contain alkali metal oxides, alkaline earth metal oxides, Sb 2 O 3 , Cl, F, and other components.

[0128] As the glass substrate in this filter, when used for a filter, in order to prevent stray light generated by reflected light on the glass surface, it is preferable to reduce the reflectivity of the glass. The reflectivity of the glass is determined by the refractive index. Typically, the refractive index at a wavelength of 588 nm is preferably 1.700 to 1.900.

[0129] As the glass substrate, when used for a so-called dual-bandpass filter having a function of selectively transmitting visible light and specific near-infrared light, it is often used with a thickness of usually 3 mm or less. From the viewpoint of reducing the weight of the component, it is preferably used with a thickness of 2 mm or less, more preferably 1 mm or less, further preferably 0.5 mm or less, and even more preferably 0.3 mm or less. In addition, from the viewpoint of ensuring the strength of the glass, the thickness is preferably 0.05 mm or more.

[0130] The glass substrate in this filter can be produced, for example, as follows.

[0131] First, weigh the raw materials so as to fall within the above composition range and mix them (mixing process). The raw material mixture is placed in a platinum crucible and heated and melted at a temperature of 1200°C to 1650°C in an electric furnace (melting process). Stir and clarify thoroughly, and then pour it into a mold and cut and grind it to form a flat plate of a specified thickness (forming process).

[0132] In the melting process of the above manufacturing method, it is preferable to adjust the maximum temperature of the glass during melting to 1650°C or less. If the maximum temperature of the glass during melting is below the above temperature, problems such as crystallization of the glass and generation of unmelted foreign substances in the glass are less likely to occur. The above temperature is more preferably 1625°C or less, and further preferably 1600°C or less.

[0133] In addition, when the temperature in the above melting process is too low, problems such as devitrification during melting and time-consuming for complete melting may occur. Therefore, it is preferably 1300°C or more, and more preferably 1350°C or more.

[0134] <Light-absorbing layer>

[0135] This filter has a light absorption layer containing a near-infrared absorbing pigment (NIR pigment) and a resin with a glass transition temperature of 200 °C or higher. Thus, it is possible to compensate for the region not shielded by the reflection characteristics of the dielectric multilayer film by the absorption characteristics that are not affected by the incident angle. In addition, even when strong stress is applied to the dielectric multilayer film 1 on the light absorption layer, since the glass transition temperature of the resin is sufficiently high, the resin is not easily deformed.

[0136] The light absorption layer preferably satisfies all of the following spectral characteristics (ii-1) to (ii-2).

[0137] (ii-1) The average transmittance of light with a wavelength of 450 nm to 600 nm is 70% or more.

[0138] (ii-2) The average transmittance of light with a wavelength of 700 nm to 900 nm is 60% or less.

[0139] As the near-infrared absorbing pigment, from the viewpoint of being able to absorb light in the near-infrared region over a wide range while maintaining the transmittance in the visible light region, it is preferable to combine two or more pigments having different maximum absorption wavelengths and within the range of 680 nm to 800 nm, and more preferably to combine three pigments having different maximum absorption wavelengths and within the range of 680 nm to 800 nm. In particular, as the near-infrared absorbing pigment, it is preferable to include a pigment having a maximum absorption wavelength in the range of 700 nm or more and less than 730 nm, a pigment having a maximum absorption wavelength in the range of 730 nm or more and less than 760 nm, and a pigment having a maximum absorption wavelength in the range of 760 nm or more and less than 800 nm.

[0140] As the NIR pigment, it is preferably selected from the group consisting of squarylium pigments, cyanine pigments, phthalocyanine pigments, naphthalocyanine pigments, dithiol metal complex pigments, azo pigments, polymethine pigments, phthalide pigments, naphthoquinone pigments, anthraquinone pigments, indophenol pigments, pyran pigments, thiopyran pigments, croconic acid pigments, tetradehydrocholine pigments, triphenylmethane pigments, ammonium pigments, and diammonium pigments.

[0141] As the NIR pigment, it is preferably to include at least one pigment selected from squarylium pigments, phthalocyanine pigments, and cyanine pigments. Among these NIR pigments, from the spectral viewpoint, squarylium pigments and cyanine pigments are preferred, and from the durability viewpoint, phthalocyanine pigments are preferred.

[0142] In order to obtain the desired optical properties, the content of the NIR pigment in the light absorption layer is preferably 10% by mass or more. In addition, when the content of the NIR pigment is excessive, the physical properties of the light absorption layer will be impaired (especially the glass transition temperature decreases), so it is preferably 20% by mass or less, more preferably 15% by mass or less. Even when the content of the NIR pigment is 10% by mass or more, since the glass transition temperature of the resin is sufficiently high, the light absorption layer is not easily thermally deformed. It should be noted that in the case of combining two or more compounds, the above content is the sum of each compound.

[0143] In addition to the above NIR pigment, the light absorption layer may further contain other pigments. As other pigments, pigments (UV pigments) having a maximum absorption wavelength in the range of 370 nm to 440 nm in the resin are preferred. Thereby, light in the near ultraviolet region can be effectively shielded.

