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 and which has a small shift of a spectral curve 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 light adsorption layer contains a near-infrared absorption pigment. The optical filter satisfies all specific spectral characteristics (i-1) to (i-6).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, in addition to a near-infrared cut filter function for transmitting visible light and faithfully reproducing an image based on the visible light, the use of an optical filter having a function of selectively transmitting specific near-infrared light, so-called a dual-band pass filter, has been considered.

[0004] Patent Document 1 describes an optical filter that combines a dielectric multilayer film and a resin substrate containing a near-infrared absorbing dye, 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, in 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, the reflection characteristic may decrease 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 making camera modules thinner, 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, excellent in the shielding property of other near-infrared light, and has a small shift in the spectral curve even at a high incident angle.

Means for Solving the Problems

[0009] The present invention provides an optical filter and the like 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 light absorption layer contains a near-infrared absorbing dye, and the optical filter satisfies all of the following spectral characteristics (i-1) to (i-6). (i-1) The average transmittance at an incident angle of 0 degrees for light having a wavelength of 450 to 600 nm is 85% or more (i-2) The absolute value of the difference between the wavelength at which the transmittance of light having a wavelength of 550 to 750 nm becomes 50% at an incident angle of 0 degrees and the wavelength at which the transmittance of light having a wavelength of 550 to 750 nm becomes 50% at an incident angle of 30 degrees is 10 nm or less (i-3) The average transmittance at an incident angle of 0 degrees for light with a wavelength of 725 to 1000 nm is 1% or less (i-4) The wavelength IR50 at which the light transmittance at an incident angle of 0 degrees is 50% is in the range of 1000 to 1150 nm (i-5) The average transmittance at an incident angle of 0 degrees for light with a wavelength of 1100 to 1200 nm is 80% or more (i-6) When at least one of the main surfaces is the incident direction, the absolute value of the difference between the wavelength at which the light reflectance at an incident angle of 5 degrees is 25% and the wavelength at which it is 85% at wavelengths of 550 to 850 nm is 20 nm or less

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. The optical filter of the present invention is particularly excellent in the transmittance in the near-infrared light region of 1000 to 1300 nm including the sensing wavelength region. Further, it is an optical filter in which the spectral transmittance curve in the boundary region between the visible light transmittance region and the wavelength region on the long wavelength side to be shielded is difficult to shift due to the 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

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described. In this specification, near-infrared absorbing dyes may also be abbreviated as "NIR dyes", and ultraviolet absorbing dyes may also be abbreviated as "UV dyes". In this specification, the compound represented by formula (I) is referred to as compound (I). The same applies to compounds represented by other formulas. 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, "~" 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 light absorption layer contains a near-infrared absorbing dye. The reflection characteristics of the dielectric multilayer film and the absorption characteristics of the light absorption layer enable the entire optical filter to achieve excellent transmittance in the visible light region and a specific near-infrared light region, as well as excellent shielding properties in other near-infrared light regions.

[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 all of the following spectral characteristics (i-1) to (i-6). (i-1) The average transmittance at an incident angle of 0 degrees for light with a wavelength of 450 to 600 nm is 85% or more (i-2) 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 degrees and the wavelength at which the transmittance of light with a wavelength of 550 to 750 nm becomes 50% at an incident angle of 30 degrees is 10 nm or less (i-3) The average transmittance at an incident angle of 0 degrees for light with a wavelength of 725 to 1000 nm is 1% or less (i-4) The wavelength IR50 at which the transmittance of light at an incident angle of 0 degrees becomes 50% is in the range of 1000 to 1150 nm (i-5) The average transmittance at an incident angle of 0 degrees for light with a wavelength of 1100 to 1200 nm is 80% or more (i-6) When at least one main surface is the incident direction, the absolute value of the difference between the wavelength at which the reflectance of light at an incident angle of 5 degrees becomes 25% and the wavelength at which it becomes 85% at wavelengths of 550 to 850 nm is 20 nm or less

[0020] Satisfying the spectral characteristic (i-1) means excellent visible light transmittance. By satisfying the spectral characteristic (i-1), the amount of light captured in the wavelength region of the camera module is large, enabling higher sensing. The average transmittance in the spectral characteristic (i-1) is preferably 86% or more, more preferably 87% or more. To satisfy the spectral characteristic (i-1), for example, providing a dielectric multilayer film with low reflectance in the visible light region, using a plurality of types of near-infrared absorbing dyes to suppress visible light absorbency, etc. can be mentioned.

