JP2000010423A - Transfer unit and conductive roller for transfer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the density unevenness of toner by eliminating the defective transfer of the toner to paper. SOLUTION: Plural ring-like notches or spiral notches are put at an elastic member constituting the outer peripheral part of a conductive roll for transfer such as a back-up roll 29 and a transfer roll, a current is made to hardly flow in the axial direction at the time of transferring toner, the sneak path of the current is eliminated and the distorsion of an outer peripheral surface member is reduced so that the density unevenness of the toner is reduced at this conductive roller for transfer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer conductive roll used in an electrophotographic apparatus such as a copying machine or a laser printer.

[0002]

2. Description of the Related Art The following technique (J01) is conventionally known as an image forming apparatus using the conductive roll. (J01) Technology shown in FIGS. 7 and 8 FIG. 7 is a schematic explanatory view of a conventional image forming apparatus using a conductive roll. FIG. 8 is a diagram illustrating the operation of the conductive roll used in the secondary transfer unit of the image forming apparatus. 7 and 8, a charging device 02, a latent image writing device 03, a rotary developing device 04, and a primary transfer are sequentially arranged around an image carrier 01 formed of a photosensitive drum along the rotation direction. A roll T1, a cleaning device 06, and the like are arranged.
The latent image writing device 03 writes an electrostatic latent image by exposing the surface of the image carrier 01 at the latent image writing position Q1. The rotary type developing device 04 has developing devices 04k, 04y, 04c, and 04m of four colors of K (black), Y (yellow), M (magenta), and C (cyan) which rotate together with the rotating shaft 04a. In the development area Q2, the electrostatic latent image on the image carrier 01 is developed into a toner image. A power supply circuit E supplies a primary transfer voltage having a polarity opposite to the charging polarity of the developing toner used in the developing device 04 to the primary transfer roll T1.

An intermediate transfer belt B which rotates between the image carrier 01 and the primary transfer roll T1 in the direction of the arrow while abutting on the surface of the image carrier 01 has a drive roll 07,
It is rotatably supported by a tension roll 08, idler rolls 09 and 09, and a backup roll 011. A secondary transfer roll 012 is disposed at a position facing the backup roll 011 with the intermediate transfer belt B interposed therebetween.
Is in contact with an electrode roll 013. Electrode roll 01
3, a secondary transfer voltage having a polarity opposite to the polarity of the toner is supplied from a power supply circuit E. The rolls 011 to 013
Constitutes a secondary transfer device T2. A primary transfer area Q3 is formed by a region where the primary transfer roll T1 is pressed against the intermediate transfer belt B, and a secondary transfer region Q4 is formed by a region where the secondary transfer roll 012 is pressed against the intermediate transfer belt B. Have been. At a position facing the drive roll 07, a belt cleaner 014 is disposed via an intermediate transfer belt B.

In the color image forming apparatus shown in FIG. 7, after the surface of the image carrier 01 rotating in the direction of arrow A is uniformly charged by the charger 02, the latent image writing device 03 uses the laser beam. A first color electrostatic latent image is formed at the latent image writing position Q1, and a toner image T is formed at the developing area Q2. When the toner image T passes through the primary transfer area Q3, it is primary-transferred electrostatically onto the intermediate transfer belt B by the primary transfer roll T1. Thereafter, similarly, on the intermediate transfer belt B carrying the toner image T of the first color,
The second color, third color, and fourth color toner images T are sequentially superimposed and primary-transferred, and a full-color multiplex toner image is finally formed on the intermediate transfer belt B.

[0005] When the multi-toner image passes through the secondary transfer area Q4, the secondary transfer unit T2 feeds the paper feed tray 015.
Is electrostatically collectively transferred to the paper S supplied at a predetermined timing from the printer. The sheet S to which the toner image has been transferred is conveyed to the fixing device 016, subjected to a fixing process when passing through the fixing area Q5, and then discharged outside the apparatus. After the primary transfer, the residual toner and the charge are removed from the image carrier 01 by the cleaning device 06, and the intermediate transfer belt B after the secondary transfer is removed by the belt cleaner 014 to prepare for the next image forming process. . When a single-color monocolor image is formed in the image forming apparatus, only one developing unit is used.

In FIG. 8, in the secondary transfer area Q 4, the intermediate transfer belt B is supported from the back side by the backup roll 011, and the paper S is supplied so as to overlap the intermediate transfer belt B, and Then, the outer transfer roll 012 is pressed against the backup roll 011. In this state, by applying a secondary transfer voltage between the outer transfer roll 012 and the backup roll 011, the toner image T on the surface of the intermediate transfer belt B is transferred onto the sheet S.
Next transfer is performed.

