JP2002311724A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent voids at the time of transfer, and also, to satisfactorily transfer images to a rough paper. SOLUTION: In the image forming device constituted of an intermediate transfer unit for primarily transferring a toner image formed on a photoreceptor 110 to an intermediate tranfer belt 360 by a primary transfer roller 320, and then, secondarily transferring the toner image to a recording medium by a secondary transfer roller 380, the circumferential speed of the photoreceptor 110 is made to differ from the circumferential speed of the intermediate transfer belt 360, the looseness apparent density of toner is >=0.35 g/cc, and the shape coefficient SF-1 of the toner is <=150 and the shape coefficient SF-2 is <=140.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intermediate transfer unit used in an image forming apparatus such as a printer, a facsimile, and a copying machine for forming an image by using an electrophotographic technique.

[0002]

2. Description of the Related Art Generally, an image forming apparatus using an electrophotographic technique includes a photosensitive member having a photosensitive layer on an outer peripheral surface, a charging device for uniformly charging the outer peripheral surface of the photosensitive member, and one charging device. Exposure means for selectively exposing the charged outer peripheral surface to form an electrostatic latent image, and applying a toner as a developer to the electrostatic latent image formed by the exposure means to form a visible image The image forming apparatus includes a developing unit that forms a (toner image), and a transfer unit that transfers the toner image developed by the developing unit to a transfer medium such as paper.

Conventionally, as a transfer means for transferring a toner image developed on a photoreceptor to a transfer medium such as paper, a toner image formed on a photoreceptor is transferred (primary transfer).
There is known an image forming apparatus including an intermediate transfer belt for further transferring (secondarily transferring) the toner image to a recording medium.

[0004]

In the above-mentioned conventional transfer means, in the primary or secondary transfer, the transfer efficiency is reduced, or the toner image is partially missing during transfer (so-called hollow).
There is a problem that occurs. Further, in the secondary transfer, there is a problem that it is difficult to transfer the image onto a recording medium such as recycled paper or bond paper having large surface irregularities without causing image defects. In particular, when high-fluidity toner is used, the toner is liable to be scattered at the time of transfer. If it is located at a distance from the transfer position, the transfer electric field at the transfer position cannot be concentrated at the transfer position, and the toner image may be scattered due to electrostatic force. In the case where the intermediate transfer belt is wound around the photoconductor without a means for substantially urging the photoconductor at the transfer position, the contact area between the photoconductor and the intermediate transfer belt at the transfer position is large. In addition, there is a problem that the toner image is likely to be disturbed due to a mechanical force due to a slight speed difference between the two.

An object of the present invention is to provide an intermediate transfer unit capable of forming a good image free from image defects such as dropouts in transfer and the like.

[0006]

In order to achieve the above object, in the image forming apparatus according to the present invention, a toner image formed on a photosensitive member is primarily transferred at a primary transfer position, and the toner image is further recorded. An intermediate transfer belt for secondary transfer to a medium at a secondary transfer position, and the intermediate transfer belt at the primary transfer position being pressed against the photosensitive member by primary transfer means disposed inside the intermediate transfer belt, At the secondary transfer position, the intermediate transfer belt is pressed against backup means arranged inside the intermediate transfer belt and secondary transfer means arranged outside the intermediate transfer belt, and further, inside the intermediate transfer belt. And an intermediate transfer unit in which a driving roller for driving the intermediate transfer belt is disposed. And an intermediate transfer belt between the primary transfer position and the driving roller is always in a tension state, wherein the loose apparent density of the toner is 0.35 g / cc. Above, and
The toner has a shape factor SF-1 of 150 or less;
F-2 is 140 or less.

[0007]

According to the intermediate transfer unit of the present invention, the primary transfer means and the secondary transfer means are pressed against the intermediate transfer belt at the respective transfer positions, thereby preventing a dropout during the transfer and making the recycled paper or the bond paper. It is possible to satisfactorily transfer to a recording medium having a large surface irregularity such as.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic view showing an example of an image forming apparatus using an embodiment of an intermediate transfer unit according to the present invention.

First, the outline of the image forming apparatus will be described, and then the intermediate transfer unit will be mainly described in detail.

[0011] This image forming apparatus includes a yellow, cyan,
This is an apparatus that can form a full-color image using a developing device using magenta and black toners.

In FIG. 1, reference numeral 50 denotes a case of the apparatus main body. In the case 50, an exposure unit 60, a sheet feeding device 70, a photosensitive unit 100, a developing unit 200,
An intermediate transfer unit 300, a fixing unit 400, and a control unit 80 for controlling the entire apparatus are provided.

The photoconductor unit 100 includes a photoconductor 110
A charging roller 120 serving as a charging unit for uniformly charging the outer peripheral surface by contacting the outer peripheral surface of the photoconductor 110; and a cleaning unit 130.

The developing unit 200 includes:
Developing unit 210Y for yellow, developing unit 210 for cyan
C, a developing device 210M for magenta and a developing device 210K for black. Each of these developing devices 210Y, 21
0C, 210M, and 210K have yellow, cyan, magenta, and black toners built therein, respectively. Further, the developing rollers 211Y, 211C, 2
11M and 211K, so that only the developing roller of any one of the developing units can contact the photoconductor 110.

The intermediate transfer unit 300 includes a driving roller 3
10, a primary transfer roller 320 as a primary transfer unit,
A wrinkle removing roller 330, a tension roller 340, a backup roller 350, an endless intermediate transfer belt 360 stretched around each of these rollers, and a cleaning unit 37 that can contact and separate from the intermediate transfer belt 360.
0.

A secondary transfer roller 380, which is a secondary transfer means, is disposed opposite the backup roller 350. The secondary transfer roller 380 is rotatably supported by an arm 382 that is swingably supported by a support shaft 381. The arm 382 swings by the operation of the cam 383, so that the secondary transfer roller 380 is attached to the intermediate transfer belt 360. To come and go.

The driving roller 310 has a gear 31 at its end.
1 (see FIG. 3) is fixed, and this gear 311
By meshing with the gear 144 (see FIG. 3) of the photoconductor unit 100, the photoconductor unit 100 is driven to rotate at substantially the same peripheral speed as the photoconductor 110, so that the intermediate transfer belt 360 circulates at substantially the same peripheral speed as the photoconductor 110. It is designed to be driven.

