Image forming apparatus

An image forming apparatus, comprising:

• a movable image bearing member;
• a rotatable member contactable to said image bearing member;
• image forming means for forming a toner image on said image bearing member with toner having a polarity;
• and
• electric field forming means for forming an electric field between said rotatable member and said image bearing member, said electric field forming means forming a first electric field effective to transfer toner having the same polarity as the polarity of the toner image on said image bearing member from said rotatable member to said image bearing member and a second electric field having a polarity opposite to said first electric field during a period in which an area of said image bearing member in which said image forming means does not form the image is at a contact position between said rotatable member and said image bearing member,
• wherein the period in which the first electric field is formed and the period in which the second electric field is formed are adjacent to each other, each of said first and second electric fields is formed at least for a period required for substantially the entire circumferential surface of said rotatable member to pass through the contactable position.

An image forming apparatus, comprising:

• a movable image bearing member;
• a rotatable member contactable to said image bearing member at a first contactable position;
• image forming means for forming a toner image on said image bearing member with toner having a polarity;
• plural contact members contactable to said rotatable member at respective second contactable positions;
• electric field forming means for forming an electric field between said rotatable member and at least one of said contact members, said electric field forming means forming a first electric field effective to transfer toner having the same polarity as the polarity of the toner image on said image bearing member from said rotatable member to said at least one contact member and a second electric field which is opposite in direction from said first electric field during a period in which an area of said image bearing member in which said image forming means does not form the toner image is at the first contactable position,
• wherein each of said first and second electric fields is formed at least for a period required for substantially the entire circumferential surface of said rotatable member to pass through at least one of the second contactable positions.

An image forming apparatus, comprising:

• plural contact members contactable to a rotatable member at respective contactable positions;
• image forming means for forming a toner image on a first one of said plural contact members with toner having a polarity;
• electric field forming means for forming an electric field between the rotatable member and at least a second one of said contact members, said electric field forming means forming a first electric field effective to transfer toner having the same polarity as the polarity of the toner image on said first contact member from the rotatable member to said second contact member and a second electric field which is opposite in direction from said first electric field during a period in which an area of said first contact member in which said image forming means does not form the toner image is at its respective contactable position,
• wherein each of said first and second electric fields is formed at least for a period required for substantially the entire circumferential surface of said rotatable member to pass through at least one of the contactable positions.

An image forming apparatus, comprising:

• a movable image bearing member;
• image forming means for forming a toner image having a plurality on said image bearing member;
• and
• image transfer means for transferring the toner image onto a transfer material at a transfer position, said transfer means including a rotatable member contactable to a side of the transfer material which is opposite from a side contactable to said image bearing member and electric field forming means for forming an electric field between said image bearing member and said rotatable member,
• wherein said electric field forming means forms a first electric field effective to transfer toner having the same polarity as the polarity of the toner image on said image bearing member from said rotatable member to said image bearing member and a second electric field with a polarity opposite to the first electric field after forming said first electric field, said first and second electric fields being formed when the transfer material is not present at the transfer position, wherein the transfer material reaches the transfer position after at least one full turn of said rotatable member after commencing formation of the second electric field.

An image forming apparatus, comprising:

• a movable image bearing member;
• a rotatable member contactable to said image bearing member at a first contactable position;
• image forming means for forming a toner image on said image bearing member with toner having a polarity;
• plural contact members each contactable to said rotatable member at respective second contactable positions;
• and
• electric field forming means for forming an electric field between said rotatable member and said plural contact members, said electric field forming means forming an electric field effective to transfer toner from said rotatable member to said plural contact members during a period in which an area of the image bearing member in which said image forming means does not form the toner image is at the first contactable position,
• wherein said electric field is formed at least for a period required for substantially the entire circumferential surface of said rotatable member to pass through at least one of the second contactable positions.