[0007]

(Problems of the technique (J01)) However, when a secondary transfer voltage is applied from the electrode roll 013 to the backup roll 011, a secondary transfer which should flow through the paper S should be performed. The transfer current is high because the electrical resistance of the sheet S sandwiched between the secondary transfer roll 012 and the intermediate transfer belt B is high.
Flows in the direction of arrow I (see FIG. 8) in the direction of arrow I (see FIG. 8), and the charges move in the axial direction (the width direction of the paper).
The transfer current escapes to the outside of both ends. Therefore, the paper S
The transfer current does not flow to both ends of the sheet S in the width direction, and the toner on the intermediate transfer belt B is not transferred to both ends of the sheet S. The above problem occurs not only when the toner image on the intermediate transfer drum is transferred onto a transfer material but also on the intermediate transfer belt.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object the following contents (O01) to (O03). (O01) When transferring the toner image on the image carrier having the toner image on the surface to the surface of the transfer material, the transfer current should not escape to both ends in the width direction of the transfer material. (O02) To prevent transfer failure. (O03) To reduce unevenness in density of a transferred toner image caused by a difference between the maximum value and the minimum value of the surface resistivity of the transfer conductive roll.

As a result of studying the above problem, the inventors of the present invention divided the surface of the roll of the backup roll or the transfer roll into circumferential cuts, or formed a spiral shape from one end to the other end in the axial direction. When the cut is made, the surface resistance in the axial direction of the outer periphery of the roll to which the transfer voltage is applied at the time of transfer of the toner increases, and the charge does not move in the axial direction on the roll surface. The difference between the maximum and minimum values of the surface resistivity of the roll surface is reduced by making a cut directly between the paper and the transfer roll. (The reduction of the difference reduces the distortion of the outer peripheral portion of the roll surface.) This is considered to be caused by the surface resistivity being uniformed), so that the density unevenness of the transferred toner image is reduced, and the toner on the image carrying belt can be uniformly transferred to the entire surface of the paper. Next, found that can improve the poor transfer of the toner, it was accomplished the present invention. The transfer conductive roll of the present invention is not limited to a backup roll or a secondary transfer roll for secondary transfer of a toner image on an intermediate transfer belt, but also a toner image on an intermediate transfer drum or a photoconductor. It can be used for various kinds of conductive rolls for transfer to transfer to a transfer roller.

[0010]

Next, a description will be given of the present invention which has solved the above-mentioned problems. In the description of the present invention, reference numerals in parentheses added after constituent elements of the present invention denote constituent elements of the present invention. Reference numerals of corresponding components of the embodiment described later. The reason why the present invention is described in association with the reference numerals of the components of the embodiments described later is to facilitate understanding of the present invention, and not to limit the scope of the present invention to the embodiments.

(1st invention) In order to solve the aforementioned problem,
The transfer device of the first invention of the present application has the following requirements: (A01) The transfer device contacts the surface of the rotating image carrier (B) and moves together with the image carrier (B). In the transfer area (Q4) where the toner image on the image carrier (B) is transferred to the surface of the transfer material (S), the transfer is pressed from the back side of the transfer material (S) toward the image carrier (B). (A02) A transfer voltage is applied between the image carrier (B) and the transfer conductive roll (30) to transfer the toner image on the surface of the image carrier (B) to a transfer material ( S) Transfer voltage applying means for transferring to the surface (E), (A03) the conductive roll for transfer having a roll surface with a circumferential cut to increase the axial resistance of the roll surface portion (30).

(Operation of the First Invention) In the transfer device of the first invention of the present application having the above configuration, the transfer area (Q4) for transferring the toner image on the image carrier (B) to the surface of the transfer material (S). In (1), the transfer material (S) contacts the surface of the rotating image carrier (B) and moves together with the image carrier (B). The transfer conductive roll (30) is provided in the transfer area (Q).
The transfer material (S) passing through 4) is pressed from the back surface side to the image carrier (B) side. The transfer voltage applying means (E) applies a transfer voltage between the image carrier (B) and the conductive roll for transfer (30) to transfer the toner image on the surface of the image carrier (B) to the surface of the transfer material (S). Transfer to A circumferential cut is formed on the roll surface of the transfer conductive roll (30) in order to increase the axial resistance of the roll surface. For this reason, the transfer conductive roll (3)
0), it becomes difficult for the transfer current to flow in the axial direction, and the current spills at the widthwise end of the transfer material (S) (current does not flow to both ends in the width direction of the transfer material (S), and the transfer material ( S)
Current flowing in a portion where the image bearing member (B) and the transfer conductive roll (30) are in direct contact with each other outside the outer end of the transfer material (S), and the density unevenness of the transfer toner image on the surface of the transfer material (S) is reduced. Decrease.

