JPH05281827A - Contact electrostatic charging member - Google Patents

Abstract

PURPOSE:To obtain a contact electrostatic charging member where the unstability of electrostatic charging and the contamination of the contact electrostatic charging member which occur because an electrostatic charging area is narrow in the case of contact electrostatic charging are eliminated, electrostatic charging performance is stable, and the stable electrostatic charging performance is maintained for a long time, and which has high durability and is hardly contaminated. CONSTITUTION:This member is the contact electrostatic charging member 1 which is allowed to abut on the surface of a body to be electrostatically charged 2 and electrostatically charges the surface of the body to be electrostatically charged by impressing voltage. It is a non-rotating body which does not follow the driving of the body 2, and provided with a surface layer 3, a middle resistance layer 4, an electrode layer 5 on which the voltage is impressed and an electrode supporting layer 6 in order from the side of the surface abutting on the body to be electrostatically charged. As for the surface layer 3, at least a part N abutting on the body 2 is formed in continuous projecting shape on the middle resistance layer 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging member in a contact type charging device, that is, a contact charging member which is brought into contact with the surface of an object to be charged and which is charged with voltage (including static elimination). Regarding

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as an electrophotographic apparatus (copier, printer, etc.) or electrostatic recording apparatus, an image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric as a member to be charged is used. A corona discharger, which is a non-contact charging type, has been mainly used as a charging processing means.

The corona discharger has advantages such as excellent uniform charging property, but requires an expensive high-voltage power source, requires a space such as itself and a shield space for the high-voltage power source, and corona products such as ozone. However, there is a problem in that the number of occurrences is relatively large, and additional means / mechanisms are required for coping with them, which are factors that increase the size and cost of the apparatus.

Therefore, recently, instead of the corona discharger, a contact charging type charging means is being adopted. In the contact charging, the surface of the charged body is charged to a predetermined polarity and potential by bringing the charging member to which a voltage is applied into contact with the charged body. The power supply can be lowered, and the generation of corona products such as ozone is small. The advantages are that the structure is simple and the cost can be reduced.

The contact type charging device is divided into the shape and the form of the charging member to be brought into contact with the body to be charged, and a roller type charging device in which the charging member is a roller-shaped member (charging roller) (Japanese Patent Laid-Open No. 63-7380). No. 56-91253), a blade type charging device using a blade-shaped member (charging blade) (Japanese Patent Laid-Open No. 64-24264 / 56-194349, etc.), and a brush type brush-shaped member (charging brush). There are chargers (Japanese Patent Laid-Open No. 64-24264, etc.) and the like.

The charging roller of the roller type charger is rotatably supported by a bearing, is pressed against the surface of the body to be charged in a predetermined manner, and is rotated by the movement of the surface of the body to be charged.

In the charging blade of the blade type charger, an electrode is arranged on a conductive / elastic blade member having a medium resistance, and the charging blade is bent against the elasticity so as to be brought into contact with the surface of the body to be charged and elastic. It is arranged in pressure contact with the surface of the body to be charged by the bending reaction force.

The voltage applied to the charging member may be a method of applying only a DC voltage (DC application method), but as the applicant has previously proposed (Japanese Patent Laid-Open No. 63-149669, etc.), a DC voltage is applied. Of the peak-to-peak voltage (PEAK TO PE
AK) oscillating electric field (alternate electric field / AC electric field; that is, electric field or voltage whose voltage value periodically changes with time) is formed between the contact charging member and the charged body to charge the surface of the charged body. The method (AC application method) is effective because it allows uniform charging.

The oscillating electric field (voltage) is an oscillating voltage component (AC component) or a superposed electric field or voltage of an AC component and a DC component (a voltage corresponding to a target charging potential, a DC component).
The waveform of the C component may be a sine wave, a rectangular wave, a triangular wave, or the like. It may be a rectangular wave voltage formed by periodically turning on and off a DC power supply.

[0010]

By the way, regarding the contact type charging, the following points can be mentioned as points for improvement.

(A) Assuming that the member to be charged is, for example, a rotating photosensitive member of an electrophotographic apparatus, in the roller type charger, the contact portion between the charging roller and the photosensitive member is located inside and the upstream side and the downstream side in the rotating direction of the photosensitive member. The charging is performed at two places in the side void portion, and the contact portion is not charged. It has been reported that the charging mechanism (charging mechanism) charges the photosensitive member by space discharge in the gap between the contact portion between the charging roller and the photosensitive member on the upstream side and the downstream side in the photosensitive member rotating direction (for example, ,
Electrophotographic Society Journal, Vol. 29, No. 4, P.410 (1990)).

That is, since the charging is performed in a very narrow range, it is disadvantageous in terms of stability of charging. For example, since the charging is unstable, the potential of the first round of the surface of the photoconductor does not reach the predetermined potential, and so-called “fog” corresponding to the first round of the photoconductor may occur.

It has been confirmed that the blade type charger is also charged by space discharge, which is disadvantageous in that the charging area is narrow and the charging is stable.

(B) In the contact charging, since the charging member is brought into contact with the member to be charged, the charging member is apt to be contaminated by spreading dirt from the surface of the member to be charged, and a charging failure is likely to occur.

