JPS61109072A - Image recording method - Google Patents

Abstract

PURPOSE:To make the surface potential of a photosensitive body uniform and to prevent an image defect during next image formation by turning off a primary electrostatic charger, transfer charger, and preliminary exposing means in order when the photosensitive body is stopped after image formation. CONSTITUTION:While the primary electrostatic charger 4 is turned off at a point T6 of time after the surface part of the photosensitive body which is transferred and charged electrostatically at time T5 of the end of transfer passes through the primary charger, a switch 17 is placed at the side of a power source 15 to adjust a current so that the surface potential of the photosensitive body after the transfer of the transfer charger 12 is nearly zero. Then, the operation of the charger 12 is stopped when the surface part of the photosensitive body which is charged by the primary charger 4 reaches a transfer position T at time T6, or at time T7 after it. The potential of the entire periphery of the photosensitive body is lowered almost to zero by the transfer charger 12 at this point of time. A light source 3 turns off when the surface part charged by the primary charger 4 reaches the preliminary exposure part P at time T7, or at time T8 after it. Thus, an image defective during next image formation is prevented.

Description

[Detailed description of the invention] A. Object of the invention [Industrial application field] Primary charged fist image exposure to photosensitive recording medium - reversal development -
-Relates to an image recording method in which the steps of transfer charging, first, and pre-exposure with polarity opposite to the next charging are performed sequentially.

[Conventional technology]

In the image recording method consisting of the above process, after the transfer, the photoreceptor is placed between the areas that have been irradiated with the beam, the areas that have not been irradiated with the beam, and the areas that have directly received the transfer corona discharge without being shielded by the transfer material. produces a surface potential difference of

Therefore, if the photoreceptor 2 is stopped immediately after the process ends, the surface potential will become non-uniform when the next process starts, resulting in a so-called charged memory phenomenon. This phenomenon is particularly severe when a photoreceptor charged with a polarity without photosensitivity is left unused.

Therefore, as a means to make the surface potential of the photoreceptor uniform,
A method has been proposed in which the actions of transfer charging and -next charging φ pre-exposure are sequentially stopped after completion of transfer. The aim is to charge the photoreceptor to a polarity that is sensitive to it, and to attenuate the surface potential through primary pre-exposure to make it uniform. However, in general, exposure to a charged polarity with photosensitivity,
This accelerates the deterioration of the photoreceptor, including image exposure, and causes phenomena such as a decrease in dark area potential and an increase in bright area potential.

Particularly in the case of organic photoreceptors, at the initial stage of deterioration, there is no change in potential, but local attenuation of surface charges occurs during negative charging. This local surface charge decay is.

In the normal development method, the developer is attached to the dark potential area by the electrostatic attraction between the developer charge and the surface charge on the photoreceptor, so the adhesion force of the developer decreases, but it is difficult to distinguish on the image, which is a problem. It is not.

However, in the reversal development method, the adhesion of the developer is mainly caused by the peripheral electric field formed at the boundary between the bright area potential and the dark area potential. This causes the developer to adhere to the image, resulting in a so-called black spot or fog phenomenon on the image.

Therefore, in a system using an organic photoreceptor as a photoreceptor, the attenuation of surface charge due to pre-exposure tends to cause black spots or fogging, which is inappropriate.

[Problem that the invention seeks to solve]

In view of the above-mentioned points, this invention uniformizes the surface potential of the photoreceptor when the photoreceptor is left to stand after the completion of transfer until the next electrophotographic process is started. Prevent image defects.

Another purpose is to suppress deterioration of the photoreceptor and obtain clear image quality without image abnormalities.

Structure of the invention [Means for solving the problems] Primary charging/image exposure/reversal development for a photosensitive recording medium -
- In an image recording method that sequentially performs a transfer charge with a polarity opposite to that of the secondary charge, and then a pre-exposure step, the surface of the photoreceptor is subjected to transfer charge at the end of transfer when the transfer material passes through the transfer section after image formation. First, the primary charging action is stopped after the part passes through the primary charging part, and the transfer charging action is stopped when the surface part of the photoreceptor that has undergone the primary charging action passes through the transfer charging part, The pre-exposure is stopped when the surface portion of the photoreceptor which has been subjected to the transfer charging action passes through the pre-exposure section. An image recording method characterized in that the image forming process is terminated by controlling as follows.

