JP2002169384A - Electrophotographic device, electrifying means provided therein and image recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate filming and image flowing and to restore toner to a developing device so as to recycle and use it by preventing a paper adhesive matter such as paper powder and a paper additive from adhering to an image carrier such as a photoreceptor and an intermediate transfer body in an electrophotographic device. SOLUTION: In the electrophotographic device where a toner image formed on the photoreceptor 40 is transferred by a transfer device 62 so that the image is recorded on paper 90, a resist roller 49 functions also as the electrifying means A when applying bias to the roller 49 and is provided at the upstream position of the device 62 in a paper carrying direction (a). At the time of transferring the image by the device 62, the paper adhesive matters 102, 103 and 104 are electrified to a polarity for attracting the matters 102, 103 and 104 to the paper 90 side by the means A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoreceptor, such as a copying machine, a printer, a facsimile, or a multifunction machine thereof, using a two-component or one-component developer and repeating charging, writing, development, transfer, and cleaning. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus in which a toner image is sequentially formed thereon, and the toner image is transferred directly or indirectly via an intermediate transfer member to record a color, two-color, or monochrome image on paper. In addition, the present invention relates to a charging unit that charges paper-attached matter attached to a sheet in such an electrophotographic apparatus. The invention also relates to an image recording method for recording an image on a sheet in such an electrophotographic apparatus.

[0002]

Conventionally, in an electrophotographic apparatus, in order to increase the whiteness, also to adjust the acidity of the paper, images on the sheet for recording, calcium carbonate and talc _{(Mg 3 (Si 4 0 10} ) (O
H) ₂ ), paper additives such as kaolin (Al ₂ O ₃ .2Si O ₂ .2H ₂ O) are added. Further, paper dust adheres to the paper.

Such paper deposits such as paper powder and paper additives are originally hardly charged to the positive electrode in consideration of the charging sequence, and almost all are charged to the negative electrode. However, the charge polarity depends on the contact person and the surrounding environment,
Not all paper deposits on paper are negatively charged.

When a toner image on an image carrier such as a photoreceptor or an intermediate transfer member is brought into contact with a sheet for transfer to the sheet, as shown in FIG. The paper 3 is transferred to the paper 2 by receiving an attractive force. On the other hand, among the paper adhering substances on the paper 2, those 3 which are charged to the positive electrode are transferred to the image carrier 4 so as to be replaced with toner. And it will move.

[0005] The paper deposit 5 charged on the negative electrode is:
The paper adhering material 6 which remains on the paper 2 as it is but has a weak charge amount and is almost neutral physically adheres to the image carrier 4. The paper additive is an indispensable substance for maintaining the properties of the paper, but if it adheres to the image carrier 4, it causes filming and image flow.

In FIG. 18, reference numeral 7 denotes a corona charger which is an example of a transfer device, which transfers a toner image on the image carrier 4 by applying a positive bias to the image carrier 4. The image is recorded on the sheet 2.

In view of the above, various methods for removing paper adhering substances adhering to an image carrier have been proposed in conventional electrophotographic apparatuses.

For example, Japanese Patent Application Laid-Open No. 8-248708 discloses an invention in which a filter effect by a mesh is expected for recycled toner collected by cleaning. However, there has been a problem that clogging due to paper powder and foreign matter is likely to occur and the collection effect is not exhibited.

Japanese Patent Application Laid-Open No. 2000-7175 discloses an invention for removing paper dust and the like from a sheet before entering a transfer section. However, in order to remove the paper adhering matter once adhered to the image carrier, a mechanism added to the machine becomes complicated, and it is difficult to completely remove the paper adhering matter.

On the other hand, in recent years, from the viewpoints of environmental problems and resource saving, it has been recommended that the untransferred toner remaining on the photoreceptor without being transferred onto the sheet or the intermediate transfer member be returned to the developing device and recycled.

However, in a color machine, for example, in a so-called revolver development-transfer system in which a plurality of developing machines are provided for one photoconductor, several colors of toner are developed by one photoconductor. In the cleaning section, toner of each color is mixed (mixed colors), and it is difficult to return the toner to the developing device and reuse it.

A so-called tandem, in which a plurality of photoconductors are used, each photoconductor performs one-color development, and a sheet is continuously contacted with a plurality of photoconductors to superimpose a plurality of color images on the paper. In the transfer method, remarkable color mixing does not occur as in the revolver development-transfer method described above. However, when the toner image is superimposed on the paper from the photoconductor, reverse transfer occurs in which the toner already existing on the paper returns to the photoconductor, so that some color mixing occurs.

Further, as shown in FIG. 17, when a contact type transfer roller 8 is used as a transfer device and a positive bias is applied to the transfer roller at the time of image transfer, of the paper adhering material adhering to the back surface of the paper 2 The material 5 charged to the negative electrode is attracted to the transfer roller 8, and the paper attachment 6 having a weak charge amount and near neutrality partially physically adheres to the transfer roller 8.

Thereafter, when the paper 2 passes and the transfer roller 8 comes into direct contact with the image carrier 4, the paper deposits 5 and 6 adhered to the transfer roller 8 adhere to the image carrier 4. Becomes For this reason, when toner is recycled,
The paper deposits 5 and 6 contained therein cause a problem such that toner is missing from the image and it is difficult to return the waste toner to the developing device. Note that, as in FIG. 18, reference numeral 1 in FIG.
Is a toner charged to the negative electrode, and 3 is a paper deposit charged to the positive electrode.

In order to solve such a problem, various types of so-called tandem type intermediate transfer systems using a plurality of photosensitive members and using an intermediate transfer member have been proposed. In this method, the transfer to the paper is performed from the intermediate transfer body, so the chance of the paper adhered to the photoreceptor is greatly reduced,
The possibility of reusing the transfer residual toner on the photoreceptor can be greatly increased.

However, the risk of filming on the intermediate transfer member still remains, and the cleaning of the intermediate transfer member cannot be completed completely, so that the possibility of mixing of paper dust or the like has not completely disappeared.

[0017]

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide an electrophotographic apparatus in which paper deposits such as paper dust and paper additives are transferred to an image carrier such as a photoreceptor or an intermediate transfer member. The object of the present invention is to prevent the toner itself from adhering to the toner, to eliminate filming and image flow, and to allow the toner to be returned to the developing device for recycling.

