JP2000227724A - Image forming device - Google Patents

Abstract

(57) Abstract: In an image forming apparatus that electrostatically transfers a toner image to a transfer member arranged in a non-contact manner, a toner image on an image carrier can be stably transferred to the transfer member. . SOLUTION: A slit electrode substrate 3 having an opening 3e is arranged in a non-contact manner between a photosensitive drum 1 and an intermediate transfer member 4, and a first electrode provided on a side of the slit electrode substrate 3 near the photosensitive drum 1 is provided. A voltage having a polarity in a direction of holding the toner image 5 formed on the photosensitive drum 1 on the photosensitive drum 1 is applied to the first and second electrodes 3a and 3c.
c, the second electrode 3 provided on the side farther from the photosensitive drum 1 than
By applying a voltage having a polarity in a direction in which the toner image 5 formed on the photosensitive drum 1 is separated from the photosensitive drum 1 to b and 3d, the toner image 5 formed on the photosensitive drum 1 is applied.
Can be transferred to the intermediate transfer body 4 through the opening 3e in a non-contact manner, so that paper powder or the like of a transfer material is prevented from adhering to the photosensitive drum 1, and toner scattering can be prevented. A high-quality image can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a toner image of a single color or a plurality of colors on an image carrier, transferring the toner image on the image carrier to a transfer material, or intermediate the toner image on the image carrier. The present invention relates to an image forming apparatus such as a printer, a facsimile, and a copying machine that obtains an image by transferring an image to a transfer material via a transfer body.

[0002]

2. Description of the Related Art In a conventional image forming apparatus such as an electrophotographic system or an electrostatic recording system, an OPC photosensitive member or an a-Si
Developing a toner image corresponding to an electrostatic latent image formed on an image carrier such as a photoconductor, bringing a transfer material into contact with the toner image, and further electrostatically attracting the toner onto the transfer material To transfer the toner image onto the transfer material, and fix the unfixed toner image on the transfer body by heating or pressing to form an image.

In the transfer step, the toner image is not directly transferred to the transfer material from the image carrier, but is temporarily transferred (primary transfer) to an intermediate transfer member that is in contact with the image carrier. 2. Description of the Related Art In an image forming apparatus of a system in which a toner image transferred to an intermediate transfer body is re-transferred (secondarily transferred) to a transfer material, it is known as a form suitable for a sequential transfer step of each color particularly when a color image is formed. .

As such an image forming apparatus, for example, Japanese Patent Publication No. 49-209 discloses a technique in which electrostatic transfer is performed in primary transfer and pressure transfer is performed in secondary transfer.

[0005] This is an improvement that eliminates so-called color misregistration in which images are displaced when multicolor printing is performed on an elastic flexible transfer material such as cloth, paper, or the like when the respective colors are superimposed and transferred. In addition, the purpose and effect of the present invention is to reduce color misregistration and print high-speed multiple colors by sequentially transferring each color image to an intermediate transfer member and then collectively transferring the images onto a transfer material.
In addition, since each color toner image is transferred to the next transfer material after the transfer of each color toner image to the intermediate transfer body, the margin for synchronization becomes large especially when the transfer material is transported, so that the transport mechanism can be simplified and the reliability is improved. I do.

[0006] Further, as a known technique for performing fixing by heating at the same time as secondary transfer from an intermediate transfer body to a transfer material, for example, JP-A-49-78559 and JP-A-57-23975. There is. Also, Japanese Unexamined Patent Publication No.
Japanese Patent Application Laid-Open No. 139070 discloses that primary transfer is performed by non-contact electrostatic transfer and pressure fixing is performed by secondary transfer. The object is to provide a device which can obtain a good printed image even when printing on plain paper using a low-resistance magnetic toner and also when the humidity is high, and which can be easily made compact.

As described above, many examples of the intermediate transfer member in the case of a multicolor toner image and examples of the simultaneous transfer and fixing have been proposed. As a multi-color image forming apparatus using such an intermediate transfer body, for example, in a multi-transfer type copying apparatus, an original is read by a CCD line sensor or the like and then subjected to various kinds of processed image signals or directly output from a computer. The image signal and the like are input to an exposure device (laser driver), and the exposure device performs laser exposure according to the image signal to form an electrostatic latent image on a photosensitive drum that is uniformly charged in advance. Then, after developing the electrostatic latent image with the toner in the developing device for the first color, the toner image is electrostatically transferred from the photosensitive drum to the intermediate transfer body in the primary transfer section. These series of steps, for example, yellow, magenta,
A full-color toner image is formed on the intermediate transfer member by repeating the operation sequentially with cyan and black toners, and then these full-color toner images are collectively transferred from the intermediate transfer member to a transfer material (for example, paper) in a secondary transfer portion. After the fixing and the completion of the full-color image forming sequence, the transfer material is discharged out of the apparatus, and the required full-color image formation is completed.

[0008]

However, in the image transfer by direct contact between the transfer material or the intermediate transfer member and the photosensitive drum as the image carrier of the image forming apparatus described in the above-mentioned conventional example, the following is required. Problems may occur. (1) Deterioration of an image over time due to environmental conditions in the apparatus on the surface of the photosensitive drum due to adhesion of paper powder of the transfer material (for example, image flow in a high humidity atmosphere) (2) Particularly in color image formation, a color image once transferred to a transfer material is re-transferred to a photosensitive drum at the time of subsequent color image transfer, or transfer failure or image disorder of the second and subsequent color images. . (3) Scattering transfer or toner scattering due to uncontrolled discharge immediately before contact between the photosensitive drum and the transfer material.

In addition, when a toner image of each color is formed on an intermediate transfer member, and a full-color image is formed by simultaneously transferring and fixing simultaneously from the intermediate transfer member to a transfer material in a secondary transfer portion, the following process is performed. Such a problem may occur. (A) In the primary transfer section, the same problems as the above (2) to (4) can occur even when an intermediate transfer body is used as the transfer body. (B) In the case of simultaneous thermal fixing in the secondary transfer section, a thermal influence on the photosensitive drum via the intermediate transfer member, and problems such as drum deterioration and toner fusion may occur. (C) Even if an intermediate transfer member is used, there is a great possibility that paper powder or the like of a transfer material is conveyed and adhered onto the photosensitive drum via a direct contact portion or a close portion, and the adverse effect of the paper dust on the photosensitive drum is large. Is essentially unavoidable.

