JP2007178599A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of uniforming particles irregularly depositing on the surface of a photoreceptor to suppress electrifying irregularity and maintaining excellent image characteristics for a long period of time, and to provide an image forming method using the apparatus. <P>SOLUTION: In the image forming apparatus, in which an electrifying means, a developing means, a transfer means and a destaticizing means are sequentially arranged around an electrophotographic photoreceptor, the electrifying means is a contact type electrifying means, a uniforming means for uniforming particles on the surface of the electrophotographic photoreceptor is arranged between the electrifying means and the destaticizing means, the uniforming means comprises a conductive brush in contact with the surface of the electrophotographic photoreceptor and a reciprocating means to reciprocate the conductive brush in a direction orthogonal to the rotation direction of the electrophotographic photoreceptor, and a value expressed by ¾ω/ω<SB>1</SB>¾ is controlled to ≥0.5, wherein ω represents an angular velocity of circular motion corresponding to the above reciprocation and ω<SB>1</SB>represents an angular velocity of the electrophotographic photoreceptor when it is rotated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic photosensitive member and an image forming method using the same, and in particular, using a uniformizing means that reciprocates (thrusts) at a predetermined angular velocity with respect to the surface of the electrophotographic photosensitive member. The present invention relates to an image forming apparatus capable of maintaining excellent image characteristics by leveling particles remaining on the surface of an electrophotographic photosensitive member, and an image forming method using the same.

2. Description of the Related Art Conventionally, an image forming apparatus used for a printer, a copy, and the like forms a latent image by exposing a surface of an electrophotographic photosensitive member to charge the electrophotographic photosensitive member and the surface of the charged photosensitive member. An exposure unit, a developing unit that transfers toner to the latent image and develops, a transfer unit that transfers the toner onto a recording sheet to form an image, and a charge eliminating unit that eliminates residual potential remaining on the surface of the photoreceptor after transfer. And an image forming process in which the means are sequentially arranged.
Here, as such charging means, a contact charging method in which a charging member such as a charging roller is brought into direct contact with the surface of the electrophotographic photosensitive member, and a non-contact charging method in which the surface of the photosensitive member is corona charged using a corona charger. However, since the overall configuration is simple and no harmful substances such as ozone are generated, the contact charging method has been put to practical use more.
However, in this contact charging method, the surface of the electrophotographic photosensitive member and the charging member are in direct contact with each other, so that the developer component particles remaining on the surface of the photosensitive member after printing adhere to the surface of the charging member. In some cases, uneven charging occurred. Such charging unevenness has become more prominent due to the presence of a so-called transfer memory in which a potential having a polarity opposite to the charging polarity remains on the surface after transfer.

In order to solve such a problem, as shown in FIG. 10, an image forming apparatus adopting a reversal development method, which includes a contact primary charging roller 202, a developing unit 204, a transfer unit 206, In the image forming apparatus 200 including the pre-exposure lamp 209, a contact type pre-charging roller 208 that is charged to the same polarity as the charging roller 202 is provided on the upstream side of the charging roller 202. There has been proposed an image forming apparatus capable of erasing a transfer memory by pulling up the surface of a photosensitive member charged to polarity to the same polarity by a pre-charging roller. (For example, refer to Patent Document 1.)
JP-A-6-83249 (Claims, FIG. 1)

  However, the image forming apparatus described in Patent Document 1 is a method in which the generated transfer memory is directly erased by the pre-charging roller 208, and foreign matter remaining on the surface of the electrophotographic photosensitive member adheres to the charging roller 202. In such a case, there was still a problem that uneven charging and uneven density on the image occurred.

Therefore, as a result of intensive investigations, the inventors of the present invention have used an image forming apparatus provided with a uniformizing means that reciprocates (thrusts) at a predetermined angular velocity between the transfer means and the static elimination means. The present invention has been completed by finding out that uneven charging can be suppressed by uniformly flattening the particles adhering to the surface of the photoreceptor and stabilizing the charged state of the electrophotographic photoreceptor. It is.
That is, the object of the present invention is to remove particles adhering unevenly to the surface of a photoreceptor by reciprocating a conductive brush at a predetermined angular velocity even when a contact charging method is adopted as a charging means. An object of the present invention is to provide an image forming apparatus and an image forming method using the image forming apparatus that can maintain uniform image quality over a long period of time by suppressing charging unevenness uniformly.

