JP2000267386A - Electrifying device and image forming device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the defect of image quality like a vertical stripe from occurring by irregular potential generated because a foreign matter such as toner or additive adheres to a holding member holding an ionic conductive medium. SOLUTION: This electrifying device 2 is provided with contact members 21 and 22 being in contact with an image carrier 1 on an upstream side and a downstream side in the moving direction of a member to be electrified, and provided with a side seal member 23 at both ends in a direction orthogonal to the moving direction of the member. By holding the liquid type ionic conductive medium 25 in an area 24 surrounded by the contact members 21 and 22 and the side seal member 23 and applying voltage to the medium 25, the member is electrified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for charging an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric, and an electrophotographic copying machine or laser beam printer provided with such a charging device. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electro-recording apparatus, and more particularly to a charging apparatus that charges a surface of a member to be charged by charge injection without discharging and an image forming apparatus using the same.

[0002]

2. Description of the Related Art As a charging device for charging an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric, a corotron for charging an image carrier using corona discharge has been widely used. Such a corotron is effective as a means for uniformly charging the image carrier, but requires applying a high voltage of several kV to charge the image carrier to a predetermined potential, and requires a high-voltage power supply. I do. In addition, the discharge products such as ozone generated by corona discharge cause deterioration of the rubber parts and the image carrier, and an ozone filter is required to prevent the ozone generated by corona discharge from being discharged outside the machine. Will be up.

Therefore, as a charging device replacing the corotron, conductive members having various shapes such as a roll, a brush, a blade, a film, and a belt are brought into contact with an image carrier, and a voltage is applied to the conductive members. A contact-type charging device that charges an image carrier by applying a voltage has been developed and is actually used. These contact-type charging devices have the advantage that very little ozone is generated and that a lower power supply voltage than that of a corotron may be used.

However, these contact-type charging devices require a process speed, which is a moving speed of the surface of the image carrier, when the image carrier is charged by applying a voltage obtained by superimposing an AC voltage on a DC voltage to the conductive member. Is faster, charging unevenness (so-called AC ripple) corresponding to the AC voltage becomes large, and appears as density unevenness in image quality. Therefore, the frequency of the AC voltage has to be set high. However, when the frequency of the AC voltage applied to the conductive member is set to a high value, the AC current flowing through the image carrier increases, so that the image carrier such as the photoconductor is easily damaged, and the photoconductor by the cleaner blade is easily damaged. This is a major factor in promoting wear of the image carrier such as a body. Therefore, at present, a contact-type charging device that applies a voltage obtained by superimposing an AC voltage on a DC voltage to a conductive member cannot be mounted on an image forming apparatus such as a medium-speed copying machine having a high process speed.

Further, the contact-type charging device charges the image carrier by applying only a DC voltage to the conductive member.
The charging uniformity is inferior to that in which a voltage obtained by superimposing an AC voltage on a DC voltage is applied. In addition, toner and the like charged in the opposite polarity to the applied voltage are greatly contaminated by toner and the like. Also have problems.

In order to solve these problems of the contact type charging device, there is known a charging device in which water or an ionic conductive medium in which an electrolyte or ionizable gas molecules are dispersed is brought into contact with the image carrier. A charging device that charges an image carrier by applying a voltage to the ionic conductive medium has been considered.

Techniques relating to this type of novel charging device are disclosed in, for example, JP-A-7-325458, JP-A-9-22160, JP-A-9-179376 and JP-A-9-179377. What has been already proposed.

[0008] These JP-A-7-325458,
JP-A-9-22160, JP-A-9-179376
In Japanese Patent Application Laid-Open No. 9-179377, a member impregnated with water such as polyurethane foam is brought into contact with a photosensitive drum, and a DC voltage is applied to the polyurethane foam impregnated with water to charge the photosensitive drum. After that, in order to prevent water from adhering to the developing device while adhering to the surface of the photoconductor drum and causing image quality defects, a wiper-shaped blade that wipes off water adhering to the photoconductor drum Is provided.

In Japanese Patent Laid-Open Nos. 7-140729 and 8-62932, a water-absorbing sponge roller impregnated with water is brought into contact with the surface of a photosensitive drum, and a DC voltage is applied to the water-absorbing sponge roller. Is applied to charge the surface of the photosensitive drum.

[0010]

However, the prior art described above has the following problems. That is, JP-A-7-325458,
-22160, JP-A-9-179376 and JP-A-9-179377, or JP-A-7-140729 and JP-A-8-179329.
In the case of the charging device disclosed in JP-A-62932,
By contacting the surface of the photosensitive drum with a water-absorbing sponge roller impregnated with water or a member impregnated with water such as polyurethane foam, the surface of the photosensitive drum is charged to a predetermined potential, Foreign materials such as toner used for development and external additives added to the outer periphery of the toner adhere to members such as a polyurethane foam and a sponge roller. Then, in the case of the above-described conventional charging device, the ionic conductive medium such as water is not partially supplied to the surface of the photoconductor drum from a member such as a polyurethane foam or a sponge roller. There is a problem that unevenness occurs in the image and a vertical streak-like image quality defect appears.