Accordingly, the present invention provides an image forming apparatus capable of preventing a retransfer, a toner scattering, and a paper powder of a transfer material from adhering to an image carrier, and stably obtaining a good image. The purpose is to do.

[0011]

In order to achieve the above object, the present invention provides a transfer method in which a charged toner image formed on a surface of an image carrier is disposed in a non-contact manner with the image carrier provided with a predetermined gap. In an image forming apparatus for electrostatically flying and transferring to a body, an opening having a predetermined width formed in a width direction of an image area of the image carrier in a non-contact manner between the image carrier and the transfer body And a plurality of electrodes arranged at least on the upstream side in the moving direction of the image carrier of the opening so as to have different distances from the image carrier over a width direction of an image area of the image carrier. A voltage having a polarity in a direction of holding the charged toner image on the surface of the image carrier is applied to a first electrode of the plurality of electrodes arranged on a side closest to the image carrier; Image bearing than the first of the electrodes A second electrode disposed farther from is characterized by applying a polarity of the voltage direction of separating the charged toner image from the image bearing member surface.

A plurality of electrodes are provided on the upstream side and the downstream side of the opening in the moving direction of the image carrier so that the distance from the image carrier varies over the width direction of the image area of the image carrier. It is characterized by being arranged.

Further, the distance between the opening and the first electrode is larger than the distance between the opening and the second electrode.

Further, the distance between the opening and the first electrode is larger than the distance including the electrode width between the opening and the second electrode.

Further, the opening is formed in a slit shape having a predetermined width over the entire width of the image area of the image carrier.

The transfer member is an intermediate transfer member that temporarily carries the charged toner image in a primary transfer portion and then transfers the toner image to a transfer material in a secondary transfer portion. The opening and the plurality of electrodes are arranged at a primary transfer portion between the carrier and the carrier.

[0017]

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

Embodiment 1 FIG. 1 is a schematic diagram showing a primary transfer section of an image forming apparatus according to the present embodiment. In the present embodiment, the toner image formed on the photoconductor drum is electrostatically flying on an intermediate transfer body which is a non-contact transfer body provided with a predetermined gap from the photoconductor drum as an image carrier. This is an image forming apparatus for transferring the image.

The present image forming apparatus includes a photosensitive drum 1 as an image carrier. The photosensitive drum 1 is provided with an OP on a surface of a conductive cylindrical base 1a such as aluminum or SUS.
It has a photoelectric layer 1b of C, a-Si or the like, and is rotationally driven at a predetermined process speed in a direction indicated by an arrow (clockwise) by a driving means (not shown). On the photosensitive drum 1, a toner image 5 of a negatively charged toner is formed by a known electrophotographic method.

A first electrode 3a, a first electrode 3a,
Slit electrode substrate 3 having 3c and second electrodes 3b, 3d
(See FIGS. 1 and 2), and constitutes a primary transfer portion which is a feature of the present invention (the detailed configuration and operation of the slit electrode substrate 3 will be described later).

The intermediate transfer member 4 is provided with a back electrode 2 so as to be in contact with the surface opposite to the slit electrode substrate 3 in the primary transfer portion.

Next, the structure of the slit electrode substrate 3 will be described.

In the primary transfer section, the slit electrode substrate 3 is disposed between the photosensitive drum 1 and the intermediate transfer member 4 in a non-contact manner.

The slit electrode substrate 3 preferably has a slit width of 0.1 to 5 mm with respect to the moving direction (rotation direction) b of the intermediate transfer member 4, and has a width direction of the image area of the photosensitive drum 1 (left and right in FIG. 3). (Direction) A slit-shaped opening 3e is provided over the entire area. In the primary transfer section, the rotation direction a of the photosensitive drum 1 and the movement direction (rotation direction) b of the intermediate transfer body 4 are the same.

Around the opening 3e, a flat plate-like first electrode 3 is provided upstream and downstream in the moving direction of the photosensitive drum 1 over the entire width of the image area of the photosensitive drum 1.
a, 3c are formed, and further, inside the first electrodes 3a, 3c (on the side of the opening 3e), close to the opening 3e, upstream of the moving direction of the photosensitive drum 1 over the entire width of the image area of the photosensitive drum 1. Plate-shaped second electrodes 3b and 3d are formed on the side and the downstream side, respectively.

The first electrodes 3a and 3c are disposed on the front side (the photosensitive drum 1 side) of the slit electrode substrate 3, and the second electrodes 3b and 3d are disposed on the rear side (the intermediate transfer body 4 side) of the slit electrode substrate 3. ), And the first electrodes 3a, 3c are
It is closer to the photosensitive drum 1 than the electrodes 3b and 3d.

In this embodiment, the distance X1 between the opening 3e and the end of the first electrodes 3a and 3c on the opening 3e side is 40 μm.
m, the distance X2 between the opening 3e and the end of the second electrode 3b, 3d on the opening 3e side is 10 μm, and the opening 3e and the second electrode 3
b, the width X21 between the opening 3e and the end opposite to the opening 3e is 6
0 μm, the closest distance L1 between the photosensitive drum 1 and the first electrodes 3a, 3c is 120 μm, and the photosensitive drum 1 and the second electrode 3
b, the closest distance L2 between 3d is 240 μm, the closest distance L3 between the photosensitive drum 1 and the intermediate transfer member 4 is 500 μm,
Distance L4 between first electrode 3a, 3c and second electrode 3b, 3d
Is set to 100 μm.

Next, the first electrode 3 of the slit electrode substrate 3
Referring to FIG. 3, conditions and operations for transferring (primary transfer) the toner image 5 formed on the surface of the photosensitive drum 1 to the intermediate transfer member 4 by the a and 3c and the second electrodes 3b and 3d will be described. explain.

In FIG. 3, the first of the slit electrode substrates 3
The voltage V1 applied between the electrodes 3a, 3c and the photosensitive drum 1 is a DC voltage or a pulse voltage (for example, -500 V) such that the first electrode 3a has a negative (-) polarity.
Is applied so that the negatively charged toner (toner image 5) on the surface of the photosensitive drum 1 is held on the surface of the photosensitive drum 1. The voltage V2 applied between the second electrodes 3b and 3d and the photosensitive drum 1 is positive (+)
A DC voltage or a pulse voltage (for example, 2.5 KV) having a polarity is applied so that the negatively charged toner (toner image 5) on the surface of the photosensitive drum 1 is separated from the surface of the photosensitive drum 1.

