JPH0673044B2 - Electrophotographic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Purpose of the Invention [Field of Industrial Application] The present invention relates to an electrophotographic apparatus using an amorphous silicon based photoreceptor.

[Prior Art] As a photoconductor for use in an electrophotographic apparatus, an inorganic semiconductor such as zinc oxide / cadmium sulfide, an organic semiconductor such as PVK, and an amorphous selenium-based photoconductor have been generally known. On the other hand, in recent years, as a new material, an electrophotographic apparatus using an amorphous silicon type photoconductor (hereinafter referred to as a-Si photoconductor) has been developed.

The a-Si photoconductor has many advantages over conventional photoconductors, such as high hardness and no pollution, high long-wavelength sensitivity, and resistance to heat. It is expected that demand will increase.

However, even though it has excellent wear resistance due to its high hardness, when a strong electric field that is not applied during normal use is applied to the photoreceptor due to excessive charging or sudden discharge,
Defects such as pinholes may occur, which greatly impairs the life of the photoconductor. In order to realize the high durability of the a-Si photoconductor, also in this respect, performance higher than that of the conventional photoconductor is required.

According to the research conducted by the present inventors, the a-Si photosensitive member is often used in a thin film state with a film thickness of mainly 5 μm to 60 μm.
In addition, since the relative dielectric constant is 10 or more, which is higher than that of general photoconductors (6 to 7 for selenium, and generally 5 or less for other types), a stronger electric field is applied during charging than when using conventional photoconductors. It is known that the electrostatic breakdown voltage of a-Si photoconductor itself is lower than that of other photoconductors (around 1000V when the thickness is 20 μm), and it must be used in a strong electric field. However, it was confirmed that when overcharged, defects such as pinholes were easily generated, even though it did not occur.

[Problems to be solved by the invention]

As a result of the observation by the present inventors, it was found that the cause of the application of the above-mentioned excessive electric field is that toner, paper powder, metal pieces, and other dust deposits on the surface of the a-Si photoconductor are a major factor. . This is most obvious especially in the case of metal pieces such as chips, but it is considered that the electric field due to charging is concentrated and pinholes are generated. However, it should be noted that similar pinholes are generated by the adhesion of toner or the like, which is considered to be one of the main causes of pinhole generation.

An object of the present invention is to eliminate the above-mentioned cause of pinhole generation.

B. Structure of the Invention [Means for Solving the Problems] The present invention is directed to a movable amorphous silicon photoconductor, one or more chargers for charging the photoconductor, and cleaning the photoconductor. In an electrophotographic apparatus having a cleaning unit, after the photosensitive member that has been stopped for a predetermined time starts to move and then the surface of the photosensitive member that has been cleaned by the cleaning unit has passed a charging region of the charger. In the electrophotographic apparatus, the charging operation by the charger is started.

[Action]

As described above, the surface of the photoconductor is cleaned to remove toner, paper dust, and other adhering substances, and then charging is started to eliminate the cause of pinholes.

〔Example〕

 Next, details of the present invention will be described with reference to examples.

FIG. 1 shows an electrophotographic apparatus using an a-Si photoconductor, and 1 is an a-Si photoconductor drum having a photoconductive layer formed by doping amorphous silicon with a small amount of hydrogen or nitrogen on a conductive drum. Rotating in the direction of the arrow in the figure, 2 is a primary charger (positive in this embodiment) that applies an ion current to the photoconductor to sensitize and charge, 3 is image exposure light, 4 is the photoconductor A developing device that supplies toner to develop a latent image, 5 is a transfer charger that applies an ion current to the transfer material / photoreceptor, 9 is a transfer material, 6 is always in contact with the photoconductor, and is always in contact with the drum during rotation. A cleaner device which acts to clean the residual toner on the photosensitive drum 1 after transfer by this, and then to which a pre-exposure light source 7 and a grid connected to the main body ground are added, and a pre-static charge eliminator 8 for giving an AC ion current to the photo conductor Thus, the photosensitive drum 1 is discharged and the reuse is repeated.