As described above, as a water-containing member for charging the surface of the photosensitive drum, a porous member such as a polyurethane foam or a sponge roller is often used because of its high water absorption. When a water-containing member is used, foreign matter such as toner used for development or an external additive added to the outer periphery of the toner easily adheres to holes of a polyurethane foam or a sponge roller. This is problematic in that cracks easily occur.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a holding member holding an ionic conductive medium with a toner or an external additive. It is an object of the present invention to provide a charging device and an image forming apparatus using the charging device, which can prevent the generation of a vertical streak-like image quality defect due to potential unevenness caused by the attachment of a foreign substance.

[0013]

According to a first aspect of the present invention, a liquid ionic conductive medium is brought into contact with a member to be charged. In a charging device that performs charging by applying a voltage, a contact member that contacts an image carrier is provided on an upstream side and a downstream side in a moving direction of the charged member, and a contact member in a direction orthogonal to the moving direction of the charged member is provided. Side seal members are provided at both ends, a liquid ionic conductive medium is held in a region surrounded by the contact member and the side seal member, and a voltage is applied to the liquid ionic conductive medium. A charging member for charging the member to be charged.

The invention according to claim 2 is the charging device according to claim 1, wherein the contact member is made of an elastic body.

Further, the invention according to claim 3 is the charging device according to claim 1 or 2, wherein the contact member has a wiper shape.

[0016] Still further, the invention described in claim 4 is:
An electrode for applying a voltage is provided on at least a part of a longitudinal direction of the liquid ionic conductive medium held in a region surrounded by the contact member and the side seal member. A charging device according to any one of 1 to 3.

Further, according to a fifth aspect of the present invention, a liquid ionic conductive medium is brought into contact with an image carrier, and a voltage is applied to the ionic conductive medium to thereby change the surface of the image carrier. Equipped with a charging device for charging to a predetermined potential,
In the image forming apparatus for forming an image by charging the surface of the image carrier to a predetermined potential by the charging device, the charging device contacts the image carrier on the upstream side and the downstream side in the moving direction of the image carrier. Providing a contact member that
Side seal members are provided at both ends in a direction orthogonal to the moving direction of the member to be charged, and a liquid ionic conductive medium is held in a region surrounded by the contact member and the side seal member; An image forming apparatus characterized in that an image carrier is charged by applying a voltage to the ionic conductive medium.

[0018]

According to the present invention, contact members for contacting the image carrier are provided upstream and downstream in the moving direction of the member to be charged, and both ends in the direction orthogonal to the moving direction of the member to be charged. Providing a side seal member in the portion, holding a liquid ionic conductive medium in a region surrounded by the contact member and the side seal member, and applying a voltage to the liquid ionic conductive medium. By charging the member to be charged with water, it is not necessary to use a water-containing member such as a sponge as in the past, and therefore, a vertical potential due to non-uniform potential generated due to the attachment of foreign substances such as toner and external additives to the water-containing member. The generation of streak-like image quality defects can be prevented.

[0019] Further, according to the fourth aspect,
In the charging device for charging the liquid ionic conductive medium by directly contacting the image bearing member or the like, which is a member to be charged, it is only necessary to provide the electrodes in a part of the longitudinal direction, so that the cost is low and the configuration is simple. Can be taken.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 2 shows an image forming apparatus to which a charging device according to Embodiment 1 of the present invention is applied.

In FIG. 2, reference numeral 1 denotes a photosensitive drum as an image bearing member. As the photosensitive drum 1, for example, a so-called organic photoconductive substance formed by coating an aluminum pipe having a diameter of 80 mm with an organic photoconductive substance is used. Those based on organic photoreceptors are used. The photosensitive drum 1 has an axis in a direction perpendicular to the plane of the drawing, and is driven to rotate at a predetermined speed by driving means (not shown) along the direction of the arrow shown in the figure. The surface of the photosensitive drum 1 is
After being negatively charged to a predetermined potential by the charging device 2 according to the first embodiment of the present invention, an image is exposed by the exposure device 3, and an electrostatic latent image corresponding to the image is formed on the surface of the photosensitive drum 1. An image is formed. The developing device 4 reversely develops the negative toner on the electrostatic latent image formed on the photoconductor drum 1 and visualizes the electrostatic latent image. Thereafter, the toner image visualized on the photosensitive drum 1 is transferred onto a transfer sheet 5 which is conveyed to a transfer position on the surface of the photosensitive drum 1 in synchronization with the toner image. The transfer is performed by the transfer electric field to be formed and the pressing force. The transfer paper 5 on which the toner image has been transferred as described above is separated from the surface of the photosensitive drum 1 and is conveyed to a fixing device (not shown).
The fixing device fixes the toner image and discharges the toner image to the outside of the device.

