| 摘要 |
PURPOSE:To improve the specular surface precision of a rotating polygonal mirror made of a resin by making each specular surface part of resin materials injected from plural pin-point gates. CONSTITUTION:A rotating polygonal mirror 20 consists of a core part 21 having a center hole 22 and specular surface,parts 23a to 23d placed on four side faces of the core part and is produced by technique of insert molding, multiple molding, or the like. Specular surface parts 23a to 23d are made of resin materials injected from plural pinpoint gates 30 or film gates. The core part 21 and specular surface parts 23a to 23d are made of different kinds of resin. Resin materials are linearly injected from film gates, and weld lines are not generated on specular surfaces 23a to 23d, and the specular surface precision is improved. When resin materials are injected from plural pinpoint gates 30, the resin pressure approximately uniformly acts on the whole of specular surfaces of specular surface parts 23a to 23d, and the specular surface precision, especially, the smoothness and the flatness are improved. |
