JP4621565B2 - Charge applying device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a charge imparting device that imparts a charge to a charge imparting surface of a charge imparting member, and an image forming apparatus such as a copying machine, a printer, and a facsimile equipped with the same.

  As this type of charge imparting device, a discharge device such as a corona charger is widely known. Generally, a discharge case is provided with a conductive case around a wire electrode made of platinum, tungsten, or the like, or a needle electrode made of a stainless material or the like. Then, by applying a DC or AC high voltage bias between the electrode and the case, the molecules present in the air around the electrode are ionized and ionized, and the ions are applied to the charge application surface of the charge application member. It is made to adhere and an electric charge is provided to the to-be-charged surface. In such a discharge device, molecules in the air are ionized by the discharge, so that discharge products such as ozone and nitrogen oxide (NOx) are generated. Such discharge products are known to cause various problems, and there is a problem of reducing the generation amount.

  On the other hand, a charge imparting device using an electron emitting member that emits electrons in an electric field is also known. As this electron emission member, it is known that a carbon nanomaterial can be used. Among carbon nanomaterials, carbon nanotubes have a high electron emission ability and are suitable for charge imparting devices. A charge imparting device using such an electron emitting member ionizes molecules by applying an electric field to the electron emitting member and attaching electrons emitted from the electron emitting member to molecules in the air. And the ion is made to adhere to the to-be-charged surface of a to-be-charged member, and an electric charge is provided to the to-be-charged surface. In the above discharge device, molecules in the air are ionized to generate ions, so a discharge product is generated. In the charge imparting device using the electron emitting member, molecules in the air are ionized to generate ions. There is no need. Therefore, according to the charge imparting device using the electron emitting member, it is possible to impart charges without generating a discharge product.

For example, Patent Document 1 discloses a carbon nanotube applied to a charge imparting device.
In the charge applying device described in Patent Document 1, the carbon nanotube formed on the electrode is disposed opposite to the photosensitive member as the member to be charged, and an electric field is formed between the electrode and the photosensitive member to generate electrons from the carbon nanotube. To release. Patent Document 1 discloses a non-contact type charge imparting device in which a carbon nanotube and a photoconductor are arranged in a non-contact manner, and a contact type charge imparting device in which a carbon nanotube and a photoconductor are brought into contact with each other. . However, the contact-type charge imparting device wears due to contact with the photoconductor on which the carbon nanotubes move or the foreign matter on the photoconductor adheres to the carbon nanotubes, so that the electron emission ability of the carbon nanotubes over time. There is a drawback that it is easy to deteriorate. Therefore, a non-contact type charge imparting device which does not have such a defect is more suitable than a contact type charge imparting device.

JP 2001-250467 A

  However, as in the non-contact type charge imparting device described in Patent Document 1, when one of the electrodes that forms an electric field for causing the electron emitting member to emit electrons is a charge imparting member, the following is performed. Problems occur. That is, it is extremely difficult to set the distance between the surface to be charged and the electrode to a desired distance due to an assembly error between the member to be charged and the electrode, an installation error, or the like. Therefore, the electric field formed between the member to be charged and the electrode cannot be kept constant. As a result, the amount of electron emission from the electron emission member is not constant, and there is a problem that a desired amount of charge cannot be applied to the surface to be charged.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a desired charge amount for the charge-giving member in a configuration in which an electron-emitting member is used to charge the charge-giving member. It is an object to provide a charge applying device and an image forming apparatus provided with the same.

In order to achieve the above object, a first aspect of the present invention provides a charge imparting device for imparting charge to a charge imparting surface of a charge imparting member for forming an electric field between two electrodes facing each other. An electric field forming portion, an electron emitting member that emits electrons in an electric field, provided in an opposite position of one of the electrodes constituting the electric field forming portion, and the other electrode and the electron emission the ions generated in the formed ion generating space between the members possess an outlet opening for discharging to the ion generating space outside the electron-emitting member is generated by the ion generating space ion Is composed of a plurality of electron emission portions arranged along a direction orthogonal to the ion movement direction moving toward the exit opening .
According to a second aspect of the present invention, in the charge imparting device according to the first aspect, the plurality of electron emission portions are arranged over a region corresponding to the charged surface in a direction orthogonal to the ion movement direction. It is characterized by.
According to a third aspect of the present invention, there is provided a charge imparting device for imparting electric charge to a charge imparting surface of a charge imparting member, an electric field forming unit for forming an electric field between two electrodes facing each other, An electron-emitting member that emits electrons in an electric field and is formed between the other electrode and the electron-emitting member, provided at an opposing position of one of the electrodes that constitute the electric field forming unit. And an exit opening for discharging ions generated in the ion generation space to the outside of the ion generation space, and ions generated in the ion generation space move toward the exit opening. A plurality of electric field forming portions are arranged along the direction, the electron emitting members are respectively provided on any one of the electrodes constituting each electric field forming portion, and in order from the electric field forming portion located on the downstream side in the ion movement direction Electric To form and is characterized in that a field control means for controlling the respective electric field forming unit.
According to a fourth aspect of the present invention, in the charge imparting device according to any one of the first to third aspects, the electrode surfaces of the two electrodes facing each other are planes parallel to each other, and the electron emission The member is an electron-emitting layer having a substantially uniform thickness provided on the electrode surface of any one of the electrodes .
Ion addition, the invention of claim 5 is the charging device according to any one of claims 1 to 4, the outlet opening or its vicinity of the ion generating space, generated in the ion generating space Is provided with a movement control electrode for forming a moving electric field for moving the electric charge to the surface to be charged, the voltage applied to one of the electrodes is A [V], and the voltage applied to the other electrode is B [ V], and when the voltage applied to the movement control electrode is C [V], each voltage satisfies the following relational expression (1).
| A |> | B |> | C | (1)
The invention according to claim 6 is the charge applying device according to any one of claims 1 to 5 , further comprising a space enclosing member surrounding the ion generation space, wherein the space enclosing member is the outlet opening. And an intake opening for taking in outside air.
The invention according to claim 7 is the charge applying device according to any one of claims 1 to 6, further comprising an electrode support mechanism that supports the two electrodes and maintains a constant distance between the electrodes. It is characterized by having.
Further, the invention according to claim 8 is the charge imparting device according to claim 7 , wherein the ions generated in the ion generation space are moved to the charge application surface at or near the exit opening of the ion generation space. An insulative fixing member having a grid type movement control electrode for forming an electric field, and fixing the electrode support mechanism to the grid type movement control electrode and the two electrodes on the movement control electrode It is characterized by comprising.
According to a ninth aspect of the present invention, a charge imparting member, charge imparting means for imparting charge to the charge imparting surface of the charge imparting member, and a recording medium using the charge imparting member are provided. in the image forming apparatus and an image forming unit for forming an image, as the charging unit, it is characterized in that using the charging device according to any one of claims 1 to 8.
According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect , the charge imparting member is a latent image carrier, and the charge imparting device uniformly charges the surface of the latent image carrier. The image forming unit forms a latent image on the surface of the latent image carrier uniformly charged by the charge applying device, and then converts the latent image into a visible image. The image is formed by transferring onto the recording material.
According to an eleventh aspect of the present invention, in the image forming apparatus according to the ninth or tenth aspect , the charge applying device has the outlet opening in a direction substantially perpendicular to an electrode facing direction in which the two electrodes face each other. And the outlet opening is arranged so as to face the charge application surface of the charge application member.

