JP2962622B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus in an electrophotographic recording apparatus such as a printer and a copying machine.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic recording apparatus, a method of forming an image by a recording process of charging, exposure, development, transfer, fixing, and cleaning is well known. Generally, a corona charger is used as a charging device in this image forming method.
The need for a high voltage power supply of 5 to 10 kV is dangerous to the human body, and the high voltage power supply is very expensive. In addition, this corona charger generates ozone in order to utilize the problem that the charging potential of the electrostatic latent image carrier fluctuates under the influence of the installation environment, particularly humidity, and the corona discharge phenomenon, There is a problem that the characteristics of the electrostatic latent image carrier are significantly deteriorated and a problem that the human body is adversely affected. To prevent this adverse effect on the human body, an ozone absorption / decomposition filter is provided in the electrophotographic recording apparatus to prevent ozone from flowing out of the apparatus. Since the service life of the ozone absorption / decomposition filter is short, there is also a problem that replacement work must be performed frequently.

In order to solve the above-mentioned problems of the corona charger, Japanese Patent Application Laid-Open Nos. 63-208878, 01-267667, 03-059682, 04-0221875 and 04-028755 have been proposed. No. 021883 and JP-A-04-051265, a conductor is brought into contact with an electrostatic latent image carrier, and a DC voltage or a DC voltage and an AC voltage are applied to the conductor in a superimposed manner. A contact-type charging device for charging a body has been proposed.

In Japanese Patent Laid-Open No. 60-147756, a conductive plate member made of a resilient metal (for example, a phosphor bronze plate) or a conductive rubber (for example, urethane rubber) is brought into contact with an electrostatic latent image carrier. A contact charging device has been proposed in which a DC voltage and an AC voltage are superimposed and applied to the conductive plate member to charge the electrostatic latent image carrier, thereby overcoming the problems of the corona charger. In addition, the charging blade and the cleaning blade of the contact type charging device are formed of the same member, and the charging process and the cleaning process are used together, thereby reducing the number of recording processes, and the electrophotographic recording device becomes complicated and large. Overcoming the problem of having

[0005]

However, in the above-mentioned conventional method, when a toner remaining on the electrostatic latent image carrier after transfer is removed by a cleaning process using a cleaning blade, a large toner having a particle diameter of 4 μm or more is used. Is easy to clean, but the particle diameter is 4μm
The following small particles (for example, a toner having a small particle diameter or an external additive contained in the toner) are difficult to clean, and therefore, the edge of the cleaning blade in contact with the electrostatic latent image carrier and the electrostatic latent image In some cases, the toner passes through the space between the image bearing member and adheres to a contact charging device disposed downstream of the image bearing member.

If such fine particles having a particle diameter of 4 μm or less adhere and adhere to the charging blade and charging roll of the contact charging device, there is a problem that the electrostatic latent image carrier cannot be charged. These fine particles are charged with a polarity opposite to the polarity of the voltage applied to the charging blade and the charging roll for charging the electrostatic latent image carrier, and the fine particles are charged by an electrostatic force. blade,
Attached to a charging roll, an electrostatic latent image carrier and a charging blade,
It is fixed to a charging blade, a charging roll, or the like by being pressed against or rubbed with the charging roll.

The present invention relates to a contact-type charging device for forming an electrostatic latent image on an electrostatic latent image carrier as described above,
When fine particles charged in the opposite polarity to the charged polarity of the electrostatic latent image carrier pass through the cleaner and adhere to the contact charging device arranged downstream thereof, and the electrostatic latent image carrier cannot be charged. It is an object of the present invention to provide an apparatus which can eliminate the above-mentioned problem and stably record a good image over a long period of time.

[0008]

SUMMARY OF THE INVENTION The present invention relates to an image forming apparatus using a contact-type charging device for forming an electrostatic latent image on an electrostatic latent image carrier. To make it difficult for particles of opposite polarity to come out of the developing device,
The developing bias potential and the supply bias potential applied to the toner carrier and the toner supply roll are optimized.

[0009]

According to the present invention, the developing bias potential applied between the electrostatic latent image carrier and the toner carrier and the supply bias applied between the toner carrier and a toner supply member provided adjacent thereto are provided. By optimizing the potential, fine particles having a polarity opposite to the charging polarity of the electrostatic latent image carrier can be transferred from the toner carrier to an adjacent toner supply member. Therefore, fine particles having a polarity opposite to the charging polarity of the electrostatic latent image carrier hardly adhere to and adhere to the contact charging device, and a good image can be stably recorded over a long period of time.

