Near-infrared cutoff filter and imaging device equipped with the filter

Abstract

The near-infrared cutoff filter comprises: a transparent substrate with a thickness of 0.16 to 0.26 mm and an average transmittance of less than 1% in the wavelength region of 800 to 1100 nm; and a resin layer formed on at least one of the main surfaces of the transparent substrate, which absorbs light of a specific wavelength.

Description

Technical Field

[0001] The present invention relates to a near-infrared cutoff filter disposed in front of a solid-state imaging element for visual sensitivity correction of the solid-state imaging element, and an imaging device having the filter. Prior Technology

[0002] In recent years, imaging devices with built-in solid-state imaging elements such as CCDs or CMOS sensors have been used in digital cameras and mobile information terminals. In these devices, since the solid-state imaging element has spectral sensitivity from the near-ultraviolet to the near-infrared domain, a near-infrared cutoff filter is provided. This filter blocks a portion of the incident near-infrared light to correct it to be closer to human visual perception. Although such a near-infrared cutoff filter is placed in the optical path to the solid-state imaging element, in order to reduce the overall size of the imaging device, near-infrared cutoff filters that also function as the cover glass of the imaging device are also used in practice (as shown in Japanese Patent Document 1).

[0003] Figure 29 shows an example of the structure of a near-infrared cutoff filter (a conventional example) described in Japanese Patent Document 1. As shown in Figure 29, the near-infrared cutoff filter described in Japanese Patent Document 1 includes: a transparent substrate 13; an absorption layer 11 formed on one main surface of the transparent substrate 13 that absorbs light in the near-infrared wavelength region and the ultraviolet wavelength region; and a reflective layer 12 formed on the other main surface of the transparent substrate 13 that controls the transmission and blocking of light in a specific wavelength region. The reflective layer 12 is composed of a dielectric multilayer film with a thickness of 2 to 10 μm, which alternately stacks a low-refractive-index dielectric film (low dielectric film) and a high-refractive-index dielectric film (high dielectric film). By configuring the spectral transmittance of the reflective layer 12 to meet predetermined requirements, especially having a spectral characteristic close to the luminosity curve on the long wavelength side, a near-infrared cutoff filter with low incident angle dependence is realized.

[0004] Patent Document 1: Japanese Patent No. 6119920

[0005] However, the near-infrared cutoff filter described in Japanese Patent Document 1 has a reflective layer 12 composed of a relatively thick (2~10μm) dielectric multilayer film. Therefore, if light is incident obliquely on the reflective layer 12, the light path length will become longer, resulting in a phase shift problem.

[0006] Figure 30 shows the spectral transmittance curves of the reflective layer 12 of the near-infrared cutoff filter in Figure 29, representing the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. Figure 31 shows the spectral transmittance curves of the near-infrared cutoff filter in Figure 29, representing the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°.

[0007] As shown in Figure 26, when light with an incident angle of 30° is incident on the reflective layer 12, due to the effect of phase shift, there are problems such as the spectral transmittance curve shifting towards the shorter wavelength side (part P1 in Figure 30) and ripples appearing in the spectral transmittance curve (part P2 in Figure 30). Furthermore, if a wavelength shift occurs in the spectral transmittance curve of the reflective layer 12, a wavelength shift will also occur in the spectral transmittance curve of the near-infrared cutoff filter (part P3 in Figure 31), and the color reproducibility of the solid-state imaging element may be reduced. Additionally, if ripples appear in the spectral transmittance curve of the reflective layer 12, ripples will also appear in the spectral transmittance curve of the near-infrared cutoff filter (part P4 in Figure 31), and ghosting may be observed on the solid-state imaging element. Therefore, a near-infrared cutoff filter with better oblique incidence characteristics is needed, which will not produce band shift or ripples even when using obliquely incident light. Summary of the Invention

[0008] The present invention was made in view of the following circumstances, and its object is to provide a near-infrared cutoff filter with very low incident angle dependence and excellent oblique incident characteristics, and an imaging device having such a near-infrared cutoff filter.

[0009] To achieve the aforementioned objectives, the inventors conducted thorough research and discovered that, in the spectral transmittance curves of transparent substrates composed of glass (e.g., fluorophosphate glass, phosphate glass, etc.), particular attention is paid to the wavelength region of 800–1100 nm. If a material with a lower average transmittance in the 800–1100 nm wavelength region is used, a cutoff filter that selectively transmits light in the visible light region can be manufactured without the need for the reflective film used in conventional near-infrared cutoff filters. This invention is based on this insight.

[0010] That is, the near-infrared cutoff filter of the present invention is characterized by: a transparent substrate with a thickness of 0.16 to 0.26 mm and an average transmittance of less than 1% in the wavelength region of 800 to 1100 nm; and a resin layer formed on at least one of the main surfaces of the transparent substrate, which absorbs light of a specific wavelength.

[0011] With this structure, since a reflective layer composed of dielectric multilayer films is not required as in traditional filters (i.e., no reflective layer is present), even if light is incident at an angle relative to the near-infrared cutoff filter, changes in the optical path length are minimal, and phase shifts are suppressed. Therefore, almost no wavelength shifts or ripples occur in the spectral transmittance curve of the near-infrared cutoff filter.

[0012] In addition, the half-value wavelength of the transmittance curve of the transparent substrate is preferably 300~400 nm on the short wavelength side and 590~670 nm on the long wavelength side.

[0013] In addition, the transparent substrate preferably has an average transmittance of less than 40% in the wavelength region of 650~720 nm.

[0014] In addition, the average transmittance of the transparent substrate is preferably less than 15% in the wavelength region of 720~750 nm.

[0015] In addition, the transparent substrate preferably has an average transmittance of less than 5% in the wavelength region of 800 to 1200 nm.

[0016] Furthermore, the resin layer may comprise a transparent resin and a pigment uniformly dispersed within the transparent resin. In this case, the pigment is preferably a UV-absorbing pigment with a maximum absorption wavelength of 340–400 nm. Alternatively, the pigment is preferably a near-infrared absorbing pigment with a maximum absorption wavelength of 650–900 nm.

[0017] In addition, the resin layer may contain Si atoms as an essential component, and one or more of Ti atoms, Zr atoms and Al atoms as optional components.

[0018] Additionally, a bonding layer can be provided between the transparent substrate and the resin layer to improve the adhesion between them. Furthermore, in this case, it is preferable to further provide a bonding layer on another main surface of the transparent substrate. The bonding layer preferably has a monolayer structure comprising Si atoms and one or more atoms selected from Ti atoms, Zr atoms, and Al atoms. Furthermore, in this case, the proportion of Ti atoms, Zr atoms, and Al atoms in the bonding layer relative to the total number of Si atoms, Ti atoms, Zr atoms, and Al atoms is preferably between 0 atomic% and 50 atomic% or less.

[0019] Alternatively, a first functional film can be provided on the resin layer, and a second functional film can be provided on another main surface of the transparent substrate. In this case, the first and second functional films preferably have at least one of the functions of an anti-reflective film, an infrared cut-off film, and an ultraviolet cut-off film. Furthermore, in this case, the first and second functional films are preferably each composed of a dielectric multilayer film with a thickness of 500 nm or less. Additionally, in this case, the dielectric multilayer film preferably has 10 layers or less.

[0020] In addition, the dielectric multilayer film is preferably formed by alternating layers of a low-refractive-index dielectric film made of a material with a refractive index of 1.1 to 1.5 and a high-refractive-index dielectric film made of a material with a refractive index of 2.0 to 2.5.

[0021] In addition, the dielectric multilayer film is preferably formed by alternating layers of a low-refractive-index dielectric film made of a material with a refractive index of 1.1 to 1.3 and a high-refractive-index dielectric film made of a material with a refractive index of 1.4 to 1.6.

[0022] In addition, the half-value wavelength of the transmittance curve is preferably 385~430 nm on the short wavelength side and 590~660 nm on the long wavelength side.

[0023] In addition, preferably, the difference between the half-value wavelength of the long wavelength side of the transmittance curve of the transparent substrate and the half-value wavelength of the long wavelength side of the transmittance curve of the near-infrared cutoff filter is less than 20 nm.

[0024] In addition, the transparent substrate is preferably made of fluorophosphate glass or phosphate glass.

[0025] From another perspective, the imaging device of the present invention is characterized by comprising a solid-state imaging element and any one of the aforementioned near-infrared cutoff filters. Furthermore, in this case, the near-infrared cutoff filter is positioned directly in front of the solid-state imaging element and can also function as a cover glass.

[0026] As described above, according to the present invention, a near-infrared cutoff filter with minimal dependence on the angle of incidence and excellent oblique incidence characteristics is realized. Furthermore, an imaging device incorporating such a near-infrared cutoff filter and exhibiting excellent color reproduction can be realized. Simple Explanation of the Diagram

[0027] Figures 1(a) and 1(b) are structural diagrams illustrating a near-infrared cutoff filter according to a first embodiment of the present invention. Figure 2 is a longitudinal cross-sectional view illustrating the structure of an imaging device equipped with a near-infrared cutoff filter according to the first embodiment of the present invention. Figure 3 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the first embodiment (Example 1) of the present invention and a glass substrate used in the near-infrared cutoff filter. Figure 4 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the first embodiment (Example 2) of the present invention and a glass substrate used in the near-infrared cutoff filter. Figure 5 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the first embodiment (Example 3) of the present invention and a glass substrate used in the near-infrared cutoff filter. Figure 6 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the first embodiment (Example 4) of the present invention and a glass substrate used in the near-infrared cutoff filter. Figure 7 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the first embodiment (Example 5) of the present invention and a glass substrate used in the near-infrared cutoff filter. Figure 8 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the first embodiment (Example 6) of the present invention and a glass substrate used in the near-infrared cutoff filter. Figure 9 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the first embodiment (Example 7) of the present invention and a glass substrate used in the near-infrared cutoff filter. Figure 10 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the first embodiment (Example 8) of the present invention and a glass substrate used in the near-infrared cutoff filter. Figure 11 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the first embodiment (Example 9) of the present invention and a glass substrate used in the near-infrared cutoff filter. Figure 12 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the first embodiment (Example 10) of the present invention and a glass substrate used in the near-infrared cutoff filter. Figure 13 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the first embodiment (Example 11) of the present invention and a glass substrate used in the near-infrared cutoff filter. Figure 14 is a longitudinal cross-sectional view illustrating the structure of a near-infrared cutoff filter according to a second embodiment of the present invention. Figure 15 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the second embodiment (Example 12) of the present invention. Figure 16 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the second embodiment (Example 13) of the present invention. Figure 17 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the second embodiment (Example 14) of the present invention. Figure 18 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the second embodiment (Example 15) of the present invention. Figure 19 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the second embodiment (Example 16) of the present invention. Figure 20 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the second embodiment (Example 17) of the present invention. Figure 21 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the second embodiment (Example 18) of the present invention. Figure 22 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the second embodiment (Example 19) of the present invention. Figure 23 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the second embodiment (Example 20) of the present invention. Figure 24 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the second embodiment (Example 21) of the present invention. Figure 25 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the second embodiment (Example 22) of the present invention. Figure 26 is a graph showing the spectral transmittance of a near-infrared cutoff filter according to the second embodiment (Example 23) of the present invention. Figure 27 is a longitudinal cross-sectional view illustrating the near-infrared cutoff filter structure according to the third embodiment (Example 24) of the present invention. Figure 28 is a longitudinal cross-sectional view illustrating the near-infrared cutoff filter structure according to the third embodiment (Example 25) of the present invention. Figure 29 is a longitudinal cross-sectional view of the structure of a conventional near-infrared cutoff filter. Figure 30 shows the spectral transmittance curve of the reflective layer used in a conventional near-infrared cutoff filter. Figure 31 shows the spectral transmittance curve of a conventional near-infrared cutoff filter. Implementation

[0028] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, identical or equivalent parts in the drawings will be labeled with the same symbols, and the description will not be repeated.