A second object of the present invention is to provide an electrophotographic apparatus in which, in addition to the above, it is possible to prevent paper deposits on both sides of a sheet from adhering to an image carrier, thereby further eliminating filming and image flow. Another object of the present invention is to make it possible to recycle toner.

A third object of the present invention is to provide an electrophotographic apparatus in which an extra stress is not applied to a sheet and the generation of paper dust and the like is prevented.

A fourth object of the present invention is to reduce costs by effectively utilizing existing parts in an electrophotographic apparatus.

A fifth object of the present invention is to provide an electrophotographic apparatus, in addition, to prevent deterioration due to pulverization of toner to prevent deterioration of image quality.

A sixth object of the present invention is to provide an electrophotographic apparatus in which the surface shape of the toner is smoothed to improve the transfer efficiency of the toner, the amount of recycled toner is reduced, the deterioration of image quality is prevented, and the image quality is reduced. To prevent a decrease in

A seventh object of the present invention is to provide an electrophotographic apparatus in which a change in toner component ratio at the time of toner recycling is eliminated to prevent deterioration in image quality and prevent deterioration in image quality.

An eighth object of the present invention is to provide an electrophotographic apparatus, in which an intermediate transfer member is brought into close contact with a photoreceptor to improve the transfer rate of toner, and also to prevent a decrease in image quality.

A ninth object of the present invention is to provide an electrophotographic apparatus for preventing paper deposits such as paper dust and paper additives from adhering to an image carrier such as a photoreceptor or an intermediate transfer body. Another object of the present invention is to provide a charging unit that eliminates filming and image flow and returns toner to a developing device to enable recycling.

[0026] A tenth object of the present invention is to provide an electrophotographic apparatus for preventing paper deposits such as paper dust and paper additives from adhering to an image carrier such as a photoreceptor or an intermediate transfer body. It is another object of the present invention to provide an image recording method that eliminates filming and image deletion, and also enables the toner to be returned to a developing device for recycling.

[0027]

According to a first aspect of the present invention, a toner image formed on an image carrier is transferred by a transfer device to form an image on paper in order to achieve the first object. In the electrophotographic apparatus for recording, a charging unit is provided at a position upstream of the transfer device in the paper transport direction, the charging unit being charged to a polarity that attracts paper adhering matter to the paper side during image transfer by the transfer device. I do.

According to a second aspect of the present invention, in order to achieve the above-mentioned second object, in the electrophotographic apparatus according to the first aspect, the paper adhering material on both sides of the paper is charged by the charging means. , Characterized in that.

According to a third aspect of the present invention, in order to achieve the third object, in the electrophotographic apparatus according to the first or second aspect, the paper adhering material is charged by the charging means in a non-contact manner with the paper. It is characterized by that.

According to a fourth aspect of the present invention, there is provided an electrophotographic apparatus according to the first or second aspect, wherein the charging means is configured to apply a bias to the registration roller. Characterized in that they are also formed by

According to a fifth aspect of the present invention, in order to achieve the fifth object, the electrophotographic apparatus according to any one of the first to fourth aspects uses a toner containing a low softening point substance. It is characterized by that.

According to a sixth aspect of the present invention, in order to achieve the sixth object, the electrophotographic apparatus according to any one of the first to fifth aspects uses a toner having a circularity of 90 or more. It is characterized by that.

According to a seventh aspect of the present invention, there is provided an electrophotographic apparatus according to any one of the first to sixth aspects, wherein (the toner charge amount) / (toner particle size). ) Has a half width of 2.2 [fC / 1
0 μm] or less.

According to an eighth aspect of the present invention, there is provided an electrophotographic apparatus according to any one of the first to seventh aspects, wherein the image carrier has a toner transferred from a photoreceptor. An intermediate transfer member for transferring an image to paper, wherein the intermediate transfer member is provided with an elastic layer.

According to a ninth aspect of the present invention, in order to achieve the above-mentioned ninth object, a charging device provided in an electrophotographic apparatus for recording an image on paper by transferring a toner image formed on an image carrier by a transfer device. Means, provided at a position upstream of the transfer device in the paper transport direction so as to be charged to a polarity that attracts paper adhering matter to the paper side during image transfer by the transfer device.

The tenth aspect of the present invention is the above-described tenth aspect.
In order to achieve the above object, in an image recording method of an electrophotographic apparatus, a charging unit located at an upstream position in a sheet conveying direction is used.
At the time of image transfer, the paper adhering material is charged to a polarity that attracts the paper to the paper side, and then the toner image formed on the image carrier is transferred to a transfer device at a downstream position in the paper transport direction to record the image on the paper. It is characterized by that.

[0037]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention and is an overall schematic configuration diagram of a tandem-type indirect transfer type color copying machine.

In the figure, reference numeral 100 denotes a copying machine main body, 200 denotes a paper feeding table on which the copying machine is mounted, 300 denotes a scanner mounted on the copying machine main body 100, and 400 denotes an automatic document feeder (ADF) further mounted thereon.

An endless belt-shaped intermediate transfer body 10 is provided at the center of the copying machine main body 100. In the intermediate transfer member 10, as shown in FIG. 2, the base layer 11 is made of a non-stretchable material such as fluororesin or canvas, and the elastic layer 1 is formed thereon.
2 is provided. The elastic layer 12 is made of, for example, fluorine rubber or acrylonitrile-butadiene copolymer rubber. The surface of the elastic layer 12 is coated with, for example, a fluorine-based resin and covered with a coat layer 13 having good smoothness.

Then, as shown in FIG.
The support rollers 14, 15, and 16 are wrapped around the support rollers 14, 15, and 16 so as to be rotatable clockwise in the drawing.

In the illustrated example, a belt cleaning device 17 for removing residual toner remaining on the intermediate transfer body 10 after image transfer is provided to the left of the second support roller 15 of the three.
Is provided.

The first support roller 14 of the three
Transfer member 10 stretched between the first support roller 15 and the second support roller 15
A tandem image forming apparatus 20 is formed by arranging four image forming units 18 of black, cyan, magenta, and yellow along the transport direction.

As shown in FIG. 1, an exposure device 21 is further provided on the tandem image forming device 20.

On the other hand, a secondary transfer device 22 is provided on the side opposite to the tandem image forming device 20 with the intermediate transfer member 10 interposed therebetween. In the illustrated example, the secondary transfer device 22 is configured by extending a secondary transfer belt 24, which is an endless belt, between two rollers 23, and presses the secondary transfer belt 24 against the third support roller 16 via the intermediate transfer body 10. The image on the intermediate transfer body 10 is transferred to a sheet.

