JP7520564B2 - Near-infrared cut filter and imaging device equipped with same - Google Patents

Description

The present invention relates to a near-infrared cut filter that is placed in front of a solid-state imaging element and is used to correct the visibility of the solid-state imaging element, and an imaging device equipped with the same.

In recent years, imaging devices incorporating solid-state imaging elements such as CCDs and CMOSs have been used in digital cameras, portable information terminal devices, and the like. In such imaging devices, the solid-state imaging elements have spectral sensitivity ranging from the near-ultraviolet to near-infrared regions, so they are equipped with near-infrared cut filters that cut the near-infrared portion of the incident light and correct it to be closer to human visual sensitivity. Such near-infrared cut filters are placed in the optical path to the solid-state imaging element, but in order to reduce the overall size of the imaging device, near-infrared cut filters that also function as the cover glass of the imaging device are also in practical use (for example, Patent Document 1).

Figure 17 shows an example of the configuration of a near-infrared cut filter (conventional example) described in Patent Document 1. As shown in Figure 17, the near-infrared cut filter described in Patent Document 1 includes a transparent substrate 13, an absorption layer 11 formed on one main surface of the transparent substrate 13 and absorbing light in the near-infrared wavelength region and the ultraviolet wavelength region, and a reflection layer 12 formed on the other main surface of the transparent substrate 13 and controlling the transmission and blocking of light in a specific wavelength region. The reflection layer 12 is composed of a dielectric multilayer film having a thickness of 2 to 10 μm, in which a low refractive index dielectric film (low dielectric film) and a high refractive index dielectric film (high dielectric film) are alternately laminated, and the reflection layer 12 is configured so that its spectral transmittance satisfies a predetermined requirement, thereby realizing a near-infrared cut filter having spectral characteristics close to the relative luminosity curve, especially on the long wavelength side, and having little incidence angle dependency.

Patent No. 6119920

However, the near-infrared cut filter described in Patent Document 1 has a reflective layer 12 made of a relatively thick (2 to 10 μm thick) dielectric multilayer film, so when light is incident on the reflective layer 12 at an angle, the optical path length becomes long, causing a phase shift.

Figure 18 is a diagram showing the spectral transmittance curve of the reflective layer 12 of the near-infrared cut filter of Figure 17, showing the spectral transmittance curve (solid line) when the incident angle is 0° and the spectral transmittance curve (dashed line) when the incident angle is 30°. Also, Figure 19 is a diagram showing the spectral transmittance curve of the near-infrared cut filter of Figure 17, showing the spectral transmittance curve (solid line) when the incident angle is 0° and the spectral transmittance curve (dashed line) when the incident angle is 30°.

As shown in FIG. 18, when light with an incident angle of 30° is incident on the reflective layer 12, there are problems such as the spectral transmittance curve shifting to the short wavelength side (part P1 in FIG. 18) and the occurrence of ripples in the spectral transmittance curve (part P2 in FIG. 18) due to the influence of phase shift. If a wavelength shift occurs in the spectral transmittance curve of the reflective layer 12, a wavelength shift also occurs in the spectral transmittance curve of the near-infrared cut filter (part P3 in FIG. 19), and there is a risk of reducing the color reproducibility of the solid-state imaging element. Furthermore, if a ripple occurs in the spectral transmittance curve of the reflective layer 12, a ripple also occurs in the spectral transmittance curve of the near-infrared cut filter (part P4 in FIG. 19), and there is a risk of a kind of ghost being observed on the solid-state imaging element. Therefore, there has been a demand for a near-infrared cut filter with excellent oblique incidence characteristics that does not cause wavelength shifts or ripples even with obliquely incident light.

The present invention was made in consideration of these circumstances, and its purpose is to provide a near-infrared cut filter that has extremely little incidence angle dependency and excellent oblique incidence characteristics, and an imaging device equipped with such a near-infrared cut filter.

The inventors conducted extensive research to achieve the above objective, and discovered that by focusing on the 800-950 nm wavelength range in the spectral transmittance curve of a transparent substrate made of fluorophosphate glass or phosphate glass, and using a substrate with a small average transmittance in the 800-950 nm wavelength range, it is possible to manufacture a cut filter that selectively transmits light in the visible light range without using the reflective film used in conventional near-infrared cut filters. The present invention was made based on this knowledge.

That is, the near-infrared cut filter of the present invention is characterized by comprising a transparent substrate made of fluorophosphate glass or phosphate glass and having an average transmittance of 3% or less in the wavelength range of 800 to 950 nm, and a resin layer formed on at least one of the main surfaces of the transparent substrate and absorbing light of a specific wavelength.

With this configuration, a reflective layer made of a dielectric multilayer film as in the conventional technology is not necessary (i.e., no reflective layer is provided), so even if light is incident on the near-infrared cut filter at an angle, the optical path length is unlikely to change, and phase shifts are suppressed. Therefore, there is almost no wavelength shift or ripple in the spectral transmittance curve of the near-infrared cut filter.

It is also preferable that the half-value wavelength on the short wavelength side of the transmittance curve of the transparent substrate is 335 to 400 nm, and the half-value wavelength on the long wavelength side is 590 to 630 nm.

It is also preferable that the transparent substrate has an average transmittance of 18% or less in the wavelength range of 650 to 720 nm.

It is also preferable that the transparent substrate has an average transmittance of 10% or less in the wavelength range of 720 to 750 nm.

The resin layer may contain a transparent resin and a dye uniformly dispersed in the transparent resin. In this case, the dye preferably contains an ultraviolet absorbing dye having a maximum absorption wavelength in the range of 340 to 400 nm. In this case, the dye preferably contains a first near-infrared absorbing dye having a maximum absorption wavelength in the range of 650 to 760 nm. In this case, the dye preferably contains a second near-infrared absorbing dye having a maximum absorption wavelength in the range of 800 to 1200 nm.

The resin layer may also contain, in addition to Si atoms, one or more atoms selected from Ti atoms, Zr atoms, and Al atoms.

A bonding layer that enhances adhesion between the transparent substrate and the resin layer can be provided between the transparent substrate and the resin layer. In this case, the bonding layer preferably has a single layer structure that contains one or more atoms selected from Ti atoms, Zr atoms, and Al atoms in addition to Si atoms. In this case, 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 in the bonding layer is preferably greater than 0 atomic % and less than or equal to 33.3 atomic %.

A first anti-reflection film may be provided on the resin layer, and a second anti-reflection film may be provided on the other main surface of the transparent substrate. In this case, it is preferable that the half-value wavelength on the short wavelength side of the transmittance curve is 385 to 430 nm, and the half-value wavelength on the long wavelength side is 590 to 630 nm. In this case, it is preferable that the first anti-reflection film and the second anti-reflection film are each composed of a dielectric multilayer film having a thickness of 500 nm or less. In this case, it is preferable that the dielectric multilayer film has 10 layers or less.

In addition, it is preferable that the dielectric multilayer film is formed by alternately stacking low-refractive index dielectric films made of materials with a refractive index of 1.1 to 1.5 and high-refractive index dielectric films made of materials with a refractive index of 2.0 to 2.5.

In addition, it is preferable that the dielectric multilayer film is formed by alternately stacking low-refractive index dielectric films made of materials with a refractive index of 1.1 to 1.3 and high-refractive index dielectric films made of materials with a refractive index of 1.4 to 1.6.

The thickness of the transparent substrate is preferably 0.01 to 1.5 mm.

From another perspective, the imaging device of the present invention is characterized by comprising a solid-state imaging element and any of the near-infrared cut filters described above. In this case, the near-infrared cut filter can be arranged immediately before the solid-state imaging element and configured to also function as a cover glass.

As described above, the present invention provides a near-infrared cut filter that has extremely little incidence angle dependency and excellent oblique incidence characteristics. It also provides an imaging device that is equipped with such a near-infrared cut filter and has excellent color reproducibility.

