JP2632899B2 - Charging member and process cartridge - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member for charging an object to be charged and a process cartridge having the same.

BACKGROUND ART Conventionally, a corona discharger has been known as a charging unit in an electrophotographic apparatus or the like. However, corona dischargers have problems such as the need to apply a high voltage and the generation of a large amount of ozone.

Therefore, recently, the use of contact charging means without using a corona discharger has been studied. More specifically, a voltage is applied to a conductive roller serving as a charging member, and the roller is brought into contact with a photosensitive member serving as a charged member to charge the surface of the photosensitive member to a predetermined potential. If such a contact charging means is used, the voltage can be reduced as compared with a corona discharger,
Ozone generation is also reduced.

For example, Japanese Patent Publication No. Sho 50-13661 enables a low voltage to be applied when photosensitive paper is charged by using a roller whose core is coated with a dielectric material made of nylon or polyurethane rubber.

However, in the above-described conventional example, when the core metal is coated with nylon, there is no elasticity of rubber or the like, so that sufficient contact with the member to be charged cannot be maintained, and poor charging occurs.
On the other hand, when the core metal is coated with polyurethane rubber, the softening agent impregnated in the rubber-based material exudes, and when the photoreceptor is used as the charged body, the charging member sticks to the photoreceptor when the photoreceptor stops at the contact portion. Or the area may cause image blurring. Also, when the softener in the rubber material of the charging member seeps out and adheres to the surface of the photoreceptor,
When the resistance of the photoreceptor is lowered to cause an image flow to be severe, the photoreceptor becomes unusable or the toner remaining on the surface of the photoreceptor adheres to the surface of the charging member to cause a filming phenomenon. When a large amount of toner adheres to the surface of the charging member, the surface of the charging member is insulated, and the charging ability of the charging member is lost, so that the charging of the surface of the photoreceptor becomes non-uniform, thereby affecting an image.

[Object of the Invention] The present invention has been made in view of the above points, and can sufficiently maintain contact between a charging member and a member to be charged, prevent sticking between the charging member and the member to be charged, and further improve charging. Provide a charging member that adheres a plasticizer contained in the rubber of the member to the member to be charged and prevents toner from sticking to the surface of the charging member, thereby preventing charging failure and uneven charging due to filming of the toner on the member to be charged. The purpose is to do.

[Constitution of the present invention] In order to achieve the above object of the present invention, the present invention provides a charging member for charging an object to be charged by contacting the object, comprising: a conductive elastic layer; a surface layer; In a charging member having an elastic layer and a resistance layer provided between the surface layer, the resistance layer includes hydrin rubber, and the surface layer includes a nylon-based resin, polyvinylidene fluoride, or polyvinylidene chloride. It is a feature. Alternatively, the present invention is a process cartridge detachable from an image forming apparatus, comprising: an image carrier; and a charging member that contacts the image carrier and charges the image carrier. A charging member including a layer and a resistance layer provided between the conductive elastic layer and the surface layer, wherein the resistance layer includes hydrin rubber, and the surface layer is a nylon-based resin or It is characterized by comprising polyvinylidene fluoride or polyvinylidene chloride.

Example An example of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an image forming apparatus to which the charging device of the present invention can be applied. In this embodiment, an image forming apparatus in which a sheet material feeding section A and a laser beam printer section B are combined is used. The device is shown.

A configuration and an image forming operation of the printer B of the present example will be described. Reference numeral 1 denotes an outer casing of the printer. In the printer of this embodiment, the right end face side in the drawing is the front face. Reference numeral 1A denotes a printer front plate. The front plate can be freely opened and closed as shown by a two-dot chain line around the hinge shaft 1B on the lower side with respect to the printer outer casing 1, and raised and closed as shown by the solid line. is there. The operation of attaching and detaching the process cartridge 2 to and from the inside of the printer, and inspection and maintenance of the inside of the printer are performed by opening the front plate 1A to open the inside of the printer.