[0010]

FIG. 1 is a schematic structural view of an image forming apparatus using the charging device of the present invention. The electrostatic latent image carrier 101 formed in a drum shape is rotated at a constant peripheral speed in a direction indicated by an arrow a in FIG. This electrostatic latent image carrier 10
Reference numeral 1 denotes a structure in which a photoconductive layer 101b is provided on a conductive support 101a. In the present embodiment, an organic photoconductor having a diameter of 30 MM was used, but a selenium photoconductor, a zinc oxide photoconductor, an amorphous silicon photoconductor, etc. Both can be used.

Next, the image forming process in this embodiment will be described in order. First, a charging device 102 serving as a charging unit provided on the surface of the electrostatic latent image carrier 101 is provided.
Is used to uniformly and uniformly charge the surface of the electrostatic latent image carrier. The charging device 102 will be described later in detail.

In the exposure process, light corresponding to an image signal is irradiated on the electrostatic latent image carrier 101 by an exposure device 103 as an exposure means to form an electrostatic latent image. As the exposure device 103, any of a combination of an LED array and a selfoc lens (trade name) and a combination of a laser and an image forming optical system can be used.

Next, a developing device 104 provided in contact with or pressure contact with the electrostatic latent image carrier 101 is
The electrostatic latent image formed on the electrostatic latent image carrier 101 is developed by adsorbing the toner 106 onto the electrostatic latent image carrier 05 and transporting the toner 106 in the direction of the arrow shown in the figure. In the present embodiment, a reversal developing method is used in which the toner 106 is developed on a portion irradiated on the electrostatic latent image carrier 101 by the exposure device 103.
A developing bias voltage is applied between the conductive support 101a and the toner carrier 105.

With such a configuration, the space between the toner carrier 105 and the electrostatic latent image carrier 101 is provided in the space between the electrostatic latent image carrier 10 and the electrostatic latent image carrier 101.
An electric field is generated due to the electrostatic latent image formed in FIG. Therefore, the charged toner 106 on the toner carrier 105 adheres to the electrostatic latent image carrier 101 by electrostatic force, and a toner image is formed. As the developing device 104, a case of a one-component non-magnetic contact developing device will be described here. However, the developing device 104 is disposed close to the two-component magnetic brush developing device, the one-component magnetic brush developing device, or the electrostatic latent image carrier 101. Any known technique such as a one-component non-magnetic non-contact developing device can be used. The developing device 104 will be described later in detail.

Thereafter, the recording paper 108 stored in the paper cassette 107 is taken out of the paper cassette 107 by the paper feed roll 109, and the rotation of the paper feed roll 1 is stopped.
10, the skew of the recording paper 108 is corrected.
Here, the paper feed roll 110 is activated, the recording paper 108 is sent to the transfer unit, and the transfer device 111 transfers the toner image formed on the electrostatic latent image carrier 101 to the recording paper 108. Then, after that, the recording paper 108 is
The sheet is conveyed to a fixing device 114 composed of a heat roller 2 and a heat roller 113. The heat of the heating roller 113 melts the toner, and the toner penetrates between the fibers of the recording paper 108 by the action of pressure, so that the toner is fixed to the recording paper 108. The fixed recording paper 108 is discharged to the outside of the apparatus by a discharge roll 115.

On the other hand, the residual toner remaining on the electrostatic latent image carrier 101 after the transfer is carried along with the rotation of the electrostatic latent image carrier 101, and is constituted by a cleaning blade 117 and a recovery blade 118. 116 to remove. Thus, the electrostatic latent image carrier 101 is repeatedly used.

