Optical filter and sensing device

Abstract

The present invention provides an optical filter which has a low transmittance with respect to obliquely incident visible light. The present optical filter comprises: a substrate which includes a first surface and a second surface that is on the side opposite from the first surface; a reflection and scattering part which is provided to the first surface, which reflects and scatters first light in at least a portion of a wavelength band in the visible region, and which transmits second light in at least a portion of a wavelength band in the infrared region; a filler which is disposed on the first surface side; and a reflection multilayer film which is disposed on the second surface side, which reflects the first light, and which transmits the second light; wherein, when light having a wavelength of 400-600 nm is incident at an incidence angle of θ degrees and the average value of transmittances is regarded as T_400-600(θ), T_400-600(0)≤9% and T_400-600(50)≤9%.

Description

Optical Filter and Sensing Device

[0001] The present disclosure relates to an optical filter and a sensing device.

[0002] For example, Patent Document 1 discloses an optical filter including a reflection and scattering portion that reflects and scatters light in at least a partial wavelength band in the visible region and transmits light in at least a partial wavelength band in the infrared region.

[0003] Japanese Patent No. 6729396

[0004] One aspect of the present disclosure aims to provide an optical filter and a sensing device with a low transmittance for obliquely incident light in the visible region.

[0005] The optical filter according to one aspect of the present disclosure includes a substrate having a first surface and a second surface located on the opposite side of the first surface, a reflection and scattering portion provided on the first surface that reflects and scatters first light, which is light in at least a partial wavelength band in the visible region, and transmits second light, which is light in at least a partial wavelength band in the infrared region, a filler disposed on the first surface side, and a reflection multilayer film disposed on the second surface side that reflects the first light and transmits the second light. When the average value of the transmittance when light with a wavelength of 400 nm or more and 600 nm or less is incident at an incident angle of θ degrees is T_400 - 600(θ), then T_400 - 600(0) ≤ 9% and T_400 - 600(50) ≤ 9%.

[0006] The optical filter according to one aspect of the present disclosure includes a substrate having a first surface and a second surface located on the opposite side of the first surface, a reflection and scattering portion provided on the first surface that reflects and scatters first light, which is light in at least a partial wavelength band in the visible region, and transmits second light, which is light in at least a partial wavelength band in the infrared region, a filler disposed on the first surface side, and a light absorption film disposed on the second surface side that absorbs the first light and transmits the second light. When the average value of the transmittance when light with a wavelength of 400 nm or more and 600 nm or less is incident at an incident angle of θ degrees is T_400 - 600(θ), then T_400 - 600(0) ≤ 9% and T_400 - 600(50) ≤ 9%.

[0007] According to one aspect of this disclosure, it is possible to provide an optical filter and a sensing device with low transmittance to obliquely incident visible light.

[0008] This is a schematic top view showing the overall configuration of the optical filter according to the first embodiment. This is a schematic cross-sectional view taken along the line II-II in Figure 1. This is a schematic cross-sectional view showing the behavior of a first light obliquely incident on the optical filter according to the first embodiment. This is a diagram showing an example of the reflectance spectrum of the reflective multilayer film of the optical filter according to the first embodiment. This is a diagram showing an example of the reflectance spectrum of the reflective multilayer film of the optical filter according to the first embodiment. This is a schematic cross-sectional view showing an optical filter according to a modified example of the first embodiment. This is a schematic cross-sectional view of the optical filter according to the second embodiment. This is a diagram showing a list of the specifications of the substrate and filler material, as well as the optical properties, of the optical filters according to Examples 1 to 4. This is a diagram showing a list of the specifications of the substrate and filler material, as well as the optical properties, of the optical filters according to Examples 1 to 4. This is a diagram showing the transmittance when light with a wavelength of 400 nm or more and 1000 nm or less is incident on the optical filters according to Examples 1 to 4 at an incident angle of 0 degrees. This is a diagram showing the transmittance when light with a wavelength of 400 nm or more and 1000 nm or less is incident on the optical filters according to Examples 1 to 4 at an incident angle of 40 degrees. This figure shows the transmittance of the optical filters according to Examples 1 to 4 when light with a wavelength of 400 nm to 1000 nm is incident at an incident angle of 50 degrees. This figure shows the transmittance of the optical filters according to Examples 1 to 4 when light with a wavelength of 400 nm to 1000 nm is incident at an incident angle of 60 degrees. This figure shows the transmittance of the optical filters according to Examples 1 to 4 when light with a wavelength of 400 nm to 1000 nm is incident at an incident angle of 70 degrees. This figure shows the average transmittance of the optical filters according to Examples 1 to 4 when light with a wavelength of 400 nm to 600 nm is incident. This figure shows the average transmittance of the optical filters according to Examples 1 to 4 when light with a wavelength of 930 nm to 950 nm is incident. This figure illustrates the slope of the cut-on wavelength in the optical filters according to Examples 1 to 4. This figure shows the evaluation results of the slope of the cut-on wavelength in the optical filters according to Examples 1 to 4. This figure shows the haze characteristics of the optical filter according to Example 1. This figure shows the haze characteristics of the optical filter according to Example 2. This figure shows the haze characteristics of the optical filter according to Example 3. This figure shows the haze characteristics of the optical filter according to Example 4.This figure shows the haze characteristics of the optical filters according to Examples 1 to 4 for visible light. This figure shows the haze characteristics of the optical filters according to Examples 1 to 4 for infrared light. This figure shows L* of the optical filters according to Examples 1 to 4. This figure shows a* and b* of the optical filters according to Examples 1 to 4. This figure shows the color difference between the first surface and the second surface of the optical filters according to Examples 1 to 4.

[0009] The embodiments for implementing this disclosure will be described in detail below with reference to the drawings. However, the embodiments shown below are illustrative examples of optical filters for realizing the technical concept of the embodiments of this disclosure, and are not limited to those shown below. Note that the size, positional relationships, etc. of the components shown in each drawing may be exaggerated for clarity of explanation. In each drawing, the same components are denoted by the same reference numeral, and redundant explanations are omitted as appropriate.

[0010] This specification and the claims may use terms to indicate specific directions or positions (e.g., “up,” “down,” and other terms including these terms). These terms are used solely for clarity to indicate relative directions or positions in the referenced drawings. Furthermore, “up” or “down” are unrelated to the direction of gravity.

[0011] Furthermore, in the diagrams shown below, a Cartesian coordinate system with X, Y, and Z axes may be used to indicate direction. The X, Y, and Z axes are orthogonal to each other. In the X direction along the X axis, the direction the arrow points is denoted as the +X side, and the opposite side of the +X side is denoted as the -X side. In the Y direction along the Y axis, the direction the arrow points is denoted as the +Y side, and the opposite side of the +Y side is denoted as the -Y side. In the Z direction along the Z axis, the direction the arrow points is denoted as the +Z side, and the opposite side of the +Z side is denoted as the -Z side. However, the above directional expressions merely describe the relative positions, orientations, and directions, and do not necessarily correspond to the actual relationships in use.

[0012] In this specification and the claims, “along the direction” may include deviations of up to ±10 degrees from that direction. “Perpendicular” may include deviations of up to ±10 degrees from 90 degrees. “To position” is not limited to direct contact, but also includes indirect positioning, for example, via other members.

[0013] [First Embodiment] <Configuration of the Optical Filter According to the First Embodiment> The configuration of the optical filter according to the first embodiment will be described with reference to Figures 1 to 3. Figure 1 is a schematic top view showing the overall configuration of the optical filter 100 according to the first embodiment. Figure 2 is a schematic cross-sectional view taken along line II-II in Figure 1. Figure 3 is a schematic cross-sectional view showing the behavior of the first light L10 obliquely incident on the optical filter 100. In Figures 2 and 3, arrows represent parts of the light incident on the optical filter 100, the light transmitted through the optical filter 100, and the light scattered by the optical filter 100.