(Second Invention) A transfer device according to a second invention of the present application has the following requirements.
1) secondary transfer of a toner image on the intermediate transfer belt (B) to the surface of a transfer material (S) that moves together with the intermediate transfer belt (B) by contacting the surface of the rotating intermediate transfer belt (B) In the transfer area (Q4), a conductive backup roll (29) in contact with the back side of the intermediate transfer belt (B) and the back side of the transfer material (S) pressed against the backup roll (29) 2 Next transfer roll (30), (B02) The backup roll (2
9) and transfer voltage applying means (E) for applying a secondary transfer voltage between the secondary transfer roll (30) and transferring the toner image on the surface of the image carrying belt (B) to the surface of the transfer material (S). B
03) The backup roll (29) or the secondary transfer roll (30) having a roll surface in which a circumferential cut is formed in order to increase an axial resistance value of a roll surface portion.

(Function of the Second Invention) In the transfer device of the second invention of the present application having the above configuration, the secondary transfer area for transferring the toner image on the intermediate transfer belt (B) to the surface of the transfer material (S). In (Q4), the transfer material (S) contacts the surface of the rotating intermediate transfer belt (B) and moves together with the intermediate transfer belt (B). The conductive backup roll (29) abuts on the back side of the intermediate transfer belt (B) passing through the secondary transfer area (Q4) and contacts the secondary transfer roll (3).
0) is pressed from the back side of the transfer material (S) passing through the secondary transfer area (Q4) toward the backup roll (29). The transfer voltage applying means (E) is provided between the backup roll (29) and the secondary transfer roll (30).
A next transfer voltage is applied to transfer the toner image on the surface of the intermediate transfer belt (B) to the surface of the transfer material (S). Circumferential cuts are formed on the roll surface of the backup roll (29) or the secondary transfer roll (30) in order to increase the axial resistance of the roll surface. For this reason, it is difficult for the transfer current flowing between the backup roll (29) and the secondary transfer roll (30) to flow in the axial direction, and the current wraps around the end of the transfer material (S) in the width direction (the transfer material (S )), The current does not flow at both ends in the width direction of the intermediate transfer belts (B) and 2 outside the outer end of the transfer material (S).
(A current flows in a portion where the next transfer roll (30) is in direct contact.) The density unevenness of the transferred toner image on the surface of the transfer material (S) is reduced.

(Third Invention) A conductive roll for transfer according to a third invention of the present application has the following requirements: (C01) The surface of a rotating image carrier (B). The image carrier (B) is disposed in a transfer area (Q4) for transferring a toner image on the image carrier (B) on the surface of the transfer material (S) that moves together with the image carrier (B) in contact with the image carrier (B). (2) Transfer conductive rolls (29, 30) to which a transfer voltage for transferring the toner image on the transfer material (S) is applied, and (C02) a circumferential surface for increasing the axial resistance of the roll surface. The transfer conductive roll (29, 30) having a roll surface with a cut in the direction.

(Operation of the Third Invention) The second embodiment having the above-described structure
The conductive roll for transfer (29, 30) of the present invention is provided on the surface of the transfer material (S) that moves together with the image carrier (B) by contacting the surface of the image carrier (B) that rotates. B)
It is arranged in a transfer area (Q4) for transferring the upper toner image. A transfer voltage for transferring the toner image on the image carrier (B) to the transfer material (S) is applied to the transfer conductive rolls (29, 30). The transfer conductive roll (29,
In the roll surface of 30), a circumferential cut is formed in order to increase the axial resistance value of the roll surface portion. Therefore, the image carrier (B) and the transfer material (S)
The transfer current flowing between the transfer conductive rolls (2
9, 30), it is difficult for the transfer material (S) to flow in the axial direction, and current spills at both ends in the width direction of the transfer material (S). (A current flows in a portion where the image carrier (B) and the transfer conductive roll (30) are in direct contact with each other outside the outer end), and the density unevenness of the transferred toner image on the surface of the transfer material (S) is reduced. I do. Also, the conductive roll for transfer (29, 3
Since the distortion of the roll surface portion of 0) is reduced, the difference between the maximum value and the minimum value of the surface resistivity based on the distortion is reduced. For this reason, the density unevenness of the toner is reduced.

(Fourth Invention) Further, the conductive roll for transfer of the fourth invention of the present application has the following requirements, (D01) the surface of the image carrier (16) which rotates and moves. The toner image on the image carrier (16) is arranged in a transfer area (Q3) where the toner image on the image carrier (16) is primarily transferred on the surface of the intermediate transfer body (B) that moves together with the image carrier (16) in contact with 1 for transferring toner image on body (16) to intermediate transfer body (B)
A transfer conductive roll (T1) to which a next transfer voltage is applied,
(D02) The transfer conductive roll (T1) having a roll surface provided with a circumferential cut in order to increase the axial resistance value of the roll surface portion.

