JP3115198B2 - Charging member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member used in an electrophotographic image forming apparatus such as a laser beam printer and a copying machine.

[0002]

2. Description of the Related Art Conventionally, copiers, laser beam printers,
Various charging members used in an electrophotographic image forming apparatus such as a facsimile, for example, a developing charging roller,
The transfer charging roller, the primary charging roller, and the like are mostly discarded without being reused. Attempts have been made to reuse only a small number of metal rollers. For example, a method is known in which a roller is immersed in a cleaning solvent to remove dirt on the outer peripheral surface of the roller with a cleaning member such as a brush.

[0003]

Recently, ecology (the idea of coexisting gently with the global environment without abusing or polluting the global environment) has been spreading worldwide. However, most of the various charging rollers provided in the electrophotographic apparatus are discarded without being reused. Therefore, there were some problems in terms of saving global resources and protecting the environment.

[0004] Most of the various charging rollers provided in the electrophotographic apparatus are made of synthetic resin, synthetic rubber, or the like. For the reasons described in (1) and (2) above, the roller cannot be used as it is as a method for cleaning a roller made of synthetic resin or synthetic rubber.

(A) Synthetic resin or synthetic rubber is dissolved by a cleaning solvent or cracks are generated, and the electric resistance, hardness, surface roughness, roundness, straightness, slipperiness (friction coefficient), etc. Various functions required for such a roller may be impaired.

(B) As this type of roller, not only a single-layer roller using a single material but also a multi-layer roller in which two or more materials are laminated is often used. In the case of a multi-layer roller, the cleaning solvent may permeate from the end of the roller, so it is necessary to pay attention not only to the solvent resistance of the material of the surface layer but also to the solvent of the inner material. For this reason, the type of cleaning solvent to be used is limited, and the adhesive strength between the layers may be reduced.

In addition, there has been a problem that the electrical characteristics of various charging rollers deteriorate during use, and they do not exhibit sufficient electrical characteristics for reuse. The decrease in the electrical characteristics of the various charging rollers may be caused by deterioration of the surface of the charging roller due to the influence of ozone or the like generated by electric discharge, or wear due to contact with the member to be charged.

Further, when the various charging rollers having the deteriorated electric characteristics as described above are reused without any means such as cleaning, there is a problem that uneven charging due to surface contamination occurs. This problem occurs in a low-temperature, low-humidity environment.

For this purpose, there is an idea of replacing the surface layer with a new one.
Separation is difficult or troublesome. In addition, there is a problem in that if the layer is forcibly peeled off, the lower layer may be damaged or the electrical characteristics may be deteriorated.

An object of the present invention is to provide a charging member which does not cause the above-mentioned problems and can easily peel off a surface layer.

[0011]

According to the present invention, the above-mentioned charging member has a multilayer structure, the surface layer is made of a semiconductive tube, and one or both ends of the semiconductive tube are longer than the lower layer, In addition, the charging member is characterized in that one or two or more cutouts are provided at the elongated end of the semiconductive tube.

[0012] Further, the charging member is characterized in that the cutout portion of the semiconductive tube is provided at least 1 mm outside the lower layer.

[0013] Further, the charging member is characterized in that the length of the notch portion of the semiconductive tube is 2 mm or more.

[0014] Further, the charging member is a roller-shaped charging member.

As the voltage applied to the charging member, any of a DC voltage, a superimposed voltage of a DC voltage and an oscillating voltage (for example, an AC voltage) and the like can be used.

The present invention has an effective shape in reusing a charging roller used in an electrophotographic apparatus.
In a charging roller used in an electrophotographic apparatus, toner or the like adheres to the surface during use, or the surface is deteriorated or worn. Then, there is a problem that uneven charging occurs due to such a cause on the surface. In some cases, dirt on the surface can be removed by washing, but deterioration or wear of the surface cannot be removed by washing. The present invention provides the charging roller having the above-described problem, by providing a cutout portion in the semiconductive tube of the surface layer of the charging roller,
A trigger for peeling off the semiconductive tube at the time of reproduction is obtained, which facilitates peeling. Further, by similarly covering the peeled charging roller with a semiconductive tube and forming a surface layer again, the electrical properties of the charging member can be recovered, and the charging roller can be reused as a charging roller.

