JP2001060044A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device capable of canceling a middle omission and preventing permanent set of a surface layer by constituting an intermediate transfer drum of plural conductive elastic layers provided on the outer peripheral surface of a conductive cylinder and a releasing layer being the surface layer with which the outer peripheral surface of the conductive elastic layer is covered or coated. SOLUTION: The intermediate transfer drum 8 is constituted of a conductive cylinder base substance 8a cylindrically formed, a sponge layer 8b being a 3rd layer and a rubber layer 8c being a 2nd layer which are the conductive elastic layer provided to be concentrically laminated on the outside of the base substance 8a, and the releasing layer 8d (1st layer) being the surface layer with which the outside of the conductive elastic layer is covered or coated concentrically and improving releasing property from a transfer material. As for the drum 8, it is set to hold the 1st layer > the 2nd layer > the 3rd layer in order that Young's modulus is high. Or it is set to hold the 1st layer > the 2nd layer > the 3rd layer in order that volume resistivity is high. Or it is set to hold the 1st layer < the 2nd layer < the 3rd layer in thickness.

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 using an intermediate transfer drum.
The present invention relates to prevention of voids and permanent distortion (claw marks) of an intermediate transfer film.

[0002]

2. Description of the Related Art As a first conventional color image forming apparatus, for example, as disclosed in JP-A-11-38749, an intermediate transfer member is provided with a medium-resistance elastic layer (rubber) or a resin layer. Forming a releasable surface layer on the outside thereof to form an intermediate transfer member, wherein the contact angle between the surface layer and water is 50 to
In some cases, the transfer auxiliary particles are attached to the surface layer to provide high transfer performance and long life.

As a second conventional color image forming apparatus, for example, as disclosed in Japanese Patent Application Laid-Open No. 11-45007, a cylindrical conductive core is provided on a cylindrical conductive core for the purpose of forming an intermediate transfer member. Formed foamed conductive layer, there is a conductive drum formed a cylindrical dielectric layer on the foamed conductive layer,
In some cases, the compression ratio of the foamed conductive layer is optimized, so that the dielectric layer does not wrinkle or shrink in outer diameter.

[0004]

However, the above-mentioned conventional color image forming apparatus has the following problems.

The intermediate transfer drum of the first color image forming apparatus uses an elastic layer, but is assumed to have high hardness rubber, and the nip pressure between the intermediate transfer drum and the photosensitive drum is set as high as 9 kgf. If you do not increase the runout accuracy, the “maximum nip pressure” will increase,
There is a problem of causing a decrease in transfer efficiency, and as a countermeasure, a device such as “transfer auxiliary particles” has been required.

Further, in the conductive drum of the second color image forming apparatus, since the resin layer is formed on the foamed conductive layer, the nip pressure can be reduced and the hollow is hard to occur, but the external force from the surface causes the nip pressure. There is a problem that the resin layer is liable to cause permanent distortion, and once deformed, permanent image defects occur.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has an image carrier for forming an electrostatic latent image and a toner image, and a plurality of colors from the image carrier. An intermediate transfer drum for multiplex primary transfer of toner images,
A transfer roller for secondary-transferring the primary-transferred toner image from the intermediate transfer drum to a transfer material, wherein the intermediate transfer drum is a rigid conductive cylinder formed in a cylindrical shape. And at least two or more conductive elastic layers provided on the outer peripheral surface of the conductive cylinder, and a release layer serving as a surface layer coated or applied on the outer peripheral surface of the conductive elastic layer. Having a color image forming apparatus.

Further, when the release layer is a first layer, the second layer and the third layer of the conductive elastic layer are arranged in the order of proximity to the release layer, the first layer is arranged in descending order of Young's modulus. The first layer> the second layer> in order of the volume resistivity so that the second layer> the third layer.
The third layer or the thickness is such that first layer <second layer <third layer.

As described above, by forming at least two or more conductive elastic layers, the third layer is formed to have the largest thickness, the lowest volume resistivity, and the lowest Young's modulus. The thinnest, the highest volume resistivity,
By forming the highest Young's modulus and forming the intermediate value of the second layer, the hollow layer is absorbed by the third layer, and the permanent distortion of the first layer is prevented by the stress dispersion effect of the second layer. Becomes possible.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram of a color image forming apparatus of the present invention, which includes a photosensitive drum 1, charging means 2 such as a scorotron charger, exposure means 3 such as a laser optical system, and four colors (for example, magenta, yellow, and cyan). It comprises four developing means 4a to 4d, a pre-transfer charge removing lamp 5, a cleaning means 6, a main charge removing lamp 7, an intermediate transfer drum 8, a transfer roller 9, a separator 10, and a pair of registration rollers 12, 13.

The first color is developed by any one of charging means 2, exposure means 3, and developing means 4a to 4d.
The primary transfer is performed from the photosensitive drum 1 onto the intermediate transfer drum 8. For the second color, after the residual toner of the first color is cleaned by the cleaning unit 6 and the charge is removed by the main discharge lamp 7,
Again, the charging means 2, the exposure means 3, and the developing means 4a-4
d, which is developed by any one of
And the primary transfer is performed on the intermediate transfer drum 8.

