Optical Filters

Abstract

To provide an optical filter having excellent transmittance for near-infrared light of 800 nm or more and excellent blocking of visible light of 400 to 680 nm. The present invention relates to a substrate and a light emitting device provided on at least one main surface of the substrate, the light emitting device having an extinction coefficient k at a wavelength of 600 nm. 600 is 0.12 or more and the minimum extinction coefficient k in the wavelength range of 1530 to 1570 nm 1530-1570MIN and a dielectric multilayer film in which at least two different layers are laminated, the optical filter being used as a cover for a sensor module that uses near-infrared light, and having a film having a maximum transmittance T 400-680MAX is 6% or less and the maximum reflectance R in the wavelength range of 400 to 680 nm 400-680MAX and the average reflectance R 400-680AVE An optical filter in which at least one of the above is 10% or less and transmits light of 1530 to 1570 nm.

Description

[Technical Field]

[0001] The present invention relates to an optical filter that blocks light in the visible range and transmits light in the near-infrared range. [Background technology]

[0002] In order to increase the sensitivity of the sensor, the cover of a sensor module that uses near-infrared light uses an optical filter that transmits light in the near-infrared wavelength range from 800 nm onwards and blocks light in the visible range. Also, from the viewpoint of making the inside of the sensor invisible from the outside and from the viewpoint of making the cover appearance black with a highly designable appearance, it is preferable that the optical filter have low transmittance of light in the visible range of 400 to 680 nm.

[0003] Known examples of optical filters include reflective filters in which dielectric thin films with different refractive indices are alternately stacked on one or both sides of a transparent substrate (dielectric multilayer film), and the filters utilize optical interference to reflect light that is to be blocked.

[0004] Patent Document 1 describes an optical filter having a dielectric multilayer film in which high-refractive index layers and low-refractive index layers are alternately stacked, where the high-refractive index layers are silicon layers having an extinction coefficient k of less than 0.0005 in the wavelength range of 800 to 1100 nm. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 9,354,369 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the optical filter described in Patent Document 1, the high refractive index layer has a small extinction coefficient in the 800 to 1100 nm range, and therefore it is presumed that the extinction coefficient in the 600 to 680 nm range, which includes the visible region, is also small, i.e., the transmittance in this wavelength range is also high. Furthermore, if the reflectance in this range is increased in order to reduce the transmittance in the 600 to 680 nm range, the reflected color will appear red, which will degrade the design.

[0007] An object of the present invention is to provide an optical filter that is excellent in transmittance of near-infrared light of 800 nm or more and in blocking visible light of 400 to 680 nm. [Means for solving the problem]

[0008] An optical filter according to one aspect of the present invention comprises a substrate and a light-transmitting element provided on at least one main surface side of the substrate, the light-transmitting element having an extinction coefficient k at a wavelength of 600 nm. 600 is 0.12 or more and the minimum extinction coefficient k in the wavelength range of 1530 to 1570 nm 1530-1570MIN and a dielectric multilayer film in which at least two different layers are laminated, the optical filter being used as a cover for a sensor module that uses near-infrared light, and having a film having a maximum transmittance T 400-680MAX is 6% or less and the maximum reflectance R in the wavelength range of 400 to 680 nm 400-680MAX and the average reflectance R 400-680AVE At least one of these is 10% or less, and light of 1530 to 1570 nm is transmitted. Furthermore, an optical filter according to another embodiment of the present invention includes a substrate and a light emitting element provided on at least one main surface side of the substrate, the light emitting element having an extinction coefficient k at a wavelength of 600 nm. 600 is 0.12 or more and the minimum extinction coefficient k in the wavelength range of 1310 to 1350 nm 1310-1350MIN and a dielectric multilayer film in which at least two different layers are laminated, the optical filter being used as a cover for a sensor module that uses near-infrared light, and having a film having a maximum transmittance T 400-680MAX is 6% or less and the maximum reflectance R in the wavelength range of 400 to 680 nm400-680MAX and the average reflectance R 400-680AVE At least one of these is 10% or less, and light of 1310 to 1350 nm is transmitted. Furthermore, an optical filter according to another embodiment of the present invention includes a substrate and a light emitting element provided on at least one main surface side of the substrate, the light emitting element having an extinction coefficient k at a wavelength of 600 nm. 600 is 0.12 or more and the minimum extinction coefficient k in the wavelength range of 800 to 1000 nm 800-1000MIN and a dielectric multilayer film in which at least two different layers are laminated, the optical filter being used as a cover for a sensor module that uses near-infrared light, and having a film having a maximum transmittance T 400-680MAX is 6% or less and the maximum reflectance R in the wavelength range of 400 to 680 nm 400-680MAX and the average reflectance R 400-680AVE At least one of these is 10% or less, and transmits light of 800 to 1000 nm. [Effects of the Invention]