[For production]

In FIG. 1, a photoreceptor 2 which has been uniformly charged and photosensitized by a negative charger 4 is exposed to a laser beam 6, and is reversely developed by a developer 10. The developed image is transferred to a transfer material 11 at a transfer section T by a transfer charger 12, and the transfer material is transferred to a fixing device 13.
The toner image is fixed.

On the other hand, the surface of the photoreceptor after the transfer is cleaned by a cleaning device 14, the surface potential is attenuated by pre-exposure by the lamp 3, and the photoreceptor is once again primarily charged to repeat the cycle.

When the image forming process is completed, the photoreceptor is stopped and left to stand.The present invention relates to processing of the photoreceptor after the transfer is completed. The relationship between the current value of the transfer charger and the surface potential of the photoreceptor is shown in FIG.

That is, the curve A@B is the dark area potential VD and the light area potential ML in the developing area, and the curve C is the potential after transfer charging. When the transfer current is increased, the surface potential of the photoreceptor after transfer changes from the same polarity to the opposite polarity, and becomes zero potential at the inflection point P2.

The present invention utilizes this phenomenon, and the surface portion of the photoreceptor that was charged at the time of transfer completion when the transfer material 11 passed through the transfer portion T, after passing through the primary charging portion,
First, the charging action of the primary charging section C is stopped, and the surface potential of the photoreceptor subjected to the above-mentioned secondary charging action is lowered (to a range of ±50 V, more preferably to approximately 0 V) due to the transfer charging action. Next, a pre-exposure is applied to the surface of the photoreceptor to eliminate some surface potential.

〔Example〕

FIG. 1 shows an example of a laser beam printer implementing the method of the present invention. The so-called Carlson process is used as the electrophotographic process.

In the figure, reference numeral 1 denotes a drum having an electrophotographic photoreceptor layer (for example, phthalocyanine-based organic photoconductor or selenium) 2 on its circumferential surface, and the photoreceptor 2 is first rotated in the direction of the arrow at zero rotation in the photosensitive charging section C. A corona charger (-charger) 4 uniformly charges the surface of the photoreceptor. When the photoreceptor 2 is an N-type photoconductor such as the above-mentioned phthalocyanine-based organic photoconductor, the charge polarity is negative by the charger 4, and when it is a P-type photoconductor such as selenium, it is positive. Note that 5 is a grid provided in the charger 4 and is grounded via a voltage generating element, and when a corona discharge current flows, a constant voltage is applied to the grid, and the surface potential of the photoreceptor by the charger 4 is kept constant. is configured to control the

The photoreceptor 2, which has been photosensitized and charged, is transferred to the primary image exposure section E.
At this point, the laser beam 6 is scanned and exposed using a laser beam 6 modulated in accordance with the image information to be recorded. This laser beam 6 is emitted by a semiconductor laser 7 which is driven to blink in accordance with the recorded image information.

The light is swept by a rotating polygon mirror 8 and imaged into a spot on the photoreceptor 2 by a lens 9. Note that the wavelength of this laser beam is approximately 770 to 1800 nIm.

The photoreceptor has sufficient sensitivity to beams in this wavelength range. stomach. Regardless of the deviation, this laser beam exposure attenuates the surface potential of the photoreceptor in the area irradiated with the beam, and VL
Thus, an electrostatic latent image is formed with the surface potential Vo of the non-irradiated portion. In addition, usually IV of>IV t, l≧
0 Theal.

The latent image is then developed by a developing device 10 using charged toner in a developing section.

In the case of a laser beam printer or a microfilm printer that uses negative film, toner is attached to the exposed part of the photoconductor 2 (bright area, that is, the part where the potential is ■), and the light of the photoconductor 2 is A developing method that does not substantially allow toner to adhere to the unexposed portion (dark area 1, that is, the portion where the potential is Vo), so-called reversal development, is often applied.

In the example shown in FIG. 1, a reversal development method is applied as the development method. Therefore, the developing device 10 supplies toner charged to the same polarity as the charging polarity by the primary charger 4 (that is, if the charging polarity of the charger 4 is positive, the toner is positive; if the charging polarity of the charger 4 is negative, it is negative) to the photoreceptor. In order to obtain a good developed image, it is preferable that a developing bias voltage having the same polarity as the charging polarity of the charger 4, preferably a developing bias voltage having a value between Vt and VD, be applied to the developing device IO.