[0021] Satisfying the spectral characteristic (i-2) means that even at a high incident angle in the boundary region (cut-off end) on the long wavelength side of the visible light transmission region, the shift of the spectral curve is small. By satisfying the spectral characteristic (i-2), since the amount of incident visible light hardly changes with the incident angle, an optical filter with excellent spectral sensitivity can be obtained. The absolute value in the spectral characteristic (i-2) is preferably 8 nm or less, more preferably 5 nm or less. To satisfy the spectral characteristic (i-2), for example, performing light shielding in the boundary region on the long wavelength side of the visible light transmission region by the absorption characteristics of near-infrared absorbing dyes or light absorbing glass, etc. can be mentioned.

[0022] Satisfying the spectral characteristic (i-3) means excellent light shielding property in the region between the transmission regions of visible light and near-infrared light of a specific wavelength, and thus an optical filter with excellent light cutting property for the region that becomes noise can be obtained. The average transmittance in the spectral characteristic (i-3) is preferably 0.9% or less. To satisfy the spectral characteristic (i-3), for example, by combining the reflection characteristics of both dielectric multilayer films 1 and 2, combining near-infrared absorbing dyes with different maximum absorption wavelengths, using light absorbing glass, etc., combining a plurality of characteristics to perform shielding in a wide region of wavelengths from 725 to 1000 nm can be mentioned.

[0023] The spectral characteristic (i-4) means an index of the boundary region (cut-off end) on the short wavelength side of the near-infrared light transmission region. The wavelength IR50 in the spectral characteristic (i-4) is preferably in the range of 1010 to 1140 nm. In order to satisfy the spectral characteristic (i-4), for example, increasing the number of layers of the multilayer film, increasing the refractive index difference of the materials used, etc. can be mentioned.

[0024] Satisfying the spectral characteristic (i-5) means having excellent transmittance of specific near-infrared light. As a result, the amount of light taken in the sensing wavelength region is large, and an optical filter with higher sensing can be obtained. The average transmittance in the spectral characteristic (i-5) is preferably 83% or more, more preferably 85% or more. In order to satisfy the spectral characteristic (i-5), for example, using a dielectric multilayer film with low reflection characteristics for light with a wavelength of 1100 to 1200 nm, blocking light on the short-wavelength side of 1100 nm with a near-infrared absorbing dye or light-absorbing glass, etc. can be mentioned.

[0025] The spectral characteristic (i-6) substantially means the reflection characteristic of the dielectric multilayer film 1 or the dielectric layer film 2. By satisfying the spectral characteristic (i-6), it means that the reflection curve of the dielectric multilayer film rises in the wavelength range of 550 to 850 nm and the rising width is steep. As a result, an optical filter with high spectral sensitivity can be obtained without reducing the transmittance in the visible light region. The incident surface in the spectral characteristic (i-6) is preferably the dielectric multilayer film 2 side. The absolute value in the spectral characteristic (i-6) is preferably 17 nm or less. In order to satisfy the spectral characteristic (i-6), for example, using the dielectric multilayer film 1 or the dielectric multilayer film 2 designed to have the above reflection characteristics, etc. can be mentioned.

[0026] This filter preferably satisfies the following spectral characteristic (i-7). (i-7) 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 degrees 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 degrees is 300 nm or more The absolute value of the difference in the above wavelengths corresponds to the distance between the visible light transmission region and the near-infrared light transmission region. It is more preferable that the absolute value is 350 nm or more. In order to satisfy the spectral characteristic (i-7), in particular, in order to sufficiently separate the position of the near-infrared light transmission region from the visible light transmission region, for example, by combining the reflection characteristics of both the dielectric multilayer films 1 and 2, combining near-infrared absorbing dyes having different maximum absorption wavelengths, using light-absorbing glass, etc., it is possible to combine a plurality of characteristics to perform light shielding in a wide region.

[0027] This filter preferably satisfies the following spectral characteristic (i-8). (i-8) The absolute value of the difference between the average transmittance at an incident angle of 0 degrees for light with a wavelength of 1100 to 1200 nm and the average transmittance at an incident angle of 30 degrees for light with a wavelength of 1100 to 1200 nm is 6% or less By satisfying the spectral characteristic (i-8), it is preferable to obtain an optical filter that has excellent near-infrared light transmittance even at a high incident angle and has a small change in the amount of light of the sensor. The absolute value in the spectral characteristic (i-8) is more preferably 5.5% or less. In order to satisfy the spectral characteristic (i-8), for example, it is possible to mention that the transmittance cut-off property at 1100 to 1200 nm is sufficient.