A fixing device 25 for fixing a transferred image on a sheet is provided beside the secondary transfer device 22. Fixing device 25
Is a pressure roller 27 attached to a fixing belt 26 which is an endless belt.
Press to configure.

The above-described secondary transfer device 22 also has a paper transport function for transporting the paper after image transfer to the fixing device 25. Of course, a non-contact charger may be arranged as the secondary transfer device 22, and in such a case, it is difficult to additionally provide the sheet conveying function.

In the illustrated example, under the secondary transfer device 22 and the fixing device 25, a sheet for reversing the sheet so as to record an image on both sides of the sheet in parallel with the tandem image forming apparatus 20 described above. An inversion device 28 is provided.

When making a copy using this color copying machine, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened and the contact glass 32 of the scanner 300 is opened.
The original is set on the upper part, and the automatic document feeder 400 is closed and pressed.

When a start switch (not shown) is pressed, when the original is set on the automatic document feeder 400, the original is conveyed and moved onto the contact glass 32, and then the original is placed on the contact glass 32. When set, the scanner 300 is immediately driven to travel on the first traveling body 33 and the second traveling body 34. And the first traveling body 3
3 emits light from the light source and further reflects the reflected light from the document surface to the second traveling body 34, where the second traveling body 3
The light is reflected by the mirror No. 4 and enters the reading sensor 36 through the imaging lens 35 to read the contents of the document.

When a start switch (not shown) is pressed, the support rollers 14, 15, 16 are driven by a drive motor (not shown).
Is rotationally driven to rotate the other two support rollers, and the intermediate transfer member 10 is rotationally conveyed. At the same time, the photoreceptor 40 is rotated by the individual image
A single color image of black, yellow, magenta, and cyan is formed on 0, respectively. Then, as the intermediate transfer body 10 is transported, the single-color images are sequentially transferred to form a composite color image on the intermediate transfer body 10.

On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated to feed out paper from one of the paper feed cassettes 44 provided in the paper bank 43 in multiple stages. 1 with separation roller 45
The sheets are separated and fed into a paper feed path 46, conveyed by a conveyance roller 47, guided to a paper feed path 48 in the copying machine main body 100, and stopped against a registration roller 49.

Alternatively, the paper feed roller 50 is rotated to feed out the paper on the manual feed tray 51, separated one by one by the separation roller 52, put into the manual paper feed path 53, and similarly hit against the registration roller 49 and stopped.

Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer member 10, and the sheet is fed between the intermediate transfer member 10 and the secondary transfer device 22, and Transfer and record a color image on paper.

The paper after image transfer is conveyed by the secondary transfer device 22 and sent to the fixing device 25, where the transfer image is fixed by applying heat and pressure by the fixing device 25, and then switched by the switching claw 55. The sheet is discharged by a discharge roller 56 and stacked on a sheet discharge tray 57. Alternatively, the sheet is switched by the switching claw 55 to enter the sheet reversing device 28, where it is reversed and guided again to the transfer position, the image is also recorded on the back surface, and then discharged onto the discharge tray 57 by the discharge roller 56.

On the other hand, the intermediate transfer member 10 after the image transfer is removed by a belt cleaning device 17 to remove the residual toner remaining on the intermediate transfer member 10 after the image transfer, and is prepared for the image formation by the tandem image forming device 20 again. .

Here, a bias is applied to the registration roller 49 using a conductive rubber roller. With diameter φ18,
The surface is made of conductive NBR rubber having a thickness of 1 mm. The electric resistance is about 10E9 Ωcm as the volume resistance of the rubber material, and the applied voltage is about −850 V on the side (front side) where the toner is transferred.

Although a voltage of about +200 V is applied to the back side of the paper, it may be grounded especially when it is not necessary to consider paper powder transfer on the back side. A DC bias is applied as an applied voltage.
An AC voltage having an offset component may be used.

The AC superimposed DC bias can charge the paper surface more uniformly. The paper surface after passing through the registration roller 49 is slightly negatively charged. Therefore, in the transfer from the intermediate transfer body 10 to the sheet, it is necessary to pay attention that the transfer condition may be changed as compared with the case where no voltage is applied to the registration roller 49.

The tandem image forming apparatus 20 described above
In detail, each of the image forming units 18 includes, for example, a charging device 60, a developing device 61, a primary transfer device 62,
A cleaning device 63, a static elimination device 64, and the like are provided. In the illustrated example, the photoreceptor 40 has a drum shape in which a photosensitive layer is formed by applying a photosensitive organic photosensitive material to a base tube made of aluminum or the like, but may have an endless belt shape.

Although not shown, at least the photosensitive member 40 is provided, and a process cartridge is formed by all or a part of the portion forming the image forming means 18.
May be made detachable collectively to improve maintainability.

Of the parts constituting the image forming means 18,
The charging device 60 is formed in a roller shape in the illustrated example, and contacts the photoreceptor 40 to apply a voltage to the photoreceptor 4.
0 is charged.

The developing device 61 may use a one-component developer, but in the illustrated example, a two-component developer composed of a magnetic carrier and a non-magnetic toner is used. Then, the agitating section 66 which transports the two-component developer while agitating it and adheres to the developing sleeve 65, and the developing section 67 which transfers the toner of the two-component developer adhered to the developing sleeve 65 to the photoconductor 40. And the agitating section 66 is positioned lower than the developing section 67.

The stirring unit 66 has two parallel screws 6.
8 is provided. The two screws 68 are partitioned by a partition plate 69 except for both ends (see FIG. 6). Further, a toner concentration sensor 71 is attached to the developing case 70.

On the other hand, a developing sleeve 65 is provided in the developing section 67 so as to face the photoconductor 40 through an opening of the developing case 70, and a magnet 72 is fixedly provided in the developing sleeve 65. In addition, a doctor blade 73 is provided with the tip approaching the developing sleeve 65. In the illustrated example, the interval at the closest part between the doctor blade 73 and the developing sleeve 65 is set to 500 μm.

Then, the two-component developer is supplied to two screws 6
The toner is conveyed and circulated while being stirred at 8, and supplied to the developing sleeve 65. The developer supplied to the developing sleeve 65 is pumped up and held by the magnet 72 to form a magnetic brush on the developing sleeve 65. The magnetic brush is cut into an appropriate amount by the doctor blade 73 as the developing sleeve 65 rotates. The cut-off developer is supplied to the stirring unit 6.
Returned to 6.

