JP2000047453A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an image quality defect caused by the leakage of an ionic conductive medium such as water from the end section of an electrification device and the wasteful consumption of the ionic conductive medium such as water by applying a liquid repellent process repulsing the ionic conductive medium at the end section in the axial direction of an image carrier. SOLUTION: A water repellent process repulsing water serving as an ionic conductive medium is applied to both the end section in the axial direction of a photoreceptor drum 1 and the end section in the longitudinal direction of a water regulating member 12 to provide water repellent process sections 1a, 12a. Even when water is stuck to the surface of the photoreceptor drum 1 and the water is moved to the end section in the axial direction of the photoreceptor drum 1, the water is repulsed by the water repellent process section 1a provided at the end section in the axial direction of the photoreceptor drum 1 and the water repellent process section 12a provided at the end section in the longitudinal direction of the water regulating member 12, and the water can be prevented from leaking from the end section of the photoreceptor drum 1. Stable electrification performance is obtained over a long period, and the occurrence of an image quality defect can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine having a charging device for charging an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric, a laser beam printer, or an image recording apparatus such as an electrostatic recording device. More particularly, the present invention relates to an image forming apparatus provided with a charging device for charging an image carrier using an ionic conductive medium.

[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 or a scorotron for charging an image carrier by performing corona discharge has been widely used. I have. These corotrons and scorotrons are effective as means for uniformly charging the image carrier, but a high voltage of several kV must be applied to charge the image carrier to a predetermined potential, and a high voltage power supply is required. Need. In addition, a discharge product such as ozone generated by corona discharge not only causes deterioration of rubber parts and an image carrier, but also leads to environmental pollution.

[0003] Therefore, as a charging device instead of a corotron or a scorotron, a roll shape, a brush shape, a blade shape,
Contact type charging devices have been developed in which a conductive member of various shapes such as a film or a belt is brought into contact with an image carrier, and a voltage is applied to the conductive member to charge the image carrier. It is actually used. These contact-type charging devices have the advantage that very little ozone is generated and that it is sufficient to use a lower power supply voltage than a corotron or the like.

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, uneven charging corresponding to the AC voltage (so-called “AC ripple”) increases,
Since the image quality appears as density unevenness, the frequency of the AC voltage must be set high. However, when the frequency of the AC voltage applied to the conductive member is set high as described above,
Since the AC current flowing through the image carrier increases, the image carrier such as the photoconductor is easily damaged, and this is a major factor in abrasion of the image carrier such as the photoconductor by the cleaner blade. Therefore, in a contact-type charging device in which a voltage obtained by superimposing an AC voltage on a DC voltage is applied to a conductive member, the life of an image carrier such as a photoconductor may be shorter than that in a case where a corotron or the like is used. There is.

In the above contact type charging device, A
In order to prevent the image carrier from being damaged by the C current, when the image carrier is charged by applying only a DC voltage to the conductive member, the charging uniformity is higher than that in which a voltage obtained by superimposing an AC voltage on a DC voltage is applied. In addition, the toner and the like charged to the opposite polarity to the applied voltage adhere to the charging member, and are greatly contaminated by the toner and the like, and have a problem in long-term maintainability.

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. As a technique relating to this type of novel charging device, those disclosed in Japanese Patent Application Laid-Open Nos. 7-140729 and 7-325458 have already been proposed.

In the contact charging method according to the above-mentioned Japanese Patent Application Laid-Open No. 7-140729, a water-impregnated water-absorbing sponge roller is brought into frictional contact with the surface of a photoreceptor, and a DC voltage is applied between the two. It is configured to charge the surface.

The method for charging an image forming member according to the above-mentioned Japanese Patent Application Laid-Open No. Hei 7-325458 is basically a method for charging a layered image forming member, in which ions are ionized from an ionic conductive medium. Although it is configured to charge a layered imaging member by transmission, the specification describes that an ionic conductive fluid, including a carrier liquid and an electrolyte, is capable of layering light by a number of different methods. It states that it can be brought into contact with the receptor and that any droplets, such as water, that can be transmitted to the surface of the photoreceptor can be wiped off, for example by means of a wiper blade.

[0009]

However, the prior art described above has the following problems. That is, in the case of the contact charging method according to JP-A-7-140729, a water-impregnated water-absorbing sponge roller or the like is brought into frictional contact with the surface of the photoreceptor, and a DC voltage is applied between the two. However, since the surface of the photoreceptor is configured to be charged, if the water content of the water-absorbing sponge roller is too large, water will flow into the developing device while adhering to the photoreceptor, causing image quality defects. On the other hand, when the water content is too small, there is a problem that poor charging occurs.

In the case of the method for charging an image forming member disclosed in JP-A-7-325458, droplets of water or the like which can be transmitted to the surface of an image forming member (image carrier) such as a photoreceptor are used. , So that it can be wiped off by a wiper blade. However, when the liquid droplets such as water supplied to the surface of the image carrier such as the photosensitive member are wiped by the wiper blade, the liquid such as water wiped by the wiper blade is used. The droplet gradually spreads, and eventually a liquid such as water leaks from the axial end of the image carrier such as a photoconductor to the surface of the image carrier, causing a problem of image quality defects. there were.

