JP3397593B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate transfer member
To an image forming apparatus. [0002] 2. Description of the Related Art Images of copiers, laser beam printers, etc.
There is a growing need for color in forming equipment. Mosquito
Image forming methods include sublimation type, thermal transfer type,
The jet method and the electrophotographic method are known.
Electrophotography is the best in terms of image formation speed
Has been done. In recent years, among the electrophotographic systems, intermediate transfer
The method is becoming mainstream. This one, choose the transfer material
Not excellent in color registration (color
There is an advantage that there is little deviation). In an electrophotographic apparatus of an intermediate transfer system, FIG.
As shown, a drum-type electrophotographic photosensitive member (hereinafter referred to as a “photosensitive
Yellow), magenta,
Drum type toner image of each color of cyan and black
Primary transfer onto the intermediate transfer member 2 of FIG.
The full color image with the colors superimposed on the transfer material
Next transfer. In this method, a transfer material is wound around an intermediate transfer body 2.
No need to attach, so it can be used for envelopes and cardboard.
Color versatility and the thickness of the transfer material
High image quality is obtained because the registration does not change.
There is a merit that can be. In the intermediate transfer system, the image is transferred onto a transfer material.
The secondary transfer residual toner remaining on the surface of the intermediate transfer body 2 without
Generally collected with a cleaning member such as a fur brush
And ready for the next image formation. However, fur
When the surface of the intermediate transfer member is rubbed with a brush, toner fusion occurs.
The image has deteriorated due to damage or surface damage
Problems, such as shortening the life of the equipment
You. In order to prevent these problems, an intermediate transfer
Charges the secondary transfer residual toner by being placed in contact with the body surface
Charging means (hereinafter referred to as “ICL roller”) 10
Primary transfer of the next image by changing the tribo of the transfer residual toner
At the same time, the secondary transfer residual toner is electrostatically transferred to the photosensitive drum 3.
Technology has been developed (hereinafter referred to as “ICL method”).
U). More specifically, charging means for secondary transfer residual toner
Using the charging roller as the
The toner is charged to the opposite polarity of the toner tribo charged in the image area,
Primary transfer of toner image from photosensitive drum 3 to intermediate transfer body 2
At the same time, secondary transfer from the intermediate transfer body 2 to the photosensitive drum 3
The residual toner is transferred and collected. [0009] SUMMARY OF THE INVENTION
According to the prior art, In the intermediate transfer body method, the intermediate transfer from the photosensitive drum 3 is performed once.
A primary transfer step of transferring toner onto the body 2 and an intermediate transfer
A secondary transfer step of transferring the toner image on the body 2 onto a transfer material;
It is said that the image is easily degraded because of the two transfer steps
Has disadvantages. Especially when a full-color image is formed,
The intermediary transfer member 2 contacts the photosensitive drum four times, and
Toner is easily scattered because the toner is overlaid
No. The primary transfer section (from the photosensitive drum 3 to the intermediate
A portion where the toner image is transferred to the transfer body 2;
When the toner is superimposed on the intermediate transfer
2. The toner transferred on has a negative polarity,
It is not possible to transfer toner of the same polarity to the same position on this
Always difficult, trying to form a secondary transfer image
There is a problem that scattering becomes severe on the transfer body 2.
Was. The secondary transfer residual toner is charged by the ICL roller 10
In the method of collecting the image on the photosensitive drum 3, the secondary transfer
It is desired to charge the residual toner efficiently. But,
For the photosensitive drum 3 generally used, such as a primary charger,
Unlike the charging method, the intermediate transfer body 2 is close to the low resistance area.
And the ICL roller 10 itself
Because of the medium resistance, it is actually
A so-called injection current flows. Because of this,
Therefore, unlike the primary charger that performs most charging, IC
All of the current flowing through the L roller 10 is the secondary transfer residual toner.
Does not contribute to the electrification. The intermediate transfer member 2 and the ICL roller 10
Both have environmental fluctuations in the resistance value.
In a high humidity environment where the
It is said that the secondary transfer residual toner is not sufficiently charged.