[0009] According to the present invention, an optical filter can be provided that is excellent in transmittance of near-infrared light of 800 nm or more and in blocking visible light of 400 to 680 nm. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of an optical filter according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically showing another example of the optical filter according to the embodiment. [Figure 3] FIG. 3 is a diagram showing the spectral transmittance curves of the optical filters of Examples 1 to 3. [Figure 4] FIG. 4 is a diagram showing the spectral reflectance curves of the optical filters of Examples 1 to 3. [Figure 5] FIG. 5 is a diagram showing the spectral transmittance curves of the optical filters of Examples 4 to 6. [Figure 6] FIG. 6 is a diagram showing the spectral reflectance curves of the optical filters of Examples 4 to 6. [Figure 7]FIG. 7 is a graph showing the relationship between the spin density and the extinction coefficient k600. DETAILED DESCRIPTION OF THE INVENTION

[0011] In this specification, a transmittance of, for example, 90% or more in a specific wavelength range means that the transmittance is not less than 90% across the entire wavelength range, i.e., the minimum transmittance is 90% or more across the wavelength range. Similarly, a transmittance of, for example, 1% or less in a specific wavelength range means that the transmittance is not more than 1% across the entire wavelength range, i.e., the maximum transmittance is 1% or less across the wavelength range. The average transmittance in a specific wavelength range is the arithmetic mean of the transmittances per 1 nm in the wavelength range. Unless otherwise specified, the refractive index refers to the refractive index for light with a wavelength of 589 nm at 20°C.

[0012] The optical properties can be measured using an ultraviolet-visible spectrophotometer, or calculated by simulation using optical thin film calculation software. The extinction coefficient can be calculated by measuring the reflectance, transmittance and film thickness of a single layer film formed on a quartz substrate and using optical thin film calculation software. The spin density can be measured using an electron spin resonance apparatus. In this specification, the use of "to" to indicate a range of values ​​includes the upper and lower limits.

[0013] <Optical filters> An optical filter according to one embodiment of the present invention (hereinafter also referred to as "this filter") is an optical filter comprising a substrate and a dielectric multilayer film laminated as an outermost layer on at least one main surface side of the substrate.

[0014] An example of the configuration of the present filter will be described with reference to the drawings. Figures 1 and 2 are cross-sectional views that schematically show an example of an optical filter according to an embodiment. 1 is an example in which a dielectric multilayer film 30 is provided on one main surface side of a substrate 10. Note that "having a specific layer on the main surface side of the substrate" does not only mean that the layer is provided in contact with the main surface of the substrate, but also includes a case in which another functional layer is provided between the substrate and the layer.

[0015] The optical filter 1B shown in FIG. 2 is an example in which the substrate 10 has a dielectric multilayer film 30 on both main surfaces thereof.

[0016] <Dielectric multilayer film> In this filter, the dielectric multilayer film is laminated as the outermost layer on at least one of the main surfaces of the substrate.

[0017] The dielectric multilayer film is designed to have wavelength selectivity, and at least one of the dielectric multilayer films is a visible light absorbing layer that blocks visible light mainly by absorption and transmits near-infrared light. When the dielectric multilayer film is laminated on both sides of the substrate, both of the dielectric multilayer films may be visible light absorbing layers, or only one of the dielectric multilayer films may be a visible light absorbing layer. When one of the dielectric multilayer films is a visible light absorbing layer, the other dielectric multilayer film may be designed as a layer having another purpose, such as an antireflection layer.

[0018] A dielectric multilayer film is a laminate consisting of alternating layers of low and high refractive index films. By stacking thin films with different refractive indices, the reflectance can be increased or decreased by utilizing the interference of light. The higher the reflectance, the lower the transmittance. The extinction coefficient also differs depending on the material that makes up the multilayer film. The larger the extinction coefficient, the greater the light absorption and the lower the transmittance. In the present invention, an optical filter having desired optical characteristics is designed by taking into consideration the refractive index and extinction coefficient of each multilayer film.

