JP2634461B2 - Method and apparatus for roughening the surface of charging roller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for roughening a charging roller used in an electrophotographic apparatus and a roughening apparatus used for the same.

<Prior Art> Until now, inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide have been known as photoconductive materials used in electrophotographic photoreceptors. These photoconductive materials have many advantages, such as being able to be charged to an appropriate potential in a dark place, having little charge dissipation in a dark place, and being able to quickly dissipate charges by light irradiation. It has various disadvantages. For example, in a selenium-based photoconductor, crystallization easily proceeds due to factors such as temperature, humidity, dust, and pressure, and particularly when the ambient temperature exceeds 40 ° C., crystallization becomes remarkable. There is a drawback such as occurrence of

Cadmium sulfide photoconductors do not provide stable sensitivity in humid environments and zinc oxide photoconductors require a sensitizing effect of a sensitizing dye represented by rose bengal. The photosensitive dye has a drawback that a stable image cannot be provided over a long period of time because charge deterioration due to charging and light fading due to exposure occur.

On the other hand, it has been discovered that certain organic compounds exhibit photoconductivity. For example, poly-N-vinyl carbazole,
Organic photoconductive polymers such as polyvinyl anthracene,
Low molecular organic photoconductors such as carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones, and polyarylalkanes, as well as phthalocyanine pigments
Organic pigments and dyes such as azo pigments, cyanine dyes, polycyclic quinone pigments, perylene pigments, indigo dyes, thioindigo dyes, and squaric acid methine dyes are known. In particular, organic pigments and dyes having photoconductivity are easier to synthesize than inorganic materials, and there have been many proposals because the variety of compounds that exhibit photoconductivity in an appropriate wavelength range has been expanded. . For example, U.S. Pat.Nos. 4,123,270, 4,216,613, 4,251,614 and 4,425
No. 6821, No. 4260672, No. 4268596, No. 4278747
No. 4,293,628, etc., an electrophotographic photosensitive member using a photoconductive disazo pigment as a charge generating material in a photosensitive layer functionally separated into a charge generating layer and a charge transport layer is known. Have been.

In a charging process in an electrophotographic process using such an electrophotographic photosensitive member, charging is performed by a corona generated by applying a high voltage (5 to 8 kV DC) to a metal wire in most cases. However, in this method, when corona is generated, the surface of the photoreceptor is deteriorated by corona products such as ozone and NOx, causing image blurring and deterioration, and dirt on the wire affects image quality, resulting in image white spots and black stripes. There was a problem. On the other hand, the electric current flowing toward the photoreceptor was only 5 to 30% of the electric power, and most of the electric current flowed to the shield plate and was inefficient as a charging means.

In order to compensate for these disadvantages, methods of directly charging have been studied and many proposals have been made. (Japanese Unexamined Patent Publication No. 57-17826
7, 56-104351, 58-40566, 58-139156, 58-150975
Etc.) The shape of the member for direct charging is a roller,
There are brushes (including magnetic brushes), blades, belts, and other shapes, which can be selected according to the specifications and form of the electrophotographic apparatus.

However, in the roller charging method, unlike the corona charging, there is a problem that the charging member is in direct contact with the photoconductor drum, so that the photoconductor drum and the charging roller are easily adhered to each other, and that the charging is likely to be uneven.

In the direct charging method using a charging roller, discharge occurs when the distance between the photosensitive drum and the charging roller becomes constant, and a voltage is applied to the drum. Therefore, since the surface of the charging roller is flat, the charging often becomes non-uniform due to the irregularities and scratches on the drum surface.

Further, when the surface of the charging roller was flat, the toner adhered to the charging roller during repeated image output, and the image was liable to be stained.

<Problem to be Solved by the Invention> A first object of the present invention is to provide an electrophotographic apparatus using a charging roller, in which an image is stained on a white background portion due to non-uniform charging or toner adheres to the charging roller. An object of the present invention is to provide a charging roller of an electrophotographic apparatus capable of stably supplying a high-quality copy image with almost no image soiling or the like.

