JPH02308281A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent generating fogging when continuously forming images by the use of a negative organic photoconductive body by providing a separating device which gives alternating current charges when an image carrier is passing through and that superimposes negative charges onto the alternating current charges when the image carrier is passing through. CONSTITUTION:When positive charges are given by a transfer charger 21 from the back plane of sheet paper, a toner image on a photosensitive body 10 is electrostatically attracted to the sheet paper and is transferred. Then, the sheet paper reaches the separating charger 22. For the separating charger 22, a switch 22a is connected to a direct current power source 22c by a controller and the charges which are the alternating current charges superimposed with the negative charges are given to a part 10a which is a part of the photosensitive body 10 and is positively electrostatically charged by the AC power source 22b and the DC power source 22C. Then, the positive charges on the photosensitive body are neutralized and removed. In such a manner, even when repeatedly copied, the belt-shaped fogging is not generated.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to an image forming apparatus such as an electrophotographic apparatus, which forms an image using a negative polarity leading conductor. .

(Prior Art) In image forming apparatuses, particularly color copying machines and laser printers, a uniformly charged photoreceptor is exposed to light.
A visible image is often obtained by a so-called reversal development method, in which an electrostatic latent image is formed on a photoreceptor, and this electrostatic latent image is further developed with a toner having a charge of the same polarity as that of the photoreceptor. There is. In such a device, during transfer, an electric charge with a polarity opposite to that of the photoreceptor is generated in the transfer section.
A visible image is transferred onto the sheet paper by applying it from the back side of the sheet paper, which is an image carrier, to obtain an image. On the other hand, in recent years, as a photoreceptor suitable for such image forming devices, it is non-polluting and does not require collection processing, and the spectral sensitivity can be changed by selecting the material, expanding versatility and reducing costs. Photoreceptors in which an inexpensive organic photoconductor is coated on a drum-shaped or belt-shaped conductive support are increasingly being used. Conventional electrical conductors for this purpose have the drawbacks of low sensitivity and short lifespan due to rapid deterioration of characteristics compared to inorganic materials such as selenium [Se3], and are slow and inexpensive. However, recently, due to the selection of materials and improvements in the layer structure,
Efforts are being made to improve these sensitivity and lifespan.

However, when an image is formed using the above-mentioned reversal development using such an organic photoconductor, especially in the case of a negative organic photoconductor formed by successively laminating a charge generation layer and a charge transport layer on a conductive support. However, when an attempt is made to continuously obtain images by repeating the image forming process, band-like fogging occurs in a part of the image, which significantly reduces the image quality.

(Problems to be Solved by the Invention) As mentioned above, conventionally, when images are formed continuously by a reversal development method using a negative organic photoconductor, some parts of the image are white. There is a problem in that fogging occurs, and in the image area, the image density becomes high, causing density unevenness and deteriorating the image quality.

Therefore, in order to eliminate the above-mentioned drawbacks, the present invention makes it possible to obtain clear images without fogging even when images are formed continuously using a negative organic photoconductor. The purpose is to provide an image forming apparatus that can.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned problems, the present invention provides a transfer device that particularly applies a positive charge as an image forming means to an organic photoconductor;
A peeling device is provided which applies an alternating current charge when the image carrier passes through, and superimposes and superimposes a negative charge on the alternating current charge when the image carrier does not pass.

(Function) By the above means, the present invention aims to improve the image quality without causing fogging in a part of the image even during continuous image formation using a negative polarity organic photoconductor. be.