Problems had arisen. As disclosed by the present applicant, the secondary transfer residual toner is
In order to charge efficiently, the AC
The intermediate transfer member 2 and the ICL roller 10
Jumping the toner between the layers can break the toner layer
It is valid. However, the intermediate transfer member 2 is a photosensitive drum
Form a nip of appropriate width at the transfer part between 3 and transfer material
Low hardness is required, and the thickness is about 5mm
It is common to provide an elastic layer of different degrees. On the contrary
The resistance layer is often formed with a thickness of several tens of microns. Therefore, most of the thickness of the ICL roller 10 is
If the resistance of the elastic layer that occupies the
Most of the AC voltage applied to the ICL roller 10 is divided
Intermediate transfer body 2 that is actually consumed
-No electric field is formed between the ICL rollers 10
The point isHad occurred. Therefore, the present invention relates to like
The problem is that toner splatters on the intermediate transfer member,
The secondary transfer residual toner is sufficiently chargedNo, etc.Will prevent
For providing an image forming apparatus
It is. [0015] Means for Solving the Problems The present invention according to claim 1
Transfers the toner image formed on the image carrier onto the intermediate transfer body.
The step of copying is performed for toners of a plurality of colors, and the intermediate transfer is performed.
A multicolor toner image is formed on a photocopy
Image forming apparatus that collectively transfers the toner image onto the transfer material
AndThe intermediate transfer member has an elastic layer and a surface layer covering the outside thereof.
And the elastic layer has a real resistance of 10 ⁶ Ω or less, the surface layer
Has a volume resistivity of 10 ¹² Ω · cm or more, thickness 30μ
m or less,Capacitance of the intermediate transfer memberBut13pF / cm
²that's allIs, Characterized in that. [0016] [0017] [0018] [0019] [0020] [0021] [0022] [0023] [0024] [0025] [0026] [0027] BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment will be described. <Embodiment 1> FIG. 1 shows an image forming apparatus according to the present invention.
It is a longitudinal cross-sectional view which shows a schematic structure. Image forming apparatus shown in FIG.
The image carrier is a drum-type electrophotographic photosensitive member (hereinafter referred to as an image carrier).
3), and an intermediate transfer member
Is a drum type transfer drum 2 having a two-layer structure.
You. The image forming apparatus shown in FIG. 1 will be described more specifically.
I do. The image forming apparatus has an intermediate transfer body 2 having a diameter of 18 mm.
6mm solid (Note that "solid" means a belt or the like.
(Used in the sense that the shape is different and constant)
The maximum paper passing size is A3 and the process speed is
110mm / sec, image exposure, reversal development method
Full-color electrophotographic image forming apparatus (laser beam
Printer). To form a full-color image, an arrow
Yellow on the photosensitive drum 3 driven to rotate in the R3 direction
(Y), magenta (M), cyan (C), black (B
k) to sequentially form toner images of each color,
The images are sequentially transferred to the surface of the intermediate transfer body 2 and toner of four colors is
The images are superimposed on the surface of the intermediate transfer member 2. This transfer is
Primary transfer formed between optical drum 3 and intermediate transfer body 2
This is performed through the nip portion N1. In addition, this photosensitive drum
The transfer of the toner image from the transfer roller 3 to the intermediate transfer member 2 is called primary transfer.
The surface of the intermediate transfer member 2 is rotated four times.
Is primarily transferred so that toner images for four colors are superimposed on
You. Next, four color toner images on the intermediate transfer member 2
Are collectively transferred onto a transfer material P such as paper. This transfer is intermediate
2 formed between the transfer body 2 and a transfer unit 1 described later
The transfer is performed through the next transfer nip N2.
It is called transcription. Two transfer units 1 as transfer means
Transfer belt 13 stretched over rollers 11 and 12
The transfer material P on the upstream side in the transport direction of the transfer material P.
The transfer belt 13 is moved by the transfer roller 11 to the intermediate transfer body 2.
To perform secondary transfer of toner and at the same time, transfer bell
The transfer material P is adsorbed to the
Separation from the object 2 is performed. The other roller is the drive low
And the intermediate transfer at the secondary transfer nip N2
The peripheral speed of the body 2 is made equal to the peripheral speed of the transfer belt 13.
To drive the unit. The transfer unit 1 is driven
An arrow R indicates the transfer roller 11 side with the roller 12 side as the center.
It is swingably supported in one direction.
So that the transfer belt 13 can be moved
Has been established. The toner image secondarily transferred onto the transfer material P is
The secondary transfer nip N2 in the transfer direction of the transfer material P
A heat fixing roller unit as a fixing device disposed on the downstream side
(Not shown), the toner image is fixed on the surface of the transfer material P. Tona
-The transfer material P after fixing the image is the image forming apparatus main body (not shown).
Is discharged. Next, each member and each unit will be described in detail.
