JPH03217874A - Contact charging member - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a contact charging member.

(Prior Art) For example, as a means for uniformly charging the surface of an image bearing member such as a photoreceptor or dielectric material as a charged member in an image forming apparatus such as a copying machine or a recording device, a method having good uniform charging properties is used. Corona dischargers such as corotrons and scorotrons are widely used.

However, corona dischargers require expensive high-voltage power supplies.
It requires space for itself and a shield space for the high-voltage power supply, and it often generates corona products such as ozone, which requires additional means and mechanisms to deal with them, which makes the device larger and more expensive. There are problems such as the factors being equal.

Therefore, in recent years, consideration has been given to adopting a contact charging method instead of a corona discharger, which has many problems.

In contact charging, an image is supported by contacting a contact charging member to which a voltage (for example, DC voltage of about 1 to 2 KV, or a superimposed voltage of DC voltage and AC voltage) is applied from a power source to the surface of an image carrier as a charged object. A device that charges the body surface to a predetermined potential. Roller charging type (JP-A-56-91253), blade charging type (JP-A-56-194349, JP-A-60-147756), charging/cleaning combination. Formula (Japanese Unexamined Patent Publication No. 5,616,5166) and the like have been devised.

However, one of the problems with this contact charging method is that if the image carrier such as a photoreceptor has a pinhole (a surface defect on the charged body), the charging of the surface of the image carrier may cause the image to become electrified. Spark discharge is likely to occur between the contact charging member that is in contact with the surface of the carrier and a voltage is applied to the via hole portion of the image carrier, and when such a discharge occurs, spark discharge occurs not only in the via hole portion but also on the image carrier surface. It is easy to see the so-called "charge leakage" phenomenon (charge leakage phenomenon) in which the charged charge is not applied over the entire charging area of the contact charging member including the via hole portion.

FIGS. 6(A) and 6(B) are explanatory model diagrams of this charge loss phenomenon. In FIG. 6(A), 1 is a photoreceptor as an image carrier (charged member) that moves in the direction of the arrow; 2 is a via hole portion existing in the photoreceptor 1, and 2 is a contact charging member (hereinafter referred to as a charging blade) in the form of a plate that is brought into contact with the photoreceptor surface in a voltage applied state to charge the surface of the photoreceptor 1. .

The figure (B) is an equivalent circuit of the figure (A).

The hole part P of the photoreceptor 1 has a lower resistance than other parts of the photoreceptor, so when it comes into contact with the charging blade 2 or the surface of the charging blade approaches, a spark discharge occurs between the charging blade 2 and the charging blade 2. When discharge S occurs, the potential VAvB applied to each part on the photoconductor in the longitudinal direction of the photoconductor (direction of the contact line between the photoconductor and the charging plate)
. . . v2 is approximately Ov in both cases, and no charge is applied to the surface of the photoreceptor 1 over the entire contact charging area with the charging blade 2, including the hole portion P.

Therefore, if a charge missing area as described above occurs during the charging process on one side of the photoreceptor, the image area corresponding to the charge missing area in the output image will be white in the case of regular development, and black in the case of reverse development. It falls out and the quality deteriorates.

Bottles P are likely to occur during manufacturing of an image bearing member (charged member) such as a photoreceptor, due to scratching, or due to electrical breakdown, and it is quite difficult to eliminate them.

(Problems to be Solved by the Invention) As a measure to prevent this charge leakage, it is necessary to increase the electrical resistance of the charging blade material. However, in order to press the charging blade 2 with appropriate pressure using rubber elasticity, the distance III (
The free length of the blade is required to be considerably larger than the thickness of the blade, and if power is supplied to the blade from the blade support member, the potential at the portion in contact with the charged object will drop. For this reason, the charging plate required a back electrode, but there was no convenient means for manufacturing it.

In view of the above, an object of the present invention is to rationally form a back electrode on a blade-shaped contact charging member.

(Means for Solving the Problems) The present invention provides a contact charging member that comes into contact with an object to be charged and applies a potential to the object, the contact charging member having a blade shape, and a charging blade. This is a contact charging member characterized in that an electrode layer is formed on a surface of the charging blade opposite to a surface in contact with a charged object after being bonded to a support member.

The present invention also provides a contact charging member, characterized in that after forming the electrode layer, the charging plate is cut into a predetermined size, and in the contact charging member, the width of the contact charging member>the width of the electrode layer. .

(Function) That is, in the present invention, by forming an electrode layer on the blade after integrating a blade support member and a charging plate which is a contact charging member, a stable electrode can be formed with high precision.
Is it possible to abbreviate the pattern? (Example) (1) Example of an image forming apparatus (Fig. 2) Fig. 2 shows an example of an image forming apparatus incorporated as a charging processing means for an image carrier, which is a contact charging device using a contact charging member according to the present invention. FIG. 2 is a schematic configuration diagram of main parts.