Next, a first embodiment of the charging device 102 will be described in detail with reference to FIG. FIG. 2 is a view showing a part of the electrostatic latent image carrier 101 of FIG. 1 and a first embodiment of the charging device 102, and a charging blade 102 as a charging member.
Is shown. This charging blade 102
It is supported by a metallic guide 119, and the antinode or edge of the open end is placed in contact or pressure contact with the electrostatic latent image carrier 101. A DC power supply 120 is connected between the guide 119 and the conductive support 101a of the electrostatic latent image carrier 101. A DC power supply 120 is applied to the charging blade 102 through the guide 119. The polarity of the voltage applied to the charging blade 102 of the DC power supply 120 indicates a negative case. This is because the negative charging type electrostatic latent image carrier 101 is used, and the positive charging type When the electrostatic latent image carrier 101 is used, the polarity of the voltage applied to the charging blade 102 of the DC power supply 120 is positive. This applied voltage value is -1.
As described below in the case of 4 kv, -1 kv to -1.6 k
By applying a voltage in the range of v, the electrostatic latent image carrier 101 can be charged to -400v to -900v.

The charging blade 102 has a short side of 25 m.
m, long side 250 mm. The length 250 mm of the long side of the charging member is determined by the length in the longitudinal direction of the photoconductive layer 101 b of the electrostatic latent image carrier 101. Since the photoconductive layer 101b is difficult to form on the circumference of both ends in the longitudinal direction of 101, the electrostatic latent image carrier is prevented from leaking the current of the DC power supply 120 to the electrostatic latent image carrier 101. The length is slightly shorter than the length of the photoconductive layer 101b in the longitudinal direction. The charging blade 102 was fixed to the guide 119 with a conductive double-sided tape. This fixing method is not limited to the conductive double-sided tape, but may be any method as long as it is electrically conductive.

As a material of the charging blade 102, for example, rubber such as butyl rubber, chloroprene rubber, urethane rubber, silicon rubber, nitrile rubber, styrene rubber, butadiene rubber, fluorine rubber, ethylene propylene rubber, carbon, graphite, ferrite, Aluminum powder, copper powder, bronze powder, stainless steel powder, conductive powder such as titanium oxide, tin oxide, etc., metal powder, metal fiber, etc. are added, and the volume resistance value is 10 ⁶ to 10 ¹³ [Ω · c.
m]. Further, the charging blade 102 is preferably an elastic body in order to make uniform contact with the electrostatic latent image carrier 101, and the thickness of the rubber material when the rubber material as described above is used is:
Those having a range of 0.5 mm to 5 mm are suitable.

Next, a second embodiment in which the charging blade has a two-layer structure of a conductive layer and a resistance layer will be described with reference to FIG. FIG. 3 shows a part of the electrostatic latent image carrier 101 of FIG. 1 and a second embodiment of the charging device 102. As a charging member, a charging blade 123 composed of a conductive layer 121 and a resistive layer 122 is used. Is shown. The charging blade 123 is supported by an insulating guide 124, and the antinode or edge of the open end on the resistance layer 122 side is
The electrostatic latent image carrier 101 is placed in contact or pressure contact with the electrostatic latent image carrier 101 in the same manner as in the first embodiment. A DC power supply 120 is connected between the conductive layer 121 and the conductive support 101a of the electrostatic latent image carrier 101. A DC power supply 120 is applied to the charging blade 123 through the conductive layer 121.
The case where the polarity of the voltage applied to the charging blade 123 of the DC power supply 120 is negative, which is similar to that described in the first embodiment, is a negative charging type electrostatic latent image carrier. When the positively charged electrostatic latent image carrier 101 is used, the DC power supply 12 is used.
The polarity of the voltage applied to the charging blade 123 of 0 is positive.

The conductive layer 121 of the charging blade 123 may be any material as long as it has a volume resistivity of 10 ⁴ Ω · cm or less. For example, a spring metal thin plate such as SK steel, stainless steel, phosphorus A thin plate having a thickness of 10 to 1000 μm such as bronze, copper, nickel silver, beryllium copper, or the like, or a volume resistance value of 10 ⁴ Ω · cm or less, and a suitable contact width with the electrostatic latent image carrier 101 is set to the contact surface. A blade-shaped conductive rubber or a conductive polymer film having a rubber hardness of 90 ° or less (JIS A) is preferable in order to obtain a uniform lengthwise direction. For example, rubber, such as butyl rubber, chloroprene rubber, urethane rubber, silicon rubber, nitrile rubber, styrene rubber, butadiene rubber, and carbon, graphite, ferrite, aluminum powder, copper powder, bronze powder, stainless powder, titanium oxide, tin oxide, etc. Conductive powder, metal powder,
What added metal fibers and the like, polyimide, polyamide, polyester, polystyrene, polycarbonate,
Conductive powder such as carbon, graphite, ferrite, aluminum powder, copper powder, bronze powder, stainless steel powder, titanium oxide, tin oxide, metal powder, metal fiber, etc. Is added.

