JP2002132051A - Separating member, process cartridge and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a separating member by which an abnormal image or toner soiling can be prevented, and to provide a process cartridge provided with the separating member and an image forming device provided with both. SOLUTION: In the device, the separating member 41 which has a surface resistance of <=107 Ω, at least on a surface that is abutted on an image carrier 1 and by which a sheet state medium 20 is separated from the image carrier 1, and the process cartridge 24 provided with it and the image forming device 100 having both are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a separation member for separating a sheet-like medium such as paper from an image carrier such as a photoreceptor, a process cartridge having the same, and an image forming apparatus such as a copier, a printer or a facsimile having the same. Related to the device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer, a facsimile, etc., FIG. 7 shows a sheet-like medium to which a developer on an image carrier is transferred from the image carrier. As described above, the configuration in which the separation member 141 is disposed in contact with the image carrier 1 is employed. Further, since it has been considered that the conventional separating member only needs to have a function of separating the sheet medium 20 from the image carrier 1,
Regardless of its electrical characteristics, an insulating resin material having excellent moldability was used for the separating member.

[0003]

However, when the separating member is formed of an insulating material, for example, when a dot image of 600 dpi is formed, as shown in FIG. It has been found that a streak-like abnormal image S is generated in any direction. The abnormal image S is displayed in the longitudinal direction of the image carrier 1 (in FIG.
(Left and right directions in the drawing), the positions corresponding to the separation members 141 disposed at two places, and when viewed with a microscope, the state was as shown in FIG. In the case of a normal image, as shown in FIG. 10, the toner particles are arranged in a matrix in an orderly manner to form each dot. In the case of such an abnormal image, as shown in FIG. 9, The toner particles are scattered.

[0004] As a result of analyzing the abnormal image S, the following facts have become clear. Since the separation member is always in contact with the image carrier, triboelectric charging occurs between the separation member and the image carrier, and the separation member is charged to a positive polarity, which is opposite to the negative polarity, which is the charging polarity of the toner. In this case, if the force of the separation member to attract the toner is greater than the force of the sheet-like medium to retain the toner, the toner moves to the separation member side as shown by an arrow C in FIG. Therefore, at the position near the separation member, as shown in FIG. 9, toner particles are scattered, and density unevenness occurs between the position near the separation member and a position other than the position. As shown in FIG. , A streak-like abnormal image S appears.

Further, as shown in FIG. 11, a part of the toner which has moved to the separation member side due to frictional charging of the separation member adheres to the separation member 141, and the toner adhered to the separation member 141 as shown in FIG. It was also found that the toner adhered to the rear end of the sheet medium 20 in the direction B, causing toner contamination T. Such toner contamination T occurs as follows. Referring to FIGS. 12 and 13, assuming that a point on image carrier 1 corresponding to the rear end of sheet-like medium 20 is point P, area Q on image carrier 1 downstream of point P in the A direction is: Since a transfer bias is applied via the sheet-shaped medium 20, the surface potential is positively charged to the negative polarity.
Since the transfer bias is applied to the region R on the upstream side in the direction A from the point without passing through the sheet medium 20, the surface potential is positively charged positive. Accordingly, when the point P approaches the separating member 141 by the rotation of the image carrier 1 in the direction A and the rear end of the sheet-like medium 20 approaches the separating member, the separating member 1
The positively charged toner on the negative electrode 41 moves toward the positively charged region R as indicated by an arrow D in FIG. 12, so that the toner adheres to the rear end of the sheet-like medium 20 and This causes stain T.

Accordingly, an object of the present invention is to provide a separation member capable of preventing such abnormal images and toner contamination, a process cartridge having the same, and an image forming apparatus such as a copying machine, a printer or a facsimile having the same. .

[0007]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a separating member for separating a sheet-like medium from an image bearing member. The surface resistance is 10 ⁷ Ω or less.

According to a second aspect of the present invention, in the separating member according to the first aspect, the material of the surface is a mixture of resin and carbon, and the surface of the surface is changed by changing the content of carbon. In the separation member whose resistance has been adjusted.

The invention described in claim 3 is the first or second invention.
A process cartridge having the separation member described above and an image carrier.

[0010] The invention according to claim 4 is the invention according to claim 1 or 2.
An image forming apparatus comprising the separation member described above or the process cartridge according to claim 3.

