JPH03217873A - Contact electrifying member - Google Patents

Abstract

PURPOSE:To omit patterns and to form stable electrodes with good accuracy by specifying the size relation between images and electrode layers concerning the width of an electrifying blade and forming the electrodes on a blade substrate, then cutting the substrate to a prescribed size. CONSTITUTION:The rubber blade as the base body of the electrifying blade is formed by patterning and forming the rear electrode layers 3 of cruciform patterns symmetrically with an axial line as a boundary for the even number of sheets of a prescribed size by a printing treatment of a conductive coating compd. The images of a photosensitive drum 1, designated as J, are formed in the relation of J<width of the rear surface L<the width M of the electrifying blade. Non-electrode parts n, n' prevent charge leakage at the right and left end faces of the blade in the contact generator direction of the photosensitive drum. The substrate is then cut along the axial line to two sizes of the blades. After conductive rigid supporting members 4 are joined to both sides, the substrate is cut along the central axial line C-C. Two sheets each of the blades having the electrodes of the good accuracy are thus formed.

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 corotron or a corotron with good uniform charging property is used. Corona dischargers such as scorotrons are widely used.

However, corona dischargers require expensive high-voltage power supplies.
It requires space for itself and the shield space of the high-voltage power supply, and it often generates corona products such as sazon, requiring additional means and mechanisms to deal with them. It has problems such as being a factor that causes problems such as

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, including roller charging type (Japanese Patent Laid-Open No. 56-91253), blade charging type (Japanese Patent Laid-Open Nos. 56-194349 and 60-14775 [i]), and charging method. A cleaning type (Japanese Unexamined Patent Publication No. Sho 5616!l+l56) has been devised.

However, one of the problems with this contact charging method is that if there is a hole in the image carrier such as a photoconductor (a surface defect on the charged body), the charging of the image carrier may cause the damage to occur. Spark discharge is likely to occur between the contact charging member that is in contact with the image carrier surface and a voltage is applied to the hole portion of the image carrier, and when such a discharge occurs, spark discharge occurs on the image carrier surface not only in the hole portion. First, it is easy to see the so-called "charge leakage" phenomenon (charge leakage phenomenon) in which the charged charge is no longer applied over the entire charging area of the contact charging member including the via hole portion.

FIGS. 7(A) and 7(B) are explanatory model diagrams of this charge loss phenomenon. In FIG. 7(A), 1 is a photoreceptor as an image carrier (charged member) that moves in the direction of the arrow; 2 is a contact charging member (hereinafter referred to as a charging blade) in the form of a blade that is brought into contact with the surface of the photoreceptor in order to charge the surface of the photoreceptor 1 and is in a state where a voltage is applied. be.

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 applied to each part of the photoconductor in the longitudinal direction of the photoconductor (direction of the contact line between the photoconductor and the charging blade) vAV8
. . . v2 is approximately Ov in both cases, and there is no charge on the surface of the photoreceptor 1 over the entire contact charging area with the charging blade 2, including the pinhole 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 a white spot in the case of regular development, and a blank spot in the case of reverse development. and deterioration of quality.

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 plate 2 with an appropriate pressure using rubber elasticity, the distance between the tip of the support part of the charging plate and the part of the charging blade that comes into contact with the object to be charged must be adjusted. (
The blade free length (blade free length) is required to be considerably larger than the blade thickness, and if power is supplied to the blade from the blade support part, the potential at the part in contact with the charged object will drop. For this reason, the charging blade required a back electrode, but there was no good manufacturing method.

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, wherein the contact charging member is in the form of a blade, and the charging blade is in the form of a blade. The contact charging member is characterized in that an electrode layer is formed on a surface opposite to a surface in contact with an object to be charged, and the charging blade is cut into a predetermined size after the electrode layer is formed.

Further, the present invention relates to an object to be charged or an image bearing member of an image forming apparatus, and the present invention relates to the width of an image formed on the surface of the image bearing member, the width of a charging blade, and the width of an electrode layer formed on the charging blade. The contact charging member is characterized in that the width dimension relationship is: image width (electrode layer width) charging blade width.

(Function) That is, in the present invention, by forming a back electrode pattern in advance on a blade or sheet as a blade-shaped contact charging member and then cutting the charging blade into a predetermined size, it is possible to form a stable electrode with high precision; ■Patterns can be abbreviated.

(Example) (1) Example of an image forming apparatus (Fig. 2) Fig. 2 shows the outline of an example of an image forming apparatus incorporating a contact charging device using a contact charging member according to the present invention as a charging processing means for an image carrier. FIG.

