JP4616501B2 - Charging device and image forming apparatus using charging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for charging an object to be charged, and in particular, an electron emission type charging device for charging a photoconductor using negative ions and electrons due to electron emission and an electrophotographic system using the charging device. The present invention relates to an image forming apparatus.
[0002]
[Prior art]
Conventionally, a charger used in an electrophotographic image forming apparatus basically generates ions by using discharge, and therefore generates ozone and NOx. Although there is a contact-type charger with relatively little adverse effect of discharge, problems such as photoreceptor wear and NOx compound surface adhesion occur. Further, there is a problem that a defective image is generated by lowering the surface potential of the photosensitive member due to the substance adhering to NOx generated by discharge adhering to the photosensitive member and absorbing moisture.
[0003]
In order to solve these problems, a non-discharge type charge generator has recently been studied. For example, a charge generator used in an electrostatic latent image forming apparatus as disclosed in JP-A-8-203418 is known. In the electrostatic latent image forming apparatus described in this publication, a charge generator in which an electron emitting element layer made of a PN junction semiconductor element or an electroluminescent material is provided on the surface of a line electrode, and this is independently driven for each pixel. The latent image is formed on the dielectric.
[0004]
[Problems to be solved by the invention]
However, since the charge generator described in JP-A-8-203418 is basically produced by integrally forming the electron-emitting device layer, a large-sized device is required to produce a large-sized electron-emitting device, and the manufacture is There remains the problem of cost. Further, simply arranging the charge generator in the image forming apparatus causes a problem that uneven charging tends to occur when a dielectric having a large width is charged.
[0005]
In addition, with the recent increase in environmental protection awareness, standards for regulating the amount of ozone generated have also been set for electrophotographic image forming devices, reducing the amount of ozone generated in the electrophotographic process. Therefore, it is required to develop a copier or a printer that does not exceed the regulation value.
[0006]
The present invention has been made in view of the above problems, and in a charging device using an electron-emitting device, even when charging a charged object having a large width, stable charging efficiency with little charging unevenness is maintained over a long period of time. An object is to provide a charging device that can be used.
[0007]
Another object of the present invention is to provide an electrophotographic image forming apparatus that generates a small amount of ozone, reduces the lifetime of the photoreceptor due to NOx, and enables stable high-quality image formation.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention described in claim 1 has an electron-emitting device that emits electrons given energy by an internal electric field, and has a predetermined width by the electrons emitted from the electron-emitting device. In a charging device for charging an object to be charged, at least a part of the electron-emitting device is brought into contact with a gas containing an electric negative gas, and negative ions generated by the emitted electrons and molecules of the electric negative gas and by a configuration in which Ru is charged member to be charged, the electron emission device is divided into a plurality of divided electron emitting portion, the plurality of arranged split electron emitting portion in a direction parallel to the width direction of the member to be charged then monitor, The width of the electrode end portion in each divided electron emission portion of the electron emission element is changed .
[0009]
The invention described in claim 2 is characterized in that an independent electrical condition is set for each divided electron-emitting portion of the electron-emitting device.
[0010]
According to a third aspect of the present invention, there is provided control means for controlling an emission current amount by controlling a voltage applied to the electron-emitting device.
[0011]
According to a fourth aspect of the present invention, the member to be charged is composed of a photosensitive member, a detecting means for detecting a charged potential or toner density of the photosensitive member, and the electron emission based on a detection result of the detecting means. It has a feedback control mechanism for determining a voltage applied to the element.
[0013]
According to a fifth aspect of the present invention, in the charging device according to the first aspect of the present invention, a minute gap is provided in the electrode portion of each divided electron emission portion in a direction perpendicular to the traveling direction of the charged body. The electrode width of the part close to the gap is made larger than the electrode width of the other part.
[0014]
According to a sixth aspect of the present invention, in the charging device according to the first aspect, the plurality of divided emission portions of the electron-emitting devices are arranged in two rows along the traveling direction of the charged body, and each row is divided. The electrode width of the part where the electrode parts of the electron emission part are close to each other is made smaller than the electrode width of the other part.
[0015]
According to a seventh aspect of the present invention, in the charging device according to any one of the first to sixth aspects, a portion of the electron-emitting device other than the electrode portion of each divided electron-emitting portion is covered with an insulator. It is characterized by that.
