Polycarbonate Sign Face Material Eliminates Hot Spots, Optimizes Light Uniformity

[Erik Sine]

Polycarbonate Sign Face Material Eliminates Hot Spots, Optimizes Light Uniformity

Sheffield Plastics

Sheffield Plastics will feature its new Makrolon LD polycarbonate sheet for LED back lit sign faces at the 2010 International Sign Association Expo. The manufacturer will showcase the product in its ISA exhibit and its presentation, “History and Evolution of Plastic Sign Faces,” as the latest technological step in these materials.

In conjunction with Bayer MaterialScience's R&D team, Sheffield developed Makrolon LD to address visible LED "hot spots" from the intense pinpoint lights that can show through traditional sign face materials. Thermoforming, which typically thins out corners and edges of sign face sheet products, heightens the hot spot problem. The inherent composition of the new polycarbonate sheet eliminates the problem by diffusing or spreading LED luminance uniformly, even in thermoformed three-dimensional faces. It also delivers high light transmittance to ensure brightness of LED back-lit signs.

Sheffield's Dr. Ted Trautman, who worked on the development of Makrolon LD polycarbonate sheet, also defined sign design techniques to enhance luminance quality of LED's in conjunction with the sign face material.

"The variability of the human factor in judging sign lighting from different sight angles was a major consideration in developing the Makrolon LD product. We devised comparative test methods and computer-aided enhancement techniques using in-house sign 'can' test fixtures to help us factor in this variable in a quantifiable and repeatable way. Evaluations included various LED types, and combinations of light spacing and positioning relative to the sign face. The results helped us define both the design guidelines and the sign face material characteristics that contribute to optimum lighting quality," said Trautman.

Makrolon LD sheet also has the inherent breakage resistance of polycarbonate, an important factor not only to avoid damage in outdoor signs but also in the production of potentially fragile complex shapes now possible with LED lighting. According to Sheffield's spokesman, "This combination of toughness, the new light diffusing technology of the sheet material and the versatility of LED lighting for free-form shapes extends the boundaries of signage design."

Trautman will be a co-presenter for Sheffield's ISA Expo session on plastic sign faces and will cover many of the tests and variables behind the development of the new material and LED sign design guidelines.