| http://www.w3.org/ns/prov#value | - The diameter of the spherical beads 20 means the average diameter of particles of 1 .mu.m or more.As a binder resin for forming said coating layer 18, such a transparent material as acryl, polystyrene, polyester, vinyl polymer or the like is used, and the ratio of the refractive index of a material for the spherical beads 20 to the refractiveindex of a binder resin is preferably in a range from 0.
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