JPH0820794B2 - Charging member and contact charging device having the charging member - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member and a contact charging device, and more particularly to a charging member capable of stably obtaining a defect-free image and contact charging having the charging member. To provide a device.

[Conventional technology]

In the electrophotographic method, perform basic processes such as charging, exposure, development, transfer, fixing, and cleaning on an electrophotographic photoreceptor using, for example, selenium, cadmium sulfide, zinc oxide, amorphous silicon, or an organic photoconductor. When obtaining an image, the charging process is performed by corona generated by applying a high voltage (DC5-8KV) to most metal wires. However, in this method, when corona occurs, corona products such as ozone and NO _X deteriorate the surface of the photoconductor to cause image blurring and deterioration, and wire stains affect image quality, resulting in image white spots and black streaks. There were problems such as occurrence.

In terms of electric power, the current flowing to the photoconductor is 5 to 30%.
%, And most of them flowed to the shield plate and were inefficient as charging means.

To compensate for such a problem, JP-A-57-178267, JP-A-56-104351, JP-A-58-40566, and JP-A-58-139156 do not use a corona discharger. No.
As proposed in JP-A-58-150975,
Methods for contact charging have been studied.

Specifically, a conductive elastic roller, etc., to which a pulsating voltage (V _DC + V _AC ) is applied by superposing a DC voltage (V _DC ) or a DC voltage and an AC voltage (V _AC ) on the surface of the photoconductor Contact the charging member to bring the surface of the photoconductor to a specified potential,
The idea is to evenly charge them.

However, when the conventional charging member is repeatedly used in an electrophotographic apparatus in which the peripheral speed of the photoconductor is high, toner or paper powder is likely to adhere to the charging member or the photoconductor, resulting in image defects. Satisfactory properties were not obtained in terms of ease.

In addition, the phenomenon as described above tends to be particularly remarkable when an alternating voltage is used as the applied voltage. It is considered that this is because the AC member vibrates due to the AC voltage, and the pressure applied to the charging member and the surface of the photosensitive member fluctuates, so that image defects are more likely to occur. If an attempt is made to solve this problem by lowering the applied AC voltage, a problem of poor charging will occur.

[Problems to be solved by the invention]

An object of the present invention is to provide a charging member having high durability and a contact charging device having the charging member, which can obtain good image quality without image defects even when it is repeatedly used in a high speed machine.

[Means for solving problems]

That is, the present invention is a charging member which is brought into contact with an electrophotographic photosensitive member and charges the electrophotographic photosensitive member by applying a voltage, wherein the surface layer of the charging member is 50 to 50% of the total weight of the surface layer. The charging member is characterized by containing 10,000 ppm of silicone oil.

Further, the present invention is a contact charging device having the above charging member.

Although various silicone oils can be used in the present invention, the weight average molecular weight of the silicone oil is preferably 200,000 to 100,000, and particularly preferably 1,000 to 10,000. If the weight average molecular weight is 200 or less, the effect of the present invention is not recognized even if it is added, and if it is 100,000 or more, the viscosity becomes too high, and it becomes difficult to remove toner, paper powder, and the like.

The addition amount of the silicone oil used in the present invention is preferably 50 ppm to 10,000 ppm, and particularly preferably 100 ppm to 5000 ppm, based on the total weight of the surface layer. If the addition amount is less than 50 ppm, the effect of the present invention is not recognized even if it is added, and if it exceeds 10,000 ppm, problems such as cracks that adversely affect the image on the photoreceptor occur.

The structure of the charging member of the present invention is basically composed of a resin layer in which conductive particles fixed to a conductive core material are dispersed. This resin layer may be a single layer or two or more layers may be laminated as proposed in JP-A-64-66674. When the charging member of the present invention has a laminated structure, at least the surface layer must contain silicone oil. The resin layer uses a coating liquid in which conductive particles are dispersed,
It can be applied and formed by a dip coating method or the like.

 An example of the structure of the contact charging device of the present invention is shown in FIG.

Examples of the resin material used for the charging member of the present invention include rubber or sponge such as chloroprene rubber, isoprene rubber, EPDM rubber, polyurethane rubber, epoxy rubber, and butyl rubber, styrene-butadiene thermoplastic elastomer, polyurethane thermoplastic elastomer, and polyester. Examples thereof include thermoplastic elastomers such as thermoplastic elastomers and ethylene-vinyl acetate thermoplastic elastomers, as well as polyamide, polyimide, polyurethane, polyvinyl alcohol and polyester. In addition, in order to adjust the resistance value of the resin layer as necessary,
Conductive particles may be added.

Examples of the conductive particles include metal oxides such as carbon black, zinc oxide and titanium oxide, and metal particles such as nickel, iron and aluminum. The preferred resistance value of the charging member is about 1 × 10 ⁴ to 8 × 10 ⁹ Ω. 1 x
If it is less than 10 ⁴ Ω, if the photoconductor has a scratch, the current concentrates on that portion to cause an image defect, and if it exceeds 8 × 10 ⁹ Ω, uniform charging becomes difficult.