In this embodiment, the process cartridge 2 includes a cartridge housing 2a and four image forming process devices including a photosensitive drum 3, a charging roller 4, a developing unit 5, and a cleaner 6. As shown by a chain line, the printer can be folded down and opened to be attached to and detached from a predetermined storage portion in the printer outer casing 1. When the cartridge 2 is properly mounted in the printer, the mechanical drive system and the electric circuit system on both the cartridge side and the printer side are connected via a mutual coupling member (not shown) to mechanically and electrically. Integrate.

Reference numeral 7 denotes a laser beam scanner disposed on the back side of the inside of the outer casing 1 of the printer, and includes a semiconductor laser and a scanner motor 7.
a, a polygon mirror 7b, a lens system 7c, etc., and an exposure window 2b of a cartridge housing 2a in which a laser beam L from the scanner 7 is mounted in the printer.
, Enters the housing 2a substantially horizontally, and passes through a passage between the cleaner 6 and the developing unit 5 arranged vertically in the housing to enter the exposure unit 3a on the left side surface of the photosensitive drum 3, and The surface of the drum 3 is scanned and exposed in the generatrix direction.

Reference numeral 8 denotes a multifeed tray which is provided on the lower side of the printer front plate 1A so as to protrude outward and is inclined upward and forward, and can set a plurality of sheet materials S at the same time.

Reference numeral 10 denotes a sheet feeding roller provided at a lower portion inside the printer front plate 1A, and reference numeral 12 denotes a conveying roller contacting the left side of the feeding roller 10. 13 is a transfer roller disposed above the feed roller 10 inside the printer front plate 1A, 15a and 15b are a pair of fixing rollers provided above the inside of the printer front plate 1A, 14
Is a sheet material guide plate provided between the transfer roller 13 and the fixing roller pair 15a / 15b, 16 is a sheet material discharge roller disposed on the sheet material exit side of the fixing roller pair 15a / 15b, and 17 is a discharged sheet material receiving tray. is there.

When an image formation start signal is input to the control system of the printer, the photosensitive drum 3 is driven to rotate at a predetermined peripheral speed in a counterclockwise direction as indicated by an arrow, and its peripheral surface is charged by a charging roller 4 at a predetermined positive or negative polarity. Is uniformly charged. The charging roller 4 is a conductive member to which a predetermined voltage is applied, and the photosensitive drum 3 is charged by the roller by a so-called contact (or direct) charging method. The charging roller 4 may be driven to rotate by the photosensitive drum 3, may be driven to rotate in the opposite direction, or may not rotate.

Next, pixel laser light L corresponding to a time-series electrical pixel signal of image information output from the laser beam scanner unit 7 is incident on the uniformly charged surface of the rotating photosensitive drum 3 at the exposure unit 3a, An electrostatic latent image of image information is formed on the surface of the photosensitive drum 3 by sequentially receiving main scanning by the laser light L on the three surfaces in the drum generatrix direction. The latent image formed on the surface of the drum 3 is successively developed with toner by a developer carried on a developing sleeve (or roller) 5a of the developing device 5. 5b is a storage room for the developer (toner) t.

On the other hand, the uppermost sheet material of the sheet material (transfer sheet) S set on the multi-feed tray 8 is drawn into the printer from the feed roller 10 which is driven to rotate in the direction of the arrow, and is continuously fed. The photosensitive drum 3 is fed at a constant speed equal to the rotational peripheral speed of the photosensitive drum 3 toward a contact portion (transfer portion) between the photosensitive drum 3 and the transfer roller 13 between the nip portion of the transfer roller 12 and the nip portion of the photosensitive roller 3.

The sheet material fed to the transfer unit sequentially passes between the photosensitive drum 3 and the transfer roller 13, and a voltage applied to the transfer roller 13 (a voltage having a polarity opposite to that of the toner) and a photosensitive drum of the transfer roller The photosensitive drum 3 is pressed by the pressing force against the drum 3.
The transfer of the toner image on the surface side is sequentially received. The voltage application to the transfer roller 13 is performed when the leading edge of the fed sheet material reaches a contact portion (transfer portion) between the photosensitive drum 3 and the transfer roller 13.

