JP2003107844A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device having the improved ability to electrostatically attracts an envelope or thick paper sheet, which cannot be carried by electrostatic attraction easily, by means of an electrostatic transfer belt. SOLUTION: A high resistance area 29 providing a volume resistivity of 10<13> Ω.cm or higher is formed in an non-image area on the edge of one side of the electrostatic carrying belt 11 having an image area with the volume resistivity of 10<12> Ω.cm or lower. The edge of a transfer material S, such an envelope, is attracted by the insulating part, thereby improving the ability to carry the transfer material S that is difficult to carry by electrostatic attraction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic system.

[0002]

2. Description of the Related Art Conventionally, a tandem type color image forming apparatus has, for example, four photoconductors for yellow, magenta, cyan, and black, which are arranged in parallel in a horizontal direction, for each color on a photoconductor. A latent image is sequentially formed by optical writing by the image exposure means, and the latent image is developed by four developing devices provided for each color to form a toner image, and each toner image is transferred to a sheet as a transfer material. The transfer image is heat-fixed on the paper.

The sheet is conveyed by a pair of rollers called a pair of registration rollers to an adsorption portion of a transfer device at an image transfer timing, and the adsorption portion causes the electrostatic transfer belt surface serving as a transfer material carrier to be statically conveyed. Is adsorbed electronically,
The images are sequentially conveyed to the image transfer section.

The electrostatic transfer belt is a film-shaped endless belt having a uniform surface resistance and is stretched by a plurality of rollers.
The four image transfer portions sandwiched by the four photoconductors and the four transfer rollers facing the photoconductors are formed. Further, the electrostatic transfer belt is restricted in its position in the paper width direction by the main body of the apparatus by a deviation restricting rib provided on the back surface, and is circularly moved in the transfer material conveyance direction by a drive roller.

The transfer material conveyed from the pair of resist rollers is electrostatically attracted to the surface of the electrostatic transfer belt by applying a pressure and an attracting voltage to the surface of the electrostatic transfer belt by applying a pressure and an attraction voltage to the surface of the electrostatic transfer belt. Is transported to the department. As a result, the transfer material is kept at a constant vertical and horizontal position.
The image is sequentially transferred to the image transfer portion at each point and the image is formed.

[0006]

However, in the case of the above-mentioned conventional technique, the electrostatic transfer belt and the transfer material have sufficiently large resistance in the normal environment and the low humidity environment. However, in a high-humidity environment, the resistance of the electrostatic transfer belt and the transfer material decreases due to moisture absorption, the charge holding power decreases, and the electrostatic adsorption force decreases.

Therefore, electrostatic attraction and conveyance of a transfer material having a strong strain such as a thick paper or an envelope or a transfer material having a rough surface is disadvantageous, and the transfer to the image transfer portion formed by the image carrier and the electrostatic transfer belt becomes difficult. Due to the shock of the material plunging, the transfer material may be displaced or peeled off from the electrostatic transfer belt, causing problems such as an image defect and a jam of the transfer material.

Therefore, in order to solve this problem, it is possible to increase the electrostatic attraction force between the transfer material and the electrostatic transfer belt by increasing the surface resistance value of the electrostatic transfer belt. However, by increasing the resistance value, the transferability is deteriorated due to the electrostatic transfer belt being charged up, and a special device for removing the charge of the transfer material from the electrostatic transfer belt is required. There was a problem that it would lead to larger size and higher prices.

It is an object of the present invention to provide an image forming apparatus capable of obtaining a high quality image while suppressing an increase in the size and cost of the apparatus.

[0010]

In order to achieve the above-mentioned object of the present invention, a plurality of image forming means for transferring a toner image on an image carrier to a transfer material at a transfer portion are arranged along the transfer material conveying direction. In addition, in the image forming apparatus that conveys the transfer material to the transfer portion by the electrostatic transfer belt that supports the transfer material by electrostatic attraction, the electrostatic transfer belt is more than the area that supports the transfer material that is easily electrostatically attracted and carried. Also has a high resistance portion in which a surface resistance value of a region carrying a transfer material, which is disadvantageous in electrostatic adsorption conveyance, is increased.