[0014] As shown in Figures 1 and 2, the optical filter 100 has a substrate 1 having a first surface 1a and a second surface 1b located on the opposite side of the first surface 1a. The optical filter 100 also has a reflection and scattering section 2 provided on the first surface 1a that reflects and scatters first light L10, which is light in at least a portion of the wavelength band in the visible region, and transmits second light L20, which is light in at least a portion of the wavelength band in the infrared region. Furthermore, the optical filter 100 has a filler material 3 arranged on the first surface 1a side and a reflective multilayer film 4 arranged on the second surface 1b side that reflects the first light L10 and transmits the second light L20. The visible region refers to the wavelength range of 360 nm to less than 830 nm. The infrared region refers to the wavelength range of 830 nm to 1 mm.

[0015] In the examples shown in Figures 1 and 2, the optical filter 100 has a counter substrate 5 positioned opposite the first surface 1a, at least via a filler material 3. However, the optical filter 100 does not necessarily have a counter substrate 5. The reflection scattering portion 2 includes a surface area 21 containing a plurality of recesses, each of which is concave toward the second surface 1b, and a reflection scattering multilayer film 22 disposed on the surface area 21. The surface area 21 is arranged in two dimensions. The filler material 3 is disposed on the reflection scattering multilayer film 22. Note that in Figure 1, the reference numerals for the surface area 21 and the reflection scattering portion 2 are shown together to indicate that the reflection scattering portion 2 includes the surface area 21.

[0016] The optical filter 100 transmits the second light L20 while reflecting and scattering the first light L10. As a result, when an observer views the optical filter 100 from the upper surface 100-1 side, for example, the -Z side, the light-receiving area of ​​the first light L10 appears to be colored with a color other than black, such as white, and the space on the lower surface 100-2 side, for example, the +Z side, is not observed. The lower surface 100-2 is the surface of the optical filter 100 opposite to the upper surface 100-1.

[0017] The optical filter 100 is used, for example, in an optical device that uses infrared light, as an infrared light transmission window that blocks visible light and transmits infrared light. The optical device can transmit and receive information with an external device using infrared light while improving its design by blocking visible light so that the inside of the optical device is not visible. The coloring observed in the light-receiving area of ​​the first light L10 is not limited to a single color, but may include a combination of multiple colors such as a mottled pattern or camouflage. The upper surface 100-1 side is the incident or outgoing side of the second light L20 in the optical filter 100, and is one of the predetermined incident sides of the first light L10.

[0018] The substrate 1 can be made of a material that is transparent to at least the second light L20. Preferably, the light transmittance is 60% or more for a specific light. The substrate 1 can be made of glass or resin, etc., that is transparent to at least the second light L20. For example, borosilicate glass can be used for the substrate 1.

[0019] The reflection-scattering section 2 has the function of reflecting and scattering the first light L10 to a certain extent or more, and transmitting the second light L20 to a certain extent or more. Preferably, the reflection-scattering section 2 has the function of scattering the first light L10 more than the second light L20. In the example shown in Figures 1 and 2, the function of scattering light by the reflection-scattering section 2 is realized by the uneven surface 21 and the reflection-scattering multilayer film 22. The reflection-scattering section 2 can scatter the first light L10 by utilizing the reflection phenomenon of the reflection-scattering multilayer film 22 arranged on the uneven surface 21.

[0020] However, the function of scattering light by the reflection scattering portion 2 is not limited to the uneven portion 21 and the reflection scattering multilayer film 22, and may also be realized by a fine particle-containing resin layer made of a resin containing fine particles, or by a diffraction structure, etc. If the reflection scattering portion 2 has a fine particle-containing resin layer, it can scatter the first light L10 mainly by utilizing the refraction phenomenon at the interface with the fine particles in the binder filler 3. Alternatively, if the reflection scattering portion 2 has a diffraction structure, it can scatter the first light L10 by utilizing the diffraction phenomenon.

[0021] In the examples shown in Figures 1 and 2, the uneven portion 21 includes a plurality of recesses 210. The plurality of recesses 210 are arranged in a matrix within the first surface 1a of the substrate 1 in two mutually orthogonal directions, the X direction and the Y direction. Each of the plurality of recesses 210 has approximately the same spherical shape. By forming a plurality of recesses 210 on the first surface 1a of the substrate 1, the substrate 1 constitutes a plano-concave lens array. In Figure 1, the center-to-center distance P represents the center-to-center distance between adjacent recesses 210 in the plurality of recesses 210 when viewed from above. In the example shown in Figure 1, the center-to-center distance P in the X direction and the center-to-center distance P in the Y direction are equal. However, the center-to-center distance P in the X direction and the center-to-center distance P in the Y direction do not necessarily have to be equal.

[0022] Each of the multiple recesses 210 is not limited to a spherical shape, but may have any concave shape, and may have different shapes from each other. The uneven portion 21 may include multiple convex portions, each of which is convex toward the first surface 1a, and may include both multiple recesses and multiple convex portions. The multiple recesses or convex portions in the uneven portion 21 do not necessarily have to be arranged in a matrix at equal intervals, for example, they may be arranged in a triangular arrangement, i.e., the multiple recesses or convex portions may be arranged alternately in the X direction and the Y direction, and may be formed in a random arrangement on the first surface 1a of the substrate 1.

[0023] The reflection-scattering multilayer film 22 is a multilayer film arranged on the uneven portion 21. A dielectric multilayer film, such as those used in the mirror layer of a dichroic mirror, can be used for the reflection-scattering multilayer film 22. Details of the composition of the reflection-scattering multilayer film 22 will be described separately with reference to Table 1.

[0024] In the example shown in Figure 2, the uneven portion 21 and the reflection-scattering multilayer film 22 are made of different materials and are shown to be in contact with each other. However, for example, a part of the material that makes up the reflection-scattering multilayer film 22 may also make up the uneven portion 21. That is, the uneven portion 21 and the reflection-scattering multilayer film 22 may be integrally formed from the same material, for example. The optical filter 100 has another functional layer between the uneven portion 21 and the reflection-scattering multilayer film 22, and the uneven portion 21 and the reflection-scattering multilayer film 22 do not have to be in contact. If the uneven portion 21 and the reflection-scattering multilayer film 22 are not in contact, it is preferable that the distance between the uneven portion 21 and the reflection-scattering multilayer film 22 be short.

[0025] The filler 3 is composed of a resin or the like. For example, an ultraviolet light-curing resin can be used for the filler 3. The filler 3 is placed in each of the multiple recesses 210 contained in the uneven portion 21 via a reflection-scattering multilayer film 22. By placing the filler 3 in the recesses 210 of the uneven portion 21 via the reflection-scattering multilayer film 22, the recesses 210 are filled by the filler 3, and the upper surface 3a of the filler 3 shown in Figure 2 becomes flat. The first light L10 incident on the optical filter 100 is reflected and scattered at the interface between the recesses 210 of the uneven portion 21 and the filler 3. In the example shown in Figure 2, the filler 3 also functions as a bonding material that joins the substrate 1 and the opposing substrate 5.

[0026] The reflective multilayer film 4 is a multilayer film disposed on the second surface 1b of the substrate 1. The reflective multilayer film 4 can be made of a dielectric multilayer film, such as the one used for the mirror layer of a dichroic mirror. Details of the configuration of the reflective scattering multilayer film 22 will be described separately with reference to Table 2.

[0027] The opposing substrate 5 can be made of a material that is transparent to at least the second light L20. The opposing substrate 5 can be made of glass or resin or the like that is transparent to at least the second light L20. For example, borosilicate glass can be used for the opposing substrate 5.

[0028] In the example shown in Figure 2, the first light beam L10 and the second light beam L20 each travel downward, for example, towards the +Z side, and are incident perpendicularly on the optical filter 100 from the upper surface 100-1 side of the optical filter 100. Incidence perpendicular to the optical filter 100 means that the light beam is incident on the upper surface 100-1 along the direction of the normal 100n of the upper surface 100-1. From another perspective, incidence perpendicular to the optical filter 100 means that the angle of incidence of the light ray incident on the optical filter 100 is 0 degrees. The angle of incidence is the angle between the normal 100n of the upper surface 100-1 of the optical filter 100 and the incident light ray.

[0029] The first light L10 incident on the optical filter 100 from the upper surface 100-1 side reaches the reflection scattering section 2 and is reflected and scattered by the reflection scattering section 2. The reflected scattered light Ls shown in Figure 2 represents a portion of the light reflected and scattered by the reflection scattering section 2. Due to the reflection and scattering of the first light L10, when the optical filter 100 is viewed from the upper surface 100-1 side, the light-receiving region of the optical filter 100 appears colored. On the other hand, the second light L20 incident on the optical filter 100 from the upper surface 100-1 side is partially scattered by the reflection scattering section 2, but most of it is transmitted through the reflection scattering section 2.

