JPH0713403A - Production of contact electrifying device - Google Patents

Abstract

PURPOSE:To facilitate a fixing work and to enhance a productive efficiency by fixing by thermal contraction by using a thermal contraction tube, and also to enable stable and uniform electrification without forming recessed and projection parts on a sheet fixing part by unnecessiating the use of adhesive and an adhesive tape. CONSTITUTION:As to the method for manufacturing the contact electrifying device provided with a hollow conductive roller which is constituted by fixing both end parts of an endless flexible conductive sheet 2 on a roller flange 6 and a conductive brush roller 3 which is coaxially installed in the roller 1 so as to be mutually rotated, and for impressing an electrifying voltage on the roller 1 through the brush roller 3 and electrifying a photoreceptive body while rotating the roller 1 in contact with the photoreceptive body physically, a small diameter part is installed outside the roller flange 6 in the shaft direction and both end parts of the sheet 2 are positioned between the thermal contraction tube 10 and the small diameter part of the roller flange 6, and then, both end parts of the sheet 2 are fixed on the roller flange 6 by contracting the thermal contraction tube 10 by heat.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a charging device for the surface of a photosensitive member used in an electrophotographic apparatus, and more specifically, it is possible to perform main charging of the surface of the photosensitive member without corona discharge. To a possible contact charging device manufacturing method.

[0002]

2. Description of the Related Art In an image forming method using an electrophotographic method, the surface of a photoconductor is uniformly charged and imagewise exposed to form an electrostatic latent image corresponding to an original image on the surface of the photoconductor. An image is formed by developing and transferring the latent image. In such an image forming method, charging (main charging) of the surface of the photoconductor is generally performed by corona charging, but this method inevitably suffers from the problem of environmental pollution such as generation of ozone. Recently, in order to avoid generation of ozone, a method has been proposed in which a conductive rubber roller is frictionally brought into contact with the surface of the photoconductor while applying a bias voltage to perform main charging of the surface of the photoconductor (special feature. Kaisho 63-1496
69 and JP-A-1-267667).

However, in the charging method using frictional contact as described above, if foreign matter such as dust or paper dust is sandwiched between the conductive rubber roller and the photosensitive member, there is a problem in that the charging uniformity is impaired and stable. It was difficult to carry out charging. Further, when the image is formed, there is a cleaning failure on the surface of the photoconductor, and if toner remains on the surface,
There is a problem that the residual toner is fixed to the surface of the photoconductor, and there is a problem that durability of the photoconductor is reduced. Further, in order to perform uniform charging, it is not enough to apply the DC bias voltage alone, and it is necessary to apply the AC bias voltage as well.

As a charging method in which such a problem has been solved, the applicant of the present application has previously used a charging device equipped with a conductive brush roller to bring a flexible conductive sheet into frictional contact with the surface of a photosensitive member. A method of frictionally charging while applying a DC voltage to the roller has been proposed (see Japanese Patent Application No. 4-68148). The contact charging device used in this charging method is composed of a conductive brush roller and a flexible hollow conductive roller which has the brush roller built therein and is provided so as to come into contact with the brush.

In this contact charging device, the flexible conductive sheet forming the hollow conductive roller is pressed by the conductive brush and adheres to the surface of the photoconductor, so that a low AC bias voltage is not applied. It is extremely excellent in that triboelectric charging can be performed uniformly by applying only the DC bias voltage of the voltage to the conductive brush.

[0006]

The hollow conductive roller in the above-mentioned contact charging device is provided such that both end portions of the endless flexible conductive sheet are rotatable with respect to the rotary shaft of the conductive brush roller. It is fixed to the roller flange, and an adhesive or an adhesive tape is used as the fixing means.

However, since the above-mentioned conductive sheet has a relatively small thickness and is flexible by itself and easily bends, when it is fixed to the roller flange with an adhesive, for example, the amount of adhesive adhered varies. Thus, unevenness is formed on the adhesive-coated portion of the sheet. Moreover, since the conductive sheet is a portion where the conductive sheet is pressed against the end portion of the photoconductor, the adhesive is not uniformly contacted with each other, resulting in uneven charging and abnormal noise during operation of the device. There's a problem. In addition, when the adhesive is applied, the conductive sheet is contaminated due to the dripping of the adhesive, and this contamination not only causes uneven charging and abnormal noise, but also takes a long time to dry the adhesive, which results in production. There is also the problem of low efficiency.
Further, when the adhesive tape is used, durability becomes a problem, it is difficult to stably fix the conductive sheet for a long period of time, and there is a disadvantage that the life of the device is short.

