JPH01273077A - Image forming method - Google Patents

Abstract

PURPOSE:To prevent image disturbance due to the influence of reverse transfer by electrostatically charging an intermediate transfer body in initial transfer in the case of multiple transfer and said body in the subsequent transfer after appropriately destaticizing said body. CONSTITUTION:In the case of multiple transfer, at the end of first exposure - development - primary transfer process, a destaticizing charger 15 destaticizes an intermediate transfer belt 10 in the 2nd and subsequent transfers, following which a belt charger 12 recharges the belt 10. Thus, electrostatic charge in a part covered with a visible image on the belt 10 is weakened, which is preferable in the 2nd and subsequent transfers. As a result, identical polarity restitution of the intermediate transfer belt 10 and a toner image and its reversely transfer onto the photosensitive body 6 can be restrained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention electrostatically transfers images of each color multiple times from a photoreceptor onto an intermediate transfer member to form a multicolor image, and transfers this at one time. It relates to an image forming method that can be transferred onto a material, and is used, for example, in copying machines and laser beam printers.

(Conventional technique (+ti)) For example, Japanese Patent Publication No. 49-209 (Conventional Example 1) describes a device that applies electrophotography to print multicolor images on flexible materials such as cloth. is multiple-transferred to an intermediate transfer body,
A multicolor image formed on this intermediate transfer member is transferred to a flexible material under pressure under an electrostatic voltage.

In addition, after sequentially multiple-transferring each color image formed on a photoreceptor to an intermediate transfer member to form a multicolor image on the intermediate transfer member, the image is electrostatically re-transferred onto a transfer paper. For example, a device for forming multicolor images without deviation is disclosed in Japanese Patent Publication No. 54-28740.
This is already known from Japanese Patent Laid-Open No. 147166/1983 (Conventional Example 3). In this device, the image on the photoreceptor 2 is transferred onto the intermediate transfer member by a transfer charger operated from the back side of the belt at a transfer portion where the intermediate transfer heald contacts the photoreceptor.

(Problem to be Solved by the Invention) However, according to the transfer method of Conventional Example 2.3, the action of the transfer charger operated from the back side of the intermediate transfer heald is as follows.
Although it is powerful, it is not concentrated at the transfer position where the photoreceptor and belt are in contact. Therefore, the action of the transfer charger extends to the pre-transfer portion of the surface of the photoreceptor near the transfer position, causing transfer. In this pre-transfer portion, the photoreceptor and the intermediate transfer heald are not yet in contact with each other and there is a gap.

Therefore, the transfer here (hereinafter referred to as pre-transfer) is not performed normally and the transferred image is disturbed.

Conventional Example 1 does not specifically mention transfer. Neither the above-mentioned problems are raised nor solutions are disclosed.

The present invention allows a charged intermediate transfer member to repeatedly come into contact with a photoreceptor, thereby performing each transfer in multiple transfer without being affected by the previous transfer, and also performing a second charge after static electricity removal during transfer after the first transfer. It is an object of the present invention to provide an image forming method that guarantees stable transfer without the adverse effects of recharging and provides high-quality images.

(Means for Solving the Problems) In order to achieve the above objects, the present invention develops an electrostatic latent image on a photoreceptor, and transfers the developed image to an intermediate transfer member. An image forming method in which after electrostatic transfer, the developed image on the intermediate transfer member is electrostatically retransferred onto the transfer material, and the surface of the intermediate transfer member is charged and brought into contact with the photoreceptor. The developed image is electrostatically transferred from the photoreceptor, and this transfer is repeated several times to perform multiple transfers, but the intermediate transfer member is charged during the first transfer, and the intermediate transfer member is appropriately neutralized during subsequent transfers. It is characterized by being carried out later.

(Function) The present invention has the above structure, and in order to transfer the developed image formed on the photoreceptor onto the intermediate transfer member, the intermediate transfer member is charged and brought into contact with the photoreceptor. It can be transcribed by As a result, the charger that charges the intermediate transfer member does not need to be at the transfer position, and it is possible to prevent its action from reaching the transfer portion and causing pre-transfer. In multiple transfer, the intermediate transfer body is charged not only during the first transfer but also after the intermediate transfer body is properly neutralized during subsequent transfers, so the intermediate transfer body must always be given a predetermined charge necessary for transfer. I can do it. In addition, recharging is performed by once removing the static electricity from the intermediate transfer member and the transferred developed image, and then applying a predetermined potential such as - to the exposed surface of the intermediate transfer member and the developed image. By weakening the charging in the covered portion, homopolar repulsion due to recharging on the intermediate transfer member and the intermediate transfer member can be suppressed.

(Embodiment) Hereinafter, a first embodiment in which the present invention is applied to a color copying apparatus will be described with reference to FIGS. 1 to 4.

