Sun Chemical Corporation has announced the sale of its fluorescent pigment business unit to Day-Glo Color Corp. of Cleveland, OH for an undisclosed sum.      The sale is a move to focus on Sun Chemical’s core competencies in high performance organic pigments, according to Robert Walsh, Sun Chemical senior vice president and COO, The Colors Group.      Sun Chemical and Day-Glo have agreed to build inventory levels to ensure uninterrupted supply to customers and to utilize Sun Chemical’s Skoki...