JPH11109769A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a failure in transfer and a defect in an image caused by sticking to a photoreceptive drum and oozing by adopting such a constitution that an elastic layer made of urethane rubber or a rubber material is provided in a transfer member and the surface of the elastic layer is reformed with post processing. SOLUTION: As a transfer roller 15 being the transfer member, the urethane rubber which is inexpensive and has a small resistance unevenness characteristic or the rubber material whose polarity is great is used in a solid rubber or foamed porous body state. A thing whose surface is post-processed with UV processing, plasma processing, an ion beam, an electron beam, etc., is used. Thus, an activated layer is formed on the surface, so that surface energy becomes small to improve releasability and the sticking of toner and a stuck paper powder quantity are reduced. Therefore, the failure in the transfer caused by the soiling of the transfer roller and the defect in the image caused by sticking to the photoreceptive drum and oozing can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to an electrophotographic image forming apparatus, and more particularly to an image forming apparatus provided with a transfer member for transferring an image on an image carrier to a material to be transferred.

[0002]

2. Description of the Related Art Conventionally, as a means for transferring a toner image on an image carrier to a transfer material such as paper, a corona transfer method and a roller transfer method have been known. Used in equipment.

Among them, the corona transfer method is advantageous in that the transfer is performed in a non-contact manner, so that damage to the image carrier can be minimized and the transfer material can be selected. However, since the ozone and NO _x are generated by corona discharge,
Means for removing these are required, and the configuration is complicated due to the use of the corona charger, and there have been problems such as a need to take measures to prevent the transfer material from rushing into the corona charger.

On the other hand, in order to solve these problems, a roller transfer system has been used in recent years. The transfer roller used in the transfer device of the roller transfer type is composed of a semiconductive rubber material and a core metal serving also as a power supply electrode, and since the applied voltage can be smaller than that of the transfer device using the corona charger, the transfer roller can be used for the transfer roller. Since the generation of NO _x is reduced, and the toner image on the image carrier is transferred to the transfer material in contact with the transfer material, the transfer of the transfer material can be stabilized.

The bias applied to the transfer roller is:
When there is no transfer material between the image carrier and the transfer roller, it is determined by a so-called ATVC method or the like, which is calculated from a voltage generated when a constant current is applied to the transfer roller by a constant current control from a power supply by a constant current control, by a preset control formula. Voltage value.
With this control, even if the resistance of the transfer roller changes due to temperature, humidity, etc., the bias applied to the transfer roller is such that an optimal transfer bias at the resistance value is applied, and a good transfer image can be obtained. .

As a material of the transfer roller, EPD is used.
M, NBR, hydrin rubber, urethane, silicone rubber, and the like are generally used. Further, each of the rubber materials is often foamed to form a porous body.

[0007]

However, in the above-described conventional image forming apparatus, urethane rubber, epichlorohydrin rubber, urethane rubber, epichlorohydrin rubber, and the like are used as roller transfer members and belt transfer members having low cost and low resistance unevenness.
When a rubber material having a large polarity such as nitrile butadiene rubber is used, there are the following concerns.

That is, when urethane rubber is used as the transfer roller, toner stain occurs on the transfer roller.
Due to the toner contamination, a high-resistance layer is formed by the toner on the surface of the transfer roller, which causes an image failure due to transfer failure and the like. Dirt is observed.

In general, by applying a bias opposite to the transfer bias to the transfer roller as a cleaning bias during post-rotation, the toner adhered to the surface of the transfer roller is transferred onto the photosensitive drum and collected by a cleaner or the like. Although excessive toner is prevented from adhering to the transfer roller, solid rubber and urethane rubber have high adhesiveness on the rubber surface, and cleaning bias alone is not sufficient.

When a transfer roller containing a rubber material having a large polarity (such as a blend of a plurality of rubber materials) is used, toner contamination becomes a problem similarly to the case where urethane rubber is used, and the transfer roller is transferred to the photosensitive drum. In the case of contact, the plasticizer, filler, additive, etc. added during the production of the transfer roller oozes out on the surface of the transfer roller, contaminating the photosensitive drum, and sticking the transfer roller to the photosensitive drum, Photoconductor drum contamination becomes a problem.

[0011] Also, these concerns are caused by foaming the transfer roller and making it porous, so that the contact area between the photosensitive drum and the transfer roller is increased, and the area of the contact portion between the photosensitive drum and the transfer roller is increased. The surface pressure is reduced, and contamination of the photosensitive drum due to seepage and sticking are improved as a level, but are still insufficient.

For this reason, it has been difficult to use urethane rubber or a rubber material having a large polarity as the transfer roller.