Reference numeral 1 denotes a rotating drum-type electrophotographic organic photoreceptor (hereinafter referred to as a photosensitive drum) as an image carrier, which is rotated clockwise as indicated by arrow A at a predetermined circumferential speed (process speed).

During its rotation, the photosensitive drum 1 is uniformly charged to a predetermined polarity and a predetermined potential by a charging blade 2 as a contact charging member of a contact charging device to be described later.

Next, the charged surface is exposed to the desired image information L (exposure using an analog optical system that image-forms and exposes the original image, scanning exposure using a digital optical system including a laser beam scanner, LED array, etc.) in an exposure section. By receiving the electrostatic latent image, an electrostatic latent image corresponding to the desired image information is formed.

The formed latent image is then normally or reversely developed by the developing device 7.

On the other hand, the transfer member Pa is fed from a paper feeding mechanism (not shown),
A sheet is fed between the photosensitive drum 1 and the transfer means 8 (for example, a transfer roller, a corona charger, etc.) (transfer section) at a predetermined timing by the registration roller 10, and the photosensitive drum is The formed images on the first side are sequentially transferred.

The transfer member Pa that has passed through the transfer section is separated from the surface of the photosensitive drum 1, and is introduced into a fixing device (not shown) by the conveyance means 11, where the image is fixed.

After the transfer, the surface of the photosensitive drum 1 is cleaned by a cleaning device 9 to remove residual unnecessary matter, and is repeatedly used for image formation.

The image forming apparatus of this example includes a photosensitive tram 1 and a charging blade 2.
- The four process devices, the developing device 7 and the cleaning device 9, are assembled into a process cartridge 6 in a predetermined positional relationship with each other. It can be inserted and mounted in a direction perpendicular to the drawing along 12, and conversely, it can be freely removed from the image forming apparatus main body.

By fully inserting and mounting the process cartridge 6 into the image forming apparatus main body, the apparatus main body side and the process cartridge 6 side are mechanically and electrically coupled to each other, and the image forming apparatus becomes operable.

(2) Contact Charging Device FIG. 1 is a model diagram of the contact charging device portion of the image forming apparatus shown in FIG. 2 above.

The charging plate 2 as a contact charging member has, for example, 10
It is a rubber blade with a thickness of 1 to 2n+m made of Hitlin, EPDM, urethane, etc. whose resistance is controlled to about 7 to 109 Ωcm, and the blade base side is integrally attached to a conductive rigid support member 4 such as a steel plate with adhesive or the like. Alternatively, the blade material is injected into a mold and the blade and support member are integrally molded and held, and the free length of the blade is l (the distance between the tip of the blade support member and the part where the blade contacts the photosensitive tram). is about 5 to 15ffIII1, and the contact angle θ to the photosensitive drum 1 (the line downstream of the blade contact point in the direction of drum surface movement among the contact lines between the plate tip and the drum at the point where the blade is in contact with the drum) The angle formed by
cm, and the tip of the blade is brought into contact with the rotation of the photosensitive drum 1 in a counter direction (the contact angle is acute). The charging blade 2 can also contact the photosensitive drum 1 in the forward direction (the contact angle is obtuse) with respect to the rotation of the drum 1.

A back electrode 3 is formed on the surface of the charging blade 2 opposite to the contact surface with the photosensitive drum 1 (on the back side of the blade) by printing a conductive paint, and a conductive material that supports the back electrode 3 and the blade 2 is formed by printing a conductive paint. It is electrically connected to the rigid support member 4.

Reference numeral 5 denotes a power source for applying voltage to the charging blade 2, and this power source 5 applies a DC voltage corresponding to the required potential of the photosensitive tram 1 to the conductive rigid support member 4 of the charging blade 2, for example.
voltage, or a bias in which the DC voltage is superimposed with an alternating electric field having a peak-to-peak voltage that is at least twice the discharge starting voltage (VK) determined by the charging blade and the photosensitive drum in order to obtain charging uniformity. Then, power is supplied to the charging blade 2 through the path of the support member 4 and the back electrode 3 that is electrically connected to the support member, and an electric field is generated at the contact portion between the charging blade 2 and the photosensitive drum 1, so that the photosensitive drum One surface is uniformly charged to a predetermined polarity and a predetermined potential.

(3) Configuration outline of charging plate 2 In FIG. 3(A), the rubber blade 2 serving as the base of the charging blade is the size of two charging blades of a predetermined size, and its longitudinal central axis C-C By cutting along the boundary, two charged blade bases of a predetermined size are produced.

Then, electrically conductive rigid support members 4 are integrally bonded symmetrically to both left and right sides of the rubber plate 2 having the size of the two rubber plates 2 using an adhesive or the like.

