JPH05100546A - Contact electrifier - Google Patents

Abstract

PURPOSE:To prevent reduction in the life of an electrifying blade caused by abrasion without damaging electrifiability and to improve the durability of a device, in a contact electrifier using the electrifying blade as an electrifying member. CONSTITUTION:In the contact electrifier executing electrification in such a manner that a conductive member 10 having the application of a voltage is brought into contact with a body to be electrified 1, the conductive member 10 is like a blade having two-layer constitutions 3 and 4, and the resistance of one layer 4 including a part abutting on the body to be electrified 1, is higher than that of the other layer 4 not including the part abutting on the body to be electrified 1, and gradually thinned frown the top end, in a direction orthogonally crossing a blade longitudinal direction, and the volume resistance of the other layer 4 not including the part abutting on the body to be electrified 1, is 1X10<6>-1X10<9>cm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a contact charging device which charges a surface of an object to be charged (including static elimination) by bringing a conductive member (charging member) to which a voltage is applied into contact with the object to be charged.

[0002]

2. Description of the Related Art Conventionally, for example, in an image forming apparatus such as a copying machine or a recording apparatus, a non-contact type has been used as a means for uniformly charging the surface of an image bearing member such as a photosensitive member or a dielectric member to be charged. Corona dischargers such as corotrons and scorotrons are widely used as the charging device.

The corona discharger has a good uniform charging property. However, it requires an expensive high-voltage power source, requires a space such as itself and a shield space for the high-voltage power source, and many corona products such as ozone are generated.
There is a problem that a mechanism is required, and these are factors that increase the size and cost of the device.

Therefore, in recent years, the use of a contact charging method is being considered in place of the corona discharger, which has many problems recently. The contact charging is performed by contacting a conductive member as 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 by a power source to the surface of the image bearing member as a member to be charged. By charging the surface of the image bearing member to a predetermined potential, a roller charging type (Japanese Patent Laid-Open No. 56-
No. 91253), a blade charging type (JP-A-56-1).
No. 94349 and No. 60-147756), a charging / cleaning combined type (Japanese Patent Laid-Open No. 56-165166), and the like have been devised.

However, there are the following problems as problems in this contact charging type charging device.

[0006] When the image bearing member such as a photoconductor has a low withstand voltage surface defect portion such as a pinhole portion, a contact charging member in a voltage applied state and an image contacted with the image bearing member surface for charging the image bearing member surface Spark discharge is likely to occur between the carrier and the pinhole portion, and when discharge occurs, the surface of the image carrier is not limited to the pinhole portion, but extends over the entire charging area of the contact charging member including the pinhole portion. And the charged electric charge will not be applied,
It is easy to see the so-called "charge loss" phenomenon.

[0007]. In the blade charging method, even if the charging blade comes into pressure contact with the image bearing member, abrasion and damage of the surface of the image bearing member and reversal of the charging blade occur, and uniform charging may not be obtained.

In order to solve the above-mentioned "charge loss" problem, the applicant uses a blade-shaped conductive member as a base for the contact charging member to be used, and the image carrier of the conductive member and an electrostatic charge. It has been previously proposed to cover the surface of the affected part with one or more kinds of resistance layers having an electric resistance value larger than that of the conductive member (JP-A-1-93760).

Another problem is the abrasion of the image carrier surface.
To prevent damage and reversal of the charging blade, it has been previously proposed to make the friction coefficient of at least the portion of the charging blade that contacts the image carrier smaller than that of the image carrier cleaning member (Japanese Patent Laid-Open No. 1-93762). Publication).

As proposed in Japanese Unexamined Patent Publication No. 1-93760, the charging blade as a contact charging member in which a resistance layer is provided on the surface layer of a conductive blade substrate is effective, but there is a problem. In addition, the number of steps is increased, and more severe precision is required, resulting in an increase in cost of the charging blade.

That is, in the case of a blade-shaped charging member, the spark discharge generated by the pinhole on the surface of the member to be charged is charged by contact with the member to be charged (eg, electrophotographic photosensitive member) 1 as shown in FIG. It occurs at two places, the edge end surface portion of the blade 100 and the area where the charging blade 100 is separated from the contact portion with the member to be charged 1. P indicates a pinhole portion of the member to be charged 1, and S indicates spark discharge.

