JPH03240077A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the stain of blurring on an image caused by a transfer memory or the strain of the trace of an APC from occurring by making the primary electrostatic charging potential of the on-image part of an image carrier higher than the specified primary electrostatic charging potential set in an image part. CONSTITUTION:A transferable image corresponding to aimed image information is formed and carried on the surface of the image carrier 1 by an image producing processing means including the primary electrostatic charging means 4 for uniformly electrostatically charging the surface of the image carrier 1, and the transferred image is transferred to a transfer material 9 by a transfer member 2 which is biased and in contact with the surface of the image carrier. As for the primary electrostatic charging potential of the surface of the image carrier by the means 4 in an image forming cycle execution process between the image part and the non-image part on the surface of the image carrier, the electrostatic charging potential in the non-image part is controlled to get higher than the specified electrostatic charging potential in the image part.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image forming apparatus such as a laser beam printer (LBP) or an electrostatic copying machine.

For more details, see rotating tram type, endless belt type, etc. #, an image forming process means including a primary charging means for uniformly charging the surface of an image bearing member such as an electrophotographic photoreceptor or an electrostatic recording dielectric material that travels in an edge-like manner, and transferable image information corresponding to the desired image information is transferred onto the surface of the image bearing member. The present invention relates to an image forming apparatus in which an image is formed and supported, and the transferable image is transferred onto a transfer material by a biased transfer member such as a transfer roller or a transfer heald that is in contact with the surface of an image carrier.

(Prior art v#) For convenience, FIG. 1 shows a schematic configuration of an example of an LBP as this type of image forming apparatus.

This LBP will be explained below as an example.

1 is a rotating drum type electrophotographic photosensitive member as an image carrier, and in this example, it is a negatively charged opcW! with a diameter of 30 mm.
, a light body tram (hereinafter abbreviated as tram). This tram 1 is rotated in the counterclockwise direction of the arrow at a predetermined circumferential speed (process speed).

4 is a corona charger as a primary charging means, and this charger charges the circumferential surface of the rotating tram 1 to -700V in this example.
(dark potential V).

5 is a laser scanner. This laser scanner consists of a semiconductor laser light source, a polygon mirror, an optical element, etc., and is a time-series electric digital digital camera for manually transmitting image information from a host device (not shown) such as a computer, word processor, image reading device, etc. to a printer controller (not shown). A laser beam (emission light) 5a modulated in accordance with an image (pixel) signal is output, and the surface of the rotating tram after primary charging is subjected to main scanning exposure in the direction of the drum generatrix.

By the main scanning by the laser beam 5a and the sub-scanning by the rotation of the tram surface, an electrostatic latent image corresponding to the desired image information is sequentially formed on the surface of the drum (image writing process, image section ).

Reference numeral 6 denotes a developing device, and the static latent image marked E formed on the surface of the rotating drum is sequentially developed as a toner image (transferable image) by this developing device.

2 is a transfer roller as a transfer member.

The one in this example is made of carbon-dispersed EPDM rubber and has a diameter of 16 mm.
The roller is pressed against the surface of the drum with a predetermined pressing force. Reference numeral 3 denotes a power source that applies a predetermined bias to the transfer roller 2. This transfer roller 2
A transfer material (transfer material sheet) 9 is supplied from a paper feeding mechanism (not shown) to the contact nip (transfer section) between the tram 1 and the tram 1 at a predetermined timing (the tip of the toner image area formed on the tram 1 surface or the drum). When the leading edge of the transfer material 9 reaches the transfer section as it rotates, the toner in the image area on the side of the drum 1 relative to the surface of the fed transfer material 9 is fed. Images are transferred one after another.

The transfer material 9 that has passed through the transfer section is separated from the surface of the drum 1 and introduced into a fixing device (not shown), where the image is fixed.

After the transfer, the tram 1 surface is cleaned by the cleaner 7 to remove residual adhesion on the tram surface such as untransferred toner, and the electrical memory is removed by the eraser lamp 8 and electric exposure 8a, and the process is repeated. offered to a statue.

(Problems to be Solved by the Invention) (1) In the case of the reversal development method in the image forming apparatus as in the above example, the transfer member has a polarity opposite to that of the toner (a polarity opposite to the primary charging polarity of the image carrier). ) bias will be added.

