JPH01273078A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent a belt and an image from being damaged by stretching an intermediate transfer belt so that it can move toward and away from both a photosensitive drum and a cleaning belt, and providing a belt electrostatic charger on the roller supporting part of said belt. CONSTITUTION:In a primary transfer process, a belt cleaner 16 is separated from the intermediate transfer belt by turning off a solenoid 22. At the end of said process, a solenoid 21 is turned off, a pressure roller 18 is moved to separate the intermediate transfer belt 10 from the photosensitive drum 6. In such a way, the intermediate transfer belt 10 is moved toward or away from the photosensitive drum 6 and the belt cleaner 16, whereby the damage of the belt 10 and of an image due to contact can be prevented. Moreover, the belt electrostatic charger 12 is provided on the supporting part consisting of a roller 17 without the influence generated by moving the intermediate transfer belt 10 toward or away from the two. As a result, an image can be transferred onto the intermediate transfer belt 10 under stable electrostatic charge.

Description

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

(Prior Art) For example, Japanese Patent Publication No. 49-209 (Prior Art Example 1) describes a device that applies electrophotography to print multicolor images on flexible materials such as cloth, and uses an intermediate transfer body to print each color image on a flexible material such as cloth. It has been disclosed that the multicolor image formed on the 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 photoconductor to an intermediate transfer body to form a multicolor image on the intermediate transfer body, the image is electrostatically re-transferred all at once to transfer paper to prevent image misalignment. There are also apparatuses for forming multi-color images, such as those disclosed in Japanese Patent Publication No. 54-28740 (Conventional Example 2) and Japanese Patent Application Laid-Open No. 56-147166 (Conventional Example 2).
Conventional example 3) is already known. This one uses an intermediate transfer belt. At a transfer portion where the belt contacts the photoreceptor, a transfer charger operated from the back side of the belt transfers the developed image on the photoreceptor onto the intermediate transfer member.

(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 belt I- is strong, but the photoreceptor and the intermediate transfer belt are in contact with each other. Do not concentrate on the transfer position. 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 belt 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.

In the present invention, since the charged intermediate transfer belt is in contact with the photoreceptor, there is no influence of previous transfer, and it can be moved into and out of contact with the image forming device such as the photoreceptor, and stable charging is possible at all times without being affected by the movement of the belt. The object of the present invention is to provide an image forming method that can successfully obtain 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 belt. In an image forming apparatus that electrostatically transfers the image on the intermediate transfer belt and then electrostatically retransfers the image on the intermediate transfer belt onto the transfer sheet, the intermediate transfer belt is provided so as to be able to contact the photoreceptor and around itself. The image forming apparatus is stretched so as to be able to come into contact with and be separated from the image forming apparatus, and the belt charger, which is one of the image forming apparatuses, is disposed opposite to the roller support portion of the intermediate transfer belt.

(Function) The present invention has the above configuration, and in order to transfer the developed image formed on the photoreceptor onto the intermediate transfer belt, the intermediate transfer belt is charged, but this charging is performed prior to the transfer. Transfer is possible by bringing the charged intermediate transfer belt into contact with the photoreceptor. This can prevent the action of the charger that charges the photoreceptor belt from reaching the transfer section and causing pre-transfer.

The intermediate transfer belt can also be brought into contact with and separated from image forming equipment such as photoreceptors and cleaning means at appropriate times to successfully form images without mechanical effects such as damage to the belt or image due to contact. can. Moreover, since the intermediate transfer belt [is charged by the charger at the roller support part that can maintain a fixed position without being affected by the contact and separation, the gap between the transfer belt and the charger can be prevented from changing due to the contact and separation, and it is always stable. It is possible to form a high quality image by receiving the transfer due to the electrification.

(Embodiment) An embodiment in which the present invention is applied to a color copying apparatus will be described below 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 1 on which a document is placed. . As shown in FIG. 2, the color separation filter unit 5 includes a blue filter plate 5B, a green filter plate 5G, and a lens filter plate 5R supported in parallel by a frame 51, and a drive motor 52 and a position sensor 53a. , 53b, filter plates 5B, 5G, 51
? The structure is such that one of the two can be selectively positioned in the exposure optical path.

A photosensitive drum 6 is provided immediately below the fifth mirror 3e. An erase lamp 7 is provided around the photoreceptor drum 6.
A charger 8 , a developing section 9 , an intermediate transfer belt 10 , and a drum cleaner 11 are sequentially arranged in the rotational direction of the photoreceptor toram 6 .