On the other hand, the toner in the developer on the developing sleeve 65 is transferred to the photosensitive member 40 by the developing bias voltage applied to the developing sleeve 65, and the electrostatic latent image on the photosensitive member 40 is visualized. . After the visualization, the developer remaining on the developing sleeve 65 separates from the developing sleeve 65 and returns to the agitating section 66 where there is no magnetic force of the magnet 72. As a result of this repetition, when the toner concentration in the stirring section 66 becomes low, the toner density is detected by the toner concentration sensor 71 and the stirring section 66 is detected.
Replenish the toner.

In the illustrated example, the linear velocity of the photosensitive member 40 is 200 mm / s, and the linear velocity of the developing sleeve 65 is 240 mm / s. The development process is performed with the diameter of the photoconductor 40 being 50 mm and the diameter of the developing sleeve 65 being 18 mm. The toner charge amount on the developing sleeve 65 is -10 to -30 μm.
It is in the range of C / g. The developing gap _GP, which is the gap between the photoconductor 40 and the developing sleeve 65, can be set in the range of 0.8 mm to 0.4 mm in the related art, and it is possible to improve the developing efficiency by reducing the value.

The thickness of the photosensitive member 40 is set to 30 μm, and the optical system
Beam spot diameter of 50 × 60 μm and light amount of 0.47
mW. Further, the charging (before exposure) of the photoconductor 40 is performed.
Rank V ₀Is -700 V, the post-exposure potential V_LIs -120V
To a developing bias voltage of -470 V, that is, a developing potential.
The developing process is performed at 350 V.

Next, the primary transfer device 62 is in the form of a roller, and is provided by pressing against the photosensitive member 40 with the intermediate transfer member 10 interposed therebetween. Separately, the present invention is not limited to the roller shape, and may be a non-contact corona charger or the like.

The cleaning device 63 has a photosensitive member 4
0 and a cleaning blade 75 made of, for example, polyurethane rubber,
And a conductive fur brush 76 rotatably provided in the direction indicated by the arrow. Further, a metal electric field roller 77 for applying a bias to the fur brush 76 is rotatably provided in the direction of the arrow, and the tip of the scraper 78 is pressed against the electric field roller 77. Further, a collecting screw 79 for collecting the removed toner is provided.

The toner remaining on the photoconductor 40 is removed by the fur brush 76 that rotates in the counter direction with respect to the photoconductor 40. The toner adhering to the fur brush 76 is removed by an electric field roller 77 that rotates in the counter direction with respect to the fur brush 76 and applies a bias. The electric field roller 77 is cleaned by a scraper 78. The toner collected by the cleaning device 63 is collected by a collecting screw 7.
At 9, it is moved to one side of the cleaning device 63, and is returned to the developing device 61 by a toner recycling device 80, which will be described in detail later, and is reused.

The static eliminator 64 is, for example, a lamp, and irradiates light to initialize the surface potential of the photoconductor 40.

Then, as the photosensitive member 40 rotates, first, the surface of the photosensitive member 40 is uniformly charged by the charging device 60, and then written by the above-described exposure device 21 using a laser, an LED, or the like in accordance with the content read by the scanner 300. Irradiation of light L forms an electrostatic latent image on photoconductor 40.

Thereafter, the electrostatic latent image is visualized by attaching toner by the developing device 61, and the visible image is transferred onto the intermediate transfer body 10 by the primary transfer device 62. The surface of the photoreceptor 40 after the image transfer is cleaned by removing the residual toner by the cleaning device 63, and the charge is removed by the charge removing device 64 to prepare for the image formation again.

FIG. 4 is an enlarged view of a main part of the color copying machine shown in FIG. In the figure, a tandem image forming apparatus 2
0, each image forming unit 18, each photoconductor 40 of the image forming unit 18, each developing device 61, each cleaning device 63,
After each code of each primary transfer device 62 provided opposite to the photoconductor 40 of each image forming unit 18, BK for black, Y for yellow, M for magenta, C is shown for cyan.

FIGS. 5 and 6 show a toner recycling apparatus 80. FIG. As shown in FIG.
A roller 82 having a pin 81 is provided at one end of the third collecting screw 79. Then, the roller portion 82
One side of the belt-shaped collected toner conveying member 83 of the toner recycling device 80 is hung, and the pin 81 is inserted into the long hole 84 of the collected toner conveying member 83. Blades 85 are provided at regular intervals on the outer periphery of the collected toner conveying member 83, and the other side is hung on a roller portion 87 of a rotating shaft 86.

The collected toner conveying member 83 is put in a conveying path case 88 shown in FIG. The transport path case 88 is formed integrally with the cartridge case 89, and one of the two screws 68 of the developing device 61 described above is inserted into the end of the developing device 61 on the side thereof.

Then, the driving force is transmitted from the outside to rotate the collecting screw 79 and the collected toner conveying member 8
3, the toner collected by the cleaning device 63 is conveyed to the developing device 61 through the conveying path case 88, and is put into the developing device 61 by the rotation of the screw 68. Thereafter, as described above, the toner is conveyed and circulated while being stirred by the two screws 68 together with the developer already in the developing device 61, supplied to the developing sleeve 65 and supplied to the
Then, the latent image is transferred to the photoconductor 40 and the latent image on the photoconductor 40 is developed.

The toner has a charge characteristic by mixing a charge control agent (CCA) and a colorant with a resin such as polyester, polyol or styrene acryl, and externally adding a substance such as silica or titanium oxide. , Increasing liquidity. The particle size of the additive is usually in the range of 0.1 to 1.5 [μm]. Coloring agents include carbon black, phthalocyanine blue, quinacridone, carmine and the like.
The charging polarity is negative charging in the illustrated example.

As the toner, a toner obtained by externally adding the above type of additive to a base toner in which wax or the like is dispersed and mixed can be used. In the above description, the toner is prepared by a pulverization method, but a toner prepared by a polymerization method or the like can also be used. Generally, a toner formed by a polymerization method, a heating method, or the like can have a shape factor of 90% or more, and further has a very high additive coverage depending on the shape.

Here, the shape factor is originally a sphericity and is defined as “surface area of sphere having the same volume as particle / surface area of actual particle * 100%”. , And the degree of circularity. The definition is “perimeter of a circle having the same projected area as a particle / projected contour length of a real particle * 100”.
% ". Then, the closer the projected circle is to a perfect circle, the closer to 100%.

