JPS61281274A - Cleaning method for image holding body - Google Patents

Abstract

PURPOSE:To suppress the wear of an image holding body surface having an OPC photosensitive layer to the minimum limit and to remove residual toner without fail by inclining a cleaning blade to the non-cleaned side of the image holding body and while an abutting load in a vertical direction to the image holding body surface is less than 50g/cm, abutting the blade under the existence of a lubricant. CONSTITUTION:A cleaning blade 2 is a blade composed of the elastic body, fitted rotatably through a supporting member 3 to a fulcrum 4, and an abutting load Fa to the image holding body is given by a spring 5 to energize in the B direction of an arrow. In such a case, a load Fn in the vertical direction is kept less than 50g/cm to the image holding body surface, and especially, it is desirable to keep the load 30g/cm or below. As the lubricant used, for example, zinc stearate, etc., are listed up.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for cleaning an image carrier, and in particular, a method for cleaning and removing residual toner adhering to the surface of an image carrier used in electronic copying machines, electronic printers, etc. The present invention relates to a method for cleaning an image carrier.

[Background of the Invention] In devices for forming images using toner, such as electrophotography, the toner is usually deposited imagewise on the surface of an image carrier such as a photoconductive photosensitive drum, and then transferred to a transfer material such as paper. The image is transferred and fixed to obtain the desired image. Although the image carrier is used repeatedly, some toner remains on its surface even after the image is transferred, so it is necessary to remove this residual toner and clean the surface of the image carrier before forming the next image. .

A cleaning method for removing residual toner on the surface of an image carrier generally involves a method in which a thin elastic plate made of polyurethane or the like called a cleaning blade is brought into contact with the surface of the moving image carrier to scrape off the residual toner adhering to the surface of the image carrier. It is used.

[Problems to be Solved by the Invention] In the leaning method as described above, it is important to maintain an appropriate contact load of the cleaning blade against the image carrier. In general, toner removal can be promoted by increasing the contact load, but as the load increases, wear □ on the surface of the image carrier due to friction between the cleaning blade and the image carrier increases rapidly. A major problem arises in that the lifespan is significantly shortened. At the same time, the cleaning blade is severely worn (which results in poor cleaning).The shortening of the life of the image carrier is particularly noticeable in organic photoconductors (hereinafter referred to as OPC). Abrasion of the photoreceptor has been a major problem in positively charged organic photoreceptors.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cleaning device that does not cause shortening of life due to surface abrasion even in the case of an image carrier using OPC, and is highly effective in removing residual toner.

[Means for Solving Problems] As a result of various studies, the present inventors have found that the wear of the image carrier surface is mainly due to the load component of the cleaning blade contact load directed perpendicular to the image carrier surface and at the contact position. The inventors have discovered that this depends on the presence or absence of a lubricant, leading to the present invention.

That is, the object of the present invention is to provide a cleaning blade made of an elastic material on the surface of an image carrier having at least one organic photoconductor layer on a support, and to tilt the cleaning blade toward the uncleaned side of the image carrier; This was achieved by a method for cleaning an image carrier, which is characterized in that the surface of the image carrier is brought into contact in the presence of a lubricant with a vertical contact load of less than 50 g/cm.

The method of the present invention will be explained below.

FIG. 1 is a side view showing the vicinity of an image carrier of an electronic copying machine equipped with a cleaning device suitable for implementing the present invention.

1 is a drum-shaped image carrier having an OPG photosensitive layer on its surface, and rotates in the direction of arrow A. The entire surface of the image carrier 1 is charged by a charging electrode II, imagewise exposed by a light beam LB from a copying optical system (not shown), and then developed by a developing device 12. The toner image formed on the image carrier is transferred onto a transfer paper P fed from a paper feed roller 13. 14 is a transfer electrode that transfers the toner to the transfer paper side, and 15 is a separation electrode that separates the transfer paper P from the surface of the image carrier.

Even after the transfer process, residual toner adhering to the surface of the image carrier is scraped off and removed by the cleaning blade 2.

The cleaning blade is a blade made of an elastic body, is rotatably attached to a fulcrum 4 via a support member 3, and is applied with a contact load Pa against the image carrier by a spring 5 biased in the direction of arrow B. There is. The contact load of the cleaning blade 2 and its direction are represented by an arrow Fa in the figure, and the load Fa can be considered by breaking it down into a load Ft in the direction of the tangent T to the image carrier surface and a load Fn in the direction perpendicular to the image carrier surface. The relationship between Fa, Ft, and Fn is the angle θ (initial contact angle) between the tangent T and the cleaning blade 2, and the angle between the line connecting the contact point C of the cleaning blade 2 with the image carrier and the fulcrum 4. Ft = Fa −5in(θ −α)Fn expressed as follows in relation to α
= Fa 伽 cosCθ −α) Here, the initial contact angle is the angle formed by the direction line and the tangent to the image carrier surface at the contact point (uncleaned side) when installing the blade, ignoring the bending of the blade due to load. say.

The toner adhering to the image carrier surface is scraped off by the leading edge of the cleaning blade, but the force effective for this action is the aforementioned endogenous Ft component, and the Fn component has a large influence on the cleaning effect load. It has been found that this force acts as a force that causes wear on the surface of the image carrier and increases the driving torque of the image carrier, and it is desirable to keep this force small. However, in order to bring the cleaning blade into uniform contact with the image carrier, it is necessary to apply a certain amount of Fn.

