JP2000330361A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which ensures a sufficiently wide range of electrification of a photoreceptor with an electrifier in high-speed printing, does not lower image characteristics even when high-speed printing is repeated and gives a stable image over a long period of time. SOLUTION: The image forming device has an organic photosensitive drum 9 with a photosensitive layer formed by successively laminating an electric charge generating layer 3, a 1st electric charge transferring layer 4 and a 2nd electric charge transferring layer 5 on an electrically conductive substrate 1 in such a way that the durability and wear resistance of the 2nd electric charge transferring layer 5 are made higher than those of the 1st electric charge transferring layer 4 and an electrifier 7 with grids 8 disposed along the curvature of the peripheral surface of the 2nd electric charge transferring layer at regular intervals in such a way that the grids confront the peripheral surface of the 2nd electric charge transferring layer. The surface of the photoreceptor 9 is electrified with the electrifier 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for repeatedly forming a large number of images in an electrophotographic method, an electrostatic printing method, an electrostatic recording method, and the like, and particularly relates to an improved charger and an electrophotographic photosensitive member. And an image forming apparatus using the same.

[0002]

2. Description of the Related Art Among various printing or recording methods, for example, in electrophotography, a photoconductive photoreceptor is charged and exposed,
An electrostatic latent image is formed on a photoreceptor, and then the electrostatic latent image is developed with a fine particle toner containing a colorant or the like, and the obtained toner image is transferred and fixed onto a recording medium such as recording paper for recording. An image is obtained.

In such an electrostatic image recording process, the surface of the photoreceptor after the transfer is often used repeatedly for a long period of time by removing the residual fine particle toner and removing the static electricity from the photoreceptor. Needless to say, electrophotographic properties are required, as well as resistance to corrosive gases such as ozone and NOx generated during charging (corona resistance). In particular, durability and abrasion resistance during repeated use are required.

Recently, with the development of information equipment, a laser beam printer that uses a laser beam for exposing a photoconductive photoreceptor and reproduces a recorded image with dots by a modulation signal instructed by a computer has been developed. Particularly, in recent laser beam printers, even higher image quality is required to be formed. Therefore, the diameter of the laser beam is reduced and reduced, and the dot density is 600 to 1200 dpi (dots / inc.
h) is higher. As a result, the durability and abrasion resistance of the photoreceptor are further required for the purpose of holding a fine electrostatic latent image.

Conventionally, an inorganic photoconductive photoreceptor using amorphous silicon, selenium, or the like has been used as an electrophotographic photoreceptor. Organic photoconductive photoconductors (hereinafter abbreviated as “organic photoconductors”), which are easy to obtain sensitivity in a wavelength region, particularly a long wavelength such as a semiconductor laser, have become mainstream.

The above-mentioned fatigue deterioration due to repeated use of the electrophotographic photosensitive member is caused by various steps such as transfer and separation of a toner image formed on the photosensitive member onto a recording medium and removal of residual toner on the photosensitive member after transfer. It is considered that the surface of the photoconductor is deteriorated due to deterioration, decomposition, etc. of the photoconductor surface layer in each step such as charging, exposure, and static elimination of the photoconductor surface due to the rubbing of the photoconductor. Therefore, it is important to improve the surface layer of the photoreceptor in order to prevent the fatigue deterioration of the photoreceptor. In particular, the organic photoreceptor is softer than the inorganic photoreceptor, and the photoconductive substance is an organic material. Fatigue deterioration during repeated use is large, and improvement of the photoconductor surface layer becomes more important.

On the other hand, the charging of the photoreceptor may be performed by a charger 20 having a grid 20b as shown in FIG. The grid 20b is interposed between the corona wire 20a and the photoreceptor 21 to suppress charging unevenness, and this type of charger is generally called a scorotron. When a high voltage is applied to the corona wire 20a, corona ions are generated by corona discharge of the corona wire 20a,
The corona ions are carried to the surface of the photoconductor 21 via the grid 20b to which a predetermined voltage is applied, and the photoconductor 21 is charged.

