JPH01273075A - Image forming method and intermediate transfer body used therein - Google Patents

Abstract

PURPOSE:To achieve multiple transfer free of image disorder by employing an intermediate transfer body forming dielectric layers on a conductive base material, electrostatically charging the dielectric layers and bringing them into contact with a photosensitive body. CONSTITUTION:An intermediate transfer belt 10 is composed by laminating the dielectric layers on the surface of the conductive base material. For the conductive base material, urethane with an inherent volume resistivity <=10<5>OMEGAcm is preferable, and for the dielectric layer, polytetrafluoroethylene with a dielectric constant of 2-4 and an inherent volume resistivity of 10<16>-10<17>OMEGAcm is preferable. In synchronization with a photosensitive drum 6, the belt 10 is driven at speed the same as the drum 6, and is electrostatically charged from the surface of the dielectric layer when it passes by an electrostatic charger 11. As a result, when the electrostatically charged part of the belt 10 comes to a primary transfer position, an image of positive toner is transferred onto the belt 10. Thus, every transfer can be surely performed without its pretransfer part adversely affected by image disorder or the occurrence of ozone.

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 present invention relates to an image forming method that can be transferred onto an image and an intermediate transfer member used therefor, and is used, for example, in a copying machine or a laser beam printer.

(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 device uses an insulating belt as an intermediate transfer member. At a transfer portion where the insulating heald contacts the photoreceptor, a transfer charger operated from the back side of the insulating 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 insulating heald is strong, but concentrated at the transfer position where the photoreceptor and the insulating heald are in contact. do not. 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 insulating 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.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming method in which a stable electrically charged intermediate transfer member is brought into contact with a photoreceptor, thereby obtaining a high-quality image without the influence of pre-transfer.

(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 that electrostatically transfers and then electrostatically retransfers a developed image on an intermediate transfer member onto a transfer material, the intermediate transfer member having a dielectric layer formed on a conductive base material. The dielectric layer of the intermediate transfer member is charged and brought into contact with the photoreceptor, thereby electrostatically transferring a developed image from the photoreceptor onto the surface of the intermediate transfer member.

As an intermediate transfer body, a dielectric layer is formed on a conductive base material, and the dielectric layer has a relative dielectric constant of 2 to 4 and a volume resistivity of 10.
'6 to 10'' (Ω·cm), and the conductive base material preferably has a volume resistivity of 10 5 (Ω·Cl11) or less.

(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 dielectric layer of the intermediate transfer member is charged. The state is stabilized by the conductive layer on the back side of the dielectric layer, making it less susceptible to environmental influences and capable of maintaining a predetermined charge for a relatively long time. For this reason, the dielectric layer is charged prior to transfer, and the charged dielectric layer is brought into contact with the photoreceptor to enable transfer. This can prevent the action of the charger that charges the dielectric layer from reaching the transfer area and causing pre-transfer, and only the stable predetermined charge given to the dielectric layer can The developed image can be reliably transferred onto the intermediate transfer member without disturbance.

In particular, the intermediate transfer body has a dielectric layer with a relative dielectric constant of 2 to 4 and a volumetric surface with a resistance of 10'6 to 10'7 (Ωcm), which improves the efficiency of charging and neutralization. In addition, the ability to retain electric charge due to charging improves.Also, since the resistance value of the conductive base material is set to 105 (Ω・mark) or less, it is possible to maintain the charged state of the dielectric layer with sufficient conductivity. It is possible to back up and further stabilize the maintenance of the charged state.

(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 red 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, 5
The structure is such that one of R 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 photoreceptor drum 6.
A charger 8 , a developing section 9 , an intermediate transfer heald 10 , and a drum cleaner 11 are sequentially arranged in the rotational direction of the photosensitive drum 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 grain cutting shutter, a toner concentration detector, a toner replenishing device, and the like.

The intermediate transfer heald 10 has a conductive base material 1 as shown in FIG.
Urethane rubber as 0a (103~104Ω・cm)
The dielectric layer 10b is made of a flexible endless heald with a polytetrafluoroethylene layer (10" Ω cm or more) formed on the surface of the dielectric layer 10b. According to experiments, the dielectric layer 10b has a dielectric constant of rate is 2 or less, volume resistivity value is 10
If it is less than 16Ω・cm, the charge retention ability will decrease,
Even if it is charged, the charge will quickly decrease. Furthermore, if the relative dielectric constant is 4 or more and the volume resistivity is 10"Ωcm or more, the charging and static elimination efficiency will be poor, making it difficult to charge and eliminate static electricity. Next, the resistance value of the conductive base material 10a is 104Ω.・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 1017 (Ωcm), and a conductive base material should have a volume resistivity of 105 (Ωcm) or less. in,
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 heald 10, there is a belt charger 12 for primary transfer that transfers an image from the photoreceptor drum 6 to the intermediate transfer heald 10, and a transfer paper S from the intermediate transfer belt.
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 heald 10 includes a heald charging roller 17 facing the heald charging charger 12 and a pressure roller 1 facing the photosensitive drum 6.
8, the secondary transfer roller 19, and the heald cleaner roller 2.
The dielectric layer 10b on the surface faces the photoreceptor drum 6. Pressure roller 18
is moved by the solenoid 21 between a first position where the intermediate transfer bell 0 is brought into pressure contact with the photoreceptor drum 6 at the primary transfer position and a second position where it is separated from the photoreceptor drum 6. configured to switch. Reference numeral 22 denotes a solenoid that presses and separates the belt cleaner 16 from the intermediate transfer belt 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 -8= via a timing roller 24. . A transfer paper conveying belt 25 is provided on the right side of the secondary transfer section, and a transfer paper conveyor belt 25 is installed on the right side of the secondary transfer section.
is sent to the fixing device 26.

