Optical filter

Abstract

To provide an optical filter which is excellent in transmissivity of visible light and a specific near-infrared ray and a shielding property relative to other near-infrared rays even at a high incident angle.SOLUTION: An optical filter includes a dielectric multilayer film 1, a light absorption layer, a glass substrate, and a dielectric multilayer film 2 in this order. The dielectric multilayer film 1 has a thickness of 1500 nm or more. The light adsorption layer contains a resin with a glass transition temperature of 200°C or more and a near-infrared absorption pigment. The optical filter satisfies specific spectral characteristics (i-1) and (i-2).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an optical filter.

Background Art

[0002] Imaging devices using solid-state imaging devices have expanded their applications to devices that image day and night, such as surveillance cameras and in-vehicle cameras. In such devices, it is necessary to acquire a (color) image based on visible light and a (black-and-white) image based on infrared light, respectively.

[0003] For this reason, the use of an optical filter, so-called a dual-bandpass filter, having a function of selectively transmitting specific near-infrared light in addition to a near-infrared cut filter function for transmitting visible light and faithfully reproducing an image based on the visible light has been studied.

[0004] Patent Document 1 describes an optical filter that combines a dielectric multilayer film and a resin substrate containing a near-infrared absorbing dye, and transmits visible light and near-infrared light around 850 nm and blocks other light. Patent Document 2 describes an optical filter that combines a dielectric multilayer film and a resin substrate containing a near-infrared absorbing dye, and transmits visible light and near-infrared light around 940 nm and blocks other light.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In recent years, with the diversification of the sensing region in the imaging field, laser light including a part of the near-infrared light region after 1000 nm, which has a different wavelength region from those of Patent Documents 1 and 2 above, is used. Therefore, an optical filter that can transmit the near-infrared light in such a sensing region and block other near-infrared light that becomes noise is required.

[0007] In addition, for an optical filter having a dielectric multilayer film, since the optical film thickness of the dielectric multilayer film changes depending on the incident angle of light, the change in the spectral transmittance curve due to the incident angle is a problem. For example, when the incident angle of light increases, the reflection characteristic shifts to the short-wavelength side, and as a result, there is a possibility that the reflection characteristic deteriorates in the region that is originally desired to be shielded. Such a phenomenon is more likely to occur as the incident angle is larger. When such a filter is used, the spectral sensitivity of the solid-state imaging device may be affected by the incident angle. In recent years, with the trend of reducing the height of camera modules, use under high incident angle conditions is assumed, and thus an optical filter that is less affected by the incident angle is required.

[0008] An object of the present invention is to provide an optical filter that is excellent in the transmittance of visible light and specific near-infrared light even at a high incident angle and is excellent in the shielding property of other near-infrared light.

Means for Solving the Problems

[0009] The present invention provides an optical filter having the following configuration. 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, wherein the dielectric multilayer film 1 has a thickness of 1500 nm or more, the light absorption layer contains a resin having a glass transition temperature of 200°C or higher and a near-infrared absorbing dye, and the optical filter satisfies the following spectral characteristics (i-1) and (i-2). (i-1) Let the sum of the transmittances of light with wavelengths of 450 to 700 nm at an incident angle of 0 degrees be S1 (0) and the sum of the transmittances of light with wavelengths of 700 to 1000 nm be S2 (0)Let the sum of the transmittances of light with wavelengths from 1000 to 1300 nm be S3 (0) When S1 (0) / S2 (0) ≥ 40, and S3 (0) / S2 (0) ≥ 40 (i - 2) Let the sum of the transmittances of light with wavelengths from 450 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 to 1000 nm be S2 (30) Let the sum of the transmittances of light with wavelengths from 1000 to 1300 nm be S3 (30) When S1 (30) / S2 (30) ≥ 40, and S3 (30) / S2 (30) ≥ 40

Advantages of the Invention

[0010] According to the present invention, an optical filter excellent in the transmittance of visible light and specific near-infrared light and excellent in the shielding property of other near-infrared light can be provided even at a high incident angle. The optical filter of the present invention is an optical filter that is particularly excellent in the transmittance of the near-infrared light region of 1000 to 1300 nm including the sensing wavelength region even at a high incident angle and is hardly affected by the incident angle.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

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

[0013] In this specification, the transmittance of glass, the transmittance of the light absorption layer including the case where the dye is contained in the resin, the transmittance measured by dissolving the dye in a solvent such as dichloromethane, the transmittance of the dielectric multilayer film, and the spectral transmittance of the optical 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".

[0014] In this specification, for a specific wavelength range, when the transmittance is, for example, 90% or more, it means that the transmittance does not fall below 90% in the entire wavelength region, that is, the minimum transmittance in that wavelength region is 90% or more. Similarly, for a specific wavelength range, when the transmittance is, for example, 1% or less, it means that the transmittance does not exceed 1% in the entire wavelength region, that is, the maximum transmittance in that wavelength region is 1% or less. The average transmittance in a specific wavelength range is the arithmetic mean of the transmittances every 1 nm in that wavelength range. The spectral characteristics can be measured using an ultraviolet-visible spectrophotometer. In this specification, the "~" representing a numerical range includes the upper and lower limits.

[0015] <Optical Filter> An optical filter according to an embodiment of the present invention (hereinafter also referred to as "this filter") is 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, wherein the dielectric multilayer film 1 has a thickness of 1500 nm or more, and the light absorption layer contains a resin having a glass transition temperature of 200 °C or more and a near-infrared absorbing dye. Due to the reflection characteristics of the dielectric multilayer film and the absorption characteristics of the light absorption layer, excellent transmittance in the visible light region and a specific near-infrared light region and excellent shielding properties in other near-infrared light regions can be realized for the entire optical filter.

[0016] A configuration example of this filter will be described with reference to the drawings. FIGS. 1 to 2 are cross-sectional views schematically showing an example of an optical filter according to an embodiment.

[0017] The optical filter 10 shown in FIG. 1 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 this order.

[0018] The optical filter 10 shown in FIG. 2 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 this order.

