JP2001175059A - Electrifying device, electrophotographic device provided therewith and electrifying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify the constitution of an electrifying member and to minimize the manufacturing cost (material cost, processing cost and the like) thereof while uniformly electrifying a body to be electrified without causing irregularity as for an electrifying device, an electrophotographic device provided with the electrifying device and an electrifying method. SOLUTION: This device is provided with an electrifying plate 2 electrifying the body to be electrified 1 because at least the most tip part 2B thereof is brought into contact with the surface of the body to be electrified 1 and a voltage applying means 3 applying voltage provided with an AC voltage component and a DC voltage component having peak-to-peak voltage being 3.5 to 5.5 times of a voltage value applied to the plate 2 when the body to be electrified 1 is started to be electrified by applying DC voltage to the plate 2 between the body to be electrified 1 and the plate 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device used for, for example, a copying machine, a printer, a facsimile, etc., for charging an object to be charged by a charging member, an electrophotographic device provided with the device, and a charging method.

[0002]

2. Description of the Related Art In a conventional charging device provided in an electrophotographic apparatus such as a copying machine, a printer, a facsimile, etc., for example, a conductive fiber bristle brush (charging brush) to which a DC voltage is applied.
Alternatively, a charging member such as a conductive elastic roller (charging roller) is brought into contact with the surface of the photoreceptor as a member to be charged, thereby injecting charge into the surface of the photoreceptor and charging the surface of the photoreceptor to a predetermined potential. I have.

[0003] However, as described above, when a charging member is brought into contact with the surface of a photosensitive member as a member to be charged, charging is performed.
Since it is difficult to bring the charging member into close contact with the photoreceptor surface, charging unevenness occurs, and it is difficult to uniformly charge. In particular, when a charging brush is used as the charging member, the charging brush does not uniformly contact the surface of the photoreceptor, so that charging unevenness easily occurs, and it is difficult to obtain a uniform charging state.

For this reason, a technique disclosed in, for example, JP-A-63-149668 has been proposed in order to uniformly charge the photosensitive member without causing charging unevenness on the surface thereof. In this technology, for example, as shown in FIG. 9A, by using a charging roller 200a as a charging member, the charging member and the photoconductor are moved downstream of the contact portion between the charging member and the photoconductor in the rotation direction of the photoconductor. The distance between them is increased, and a DC voltage component is applied to the charging roller 200a as a charging member, and a voltage value applied to the charging member when a DC voltage is applied to the charging member to start charging the photosensitive member. By applying a voltage having an AC voltage component having a peak-to-peak voltage that is twice or more of the (discharge start voltage value) and charging the photoconductor, it is possible to reduce the generation of ozone and without causing charging unevenness. , So that uniform charging can be achieved. Note that, in FIG. 9A, arrows indicate the rotation directions of the photoconductor and the charging roller.

[0005]

However, such a charging roller 200a is generally formed by forming a conductive rubber in which carbon is dispersed around a metal core into a roll shape. Since the cost is high and the processing cost for processing into a roll is high, it is difficult to keep the cost of manufacturing the charging member low.

[0006] The above-mentioned publication discloses, for example, FIG.
As shown in FIG. 2, a flat charging plate 2 is used as a charging member.
Also, there is a technique of forming the charging plate 200b so that the distance between the charging plate 200b and the photoconductor 100 becomes larger downstream of the contact portion between the charging plate 200b and the photoconductor 100 in the photoconductor rotation direction. It has been disclosed. Note that in FIG. 9B, arrows indicate the rotation direction of the photoconductor.

However, in this technique, even if the charging plate 200b is used as the charging member, the material cost and processing cost of the conductive rubber can be suppressed lower than when the charging roller 200a is used as the charging member. 9
As shown in (b), the charging plate 200b and the photoconductor 1
In order to increase the distance between the charging plate 200b and the photoconductor 100 on the downstream side in the photoconductor rotation direction of the contact portion with the photoconductor 100, the leading end of the charging plate 200b is moved to the charging plate 200b and the photoconductor 100. It is necessary to protrude downstream from the contact portion with the photoconductor in the rotation direction of the photoconductor so that the thickness of the photoconductor gradually decreases.

For this reason, the material cost of the conductive rubber is increased by an amount corresponding to the leading end of the charging plate 200b protruding downstream in the rotation direction of the photoconductor from the contact portion between the charging plate 200b and the photoconductor 100. In addition, the charging plate 20
It is necessary to perform processing so that the thickness of the leading end of Ob gradually decreases, and the processing cost required for such processing is high.

Further, as described above, the charging plate 2
In the case of forming 00b, it is necessary to first cut the conductive rubber formed in a plate shape into a substantially right angle to obtain a predetermined length, and then to process it diagonally so that the thickness of its tip portion gradually decreases. Therefore, the number of processing steps for forming the charging member increases. On the other hand, the material cost and processing cost of the conductive rubber used as the material of the charging member are high, and
No. 5150 discloses that the charging member is formed of a conductive sheet.

