JP2000206800A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably transfer a toner image on an image carrier to a transfer body in a noncontact state in an image forming device transferring the toner image by the electrostatic flying of the toner image to the transfer body in the noncontact state. SOLUTION: This image forming device is provided with a slit electrode base plate 3, on which plural aperture parts 30 are formed in the width direction of the image area of a photoreceptor drum 1 between the photoreceptor drum 1 and an intermediate transfer body 4, a first electrode 3a is provided around and close to the part 30, and a second electrode 3b is provided on a side away from the electrode 3a with respect to the part 30, a voltage having a polarity in a direction where a toner image 5 is separated from the surface of the photoreceptor drum 1 is applied to the electrode 3a, a voltage having polarity in a direction where the image 5 is held on the surface of the drum 1 is applied on the electrode 3b, and the image 5 is transferred to the body 4 through the part 30, so that the image 5 on the surface of the drum 1 can be stably transferred to the body 4 in a noncontact state.

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 the formation of a color image, the color image once transferred to the transfer material is re-transferred to the image carrier at the time of the subsequent color image transfer, or the transfer failure or image disorder of the second and subsequent color images is performed. . (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, an object of the present invention is to provide an image forming apparatus capable of stably electrostatically flying and transferring a charged toner image on the surface of an image carrier to a transfer member arranged in a non-contact manner. I 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, a plurality of image forming apparatuses are formed at predetermined intervals 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 Openings formed in a plurality of rows along the width direction of the image region of the image carrier, and the image carrier in the vicinity of each of the openings and at least upstream of the opening in the moving direction of the image carrier. A first electrode provided along the width direction of the image area, and at least an upstream side of each of the openings in a direction in which the image carrier moves in a direction away from the first electrode with respect to the opening. A second electrode provided along the width direction of the image area of the carrier. Then, a voltage having a polarity in a direction in which the charged toner image is separated from the surface of the image carrier is applied to the first electrode, and the charged toner image is held on the surface of the image carrier by the second electrode. And applying a voltage to transfer the charged toner image to the transfer body through the opening.

In addition, a first electrode is provided close to each of the openings and upstream and downstream of the opening in the moving direction of the image bearing member, and is farther from each of the openings than the first electrode. Characterized in that the second electrode is provided around the side.

[0013] A power supply lead line connected to the first electrode for applying a voltage to the first electrode may be arranged downstream of the opening in the moving direction of the image carrier. .

Further, the openings are formed in a slit shape having a predetermined width, and the ends of the openings adjacent to each other in the rows overlap in the moving direction of the image carrier. I have.

Further, the transfer member is an intermediate transfer member which once carries the charged toner image in a primary transfer portion and transfers it to a transfer material in a secondary transfer portion. The opening and the first and second portions are provided in a primary transfer portion between
An electrode is provided.

[0016]

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

Embodiment 1 FIG. 1 is a schematic configuration diagram showing an image forming apparatus according to the present embodiment (a full-color image forming apparatus in the present embodiment).

The present image forming apparatus includes a photosensitive drum 1 as an image bearing member.
A charger 301, an exposure device (laser scanner unit) 302 that irradiates a laser beam E corresponding to an image signal of each color via a mirror 303, and four developing devices that respectively store yellow, magenta, cyan, and black toners A developing device 304, a photosensitive drum cleaning device 305, a drum-shaped intermediate transfer member 4, and the like are provided.

A slit electrode substrate 3 having a first electrode 3a and a second electrode 3b is disposed between the photosensitive drum 1 and the intermediate transfer member 4 (see FIG. 2). A certain primary transfer portion is configured (the detailed configuration and operation of the slit electrode substrate 3 will be described later).

Further, a pressure roller 307a and a heating roller 307b, which can make contact with and separate from each other, constituting the secondary transfer portion 307 are provided below the intermediate transfer member 4. An intermediate transfer member cleaning device 30 that can be brought into contact with and separated from the intermediate transfer member 4
6 and the like are arranged.

As shown in FIG. 2, the photosensitive drum 1 has a photoelectric layer 10 such as OPC or a-Si on the surface of a conductive cylindrical substrate 11 such as aluminum or SUS. (Not shown) at a predetermined process speed in the direction of the arrow (clockwise).

