Near-infrared absorbing composition and near-infrared absorbing filter
A near-infrared absorbing composition which is imparted with a function of absorbing near-infrared rays emitted from a display such as a plasma display, capable of reducing the number of lamination steps resulting in excellent production efficiency, capable of resisting to color non-uniformity of a filter even after a long-term use at high temperature or high humidity, and capable of preventing an increase in haze, and a near-infrared absorbing filter having a near-infrared absorbing layer comprising the composition. The near-infrared absorbing composition has composite tungsten oxide fine particles which are dispersed in a resin including carboxyl groups and has an acid number of 0.6 or more and 30 or less.
1. A near-infrared absorbing composition in which, as a near-infrared absorbing agent, composite tungsten oxide fine particles having an average dispersed particle diameter of the composite tungsten oxide fine particles is 800 nm or less and represented by the general formula MwWyOz, wherein element M is one or more elements selected from the group consisting of H, He, alkali metals, alkaline-earth metals, rare-earth metals, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi and I; W is tungsten; O is oxygen; and 0.001≦/y≦1.1 and 2.2≦z/y≦3.0, are dispersed in a resin which comprises carboxyl groups and has an acid number of 0.6 or more and 30 or less.
2. The near-infrared absorbing composition according to claim 1 , wherein the resin is an acrylic resin.
3. The near-infrared absorbing composition according to claim 1 , wherein the resin is an adhesive resin.
4. The near-infrared absorbing composition according to according to claim 1 , wherein the acid number is 1 or more and 19 or less.
5. The near-infrared absorbing composition according to claim 1 , wherein the composite tungsten oxide fine particles have any one or more of a structure selected from the group consisting of a hexagonal crystal structure, a tetragonal crystal structure and a cubic crystal structure.
6. The near-infrared absorbing composition claim 1 , wherein element M in the general formula representing the composite tungsten oxide fine particles, MxWyOz, is cesium (Cs), and the composite tungsten oxide fine particles have a hexagonal crystal structure.
7. The near-infrared absorbing composition according to claim 1 , wherein surfaces of the composite tungsten oxide fine particles are covered with an oxide comprising one or more elements selected from the group consisting of Si, Ti, Zr and Al.
8. The near-infrared absorbing composition according to claim 1 , further comprising zirconium oxide fine particles having a smaller average particle diameter than that of the composite tungsten oxide fine particles.
9. A near-infrared absorbing filter having a near-infrared absorbing layer comprising any of the near-infrared absorbing compositions defined by claim 1 .