According to the above-mentioned structure, the transportability of the transfer material such as an envelope which is difficult to be electrostatically attracted and transported is improved without complicating the apparatus, peeling or deviation of the transfer material is prevented, and image defects and jams occur. Prevent.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on the embodiments shown in the drawings. Note that the examples in this embodiment do not limit the present invention.

(Embodiment 1) Hereinafter, Embodiment 1 of the present invention will be described with reference to the color image forming apparatus shown in FIGS. In addition, the same reference numerals are given to members common to each drawing.

First, the overall structure of the color image forming apparatus will be outlined with reference to FIG. FIG. 1 is a vertical cross-sectional view showing the overall configuration of a four-color full-color laser beam printer 100 as one form of a color image forming apparatus.

In FIG. 1, a full-color laser beam printer 100 includes four photoconductors (hereinafter referred to as photoconductor drums) 1a, 1b as image bearing bodies arranged in parallel in a horizontal direction.
1c and 1d are provided.

In the following description, the photosensitive drums 1a ...
Since the respective members acting on 1b and the photoconductor drums 1a to 1d have the same configuration for each of the photoconductor drums 1a to 1d, the suffix of the reference numeral indicating each component is omitted.

The photosensitive drum 1 is rotationally driven in the clockwise direction in the figure by a driving means (not shown). Around the photosensitive drum 1, according to the rotation direction,
A charging device 2 that uniformly charges the surface of the photosensitive drum 1, a scanner unit 3 that irradiates a laser beam based on image information to form an electrostatic latent image on the photosensitive drum 1, and toner on the electrostatic latent image. A developing device 4 for adhering the toner to develop a toner image, and an electrostatic transfer device 5 for conveying the transfer material S to a portion facing the photosensitive drum 1 and transferring the toner image on the photosensitive drum 1 to the transfer material S. A cleaning device 6 for removing the transfer residual toner remaining on the surface of the photosensitive drum 1 after the transfer is provided.

Further, a process cartridge 7 in which the photosensitive drum 1, the charging device 2, the developing device 4, and the cleaning device 6 for removing the toner are integrally formed into a cartridge to form a process cartridge 7 which can be attached to and detached from the full-color laser beam printer 100. I am trying.

The above-mentioned respective constituent members will be described in detail below.

The photoconductor drum 1 includes an organic light guide layer (OP) on the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm, for example.
C photoconductor) is applied. The photosensitive drum 1 is rotatably supported at both ends in the longitudinal direction by supporting members (not shown), and a driving force from a driving motor (not shown) is transmitted to one end of the photosensitive drum 1, so that the timepiece in the figure It is driven to rotate in the circumferential direction.

As the charging device 2, a contact charging type can be used. The charging member is a conductive roller formed in the shape of a roller. By bringing this roller into contact with the surface of the photosensitive drum 1 and applying a charging bias voltage to this roller by a power source (not shown),
The surface of the photosensitive drum 1 is uniformly charged.

The scanner unit 3 is arranged above the photosensitive drum 1 in a substantially vertical direction and has a laser diode (not shown).
The image light corresponding to the image signal is applied to the polygon mirror 9 rotated at high speed by a scanner motor (not shown). The image light reflected by the polygon mirror 9 is configured to selectively expose the charged surface of the photosensitive drum 1 via the imaging lens 10 to form an electrostatic latent image.

The developing devices 4a, 4b, 4c, and 4d are each composed of a developing device that develops toner of each color of yellow, magenta, cyan, and black, and stores the toner of each color. At the time of developing the electrostatic latent image on the photoconductor drum 1, the toner in the container of the corresponding developing device is sent to the application rollers 4a1, 4b1, 4c1, 4d1 by the sending mechanism, and the developing sleeves 4a2, 4b2 are rotated. 4c2, 4
A thin layer of toner is applied to the outer periphery of d2, and an electric charge is applied to the toner (friction charging).

