JP2767950B2 - 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 contron having a 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. In other words, the so-called “charge loss” phenomenon (charge leak phenomenon), in which the charged electric charge does not ride over the entire charging region of the above, is easily observed.

7 (A) and 7 (B) are model diagrams for explaining the charge bleeding phenomenon. In FIG. 7 (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, when the above-described charge bleeding portion occurs in the charging process on the surface of the photoreceptor, the output image of the image corresponding to the charge bleeding portion is blank in the case of normal development and is missing in the case of reversal development. And degrade. 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 pressed by rubber elasticity with an appropriate pressure, the distance (blade free length) between the tip of the supporting portion of the charging blade and the contacting portion of the charging blade with the member to be charged needs to be considerably larger than the blade thickness. However, when power is supplied to the blade from the blade supporting 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 member to be charged in order to charge the member, and a blade member and an electrode provided on a surface of the blade member that faces the surface that contacts the member. A contact charging member, comprising: forming the electrode layer, cutting the electrode layer and the blade member simultaneously, and contacting the charged object with the cut surface exposed. .

(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 forms the back electrode pattern on a blade or sheet as a contact charging member in the form of a blade in advance, and then cuts the charging blade into a predetermined size.
It is possible to form a stable electrode with high accuracy and to omit a pattern.

(Example) (1) Example of Image Forming Apparatus (FIG. 2) FIG. 2 is a view showing 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 block diagram of a part.

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 become operable as an image forming apparatus.

(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 having a thickness of 1 to 2 mm, such as EPDM or urethane. The blade base is integrally attached to a conductive rigid support member (support) 4 such as a steel plate with a conductive adhesive 13 and held. The free length l (the distance between the tip of the support portion of the blade and the contact portion of the blade with the photosensitive drum) is about 5 to 15 mm, and the contact angle θ with respect to the photosensitive drum 1 (the tip of the blade and the blade contact the drum). Angle between the tangent line of the drum at the point and the line downstream of the blade contact point in the drum surface movement direction) of about 8 to 25 degrees, and the contact pressure of 4 to 40 gr.
/ cm, and the tip of the blade 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 on a surface (blade rear side) of the charging blade 2 opposite to the contact surface with the photosensitive drum 1 by printing a conductive paint. The rigid support member 4 is electrically connected to the rigid support member 4 through a conductive adhesive 13.

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. By doing so, the support member 4, the conductive adhesive 13 joining the support member and the charging blade,
Electric power is supplied to the charging blade 2 along the path of the back electrode 3, and an electric field is generated at the contact portion between the charging blade 2 and the photosensitive drum 1, so that the surface of the photosensitive 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.

On the back surface of the rubber blade 2 of two sizes, the back electrode layer 3 is patterned by printing a conductive paint like a substantially cross-shaped pattern region shown by oblique lines symmetrically with respect to the longitudinal center axis CC. I have.

After the conductive rigid support members 4 and 4 are integrally joined to the left and right sides of the two rubber blades 2 with the conductive adhesive (13), respectively, the rubber blade 2 is connected to the longitudinal center axis C. By cutting at -C and dividing into two,
Two charging blades are obtained.

By cutting after bonding as described above, it can be created accurately with the cut surface C ₁ as of FIG. 3 (B).

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

If the electrode layer 3 'is coated on the back surface of the rubber blade 2 after the joining and cutting as shown in FIG. 3 (C), the leakage occurs due to the wraparound of the coated electrode layer material near the contact portion as indicated by reference numeral 3 ". In some cases.

FIG. 4 shows a rubber sheet 2 serving as a base of the charging blade having a size capable of taking eight charging blades of a predetermined size. The back electrode layer 3 is formed by forming a pattern by printing a conductive paint.

By cutting the rubber sheet 2 along the line FF and the line GG, four rubber blades 2 of two sizes shown in FIG. 3 (A) are prepared, and each of them is shown in FIG. (A)
By joining the support members 4 in the same manner as described above and cutting them into two parts, eight charging blades can be conveniently prepared.

As shown in FIG. 5, after the electrode layer 3 is formed on the blade 2, the blade 2 is formed one by one and cut, and then the blade 2 is joined to the support member 4 according to the position reference K of the support member 4 (1).
3) You may. The back electrode pattern 3 in this example is 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.

As those of FIG. 6 (A) · (B), the charging blade photosensitive drum in contact generatrix direction n-n 'left and right ends of the charging blade by providing a non-electrode layer part to the part surface 2 ₁ - 2 ₁ The charge leakage phenomenon is effectively prevented.

As a matter of course, when the image forming area width (image width) of the photosensitive drum 1 is J, the relationship of image width J <back electrode width L <charging blade width M is satisfied.

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

[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 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 configuration example of the charging blade. 6 (A) and 6 (B) are explanatory diagrams of still another example of the configuration of the charging blade, FIG. 7 (A) is an explanatory model diagram of a charge bleeding 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 (support), 13 is a conductive adhesive, 5
Is the bias power supply.

Claims (7)

(57) [Claims] 1. A contact charging member for contacting an object to be charged to charge the object to be charged, the contact member being provided on a blade member and a surface of the blade member opposed to a surface contacting the object to be charged. A contact charging member having the electrode layer, wherein after the electrode layer is formed, the electrode layer and the blade member are simultaneously cut, and the cut surface is exposed to contact the charged object. Charging member. 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. A contact charging member according to claim 5, wherein said image bearing member is an electrophotographic photosensitive member.