JP2773342B2 - Contact charging member - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a contact charging member.

(Prior Art) For example, as means for uniformly charging the surface of an image carrier such as a photoreceptor or a derivative as a member to be charged in an image forming apparatus such as a copying machine or a recording apparatus, a corotron or a scorotron having good uniform chargeability is used. Are widely used.

However, a corona discharger requires an expensive high-voltage power supply, requires a space such as a shield space for itself and a high-voltage voltage, 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.

The extraction charging is performed by bringing a contact charging member to which a voltage (for example, a DC voltage of about 1 to 2 KV or a superimposed voltage of a DC voltage and an AC voltage) is applied from a power supply into contact with the surface of the image carrier as a member to be charged. Roller charging type (JP-A-56-91253), blade charging type (JP-A-56-194349 and JP-A-60-147756), and charging-cleaning type. (JP-A-56-165166)
Publication) 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.

8 (A) and 8 (B) are model diagrams for explaining the charge bleeding phenomenon. In FIG. 8 (A), reference numeral 1 denotes a photosensitive member as an image carrier (a 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 by 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 none of OV, and the 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.

When the above-described charge loss portion occurs in the charging process on the photoconductor 1 surface, the output image has an image portion corresponding to the charge loss portion,
In the case of regular development, white spots occur, and in the case of reversal development, black spots occur, and the quality deteriorates.

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 countermeasure for preventing the charge leakage, it is sufficient to form a resistance layer on the contact surface side of the charging blade with the member to be charged, so as not to cause the charge leakage, but with high accuracy at a predetermined position. It was difficult to form.

The present invention has been proposed in view of the above, and an object of the present invention is to rationally form an electric resistance layer on a contact charging member in the form of a blade.

(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 body to charge the charged body, the contact charging member including a blade member, and a resistive layer provided on the blade member and in contact with the charged body. A contact charging member, wherein after the formation of the resistance layer, the resistance layer and the blade member are cut at the same time, and the cut surface is exposed to make contact with the member to be charged.

(2) The contact charging member according to (1), wherein the contact charging member includes an electrode layer provided on a side of the blade member opposite to a side on which the resistance layer is provided.

(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 member to be charged is an image carrier for carrying an image.

(5) The contact charging member according to (4), wherein the contact charging member is provided together with the image carrier in a process cartridge that is removable from an image forming apparatus.

(6) The contact charging member according to (4) or (5), wherein the image carrier is an electrophotographic photosensitive member.

(Operation) That is, the present invention provides a blade contact portion for a charged object, in which a resistive layer is formed on a charging blade in advance and then the charging blade is cut into a predetermined size so that the resistive layer can be formed accurately and stably. And a stable contact can be obtained.

(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 normal or reversal 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 a controlled resistance of about ⁵ to 10 ⁸ Ωcm
A rubber blade with a thickness of 1 to 2 mm, such as EPDM, urethane, or NBR, which is integrally attached to and held by a conductive rigid support member (support) 4 such as a steel plate on the blade base side with a conductive adhesive 13. And the free length l of the blade (the distance between the tip of the blade supporting member and the contact portion of the blade with the photosensitive drum) is 5 to 20.
mm, the contact angle θ with respect to the photosensitive drum 1 (between the tip of the blade and the line of the tangent 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) Angle) about 8 ~ 25mm, contact pressure 4 ~ 40
gr / cm and set the blade tip to photosensitive drum 1
(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 acute) with respect to the rotation of the drum 1.

Reference numeral 3 denotes a surface resistance layer provided at a contact portion of the charging blade 2 with respect to the photosensitive drum 1. The surface resistance layer has a thickness of about 10 ⁸ to 10 ¹² Ω · cm and a resistance of 2 to 100 μm, such as nylon or urethane, whose resistance is controlled. Printed on the charging blade 2 in layers.

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 via the support member 4, and an electric field is generated at a contact portion between the charging blade 2 having the surface resistance layer 3 and the photosensitive drum 1, so that the surface of the photosensitive drum 1 has a predetermined polarity and a predetermined polarity. It is uniformly charged to a 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, and is separated by a longitudinal center axis CC. Then, two charged blade substrates having a predetermined size are formed.

The surface resistance layer 3 is patterned by printing on the surface side of the rubber blade 2 having a size corresponding to the two blades, like a band-shaped pattern area along a CC line indicated by oblique lines symmetrically with respect to the longitudinal central axis CC along the longitudinal center axis CC. It is formed.

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.

Since the cutting C-C leading edge of the blade 2 is formed and can create good cut-away view C ₁ is accurate as Figure 3 for cutting accuracy can be obtained (B), executes a uniform and leakage-free charged It becomes possible.

The formation of the surface resistance layer 3 on the blade 2 does not need to cover the entire surface of the blade or the entire area of the contact surface with the member 1 to be charged, but the necessary and effective width l _{2 of} the contact surface.
It may be up to about 3 mm, that is, a portion having a gap where the charge does not leak directly from the charging blade 2 to the photosensitive drum 1 at the blade contact portion with the photosensitive drum as the member to be charged.