[0019] This filter satisfies the following spectral characteristics (i-1) and (i-2). (i-1) Let the sum of the transmittances of light with wavelengths of 450 to 700 nm at an incident angle of 0 degrees be S1 (0) and the sum of the transmittances of light with wavelengths of 700 to 1000 nm be S2 (0) and the sum of the transmittances of light with wavelengths of 1000 to 1300 nm be S3 (0) When this is done, S1 (0) / S2 (0) ≧ 40, and S3 (0) / S2 (0) ≧ 40 (i-2) Let the sum of the transmittances of light with wavelengths of 450 to 700 nm at an incident angle of 30 degrees be S1 (30) and the sum of the transmittances of light with wavelengths of 700 to 1000 nm be S2 (30) and the sum of the transmittances of light with wavelengths of 1000 to 1300 nm be S3 (30)When S1 (30) / S2 (30) ≥ 40, and S3 (30) / S2 (30) ≥ 40

[0020] S1 (0) and S1 (30) correspond to the transmittance of visible light at incident angles of 0 degrees and 30 degrees, respectively. S2 (0) and S2 (30) correspond to the transmittance of light with wavelengths of 700 to 1000 nm at incident angles of 0 degrees and 30 degrees, respectively. S3 (0) and S3 (30) correspond to the transmittance of light with wavelengths of 1000 to 1300 nm at incident angles of 0 degrees and 30 degrees, respectively. S1 is the wavelength region of the camera module, and S3 is the sensing region. The larger the light transmittance, the larger the amount of light that can be captured, and higher sensing is possible. On the other hand, since S2 is a light-shielding region, it is preferably smaller from the viewpoint of reducing noise that causes a decrease in sensor sensitivity. This filter that satisfies the spectral characteristics (i-1) to (i-2) is a dual-bandpass filter with an excellent balance between the transmission region and the light-shielding region even at a high incident angle. The sum of the transmittances of S1 to S3 can be obtained by summing the transmittances (%) for each 1 nm wavelength.

[0021] Preferably, S1 (0) / S2 (0) ≥ 100, and S3 (0) / S2 (0) ≥ 100. Preferably, S1 (30) / S2 (30) ≥ 200, and S3 (30) / S2 (30) ≥ 200. In order to satisfy the spectral characteristics (i-1) to (i-2), for example, the light-shielding region of S2 can be shielded by the absorption characteristics of a near-infrared absorbing dye or a light-absorbing glass whose spectral characteristics are not affected by the incident angle.

[0022] This filter preferably satisfies the following spectral characteristic (i-3). (i-3) The absolute value of the difference between the wavelength at which the transmittance of light with a wavelength of 550 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 to 1150 nm is 50% at an incident angle of 0 degrees is 300 nm or more

[0023] 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. It is more preferable that the absolute value is 350 nm or more. In order to satisfy the spectral characteristic (i-3), in particular, in order to sufficiently separate the position of the near-infrared light transmission region S3 from the visible light transmission region S1, for example, by combining the reflection characteristics of both the dielectric multilayer films 1 and 2, combining near-infrared absorbing dyes with different maximum absorption wavelengths, using light-absorbing glass, etc., a plurality of characteristics are combined to perform light shielding in a wide region.

[0024] This filter preferably satisfies the following spectral characteristics (i-4) and (i-5). (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 (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 Satisfying the spectral characteristic (i-4) means that the amount of visible light transmitted and the amount of light transmitted through the light-shielding region of near-infrared light do not change even when the incident angle increases. Satisfying the spectral characteristic (i-5) means that the amount of light with a wavelength of 1000 to 1300 nm transmitted and the amount of light transmitted through the light-shielding region of near-infrared light do not change even when the incident angle increases. That is, it means that the function as a dual-band pass filter is less affected by the incident angle. The absolute value of the difference in the spectral characteristics (i-4) is more preferably 130 or less, and even more preferably 120 or less. The absolute value of the difference in the spectral characteristics (i-5) is more preferably 130 or less, and even more preferably 120 or less. In order to satisfy the spectral characteristics (i-4) and (i-5), for example, the light shielding property due to the reflection characteristics in the light shielding region of near-infrared light is borne by both the dielectric multilayer film 1 and the dielectric multilayer film 2, providing a dielectric multilayer film 3 described later between the light absorption layer and the glass substrate, and using light absorption glass as the glass substrate.

[0025] This filter preferably satisfies all of the following spectral characteristics (i-6) to (i-8). (i-6) When the incident direction is the side of the dielectric multilayer film 1, 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 to 830 nm (i-7) When the incident direction is the side of the dielectric multilayer film 1, 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 to 1200 nm (i-8) The wavelength IR 50S and the wavelength IR 50L the absolute value of the difference between them is 230 nm or more The spectral characteristics (i-6) to (i-8) substantially represent the reflection characteristics of the dielectric multilayer film 1 on the light absorption layer side, meaning that the dielectric multilayer film 1 has reflection characteristics between the visible light region of 650 to 830 nm and the near-infrared light region of 950 to 1200 nm. Wavelength IR 50S is more preferably in the range of 700 to 780 nm, wavelength IR 50L is more preferably in the range of 970 to 1150 nm, wavelength IR 50S and wavelength IR 50L the absolute value of the difference between them is more preferably 240 nm or more. To satisfy the spectral characteristics (i-6) to (i-8), for example, providing a dielectric multilayer film 1 designed to satisfy the above reflection characteristics can be mentioned.

[0026] This filter preferably satisfies all of the following spectral characteristics (i-9) to (i-10). (i-9) When the incident direction is from the side of the dielectric multilayer film 1, the average reflectance of light with a wavelength of 450 to 600 nm at an incident angle of 5 degrees is 5% or less (i-10) When the incident direction is from the side of the dielectric multilayer film 2, the average reflectance of light with a wavelength of 450 to 600 nm at an incident angle of 5 degrees is 5% or less The spectral characteristic (i-9) substantially represents the reflection characteristic of the dielectric multilayer film 1 in the visible light region, and the spectral characteristic (i-10) substantially represents the reflection characteristic of the dielectric multilayer film 2 in the visible light region. Both mean that the reflection characteristic with respect to visible light is small. The average reflectance in the spectral characteristic (i-9) is more preferably 4.8% or less. The average reflectance in the spectral characteristic (i-10) is more preferably 4.8% or less. To satisfy the spectral characteristics (i-9) to (i-10), for example, it may include the dielectric multilayer film 1 and the dielectric multilayer film 2 designed to satisfy the above reflection characteristics.

[0027] This filter preferably satisfies all of the following spectral characteristics (i-11). (i-11) The absolute value of the difference between the average reflectance of light with a wavelength of 450 to 600 nm at an incident angle of 5 degrees when the incident direction is from the side of the dielectric multilayer film 1 and the average reflectance of light with a wavelength of 450 to 600 nm at an incident angle of 5 degrees when the incident direction is from the side of the dielectric multilayer film 2 is 0.5% or less The spectral characteristic (i-11) corresponds to the difference in the reflection characteristics of the dielectric multilayer film 1 and the dielectric multilayer film 2 in the visible light region, and satisfying the above range means that the reflection characteristics are about the same. The absolute value of the difference in the spectral characteristic (i-11) is more preferably 0.4% or less. To satisfy the spectral characteristic (i-11), for example, it may include the dielectric multilayer film 1 and the dielectric multilayer film 2 designed to satisfy the above reflection characteristics.

[0028] <Glass substrate> This filter includes a glass substrate. Since this filter includes at least two dielectric multilayer films, a material with high rigidity such as glass is preferred as the base material rather than a resin film. This can reduce warping during film formation.