In FIG. 1, an optical system consisting of an exposure lamp 2, first to fifth mirrors 3a to 3e, a lens 4, and a color separation filter unit 5 is arranged below a document table glass plate 1 on which a document is placed. . As shown in FIG. 2, in the color separation filter unit 5, a filter plate 5B, a green filter plate 5G, and a red filter plate 5R are supported by a frame 51 in parallel, and a drive motor 52 and a red filter plate 5R are supported in parallel. At the position sensors 53a and 53b, the filter plate 5B,
The structure is such that one of 5G and 5R can be selectively positioned in the exposure optical path.

A photosensitive tram 6 is provided beneath the fifth mirror 3e. An erase lamp 7 is provided around the photoconductor tram 6.
A charger 8, a developing section 9, an intermediate transfer roller 0, and a drum cleaner 11 are sequentially arranged in the rotational direction of the photoreceptor 1 and the ram 6.

The developing section 9 includes a yellow developing device 9Y and a macenter developing device 9Y.
M and a cyan developer 9C are installed. Further, each developing device is equipped with a developing sleeve, a tip shank, a 1-toner concentration detector, a toner replenishing device, and the like.

The intermediate transfer belt 10 is electrically conductive as shown in FIG.
Urethane rubber (103-104 as s 1o a
It is composed of a flexible endless heald in which a polytetrafluoroethylene layer (10"Ω・C1n or more) is formed as a dielectric layer 10b on the surface of the dielectric layer 10b. According to experiments, the dielectric layer If the relative dielectric constant of 10b is 2 or less and the volume resistivity value is 1016 Ωcm or less, the charge retention ability will decrease, and even if it is charged, the charge will decrease quickly.Also, if the relative dielectric constant is 4 or more , volume resistivity is 1017Ω
- If it is more than cm, the charging and static elimination efficiency will be poor and it will be difficult to charge and eliminate static electricity. Next, when the resistance value of the conductive base material 10a becomes 104 Ω·cm or more, the conductivity deteriorates and charging becomes uneven and unstable, and problems such as a large potential drop during toner image transfer occur. .

From the above, the dielectric layer should have a relative permittivity of 2 to 4, a volume resistivity of 10'6 to 10'7 (Ω・cTII), and a conductive profiteering with a volume resistivity of 105 (Ω・cm) or less. As a result, charging and static elimination efficiency is good, and the charge caused by charging can be stably maintained for a relatively long time without being affected by the environment, making it effective as an intermediate transfer member.

Around the intermediate transfer belt 10, there is a heald charger 12 for primary transfer, which transfers the image from the photoreceptor drum 6 to the intermediate transfer belt 10, and a secondary charger 12, which transfers the image from the intermediate transfer belt 10 to the transfer paper S. A transfer charger 13, a separation charger 13a, a bell 1 static elimination charger 15, a heald cleaner 16, and the like are provided.

Further, as shown in detail in FIG. 3, the intermediate transfer heald 10 includes a heald charging roller 17 facing the heald charging charger 12, a pressure roller 18 facing the photosensitive drum 6, and a secondary transfer roller 19. It is stretched by five straight rollers including a heald cleaner roller 20 and a tension roller 14, and the dielectric layer 10b on the surface faces the photosensitive drum 6. The pressure roller 18 is moved by the solenoid F21, so that the intermediate transfer heald 10 can be moved between a first position where the intermediate transfer heald 10 is pressed against the photoreceptor drum 6 at the primary transfer position and a second position where it is separated from the photoreceptor tram 6. It is configured to switch between. 22 is a solenoid that presses and separates the heald cleaner 16 from the intermediate transfer bell 1-10.

A paper feed cassette 23 is provided on the left side of the secondary transfer section, and is configured to feed the transfer paper S sent out by a paper feed roller 23a to the secondary transfer section via a timing roller 24. A transfer paper conveyance heald 25 is provided on the right side of the secondary transfer section, and sends the transfer paper S after the secondary transfer to a fixing device 26.

Next, to explain the operation, the original placed on the original platen glass 1 is sequentially scanned in the horizontal direction, and the reflected light is reflected from the first to third mirrors 3a to 3C1 color separation filter units 5
, an image is formed on the photosensitive surface of the photosensitive drum 6 via the lens 4 and the fourth and fifth mirrors 3d and 3e. After being exposed and neutralized by the photosensitive drum 6 and the erase lamp 7, it is charged to, for example, a constant negative potential by the charger 8, and is rotated and exposed in synchronization with the scanning. When the photosensitive surface is irradiated with reflected light from the original, the surface potential changes depending on the intensity of the light, and an electrostatic latent image is formed.

electrostatic latent image 4J, yellow developer 9Y of the developer section 9
, magenta developer 9M, or cyan developer 9C.
The image is developed with toner of each color. For example, in the color separation filter unit 5, the blue filter plate 5
When B is located in the optical path, the yellow developer 9Y, which is the complementary color of blue, is selected, and the other developers 9M and 9C scrape off the developer on the developing sleeves with the ear-cutting shutters at the rear of each developing sleeve. After that, the yellow developing device 9Y is driven, and the electrostatic latent image is developed with yellow toner and made visible. Note that the toner is charged to, for example, a positive potential, which is opposite to that of the photoreceptor tram 6.

