JP2000258973A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the occurrence of failure in electrification under low humidity and to maintain image quality of black characters without increasing the cost even under high humidity by installing an image forming means part provided with a black color toner in developer in a position with higher temperature than the other image forming means parts. SOLUTION: In this image forming device, all of a 1st to 4th image forming means parts Ua to Ud are provided respectively with photoreceptor drums 1 (a to d) as image carriers, magnetic brush electrifying devices 2 (a to d) as contact electrifying members, LED alley 3 (a to d) as image exposure means, developing devices 4 (a to d) and fur brush electrifying devices 5 (a to d) as auxiliary contact electrifying members. The rise in temperature is the highest in the 4th image forming means part Ud that is closest to a heat fixing device 8. The image forming means part Ud that is closest to the heat fixing device 8 is designated as the black image forming means part. Failure in electrification is not generated under the low humidity and the image quality (high definition) of black characters can be maintained even under high humidity concerning the black image forming means part Ud.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for manufacturing a semiconductor device having a surface having a resistance value of 1 ×
An object to be charged having a layer made of a material of 10 ⁹ to 1 × 10 ¹⁴ Ω · cm, a contact charging member for charging the object to be charged, and a latent image for forming an electrostatic latent image on the charged surface of the object to be charged Forming means;
The present invention relates to an image forming apparatus having a plurality of image forming units including a developing unit configured to develop the electrostatic latent image with a developer to form a toner image.

[0002]

2. Description of the Related Art An image forming apparatus using an electrophotographic method, an electrostatic recording method, or the like, charges a surface of a member to be charged (hereinafter, referred to as an image carrier) such as an electrophotographic photosensitive member or an electrostatic recording dielectric. , Which uniformly charges to a predetermined polarity and potential to form an electrostatic latent image by selectively discharging the charged surface of the image bearing member by an image exposure means or a discharging means to form an image. It is.

A non-contact type corona charger (corona discharger) has been used as a charging means for the image carrier, but recently, a contact charging member (conductive member) which applies a voltage to the image carrier. ) Is in practical use because it has advantages such as low ozone and low power as compared with corona chargers.

[0004] Examples of the contact charging member include a conductive roller (charging roller), a fur brush roller, a magnet roller (magnetic brush roller) carrying magnetic particles, and a charging blade.

[0005] Contact charging mechanism (charging mechanism)
Has a discharge charging mechanism and an injection charging mechanism,
Each characteristic appears depending on which is dominant.

In the injection charging, the contact charging member is brought into contact with the surface of the image carrier as a member to be charged, and does not pass through a discharge phenomenon, that is, directly on the surface of the image carrier without basically using a discharge mechanism. by performing charge injection to are those for charging the surface of the image bearing member, the surface resistance value as an image bearing member 1 × 10 ⁹ ~
One having a layer (OCL layer) made of a material of 1 × 10 ¹⁴ Ω · cm, more specifically, one having a surface layer in which conductive fine particles are dispersed on a normal organic photoreceptor, or one having amorphous silicon (non-conductive) When an image carrier having a surface layer of crystalline silicon) is used, the injection charging mechanism becomes dominant, and a charging potential substantially equal to the DC component of the bias applied to the contact charging member is obtained on the surface of the image carrier. Is possible.

The use of this injection charging does not utilize a discharge phenomenon in which charging of the image carrier is performed using a corona charger, so that complete ozone-less and low-power-consumption charging is possible, which has attracted attention. ing.

[0008]

However, in an image forming apparatus using such an injection charging method, the charge after exposure is diffused due to a decrease in the resistance of the surface layer of the image carrier, especially under high humidity. And the charge pattern is blurred,
For example, there is a disadvantage that the sharpness of characters is reduced.

This is different from the so-called image flow that occurs under high humidity when the image carrier is charged by so-called corona charging. That is, in this case, an ozone product or the like due to corona discharge adheres to the surface of the image carrier and has a low resistance under high humidity. This results in a disturbed image flow. Alternatively, talc, carion, calcium carbonate, or the like, which is a filler of paper as a transfer material, adheres to the surface of the image carrier, and the resistance becomes low under high humidity.

On the other hand, in the injection charging method, no ozone product is generated or very little because corona discharge is not basically used. When a magnetic brush is used as the contact charging member (contact charger), it is possible to prevent the filler from adhering to the paper due to the high rubbing force on the image carrier. Therefore, in the image forming apparatus using the injection charging method, the image deletion due to the above-described matter when the charging of the image carrier is corona charging does not occur.

Since the image carrier for injection charging has a resistance layer on the surface layer as described above, for example, when a charge transport layer is provided below the surface layer, the injected charge is transferred between the surface layer and the charge transport layer. And a charge pattern is formed near the boundary surface as a latent image. When the relative humidity is high, especially when the relative humidity is high, the volume resistance of the surface layer becomes small, and the electric charge moves due to the electric field generated by the electric charge pattern, and the latent image is blurred.

If the resistance of the surface layer is increased in order to avoid a decrease in the resistance of the surface layer under high humidity, the increase in the resistance of the surface layer under low humidity makes it difficult to perform injection charging. Occurred.

As a method for preventing image deletion, there is a method for preventing image deletion by disposing a heat source on the inner surface of the image carrier.
For example, as in a so-called tandem type full-color image forming apparatus, an image carrier, a contact charging member that charges the image carrier, a latent image forming unit that forms an electrostatic latent image on a charged surface of the image carrier, Particularly, in the case of an image forming apparatus having a plurality of image forming units provided with a developing unit for developing the electrostatic latent image with a developer to form a toner image, a heat source is required as many as the plurality of image forming units. Cost increase was inevitable.

Therefore, as described above, according to the present invention, the image carrier is charged by the injection charging method, and the image forming apparatus includes a plurality of image forming means sections each including an image carrier, a contact charging member, a latent image forming means, and a developing means. Regarding the device, it has become possible to maintain the image quality of black characters in particular without high cost even under high humidity without causing charging failure under low humidity, that is, the resistance value of the surface layer of the image carrier under high humidity It is an object of the present invention to provide an apparatus capable of preventing deterioration of black character quality due to down.

[0015]

SUMMARY OF THE INVENTION The present invention is an image forming apparatus having the following configuration.

(1) The surface has a resistance value of 1 × 10 ⁹ to 1 × 10
^A member to be charged having a layer made of a material of ¹⁴ Ω · cm; a contact charging member for charging the member to be charged; a latent image forming means for forming an electrostatic latent image on a charged surface of the member to be charged; In an image forming apparatus having a plurality of image forming units having a developing unit for developing an electro-latent image with a developer to form a toner image, an image forming unit having a developing unit having at least a black toner in a developer is another An image forming apparatus, wherein the image forming apparatus is arranged at a higher temperature in the image forming apparatus main body than the image forming means.

