JP3086370B2 - Color image forming equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus for obtaining a color image by transferring a toner image of each color formed on an image carrier onto a transfer material by a transfer device, and more particularly to a color image forming device provided in the transfer device. A transfer material carrying means.

[0002]

2. Description of the Related Art In a color image forming apparatus for obtaining a color image on a transfer material by superimposing toner images of a plurality of colors, a toner image is formed on an image carrier by charging, exposing, and developing. There is a method of obtaining a color image by superposing toner images of a plurality of colors on the transfer material by repeating the process of transferring the toner image onto the transfer material each time it is obtained. A color image forming apparatus of this type is disclosed in German Patent DE.
It has been put to practical use with a configuration described in Japanese Patent Application Laid-Open No. 2607727 and Japanese Patent Application Laid-Open No. 50-50935.

FIG. 7 is a sectional view showing the above-described color image forming apparatus. As shown, a photosensitive drum 1 is provided as an image carrier in the apparatus, and a roller charger is provided around the photosensitive drum 1. A primary charging device 3, a rotary developing device 4 having a plurality of developing devices, a transfer device 10A, and a cleaner 26 are provided. Above the photosensitive drum 1, a laser diode 11 constituting an exposure device, a polygon mirror 13 rotated by a high-speed motor 12, a lens 14, and a folding mirror 15 are arranged.

The photosensitive drum 1 is formed by coating a photoconductor made of an organic photoconductor (OPC) on an outer peripheral surface of an aluminum cylinder having a diameter of 40 mm. The photoconductor may be amorphous Si, CdS, Se, or the like. The photosensitive drum 1 is rotated in a direction indicated by an arrow at a peripheral speed of 100 mm / sec by a driving unit (not shown).

[0005] The developing device 4 has a support 9 which rotates around a central rotation axis 9a. The support 9 is provided with a yellow developing device 4a, a magenta developing device 4b, a cyan developing device 4c and a black developing device 4d. It is doing. Developing unit 4a,
4b, 4c, and 4d respectively contain yellow toner, magenta toner, cyan toner, and black toner of a one-component developer.

In each of the developing devices 4a, 4b, 4c and 4d,
As shown in FIG. 8, the opening surfaces 5a, 5b, 5c, 5d
, A developing sleeve 8a as a developer carrier,
8b, 8c and 8d are provided. Furthermore, each developing unit 4
a, 4b, 4c, 4d, the application rollers 6a, 6b,
6c, 6d and toner regulating members 7a, 7b, 7c, 7
d is installed. Developing sleeves 8a, 8b, 8c,
8d, the application rollers 6a, 6b, 6c, 6d
The toner is applied onto the developing sleeves 8a, 8b, 8c, and 8d by the toner, and the applied toner is regulated by the toner regulating members 7a, 7b, 7c, and 7d, so that a triboelectric charge is given to the toner and 8a, 8b, 8
A thin toner layer is formed on c and 8d. The toner regulating members 7a to 7d are preferably made of a material which is charged in the opposite direction to the charging polarity of the toner, such as nylon when the toner is negatively charged and silicone rubber when the toner is positively charged. .

The developing sleeves 8a to 8d of the developing units 4a to 4d
The peripheral speed of 8d is 1.0 to 1.0 in the peripheral speed ratio to the photosensitive drum 1.
It is preferable to select so as to be in the range of 2.0 times.
When the developing units 4a to 4d face the photosensitive drum 1, the developing units 4a to 4d are driven such that their opening surfaces 5a to 5d always face the photosensitive drum 1. The details of the driving method of these developing devices 4a to 4d are as described in JP-A-50-93437.

The transfer device 10A includes a transfer drum 10 as a transfer material holding means. Around the transfer drum 10, an attraction roller 23, a static eliminator 2, a separation claw 24, and a cleaner 27 are provided.
And a static elimination roller 28. Transfer drum 10
A gripper 2 of a transfer material gripping member
Two. The transfer drum 10 is rotated in a direction indicated by an arrow at substantially the same speed as the photosensitive drum 1 by a driving unit (not shown).