In the same manner as the second color, the third and fourth colors are transferred from the photoreceptor 1 onto the intermediate transfer drum 8, and then secondary-transferred from the intermediate transfer drum 8 to the transfer material by the transfer roller 9, and the transfer material is separated. The charge is erased by 10 and separated from the intermediate transfer drum 8, and the toner on the transfer material is melted and fixed to obtain a full-color image.

The photosensitive drum 1 is preferably a cylindrical a-Si drum. This is because when the photoconductor is OPC, the film thickness of the photoconductor decreases with the number of prints, or the dielectric thickness and resistivity in charging and transfer change due to electrical deterioration, so that long-term stable quality is maintained. This is because complicated control is required to perform the control.

The pre-transfer static elimination lamp 5 emits light when the second and subsequent colors of toner are primarily transferred. The wavelength is 660 nm, which is the wavelength at which the a-Si photoreceptor has sensitivity. Since the a-Si photoreceptor has a linear characteristic of the surface charge decay amount with respect to the exposure amount, the light amount of the pre-transfer neutralization lamp 5 is a- S
3 times or less, preferably 0.5 to less than half the exposure amount of the i photoreceptor
Preferably, it is set to twice. By setting such a value, the charge can be removed so that the potential is slightly higher than the potential of the portion where the toner is placed, and the gap voltage on the upstream side of the primary transfer nip becomes higher than the discharge starting voltage and the Since “reverse transfer development” in which the toner once transferred from the body drum 1 onto the intermediate transfer drum 8 is reversely transferred to the photosensitive drum 1 can be avoided, a good transfer image can be obtained over a wide range. Further, by optimizing the amount of static elimination light before transfer, not only is unnecessary strengthening not to affect the next charging potential, but also the residual charge of the non-developed portion on the photosensitive drum 1 before transfer is completely removed. As a result, the phenomenon of “transfer scattering”, in which the toner image is scattered around, can be prevented.

As shown in FIG. 2, the intermediate transfer drum 8 has a conductive cylinder base 8a formed in a cylindrical shape, and a conductive elastic layer provided concentrically laminated outside the cylinder base 8a. The sponge layer 8 which becomes the third layer in layers
b, a release layer 8d for improving the releasability of a rubber layer 8c as a second layer and a transfer material as a surface layer concentrically coated or coated on the outside of the conductive elastic layer.

The release layer 8d may be made of any material that improves the releasability from the transfer material. For example, a fluorine resin (ETFE,
Resins such as PVD), polyether ether ketone, and polycarbonate may be used. In the case of a fluororesin, a conductive agent needs to be selected in order to moderate the electric field dependence. Also, the release layer 8d may have elasticity. For example, a material obtained by blending fluorine rubber or urethane rubber with a fluorine resin may be used.

In the present invention, since the intermediate transfer drum 8 has two conductive elastic layers, a "hollow-out phenomenon" caused by an increase in the maximum nip pressure between the photosensitive drum 1 and the intermediate transfer drum 8 is achieved. In addition, "permanent distortion" of the surface layer of the intermediate transfer member due to concentrated stress from the outside can be prevented.

More specifically, (1) in order of decreasing Young's modulus,
(1) First layer> Second layer> Third layer. (2) First layer> Second layer> Third layer in order of decreasing volume resistivity. (3) Thickness of first layer <Second. It is preferable that the layer <the third layer.

Under these conditions, the "increase in the maximum nip pressure" between the photosensitive drum 1 and the intermediate transfer drum 8 caused by the eccentricity of the drum can be absorbed by the deformation of the third layer. Phenomenon "can be prevented. Further, the permanent distortion of the first layer due to the concentrated stress applied from the outside of the intermediate transfer drum 8 can be prevented by the stress dispersion effect of the second layer. This solves the two problems of the "hollow-out phenomenon" and the "permanent set" of the surface layer. The object of the present invention can be achieved by satisfying any one of the above conditions (1) to (3), but the object of the present invention can be more remarkably achieved by satisfying all three conditions. it can.

In this embodiment, the case where the number of the conductive elastic layers is two has been described. However, the number of the layers may be three or more, and it is sufficient if at least two layers close to the surface have the above-mentioned relationship.

Here, the color image forming apparatus was constructed under the following conditions, and color printing was performed.
, And "permanent distortion" of the surface layer can be prevented.

The photosensitive drum 1 is an a-Si drum and has a diameter of 30 to 80 mm.

The intermediate transfer drum 8 has a finished body diameter of 70 to
240mm, cylinder base 8a diameter 30-238m
m, the material of the first release layer 8d is a fluorocarbon resin, the thickness is 5 to 50 μm, and the volume resistivity is 10 ¹⁰ to 10 ¹⁵ Ω · c.
m, the Young's modulus is 1-3 × 10 ⁷ g / cm ² , the material of the rubber layer 8c as the second layer is polyurethane rubber, and the thickness is 0.1.
~ 1.0mm, volume resistivity 10 ⁷ ~ 10 ¹⁰ Ω · cm,
Young's modulus is 10 ³ to 10 ⁵ g / cm ² , the material of the third sponge layer 8b is polyurethane foam, and the thickness is 3
The volume resistivity is 10 ⁴ to 10 ⁷ Ω · cm, and the Young's modulus is 10 ² to 10 ⁴ g / cm ² .

