Electrophotographic recording apparatus

Claim 2

An electrophotographic recording apparatus including a photosensitive belt (1) having an electrically conductive layer (1a) and a photoconductive layer (1b) formed on the surface thereof and applied rotatably, means (8, 9) for sequentially forming a plurality of kinds of electrostatic latent images for different colors on said photosensitive belt, developing means (4, 5, 6, 7) for forming a plurality of toner images by depositing charged toner of colors corresponding to the electrostatic latent images, an intermediate transfer drum (11) to which said plurality of toner images are transferred in overlapping fashion to complete a color toner image as it rotates synchronously with said photosensitive belt while making contact thereto, and means (20) for transferring the color toner image formed on said intermediate transfer drum to a secondary recording medium (15), said apparatus comprising: said intermediate transfer drum including a dielectric layer (11b) connected to earth potential; first transfer means for transferring the toner image from said photosensitive belt to said intermediate transfer drum including a first bias power supply (31) for applying a first transfer bias voltage which biases said photosensitive belt to potential having the same polarity as charging polarity of the toner relative to earth potential; and second transfer means for transferring the toner image on said intermediate transfer drum to said secondary recording medium including a second bias power supply (34) for applying a second transfer bias which biases the back of said secondary recording medium to potential having opposite polarity to charging polarity of the toner relative to earth potential.

Claim 3

An electrophotographic recording apparatus including a photosensitive belt (1) having an electrically conductive layer (1a) and a photoconductive layer (1b) formed on the surface thereof and applied rotatably, means (8, 9) for sequentially forming a plurality of kinds of electrostatic latent images for different colors on said photosensitive belt, developing means (4, 5, 6, 7) for forming a plurality of toner images by depositing charged toner of colors corresponding to the electrostatic latent images, an intermediate transfer drum (11) to which said plurality of toner images are transferred in overlapping fashion to complete a color toner image as it rotates synchronously with said photosensitive belt while making contact thereto, and means (20) for transferring the color toner image formed on said intermediate transfer drum to a secondary recording medium (15), said apparatus comprising: said intermediate transfer drum including a dielectric layer (11b) formed on the surface of an electrically conductive substrate (11a) connected to earth potential; first transfer means for transferring the toner image from said photosensitive belt to said intermediate transfer drum including a first bias power supply (31) for applying a first transfer bias voltage which biases said electrically conductive layer of said photosensitive belt to potential having the same polarity as charging polarity of the toner relative to earth potential; and second transfer means for transferring the toner image on said intermediate transfer drum to said secondary recording medium including a second bias power supply (34) for applying a second transfer bias which biases the back of said secondary recording medium to potential having opposite polarity to charging polarity of the toner relative to earth potential.

Claim 4

An electrophotographic recording apparatus according to Claim 3 wherein said first transfer bias voltage has a voltage difference of 200 V or more relative to earth potential.

Claim 5

An electrophotographic recording apparatus according to Claim 3 wherein said second transfer means comprises a corona discharger (20) energized by said second bias power supply to charge on the back of said secondary recording medium an electric charge having opposite polarity to that of the toner.

Claim 6

An electrophotographic recording apparatus according to Claim 3 wherein said second transfer means comprises a roll electrode (37b) energized by said second bias power supply and pushed against the back of said secondary recording medium.

Claim 7

An electrophotographic recording apparatus according to Claim 6 wherein said roll electrode includes an electrically conductive metal shaft (37a) and a resilient layer (37b) having a resistance of 10⁴ to 10⁹ Ω.

Claim 8

An electrophotographic recording apparatus according to Claim 6 wherein said roll electrode includes an electrically conductive metal shaft (37a) and a resilient layer (37b) having a resistance of 10⁴ to 10⁹ Ω and said second bias power supply applies a bias voltage having a voltage difference of 600 to 2000 V relative to earth potential to said metal shaft.

Claim 9

An electrophotographic recording apparatus according to Claim 3 wherein said dielectric layer (11b) of said intermediate transfer drum (11) has a resistance of 10⁷ to 10¹¹ Ωcm.

Claim 10

An electrophotographic recording apparatus including a photosensitive belt (1) having an electrically conductive layer (1a) and a photoconductive layer (1b) formed on the surface thereof and applied rotatably, means (8, 9) for sequentially forming a plurality of kinds of electrostatic latent images for different colors on said photosensitive belt, developing means (4, 5, 6, 7) for forming a plurality of toner images by depositing charged toner of colors corresponding to the electrostatic latent images, an intermediate transfer drum (11) to which said plurality of toner images are transferred in overlapping fashion to complete a color toner image as it rotates synchronously with said photosensitive belt while making contact thereto, and means (20) for transferring the color toner image formed on said intermediate transfer drum to a secondary recording medium (15) said apparatus comprising: said intermediate transfer drum including a dielectric layer (11b) formed on the surface of an electrically conductive layer (11a) connected to earth potential; first transfer means for transferring the toner images from said photosensitive belt to said intermediate transfer drum including a first bias power supply (31) for applying a first transfer bias voltage which biases said electrically conductive layer of said photosensitive belt to potential having the same polarity as charging polarity of the toner relative to earth potential; and second transfer means for transferring the toner image on said intermediate transfer drum to said secondary recording medium including a second bias power supply (34) for generating a second transfer bias voltage having opposite polarity to charging polarity of the toner and a corona discharger (20) energized by said bias power supply to charge said secondary recording medium at opposite polarity to charging polarity of the toner relative to earth potential.