However, in this technique, although the leading end of the conductive sheet is in contact with the surface of the photosensitive drum, the voltage applied to the conductive sheet is not considered at all, so that there is no uneven charging. It is difficult to obtain a uniform charging state. Further, the above-mentioned Japanese Patent Application Laid-Open No. 63-149668
As in the technique disclosed in Japanese Patent Laid-Open No. H10-207, a DC voltage component and twice the applied voltage value (discharge start voltage value) of the charging member when the DC voltage is applied to the charging member to start charging the photosensitive member. It is conceivable to apply a voltage having an AC voltage component having the above-mentioned peak-to-peak voltage to the chargeable sheet. However, even when the voltage is applied in this manner, a uniform charge state without charge unevenness can be obtained. Not necessarily.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a simple configuration of a charging member while allowing a member to be charged to be uniformly charged without charging unevenness. It is an object of the present invention to provide a charging device, an electrophotographic apparatus including the charging device, and a charging method, which can reduce material costs, processing costs, and the like.

[0012]

For this reason, a charging device according to the present invention (Claim 1) comprises a charging plate for charging a member to be charged by contacting at least the foremost part with the surface of the member to be charged, 3.5 times to 5.5 times the applied voltage value of the charging plate when the charging of the member to be charged is started by applying a DC voltage.
It is characterized by comprising voltage applying means for applying a voltage having an AC voltage component and a DC voltage component having a double peak-to-peak voltage between the member to be charged and the charging plate.

Preferably, the charging plate is in contact with an object to be charged.
The end on the side to be touched is formed in a substantially right angle (claim 2). Ma
Further, the volume resistivity of the charging plate is set to 1.0 × 10⁷Ω
cm ~ 1.0 × 10 ¹¹Ω · cm (preferably
Claim 3). Also, charge the charging plate to the surface of
It is preferable to use a conductive elastic member to be touched.
Claim 4).

Further, the charging plate is constituted by a flat conductive resistor in contact with the surface of the member to be charged, and a pressing force applying means supports the conductive resistor and fixes the conductive resistor to the member to be charged. (Claim 5). Further, the charging plate may be formed of a conductive polymer film in contact with the surface of the member to be charged, and the pressing means may be configured to press the conductive polymer film against the surface of the member to be charged ( Claim 6).

Preferably, the pressing force by the charging plate is 9.8 N / m to 49.0 N / m. According to the electrophotographic apparatus of the present invention (claim 8), a charging plate for charging the photoreceptor with at least the leading end portion contacting the surface of the photoreceptor, and charging of the photoreceptor is started by applying a DC voltage to the charging plate. Voltage application that applies a voltage having an AC voltage component and a DC voltage component having a peak-to-peak voltage of 3.5 to 5.5 times the applied voltage value of the charged plate between the charged object and the charged plate. Means.

Preferably, the photoreceptor is constituted to have an organic photoconductor layer. According to the charging method of the present invention (claim 10), a charging plate forming step of forming an end portion of the charging plate in a substantially right angle, and at least a foremost end of the substantially right end of the charging plate is formed on a surface of the member to be charged. A charging plate arranging step of arranging the charging plate so as to be in contact with the charging plate, and applying a DC voltage to the charging plate to 3.5 to 5.5 times an applied voltage value of the charging plate when charging of the member to be charged starts. A charging step of applying a voltage having an AC voltage component and a DC voltage component having a double peak-to-peak voltage between the charged body and the charging plate to charge the charged body.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. First, a charging device according to a first embodiment of the present invention, an electrophotographic apparatus including the charging device, and a charging method will be described. The electrophotographic apparatus according to the present embodiment is used for, for example, an electrophotographic printer, copier, facsimile, and the like. Here, a case where the present invention is applied to an electrophotographic laser printer will be described.

An electrophotographic laser printer is shown in FIG.
As shown in FIG. 1, a photosensitive drum (also simply referred to as a photosensitive member) 1 as a member to be charged, a charging device 10 for charging the surface of the photosensitive drum 1, and a photosensitive drum 1
Exposure device 11 for irradiating laser beam LB to form an electrostatic latent image on the surface of photoconductor drum 1, and developing device 12 for developing electrostatic latent image formed on the surface of photosensitive drum 1 to form a toner image
And a transfer roller 13 as a transfer device for transferring the toner image formed on the surface of the photosensitive drum 1 to a recording medium 15 such as recording paper, and fixing the toner image transferred to the recording medium 15 to the recording medium 15. Fixing device 14 and photosensitive drum 1
And a cleaning device 16 having a cleaning blade 16A for removing toner and dirt remaining on the surface of the cleaning device. In FIG. 2, reference numeral 12a denotes a developing roller, reference numeral 12b denotes a toner collection and supply roller, and reference numeral 12c.
Denotes a layer thickness regulating blade, and reference numeral 12d denotes a toner stirrer.

Here, the photosensitive drum (image carrier) 1 is
For example, a photoconductor layer 1B is formed on the outer peripheral surface of a cylindrical drum base 1A made of aluminum or the like, and a predetermined speed (for example, a circumferential speed of about 70 mm /
s). This photosensitive drum 1
Has a diameter of about 30 mm, for example. Here, the photoconductor layer 1B is formed of an organic photosensitive material layer [a photoconductive organic semiconductor layer (O
PC layer)], the photosensitive drum 1 is
Also called C photoconductor drum. The OPC photosensitive drum 1 is grounded.