The developing section 9 includes a yellow developing device 9Y and a magenta 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 toner concentration detector, a toner replenishing device, and the like.

Intermediate transfer bell number 0 is the conductive base material 10 as shown in FIG.
It is composed of a flexible endless belt in which a polytetrafluoroethylene layer (10'' Ω·cm or more) is formed as a dielectric layer tab on the surface of urethane rubber (10 3 to 10 4 Ω·cm) as a. According to experiments, the relative dielectric constant of the dielectric layer 10b is 2 or less, and the volume resistivity value is 101.
If it is less than 6Ω·0m, the ability to retain electric charge will decrease, and even if it is charged, the electric charge will decrease quickly. Further, if the relative dielectric constant is 4 or more and the volume resistivity is 1017 Ω·cm or more, the charging and static elimination efficiency will be poor, and it will be difficult to charge and eliminate static electricity. Next, the resistance value of the conductive base material 10a is 10'Ω·c
If it exceeds m, the conductivity deteriorates, 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 specific dielectric constant of 2 to 4, a volume resistivity of 10'6 to 101" (Ωcm), and a conductive base material should have a volume resistivity of 105 (Ωcm) or less. By that,
It is effective as an intermediate transfer member because it has good charging and neutralizing efficiency, and the charge generated by charging can be stably maintained for a relatively long time without being affected by the environment.

Around the intermediate transfer belt 10, a belt electrification charger 12 for primary transfer of an image from the photoreceptor drum 6 to the intermediate transfer belt 10, and a transfer paper S from the intermediate transfer belt are provided.
A secondary transfer charger 13, a separation charger 13a, a belt static elimination charger 15, a belt cleaner 16, and the like are provided for transferring an image to the belt.

Further, as shown in detail in FIG. 3, the intermediate transfer belt 10 includes a belt charging roller 17 facing the belt charging charger 12, a pressure roller 1B facing the photosensitive drum 6, and a secondary transfer roller 19. It is stretched by five straight rollers: a belt cleaner roller 20 and a tension roller 14, and the dielectric layer 10b on the surface faces the photoreceptor drum 6. The pressure roller 18 is moved by the solenoid 21, so that it can be moved between a first position where the intermediate transfer belt 0 is pressed against the photoreceptor drum 6 at the primary transfer position and a second position where it is separated from the photoreceptor drum 6. 62 configured to switch between
Reference numeral 2 designates a solenoid that presses and separates the helmet cleaner 16 from the intermediate transfer bell O.

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 belt 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, an original placed on the original table glass 1 is sequentially scanned in the horizontal direction, and the reflected light is transmitted to the first to third mirrors 3a to 3c and the color separation filter unit 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.

This electrostatic latent image is formed by the yellow developing device 9y of the developing section 9;
The image is developed with toner of each color in either the magenta developer 9M or the cyan developer 9C. For example, in the color separation filter unit 5, the blue filter plate 5B
is located in the optical path, the yellow developing device 9v, which is a complementary color to blue, is selected, and the developer on the developing sleeve is scraped off by the ear-cutting shutter at the rear of each developing sleeve in the other developing devices 9M and 9C. 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 stored on the photoreceptor drum 6.
It is charged to the opposite potential, for example, to a positive potential.

The intermediate transfer belt 10 is driven at the same speed as the photoreceptor drum 6 in synchronization with the photoreceptor drum 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 belt 10.
dielectric layer 10b is negatively charged. This charging is performed with high efficiency due to the material of the dielectric layer 10b and the fact that it is performed directly from the surface of the dielectric layer 10b.

Due to this charging, a --like negative potential is formed on the surface of the dielectric layer 10b. This state is stabilized by hacking up the conductive base material 1[1a on the back surface of the dielectric material jiJ10b, 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 belt 10 against the photosensitive drum 6 by the action of the solenoid 21 .

In this state, the charged portion of the intermediate transfer bell 0 reaches the primary transfer position (then, due to the negative potential on its surface, the yellow toner image T7 with a positive potential on the photoreceptor tram 6 moves to the intermediate transfer position as shown in FIG. The image is transferred onto the transfer belt 10. This transfer is not affected by the effect of the belt charging charger 12 because it is far from the primary transfer position, and is carried out beforehand by the stable predetermined surface potential of the intermediate transfer belt 10. This is reliably achieved without any disturbance caused by the transfer.However, the negative potential of the intermediate transfer belt 10 is set to a predetermined value higher than the negative potential of the photoreceptor drum 6.