[0029] As the glass substrate, a transparent glass substrate or a light-absorbing glass substrate may be used, but a light-absorbing glass substrate is preferred. The reflection characteristics of the dielectric multilayer film shift the light-shielding region depending on the incident angle of light. In contrast, the absorption characteristics of the light-absorbing glass substrate have a small shift in the light-shielding region due to the incident angle of light and can exhibit high light-shielding properties even at high incident angles.

[0030] As the light-absorbing glass, glass containing ytterbium is preferred. Glass containing ytterbium has the property of absorbing the near-infrared light region with a wavelength of 900 to 1000 nm. Furthermore, since the waveform of the absorption band is steep, it has excellent permeability in regions other than the maximum absorption wavelength region. Therefore, it has excellent permeability in the visible light region, from visible light to near-infrared light regions with a wavelength of about 800 nm and longer than 1000 nm.

[0031] Hereinafter, each component that can constitute the glass and its preferred content (expressed in mol% based on oxides) will be described. In this specification, unless otherwise specified, the content of each component and the total content are expressed in mol% based on oxides.

[0032] Yb2O3 is a component for efficiently absorbing light near a wavelength of 900 to 1000 nm, particularly light with a wavelength of 940 nm, and reducing the transmittance. If the content of Yb2O3 in the glass of this embodiment is 20% or more, the effect can be sufficiently obtained. If it is 60% or less, problems such as deterioration of the devitrification property of the glass, deterioration of the meltability, and generation of stray light due to fluorescence are less likely to occur. Therefore, the content of Yb2O3 is preferably 20 to 60%, more preferably 25 to 60%, still more preferably 30 to 60%, even more preferably 35 to 60%, particularly preferably more than 40% and 60% or less, and most preferably 45% to 60%.

[0033] SiO2 is the main component forming the glass and is a component for increasing the devitrification resistance of the glass and the viscosity with respect to the liquidus temperature. If the content of SiO2 in the glass of the present embodiment is 0.1% or more, problems such as the glass becoming unstable, the weather resistance deteriorating, and veins occurring in the glass are less likely to occur. If the content of SiO2 is 50% or less, problems such as the meltability of the glass deteriorating are less likely to occur. Therefore, the content of SiO2 is preferably 0.1 to 50%, more preferably 0.1 to 40%, still more preferably 0.1 to 30%, even more preferably 0.1 to 20%, particularly preferably 0.1 to 10%, and most preferably 0.1% to 9%.

[0034] B2O3 is the main component forming the glass and is a component for increasing the devitrification resistance of the glass and the viscosity with respect to the liquidus temperature. If the content of B2O3 in the glass of the present embodiment is 15% or more, problems such as the glass becoming unstable are less likely to occur. If the content of B2O3 is 40% or less, problems such as the weather resistance of the glass deteriorating and veins occurring in the glass are less likely to occur. Therefore, the content of B2O3 is preferably 15 to 40%, more preferably 15 to 38%, still more preferably 15 to 36%, even more preferably 15 to 34%, particularly preferably 15 to 32%, and most preferably 15 to 30%.

[0035] From the viewpoint of obtaining a stable glass, it is preferable that the light-absorbing glass contains at least one of SiO2 and B2O3. The total content of the above components is preferably more than 65% from the viewpoint that problems such as the glass becoming unstable are less likely to occur, and is preferably 80% or less from the viewpoint that problems such as the meltability of the glass deteriorating are less likely to occur. Therefore, it is more preferably more than 65% and 79% or less, still more preferably more than 65% and 78% or less, even more preferably more than 65% and 77% or less, particularly preferably more than 65% and 76% or less, and most preferably more than 65% and 75% or less.

[0036] P2O5 is a component for improving the meltability and stability of glass. In the glass of this embodiment, the content of P2O5 is preferably 0 to 15%. If the content of P2O5 is 15% or less, problems such as deterioration of the weather resistance of the glass, phase separation of the glass, and generation of veins in the glass are less likely to occur. The content of P2O5 is more preferably 1 to 13%, still more preferably 2 to 12%, even more preferably 3 to 11%, and most preferably 4 to 10%.

[0037] GeO2 is a component for increasing the devitrification resistance of glass and the viscosity with respect to the liquidus temperature. In the glass of this embodiment, the content of GeO2 is preferably 0 to 15%. If the content of GeO2 is 15% or less, problems such as deterioration of the meltability of the glass are less likely to occur. The content of GeO2 is more preferably 0 to 13%, still more preferably 0 to 11%, even more preferably 0 to 9%, and most preferably 0 to 7%.

[0038] Ga2O3 is a component for increasing the Young's modulus of glass and improving the meltability and stability. In the glass of this embodiment, the content of Ga2O3 is preferably 0 to 30%. If the content of Ga2O3 is 30% or less, problems such as deterioration of the devitrification resistance of the glass and an increase in reflectivity with the generation of stray light due to reflected light are less likely to occur. The content of Ga2O3 is more preferably 0.5 to 28%, still more preferably 1 to 26%, even more preferably 2 to 24%, and most preferably 3 to 22%.

[0039] ZrO2 is a component for increasing the Young's modulus of glass and increasing the viscosity with respect to the liquidus temperature of the glass. In the glass of this embodiment, the content of ZrO2 is preferably 0 to 7%. If the content of ZrO2 is 7% or less, problems such as deterioration of the devitrification resistance of the glass and deterioration of the meltability are less likely to occur. The content of ZrO2 is more preferably 0 to 6%, still more preferably 0 to 5%, even more preferably 0 to 4%, and most preferably 0 to 3%.

[0040] La2O3 is a component for increasing the Young's modulus of the glass and improving the meltability. In the glass of the present embodiment, the content of La2O3 is preferably 0.1 to 20%. If the content of La2O3 is 0.1% or more, the effect can be sufficiently obtained. If it is 20% or less, problems such as deterioration of the devitrification resistance of the glass, an increase in the reflectance, and generation of stray light due to the reflected light are less likely to occur. The content of La2O3 is more preferably 0.5 to 19%, still more preferably 1 to 18%, even more preferably 2 to 17%, and most preferably 2 to 16%.

[0041] Al2O3 is a component for increasing the Young's modulus of the glass and lowering the refractive index of the glass. In the glass of the present embodiment, the content of Al2O3 is preferably 0.1 to 20%. If the content of Al2O3 is 0.1% or more, the effect can be sufficiently obtained. If it is 20% or less, problems such as deterioration of the devitrification resistance of the glass, an increase in the reflectance, and generation of stray light due to the reflected light are less likely to occur. More preferably, it is 0.1 to 18%, still more preferably 0.1 to 15%, even more preferably 0.1 to 13%, and most preferably 0.1 to 11%.