The voltage V3 applied between the photosensitive drum 1 and the back electrode 2 is positive (+) on the back electrode 2 side.
A DC voltage or a pulse voltage (for example, 5 KV) having a polarity is applied.

In the state in which the voltages V1, V2, and V3 are applied, the first electrode to which the negative voltage (-500 V) is applied because the negatively charged toner is used in the present embodiment. 3a and 3c, the toner image 5 carried on the surface of the photosensitive drum 1 at a position facing the photosensitive drum 1
The force in the direction that is held works.

Further, a region where the first electrodes 3a and 3c do not exist, that is, the opening 3 located inside the first electrodes 3a and 3c.
On the photosensitive drum 1 facing e and its periphery, the vicinity of the peripheral surface of the opening 3e is affected by the first electrodes 3a and 3c, and the action of the second electrodes 3b and 3d by the electric field is inhibited. On the other hand, on the photosensitive drum 1 facing the vicinity of the center of the opening 3e, the influence of the electric field of the first electrodes 3a, 3c is weakened, and the second positive voltage (2.5 KV) is applied. Due to the action of the electrodes 3b, 3d by the electric field,
A force acts in a direction to separate the toner image 5 on the surface of the photosensitive drum 1 from the photosensitive drum 1. The force acting on the toner image 5 on the surface of the photosensitive drum 1 at this portion (near the center of the opening 3e) changes abruptly from the direction of holding the photosensitive drum 1 to the direction of separating from the photosensitive drum 1.

Further, the first electrodes 3a and 3c are
Since they are arranged closer to the photosensitive drum 1 than b and 3d, the toner image 5 can be carried on the photosensitive drum 1 by further narrowing down the opening width of the first electrodes 3a and 3c. Therefore, as shown in FIGS. 1 and 3, the first electrodes 3a, 3c
The ends of the second electrodes 3b and 3d closer to the opening 3e than the ends closer to the opening 3e are arranged closer to the center of the opening 3e.
By optimizing the position, the toner image 5 on the surface of the photosensitive drum 1 facing the opening 3e can be separated from the photosensitive drum 1, and applied to the second electrodes 3b and 3d as described later. The voltage can be reduced.

In the state where the voltages V1, V2 and V3 are applied, as shown in FIG. 4, an equipotential surface c shown by a curve is formed near the opening 3e, and is indicated by an arrow in the opening 3e. A line of electric force in a direction opposite to the direction is formed.

As a result, as shown in FIG. 3, the toner image 5 formed on the surface of the photoreceptor drum 1 is stable except for the portion facing the opening 3e. The toner image 5 on the photosensitive drum 1 is held at a position that is held on the photosensitive drum 1 and faces the opening 3e.
Fly electrostatically onto the intermediate transfer member 4 and the toner image 6 is transferred in a non-contact manner.

At this time, the strength of the electric field in the direction along the line of electric force in the direction in which the toner image 5 carried on the surface of the photosensitive drum 1 is separated from the photosensitive drum 1 is as shown in FIG. The electric potential surface c is strongest at the position closest to the surface of the photosensitive drum 1 (the center of the opening 3e), and is exposed straightly in the direction of the arrow only from a narrowed area near the closest position of the equipotential surface c. The toner image 5 on the surface of the body drum 1 can be separated and moved onto the intermediate transfer body 4.

As described above, the toner image 5 is stably held on the surface of the photosensitive drum 1 by the first electrodes 3a and 3c, and the lines of electric force formed by the first electrodes 3a and 3c and the second electrodes 3b and 3d. By virtue of the aperture effect, the transfer of the toner image 5 straight from the limited area of the opening 3e to the intermediate transfer member 4 can be favorably performed without contact.

Toner image 6 transferred onto intermediate transfer member 4
Is transferred and fixed to a transfer material such as paper (not shown) and output.

Hereinafter, a preferred embodiment of the slit electrode substrate 3 constituting the primary transfer section will be described in more detail.

Distance L between photosensitive drum 1 and intermediate transfer member 4
3 is preferably 200 μm to 1 mm. The shorter the distance L1, the stronger the regulation of supporting the toner on the photosensitive drum 1 can be sharpened. Therefore, the force acting on the toner image 5 is suppressed (the toner image 5 is supported on the photosensitive drum 1) from the direction of promotion (toner image). 5 can be rapidly changed in the direction of separating the photosensitive drum 1 from the photosensitive drum 1), and the transfer area can be narrowed down, so that a good image can be maintained.

The distance L1 between the photoconductor drum 1 and the first electrodes 3a, 3c of the slit electrode substrate 3 is set within a range not in contact with the toner image 5 on the photoconductor drum 1 surface.
The slit electrode substrate 3 is provided in a range smaller than 1/2 of 3 and is preferably in a range of 30 μm to 500 μm, and particularly preferably in a range of 100 μm to 250 μm.
Further, a distance L between the photosensitive drum 1 and the second electrodes 3a and 3b.
2 is more suitable for reducing the voltage applied to the second electrodes 3a and 3b, so that the first electrodes 3a and 3c and the second
It is preferable that the distance L4 between the electrodes 3b and 3d is small. However, if the distance is too small, the distance X1 and the distance X
Since the influence of the second electrodes 3a and 3b other than the area shielded by the first electrodes 3a and 3c, which is the difference (X1−X2), becomes large and the setting accuracy becomes strict, the distance L4 is 30 μm to 200 μm. Is preferable, and a particularly easy design range is 50 μm to 100 μm.

Further, by making the distance X1 larger than the distance X2, the voltage applied to the second electrodes 3b and 3d can be advantageously reduced. Further, the distance X1 is changed to the distance X2.
If the second electrode 3b is smaller than the first electrode 3b,
a, 3c, the toner image 5 on the surface of the photosensitive drum 1 cannot be separated with a normal applied voltage,
When the distance X1 is substantially equal to the distance X2, the second electrode 3b,
Most of 3d is shielded by the first electrodes 3a and 3c, and unless the voltage applied to the second electrodes 3b and 3d is considerably increased,
It becomes difficult to separate the toner image 5 on the surface of the photosensitive drum 1.