[0144] Examples of the UV pigment include: azole pigments, merocyanine pigments, cyanine pigments, naphthalimide pigments, diazole pigments, azine pigments, oxazolidine pigments, naphthalenedicarboxylic acid pigments, styryl pigments, anthracene pigments, cyclic carbonyl pigments, triazole pigments, etc. Among them, merocyanine pigments are particularly preferred. In addition, one kind can be used alone, or two or more kinds can be used in combination.

[0145] For the resin in the light absorption layer of this filter, from the viewpoint of preventing deformation as described above, a resin having a glass transition temperature of 200 °C or higher is used. In addition, from the viewpoint of not affecting the spectral characteristics, a transparent resin is preferred. As the resin having a glass transition temperature of 200 °C or higher, one or more resins selected from polyimide resins, polycarbonate resins, polyester resins, and acrylic resins are preferred. The glass transition temperature of the resin is preferably 250 °C or higher, more preferably 300 °C or higher.

[0146] When using multiple compounds as the NIR pigment or other pigments, they can be contained in the same light absorption layer, or they can be contained in different light absorption layers respectively.

[0147] The light absorption layer can be formed in the following manner: Prepare a coating solution by dissolving or dispersing the pigment, resin or raw material components of the resin and each component added as required in a solvent, coat it on a support and dry it, and then cure it as required. The support can be a light absorption glass substrate or a peelable support used only when forming the light absorption layer. In addition, the solvent can be a dispersion medium that can stably disperse or a solvent that can dissolve.

[0148] In addition, the coating liquid may contain a surfactant in order to improve voids caused by minute bubbles, depressions caused by the adhesion of foreign substances, etc., and shrinkage holes in the drying process. Further, when applying the coating liquid, for example, a dipping method, a casting coating method, a spin coating method, etc. may be used. 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.

[0149] In addition, the light absorption layer can also be formed into a film shape by extrusion molding. The obtained film-shaped absorption layer is laminated on a light absorption glass substrate and integrated by thermocompression bonding or the like, whereby this optical filter can be manufactured.

[0150] The optical filter may have one light absorption layer or two or more light absorption layers. When there are two or more light absorption layers, each layer may have the same configuration or different configurations.

[0151] From the viewpoints of coatability, in-plane film thickness distribution within the substrate after coating, and appearance quality, the thickness of the light absorption layer is preferably 5 μm or less. In addition, from the viewpoint of reducing the thermal expansion amount of the resin, the thickness of the light absorption layer is more preferably 2 μm or less. In addition, from the viewpoint of exhibiting desired spectral characteristics at an appropriate pigment concentration, the thickness of the light absorption layer is preferably 0.5 μm or more. It should be noted that when the optical filter has two or more light absorption layers, the total thickness of each light absorption layer is preferably within the above range.

[0152] <Dielectric multilayer film>

[0153] This optical filter has a dielectric multilayer film 1 on the surface of the light absorption layer and a dielectric multilayer film 2 on one main surface side of the glass substrate. When the thickness of the dielectric multilayer film is large, it is easy to control the spectral characteristics. On the other hand, when the dielectric multilayer film is too thick, stress is likely to occur, which becomes one of the causes of deformation. By having dielectric multilayer films at two locations, it is possible to disperse the action in the control of spectral characteristics or to avoid concentrating the thickness on one multilayer film.

[0154] Both the dielectric multilayer film 1 and the dielectric multilayer film 2 are preferably designed as reflection films (hereinafter also referred to as "NIR reflection films") that reflect a part of near-infrared light. The NIR reflection film can be further appropriately designed to also reflect light in a wavelength range other than near-infrared light, such as near-ultraviolet light.

[0155] The dielectric multilayer film 1 preferably satisfies all of the following spectral characteristics (iii-1-1) to (iii-1-3).

[0156] (iii-1-1) The average reflectance of light with a wavelength of 450 nm to 600 nm at an incident angle of 5 degrees is 2.0% or less.

[0157] (iii-1-2) When the incident angle is 5 degrees, the average reflectance of light with a wavelength of 430 nm to 700 nm is 2.5% or less.

[0158] (iii-1-3)When the incident angle is 5 degrees, the average reflectance of light with a wavelength of 1110 nm to 1200 nm is 5.0% or less.

[0159] By satisfying the above characteristics, particularly a filter that easily satisfies spectral characteristics (i-6) to (i-8) and spectral characteristic (i-9) is obtained, and thus it is preferred. In addition, the total sum S1 of the visible light transmittance can be increased, and the total sum S2 of the transmittance of light with a wavelength of 700 nm to 1000 nm can be decreased, so it is easy to obtain S1 that satisfies spectral characteristic (i-1) （0） / S2 （0） and S1 that satisfies spectral characteristic (i-2) （30） / S2 （30） of the filter.

[0160] The dielectric multilayer film 2 preferably satisfies all of the following spectral characteristics (iii-2-1) to (iii-2-3).

[0161] (iii-2-1)When the incident angle is 5 degrees, the average reflectance of light with a wavelength of 450 nm to 600 nm is 2.0% or less.

[0162] (iii-2-2)When the incident angle is 5 degrees, the average reflectance of light with a wavelength of 430 nm to 700 nm is 2.5% or less.

