Optical filter
An optical filter ( 1 a ) includes a UV-IR-absorbing layer and has the following characteristics (i) to (v) when light with wavelengths of 300 nm to 1200 nm is incident at an incident angle of 0°: (i) an average transmittance of 78% or more in the wavelength range of 450 nm to 600 nm; (ii) a spectral transmittance of 1% or less in the wavelength range of 750 nm to 1080 nm; (iii) a spectral transmittance of 1% or less in the wavelength range of 300 nm to 350 nm; (iv) a decreasing spectral transmittance with increasing wavelength in the wavelength range of 600 nm to 750 nm and a first IR cut-off wavelength in the wavelength range of 620 nm to 680 nm; and (v) an increasing spectral transmittance with increasing wavelength in the wavelength range of 350 nm to 450 nm and a first UV cut-off wavelength in the wavelength range of 380 nm to 430 nm.
1. An optical filter comprising:
a UV-IR-absorbing layer comprising a UV-IR absorber that comprises a phosphonic acid and copper ion,
wherein when light with wavelengths of 300 nm to 1200 nm is incident on the optical filter at an incident angle of 0°,
(i) the optical filter has an average transmittance of 78% or more in the wavelength range of 450 nm to 600 nm,
(ii) the optical filter has a maximum transmittance of 1% or less in the wavelength range of 750 nm to 1080 nm,
(iii) the optical filter has a maximum transmittance of 1% or less in the wavelength range of 300 nm to 350 nm,
(iv) the optical filter has a decreasing spectral transmittance with increasing wavelength in the wavelength range of 600 nm to 750 nm and a first IR cut-off wavelength at which the spectral transmittance is 50% is in the wavelength range of 620 nm to 680 nm, and
(v) the optical filter has an increasing spectral transmittance with increasing wavelength in the wavelength range of 350 nm to 450 nm and a first UV cut-off wavelength at which the spectral transmittance is 50% is in the wavelength range of 380 nm to 430 nm.
2. The optical filter according to claim 1 , wherein when light with wavelengths of 300 nm to 1200 nm is incident on the optical filter at an incident angle of 0°,
(vi) the optical filter has a maximum transmittance of 3% or less in the wavelength range of 1000 nm to 1100 nm.
3. The optical filter according to claim 1 , wherein when light with wavelengths of 300 nm to 1200 nm is incident on the optical filter at an incident angle of 0°,
(vii) the optical filter has a maximum transmittance of 15% or less in the wavelength range of 1100 nm to 1200 nm.
4. The optical filter according to claim 1 , wherein when light with wavelengths of 300 nm to 1200 nm is incident on the optical filter at an incident angle of 40°, the optical filter has a second IR cut-off wavelength at which the spectral transmittance is 50% in the wavelength range of 600 nm to 750 nm, and
wherein an absolute value of a difference between the first IR cut-off wavelength and the second IR cut-off wavelength is 10 nm or less.
5. The optical filter according to claim 1 , wherein when light with wavelengths of 300 nm to 1200 nm is incident on the optical filter at an incident angle of 50°, the optical filter has a third IR cut-off wavelength at which the spectral transmittance is 50% in the wavelength range of 600 nm to 750 nm, and
wherein an absolute value of a difference between the first IR cut-off wavelength and the third IR cut-off wavelength is 15 nm or less.
6. The optical filter according to claim 1 , wherein when light with wavelengths of 300 nm to 1200 nm is incident on the optical filter at an incident angle of 40°, the optical filter has a second UV cut-off wavelength at which the spectral transmittance is 50% in the wavelength range of 350 nm to 450 nm, and
wherein an absolute value of a difference between the first UV cut-off wavelength and the second UV cut-off wavelength is 10 nm or less.
7. The optical filter according to claim 1 , wherein when light with wavelengths of 300 nm to 1200 nm is incident on the optical filter at an incident angle of 50°, the optical filter has a third UV cut-off wavelength at which the spectral transmittance is 50% in the wavelength range of 340 nm to 450 nm, and
wherein an absolute value of a difference between the first UV cut-off wavelength and the third UV cut-off wavelength is 15 nm or less.
8. The optical filter according to claim 1 , wherein the phosphonic acid comprises a first phosphonic acid having an aryl group.
9. The optical filter according to claim 8 , wherein the first phosphonic acid comprises a portion that has a halogenated phenyl group in which at least one hydrogen atom of a phenyl group is substituted by a halogen atom.
10. The optical filter according to claim 8 , wherein the phosphonic acid further comprises a second phosphonic acid having an alkyl group.
11. The optical filter according to claim 1 , wherein the UV-IR-absorbing layer is formed as a single layer.