JP2001125346A - Electrifying device and image forming device utilizing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently decrease generated discharge product such as ozone and nitrogen oxides. SOLUTION: An electrifying device 2 is provided with an inducting electrode 13 and an ion generating electrode 11 sandwiching a dielectric layer 12 in between and AC+DC bias is applied to the ion generating electrode 11 by an AC power source 15 and a DC power source 16. Furthermore, only the DC bias is applied to the inducting electrode 13 by a DC power source 17. Thus, a photoreceptor is electrified by generating ion by causing aerial discharge. Member having a characteristic of absorbing the generated discharge product such as activated carbon consisting of a porous member is utilized for the ion generating electrode 11. Thus, generated discharge product such as ozone and nitrogen oxides (Nox) generated during an electrifying operation can be efficiently absorbed by the ion generating electrode 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device having an induction electrode and an ion generating electrode sandwiching a dielectric, and an image forming apparatus using the charging device.

[0002]

2. Description of the Related Art Heretofore, there has been a charging device in which a layer formed of a dielectric material is sandwiched between an induction electrode and an ion generation electrode, and the induction electrode is formed on an insulating substrate. For example, JP-A-5-278258). A charging device including such a dielectric layer, an induction electrode, and an ion generation electrode can charge an image carrier without using a discharge wire as seen in a corona charger, and thus has a very large wire diameter. In the case of a thin discharge wire, there is a possibility of disconnection, but there is an advantage that there is no such a fear.

[0003]

However, in the case of such a charging device using an ion generator which generates ions by causing an air discharge, such as ozone and nitrogen oxides (NOx) during discharge operation. There is a problem that a large amount of discharge products are generated. In such a case, when the discharge product forms a film of nitric acid or a nitrate on the surface of the image carrier due to the discharge product, the film adversely affects image formation. As a result, a good image may not be obtained.

The present invention has been made in view of the above problems, and has a charging device for charging an object to be charged using an ion generator that generates ions by causing air discharge, and an image using the charging device. An object of the present invention is to enable a forming apparatus to efficiently reduce generated discharge products such as ozone and nitrogen oxides.

[0005]

In order to achieve the above object, the present invention comprises an induction electrode and an ion generation electrode provided so as to sandwich a dielectric, and applies a voltage to each of the induction electrode and the ion generation electrode. In the charging device for charging an object to be charged by using an ion generator for generating ions by causing aerial discharge, the ion generating electrode is formed of a member having a property of adsorbing a discharge product. The ion generating electrode may be a porous member. The porous member is preferably made of activated carbon.

In the charging device, first voltage applying means for applying an AC + DC voltage to the ion generating electrode may be provided, and second voltage applying means for applying a DC voltage to the dielectric electrode may be provided. .

Further, there is provided an image forming apparatus using any one of the above charging devices, wherein the charging device is arranged at a position where the ion generating electrode is not in contact with the surface of the image carrier to be charged. It is better to do it. Also, in the image forming apparatus using the charging device provided with the first and second voltage applying means, the maximum value of the absolute value of the voltage applied to the ion generating electrode by the first voltage applying means is affected. Provided is an image forming apparatus which does not exceed a discharge starting voltage between a charged member and an ion generating electrode.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an embodiment of a charging device according to the present invention, and FIG. 2 is a schematic configuration diagram showing an image forming unit of an image forming apparatus using the charging device.

The image forming apparatus shown in FIG. 2 is an image forming apparatus. A charging device 2 and an exposure device are provided around a drum-shaped photosensitive member 1 which is a member to be charged and is also an image bearing member and which can rotate in the direction of arrow A. 3,
A developing device 4, a transfer device 5, a cleaning device 6, and a charge removing lamp 7 are provided. The charging device 2 is a charging device that negatively charges the photoconductor 1 using an ion generator that generates ions by causing air discharge.
The ion generating electrode 11 provided there is arranged in a non-contact manner so that the gap G is 0.1 to 4 mm with respect to the surface of the photoreceptor 1. The detailed description of the charging device 2 will be described later. I do.

The exposure device 3 forms a latent image on the charged surface of the photoreceptor 1 by irradiating the charged surface with a laser beam L corresponding to an image. The developing device 4 includes the photoconductor 1
By attaching a negatively charged toner to the latent image formed thereon by the developing roller 8, the latent image is developed into a toner image. The transfer device 5 transfers the toner image developed by the developing device 4 to the transfer material P by applying an electric force (electrostatic force) to the transfer material P by using a corona charger (a roller may be used). Things.