While the intermediate transfer belt 360 is being driven to circulate, the toner image on the photosensitive member 110 is transferred between the primary transfer roller 320 and the photosensitive member 110 by the intermediate transfer belt 36.
The toner image transferred onto the intermediate transfer belt 360 is transferred onto a recording medium S such as a sheet supplied between the secondary transfer roller 380 and the toner image. The recording medium S is supplied from the sheet feeding device 70.

The paper feeding device 70 includes a tray 71 on which a plurality of recording media S are placed in a stacked state, a pickup roller 72, and a recording medium S placed on the tray 71 facing the pickup roller 72. It has a hopper 73 for urging and a pair of separation rollers 74 for surely separating sheets fed by the pickup roller 72 one by one.

The recording medium S fed by the paper feeding device 70
Passes through a first transport roller pair 91, a first paper sensor 91S, a second transport roller pair 92, a second paper sensor 92S, and a gate roller pair 93 to the second transfer unit, ie, the intermediate transfer belt 360 and the secondary transfer roller 380. And then discharged onto the case 50 via the fixing unit 400, the first pair of paper discharge rollers 94, and the second pair of paper discharge rollers 95.

The fixing unit 400 includes a fixing roller 410 having a heat source and a pressing roller 42 pressed against the fixing roller 410.
0.

The operation of the entire image forming apparatus as described above is as follows.

(I) When a print command signal (image forming signal) from a not-shown host computer (such as a personal computer) is input to the control unit 80, the photosensitive member 110, the developing roller of the developing unit 200, etc., and the intermediate transfer The belt 360 is driven to rotate.

(Ii) The outer peripheral surface of the photoconductor 110 is uniformly charged by the charging roller 120.

(Iii) The exposure unit 60 selectively exposes the outer peripheral surface of the uniformly charged photosensitive member 110 in accordance with the image information of the first color (for example, yellow).
An electrostatic latent image for yellow is formed.

(Iv) The developing roller 211 of the developing device 210Y for the first color (for example, yellow) is provided on the photosensitive member 110.
Only the Y contacts, the electrostatic latent image is developed, and the toner image of the first color (for example, yellow) is
10 is formed.

(V) The toner image formed on the photosensitive member 110 is transferred onto the intermediate transfer belt 360 at a primary transfer portion, that is, between the photosensitive member 110 and the primary transfer roller 320. At this time, the cleaning unit 370 and the secondary transfer roller 380 are separated from the intermediate transfer belt 360.

(Vi) After the toner remaining on the photoreceptor 110 is removed by the cleaning means 130,
The photoconductor 110 is neutralized by the neutralization light L ′ from the neutralization unit.

(Vii) The above operations (ii) to (vi) are repeated as necessary. That is, the second color, the third color, and the fourth color are repeated in accordance with the content of the print command signal, and the toner images corresponding to the content of the print command signal are superimposed on the intermediate transfer belt 360 to form an intermediate image. It is formed on the transfer belt 360.

(Viii) Paper feeder 7 at a predetermined timing
0, the recording medium S is supplied.
Immediately before or after reaching the transfer portion (that is, at a timing when the toner image on the intermediate transfer belt 360 is transferred to a desired position on the recording medium S).
80 is pressed against the intermediate transfer belt 360, and the toner image (basically a full-color image) on the intermediate transfer belt 360 is transferred onto the recording medium S. Cleaning means 3
70 contacts the intermediate transfer belt 360, and the toner remaining on the intermediate transfer belt 360 after the secondary transfer is removed.

(Ix) The recording medium S is a fixing unit 400
, The toner image is fixed on the recording medium S, and then the recording medium S is discharged onto the case 50 via the pair of paper discharge rollers 94 and 95.

The outline of the image forming apparatus has been described above. Next, details of the intermediate transfer unit 300 will be mainly described.

FIG. 2 is a partially omitted side view mainly showing the intermediate transfer unit 300.

As described above, the intermediate transfer unit 300
Includes a drive roller 310, a primary transfer roller 320, a wrinkle removing roller 330, a tension roller 340, a backup roller 350, an endless intermediate transfer belt 360 stretched around these rollers, Cleaning means 370 that can be moved toward and away from belt 360
These members are attached to a frame 301 as shown in FIG.

The frame 301 is composed of a pair of side plates (a side plate on the near side is omitted in FIG. 2), and the above members are attached between the side plates. Conversely, it has a structure in which a pair of side plates are connected by a shaft of each of the above members. Note that, in FIG. 2, for a pair of members described below, all members on the near side are omitted.

The drive roller 310 is rotatably supported on the frame 301 by a shaft 312, and the above-described gear 311 (see FIG. 3) is fixed to one end of the drive roller 310. By meshing with the gear 144, the photosensitive member 100 is driven to rotate at substantially the same peripheral speed. In FIG. 3, reference numeral 500 denotes a drive motor, and a pinion 510 fixed to an output shaft 501 of the drive motor is engaged with a gear 144 provided at an end portion of the photoconductor 110 via a reduction gear 520, whereby the photoconductor 110 is driven. Are driven to rotate. The gear 311 is connected to the drive gear 13 of the toner conveying screw 133 of the photoconductor unit 100 (see FIG. 1) via the intermediate gear 520 and the reduction gear 521.
3b, whereby the toner conveying screw 133 is rotationally driven.

As shown in FIG. 2, the primary transfer roller 320
The shaft 321 is rotatably supported by the frame 301 via a pair of bearing members 322. The electrode plate 323 for applying a voltage to the primary transfer roller 320 has a long hole 323 a provided in the frame 301 and a screw hole 30.
2 is supported by being screwed. Also,
The bearing member 322 is provided in the recess 3 provided in the frame 301.
A compression coil spring 324 is provided between the bearing member 322 and the frame 301 so as to be slidable (movable up and down in FIG. 2).

Therefore, the primary transfer roller 320 is pressed against the photoreceptor 110 via the intermediate transfer belt 360 when both ends of the shaft 321 are urged by the pair of compression coil springs 324.

The wrinkle removing roller 330 is rotatably supported on the frame 301 by its shaft 331.

The tension roller 340 has its shaft 341
Are rotatably and slidably supported by a long hole 304 provided in the frame 301. The shaft 341 has one end 3 of a pair of arms 342 at both ends.
42a is in contact. The arm 342 is swingably supported by a shaft 343 with respect to the frame 301, and a tension spring 344 is provided between the other end 342 b and the frame 301.

