Upon exposure to light, DNQ converts to a derivative that is susceptible to etching.

[1] Diazonaphthoquinone sulfonic acid esters are components of common photoresist materials.

[2][3][4] In this application DNQs are mixed with Novolac resin, a type of phenolic polymer.

During the masking/patterning process, portions of the photoresist film are exposed to light while others remain unexposed.

The exposed regions of the photoresist film become soluble in aqueous base; thus allowing the formation of a relief image during development.