Near-infrared cut filter
There is provided a near-infrared cut filter which has a visible light transmitting property and a near-infrared shielding property both at high levels by that its transmission spectrum has a steep inclination in the vicinity of the boundary between the visible light and the near-infrared, and which can also be sufficiently reduced in size and thickness. The near-infrared cut filter has a near-infrared absorbing layer which contains a near-infrared absorbing dye containing at least one dye in which a condensed ring structure containing at least a benzene ring and a ring having nitrogen atom is bonded to both sides of a squarylium skeleton and which have a carboxylic acid amide structure at a second position of the benzene ring (where the carboxylic acid has a substituent having 5 to 25 having one or more branches), and a transparent resin with a refractive index of 1.45 or more.
1. A near-infrared cut filter comprising a near-infrared absorbing layer, wherein:
the near-infrared absorbing layer comprises a near-infrared absorbing dye and a transparent resin;
the transparent resin has a refractive index of 1.45 or more; and
the near-infrared absorbing dye comprises at least one dye according to formula (A1):
where:
each X is independently a bivalent organic group according to formula (1) or formula (2):
—(CH 2 ) n1 — (1)
where n1 is 2 or 3 ;
—(CH 2 ) n2 —O—(CH 2 ) n3 — (2)
where each n2 and n3 is independently an integer of 0 to 2, and n2+n3 is 1 or 2;
one or more hydrogen atoms in formula (1) and formula (2) may be substituted with an alkyl group of alkoxy group having 1 or 12 carbon atoms;
each R 1 is independently a saturated or unsaturated hydrocarbon group having 1 to 12 carbon atoms which may include a saturated ring structure and may have a branch, a saturated cyclic hydrocarbon group having 3 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or an alaryl group having 7 to 13 carbon atoms;
each R 2 and R 3 is independently a hydrogen atom, a halogen atom, or an alkyl group or alkoxy group having 1 to 10 carbon atoms; and
each R 4 is independently a hydrocarbon group having 5 to 25 carbon atoms with at least one branch, in which one or more hydrogen atoms may be substituted by a halogen atom, a hydroxyl group, a carboxy group, a sulfo group, or a cyano group, and in which the hydrocarbon group may contain an unsaturated bond, an oxygen atom, or a saturated or unsaturated ring structure between carbon atoms.
2. The near-infrared cut filter according to claim 1 , wherein:
each X in formula (A1) is independently a bivalent organic group according to formula (3),
—CR 11 2 —(CR 12 2 ) n4 — (3),
where;
the left side of the structure in formula (3) is bonded to the adjacent benzene ring in formula (A1);
the right side of the structure in formula (3) is bonded to the adjacent nitrogen atom in formula (A1);
n4 is 1 or 2;
each R 11 is independently an alkyl group or alkoxy group having 1 to 12 carbon atoms which may have a branch; and
each R 12 is independently a hydrogen atom or an alkyl group or alkoxy group having 1 to 12 carbon atoms which may have a branch.
3. The near-infrared cut filter according to claim 2 , wherein, in formula (3):
each R 11 is independently an alkyl group or alkoxy group having 1 to 6 carbon atoms which may have a branch; and
each R 12 is independently a hydrogen atom or an alkyl group or alkoxy group having 1 to 6 carbon atoms which may have a branch.
4. The near-infrared cut filter according to claim 1 , wherein X in formula (A1) is independently a bivalent organic group according to any of formula (11-1) to formula (12-3):
—C(CH 3 ) 2 —CH(CH 3 )— (11-1),
—C(CH 3 ) 2 —CH 2 — (11-2),
—C(CH 3 ) 2 —CH(C 2 H 5 )— (11-3),
—C(CH 3 ) 2 —CH 2 —CH 2 — (12-1),
—C(CH 3 ) 2 —CH 2 —CH(CH 3 )— (12-2),
—C(CH 3 ) 2 —CH(CH 3 )—CH 2 — (12-3),
where the left side of the structure in each of formula (11-1) to formula (12-3), is bonded to the adjacent benzene ring in formula (A1), and the right side of the structure in each of formula (11-1) to formula (12-3) is bonded to the adjacent nitrogen atom in formula (A1).
5. The near-infrared cut filter according to claim 1 , wherein, in formula (A1) each R 4 is independently a branched hydrocarbon group having 5 to 25 carbon atoms with no substituent according to formula (4):
—CH 3-m R 13 m (4)
where:
m is 1, 2 or 3;
each R 13 is independently a linear or branched hydrocarbon group, R 13 being branched when m is 1, and R 13 optionally containing an usaturated bond, an oxygen atom, or a saturated or unsaturated ring structure between carbon atoms; and
a total number of carbon atoms of the group or groups R 13 is 4 to 24.
6. The near-infrared cut filter according to claim 1 , wherein a total number of carbon atoms of each group R 4 in formula (A1) is independently 6 to 20.
7. The near-infrared cut filter according to claim 1 , wherein, when the near-infrared absorbing dye is present in an amount sufficient to satisfy conditions (ii-1) and (ii-2), the near-infrared absorbing layer satisfies condition (ii-3):
(ii-1) a shortest wavelength λ a with transmittance of 1% in a wavelength region of 650 nm to 800 nm is 675 nm≤λ a ≤720 nm;
(ii-2) a relation between a longest wavelength λ b with transmittance of 1% in the wavelength region of 650 nm to 800 nm and λ a is λ b −λ a =30 nm; and
(ii-3) a relation of a wavelength λ c with transmittance of 70% on a shorter wavelength side than λ a in the wavelength region of 650 nm to 800 nm, λ a , and a refractive index n d (B) of the transparent resin is n d (B)×(λ a −λ c )≤115.
8. The near-infrared cut filter according to claim 1 , wherein the transparent resin comprises at least one resin selected from the group consisting of 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, polyamide-imide resin, polyolefin resin, cyclic olefin resin, and polyester resin.
9. The near-infrared cut filter according to claim 1 , wherein the near-infrared absorbing dye is present in an amount of 0.1 to 20 parts by mass relative to 100 parts by mass of the transparent resin.
10. The near-infrared cut filter according to claim 1 , further comprising a selected wavelength shielding layer on one of both sides of the near-infrared absorbing layer wherein the selected wavelength shielding layer has characteristics (iii-1) and (iii-2):
(iii-1) a transmittance of 90% or more in a wavelength region of 420 nm to 695 nm; and
(iii-2) a transmittance of 2% or less in a wavelength region from a wavelength λ b to 1100 nm, the wavelength λ b being a longest wavelenght in a wavelength region of 650 nm to 800 nm at which the near-infrared absorbing layer has a transmittance of 1%.
11. The near-infrared cut filter according to claim 10 , wherein the selected wavelength shielding layer comprises a dielectric multilayer film comprising and alternation stack of a first dielectric film and a second dielectric film, wherein:
the first dielectric film has a refractive index of 1.45 or more and less than 1.55; and
the second dielectric film has a refractive index of 2.2 to 2.5.
12. The near-infrared cut filter according to claim 10 , wherein the near-infrared cut filter satisfies conditions (iv-1), (iv-2) and (iv-3):
(iv-1) an average transmittance is 80% or more in a wavelength region of 420 nm to 620 nm;
(iv-2) a transmittance of 2% or less in a wavelength region of 710 nm to 1100 nm; and
(iv-3) a difference of 3 nm or less between a wavelength with 20% transmittance of light incident from a direction orthogonal to a main surface and a wavelength with 20% transmittance of light incident from a direction making an angle of 30 degrees relative to a line orthogonal to the main surface, in a wavelength region of 600 nm to 700 nm.