The range of the volume average particle diameter of the toner is 3 to 12
μm is preferred. In the illustrated example, it is 6 μm and 1200 μm.
It is possible to sufficiently cope with high-resolution images of dpi or more.

The magnetic particles contain a metal or resin as a core and contain a magnetic material such as ferrite, and the surface layer is coated with a silicon resin or the like. The particle size is preferably in the range of 20 to 50 μm. The optimum resistance is a dynamic resistance in the range of 10 ⁴ to 10 ⁶ Ω. However, the measuring method is a roller with a magnet inside (φ20; 600 RPM)
An electrode having an area of 65 mm in width and 1 mm in length is brought into contact with a gap of 0.9 mm, and an applied voltage of an upper limit level of withstand voltage (400 V for high-resistance silicon-coated carrier to several V for iron powder carrier) is applied. This is the measured value when the measurement is performed.

The developing sleeve 65 has a non-magnetic rotatable sleeve-like shape, and includes a plurality of magnets 7 therein.
2 are arranged. Since the magnet 72 is fixed, a magnetic force can be applied when the developer passes through a predetermined place. In the illustrated example, the diameter of the developing sleeve 65 is φ18, and the surface is subjected to sandblasting or a process of forming a plurality of grooves having a depth of 1 to several mm so as to be within a range of 10 to 30 μm RZ.

The magnet 72 moves N ₁ , S ₁ , N ₁ from the doctor blade 73 in the rotation direction of the developing sleeve 65.
₂ , S ₂ , and S ₃ . The (toner + magnetic particles) formed by the magnet 72 is carried on the developing sleeve 65 as a developer, and the toner obtains a prescribed charge amount by being mixed with the magnetic particles. In the illustrated example, -10 to
A range of −30 [μC / g] is preferable. Developing sleeve 6
5 is a magnet 72 formed with a magnetic brush of developer.
In the area on the S1 side of the photoconductor 40, the photoconductor 40 is disposed.

In the illustrated example, as shown in FIG. 7, by applying a desired bias to the registration roller 49, the registration roller 49 also serves as the charging means A according to the present invention. As a result, in the paper transport direction a, 2
At the upstream position of the next transfer device 22, when the image is transferred by the secondary transfer device 22, the paper adhering material on both the front and back surfaces of the paper is charged to a polarity to attract the paper to the paper side.

For example, when the toner is charged to the negative electrode, the paper adhering material such as paper dust or paper adhering material on the front side to which the toner image is transferred is transferred to the negative electrode having the same polarity as the toner, and the paper adhering material on the back side is applied. Charge the positive electrode.

As a result, paper deposits such as paper dust and paper additives can be prevented from adhering to the intermediate transfer member (image carrier) 10 and filming and image deletion can be eliminated. Further, it is possible to prevent the paper adhering matter adhering to the intermediate transfer body 10 from further adhering to the photoreceptor 40 and mixing into the toner collected by the cleaning device 63, and remove the toner from the developing device 61.
Can be recycled for reuse.

In the illustrated example described above, the registration roller 49 also serves as the charging means A according to the present invention. However, the charging means A may be provided at a position upstream of the transfer device 22 in the sheet transport direction, separately from the registration roller 49, so as to inject charges or apply charges by a discharge phenomenon.

For example, as shown in FIG.
May be sandwiched between charging rollers 91 different from the registration roller 49 from both sides to charge paper adhering matter by contacting the paper 90. As shown in FIG. Alternatively, the paper 90 may be charged in a non-contact manner by being sandwiched between the sheets 90 or by other proximity charging devices. As shown in (C), charging may be performed by a charging brush 93 provided on the front surface (image surface) side.

Further, as shown in (D), a corona charger 92 is brought into contact with the front side, and the charging roller 91 is brought into contact with the back side.
Or a corona charger 92 on the front side, and a conductor 94 in contact with the back side, as shown in (E), and a contact type and a non-contact type. It may be charged. Charging roller 9
1 can also serve as a transport roller for the paper 90.

Here, as shown in FIG. 8 (B), an experiment was conducted in a case where charges were applied from the front and back sides of the paper 90 by the corona charger 92 in the pre-transfer process to charge the paper adhering substance to a desired polarity. .

The corona charger 92 was placed immediately after the registration roller 49 with the positive and negative electrodes facing each other with a distance of about 4 mm. Then, the paper 90 passing through the registration rollers 49 is guided by the guide plate and enters between the corona chargers 92. A wire voltage of ± 5.2 kV is applied to each corona charger 92, and the discharge current is applied to the wires. Was generated.

A part of the discharge current flows into the surface of the paper 90, and its amount is set so as to flow about 20 μA to the paper surface by subtracting from the case current. Using an organic photoreceptor, a negatively charged black toner, no intermediate transfer function, and a transfer roller method for paper, about 1000 sheets of A4 PPC paper were printed without images. Only the image was not printed, and the other conditions were not different from those of a normal copying machine.

When the corona charger 92 was not operated, it was confirmed that a white substance dropped from the paper 90, which is considered to be mainly kaolin or talc, adhered to the cleaning blade of the photosensitive member. However, when the corona charger 92 is operated in the above state, the photosensitive member
The effect of preventing the adhesion of paper dust and paper additives was observed, and the adhesion of the white substance to the cleaning blade was greatly reduced as compared with when the blade was not operated.

In the above description, the paper adhering material on both the front and back sides of the paper 90 is charged. However, only the paper adhering material on the surface (image surface) of the paper 90 is charged by the charging means A as shown in FIG. You may make it.

In the charging means A shown in FIG. 9, (A) to (C) are in non-contact with the paper 90, (A) is a corona charger, (B) is a scorotron charger, and (C) is a proximity charging member. is there. Here, the proximity charging member may be fixed or movable (rotation, lateral swing, etc.),
A gap of 0 to 100 μm is provided. On the other hand,
(D) to (F) are in contact with the sheet 90, (D) is a charging roller, (E) is a charging brush, and (F) is a charging blade.

In the example described above, the case where the toner image formed on the photosensitive member 40 is applied to a tandem type indirect transfer type electrophotographic apparatus for transferring the toner image to the sheet 90 via the intermediate transfer member 10 has been described. In such a tandem-type indirect transfer type electrophotographic apparatus, the intermediate transfer body 10 as an image carrier is not limited to a belt-like one as shown in FIG. 1 and may be a drum-like one.