In the present invention, an electron-emitting member is provided on one of the two electrodes facing each other, and the other electrode is provided so as to face this. As a result, electrons are emitted from the electron emission member by the electric field formed between the two electrodes, and the electrons adhere to the molecules in the air, so that they are formed between the other electrode and the electron emission member. Ions can be generated in the ion generation space. Then, the charge imparting surface of the charge imparting member is made to face the outlet opening, and ions discharged from the outlet opening move to the charge imparting member, so that charge is imparted to the charge imparting surface. Is done.
In the present invention, the other electrode is not a member to be charged, but is a component of the charge applying device like any one of the electrodes. Therefore, it becomes easier to set the distance between these electrodes to a desired distance as compared to the conventional configuration in which the other electrode is a member to be charged. Therefore, it becomes easy to maintain the electric field formed in the electric field forming part constant, and as a result, the amount of electron emission from the electron emission member can be easily made constant.

  As described above, according to the present invention, it is possible to obtain an excellent effect that it is easier to apply a desired amount of charge to the member to be charged than in the conventional configuration.

Hereinafter, an embodiment in which the present invention is applied to a laser printer (hereinafter simply referred to as “printer”) as an image forming apparatus will be described.
FIG. 2 is a schematic configuration diagram of the printer according to the present embodiment.
This printer is a printer for forming a monochromatic image, and has a photosensitive drum 1 as a latent image carrier as a member to be charged. The photosensitive drum 1 has a diameter of 30 [mm], and is driven to rotate at a surface movement speed of 200 [mm / sec] in the direction of arrow A in the figure by a driving unit (not shown). The surface (charged imparting surface) of the photosensitive drum 1 is uniformly charged by a charging device 10 that is a charge imparting device. The distance between the outlet opening of the charging device 10 and the surface of the photosensitive drum 1 is set to 1 [mm]. The charging device 10 discharges negative ions from the exit opening and attaches them to the surface of the photosensitive drum 1 to perform a charging process. Details of the charging device 10 will be described later.

  The surface of the photosensitive drum 1 after the charging process is irradiated while scanning with light L based on image information by an optical writing unit (not shown) as a latent image forming unit. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 1. This electrostatic latent image becomes a toner image by being developed by the developing device 2 as developing means. The toner image moves to a region (transfer region) facing the transfer roller 3 as a transfer unit by the rotation of the photosensitive drum 1. On the other hand, the transfer paper P as a recording material fed from a paper feed cassette (not shown) is sent toward the transfer area at a predetermined timing by a pair of registration rollers (not shown). The transfer paper P is transported so as to pass through the transfer region in a state where it is supported on the surface of the paper transport belt 4 as a recording material transport means. A predetermined transfer bias is applied to the transfer roller 3 to form a transfer current in the transfer region. As a result, when the transfer paper P passes through the transfer region, the toner image on the photosensitive drum 1 is moved to the transfer paper P side due to the influence of the transfer current, and transfer is performed. After the transfer is completed, the transfer paper P is conveyed into a fixing device 5 as fixing means. The fixing device 5 fixes the toner image on the transfer paper P to the transfer paper P by heat and pressure. The transfer paper P after fixing is discharged out of the apparatus.

  Untransferred toner remaining on the photosensitive drum 1 without being transferred is removed from the surface of the photosensitive drum 1 by a cleaning unit 6 as a cleaning unit. Further, the residual charge on the photosensitive drum 1 is removed by a static elimination lamp 7 as a static elimination means. In this embodiment, the transfer residual toner is removed by the cleaning unit 6. However, a known cleaner-less configuration is adopted, and the transfer residual toner may be collected by the developing device 2 or the like without providing the cleaning unit 6. Good.

Next, the charging device 10 which is a characteristic part of the present invention will be described in detail.
FIG. 1 is a schematic configuration diagram of the charging device 10 according to the present embodiment when viewed from the photosensitive drum axial direction.
The charging device 10 includes electrodes (hereinafter referred to as “electron emission side electrodes”) 11a and 11b made of aluminum or the like on both sides of the photosensitive drum surface movement direction (left and right direction in the drawing). Electron emission layers 12a and 12b, which are electron emission members, are formed on the inner surfaces of the charging devices of the electron emission side electrodes 11a and 11b, respectively. The electron emission layers 12a and 12b are obtained by dispersing and fixing thin film or powder electron emission elements. Further, the charging device 10 includes a counter electrode 13 made of aluminum or the like at the center of the photosensitive drum surface movement direction (left and right direction in the figure). These electrodes 11a, 11b, and 13 are respectively fixed to an insulating support member 14 made of resin or the like that constitutes an electrode support mechanism. By this insulating support member 14, the distance between each electron emission side electrode 11 a, 11 b and the counter electrode 13 is maintained at a desired distance. The space (ion generation space) B between the electron emission side electrodes 11a and 11b and the counter electrode 13 is closed by the insulating support member 14 on the side opposite to the side facing the photoconductive drum 1. The side facing the photosensitive drum 1 is opened, and outlet openings 15a and 15b are formed.

  In the present embodiment, the charging device 10 has an electric field forming portion formed by each of the electron emission side electrodes 11a and 11b to which a voltage is applied from a DC power source (not shown) as a voltage applying unit and the grounded counter electrode 13. The When a voltage is applied to each of the electron emission side electrodes 11a and 11b, an electric field is formed between the electron emission side electrodes 11a and 11b and the counter electrode 13. Thereby, electrons are emitted from the electron-emitting devices constituting the electron-emitting layers 12a and 12b. The emitted electrons are attached to gas molecules (oxygen, carbon dioxide, nitrogen, etc.) existing in the ion generation space B, or molecules to which water is attached, and negatively ionize these molecules. The negative ions generated in this manner exit from the exit openings 15 a and 15 b and adhere to the surface of the photosensitive drum 1. As a result, the surface of the photosensitive drum 1 is negatively charged.

According to the charging device 10 of the present embodiment, the generation amount of ozone, NOx, etc. generated in a conventional charging device (discharge device) employing a corona charging method or the like can be greatly reduced. Hereinafter, this point will be described.
Generally, when charging is performed using corona discharge, a great amount of ozone and NOx are generated. This is because ions generated by corona discharge collide with gas molecules and are ionized to generate ions. Specifically, the energy of electrons emitted from the corona wire is 30 [eV] or more, whereas the ionization energy of nitrogen molecules is 24.3 [eV] and the ionization energy of oxygen molecules is 8 [eV]. This is because when electrons from a corona wire collide with nitrogen molecules or oxygen molecules, these molecules are easily ionized.
On the other hand, in the charging device 10 of the present embodiment, the voltage applied to the electron emission side electrodes 11a and 11b is a voltage that does not generate discharge in the ion generation space B, in other words, a voltage that does not exceed the threshold voltage according to Paschen's discharge law. Therefore, no discharge occurs in the ion generation space B. In addition, in the present embodiment, an electron-emitting device made of an sp3 binding 5H-BN material is used. When this electron-emitting device is used, the energy emitted from the electron-emitting device is about 6 [eV], so that ionization does not occur even when the emitted electrons collide with gas molecules. Therefore, according to the present embodiment, ions can be generated without generating discharge products such as ozone and NOx.

The sp3 bonding 5H-BN material is a kind of boron nitride which has the same bonding state as diamond and is hard next to diamond. Boron nitride is a material generally used for crucibles and the like, and has excellent heat resistance and resistance to chemical substances. Therefore, boron nitride is an electronic material that has unprecedented durability and can withstand high loads. The manufacturing method is that a mixed gas plasma (diborane: borohydride B ₂ H ₆ , hydrogen, ammonia, argon) is simultaneously defocused (slightly condensed) on a substrate such as silicon or nickel (wavelength λ: 193 [nm]). , Frequency f: 1030 [Hz]). A feature is that a large number of spindle shapes with sharp tips of about 10 [μm] are formed on the surface of the thin film aligned with the laser irradiation direction and function as an electron emission emitter.

