JPH0451183A - Image forming device - Google Patents

Abstract

PURPOSE:To effectively prevent image flowing by arranging a cleaning device for cleaning a photosensitive body close to a corona discharger. CONSTITUTION:This device is provided with the cleaning device for cleaning the photosensitive body and the corona discharger equipped with a shielding case in parallel. In such a case, the cleaning device 10 for the cleaning the photosensitive body is constituted of a case 11 and a cleaner 12. The suction efficiency of corona product by discharge is more improved when upper and lower gaps between the cleaning device 10 and the shielding case of the corona discharger 2 are not formed to the utmost. Therefore, the corona product stuck to the surface of the photosensitive body is always removed by the cleaning member. Thus, the image flowing is prevented.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an electrophotographic copying machine and a laser printer.

The present invention relates to an image forming apparatus such as a facsimile machine, and more particularly to an image forming apparatus that prevents image deletion.

(Prior Art) In image forming apparatuses such as electrophotographic copying machines, laser printers, and facsimile machines, amorphous silicon (a
-8i irritability), Ss, As, Se,.

Photoconductors using inorganic photoconductive materials (Ss photoconductors) such as 5eTe, and organic photoconductive materials (OPC photoconductors) such as poly-N-vinylcarbazole, trinitrofluorenone, and various azo pigments are available. For example, oPC photoreceptors have good electrical properties and spectral sensitivity, are inexpensive to manufacture, are non-polluting, and can be relatively easily processed into belt- or drum-shaped photoreceptors; It is used in many medium-speed machines. On the other hand, although the a-5i photoreceptor has a lower charging ability than other photoreceptors, it is used in high-speed copying machines, laser printers, etc. because of its high sensitivity and high abrasion resistance.

An example of a conventional image forming apparatus using such a photoreceptor is shown in FIG. In FIG. 3, 31 is a photoreceptor, 32
33 is an exposure unit, 34 is a developing device, 35 is a transfer corona discharger (transfer charger), 36 is a separation corona discharger (separation charger), 37 is a cleaning device, 38 is a static elimination lamp, 39 is copy paper, and 40 is a fixing device.

Next, the operation of the above conventional image forming apparatus will be explained.

In FIG. 3, a photoreceptor 31 is uniformly charged by a charging charger 32. In FIG. There are two types of corona dischargers: the corotron type, in which a tungsten wire with a diameter of 40 to 100 μm is stretched, and the scorotron type, in which a grid is further stretched near the opening of the corona discharger to equalize uneven discharge.
A high voltage of 4000-8000 volts is applied. After forming an electrostatic latent image through image exposure in the exposure section 33, the developing device 3
4, a toner image is formed. After the toner image is transferred to the copy paper 39 by the transfer charger 35, the copy paper is separated from the photoreceptor by the separation charger 36, and then transferred to the fixing device 4.
It is fixed at 0 and becomes a hard copy. On the other hand, the toner image on the photoreceptor 31 after the transfer is cleaned by a cleaning device 37, and the series of copying steps is completed.

By the way, in an image forming apparatus using a corona discharger, corona products such as ozone and nitrogen oxides are generated during corona discharge, and when these corona products adhere to the surface of the photoreceptor, the surface layer of the photoreceptor is damaged. It is known that image quality characteristics deteriorate due to a decrease in the surface resistance of the photoreceptor and deterioration of the photosensitive characteristics of the photoreceptor. In particular, the surface resistance decreases with humidity, causing image blurring, and in the worst case, no image may be formed at all. Therefore, in order to maintain the initial image for a long period of time, it is necessary to eliminate the influence of corona products. The degree of occurrence of such image blurring differs depending on the material that makes up the photoreceptor, and the substances that cause the image blurring also differ, but in all cases, corona products are the cause of the image blurring. ing.

As a method for preventing the deterioration of image characteristics caused by the above-mentioned corona products, the following are known.

(2) Photoreceptors are known in which the reduction in surface resistance is prevented by improving the constituent materials themselves. Specifically, there are two types of photoreceptors: one in which a photosensitive layer is formed on a conductive support, and one in which a protective layer is further laminated on the photosensitive layer. When these photosensitive layers and protective layers are formed by spraying or coating methods, antioxidants (amines, hydroxylamines) are added or rubbed in from the outside.
We are trying to eliminate the effects of corona products.

(2) Improvements in corona dischargers are known that suppress the generation of corona products and prevent corona products from adhering to the photoreceptor.