[0030] Figure 3 shows the first light beam L10 obliquely incident on the optical filter 100. Here, oblique incidence means that the light is incident on the optical filter 100 at an angle that is inclined with respect to the normal 100n of the upper surface 100-1 of the optical filter 100. The incidence angle θ in Figure 3 represents the angle of the incident light beam on the optical filter 100 with respect to the normal 100n. When light is incident obliquely, the incidence angle θ is greater than 0 degrees.

[0031] For example, in an optical filter that reflects and scatters the first light L10 and transmits the second light L20, the reflectivity and scattering of the first light L10 that is incident at an oblique angle may decrease. When the reflectivity and scattering decreases, the transmittance of the first light L10 increases, and the space on the opposite side of the optical filter may become visible. When the space on the opposite side of the optical filter becomes visible, the aesthetic appeal of the optical filter decreases. Furthermore, when the space on the opposite side of the optical filter becomes visible, the effect of obscuring the interior of the optical device containing the optical filter is impaired, and the aesthetic appeal of the optical device decreases.

[0032] In this embodiment, the optical filter 100 is arranged on the second surface 1b side of the substrate 1 and has a reflective multilayer film 4 that reflects the first light L10 and transmits the second light L20. Furthermore, if the average value of the transmittance when light with a wavelength of 400 nm or more and 600 nm or less is incident at an incident angle θ degrees is T_400-600(x), then T_400-600(0) ≤ 9% and T_400-600(50) ≤ 9%.

[0033] Furthermore, even when the angle of incidence of light becomes wider, it is preferable that T_400-600(60) ≤ 10% from the viewpoint of making the space on the opposite side of the optical filter 100 more difficult to see. Also, from the same viewpoint, it is preferable that T_400-600(70) ≤ 15%.

[0034] In the example shown in Figure 3, the optical filter 100 reflects the transmitted light Lt that has passed through the reflection scattering section 2 from the first light L10 incident on the optical filter 100 from the upper surface 100-1 side at an incident angle θ degrees, using the reflective multilayer film 4. The reflected light Lr shown in Figure 3 represents the reflected light of the transmitted light Lt by the reflective multilayer film 4. By reflecting the transmitted light Lt with the reflective multilayer film 4, the transmittance of the first light L10 that is obliquely incident on the optical filter 100 at an incident angle θ is reduced, making it difficult to see through to the lower surface 100-2 side of the optical filter 100, for example, the space on the +Z side. As a result, in this embodiment, an optical filter 100 with low transmittance to obliquely incident visible light can be provided. For example, in an optical device having the optical filter 100, the design can be improved by blocking visible light to make the inside of the optical device invisible, while information can be transmitted and received with an external device using infrared light.

[0035] From the viewpoint of making the space on the opposite side of the optical filter 100 less visible, regardless of the angle of incidence, it is more preferable that |T_400-600(50)-T_400-600(0)| ≤ 5%.

[0036] Furthermore, from the viewpoint of making the space on the opposite side of the optical filter 100 less visible regardless of the angle of incidence, it is more preferable that |T_400 - 600(60) - T_400 - 600(0)| ≤ 8%.

[0037] Furthermore, from the viewpoint of making the space on the opposite side of the optical filter 100 less visible regardless of the angle of incidence, it is more preferable that |T_400-600(70)-T_400-600(0)| ≤ 10%.

[0038] The reflection scattering portion 2 includes an uneven portion 21 containing a plurality of recesses, each of which is concave on the second surface 1b side, and a reflection scattering multilayer film 22 disposed on the uneven portion 21, wherein the plurality of recesses are arranged in two dimensions, and preferably the filler 3 is disposed on the reflection scattering multilayer film 22. By including the uneven portion 21 and the reflection scattering multilayer film 22 in the reflection scattering portion 2, a reflection scattering portion 2 with superior reflection scattering performance can be easily manufactured compared to cases where the reflection scattering portion 2 has a fine particle-containing resin layer or a diffraction structure.

[0039] The optical filter 100 preferably has a counter substrate 5 disposed opposite to the first surface 1a at least via the filler 3. Since the filler 3 is not exposed to the outside when the optical filter 100 has the counter substrate 5, it is possible to prevent the filler 3 from peeling off or being damaged from the substrate 1.

[0040] In the optical filter 100, when viewed from the upper surface 100-1 side, the first light L10 is reflected and scattered by the reflection and scattering portion 2, so that the light receiving region of the first light L10 is observed as being colored in a color other than black such as white. On the other hand, when viewed from the lower surface 100-2 side, the first light L10 is reflected by the reflection multilayer film 4, so that the light receiving region of the first light L10 is observed as a mirror surface. That is, the optical filter 100 can have different design characteristics when viewed from the upper surface 100-1 side and when viewed from the lower surface 100-2 side.

[0041] Since the design characteristics of the optical filter 100 are different when viewed from the upper surface 100-1 side and when viewed from the lower surface 100-2 side, it is easy to distinguish between the front and back of the optical filter 100. Therefore, when assembling a device or apparatus having the optical filter 100 as a component, etc., the handling of the optical filter 100 becomes easy, and the assembly efficiency of the device or apparatus can be increased. Further, since the design characteristics of the optical filter 100 are different when viewed from the upper surface 100-1 side and when viewed from the lower surface 100-2 side, the optical filter 100 having the same configuration can be used for a plurality of applications without preparing optical filters 100 having different configurations for each application. For example, in an application where a white window material is required, the optical filter 100 is arranged so that the upper surface 100-1 side is visible, and in an application where a mirror window material is required, the optical filter 100 is arranged so that the lower surface 100-2 side is visible. Thereby, the optical filter 100 having the same configuration can be used for a plurality of applications.

[0042] For example, when a multilayer film is formed only on one surface of a substrate having a front surface and a back surface, the surface side of the substrate on which the multilayer film is formed may shrink, causing the substrate to warp. In the present embodiment, a reflection-scattering multilayer film 22 is formed on the first surface 1a of the substrate 1, and a reflection multilayer film 4 is formed on the second surface 1b of the substrate 1. That is, multilayer films are formed on both surfaces of the substrate 1. By forming multilayer films on both surfaces of the substrate 1, the amount of shrinkage due to film formation becomes nearly the same on both surfaces. As a result, the magnitudes of the forces acting on both surfaces of the substrate 1 due to the formation of the multilayer film become close, and the warping of the substrate 1 is reduced.

[0043] In the present embodiment, the plurality of recesses 210 are aligned in the X direction and the Y direction perpendicular to each other in the XY plane along the first surface 1a of the substrate 1. In a top view, the average value of the center-to-center distance P between adjacent recesses 210 among the plurality of recesses 210 is preferably 15 μm or more and 150 μm or less. By satisfying this condition, the transmittance can be suitably lowered for obliquely incident light in the visible range. When the concavo-convex portion 21 includes a plurality of convex portions, by setting the average value of the center-to-center distance between adjacent convex portions among the plurality of convex portions to 15 μm or more and 150 μm or less, the same effect as described above can be obtained. However, the center-to-center distance P is not limited to 15 μm or more and 150 μm or less and can be appropriately selected.

[0044] For light with a wavelength of 930 nm or more and 950 nm or less, when the average value of the refractive index of the substrate 1 is n1 and the average value of the refractive index of the filling material 3 is n2, it is preferable to satisfy |n1 - n2| ≤ 0.05. By satisfying this condition, the transmittance can be lowered for obliquely incident light in the visible range, and the transmittance for light with a wavelength of 930 nm or more and 950 nm or less can be increased.

[0045] For light with a wavelength of 840 nm or more and 860 nm or less, when the average value of the refractive index of the substrate 1 is n3 and the average value of the refractive index of the filling material 3 is n4, it is preferable to satisfy |n3 - n4| ≤ 0.05. By satisfying this condition, the transmittance can be lowered for obliquely incident light in the visible range, and the transmittance for light with a wavelength of 840 nm or more and 860 nm or less can be increased.