[0028] This filter preferably satisfies the following spectral characteristic (i-9). When any main surface is the incident direction, the absorption loss amount at a wavelength of X nm X is defined as follows. (Absorption loss amount X ) [%] = 100 - (transmittance at an incident angle of 0 degrees) - (reflectance at an incident angle of 5 degrees) (i-9) The wavelengths at which the absorption loss amount of light is 30% are in the ranges of 600 to 750 nm and 800 to 1200 nm Absorption loss amount X is an index indicating the degree of light shielding due to the absorption characteristic at a wavelength of X nm, and the larger the value, the more the light of the wavelength X is shielded by absorption. The wavelength in the spectral characteristic (i-9) is more preferably in the range of 605 to 700 nm and in the range of 805 to 1150 nm. In order to satisfy the spectral characteristic (i-9), for example, using a near-infrared absorbing dye having a maximum absorption wavelength between a wavelength region of 600 to 750 nm and a wavelength region of 800 to 1200 nm can be mentioned.

[0029] This filter preferably satisfies the following spectral characteristic (i-10). (i-10) The absolute value of the difference between the wavelength at which the transmittance of light with a wavelength of 950 to 1150 nm becomes 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 becomes 50% at an incident angle of 30 degrees is 70 nm or less Satisfying the spectral characteristic (i-10) means that even at a high incident angle in the boundary region (cut-off edge) on the short-wavelength side of the near-infrared light transmission region (wavelength 1100 to 1200 nm), the shift of the spectral curve is small. By satisfying the spectral characteristic (i-10), since the amount of incident light of near-infrared light hardly changes depending on the incident angle, an optical filter excellent in spectral sensitivity can be obtained. The absolute value in the spectral characteristic (i-10) is more preferably 65 nm or less, and even more preferably 60 nm or less. In order to satisfy the spectral characteristic (i-10), for example, the light shielding in the boundary region on the short-wavelength side of the near-infrared light transmission region (wavelength 1100 to 1200 nm) can be performed by the absorption characteristics of a near-infrared absorbing dye or a light-absorbing glass.

[0030] <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 preferable as the base material rather than a resin film. Thereby, warpage during film formation can be reduced.

[0031] As the glass substrate, it may be a transparent glass substrate or a light-absorbing glass substrate, 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 high light-shielding properties can be exhibited even at high incident angles.

[0032] 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 transmittance in regions other than the maximum absorption wavelength region. Therefore, it has excellent transmittance in the visible light region and in the near-infrared light region from visible light to about 800 nm in wavelength and longer than 1000 nm in wavelength.

[0033] 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.

[0034] Yb2O3 is a component for efficiently absorbing light in the vicinity of 900 to 1000 nm in wavelength, 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, and 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%.

[0035] SiO2 is the main component for forming glass and is a component for increasing the devitrification resistance of glass and the viscosity with respect to the liquidus temperature. If the content of SiO2 in the glass of this embodiment is 0.1% or more, problems such as the glass becoming unstable, the weather resistance decreasing, 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%.

[0036] B2O3 is the main component for forming glass and is a component for increasing the devitrification resistance of glass and the viscosity with respect to the liquidus temperature. If the content of B2O3 in the glass of this 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 decreasing 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%.

[0037] 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.

[0038] 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%.

[0039] 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%.

[0040] 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 and 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%.

[0041] 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%.

[0042] La2O3 is a component for increasing the Young's modulus of the glass and improving its meltability. In the glass of this 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 property of the glass, 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%.

[0043] 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 this 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 property of the glass, 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%.

[0044] From the viewpoint of vitrifying the glass without devitrifying the glass containing the Yb component, 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.

[0045] As the light-absorbing glass, within a range that does not impair the object of the present invention, it may contain alkali metal oxides, alkaline earth metal oxides, Sb2O3, Cl, F, and other components.

[0046] As the glass substrate in this filter, when 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.