In the roller type charger, when a foreign matter is caught between the charging roller and the photosensitive member, the charging roller is easily contaminated and charging failure is likely to occur.

Since the blade type charger has a narrow charging area,
It is easily affected by the inclusion of foreign matter, and the photoconductor is also easily soiled.

The brush type charger has the advantages that it realizes uniform charging and that the charging brush does not wear out due to defects in the photoconductor. However, when the contact pressure of the charging brush is low, foreign matter and the like enter the charging area, and the brush-constituting wire is aligned in a certain direction at that location, so that charging failure is likely to occur, and when the contact pressure is high, In addition to easily damaging the photoconductor, there is a problem that the brush-constituting wire easily comes off the carrier due to contact with the photoconductor.

The present invention is a contact charging member having a stable charging property capable of solving the above problems (a) of charging instability of contact charging and (b) the problem of contamination, and maintaining stable charging property for a long period of time. An object of the present invention is to provide a contact charging member that has high durability and is unlikely to cause contamination.

[0019]

The present invention is a contact charging member characterized by the following constitutions.

(1) A contact charging member which is brought into contact with the surface of the body to be charged and which applies a voltage to charge the surface of the body to be charged,
The contact charging member is a non-rotating body that does not follow the drive of the charged body, and in order from the contact surface side with the charged body, the surface layer, the intermediate resistance layer, the electrode layer to which a voltage is applied, and the electrode supporting layer. Have
A contact charging member, wherein at least a portion of the surface layer that abuts on a member to be charged is provided in a continuous convex shape on the medium resistance layer.

(2) The height of the convex shape of the surface layer is 10 to 5
The contact charging member according to (1), which has a thickness of 00 μm.

(3) The contact charging member as described in (1), wherein two or more convex shapes of the surface layer are in contact with the surface of the charged body when the contact charging member is in contact with the charged body.

(4) The contact charging member according to (1), wherein the volume resistivity R1 of the surface layer is R1> R2 with respect to the volume resistivity R2 of the medium resistance layer.

(5) The dynamic friction coefficient of the surface layer is JIS K
The contact charging member according to (1), which is 0.3 or less in the test method specified in 7125.

(6) The contact charging member according to (1), wherein the surface layer is made of a synthetic resin containing a solid lubricant.

(7) The contact charging member according to (1), wherein the voltage applied to the electrode layer is an oscillating voltage.

(8) The contact charging member according to (7), wherein the oscillating voltage is a superposed voltage of an AC voltage and a DC voltage.

(9) The oscillating voltage is an AC voltage having a peak-to-peak voltage which is more than twice the charging start voltage of the charged body when a DC voltage is applied to the contact charging member in contact with the charged body, and a DC voltage. It is a superimposed voltage of voltage (7)
The contact charging member according to.

(10) The member to be charged is a rotating image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric in an image forming apparatus such as an electrophotographic device or an electrostatic recording device (10) ) The contact charging member as described in the above.

[0030]

In the surface layer of the contact charging member, as in the surface layer 3 of the model diagram of FIG. 4A, at least the portion N in contact with the member to be charged 2 has a continuous convex shape on the medium resistance layer 4. By providing the charging target member 2 and the contact charging member 1 with the contact portion N therebetween, the charging target member 2 is charged by the space discharge α in the gaps on the upstream side and the downstream side in the rotation direction of the charging target member 2 as well as the charging target member 1. A void is also formed in the contact portion N between the body 2 and the contact charging member 1, so that the space is charged by the space discharge β and the charging property is stabilized.

When the surface layer 3 is not formed into a convex shape as shown in FIG. 4B but is formed into a plain layer 3 ′, the charged layer 2 and the contact charging member 1 are contacted with each other in the contact portion N. Does not form a void, and the charging is performed only by the space discharge α in the void on the upstream side and the downstream side in the rotation direction of the body to be charged with the contact portion N in the middle, and the charging area is narrow.

When the surface layer 3 comes into contact with the body to be charged 2, it is necessary that two or more convex portions come into contact with each other. In other words, at least one void portion can be provided in the contact portion N by contacting two or more convex portions of the surface layer 3 with the member to be charged 2.

The height h of the surface layer 3 is 5 to 700 μm, particularly 10 to 500 μm in order to be stably charged by the space discharge β in the gap between the medium resistance layer 4 and the body 2 to be charged. Is necessary. When the height h of the surface layer 3 is 5 μm or less, the medium resistance layer 4 and the charged body 2 are likely to come into direct contact with each other, and the void between the medium resistance layer 4 and the charged body 2 is stabilized. It is disadvantageous because it is difficult to secure the space discharge and the space discharge β may not be performed. Also, the height h of the surface layer 3
Is 700 μm or more, a high applied voltage is required to start the space discharge, and thus there is a risk that the intermediate resistance layer 4 or the member to be charged 2 may cause dielectric breakdown.

Further, the resistance value of the surface layer 3 is preferably higher than that of the medium resistance layer 4. The relationship between the low volume efficiency R1 of the surface layer 3 and the low volume efficiency R2 of the medium resistance layer 4 is R1> R2. In the case of R1 <R2, space discharge is not performed in the gap between the medium resistance layer 3 and the body to be charged 2, and charging is not stable. That is, the charging due to the space discharge between the surface layer 3 and the charged body 2 becomes dominant, and the charging becomes unstable. The same applies when R1 = R2.