I do. The photosensitive drum 3 is 64 mm in diameter and is negatively chargeable.
OPC (organic optical semiconductor) drum
Is uniformly charged by a charging roller 4 as a primary charger.
The bias applied to the charging roller 4 includes a DC component and an AC component.
Component is a superimposed bias, and the DC component is −60.
0V, AC component is 2000V_pp, 1000Hz, positive
It is a chord wave. As a result, the surface of the photosensitive drum 3
Regardless of the environment, it is charged to about -600V. Next, the surface of the photosensitive drum 3 is exposed to a laser exposure device.
Exposure. In this embodiment, an infrared laser having a wavelength of 760 nm is used.
Combines a laser diode 5 and a polygon scanner 6
Dew with a lens and a mirror (both not shown)
Image exposure is performed using an optical device. Next, the static electricity formed by laser exposure
The latent image is developed with toner by a developing device. Of this embodiment
In the image forming apparatus, four color toners of Y, M, C, and Bk are used.
Although it was used, specifically, as shown in FIG.
And a rotary color developing unit 8. The black developing device 7 uses a magnetic one-component toner.
It uses a jumping development method. Fixed magnet
16 mm diameter conductive non-magnetic current containing the roll 71
The toner having a particle diameter of 6 μm is applied to the image sleeve 72 by the elastic blade 7.
3 and DC applied to the developing sleeve 72
Component -350V, AC component 1600V_pp, Frequency 200
A 0 Hz rectangular wave causes a jump between the photosensitive drum 3 and the photosensitive drum 3.
Ping and reverse development. The color developing unit 8 comprises three yellow
The developing units 81, 82 and 83 for the respective colors of magenta and cyan are rotated
Color toner to be incorporated into rotary roller 8a and provided for development
By rotating the rotary rotary 8
It is arranged at a development position facing the photosensitive drum 3 to perform development.
U. The developing units 81, 82, 83 for each color are non-magnetic one-component toners.
Development is performed by a jumping development method using toner
Has a core / shell structure with a wax inside and a particle size of 6.
μm polymerized toner that is applied by an application roller (not shown).
Coated on the developing sleeve (not shown)
(Not shown), the layer thickness is regulated and sent to the developing position.
Development is performed under the same bias conditions as in the case of the imager 7. In the primary transfer, a voltage is applied to the intermediate transfer member 2
The primary transfer residual toner on the photosensitive drum 3 is c
Cleaner having cleaning blade 91 made of urethane
Is scraped off by the operating unit 9. Note that this implementation
Secondary transfer residual toner on the intermediate transfer body 2
To an ICL roller (toner charging means) as a charging roller
10 to recharge the toner and transfer it to the photosensitive drum 3 (collect
To the photosensitive drum 3
In the same manner, the secondary transfer residual toner
Is scraped by the card 91. The ICL roller 10 has a single-layer structure composed of an elastic layer.
The resistance value is obtained by dispersing carbon in EPDM rubber.
Is a solid roller having a diameter of 20 mm and adjusted. In the case of monochromatic printing, primary transfer was performed.
Thereafter, the toner image remains on the intermediate transfer body 2 as it is in the secondary transfer nip.
And is subjected to secondary transfer. In the case of full-color printing, an intermediate transfer member
2 is rotated 4 times and each toner of YMCK is superimposed and 1
Next transfer. In the case of monochrome printing, the primary transfer bias is
+ 100V. When performing full color printing,
As shown in FIG. 2, the toner of the first color is already
At the place where T1 is, a second color toner T2 is further superimposed.
When trying to perform primary transfer, the previous toner potential
As a result, the transfer contrast is reduced,
Therefore, it is necessary to increase the transfer bias. On the other hand,
If the imaging bias is too high, the photosensitive drum 3 and the intermediate transfer body 2
Discharge occurs between the toner and the toner, causing image deterioration and toner on the intermediate transfer body 2.
Take too high values because tribo changes
Can not. Further, in the image forming apparatus of the present embodiment, 1
Cleaning of the intermediate transfer body 2 is performed simultaneously with the next transfer.
Therefore, multi-color image formation (hereinafter referred to as “multi-color print”)
The fourth rotation is the first rotation of the next image.
It must be an ias value. In consideration of these circumstances, the multicolor printing
The primary transfer bias is sequentially changed for each rotation of Y, M, C, and Bk.
