JP2767951B2 - Contact charging member - Google Patents

Description

Description: TECHNICAL 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 carrier such as a photoreceptor or a dielectric as a member to be charged in an image forming apparatus such as a copying machine or a recording apparatus, a corotron having good uniform chargeability is used. Corona dischargers such as scorotrons are widely used.

However, the corona discharger requires an expensive high-voltage power supply, requires a space such as the shield space of the high-voltage power supply itself, and generates a lot of corona products such as ozone. Are required, which are factors that increase the size and cost of the apparatus.

Therefore, recently, the use of a contact charging system instead of the corona discharger, which has many problems, has been studied.

Contact charging is carried out by bringing a contact charging member to which a voltage (for example, a DC voltage of about 1 to 12 KV, or a superimposed voltage of a DC voltage and an AC voltage, etc.) is applied from a power supply to the surface of the image carrier as a member to be charged. It charges the body surface to a predetermined potential, and is a roller charging type (JP-A-56-91253) and a blade charging type (JP-A-56-194349 / 60-147756).
Japanese Patent Application Laid-Open No. 56-1651)
No. 66) has been devised.

However, one of the problems in this contact charging system is
First, when an image carrier such as a photoreceptor has a pinhole (a surface defect of a member to be charged), the voltage applied to the surface of the image carrier is charged to charge the surface of the image carrier. Spark discharge easily occurs between the contact charging member and the pinhole portion of the image carrier, and when such a discharge occurs, the contact charging member including the pinhole portion is not limited to the pinhole portion on the image carrier surface. And no charged charge is applied over the entire charging area. The so-called “charge loss” phenomenon (charge leak phenomenon) is easily observed.

6 (A) and 6 (B) are model diagrams for explaining the charge bleeding phenomenon. In FIG. 6 (A), reference numeral 1 denotes a photosensitive member as an image bearing member (member to be charged) which moves in the direction of the arrow, and P Is photoconductor 1
The pinhole portion 2 is a contact charging member (hereinafter, referred to as a charging blade) in the form of a blade in a voltage-applied state brought into contact with the surface of the photoconductor 1 for charging the surface of the photoconductor 1. FIG. 3B is an equivalent circuit of FIG.

The pinhole portion P of the photoreceptor 1 has a lower resistance than the other photoreceptor portions, so that a spark is generated between the photoreceptor 1 and the charging blade 2 upon contact with the charging blade 2 or when the charging blade surface approaches. prone to discharge S, the discharge S to occur between the photosensitive member longitudinal direction each part of the potential V _a · V _B applied on the photoreceptor with respect to (photosensitive member and the contact line direction of the charging blade)
· · · V _Z almost any becomes 0V, charge over the contact charging zone entirely between the charging blade 2 comprising a pinhole P is the not ride on the surface of the photosensitive member 1.

Thus, if the above-described charge bleeding occurs in the charging process on the surface of the photoreceptor, the output image of the image corresponding to the charge bleeding becomes white in the case of normal development and black in the case of reversal development. It falls off and degrades.

The pinhole P is easily generated at the time of manufacturing an image carrier (charged body) such as a photoreceptor, is easily generated due to scratching, or is easily generated due to electrical insulation breakdown.

(Problems to be Solved by the Invention) As a measure for preventing the charge leakage, the electric resistance of the charging blade material must be increased. However, since the charging blade 2 is pressurized by rubber elasticity with an appropriate pressure, the distance (blade free length) from the tip of the blade support member to the charged blade contact portion of the charging blade is required to be considerably larger than the blade thickness. When power is supplied to the blade from the portion, the potential of the charged member contact portion decreases. For this reason, the charging blade requires a back electrode, but there is no means excellent in manufacturing.

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to rationally form a back electrode on a blade-type contact charging member.

(Means for Solving the Problems) The present invention is a contact charging member having the following configuration.

(1) A contact charging member that contacts the charged member to charge the charged member, and electrically connects the blade member, the support member supporting the blade member, and the blade member and the support member. And an electrode layer provided on the blade member for bonding to the support member. After joining the blade member to the support member, the electrode layer is configured so that the electrode layer does not contact the member to be charged. A contact charging member comprising a layer.

(2) The charged member is rotatable, and a width of the blade member is larger than a width of the electrode layer in a direction perpendicular to a rotation direction of the charged member. Contact charging member.

(3) The contact charging member according to (1) or (2), wherein the blade member includes an elastic member.

(4) The contact charging member according to any one of (1) to (3), wherein the electrode layer extends near a free end of the blade member.

(5) The contact charging member according to any one of (1) to (4), wherein the member to be charged is an image carrier for carrying an image.

(6) The contact charging member according to (5), wherein the contact charging member is provided in a process cartridge that is detachable from an image forming apparatus together with the image carrier.

(7) The contact charging member according to (5) or (6), wherein the image carrier is an electrophotographic photosensitive member.