  In the present embodiment, electron emission layers 12a and 12b in which a thin film layer made of sp3-bonded 5H-BN material or a layer in which powder is fixed are formed on the electron emission side electrodes 11a and 11b are used as the electron emission members. As a fixing method, a binder such as a conductive resin may be used, and the production may be performed by a printing method, sputtering, or the like. Preferably, it is desirable to deposit a large amount of particles on the surface of the electron emission layer. In this embodiment, the electron emission layers 12a and 12b obtained by dispersing and bonding the sp3 bonding 5H-BN material by dispersing a thin film or particles are adhered to the surfaces of the electron emission side electrodes 11a and 11b with a conductive adhesive. The electron emission side electrodes 11a and 11b on which the electron emission layers 12a and 12b are formed are arranged to face each other with a gap between them. When a voltage is applied to each of the electron emission side electrodes 11a and 11b, the emission of electrons from the electron emission layers 12a and 12b is started, and the emitted electrons adhere to gas molecules, so that the counter electrode 13 and the electron emission layer are Negative ions are generated in each ion generation space B between 12a and 12a.

  In this embodiment, sp3 binding 5H-BN is used as a material constituting the electron emission member from the viewpoint of stability and life, but other electron emission materials such as CNT (carbon nanotube), DLC (diamond) are used. A material such as (like carbon) can be used in the same manner.

Here, in order to obtain the amount of electron emission required to charge the surface of the photosensitive drum to a desired potential, the surface areas of the electron emission layers 12a and 12b need to be sufficiently large. In order to obtain the same charging ability as that of the present embodiment by using the configuration in which the electron emission layer 12a is opposed to the photosensitive drum 1 as in the prior art, assuming that the voltage conditions are the same, the photosensitive in the conventional charging device is the same. The length of the body drum surface moving direction (left and right direction in FIG. 1) is equal to or longer than the total length of the two electron emitting layers 12a and 12b in FIG.
In contrast, in the present embodiment, as shown in FIG. 1, the electron emission layer 12a is disposed opposite to the counter electrode 13 different from the photosensitive drum 1, and the surface directions of the electron emission layer 12a and the counter electrode 13 are photosensitive. The body drum 1 is configured to be parallel to the surface normal direction. In this case, the length in the moving direction of the photosensitive drum surface in the charging device 10 does not depend on the surface area of the electron emission layers 12 a and 12 b and is determined by the distance between the electron emission side electrode 11 a and the counter electrode 13. Since this interval is very narrow, 300 [μm] in this embodiment, the length of the charging device 10 in the moving direction of the photosensitive drum surface is significantly shorter than that of the conventional charging device. Therefore, according to this embodiment, space saving around the photosensitive drum can be achieved. In this embodiment, the length of the charging device 10 in the movement direction of the photosensitive drum surface is about 1.5 mm.

[ Layer Reference Example 1 ]
Next, a reference example of the electron emission layers 12a and 12b provided on the electron emission side electrodes 11a and 11b (hereinafter, this reference example is referred to as “ layer reference example 1 ”) will be described.
FIG. 3 is a front view of the electron emission layer 12a provided on one of the electron emission side electrodes 11a in Reference Example 1 of this layer . Since the same applies to the other electron emission layer 12b, the description thereof is omitted.
In the present embodiment, the electron emission side electrode 11 a is a rectangular parallelepiped member that is elongated along the axial direction of the photosensitive drum 1, and the length in the longitudinal direction is an image region (electrostatic potential) on the surface of the photosensitive drum 1. Longer than the area where a latent image can be formed. The electron emission side electrode 11a is disposed so as to face the entire image region in the longitudinal direction. In Reference Example 1 of this layer , the electron emission layer 12a provided on the electron emission side electrode 11a is a single layer formed integrally, and faces the entire image region in the longitudinal direction. Placed in.

In this layer reference example 1 , an applied voltage of −1200 [V] is applied to the electron emission side electrode 11a, and as a result, the photoreceptor is driven to rotate at a surface moving speed (linear velocity) of 200 [mm / s]. The surface of the drum 1 was charged uniformly at −400 [V].

[ Layer Reference Example 2 ]
Next, another reference example of the electron emission layers 12a and 12b provided on the electron emission side electrodes 11a and 11b (hereinafter, this reference example is referred to as “ layer reference example 2 ”) will be described.
FIG. 4 is a front view of the electron emission layer 12a provided on one electron emission side electrode 11a in Reference Example 2 of this layer . Since the same applies to the other electron emission layer 12b, the description thereof is omitted.
In this layer reference example 2 , the electron emission layer 12a provided on the electron emission side electrode 11a is composed of two electron emission portions elongated in the longitudinal direction of the electron emission side electrode 11a (photosensitive drum axis direction). The electron emission portions are arranged side by side in a direction orthogonal to the longitudinal direction. As in the case of the layer reference example 1 , the electron emission layer 12a is also arranged so as to face the entire image region in the longitudinal direction.
In this layer reference example 2 , the same charging ability as in the case of the layer reference example 1 was obtained.

[Layer configuration example 3]
Next, a configuration example of the electron emission layers 12a and 12b provided on the electron emission side electrodes 11a and 11b (hereinafter, this configuration example will be referred to as “layer configuration example 3”) will be described.
FIG. 5 is a front view of the electron emission layer 12a provided on one of the electron emission side electrodes 11a in the third layer configuration example 3. Since the same applies to the other electron emission layer 12b, the description thereof is omitted.
In this layer configuration example 3, the electron emission layer 12a provided on the electron emission side electrode 11a is a row in which a large number of electron emission portions are arranged in the longitudinal direction of the electron emission side electrode 11a (photosensitive drum axis direction). These two rows are arranged side by side in a direction perpendicular to the longitudinal direction. As in the case of the layer reference example 1 and the layer reference example 2 , the electron emission layer 12a is also arranged so as to face the entire image region in the longitudinal direction. And in this layer structural example 3, it is comprised so that the electron emission part of the other row | line | column may be located in the location corresponding to the clearance gap between the electron emission parts in one row | line | column. Thereby, even when a large number of electron emission portions are arranged side by side in the longitudinal direction of the electron emission side electrode 11a, unevenness of the electron emission amount of the entire charging device in the longitudinal direction can be reduced.
Also in this layer configuration example 3, the same charging ability as in the case of the layer reference example 1 and the layer reference example 2 was obtained.

In the above-described layer reference examples 1 , 2 and 3, the case where the two electron emission layers 12a and 12b have the same layer configuration has been described. However, the electron emission layers 12a and 12b have different layer configurations. Also good. For example, it is also possible to the layer in Reference Example 1 was employed in one of the electron emission layer 12a, adopting the layer in Reference Example 2 in the other of the electron-emitting layer 12b.

[Layer configuration example 4]
Next, another configuration example of the electron emission layers 12a and 12b provided on the electron emission side electrodes 11a and 11b (hereinafter, this configuration example will be referred to as “layer configuration example 4”) will be described.
FIG. 6 is a front view showing electron emission layers 12a and 12b provided on the two electron emission side electrodes 11a and 11b in the present layer configuration example 4, respectively.
In this layer configuration example 4, the electron emission layer 12a provided on one electron emission side electrode 11a has a large number of electron emission portions arranged side by side in the longitudinal direction of the electron emission side electrode 11a (photosensitive drum axis direction). It is a thing. The electron emission layer 12b provided on the other electron emission side electrode 11b also has a large number of electron emission portions arranged side by side in the longitudinal direction of the electron emission side electrode 11b (photosensitive drum axis direction). These electron emitting layers 12a, 12b, as in the case of each layer in Reference Example 1, 2 and 3 described above, For the longitudinal direction are arranged so as to face the image area throughout. Then, this layer configuration example 4 is configured such that the electron emission portion on the other electron emission side electrode 11b is located at a position corresponding to the gap of the electron emission portion provided on one electron emission side electrode 11a. ing. Thereby, even when a large number of electron emission portions are arranged side by side in the longitudinal direction of each of the electron emission side electrodes 11a and 11b, it is possible to reduce unevenness of the electron emission amount of the entire charging device in the longitudinal direction.
Even the layer configuration example 4, the same charge capacity as that of each layer in Reference Example 1, 2 and 3 described above were obtained.

