Positional-Dependent Photoluminescence (PL) Property from Crystal-Oriented β-Sialon:Eu2+ Phosphor Layer Fabricated by Electrophoretic Deposition Process (EPD) Assisted with a Strong Magnetic Field (強磁場中電気泳動堆積(EPD)プロセスによる結晶面依存のPL特性を持つβ-Sialon:Eu2+蛍光層の配向実装)