[0042] The ratio of the total amount of the Al2O3, GeO2, Ga2O3, and P2O5 components to the total content of the SiO2 and B2O3 components, that is, (total content of Al2O3, GeO2, Ga2O3 and P2O5) / (total content of SiO2 and B2O3), is preferably less than 0.1 from the viewpoint of vitrifying the glass without devitrifying the glass containing the Yb component.

[0043] As the light-absorbing glass, within a range not impairing the object of the present invention, it may contain alkali metal oxides, alkaline earth metal oxides, Sb2O3, Cl, F, and other components.

[0044] As for the glass substrate in this filter, when it is used in an optical filter, it is desirable to lower the reflectivity of the glass in order to prevent stray light caused by reflected light on the glass surface. The reflectivity of the glass is determined by the refractive index, and typically, it is preferable that the refractive index at a wavelength of 588 nm is 1.700 to 1.900.

[0045] When used as a glass substrate for a so-called dual-band pass filter having a function of selectively transmitting visible light and specific near-infrared light, the thickness is usually used at 3 mm or less, and often at 2 mm or less, more preferably 1 mm or less, still more preferably 0.5 mm or less, and even more preferably 0.3 mm or less from the viewpoint of reducing the weight of the component. Also, from the viewpoint of ensuring the strength of the glass, 0.05 mm or more is preferable.

[0046] The glass substrate in this filter can be produced, for example, as follows. First, raw materials are weighed and mixed so as to be within the above composition range (mixing step). This raw material mixture is placed in a platinum crucible and heated and melted at a temperature of 1200 to 1650 °C in an electric furnace (melting step). After sufficient stirring and clarification, it is poured into a mold, cut and polished to form a flat plate of a predetermined thickness (forming step).

[0047] In the melting step of the above manufacturing method, it is preferable that the highest temperature of the glass during glass melting is 1650 °C or lower. If the highest temperature of the glass during glass melting is below the above temperature, problems such as the glass crystallizing or unmelted foreign substances occurring in the glass are less likely to occur. The above temperature is more preferably 1625 °C or lower, and still more preferably 1600 °C or lower.

[0048] Also, if the temperature in the above melting step is too low, problems such as devitrification occurring during melting or taking a long time to melt off may occur, so it is preferably 1300 °C or higher, more preferably 1350 °C or higher.

[0049] <Light absorption layer> This filter includes a light absorption layer containing a resin with a glass transition temperature of 200°C or higher and a near-infrared absorbing dye (NIR dye). Thereby, the region not shielded by the reflection characteristics of the dielectric multilayer film can be compensated by the absorption characteristics not affected by the incident angle. Further, even when a strong stress is applied to the dielectric multilayer film 1 on the light absorption layer, the resin is difficult to deform because the glass transition temperature of the resin is sufficiently high.

[0050] The light absorption layer preferably satisfies all of the following spectral characteristics (ii-1) to (ii-2). (ii-1) The average transmittance of light with a wavelength of 450 to 600 nm is 70% or more (ii-2) The average transmittance of light with a wavelength of 700 to 900 nm is 60% or less

[0051] As the near-infrared absorbing dye, from the viewpoint of being able to widely absorb the near-infrared region while maintaining the permeability in the visible light region, preferably two or more dyes having different maximum absorption wavelengths and in the region of 680 to 800 nm, more preferably three are combined. In particular, it preferably contains a dye having a maximum absorption wavelength of 700 nm or more and less than 730 nm, a dye having a maximum absorption wavelength of 730 nm or more and less than 760 nm, and a dye having a maximum absorption wavelength of 760 nm or more and less than 800 nm as the near-infrared absorbing dye.

[0052] As the NIR dye, at least one selected from the group consisting of squarylium dyes, cyanine dyes, phthalocyanine dyes, naphthalocyanine dyes, dithiol metal complex dyes, azo dyes, polymethine dyes, phthalide dyes, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, pyrylium dyes, thiopyrylium dyes, croconium dyes, tetra-dehydroocorin dyes, triphenylmethane dyes, aminium dyes and diimonium dyes is preferable.

[0053] As the NIR dye, it is preferable to contain at least one dye selected from squarylium dyes, phthalocyanine dyes, and cyanine dyes. Among these NIR dyes, squarylium dyes and cyanine dyes are preferable from the spectroscopic viewpoint, and phthalocyanine dyes are preferable from the viewpoint of durability.

[0054] In order to obtain desired optical properties, the content of the NIR dye in the light absorption layer is preferably 10% by mass or more. Also, if the content of the NIR dye is too high, the physical properties of the light absorption layer will be impaired (especially because the glass transition point decreases), so it is preferably 20% by mass or less, and more preferably 15% by mass or less. Even when the content of the NIR dye is 10% by mass or more, the light absorption layer is less likely to undergo thermal deformation because the glass transition temperature of the resin is sufficiently high. When combining two or more compounds, the above content is the sum of each compound.

[0055] The light absorption layer may contain other dyes in addition to the above NIR dye. As the other dye, a dye having a maximum absorption wavelength in the range of 370 to 440 nm in the resin (UV dye) is preferable. Thereby, the near-ultraviolet light region can be efficiently shielded.

[0056] Examples of the UV dye 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, triazole dyes, and the like. Among these, merocyanine dyes are particularly preferable. Also, one kind may be used alone, or two or more kinds may be used in combination.

[0057] As the resin in the light absorption layer of this filter, a resin having a glass transition temperature of 200°C or higher is used from the viewpoint of preventing deformation as described above. Also, from the viewpoint of not affecting the spectroscopic characteristics, it is preferably a transparent resin. 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 preferable. The glass transition temperature of the resin is preferably 250°C or higher, and more preferably 300°C or higher.

[0058] When using a plurality of compounds as NIR dyes and other dyes, they may be included in the same light absorption layer or in separate light absorption layers, respectively.

[0059] The light absorption layer can be formed by dissolving or dispersing a dye, a resin or a raw material component of the resin, and each component compounded as required in a solvent to prepare a coating solution, coating this on a support, drying it, and further curing it as required. The support may be a light absorption glass substrate or a peelable support used only when forming the light absorption layer. Also, the solvent may be a dispersion medium that can be stably dispersed or a solvent that can be dissolved.

[0060] Also, the coating solution may contain a surfactant for improving voids due to minute bubbles, dents due to adhesion of foreign substances, etc., and repelling in the drying process. Further, for coating the coating solution, for example, an immersion coating method, a cast coating method, a spin coating method, etc. can be used. Also, when the coating solution contains a raw material component of a transparent resin, a curing treatment such as heat curing or photocuring is further performed.

[0061] Also, the light absorption layer can be manufactured in film form by extrusion molding. This filter can be manufactured by laminating the obtained film-shaped absorption layer on a light absorption glass substrate and integrating them by thermocompression bonding or the like.