As shown in FIG. 2, a metal foil (4) with a width of 1 cm is wound around the contact charging device (3) and 250 V is applied as an electrode between the conductive core metal portion (3-a) and the metal foil, and 1 min. The current value after that is measured and the resistance value is calculated from it.

In the present invention, when the AC voltage and the DC voltage are superimposed and applied to the charging member, the peak-to-peak voltage of the AC voltage is preferably twice or more the DC voltage value.

Further, the AC wave to be used is not limited to a sine wave, but may be, for example, a rectangular wave or a triangular wave.

Specific examples will be shown below, but the invention is not limited thereto.

Example 1 100 parts by weight of EPDM compound, Ketsch embrac 5
Parts by weight and 10 parts by weight of paraffin oil are mixed and dispersed for 30 minutes on a two-roll roll cooled to 20 ° C. to prepare a raw material compound.

To 100 parts by weight of this raw material, 2 parts by weight of dicumyl peroxide as a vulcanizing agent is added and further mixed on a roll for 2 hours.

By using this compound, a core metal made of φ6 stainless steel is flown and molded to have an outer diameter of φ12.

Furthermore, 100 parts by weight of methylolated nylon, 2 parts by weight of Ketjen black and 200 ppm of dimethyl silicone oil (weight average molecular weight 2000) are dissolved and dispersed in a mixed solvent of methanol / toluene to prepare a coating solution, which is prepared by the dipping method. A 20 μ surface layer was laminated to prepare a charging member.

The resistance of this charging member was measured and found to be 1 × 10 ⁶ Ω.

This charging member is attached to the position of the contact charging device in the cartridge of LBP-8II (manufactured by Canon Inc.), and the bias to apply weight to the core metal is DC voltage (V _DC ) = -700v and frequency (f) = 1000Hz. AC voltage (V _AC ) = 2000v, and
LBP process speed from 8 sheets / minute (A4 size) to 15
A paper passing test was conducted on 200,000 sheets at a rate of 1 sheet / minute (same).

As a result, good images without defects were stably obtained from the initial stage up to 200,000 sheets.

Example 2 A charging member was produced in the same manner as in Example 1 except that the amount of silicone oil in the surface layer was changed to 50 ppm and evaluated under the same conditions.

As a result, a slight amount of toner adhered to the photoconductor from 170,000 sheets, but no remarkable defect was observed on the image.

Example 3 A charging member was prepared in the same manner as in Example 1 except that the amount of silicone oil in the surface layer was changed to 5000 ppm and evaluated under the same conditions. Occurrence of muscle was observed, but no image defect was observed.

Comparative Example 1 A charging member was produced in the same manner as in Example 1 except that silicone oil was not used for the surface layer, and evaluation was performed under the same conditions.

As a result, image defects due to toner adhesion to the charging member and the photoconductor occurred from 100,000 sheets.

Further, cells were generated in the surface layer, and bleeding phenomenon of paraffin oil in the elastic layer to the photoconductor was observed.

Example 4 A charging member was produced in the same manner as in Example 1 except that the weight average molecular weight of the silicone oil was changed to 20,000, and evaluated under the same conditions. As a result, a slight amount of toner adhered to the charging member and the photoconductor from 170,000 sheets, but no image defect was observed.

Example 5 A charging member was prepared in the same manner as in Example 1 except that the dimethyl silicone oil was changed to an amino-modified silicone oil, and was evaluated under the same conditions. It was stable up to 200,000 sheets from the initial stage and had no defects. A good image could be obtained.

〔The invention's effect〕

As described above, when the charging member and the contact charging device of the present invention are used, adhesion of toner and paper powder to the charging member and the photoconductor does not occur, and there is no image defect even when repeatedly used by a high speed machine. Images can be stably obtained.

[Brief description of drawings]

 FIG. 1 is a structural example of the contact charging device of the present invention. 1 ... Photosensitive member 2 ... Bias power supply 3 ... Contact charging device (3a: conductive core material, 3b: resin layer) FIG. 2 is a schematic diagram of a resistance measuring device. 4 …… Metal foil 5 …… 250V DC power source 6 …… Ammeter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Tanaka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Sasame 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation (56) References JP-A-56-144453 (JP, A)

Claims (2)

[Claims] 1. A charging member which is brought into contact with an electrophotographic photosensitive member and charges the electrophotographic photosensitive member when a voltage is applied thereto, wherein the surface layer of the charging member is 50 to 50% of the total weight of the surface layer.
A charging member characterized by containing 10,000 ppm of silicone oil. 2. A contact charging device for charging a charging member, which is brought into contact with an electrophotographic photosensitive member, by applying a voltage to the charging member, wherein the surface layer of the charging member has a total weight of the surface layer. A contact charging device characterized by containing 50 to 10,000 ppm of silicone oil.