(Function of the Fourth Invention) The transfer conductive roll (T1) according to the fourth invention of the present application having the above-mentioned structure comes into contact with the surface of the rotating image carrier (16), and the image carrier is formed. (1
6) The transfer area (Q) where the toner image on the image carrier (16) is primarily transferred onto the surface of the intermediate transfer body (B) that moves together with (6).
3) placed and used. The transfer conductive roll (T1) is applied with a transfer voltage for primary transfer of the toner image on the image carrier (B) to the intermediate transfer body (B). A circumferential cut is formed on the roll surface of the transfer conductive roll (T1) in order to increase the axial resistance of the roll surface portion. For this reason, the transfer conductive roll (T1) disposed in the primary transfer area (Q3) is the same as the transfer conductive roll (29, 30) of the third aspect of the present invention. 2) reduces the current wraparound at both ends in the width direction, and reduces the density unevenness of the transferred toner image on the surface of the intermediate transfer member (B). Further, the unevenness of the toner image is reduced due to the cut.

[0019]

(Embodiment 3 of the Third Invention) Third Embodiment
The transfer conductive roll (29, 3) according to the first embodiment of the present invention.
0) The third aspect of the present invention has the following requirements. (C03) The circumferential cut that divides the roll surface portion into a plurality of cylindrical portions.

(Operation of the Third Embodiment of the Third Invention) In the transfer conductive roll (29, 30) of the first embodiment of the second invention having the above-described configuration, the surface of the roll has a circumferential surface. It is divided into a plurality of cylindrical parts by the cuts. For this reason, the current sneak at both ends in the width direction of the transfer material (S) is reduced, and the transfer conductive rolls (29, 30) are reduced.
Of the surface of the roll is reduced.

(Embodiment 2 of the Third Invention) The conductive roll for transfer (29, 30) of the second embodiment of the third invention is the same as the conductive roll for transfer (29, 30) of the first embodiment of the third invention. 2
(C04) formed in a spiral form from end to end in the axial direction in order to increase the resistance value in the axial direction of the roll surface portion, characterized in that: The circumferential cut.

(Operation of Third Embodiment of Third Invention) In the transfer conductive roll (29, 30) of the third embodiment of the present invention having the above-described structure, the axial end of the roll surface portion is provided. The circumferential cut formed in a spiral shape from the end to the end increases the resistance value in the axial direction. For this reason, it is possible to reduce the current sneak at both ends in the width direction of the transfer material, thereby reducing the density unevenness of the transfer toner on the transfer material (S). In addition, the transfer conductive roll (2
Since the distortion of the roll surface portion of (9, 30) is reduced, the difference between the maximum value and the minimum value of the surface resistivity based on the distortion is reduced. For this reason, the density unevenness of the toner is further reduced.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific examples (embodiments) of embodiments of a transfer device and a transfer conductive roll (29, 30) of the present invention will be described with reference to the drawings. It is not limited to the example. FIG. 1 is an explanatory diagram of Embodiment 1 of an image forming apparatus provided with an embodiment of a transfer unit and a transfer conductive roll (29, 30) of the present invention. In FIG. 1, an image forming apparatus F includes a UI (user interface).
And a transparent platen glass 2 on which a document (not shown) is placed.

The original placed on the platen glass 2 is illuminated by the light source 4 of the original illumination unit 3. The original reflected light is reflected by the first mirror 5 of the original illuminating unit 3 and the second mirror 7 and the third mirror 8 of the mirror unit 6, passes through the imaging lens 9, and is converted by the CCD into an analog signal of R, G, and B. Is read as The image signal read by the CCD is input to the IPS controlled by the controller C. The IPS image read data output unit 11 converts the input read image signal from analog to digital and outputs the read image signal.
Reference numeral 2 denotes an image memory 13 for converting the AD-converted data into Y, M, C, and K image data, performing data processing such as density correction and enlargement / reduction correction, and writing image data (laser Drive data).

The laser drive signal output device 14 is provided with the IP
A laser drive signal of an image corresponding to the image data output from S is output to a ROS (optical scanning device, that is, a latent image forming device) at a predetermined timing. The ROS outputs a laser beam L modulated by the laser drive signal. After the rotating image carrier 16 is charged by the charger 17, at the latent image writing position Q 1, K (black), Y (yellow), M (magenta), and C (cyan) are applied by the laser beam L. An electrostatic latent image corresponding to the image of each color component is written. A rotary developing unit 18 that develops the electrostatic latent image into a toner image includes a developing device 18K for each of K (black), Y (yellow), M (magenta), and C (cyan) that rotates together with a rotation shaft 18a. The developing devices 18K to 18C rotate and move to a developing area Q2 facing the image carrier 16 to form an electrostatic latent image corresponding to the image of each color component into a toner of each color. Develop into image T.