[0046] <Detailed Configuration of Reflective Scattering Multilayer Film 22 and Reflective Multilayer Film 4> Table 1-1 shows an example of the detailed configuration of the reflective scattering multilayer film 22 for a wavelength of 940 nm. In the example shown in Table 1-1, the reflective scattering multilayer film 22 contains 43 layers. Table 1-1 shows the layer name, material, and film thickness of each of the 43 layers, as well as the total film thickness of the 43 layers. Note that "for a wavelength of 940 nm" means that it has the property of transmitting light with a wavelength of around 940 nm. An "optical filter for a wavelength of 940 nm" refers to an optical filter with a wavelength of 930 nm to 950 nm and an average transmittance of 75% or more for light incident at an incident angle of 0 degrees.

[0047]

[0048] Figure 4 shows an example of the reflectance spectrum of the reflective-scattering multilayer film 22 of the optical filter 100 for a wavelength of 940 nm. Figure 4 shows the simulation results of the reflectance spectrum for light with a wavelength of 400 nm to 1000 nm that is incident on the optical filter 100 from the top surface 100-1. The reflectance spectrum on the vertical axis is the average value of the reflectance spectra for P-polarized and S-polarized light, respectively.

[0049] Graph 71 shows the reflectance spectrum when the incident angle θ is 0 degrees. Graph 72 shows the reflectance spectrum when the incident angle θ is 40 degrees. Graph 73 shows the reflectance spectrum when the incident angle θ is 50 degrees. Graph 74 shows the reflectance spectrum when the incident angle θ is 60 degrees. Graph 75 shows the reflectance spectrum when the incident angle θ is 70 degrees.

[0050] As shown in Graph 71, when the incident angle θ is 0 degrees, the reflectance is 80% or more at wavelengths below 940 nm, and 5% or less at wavelengths longer than 940 nm. In other words, the reflective-scattering multilayer film 22 reflects more than 80% of light at wavelengths below 940 nm and transmits more than 95% of light at wavelengths longer than 940 nm.

[0051] As shown in Graphs 72 to 75, when the incident angle θ for oblique incidence is 40 degrees or more, compared to the case where the incident angle θ is 0 degrees, the wavelength range with high reflectivity shifts to the shorter wavelength side of the visible range, and the reflectivity on the longer wavelength side of the visible range decreases, in other words, the transmittance increases. From this, it can be seen that when visible light is incident at an oblique angle, the reflective scattering properties of the reflective scattering multilayer film 22 decrease, making it easier for visible light to pass through the reflective scattering multilayer film 22.

[0052] Table 1-2 shows the detailed configuration of the reflective multilayer film 4 for a wavelength of 940 nm. In the example shown in Table 1-2, the reflective multilayer film 4 contains 43 layers. Table 1-2 shows the layer name, material, and film thickness of each of the 43 layers, as well as the total film thickness of the 43 layers.

[0053]

[0054] Figure 5 shows an example of the reflectance spectrum of the reflective multilayer film 4 of the optical filter 100 for a wavelength of 940 nm. Figure 5 shows the simulation results of the reflectance spectrum for light with a wavelength of 400 nm to 1000 nm that is incident on the optical filter 100 from the lower surface 100-2 side of the optical filter 100. The reflectance spectrum on the vertical axis is the average value of the reflectance spectra for P-polarized and S-polarized light, respectively.

[0055] Graph 81 shows the reflectance spectrum when the incident angle θ is 0 degrees. Graph 82 shows the reflectance spectrum when the incident angle θ is 40 degrees. Graph 83 shows the reflectance spectrum when the incident angle θ is 50 degrees. Graph 84 shows the reflectance spectrum when the incident angle θ is 60 degrees. Graph 85 shows the reflectance spectrum when the incident angle θ is 70 degrees. In the simulation results shown in Figure 5, the incident angle θ refers to the angle of the light ray incident from the lower surface 100-2 side of the optical filter 100 with respect to the normal 100n of the upper surface 100-1 of the optical filter 100.

[0056] As shown in Graph 81, when the incident angle θ is 0 degrees, the reflectance is 75% or more at wavelengths below 940 nm, and 5% or less at wavelengths longer than 940 nm. In other words, the reflective multilayer film 4 reflects 75% or more of the light at wavelengths below 940 nm and transmits 95% or more of the light at wavelengths longer than 940 nm.

[0057] As shown in Graphs 82 to 85, when the incident angle θ for oblique incidence is 40 degrees or more, compared to the case where the incident angle θ is 0 degrees, the wavelength range with high reflectivity shifts to the shorter wavelength side of the visible range, and the reflectivity on the longer wavelength side of the visible range decreases, in other words, the transmittance increases. From this, it can be seen that when visible light is incident at an oblique angle, the reflectivity of the reflective multilayer film 4 decreases, and visible light is more easily transmitted through the reflective multilayer film 4.

[0058] As described above, the reflective scattering multilayer film 22 and the reflective multilayer film 4 individually have high transmittance to obliquely incident visible light. It is difficult to lower the transmittance of the reflective scattering multilayer film 22 and the reflective multilayer film 4 to obliquely incident visible light by adjusting the material or thickness of the multilayer film. In this embodiment, by having a reflective scattering multilayer film 22 and a reflective multilayer film 4 in the optical filter 100, the reflectance to obliquely incident visible light can be increased and the transmittance can be lowered.

[0059] Table 2-1 shows an example of the detailed configuration of a reflection-scattering multilayer film 22 for a wavelength of 850 nm. In the example shown in Table 2-1, the reflection-scattering multilayer film 22 contains 43 layers. Table 2-1 shows the layer name, material, and film thickness of each of the 43 layers, as well as the total film thickness of the 43 layers. Note that "for 850 nm" means that it has the property of transmitting light with a wavelength of around 850 nm. An "optical filter for 850 nm" refers to an optical filter with an average transmittance of 75% or more for light with a wavelength of 840 nm to 860 nm and an incident angle of 0 degrees.

[0060]

[0061] Table 2-2 shows the detailed configuration of the reflective multilayer film 4 for a wavelength of 850 nm. In the example shown in Table 2-2, the reflective multilayer film 4 contains 43 layers. Table 2-2 shows the layer name, material, and film thickness of each of the 43 layers, as well as the total film thickness of the 43 layers.

[0062]

[0063] <Method for Manufacturing Optical Filter 100> An example of a method for manufacturing optical filter 100 is described below.

[0064] In the method for manufacturing the optical filter 100, first, the uneven surface 21 of the reflection and scattering portion 2 is formed on the first surface 1a of the substrate 1. Specifically, a Mo mask and a resist mask are deposited on the first surface 1a of the substrate 1 in this order. Next, the Mo mask and resist mask on the first surface 1a of the substrate 1 are exposed and developed. Subsequently, the Mo mask and resist mask after exposure and development are dry etched. For dry etching, Ar, CF4, O ２ Plasma or the like can be used. Subsequently, after dry etching, wet etching is performed using an acid etching solution or the like. This forms uneven surfaces 21 on the first surface 1a of the substrate 1.

[0065] After the uneven surface 21 is formed, a reflection-scattering multilayer film 22 is deposited on the uneven surface 21. As a result, a reflection-scattering portion 2 is provided on the first surface 1a of the substrate 1.

[0066] After the reflection scattering section 2 is provided, a filler material 3 is placed in the reflection scattering section 2. The filler material 3 is an ultraviolet light-curing resin or the like. By placing the filler material 3 so as to fill the irregularities of the reflection scattering section 2, the upper surface 3a of the filler material 3 placed in the reflection scattering section 2 is flattened.

[0067] Next, the opposing substrate 5 is placed on the filler material 3. Then, ultraviolet light is irradiated onto the filler material 3 to cure it. As the filler material 3 hardens, the opposing substrate 5 and the substrate 1 are joined together via the filler material 3.

[0068] The optical filter 100 can be manufactured in the manner described above.

[0069] The method for manufacturing the optical filter 100 is not limited to the method described above. For example, a blasting method may be used to form the uneven surface 21. The blasting method is preferable from the viewpoint of efficiently manufacturing the uneven surface 21 which includes at least one of a plurality of randomly arranged recesses and protrusions. On the other hand, the etching method is preferable from the viewpoint of manufacturing the uneven surface 21 which includes at least one of a plurality of recesses and protrusions arranged in a predetermined pattern with high precision.