(Operation) That is, the present invention can form a stable electrode with high accuracy by forming an electrode layer on a blade after integrating a blade supporting member and a charging blade as a contact charging member.
The pattern can be omitted, and the bonding force can be stabilized for a long time.

(Embodiment) (1) Example of Image Forming Apparatus (FIG. 2) FIG. 2 shows an example of an image forming apparatus in which a contact charging device using a contact charging member according to the present invention is incorporated as a charging means for an image carrier. It is a schematic structure figure of an important section.

Reference numeral 1 denotes a rotating drum type electrophotographic organic photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier, which is driven to rotate at a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow A.

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 described later during the rotation process.

Then, exposure L (exposure using an analog optical system for forming and exposing an original image, scanning exposure using a digital optical system including a laser beam scanner or an LED array, etc.) is performed on the charged surface by an exposure unit. Upon receipt, an electrostatic latent image corresponding to the target image information is formed.

The formed latent image is then subjected to regular or reverse development by the developing device 7.

On the other hand, a transfer member Pa is fed from a paper feed mechanism (not shown), and is transferred between the photosensitive drum 1 and transfer means 8 (for example, a transfer roller or a corona charger) at a predetermined timing by a registration roller 10 (transfer). ), And the formed visible image on the photosensitive drum 1 side is sequentially transferred to the sheet transfer member Pa.

The transfer member Pa that has passed through the transfer unit is separated from the surface of the photosensitive drum 1, and is introduced into a fixing device (not shown) by the transport unit 11 to receive an image.

After the transfer, the surface of the photosensitive drum 1 is removed and cleaned by the cleaning device 9 to remove unnecessary substances, and is repeatedly provided for image formation.

The image forming apparatus according to the present embodiment is configured as a process cartridge 6 in which four process devices of a photosensitive drum 1, a charging blade 2, a developing device 7, and a cleaning device 9 are collectively incorporated in a predetermined positional relationship with each other. The cartridge 6 can be inserted into the main body of the image forming apparatus along the support rails 12 in the direction perpendicular to the drawing, and can be pulled out of the main body of the image forming apparatus.

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 is operable.

(2) Contact charging device FIG. 1 is a schematic diagram of a contact charging device portion of the image forming apparatus of FIG.

The charging blade 2 as a contact charging member has, for example, 10
Hydrin with resistance controlled to about ⁷ to 10 ⁹ Ωcm
A rubber blade of EPDM, urethane, etc. with a thickness of 1 to 2 mm. The base of the blade is integrally attached to the conductive rigid support member 4 such as a steel plate with an adhesive or the like, or the blade material is injected into a mold to form the blade. The support member is integrally molded and held, and the free length l of the blade (the distance between the tip of the support member of the blade and the contact portion of the blade with the photosensitive drum) is about 5 to 15 mm. Tangent angle θ
(The angle between the tip of the blade and the line of the tangent line of the drum at the point where the blade is in contact with the drum on the downstream side in the drum surface moving direction from the blade contact point) is about 8 ° to 25 °. The contact pressure is set to about 4 to 40 gr / cm, and the blade tip is brought into contact with the rotation of the photosensitive drum 1 in the counter direction (the contact angle is an acute angle). The contact of the charging blade 2 with the photosensitive drum 1 may be in a forward direction (the contact angle is obtuse) with respect to the rotation of the drum 1.

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

Reference numeral 5 denotes a power supply for applying voltage to the charging blade 2.
For example, DC corresponding to the required potential of the photosensitive drum 1
A bias in which the DC voltage is superimposed on a voltage or an alternating electric field having a peak-to-peak voltage of at least twice the discharge starting voltage (V _K ) determined by the charging blade and the photosensitive drum to obtain charging uniformity is supplied. As a result, 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, and the photosensitive The surface of the drum 1 is uniformly charged to a predetermined polarity and a predetermined potential.

(3) Configuration of charging blade 2 In FIG. 3 (A), the rubber blade 2 as a base of the charging blade has a size corresponding to two charging blades of a predetermined size. When cutting is performed at the boundary, two charged blade substrates having a predetermined size are formed.

Then, the conductive rigid support members 4 are integrally joined to the right and left sides of the rubber blade 2 of two sizes by an adhesive or the like, respectively, symmetrically. Thereafter, the back electrode layer 3 is printed on the back surface of the rubber blade 2 of the size of two sheets with a conductive paint like a substantially cruciform pattern region shown by oblique lines symmetrically with respect to the longitudinal center axis CC. The pattern is formed. In this case, a part of the back electrode layer 3 is formed on the left and right pre-installed support members 4.4 with respect to the respective surfaces, so that the support members 4 and the electrode layer 3 are electrically connected. Conducted. After this printing process, two rubber blades 2 each having a size corresponding to the two blades are cut by dividing the rubber blade 2 at the longitudinal center axis CC and divided into two to obtain two charging blades.