[0029] (First Embodiment) Figures 1(a) and 1(b) are structural diagrams illustrating the near-infrared cut-off filter 100 according to the first embodiment of the present invention, wherein Figure 1(a) is a top view and Figure 1(b) is a longitudinal cross-sectional view. Figure 2 is a longitudinal cross-sectional view illustrating the structure of an imaging device 1 that seals the opening of the package 300 of the solid-state imaging element 200 using the near-infrared cut-off filter 100 of this embodiment. As shown in Figures 1(b) and 2, the near-infrared cut-off filter 100 of this embodiment is installed in front of the package 300 used to house the solid-state imaging element 200, serving as an optical element for protecting the solid-state imaging element 200 and also for visual sensitivity correction of the solid-state imaging element 200.

[0030] As shown in Figure 1(a), the near-infrared cutoff filter 100 of this embodiment has a rectangular plate shape (e.g., 6 mm (horizontal) × 5 mm (vertical)) and is composed of a glass substrate 101 (transparent substrate) and a resin layer 102 formed on a main surface of the glass substrate 101 (the upper surface in Figure 1(b)).

[0031] [Glass substrate] The glass substrate 101 of this embodiment is, for example, an absorbent glass substrate made of phosphate-based glass or fluorophosphate-based glass. From the viewpoint of miniaturization and weight reduction, the thickness of the glass substrate 101 of this embodiment is preferably 0.35 mm or less, and more preferably 0.16 to 0.26 mm.

[0032] In this embodiment, phosphate-based glass refers to glass containing P, O, and other arbitrary components as essential elements, preferably glass containing CuO. Because phosphate-based glass contains CuO, it can absorb near-infrared light more effectively. Other arbitrary components of phosphate-based glass include, for example, Ca, Mg, Sr, Ba, Li, Na, K, Cs, etc.

[0033] Specific examples of phosphate-based glasses preferably include: P₂O₅: exceeding 0% by mass but below 80% by mass, Al₂O₃: 0~40% by mass BaO: 0~40% by mass CuO: 0~40% by mass.

[0034] Furthermore, the fluorophosphate-based glass in this embodiment refers to glass containing P, O, F, and other arbitrary components as essential elements, and preferably glass containing CuO. Because fluorophosphate-based glass contains CuO, it can more effectively absorb near-infrared light. Other arbitrary components of fluorophosphate-based glass include, for example, Ca, Mg, Sr, Ba, Li, Na, K, Cs, etc.

[0035] Furthermore, as a fluorophosphate-based glass, glass containing BaO is preferred. Using BaO content of 0% or more can improve the glass's resistance to devitrification and its solubility. If it exceeds 10%, devitrification is likely, therefore 0-10% is preferable. Moreover, the BaO content is more preferably 1-10%, and optimally 1-5%.

[0036] Furthermore, for fluorophosphate-based glasses, glass containing Al₂O₃ is preferred. Using Al₂O₃ content of 0% or more improves the stability and chemical durability of the glass. If it exceeds 10%, devitrification is likely, therefore 0-10% is preferable. Moreover, the Al₂O₃ content is more preferably 1-10%, and optimally 1-5%.

[0037] Furthermore, as a fluorophosphate-based glass, glass containing Y₂O₃ is preferred. Using more than 0% Y₂O₃ can improve the refractive index while maintaining thermal stability. If it exceeds 10%, devitrification is likely, and the glass transition temperature or deformation point temperature increases; therefore, 0-10% is preferable. More preferably, the Y₂O₃ content is 1-10%, and most preferably 1-5%.

[0038] Furthermore, for fluorophosphate-based glasses, glasses containing BaCl₂ are preferred. By introducing an appropriate amount of Cl into the glass using BaCl₂, the difference between the glass's initial crystallization temperature (Tx) and glass transition temperature (Tg) is increased, thus improving the glass's stability against devitrification. If the content exceeds 10%, devitrification is likely to occur; therefore, 0-10% is preferable. Moreover, the BaCl₂ content is more preferably 1-10%, and optimally 1-5%.

[0039] Specific examples of fluorophosphate-based glasses include: P₂O₅: exceeding 0% by mass but below 70% by mass, Al₂O₃: 0~40% by mass BaO: 0~40% by mass CuO: 0~40% by mass In addition, it preferably contains 0% to 40% by mass of fluoride.

[0040] In addition, it includes: P₂O₅: 20~60% by mass Al₂O₃: 0~10% by mass BaO: 0~10% by mass CuO: 0~10% by mass In addition, it preferably contains 1 to 30% by mass of fluoride.

[0041] In addition, it includes: P₂O₅: 20~60% by mass Al₂O₃: 1~10% by mass BaO: 1~10% by mass CuO: 1~10% by mass In addition, it is preferable to contain 2 to 30% by mass of fluoride.

[0042] In addition, one or more of the fluorides mentioned above can be selected from MgF2, CaF2, SrF2, etc.

[0043] As a specific example of such a fluorophosphate glass, it preferably includes: P₂O₅: 40~50% by mass Al₂O₃: 1~10% by mass BaO: 1~10% by mass CuO: 1~10% by mass MgF2: 1~10% by mass CaF2: 1~10% by mass SrF 2: 1-10% by mass Y₂O₃: 1-10% by mass BaCl₂: 0-1% by mass.

[0044] Furthermore, as will be described in detail later, the glass substrate 101 of this embodiment is preferably configured such that the average transmittance in the wavelength region of 800-1100 nm is 3% or less, and more preferably 1% or less. In this way, if a glass substrate 101 with a low average transmittance in the wavelength region of 800-1100 nm is used, a cutoff filter that selectively transmits light in the visible light region can be manufactured without using the reflective film (dielectric multilayer film) used in conventional near-infrared cutoff filters.

[0045] In addition, the average transmittance of the glass substrate 101 in the wavelength region of 720~750 nm is preferably 15% or less, more preferably 10% or less, and even more preferably 8% or less. In addition, the average transmittance of the glass substrate 101 in the wavelength region of 650~720 nm is preferably 40% or less, more preferably 10% or less, and even more preferably 8% or less. In addition, the average transmittance of the glass substrate 101 in the wavelength region of 800~1200 nm is preferably less than 5%, more preferably less than 3%, and even more preferably less than 2%.

[0046] Furthermore, the half-value wavelength (UV_λ50) of the transmittance curve of the glass substrate 101 on the short wavelength side is preferably in the range of 300~400 nm, more preferably in the range of 305~350 nm, and even more preferably in the range of 310~340 nm. Additionally, the half-value wavelength (NIR_λ50) of the transmittance curve of the glass substrate 101 on the long wavelength side is preferably in the range of 590~670 nm, more preferably in the range of 610~650 nm. Furthermore, in this specification, the half-value wavelength refers to the wavelength at which transmittance reaches 50%, the half-value wavelength (UV_λ50) on the short wavelength side refers to the wavelength at which transmittance reaches 50% when the transmittance curve rises, and the half-value wavelength (NIR_λ50) on the long wavelength side refers to the wavelength at which transmittance reaches 50% when the transmittance curve falls.

[0047] [Resin Layer] In this embodiment, the resin layer 102 is a layer composed of pigments that absorb light of a specific wavelength and resin. The resin layer 102 may contain, for example, at least one of near-infrared absorbing pigments and ultraviolet absorbing pigments, and a transparent resin, preferably with the pigments uniformly dissolved or dispersed in the transparent resin. In addition, the resin layer 102 of this embodiment preferably contains Si atoms as an essential component and contains one or more selected from Ti atoms, Zr atoms and Al atoms as arbitrary components.

[0048] As the near-infrared absorbing pigment constituting the resin layer 102, conventionally known substances can be used, such as one or more selected from cyanine pigments, polymethystyl pigments, squaric acid pigments, porphyrin pigments, metal dithiol complex pigments, phthalocyanine pigments, diimide pigments, and inorganic oxide particles, and more preferably one or more selected from squaric acid pigments, cyanine pigments, and phthalocyanine pigments.

[0049] As the ultraviolet-absorbing pigment constituting the resin layer 102, conventionally known substances can be used. For example, one or more of the following compounds can be used: benzotriazole compounds, benzophenone compounds, triazine compounds, styrene compounds, benzoxazinone compounds, cyanoacrylates, oxaza compounds, salicylates, formamidinides, indole compounds, and azobenzene compounds. More preferably, one or more of the following compounds can be used: benzotriazole compounds, benzophenone compounds, triazine compounds, and styrene compounds.

[0050] The resin constituting the resin layer 102 can be a conventionally known transparent resin, and can be selected from one or more of acrylic resins, epoxy resins, mercapto resins, polycarbonate resins, polycarbonates, polyaryl compound resins, polyurethane resins, polyether resins, poly(terephthalic acid) resins, polyaryl ether phosphine oxide resins, polyimide resins, polyamide-imide resins, polyolefin resins, cyclic olefin resins, and polyester resins. From the viewpoints of transparency, solubility of near-infrared absorbing pigments in transparent resins, and heat resistance, a transparent resin with a high glass transition point (Tg) is preferred; therefore, a thermosetting resin is preferable. Specifically, one or more of polyester resins, polycarbonate resins, polyether resins, polyaryl compound resins, polyimide resins, and epoxy resins can be used. As a polyester resin, one or more of polyethylene terephthalate resins and polyethylene naphthalate resins are preferred. Furthermore, even slightly thermoplastic resins can be used as transparent resins by improving their heat resistance through adjusting functional groups. For example, acrylic resins, polyamide resins, and polyolefin resins, whose heat resistance can be improved by adjusting functional groups, can also be used as transparent resins.

[0051] In addition to the near-infrared absorbing pigment and transparent resin mentioned above, the resin layer 102 may also contain any components such as color-correcting pigments, leveling agents, antistatic agents, heat stabilizers, light stabilizers, antioxidants, dispersants, flame retardants, lubricants, and plasticizers, without impairing the effects of the present invention.

