Claims
- 1. An image forming apparatus, comprising: a latent image-bearing member for holding an electrostatic image thereon, a toner-carrying member for carrying a layer of a magnetic toner thereon, a toner vessel for holding the magnetic toner to be supplied to the toner-carrying member, a toner layer-regulating member for regulating the magnetic toner layer on the toner-carrying member, and a bias application means for applying an alternating bias voltage comprising a DC bias voltage and an unsymmetrical AC bias voltage in superposition between the toner-carrying member and the latent image-bearing member, wherein
- the latent image-bearing member and the toner-carrying member are disposed with a prescribed gap therebetween at a developing station;
- the toner layer-regulating means is disposed to regulate the magnetic toner layer on the toner-carrying member in a thickness thinner than the prescribed gap;
- the magnetic toner comprises a binder resin and magnetic powder and has a volume-average particle size of 4-10 microns, the binder resin comprises a vinyl copolymer having an acid anhydride group, and the binder resin has a total acid value (A) of 2-100 mgKOH/g and a total acid value (B) attributable to acid anhydride group of below 6 mgKOH/g so that [(B)/(A)].times.100 is 60% or less; and
- the bias application means is disposed to provide an alternating bias electric field comprising a development-side voltage component and a reverse-development side voltage component, the development-side voltage component having a magnitude equal to or larger than that of the reverse development-side voltage component and a duration smaller than that of the reverse-development side voltage component, so that the magnetic toner on the toner-carrying member is transferred to the latent image-bearing member to develop the electrostatic image thereon at the developing station.
- 2. The image forming apparatus according to claim 1, wherein the bias application means applies an alternating bias voltage having a frequency of 1.0-5.0 KHz.
- 3. The image forming apparatus according to claim 1, wherein the bias application means provides an alternating bias voltage having a duty factor of 10-40%.
- 4. The image forming apparatus according to claim 1, wherein the alternating bias voltage has a peak-to-peak value of 1.0-2.0 KV.
- 5. The image forming apparatus according to claim 1, wherein said alternating bias voltage has a frequency of 1.0-5.0 KHz, a peak-to-peak voltage of 1.0-2.0 KV and a duty factor of 10-40%, and the magnetic toner contains 12-60% by number of toner particles of 5 microns or smaller.
- 6. The image forming apparatus according to claim 1, wherein the latent image-bearing member comprises a photosensitive layer of a-Si.
Priority Claims (2)
Number |
Date |
Country |
Kind |
1-289882 |
Nov 1989 |
JPX |
|
2-051196 |
Mar 1990 |
JPX |
|
Parent Case Info
This application is a division of application Ser. No. 07/604,207, filed Oct. 29, 1990, now U.S. Pat. No. 5,169,738.
US Referenced Citations (8)
Foreign Referenced Citations (7)
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59-139053 |
Aug 1984 |
JPX |
61-123855 |
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JPX |
61-123857 |
Jun 1986 |
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Divisions (1)
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Number |
Date |
Country |
Parent |
604207 |
Oct 1990 |
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