JPH0580636A - Electrifying roll - Google Patents

Abstract

PURPOSE:To prolong the life of the above-mentioned roll by providing a cylindrical sleeve made of a semiconductive synthetic resin and a conductive inside layer formed along the circumference on the inner peripheral surface of the cylindrical sleeve. CONSTITUTION:Semiconductive cylindrical sleeve forming materials are respectively compounded and this compd. is kneaded to obtain a mixture. This mixture is charged into an extruder and the semiconductive cylindrical sleeve 21 is produced by extrusion molding. Further, the sleeve is subjected to polishing if dimensional accuracy is required. Conductive inside layer 22 forming materials are then compounded and the inner peripheral surface of the cylindrical sleeve 21 is coated with the compd. thereof. The coating is dried and cured by heating, by which the electrifying roll 20 having a two-layered structure is produced. The molding materials prepd. by compounding high-polymer materials, such as thermoplastic resin and thermosetting resin and conductive powder, such as carbon black, are used in such a case. The conductive inside layer 22 is also obtd. by using a similar resin compsn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging roll used in an electrophotographic copying machine, a printer or the like which uses a belt-shaped photoreceptor.

[0002]

2. Description of the Related Art A full-color toner image formed on a photosensitive member is once transferred onto the outer peripheral surface of an intermediate transfer endless belt made of a thermoplastic resin endless belt, and then retransferred onto copy paper. A full-color electrophotographic copying machine using a belt-shaped photoconductor is constructed as shown in FIG. That is, the electrophotographic copying machine includes an optical device 2 for guiding the reflected light of the original 1 and red, green, and
A filter 3 that decomposes into the three primary colors of blue, a belt-shaped photoconductor 4 having photoconductivity, a developing device 5, and a toner image formed on the photoconductor 4 before copying onto the copy paper 6 An intermediate transfer endless belt 7 for temporarily transferring to the outer peripheral surface and a fixing device 8 are provided. More specifically, a charging charger (corotron) 9 is provided in the vicinity of the starting end side portion of the photoconductive belt-shaped photosensitive member 4, and three developing portions 5a, 5a are provided in the intermediate portion of the photosensitive member 4. 5b and 5c are provided. The belt-shaped photosensitive member 4 is charged by corona discharge from the charging charger 9, and then exposed by the reflected light of the original document projected from the optical device 2, and an electrostatic latent image is formed on the photosensitive member 4. In this case, a filter 3 for separating the reflected light of the original into the three primary colors of red, green, and blue is provided in the projection path of the optical device 2 for projecting the reflected light of the original onto the photoconductor 4 as described above. The primary color light is led to the belt-shaped photoconductor 4 in order, for example, red is first, and then green, to form respective electrostatic latent images. The developing device 5 is provided with three developing units 5a, 5b and 5c so as to correspond to the above-mentioned three types of primary colors, and respectively stores toners of three types of colors corresponding to the above-mentioned separated three primary colors. .. The electrostatic latent image formed by the color-separated light is color-developed with the corresponding toner of that color. That is, a colored toner image is formed for each color by the toners of the above-mentioned three kinds of colors, and this is the primary transfer roller 10
By the action of, the intermediate transfer endless belt 7 is sequentially transferred to the outer surface, and a full-color toner image is formed on the intermediate transfer endless belt 7. As described above, the copying machine does not transfer the colored toner image formed for each color to the copy paper 6 in order and form the colored toner image on the copy paper 6, but expand and contract with humidity or the like. A colored toner image is once formed on the endless intermediate transfer belt 7. Then, the toner image is retransferred onto the copy paper 6 supplied from the paper cassette 11 by the action of the secondary transfer roller 12. The re-transferred full-color toner image is sent to the fixing device 8 as the copy paper 6 is conveyed and fixed, and the copy paper 6 on which the toner image is fixed is sent out from the copying machine as shown by an arrow. In the figure, 13 is a conveyor belt, 14 is a cleaning device, and 15 is a cleaning blade.

As described above, the corotron system in which the photoconductor 4 is charged by corona discharge using the charging charger 9 generally uses a high voltage power source of 5 to 10 kV, and therefore it is necessary to take thorough safety measures. However, it has a drawback that harmful ozone is generated by corona discharge.
For this reason, recently, a method of charging the surface of the photoconductor 4 has been proposed and implemented in addition to using the charging charger 9. As such a method, there is a contact charging method in which a charging roll 20 as shown in FIG. 5 is brought into sliding contact with the surface of the photoconductor 4 to charge the surface of the photoconductor 4.