(Example) First, a photoreceptor made of a negative organic photoconductor was used,
The cause of fogging during continuous copying will be explained. For example, if a reversal development method is used as a one-time development method for continuous copying, in which development is performed using a negative toner with the same polarity as the surface potential of the photoreceptor, the visible image will not be visible after the reversal development is completed. When transferring a certain toner image from a photoreceptor to a sheet of paper that is an image carrier, a transfer device applies a positive charge from the back side of the sheet, thereby electrostatically absorbing and transferring the toner image to the sheet of paper. It happens. On the other hand, when copying is performed continuously, sheet paper is continuously fed to the transfer unit according to the toner image on the photoreceptor, but
A preceding sheet of paper and a subsequent sheet of paper are separated by a constant distance, and a gap is formed between each sheet of paper. Moreover, during continuous copying, the transfer device remains in continuous operation, so a positive charge is directly applied to the gap between each sheet by the transfer device, and that part on the photoreceptor is positively charged. This will result in In addition, a negative polarity organic photoconductor has a layered structure in which a charge generation layer and a charge transport layer are sequentially laminated on a conductive support, and the charge transport layer on the surface becomes a charge generation layer when exposed to light. Among the generated carriers, it has the property of allowing holes to pass through but not electrons. For this reason, when a negative organic photoconductor is positively charged, the positive charge cannot be removed by light irradiation. For this reason, the positively charged gap between each sheet of paper on the photoreceptor is not neutralized and reaches the next charging step with a positive charge, and is not charged by the charging device. However, the desired surface potential cannot be obtained, which causes fog to occur during the next copy.

Based on the above-mentioned causes, next, one embodiment of the present invention will be described as the first embodiment.
This will be explained with reference to FIGS. 3 to 3.

FIG. 1 is a schematic explanatory diagram showing a part of a laser printer which is an image forming apparatus, and 10 is a drum-shaped conductive support 11 and a charge generation layer 12a supported by the conductive support 11. The photoreceptor is made of a negative organic photoconductor 12 in which a charge transport layer 12b and a charge transport layer 12b are sequentially laminated. The charge generation layer 12a is composed of an azo pigment represented by the formula (1st formula) and a binder resin, and has the formula (1st formula).
(The conductive support 11 is immersed in a liquid in which phenoxy represented by No. b0 is mixed and dissolved in a solvent of 1,1,2-trichloroethane, and then dried to form the conductive support 11.

Next, the charge transport layer 12b is formed by mixing hydrazone represented by the formula with phenoxy represented by the formula (2nd formula) and dissolving these in a cyclohexane solvent. The body 11 is soaked, dried and formed. Also, the photoreceptor 10
Each image forming means 13 is provided around the periphery. The image forming means 13 includes a charging device 14 to which a voltage of -6 [kV] is applied, an exposure device 17 that irradiates image information from a document (not shown), etc., and a magnet roller 18a with a voltage of -45 kV.
A developing bias of 0 [V] is applied to the negative polarity toner 18b.
A developing device 18 having a transfer section, a transfer device 18 provided in a transfer section, and a transfer charger 2L to which a voltage of +5K [V] is applied by the first power supply 20 to generate a positive charge, a stripping device provided in a stripping section, and a switch Peak-to-peak +6.5K -7,2KV that can be connected and separated by 22a
[It is equipped with a peeling charger 22, a cleaning device 23, and a static elimination lamp 24 having an AC power source 22b of V and a DC power source 22c of -2K [V].

Next, we will discuss the effect. When copying starts, the photoreceptor 10 is rotated in the direction of arrow X, and the photoreceptor 10 is rotated accordingly.
is uniformly charged to about -650 [V] by the charging device 14. Next, an image portion of the photoreceptor 10 is irradiated with light by an exposure device 17 to form an electrostatic latent image. Thereafter, a developing device 18 applies a negative polarity toner to the image portion of the photoreceptor 10 irradiated with light, and a toner image is formed by reversal development. Next, the photoreceptor IO reaches the transfer section, and a sheet of paper (not shown) serving as an image carrier is also fed to the transfer section in synchronization with this toner image. When a positive charge is applied from the back side of the sheet paper by the transfer charger 22, the photoreceptor 10
The upper toner image will be electrostatically attracted to and transferred to a sheet of paper (not shown). Next, the sheet paper (not shown) reaches the peeling charger 22, but at this time the switch 22a is turned off to the other image forming means 1, as shown by the solid line in FIG.
3. A control device (not shown) that controls the image forming apparatus.
is connected to the ground side by the stripping charger 22.
By applying voltage from the AC power supply 22b, the photoreceptor 1
An alternating current charge is applied to the sheet paper and the sheet paper, and the sheet paper is peeled off. After this, the sheet paper passes through a preparatory device (not shown) to complete a copy image, and the photoreceptor 1o has residual l/toner removed by a cleaning device 23, and then static electricity is eliminated by a static elimination lamp 24. The following can be copied. On the other hand, during continuous copying, the transfer charger continues to operate even after the preceding sheet passes, and until the next sheet arrives, the transfer charger 21 keeps the photosensitive A positive charge is applied directly onto the body 10, and a portion 10a of the photoreceptor 1o is positively charged in a band shape as shown in FIG. On the other hand, the peeling charger 22
In this case, the switch 22a is controlled by a control device (not shown).
is connected to the DC power source 22c side, as shown by the dotted line in FIG. Further, a superimposed charge of negative polarity is applied to the photoreceptor, thereby neutralizing and removing the positive charge on the photoreceptor.