On the other hand, the difference between the distance X1 and the distance X2 (X1-X
If 2) is too large, the area where the second electrodes 3b and 3d are not shielded by the first electrodes 3a and 3c becomes too large,
When the effect of effectively narrowing the transfer area is weakened and severe, the toner may go straight toward the second electrodes 3b and 3d instead of the openings 3e, and may accumulate on the slit electrode substrate 3.

The appropriate range of each of the above-mentioned distances depends on the charging characteristics of the photosensitive drum 1 and the toner, the above-mentioned L1, L2, L3, or the voltage values V1, V2, V3, etc., which will be described later. However, the distance X1 is 0 μm to 200 μm.
The range of μm is preferable, and a more preferable range is 10 μm.
m to 100 μm. The distance X2 is 0
The range is preferably from 100 μm to 100 μm, and more preferably from 10 μm to 600 μm. In addition, the above (X1
-X2) is preferably in the range of 0 μm to 100 μm,
A more preferred range is 10 μm to 60 μm.

When the distance X1 between the opening 3e and the first electrodes 3a and 3c is larger than the distance X21 including the electrode width between the opening 3e and the second electrodes 3b and 3d, the first electrode 3
This is advantageous for preventing a leak between a, 3c and the second electrodes 3b, 3d.

The range conditions selected as the voltages V1, V2, and V3 are set so as to satisfy V1 <V2 <V3. In order to improve the convergence of the lines of electric force, V2 / V2 It is set so as to satisfy L2> V1 / L1.

The optimum values of the voltages V1, V2, and V3 are determined by the charging characteristics of the photosensitive drum 1 and the toner used,
1, L2, L3, X1, X2, etc., but as a common sense voltage value range, Vl is 0V to -1.5KV,
More preferably, it is -200 V to -1 KV, and V2 is 1
00V to 4KV, more preferably 1KV to 3KV, V3 is 200V to 8KV, more preferably 2KV to
6 KV.

In the case of a positively charged toner, the voltage V
The signs of 1, V2, and V3 are opposite to those of the above case. Therefore, V1>V2> V3, | V2 / L2 |> | V1 / L1
| May be set.

As shown in FIG. 5, in the case where there is no first electrode on the downstream side in the moving direction b of the intermediate transfer member 4 in the opening 3e, as shown in FIG. In the case where the first electrode and the second electrode on the downstream side in the moving direction b of the intermediate transfer member 4 are not provided, the above-described bending of the equipotential surface c is formed although not as much as the case shown in FIG. . As a result, the effect of restricting the transfer region due to the convergence of the lines of electric force is shown in FIG.
In the same way, non-contact transfer can be favorably achieved. Other configurations are the same as those of the slit electrode substrate 3 shown in FIG.

The method for forming the slit electrode substrate 3 is as follows.
For example, an electrode pattern (the first electrodes 3a, 3c and the first electrode 3a, 3c) is formed on the copper foil by a known photolithography method on a 100-μm-thick polyimide or glass epoxy resin substrate provided with a copper foil laminated on both surfaces at a thickness of 18 μm. 2 electrodes 3
b, 3d), and after further laminating a 20 μm-thick polyimide film or the like, a slit-shaped opening 3e is formed by press punching or punching irradiation of an ultraviolet laser or a carbon dioxide gas laser to form a slit electrode. The substrate 3 can be obtained. Further, as the electrode formation, those formed as an electrode substrate by another method (for example, electroforming) can be used.

As the toner used in the present image forming apparatus, any of conductive, insulating, magnetic and non-magnetic toners can be used.
Alternatively, in order to enhance transfer controllability, an insulating non-magnetic toner is preferable, and a non-magnetic toner whose charge amount (Q / M) is not so large (about 5 μC / g to 30 μC / g) is preferably used. The reason for this is that it is preferable for stabilization that the electric field generated by the toner transferred onto the intermediate transfer member 4 does not significantly affect the transfer of the toner to be transferred thereafter.

Further, as the toner to be used, spherical particles having a sharp particle size distribution are preferable.
Optimum is a toner obtained by a polymerization method of m to 10 μm. The reason for this is that, in the case of the polymerized toner having a spherical shape and a small amount of fine powder, the physical attraction force to the surface of the photosensitive drum 1 can be reduced as compared with a general pulverized toner (to the intermediate transfer member 4). And the central particle diameter can be reduced, so that it is possible to minimize the contamination and clogging of the opening 3e.

As described above, in this embodiment, the photosensitive drum 1 and the intermediate transfer member 4 are not in contact with each other,
Can be separated from the intermediate transfer member 4 except for the opening portion 3e formed in the slit electrode substrate 3, so that paper powder or the like of a transfer material is prevented from adhering to the photosensitive drum 1, and particularly in high humidity. And the periphery of the photosensitive drum 1 can be shielded from the intermediate transfer member 4 except for opposing the opening 3e of the slit electrode substrate 3, so that toner having a fine particle diameter is scattered. Can be prevented, and a high-quality image can be obtained.

<Embodiment 2> FIG. 7 is a schematic configuration diagram showing an image forming apparatus according to the present embodiment.

In the present embodiment, the toner images 5 of the negatively charged polarities of yellow, magenta, cyan, and black sequentially formed on the photosensitive drum 1 are caused to fly by the action of the slit electrode substrate 3 described above. This is an image forming apparatus that sequentially transfers images onto a film-like intermediate transfer body 4 to obtain a color image.

Also in the present embodiment, the slit electrode substrate 3 described in the first embodiment is placed between the photosensitive drum 1 and the intermediate transfer member (in the present embodiment, an OHP film having a thickness of 100 μm) 4. It is a configuration arranged by contact. In the slit electrode substrate 3 of the present embodiment, the distance X1 between the opening 3e and the first electrodes 3a and 3c shown in FIG. 1 is 40 μm, and the distance L4 between the first electrodes 3a and 3c and the second electrodes 3b and 3d. Is set to 50 μm, and the other configuration is the same as that of the first embodiment.
The slit electrode substrate 3 is 150 μm from the photosensitive drum 1.
Are arranged close to each other without contact.

In the present embodiment, a back electrode 2 in the form of a conductive rubber roller is provided on the surface of the intermediate transfer member 4 in the form of a film opposite to the surface of the photosensitive drum 1. And at a distance of 600 μm.