The developing sleeves 4a2, 4b2, 4c
By applying a developing bias between the photosensitive drum 1 and the photosensitive drum 1 on which the electrostatic latent image is formed, toner is attached to the electrostatic latent image and developed as a toner image.

The cleaning device 6 removes the so-called transfer residual toner remaining on the surface of the photosensitive drum 1 without being transferred after the toner developed on the photosensitive drum 1 by the developing device 4 is transferred to the transfer material S. It is a thing.

The electrostatic transfer device 5 is provided with an electrostatic transfer belt 11 as a transfer material carrier which faces all the photoconductor drums 1a, 1b, 1c and 1d and cyclically moves while contacting them. Here, the electrostatic transfer belt 11 is 10 ¹² Ω · c.
It is composed of a film-like member having a thickness specific resistance of not more than m and a thickness of about 150 μm.

The electrostatic transfer belt 11 has a vertical direction of 4
The transfer material S is electrostatically attracted to the outer peripheral surface (the outer peripheral surface on the upper side in the drawing) of the electrostatic transfer belt 11 stretched by the rollers 13, 14a, 14b, 15 of the shaft and stretched by the rollers 13, 14a. The transfer material S is circulated while being brought into contact with the photosensitive drum 1. As a result, the transfer material S is conveyed to the transfer position by the electrostatic transfer belt 11, and the toner images on the photosensitive drum 1 are sequentially transferred.

The transfer rollers 12a, 12b, 12
c and 12d contact the inner peripheral surface of the electrostatic transfer belt 11,
The four photoconductor drums 1a, 1b, 1c, and 1d are arranged in parallel, respectively. The transfer roller 12 is connected to a transfer bias power source (not shown) and faces the photosensitive drum 1 to form a transfer portion. A positive charge is applied from the transfer roller 12 to the transfer material S via the electrostatic transfer belt 11, and the electric field generated by this charge causes the transfer material S in contact with the photosensitive drum 1.
The negative toner image on the photoconductor drum 1 is transferred to.

The electrostatic transfer belt 11 has, for example, a circumference of about 700.
The driving roller 13 is a belt having a thickness of 150 mm and a thickness of 150 mm.
The driven rollers 14a, 14b and the tension roller 15 are wound around each other and rotate counterclockwise in the drawing. As a result, the toner image on the photosensitive drum is transferred while the electrostatic transfer belt 11 circulates and the transfer material S is conveyed from the driven roller 14a side to the drive roller 13 side.

The paper feeding unit 16 feeds and conveys the transfer material S to the image forming unit. A plurality of transfer materials S are stored in the paper feed cassette 17, and at the time of image formation, the half-moon roller-shaped paper feed roller 18 and the registration roller pair 19 are rotationally driven according to the image forming operation, and the transfer in the paper feed cassette 17 is performed. Material S
While the sheets are separated and fed one by one, the leading end of the transfer material S hits the registration roller pair 19 and is temporarily stopped to form a loop. Then, the rotation of the electrostatic transfer belt 11 and the transfer material S
The transfer material S is re-fed to the electrostatic transfer belt 11 by the registration roller pair 19 in synchronization with the upper image writing position.

The fixing section 20 is for fixing the toner images of a plurality of colors transferred to the transfer material S, and the heating roller 21 which is rotationally driven, and the heat roller 21 is pressed against the heating roller 21 to apply heat and pressure to the transfer material S. The pressure roller 22. That is, the transfer material S onto which the toner image on the photosensitive drum 1 has been transferred is conveyed by the fixing roller pairs 21 and 22 when passing through the fixing section 20, and heat and pressure are applied by the fixing roller pairs 21 and 22. Is applied. As a result, the toner images of a plurality of colors are fixed on the surface of the transfer material S.

The image forming operation of the full-color laser beam printer having the above structure will be described below.