[0019] In the present invention, either the low refractive index film or the high refractive index film satisfies the following optical property (i-1) in the visible light region, and also satisfies any of the optical properties (i-2A) to (i-2C) in the near-infrared light region. (i-1) Extinction coefficient k at a wavelength of 600 nm 600 is 0.12 or more (i-2A) Minimum extinction coefficient k in the wavelength range of 1530 to 1570 nm 1530-1570MIN is 0.01 or less (i-2B) Minimum extinction coefficient k in the wavelength range of 1310 to 1350 nm 1310-1350MIN is 0.01 or less (i-2C) Minimum extinction coefficient k in the wavelength range of 800 to 1000 nm 800-1000MIN is 0.01 or less

[0020] Regarding the optical properties (i-1), in any dielectric film, k 600 By setting k to 0.12 or more, red light in the vicinity of 600 nm can be blocked by absorption rather than reflection. This eliminates the need to increase the reflectance in the vicinity of 600 nm, resulting in an optical filter in which the reflected color is less likely to be red. 600 is preferably 0.18 or more and preferably 1.00 or less.

[0021] k of the dielectric film 600 In order to make k fall within the above range, for example, in the case of a high refractive index film, amorphous silicon that is not doped with hydrogen or amorphous silicon that is doped with hydrogen at a rate of 20 sccm or less can be used, and it is preferable to use amorphous silicon that is not doped with hydrogen. Also, k can be obtained by changing the method of forming the dielectric film. 600 can be adjusted.

[0022] Optical properties (i-2A) to (i-2C) define the minimum extinction coefficient of the dielectric film in each near-infrared region. Satisfying any of optical properties (i-2A) to (i-2C) means that the absorption in the wavelength region defined by each property is low. Then, by designing the reflectance in that wavelength region to be low, near-infrared light in that wavelength region can be sufficiently transmitted. Regarding optical properties (i-2A), the minimum extinction coefficient k in the wavelength range of 1530 to 1570 nm 1530-1570MIN When k is 0.01 or less, near-infrared light in the range of 1530 to 1570 nm can be sufficiently transmitted. 1530-1570MIN is preferably 0.002 or less. Regarding optical properties (i-2B), the minimum extinction coefficient k in the wavelength range of 1310 to 1350 nm 1310-1350MIN When k is 0.01 or less, near-infrared light in the range of 1310 to 1350 nm can be sufficiently transmitted. 1310-1350MINis preferably 0.005 or less. Regarding optical properties (i-2C), the minimum extinction coefficient k in the wavelength range of 800 to 1000 nm 800-1000MIN When k is 0.01 or less, near-infrared light in the range of 800 to 1000 nm, particularly in the range of 880 to 920 nm, can be sufficiently transmitted. 800-1000MIN is preferably 0.005 or less. 600 From the viewpoint of blocking red light around 600 nm by absorption rather than reflection, the value of k is set to a moderate value. 800-1000MIN is preferably 0.0005 or more.

[0023] k of the dielectric film 1310-1350MIN , k 1530-1570MIN , k 800-1000MIN In order to set the extinction coefficient within the above range, for example, in the case of a high refractive index film, amorphous silicon that is not doped with hydrogen or amorphous silicon that is doped with hydrogen at a doping rate of 20 sccm or less can be used, and it is preferable to use amorphous silicon that is not doped with hydrogen. Also, each extinction coefficient can be adjusted by changing the film formation method of the dielectric film.

[0024] Hereinafter, an optical filter in which any of the dielectric films satisfies the above optical characteristic (i-2A) will be referred to as "optical filter A," an optical filter that satisfies the above optical characteristic (i-2B) will be referred to as "optical filter B," and an optical filter that satisfies the above optical characteristic (i-2C) will be referred to as "optical filter C."

[0025] In optical filter A or optical filter B, it is preferable that either the low refractive index film or the high refractive index film further satisfy the following optical property (i-3). (i-3) Minimum extinction coefficient k in the wavelength range of 800 to 1000 nm 800-1000MIN is 0.0005 or more k 800-1000MIN is 0.0005 or more, k 600 The value of is set to a moderate value. In addition, it can block red light around 600 nm by absorption rather than reflection. 800-1000MINis preferably 0.001 or more, and is preferably 0.1 or less.