According to the present invention, in the image forming apparatus in which the charging unit, the developing unit, the transfer unit, and the charge eliminating unit are sequentially arranged around the electrophotographic photosensitive member, the charging unit is a contact type charging unit. In addition, a uniformizing means for leveling the particles on the surface of the electrophotographic photosensitive member is disposed between the charging means and the discharging means, and the uniformizing means is a conductive brush that contacts the surface of the electrophotographic photosensitive member. And reciprocating means for reciprocating the conductive brush in a direction perpendicular to the rotation direction of the electrophotographic photosensitive member, and the angular velocity of the circular motion corresponding to the reciprocating motion is ω, Provided is an image forming apparatus characterized in that a value represented by | ω / ω ₁ | is 0.5 or more when an angular velocity when the body is rotated is ω _1, and solves the above-described problem can do.
That is, according to the image forming apparatus of the present invention, the conductive brush can reciprocate at a predetermined angular velocity, and the particles adhering to the surface of the electrophotographic photosensitive member can be made uniform. Since the uniformized particles adhere to the surface of the charging member, there is little occurrence of charging unevenness, and excellent charging characteristics can be maintained.
In the present invention, the angular velocity ω of the circular motion corresponding to the reciprocating motion means an angular velocity in the circular motion when the reciprocating motion is regarded as an orthogonal projection of the circular motion (constant speed circular motion).

In constituting the present invention, the reciprocating means includes a drum gear concentrically coupled to the end of the electrophotographic photosensitive member, a thrust gear meshing with the drum gear, and a concentric coupling with the thrust gear on the outer side surface. A cam disk having an inclined surface; an urging means provided at one end of the conductive brush for urging the conductive brush toward the cam disk; and one end abutting the inclined surface and the other end being conductive. It is preferable that the contact piece is fixed to the conductive brush.
With this configuration, the reciprocating motion of the conductive brush is interlocked with the rotating motion of the photosensitive drum via the gear, and the number of parts is larger than when an independent power source is disposed as the reciprocating means. And a simple configuration with little.
Also, the value represented by | ω / ω ₁ | described above can be uniquely defined by the gear ratio between the drum gear and the thrust gear, and the speed can be adjusted effectively.

In constructing the present invention, the conductive brush is composed of a conductive base material and conductive brush fibers, and the conductive base material is applied with a voltage for applying a predetermined voltage to the electrophotographic photosensitive member. Preferably the means are connected.
With this configuration, it is possible to apply a predetermined voltage to the surface of the photoreceptor using the uniformizing means, and it is possible to erase the transfer memory existing on the surface of the electrophotographic photoreceptor.
That is, the uniformizing means can have a function as a pre-charging means for erasing the transfer memory, and higher quality image characteristics can be maintained.

In constituting the present invention, it is preferable to set the raw yarn resistance of the conductive brush fiber to a value of 1 × 10 ¹¹ (Ω · cm) or less.
With this configuration, it is possible to effectively remove static electricity generated when contacting the surface of the electrophotographic photosensitive member, and when the voltage is applied to the uniformizing means, the conductive brush fibers The transfer memory can be more effectively removed by functioning as a conductor.

In configuring the present invention, a stainless steel plate is preferably used as the conductive substrate.
By comprising in this way, it can be set as the electroconductive brush excellent in electroconductivity and mechanical strength. Therefore, even when the frequency of reciprocating motion is changed, the conductive brush can exhibit an excellent uniformizing effect without plastic deformation.

In constructing the present invention, it is preferable that the electrophotographic photosensitive member is a single layer type electrophotographic photosensitive member.
By comprising in this way, an electrophotographic photoreceptor can be made into a simple structure and the manufacturing process can be simplified.

In constituting the present invention, it is preferable to set the initial charging potential of the electrophotographic photosensitive member by the charging means to a value of 400 (V) or more.
With this configuration, the uniformizing means as the pre-charging means can erase the transfer memory while maintaining the desired image characteristics, and an excellent charge eliminating effect can be exhibited.

Another aspect of the present invention is an image forming method using an image forming apparatus in which a charging unit, a developing unit, a transfer unit, and a charge eliminating unit are sequentially arranged around an electrophotographic photosensitive member. The charging means is a contact-type charging means, and a uniformizing means for leveling the particles on the surface of the electrophotographic photosensitive member is disposed between the charging means and the charge eliminating means. The uniformizing means is an electrophotographic photosensitive member. A conductive brush in contact with the body surface, and reciprocating means for reciprocating the conductive brush in a direction orthogonal to the rotation direction of the electrophotographic photosensitive member, and having a circular motion corresponding to the reciprocating motion An image forming method characterized in that the value represented by | ω / ω ₁ | is 0.5 or more, where ω is the angular velocity and ω ₁ is the angular velocity when the electrophotographic photosensitive member is rotated. is there.