FIG. 1 is a diagram illustrating the configuration of a near-infrared cut filter according to a first embodiment of the present invention. FIG. 2 is a vertical cross-sectional view illustrating the configuration of an imaging device equipped with a near-infrared cut filter according to the first embodiment of the present invention. FIG. 3 is a diagram showing the spectral transmittance curve of a glass substrate used in the near-infrared cut filter according to the first embodiment (Example 1) of the present invention. FIG. 4 is a diagram showing a spectral transmittance curve of the near-infrared cut filter according to the first embodiment (Example 1) of the present invention. FIG. 5 is a diagram showing the near-infrared cut filter according to the first embodiment (Example 2) of the present invention and the spectral transmittance curve of a glass substrate used in the near-infrared cut filter. FIG. 6 is a diagram showing the near-infrared cut filter according to the first embodiment (Example 3) of the present invention and the spectral transmittance curve of a glass substrate used in the near-infrared cut filter. FIG. 7 is a diagram showing the near-infrared cut filter according to the first embodiment (Example 4) of the present invention and the spectral transmittance curve of a glass substrate used in the near-infrared cut filter. FIG. 8 is a diagram showing the near-infrared cut filter according to the first embodiment (Example 5) of the present invention and the spectral transmittance curve of the glass substrate used in the near-infrared cut filter. FIG. 9 is a diagram showing a near-infrared cut filter according to a comparative example of the present invention and a spectral transmittance curve of a glass substrate used in the near-infrared cut filter. FIG. 10 is a vertical sectional view illustrating the configuration of a near-infrared cut filter according to a second embodiment of the present invention. FIG. 11 is a diagram showing a spectral transmittance curve of the near-infrared cut filter according to the second embodiment (Example 6) of the present invention. FIG. 12 is a diagram showing a spectral transmittance curve of the near-infrared cut filter according to the second embodiment (Example 7) of the present invention. FIG. 13 is a diagram showing a spectral transmittance curve of the near-infrared cut filter according to the second embodiment (Example 8) of the present invention. FIG. 14 is a diagram showing a spectral transmittance curve of the near-infrared cut filter according to the second embodiment (Example 9) of the present invention. FIG. 15 is a diagram showing a spectral transmittance curve of the near-infrared cut filter according to the second embodiment (Example 10) of the present invention. FIG. 16 is a vertical sectional view illustrating the configuration of a near-infrared cut filter according to a third embodiment (Example 11) of the present invention. FIG. 17 is a vertical cross-sectional view showing the configuration of a conventional near-infrared cut filter. FIG. 18 is a diagram showing the spectral transmittance curve of a reflective layer used in a conventional near-infrared cut filter. FIG. 19 is a diagram showing a spectral transmittance curve of a conventional near-infrared cut filter.

The following describes in detail an embodiment of the present invention with reference to the drawings. Note that the same or corresponding parts in the drawings are given the same reference numerals and their description will not be repeated.

First Embodiment
Fig. 1 is a diagram for explaining the configuration of a near-infrared cut filter 100 according to a first embodiment of the present invention, Fig. 1(a) is a plan view, and Fig. 1(b) is a longitudinal sectional view. Fig. 2 is a longitudinal sectional view for explaining the configuration of an imaging device 1 in which an opening of a package 300 of a solid-state imaging element 200 is sealed by the near-infrared cut filter 100 of this embodiment. As shown in Figs. 1 and 2, the near-infrared cut filter 100 of this embodiment is attached to the front surface of the package 300 that houses the solid-state imaging element 200, and is an optical element that protects the solid-state imaging element 200 and is used for luminosity correction of the solid-state imaging element 200.

As shown in FIG. 1, the near-infrared cut filter 100 of this embodiment has a rectangular plate-like appearance (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 one of the main surfaces of the glass substrate 101 (the upper surface in FIG. 1 (b)).

[Glass substrate]
The glass substrate 101 of this embodiment is an absorbing glass substrate made of phosphate glass or fluorophosphate glass. The thickness of the glass substrate 101 of this embodiment is not particularly limited, but from the viewpoint of achieving small size and weight reduction, it is preferably in the range of 0.01 to 1.5 mm, more preferably 0.01 to 0.70 mm, and even more preferably 0.01 to 0.30 mm.

In this embodiment, the phosphate-based glass is glass containing the essential components P and O and other optional components, and glass containing CuO is particularly preferred. When the phosphate-based glass contains CuO, it can absorb near-infrared light more effectively. Examples of other optional components of the phosphate-based glass include Ca, Mg, Sr, Ba, Li, Na, K, and Cs.

Specific examples of phosphate-based glasses include:
_{P2O5 :} more than 0 mass% and 70 mass% or less,
Al ₂ O ₃ : 0 to 40% by mass,
BaO: 0 to 40% by mass,
CuO: 0 to 40% by mass
It is preferred that the compound contains

Also,
P ₂ O ₅ : 20 to 60% by mass,
Al ₂ O ₃ : 0 to 10% by mass,
BaO: 0 to 10% by mass,
CuO: 0 to 10% by mass
More preferably, it contains:

Also,
P ₂ O ₅ : 20 to 60% by mass,
Al ₂ O ₃ : 1 to 10% by mass,
BaO: 1 to 10% by mass,
CuO: 1 to 10% by mass
More preferably, it comprises:

The fluorophosphate glass in this embodiment is a glass containing P, O, and F as essential components and other optional components, and is particularly preferably one containing CuO. When the fluorophosphate glass contains CuO, it can absorb near-infrared light more effectively. Examples of other optional components of the fluorophosphate glass include Ca, Mg, Sr, Ba, Li, Na, K, and Cs.

As for the fluorophosphate glass, those containing BaO are preferably used. By containing 0% or more BaO, the devitrification resistance and melting properties of the glass can be improved. If the content is more than 10%, the glass becomes more susceptible to devitrification, so 0 to 10% is preferable. Furthermore, the BaO content is more preferably 1 to 10%, and even more preferably 1 to 5%.

In addition, fluorophosphate-based glass containing Al ₂ O ₃ is preferably used. By containing 0% or more of Al ₂ O ₃ , the stability and chemical durability of the glass can be improved. If the content is more than 10%, the glass is prone to devitrification, so 0 to 10% is preferable. In addition, the content of Al ₂ O ₃ is more preferably 1 to 10%, and further preferably 1 to 5%.

In addition, as the fluorophosphate glass, one containing Y ₂ O ₃ is preferably used. By containing 0% or more of Y ₂ O ₃ , it is possible to increase the refractive index while maintaining thermal stability. If it is more than 10%, devitrification is likely to occur, and the glass transition temperature and yield point temperature increase, so 0 to 10% is preferable. In addition, the content of Y ₂ O ₃ is more preferably 1 to 10%, and further preferably 1 to 5%.

In addition, as the fluorophosphate glass, one containing _BaCl2 is preferably used. By introducing an appropriate amount of Cl into the glass by _BaCl2 , the difference between the crystallization onset temperature (Tx) and the glass transition temperature (Tg) of the glass becomes large, and the stability of the glass against devitrification is improved. If the content is more than 10%, devitrification is likely to occur, so 0 to 10% is preferable. In addition, the content of _BaCl2 is more preferably 1 to 10%, and even more preferably 1 to 5%.

Specific examples of fluorophosphate glasses include:
_{P2O5 :} more than 0 mass% and 70 mass% or less,
Al ₂ O ₃ : 0 to 40% by mass,
BaO: 0 to 40% by mass,
CuO: 0 to 40% by mass
and further contains more than 0 mass % to 40 mass % of fluoride.

Also,
P ₂ O ₅ : 20 to 60% by mass,
Al ₂ O ₃ : 0 to 10% by mass,
BaO: 0 to 10% by mass,
CuO: 0 to 10% by mass
and more preferably contains 1 to 30 mass % of fluoride.

Also,
P ₂ O ₅ : 20 to 60% by mass,
Al ₂ O ₃ : 1 to 10% by mass,
BaO: 1 to 10% by mass,
CuO: 1 to 10% by mass
and more preferably contains 2 to 30 mass % of fluoride.

The fluoride may be one or more selected from the group consisting of MgF ₂ , CaF ₂ , SrF ₂ and the like.