[0026] From the viewpoint of design freedom, the dielectric film satisfying the optical properties (i-1) and any one of (i-2A) to (i-2C) is preferably a high refractive index film. In this case, the extinction coefficient k 600 is preferably 0, the minimum extinction coefficient k in the wavelength range of 1530 to 1570 nm is preferably 0, the minimum extinction coefficient k in the wavelength range of 1310 to 1350 nm is preferably 0, and the minimum extinction coefficient k in the wavelength range of 800 to 1000 nm is preferably 0.

[0027] Examples of materials for the high refractive index film include silicon, Ta2O5, TiO2, Nb2O5, and SiN. Of these, silicon is preferred, and amorphous silicon is particularly preferred, from the viewpoint of easily achieving the above-mentioned specific extinction coefficient. The high refractive index film preferably has a refractive index of 3.5 or more, more preferably 4.0 or more.

[0028] Also, for silicon, k 600 From the viewpoint of achieving a value of 0.12 or more, silicon that is not doped with hydrogen or silicon that is doped with a reduced amount of hydrogen is preferred, and silicon that is not doped with hydrogen is particularly preferred. Hydrogen can be doped by a known method, and the doping amount is preferably 20 sccm or less.

[0029] The low refractive index film may be made of, for example, SiO2, SiO x N y Among these, materials having a refractive index lower than that of the high refractive index film material can be used in combination. Among these, SiO2 is preferred from the viewpoint of productivity. The low refractive index film preferably has a refractive index of 2.5 or less, more preferably 1.5 or less.

[0030] The high refractive index film preferably has a spin density of 5.0E+10 or more (number / (nm*cm 2)), more preferably 1.0E+12 or more (pieces / (nm*cm 2 )) Here, the spin density represents the amount of dangling bonds in the film. When the spin density of the high refractive index film is in this range, the above-mentioned specific extinction coefficient is easily achieved. In addition, in order to set the spin density of the high refractive index film within the above range, for example, silicon that is not doped with hydrogen, or silicon that is doped with hydrogen but with a reduced amount of doping, can be used.

[0031] Spin density can be measured using an electron spin resonance spectrometer. The spins that can be measured with an electron spin resonance spectrometer include not only dangling bonds of silicon, but also dangling bonds of silica films and transition metal ions in glass, so sample processing before measurement and peak separation after measurement are required. To process the sample, the optical filter containing the multilayer film is cut appropriately, and then the substrate glass on which the multilayer film is applied is polished to remove as much of it as possible. This reduces the influence of the spin signal from the substrate glass. Furthermore, peak separation after measurement is possible, for example, by curve fitting. The signal from silicon dangling bonds is observed as an isotropic signal with g = 2.004-2.007 and a linewidth of 4-8 gauss. This parameter is obtained as the result of peak separation by curve fitting using a linear combination of a Gaussian function and a Lorentzian function with the same linewidth. The linewidth here refers to the difference in magnetic field between the peak top and bottom of the electron spin resonance spectrum obtained in the differential form.

[0032] When the dielectric multilayer film is designed as a visible light absorption layer, from the viewpoint of light blocking properties in the visible light region, the total number of layers is preferably 10 or more, more preferably 15 or more, and even more preferably 20 or more. However, since a large total number of layers can cause warping or an increase in film thickness, the total number of layers is preferably 70 or less, more preferably 60 or less, and even more preferably 50 or less.

[0033] From the viewpoint of productivity, the thickness of the dielectric multilayer film is preferably 2.0 μm or less, more preferably 1.5 μm or less, and particularly preferably 1.0 μm or less. When the dielectric multilayer film has one or more layers (one group of dielectric multilayer films), the total thickness of the films is preferably 2.0 μm or less. In the present invention, the visible light region can be sufficiently blocked even if the number of layers or thickness of the dielectric multilayer film is small. This is because the dielectric multilayer film in the present invention has a large extinction coefficient in the visible light region and can block visible light by absorption.

[0034] The dielectric multilayer film preferably further satisfies the following optical properties. The maximum transmittance T in the wavelength range of 400 to 680 nm is set so that both the transmitted and reflected colors are black. 400-680MAX is preferably 6% or less, and the maximum reflectance R 400-680MAX is preferably 10% or less.