In the present embodiment, the charger 301 is a charging roller serving 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 302 forms an electrostatic latent image by performing image exposure with a laser beam E on a surface of the charged photosensitive drum 1 via a mirror 303 in accordance with an input image signal of each color.

The developing device 304 includes a yellow developing device 304Y and a magenta developing device 304 mounted on a rotating body 304a.
M, cyan developing device 304C, black developing device 304BK
The developing device of the color used for developing the electrostatic latent image on the photosensitive drum 1 is arranged at a developing position facing the surface of the photosensitive drum 1 by the rotation of the rotating body 304a. A negative toner is adhered to the image to develop (visualize) as a toner image.

As shown in FIG. 2, the intermediate transfer member 4 has a back electrode 2 formed of a conductive rubber roller so as to be located on the back side of 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, an image forming operation of the above-described image forming apparatus will be described.

At the time of image formation, the photosensitive drum 1 is rotationally driven 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 301 to which a predetermined charging bias is applied.

Then, image exposure is performed on the charged photosensitive drum 1 by a laser beam E pulse-modulated in accordance with an image signal by an exposure device 302, and a first color image of a target color image (for example, (Yellow image). The electrostatic latent image of this yellow image is
By the rotation of the developing device 304, the toner is developed with the toner by the yellow developing device 304Y fixed at the developing position in advance.

Then, the yellow toner image is applied to the first electrode 3a of the slit electrode substrate 3 on the film 4a on the surface of the intermediate transfer member 4 in the primary transfer portion between the photosensitive drum 1 and the intermediate transfer member 4. It is electrostatically transferred under the condition of applying a voltage to the second electrode 3b and the back electrode 2 (details will be described later).

Here, the intermediate transfer member 4 is a 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).

On the other hand, the surface of the photosensitive drum 1 is cleaned by the photosensitive drum cleaning device 305 and then uniformly charged again by the charger 301, and the image is formed by the laser beam E in accordance with the next magenta image signal. Receive exposure. The developing device 304 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 304M at a developing position to perform magenta development. In the primary transfer section, the magenta toner image is electrostatically transferred onto the film 4a on the surface of the intermediate transfer member 4 under the condition of applying voltage to the first electrode 3a, the second electrode 3b of the slit electrode 3, and the back electrode 2. You. 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 the four colors to the intermediate transfer member 4 is completed, or during the transfer of the final color black. , Paper cassette 10
A transfer material P such as a sheet stored in the sheet P is fed by a sheet feed roller 101 and conveyed to a secondary transfer unit 307 of the intermediate transfer body 4 via a sheet feed guide 104. here,
The four color toner images formed on the intermediate transfer member 4 are transferred to the transfer material in a secondary transfer portion 307 by heat generated by a heating roller 307b disposed in the intermediate transfer member 4 and pressure generated by a pressure roller 307a. After being strongly or lightly fixed on the sheet P at the same time as the transfer, the sheet is discharged onto the discharge tray 103, 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 306 such as a felt pad which comes into contact with the sheet 4a, and is prepared for the next step.

In the above-described image forming apparatus, if the fixing in the secondary transfer unit 307 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.

Further, in this embodiment, a system using a semiconductor laser has been described as the 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, and 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 having 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.

In the secondary transfer section 307, the heating roller 307a and the pressure roller 307b can be configured to have a heating means in both or one of them, and have a halogen heater or a linear heater therein. Those having the above ceramic heater can be used.

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

FIG. 2 is a sectional view of the slit electrode substrate 3, and FIG. 3 is an enlarged plan view of the slit electrode substrate 3.

In the primary transfer section, the slit electrode substrate 3 is arranged in a non-contact manner between the photosensitive drum 1 and the back electrode 2 provided in the intermediate transfer member 4.

The slit electrode substrate 3 is provided on the photosensitive drum 1
The slit width with respect to the moving direction (rotation direction) 31 of the (intermediate transfer body 4) is preferably 0.1 to 5 mm, and the slits are provided at predetermined intervals in the width direction of the image area of the photosensitive drum 1 (the left-right direction in FIG. 3). It has a plurality of openings 30 in a shape.