After the toner image has been transferred onto the transfer paper 5, the surface of the photosensitive drum 1 is cleaned of residual toner and paper dust by a disturber brush 8 and a cleaner blade 9 of a cleaning device 7. Then, it is prepared for the next image forming step. Further, between the cleaning device 7 and the charging device 2, an unillustrated static eliminator for neutralizing the surface of the photosensitive drum 1 may be provided.

In FIG. 2, reference numeral 10 denotes a DC power supply for applying a predetermined DC voltage to the charging device 2.

FIG. 1 shows a charging device according to Embodiment 1 of the present invention.

Charging device 2 according to Embodiment 1 of the present invention
The contact member mainly comes into contact with the surface of the photosensitive drum 1 on the upstream and downstream sides in the rotation direction of the photosensitive drum 1 as an image carrier, and the contact member on both ends in the axial direction of the photosensitive drum 1 A side seal member is provided in contact with the surface of the photoreceptor drum 1, and a liquid ionic conductive medium is held in a space surrounded by the contact member and the side seal member. The surface of the photosensitive drum 1 is charged by applying a voltage to the medium.

As shown in FIG. 1, a pair of wiper blades 21 and 22 are arranged on the surface of the photosensitive drum 1 at predetermined intervals on the upstream and downstream sides in the rotation direction of the photosensitive drum 1. And the photosensitive drum 1 of the pair of wiper blades 21 and 22
The brushes 23 and 23 for insulating side seals in which Teflon particles are dispersed are in contact with both ends in the axial direction. In a region 24 surrounded by the pair of wiper blades 21 and 22 and brushes 23 and 23 for side sealing at both ends, pure water obtained as ordinary ion-exchanged water as a liquid ionic conductive medium is provided. Water 25 is retained. Pure water 25 is used as the liquid ionic conductive medium.
Is supplied from the water supply port 26 located at the base end (upper end) of the pair of wiper blades 21 and 22 as necessary.

The wiper blade 21 located on the upstream side in the rotation direction of the photosensitive drum 1 has a photosensitive member on the inner surface (downstream side) and near the contact portion of the photosensitive drum 1. A metal power supply electrode 27 is deposited along the axial direction of the drum 1. This power supply electrode 27
Is supplied with a predetermined DC voltage by the charging device power supply 10.

In the first embodiment, a pair of wiper blades 21 and 22 and brushes 2 for side sealing at both ends are provided.
Pure water 25 is held as a liquid ionic conductive medium in a region 24 surrounded by 3 and 23. However, the present invention is not limited to this. Examples of the liquid ionic conductive medium include: Water such as distilled water or tap water, or a liquid in which an electrolyte or ionizable gas molecules are dissolved in a solvent such as water or alcohol can be used. In addition, as the electrolyte dissolved in a solvent such as water or alcohol,
LiClO ₄ , Na ₂ SO ₄ , Na ₂ CO ₃ , NaHC
O ₃ , NaCl, KCl, LiCl, MgCl ₂ , Ca
Various electrolytes such as Cl ₂ and (NH ₄ ) ₂ SO ₄ can be used. On the other hand, examples of ionizable gas molecules include CO ₂ . As the ionizable gas molecules such as CO ₂ , those which are naturally dissolved in water or the like may be used, or those which are positively dissolved may be used.

The liquid ionic conductive medium 2
The volume resistivity of 5 is appropriately set within a range of about 10 ² to 10 ⁹ Ωcm. The resistance value of the pure water 25 used here was about 10 ⁵ Ω.

Further, in the first embodiment, the liquid ionic conductive medium 2 contacts the surface of the photosensitive drum 1
Although a pair of wiper blades 21 and 22 were used as a contact member for holding 5, a pair of a doctor blade or a combination of a wiper blade and a doctor blade,
Alternatively, those having various shapes such as a cylindrical contact member can be used, and are appropriately selected. Also, as the material, urethane rubber, nitrile rubber, chloroprene rubber, silicone rubber, natural rubber, NBR, fluorine rubber, copolymer of siloxane and methacrylate, polyvinyl acetate, PVA, polyvinyl chloride, cellulose,
Various polymers such as PMMA can be used and are appropriately selected. In particular, the elastic material such as rubber has good adhesion to the photosensitive drum 1 and is most suitable for sealing.

