Patent ID: 11914177
Assignee: NITTO DENKO CORPORATION
Field: Optics (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. An optical filter having a value of L* measured by a specular component excluded (SCE) method of 20 or larger, the optical filter comprising:
a matrix and fine particles dispersed in the matrix;
wherein the optical filter is configured to have a regular transmittance of 60% or higher for light having a wavelength in at least a part of a wavelength range not shorter than 760 nm and not longer than 2000 nm,
wherein the optical filter is configured such that in a state in which a light resistance test of irradiating the optical filter for 300 hours with light from a xenon arc lamp having a wavelength not shorter than 300 nm and not longer than 400 nm and a wattage of 120 W/m2 is performed, the optical filter exhibits a change in C* having an absolute value of 6 or smaller between before and after the light resistance test, the C* being measured by the SCE method by use of a spectrophotometer, and
wherein the fine particles form at least a colloidal amorphous array so as not to cause Bragg reflection and such that a transmittance curve of the filter in a visible light wavelength region includes a curved portion where the regular transmittance is decreased monotonously from a longer wavelength side to a shorter wavelength side, and the curved portion is shifted to the longer wavelength side as an angle of incidence is increased.