Magnetic developing method under A.C. electrical bias and apparatus therefor
AssigneeCanon Kabushiki Kaisha
InventorsJunichiro Kanbe, Tsutomu Toyono, Nagao Hosono, Tohru Takahashi
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Abstract
This specification discloses a method of toner transfer development in which one-component magnetic developer is conveyed to a developing position by the action of a magnetic field and a low frequency alternating electrical bias is applied to the space between a latent image bearing member and a developer carrying member at that position to thereby develop a latent image. This development provides visible images excellent in sharpness and tone reproduction.
Claims32
A dry developing method for developing a latent image comprising the steps of:
- defining a developing zone wherein a latent image bearing member having a latent image with an image area and a non-image area, and a non-magnetic conductive member carrying a layer of one component magnetic developer on the surface thereof are disposed in opposed relationship with a clearance between the surface of the latent image bearing member and the surface of the non-magnetic conductive member, the clearance being greater than the thickness of said developer layer so as to create an air gap;
- providing a magnetic field in said developing zone;
- moving said latent image bearing member and said non-magnetic conductive member;
- and
- imparting an alternating electric field sufficient to produce electric fields across said developing clearance which alternate both in the image area and the non-image area.
A dry developing method comprising the steps of defining a developing zone wherein a latent image bearing member and a non-magnetic developer carrier carrying thereon a layer of one-component magnetic developer are disposed in opposed relationship in a developing station with a clearance therebetween, the clearance being greater than the thickness of said developer layer so as to create an air gap, providing a magnetic field in said developing zone and effecting development while applying an alternating electric field in a range satisfying the relations:
- 400 V.ltoreq.V.sub.p-p .ltoreq.2500 V
- 40 Hz.ltoreq.f.ltoreq.1.5 KHz
- where V.sub.p-p represents the amplitude of the alternating electric field (V:
- peak-to-peak value) and f represents the alternating frequency of the alternating electric field, to apply an alternating electric field having a phase of a particular polarity which causes said developer to one-sidedly reach both the image area and the non-image area of said latent image bearing member from said developer carrier in said developing clearance and a phase of the opposite polarity to said particular polarity for applying a bias in a direction to cause said developer having reached at least said non-image area to return to said developer carrier side.
A dry developing method comprising the steps of defining a developing zone wherein an electrostatic latent image bearing member and a non-magnetic sleeve carrying thereon a layer of one-component magnetic developer are disposed in opposed relationship in a developing station with a clearance therebetween, the clearance being greater than the thickness of said developer so as to create an air gap, providing a magnetic field in said developing zone and effecting development while applying an alternating electric field in a range satisfying
- 400 V.ltoreq.V.sub.p-p .ltoreq.2500 V
- 40 Hz.ltoreq.f.ltoreq.1.5 KHz
- where V.sub.p-p represents the amplitude of the alternating electric field (V:
- peak-to-peak value) and f represents the alternating frequency of the alternating electric field, so that the electric field in said developing clearance applies an alternating electric field having a phase of a particular polarity which causes the magnetic developer to one-sidedly reach both the image area and the non-image area of said electrostatic latent image bearing member from said sleeve and a phase of the opposite polarity to said particular polarity which causes magnetic developer which has reached at least said non-image area to return to said sleeve side.
A dry developing method for developing an electrostatic image comprising the steps of:
- defining a developing zone wherein an electrostatic image bearing member and a non-magnetic carrier carrying thereon a layer of one-component magnetic developer are disposed in opposed relationship with a clearance therebetween to create an air gap;
- providing a magnetic field in said developing zone;
- applying an alternating electric field of low frequency to said developing zone, said alternating electric field acting on said developing clearance to realize the following developing processes:
- a first developing process in said developing zone in which the developing clearance is greater than the developer layer on said developing carrier and said alternating electric field which acts on said clearance has a transition phase which causes the magnetic developer to one-sidedly reach both the image area and the non-image area of said electrostatic image bearing member from said developer carrier and a back transition phase which tends to cause the developer which has reached said image member to one-sidedly return to said developer carrier, said two phases being repeated in said first developing process;
- and
- and a second developing process in the developing zone in which the developing clearance is wider than that in said first developing process and said alternating electric field which acts on said clearance has a transition phase which causes the magnetic developer to one-sidedly reach only the image area of said electrostatic image bearing member from said developer carrier and a back transition phase which tends to cause the magnetic developer present in the non-image area of said electrostatic image bearing member to one-sidedly return to said developer carrier, said two phases being repeated in said second developing process.