Therefore, basically, when the charging member has a blade shape, it is necessary to provide the resistance layer on two surfaces, that is, the contact surface of the blade with the member to be charged 1 and the blade edge end surface portion. However, if it is attempted to coat the resistance layer on the edge facet and the edge of the blade, the coat layer thickness of the edge part decreases, and in order to ensure the necessary minimum coat layer thickness evenly on the edge part, the coat It is necessary to increase the thickness, which not only takes time and labor such as increasing the number of coatings, but also increases the layer thickness of the resistance layer, which causes a problem that the chargeability is deteriorated.

Even when a sheet-like (solid) resistor having a thickness of 100 μm or less is used as a resistance layer and this is attached to the conductive blade base layer, it is considerably difficult to attach it particularly accurately to the edge facet in terms of manufacturing. Therefore, it is necessary to further fill the gap between the resistance layer and the corner between the contact surface portion and the edge end surface portion, which is more difficult to manufacture.

FIG. 9 shows a configuration in which a resistance layer is not provided on the edge surface of the charging blade 100. That is, the edge surface of the conductive base layer 100a of the charging blade 100 is chamfered into a curved shape so that the conductive base layer 100a is not exposed at the edge surface d. 100
b is the resistance layer and L is the free length of the charging blade.

However, this embodiment of the charging blade 10
Even in the case of 0, a step of chamfering the edge end face portion into a curved shape is required, and also the accuracy of attaching the resistance layer 100b is required. In addition, there is a problem that the contact state tends to be unstable because the conductive base layer 100a of the charging blade 100 is thin at the contact portion with the body to be charged 1.

The above problems in manufacturing occur when the charging member is formed into a blade shape. In the case of a roller shape, a roller-shaped conductive base layer is covered with a sillable tube as a resistance layer, or a resistance is formed. The layers are also easy to coat and do not pose significant manufacturing difficulties.

As described above, coating the charging blade with the resistance layer in order to prevent "charge loss" is a little complicated in manufacturing and also involves difficulties.

On the other hand, even in the structure proposed in Japanese Patent Application Laid-Open No. 1-93762, the friction coefficient of the surface of the charging blade is made smaller than that of the cleaning blade for wiping the surface of the image carrier as the charged body 1. In order to prevent the above "charge loss", the surface layer having a low friction coefficient needs to act as a resistance layer having a resistance value above a certain level. According to the examples described in the publication, a sheet layer of a low friction coefficient material having a resistance value controlled by containing a conductive material in a resin having a lubricant property such as nylon-based / PFA-based is bonded, and more specifically, Specifically, a conductive EPDM of 10 ² to 10 ⁶ Ω · cm as a charging blade substrate (underlying rubber layer) and a nylon resin of 10 ⁸ Ω · cm, which is both a slip coat layer and a resistance layer, to 50 μm are used. I am using a coated one.

Nylon-based resins and PFA-based resins have the characteristic of having a low coefficient of friction, but on the other hand, they have high hardness and have poor adhesion and adhesiveness with the underlying conductive rubber layer. By forming a coat layer, the rubber elasticity of the underlying rubber layer is impaired, the bending of the underlying rubber elastic layer cannot be followed and the coat layer peels off, or the blade tip is cut after the coat layer is formed. When doing so, it may not be possible to obtain a clean cut surface due to the difference in elastic modulus between the coat layer and the underlying rubber layer, and if unevenness is left on the blade edge part, uneven charging due to that part will occur. May occur.

As described above, in order to make the surface of the charging blade have a low coefficient of friction, coating and bonding the resin having lubricity by itself impairs the rubber elasticity of the charging blade or the edge of the blade tip. It is difficult to obtain accuracy and there is a possibility that charging failure may occur.

In order to solve the above problems, the present applicant has proposed that the charging blade has a blade shape in which a conductive member has a two-layer structure, and one layer including a contact portion with a member to be charged has soft elasticity. The layer has a surface resistivity of 5 × 10 ⁷ Ω / □ or more in which the fluororesin powder is dispersed, and the volume resistivity of the other layer not including the contact portion is 1 × 10 ⁶ to 1 × 10 ⁹ Ω.
・ We proposed a device characterized by being cm (Japanese Patent Application No. 2-014092). With this charging blade structure, it is possible to obtain a charging blade that has a simple structure, has a small number of manufacturing steps, and can be stably mass-produced at low cost.

