METHOD OF INCREASING RETROREFLECTIVE BRIGHTNESS IN A RETROREFLECTIVE SHEET MATERIAL

摘要

A method of increasing retroreflective brightness in a retroreflective sheet material. The retroreflective sheet material has a multitude of prism-like reflective elements imbedded in a transparent polymer plastic top film and glued by a grid of adhesive to a backing sheet. The method includes the step of heating the retroflective sheet material until bubbles form in the transparent polymer plastic top film containing the prism-like reflective elements. The bubbles are confined by the grid. The bubbles serve as miniature magnifying lenses which increase retroreflective brightness and increase the exposure area thereby providing a wider observation angle.