Accordingly, the present invention relates to a contact-type electrostatic transfer type image forming apparatus which reduces the amount of toner adhesion and paper dust adhesion, prevents sticking to a photosensitive drum, and prevents exudation. It is an object of the present invention to provide a low-cost transfer roller using urethane or a rubber material having a large polarity, which can prevent transfer failure due to dirt, sticking to a photosensitive drum, and image failure due to seepage.

[0014]

In order to achieve the above object, the present invention relates to a contact-type electrostatic transfer type image forming apparatus, wherein urethane rubber and a rubber material having a large polarity are used for a transfer roller and solid rubber is used. Alternatively, it is foamed and used in the state of a porous body, and the surface is post-treated with heat treatment, UV treatment, plasma treatment, ion beam, electron beam, or the like, thereby modifying the surface. As a result, an activation layer (cross-linked layer, etc.) is formed on the rubber surface
Are formed, and the molecular structure of the surface becomes dense. Therefore, the surface energy is reduced, the releasability is improved, and the toner adhesion,
The polymer on the surface takes on a three-dimensional network structure due to the formation of a cross-linked layer (a layer in which cross-linking has progressed before the post-treatment), which is one of the activation layers, and reduces the amount of paper powder attached. It is possible to prevent the plasticizer sometimes used from migrating, prevent sticking to the photosensitive drum, and prevent contamination of the photosensitive drum.

Further, when the roller is foamed and vulcanized to form a porous body, and in the state where cells of the porous body are present on the roller surface, the surface area is large and the effect of post-treatment is also large.

The effect of the post-treatment can be changed from several hundred nm to several cm, but several tens μm is appropriate in consideration of the durability of the roller. In addition, if the post-processing is performed too much, the surface layer may be deteriorated.

As described above, transfer failure due to contamination of the transfer roller, sticking to the photosensitive drum, and image failure due to contamination of the photosensitive drum are prevented, and transfer using low-cost urethane rubber having small resistance unevenness or rubber material having large polarity is performed. Rollers can be provided.

[0018]

FIG. 1 shows a schematic configuration of an image forming apparatus of a laser beam printer (hereinafter, referred to as LBP) as one embodiment of the present invention.

In FIG. 1, an image forming apparatus includes a photosensitive drum 11 having a photosensitive layer 11b formed on a conductive support 11a as an image carrier to be charged, and a charging device for applying an AC voltage on which a DC voltage is superimposed. A charging roller 12 serving as a charging device connected to a power source 18; an exposure light 13; a developing device 14 connected to a developing power source 19; a transfer roller 15 serving as a transfer member connected to a transfer power source 20;
6. The paper transport guides 21 and 22 and the fixing device 17 are configured as main elements.

In the image forming apparatus configured as described above, the photosensitive drum 11 rotates in a fixed direction (clockwise direction in the figure), and the charging roller 12 makes the surface of the photosensitive drum 11 uniform while being pressed against the photosensitive drum 11. Charges. After that, the photosensitive drum 11 is exposed by the exposure light 13 to form an electrostatic latent image on the photosensitive drum 11. The electrostatic latent image is visualized as a toner image as a developer powder by the developing device 14, and the toner image is transferred between the photosensitive drum 11 and the transfer roller 15 by the transfer guide 21. 23. After that, the transfer material 23 is separated from the photosensitive drum 11 by the grounded static elimination needle 24, moves on the transport guide 22, is introduced into the fixing device 17, and is then heated under pressure by the fixing device 17, so that a permanent image is formed. It is established as. On the other hand, the waste toner remaining on the photosensitive drum 11 is collected by the cleaner 16.

FIG. 2 shows the structure of the transfer roller 15 used in the image forming apparatus. FIG. 2 is a cross-sectional view of the transfer roller 15. In FIG. 2, the transfer roller 15 has a configuration in which an elastic layer 15b made of urethane rubber or a rubber material having a large polarity is provided on an 8φ conductive shaft 15a also serving as a power supply electrode.

The transfer roller 15 having the above-described structure is contaminated by the transfer of the fogging toner on the photosensitive drum 11 due to long-term use, or adheres to the photosensitive drum 11 when left in contact with the photosensitive drum 11 for a long time. Transfer roller 15
The transfer of the plasticizer to the surface of the photosensitive drum 11 may cause contamination of the photosensitive drum, which may cause an image defect.

In the present embodiment, in the image forming apparatus of the contact electrostatic transfer type, the transfer roller 15 is made of urethane rubber having characteristics of low cost and small resistance unevenness, or a rubber material having a large polarity in a solid rubber state. A foamed and porous body is used, and the surface thereof is post-treated by UV treatment, plasma treatment, ion beam, electron beam or the like. As a result, an activation layer (such as a crosslinked layer) is formed on the surface, so that the surface energy is reduced, the releasability is improved, and the amount of toner adhesion and paper powder adhesion is reduced. In addition, a cross-linked layer (a layer in which cross-linking has progressed before the post-treatment), which is one of the activation layers, is formed, and the polymer on the surface has a three-dimensional network structure. There is no gap to rub through, and the migration of the plasticizer to the surface is prevented, and sticking to the photosensitive drum and bleeding are prevented.