Examples of the material of the resistance layer 122 of the charging blade 123 include rubber materials such as butyl rubber, chloroprene rubber, urethane rubber, silicon rubber, nitrile rubber, styrene rubber, butadiene rubber, fluorine rubber, and ethylene propylene rubber; Polycarbonate, graphite, ferrite, aluminum powder, copper powder, bronze powder, stainless steel powder, titanium oxide, tin oxide, etc. on soft oily polymer film made of resin such as polyimide, polyamide, polyester, polystyrene, polycarbonate, fluorine resin A conductive powder, a metal powder, a metal fiber, or the like is added, and the volume resistance value of the resistance layer 122 is set to 10 ⁶ to 10 ¹³ [Ω · cm].
Any of these may be used. In the case of a rubber material in order to obtain a suitable contact width with the electrostatic latent image carrier 101 in the longitudinal direction of the contact surface, the rubber hardness is preferably 90 ° or less (JIS A).

In this embodiment, the charging blade 123
The conductive layer 121 is a thin plate of spring stainless steel having a thickness of 100 μm.
m, short side 25mm, long side 250mm urethane rubber with conductive carbon added, volume resistivity 10 ⁸ Ω · c
m, a conductive rubber blade having a rubber hardness of 60 ° (JIS A) was used.

The conductive layer 121 has a volume resistance of 10
Any material may be used as long as it is ⁴ Ωcm or less.
In addition to the above, a metal foil such as an aluminum foil and a copper foil, a conductive tape having a volume resistance value of 10 ⁴ Ω · cm or less may be attached to the resistance layer 122, or various metals may be used. Resistive layer 1 by plating, sputtering, thick film printing, etc.
20 may be formed as the conductive layer 119.

Further, since the charging blade 123 must be elastic to weakly contact or contact the electrostatic latent image carrier 101, at least the conductive layer 121
Alternatively, the resistance layer 122 may be an elastic body.

The method of disposing the charging blade 102 or the charging blade 123 is as follows.
The mounting direction of the first and the second latent images 23 can be changed from the trailing direction as shown in FIGS. 2 and 3 to the counter direction as shown in FIG. The same result as that of the embodiment is obtained.

Next, the third charging member of the charging device 102
5 is shown in FIG. FIG. 5 shows the conductive rubber roll 12.
6 is used as the charging device 102, in which a rubber resistance layer 128 is formed on a conductive shaft 127. The conductive shaft 127 is a metal shaft such as stainless steel, steel, or aluminum. A DC power supply 120 is connected to the conductive shaft 127 and the conductive support 101 a of the electrostatic latent image carrier 101. . Examples of the material of the rubber resistance layer 128 include, for example, butyl rubber, chloroprene rubber, urethane rubber, silicon rubber, nitrile rubber, styrene rubber, butadiene rubber, fluorine rubber, ethylene propylene rubber, and other carbon materials such as carbon, graphite, ferrite, and the like. Conductive powder such as aluminum powder, copper powder, bronze powder, stainless steel powder, titanium oxide, tin oxide, metal powder, metal fiber, etc. are added to make the volume resistance value of the rubber resistance layer 125 10 ⁶ to 10 ¹³ [Ω · c
m]. Further, the rubber hardness is 90 ° or less (JIS A) in order to obtain a suitable contact width with the electrostatic latent image carrier 101 uniformly in the longitudinal direction of the contact surface.
Are preferred.

Further, similarly to the first and second embodiments, the electrostatic latent image carrier 101 and the conductive rubber roll 126 are pressed or contacted to the extent that the residual toner 106 passes. The conductive rubber roll 126 is driven by a driving system (not shown) in a direction (b direction) similar to the rotation direction (a direction) of the electrostatic latent image carrier 101 or a rotation direction of the electrostatic latent image carrier 101. It may be rotated in the same direction (a direction) as above or fixed so as not to rotate.

When the conductive rubber roll 126 is rotated in the following direction (b direction), the peripheral speed of the electrostatic latent image carrier 101 and the peripheral speed of the conductive rubber roll 126 may be different or the same. In particular, when the peripheral speed of the electrostatic latent image carrier 101 and the peripheral speed of the conductive rubber roll 126 are the same, it is particularly preferable that the conductive rubber roll 126 does not become a rotational load of the electrostatic latent image carrier 101. Even when such a conductive rubber roll 126 is used as a charging member, good results can be obtained as in the first and second embodiments.

