Luminous paints are well-known for their application to alarm-clock dial plates."Phosphorescence" refers to the phenomenon whereby a material that is excited by some form of energy continues to produce light even after the excitation ceases.
The term "phosphor" refers to a material that is capable of exhibiting luminescence. Luminous paints are made by using phosphors with an exceptionally long afterglow time.

The cadmium sulfide type (CaS/Bi - using bismuth as an activator agent to cadmium sulfide; CaS+SrS/Bi) and the zinc sulfide type (ZnS/Cu, ZnS+CdS/Cu - using copper as an activator agent) are available as a phosphor. The luminescent color varies from blue to red (including blue, pale blue, green, yellow, orange, and reddish orange).

To use luminous paints, the phosphor is mixed with the vehicle at the point of use.Since these inorganic phosphors are crystallized, adding pressure or mixing by a roll mill will crush crystals and result in a degradation of the light luminance.Zinc/copper sulfide and cadmium sulfide/bismuth have an exceptionally long afterglow time and are used as a phosphor.

Phosphors used for luminous paints are shown in [Table 1].

[Table 1] Phosphor used for luminous paints

Luminous paints are excited by cathode rays, long/short wave ultraviolet, and X rays, and others. Based on the afterglow time dependence, they are classified into very short, short, long, and very long types.
Classification and application of luminous paints are shown in [Table 2].

[Table 2] Classification and application of luminous paints