[0163] (iii-2-3)When the incident angle is 5 degrees, the average reflectance of light with a wavelength of 1110 nm to 1200 nm is 5.0% or less.

[0164] By satisfying the above characteristics, particularly a filter that satisfies spectral characteristic (i-10) is easily obtained, and thus it is preferred.

[0165] This filter preferably has a dielectric multilayer film 3 between the light absorption layer and the glass substrate. With three dielectric multilayer films, more flexible control of spectral characteristics can be achieved. Specifically, the absolute value of the difference between S1 （0） / S2 （0） and S1 （30） / S2 （30） , and the absolute value of the difference between S3 （0） / S2 （0） and S3 （30） / S2 （30） can be further reduced, and a filter that satisfies spectral characteristics (i-4) and (i-5) is easily obtained.

[0166] The dielectric multilayer film is a laminate of dielectric films having different refractive indices. More specifically, examples include: a low refractive index dielectric film (low refractive index film), a medium refractive index dielectric film (medium refractive index film), and a high refractive index dielectric film (high refractive index film), which are composed of a dielectric multilayer film formed by laminating two or more of them. By combining dielectric films with different spectral characteristics when transmitting and selecting a desired wavelength band, the reflection characteristics can be adjusted.

[0167] The refractive index of the high refractive index material at a wavelength of 500 nm is preferably 1.8 or more and 2.5 or less, more preferably 1.9 or more and 2.5 or less. Examples of the high refractive index material include: Ta 2 O 5 、TiO 2 、TiO、Nb 2 O 5 。Examples of other commercially available products include: OS50 (Ti 3 O 5 ), OS10 (Ti 4 O 7 ), OA500 (a mixture of Ta 2 O 5 and ZrO 2 ), OA600 (a mixture of Ta 2 O 5 and TiO 2 ), etc. Among them, from the viewpoints of film formability, reproducibility of refractive index, stability, etc., TiO 2 is preferred.

[0168] The refractive index of the medium refractive index material at a wavelength of 500 nm is preferably greater than 1.5 and less than 1.8, more preferably greater than or equal to 1.55 and less than 1.8. Examples of the medium refractive index material include: ZrO 2 、Nb 2 O 5 、Al 2 O 3 、HfO 2 、OM-4 and OM-6 (a mixture of Al 2 O 3 and ZrO 2 ) sold by Canon Optron Co., Ltd., OA-100, H4 and M2 (aluminum oxide - lanthanum oxide) sold by Merck & Co., Inc., etc. Among them, from the viewpoints of film formability, reproducibility of refractive index, stability, etc., Al 2 O 3 -type compounds and a mixture of Al 2 O 3 and ZrO 2The mixture. It should be noted that the medium refractive index film may not use the above medium refractive index material, but may be replaced with an equivalent film including a high refractive index film and a low refractive index film.

[0169] The refractive index of the low refractive index material at a wavelength of 500 nm is preferably 1.4 or more and 1.5 or less, more preferably 1.45 or more and 1.5 or less. As the low refractive index material, for example, SiO 2 、SiO x N y、 MgF 2 etc. As other commercially available products, for example, S4F and S5F manufactured by Canon Optron Co., Ltd. (a mixture of SiO 2 and Al 2 O 3 ). Among them, from the viewpoints of reproducibility, stability, economy, etc. of film formation, SiO 2 is preferred.

[0170] From the viewpoint of easily controlling spectral characteristics, the film thickness (physical film thickness) of the dielectric multilayer film 1 is preferably 1500 nm or more, more preferably 2000 nm or more. In addition, from the viewpoints of productivity and suppressing reflection ripples in the visible light region, the film thickness (physical film thickness) of the dielectric multilayer film 1 is preferably 6000 nm or less.

[0171] From the viewpoints of productivity and feasibility, the total number of stacked layers of the dielectric multilayer film 1 is preferably 100 layers or less, more preferably 80 layers or less, and further more preferably 70 layers or less.

[0172] From the viewpoint of easily controlling spectral characteristics, the film thickness (physical film thickness) of the dielectric multilayer film 2 is preferably 1500 nm or more, more preferably 2000 nm or more. In addition, from the viewpoints of productivity and suppressing reflection ripples in the visible light region, the film thickness (physical film thickness) of the dielectric multilayer film 2 is preferably 6000 nm or less.

[0173] From the viewpoints of productivity and feasibility, the total number of stacked layers of the dielectric multilayer film 2 is preferably 100 layers or less, more preferably 80 layers or less, and further more preferably 70 layers or less.

[0174] From the viewpoint of easily controlling spectral characteristics, the film thickness (physical film thickness) of the dielectric multilayer film 3 is preferably 150 nm or more, more preferably 200 nm or more. In addition, from the viewpoints of productivity and suppressing reflection ripples in the visible light region, the film thickness (physical film thickness) of the dielectric multilayer film 3 is preferably 6000 nm or less.

[0175] From the viewpoints of productivity and feasibility, the total number of stacked layers of the dielectric multilayer film 3 is preferably 100 layers or less, more preferably 50 layers or less, and further more preferably 25 layers or less.

[0176] In the formation of the dielectric multilayer film, for example, vacuum film-forming processes such as CVD method, sputtering method, and vacuum evaporation method can be used; wet film-forming processes such as spraying method and dipping method, etc.