Therefore, the tension roller 340 is
The tension spring 344 constantly urges the intermediate transfer belt 360 through the arm 342 in a direction in which the intermediate transfer belt 360 is stretched.

The backup roller 350 as backup means is rotatably supported by the frame 301 by its shaft 351.

The intermediate transfer belt 360 includes the rollers 3
It is stretched around 10, 320, 330, 340, 350, and is circulated by the drive roller 310 in the direction of the arrow (clockwise) in FIG.

The cleaning means 370 includes a fur brush 371 for cleaning off the toner remaining on the outer peripheral surface of the intermediate transfer belt 360 and the intermediate transfer belt 36
A cleaner blade 372 for scraping off the toner remaining on and adhering to the outer peripheral surface of the toner cartridge 0, and a toner conveying screw 373 as a conveying means for conveying the toner brushed off or scraped off by the fur brush 371 or the cleaner blade 372. , And these members are incorporated in the case 374.

The lower part of the case 374 has a toner collection chamber 3
75 is formed in the toner collecting chamber 375.
The fur brush 371, the cleaner blade 372, and the toner conveying screw 373 are arranged.

The fur brush 371 is fixed to a shaft 371a penetrating the side plate of the case 374, and the shaft 371a is driven by driving means (not shown) to
It is rotationally driven in the direction of the arrow in FIG.

The cleaner blade 372 is attached to the mounting plate 372.
The end (lower end) is attached to the case 374 by a to scrape off the toner by contacting the outer peripheral surface of the intermediate transfer belt 360.

The toner conveying screw 373 is connected to the case 3
The shaft 373a penetrating the side plate 74 is driven by a driving unit (not shown) to rotate in the direction of the arrow in FIG. 2, and the toner collected in the toner collecting chamber 375 is used as waste toner in a waste toner box (not shown). Transport.

The case 374 has cylindrical portions 374 a provided on both side surfaces of the case 374.
01 is rotatably supported.

A hook 37 is provided on both sides of the lower end of the case 374.
7, and a tension spring 378 is provided between the hook 377 and the frame 301.

Therefore, the case 374 is always urged by the tension spring 378 in the direction (clockwise) in which the fur brush 371 and the cleaner blade 372 are pressed against the intermediate transfer belt 360. The cam 300 is provided with a cam 55 (see FIG. 1), and the rotation of the case 374 is restricted by the cam 55 being in contact with the lower end of the case 374.

The cam 55 is driven by driving means (not shown). When the cam 55 is at the position shown in FIG. The transfer belt 360 is separated from the transfer belt 360.

In FIG. 2, reference numeral 56 denotes a driving roller 310.
This is a position detection sensor provided in the image forming apparatus main body so as to be located at a position facing the image forming apparatus (see FIG. 1), and is for detecting the position of the intermediate transfer belt 360.

The intermediate transfer unit 300 as described above is
It is detachable from the image forming apparatus main body.

Further, in the present embodiment, various measures can be made or can be made.

<Regarding the Driving Roller 310> (1) The outer diameter of the driving roller 310 is set so that the peripheral speed of the intermediate transfer belt 360 is slightly higher (within a tolerance) than the peripheral speed of the photoconductor 110. It is composed.

It is desirable that the peripheral speed of the photoconductor 110 and the peripheral speed of the intermediate transfer belt 360 to which the toner image is transferred from the photoconductor 110 completely match.

However, since there is a tolerance between the outer diameter of the photosensitive member 110 and the outer diameter of the drive roller 310, it is impossible to completely match the peripheral speeds. In such a situation, assuming that the peripheral speed of the intermediate transfer belt 360 in the portion wound around the drive roller 310 becomes slightly slower than the peripheral speed of the photoconductor 110, the pressure contact position between the photoconductor 110 and the primary transfer roller 320 (Primary transfer position T1)
Between the drive roller 310 and the driving roller 310, the force for loosening the intermediate transfer belt 360 acts on the intermediate transfer belt 360, though very slight, and the state of the intermediate transfer belt 360 at the primary transfer position T1 becomes unstable. turn into.

Therefore, in this embodiment, the outer diameter of the drive roller 310 is set such that the peripheral speed of the intermediate transfer belt 360 is slightly (within a tolerance) faster than the peripheral speed of the photoconductor 110. did.

With this configuration, the pressure contact position between the photosensitive member 110 and the primary transfer roller 320 (primary transfer position T1).
And the drive roller 310, the intermediate transfer belt 360 is always in a slightly tensioned state, so that the state of the intermediate transfer belt 360 at the primary transfer position T1 is stabilized.

The amount of runout on the outer peripheral surface of the drive roller 310 was set to ± 0.05 mm or less.

(2) The period of the intermediate transfer belt 360 is set to be an integral multiple of the period of the driving roller 310.

With this configuration, the driving roller 310
The amount of deviation between the toner images of each color superimposed on the intermediate transfer belt 360, which is caused by the vibration of the shaft or the outer peripheral surface of the intermediate transfer belt 360, can be reduced.

Note that, specifically, the above ratio was 5: 1.

(3) The period of the intermediate transfer belt 360 is configured to be an integral multiple of the period of the photosensitive member 110.

With this configuration, it is possible to reduce the amount of deviation between the toner images of each color superimposed on the intermediate transfer belt 360, which is caused by the deflection of the shaft or the outer peripheral surface of the photoconductor 110.

Incidentally, specifically, the above ratio was 2: 1.

(4) The winding angle of the intermediate transfer belt 360 around the drive roller 310 is 90 ° or more, and
It was made larger than the wrapping angle for other rollers.

With this configuration, the driving roller 310
The intermediate transfer belt 360 can be driven stably even if the coefficient of friction between the belt and the intermediate transfer belt 360 is small, or is reduced by long-term use.

Specifically, the wrapping angle is 15
It was about 1 mm.

The outer peripheral surface of the drive roller 310 was coated with urethane to increase the coefficient of friction.

<Regarding the Backup Roller 350> The method of separating the intermediate transfer belt 360 and the recording medium S at the pressure contact portion between the backup roller 350 and the secondary transfer roller 380, that is, at the secondary transfer portion T2 (see FIG. 2) is as follows. The diameter of the backup roller 350 is φ3
The winding angle of the intermediate transfer belt 360 with respect to the backup roller 350 was set to 90 ° or more.

With this configuration, the recording medium S can be reliably separated from the intermediate transfer belt 360.

