JPH0451168A - Electrophotographic copying method - Google Patents

Abstract

PURPOSE:To always keep high image quality even when a photosensitive body is repeatedly used for a long time by allowing a member having electrical conductivity to contact with the surface of the photosensitive body and impressing positive or negative voltage on the member. CONSTITUTION:An electrostatic charger 2, an image exposing unit 3, a develop ing unit 4, a transfer charger 5, a separation charger 6, a cleaning unit 7, a destaticizing lamp 8, a transfer paper 9, a fixing unit 10 and conductive brush- like structural bodies or conductive felt-like structural bodies 11 and 12 are provided around the photosensitive body 1. In such a case, a conductive fiber is used as an element for forming the brush-like structural body or the felt-like structural body having the electrical conductivity in substance. It is good to use a DC electric field or an alternating electric field biased to be positive or negative as the positive or the negative voltage impressed on the surface of the photosensitive body through the conductive brush-like structural body or the conductive felt-like structural body. Thus, the ionic hydrophilic substance which is stuck and accumulated on the surface of the photosensitive body is removed and the stable high image quality is maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for maintaining high image quality over a long period of time in an electrophotographic method, that is, an electrostatic copying method using the Carlson process.

[Prior Art] Currently, the electrostatic copying method using the Carlson process, the so-called electrophotographic method, is the most widely used copying printing method.

The electrophotographic method here refers to a photoconductive material called a photoreceptor formed on a conductive support, which is first charged (electrostatically) in a dark place.
- Corona discharge is used as a charging means for boat fishing. ), and then imagewise exposed to selectively dissipate the charge only in the exposed area to obtain an electrostatic latent image. This is an image forming method in which the image is developed with electrostatic fine particles called toner, and then transferred and fixed onto an image carrier such as paper to form an image.

FIG. 2 shows an example of an image forming apparatus using electrophotography.

Photoreceptor 1 is a charging corona discharger (charging charger 2)
It is charged like -.

There are two types of corona dischargers: the corotron type, in which a tungsten wire with a diameter of 40 to 100μ is stretched, and the scorotron type, in which a grid is stretched near the discharger opening to even out uneven discharge. A high voltage of ~8000 volts is applied. After imagewise exposure is performed in the exposure section 3 to form an electrostatic latent image, a toner image is formed in the developing device 4.

The toner image is transferred using a corona discharger (transfer charger) 5
After being transferred onto copy paper 9, the copy paper is separated from the photoreceptor by a separation corona discharger (separation charger) 6, and fixed by a fixing device 10 to become a hard copy.

On the other hand, the toner image on the photoreceptor 1 after transfer is cleaned by a cleaning device 7, and a series of copying steps is completed.

The photoreceptor used in this electrophotographic method is Se or Se alloy (Se-As, 5e
-Te, 5e-As-Te, etc.)), those with a photoconductive layer containing inorganic photoconductive materials such as zinc oxide and cadmium sulfate dispersed in a binder, and poly-N-
Products using organic photoconductive materials such as vinyl carbazole and trinitrofluorenone or azo pigments (OPC)
, and those using amorphous silicon-based materials are generally known.

The basic characteristics required of these photoreceptors are (1) ability to be charged to an appropriate potential in the dark, (2) low dissipation of charge in the dark, and (3) rapid dissipation of charge when irradiated with light. Examples include doing the following.

Another characteristic required in practical use is that it is resistant to the mechanical and chemical loads received in the electrophotographic process.

When each of the above-mentioned photoreceptors is viewed from these points of view, each of them has excellent characteristics and drawbacks.

For example, amorphous silicon photoreceptors have high surface hardness, excellent durability against mechanical loads (contact with various parts in the cleaning section, development section, transfer section, etc.), and relatively high photosensitivity. However, on the other hand, the charging ability is relatively low, the manufacturing cost is high, and the chemical load (O3 and N generated by corona discharge) is high.
It has the disadvantage that the surface resistance decreases depending on the humidity, resulting in abnormal images such as so-called image deletion.