After the transfer device 5 transfers the toner image on the photosensitive member 1 to the transfer material P, the cleaning device 6
This is a device for scraping off and removing transfer residual toner remaining on the upper surface by a cleaning blade 9. The charge removing lamp 7 removes the residual potential by removing the charge on the surface of the photoconductor 1 cleaned by the cleaning device 6 with the charge removing light.

Next, the charging device 2 will be described with reference to FIGS.
This will be described in detail with reference to FIG. As shown in FIG. 1, the charging device 2 includes an induction electrode 13 and an ion generation electrode 11 provided so as to sandwich a dielectric layer (hereinafter referred to as a dielectric layer) 12, and the ion generation electrode 11 is provided with AC + DC. By applying a bias from the AC power supply 15 and the DC power supply 16 and applying only a DC bias to the induction electrode 13 from the DC power supply 17, air discharge occurs to generate ions and the photoconductor 1 (FIG. 2). Is charged.

The ion generating portion of the charging device 2 has an induction electrode 1 on a lower surface of the substrate 14 made of ceramic or the like in FIG.
3, a dielectric layer 12 made of glass or the like is formed below the induction electrode 13 so as to cover the induction electrode 13, and three dielectric layers 12 are formed on the lower surface of the dielectric layer 12 in FIG. The ion generating electrodes 11 are respectively formed.

It is preferable that the dielectric layer 12 has a dielectric constant as high as possible because the capacitance of the dielectric layer 12 becomes large. The induction electrode 13 shown in FIG.
4, the upper and lower surfaces are respectively formed in a plane shape in the same figure, but when the substrate 14 has a surface having a curvature such as a roller, the upper surface is formed along the curved surface. To form a curved surface.

In this embodiment, the ion generating electrode 11 is formed of a member having a property of adsorbing discharge products, for example, activated carbon formed of a porous member. Then, as shown in FIG. 3, the ion generating portion of the charging device 2 is viewed from the side of the ion generating electrode 11, the ion generating electrode 11 is made up of three thin stripe-shaped electrodes, which are arranged in parallel. are doing. By forming the ion generating electrodes 11 in a stripe shape in this manner, a large number of discharge points are formed.
The ion generation efficiency is improved.

The ion generating electrode 11 may be formed in a mesh form. In this case, a large number of discharge points are formed, so that the charging efficiency is further improved. Therefore, it is better to keep the discharge point at the minimum necessary. The ion generating electrode 1
The required number of 1 is determined by the bias applied to the charging device 2, the thickness t of the dielectric layer 12 (FIG. 1), the process speed of the image forming apparatus, and the like.

An AC + DC bias is applied to the ion generating electrode 11 by the AC power supply 15 and the DC power supply 16 as shown in FIG. Further, only a DC bias is applied to the induction electrode 13 by the DC power supply 17. Then, air near the ion generation electrode 11 is ionized, and positive and negative ions are generated in the vicinity (ion generation space).

The high-frequency high voltage applied by the AC power supply 15 uses a sine wave here, but may use a square wave. Here, when the bias voltage applied to the ion generating electrode 11 is a negative voltage, only negative ions are extracted from the ion part. Conversely, when the bias voltage is positive, positive ions are extracted.

The charging device 2 can perform charging with a smaller voltage than a corona charger using a corona wire. Therefore, the amount of discharge products such as ozone and nitrogen oxides can be reduced by the amount by which the voltage can be reduced.

FIG. 4 is a schematic view similar to FIG. 1 showing another embodiment of the charging device according to the present invention, and portions corresponding to FIG. 1 are denoted by the same reference numerals. The charging device according to this embodiment has a frequency between several hundred Hz to several hundred kHz and a peak value of 1 to 5 k between the induction electrode 13 and the ion generation electrode 11.
A high frequency high voltage of V is applied by an AC power supply 18, and a DC bias voltage is applied to the ion generating electrode 11 by a DC power supply 19. Even in this case, the same effect as the charging device described with reference to FIG. 1 can be obtained.

[0021]

Next, experimental results when the present invention is implemented and when it is not implemented will be described with reference to FIGS. First, experimental results when the present invention was not implemented first, that is, experimental results when the member having the property of adsorbing the discharge product was not used for the ion generating electrode with reference to FIGS. explain.

FIG. 5 is a graph showing experimental results of the relationship between the bias voltage Vdc applied to the ion generating electrode and the charged potential of the member to be charged in the experiment. The experimental results were obtained at an AC bias frequency of 5 kHz, Vpp (peak to peak voltage) of 3.5 kV, and a process speed of the image forming apparatus at a linear speed of 300 mm / sec.