[0004]

However, the charging roll used in the above-mentioned contact charging system is only put into practical use as a photoreceptor having a rigid metal drum as a base material. As shown in FIG. 3, the charging roll is provided with a low hardness conductive elastic body 33 on the outer periphery of the cored bar 34 so that a constant contact width between the photoreceptor and the charging roll can be obtained. The low hardness conductive elastic body 3 in order to prevent discharge to
3 is provided with a semiconductive layer 32, and a protective layer 31 is provided on the outer periphery of the semiconductive layer 32 to prevent contamination of the photoconductor. In order to obtain the low hardness conductive elastic body 33, a rubber composition containing a large amount of liquid component is used. However, even if the semiconductive layer 32 and the protective layer 31 are provided on the outer periphery, the rubber composition is completely used. It is difficult to prevent bleeding of the liquid component in the low hardness conductive elastic body 33, and when left in an extreme environment such as high temperature and high humidity for a long period of time, the surface of the photoreceptor may be contaminated. is there. In addition, the semiconductive layer 32,
Since it is necessary to use a material that is as flexible as possible so as not to increase the hardness of the charging roll for the protective layer 31, there is a problem that wear due to sliding contact with the photoconductor is inevitably shortened and the life is shortened. .. When such a charging roll is used in an electrophotographic copying machine, a printer or the like using a belt-shaped photoconductor, the same problems as those of the photoconductor using the metal drum as a base material occur.

The present invention has been made in view of the above circumstances, and provides a charging roll which is used in the contact charging method among the charging methods for the surface of the belt-shaped photosensitive member, has no bleeding problem, and has a long life. To that end.

[0006]

In order to achieve the above object, the charging roll of the present invention is formed of a semi-conductive synthetic resin cylindrical sleeve and an inner peripheral surface of the cylindrical sleeve along the circumference. And a conductive inner layer that is formed.

[0007]

The present inventors have conducted a series of studies in order to obtain a charging roll which is used in a contact charging system for a belt-shaped photoreceptor and which does not cause bleeding. As a result, in the case of a belt-shaped photoconductor, when the charging roll 20 is arranged at the position shown in FIG. 5, the back surface of the belt-shaped photoconductor is free even if the hardness of the charging roll is high. And found that the contact width of the charging roll was obtained. That is, when a conductive layer which is an electrode layer is formed on the inner peripheral surface of a semi-conductive cylindrical sleeve made of a synthetic resin containing no liquid component, bleeding does not occur even if it is pressed against the photoconductor for a long period of time, and moreover The present inventors have found that the conductive cylindrical sleeve is made of synthetic resin and is not easily worn, and has reached the present invention.

Next, the present invention will be described in detail.

The charging roll of the present invention comprises a semi-conductive synthetic resin cylindrical sleeve and a conductive inner layer formed along the circumference on the inner peripheral surface of the cylindrical sleeve.

The above-mentioned synthetic resin cylindrical sleeve is hard, and is made of a polymer material such as thermoplastic resin or thermosetting resin.
It can be obtained by using a forming material in which a conductive powder such as carbon black, graphite, tin oxide-antimony oxide solid solution is mixed. Among the above polymer materials, a phenol resin is preferably used. Further, as long as it can be set within a predetermined electric resistance value region, an ion conductive system may be used in addition to the electronic conductive system prepared by blending the conductive powder. The blending ratio of the above forming material is the polymer material 10
0 parts by weight (hereinafter abbreviated as "part") of conductive powder
It is preferably set to 0 to 80 parts.

The conductive inner layer formed on the inner peripheral surface of the cylindrical sleeve is a resin composition in which a polymer material such as a thermoplastic resin or a thermosetting resin is mixed with a conductive powder such as carbon black. Is obtained by using. Among the above polymer materials, acrylic resin is preferably used because of its excellent coating properties and adhesion. The mixing ratio of each of the above-mentioned forming materials is such that the conductive powder is 3 to 10 relative to 100 parts of the polymer material.
It is preferably set to 0 part.

