For back-lighting applications such as signs or light boxes, textured finished sheets or white sheets are often used between the light source and the sign face to improve light diffusion. This helps to eliminate bright spots caused by the light source.
Sometimes textured sheets are used in combination with edge lighting. The textured surface provides a means of re-directing some of the piped light to the face of the sheet. Generally, this is not a very efficient method of back-lighting because textured sheet is not specifically designed or optimized for this purpose.
For more efficient back lighting using an edge mounted light source, a special type of sheet has been developed – ACRYLITE® LED light guiding edge lit acrylic sheet. Various grades are available--S, L, XL, and XXL--which are designed to accommodate different sizes of signs. The efficiency of this back-lighting sheet has been optimized for edge lighting applications.
Alternately, back lighting using an edge mounted light source can also be accomplished by employing a sheet printed or painted with a white light diffusing pattern on one surface. The pattern density can be varied across the sheet surface as the distance from the light source changes to adjust the amount of light being reflected to the sheet surface.