In the above three embodiments, the charging device 102
Although the case of the charging blades 102 and 123 and the charging roller 126 as the charging member has been described, the charging member is not limited to only these shapes.
A charging belt or the like may be used as long as the volume resistance value of the portion in contact with the electrostatic latent image carrier 101 is in the range of 10 ⁶ to 10 ¹³ [Ω · cm]. Also, the arrangement method is not limited to this, and various changes can be made.

When recording is performed for a long period of time, fine particles adhere to the charging member 102,
In some cases, the electrostatic latent image carrier 101 cannot be charged. The charge polarity and the particle diameter of the substance attached to the charging member 102 were examined. The fine particle toner 106 having a particle diameter of 4 μm or less smaller than the average particle diameter of the positively charged toner 106 and the positively charged toner contained in the toner 106 were measured. They were an external additive, a charge control agent, an internal additive and the like.
Then, in the charging member 102, the area where the charging member 102 and the electrostatic latent image carrier 101 are in contact (the area A in FIG. 2) and the positively charged fine particles before and after the area are in contact with the charging member 102. Can charge the electrostatic latent image carrier 101, but the above-mentioned fine particles positively charged before and after the area where the charging member 102 and the electrostatic latent image carrier 101 are in contact (the area A in FIG. 2) It has been found that if it is fixed, the electrostatic latent image carrier 101 cannot be charged.

Next, the mechanism of generation of positively charged fine particles will be described. FIG. 6 is a cross-sectional view of the non-magnetic one-component contact developing device.
04 is described in detail.
Is a toner supply roll, 130 is a toner layer thickness regulating member, 1
32 is a toner hopper. The toner 106 is stored in the toner hopper 132, and a toner supply roll 131 is disposed below the toner hopper 132. The toner supply roll 131 has an elastic volume resistance around the conductive support (metal core) of 10 ³ to 10.
^A semiconductive surface layer of ¹⁰ [Ω · cm], for example, formed by applying a foaming agent such as a semiconductive foam containing conductive particles such as carbon to silicon rubber, ethylene propylene rubber, or urethane rubber; The surface of the toner supply roll 131 is always covered with the toner 106. When the toner supply roll 131 is driven to rotate in the direction indicated by the arrow (counterclockwise) in the figure, the toner 106 is rotated with the rotation.
Is transported to the toner carrier 105 provided in contact with the toner supply roll 131. Conveyed toner 106
Is a supply bias of a DC power supply 134 connected to the conductive support 101 a of the electrostatic latent image carrier 101 and the toner supply roll 131 and charged by friction when the toner carrier 105 and the toner supply roll 131 come into contact with each other. The toner carrier 105 is transferred to the toner carrier 105 by an electrostatic force due to the potential V _sb, and adheres to the surface of the toner carrier 105 by a self-mirror image generated by the electric charge of the toner 106, and then rotates in a direction indicated by an arrow (counterclockwise) in the figure. It is transported through 105.

A toner layer thickness regulating member 130 is provided on the downstream side where the toner 106 is conveyed. The toner layer thickness regulating member 130 has a uniform thickness of about one to two layers of toner 106 particles on the toner carrier 105. A thin layer is formed and the toner 10
6 is further charged by friction with the toner layer thickness regulating member 130. Toner 1 charged and attached to toner carrier 105
Reference numeral 06 denotes a toner corresponding to the electrostatic latent image formed on the electrostatic latent image carrier 101, which is conveyed to the electrostatic latent image carrier 101 provided in contact with the toner carrier 105 and is exposed by the exposure device 103. the image is developed by the developing bias potential V _db of the DC power supply 133 is connected between the conductive support 101a of the toner carrying member 105 and the latent electrostatic image bearing member 101.

The toner 106 not contributing to the development is transported to the toner supply roll 131 again and collected. In this embodiment, the toner carrier 105 needs to be in contact with the electrostatic latent image carrier 101 with a uniform pressing force over the entire length in the longitudinal direction, and also have a property as a developing electrode near the surface layer. . Therefore, an elastic electric resistance layer (conductive rubber) was applied to a conductive support (metal core), and a thin insulating layer was applied thereon.