Specific examples of such fluorophosphate-based glasses include:
P ₂ O ₅ : 40 to 50% by mass,
Al ₂ O ₃ : 1 to 10% by mass,
BaO: 1 to 10% by mass,
CuO: 1 to 10% by mass,
MgF ₂ : 1 to 10% by mass,
CaF ₂ : 1 to 10% by mass,
SrF ₂ : 1 to 10% by mass,
Y ₂ O ₃ : 1 to 10% by mass,
BaCl ₂ : 0 to 1% by mass,
Particularly preferred are those containing:

Although details will be described later, the glass substrate 101 of this embodiment is configured to have an average transmittance of 3% or less in the wavelength range of 800 to 950 nm. In this way, by using a glass substrate 101 with a small average transmittance in the wavelength range of 800 to 950 nm, it is possible to manufacture a cut filter that selectively transmits light in the visible light range without using a reflective film (dielectric multilayer film) that was used in conventional near-infrared cut filters.

Furthermore, the glass substrate 101 preferably has an average transmittance of 10% or less in the wavelength range of 720 to 750 nm, more preferably 8% or less, and even more preferably 7% or less.

In addition, the glass substrate 101 preferably has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve in the range of 335 to 400 nm, more preferably in the range of 335 to 380 nm, and even more preferably in the range of 340 to 350 nm. In addition, the glass substrate 101 preferably has a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve in the range of 590 to 630 nm, and more preferably in the range of 610 to 624 nm. In this specification, the half-value wavelength refers to the wavelength at which the transmittance is 50%, the half-value wavelength (UV_λ50) on the short wavelength side refers to the wavelength at which the transmittance is 50% at the rising edge of the transmittance curve, and the half-value wavelength (NIR_λ50) on the long wavelength side refers to the wavelength at which the transmittance is 50% at the falling edge of the transmittance curve.

Furthermore, the glass substrate 101 preferably has an average transmittance in the wavelength range of 650 to 720 nm of 18% or less, more preferably 17% or less, and even more preferably 16% or less.

[Resin layer]
The resin layer 102 of the present embodiment is a layer composed of a dye that absorbs light of a specific wavelength and a resin. The resin layer 102 contains, for example, at least one of a near-infrared absorbing dye and an ultraviolet absorbing dye, and a transparent resin, and preferably contains the dye uniformly dissolved or dispersed in the transparent resin.

The near-infrared absorbing dye constituting the resin layer 102 may be any of the conventionally known dyes, such as one or more selected from cyanine dyes, polymethine dyes, squarylium dyes, porphyrin dyes, metal dithiol complex dyes, phthalocyanine dyes, diimonium dyes, and inorganic oxide particles, and more preferably one or more selected from squarylium dyes, cyanine dyes, and phthalocyanine dyes.

The ultraviolet absorbing dye constituting the resin layer 102 may be any conventionally known dye, such as one or more selected from benzotriazole-based compounds, benzophenone-based compounds, triazine-based compounds, benzoxazinone-based compounds, cyanoacrylate-based compounds, oxanilide-based compounds, salicylate-based compounds, formamidine-based compounds, indole-based compounds, and azomethine-based compounds, and more preferably one or more selected from benzotriazole-based compounds, benzophenone-based compounds, and triazine-based compounds.

As the resin constituting the resin layer 102, a conventionally known transparent resin can be adopted, and one or more selected from acrylic resin, epoxy resin, ene-thiol resin, polycarbonate resin, polyether resin, polyarylate resin, polysulfone resin, polyethersulfone resin, polyparaphenylene resin, polyarylene ether phosphine oxide resin, polyimide resin, polyamideimide resin, polyolefin resin, cyclic olefin resin and polyester resin can be mentioned. As the transparent resin, from the viewpoint of transparency, solubility of the near infrared absorbing dye in the transparent resin and heat resistance, those with a high glass transition point (Tg) are preferable, and therefore, thermosetting resins are suitable. Specifically, one or more selected from polyester resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, polyimide resin and epoxy resin can be used. As the polyester resin, one or more selected from polyethylene terephthalate resin and polyethylene naphthalate resin are preferable. In addition, even if the resin is thermoplastic, it can be suitably used as a transparent resin by increasing heat resistance by adjusting functional groups, etc. For example, acrylic resins, polyamide resins, polyolefin resins, etc., whose heat resistance can be improved by adjusting functional groups, etc., can also be used as transparent resins.

In addition to the near-infrared absorbing dye and transparent resin, the resin layer 102 may further contain optional components such as color correction dyes, leveling agents, antistatic agents, heat stabilizers, light stabilizers, antioxidants, dispersants, flame retardants, lubricants, and plasticizers, as long as the effects of the present invention are not impaired.

The resin layer 102 can be formed, for example, by dissolving or dispersing a pigment, a transparent resin, and optional ingredients in a solvent to prepare a resin film-forming liquid, which is then coated, dried, and cured as necessary. The resin film-forming liquid may contain a known surfactant such as a cationic, anionic, or nonionic surfactant.

The resin film-forming liquid can be applied by one or more coating methods selected from the dip coating method, cast coating method, spray coating method, spin coating method, etc.

In this way, the resin layer 102 is a layer formed on the glass substrate 101 and configured to absorb light of a specific wavelength, and by setting the absorption wavelength in accordance with the spectral transmittance characteristics of the glass substrate 101 (i.e., selecting an optimal dye), light in the desired visible light region can be extracted.
Specifically, the resin layer 102 of this embodiment may contain an ultraviolet absorbing dye having a maximum absorption wavelength in the range of 340 to 400 nm and a near-infrared absorbing dye (first near-infrared absorbing dye) having a maximum absorption wavelength in the range of 650 to 760 nm. The resin layer 102 may further contain a near-infrared absorbing dye (second near-infrared absorbing dye) having a maximum absorption wavelength in the range of 800 to 1200 nm.
In addition, the resin layer 102 in this embodiment is formed on one main surface of the glass substrate 101 (the upper surface in FIG. 1(b)), but is not limited to this configuration. The resin layer 102 may be formed on the other main surface of the glass substrate 101 (the lower surface in FIG. 1(b)), or 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, and may be configured with multiple layers.

The spectral transmittance curve of the near-infrared cut filter 100 on which such a resin layer 102 is formed has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of 385 to 430 nm, a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of 590 to 630 nm, and an average transmittance of 3.0% or less in the wavelength range of 800 to 950 nm, which is close to the visual sensitivity of humans (details will be described later).

[Imaging device]
Next, an imaging device according to the present invention will be described. As shown in Fig. 2, the imaging device 1 according to the present invention includes a solid-state imaging element 200, a package 300 that houses the solid-state imaging element 200, and a near-infrared cut filter 100 that is attached to the front surface of the package 300.

Examples of the solid-state imaging element 200 include image sensors such as a CCD (Charge-Coupled Device) and a CMOS (Complementary Metal Oxide Semiconductor).

The solid-state imaging element 200 is disposed in the approximate center of the bottom surface of the square-shaped package 300, and is attached to the opening of the package 300 so that the other main surface side of the near-infrared cut filter 100 (the lower side in FIG. 1(b)) faces the solid-state imaging element 200. Note that in FIG. 2, the resin layer 102 side of the near-infrared cut filter 100 is the incident surface on which light toward the solid-state imaging element 200 is incident, and the other main surface side of the near-infrared cut filter 100 is the exit surface, but this is not necessarily limited to such a configuration, and the near-infrared cut filter 100 may be attached upside down (i.e., so that the resin layer 102 faces the solid-state imaging element 200).

In addition, in the imaging device 1 of FIG. 2, the near-infrared cut filter 100 is attached to the opening of the package 300 and is configured to also function as a so-called cover glass, but this is not necessarily limited to such a configuration. For example, the imaging device 1 may include a lens group (not shown) that guides light to the solid-state imaging element 200. In this case, for example, the near-infrared cut filter 100 may be disposed closer to the imaging device 1 than the lens group, and a cover glass may be provided even closer to the imaging device 1 than the near-infrared cut filter 100.

The near-infrared cut filter 100 of this embodiment will be further described below with examples and comparative examples, but the present invention is not limited to the following examples.