In the image forming apparatus having the above-described configuration, first, a DC voltage of -700 V
A voltage on which an AC voltage of pp (peak-to-peak voltage) of -1500 V is superimposed is applied, and the surface of the photosensitive drum 1 is primarily charged to about -700 V by the charger 3. Then
A signal according to a first color, for example, a yellow image pattern is input to the laser diode 11 to generate light of a yellow image pattern, and the light is irradiated to the photosensitive drum 1 through an optical path 16 to expose the photosensitive drum 1. Then, an electrostatic latent image having a yellow image pattern with a light irradiation part of approximately −100 V is formed. The electrostatic latent image of the yellow image pattern formed on the photosensitive drum 1 is developed by a yellow developing unit 4a located there at a developing unit facing the developing device 4 as the photosensitive drum 1 rotates. A first color yellow toner image is formed on the drum 1.

On the other hand, transfer paper is supplied to the transfer drum 10 of the transfer device 10A from the transfer material cassette 17 by the pickup roller 18 in synchronization with the image on the photosensitive drum 1. The transfer drum 10 transfers the supplied transfer paper to the gripper 2.
2 and rotate in the direction of the arrow in the figure, thereby transporting the photosensitive drum 1 to the image transfer unit facing the photosensitive drum 1. The transfer paper conveyed to the image transfer section transfers a yellow toner image on the photosensitive drum 1 by a transfer voltage applied between the transfer drum 10 and the photosensitive drum 1 by a power supply (not shown).

At the same time as the transfer, electric charges are injected into the transfer paper by the transfer voltage, and the transfer paper is electrostatically attracted and held on the surface of the transfer drum 10. In order to enhance the electrostatic attraction of the transfer paper to the transfer drum 10, the gripper 23 is installed near the paper feeding portion of the transfer drum 10 and a voltage for suction is applied to the transfer roller 10. In many cases, the transfer paper is electrostatically adsorbed in advance after the holding by the grip 22.

The photosensitive drum 1 on which the transfer of the yellow toner image has been completed is cleaned and removed of the residual toner on the surface thereof by a cleaning member such as a fur brush or a blade provided on a cleaner 26, and then the primary charging by the charger 3 is performed. An image forming operation is performed.

The primary charging of the photosensitive drum 1 as described above, the formation of an electrostatic latent image by exposure, the formation of a toner image by developing the electrostatic latent image, and the superimposed transfer of the obtained toner image onto transfer paper are performed. By performing the same for magenta, cyan, and black of the second and subsequent colors, a color image in which toner images of four colors of yellow, magenta, cyan, and black are superimposed and transferred on transfer paper is obtained.

The transfer paper on which the transfer of the four color toner images has been completed is then neutralized by the static eliminator 2 arranged around the transfer drum 10 and then separated from the transfer drum 10 by the separation claw 24 on the downstream side. To the fixing device 25. Then, the toner images of four colors are fixed by heating and pressurizing, and the color mixture of the toner images and fixing to the transfer paper are performed to form a full-color permanent image, which is then discharged outside the image forming apparatus. Preferably, residual toner on the surface of the transfer drum 10 from which the transfer paper has been removed is cleaned by a cleaner 27 having a cleaning member such as a fur brush or a web.

[0015]

By the way, the transfer device 1
As shown in FIG. 9, the 0A transfer drum 10 is provided with a conductive elastic layer 10b made of a flexible conductive foamed rubber or a foamed resin foam on a metal cylinder 10a serving as a core metal. A dielectric layer 10c is provided.

In this embodiment, the metal cylinder 10a is made of aluminum, and the elastic layer 10b has a thickness of 50 to 200 μm.
m, a conductive sheet having a volume resistivity of 10 ⁴ to 10 ⁵ Ω · cm is formed by winding, and the dielectric layer 10c is formed by winding a PVdF (polyvinylidene fluoride) film having a thickness of 50 to 100 μm as a dielectric sheet. did.

The transfer drum 10 and the photosensitive drum 1 are in contact with each other.
10. mm, and the surface of the transfer drum 10 is concave. As shown in FIG.
0 rotates in the direction of the arrow, and when the transfer paper is sucked on the transfer drum 10 by the suction roller 23, the suction roller 23
Is released and separated from the transfer drum 10.