[0016]
The invention described in claim 8 is the charging device according to claim 7, wherein the insulator is characterized by comprising the resistance to dielectric edge resin.
[0017]
According to a ninth aspect of the present invention, there is provided an image forming apparatus for forming an image by holding an electrostatic latent image on a photosensitive member, wherein the photosensitive member is charged using the charging device according to the first to eighth aspects. It is characterized by.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.
[0019]
FIG. 1 shows a basic configuration example of the electron-emitting device of the charging device according to the present invention. FIG. 1 shows such a plane for convenience.
[0020]
As shown in FIG. 1, the electron-emitting device 1 applied to the charging device of the present invention has a semiconductor layer 4 (for example, single crystal silicon) formed on a substrate electrode 5 formed on a quartz substrate 6, The semiconductor layer 4 is made porous by anodic oxidation, and then a porous semiconductor layer (porous silicon) 2 is formed by rapid thermal oxidation (RTO). The porous semiconductor layer 2 is covered with a thin oxide film, and finally a thin film electrode 7 is formed on the surface so that electrons can pass through the tunnel effect.
[0021]
The member to be charged shown in FIG. 1 is usually an electrophotographic photoreceptor. The illustrated electrode of the member to be charged can be considered as an aluminum drum of the photosensitive member. In this case, it is assumed that the member to be charged moves at a constant linear velocity S with respect to the electron-emitting device 1.
[0022]
When a voltage of about 20 V is applied with the power supply 8, a current of about 1 mA / cm ² is observed as electrons in a vacuum. In the configuration shown in FIG. 1, since it is an atmospheric pressure gas, the current value is lower than this due to the efficiency of ionization and the like. However, it can be charged by these ions in the same way as a negatively charged scorotron charger.
[0023]
The electron-emitting device 1 shown in FIG. 1 uses a porous semiconductor layer (porous silicon) made of polysilicon. A method for producing this porous silicon is known, and is used in, for example, a field emission electron source disclosed in Japanese Patent No. 2966842. However, the electron-emitting device of the present invention is not limited to this, and it is sufficient that it emits electrons from the solid as in the example shown in FIG. The present invention is applicable if the charging efficiency changes.
[0024]
For example, the electron-emitting device applicable to the charging device of the present invention may have an MIS (metal-insulator-semiconductor) structure or an MIM (metal-insulator-metal) structure. .
[0025]
Also, (a) a semiconductor substrate, (b) a porous semiconductor layer in which the surface of the semiconductor substrate is made porous by anodization, (c) a metal thin film electrode formed on the porous semiconductor eyebrow, (D) You may have an ohmic electrode formed in the back surface of the said semiconductor substrate.
[0026]
Furthermore, the lower electrode, the tantalum oxide (Ta ₂ O ₅ ) film formed on the lower electrode, the ZnS film formed on the tantalum oxide (Ta ₂ O ₅ ) film, and the ZnS film are formed. It may be an electroluminescent element constituted by an upper electrode, or the like.
[0027]
The charging mechanism in ionization by the electron-emitting device of the present invention generates very little ozone and NOx. However, in a process using a normal semiconductor, single crystal silicon is about 300 mm, and polysilicon or amorphous silicon is limited in terms of a film forming apparatus. In addition, the degree of variation increases with an increase in size. In this configuration, for example, a large number of chips can be manufactured by a 6-inch single crystal process and classified according to characteristics to reduce charging unevenness.
[0028]
FIG. 2 is a view for explaining negative ionization of an electrically negative gas due to electron emission of the charging device of the present invention.
[0029]
The structure of the negative ions of the electrically negative gas due to electron emission varies depending on the atmospheric conditions, so it is not necessarily fixed to this, but when charges are transmitted in the form shown in FIG. Conceivable.
[0030]
The mean free path of electrons in the atmosphere is said to be about 0.34 μm, and it is considered that charge transport in electrons is not dominant as long as it is in the atmosphere. The charging mechanism for ionization by these electron-emitting devices generates very little ozone and NOx. However, since the electron emission amount directly affects the charge amount, this unevenness directly affects the charging potential. A configuration to prevent this is necessary.
[0031]
FIG. 3 shows a configuration example for explaining the first embodiment of the present invention.