Example 1
[1. Selection of glass substrate 101]
Fluorophosphate glass (CXD700, thickness 0.21 mm) manufactured by HOYA Corporation was selected as the glass substrate 101 of Example 1. Fig. 3 is a diagram showing the spectral transmittance curve of the glass substrate 101 of Example 1, where the vertical axis represents the transmittance (%) and the horizontal axis represents the wavelength (nm).
As shown in FIG. 3, the glass substrate 101 of this embodiment has an average transmittance of 1.4% (that is, 3% or less) in the wavelength range of 800 to 950 nm.
Moreover, the glass substrate 101 of this embodiment has an average transmittance of 4.5% (that is, 10% or less) in the wavelength range of 720 to 750 nm.
In addition, the glass substrate 101 of this embodiment has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of approximately 343 nm (i.e., within the range of 335 to 400 nm) and a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of approximately 619 nm (i.e., within the range of 590 to 630 nm).
Moreover, the glass substrate 101 of this embodiment has an average transmittance of 15.5% (that is, 18% or less) in the wavelength range of 650 to 720 nm.

2. Formation of resin layer 102
In a container, an acrylic resin (transparent resin), a benzotriazole compound and a triazine compound (ultraviolet absorbing dye), and a squarylium compound and a cyanine compound (first near-infrared absorbing dye) were mixed in a predetermined mixing ratio to prepare a resin film forming liquid, and the obtained resin film forming liquid was applied onto a glass substrate 101 using a spin coater. Then, the glass substrate 101 to which the resin film forming liquid was applied was placed on a hot plate heated to 160° C., and heated for 20 minutes to harden, thereby producing the near-infrared cut filter 100 of this embodiment.

4 is a diagram showing the spectral transmittance curve of the near-infrared cut filter 100 of Example 1, showing the spectral transmittance curve (solid line) at an incident angle of 0° and the spectral transmittance curve (dashed line) at an incident angle of 30°. As shown in FIG. 4, the spectral transmittance curve of the near-infrared cut filter 100 of this example has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of about 410 nm, a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of about 610 nm, and an average transmittance of 1.3% in the wavelength range of 800 to 950 nm, which is close to the visual sensitivity of humans.
Furthermore, since the near-infrared cut filter 100 of this embodiment does not have a reflective film like conventional near-infrared cut filters, even if light with an incident angle of 30° is incident, the occurrence of phase shift, wavelength shift, and ripples that significantly impair the performance as a cut filter is suppressed.

Example 2
The near-infrared cut filter 100 of Example 2 differs from Example 1 in that a fluorophosphate glass (CXD700) having a thickness of 0.8 mm manufactured by HOYA Corporation is selected as the glass substrate 101, and that the resin layer 102 is formed from an acrylic resin (transparent resin), a benzotriazole compound, and a triazine compound (ultraviolet absorbing pigment) (i.e., does not contain a near-infrared absorbing pigment).

Figure 5 shows the spectral transmittance curve (dotted line) of the glass substrate 101 of Example 2 and the spectral transmittance curves (solid line, dashed line) of the near-infrared cut filter 100 of Example 2. Note that the spectral transmittance curve of the near-infrared cut filter 100 shows the spectral transmittance curve (solid line) at an incident angle of 0° and the spectral transmittance curve (dashed line) at an incident angle of 30°.

As shown in FIG. 5, the glass substrate 101 of this embodiment has an average transmittance of 0.1% or less (that is, 3% or less) in the wavelength range of 800 to 950 nm.
Moreover, the glass substrate 101 of this embodiment has an average transmittance of 0.2% (that is, 10% or less) in the wavelength range of 720 to 750 nm.
In addition, the glass substrate 101 of this embodiment has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of approximately 353 nm (i.e., within the range of 335 to 400 nm), and a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of approximately 591 nm (i.e., within the range of 590 to 630 nm).
Moreover, the glass substrate 101 of this embodiment has an average transmittance of 3.1% (that is, 18% or less) in the wavelength range of 650 to 720 nm.

The near-infrared cut filter 100 of this embodiment has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of approximately 405 nm, a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of approximately 591 nm, and an average transmittance of 0.1% or less in the wavelength range of 800 to 950 nm, which is close to the visual sensitivity of humans.
The near-infrared cut filter 100 of the present embodiment also does not have a reflective film like conventional near-infrared cut filters, and therefore even when light with an incident angle of 30° is incident, the occurrence of phase shift, wavelength shift, and ripples that significantly impair the performance of the cut filter is suppressed.

Example 3
The near-infrared cut filter 100 of Example 3 is different from Example 1 in that a fluorophosphate glass (CXD700) having a thickness of 1.0 mm manufactured by HOYA Corporation is selected as the glass substrate 101 .

Figure 6 shows the spectral transmittance curve (dotted line) of the glass substrate 101 of Example 3 and the spectral transmittance curves (solid line, dashed line) of the near-infrared cut filter 100 of Example 3. Note that the spectral transmittance curve of the near-infrared cut filter 100 shows the spectral transmittance curve (solid line) at an incident angle of 0° and the spectral transmittance curve (dashed line) at an incident angle of 30°.

As shown in FIG. 6, the glass substrate 101 of this embodiment has an average transmittance of 0.2% (that is, 3% or less) in the wavelength range of 800 to 950 nm.
Moreover, the glass substrate 101 of this embodiment has an average transmittance of 1.0% (that is, 10% or less) in the wavelength range of 720 to 750 nm.
In addition, the glass substrate 101 of this embodiment has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of approximately 347 nm (i.e., within the range of 335 to 400 nm), and a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of approximately 602 nm (i.e., within the range of 590 to 630 nm).
Moreover, the glass substrate 101 of this embodiment has an average transmittance of 6.8% (that is, 18% or less) in the wavelength range of 650 to 720 nm.

The near-infrared cut filter 100 of this embodiment has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of approximately 404 nm, a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of approximately 596 nm, and an average transmittance of 0.2% in the wavelength range of 800 to 950 nm, which is close to the visual sensitivity of humans.
The near-infrared cut filter 100 of the present embodiment also does not have a reflective film like conventional near-infrared cut filters, and therefore even when light with an incident angle of 30° is incident, the occurrence of phase shift, wavelength shift, and ripples that significantly impair the performance of the cut filter is suppressed.

Example 4
The near-infrared cut filter 100 of Example 4 differs from Example 1 in that a fluorophosphate glass (CXD700) having a thickness of 0.23 mm manufactured by HOYA Corporation is selected as the glass substrate 101, and the content of the cyanine compound (near-infrared absorbing dye) in the resin layer 102 is changed.

Figure 7 shows the spectral transmittance curve (dotted line) of the glass substrate 101 of Example 4 and the spectral transmittance curves (solid line, dashed line) of the near-infrared cut filter 100 of Example 4. Note that the spectral transmittance curve of the near-infrared cut filter 100 shows the spectral transmittance curve (solid line) at an incident angle of 0° and the spectral transmittance curve (dashed line) at an incident angle of 30°.

As shown in FIG. 7, the glass substrate 101 of this embodiment has an average transmittance of 1.0% (that is, 3% or less) in the wavelength range of 800 to 950 nm.
Moreover, the glass substrate 101 of this embodiment has an average transmittance of 3.4% (that is, 10% or less) in the wavelength range of 720 to 750 nm.
In addition, the glass substrate 101 of this embodiment has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of approximately 344 nm (i.e., within the range of 335 to 400 nm), and a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of approximately 615 nm (i.e., within the range of 590 to 630 nm).
Moreover, the glass substrate 101 of this embodiment has an average transmittance of 13.2% (that is, 18% or less) in the wavelength range of 650 to 720 nm.

The near-infrared cut filter 100 of this embodiment has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of approximately 404 nm, a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of approximately 603 nm, and an average transmittance of 0.9% in the wavelength range of 800 to 950 nm, which is close to the visual sensitivity of humans.
The near-infrared cut filter 100 of the present embodiment also does not have a reflective film like conventional near-infrared cut filters, and therefore even when light with an incident angle of 30° is incident, the occurrence of phase shift, wavelength shift, and ripples that significantly impair the performance of the cut filter is suppressed.

