JPH04241375A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To offer a reliable new transfer method with high transfer efficiency where color unevenness caused by the omission of transfer occurring on an image such as a color image whose toner adhesive quantity is large and the fluctuation of toner transfer efficiency caused by ambient temperature and humidity or the environmental change and the change of the material and the thickness of a transfer sheet are small. CONSTITUTION:A transfer mechanism is provided, where a repulsive transfer roller 13 on which voltage having the same polarity as the electrostatically charged polarity of the toner of a toner image can be impressed is arranged on the inner peripheral surface side of an intermediate transfer drum 9 which corresponds to a transfer position in order to transfer the toner image on the drum 9 to a transfer sheet 12. By allowing repulsive transfer electric field to act on the toner layer of the surface of the intermediate transfer body, the high transfer efficiency is attained with hardly receiving the effect of the toner adhesive quantity, the environmental change and the transfer sheet.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus.

0002

2. Description of the Related Art Conventionally, electrophotographic devices have been used in copying machines, laser printers, and the like.

A conventional electrophotographic apparatus will be explained below. FIG. 5 is a schematic diagram of a conventional electrophotographic apparatus, and FIG. 6 is a schematic diagram of another example of a conventional electrophotographic apparatus. Figure 5,
In FIG. 6, 1 is a photoorganic conductive semiconductor belt (hereinafter abbreviated as OPC belt), and 2 is an OPC drive for driving the OPC belt 1 while winding and tensioning the OPC belt 1 around its outer circumference. A roller 4 is a charger that is attached close to the OPC belt 1 and uniformly charges the surface of the OPC belt 1, 7 is a laser irradiator that irradiates the OPC belt 1 with light according to image information, and 8a is a charger that applies black toner. A developing device 8b is a developer that attaches cyan toner to the electrostatic latent image formed on the OPC belt 1 and visualizes it. 8c is a developing device that applies magenta toner to the electrostatic latent image formed on the OPC belt 1 and develops it; 8d is a developer that applies yellow toner to the electrostatic latent image formed on the OPC belt 1; This is a developing device that attaches and visualizes the image. 9a is an intermediate transfer belt;
Reference numeral 3 denotes an intermediate transfer drive roller for winding and tensioning the intermediate transfer belt 9a around its outer periphery and driving the intermediate transfer belt 9a. Reference numeral 11 denotes an intermediate transfer roller for transferring the toner attached to the OPC belt 1 onto the intermediate transfer belt 9a. , 5 is an OPC cleaning device that scrapes off residual toner on the OPC belt 1 after the transfer, and 6 is a static eliminator that removes the charge on the OPC belt 1 after cleaning. 12
is copy paper, 17 is a paper cassette for storing copy paper, 1
8 is a conveyance roller that conveys the copy paper 12. In FIG. 5, 15 is a transfer roller that presses the copy paper 12 against the intermediate transfer belt 9a and applies a transfer voltage to transfer the toner adhering to the intermediate transfer belt 9a onto the copy paper 12. In FIG. 6, 15a is a corona. This is a transfer corona that applies a charge to the copy paper 12 and transfers the toner adhering to the intermediate transfer belt 9a to the copy paper 12. 10 is a cleaning device for scraping off residual toner on the intermediate transfer belt 9a after transfer;
A fixing device 16 fixes the toner transferred to the copy paper 12.

The operation of the image forming apparatus configured as described above will be explained below. First, OPC belt 1
When a voltage is applied to the charger 4 while being rotationally driven by the OPC drive roller 2, the surface of the OPC belt 1 becomes uniformly charged. OPC belt 1 in this state
When the surface of the OPC belt 1 is irradiated with a laser beam given black image information by the laser irradiator 7, the charge disappears from the irradiated portion of the surface of the OPC belt 1, and an electrostatic latent image is formed.

Next, in the developing device 8a, the electrostatic latent image formed on the surface of the OPC belt 1 is visualized with black toner, and this black toner is transferred to the intermediate transfer roller 11 to which a transfer voltage is applied. By pressing the transfer belt 9a against the OPC belt 1, the toner is transferred to the intermediate transfer belt 9a, and residual toner remaining on the surface of the OPC belt 1 is removed by OP.
The residual toner scraped off by the C cleaning device 5 is collected into the inside of the OPC cleaning device 5, and the OPC belt 1 from which the residual toner has been scraped off is neutralized by the static eliminator 6. Similarly, the electrostatic latent images of each component are visualized in the order of cyan, magenta, and yellow and transferred to the intermediate transfer belt 9a, thereby forming a color toner image on the intermediate transfer belt 9a.