In addition, Se or Se alloy (Se-Te, SeAs,
Photoreceptors based mainly on S e -T e -A s systems, etc.) have been commonly used since the earliest times, and while they have excellent photosensitivity and charging ability, they are susceptible to mechanical loading. A drawback is that scratches on the surface of the photoreceptor tend to result in abnormal images such as white stripes or black stripes in terms of image quality.

Furthermore, in recent years, organic photoreceptors have made remarkable progress due to their low manufacturing cost, low environmental pollution, and relatively flexible photoreceptor design.

In general, an organic photoreceptor is a material in which a charge-generating material and a charge-transporting material are dispersed or dissolved in a binder resin and coated on a conductive support. Single layer type with transport function, charge generation layer (CGL) with charge generation function, charge retention and CG
A charge transport layer having a function of transporting charges injected from L (
CTL), and a function-separated type is known, which has a laminated layer with functions such as blocking charge injection from the support or preventing light reflection from the support, if necessary. ing.

These organic photoreceptors have excellent features as mentioned above, but because they are made of organic materials, their surface hardness is low, and they are prone to wear and scratches due to mechanical loads during the copying process. It also has essential drawbacks.

This abrasion of the photosensitive layer causes a decrease in the charging potential, and local scratches cause streak-like abnormal images on copies, both of which are important problems that affect the life of the photoreceptor.

In order to overcome these drawbacks regarding the mechanical durability of Se-based and OPC-based materials, a method has been proposed in which a protective layer is provided on the surface of the photosensitive layer to improve the durability against mechanical loads received inside and outside the copying machine. There is.

For example, a method of providing an organic film on the surface of the photosensitive layer (Japanese Patent Publication No. 38-015446), a method of providing an inorganic oxide (Japanese Patent Publication No. 43-014517) After providing an adhesive layer,
A-3 by a method of laminating insulating layers (Japanese Patent Publication No. 43-27591), or by Ihabraz vCVD method, photo-CVD method, etc.
Method of stacking t layer, 5-Si:N:H layer, a-3t:O;H layer, etc. (JP-A-57-179859, JP-A-59-
058437) etc. have been disclosed.

In addition, as a technique to compensate for the increase in residual potential that occurs when protective layers are laminated and the accumulation during repeated cycles, a method of using a photoconductive layer as a protective layer (Japanese Patent Publication No. 48-38427, Japanese Patent Publication No. 43-1988) has been proposed.
16198, Special Publication No. 49-10258, U.S.P. 2
901348), a method of adding a transfer agent such as a dye or a Lewis acid into the protective layer (Japanese Patent Publication No. 44-834, Japanese Unexamined Patent Application Publication No. 138444-1983), or adding metal or metal oxide fine particles to the protective layer. A method for controlling resistance (Japanese Patent Application Laid-Open No. 53-3338) has been proposed.

Furthermore, in recent years, the application of carbon or highly hard thin films containing carbon as a main component has become active as a protective layer material for photoreceptors.

For example, one in which a protective layer made of amorphous carbon or hard carbon is provided on the photosensitive layer (JP-A-6O-249155), one in which a diamond-like carbon protective layer is provided on the outermost surface (JP-A-6L-255152), photosensitive layer. A high-hardness insulating layer containing carbon as a main component is formed on the layer (Japanese Patent Application Laid-Open No. 61-28485)
5) Alternatively, a protective layer made of a plasma organic polymer film containing at least atoms such as nitrogen atoms, oxygen atoms, halogen atoms, alkali metal atoms, etc. is provided on the organic photosensitive layer (Japanese Unexamined Patent Publication No. 63-97961-4); A protective layer made of an amorphous hydrocarbon film generated by glow discharge containing at least chalcogen atoms, group II atoms, group II atoms, group V atoms, etc. is provided on the photosensitive layer (Japanese Unexamined Patent Application Publication No. 1983-1999) 22016
8 to 9), etc.

