JPH04194963A - Corona discharger - Google Patents

Abstract

PURPOSE:To effectively prevent image flowing, to hold the uniformity of an image and furthermore, to obtain a discharger having a little small of ozone by providing an exhaust device on the back surface part of a corona discharger through a ventilating hole on the corona discharger of an image forming device using an electrophotographic method. CONSTITUTION:This discharger is constituted of a shielding case 1 formed of iron plated by nickel and stainless steel, a charging wire 2 made of tungsten, and a grid 3 to uniformize discharging. And plural ventilating holes 7 are bored on the connecting surface with the exhaust device 19 set on the back surface part, corona product material produced by the corona discharging is sent inside the exhaust device 19. Thus, the corona product material is restrained from adhering to a photosensitive body, and the lowering of resistance of the photosensitive body surface is prevented, so that the image flowing under high temperature environment is restrained, and initial high quality image having nonuniformity can be maintained for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a corona discharger used in an electrophotographic image forming apparatus, such as an electrophotographic copying machine, a laser printer, a facsimile, and the like.

(Prior Art) In the image forming apparatus described above, the conductive support is made of amorphous silicon (a-8i photoreceptor), Se, As, Se,
.

Generally, photoconductors using inorganic photoconductive materials such as 5eTe (Se photoconductor) and organic photoconductive materials such as poly-N-vinylcarbazole, trinitrofluorenone, and various azo pigments (○PC photoconductor) are used. Are known.

For example, OPC photoreceptors have good electrical properties and spectral sensitivity, are inexpensive to manufacture, and are non-polluting.

Because it can be relatively easily processed into belt- or drum-shaped photoreceptors, it is used in many low- to medium-speed machines.

On the other hand, although a-8] bad photoreceptor has inferior charging ability compared to other photoreceptors, it is used in high-speed copying machines, laser printers, etc. because it has high sensitivity and high #J abrasion resistance.

FIG. 3 shows a main part of an example of an image forming apparatus using such a photoreceptor.

The photoreceptor 10 is a charging corona discharger (charging charger)
11 to be uniformly charged.

The corona discharger 11 has a corotron system in which a tungsten wire 2 with a diameter of 40 ~], ], Oprn is stretched, and in order to equalize uneven discharge, a grid 3 is stretched near the corona discharge lid. There is a scorotron system that applies a high voltage of 4,000 to 8,000 volts.

After forming an electrostatic latent image by imagewise exposure in the exposure section 12, a toner image is formed in the developing device 13.

The toner image is transferred using a corona discharger (transfer charger) 1
After being transferred to the copy paper 17 in step 4, the copy paper is transferred to the photoreceptor 10 in a separation corona discharger (separation charger) 15.
The image is then separated and fixed by the fixing device 18 to become a hard copy.

On the other hand, the toner image on the photoreceptor 10 after the transfer is cleaned by a cleaning device 16, and the series of copying steps is completed.

By the way, in the image forming apparatus using the above-mentioned 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 resistance of the photoreceptor surface layer may decrease, or the photoreceptor characteristics of the photoreceptor may deteriorate.
It is known that image quality characteristics deteriorate.

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 over 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 there are also differences in the substances that cause image blurring, but in all cases, corona products are the trigger for image blurring. There is.

The following are known as devices designed to prevent the deterioration of image characteristics caused by corona products as described above.

As a first example, by improving the constituent materials of the photoreceptor itself,
Products that prevent a decrease in surface resistance are known. Specifically, photoreceptors include those in which a photosensitive layer is formed on a conductive support, and those 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 to prevent the effects of corona products. I'm trying to exclude it.

As a second example, it is known that corona dischargers are improved to suppress the generation of corona products and prevent corona products from adhering to the photoreceptor.

The former contains Au and Ag, which act as ozone decomposers.

Pt:, Pd, Ni, Fe, Ni2O, BaO, alumina.

The charge wire, shield case, or grid is plated with metal such as chromium oxide or metal oxide to suppress the generation of corona products during corona discharge.

On the other hand, in the latter case, the inner wall and grid of the shield case are treated with activated carbon fiber, manganese oxide, or metal chelate compounds to absorb corona products and prevent them from adhering to the photoreceptor. . In addition, there are other solutions that include making the grid carbon fiber-based, attaching an absorbing member, or creating a shield case shape that takes into account wind flow. Furthermore, there are also cases in which an absorbent made of activated carbon is used in combination with Pt or Ag plating such as a shield case.

As a third example, it is known that the photoreceptor is heated with a heater or dried with hot air to eliminate the influence of humidity and prevent the surface resistance of the photoreceptor from decreasing.

As a fourth example, one is known in which corona products adhering to the surface of the photoreceptor are removed by polishing or wet cleaning. For polishing, a roller or blade made of a looped steel wire is used, for example, and for wet cleaning, water or a solvent is used to remove corona products on the surface of the photosensitive layer.

(Problems to be Solved by the Invention) Although each aspect of preventing the deterioration of image characteristics caused by corona products as described above has its own advantages and disadvantages, it is possible to suppress the effects of corona products using relatively simple means. There isn't.