Next, the charging device 10 according to the present embodiment will be described. As shown in FIG. 1, the charging device 10 includes a charging plate (charging member) 2 that contacts the surface of the OPC photosensitive drum 1 as a member to be charged and charges the surface of the OPC photosensitive drum 1, And a power supply (voltage applying means) 3 for applying a voltage to the power supply 2. Note that, in FIG. 1, the arrows indicate the drum rotation direction.

The charging plate 2 includes not only a sheet-shaped plate having a certain thickness but also a film-shaped thin plate, and further includes not only a flat plate but also a curved plate. In this embodiment, the charging plate 2
Is composed of a conductive polymer film 4 as shown in FIG. In FIG. 1, the thickness of the conductive polymer film 4 is shown thick for easy understanding.

The conductive polymer film 4 is made of, for example, polycarbonate resin, polyimide resin, ETFE resin,
Nylon resin, polyethylene terephthalate (PET)
It is formed by kneading carbon or the like in order to impart conductivity to a polymer material such as, and forming the film into a film shape. The thickness of the conductive polymer film 4 is about 100
It is on the order of microns (μm) to about 200 microns (μm).

In order to improve the slidability and abrasion resistance between the conductive polymer film 4 and the OPC photosensitive drum 1, a fluorine-based additive is added to the material of the conductive polymer film 4. It may be mixed or a fluorine-based additive may be applied to the surface of the conductive polymer film 4. Next, the volume resistivity of the charging plate 2 will be described.

FIG. 3 is a diagram showing the relationship between the volume resistivity of the charging plate 2 and the surface potential of the OPC photosensitive drum 1. In FIG. 3, the volume resistivity is about 1.0 × 10
Volume resistivity and OPC of charged plate 2 of ⁸ Ω · cm or more
The relationship with the surface potential of the photosensitive drum 1 is as follows.
Is a conductive polymer film formed of a polycarbonate resin, and has a volume resistivity of about 1.
The relationship between the volume resistivity of the charging plate 2 of 0 × 10 ⁷ Ω · cm or less and the surface potential of the OPC photosensitive drum 1 is when the charging plate 2 is made of NBR rubber. The elastic member that applies the pressing force to the charging plate 2 is sponge rubber, and the sponge rubber exerts a force per unit length on the tip of the charging plate 2 of about 29.4 N.
/ M (ie, about 30 g / cm). Further, the DC component of the voltage applied to the charging plate 2 is set to about -700 V, and the peak-to-peak voltage of the AC component is set to about 3
It is set to 500V.

As shown in FIG. 3, when the volume resistivity of the charging plate 2 is about 1.0 × 10 ⁶ Ω · cm or less, the volume resistivity of the charging plate 2 is too low and the OPC photosensitive drum Since an excessive charge is given to the surface of No. 1, an unstable charge state such as a trace of discharge remains. on the other hand,
The volume resistivity of the charging plate 2 is about 1.0 × 10 ¹² Ω · c
If it is more than m, the volume resistivity of the charging plate 2 is too high and sufficient charge is not applied to the surface of the OPC photosensitive drum 1, so that a sufficient surface potential cannot be obtained.

Therefore, in this embodiment, the charging plate 2
Has a volume resistivity of about 1.0 × 10 ^{7 to} 1.0 × 10 ¹¹ Ω ·
cm range. With this, OPC
Good charging stability can be ensured without causing damage to the photosensitive drum 1. By the way, in the present embodiment, in order to realize uniform charging without causing charging unevenness by bringing the charging plate 2 into close contact with the OPC photosensitive drum 1, the conductive polymer film 4 as the charging plate 2 is used.
Porous elastic member such as sponge rubber (pressing force applying means)
5, a predetermined pressing force is applied to the conductive polymer film 4 by the porous elastic member 5,
The conductive polymer film 4 is pressed against the surface of the OPC photosensitive drum 1. The porous elastic member 5 is attached to the housing 6, so that the conductive polymer film 4 is connected to the housing 6 via the porous elastic member 5.
Is to be supported.

Here, the porous elastic member 5 such as sponge rubber is used as the pressing force applying means, but a pressing force for pressing the conductive polymer film 4 against the surface of the OPC photosensitive drum 1 can be applied. What is necessary is just a thing, and it does not necessarily need to be a porous elastic member. For example, the pressing force applying means may be an elastic member such as a leaf spring. Next, the pressing force by the charging plate 2 will be described.

FIG. 4 is a graph showing the relationship between the pressing force of the charging plate and the surface potential of the OPC photosensitive drum. The pressing force of the charging plate 2 is a linear pressure of a contact portion between the charging plate 2 and the OPC photosensitive drum 1. As shown in FIG. 4, the pressing force (force per unit length) by the charging plate 2 is about 4.9 N / m (that is, about 5 N / m).
g / cm) or less, the stability of the surface potential of the OPC photosensitive drum 1 is poor, and uneven charging occurs, which tends to cause density fog and the like. On the other hand, the pressing force by the charging plate 2 is about 68.6 N / m (that is, about 7
If it is not less than 0 g / cm), the surface of the OPC photosensitive drum 1 tends to be damaged (scratched or scraped) when about 5,000 sheets are printed.