Further, in the case of the method for charging an image forming member according to Japanese Patent Application Laid-Open No. 7-325458, droplets of water or the like that can be transmitted to the surface of the image carrier are deposited on the end of the wiper blade in the longitudinal direction. There is a problem that the liquid evaporates more and the liquid such as water is wasted.

Therefore, there is a problem that a liquid such as water leaks from an axial end of the image carrier, or a liquid such as water evaporates from a longitudinal end of the wiper blade and is wasted. A technique that can be solved is disclosed in Japanese Patent Application Laid-Open No. 9-179.
As disclosed in Japanese Patent No. 377, the donor member is sandwiched between a pair of blade members, and a hydrophobic member is further provided on the side of the donor member to seal the periphery of the donor member and to remove liquid such as water. A device that is configured to prevent leakage and evaporation has already been proposed.

To explain further, this Japanese Patent Application Laid-Open No. Hei 9-1793
No. 77 is a charging device for supplying a charge to a member to be charged, and includes a donor member, the donor member is configured to contact the conductive member with ions through the charging member. The donor member includes a hydrophilic material layer containing an ion conductive liquid, and includes a pair of non-porous elastomer blade elements, wherein each elastomer blade element is formed of the hydrophilic material layer. Each side is located on each side to prevent leakage of the ionic conductive liquid along an elongated side of the donor member, including a pair of hydrophobic end segments, wherein each pair of hydrophobic segments is a pair of the non-porous Each end of the blade element and between the pair of non-porous blade elements are positioned along the respective ends of the donor member from the hydrophilic material layer. The ion-conducting liquid is prevented from leaking, and an electric bias is applied to the ion-conducting liquid to transfer the ions to a member charged with ions through the ion-conducting liquid. .

However, the method disclosed in Japanese Patent Application Laid-Open No.
7, the non-porous blade element 100 is deformed with the rotation of the image carrier 101 which is a member to be charged, and as shown in FIG. And a hydrophobic segment 10 such as a rubber seal provided at the end thereof through a cushion 103.
There is a new problem in that a gap is formed between the second and the second and an ion conductive liquid such as water leaks from the gap. In the case of the charging device disclosed in Japanese Patent Application Laid-Open No. 9-179377, when the image forming device such as a copying machine to which the charging device is attached is moved, the charging device is not moved due to vibration or inclination of the image forming device main body. An ionic conductive liquid such as water easily adheres to the periphery of the end of the porous blade element. At this time, there is a problem that the ionic conductive liquid such as water leaks, though it is very small.

As described above, when the ionic conductive liquid such as water leaks from the end of the non-porous blade element, it adheres to other members of the image forming apparatus and causes a malfunction, and is used for charging. Water is reduced, and the developer adheres to the ionic conductive liquid such as water adhered to the edge of the image carrier such as the photoreceptor, causing black spot-like image defects on both sides of the paper. Problems.

In the case of the charging device according to the above-mentioned Japanese Patent Application Laid-Open No. 9-179377, in order to reliably prevent leakage of an ion-conducting liquid such as water from the end of the non-porous blade element, the non-porous blade element is used. If an attempt is made to increase the degree of sealing at the ends of the conductive blade elements, the load applied to the image carrier increases, causing another problem such as an increase in driving torque and generation of abnormal noise.

Further, in the case of the charging device according to the above-mentioned Japanese Patent Application Laid-Open No. 9-179377, in order to stably charge the image carrier over a long period of time, the water content of the donor member is set large, and It is desirable that a large amount of an ionic conductive liquid such as water is present in the vicinity of the contact portion with the image carrier. The problem that the ionic conductive liquid leaks becomes more remarkable.

Therefore, 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 prevent leakage of an ion-conductive medium such as water from the end of a charging device. It is an object of the present invention to provide an image forming apparatus capable of reliably preventing image quality defects due to leakage of an ion conductive medium such as water and preventing waste of an ion conductive medium such as water. .

[0019]

According to the first aspect of the present invention, an ionic conductive medium is brought into contact with a member to be charged, and a voltage is applied to the ionic conductive medium. In the image forming apparatus having a charging device for charging the image carrier by doing so, the end portion of the image carrier in the axial direction is subjected to lyophobic treatment for repelling an ionic conductive medium.

According to a second aspect of the present invention, there is provided a charging device for charging an image carrier by bringing an ionic conductive medium into contact with a member to be charged and applying a voltage to the ionic conductive medium. In the image forming apparatus having the charging device, the charging device has a regulating member for preventing the ionic conductive medium from leaking to the downstream side in the moving direction of the image carrier, and an end portion of the regulating member and an image carrier. At least one of the ends in the axial direction is configured to be subjected to a liquid-repellent treatment for repelling an ionic conductive medium.

Further, the invention according to claim 3 provides a charging device for charging an image carrier by bringing an ionic conductive medium into contact with a member to be charged and applying a voltage to the ionic conductive medium. In the image forming apparatus, a brush-like member having liquid repellency for preventing the ionic conductive medium from leaking from an axial end of the image carrier is provided at an end of the charging device.