FIG. 6 shows the state of the ion generating electrode 5 when the charging operation is performed.
This is the result of measuring the ozone concentration in the air by sucking air at a position separated by a distance of 5 mm with a pipe having a diameter of 5 mm. The measurement was performed at 10 points at 12-second intervals, and the average value of the measurement results was plotted on a graph. From this experimental result,
It is understood that ozone of 10 ppm or more at a frequency of 5 kHz is measured at the above position unless a member having a property of adsorbing discharge products is used for the ion generating electrode.

FIG. 7 shows the result of similarly measuring the NOx concentration in the air at a position 5 mm away from the ion generating electrode by a pipe having a diameter of 5 mm during the charging operation. The measurement was performed at 10 points at intervals of 60 seconds, and the average value of the measurement results was plotted on a graph. As shown in the experimental results, when the bias voltage Vdc is 5 kV,
NOx concentrations as high as about 0.5 ppm have been measured.

Next, experimental results when the present invention is implemented, that is, experimental results when a member having a property of adsorbing a discharge product is used for an ion generating electrode will be described with reference to FIGS. . In this embodiment, a member that easily adsorbs the discharge product to the ion generating electrode 11 shown in FIG. 1, that is, activated carbon is used. Activated carbon is a porous material having a large number of fine pores, has very good electric conductivity, and can be used instead of a metal electrode.

Therefore, in this embodiment, the specific surface area is 800
m ² / g, a basis weight 250 g / m ^2, was used thickness 400 [mu] m, an average pore diameter of 25 [mu] m, the electric conductivity of 1 × 10- ⁴ S / cm comprising activated carbon sheet. In addition, the ion generation electrode 11
A strip having a width of 3 mm and a length of 3 cm was cut, and the strip was attached to the surface of the dielectric layer 12 as shown in FIG.

The number of the ion generating electrodes 11 is three,
The same bias was applied to each of the three ion generating electrodes 11. The induction electrode 13 is a solid electrode and exists on the opposite side of the ion generation electrode 11 with the dielectric layer 12 interposed therebetween. Then, as described with reference to FIG. 1, an AC + DC bias is applied to the ion
3, only a DC bias was applied. The AC bias frequency is 5 kHz, Vpp (peak to peak voltage) is 4 kV, and the distance from the ion generating electrode 11 to the PET sheet is 500
μm, and the sheet moving speed is 300 mm / s.

FIG. 8 shows the relationship between the bias voltage Vdc applied to the ion generating electrode and the charging potential when a 25 μm-thick PET sheet is charged. Then, the PET sheet after being charged by the charging device is charged with a charge amount of −20 μm.
When cascade development was performed with C / g toner, no charging unevenness was observed.

FIG. 9 is a diagram similar to FIG. 6, showing the result of measuring the ozone concentration during the charging operation by the charging device used to obtain the data of FIG. The measurement conditions are the same as those for the data measurement in FIG. 6, and the same applies to the position where the air to be measured is sampled, the diameter of the pipe that sucks the air, and the like.

Comparing the experimental results with those of FIG. 6, for example, in the case of the conventional apparatus in which the ion generating electrode described in FIG. Was 10 ppm, but in the case of using the ion generating electrode according to the present invention, FIG.
As shown in the figure, the amount of generated ozone is 1.2 at a frequency of 5 kHz.
ppm, which is a drastic decrease to a small value.

FIG. 10 is a diagram similar to FIG. 7 showing the result of measuring the NOx concentration during the charging operation by the charging device used to obtain the data of FIG. This measurement was also performed under the same measurement conditions as when obtaining the data in FIG. Comparing the experimental results with those of FIG. 7, it is clear that the one using the ion generating electrode according to the present invention has a large N value.
Ox concentration is reduced. As described above, when the charging device according to the present invention is used, both the amount of generated ozone and the NOx concentration can be significantly reduced.

Next, with the same configuration as the above-described embodiment,
After conducting an experiment in which only the bias was gradually increased,
At Vpp = 5.5 kV or more, charging unevenness occurred. Then, when the discharge light was observed in a dark room, a spark was observed between the ion generating electrode and the PET sheet. This is because the bias is too high and the PET is directly
This is because discharge has occurred in the sheet. Under normal conditions, pale light is observed on the head surface, and no spark is observed. In order to perform uniform and uniform charging, discharge between the ion generating electrode and the PET sheet should not occur.
It is necessary to control AC and DC bias.

Therefore, the AC power supply 15 and the DC power supply 16 functioning as the first voltage applying means shown in FIG.
It is necessary that the maximum value of the absolute value of the voltage applied to the ion generating electrode 11 does not exceed the discharge starting voltage between the photoconductor 1 and the ion generating electrode 11. If the applied voltage is regulated in this manner, no direct discharge occurs between the ion generating electrode 11 and the photoreceptor 1, so that charging unevenness can be prevented and uniform charging can be performed.