Here, the "wiper blade" refers to the one shown in FIG.
As shown in the figure, the tip 21a of the blade 21 is pressed against the downstream side in the rotation direction of the photosensitive drum 1 and
1 is located on the upstream side in the rotation direction of the photosensitive drum 1 and the blade 21 is arranged such that the base end 21b side of the blade 21 is inclined with respect to the surface of the photosensitive drum 1. means. The wiper blade 21
Is made of an elastic material such as urethane rubber, and when it is pressed against the surface of the photosensitive drum 1 by a predetermined amount, FIG.
As shown in (2), when the front end portion is pressed against the surface of the photosensitive drum 1, the shape is curved so as to curve upward.

In this embodiment, as described above, a polyurethane blade which is often often used as a cleaner blade of the photosensitive drum 1 is used as the pair of contact members. As shown in FIG. 3, the blade 21 is formed with a thickness t = 2 mm, a width l = 15 mm, a free length L = 10 mm, and a length substantially equal to the entire width of the photosensitive drum 1. SA ”) is set to 60 °, and the amount of biting into the photosensitive drum 1 (hereinafter, referred to as“ nip amount ”) is mainly set to 0.4 mm. However, it goes without saying that the SA and the nip amount of the wiper blade 21 may be set to other values. On the surface side of the base end of the wiper blade 21,
A sheet metal 28 made of stainless steel, aluminum, or the like is fixed by means such as adhesion, and the wiper blade 51 is attached to the charging device main body (not shown) so that the wiper blade 51 is pressed against the photosensitive drum 1 in the state described above. The setting angle SA is set as described above.

In the first embodiment, the brushes 23 are used as the side seal members. However, the present invention is not limited to this, and a side seal made of rubber or the like may be used. These side seal members use a Teflon (registered trademark) brush because the sealing effect increases when the water repellency is high.

In the charging device according to the first embodiment having the above structure, foreign matters such as toner and external additives adhere to the holding member for holding the liquid ionic conductive medium in the following manner. It is possible to prevent the occurrence of vertical stripe-like image quality defects due to the resulting potential unevenness.

That is, in the charging device 2 according to the first embodiment, as shown in FIG. 1, a pair of wipers are provided on the surface of the photosensitive drum 1 on the upstream and downstream sides in the rotation direction of the photosensitive drum 1. The blades 21 and 22 are in parallel contact with each other at a predetermined interval, and both ends of the pair of wiper blades 21 and 22 in the axial direction of the photosensitive drum 1 are made of insulating material in which Teflon particles are dispersed. The side seal brushes 23, 23 are in contact,
In a region 24 surrounded by the pair of wiper blades 21 and 22 and brushes 23 and 23 for side sealing at both ends, pure water 25 obtained as ordinary ion-exchanged water as a liquid ionic conductive medium is used. Is held. The charging device 2 includes a pair of wiper blades 2.
1, 22 and pure water 25 as a liquid ionic conductive medium held in a region 24 surrounded by brushes 23, 23 for side seals at both ends.
By applying a predetermined voltage through the power supply electrode 27 provided on the inner surface of the pure water 1, pure water 25 obtained as ordinary ion-exchanged water and an ionizable gas dissolved in the pure water 25 CO ₂ or the like is, ionized by ionizing as shown below, by applying a voltage of negative polarity to the water 25, electrostatically deposited ions ionized negatively on the surface of the photosensitive drum 1 The surface of the photosensitive drum 1 is charged to a predetermined potential. ^{_{H 2 O⇔H + + OH - CO}} 2 + H 2 O⇔H 2 CO 3 H 2 CO 3 ⇔H + + HCO 3 - HCO 3 - ⇔H + + CO 3 2-

For this reason, pure water 25 as a liquid ionic conductive medium held in a region 24 surrounded by a pair of wiper blades 21 and 22 and side seals 23 and 23 of the charging device 2 includes: What is necessary is just to apply a DC voltage equal to the charging potential of the photosensitive drum 1, and since corona discharge or the like basically does not occur, generation of ozone can be almost completely suppressed. In a region 24 surrounded by the pair of wiper blades 21 and 22 and the side seals 23 and 23, pure water 25 obtained as normal ion-exchanged water for generating ions or ionized water It is sufficient to supply a liquid in which CO ₂ or the like, which is a possible gas, is dissolved, and the pure water 25 is ionized and ionized, so that the surface of the photosensitive drum 1 can be immediately charged to a predetermined potential. Therefore, the present invention can be sufficiently used even in an image forming apparatus such as a medium-speed copying machine. Further, the pair of wiper blades 21 and 22 and the side seal 23,
Since the voltage applied to the liquid ionic conductive medium 25 held in the region 24 surrounded by 23 may be a DC voltage equal to the charging potential of the photosensitive drum 1, an AC voltage is applied to the contact-type charging member. There is no need to apply a DC voltage on which is superimposed, so that there is no danger of damaging the surface of the photosensitive drum 1 by applying an AC voltage, and there is no problem of abrasion of the photosensitive drum 1.

