Developing method for developer transfer under A.C. electrical bias and apparatus therefor

A method of applying dry developer to an electrostatic image bearing member bearing an electrostatic image thereon, comprising the steps of:

• forming a layer of one-component developer on the surface of a developer carrier disposed in opposed relationship with the image bearing member in a developer station with a clearance maintained therebetween which is greater than the thickness of the developer layer;
• applying an alternating electric field across the developing clearance, the field having a frequency sufficient to cause reciprocating movement of the one-component developer particles between the electrostatic image bearing member and the developer carrier in accordance with the alternating electric field;
• and
• changing the intensity of the alternative electric field acting on the developing clearance to thereby convert the reciprocating movement to one-sided movement of the developer particles in a direction from the developer carrier to the image area of the electrostatic image bearing member in the image area and to one-sided movement of the developer particles in a direction from the non-image area of the electrostatic image bearing member to the developer carrier in the non-image area.

A method of applying dry developer to an electrostatic image bearing member bearing an electrostatic image thereon, comprising the steps of:

• forming a layer of one-component developer on the surface of a developer carrier disposed in opposed relationship with the image bearing member in a developer station with a clearance maintained therebetween which is greater than the thickness of the developer layer;
• applying an alternating electric field across the developing clearance, the field having a frequency sufficient to cause the developer particles to transit from the developer layer through the clearance and contact the image area and the non-image area of the electrostatic image bearing member, and then to cause the developer particles having so contacted the image bearing member to return to the developer carrier and such reciprocating movement of the developer is repeated;
• and
• changing the intensity of the alternative electric field acting on the developing clearance to thereby convert the reciprocating movement to one-sided movement in which the developer particles one-sidedly transit from the developer carrier to the image area of the electrostatic image bearing member and contact the image area and the developer particles present in the non-image area one-sidedly return to the developer carrier and such movement of the developer is repeated.

A method of applying dry developer to an electrostatic image bearing member, comprising the steps of:

• disposing an electrostatic image bearing member bearing an electrostatic image thereon and a developer carrier carrying a layer of one-component developer on the surface thereof in opposed relationship in a developing station with a clearance maintained therebetween which is greater than the thickness of the developer layer;
• applying an alternating electric field across the developing clearance, the field having a sufficient frequency so that its direction in the developing clearance alternates in at least the non-image area of the electrostatic image bearing member, to thereby cause the developer to reach the non-image area as well, and then cause the developer to return to the developer carrier, such reciprocal movement of the developer particles taking place repeatedly in the developing clearance;
• and
• adjusting the intensity of the alternating electric field to cause the transition of the developer particles to take place in the image area one-sidedly in a direction from the developer carrier to the image area and to take place in the non-image area one-sidedly in a direction from the non-image area to the developer carrier.

A method of applying dry developer to an electrostatic image bearing member, comprising the steps of:

• disposing an electrostatic image bearing member bearing an electrostatic image thereon and a developer carrier carrying a layer of one-component developer on the surface thereof in opposed relationship in a developing station with a clearance maintained therebetween which is greater than the thickness of the developer layer;
• applying an alternating electric field in the clearance, the field having a sufficient frequency so that the electric field in the developing clearance alternates both in the image area and the non-image area of the electrostatic image bearing member, thereby causing reciprocal movement of the developer particles between the electrostatic image bearing member and the developing clearance;
• and
• adjusting the alternating electric field in the developing clearance to cause one-sided transition of the developer particles in a direction from the developer carrier to the image area of the electrostatic image bearing member and one-sided transition of developer particles in a direction from the non-image area of the electrostatic image bearing member to the developer carrier.