Next, the schematic structure of the charging member of the present invention will be described.

FIG. 1 or FIG.
(A) As shown in (B), a conductive core layer 2a is formed in a roller shape, and a conductive elastic layer 2 formed integrally with the outer periphery thereof.
b, if necessary, a resistance control layer 2d, a protective layer 2c formed on the outer periphery of the conductive elastic layer, and a tube layer 2f formed on the outer periphery.

FIG. 1 is a schematic diagram showing an example of an electrophotographic apparatus (laser beam printer) using a contact charging device using a charging member according to the present invention as a primary charging means of an image carrier.

Reference numeral 1 denotes a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) as a member to be charged, and is driven to rotate at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow. 1a is a conductive drum base made of aluminum or the like of the photosensitive drum 1, and 1b is a photosensitive layer formed on the outer peripheral surface of the drum base 1a.

Reference numeral 2 denotes a contact charging member. In this embodiment, a roller body (hereinafter, referred to as a charging roller) arranged in pressure contact with a predetermined pressing force in parallel with the drum generatrix direction of the photosensitive drum 1 surface.
Then, the photosensitive drum 1 is driven to rotate.

The charging roller 2 of this embodiment is a core metal (2a) for applying a DC voltage or a superimposed voltage of a DC voltage and an AC voltage.
Then, a conductive elastic layer (2b) for providing elasticity and conductivity is formed. Further, if necessary, a resistance control layer (2d) for controlling the resistance of the charging member is provided thereon, and a protective layer (2c) is further provided outside the conductive elastic layer or when a resistance control layer is provided. You may. The outer surface is covered with a tube layer (2f). The aforementioned charging roller 2
The conductive elastic layer 2b, resistance control layer 2d, protective layer 2c, and tube layer 2f will be described later.

Reference numeral 3 denotes a power supply for applying a voltage to the charging roller 2, and a conductive core (shaft) of the charging roller 2 is supplied from the power supply.
By applying a predetermined voltage to 2a, the surface of the rotating photosensitive drum 1 is charged to a predetermined potential by a contact charging method.

The voltage applied to the charging roller 2 may be a DC voltage only or a DC voltage with an oscillating electric field such as an AC voltage superimposed thereon. In terms of uniform charging, it is more advantageous to superimpose an oscillating electric field.

Exposure means 4 (not shown), which forms an electrostatic latent image by exposing according to image information of a document, is provided around the photosensitive drum 1 which has been uniformly primary-charged to a predetermined potential by the charging roller 2. Developing device 5 for forming toner image by attaching toner to electro-latent image, transfer material P supplied from paper feed cassette 6
And a cleaning device 9 for removing residual toner on the photosensitive drum 1 after transfer, not shown for removing charges on the photosensitive drum 1 in preparation for the next primary charging. Are provided. Further, a fixing device 8 for fixing the toner image transferred onto the transfer material P to the transfer material P is disposed downstream of the transfer charger 7.

The conductive metal core 2a used in the present invention comprises:
A round bar of a metal material such as iron, copper, stainless steel, aluminum, and nickel can be used. Further, these metal surfaces may be subjected to plating treatment for the purpose of rust prevention and imparting scratch resistance, but it is necessary that the conductivity is not impaired.

In the charging roller 2, the conductive elastic layer 2b
Are provided with appropriate conductivity and elasticity in order to supply power to the photosensitive drum 1 as an object to be charged and to ensure good uniform adhesion of the charging roller 2 to the photosensitive drum 1. In order to ensure uniform adhesion between the charging roller 2 and the photosensitive drum 1, the conductive elastic layer 2b may be polished so as to have a shape in which the central portion is thickest and becomes thinner toward both ends, that is, a so-called crown shape. Many. Since the generally used charging roller 2 is brought into contact with the photosensitive drum 1 by applying a predetermined pressing force to both ends of the cored bar 2a, the pressing force at the center is small, and the pressing force at the both ends is larger. Therefore, there is no problem if the straightness of the charging roller 2 is sufficient, but if it is not sufficient, density unevenness may occur in the images corresponding to the central portion and both ends. The crown shape is formed to prevent this.

