Screen photosensitive member and electrophotographic method

An electrophotographic method for forming an image on a chargeable surface by modulation of ion current by an electric field formed on a photosensitive screen member which is essentially constructed with an electrically conductive member having a multitude of fine openings, a photoconductive layer provided on said electrically conductive member, a surface insulative layer constituting a surface of said photosensitive member on the side opposite to a modulating corona ion source for holding a latent image charge thereon, and an electric potential holding layer provided on the surface of the photosensitive member on the modulating corona source side for maintaining a surface potential of a predetermined value during a modulation operation, wherein the predetermined value is sufficient to form, at the portion of said screen where the flow of ions is to be blocked, a potential difference between the surface potential of the insulating layer and the surface potential of the holding layer which is sufficient to block the passage of ions at least through the associated openings, said electrophotographic method comprising:

• forming a primary latent image on said photosensitive member by at least the steps of:
• (a) uniformly charging said surface insulating layer to a particular polarity;
• (b) irradiating bright and dark patterns of an image on said photosensitive member;
• and
• (c) uniformly charging said photosensitive member to a polarity opposite to the charge polarity in step (a), said charging step being effected either simultaneously with, or subsequent to, said step (b):
• subsequently applying said modulating corona ion current from the side of said potential holding layer, while maintaining said potential holding layer at the predetermined electric potential;
• and
• forming an image on the chargeable surface due to the modulated corona ion current.

In an electrophotographic method for forming an image by modulation of ion current by an electric field formed on a photosensitive screen member which is essentially constructed with an electrically conductive member having a multitude of fine openings, a photoconductive layer provided on said electrically conductive member, a surface insulative layer constituting a surface of the photosensitive member on the side opposite to a modulating corona ion source for holding a latent image thereon, and an electric potential holding layer provided on the surface of the photosensitive member at the modulating corona source side for maintaining a surface potential of a predetermined value during a modulating operation, the predetermined value being sufficient to form, at a portion of the screen where the flow of ions is to be blocked, a potential difference between the surface potential of the insulating layer and the surface potential of the holding layer which is sufficient to block the passage of ions at least through the associated openings, the steps of:

• regulating the passage of ion current at the openings in said photosensitive member with a first electric field caused by a potential difference between the electric charge on said surface insulative layer and an electric charge on said potential holding layer which has been automatically charged to the predetermined potential at the time of modulation creating a second electric field between said screen photosensitive member and said modulating ion source for directing the ion current to said photosensitive screen member and creating a third electric field between said photosensitive screen member and a chargeable surface for directing said ion current, the passage of which is regulated at said openings, to said chargeable surface.