Incidentally, the present invention is not limited to the tandem type indirect transfer type electrophotographic apparatus as described above.
0, a plurality of image forming means 18 are arranged side by side along the sheet transport direction a, and the photosensitive member 4 serving as an image carrier is arranged.
The present invention can be similarly applied to a tandem-type direct transfer type electrophotographic apparatus in which the toner images formed on the sheet 0 are sequentially transferred to the sheet 90 directly without passing through the intermediate transfer body by the transfer device 62.

In FIG. 10, reference numeral 96 denotes a paper transport belt that transports the paper 90 along the paper transport direction a, and is wound around three support rollers 97 in the illustrated example. Reference numeral 98 denotes a belt cleaning device that removes toner attached to the paper transport belt 96.

In such a tandem type direct transfer type electrophotographic apparatus, similarly, for example, by applying a desired bias to the registration roller 49, the registration roller 49 also serves as the charging means A according to the present invention. . Thus, the charging means A is provided at a position upstream of the transfer device 62 in the paper transport direction a, and the charging device A
2 is charged to a polarity that attracts the paper deposits on both the front and back sides of the paper to the paper side during image transfer.

For example, as shown in FIG. 11, a negatively charged paper adhering substance 10 adhering to both the front and back surfaces of a paper 90.
2. The paper deposit 103 charged to near neutral polarity and the paper deposit 104 charged to the positive electrode are aligned with the negative electrode on the front side, and are aligned with the positive electrode on the back side.

Thus, when a positive bias is applied to the photoconductor 40 by the transfer device 62, the paper deposits 102, 103, and 104 on the paper 90 are removed from the photoconductor 40 on the front side.
While being prevented from adhering, the toner 105 charged to the negative electrode on the photoconductor 40 is attracted and transferred to the paper 90. At the same time, on the back side,
2. 103 and 104 can be prevented from adhering to the transfer device 62.

In the case of the direct transfer type as well, the charging means A may be provided separately from the registration roller 49 at a position upstream of the transfer device 62 in the sheet transport direction a as shown in FIG. Good.

In FIG. 12, reference numerals 102, 103, 1
Similarly, reference numeral 04 denotes a negatively charged paper deposit, a neutrally charged paper deposit, and a positively charged paper deposit, which similarly adhere to the front and back surfaces of the paper 90, respectively. It is. Then, by applying a charge with the charging means A,
On the front side of the paper 90, they are aligned with the negative electrode, and on the back side, they are aligned with the positive electrode.

Thus, when a positive bias is applied to the photosensitive member 40 by the transfer device 62, the paper attachments 102, 103, and 104 on the sheet 90 are similarly attached to the photosensitive member 40 on the front surface side. On the other hand, the negatively charged toner 105 on the photoreceptor 40 is attracted and transferred to the paper 90 while preventing the toner 105 from being charged. At the same time, it is possible to prevent the paper attachments 102, 103 and 104 on the paper 90 from adhering to the transfer device 62 on the back side.

Incidentally, as shown in FIG.
When a non-contact type corona charger or the like is used, there is little possibility that the paper adhering substances 102, 103, and 104 on the paper 90 adhere to the transfer device 62. It is sufficient to provide only the front side of the paper 90, and the paper adhering substance 10 on the front side of the paper 90
Only 2.103.104 is arranged to be a negative electrode.

Thus, when a positive bias is applied to the photosensitive member 40 by the transfer device 62, the paper deposits 102, 103, and 104 on the paper 90 are removed from the photosensitive member 40 on the front surface side.
While being prevented from adhering, the toner 105 charged to the negative electrode on the photoconductor 40 is attracted and transferred to the paper 90.

Incidentally, in such a tandem type direct transfer type electrophotographic apparatus, the photosensitive member 40 as an image carrier is not limited to a drum-shaped one as shown in FIG. It may be.

As described above, the charging means for charging the paper adhering substances 102, 103 and 104 to the paper 90 side at the time of image transfer by the transfer device 62 at the position upstream of the transfer device 62 in the paper transport direction a. A
Paper deposits 102, 103, 104 such as paper powder and paper additives
However, the toner itself can be prevented from adhering to the photoreceptor (image carrier) 40, filming and image flow can be eliminated, and the toner can be returned to the developing device 61 for recycling.

Next, the toner used in the above-described electrophotographic apparatus of the illustrated example will be described.

The illustrated electrophotographic apparatus uses a toner containing a substance having a low softening point, so-called wax. Waxes include natural and synthetic waxes. A typical example of the former is carnauba wax, and a typical example of the latter is polypropylene. These substances are present alone without ever reacting with the toner resin.

The presence of the wax outside the toner resin serves as a lubricant, so to speak. Due to this effect, the toner resin itself is not crushed even if it comes into contact with the cleaning member without pain. By the way, when we performed a quality test over time with or without wax,
In the case of the toner without wax, the toner deteriorates at 190K sheets, the degree of aggregation increases, the developing ability decreases, and the image quality deteriorates. However, the toner containing 3% by weight of carnauba wax deteriorates up to 250K sheets. It was possible to maintain image quality by continuing recycling without recycling.

As the toner, those prepared by a pulverization method and a polymerization method can be used. The surface of the toner produced by this method can be smoothed, and a toner having a shape factor, that is, a circularity of 90% or more can be produced. Spherical toner generally has an index represented by sphericity. With the true sphere being 1, the sphericity decreases as the pulverized toner becomes.

Assuming that the circularity of the projected image of the sphericity is SR, SR = (perimeter of a circle having the same area as the particle projection area /
It can be defined as (perimeter of a particle projected image) × 100%, and the closer the toner is to a true sphere, the closer to 100%.

The effect of toner sphering will be described in comparison with a conventional pulverized (irregular) toner. Similarly, the toner B (this embodiment) has 0.5% by weight of silica and 0.7% by weight of titanium oxide with respect to the conventional toner A (0.2% by weight of silica and 0.3% by weight of titanium oxide). One of the main functions of the additive is to reduce the cohesive force of the toners to prevent the toners from forming agglomerated masses, and to make them as “unraveled” as possible for uniform development,
The purpose is to obtain transfer characteristics. At this time, considering the ratio of the toner B adhering around the mother toner in terms of the coverage, the toner B has a small surface area compared to the conventional toner A because the toner B is nearly spherical. To that extent, the coverage of the toner B with the additive is increased, and the fluidity is improved, so that the toner B can easily move on the developing sleeve 65 and the developing ability is increased. When a toner having a circularity of 90 or more is used, the transfer rate is improved by smoothing the surface, and a value of 92% is obtained for the transfer rate of 88% with the conventional pulverized toner. As a result, the amount of recycled toner is reduced and the image is not deteriorated because it is less susceptible to toner crushing during recycling.