Around the opening 30, a narrow strip-shaped first electrode 3a is arranged close to the opening 30, and a planar second electrode 3b is arranged outside the first electrode 3a. I have.
That is, in the present embodiment, the first electrode 3a is
Has a longitudinal portion on both sides in the slit direction (the width direction of the image area of the photosensitive drum 1 on the upstream and downstream sides of the opening 30 in the moving direction of the photosensitive drum 1), and the second electrode 3b has an opening. It is provided around the portion 30 farther from the first electrode 3a.

A plurality of openings 30 provided at predetermined intervals in the width direction of the image area of the photosensitive drum 1 are provided in two rows (rows 30a, 30a) along the width direction of the image area of the photosensitive drum 1.
b), and the ends of the openings 30 adjacent to each other in the rows 30 a and 30 b are arranged so as to overlap with the moving direction 31 of the photosensitive drum 1.

In a longitudinal portion of the first electrode 3a located on the downstream side in the moving direction of the photosensitive drum 1, power is drawn out in a non-contact manner with the second electrode 3b along the moving direction 31 of the photosensitive drum 1 through the opening 30. Line 3c is connected. Feeding lead 3c
Supplies power to the first electrode 3a from a power supply (not shown) to apply a voltage.

The second electrode 3b is formed at an interval of about 10 to 200 μm with respect to the first electrode 3a and the electrode lead 3c of the first electrode 3a. In this embodiment, the distance L1 between the photosensitive drum 1 and the intermediate transfer member 4 is set to 5
The distance L2 between the photosensitive drum 1 and the first and second electrodes 3a, 3b of the slit electrode substrate 3 is set to 200 μm.

Next, conditions and effects for transferring (primary transfer) the toner image formed on the surface of the photosensitive drum 1 to the transfer material P by the first and second electrodes 3a and 3b of the slit electrode substrate 3 will be described. This will be described with reference to FIG.

In FIG. 4, as the voltage Vl applied between the photosensitive drum 1 and the back electrode 2, a DC voltage (for example, 2 KV) that causes the back electrode 2 to be a positive (+) pole is applied.

Further, the first electrode 3a and the photosensitive drum 1 provided close to the slit opening 30 of the slit electrode substrate 3
And a pulse voltage (for example, 300 V) such that the first electrode 3a has a positive (+) polarity, and a negatively charged toner (toner image) on the surface of the photosensitive drum 1 is applied. 5) is separated from the photosensitive drum 1 surface. The voltage V3 applied between the photosensitive drum 1 and the second electrode 3b located outside each of the first electrodes 3a with respect to the slit opening 30 is such that the second electrode 3b has a negative (-) polarity. Such a DC or a pulse voltage (for example, -300 V) synchronized with the above pulse voltage 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. .

When the voltages V1, V2, and V3 are applied, an equipotential surface shown by a curve is formed near the slit opening 30 as shown in FIG. , Electric lines of force in the direction opposite to the direction indicated by the arrow are formed.

As a result, in the developing step, the photosensitive drum 1
The negative toner image 5 of each color formed on the surface (FIG. 2)
4), as shown in FIG. 4, the toner image 5 is stably held on the photosensitive drum 1 in a portion other than the portion opposed to the slit opening 30, and in a position opposed to the slit opening 30. Then, the toner image 5 on the photosensitive drum 1 flies electrostatically onto the intermediate transfer member 4 and the toner image 6 is transferred without contact.

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.
(A) is the strongest at the position where the equipotential surface is closest to the surface of the photosensitive drum 1 (the center of the slit opening 30), and goes straight only from a narrowed area near the closest position of the equipotential surface. Then, the toner image 5 on the surface of the photosensitive drum 1 can be separated and moved on the intermediate transfer member 4 in the arrow direction.

As described above, in the present embodiment, the second electrode 3
b, the toner image 5 is stably held on the surface of the photosensitive drum 1, and from the limited area of the slit opening 30 to the middle due to the aperture effect of the lines of electric force formed by the first electrode 3 a and the second electrode 3 b. Since the transfer of the toner image 5 to the transfer body 4 in a straight line can be performed without contact, the toner image 5 is favorably transferred from the photosensitive drum 1 to the intermediate transfer body 4 without contact in the primary transfer unit. be able to.

Hereinafter, a preferred embodiment of the above-described slit electrode substrate 3 constituting the primary transfer section will be described.