The transfer of the toner image on the photosensitive drum 1 to the transfer paper carried on the transfer drum 10 is as follows.
The first color magenta toner image on the photosensitive drum 1 is transferred by applying a transfer bias of 1.0 kV to the cylinder 10a of the transfer drum 10, and after the transfer drum 10 makes one rotation, the second color magenta toner image is then transferred. 1.5 for cyan toner image
The transfer is performed by applying a transfer bias of kV, the transfer bias is sequentially changed, the third color yellow toner image is transferred at a transfer bias of 2.0 kV, and the fourth color black toner image is transferred at a transfer bias of 2.5 kV. Is transcribed.

However, this conventional transfer drum 10
Then, the conductive foamed rubber or foamed resin constituting the conductive elastic layer 10b becomes a single foam having air holes h alone in a matrix R of rubber or resin as shown in FIG. Therefore, it is difficult to make the surface of the transfer drum 10 sufficiently flexible.
A load is applied to the transfer paper and toner image interposed between the transfer drum 10 and the transfer drum 10, and this causes a color image obtained by transferring the toner image of each color to have a low density, particularly at the center of the line, There was a drawback of causing disturbance.

According to the study by the present inventors, it has been found that this problem can be solved by forming the conductive elastic layer 10b of a continuous foam. That is, as shown in FIG. 10, a foam in which air holes h in a matrix R of rubber or resin are continuously connected is used.

When the hardness of the foam is measured with an Asker hardness meter (for example, Asker hardness meter F type, manufactured by Kobunshi Keiki Co., Ltd.),
In the case of the single foam in which the air holes h in FIG. 11 exist alone in the matrix, the hardness is 90 degrees or more, while FIG.
In a continuous foam in which the 0 air holes h are continuously connected in the matrix R, the hardness can be reduced to 70 degrees or less. That is, the surface of the transfer drum 10 can be made sufficiently flexible, and the image disturbance can be improved.

However, as a result of further studies by the present inventors, the following inconveniences have been found.

1) Since the continuous foam has more air holes than the single foam, the elastic layer 10b of the continuous foam is
2) Since the continuous foam has many air holes, when the elastic layer 10b of the continuous foam comes into contact with the dielectric layer 10c as shown in FIGS. The area where the matrix R actually contacts is smaller than in the case of the elastic layer of the body.

For this reason, the following problem occurs.

1) As described above, the transfer drum 10 is in a contact position with the photosensitive drum 1 and is 0.1 to 10 m in the center direction.
m, and the surface of the transfer drum is concave. In this example, the outer diameter of the photosensitive drum 1 is 41 mm, the outer diameter of the transfer drum 4 is 164 mm, and the nip is 0.5 mm.
In the case of mm, the image expands by about 1% (1.5 mm in length). That is, the rotation of the transfer drum is 1% faster, and conversely, the transfer drum is pulled by the photosensitive drum. Therefore, the elastic layer 10b of the transfer drum 10 is pulled in the circumferential direction by the photosensitive drum 1 during rotation for a long period of use, so that the elastic layer 10b and the aluminum cylinder 10a slide, and the elastic layer expands. As a result, the nip amount with the photosensitive drum changes from the initial setting. For this reason, the contact area between the photosensitive drum and the transfer drum changes, and the transfer condition (transfer bias condition) changes. Specifically, the contact area is reduced, the transfer current is reduced, the amount of transferred toner is reduced, and the image density is reduced. Alternatively, when the elastic layer is pulled for a longer time, the amount of displacement from the aluminum cylinder increases, and the elastic layer itself may be damaged.

2) When the elastic layer 10b is made of a continuous foam, the contact area with the dielectric layer 10c is small and the capacitance C of the dielectric layer is small as compared with the case of a single foam. Since the charge amount Q also decreases, the amount of toner moving from the photosensitive drum 1 to the transfer paper side also decreases, and the image density decreases. There is a problem that the so-called transfer efficiency deteriorates.

An object of the present invention is to prevent the elastic layer of the transfer material carrying means from peeling off or cracking from the core metal and reduce the load applied to the transfer material and the toner image interposed between the transfer material and the image carrier during transfer. An object of the present invention is to provide a color image forming apparatus capable of easily obtaining a high-quality color image without low density or image disturbance by performing good transfer with high transfer efficiency.