Next, the distribution curve of (toner charge amount) / (toner particle size) will be described below.

The particle size and charge distribution of the toner on the developing sleeve 65 are measured. For measurement, E-SPART ANALYZER manufactured by Hosokawa Micron Corporation was used. Although a detailed description of the E-SPART ANALYZER is omitted, air of the toner on the developing sleeve 65 is blown off to catch the movement in the electric field, thereby obtaining data of the particle size and charge amount of each toner. . Incidentally, in this confirmation experiment, 3000 toners were sampled, and the difference in distribution was observed. Here, the distribution of q / d is mainly compared by dividing the charge amount of the toner by the toner particle size. This is because the charge amount depends on the particle size of the toner.

The toner used in the examples is optimally a dry toner containing a modified polyester at least as a toner binder and a toner prepared by a polymerization method.
The case using the former toner will be described. The shape factor of the toner is SF = 95%. Therefore, when the particle size and the charge amount distribution of the toner on the developing sleeve were measured initially, the charge amount distribution became sharp as shown in FIG. The half width is 1.1 [fC / 10 μm].
Met.

An index relating to sharpness is generally represented by a half width, and the smaller the value, the sharper the image. Generally, when the distribution is sharp, there are many toners having q / d values close to each other, and uniform development can be achieved because the developing ability is the same. Conversely, when the distribution is broad, the range of the toner charge amount existing is widened and the range of the developing ability is also widened, so that the development amount fluctuates, and when the low charge amount side increases, background fouling is likely to occur. .

Next, the same half width after recycling was found to be 1.7 [fC / 10 μm]. Further, when the value after recycling was measured by a system using a general pulverized toner, it was 2.7 [fC / 10 μm].

FIG. 15 shows the relationship between the above-mentioned half-value width and background dirt.
It is known that the difference between the reflection densities with respect to the undeveloped transfer paper is used as ΔID. As a result, in the case of the conventional pulverized toner, the background fouling property after recycling is reduced. However, when a toner having a half width of 2.2 or less is used, a sufficient amount of charge is maintained and image quality is not deteriorated even if recycling is performed.

Next, the elasticity of the intermediate transfer member 10 will be described.
This will be described below.

The range of the hardness HS of the intermediate transfer member 10 is preferably set to 10 ≦ HS ≦ 60 ° (JIS-A). When a belt is used, the hardness is sufficiently low, but there is a possibility that the belt will slip at the drive transmission unit. On the other hand, when a rigid roller is used, unevenness in rotation, that is, running, can be extremely reduced. However, if the hardness is too high, the margin due to accuracy is narrowed, and there is a possibility that the photoconductor 40 does not adhere well. Therefore, the intermediate transfer member 1
By providing the elastic layer 12 at 0, the hardness is reduced, the flexibility is given, the degree of close contact with the photoreceptor 40 is improved, the transfer rate is improved, and the image quality is reduced by reducing the amount of recycled toner. This is to avoid and maintain image quality.

If the hardness is less than 10 ° JIS-A, it is very difficult to mold with high dimensional accuracy. this is,
This is due to the fact that they tend to contract and expand during molding. Also,
In the case of softening, it is a general method to contain an oil component in the base material, but it has a drawback that when it is operated continuously in a pressurized state, it oozes out. Thereby, the toner carried on the surface of the intermediate transfer body 10 is contaminated,
It was found that the transfer rate was significantly reduced.

On the other hand, those having a hardness of 60 ° JIS-A or more can be molded with high precision by the increased hardness.
Since the oil content can be kept low, the contamination of the toner can be reduced. However, since the usable range in consideration of the contact pressure is narrowed, it is necessary to set the biting amount or the contact pressure accurately.

FIG. 16 shows the relationship between the hardness of the intermediate transfer member 10 and the amount of biting into the photoreceptor 40 using the contact pressure as a parameter. 3 to 8 gf / mm for A, 3 to 12 gf for intermediate transfer roller B
/ Mm, the bite widths are 0.02 mm and 0.05 mm, respectively. The intermediate transfer roller A has a dimensional accuracy of about 2. That would have to be increased by a factor of five.

Therefore, the type of the intermediate transfer roller B has a wider margin. Compared with the conventional intermediate transfer roller A (hardness of 61 JIS-A) having relatively high hardness, the transfer ratio of the intermediate transfer roller B (hardness of 40 JIS-A) of the present invention is measured. With the intermediate transfer roller B of the present invention, a value of 94% is obtained with respect to 90%, and the amount of recycled toner is reduced, and the image is deteriorated because it is less susceptible to toner pulverization at the time of recycling. do not do.

[0129]

As described above, according to the first aspect of the present invention, in an electrophotographic apparatus, paper adhering material is transferred to an upstream position of a transfer device in a sheet transport direction when an image is transferred by the transfer device. Since there is a charging means that charges to the polarity attracting to the side, paper deposits such as paper dust and paper additives,
It is possible to prevent the toner itself from adhering to an image carrier such as a photoconductor or an intermediate transfer body, eliminate filming and image flow, and return the toner to the developing device for recycling.

According to the second aspect of the present invention, in such an electrophotographic apparatus, the paper adhering material on both sides of the paper is charged by the charging means. It is possible to prevent the toner from adhering to the image carrier, further reduce filming and image flow, and enable the toner to be recycled.

According to the third aspect of the present invention, in the above-described electrophotographic apparatus, the paper adhering material is charged in a non-contact manner by the charging means such as a corona charger.
In addition, extra stress is not applied to the paper, and the generation of paper dust and the like can be prevented.

According to the fourth aspect of the present invention, in the above-described electrophotographic apparatus, the charging means is formed by applying a bias to the registration roller so that the charging roller is also used by the registration roller. The cost can be reduced by effectively using the parts.

According to the fifth aspect of the present invention, in the above-described electrophotographic apparatus, the toner containing the low softening point substance is used. Deterioration can be prevented, and a decrease in image quality can be prevented.

According to the sixth aspect of the present invention, in the above-described electrophotographic apparatus, the toner having a circularity of 90 or more is used. In addition, the surface shape of the toner is smoothed to improve the transfer rate of the toner. In addition, the amount of recycled toner can be reduced to prevent image quality from deteriorating, thereby preventing image quality from deteriorating.