For this reason, during the pre-rotation process of the image carrier during the image forming cycle (printing), and between sheets (after the trailing edge of one transfer material passes the transfer section, the leading edge of the next transfer material reaches the transfer section). During the paper non-passing period (non-image area on the image carrier surface) during
When the transfer member to which the above-mentioned reverse polarity bias is applied directly contacts the image carrier surface, there is a possibility that "transfer memory" of the opposite polarity remains on the image carrier surface.

If transfer memory remains on the surface of the image carrier, the primary charging potential (dark potential VO) of the surface of the image carrier in the next primary charging process or, for the portion of the surface of the image carrier where the transfer memory remains, the image other than that portion. It is lower than the surface of the carrier, and is likely to be developed in the developing section, resulting in so-called "fogging stains" on the image.

Dust stains caused by transfer memory are less likely to occur if the image carrier potential at the time of transfer is high, but if the image carrier potential or bright area potential v
This is likely to occur when the temperature is low like L.

Regarding the printer in the above example, the surface of the drum is charged with a negative primary charge, and the surface is subjected to laser scanning exposure 5a to form a latent image in the image area. When the toner image is transferred onto the surface of the transfer material 9 by the transfer roller 2, which has the opposite polarity to the toner, that is, a positive bias is applied, a positive transfer occurs on the tram surface during the non-paper passing period when the transfer roller 2 is in direct contact with the tram 1. Memory tends to remain and cause fogging and stains.

(2) Furthermore, in an image forming apparatus such as the above-mentioned printer that writes an image on the image carrier surface using laser scanning exposure 5a, the light intensity of the light emitted from the semiconductor laser light source modulated by the image signal is corrected to a predetermined level. The step of exposing the image carrier surface to the image carrier surface during the pre-rotation process of the image carrier during the image forming cycle or/and between the sheets (
(hereinafter referred to as APC exposure).

In the APC exposure area of the image carrier surface, the image carrier potential becomes the bright area potential VL and becomes low. Then, by directly contacting this APCi light area with a transfer member to which a reverse polarity bias is applied, a transfer memory remains in the APC exposure area of the image carrier surface, and in the next primary charging process of the image carrier surface, this APC exposure The primary charging potential (dark potential VO) of the transfer memory portion remaining in the area becomes low, and it is developed in the developing section and rA is formed on the image.
6. It is easy to cause a so-called "PC trace".

FIG. 6 is a sequence diagram of a conventional image forming cycle of the aforementioned printer, and the generation of transfer memory by the aforementioned APC exposure area will be explained with reference to this diagram.

(2) By the printer control system (not shown), primary charging is turned on at the same time as the tram 1 is driven to rotate, and the surface of the drum 1 has a dark potential of V. =-700V. This primary charging potential remains constant throughout the entire image forming cycle.

(2) In this example, the application of bias (positive bias) to the transfer roller 2 is turned ON after the pre-rotation period of the tram 1 has ended.

(2) APC: i-light is executed during the pre-rotation period of the drum 1, which is a non-sheet passing period, and between sheets.

(2) The potential of the first surface of the tram exposed to APC drops to the bright area potential VL=100V.

(2) In each APCi light, the APC exposure area of the drum 1 surface during the tram pre-rotation period is the transfer bias between the drum 1 and the transfer roller at the transfer section since the transfer bias for the transfer roller 2 is turned off during this period in this example. Even if 2 is in direct contact with the APC exposure area, no transfer memory remains in the APC exposure area, and the potential of the 1APc exposure area is maintained at the bright area potential VL of -100V.
Next, by receiving a primary charge, the dark potential becomes -700V.

, and there are no APC traces on the image.

(2) However, due to the direct contact of the transfer roller 2 to which a positive bias is applied at the transfer section, the potential of the drum surface between each paper is -10.
Since the potential of the drum surface in the APC exposure area is originally lowered to a bright area potential vL of -100V by APC exposure, the potential is further lowered to the positive side, and a positive transfer memory M remains.

Then, in the area of the drum surface between each paper, the area other than the APCg light area where the potential has decreased to -100V is then subjected to a primary charging process to have a dark area potential of -700V. Returning to , the potential of the APC exposure area that has become a positive transfer memory M remains a dark area potential V of -7-00V even after the primary charging process.