[0052] The resin layer 102 can be formed, for example, by dissolving or dispersing a pigment, transparent resin, and any coordinating components in a solvent to prepare a resin film-forming liquid, coating it, drying it, and then curing it as needed. Alternatively, the resin film-forming liquid may also contain well-known surfactants such as cationic, anionic, and nonionic surfactants.

[0053] In addition, the coating of the resin film forming liquid can be carried out by one or more coating methods selected from dip coating, cast coating, spray coating, spin coating, etc.

[0054] In this way, the resin layer 102 is formed on the glass substrate 101 and is a layer that absorbs light of a specific wavelength. By setting the absorption wavelength according to the spectral transmittance characteristics of the glass substrate 101 (that is, selecting the most suitable pigment), light in the desired visible light area is extracted. Specifically, in the resin layer 102 of this embodiment, a resin layer containing ultraviolet absorbing pigments with a maximum absorption wavelength of 340~400 nm and near-infrared absorbing pigments with a maximum absorption wavelength of 650~900 nm may be used. Furthermore, in this embodiment, the resin layer 102 is formed on one main surface of the glass substrate 101 (as shown on the upper surface in Figure 1(b)), but is not limited to this configuration. The resin layer 102 may be formed on another main surface of the glass substrate 101 (as shown on the lower surface in Figure 1(b)), or it may be formed on both surfaces of the glass substrate 101. In addition, the resin layer 102 does not necessarily have to be a single layer, but may be composed of multiple layers.

[0055] Furthermore, the spectral transmittance curve of the near-infrared cutoff filter 100 with such a resin layer 102 has an average transmittance of less than 3.0% in the wavelength regions of 385~430 nm on the short wavelength side (UV_λ50) and 590~660 nm and 800~1100 nm on the long wavelength side (NIR_λ50), which is similar to human visual perception (details will be described later). Furthermore, since the near-infrared cutoff filter 100 of this embodiment is mounted in front of the solid-state imaging element 200, from the viewpoint of the amount of incident light onto the solid-state imaging element 200, it is preferable to have a larger difference between the half-value wavelength (UV_λ50) on the short-wavelength side and the half-value wavelength (NIR_λ50) on the long-wavelength side of the transmittance curve, especially within the range of human visual perception, the longer the half-value wavelength (NIR_λ50) on the long-wavelength side, the better. Therefore, in this embodiment, the half-value wavelength (NIR_λ50) on the long-wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is set to be close to the half-value wavelength (NIR_λ50) on the long-wavelength side of the transmittance curve of the glass substrate 101. More specifically, in this embodiment, the difference between the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is 20 nm or less. Furthermore, the difference is preferably 15 nm or less, and more preferably 10 nm or less.

[0056] [Imaging device] Next, the imaging apparatus of the present invention will be described. As shown in Figure 2, the imaging apparatus 1 of the present invention includes: a solid-state imaging element 200, a package 300 for housing the solid-state imaging element 200, and a near-infrared cut-off filter 100 mounted in front of the package 300.

[0057] Solid-state imaging elements 200 can include image sensors such as CCD (Charge-Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor).

[0058] The solid-state imaging element 200 is disposed at approximately the center of the bottom surface of the box-shaped package 300, and is mounted at the opening of the package 300 with the main surface side of the other side of the near-infrared cut-off filter 100 (as shown on the lower side in Figure 1(b)) facing the solid-state imaging element 200. Additionally, in Figure 2, the resin layer 102 side of the near-infrared cut-off filter 100 serves as the incident surface for light incident towards the solid-state imaging element 200, and the main surface side of the other side of the near-infrared cut-off filter 100 serves as the emission surface. However, this configuration is not necessarily limited to this; the near-infrared cut-off filter 100 can also be mounted vertically in reverse (i.e., the resin layer 102 is opposite to the solid-state imaging element 200).

[0059] Furthermore, in the imaging device 1 shown in Figure 2, the near-infrared cut-off filter 100 is installed at the opening of the package 300, serving as a cover glass structure, but it is not necessarily limited to this structure. For example, the imaging device 1 may also have a lens group (not shown) that guides light toward the solid-state imaging element 200. In this case, for example, the near-infrared cut-off filter 100 may be positioned closer to the imaging device 1 than the lens group, or a cover glass may be provided closer to the imaging device 1 than the near-infrared cut-off filter 100.

[0060] The present invention is not limited to the following embodiments and comparative examples, which provide further explanation of the near-infrared cutoff filter 100.

[0061] (Example 1) [1. Selection of glass substrate 101] As the glass substrate 101 in Example 1, fluorophosphate glass (CXD700, 0.35 mm thick) manufactured by HOYA Corporation was selected. Figure 3 shows the spectral transmittance curves (dashed line) of the glass substrate 101 in Example 1 and the spectral transmittance curves (solid line and dashed line) of the near-infrared cutoff filter 100 in Example 1. In Figure 3, the vertical axis represents transmittance (%), and the horizontal axis represents wavelength (nm). Regarding the spectral transmittance curves of the near-infrared cutoff filter 100, the figures show the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. As shown in Figure 3, the average transmittance of the glass substrate 101 in this embodiment is 0.34% (i.e., less than 1%) in the wavelength range of 800~1100 nm. In addition, the average transmittance of the glass substrate 101 in this embodiment is 0.62% (i.e., less than 15%) in the wavelength range of 720~750 nm. In addition, the average transmittance of the glass substrate 101 in the wavelength range of 650~720 nm is 5.3% (that is, less than 40%). In addition, the average transmittance of the glass substrate 101 in the wavelength range of 800~1200 nm is 0.93% (that is, less than 5%). In addition, the half-value wavelength (UV_λ50) of the transmittance curve of the glass substrate 101 in this embodiment is about 350 nm on the short wavelength side (that is, in the range of 300~400 nm), and the half-value wavelength (NIR_λ50) on the long wavelength side is about 599 nm (that is, in the range of 590~670 nm).

[0062] [2. Formation of resin layer 102] In a container, acrylic resin (transparent resin), styrene compounds, triazine compounds (UV-absorbing pigments), and squaric acid ester compounds (near-infrared absorbing pigments) are mixed in a predetermined mixing ratio to prepare a resin film forming liquid. The resulting resin film forming liquid is then coated onto a glass substrate 101 using a spin coater. The glass substrate 101 coated with the resin film forming liquid is then placed on a hot plate heated to 160°C and heated for 20 minutes to harden it, thus producing the near-infrared cutoff filter 100 of this embodiment.

[0063] As shown in Figure 3, the spectral transmittance curves (solid and dashed lines) of the near-infrared cutoff filter 100 in this embodiment show that the half-value wavelength (UV_λ50) on the short-wavelength side of the transmittance curve is approximately 413 nm, and the half-value wavelength (NIR_λ50) on the long-wavelength side is approximately 591 nm. The average transmittance in the wavelength region of 800~1100 nm is 0.34%, which achieves characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is 8 nm. Furthermore, the near-infrared cutoff filter 100 of this embodiment does not have a reflective film like conventional near-infrared cutoff filters, so even if light is incident at an incident angle of 30°, it can suppress the occurrence of phase shift, wavelength shift, and ripple that significantly impair the performance of the cutoff filter.

[0064] (Example 2) The near-infrared cutoff filter 100 of Example 2 differs from that of Example 1 in that the glass substrate 101 is made of 0.3 mm thick fluorophosphate glass (CXD700) manufactured by HOYA Corporation, and the content of squaric acid compound (near-infrared absorbing pigment) in the resin layer 102 is changed.

[0065] Figure 4 shows the spectral transmittance curves (dashed line) of the glass substrate 101 in Example 2 and the spectral transmittance curves (solid line and dashed line) of the near-infrared cutoff filter 100 in Example 2. Furthermore, regarding the spectral transmittance curves of the near-infrared cutoff filter 100, the figures show the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°.

[0066] As shown in Figure 4, the average transmittance of the glass substrate 101 in this embodiment is less than 0.71% (i.e., less than 1%) in the wavelength range of 800~1100 nm. In addition, the average transmittance of the glass substrate 101 in this embodiment is 1.26% (i.e., less than 15%) in the wavelength range of 720~750 nm. In addition, the average transmittance of the glass substrate 101 in the wavelength range of 650~720 nm is 7.7% (that is, less than 40%). In addition, the average transmittance of the glass substrate 101 in the wavelength range of 800~1200 nm is 1.65% (that is, less than 5%). In addition, the half-value wavelength (UV_λ50) of the transmittance curve of the glass substrate 101 in this embodiment is about 348 nm on the short wavelength side (that is, in the range of 300~400 nm), and the half-value wavelength (NIR_λ50) on the long wavelength side is about 604 nm (that is, in the range of 590~670 nm).

[0067] Furthermore, the transmittance curve of the near-infrared cutoff filter 100 in this embodiment has a half-value wavelength (UV_λ50) of about 411 nm on the short wavelength side and a half-value wavelength (NIR_λ50) of about 600 nm on the long wavelength side. The average transmittance in the wavelength region of 800~1100 nm is less than 0.71%, which obtains characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is 4 nm. Furthermore, the near-infrared cutoff filter 100 of this embodiment does not have a reflective film like conventional near-infrared cutoff filters. Therefore, even if light is incident at an incident angle of 30°, the occurrence of phase shift, wavelength shift, and ripple, which significantly impair the performance of the cutoff filter, is suppressed.

[0068] (Example 3) The near-infrared cutoff filter 100 of Example 3 differs from that of Example 1 in the following aspects: As the glass substrate 101, a phosphate-based glass with a thickness of 0.30 mm, newly developed by HOYA Corporation, was selected (patent pending (Japanese Patent Application 2020-119553 (application date: July 10, 2020))). The resin layer 102 is formed of acrylic resin (transparent resin), styrene-based compounds and triazine compounds (ultraviolet absorbing pigments), squaric acid compounds and anthocyanin compounds (near-infrared absorbing pigments) (that is, the types of near-infrared absorbing pigments are changed).

[0069] Figure 5 shows the spectral transmittance curves (dashed line) of the glass substrate 101 in Example 3 and the spectral transmittance curves (solid line and dashed line) of the near-infrared cutoff filter 100 in Example 3. Furthermore, regarding the spectral transmittance curves of the near-infrared cutoff filter 100, the figures show the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°.

[0070] As shown in Figure 5, the average transmittance of the glass substrate 101 in this embodiment is 0.03% (i.e., less than 1%) in the wavelength region of 800~1100 nm. In addition, the average transmittance of the glass substrate 101 in this embodiment is 1.03% (i.e., less than 15%) in the wavelength range of 720~750 nm. In addition, the average transmittance of the glass substrate 101 in the wavelength range of 650~720 nm is 11.1% (that is, less than 40%). In addition, the average transmittance of the glass substrate 101 in the wavelength range of 800~1200 nm is 0.11% (that is, less than 5%). In addition, the half-value wavelength (UV_λ50) of the transmittance curve of the glass substrate 101 in this embodiment is about 319 nm on the short wavelength side (that is, in the range of 300~400 nm), and the half-value wavelength (NIR_λ50) on the long wavelength side is about 622 nm (that is, in the range of 590~670 nm).