Incidentally, in an image forming apparatus as shown in Fig. 3, a corona discharger is used to perform charging, transfer, separation, etc., and ozone (03) and nitrogen oxides (Nox) are emitted from the corona discharger along with the discharge. I mentioned that corona products such as these are generated. 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. 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 white spots due to image deletion, which significantly deteriorate copy quality.

This phenomenon occurs in most photoreceptors to a greater or lesser degree, but it is especially true for photoreceptors using an A-81 layer, where 810
Due to the formation of second class hydrophilic substances, image blurring is likely to occur.
In addition to being highly durable, it was also thought to have excellent weather resistance.
-C: A photoreceptor using I-( as a protective layer also has the same problem as a-3j bad sensitivity.

In these photoreceptors, the higher the temperature, the more image deletion occurs and sometimes no image is displayed at all.

Also, when A, s, Se, and photoreceptors are used alone, image deletion is not a problem, but when using Sn○2, SnO, /5b2
03. It is also known that even when an organic resin such as an ester or urethane crosslinked styrene-MMA resin in which ultrafine particles such as TlO2 are dispersed is overcoated, significant image blurring occurs.

As described above, the process by which image deletion occurs differs depending on the configuration of the photoreceptor, but in all cases it occurs due to corona products.

This phenomenon does not occur when the photoconductor used is new, but after repeated use in an image forming device, the surface of the photoconductor becomes contaminated and loses water repellency, and the surface of the photoconductor becomes extremely hard and scratches. This is thought to be due to the fact that the hydrophilic substances remain for a long time.

In order to prevent such image deletion from occurring, it is necessary to prevent corona products from corona discharge from adhering to the photoreceptor.

−7= Therefore, the present invention solves the above problems,
It is an object of the present invention to provide a corona discharger equipped with an exhaust device that has means for effectively preventing image deletion, maintains image uniformity, and has extremely little ozone odor.

(Means for Solving the Problems) In order to solve the above-mentioned problems and achieve the objects, the present invention provides a corona discharger for an image forming apparatus using an electrophotographic method, through which air is exhausted through a ventilation hole in the back side of the corona discharger. It is characterized by being equipped with a device.

The exhaust device is composed of a runner for sucking and exhausting corona products generated by corona discharge, and a member for absorbing and decomposing corona products attached to surround the runner. It is mainly composed of activated carbon fiber as a member.

(Function) According to the present invention, corona products generated by corona discharge are passed through the ventilation hole by the rotating runner of the exhaust device installed at the back of the corona discharger, and are transferred to the absorption/decomposition member installed on the inner wall of the cover. It is attached and absorbed, and the influence of corona products on the photoreceptor is suppressed.

(Embodiment) FIG. 1 is a front view showing a structure according to an embodiment of the present invention, and FIG. 2 is a perspective external view of FIG. 1. As shown in the figure, the corona discharger 11 consists of a shield case 1 made of nickel-plated iron or stainless steel, a charge wire 2 made of tungsten, and a grid 3 for making the discharge uniform. .

Here, the grid 3 is made of about 3 to 6 tungsten wires of about 60 to 100 μm stretched parallel or diagonally to the charger wire 2 at intervals of 2 to 5 mm, or with a thickness of 0.05 to 0.2 mm. A stainless steel sheet of about 2 to 4. A sheet-like grid etched into a honeycomb structure of approximately 1.0 mm in size is used.

The corona discharger 11 of this embodiment has a plurality of ventilation holes 7 in the adhesive surface with the exhaust device 19 installed on the back side thereof, so that corona products generated by corona discharge are sent into the exhaust device 19. ing. Note that this corona discharger 11 can be removed individually.

Next, the exhaust device 19 is composed of a runner 4 connected to a drive shaft (not shown), a cover 5 for the runner, and an absorption/decomposition member 6 provided on the inner wall surface of the cover 5.

Here, the runner 4 has at least four or more wings,
The rotating body is long enough to cover 273" or more of the longitudinal length of the corona discharger 11, and has a diameter of about 10 to 25 mm. In addition, the runner 4 may be coated with an aluminum-containing resin or d-limonene-based material that decomposes corona products, or it may be coated with, for example, activated carbon fiber that absorbs and prevents diffusion. You can also paste it.

In addition, an absorption/decomposition member 6 provided on the inner wall surface of the cover 5
activated carbon fiber is used. This activated carbon fiber is mainly made of four types (cellulose type).

Polyacrylonitrile fiber, phenolic resin.

It was created based on pitch. Each fiber has a diameter of 10 to 30 μm and a diameter of a pore (pore) of about 20 μm. Therefore, for example, compared to granular activated carbon,
Several hundred times more mercaptan and monoacid sulfur.

It has an excellent absorption effect on nitrogen dioxide, etc. In addition, activated carbon fibers can have a density of 200 to 350, depending on their use, in the form of felt, fiber, mat, cylinder, or electrodeposited.
There are sheet-like products that can be used at temperatures as low as 30°F, but felt-like and mat-like products with high air permeability and a large effective area are effective in maintaining durability and It is desirable to have as much carbon fiber as possible. In this case, the felt type is 100%, and the matte type is 90% or more.

