JPH03293682A - Electrically charging member - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a charging member used in electrophotography to charge an electrophotographic photoreceptor, such as by blow-on charging, transfer charging, and neutralization charging. It is.

[Conventional technology]

The charging process in the electrophotographic process using an electrophotographic photoreceptor has conventionally applied a high voltage (DC) to a metal wire.
5 to 8 KV) is applied, and charging is performed by the generated corona. However, with this method, when corona occurs, corona products such as ozone and NOx alter the surface of the photoreceptor, causing image blurring and deterioration, and dirt on the wires affects image quality, resulting in white spots and black lines in the image. There were other problems.

On the other hand, in terms of power, the current flowing to the photoreceptor is 5 to 30
%, and most of it flowed to the shield plate, making it inefficient as a charging means.

[Problem to be solved by the invention]

In order to compensate for these drawbacks, many direct charging methods have been researched and proposed (Japanese Unexamined Patent Publications No. 178267-1982, No. 104351-1983, No. 104351-1983, and No. 58-1983).
No. 40566, Japanese Patent Application Laid-Open No. 139156/1983,
(Japanese Unexamined Patent Publication No. 150975/1983). However, in reality, even if the photoreceptor is charged by the contact charging method as described above, the surface of the photoreceptor is not uniformly charged at each part, and uneven charging occurs. For example, in the reversal development method, even if a process below photoimage exposure is applied to a photoconductor with spotty charging unevenness, the output image will be a spotty black dot image corresponding to the spotty charging unevenness, and high-quality images will not be obtained. It has not been done.

Also in the contact charging method, discharge occurs during charging, and ozone, NOx, etc. are generated, although the amount is 1/10 to 1/100 less than in corona charging. Ozone, NO8, etc. alter the quality of the photoreceptor, causing image blurring and deterioration. Furthermore, ozone, NOx, and the like are adsorbed to the charging member and pressed against the photoreceptor, causing further deterioration.

Furthermore, since the charging member is in direct contact with the photoreceptor, the developing side adhering to the surface of the photoreceptor transfers to the charging member, causing uneven charging, image unevenness due to poor cleaning, and image stains. .

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a charging member that solves the above-mentioned drawbacks and prevents cleaning defects and image stains caused by toner adhesion to the surface of a photoreceptor.

[Means to solve the problem]

That is, the present invention provides a charging member used in a charging method of contacting an electrophotographic photoreceptor to charge the photoreceptor,
A charging member characterized in that the surface of the charging member contains particles of a fluororesin, and a charging member used in a charging method of contacting an electrophotographic photoreceptor to charge the photoreceptor. The charging member is characterized by having a layer containing particles of fluororesin on the surface of the charging member.

Specific examples of the fluororesin are shown below.

Among the above fluororesins, PTFB, PFA, P
VDF is preferably used.

The shape of the fluororesin particles is preferably spherical or nearly spherical, and the particle size is preferably about 0.03 to 10 μm.

Materials for the charging member include metals such as aluminum, iron, and copper, conductive polymer materials such as polyacetylene, polypyrrole, and polythiophene, rubbers such as isoprene rubber and chloroprene rubber that have been treated to be conductive by dispersing carbon, and polycarbonate. , polyethylene, polypropylene,
Resins such as polyvinyl chloride, polyethylene terephthalate, acrylic resin, etc. can be used. The volume resistivity of the surface of the charging member is 10° to 10'2 Ωcm, particularly 102 to 1010, from the viewpoint of good charging and prevention of dielectric breakdown.
A range of Ω·cm is preferable.

In addition, in order to reduce the voltage drop caused by excessive current flowing when the photoreceptor has a defect such as dielectric breakdown, the surface layer of the charging member is made of a material with a volume resistance of 106 to 1012 Ω, such as alkoxymethylated nylon. - It is also possible to have a multilayer structure with a resin layer of about cm.

The charging member used in the electrophotography of the present invention includes, for example, a structure in which a single layer containing the above-mentioned additive or a multilayer having a surface layer containing the above-mentioned additive is provided on a conductive substrate.

Further, examples of the shape of the charging member include a roller shape and a blade shape.

Examples of the conductive substrate include iron, copper, and stainless steel.

The charging member of the present invention can be applied to, for example, an electrophotographic apparatus as shown in FIG. In this device, a roller-shaped charging member 2, image exposure means 3, developing means 4, transfer charging means 6, separation charging means 7, cleaning means 8, and pre-exposure means 10 are arranged on the circumferential surface of an electrophotographic photoreceptor 1. has been done.

Charging member 2 placed in contact with electrophotographic photoreceptor 1
voltage (e.g. 200V or higher) from the external power supply 11.
A pulsating current voltage in which a DC voltage of 0 V or less and an AC voltage of 400°■ or less between peaks is superimposed is applied to charge the surface of the electrophotographic photoreceptor 1, and the image on the document is transferred to the photoreceptor by the image exposure means 3. image exposure to form an electrostatic latent image. Next, the electrostatic latent image on the photoreceptor is developed (visualized) by adhering the developer in the developing means 4 to the photoreceptor, and then the developer on the photoreceptor is transferred by the charging means 6. The image is transferred onto a material to be transferred such as paper that has passed through the paper feed roller and paper feed guide 5,
A cleaning means 8 collects the developer remaining on the photoreceptor without being transferred during transfer. On the other hand, the transferred member is separated by the separating and charging means 7, and is sent to a fixing device (not shown) by the paper conveying means 9 after transfer.