The toner image T formed on the surface of the image carrier 16
Passes through a primary transfer area Q3 facing the intermediate transfer belt B. A primary transfer roll (transfer conductive roll) T1 disposed on the back side of the intermediate transfer belt B in the primary transfer area Q3 is a primary transfer voltage (transfer voltage applying means) E supplied from a power supply circuit (transfer voltage applying means). The toner image on the image carrier 16 is primarily transferred to the intermediate transfer belt B by a voltage having a polarity opposite to the charging polarity of the toner (for example, about + (plus) 1-4 kV). The image carrier 16 having passed through the primary transfer area Q3
The residual toner on the surface is removed by the image carrier cleaner 19.

The intermediate transfer belt B includes a driving roll 26,
A plurality of belt support rolls (belt support members) 26 to 29 including a tension roll 27, an idler roll 28, and a backup roll 29 are rotatably supported. The backup roll 29, which is a support roll for the intermediate transfer belt B, is configured as a counter electrode of the secondary transfer roll 30, and an electrode roll 31 is in contact with the surface thereof. The secondary transfer roll 30 is disposed so as to be separated or approachable between a separated position separated from the backup roll 29 and a pressed close position, and is grounded (grounded). The backup roll 29,
The secondary transfer roll T2 is constituted by the secondary transfer roll 30 and the electrode roll 31.

A secondary transfer voltage (a voltage having the same polarity as the charged polarity of the toner) is applied from the power supply circuit E to the electrode roll 31 of the secondary transfer device T2. When the recording sheet (that is, the transfer material) S passes through the secondary transfer area Q4 formed by the nip (contact area) of the secondary transfer roll 30 and the intermediate transfer belt B, the secondary transfer unit T2 The toner image primarily transferred onto the intermediate transfer belt B is secondarily transferred onto the recording sheet S. The electrode roll 31
As is not particularly limited as long as it is a conductive member having good conductivity, for example, aluminum, stainless steel, a metal roll made of copper, a conductive rubber roll, a conductive brush,
Electrode members such as a metal plate and a conductive resin plate can be used. A transfer voltage of -1 to -5 kV is applied from the electrode member through the backup roll 29.
The polarity of the voltage applied to the electrode roll 31 is as follows:
The polarity is opposite to the charging polarity of the toner. Note that the electrode roll 31 is not always a necessary member. For example, the secondary transfer voltage can be applied to the conductive shaft of the secondary transfer roll (backup roll) 29 or the secondary transfer roll 30.

The secondary transfer roll cleaner 33 is a member for removing the toner adhered to the secondary transfer roll 30, and separates from or approaches the backup roll 29 together with the secondary transfer roll 30. Move in the direction. Further, along the surface of the intermediate transfer belt B,
A belt cleaner 34 is provided downstream of the secondary transfer area Q4.
Is arranged. The belt cleaner 34 is disposed so as to be separated from or contact with the intermediate transfer belt B. When a color image is formed, the secondary transfer roll 30, the secondary transfer roll cleaner 33, and the belt cleaner 34 perform the intermediate transfer until the final unfixed toner image is primarily transferred to the intermediate transfer belt B. It is held at a position separated from the belt B.

Further, a belt position sensor SN1 for detecting a position detection mark (not shown) formed at the outer end of the intermediate transfer belt B in the width direction is provided.
The timing of writing the latent image on the image carrier 16 is controlled by the position detection signal of the intermediate transfer belt B output from the belt position sensor SN1. The recording sheets S stored in the paper feed tray 41 are taken out by a pickup roll 42 and separated one by one by a separation roll 43.
The sheet is temporarily stopped by the registration roller 44, and is conveyed from the guide conveyance path 45 to the secondary transfer area Q4 at a predetermined timing. The recording sheet S on which the toner image has been secondarily transferred when passing through the secondary transfer area Q4 is conveyed to the fixing area Q6 by the sheet guide 46 and the sheet conveying belt 47. The fixing area Q6
When passing through the recording sheet S, the secondary transfer toner image on the recording sheet S is fixed by a pair of fixing rolls of a fixing device 48 and is discharged to a discharge tray 49. Reference numerals 42 to 47
The recording sheet (that is, the transfer material)
A transport device (42 to 47) is configured.

When a single color image is formed, the primary transfer area, Q3
The toner image primarily transferred to the intermediate transfer belt B is secondarily transferred to the recording sheet S immediately in the secondary transfer area Q4. At the time of full-color image formation, each time the intermediate transfer belt B passes through the primary transfer area Q3, the toner image of each color is sequentially superimposed on the intermediate transfer belt B and primary-transferred. After the primary transfer on B
The secondary transfer is collectively performed on the recording sheet S in the secondary transfer area.