As the conductive rubber material, the same material as the rubber resistance layer 128 of the conductive rubber roll 126 in FIG. 5 can be used, and the volume resistance value is 10 ³ to 10 ¹⁰ [Ω · cm].
What is necessary is just to make it. Further, the electrostatic latent image carrier 101
It is desirable to have elasticity with a rubber hardness of 60 degrees (JISA) or less from the necessity of providing a certain contact width by pressing uniformly in the longitudinal direction. Further, since the insulating layer is applied on the elastic member, it has elastic properties such that it can follow the displacement of the conductive rubber thereunder when pressed against the electrostatic latent image carrier 101. You need to have. Urethane, silicon rubber and the like correspond to this.

The specifications of an embodiment of the toner carrier 105 are as follows. A chloroprene rubber having a rubber hardness of 30 degrees (JISA) and a volume resistance of 10 ⁴ Ω · cm is adhered around a metal core having a diameter of 8 MM. About 20 urethane paints
The toner carrier 105 is formed with a thickness of about 100 μm and a final outer mold of about 20 mm with a surface layer roughness of 0.5 to 5 μRZ. Although the toner carrier 105 has a three-layer structure, it may have a two-layer structure in which an elastic electric resistance layer is applied to a conductive support.

On the other hand, the toner 106 is
01 has a negative charge polarity, so that the average volume particle size filled with a negative charge control agent is 9-1.
A non-magnetic toner formed of a styrene-based or polyester-based resin of about 2 μm was used. The friction between the toner supply roll 131 and the toner carrier 105 causes the toner 106 interposed therebetween to be charged to a negative polarity and adhere to the toner carrier 105. The toner 106 may be a magnetic toner obtained by adding a magnetic powder such as iron or ferrite to a resin.

As the toner layer thickness regulating member 130, urethane rubber is used, and the thickness of the toner 106 on the toner carrier 105 is made uniform and uniform, and further charged. In addition to rubber, stainless steel, metal thin plates such as phosphor bronze, nylon, polyester and other high molecular compound materials, or rubber and metal coated with the above high molecular compound can be used to obtain good printing. Can be Further, in order to make the thin layer of the toner 106 adhere uniformly and uniformly on the toner carrier 105 and to perform the optimal triboelectric charging, 40 to 90
A rubber hardness of the degree (JISA) is desirable. When the charge polarity of the electrostatic latent image carrier 101 is positive, a toner that is positively charged is also used.

As described above with reference to FIG. 6, since the developing device 104 has such a structure, the toner 106 is initially contained in the developing device 104 in the developing device.
5. Toner layer thickness regulating member 130, toner supply roll 13
1 charges to a desired negative polarity. However, when recording is performed for a long period of time, the toner 106 that comes into contact with the toner layer thickness regulating member 130, the toner supply roll 131, the electrostatic latent image carrier 101, and the like in the developing device 104 for a long period I will.

The toner 106 is subjected to a mechanical stress, and the external additives, the charge control agent, the internal additives and the like constituting the toner 106 are released from the toner 106, and the external additives, the charge control agent It is thought that some internal additives and the like are charged to a positive polarity. The toner 106 has a certain degree of particle size by a classifier in the production stage of the toner 106, but contains a small amount of fine particles of toner having a particle size much smaller than the average particle size. In addition, due to the mechanical stress as described above, the toner 106 is pulverized in the developing device 104, and the fine particle toner 106 having an extremely small average particle size is generated. Since the toner 106 has been pulverized, the external additives, the charge control agent, the
And is expected to be released from the polymer and to be charged to a positive polarity opposite to the desired polarity.

The positively charged fine particle toner 106 and the like are regularly developed on a non-image portion on the electrostatic latent image carrier 101 to which the light from the exposure device 103 is not irradiated during recording, so that the developing device 104 is developed. From the cleaning blade 117 and the electrostatic latent image carrier 101 along with the rotation of the electrostatic latent image carrier 101, and is carried to the charging member 102, The charging member 102 is electrostatically charged to a positive polarity by an electric field between the electrostatic latent image holding member 101 and the charging member 102 generated by a negative voltage applied to the charging member 102 to charge the electrostatic latent image holding member 101. Fine particle toner 1
06 and an external additive, a charge control agent, an internal additive, etc., which are positively charged and released from the toner 106, adhere to and rub against or press against the electrostatic latent image carrier 101 for a long period of time. It is thought that it will stick.