The transfer material S is separated and fed one by one from the paper feed section 16, hits the registration roller pair 19, and is temporarily stopped to form a loop. The photosensitive drum 1 rotates clockwise in the figure in synchronization with the rotation of the electrostatic transport belt 11. The tip of the toner image formed on the peripheral surface of the photoconductor drum 1a, which is positioned most upstream with respect to the moving direction of the electrostatic transport belt 11, is located at a facing point where the electrostatic transfer belt 11 and the photoconductor drum 1a face each other. At the timing when the transfer material S is rotated, the transfer material S waiting by the registration roller pair 19 is re-fed to the electrostatic transfer belt 11 so that the print start position on the transfer material S coincides with the facing point.

On the other hand, the surface of each photoconductor drum 1 is uniformly charged by the charging device 2, and the peripheral surface of the photoconductor drum 1 is exposed by the exposing means 3 in accordance with an image signal. An electrostatic latent image is formed on the surface.

The developing roller 4a2 installed opposite to the photosensitive drum 1a has almost the same polarity as the charging polarity of the photosensitive drum 1a so that the yellow toner adheres to the electrostatic latent image on the photosensitive drum 1a. A voltage of the same potential is applied, yellow toner is attached to the electrostatic latent image on the photosensitive drum 1a, and yellow development is performed. With the same configuration as that for yellow development, magenta development is performed on the photoconductor drum 1b, cyan development is performed on the photoconductor drum 1c, and black development is performed on the photoconductor drum 1d.

Further, the suction roller 8 and the driven roller 14a
Holds the re-fed transfer material S together with the electrostatic transfer belt 11. The attraction roller 8 conveys the transfer material S while electrostatically attracting and pressing the transfer material S onto the electrostatic transfer belt 11.
The leading end of the transfer material S is conveyed by being sandwiched by the driven roller 14a and the attraction roller 8, and is stably attracted to the electrostatic transfer belt 11 even after leaving the nipping portion, so that the photosensitive drum 1a
And the transfer roller 12a. After this, the electrostatic transfer belt 11 and the transfer material S
Since electrostatic attraction occurs due to the electric field of the transfer portion between the transfer material S and the transfer material S, the transfer material S is sequentially conveyed to the next transfer portion along the electrostatic transfer belt 11.

As described above, the transfer material S is successively conveyed while the toner images on the respective photosensitive drums 1 are transferred by the voltage application from the respective transfer rollers 12a, 12b, 12c and 12d.

The transfer material S on which the four color toner images have been transferred is
Separated from the electrostatic transfer belt 11 by the drive roller 13 part,
It reaches the fixing unit 20. Then, the transfer material S, after the toner image is heat-fixed, is ejected outside the apparatus by the paper ejection roller 25.

The electrostatic transfer belt according to the first embodiment will be described in detail with reference to FIGS. 2 and 3.

FIG. 2 is an enlarged perspective view of the electrostatic transfer device 5.

In the first embodiment, when the recording material is plain paper, the image is formed by the center reference, and the image is transferred to the recording material conveyed with the center portion in the direction orthogonal to the conveying direction as the reference. I am able to do it again, envelopes,
When a thick recording material such as thick paper having a basis weight of 105 g / m ² or more is used, an image is formed on the basis of one side. For example, if an envelope is conveyed along one side of the electrostatic transfer belt, it is exposed to light. The toner image formed on one side of the drum is transferred to a predetermined position on the envelope.

In the first embodiment, the electrostatic transfer belt includes an envelope, plain paper, and the like as one form of the transfer material S. When printing on plain paper, which is easier to be electrostatically adsorbed and conveyed than the envelope. The volume specific resistance value of the central portion of the electrostatic transfer belt 11 is set within the range of 10 ¹² Ω · cm or less, so that the electrostatic transfer belt 11 can be transported by electrostatic attraction.