[Modification 1]
Next, a modification of the charging device in the above embodiment (hereinafter, this modification is referred to as “modification 1”) will be described.
FIG. 7 is an explanatory diagram when the charging device 110 of the first modification is viewed from the photosensitive drum axial direction.
The basic configuration of the charging device 110 is the same as that of the above-described embodiment, but the modification 1 is different in that the electron emission layers 112a and 112b are provided on the counter electrode 13 side in the above-described embodiment. That is, in the first modification, the counter electrode 13 in the above embodiment functions as the electron emission side electrode 111, and the electron emission side electrodes 11a and 11b in the above embodiment function as the counter electrodes 113a and 113b.
In the first modification, a grid type for forming a moving electric field for moving negative ions generated in the ion generation space B to the surface of the photosensitive drum 1 between the ion generation space B and the surface of the photosensitive drum 1. This is also different from the above embodiment in that a grid electrode 116 which is a movement control electrode is provided.

  In the charging device 110 according to the first modification, electron emission layers 112a and 112b, which are electron emission members, are provided on both surfaces of the electron emission side electrode 111 provided in the center of the photosensitive drum surface movement direction (left and right direction in the drawing). Each is formed. The electron emission layers 112a and 112b are the same as those in the above embodiment. In the first modification, the electric field forming section is formed by the electron emission side electrode 111 to which a voltage is applied from the first DC power supply 117 and the counter electrodes 113a and 113b to which a voltage is applied from the second DC power supply 118, respectively. It is formed. When a voltage is applied to these electrodes 111, 113a, 113b, an electric field is formed between the electron emission side electrode 111 and the counter electrodes 113a, 113b. As a result, electrons are emitted from the electron-emitting devices constituting the electron-emitting layers 112a and 112b, and negative ions are generated in the ion generation space B.

  Further, the grid electrode 116 provided in the charging device 110 of the first modification is made of stainless steel, and a voltage is applied to the grid electrode 116 from the grid power source 119. As the grid electrode 116, a stainless steel plate having a honeycomb structure conventionally used in a scorotron charger is used. However, the grid electrode 116 is not limited to this. A conductive plate member having a conductive film or a hole can also be used. The distance between the electron emission side electrode 111 and the ends of the counter electrodes 113a and 113b and the grid electrode 116 is set to a distance at which Paschen discharge does not occur. In the first modification, the distance is set to 500 [μm]. The interval between the grid electrode 116 and the surface of the photosensitive drum 1 is 1 [mm].

In the first modification, after negative ions are generated in the ion generation space B, the negative ions are generated on the surface of the photosensitive drum 1 by the moving electric field formed by the voltage applied to the grid electrode 116. Move towards. In order to realize the generation and movement of such negative ions, the voltage applied to the electron emission side electrode 111 is set to A [V], the voltage applied to the counter electrodes 113a and 113b is set to B [V], and the grid electrode 116 is set. When the voltage applied to is C [V], each voltage satisfies the following relational expression (1).
| A |> | B |> | C | (1)
By satisfying this relational expression (1), electrons emitted from the electron emission layers 112a and 112b on the electron emission side electrode 111 move toward the counter electrodes 113a and 113b, which are gas molecules in the ion generation space B. And negative ions are generated. Then, the generated negative ions move to the grid electrode 116 side. Since the surface charge amount of the photosensitive drum 1 before the start of the charging process is reduced to near 0 [V] by the charge eliminating lamp 7, the negative ions that have moved to the grid electrode 116 side pass through the grid electrode 116 and are exposed to light. It adheres to the surface of the body drum 1. Then, when the surface charge amount of the photosensitive drum 1 becomes substantially equal to the voltage applied to the grid electrode 116, the movement of negative ions to the surface of the photosensitive drum 1 is stopped. Thus, according to the first modification, the movement of negative ions to the surface of the photosensitive drum 1 can be promoted by the moving electric field formed by the voltage applied to the grid electrode 116.

  In the first modification, −1200 [V] is applied from the first DC power supply 117 to the electron emission side electrode 111, and −800 [V] is applied from the first DC power supply 118 to each of the counter electrodes 113 a and 113 b, and the grid −650 [V] was applied from the power source 119 to the grid electrode 116. As a result, the surface of the photosensitive drum 1 that was rotationally driven at a surface moving speed (linear speed) of 200 [mm / s] was charged uniformly at −600 [V]. In the above embodiment, as described above, since the surface charge amount of the photosensitive drum 1 was −400 [V], it was confirmed that the charging ability was improved by the grid electrode 116.

[Modification 2]
Next, another modified example of the charging device in the above embodiment (hereinafter, this modified example is referred to as “modified example 2”) will be described.
FIG. 8 is a schematic configuration diagram when the charging device 210 according to the second modification is viewed from the photosensitive drum axial direction.
The basic configuration of the charging device 210 is the same as that of the first modification, but the second modification is different in that four ion generation spaces B are provided. Specifically, counter electrodes 213a, 213b, and 213c are provided at three locations on the center and both sides in the direction of movement of the photosensitive drum surface (left and right in the figure), and electrons are respectively disposed between the counter electrodes 213a, 213b, and 213c. Emission side electrodes 211a and 211b are provided. Electron emission layers 212a, 212b, 212c, and 212d, which are electron emission members, are formed on both surfaces of each electron emission side electrode 211a and 211b. Note that the voltage applied to each electrode is the same as in the first modification.

  According to the second modification, the total area of the electron emission layers 212a, 212b, 212c, and 212d is about twice that of the first modification, and the amount of electron emission in the entire charging device can be greatly increased. As a result, the amount of ions generated in the ion generation space B per unit time can be greatly increased, and the charging ability can be greatly increased. As a result, when the photosensitive drum 1 is rotated at a high speed, even in the case where it is difficult to sufficiently charge in the first modification, the second modification can be sufficiently charged.

[Modification 3]
Next, still another modified example of the charging device in the above embodiment (hereinafter, this modified example is referred to as “Modified Example 3”) will be described.
FIG. 9 is a schematic configuration diagram of the charging device 310 according to the third modification as viewed from the photosensitive drum axial direction.
The basic configuration of the charging device 310 is the same as that of the first modification. However, in the third modification, intake openings 320 a and 320 b for taking outside air into each ion generation space B are provided in the insulating support member 314. Is provided. That is, the charging device 310 of the third modification includes an insulating support member 314 and electrodes 311, 313 a, and 313 b as space enclosing members, and encloses the ion generation space B by these. Then, exit openings 315a and 315b in the ion movement direction (downward in the drawing) in which ions generated in the ion generation space B move in the ion generation space toward the surface of the photosensitive drum 1, and in the ion generation space B And intake openings 320a and 320b for taking in outside air.

In the above-described embodiment and Modifications 1 and 2, since the ion generation space B is configured to communicate with the outside only by the outlet openings 315a and 315b, the air flow is poor and negative from the outlet openings 315a and 315b. It is difficult to extract ions efficiently. In the third modification, since the intake openings 320a and 320b are provided in addition to the outlet openings 315a and 315b, the intake openings are formed in the ion generation space due to the movement of negative ions exiting from the outlet openings 315a and 315b. An airflow is generated from 320a and 320b toward the outlet openings 315a and 315b. Due to this air flow, negative ions in the ion generation space are more likely to exit from the outlet openings 315a and 315b. As a result, the negative ions generated in the ion generation space can be efficiently moved to the surface of the photosensitive drum 1, and the charging ability can be improved.
In particular, if the intake openings 320a and 320b are provided at positions facing the outlet openings 315a and 315b as in the third modification, a linear air flow can be created in the ion generation space B. The negative ions in the ion generation space can be extracted from the outlet openings 315a and 315b more efficiently.