Since the surface layer 3 is formed in a convex shape on the medium resistance layer 4, the contact area with the member to be charged 2 becomes smaller than that in the case where the surface layer 3 is formed on the entire surface, and It is also effective to reduce the abrasion of the charged body 2.

The surface layer 3 has a dynamic friction coefficient according to JIS K712.
By setting it to 0.3 or less in the test method stipulated in 5, the inclusion of foreign matter is reduced, the abrasion of the charged body 2, the contamination of the surface layer 3 caused by it, the charging failure, etc. are reduced,
Stable chargeability can be obtained over a long period of time.

[0037]

【Example】

Example A (1) Structure of Contact Charging Member FIG. 1 is a schematic diagram of the layer structure of the contact charging member according to the present invention. It should be noted that this diagram is an exaggerated model diagram for explaining the layer structure, and the relationship of the thickness and the ratio of dimensions between the constituent layers is not accurate.

Reference numeral 2 denotes a member to be charged, which is a rotating drum type photosensitive member in the electrophotographic apparatus in this embodiment. The photoconductor 2 is rotationally driven in the clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed). Reference numeral 2b is a conductive drum base made of aluminum or the like, and 2a is a photosensitive layer formed on the outer peripheral surface of the drum base.

Reference numeral 1 is a contact charging member, which is fixedly supported by a holder (frame of the image forming apparatus) 8, and the holder 8 and the photosensitive member 2 are provided.
Between them and the photoconductor 2 with a predetermined pressing force.

This contact charging member 1 is a laminated body of a surface layer 3, a medium resistance layer 4, an electrode layer 5 and an electrode supporting layer 6 in this order from the side of the photoconductor 2 toward the side of the holder 8 and has a cross section on the photoconductor surface. The shape (cross-sectional shape of the photosensitive member rotating surface) is a non-rotating member (non-driven), and at least the portion (nip region) N where the surface layer 3 contacts the photosensitive member 2 is a continuous convex shape on the medium resistance layer 4. It is provided.

A power supply 7 is applied to the electrode layer 5 of the contact charging member 1.
By applying a predetermined charging bias by a DC application method or an AC application method, the peripheral surface of the rotating photoconductor 2 is charged to a predetermined polarity and potential by contact charging.

A. Surface layer 3 The pattern shape of the surface layer 3 is as shown in (A) and (C) of FIG. 2, a fine line pattern parallel to the rotation axis of the photoconductor 2 that abuts, as shown in (B) and (D). It can be a diagonal line pattern.

As shown in FIG. 4A, with the contact portion N between the photosensitive member 2 and the contact charging member 1 being in the middle, charging by the space discharge α in the gaps on the upstream side and the downstream side of the photosensitive member rotating direction is performed. In addition, in order to stabilize the chargeability by forming a void in the contact portion N between the photoconductor 2 and the contact charging member 1 and performing charging by the space discharge β of the void, the surface layer 3 is It is necessary that two or more protrusions contact each other when contacting with the photoconductor 2. That is, at least two voids are formed in the contact portion N by contacting two or more convex portions of the surface layer 3 with the photoconductor 2.
More than one place can be provided.

As described in the above-mentioned action section, the surface layer 3
Has a height h of 5 to 700 μm in order to stably charge by a space discharge in the gap between the medium resistance layer 4 and the photoreceptor 2.
Particularly, a height of 10 to 500 μm is required.

When the height h of the surface layer 3 is 5 μm or less,
The medium resistance layer 4 and the photoconductor 2 are likely to come into direct contact with each other, it is difficult to stably secure a gap between the medium resistance layer 4 and the photoconductor 2, and space discharge may not be performed. It is a disadvantage. The height h of the surface layer 3 is 700 μm.
In the above, a high applied voltage is required to start the space discharge, and therefore there is a risk that the medium resistance layer 4 or the photoconductor 2 may cause dielectric breakdown.

The surface layer 3 may be formed on the entire surface of the medium resistance layer 4 as shown in FIGS. 2A and 2B.
As in (C) and (D), the surface layer 3 may be provided only in the portion corresponding to the contact portion N between the contact charging member 1 and the photoconductor 2.

Further, the resistance value of the surface layer 3 is preferably higher than that of the medium resistance layer 4. The relationship between the low volume efficiency R1 of the surface layer 3 and the low volume efficiency R2 of the medium resistance layer 4 is R1> R2. In the case of R1 <R2, space discharge is not performed in the gap between the medium resistance layer 3 and the photoconductor 2, and the charging is not stable. That is,
The charging due to the space discharge between the surface layer 3 and the photoconductor 2 becomes dominant, and the charging becomes unstable. The same applies when R1 = R2.

Since the surface layer 3 is formed in a convex shape on the medium resistance layer 4, the contact area with the photoconductor 2 is smaller than that in the case where the surface layer 3 is formed on the entire surface, and the photoconductor is reduced. It is also effective to reduce the abrasion of 2.

The surface layer 3 is composed of, for example, a synthetic resin layer or a synthetic resin layer in which a pigment is dispersed. As the synthetic resin used for the surface layer 3, a synthetic resin such as a polyurethane resin, a polyamide resin, a butyral resin, a polyester resin, a silicone resin or an epoxy resin can be appropriately used. In addition, various pigments such as titanium oxide, zinc oxide, carbon black, calcium carbonate, and aluminum oxide can be appropriately used as the pigment.