The former is disclosed in, for example, Japanese Unexamined Patent Publication No. 64-68774,
JP-A-47-37547, JP-A-49-4073
No. 9 and Japanese Patent Application Laid-open No. 49-84660, etc., Au, Ag, and Pt are used as ozone decomposing materials.
, PdtNi, Fe, Ni, O, Bad, alumina, chromium oxide, or other metal or metal oxide to plate the charge wire, shield case, or grid to suppress the generation of corona products during corona discharge. ing. On the other hand, the latter is, for example, JP-A-63-3
11365, the inner wall and grid of the shield case are treated with activated carbon fibers, manganese oxide, or metal chelate compounds to absorb corona products and prevent them from adhering to the photoreceptor. There is. Other countermeasures include forming the grid with activated carbon fiber, adding an absorbing member (for example, Japanese Patent Application Laid-open No. 1-210974), and creating a shield case shape that takes into account wind flow. There are some things. Furthermore, there are also shield cases that use PT or Ag plating in combination with an absorbent made of activated carbon.
Publication No. 0-34828 and JP-A-52-133894
It is stated in the No.

(2) A known method is to heat the photoreceptor with a heater or dry it with hot air to eliminate the influence of humidity and prevent a decrease in the surface resistance of the photoreceptor.

(For example, JP-A-59-208558, JP-A-60
-095467, JP-A No. 61-132977, JP-A No. 62-262065, etc.) There are known devices in which corona products attached to the surface of the photoreceptor are removed by polishing or wet cleaning. ing. For polishing, for example, a roller or blade made of steel wire wound in a loop is used (for example, as described in Japanese Patent Application Laid-Open No. 1-1612).
No. 81), wet cleaning uses water or a solvent to remove corona products on the surface of the photosensitive layer.

In addition to the above, there are other publications aimed at preventing image deterioration caused by corona products, such as JP-A-58-28581, JP-A-60-95459, and JP-A-60-1.
No. 89769, JP-A-60-102659,
JP-A-59-219770, JP-A-60-134
Publication No. 254.

JP-A-60-17765, JP-A-55-1553
The one described in Publication No. 69 is known.

(Issue 111i to be Solved by the Invention) In an image forming apparatus as shown in FIG. 3, charging occurs.

A corona discharger is used to perform transfer, separation, etc., but as a result of the discharge, ozone (0,),
Corona products such as nitrogen oxides (NOx) are produced.

This is particularly likely to occur when negative or alternating high voltage is applied to the corona discharger, and the effects are large. These corona products are converted into hydrophilic compounds such as nitrogen compounds, aldehyde groups, and carboxyl groups by the action of discharge energy and moisture, carbon dioxide, and nitrogen gas in the atmosphere. There is a problem in that the electrical resistance (surface resistance) of the photoreceptor decreases due to the adsorption of water and the absorption of moisture in the atmosphere, resulting in image blurring and, even worse, white spots due to image deletion, which significantly deteriorate copy quality during development.

The above development occurs to a greater or lesser extent with most photoreceptors, but especially with photoreceptors using an a-8i layer, there is 5i02 on the surface of the photoreceptor.
Because hydrophilic substances such as these are generated, image smearing is likely to occur. In addition to being highly durable, a-
It was found that a photoreceptor using C:H as a protective layer also had the same problem as the a-8i photoreceptor. In these photoreceptors, the higher the humidity, the more severe the image smearing becomes, and sometimes no image is displayed at all. In addition, when As2Se or photoreceptor is used alone, image deletion does not become a problem, but when using S n O or S
nO.

/5b20. It is known that even when an organic resin such as an ester or urethane cross-linked styrene-MMA resin in which ultrafine particles such as Tilt are dispersed is overcoated, significant image blurring occurs. This development does not occur when the photoreceptor is new, but as it is repeatedly used in an image forming device, the surface of the photoreceptor becomes contaminated and loses water repellency, and the surface of the photoreceptor is hard and difficult to scratch. This is thought to be because hydrophilic substances remain forever.

The present invention is intended to solve the above-mentioned problems, and it is an object of the present invention to provide an image forming apparatus having means for effectively preventing image deletion.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an image forming apparatus that includes:
A cleaning device for cleaning the photoreceptor is disposed between the toner cleaning device and the charging corona discharger in close proximity to the corona discharger. The side plate of the shield case constituting the corona discharger, particularly the side plate of the example cleaning device, is provided with ventilation holes for quickly discharging products caused by corona discharge that remain within the shield case. On the other hand, the support of the cleaning body that constitutes the cleaning device is composed of a double-structured cylinder that has ventilation holes inside and outside for sucking corona products, and a corona absorbing member is placed between the two cylinders and A cleaning member is attached to the cylinder surface. The internal cylinder is also connected to an exhaust fan via a hose.