[0032]
As shown in FIG. 3, the electron-emitting device 1 of the present embodiment is divided into a plurality of divided electron-emitting portions 31, 32, 33, and 34 (only the electrode portions are shown), and the insulating portions 51, 52, 53 and 54 are separated from each other. These divided electron emission portions 31, 32, 33, and 34 are arranged in a direction parallel to the width direction of the member to be charged (for example, the direction perpendicular to the paper surface of FIG. 7) (the direction of the dashed line A in FIG. 3). Is done.
[0033]
As in the configuration of FIG. 1, the power supply voltage supplied from the power supply 8 is applied between the substrate electrode 5 of the electron-emitting device 1 and each electrode portion of the divided electron emission portions 31, 32, 33, 34. The connection between the power supply 8 and each electrode portion is made through variable resistors 61, 62, 63, 64. Therefore, an independent electrical condition is set for each divided electron emission portion.
[0034]
In the configuration example of FIG. 3, the variable resistors 61, 62, 63, and 64 can independently change the potential of the thin-film electrode (extraction electrode) 7 of each divided electron emission portion. Thereby, the dispersion | variation between each chip | tip can be adjusted.
[0035]
Further, a control unit 42 that outputs control signals C1, C2, C3, and C4 for controlling the resistance values of the variable resistors 61, 62, 63, and 64 is provided. Therefore, it is possible to control the amount of emission current by controlling the voltage applied to each divided electron emission portion of the electron emission element 1.
[0036]
Further, in the configuration example of FIG. 3, a detection unit 41 that detects a charging potential of the photosensitive member of the member to be charged (photosensitive member) 12 or a charge-causing factor such as a toner concentration is provided. A feedback control mechanism that supplies a detection signal indicating a detection result such as from the detection unit 41 to the control unit 42 and determines a voltage to be applied to the electron-emitting device 1 by the control unit 42 based on the detection result of the detection unit 41 It is configured as. By feeding back the information of the charge sensor and the toner density sensor as the detection unit 41, it is possible to form a detector with little temporal unevenness.
[0037]
FIG. 4 shows a configuration example for explaining the second embodiment of the present invention. FIG. 5 shows a configuration example for explaining a modification of the electron-emitting device of the charging device shown in FIG.
[0038]
4 and 5, only the chip configuration of the electron-emitting device 1 is shown.
[0039]
In the configuration example of FIG. 4, the electron-emitting device 1 is divided into a plurality of divided electron emission portions 30A, and the width of the electrode end portion in each divided electron emission portion 30A is changed. More specifically, a minute amount is formed on the electrode portion of each divided electron emission portion 30A in a direction (direction of the dashed line A in FIG. 4) perpendicular to the traveling direction of the charged body (direction of the dashed line T in FIG. 4). The arrangement is such that a gap is provided, and the electrode width of the portion adjacent to the gap is larger than the electrode width of the other portion.
[0040]
When arranged horizontally as shown in FIG. 4, a gap is inevitably formed in a direction perpendicular to the moving direction of the member to be charged, and the amount of spatial current is reduced. However, this is prevented by increasing the electrode area of this portion.
[0041]
In the modification shown in FIG. 5, a plurality of divided electron emission portions 30B of the electron-emitting device 1 are arranged in two rows along the traveling direction of the charged body (the direction of the one-dot chain line T in FIG. 5). The electrode width of the portion where the electrode portions of the electron emission portion 30B are close to each other is made smaller than the electrode width of the other portion. In the case of this configuration, the member to be charged is arranged so as to receive a current similarly.
[0042]
FIG. 6 shows a configuration example for explaining the third embodiment of the present invention.
[0043]
In the configuration example of FIG. 6, the electron-emitting device 1 is divided into a plurality of divided electron emission portions 30 </ b> C, and portions other than the electrode portions of each divided electron emission portion 30 </ b> C are covered with an insulator 70. The insulator 70 is shaped as a resin coat made of an insulating resin, for example.
[0044]
In the third embodiment, only the electron emission electrode surface is left and is coated with resin. Thereby, unstable factors such as alkali metal ions such as sodium ions and moisture do not enter the chip, and stable operation is possible. For this purpose, a semiconductor adhesive with a very small amount of impurities, for example, an epoxy adhesive, can be applied as a resin coat. In addition, a polyimide-based material used as an interlayer insulating film is applied. This was developed with a dispenser after the normal production process was completed.