[0177] This filter can, for example, include constituent elements (layers) that generate absorption using inorganic fine particles that control the transmission and absorption of light in a specific wavelength range as other constituent elements. Specific examples of the inorganic fine particles include: ITO (indium tin oxide), ATO (antimony-doped tin oxide), cesium tungstate, lanthanum boride, etc. ITO fine particles and cesium tungstate fine particles have high visible light transmittance and have light absorbability in a wide range of infrared wavelength regions greater than 1200 nm, so they can be used when shielding of this infrared light is required.

[0178] <Imaging device>

[0179] The imaging device according to an embodiment of the present invention preferably includes the filter according to the embodiment of the present invention described above. The imaging device preferably further includes a solid-state imaging element and an imaging lens. The filter of this embodiment can be used, for example, by being disposed between the imaging lens and the solid-state imaging element, or by being directly adhered to the solid-state imaging element, imaging lens, etc. of the imaging device through an adhesive layer. By including this filter that has excellent transmittance of visible light and specific near-infrared light, has shielding properties for specific near-infrared light, and whose spectral curve is not easily shifted even at a high incident angle, an imaging device with excellent color reproducibility even for light at a high incident angle can be obtained.

[0180] When installing the filter in the imaging device, it is generally preferable to make the dielectric multilayer film 2 (substrate side) face the lens side and make the dielectric multilayer film 1 (light absorption layer side) face the sensor side.

[0181] As described above, the following filters, etc. are disclosed in this specification.

[0182] [1] A filter, which successively has a dielectric multilayer film (1), a light absorption layer, a glass substrate, and a dielectric multilayer film (2), wherein,

[0183] the thickness of the dielectric multilayer film (1) is 1500 nm or more,

[0184] the light absorption layer contains a near-infrared absorbing pigment and a resin having a glass transition temperature of 200 °C or more,

[0185] the filter satisfies the following spectral characteristics (i-1) and (i-2):

[0186] (i-1) Let the sum of the transmittances of light with wavelengths of 450 nm to 700 nm at an incident angle of 0 degrees be S1 （0）Let the sum of the transmittances of light with wavelengths from 700 nm to 1000 nm be S2 （0） Let the sum of the transmittances of light with wavelengths from 1000 nm to 1300 nm be S3 （0） When

[0187] S1 （0） / S2 （0） ≥ 40, and S3 （0） / S2 （0） ≥ 40;

[0188] (i - 2) Let the sum of the transmittances of light with wavelengths from 450 nm to 700 nm at an incident angle of 30 degrees be S1 （30） Let the sum of the transmittances of light with wavelengths from 700 nm to 1000 nm be S2 （30） Let the sum of the transmittances of light with wavelengths from 1000 nm to 1300 nm be S3 （30） When

[0189] S1 （30） / S2 （30） ≥ 40, and S3 （30） / S2 （30） ≥ 40.

[0190] [2] The filter according to [1], wherein the filter satisfies the following spectral characteristic (i - 3):

[0191] (i - 3) The absolute value of the difference between the wavelength at which the transmittance of light with wavelengths from 550 nm to 750 nm is 50% at an incident angle of 0 degrees and the wavelength at which the transmittance of light with wavelengths from 950 nm to 1150 nm is 50% at an incident angle of 0 degrees is 300 nm or more.

[0192] [3] The filter according to [1] or [2], wherein the filter satisfies the following spectral characteristics (i - 4) and (i - 5):

[0193] (i - 4) The absolute value of the difference between the S1 （0） / S2 （0） and the S1 （30） / S2 （30） is 200 or less;

[0194] (i - 5) The absolute value of the difference between the S3 （0） / S2 （0） and the S3 （30） / S2 （30） is 200 or less.

[0195] [4] The filter according to any one of [1] to [3], wherein the filter satisfies all of the following spectral characteristics (i-6) to (i-8):

[0196] (i-6) When the medium multilayer film (1) side is the incident direction, the wavelength IR at which the reflectance of light at an incident angle of 5 degrees is 50%; 50S is in the range of 650 nm to 830 nm;

[0197] (i-7) When the medium multilayer film (1) side is the incident direction, the wavelength IR at which the reflectance of light at an incident angle of 5 degrees is 50%; 50L is in the range of 950 nm to 1200 nm;

[0198] (i-8) The wavelength IR 50S and the wavelength IR 50L have an absolute value of the difference of 230 nm or more.

[0199] [5] The filter according to any one of [1] to [4], wherein the filter satisfies the following spectral characteristics (i-9) to (i-10):

[0200] (i-9) When the medium multilayer film (1) side is the incident direction, the average reflectance of light with wavelengths from 450 nm to 600 nm at an incident angle of 5 degrees is 5% or less;

[0201] (i-10) When the medium multilayer film (2) side is the incident direction, the average reflectance of light with wavelengths from 450 nm to 600 nm at an incident angle of 5 degrees is 5% or less.

[0202] [6] The filter according to any one of [1] to [5], wherein the filter satisfies the following spectral characteristics (i-11):

[0203] (i-11) The absolute value of the difference between the average reflectance of light with wavelengths from 450 nm to 600 nm at an incident angle of 5 degrees when the medium multilayer film (1) side is the incident direction and the average reflectance of light with wavelengths from 450 nm to 600 nm at an incident angle of 5 degrees when the medium multilayer film (2) side is the incident direction is 0.5% or less.