Further, in the charging device 2 according to the first embodiment, pure water 25 as a liquid ionic conductive medium is used.
However, as described above, the surface of the photosensitive drum 1 is charged to a predetermined potential by coming into direct contact with the surface of the photosensitive drum 1, so that foreign matters such as toner and external additives adhere to the surface of the photosensitive drum 1. Even in the case where the potential is uneven, the potential unevenness does not occur, and it is possible to prevent the occurrence of a vertical streak-like image quality defect due to the potential unevenness.

Experimental Example 1 Next, in order to confirm the effects of the present invention, as described above, the present inventors prototyped a charging device 2 using a polyurethane blade as a pair of contact members. An image forming test was performed.

As shown in FIG. 3, the wiper blade 21 of this experimental example has a thickness t = 2 mm and a width l =
15 mm, free length L = 10 mm, length: photosensitive drum 1
, The nip amount was set to 0.4 mm.

The process speed of the photosensitive drum 1 is 160 mm / s.
V DC voltage was applied.

Under the above conditions, a durability test was performed on 10,000 sheets by repeating the operation of printing 10 sheets and pausing for 1 second.

For comparison, a similar endurance trial paper-through test was performed with a conventional wet pad charging device as shown in FIG.

In this comparative example, a charging member 50 in which the photosensitive drum 1 is impregnated with water is arranged so as to contact with a constant pressure by a spring 52 via a pressing member 51. Here, the pressing member 51 is formed of aluminum, and also functions as an electrode. A DC voltage was supplied to the pressing member 51 by a charging device power supply 53. The charging member 50 is a pad-shaped member made of PVA and having a thickness of 2.0 mm, and a member impregnated with pure water obtained as ordinary ion-exchanged water is used.
The contact width between the charging pad 50 and the photosensitive drum 1 was 5 mm. Further, the resistance value of the charging pad 50 in this water-containing state was about 10 ⁶ Ω. Further, a wiper blade 54 for wiping off water is disposed downstream of the charging pad 50. This wiper blade 54
Is similar to the blade 21.

In this comparative example, water was manually supplied to the charging pad 50 from the water supply port 55 as needed.

Other configurations and operations are performed by a pair of blades 2.
This is the same as in the case of the charging device 2 in which the pure water 25 is held by the first and second side seals 23 and 23, and therefore the description is omitted.

Hereinafter, the result of the durability paper passing test will be described.

In the comparative example, the water-containing pad-type charging device has
At the time of 000 sheets, several high-density vertical streak image quality defects and some low-density vertical streak image quality defects appeared on the print.

As shown in Table 1 of FIG. 5, the surface potentials of the photoreceptor corresponding to the high-density streaks and the low-density streaks were -630 V and -670 V, respectively. The potential of the normal part was -650 V. Therefore, it is considered that the high-concentration muscle portions could not be raised to a normal potential, and the low-concentration muscle portions occurred because the potential had risen above the normal potential.

Further, as shown in FIG.
Take out and observe the water-containing pad 50 that is in contact with
Streak-like contamination was observed in which a large amount of foreign matter such as toner was deposited on portions corresponding to the vertical streak portions.

When the contaminants on the pad 50 corresponding to the high density streak were analyzed, it was almost toner. It is probable that water was not sufficiently supplied to the photoreceptor because a large amount of toner was deposited, and the potential was not sufficiently raised, resulting in low charge and high-density streak-like image quality defects.

When the contaminants on the pad 50 corresponding to the low-density streaks were analyzed, a large amount of TiO ₂ externally added to the toner was detected in addition to the toner.

Separately from the endurance paper passing test, for confirmation, a water content of 50 mg / cm ² sufficient for normal electrification.
When the potential is measured with a configuration in which TiO ₂ is coated on the charging pad of (1), the potential of the photosensitive drum 1 becomes about −6 in the same manner as described above.
The voltage rose to about 70 V, and a low-density vertical stripe-like image quality defect occurred on the print.

From these results, probably due to the TiO ₂ adhered to the charging pad 50, triboelectric charging occurred,
It is considered that the potential increased to a predetermined value or more, and low-concentration vertical streaks occurred.

On the other hand, in the endurance paper passing test of the present experimental example, the surface potential of the photosensitive drum 1 was maintained at a normal potential of about -650 V over 10,000 sheets, and the vertical streak appeared on the print. No image quality defects or the like occurred.