[0028]

The above object is achieved by a color image forming apparatus according to the present invention. In summary, the present invention provides a conductive substrate, a conductive elastic layer provided on the conductive substrate via a conductive adhesive layer, and a dielectric layer provided on the conductive elastic layer and carrying a transfer material. And a transfer material carrying means comprising: an image carrier and a transfer material carried by the transfer material carrier means are brought into contact with each other to transfer each color from the image carrier to the transfer material carried by the transfer material carrier means. Wherein the conductive elastic layer comprises a continuous foam supporting at least the entire transfer material via the dielectric layer, wherein the transfer material supporting means Is a color image forming apparatus, comprising a conductive layer between the continuous foam and the dielectric layer, wherein the conductive layer is formed by a skin layer of the continuous foam.

[0029]

[0030]

Embodiment 1 FIGS. 1 and 2 best illustrate a characteristic portion of the present invention. FIG. 1 shows a transfer device and its peripheral portion in one embodiment of a color image forming apparatus of the present invention. The sectional view and FIG.
FIG. 3 is a cross-sectional view illustrating a layer configuration of a transfer drum as a transfer material holding unit provided in the transfer device.

In the present image forming apparatus, the transfer paper P is taken out from the transfer material cassette 17 of FIG. 1 by a pickup roller 18 and supplied to a transfer drum 20 of the transfer device. It is wound around the transfer drum 20. Thus, the transfer drum 20
Is transported a plurality of times through an image transfer section facing the photosensitive drum 1 with the rotation of the transfer drum 20, and when passing through the transfer section, the transfer paper P is transferred by a transfer charging unit (not shown). The toner images of the respective colors on 1 are sequentially superimposed and transferred. The transfer paper P on which the color images are formed by superimposing the toner images of four colors in this manner is separated from the transfer drum 20 by an unillustrated static eliminator and a separation claw 24 downstream thereof, and is conveyed to the fixing roller 25. Then, after the toner image is fixed, the toner image is discharged outside the image forming apparatus. After the transfer paper P is discharged, the surface of the transfer drum 20 is discharged by the discharging roller 28.

The bias conditions for transfer, adsorption, and static elimination in this embodiment are as follows.

First-color transfer bias: 500 V Second-color transfer bias: 700 V Third-color transfer bias: 900 V Fourth-color transfer bias: 1100 V Suction bias: DC, voltage = −1000 V Static elimination bias: AC, frequency = 500 to 700 H
z, peak-to-peak voltage = 4 kV

In this embodiment, as shown in FIG. 2, the transfer drum 20 is a metal cylinder 2 serving as a conductive substrate.
A conductive double-sided adhesive tape 2 as a conductive adhesive layer
0e, a conductive elastic layer 20b is provided, a conductive layer 20c is further provided thereon, and then a dielectric layer 20d is provided.
0a.

The major feature of the present invention is that the conductive elastic layer 20
In order to provide b firmly on the metal cylinder 20a, the elastic layer 20b is bonded by a conductive adhesive layer made of a conductive double-sided tape 20e or the like, and the contact resistance between the elastic layer 20b and the dielectric layer 20d is reduced. To this end, a dielectric layer 20d is provided on the elastic layer 20b via the conductive layer 20c.

According to this embodiment, the metal cylinder 20a
Consists of a 3.5 mm thick aluminum cylinder,
The adhesive tape 20e has a thickness of 100 μm and a volume resistivity of 1 ×
The whole of 10 ⁴ Ω · cm or less was made of a conductive double-sided adhesive tape, and an adhesive tape 20e was stuck on the surface of the metal cylinder 20a to form a conductive adhesive layer. Conductive elastic layer 20
b is 5.5 mm in thickness and 1 × 10 ⁴ Ω · cm in volume resistivity
And was provided on the metal cylinder 20a by sticking with an adhesive tape 20e. This foamed sponge is a continuous foam in which the air holes h shown in FIG.

The conductive layer 20c is made of a polyethylene or polypropylene sheet in which carbon is dispersed, has a thickness of 40 to 60 μm, and has a volume resistivity of 1 × 10 ³ to 1 × 10 ^5.
Ω · cm. The dielectric layer 20e is made of a PVdF (polyvinylidene fluoride) sheet, and has a thickness of 75 μm.
The volume resistivity is 5 × 10 ¹³ to 1 × 10 ¹⁶ Ω · cm.