(2) The image forming apparatus according to (1), wherein the member to be charged has a photosensitive layer and a surface layer, and the surface layer has a resin and conductive fine particles.

(3) The image forming apparatus according to (2), wherein the conductive fine particles are SnO ₂ .

(4) The image forming apparatus according to any one of (1) to (3), wherein the magnetic particles are in contact with the member to be charged in the contact charging member for charging the member to be charged.

(5) The image forming apparatus according to any one of (1) to (3), wherein a conductive fiber is in contact with the member to be charged in the contact charging member for charging the member to be charged. apparatus.

(6) The developing means is a contact developing system for developing an electrostatic latent image as a toner image in a state in which the developer contacts the member to be charged (1) to (5). The image forming apparatus according to any one of the above.

(7) The developer contained in the developing means is a developer comprising toner particles and magnetic particles having a resistance value of 1 × 10 ¹¹ Ω · cm or more (1) to (6). The image forming apparatus according to any one of the above.

(8) The image forming apparatus according to any one of (1) to (7), wherein the toner particles in the developer contained in the developing means are toners produced by a polymerization method. .

(9) There is a transfer unit for transferring the toner image formed on the member to be charged of the image forming unit to another member, and the toner remaining on the member to be charged after the transfer of the toner image is contacted. Any one of (1) to (8), wherein the toner is redeposited on the member to be charged simultaneously with charging after being collected by the charging member, and a part or all of the adhered toner is collected and reused by the developing means. An image forming apparatus according to any one of the above.

(10) The image forming apparatus according to any one of (1) to (9), wherein a heat source that operates at least when the power of the main body is turned off is provided in the main body of the image forming apparatus at a position away from the image forming unit. Image forming device.

<Operation> The resistance value of the surface layer of the injection-chargeable member to be charged decreases as the absolute moisture content increases, but even under the same absolute moisture content environment, the resistance value increases as the relative humidity decreases.
Therefore, for an image forming apparatus adopting an injection charging method and having a plurality of image forming means, at least an image forming means (black image forming means) having a developing means having a black toner as a developer is provided. By arranging the black image forming unit at a higher temperature in the image forming apparatus main body than other image forming units, for example, in the vicinity of the heat fixing unit, at least the black image forming unit may cause poor charging under low humidity. Not
The image quality (sharpness) of black characters can be maintained without increasing the cost even under high humidity.

Therefore, in the mode in which black and white image formation is performed by the black image forming means, the image quality is maintained even under high humidity, and the black image forming means and other image forming means are maintained. Thus, even in a mode in which a full-color image or a multi-color image is formed, the quality (sharpness) of the black image component image is maintained even at high humidity at least for the black image forming means as described above. The overall image quality of the combined full-color image or combined multicolor image including the black image component image is maintained.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 (FIGS. 1 to 9) FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus according to the present invention.

The image forming apparatus of this embodiment is a full-color image forming apparatus of a transfer type electrophotographic process, an injection charging system, a reversal developing system, a cleanerless system, and a tandem system. A is a printer unit, and B is a color image reading device (color image reader) mounted thereon.

(1) Color Image Reading Apparatus B In the color image reading apparatus B, reference numeral 101 denotes a fixed document table (a transparent plate such as glass). The original is placed on the original, and an original cover (not shown) is placed on the original.

Reference numeral 102 denotes a color image reading unit provided with a document irradiation lamp 102a, a short focus lens array 102b, a CCD sensor 102c, and the like. When a copy start signal is input, the unit 102
At the lower side of the document table 1, the document table is driven forward from the left side home position to the right side along the document table lower surface, and when it reaches a predetermined forward end point, it is driven backward to return to the first home position.

In the forward drive process of the unit 102, the downward image surface of the placed document G on the document table 101 is sequentially illuminated and scanned by the document irradiating lamp 102a of the unit 102 from the left side to the right side. The document light reflected from the original surface of the illumination scanning light is imaged and incident on the CCD sensor 102c by the short focus lens array 102b.

The CCD sensor 102c comprises a color separation light receiving section, a transfer section, and an output section. Each color separation light signal of the original image is converted into a charge signal in the color separation light receiving section, and is sequentially transferred to the output section in synchronization with the clock pulse in the transfer section, and the charge signal is converted into a voltage signal in the output section, and is amplified. Output with low impedance. The analog signal thus obtained is subjected to well-known image processing, converted into a digital signal, and sent to the printer unit A.

That is, the color-separated image information of the color original G is photoelectrically read by the color image reading device B as a time-series electric digital pixel signal.

The original G may be a black and white original, and in this case also, monochrome image information is photoelectrically read as a time-series electric digital pixel signal.

(2) Printer unit A Ua, Ub, Uc, Ud are first to fourth four image forming means units (image forming unit, image forming station) arranged in order from left to right in printer unit A. It is.

In this embodiment, the first image forming unit Ua is a yellow image forming unit, the second image forming unit Ub is a magenta image forming unit, and the third image forming unit Uc is a cyan image forming unit. The image forming unit and the fourth image forming unit Ua are black image forming units.

Each of the first to fourth image forming means Ua to Ud has a photosensitive drum 1 (a to d) as an image carrier and a magnetic brush charger 2 (a) as a main contact charging member. ~ D)
And LED arrays 3 (a to d) as image exposure means;
The image forming apparatus includes a developing device 4 (ad) and a fur brush charger 5 (ad) as an auxiliary contact charging member.

The developing device 4a of the first image forming means Ua is a developing device having a yellow toner as a developer, and the developing device 4b of the second image forming means Ub is a developing device having a magenta toner as a developer. The developing device 4c of the third image forming unit Uc is a developing device having cyan toner in the developer, and the developing device 4d of the fourth image forming unit Ud is a developing device having black toner in the developer. It is.

Reference numeral 7 denotes first to fourth image forming units Ua to Ud.
Is a transfer belt device disposed substantially horizontally in the left-right direction across the image forming means units Ua to Ud, and an endless belt 71 between a driving roller 72 and a driven roller 73 on the left and right sides.
The endless belt 71 is rotated clockwise as indicated by an arrow. Inside the endless belt 71, the ascending side belt portion of the endless belt 71 is pressed against the lower surface of the photosensitive drums 1 a to 1 d of each of the image forming units Ua to Ud, and the
Four transfer charging blades 74a to 74d forming the fourth to fourth transfer nip portions 7a to 7d are provided.