[0062] The light absorption layer may have one layer or two or more layers in the optical filter. When having two or more layers, each layer may have the same configuration or different configurations.

[0063] The thickness of the light absorption layer is preferably 5 μm or less from the viewpoints of coatability, in-plane film thickness distribution in the substrate after coating, and appearance quality, more preferably 2 μm or less from the viewpoint of reducing the thermal expansion amount of the resin, and preferably 0.5 μm or more from the viewpoint of expressing desired spectral characteristics at an appropriate dye concentration. When the optical filter has two or more light absorption layers, it is preferable that the total thickness of each light absorption layer is within the above range.

[0064] <Dielectric Multilayer Film> This filter includes 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. For the dielectric multilayer film, the larger the thickness, the easier it is to control the spectral characteristics. On the other hand, if it is too thick, stress is likely to occur and it becomes a cause of deformation. By providing the dielectric multilayer film at two locations, the role in controlling the spectral characteristics can be dispersed, and concentrating the thickness on one multilayer film can be avoided. Both the dielectric multilayer films 1 and 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 may be appropriately designed to further reflect light in a wavelength range other than near-infrared light, for example, near-ultraviolet light.

[0065] The dielectric multilayer film 1 preferably satisfies all of the following spectral characteristics (iii-1-1) to (iii-1-3). (iii-1-1) The average reflectance at an incident angle of 5 degrees for light with a wavelength of 450 to 600 nm is 2.0% or less (iii-1-2) The average reflectance at an incident angle of 5 degrees for light with a wavelength of 430 to 700 nm is 2.5% or less (iii-1-3) The average reflectance at an incident angle of 5 degrees for light with a wavelength of 1110 to 1200 nm is 5.0% or less By satisfying the above characteristics, in particular, an optical filter that satisfies the spectral characteristics (i-6) to (i-8) and the spectral characteristics (i-9) is easily obtained, which is preferable. Also, since the total sum S1 of the transmittance of visible light can be increased and the total sum S2 of the transmittance of light with a wavelength of 700 to 1000 nm can be decreased, for the S1 of the spectral characteristic (i-1) (0) / S2 (0) and for the S1 of the spectral characteristic (i-2) (30) / S2 (30) an optical filter that satisfies it is easily obtained.

[0066] The dielectric multilayer film 2 preferably satisfies all of the following spectral characteristics (iii-2-1) to (iii-2-3). (iii-2-1) The average reflectance at an incident angle of 5 degrees for light with a wavelength of 450 to 600 nm is 2.0% or more (iii-2-2) The average reflectance at an incident angle of 5 degrees for light with a wavelength of 430 to 700 nm is 2.5% or less (iii-2-3) The average reflectance at an incident angle of 5 degrees for light with a wavelength of 1110 to 1200 nm is 5.0% or less By satisfying the above characteristics, it is particularly preferable because an optical filter that satisfies the spectral characteristic (i-10) can be easily obtained.

[0067] This filter preferably includes a dielectric multilayer film 3 between the light absorption layer and the glass substrate. The use of three dielectric multilayer films enables more flexible control of the spectral characteristics. Specifically, S1 (0) / S2 (0) and S1 (30) / S2 (30) The absolute value of the difference between and S3 (0) / S2 (0) and S3 (30) / S2 (30) The absolute value of the difference between and can be made smaller, and an optical filter that satisfies the spectral characteristics (i-4) and (i-5) can be easily obtained.

[0068] The dielectric multilayer film is a laminate of dielectric films with different refractive indices. More specifically, 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) can be mentioned, and it is composed of a dielectric multilayer film in which two or more of these are laminated. By combining several types of dielectric films with different spectral characteristics when transmitting and selecting a desired wavelength band, the reflection characteristics can be adjusted.

[0069] The high refractive index material preferably has a refractive index at a wavelength of 500 nm of 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 Ta2O5, TiO2, TiO, and Nb2O5. Other commercially available products include OS50 (Ti3O5), OS10 (Ti4O7), OA500 (a mixture of Ta2O5 and ZrO2), OA600 (a mixture of Ta2O5 and TiO2) manufactured by Canon Optron Co., Ltd. Among these, TiO2 is preferable in terms of film formability, reproducibility in refractive index, stability, etc.

[0070] The medium refractive index material preferably has a refractive index at a wavelength of 500 nm of more than 1.5 and less than 1.8, more preferably 1.55 or more and less than 1.8. Examples of the medium refractive index material include ZrO2, Nb2O5, Al2O3, HfO2, OM-4, OM-6 (a mixture of Al2O3 and ZrO2), OA-100 sold by Canon Optron Co., Ltd., H4, M2 (aluminum lanthanum oxide) sold by Merck Co., Ltd., and the like. Among these, from the viewpoints of film formability, reproducibility in refractive index, stability, etc., compounds of the Al2O3 type or mixtures of Al2O3 and ZrO2 are preferred. Note that the medium refractive index film may be replaced with an equivalent film composed of a high refractive index film and a low refractive index film without using the above-mentioned medium refractive index material.

[0071] The low refractive index material preferably has a refractive index at a wavelength of 500 nm of 1.4 or more and 1.5 or less, more preferably 1.45 or more and 1.5 or less. Examples of the low refractive index material include, for example, SiO2, SiO x N y、 MgF2 and the like. Other commercially available products include S4F and S5F (a mixture of SiO2 and Al2O3) manufactured by Canon Optron Co., Ltd. Among these, SiO2 is preferred from the viewpoints of reproducibility in film formability, stability, economy, etc.

[0072] The film thickness (physical film thickness) of the dielectric multilayer film 1 is 1500 nm or more, more preferably 2000 nm or more, from the viewpoint of easily controlling the spectral characteristics, and is preferably 6000 nm or less from the viewpoints of productivity and suppression of reflection ripple in the visible light region.

[0073] 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 even more preferably 70 layers or less, from the viewpoints of productivity and feasibility.

[0074] The film thickness (physical film thickness) of the dielectric multilayer film 2 is preferably 1500 nm or more, more preferably 2000 nm or more, from the viewpoint of easily controlling the spectral characteristics, and is preferably 6000 nm or less from the viewpoints of productivity and suppression of reflection ripple in the visible light region.

[0075] 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 even more preferably 70 layers or less from the viewpoints of productivity and feasibility.

[0076] The film thickness (physical film thickness) of the dielectric multilayer film 3 is preferably 150 nm or more, more preferably 200 nm or more, from the viewpoint of easily controlling spectral characteristics, and is preferably 6000 nm or less from the viewpoints of productivity and suppressing reflection ripple in the visible light region.

[0077] 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 even more preferably 25 layers or less from the viewpoints of productivity and feasibility.