The cleaning body rotates in contact with the photoreceptor, thereby cleaning corona products adhering to the surface of the photoreceptor. Corona products removed from the photoreceptor and products due to corona discharge are adsorbed onto the absorbing member through the ventilation holes of the cylinder by operating the exhaust fan. The above configuration and operation are performed.

(Function) Therefore, according to the present invention, image deletion can be prevented by constantly removing corona products adhering to the photoreceptor surface with a cleaning member, and furthermore, corona products generated by corona discharge can be removed by suction. can.

(Embodiment) FIG. 1 shows a partial outline of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, 1 is a photoreceptor, such as an OPC photoreceptor or an a-8i photoreceptor.
Further a-C:H layer and a-8iN:H layer are formed on these photoreceptors.
, a-3iC:H.

It is possible to use a photoreceptor in which a protective layer is an inorganic thin film such as an a-5iF:H layer, or an organic thin film in which a resistance control agent or the like is dispersed. 2 is a charging corona discharger having a grid electrode 22, a shield case 20 is provided to surround the charge wire 21, and a side plate of the shield case 20 is provided to prevent corona products from accumulating from the corona discharger. It has an exhaust hole 23. This exhaust hole is open over the entire surface of the side plate of the shield case on the side of the cleaning device. 3 is an exposure section, 7 is a toner cleaning device, 10
is a cleaning device for cleaning a photoreceptor, and Case 1
1 and a cleaning body 12. In this embodiment, it is installed between the toner cleaning device 7 and the corona discharger 2.
This is not the case as long as it does not cause disturbance to the image. The suction efficiency of corona products caused by discharge is improved by leaving as little space between the top and bottom of the cleaning device W10 and the shield case of the corona discharger 2 as possible.

FIG. 2 schematically shows a cleaning body according to an embodiment of the present invention. In FIG. 2, reference numeral 13 denotes a cylinder having ventilation holes 15, which can be made of metal, paper products, plastic products, etc., and is preferably treated to be electrically conductive. The ventilation hole 15 may be a hole of about 1 to 3 m++φ or equivalent, or a slit with a width of 1 to 2 m may be provided as long as the strength of the cylinder is not reduced. The diameter of the cinder may be set as appropriate within the range of 15 to 30!1IIIφ. It is preferable that the ventilation holes 15 are spirally formed in the cylinder 13 at equal intervals, but the purpose can also be achieved by opening them in the longitudinal direction of the cylinder. A cleaning member I4 is spirally attached to the outside of the cylinder 13 along or across the ventilation hole 15. This cleaning member 14 has a brush shape, a fabric shape,
A felt-like form is used. As for the material, it is also effective to process a non-woven fabric made of ultra-fine fibers with a fiber diameter of 2 to 5 μm into a string shape and stick it on, but in particular, it is more effective to use activated carbon fiber for cleaning members.Activated carbon Some fibers are made from cellulose fibers, some are made from polyacrylonitrile fibers, some are made from phenolic resins, and some are made from pitch.
Polyacrylonitrile-based materials have excellent adsorption ability for corona products such as ox. In the case of the present invention, a material in which activated carbon fibers are electrodeposited on a nylon support, or a material in which woven activated carbon fibers are processed into a string shape can be used in terms of strength.

Reference numeral 16 denotes an absorbing member for adsorbing corona products that enter through the ventilation hole 15, and this absorbing member is preferably made of activated carbon fiber with good air permeability, such as felt, mat, or cloth, or other absorbent material. For example, when using absorbing materials such as compounds containing amino groups, metal complex compounds, nitrogen-containing compounds, or reactive metals that absorb corona products (e.g., nickel, silver, platinum, lead, etc.), It is desirable to ensure air permeability and adsorption area. Reference numeral 17 is a cylinder having an exhaust hole 18 of about 1 to 4 inches in diameter and having a diameter of about 5 to 10 inches, and the end of the cylinder 17 is connected to an exhaust fan by a hose.

For example, the exhaust fan has a maximum air volume of 0.2 rrr/
It is sufficient to use a fan of about mj, n. Bearings 19 allow the cylinder 17 to rotate freely, and are installed at two locations, one at the back and one at the front. The cleaning body 12 may be rotated by a combination of a gear, a timing belt, a ladder chain, etc., and a motor, and the rotation speed of the photoconductor should be 2.
It can be removed efficiently by rotating at ~5 times the speed.