Reference numeral 6 denotes a paper feed cassette mounted on a mounting portion provided on the left side plate side of the printer unit A, 6a denotes a paper feed roller, and 6b denotes a registration roller.

Reference numeral 8 denotes a thermal fixing device (thermal fixing device) disposed between the right end of the transfer belt device 7 and the right side plate of the printer unit A, 9 denotes a paper discharge roller, and 10 denotes a paper discharge tray.

The image forming operation in each of the image forming means Ua to Ud is the same. The photosensitive drums 1 (ad) in each of the image forming means Ua to Ud are negatively charged organic photoconductors having a charge injection layer on the surface and having a diameter of about 30 mm as described in detail in (3). Peripheral speed 100mm / s in the counterclockwise direction of the arrow
It is driven to rotate at ec.

A) Charging Step The outer peripheral surface of the photosensitive drum 1 is substantially -7 by a magnetic brush charger 2 as a main contact charging member during the rotation process.
The injection charging process is uniformly performed at 00V. The magnetic brush charger 2 will be described in detail in section (4).

B) Image exposure step Image exposure corresponding to image information is performed on the uniformly charged surface of the rotary photosensitive drum 1 by the LED array 3 as an image exposure means, and the potential of the exposed portion irradiated with light drops. An electrostatic latent image corresponding to the image exposure pattern is formed by contrast between the (light portion potential) and the potential of the non-exposed portion that has not been irradiated (dark portion potential).

The LED array 3 is turned ON / OFF in response to a time-series electric digital pixel signal of each color separation image information of the color original G sent from the color image reading device B to the printer unit A.
The light emission is controlled to be OFF, and the uniformly charged surface of the rotating photosensitive drum 1 is subjected to image exposure.

In this embodiment, the resolution is 600 dpi, the wavelength is 680 μm, and the diameter of the stationary spot on the photosensitive drum is about 50 μm (approximate to the Gaussian distribution approx.
(A value that gives a light amount of 0 ² ).

On the surface of the photosensitive drum 1a of the first image forming means Ua, an image exposure corresponding to the yellow component image of the full-color image read by the color image reading device B by color separation is LED.
The electrostatic latent image is formed by the array 3a.
On the surface of the photosensitive drum 1b of the second image forming means Ub, image exposure corresponding to the magenta component image is performed by the LED array 3b to form an electrostatic latent image thereof. Third image forming unit Uc
On the surface of the photosensitive drum 1c, an image exposure corresponding to the cyan component image is performed by the LED array 3c to form an electrostatic latent image thereof. Image exposure corresponding to the black component image is performed on the surface of the photosensitive drum 1d of the fourth image forming means Ud by the LED array 3d to form an electrostatic latent image thereof.

C) Developing Step The electrostatic latent image on the surface of the rotating photosensitive drum 1 is reversely developed by the developing device 4 as a toner image in the case of this embodiment. Developing device 4
The configuration of (1) will be described in detail in section (5).

The electrostatic latent image on the photosensitive drum 1a of the first image forming unit Ua is developed as a yellow toner image by the developing device 4a. The photosensitive drum 1b of the second image forming unit Ub
Is developed as a magenta toner image by the developing device 4b. Photosensitive drum 1 of third image forming unit Uc
The electrostatic latent image of c is developed by the developing device 4c as a cyan toner image. Photosensitive drum 1 of fourth image forming unit Ud
The electrostatic latent image d is developed by the developing device 4d as a black toner image.

D) Transfer Step On the other hand, the transfer material (recording material) P loaded and stored in the paper feed cassette 6 is fed out one by one by the paper feed roller 6a and fed, and is transferred to a predetermined position by the registration roller 6b. The sheet is fed onto the ascending side belt of the endless belt 71 of the transfer belt device 7 at the control timing.

The transfer material P fed onto the belt 71 is electrostatically attracted and held on the belt surface or held by a chuck or the like, and the first to fourth transfer nip portions 7a are rotated by the rotation of the belt 71.
7b are sequentially conveyed to transfer the yellow toner image on the surface of the photosensitive drum 1a of the first image forming unit Ua at the first transfer nip unit 7a, and to the second image forming unit at the second transfer nip unit 7b. The transfer of the magenta toner image on the surface of the photosensitive drum 1b of the portion Ub, the third transfer nip portion 7c
The transfer of the cyan toner image on the surface of the photosensitive drum 1c of the image forming unit Uc and the transfer of the black toner image on the surface of the photosensitive drum 1d of the fourth image forming unit Ud in the fourth transfer nip 7d are performed four times. The toner image undergoes superimposed transfer. As a result, a desired full-color toner image is synthesized and formed on the transfer material surface.

The image formation of the toner image in each of the image forming units Ua to Ud is performed in a predetermined synchronization with each other.
The toner images a to Ud are transferred to the same transfer material P surface conveyed by the transfer belt device 7 so as to be aligned at predetermined positions and sequentially overlap.

Each of the transfer charging blades 74a to 74d connects the ascending belt portion of the transfer belt 71 to each of the image forming means units Ua to Ud.
d, the transfer nip portions 7a to 7d are formed by applying pressure to the lower surface of the photosensitive drum 1 and a transfer bias is applied from a transfer bias application power source (not shown). Perform charging. As a result, the toner image on the side of the rotating photosensitive drum 1 is sequentially electrostatically transferred to the surface of the transfer material P passing through the transfer nip portions 7a to 7d.

E) Fixing step The final fourth transfer nip 7d conveyed by the belt 71
Is separated from the belt 71 and introduced into the thermal fixing device 8. The heat fixing device 8 in this example is a heat roller fixing device, and the transfer material is nipped and conveyed through the fixing nip portion of the heat roller fixing device 8 so that the unfixed full-color toner image on the transfer material surface is heated and pressed. The image is fixed as a permanently fixed image.

The transfer material on which the image has been fixed by the heat fixing device 8 is discharged by a discharge roller 9 onto a discharge tray 10 outside the apparatus.

F) Simultaneous recovery of untransferred toner during development (simultaneous development cleaning) In each of the image forming units Ua to Ud, the untransferred toner is transferred onto the surface of the photosensitive drum 1 (a to d) after the transfer of the toner image onto the transfer material P. Toner remains. In the case of this embodiment, the developing device 4 (a) is not provided with a dedicated cleaner for removing the transfer residual toner.
-D) to collect simultaneously with development (cleanerless system). This will be described in detail in section (7).