[0045]
FIG. 7 is a schematic configuration diagram for explaining an image forming apparatus using the charging device according to the present invention.
[0046]
The case where the charging device 10 according to the present invention is applied to an image forming apparatus will be described with reference to FIG. In this example, the image forming apparatus is an electrostatic latent image forming apparatus used as an electrophotographic copying machine or printer.
[0047]
The image forming apparatus includes a drum-shaped photoconductor 12 provided to be rotatable around a central axis O. The photoreceptor 12 is a member to be charged that is charged by electrons and ions emitted from the charging device 10 of the present invention. When the image forming operation is started, the photoconductor 12 is rotated around the central axis O in the direction of the arrow S at a constant linear velocity.
[0048]
In the charging device 10, a direction T in which the arrangement direction A of the plurality of divided electron emission portions 30 of the electron-emitting device 1 is parallel to the axial direction (direction perpendicular to the paper surface) of the photosensitive member 12 and perpendicular to the arrangement direction A. It is arranged so that the direction of the arrow T in FIG. Therefore, even in the case of a photoconductor having a large width, charging unevenness hardly occurs.
[0049]
Around the photoreceptor 12, the charging device 10, the developing roller 16, the transfer charger 14, and the charge eliminating brush 18 are disposed. The photosensitive member 12 charged by the charging device 10 is subjected to optical scanning of a light beam generated by the exposure device 20 according to image information, and an electrostatic latent image is recorded on the photosensitive member. Charged toner is supplied to the surface of the developing roller 16 close to the photoconductor 12, and this toner adheres to the electrostatic latent image on the photoconductor 12 to visualize the image. That is, a toner image is formed.
[0050]
On the other hand, the recording medium 13 (usually recording paper is used as the recording medium) is conveyed to the vicinity of the transfer charger 14 of the photosensitive member 12 in accordance with the recording timing by a paper conveying means (not shown). When the recording paper 13 passes through the photoreceptor 12, the toner image is transferred by the transfer charger 14. The recording paper 13 is further conveyed to the fixing roller 20, fixed by the fixing roller 20, and discharged to a paper discharge tray provided outside the image forming apparatus. The neutralizing brush 18 removes the charge remaining on the photoconductor 12 and prepares for the recharging of the photoconductor 12 by the charging device 10.
[0051]
As shown in FIG. 7, by applying the charging device 10 of the present invention as a charger in an electrophotographic electrostatic latent image forming apparatus, ozone and nitrogen oxidation can be performed without substantially changing the conventional electrophotographic process. An image forming apparatus with very few objects can be configured. In addition, since the plurality of divided electron emitting portions of the electron-emitting device are arranged in an arrangement direction parallel to the width direction of the charged body, even when charging a charged body having a large width, charging unevenness is reduced and stable. It is possible to realize the charging efficiency.
[0052]
【The invention's effect】
As described above, according to the charging device of the present invention, the amount of generated ozone and NOx is generated because the electron-emitting device that charges an object to be charged by negative ion formation without discharge by low energy electrons is used. There is very little. In addition, since the electron-emitting device has a configuration in which a plurality of divided electron emission portions are arranged in the arrangement direction corresponding to the width direction of the charged body, even when charging a charged body having a large width, the uneven charging is reduced and stable. It is possible to realize the charging efficiency.
[0053]
According to the charging device of the first aspect, a charger that can be applied to a large-sized electrophotographic image forming apparatus or the like can be manufactured by separating and arranging the electron-emitting devices.
[0054]
According to the second aspect of the present invention, uneven charging can be reduced by making the emission current constant under electrical conditions independent of the chip characteristics of the divided portions.
[0055]
In the charging device according to the third aspect, the amount of emission current can be controlled by the voltage applied to the element, and this can be used to reduce charging unevenness.
[0056]
The charging device according to claim 4 can further reduce charging unevenness on the time axis by feedback based on the charging potential and toner density which are actually problematic.
[0057]
In the charging device according to the fifth aspect, there is no discharge current between the electrodes of the chip.
However, since negative ions and the like diffuse in the gas, the charge amount does not drop abruptly. Nevertheless, since there is a change in level that causes uneven charging, the width is adjusted according to the arrangement of the chips in order to correct it, thereby enabling uniform charging.
[0058]
In the charging device according to the sixth aspect, there is no emission current to the space between the electrodes of the chip.