(Embodiment 1 of Backup Roll 29) FIG. 2 is an explanatory view of a back roll and a transfer roll of a secondary transfer unit used in the image forming apparatus shown in FIG. It is the figure seen from II. FIG.
9 is a perspective view of a backup roll (transfer conductive roll) 29 used in the secondary transfer device T2 shown in FIG. 2 and 3, the backup roll 29 is, for example,
It has a shaft 29a made of a steel pipe having a small diameter portion having a diameter of 8 mm and a large diameter portion having a diameter of 15 mm. An elastic layer 29b is formed on the outer periphery of the large diameter portion of the shaft 29a, and the elastic layer is a semiconductive rubber layer (foam E) having a rubber hardness of 50 °.
PDM) and a thin conductive film (EPDM) formed on the surface thereof. And this elastic layer 29b
Is divided into 17 cylindrical members having a width of 20 mm by a plurality of ring-shaped slits (cuts) having a width of 1 mm orthogonal to the axis.

The elastic layer 29b is divided by a plurality of slits perpendicular to the axis, thereby reducing the current flowing in the axial direction and reducing the current wraparound at both ends in the width direction of the recording sheet S. In addition, the toner density unevenness is that there is a difference between the maximum value and the minimum value of the partial surface resistivity of the backup roll 29 (the surface resistivity of each of the finely divided portions) (the partial surface resistivity varies). However, when the elastic layer 29b is divided, the distortion is reduced, and the difference between the maximum value and the minimum value of the surface resistivity is reduced, thereby making it possible to eliminate the density unevenness of the transferred toner image.

FIG. 4 is a schematic explanatory view of a surface resistance measuring device for measuring the surface resistance of the backup roll 29.
FIG. 4A is a diagram illustrating a method of measuring surface resistance between the same blocks using an axial surface resistance measuring device, FIG. 4B is a diagram illustrating a method of measuring surface resistance between adjacent blocks using an axial surface resistance measuring device, and FIG. It is a figure which shows the surface resistance measuring device of a direction. The surface current value in the axial direction in the block of the backup roll after the slit processing was measured as shown in FIG. 4A,
Table 1 shows the measurement results. The average value (A) in Table 1
The suffix “1” of 1 indicates a measurement value in the same block.

[Table 1]

Next, the surface current value in the axial direction between the blocks of the backup roll after slit processing was measured by the measuring method shown in FIG. 4B, and the measurement results are shown in Table 2. Table 2
The subscript “2” of the average value (A) 2 of the above indicates that it is a measurement value between adjacent blocks.

[Table 2]

Next, in order to compare the current value (A) 2 of the surface flowing in the axial direction between the blocks of the backup roll 29 and the current value (A) 1 of the surface flowing in the axial direction in the block, after the slit processing, Table 3 shows the difference between the surface current values of the backup roll 29 in the axial direction between the blocks and in the block.
Shown in

[Table 3]

As shown in Table 3, the current value (A) 2 of the surface of the backup roll 29 flowing in the axial direction between the blocks is 1/1 of the current value (A) 1 of the surface flowing in the axial direction of the block.
It decreased greatly from 1700 to 1/30. From the above, when a ring-shaped slit (cut) orthogonal to the axis is formed in the elastic layer 29b of the backup roll 29 and divided into a plurality of blocks, the current sneak shown in FIG. The electric charges travel along the rubber layer surface and move in the axial direction, so that the transfer current escapes to a portion where the sheet S is not present between the transfer roll 30 and the intermediate transfer belt B, that is, outside the both ends in the width direction of the sheet. No transfer current flows). Therefore, it is possible to reduce the problem that the toner on the intermediate transfer belt B is not transferred to both ends of the sheet.

Next, Table 4 shows the values of the surface resistivity of the backup roll 29 before slitting, which were measured using the circumferential surface resistivity measuring device shown in FIG. 4B. Table 5 shows the values of the surface resistivity of No. 29. In FIG. 4B, the angle with respect to the center of the pair of rod-shaped electrodes abutting on the backup roll 29 is 1
It is about 18 °.

The measured values in Tables 4 and 5 are measured at positions where the surface measuring device shown in FIG. 4B is rotated by 45 degrees in the circumferential direction of the backup roll 29. In Tables 4 and 5, “overall” in the column of the measurement point in the axial direction means a measurement value in a state where the pair of rod-shaped electrodes are in contact with the entire length of the backup roll 29 in the axial direction. The “long” refers to the shaft 29a protruding from both ends of the elastic layer 29b of the backup roll 29 shown in FIGS.
Means the measured value at the end where the protrusion amount is long, "center"
Means the measured value at the center in the axial direction, and "short" means
9a means a measured value at the end on the side where the protrusion amount is short.