Further, according to a fourth aspect of the present invention, there is provided a charging device for charging an image carrier by bringing an ionic conductive medium into contact with a member to be charged and applying a voltage to the ionic conductive medium. The charging device has a regulating member for preventing the ionic conductive medium from leaking to the downstream side in the moving direction of the image carrier, and an end of the regulating member and the image carrier. And a liquid repellent treatment for repelling the ionic conductive medium to at least one of the axial ends of the image carrier to prevent the ionic conductive medium from leaking from the axial end of the image carrier to the end of the charging device. It is configured such that a brush-like member having liquid repellency is provided.

According to a fifth aspect of the present invention, there is provided a charging device for charging an image carrier by bringing an ionic conductive medium into contact with a member to be charged and applying a voltage to the ionic conductive medium. In the image forming apparatus, the charging device includes a charging member for supplying the ionic conductive medium to the image carrier, and a charging member for preventing the ionic conductive medium from leaking downstream in the moving direction of the image carrier. And a lyophobic treatment for repelling an ionic conductive medium on at least one of the end of the regulating member and the axial end of the image carrier, and the end of the regulating member and the image carrier. Length excluding the liquid-repellent treatment part provided on at least one of the axial ends ≧
The length of the charging member is set so as to satisfy a relationship of “length of developing member ≧ length of developing area”.

[0024]

According to the first aspect of the invention, the axial end of the image carrier is subjected to a liquid-repellent treatment for repelling an ionic conductive medium. Even when the ionic conductive medium such as water moves to the axial end of the image carrier, the liquid-repellent processing unit provided at the axial end of the image carrier, Flipped by
Leakage from the end of the image carrier can be prevented, stable charging performance can be obtained over a long period, and contamination and charging in the image forming apparatus due to leakage of an ionic conductive medium such as water can be prevented. In this case, the amount of ionic conductive medium such as water can be reduced, and the occurrence of image quality defects can be prevented.

According to a second aspect of the present invention, the charging device has a regulating member for preventing the ionic conductive medium from leaking downstream in the moving direction of the image carrier. At least one of the end and the axial end of the image carrier is configured to be subjected to a liquid-repellent treatment for repelling the ionic conductive medium, so that at least the end of the regulating member and the axial end of the image carrier. The lyophobic treatment section provided on one side can prevent the ionic conductive medium such as water from leaking from the end of the image carrier, and can obtain a stable charging performance for a long time, It is possible to prevent contamination in the image forming apparatus due to leakage of the ionic conductive medium such as water, decrease of the ionic conductive medium such as water for charging and the like, and further prevent occurrence of image quality defects.

Further, according to the present invention, a brush-like member having liquid repellency for preventing the ionic conductive medium from leaking from the axial end of the image carrier is provided at the end of the charging device. With such a configuration, the flexible brush-like member can reliably prevent a gap from being formed at the end of the charging device, and can prevent the ionic conductive medium from leaking from the end of the image carrier. Can be prevented.

According to a fourth aspect of the present invention, in the charging device, the charging device has a regulating member for preventing the ionic conductive medium from leaking to the downstream side in the moving direction of the image carrier. At least one of the end of the image carrier and the axial end of the image carrier is subjected to a lyophobic treatment for repelling an ionic conductive medium, and the end of the charging device is subjected to ionic conductive Since the brush-like member having the liquid repellency for preventing the medium from leaking is provided, the functions of the inventions according to the second and third aspects can be simultaneously achieved.

According to a fifth aspect of the present invention, there is provided a charging device, comprising: a charging member for supplying the ionic conductive medium to the image carrier; and the ionic conductive medium being provided on the downstream side in the moving direction of the image carrier. A regulating member for preventing leakage, and at least one of an end of the regulating member and an axial end of the image carrier is subjected to a liquid-repellent treatment for repelling an ionic conductive medium. The length excluding the liquid-repellent portion provided on at least one of the end portion and the axial end portion of the image carrier is set to satisfy the relationship of ≧ length of the charging member ≧ length of the developing region. Even when the ionic conductive medium such as water leaks from the end of the image carrier, the length of the image carrier excluding the lyophobic processing portion is longer than the length of the charging member, and furthermore, the length of the developing member is further increased. Since the length is longer than the length of the area, Sex conductive medium, it is possible to reliably prevent the image defect adhering to the developer occurs.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in the drawings.

FIG. 2 shows an embodiment of an image forming apparatus having a charging device according to the present invention.

In FIG. 2, reference numeral 1 denotes a photosensitive drum as an image bearing member. The photosensitive drum 1 has an axis in a direction perpendicular to the plane of the drawing and is not shown in the direction of the arrow shown in the figure. The driving means is driven to rotate at a predetermined rotation speed. After the surface of the photosensitive drum 1 is uniformly charged to a predetermined potential by a charging device 2, an image is exposed by an exposure device 3 that exposes a laser beam or the like according to image information. An electrostatic latent image corresponding to the image information is formed on the surface of. The electrostatic latent image formed on the photosensitive drum 1 is
The toner image formed on the photosensitive drum 1 is transferred to a transfer sheet 5 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 and the pressing force formed by the roll 6. 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 transported to a fixing device (not shown), and the toner image is fixed on the transfer paper 5 by the fixing device. Discharged outside the device.