[0022]

However, this Japanese Patent Application No. 2-
Even in the charging blade proposed in No. 014092, it is difficult to avoid abrasion of the contact portion with the body to be charged. To extend the life of the charging blade, Increase the wear resistance of the material of the coating layer that contacts the charged body. Increase the thickness of the coat layer so that a sufficient coat layer remains even after abrasion. A possible method is to soften the surface of the power receiving object to make it easier to scrape and reduce the amount of wear of the coating layer of the charging blade. However, the method
As the performance required for the coat layer is resistance controllable, soft and flexible, and has a low friction coefficient, there is not much room for selection of the material, and especially when the wear resistance is improved, the coat layer is generally hard. Since it is fragile, it does not have a great flexibility, which hinders the rubber elasticity of the blade, and the adhesion is poor, which is not good.

The method (1) is not practical because it has the drawbacks of scratches and damages on the body to be charged and shortened life.

Therefore, it is considered easiest to increase the thickness of the coating layer by the remaining method. However, this method also has disadvantages. That is, the volume resistance of the blade base layer is originally high to some extent (1 × 10
⁶ to 1 × 10 ⁹ Ω · cm) is coated with a layer having a higher resistance, so if the resistance of the coating layer is increased by increasing the film thickness, the charging property is impaired. come.

Therefore, in order to prevent the electric charge from being discharged without increasing the resistance value even if a certain amount of thickness is applied, and to prevent the charge from being discharged, 5
A surface resistance of × 10 ⁷ Ω / □ or more is required, and there is a drawback that the range of resistance value control of the coat layer is narrowed.
Further, as the thickness of the coat layer becomes thicker, the rubber property of the blade itself deteriorates, so that the creep characteristics / sag characteristics of the blade deteriorate, and it is necessary for stable charging due to the blade sag over time. There is also a risk that the pressure will not be applied.

Therefore, an object of the present invention is to improve the durability of the contact charging device using a two-layer charging blade as a charging member by preventing the life of the charging blade from being shortened due to wear of the charging blade without impairing the charging property. It is to plan.

[0027]

SUMMARY OF THE INVENTION The present invention is a contact charging device for charging a conductive member to which a voltage is applied by contacting it with a member to be charged, wherein the conductive member has a blade shape having a two-layer structure. Therefore, the one layer including the contact portion with the charged body has a higher resistance than the other layer not including the contact portion with the charged body, and the thickness is gradually smaller than the tip in the direction orthogonal to the blade longitudinal direction. The volume resistance value of the other layer not including the contact portion with the body to be charged is 1 × 10 ⁶ to 1 × 10 ⁹ Ωc.
m is a contact charging device.

[0028]

The wear of the charging blade occurs at the tip edge portion of the blade, which is the contact portion with the member to be charged. On the other hand, the main part of the charging blade that contributes to the charging of the member to be charged is not the contact portion with the member to be charged but is opposed to the member to be charged in the vicinity of the contact portion via a minute air gap. It is a blade portion, and the worn portion of the charging blade and the main portion that contributes to the charging of the body to be charged do not necessarily match.

Therefore, in the blade having the two-layer structure as described above, one layer including the contact portion for the member to be charged is
A layer having a higher resistance than other layers not including an abutting portion and having a thickness gradually smaller than the tip in a direction orthogonal to the blade longitudinal direction, thereby forming a layer in a portion actually abutting on a member to be charged. Since the thickness is thick, the abrasion resistance of the charging blade can be ensured, and the layer thickness of the portion of the charging blade that contributes to the charging of the member to be charged is thin, so that the charging property at the portion is not impaired. That is, it is possible to prevent the life of the charging blade from being shortened due to wear of the charging blade without impairing the charging property, and to improve the durability of the apparatus.

[0030]

【Example】

<Embodiment 1> (FIGS. 1 to 4) FIGS. 1 and 2 show a first embodiment of the present invention.
2 is a cross-sectional view showing a state where a charging blade of the contact charging device is in contact with the photosensitive drum 1, and FIG. 2 is a schematic configuration diagram of a main part of an example of an image forming apparatus using the contact charging device shown in FIG. is there.