[0070] <Modification of the First Embodiment> Next, an optical filter according to a modification of the first embodiment will be described. Note that names and reference numerals identical to those used in the previously described embodiments indicate identical or similar components or configurations, and detailed explanations will be omitted as appropriate. This also applies to the embodiments, modifications, and examples described hereafter.

[0071] Figure 6 is a schematic cross-sectional view showing an optical filter 100a according to a modified example of the first embodiment. Figure 6 shows, for example, a cross-section of the optical filter 100a corresponding to the line II-II in Figure 1.

[0072] In this modified example, the uneven portion 21 differs from the optical filter 100 according to the first embodiment in that it includes a convex array in which a plurality of convex portions 210a are arranged in a matrix in the X direction and the Y direction, respectively.

[0073] The protrusions 210a have, for example, a spherical shape. By forming a plurality of protrusions 210a on the first surface 1a of the substrate 1, the substrate 1 constitutes a plano-convex lens array. However, the protrusions 210a are not limited to a spherical shape and may have any convex shape. The plurality of protrusions 210a may have different shapes from each other. The distance between the centers of adjacent protrusions 210a can be appropriately selected. The shapes of the plurality of protrusions 210a can also be appropriately selected. Furthermore, the plurality of protrusions 210a are not limited to a matrix arrangement and may be formed in a random arrangement.

[0074] The effects of the optical filter 100a according to this modified example are the same as those of the optical filter 100 according to the first embodiment.

[0075] [Second Embodiment] Next, an optical filter according to the second embodiment will be described. Figure 7 is a schematic cross-sectional view of the optical filter 100b according to the second embodiment. Figure 7 shows a cross-section of the optical filter 100b corresponding to the line II-II in Figure 1.

[0076] As shown in Figure 7, the optical filter 100b according to this embodiment differs from the optical filter 100 according to the first embodiment in that it has a light-absorbing film 6 arranged on the second surface 1b side, which absorbs the first light L10 and transmits the second light L20. The optical filter 100b has the light-absorbing film 6 instead of the reflective multilayer film 4 that the optical filter 100 according to the first embodiment has.

[0077] The light-absorbing film 6 can be a coating or the like colored in a color other than white. From the viewpoint of being able to absorb almost all colors in the visible light, or from the viewpoint of having high light absorption efficiency, the light-absorbing film 6 is preferably a black coating. Specifically, it is preferably a resin film having a black pigment.

[0078] The black pigment may be a pigment in which molecules aggregate within the resin, but a black dye that remains transparent after dissolving in the resin is preferred because it reduces concerns about scattered light generation. Specifically, it is preferable to use dyes such as azo, anthraquinone, perylene, methine, quinoline, or azine as the dyes that make up the black dye.

[0079] In the example shown in Figure 7, the optical filter 100b absorbs the transmitted light Lt that has passed through the reflection and scattering portion 2 of the first light L10 incident on the optical filter 100b at an incident angle θ degrees, using the light absorption film 6. By absorbing the transmitted light Lt with the light absorption film 6, the transmittance of the first light L10 that is obliquely incident on the optical filter 100b at an incident angle θ is reduced, making it difficult for light to pass through the +Z side of the optical filter 100b. As a result, this embodiment provides an optical filter 100b with low transmittance to obliquely incident visible light. For example, in an optical device having the optical filter 100b, the interior of the optical device can be preferably obscured by blocking visible light, thereby improving the aesthetic appearance, while information can be preferably transmitted and received with an external device using infrared light.

[0080] In the optical filter 100b, when viewed from the top surface 100-1, the first light L10 is reflected and scattered by the reflection and scattering section 2, so the light-receiving area of ​​the first light L10 appears to be colored with a color other than black, such as white. On the other hand, when viewed from the bottom surface 100-2, the color of the light-absorbing film 6 is observed. In other words, the design of the optical filter 100b can be made different when viewed from the top surface 100-1 and when viewed from the bottom surface 100-2.

[0081] In the case of the reflective scattering multilayer film 22 formed on the first surface 1a of the substrate 1 and the light absorbing film 6 formed on the second surface 1b of the substrate 1, the forces acting on the first surface 1a and the second surface 1b of the substrate 1 during film formation may not be balanced. Therefore, from the viewpoint of reducing warping of the substrate 1, it is preferable that the film formed on the second surface 1b is the reflective multilayer film 4 of the optical filter 100 according to the first embodiment, rather than the light absorbing film 6.

[0082] The effects and advantages of the optical filter 100b according to this embodiment, other than those described above, are the same as those of the optical filter 100 according to the first embodiment.

[0083] <Modified Example of the Second Embodiment> Next, an optical filter according to a modified example of the second embodiment will be described.

[0084] Figure 8 is a schematic cross-sectional view showing an optical filter 100c according to a modified example of the second embodiment. Figure 8 shows, for example, a cross-section of the optical filter 100c corresponding to the line II-II in Figure 1.

[0085] In this modified example, the uneven portion 21 is an array of protrusions in which a plurality of protrusions 210c are arranged in a matrix along the X and Y directions, respectively, which is different from the optical filter 100b according to the second embodiment.

[0086] The convex portion 210c has, for example, a spherical shape. By forming a plurality of convex portions 210c on the first surface 1a of the substrate 1, the substrate 1 constitutes a plano-convex lens array. However, the convex portion 210c is not limited to a spherical shape and may have any convex shape. The distance between the centers of adjacent convex portions 210c among the plurality of convex portions 210c included in the concave-convex portion 21 can be appropriately selected. The shapes of the plurality of convex portions can also be appropriately selected. Furthermore, the plurality of convex portions 210c included in the concave-convex portion 21 are not limited to a matrix arrangement and may be formed in a random arrangement.

[0087] The effects of the optical filter 100c according to this modified example are the same as those of the optical filter 100b according to the second embodiment.

[0088] [Examples and Comparative Examples] Next, examples and comparative examples will be described. However, this disclosure is not limited to these examples.

[0089] In the examples and comparative examples, optical filters according to each of Examples 1 to 8 were fabricated and evaluated. Examples 1, 2, 5, and 6 are examples. Examples 3, 4, 7, and 8 are comparative examples.

[0090] (Example 1) Example 1 is an optical filter 100 according to the first embodiment for a wavelength of 940 nm. The reflection-scattering multilayer film 22 in Example 1 is the one with the configuration shown in Table 1-1 above. The reflection-scattering multilayer film 4 in Example 1 is the one with the configuration shown in Table 1-2 above.

[0091] (Example 2) Example 2 is an optical filter 100b according to the second embodiment for a wavelength of 940 nm. The reflection-scattering multilayer film 22 in Example 2 is the one with the configuration shown in Table 1-1 above. A resin film containing a black dye is used as the material for the light-absorbing film 6.

[0092] (Example 3) Example 3 is an optical filter that differs from Example 1 in that it does not have a reflective multilayer film 4.

[0093] (Example 4) In Example 4, SiO is used instead of reflective multilayer film 4. ２ This optical filter differs from Example 1 in that it has a film.

[0094] (Example 5) Example 5 is an optical filter 100 according to the first embodiment for a wavelength of 850 nm. The reflection-scattering multilayer film 22 in Example 5 is the one with the configuration shown in Table 2-1 above. The reflection-scattering multilayer film 4 in Example 5 is the one with the configuration shown in Table 2-2 above.

[0095] (Example 6) Example 6 is an optical filter 100b according to the second embodiment for a wavelength of 850 nm. The reflection-scattering multilayer film 22 in Example 6 is the one with the configuration shown in Table 2-1 above. A resin film containing a black dye is used as the material for the light-absorbing film 6.

[0096] (Example 7) Example 7 is an optical filter that differs from Example 5 in that it does not have a reflective multilayer film 4.

[0097] (Example 8) In Example 8, SiO is used instead of the reflective multilayer film 4. ２ This optical filter differs from Example 5 in that it has a film.

[0098] Figure 9 shows a list of the specifications and optical properties of the substrate and filler material for each of Examples 1 to 4. Figure 10 shows a list of the specifications and optical properties of the substrate and filler material for each of Examples 5 to 8.