On the other hand, in the case of printing on an envelope which is disadvantageous in electrostatic attraction conveyance, the envelope is peeled off from the electrostatic transfer belt 11 or is formed by the photosensitive drum 1 and the electrostatic transfer belt 11 in the course of the conveyance in the above-mentioned configuration. There is a problem that the envelope is displaced due to the shock of plunging into the transfer section.

Therefore, as shown in FIG. 3, in the non-image area portion located at one end of the transfer belt in the direction orthogonal to the moving direction of the electrostatic transfer belt 11, with respect to the conveying direction of the transfer material S. The portion that overlaps the non-image area located at the end in the direction orthogonal to each other is a high resistance portion 29 having a high volume specific resistance value over the circumference of the electrostatic transfer belt 11. The volume resistivity of the high resistance part 29 is 10
¹³ Ω · cm or more is desirable. With such a configuration, the charge holding force in the high resistance portion 29 is strengthened, and the electrostatic attraction force can be strengthened.

As described above, according to the first embodiment, the transfer material S, such as an envelope or a cardboard, which is difficult to be electrostatically conveyed by electrostatic attraction can be held and conveyed by a strong adsorption force by aligning it with one side of the transfer belt, so that the conveyance property is improved. Therefore, the transfer material S can be prevented from being peeled off or displaced from the electrostatic transfer belt 11, and image defects such as image unevenness and color misregistration can be prevented.

Further, since the high resistance portion 29 is formed on the non-image portion of the electrostatic transfer belt 11, the photosensitive drum 1
It is possible to reduce the influence on the image when the toner image is transferred from the electrostatic transfer belt 11 to the electrostatic transfer belt 11. Further, in such a configuration, the area of the high resistance portion 29 is limited, so that the transfer material S can be separated from the electrostatic transfer belt 11 with a simple configuration.

The first embodiment is a tandem type image forming apparatus in which a plurality of photosensitive drums 1 are arranged in parallel in the horizontal direction, and the electrostatic transfer belt 11 faces each of the photosensitive drums 1. It can be applied in any form.

Further, as shown in FIG. 4, a plurality of photosensitive drums 4 as image bearing members are arranged in the vertical direction with respect to the main body of the apparatus, not limited to the configuration of the first embodiment, and electrostatic discharge is performed. In an image forming apparatus configured to obtain an image by electrostatically conveying the transfer material S from the lower side to the upper side by the transfer belt 11, the transfer material S is easily peeled off because its own weight is applied to the transfer material S. Although the shift is more disadvantageous than the image forming apparatus having the configuration in which the photoconductor drums 4 are arranged in the lateral direction, the effects described above can be sufficiently obtained by applying the first embodiment.

(Second Embodiment) An image forming apparatus according to the second embodiment will be described below with reference to FIG. The same reference numerals are given to the members common to each drawing including the above-mentioned drawings, and the portions that are not particularly described have the same configurations as those in the above-described first embodiment.

In the first embodiment described above, the high resistance portion 29 is provided at one end of the transfer belt along the circumferential direction, but in the second embodiment shown in FIG. 5, the electrostatic transfer belt 11 is provided. A high resistance portion 29 having a high volume specific resistance value is provided in a strip shape along a direction orthogonal to the moving direction of the. When the transfer material S, such as an envelope or a thick paper, which has a poor electrostatic attraction and transportability compared to the plain paper is transported, the non-image area located at the leading end in the transport direction of the transfer material S is the high resistance portion 29. The electrostatic attraction force of the electrostatic transfer belt 11 to the transfer material S can be strengthened. In the second embodiment, the volume resistivity value of the high resistance portion 29 is set to 10 ¹³ Ω · cm or more.

As described above, according to the second embodiment, the same effect as that of the first embodiment can be obtained.

[0052]

As described above, according to the present invention,
The transferability of transfer materials, such as envelopes and thick paper, which are conventionally difficult to be electrostatically transferred, has been improved, and it has become possible to prevent image defects such as image unevenness and color misregistration, and jamming of transfer materials.