This is because, unlike the comparative example, water does not come into contact with the photosensitive drum via a member such as a pad on which foreign substances such as toner and external additives are likely to accumulate, and a pair of wiper blades is used. 21, 22 and a pair of side seals 2
The reason is that water can be brought into direct contact with the photosensitive drum 1 by the methods 3 and 23, so that the deterioration of charging uniformity due to contamination can be prevented.

Second Embodiment FIGS. 7 and 8 show a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals and described. In the second embodiment, a contact member for holding the liquid ionic conductive medium in contact with the upstream side and the downstream side in the rotation direction of the image carrier is configured differently from the first embodiment. .

That is, in the embodiment shown in FIG.
On the surface of the photoconductor drum 1, a pair of columnar members 31 on the upstream side and the downstream side in the rotation direction of the photoconductor drum 1,
32 are in contact with each other in parallel at a predetermined interval. As the pair of columnar members 31 and 32, for example, a member made of a fluorine rubber-based elastic body having a diameter of 10 mm is used, but is not limited to this. The pair of columnar members 31 and 32 are
4 and 35, and is brought into contact with the surface of the photosensitive drum 1 at a predetermined pressure by the elastic force of the springs 36 and 37 via the holders 34 and 35. As in the first embodiment, brushes 23 for insulating side seals in which Teflon particles are dispersed are provided on both ends of the pair of columnar members 31 and 32 in the axial direction of the photosensitive drum 1. 23 are used. In a region 24 surrounded by the pair of columnar members 31 and 32 and the side sealing brushes 23 at both ends, ordinary ion exchange water was obtained as a liquid ionic conductive medium. Pure water 25 is held. The pure water 25 as the liquid ionic conductive medium includes a pair of holders 34,
From the water supply port 26 located at the base end (upper end) of 35,
Supplied as needed.

The holder 34 located on the upstream side in the rotation direction of the photosensitive drum 1 has an axial surface of the photosensitive drum 1 on its inner surface and near the contact portion of the photosensitive drum 1. A metal power supply electrode 27 is deposited. A predetermined DC voltage is supplied to the power supply electrode 27 by the power supply 10 for the charging device.

On the other hand, in the embodiment shown in FIG. 8, a pair of doctor blades 4 are provided on the surface of the photosensitive drum 1 on the upstream and downstream sides in the rotation direction of the photosensitive drum 1.
1 and 42 are in parallel contact with each other at a predetermined interval, and the pair of doctor blades 41 and 42
At the opposite ends of the photosensitive drum 1 in the axial direction, brushes 23, 2 for insulating side seals in which Teflon particles are dispersed are provided.
3 are in contact. Then, the pair of doctor blades 41, 42 and the brushes 23, 2 for side sealing at both ends are provided.
In a region 24 surrounded by 3, pure water 25 obtained as ordinary ion-exchanged water is used as a liquid ionic conductive medium.
Is held. Pure water 25 as the liquid ionic conductive medium is supplied as necessary from a water supply port 26 located at the base end (upper end) of the pair of doctor blades 41 and 42. I have.

The daughter blade 41 located on the upstream side in the rotation direction of the photosensitive drum 1 has a photosensitive member on its inner surface (downstream side) and near the contact portion of the photosensitive drum 1. A metal power supply electrode 27 is deposited along the axial direction of the drum 1. This power supply electrode 27
Is supplied with a predetermined DC voltage by the charging device power supply 10.

Here, the “doctor blade” is the one shown in FIG.
As shown in the figure, the tip 41a of the blade 21 comes into pressure contact with the rotation direction upstream side of the photosensitive drum 1 and the blade 2
1 is located on the downstream side in the rotation direction of the photoconductor drum 1 and the blade 41 is arranged such that the base end 41b side of the blade 41 is inclined with respect to the surface of the photoconductor drum 1. means.

As shown in FIG. 9, the doctor blade 41 has a thickness t = 2 mm, a width l = 15 mm, and a free length L =
10 mm, the length is formed over substantially the entire width of the photosensitive drum 1,
The setting angle (hereinafter, referred to as “SA”) is set to 20 °, and the amount of biting into the photosensitive drum 1 (hereinafter, referred to as “nip amount”) is mainly set to 0.6 mm.
However, it goes without saying that the SA and the nip amount of the doctor blade 41 may be set to other values.

The pair of doctor blades 4
As in the first embodiment, brushes 23 and 23 for insulating side seals in which Teflon particles are dispersed are used at both ends in the axial direction of the photosensitive drums 1 and 42. A region 24 surrounded by the pair of doctor blades 41 and 42 and brushes 23 and 23 for side sealing at both ends is provided as a liquid ionic conductive medium with pure ion exchange water obtained as ordinary ion exchange water. Water 25 is retained. Pure water 25 is used as the liquid ionic conductive medium.
Is supplied from the water supply port 26 located at the base end (upper end) of the pair of doctor blades 41 and 42 as necessary.