Therefore, in this embodiment, the charging plate 2
Is about 9.8 N / m to about 49.0 N / m (that is, about 10 g / cm to about 50 g / cm). More specifically, at least the most distal end 2 of the end 2A of the charging plate 2 to which the porous elastic member 5 is attached as described above.
B is disposed so as to contact the surface of the OPC photosensitive drum 1, and the force per unit length applied to the contact portion between the charging plate 2 and the OPC photosensitive drum 1 is about 9.8 N / m to about 4
9.0 N / m (ie, from about 10 g / cm to about 50 g / c
The pressing force by the charging plate 2 is applied so as to fall within the range of m). As a result, the charging plate 2 is brought into contact with the surface of the OPC photosensitive drum 1 to be charged.

By the way, the power supply 3 applies a voltage (a sine wave) in which a DC voltage (also referred to as a DC offset voltage) and an AC voltage are superimposed on the charging plate 2 configured as described above. It has become. And
When the charging plate 2 to which the voltage is applied comes into contact with the organic photosensitive material layer 1B of the OPC photosensitive drum 1, a uniform charged area is formed on the organic photosensitive material layer 1B of the OPC photosensitive drum 1. Has become.

Here, the peak-to-peak voltage of the AC component (AC voltage) of the voltage applied to the charging plate 2 (AC component pea)
(k-to-peak value) is about 3.5 times to about 5.5 times the firing voltage. Among these ranges, it is particularly preferable to set the range from about 4.0 times to about 4.5 times the discharge starting voltage. Here, the setting of the peak-to-peak voltage of the AC component of the voltage applied to the charging plate 2 will be described.

FIG. 5 is a diagram showing the relationship between the surface potential of the OPC photosensitive drum 1 and the voltage applied to the charging plate 2 when only a DC voltage is applied to the charging plate 2.
Note that the relationship shown in FIG. 5 is obtained under the following conditions. That is, the charging plate 2 was a conductive polymer film formed of a polycarbonate resin. The volume resistivity of the charging plate 2 is about 3.5.
It is 3 × 10 ⁹ Ω · cm. The elastic member for applying the pressing force to the charging plate 2 is sponge rubber, and the force per unit length applied to the tip of the charging plate 2 by the sponge rubber is about 29.4 N / m (that is, about 30 g / m).
cm).

In FIG. 5, the voltage at the rising portion of the surface potential of the OPC photosensitive drum 1 is a discharge starting voltage at which charging of the OPC photosensitive drum 1 is started.
It is 0V. The change in the surface potential of the OPC photosensitive drum 1 with respect to the applied voltage of about -850 V or more at the discharge starting voltage has a characteristic that changes substantially linearly. Next, FIG. 6 is a view showing the relationship between the peak-to-peak voltage of the AC component of the voltage applied to the charging plate 2 (peak-to-peak value of the AC component) and the surface potential of the OPC photosensitive drum 1. In FIG. 6, the solid line A indicates the case where the DC component of the applied voltage is -500 V, the broken line B indicates the case where the DC component of the applied voltage is -700 V, and the dashed line C indicates the case where the DC component of the applied voltage is -1000 V.
Is shown.

The relationship shown in FIG. 6 is obtained under the following conditions. That is, the charging plate 2 was a conductive polymer film formed of a polycarbonate resin. The volume resistivity of the charging plate 2 is about 3.53 × 10 ⁹ Ω · cm. The elastic member that applies the pressing force to the charging plate 2 is sponge rubber, and a force per unit length applied to the tip of the charging plate 2 by the sponge rubber is about 29.4 N / m (that is, about 30 g / cm). ) Is applied.

As shown by curves A, B, and C in FIG. 6, even when the DC component of the voltage applied to the charging plate 2 is different, the peak-to-peak voltage of the AC component of the applied voltage is large. As the surface potential of the OPC photosensitive drum 1 increases, the peak-to-peak voltage of the AC component of the applied voltage becomes about 2975 V, which is about 3.5 times the above-described discharge starting voltage (about -850 V). As shown by curves A, B, and C, the surface potential of the OPC photosensitive drum 1 is substantially equal to the DC component voltage of each applied voltage, and is approximately 5.5 times the peak-to-peak voltage of the AC component of the applied voltage. About 4675V
When the temperature reaches the level, the surface potential of the OPC photosensitive drum 1 has a characteristic of gradually decreasing again.