(1) Configuration of Image Forming Apparatus The image forming apparatus of this example is a copying apparatus of the process cartridge removable type utilizing the transfer type electrophotographic process.

In FIG. 2, reference numeral 1 denotes a rotary drum type electrophotographic photosensitive member as an image bearing member (in this example, the photosensitive layer 1a has a thickness of 2).
An OPC photoreceptor having a thickness of 5 μm and a dielectric constant of about 3 is a conductive substrate (AL), which is hereinafter referred to as a photosensitive drum, and is rotationally driven in a clockwise direction indicated by an arrow A at a predetermined peripheral speed (process speed). In the present embodiment, the image carrier 1 is a drum type, but it may be a rotating belt type or the like. Also, seamless drums and belts can be used, and seams can also be used by performing the respective copying steps by synchronizing signals.

A charging blade 10 serves as a contact charging member of the contact charging device, and is in contact with the surface of the photosensitive drum 1. By applying a predetermined voltage from the power source E to the charging blade 10, the surface of the rotating photosensitive drum 1 is uniformly charged by the charging blade 10 to a predetermined polarity and potential by a contact method. The charging blade 10 will be described in detail later in (2).

Reference numeral 7 denotes a short focus lens array as an image exposure means. By this array, image information of a document on a document table (not shown) is imagewise exposed on the surface of the charged photosensitive drum 1 described above. , An electrostatic latent image of the exposure image is formed on the drum surface.

A developing device 8 develops the electrostatic latent image on the drum surface as a toner image.

Reference numeral 9 is a transfer roller as a transfer means,
The toner image on the surface of the photosensitive drum is transferred onto the transfer material K that is conveyed one by one from a paper feeding unit (not shown) between the photosensitive drum 1 and the transfer roller 9 (transfer unit). Reference numeral 13 denotes the transfer material K in synchronism with the rotation of the photosensitive drum 1, and the photosensitive drum 1 and transfer roller 9
A timing roller (registration roller) 14 is provided between the timing roller 13 and the transfer roller 9, and is a transfer guide that guides the transfer material K.

The transfer material K, which has passed through the space between the photosensitive drum 1 and the transfer roller 9 and has undergone the toner image transfer, is introduced into a fixing device (not shown) by the conveying device 15 to be fixed with the toner image to form an image. It is discharged as a thing. The photosensitive drum 1 after the transfer of the toner image onto the transfer material K is subjected to removal of adhering residues such as residual toner by 16 to be cleaned, and is repeatedly used for image formation.

The copying apparatus of this embodiment has a process cartridge 20 in which four process devices, that is, a photosensitive drum 1, a charging blade 10, a developing device 8 and a cleaning device 16 are collectively incorporated in a predetermined positional relationship.
The cartridge 20 can be inserted into the main body of the copying apparatus along the support rails 11 and 12 in a direction perpendicular to the drawing, and can be removed from the main body of the copying apparatus. ..

By fully inserting the process cartridge 20 into the main body of the copying apparatus and mounting it, the main body of the copying apparatus and the side of the process cartridge 20 are mechanically and electrically coupled to each other to be operable as the copying apparatus. Become.

(2) Contact Charging Device FIG. 1 is an enlarged schematic view of the charging blade 10 of the copying apparatus shown in FIG.

The charging blade 10 is fixedly supported on the blade supporting sheet metal 2 with an adhesive 2a, and a contact angle of θ ° with respect to a tangent line at a position α ° from the horizontal direction of the photosensitive drum 1 as a member to be charged ( A counter direction with respect to the rotation of the photosensitive drum 1 is defined by an angle formed by the tip of the blade and a line of the tangent line of the drum at the point where the blade contacts the drum Abutting (the contact angle is an acute angle).

The contact position angle α ° is appropriately selected depending on the arrangement of each process apparatus and the diameter of the photosensitive drum used.

The contact angle θ ° of the charging blade 10 is preferably 30 ° or less in view of stability of charging.