The charging roll of the present invention can be manufactured, for example, as follows. .. That is, first, the semiconductive cylindrical sleeve-forming materials are mixed, and the mixture is kneaded to obtain a mixture. This mixture is put into an extruder and extrusion-molded to produce a semiconductive cylindrical sleeve. Further, polishing is performed when dimensional accuracy is required. Next, a conductive inner layer forming material is compounded, and the compound is coated on the inner peripheral surface of the cylindrical sleeve, dried and cured by heating to produce a two-layer charge roller 20 as shown in FIG. can do. In the figure, 21 is a semi-conductive cylindrical sleeve and 22 is a conductive inner layer. The cylindrical sleeve 21 and the conductive inner layer 2
When the adhesiveness with 2 is low, a primer may be used between them to enhance the adhesiveness.

The charging roll 20 thus obtained
The semi-conductive cylindrical sleeve 21 has a thickness of 0.5 to 3.
The thickness of the conductive inner layer 22 is preferably set to 0 mm, and the thickness of the conductive inner layer 22 is preferably set to 2 to 100 μm. If the thickness of the semi-conductive cylindrical sleeve 21 is less than 0.5 mm, the rigidity in the axial direction of the sleeve is insufficient, and processing such as extrusion becomes difficult, and if it exceeds 3.0 mm, the inner diameter becomes small (this type of charging roll). The outer diameter is restricted to about 10 to 15 mm due to the space limitation, and it becomes difficult to coat the material for forming the conductive inner layer 22 and the weight of the roll itself increases.
Further, if the thickness of the conductive inner layer 22 is less than 2 μm, the reliability of the electrode layer may be deteriorated. On the contrary, if the thickness exceeds 100 μm, a large number of processing steps are required for coating by coating.

Further, in the charging roll 20 of the present invention, the electric resistance of the semiconductive cylindrical sleeve 21 is 10 ⁵ to 1 1.
It is preferably formed so as to have a resistance of 0 ⁸ Ω, and a value of 10 ⁶ to 10 ⁷ Ω is particularly preferable. (The electric resistance is measured by using a silver paste on the semi-conductive cylindrical sleeve 21 and a thickness of 10 mm.
Scratch an electrode of × 10 mm and measure the electric resistance between the silver paste electrode and the conductive inner layer 22). It is preferable that the cylindrical sleeve 21 is made of a material having a Young's modulus of 50,000 kg / cm ² or more, since it does not bend when it comes into pressure contact with the belt-shaped photoreceptor. Further, the electric resistance value of the conductive inner layer 22 is set to a value lower than the electric resistance value of the semiconductive cylindrical sleeve 21, and it is particularly preferable to form it so as to be 10 ⁴ Ω or less. In this way, the belt-shaped photoreceptor can be sufficiently charged by setting the electric resistance of each layer to the above value.

When the charging roll of the present invention is used as a charging roll for charging the surface (see FIG. 5) of the belt-shaped photoreceptor 4 of a full-color electrophotographic copying machine, for example, as shown in FIG. A bearing (cap) 23 is inserted into the opening portions at both ends of the device and used. in this case,
The entire circumference or a part of the cap 23 is a conductive inner layer 2
It is inserted so that it contacts 2. If necessary, the cap 23 and the charging roll 20 may be bonded and fixed with an adhesive agent. The cap 23 may be made of metal or synthetic resin, and it is preferable to use one having an electric resistance value of 10 ⁴ Ω or less.

[0016]

As described above, the charging roll of the present invention has the conductive inner layer formed on the inner peripheral surface of the semiconductive cylindrical sleeve. For this reason, for example, when the charging roll of the present invention is incorporated in a full-color electrophotographic copying machine and is charged by sliding on the surface of the belt-shaped photoreceptor, the charging roll does not contain a liquid component, so that bleeding from the charging roll is caused. Can be prevented, and contamination of the surface of the photoconductor can be prevented. Further, the charging roll of the present invention has a simple structure and can realize cost reduction. Furthermore, since the semi-conductive cylindrical sleeve on the surface of the charging roll is made of a rigid and rigid polymer compound, wear is reduced and a long life is realized. Moreover, because of the cylindrical sleeve, the weight can be reduced. Therefore, by using the charging roll of the present invention in place of the conventional corotron system, it is possible to effectively charge the surface of the photoconductor, so that the generation of ozone and the use of a high-voltage power supply, the use of an ozone filter, etc. are avoided. can do.

Next, examples will be described together with comparative examples.