That is, when the peak-to-peak voltage of the AC component of the applied voltage is in the range of about 3.5 times to about 5.5 times the above-mentioned discharge starting voltage, there is a characteristic that the voltage becomes substantially equal to the DC component of the applied voltage. . In this range, particularly, in the range of about 4.0 times to about 4.5 times the discharge starting voltage, there is a characteristic that substantially matches the voltage of the DC component of the applied voltage. Therefore, the peak-to-peak voltage of the AC component of the applied voltage is about 3.5 times to about 5.5 times (here, about 2 times) the above-described discharge starting voltage (here, about -850 V).
975 V to about 4675 V), the voltage applied to the charging plate 2 is set, the image is developed using the OPC photosensitive drum 1 charged by the applied voltage, and transferred to a recording medium 15 such as recording paper. As a result, a uniform image without unevenness was obtained.

This is because the peak-to-peak voltage of the AC component of the applied voltage is about 3.5 times to about 5.5 times (here, about 2975 V to about 46 times) the above-mentioned discharge starting voltage (about -850 V).
When the voltage applied to the charging plate 2 is set so as to be in the range of 75 V), the surface potential of the OPC photosensitive drum 1 becomes substantially equal to the DC component voltage of the applied voltage, and becomes substantially constant. It is considered that uniform and uniform charging is not performed.

Therefore, in the present embodiment, as described above,
The voltage applied to the charging plate 2 is set so that the peak-to-peak voltage of the AC component of the voltage applied to the charging plate 2 is about 3.5 to about 5.5 times the discharge starting voltage. The range of the peak-to-peak voltage of the AC component of the applied voltage is such that the surface potential of the OPC photosensitive drum 1 is substantially equal to the DC component of the applied voltage even when the voltage of the DC component of the applied voltage is changed. Only the range shifts and the position of this range with respect to the peak-to-peak voltage is constant. Such characteristics are the same even if the frequency of the AC voltage of the applied voltage is changed.

Therefore, according to the charging device, the electrophotographic apparatus provided with the device, and the charging method according to the present embodiment, the charging plate 2 is configured such that the foremost portion of the charging plate 2 is in contact with the surface of the OPC photosensitive drum 1, Since it is not necessary to provide the plate 2 with a tip portion projecting beyond a portion where the charging plate 2 and the OPC photosensitive drum 1 are in contact with each other, the material cost of the charging plate 2 can be reduced accordingly.
As a result, the cost required for manufacturing the charging plate 2 can be reduced. On the other hand, when the DC voltage is applied to the charging plate 2 to start charging the OPC photosensitive drum 1, the voltage applied to the charging plate 2 becomes 3. Since a voltage having an AC voltage component and a DC voltage component having a peak-to-peak voltage of 5 to 5.5 times is applied between the OPC photosensitive drum 1 and the charging plate 2, the OPC photosensitive drum 1 is charged unevenly. There is an advantage that the toner can be uniformly charged without being charged.

Further, since the end 2A of the charging plate 2 on the side in contact with the OPC photosensitive drum 1 is formed in a substantially right angle, the processing of the charging plate 2 becomes easier and the processing cost can be reduced. Thus, there is also an advantage that the cost for manufacturing the charging plate 2 can be further reduced. Furthermore, since the volume resistivity of the charging plate 2 is set to 1.0 × 10 ^{7 to} 1.0 × 10 ¹¹ Ω · cm, the surface potential of the OPC photosensitive drum 1 is kept stable to cause uneven charging. There is the advantage that it can be avoided.

Further, since the charging plate 2 is formed of the conductive polymer film 4, there is an advantage that the material cost and the processing cost of the charging plate 2 can be reduced. Further, since the conductive polymer film 4 as the charging plate 2 is pressed against the surface of the OPC photosensitive drum 1 by the porous elastic member 5, the conductive polymer film 4 is pressed against the surface of the OPC photosensitive drum 1 with an appropriate pressing force. This has the advantage that a more uniform charged state can be obtained.

Next, a second embodiment will be described. In this embodiment, as shown in FIG. 7, similarly to the first embodiment, the charging device 20 contacts the surface of the OPC photosensitive drum 1 as a member to be charged and charges the OPC photosensitive drum 1. A charging plate (charging body) 2 to be charged and a power supply (voltage applying means) 3 for applying a voltage to the charging plate 2 are provided, but the configuration of the charging plate 2 is different.

That is, in this embodiment, the charging plate 2
However, as shown in FIG. 7, it is configured as a flat conductive resistor 7. Note that, in FIG. 7, arrows indicate the drum rotation direction. Here, the conductive resistor 7 is made of a conductive elastic member such as NBR rubber, EPDM rubber, urethane rubber, and silicone rubber. For example, NBR rubber,
It may have a two-layer structure of an elastic rubber layer of EPDM rubber or the like and a urethane rubber layer in which carbon is dispersed, or a foamed urethane rubber layer in which carbon is dispersed.

Here, as described later, a metal member 8 is attached to the conductive resistor 7, and the conductive resistor 7 is pressed against the surface of the OPC photosensitive drum 1 by the metal member 8. It is not necessary to constitute the resistive element 7 itself as having a function of pressing the resistive element 7 against the surface of the OPC photosensitive drum 1, and the conductive resistive element 7 is formed of an amount of material necessary for charging the OPC photosensitive drum 1. Therefore, the thickness of the conductive resistor 7 is set to, for example, about 0.5 mm.
About 1.0 mm.