It is more desirable that the diameter of the backup roller 350 be equal to or less than φ30 mm, and the winding angle of the intermediate transfer belt 360 around the backup roller 350 be 1
05 ° or more. Specifically, the diameter was 30 mm and the winding angle was 109 °.

It is desirable that the surface resistance of the intermediate transfer belt 360 be 10 ¹² Ω or less.

<Regarding Cleaning Means 370> (1) The tension roller 340 is shifted (closed) to the cleaning means 370 side in the horizontal direction as compared with the backup roller 350, so that the contact between the fur brush 371 and the intermediate transfer belt 360 is achieved. A part of the toner recovery chamber 375 is opened below the contact portion.

With this configuration, the fur brush 37
1 is transferred to the toner collection chamber 37.
5, it becomes easy to be collected.

More preferably, the tension roller 340
The angle θ between the intermediate transfer belt 360 and the vertical line V (ie, the angle θ between the common tangent line between the tension roller 340 and the backup roller 350 and the vertical line V) between the roller and the backup roller 350 is 10 ° or more, and more desirably. Is 15 ° or more.

With this configuration, the fur brush 37
1 is transferred to the toner collection chamber 37.
5 makes it easy to be surely collected, and the toner that falls when the cleaning unit 370 separates from the intermediate transfer belt 360 is also easily collected in the toner collecting chamber 375.

(2) The means for receiving the urging force of the cleaning means 370 against the intermediate transfer belt 360 is also used by the tension roller 340.

With this configuration, the manufacturing cost can be reduced. In addition, it is not necessary to provide a tension roller separately, and the number of rollers can be reduced, so that each roller can have a large winding angle.

<Regarding Wrinkle Removal Roller 330> The wrinkle removal roller 330 is disposed close to the primary transfer position T1 on the upstream side in the circulation direction of the intermediate transfer belt 360, and the winding of the intermediate transfer belt 360 around the wrinkle removal roller 330 is performed. The hanging angle was 10 ° or more.

With such a configuration, wrinkles generated in the intermediate transfer belt 360 between the tension roller 340 and the wrinkle removing roller 330 (a wavy state when the direction of the tension roller 340 is viewed from the wrinkle removing roller 330) are reduced. The intermediate transfer belt 360 at the primary transfer position T1 can be smoothed by the removal by the take-off roller 330.

More preferably, the wrinkle removing roller 33
The winding angle of the intermediate transfer belt 360 with respect to 0 is set to 15 ° or more. Specifically, it was 17.6 °.

In place of the wrinkle removing roller 330, a means (for example, a guide plate) for changing the traveling direction of the intermediate transfer belt 360 by 10 ° or more may be provided.

<Regarding Primary Transfer Position T1> (1) At the primary transfer position T1, the intermediate transfer belt 3
The driving roller 310, the primary transfer roller 320, and the
And a wrinkle removing roller 330 were arranged.

With such a configuration, the transfer nip can be stabilized regardless of the belt tension. Assuming that the intermediate transfer belt 360 is wound around the primary transfer roller 320 and the primary transfer position T1 is formed at the winding portion, the fluctuation of the tension of the intermediate transfer belt 360 greatly affects the primary transfer position T1. However, the effect can be reduced by arranging the intermediate transfer belt 360 in a tangential direction with respect to the photoconductor 110 without winding the intermediate transfer belt 360 around the primary transfer roller 320.

(2) Move the primary transfer position T1 to the drive roller 31
It was arranged close to 0.

When the distance between the primary transfer position T1 and the drive roller 310 increases, the amount of expansion and contraction of the intermediate transfer belt 360 during this time increases, and the primary transfer position T1
, The running speed of the intermediate transfer belt 360 becomes unstable.

Therefore, in this embodiment, the primary transfer position T1 is arranged close to the drive roller 310, thereby stabilizing the traveling speed of the intermediate transfer belt 360 at the primary transfer position T1.

The distance L1 (see FIG. 2) between the primary transfer position T1 and the drive roller 310 is desirably 40 mm or less, more desirably 35 mm or less. Specifically, it was about 30.5 mm.

(3) The length of the linear portion of the intermediate transfer belt 360 from the wrinkle removing roller 330 to the drive roller 310 is 0.25 or less in aspect ratio, more preferably 0.15 or less.
15 or less.

This is for more effectively suppressing the influence of the wrinkles.

More specifically, the length of the linear portion is set to 5
It was about 5.5 mm.

<Regarding Position Detection> As described above, the position detection sensor 56 is disposed at a position facing the drive roller 310, and the position of the intermediate transfer belt 360 is detected on the drive roller 310.

Thus, the running cycle of the intermediate transfer belt 360 can be accurately detected.

The position detection sensor 56 is a reflection type optical sensor, and a mark to be detected by the position detection sensor 56 is provided on the intermediate transfer belt 360 by printing.

The position detecting sensor is a transmission type optical sensor,
The holes to be detected by this are transferred to the intermediate transfer belt 360.
If the hole is opened, stress may concentrate on the hole and its shape may be deformed, so that accurate detection may not be performed. In this embodiment, however, the position detection sensor 56
Is a reflection type optical sensor, and a mark to be detected by this is provided on the intermediate transfer belt 360 by printing, so that the running cycle of the intermediate transfer belt 360 can be accurately detected.

<Stretching Structure of Intermediate Transfer Belt 360> The stretching structure of the intermediate transfer belt 360 is such that the length on the intermediate transfer belt 360 from the primary transfer position T1 to the secondary transfer position T2 is A4. The length on the intermediate transfer belt 360 from the secondary transfer position T2 to the primary transfer position T1 is also equal to or greater than the horizontal length of the A4 size paper. That is, the intermediate transfer belt 360 was stretched to have such a length.

With such a configuration, the secondary transfer roller 3 can be used for continuous printing on A4 size paper.
The timing at which the roller 80 contacts the intermediate transfer belt 360 can be set between the sheets, that is, the secondary transfer roller 380 can be prevented from contacting during the primary transfer.

If the secondary transfer roller 380 is brought into contact with the intermediate transfer belt 360 during the primary transfer, the shock may cause an image to be disturbed by the primary transfer. The situation can be prevented.

<Regarding the Cleaning Means 370> (1) The cleaner blade 372 is made of urethane rubber, has a free length of about 8 mm, a thickness of about 3 mm, a Young's modulus of about 7 to 9 MPa, and a holder angle (without load). The angle between the blade and the tangent of the roller at the contact position was about 20 °, and the contact pressure against the intermediate transfer belt 360 was about 45 gf / cm.