However, since negative ions and the like diffuse in the gas, the charge amount does not drop abruptly. Still, since there is a level change that causes uneven charging, the width can be increased and uniformed to correct it.
[0059]
The charging device according to claim 7 is adjusted by placing a plurality of chips in the linear velocity direction in order to reduce unevenness between the chips, but in order to adjust the total charge amount, the end of the electrode is narrowed and uniform charging is performed. it can.
[0060]
In the charging device according to the eighth aspect of the present invention, it is possible to prevent discharge at the electrode portion and the chip and prevent deterioration of the chip by blocking the deterioration caused by the entry of moisture, air, and the like into the chip with an insulator.
[0061]
The charging device according to claim 9 is capable of preventing discharge at the electrode portion and the chip and preventing deterioration of the chip by blocking deterioration caused by the ingress of moisture and air into the chip with an insulator. Therefore, other functional chips can be easily mounted on the substrate.
[0062]
The image forming apparatus according to claim 10 can constitute an electrophotographic image forming apparatus with less generation of ozone and NOx by using the charging device according to claims 1 to 9, and the deterioration factor of the photoreceptor is reduced. A long-life and environmentally-friendly image forming apparatus can be created.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a basic configuration example of an electron-emitting device applied to a charging device according to the present invention.
FIG. 2 is a diagram for explaining negative ionization of an electrically negative gas by electron emission of the charging device of the present invention.
FIG. 3 is a diagram showing a configuration example for explaining a first embodiment of the present invention;
FIG. 4 is a diagram showing a configuration example for explaining a second embodiment of the present invention.
FIG. 5 is a diagram showing a configuration example for explaining a third embodiment of the present invention.
FIG. 6 is a diagram showing a configuration example for explaining a fourth embodiment of the present invention.
FIG. 7 is a schematic configuration diagram for explaining an image forming apparatus using the charging device according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electron emission element 2 Porous semiconductor layer 4 Semiconductor layer 5 Substrate electrode 6 Quartz glass 7 Thin film electrode 8 Power supply 9 Bias power supply 10 Charging device 12 Photoconductor 31, 32, 33, 34 Split electron emission part 30A, 30B, 30C Split electron Emitter 51, 52, 53, 54 Insulator

Claims (9)

In a charging device having an electron-emitting device that emits electrons energized by an internal electric field, and charging an object to be charged having a predetermined width by the electrons emitted from the electron-emitting device,
A gas containing an electric negative gas is brought into contact with at least a part of the electron-emitting device, and the charged object is charged with the emitted electrons and negative ions generated by the molecules of the electric negative gas.
The electron-emitting device is divided into a plurality of divided electron emission portions, and the plurality of divided electron emission portions are arranged in a direction parallel to the width direction of the charged body ,
2. A charging device according to claim 1, wherein a width of an electrode end portion in each divided electron emission portion of the electron emission element is changed .   2. The charging device according to claim 1, wherein an independent electrical condition is set for each divided electron emission portion of the electron emission element.   3. The charging device according to claim 1, further comprising a control unit that controls the amount of emission current by controlling a voltage applied to the electron-emitting device.   The charging target is constituted by a photosensitive member, a detecting unit for detecting a charging potential or toner density of the photosensitive member, and feedback control for determining a voltage to be applied to the electron-emitting device based on a detection result of the detecting unit. The charging device according to claim 1, further comprising a mechanism. In the direction perpendicular to the traveling direction of the charged body, a small gap is provided in the electrode part of each divided electron emission part, and the electrode width of the part adjacent to the gap is made larger than the electrode width of the other part. The charging device according to claim 1 . The plurality of divided emission portions of the electron-emitting device are arranged in two rows along the traveling direction of the charged body, and the electrode width of the portion where the electrode portions of the divided electron emission portions of each row are close to each other is set as the electrode of the other portion The charging device according to claim 1 , wherein the charging device is smaller than the width. The electron-emitting device, a portion other than the electrode portions of the divided electron emitting portion, a charging device of claims 1 to 6, wherein the covered with an insulator. The charging device according to claim 7, wherein the insulator is made of an insulating resin. An image forming apparatus for forming an image by holding the electrostatic latent image on the photosensitive member, an image forming apparatus characterized by charging the photosensitive member using the charging device of claims 1 to 8, wherein.

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