The configuration in which the intake openings 320a and 320b are provided as in the third modification is effective even in a configuration in which no grid electrode is present as in the above embodiment.
In the third modification, the case where the intake openings 320a and 320b are provided at positions facing the outlet openings 315a and 315b has been described. However, the intake openings 320a and 320b may be provided at positions not facing the outlet openings 315a and 315b. . For example, as shown in FIG. 10, intake openings 320a and 320b may be formed in the counter electrodes 313a and 313b. In this case, as shown in FIG. 10, the intake openings 320a and 320b are preferably formed at positions away from the outlet openings 315a and 315b, and the electron emission layers 312a and 312b on the electron emission side electrode 311 are formed. It is preferable to form in the location which does not oppose. Further, a passage 321 for communicating the two ion generation spaces B may be provided in the electron emission side electrode 311.
In the third modification, each of the intake openings 320a and 320b is one opening that opens over almost the entire length of each ion generation space B in the longitudinal direction (axial direction of the photosensitive drum). You may make it open only to a part of scale direction, and you may make it comprise by several opening part.
Further, a fan or the like as an airflow generation means may be provided so that outside air is actively sent into the ion generation space B from the intake openings 320a and 320b. In this case, a fast air flow toward the exit openings 315a and 315b can be generated in the ion generation space B, and negative ions in the ion generation space can be more efficiently emitted from the exit openings 315a and 315b. Become. As the airflow generation means used in this case, a fan or the like installed for other purposes in the printer body may be used.

[Modification 4]
Next, still another modification of the charging device according to the above-described embodiment (hereinafter, this modification is referred to as “Modification 4”) will be described.
FIG. 11 is an explanatory diagram when the charging device 410 of the fourth modification is viewed from the photosensitive drum axial direction.
The basic configuration of the charging device 410 is the same as that of the third modification, but in the fourth modification, the layer reference example 2 described above is adopted as the electron emission layers 412a and 412b provided on the electron emission side electrode 411. Is different in that The counter electrode is also different from Modification 3 in that each counter electrode is provided at a position facing each of the two electron emission portions in each of the electron emission layers 412a and 412b.
Specifically, insulating electrode support members 422a and 422b are provided on both sides of the photosensitive drum surface movement direction (left and right direction in the figure), respectively, and electrodes facing the electron emission portions constituting the electron emission layers 412a and 412b are provided. Opposing electrodes 413a, 413b, 413c, and 413d are provided at locations on the support members 422a and 422b, respectively. The counter electrodes 413a and 413c are electrodes arranged at positions away from the outlet openings 415a and 415b, and the counter electrodes 413b and 413d are electrodes arranged at positions near the outlet openings 415a and 415b. .

  In the fourth modification, in each of the two ion generation spaces B, an electric field forming portion constituted by the electron emission side electrode 411 and each of the counter electrodes 413a, 413b, 413c, 413d is a negative generated in the ion generation space B. Two ions are arranged along the ion movement direction (downward in the drawing) in which the ions move in the ion generation space B toward the surface of the photosensitive drum 1. Hereinafter, the electric field forming part on the side away from the outlet openings 415a and 415b is referred to as an upstream electric field forming part, and the electric field forming part on the side close to the outlet openings 415a and 415b is referred to as a downstream electric field forming part.

  In the fourth modification, the voltage from the second DC power supply 118 applied to each counter electrode 413a, 413b, 413c, 413d is controlled by the control unit 423 as an electric field control means. Specifically, the applied voltage to each of the counter electrodes 413a, 413b, 413c, and 413d is controlled so that an electric field is formed in order from the downstream electric field forming unit located on the downstream side in the ion movement direction (downward in the figure).

  Specifically, first, the control unit 423 applies a voltage of −800 [V] to the counter electrodes 413b and 413d in order to form an electric field in the downstream electric field forming unit, and an electric field is applied to the upstream electric field forming unit. A voltage of −1200 [V] is applied to the counter electrodes 413a and 413c so as not to be formed. The applied voltage of the electron emission side electrode 411 is −1200 [V] as described above. Thereby, a region corresponding to the downstream electric field forming portion in the ion generation space B (hereinafter referred to as “downstream region”), that is, a region in the ion generation space B near the outlet openings 415a and 415b (in the drawing). Negative ions are generated in the lower half region), and a region corresponding to an upstream electric field forming portion in the ion generation space B (hereinafter referred to as “upstream region”), that is, an outlet opening 415a in the ion generation space B, Negative ions are not generated in the region away from 415b (the upper half region in the figure). Then, the negative ions generated in the downstream region in the ion generation space B are applied to the surface of the photosensitive drum 1 by the electric field generated by the voltage applied to the upstream region in addition to the moving electric field generated by the grid electrode 416. Move efficiently toward.

  Subsequently, the control unit 423 applies a voltage of −800 [V] to the counter electrodes 413a and 413c so as to form an electric field in the upstream electric field forming unit, and opposes so that no electric field is formed in the downstream electric field forming unit. A voltage of −1200 [V] is applied to the electrodes 413b and 413d. As a result, negative ions are generated in the upstream region in the ion generation space B, and no negative ions are generated in the downstream region in the ion generation space B. At this time, a voltage of −1200 [V] is applied to the portion of the electron emission side electrode 411 constituting the downstream side electric field forming portion and the counter electrodes 413b and 413d, and therefore the upstream region in the ion generation space B. The negative ions generated in (1) cannot move to the downstream region but remain in the upstream region.

  Next, the control unit 423 again applies a voltage of −800 [V] to the counter electrodes 413b and 413d so as to form an electric field in the downstream electric field forming unit, and prevents an electric field from being formed in the upstream electric field forming unit. A voltage of −1200 [V] is applied to the counter electrodes 413a and 413c. As a result, negative ions are generated in the downstream region in the ion generation space B, and the negative ions remaining in the upstream region in the ion generation space B move to the downstream region. Then, the negative ions generated in the downstream region and the negative ions that have moved from the upstream region to the downstream region move toward the surface of the photosensitive drum 1 by the moving electric field by the grid electrode 416.

By repeatedly performing such voltage control, negative ions generated in the upstream region in the ion generation space B can be sequentially moved to the surface of the photosensitive drum, and are generated in the upstream region in the ion generation space B. The movement of negative ions can be promoted. When such voltage control is not performed, the negative ions generated in the region in the ion generation space B far from the surface of the photosensitive drum 1 are on the counter electrode side from the outlet opening side even when the grid electrode is provided. The power drawn to is stronger. For this reason, it becomes difficult to efficiently move the negative ions generated in the region to the exit opening side, and as a result, the negative ions generated in the ion generation space B are efficiently attached to the surface of the photosensitive drum 1. I can't. On the other hand, in the fourth modification, by performing the voltage control as described above, negative ions generated in the region (upstream region) in the ion generation space B away from the surface of the photosensitive drum 1 are efficiently generated. Since it can be moved to the exit opening side, the negative ions generated in the ion generation space B can be efficiently attached to the surface of the photosensitive drum 1.
In particular, by appropriately setting the voltage application switching timing between the upstream electric field forming unit and the downstream electric field forming unit, the negative ions are moved to the surface of the photosensitive drum 1 while accelerating the moving speed of the negative ions. Can be made. In this case, higher charging ability can be obtained.

In the fourth modification, the layer reference example 2 is adopted as the electron emission layers 412a and 412b. However, the same effect can be obtained by using other layer configuration examples. For example, when the layer reference example 1 is adopted, the configuration is as shown in FIG.