With this configuration, it is possible to prevent the occurrence of cleaning failure due to slippage of the toner, vibration of the blade, or turning over.

(2) A waste toner box was provided separately from the case 374.

With this configuration, since a large amount of waste toner does not accumulate in the case 374, the load at the time of swinging the case 374 and the fluctuation of the force acting on the case 374 after the swinging are reduced. As a result, the contact pressure of the cleaner blade 372 against the intermediate transfer belt 360 can be stabilized.

(3) Shaft 3 of Toner Conveying Screw 373
73a (see FIG. 2) is the center of rotation of the case.

With this configuration, it is easy to secure a relative positional relationship between another fixing member, for example, the waste toner carrying port of the case 374 and the toner receiving port of the waste toner box.

(4) The cam 55 is a SIN cam.

With this configuration, the impact on the intermediate transfer belt 360 can be reduced.

<Regarding Patch Sensing> Patch sensing, that is, toner amount detection at the time of test printing, is performed by the intermediate transfer belt 360 on the drive roller 310.

With this configuration, it is possible to perform the operation at a place where the winding angle is large and the speed is stable.

<Regarding Beads> A bead is a ridge provided on the back surface of the intermediate transfer belt 360 along the circulation direction, and the ridge is formed by a concave groove (regulating groove) formed on a roller around which the belt is wound. To determine the position of the belt (in the axial direction of the roller).

This bead need not always be provided, and is not provided in the embodiment shown in FIG. 2, but when it is provided, the following configuration is adopted.

(1) Silicon rubber is used as the bead, and its thickness (projection height) is about 1.5 mm and its width is about 4 mm.

(2) The coefficient of friction of the bead with respect to the regulating groove is made smaller than the coefficient of friction of the base material of the intermediate transfer belt 360 with any roller.

With this configuration, it is possible to reduce the occurrence of a tension gradient in the belt axial direction due to the frictional force between the bead and the restriction groove.

The intermediate transfer belt 36 with respect to the rollers
The coefficient of friction of the base material of 0 is about 0.4.

(3) The elastic strength of the bead is E = 2.0
To about 8.0 MPa.

[0119] If it is too soft, the stress in the thrust direction at the regulating portion is concentrated at one location, and it is concentrated in a narrow area of the bead bonding portion.

On the contrary, if the belt is too hard, the involvement of the bead in the bent portion of the belt increases.

More preferably, the elastic strength of the bead is 1.0 to ((t1: belt film thickness t2: bead thickness E1: belt Young's modulus (率 4.0 × 10 ³ [MPa])). t1 / t2) 2E1 [MPa].

(4) The bead regulating groove is located at the primary transfer position T
Provided on rollers not adjacent to 1.

With this configuration, it is possible to reduce the positional deviation between the toner images of the respective colors superimposed on the intermediate transfer belt 360 due to the random fluctuation of the intermediate transfer belt 360 due to the contact between the beads and the regulating grooves.

For example, the bead regulating groove is formed by attaching a stepped flange to the end of the backup roller 350.

(5) The width of the regulating groove is slightly increased with respect to the bead width, and a margin is provided for the straightness of the bead attachment.

For example, if the bead width is about 4 mm,
The width of the restriction groove is about 4.2 mm.

<Regarding Replacement and Handling of Intermediate Transfer Unit 300> (1) When the intermediate transfer unit 300 is placed on a desk or the like, the intermediate transfer belt 360 has a structure that does not come into contact with the desk surface or the like. And adhesion of foreign matter.

(2) When the intermediate transfer unit 300 is placed on a desk or the like, the drive transmission unit (for example, the gear 311) does not come into contact with the desk surface or the like, thereby preventing the drive transmission unit from being deformed or damaged.

(3) The structure in which the electrode section of the intermediate transfer unit 300 is provided on the opposite side of the drive transmitting section prevents contamination of the electrodes and defective contacts.

(4) Since the photoconductor unit 100 cannot be mounted unless the intermediate transfer unit 300 is mounted, erroneous mounting is prevented.

(5) The capacity of the waste toner box is made to correspond to the life of the intermediate transfer belt 360,
00 and the waste toner box can be replaced.
Improve handling.

<Regarding the Sequence> (1) When detecting the position of the intermediate transfer belt 360 as a reference for the exposure / writing timing, a primary transfer bias is applied, that is, the primary transfer bias is applied before the position detection. It shall be applied.

In this manner, the load on the intermediate transfer belt 360 at the primary transfer position T1 from the position detection to the primary transfer for each of the four colors becomes substantially equal, and the respective color toner images superimposed on the intermediate transfer belt 360 It is possible to suppress a positional deviation between them (this deviation is referred to as a resist deviation).

(2) When the intermediate transfer belt 360 is stopped, the position of the position detection mark is the primary transfer position T1.
More upstream. For example, it is located at the position indicated by M in FIG.

By doing so, the intermediate transfer belt 360
When the tension of the intermediate transfer belt 360 due to the application of the bias is unstable at the initial stage of the rotation of, position detection can be performed, and registration deviation due to a period shift can be avoided.

<Frame 30 of Intermediate Transfer Unit 300
Concerning 1> By forming the side plate of the frame 301 with an insulating member, there is no need to insulate the roller shaft (and / or bearing member) for applying a bias to the roller.

Further, by using ABS resin as the insulating member, the coefficient of thermal expansion of the frame 301 can be made substantially the same as that of the intermediate transfer belt 360, and relative displacement due to temperature change can be prevented.

[0138]

EXAMPLES Hereinafter, more specific examples will be described.

The following description is mainly about the transfer process.

<To Stabilize Primary Transfer Efficiency> (1) When the impedance of primary transfer is large (approximately 3
When the impedance was small (when it was about 30 MΩ or less), a high-voltage power supply for constant voltage control was used.

Thus, the toner amount (film thickness), environment,
Even if there is a variation in the resistance of the members, good transfer is performed.

(2) The surface resistance of the intermediate transfer belt 360 is 10 ⁸ to 10 ¹² Ω / □, and the volume resistivity is 10 ⁸ to 10 ¹² Ω.
cm.

The primary transfer roller 320 is a roller (diameter 2 mm) in which an elastic layer made of urethane resin in which carbon is dispersed is formed on the outer peripheral surface of a metal shaft (diameter 12 mm).
2 mm), the resistance is 10 ⁶ to 10 ⁸ Ω (more preferably about 10 ⁷ Ω), the hardness is 45 ± 5 °, and the pressure contact load on the photoconductor 110 is 1.0 to 3.5 kg (more preferably). 2.5 kg).

