Electrophotographic image forming method

Details Electrophotographic image forming method Electrophotographic image forming method

1989-10-16

1991-06-11

Miller, Jr., George H.

Recorders

Electric recording

Electrochemical

346154, 355326, G03G 1501, G01D 1506

Patent

active

050236326

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to an electrophotographic image forming method which can be utilized for a hard copy apparatus such as a copying machine, a printer or the like.


BACKGROUND ART

There have been proposed heretofore various methods for the formation of electrophotographic color images wherein the cycle of charging, exposure and developing is repeated a plurality of times to form a plurality of toner images of different colors on an electrophotographic photoconductor (hereinafter called a photoconductor), the toner images then being transferred onto paper to reproduce a color copy image thereon.
As an example of apparatuses using such electrophotographic color image forming methods, the apparatus has been proposed by the inventors of the present invention in Japanese Patent Application No. 62-4367, is described below with reference to FIG. 2.
The reference numerals 1, 2, 3 and 4 indicate mono-component, non-magnetic developer units of non-contact type which project toner in a direct current electric field. The toner is charged triboelectrically with conductive fur brushes 5, 6, 7 and 8 which are disposed in a contacting array with respective developing rollers, thereby causing a thin layer of toner to form on the aluminum developing rollers 9, 10, 11 and 12 by means of respective blades 13, 14, 15 and 16. The developer unit 1 contains insulative toner of yellow (Y), the developer unit 2, magenta (M), the developer unit 3, cyan (C), and the developer unit 4 black (Bk). The developer units are disposed facing the circumference of a photoconductor 17, with a given gap (developing gap) provided between each of the developing rollers 9, 10, 11 and 12 and the photoconductor 17. Each developer unit is provided with a moving mechanism for causing it to move closer to the photoconductor 17 when developing is performed and to retract when developing is not performed. The following shows the specification and developing conditions of each developer unit, and the properties of the toner used.


SPECIFICATION OF DEVELOPER UNIT AND DEVELOPING CONDITIONS

Diameter of developing roller: 16 mm
Surface speed of developing roller: 150 mm/s
Rotating direction of developing roller:
With-direction of photoconductor Toner layer thickness on developing roller: 30 .mu.m Developing gap (gap between developing roller surface and photoconductor surface): 150 .mu.m in developing condition, 700 .mu.m in non-developing condition


PROPERTIES OF TONER

Charge amount of toner: +3 .mu.C/g
Average particle diameter: 10 .mu.m
Relative permittivity: Approximately 2
An amorphous Se-Te photoconductive drum of 100 mm in diameter having increased sensitivity to the longer wavelength in the infrared region is used for the photoconductor 17 (with a thickness of 60 .mu.m and a relative permittivity of 6.3), which is made to rotate at the surface speed of 150 mm/s. The photoconductor 17 is charged at the surface potential of +700 V by means of a corona charger 18 (scorotron charger, corona voltage: +7 kV, grid voltage: +820 V).
Next, a light emitting diode array 19 is energized to emit light of 670 nm wavelength, exposing the photoconductor through a self-focusing rod lens array 20. At this time, the light intensity on the photoconductor surface is 2.2 .mu.J/cm.sup.2. Using the light emitting diode array 19, a negative yellow signal is first projected onto the photoconductor 17 to form an electrostatic latent image. The latent image is then reversely developed by the yellow developer unit 1 which is put in a developing condition with +600 V applied to the developing roller 9. Thereafter, the photoconductor 17 is made to pass the magenta developer unit 2, the cyan developer unit 3 and the black developer unit 4, all in a non-developing condition, to form a yellow toner image.
The photoconductor 17 is again charged at +850 V by the corona charger 18. The photoconductor 17 is then exposed to the light of the signal corresponding to magenta by means of the light emitting diode array 19, to form a magenta electrostatic latent

REFERENCES:
patent: 4159174 (1979-06-01), Rising
patent: 4734735 (1988-03-01), Haneda
patent: 4809037 (1989-02-01), Sato
patent: 4841337 (1989-06-01), Hiratsuka et al.

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