Near infrared (NIR) transparent neutral black perylene solid solutions

The invention relates to a solid solution comprising (a) at least one compound of formula (I), and (b) at least one compound of formula (II), or at least one compound of formula (III), or a mixture of at least one compound of formula (II) and at least one compound of formula (III) wherein R1 and R2 may represent independently of each other-(CH2) n-X, wherein X represents hydrogen, a methyl group, a C1-C5 alkoxy group, a hydroxyl group, a phenyl group, a C1-C5 alkyl phenyl group, a C1-C5 alkoxy phenyl group, a hydroxyphenyl group, a halogenated phenyl group, a pyridyl group, a C1-C5 alkyl pyridyl group, a C1-C5 alkoxy pyridyl group, a halogenated pyridyl group, a pyridyl vinyl group or a naphthyl group; wherein n represents 0, 1, 2, 3, 4 or 5; r3 and R4 may represent independently of each other a phenylene group, a C1-C5 alkyl phenylene group, a C1-C5 alkoxy phenylene group, a hydroxyphenylene group, a halogenated phenylene group, a pyridinediyl group, a C1-C5 alkyl pyridinediyl group, a C1-C5 alkoxy pyridined