The operation of transferring the toner image 5 on the photosensitive drum 1 to the intermediate transfer member 4 according to the present embodiment will be briefly described with reference to FIGS.

A toner image 5 is formed on the photosensitive drum 1 by a known electrophotographic method. Then, by the rotation of the back electrode roller 2 that rotates in synchronization with the photosensitive drum 1,
While feeding the intermediate transfer member 4 in synchronization with the toner image formed on the photosensitive drum 1, a voltage of 5 KV is applied to the back electrode 2 with respect to the grounded photosensitive drum base, and the By applying a voltage of -300 V to the first electrodes 3a and 3c and applying a voltage of 2.5 KV to the second electrodes 3b and 3d, the potential shown in FIG.
e, and the yellow toner image 5 of the first color is satisfactorily transferred onto the intermediate transfer member 4 in the same manner as in the first embodiment.

Similarly, the magenta toner image 5 of the second color on the photosensitive drum 1 is aligned with the yellow toner image previously transferred to the intermediate transfer member 4, and the same voltage application condition is applied. And superimpose and transfer.
The cyan and black toner images 5 are sequentially superimposed and transferred to obtain a color image. The color image transferred onto the intermediate transfer member 4 is transferred and fixed to a transfer material such as paper (not shown) and output.

As described above, also in the present embodiment, the same effect as that of the first embodiment can be obtained, so that the toner image 5 on the photosensitive drum 1 is transferred to the film-like intermediate transfer member 4.
The image can be transferred satisfactorily in a non-contact manner, and a high-quality color image can be obtained.

<Embodiment 3> In the present embodiment, in the image forming apparatus shown in Embodiment 2, the photosensitive drum 1 and the intermediate transfer body (OHP film) 4 are synchronized with each other to make the slit electrode substrate Step 3 is carried out in small increments at a pitch (opening width) in the moving direction of the photosensitive drum 1 of the opening 3e formed in 3. Other configurations are the same as those of the second embodiment.

In this embodiment, the first electrodes 3a and 3c of the slit electrode substrate 3 are always supplied with a DC voltage of -600V.
And 2.5 V to the second electrodes 3 b and 3 d.
By applying a pulse of the voltage of KV in synchronization with the above-mentioned step feed at rest, better transfer can be performed.

<Embodiment 4> FIG. 9 is a schematic configuration diagram showing an image forming apparatus according to the present embodiment.

In this embodiment, the toner images 5 of the negatively charged colors of yellow, magenta, cyan, and black sequentially formed on the photosensitive drum 1 are caused to fly by the action of the slit electrode substrate 3 described above. This is an image forming apparatus that sequentially transfers images onto an endless film-like intermediate transfer member 4 to obtain a color image.

Also in the present embodiment, the slit electrode substrate 3 described in the first embodiment is connected to the photosensitive drum 1 and the intermediate transfer member (in this embodiment, an endless polyimide film having a thickness of 25 μm). This is a configuration in which they are arranged in a non-contact manner therebetween. The belt-shaped intermediate transfer member 4 is stretched between the driving roller 4a and the driven rollers 4b and 4c, and is moved in the direction of the arrow.

In this embodiment, the surface of the intermediate transfer member 4 on the side opposite to the photosensitive drum 1 is provided with a back electrode 2 in the form of a flat electrode.
And the back electrode 2 is connected to the photosensitive drum 1 by 450 μm.
They are arranged facing each other at a distance of m.

In the slit electrode substrate 3 of the present embodiment,
The distance X1 between the opening 3e and the first electrodes 3a and 3c shown in FIG. 1 is 30 μm, and the distance X2 between the opening 3e and the second electrodes 3b and 3d is 10 μm. The first electrode 3a, 3c and the second electrode 3
The distance L4 between b and 3d is set to 50 μm, and the other configuration is the same as that of the first embodiment. The slit electrode substrate 3 is arranged in a non-contact and close proximity to the photosensitive drum 1 at a distance of 100 μm.

The operation of transferring the toner image 5 on the photosensitive drum 1 to the intermediate transfer member 4 according to the present embodiment will be briefly described with reference to FIGS.

A toner image 5 is formed on the photosensitive drum 1 by a known electrophotographic method. The intermediate transfer member 4 is fed in synchronization with the toner image formed on the photosensitive drum 1 by the rotation of the drive roller 4 a which rotates in synchronization with the photosensitive drum 1, and moves with respect to the grounded photosensitive drum base. ,
By applying a voltage of 4 KV to the back electrode 2, applying a voltage of -600 V to the first electrodes 3a and 3c of the slit electrode substrate 3, and applying a voltage of 2 KV to the second electrodes 3b and 3d, as shown in FIG. Is formed in the opening 3e, and the yellow toner image 5 of the first color is satisfactorily transferred onto the intermediate transfer member 4 as in the first embodiment.

Similarly, the magenta toner image 5 of the second color on the photosensitive drum 1 is aligned with the yellow toner image previously transferred to the intermediate transfer member 4, and the same voltage application condition is applied. And superimpose and transfer.
The cyan and black toner images 5 are sequentially superimposed and transferred to obtain a good color image. Intermediate transfer member 4
The transferred color image is transferred and fixed to a transfer material such as paper (not shown) and output.

As described above, also in the present embodiment, the same effect as that of the first embodiment can be obtained, so that the toner image 5 on the photosensitive drum 1 is brought into contact with the belt-like intermediate transfer member 4 without contact. Good transfer can be achieved, and a high-quality color image can be obtained.

<Embodiment 5> In this embodiment, in the image forming apparatus shown in Embodiment 4, the photosensitive drum 1 and the intermediate transfer body (endless polyimide film) 4 are synchronized with each other, Opening 3 formed in slit electrode substrate 3
Step e is performed in small increments at a pitch (opening width) in the moving direction of the photosensitive drum 1 of e. Other configurations are the same as those of the fourth embodiment.

Further, in this embodiment, better transfer can be performed by applying a pulse of 2 KV to the second electrodes 3b and 3d of the slit electrode substrate 3 in synchronism with the above-mentioned step feed stationary. it can.