Therefore, an object of the present invention is to provide a method capable of manufacturing a contact charging device by fixing an endless flexible conductive sheet to a roller flange without using an adhesive or an adhesive sheet. It is in.

[0009]

According to the present invention, there is provided a hollow conductive roller formed by fixing both ends of an endless flexible conductive sheet to roller flanges, and a hollow conductive roller coaxial with the hollow conductive roller. A conductive brush roller rotatably provided to each other, and applying a charging voltage to the hollow conductive roller through the conductive brush roller to bring the hollow conductive roller into physical contact with the photoconductor. In a method of manufacturing a contact charging device that charges a photosensitive member while rotating, a small diameter portion is provided on an outer side in an axial direction of the roller flange, and the endless end portion is provided between a heat-shrinkable tube and the small diameter portion of the roller flange. A method is provided that positions both ends of a flexible conductive sheet and heat-shrinks the heat-shrinkable tube to secure both ends of the sheet to a roller flange.

[0010]

That is, according to the present invention, the endless flexible conductive sheet constituting the hollow conductive roller is fixed to both ends of the roller flange by using the heat shrinkage of the heat shrinkable tube. It is not necessary to use adhesive tapes or adhesive tapes at all, and it is possible to effectively avoid various inconveniences that may occur when these adhesive tapes are used, and it is possible to perform fixing with high bonding strength. Moreover, according to the present invention, the fixed portions at both ends of the endless flexible conductive sheet are small-diameter portions formed on the outer side in the axial direction of the roller flange. The tension is applied to the outer side in the axial direction, and there is no inconvenience that the sheet is loosened, and uniform contact charging can be stably performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to specific examples shown in the accompanying drawings. FIG. 1 is an explanatory view for explaining the method of the present invention, and FIG. 2 is a side sectional view briefly showing a usage state of a contact charging device manufactured by the method of the present invention.

The contact charging device manufactured according to the present invention roughly includes a hollow conductive roller 1 including a flexible endless conductive sheet 2 and rigid flange rings 3 provided at both ends thereof. And a conductive brush roller 3 coaxially and rotatably provided in the flexible roller 1. The brush roller 3 is composed of a drive shaft 4 and a brush 5 planted on the shaft. The drive shaft 4 is connected to an appropriate drive source for drive rotation.

The inner surface of the flexible conductive sheet 2 of the flexible roller 1 is in contact with the brush 5 of the conductive brush roller 3 housed therein, and is supported by the brush 5. Has become. Flange ring 6
Are rotatably provided on the drive shaft 4 by bearings 7.

In the present invention, this flange ring 6
Is made up of a rigid resin body 6a and a rubber ring 6b fitted on the outer surface of the body. As shown in FIG. 1, the rigid resin body 6a has a large diameter portion at its axial end. 6
c is formed. Further, the outer side in the axial direction of the rubber ring 6b has a small diameter so that a recess 6d is formed.
That is, in the large-diameter portion 6c, the flange 6 is sufficiently pressed into contact with the end portion of the photoconductor drum 30, so that the conductive sheet 2 of the flexible roller 1 and the photoconductor drum 30 are fixed. The contact (nip) width is secured.