The intermediate transfer belt 10 is driven at the same speed as the photoreceptor drum 6 in synchronization with the photoreceptor tram 6, and as it passes through the belt charger 12 located in front of the next transfer section, as shown in FIG. Receives electrical charge. Belt charger 12
A negative potential is applied to the intermediate transfer heald 10.
dielectric layer 10b is negatively charged. This charging is performed with high efficiency due to the material of the dielectric layer 101+ and the fact that it is performed directly from the surface of the dielectric layer 10)+.

Due to this charging, a --like negative potential is formed on the surface of the dielectric layer 10b. This state is stabilized by the bank up of the conductive base material 10a on the back surface of the dielectric layer 10b, is less susceptible to environmental influences, and can be maintained for a relatively long time.

On the other hand, at the primary transfer position, the pressure roller 18 presses the intermediate transfer heald 0 against the photosensitive drum 6 under the action of the solenoid 21 .

When the charged portion of the intermediate transfer belt 10 comes to the primary transfer position in this state, the yellow toner image T7 with a positive potential on the photoreceptor drum 6 is transferred to the intermediate transfer position as shown in FIG. 6 due to the negative potential on its surface. It is transferred onto Heald 10. This transfer is not affected by the fact that the belt charger 12 is far from the primary transfer position, and is reliably achieved without any disturbance caused by the previous transfer due to the stable and predetermined surface potential of the intermediate transfer heald 10. be done. Thereafter, the photosensitive surface of the photosensitive drum 6 is cleaned by a drum cleaner 11, and the exposure-development--next transfer process is completed.

In the case of full-color copying, when the first exposure, development and primary transfer steps for yellow are completed, the green filter plate 5G is selected in the color separation filter unit 5 and positioned on the optical path. The photosensitive surface of the photosensitive drum 6 is exposed to the reflected light from the original that has passed through the document, and an electrostatic latent image is formed. This electrostatic latent image is visualized by a magenta developer 9M, which is a complementary color to green, and is visualized by the intermediate transfer belt 10.
A magenta toner image T is transferred onto the upper yellow toner image T7.

During this second transfer, the potential of the intermediate transfer belt 10 decreases from the first transfer (for example, about 200 V) and the transfer ability weakens, so in order to prevent this, it must be recharged. conduct. However, if recharging is simply performed, the toner image T7 will be reversely transferred to the photoreceptor drum 6 side due to the repulsion between the intermediate transfer belt 10 whose potential has been restored and the negatively charged toner image TV thereon. There is.

Therefore, this recharging is performed by the heald charging charger 12 after the intermediate transfer heald 1o is neutralized together with the toner image T by the neutralizing charger 15, as shown in the seventh section.

As a result, the intermediate transfer belt 1 is recharged as shown in the figure.
A predetermined negative potential such as - is applied to the exposed surface of the toner image T and the toner image T of the intermediate transfer bell.
The portion covered by Y is not significantly charged.

Therefore, when the intermediate transfer heald 10 contacts the photoreceptor drum 6 and performs the second transfer as shown in FIG. In addition, the toner image T on the photosensitive drum 6 is strongly and reliably transferred onto the intermediate transfer heald 0 and the toner image TY.

When the second exposure-development and primary transfer process is completed,
For the third time, the red filter plate 5R is selected in the color separation filter unit 5 and positioned on the optical path, and the light reflected from the original that passes through it exposes the photosensitive surface of the photosensitive tram 6 to form an electrostatic latent image. be done. This electrostatic latent image is visualized by a cyan developer 9C, which is a complementary color to red. At the same time, the intermediate transfer heald 0 is now charged at the 9th stage as in the second charging.
As shown in the figure, after being sequentially subjected to charge removal by the charger 15 and charging by the charger 12, the yellow toner image T7 and the magenta toner image T are brought into pressure contact with the photoreceptor drum 6 again as shown in FIG. As shown in , a cyan toner image Tc is further superimposed on the yellow and magenta toner images T, , T, without reverse transfer of the previously transferred toner images T7 and TI4, as in the case of the toner image T. The toner images are transferred to form a full-color toner image TF of yellow, magenta, and cyan.

During this next transfer process, the heald cleaner 16 of the intermediate transfer bell number 0 is separated from the intermediate transfer heald 10 because the solenoid 22 is turned off. On the other hand, when the -next transfer step is completed, the solenoid 21 is turned off, the pressure roller 18 is moved, and the intermediate transfer heald 10 is separated from the photosensitive drum 6, and in this state, the intermediate transfer heald 10 is driven as it is. Ru.