[0099] In Examples 1, 2, 5, and 6, it is preferable that the average value of the absolute radius of curvature of the uneven portion 21 is between 20 μm and 620 μm. In Examples 1, 2, 5, and 6, it is preferable that the average value of the sag amount of the uneven portion 21 is between 0.5 μm and 21.0 μm. In Examples 1, 2, 5, and 6, it is preferable that the average value of the maximum inclination angle of the surface in the uneven portion 21 is between 8 degrees and 30 degrees.

[0100] <Evaluation Results> The evaluation results for the optical filters in each example are shown below.

[0101] <Transmittance for light with a wavelength of 400 nm to 1000 nm> Referring to Figures 11 to 15, the transmittance when light with a wavelength of 400 nm to 1000 nm is incident on the optical filters according to Examples 1 to 4 will be explained. Figure 11 shows the case when the incident angle is 0 degrees. Figure 12 shows the case when the incident angle is 40 degrees. Figure 13 shows the case when the incident angle is 50 degrees. Figure 14 shows the case when the incident angle is 60 degrees. Figure 15 shows the case when the incident angle is 70 degrees. A UV-Vis-Near-Infrared Spectrophotometer V-770 manufactured by JASCO Corporation was used as the transmittance measuring device.

[0102] As shown in Figure 11, when the angle of incidence was 0 degrees, the transmittance of visible light was 10% or less in all of Examples 1 to 4. As shown in Figures 12 to 15, when the angles of incidence were 40 degrees, 50 degrees, 60 degrees, and 70 degrees, the transmittance of visible light was higher than 10% in Examples 3 and 4. On the other hand, in Examples 1 and 2, the transmittance of visible light was 10% or less even when the angles of incidence were 40 degrees, 50 degrees, 60 degrees, and 70 degrees. From the above, it was found that the transmittance of obliquely incident visible light is low in Examples 1 and 2.

[0103] <Average transmittance for light in a specific wavelength range> Next, with reference to Figures 16 and 17, the average transmittance when light in a specific wavelength range is incident on the optical filters according to Examples 1 to 4 will be described. Figure 16 shows the average transmittance when light with a wavelength of 400 nm or more and 600 nm or less is incident on the optical filters according to Examples 1 to 4. Figure 17 shows the average transmittance when light with a wavelength of 930 nm or more and 950 nm or less is incident on the optical filters according to Examples 1 to 4. A V770 manufactured by JASCO Corporation was used as the average transmittance measuring device.

[0104] As shown in Figure 16, for light with wavelengths between 400 nm and 600 nm, both Example 1 and Example 2 had lower transmittances than both Example 3 and Example 4. In particular, when the incident angle was 40 degrees, 50 degrees, 60 degrees, and 70 degrees, the range of change in transmittance was larger for Examples 3 and Example 4 compared to the case where the incident angle was 0 degrees. In contrast, for Examples 1 and Example 2, the range of change in transmittance was smaller even when the incident angle was 40 degrees, 50 degrees, 60 degrees, and 70 degrees compared to the case where the incident angle was 0 degrees. The transmittances of both Example 1 and Example 2 were lower than the transmittances of both Example 3 and Example 4.

[0105] Table 3 shows a list of average transmittances for each incident angle of optical filters according to Examples 1 to 4 for light with wavelengths between 400 nm and 600 nm.

[0106]

[0107] As shown in Figure 17, the transmittances of each of Examples 1 to 4 were approximately the same for light with wavelengths between 930 nm and 950 nm.

[0108] Table 4 shows a list of transmittances for optical filters according to Examples 1 to 4 for light with wavelengths between 930 nm and 950 nm, at incident angles of 0, 40, 50, 60, and 70 degrees. The transmittances for Examples 1 to 4 were 81% or higher at an incident angle of 0 degrees, 78% or higher at an incident angle of 40 degrees, 76% or higher at an incident angle of 50 degrees, 68% or higher at an incident angle of 60 degrees, and 51% or higher at an incident angle of 70 degrees.

[0109]

[0110] Table 5 shows a list of transmittances for optical filters from Examples 5 to 8 for light with wavelengths between 840 nm and 860 nm, at incident angles of 0 and 50 degrees, respectively.

[0111]

[0112] When light with a wavelength between 930 nm and 950 nm is incident at an incident angle θ, the average value of the transmittance is defined as T_930-950(θ). From Table 4, in Example 1 and Example 2, T_930-950(0) ≥ 75% and T_930-950(50) ≥ 70%. This indicates that in Example 1 and Example 2, the transmittance is high for light with a wavelength between 930 nm and 950 nm at both incident angles of 0 and 50 degrees.

[0113] When light with a wavelength between 840 nm and 860 nm is incident at an incident angle θ, the average transmittance is defined as T_840-860(θ). From Table 5, in Examples 5 and 6, T_840-860(0) ≥ 75% and T_840-860(50) ≥ 70%. This indicates that in Examples 5 and 6, the transmittance is high for light with a wavelength between 840 nm and 860 nm at both incident angles of 0 and 50 degrees.

[0114] When light with a wavelength of 930 nm to 950 nm is incident at an incident angle θ, the average value of the transmittance is T_930-950(θ). According to Table 4, in Example 1 and Example 2, |T_930-950(50)-T_930-950(0)| ≤ 10%. This shows that in Example 1 and Example 2, the difference between the transmittance when the incident angle is 50 degrees and the transmittance when the incident angle is 0 degrees is small for light with a wavelength of 930 nm to 950 nm.

[0115] When light with a wavelength of 840 nm to 860 nm is incident at an incident angle θ, the average transmittance is given by T_840-860(θ). According to Table 5, in Examples 5 and 6, |T_840-860(50)-T_840-860(0)| ≤ 10%. This indicates that in Examples 5 and 6, the difference between the transmittance at an incident angle of 50 degrees and the transmittance at an incident angle of 0 degrees is small for light with a wavelength of 840 nm to 860 nm.

[0116] <Cut-on Wavelength Slope> Next, the cut-on wavelength slope in the optical filters according to Examples 1 to 4 will be explained with reference to Figures 18 and 19. Figure 18 is a diagram illustrating the cut-on wavelength slope in the optical filters according to Examples 1 to 4. Figure 19 is a diagram showing the evaluation results of the cut-on wavelength slope in the optical filters according to Examples 1 to 4.

[0117] As shown in Figure 18, in the transmittance spectrum graph, Slope_7030 is defined as the slope of the straight line connecting the portion with a transmittance of 70% and the portion with a transmittance of 30% in the wavelength range of 400 nm to 2000 nm. Figure 18 shows Slope_7030 for each of Examples 1 to 4 when the incident angle is 0 degrees.

[0118] Figure 19 shows the Slope_7030 of each optical filter according to Examples 1 to 4 when the incident angles are 0 degrees, 40 degrees, and 50 degrees.

[0119] Table 6 lists the Slope_7030 for each optical filter according to Examples 1 to 4 when the incident angles are 0 degrees, 40 degrees, and 50 degrees.

[0120]

[0121] From Figures 18 and 19 and Table 6, it can be seen that Slope_7030 in Example 1 is larger than Slope_7030 in Examples 2 and 3, and Slope_7030 in Examples 2 and 3 is larger than Slope_7030 in Example 4. The optical filter according to Example 1 has two multilayer films, including a reflective scattering multilayer film 22 and a reflective multilayer film 4. The transmittance shape of the entire filter is equivalent to multiplying the "transmittance shape of the reflective scattering multilayer film 22" and the "transmittance shape of the reflective multilayer film 4," so it is considered that Slope_7030 in Example 1 is larger than Slope_7030 in Examples 2 to 4.

[0122] From Table 6, in the transmittance spectrum at an incident angle θ, if the slope of the line connecting the 70% and 30% transmittance portions is defined as Slope70-30(θ), then in Example 1, |Slope70-30(0)| ≥ 1.0 and |Slope70-30(50)| ≥ 1.0. This indicates that in Example 1, for light with wavelengths between 930 nm and 950 nm, the steepness of the transmittance change with respect to wavelength near the cut-on wavelength is good at incident angles of 0, 40, and 50 degrees.