The conveyance roller 18 aligns the copy paper 12 from the paper cassette 17 with the toner image on the intermediate transfer belt 9a, and moves the intermediate transfer belt 9a and the transfer roller 15 at the same conveyance speed as the intermediate transfer belt 9a. The toner particles are conveyed to the intermediate transfer belt 9a and brought into close contact with the intermediate transfer belt 9a, and a voltage having a polarity opposite to the charged polarity of the toner particles constituting the toner image is applied from the back side of the copy paper 12 when viewed from the toner image on the intermediate transfer belt 9a as shown in FIG. Intermediate transfer is performed by applying a corona charge to the transfer roller 15 shown in FIG. The toner image on the belt 9a is transferred to the copy paper 12, and the residual toner remaining on the surface of the intermediate transfer belt 9a is scraped off by a cleaning device 10, and the scraped residual toner is collected inside the cleaning device 10. . The toner image transferred to the copy paper 12 is fixed by a fixing device 16.

[0007]

[Problems to be Solved by the Invention] However, in the above-mentioned conventional configuration, when there are areas with a large amount of toner adhesion and areas with a small amount of toner adhesion within one screen, such as a color image, the transfer conditions are different from those in which the amount of toner adhesion is low. The toner transfer efficiency differs depending on the area, and in an image area where two, three or four color toners are superimposed and have a very large amount of toner adhering, the toner layer on the intermediate transfer belt 9a is sufficiently transferred to the lowest toner layer. If you try to do this, it is necessary to set the transfer voltage to a certain level, but if the transfer voltage is set too high, the transfer electric field will become too strong, which may cause dielectric breakdown inside the toner layer in image areas where the amount of toner adhering within one screen is small. However, there is a problem in that a phenomenon called transfer dropout occurs in which the transfer efficiency is significantly reduced.

[0008]

[Means for Solving the Problems] In order to solve the above problems, the present invention applies a voltage having the same polarity as the charged polarity of the toner according to image information from the side opposite to the toner adhesion surface of the toner adhesion member to which the toner adheres. It is equipped with an application means for applying the voltage.

[0009]

[Operation] With the above-described configuration, the present invention applies an electric field that causes the toner adhering to the toner adhering member to be repulsed and peeled off from the toner adhering member to the toner adhering surface of the toner adhering member. It can be given from the other side.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic diagram of an electrophotographic apparatus according to an embodiment of the present invention. In Figure 1, 1 is O
PC belt, 2 OPC drive roller, 4 charger, 5 OPC cleaner, 6 static eliminator, 7 laser irradiator, 8a, 8b, 8c, 8d developing device, 10 cleaning device, 11 intermediate A transfer roller, 12 is copy paper, 16 is a fixing device, 17 is a paper cassette, 18 is a conveyance roller,
Since these are similar to the configuration of the conventional example, detailed explanation will be omitted. 9 is an intermediate transfer drum, 13 is a repulsive transfer roller provided in close contact with the inside of the intermediate transfer drum 9, and 14 is a separable pressure roller that presses the copy paper 12 against the intermediate transfer drum 9.

The operation of the electrophotographic apparatus of the present invention constructed as described above will be explained below. After applying a potential to the OPC belt 1 to a predetermined charging potential using the charger 4, laser exposure is performed using the laser irradiator 7. Thereafter, the developing device 8a performs development with black toner, and then the black toner image is transferred onto the intermediate transfer drum 9 by an intermediate transfer roller 11 disposed on the back surface of the intermediate transfer drum 9. Similarly, the cyan toner image developed by the developing device 8b is transferred to be superimposed on the previously transferred black toner image on the intermediate transfer drum 9. Similarly, a color toner image is temporarily stored on the intermediate transfer drum 9 using toner of a total of four colors in the order of magenta and yellow.

Next, the copy paper 12, which is conveyed by the conveyance roller 18 while being aligned with the toner image on the intermediate transfer drum 9, is conveyed to the intermediate transfer drum 9 at the same conveyance speed as the intermediate transfer drum 9. When the toner particles are conveyed between the pressure rollers 14, a high voltage having the same polarity as the charging polarity of the toner particles constituting the toner image is applied to the repulsive transfer roller 13 provided inside the intermediate transfer drum 9. A high voltage having the same polarity as the charge polarity of the toner particles constituting this toner image is applied to the repulsive transfer roller 13, that is, an electric field is applied from the inside of the intermediate transfer drum 9 to cause the toner particles to be repelled and peeled off from the intermediate transfer drum 9. As a result, an electric field can be uniformly applied to the toner in the bottom layer regardless of whether the amount of toner adhering to the intermediate transfer drum 9 is large or small, and the toner in the bottom layer repulses and peels off, so that the toner in the top layer is not affected. toner can be reliably removed and toner transfer can be performed reliably. Further, when a high voltage is applied to the repulsive transfer roller 13, the copy paper 12 is brought into close contact with the intermediate transfer drum 9 by the pressure roller 14 in order to improve transfer efficiency and prevent toner from scattering during transfer. The toner image on copy paper 9 is transferred to copy paper 12, and the toner image transferred to copy paper 12 is fixed by fixing device 16.