[0204] [7] The filter according to [3], wherein the filter has a medium multilayer film (3) between the light absorption layer and the glass substrate, and

[0205] the filter satisfies:

[0206] In the spectral characteristic (i-4), the S1 （0） / S2（0） The absolute value of the difference from the said S1 （30） / S2 （30） is 130 or less;

[0207] Among the said spectral characteristics (i-5), the said S3 （0） / S2 （0） The absolute value of the difference from the said S3 （30） / S2 （30） is 130 or less.

[0208] [8] The filter according to [3], wherein the glass substrate is a glass substrate containing ytterbium, and

[0209] the filter satisfies:

[0210] Among the said spectral characteristics (i-4), the said S1 （0） / S2 （0） The absolute value of the difference from the said S1 （30） / S2 （30） is 130 or less;

[0211] Among the said spectral characteristics (i-5), the said S3 （0） / S2 （0） The absolute value of the difference from the said S3 （30） / S2 （30） is 130 or less.

[0212] [9] The filter according to any one of [1] to [8], wherein the resin in the light absorption layer contains a polyimide resin.

[0213]

[10] The filter according to any one of [1] to [9], wherein the near-infrared absorbing pigment in the light absorption layer contains: a pigment having a maximum absorption wavelength in the range of a wavelength greater than or equal to 700 nm and less than 730 nm; a pigment having a maximum absorption wavelength in the range of a wavelength greater than or equal to 730 nm and less than 760 nm; and a pigment having a maximum absorption wavelength in the range of a wavelength greater than or equal to 760 nm and less than 800 nm.

[0214]

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

[10] , wherein the thickness of the light absorption layer is 2 μm or less, and

[0215] the content of the near-infrared absorbing pigment in the light absorption layer is 10% by mass or more.

[0216]

[12] An imaging device, wherein the imaging device includes the filter according to any one of [1] to

[11] .

[0217] Examples

[0218] Next, the present invention will be described more specifically by way of examples.

[0219] In the measurement of each spectral characteristic, a UV-visible spectrophotometer (manufactured by Hitachi High-Technologies Corporation, model UH-4150) was used.

[0220] In addition, the spectral characteristics in the case where the incident angle is not specifically described are the values measured under the condition of an incident angle of 0 degrees (the direction perpendicular to the main surface of the filter).

[0221] The pigments used in each example are as described below.

[0222] Compound 1 (squaraine salt compound): Synthesized based on U.S. Patent No. 5,543,086.

[0223] Compound 2 (squaraine salt compound): Synthesized based on International Publication No. 2017 / 135359.

[0224] Compound 3 (mero-cyanine compound): Synthesized based on the specification of German Patent Gazette No. 10109243.

[0225] Compound 4 (cyanine compound): Synthesized based on Dyes and pigments 73 (2007) 344-352.

[0226] Compound 5 (cyanine compound): Synthesized based on Dyes and pigments 73 (2007) 344-352.

[0227] It should be noted that Compound 1, Compound 2, Compound 4, and Compound 5 are near-infrared absorbing pigments (NIR pigments), and Compound 3 is a near-ultraviolet absorbing pigment (UV pigment).

[0228]

[0229] <Spectral characteristics of pigments>

[0230] The maximum absorption wavelengths in the absorption spectra measured by dissolving the above pigments (Compound 1 to Compound 5) in dichloromethane are shown in Table 1 described later.

[0231] <Glass substrate>

[0232] Glass A as a light-absorbing glass and non-absorbing glass B were prepared as the glass substrates.

[0233] For Glass A, in terms of mol% on an oxide-converted basis, to make SiO 2 7.5%, B2 O 3 23.6%, P 2 O 5 7.5%, Yb 2 O 3 47.2%, Ga 2 O 3 11.8%, La 2 O 3 The raw materials are weighed and mixed in the following proportions: 23.6% of O, 7.5% of Yb, 47.2% of Ga, 11.8% of La, and 2.4% of other components. The mixed raw materials are placed in a crucible with an internal volume of about 400 cc and melted at 1400°C to 1650°C for 2 hours in an atmospheric atmosphere. Then, clarification and stirring are carried out, and the molten material is cast into a rectangular mold with a length of 100 mm, a width of 50 mm, and a height of 20 mm preheated to about 300°C to about 500°C. It is slowly cooled to room temperature at a rate of about -1°C / minute and cut to a specified thickness within the range of 40 mm in length, 30 mm in width, and 0.3 mm to 1.5 mm in thickness. Both sides are optically polished to obtain a plate-shaped glass.

[0234] In addition, Glass B is a non-absorbing glass and uses D263 glass (manufactured by Schott, borosilicate glass, commercially available).

[0235] It should be noted that the raw materials for each glass are as follows.

