PURPOSE: To linearly transmit light by forming an adhesion accelerating layer composed of a transparent substance having affinity to the surface of a hydrophobic transparent substrate and printing this adhesion accelerating layer with light pervious phase change ink and uniformizing the thickness of the phase change ink layer after the coagulation of the ink.

CONSTITUTION: An adhesion accelerating layer composed of a transparent substance having affinity is formed on one surface of a hydrophobic transparent substrate 14 and printed with light pervious phase change ink to form a predetermined pattern non-linearly transmitting light. After the ink is coagulated, the pattern of the phase change ink is treated to almost uniformize the thickness of the phase change ink layer 20 on the substrate 14. By this method, light can be transmitted along an almost linear route.