[0078] For forming the dielectric multilayer film, for example, vacuum film forming processes such as CVD method, sputtering method, vacuum evaporation method, and wet film forming processes such as spray method, dip method, etc. can be used.

[0079] This filter may include, as other components, for example, a component (layer) that provides absorption by inorganic fine particles or the like that controls the transmission and absorption of light in a specific wavelength range. Specific examples of the inorganic fine particles include ITO (Indium Tin Oxides), ATO (Antimony-doped Tin Oxides), cesium tungstate, lanthanum boride, etc. ITO fine particles and cesium tungstate fine particles can be used when such infrared light shielding property is required because they have a high visible light transmittance and light absorbency in a wide range of infrared wavelength regions exceeding 1200 nm.

[0080] <Imaging device> The imaging device according to an embodiment of the present invention preferably includes the optical filter according to the embodiment of the present invention. The imaging device preferably further includes a solid-state imaging device and an imaging lens. The optical filter according to the present embodiment can be used, for example, by being disposed between the imaging lens and the solid-state imaging device, or by being directly attached to the solid-state imaging device, the imaging lens, etc. of the imaging device via an adhesive layer. By providing this filter, which has excellent transmittance for visible light and specific near-infrared light, has shielding properties for specific near-infrared light, and has a spectral curve that is difficult to shift even at a high incident angle, an imaging device with excellent color reproducibility for light at a high incident angle can be obtained.

[0081] When mounting the optical filter on the imaging device, it is usually preferable to place the dielectric multilayer film 2 (substrate side) on the lens side and the dielectric multilayer film 1 (light absorption layer side) on the sensor side.

[0082] As described above, the following optical filters and the like are disclosed in this specification. [1] 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, wherein the dielectric multilayer film 1 has a thickness of 1500 nm or more, the light absorption layer contains a resin having a glass transition temperature of 200°C or more and a near-infrared absorbing dye, and the optical filter satisfies the following spectral characteristics (i-1) and (i-2). (i-1) Let the sum of the transmittances of light with wavelengths of 450 to 700 nm at an incident angle of 0 degrees be S1 (0) and the sum of the transmittances of light with wavelengths of 700 to 1000 nm be S2 (0) and the sum of the transmittances of light with wavelengths of 1000 to 1300 nm be S3 (0) When this is done, S1 (0) / S2 (0) ≧40, and S3 (0) / S2 (0) ≧40 (i-2) Let the sum of the transmittances of light with wavelengths of 450 to 700 nm at an incident angle of 30 degrees be S1 (30) and the sum of the transmittances of light with wavelengths of 700 to 1000 nm be S2(30) Let the sum of the transmittances of light with wavelengths from 1000 to 1300 nm be S3 (30) When S1 (30) / S2 (30) ≥ 40, and S3 (30) / S2 (30) ≥ 40 〔2〕The optical filter according to 〔1〕, wherein the optical filter satisfies the following spectral characteristic (i-3). (i-3) The absolute value of the difference between the wavelength at which the transmittance of light with wavelengths from 550 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 to 1150 nm is 50% at an incident angle of 0 degrees is 300 nm or more 〔3〕The optical filter according to 〔1〕 or 〔2〕, wherein the optical filter satisfies the following spectral characteristics (i-4) and (i-5). (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 (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 〔4〕The optical filter according to any one of 〔1〕 to 〔3〕, wherein the optical filter satisfies all of the following spectral characteristics (i-6) to (i-8). (i-6) When the incident direction is the side of the dielectric multilayer film 1, 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 to 830 nm (i-7) When the incident direction is the side of the dielectric multilayer film 1, 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 to 1200 nm (i-8) The absolute value of the difference between the above wavelength IR 50S and the above wavelength IR 50L is 230 nm or more 〔5〕The optical filter according to any one of 〔1〕 to 〔4〕, wherein the optical filter satisfies all of the following spectral characteristics (i-9) to (i-10). When the incident direction is from the side of the dielectric multilayer film 1, the average reflectance of light with a wavelength of 450 to 600 nm at an incident angle of 5 degrees is 5% or less. When the incident direction is from the side of the dielectric multilayer film 2, the average reflectance of light with a wavelength of 450 to 600 nm at an incident angle of 5 degrees is 5% or less. 〔6〕The optical filter according to any one of 〔1〕to 〔5〕, wherein the optical filter satisfies the following spectral characteristic (i-11). (i-11) When the incident direction is from 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 to 600 nm at an incident angle of 5 degrees and the average reflectance of light with a wavelength of 450 to 600 nm at an incident angle of 5 degrees when the incident direction is from the side of the dielectric multilayer film 2 is 0.5% or less. 〔7〕A dielectric multilayer film 3 is provided between the light absorption layer and the glass substrate. In the spectral characteristic (i-4), the S1 (0) / S2 (0) and the S1 (30) / S2 (30) The absolute value of the difference between them is 130 or less. In the spectral characteristic (i-5), the S3 (0) / S2 (0) and the S3 (30) / S2 (30) The absolute value of the difference between them is 130 or less. The optical filter according to 〔3〕, which satisfies the above conditions. 〔8〕The glass substrate is a glass substrate containing ytterbium, In the spectral characteristic (i-4), the S1 (0) / S2 (0) and the S1 (30) / S2 (30) The absolute value of the difference between them is 130 or less. In the spectral characteristic (i-5), the S3 (0) / S2 (0) and the S3 (30) / S2 (30) The absolute value of the difference between them is 130 or less. The optical filter according to 〔3〕, which satisfies the above conditions. 〔9〕The resin in the light absorption layer contains a polyimide resin. The optical filter according to any one of 〔1〕to 〔8〕. 〔10〕The near-infrared absorbing dye in the light absorption layer includes a dye having a maximum absorption wavelength in the range of 700 nm or more and less than 730 nm, a dye having a maximum absorption wavelength in the range of 730 nm or more and less than 760 nm, and a dye having a maximum absorption wavelength in the range of 760 nm or more and less than 800 nm. The optical filter according to any one of 〔1〕~〔9〕. 〔11〕The thickness of the light absorption layer is 2 μm or less, and the content of the near-infrared absorbing dye in the light absorption layer is 10% by mass or more. The optical filter according to any one of 〔1〕~〔10〕. 〔12〕An imaging device including the optical filter according to any one of 〔1〕~〔11〕.

Examples

[0083] Next, the present invention will be described more specifically by way of examples. For the measurement of each spectroscopic characteristic, a UV-visible spectrophotometer (UH-4150 type, manufactured by Hitachi High-Technologies Corporation) was used. Note that the spectroscopic characteristics when the incident angle is not particularly specified are the values measured at an incident angle of 0 degrees (perpendicular to the main surface of the optical filter).