The doctor blade 41, which is located on the upstream side in the rotation direction of the photosensitive drum 1, has an axial surface of the photosensitive drum 1 on its inner surface and near the contact portion of the photosensitive drum 1. Power supply electrode 2 made of metal over the direction
7 has been deposited. A predetermined DC voltage is supplied to the power supply electrode 27 by the power supply 10 for the charging device.

The other configuration and operation are the same as those of the charging device according to the first embodiment in which water is held by a pair of blades and side seals, and a description thereof will be omitted.

With the configuration shown in FIGS. 7 and 8, respectively,
When a paper-passing test similar to that of Experimental Example 1 was performed, the surface potential of the photosensitive drum was normal, and no vertical stripe-like image quality defect was observed.

In the second embodiment, good results were obtained by using a columnar fluorine rubber as shown in FIG. 7 as the contact member. The shape is not limited to a columnar shape if an elastic body that easily adheres is used.

However, the blade shape in which the edge is brought into contact with the surface of the photoreceptor as shown in FIG. 8 is more desirable than the method in which the surface is brought into contact with the surface as shown in FIG. .

From the viewpoint of space, the wiper blade is more preferable because it does not require a space in the circumferential direction of the photosensitive drum 1. In particular, the wiper blade is more preferable in consideration of the recent reduction in the diameter of the photosensitive drum.

Third Embodiment FIG. 10 shows a third embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals and will be described.
In this embodiment, the configuration of the electrode for supplying a DC voltage to the liquid ionic conductive medium is different from that of the first embodiment.

That is, in the third embodiment, the electrode 2 for supplying a DC voltage to the liquid ionic conductive medium 25 is used.
7 is not deposited on the wiper blade 21 located on the upstream side in the rotation direction of the photosensitive drum 1,
As shown in FIG. 2, a rod-shaped Au electrode 27 having a diameter of 2 mm and a length of 5 mm is formed by a pair of wiper blades 21 and 22 and brushes 23 and 23 for side seals at both ends in an area 24 surrounded by the electrodes.
And a DC voltage of −650 V is applied to the electrode 27 from the charging device power supply 10. The electrode 27 is, for example,
The pure water 25 held in a region 24 surrounded by a pair of wiper blades 21 and 22 and brushes 23 and 23 for side sealing at both ends is disposed at the center in the longitudinal direction (axial direction of the photosensitive drum) of the pure water 25.

Other configurations and operations are the same as those of the first embodiment.
The description is omitted because it is the same as the case of

The inventors of the present invention charged the surface of the photosensitive drum using the charging device constructed as described above, and measured the axial surface potential of the photosensitive drum at 10 points. And very excellent charging uniformity was exhibited.

This is because, in a charging device in which water 25 as a liquid ionic conductive medium is brought into direct contact with the photosensitive drum 1 to charge the photosensitive drum 1, the electrode 25 can be used without consciously extending the electrode in the axial direction. If the electrode 27 is provided even in one place as in the embodiment, since water is a conductor, the water held in the region 24 has the same voltage as the applied voltage, and as a result, a voltage drop is caused. This is because uneven charging does not occur.

Therefore, the electrode 27 may be provided at any position in the axial direction of the photosensitive drum 1 as long as it is in stable contact with the water 25. For example, it can be easily formed by a method of evaporating a metal on a part of an upstream or downstream blade. Also, the shape, size, length, and the like are not limited. As in this embodiment, the electrode 2
7 may be provided at one location, or may be stretched along the axial direction of the photosensitive drum as in the first or second embodiment.

As described above, the charging device that charges water by directly contacting the photosensitive drum has a great advantage in terms of cost and structure because it is only necessary to provide an electrode in a part of the longitudinal direction.

COMPARATIVE EXAMPLE As shown in FIG. 11, for comparison, a case will be described in which the electrode is provided only at one place in the wet pad system.

In this comparative example, the charging member 50 containing water is placed on the photosensitive drum 1 so as to be in contact with the pressing member 51 made of synthetic resin. A power supply electrode 54 is vapor-deposited on one surface of the synthetic resin pressing member 51 at a central portion in the axial direction, which is in contact with the water-containing pad 50, and a DC voltage of −650 V is applied to the electrode 54. 55
Is supplied with power. Charging member 50
Is a pad-shaped member made of PVA and having a thickness of 2.0 mm, in which the charging pad 50 is impregnated with pure water obtained as ordinary ion-exchanged water. The contact width between the charging pad 50 and the photosensitive drum 1 was 5 mm. The resistance value of the charging pad 50 in this water-containing state was about 10 ⁶ Ω.