According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the fourth aspect, further comprising a transfer unit disposed to face the image carrier, wherein a transfer unit is provided between the image carrier and the transfer unit. It is characterized in that the developer on the image carrier is transferred to a sheet medium by applying a bias voltage.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A schematic configuration of an image forming apparatus to which the present invention is applied will be described below with reference to FIG. The image forming apparatus 100 includes a drum-shaped photoconductor 1 as an image carrier.
have. The photoreceptor 1 is rotated in a direction indicated by an arrow A (clockwise) in FIG. The photoreceptor 1 has a thickness of 30 μm on a conductive substrate of about 100 μm.
It is coated with an organic photoreceptor (OPC). Actually, application is performed by dividing into several layers according to functions, but is omitted in this embodiment. The surface has an Rz of about 20 μm, and the main material is a transparent resin such as PC. The transport speed is usually about 100 mm / s during image formation.

Reference numeral 4 denotes a charging roller as charging means for uniformly charging the surface of the photoreceptor 1. Note that a charging charger may be provided instead of the charging roller. Code 22
Denotes a cleaning blade disposed in contact with the surface of the photoreceptor 1. The cleaning blade 22 transfers the toner image formed by the toner as the developer onto the sheet 20 as the sheet medium. This is for removing the toner remaining on the surface of the photoconductor 1 from the photoconductor 1. Reference numeral 41 denotes a sheet 20 on which the toner image is transferred in contact with the surface of the photoconductor 1 and the toner image is transferred.
The figure shows a blade which is a separation claw as a separation member for separating from the blade.

Reference numeral 5 denotes an optical scanning device using a laser as exposure means for forming an electrostatic latent image. The optical scanning device 5 includes a polygon mirror 2 as an optical writing unit for optically writing an image by scanning the photosensitive member 1, and a motor 3 as a driving unit for driving the polygon mirror 2 to rotate.
A mirror 7 for reflecting the light reflected by the polygon mirror 2 toward the photoreceptor 1; a housing 10; and a part of the housing 10, which is located above the motor 3 and the polygon mirror 2 to cover the motor 3. , Specifically, a cover 11 made of aluminum.

Reference numeral 6 denotes a developing device which is a contact-type one-component developing device as a developing means for supplying a black toner to the photosensitive member 1. The developing device 6 includes a developing roller 13 disposed opposite to the photoconductor 1 and a blade 21 for supplying toner to the developing roller 13 while stirring the toner in the developing device 6. A bias voltage (development bias) can be applied by a bias unit (not shown). This bias voltage is variable. The developing device 6 can be freely attached to and detached from the casing 23, and the developing roller 13 occupies a predetermined position facing the photoconductor 1 in a state where the developing device is mounted on the casing 23.

As shown in FIGS. 1 and 2, the developing device 6, the casing 23, the photosensitive member 1, the charging roller 4, the blade 22,
Reference numeral 41 denotes a process unit 24 which is a process cartridge as an image forming unit. A transfer roller 25 as a transfer unit is provided outside the process unit 24 and below the photoconductor 1 so as to face the photoconductor 1. The transfer roller 25 applies a transfer bias to the photoconductor 1 to apply toner on the photoconductor 1 to the paper 20.
Is transferred to The bias voltage of the transfer bias is +5 in accordance with the temperature inside the image forming apparatus 100 main body.
It is controlled between 0 and 5 kV. The transfer unit may be of a type that performs corona transfer instead of the transfer roller 25. Reference numeral 17 denotes a sheet feeding table including a sheet cassette on which sheets 20 are stacked. As the sheet medium, thick paper or special paper in the form of an OHP sheet can be used in addition to the paper 20 which is plain paper.

Reference numeral 31 denotes a manual tray that can be turned upside down with respect to the image forming apparatus 100 main body.
When the sheet 20 is placed on the manual feed tray 31 in the state where the sheet 1 is folded down, the sheet 20 is transported by the sheet feeding roller 32 toward the registration roller pair 19. As shown in FIG. 3, when the manual feed tray 31 is in the down position, a part of the housing 33 is opened (not shown), so that the entire process unit 24 can be attached to and detached from the image forming apparatus 100. The developing device 6 can be detached from the image forming apparatus 100 by itself. Reference numeral 34 denotes a slide tray that is slidable with respect to the main body of the image forming apparatus 100 and is disposed below the paper discharge tray 82.
The slide tray 34 is slidable in the discharge direction of the paper 20 through a slide opening 35 formed in the housing 33, and is drawn out from the slide opening 35 when forming an image on the large-sized paper 20. This is to assist the stacking of the paper 20 by the paper tray 82.

