MIXTURE OF NICKEL FORMAZAN PIGMENT

PROBLEM TO BE SOLVED: To obtain the subject mixture comprising specific symmetric and asymmetric nickel formazan pigments, capable of expressing high solubility, good incubation stability and excellent coating workability and useful for optical recording elements, etc. SOLUTION: This mixture comprises prescribed symmetric compounds and asymmetric compounds among compounds of the formula (R, R1 -R3 are each a substituent). For example, the mixture comprises a synthetic compound wherein R and R3 are 2-ethoxy group, respectively, and R1 and R2 are 4-methyl, respectively, a symmetric compound wherein R1 and R are 4-isopropyl, and an asymmetric compound wherein R1 is 4-methyl and R2 is 4-isopropyl. The mixture is obtained by a conventional nickel formazan pigment synthetic method wherein an amine mixture is used in a diazotization process or wherein a hydrazone mixture as a starting material is coupled with a single diazotized amine.