[0236] SiO 2 : Oxide

[0237] B 2 O 3 : Selected from oxide, PBO 4 and H 3 BO 3 One or more of the above

[0238] P 2 O 5 : H 3 PO 4 and PBO 4 Any one or more of the above

[0239] GeO 2 : Oxide

[0240] ZrO 2 : Oxide

[0241] Ga 2 O 3 : Oxide

[0242] Yb 2 O 3 : Oxide

[0243] La 2 O3 : Oxide

[0244] Al 2 O 3 : Any one or more of oxide and Al(OH) 3 above

[0245] It should be noted that the raw materials of the glass are not limited to the above raw materials, and known raw materials can be used.

[0246] The transmittance curves of light with wavelengths of 350 nm to 1200 nm for Glass A and Glass B (both Glass A and Glass B have a plate thickness of 0.4 mm and an internal transmittance) are shown in Figure 3 .

[0247] <Light absorption layer>

[0248] Any one of Compounds 1 to 5 was dissolved in a polyimide resin (manufactured by Mitsubishi Gas Chemical Company, Inc., C-3G30G) or a polyester resin (manufactured by Osaka Gas Chemical Co., Ltd., polyester resin), and mixed at the concentrations recorded in the following table respectively, and stirred and dissolved at 50 °C for 2 hours to obtain a coating solution.

[0249] The obtained coating solution was coated on an alkali glass (manufactured by Schott AG, D263 glass, thickness 0.2 mm) by spin coating to form a light absorption layer with the film thickness shown in Table 1 below.

[0250] In addition, the transmittance curves of light with wavelengths of 350 nm to 1200 nm for Light Absorption Layer 1 to Light Absorption Layer 2 are shown in Figure 4 .

[0251] [Table 1]

[0252]

[0253] <Example 1: Filter>

[0254] On one main surface of a glass substrate (Glass B without light absorption), SiO was alternately laminated by evaporation 2 and TiO 2 to form a dielectric multilayer film 2A.

[0255] On the other main surface of the glass substrate, a resin solution was coated with the same composition as that of the light absorption layer 1, and the organic solvent was removed by sufficient heating to form a light absorption layer.

[0256] On the surface of the light absorption layer, SiO was alternately laminated by evaporation 2 and TiO 2 to form a dielectric multilayer film 1A.

[0257] The filter of Example 1 was manufactured in the above manner.

[0258] <Example 2>

[0259] Using light-absorbing glass A instead of glass B as the glass substrate and using dielectric multilayer film 1B instead of dielectric multilayer film 1A, the filter of Example 2 was manufactured by operating in the same manner as in Example 1 except for this.

[0260] <Example 3>

[0261] Between the glass substrate and the light-absorbing layer, SiO was alternately laminated by evaporation 2 and TiO 2 to form dielectric multilayer film 3A in this way. The filter of Example 3 was manufactured by operating in the same manner as in Example 1 except for this.

[0262] <Example 4>

[0263] Between the glass substrate and the light-absorbing layer, SiO was alternately laminated by evaporation 2 and TiO 2 to form dielectric multilayer film 3A in this way. The filter of Example 4 was manufactured by operating in the same manner as in Example 2 except for this.

[0264] <Example 5>

[0265] On one main surface of the glass substrate (glass B without light-absorbing property), SiO was alternately laminated by evaporation 2 and TiO 2 to form dielectric multilayer film 2B in this way.

[0266] On the other main surface of the glass substrate, a resin solution was coated with the same composition as the light-absorbing layer 2, and the organic solvent was removed by sufficient heating to form a light-absorbing layer in this way.

[0267] On the surface of the light-absorbing layer, SiO was alternately laminated by evaporation 2 and TiO 2 to form dielectric multilayer film 1C in this way.

[0268] The filter of Example 5 was manufactured in the above manner.

[0269] <Example 6>

[0270] On one main surface of the glass substrate (glass B without light-absorbing property), SiO was alternately laminated by evaporation 2 and TiO 2 to form dielectric multilayer film 2C in this way.

[0271] On the other main surface of the glass substrate, a resin solution was coated with the same composition as the light absorption layer 1, and the organic solvent was removed by sufficient heating, thereby forming a light absorption layer.

[0272] On the surface of the light absorption layer, SiO was alternately laminated by vapor deposition 2 and TiO 2 , thereby forming a dielectric multilayer film 1D.

[0273] The filter of Example 6 was manufactured in the above manner.

[0274] <Example 7>

[0275] On one main surface of a glass substrate (glass B without light absorption), SiO was alternately laminated by vapor deposition 2 and TiO 2 , thereby forming a dielectric multilayer film 2D.

[0276] On the other main surface of the glass substrate, a resin solution was coated with the same composition as the light absorption layer 1, and the organic solvent was removed by sufficient heating, thereby forming a light absorption layer.

[0277] On the surface of the light absorption layer, SiO was alternately laminated by vapor deposition 2 and TiO 2 , thereby forming a dielectric multilayer film 1E.

[0278] The filter of Example 7 was manufactured in the above manner.

[0279] <Example 8>

[0280] On one main surface of a glass substrate (glass B without light absorption), SiO was alternately laminated by vapor deposition 2 and TiO 2 , thereby forming a dielectric multilayer film 2E.

[0281] On the other main surface of the glass substrate, a resin solution was coated with the same composition as the light absorption layer 1, and the organic solvent was removed by sufficient heating, thereby forming a light absorption layer.