Next, the operation and results of this example will be explained. T is sequentially attached to an aluminum support with an outer diameter of 40 m and a length of 250 cm.
i A subbing layer made of O2 and a polyamide resin, a charge generation layer (0.2μ ugly) made of a trisazo pigment and a polyvinyl butyral resin, and a charge transfer layer (25μ layer) made of hydrazone and a polycarbonate resin are laminated. Furthermore, C, H, and gas raw materials are added to this ○PC photoconductor to give a Knoop hardness of 1300 to 1500 kg/+w2. Film thickness approximately 850
0 people, a-C:H layer laminated by plasma CVD method, 78
It is mounted on an experimental laser beam printer (negative charging) that uses an LED with a wavelength of 0 nm as a light source (however, there is no corona discharger for separation).

The cleaning member 14 of the cleaning device is made of woven activated carbon fiber (fingered fabric: manufactured by Toho Rayon) processed into a string shape to prevent fraying, and ventilation holes 15 (front, rear, left, right hole spacing 15m, angle 2
0°) was used. Furthermore, Fell I-shaped activated carbon fiber (Fingered Felt, manufactured by Toho Rayon) (specific surface area: 700 rrr/g, basis weight: 100 g/%) was used for the absorbing member 16 between the cylinders. Furthermore, the exhaust fan is 60nn x 60m x 25m+
A custom-made rubber hood cover is attached to a + size fan, and a hose is inserted into the tip of the hood cover.The following methods are used: ■Cleaning device and exhaust fan are activated.■Cleaning device only is activated.■Exhaust fan is only activated.■ For the four ways in which both stopped, 2500 sheets of A-4 size were run, 20,000 sheets were run at a 7-day rate, and 25 sheets were printed after each number of sheets was completed.
Image quality was checked in an environment of 80% RH. The results are shown in Table 1.

The effect of using activated carbon fibers is recognized for ■ and ■, but in the case of ■, thinning of the characters is observed as the image fades, and a decrease in density is observed overall. If only the exhaust fan (■) operates, the exhaust capacity will be insufficient, and the unabsorbed portion will adhere to the photoreceptor, causing the transfer corona discharger (plus)
Ozone and Nox generated from the discharge have less influence than negative discharge, but they have an influence on image blurring, so the effect is small.

Note that the effectiveness depends on the material and type of the cleaning member of the cleaning device, so it can be expected that there will be a member that can handle 20,000 sheets without any problem.

(Effects of the Invention) As is clear from the above embodiments, the present invention can prevent image deletion by constantly removing corona products adhering to the photoreceptor surface with a cleaning member. By suctioning and removing it, a negative layer prevention effect can be obtained and a stable image can be maintained over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a partial schematic diagram of an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a schematic diagram of a cleaning body according to an embodiment of the present invention,
FIG. 3 is a schematic diagram of an example of a conventional image forming apparatus. 1.31...Photoreceptor, 2,32...Charging corona discharger, 3,33...Exposure section, 7...Toner cleaning device, 10...Cleaning device, 11
...Case, 12...Cleaning body, 13, 17...
Cylinder, 14... Cleaning member, 15... Ventilation hole, 16... Absorption member, 18... Exhaust hole, 19
...Bearing, 20...Shield case, 2
1... Charge wire 22... Grid electrode,
23...Exhaust hole, 34...Developing device, 35...
・Transfer charger 36...separation charger, 3
7... Cleaning device, 38... Static elimination lamp,
39... Copy paper, 40... Fixing device. Patent Applicant Rico Co., Ltd. Part 1 Figure 2] 4-11-groove retaining material +5--ji air hole 16--bore V-side material 17----cylinder °-18-1-DEi hole

Claims (4)

[Claims] (1) In an image forming apparatus that repeats a series of electrophotographic copying processes such as charging, image exposure, development, toner image transfer, copy paper separation, and toner image cleaning, there is a cleaning device for cleaning the photoreceptor and a shield having ventilation holes. An image forming apparatus characterized in that it is equipped with a corona discharger having a case. (2) The image forming apparatus according to claim 1, wherein the cleaning device also serves as a device for absorbing and removing corona products. (3) The supporting body of the cleaning body used in the cleaning device is composed of a double-structured cylinder having ventilation holes both inside and outside, and the cleaning member is arranged on the cylinder surface that contacts the photoreceptor. The image forming apparatus according to claim (1). (4) The image forming apparatus according to claim 2, wherein a corona product member is disposed between the inner and outer cylinders.