US 11,914,177 B2
Optical filter, method for manufacturing same, and optical module
Masato Katsuda, Osaka (JP); Yudai Numata, Osaka (JP); and Shoichi Matsuda, Osaka (JP)
Assigned to NITTO DENKO CORPORATION, Osaka (JP)
Appl. No. 17/911,915
Filed by NITTO DENKO CORPORATION, Osaka (JP)
PCT Filed Mar. 15, 2021, PCT No. PCT/JP2021/010415
§ 371(c)(1), (2) Date Sep. 15, 2022,
PCT Pub. No. WO2021/187432, PCT Pub. Date Sep. 23, 2021.
Claims priority of application No. 2020-045671 (JP), filed on Mar. 16, 2020; and application No. 2020-163411 (JP), filed on Sep. 29, 2020.
Prior Publication US 2023/0119681 A1, Apr. 20, 2023
Int. Cl. G02B 5/20 (2006.01)
CPC G02B 5/206 (2013.01) [G02B 5/208 (2013.01)] 18 Claims
OG exemplary drawing
 
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.