<Embodiment 6> FIG. 9 shows an image forming apparatus according to the present embodiment provided with the above-described slit electrode substrate (in this embodiment, four color toner images are sequentially formed on a photosensitive drum). FIG. 1 is a schematic configuration diagram illustrating a full-color image forming apparatus provided with a rotary developing device.

The present image forming apparatus includes a photosensitive drum 1 as an image bearing member.
Charger 31, an exposure device (laser scanner unit) that irradiates laser light L according to an image signal of each color via mirror 33.
A developing device 3 having four developing devices for respectively containing yellow, magenta, cyan, and black toners;
4, a photosensitive drum cleaning device 35, a drum-shaped intermediate transfer member 4, and the like.

The first electrodes 3a and 3c and the second electrodes 3b and 3d are provided between the photosensitive drum 1 and the intermediate transfer member 4.
A slit electrode substrate 3 having
2), and constitutes a primary transfer section which is a feature of the present invention. The configuration and operation of the slit electrode substrate 3 are the same as those of the slit electrode substrate 3 described in the first embodiment, and a description thereof will be omitted in the present embodiment.

Further, a pressure roller 37a and a heating roller 37b, which can make contact with each other and constitute a secondary transfer section 37, are provided below the intermediate transfer member 4. Outside the intermediate transfer member 4, an intermediate transfer member cleaning device 36 and the like which can be separated from and separated from each other are arranged.

The photosensitive drum 1 is, as shown in FIG.
A conductive cylindrical substrate 1a such as aluminum or SUS has a photoelectric layer 1b such as OPC or a-Si on the surface thereof, and is driven by a driving means (not shown) at a predetermined process speed in a direction indicated by an arrow (clockwise). It is driven to rotate.

In the present embodiment, the charging device 31 is a charging roller as a contact charging unit that comes into contact with the surface of the photosensitive drum 1, and charges the photosensitive drum 1 to a predetermined polarity and potential.

The exposure device 32 forms an electrostatic latent image by performing image exposure with a laser beam L on a surface of the charged photosensitive drum 1 via a mirror 33 in accordance with an input image signal of each color.

The developing device 34 includes a yellow developing unit 34Y, a magenta developing unit 34M, a cyan developing unit 34C, and a black developing unit 34BK mounted on a rotating body 34a. The developing device of the color used for developing the electrostatic latent image on the photosensitive drum 1
Developed as a toner image by attaching negative polarity toner to the electrostatic latent image, located at the development position facing the surface (visualization)
I do.

The intermediate transfer member 4 is provided with the back electrode 2 made of a conductive rubber roller so as to be in contact with the surface opposite to the slit electrode substrate 3 in the primary transfer portion.
The surface including the surface is covered with a film 4a made of OHP or the like.

Next, the image forming operation of the above-described image forming apparatus will be described.

At the time of image formation, the photosensitive drum 1 is driven to rotate in a direction indicated by an arrow at a predetermined process speed by a driving means (not shown), and is uniformly charged by a charger 31 to which a predetermined charging bias is applied.

Then, image exposure is performed on the charged photosensitive drum 1 by a laser beam L pulse-modulated in accordance with an image signal by an exposure device 32, and a first color image of a target color image (for example, (Yellow image). The electrostatic latent image of the yellow image is developed by the rotation of the rotating body 34a with the toner by the yellow developing device 34Y fixed at the developing position in advance.

The yellow toner image is formed on the film 4a on the surface of the intermediate transfer member 4 at the primary transfer portion between the photosensitive drum 1 and the intermediate transfer member 4, as described in the first embodiment. The first electrodes 3a, 3c of the electrode substrate 3,
Electrostatic transfer is performed under the condition of voltage application to the second electrodes 3b, 3d and the back electrode 2.

Here, the intermediate transfer member 4 is the photosensitive drum 1
And rotates in the direction of the arrow in synchronization with the yellow toner image on the surface, and prepares for the transfer of the next color (magenta in the figure). In order to enhance the transferability, the photosensitive drum 1 and the intermediate transfer member 4 are synchronously step-fed with a period correlated with the pulse voltage applied to the second electrodes 3b and 3d of the slit electrode substrate 3. It may be.

On the other hand, the surface of the photosensitive drum 1 is cleaned by the photosensitive drum cleaning device 35, and is uniformly charged again by the charger 31. The image is formed by the laser beam L in accordance with the next magenta image signal. Receive exposure. The developing device 34 rotates while an electrostatic latent image is formed on the surface of the photosensitive drum 1 in accordance with the magenta image signal by the image exposure, and places the magenta developing device 34M at a developing position to perform magenta development. In the primary transfer section, the magenta toner image is transferred to the film 4 on the surface of the intermediate transfer member 4.
A is electrostatically transferred onto the “a” under the condition of voltage application to the first electrodes 3 a, 3 c of the slit electrode 3, the second electrodes 3 b, 3 d and the back electrode 2. At this time, the magenta toner image is also transferred with good efficiency without the yellow toner image previously transferred being transferred onto the photosensitive drum 1 again.

The above-described image forming process is similarly performed for the cyan and black colors, respectively, when the transfer of four colors to the intermediate transfer member 4 is completed, or during the transfer of the final color black. , Paper cassette 38
The transfer material P such as paper stored in the paper feed roller 3
9 and is conveyed to a secondary transfer section 37 of the intermediate transfer body 4 via a paper feed guide 40. Here, the four-color toner images formed on the intermediate transfer member 4 are
, The heating roller 37 disposed in the intermediate transfer member 4
After being transferred onto the transfer material P strongly or lightly simultaneously with the transfer by the heat of b and the pressure of the pressure roller 37a, it is discharged onto the discharge tray 41, and the full-color image formation is completed.

Thereafter, the residual toner remaining on the sheet 4a on the surface of the intermediate transfer member 4 is cleaned by an intermediate transfer member cleaning device 36 such as a felt pad which comes into contact with the sheet 4a, and is prepared for the next step.

As described above, also in the present embodiment, the same effect as that of the first embodiment can be obtained, so that the toner image 5 on the photosensitive drum 1 is brought into contact with the drum-shaped intermediate transfer member 4 without contact. Good transfer can be achieved, and a high-quality full-color image can be obtained.