The conductivity of the conductive elastic layer 2b is adjusted by adding a conductive agent such as carbon black to an elastic material such as rubber. The elasticity is adjusted by adding a process oil, a plasticizer or the like. Specific elastic materials of the conductive elastic layer 2b include, for example, natural rubber, synthetic rubber such as EPDM, SBR, silicon rubber, urethane rubber, IR, BR, NBR, CR, and polyamide resin, polyurethane resin, and silicon resin. And the like. Further, a foam of the above-described elastic material may be used for the conductive elastic layer 2b.

The resistance control layer 2d is often provided to control the resistance of the charging member. Specific materials of the resistance control layer 2d include resins such as polyamide resin, polyurethane resin, fluororesin, and silicone resin, as well as epichlorohydrin, urethane rubber, chloroprene, acrylonitrile rubber, and the like. A conductive agent such as carbon black, tin oxide, or titanium oxide is often dispersed also in the resistance control layer 2d.

The protective layer 2c is often provided to prevent bleed-out of the plasticizer or the like in the conductive elastic layer 2b to the surface of the charging roller. Specific materials for the protective layer include:
Resins such as polyamide resin, polyurethane resin, fluororesin, and silicone resin, as well as epichlorohydrin, urethane rubber, chloroprene, acrylonitrile rubber, and the like. A conductive agent such as carbon black, tin oxide, or titanium oxide is often dispersed in order to provide the protective layer with appropriate conductivity. Moreover, it is good also as tube shape.

The tube layer 2f is made of conductive particles such as carbon black and carbon graphite, conductive metal oxides such as conductive titanium oxide, conductive zinc oxide and conductive tin oxide, or alkali metal salts and ammonium salts. Can be used.

As the synthetic resin used for the tube layer 2f, nylon 12, PFA (ethylene tetrafluoride-perfluoroalkyl vinyl ether copolymer resin), PVD
F (polyvinylidene fluoride), FEP (tetrafluoroethylene-6-fluoropropylene copolymer resin), and thermoplastic elastomers such as polystyrene, polyolefin, polyvinyl chloride, polyurethane, polyester and polyamide No.

The tube layer 2f may be formed of a heat-shrinkable tube or a non-heat-shrinkable tube.

The volume resistivity of the tube layer 2f is 10
It is preferably in the range of ⁴ to 10 ¹² Ωcm.

The thickness of the tube layer 2f is 3 to 20.
It is about 00 μm, preferably about 3 to 500 μm.

As a method for providing the notch 21 in the tube layer 2f, a pressing method, a method using an ultrasonic cutter, or the like can be used. In the case of a heat-shrinkable tube, the notch 21 may be provided before or after the heat-shrinkage. In the case of a non-heat-shrinkable tube, the notch 21 is preferably provided after coating as a surface layer. In addition, before coating as a surface layer, either a pressing method or a method using an ultrasonic cutter may be used, but after coating as a surface layer, a method using an ultrasonic cutter is preferably used.

Regarding the cutout portion 21 of the tube layer 2f, if the cutout portion 21 is formed on the lower layer, the same situation as when a defect occurs in the tube layer 2f is caused, and there is a possibility of causing uneven charging. Therefore, it is preferable to set the distance (a) between the notch 21 of the tube layer 2f and the lower layer end to 1 mm or more. (FIG. 2 (A)) In addition, if the length of the notch 21 is too short, it is difficult to peel off. Therefore, the length (b) of the notch 21 is preferably 2 mm or more. (FIG. 2 (A)) Further, the notch 21 may be perforated (broken line) as shown in FIG. 2 (B), and may have any shape as long as it serves as a trigger for peeling the surface layer.

With the charging member having the structure as in the present invention, the semiconductive tube on the surface layer can be easily peeled off. Furthermore, by covering the peeled charging roller with a semiconductive tube and forming a surface layer again, the electrical characteristics of the charging member are restored, and an output image quality almost equivalent to that of a new charging member can be obtained. Is also possible.

[0039]

Embodiments of the present invention will be described below.