Further, the contact direction is not limited to the counter, but the counter contact causes a residue such as toner to reach the blade edge portion rather than the forward contact (the contact angle is an acute angle). However, since the residue is dammed at the blade edge and it becomes difficult for the residue to reach the charging surface downstream of the edge in the drum surface movement direction, uneven charging tends to occur. Is more desirable.

The base layer rubber 3 is provided with a coat layer 4 on the contact surface side with the photosensitive drum 1 and a back electrode 5 on the back side thereof. The base rubber 3 including the two layers 4 and 5 is fixed to the blade supporting sheet metal 2. In this embodiment,
The back electrode 5 is provided on the entire back surface of the base layer rubber 3, and the back electrode 5 and the base layer rubber 3 are electrically connected to each other, but the blade supporting sheet metal 2 and the back electrode layer 5 are electrically connected via the adhesive 2a. It is glued in an insulated state. Therefore, the conductive paint 6 is provided to electrically connect the back electrode layer 5 and the blade supporting sheet metal 2.

The voltage applied from the power source E to the charging blade 10 is applied to the base layer rubber 3 via the blade supporting sheet metal 2, the conductive paint 6 for electrically connecting the blade supporting sheet metal 2 and the back electrode 5, and the back electrode 5. It is applied, and finally applied to the coat layer 4.

The base rubber 3 is epichlorohydrin rubber / E
Conductive powders such as carbon black and metal oxides (zinc oxide, titanium oxide, etc.) are added to rubber such as PDM to control the resistance value to 1 × 10 ⁶ to 1 × 10 ⁹ Ω · cm.

When the resistance is smaller than 1 × 10 ⁶ Ω · cm, current leakage occurs when there is a defect such as a spot on the photosensitive drum 1, and so-called “horizontal white spots”.
(In the case of reversal development, an image defect of "horizontal black band") occurs. On the other hand, when it is 1 × 10 ⁹ Ω · cm or more, the resistance of the blade between the back electrode layer 5 and the coat layer 4 is increased, the applied voltage is greatly attenuated, and the charging property is deteriorated. .. Therefore, the resistance value of the base rubber 3 is 1
× 10 ⁶ Ω · cm to 1 × 10 ⁹ Ω · cm is desirable.

Next, the coat layer 4 will be described. In this embodiment, the coat layer 4 is a urethane elastomer in which zinc oxide is dispersed, and has a thickness of about 20 to 50 μm. The coating layer is coated so that it has the largest thickness at the tip of the charging blade 10 and gradually decreases toward the root of the charging blade 10. In FIG. 1, the coating layer 4 of the charging blade 10 is present only at the tip of the blade, and the base layer rubber 3 is exposed at the root of the blade. However, the thickness of the coating layer 4 gradually increases from the tip. The coat layer 4 may be present on the entire surface of the base rubber layer 3 as long as it is smaller.

The manufacturing procedure of the charging blade 10 having the above-described form will be described with reference to FIG. First, the coating layer 4 is coated on the base layer rubber 3 having a width of two charging blades and the electrode layer 5 provided on one surface thereof.

According to this coating method, the base rubber 3 is supplied while a certain amount of paint is flown out of the nozzle from the gear pump.
Is moved in the longitudinal direction (direction perpendicular to the paper surface) at a constant speed. The layer thickness / shape of the coat layer 4 is determined by the viscosity / solid amount / outflow amount of the paint and the moving speed of the base layer rubber 3. The thickness of the end portion 4a of the coat layer 4 gradually decreases due to the viscosity and surface tension of the coating material.

With this coating method, about 6 mm
FIG. 4 shows a coating obtained by coating (the width of one blade is 3 mm, which is half this width) and measuring the thickness distribution of the coating layer 4. This thickness distribution is obtained by measuring the layer thickness of the coat layer 4 of the charging blade on the right side of the two charging blades 10 obtained by cutting along the line BB in FIG. From Figure 4, the blade tip is about 60μm,
About 50 μm at 1 mm from the tip, 2 from the tip
At the position of mm, the thickness distribution is about 30 μm. This thickness distribution can be changed by adjusting the nozzle shape and the viscosity of the coating liquid. Also, in the coat layer thickness distribution shown in FIG. 4, for example, the cutting position is 1 mm.
Position, the coating thickness is about 50μ at the blade tip.
m, a coating layer having a thickness distribution of about 30 μm is obtained at a position 1 mm from the tip.