[Modification 5]
Next, still another modified example of the charging device in the above embodiment (hereinafter, this modified example is referred to as “modified example 5”) will be described.
FIG. 13 is a schematic configuration diagram of the charging device 510 according to the fifth modification as viewed from the photosensitive drum axial direction.
The basic configuration of the charging device 510 is the same as that of the fourth modification, but the fifth modification is different in that the voltage applied to the electron emission side electrodes 511a, 511b, 511c, and 511d is controlled. Specifically, counter electrodes 513a and 513b are provided on both sides of the photosensitive drum surface movement direction (left and right direction in the figure), and an insulating electrode support member 522 is provided at the center of the photosensitive drum surface movement direction. Then, two electron emission side electrodes 511a, 511b, 511c, and 511d are provided on both surfaces of the electrode support member 522 along the ion movement direction (vertical direction in the figure), respectively, and electron emission is performed on each electron emission side electrode. Layers 512a, 512b, 512c, and 512d are formed. The electron emission side electrodes 511a and 511c are electrodes arranged at positions away from the outlet openings 515a and 515b, and the electron emission side electrodes 512b and 512d are arranged at positions near the outlet openings 515a and 515b. Electrode. Therefore, in the fifth modification, in each of the two ion generation spaces B, the upstream-side electric field forming unit constituted by the electron emission side electrodes 511a and 511c and the counter electrodes 513a and 513b, the electron emission side electrode 511b, A downstream-side electric field forming unit configured by 511d and the counter electrodes 513a and 513b is provided.

  Even in such a configuration, negative ions generated in the upstream region within the ion generation space B are sequentially moved to the surface of the photosensitive drum by performing the same control as the voltage control described in the fourth modification. And the movement of the negative ions generated in the upstream region in the ion generation space B can be promoted. As a result, negative ions generated in the ion generation space B can be efficiently attached to the surface of the photosensitive drum 1.

[Modification 6]
Next, still another modified example (hereinafter, this modified example is referred to as “modified example 6”) of the charging device according to the above-described embodiment will be described.
FIG. 14 is a schematic configuration diagram of the charging device 610 of Modification 6 when viewed from the photosensitive drum axial direction.
The basic configuration of the charging device 610 is the same as that of the first modification, but in the sixth modification, movement control counter electrodes 624a and 624b are arranged on the insulating support member 614 that faces the grid electrode 616. Is different. A voltage higher than the applied voltage (−650 [V]) of the grid electrode 616, for example, −800 [V] is applied to the movement control counter electrodes 624a and 624b from a power source (not shown). Thereby, a stronger moving electric field that moves negative ions in the ion generation space B to the outlet openings 615a and 615b can be formed between the grid electrode 616 and the movement control counter electrodes 624a and 624b. As a result, the movement of the negative ions generated in the ion generation space B can be promoted, and the negative ions generated in the ion generation space B can be efficiently attached to the surface of the photosensitive drum 1.

  In particular, by controlling the applied voltage of at least one of the electron emission side electrode 611 and the counter electrodes 613a and 613b, the time when the electric field is formed in the electric field forming part constituted by these electrodes 611, 613a and 613b and the electric field are not formed. The timings may be alternately realized, and the voltage may be applied to the movement control counter electrodes 624a and 624b only in the latter timing. In this case, during voltage application to the movement control counter electrodes 624a and 624b, a moving electric field is formed in the ion generation space B to move the negative ions straight from the movement control counter electrodes 624a and 624b to the grid electrode 616. Therefore, negative ions generated in the ion generation space B can be more efficiently attached to the surface of the photosensitive drum 1.

[Modification 7]
Next, still another modified example of the charging device in the above embodiment (hereinafter, this modified example is referred to as “modified example 7”) will be described.
FIG. 15 is a schematic configuration diagram of the charging device 710 according to Modification 7 when viewed from the photosensitive drum axial direction.
The basic configuration of the charging device 710 is the same as that of the first modification. In the seventh modification, an electrode support mechanism that maintains a constant distance between the electron emission side electrode 711 and the counter electrodes 713a and 713b is used. The difference is that an insulating spacer 725 is used. More specifically, the spacer 725 has an insertion portion 725a, and the insertion portion 725a is fitted between the electron emission side electrode 711 and the counter electrodes 713a and 713b so that each of the electrodes 711, 713a and 713b It is attached to both ends in the longitudinal direction (left and right direction in the figure). By providing such a spacer 725, the distance between the electron emission side electrode 711 and the counter electrodes 713a and 713b can be stably maintained at a distance corresponding to the thickness of the insertion portion 725a. Since the insertion portion 725a can be easily manufactured with high accuracy so that the thickness thereof becomes a desired thickness, the distance between the electron emission side electrode 711 and the counter electrodes 713a and 713b is set to a desired distance. It can be maintained stably. As a result, a stable electric field can be formed in the electric field forming portion, and unevenness in the amount of electron emission from the electron emission layers 712a and 712b can be suppressed. Therefore, a stable amount of negative ions can be generated in the ion generation space B. As a result, the surface of the photosensitive drum 1 can be charged uniformly.

[Modification 8]
Next, still another modified example (hereinafter, this modified example is referred to as “modified example 8”) of the charging device according to the above-described embodiment will be described.
FIG. 16 is a schematic configuration diagram of the charging device 810 according to Modification 8 when viewed from the photosensitive drum axial direction.
The basic configuration of the charging device 810 is the same as that of the first modification, but in this eighth modification, an electrode support mechanism that maintains a constant distance between the electron emission side electrode 811 and the counter electrodes 813a and 813b. The difference is that the grid electrode 816 is used. More specifically, the electrode support mechanism of Modification 8 includes a grid electrode 816, a fixing portion as an insulating fixing member for fixing the electron emission side electrode 811 and the counter electrodes 813 a and 813 b on the grid electrode 816. 816a. The fixing portion 816a is fixed on the grid electrode 816 with a predetermined interval, and the electron emission side electrode 811 and the counter electrodes 813a and 813b are attached to each fixing portion 816a. Thus, the distance between the electron emission side electrode 811 and the counter electrodes 813a and 813b can be stably maintained at a distance corresponding to the interval between the fixing portions 816a provided on the grid electrode 816. Since each fixing portion 816a can be fixed on the grid electrode 816 with high accuracy and easily so as to have a desired interval, the distance between the electron emission side electrode 811 and the counter electrodes 813a and 813b is set to a desired value. The distance can be maintained stably. As a result, a stable electric field can be formed in the electric field forming portion, and unevenness in the amount of electron emission from the electron emission layers 812a and 812b can be suppressed. Therefore, a stable amount of negative ions can be generated in the ion generation space B. As a result, the surface of the photosensitive drum 1 can be charged uniformly.