Example 5
The near-infrared cut filter 100 of Example 5 differs from Example 1 in that a fluorophosphate glass (CXD700) having a thickness of 0.30 mm manufactured by HOYA Corporation is selected as the glass substrate 101, and that the resin layer 102 is formed from an acrylic resin (transparent resin), a benzotriazole compound and a triazine compound (ultraviolet absorbing dye), a squarylium compound and a cyanine compound (first near-infrared absorbing dye), and a diionium compound (second near-infrared absorbing dye) (i.e., a second near-infrared absorbing dye is added).

Figure 8 shows the spectral transmittance curve (dotted line) of the glass substrate 101 of Example 5 and the spectral transmittance curves (solid line, dashed line) of the near-infrared cut filter 100 of Example 5. Note that the spectral transmittance curve of the near-infrared cut filter 100 shows the spectral transmittance curve (solid line) at an incident angle of 0° and the spectral transmittance curve (dashed line) at an incident angle of 30°.

As shown in FIG. 8, the glass substrate 101 of this embodiment has an average transmittance of 0.2% (that is, 3% or less) in the wavelength range of 800 to 950 nm.
Moreover, the glass substrate 101 of this embodiment has an average transmittance of 1.3% (that is, 10% or less) in the wavelength range of 720 to 750 nm.
In addition, the glass substrate 101 of this embodiment has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of approximately 348 nm (i.e., within the range of 335 to 400 nm) and a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of approximately 604 nm (i.e., within the range of 590 to 630 nm).
Moreover, the glass substrate 101 of this embodiment has an average transmittance of 7.7% (that is, 18% or less) in the wavelength range of 650 to 720 nm.

The near-infrared cut filter 100 of this embodiment has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of approximately 406 nm, a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of approximately 604 nm, and an average transmittance of 0.1% in the wavelength range of 800 to 950 nm, which is close to the visual sensitivity of humans.
In addition, the near-infrared cut filter 100 of this embodiment also does not have a reflective film like the conventional near-infrared cut filter, so even if light with an incident angle of 30° is incident, the occurrence of phase shift, wavelength shift, and ripples that significantly impair the performance as a cut filter is suppressed. (Comparative Example 1)
The near-infrared cut filter of Comparative Example 1 differs from Example 1 in that a fluorophosphate glass (CXA700, thickness 0.21 mm) manufactured by HOYA Corporation is selected as the glass substrate, and the resin layer is the same as the resin layer 102 of Example 1.

Figure 9 shows the spectral transmittance curve (dotted line) of the glass substrate of Comparative Example 1 and the spectral transmittance curves (solid line, dashed line) of the near-infrared cut filter of Comparative Example 1. Note that the spectral transmittance curve of the near-infrared cut filter shows the spectral transmittance curve (solid line) at an incident angle of 0° and the spectral transmittance curve (dashed line) at an incident angle of 30°.

As shown in FIG. 9, the glass substrate of this modified example has an average transmittance of 4.3% (that is, greater than 3%) in the wavelength range of 800 to 950 nm.
Moreover, the glass substrate of this modified example has an average transmittance of 9.7% (that is, 10% or less) in the wavelength range of 720 to 750 nm.
In addition, the glass substrate of this modified example has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of approximately 338 nm (i.e., within the range of 335 to 400 nm), and a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of approximately 632 nm (i.e., outside the range of 590 to 630 nm).
Moreover, the glass substrate of this modified example has an average transmittance of 23.8% (that is, greater than 18%) in the wavelength range of 650 to 720 nm.

The near-infrared cut filter of this comparative example had a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of about 404 nm, a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of about 610 nm, and an average transmittance in the wavelength range of 800 to 950 nm of 4.1%. In other words, the near-infrared cut filter of this comparative example had a higher average transmittance in the wavelength range of 800 to 950 nm than the near-infrared cut filters 100 of Examples 1 to 5.
Like the near-infrared cut filters 100 of Examples 1 to 5, the near-infrared cut filter 100 of this modified example does not have a reflective film like the conventional near-infrared cut filters. Therefore, even if light with an incident angle of 30° is incident, the occurrence of phase shift, wavelength shift, and ripples that significantly impair the performance as a cut filter is suppressed.

Thus, the near-infrared cut filter of Comparative Example 1 has a higher average transmittance (i.e., greater than 3%) in the wavelength range of 800 to 950 nm, and therefore has poor color reproducibility, compared to the near-infrared cut filters 100 of Examples 1 to 5. In order to address this problem, it is effective to form a reflective layer as is used in conventional near-infrared cut filters, but the use of a reflective layer causes problems such as a phase shift, wavelength shift, and ripples.
That is, in the near-infrared cut filter 100 of the present embodiment (Examples 1 to 5), in order to solve such problems, a glass substrate 101 having a very low average transmittance (i.e., 3% or less) in the wavelength range of 800 to 950 nm is used, and characteristics close to the visual sensitivity of humans are obtained without using a conventional reflective layer.

As described above, the near-infrared cut filter 100 of this embodiment does not use a conventional reflective layer, and therefore has very little incidence angle dependency and excellent oblique incidence characteristics. In addition, an imaging device 1 using such a near-infrared cut filter 100 can obtain images with excellent color reproducibility because the occurrence of ghosts is suppressed.

The above is an explanation of an embodiment of the present invention, but the present invention is not limited to the configuration of the above embodiment, and various modifications are possible within the scope of the technical concept.

For example, in the present embodiment (Examples 1 to 5), a near-infrared cut filter 100 is exemplified in which the half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve is about 404 to 410 nm, and the half-value wavelength (NIR_λ50) on the long wavelength side is about 591 to 610 nm, but the characteristics are not limited to these. By appropriately selecting the ultraviolet absorbing pigment, the first near-infrared absorbing pigment, and the second near-infrared absorbing pigment of the resin layer 102 and adjusting the mixing ratio thereof, the half-value wavelength on the short wavelength side of the transmittance curve can be adjusted within the range of 385 to 430 nm, and the half-value wavelength on the long wavelength side can be adjusted within the range of 590 to 630 nm.

Second Embodiment
Fig. 10 is a vertical cross-sectional view illustrating the configuration of a near-infrared cut filter 100A according to a second embodiment of the present invention. As shown in Fig. 10, the near-infrared cut filter 100A of this embodiment is different from the near-infrared cut filter 100 of the first embodiment in that it has an anti-reflection film 103 on the upper surface of the resin layer 102 (the surface opposite to the glass substrate 101) and an anti-reflection film 104 on the other main surface of the glass substrate 101 (the lower surface in Fig. 10).
By forming the antireflection films 103 and 104 in this manner, reflection at the interfaces (that is, the entrance surface and exit surface) of the near-infrared cut filter 100A can be suppressed, and therefore the transmittance can be increased (improved).

The anti-reflection films 103 and 104 in this embodiment are layers that prevent reflection at the interface between the entrance surface and the exit surface of the near-infrared cut filter 100A, and are specifically composed of a dielectric multilayer film in which low-refractive index dielectric films and high-refractive index dielectric films are alternately stacked.

The material of the dielectric film constituting the dielectric multilayer film can be freely selected according to the desired optical properties, but the refractive index of the low refractive index material for constituting the low refractive index dielectric layer is preferably in the range of 1.1 to 1.5, and examples of the low refractive index material include SiO ₂ , MgF ₂ , SiO ₂ hollow particles, and low refractive index sol-gel coats having an aerosol structure. The refractive index of the high refractive index material for constituting the high refractive index dielectric layer is preferably in the range of 2.0 to 2.5, and examples of the high refractive index material include ZrO ₂ , Ta ₂ O ₅ , TiO ₂ , and Nb ₂ O ₅ .
Also, a material with a refractive index of 1.4 to 1.6 (for example, SiO ₂ ) can be used as the high refractive index material, and in this case, a material with a refractive index of 1.1 to 1.3 (for example, aerosol coat) can be applied as the low refractive index material.