[0047] When used as a glass substrate in a so-called dual-bandpass filter having a function of selectively transmitting visible light and specific near-infrared light, the thickness is usually used at 3 mm or less, often. From the viewpoint of reducing the weight of the component, it is preferably 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. Also, from the viewpoint of ensuring the strength of the glass, 0.05 mm or more is preferable.

[0048] The glass substrate in this filter can be manufactured, 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 and cut and polished to form a flat plate of a predetermined thickness (forming step).

[0049] 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 less. If the highest temperature of the glass during glass melting is below the above temperature, problems such as the glass crystallizing and unmelted foreign substances occurring in the glass are less likely to occur. The above temperature is more preferably 1625 °C or less, and still more preferably 1600 °C or less.

[0050] Also, if the temperature in the above melting step is too low, problems such as devitrification occurring during melting and taking a long time to melt off may occur, so it is preferably 1300 °C or more, more preferably 1350 °C or more.

[0051] <Light absorption layer> This filter includes a light absorption layer containing a near-infrared absorbing dye (NIR dye). Thereby, the region not shielded by the reflection characteristics of the dielectric multilayer film can be compensated for by the absorption characteristics not affected by the incident angle.

[0052] 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

[0053] As the near-infrared absorbing dye, from the viewpoint of being able to widely absorb the near-infrared region while maintaining the transmittance 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 kinds are combined. In particular, it is preferable to include 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.

[0054] 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, tetradehydroocorin dyes, triphenylmethane dyes, aminium dyes and diimonium dyes is preferable.

[0055] As the NIR dye, it is preferable to include 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 a spectral viewpoint, and phthalocyanine dyes are preferable from a durability viewpoint.

[0056] The content of the NIR dye in the light absorption layer is preferably 10% by mass or more in order to obtain desired optical properties. 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 will decrease), so it is preferably 20% by mass or less, and more preferably 15% by mass or less. When combining two or more compounds, the above content is the sum of each compound.

[0057] The light absorption layer preferably contains a near-infrared absorbing dye and a resin. The resin is not limited as long as it is a transparent resin, and one or more transparent resins selected from polyester resins, acrylic resins, epoxy resins, ene-thiol resins, polycarbonate resins, polyether resins, polyarylate resins, polysulfone resins, polyethersulfone resins, polyphenylene resins, polyarylene ether phosphine oxide resins, polyamide resins, polyimide resins, polyamideimide resins, polyolefin resins, cyclic olefin resins, polyurethane resins, and polystyrene resins are used. These resins may be used alone or in combination of two or more. From the viewpoints of the spectral characteristics, glass transition point (Tg), and adhesion of the light absorption layer, one or more resins selected from polyimide resins, polycarbonate resins, polyester resins, and acrylic resins are preferred.

[0058] When using a plurality of compounds as the NIR dye and other dyes, these may be contained 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 blended 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] In addition, the coating liquid may contain a surfactant to improve voids caused by minute bubbles, dents caused by adhesion of foreign substances, etc., and repulsion during the drying process. Further, for coating the coating liquid, for example, a dipping coating method, a cast coating method, a spin coating method, or the like can be used. When the coating liquid contains a raw material component of a transparent resin, a curing treatment such as thermosetting or photocuring is further performed.

[0061] In addition, the light absorption layer can also be manufactured in a 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 there are 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. The larger the thickness of the dielectric multilayer film, 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, or concentrating the thickness on one multilayer film can be avoided. Both the dielectric multilayer films 1 and 2 are preferably designed as reflection films that reflect a part of near-infrared light (hereinafter also referred to as "NIR reflection film"). 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, it is preferable because an optical filter that satisfies the spectral characteristics (i-1) and (i-3) can be 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 less (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 preferable because an optical filter that satisfies the spectral characteristics (i-1) and (i-3) can be easily obtained.

[0067] The dielectric multilayer film 2 also preferably has an absolute value of the difference between the wavelength at which the reflectance of light at an incident angle of 5 degrees is 25% and the wavelength at which the reflectance is 85% of 20 nm or less at a wavelength of 550 to 850 nm. This is preferable because an optical filter that satisfies the spectral characteristic (i-6) can be easily obtained.

[0068] This filter preferably includes a dielectric multilayer film 3 between the light absorption layer and the glass substrate. With the three dielectric multilayer films, more flexible control of the spectral characteristics becomes possible, and an effect of relaxing the interference waveform generated in the light absorption layer can be expected.