According to the present invention, first, as shown in FIG. 1 (a), the endless or cylindrical conductive sheet 2 is provided with the above-mentioned flange ring 6 and is electrically conductive. The brush roller 3 is accommodated, and both ends of the sheet 2 (only one end is shown in the drawing) are arranged on the recess 6d formed in the flange ring 6, and this is further arranged. The heat-shrinkable tube 10 is arranged so as to cover it. In this state, as shown in FIG. 2, the tube 1
Both ends of the sheet 2 are firmly fixed to the flange ring 6 by heating the sheet 0 to cause heat shrinkage. In this case, the heating of the tube 10 can be easily performed by blowing hot air with a dryer or the like, and although it varies depending on the type of the tube 10, generally heat shrinks quickly and the tube 10 is fixed in an extremely short time. You can

In the present invention, the material of the heat-shrinkable tube 10 described above is a heat-shrinkable polymer known per se, such as polyethylene, polypropylene, ethylene-butene copolymer, ion-crosslinked olefin copolymer methylene. -Olefin resin such as acrylic copolymer, polyvinyl fluoride, polyvinylidene fluoride, vinyl fluoride / vinylidene fluoride copolymer, tetrafluoroethylene resin (PT
FE), tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin (PFA), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP) and other fluororesins,
Chlorine resins such as polyvinyl chloride and chlorinated polyethylene, thermoplastic polyesters such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate, polyamides such as nylon 6, nylon 12, nylon 66, nylon 610, various acrylic resins, etc. Alternatively, two or more kinds can be used in combination. Further, the tube 10 preferably has a high electric insulation property, and from this point of view, a fluororesin such as PFA or FEP is preferable. That is, by using the electrically insulative tube 10 as described above, the flexible conductive sheet 2 comes into contact with the conductive portion at the end of the photosensitive drum 30, that is, current leakage is effectively avoided. Therefore, it becomes possible to perform uniform charging stably. (Because the organic photoreceptor has a photosensitive layer provided on a conductive base such as aluminum, the conductive base is exposed at the end of the photosensitive drum 30 where the photosensitive layer is not formed. It is electrically conductive.) Furthermore, the thickness of the tube 10 is appropriately set according to the type of the material so that the tube 10 exhibits satisfactory strength and thermal contraction occurs quickly.

Further, according to the present invention, since the fixed portion of the conductive sheet 2 is the concave portion 6d and the concave portion 6d is formed on the rubber ring 6b, the tube 10 is formed.
Since the rubber ring 6b is compressed by the heat contraction, the conductive sheet 2 sandwiched between the two is pulled outward in the axial direction, the occurrence of slack is effectively prevented, and the conductive sheet 2 is firmly fixed. Moreover, the portion 2a of the conductive sheet 2 located in the portion other than the concave portion of the rubber ring 6b can be brought into surface contact with the drum 30 by pressing the flange ring 6 to the end portion of the photosensitive drum 30, so that it is constant. The advantage that the nip width is easily secured is also achieved. Of course, it is also possible to directly form the recess in the rigid resin body 6a without using such a rubber ring, but in this case, the conductive sheet 2 that is sandwiched by the tension is applied. Be careful because it may cause inconvenience such as slipping.

The contact charging device obtained as described above is housed in a box 25 having an opening on one side, and the hollow conductive roller 1 (conductive sheet 2) of the photosensitive drum is held by means of a pressing spring 26 or the like. It is arranged so as to abut against 30 (see FIG. 2). The drive shaft 4 is connected to the rotary shaft of the motor by a transmission means such as a belt pulley, and is set so as to rotate the brush roller 3 independently.

In the above-described charging device, the flexible endless conductive sheet 2 is made of any material as long as it satisfies the condition of being conductive and flexible. For example, it may be made of a conductive resin or rubber, a metal such as a foil, or a laminate of metal and a resin or rubber.

As the conductive resin or rubber, resins or rubbers containing various conductive agents are used. As such a resin, various thermoplastic elastomers such as polyester elastomers, polyamide elastomers, polyurethane elastomers, soft vinyl chloride resins, styrene-butadiene-styrene block copolymer elastomers, acrylic elastomers are preferable, but Nylon 6, nylon 6,6, nylon 6-nylon 6,6 copolymer, nylon 6,6-nylon 6,10 copolymer, polyamide such as alkoxymethylated nylon such as methoxymethylated nylon, copolyamide or Modified products thereof can also be used. Of course, the resin used is not limited to these, and for example, silicone resin, acetal resin such as polyvinyl butyral, polyvinyl acetate, ethylene-vinyl acetate copolymer, ionomer and the like can be used. Examples of the rubber include natural rubber, butadiene rubber, styrene rubber, butadiene-styrene rubber, nitrile-butadiene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-non-conjugated diene copolymer rubber, chloroprene rubber, butyl rubber, silicone rubber. , Urethane rubber, acrylic rubber and the like are preferable.