In this way, by using the dielectric multilayer film for the antireflection films 103 and 104, the antireflection function can be easily imparted by utilizing the interference of light occurring in each dielectric film. However, when the number of film layers is increased, the optical path length becomes longer when the light is obliquely incident, and the interference condition of the reflected light in each layer is broken, which causes problems such as wavelength shift and ripple. In addition, such wavelength shift and ripple cause an increase in the reflected light, which is observed as a kind of ghost on the solid-state imaging element 200, and there is also a problem that accurate color reproducibility cannot be obtained. Therefore, in this embodiment, in order to avoid such problems, the number of film layers of the dielectric multilayer film is configured to be 10 layers or less. It is preferable that the number of film layers is particularly 5 layers or less, and more preferably 3 layers or less.
The thickness of the dielectric films constituting the dielectric multilayer film can be freely selected depending on the desired optical properties, but is preferably 50 nm to 1 μm, and more preferably 50 nm to 500 nm.
Moreover, the thickness of the entire dielectric multilayer film (that is, the antireflection films 103 and 104) is set to 500 nm or less.

In this embodiment, the resin layer 102 is formed on one of the main surfaces of the glass substrate 101 (the upper surface in FIG. 10), but similar to the first embodiment, the resin layer 102 may be formed on the other main surface of the glass substrate 101 (the lower surface in FIG. 10), or 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, and may be composed of multiple layers.

The near-infrared cut filter 100A of this embodiment will be further described below with examples, but the present invention is not limited to the following examples.

(Example 6)
The near-infrared cut filter 100 of Example 1 was further formed with anti-reflection films 103 and 104 by the following procedure (3. Formation of anti-reflection films 103 and 104), to prepare a near-infrared cut filter 100A of Example 6.
[3. Formation of anti-reflection films 103 and 104]
The dielectric thin films (dielectric layers 1 to 5) in Table 1 were formed in order (i.e., antireflection films 103 and 104) by using a so-called sol-gel method on the upper surface (the surface opposite to the glass substrate 101) of the resin layer 102 of the near-infrared cut filter 100 of Example 1 and on the other main surface of the glass substrate 101 (the lower surface in FIG. 10 ), thereby obtaining the near-infrared cut filter 100A of Example 6.

11 is a diagram showing the spectral transmittance curve of the near-infrared cut filter 100A of Example 6, which shows the spectral transmittance curve (solid line) when the incident angle is 0° and the spectral transmittance curve (dashed line) when the incident angle is 30°. As shown in FIG. 11, the near-infrared cut filter 100A of this example has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of about 390 nm, a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of about 610 nm, and an average transmittance of 1.2% in the wavelength range of 800 to 950 nm, which is close to the visual sensitivity of humans.
Furthermore, although the near-infrared cut filter 100A of this embodiment has a dielectric multilayer film as the anti-reflection films 103 and 104, the thickness of the film is sufficiently thin (500 nm or less), so that even when light with an incident angle of 30° is incident, the occurrence of phase shift, wavelength shift, and ripple that significantly impair the performance of the cut filter is suppressed.
Furthermore, since the near-infrared cut filter 100A of this embodiment has anti-reflection films 103 and 104, it has a higher transmittance than the near-infrared cut filter 100 of Example 1 (i.e., compared to FIG. 4), with the peak transmittance being approximately 95%.

(Example 7)
The antireflection films 103 and 104 were formed on the near-infrared cut filter 100 of Example 2 in the same manner as in Example 6, to prepare a near-infrared cut filter 100A of Example 7.

12 is a diagram showing the spectral transmittance curve of the near-infrared cut filter 100A of Example 7, which shows the spectral transmittance curve (solid line) when the incident angle is 0° and the spectral transmittance curve (dashed line) when the incident angle is 30°. As shown in FIG. 12, the near-infrared cut filter 100A of this example has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of about 403 nm, a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of about 596 nm, and an average transmittance of 0.1% or less in the wavelength range of 800 to 950 nm, and thus has characteristics close to the visual sensitivity of humans.
Furthermore, although the near-infrared cut filter 100A of this embodiment has a dielectric multilayer film as the anti-reflection films 103 and 104, the thickness of the film is sufficiently thin (500 nm or less), so that even when light with an incident angle of 30° is incident, the occurrence of phase shift, wavelength shift, and ripple that significantly impair the performance of the cut filter is suppressed.
Furthermore, since the near-infrared cut filter 100A of this embodiment has anti-reflection films 103 and 104, it has a higher transmittance than the near-infrared cut filter 100 of Example 2 (i.e., compared to FIG. 5 ), with the peak transmittance being approximately 95%.

(Example 8)
The near-infrared cut filter 100 of Example 3 was formed with the antireflection films 103 and 104 in the same manner as in Example 6 to prepare a near-infrared cut filter 100A of Example 8.

13 is a diagram showing the spectral transmittance curve of the near-infrared cut filter 100A of Example 8, which shows the spectral transmittance curve (solid line) when the incident angle is 0° and the spectral transmittance curve (dashed line) when the incident angle is 30°. As shown in FIG. 13, the near-infrared cut filter 100A of this example has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of about 402 nm, a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of about 601 nm, and an average transmittance of 0.2% in the wavelength range of 800 to 950 nm, which is close to the visual sensitivity of humans.
Furthermore, although the near-infrared cut filter 100A of this embodiment has a dielectric multilayer film as the anti-reflection films 103 and 104, the thickness of the film is sufficiently thin (500 nm or less), so that even when light with an incident angle of 30° is incident, the occurrence of phase shift, wavelength shift, and ripple that significantly impair the performance of the cut filter is suppressed.
Furthermore, since the near-infrared cut filter 100A of this embodiment has anti-reflection films 103 and 104, it has a higher transmittance than the near-infrared cut filter 100 of Example 3 (i.e., compared to FIG. 6 ), with the peak transmittance being approximately 97%.

(Example 9)
The near-infrared cut filter 100 of Example 4 was formed with the antireflection films 103 and 104 in the same manner as in Example 6 to prepare a near-infrared cut filter 100A of Example 9.

14 is a diagram showing the spectral transmittance curve of the near-infrared cut filter 100A of Example 9, which shows the spectral transmittance curve (solid line) when the incident angle is 0° and the spectral transmittance curve (dashed line) when the incident angle is 30°. As shown in FIG. 14, the near-infrared cut filter 100A of this example has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of about 402 nm, a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of about 608 nm, and an average transmittance of 0.9% in the wavelength range of 800 to 950 nm, which is close to the visual sensitivity of humans.
Furthermore, although the near-infrared cut filter 100A of this embodiment has a dielectric multilayer film as the anti-reflection films 103 and 104, the thickness of the film is sufficiently thin (500 nm or less), so that even when light with an incident angle of 30° is incident, the occurrence of phase shift, wavelength shift, and ripple that significantly impair the performance of the cut filter is suppressed.
Furthermore, since the near-infrared cut filter 100A of this embodiment has anti-reflection films 103 and 104, it has a higher transmittance than the near-infrared cut filter 100 of Example 4 (i.e., compared to FIG. 7 ), with the peak transmittance being approximately 98%.

Example 10
The near-infrared cut filter 100 of Example 5 was formed with the antireflection films 103 and 104 in the same manner as in Example 6 to prepare a near-infrared cut filter 100A of Example 10.

15 is a diagram showing the spectral transmittance curve of the near-infrared cut filter 100A of Example 10, which shows the spectral transmittance curve (solid line) when the incident angle is 0° and the spectral transmittance curve (dashed line) when the incident angle is 30°. As shown in FIG. 15, the near-infrared cut filter 100A of this example has a half-value wavelength (UV_λ50) on the short wavelength side of the transmittance curve of about 404 nm, a half-value wavelength (NIR_λ50) on the long wavelength side of the transmittance curve of about 604 nm, and an average transmittance of 0.1% in the wavelength range of 800 to 950 nm, which is close to the visual sensitivity of humans.
Furthermore, although the near-infrared cut filter 100A of this embodiment has a dielectric multilayer film as the anti-reflection films 103 and 104, the thickness of the film is sufficiently thin (500 nm or less), so that even when light with an incident angle of 30° is incident, the occurrence of phase shift, wavelength shift, and ripple that significantly impair the performance of the cut filter is suppressed.
Furthermore, since the near-infrared cut filter 100A of this embodiment has anti-reflection films 103 and 104, it has a higher transmittance than the near-infrared cut filter 100 of Example 5 (i.e., compared to FIG. 8), with the peak transmittance being approximately 93%.