[0084] The dyes used in each example are as follows. Compound 1 (squarylium compound): Synthesized based on U.S. Patent No. 5,543,086. Compound 2 (squarylium compound): Synthesized based on International Publication No. 2017 / 135359. Compound 3 (merocyanine compound): Synthesized based on the specification of German Patent Publication No. 10109243. Compound 4 (cyanine compound): Synthesized based on Dyes and pigments 73(2007) 344-352. Compound 5 (cyanine compound): Synthesized based on Dyes and pigments 73(2007) 344-352. Note that Compound 1, Compound 2, Compound 4, and Compound 5 are near-infrared absorbing dyes (NIR dyes), and Compound 3 is a near-ultraviolet absorbing dye (UV dye).

[0085]

Chem.

[0086] <Spectral Characteristics of Pigments> The maximum absorption wavelengths in the absorption spectra measured by dissolving the above pigments (Compounds 1 to 5) in dichloromethane are shown in Table 1 below.

[0087] <Glass Substrate> As the glass substrates, Glass A which is a light-absorbing glass and non-absorbing Glass B were prepared. For Glass A, raw materials were weighed and mixed so that in terms of mol% in oxide conversion, it was SiO2 7.5%, B2O3 23.6%, P2O5 7.5%, Yb2O3 47.2%, Ga2O3 11.8%, La2O3 2.4%. They were put into a crucible with an internal volume of about 400 cc and melted at 1400 to 1650 °C for 2 hours in an air atmosphere. Then, it was clarified, stirred, and cast into a rectangular mold of 100 mm in length × 50 mm in width × 20 mm in height preheated to about 300 °C to 500 °C, and slowly cooled to room temperature at about -1 °C / min. It was cut to a predetermined thickness in the range of 40 mm in length × 30 mm in width × 0.3 to 1.5 mm in thickness, and both sides were optically polished to obtain a plate-shaped glass. Also, Glass B is a non-absorbing glass, and D263 glass (manufactured by Schott, borosilicate glass, commercially available product) was used.

[0088] Note that the following raw materials were used for each glass. SiO2: Oxide B2O3: One or more selected from oxide, PBO4, and H3BO3 P2O5: Any one or more of H3PO4 and PBO4 GeO2: Oxide ZrO2: Oxide Ga2O3: Oxide Yb2O3: Oxide La2O3: Oxide Al2O3: Any one or more of oxide and Al(OH)3 Note that the raw materials of the glass are not limited to the above, and known materials can be used.

[0089] The transmittance curves of light with wavelengths of 350 to 1200 nm for Glass A and Glass B (both Glass A and Glass B have a plate thickness of 0.4 mm and internal transmittance) are shown in Fig. 3.

[0090] <Light absorption layer> Any one of the dyes of Compounds 1 to 5 was dissolved in a polyimide resin (C-3G30G manufactured by Mitsubishi Gas Chemical Company) or a polyester resin (polyester resin manufactured by Osaka Gas Chemical Company), and mixed 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 spin coating to form a light absorption layer with a film thickness shown in Table 1 below. In addition, the transmittance curves of light with wavelengths of 350 to 1200 nm for Light Absorption Layers 1 to 2 are shown in Fig. 3.

[0091]

Table 1

[0092] <Example 1: Optical filter> On one main surface of a glass substrate (Glass B without light absorption), a dielectric multilayer film 2A was formed by alternately depositing SiO2 and TiO2 by vapor deposition. On the other main surface of the glass substrate, a resin solution was applied with the same composition as that of the light absorption layer 1, and heated sufficiently to remove the organic solvent to form a light absorption layer. On the surface of the light absorption layer, a dielectric multilayer film 1A was formed by alternately depositing SiO2 and TiO2 by vapor deposition. From the above, the optical filter of Example 1 was manufactured.

[0093] <Example 2> An optical filter of Example 2 was manufactured in the same manner as in Example 1, except that light-absorbing Glass A was used instead of Glass B as the glass substrate, and dielectric multilayer film 1B was used instead of dielectric multilayer film 1A.

[0094] <Example 3> An optical filter of Example 3 was manufactured in the same manner as in Example 1, except that a dielectric multilayer film 3A was formed by alternately depositing SiO2 and TiO2 between the glass substrate and the light absorption layer by vapor deposition.

[0095] <Example 4> An optical filter of Example 4 was manufactured in the same manner as in Example 2, except that a dielectric multilayer film 3A was formed by alternately depositing SiO2 and TiO2 between the glass substrate and the light absorption layer by vapor deposition.

[0096] <Example 5> A dielectric multilayer film 2B was formed on one main surface of a glass substrate (glass B having no light absorption property) by alternately depositing SiO2 and TiO2 by vapor deposition. A resin solution was applied to the other main surface of the glass substrate with the same composition as the light absorption layer 2, and heated sufficiently to remove the organic solvent, thereby forming a light absorption layer. A dielectric multilayer film 1C was formed on the surface of the light absorption layer by alternately depositing SiO2 and TiO2 by vapor deposition. From the above, an optical filter of Example 5 was manufactured.

[0097] <Example 6> A dielectric multilayer film 2C was formed on one main surface of a glass substrate (glass B having no light absorption property) by alternately depositing SiO2 and TiO2 by vapor deposition. A resin solution was applied to the other main surface of the glass substrate with the same composition as the light absorption layer 1, and heated sufficiently to remove the organic solvent, thereby forming a light absorption layer. A dielectric multilayer film 1D was formed on the surface of the light absorption layer by alternately depositing SiO2 and TiO2 by vapor deposition. From the above, an optical filter of Example 6 was manufactured.

[0098] <Example 7> A dielectric multilayer film 2D was formed on one main surface of a glass substrate (glass B having no light absorption property) by alternately depositing SiO2 and TiO2 by vapor deposition. 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 was sufficiently heated to remove the organic solvent, thereby forming a light absorption layer. On the surface of the light absorption layer, a dielectric multilayer film 1E was formed by alternately depositing SiO2 and TiO2 by vapor deposition. From the above, the optical filter of Example 7 was manufactured.

[0099] <Example 8> On one main surface of a glass substrate (glass B without light absorption properties), a dielectric multilayer film 2E was formed by alternately depositing SiO2 and TiO2 by vapor deposition. 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 was sufficiently heated to remove the organic solvent, thereby forming a light absorption layer. On the surface of the light absorption layer, a dielectric multilayer film 1C was formed by alternately depositing SiO2 and TiO2 by vapor deposition. From the above, the optical filter of Example 8 was manufactured.

[0100] <Example 9> An optical filter of Example 9 was manufactured in the same manner as in Example 2, except that a light absorption layer was formed with the same composition as the light absorption layer 3 instead of the light absorption layer 1.

[0101] The configurations of the dielectric multilayer films 1A, 1B, 2A, and 3A are shown in Tables 2 to 4 below. Note that the order of the numbers (No.) corresponds to the stacking order.