It has already been proposed that the above-mentioned object is achieved by providing the surface of the charging roller with irregularities whose ten-point average surface roughness is not less than 0.3 μm and not more than 5.0 μm, but the surface is roughened. Is still difficult to control, which has caused uneven charging.

Therefore, a second object of the present invention is to uniformly perform the surface roughening of the charging roller, and an object of the present invention is to provide an apparatus having a mechanism installed so that both edge portions of the belt-shaped abrasive are not brought into contact with the charging roller. It can be achieved by roughening the surface.

<Means for Solving the Problems> The present invention relates to a method for roughening the surface of a charging roller using a belt-shaped abrasive having a width shorter than the axial length of the charging roller to roughen the surface of the charging roller. While keeping both edges of the belt-shaped abrasive material from contacting the charging roller surface, the surface roughness of the charging roller is 0.3
This is a method for roughening the surface of the charging roller, characterized in that the surface is roughened to a thickness of about 5.0 μm.

Further, the present invention provides a band-shaped abrasive having a width shorter than the length of the charging roller in the axial direction, and a holding member for bringing the band-shaped abrasive into contact with the charging roller by pressing the band-shaped abrasive against the charging roller from the opposite side of the charging roller. An apparatus for roughening the surface of a charging roller having a roller, comprising: a suspending member that lifts both edge portions of the belt-shaped abrasive from the charging roller side to keep the portion out of contact with the charging roller; The roughness is 0.
A charging roller surface roughening apparatus characterized in that the surface of the charging roller is roughened to 3 to 5.0 μm.

 Hereinafter, the present invention will be described in more detail.

Examples of the material of the charging roller used in the present invention include metals such as aluminum, iron, and copper, and conductive polymers such as polyacetylene, polypyrrole, and polythiophene, and carbon,
Rubber or artificial fiber obtained by dispersing a metal or the like, or an insulating material such as polycarbonate, polyvinyl acetate, or polyester coated on the surface with a metal or another conductive material can be used. The volume resistivity of these conductive member 10 ⁰ ~10 ¹² Ω · cm, optimally from ^{10 2} ~10 10 Ω · cm.

When an image is formed using the charging roller and the photosensitive drum in a state where the surface of the charging roller is not roughened, the charging roller and the photosensitive drum are likely to stick together, and the probability that toner adheres to the charging roller is high. In addition, since the surface of the charging roller is flat, defects (unevenness and scratches) on the photosensitive drum are easily picked up at the time of discharging, and uneven charging is likely to occur.

For the above reasons, it is preferable to previously roughen the surface of the charging roller.

As a method of this roughening, mechanical polishing is excellent,
Among them, a method using a band-shaped abrasive is more preferable. The reason is presumed that in the case of the sand blast method or the like, the abrasive is easily embedded in the charging roller and causes uneven charging, whereas in the case of the belt-shaped abrasive, it is presumed that there is almost no embedding. You.

However, it is still difficult to uniformly roughen the charging roller by the conventional polishing method, thereby causing a phenomenon that uniform charging is not performed during charging.

The present inventors have conducted intensive studies on the roughening of the surface of the charging roller, and as a result, in a method of roughening the surface of the charging roller using a belt-shaped abrasive, preferably both edge portions of the belt-shaped abrasive are each By installing so that it does not come into contact with the charging roller over 0.3 mm width, especially over 0.8 mm width,
The maximum, average, and minimum values determined by the ten-point average roughness (R _Z ) measurement method defined in JIS standard B0601 (in the present specification, these are referred to as the maximum surface roughness, the average surface roughness, respectively). And the minimum surface roughness) are all within the range of 0.3 to 5.0 μm, and it has been found that uneven charging can be prevented.

In other words, the present invention provides a method for roughening the surface of an elementary charging roller using a band-shaped abrasive, in which both edges of the band-shaped abrasive are placed so as not to contact the charging roller to roughen the surface. Features.