It should be noted that the static eliminator 8 is not always required as long as the light source 7 is provided, but in the present specification, a device that gives an ion current to neutralize the photoconductor is also called a charger.

In this case, when the drum is stopped for a predetermined period of time, if the adhering matter is present on the surface of the photosensitive drum 1 downstream in the rotation direction of the cleaner 6, the primary charger 2 is started at the drum start.
There is a possibility that a pinhole may be generated by being charged by either the transfer charger 5 or the front static eliminator 8.

The conventional electrophotographic apparatus is performed at the above process timing.

Therefore, according to the present invention, at the start of drum rotation, a known timer is used to start the operation of each of the chargers 2 and 5 and the static eliminator 8 after the surface of the photosensitive drum 1 cleaned by the cleaner 6 has passed the charging area. The sequence control is performed by using such as.

FIG. 2 shows an example of the sequence at this time. Figure t ₁ · t ₂ · t ₃ is shows a timing to start operating each charger after the photosensitive drum 1 starts rotating started by copy button, the distance a · b in Figure 3
・ The relations of t ₁ ta, t ₂ tb, and t ₃ tc are satisfied when the time to move c is ta, tb, and tc, respectively. The distances a, b, and c all indicate the most downstream portion in the direction of rotation of the photoconductor in the region that is charged by the charging of each charger, and is approximately the rear end (downstream side) of the charger opening and the cleaner 6. Equivalent to the distance.

The cleaner is the same as that shown in FIGS. 1 and 3 as well as when a fur brush, a web or other various cleaning means is used. Incidentally, in the case of rotating and moving a fur brush or a web, these operations are started at the same time as or before the start of rotation of the photosensitive drum.

FIG. 4 illustrates a case where a scraping-type blade 11 is provided downstream of the fur brush 10 as an auxiliary means, and FIG. 5 illustrates a case where the blade 12 is integrally provided on the upstream side wall of the primary charger 2. In the figure, the blades 11 and 12 are contacted in the forward direction with respect to the rotation direction of the photosensitive drum 1, but they may be contacted in the counter direction.

Further, in the present embodiment, the charger 2 has a positive polarity, but the a-Si photoconductor is generally capable of being charged in both polarities.
It goes without saying that the invention itself is independent of the polarity of the charger. Further, since the charging polarity of the transfer charger 5 is opposite to that of the toner, the polarity is opposite to that of the charger 2 when the reversal development for adhering the toner to the light potential portion is adopted, and otherwise. It has the same polarity.

C. Effects of the Invention As described above, by starting the charging after cleaning the surface of the photoconductor, pinholes due to adhered substances on the a-Si photoconductor are hardly generated, and the a-Si photoconductor is almost eliminated. The extremely high wear resistance inherent in the body can be fully exerted, and the durability performance has dramatically improved.

[Brief description of drawings]

1 and 3 are examples of an electrophotographic apparatus using an a-Si photoconductor, FIG. 2 is an example of a timing chart showing the timing of applying a charger in the present invention, and FIGS. 4 and 5 are The figure which shows the other Example of the cleaning means in this invention. 1 ... a-Si photosensitive drum, 2 ... charger, 3 ... image exposure, 4
... developing device, 5 ... transfer charger, 6 ... blade type cleaner,
7 ... Pre-exposure lamp, 8 ... Front static eliminator, 9 ... Transfer material, 10 ... Fur brush type cleaner, 11.12 ... Cleaning auxiliary means.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Tatsuyuki Aoike 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Osamu Sugino 3-30-2 Shimomaruko, Ota-ku, Tokyo Kya Non-Incorporated (56) Reference JP-A-58-14876 (JP, A) JP-A-60-168166 (JP, A)

Claims (1)

[Claims] 1. An electrophotographic apparatus having a movable amorphous silicon photoconductor, a charger or a plurality of chargers for charging the photoconductor, and a cleaning unit for cleaning the photoconductor. The charging operation by the charger is started after the surface of the photoreceptor that has been cleaned by the cleaning unit has passed the charging area of the charger after the movement of the photoreceptor has started. Electrophotographic device.