[0071] Furthermore, the transmittance curve of the near-infrared cutoff filter 100 in this embodiment has a half-value wavelength (UV_λ50) of approximately 413 nm on the short wavelength side and a half-value wavelength (NIR_λ50) of approximately 610 nm on the long wavelength side, with an average transmittance of 0.03% in the wavelength region of 800~1100 nm, thus achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is 12 nm. Furthermore, the near-infrared cutoff filter 100 of this embodiment does not have a reflective film like conventional near-infrared cutoff filters. Therefore, even if light is incident at an incident angle of 30°, the occurrence of phase shift, wavelength shift, and ripple, which significantly impair the performance of the cutoff filter, is suppressed.

[0072] (Example 4) The near-infrared cutoff filter 100 of Example 4 differs from that of Example 3 in that it uses a glass substrate 101 with a thickness of 0.26 mm and changes the type and content of near-infrared absorbing pigments in the resin layer 102.

[0073] Figure 6 shows the spectral transmittance curve (dashed line) of the glass substrate 101 of Example 4 and the spectral transmittance curve (solid line and dashed line) of the near-infrared cutoff filter 100 of Example 4. In addition, regarding the spectral transmittance curves of the near-infrared cutoff filter 100, the spectral transmittance curves at an incident angle of 0° (solid line) and at an incident angle of 30° (dashed line) are shown.

[0074] As shown in Figure 6, the average transmittance of the glass substrate 101 in this embodiment is 0.09% (i.e., less than 1%) in the wavelength range of 800~1100 nm. In addition, the average transmittance of the glass substrate 101 in this embodiment is 1.85% (i.e., less than 15%) in the wavelength range of 720~750 nm. In addition, the average transmittance of the glass substrate 101 in the wavelength range of 650~720 nm is 14.3% (that is, less than 40%). In addition, the average transmittance of the glass substrate 101 in the wavelength range of 800~1200 nm is 0.25% (that is, less than 5%). In addition, the half-value wavelength (UV_λ50) of the transmittance curve of the glass substrate 101 in this embodiment is about 317 nm on the short wavelength side (that is, in the range of 300~400 nm), and the half-value wavelength (NIR_λ50) on the long wavelength side is about 628 nm (that is, in the range of 590~670 nm).

[0075] Furthermore, the transmittance curve of the near-infrared cutoff filter 100 in this embodiment has a half-value wavelength (UV_λ50) of approximately 411 nm on the short wavelength side and a half-value wavelength (NIR_λ50) of approximately 619 nm on the long wavelength side, with an average transmittance of 0.08% in the wavelength region of 800~1100 nm, thus achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is 9 nm. Furthermore, the near-infrared cutoff filter 100 of this embodiment does not have a reflective film like conventional near-infrared cutoff filters. Therefore, even if light is incident at an incident angle of 30°, the occurrence of phase shift, wavelength shift, and ripple, which significantly impair the performance of the cutoff filter, is suppressed.

[0076] (Example 5) The near-infrared cutoff filter 100 of Example 5 differs from that of Example 3 in that it selects a glass substrate 101 with a thickness of 0.25 mm and changes the type and content of near-infrared absorbing pigments in the resin layer 102.

[0077] Figure 7 shows the spectral transmittance curve (dashed line) of the glass substrate 101 of Example 5 and the spectral transmittance curve (solid line and dashed line) of the near-infrared cutoff filter 100 of Example 5. In addition, regarding the spectral transmittance curves of the near-infrared cutoff filter 100, the spectral transmittance curves at an incident angle of 0° (solid line) and at an incident angle of 30° (dashed line) are shown.

[0078] As shown in Figure 7, the average transmittance of the glass substrate 101 in this embodiment is 0.11% (i.e., less than 1%) in the wavelength range of 800~1100 nm. In addition, the average transmittance of the glass substrate 101 in this embodiment is 2.15% (i.e., less than 15%) in the wavelength range of 720~750 nm. In addition, the average transmittance of the glass substrate 101 in the wavelength range of 650~720 nm is 15.3% (that is, less than 40%). In addition, the average transmittance of the glass substrate 101 in the wavelength range of 800~1200 nm is 0.31% (that is, less than 5%). In addition, the half-value wavelength (UV_λ50) of the transmittance curve of the glass substrate 101 in this embodiment is about 316 nm on the short wavelength side (that is, in the range of 300~400 nm), and the half-value wavelength (NIR_λ50) on the long wavelength side is about 629 nm (that is, in the range of 590~670 nm).

[0079] Furthermore, the transmittance curve of the near-infrared cutoff filter 100 in this embodiment has a half-value wavelength (UV_λ50) of approximately 411 nm on the short wavelength side and a half-value wavelength (NIR_λ50) of approximately 620 nm on the long wavelength side, with an average transmittance of 0.31% in the wavelength region of 800~1100 nm, thus achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is 9 nm. Furthermore, the near-infrared cutoff filter 100 of this embodiment does not have a reflective film like conventional near-infrared cutoff filters. Therefore, even if light is incident at an incident angle of 30°, the occurrence of phase shift, wavelength shift, and ripple, which significantly impair the performance of the cutoff filter, is suppressed.

[0080] (Example 6) The near-infrared cutoff filter 100 of Example 6 differs from that of Example 3 in that it selects a glass substrate 101 with a thickness of 0.227 mm and changes the type and content of near-infrared absorbing pigments in the resin layer 102.

[0081] Figure 8 shows the spectral transmittance curve (dashed line) of the glass substrate 101 of Example 6 and the spectral transmittance curve (solid line and dashed line) of the near-infrared cutoff filter 100 of Example 6. In addition, regarding the spectral transmittance curves of the near-infrared cutoff filter 100, the spectral transmittance curves at an incident angle of 0° (solid line) and at an incident angle of 30° (dashed line) are shown.

[0082] As shown in Figure 8, the average transmittance of the glass substrate 101 in this embodiment is 0.20% (i.e., less than 1%) in the wavelength region of 800~1100 nm. In addition, the average transmittance of the glass substrate 101 in this embodiment is 3.02% (i.e., less than 15%) in the wavelength range of 720~750 nm. In addition, the average transmittance of the glass substrate 101 in the wavelength range of 650~720 nm is 17.7% (i.e., less than 4.0%). In addition, the average transmittance of the glass substrate 101 in the wavelength range of 800~1200 nm is 0.49% (that is, less than 5%). In addition, the half-value wavelength (UV_λ50) of the transmittance curve of the glass substrate 101 in this embodiment is about 315 nm on the short wavelength side (that is, in the range of 300~400 nm), and the half-value wavelength (NIR_λ50) on the long wavelength side is about 633 nm (that is, in the range of 590~670 nm).

[0083] Furthermore, the transmittance curve of the near-infrared cutoff filter 100 in this embodiment has a half-value wavelength (UV_λ50) of approximately 411 nm on the short wavelength side and a half-value wavelength (NIR_λ50) of approximately 625 nm on the long wavelength side, with an average transmittance of 0.20% in the wavelength region of 800~1100 nm, thus achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is 8 nm. Furthermore, the near-infrared cutoff filter 100 of this embodiment does not have a reflective film like conventional near-infrared cutoff filters. Therefore, even if light is incident at an incident angle of 30°, the occurrence of phase shift, wavelength shift, and ripple, which significantly impair the performance of the cutoff filter, is suppressed.

[0084] (Example 7) The near-infrared cutoff filter 100 of Example 7 differs from that of Example 3 in two aspects: the glass substrate 101 is selected with a thickness of 0.210 mm, and the near-infrared absorbing pigment of the resin layer 102 is only a squaric acid compound.

[0085] Figure 9 shows the spectral transmittance curve (dashed line) of the glass substrate 101 of Example 7 and the spectral transmittance curve (solid line and dashed line) of the near-infrared cutoff filter 100 of Example 7. In addition, regarding the spectral transmittance curves of the near-infrared cutoff filter 100, the spectral transmittance curves at an incident angle of 0° (solid line) and at an incident angle of 30° (dashed line) are shown.

[0086] As shown in Figure 9, the average transmittance of the glass substrate 101 in this embodiment is 0.31% (i.e., less than 1%) in the wavelength range of 800~1100 nm. In addition, the average transmittance of the glass substrate 101 in this embodiment is 3.88% (i.e., less than 15%) in the wavelength range of 720~750 nm. In addition, the average transmittance of the glass substrate 101 in the wavelength range of 650~720 nm is 19.9% ​​(that is, less than 40%). In addition, the average transmittance of the glass substrate 101 in the wavelength range of 800~1200 nm is 0.70% (that is, less than 5%). In addition, the half-value wavelength (UV_λ50) of the transmittance curve of the glass substrate 101 in this embodiment is about 314 nm on the short wavelength side (that is, in the range of 300~400 nm), and the half-value wavelength (NIR_λ50) on the long wavelength side is about 636 nm (that is, in the range of 590~670 nm).

[0087] Furthermore, the transmittance curve of the near-infrared cutoff filter 100 in this embodiment has a half-value wavelength (UV_λ50) of approximately 418 nm on the short wavelength side and a half-value wavelength (NIR_λ50) of approximately 625 nm on the long wavelength side, with an average transmittance of 0.27% in the wavelength region of 800~1100 nm, thus achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is 11 nm. Furthermore, the near-infrared cutoff filter 100 of this embodiment does not have a reflective film like conventional near-infrared cutoff filters. Therefore, even if light is incident at an incident angle of 30°, the occurrence of phase shift, wavelength shift, and ripple, which significantly impair the performance of the cutoff filter, is suppressed.

[0088] (Example 8) The near-infrared cutoff filter 100 of Example 8 differs from that of Example 7 in that the content of near-infrared absorbing pigment in the resin layer 102 is changed.

[0089] Figure 10 shows the spectral transmittance curve (dashed line) of the glass substrate 101 of Example 8 and the spectral transmittance curve (solid line and dashed line) of the near-infrared cutoff filter 100 of Example 8. In addition, regarding the spectral transmittance curves of the near-infrared cutoff filter 100, the spectral transmittance curves at an incident angle of 0° (solid line) and at an incident angle of 30° (dashed line) are shown.

[0090] As shown in Figure 10, the transmittance curve of the near-infrared cutoff filter 100 in this embodiment has a half-value wavelength (UV_λ50) of about 412 nm on the short wavelength side and a half-value wavelength (NIR_λ50) of about 630 nm on the long wavelength side. The average transmittance in the wavelength region of 800~1100 nm is 0.29%, which obtains characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is 6 nm. Furthermore, the near-infrared cutoff filter 100 of this embodiment does not have a reflective film like conventional near-infrared cutoff filters. Therefore, even if light is incident at an incident angle of 30°, the occurrence of phase shift, wavelength shift, and ripple, which significantly impair the performance of the cutoff filter, is suppressed.