100 V, 500 V, 500 V, and 100 V were set. In this embodiment, the secondary transfer efficiency is improved.
In FIG. 1, the toner on the intermediate transfer body 2 is
Corona charger before secondary transfer arranged to the right of intermediate transfer body 2
15 performs corona charging. Corona charger in the figure
Reference numeral 15 denotes a corotron type, and a corona wire 1
Apply a current of -100 μA as a DC component to
7kV to prevent contamination of the wire 15a_pp, 500H
The sine wave of z is superimposed. The shield potential is grounded. Ko
The toner tribo on the intermediate transfer member 2 is black due to the Rona charging.
From -10μC / g to -20μC / g for toner
The negative charge rises. At the time of the secondary transfer, the transfer material P is supplied to the sheet feeding section (not shown).
Transfer belt 13 which is supplied from
It comes into contact with Photograph 2. The secondary transfer bias is fixed at +20 μA.
Current control is performed, and the transfer belt 13 transfers the transfer material P
The electric charge is supplied and the toner image on the intermediate transfer body 2 is transferred to the transfer material P.
Is secondarily transferred. The transfer unit 1 includes a transfer roller 11 and a drive
The transfer roller 13 includes a transfer roller 13 and a transfer belt 13.
The roller and the drive roller are both volume resistively mounted on a 14 mm diameter cored bar.
Resistance value is 10^Five Ω · cm conductive rubber layer is formed and diameter is 20m
m. The core of the transfer roller 11 is a power supply bar.
The transfer belt 13 is connected to a high-voltage power supply
It follows and rotates. The drive roller 12 has a gear at the end of the cored bar.
Is attached, and meshes with the gear train of the image forming apparatus main body.
Driven by interlocking. The transfer belt 13 is a seamless two-layer belt.
The base layer 13a is formed by dispersing carbon.
Product resistance value of 10⁷ 300μm thickness adjusted to Ωcm
Urethane rubber. The surface layer 13b adsorbs the transfer material P
If a small-size transfer material P is passed
Prevents transfer current from flowing excessively into the non-paper passing area
Must be high resistance to clean
It is necessary to select a material that is difficult to get. In order to satisfy such characteristics, the present embodiment
In the form, a fluorine-based resin paint is used as the material of the surface layer 13b.
Using. Specifically, PVDF, or PVDF or PTFE
Base layer of resin copolymerized with olefin resin
Those coated on 13a were used. More specifically, the surface layer 13 b is
Molded to a thickness of μm and crosslinked, then urethane conductive base layer
13a is molded into a transfer belt 13 with a thickness of 300 μm.
Was. The transfer belt 1 used in this embodiment is
Reference numeral 3 denotes a seamless belt having an inner diameter of 65 mm, which is extended by 5%.
Then, it is stretched between the rollers 11 and 12. Next, the intermediate transfer member 2 will be described. First
First, as an intermediate transfer member 2, on a substrate (aluminum drum) 21
An elastic layer (conductive rubber layer) 22 having a thickness of 5 mm is formed to
5 × 10⁶ Intermediate transfer body 2 with single layer structure as Ω · cm
Was used for image evaluation. The resistance value of the intermediate transfer member 2 is
30cm x 5mm width contact with metal roller in contact with body 2
Form a nip and rotate at a peripheral speed of 110mm / sec
Change from the current flowing when a voltage of 1000 V is applied
The calculated value is used as the actual resistance value. As evaluation images, magenta toner and cyan
A blue fir image on which toner was superimposed was output. First, magenta toner has a primary transfer voltage of +5.
The primary transfer from the photosensitive drum 3 to the intermediate transfer
Then, a cyan toner of the same +50 is applied on the toner image.
Primary transfer is performed at a voltage of 0V. At this point, the image forming apparatus
The operation is stopped, and the toner image formed on the intermediate transfer body 2 is stopped.
Observed that the second color cyan toner jumped
It was confirmed that scattering occurred. On the other hand, the first color
Spattering does not occur with Zenta toner. This is, as shown in FIG.
The magenta toner T1 transferred onto the transfer body 2
The potential generated by this
Gnar T2 splattered. Ma on the intermediate transfer member 2
Measurement of the toner potential of the senda toner T1 indicated -10.
A potential of about 0 V was observed. Within the primary transfer nip N1
Is that the photosensitive drum 3 and the intermediate transfer body 2 come into contact with each other under pressure.
No splattering has occurred, but the primary transfer nip
At the position outside the portion N1, the cyan toner T2 on the front side
Jumps onto the intermediate transfer member due to the repulsive force of the toner T2.