The distance L between the photosensitive drum 1 and the intermediate transfer member 4
1 is preferably 200 μm to 1 mm, and it is advantageous that the distance L1 is shorter because the voltage Vl can be reduced. The distance L2 between the photoconductor drum 1 and the first and second electrodes 3a and 3b 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 arrangement of the slit electrode substrate 3 in a range smaller than 1/2 of the range of 50 μm to 50 μm is preferable for reducing the respective voltages applied to the first electrode 3a or the second electrode 3b.
The range of 500 μm, particularly 10
0 μm to 250 μm.

When the voltage to be applied to the first electrode 3a is determined, the larger the value of L2 is, the larger the curvature of the equipotential surface shown in FIG. 5A is, so that the toner is separated from the photosensitive drum 1. Although the area can be narrowed down as such, it is more practical to set the applied voltage V1 to about 1/2 of L2 as described above in order to reduce the applied voltage V1.

The range condition selected as the applied voltage V2 is set such that V2 / L2 <V1 / L1 in order to improve the convergence of the lines of electric force. The optimum values of the voltages Vl and V2 depend on the photosensitive drum 1 to be used.
And Ll, L2, etc., but a common sense voltage value range is 10
0V-4KV, V2 is about 50V-2KV,
It is preferably selected in accordance with the convergence range condition of the line of electric force.

Further, as shown in FIGS. 5B and 6, the configuration is such that there is no first electrode downstream of the slit opening 30 in the moving direction 31 of the photosensitive drum 1 (intermediate transfer member 4). However, the above-described bending of the equipotential surface is formed. As a result, the effect of narrowing the transfer region by the convergence of the lines of electric force can be obtained, so that the non-contact transfer can also be favorably achieved. Also,
The slit electrode substrate 3 shown in FIGS. 5B and 6 has a configuration in which the first electrodes 3a adjacent to each other in the columns 30a and 30b are connected to each other by a wiring portion 3d. Other configurations are the same as those of the slit electrode substrate 3 in FIG.

Although the back electrode 2 and a part of the intermediate transfer member 4 shown in FIGS. 2 to 5 are formed in a plane, they are actually curved.

In the slit electrode substrate 3 shown in FIGS. 5B and 6, the first electrode and the first electrode are located downstream of the slit opening 30 in the moving direction 31 of the photosensitive drum 1 (intermediate transfer member 4). Even if the configuration is such that two electrodes are not provided, the above-described bending of the equipotential surface is formed. As a result, the effect of narrowing the transfer region by the convergence of the lines of electric force can be obtained, so that the non-contact transfer can also be favorably achieved.

The method for forming the slit electrode substrate 3 is as follows.
For example, an electrode pattern (the first electrode 3a and the second electrode 3b) is formed on the copper foil by a known photolithography method on a substrate such as a polyimide or glass epoxy resin having a thickness of 100 μm provided with a copper foil laminated with a thickness of 5 μm. ) Is formed, and a 40 μm polyimide film or the like is further laminated, and then a slit-shaped opening 30 is formed by press punching or punching irradiation of an ultraviolet laser or a carbon dioxide gas laser to obtain a slit electrode substrate 3. be able to. Further, as the electrode formation, those formed as an electrode substrate by another method (for example, electroforming) can be used.

Further, in the present invention, a plurality of slit-shaped openings 30 are formed in the width direction of the image forming area (the longitudinal direction of the photosensitive drum 1) because the slits are thin (for example, 100 μm) as described above. Even when an electrode substrate is used, the shape is maintained as a continuous substrate,
This is because each slit width of the plurality of openings 30 is favorably held, and the slits are accurately arranged even in a narrow gap between the photosensitive drum 1 and the intermediate transfer body 4.

In other words, in contrast to the case where one continuous slit-shaped opening is formed across the width of the image forming area of the photosensitive drum 1, this is formed in a plurality of rows (in FIGS. 3 and 6,
Rows 30a, 30b), rows 30a, 30b
The two ends of each of the openings 30 in the width direction of the image forming area are formed so as to overlap with the moving direction 31 of the photosensitive drum 1 (or the intermediate transfer body 4), and the toner on the surface of the photosensitive drum 1 is formed. By moving the image and the intermediate transfer member 4 at a constant speed,
Transfer of the toner image over the entire width of the image forming area is not hindered.

Further, since it can be held as one slit electrode substrate 3, the above-mentioned electric convergence effect of the slit width of the slit opening 30 and the electrodes (the first electrode 3a and the second electrode 3b) corresponding to the slit opening 30 is obtained. You can maintain a subtle interval to get.