[0091] (Example 9) The near-infrared cutoff filter 100 of Example 9 differs from that of Example 8 in that it selects a glass substrate 101 with a thickness of 0.165 mm and changes the type and content of near-infrared absorbing pigments in the resin layer 102.

[0092] Figure 11 shows the spectral transmittance curves (dashed line) of the glass substrate 101 of Example 9 and the spectral transmittance curves (solid line and dashed line) of the near-infrared cutoff filter 100 of Example 9. Furthermore, regarding the spectral transmittance curves of the near-infrared cutoff filter 100, the figures show the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°.

[0093] As shown in Figure 11, the average transmittance of the glass substrate 101 in this embodiment is 1.02% (i.e., less than 3%) in the wavelength range of 800~1100 nm. In addition, the average transmittance of the glass substrate 101 in this embodiment is 7.58% (i.e., less than 15%) in the wavelength range of 720~750 nm. In addition, the average transmittance of the glass substrate 101 in the wavelength range of 650~720 nm is 26.9% (that is, less than 40%). In addition, the average transmittance of the glass substrate 101 in the wavelength range of 800~1200 nm is 1.80% (that is, less than 5%). In addition, the half-value wavelength (UV_λ50) of the transmittance curve of the glass substrate 101 in this embodiment is about 311 nm on the short wavelength side (that is, in the range of 300~400 nm), and the half-value wavelength (NIR_λ50) on the long wavelength side is about 647 nm (that is, in the range of 590~670 nm).

[0094] Furthermore, the transmittance curve of the near-infrared cutoff filter 100 in this embodiment has a half-value wavelength (UV_λ50) of about 410 nm on the short wavelength side and a half-value wavelength (NIR_λ50) of about 645 nm on the long wavelength side, with an average transmittance of 0.96% in the wavelength region of 800~1100 nm, thus obtaining characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) of the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is 2 nm. Furthermore, the near-infrared cutoff filter 100 of this embodiment does not have a reflective film like conventional near-infrared cutoff filters. Therefore, even if light is incident at an incident angle of 30°, the occurrence of phase shift, wavelength shift, and ripple, which significantly impair the performance of the cutoff filter, is suppressed.

[0095] (Example 10) The near-infrared cutoff filter 100 of Example 10 differs from that of Example 9 in that it uses a glass substrate 101 with a thickness of 0.150 mm and changes the content of near-infrared absorbing pigments in the resin layer 102.

[0096] Figure 12 shows the spectral transmittance curves (dashed line) of the glass substrate 101 of Example 10 and the spectral transmittance curves (solid line and dashed line) of the near-infrared cutoff filter 100 of Example 10. Furthermore, regarding the spectral transmittance curves of the near-infrared cutoff filter 100, the figures show the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°.

[0097] As shown in Figure 12, the average transmittance of the glass substrate 101 in this embodiment is 1.52% (i.e., less than 3%) in the wavelength range of 800~1100 nm. In addition, the average transmittance of the glass substrate 101 in this embodiment is 9.48% (i.e., less than 15%) in the wavelength range of 720~750 nm. In addition, the average transmittance of the glass substrate 101 in the wavelength range of 650~720 nm is 29.9% (i.e., less than 40%). In addition, the average transmittance of the glass substrate 101 in the wavelength range of 800~1200 nm is 2.50% (that is, less than 5%). In addition, the half-value wavelength (UV_λ50) of the transmittance curve of the glass substrate 101 in this embodiment is about 310 nm on the short wavelength side (that is, in the range of 300~400 nm), and the half-value wavelength (NIR_λ50) on the long wavelength side is about 651 nm (that is, in the range of 590~670 nm).

[0098] Furthermore, the transmittance curve of the near-infrared cutoff filter 100 in this embodiment has a half-value wavelength (UV_λ50) of about 410 nm on the short wavelength side and a half-value wavelength (NIR_λ50) of about 650 nm on the long wavelength side, with an average transmittance of 1.46% in the wavelength region of 800~1100 nm, thus obtaining characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is 1 nm. Furthermore, the near-infrared cutoff filter 100 of this embodiment does not have a reflective film like conventional near-infrared cutoff filters. Therefore, even if light is incident at an incident angle of 30°, the occurrence of phase shift, wavelength shift, and ripple, which significantly impair the performance of the cutoff filter, is suppressed.

[0099] (Example 11) The near-infrared cutoff filter 100 of Example 11 differs from Example 3 in that the glass substrate 101 is selected with a thickness of 0.134 mm and the near-infrared absorbing pigment of the resin layer 102 is only anthocyanin compounds.

[0100] Figure 13 shows the spectral transmittance curves (dashed line) of the glass substrate 101 of Example 11 and the spectral transmittance curves (solid line and dashed line) of the near-infrared cutoff filter 100 of Example 11. Furthermore, regarding the spectral transmittance curves of the near-infrared cutoff filter 100, the figures show the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°.

[0101] As shown in Figure 13, the average transmittance of the glass substrate 101 in this embodiment is 2.33% (i.e., less than 3%) in the wavelength range of 800~1100 nm. In addition, the average transmittance of the glass substrate 101 in this embodiment is 12.05% (i.e., less than 15%) in the wavelength range of 720~750 nm. In addition, the average transmittance of the glass substrate 101 in the wavelength range of 650~720 nm is 33.5% (i.e., less than 40%). In addition, the average transmittance of the glass substrate 101 in the wavelength range of 800~1200 nm is 3.63% (i.e., less than 5%). In addition, the half-value wavelength (UV_λ50) of the transmittance curve of the glass substrate 101 in this embodiment is about 309 nm on the short wavelength side (that is, in the range of 300~400 nm), and the half-value wavelength (NIR_λ50) on the long wavelength side is about 656 nm (that is, in the range of 590~670 nm).

[0102] Furthermore, the transmittance curve of the near-infrared cutoff filter 100 in this embodiment has a half-value wavelength (UV_λ50) of approximately 410 nm on the short wavelength side and a half-value wavelength (NIR_λ50) of approximately 651 nm on the long wavelength side, with an average transmittance of 1.96% in the wavelength region of 800~1100 nm, thus achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100 is 5 nm. Furthermore, the near-infrared cutoff filter 100 of this embodiment does not have a reflective film like conventional near-infrared cutoff filters. Therefore, even if light is incident at an incident angle of 30°, the occurrence of phase shift, wavelength shift, and ripple, which significantly impair the performance of the cutoff filter, is suppressed.

[0103] In this way, in the near-infrared cutoff filter 100 of this embodiment (Examples 1 to 11), the glass substrate 101 is a substrate with a very low average transmittance in the wavelength region of 800 to 1100 nm (that is, less than 3% or less than 1%), instead of using a conventional reflective layer, thereby obtaining characteristics similar to human visual perception. Therefore, the near-infrared cutoff filter 100 of this embodiment has extremely low incident angle dependence and excellent oblique incident characteristics. In addition, the imaging device 1 using this near-infrared cutoff filter 100 can obtain images with excellent color reproduction because it can suppress the occurrence of ghost images.

[0104] The above is a description of the embodiments of the present invention, but the present invention is not limited to the structure of the above embodiments, and various modifications can be made within the scope of its technical concept.

[0105] For example, in this embodiment (Examples 1-11), a near-infrared cutoff filter 100 with a half-value wavelength (UV_λ50) of approximately 410-418 nm on the short-wavelength side and a half-value wavelength (NIR_λ50) of approximately 591-651 nm on the long-wavelength side of the transmittance curve is illustrated, but filters with these characteristics are not limited to this type. By appropriately selecting the ultraviolet-absorbing pigment and the near-infrared-absorbing pigment in the resin layer 102 and adjusting their mixing ratio, the half-value wavelength on the short-wavelength side of the transmittance curve can be adjusted within the range of 385-430 nm, or the half-value wavelength on the long-wavelength side can be adjusted within the range of 590-670 nm.

[0106] (Second Embodiment) Figure 14 is a longitudinal cross-sectional view illustrating the structure of the near-infrared cut-off filter 100A according to the second embodiment of the present invention. As shown in Figure 14, the near-infrared cut-off filter 100A of this embodiment has an anti-reflection film 103 (first anti-reflection film) on the top surface of the resin layer 102 (the surface opposite to the glass substrate 101), and an anti-reflection film 104 (second anti-reflection film) on the other main surface of the glass substrate 101 (the lower side surface in Figure 14). These features differ from those of the near-infrared cut-off filter 100 of the first embodiment. If the anti-reflective films 103 and 104 are formed in this way, the transmittance can be improved because the reflection at the interface (i.e., the incident surface and the exit surface) of the near-infrared cutoff filter 100A can be suppressed.

[0107] In this embodiment, the anti-reflection films 103 and 104 are layers used to prevent reflection at the interface between the incident surface and the exit surface of the near-infrared cutoff filter 100A. Specifically, they are composed of a dielectric multilayer film consisting of alternating layers of low-refractive-index dielectric films and high-refractive-index dielectric films.

[0108] The materials used to form the dielectric multilayer film can be freely selected based on the desired optical properties. However, the refractive index of the low-refractive-index material used to form the low-refractive-index dielectric layer is preferably in the range of 1.1 to 1.5. Examples of low-refractive-index materials include SiO₂, MgF₂, SiO₂ hollow layers, and low-refractive-index sol-gel coatings with aerosol structures. Conversely, the refractive index of the high-refractive-index material used to form the high-refractive-index dielectric layer is preferably in the range of 2.0 to 2.5. Examples of high-refractive-index materials include ZrO₂, Ta₂O₅, TiO₂, and Nb₂O₅. Additionally, materials with a refractive index of 1.4 to 1.6 (such as SiO₂) can also be used as high-refractive-index materials, in which case materials with a refractive index of 1.1 to 1.3 (such as aerosol coatings) can be used as low-refractive-index materials.

[0109] In this way, by using dielectric multilayer films in the antireflective films 103 and 104, and by utilizing the interference of light generated in each dielectric film, antireflection function can be easily achieved. However, if the number of film layers increases, the light path becomes longer when the light is incident obliquely, and the interference conditions of the reflected light from each layer will be disrupted, thus causing wavelength shift and ripple problems. In addition, such wavelength shift and ripple lead to an increase in reflected light, which is observed as a ghosting on the solid-state imaging element 200, resulting in problems with obtaining correct color reproduction. Therefore, in this embodiment, to avoid such problems, the number of dielectric multilayer films is configured to be 10 layers or less, and preferably 5 layers or less, or even 3 layers or less. The thickness of the dielectric films constituting the dielectric multilayer films can be freely selected according to the desired optical characteristics, preferably 50 nm to 1 μm, more preferably 50 nm to 500 nm. In addition, the overall thickness of the dielectric multilayer films (i.e., antireflective films 103 and 104) is set to 500 nm or less.