Example 1 A charging roller 2 as a charging member according to the present invention was manufactured in the following manner.

SBR 1OO parts by weight Conductive carbon black 30 parts by weight Zinc oxide 5 parts by weight Fatty acid 2 parts by weight The following materials were mixed in a closed mixer adjusted to 60 ° C.
After kneading for 20 minutes, 20 parts by weight of a naphthenic oil is added to 100 parts by weight of SBR, and the mixture is kneaded for 20 minutes with a closed mixer cooled to 20 ° C. to prepare a raw material compound. Further, sulfur O.V. 5 parts by weight, 1 part by weight of a thiazole type and 1 part by weight of a thiuram type as a vulcanization accelerator are added to the raw material compound, and kneaded for 10 minutes by a two-roll machine cooled to 20 ° C. Using this compound, a conductive elastic layer 2b was vulcanized and formed into a roller shape by transfer molding around a φ6 stainless steel core 2a so that the outer shape became φ12.

As a material for the tube layer 2f, 100 parts by weight of nylon 12 and 20 parts by weight of conductive carbon black are melt-kneaded, extruded, stretched, and stretched to form a tube having an inner diameter of 15 mm before heat shrinkage and a thickness of 200 μm. Get
A cut 4 having a length of 4 mm was provided at one end of the tube by pressing. After inserting the elastic layer 2b previously obtained into the tube, the tube is heated at 100 ° C. for 2 minutes, and the elastic layer 2b is heated.
The tube was covered by heat shrinkage on b to form a tube layer 2f 5 mm longer at one end than at the end of the elastic layer 2b, and a charging roller 2 according to the present invention was obtained.

The charging roller 2 is incorporated in an unused process cartridge (trade name: EP-E toner cartridge (Canon Inc.)) and a laser beam printer "LBP-8Mark IV (Canon Inc.) as shown in FIG. )) "Charging roller 2 at the position of the primary charger
And a 6000-sheet image output durability test was performed. The images were evaluated by visually observing the images obtained at the initial stage and after the 6OOOO sheet durability test. Table 1 shows the results. In the table, ○ indicates that the obtained image is good, Δ indicates that the image is practical, and X indicates that the image is not practical.

[0044]

[Table 1]

The above-mentioned image output durability test was conducted at a temperature of 2
3.5 ° C, humidity 50% (environment 1) and temperature 15 °
C, humidity 10% (environment 2), temperature 30 ° C, humidity 8
The test was performed under 0% (environment 3).

Table 1 also shows the releasability of the surface layer from the cut portion of the charging roller 2 after the durability.

(Example 2) The charging roller 2 was obtained and evaluated in the same manner as in Example 1 except that the cut portion 21 provided in the tube layer 2f was perforated with an ultrasonic cutter. went. Table 1 shows the results.

Example 3 A charging roller 2 was obtained and evaluated in the same manner as in Example 1 except that two cut portions 21 were provided at one end of the tube layer 2f.
Table 1 shows the results.

Example 4 A charging roller 2 was obtained and evaluated in the same manner as in Example 1 except that the cut portions 21 were provided at both ends of the tube layer 2f. Table 1 shows the results.

(Example 5) The elastic layer 2b was prepared in the same manner as in Example 1, and 100 parts by weight of PVDF (polyvinylidene fluoride resin) and 20 parts by weight of conductive carbon black were melt-kneaded as a material of the tube layer 2f. Inner diameter is 10.5m by extrusion molding
m, a tube having a thickness of 250 μm was obtained. Blowing compressed air into the tube, inserting the elastic layer 2b obtained earlier while expanding the inner diameter of the tube, 5 m at one end from the lower layer end
An m-long tube layer 2f was formed, and one notch 21 having a length of 3 mm was provided at the end of the tube with an ultrasonic cutter to obtain a charging roller 2 according to the present invention.

The obtained charging roller 2 was evaluated in the same manner as in Example 1. Table 1 shows the results.