[0069] The dielectric multilayer film is a laminate of dielectric films with different refractive indices. More specifically, it includes a low refractive index dielectric film (low refractive index film), a medium refractive index dielectric film (medium refractive index film), and a high refractive index dielectric film (high refractive index film), and is composed of a dielectric multilayer film in which two or more of these are laminated. By combining several dielectric films with different spectral characteristics when transmitting and selecting a desired wavelength band, the reflection characteristics can be adjusted.

[0070] 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), etc. manufactured by Canon Optron. Among these, TiO2 is preferred in terms of film formability, reproducibility in refractive index, stability, etc.

[0071] 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, H4, M2 (aluminum lanthanum oxide) sold by Merck, etc. Among these, compounds of the Al2O3 system or mixtures of Al2O3 and ZrO2 are preferred in terms of film formability, reproducibility in refractive index, stability, etc. 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 aforementioned medium refractive index material.

[0072] 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、Examples include MgF2. 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, stability, and economy in film formation.

[0073] The film thickness (physical film thickness) of the dielectric multilayer film 1 is preferably 1500 nm or more, more preferably 2000 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 ripples in the visible light region.

[0074] 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.

[0075] 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 spectral characteristics, and is preferably 6000 nm or less from the viewpoints of productivity and suppressing reflection ripples in the visible light region.

[0076] 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.

[0077] 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 ripples in the visible light region.

[0078] 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.

[0079] For forming the dielectric multilayer film, for example, vacuum film-forming processes such as CVD method, sputtering method, vacuum evaporation method, etc., and wet film-forming processes such as spray method, dip method, etc. can be used.

[0080] As other components, this filter may include, 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 have a high transmittance of visible light and have light absorbency in a wide range of infrared wavelength regions exceeding 1200 nm, so they can be used when such infrared light shielding properties are required.

[0081] <Imaging device> The imaging device according to an embodiment of the present invention preferably includes the optical filter according to the above 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, imaging lens, etc. of the imaging device via an adhesive layer. By providing this filter that is excellent in the transmittance of visible light and specific near-infrared light, has the shielding property of specific near-infrared light, and has a spectral curve that is difficult to shift even at a high incident angle, an imaging device excellent in color reproducibility can be obtained even for light at a high incident angle.

[0082] 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.

[0083] 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 light absorption layer contains a near-infrared absorbing dye, The optical filter that satisfies all of the following spectral characteristics (i-1) to (i-6). (i-1) The average transmittance at an incident angle of 0 degrees for light with a wavelength of 450 to 600 nm is 85% or more (i-2) 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 degrees and the wavelength at which the transmittance of light with a wavelength of 550 to 750 nm becomes 50% at an incident angle of 30 degrees is 10 nm or less (i-3) The average transmittance at an incident angle of 0 degrees for light with a wavelength of 725 to 1000 nm is 1% or less (i-4) The wavelength IR50 at which the transmittance of light at an incident angle of 0 degrees becomes 50% is in the range of 1000 to 1150 nm (i-5) The average transmittance at an incident angle of 0 degrees for light with a wavelength of 1100 to 1200 nm is 80% or more (i-6) When at least one of the main surfaces is the incident direction, the absolute value of the difference between the wavelength at which the reflectance of light at an incident angle of 5 degrees becomes 25% and the wavelength at which it becomes 85% at wavelengths of 550 to 850 nm is 20 nm or less 〔2〕The optical filter according to 〔1〕, wherein the optical filter satisfies the following spectral characteristic (i-7). (i-7) 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 degrees 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 degrees is 300 nm or more 〔3〕The optical filter according to 〔1〕 or 〔2〕, wherein in the spectral characteristic (i-5), the average transmittance at an incident angle of 0 degrees for light with a wavelength of 1100 to 1200 nm is 85% or more. 〔4〕The optical filter according to any one of 〔1〕 to 〔3〕, wherein the optical filter satisfies the following spectral characteristic (i-8). (i-8) The absolute value of the difference between the average transmittance at an incident angle of 0 degrees for light with a wavelength of 1100 to 1200 nm and the average transmittance at an incident angle of 30 degrees for light with a wavelength of 1100 to 1200 nm is 6% or less 〔5〕The optical filter according to any one of 〔1〕 to 〔4〕, wherein the optical filter satisfies the following spectral characteristic (i-9). When any of the main surfaces is the incident direction, the absorption loss amount at a wavelength of X nm Xis defined as follows. (Absorption loss X ) [%] = 100 - (transmittance at an incident angle of 0 degrees) - (reflectance at an incident angle of 5 degrees) (i-9) The wavelength at which the absorption loss of light is 30% is in the range of 600 to 750 nm and 800 to 1200 nm [6] The optical filter according to any one of [1] to [5], wherein the thickness of the dielectric multilayer film 1 is 1500 nm or more. [7] The optical filter according to any one of [1] to [6], further comprising a dielectric multilayer film 3 between the light absorption layer and the glass substrate. [8] The optical filter according to any one of [1] to [7], wherein the glass substrate is a glass substrate containing ytterbium. [9] The optical filter according to any one of [1] to [8], wherein the optical filter satisfies the following spectral characteristic (i-10). (i-10) The absolute value of the difference between the wavelength at which the transmittance of light having a wavelength of 950 to 1150 nm is 50% at an incident angle of 0 degrees and the wavelength at which the transmittance of light having a wavelength of 950 to 1150 nm is 50% at an incident angle of 30 degrees is 70 nm or less