As shown in FIG. 4, the blade 41 is formed in a flat plate shape, and has a sharp tip end 42 in contact with the photosensitive member 1, and is a so-called claw type. Blade 41
Are disposed on the casing 23 of the process unit 24 at two positions in the longitudinal direction of the photoconductor 1, that is, in the direction perpendicular to the sheet of FIG. 1. Therefore, as shown in FIG. 3, the blade 41 is detachable from the image forming apparatus 100 integrally with the process unit 24.

The blade 41 is integrally molded as a whole.
It is a mixture of a fluororesin and carbon and has a resistance value of 10 ⁴ Ω. As shown in FIG. 5, according to the experiment by the present inventors, if the surface resistance of the contact surface of the separation member to the photoreceptor 1 is 10 ⁷ Ω or less, the image is allowed within the allowable range, that is, the above-described streak-like shape. It has been found that the image rank is 3 or higher, which is a range in which image deterioration such as an abnormal image or toner stain does not cause a problem. Therefore, the resistance value of the blade 41 is not limited to 10 ⁴ Ω, but may be in a range of 10 ⁷ Ω or less. The resistance value can be adjusted by changing the content of carbon. As the resin to be mixed with carbon, polycarbonate or polyamide imide can be used in addition to the fluorine-based resin. However, the fluorine-based resin is excellent in view of the slipperiness with respect to the photoreceptor 1.

The blade 41 does not have a constant resistance as a whole as in this embodiment, but is formed by forming a layer having a resistance of 10 ⁷ Ω or less on the surface of a resin base. Any material may be used as long as the surface resistance of at least the surface in contact with the photoreceptor 1 is 10 ⁷ Ω or less.
In this case, the base is not limited to a resin, but may be made of another material such as a metal. If you consider the wear over time,
As in this embodiment, it is desirable to integrally mold the entire separation member from a material having such a resistance value. As the separating member, instead of the claw type as described above, as shown in FIG.
A bar-shaped, so-called needle-type blade 44 having a bent and pointed tip portion 43 that contacts the photoconductor 1
May be used. In the present embodiment, one-component development is performed. However, even in the case of performing two-component development, it is understood that such image deterioration does not occur if the surface resistance of the separating member is set to 10 ⁷ Ω or less. ing.

The image forming operation of the image forming apparatus 100 will be described. After the photoconductor 1 is uniformly charged by the charging roller 4, the photoconductor 1 is scanned and exposed by the optical scanning device 5 based on image information to form an electrostatic latent image on the surface. Here, the image information to be exposed is image information transmitted from outside the image forming apparatus 100, and a laser beam Lb generated by a semiconductor laser (not shown) by this image information is scanned by an optical device (not shown). , And the optical path is adjusted to scan the photosensitive member 1 to carry an electrostatic latent image. The formed electrostatic latent image is developed by the developing device 6.

The paper 20 is fed from the paper feed table 17 to the paper feed roller 1.
8. The toner image conveyed toward the photoreceptor 1 via the registration roller pair 19 and formed on the photoreceptor 1 passes onto the paper 20 when passing between the transfer roller 25 and the photoreceptor 1. Transcribed. After the transfer, the paper 20 is separated from the photoreceptor 1 by the blade 41 without causing image deterioration, guided by the fixing device 80 by the guide 26, and the toner image is fixed on the paper 20 by the fixing device 80. The sheet 20 is discharged via a guide roller pair 81 and a sheet discharge roller pair 27 to a sheet discharge tray 82 located above the optical scanning device 5 and serving as a sheet discharge stack unit. On the other hand, after the transfer, the toner remaining on the photoconductor 1 is removed by the blade 22, and the toner is again supplied to the charging roller 4.

Although the embodiment to which the present invention is applied has been described above, the image forming apparatus 100 is not limited to forming a monocolor image, but may be a device for forming a color image. The information read by this image reading means may be used.