Scatter. In order to prevent the scattering, a multilayer structure is required.
Using the intermediate transfer body 2 having a high capacitance
It is effective to increase the electrostatic force acting between the transfer body 2
is there. The surface layer toner has a repulsion that acts between the lower layer toner
Between the force and the intermediate transfer member 2 and the charge of the toner itself
Coulomb force (gravitational force) acting by
Splattering is suppressed by increasing the capacitance of the transfer body 2
It is possible to control. In order to increase the capacitance, the present embodiment
Has a two-layer structure of the intermediate transfer member 2 and has a low elastic layer resistance.
The surface layer was formed as a thin layer with a high-resistance material. As a comparative example, the actual resistance of the elastic layer resistance was set at two levels.
Volume resistance and film thickness of the material forming the surface layer
In this way, a trial production of the intermediate transfer body 2 was performed, and image evaluation was performed. The results are shown in the following table. 〇 × evaluation is scattered
It is about ri. [0061]                   Elastic layer actual resistance 10⁶ Ω elastic layer actual resistance 5 × 10⁶ Ω 10^Ten, 15 μm 150 pF x 100 pF x 10^Ten, 30 μm 130 pF × 90 pF × 10^Ten, 45 μm 100 pF × 80 pF × 10¹², 15 μm 300 pF １８０ 180 pF × 10¹², 30 μm 200 pF △ 130 pF × 10¹², 45 μm 130 pF × 90 pF × 10¹⁴, 15 μm 500 pF ２００ 200 pF △ 10¹⁴, 30 μm 250 pF １８０ 180 pF × The capacitance of the intermediate transfer member 2 is different from that of the intermediate transfer member 2 by a metal plate.
To form a 30cm x 5mm nip,
The value measured by the LCR meter in this state was used. LCR meter
Is 1 V and the measurement is performed under the condition of 1000 Hz. In the present embodiment, the degree of improvement in scattering is
To evaluate, the indices of 〇, △, and × were used as indices.
There is no problem even if the scattering is about △ level above. From the above results, to improve the scattering
It is required that the capacitance of the intermediate transfer member 2 is 200 pF or more.
It is desirable to convert this to the capacitance per unit area
Then 13pF / cm^Two That is all. As means for realizing this value, an intermediate
The actual resistance of the elastic layer 22 of the transfer body 2 is 10⁶ Ω or less, elastic layer
22 has a surface layer that covers the outside of
Has a volume resistivity of 10¹²Ωcm or more, film thickness 30μm or less
It turns out that it is desirable to be below. The use of the intermediate transfer member 2 as described above
, The second and subsequent colors generated in the primary transfer nip N1
It is now possible to prevent the falling toner from scattering.
Was. <Embodiment 2> In Embodiment 2, the ICL roller 1
DC current flowing directly from 0 to the intermediate transfer member 2
As a result, the cleaning property of the intermediate transfer body 2 is improved.
The porpose is to do. As described in the first embodiment, the present invention
The secondary transfer residual toner on the intermediate transfer body 2 is transferred to the ICL roller 1
0 is positively charged, and the primary transfer of the toner image of the next color
A method of collecting the image on the photosensitive drum 3 simultaneously with copying is adopted. The secondary transfer on the intermediate transfer body 2 is performed by the ICL roller 10.
The mechanism for charging the transfer residual toner is based on discharge.
It is. Intermediate rotation with the applied ICL roller 10
In the discharge (small) gap between object 2 and Paschen's
The discharge is excited according to the law. Generally such a release
As a charging means based on electricity, a charging roller of the photosensitive drum 3 is used.
Is well known, but in this case it is supplied from the charging roller
The DC current that is applied is the charging current of the photosensitive drum 3.
You. However, in the above-described method, the intermediate transfer member 2
Since both ICL rollers 10 are medium resistance members,
All the DC current supplied to the roller 10 contributes to charging.
Not directly, most of which flow directly
Input current. For this reason, the ICL current is set to constant current control.
The resistance value of the member changes due to environmental fluctuations and manufacturing variations.
The direct injection current and the current that contributes to toner charging
And the ratio after passing the ICL roller 10
There was a problem that the nursery was not stable. In order to solve such a problem, the present embodiment
In Embodiment 2, the ICL roller 10 directly contributes to the injection current.
