| 摘要 |
PURPOSE:To improve productivity of the mirror and enhance the molding accuracy thereof by providing a mirror part, which forms a polygonal mirror face, and shaft parts, which coaxially extend on both end faces of the mirror part, and further providing recessed parts on the end faces of the mirror part. CONSTITUTION:A polygonal mirror 1 consists of a regular hexagonal mirror part 2 and shaft parts 3 coaxially extended on both end faces of the mirror part 2 and is molded in a unitary structure with plastic. The mirror part 2 consists of a main body part 4, a mirror layer 5 formed on the outer peripheral face of the main body part and annularly recessed parts 6, while the mirror layer 5 consists of an ultraviolet-curing resin layer 7 and a vapor deposition layer 9 comprising Al, Au and silicon dioxide SiO2 and forming a mirror part 8. Since shrinking generated at the time of injection molding is concentrated to the recessed parts 6 to inhibit shrinkage on the mirror part 2 side, the surface accuracy of the mirror face 8 can be maintained at a high level. In this production method, a molten resin is injected into a cavity axially toward one end of the shaft parts or toward the positions arranged at equal intervals at the mirror part, so that productivity can be enhanced. |