The urethane foam sponge sheet (5.5 mm thick) constituting the conductive elastic layer 20b has a hardness of 45 to 55 degrees as measured by Asker F (a hardness measured by an Asker hardness meter F manufactured by Kobunshi Keiki Co., Ltd.). there were. A 50 μm thick polypropylene sheet serving as the conductive layer 20c is stacked on the elastic layer 20b, and a 75 μm thick P serving as the dielectric layer 20d is placed thereon.
The VdF sheets were stacked to form a laminate that reproduced the layer configuration of the transfer drum 20, and the hardness was measured on the surface of the PVdF sheet of the laminate. Asker C2 hardness (Asker hardness tester manufactured by Kobunshi Keiki Co., Ltd.) 30 in C2 type hardness)
It was ~ 35 degrees.

The conductive elastic layer 20b needs to be provided in an area at least larger than the area of the transfer paper carried on the transfer drum 20. In this embodiment, the maximum width is 215 m
For the transfer of m and 410 mm in length, the dimensions of the urethane foam sponge sheet were 220 mm in width and 450 mm in length. The metal cylinder 20
a, 420 mm from the vicinity of the leading end of the transfer paper in the circumferential direction.
Up to 215mm in width and 2.5mm in width direction
((220-215) /2=2.5), the longitudinal direction is 15
mm ((450−420) ÷ 2 = 15) and not bonded. At this time, the photosensitive drum 1 (41 m in diameter)
m) and the nip amount in the center direction at the contact portion between the transfer drum 20 (diameter 164 mm) was 0.2 to 0.6 mm.

FIG. 3 shows a transfer drum 20 having the structure of this embodiment.
7 shows the relationship between the transfer efficiency and the transfer bias in the case of the transfer drum of the comparative example in which the conductive layer 20c is omitted. In FIG. 3, a solid line indicates the case of the transfer drum of the first embodiment, and a broken line indicates the case of the transfer drum of the comparative example. In the transfer drum without the conductive layer 20c of the comparative example, the dielectric layer 20d made of a PVdF sheet is in direct contact with the elastic layer 20b.

As shown in FIG. 3, the amount of toner moving from the photosensitive drum to the surface of the transfer drum by the electric field due to the transfer bias, that is, the bias region where the transfer efficiency is 80% or more, is as follows: V1 = 820V Comparative Example : V2 = 480 V, and it is clear that in this embodiment, the area where the toner can be efficiently transferred onto the transfer paper is wider. Also, the proper transfer bias at which the transfer efficiency becomes 80% or more is shifted to the lower bias side in the present embodiment.

As described above, according to the present invention, since the conductive layer 20c is interposed between the conductive elastic layer 20b and the dielectric layer 20d to reduce the contact resistance therebetween, the transfer efficiency is improved. And thus a clear image can be obtained.

When the transfer drum 20 and the photosensitive drum 2 were driven to rotate 300,000 times in a sliding state, the elastic layer 20b of the transfer drum 20 of the present embodiment was peeled from the aluminum cylinder 20a or damaged. Without
It had enough durability.

As described above, according to the present invention, the elastic layer 20b is formed on the metal cylinder 20a by the conductive double-sided tape 20.
e and the like, so that the elastic layer 20b can have high durability because it is firmly bonded through the conductive adhesive layer.

Another effect is that the resistance of the conductive layer 20c itself is 1 × 10 ⁶ Ω · c even if the contact area with the conductive layer 20c is small because the elastic layer 20b is a continuous foam.
m or less, power can be sufficiently supplied from the elastic layer 20b to the dielectric layer 20d via the conductive layer 20c. Unlike the case where power is supplied to the conductive layer 20c from the axial end of the transfer drum 20, the transfer drum 20 is transferred from the aluminum metal cylinder 20a to the conductive adhesive layer 20e, the elastic layer 20b, the conductive layer 20c, and the dielectric layer 20d. Since the power is supplied from the center to the outside in the cross-sectional direction, uniform charging is obtained over the entire surface of the dielectric layer 20d.

Embodiment 2 FIG. 4 is a structural view showing a transfer drum according to another embodiment of the present invention. In this embodiment, a PVdF sheet having an aluminum vapor-deposited layer on one surface of a dielectric layer 20d instead of providing the conductive layer 20c made of a conductive sheet on the conductive elastic layer 20b of the transfer drum 20 in the first embodiment. Is characterized in that a conductive layer 20c 'made of an aluminum vapor deposition layer is formed inside the dielectric layer 20d simultaneously with the dielectric layer 20d.