[0102]

Table 2

[0103]

Table 3

[0104]

Table 4

[0105] For each of the optical filters obtained as described above, using an ultraviolet-visible spectrophotometer, 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 in the wavelength range of 350 to 1200 nm were measured. From the obtained spectral characteristic data, each characteristic shown in Table 6 below was calculated. In addition, the spectral transmittance and reflectance curves of the optical filters of Example 3 and Example 5 are shown in FIGS. 5 to 8, respectively.

[0106] Note that Examples 1 to 4 are examples, and Examples 5 to 9 are comparative examples.

[0107]

Table 5

[0108]

Table 6

[0109] From the above results, the optical filters of Examples 1 to 4 have S1 (0) / S2 (0) and S1 (30) / S2 (30) both being above a certain level. Therefore, even at a high incident angle, the transmittance in the visible light region is maintained high, and the transmittance in the wavelength region of 700 to 1000 nm where light shielding is desired is kept low. Also, since S3 (0) / S2 (0) and S3 (30) / S2 (30) are both above a certain level, even at a high incident angle, the transmittance in the near-infrared light region of 1000 to 1300 nm is maintained high, and the transmittance in the wavelength region of 700 to 1000 nm where light shielding is desired is kept low. Also, from the comparison between Example 1 and Example 2 and the comparison between Example 3 and Example 4, by using light-absorbing glass as the glass substrate, 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) It can be seen that the absolute value of the difference from [the reference] becomes smaller, and the change in the spectral characteristics due to the incident angle is suppressed. Furthermore, from the comparison between Example 1 and Example 3, and the comparison between Example 2 and Example 4, by providing the dielectric multilayer film 3 between the substrate and the light absorption layer, S1 (0) / S2 (0) and S1 (30) / S2 (30) and the absolute value of the difference between them, and S3 (0) / S2 (0) and S3 (30) / S2 (30) It can be seen that the absolute value of the difference between them could be reduced. On the other hand, for the optical filters of Examples 5 to 7, S1 (0) / S2 (0) , S1 (30) / S2 (30) and, and S3 (0) / S2 (0) , S3 (30) / S2 (30) were less than 40. This is because the wavelengths for maintaining a high transmittance in the near-infrared light region are different. For the optical filter of Example 8, since the film thickness of the dielectric multilayer film 1 laminated on the light absorption layer side is small, it is necessary to increase the film thickness of the other dielectric multilayer film 2 in order to ensure light shielding properties, and the spectral characteristics are easily affected by the incident angle. In addition, for the optical filter of Example 9, since the glass transition temperature of the resin in the light absorption layer is low, it is easily affected by the stress of the dielectric multilayer film 1 laminated on the light absorption layer.

[0110] <Heat Resistance Test> The optical filters obtained in Example 3 and Example 9 were cut into a size of 5 mm square by blade dicing. The obtained test pieces were heated on a hot plate at 200 °C for 10 minutes, and the appearance was confirmed with a metallurgical microscope. For the optical filter of Example 3 using a polyimide resin with a glass transition temperature of 320 °C for the light absorption layer, there was no change in appearance. Example 9, in which a polyester resin with a glass transition temperature of 150°C was used for the light absorption layer, had wrinkles on the light absorption layer. This is presumably because the resin became soft at high temperatures and deformed due to the stress of the dielectric multilayer film because it is a resin with a low glass transition temperature.

Industrial Applicability

[0111] The optical filter according to this embodiment is excellent in the transmittance of visible light and specific near-infrared light even at a high incident angle, and excellent in the shielding property of other near-infrared light. In recent years, with the progress of high performance, for example, it is useful for applications of imaging devices such as cameras and sensors for transportation machines.

Explanation of Signs

[0112] 1 Dielectric Multilayer Film 2 Dielectric Multilayer Film 3 Dielectric Multilayer Film 4 Light Absorption Layer 5 Glass Substrate 10 Optical Filter

Claims

1. 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, wherein the dielectric multilayer film 1 has a thickness of 1500 nm or more, the light absorption layer contains a resin having a glass transition temperature of 200° C. or more and a near-infrared absorbing dye, and the optical filter satisfies the following spectral characteristics (i-1) and (i-2). Let the sum of the transmittances of light with wavelengths from 450 to 700 nm at an incident angle of 0 degrees be S1 （０） and let the sum of the transmittances of light with wavelengths from 700 to 1000 nm be S2 （０） and let the sum of the transmittances of light with wavelengths from 1000 to 1300 nm be S3 （０） when this is done, S1 （０） / S2 （０） ≥40, and S3 （０） / S2 （０） ≥40 Let the sum of the transmittances of light with wavelengths from 450 to 700 nm at an incident angle of 30 degrees be S1 （３０） and the sum of the transmittances of light with wavelengths from 700 to 1000 nm be S2 （３０） and the sum of the transmittances of light with wavelengths from 1000 to 1300 nm be S3 （３０） when this is done S1 （３０） / S2 （３０） ≥40, and S3 （３０） / S2 （３０） ≥40

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

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

4. The optical filter according to claim 1, wherein the optical filter satisfies all of the following spectral characteristics (i-6) to (i-8). When the dielectric 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 to 830 nm When the incident direction is the side of the dielectric multilayer film 1, 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 to 1200 nm (i-8) the wavelength IR ５０Ｓ and the wavelength IR ５０Ｌ and the absolute value of the difference is 230 nm or more

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

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

7. The optical filter according to claim 3, further comprising a dielectric multilayer film 3 between the light absorption layer and the glass substrate, In the spectral characteristic (i-4), the S1 （０） / S2 （０） and the S1 （３０） / S2 （３０） The absolute value of the difference from is 130 or less In the spectral characteristic (i-5), the S3 （０） / S2 （０） and the S3 （３０） / S2 （３０） The absolute value of the difference from is 130 or less satisfying the above.

8. The optical filter according to claim 3, wherein the glass substrate is a glass substrate containing ytterbium, In the spectral characteristic (i-4), the S1 （０） / S2 （０） and the S1 （３０） / S2 （３０） The absolute value of the difference from is 130 or less In the spectral characteristic (i-5), the S3 （０） / S2 （０） and the S3 （３０） / S2 （３０） The absolute value of the difference from is 130 or less satisfying the above.

9. The optical filter according to claim 1, wherein the resin in the light absorption layer contains a polyimide resin.

10. The near-infrared absorbing dye in the light absorption layer includes a dye having a maximum absorption wavelength in the wavelength range of 700 nm or more and less than 730 nm, a dye having a maximum absorption wavelength in the wavelength range of 730 nm or more and less than 760 nm, and a dye having a maximum absorption wavelength in the wavelength range of 760 nm or more and less than 800 nm. The optical filter according to claim 1.

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

12. An imaging device including the optical filter according to any one of claims 1 to 11.

Images