[0018]

Examples 1 and 2 A two-layer charging roller 20 (outer diameter 15 mm) as shown in FIG. 1 was produced as follows.
That is, as the material for forming the cylindrical sleeve 21, the materials shown in Table 1 below were blended, kneaded with an intermix and two rolls, and then pulverized. This material was supplied to an extruder and extruded to form a cylindrical sleeve 21. Next, as a material for forming the conductive inner layer 22, an acrylic resin was dissolved in toluene, carbon black was mixed at a blending ratio shown in Table 1 below, and the mixture was dispersed by a sand mill. The inner peripheral surface of 21 was coated by a known method. Next, this is 50
A charging roll was produced by drying at ℃ × 1 hour.
With respect to the obtained charging roll, the thickness of each layer, the electric resistance value, and the Young's modulus of the cylindrical sleeve material were measured and are also shown in Table 1 below. Regarding the electric resistance of the conductive inner layer, the conductive inner layer forming material was coated on the metal plate by dipping and dried at 50 ° C. for 1 hour, and then a 10 mm × 10 mm electrode was scratched on the surface with silver paste to remove the metal plate. The resistance between the silver paste electrode and the silver paste electrode was measured.

[0019]

[Table 1]

* 1: Hexamethylenetetramine. * 2: Calcium hydroxide (slaked lime). * 3: Zinc stearate.

[0021]

Comparative Example As a comparative example, a charging roll having a three-layer structure as shown in FIG. 3 was produced. That is, ethylene-propylene rubber as a low-hardness conductive elastic body is blended with carbon black, procell oil, a vulcanizing agent, and a vulcanization aid, and after kneading and vulcanization, the hardness is 20 ° (JIS A) and the electrical resistance is 10
A rubber mixture of ³ Ω · cm was obtained. This rubber mixture is poured into a predetermined mold and vulcanized to obtain a core metal diameter of 6 mm,
A low hardness conductive roll having an outer diameter of 15 mm was obtained. Next, as a material for forming the semiconductive layer, a solution of a tin oxide-antimony oxide solid solution powder in a toluene-methylethylketone (MEK) solution of urethane resin was added to 80 parts of 100 parts of the urethane resin and dispersed by a sand mill. The viscosity of this mixture was adjusted, and then it was dipped on the low-hardness conductive elastic body to obtain a 120 μm semiconductive layer. Furthermore, 10 μm made of N-methoxymethylated nylon on the outer circumference.
m protective layer was provided by dipping. The electric resistance value of this charging roll was 7.0 × 10 ⁶ Ω. The above electrical resistance value is 10mm x 10mm with silver paste on the surface of the protective layer.
The electrode was scratched and the electric resistance value between the core metal and the silver paste electrode was measured.

As shown in FIG. 2, a cap 23 is provided at the opening of both ends of the charging roll of the embodiment product thus obtained.
Those fitted (hereinafter electrical resistance 10 ⁰ Ω · cm) was used incorporated in an electrophotographic copying machine. Then, the example product and the comparative example product were incorporated into a full-color electrophotographic copying machine equipped with a belt-shaped photoconductor, and a voltage was applied from an external power source to charge the photoconductor. As a result of continuous operation, surface wear was observed in the comparative example product at the time of 10,000 sheets, but no surface wear was observed in the example product. Also, regarding the contamination state of the photoconductor, the charging roll and the photoconductor are brought into contact with each other at 45 ° C. × 90% RH
After being left for 1 month under the conditions of 1 above, the stain on the surface of the photoreceptor was observed. As a result, in the comparative example product, the roll contact portion was found to be contaminated, whereas the example product was not contaminated at all.

In addition, the contact charging system using the above-mentioned products does not generate ozone unlike the conventional corotron system, and does not require the use of a high voltage power source, and is safe and environmentally friendly. It turns out to be excellent.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a charging roll of the present invention.

FIG. 2 is a longitudinal sectional view showing a state where caps are fitted on both ends of the charging roll of the present invention.

FIG. 3 is a vertical cross-sectional view of a conventional charging roll.

FIG. 4 is a configuration diagram of a corotron type electrophotographic copying machine in which an intermediate transfer endless belt is incorporated.

FIG. 5 is a configuration diagram of a contact charging type electrophotographic copying machine incorporating an intermediate transfer endless belt.

[Explanation of symbols]

 20 Charging Roll 21 Semi-Conductive Cylindrical Sleeve 22 Conductive Inner Layer

Claims (1)

[Claims] 1. A cylindrical sleeve made of semi-conductive synthetic resin,
A charging roll comprising an inner peripheral surface of the cylindrical sleeve and a conductive inner layer formed along the circumference.