▎ 摘　　要

NOVELTY - Ink composition comprises a dielectric matrix having a hydroxyl group, graphene quantum dots dispersed in the dielectric matrix and having an oxygen content of 10 atmosperic.% or less, and a graphene quantum dot composite having afterglow properties emitting phosphorescence at room temperature. USE - The ink composition is useful for security printing and security sign, and used in manufacturing security indicia. ADVANTAGE - The composition forms the security label that exhibits long-lived afterglow (room temperature phosphorescence or delayed fluorescence) properties, and forms patterns having different afterglow properties by controlling the oxidation degree of graphene quantum dots. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a security sign comprising a graphene quantum dot composite comprising a dielectric matrix having a hydroxyl group and graphene quantum dots dispersed in the dielectric matrix and having an oxygen content of 10 atmospheric.% or less, and having afterglow properties emitting phosphorescence at room temperature.