[0282] On the surface of the light absorption layer, SiO was alternately laminated by vapor deposition 2 and TiO 2 , thereby forming a dielectric multilayer film 1C.

[0283] The filter of Example 8 was manufactured in the above manner.

[0284] <Example 9>

[0285] A light absorption layer was formed with the same composition as the light absorption layer 3 to replace the light absorption layer 1, and except for this, the same operations as in Example 2 were performed, thereby manufacturing the filter of Example 9.

[0286] The configurations of the dielectric multilayer films 1A, 1B, 2A, and 3A are shown in Tables 2 to 4 below. In addition, the order of the numbers (No.) corresponds to the stacking order.

[0287] [Table 2]

[0288]

[0289] [Table 3]

[0290]

[0291] [Table 4]

[0292]

[0293] For each of the filters obtained in the above manner, the spectral transmittance curve at an incident angle of 0 degrees and the spectral reflectance curves at incident angles of 5 degrees and 30 degrees were measured in the wavelength range of 350 nm to 1200 nm using an ultraviolet-visible spectrophotometer.

[0294] Based on the obtained spectral characteristic data, each characteristic shown in Table 6 below was calculated.

[0295] In addition, the spectral transmittance and reflectance curves of the filters of Example 3 and Example 5 are shown in Figures 5 to 8 respectively.

[0296] It should be noted that Examples 1 to 4 are examples, and Examples 5 to 9 are comparative examples.

[0297] [Table 5]

[0298]

[0299] [Table 6]

[0300]

[0301] Based on the above results, in the filters of Examples 1 to 4, S1 （0） / S2 （0） and S1 （30） / S2 （30） are both above a certain value. Therefore, even at a high incident angle, the transmittance in the visible light region is maintained high, and the transmittance in the region of the wavelength 700 nm to 1000 nm to be shielded is suppressed low. In addition, S3 （0） / S2 （0） and S3 （30） / S2 （30）They are all above a certain value. Therefore, even at a high incident angle, the transmittance in the near-infrared light region with a wavelength of 1000 nm to 1300 nm is maintained high, and the transmittance in the region with a wavelength of 700 nm to 1000 nm that is desired to be shielded is suppressed low.

[0302] In addition, from the comparison between Example 1 and Example 2, and the comparison between Example 3 and Example 4, it can be seen that by using light-absorbing glass as the glass substrate, S1 （0） / S2 （0） and the absolute value of the difference between S1 （30） / S2 （30） and the absolute value of the difference between S3 （0） / S2 （0） and S3 （30） / S2 （30） become smaller, suppressing the change in spectral characteristics caused by the incident angle.

[0303] Furthermore, from the comparison between Example 1 and Example 3, and the comparison between Example 2 and Example 4, it can be seen that by providing the dielectric multilayer film 3 between the substrate and the light-absorbing layer, it is also possible to reduce the absolute value of the difference between S1 （0） / S2 （0） and S1 （30） / S2 （30） and the absolute value of the difference between S3 （0） / S2 （0） and S3 （30） / S2 （30） and the absolute value of the difference between S3

[0304] On the other hand, in the filter of Examples 5 to 7, S1 （0） / S2 （0） , S1 （30） / S2 （30） , and S3 （0） / S2 （0） , S3 （30） / S2 （30） are less than 40. This is because the wavelengths for maintaining high transmittance in the near-infrared light region are different.

[0305] In the filter of Example 8, the film thickness of the dielectric multilayer film 1 laminated on the light-absorbing layer side is small. Therefore, in order to ensure light-shielding properties, it is necessary to increase the film thickness of the other dielectric multilayer film 2, and the spectral characteristics are easily affected by the incident angle.

[0306] In addition, in the filter of Example 9, the glass transition temperature of the resin in the light-absorbing layer is low. Therefore, it is easily affected by the stress of the dielectric multilayer film 1 laminated on the light-absorbing layer.

[0307] <Heat resistance test>

[0308] The filter obtained in Example 3 and Example 9 was cut into a size of 5 mm square by blade cutting. The obtained test piece was heated on a hot plate at 200 °C for 10 minutes, and then the appearance was confirmed using a metallurgical microscope.

[0309] In Example 3 where a polyimide resin having a glass transition temperature of 320 °C was used in the light absorption layer, the appearance of the filter did not change.

[0310] On the other hand, in Example 9 where a polyester resin having a glass transition temperature of 150 °C was used in the light absorption layer, wrinkles were generated on the light absorption layer. It is considered that this is because the resin becomes soft at high temperatures, and if the resin has a low glass transition temperature, it deforms due to the stress of the dielectric multilayer film.

[0311] The present invention has been described in detail with reference to specific embodiments, but it is obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Japanese Patent Application No. 2023-210430) filed on December 13, 2023, the content of which is incorporated herein by reference.

[0312] Industrial Applicability

[0313] The filter of the present embodiment has excellent transmittance of visible light and specific near-infrared light even at high incident angles, and also has excellent shielding properties for near-infrared light other than that. It is useful in applications such as imaging devices such as cameras and sensors for conveyors, which have been recently improved in performance.

