Optical Brightening Agent

Overview

Optical Brightening Agent enhances the apparent whiteness and brightness of paper by absorbing ultraviolet and violet light and re-emitting it as visible blue light. Different OBA chemistries can be selected for wet-end or dry-end applications depending on the papermaking process. Most paper brighteners are stilbene derivatives, distinguished by their degree of sulfonation: di-, tetra-, and hexasulfonated types trade fibre affinity against solubility, which is why the right chemistry depends on whether it is applied at the wet end, the size press, or in a coating.