Next, to explain the operation, the original placed on the original table glass l 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.
, the 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 toners are developed using the respective color toners in either the magenta developer unit 9c or the cyan developer unit 9c. for example,
In the color separation filter unit 5, when the blue filter plate 5B is located in the optical path, the yellow developing device 9y, which is a complementary color to blue, is selected, and the other developing devices 9M and 9C are used to cut the ears at the rear of each developing sleeve. After the developer on the developing sleeve is scraped off by the shutter, 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 drum 6.

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. Held 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 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 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 belt 0 against the photosensitive drum 6 by the action of the solenoid 21 .

When the charged portion of the intermediate transfer belt 1o comes to the primary transfer position in this state, the negative potential on its surface causes the yellow toner image T7 at a positive potential on the photoreceptor drum 6 to move onto the intermediate transfer belt 1o as shown in FIG. It is transferred onto HO. This transfer is not affected by the fact that the heald 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 1o. be done. However, the negative potential of the intermediate transfer belt 10 is set to a predetermined value higher than the negative potential of the photosensitive drum 6.

Thereafter, the photosensitive surface of the photosensitive drum 6 is cleaned by a drum cleaner 11.
After cleaning, the exposure-development--=11- next transfer step 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 in magenta, which is a complementary color to green. At the same time, the intermediate transfer bell 0 is brought into pressure contact with the photosensitive drum 6 again with the yellow toner image TV transferred thereon, and by maintaining a predetermined potential at this time, the yellow toner image TV is transferred as shown in FIG. A magenta toner image TM is transferred on top of the toner image TM in substantially the same manner as in the case of toner images 1-7.

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 drum 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 bell 0 is brought into pressure contact with the photoreceptor drum 50 again with the yellow toner image TV and magenta toner image TM transferred thereto, and at this time, by maintaining a predetermined potential, as shown in FIG. Then, a cyan toner image T is further superimposed on the yellow and magenta toner images Tv and TH.

is transferred in almost the same way as the toner image TV, T,
A full-color toner image TF of yellow, magenta, and cyan is formed.

During this next transfer step, 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 heald 10 is brought into pressure contact with the photoreceptor drum 6 only in the next transfer step, 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 heald 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 force center 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 heald 10, 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 13. Here, the transfer paper S is negatively charged as shown in FIG. 9 by the secondary transfer charger 13 to which a negative potential is applied, and the full-color toner image TF with a positive potential on the intermediate transfer heald 10 is electrostatically attracted. and is transferred onto transfer paper S.

The transfer paper S on which the I.color image TF 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 heald 1o that has completed the secondary transfer is first neutralized by the action of the heald static elimination charger 15, and cleaned by the action of the heald cleaner 16 when the solenoid 22 is turned on, in preparation for the next step.

Photosensitive drum 6 and intermediate transfer belt 1 in the above steps
FIG. 11 shows the operation timings of the solenoid 0, the solenoid 21, 22, the heald cleaner 16, and each of 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.

In addition, in the above explanation, the primary transfer is performed on the intermediate transfer bell) 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 middle transfer belt 10 is used as 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 photosensitive drum by charging the intermediate transfer member which is not easily influenced by the environment and easily retains charge, the transferred image is not affected by the influence of the previous transfer. This is done reliably and without disturbance, and the image quality can be improved. In addition, the intermediate transfer member has good charging/static charge removal efficiency and improved charge retention ability due to the combination of a specific dielectric layer and a conductive base material, so that the primary transfer of toner images can be performed advantageously.

[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 A perspective view of the belt and its surroundings, the fourth is an enlarged cross-sectional view of the intermediate transfer heald, FIG. FIG. 9 is an enlarged sectional view of the primary transfer section showing the state of primary transfer of an 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, and FIG. 10 is an enlarged sectional view of the transfer paper after secondary transfer. The 11th enlarged cross-sectional view shown is a diagram showing the operation timing of each part.

Claims (2)

[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. An image forming method using electrostatic retransfer, which uses an intermediate transfer body in which a dielectric layer is formed on a conductive base material, and the dielectric layer of this intermediate transfer body is charged and brought into contact with a photoreceptor. An image forming method characterized by electrostatically transferring a developed image from a photoreceptor onto its surface. (2) A dielectric layer is formed on the conductive base material, and the dielectric layer has a relative dielectric constant of 2 to 4 and a volume resistivity of 10^1^6 to 1.
0^1^7 (Ω cm), and the conductive base material has a volume resistivity of 10^5 (Ω cm) or less. intermediate transfer body.