This is because, in the method of roughening the surface of the charging roller using a belt-shaped abrasive, it is difficult to apply a uniform pressing force to both edge portions of the abrasive, which causes unevenness in the surface state of the charging roller surface. Therefore, both edge portions of the abrasive are separated from the charging roller, and the other portions are roughened, thereby enabling uniform roughening.

In carrying out the surface roughening method of the present invention, a roughening apparatus schematically shown in a sectional view in FIG. 2 can be used as an example. The charging roller 11 is rotated clockwise or counterclockwise. On the other hand, the belt-shaped abrasive 12
Then, it is moved in the direction of the arrow 16 toward the winding roller 15 via the rubber pressing roller 14 pressed against the charging roller 11. At this time, the belt-shaped abrasive 12 rubs the surface of the charging roller 11 at the pressing position of the pressing roller 14. Further, the device of the present invention can be schematically illustrated in FIG. 3 by way of example. That is, in the rubbing portion of the charging roller 17, both edges of the belt-shaped abrasive 18 are
Only the portion which is separated from the pressing member 17 and pressed by the pressing roller 20 is roughened.

Examples of the belt-shaped abrasive used in the practice of the present invention include those in which fine particles such as aluminum oxide, silicon carbide, chromium oxide, and diamond are coated and fixed on a film of polyester or the like.

The surface-roughened charging roller obtained by the method of the present invention can be used not only in copying machines but also in electrophotographic application fields such as laser printers, LED printers, CRT printers, and electrophotographic plate making systems.

 Hereinafter, the present invention will be described in detail with reference to specific examples.

Example 1 A copying machine (NP-3525 manufactured by Canon) was modified as shown in FIG. 1 is a photoreceptor incorporated in the copying machine, 2 is a charging roller for performing direct charging, 3 is an image exposure, 4 is a developing device, 5 is a paper feeding roller and paper feeding guide for transfer paper, 6 is a transfer charging device, Reference numeral 7 denotes a separation charger, 8 denotes a transport unit for sending transfer paper to a fixing device (not shown), 9 denotes a cleaner, 10 denotes a pre-exposure light source,
Reference numeral 0 denotes a power supply device that applies a voltage to the charging member 2.

 The charging roller No. 2 was manufactured by the following method.

Chloroprene rubber (trade name: Denka chloroprene M-
30 parts, manufactured by Denki Kagaku Kogyo Co., Ltd.) 100 parts by weight of conductive carbon and 5 parts by weight of conductive carbon (trade name: Conductex 900, manufactured by Columbian Chemical Co., Ltd.) are melt-kneaded and molded through a stainless steel shaft at the center to form a charging roller. .

The average surface roughness (R _Z ) of the surface of the charging roller according to the ten-point method was 0.2 μm, and the minimum and maximum surface roughness were 0.0 μm and 0.3 μm, respectively.

This charging roller 11 is formed by using the apparatus shown in FIG.
While holding the belt-shaped abrasive so as not to contact the charging roller by 1.0 mm width at both edges, the pressing roller 14 contacted the charging roller to roughen the surface. The surface average surface roughness (R _Z ) of the charging roller after the surface roughening was 1.0 μm, and the minimum and maximum surface roughness were 0.8 μm and 1.2 μm, respectively. When the surface-roughened charging roller 11 was installed in the above-mentioned modified copying machine to perform paper passing durability, no problem occurred up to 5,000 sheets. The results are shown in Table 1 as Example 1.

The charging exposure conditions were such that a DC voltage of -750 V and an AC peak-to-peak voltage of 1500 V were superimposed on the charging roller, and the image exposure was 3.0 lux-seconds and the pre-exposure amount was 10.0 lux-seconds.

<Comparative Example 1> An elementary charging roller similar to that of Example 1 was prepared and subjected to paper-passing durability under the same copying apparatus and conditions as in Example 1 without roughening. The horizontal streaks caused by the adhesion between the photoconductor 1 and the photoconductor 1 began to appear on the image. The results are shown in Table 1 as Comparative Example 1.