With such a configuration, when the charging pad 50 is not contaminated at all, the surface potential in the axial direction of the photosensitive drum 1 is measured at ten places, and all are about -650.
V, showing very excellent charging uniformity.

Here, as shown in FIG. 12, when the toner is intentionally deposited on a part of the charging pad 50 in the form of a streak, a region (B) opposite to the electrode 54 across the streak (A) is obtained. )
Are all -62.
The voltage was about 0 V, and a large potential drop occurred, causing fog on the print.

This is considered to have occurred for the following reasons. In the configuration shown in FIG.
Since there is only one place, there is no voltage drop in the entire area (C) from the streak (A) of the charging pad 50 to the electrode 54 side, and the same voltage as the applied voltage is applied. )
A voltage drop occurs at the point (A) in the area (B).
It is considered that since only the voltage after the same voltage drop as that described above is applied, the surface potential of the photosensitive drum 1 has decreased, and fog has occurred.

[0083]

As described above, according to the present invention, the contact members for contacting the image carrier are provided on the upstream side and the downstream side in the moving direction of the member to be charged.
Side seal members are provided at both ends in a direction orthogonal to the moving direction of the member to be charged, and a liquid ionic conductive medium is held in a region surrounded by the contact member and the side seal member; By applying a voltage to the ionic conductive medium, the member to be charged is charged, so that a water-containing member such as a sponge is not used as in the past. It is possible to prevent a vertical streak-like image quality defect from occurring due to potential unevenness caused by the attachment of the foreign matter.

Further, according to the fourth aspect,
In the charging device for charging the liquid ionic conductive medium by directly contacting the image bearing member or the like, which is a member to be charged, it is only necessary to provide the electrodes in a part of the longitudinal direction, so that the cost is low and the configuration is simple. Can be taken.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram showing Embodiment 1 of the image forming apparatus to which the charging device according to the present invention is applied.

FIGS. 3A and 3B are configuration diagrams showing wiper blades, respectively.

FIG. 4 is a configuration diagram showing a conventional charging device.

FIG. 5 is a table showing the surface potential of the photosensitive drum.

FIG. 6 is an explanatory diagram showing a pad member photoconductor contact surface and a copy sample of a comparative example.

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

FIG. 8 is a configuration diagram showing a modification of the charging device according to Embodiment 2 of the present invention.

FIGS. 9A and 9B are configuration diagrams showing doctor blades, respectively.

FIG. 10 is a configuration diagram showing a third embodiment of the charging device according to the present invention.

FIG. 11 is a configuration diagram showing a charging device as a comparative example.

FIG. 12 is an explanatory diagram showing a pad member photoconductor contact surface and a copy sample of a comparative example.

[Explanation of symbols]

1: photosensitive drum (member to be charged, image carrier) 2: charging device 21, 22: wiper blade, 23: brush for side seal, 24: holding area for ionic conductive medium,
25: pure water (liquid ionic conductive medium), 27: electrode.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Tomomi Kutta 2274 Hongo, Ebina-shi, Kanagawa F-Xerox Co., Ltd. F-term (reference) 2H003 BB11 CC04 EE01 EE12 EE16

Claims (5)

[Claims] 1. A charging device that contacts a member to be charged with a liquid ionic conductive medium and charges the ionic conductive medium by applying a voltage to the member. A contact member that contacts the image carrier is provided on the side and the downstream side, and side seal members are provided at both ends in a direction orthogonal to the moving direction of the member to be charged, and are surrounded by the contact member and the side seal member. A charging device, comprising: holding a liquid ionic conductive medium in a region; and charging a member to be charged by applying a voltage to the liquid ionic conductive medium. 2. The charging device according to claim 1, wherein said contact member is made of an elastic body. 3. The charging device according to claim 1, wherein the contact member has a wiper shape. 4. An electrode for voltage application is provided on at least a part of a longitudinal direction of a liquid ionic conductive medium held in a region surrounded by the contact member and the side seal member. The charging device according to any one of claims 1 to 3, wherein 5. A charging device for bringing a liquid ionic conductive medium into contact with an image carrier and applying a voltage to the ionic conductive medium to charge the surface of the image carrier to a predetermined potential. An image forming apparatus that forms an image by charging the surface of the image carrier to a predetermined potential by the charging device, wherein the charging device includes an image carrier on an upstream side and a downstream side in a moving direction of the image carrier. And a side seal member provided at both ends in a direction orthogonal to the moving direction of the member to be charged, and a liquid ionic conductive material is provided in a region surrounded by the contact member and the side seal member. An image forming apparatus, wherein an image carrier is charged by holding a conductive medium and applying a voltage to the liquid ionic conductive medium.