Claims

1. A filter, comprising a dielectric multilayer film (1), a light absorption layer, a glass substrate and a dielectric multilayer film (2) in sequence, wherein: The thickness of the dielectric multilayer film (1) is greater than 1500 nm. The light absorbing layer comprises a near infrared absorbing pigment and a resin having a glass transition temperature of 200° C. or higher. The filter satisfies the following spectral characteristics (i-1) and (i-2): (i-1) The total transmittance of light with a wavelength of 450 nm to 700 nm at an incident angle of 0 degrees is defined as S1. （0） The sum of the transmittance of light with a wavelength of 700nm to 1000nm is set to S2 （0） The sum of the transmittance of light with a wavelength of 1000nm to 1300nm is S3 （0） hour, S1 （0） / S2 （0） ≥40 and S3 （0） / S2 （0） ≥40; (i-2) The total transmittance of light with a wavelength of 450 nm to 700 nm at an incident angle of 30 degrees is defined as S1. （30） The sum of the transmittance of light with a wavelength of 700nm to 1000nm is set to S2 （30） The sum of the transmittance of light with a wavelength of 1000nm to 1300nm is S3 （30） hour, S1 （30） / S2 （30） ≥40 and S3 （30） / S2 （30） ≥40.

2. The optical filter according to claim 1, wherein: The filter satisfies the following spectral characteristics (i-3): (i-3) The absolute value of the difference between the wavelength at which the transmittance of light with a wavelength of 550 nm to 750 nm is 50% at an incident angle of 0 degrees and the wavelength at which the transmittance of light with a wavelength of 950 nm to 1150 nm is 50% at an incident angle of 0 degrees is 300 nm or more.

3. The optical filter according to claim 1, wherein: The filter satisfies the following spectral characteristics (i-4) and (i-5): (i-4) S1 （0） / S2 （0） With the S1 （30） / S2 （30） The absolute value of the difference is less than 200; (i-5) S3 （0） / S2 （0） With the S3 （30） / S2 （30） The absolute value of the difference is less than 200.

4. The optical filter according to claim 1, wherein: The filter satisfies all of the following spectral characteristics (i-6) to (i-8): (i-6) When the dielectric multilayer film (1) side is the incident direction, the wavelength IR at which the reflectivity of light at an incident angle of 5 degrees is 50% 50S In the range of 650nm~830nm; (i-7) When the dielectric multilayer film (1) side is the incident direction, the wavelength IR at which the reflectivity of light at an incident angle of 5 degrees is 50% 50L In the range of 950nm~1200nm; (i-8) Wavelength IR 50S With the wavelength IR 50L The absolute value of the difference is greater than 230 nm.

5. The optical filter according to claim 1, wherein: The filter satisfies the following spectral characteristics (i-9) to (i-10): (i-9) When the dielectric multilayer film (1) side is taken as the incident direction, the average reflectivity of light with a wavelength of 450 nm to 600 nm at an incident angle of 5 degrees is 5% or less; (i-10) When the dielectric multilayer film (2) side is the incident direction, the average reflectivity of light with a wavelength of 450 nm to 600 nm at an incident angle of 5 degrees is 5% or less.

6. The optical filter according to claim 1, wherein: The filter satisfies the following spectral characteristics (i-11): (i-11) The absolute value of the difference between the average reflectivity of light with a wavelength of 450nm to 600nm at an incident angle of 5 degrees when the dielectric multilayer film (1) side is the incident direction and the average reflectivity of light with a wavelength of 450nm to 600nm at an incident angle of 5 degrees when the dielectric multilayer film 2 side is the incident direction is less than 0.5%.

7. The optical filter according to claim 3, wherein: The optical filter comprises a dielectric multilayer film (3) between the light absorbing layer and the glass substrate, and The filter satisfies: In the spectral characteristics (i-4), the S1 （0） / S2 （0） With the S1 （30） / S2 （30） The absolute value of the difference is less than 130; In the spectral characteristics (i-5), the S3 （0） / S2 （0） With the S3 （30） / S2 （30） The absolute value of the difference is less than 130.

8. The optical filter according to claim 3, wherein: The glass substrate is a glass substrate containing ytterbium, and The filter satisfies: In the spectral characteristics (i-4), the S1 （0） / S2 （0） With the S1 （30） / S2 （30） The absolute value of the difference is less than 130; In the spectral characteristics (i-5), the S3 （0） / S2 （0） With the S3 （30） / S2 （30） The absolute value of the difference is less than 130.

9. The optical filter according to claim 1, wherein: The resin in the light absorbing layer includes a polyimide resin.

10. The optical filter according to claim 1, wherein: The near infrared absorbing pigment in the light absorbing layer includes: a pigment having a maximum absorption wavelength in a range of wavelengths greater than or equal to 700 nm and less than 730 nm; a pigment having a maximum absorption wavelength in a range of wavelengths greater than or equal to 730 nm and less than 760 nm; And a pigment having a maximum absorption wavelength in a range of wavelengths greater than or equal to 760 nm and less than 800 nm.

11. The optical filter according to claim 1, wherein: The thickness of the light absorbing layer is less than 2 μm, and The content of the near-infrared absorbing pigment in the light absorbing layer is 10% by mass or more.

12. An imaging device, wherein: The imaging device comprises the optical filter according to any one of claims 1 to 11.

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