[0024]

According to the first aspect of the present invention, the first aspect is provided.
According to the invention described above, in the separation member for separating the sheet-like medium from the image carrier, at least the surface resistance of the surface in contact with the image carrier is 10 ⁷ Ω or less. It is possible to provide a separation member capable of preventing an abnormal image and toner contamination due to movement.

According to a second aspect of the present invention, in the separation member according to the first aspect, the material of the surface is a mixture of resin and carbon, and the surface of the surface is changed by changing the content of carbon. Since the separation member has the adjusted resistance, it is possible to provide a separation member capable of freely selecting the surface resistance of the surface.

The third aspect of the present invention is the first or second aspect.
Since the separation member and the image carrier are provided in the process cartridge, when the separation member deteriorates with time, the entire process cartridge is replaced, or only the separation member is detached from the main body while the process cartridge is detached from the main body. The separation member can be exchanged, the maintenance property can be improved, and it is not necessary to extend the life of the separation member, and a low-cost material can be selected for the separation member, so that an inexpensive process cartridge can be provided.

The invention according to claim 4 is the first or second invention.
In the image forming apparatus having the separating member described above or the process cartridge according to claim 3, an abnormal image or toner smear due to toner movement due to charging of the separating member can be prevented, so that the user can obtain high quality images. An image forming apparatus that has high reliability and can select the resistance value of the separation member according to the usable sheet-like medium can prevent occurrence of such an abnormal image on various kinds of sheet-like media. Can be provided.

According to a fifth aspect of the present invention, there is provided the image forming apparatus according to the fourth aspect, further comprising a transfer unit disposed to face the image carrier, wherein a transfer unit is provided between the image carrier and the transfer unit. Since the developer on the image carrier is transferred to the sheet-like medium by applying a bias voltage, an image forming apparatus with high image quality and high user reliability is provided even if the transfer is performed in this manner. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic view of a separation member, a process cartridge having the same, and an image forming apparatus having the same, to which the present invention is applied.

FIG. 2 is an enlarged view of a separation member shown in FIG. 1 and a process cartridge having the same.

FIG. 3 is a front view of an essential part showing an aspect of attachment and detachment of a separation member and a process cartridge having the same with respect to the image forming apparatus shown in FIG.

FIG. 4 is an enlarged perspective view of a separation member.

FIG. 5 is a correlation diagram showing a relationship between a surface resistance of a separation member on a photosensitive member side as an image carrier and an image rank.

FIG. 6 is an enlarged perspective view of another separation member.

FIG. 7 is a main part front view showing a state of movement of a developer from a sheet-like medium to a separating member in an image forming apparatus having a conventional separating member.

FIG. 8 is a plan view showing a streak-like abnormal image generated in the image forming apparatus shown in FIG. 7;

FIG. 9 is an enlarged plan view of the streak-like abnormal image shown in FIG. 8;

FIG. 10 is an enlarged plan view of a normal image.

11 is an enlarged front view of a main part showing a state in which a developer has adhered to a separating member in the image forming apparatus shown in FIG. 7;

12 is a main part front view showing a state of re-adhesion of a developer from a separation member to a sheet-like medium in the image forming apparatus shown in FIG. 7;

FIG. 13 is a correlation diagram showing a correspondence relationship between a point P on the image carrier corresponding to the rear end of the sheet medium and the charging polarity of the image carrier.

[Explanation of symbols]

 Reference Signs List 1 image carrier 20 sheet medium 24 process cartridge 25 transfer means 41, 44 separation member 100 image forming apparatus

Claims (5)

[Claims] 1. A separating member for separating a sheet medium from an image carrier, wherein at least a surface resistance of a surface in contact with the image carrier is 10 ⁷ Ω or less. 2. The separation member according to claim 1, wherein the material of the surface is a mixture of resin and carbon, and the surface resistance of the surface is adjusted by changing the content of carbon. Element. 3. A process cartridge comprising the separation member according to claim 1 and an image carrier. 4. An image forming apparatus comprising the separating member according to claim 1 or the process cartridge according to claim 3. 5. The image forming apparatus according to claim 4, further comprising a transfer unit disposed opposite to the image carrier, and applying a bias voltage between the image carrier and the transfer unit. An image forming apparatus for transferring a developer on an image carrier to a sheet-shaped medium by using the method.