These methods have made it possible to dramatically improve the mechanical durability of Se-based photoreceptors, OPCs, and the like. However, it has been found that when these photoreceptors are used for a long period of time, they suffer from the same problem as amorphous silicon-based photoreceptors, such as image blurring under high humidity.

The estimated mechanism for the occurrence of image blurring can be roughly divided into: (1) Repeated exposure to corona discharge used for charging purposes, chemical deterioration (oxidation, etc.) of the photoreceptor surface due to ozone generated by corona discharge, etc. , changes to hydrophilicity.

■ Ozone and various ions caused by corona discharge react with impurities such as moisture and carbon dioxide in the air to form hydrophilic compounds containing nitrogen compounds, carboxyl groups, aldehyde groups, etc., which adhere and accumulate on the photoreceptor surface. By doing so, it becomes hydrophilic.

The above two methods are considered, and in either case, abnormal images occur because water is adsorbed to the surface of the photoreceptor, which has become hydrophilic, and the two-dimensional resistance of the surface decreases.

In the case of the aforementioned amorphous silicon-based photoreceptor, ■ is thought to be the dominant cause, and image blurring on protective layer-formed photoreceptors is also thought to be caused by ■ or ■. Reliability of photoreceptors has become an important issue.

As a method for preventing image blurring, (1) a method of heating the photoreceptor (Japanese Patent Application Laid-Open No. 59-208558, JP-A No. 80-9548)
(2) The corona product from the corona discharger is used as activated carbon fiber or Ni.

A method of absorbing and decomposing Pt, Au, beryllium alloys, etc. in grids, shield cases, or charge wires (JP-A-50-34828, JP-A-63-31136)
5. 64-88774. JP 1-210974. 1-319062, etc.) (3) Method for controlling corona discharge current (Japanese Patent Application Laid-Open No. 1-237569, etc.). However, although the heating method is highly effective, it is still insufficient.
Although the decomposition method is recognized to be effective, it still has problems with continuity, etc. [Problems to be solved by the invention] Therefore, the present invention provides an electrophotographic method that can always maintain high image quality even after repeated use over a long period of time. This is what we are trying to provide.

Means for Solving Problem C] The structure of the present invention for solving the above problem is (1) charging;
In an electrophotographic method comprising exposure, development, transfer, cleaning, and fixing steps, at least one substantially conductive member is further brought into contact with the surface of the photoreceptor, and a substantially positive or negative conductive member is contacted with the surface of the photoreceptor. An electrophotographic method characterized by comprising means for applying a voltage of .

(2) The electrophotographic method according to item (1) above, characterized in that there is at least one member for applying a substantially positive or negative voltage, and at least one member for applying a substantially positive voltage and at least one member for applying a negative voltage.

(3) The electrophotographic method as described in items (1) and (2) above, wherein the substantially conductive member is composed of conductive fibers.

(4) The electrophotographic method according to item (3) above, wherein the member made of conductive fibers has a brush-like structure or a felt-like structure.

(5) The electrophotographic method according to item (4), characterized in that activated carbon fiber is used as at least one of the elements constituting the brush-like structure or the felt-like structure.

That is, the present invention brings a substantially conductive member into contact with the surface of the photoreceptor and applies a substantially positive or negative voltage to remove the hydrophilic substances (ions) attached to the surface of the photoreceptor. This is an electrophotographic method that allows stable images to be obtained over a long period of time by effectively removing the majority of the

The present invention will be explained below with reference to the drawings.

FIG. 1 shows an example of a device equipped with a conductive brush-like structure and a conductive felt-like structure according to the present invention. Further, FIG. 3 shows a modification thereof. That is, the structure includes a charging charger 2, an image exposure unit 3, a developing unit 4, a transfer charger 5, a separation charger 6, a cleaning unit 7, a static elimination lamp 8, a transfer paper 9, a fixing unit 10, and a conductive brush around the photoreceptor 1. shaped structure or conductive felt-like structure 1
1.12.

