JPH0664374B2 - Image forming method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image forming method for forming a high-quality visible image on a photoconductor layer using a conductive toner.

[Conventional technology]

In the conventional electrophotographic method, a photoconductor is uniformly charged by a corona charger, an electrostatic latent image is formed by image exposure, a toner image is obtained by a developing machine, transferred to a recording paper, and left on the photoconductor. A process such as removing toner with a cleaning device is required. The above method requires a corona charger, a cleaning device, etc., and the device is complicated and requires a high voltage. As a method for solving this problem, there is a recording method in which development, exposure and cleaning are performed almost at the same time.
No. 98746 and JP-A No. 58-153957.

[Problems to be solved by the invention]

In these methods, since the photoconductor is not sufficiently charged, the electric repulsive force generated between the toner and the photoconductor is weak and fog occurs, and stable recording cannot be performed. As means for removing this background fog, JP-A-59-154874
In the publication, a developing bias is synchronized with a pulsed exposure signal and a high frequency power source of 200 to 500 V is used. Therefore, an extra high frequency power source is required in addition to the DC power source used at the time of transfer, and there is a problem that electrical control becomes complicated. In the above method, the ground fog during the main scanning can be suppressed, but a high bias is applied to the ground fog in the sub-investigation direction, so that it is essentially difficult to remove the ground fog. It was

An object of the present invention is to provide an image forming method which solves the problem of background fog in an electrophotographic method in which development, exposure and cleaning are performed almost simultaneously.

[Means for solving problems]

In the image forming method according to the present invention, the position of the magnet of the developing machine is fixed, the conductive magnetic toner is conveyed by the rotation of the sleeve, the conductive magnetic toner is brought into contact with the photoconductor, and the surface of the photoconductor is charged. , To prevent toner accumulation on the side where the photoconductor and toner layer start contact with each other from the vertical line passing through the center of the cylindrical sleeve, and to prevent toner accumulation on the side where the toner layer separates from the photoconductor from the vertical line. To do.

[Action]

In the present invention, the toner accumulation is on the side where the photoconductor and the toner layer start contact with each other with respect to the vertical line passing through the center of the sleeve, and there is no toner accumulation on the side where the photoconductor and the toner layer are separated from each other, so that fog does not occur. .

〔Example〕

 Next, examples will be described.

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention. 1 is a photoconductor layer, 2 is a transparent electrode layer, 3 is a transparent support,
The photoreceptor 4 is configured as described above. The developing machine 5 comprises a magnetic roller 6 and a conductive non-magnetic sleeve 7,
A developing bias V _D of ± 50 V or less is applied to this sleeve 7. Reference numeral 8 is a conductive magnetic toner (hereinafter simply referred to as toner). The exposure device 9 using a light emitting diode array irradiates a light image from the transparent support 3 side toward the developing device 5 through the light converging lens 17. After the development, the toner 10 attached to the photoconductor 4 is transferred to the recording paper 12 by the transfer conductive roller 11.

The residual toner 13 after transfer is carried to the developing device 5 and collected. Bias V _t at the time of transfer is the development Baaisu V _D opposite polarity.

FIG. 2 shows the principle of adhesion of the toner 8. The toner 8 is carried by the rotation of the conductive, non-magnetic sleeve 7. The magnetic roller 6 is fixed, and the toner 8 is the magnetic pole 6.
The head height increases at positions -1, 6-2, 6-3 and decreases between the magnetic poles. The developing interval, that is, the surface interval between the surface of the photosensitive member 4 and the surface of the sleeve 7 is made narrower than the height of the toner layer on the developing device 5, whereby the accumulation of the toner 8 on the left side of the position 15 (on the vertical line of the cylindrical sleeve). A region is generated, and a region where the toner layer and the photoconductor 4 are in contact with each other is expanded. However, the developing interval is selected so that the toner 8 does not overflow. Since the peripheral speed of the sleeve 7 is set to be higher than the moving speed of the photoconductor 4, the surface of the photoconductor 4 is rubbed by the brush made of the conductive toner 8 and the surface of the photoconductor 4 is rubbed. It is charged to the same potential as the developing bias V _D. In this state, there is no force to attract the toner 8 to the photoconductor 4 side. Therefore, unless light is emitted from the exposure device 9, the toner 8 is attracted to the developing device 5 side by the magnetic force and the toner 8 does not adhere to the surface of the photoconductor 4. Reference numeral 18 indicates a sleeve moving direction, and 19 indicates a photosensitive member moving direction.

Although FIG. 1 shows the case where the exposure device 9 is an LED, the exposure device 9 may use a light source such as a liquid crystal shutter and an EL light source in addition to the LED. A light image is irradiated onto the exposure position 16 shown in FIG. 2 by using the light source. The exposure position 16 is near the right edge of the toner contact area 14. On the other hand, when irradiated by the exposure device 9, the potential of the photoconductor 4 at the exposure position 16 decreases, and the charged toner 10 adheres to the photoconductor 4 by the Coulomb force generated between the toner 10 and the transparent electrode layer 2. It is important that this exposure position 16 is close to the place where the toner layer and the photoconductor 4 are separated.
When 6 enters the toner contact area 14 too much, the exposed area is charged again and becomes the same potential as the developing bias V _D , so that the toner 10 does not adhere to the photoconductor 4.