Claim 11

An electrophotographic recording apparatus including a photosensitive belt (1) having an electrically conductive layer (1a) and a photoconductive layer (1b) formed on the surface thereof and applied rotatably, means (8, 9) for sequentially forming a plurality of kinds of electrostatic latent images for different colors on said photosensitive belt, developing means (4, 5, 6, 7) for forming a plurality of toner images by depositing charged toner of colors corresponding to the electrostatic latent images, an intermediate transfer drum (11) to which said plurality of toner images are transferred in overlapping fashion to complete a color toner image as it rotates synchronously with said photosensitive belt while making contact thereto, and means (20) for transferring the color toner image formed on said intermediate transfer drum to a secondary recording medium (15), said apparatus comprising: said intermediate transfer drum including a dielectric layer (11b) connected to earth; first transfer means for transferring the toner images from said photosensitive belt to said intermediate transfer drum including a first bias power supply (31) for applying a first transfer bias voltage which biases said electrically conductive layer of said photosensitive belt to potential having the same polarity as charging polarity of the toner relative to earth potential; second transfer means for transferring the toner image formed on said intermediate transfer drum to said secondary recording medium including a second bias power supply for applying a second transfer bias which biases the back of said secondary recording medium to potential having opposite polarity to charging polarity of the toner relative to earth potential; said means for formation of the electrostatic latent images including means for forming on the surface of said photosensitive belt electrostatic latent images by using the second transfer bias potential as reference potential; and said developing means including means for developing the electrostatic latent images by using the second transfer bias potential as reference potential.

Claim 12

An electrophotographic recording apparatus including an endless photosensitive belt (1) applied rotatably, means (8, 9) for forming electrostatic latent images on said photosensitive belt, a plurality of developing units (4, 5, 6, 7) for forming toner images by depositing charged toner on the electrostatic latent images, an intermediate transfer drum (11) to which the toner images are transferred in overlapping fashion to complete a color toner image as it rotates synchronously with said photosensitive belt while making contact thereto, and means (20) for transferring the color toner image formed on said intermediate transfer drum to a secondary recording medium (15), said apparatus comprising: photosensitive belt rotating and supporting means (2, 3a, 3b) on which said photosensitive belt is applied in the form of a substantial triangle to form a horizontal top surface; developing unit supporting means (46) for supporting said plurality of developing units such that said developing units are detachable from above and oppose said horizontal top surface of said photosensitive belt; an openable top cover (25) for providing a covering above said plurality of developing units; transfer drum supporting means (11a) for maintaining said intermediate transfer drum at earth potential; first transfer means for applying a first transfer bias voltage which biases said photosensitive belt to potential having the same polarity as charging polarity of the toner relative to earth potential; and a second bias power supply (34), provided for second transfer means for transferring the toner image on said intermediate transfer drum to said secondary recording medium, for applying a second transfer bias which biases said second recording medium to potential having opposite polarity to charging polarity of the toner image relative to earth potential.

Claim 13

An electrophotographic recording apparatus according to Claim 12 wherein said photosensitive belt rotating and supporting means rotatably supports said photosensitive belt applied thereon to form a substantially horizontal top surface, a substantially vertical surface and an inclined surface, and said intermediate transfer drum contacts said photosensitive belt at said substantially vertical surface.

Claim 14

An electrophotographic recording apparatus including an endless photosensitive belt (1) applied rotatably, means (8, 9) for forming electrostatic latent images on said photosensitive belt, a plurality of developing units (4, 5, 6, 7) for forming toner images by depositing charged toner on said electrostatic latent images, an intermediate transfer drum (11) to which the toner images are transferred as it rotates synchronously with said photosensitive belt while making contact thereto, and means (20) for transferring the toner images to a secondary recording medium (15), said apparatus comprising: photosensitive belt rotating and supporting means (2, 3a, 3b) on which said photosensitive belt is applied in the form of a substantial triangle to form a substantially horizontal top surface; developing unit supporting means (46) for supporting said plurality of developing units above said photosensitive belt such that said developing units are detachable from above and oppose said horizontal top surface of said photosensitive belt; an openable top cover (25) for providing a covering above said plurality of developing units; transfer drum supporting means (11a) for maintaining said intermediate transfer drum at earth potential and supporting it laterally of said photosensitive belt so that said intermediate transfer drum may contact a substantially vertical surface of said photosensitive belt; first transfer means for applying a first transfer bias voltage which biases said photosensitive belt to potential having the same polarity as charging polarity of the toner relative to earth potential; second transfer means supported laterally of said intermediate transfer drum away from said photosensitive belt and interiorly of a side cover (48) and applied with a second transfer bias which biases said secondary recording medium to potential having opposite polarity to charging polarity of the toner relative to earth potential; and support means (49) for openably supporting said side cover.