In this embodiment, a high voltage having the same polarity as the charging polarity of the toner particles constituting the toner image is applied to the repulsive transfer roller 13 to transfer the toner image on the intermediate transfer drum 9 to the copy paper 12. The repulsive transfer roller 13 may be a conductive brush 13a to which a voltage is applied as shown in FIG. 2, or a conductive plate 13b as shown in FIG.

Furthermore, instead of the repellent transfer roller 13, the roller shown in FIG.
When using a corona charger 13c as shown in
While transferring the toner to the copy paper 12, the intermediate transfer drum 9
Since it is necessary to hold a corona charge on the inner circumferential surface of the intermediate transfer drum 9 at the position where the copy paper 12 and the copy paper 12 come into contact with each other, the inner circumferential surface of the intermediate transfer drum 9 needs to have high electrical resistance. At the same time, after passing the transfer area, it is necessary to eliminate static electricity from the intermediate transfer drum 9 using a static elimination brush 19 in order to prevent problems due to accumulation of electric charges.

Further, in this embodiment, a high voltage having the same polarity as the charging polarity of the toner particles constituting the toner image is applied to the intermediate transfer drum 9 by the repulsive transfer roller 13 provided inside the intermediate transfer drum 9. The above toner image is transferred to the copy paper 12, and this intermediate transfer drum 9 has a uniform and appropriate electrical resistance that is less affected by changes in ambient temperature and humidity by dispersing carbon black or the like. Because it is composed of dielectric materials or conductive materials such as polycarbonate and polyethylene terephthalate,
In the conventional corona transfer method or roller transfer method from the back side of the copy paper 12, when the surrounding temperature and humidity are high, the copy paper 12
absorbs moisture and the electrical resistance of the copy paper 12 becomes extremely low, and the thickness and material of the copy paper 12 change, resulting in changes in the electrical resistance and dielectric constant, and the accompanying change in the transfer electric field, resulting in stable toner production. In contrast to the transfer efficiency that could not be maintained, in this example, stable transfer efficiency can be maintained, and image quality deterioration such as transferred missing images or color unevenness in color images due to transfer failure does not occur. It is possible to achieve high image quality.

[0016]

As described above, the electrophotographic apparatus of the present invention has an application means that applies a voltage having the same polarity as the charging polarity of the toner from the side opposite to the toner adhesion surface of the toner adhesion member to which the toner adheres in accordance with image information. By providing this, an electric field is applied to the toner adhering to the toner adhering member from the opposite side of the toner adhering surface of the toner adhering member to cause the toner adhering to the toner adhering member to be repelled and peeled off from the toner adhering member. This makes it possible to apply an electric field that causes the toner adhering to the toner adhering member to repel and peel off from the toner adhering member evenly to the lowest layer of toner adhering to the toner adhering member, which improves color images, etc. Even if there are areas with a large amount of toner adhesion and areas with a small amount of toner adhesion within the screen, the toner in the bottom layer can be reliably transferred.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus in an embodiment of the present invention.

[Fig. 2] Partially enlarged view of the sheet transfer section in the second embodiment of the present invention.

[Fig. 3] Partially enlarged view of the sheet transfer section in the third embodiment of the present invention.

FIG. 4 is a partially enlarged view of the sheet transfer section in the fourth embodiment of the present invention.

[Fig. 5] Schematic configuration diagram of a conventional electrophotographic device

FIG. 6 is a schematic configuration diagram of another example of a conventional electrophotographic device.

[Explanation of symbols]

1 OPC belt 2 OPC drive roller 3 Intermediate transfer drive roller 4 Charger 5 OPC cleaning device 6 Static eliminator 7 Laser irradiator 8a Developing device 8b Developing device 8c Developing device 8d Developing device 9 Intermediate transfer drum 9a Intermediate transfer belt 10 Cleaning device 11 Intermediate transfer roller 12 Copy paper 13 Repulsion transfer roller 13a Repulsion transfer brush 13b Repulsion transfer blade 13c Repulsion transfer corona 14 Pressure roller 15 Transfer roller 15a Transfer corona 16 Fuser 17 Paper cassette 18 Conveyance roller 19 Static elimination brush

Claims (1)

[Claims] 1. A toner adhering member to which toner adheres in accordance with image information, and a recording medium conveyed while being in contact with the toner adhering surface side of the toner adhering member, the recording medium having a voltage having the same polarity as the charging polarity of the toner. An electrophotographic apparatus characterized in that the electrophotographic apparatus is provided with an application means for applying from the side opposite to the toner adhesion surface of the toner adhesion member.