Until the toner 106 of fine particles charged to the positive polarity, the external additive charged to the positive polarity released from the toner 106, the charge control agent, the internal additive, and the like are fixed to the charging member 102 and the charging failure occurs. Of the number of recorded sheets varies depending on the composition and composition ratio of the toner to be used.
There is no toner that causes charging failure with 0 sheets.
Some toners do not cause charging failure even on sheets. But,
As the toner, it is necessary to faithfully develop the electrostatic latent image formed on the electrostatic latent image carrier 101, and the transfer device 11
Characteristics 1 such as charging performance for improving transferability to the recording paper 108, fixing performance for the recording paper 108 by the fixing device 114, and preservability for storing toner for a long period of time are mainly required. is there. While satisfying these characteristics,
To prevent the toner 106 of fine particles charged to the positive polarity, the external additive positively charged to the positive polarity released from the toner 106, the charge control agent, the internal additive, and the like from being fixed to the charging member 102, and to prevent the occurrence of poor charging. Another solution is to control the composition and composition ratio.

Without changing the composition and composition ratio of the toner,
Regarding a method of not causing charging failure of the charging member 102 or a method of extending the charging life of the charging member 102,
It is described below. A DC power supply 134 connected to the conductive support 101a of the electrostatic latent image carrier 101 and the toner supply roll 131 in the non-magnetic one-component contact developing device of FIG.
A supply bias potential V _sb of the developing bias potential V _db of the DC power supply 133 is connected between the conductive support 101a of the toner carrying member 105 and the latent electrostatic image bearing member 101 2
One bias potential and the charge potential V _s of the latent electrostatic image bearing member 101
Tables 1 to 4 show the relationship with the life of the charging member 102 when the value is changed.

As the charging member 102, the charging blade 10
2 or 123, black streaks are generated in the sub-scanning direction of the recording paper 108, and when the conductive rubber roll 126 is used as the charging member 102, the conductive rubber roll in the sub-scanning direction of the recording paper 108 is used. A black dot having the same pitch as the circumference of the recording paper 126 is generated, and eventually a black stripe is generated in the sub-scanning direction of the recording paper 108. The number of printed sheets on which the image was faithfully developed was defined as the charging life of the charging member 102.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

[0048]

[Table 4]

[0049] Table 1, -900 V charge potential V _s of the latent electrostatic image bearing member 101, a development bias potential V _db -400 V
This is a result when the supply bias potential V _sb is changed while _{keeping the} voltage constant. Table 2 shows the charged potential V of the electrostatic latent image carrier 101.
_s a -700 V, the developing bias potential V _db and -400V constant is the result when varying the supplied bias voltage V _sb.

From Tables 1 and 2, the difference between the supply bias potential V _sb and the developing bias potential V _db is | V _sb −V _db |> 200 (1) However, | V _sb |> | V _db | For example, the charging life of the charging device 102 is 6,000 or more in terms of the number of printed sheets, which is good. However, | V _sb −V _db | ≦ 200 (2) However, in the case of | V _sb |> | V _db | The charging life of 102 is 600
0 or less.

Next, under the conditions satisfying the expression (1), -900 V charge potential V _s of the latent electrostatic image bearing member 101, | V _sb -
V _db | = a 300V constant, the result when changing the developing bias potential V _db in Table 3, -700 V charge potential V _s of the latent electrostatic image bearing member _{101, | V sb -V db |} = 300V
Table 4 shows the results when the developing bias potential _Vdb was changed to be constant.

[0052] From Table 3 and 4, the difference between the charge potential V _s of the latent electrostatic image bearing member 101 and the developing bias potential V _db is _{| V s -V db | <700} (3) However, | V _s |> if, charging life of the charging device 102 is turned over 6,000 sheets in the number of printed sheets, is good, even under the conditions satisfying the expression _{(1), | | | V db V s} -V db | ≧ 700 However, | V _s |> | V _db | (4), the charging life of the charging device 102 is 600
It will be 0 or less.