Nip N3 between the toner and the intermediate transfer body 2
Is to maintain a discharge gap of 5 to 500 μm
It is intended to ensure the chargeability of the toner. No contact between the ICL roller 10 and the intermediate transfer member 2
, The actual discharge nip increases as shown in FIG.
I do. This is a discharge of 5 μm or less according to Paschen's law.
This is based on the fact that discharge is unlikely to occur in the gap.
When they are in contact, discharge occurs in the contact nip N3.
The toner charge is limited to the narrow area at both ends of the flaw contact nip.
This is because it is not performed. When both touch, the left of FIG.
As shown in the figure, when the nip width is large, the actual discharge area
Is narrow, and the nip width is
Is smaller, the discharge area becomes larger. And furthermore, both
As shown in the figure on the right, the actual discharge
The area is enlarged as described above. Practical bias
When applied to the ICL roller 10, toner charging is possible
The discharge gap is considered to be 500 μm or less.
It is desirable to maintain a discharge gap. In this embodiment, as shown in the right diagram of FIG.
In addition, the gap is used as a spacer at the end of the ICL roller 10.
B (abutting roller) 16 is provided, and this gap roller 16 is
200 μm by contacting the surface of the intermediary transfer member 2D
Is maintained. The ICL roller 10 having such a configuration is
An experiment was conducted using a conventional contact type ICL roller.
The bias applied to the ICL roller 10 is a DC component.
To perform constant current control, and the AC component is 2 kHz, 3 kV_ppof
A square wave was superimposed. The following are constant current control values and ICL low
Amount of change in toner tribo before and after passing through la 10 (unit is μC
/ G). [0074]                 10μA 20μA 30μA 40μA 50μA With discharge gap 5 15 25 35 45 Contact 1 3 8 15 25 In this way, providing a discharge gap has the same constant current value.
Also, the amount of change in toner tribo is large, and charging can be performed satisfactorily.
I understand. This phenomenon occurs particularly when the ICL roller 10
This becomes significant when a bias is superimposed. The discharge occurs only in one direction due to only the DC bias.
Although the charge amount is small, the AC is superimposed on the toner.
Discharge from both the intermediate transfer body 2 and the ICL roller 10
, The discharge gap can be increased by increasing the discharge gap.
Electricity is improved. The left figure of FIG. 3 is compared with the center figure.
Contact nip with a roller, etc.
Discharge (reducing the nip width)
It is obvious that the area is expanded, and in this embodiment, the IC
The discharge gap is the distance between the L roller 10 and the intermediate transfer body 2.
The main goal is to keep the value at
You. As described above, in the present embodiment, the IC
Limit the contact nip between the L roller 10 and the intermediate transfer body 2
In this way, the injection current is suppressed, and
Good transfer of toner remaining after transfer
I got it. <Embodiment 3> In Embodiment 3, the thickness of the intermediate transfer body 2 is
The actual resistance of the surface layer 22 occupying a large part of the⁶ Ω
cm or less, the AC applied to the ICL roller 10
It is intended to effectively apply a voltage to the toner. The intermediate transfer member 2 has a solid drum-shaped intermediate transfer
Possible shapes include drums and belt-like intermediate transfer belts.
To form a nip with the photosensitive drum 3 and the transfer material P.
For these, elasticity is required. Intermediate transfer drum
In this case, as shown in Embodiment 1,
Da) Elastic layer (conductive rubber layer) 2 having a thickness of about 5 mm on 21
2 and a surface layer (resistance layer) of about 15 μm
Workout. In the intermediate transfer belt, a color resist is used.
Strong enough to keep the belt from stretching
Required, and prevent belt meandering, buckling, and leaning
To stop, a certain thickness is also required. In such a drum or belt, the thickness is
The base layer and the elastic layer occupy most of the area,
Will play a dominant role. However, when the ICL method is used, I
Applying an AC voltage to the CL roller 10 is an intermediate transfer member.
2 has been found to be effective for cleaning. A
C voltage is the standard of the core metal of the ICL roller 10 and the intermediate transfer body 2
Applied to potential, but actually formed an AC electric field
Ino is the discharge between the ICL roller 10 and the surface of the intermediate transfer member 2.
Electric gap. Therefore, in this embodiment, the intermediate transfer member 2
Intermediate transfer to minimize AC bias split
Resistance of elastic layer 22 of body 2 and resistance of ICL roller 10
10⁶ Ω or less. The intermediate transfer member 2 and the IC
An example in which an experiment was performed using the L roller 10 is shown below. As the intermediate transfer member 2, the elastic member according to the first embodiment is used.
