Color image forming apparatus

An image forming apparatus comprising:

• an image forming section for forming a toner image with toner particles having a first electric polarity;
• a second transfer section for transferring the toner image to a recording medium;
• a charger for applying an electric charge to the toner image before the toner image is transferred to the recording medium, the charger having a discharge electrode and a grid electrode;
• a sensor for sensing a first electric surface potential of a background part of the toner image and a second electric surface potential of a certain density part of the toner image;
• a charge control section for applying a first voltage and a second voltage to the discharge electrode and the grid electrode, respectively, based on the first and second electric surface potentials sensed by the sensor.

An image forming apparatus comprising:

• an image forming section for forming a toner image with toner particles having a first electric polarity;
• an intermediate transfer body for bearing the toner image;
• a first transfer section for transferring the toner image from the image forming section to the intermediate transfer body;
• a second transfer section for transferring the toner image from the intermediate transfer body to a recording medium;
• a charger for applying an electric charge to the toner image on the intermediate transfer body before the toner image is transferred to the recording medium;
• and
• a charge control section for applying a voltage to the charger, the voltage being suitable for lowering an electric surface potential of a high density portion of the toner image and for substantially preventing an electric surface potential of a low density portion of the toner image from lowering.