[0035] In addition, to increase the sensitivity of the sensor, the dielectric multilayer film in optical filter A has a minimum transmittance T 1530-1570MIN is preferably 90% or more, and the dielectric multilayer film in the optical filter B has a minimum transmittance T 1310-1350MIN is preferably 90% or more, and the dielectric multilayer film in the optical filter C has a minimum transmittance T 800-1000MIN is preferably 90% or more. The minimum transmittance in the above wavelength region can be set within this range by using a multilayer film whose minimum extinction coefficient in the wavelength region satisfies any one of the optical properties (i-2A) to (i-2C) above, and by designing the reflectance in the wavelength region to be small.

[0036] The dielectric multilayer film can be formed by, for example, a vacuum film-forming process such as a CVD method, a sputtering method, or a vacuum deposition method, or a wet film-forming process such as a spray method or a dipping method.

[0037] The dielectric multilayer film may provide predetermined optical characteristics with one layer (one group of dielectric multilayer films), or may provide predetermined optical characteristics with two or more layers. When there are two or more layers, the dielectric multilayer films may have the same or different configurations. When two dielectric multilayer films are provided, one may be a visible light absorbing layer that transmits near-infrared light and blocks visible light, and the other may be a visible / near-infrared light transmitting layer that transmits both near-infrared and visible light.

[0038] Furthermore, when the present filter has two or more dielectric multilayer films, it is preferable that at least one of them satisfy the optical characteristic (i-1) and any one of the optical characteristics (i-2A) to (i-2C).

[0039] When a dielectric multilayer film is designed as an antireflection layer, it is obtained by alternately laminating dielectric films with different refractive indices, as in the visible light absorption layer. Note that the antireflection layer may be formed from an intermediate refractive index medium, a moth-eye structure in which the refractive index changes gradually, or the like, in addition to a dielectric multilayer film.

[0040] <Base material> The substrate in the present filter may have a single-layer structure or a multi-layer structure. The material of the substrate is not particularly limited, and may be an organic or inorganic material as long as it is a transparent material that transmits near-infrared light. A combination of different materials may also be used.

[0041] As the transparent inorganic material, glass or crystalline material is preferred. Examples of glass include soda lime glass, borosilicate glass, alkali-free glass, quartz glass, and aluminosilicate glass. The glass may be chemically strengthened glass obtained by ion exchange at a temperature equal to or lower than the glass transition point to exchange alkali metal ions (e.g., Li ions, Na ions) having a small ionic radius present on the main surface of the glass plate with alkali ions having a larger ionic radius (e.g., Na ions or K ions for Li ions, and K ions for Na ions).

[0042] Examples of the crystalline material include birefringent crystals such as quartz, lithium niobate, and sapphire.

[0043] The shape of the substrate is not particularly limited, and may be a block, plate, or film. The thickness of the substrate is preferably 0.1 mm or more and 5 mm or less, more preferably 2 to 4 mm, from the viewpoints of reducing warpage during the formation of the dielectric multilayer film, reducing the height of the optical element, and preventing cracks.

[0044] <Optical filters> The optical filter of the present invention, which comprises the above-mentioned substrate and dielectric multilayer film, functions as an IR bandpass filter that blocks visible light and transmits near-infrared light.

[0045] The optical filter A of the present invention satisfies the following optical property (ii-1A). (ii-1A) Blocks light from 400 to 680 nm and transmits light from 1530 to 1570 nm The optical filter B of the present invention satisfies the following optical property (ii-1B). (ii-1B) Blocks light of 400 to 680 nm and transmits light of 1310 to 1350 nm The optical filter C of the present invention satisfies the following optical property (ii-1C). (ii-1C) Blocks light of 400 to 680 nm and transmits light of 800 to 1000 nm

[0046] By transmitting light in the wavelength range of 1530 to 1570 nm, light in the wavelength range of 1310 to 1350 nm, or light in the wavelength range of 800 to 1000 nm, the sensitivity of the sensor is increased according to the wavelength range.