Here, the conductive resistor 7 is provided so that it can elastically contact the surface of the OPC photosensitive drum 1.
Is configured as a conductive elastic member, but the present invention is not limited to this. Any conductive member that can contact the surface of the OPC photosensitive drum 1 as a member to be charged and charge the OPC photosensitive drum 1 can be used. Good. The charging plate 2 constituted by the conductive resistor 7 charges the surface of the OPC photosensitive drum 1 by contacting at least the foremost portion 2B with the surface of the OPC photosensitive drum 1. That is, the charging plate 2 has an end 2A on the side in contact with the OPC photosensitive drum 1 formed in a substantially right-angled shape, and the most distal end 2B of the end 2A formed in the substantially right-angled shape has an OPC photosensitive drum 1 The surface of the OPC photosensitive drum 1 is electrically charged.

The conductive resistor 7 serving as the charging plate 2 thus configured is supported by the housing 6 via a flat metal member 8 serving as a support member. Here, the conductive resistor 7 is attached to the tip of the metal member 8 along the axial direction of the OPC photosensitive drum 1.
In the present embodiment, the metal member 8 sets the charging plate 2 to OP.
To achieve uniform charging without causing charging unevenness by bringing the charging plate 2 into close contact with the C photosensitive drum 1, the charging plate 2 is
It functions as a pressing force applying means for pressing the surface of the PC photosensitive drum 1 with a predetermined pressing force. That is, one end is fixed to the housing 6 while the metal member 8 is curved as shown in FIG. 7, and the other end is the surface of the OPC photosensitive drum 1 so that the metal member 8 can function as a leaf spring. It is arranged so that it contacts. Thereby, the metal member 8
As a result, the conductive resistor 7 presses the surface of the OPC photosensitive drum 1 with a predetermined pressing force of about 9.8 N / m to about 49.0 N / m.
m (i.e., about 10 g / cm to about 50 g / cm).

Further, in this embodiment, since the conductive resistor 7 as the charging plate 2 is supported by the metal member 8, as shown in FIG. 8, a voltage is applied to the charging plate 2
Is applied. The other configuration is the same as that of the above-described first embodiment, and the description thereof will not be repeated.

Therefore, according to the charging device, the electrophotographic device including the device, and the charging method according to the present embodiment, the thickness of the conductive resistor 7 can be reduced as described above, and the material cost is reduced. Has the advantage that the material cost of the charging plate 2 can be further reduced. In this embodiment, the conductive resistor 7 is supported by the metal member 8, and a voltage is applied to the metal member 8 to apply a voltage to the conductive resistor 7 as the charging plate 2. However, the present invention is not limited to this, and the power supply 3 is connected to the conductive resistor 7 and, as in the above-described first embodiment,
You may comprise so that a voltage may be applied.

Next, a third embodiment will be described. In the present embodiment, as shown in FIG. 8, similarly to the first embodiment, the charging device 21 contacts the surface of the OPC photosensitive drum 1 as a member to be charged and charges the OPC photosensitive drum 1. A charging plate (charging body) 2 to be charged and a power supply (voltage applying means) 3 for applying a voltage to the charging plate 2 are provided, but the configuration of the charging plate 2 is different.

That is, in this embodiment, the charging plate 2
However, as shown in FIG. Here, the conductive elastic member 9 is, for example, N
It is made of an elastic member such as BR rubber, urethane rubber, silicon rubber or the like. For example, it may have a two-layer structure of an elastic rubber layer such as NBR rubber or EPDM rubber and a urethane rubber layer in which carbon is dispersed, or a foamed urethane rubber layer in which carbon is dispersed in the periphery. Good. The thickness of the conductive elastic member 9 is, for example, about 2.0 mm.

The charging plate 2 has an OPC photosensitive drum 1 having at least a leading edge portion 2B in contact with the surface thereof.
The surface of the PC photosensitive drum 1 is charged. That is, the charging plate 2 includes the OPC photosensitive drum 1
The end 2A on the side in contact with the OPC photosensitive drum 1 is formed so as to contact the surface of the OPC photosensitive drum 1 so that the end 2A of the end 2A formed substantially in a right angle is in contact with the surface of the OPC photosensitive drum 1.
The surface of the C photosensitive drum 1 is charged.

Here, the charging plate 2 formed by the conductive elastic member 9 is moved by the elastic force of the charging plate 2 to the O position.
For example, one end is fixed to the housing 6 with the charging plate 2 being curved as shown in FIG. 8 so that it can be pressed against the surface of the PC photosensitive drum 1, and at least the other end of the other end is OPC photosensitive. It is arranged so as to be in contact with the surface of the body drum 1. As a result, the end of the charging plate 2 becomes OP
The photosensitive drum 1 is pressed against the surface of the C photosensitive drum 1 with a predetermined pressing force. Thus, here, the conductive elastic member 9 functions as the pressing force applying means.

The other configuration is the same as that of the first embodiment described above, and the description is omitted here. The charging device 21 provided in the electrophotographic apparatus according to the present embodiment is configured as described above. The charging device 21 is manufactured as follows. First,
The charging plate 2 is formed by cutting the plate at substantially right angles. In this way, the tip 2A of the charging plate 2 is formed in a substantially right angle. This step is called a charging plate forming step.