Further, by forming the porous body by foaming and vulcanizing the roller, the surface area is large and the effect of the post-treatment is increased in a state where the porous cell is present on the roller surface.

The effect of the post-treatment can be changed from several hundred nm to several cm, but several tens μm is necessary in consideration of the durability of the roller. Also, if you apply too much post-processing,
Care must be taken in setting the post-processing time and the like because the surface layer also deteriorates.

As described above, transfer failure due to transfer roller contamination, image sticking to the photosensitive drum, and image failure due to bleeding are prevented, and a low-cost urethane rubber or a rubber material having a large characteristic with small resistance unevenness is used. Transfer roller 15 can be realized.

FIG. 3 shows an LBP according to another embodiment of the present invention.

In this embodiment, a transfer belt 31 is applied to the image forming apparatus of the present invention. This transfer belt 31
Is composed of one or more layers. An active layer is formed on the surface of such a transfer belt 31 by post-processing. As a method of the post-treatment, as in the case of the first embodiment, a thermosetting treatment, a plasma treatment, an ultraviolet irradiation treatment and the like can be mentioned. Examples of the material of the transfer belt 31 include a urethane elastomer and a rubber material. Further, on the surface of the transfer belt 31, 1
When a layer is provided, a post-treatment is required to improve the strength of the release layer and the adhesion to the lower layer.

In this embodiment, since the active layer is formed on the surface of the transfer belt 31 by post-processing, the toner stain is reduced, and the transfer belt 31 surface becomes high due to the stain on the back surface of the transfer material caused by the toner stain. An image defect caused by resistance is prevented, and a plasticizer is prevented from migrating to the surface of the transfer belt 31. The image defect is caused by sticking to the photosensitive drum 11 and contamination of the photosensitive drum due to bleeding. Sticking to the transfer belt 31 is prevented.

[0030]

【Example】

(Example 1) The present invention was applied to a cartridge type LBP of 24 sheets per minute.

FIG. 2 shows the structure of the transfer roller 15 of the image forming apparatus used in the present invention. The transfer roller 15 uses urethane rubber, is formed by a casting method, and is not polished because it has a roller shape. By irradiating the thus configured transfer roller 15 with ultraviolet light as a post-process, an activation layer was formed on the surface of the transfer roller 15. As a method of the post-treatment at this time, another method such as a plasma treatment or a heat treatment may be used.

As a result, the toner stain on the transfer roller 15 is reduced, and the image defect due to the stain on the back surface of the transfer material caused by the toner stain and the increase in the resistance of the transfer roller 15 surface due to the stain is prevented.

In this embodiment, the roller has not been polished and the desired outer diameter accuracy is obtained by the mold shape. However, after forming, the roller is polished to increase the outer diameter accuracy, and the active layer is formed on the roller surface by post-processing. The same effect can be obtained by forming. The effect of the post-treatment does not change even in a type using a different urethane rubber such as a thermoplastic type and a kneading type.

(Embodiment 2) The present invention was applied to a cartridge type LBP of 24 sheets per minute.

The transfer roller 15 of the image forming apparatus used in the present invention has the structure shown in FIG. The transfer roller 15 is made of urethane rubber and foamed in a mold. Since it is shaped by a mold, it is not polished. Since there is no skin layer, porous cells appear on the roller surface.
An activation layer was formed on the surface of the transfer roller 15 by subjecting the transfer roller 15 thus configured to a thermosetting treatment as a post-treatment. As a method of the post-treatment at this time, another method such as a plasma treatment or an ultraviolet irradiation treatment may be used.

As a result, the toner stain on the transfer roller 15 is reduced, and the image defect due to the stain on the back surface of the transfer material caused by the toner stain and the increase in the resistance of the transfer roller 15 surface due to the stain is prevented.

In this embodiment, the outer diameter accuracy is obtained by the accuracy of the mold. However, the same effect can be obtained by performing post-processing after obtaining the outer diameter accuracy by polishing. Further, even when the polishing is not performed and the skin layer is provided and the surface is smooth, the same effect as in the present embodiment can be obtained by the post-processing. The effect of the post-treatment does not change even in a type using a different urethane rubber such as a thermoplastic type and a kneading type.

(Embodiment 3) The present invention was applied to a cartridge type LBP of 24 sheets per minute.