In the case where the slit electrode substrate 3 is arranged in the above-mentioned primary transfer section, each of the rows 3
Although the distance between the photosensitive drum 1 and the back electrode 2 at the positions of 0a and 30b should not be greatly different, according to the above-described slit forming method, the distance between the rows 30a and 30b and the respective slits of the opening 30 are different. The dimensions including the width can be formed to be 1 mm or less or about several mm. Therefore, as long as the photoconductor drum 1 or the back electrode 2 in the primary transfer section does not have an extreme curvature, each row 30a, 30b. Can be sufficiently equalized.

In the present embodiment, as described above, the electrode lead 3c is arranged on the downstream side in the moving direction 31 of the photosensitive drum 1 (or the intermediate transfer member 4). Therefore, it is not necessary to consider the disturbance of the toner image due to the electrode lead line 3c. Further, the second electrode 3b is arranged also close to the periphery of the electrode lead wire 3c, and the distance between the second electrode 3b and the second electrode 3b is reduced. The electric field separated from the drum 1 is blocked. Similarly, in the slit electrode substrate 3 shown in FIG. 6, the wiring portion 3d of the first electrode 3a on the upstream side of the row 30b with respect to the moving direction 31 of the photosensitive drum 1 (or the intermediate transfer member 4) also has By making the interval between the portion and the second electrode 3b smaller,
In effect, there is no unnecessary separation of the toner image.

As the toner used in the developing device 304, 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 size can be reduced, so that the contamination and clogging of the opening 30 can be minimized.

<Embodiment 2> FIG. 7 is a schematic configuration diagram showing an image forming apparatus according to the present embodiment (a full-color image forming apparatus in the present embodiment).

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,
In the vicinity of 1BK, chargers 301Y and 301 are respectively provided.
M, 301C, 301BK, and exposure devices 302Y, 302M, 302 for irradiating image exposure corresponding to image signals of respective colors.
C, 302BK, and each developing device 301 for storing yellow, magenta, cyan, and black toners respectively.
Y, 301M, 301C, 301BK, 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 portion is formed between the intermediate transfer member 4 and the intermediate transfer member 4, and a slit electrode substrate 3 is disposed between the primary transfer portions and the back side of the slit electrode substrate 3 facing the intermediate transfer member 4 therebetween. Are provided with back electrodes 2Y, 2M, 2C and 2BK. The gap between the surface of each photoconductor drum 1Y, 1M, 1C, 1BK and the back electrode 2Y, 2M, 2C, 2BK is 450
μm, and each slit electrode substrate 3 is arranged in a non-contact and close proximity to the surface of each photoconductor drum 1Y, 1M, 1C, 1BK at a distance of about 150 μm. The configuration of the slit electrode substrate 3, the conditions of the applied voltage, and the like are the same as those in the first embodiment, and a description thereof will be omitted in the present embodiment.

On the lower side of the intermediate transfer member 4, the secondary transfer portion 3
07, a pressure roller 307a and a heating roller 307b which can be separated from each other and a heating roller 307b are provided, and an intermediate transfer member cleaning device 306 and the like which can be separated from each other are disposed outside the intermediate transfer member 4.

The structure and operation of each member other than the intermediate transfer member 4 are the same as those in the first embodiment, and a description thereof will be omitted in the present embodiment (the structure of the intermediate transfer member 4 in the present embodiment). Will be described later).

Next, the 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 in the direction of the arrow (clockwise) at a predetermined process speed by a driving means (not shown), and is uniformly driven by a charger 301Y 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 302Y, and an electrostatic latent image corresponding to a target yellow image is formed. Is done. The electrostatic latent image of the yellow image is developed by the toner of the yellow developing device 304Y which is previously set at the developing position by the rotation of the developing device 304Y.

Then, the yellow toner image is formed 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. It is electrostatically transferred under the condition of applying a voltage to the back electrode 2.

Here, the intermediate transfer member 4 is a 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
The surface is cleaned and uniformly charged by Y, and receives image exposure by a laser beam in accordance with the next yellow image signal.