G) Black-and-white image forming mode In the black-and-white image mode, only the fourth image forming means Ud, which is the black image forming means, of the first to fourth image forming means Ua to Ud. Performs the image forming operation, the black toner image formed on the photosensitive drum 1d of the image forming unit Ud is transferred to the transfer material P conveyed by the transfer belt device 7, and the transfer material is transferred to the heat fixing device 8 and the paper ejection. The paper is printed out on the paper discharge tray 10 through the rollers 9.

(3) Photosensitive Drum 1 As the photosensitive drum 1 (a to d) as an image carrier, a commonly used organic photoreceptor or the like can be used. Resistance is 1 × 10 ⁹
If a material having a surface layer having a material of about 1 × 10 ¹⁴ Ω · cm or an amorphous silicon photoreceptor is used, charge injection charging can be realized, which is effective in preventing ozone generation and reducing power consumption. Further, the chargeability can be improved.

The photosensitive drum 1 used in this example is a negatively charged organic photosensitive member having a charge injection layer on the surface, and is formed on a 30 mm-diameter aluminum drum base (hereinafter referred to as an aluminum base). Are provided in order from the bottom. FIG. 2 is a model diagram of the layer structure.

The first layer 12 is a subbing layer and has a thickness of 20 μm provided to smooth out defects and the like of the aluminum base 11.
m of the conductive layer.

A second layer 13; a positive charge injection preventing layer, which functions to prevent positive charges injected from the aluminum substrate 11 from canceling out negative charges charged on the surface of the photoreceptor; 1 × 1
0 is the resistance layer in the ⁶ Omega · cm about the resistance adjusted thickness 1 [mu] m.

The third layer 14 is a charge generation layer, a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and generates positive and negative charge pairs upon exposure.

The fourth layer 15 is a charge transport layer, in which hydrazone is dispersed in a polycarbonate resin, and is a P-type semiconductor. Therefore, negative charges charged on the surface of the photoreceptor cannot move through this layer, and only positive charges generated in the charge generation layer 14 can be transported to the surface of the photoreceptor.

Fifth layer 16: a charge injection layer, which is a coating layer of a material in which ultrafine SnO ₂ particles as conductive particles 16a are dispersed in a binder of an insulating resin. Specifically, a particle diameter of about 0.03 μm obtained by doping an insulating resin with antimony, which is a light-transmitting insulating filler, to reduce the resistance (to make it conductive).
This is a coating layer of a material in which m SnO ₂ particles are dispersed in a resin by 70% by weight.

The coating solution thus prepared was applied to a thickness of about 3 μm by a suitable coating method such as dipping coating method, spray coating method, roll coating method, beam coating method, etc. to form a charge injection layer.

(4) Magnetic brush charger 2 and fur brush charger 5 The magnetic brush chargers 2 (a to d) as the main contact charging members in this embodiment are of a rotary sleeve type and are fixed to non-rotation. A supported magnet roll 21 and a non-magnetic sleeve 16 mm in outer diameter (non-magnetic, conductive,
A non-magnetic sleeve 22;
And a magnetic brush portion 23 of conductive magnetic particles (magnetic carrier for charging) formed by being attracted and held on the outer peripheral surface by the magnetic force of the magnet roll 21 inside the sleeve.

The magnetic brush charger 2 is disposed substantially parallel to the photosensitive drum 1 with the magnetic brush portion 23 in contact with the surface of the photosensitive drum 1. In this case, the magnetic brush charger 2
To the magnetic brush portion 23 formed on the photosensitive drum 1
Was adjusted so that the contact nip width (charging area) n was about 6 mm.

The charging magnetic particles constituting the magnetic brush part 23 have an average particle diameter of 10 to 100 μm, a saturation magnetization of 20 to 250 emu / cm ³ , and a resistance of 1 × 10 ² to 1 × 10 ^2.
It is preferably ¹⁰ Ω · cm. Considering that the photosensitive drum 1 has an insulation defect such as a pinhole, it is preferable to use a photosensitive drum having a resistance of 1 × 10 ⁶ Ω · cm or more. In order to improve the charging performance, it is better to use a material having as small a resistance as possible.
2 μm, saturation magnetization 200 emu / cm ³ , resistance 5 × 10 ⁶ Ω
Cm magnetic particles were used.

The resistance value of the magnetic particles is such that the bottom area is 228 mm.
After placing 2g of the magnetic particles in the ^second metal cell, 6.6kg /
The weight was measured in cm ² and a voltage of 100 V was applied for measurement.

The average particle size of the magnetic particles is represented by the maximum chord length in the horizontal direction, and the measurement was performed by microscopically selecting 300 or more particles at random, measuring the diameter, and taking the arithmetic average.

For the measurement of the magnetic characteristics of the magnetic particles, a DC magnetization BH characteristic automatic recording device BHH-50 manufactured by Riken Denshi Co., Ltd. can be used. At this time, the diameter (inner diameter) is 6.5 m
m, magnetic particles in a cylindrical container with a height of 10 mm
The filling is carried out at about g weight, and the saturation magnetization is measured from the BH curve while keeping the particles from moving in the container.

As the magnetic particles, a resin carrier formed by dispersing magnetite as a magnetic material in a resin and dispersing carbon black for conductivity and resistance adjustment;
Alternatively, a material in which the surface of a single magnetite such as ferrite is oxidized and reduced to adjust the resistance, or a material in which the surface of a single magnetite such as ferrite is coated with a resin and the resistance is adjusted may be used.

Non-magnetic sleeve 22 of magnetic brush charger 2
In the charging area n, the counterclockwise direction indicated by an arrow opposite to the rotation direction of the photosensitive drum 1 (counter direction) indicates that the rotation speed of the photosensitive drum 1 is 100 mm / sec.
It was rotated at mm / sec.

A predetermined charging bias was applied to the non-magnetic sleeve 22 from a charging bias applying power source S1. In this example, a rectangular alternating voltage 10
By applying a bias in which 00 Hz and 700 V were superimposed, good chargeability could be obtained.

That is, with the rotation of the non-magnetic sleeve 22, the magnetic brush portion 23 rotates in the same direction and rubs the surface of the photosensitive drum 1 in the charging area n. An electric charge is applied to the photosensitive drum 1, and the surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and potential. In the case of this example, as described above, the photosensitive drum 1
Has a charge injection layer 16 on the surface thereof, so that the photosensitive drum 1 is charged by charge injection charging. By applying a predetermined charging bias voltage to the non-magnetic sleeve 22, electric charges are given to the photosensitive drum 1 from the magnetic particles constituting the magnetic brush portion 23, and the surface of the photosensitive drum 1 has a potential corresponding to the charging bias voltage. Is charged. The non-magnetic sleeve 22 tends to have better charging uniformity as the rotation speed is higher.