The transfer roller 15 of the image forming apparatus used in the present invention has the structure shown in FIG. The transfer roller 15 is a mixture of epichlorohydrin rubber having a strong negative polarity and NBR at a ratio of 1: 1. Since a resistance value is adjusted by a polymer, a conductive agent is not particularly used. The transfer roller 15 made of such a material is foamed and vulcanized, and the transfer roller 15 is formed into a porous body and polished to form an outer diameter. By irradiating the thus configured transfer roller 15 with ultraviolet light as a post-process, an activation layer was formed on the surface of the transfer roller 15. As a method of the post-treatment at this time, another method such as a plasma treatment or a thermosetting treatment may be used.

As a result, toner stains on the transfer roller 15 are reduced, and image defects due to stains on the back surface of the transfer material caused by toner stains and an increase in the resistance of the transfer roller 15 surface due to stains are prevented. Transfer of the agent to the surface of the transfer roller 15 was prevented, and sticking to the photosensitive drum and image defects due to contamination of the photosensitive drum due to bleeding were prevented.

Embodiment 4 The present invention was applied to a cartridge type LBP of 24 sheets per minute.

The transfer roller 15 of the image forming apparatus used in the present invention has the structure shown in FIG. The transfer roller 15 is formed of NBR having a strong negative polarity. The transfer roller 15 made of such a material is foamed and vulcanized in a mold to form a porous body. In addition, since the outer diameter shape is adjusted by the mold, it is not polished. Therefore, 1 to 100 μm
There is a degree of skin layer.

The transfer roller 15 configured as described above has
An activation layer was formed on the surface of the transfer roller 15 by performing a thermosetting treatment as a post-treatment. As a method of the post-treatment at this time, another method such as a plasma treatment or an ultraviolet irradiation treatment may be used.

As a result, toner stains on the transfer roller 15 are reduced, and image defects due to stains on the back surface of the transfer material caused by toner stains and high resistance of the surface of the transfer roller 15 due to stains are prevented. Transfer of the agent to the surface of the transfer roller 15 was prevented, and sticking to the photosensitive drum and image defects due to contamination of the photosensitive drum due to bleeding were prevented.

In addition, even when polishing is not performed, and a cell of a porous body appears on the roller surface without a skin layer, the same effect as in the present embodiment can be obtained by the post-treatment.

[0046]

According to the present invention, a contact-type electrostatic transfer type image forming apparatus is used in which a transfer roller is used in a state of urethane, a rubber material having a large polarity, a solid rubber or a foamed porous body, and the surface thereof is used. Is post-treated with heat treatment, UV treatment, plasma treatment, ion beam, electron beam, etc. to form an active layer on the surface and modify the surface of the transfer roller and transfer belt. Prevents sticking to the photosensitive drum and exuding, preventing transfer failure due to transfer roller dirt, sticking to the photosensitive drum, and defective image due to exuding, low-cost urethane or large polarity A transfer roller using a rubber material can be provided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing a configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a transfer roller used in the image forming apparatus of FIG.

FIG. 3 is a longitudinal sectional view schematically showing a configuration of an image forming apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 photosensitive drum 11a conductive support 11b photosensitive layer 12 charging roller 13 exposure light 14 developing device 15 transfer roller 16 cleaner 17 fixing device 18 charging power supply 19 developing power supply 20 transfer power supply 21, 22 paper transport guide 24 discharging needle 31 transfer belt

Claims (9)

[Claims] In a transfer type image forming apparatus, a transfer bias is applied to a transfer member to transfer a transferable image formed and carried on an image carrier to a material to be transferred, wherein the transfer member is made of urethane rubber or urethane rubber. An image forming apparatus, comprising: an elastic layer formed of a rubber material, wherein the surface of the elastic layer is modified by a post-treatment. 2. The image forming apparatus according to claim 1, wherein the post-treatment is performed by modifying the surface of the transfer member with a heat treatment, a UV treatment, a plasma treatment, an ion beam, or an electron beam. 3. The image forming apparatus according to claim 1, wherein the transfer member has a roller shape. 4. The image forming apparatus according to claim 3, wherein the transfer member is formed by vulcanizing a urethane rubber material and then performing a post-treatment for modifying the surface. 5. The image forming apparatus according to claim 3, wherein the transfer member is formed by subjecting a urethane rubber material to foam vulcanization to form a porous body, and post-treated to modify the surface. 6. The transfer member according to claim 3, wherein the transfer member is formed by foaming and vulcanizing a rubber material to form a porous body while holding the skin layer, and post-treating the skin layer to modify the surface. Image forming apparatus. 7. The image forming apparatus according to claim 3, wherein the transfer member is formed by foaming and vulcanizing a rubber material to form a porous body, and is post-processed to modify the surface. 8. The image forming apparatus according to claim 1, wherein the transfer member has a belt shape. 9. The image forming apparatus according to claim 8, wherein the surface of the belt-shaped transfer member is coated with a material having high releasability.