Patent ID: 7582250

Claim:
An injection molding method using an injection mold, the injection mold comprising a gate, a cavity connected with the gate, and a flow channel having an opening which opens toward a back surface of a molded product, the method comprising: a molten resin injection step of injecting molten resin from the gate into the cavity; a pressure keeping step of applying pressure from the gate against the injected resin within the cavity after the molten resin injection step; and a pressurized fluid injection step of injecting a pressurized fluid via the flow channel, the pressurized fluid injection step being started during the molten resin injection step, wherein the pressure keeping step and the pressurized fluid injection step are simultaneously executed, the pressure applied in the pressure keeping step is lower than injection pressure applied in the molten resin injection step, fluid pressure applied in the pressurized fluid injection step is lower than the pressure applied in the pressure keeping step, the pressure applied in the pressure keeping step is pressure that would not be sufficient to prevent a design surface of the molded product from separating from a surface of the cavity unless the pressurized fluid injection step is simultaneously executed, and the fluid pressure applied in the pressurized fluid injection step is pressure that would not be sufficient to prevent the design surface of the molded product from separating from the surface of the cavity unless the pressure keeping step is simultaneously executed.