The surface layer 3 may be formed by screen printing, offset printing, or the like on the surface of the medium resistance layer 4, which will be described later.
It can be provided with a predetermined line width w, a predetermined height h, and a predetermined pitch p ((B) in FIG. 4) by using a method such as gravure printing or thermal transfer.

When the height h of the surface layer 3 is 100 μm or more, a synthetic resin sheet or a synthetic resin wire material cut into a predetermined shape may be used by bonding.

B. Medium Resistance Layer 4 The medium resistance layer 4 has a volume resistivity R2 so that good charging without a so-called “charge loss” phenomenon is possible when a pinhole is present on the surface of the photoreceptor 2 which is the member to be charged. 1 x 1
It is preferably in the range of 0 ⁷ to 1 × 10 ⁹ Ω · cm. When R2 is lower than 1 × 10 ⁷ Ω · cm, “charge loss” is apt to occur and R2 is 1 × 10 ⁹ Ω · cm. If it exceeds, the applied voltage causes a voltage drop in the intermediate resistance layer 4, and the chargeability of the photoconductor 2 deteriorates, so that the so-called “fog” phenomenon easily occurs.

As the material of the medium resistance layer 4, it is preferable to use a synthetic resin in which a conductive pigment is dispersed. Medium resistance layer 4
Examples of the synthetic resin that can be used for polyurethane resin, polyamide resin, polyester resin, polycarbonate resin, polyvinyl butyral resin, polyethylene resin, ethylene-vinyl acetate copolymer resin, vinyl chloride-
Examples thereof include vinyl acetate copolymer resin.

Examples of the conductive pigment that can be used in the medium resistance layer 4 include carbon black, carbon graphite, zinc oxide, titanium oxide, tin oxide, tin oxide-coated titanium oxide, tin oxide-coated potassium titanate and the like. ..

For the medium resistance layer 4, a material such as a conductive paint, a conductive ink, a conductive film or a conductive sheet in which the above conductive pigment is dispersed in the above synthetic resin according to the resistance value is used. it can. Among these, it is more preferable to use a conductive sheet and a conductive film that can have a uniform thickness.

C. Electrode Layer 5 The electrode layer 5 preferably has a uniform thickness and a low electric resistance in order to uniformly conduct a voltage applied from the power source 7 to the medium resistance layer 4. For this reason, the electrode layer 5 includes a metal foil such as aluminum, nickel, iron, copper, silver, tin, and stainless steel, a metal vapor deposition film, or a conductive pigment such as carbon black, carbon graphite, silver, copper, and nickel in a synthetic resin. Materials such as a conductive paint, a conductive ink, a conductive sheet, and a conductive film dispersed in can be used.

D. Electrode Supporting Layer 6 The electrode supporting layer 6 is preferably made of a material having a hardness defined by SRIS 0101 in the range of 5 ° to 75 °. This is a characteristic required to bring the contact charging member 1 into uniform contact with the surface of the photoconductor 2. SRIS
When the hardness specified by 0101 is lower than 5 °,
The electrode supporting layer 5 is not preferable because so-called "fatigue" occurs.

When the hardness exceeds 75 degrees, the shape of the photoconductor, for example, the curvature cannot be followed and it becomes difficult to secure the contact portion N. In this case, increasing the contact pressure in order to secure the contact portion N promotes abrasion of the surfaces of the surface layer 3 and the photoconductor 2, which is not preferable.

As a material which can be used for the electrode supporting layer 6,
It is possible to appropriately use polyurethane resin, vinyl chloride resin, polypropylene resin, polyethylene resin, synthetic resin such as ethylene-vinyl acetate copolymer resin, rubber such as urethane rubber, silicone rubber, chloroprene rubber and natural rubber, or foams thereof. it can.

E. Method for Manufacturing Contact Charging Member 1 An example of a method for manufacturing the contact charging member 1 will be described. First, the electrode layer 5 is formed on the medium resistance layer 4. When a conductive paint or conductive ink is used as the medium resistance layer 4, the material of the electrode layer 5 is coated on one side of a metal foil or a metal vapor deposition film. As a coating method, a method such as spray coating, roll coating, flow coating, blade coating, gravure printing, or screen printing can be used.

When a conductive sheet or a conductive film is used for the medium resistance layer 4, the electrode layer 5 is formed on one surface of the medium resistance layer 4.
A conductive sheet or a conductive film made of the above material is laminated with a conductive adhesive, or a conductive paint or a conductive ink is coated as the electrode layer 5. The coating method is
The same method as for the medium resistance layer 4 can be used.

Then, the surface layer 3 is provided in a predetermined shape on the surface of the intermediate resistance layer 4 opposite to the electrode layer forming side. As the method of forming the surface layer 3, the method described above can be used.

Next, the electrode support layer 6 is adhesively laminated on the side opposite to the medium resistance layer of the electrode layer 5 with an adhesive or pressure-sensitive adhesive.