[0110] In addition, in this embodiment, the resin layer 102 is formed on one main surface of the glass substrate 101 (the upper surface in Figure 14). However, similar to the first embodiment, the resin layer 102 can also be formed on another main surface of the glass substrate 101 (the lower surface in Figure 14). Furthermore, it can also be formed on both surfaces of the glass substrate 101. In addition, the resin layer 102 does not necessarily have to be a single layer; it can also be composed of multiple layers.

[0111] Furthermore, although anti-reflective films 103 and 104 are provided in this embodiment, the embodiment is not limited to this structure. Optical films with other functions, such as infrared cut-off films and ultraviolet cut-off films, can also be used instead of anti-reflective films 103 and 104. That is, the near-infrared cut-off filter 100A of this embodiment can have an optical film with at least one of the functions of anti-reflective film, infrared cut-off film, and ultraviolet cut-off film.

[0112] Although the following examples illustrate and further explain the near-infrared cutoff filter 100A of this embodiment, the present invention is not limited to the following examples.

[0113] (Example 12) On the near-infrared cutoff filter 100 of Example 1, anti-reflection films 103 and 104 are further formed according to the following steps (3. Formation of anti-reflection films 103 and 104), and the near-infrared cutoff filter 100A of Example 11 is made. [3. Prevent the formation of reflective films 103 and 104] On the resin layer 102 of the near-infrared cut-off filter 100 of Example 1 (the side opposite to the glass substrate 101) and on another main surface of the glass substrate 101 (the lower side in Figure 14), the dielectric films (dielectric layers 1 to 5) of Table 1 are sequentially formed using the so-called sol-gel method (that is, anti-reflection films 103 and 104 are formed), thereby obtaining the near-infrared cut-off filter 100A of Example 11.

[0114] [Table 1] Thickness (nm) Refractive index Material Dielectric layer 5 85 1.48 SiO 2 Dielectric layer 4 107 2.42 TiO2 Dielectric layer 3 35 1.48 SiO 2 Dielectric layer 2 11 2.42 TiO2 Dielectric layer 1 98 1.48 SiO 2 Glass 1.52 Phosphoric acid / Fluorophosphate

[0115] Figure 15 shows the spectral transmittance curves of the near-infrared cutoff filter 100A of Example 12, displaying the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. As shown in Figure 15, the half-value wavelength (UV_λ50) on the short-wavelength side of the transmittance curve of the near-infrared cutoff filter 100A of this embodiment is approximately 411 nm, and the half-value wavelength (NIR_λ50) on the long-wavelength side is approximately 596 nm. The average transmittance in the wavelength region of 800~1100 nm is 0.3%, achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100A is 3 nm. Furthermore, although the near-infrared cutoff filter 100A of this embodiment has a dielectric multilayer film serving as anti-reflection films 103 and 104, its thickness is very thin (less than 500 nm). Therefore, even with light incident at an angle of 30°, it can suppress phase shift, wavelength shift, and ripple, which significantly impair the performance of the cutoff filter. Additionally, because the near-infrared cutoff filter 100A of this embodiment has anti-reflection films 103 and 104, it has higher transmittance compared to the near-infrared cutoff filter 100 of Embodiment 1 (i.e., compared to Figure 3), with a peak transmittance of approximately 98%.

[0116] (Example 13) On the near-infrared cutoff filter 100 of Example 2, anti-reflection films 103 and 104 are formed using the same steps as in Example 12 to produce the near-infrared cutoff filter 100A of Example 13.

[0117] Figure 16 shows the spectral transmittance curves of the near-infrared cutoff filter 100A of Example 13, displaying the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. As shown in Figure 16, the half-value wavelength (UV_λ50) on the short-wavelength side of the transmittance curve of the near-infrared cutoff filter 100A of this embodiment is approximately 410 nm, and the half-value wavelength (NIR_λ50) on the long-wavelength side is approximately 605 nm. The average transmittance in the wavelength region of 800~1100 nm is 0.6%, achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100A is 1 nm. Furthermore, although the near-infrared cutoff filter 100A of this embodiment has a dielectric multilayer film as an anti-reflection film 103, 104, its thickness is very thin (less than 500 nm). Therefore, even if light is incident at an incident angle of 30°, it can suppress the occurrence of phase shift, wavelength shift and ripple that significantly impair the performance of the cutoff filter. Furthermore, the near-infrared cut-off filter 100A of this embodiment has a higher transmittance than the near-infrared cut-off filter 100 of Embodiment 2 (that is, compared with Figure 4) because it has anti-reflection films 103 and 104, with a peak transmittance of about 97%.

[0118] (Example 14) On the near-infrared cutoff filter 100 of Example 3, anti-reflection films 103 and 104 are formed using the same steps as in Example 12 to produce the near-infrared cutoff filter 100A of Example 14.

[0119] Figure 17 shows the spectral transmittance curves of the near-infrared cutoff filter 100A of Example 14, displaying the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. As shown in Figure 17, the half-value wavelength (UV_λ50) on the short-wavelength side of the transmittance curve of the near-infrared cutoff filter 100A of this embodiment is approximately 410 nm, the half-value wavelength (NIR_λ50) on the long-wavelength side is approximately 615 nm, and the average transmittance in the wavelength region of 800~1100 nm is 0.03%, achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100A is 7 nm. Furthermore, although the near-infrared cutoff filter 100A of this embodiment has a dielectric multilayer film as an anti-reflection film 103, 104, its thickness is very thin (less than 500 nm). Therefore, even if light is incident at an incident angle of 30°, it can suppress the occurrence of phase shift, wavelength shift and ripple that significantly impair the performance of the cutoff filter. Furthermore, the near-infrared cut-off filter 100A of this embodiment has higher transmittance than the near-infrared cut-off filter 100 of Embodiment 3 (that is, compared with Figure 5) because it has anti-reflection films 103 and 104, with a peak transmittance of about 97%.

[0120] (Example 15) On the near-infrared cutoff filter 100 of Example 4, anti-reflection films 103 and 104 are formed using the same steps as in Example 12 to produce the near-infrared cutoff filter 100A of Example 15.

[0121] Figure 18 shows the spectral transmittance curves of the near-infrared cutoff filter 100A of Example 15, displaying the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. As shown in Figure 18, the half-value wavelength (UV_λ50) on the short-wavelength side of the transmittance curve of the near-infrared cutoff filter 100A of this embodiment is approximately 409 nm, and the half-value wavelength (NIR_λ50) on the long-wavelength side is approximately 625 nm. The average transmittance in the wavelength region of 800~1100 nm is 0.07%, achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100A is 3 nm. Furthermore, although the near-infrared cutoff filter 100A of this embodiment has a dielectric multilayer film as an anti-reflection film 103, 104, its thickness is very thin (less than 500 nm). Therefore, even if light is incident at an incident angle of 30°, it can suppress the occurrence of phase shift, wavelength shift and ripple that significantly impair the performance of the cutoff filter. In addition, the near-infrared cut-off filter 100A of this embodiment has anti-reflection films 103 and 104. Therefore, compared with the near-infrared cut-off filter 100 of Embodiment 4 (that is, compared with Figure 6), the transmittance is high, and the peak transmittance is about 97%.

[0122] (Example 16) On the near-infrared cutoff filter 100 of Example 5, anti-reflection films 103 and 104 are formed using the same steps as in Example 12 to produce the near-infrared cutoff filter 100A of Example 16.

[0123] Figure 19 shows the spectral transmittance curves of the near-infrared cutoff filter 100A of Example 16, displaying the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. As shown in Figure 19, the half-value wavelength (UV_λ50) on the short-wavelength side of the transmittance curve of the near-infrared cutoff filter 100A of this embodiment is approximately 410 nm, and the half-value wavelength (NIR_λ50) on the long-wavelength side is approximately 625 nm. The average transmittance in the wavelength region of 800~1100 nm is 0.09%, achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100A is 4 nm. Furthermore, although the near-infrared cutoff filter 100A of this embodiment has a dielectric multilayer film as an anti-reflection film 103, 104, its thickness is very thin (less than 500 nm). Therefore, even if light is incident at an incident angle of 30°, it can suppress the occurrence of phase shift, wavelength shift and ripple that significantly impair the performance of the cutoff filter. In addition, the near-infrared cut-off filter 100A of this embodiment has anti-reflection films 103 and 104. Therefore, compared with the near-infrared cut-off filter 100 of Embodiment 5 (that is, compared with Figure 7), it has higher transmittance, and the peak transmittance is about 98%. (Example 17) On the near-infrared cutoff filter 100 of Example 6, anti-reflection films 103 and 104 are formed in the same steps as in Example 12 to produce the near-infrared cutoff filter 100A of Example 17.

[0124] Figure 20 shows the spectral transmittance curves of the near-infrared cutoff filter 100A of Example 17, displaying the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. As shown in Figure 20, the half-value wavelength (UV_λ50) on the short-wavelength side of the transmittance curve of the near-infrared cutoff filter 100A of this embodiment is approximately 409 nm, and the half-value wavelength (NIR_λ50) on the long-wavelength side is approximately 630 nm. The average transmittance in the wavelength region of 800~1100 nm is 0.2%, achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100A is 3 nm. Furthermore, although the near-infrared cutoff filter 100A of this embodiment has a dielectric multilayer film as an anti-reflection film 103, 104, its thickness is very thin (less than 500 nm). Therefore, even if light is incident at an incident angle of 30°, it can suppress the occurrence of phase shift, wavelength shift and ripple that significantly impair the performance of the cutoff filter. Furthermore, the near-infrared cut-off filter 100A of this embodiment has a higher transmittance than the near-infrared cut-off filter 100 of Embodiment 6 (that is, compared with Figure 8) because it has anti-reflection films 103 and 104, with a peak transmittance of about 98%.

[0125] (Example 18) On the near-infrared cutoff filter 100 of Example 7, anti-reflection films 103 and 104 are formed using the same steps as in Example 12 to produce the near-infrared cutoff filter 100A of Example 18.

[0126] Figure 21 shows the spectral transmittance curves of the near-infrared cutoff filter 100A of Example 18, displaying the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. As shown in Figure 21, the half-value wavelength (UV_λ50) on the short-wavelength side of the transmittance curve of the near-infrared cutoff filter 100A of this embodiment is approximately 414 nm, and the half-value wavelength (NIR_λ50) on the long-wavelength side is approximately 630 nm. The average transmittance in the wavelength region of 800~1100 nm is 0.2%, achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100A is 6 nm. Furthermore, although the near-infrared cutoff filter 100A of this embodiment has a dielectric multilayer film as an anti-reflection film 103, 104, its thickness is very thin (less than 500 nm). Therefore, even if light is incident at an incident angle of 30°, it can suppress the occurrence of phase shift, wavelength shift and ripple that significantly impair the performance of the cutoff filter. In addition, the near-infrared cut-off filter 100A of this embodiment has anti-reflection films 103 and 104. Therefore, compared with the near-infrared cut-off filter 100 of Embodiment 7 (that is, compared with Figure 9), it has higher transmittance, and the peak transmittance is about 95%.