With the above range of the resistance value, 12
Transfer is possible at 00V or less.

When the hardness and the load are within the ranges described above, so-called hollow holes can be prevented.

The hardness is determined by an Aske well known to those skilled in the art.
It is measured by an rC hardness tester. It should be noted that such a hardness tester is what is called indentation hardness and is affected by the thickness of the elastic layer. The hardness in the present invention is not a result of measuring an elastic body constituting the elastic layer, but a result of measurement in a state of being formed into a roller.

(3) Regarding the amount of the external additive of the toner to be used, the amount of the external additive having a large particle diameter is 0.5 to 4.0 wt%.
(More preferably about 0.7 wt%), and the amount of the external additive having a small particle size is 1.5 to 4.0 wt% (more preferably 2.
(About 0 wt%).

The external additive having a large particle size is necessary mainly for improving the durability stability of the toner. In view of this point, the more it is, the better. However, if it exceeds 4.0% by weight, the fluidity of the toner is increased. Is worsened, and it is not preferable because it affects hollowing out and the like.

An external additive having a small particle size is necessary mainly for improving the transferability of rough paper. In this respect, the larger the amount, the better. Triggers the photoconductor 110 and the intermediate transfer belt 360
Is unfavorable because filming is likely to occur.

Under the above conditions (1) to (3), the primary,
While preventing image deterioration due to interference during secondary simultaneous transfer,
The capacity of the high-voltage power supply can be minimized.

(4) The particle size of the toner was 9 μm or less.

If the thickness is 9 μm or more, the resolution is reduced.

Note that the particle size distribution of the toner used this time is shown in FIG.
It was shown to. The particle size distribution of the toner was measured using a Coulter counter model TA-II. The aperture diameter is 100 μm, and the electrolyte is ISOTON-II
Was used.

In the table shown in FIG. 4A, the number is shown in the right column.
The left column shows the volume, the lower row shows the measurement results, and the upper row shows the calculated values based on the measurement results. The “volume” is the volume when the measured toner particles are regarded as spheres.

In the graphs shown in FIGS. 4B and 4C,
The bar graph shows the number data, and the line graph shows the accumulated data.

In the table shown in FIG. 4A, the meanings of the items indicating the measurement results in the lower row are as follows. DIF N: This is the most basic data, and indicates the number data (the number data of toner) input from the I / O for each channel. DIF%: The above number data (DIF N) is displayed in% for each channel. CUM N: The above number data (DIF N) is accumulated and displayed. CUM%: The above DIF% is accumulated and displayed.

The meanings of the items indicating the calculated values in the upper row are as follows. 25.4 μ ↑: The cumulative% value of those having a value of 25.4 μm or more is displayed. 6.35 μ ↓: The cumulative% value of those having a diameter of 6.35 μm or less is displayed. KURTSIS: represents the kurtosis (sharpness) of the distribution. By setting the volume particle size distribution to 0.8 or more and the number particle size distribution to 0.3 or more, it is possible to obtain an image with good transferability and without a decrease in resolution. SKEWNESS: Represents the skewness of the distribution. By setting the absolute value to 0.6 or less in the volume particle size distribution and the absolute value to 0.1 or less in the number particle size distribution, it is possible to obtain an image with good transferability and without a decrease in resolution. Average: The arithmetic average particle diameter is displayed. 25%: The value of the particle diameter when the cumulative% reaches 25% (see the graphs of FIGS. 4B and 4C). 50%: The particle diameter when the cumulative% reaches 50%. 75%: The value of the particle size when the cumulative% reaches 75% (see the graphs of FIGS. 4B and 4C). CV %: Coefficient of variation (%). By setting both the volume particle size distribution and the number particle size distribution to 28% or less, it is possible to obtain an image with good transferability and without a decrease in resolution. SDμ: Standard deviation (μm).

(5) Shape of Toner The shape factor of the toner is, for example, FE-SEM manufactured by Hitachi, Ltd.
Using (S-800), 100 toner images magnified at a magnification of 500 times are randomly sampled, and the image information is analyzed by introducing, for example, an image analyzer (LuzexIII) manufactured by Nicole Corporation via an interface, The value calculated from the following equation is defined as a shape factor.

Shape factor (SF-1) = (MXLNG) ²
/ AREA × π / 4 × 100 Shape factor (SF-2) = (PERI) ² / AREA × 1
/ 4π × 100 In the above equation, MXLNG indicates the absolute maximum length of the toner,
PERI indicates the circumference of the toner, and AREA indicates the projected area of the toner.

The shape coefficient SF-1 indicates the degree of roundness of the toner, and the shape coefficient SF-2 indicates the degree of unevenness of the toner.
The shape factor SF-1 of the toner is preferably 100 to 1
50, more preferably 100 to 130. Also,
The shape factor SF-2 of the toner is preferably 100 to 1
40, more preferably 100 to 125. By configuring the shape factors SF-1 and SF-2 in this manner, transfer efficiency in primary transfer and secondary transfer is improved.

In the embodiment of the present invention, regarding the fluidity of the toner, A.I. Even when a high-fluidity toner of D 0.35 g / cc or more is used, when such a high-fluidity toner is used, the primary or secondary functioning as a transfer electrode for applying a transfer voltage to a transfer position is obtained. Since the next transfer means is in contact with each transfer position, the transfer electric field at the transfer position can be concentrated on the transfer position. Further, the transfer means is pressed at the transfer position, and the shape is substantially spherical and the surface is By using a smooth toner with a small amount of unevenness, it is easy to compress the toner image in the height direction at the transfer position, so that the cohesive force between the toners is increased, and as a result, the transfer efficiency is improved, and at the same time, the transfer efficiency is improved. , Can be prevented more favorably. Further, it is possible to satisfactorily prevent the toner image from being disturbed by a mechanical force due to a slight speed difference between the transfer position between the photosensitive member (or the recording medium) and the intermediate transfer belt.

Further, since the toner image can be easily compressed in the height direction without causing image disturbance, when the toner image is fixed on the recording medium, the mutual fusion of the toner is promoted, and the color development is performed. There is also an effect that an image having good transparency and transparency can be formed.

<To Stabilize Secondary Transfer Efficiency> (1) When the impedance of the secondary transfer is large (approximately 2
When the impedance was small (when it was about 20 MΩ or less), a high-voltage power supply for constant voltage control was used.