F. Power supply 7 The power supply 7 is a power supply applied to the contact charging member 1, and for the electrode layer 5 of the contact charging member 1, for example, a DC voltage (DC application method) according to a predetermined potential of the photoconductor 2 or charging uniformity. In order to obtain the above, a bias (AC application method) in which an alternating electric field having a peak-to-peak voltage that is at least twice the discharge start voltage determined between the contact charging member 1 and the photoconductor 2 and the above DC voltage are superimposed is supplied. Then, power is supplied to the intermediate resistance layer 4 through the electrode layer 5, and an electric field is generated in the gap between the intermediate resistance layer 4 and the photoconductor 2 to uniformly charge the surface of the photoconductor to a predetermined polarity and a predetermined potential.

(2) Example of image forming apparatus FIG. 3 is a schematic configuration diagram of an example of an image forming apparatus using the contact charging member according to the present invention. The image forming apparatus of this example is a copying machine or printer using a transfer type electrophotographic process.

Reference numeral 2 is the above-mentioned rotary photosensitive member (OPC photosensitive drum), and 1 is the above-mentioned contact charging member arranged in contact therewith. A charging bias is applied to the electrode layer 5 of this charging member 1 from the power source 7. Thus, the peripheral surface of the rotating photoconductor 2 is subjected to the primary charging process.

Exposure of a target image to the charging surface of the rotary photoconductor 2 by an image forming information exposure device (not shown) L
(Slit imaging exposure of the original image, laser beam scanning exposure, etc.) is performed to form an electrostatic latent image of the target image.

The latent image is developed as a toner image by the developing device 9, and the toner image is transferred from a paper feeding portion (not shown) to the pressure contact nip portion (transfer portion) between the photoconductor 2 and the transfer roller 10 at a predetermined timing. The images are sequentially transferred to the transferred transfer material 13.

The transfer material 13 to which the toner image has been transferred is separated from the surface of the photoconductor 2 and conveyed to the fixing device 11, where it is subjected to the toner image fixing and output as an image-formed product. The surface of the rotating photoconductor 2 after the transfer material is separated is cleaned by a cleaning device 12 after removing residual adhered substances such as transfer residual toner, and is repeatedly used for image formation.

The image forming apparatus according to the present embodiment includes the photosensitive member 2
The four process devices of the contact charging member 1, the developing device 9, and the cleaning device 12 are incorporated into the process cartridge housing 14 in a predetermined positional relationship, so that the cartridge can be attached and detached to and from the main body of the image forming apparatus at once.

(3) Example 1 As the medium resistance layer 4 of the contact charging member 1, T-die extrusion was carried out using a thermoplastic polyurethane resin (trade name: Rezamin EC-530, manufactured by Dainichiseika Kogyo Co., Ltd.) in which carbon black was dispersed. A sheet (thickness 500 μm) produced by the method was used.

The volume resistivity R2 of the medium resistance layer 4 is JI
2.5 × 10 when measured according to SK6911
^The value was ⁸ Ω · cm (10 V applied, 1 minute value).

On one surface of the medium resistance layer 4, the electrode layer 5 was formed on the entire surface by a screen printing method using a conductive ink of the following formulation in which carbon black was dispersed in a two-component curing type urethane resin.

Formulation of conductive ink Main component conductive carbon black 30 parts by weight Urethane polyol 30 parts by weight Vinyl chloride-vinyl acetate copolymer resin 6 parts by weight Additive 2 parts by weight Ketone-based solvent 40 parts by weight Aromatic hydrocarbon-based solvent 20 parts by weight Cellosolve-based solvent 10 parts by weight Ester-based solvent 10 parts by weight Curing agent Aliphatic diisocyanate 70 parts by weight Ester-based solvent 30 parts by weight The above main agent and the curing agent are mixed at a weight ratio of 100: 5 and screen-printed. After performing drying (drying condition: 80 ° C., 20 minutes), an electrode layer 5 (thickness 20 μm) was obtained.

Then, the surface layer 3 was formed on the side of the intermediate resistance layer 4 opposite to the electrode layer by a urethane resin screen ink (trade name SG
410 white, manufactured by Seiko Advance Co., Ltd., and printed in the form of the parallel line pattern of FIG.

After drying (drying condition 80 ° C., 20 minutes), height h35 μm, line width w0.3 mm, pitch p0.3 mm
Surface layer 3 of was obtained.

The volume resistivity R1 of the surface layer unit is 100 × 100 mm on an aluminum sheet (thickness 100 μm).
When screen-printed with □ and measured according to JIS K6911, it was found to be 7.2 × 10 ¹² Ω · cm (10 V applied,
1 minute value).

Then, a foamed urethane resin sheet (SRIS hardness 5) was formed as an electrode support layer 6 on the side opposite to the medium resistance layer of the electrode layer 5.
0 ° thickness 4 mm) was attached with a double-sided adhesive tape.

The contact charging member 1 produced by the above method was evaluated by the following method.

As shown in FIG. 3, the contact position with the photosensitive member 2 is at the center of the charging member 1 at the primary charging position of the cartridge used for the laser beam printer (trade name: Laser Shot A408, manufactured by Canon Inc.), and It was attached so that the contact surface with 2 was parallel to the tangent line of the contact surface (contact pressure 10 g / cm, width of the contact portion N was 2.5 mm).

Then, this cartridge is attached to the printer body to output an image, and the output image is set to the initial and 300
Visual evaluation was made after 0 sheets were run. The durability evaluation conditions are as follows.