The developed image obtained in the development section is then transferred to the transfer section T.
, the image is transferred to a transfer material 11 being conveyed in the direction of the arrow under the action of a transfer corona charger 12. When the reversal development is employed, the charging polarity of the charger 12 is opposite to the charging polarity of the primary charger 4. That is, if the photoreceptor is of N type, it is positive, and if it is of P type, it is negative. Generally, even if the photoreceptor is charged by this transfer charging, the photoreceptor exhibits no or very little leading charge.

The transfer material 11 that has passed through the transfer station T is guided to a fixing device 13, where the toner image is fixed. On the other hand, toner remaining on the surface of the photoreceptor after transfer is cleaned by a cleaning device 14 in a cleaning station C9. After cleaning, the photoreceptor 2 is exposed to light by a pre-exposure lamp 3 to erase residual potential, and is charged again by a primary charger 4.

The present invention removes the charging memory of the photoreceptor that has passed through the transfer section, and the photoreceptor 2 starts rotating at time 6 To, the process of which will be explained with reference to the time chart of FIG. Simultaneously with the start of rotation of the photoreceptor, the pre-exposure light source 3 starts lighting, and the primary charger 4 for photosensitization also starts operating.

However, the start of lighting of the lamp 3 and/or the start of operation of the charger 4 do not have to be at the same time as the start of rotation of the photoreceptor 2, but may be performed before or after the rotation of the photoreceptor 2. It is preferable to do this after the start of the process in order to avoid locally exposing the photoreceptor to a large amount of light or applying a large amount of corona discharge.

The transfer charger 12 turns on the switch 17 to be described later to the power source 1 at time τm.
6 and start operation. It is preferable that this time T is a time after the time when the photoconductor portion that has started being charged by the primary charger 4 reaches the transfer station T. This is because when the transfer charger 12 acts on the body surface portion, the shameful portion is strongly charged with a polarity opposite to that charged by the charger 4, and this may become a charging memory. Therefore, it is preferable that the surface portion of the photoreceptor where the transfer charger 12 starts to act is charged in advance with the primary charger 4 having the opposite polarity to that of the charger 12. In this way, the photoreceptor 2 matches the polarity of the transfer charger 12. Since it is no longer strongly charged, it is effective in preventing the above-mentioned disadvantages (in the case of an N-type photoreceptor, positive charges are difficult to attenuate, and in the case of a P-type photoreceptor, negative charges are difficult to attenuate).

The above-described FIG. 3 shows the relationship between the current value of the transfer charger 12 and the surface potential of the photoreceptor.

On the other hand, the relationship between the transfer current and the transfer efficiency (indicating what percentage of the toner on the photoreceptor is transferred to the transfer paper) is as shown in FIG. The transfer efficiency reaches a peak value at P+ (point of transfer current I), and thereafter decreases due to reverse transfer. P3 (point of transfer current I3) is a point with practical transfer efficiency and no image disturbance, and P2 (point of transfer current 2) is a point with zero potential after transfer. To prevent image distortion when , instead of 0) the value of 3 is used
Generally, 11 <I2 <I3, but sometimes EI2 and I3 are almost the same eI2 - If EI4 is different, when carrying out the present invention, the transfer charging transformer should have a transfer current of 12. It is necessary to design them separately into 1'5 and 16, which uses a transfer current of 3. and trance 1
5-16 is selectively connected to the charger 12 by a switch 17. In Figure 2, transcription ■ and transcription ■ are for each power supply 1.
5φ16 is connected to the charger 12.

If ZIII3 are almost the same, you only need to use one power supply that sets the transfer current to I2 (': I3) or I3 (''5 to 2), and turn on the transfer charge at the transfer ■ timing. Turn off.

Laser beam 6 modulated by recorded image information signal
At time T2, exposure of the photoreceptor 2, which has been pre-exposed with the light source 3 and uniformly sensitized and charged with the charger 4, is started. The electrostatic latent image formed by the beam exposure is reversely developed by the developing device 10 as described above, and the toner image thus formed is transferred to the transfer material 1 that has been conveyed in synchronization with the leading edge of the image.
1. The point in time when the leading edge of the transfer material 11 reaches the transfer station T is time T3. Then, at time T4, the beam exposure is completed.