The sheet material that has passed through the transfer unit is separated from the surface of the photosensitive drum 3, guided by the guide plate 14, and introduced into the pair of fixing rollers 15a and 15b. Among the fixing roller pairs 15a and 15b, the roller 15a on the side contacting the image transfer surface of the sheet material is a heating roller having a built-in halogen beater, and the roller 15b on the side contacting the back side of the sheet material is made of an elastic material. The sheet material to which the image is transferred is a pressure roller, and the toner image transferred in the process of passing through the pair of rollers 15a and 15b is fixed to the sheet material surface by heat and pressure, and the tray is It is discharged on 17 as an image formed product (print).

After the transfer of the toner image, the surface of the photosensitive drum 3 is cleaned and cleaned by the cleaning blade 6a of the cleaner 6 to remove the transfer residual toner and other contaminants, and is repeatedly used for image formation.

When the sheet is fed from the cassette 40 of the sheet feeding device A instead of using the multi-feed tray 8, the top sheet among the sheets S stacked on the cassette 40 is registered by the pick-up roller 26 by the registration roller. The sheet material is sent to the feed rollers 28 and 55 in the direction of the arrow, and the sheet material is fed between the feed roller 10 and the transport roller 12 as described above.

Next, the contact charging device of the present invention applicable to the image forming apparatus will be specifically described.

FIG. 2 is a schematic configuration diagram of a contact charging device showing one embodiment of the present invention. Reference numeral 3 denotes a photosensitive drum as an object to be charged, which is formed by forming an organic photoconductor (OPC) 3b as a photosensitive layer on an outer peripheral surface of a drum base 3a made of aluminum. Rotate. In this embodiment,
The photosensitive drum 3 has an outer diameter of 30 mmφ. Reference numeral 4 denotes a charging roller which is a charging member which is brought into contact with the photosensitive drum 3 with a predetermined pressure. The charging roller 4 is provided with a conductive rubber layer 4b on a metal core 4a. Was provided. If the resistance of the release coating is too high, the photosensitive drum 3
There is not charged, the resistance is too takes large voltage too the photosensitive drum 3 small, damage to the drum, the occurrence of pinholes caused moderate resistance, i.e. volume resistivity 10 ⁹ 10 ¹⁰
Ωm is good, and the thickness of the release film at this time is preferably within 30 μm. In addition, the lower limit of the thickness of the coating is considered to be about 5 μm if the coating is free of peeling and burrs.

In this embodiment, the outer diameter of the charging roller 4 is 12 mmφ,
EPDM was used for the conductive rubber layer 4b, and nylon resin having a thickness of 10 μm was used for the surface layer 4c. The hardness of the charging roller 4 is 54.5 ° (AS
KER-C). E is a power supply unit that applies a voltage to the charging roller 4 and supplies a predetermined voltage to the metal core 4 a of the charging roller 4. In FIG. 2, E indicates a DC voltage, but may be obtained by superimposing an AC voltage on a DC voltage.

FIG. 3 shows the result of a durability test performed using the above charging roller. 5 is a graph showing a decrease in the charging efficiency after the charging efficiency at the start of durability is set to 100%. The solid line uses the above charging roller, and the dotted line uses a conventional charging roller without a surface release coating as a comparative example. Thus, it can be seen that the use of the charging roller of the present invention causes a very small decrease in charging efficiency. This is because the charging roller, which is the charging member of the present invention, uses a nylon-based resin, which is a releasable coating, on the outer side of the conductive rubber layer. This is because the softener is prevented from exuding. Therefore, when the softener adheres to the photoreceptor, it is possible to prevent an image from flowing due to a reduction in the resistance of the photoreceptor and a decrease in the charging ability due to filming of the residual toner on the photoreceptor, thereby suppressing a decrease in charging efficiency.