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

During the rotation process, the photosensitive drum 1 is uniformly charged to a predetermined polarity and a predetermined potential by a charging plate 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 in an exposure unit (exposure using an analog optical system that forms and exposes the original image, scanning exposure using a digital optical system including a laser dome scanner, LED array, etc.) etc.), 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),
Paper is fed between the photosensitive drum 1 and the transfer stage 8 (for example, a transfer roller, a corona charger, etc.) (transfer section) at a predetermined timing by the registration roller 10, and the paper is exposed to light on the feeding transfer member Pa. The formed visible images on the drum 1 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 plate 2.
- The four process devices of 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 installed in a direction perpendicular to the drawing along line 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 blade 2 as a contact charging member has, for example, 10
It is a rubber blade with a thickness of 1 to 2 mm made of hydrin, EPDM, urethane, etc. whose resistance is controlled to about 7 to 109 ΩcI [1. The blade is attached and held together with an adhesive 13, and the free length il of the blade (the length S from the tip of the supporting part of the blade to the part where the blade contacts the photosensitive drum) is about 5 to 15 mm, and the blade is brought into contact with the photosensitive drum 1 by approximately 5 to 15 mm. The angle θ (the angle between the tip of the blade and the tangent line of the drum at the point where the blade contacts the drum, which is downstream in the drum surface movement direction from the blade contact point) is 8° to 25°.
The contact pressure is set to approximately 4 to 40 gr/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 contact of the charging blade 2 with the photosensitive tram 1 can also be made in the forward direction (at a contact angle or at an obtuse angle) with respect to the rotation of the tram 1.

A back electrode 3 is formed by printing conductive paint on the surface of the charging blade 2 facing the contact surface with the photosensitive tram 1 (on the back side of the blade), and this back electrode 3 and the charging blade 2
It is joined to the conductive rigid support member 4 via a conductive adhesive 13 and is electrically connected to the conductive 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 drum 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, the conductive adhesive 13 joining the support member and the charging blade, and the back electrode 3,
An electric field is generated at the contact portion between the charging blade 2 and the photosensitive drum 1, and the surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity and a predetermined potential.

(3) Configuration outline of the charging blade 2 In FIG. 3(A), the rubber blade 2 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 is By cutting along the border, two charged blade bases of a predetermined size are produced.

The back electrode layer 3 is patterned by printing 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. It has been done.

After bonding the conductive rigid support members 4, 4 symmetrically to both left and right sides of the rubber blade 2 of the size of the two rubber blades 2 with conductive adhesive (13), the rubber blade 2 is attached to the longitudinal center. By cutting and dividing into two along the axis line C-C,
Two charged blades are obtained.

By cutting after joining as described above, Figure 3 (B)
It can be created with high accuracy using the cut plane C, as shown in FIG.

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

If an electrode layer 3/ is coated on the back surface of the rubber blade 2 after the bond is cut as shown in FIG. 3(C), leakage may occur due to the coated electrode layer material wrapping around the contact area as shown in 37/. There have been cases where this has resulted in the occurrence of

In Fig. 4, the rubber sheet 2 as the base of the charging blade is sized to hold eight charging blades of a predetermined size, and the back side of the rubber sheet 2 of the size for eight sheets has a grid or grid pattern area shown with diagonal lines. The back electrode layer 3 is pattern-formed by printing with conductive paint.

By cutting this rubber sheet 2 along the F-F line and the G-G line, four rubber blades 2 of the size of the two sheets shown in FIG. By joining the supporting members 4 and 4 and cutting them into two pieces in the same manner as in FIG. 3(A), a total of eight charging plates can be made.

As shown in FIG. 5, after forming the electrode layer 3 on the blade 2,
After creating and cutting the blades 2 one by one, the blades 2 are joined to the support member 4 according to the position reference K of the support member 4 (13
) L/ is also fine. The back electrode pattern 3 in this example 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 blade.

As shown in FIGS. 6(A) and 6(B), the left and right end surfaces 2, 2 of the charging blade are provided by providing a non-electrode layer portion at the n''n' portion in the direction of the photosensitive drum abutting generatrix of the charging blade.
, the charge leak phenomenon is effectively prevented.

Of course, the image forming area width (image width) of the photosensitive drum 1
When J is the image width J x the back electrode width L <the charging blade width M.

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 provides a highly accurate and stable electrode by forming a back electrode pattern on a blade substrate in advance and then cutting the charging blade into a predetermined size for a charging blade as a contact charging member. can be formed and the pattern can be omitted.

[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.
FIG. 3 is a diagram showing a state in which the coated electrode layer material wraps around the end surface of the cutting tip of the blade. FIG. 4 is a diagram showing a back electrode pattern formed on the back surface of a rubber blade having a size of eight charging blades. FIG. 5 is a plan view of another example of the configuration of the charging blade. Figures 6 (A) and (B) are further explanatory diagrams of other examples of the configuration of charging blades, Figure 7 (A) is an explanatory model diagram of the charge loss phenomenon, and Figure 7 (B)
) is its equivalent circuit. 1 is an image carrier (photosensitive drum) as a charged body, 2 is a charging blade as a contact charging member, 3 is a back electrode, 4 is a conductive rigid support member (support body), 13 is a conductive adhesive,
5 is a bias power supply.

Claims (2)

[Claims] (1) 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 being in the form of a blade, and a surface of the charging blade opposite to the contact surface with the object to be charged. A contact charging member characterized in that an electrode layer is formed on the electrode layer, and the charging blade is cut into a predetermined size after the electrode layer is formed. (2) The object to be charged is an image bearing member of an image forming apparatus, and the width dimension relationship between the width of the image formed on the surface of the image bearing member, the width of the charging blade, and the width of the electrode layer of the charging blade is 2. The contact charging member according to claim 1, wherein image width<electrode layer width<charging blade width.