The fur brush chargers 5 (a to d) as auxiliary contact charging members are magnetic brush chargers 2 (a to d) as main contact charging members downstream of the transfer nip in the photosensitive drum rotation direction. ), The fur brush portion is disposed in contact with the surface of the photosensitive drum 1 on the downstream side in the photosensitive drum rotation direction.
mm, a conductive fiber brush member having a contact nip with the photosensitive drum of about 3 mm (flocking density 100,000 / inch ² , resistance value 5
× 10 ⁶ Ω).

In this embodiment, the fur brush charger 5
In contrast, +500 V having a polarity opposite to the DC charging polarity of the magnetic brush charger is applied from the power supply S3.

(5) Developing Apparatus 4 As a toner developing method for an electrostatic latent image, generally, the following a to d
Are roughly divided into four types.

A. Non-magnetic toner is coated on the sleeve with a blade or the like, and magnetic toner is coated by magnetic force, transported, and developed in a non-contact state with the photoreceptor (one-component non-contact development). B. A method in which the toner coated as described above is developed in contact with the photoreceptor (one-component contact development). C. A method in which a mixture of toner particles and a magnetic carrier is used as a developer and conveyed by magnetic force to develop in contact with a photoreceptor (two-component contact development). D. Method of Developing the Two-Component Developer in a Non-Contact State (Two-Component Non-Contact Development) Among these, the two-component contact development method of c is often used from the viewpoint of high image quality and high stability. ing.

FIG. 4 shows the developing devices 4 (a to d) used in this embodiment.
FIG. The developing device 4 of the present embodiment uses a mixture of non-magnetic toner particles and magnetic carrier particles as a developer, causes the developer to be held as a magnetic brush layer by a magnetic force on a developer carrying member, and This is a two-component magnetic brush contact development type apparatus that transports and contacts the surface of the photosensitive drum 1 to develop an electrostatic latent image as a toner image.

Reference numeral 41 denotes a developing container; 42, a developing sleeve as a developer carrying member; 43, a magnet roller as magnetic field generating means fixedly arranged in the developing sleeve 42;
44 is a developer layer thickness regulating blade for forming a thin layer of the developer on the surface of the developing sleeve, 45 is a developer stirring and conveying screw, 46 is a two-component developer housed in the developing container 41, and is a non-magnetic developer. Toner particles t and magnetic carrier particles c
Are mixed.

The developing sleeve 42 has a closest distance (gap) of about 5 to the photosensitive drum 1 at least during development.
The developer magnetic brush thin layer 46 a carried on the outer surface of the developing sleeve 42 is set to be in contact with the surface of the photosensitive drum 1. The contact nip m between the developer magnetic brush layer 46a and the photosensitive drum 1
Is a development area (developing part).

The developing sleeve 42 is driven at a predetermined rotation speed in a counterclockwise direction indicated by an arrow around the outer periphery of the fixedly disposed magnet roller 43, and the developer 46 is applied to the outer surface of the sleeve in the developing container 41 by the magnetic force of the magnet roller 43. A magnetic brush is formed. The developer magnetic brush is sleeve 4
2 is conveyed together with the rotation of the roller 2, and is regulated by the blade 44 so as to be taken out of the developing container as a developer magnetic brush thin layer 46a having a predetermined thickness, conveyed to the developing section, and contacts the surface of the photosensitive drum 1 and continues. The rotation of the sleeve 42 returns the developer to the inside of the developing container 41 and is conveyed again.

That is, first, the developer 46 pumped up by the N ₃ pole of the magnet roller 43 with the rotation of the developing sleeve 42 is transported from the S ₂ pole to the N ₁ pole in the process of being transported vertically to the developing sleeve 42. The thin layer 46 a of the developer 46 is formed on the developing sleeve 42 by being regulated by the regulating blade 44 disposed at the position. Developer layer 46a which is a thin layer formed brush is formed by the conveyed to the developing main pole S ₁ of the developing unit magnetic force. The electrostatic latent image on the photosensitive drum 1 is developed as a toner image by the spike-shaped developer layer 46a, and then the developer on the developing sleeve 42 is changed to a developing container 41 by a repulsive magnetic field of N ₂ pole and N ₃ pole.
Will be returned within.

A developing bias of a DC voltage (DC) and an alternating voltage (AC, AC voltage) is applied between the developing sleeve 42 and the conductive drum substrate of the photosensitive drum 1 by a developing bias applying power source S2.

In this example, DC voltage: -500 V alternating voltage; amplitude Vpp = 1500 V, frequency Vf = 20
A developing bias of 00 Hz is applied, and the toner t in the developer magnetic brush thin layer 46 a on the developing sleeve 42 side selectively adheres to the electrostatic latent image on the photosensitive drum 1 side in the developing section, so that the electrostatic latent image is It is developed as an image.

In general, in the two-component developing method, when an alternating voltage is applied, the developing efficiency is increased, and the quality of an image becomes high. On the contrary, there is a risk that fogging is likely to occur. For this reason, fog is generally prevented by providing a potential difference between the DC voltage applied to the developing device 4 and the surface potential of the photosensitive drum 1.

The potential difference for preventing fogging is called a fog removing potential (Vback). This potential difference prevents toner from adhering to a non-image area of the photosensitive drum 1 during development.

The toner concentration (mixing ratio with the carrier) of the developer 46 in the developing container 41 gradually decreases as the toner is consumed for developing the electrostatic latent image. The toner concentration of the developer 46 in the developing container 41 is detected by a detection unit (not shown), and when the toner concentration falls to a predetermined allowable lower limit concentration, the toner replenishing unit 47.
Then, the toner t is supplied to the developer 46 in the developing container 41, and the toner replenishment is controlled so that the toner concentration of the developer 46 in the developing container 41 is always kept within a predetermined allowable range.

The two-component developer 46 used in this example is composed of toner particles t; an average particle diameter of 6 μm produced by a pulverization method.
m negatively charged toner, the average particle size of 50 nm Si
O ₂ and titanium oxide having an average particle diameter of 20 nm, each of which is externally added by 0.7% by weight Carrier c; A resin-polymerized magnetic carrier having an average particle diameter of 35 μm and a saturation magnetization of 150 emu / cm ³ is mixed in a weight ratio of 6:94. It was done.

The reason why the above-mentioned carrier c was used is that, in the conventional ferrite carrier, charge injection occurs during development, resulting in fogging or low density.