Further, according to the present invention, by forming the high resistance portion in the non-image area of the electrostatic transfer belt, it is possible to improve the transportability of the transfer material without affecting the image.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an electrophotographic color image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a perspective view of the electrostatic transfer device according to the first embodiment of the present invention during electrostatic conveyance of plain paper.

FIG. 3 is a perspective view of the electrostatic transfer device according to the first embodiment of the present invention during electrostatic transport of an envelope.

FIG. 4 is a vertical cross-sectional view of the image forming apparatus in which the photosensitive drums are arranged in the vertical direction according to the first embodiment of the present invention.

FIG. 5 is a perspective view of the electrostatic transfer device according to the second embodiment of the present invention during electrostatic transport of an envelope.

[Explanation of symbols]

1a, 1b, 1c, 1d ... Photosensitive drum 2a, 2b, 2c, 2d ... Charging device 3a, 3b, 3c, 3d ... Exposure means 4a, 4b, 4c, 4d ... Developing device 4a1, 4b1, 4c1, 4d1 ... Coating roller 4a2, 4b2, 4c2, 4d2 ... Developing sleeve 5 ... Electrostatic transfer device 6a, 6b, 6s, 6d ... Cleaning device 7a, 7b, 7c, 7d ... Process cartridge 8 ... Suction roller 9a, 9b, 9c, 9d ... Polygon mirror 10a, 10b, 10c, 10d ... Imaging lens 11 ... Electrostatic transfer belt 12a, 12b, 12c, 12d ... Transfer roller 13 ... Drive roller 14a, 14b ... Driven rollers 15 ... Tension roller 16 ... Paper feeder 17 ... Paper feed cassette 18 ... Paper feed roller 19: Registration roller pair 20 ... Fixing unit 21 ... Heating roller 22 ... Pressure roller 25 ... Paper ejection roller 29 ... High resistance part 100 ... Full color laser beam printer S ... Transfer material

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H030 AA01 AA06 AB02 AD05 BB02                       BB23 BB44 BB46 BB54                 2H072 CA05 JA03 JC02 JC09                 2H200 FA17 FA18 GA12 GA16 GA23                       GA34 GA44 GA47 GA49 GB12                       GB22 GB25 HA02 HA28 HB12                       HB22 JA02 JB06 JB39 JB40                       JB46 MB04 MB05 MB06                 3F049 AA06 BA11 LA01 LB03                 3F101 LA01 LB03

Claims (5)

[Claims] 1. An electrostatic transfer system in which a plurality of image forming units for transferring a toner image on an image carrier to a transfer material at a transfer unit are arranged along the transfer material conveying direction, and the transfer material is carried by electrostatic attraction. In the image forming apparatus that conveys the transfer material to the transfer unit by a belt, the electrostatic transfer belt has an area of a transfer material that is disadvantageous to electrostatic attraction and conveyance rather than an area of a transfer material that is easily electrostatically attracted and conveyed. An image forming apparatus having a high resistance portion having a high surface resistance value. 2. The image forming apparatus according to claim 1, wherein the high resistance portion is formed in a non-image area of the electrostatic transfer belt. 3. An electrostatic transfer method in which a plurality of image forming means for transferring a toner image on an image carrier to a transfer material at a transfer portion are arranged along the transfer material conveying direction, and the transfer material is carried by electrostatic attraction. In the image forming apparatus that conveys the image to the transfer portion by a belt, the electrostatic transfer belt is provided with a high resistance portion having a surface resistance value higher than that of other areas in a direction orthogonal to the conveyance direction. Forming equipment. 4. The electrostatic transfer belt is characterized in that a non-image area of the transfer material is overlapped with the high resistance portion when a transfer material which is disadvantageous in electrostatic attraction and conveyance is conveyed. Item 3. The image forming apparatus according to item 3. 5. The surface resistance value of the high resistance portion is 10 ¹³ Ω.
The image forming apparatus according to claim 1, wherein the image forming apparatus has a size of not less than cm.