(Embodiment 6) In Embodiment 1, the elastic layer 2b
The elastic layer was prepared in the same manner as in Example 1 except that the raw rubber and carbon black used therein were 100 parts by weight of EPDM, 40 parts by weight of conductive carbon black, and 25 parts by weight of paraffinic oil instead of naphthenic oil. 2b was formed, and a resistance control layer 2d was formed thereon as follows.

As a material of the resistance control layer 2d, polyurethane resin 1OO parts by weight titanium oxide 90 parts by weight is dispersed and dissolved in a methyl ethyl ketone solvent, and is applied on the elastic layer 2b by a dipping method to form a 100 μm resistance control layer 2d. Was formed. Further, the tube layer 2f and the notch 21 were formed on the resistance control layer 2d in the same manner as in Example 1, and the charging roller 2 according to the present invention was obtained and evaluated. Table 1 shows the results.

Each of the charging rollers of Examples 1 to 6
Good images were obtained even after 2,000 sheets of durability. Further, the tube layer 2f could be cut off from the cutout portion 21, and the surface layer could be easily peeled off. Further, the roller peeled off in the same manner as described in the embodiment is coated again with the tube layer 2f, whereby a charging roller similar to a new one can be obtained.

Comparative Example 1 A charging roller 2 was obtained and evaluated in the same manner as in Example 1 except that the length (b) of the notch 21 was 1 mm. Table 1 shows the results
Shown in

Although a good image was obtained even after 6,000 sheets of the charging roller had been used, the surface layer was peeled off from the notch, and an attempt was made to grip the edge of the notch. The layers could not be peeled.

(Comparative Example 2) A charging roller 2 was obtained and evaluated in the same manner as in Example 1 except that the notch 21 was 5 mm and 1 mm of the notch 21 overlapped the elastic layer 2b. Table 1 shows the results.

The elastic layer is visible at the end of the charging roller, and a pinhole of the photosensitive drum is generated in the durable 200000 sheets, and a horizontal black streak image is generated due to a leak at a position corresponding to the cutout portion. Charging could not be performed.

[0059]

As described above, according to the present invention, the surface layer of the charging roller used in the electrophotographic apparatus can be easily separated, and can be reused to save the earth resources and protect the environment. To contribute.

Further, when the charging roller is regenerated through the present invention, cleaning with an organic solvent is not required, so that electric resistance caused by cracks and the like due to the organic solvent cleaning,
Hardness, surface roughness, roundness, straightness, slipperiness (friction coefficient)
And the like, there is no danger of loss of various functions required for the charging roller.

Furthermore, since the charging roller reproduced through the present invention has recovered the electrical characteristics as a charging member in the electrophotographic apparatus, stable output image quality and durability can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an electrophotographic apparatus in which a contact charging device using a charging member according to the present invention is used as a primary charging unit of an image carrier.

FIG. 2 is a schematic view of a contact-type charging member showing an embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of another contact-type charging member according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... To-be-charged body (photosensitive drum) 2 ... Charging roller as a charging member, charging blade, charging block 2a ... Core 2b ... Conductive elastic layer 2f ... Surface layer 3 ... Power supply 4 ... Exposure means 5 ... Developing device 6 ... Paper cassette 7 Transfer charger 8 Fixing device 9 Cleaning device 10 Pre-exposure device P Transfer material 21
… Notch

Continuation of the front page (56) References JP-A-5-310338 (JP, A) JP-A-6-149018 (JP, A) JP-A-6-28860 (JP, U) JP-A-5-17224 (JP) , U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/02 G03G 15/16 G03G 15/20 F16C 13/00-15/00 B65H 5/06 B65H 29/20

Claims (4)

(57) [Claims] 1. A charging member for applying a voltage to a charging member to perform a charging treatment on a surface to be charged, wherein the charging member has a multilayer structure, and a surface layer is formed of a semiconductive tube. A charging member having one or both ends of a tube longer than a lower layer, wherein one or two or more cutouts are provided at the elongated end of the semiconductive tube. 2. The charging member according to claim 1, wherein the cutout portion of the semiconductive tube is provided at least 1 mm outside the lower layer end. 3. The charging member according to claim 1, wherein the length of the cutout portion of the semiconductive tube is 2 mm or more. 4. The charging member according to claim 1, wherein said charging member has a roller shape.