Further, by synchronizing the image formation with the yellow image, 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 developing unit 304M develops the magenta image. 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 on the photosensitive drums 1C and 1BK of cyan and black, respectively, and the transfer of the four colors to the intermediate transfer member 4 is completed or finished. During the transfer of the black color, a transfer material P such as a sheet stored in the sheet cassette 100 is fed by the sheet feed roller 101,
The sheet is conveyed to the secondary transfer section 307 of the intermediate transfer body 4 via the sheet feed guide 104.

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 on the transfer material P at the same time as the transfer on the transfer material P by the heat from the pressure roller 07b and the pressure from the pressure roller 307a, the paper is discharged onto the discharge tray 103, 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 306 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 a thickness of at least 100 μm or less, more preferably 40 μm or less as an insulating layer. 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 306. It may be provided so as to contact the outer surface of the intermediate transfer member 4. In the secondary transfer section 307, the heating roller 307a and the pressure roller 307b can be configured to have heating means on both or one of them, and a halogen heater or a linear ceramic heater is provided inside. Can be used.

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

[0091]

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 is a schematic configuration diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic sectional view of a primary transfer unit of the image forming apparatus according to the first embodiment.

FIG. 3 is a schematic plan view of a slit electrode substrate of the image forming apparatus according to the first embodiment.

FIG. 4 is a diagram illustrating transfer of a toner image at a primary transfer unit of the image forming apparatus according to the first embodiment.

FIG. 5A is a diagram illustrating an equipotential surface of lines of electric force in a primary transfer unit of the image forming apparatus according to the first embodiment;
FIG. 4B is a diagram illustrating an equipotential surface of lines of electric force in a primary transfer unit of the image forming apparatus according to another example of the first embodiment.

FIG. 6 is a schematic plan view of a slit electrode substrate according to another example of the first embodiment.

FIG. 7 is a schematic configuration diagram illustrating an image forming apparatus according to a second embodiment of the present invention.

[Explanation of symbols]

1, 1Y, 1M, 1C, 1BK Image carrier (photosensitive drum) 2, 2Y, 2M, 2C, 2BK Back electrode 3 Slit electrode substrate 3a First electrode 3b Second electrode 3c Lead wire 4 Intermediate transfer member (transfer Body) 5, 6 Toner image 30 Opening 301, 301Y, 301M, 301C, 301BK
Charger 302, 302Y, 302M, 302C, 302BK
Exposure device 304 Developing device 304Y Yellow developing device 304M Magenta developing device 304C Cyan developing device 304BK Black developing device

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masaaki Yamaji 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H032 AA15 BA01 BA07 BA23 BA27 CA12

Claims (5)

[Claims] 1. An image forming apparatus for transferring a charged toner image formed on a surface of an image carrier to a transfer body disposed in a non-contact manner with a predetermined gap provided between the image carrier and the toner image. A plurality of lines are formed at predetermined intervals over the width direction of the image area of the image carrier in a non-contact manner between the image carrier and the transfer body, and a plurality of rows are formed along the width direction of the image area of the image carrier. And a first electrode provided in the width direction of the image area of the image carrier at least upstream of the opening in the moving direction of the image carrier in proximity to each of the openings. A second provided at least upstream of each of the openings in the moving direction of the image carrier and farther than the first electrode with respect to the openings along a width direction of an image area of the image carrier. An electrode, wherein the charged toner image is the image on the first electrode. A voltage having a polarity in a direction in which the charged toner image is held away from the surface of the image carrier is applied to the second electrode, and the charged toner image is passed through the opening. An image forming apparatus, wherein the image is transferred onto the transfer body. 2. A first electrode is provided close to each of the openings and upstream and downstream of the openings in the moving direction of the image carrier, and is farther from each of the openings than the first electrode. The image forming apparatus according to claim 1, wherein the second electrode is provided around a side. 3. A power supply lead line connected to the first electrode for applying a voltage to the first electrode is disposed downstream of the opening in the moving direction of the image carrier. 3. The image forming apparatus according to 2. 4. The image forming apparatus according to claim 1, wherein the openings are formed in a slit shape having a predetermined width, and ends of the openings adjacent to each other in the row overlap in the moving direction of the image carrier. 4. The image forming apparatus according to 2, 3 or 4. 5. 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. 5. The image forming apparatus according to claim 1, wherein the opening and the first and second electrodes are provided in a primary transfer portion between the carrier and the carrier.