In Tables 4 and 5, the “average value of the difference between the maximum value and the minimum value at the three points in the axial direction” refers to the eight measurement positions (8 points) at 45 ° intervals in the circumferential direction of the backup roll 29. =
(360 ° / 45 °) means the average value of the difference between the maximum value and the minimum value of the surface resistivity at three measurement positions on the entire surface in the axial direction, on the long side, on the short side, and at three measurement positions. In Tables 4 and 5, the “difference between the maximum value and the minimum value at 24 points” is the value of eight measurement positions (8 = 360 ° / 45 °) at 45 ° intervals in the circumferential direction of the backup roll 29. In each case, the whole surface in the axial direction,
It means the difference between the maximum value and the minimum value of the surface resistivity at three measurement positions on the long side and the short side, ie, 3 × 8 = 24 in total. As can be seen from Tables 4 and 5, the difference between the maximum value and the minimum value of the surface resistivity was reduced by forming the slits (cuts).

[0041]

[Table 4]

[0042]

[Table 5]

According to Tables 4 and 5, the difference between the maximum value and the minimum value of the surface resistivity became smaller when the slit processing was performed.
The cause is presumed to be that the difference between the maximum value and the minimum value of the surface resistivity became small because the distortion of the elastic layer 29b of the backup roll was reduced by the slit processing. Since the unevenness in the density of the toner on the paper becomes significant when the difference between the maximum value and the minimum value of the surface resistivity is large, the unevenness in the density of the toner can be reduced by performing the slit processing.

(Embodiment 2) FIG. 5 is an explanatory view of Embodiment 2 of the secondary transfer unit T2 used in the image forming apparatus shown in FIG. 1, and corresponds to FIG. 2 of Embodiment 1. is there. FIG.
FIG. 6 is a perspective view of a backup roll (transfer conductive roll) 29 used in the secondary transfer device T2 shown in FIG. 5 and 6, the transfer of the full-color toner image from the intermediate transfer belt B to the sheet S is performed by the intermediate transfer belt B.
The transfer roller 30 is pressed against the backup roller 29 with the transfer roller 30 pressed against the backup roller 29, thereby applying a transfer voltage while pressing the full-color toner image on the intermediate transfer belt B against the sheet S.

As shown in FIGS. 5 and 6, the backup roll 29 has, for example, a small diameter portion having a diameter of 8 mm and a large diameter portion having a diameter of 1 mm.
It has a shaft 29a made of a 5 mm steel pipe. The outer periphery of the shaft 29a is covered with an elastic layer 29b of an elastic body having a rubber hardness of 50 °. And this elastic layer 29b extends along the axis,
A 1 mm wide cut is made spirally from end to end.

By making a cut in the elastic layer 29b in a spiral shape from end to end along the axis, electricity does not flow in the axial direction due to transmission along the surface layer of the elastic layer 29b of the backup roll 29 during transfer to the paper S. Therefore, as in the first embodiment, the transfer current escapes to a portion where the sheet S is not present between the transfer roll 30 and the intermediate transfer belt B, that is, to the side of both ends of the sheet S, or the transfer current flows to both ends of the sheet S. It is possible to solve the problem that the toner on the intermediate transfer belt B is not transferred to both ends of the sheet S without flowing.

(Modifications) Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, but falls within the scope of the present invention described in the appended claims. Thus, various changes can be made. Modified embodiments of the present invention will be exemplified below. (H01) The transfer conductive roll of the present invention can be used in an image forming apparatus using an intermediate transfer drum instead of the intermediate transfer belt, and can be used not only for the transfer of the secondary transfer area but also for the primary transfer area. Can also be used for the transfer of Further, the transfer conductive roll of the present invention can be used in a transfer area where a toner image on an image carrier such as a photosensitive drum or a photosensitive belt is directly transferred to a transfer material. (H02) In the present invention, an electrostatic latent image is formed on the surface of a photoreceptor instead of a secondary transfer device or a secondary transfer roll for transferring a toner image on an intermediate transfer belt B onto a recording sheet (transfer material). The present invention is also applicable to a transfer device or a transfer roll that transfers a toner image on a toner image carrying belt (photosensitive belt), which is developed into a toner image, to a recording sheet (transfer material). (H03) As the belt supporting member for supporting the intermediate transfer belt B, one large-diameter drum having an elastic layer formed on its surface may be used instead of using a plurality of belt supporting rolls 26 to 29. It is possible. (H04) The cut formed on the surface of the conductive roll does not need to be formed up to the center of the elastic layer 29b (joining portion with the shaft 29a), but can be formed to an arbitrary constant depth.