The resistance of layer 22 is 10⁶ Ω, 10⁷ Prototype as two levels of Ω
What was used was used. In addition, the actual ICL roller 10 is used.
Resistance 10⁶ Ω, 10⁷ Each volume on the elastic layer of Ω
Resistance value 10¹⁴Ω ・ cm urethane resin 70μm coated
An experiment was conducted with a prototype of the garment. The actual resistance of the elastic layer of the ICL roller 10 is intermediate.
As with the measurement of the resistance value of the transfer body 2, a total pressure of 1 k is applied to the metal roller.
contact the ICL roller 10 with g and apply a voltage of 1 kV
Flows when rotated at a peripheral speed of 100 mm / sec
Defined by the value converted from the current value. The ICL roller 10 has a DC component of +1
000V, 2kHz, 3kV as AC component_ppSquare wave of
And applied to the core of the ICL roller 10. This article
Prints a character image on the screen and prints the image
Before and after the transfer residual toner passes through the ICL roller 10
Measurement of the triboelectricity of the
Observed.           ICL roller elastic layer resistance 10⁶ Ω 10⁷ Ω Intermediate transfer body elastic layer resistance         10⁶ Ω 30μC / g 18μC / g     10⁷ Ω 18μC / g 5μC / g The change amount of the tribo before and after passing through the ICL roller 10 is as described above.
An AC electric field was applied by lowering the resistance of the elastic layer.
It is found that the charging ability of the ICL roller 10 is higher.
You. The toner before and after passing through the ICL roller 10
FIGS. 4 (a) and 4 (b) are conceptual diagrams when observing
Shown in Elastic layer resistance 10⁶ Ω intermediate transfer body 2, IC
When the L roller 10 is used, as shown in FIG.
Transfer not transferred secondarily before passing through ICL roller 10
The remaining toner can read the character image as it is, but the ICL roller
After 10 passes, the toner is disturbed by the AC electric field, and the intermediate transfer is performed.
The transfer residual toner on the body 2 is observed as a uniform fog.
Was. On the other hand, the elastic layer resistance shown in FIG.⁷ Ω
The toner image after passing through the ICL roller 10
Does not scatter and AC field is not formed in the discharge gap
I knew it. As described above, in the present embodiment, the intermediate
The elastic layer 22 of the transfer body 2 and I as a toner charging unit
The actual resistance of the elastic layer of the CL roller 10 is set to 10⁶ Ω or less
Charging the toner while disturbing it.
And more effective simultaneous transfer cleaning
Was. <Embodiment 4> In the present embodiment, the rotation of the intermediate transfer body 2
A member on which an AC bias is superimposed, and
In an electrophotographic apparatus using the ICL method, an intermediate transfer member
A capacitor is provided between the ground 2 and the ground. The image of the intermediate transfer system used in the first embodiment
The forming apparatus performs processing on the intermediate transfer member 2.
Photosensitive drum 3, corona charging before secondary transfer
Unit 15, transfer belt (secondary transfer member) 13, ICL low
La 10 and the like. [0093] The material flows into the intermediate transfer member 2 from such a member.
The power supplied to the intermediate transfer body 2 is
Flow into Intermediate transfer member 2 bias performs primary transfer
Voltage when the voltage changes.
Next transfer efficiency may be reduced. But general high
Voltage transfer, secondary transfer current of several tens μA, ICL
The bias does not fluctuate due to the flow of current.
Absent. However, AC current is applied to these members.
ICL system that cleans at the same time as transfer and transfer
The situation will be different if you use. As described in the third embodiment, the intermediate rotation
For example, the elastic layer resistance of the imaging body 2 and the ICL roller 10 can be reduced,
In order to improve the scattering of the second color, the intermediate transfer member 2
When the electrostatic capacity of the
The AC current has a very large value. As described in the second embodiment.
As described above, a discharge gap is provided between the intermediate transfer body 2 and the ICL roller 10.
The provision of the nip is performed by the ICL roller 10 and the intermediate transfer member 2.
To suppress the direct injection current of DC component flowing into
Effective, but for AC current flowing through the capacitance
Not so effective. The image forming apparatus used in the first embodiment as an example
Flows into the intermediate transfer member 2 from the ICL roller 10
The AC current reaches 1500 μA. Besides this, secondary
Prevents wire contamination on corona charger 15 charged before transfer
When an AC voltage of
It flows into the intermediate transfer member 2. These currents are applied to the intermediate transfer member 2.