(Durability Evaluation Conditions) Process Speed 48 mm / s Photoconductor (drum) Diameter φ30 mm Applied Bias for Electrode Layer 5 DC + AC DC Voltage 700V AC Voltage 1.8KV Frequency 350Hz (Evaluation of potential convergence) Photoconductor as charging property The convergence of the surface potential on the drum was evaluated. That is, after removing the charge on the surface of the photoconductor, the bias is applied to continuously charge the photoconductor,
The surface potential of the photoconductor is measured by a surface electrometer (trade name: TREC Mo
del 344, manufactured by Trek Japan). The difference between the surface potentials of the first and fifth rounds of the photosensitive member was taken as the convergence property.

◎ Surface potential difference is within 5 V ◯ Surface potential difference is within 6 V to 10 V Δ Surface potential difference is within 11 V to 20 V × Surface potential difference is 21 V or above The results are shown in [Table 1].

(4) Example 2 The surface layer 3 was formed in the same manner as in Example 1 in the form of the diagonal line pattern of FIG. 2B (height h 40 μm, line width w).
0.3 mm, pitch p 0.5 mm, angle of oblique line to long side 45 °). A contact charging member 1 having the same structure as in Example 1 except for the surface layer 3 was prepared.

In the same manner as in Example 1, the initial image quality, durability evaluation, and potential convergence were evaluated. The results are shown in [Table 1].

(5) Example 3 A polyamide sheet (300 μm) cut to a width w of 0.5 mm was adhered onto the medium resistance layer 4 similar to that of Example 1 with a urethane adhesive to obtain the structure shown in FIG. 2 (A). The surface layer 3 was formed in the form of a parallel line pattern (height h350 μm, line width w0.5 mm, pitch p0.5 mm). This surface layer 3
Other than the above, the contact charging member 1 has the same structure as that of the first embodiment.
Was produced.

In the same manner as in Example 1, the initial image quality, durability evaluation, and potential convergence were evaluated. The results are shown in [Table 1].

(6) Comparative Example 1 The surface layer 3a was formed in the same manner as in Example 1 as shown in FIG.
In the form of a line width pattern of (height h30μ
m, line width w 2.5 mm ). A contact charging member 1A having the same structure as that of Example 1 except for the surface layer 3a was manufactured.

In the same manner as in Example 1, the initial image quality, durability evaluation, and potential convergence were evaluated. The results are shown in [Table 1].

(7) Comparative Example 2 A surface layer having a parallel line pattern in FIG. 2A was formed by the same method as in Example 1 ( height h35 μm).
m 2 , line width w 0.3 mm, pitch p 0.3 mm). A contact charging member having the same structure as in Example 1 except for the surface layer was prepared.

In the same manner as in Example 1, the initial image quality, durability evaluation, and potential convergence were evaluated. The results are shown in [Table 1].

(8) Comparative Example 3 On the medium resistance layer 4 similar to that of Example 1, the line width w as a surface layer was used.
Polyamide sheet cut to 0.5 mm (thickness 700μ
2) by bonding m) with a urethane adhesive.
The parallel line pattern of (A) was formed ( height
h750 μm , line width w0.5 mm, pitch p0.5 m
m). A contact charging member having the same structure as in Example 1 except for the surface layer was prepared.

In the same manner as in Example 1, initial image quality, durability evaluation, and potential convergence were evaluated. The results are shown in [Table 1].

(9) Comparative Example 4 The same parallel line pattern as in Example 1 (((2) in FIG. 2) was used for the surface layer using a screen ink having the following formulation in which conductive titanium oxide was dispersed in a two-component curing type urethane resin. A)) was formed on the medium resistance layer 4 (height h33 μm, line width w0.3 mm, pitch p0.3 mm).

Formulation of Screen Ink Used as Surface Layer Main component Tin oxide coating titanium oxide 85 parts by weight Urethane polyol 50 parts by weight Vinyl chloride-vinyl acetate copolymer resin 5 parts by weight Additive 5 parts by weight Ketone solvent 40 parts by weight Aroma Group hydrocarbon-based solvent 20 parts by weight Cellosolve-based solvent 10 parts by weight Ester-based solvent 10 parts by weight Curing agent Aliphatic diisocyanate 70 parts by weight Ester-based solvent 30 parts by weight The above main agent and curing agent are mixed at a weight ratio of 100: 5. After that, screen printing was performed, and after drying (drying condition: 80 °, 20 minutes), a surface layer was obtained. A contact charging member having the same configuration as in Example 1 except for this surface layer was produced.

In the same manner as in Example 1, the initial image quality, durability evaluation, and potential convergence were evaluated. The results are shown in [Table 1].

[0097]

[Table 1] Fogging on the whole surface --- Charge failure due to insufficient potential Black streaks --- Charge failure due to abrasion of photosensitive drum Contact-charging member 1 of Examples 1 to 3 comes into contact with photoreceptor 2 by patterning surface layer 3. As shown in (A) of FIG. 4, the space N in the contact portion N also stabilizes the charging due to the space discharge β. Further, the height h of the surface layer 3 can ensure a uniform distance between the photoconductor 1 and the medium resistance layer 4.