The magnetic particles as the carrier c have a resistance value of 1 ×
It is preferably at least 10 ¹¹ Ω · cm.

(6) Transfer Belt Device 7 The transfer belt device 7 used was a belt 71 made of a polyimide resin having a thickness of 75 μm.

The material of the belt 6a is not limited to a polyimide resin, but may be a polycarbonate resin,
Plastics such as polyethylene terephthalate resin, polyvinylidene fluoride resin, polyethylene naphthalate resin, polyether ether ketone resin, polyether sulfone resin, and polyurethane resin, and fluorine-based and silicon-based rubbers can be suitably used. The thickness is not limited to 75 μm, but is
000 μm, preferably 50 to 150 μm can be suitably used.

Further, the transfer charging blade 74 (ad) has a resistance of 1 × 10 ⁵ to 1 × 10 ⁷ Ω and a thickness of 2 × 10 ⁵ Ω.
mm and a length of 306 mm were used. Transfer was performed by applying a bias of +15 μA to the transfer charging blade 74 under constant current control.

(7) Simultaneous recovery of transfer residual toner during development In each of the image forming units Ua to Ud, transfer residual toner remains on the surface of the photosensitive drum 1 (a to d) after the transfer of the toner image onto the transfer material P. . In the case of this embodiment, the developing device 4 (a) is not provided with a dedicated cleaner for removing the transfer residual toner.
-D) to collect simultaneously with development.

Simultaneous recovery of the development involves developing the transfer residual toner on the photosensitive drum in the next and subsequent steps, that is, charging and exposing the photosensitive drum to form an electrostatic latent image, and developing the electrostatic latent image. This is a method of recovering by a fogging bias (fogging potential difference Vback which is a potential difference between a DC voltage applied to the developing device and a surface potential of the photoconductor). According to this method, the transfer residual toner is collected in the developing device and reused in the subsequent steps, so that waste toner can be eliminated and troublesome maintenance can be reduced. Further, the cleanerlessness has great advantages in terms of space and cost of the apparatus.

The transfer polarity of the transfer residual toner on the photosensitive drum surface after the transfer is often inverted due to peeling discharge or the like at the time of transfer. Is difficult to do.

Therefore, in this embodiment, the toner having a particularly large negative charge amount among the transfer residual toner is used as an auxiliary contact charging member, and a fur brush charger 5 (a to d) to which a positive bias is applied. After the charge is removed or charged to the positive electrode, and then discharged again to the surface of the photosensitive drum 1.

As a result, the transfer residual toner that reaches the magnetic brush chargers 2 (a to d), which are the next main contact charging members, is in a state where the polarity is inverted to the positive electrode, reaches the charging nip n, and The toner is taken into the unit 23 (temporary collection of toner remaining after transfer to the magnetic brush charger). At this time, when not only a negative bias but also an alternating voltage is applied to the magnetic brush charger 2, the transfer residual toner is taken into the magnetic brush portion 23 by the vibration effect of the AC electric field between the photosensitive drum 1 and the magnetic brush charger 2. Is easily performed.

The transfer residual toner taken into the magnetic brush unit 23 becomes a normally charged toner (negatively charged in this embodiment) by rubbing with the magnetic brush, and is simultaneously transferred from the magnetic brush unit 23 to the photosensitive drum 1 surface. The developer is discharged to reach the developing area m, and is simultaneously collected by the developing device 4 by the fogging electric field applied to the developing device 4 and the mechanical rubbing force.

(8) Maintenance of Black Image Quality By the way, the external additive (S) contained in the developer 46 (t + c)
When iO ₂ or titanium oxide) adheres to the charging member 2 or when the resin of the toner adheres to the charging member 2, the resistance value increases and the charging is inhibited. This phenomenon is particularly remarkable at low humidity. A factor for maintaining the chargeability in this state is the resistance value of the charge injection layer 16 of the photoconductor.

According to the studies and experiments conducted by the present inventors, the resistance value of the charge injection layer 16 of the photosensitive member is 23 degrees (° C.) and the relative humidity is 5 degrees.
% Environment, a 6% image ratio, A4 size, 30,000 sheet durability test requires at least 1 × 10 ¹⁴ Ω · cm or less, and preferably 5 × 10 ¹² Ω · cm.

Therefore, in an environment of 23 degrees and a relative humidity of 5%, 5
When the resistance of the charge injection layer 16 is adjusted to be × 10 ¹² Ω · cm, the resistance value variation with respect to the mixing ratio (the weight of water in 1 kg of air) is as shown in FIG. 23 degrees, relative humidity 6
0% is a mixing ratio of 10.5 g / kg, and it can be seen that when the mixing ratio is more than 0%, the resistance value is greatly reduced. At 30 degrees and a relative humidity of 80%, the mixing ratio is 21.6 g / kg, and the resistance value is 3
× 10 ¹⁰ Ω · cm.

FIG. 6 shows the relationship between the sharpness of a 7-point character and the resistance value when the sharpness of the character is evaluated as 5 ranks by a solid line. Although the reproducibility of characters greatly depends on the characteristics of the exposure device 3, in this embodiment, the resolution is 600 dp.
This is the result of performing i.

For reference, the evaluation result at 300 dpi is shown by a dotted line graph. At least 300 dpi
It was found that 1 × 10 ⁹ Ω · cm or more was necessary.
It can be seen that the character image quality does not deteriorate at 00 dpi, preferably at 1 × 10 ¹¹ Ω · cm or more.

FIG. 7 is a diagram showing a change in resistance value with respect to a change in temperature at a mixing ratio of 21.6 g / kg. From this, it was found that the resistance value was increased by the temperature increase, and 1 × 10
^It can be seen that the case where the resistance becomes ¹¹ Ω · cm or more is at least 35 degrees (relative humidity 60%).

Therefore, it can be seen that the character quality is good if the temperature is 35 ° C. or more even in an atmosphere having a mixing ratio of 21.6 g / kg.

FIG. 8 shows the photoconductors around the first to fourth image forming means Ua to Ud from when the main body was turned on in an atmosphere of 30 degrees / 80% (mixing ratio: 21.6 g / kg). FIG. 4 is a diagram illustrating an example of a temperature change. The heat fixing device 8 is provided with a 600 W heater, and the temperature is controlled to 190 ° C. by a thermistor (not shown). When the copying operation is not performed, the heat fixing device 8 serves as a heat source, and the temperature inside the printer body rises.