After the transfer of the toner image, the surface of the photosensitive drum 1 is cleaned by a disturber brush 8 and a cleaner blade 9 of a cleaning device 7 to remove residual toner and paper dust. The image forming process is prepared.

FIG. 1 shows a charging device according to the first embodiment.

In the charging device 2 according to the first embodiment, an ionic conductive medium such as water or an electrolyte or ionizable gas molecules is brought into contact with the surface of a photosensitive drum 1 as an image carrier, and By applying a voltage to the non-conductive medium, the ion-conductive medium such as water or an electrolyte or ionizable gas molecules is ionized and ionized, and ions of a predetermined polarity are deposited on the surface of the photosensitive drum 1. The surface of the photoreceptor drum 1 is charged to a predetermined potential by being electrostatically attached.

As shown in FIG. 1, the charging device 2 mainly includes a water-containing charging member 11 serving as a holding member for holding water or an ionic conductive medium such as an electrolyte or ionizable gas molecules. A water regulating member 12 disposed downstream of the charging member 11;
1 and a seal member 13 arranged on the upstream side. The hydrated charging member 11 includes a pressing member 15
To contact the surface of the photosensitive drum 1. Further, a DC voltage is supplied to the hydrated charging member 11 via a pressing member 15 by a charging device power supply 14 of the image forming apparatus main body. Then, in the charging device 2, the charging member 11 charges the photosensitive drum 1 in a state where a puddle 16 is formed upstream of the water regulating member 12 with the rotation of the photosensitive drum 1.

The charging member 11 is formed of a material appropriately selected from water-absorbing materials such as hydrophilic PVA (polyvinyl alcohol) sponge and urethane sponge. As the shape of the charging member 10, various shapes such as a pad shape, a roll shape, and a blade shape can be used.

Further, pure water, pure water,
An ionic conductive medium in which an electrolyte or an ionizable gas molecule is dissolved in water such as distilled water or tap water, or a solvent such as water or alcohol is supplied and impregnated by a supply unit (not shown). Examples of the electrolyte dissolved in a solvent such as water or alcohol include LiClO ₄ , N
a ₂ SO ₄ , Na ₂ CO ₃ , NaHCO ₃ , NaCl,
KCl, LiCl, MgCl ₂ , CaCl ₃ , (N
Various electrolytes such as H ₄ ) ₂ SO ₄ can be used. On the other hand, as ionizable gas molecules, CO ₂
And the like. As the ionizable gas molecules such as CO ₂ , those naturally dissolved in water or the like may be used, or those naturally dissolved positively may be used.

The volume resistivity of the charging member 11 impregnated with the above substance is, for example, 10 ² to 10 ¹⁴ Ω.
It is set appropriately within a range of about cm.

The charging member 11 used in this embodiment
As shown in FIG. 1, is formed in a pad shape of PVA having a thickness of 3 mm.
Pure water obtained as ordinary ion-exchanged water is impregnated. The charging pad 11 is arranged so as to contact the surface of the photosensitive drum 1 with a contact width of 5 mm along the moving direction thereof and over substantially the entire length of the photosensitive drum 1 in the axial direction. . Further, the charging pad 11 has both ends on the upstream side and the downstream side along the moving direction of the photosensitive drum 1 bent upward by several mm. In addition, the resistance value of the charging pad 11 in this water-containing state was about 10 ⁶ Ω.

As shown in FIG. 1, the charging pad 11 comes into contact with the surface of the photosensitive drum 1 with a predetermined pressing force by a pressing member 15 formed in a vertically long box shape having a rectangular cross section. Are arranged as follows. A supply port (not shown) for supplying pure water obtained as ordinary ion exchange water to the charging pad 11 is opened in the pressing member 15 as necessary.

As shown in FIG. 1, a predetermined DC voltage is supplied to the charging pad 11 by a power supply 14 for the charging device. It is sufficient to bring a lead wire or the like connected to the power supply 14 for the charging device into contact with a part of the charging pad 11, but it is sufficient to supply current to an electrode provided along the longitudinal direction of the charging pad 11. Of course, you can.

By the way, in this embodiment, a liquid-repellent treatment for repelling the ionic conductive medium is performed on the axial end of the image carrier.

That is, as shown in FIG. 2, the charging device 2 according to this embodiment is provided with water or the like flowing out of the charging pad 11 downstream of the charging pad 11 in the rotation direction of the photosensitive drum 1. Block the liquid 17 and remove the liquid 17 such as water.
Is provided with a blade-shaped water regulating member 12 for preventing the water from flowing out to the downstream side. As shown in FIG. 1, the blade-shaped water regulating member 12 has a distal end portion of the water regulating member 12 pressed against the downstream side in the rotation direction of the photosensitive drum 1 and a proximal end portion of the water regulating member 12. The water regulating member 12 is disposed so as to be inclined with respect to the surface of the photosensitive drum 1. The water regulating member 12 is formed of an elastic material, and is curved so as to curve upward with its tip end pressed against the surface of the photosensitive drum 1 as shown in FIGS. 4 and 5B. Shape.