(3) Abrasion of Blade Here, the abrasion of the blade and the part actually involved in charging will be described. First, regarding the wear of the blade, the wear state naturally changes depending on the contact state. However, in the case of counter abutment, edge abutment or abdominal abutment abutment including an edge is desirable in the sense that residual substances such as toner are dammed at the edge, and the abrasion at that time naturally occurs at the edge.

Even in the forward direction contact, the vicinity of the edge portion is worn unless it is contacted with an extreme belly. Therefore, wear of the blade occurs at the edge portion or near the edge portion.

On the other hand, the part that contributes to the charging of the charging blade 10 is not the part that is in contact with the photosensitive drum 1 but the part that has an air gap of several μm to several 100 μm. It The reason for this is that when the photosensitive drum 1 is an OPC, charging by charge injection is hardly performed, and charging is performed by a discharge phenomenon that occurs when an electric field of a certain level or more is applied to the minute air gap. Is to be the main.

As explained above, the part of the blade that wears and the part that contributes to charging do not necessarily match.
The part worn by the blade varies depending on the conditions such as the contact angle of the blade, but in the case of abdominal contact including the edge due to counter contact, when the contact angle θ is about 15 ° to 20 °, the blade is worn at the blade edge. Only about 50 μm from the tip is worn. On the other hand, the part that contributes to charging is at least 0.3 mm and 1 m from the blade tip.
It is estimated to be up to about m.

In the present embodiment, the coating thickness of the coating layer 4 is about 60 μm at the tip of the blade edge, and the coating layer thickness is about 50 μm at a position 1 mm from the tip. 50 μm
Abrasion is advantageous by 10 μm as compared with a coat layer having a uniform thickness, and the film thickness remains 50 μm without increasing the thickness at the part that contributes to charging, so that the charging performance is not affected at all. Further, since the film thickness is gradually changed, there is no adverse effect that abnormal discharge occurs in the step of the film thickness.

The charging blade 10 having the coating layer thickness distribution shown in FIG. 4 was set to have a free length L6 mm and a base layer rubber thickness of 1.5 m.
A durability test was conducted under the conditions of m, contact angle θ ° = 15 °, and contact pressure 20 g / cm. The conditions for image output are as follows.

[0059] Images were reproduced condition process speed 50 mm / sec photosensitive drum diameter φ30 applied bias _{AC + DC AC 500H Z, 1800V} PP DC -700V without pre-exposure potential setting dark portion V _D = -700 V light portion V _L = -230V halftone portion V _H = −400 V As a result of durability, the charging property was not impaired until about 8,000 sheets, and after the durability, the photosensitive drum 1 was artificially made a defect and a current leak test was conducted, but no leakage occurred.

When the amount of wear of the blade after running was measured,
It was worn about 50 μm in the thickness direction and about 80 μm in the width direction. This is because the conventional blade with a uniform film thickness of 50 μm is 500
Leakage occurs in the durability of 0 to 6000 sheets,
Compared to the case where the base layer rubber directly contacts the photosensitive drum 1 due to the loss of the coat thickness, which causes an increase in torque, noise, etc., the life extension effect is 1.3 to 1.6 times longer. Admitted.

<Embodiment 2> (FIG. 5) In this embodiment, as in the case of Embodiment 1, the back electrode 5 is provided on the entire back surface of the base layer rubber 3 for two blade widths, and then the coating 2 is applied. The coat layer 4 is formed by repeating the process.

That is, FIG. 5A shows a stage where the first coating of the coating layer is completed, and the coating is performed with the width x. The coating method at this time is a method of printing through a screen mesh, but masking may be performed and spray coating may be performed.

When the coating film 4 of the first coat layer coating is dried, the second coat layer coating 4'is further formed on the coat layer 4 by the same method as the first coat as shown in FIG. 5B. To coat. Due to the viscosity and fluidity of the paint itself, a sagging portion occurs at the end of the coat width y, and a comparatively gentle change in layer thickness can be realized at the boundary between the coat layer 4 and the coat layer 4 '.

After the coating layer 4'has been dried, the blade is cut at the position of the center line B-B to increase the coating layer thickness at the edge portion and gradually decrease the coating thickness. Can be created. Compared to the first embodiment, this embodiment can easily increase the area, and has an advantage of being suitable for mass production.