FIG. 1 shows the structure in the form of a roller, and FIGS. 3a and 3 show the structure in the form of a blade.

In the present invention, conductive fibers are used as a bulk element for forming a brush-like structure or a felt-like structure that is substantially electrically conductive.

Conductive fibers include those processed into fibers from the metal itself, those coated with metal on the surface of ordinary fibers by plating, vacuum deposition, sputtering, etc., and those coated with conductive fine particles (carbon, metal, etc.) on the fiber surface. Examples include those in which a dispersed organic layer is formed, and those in which conductive fine particle dispersed polymers are blended or multicore composite spun. It is desirable that the volume resistivity of the conductive fiber used in the present invention is 10I0Ω·(1) or less.

Generally, the fibers have a thickness of 5 to 15 [denier/filament]. The appropriate brush density is 10,000 to 100,000 [pieces/1 nch2], and the bristles length of the brush is 1 to 10 mm.

To construct a brush-like structure, there are methods such as directly fixing the fibers constituting the brush on a support, or fixing a woven fabric (pile) of brush fibers on a support by adhesive or other means. .

The bristles of the brush may be in a state where the brush fibers are cut or in a looped state.

On the other hand, a felt-like structure is a sheet-like or block-like structure composed of fibers that are significantly entangled. It can be manufactured by a method such as a method of poking it from the outside and a method of manufacturing a non-woven fabric.

When fibers having catalytic activity (adsorption ability, etc.) are used as the conductive fibers constituting the conductive brush-like structure or the conductive felt-like structure or as constituent elements other than the conductive fibers, the electric field application of the present invention can be improved. Hydrophilic substances such as ionic substances adhering to the surface of the photoreceptor can be removed more efficiently by interaction with the photoreceptor.

The above-mentioned fibers having catalytic activity may be those having catalytic activity themselves or those having a material having catalytic activity retained on the fiber surface by a method such as coating.

Activated carbon fibers can be mentioned as fibers having this catalytic activity.

Activated carbon fiber is a porous carbonaceous fibrous material with a large specific surface area and adsorption capacity, and is made from polyacrylonitrile fiber, cellulose fiber, phenolic resin, pitch, etc., and each fiber is pretreated (flame-resistant). It can be obtained by performing activating treatment (activation) and activation treatment.

Its typical physical properties include a specific surface area of 500 to 1500.
m2/g-fiber diameter is 5 to 200 am, average pore diameter is 10 to 40 mm, and because it is fibrous, it can be processed into various shapes such as fabric, paper, and felt. be.

The substantially positive or negative voltage applied to the photoreceptor surface through these conductive brush-like structures or conductive felt-like structures may be a direct current electric field or an alternating electric field biased positively or negatively. Either one may be used. The electric field applied to the surface of the photoreceptor has a direct current component and is suitably in the range of 1 to 100 V for both positive and negative electric fields.

Even if the conductive brush-like structure or felt-like structure that is brought into contact with the photoreceptor surface in this way is in constant contact with the photoreceptor surface, it is brought into contact with the photoreceptor surface at the appropriate timing by using means such as retracting it. I don't mind if you let me. or,
The substantially positive or negative voltage applied to the photoreceptor through these members may be applied all the time or may be applied at appropriate timing. Furthermore, when bringing these members into contact with the photoreceptor surface, the linear velocity of the member surface and the photoreceptor surface may be the same, or a linear velocity difference may be provided to improve the contact efficiency, or the linear velocity may be set to be rotated in the reverse direction. I don't mind if you let me.

Note that the ionic properties attached to the photoreceptor surface can be removed by contacting the photoreceptor surface with a substantially conductive brush-like structure or felt-like structure and applying a substantially positive or negative electric field. Any method that removes hydrophilic substances belongs to the present invention, and is not limited to the examples of the apparatus shown in FIGS. 1 and 3.

Furthermore, the present invention can be applied to all photoreceptors that produce abnormal images due to adhesion of hydrophilic substances, mainly ionic substances, and is not limited to photoreceptors to which it can be applied.