According to the seventh aspect of the present invention, in the above electrophotographic apparatus, the half width of the distribution curve of (toner charge amount) / (toner particle size) is 2.2 [fC / 1].
0 μm] or less, in addition, the distribution curve is maintained sharp, and the toner component ratio does not fluctuate at the time of toner recycling to prevent deterioration in image quality.
It is possible to prevent a decrease in image quality.

According to the eighth aspect of the present invention, in the above-described electrophotographic apparatus, the image carrier is an intermediate transfer member for transferring the toner image transferred from the photosensitive member onto a sheet, and In addition, since the elastic layer is provided, the intermediate transfer member is brought into close contact with the image carrier, thereby improving the transfer rate of the toner and preventing the image quality from deteriorating.

According to the ninth aspect of the present invention, in the electrophotographic apparatus, charging means is provided upstream of the transfer apparatus in the paper transport direction so as to charge the paper adhering substance to the paper side at the time of image transfer by the transfer apparatus. Position, it prevents paper adhering substances such as paper dust and paper additives from adhering to the image carrier such as the photoreceptor and the intermediate transfer body. It is possible to provide a charging unit that can be returned to the developing device and used for recycling.

According to the tenth aspect of the present invention, the charging means located at the upstream position in the paper transport direction is charged to a polarity that attracts the paper adhering material to the paper side at the time of image transfer, and then is charged to the downstream position in the paper transport direction. A certain transfer device transfers the toner image formed on the image carrier and records the image on the paper, so that paper adhering substances such as paper dust and paper additives are transferred to the image carrier such as a photoconductor or an intermediate transfer body. Prevent itself from sticking to the body,
It is possible to provide an image recording method that eliminates filming and image bleeding, and enables recycling by returning toner to a developing device.

[Brief description of the drawings]

FIG. 1 shows an embodiment of the present invention and is an overall schematic configuration diagram of a tandem-type indirect transfer type color copying machine.

FIG. 2 is a partially enlarged sectional view showing a sectional structure of an intermediate transfer member used in the color copying machine.

FIG. 3 is a partially enlarged configuration diagram of a dandem image forming apparatus used in the color copying machine.

FIG. 4 is an enlarged configuration diagram of a main part of the color copying machine.

FIG. 5 is an exploded perspective view illustrating a toner recycling device used in the color copying machine.

FIG. 6 is a cutaway perspective view on the developing device side of the toner recycling device.

FIG. 7 is an enlarged configuration diagram of a transfer portion to a sheet in the color copying machine.

FIG. 8 is an explanatory view of various double-side charging means used in the color copying machine.

FIG. 9 is an explanatory diagram of various one-side charging means.

FIG. 10 is a main part configuration diagram of a tandem type direct transfer type electrophotographic apparatus.

FIG. 11 is a state explanatory view showing a state of change of toner and paper adhering matter in the electrophotographic apparatus.

FIG. 12 is a state explanatory diagram showing a state of change of toner and paper adhering matter when a charging unit is used separately from a registration roller.

FIG. 13 is a state explanatory diagram showing a state of change of toner and paper adhering material when a charging unit is provided only on the front side of a sheet.

FIG. 14 is a distribution curve diagram of (toner charge amount) / (toner particle size).

FIG. 15 is a diagram showing the relationship between the half width of the distribution curve and background contamination.

FIG. 16 is a relationship diagram between the hardness of the intermediate transfer member and the amount of bite into the image carrier.

FIG. 17 is a state explanatory view showing a state of a change in toner and paper adhering matter in a conventional electrophotographic apparatus.

FIG. 18 is a state explanatory view showing another state of change of toner and paper adhering matter in a conventional electrophotographic apparatus.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 intermediate transfer member (image carrier) 12 elastic layer 18 image forming means 20 tandem image forming device 40 photoconductor (image carrier) 49 registration roller 62 transfer device 80 toner recycling device 90 paper 102 paper with negatively charged paper Kimono 103 Paper attached matter charged to near neutral polarity 104 Paper attached matter charged to positive electrode 105 Toner charged to negative electrode A Charging means a Paper transport direction d Toner particle size q Toner charge amount

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuto Koyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Yuji Sawai 1-3-6 Nakamagome, Ota-ku, Tokyo Share In Ricoh Company (72) Inventor Mitsuru Takahashi 1-3-6 Nakamagome, Ota-ku Tokyo BA06 CA01 CA02 CB09

Claims (10)

[Claims] 1. An electrophotographic apparatus for recording an image on paper by transferring a toner image formed on an image carrier by a transfer device, wherein the transfer device is provided at an upstream position of the transfer device in a paper transport direction. It is provided with charging means for charging to a polarity that attracts paper adhering matter to the paper side during image transfer,
Electrophotographic equipment. 2. The electrophotographic apparatus according to claim 1, wherein said adhering means charges paper deposits on both sides of the paper. 3. The electrophotographic apparatus according to claim 1, wherein the paper adhering member is charged by the charging unit without contacting the paper. 4. The electrophotographic apparatus according to claim 1, wherein the charging unit is formed by applying a bias to the registration roller and also using the registration roller. 5. The electrophotographic apparatus according to claim 1, wherein a toner containing a low softening point substance is used. 6. The electrophotographic apparatus according to claim 1, wherein a toner having a circularity of 90 or more is used. 7. The toner according to claim 1, wherein a half value width of the toner is 2.2 [fC / 10 μm] or less in a distribution curve of (toner charge amount) / (toner particle size). 2. The electrophotographic apparatus according to 1. 8. The image carrier according to claim 1, wherein the image carrier is an intermediate transfer member for transferring a toner image transferred from a photosensitive member onto a sheet, and the intermediate transfer member is provided with an elastic layer. 2. The electrophotographic apparatus according to claim 1. 9. An electrophotographic apparatus in which a toner image formed on an image carrier is transferred by a transfer device and an image is recorded on a sheet of paper. Charging means provided at a position upstream of the transfer device in the paper transport direction. 10. An image carrier is charged by a charging unit located at an upstream position in the sheet conveying direction to a polarity that attracts paper adhering matter to the sheet side at the time of image transfer, and then by a transfer device located at a downstream position in the sheet conveying direction. An image recording method for an electrophotographic apparatus, wherein an image is recorded on a sheet by transferring a toner image formed thereon.