[0127] (Example 19) On the near-infrared cutoff filter 100 of Example 8, anti-reflection films 103 and 104 are formed using the same steps as in Example 12 to produce the near-infrared cutoff filter 100A of Example 19.

[0128] Figure 22 shows the spectral transmittance curves of the near-infrared cutoff filter 100A of Example 19, displaying the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. As shown in Figure 22, the half-value wavelength (UV_λ50) on the short-wavelength side of the transmittance curve of the near-infrared cutoff filter 100A of this embodiment is approximately 410 nm, and the half-value wavelength (NIR_λ50) on the long-wavelength side is approximately 635 nm. The average transmittance in the wavelength region of 800~1100 nm is 0.2%, achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100A is 1 nm. Furthermore, although the near-infrared cutoff filter 100A of this embodiment has a dielectric multilayer film as an anti-reflection film 103, 104, its thickness is very thin (less than 500 nm). Therefore, even if light is incident at an incident angle of 30°, it can suppress the occurrence of phase shift, wavelength shift and ripple that significantly impair the performance of the cutoff filter. Furthermore, the near-infrared cut-off filter 100A of this embodiment has a higher transmittance than the near-infrared cut-off filter 100 of Embodiment 8 (that is, compared with Figure 10), as it has anti-reflection films 103 and 104, with a peak transmittance of approximately 97%.

[0129] (Example 20) On the near-infrared cutoff filter 100 of Example 9, anti-reflection films 103 and 104 are formed using the same steps as in Example 12 to produce the near-infrared cutoff filter 100A of Example 20.

[0130] Figure 23 shows the spectral transmittance curves of the near-infrared cutoff filter 100A of Example 20, displaying the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. As shown in Figure 23, the half-value wavelength (UV_λ50) on the short-wavelength side of the transmittance curve of the near-infrared cutoff filter 100A of this embodiment is approximately 409 nm, the half-value wavelength (NIR_λ50) on the long-wavelength side is approximately 651 nm, and the average transmittance in the wavelength region of 800~1100 nm is 0.8%, achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100A is 4 nm. Furthermore, although the near-infrared cutoff filter 100A of this embodiment has a dielectric multilayer film as an anti-reflection film 103, 104, its thickness is very thin (less than 500 nm). Therefore, even if light is incident at an incident angle of 30°, it can suppress the occurrence of phase shift, wavelength shift and ripple that significantly impair the performance of the cutoff filter. Furthermore, the near-infrared cut-off filter 100A of this embodiment has a higher transmittance than the near-infrared cut-off filter 100 of Embodiment 9 (that is, compared with Figure 11) because it has anti-reflection films 103 and 104, with a peak transmittance of about 98%.

[0131] (Example 21) On the near-infrared cutoff filter 100 of Example 10, anti-reflection films 103 and 104 are formed using the same steps as in Example 12 to produce the near-infrared cutoff filter 100A of Example 21.

[0132] Figure 24 shows the spectral transmittance curves of the near-infrared cutoff filter 100A of Example 21, displaying the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. As shown in Figure 24, the half-value wavelength (UV_λ50) on the short-wavelength side of the transmittance curve of the near-infrared cutoff filter 100A of this embodiment is approximately 408 nm, and the half-value wavelength (NIR_λ50) on the long-wavelength side is approximately 656 nm. The average transmittance in the wavelength region of 800~1100 nm is 1.3%, achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100A is 5 nm. Furthermore, although the near-infrared cutoff filter 100A of this embodiment has a dielectric multilayer film as an anti-reflection film 103, 104, its thickness is very thin (less than 500 nm). Therefore, even if light is incident at an incident angle of 30°, it can suppress the occurrence of phase shift, wavelength shift and ripple that significantly impair the performance of the cutoff filter. In addition, the near-infrared cut-off filter 100A of this embodiment has anti-reflection films 103 and 104. Therefore, compared with the near-infrared cut-off filter 100 of Embodiment 10 (that is, compared with Figure 12), it has higher transmittance, and the peak transmittance is about 98%.

[0133] (Example 22) On the near-infrared cutoff filter 100 of Example 11, anti-reflection films 103 and 104 are formed in the same steps as in Example 12 to produce the near-infrared cutoff filter 100A of Example 22.

[0134] Figure 25 shows the spectral transmittance curves of the near-infrared cutoff filter 100A of Example 22, displaying the spectral transmittance curves (solid line) at an incident angle of 0° and (dashed line) at an incident angle of 30°. As shown in Figure 25, the half-value wavelength (UV_λ50) on the short-wavelength side of the transmittance curve of the near-infrared cutoff filter 100A of this embodiment is approximately 409 nm, and the half-value wavelength (NIR_λ50) on the long-wavelength side is approximately 657 nm. The average transmittance in the wavelength region of 800~1100 nm is 1.7%, achieving characteristics similar to human visual perception. In addition, in this embodiment, the difference between the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the glass substrate 101 and the half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of the near-infrared cutoff filter 100A is 1 nm. Furthermore, although the near-infrared cutoff filter 100A of this embodiment has a dielectric multilayer film as an anti-reflection film 103, 104, its thickness is very thin (less than 500 nm). Therefore, even if light is incident at an incident angle of 30°, it can suppress the occurrence of phase shift, wavelength shift and ripple that significantly impair the performance of the cutoff filter. Furthermore, the near-infrared cut-off filter 100A of this embodiment has a higher transmittance than the near-infrared cut-off filter 100 of Embodiment 11 (that is, compared with Figure 13) because it has anti-reflection films 103 and 104, with a peak transmittance of about 98%.

[0135] Thus, the near-infrared cutoff filters 100A of Examples 12-22 have excellent oblique incidence characteristics and high transmittance. Furthermore, imaging devices 1 using such near-infrared cutoff filters 100 can obtain bright images with good color reproduction.

[0136] (Third Embodiment) Figure 26 is a longitudinal cross-sectional view illustrating the structure of the near-infrared cut-off filter 100B according to the third embodiment of the present invention. As shown in Figure 26, the near-infrared cut-off filter 100B of this embodiment has a bonding layer 105 between the glass substrate 101 and the resin layer 102 to bond the two together, which is different from the near-infrared cut-off filter 100 of the first embodiment. When the bonding layer 105 is formed in this way, the adhesion between the glass substrate 101 and the resin layer 102 can be improved, thereby increasing reliability.

[0137] The inventors' in-depth research has revealed that using a bonding component containing Si atoms and one or more selected from Ti atoms, Zr atoms, and Al atoms can improve the adhesion between the glass substrate 101 and the resin layer 102. Based on the above insights, the bonding layer 105 of this embodiment has a monolayer structure containing Si atoms and one or more selected from Ti atoms, Zr atoms, and Al atoms. In addition, in this specification, a single-layer structure refers to a layer structure formed from a material with the same composition, as determined by the measurement image (image contrast) or elemental analysis results obtained under the following measurement conditions using a scanning transmission electron microscope-energy dispersive X-ray spectrometer (STEM-EDX). <Measurement Conditions> Scanning transmission electron microscope: ARM200F manufactured by NEC Corporation Energy-dispersive X-ray spectrometer: JED-2300T manufactured by Nippon Electron Ltd. Sample preparation: Focused ion beam processing (FIB) Accelerating voltage: 200 kV Elemental analysis: EDX mapping (resolution: 256 x 256)

[0138] The thickness of the bonding layer 105 is preferably less than 1000 nm, more preferably 10~500 nm, and even more preferably 30~300 nm. By making the thickness of the bonding layer 105 less than 1000 nm, it is easy to suppress the non-uniformity that occurs during the formation (sintering) of the bonding layer 105, and the film surface of the bonding layer 105 can be easily homogenized. In addition, when the thickness of the bonding layer 105 is 10 nm or more, the bonding layer 105 can easily exert sufficient bonding strength, which can easily improve the mechanical strength of the near-infrared cut-off filter 100B. In addition, in this specification, the thickness of the bonding layer 105 refers to the arithmetic mean of 50 points when measuring the thickness of the bonding layer 105 in the measurement image (image contrast) of the cross section of the near-infrared cutoff filter 100B obtained by measuring using the above-mentioned STEM-EDX.

[0139] In this embodiment, the bonding layer 105, together with the Si atoms, contains one or more selected from Ti atoms, Zr atoms, and Al atoms. However, it is preferable that the bonding layer 105 contains one or more selected from Ti atoms, Zr atoms, and Al atoms together with the Si atoms, and is composed of Ti atoms.

[0140] In the bonding layer 105 of this embodiment, the ratio α (atomic percentage) of the total number of Ti atoms, Zr atoms, and Al atoms to the total number of Si atoms, Ti atoms, Zr atoms, and Al atoms (total number of atoms) is preferably greater than 0 atomic percentage and less than 50 atomic percentage, more preferably 9 to 50 atomic percentage, and even more preferably 12 to 50 atomic percentage. Furthermore, in this specification, the ratio α (atomic percentage) of the total number of Ti atoms, Zr atoms, and Al atoms to the total number of Si atoms, Ti atoms, Zr atoms, and Al atoms constituting the bonding layer 105 refers to a value calculated using the following method. (1) Perform STEM-EDX measurement of the optical filter according to the above measurement conditions to obtain STEM-EDX lines (the detection intensity lines of the EDX lines (K lines) of each element constituting the optical filter in the depth direction). (2) Calculate the EDX line integral intensity XSi of Si atoms, the EDX line integral intensity XTi of Ti atoms, the EDX line integral intensity XZr of Zr atoms and the EDX line integral intensity XAl of Al atoms in the region constituting the bonding layer 105. (3) The k-factor (a correction factor that varies for each atom number depending on the accelerating voltage and detection efficiency) multiplied by the EDX line integration intensity obtained in (2) can be considered as corresponding to the weight ratio of each constituent element. Therefore, for example, the weight ratio ATi (weight%) of Ti atoms constituting the bonding layer can be calculated using the following mathematical formula. [Mathematical Expression 1] (4) Furthermore, by multiplying the EDX linear integrator intensity X of each atom by the value of the k factor and then dividing by the value of each atomic weight M, it can be regarded as the ratio of the number of atoms of each constituent element. Therefore, if the atomic weight of Si is MSi, the atomic weight of Ti is MTi, the atomic weight of Zr is MZr, and the atomic weight of Al is MAl, for example, the proportion of Ti atoms constituting the bonding layer 105, αTi (atomic %), can be calculated by the following mathematical formula. [Mathematical Expression 2] Furthermore, the proportion α (atomic percentage) of the total number of Ti atoms, Zr atoms, and Al atoms constituting the bonding layer 105 can be calculated using the following mathematical formula. [Mathematical Expression 3] For example, the bonding layer 105 contains Si atoms and Ti atoms, but does not contain Zr atoms and Al atoms. The proportion α (atomic percentage) of the total number of Ti atoms, Zr atoms and Al atoms constituting the bonding layer 105 can be calculated by the following mathematical formula. [Mathematical Expression 4] In addition, in this embodiment, KSi=1.000, KTi=1.033, KZr=5.696, and KAl=1.050.