[0047] In the optical properties (ii-1A) to (ii-1C), blocking light of 400 to 680 nm preferably means satisfying the following optical properties (ii-2) to (ii-3). That is, it is preferable that the present filter further satisfies the following optical properties (ii-2) to (ii-3). (ii-2) Maximum transmittance T in the wavelength range of 400 to 680 nm 400-680MAXis 6% or less (ii-3) Maximum reflectance R in the wavelength range of 400 to 680 nm 400-680MAX and the average reflectance R 400-680AVE At least one of the following is 10% or less

[0048] The optical property (ii-2) means that it blocks light (visible light) in the wavelength range of 400 to 680 nm. 400-680MAX is preferably 2% or less. By utilizing the reflectivity and absorptivity of the dielectric multilayer film, an optical filter having a high blocking ability for visible light can be obtained.

[0049] Regarding the optical property (ii-3), the reflectance in the visible light region as viewed from one of the main surfaces is low, so that an optical filter that does not exhibit a reflected color and exhibits a highly attractive black color can be obtained. 400-680MAX and the average reflectance R 400-680AVE At least one of these is preferably 5% or less. The reflectance R of the optical filter 400-680AVE is a value measured from the dielectric multilayer film (visible anti-reflection and near-infrared transmitting layer) side.

[0050] In the optical property (ii-1A), transmitting light of 1530 to 1570 nm preferably means satisfying the following optical property (ii-4A). That is, it is preferable that the present filter A further satisfies the following optical property (ii-4A), which further enhances the sensitivity of the sensor. (ii-4A) Minimum transmittance T in the wavelength range of 1530 to 1570 nm 1530-1570MIN Over 90% T 1530-1570MIN is more preferably 95% or more. T 1530-1570MIN In order to set the value in the above range, for example, the above optical property (i-2 A multilayer film that satisfies A), that is, a multilayer film that has low absorption in the wavelength region of 1530 to 1570 nm, and a dielectric multilayer film that is designed to have low reflectance in the wavelength region of 1530 to 1570 nm, can be used.

[0051] In the optical property (ii-1B), transmitting light of 1310 to 1350 nm preferably means satisfying the following optical property (ii-4B). That is, it is preferable that the present filter B further satisfies the following optical property (ii-4B), which further increases the sensitivity of the sensor. (ii-4B) Minimum transmittance T in the wavelength range of 1310 to 1350 nm 1310-1350MIN Over 90% T 1310-1350MIN is more preferably 95% or more. T 1310-1350MIN In order to set the value within the above range, for example, a multilayer film that satisfies the above-mentioned optical property (i-2B) may be used, that is, a multilayer film that has low absorption in the wavelength region of 1310 to 1350 nm, and a dielectric multilayer film that is designed to have low reflectance in the wavelength region of 1310 to 1350 nm may be used.

[0052] In the optical property (ii-1C), transmitting light of 800 to 1000 nm preferably means satisfying the following optical property (ii-4C). That is, it is preferable that the present filter C further satisfies the following optical characteristic (ii-4C), which further enhances the sensitivity of the sensor. (ii-4C) Minimum transmittance T in the wavelength range of 880 to 920 nm 880-920MIN Over 90% T 880-920MIN is more preferably 92% or more. T 880-920MIN In order to set the value within the above range, for example, a multilayer film that satisfies the above-mentioned optical characteristic (i-2C) may be used, that is, a multilayer film that has low absorption in the wavelength region of 800 to 1000 nm and a dielectric multilayer film that is designed to have low reflectance in the wavelength region of 880 to 920 nm.

[0053] According to the optical filter of the embodiment described above, it is possible to improve the blocking property of the visible range and the transmittance of near-infrared light. [Example]

[0054] Next, the present invention will be described in more detail by way of examples. The spectral transmittance curves and spectral reflectance curves of the optical filters in the examples were calculated by simulation using optical thin film calculation software. The extinction coefficient of amorphous silicon in the examples was determined by measuring the reflectance, transmittance and film thickness of a single layer film formed on a quartz substrate, and using optical thin film calculation software. The spin density of amorphous silicon in the example is determined by the extinction coefficient k 600 Based on this, the approximate formula in Figure 7 was used for calculation.

[0055] (Example 1) On one main surface of a white glass plate used as a transparent substrate, 24 layers of amorphous silicon (refractive index 4.5) and SiO2 (refractive index 1.5) were alternately laminated by vacuum deposition to form a visible-absorbing near-infrared-transmitting layer made of a 1.0 μm-thick dielectric multilayer film. Next, on the other main surface of the glass plate, 24 layers of amorphous silicon (refractive index 4.5) and SiO2 (refractive index 1.5) were alternately laminated by vacuum deposition to form a visible-absorbing near-infrared-transmitting layer made of a 1.0 μm-thick dielectric multilayer film, thereby obtaining optical filter 1.