After cutting, the back electrode layer 3 is printed with conductive paint on the back side of the rubber blade 2, which is the size of two pieces, in a substantially cross-shaped pattern area indicated by diagonal lines symmetrically with respect to the central longitudinal axis C-C. Patterns are formed through processing. In this case, a part of the back electrode layer 3 is formed on the left and right pre-attached support members 4 by extending with respect to the respective surfaces.
4 and the electrode layer 3 are electrically conductive. After this printing process, the rubber blade 2 of the size of the two sheets is cut and divided into two along the longitudinal central axis MC-C as a border.
Two charged blades are obtained.

By using the post-cutting method as described above, the cut surface C1 has a good finish and can be formed without the electrode layer material flowing into the charged object contacting portion of the plate.

The back electrode layer 3 does not need to be formed on the entire back surface of the blade, and is formed on the tip side of the plate 2 in contact with the charged object 1, as in the approximately T-shaped pattern of this example (the pattern after cutting C-C). It is sufficient to have a blade back surface portion corresponding to the portion, and a connecting portion that connects that portion with the support member 4, which is the power supply side.

When an electrode layer 3I is coated on the back surface of the rubber blade 2 after the bond is cut as shown in FIG. 3(C), the coated electrode layer material wraps around near the abutting portion as shown at 32, resulting in
In some cases, this may actually cause a leak.

In the case of FIG. 3 above, even if the electrode layer 3 is formed on the back surface of the blade 2 by printing with a high degree of machining, as shown in 33 in FIG. 4(B), one or both of the left and right sides of the blade 2 In some cases, the electrode layer material wraps around the end surface of the electrode layer material 33 and flows out.
The presence of may cause a new charge leak, so
As a countermeasure against this, it is also effective to pattern the electrode layer 3 in advance so that the relationship is as follows: charging plate width T2>electrode layer width T, as shown in FIG. 4(A).

Alternatively, as shown in FIG. 5(A), after extending the width of the blade 2 by α and α on both the left and right ends, attaching the supporting members 4, 4 to the blade, and forming the back electrode 3. , cut the blade 2 into two parts C-C at the center, and
Cut the left and right extra width α・α of blade 2 U, −U,,
By removing U2U2L/, the finishing accuracy of the left and right end surfaces of the plate 2 can be improved as shown in FIG. 5(B), and the charge leakage trouble caused by the inflow of the electrode layer material into the left and right end surfaces can be eliminated.

The back electrode pattern 3 in the example of FIG. 5 is a substantially U-shaped pattern with a portion along the front edge of the plate and a portion along the left and right sides on the back of the plate.

The electrode layer 3 may be a full-surface electrode layer on the back side of the blade. For example, the electrode layer 3 may be coated on the entire back surface of the blade by spray coating, and then the cutting process described above may be performed. Furthermore, if you have two chamfers, you can cut along the C-C line in the center of both.

Note that although the rubber blade has been described above, the substrate of the charging blade may be a sheet material or a film material, and the preparation and configuration of the back electrode layer 3 are the same.

(Effects of the Invention) As described above, the present invention forms an accurate and stable electrode by forming an electrode layer on the charging blade as a contact charging member after integrating the charging blade with a supporting member. The pattern can be omitted, and the bonding force can be stabilized over a long period of time.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a charging blade portion of a contact charging device. FIG. 2 is a schematic diagram of an example of an image forming apparatus incorporating a contact charging device using a charging blade. Figure 3 (A) is an explanatory diagram of the procedure for making a charged blade, and Figure 3 (B)
) is an enlarged view of the cutting tip of the charged blade, and (C) is an enlarged view of the cutting tip of the charged blade.
2 is a diagram showing a state in which the material of the coated electrode layer wraps around the end surface of the cutting tip of the plate. FIG. 4(A) is an explanatory diagram of another example of the structure of the charging blade, and FIG. 4(B) is a diagram showing a state in which the electrode layer material wraps around the side end portion of the plate. FIGS. 5(A) and 5(B) are explanatory diagrams of still another example of the configuration of the charging plate. Figure 6 (A) is an explanatory model diagram of the charge loss phenomenon, and Figure 6 (B)
) is its equivalent circuit. Reference numeral 1 denotes an image carrier (photosensitive drum) as an object to be charged, 2 a charging blade as a contact charging member, 3 a back electrode, 4 a conductive rigid support member, and 5 a bias power source.

Claims (3)

[Claims] (1) A contact charging member that applies a potential to the charged object by coming into contact with the charged object, the contact charging member having a blade shape, and the charging blade being covered with the charging blade after the charging blade is joined to the support member. A contact charging member characterized in that an electrode layer is formed on a surface opposite to a surface in contact with a charged body. (2) The contact charging member according to claim 1, wherein the charging blade is cut into a predetermined size after forming the electrode layer. (3) The contact charging member according to claim 1, wherein the width of the contact charging member is greater than the width of the electrode layer.