As a result, even if the paper type, the environment, and the member resistance are varied, good transfer is performed.

(2) The surface resistance of the intermediate transfer belt 360 is 10 ⁸ to 10 ¹² Ω / □, and the volume resistivity is 10 ⁸ to 10 ¹²
Ωcm.

The secondary transfer roller 380 has an elastic layer in which an ion conductive agent such as lithium perchlorate is dispersed or dissolved in a urethane resin.
mm), a roller (diameter 25 mm) formed on the outer peripheral surface, the resistance of which is 10 ⁶ to 10 ⁸ Ω, and the hardness is 60 ± 5.
And the pressing load on the backup roller 350 is 5.0 to 9.0 kg (more preferably, about 7.0 kg).
And

With the above range of resistance, 40
Transfer can be performed at 00 V or less and 200 μA or less.

[0168] The hardness is determined by Aske well known to those skilled in the art.
The hardness is measured by an rC hardness meter, and as described above, the hardness in the present invention is not measured on an elastic body constituting the elastic layer, but is measured on a roller. The result.

The backup roller 350 was grounded and used as an earth roller.

(3) Regarding the amount of the external additive of the toner to be used, the amount of the external additive having a large particle diameter is 0.5 to 4.0 wt%.
(More preferably about 0.7 wt%), and the amount of the external additive having a small particle size is 1.5 to 4.0 wt% (more preferably 2.
(About 0 wt%).

The reason is as described above.

<In order to prevent the back surface of the recording medium S such as paper from being stained> The secondary transfer roller 380 is
0, and a voltage (0 to -60) in a direction in which the toner is returned to the intermediate transfer belt 360 during a paper interval or a color interval.
(Approximately 0 V).

With this configuration, the secondary transfer roller 3
The toner adhering to the recording medium S is reduced, and the stain on the back surface of the recording medium S is reduced.

<To ensure good transfer to rough paper (bond paper)> (1) The secondary transfer roller 380 has a hardness of 60 ± 5.
And the pressing load on the backup roller 350 is 5.0 to 9.0 kg (more preferably, about 7.0 kg).
And

(2) Regarding the amount of the external additive of the toner to be used, the amount of the external additive having a large particle diameter is 0.5 to 4.0 wt%.
(More preferably about 0.7 wt%), and the amount of the external additive having a small particle size is 1.5 to 4.0 wt% (more preferably 2.
(About 0 wt%).

As the toner, a high-concentration pigment toner having a particle size of about 7 μm was used.

(3) The toner amount before the secondary transfer, that is, the toner amount on the intermediate transfer belt 360 is 1.5 mg
/ Cm 2 or less.

By adopting the above constitutions (1) to (3), a good transfer state can be obtained even on rough paper such as Nina bond paper.

That is, by making the secondary transfer roller 380 high in hardness as described above and increasing the load applied thereto, the surface of the paper can be brought into close contact with the toner, and even if a high electric field is formed, the discharge due to electric discharge will occur. Transfer defects are suppressed.
Note that the transport state of the sheet is also stabilized by the high load.

Furthermore, by reducing the amount of toner before the secondary transfer as described above, the transfer efficiency of the toner can be increased.

<In order to prevent voids> (1) The material of the intermediate transfer belt 360 is ETFE in which carbon black or the like is dispersed as a conductive agent or aluminum vapor-deposited PE coated with urethane paint containing fine fluorine particles.
T or polyimide in which carbon black or the like was dispersed as a conductive agent.

The material of the photoreceptor 110 was polycarbonate.

(2) The primary transfer roller 320 has a hardness of 45 ± 5 ° and a pressing load on the photosensitive member 110 of 1.0 to 3.5 kg (note that contact at the primary transfer position in the axial direction of the roller). The width is 358 mm).

(3) The secondary transfer roller 380 has a hardness of 60 ± 5 ° and a pressure contact load on the backup roller 350 of 5.0-9.0 kg (note that the secondary transfer roller 380 is in the roller axial direction at the secondary transfer position). Is 332 mm).

(4) Regarding the amount of the external additive of the toner to be used, the amount of the external additive having a large particle diameter is 0.5 to 4.0 wt%.
(More preferably about 0.7 wt%), and the amount of the external additive having a small particle size is 1.5 to 4.0 wt% (more preferably 2.
(About 0 wt%).

As for the fluidity, A.I. D 0.35
g / cc.

With the above configuration, the following operation and effect can be obtained.

That is, in the primary transfer section, since the transfer condition from the photoreceptor 110 to the intermediate transfer belt 360 is low hardness, low load, and high fluidity toner, the dropout is prevented.

In the secondary transfer section, the intermediate transfer belt 3
Although the transfer conditions from 60 are high hardness and high load,
The material of the intermediate transfer belt 360 is fluorine-based,
Since the toner has high fluidity, the void is prevented.

By setting the load on the secondary transfer means higher than the load on the primary transfer means, the durability of the intermediate transfer belt can be improved. This is because, in the filming of the toner on the intermediate transfer belt, the external additive of the toner remaining on the intermediate transfer belt is embedded in the intermediate transfer belt by a cleaning means such as a cleaning blade for cleaning the surface of the intermediate transfer belt, and the toner is added thereto. It is generated at the starting point, the release of the external additive is likely to occur when successively superimposing colors at the time of the primary transfer, and the external additive released from the toner and adhered on the intermediate transfer belt is formed of toner or paper. When pressed with a certain load or more in the presence, the present invention reattaches to toner and paper fibers which are relatively softer than the intermediate transfer belt, so that the present inventors can remove external additives from the intermediate transfer belt. It is based on the findings of By the way, generally, the primary transfer roller 320 is always in pressure contact with the intermediate transfer belt 360, while the secondary transfer roller 380 is in pressure contact with the intermediate transfer belt 360 when transferring a full-color image in which color superposition has been completed. While the image of each color is sequentially formed, the image is separated from the intermediate transfer belt 360. However, in such a configuration, if the load of the primary transfer roller 320 is set to be equal to or more than the load at which the loose external additives on the intermediate transfer belt can be removed by the toner, the n-th color already formed on the intermediate transfer belt can be used. When the image of the (n + 1) th color is superimposed on the image, a phenomenon that a part of the image of the nth color returns from the intermediate transfer belt to the photoconductor (so-called reverse transfer) occurs, so that the load on the secondary transfer roller 380 is reduced to a certain level or more. Preferably, the load on the primary transfer roller 320 is set to be equal to or less than a certain value. In the embodiment of the present invention, the load experimentally obtained (the load required for the external additive to be removed from the intermediate transfer belt in the presence of the toner) is 150 g / cm or more;
Preferably it is 200 g / cm or more.