Example 3 (FIG. 6) In this example, the coat layer 4 is formed by a dipping method. 6 (a), (b), (c), and (d) show the procedure procedure.

(A) 40 is a coating liquid for the coating layer 4,
Reference numeral 2 is a masking member for preventing the coating layer from being attached to the portion of the charging blade 10 where the back electrode is provided.

After the base rubber layer 3 is bonded to the blade supporting sheet metal 2 with the adhesive 2a in advance, the masking member 22 is attached to the portion where the back electrode 5 is provided.

In this embodiment, the masking member 22 is required to provide the back electrode 5 later, but if the back electrode 5 is provided before the coat layer 4 is applied, the masking member 22 is not required. Absent.

The blade 3 provided with the masking member 22 is immersed in the coating liquid 40 of the coating layer 4 and pulled up in the direction of arrow v in the figure at an appropriate speed. It is possible to increase the coating thickness on the tip of the blade by increasing the pulling speed at the start of pulling and then gradually decreasing the pulling speed.

(B) After coating, the dried coat layer 4 is cut at its tip so as to have a predetermined free length L along line HH.

(C) After cutting, the masking member 22 is removed together with the coat layer 4 attached to the masking member 22.

(D) Then, the back electrode 5 is provided, and the back electrode 5 and the blade supporting sheet metal 2 are electrically connected by the conductive paint 6.

The charging blade 10 is manufactured through the above steps (a) to (d). In this embodiment, there is an advantage that the thickness distribution of the coat layer 4 can be freely and easily set by controlling the pulling speed V during dipping.

<Embodiment 4> (FIG. 7) In this embodiment, the coating method of the coat layer 4 is the same as that of Embodiment 1 or 2. However, the cross-sectional shape of the base rubber layer 3 is different. That is,
The thickness of the base rubber layer 3 having the width of two blades is set to the central portion d.
Molded so that ₁ is thin. The central part c ₁ is the end part c
_The thickness is made to be thinner by about 50 μm to 200 μm than that of ₂ . The base layer rubber 3 is uniformly coated with the coating layer 4 centered on the central portion c _{1 so} that the coating layer 4 on the edge portion and the blade tip portion when cut BB from the central portion.
Thickens.

[0075]

As described above, according to the present invention, in the contact charging device using the charging blade as the charging member, the life of the device is improved by preventing the deterioration of the life due to the abrasion of the charging blade without impairing the charging property. Can be planned.

[Brief description of drawings]

FIG. 1 is a photosensitive drum 1 in which a charging blade of a contact charging device is used.
Cross-sectional view showing how it is in contact with the

2 is a schematic configuration diagram of a main part of an example of an image forming apparatus using the contact charging device shown in FIG.

[Fig. 3] Manufacturing procedure diagram of charging blade

FIG. 4 Graph of thickness distribution of coat layer

5 (a) and 5 (b) are manufacturing process diagrams of the charging blade of the second embodiment.

FIG. 6A to FIG. 6D are manufacturing process diagrams of the charging blade of the third embodiment.

FIG. 7 is a manufacturing procedure diagram of the charging blade of the fourth embodiment.

FIG. 8 is an explanatory diagram of spark discharge caused by a pinhole on a body to be charged when the charging member is a charging blade.

FIG. 9 is a cross-sectional view of a charging blade in which a resistance layer is not provided on an edge facet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charged object (image bearing member, photosensitive drum) 10 Charging blade 2 Blade supporting sheet metal 3 Base layer rubber 4 Coat layer 5 Back electrode layer 6 Conductive paint E Power supply

Claims (1)

[Claims] 1. A contact charging device for charging by charging a conductive member to which a voltage is applied to a member to be charged, wherein the conductive member has a blade shape having a two-layer structure and is in contact with the member to be charged. The one layer including the contact portion has higher resistance than other layers not including the contact portion with the charged body, and the thickness is gradually smaller than the tip in the direction orthogonal to the blade longitudinal direction, The contact charging device, wherein the volume resistance value of the other layer not including the contact portion is 1 × 10 ⁶ to 1 × 10 ⁹ Ωcm.