[0048]

The transfer device or the transfer conductive belt of the present invention has the following effects. (E01) When the toner image on the image carrying belt is transferred to the surface of the transfer material, the transfer current can be prevented from escaping to both ends in the width direction of the transfer material. (E02) Transfer defects can be prevented. (E03) Density unevenness of a transferred toner image caused by a difference between the maximum value and the minimum value of the surface resistivity of the transfer conductive roll can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of Embodiment 1 of an image forming apparatus including an embodiment of a transfer unit and a transfer conductive roll of the present invention.

FIG. 2 is an explanatory view of a secondary transfer unit T2 used in the image forming apparatus shown in FIG. 1;
It is the figure seen from -II.

FIG. 3 is a backup roll (conductive roll for transfer) used in the secondary transfer device T2 shown in FIG. 2;
It is a perspective view of 29.

FIG. 4 is a schematic explanatory view of a surface resistance measuring device for measuring the surface resistance of the backup roll 29, and FIG.
FIG. 4B is a diagram showing a method of measuring the surface resistance between the same blocks using an axial surface resistance measuring device, FIG. 4B is a diagram showing a method of measuring the surface resistance between adjacent blocks using an axial surface resistance measuring device, and FIG. 4C is a circumferential direction. FIG. 2 is a view showing a surface resistance measuring device of FIG.

FIG. 5 is an explanatory diagram of a second embodiment of the secondary transfer device T2 used in the image forming apparatus shown in FIG. 1 and corresponds to FIG. 2 of the first embodiment.

FIG. 6 is a backup roll (conductive roll for transfer) used in the secondary transfer device T2 shown in FIG. 5;
It is a perspective view of 29.

FIG. 7 is a schematic explanatory view of a conventional image forming apparatus using a conductive roll.

FIG. 8 is a diagram illustrating the operation of a conductive roll used in a secondary transfer device of the image forming apparatus.

[Explanation of symbols]

B: image carrying belt (intermediate transfer belt), E: transfer voltage applying means, Q4: transfer area (secondary transfer area), S: transfer material (recording paper), 29: backup roll, 30: conductive roll for transfer , (29, 30) ... conductive roll for transfer.

Continued on the front page (72) Inventor Shoichi Morita 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture F-Xerox Co., Ltd. F-term (reference) 2H032 AA05 BA09 BA23 3J103 AA02 AA63 AA72 FA30 GA02 GA33 GA57 GA58 GA74 HA20

Claims (4)

[Claims] 1. A transfer device characterized by the following requirements: (A01) a transfer device which contacts a surface of a rotatable image carrier and moves on the surface of the transfer material which moves together with the image carrier. (A02) a transfer voltage is applied between the transfer roller and the transfer roller, which is pressed from the back side of the transfer material to the image carrier in the transfer area where the toner image is transferred. (A03) a transfer voltage applying means for transferring the toner image on the surface of the image carrier to the surface of the transfer material, and (A03) removing the roll surface on which a circumferential cut is formed in order to increase the axial resistance of the roll surface portion. The conductive roll for transfer having. 2. A transfer device characterized by the following requirements: (B01) a transfer device that contacts a surface of a rotating intermediate transfer belt and moves on the surface of a transfer material that moves together with the intermediate transfer belt; In a secondary transfer area for transferring a toner image, a conductive backup roll abutting on the back side of the intermediate transfer belt and a secondary transfer roll pressed from the back side of the transfer material to the backup roll side;
(B02) a transfer voltage applying means for applying a secondary transfer voltage between the backup roll and the secondary transfer roll to secondary transfer the toner image on the surface of the image bearing belt to the surface of a transfer material;
(B03) The backup roll or the secondary transfer roll having a roll surface in which a circumferential cut is formed to increase an axial resistance value of a roll surface portion. 3. A conductive roll for transfer, characterized by the following requirements: (C01) the image bearing member on a surface of a transfer material which moves together with the image carrier in contact with the surface of the rotating image carrier. A transfer conductive roll disposed in a transfer area for transferring the toner image on the body and transferring a toner image on the image carrier to a transfer material; (C02) an axial direction of a roll surface portion; The conductive roll for transfer having a roll surface in which a circumferential cut is formed in order to increase a resistance value of the transfer. 4. A conductive roll for transfer, characterized by having the following requirements: (D01) an image on the surface of an intermediate transfer member that moves together with the image carrier by contacting the surface of the image carrier that rotates. A transfer conductive roll that is arranged in a transfer area where the toner image on the carrier is primarily transferred, and to which a transfer voltage for transferring the toner image on the image carrier to the intermediate transfer body is applied;
(D02) The conductive roll for transfer having a roll surface in which a circumferential cut is formed in order to increase an axial resistance value of a roll surface portion.