Finish precision of the cut surface C ₁ by the rear cut method as described above may be made without inflow of the electrode layer material to the member to be charged abutment side of the blade.

The back electrode layer 3 does not need to be formed on the entire back surface of the blade, and abuts on the tip side of the blade 2 with the member 1 to be charged, as in the substantially T-shaped pattern (the pattern after cutting CC) in this example. It suffices if there is a blade back portion corresponding to the portion and a connecting portion for conducting the portion and the supporting member 4 on the power supply side.

Figure 3 joining as (C) - by wraparound etc. coated electrode layer material to the abutment portion near as code 3 ₂ be formed by coating an electrode layer 3 ₁ to the back of the rubber blade 2 after cutting, rather leak In some cases.

Even when the electrode layer 3 is formed on the back surface of the blade 2 by high-precision printing in the case of FIG. ₃ described above, one or both of the left and right end faces of the blade 2 as indicated by 33 in FIG. may become a state in which the electrode layer material has been wrapped around is outflow in part, because in some cases the presence of such efflux electrode layer material 3 ₃ becomes the new charge leakage caused, Figure 4 as a countermeasure (a It is also effective to pre-pattern the electrode layer 3 so that the relationship of charging blade width T ₂ > electrode layer width T ₁ is satisfied, as in ( ₂ ).

Alternatively, as shown in FIG. 5 (A), the width dimension of the blade 2 is further extended to the left and right ends by α · α, respectively, and the supporting members 4.4 are attached to the blade to form the back electrode 3. , The blade 2 is cut in two at the center, and the extra width α · α on the left and right of the blade 2 is cut U ₁ -U ₁ ,
By removing by U ₂ -U _2, the finishing accuracy of the left and right end faces of the blade 2 is good as shown in FIG. 5 (B), and the charge leakage trouble due to the inflow of the electrode layer material into the left and right end faces can be eliminated. .

The back electrode pattern 3 in the example of FIG. 5 has a substantially U-shaped pattern of a portion along the blade tip side and a portion along the left and right sides on the blade back surface.

The electrode layer 3 may be a full-surface electrode layer on the back surface of the blade. For example, the above-described cutting process may be performed after the electrode layer 3 is formed on the entire back surface of the blade by spray coating. Further, in the case of two chamfers, it is sufficient to cut the line CC at the center of both.

Although the above description has been made with the rubber blade, the substrate of the charging blade may be a sheet material or a film material, and the formation and configuration of the back electrode layer 3 are the same.

(Effects of the Invention) As described above, the present invention forms a stable and accurate electrode by forming an electrode layer on the charging blade as a contact charging member after integrating the charging blade and the support member. Yes, patterns can be omitted, and bonding strength can be stabilized for a long time.

[Brief description of the drawings]

FIG. 1 is a schematic view of a charging blade portion of a contact charging device. FIG. 2 is a schematic view of an example of an image forming apparatus incorporating a contact charging device using a charging blade. FIG. 3 (A) is an explanatory view of the procedure for preparing a charging blade, FIG. 3 (B) is an enlarged view of a cutting tip portion of the charging blade, and FIG. 3 (C) is an end surface of the cutting tip portion of the blade where the material of the coated electrode layer is coated. The figure which shows the state which goes around. FIG. 4 (A) is an explanatory view of a configuration example of another charging blade, and FIG. 4 (B) is a view showing a state in which an electrode layer material wraps around a side end of the blade. FIGS. 5A and 5B are explanatory views of still another example of the configuration of the charging blade. FIG. 6 (A) is an explanatory model diagram of the charge loss phenomenon, and FIG. 6 (B) is an equivalent circuit thereof. 1 is an image carrier (photosensitive drum) as a member to be charged, 2 is a charging blade as a contact charging member, 3 is a back electrode, 4 is a conductive rigid support member, and 5 is a bias power supply.

Claims (7)

(57) [Claims] 1. A contact charging member that contacts a member to be charged to charge the member, comprising: a blade member; a support member supporting the blade member; and the blade member and the support member. An electrode layer provided on the blade member for electrical coupling, wherein after the blade member is joined to the support member, the electrode layer does not contact the member to be charged. A contact charging member provided with the electrode layer. 2. The apparatus according to claim 1, wherein said member to be charged is rotatable, and a width of said blade member is larger than a width of said electrode layer in a direction perpendicular to a rotating direction of said member to be charged. 1 contact charging member. 3. The contact charging member according to claim 1, wherein said blade member includes an elastic member. 4. The contact charging member according to claim 1, wherein said electrode layer extends close to a free end of said blade member. 5. The contact charging member according to claim 1, wherein said member to be charged is an image carrier for carrying an image. 6. The contact charging member according to claim 5, wherein said contact charging member is provided in a process cartridge detachably mountable to an image forming apparatus together with said image carrier. 7. The contact charging member according to claim 5, wherein said image bearing member is an electrophotographic photosensitive member.