The transfer roller 9 has a diameter of 20 to 30 mm,
The volume resistivity is 10 ⁷ to 10 ⁹ Ω · cm, and the thickness of the elastic body is 5 to 10 mm.

The contact pressure (nip pressure) between the photosensitive drum 1 and the intermediate transfer drum 8 and between the intermediate transfer drum 8 and the transfer roller 9 is set to 100 g / cm ² or less.

The separator 10 is formed by an AC saw-tooth discharger, and the bias conditions are DC current +54 μA, AC 10.5 Vpp
(Frequency: 1 kHz) and rectangular waves.

The registration roller pair 12, 13 constitutes a plastic deformation means, and the registration roller 12, which is in contact with the back surface of the image forming surface of the transfer material, is a rigid roller formed of a rigid body such as a metal and has a diameter of 3 to 3. 12.5 mm. The registration roller 13 which is in contact with the image forming surface of the transfer material is an elastic roller formed of an elastic body such as rubber, and has a diameter of 18 to 26 mm and a diameter of a rigid core of the shaft core of 12 to 1.
The diameter is set to 6 mm, which is larger than the diameter of the registration roller 12. By increasing the size in this way, it is possible to suppress the core metal from bending even when a high load is applied from the registration roller 12. By using such a pair of registration rollers 12 and 13, it is possible to plastically deform the surface of the transfer material on which the image is to be formed in a convex shape on the front side of the intermediate transfer drum 8 in the transfer material transport direction. Thus, even when the diameter of the intermediate transfer drum 8 is large, it is possible to prevent the transfer material from being easily peeled off from the intermediate transfer drum 8.

[0028]

As described above, according to the color image forming apparatus of the present invention, the conductive elastic layer has two or more layers, the release layer is the first layer, and the conductive elastic layer is a release layer. In the case where the second layer and the third layer are arranged in order from the closest to the first layer, the first layer> the second layer> the third layer, and the first layer> the second layer> the third layer in descending order of the Young's modulus. By setting the thickness to be 1st layer <2nd layer <3rd layer, the maximum nip pressure does not increase even with the combination of the photoreceptor drum and the intermediate transfer drum, so that the "hollow-out phenomenon" can be prevented and the surface can be prevented. Since the concentrated stress applied to the release layer is dispersed by the second layer, "permanent distortion" of the surface layer can be prevented, and high image quality can be maintained. In addition, since the surface is formed as a release layer, it is excellent in cleaning property and abrasion resistance, can provide a highly durable intermediate transfer drum, and has a high effect of absorbing run-out compared to a case where the elastic layer is formed only of rubber. Therefore, it is not necessary to add an extra processing step such as outer diameter polishing when forming the elastic layer, so that the manufacturing cost can be reduced and the defect rate can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a color image forming apparatus of the present invention.

FIG. 2 is a schematic sectional view showing an intermediate transfer drum of the color image forming apparatus of the present invention.

[Explanation of symbols]

 1: photosensitive drum 2: charging means 3: exposing means 4a to 4d: developing means 5: pre-transfer charge removing lamp 6: cleaning means 7: main charge removing lamp 8: intermediate transfer drum 9: transfer roller 10: separators 12, 13 : Registration roller 8a: Cylinder base 8b: Sponge layer (third layer) 8c: Rubber layer (second layer) 8d: Release layer (first layer)

Claims (4)

[Claims] An image carrier for forming an electrostatic latent image and a toner image, an intermediate transfer drum for multiplex primary transfer of toner images of a plurality of colors from the image carrier, and the primary-transferred toner image A transfer roller for performing a secondary transfer from the intermediate transfer drum to a transfer material, wherein the intermediate transfer drum is a rigid conductive cylinder formed in a cylindrical shape, and the conductive cylinder Characterized in that it has at least two or more conductive elastic layers provided on the outer peripheral surface thereof, and a release layer which is coated or applied on the outer peripheral surface of the conductive elastic layer to become a surface layer. Color image forming apparatus. 2. When the release layer is a first layer, the second layer and the third layer of the conductive elastic layer are arranged in the order from the order close to the release layer, the first layer> 2. The color image forming apparatus according to claim 1, wherein the second layer is larger than the third layer. 3. When the release layer is a first layer, the second layer and the third layer of the conductive elastic layer are arranged in the order of proximity to the release layer, and the first layer is arranged in order of volume resistivity. 2. The color image forming apparatus according to claim 1, wherein the second layer> the third layer. 4. When the release layer is a first layer, a second layer and a third layer of the conductive elastic layer in the order of proximity to the release layer, the thickness is: first layer <second layer <The color image forming apparatus according to claim 1, wherein the third layer is formed.