As described above, the charging devices 10, 110, 210, 310, 410, 510, 610, 710, and 810 of the above-described embodiment (including the above-described configuration examples and modifications of the respective layers) are the charge-giving members. 2 is a charge imparting device that imparts an electric charge to an image area surface that is a surface to be charged of the photosensitive drum 1. The charging device includes two electrodes 11a, 11b, 1111, 211a, 211b, 311, 411, 511a, 511b, 511c, 511d, 611, 711, 811 which are two electrodes facing each other, 113a, 113b, 213a, 213b, 213c, 313a, 313b, 413a, 413b, 413c, 413d, 513a, 513b, 613a, 613b, 713a, 713b, 813a, 813b And electron emission as an electron emission member that emits electrons in an electric field, provided at an opposite position of one of the electrodes (electron emission side electrode) that constitutes the electric field forming portion, facing the other electrode (counter electrode) Layers 12a, 12b, 112a, 112b, 212a, 212b, 212c, 2 2d, 312a, 312b, 412a, 412b, 412c, 412d, 512a, 512b, 512c, 512d, 612a, 612b, 712a, 712b, 812a, 812b, and ion generation formed between the counter electrode and the electron emission layer It has exit openings 15a, 15b, 115a, 115b, 315a, 315b, 415a, 415b, 515a, 515b, 615a, 615b for discharging ions generated in the space B to the outside of the ion generation space. . Thus, when an electric field is formed in the electric field forming portion, electrons are emitted from the electron emission layer, and the electrons adhere to molecules in the air, thereby generating negative ions in the ion generation space B. By moving to the drum 1, negative ions adhere to the image area surface of the photosensitive drum 1, and charge is applied to the image area surface. In the above embodiment, the counter electrode is not the photosensitive drum 1 but is a component of the charging device like the electron emission side electrode. Therefore, compared to the conventional configuration in which the counter electrode is the photosensitive drum 1, it is easy to set the distance between these electrodes to a desired distance. As a result, it becomes easy to maintain the electric field formed in the electric field forming portion constant. As a result, the amount of electron emission from the electron emission layer can be easily stabilized, and a desired charge amount can be imparted to the photosensitive drum 1. Easy to do. Moreover, in the charging device of the above embodiment, since the counter electrode of the electron emission layer is not the photosensitive drum 1, the photosensitive material is not attacked and oxidized and burned by attacking an organic material such as polycarbonate. Film abrasion can also be reduced and the life of the photoreceptor can be extended. In addition, according to the charging device of the above-described embodiment, it is not necessary to generate discharge products such as ozone and NOx when the photosensitive drum 1 is charged. Further, since the voltage applied to the charging device can be reduced as compared with the conventional corona charging and roller charging methods, energy saving can be achieved.
In the above embodiment, the electrode surfaces of the electron emission side electrode and the counter electrode facing each other are planes parallel to each other, and the electron emission member is provided on the electrode surface of the electron emission side electrode with a substantially uniform thickness. This is an electron emission layer. With such a configuration, unevenness in the amount of electron emission from the electron emission layer can be easily suppressed. As a result, it becomes easy to impart a desired charge amount to the photosensitive drum 1 without unevenness.
In the layer reference example 1 and the layer reference example 2 , the electron emission layer is in a direction orthogonal to the ion movement direction in which the negative ions generated in the ion generation space B move toward the exit opening. It extends over a region corresponding to the image region surface of the photosensitive drum (in the longitudinal direction). Thereby, it becomes possible to secure the maximum surface area of the electron emission layer within a limited range, and a large electron emission amount can be ensured.
In the layer configuration example 3 and the layer configuration example 4, a plurality of electron emission portions are arranged along the longitudinal direction. When the electron emission layer is a layer that is long in the longitudinal direction as in the layer reference example 1 and the layer reference example 2 , unevenness in the electron emission ability occurs in the longitudinal direction due to manufacturing errors of the layer. There are many cases. For this reason, unevenness in the amount of electron emission occurs in the longitudinal direction, resulting in unevenness in the amount of generated ions, and uneven charging is likely to occur on the photosensitive drum 1 in the longitudinal direction. On the other hand, if a plurality of electron emission portions are arranged along the longitudinal direction, even if there is some unevenness in the electron emission ability between the individual electron emission portions, these electron emission portions are randomly selected. By disposing a plurality along the longitudinal direction, the unevenness of electron emission ability in the entire longitudinal direction is averaged. As a result, unevenness in the amount of electron emission in the longitudinal direction is suppressed, so that unevenness in the amount of generated ions is also suppressed, and uneven charging on the photosensitive drum 1 in the longitudinal direction can be suppressed.
In particular, in the layer configuration example 3 and the layer configuration example 4, a plurality of electron emission portions are arranged over a region corresponding to the image region surface of the photosensitive drum 1 in the longitudinal direction. That is, in the longitudinal direction, the electron emission portions are arranged without a gap in a region corresponding to the image region surface of the photosensitive drum 1. Therefore, uneven charging on the photosensitive drum 1 in the longitudinal direction can be further suppressed.
Moreover, in the said modification 4, a some electric field formation part is arrange | positioned along the said ion movement direction, and electron emission layer 412a, 412b, 412c, 412d is respectively arranged in the electron emission side electrode 411 which comprises each electric field formation part. A control unit 423 is provided as an electric field control means for controlling each electric field forming unit so as to form an electric field in order from the downstream electric field forming unit located on the downstream side in the ion movement direction. As a result, negative ions generated in a region in the ion generation space B away from the image region surface of the photosensitive drum 1 can be efficiently moved toward the exit openings 415a and 415b. as possible out to impart negative ions generated efficiently to the image area surface of the photosensitive drum 1.
Further, in each of the above modifications, a movement control electrode for forming a moving electric field for moving negative ions generated in the ion generation space B to the image region plane at or near the exit opening of the ion generation space B Grid electrodes 116, 216, 316, 416, 516, 616, 716, and 816, the voltage applied to the electron emission side electrode is A [V], the voltage applied to the counter electrode is B [V], When the voltage applied to the grid electrode is C [V], each voltage satisfies the above relational expression (1). Thus, negative ions generated in the ion generation space B can be moved toward the image area surface of the photosensitive drum 1 by the action of the electric field generated in the ion generation space B. Therefore, negative ions in the ion generation space B can be efficiently applied to the image area surface of the photosensitive drum 1.
Moreover, in the said modification 3, it has the insulating support member 314 and the electrodes 311, 313a, and 313b as a space enclosure member surrounding the ion generation space B, and this space enclosure member includes the outlet openings 315a and 315b and the outside air. Intake openings 320a and 320b for taking in. As a result, an air flow from the intake openings 320a and 320b toward the exit openings 315a and 315b can be generated in the ion generation space, and negative ions in the ion generation space B can be easily emitted from the exit openings 315a and 315b. . As a result, the negative ions generated in the ion generation space can be efficiently moved to the image area surface of the photosensitive drum 1, and the charging ability can be improved. In addition, as a result of being able to take in new air into the ion generation space B, ionization of gas molecules by electrons emitted from the electron emission layer can be stabilized, and stable charging becomes possible.
In the above embodiment, the insulating support members 14, 214, 314, 414, 514, and 614 serve as an electrode support mechanism that supports the electron emission side electrode and the counter electrode and maintains the distance between these electrodes constant. , 714, 814. As a result, the distance between the electron emission side electrode and the counter electrode can be stably maintained at a desired distance. As a result, a stable electric field can be formed in the electric field forming portion, and unevenness in the amount of electron emission from the electron emission layer can be suppressed. Therefore, a stable amount of negative ions can be generated in the ion generation space B. As a result, the surface of the photosensitive drum 1 can be charged uniformly. In particular, in Modification Example 7, since the electrode support mechanism is configured by the insulating support member 714 and the spacer 725, the distance between the electron emission side electrode and the counter electrode can be easily set to a desired distance. It is.
Moreover, in the said modification 8, the electrode support mechanism is comprised from the grid electrode 816 and the fixing | fixed part 816a as an insulating fixing member for fixing an electron emission side electrode and a counter electrode on a grid electrode. . Thereby, it becomes easy to set the distance between the electron emission side electrode and the counter electrode to a desired distance.
The printer according to the above embodiment uses the photosensitive drum 1 as a member to be charged, charge applying means for applying charge to the image area surface of the photosensitive drum 1, and the photosensitive drum 1. The image forming apparatus includes an image forming unit that forms an image on the transfer paper P that is a recording material. The charging devices 10, 110, 210, 310, 410, 510, 610, 710, and 810 are used as the charge applying means.
In particular, in the above-described embodiment, the charging device has an outlet opening in a direction (ion movement direction) substantially orthogonal to the electrode facing direction in which the electron emission side electrode and the counter electrode face each other. Are arranged so as to face the image area surface of the photosensitive drum 1. As a result, the length of the charging device in the moving direction of the photosensitive drum surface does not depend on the surface area of the electron emission layer, but is determined by the distance between the electron emission side electrode and the counter electrode. Therefore, even if the surface area of the electron emission layer is increased in order to increase the amount of electron emission so as to obtain a large charging capability, the length of the charging device in the moving direction of the surface of the photosensitive drum is not increased, and the area around the photosensitive drum is saved. Space can be achieved.