As the conductive agent to be blended with the above resin or rubber, conductive carbon black, metal powder such as silver, gold, copper, brass, nickel, aluminum and stainless steel, tin oxide conductive agent, etc. A powder conductive agent can be used, and in addition, a nonionic, anionic, cationic, amphoteric organic conductive agent, or an organic tin conductive agent can also be used.

The conductive resin or rubber is generally
The electric resistance (specific resistance) is preferably in the range of 10 to 10 ⁸ Ω · cm, particularly 10 ^{2 to} 10 ⁶ Ω · cm.
The conductive agent is mixed with 100 parts by weight of resin or rubber in an amount of 1 to 20 parts by weight, particularly 5 to 15 parts by weight, so that the above resistance value can be obtained, though it varies depending on the kind. Generally, higher conductivity can be obtained when the conductive agent particles form a chain structure in the resin or rubber, but in this case, a dot-shaped high potential portion is generated when a voltage is applied, and charging is performed. May cause unevenness. Therefore, it is preferable that these conductive agents are uniformly and finely dispersed in the resin or rubber, and for this purpose, it is important to sufficiently knead the conductive agent-containing resin or rubber.
Further, in order to effectively disperse the conductive agent uniformly, some acid-modified resins or rubbers obtained by copolymerizing an ethylenically unsaturated carboxylic acid such as acrylic acid, methacrylic acid, or maleic anhydride should be used. Is also effective.

Although the thickness of the above-mentioned flexible conductive sheet 2 varies depending on its flexibility, it is generally desired to be in the range of 50 to 400 μm, particularly 100 to 300 μm. The surface is preferably as smooth as possible, and the average roughness according to JIS B 0601 is 5 μm or less,
Particularly, it is desirable that the thickness is 1 μm or less.

In the present invention, the flexible conductive sheet 2 is used.
Alternatively, a seamless metal foil can be used. Examples of the metal foil include nickel, aluminum, copper, brass, tin and the like, which are obtained by electroforming or extrusion. The thickness of the metal foil is 20 to 80μ
It is preferably in the range of m, especially 30 to 50 μm.

The flexible conductive sheet 2 may be made of a single layer material or a laminated material. In particular, when the surface of the conductive sheet 2 that comes into contact with the surface of the photoconductor is formed of a high resistance layer, even when there are defects such as pinholes on the surface of the photoconductor, leakage such as discharge can be prevented. This is advantageous in that it can be done. The resistivity of this high resistance layer is 10 ^{8 to} 10 ¹³ Ω · cm, especially 10 ⁹
The thickness is preferably in the range of 10 to 10 ¹² Ω · cm, and the thickness thereof is preferably in the range of 40 to 60 μm. The electric resistance can be easily adjusted by adjusting the amount of the conductive agent mixed in the resin or the rubber. As the conductive agent or rubber, those mentioned above can be used, but in addition to them, fluorine-based resins or rubbers such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene. A copolymer (PTFE / HFP), a perfluoroalkoxy-based fluororesin, etc. are preferably used. When these resins or rubbers are used for the high resistance layer, they are inert and have a small friction coefficient, so that there is a great merit in the life of the photoconductor and the life of the sheet.

In the present invention, a brush in which a conductive roller made of conductive organic or inorganic fibers is planted on a conductive roller is preferably used as the brush 5. The brush has a volume resistivity of 10 ² to 10 ^2. It is preferably in the range of 10 ⁸ Ω · cm, particularly 10 ^{3 to} 10 ⁶ Ω · cm. The thickness of the brush fiber is 2 to 10 denier (d), especially 3 to 6 d,
Fiber length (hair length) is 2 to 7 mm, especially 3 to 5 m
m should be in the range and the flock density should be 10,000 to 20
It is preferable that the pressure is in the range of 10,000 / square inch, particularly 30,000 to 100,000 / square inch, in order to provide a smooth and uniform pressing force. Further, it is preferable to round the tip of the brush in order to suppress abrasion of the flexible sheet 2.