<Embodiment B> In order to prevent or reduce the abrasion of the photoconductor due to the sliding of the photoconductor 2 and the contact charging member 1, the dynamic friction coefficient μ _K of the surface layer 3 of the contact charging member 1 is set to 0.
It should be 3 or less. When the dynamic friction coefficient μ _K is 0.5 or more, the photoconductor is often scraped, and there is a risk of defective charging due to it.

Therefore, in this embodiment, as the surface layer 3 of the contact charging member 1, a synthetic resin layer or a synthetic resin layer in which a solid lubricant is dispersed is used. As the synthetic resin used for the surface layer 3, for example, a synthetic resin such as a polyurethane resin, a polyamide resin, a polyvinyl butyral resin, a polyester resin, a silicone resin or an epoxy resin can be appropriately used.

Further, as a lubricant for improving the slipperiness of the surface layer 3, molybdenum disulfide, tungsten disulfide, ethylene tetrafluoride resin, perfluoro-alkoxy resin, propylene hexafluoride copolymer resin, tetrafluoride are used. Ethylene-ethylene copolymer resin, vinylidene fluoride resin, trifluoroethylene chloride resin, low molecular weight tetrafluoroethylene resin, tetrafluoroethylene-hexafluoroethylene propylene copolymer resin, various lubricants such as graphite fluoride It can be used as appropriate.

The dynamic friction coefficient when the surface layer 3 is formed by the method as described in <Example A> -a, is prepared by dispersing the above lubricants in the above synthetic resin to form a coating material. In the test method specified in JIS K7125, it is preferably 0.3 or less.

(1) Example 4 The surface layer 3 was formed by using the screen ink for forming the surface layer in Example 1 having the following formulation in which molybdenum disulfide (solid lubricant) was distributed and dispersed. A contact charging member 1 was produced in the same manner as in Example 1 except for the other layer constitution, layer materials, dimensions, manufacturing method and the like.

Formulation of Screen Ink for Forming Surface Layer Main Agent Molybdenum Disulfide 70 parts by weight 70 parts by weight (average particle size 0.6 μm) Urethane polyol 50 parts by weight Vinyl chloride-vinyl acetate copolymer resin 5 parts by weight Additive 5 Parts by weight ketone solvent 40 parts by weight aromatic hydrocarbon solvent 20 parts by weight cellosolve solvent 10 parts by weight ester solvent 10 parts by weight curing agent aliphatic diisocyanate 70 parts by weight ester solvent 30 parts by weight The above main agent and curing agent Were mixed in a weight ratio of 100: 5 to form a surface layer 3 by screen printing.

The dynamic friction coefficient of the surface layer alone is defined as μ _K in JIS
It was measured according to K7125. That is, a sample in which a parallel line pattern was formed by screen printing on an aluminum sheet (thickness 100 μm) was used for the measurement. Sliding piece (load 200
A long wool felt (thickness: 2 mm) was attached to one surface of g), and the friction coefficient μ _K was measured by sliding the felt on the surface layer at a speed of 100 mm / min. Tensile tester (trade name "Tensilon RTM-250", Orientec Co., Ltd.)
Manufactured) was used.

This contact charging member 1 was mounted on a laser beam printer in the same manner as in Example 1, and an image was output under the same durability evaluation conditions as in Example 1, and the output image was initial and 300.
Visual evaluation was made after 0 sheets were run.

Before and after the durability evaluation, the amount of abrasion of the photoconductor (photosensitive drum surface layer; polycarbonate resin) was measured by an electromagnetic film thickness meter (trade name: Kett VL-30B, manufactured by HELMUT FISHER).

[Table 2] shows the coefficient of dynamic friction of the contact charging member, the amount of abrasion of the photoconductor, and the result of durability evaluation. (2) Example 5 Polytetrafluoroethylene resin powder (average particle size 0.3 μm, solid lubricant) as a screen ink for forming a surface layer
The surface layer 3 was formed in the form of the diagonal line pattern of FIG. 2B by the same method as in Example 1 using a urethane resin-based screen ink having the following formulation, in which titanium oxide (solid lubricant) was dispersed. Height h 40 μm, line width w 0.3 mm, pitch p 0.5 mm, angle of oblique line to long side 45 °).

Formulation of screen ink for forming surface layer Main agent Polytetrafluoroethylene resin powder 30 parts by weight (average particle size 0.6 μm) Titanium oxide 20 parts by weight Urethane polyol 50 parts by weight Vinyl chloride-vinyl acetate copolymer resin 5 Parts by weight additives 5 parts by weight ketone solvent 40 parts by weight aromatic hydrocarbon solvent 20 parts by weight cellosolve solvent 10 parts by weight ester solvent 10 parts by weight curing agent aliphatic diisocyanate 70 parts by weight ester solvent 30 parts by weight above The main component and the curing agent were mixed in a weight ratio of 100: 5 to form the surface layer 3 by screen printing.

A contact charging member 1 having the same structure as in Example 1 except for the surface layer 3 was prepared. In the same manner as in Example 4, the dynamic friction coefficient of each surface layer, the abrasion amount of the photoconductor, and the durability evaluation were performed. The results are shown in [Table 2].