To explain the operational function of the exhaust device 19 having the configuration described in 1., the corona products generated by the corona discharge of the corona discharger II are as follows:
The air passes through the ventilation hole 7 by the runner 4, adheres to the absorption/decomposition member 6 provided on the inner wall surface of the cover 5, and is sucked. The rotation of the runner 4 and the generated wind are sent out in the direction of the arrow or in the direction of the long axis B through numerous ventilation holes 5A on the two sides and sides of the cover 5, but at this time, ozone and nitrates are removed. It has already been absorbed and there is very little environmental pollution.

Therefore, the influence on the photoreceptor is suppressed and good images can be obtained over a long period of time.

Next, a specific example will also be explained. First, the photoreceptor is an aluminum support with an outer diameter of 40 mm and a length of 250 mm.Secondly, a subbing layer made of TlO2 and polyamide resin, a charge generation layer (0,2p+n) made of tris-aiso pigment and polyvinyl butyral resin, and hydrazone. An OPC photoreceptor is prepared by laminating a charge transfer layer (25 plTl) made of a polycarbonate resin and a charge transfer layer (25 plTl).

Furthermore, on this ○PC photoconductor, Knoop hardness of 1100 to 1
300 kg/mm”, film thickness] pm a-
A CiH layer is laminated by plasma CVD at room temperature using C, H, and gas as raw materials.

The photoreceptor thus obtained was exposed to a light beam of 780 nm wavelength.
It will be installed on an experimental laser beam printer that uses ED as a light source. The copying capacity of the experimental machine is 8 ppm,
Do not use a separate corona discharger.

The exhaust device for the corona discharger is installed so that it is in close contact with the second part of the charging charger. The runner has a diameter of 15 mm, an angle of 60 degrees, and 6 blades, and is made of aluminum that has been subjected to corrosion treatment. The length was +80 leaves. The small motor that rotates the runner is an external DC motor.

On the other hand, the absorbent member is made of felt-like activated carbon fiber (Fine Guard Felt: manufactured by Toho Rayon, specific surface area 700 mm).
'/g basis weight, ]OOg/n () was attached to the entire inner wall of the cover. For the ventilation holes of the exhaust system, numerous holes with a diameter of 4 mm are drilled on the 16-sided part, and the exhaust air is vented to the outside through a duct.

As an experimental method■ Exhaust device operation Runner rotation speed 80 rpm■
〃 Approximately 20 Orpm ■ 3000 sheets of A-4 size for each of the 3 ways to stop the exhaust system 7
Running 12,000 pieces per day, the next day after finishing each number 2
2 to 24℃, 60 to 65% RI-( band-shaped white spots, after 6,000 sheets, 12,000 sheets, 25℃, 80
The results of checking the overall image blur in an environment of %RH are shown in the table below.

A: Band-like white spots ○: No problem B: Full image blur △: Slight signs are observed - ・
Not checked ×: Obviously occurrence is observed.”
-As you can see from the table, by operating the exhaust system,
Image quality deterioration caused by corona products is improved. However, if the suction effect is increased too much, the charging potential will become lower than a predetermined potential, and uneven charging will occur, which is not preferable. The rotation speed of the runner is influenced by the shape of the absorbing member, the linear density between fibers, the size and angle of the number of runner blades, the internal volume of the exhaust device, etc.

Although the runner length was approximately 86% of the aperture length of the corona discharger, the uniformity of the image was good and there was no image unevenness in the 2×2 dot pattern.

(Effects of the Invention) As explained above, according to the present invention, adhesion of corona products, which are considered to be the main cause of image deletion generated by corona discharge, to the photoreceptor is suppressed, and as a result, Since a decrease in resistance on the surface of the photoreceptor is prevented, image fading in high-temperature environments is suppressed, making it possible to maintain initial high image quality without unevenness over a long period of time.

Furthermore, since the generated corona products are immediately absorbed and treated, leakage of ozone odor to the outside is well suppressed, and contamination of the surrounding area is also suppressed.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a structure according to an embodiment of the present invention, FIG. 2 is a perspective external view of FIG. 1, and FIG. 3 is a main part configuration diagram showing an example of an image forming apparatus. l...Shield case, 2 Charge wire, 3 Grid, 4...Runner, 5
... Cover, 5A, 7 ... Ventilation hole, 6 ・
・・Absorption/decomposition member, 1O ・・Photoreceptor, 11 ・Corona discharger, 19 ・Exhaust device. Patent applicant: Ricoh Co., Ltd.

Claims (3)

[Claims] (1) A corona discharger for an electrophotographic image forming apparatus, characterized in that the corona discharger is equipped with an exhaust device through a ventilation hole on the back side of the corona discharger. (2) The exhaust device is characterized by comprising a runner for sucking and exhausting corona products generated by corona discharge, and a corona product absorption and decomposition member attached to surround the runner. The corona discharger according to claim (1). (3) The corona discharger according to claim (2), wherein the corona product absorption/decomposition member is mainly composed of activated carbon fiber.