[0056] (Example 2) On one main surface of a white glass plate used as a transparent substrate, 13 layers of amorphous silicon (refractive index 4.7) and SiO2 (refractive index 1.5) were alternately laminated by sputtering to form a visible-absorbing near-infrared-transmitting layer made of a 0.7 μm-thick dielectric multilayer film. Next, on the other main surface of the glass plate, 14 layers of amorphous silicon (refractive index 4.7) and SiO2 (refractive index 1.5) were alternately laminated by sputtering to form a visible-absorbing near-infrared-transmitting layer made of a 1.0 μm-thick dielectric multilayer film, thereby obtaining optical filter 2.

[0057] (Example 3) On one main surface of a white glass plate used as a transparent substrate, 21 layers of hydrogen-doped amorphous silicon (refractive index 4.3) and SiO2 (refractive index 1.5) were alternately laminated by sputtering to form a visible-absorbing near-infrared-transmitting layer made of a 1.1 μm-thick dielectric multilayer film. Next, on the other main surface of the glass plate, 19 layers of hydrogen-doped amorphous silicon (refractive index 4.3) and SiO2 (refractive index 1.5) were alternately laminated by sputtering to form a visible-absorbing near-infrared-transmitting layer made of a 0.8 μm-thick dielectric multilayer film, thereby obtaining optical filter 3.

[0058] (Example 4) On one main surface of a white glass plate used as a transparent substrate, 11 layers of amorphous silicon (refractive index 4.7) and SiO2 (refractive index 1.5) were alternately laminated by sputtering to form a visible-absorbing near-infrared-transmitting layer made of a 1.3 μm-thick dielectric multilayer film. Next, on the other main surface of the glass plate, 23 layers of amorphous silicon (refractive index 4.7) and SiO2 (refractive index 1.5) were alternately laminated by sputtering to form a visible-absorbing near-infrared-transmitting layer made of a 1.8 μm-thick dielectric multilayer film, thereby obtaining optical filter 4.

[0059] (Example 5) On one main surface of a white glass plate used as a transparent substrate, nine layers of amorphous silicon (refractive index 4.7) and SiO2 (refractive index 1.5) were alternately laminated by sputtering to form a visible-absorbing near-infrared-transmitting layer made of a 1.1 μm-thick dielectric multilayer film. Next, on the other main surface of the glass plate, 22 layers of amorphous silicon (refractive index 4.7) and SiO2 (refractive index 1.5) were alternately laminated by sputtering to form a visible-absorbing near-infrared-transmitting layer made of a 1.5 μm-thick dielectric multilayer film, thereby obtaining optical filter 5.

[0060] (Example 6) On one main surface of a white glass plate used as a transparent substrate, 21 layers of amorphous silicon (refractive index 4.7) and SiO2 (refractive index 1.5) were alternately laminated by sputtering to form a visible-absorbing near-infrared-transmitting layer made of a 0.9 μm-thick dielectric multilayer film. Next, on the other main surface of the glass plate, 11 layers of amorphous silicon (refractive index 4.7) and SiO2 (refractive index 1.5) were alternately laminated by sputtering to form a visible-absorbing near-infrared-transmitting layer made of a 0.3 μm-thick dielectric multilayer film, thereby obtaining optical filter 6.

[0061] The optical characteristics of the optical filters of the above examples, the extinction coefficients of the amorphous silicon layers, and the spin densities calculated from the extinction coefficients are shown in the table below. The spectral transmittance curves (incident angle 0 degrees) of the optical filters obtained in Examples 1 to 3 are shown in Figure 3, and the spectral reflectance curves (incident angle 0 degrees) are shown in Figure 4. The spectral transmittance curves (incident angle 0 degrees) of the optical filters obtained in Examples 4 to 6 are shown in Figure 5, and the spectral reflectance curves (incident angle 0 degrees) are shown in Figure 6. The spectral reflectance curves were measured from the dielectric multilayer film (visible anti-reflection near-infrared transmitting layer) side. The reflectance R 400-680 is measured from the dielectric multilayer film (visible anti-reflection near-infrared transmission layer) side, and the reflectance R 880-920 , R 1310-1350 , R 1530-1570 is a value measured from the dielectric multilayer film (visible light absorbing near-infrared transmitting layer) side. Examples 1, 2, 4, 5, and 6 are working examples, and Example 3 is a comparative example.