As the organic conductive fibers, synthetic or regenerated fibers in which conductive agent particles are dispersed are used. For example, polyamide fibers such as nylon 6, nylon 6,6, polyester fibers such as polyethylene terephthalate, acrylic fibers,
Examples thereof include polyvinyl alcohol fiber, polyvinyl chloride fiber, rayon and acetate. The method of imparting conductivity to the fiber is not limited to the method of blending a conductive agent, and may be a method of metallizing the surface of the fiber. When the conductive agent is used, the conductive agent described above can be used. Carbon fibers are preferably used as the conductive inorganic fibers, but metal fibers such as stainless steel and brass are also used.

Charging using the contact charging device installed as shown in FIG. 2 is performed as follows. For example, since the endless conductive sheet 2 in the flexible hollow conductive roller 1 is pressed against the end of the photosensitive drum 30 by the flange ring 6 at the end, the rotation speed of the drum 30 is It is driven or driven at a synchronized speed. On the other hand, the rotation of the brush roller 3 is such that the brush 5 rotates at a peripheral speed of 0.9 to 0.95 times the moving speed of the photosensitive drum, that is, the moving speed of the hollow conductive roller 1, and the driving direction thereof is conductive. Setting in the same direction as the driving direction of the sheet 2 is preferable in order to effectively prevent the generation or expansion of the twist of the conductive sheet 2.

A DC power source 20 is connected to the conductive brush 5, and the brush 5 presses the flexible conductive sheet 2 over the entire axial direction to bring it into contact with the surface of the rotating photosensitive drum 30. Conductive sheet 2 through 5
A DC voltage is applied to the surface of the photosensitive drum 30 to charge it.

The charging voltage applied to the conductive sheet 2 is 1.5 to the charging start voltage value of the surface of the photosensitive drum 30.
It is preferably set to 3.5 times, especially 2 to 3 times. As a result, it is possible to perform uniform and even charging only by using the DC voltage. However, in order to perform even charging, the AC power supply 21 is combined with the DC power supply 20,
It is also possible to apply a voltage in which an AC voltage is further superimposed on the DC voltage described above. Such alternating current has a frequency of 300 to 1500 Hz, especially 400 to 1000 H.
z, and the peak-to-peak voltage is 2.5 to 4 of the above DC voltage.
It is preferred to use a double, especially 2.8 to 3.5 times alternating current.

The contact charging device manufactured by the method of the present invention is extremely useful for charging a photoconductor used in an electrophotographic method such as a copying machine, a facsimile, and a laser printer. Particularly, as the photoconductor, a single-layer or laminated structure is used. Although various organic photoconductors are suitable, of course, in addition to these, a-Si photoconductors,
It is also suitably applied to contact charging of an inorganic photoconductor such as a selenium photoconductor.

[0032]

According to the present invention, the endless flexible conductive sheet can be fixed to the flange roller with high joining strength and without causing slack. In particular, since fixing is performed by heat shrinkage using a heat shrinkable tube, the fixing work is easy, the production efficiency can be improved, and there is no need to use an adhesive or an adhesive tape. No unevenness is formed on the fixed portion, and stable uniform charging can be performed.

[Brief description of drawings]

FIG. 1 is a diagram for explaining a method of manufacturing a contact charging device of the present invention.

FIG. 2 is a side cross-sectional view of a contact charging device manufactured by the method of the present invention together with a photosensitive drum.

Claims (2)

[Claims] 1. A hollow conductive roller formed by fixing both ends of an endless flexible conductive sheet to roller flanges, and a conductive material coaxially and rotatably provided in the hollow conductive roller. A contact that consists of a brush roller and applies a charging voltage to the hollow conductive roller via the conductive brush roller to charge the photosensitive member while physically contacting the hollow conductive roller with the photosensitive member and rotating the same. In the method for manufacturing the charging device, a small diameter portion is provided on the outer side in the axial direction of the roller flange,
Both ends of the endless flexible conductive sheet are positioned between the heat-shrinkable tube and the small diameter portion of the roller flange, and the heat-shrinkable tube is heat-shrinked so that both ends of the sheet are rolled. A method characterized by fixing to a flange. 2. The method of claim 1, wherein the heat shrinkable tube is electrically insulating.