In this embodiment, as shown in FIG.
The water regulating member 12 is a polyurethane blade. The water regulating member 12 has a thickness t = 2 mm and a width l = 1.
The photosensitive drum 1 has a length of 0 mm and a length substantially equal to the entire length of the photosensitive drum 1, and its setting angle (hereinafter, referred to as “SA”) is 6 mm.
0 °, the bite amount into the photosensitive drum 1 (hereinafter referred to as “nip amount”) is set to about 0.5 mm. However, it goes without saying that the SA and the nip amount of the water regulating member 12 may be set to other values. Further, a sheet metal 18 made of stainless steel, aluminum, or the like is fixed to the back surface of the base end of the water regulating member 12 by means such as adhesion, and the water regulating member 12 is attached to the holder via the sheet metal 18. 19, the setting angle SA is set as described above.

Also, in this embodiment, as shown in FIG. 1, the charging device 2 is provided with an airtightness upstream of the charging pad 11 in the rotation direction of the photosensitive drum 1 to evaporate liquid such as water. A seal member 13 for preventing the above is provided.
The seal member 13 is formed of, for example, urethane rubber having a thickness of 1 mm. Further, the sealing member 13
Is mounted on the holder 19 at its base end.

FIG. 3 is a schematic diagram showing the vicinity of the end of the water regulating member of the charging device according to the first embodiment. The charging pad is not shown. FIG. 4 is a side view for explaining the relationship between the photosensitive drum and the water regulating member.

In the first embodiment, as shown in FIG. 3, a water-repellent treatment section 1a is provided on both axial surfaces of a photosensitive drum 1 as an image carrier. Various methods are conceivable for forming the water-repellent portion 1a. For example, a method of coating the surface of the photosensitive drum 1 with a water-repellent material such as a fluororesin or a silicon resin is relatively easy. . In addition, the surface of the photosensitive drum 1 is subjected to a plasma treatment, and the surface of the photosensitive drum 1 is bonded with a fluororesin. 1a may be provided. However, since the water-repellent treatment section 1a is provided in an area other than the image forming section at the axial end of the photosensitive drum 1, it does not need to have photoconductive properties, and the method of the water-repellent treatment is particularly limited. Not something.

In the first embodiment, as shown in FIG. 3, the water-repellent processing section 1a of the photosensitive drum 1 is
At the longitudinal end of the blade-shaped water regulating member 12, a water-repellent treatment portion 12a is provided on the surface on the charging pad 11 side. The water-repellent portion 12a is formed by the same method as the water-repellent portion 1a of the photosensitive drum 1.

In the first embodiment, as described above, the axial end of the photosensitive drum 1 and the water regulating member 12
The water-repellent treatment parts 1a and 12a
Has been described, but the water-repellent treatment section may be provided on at least one of the photosensitive drum and the water regulating member,
It is sufficiently effective for preventing leakage of the liquid ionic conductive medium.

The water-repellent treatment sections 1a and 12a here are designed to increase the contact angle of water in the processing section with respect to the contact angle of water in the untreated section of the photosensitive drum 1 and the water regulating member 12 so that water or the like is removed. It is provided for the purpose of flipping a liquid. When the contact angle of water between the water-repellent portion 1a and the untreated portion of the photosensitive drum 1 was measured,
20 °, and 85 ° in the untreated portion. Similarly, the water-repellent portion 12a and the untreated portion 1 of the blade-shaped water regulating member 12
When the contact angle of water of No. 2 was measured, it was 110 ° in the water-repellent portion 12a and 85 ° in the untreated portion. Note that FIG.
Reference numeral 23 denotes a seal member made of rubber or the like attached to a longitudinal end of the holder 19 of the charging device 2 via a cushion member 22.

In the above configuration, in the image forming apparatus to which the charging device according to this embodiment is applied, the leakage of the ion conductive medium such as water from the end of the charging device is reliably prevented as follows. This makes it possible to prevent image quality defects due to leakage of the ion-conductive medium such as water and wasteful consumption of the ion-conductive medium such as water.

That is, in the image forming apparatus according to this embodiment, as shown in FIG. 2, the photosensitive drum 1 is driven at a predetermined rotational speed in the direction of the arrow. The surface is negatively charged to a predetermined potential by applying a negative DC voltage to the water-containing charging pad 11 by the charging device power supply 14. At this time, depending on the water content of the charging pad 11, water as a liquid ionic conductive medium may be charged.
From the surface of the photosensitive drum 1 to the downstream side of the contact portion of the charging pad 11 of the photosensitive drum 1 as the photosensitive drum 1 rotates.

However, in the charging device 2 according to the present embodiment, a blade-shaped water regulating member 12 for regulating water or the like is provided downstream of the charging pad 11 in the rotation direction of the photosensitive drum 1. Therefore, the water on the photosensitive drum 1 that has flowed downstream from the contact portion of the charging pad 11 is blocked by a water regulating member 12 for regulating the water and the like, forming a puddle 16, After that, it does not flow out to the downstream side in the rotation direction of the photosensitive drum 1.