In this way, the near-infrared cut filters 100A of Examples 6 to 10 have excellent oblique incidence characteristics and high transmittance. Furthermore, an imaging device 1 using such near-infrared cut filters 100 can obtain bright images with excellent color reproducibility.

Third Embodiment
Fig. 16 is a vertical cross-sectional view illustrating a configuration of a near-infrared cut filter 100B according to a third embodiment of the present invention. As shown in Fig. 16, the near-infrared cut filter 100B of this embodiment is different from the near-infrared cut filter 100 of the first embodiment in that a bonding layer 105 that bonds the glass substrate 101 and the resin layer 102 to each other is provided between them.
By forming the bonding layer 105 in this manner, the adhesion between the glass substrate 101 and the resin layer 102 can be increased, and therefore the reliability can be improved.

As a result of intensive research, the present inventors have found that the use of a bonding component containing Si atoms and one or more atoms selected from Ti atoms, Zr atoms, and Al atoms can improve the adhesion between the glass substrate 101 and the resin layer 102. The bonding layer 105 of the present embodiment is based on this finding, and has a single layer structure containing Si atoms and one or more atoms selected from Ti atoms, Zr atoms, and Al atoms.
In this specification, the single layer structure means a layer structure that is identified as being made of forming materials having the same composition from the measurement image (image contrast) or elemental analysis results obtained when measured with a scanning transmission electron microscope-energy dispersive X-ray spectrometer (STEM-EDX) under the following measurement conditions.
<Measurement conditions>
Scanning transmission electron microscope: ARM200F manufactured by JEOL Ltd.
Energy dispersive X-ray spectrometer: JED-2300T manufactured by JEOL Ltd.
Sample preparation: focused ion beam processing (FIB)
Acceleration voltage: 200 kV
Elemental analysis: EDX mapping (resolution: 256 x 256)

The thickness of the bonding layer 105 is preferably 1000 nm or less, more preferably 10 to 500 nm, and further preferably 30 to 300 nm.
By making the thickness of the bonding layer 105 1000 nm or less, it becomes easier to prevent unevenness from occurring during the formation (firing) of the bonding layer 105, and the film surface of the bonding layer 105 can be easily made uniform.
Furthermore, when the thickness of the bonding layer 105 is 10 nm or more, the bonding layer 105 is likely to exhibit sufficient bonding strength, and the mechanical strength of the near-infrared cut filter 100B can be easily improved.
In this specification, the thickness of the bonding layer 105 means the arithmetic average value when the thickness of the bonding layer 105 is measured at 50 points in a measurement image (image contrast) of the cross section of the near-infrared cut filter 100B obtained by measurement using the above-mentioned STEM-EDX.

The bonding layer 105 of this embodiment contains one or more atoms selected from Ti atoms, Zr atoms, and Al atoms in addition to Si atoms, but it is preferable that the one or more atoms selected from Ti atoms, Zr atoms, and Al atoms contained in the bonding layer 105 together with Si atoms are Ti atoms.

（４）さらに、上記各原子のＥＤＸ線積算強度Ｘにｋファクターを掛けた値を、各々の原子量Ｍで除した値が、各構成元素の原子数の比に対応するとみなし得る。このため、Ｓｉ原子の原子量をＭ_Ｓｉ、Ｔｉ原子の原子量をＭ_Ｔｉ、Ｚｒ原子の原子量をＭ_Ｚｒ、Ａｌ原子の原子量をＭ_Ａｌとした場合、例えば接合層１０５を構成するＴｉ原子の原子数の割合α_Ｔｉ（ａｔｏｍｉｃ％）は下記式により算出することができる。

また、接合層１０５を構成するＴｉ原子、Ｚｒ原子およびＡｌ原子の合計原子数の割合α（ａｔｏｍｉｃ％）は、下記式により算出することができる。

例えば、接合層１０５中にＳｉ原子およびＴｉ原子が含まれるが、Ｚｒ原子およびＡｌ原子が含まれない場合、接合層１０５を構成するＴｉ原子、Ｚｒ原子およびＡｌ原子の合計原子数の割合α（ａｔｏｍｉｃ％）は、下記式により算出することができる。

なお、本実施形態においては、Ｋ_Ｓｉ＝１．０００、Ｋ_Ｔｉ＝１．０３３、Ｋ_Ｚｒ＝５．６９６、Ｋ_Ａｌ＝１．０５０とした。 In the bonding layer 105 of this embodiment, the ratio α (atomic%) of the total number of Ti atoms, Zr atoms and Al atoms to the total number (total atomic number) of Si atoms, Ti atoms, Zr atoms and Al atoms is preferably more than 0 atomic% and 33.3 atomic% or less, more preferably 9 to 33.3 atomic%, and even more preferably 12 to 33.3 atomic%. In this specification, the ratio α (atomic%) of the total number of Ti atoms, Zr atoms and Al atoms to the total number (total atomic number) of Si atoms, Ti atoms, Zr atoms and Al atoms constituting the bonding layer 105 means a value calculated by the following method.
(1) An STEM-EDX measurement of the optical filter is performed under the above-mentioned measurement conditions to obtain STEM-EDX lines (EDX-ray (K-line) detection intensity lines in the depth direction of each element constituting the optical filter).
(2) In the region constituting the bonding layer 105, the EDX-ray integrated intensity X _Si of Si atoms, the EDX-ray integrated intensity X _Ti of Ti atoms, the EDX-ray integrated intensity X _Zr of Zr atoms, and the EDX-ray integrated intensity X _Al of Al atoms are determined.
(3) The value obtained by multiplying each EDX-ray integrated intensity obtained in (2) by a k-factor (a correction coefficient that depends on the accelerating voltage and detection efficiency and differs for each atomic number. For convenience, the k-factor of Si atoms is _KSi , the k-factor of Ti atoms is _KTi , the k-factor of Zr atoms is _KZr , and the k-factor of Al atoms is _KAl ) can be considered to correspond to the weight ratio of each constituent element. For this reason, for example, the weight ratio _ATi (wt%) of Ti atoms constituting the bonding layer can be calculated by the following formula.

(4) Furthermore, the value obtained by multiplying the EDX-ray integrated intensity X of each atom by the k-factor and dividing the result by each atomic weight M can be considered to correspond to the atomic ratio of each constituent element. For this reason, when the atomic weight of a Si atom is M _Si , the atomic weight of a Ti atom is M _Ti , the atomic weight of a Zr atom is M _Zr , and the atomic weight of an Al atom is M _Al , for example, the atomic ratio α _Ti (atomic %) of the number of Ti atoms constituting the bonding layer 105 can be calculated by the following formula.

The ratio α (atomic %) of the total number of Ti atoms, Zr atoms, and Al atoms constituting the bonding layer 105 can be calculated by the following formula.

For example, when the bonding layer 105 contains Si atoms and Ti atoms but does not contain Zr atoms and Al atoms, the ratio α (atomic %) of the total number of Ti atoms, Zr atoms, and Al atoms constituting the bonding layer 105 can be calculated by the following formula.

In this embodiment, K _Si =1.000, K _Ti =1.033, K _Zr =5.696, and K _Al =1.050.

The near-infrared cut filter 100B of this embodiment will be further described below with examples, but the present invention is not limited to the following examples.

