Patent ID: 11898075
Assignee: BASF SE
Field: Basic materials chemistry (Chemistry)
Classification: CPC C  H  Y | IPC C  H

Claim 17:
18. A method of providing yellow light, wherein at most 1% of total radiant power is within a spectral range of less than 520 nm, the method comprising:
arranging, to receive at least a part of light emitted by a light source comprising a blue light emitting diode with a center wavelength of emission in a range of from 400 nm to 480 nm and/or a white light emitting diode having a correlated color temperature in a range of from 2 700 to 30 000 K;
a color converter comprising an organic fluorescent dye in a polymer matrix, the organic fluorescent dye comprising a structural unit of formula (I), wherein one or more CH groups of the six-membered ring of the benzimidazole structure is optionally replaced by nitrogen,
n1 is a number from 0 to (10-p1) for each structural unit of the formula (I); p1 being a number of the CH units replaced by nitrogen in the six-membered ring of the benzimidazole structure,
X1 is a chemical bond, O, S, SO, SO2, or NR1, and
R is an aliphatic radical, cycloaliphatic radical, aryl, or heteroaryl, or an aromatic or heteroaromatic ring or ring system, fused to other aromatic rings of the structural unit of the formula (I), or F, Cl, Br, CN, or H when X1 is not a chemical bond, two R radicals being optionally joined to give one cyclic radical,
X1 and R, when n1>one, being the same or different,
R1 is independently hydrogen, C1-C18-alkyl, or cycloalkyl, the carbon chain of which optionally comprising an —O—, —S—, —CO—, —SO—, and/or —SO2 moiety, or aryl or heteroaryl, and
wherein the organic fluorescent dye is capable of absorbing at least a part of the light emitted by the light source and emitting light comprising a wavelength in a range of from 520 to 590 nm,
wherein the organic fluorescent dye has a weight percentage in the color converter satisfying equation (A)

20[%×μm]≤w1×d≤100[%×μm]  (A),

wherein w1 is a weight percentage of the organic fluorescent dye in the polymer matrix based on total polymer weight, and d is a thickness of the color converter in μm.