<Comparative Example 2> In Example 1, the charging roller 11 was brought into contact with the charging roller 11 so as to be spaced apart from the charging roller 11 by a width of 1.0 mm on one side of the belt-shaped abrasive 12 to roughen the surface. The average surface roughness (R _Z ) of the roughened charging roller was 1.4 μm, and the minimum and maximum surface roughness were 0.2 μm and 5.5 μm, respectively. An experiment was conducted by incorporating this roughened charging roller in the same apparatus as in Example 1. As a result, image unevenness due to charging unevenness and white background stains occurred from the initial stage of paper passing durability.
When about 50 sheets had passed, horizontal streaks due to the adhesion between the charging roller and the photosensitive member began to appear on the image. The results are shown in Table 1 as Comparative Example 2.

<Comparative Example 3> In Example 1, the entire surface of the belt-shaped abrasive 12 was brought into contact with the charging roller 11 to roughen the surface. This roughened charging roller 11
Had a surface average surface roughness (R _Z ) of 1.5 μm, and the minimum and maximum surface roughness were 0.2 μm and 7.0 μm, respectively. An experiment was conducted by incorporating this roughened charging roller in the same apparatus as in Example 1. As a result, image unevenness due to charging unevenness and stain on a white background occurred from the initial stage of paper passing durability.
When the sheet was durable, horizontal streaks due to the adhesion between the charging roller and the photosensitive drum began to appear on the image. The results are shown in Table 1 as Comparative Example 3.

As described above, as shown in Example 1 and Comparative Examples 1 to 3, the surface of the belt-shaped abrasive 12 was set using the apparatus shown in FIGS. By performing the processing, it is possible to obtain a good image with almost no image unevenness, background contamination, and horizontal stripes due to sticking to the photoreceptor.

The surface-roughened charging roller according to the present invention can be used not only for primary charging but also for charging members such as transfer charging and separation charging.

<Effect of the Invention> When the roughened charging roller obtained by the present invention is used, sticking and uneven charging of the charging roller and the photosensitive drum, and ground contamination due to toner adhesion to the charging roller hardly occur, and stable repetition is achieved. Images were obtained.

[Brief description of the drawings]

FIG. 1 is a structural view of a copying machine incorporating a charging roller roughened by the method of the present invention, FIG. 2 is a structural view of an apparatus for implementing the method of the present invention, and FIG. 3 is an apparatus for implementing the method of the present invention. It is a schematic diagram which shows the contact state of a belt-shaped abrasive. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... Charge roller, 3 ... Image exposure, 4 ... Developer, 5 ... Transfer paper feed roller and feed guide, 6 ... Transfer charger, 7 ... Separation Charger, 8 ...
... Conveying section for sending transfer paper to a fixing device (not shown), 9 ... Cleaner, 10 ... Pre-exposure light source, 11 ... Charging roller, 12 ...
... Strip-shaped abrasive, 13 ... Sending roller, 14 ... Retaining roller, 15 ... Rewind roller, 17 ... Charging roller, 18 ... Strip-shaped abrasive, 19 ... …… Presser roller, 100 …… Power supply

Claims (2)

(57) [Claims] 1. A method for roughening the surface of a charging roller using a belt-shaped abrasive having a width shorter than the axial length of the charging roller, wherein both edge portions of the belt-shaped abrasive are provided. While keeping the surface of the charging roller from contacting the surface of the charging roller.
A method for roughening the surface of a charging roller, wherein the surface is roughened to have a thickness of 5.0 μm. 2. A band-shaped abrasive having a width shorter than the axial length of the charging roller, and a pressing roller for pressing the band-shaped abrasive against the charging roller by pressing the band-shaped abrasive against the charging roller from the opposite side of the charging roller. A surface-roughening device for the surface of the charging roller having a suspension member that lifts both edge portions of the belt-shaped abrasive from the charging roller side to keep the portion out of contact with the charging roller; 0.3
An apparatus for roughening the surface of a charging roller, wherein the surface of the charging roller is roughened so as to have a thickness of about 5.0 μm.