Escape to ground via primary transfer bias high voltage power supply
You. Since there is a transformer and a resistor inside the high voltage power supply, AC
When current passes through these impedance components,
And a voltage applied to the intermediate transfer body 2
Is superimposed on the AC voltage. A general high-voltage DC power supply has one between the output terminals.
A capacitor of about 000 pF is provided.
Source is inserted in parallel with the
However, when using such a general power supply,
In the configuration of the present embodiment, it is superimposed on the primary transfer bias.
The amplitude of the AC voltage can be as high as 500V. In this state
Cleaning failed in the intermediate transfer body 2
Occurred. This can clean the intermediate transfer body 2
The range of the primary transfer bias is
This is because the peak has been exceeded. In order to prevent such a situation, the present embodiment
In the embodiment, at least 2 is provided between the intermediate transfer member 2 and the ground.
Capacitor 2 with a value between 000 pF and 50,000 pF
0 is provided. The primary high-voltage power supply originally provided 1
With a capacitor of 000 pF, A superimposed on the bias
The amplitude of the C voltage was 500 V.
F to 200V and 5000pF
The amplitude was reduced to almost negligible. one
On the other hand, using a 50,000pF capacitor,
The rise of the transfer bias is delayed by about 1 second.
If a value higher than this value is used, transfer failure at the leading edge of the image will occur.
Was not preferred. The gist of the present embodiment is that the ICL roller 10
Current of the intermediate transfer body 2 by the AC current flowing from the corona charger
Because it is to prevent the voltage from fluctuating,
The position for inserting the sensor 20 is provided in the high voltage power supply.
In addition to the method, the base (drum cylinder) 2 of the intermediate transfer body 2
1 and the elastic layer 22 by directly contacting the terminals,
It is also possible to use a method of grounding via a capacitor. As described above, in the present embodiment, the intermediate
ICL row with AC bias applied around transfer body 2
In the device having the corona charger 15 and the
The transfer member 2 is grounded via the capacitor 20 so that the primary
Prevent transfer failure and cleaning failure of the intermediate transfer body 2
Now you can do it. [0103] As described above, according to the present invention,
The capacitance of the intermediate transfer member is 13 pF / cm^Two Set above
As a result, the electrostatic force acting between the toner and the intermediate transfer member is reduced.
To prevent toner scattering.
Can be Further, the spacer and the intermediate transfer member are connected by a spacer.
Maintains a constant distance to the charging means without contact
Can be transferred from the toner charging means to the intermediate transfer member.
To charge toner efficiently by limiting direct injection
Can be. Further, the actual resistance of the elastic layer of the intermediate transfer member is set to 1
0⁶ Ω or less, the AC voltage applied to the elastic layer
Can be minimized, and the toner charging means
The toner can be effectively disturbed with the intermediary transfer member.
It became so. [0106]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to the present invention. FIG. 2 is a conceptual diagram illustrating how a second color toner scatters when a second color toner is superimposed on a first color toner on an intermediate transfer member. FIG. 3 is a conceptual diagram showing a discharge area between an ICL roller 10 and an intermediate transfer member 2. FIGS. 4A and 4B are conceptual diagrams illustrating images of secondary transfer residual toner before and after an ICL roller. [Description of Signs] 1 Transfer unit 2 Intermediate transfer member (transfer drum) 3 Image carrier (photosensitive drum) 4 Charging roller 7 Black developing device 8 Color developing unit 9 Cleaning unit 10 Toner charging unit (ICL roller) 13 Transfer unit 15 Corona charger before secondary transfer 16 Spacer (abutting roller) 20 Capacitor 21 Base 22 Elastic layer

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/16 G03G 15/01 114

Claims (1)

(57) Claims 1. A step of transferring a toner image formed on an image carrier onto an intermediate transfer body is performed for a plurality of color toners, and a plurality of color toners are formed on the intermediate transfer body. In an image forming apparatus which forms an image and collectively transfers the toner images of a plurality of colors onto a transfer material, the intermediate transfer body has an elastic layer and a surface layer covering the outside thereof.
The elastic layer has a real resistance of 10 ⁶ Ω or less, and the surface layer has a body resistance.
Product specific resistance is 10 ¹² Ω · cm or more and thickness is 30 μm or less
Below, the capacitance of the intermediate transfer member is 13 pF / cm ² or more, the image forming apparatus according to claim.