Next, the leading edge of the charging plate 2 is
The charging plate 2 is provided so as to be in contact with the surface of the photosensitive drum 1 (charging plate providing step). Then, a power supply 3 is connected to the charging plate 2, and the power supply 3 causes the discharge start voltage (that is, a voltage at which the charging of the OPC photosensitive drum 1 starts when a DC voltage is applied) to about 3. A superimposed voltage of the AC voltage and the DC voltage, which is a voltage between the peaks of 5 to 5.5 times, is applied to the charging plate 2 to
The PC photosensitive drum 1 is charged (charging step).

Therefore, according to the charging device, the electrophotographic apparatus provided with the device, and the charging method according to the present embodiment, the charging plate 2 is constituted by the conductive elastic member 9, and charged by the elastic force of the conductive elastic member 9. Since the plate 2 is pressed against the surface of the OPC photosensitive drum 1, there is an advantage that the OPC photosensitive drum 1 can be uniformly charged without charging unevenness while the charging plate 2 has a simple configuration.

In each of the above embodiments, the member to be charged (photosensitive member) is configured as an OPC photosensitive drum having an organic photoconductive semiconductor layer. However, the member to be charged is not limited to this. For example, it may be configured to include an amorphous silicon photoconductive semiconductor layer (amorphous silicon layer), or may be configured to include a selenium photoconductive semiconductor layer (selenium layer).

Further, the charging device of each of the above embodiments can be housed in a cartridge used for a copying machine, a printer, or the like.

[0058]

As described in detail above, according to the charging device of the first aspect of the present invention, the leading end of the charging plate is configured to be in contact with the surface of the member to be charged. It is not necessary to provide a tip portion that is more protruding than a portion in contact with the member to be charged, so that the material cost of the charging plate can be reduced accordingly, thereby reducing the cost of manufacturing the charging plate. On the other hand, when the DC voltage is applied to the charging plate to start charging the member to be charged, the voltage applied to the charging plate becomes 3.5.
Since a voltage having an AC voltage component and a DC voltage component having a peak-to-peak voltage that is twice to 5.5 times is applied between the charged object and the charging plate, the charged object can be uniformly charged without charging unevenness. There are advantages.

According to the charging device of the second aspect of the present invention, the end of the charging plate in contact with the member to be charged is formed at a substantially right angle, so that the processing of the charging plate becomes easier and the processing thereof is simplified. The cost can be reduced, which has the advantage that the cost of manufacturing the charging plate can be further reduced. According to the charging device of the present invention, the volume resistivity of the charging plate is set to 1.
Since it is set to 0 × 10 ⁷ Ω · cm to 1.0 × 10 ¹¹ Ω · cm, there is an advantage that it is possible to prevent charging unevenness by securing the stability of the surface potential of the member to be charged. .

According to the charging device of the present invention, the charging plate is made of a conductive elastic member, and the charging plate is pressed against the surface of the member to be charged by the elastic force of the conductive elastic member. There is an advantage that the object to be charged can be uniformly charged without charging unevenness while having a simple structure. According to the charging device of the fifth aspect of the present invention, the charging plate is made of a conductive resistor, and the conductive resistor is pressed against the surface of the charged object by the pressing force applying means. There is no need to provide a structure that also has a function of pressing against the surface of the charged member, and the conductive resistor can be formed of an amount of material necessary for charging the charged member, so that the material cost of the charging member can be reduced. There is an advantage that can be.

According to the charging device of the present invention, the charging plate is made of a conductive polymer film, and the conductive polymer film is pressed against the surface of the member to be charged by the pressing force applying means. There is an advantage that the material cost and processing cost of the member can be reduced. According to the charging device of the present invention, since the pressing force by the charging plate is set to 9.8 N / m to 49.0 N / m, the stability of the surface potential of the member to be charged is ensured. While preventing charging unevenness, for example, about 50
There is an advantage that damage (scratch or scraping) on the surface of the member to be charged can be prevented after printing 00 sheets.

According to the electrophotographic apparatus of the present invention, the foremost part of the charging plate is configured to be in contact with the surface of the photoreceptor, and the charging plate is more contacted with the charging plate than the portion where the charging plate and the photoreceptor are in contact. Since there is no need to provide a protruding tip portion, the material cost of the charging plate can be kept low by that much, thereby reducing the cost of manufacturing the charging plate and applying a DC voltage to the charging plate. And a voltage having an AC voltage component and a DC voltage component having a peak-to-peak voltage of 3.5 to 5.5 times the voltage applied to the charging plate when charging of the photosensitive member is started. Since the voltage is applied between the photoconductors, there is an advantage that the photoconductor can be uniformly charged without charging unevenness.