(3) Example 6 A polyamide sheet (nylon 12; thickness 300 μm) obtained by cutting the surface layer 3 to have a line width w of 0.5 mm was adhered onto the medium resistance layer 4 by using a urethane type adhesive, and thus FIG. (A) in the form of a parallel line pattern (height h35
0 μm, line width w 0.5 mm, pitch p 0.5 mm).

A contact charging member 1 having the same structure as in Example 1 except for the surface layer 3 was prepared. In the same manner as in Example 4, the dynamic friction coefficient, the abrasion loss of the photoconductor, and the durability evaluation were performed. The results are shown in [Table 2].

(4) Comparative Example 5 A vinyl resin screen ink (trade name G) was used as the surface layer.
S700, manufactured by Seiko Advance Co., Ltd.) was used to form a parallel line pattern in FIG. 2A (height h30 μm, line width w0.3 m) in the same manner as in Example 1.
m, pitch p 0.3 mm). The structure other than this surface layer is
A contact charging member having the same structure as in Example 1 was produced.

In the same manner as in Example 4, the dynamic friction coefficient, the abrasion amount of the photosensitive member were measured, and the durability was evaluated. The results are shown in [Table 2].

(5) Comparative Example 6 As a surface layer, a soft polyvinyl chloride sheet (thickness: 200 μm) cut to have a line width w of 0.5 mm was adhered onto the medium resistance layer 4 by using a urethane type adhesive. (A) A surface layer in the form of a parallel line pattern was formed (height h 240 μm, line width w 0.5 mm, pitch p 0.5 m).
m).

A contact charging member having the same structure as the surface layer of Example 1 was prepared.

In the same manner as in Example 4, the dynamic friction coefficient, the abrasion amount of the photoconductor, and the durability evaluation were performed. The results are shown in [Table 2].

[0117]

[Table 2] The contact charging member 1 of Examples 4 to 6 has a space discharge due to the presence of voids also in the contact portion N with the photoconductor 2 due to the patterning of the surface layer 3 as in the case of Examples 1 to 3 above. β
((A) of FIG. 4) In addition to stabilizing the charging,
Since the coefficient of kinetic friction of the surface layer 3 is 0.3 or less, the inclusion of foreign matter is reduced, the abrasion of the photoconductor, the contamination of the surface layer due to it, the charging failure and the like are reduced, and a stable image can be obtained for a long time.

[0118]

As described above, according to the present invention, in the contact charging, the problem of the charging instability due to the narrow charging area and the problem of the contamination of the charging member can be solved. It is possible to obtain a charging member, a contact charging member which is capable of maintaining stable charging properties for a long period of time, has high durability, and is unlikely to cause contamination.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a layer structure of a contact charging member according to the present invention.

2A to 2E are plan views of a pattern side of a surface layer, respectively.

3 is a schematic configuration diagram of an example of an image forming apparatus in which the contact charging member of FIG. 1 is mounted.

4A and 4B are schematic model diagrams of a space discharge gap between a photoconductor and a contact charging member.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 General reference numeral of contact charging member 2 Rotating photosensitive member (charged member) 3 Surface layer 4 Medium resistance layer 5 Electrode layer 6 Electrode support 7 Power supply 8 Contact charging member holder 9 Developing device 10 Transfer roller 11 Fixing device 12 Cleaning device 13 Transfer material 14 Process cartridge housing L Exposure light α / β space discharge part

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Masato Yoshioka 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (10)

[Claims] 1. A contact charging member which is brought into contact with a surface of an object to be charged and which applies a voltage to charge the surface of the object to be charged, wherein the contact charging member is a non-rotating body which is not driven by the driving of the object to be charged. A surface layer, a medium resistance layer, an electrode layer to which a voltage is applied, and an electrode supporting layer, in order from the contact surface side with the member to be charged,
A contact charging member, wherein at least a portion of the surface layer that abuts on a member to be charged is provided in a continuous convex shape on the medium resistance layer. 2. The height of the convex shape of the surface layer is 10 to 500.
The contact charging member according to claim 1, wherein the contact charging member has a thickness of μm. 3. The contact charging member according to claim 1, wherein in the contact state of the contact charging member with the charged body, two or more convex shapes of the surface layer contact the surface of the charged body. 4. The contact charging member according to claim 1, wherein the volume resistivity R1 of the surface layer is R1> R2 with respect to the volume resistivity R2 of the medium resistance layer. 5. The dynamic friction coefficient of the surface layer is JIS K71.
The contact charging member according to claim 1, wherein the contact charging member has a value of 0.3 or less in the test method specified in 25. 6. The contact charging member according to claim 1, wherein the surface layer is made of a synthetic resin containing a solid lubricant. 7. The contact charging member according to claim 1, wherein the voltage applied to the electrode layer is an oscillating voltage. 8. The contact charging member according to claim 7, wherein the vibration voltage is a superimposed voltage of an AC voltage and a DC voltage. 9. An AC voltage whose oscillating voltage has a peak-to-peak voltage that is at least twice the charging start voltage of the charged body when a DC voltage is applied to the contact charging member that is in contact with the charged body,
The contact charging member according to claim 7, which is a superimposed voltage of a DC voltage. 10. The member to be charged is a rotating image carrier such as an electrophotographic photosensitive member or an electrostatic recording dielectric in an image forming apparatus such as an electrophotographic device or an electrostatic recording device. The contact charging member according to.