In order to prevent reverse transfer from occurring in the primary transfer, in the embodiment of the present invention, the experimentally obtained load is 100 g / cm or less, preferably 70 g / cm or less. .

Therefore, the ratio of the respective loads of the primary transfer means and the secondary transfer means is 1.5 or more, preferably 2 or more.

Further, in order to prevent the primary and secondary transfer rollers from bending due to the load, it is necessary that the shaft of each roller has a rigidity corresponding to the load. Therefore, the secondary transfer roller has a higher rigidity than the primary transfer roller. Preferably, the outer diameter of the shaft is larger.

<To reduce scattering (scattering of toner)> (1) A wrinkle removing roller 330 is provided near the upstream side of the primary transfer position (primary transfer portion) T1.

(2) Regarding the amount of the external additive of the toner to be used, the amount of the external additive having a large particle diameter is set to 0.5 to 4.0 wt% (more preferably, about 0.7 wt%), The amount of the external additive having a diameter of 1.5 to 4.0 wt% (more preferably, 2.0 w
t%).

Regarding the fluidity, A.I. D 0.35
g / cc, and the charge amount was −10 μC / g or more.

(3) The surface roughness of the intermediate transfer belt 360 was set to Rmax 1 μm (more preferably 0.7 μm) or less.

The surface resistance of the intermediate transfer belt 360 is 10 ⁸ to 10 ¹² Ω / □, and the volume resistivity is 10 ⁸ to 10 ¹² c.
m.

With the above configuration, the following operation and effect can be obtained.

That is, in the primary transfer section, the wrinkle removing roller 330 reduces wrinkles of the intermediate transfer belt 360 and suppresses scattering.

In the secondary transfer section, the intermediate transfer belt 3
The toner on 60 is stably conveyed, and the scattering is suppressed.

<In order to reduce costs> (1) The intermediate transfer belt 360 is formed by applying a urethane-based paint in which PEFT particles and SnO as a conductive agent are dispersed on a sheet-shaped PET on which AL is deposited. And
Endless intermediate transfer belt 3 with both ends adhered by ultrasonic fusion
60 are configured.

The step caused by the adhesion at both ends is 50 steps.
μm or less, more preferably 30 μm or less. The Young's modulus of the paint is about 1.5 × 10 ⁴ kgf / cm ² . The paint has a surface resistance of about 10 ⁸ to 10 ¹² Ω / □ and a surface roughness of Rmax 1 μm (more preferably 0.7 μm).
μm) or less. The electrode configuration is such that a conductive layer is printed on the AL surface at the edge and bias is applied by a roller electrode (1 MΩ or less).

(2) The high voltage power supply is a current-sinking type constant voltage control for the primary transfer section, and applies the primary transfer voltage until the secondary transfer is completed.

With the above configuration (1) and (2),
Transfer efficiency and cleanability can be improved.

Further, the primary transfer roller functions only as a backup roller and does not need to function as an electrode.

Further, by adopting the above-described electrode configuration and power supply configuration, it is possible to suppress image quality deterioration due to interference at the time of primary and secondary simultaneous transfer.

There is a remarkable effect that the driving torque of the supply roller is reduced.

Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above-described embodiments or examples, and can be appropriately modified within the scope of the present invention. It is.

[0210]

According to the intermediate transfer unit of the present invention, it is possible to prevent slippage during transfer, achieve good transfer to rough paper, and improve the durability of the intermediate transfer belt. I can do it.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an image forming apparatus using an embodiment of an intermediate transfer unit according to the present invention.

FIG. 2 is a partially omitted side view mainly showing an intermediate transfer unit 300;

FIG. 3 is a diagram showing a main part of a gear train.

FIG. 4 is a diagram illustrating an example of a particle size distribution of a toner according to the embodiment of the present invention.

[Explanation of symbols]

 110 Photoconductor T1 Primary transfer position T2 Secondary transfer position 360 Intermediate transfer belt

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] May 22, 2002 (2002.5.2)
2)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshiya Takahata 3-3-5 Yamato, Suwa City, Nagano Prefecture Inside Seiko Epson Corporation (72) Inventor Hiroshi Ito 3-3-5 Yamato Suwa City, Nagano Prefecture Seiko Epson (72) Inventor Takehiko Okamura 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation (72) Inventor Nobumasa Abe 3-3-5, Yamato, Suwa-shi, Nagano Seiko Epson Corporation F Terms (reference) 2H005 AA15 2H030 AA01 BB23 BB42 BB46 2H200 FA04 GA50 GB12 JA02 JA25 JA26 JB10 JB13 JB16 JC03 JC07 JC09 JC10 JC16 JC17 KA03 KA11 LA14 LA17 LA18 LA23 LA25 LA29 MA04 MA14 MB04 MC05 MB06 MC06

Claims (3)

[Claims] An intermediate transfer belt for primary-transferring a toner image formed on a photoconductor at a primary transfer position, and further secondary-transferring the toner image to a recording medium at a secondary transfer position; The intermediate transfer belt is pressed against the photosensitive member by a primary transfer unit disposed inside the intermediate transfer belt, and at the secondary transfer position, the intermediate transfer belt is placed inside the intermediate transfer belt. And an intermediate transfer unit which is pressed by a secondary transfer means disposed outside the intermediate transfer belt and further includes a drive roller disposed inside the intermediate transfer belt and driving the intermediate transfer belt. Providing a speed difference between the peripheral speed of the photoreceptor and the peripheral speed of the intermediate transfer belt, and providing a speed difference between the primary transfer position and the driving roller. Wherein the loose apparent density of the toner is 0.35 g / cc or more, the shape factor SF-1 of the toner is 150 or less, and SF-2. Is less than or equal to 140. 2. The image forming apparatus according to claim 1, wherein a driving roller is disposed between the primary transfer position and the secondary transfer position, and the peripheral speed of the intermediate transfer belt is made faster than the peripheral speed of the photosensitive member. 2. The image forming apparatus according to 1. 3. The image forming apparatus according to claim 1, wherein a load of said secondary transfer means is higher than a load of said primary transfer position.