Thereafter, the photosensitive surface of the photosensitive drum 6 is cleaned by a tram cleaner 11.
After cleaning, the exposure-development-next transfer process is completed.

In the case of full-color copying, when the first exposure-development-next transfer process for yellow is 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 tram 6 is exposed to the reflected light of the original that has passed through the photosensitive tram 6, 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. At the same time, the intermediate transfer belt 10 is brought into pressure contact with the photoreceptor drum 6 again with the yellow toner image T7 transferred thereto, and by maintaining a predetermined potential at this time, the yellow toner image TY is transferred as shown in FIG. A magenta toner image T is superimposed thereon and transferred in substantially the same manner as the toner image Ty.

When the second exposure-development-next transfer process is completed,
For the third time, the color separation filter unit 5 selects the filter plate 5R and positions it 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 the cyan developing device 9C, which is a complementary color to Lett. At the same time, the intermediate transfer bell 0 is brought into pressure contact with the photoreceptor tram 6 again with the yellow toner image T9 and the magenta toner image T transferred thereto, and by maintaining a predetermined potential at this time, as shown in No. 80, , yellow and magenta toner images T7, To, a cyan toner image TC is transferred in substantially the same manner as the toner images Tv, TM to form a full-color toner image TF of yellow, magenta and cyan. .

During this next transfer process, the belt cleaner 16 of the intermediate transfer belt 10 is separated from the intermediate transfer belt 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 and the pressure roller 18 is moved to separate the intermediate transfer belt 10 from the photosensitive drum 6, and in this state, the intermediate transfer belt 10 is driven as it is. .

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. Further, since the photoreceptor 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) of the intermediate transfer belt 10, and is transferred to the timing roller 24 for secondary transfer at a predetermined timing. Transfer paper is sent to the charger 13. Here, the transfer paper S is negatively charged by the secondary transfer charger 13 to which a negative potential is applied, as shown in FIG.
Full-color toner image T at positive potential on ~lO.

is electrostatically attracted and transferred onto the transfer paper S.

The transfer paper S onto which the toner image T has been transferred as shown in FIG. , heated fuser 26
The image is sent to the printer, fixed, and then discharged.

On the other hand, the intermediate transfer belt 10 that has completed the secondary transfer is first neutralized by the operation of the belt neutralization charger 15, and cleaned by the action of the belt cleaner 16 when the solenoid 22 is turned on, in preparation for the next process.

Photoreceptor tram 6 and intermediate transfer belt 1 in the above steps
FIG. 11 shows the operation timings of the belt cleaner 0, the solenoids 21, 22, the belt cleaner 16, and the chargers 12, 13, 13a, and 15.

Note that in the above explanation, the photosensitive drum 6 and the intermediate transfer belt 1 are
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.

Furthermore, instead of bringing the belt cleaner into and out of contact with the intermediate transfer belt, the belt may be brought into contact with and away from the cleaner.

In addition, in the above description, three primary transfers are performed on the intermediate transfer belt 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 belt 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, since the developed image is electrostatically transferred from the photoreceptor drum by charging the intermediate transfer belt, there is no influence of previous transfer, and the intermediate transfer belt can be transferred to the image forming equipment in a timely manner. By separating them from each other, they are not affected mechanically by contact with the image forming equipment, and transfer can be performed by stable charging without the effects of the separation, so it is possible to successfully and stably obtain high-quality images. .

[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 belt, FIG. 5 is an enlarged sectional view showing the charging state of the intermediate transfer belt, and FIGS. 6 to 8 are diagrams of each color for full-color copying. FIG. 9 is an enlarged sectional view of the primary transfer section showing the state of primary transfer of a toner image. FIG. 9 is an enlarged sectional view of the secondary transfer section showing the state of secondary transfer of a full-color toner image. FIG. 10 is the transfer paper after the secondary transfer. FIG. 11 is an enlarged sectional view showing the operation timing of each part. 6---------One photosensitive drum 10------
----- -Intermediate transfer belt 10a---- Conductive base material

Claims (1)

[Claims] (1) After developing the electrostatic latent image on the photoreceptor and electrostatically transferring the developed image to the intermediate transfer belt, the developed image on the intermediate transfer belt is statically transferred onto the transfer material. In an image forming apparatus that performs electrical retransfer, an intermediate transfer belt is stretched so as to be able to contact the photoreceptor and to be able to come into contact with and separate from an image forming device installed around the intermediate transfer belt, and one of the image forming devices is connected to the intermediate transfer belt. An image forming apparatus characterized in that a belt charging charger is provided opposite to a roller support portion of an intermediate transfer belt.