In the above-described image forming apparatus, if the fixing in the secondary transfer unit 37 is a condition for light fixing, the fixing unit may be further heated and pressurized, if necessary, to a position before the sheet is discharged. May be arranged. In the secondary transfer section 37, the heating roller 37a and the pressure roller 37b can be configured to have a heating means in both or one of them, and have a halogen heater or a linear ceramic heater therein. Can be used.

In the present embodiment, a method using a semiconductor laser has been described as an electrostatic latent image forming means. However, the present invention is not limited to this. For example, a digital electrostatic latent image such as an LED, a liquid crystal, or an ionograph is used. It is also effective in an image forming unit or a so-called analog electrostatic latent image forming unit.

In this embodiment, a full-color image forming apparatus including a four-color developing system has been described. However, it is needless to say that the present invention can be applied to a single-color or two-color image forming apparatus.

Further, in the present embodiment, a static elimination means (not shown) is provided upstream of the primary transfer position of the intermediate transfer member 4, and the toner previously transferred before the primary transfer of each of the second and subsequent colors sequentially performed is performed. , It is possible to further stabilize the superposition of the toner images of the respective colors.

<Embodiment 7> FIG. 10 shows an image forming apparatus according to the present embodiment provided with the above-mentioned slit electrode substrate (in this embodiment, a tandem type full-color image forming apparatus having four image forming units). FIG. 2 is a schematic configuration diagram illustrating an image forming apparatus.

In the present embodiment, a photosensitive drum 1Y carrying a yellow toner image, a photosensitive drum 1M carrying a magenta toner image, a photosensitive drum 1C carrying a cyan toner image, a photosensitive body carrying a black toner image Drum 1
BK, and each photosensitive drum 1Y, 1M, 1C,
The chargers 31Y, 31M, 3
1C, 31BK, and exposure devices 32Y, 32M, 32C, 32BK for irradiating image exposure corresponding to image signals of respective colors;
Developing units 34Y, 34M, 34C, and 3 that respectively store yellow, magenta, cyan, and black toners.
4BK, an endless film-like intermediate transfer member 4 and the like are provided.

Each photosensitive drum 1Y, 1M, 1C, 1BK
A non-contact primary transfer section is formed between the intermediate transfer member 4 and the intermediate transfer member 4, and the above-described slit electrode substrates 3 are disposed therebetween, and are opposed to each other with the intermediate transfer member 4 of each slit electrode substrate 3 interposed therebetween. Back electrodes 2Y, 2M, 2C, and 2BK made of conductive rubber rollers are provided on the back side of the intermediate transfer member 4, respectively.

Each photosensitive drum 1Y, 1M, 1C, 1BK
The gap between the front surface and the back electrodes 2Y, 2M, 2C, 2BK is 6
The width of each slit electrode substrate 3 is 150 μm from the surface of each of the photosensitive drums 1Y, 1M, 1C and 1BK.
They are arranged close to each other in a non-contact manner at a certain distance. The configuration of the slit electrode substrate 3 and the conditions of the applied voltage are the same as those in the first embodiment.
The configuration is the same as that described above, and the description thereof is omitted in the present embodiment.

The secondary transfer section 3 is located below the intermediate transfer member 4.
7, a pressure roller 37a and a heating roller 37b which can be separated from and separated from each other are arranged, and an intermediate transfer member cleaning device 36 which can be separated from the intermediate transfer member 4 is disposed outside the intermediate transfer member 4.

Next, an image forming operation of the above-described image forming apparatus will be described.

At the time of image formation, first, the photosensitive drum 1Y is rotationally driven at a predetermined process speed by a driving means (not shown) in the direction of the arrow (clockwise), and is uniformly formed by the charger 31Y to which a predetermined charging bias is applied. Be charged.

Then, image exposure is performed on the charged photosensitive drum 1Y by a laser beam pulse-width-modulated according to an image signal by the exposure device 32Y to form an electrostatic latent image corresponding to a target yellow image. Is done. The electrostatic latent image of the yellow image is developed with the toner by the yellow developing unit 34Y which is fixed at the developing position in advance by the rotation of the developing device 34Y.

The yellow toner image is applied to the surface of the intermediate transfer member 4 at the primary transfer portion between the photosensitive drum 1 and the intermediate transfer member 4 by the slit electrode 3 and the back electrode described in the first embodiment. 2 is electrostatically transferred under the condition of voltage application to 2.

Here, the intermediate transfer member 4 is the photosensitive drum 1
It moves in the direction of the arrow in synchronization with Y, 1M, 1C, and 1BK, continues to move while holding the yellow toner image on the surface, and prepares for transfer of the next color (magenta in the figure).

On the other hand, the photosensitive drum 1Y is provided with a charger 31Y.
The surface is cleaned and uniformly charged, and is subjected to image exposure by laser light according to the next yellow image signal.

Further, in synchronism with the above-described yellow image formation, an electrostatic latent image is formed on the surface of the photosensitive drum 1M in accordance with a magenta image signal by image exposure, and the magenta image is formed by the magenta developing unit 34M. Is performed, and the magenta toner image is transferred onto the intermediate transfer member 4 at the primary transfer portion where the slit electrode substrate 3 is located.

Subsequently, the above-described image forming process is similarly performed for the cyan and black photosensitive drums 1C and 1BK, respectively, and the transfer of the four colors to the intermediate transfer member 4 is completed or finalized. During the transfer of the color black, a transfer material P such as a sheet housed in a sheet cassette 38 is fed by a sheet feeding roller 39, and is secondary-transferred to the intermediate transfer body 4 via a sheet feeding guide 40. It is transported to the unit 37.

Here, the 4 formed on the surface of the intermediate transfer member 4
The color toner image is transferred to the heating element 3 provided in the intermediate transfer member 4.
After being fixed onto the transfer material P at the same time as the transfer by the heat from the pressure roller 7a and the pressure from the pressure roller 37a, the transfer material P is discharged onto the discharge tray 41, and the full-color image formation is completed.

Thereafter, the residual toner remaining on the surface of the intermediate transfer member 4 is cleaned by an intermediate transfer member cleaning device 36 such as a felt pad which comes into contact with the intermediate transfer member 4, and is prepared for the next step.

Next, the intermediate transfer member 4 of the present embodiment will be described.