An image can be formed by such an electrophotographic process, but if residual charges remain on the photoreceptor, the photoreceptor is exposed to light by the pre-exposure means 10 to remove the residual charges before performing primary charging. It is better to eliminate static electricity.

The charging member of the present invention can exhibit its characteristics significantly when applied to an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductor, which easily deteriorates in terms of mechanical strength and chemical stability. can do.

In the present invention, the method for installing the charging member in contact with the photoreceptor is not limited to a specific method.
Any method of movement such as rotation in the same direction as the photoreceptor or in the opposite direction can be used. Furthermore, it is also possible to cause the charging member to function as a developer cleaning device on the photoreceptor.

Regarding the voltage applied to the charging member and the application method in the direct charging of the present invention, it depends on the specifications of each electrophotographic device, but in addition to the method of instantly applying the desired voltage, there are also methods for protecting the photoreceptor. A method can be adopted in which the applied voltage is increased stepwise, or in the case of applying a superimposed alternating current on direct current, a method can be adopted in which the voltage is applied in the order of direct current to alternating current or alternating current to direct current.

Note that when direct current is applied in the form of superimposed alternating current, the current increases, and products such as ozone and NO8 are generated in a larger amount than when direct current is applied, which tends to cause deterioration of the photoreceptor. It is valid.

Furthermore, in the present invention, processes such as image exposure, development, and cleaning can be performed using any method known in the field of electrostatic photography, and are not limited to a specific type of developer. .

The charging member of the present invention can be used not only in copying machines but also in electrophotographic applications such as laser printers, CRT printers, and electrophotographic plate making systems.

〔Example〕

The present invention will be explained below using examples.

Example 1 100 parts by weight of chloroprene rubber and 5 parts by weight of conductive carbon were melt-kneaded and molded through a stainless steel shaft of φ8 x 360 mm in the center to provide a base layer of a charging member.

The volume resistivity of this base layer was measured in an environment of temperature 22° C. and humidity 60% and found to be 3×10′Ω·C.

Next, the PTFH particles (particle size: about 0.3
0.1 parts by weight, 0.5 parts by weight, and 2 parts by weight of 0.1 parts by weight, 0.5 parts by weight, and 2 parts by weight, respectively, were dip-coated on the charging member base layer, and after drying, a surface layer with a film thickness of 200 μm was formed. We manufactured parts for this purpose. The charging rollers are 1, 2, and 3, respectively.

Further, as a comparative sample, a charging roller 4 to which PTFE was not added was manufactured. Using a Canon copying machine NP-3525 modified to the configuration shown in FIG. 1 using a charging roller, printing durability was carried out on 5000 sheets in an environment of 35 DEG C. and 190%, and image unevenness, poor cleaning, etc. were evaluated. The results are shown in Table 1.

The amounts added in the table are the ratios to the total weight of the surface layer to which PTFE is added, that is, the ethoxymethylated nylon layer here.

As is clear from Table 1, when a charging roller that does not contain fluororesin powder was used, image unevenness and poor cleaning were observed due to toner adhesion to the roller; When a charging roller provided on the surface was used, a clear image could be provided.

Example 2 In Example 1, PTFE was mixed with the PVDF particles (particle size of about 0.5 mm).
Three types of samples were prepared and tested in the same manner as in Example 1, except that PVDF was used (2 μm).
The charging roller that did not contain PVDF showed uneven images and poor cleaning, but the charging roller that had a layer containing PVDF on its surface was able to obtain clear images.

Example 3 Three types of samples were prepared and tested in the same manner as in Example 1 except that polyether urethane resin was used instead of ethoxymethylated nylon 6 in Example 1. At the same time, a durability test was conducted on a charging roller without a Teflon layer, and Table 2 shows the results.

Table Example 4 Under the same conditions as Example 1, Canon LBP was used in the test equipment.
-3X (laser beam printer) was used to test three different samples and similar results were obtained.

[Effects of the Invention] As described above, the charging member used in electrophotography of the present invention has almost no toner adhesion even after long-term use, and can always stably obtain clear images.

[Brief explanation of drawings]

FIG. 1 shows a schematic cross-sectional view of one example of an electrophotographic apparatus used in the present invention. 1: Electrophotographic photoreceptor, 2: Roller-shaped charging member, 3:
Image exposure means, 4: Developing means, 5: Transfer paper conveying means, 6:
Transfer charging means, 7: Separation charging means, 8: Cleaning means, 9: Transfer paper conveying means, 10: Pre-exposure means, 11: External power source.

Claims (4)

[Claims] (1) A charging member used in a charging method of charging an electrophotographic photoreceptor by contacting the same, characterized in that the surface of the charging member contains particles of a fluororesin. (2) The charging member according to claim 1, wherein the particles of the fluororesin are particles made of PTFE, PVDF, or PFA. (3) A charging member used in a charging method of charging an electrophotographic photoreceptor by contacting the same, characterized in that the charging member has a layer containing particles of fluororesin on the surface thereof. Parts for use. (4) The charging member according to claim 3, wherein the particles of the fluororesin are particles made of PTFE, PVDF, or PFA.