[0123] <Haze Characteristics> The haze characteristics of the optical filters according to Examples 1 to 4 will be explained with reference to Figures 20 to 25. Figure 20 is a diagram showing the haze characteristics of the optical filter according to Example 1. Figure 21 is a diagram showing the haze characteristics of the optical filter according to Example 2. Figure 22 is a diagram showing the haze characteristics of the optical filter according to Example 3. Figure 23 is a diagram showing the haze characteristics of the optical filter according to Example 4. Figure 24 is a diagram showing the visible region haze characteristics of the optical filters according to Examples 1 to 4. Figure 25 is a diagram showing the infrared region haze characteristics of the optical filters according to Examples 1 to 4.

[0124] Figures 20 to 23 show the total light transmittance Tt (shown by a solid line), the diffuse light transmittance Td (shown by a dashed line), and the haze value Haze (shown by a dashed-dotted line). Figure 24 shows the average haze value for light with wavelengths between 400 nm and 600 nm. Figure 25 shows the average haze value for light with wavelengths between 930 nm and 950 nm. The total light transmittance Tt, diffuse light transmittance Td, and haze value Haze were measured using the HSP-150Vis and HSP-150VIR spectroscopic haze meters manufactured by Murakami Color Technology Laboratory.

[0125] Table 7 is a list of the average values ​​of total light transmittance Tt, diffuse light transmittance Td, and haze value Haze for each optical filter from Example 1 to Example 4 for light with wavelengths between 400 nm and 600 nm.

[0126]

[0127] Table 8 is a list of the average values ​​of total light transmittance Tt, diffuse light transmittance Td, and haze value Haze for optical filters related to Examples 1 to 4 for light with wavelengths between 930 nm and 950 nm.

[0128]

[0129] Table 9 is a list of the average values ​​of the diffuse light transmittance Td and haze value Haze for optical filters related to Examples 5 to 8 for light with wavelengths between 840 nm and 860 nm.

[0130]

[0131] From Figures 20 to 25 and Tables 7 to 9, in Examples 1 and 2, the haze value for visible light was 71.12% or higher, and the haze value for infrared light was 3.29% or lower. In Examples 3 and 4, the haze value for visible light was 57.13% or higher, which was lower than in Examples 1 and 2. Also, in Examples 3 and 4, the haze value for infrared light was 3.14% or lower, which was about the same as in Examples 1 and 2.

[0132] From another perspective, as shown in Table 8, if we define the average value of diffuse transmittance for light with wavelengths between 400 nm and 600 nm as Td_400 - 600, then in Example 1 and Example 2, Td_400 - 600 ≤ 10%. This indicates that in Example 1 and Example 2, the diffuse light transmittance Td for visible light is low.

[0133] Table 7 shows that if we define Haze_400-600 as the average haze value for light with wavelengths between 400 nm and 600 nm, then in both Example 1 and Example 2, Haze_400-600 ≥ 50%. This indicates that in both Example 1 and Example 2, the haze value (Haze) for visible light is high.

[0134] Table 8 shows that if we define Td_930-950 as the average value of the diffuse transmittance for light with wavelengths between 930 nm and 950 nm, then in Example 1 and Example 2, Td_930-950 ≤ 5%. This indicates that in Example 1 and Example 2, the diffuse transmittance for light with wavelengths between 930 nm and 950 nm is low.

[0135] Table 9 shows that, if we define Td_840-860 as the average value of the diffuse transmittance for light with wavelengths between 840 nm and 860 nm, then in the 5th and 6th cases, Td_840-860 ≤ 5%. This indicates that the diffuse transmittance for light with wavelengths between 840 nm and 860 nm was low in the 5th and 6th cases.

[0136] From Table 8, if we define Haze_930-950 as the average haze value for light with wavelengths between 930 nm and 950 nm, then in Example 1 and Example 2, Haze_930-950 ≤ 5%. This indicates that in Example 1 and Example 2, the haze value for light with wavelengths between 930 nm and 950 nm is low.

[0137] Table 9 shows that if we define Haze_840-860 as the average haze value for light with wavelengths between 840 and 860 nm, then in the 5th and 6th examples, Haze_840-860 ≤ 5%. This indicates that the haze values ​​for light with wavelengths between 840 and 860 nm were low in the 5th and 6th examples.

[0138] <Color Characteristics> The color characteristics of the optical filters according to Examples 1 to 4 will be described with reference to Figures 26 to 28. Figure 26 is a diagram showing L* of the optical filters according to Examples 1 to 4. Figure 27 is a diagram showing a* and b* of the optical filters according to Examples 1 to 4. Figure 28 is a diagram showing the color difference ΔE*ab between the top and bottom surfaces of the optical filters according to Examples 1 to 4. A CM-700d manufactured by Konica Minolta, Inc. was used as the measuring device for L*, a*, and b*.

[0139] Table 10 lists the L*, a*, and b* values ​​for each of the optical filters related to Examples 1 to 4 for a wavelength of 940 nm. In Table 10, "top surface" refers to the top surface 100-1 of the optical filter, and "bottom surface" refers to the bottom surface 100-2 of the optical filter.

[0140]

[0141] Table 11 lists the L*, a*, and b* values ​​for each of the optical filters for the 5th to 8th examples, which are for a wavelength of 850 nm. In Table 11, "top surface" refers to the top surface 100-1 of the optical filter, and "bottom surface" refers to the bottom surface 100-2 of the optical filter.

[0142]

[0143] Table 12 is a list of the color differences ΔE*ab for each optical filter related to Examples 1 to 4 for a wavelength of 940 nm. The color difference ΔE*ab was calculated from the following equations (1), (2), (3), and (4). In equation (2), L* (top surface) represents L* of the top surface 100-1 of the optical filter, and L* (bottom surface) represents L* of the bottom surface 100-2 of the optical filter. In equation (3), a* (top surface) represents a* of the top surface 100-1 of the optical filter, and a* (bottom surface) represents a* of the bottom surface 100-2 of the optical filter. In equation (4), b* (top surface) represents b* of the top surface 100-1 of the optical filter, and b* (bottom surface) represents b* of the bottom surface 100-2 of the optical filter. ΔE*ab = [(ΔL*)] ２ + (Δa*) ２ + (Δb*) ２ ] １／２ ... (1) ΔL*= L* (top surface) - L* (bottom surface) ... (2) Δa*=a* (top surface) - a* (bottom surface) ... (3) Δb*=b* (top surface) - b* (bottom surface) ... (4)

[0144]

[0145] Table 13 is a list of the chromatic differences ΔE*ab for each of the optical filters for the 5th to 8th examples, which are for a wavelength of 850 nm. The chromatic differences ΔE*ab were calculated from the above equations (1), (2), (3), and (4).

[0146]

[0147] In this embodiment, it is preferable that, when viewed from above, L* ≥ 80, -10 ≤ a* ≤ 10, and -10 ≤ b* ≤ 10. In Figures 26 and 27, Table 10, and Table 11, Examples 1 to 8 satisfy this condition. It was found that by satisfying this condition, each of the optical filters according to Examples 1 to 8 becomes brighter and whiter in color, improving their aesthetic appeal.

[0148] In this embodiment, if ΔE*ab is the difference in chromaticity between the chromaticity of the upper surface 100-1 measured from the upper surface 100-1 side of the optical filter and the chromaticity of the lower surface 100-2 measured from the lower surface 100-2 side of the optical filter, it is preferable that ΔE*ab ≥ 5. In Figure 28, Table 12, and Table 13, Examples 1, 2, 5, and 6 satisfy this condition. By satisfying this condition, the colors of the upper surface 100-1 and the lower surface 100-2 of the optical filter are different, so the design of the optical filter can be made different when viewed from the upper surface 100-1 side and when viewed from the lower surface 100-2 side.

[0149] Although preferred embodiments have been described in detail above, the embodiments of this disclosure are not limited to those described above, and various modifications and substitutions can be made to the embodiments of this disclosure without departing from the scope of the claims.

[0150] The ordinal numbers, quantities, and other figures used in the description of the embodiments of this disclosure are all illustrative to specifically illustrate the technology of this disclosure, and this disclosure is not limited to the illustrative figures. Furthermore, the connection relationships between the components are illustrative to specifically illustrate the technology of this disclosure, and are not limited to the connection relationships that realize the functions of this disclosure.