The intermediate transfer member 4 includes, for example, a base layer (base film) and a high release layer (surface layer) having a heat resistance of 5 μm thickness.
And an endless film composed of

The base layer is made of a heat-resistant resin such as polyester, PET (polyethylene terephthalate), PFA
(Tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyphenylene sulfide, polyamide imide, polyimide, polyether ether ketone, high heat resistant resin such as liquid crystal polymer, aluminum, nickel, etc. It is made of a metal sheet or a composite material of these with ceramics, metal, glass, and the like.

The high release layer is made of, for example, the same PE as the above-mentioned base layer.
A fluorine resin such as T, PFA, PTFE, a fluorine rubber, a silicone resin or a silicone rubber is used as a surface layer.

A more preferable structure of the intermediate transfer member 4 is that the base layer of these heat-resistant sheets has a low-resistance layer as a lower layer, and the metal sheet or a composite material having a low resistance is used. The use as a base layer is desirable for stabilizing the voltage application of the non-contact primary transfer described above.

The intermediate transfer member 4 preferably has at least an insulating layer having a thickness of preferably 100 μm or less, more preferably 40 μm or less. For example, as a base layer (base film) of the intermediate transfer member 4, a 25 μm-thick polyimide film A PFA layer having a thickness of 5 μm may be used as the high release layer on the surface.

The intermediate transfer member 4 configured as described above is
In particular, since the releasability is excellent, the transfer efficiency to the transfer material P in the secondary transfer is close to 100%. The intermediate transfer member 4 of the present embodiment used in the image forming apparatus includes a cleaning and oil supply felt pad impregnated with a release agent such as silicone oil as an intermediate transfer member cleaning device 36. It may be provided so as to contact the outer surface of the intermediate transfer member 4.

In the secondary transfer section 37, the heating roller 37a and the pressing roller 37b can be configured to have a heating means on both or one of them.
A heater having a halogen heater or a linear ceramic heater therein can be used.

As described above, also in the present embodiment, the same effects as those of the first embodiment can be obtained, so that the toner images 5 on the photosensitive drums 1Y, 1M, 1C, and 1BK are transferred to an endless film. Satisfactorily non-contact transfer to the intermediate transfer member 4 made of, and a high-quality full-color image can be obtained.

Further, in each of the above embodiments, an example was described in which an intermediate transfer member was used as a transfer member, but plain paper on which a toner image is directly transferred in a non-contact manner without using an intermediate transfer member as a transfer member. The present invention can be similarly applied to transfer materials such as OHP and OHP.

[0122]

As described above, according to the present invention, the toner image on the image carrier can be stably transferred to the transfer body through the opening without contact, so that toner scattering and image carrier It is possible to prevent paper powder and the like of the transfer material from adhering to the sheet, and to obtain a stable and good image.

[Brief description of the drawings]

FIG. 1 shows an image forming apparatus according to a first embodiment of the present invention.
FIG. 3 is a schematic configuration diagram illustrating a next transfer unit.

FIG. 2 is a schematic plan view of a slit electrode substrate of the image forming apparatus according to the first embodiment.

FIG. 3 is a diagram illustrating transfer of a toner image in a primary transfer unit of the image forming apparatus according to the first embodiment.

FIG. 4 is a view for explaining equipotential surfaces and lines of electric force in a primary transfer portion of the image forming apparatus according to the first embodiment.

FIG. 5 is a view for explaining equipotential surfaces and lines of electric force in a primary transfer portion of an image forming apparatus according to another example of the first embodiment.

FIG. 6 is a diagram for explaining equipotential surfaces and lines of electric force in a primary transfer unit of an image forming apparatus according to another example of the first embodiment.

FIG. 7 is a schematic configuration diagram showing an image forming apparatus according to Embodiments 2 and 3 of the present invention.

FIG. 8 is a schematic configuration diagram showing an image forming apparatus according to Embodiments 4 and 5 of the present invention.

FIG. 9 is a schematic configuration diagram showing an image forming apparatus according to Embodiment 6 of the present invention.

FIG. 10 is a schematic configuration diagram showing an image forming apparatus according to Embodiment 7 of the present invention.

[Explanation of symbols]

1, 1Y, 1M, 1C, 1BK Photosensitive drum (image carrier) 2, 2Y, 2M, 2C, 2BK Back electrode 3 Slit electrode substrate 3a, 3c First electrode (first electrode) 3b, 3d Second electrode ( Second electrode) 4 Intermediate transfer member (transfer member) 5, 6 Toner image 3e Opening 31, 31Y, 31M, 31C, 31BK Charger 32, 32Y, 32M, 32C, 32BK Exposure device 34 Developing device 34Y Yellow developing device 34M magenta developing device 34C cyan developing device 34BK black developing device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shuzo Kaneko 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H032 AA05 BA05 BA07 CA02

Claims (6)

[Claims] An image forming apparatus for transferring a charged toner image formed on a surface of an image carrier to a transfer body arranged in a non-contact manner with a predetermined gap provided between the image carrier and the toner image. An opening having a predetermined width formed in a width direction of an image area of the image carrier in a non-contact manner between the image carrier and the transfer body; On the side, a plurality of electrodes arranged so that the distance from the image carrier is different over the width direction of the image area of the image carrier,
A voltage having a polarity in a direction of holding the charged toner image on the surface of the image carrier is applied to a first electrode disposed on a side closest to the image carrier among the plurality of electrodes. A second electrode of the plurality of electrodes, which is arranged on a side farther from the image carrier than the first electrode, has a polarity voltage in a direction of separating the charged toner image from the surface of the image carrier. Applying an image. 2. A plurality of electrodes are provided on the upstream side and the downstream side of the opening in the moving direction of the image carrier so that the distance from the image carrier is different over the width direction of the image area of the image carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is arranged. 3. The image forming apparatus according to claim 1, wherein a distance between the opening and the first electrode is larger than a distance between the opening and the second electrode. 4. The image forming apparatus according to claim 1, wherein a distance between the opening and the first electrode is larger than a distance including an electrode width between the opening and the second electrode. 5. The image forming apparatus according to claim 1, wherein the opening is formed in a slit shape having a predetermined width over the entire width of an image area of the image carrier. 6. The transfer member is an intermediate transfer member that temporarily holds the charged toner image in a primary transfer portion and transfers the charged toner image to a transfer material in a secondary transfer portion. The image forming apparatus according to claim 1, wherein the opening and the plurality of electrodes are arranged in a primary transfer unit between the carrier and the carrier.