On the other hand, by using a conductive rubber layer for the charging roller, sufficient contact between the charging roller and the photoconductor can be maintained, and no charging failure occurs.

FIG. 4 is a schematic structural view of a contact charging member showing another embodiment of the present invention. The same reference numerals are given to the same members as those of the apparatus shown in FIG. 2 and the description will not be repeated.

The contact charging member 4 'of this embodiment is in the form of a blade which is brought into contact with the photosensitive drum 3 in a forward direction at a predetermined pressure. The blade 4' is electrically connected to a metal supporting member 4'a to which a voltage is supplied. Rubber 4'b is supported on the photosensitive drum 3
A 10 μm-thick nylon was used as a surface layer 4 ′ c provided with a surface layer 4 ′ c serving as a releasable coating at the contact portion with the surface layer 4 ′. According to this embodiment, the same function and effect as those of the above embodiment can be obtained without any trouble such as adhesion between the blade and the photosensitive drum.

In the above-described embodiment, a roller-shaped or blade-shaped charging member is used. However, the present invention is not limited to this, and the present invention can be applied to other shapes.

Further, in this embodiment, the charging member is composed of the conductive rubber layer and the release coating, but the invention is not limited to this. It is preferable to form a resistance layer, for example, a hydrin rubber layer with small environmental fluctuation.

Also, PVDF is used as a release coating instead of nylon resin.
(Polyvinylidene fluoride) or PVDC (polyvinylidene chloride) may be used. As the photoreceptor, amorphous silicon, selenium, ZnO or the like can also be used. In particular, when amorphous silicon is used for the photoreceptor, if the softener of the conductive rubber layer adheres to the photoreceptor even a little, compared to when other materials are used, the image flow becomes severe, so the outside of the conductive rubber layer The effect of having an insulating coating on the substrate is significant. Further, the charging device of the present invention can be used for transfer.

[Effects of the Invention] In the present invention, since the charging member has a rubber layer, contact between the charging member and the member to be charged can be sufficiently maintained, and the resin layer is provided closer to the member to be charged than the rubber layer. Prevents sticking of the member and the member to be charged and prevents the softener in the conductive rubber of the charging member from adhering to the member to be charged. Poor charging and uneven charging due to filming could be prevented.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a laser beam printer using the present invention, FIG. 2 is an explanatory view schematically showing a charging roller of the present invention, and FIG. FIG. 4 is an explanatory view schematically showing a blade according to another embodiment of the present invention. 2 ... cartridge 3 ... photosensitive drum 4,4 '... charging member E ... power supply

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masanobu Saito 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Shunji Nakamura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Junji Araya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-64-66673 (JP, A) JP-A-54-156548 ( JP, A) JP-A-58-194061 (JP, A) JP-A-60-150071 (JP, A) JP-A-64-66674 (JP, A) JP-A-1-142569 (JP, A) JP JP-A-60-19178 (JP, A) JP-A-58-87572 (JP, A) JP-B-50-13661 (JP, B2)

Claims (4)

(57) [Claims] 1. A charging member for charging an object to be charged by contacting the object, comprising a conductive elastic layer, a surface layer, and a resistive layer provided between the conductive elastic layer and the surface layer. Wherein the resistance layer includes hydrin rubber, and the surface layer includes a nylon-based resin, polyvinylidene fluoride, or polyvinylidene chloride. 2. The charging member according to claim 1, wherein said charging member has a roller shape. 3. The charging member according to claim 1, wherein said charging member has a blade shape. 4. A process cartridge detachable from an image forming apparatus, comprising: an image carrier; a charging member for charging the image carrier by contacting the image carrier; a conductive elastic layer; A charging member comprising: a layer and a resistance layer provided between the conductive elastic layer and the surface layer.A process cartridge comprising: a resistance layer comprising hydrin rubber; andthe surface layer comprising a nylon-based resin or A process cartridge comprising polyvinylidene fluoride or polyvinylidene chloride.