A dry developing method comprising the steps of defining a developing zone wherein an electrostatic image bearing member and a non-magnetic developer carrier carrying thereon a one-component magnetic developer layer are disposed in opposed relationship in a developing station with a clearance therebetween to create an air gap providing a magnetic field in said developing zone, and effecting development by applying an alternating voltage having a frequency lower than 1.5 KHz between a back electrode of said electrostatic image bearing member and said developer carrier, said frequency and said alternating voltage value being selectively changed over in accordance with the characteristics of the image.
A dry developing method comprising the steps of defining a developing zone wherein an electrostatic latent image bearing member and a non-magnetic sleeve carrying thereon a layer of one-component magnetic developer are disposed in opposed relationship in a developing station with a clearance therebetween, the clearance being greater than the thickness of said developer layer so as to create an air gap, providing a magnetic field in said developing zone, and effecting development while applying an alternating electric field in a range satisfying the relations:
- ##EQU4## where V.sub.p-p represents the amplitude of the alternating electric field and f represents the alternating frequency of the alternating electric field, so that the electric field in the developing zone applies an alternating electric field having a phase of a polarity which causes the magnetic developer to one-sidedly reach both the image area and the non-image area of said electrostatic latent image bearing member from said sleeve and a phase of the opposite polarity which causes said magnetic developer which has reached at least said non-image area to return to said sleeve side, said frequency and said amplitude value being selectively changeable within said range in accordance with the characteristics of the image.
A dry developing method for developing a latent image comprising the steps of:
- defining a developing zone wherein a latent image bearing member and a non-magnetic conductive member carrying one-component magnetic developer particles thereon are disposed in opposed relationship in a developing station with a clearance therebetween, said clearance being greater than the thickness of said developer particles carried on the non-magnetic conductive member so as to create an air gap;
- providing a magnetic field in said developing zone;
- and
- applying an alternating electric field to said clearance to effect development, said clearance being in the range of between 100 microns and 500 microns, and said alternating electric field having its peak-to-peak amplitude value in said clearance in the range of between 400 v and 2500 v.
A dry developing device for developing an electrostatic latent image carried on a latent image bearing member comprising:
- non-magnetic means for carrying a one-component magnetic developer;
- means for defining a developing zone by disposing said latent image bearing means and said non-magnetic carrying means in opposed relationship in a developing station with a predetermined clearance therebetween;
- means for providing a magnetic field in said developing zone;
- and
- means for moving said latent image bearing means and said non-magnetic carrying means;
- means for applying an alternating electric field to said developing zone, said alternating electric field producing electric fields in said developing clearance which alternate both in the image area and in the non-image area of said latent image bearing means.
A developing device comprising an image bearing member having a back electrode and having an electrostatic latent image thereon, a non-magnetic sleeve carrying thereon a one-component magnetic developer and having a magnet therewithin, means for disposing said image bearing member and said non-magnetic sleeve in opposed relationship in a developing station with a predetermined clearance therebetween, means for applying an alternating electric field to said developing clearance, said alternating electric field having a phase of a particular polarity which causes the magnetic developer in said developing clearance to one-sidedly reach both the image area and the non-image area of said image bearing member and a phase of the opposite polarity to said particular polarity which causes the magnetic developer which has reached at least said non-image area to return to said sleeve side, and means whereby from said alternate electric field having a range satisfying ##EQU7## where V.sub.p-p represents the amplitude of said alternating electric field (V:peak-to-peak value) and f represents the alternating frequency of said alternating electric field, said frequency and amplitude value are selectively changed over in accordance with the characteristics of the image.
Dependencies are inferred from the claim text.