[0141] The present invention is not limited to the following embodiments, although examples are given and the near-infrared cut-off filter 100B of this embodiment is further described.

[0142] (Example 23) On the glass substrate 101 of Example 1, a bonding layer 105 is formed according to the following steps (4. Formation of bonding layer 105). Then, on top of the bonding layer 105, a resin layer 102 is formed according to the same steps as in Example 1 (2. Formation of resin layer 102) to produce a near-infrared cutoff filter 100B. [4. Formation of bonding layer 105] 1. Preparation of coating solution containing coupling agent (1) Weigh 0.3 mL of 0.5 N (mol / L) HCl aqueous solution and 2.2 mL of 2-methoxyethanol in a container and mix them in a sealed container. (2) Add tetraethyl orthosilicate (Si(OC2H5)4) to the above container and mix for 30 minutes under a closed system to produce the reaction shown in the following reaction formula. Si(OC 2H 5) 4+H 2O→HO-Si(OC 2H 5) 3+C 2H 5OH Through the above reaction, since all water is consumed and hydroxyl groups are generated, even if an alkoxide of Ti with a fast hydrolysis rate is added, hydroxide will not precipitate, and the solution is expected to become homogeneous. (3) Add titanium(IV)n-butoxy (Ti(OC4H9)4) to the above container to achieve a predetermined ratio (e.g., 3~20 moles), and mix under sealed conditions for 30 minutes to prepare a coating solution containing a coupling agent. Furthermore, it is believed that the reaction shown in the following equation will occur inside the container at this time. 4OH-Si(OC 2H 5) 3+Ti(OC 4H 9) 4→Ti(O-Si(OC 2H 5) 3) 4+4C 4H 9OH

[0143] 2. Formation of the coating film In a container containing the above-mentioned coating solution containing the coupling agent, weigh 1.2 mL of 0.5N HCl aqueous solution, 4.7 mL of water, and 8.1 mL of 2-methoxyethanol, and mix them under a closed system for 30 minutes to prepare a coating film forming solution. It is assumed that the reaction shown in the following equation will occur inside the container at this time. Ti{(O-Si(OC 2H 5) 3} 4+12H 2O→Ti{(O-Si(OH) 3} 4+12C 2H 5OH HO-Si(OC 2H 5) 3+3H 2O→Si(OH) 4+3C 2H 5OH The obtained coating film forming liquid was applied to the glass substrate 101 using a spin coater to achieve a concentration of 0.03 mL / cm². The glass substrate 101 coated with the above-mentioned coating film forming liquid is placed on a hot plate heated to 250°C and heated for 30 minutes to dehydrate and condense, thereby forming a hardened film (bonding layer 105) on the surface.

[0144] Next, on top of the bonding layer 105, a resin layer 102 is formed using the same steps as in Example 1 (2. Formation of resin layer 102) to produce a near-infrared cutoff filter 100B.

[0145] In this way, if an bonding layer 105 is formed between the glass substrate 101 and the resin layer 102, the adhesion between the glass substrate 101 and the resin layer 102 can be significantly improved, thus rapidly improving reliability.

[0146] In addition, in this embodiment, the bonding layer 105, together with the Si atoms, contains one or more selected from Ti atoms, Zr atoms, and Al atoms. However, instead of forming the bonding layer 105, the components of the bonding layer 105 can be included in the resin layer 102. That is, the resin layer 102 can be configured to contain one or more selected from Ti atoms, Zr atoms, and Al atoms together with the Si atoms.

[0147] In addition, the bonding layer 105 of this embodiment contains one or more of Ti atoms, Zr atoms and Al atoms together with Si atoms, as long as it can improve the adhesion between the glass substrate 101 and the resin layer 102, for example, a transparent vapor-deposited or coating adhesive can also be used.

[0148] In addition, in this embodiment, the resin layer 102 is formed on one main surface of the glass substrate 101 (the upper surface in Figure 26) through the bonding layer 105. However, similar to the first embodiment, the resin layer 102 can also be formed on another main surface of the glass substrate 101 (the lower surface in Figure 26) through the bonding layer 105. Alternatively, it can be formed on both surfaces of the glass substrate 101. Furthermore, the resin layer 102 does not necessarily have to be a single layer; it can also consist of multiple layers.

[0149] In addition, although the bonding layer 105 in this embodiment is used for bonding the glass substrate 101 and the resin layer 102, it can also be used as a protective layer (AD (Anti-Dimming) coating) to protect the glass substrate 101.

[0150] (Example 24) Figure 27 illustrates an embodiment in which the bonding layer 105 of this embodiment is applied to the protective layer 107 (AD). As shown in Figure 27, in this embodiment, the protective layer 107, the resin layer 102, and the anti-reflective film 103 are sequentially formed on one main surface of the glass substrate 101, and the protective layer 107 is formed on the other main surface. Thus, in this embodiment, since a protective layer 107 is formed on both main surfaces of the glass substrate 101, the deterioration (burning, etc.) of the glass substrate 101 can be prevented.

[0151] (Example 25) Figure 28 shows that an anti-reflective film 104 is further formed on the protective layer 107 (on the other main surface) shown in Figure 27. Thus, in this embodiment, since an anti-reflection film 104 is further formed on the protective layer 107, reflection at the interface (i.e., the incident surface and the exit surface) can be suppressed, thereby improving transmittance.

[0152] Furthermore, the embodiments disclosed herein are illustrative in all respects and should not be considered restrictive. The scope of this invention is indicated by the scope of the claims, not by the foregoing description, and is intended to include all modifications within the scope and equivalent meaning of the claims.

[0153] 1: Imaging device 11: Absorption Layer 12: Reflective layer 13: Transparent substrate 100: Near-infrared cutoff filter 100A: Near-infrared cutoff filter 100B: Near-infrared cutoff filter 101: Glass substrate 102: Resin layer 103: Anti-reflective film 104: Anti-reflective film 105: Bonding layer 107: Protective layer 200: Solid-state imaging element 300: Package

Claims

1. A near-infrared cutoff filter, comprising: A transparent substrate with a thickness of 0.16–0.26 mm and an average transmittance of less than 1% in the wavelength range of 800–1100 nm; And a resin layer, formed on at least one of the main surfaces of the transparent substrate, which absorbs light of a specific wavelength.

2. The near-infrared cutoff filter as claimed in claim 1, wherein the half-value wavelength of the transmittance curve of the transparent substrate is 300-400 nm on the short wavelength side and 590-670 nm on the long wavelength side.

3. The near-infrared cutoff filter as described in claim 1 or 2, wherein the transparent substrate has an average transmittance of less than 40% in the wavelength range of 650 to 720 nm.

4. The near-infrared cutoff filter as described in claim 1 or 2, wherein the transparent substrate has an average transmittance of less than 15% in the wavelength range of 720 to 750 nm.

5. The near-infrared cutoff filter as described in claim 1 or 2, wherein the transparent substrate has an average transmittance of less than 5% in the wavelength range of 800 to 1200 nm.

6. The near-infrared cutoff filter as claimed in claim 1 or 2, wherein the resin layer comprises a transparent resin and a pigment uniformly dispersed in the transparent resin.

7. The near-infrared cutoff filter as claimed in claim 6, wherein the pigment contains an ultraviolet-absorbing pigment having a maximum absorption wavelength of 340–400 nm.

8. The near-infrared cutoff filter as claimed in claim 6, wherein the pigment contains an ultraviolet-absorbing pigment having a maximum absorption wavelength of 650–900 nm.

9. The near-infrared cutoff filter as claimed in claim 1 or 2, wherein the resin layer contains Si atoms as an essential component and contains one or more selected from Ti atoms, Zr atoms and Al atoms as optional components.

10. The near-infrared cutoff filter as claimed in claim 1 or 2, wherein a bonding layer is provided between the transparent substrate and the resin layer to improve the adhesion between the transparent substrate and the resin layer.

11. The near-infrared cutoff filter as claimed in claim 10, wherein the bonding layer is further provided on another main surface of the transparent substrate.

12. The near-infrared cutoff filter as claimed in claim 10, wherein the bonding layer has a monolayer structure comprising Si atoms and one or more selected from Ti atoms, Zr atoms and Al atoms.

13. The near-infrared cutoff filter as claimed in claim 12, wherein in the bonding layer, the ratio of the total number of Ti atoms, Zr atoms and Al atoms to the total number of Si atoms, Ti atoms, Zr atoms and Al atoms is greater than 0 atomic% and less than or equal to 50 atomic%.

14. The near-infrared cutoff filter as claimed in claim 1 or 2, wherein the resin layer has a first functional film and the other main surface of the transparent substrate has a second functional film.

15. The near-infrared cutoff filter as claimed in claim 14, wherein the first functional film and the second functional film are optical thin films having at least one of the functions of an anti-reflection film, an infrared cutoff film, and an ultraviolet cutoff film.

16. The near-infrared cutoff filter as claimed in claim 15, wherein the first functional film and the second functional film are each composed of a dielectric multilayer film with a thickness of less than 500 nm.

17. The near-infrared cutoff filter as described in claim 16, wherein the dielectric multilayer film has 10 layers or less.

18. The near-infrared cutoff filter as claimed in claim 16, wherein the dielectric multilayer film is formed by alternating layers of a low-refractive-index dielectric film made of a material with a refractive index of 1.1 to 1.5 and a high-refractive-index dielectric film made of a material with a refractive index of 2.0 to 2.

5.

19. The near-infrared cutoff filter as claimed in claim 16, wherein the dielectric multilayer film is formed by alternating layers of a low-refractive-index dielectric film made of a material with a refractive index of 1.1 to 1.3 and a high-refractive-index dielectric film made of a material with a refractive index of 1.4 to 1.

6.

20. The near-infrared cutoff filter as claimed in claim 1 or 2, wherein the half-value wavelength on the short-wavelength side of the transmittance curve is 385–430 nm and the half-value wavelength on the long-wavelength side is 590–660 nm.

21. The near-infrared cutoff filter as claimed in claim 1 or 2, wherein the difference between the half-value wavelength of the long wavelength side of the transmittance curve of the transparent substrate and the half-value wavelength of the long wavelength side of the transmittance curve of the near-infrared cutoff filter is less than 20 nm.

22. The near-infrared cutoff filter as claimed in claim 1 or 2, wherein the transparent substrate is made of fluorophosphate glass or phosphate glass.

23. An imaging apparatus comprising a solid-state imaging element and a near-infrared cutoff filter as described in any one of claims 1 to 22.

24. The imaging apparatus of claim 23, wherein the near-infrared cutoff filter is disposed directly in front of the solid-state imaging element and also serves as a cover glass.

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