In addition, when I repeatedly copied in this way, the result was 40K[
Even with a single sheet of paper, it was possible to prevent the deterioration of image quality due to fog without producing the band-like fog that had conventionally occurred, and to obtain a good image.

With the configuration described above, even if continuous copying is performed by the photoreceptor 10 made of the negative organic photoconductor 12 and a portion 10a of the photoreceptor 10 is positively charged by the transfer charger 21, the In the peeling charger 22, a negative charge is applied together with an alternating current charge to the part, and the positive charge is neutralized and removed, so that the photoreceptor IO is uniformly charged with the desired charge over its entire surface during the next charging. Charged to surface potential. Therefore, it is possible to eliminate the band-like fog that conventionally occurs due to the inability to obtain a desired surface potential during charging, and it is possible to obtain good images for a long time.

Note that the present invention is not limited to the above-mentioned embodiments, and the magnitude of the power supply applied to the transfer device or the stripping device is arbitrary, but the magnitude of the negative polarity DC voltage in the stripping device is as follows:
At least one node of the peak-to-peak of the AC voltage is applied so that the negative component of the AC voltage during positive charge neutralization is 1.5 [times] or more of the negative component of the AC voltage during peeling off the image carrier. 4
It is desirable to set the value above. Further, the power applied to the peeling device may be switched arbitrarily, such as in response to a signal from a switch that detects the image carrier in the conveyance path. Furthermore, the material of the organic photoconductor is also optional.

[Effects of the Invention] As detailed above, according to the present invention, even if the image forming process is performed continuously using a negative polarity organic photoconductor suitable for color copying machines, laser printers, etc. The next image forming process is not performed while a part of the negative organic photoconductor remains positively charged, and the positive charges are neutralized before the start of the next charging process. When charged,
The organic photoconductor can uniformly obtain a desired surface potential, eliminate the band-like fog that has conventionally occurred, and make it possible to obtain clear and good images.

[Brief explanation of drawings]

1 to 3 show one embodiment of the present invention. FIG. 1 is a schematic explanatory diagram of the surroundings of a photoreceptor, FIG. 2 is a partial sectional view of the photoreceptor, and FIG. 3 is a diagram of the photoreceptor. It is a schematic perspective view. 10... Photoreceptor, 11... Conductive support,
12a...charge generation layer, 12b...charge transport layer,
12... Organic photoconductor 13... Image forming means,
14...Charging device, 21...Transfer charger, 22...Peeling charger, 22a...Switch, 22b...AC power supply, 22c...DC power supply. Agent Patent Attorney Norio Ogo No. 1 Figure n

Claims (1)

[Claims] An image forming apparatus comprising a negative organic photoconductor and an image forming means for forming an image on the negative organic photoconductor, wherein the image forming means is configured to form an image on the negative organic photoconductor at least in a transfer section. a transfer device that faces the negative organic photoconductor and applies a positive charge; and an AC power supply and a negative DC power supply that face the negative organic photoconductor in the peeling section, and when the image carrier passes through, the application of the AC power An image forming apparatus comprising a peeling device that applies an AC charge and, when the image carrier does not pass, applies an AC charge and a negative charge in a superimposed manner by applying the AC power source and the DC power source.