As can be seen from FIG. 8, the temperature of the fourth image forming means Ud closest to the heat fixing device 8 is the highest,
Degree. Hereinafter, it gradually moves away from the heat fixing device 8,
The temperature rise becomes lower in the order of the third imaging unit Uc, the second imaging unit Ub, and the first imaging unit Ua.

FIG. 9 shows an example of a temperature change around the photoreceptor of each of the first to fourth image forming means Ua to Ud during continuous copying in an atmosphere environment of 30 degrees and a relative humidity of 80%. It is. Also in this case, the temperature rise of the fourth image forming unit Ud closest to the heat fixing device 8 was the highest, that is, 39 degrees. Hereinafter, the third image forming unit Uc, the second image forming unit Ub, and the first image forming unit U sequentially move away from the heat fixing device 8.
The temperature rise decreases in the order of a.

As shown in FIG. 7, 30 ° C. and relative humidity 8
In an atmosphere environment with a 0% mixing ratio of 21 g / kg, 35
When the temperature is higher than 1, the resistance of the photoconductor surface layer is 1 × 10 ¹¹ Ω · cm.
It can be seen that, at the position of the fourth image forming hand projection unit Ud close to the heat fixing device 8, the condition is that the sharpness is sufficient except immediately after the power is turned on. On the other hand, in the other first to third image forming means units Ua to Uc, depending on the frequency of continuous use,
The condition tends to be lower than 5 degrees, and the sharpness is slightly lowered.

Therefore, in this embodiment, the image forming means Ud closest to the heat fixing device 8 is used as a black image forming means. That is, at least the black image forming unit Ud is arranged near the heat fixing device 8 having a higher temperature in the image forming apparatus main body than the other image forming units Ua to Uc.
At least with respect to the black image forming means Ud, it is possible to maintain the image quality (sharpness) of black characters without causing a charge failure under low humidity and without increasing the cost even under high humidity.

Therefore, in the mode in which black-and-white image formation is performed by the black-image formation means Ud, the image quality is maintained even under high humidity, and the black-image formation means and other image formation means are maintained. Even in a mode in which the full-color image or the multi-color image is synthesized and formed by the unit, the quality (sharpness) of the black image component image is maintained even at high humidity, at least for the black image forming unit as described above. Thus, the overall image quality of the combined full-color image or the combined multicolor image including the black image component image is maintained.

<Embodiment 2> (FIGS. 10 and 11) In this embodiment, a case where an atmosphere heater is further used in the image forming apparatus of FIG. In this embodiment, the atmosphere heater is, for example, the heater 50 shown in FIG. A wattage of 30 W was used. The heater 50 is turned on at least when the power of the main body of the printer unit A is turned off, and raises the temperature of the entire main body of the printer unit. Other configurations of the apparatus are the same as those of the image forming apparatuses A and B in FIG.

In the first embodiment, in an atmosphere environment of 30 degrees and a relative humidity of 80%, the image forming means (black image forming means) closest to the heat fixing device 8 until the temperature rises after the power of the main body is turned on. )
Even with Ud, the resistance of the photoconductor surface layer is 1 × 10 ¹⁰ Ω · cm.
In this case, the sharpness of the black image is not sufficient.

In the present embodiment, the problem in this case is improved. That is, FIG.
FIG. 9 is a diagram illustrating an example of a temperature change around the photoconductor of each image forming hand projection unit Ua to Ud when the atmosphere heater 50 is used after the main body power is turned off in a 0% environment.

In this case as well, the lowest point temperature of the fourth image forming means Ud closest to the heat fixing device 8 was 35 ° C., which is the highest. Hereinafter, the lowest point temperature becomes lower in the order of the third image forming unit Uc, the second image forming unit Ub, and the first image forming unit Ua, which sequentially move away from the heat fixing device 8.

Therefore, in this embodiment, the image forming means Ud closest to the heat fixing device 8 is used as a black image forming means. That is, at least the black image forming unit Ud is arranged near the heat fixing device 8 having a higher temperature in the image forming apparatus main body than the other image forming units Ua to Uc.
At least with respect to the black image forming means Ud, it is possible to maintain the image quality (sharpness) of black characters without causing a charge failure under low humidity and without increasing the cost even under high humidity.

Therefore, in the mode in which black-and-white image formation is performed by the black-image formation means Ud, the image quality is maintained even under high humidity, and the black-image formation means and other image formation means are maintained. Even in a mode in which the full-color image or the multi-color image is synthesized and formed by the unit, the quality (sharpness) of the black image component image is maintained even at high humidity, at least for the black image forming unit as described above. Thus, the overall image quality of the combined full-color image or the combined multicolor image including the black image component image is maintained.

<Embodiment 3> In Embodiments 1 and 2,
Although the toner produced by the pulverization method was used as the toner particles t of the developer 46, in this embodiment, the spherical toner t having an average particle diameter of 6 μm produced by the suspension polymerization method has an average diameter of 50 nm. A carrier obtained by externally adding SiO ₂ and titanium oxide having an average particle diameter of 20 nm in a weight ratio of 0.7% was used. As the carrier c, a resin-polymerized magnetic carrier having a saturation magnetization of 150 emu / cm ^{3 and} an average particle diameter of 35 μm was used. A mixture of the toner t and the carrier c at a weight ratio of 6:94 was used as the developer 46.

Since the toner produced by the polymerization method has a nearly spherical shape, the external additive is uniformly coated. For this reason,
The releasability from the photosensitive drum is extremely good. For example, when comparing the transfer efficiency [(toner amount per unit area transferred on paper) / (toner amount per unit area on photosensitive drum)] of the above-mentioned ground toner and polymerized toner, Compared with 90%, the efficiency was as high as 97% when the polymerized toner was used.

Accordingly, the amount of the toner and the external additives collected in the magnetic brush charger 2 is reduced, and the life can be extended in a low humidity environment as compared with the case of the pulverized toner.

According to the research and experiments of the present inventors, in an environment of 23 ° C. and 5% of relative humidity, 6% image ratio, A4 size, 5
In the durability test for 10,000 sheets, the resistance value of the surface layer of the photoconductor is 1 × 1
At 0 ¹⁴ Ω · cm or less, preferably 5 × 10 ¹² Ω · cm, good charge without image defects could be maintained.

<Others> 1) The configuration of the present invention is not limited to the above-described embodiment. In an image forming apparatus in which the developing device 4 also serves as a cleaner, for example, a conductive rubber or a conductive rubber is used as the charging device 2. It is also possible to use a charging roller using a conductive sponge, a charging device that does not rotate even if it is a magnetic brush or a fur brush, or the like.