The above PVdF sheet has a thickness of 75 μm,
It is 232 mm wide and 510 mm long, and the aluminum vapor-deposited layer is 800-1200 on one side of the PVdF sheet.
It was formed with a thickness of Å. Since there is no adhesion between the conductive layer 20c 'of the aluminum vapor-deposited layer and the elastic layer 20b on the inner side, an air layer intervenes when viewed microscopically. Even if the space between the elastic layer 20b and the dielectric layer 20d is made of such a conductive layer 20c 'of an aluminum vapor-deposited layer, the effect of the transfer drum configuration of the present invention is exhibited as in the case of the first embodiment. And a clear image can be obtained.

The hardness of the transfer drum 20 of this embodiment is slightly lower than that of the transfer drum 20 of the first embodiment, and a urethane foam sponge sheet (5.5 mm thick) constituting the conductive elastic layer 20b is used.
A PVdF sheet having a thickness of 75 μm having an aluminum vapor-deposited layer (thickness: 1000 °) was superposed on the above, and the hardness was measured on the surface of the PVdF sheet. As a result, the Asker C2 hardness was 30 to 33 degrees. The Asker F hardness on the elastic layer 20b was 50 to 55 degrees.

The elastic layer 20b has the same structure as that of the first embodiment, and is made of a metal cylinder 20 of an aluminum cylinder.
A urethane foam sponge sheet is adhered to the entire surface of a with a conductive double-sided adhesive tape 20e to form an elastic layer 20b.

According to this embodiment, the contact resistance between the conductive elastic layer 20b and the dielectric layer 20d of the transfer drum 20 is reduced, and a clear image is obtained by improving the transfer efficiency. Effects such as improvement in durability can be obtained.

Embodiment 3 FIG. 5 is a structural view showing a transfer drum according to another embodiment of the present invention. In this embodiment, as shown in FIG. 5, a conductive elastic layer 20b is bonded to an aluminum cylinder 20a via a conductive bonding layer 20e ', and the bonding area is 420 mm in the circumferential direction and in the width direction. It was 215 mm. The adhesive layer 20e 'is made of aluminum cylinder 20a.
It is provided by applying a conductive adhesive thereon, and has an electric resistance value of 1 × 10 ⁶ Ω · cm or less and a thickness of 100 μm or less.

The conductive elastic layer 20b is made of a continuous foam foam sponge made of EPDM rubber and has a thickness of 5.5 mm.
It was formed thick. The foamed sponge has Asker F hardness of about 60 to 65 degrees, and Asker C on the dielectric layer 20d.
2 Hardness is about 50-53 degrees and electric resistance value is 5 × 1
0 ⁵ Ω · cm or less.

When such an EPDM rubber foamed sponge is used, a skin layer which is a thin skin-like formed layer is formed at the time of foaming.
And the dielectric layer 20d. In this embodiment, the skin layer of the elastic layer 20b made of the EPDM rubber foam sponge was used as the conductive layer 20c '.

The dielectric layer 20d is made of PV as in the first embodiment.
It is formed using a dF sheet, and is formed by winding it on the elastic layer 20b from above the conductive layer 20c '.

In this embodiment, as in the first and second embodiments, the transfer drum characteristic of the present invention makes it possible to improve the transfer efficiency and obtain a clear image.
The durability of b can also be improved.

Embodiment 4 FIG. 6 is a structural view showing a transfer drum according to another embodiment of the present invention. In the present embodiment, in the transfer drum 20 shown in FIG. 6, a foamed sponge sheet obtained by mixing continuous foaming and single foaming made of EPDM rubber was used as the conductive elastic layer 20b provided on the aluminum cylinder 20a.
The hardness of the foamed sponge is 60 to 70 degrees with Asker F, and the electric resistance value is 1 × 10 ⁶ Ω · cm or less.

The adhesion of the conductive elastic layer 20b to the cylinder 20a was performed by the conductive adhesive layer 20e 'as in the third embodiment. As described above, it is necessary that the area where the transfer paper is carried is at least adhered. In the present embodiment, the adhesion area of the elastic layer 20b is made circular for the transfer paper having a maximum width of 215 mm and a length of 220 mm. 420m in circumferential direction
m and 220 mm in the width direction.