In the present invention, by providing a lubricant on the contact surface between the cleaning blade and the image carrier and applying a sufficient Fn load, abrasion of the OPC photosensitive layer on the surface of the image carrier is prevented, and at the same time, stable leaning is possible. It is said that

Examples of the lubricant used in the present invention include fatty acid metal salts such as zinc stearate, magnesium stearate, copper stearate, and others disclosed in JP-A No. 48-413.
Examples include friction-reducing substances described in Publication No. 45.

These lubricants can be supplied to the contact portion of the cleaning blade by various methods, such as adding them to the developer or making them adhere to the surface of the image carrier with a brush.

Further, as the elastic body of the cleaning blade used in the present invention, rubbers such as polyurethane rubber, silicone rubber, and fluorine rubber are preferably used.

The hardness of these rubbers is rubber hardness (JIS) 60°~
85@ is preferable. The shape, thickness, etc. of the cleaning blade may be appropriately determined as necessary and are not particularly limited.

As shown in FIG. 1, the cleaning blade is attached so as to be inclined and contact the uncleaned side of the image carrier.

The contact load components Fn and Ft of the cleaning blade are determined by the blade attachment angle (θ, α) and the total load Fa. In the present invention, it is necessary to keep Fn below 50 g/cm, and it is particularly preferable to keep it below 30 g/cm. θ, α, and Fa may be set so as to obtain sufficient F'L to remove toner when Fn is less than 50 g/cs, and for this purpose, it is preferable to set θ to 60° or more.

[Example] An image carrier (diameter 100 mm, surface movement speed +
70 I@m/5ec) and a cleaning blade made of polyurethane rubber (rubber hardness (JIS) 70°, thickness 2III11) with a free length IJ = 2mm, and an electrophotographic image having a cleaning section as shown in Fig. 1. A copying machine was constructed, and a copying experiment was carried out by changing the angles θ and α and the contact load Fa. Under each condition, the Fa required to completely remove the residual toner was measured, and the results shown in FIG. 2 were obtained. A two-component developer containing 0.2% by weight of zinc stearate as a lubricant was used as the developer.

From the results shown in FIG. 2, Fn and Ft were determined and FIGS. 3 and 4 were obtained. The vertical axis of the figure indicates the values of Fn and Fa when residual toner can be removed under each condition, and the area above this curve is the toner removable area.

Fn when residual toner could be removed was almost constant in the region of angle θ>60°. I will not go into details, but there is a separate Fn.

As a result of conducting a cleaning experiment while changing the magnitude of Ft, it was confirmed that toner removal mainly depends on the value of Ft, and that Fn does not have a large effect.

Further, a large number of continuous copying tests were carried out using 84-size paper under various conditions to determine the relationship between the amount of wear of the photosensitive layer and the Fn value, and the relationship shown by curve I in FIG. 5 was obtained. The wear amount of the photosensitive layer in the figure is the steady wear amount per 10,000 copies of 84 size, excluding initial wear. The curve ■ was obtained in the same way,
Wear curves using a developer without lubricant, showing that in the presence of lubricant, the wear of the photosensitive layer is significantly reduced.

The less abrasion of the photosensitive layer, the better, but for practical purposes, 84 size 100
0.5 .mu.m per 00 copies is preferable, and the limit is 1 .mu.m, and any wear beyond that is considered to be below the practical limit in terms of the lifespan of the image bearing member. Therefore, from this data, Fn
It is confirmed that it is essential to make the amount less than 50 g/cI11.

Next, an example in which 0.05% to 0.4% of a lubricant is added to the developer will be described. Figures 6, 7, and 8 show the lubricant (
Zinc stearate) content 0.05%, 0.2%.

It is a graph showing the amount of photosensitive layer wear when using 0.4% developer. In either case, the cleaning blade contact conditions are θ-73°, α=IO, 5”, Fn=1
6g/cn+ closed. The horizontal axis of the figure is the number of copies in 84 format. Curve C in FIG. 6 is a wear curve when a developer without lubricant is used.

As is clear from each figure, in the method of the present invention where a lubricant is present! Almost no wear is observed except for the initial wear that occurs up to 0,000 copies. On the other hand, it can be seen that when no lubricant is present, wear progresses steadily.

Although this embodiment shows a preferable example of adding a lubricant to the developer, the present invention is not limited to this, and a coating member may be provided around the photoreceptor to apply the lubricant as the photoreceptor rotates. Good too.

[Effects of the Invention] The cleaning method of the present invention makes it possible to minimize the wear on the surface of the image carrier having the OPC photosensitive layer and to reliably remove residual toner.

[Brief explanation of drawings]

FIG. 1 is a side view showing an outline of a cleaning device suitable for carrying out the present invention, and FIG. 2 is a graph showing the relationship between the angle θ and the leaning blade contact load Pa necessary for removing residual toner.
Figures 3 and 4 are graphs showing the relationship between angle θ and Pn and PL when residual toner can be removed, Figure 5 is a graph showing Pn and wear of the photosensitive layer, Figures 6, 7, and FIG. 8 is a graph showing the thickness of the photosensitive layer when the amount of lubricant in the developer is varied.

Claims (1)

[Claims] A cleaning blade made of an elastic material is placed on the surface of the image carrier having at least one organic photoconductor layer on the support, inclined toward the uncleaned side of the image carrier and perpendicular to the surface of the image carrier. 1. A method for cleaning an image carrier, comprising contacting the image carrier in the presence of a lubricant with a contact load of less than 50 g/cm.