In this way, the intermediate transfer belt 10 is brought into pressure contact with the photoreceptor drum 6 only in the -next transfer process, and is kept apart at other times, so that the photoreceptor drum 6 is stopped when the -next transfer is completed. Furthermore, since the photosensitive drum 6 and the intermediate transfer belt 10 are separated from each other, there is no possibility of damage or electrical fatigue due to repetition of frictional charging and peeling discharge during this time.

On the other hand, the transfer paper S is sent out from the paper feed cassette 23 by the paper feed roller 23a at a predetermined timing based on a signal from a position detection device (not shown) at the intermediate transfer bell 0, and transferred to the secondary transfer paper S via the timing roller 24 at a predetermined timing. Transfer paper is fed to the transfer charger 14. Here, the transfer paper S is transferred to the first stage at 13 during the secondary transfer charge to which a negative potential is applied.
As shown in FIG. 1, the full-color toner image TF, which is negatively charged and has a positive potential on the intermediate transfer belt 0, is electrostatically attracted and transferred to the transfer paper S.

)・The transfer paper S on which the toner image T has been transferred as shown in FIG. Fuser 2 transported and heated
6, where it is fixed and discharged.

On the other hand, the intermediate transfer bell number 0, which is designated for secondary transfer, is first neutralized by the operation of the heald static elimination charger 15, and the solenoid 2
2 is turned on, the heald cleaner 16 is cleaned and prepared for the next process.

Photosensitive drum 6 and intermediate transfer belt 1 in the above steps
FIG. 13 shows the operation timings of the solenoid 0, the solenoids 21, 22, the heald cleaner 16, and the chargers 12, 13, 13a, and 15.

In addition, in the above explanation, the photosensitive drum 6, the intermediate shaft photographing belt 1
Although an example has been described in which the toner is charged negatively and the toner is charged positively, the toner may be charged in the opposite manner.

In addition, in the above explanation, three primary transfers are performed on the intermediate transfer heald 10.
Although an example has been shown in which a full-color toner image is formed by rotating the toner image and transferred to a transfer paper, it is of course possible to provide a mode in which a monochromatic color image is formed and transferred.

Further, in the above embodiment, the intermediate transfer heald 10 is used as an example of the intermediate transfer member, but an intermediate transfer drum may also be used.

(Effects of the Invention) According to the present invention, by charging the intermediate transfer member and bringing it into contact with the photoreceptor to perform electrostatic transfer from the photoreceptor to the intermediate transfer member, pre-transfer does not occur, and the In addition to charging at the time of the first transfer in the case of multi-transfer, by removing the charge from the intermediate transfer body appropriately during subsequent transfers, each electrostatic transfer is performed with a sufficient charging potential, and at the same time, the intermediate transfer body is transferred first. Since reverse transfer due to homopolar repulsion with the previously developed image is suppressed, each transfer is reliably achieved without image disturbance due to the effects of previous transfer and reverse transfer, resulting in a high-quality multicolor image. .

[Brief explanation of the drawing]

1 to 4 show an embodiment in which the present invention is applied to a full-color copying apparatus, in which FIG. 1 is a general schematic diagram, FIG. 2 is a perspective view of a color selection filter unit, and FIG. 3 is an intermediate transfer FIG. 4 is an enlarged sectional view of the intermediate transfer heald, FIG. 5 is an enlarged sectional view showing the charging state of the intermediate transfer heald, and FIGS. 6 to 10 show toner of each color for full-color copying. The primary image transfer process is shown, and FIG. 6 shows the first transfer state, FIG. 7 shows the charge removal and charging process before the second transfer, FIG. 8 shows the second transfer state, and FIG. 9 shows the 3rd transfer state. 10 is an enlarged cross-sectional view showing the third transfer state, and FIG. 11 is an enlarged cross-sectional view of the secondary transfer section showing the secondary transfer state of a full-color toner image. Figure 12 is an enlarged sectional view showing the transfer paper after secondary transfer;
The figure is a diagram showing the operation timing of each part.

Claims (1)

[Claims] (1) After developing the electrostatic latent image on the photoreceptor and electrostatically transferring the developed image to an intermediate transfer member, transfer the developed image on the intermediate transfer member onto a transfer material. This is an image forming method in which electrostatic retransfer is performed, in which a developed image from the photoreceptor is electrostatically transferred onto the surface of the intermediate transfer member by charging the intermediate transfer member and bringing it into contact with the photoreceptor, and this transfer is repeated several times. 1. An image forming method which is repeated multiple times and is characterized in that the intermediate transfer member is charged at the time of the first transfer and also after the intermediate transfer member is appropriately neutralized in subsequent transfers.