It does not reach the point where it returns to , and the dark potential becomes lower than that.
This low potential area is developed in the developing section and rAPC is formed on the image.
It will appear in the form of dirt as a trace.

APCii of the first drum surface during the drum pre-rotation period of (■) above
If a positive bias is applied to the transfer roller 2 during this drum pre-rotation period in the W light region as well, a positive transfer memory or residual rAPC trace will be generated in the same way as described above.

The present invention aims to prevent the occurrence of "fogging stains" and rAPC marks on images caused by transfer memory as described in (1) and (2) above.

(Means for Solving the Problems) The present invention forms and carries a transferable image corresponding to target image information on the surface of the image carrier using an image forming process means including a primary charging means for uniformly charging the surface of the image carrier. , an image forming apparatus of a type in which the transferable image is transferred to a transfer material by a biased transfer member in contact with the image carrier surface, and the image carrier surface is primarily charged by a primary charging means in the image forming cycle execution process. This image forming apparatus is characterized in that the processing potential is controlled so that the processing potential of the image portion and the non-image portion of the surface of the image carrier is made stronger than the predetermined charging processing potential of the image portion.

The present invention also provides an image forming apparatus as described above, in which the strengthening control of the primary charging potential for the non-image portion of the surface of the image bearing member is performed during the pre-rotation process of the image bearing member during execution of an image forming cycle or/and when the paper is rotated. During the process, an image is written on the image carrier surface by scanning exposure using light emitted from a semiconductor laser light source modulated by an image signal, and the light intensity of the emitted light is corrected and controlled to a predetermined level, or an image forming cycle is executed. It is characterized in that it is performed during the pre-rotation process of the image carrier and/or between sheets.

(Function) In other words, when the biased transfer member comes into direct contact with the image carrier surface, the primary charging potential as the dark area potential and the APC
The non-image area of the image carrier where the bright area potential after exposure further decreases (
Regarding the primary charging potential of the non-sheet passing area), in anticipation of the degree of decrease mentioned above, even if the potential decreases, it is permissible not to leave transfer memory that can appear as fog stains or APC trace stains on the image. This method effectively prevents fog stains and APC trace stains on images caused by transfer memory. can.

(Embodiment) The image forming apparatus of this embodiment is the same as the printer (LBP) shown in FIG. 1 above.

Sequence example 1 (Fig. 2) ■.The printer control system (not shown) turns on the primary charging at the same time as the rotation of the tram 1, and changes the primary charging processing potential of the drum 1 surface by the primary charger 4 to the drum ■ in the image portion of the pre-rotation period and each image forming cycle. = -700V, and a higher potential V between each paper. up=-soov
The primary charger 4 is drive-controlled so that.

(2) Application of bias (positive bias) to the transfer roller 2 is turned on after the previous rotation of the tram 1 is completed.

(2) APC exposure is performed during the pre-rotation period of tram l, which is a non-sheet passing period, and between sheets.

(2) Since the bias application to the transfer roller 2 is OFF during the drum pre-rotation period, the APC exposure of the first surface of the drum during the drum pre-rotation period is performed in the same way as explained in section (2) in the conventional sequence shown in FIG. No transfer memory remains in the area due to direct contact of the transfer roller.

■, Primary charging potential V between each paper. As mentioned above, since up is originally as high as -5oov, the potential V Lup of the APC exposure area on the tram surface due to APC exposure between each paper drops to only about -200V.

The tram potential V between each sheet. UP ” Regarding V Lup, due to direct contact of the transfer roller 2 to which a positive bias is applied at the transfer section, the potential V Dup of the drum surface portion other than the APC exposure area drops to about -200V.
Although the potential VLup of the drum surface portion in the APCu light area further decreases, the potential VLup after APC exposure is 1200.
Since the voltage V is originally high, the voltage cannot be lowered to a positive potential, and no positive transfer memory remains. The potential of the drum surface portion between the sheets that has been lowered due to direct contact with the transfer roller 2 returns to vDup=-800V in the drum surface portion as a whole upon receiving the next primary charge.

In this way, the primary charging potential V Dup for the portion of the drum surface that directly contacts the transfer roller 2 or the drum 1 where bias application is ON, such as between each paper interval (period of paper non-passing to the transfer section) in this example. is a predetermined primary charging potential V for the image area. The occurrence of transfer memory can be prevented by controlling the temperature to be higher than that. In particular, areas where the drum potential is at the bright potential VL, such as the APC exposure area on the tram surface, come into direct contact with the transfer roller to which a bias is applied, further lowering the potential and causing the next primary charging of this area. The generation of APC traces on images due to a decrease in processing potential is effectively prevented.