Thereafter, an image is exposed by the exposure device 3 on the surface of the photosensitive drum 1 negatively charged to a predetermined potential by the charging device 2 as described above, and an electrostatic latent image is formed. Subsequently, the electrostatic latent image formed on the photosensitive drum 1 is reversely developed with negative toner supplied from the developing device 4 to be visualized on the photosensitive drum 1. Thereafter, the visualized toner image on the photosensitive drum 1 is transferred onto the transfer paper 5 by the transfer roll 6. After the transfer of the toner image, the toner remaining on the photosensitive drum 1 is scraped off by a disturber brush 8 and a cleaner blade 9, and
Is cleaned and ready for the next image formation.

As described above, in the image forming apparatus to which the charging device according to the above-described embodiment is applied, by applying a predetermined voltage to the charging pad 11 of the charging device 2, the charging pad 11 is impregnated. Pure water obtained as ordinary ion-exchanged water, and ionizable gas such as CO ₂ dissolved in this pure water are ionized and ionized as shown below, and negatively ionized ions are charged. Pad 11
By applying a negative voltage to the photosensitive drum 1, as shown in FIG. 6, the photosensitive drum 1 is electrostatically attached to the surface thereof, and 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 -

Therefore, a DC voltage equal to the charging potential of the photosensitive drum 1 may be applied to the charging pad 11 of the charging device 2, and corona discharge or the like basically does not occur. Almost completely suppressed. Further, if the charging pad 11 is impregnated with pure water obtained as ordinary ion-exchanged water for generating ions or CO ₂ which is an ionizable gas dissolved in the pure water, Since the surface of the photosensitive drum 1 can be immediately charged to a predetermined potential by ionizing and ionizing the pure water or the like, the photosensitive drum 1 can be sufficiently used even in an image forming apparatus such as a medium-speed copying machine. It is. Further, since the voltage applied to the charging pad 11 may be a DC voltage equal to the charging potential of the photosensitive drum 1, there is no need to apply a DC voltage in which an AC voltage is superimposed on a contact-type charging member. There is no danger of damaging the surface of the photosensitive drum 1 by applying the AC voltage, and wear of the photosensitive drum 1 hardly causes a problem. Further, even if water or the like flows out of the charging pad 11 onto the photosensitive drum 1, a liquid such as water is provided downstream of the charging pad 11 in the rotation direction of the photosensitive drum 1. Since the water regulating member 12 for preventing the water from flowing out to the downstream side is provided, liquid such as water flowing out to the downstream side of the charging pad 11 is surely closed by the water regulating member 12. The charging pad 1 can be stopped to a certain extent to prevent it from flowing downstream.
Even when water or the like is supplied to the apparatus 1, the liquid or the like does not flow into the developing device 4 side to cause a defect in an image, and the configuration of a system for supplying the liquid or the like becomes complicated, resulting in high cost. Not only can be avoided, but also consumption of water, ionic conductive medium, etc. can be reduced, and further, water, ionic conductive medium, etc. remain adhered on the photosensitive drum 1. This makes it possible to prevent image quality defects from occurring.

Further, in this embodiment, both the axial end of the photosensitive drum 1 and the longitudinal end of the water regulating member 12 are subjected to a water-repellent treatment for repelling water as an ionic conductive medium. And water-repellent treatment sections 1a and 12a are provided, so that even if water 17 adheres to the surface of the photosensitive drum 1 and the water 17 moves to the axial end of the photosensitive drum 1, An end of the photosensitive drum 1 is repelled by a water-repellent treatment portion 1a provided at an axial end of the photosensitive drum 1 and a water-repellent treatment portion 12a provided at a longitudinal end of the water regulating member 12. Part can be prevented from leaking, and stable charging performance can be obtained for a long time,
Further, it is possible to prevent contamination of the image forming apparatus due to leakage of the ionic conductive medium such as water, decrease of the ionic conductive medium such as water for charging, and the occurrence of image quality defects.

Next, to confirm the effects of the above embodiment, the present inventors, as shown in FIG.
Prototype of a bench machine capable of observing the surrounding puddles 16 and the like, supplying an appropriate amount of water upstream of the water regulating member 12,
An experiment was conducted to observe the state of water leakage while rotating the photosensitive drum 1.

As a result, as shown in FIG. 3, the water is repelled by the water-repellent processing section 1a provided at the axial end of the photosensitive drum 1.
In addition, the water regulating member 12 was satisfactorily held inside the water-repellent treatment portion 12a provided at the longitudinal end, and no water leakage from the end of the charging device 2 occurred. Also, the photosensitive drum 1
When the bench machine was tilted while rotating
Even when tilted by about 0 °, water did not leak, and water could be held well.

Second Embodiment FIG. 7 shows 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. Further, a liquid-repellent brush-like member for preventing the ionic conductive medium from leaking from the axial end of the image carrier is provided at the end of the charging device.

That is, in the second embodiment, as shown in FIG. 7, water is prevented from leaking from the axial end of the photosensitive drum 1 to the longitudinal end of the blade-shaped water regulating member 12. A brush seal member 41 is provided as a brush-like member having water repellency.

Next, the material of the brush seal member 41 used in the second embodiment will be described.