[0008]

By the way, when the grid 20b is flat as shown in FIG. 4, only the central portion approaching the photoreceptor surface contributes to charging, and both ends of the grid which are distant from the photoreceptor surface. Does not contribute much to charging. In addition, the printing speed of the printer tends to increase year by year, and the size of the apparatus has been reduced, and it has become difficult to obtain a sufficient charging width.

If the charging width is not sufficient, the surface potential of the photoreceptor is greatly deteriorated, and the contrast potential decreases with time, causing fogging. Further, recently, a charge control agent contained in the toner to control the charge amount of the toner to an appropriate range, a fluidizing agent added to the toner surface to improve the fluidity of the toner, and a rise in charge are improved. Therefore, a conductive agent tends to be added to the toner surface.
However, the fluidizing agent and the conductive agent are materials of high hardness, and the toner to which these are added improves the abrasiveness of the toner as compared with the case where they are not added, wears the photoreceptor surface more, and especially the soft organic photoreceptor. In this case, the life of the photoconductor is shortened.

As a result, the replacement period of the photosensitive member is shortened, the cost of consumables required per printed page is increased, and
There has been a problem that it is difficult to apply an organic photoreceptor to an image forming apparatus that requires printing of a large number of sheets with high image quality.

An object of the present invention is to provide an image forming apparatus which can secure a sufficient charging width of a photoreceptor by a charger in high-speed printing, and does not degrade image characteristics even after repeated high-speed printing, and can obtain a stable image for a long period of time. It is to provide a device.

[0012]

SUMMARY OF THE INVENTION The object of the present invention is to provide a charge generating layer provided on a conductive substrate, a first charge transporting layer provided on the charge generating layer, and a first charge transporting layer. A second charge transport layer provided on the layer, wherein the durability and abrasion resistance of the second charge transport layer are defined to be greater than that of the first charge transport layer. An organic photoreceptor drum having a layer, and a charger having a grid opposed to the outer peripheral surface of the second charge transport layer so as to be at equal intervals along the curvature of the outer peripheral surface of the second charge transport layer. This is achieved by:

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

First, the structure of the photoconductor applied in the present invention will be described with reference to FIG. The photosensitive member includes a conductive substrate 1, a charge generation layer 3 provided on the conductive substrate 1 via the intermediate layer 2, a first charge transport layer 4 provided on the charge generation layer 3, It is configured as a multilayer organic photoreceptor obtained by laminating a second charge transport layer 5 provided on the charge generation layer 4. Further, the concentration of the charge transport agent in the charge transport layer 5 was 20% by weight and the film thickness was 10 μm, and the concentration of the charge transport agent in the charge transport layer 4 was 50% by weight and the film thickness was 18 μm.

As shown in FIG. 2, a charger 7 includes a grid 8 interposed between the corona wire 6 and the surface of the photoreceptor 9.
Are arranged opposite to the outer peripheral surface of the photoreceptor at equal intervals along the curvature of the outer peripheral surface of the photoreceptor (the outer peripheral surface of the second charge transport layer).

In order to compare the effects obtained when the above-mentioned photoreceptor and the charger are used, an organic photoreceptor of a type in which a charge generation layer and a single-layer charge transport layer are laminated on a conductive substrate is prepared. A 300,000-page continuous printing experiment was performed with a laser printer having the configuration shown in FIG. 3, and the deterioration of the surface potential was compared. In the organic photoreceptor having a single-layer charge transport layer, the charge transport layer having a charge transport agent concentration of 45% by weight was used.