Next, a description will be given of an experimental result in the case where only the bias application is changed with the same configuration as the above-described embodiment. An experiment was performed by applying only a DC bias to the ion generation electrode 11 and an AC + DC bias to the induction electrode 13 shown in FIG. 1, but the PET sheet was not charged. Then, when the AC bias Vpp was raised to 6 kV, charging started. However, when the DC bias was increased, the dielectric layer 12 caused insulation breakdown and became unusable.

[0035]

As described above, according to the present invention, the following effects can be obtained. According to the charging device of claims 1 to 3, since the ion generating electrode is formed of a member having a property of adsorbing the discharge product, the discharge product such as ozone and nitrogen oxide (NOx) generated during the charging operation is ionized. Since it can be efficiently adsorbed to the generating electrode, the scattering of the discharge product to the member to be charged can be greatly reduced.

According to the charging device of the fourth aspect and the image forming apparatus of the sixth aspect, it is possible to prevent a direct discharge from occurring between the ion generating electrode and the member to be charged. No uniform charging is possible. According to the image forming apparatus of the present invention, the charging device is arranged at a position where the ion generating electrode is not in contact with the surface of the member to be charged. Since it is possible to prevent dirt and wear from being brought into sliding contact with the charged body, it is possible to prevent deterioration of the head portion.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a charging device according to the present invention.

FIG. 2 is a schematic configuration diagram showing an image forming unit of an image forming apparatus using the charging device.

FIG. 3 is a view of the charging device as viewed from an ion generating electrode side.

FIG. 4 is a schematic view similar to FIG. 1, showing another embodiment of the charging device according to the present invention.

FIG. 5 shows the results of an experiment in the case where a member having a property of adsorbing a discharge product was not used on the ion generating electrode;
FIG. 3 is a diagram illustrating a relationship between dc and a charged potential.

FIG. 6 is a graph showing the results of measuring the ozone concentration in air at a position 5 mm away from the ion generation electrode when no member having the property of adsorbing discharge products was used on the ion generation electrode. is there.

[FIG. 7] In the same experiment, 5
It is a diagram showing the result of having measured the concentration of NOx in air at a position separated by mm.

8 is a diagram similar to FIG. 5, showing the relationship between the bias voltage Vdc and the charging potential in the experimental results of the charging device embodying the present invention.

FIG. 9 is a diagram similar to FIG. 6, showing the result of measuring the ozone concentration during the charging operation by the charging device used to obtain the data of FIG. 8;

FIG. 10 is a diagram similar to FIG. 7, showing the result of measuring the NOx concentration during the charging operation by the charging device used to obtain the data of FIG. 8;

[Explanation of symbols]

 1: Photoconductor (charged body) 2: Charging device 11: Ion generation electrode 12: Dielectric layer 13: Induction electrode 14: Substrate 15: AC power supply (first voltage applying means) 16: DC power supply (first power supply) 17: DC power supply (second voltage applying means) 18: AC power supply 19: DC power supply

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kenji Sugiura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Makoto Shino 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H003 AA18 BB11 CC01 DD03 EE08 EE11 5C094 AA03 AA60 BA99 HA10

Claims (6)

[Claims] 1. An ion generator comprising an induction electrode and an ion generation electrode provided so as to sandwich a dielectric, and applying a voltage to each of the induction electrode and the ion generation electrode to cause an air discharge to generate ions. A charging device for charging an object to be charged by using, wherein the ion generating electrode is formed of a member having a property of adsorbing a discharge product. 2. The charging device according to claim 1, wherein said ion generating electrode is made of a porous member. 3. The charging device according to claim 2, wherein said porous member is activated carbon. 4. The charging device according to claim 1, further comprising first voltage applying means for applying an AC + DC voltage to said ion generating electrode, and second voltage applying means for applying a DC voltage to said dielectric electrode. A charging device comprising: 5. An image forming apparatus using the charging device according to claim 1, wherein the charging device is provided on a surface of an image carrier on which the ion generating electrode is a member to be charged. An image forming apparatus, wherein the image forming apparatus is disposed at a position where the image forming apparatus does not contact the image forming apparatus. 6. An image forming apparatus using the charging device according to claim 4, wherein a maximum value of an absolute value of a voltage applied to the ion generating electrode by the first voltage applying unit is different from the charged object. An image forming apparatus, wherein a discharge starting voltage between the electrode and the ion generating electrode is not exceeded.