Further, the primary charging of the image area on the drum surface in each image forming cycle is a predetermined dark area potential V. Because the charging process is carried out in the 300°C, there is no need to change the development conditions.

Sequence Example 2 (Fig. 3) In Sequence Example 1 described above, the bias application to the transfer roller 2 was turned off during the tram pre-rotation period, but in the sequence of this example, the primary charging and the transfer roller 2 are performed at the same time as the tram is driven. Bias application is turned on. In this case, the APC to be executed during the tram pre-rotation period
In order to prevent the occurrence of APC traces on the image due to exposure, the t-order charging potential of the drum surface during the drum pre-rotation period is also set to VDup=-800V, as in the case between each sheet. The rest is the same as sequence example 1.

Sequence Example 3 (FIG. 4) In Sequence Example 1, the primary charging potential V Dup on the surface of the drum between each sheet is set to 1800 V over the entire area, but in the sequence of this example, the primary charging potential V Dup is set to V Dup. =-700V to vDu,,=-8oov synchronize the timing with APCiii light and AP
C. V limited to only the portion of the drum surface that is exposed. up
=-soov. The rest is the same as sequence example 1.

Even if this is done, the effect of preventing the occurrence of APC marks is not changed at all, and the occurrence of APC marks can be prevented.

Sequence Example 4 (FIG. 5) In the sequence of this example, (1) At the same time as the rotation of the tram 1, primary charging and bias application to the transfer roller 2 are turned on.

(2) The primary charging potential of the tram surface by the primary charger 4 is set to V=-700V in the image area of each image forming cycle, and a higher potential VDup"800V is set during the drum pre-rotation period and between each sheet. At the same time, during this pre-rotation period of the drum and between each paper, the primary band of only the drum surface portion where APC exposure is performed is set to a higher potential V'Dup=-1000V in synchronization with APC exposure. The primary charger 4 is driven and controlled.

In the case of this example, the drum potential after laser exposure (after APC exposure) during the drum pre-rotation period and between each sheet is determined by such primary charging treatment. It becomes constant at ``up''-5oov, and has the effect of completely preventing the occurrence of APC traces.

(Effects of the Invention) As described above, according to the present invention, it is possible to prevent the occurrence of fog stains and APC trace stains on images caused by the aforementioned transfer memory, which have been problems in this type of image forming apparatus. The intended purpose is well achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an example of a laser beam printer. 2 to 5 are diagrams each showing an example of a sequence of an image forming cycle according to the present invention. FIG. 6 is a conventional sequence diagram. 1 is a rotating drum-type electrophotographic photoreceptor as an image carrier;
4 is a corona charger as a primary charging means, 5 is a laser scanner, 6 is a developer, 2 is a transfer roller as a transfer member, 3 is a bias application E'S, 7 is a cleaner, 8 is an eraser lamp, 9 is a Transfer material.

Claims (3)

[Claims] (1) A transferable image corresponding to desired image information is formed and carried on the image bearing surface by an image forming process means including a primary charging means that uniformly charges the image bearing surface, and the transferable image is brought into contact with the image bearing surface. The image forming apparatus uses a biased transfer member to transfer the image to the transfer material, and the primary charging potential of the image bearing surface by the primary charging means during the image forming cycle execution process is applied to the image portion of the image bearing surface. An image forming apparatus characterized in that the non-image area is controlled to have a higher charging potential than the predetermined charging potential of the image area. (2) A claim characterized in that the strengthening control of the primary charging potential for the non-image area on the surface of the image carrier is performed during a pre-rotation process of the image carrier during execution of an image forming cycle and/or between sheets. 1. The image forming apparatus according to 1. (3) An image is written on the surface of the image carrier by scanning exposure using light emitted from a semiconductor laser light source that is modulated by an image signal, and the process of correcting and controlling the light intensity of the emitted light to a predetermined level is performed during execution of an image forming cycle. 2. The image forming apparatus according to claim 1, wherein the image forming process is performed during a pre-rotation process of the image carrier and/or between sheets.