Further, even if a cleaning means is provided before the charging means 2, the present invention can be applied to all contact-type charging devices.

2) Examples 1 and 2,
In the case of 3, the two-component contact developing method is used, but other developing methods are also effective. Preferably, one-component contact development or two-component contact development, in which the developer is developed in contact with the photoreceptor, is effective in enhancing the simultaneous recovery effect during development.

When the polymerized toner is used as toner particles in the developer as in Example 3, the above-described one-component contact development and two-component contact development, as well as one-component non-contact development and two-component non-contact A sufficient recovery effect can be obtained in other developing methods such as contact development.

3) As an image exposure means for forming an electrostatic latent image, means capable of performing image exposure corresponding to image information, such as laser scanning exposure means and analog image exposure means, can be used.

4) The image carrier may be an electrostatic recording dielectric or the like. In this case, after uniformly injecting and charging the dielectric surface to a predetermined polarity / potential, a static elimination means such as a static elimination needle head, an electron gun, or the like is selectively erasable to write and form an electrostatic latent image.

5) The transfer unit superimposes and transfers the toner image of each image forming unit to an intermediate transfer body such as a transfer belt or a transfer drum in direct synchronization, and then collectively transfers the toner image onto the transfer material P. A transfer method can also be used.

6) A multicolor image forming apparatus can be provided.

7) When an AC voltage (alternating voltage) is included in the bias applied to the contact charging member 2 and the developing device 4, the waveform of the AC voltage may be a sine wave, a rectangular wave, or the like.
A triangular wave or the like can be used as appropriate. Alternatively, a rectangular wave formed by periodically turning on / off a DC power supply may be used. As described above, a bias whose voltage value periodically changes can be used as the waveform of the alternating voltage.

8) A toner image corresponding to required image information is formed and held on the image carrier, and the toner image forming section is positioned at the reading / displaying section to display an image. The image carrier repeatedly forms a display image. There is also an image display device (display device) used for (1). The image forming apparatus of the present invention includes such an image display device.

9) The image forming apparatus may be a direct type image forming apparatus instead of the transfer type.

[0137]

As described above, according to the present invention, in an image forming apparatus using injection charging and having a plurality of image forming means, the developing means having black toner can be used without causing charging failure at low humidity. By arranging the image forming means having a higher temperature than the other image forming means, it becomes possible to maintain the image quality of black characters without increasing the cost even when the humidity is high.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a schematic configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is a schematic diagram of a layer configuration of a photosensitive drum.

FIG. 3 is a schematic diagram of a magnetic brush charger.

FIG. 4 is a structural model diagram of a developing device.

FIG. 5 is a diagram showing a relationship between a mixing ratio and a resistance value of a photoconductor surface layer.

FIG. 6 is a diagram showing a relationship between the sharpness of a character and the resistance value of a photoconductor surface layer.

FIG. 7 is a diagram showing an example of a resistance value change with respect to a temperature change at a mixing ratio of 21 g / kg.

FIG. 8 is a diagram showing an example of a temperature change around the photoconductor of each image forming unit after the main body power is turned on.

FIG. 9 is a diagram illustrating an example of a temperature change around a photoconductor of each image forming unit during continuous copying.

FIG. 10 is a schematic configuration model diagram of an image forming apparatus (provided with an atmosphere heater) according to a second embodiment.

FIG. 11 is a diagram illustrating an example of a temperature change around the photoconductor of each image forming unit when the atmosphere heater is used after the main body power is turned off.

[Explanation of symbols]

A..Printer unit, B..Color image reader, Ua
... Ud... First to fourth image forming means, 1 (a to d).
Photosensitive drum, 2 (ad), magnetic brush charger, 3
(Ad) LED array, 4 (ad) developing device, 6 paper feed cassette, 7 transfer belt device, 8
・ Thermal fixing device, 9 ・ ・ Discharge roller, 10 ・ ・ Discharge tray

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 9/10 G03G 15/02 101 15/02 101 9/10 15/08 507 15/08 507B (72) Inventor Yoshiyuki Komiya 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Koichi Hashimoto 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo F-term (reference) 2H003 BB11 CC04 CC06 2H005 AB06 BA02 CB18 EA01 FA02 2H030 AB02 BB23 BB44 BB63 2H068 AA03 AA05 AA08 AA11 CA37 FC01 FC08 2H077 AD02 AD06 AD13 AD18 AD36 AE06 BA07 DA10 EA03 GA13

Claims (10)

[Claims] The surface has a resistance value of 1 × 10 ⁹ to 1 × 10 ¹⁴ Ω.
An object to be charged having a layer made of a material of cm, a contact charging member for charging the object to be charged, a latent image forming means for forming an electrostatic latent image on a charged surface of the object to be charged, In an image forming apparatus having a plurality of image forming units having a developing unit for developing an image with a developer to form a toner image, at least an image forming unit having a developing unit having a black toner in a developer is used to form another image. An image forming apparatus, wherein the image forming apparatus is disposed at a higher temperature in the image forming apparatus main body than the means section. 2. The image forming apparatus according to claim 1, wherein the member to be charged has a photosensitive layer and a surface layer, and the surface layer has a resin and conductive fine particles. 3. The image forming apparatus according to claim ₂ , wherein the conductive fine particles are SnO ₂ . 4. The image forming apparatus according to claim 1, wherein magnetic particles are in contact with the member to be charged in the contact charging member for charging the member to be charged. 5. The image forming apparatus according to claim 1, wherein a conductive fiber is in contact with the member to be charged in the contact charging member for charging the member to be charged. 6. The developing device according to claim 1, wherein said developing means is a contact developing system for developing an electrostatic latent image as a toner image in a state in which the developer contacts the member to be charged. An image forming apparatus according to claim 1. 7. The developer according to claim 1, wherein the developer contained in said developing means is a developer comprising toner particles and magnetic particles having a resistance value of 1 × 10 ¹¹ Ω · cm or more. An image forming apparatus according to claim 1. 8. The image forming apparatus according to claim 1, wherein the toner particles in the developer contained in the developing unit are toners generated by a polymerization method. 9. A transfer device for transferring a toner image formed on a member to be charged of the image forming unit to another member, wherein the toner remaining on the member after transfer of the toner image is contact-charged. 9. The method according to claim 1, wherein the toner is re-attached to the member to be charged after charging by the member, and part or all of the adhered toner is collected and reused by the developing means.
The image forming apparatus according to any one of the above. 10. The image forming apparatus according to claim 1, wherein a heat source that operates at least when the main body is turned off is provided in the image forming apparatus main body at a position distant from the image forming unit. .