By the way, in order to remove the background fog, as a method of causing the toner 8 to collect on the side where the photosensitive member 4 and the toner layer start to contact with each other from the perpendicular line passing through the center of the cylindrical sleeve 7, the magnetic poles 6-1 to 6-1 in the sleeve 7 are formed. It can be realized by adjusting the position of 6-3.

FIG. 3 shows the relationship between the magnetic pole position and the background fog density when the sleeve moving direction 18 and the photoconductor moving direction 19 are opposite. The rotation angle of 0 ° represents a state in which the magnetic poles are located on the perpendicular line passing through the center of the sleeve 7. The clockwise rotation direction of the magnetic roller 6 is defined as a positive rotation direction. Magnetic roller 6
Is 8 poles, 500 gauss, Se is used as the photoconductor layer 1, and the developing bias is + 200V. With the rotation angle of the magnetic roller 6 being θ, θ = −15, +
There was no fog at 25 °, while a high density of 0.68 was obtained at θ = 10 °. The drastic change in the density of the background fog can be explained by referring to the magnetic pole positional relationship diagram in FIG.

FIG. 4 (a) shows a state diagram without ground fog. A region where the photoconductor 4 and the toner 8 are in contact with each other, a region 20 to the left of the exposure position 16 and a region 21 to the right of the exposure position 16. Area 21 is where charging and cleaning are performed. Exposure position 16
Since the thickness of the toner layer and the developing interval are almost the same and the contact force of the tips of the toner 8 with the photoconductor 4 is weak, the toner 8 is exposed to the sleeve 7 by magnetic force when it is not exposed. Pass position 16. The region 20 acts to disturb the toner image adhered to the photoconductor 4 by exposure, and thus it is preferable that the region 20 is as narrow as possible. FIG. 4 (b) shows a state in which ground fog occurs. Since the toner layer is larger than the gap at the magnetic pole position in FIG. 4B, the toner 8 is compressed and the region 20 is expanded. This expanded area is called area 22
Then, since the toner 8 in the area 22 is farther from the magnetic pole S6-2 than the toner 8 in the area 20, the magnetic force acting on the toner 8 is weakened. Further, since the moving direction of the toner 8 is opposite to the moving direction 19 of the photoconductor, this serves as a force for separating the toner 8 from the sleeve 7. Area 22 in this state
Toner 8 adheres to the photoconductor 4 and causes fog.

On the other hand, when the sleeve moving direction 18 and the photoconductor moving direction 19 are the same direction, the relationship between the magnetic pole position and the ground fog is
Shown in the figure. In the opposite direction, no ground fog occurs when θ = 0 ° and 45 °. Ground fogging occurs near θ = −15 ° and + 30 °. However, the background fog density in the same direction is lower than that in the opposite direction because the developing gap on the perpendicular line passing through the center of the sleeve 7 limits the height of the brush and the toner 8 accumulates on the side where the toner layer is separated. This is because it is less likely to occur.

Although the number of magnetic poles of the magnetic roller 6 is eight in the above description, it is needless to say that n poles other than eight (n = 1, 2, 3, ...) May be used.

Further, it is obvious that the developing device 5 may be incorporated in a conventional electrophotographic process as an exposing device 9 for both charging and cleaning, without using the developing device 5 as a developing device.

〔The invention's effect〕

As described above, according to the present invention, the magnetic pole position in the sleeve is set to an appropriate position to cause toner accumulation on the side where the photosensitive member and the toner layer start contact with each other from the perpendicular line passing through the center of the cylindrical sleeve, Since the toner is prevented from accumulating on the side where the toner layer is separated from the photoconductor with respect to the vertical line, there is an advantage that the toner can be stably charged and the fog can be eliminated.

[Brief description of drawings]

FIG. 1 is a block diagram showing a conventional example of the present invention, FIG. 2 is a diagram illustrating the principle of the present invention, FIG. 3 is a diagram showing the relationship between the position of a magnetic pole roller and the background fog density, and FIG. 4 (a). , (B) are diagrams for explaining the occurrence of background fog, and FIG. 5 is a diagram showing the relationship between the position of the magnetic roller and the background fog density. In this figure, 1 is a photoconductor layer, 2 is a transparent electrode layer, 3
Is a transparent support, 4 is a photoreceptor, 5 is a developing machine, 6 is a magnetic roller, 7 is a sleeve, 8 is toner, 9 is an exposing device, 10 is toner, 11 is a conductive roller, 12 is recording paper, 13 is Residual toner, 17 is a light converging lens, 18 is a sleeve moving direction, and 19 is a photoconductor moving direction.

Claims (1)

[Claims] 1. A photoreceptor having a transparent electrode layer and a photoconductor layer provided on a transparent support, and a developing device having a cylindrical conductive non-magnetic sleeve disposed in the vicinity of the photoconductor layer and a magnet inside. In the method of forming an image by applying a developing bias between the developing device and the transparent electrode layer between the developing device and the transparent support, the position of the magnet of the developing device is fixed and the sleeve is The conductive magnetic toner is conveyed by rotation, the conductive magnetic toner is brought into contact with the photoconductor to charge the surface of the photoconductor, and the perpendicular line or the cylinder drawn from the center of the cylindrical sleeve to the photoconductor The toner is accumulated on the side where the photosensitive layer and the toner layer start contacting with each other from the line connecting the center of the cylindrical sleeve and the center of the cylindrical photosensitive body, and the perpendicular line or the sleeve and the cylindrical photosensitive body are respectively formed. The image forming method according to Mezzanine that toner layer from a line connecting the centers of development without causing reservoir of toner on the side away from the photosensitive member.