The dielectric layer 20d 'is formed by coating the conductive sheet used for the conductive layer 20c with a silicone resin of 50-100 μm.
And dried. The volume resistivity of the dielectric layer 20d 'made of the silicone resin coating layer is 1 × 10 ⁴
１1 × 10 ⁶ Ω · cm.

The hardness of the transfer drum 20 of this embodiment was 30 to 35 degrees or less as Asker C2 on the dielectric layer 20d '.

According to this embodiment, the same effect as before can be obtained by the characteristic transfer drum configuration of the present invention.

[0061]

As described above, according to the present invention, a conductive substrate, a conductive elastic layer provided on a conductive substrate via a conductive adhesive layer, and a transfer material provided on the conductive elastic layer are provided. A transfer material carried by the image carrier and the transfer material carried by the transfer material carrier by contacting the image carrier with the transfer material carried by the transfer material carrier. In a color image forming apparatus that sequentially superimposes and electrostatically transfers toner images of each color, the conductive elastic layer includes a continuous foam that supports at least the entire transfer material via a dielectric layer, and the transfer material supporting unit is A conductive layer is provided between the continuous foam and the dielectric layer, and the conductive layer is formed by the skin layer of the continuous foam, so that a clear image can be obtained by improving the transfer efficiency, and the elastic layer Durability can also be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a transfer device and a peripheral portion thereof in an embodiment of a color image forming apparatus of the present invention.

FIG. 2 is a cross-sectional view illustrating a layer configuration of a transfer drum installed in the transfer device of FIG.

FIG. 3 is a graph showing a difference in transfer efficiency between the transfer drum having the configuration of FIG. 2 and a transfer drum of a comparative example lacking a conductive layer.

FIG. 4 is a cross-sectional view illustrating a layer configuration of a transfer drum according to another embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a layer configuration of a transfer drum according to still another embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a layer configuration of a transfer drum according to still another embodiment of the present invention.

FIG. 7 is a sectional view showing a conventional color image forming apparatus.

FIG. 8 is a cross-sectional view illustrating a developing device installed in the image forming apparatus of FIG.

9 is a cross-sectional view illustrating a layer configuration of a transfer drum of a transfer device provided in the image forming apparatus of FIG.

FIG. 10 is an explanatory diagram showing a foaming form of a continuous foam used for a conductive elastic layer of a transfer drum in the present invention.

FIG. 11 is an explanatory view showing a foaming form of a single foam used for a conductive elastic layer of a transfer drum in a conventional example.

FIG. 12 is an explanatory diagram showing a contact state between an elastic layer made of the continuous foam of FIG. 10 and a dielectric layer.

FIG. 13 is an explanatory diagram showing a contact state between an elastic layer made of the single foam body of FIG. 5 and a dielectric layer.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 20 transfer drum 20a metal cylinder 20b conductive elastic layer 20c conductive layer 20c 'conductive layer 20d dielectric layer 20d' dielectric layer 20e conductive double-sided adhesive tape 20e 'conductive adhesive layer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiaki Miyashiro 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Motoi Kato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Akihiko Takeuchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-3-35255 (JP, A) JP-A-5-204263 (JP) JP-A-2-310566 (JP, A) JP-A-4-214579 (JP, A) JP-A-5-6074 (JP, A) JP-A-57-111573 (JP, A) 1-113477 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/16 G03G 15/01 114

Claims (1)

(57) [Claims] 1. A conductive substrate, a conductive elastic layer provided on the conductive substrate via a conductive adhesive layer, and a dielectric layer provided on the conductive elastic layer and supporting a transfer material. A transfer material carrying means provided with the image carrier and a transfer material carried by the transfer material carrying means, and the toner image of each color is transferred from the image carrier to the transfer material carried by the transfer material carrying means. In the color image forming apparatus, the conductive elastic layer includes a continuous foam that supports at least the entire transfer material via the dielectric layer, and the transfer material supporting unit includes the continuous foam. A color image forming apparatus comprising a conductive layer between a foam and the dielectric layer, wherein the conductive layer is formed by a skin layer of the continuous foam.