[10] The optical filter according to any one of [1] to [9], wherein 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.

[11] An imaging device including the optical filter according to any one of [1] to

[10] .

Example

[0084] Next, the present invention will be described more specifically with reference to examples. For the measurement of each spectral characteristic, a UV-visible spectrophotometer (UH-4150 type, manufactured by Hitachi High-Technologies Corporation) was used. Note that the spectral 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). 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. WO2017 / 135359. Compound 3 (merocyanine compound): Synthesized based on the specification of German Patent Publication No. DE10109243. 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] [Chemical formula]

[0086] [Spectral characteristics of the dyes] The maximum absorption wavelengths in the absorption spectra measured by dissolving the above - mentioned dyes (Compound 1 - 5) in dichloromethane are shown in Table 1 below.

[0087] [Glass substrate] As the glass substrates, glass A which is light - absorbing glass and non - absorbing glass B were prepared. For glass A, the 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%. Then it was put into a crucible with an internal volume of about 400 cc, melted at 1400 - 1650 °C for 2 hours in an air atmosphere. After that, it was clarified, stirred, and cast into a rectangular mold with a length of 100 mm × width of 50 mm × height of 20 mm pre - heated to about 300 °C - 500 °C, and slowly cooled to room temperature at about - 1 °C / min. Then it was cut to a predetermined thickness in the range of length 40 mm × width 30 mm × thickness 0.3 - 1.5 mm, and both sides were optically polished to obtain a plate - shaped glass. In addition, Glass B is a non-absorbing glass, and D263 glass (manufactured by Schott, borosilicate glass, commercially available product) was used.

[0088] Note that the raw materials for each glass were those shown below. SiO2: oxide B2O3: one or more selected from oxides, 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 for 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 an 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 (manufactured by Mitsubishi Gas Chemical Company, C-3G30G), 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 (manufactured by SCHOTT, D263 glass, 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 each light absorption layer 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 coated with the same composition as the light absorption layer 1, and heated sufficiently to remove the organic solvent, thereby forming 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 Example 1, except that light absorption glass A was used instead of glass B as the glass substrate, and a dielectric multilayer film 1B was used instead of the dielectric multilayer film 1A.

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

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

[0096] <Example 5> On one main surface of a glass substrate (glass B without light absorption), a dielectric multilayer film 2B 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 2, and heated sufficiently 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 5 was manufactured.

[0097] <Example 6> On one main surface of a glass substrate (glass B without light absorption), a dielectric multilayer film 2C was formed by alternately depositing SiO2 and TiO2 by vapor deposition. On the other main surface of the glass substrate, a light absorption layer was formed by applying a resin solution with the same composition as the light absorption layer 1, heating it sufficiently to remove the organic solvent. On the surface of the light absorption layer, a dielectric multilayer film 1D was formed by alternately depositing SiO2 and TiO2 by vapor deposition. From the above, the optical filter of Example 6 was manufactured.