[0151] The optical filter according to the embodiment of this disclosure has low transmittance to obliquely incident visible light, thereby improving the aesthetics by blocking visible light and making the inside of the optical device invisible, while allowing information to be transmitted and received with an external device using infrared light. As a result, the optical filter according to the embodiment of this disclosure can be suitably used, for example, as a window material for an optical device. Examples of optical devices include sensing devices such as facial recognition devices or gesture sensors, industrial equipment, and AR (Augmented Reality) / VR (Virtual Reality) devices. Sensing devices are particularly suitable because, by having the optical filter according to the embodiment of this disclosure, they can transmit and receive information with an external device using infrared light while improving their aesthetics.

[0152] This application claims priority based on Japanese Patent Application No. 2024-207123, filed on 28 November 2024, and incorporates all of its disclosures herein.

[0153] 1 Substrate 1a First surface 1b Second surface 2 Reflection and scattering portion 3 Filler 3a Top surface 4 Reflection multilayer film 5 Opposing substrate 6 Light absorption film 21 Uneven portion 22 Reflection and scattering multilayer film 71, 72, 73, 74, 75, 81, 82, 83, 84, 85 Graph 100, 100a, 100b, 100c Optical filter 100n Normal 100-1 Top surface 100-2 Bottom surface 210 Recess 210a, 210c Convex portion L10 First light L20 Second light Lr Reflected light Ls Reflection and scattering light Lt Transmitted light P Center-to-center distance θ Incident angle

Claims

1. An optical filter comprising: a substrate having a first surface and a second surface located opposite to the first surface; a reflection and scattering portion provided on the first surface that reflects and scatters first light, which is light in at least a portion of the wavelength band in the visible region, and transmits second light, which is light in at least a portion of the wavelength band in the infrared region; a filler disposed on the first surface side; and a reflective multilayer film disposed on the second surface side that reflects the first light and transmits the second light, wherein when light with a wavelength of 400 nm or more and 600 nm or less is incident at an incident angle θ degrees, the average value of the transmittance is T_400-600(θ), then T_400-600(0) ≤ 9% and T_400-600(50) ≤ 9%.

2. An optical filter comprising: a substrate having a first surface and a second surface located opposite to the first surface; a reflection and scattering portion provided on the first surface that reflects and scatters first light, which is light in at least a portion of the wavelength band in the visible region, and transmits second light, which is light in at least a portion of the wavelength band in the infrared region; a filler disposed on the first surface side; and a light-absorbing film disposed on the second surface side that absorbs the first light and transmits the second light, wherein when light with a wavelength of 400 nm or more and 600 nm or less is incident at an incident angle θ degrees, the average value of the transmittance is T_400-600(θ), then T_400-600(0) ≤ 9% and T_400-600(50) ≤ 9%.

3. The optical filter according to claim 1 or 2, wherein the reflection scattering portion includes an uneven portion comprising at least one of a plurality of recesses that are concave toward the second surface and a plurality of protrusions that are convex toward the first surface, and a reflection scattering multilayer film disposed on the uneven portion, wherein at least one of the plurality of recesses and the plurality of protrusions is arranged in two dimensions, and the filler is disposed on the reflection scattering multilayer film.

4. The optical filter according to claim 1 or claim 2, further comprising a counter substrate positioned opposite the first surface via at least the filler material.

5. The optical filter according to claim 1 or claim 2, wherein the average transmittance when light with a wavelength of 930 nm or more and 950 nm or less is incident at an incident angle θ is T_930-950(θ), and the average transmittance when light with a wavelength of 840 nm or more and 860 nm or less is incident at an incident angle θ is T_840-860(θ), such that T_930-950(0) ≥ 75% and T_930-950(50) ≥ 70%, or T_840-860(0) ≥ 75% and T_840-860(50) ≥ 70%.

6. The optical filter according to claim 1 or claim 2, wherein the average transmittance when light with a wavelength of 930 nm or more and 950 nm or less is incident at an incident angle θ is T_930-950(θ), and the average transmittance when light with a wavelength of 840 nm or more and 860 nm or less is incident at an incident angle θ is T_840-860(θ), such that |T_930-950(50)-T_930-950(0)| ≤ 10%, or |T_840-860(50)-T_840-860(0)| ≤ 10%.

7. An optical filter according to claim 1 or claim 2, wherein |T_400-600(50)-T_400-600(0)| ≤ 5%.

8. In the transmittance spectrum at an incident angle θ degrees, if the slope of the line connecting the portion with a transmittance of 70% and the portion with a transmittance of 30% is defined as Slope70-30(θ), then |Slope70-30(0)| ≥ 1.0% / nm and |Slope70-30(50)| ≥ 1.0% / nm, the optical filter according to claim 1 or claim 2.

9. The optical filter according to claim 1 or claim 2, wherein the average value of the diffuse transmittance for light with a wavelength of 400 nm or more and 600 nm or less is Td_400-600, and Td_400-600 ≤ 10%.

10. The optical filter according to claim 1 or claim 2, wherein if the average value of the haze for light with a wavelength of 400 nm or more and 600 nm or less is defined as Haze_400-600, then Haze_400-600 ≥ 50%.

11. The optical filter according to claim 1 or claim 2, wherein the average value of the diffuse transmittance for light with a wavelength of 930 nm or more and 950 nm or less is Td_930-950, and the average value of the diffuse transmittance for light with a wavelength of 840 nm or more and 860 nm or less is Td_840-860, such that Td_930-950 ≤ 5% or Td_840-860 ≤ 5%.

12. The optical filter according to claim 1 or claim 2, wherein if the average value of the haze for light with a wavelength of 930 to 950 nm is Haze_930-950, and the average value of the haze for light with a wavelength of 840 to 860 nm is Haze_840-860, then Haze_930-950 ≤ 5% or Haze_840-860 ≤ 5%.

13. The optical filter according to claim 1 or claim 2, wherein when the chromaticity is measured from the upper surface of the optical filter, L* ≥ 80, -10 ≤ a* ≤ 10, and -10 ≤ b* ≤ 10.

14. The optical filter according to claim 1 or claim 2, wherein ΔE*ab is the difference in chromaticity between the chromaticity of the upper surface measured from the upper side of the optical filter and the chromaticity of the lower surface measured from the lower side opposite to the upper surface of the optical filter, and ΔE*ab ≥ 5.

15. The optical filter according to claim 3, wherein, in a top view, the average value of the distance between the centers of adjacent recesses in the plurality of recesses, or the average value of the distance between the centers of adjacent protrusions in the plurality of protrusions, is 15 μm or more and 150 μm or less.

16. An optical filter according to claim 1 or claim 2, wherein, with respect to light with a wavelength of 930 nm or more and 950 nm or less, if the average refractive index of the substrate is n1 and the average refractive index of the filler is n2, then |n1 - n2| ≤ 0.

05.

17. For light with a wavelength of 840 nm or more and 860 nm or less, the optical filter according to claim 1 or claim 2, wherein, if the average refractive index of the substrate is n3 and the average refractive index of the filler is n4, then |n3 - n4| ≤ 0.

05.

18. An optical filter comprising: a substrate having a first surface and a second surface located opposite to the first surface; a surface on the first surface including at least one of a plurality of recesses, each concave toward the second surface, and a plurality of protrusions, each convex toward the first surface; a multilayer film disposed on the surface; a filler disposed on the first surface side; and a multilayer film disposed on the second surface side, wherein when light with a wavelength of 400 nm to 600 nm is incident at an incident angle θ degrees, the average value of transmittance is T_400-600(θ), such that T_400-600(0) ≤ 9% and T_400-600(50) ≤ 9%.

19. An optical filter comprising: a substrate having a first surface and a second surface located opposite to the first surface; a surface on the first surface including at least one of a plurality of recesses, each concave toward the second surface, and a plurality of protrusions, each convex toward the first surface; a multilayer film disposed on the surface; a filler disposed on the first surface side; and a light-absorbing film disposed on the second surface side, wherein when light with a wavelength of 400 nm to 600 nm is incident at an incident angle θ degrees, the average value of transmittance is T_400-600(θ), such that T_400-600(0) ≤ 9% and T_400-600(50) ≤ 9%.

20. A sensing device having the optical filter described in claim 1 or claim 2.

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