FIG. 9 shows the results of a study on the material of the brush. As a material for the brush, Teflon fiber having a high water-repellent effect was the best. Conversely, in the case of nylon having water absorbency, the brush absorbed water and water leaked easily. However, even a fiber such as nylon can be used because a water-repellent effect can be obtained by applying a water-repellent treatment by applying a coating of Teflon or silicon on the surface.

Further, the present inventors have examined preferable parameters when using a Teflon brush. As a result, it was found that a brush density of 20,000 brushes / inch ² or more can be used. In consideration of the manufacturability of the brush and the sealing property of water, 100,000 brushes / in.
Those having about ch ² are preferable for use.

It was also found that the brush could be used if the amount of interference between the brush and the surface of the photosensitive drum 1 was 0.5 mm or more. If the amount of interference of the brush is too large, the brush hits the belly and the sealing effect is reduced. The amount of interference of the brush is preferably about 1 mm to 3 mm in use.

When the brush seal member 41 was attached to the end of the blade-shaped water regulating member 12 under the following experimental conditions, water was held at the end of the brush seal member 41 as shown in FIG. No water leakage occurred when the drum 1 was tilted by 30 °.・ Photoreceptor drum diameter: 84 mm ・ Brush material: Teflon ・ Density: 160,000 / inch ²・ Pile height (brush length): 5 mm ・ Interference amount: 2 mm However, these brush parameters depend on the diameter of the image carrier and the like. Needless to say, a suitable level can be appropriately selected depending on the size of the charging device and the like.

As described above, the brush seal member 41 is used in the second embodiment of the present invention shown in FIG. Since the brush seal member 41 is flexibly deformed in response to the deformation of the water regulating member 12, even when the brush sealing member 41 is brought close to the blade-shaped water regulating member 12, the brush sealing member 41 does not interfere with the movement of the blade-shaped water regulating member 12. No leakage occurs.

FIG. 8 is a comparative example corresponding to FIG. 7, in which a rubber seal member 51 is used instead of the brush seal member 41. Behind the rubber seal member 51, a cushion member 52 is provided.

In the rubber member seal shown in FIG. 8, water entered the minute gap between the blade and the rubber member, and a small amount of water continuously leaked. Further, when the bench machine was inclined, water leakage became severe even at an inclination angle of about 10 °. Further, in order to make the gap between the blade and the rubber member 51 as small as possible, if the rubber member is brought as close to the blade as possible, the movement of the blade end will cause the seal member 51 to move.
Interfered and the blades vibrated causing irregular water leakage.

Other configurations and operations are the same as those of the first embodiment, and therefore, the description thereof will be omitted.

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 described. This is a combination of the first embodiment and the second embodiment.

That is, the charging device 2 according to the third embodiment has a regulating member for preventing the ionic conductive medium from leaking to the downstream side in the moving direction of the image carrier. And at least one of the axial ends of the image carrier is subjected to a liquid-repellent treatment to repel the ionic conductive medium, and the ionic conductive medium is applied to the end of the charging device from the axial end of the image carrier. It is configured to provide a brush-like member having liquid repellency for preventing leakage.

In this configuration, during normal use, the water does not reach the end of the photosensitive drum 1 by repelling the water by the water-repellent treatment sections 1a and 12a. Also, when the machine is tilted or vibrated, the brush seal member 41 may be used.
Thus, a more reliable seal is possible, and leakage of water can be more reliably prevented. In FIG. 3, reference numeral 23 denotes a sealing member made of rubber or the like attached to a longitudinal end of the holder 19 of the charging device 2 via a cushion member 22.

Other structures and operations are the same as those of the first embodiment, and the description is omitted.

Fourth Embodiment FIG. 11 shows a fourth embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals and described. Such a charging device has a charging member for supplying the ionic conductive medium to the image carrier, and a regulating member for preventing the ionic conductive medium from leaking downstream in the moving direction of the image carrier. A liquid-repellent treatment for repelling an ionic conductive medium on at least one of the end of the regulating member and the axial end of the image carrier, and at least one of the end of the regulating member and the axial end of the image carrier. The length is set so as to satisfy the following relationship: length excluding the lyophobic treatment section provided on one side ≧ length of charging member ≧ length of development area.

In connection with the above embodiment, in order to mount a charging device using a liquid ionic conductive medium in an electrophotographic device or the like, it is more effective to adopt the following configuration. is there.

That is, as shown in FIG.
, The width L2 of the non-water-repellent portion of the blade-shaped water regulating member 12, and the width L4 of the non-water-repellent portion of the photosensitive drum 1 are L4 ≧ L3 ≧ L2. ≧ L1
By setting so as to satisfy the following relationship, it is possible to more effectively prevent the ionic conductive medium such as water from leaking from the end of the charging device 2.

FIG. 12 shows the results of confirming problems such as water leakage when the charging device shown in FIG. 11 was attached to an actual electrophotographic apparatus and the relationship among L1, L2, L3 and L4 was changed. is there. As is apparent from FIG.
To 5 can be used, but it is desirable to configure so as to satisfy the condition of 1 or 2.