According to the electrophotographic apparatus of the present invention, since the photosensitive member is configured to have the organic photoconductive layer, the cost for manufacturing the charging device can be further reduced. Further, there is an advantage that the photosensitive member can be uniformly charged without charging unevenness while reducing the manufacturing cost of the electrophotographic apparatus. According to the charging device of the present invention, since the end portion of the charging plate is formed substantially at a right angle, the processing for forming the charging plate is easy. Even if the charging plate is formed in the charging plate, the charging plate is arranged such that at least the most distal end of the substantially right-angled end of the charging plate is in contact with the surface of the charging member, and a DC voltage is applied to the charging plate to charge the charging member. A voltage having an AC voltage component and a DC voltage component having a peak-to-peak voltage of 3.5 to 5.5 times the applied voltage value of the charged plate at the start of the charging is applied between the charged object and the charged plate. Thus, there is an advantage that the object to be charged can be uniformly charged without charging unevenness.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a charging device according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating an electrophotographic apparatus including the charging device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a relationship between a volume resistivity of a charging plate and a surface potential of an OPC photosensitive drum in the charging device and the charging method according to the first embodiment of the present invention.

FIG. 4 is a diagram for explaining an influence of a pressing force by a charging plate in the charging device and the charging method according to the first embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the DC voltage applied in the charging device and the charging method according to the first embodiment of the present invention and the surface potential of the OPC photosensitive drum.

FIG. 6 is a graph showing the relationship between the peak-to-peak voltage of the AC voltage applied in the charging device and the charging method according to the first embodiment of the present invention and OP
FIG. 4 is a diagram illustrating a relationship with a surface potential of a C photosensitive drum.

FIG. 7 is a schematic diagram illustrating a charging device according to a second embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating a charging device according to a third embodiment of the present invention.

9A and 9B are schematic diagrams illustrating a charging member provided in a conventional electrophotographic apparatus, wherein FIG. 9A illustrates a roll-shaped charging member, and FIG. 9B illustrates a charging plate.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 OPC photoreceptor drum 1 A Roll base 1 B Photoreceptor layer (organic photoreceptor layer, OPC layer) 2 Charging plate 2 A Tip 2 B Foremost end 3 Power supply (voltage applying means) 4 Conductive polymer film 5 Porous elastic member ( Pressing force applying means) 6 housing 7 conductive resistor 8 metal member (support member, pressing force applying means) 9 conductive elastic member (pressing force applying means) 10, 20, 21 charging device 11 exposure device 12 developing device 12a Developing roller 12b Toner collecting and supplying roller 12c Layer thickness regulating blade 12d Toner stirrer 13 Transfer device (transfer roller) 14 Fixing device 15 Recording medium 16 Cleaning device 16A Cleaning blade

Claims (10)

[Claims] 1. A charging plate for charging an object to be charged by contacting at least a foremost portion with a surface of the object to be charged, and a charging plate for applying a DC voltage to the charging plate to start charging the object to be charged. 3.5 of the applied voltage value of the charging plate
Voltage applying means for applying a voltage having an AC voltage component having a peak-to-peak voltage of double to 5.5 times and a DC voltage component between the member to be charged and the charging plate. Charging device. 2. The charging device according to claim 1, wherein an end of said charging plate on a side in contact with said member to be charged is formed in a substantially right angle. 3. The charging plate having a volume resistivity of 1.0 ×
The charging device according to claim 1, wherein the charging device has a resistivity of 10 ⁷ Ω · cm to 1.0 × 10 ¹¹ Ω · cm. 4. The charging device according to claim 1, wherein the charging plate is formed of a conductive elastic member that comes into contact with the surface of the member to be charged. 5. The charging plate is composed of a flat conductive resistor in contact with the surface of the charged body, supports the conductive resistor, and connects the conductive resistor to the surface of the charged body. The charging device according to any one of claims 1 to 3, further comprising a pressing force applying unit that presses the surface. 6. The charging plate is constituted by a conductive polymer film that comes into contact with the surface of the member to be charged, and has a pressing force applying means for pressing the conductive polymer film against the surface of the member to be charged. 2. The method according to claim 1, wherein
The charging device according to any one of claims 1 to 3. 7. The pressing force of the charging plate is 9.8N.
/ M to 49.0 N / m. 8. A charging plate for charging the photoreceptor by contacting at least the foremost portion with the surface of the photoreceptor, and a charging plate when a DC voltage is applied to the charging plate to start charging the photoreceptor. Voltage applying means for applying a voltage having an AC voltage component and a DC voltage component having a peak-to-peak voltage of 3.5 to 5.5 times the applied voltage value between the member to be charged and the charging plate; An electrophotographic apparatus, comprising: 9. The electrophotographic apparatus according to claim 8, wherein said photoconductor has an organic photoconductor layer. 10. A charging plate forming step of forming an end of the charging plate in a substantially right-angled shape, and the charging plate such that at least the most distal end of the substantially right-angled end of the charging plate is in contact with the surface of the member to be charged. A charging plate arranging step, and applying a DC voltage to the charging plate to start charging the member to be charged by 3.5 of the voltage applied to the charging plate.
Charging a charged object by applying a voltage having an AC voltage component and a DC voltage component having a peak-to-peak voltage of 2 to 5.5 times between the charged object and the charging plate. A charging method, comprising: