Image forming apparatus

An image forming apparatus for forming an image on a recording medium by allowing development particles to fly, comprising:

• positively charged development particles;
• a holder for holding said development particles;
• a counter electrode provided opposite to said holder;
• a control electrode formed with a plurality of circular gates for allowing the development particles to pass, said control electrode being located between said holder and said counter electrode;
• electric field forming means for forming a fixed electric field for allowing said development particles to fly from said holder to said counter electrode by generating a fixed potential difference across said holder and said counter electrode;
• and
• control means supplying a time-varying potential to said control electrode, thereby controlling passage of said development particles through said gates,
• wherein said control means controls the time-varying potential supplied to said control electrode so that, when said development particles are allowed to pass through said gates, the time-varying potential becomes higher than a potential that is generated on center portions of the gates by the electric field, whereby dots having diameters smaller than diameters of said gates are formed on said recording medium.

An image forming apparatus for forming an image on a recording medium by allowing development particles to fly, comprising:

• negatively charged development particles;
• a holder for holding said development particles;
• a counter electrode provided opposite to said holder;
• a control electrode formed with a plurality of circular gates for allowing the development particles to pass, said control electrode being located between said holder and said counter electrode;
• electric field forming means for forming a fixed electric field for allowing said development particles to fly from said holder to said counter electrode by generating a fixed potential difference across said holder and said counter electrode;
• and
• control means supplying a time-varying potential to said control electrode, thereby controlling passage of said development particles through said gates,
• wherein said control means controls the time-varying potential supplied to said control electrode so that, when the time-varying particles are allowed to pass through said gates, the potential becomes lower than a potential that is generated on center portions of the gates by the electric field, whereby dots having diameters smaller than diameters of said gates are formed on said recording medium.

An image forming apparatus for forming an image on a recording medium by allowing developing particles to fly, comprising:

• charged developing particles;
• a holder for holding said developing particles that can move so that said holder's surface moves at a relative speed to a control electrode;
• a counter electrode provided so as to be opposite to said holder;
• a control electrode formed with a plurality of gates for allowing the developing particles, said control electrode being provided between said holder and said counter electrode;
• electric field forming means for forming a prescribed electric field that allows said developing particles to fly from said holder towards said counter electrode by generating a prescribed potential difference across said hold and said counter electrode;
• and
• control means for controlling passage of said developing particles through each of said gates by changing a potential to be supplied to said control electrode at a prescribed period,
• wherein said control means controls a time for continuously supplying a potential, which allows said development particles to pass, to said control electrode becomes longer than a time required for allowing said development particles, which are held on positions on the surface of said holder corresponding to the gates, to fly.

An image forming apparatus for allowing developing particles to fly and adhere directly to a recording medium, whereby forming an image on the recording medium, comprising:

• charged developing particles;
• a holder for holding said developing particles;
• a counter electrode provided so as to be opposite to said holder;
• a control electrode formed with a plurality of circular gates for allowing the developing particles to pass, said control electrode being located between said holder and said counter electrode;
• electric field forming means for forming a prescribed electric field for allowing said developing particles to fly form said holder towards said counter electrode by generating a prescribed potential difference across said holder and said counter electrode;
• and
• control means for controlling passage of said developing particles through said gates by supplying a time-varying potential to be applied to said control electrode,
• wherein said control means controls the time-varying potential supplied to said control electrode so that the following equation is fulfilled:
• 2qvP(S/.pi.).sup.1/2 .gtoreq.(.pi.MR.sup.3 tan .theta.)/3-qS
• where q (g/cm.sup.2) is a density of said development particles on the surface of said holder per unit area, S (cm.sup.2) is an area of a range where an electric field which makes said development particles possible to fly is formed on the surface of said holder, v(cm/sec) is a relative speed of the surface of said holder to said control electrode, M(g/cm.sup.3) is specific gravity of said development particles, .theta.(.degree.) is an angle of repose of said development particles on the recording medium, P(sec) is a time for continuously supplying the time-varying potential, which allows said development particles to pass, to said control electrode, and 2R(cm) is a maximum length of a range on the recording medium to which said development particles adhere at a substantial moment the time-varying potential starts to be supplied to said control electrode.

An image forming apparatus for forming an image on a recording medium by allowing developing particles to, comprising:

• charged developing particles;
• a holder for holding said developing particles;
• a counter electrode provided so as to be opposite to said holder;
• a control electrode formed with a plurality of circular gates for allowing the developing particles to pass, said control electrode being located between said holder and said counter electrode;
• electric field forming means for forming a prescribed electric field for allowing said developing particles to fly from said holder towards said counter electrode by generating a prescribed potential difference across said holder and said counter electrode;
• control means for controlling passage of said developing particles through said gates by supplying a time-varying potential to be applied to said control electrode so as to allow said developing particles to adhere to said counter electrode;
• and
• transfer means for transferring an image formed on said counter-electrode onto the recording medium,
• wherein said control means controls the time-varying potential supplied to said control electrode so that the following equation is fulfilled:
• 2qvP(S/.pi.).sup.1/2 .gtoreq.(.pi.MR.sup.3 tan .theta.)/3-qS
• where q (g/cm.sup.2) is a density of said development particles on the surface of said holder per unit area, S (cm.sup.2) is an area of a range where an electric field which makes said development particles possible to fly is formed on the surface of said holder, v(cm/sec) is a relative speed of the surface of said holder to said control electrode, M(g/cm.sup.3) is specific gravity of said development particles, .theta.(.degree.) is an angle of repose of said development particles on the recording medium, P(sec) is a time for continuously supplying the time-varying potential, which allows said development particles to pass, to said control electrode, and 2R(cm) is a maximum length of a range on the recording medium to which said development particles adhere at a substantial moment the time-varying potential starts to be supplied to said control electrode.

An image forming apparatus for forming an image on a recording medium by allowing development particles to fly, comprising:

• charged development particles;
• a holder for holding said development particles;
• a counter electrode provided opposite to said holder;
• a control electrode formed with a plurality of circular gates for allowing the development particles to pass, said control electrode being located between said holder and said counter electrode;
• electric field forming means for forming a prescribed electric field for allowing said development particles to fly from said holder to said counter electrode by generating a prescribed potential difference across said holder and said counter electrode;
• and
• control means for controlling passage of said developing particles through said gates by changing the time-varying potential applied to said control electrode,
• wherein said control means includes:
• an insulating substrate having a plurality of gates;
• a first electrode layer to which a first time-varying potential is supplied, said first electrode layer being form on a holder side of said substrate;
• and
• a second electrode layer to which a second time-varying potential is supplied, said second electrode layer being formed on a counter electrode side of said substrate,
• wherein said control means controls the second time-varying potential so that the second time-varying potential becomes closer to a potential of said holder than a potential on center portions of the gates that is caused by the electric field, whereby dots having diameters smaller than diameters of said gates are formed on said recording medium.