FIG. 4 shows that the rubber sheet 2 as a base of the charging blade has a size capable of taking eight charging blades of a predetermined size, and a surface resistance 3 is formed on the surface of the rubber sheet 2 of the size of eight sheets as shown by a hatched area. This is a pattern formed by print processing.

By cutting the rubber sheet 2 along the line EE and the line FF, 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. Further, as shown in FIG. 4, after forming the resistance layer on the blade, the blade may be cut into eight blades of a predetermined size, and then the blades may be joined to the support member 4 one by one.

That is, the number of charging blades can be efficiently created by shortening the process.

FIG. 5 shows a configuration to cope with the case where the resistance value of the charging blade 2 drops at the contact portion Q with the photosensitive drum 1 due to the power supply from the support 4.

That is, an electrode layer 10 is formed on the back surface of the blade 2, and this electrode layer 10 is formed on the conductive rigid support member 4 on the power supply side.
When the bias is supplied to the support member 4, the bias is supplied to the charging blade 2 via the back electrode 10, whereby the contact portion Q between the charging blade 2 and the photosensitive drum 1 is An electric field effective for charging is provided.

FIG. 6 is a perspective view of a blade 2 having a surface resistance layer 3 formed to a necessary minimum.

In order to stabilize the contact pressure of the charging blade 2 against the photoreceptor 1, the width of the surface resistance layer 3 was set to l ₂ and the width of the non-resistance layer portion was set to l ₁ with respect to the free displacement length l of the blade substrate. Things. In the case where the surface resistance layer 3 is formed by coating over the entire free length 1 of the blade, it depends on the coating material for the resistance layer. Is weakened and undergoes a plastic-like bending elastic behavior, so that creep and permanent deformation of the blade 2 in the pressed state against the photosensitive drum 1 are large, and the contact state (pressure) changes. That is, the G portion to which the stress caused by the bending of the blade is required to have at least the behavior of rubber, and the eccentricity of the photosensitive drum 1 and the rubber viscoelastic behavior that absorbs vibrations can be obtained by contacting the blade 2 with the photosensitive drum 1. And the charging potential can be made uniform without unevenness.

FIGS. 7 (A) and 7 (B) further show the stability of the contact portion Q and the difficulty of interfering with the foreign matter 15 on the charging portion (resistance layer portion) 3. Is formed at an acute angle (preferably 60 ° to 85 °). The moving part on the blade tip surface of the foreign matter 15 is (180 ° -H) and the slope J
, And moves in the direction of the arrow, so that no force is applied in the direction of intervening in the contact portion Q.

As a result, uneven charging due to foreign matter intervention can be prevented. In addition, by making the hardness and elasticity of the surface resistance layer 3 less deformable than the base rubber of the blade 2, the tip of the blade 2 more reliably contacts the surface of the photosensitive drum 1, and in extreme cases, the blade 2 may be turned over Thus, a configuration that does not cause wear or chipping can be obtained.

That is, a resin layer as a surface resistance layer which is hardly deformed is provided on the rubber base material of the blade, and the resin layer is applied to the photosensitive drum 1.
Is in contact with.

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

(Effect of the Invention) As described above, according to the present invention, a resistive layer can be accurately and stably formed by forming a resistive layer on a charging blade and then cutting the charging blade to a predetermined size.
The edge precision of the blade contact portion with respect to the member to be charged can be favorably obtained, and patterning can be omitted, and stable contact can be obtained.

[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 (plan view) of a charging blade preparation procedure, and FIG. 3 (B) is an enlarged view of a cutting tip portion of the charging blade. FIG. 4 is a plan view showing a back electrode pattern formed on a back surface of a rubber blade having a size of eight charging blades. FIG. 5 is a diagram (side view) of another configuration example of the charging blade. 6A, 6B, 7A, and 7B are explanatory views of still another example of the configuration of the charging blade. FIG. 8A is an explanatory model diagram of the charge loss phenomenon, and FIG. 8B 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 surface resistance layer, 10
Is a back electrode, 4 is a conductive rigid support member (support), 13 is a conductive adhesive, and 5 is a bias power supply.

Claims (6)

(57) [Claims] 1. A contact charging member for contacting an object to be charged to charge the object, comprising: a blade member; and a resistance layer provided on the blade member and in contact with the object to be charged. In the contact charging member, the resistance layer and the blade member are cut at the same time after the formation of the resistance layer, and the contact member is brought into contact with the charged member with the cut surface exposed. 2. The contact charging member according to claim 1, wherein said contact charging member includes an electrode layer provided on a side of said blade member opposite to a side on which said resistance layer is provided. 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 member to be charged is an image carrier for carrying an image. 5. The contact charging member according to claim 4, wherein said contact charging member is provided in a process cartridge detachably mountable to an image forming apparatus together with said image carrier. 6. The contact charging member according to claim 4, wherein said image bearing member is an electrophotographic photosensitive member.