The results of Tables 1 to 4 are summarized as follows.
Assuming that the charging potential of the electrostatic latent image carrier 101 is V _s , the developing bias potential is V _db , and the supply bias potential is V _sb , equation (1)
By setting the developing bias potential V _db and the supply bias potential V _sb so as to satisfy the following condition, the fine particles charged to the positive polarity are supplied from the toner supply roll 131 to the toner carrier 1.
05, the positively charged fine particles on the toner carrier 105
Can be transferred to

[0054] Also, the charge potential of the electrostatic latent image bearing member 101 so as to satisfy the equation (3) and V _s development bias potential V _db
Is set, it is possible to make it difficult for the positively charged fine particles on the toner carrier 105 to be transferred to the electrostatic latent image carrier 101.

That is, an electric field is applied to the toner carrier 105 and the electrostatic latent image carrier 1 so that the positively charged fine particles hardly transfer from the toner carrier 105 to the electrostatic latent image carrier 101.
It can be seen that it suffices to form the gap between the two. Also, an electric field in which positively charged fine particles hardly transfer from the toner supply roll 131 to the toner carrier 105 or an electric field in which positively charged fine particles easily transfer from the toner support 105 to the toner supply roll 131. Can be formed between the toner carrier 105 and the toner supply roll 131.

In this embodiment, the voltage to the charging member 102 at the time of recording is shown only by the DC voltage, but a contact charging method in which DC and AC are superimposed and applied to the charging member 102 may be used. In this case, by optimizing the bias potentials V _sb and V _db of the positive polarity fine particles adhering to the charging member 102,
It is possible to make it hard to come out of the developing device 104. Also,
Needless to say, the charging blade of the contact-type charging device can be used in various contact charging methods such as a method in which the cleaning blade is formed of the same member and the charging process and the cleaning process are combined.

The image forming apparatus according to the present invention includes a cleaner 116.
However, in the case where the cleaner 116 for collecting the residual toner after the transfer on the electrostatic latent image carrier 101 is not provided, not only the positively charged fine particles but also the positively charged toner It may adhere to the charging device 102. Thus, the method can be used even without known cleaners such as rubber blades, brushes, etc., and is more effective than with a cleaner.

[0058]

As described above, according to the present invention, in an image forming apparatus using a contact-type charging device for forming an electrostatic latent image on an electrostatic latent image carrier, an electrostatic latent image is formed. By optimizing the development bias potential applied between the image carrier and the toner carrier and the supply bias potential applied between the toner carrier and the toner supply member provided adjacent thereto, the electrostatic latent Fine particles having a polarity opposite to the charge polarity of the image carrier can be transferred from the toner carrier to an adjacent toner supply member, and the fine particles having the opposite polarity can be hardly emitted from the developing device for a long period of time. Fine particles having a polarity opposite to the charge polarity of the electrostatic latent image carrier hardly adhere to and adhere to a contact charging device such as a charging roll, and an excellent effect that a good image can be stably recorded over a long period of time can be obtained. It is.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus using a charging device of the present invention.

FIG. 2 is a diagram showing a first embodiment of a charging device.

FIG. 3 is a diagram showing a second embodiment of the charging device.

FIG. 4 is a diagram showing a modification of the charging device.

FIG. 5 is a view showing a third embodiment of the charging device.

FIG. 6 is a sectional view of a non-magnetic one-component contact developing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Electrostatic latent image carrier 102 Charging device 103 Exposure device 104 Developing device 105 Toner carrier 106 Toner 107 Paper cassette 108 Recording paper 109 Feed roll 110 Feed roll 111 Transfer device 112 Pressure roll 113 Heating roll 114 Fixing device 115 Discharge Roll 116 Cleaner 117 Cleaning Blade 118 Recovery Blade 119 Guide

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/08 G03G 15/00 303 G03G 15/06 101

Claims (1)

(57) [Claims] An electrostatic latent image carrier for carrying an electrostatic latent image;
A charging device provided in contact with the electrostatic latent image carrier, a developing device having at least a toner carrier for carrying toner, and a toner supply member for supplying the toner to the toner carrier; In a reversal development type image forming apparatus for forming a toner image corresponding to the electrostatic latent image formed on the electrostatic latent image carrier on the surface of the electrostatic latent image carrier, the toner supply member is provided with the toner carrier The relationship between the charging potential Vs of the electrostatic latent image carrier, the bias potential Vdb applied to the toner carrier, and the bias potential Vsb applied to the toner supply member, An image forming apparatus characterized by setting so as to satisfy the following.