Near-infrared cut-off filter and imaging device including the same
Provided is a near-infrared cut-off filter having excellent oblique incidence characteristics due to extremely low dependence on the angle of incidence, and a low transmittance in a wavelength region of 1000 nm or more. More particularly, the near-infrared cut-off filter includes a transparent substrate that is formed of glass containing iron atoms and has a half-value wavelength of greater than 630 nm on a long wavelength side of a transmittance curve and an average transmittance of 1% or less in a wavelength region of 1000 to 1200 nm; and a resin layer formed on at least one main surface of the transparent substrate to absorb light of a specific wavelength.
1. A near-infrared cut-off filter, comprising:
a transparent substrate that is formed of glass containing iron atoms and has a half-value wavelength of greater than 630 nm on a long wavelength side of a transmittance curve and an average transmittance of 1% or less in a wavelength region of 1000 to 1200 nm; and
a resin layer formed on at least one main surface of the transparent substrate to absorb light of a specific wavelength;
wherein said transparent substrate does not include a multi-layer dielectric film.
2. The near-infrared cut-off filter according to claim 1 , wherein a half-value wavelength on a short wavelength side of a transmittance curve of the transparent substrate is 300 to 420 nm, and a half-value wavelength on a long wavelength side thereof is 630 to 750 nm.
3. The near-infrared cut-off filter according to claim 1 , wherein the resin layer comprises a transparent resin; and a dye uniformly dispersed in the transparent resin.
4. The near-infrared cut-off filter according to claim 3 , wherein the dye comprises an ultraviolet absorbing dye having a maximum absorption wavelength of 350 to 400 nm; and a first near-infrared absorbing dye having a maximum absorption wavelength of 650 to 750 nm.
5. The near-infrared cut-off filter according to claim 4 , wherein the dye further comprises a second near-infrared absorbing dye having a maximum absorption wavelength of 750 to 950 nm.
6. The near-infrared cut-off filter according to claim 1 , wherein the resin layer comprises one or more selected from Ti atom, Zr atom and Al atom, together with Si atom.
7. The near-infrared cut-off filter according to claim 1 , wherein a bonding layer is provided between the transparent substrate and the resin layer so as to improve adhesion of the resin layer to the transparent substrate.
8. The near-infrared cut-off filter according to claim 7 , wherein the bonding layer has a single-layer structure comprising one or more selected from Ti atom, Zr atom and Al atom, together with Si atom.
9. The near-infrared cut-off filter according to claim 8 , wherein, in the bonding layer, a ratio of the total number of atoms of Ti atom, Zr atom and Al atom to the total number of atoms of Si atom, Ti atom, Zr atom and Al atom is greater than 0 atomic % and 33.3 atomic % or less.
10. The near-infrared cut-off filter according to claim 1 , wherein a first antireflection film is formed on the resin layer, and a second antireflection film is formed on another main surface of the transparent substrate.
11. The near-infrared cut-off filter according to claim 10 , wherein the near-infrared cut-off filter has a half-value wavelength of 385 to 420 nm on a short wavelength side of a transmittance curve, and a half-value wavelength of 600 to 680 nm on a long wavelength side thereof.
12. The near-infrared cut-off filter according to claim 10 , wherein each of the first and second antireflection films is formed of a multilayer dielectric film having a thickness of 500 nm or less.
13. The near-infrared cut-off filter according to claim 12 , wherein the number of layers constituting the multilayer dielectric film is 10 or less.
14. The near-infrared cut-off filter according to claim 12 , wherein the multilayer dielectric film is formed by alternately laminating a low-refractive-index dielectric film formed of a material having a refractive index of 1.1 to 1.5, and a high-refractive-index dielectric film formed of a material having a refractive index of 2.0 to 2.5.
15. The near-infrared cut-off filter according to claim 12 , wherein the multilayer dielectric film is formed by alternately laminating a low-refractive-index dielectric film formed of a material having a refractive index of 1.1 to 1.3, and a high-refractive-index dielectric film formed of a material having a refractive index of 1.4 to 1.6.
16. The near-infrared cut-off filter according to claim 1 , wherein the transparent substrate has a thickness of 0.01 to 1.5 mm.
17. An imaging device, comprising a solid-state imaging device;
and the near-infrared cut-off filter according to claim 1 .
18. The imaging device according to claim 17 , wherein the near-infrared cut-off filter is disposed immediately in the front of the solid-state imaging device to function as a cover glass.