[Examples] The present invention will be explained in more detail below using Examples and Comparative Examples.

Example 1 Conductive synthetic fiber (
Toshisha rJ: 5A-7) and polyacrylonitrile-based activated carbon fiber (manufactured by Toho Rayon Co., Ltd.; Fine Guard) were mixed at a ratio of 2:1, and a pile was fixed to a density of 5 (10,000 pieces/Inch2 ), bristles length B, and a conductive brush roller having loop-shaped bristles was formed to produce the conductive brush-like structure of Example 1.

Example 2 Conductive synthetic fiber (
5A-7) manufactured by Toshisha Co., Ltd. and polyacrylonitrile activated carbon fiber (Ni Fine Guard manufactured by Toho Rayon Co., Ltd.).
Felt sheet made by blending at a ratio of 1:1 (medium 30
mm, thickness 8 mm) was spirally wound and fixed to form a conductive felt roller, thereby producing the conductive felt-like structure of Example 2.

Using a plain paper copying machine equipped with these conductive brush-like structures or conductive felt-like structures, continuous images were taken and image quality was evaluated. Image rating: 5/
The characteristic value was whether the +am resolution chart was well resolved on the copy.

In this test, the photoreceptor used was As-5e type (As
: 35.5 wt%) A protective layer of polyurethane resin containing SnOz dispersed therein as a resistance control agent was formed on the photosensitive layer.

Further, tests were conducted by applying a DC electric field and an alternating electric field to the brush-like structure and the felt-like structure, respectively.

In the case of a direct current electric field, 20V was applied to the surface of the photoreceptor for both positive and negative sides. Frequency 1 kHz in case of alternating electric field
% V p-p 20 V s DC component and positive.

20V was applied to both the negative and negative terminals. The polarity of the electric field was negative to the brush-like structure 11 and positive to the felt-like structure 12. Furthermore, as a comparative example, evaluation was also conducted in the case where no brush-like structure or felt-like structure was provided.

In addition, during this test, a brush-like roller or a felt-like roller was rotated in the reverse direction with respect to the photoreceptor to increase the contact efficiency.

The test results are shown in Table-1.

Table-1 ◎ Very good resolution O Good resolution △ Slightly poor resolution × Not at all resolved As is clear from Table-1, in the case of the comparative example, the Image blurring occurred in a high temperature and humidity environment after copying the cycle, but when a substantially positive or negative electric field was applied using a conductive brush-like structure or a conductive felt-like structure, either a direct current or an alternating electric field Nevertheless, no image deletion was observed even after 50,000 cycles, and a stable image was obtained.

[Effects of the Invention] As explained above, according to the method of the present invention, particles adhere to the surface of a photoreceptor by receiving corona discharge.

As the ionic hydrophilic substances that accumulate are removed in a timely manner,
It is possible to maintain stable high image quality over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of an example of an apparatus suitable for carrying out the electrophotographic method of the present invention. FIG. 2 is an explanatory diagram of an example of an image forming apparatus using electrophotography. FIGS. 3(a) and 3(b) are explanatory diagrams of another modification of the present invention. l...Photoconductor, 2...Charging charger 3...Image exposure unit, 4...Developing unit, 5...Transfer charger 6...Separation charger 7...Cleaning unit, 8... - Static elimination lamp, 9... Transfer paper, 10... Fixing unit, 11.12... Conductive brush-like structure or conductive felt-like structure. Figure 1 Figure 2

Claims (2)

[Claims] (1) In an electrophotographic method consisting of charging, exposure, development, transfer, cleaning, and fixing steps, at least one substantially conductive member is further brought into contact with the surface of the photoreceptor, and the member is An electrophotographic method characterized by applying a substantially positive or negative voltage. (2) The electrophotographic method according to claim 1, wherein the substantially conductive member in contact with the surface of the photoreceptor has at least one for positive voltage and at least one for negative voltage.