In the above-described embodiment, a printer for forming a single color image has been described as an example. However, the present invention can be similarly applied to an image forming apparatus for forming a multicolor image. In particular, in a so-called tandem type image forming apparatus provided with a photoconductor for each color as shown in FIG. 17, downsizing around the photoconductor is very useful, and the above-described charging device provided for each photoconductor is described above. It is extremely useful to use the charging devices 10, 210, 310, 410, 510, 610, 710, and 810.
In the above-described embodiment, the case where the present invention is applied to a charging device that uniformly charges the photosensitive drum 1 has been described. However, the present invention can also be applied to other charge applying devices. For example, a static eliminator to which the present invention is applied instead of the static eliminator lamp 7 can be used as the static eliminator, or a transfer apparatus to which the present invention is applied instead of the transfer roller 3 can be used as the transfer means.
Further, the present invention can be similarly applied to a charge applying device mounted on a device other than the image forming apparatus.

FIG. 2 is a schematic configuration diagram when the charging device of the printer according to the embodiment is viewed from the photosensitive drum axial direction. FIG. 2 is a schematic configuration diagram of the printer. The front view of the electron emission layer provided on the electron emission side electrode in layer reference example 1 . The front view of the electron emission layer provided on the electron emission side electrode in Layer Reference Example 2 . 14 is a front view of an electron emission layer provided on an electron emission side electrode in Layer Configuration Example 3. FIG. The front view of the electron emission layer provided on the electron emission side electrode in the layer structural example 4. FIG. FIG. 6 is an explanatory diagram when the charging device of Modification 1 is viewed from the photosensitive drum axial direction. FIG. 9 is a schematic configuration diagram when the charging device of Modification 2 is viewed from the photosensitive drum axial direction. FIG. 10 is a schematic configuration diagram when the charging device of Modification 3 is viewed from the photosensitive drum axial direction. The schematic block diagram which shows the other example of the charging device. Explanatory drawing when the charging device of the modification 4 is seen from the photosensitive drum axial direction. The schematic block diagram which shows the other example of the charging device. FIG. 10 is a schematic configuration diagram when the charging device of Modification 5 is viewed from the photosensitive drum axial direction. FIG. 10 is a schematic configuration diagram when the charging device of Modification 6 is viewed from the photosensitive drum axial direction. FIG. 10 is a schematic configuration diagram when the charging device of Modification 7 is viewed from the photosensitive drum axial direction. FIG. 10 is a schematic configuration diagram when the charging device of Modification 8 is viewed from the axial direction of the photosensitive drum. 1 is a schematic configuration diagram of a tandem type image forming apparatus.

Explanation of symbols

1 Photosensitive drum 10, 210, 310, 410, 510, 610, 710, 810 Charging device 11a, 11b, 1111, 211a, 211b, 311, 411, 511a, 511b, 511c, 511d, 611, 711, 811 Electron emission Side electrodes 12a, 12b, 112a, 112b, 212a, 212b, 212c, 212d, 312a, 312b, 412a, 412b, 412c, 412d, 512a, 512b, 512c, 512d, 612a, 612b, 712a, 712b, 812a, 812b Release layer 13, 113a, 113b, 213a, 213b, 213c, 313a, 313b, 413a, 413b, 413c, 413d, 513a, 513b, 613a, 613b, 713a, 713b, 813a, 813b Pole 14, 214, 314, 414, 514, 614, 714, 814 Insulating support members 15a, 15b, 115a, 115b, 315a, 315b, 415a, 415b, 515a, 515b, 615a, 615b Outlet openings 116, 216 316, 416, 516, 616, 716, 816 Grid electrode 117 First DC power source 118 Second DC power source 119 Grid power source 320a, 320b Intake opening 422a, 422b, 522 Electrode support member 423 Control unit 624a, 624b Movement control counter electrode 725 spacer

Claims (11)

In the charge imparting device for imparting charge to the charge imparting surface of the charge imparting member,
An electric field forming part for forming an electric field between two electrodes facing each other;
An electron-emitting member that is provided at an opposite location facing the other electrode in any one of the electrodes constituting the electric field forming portion, and emits electrons in an electric field;
The ions generated in the ion generating space formed between the said other electrode and the electron emitting member possess an outlet opening for discharging to the ion generating space outside,
The electron emission member includes a plurality of electron emission portions arranged along a direction orthogonal to an ion movement direction in which ions generated in the ion generation space move toward the exit opening. A charge imparting device characterized by that.   The charge imparting device according to claim 1.
  The charge application device, wherein the plurality of electron emission portions are arranged over a region corresponding to the charge application surface in a direction orthogonal to the ion movement direction.   In the charge imparting device for imparting charge to the charge imparting surface of the charge imparting member,
  An electric field forming part for forming an electric field between two electrodes facing each other;
  An electron-emitting member that is provided at an opposite location facing the other electrode in any one of the electrodes constituting the electric field forming portion, and emits electrons in an electric field;
  An exit opening for discharging ions generated in the ion generation space formed between the other electrode and the electron emission member to the outside of the ion generation space;
  A plurality of electric field forming portions are arranged along an ion movement direction in which ions generated in the ion generation space move toward the exit opening,
  The electron emission member is provided on any one of the electrodes constituting each electric field forming unit,
  An electric charge imparting device comprising an electric field control means for controlling each electric field forming unit so as to form an electric field in order from an electric field forming unit located downstream in the ion movement direction. The charge imparting device according to any one of claims 1 to 3 ,
The electrode surfaces of the two electrodes facing each other are planes parallel to each other,
The charge giving device, wherein the electron emission member is an electron emission layer having a substantially uniform thickness provided on the electrode surface of any one of the electrodes . In charging device according to any one of 請 Motomeko 1 to 4,
A movement control electrode for forming a moving electric field for moving ions generated in the ion generation space to the charged surface is provided at or near the exit opening of the ion generation space,
When the voltage applied to one of the electrodes is A [V], the voltage applied to the other electrode is B [V], and the voltage applied to the movement control electrode is C [V], A charge applying device characterized in that the voltage satisfies the following relational expression (1).
| A |> | B |> | C | (1) The charge imparting device according to any one of claims 1 to 5 ,
A space enclosing member surrounding the ion generation space;
The space enclosing member includes the outlet opening and an intake opening for taking in outside air. The charge imparting device according to any one of claims 1 to 6 ,
A charge imparting device having an electrode support mechanism for supporting the two electrodes and maintaining a constant distance between the electrodes. The charge imparting device according to claim 7 .
A grid-type movement control electrode for forming a moving electric field for moving the ions generated in the ion generation space to the charged surface, at or near the exit opening of the ion generation space;
A charge applying device, wherein the electrode support mechanism includes the grid type movement control electrode and an insulating fixing member for fixing the two electrodes on the movement control electrode. A charge imparting member;
A charge imparting means for imparting a charge to the charge imparting surface of the charge imparting member;
In an image forming apparatus having an image forming unit that forms an image on a recording material using the charged member.
As the charging unit, the image forming apparatus characterized by using a charging device according to any one of claims 1 to 8. The image forming apparatus according to claim 9 .
The charged member is a latent image carrier,
The charge applying device is a charging device for uniformly charging the surface of the latent image carrier,
The image forming unit forms a latent image on the surface of the latent image carrier uniformly charged by the charge applying device, and then transfers the image obtained by visualizing the latent image onto the recording material. An image forming apparatus for performing image formation. The image forming apparatus according to claim 9 or 10 ,
The charge application device has the outlet opening in a direction substantially orthogonal to the electrode facing direction in which the two electrodes are opposed to each other, and the outlet opening is formed on the charge application surface of the charge application member. An image forming apparatus, which is disposed so as to face each other.

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