Fifth Embodiment FIG. 13 shows a fifth embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals and described. Such a charging device, even when the charging device is configured as shown in the drawing from the viewpoint of cost reduction, the seal member using the water repellent treatment or the water repellent brush of the image bearing member and the water regulating member according to the present invention is excellent. Works. Note that there is a method for attaching the brush as shown in FIGS. In addition, even if it is a brush, FIG.
As in the case of the blades shown in FIGS.

In the charging device 2 shown in FIG.
Reference numeral 3 is integrally formed with the regulating member 82, and is formed using a material such as urethane rubber using a mold. Further, as the charging member 81, a member made of PVA or the like is used as in the above-described embodiments. Further, a brush seal member 82 is provided at an end of the charging member 81. The brush seal member 82 may be provided so as to surround the end of the charging member 81 as shown in the figure so as to enhance the sealing effect. Further, a water-repellent treatment may be applied to the end of the main body 83.

Further, the position of the charging device 2 is not limited to the position of 12:00, but is located at any position of 3 o'clock, 6 o'clock, 9 o'clock, etc., with respect to the image carrier described in this embodiment. Even if the effect is obtained.

Further, the present invention is not limited to the one having the water regulating member as shown in the above embodiments,
It goes without saying that the present invention can be applied to a device using a water-containing pad or a water-containing roll without using a water regulating member.

[0083]

As described above, according to the present invention, it is possible to reliably prevent the ion-conductive medium such as water from leaking from the end of the charging device, and to reduce the leakage of the ion-conductive medium such as water. It is possible to provide an image forming apparatus capable of preventing image quality defects due to leakage and wasteful consumption of an ion conductive medium such as water.

[Brief description of the drawings]

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

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

FIG. 3 is a configuration diagram showing an end of a charging device.

FIG. 4 is a side view showing a blade of the charging device.

5 (a) and 5 (b) are explanatory views showing the state of attachment of the blade, respectively.

FIG. 6 is an explanatory diagram showing the principle of charging of the charging device.

FIG. 7 is a configuration diagram showing an image forming apparatus using a charging device according to Embodiment 2 of the present invention.

FIG. 8 is a configuration diagram showing a conventional charging device.

FIG. 9 is a chart showing evaluation results of the seal brush.

FIG. 10 is a configuration diagram showing an image forming apparatus using a charging device according to Embodiment 3 of the present invention.

FIG. 11 is a configuration diagram showing an image forming apparatus using a charging device according to Embodiment 4 of the present invention.

FIG. 12 is a chart showing a longitudinal positional relationship and an evaluation result according to the fourth embodiment.

FIG. 13 is a configuration diagram showing an image forming apparatus using a charging device according to Embodiment 5 of the present invention.

[Explanation of symbols]

1: photoreceptor drum (image carrier), 1a: water-repellent treatment section,
2: charging device, 11: charging member, 12: water regulating member,
12a: water-repellent treatment section, 13: seal member, 14: power supply for charging device.

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

Claims (5)

[Claims] 1. An image forming apparatus comprising: a charging device for charging an image carrier by bringing an ionic conductive medium into contact with a member to be charged and applying a voltage to the ionic conductive medium; An image forming apparatus, wherein a liquid-repellent treatment for flipping an ionic conductive medium is applied to an axial end of a body. 2. An image forming apparatus comprising: a charging device for charging an image carrier by bringing an ionic conductive medium into contact with a member to be charged and applying a voltage to the ionic conductive medium. Has a regulating member for preventing the ionic conductive medium from leaking to the downstream side in the moving direction of the image carrier, and the ion is attached to at least one of the end of the regulating member and the axial end of the image carrier. An image forming apparatus which has been subjected to a liquid repellent treatment for flipping a conductive conductive medium. 3. An image forming apparatus having a charging device for charging an image carrier by bringing an ionic conductive medium into contact with a member to be charged and applying a voltage to the ionic conductive medium. An image forming apparatus, comprising: a liquid-repellent brush-like member for preventing an ionic conductive medium from leaking from an axial end of an image carrier at an end of the image carrier. 4. An image forming apparatus having a charging device for charging an image carrier by bringing an ionic conductive medium into contact with a member to be charged and applying a voltage to the ionic conductive medium. Has a regulating member for preventing the ionic conductive medium from leaking to the downstream side in the moving direction of the image carrier, and the ion is attached to at least one of the end of the regulating member and the axial end of the image carrier. A liquid-repellent treatment for repelling the non-conductive medium is provided, and a brush member having a liquid-repellent property for preventing the ionic conductive medium from leaking from the axial end of the image carrier is provided at the end of the charging device. An image forming apparatus characterized in that: 5. An image forming apparatus having a charging device for charging an image carrier by bringing an ionic conductive medium into contact with a member to be charged and applying a voltage to the ionic conductive medium. Has a charging member for supplying the ionic conductive medium to the image carrier, and a regulating member for preventing the ionic conductive medium from leaking to the downstream side in the moving direction of the image carrier. At least one of the end of the member and the axial end of the image carrier is subjected to a liquid-repellent treatment to repel an ionic conductive medium, and is provided on at least one of the end of the regulating member and the axial end of the image carrier An image forming apparatus that satisfies a relationship of a length excluding a liquid-repellent treatment section ≧ a length of a charging member ≧ a length of a development area.