In FIG. 3, the photosensitive drum 9 is constituted by providing a photosensitive layer 9b on a base tube 9a.
Are supported rotatably clockwise. The photoconductor drum 9 is uniformly charged by the charger 7 with the rotation operation, and is then exposed by the exposure device 10 to hold the electrostatic latent image. The electrostatic latent image formed on the photosensitive drum 9 is visualized as a toner image in a developing area of the developing device 11,
This toner image is carried to a transfer position as the photosensitive drum 9 rotates, and is transferred onto a recording medium 13 by the transfer device 12.
The recording medium 13 holding the toner image is fed between the heating roller 14 and the pressure roller 15 pressed against each other, and the toner image is fixed on the recording medium 13 by the heating and pressing action while being nipped and conveyed. On the other hand, at the transfer position, the recording medium 1
The toner remaining on the photosensitive drum 9 without being transferred to the photosensitive drum 3 is removed from the surface of the photosensitive drum 9 by the cleaning device 16.

In the above laser printer, the charged potential is:
-700 V, residual potential: -70 V, developing bias potential:
−400 V, developing section contrast potential: set to 300 V, and print speed of 70 sheets per minute (print process speed 31 cm)
/ Sec) and 300,000 pages were continuously printed. At this time, the photosensitive drum and the charger of the laser printer are constituted by (1) a combination of a multi-layer charge transport layer type organic photoreceptor and a charger having a grid having a curvature, and (2) a multi-layer charge transport layer type. (3) a configuration in which an organic photoreceptor is combined with a charger having a flat grid, (3) a configuration in which a charge transport layer type organic photoreceptor is combined with a charger having a grid having a curvature, and (4)
The above four configurations, that is, a configuration in which a one-layer charge transport layer type organic photoreceptor is combined with a charger having a flat grid were examined.

As a result, when the continuous printing of 300,000 pages was completed, the abrasion loss of the photoreceptor was 5.8 μm in the case of the multi-layer charge transport layer type organic photoreceptor. The thickness of the organic photoreceptor was 10.2 μm, and it was confirmed that the charge transport layer type organic photoreceptor was significantly worn.

Regarding the deterioration of the photoconductor surface potential,
The configuration of (1) is 22V, the configuration of (2) is 58V, the configuration of (3) is 45V, and the configuration of (4) is 98V. It was confirmed that the configuration of the above (1) in which the organic photoreceptor and the charger having the grid having the curvature were combined had the least deterioration of the surface potential.

[0021]

As described above, according to the present invention, the charging width of the photoreceptor by the charger can be sufficiently secured in high-speed printing, and the image characteristics do not deteriorate even if high-speed printing is repeated. An image forming apparatus capable of obtaining a stable image can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating the structure of a photosensitive layer of an organic photosensitive member applied to the present invention.

FIG. 2 is a schematic configuration diagram showing a relationship between a photosensitive member and a charger in the present invention.

FIG. 3 is a schematic configuration diagram of a laser printer to which the present invention is applied.

FIG. 4 is a schematic configuration diagram showing a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Conductive support, 2 ... Intermediate layer, 3 ... Charge generation layer, 4 ...
First charge transport layer, 5 second charge transport layer, 6 corona wire, 7 charger, 8 grid, 9 photosensitive drum.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tsutomu Nakagawa 1060 Takeda, Hitachinaka-shi, Ibaraki F-term in Hitachi Koki Co., Ltd. (reference) 2H003 BB11 CC01 DD01 EE03 EE08 2H068 AA29 AA37 AA39 FA03 FC01

Claims (2)

[Claims] 1. A charge generation layer provided on a conductive substrate,
A first charge transport layer provided on the charge generation layer; and a second charge transport layer provided on the first charge transport layer, and the durability of the second charge transport layer And an organic photoreceptor drum having a photosensitive layer whose abrasion resistance is defined to be greater than that of the first charge transport layer; and an equal interval along the curvature of the outer peripheral surface of the second charge transport layer. An image forming apparatus, comprising: a charger having a grid arranged to face the outer peripheral surface of the second charge transport layer. 2. The image forming apparatus according to claim 1, wherein the concentration of the charge transport material in the second charge transport layer is lower than the concentration of the charge transport material in the first charge transport layer. apparatus.