(Example 11)
A bonding layer 105 was formed on the glass substrate 101 of Example 1 by the following procedure (4. Formation of bonding layer 105). Then, a resin layer 102 was formed on the upper surface of the bonding layer 105 by the same procedure as in Example 1 (2. Formation of resin layer 102), thereby producing a near-infrared cut filter 100B.
4. Formation of bonding layer 105
1. Preparation of Coupling Agent-Containing Coating Solution (1) 0.3 mL of 0.5 N (mol/L) HCl aqueous solution and 2.2 mL of 2-methoxyethanol were weighed into a container and mixed in a sealed container.
(2) Tetraethyl orthosilicate (Si(OC ₂ H ₅ ) ₄ ) was added to the container and mixed for 30 minutes in a sealed state, causing a reaction represented by the following reaction formula.
Si(OC ₂ H ₅ ) ₄ +H ₂ O → HO-Si(OC ₂ H ₅ ) ₃ +C ₂ H ₅ OH
Because all water is consumed by the above reaction and hydroxyl groups are generated, it was expected that even if Ti alkoxide, which has a fast hydrolysis rate, is added, hydroxides will not precipitate and the solution will become homogeneous.
(3) Titanium (IV) n-butoxide (Ti(OC ₄ H ₉ ) ₄ ) was further added to the above container in a predetermined ratio (e.g., 3 to 20 mol %) and mixed for 30 minutes in a sealed state to prepare a coupling agent-containing coating liquid.
At this time, it is believed that the reaction represented by the following reaction formula occurred inside the container.
4OH-Si(OC ₂ H ₅ ) ₃ +Ti(OC ₄ H ₉ ) ₄ →Ti(O-Si(OC ₂ H ₅ ) ₃ ) ₄ +4C ₄ H ₉ OH

2. Formation of a coating film Into the container containing the coupling agent-containing coating liquid, 1.2 mL of a 0.5 N HCl aqueous solution, 4.7 mL of water, and 8.1 mL of 2-methoxyethanol were further weighed and mixed in a sealed state for 30 minutes to prepare a coating film-forming liquid.
At this time, it is believed that the reaction represented by the following reaction formula occurred inside the container.
Ti{(O-Si(OC ₂ H ₅ ) ₃ } } ₄ +12H ₂ O→Ti{(O-Si(OH) ₃ } ₄ +12C ₂ H ₅ OH
HO-Si(OC ₂ H ₅ ) ₃ +3H ₂ O→ Si(OH) ₄ + 3C ₂ H ₅ OH
The obtained coating film forming liquid was applied onto the glass substrate 101 using a spin coater so as to be 0.03 mL/cm 2 .
The glass substrate 101 coated with the coating film forming liquid was placed on a hot plate heated to 250° C. and heated for 30 minutes to cause dehydration and condensation, thereby forming a cured film (bonding layer 105) on the surface.

Next, a resin layer 102 was formed on the upper surface of the bonding layer 105 using the same procedure as in Example 1 (2. Formation of resin layer 102), to produce a near-infrared cut filter 100B.

In this way, by forming the bonding layer 105 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, thereby dramatically improving reliability.

In addition, the bonding layer 105 of this embodiment contains one or more atoms selected from Ti atoms, Zr atoms, and Al atoms, as well as Si atoms. Instead of forming the bonding layer 105, each component of the bonding layer 105 can be contained in the resin layer 102. In other words, the resin layer 102 can be configured to contain one or more atoms selected from Ti atoms, Zr atoms, and Al atoms, as well as Si atoms.

In addition, the bonding layer 105 of this embodiment contains at least one selected from Ti atoms, Zr atoms, and Al atoms in addition to Si atoms. However, any other material that can increase the adhesion between the glass substrate 101 and the resin layer 102 may be used, for example, a transparent vapor deposition or coating type adhesive.

In addition, the resin layer 102 in this embodiment is formed on one main surface of the glass substrate 101 (the upper surface in FIG. 16) via the bonding layer 105, but similar to the first embodiment, the resin layer 102 may be formed on the other main surface of the glass substrate 101 (the lower surface in FIG. 16) via the bonding layer 105, or may be formed on both sides of the glass substrate 101. In addition, the resin layer 102 does not necessarily have to be a single layer, and may be composed of multiple layers.

It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is indicated by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

1: Imaging device 11: Absorption layer 12: Reflection layer 13: Transparent substrate 100: Near-infrared cut filter 100A: Near-infrared cut filter 100B: Near-infrared cut filter 101: Glass substrate 102: Resin layer 103: Anti-reflection film 104: Anti-reflection film 105: Bonding layer 200: Solid-state imaging element 300: Package

Claims (21)

A transparent substrate made of fluorophosphate glass or phosphate glass and having an average transmittance of 3% or less in a wavelength range of 800 to 950 nm;
a resin layer formed on at least one main surface of the transparent base material and absorbing light of a specific wavelength;
Equipped with
The near infrared cut filter, wherein the resin layer contains at least one atom selected from the group consisting of Ti atoms, Zr atoms and Al atoms, in addition to Si atoms. 2. The near-infrared cut filter according to claim 1, further comprising a bonding layer between the transparent substrate and the resin layer, the bonding layer enhancing adhesion between the transparent substrate and the resin layer. 3. The near infrared cut filter according to claim 2, wherein the bonding layer has a single layer structure containing at least one atom selected from the group consisting of Ti atoms, Zr atoms and Al atoms, together with Si atoms. A transparent substrate made of fluorophosphate glass or phosphate glass and having an average transmittance of 3% or less in a wavelength range of 800 to 950 nm;
a resin layer formed on at least one main surface of the transparent base material and absorbing light of a specific wavelength;
an adhesive layer provided between the transparent substrate and the resin layer to enhance adhesion between the transparent substrate and the resin layer;
Equipped with
The near infrared cut filter, wherein the bonding layer has a single layer structure containing, in addition to Si atoms, one or more atoms selected from the group consisting of Ti atoms, Zr atoms and Al atoms. 5. The near-infrared cut filter according to claim 3, wherein in the bonding layer, a ratio of a total number of Ti atoms, Zr atoms and Al atoms to a total number of Si atoms, Ti atoms, Zr atoms and Al atoms is more than 0 atomic % and is 33.3 atomic % or less. The near infrared cut filter according to any one of claims 1 to 5, characterized in that the half-value wavelength on the short wavelength side of the transmittance curve of the transparent substrate is 335 to 400 nm, and the half-value wavelength on the long wavelength side is 590 to 630 nm. 7. The near-infrared cut filter according to claim 1, wherein the transparent substrate has an average transmittance of 18% or less in a wavelength range of 650 to 720 nm. 8. The near-infrared cut filter according to claim 1, wherein the transparent substrate has an average transmittance of 10% or less in a wavelength range of 720 to 750 nm. 9. The near-infrared cut filter according to claim 1, wherein the resin layer contains a transparent resin and a dye uniformly dispersed in the transparent resin. 10. The near infrared cut filter according to claim 9 , wherein the dye contains an ultraviolet absorbing dye having a maximum absorption wavelength in the range of 340 to 400 nm. 11. The near infrared cut filter according to claim 9 , wherein the dye comprises a first near infrared absorbing dye having a maximum absorption wavelength in the range of 650 to 760 nm. 12. The near infrared cut filter according to claim 11 , wherein the dye contains a second near infrared absorbing dye having a maximum absorption wavelength in the range of 800 to 1200 nm. The near-infrared cut filter according to any one of claims 1 to 12, characterized in that a first anti-reflection film is provided on the resin layer, and a second anti-reflection film is provided on the other main surface of the transparent substrate. The near-infrared cut filter according to claim 13, characterized in that the half-value wavelength on the short wavelength side of the transmittance curve is 385 to 430 nm, and the half-value wavelength on the long wavelength side is 590 to 630 nm. The near-infrared cut filter according to claim 13 or 14, characterized in that the first antireflection film and the second antireflection film are each composed of a dielectric multilayer film having a thickness of 500 nm or less. The near-infrared cut filter according to claim 15, characterized in that the dielectric multilayer film has 10 layers or less. The near-infrared cut filter according to claim 15 or 16, characterized in that the dielectric multilayer film is formed by alternately stacking low-refractive dielectric films made of a material with a refractive index of 1.1 to 1.5 and high-refractive dielectric films made of a material with a refractive index of 2.0 to 2.5. The near-infrared cut filter according to claim 15 or 16, characterized in that the dielectric multilayer film is formed by alternately stacking low-refractive dielectric films made of a material with a refractive index of 1.1 to 1.3 and high-refractive dielectric films made of a material with a refractive index of 1.4 to 1.6. The near-infrared cut filter according to any one of claims 1 to 18, characterized in that the transparent substrate has a thickness of 0.01 to 1.5 mm. An imaging device comprising a solid-state imaging element and a near-infrared cut filter according to any one of claims 1 to 19. 21. The imaging device according to claim 20, wherein the near-infrared cut filter is disposed immediately in front of the solid-state imaging element and serves as a cover glass.

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