The rear end of the transfer material 11 passes through the transfer station after the time Ts when the toner image formed by development has been transferred to the transfer material.

Now, in the present invention, at time T6 after the time when the surface portion of the photoreceptor that has received the transfer charge at the transfer end time T5 passes through the charger, the switch is first turned off at the same time as the charger 4 is turned off. 17 is switched to Tj and the source 15, and the operation of the transfer charger 12 is adjusted so that the surface potential of the transfer photoreceptor becomes approximately zero (as mentioned above, if points P2 and 23 are almost the same, (This process does not need to be performed, and the same current is used for the time of transfer (2).) Next, at time T6, the portion of the surface of the photoreceptor on which the primary charger 4 acted reaches the transfer station T, or at a later point. At time T7, the operation of the charger 12 (for transfer) stops.

At this point, the transfer charger 12 brings the potential of the photoreceptor to approximately zero over its entire circumference. and.

The light source 3 is turned off at the time when the surface portion of the photoreceptor on which the primary charger 4 acted reaches the pre-exposure station P at time T7, or at time T8 later. As a result, the surface of the photoreceptor, which has been brought to approximately zero potential by the action of the transfer charger 12,
All are exposed to light by the light source 3 and the potential memory is erased. In this way, the entire circumference of the photoreceptor 2 has a uniform very low potential to zero potential, and even if the photoreceptor is left unattended, no inconvenient charging memory is formed, and there is no deterioration of the photoreceptor that would impede its use. Then, when the light source 3 is turned off, the rotation of the photoreceptor 2 is stopped at the same time T8 or later.

Incidentally, the developing device 10 may be operated for only one period during which the electrostatic latent image formed on the photoreceptor by exposure with the beam 6 passes through the developing section, but it may be operated for any length including this period. However, in the case of reversal development, the toner adheres to the bright area potential area, so in order to prevent excess developer consumption, the photoreceptor surface area where the primary charger 4 starts to act is From the moment you reach the developing section, the charger 4
It is desirable to set the value appropriately up to the time when the surface portion of the photoreceptor reaches the developing section after the completion of its action.

Furthermore, the present invention is applicable not only to laser beam printers, but also to copying machines that project an image of an original onto a photoreceptor through a lens, microfilm printers, and exposure of information light corresponding to recorded image information using an LED array or a liquid crystal shutter array. It can also be applied to electrophotographic methods that form latent images.

C. Effects of the Invention As described above, the present invention provides a photosensitive (-) charger, a transfer charger, a
The surface potential of the photoreceptor is attenuated to a uniform low potential to zero potential by stopping the action of each pre-exposure means in order, and as a result, the photoreceptor is left at rest with the charging memory and optical memory erased. This makes it possible to improve the image quality during the next image formation. Furthermore, it has become possible to suppress deterioration of the photoreceptor and extend its life.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of an example of an electrophotographic method to which the present invention can be applied, Fig. 2 is a time chart showing the steps of an embodiment of the present invention, and Fig. 3 is a diagram showing transfer current, surface potential of the photoreceptor, and transfer efficiency. FIG. 4 is a graph showing the relationship between transfer current and transfer efficiency. 2 is an electrophotographic photoreceptor, 3 is a pre-exposure light source, 4 is a primary charger for photosensitization, and 12 is a transfer charger.

Claims (2)

[Claims] (1) In an image recording method in which a photosensitive recording material is sequentially subjected to the steps of primary charging, image exposure, reversal development, transfer charging with the opposite polarity to the primary charging, and then pre-exposure, after image formation, the transfer material is transferred. After passing through the primary charging section, the surface of the photoconductor that was receiving the transfer charge at the end of the transfer stops the primary charging action, and the surface of the photoconductor that has received the above primary charging action stops. Image formation is performed by controlling the transfer charging action to stop when the photoreceptor passes through the transfer charging section, and to stop the pre-exposure when the photoreceptor surface area subjected to the transfer charging action passes through the pre-exposure section. An image recording method characterized by terminating the process. (2) The image recording method according to claim (1), characterized in that the transfer current is adjusted.