[0062] [Table 1]

[0063] The above results show that the optical filters of Examples 1 to 2 and Examples 4 to 6, in which the high refractive index film satisfies the specified characteristics, have excellent blocking properties in the visible light region of 400 to 680 nm and excellent transmittance in the near-infrared light region from 800 nm onwards. On the other hand, the extinction coefficient k of the high refractive index film 600 The optical filter of Example 3, in which the value was not 0.12 or more, resulted in a low blocking ability in the visible light region of 400 to 680 nm. [Industrial Applicability]

[0064] The optical filter of the present invention has excellent near-infrared light transmittance and visible light blocking properties, and is therefore useful for applications in information acquisition devices such as cameras and sensors for transport aircraft, which have become increasingly sophisticated in recent years. [Explanation of symbols]

[0065] 1A, 1B... optical filter, 10... substrate, 30... dielectric multilayer film

Claims

1. A substrate; The spin density is 5.0E+10 or more (number / (nm*cm) ２ a dielectric multilayer film having a film in which at least two different films are stacked; An optical filter used as a cover for a sensor module that uses near-infrared light, comprising: The film having a spin density of 5.0E+10 or more (spins / (nm*cm 2 )) is an amorphous silicon film that is not doped with hydrogen, Maximum transmittance T in the wavelength range of 400 to 680 nm ４００－６８０ＭＡＸ is 6% or less and the maximum reflectance R in the wavelength range of 400 to 680 nm ４００－６８０ＭＡＸ and the average reflectance R ４００－６８０ＡＶＥ an optical filter that transmits light of 1530 to 1570 nm, and at least one of the above is 10% or less.

2. A substrate; The spin density is 5.0E+10 or more (number / (nm*cm) ２ a dielectric multilayer film having a film in which at least two different films are stacked; An optical filter used as a cover for a sensor module that uses near-infrared light, comprising: The film having a spin density of 5.0E+10 or more (spins / (nm*cm 2 )) is an amorphous silicon film that is not doped with hydrogen, Maximum transmittance T in the wavelength range of 400 to 680 nm ４００－６８０ＭＡＸ is 6% or less and the maximum reflectance R in the wavelength range of 400 to 680 nm ４００－６８０ＭＡＸ and the average reflectance R ４００－６８０ＡＶＥ an optical filter that transmits light of 1310 to 1350 nm, and at least one of the above is 10% or less.

3. A substrate; The spin density is 5.0E+10 or more (number / (nm*cm) ２ a dielectric multilayer film having a film in which at least two different films are stacked; An optical filter used as a cover for a sensor module that uses near-infrared light, comprising: The film having a spin density of 5.0E+10 or more (spins / (nm*cm 2 )) is an amorphous silicon film that is not doped with hydrogen, Maximum transmittance T in the wavelength range of 400 to 680 nm ４００－６８０ＭＡＸ is 6% or less and the maximum reflectance R in the wavelength range of 400 to 680 nm ４００－６８０ＭＡＸ and the average reflectance R ４００－６８０ＡＶＥ an optical filter in which at least one of the above is 10% or less and transmits light in the range of 800 to 1000 nm.

4. Minimum transmittance T in the wavelength range of 1530 to 1570 nm １５３０－１５７０ＭＩＮ 2. The optical filter according to claim 1, wherein the ratio of the reflection coefficient to the reflection coefficient is 90% or more.

5. Minimum transmittance T in the wavelength range of 1310 to 1350 nm １３１０－１３５０ＭＩＮ 3. The optical filter according to claim 2, wherein the ratio of the reflection coefficient to the reflection coefficient is 90% or more.

6. Minimum transmittance T in the wavelength range of 880 to 920 nm ８８０－９２０ＭＩＮ 4. The optical filter according to claim 3, wherein the ratio of the total reflection coefficient to the total reflection coefficient is 90% or more.

7. 7. The optical filter according to claim 1, wherein the dielectric multilayer film has a thickness of 2.0 μm or less.

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