[0098] <Example 7> On one main surface of a glass substrate (glass B without light absorption), a dielectric multilayer film 2D was formed by alternately depositing SiO2 and TiO2 by vapor deposition. On the other main surface of the glass substrate, a light absorption layer was formed by applying a resin solution with the same composition as the light absorption layer 1, heating it sufficiently to remove the organic solvent. 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), 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 dielectric multilayer film 1F 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 Example 8, except that a light absorption layer with the same composition as the light absorption layer 1 was formed between the glass substrate and the dielectric multilayer film 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 curves at incident angles of 0 degrees and 30 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 data of the obtained spectral characteristics, each characteristic shown in Table 5 below was calculated. In addition, the spectral transmittance curve and spectral reflectance curve of the optical filter of Example 1 are shown in FIGS. 5 to 6, and the spectral transmittance curve of the optical filter of Example 5 is shown in FIG. 7, 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 high transmittance for visible light with wavelengths of 450 to 600 nm and near-infrared light with wavelengths of 1100 to 1200 nm, and the transmittance in the light region with wavelengths of 725 to 1000 nm, which is between these transmission regions, is suppressed low. On the other hand, all of the optical filters of Examples 5 to 9 resulted in low transmittance of near-infrared light with wavelengths of 1100 to 1200 nm.

Industrial Applicability

[0110] The optical filter according to this embodiment is excellent in the transmittance of visible light and specific near-infrared light, excellent in the shielding property of other near-infrared light, and has spectral characteristics with a small shift in the spectral curve even at a high incident angle. 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 Reference Numerals

[0111] 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 light absorption layer contains a near-infrared absorbing dye, and the optical filter satisfies all of the following spectral characteristics (i-1) to (i-6). (i-1) The average transmittance at an incident angle of 0 degrees for light with a wavelength of 450 to 600 nm is 85% or more (i-2) 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 degrees and the wavelength at which the transmittance of light with a wavelength of 550 to 750 nm becomes 50% at an incident angle of 30 degrees is 10 nm or less (i-3) The average transmittance at an incident angle of 0 degrees for light with a wavelength of 725 to 1000 nm is 1% or less (i-4) The wavelength IR50 at which the transmittance of light at an incident angle of 0 degrees becomes 50% is in the range of 1000 to 1150 nm (i-5) The average transmittance at an incident angle of 0 degrees for light with a wavelength of 1100 to 1200 nm is 80% or more (i-6) When at least one main surface is the incident direction, the absolute value of the difference between the wavelength at which the reflectance of light at an incident angle of 5 degrees becomes 25% and the wavelength at which it becomes 85% at wavelengths of 550 to 850 nm is 20 nm or less

2. The optical filter according to claim 1, wherein the optical filter satisfies the following spectral characteristic (i-7). (i-7) 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 degrees 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 degrees is 300 nm or more

3. The optical filter according to claim 1, wherein in the spectral characteristic (i-5), the average transmittance at an incident angle of 0 degrees for light with a wavelength of 1100 to 1200 nm is 85% or more.

4. The optical filter according to claim 1, wherein the optical filter satisfies the following spectral characteristic (i-8). (i-8) The absolute value of the difference between the average transmittance at an incident angle of 0 degrees for light with a wavelength of 1100 to 1200 nm and the average transmittance at an incident angle of 30 degrees for light with a wavelength of 1100 to 1200 nm is 6% or less

5. The optical filter according to claim 1, wherein the optical filter satisfies the following spectral characteristic (i-9). When any main surface is taken as the incident direction, the absorption loss amount at a wavelength of X nm Ｘ is defined as follows. (Absorption loss amount Ｘ ) [%] = 100 - (Transmittance at an incident angle of 0 degrees) - (Reflectance at an incident angle of 5 degrees) (i-9) The wavelengths at which the light absorption loss amount becomes 30% are in the ranges of 600 to 750 nm and 800 to 1200 nm

6. The optical filter according to claim 1, wherein the thickness of the dielectric multilayer film 1 is 1500 nm or more.

7. The optical filter according to claim 1, comprising a dielectric multilayer film 3 between the light absorption layer and the glass substrate.

8. The optical filter according to claim 1, wherein the glass substrate is a glass substrate containing ytterbium.

9. The optical filter according to claim 1, wherein the optical filter satisfies the following spectral characteristics (i-10). (i-10) The absolute value of the difference between the wavelength at which the transmittance of light with a wavelength of 950 to 1150 nm becomes 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 becomes 50% at an incident angle of 30 degrees is 70 nm or less.

10. The optical filter according to claim 1, wherein 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.

11. An imaging device including the optical filter according to any one of claims 1 to 10.

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