[First Embodiment]
Hereinafter, as an image forming apparatus according to the first embodiment of the present invention, an image forming apparatus in which a charging unit, a developing unit, a transfer unit, and a charge eliminating unit are sequentially arranged around an electrophotographic photosensitive member. The charging means is a contact-type charging means, and a uniformizing means for leveling the particles on the surface of the electrophotographic photosensitive member is disposed between the transfer means and the charge eliminating means. A conductive brush in contact with the surface of the photographic photosensitive member, and reciprocating means for reciprocating the conductive brush in a direction perpendicular to the rotation direction of the electrophotographic photosensitive member. Taking an example of an image forming apparatus in which the value represented by | ω / ω ₁ | is 0.5 or more, where ω is the angular velocity of motion and ω ₁ is the angular velocity when the electrophotographic photosensitive member is rotated. Specific description with reference to FIGS. To do.

1. Basic Configuration FIG. 1 shows a basic configuration of an image forming apparatus according to the present invention. The image forming apparatus 10 includes a drum-type electrophotographic photosensitive member (hereinafter also referred to as a photosensitive member) 11, and around the photosensitive member 11 along a rotation direction indicated by an arrow A. A charging unit 12, an exposure unit 13 for forming a latent image on the surface of the photosensitive member, a developing unit 14 for developing the latent image by attaching toner to the surface of the photosensitive member, and the toner on the recording paper 20. A transfer means 15 for transferring to the surface of the photosensitive member, a cleaning device 17 for removing residual toner on the surface of the photoconductor, and a uniformization for leveling particles that cannot be completely removed by the cleaning device 17 but remain unevenly on the surface of the photoconductor. Means 2 and static elimination means 18 for removing the residual potential on the surface of the photoreceptor are sequentially arranged.
The charging unit 12 is connected to a power source 19 for applying a charging application voltage.
The power source 19 can apply only a direct current component (DC), and can also be a superimposed voltage obtained by superimposing an alternating current component (AC) on the direct current component. At this time, the polarity of the power source 19 is connected so that the charging means 12 side is a positive electrode, whereby the image forming apparatus can be of a positive charging type.
A power source 22 is connected to the transfer means 15. The power source 22 is a power source to which a direct current component (DC) can be applied, and its polarity is connected so that the transfer means side is a negative electrode. By connecting in this way, the image forming apparatus can be a reversal developing type image forming apparatus.
Further, the uniformizing means 2 includes a conductive brush 50 in contact with the surface of the electrophotographic photosensitive member 11 and a reciprocating means 70 for reciprocating the conductive brush 50 in a direction perpendicular to the rotation direction of the electrophotographic photosensitive member. And is composed of. Particles that could not be completely removed by the cleaning device 17, for example, inorganic fine particles as external additives such as titanium oxide, can be made uniform on the surface of the electrophotographic photosensitive member 11 by the homogenizing means 2.

2. Uniformizing means (1) Reciprocating means Next, the configuration and operating principle of the reciprocating means 70 will be described with reference to FIGS. 2 and 3A to 3C.
2 is a schematic perspective view of the reciprocating means 70 and the conductive brush 50 viewed from an oblique direction, and FIGS. 3A to 3C are schematic plan views when viewed from the arrow Y direction in FIG. is there.
As shown in FIG. 2, the reciprocating means 70 includes a drum gear 71 concentrically coupled to the end of the electrophotographic photosensitive member 11, a thrust gear 72 disposed so as to mesh with the drum gear 71, and the thrust gear 72. And a cam disc 73 having an inclined surface 73a on the outer side surface, a contact piece 74 having one end in contact with the inclined surface 73a and the other end fixed to the conductive brush 50, and the conductive brush 50. And a spring coil (biasing means) 75 that urges the conductive member 50 toward the cam disk 73.
The conductive brush 50 to which the contact piece 74 is fixed includes a conductive base material 51 having a plate shape, and conductive brush fibers 52 provided so as to be planted on the conductive base material 51. , Is composed of.
The conductive brush 50 configured as described above is arranged so as to be always pressed in the direction of arrow X in the figure by the spring coil 75, and the contact piece 74 that is in contact with the center of rotation of the inclined surface 73a is displaced. Accordingly, the particles remaining on the surface of the electrophotographic photosensitive member 11 can be smoothed by reciprocating (thrusting) in the X direction and the −X direction.

Here, the principle of operation of the reciprocating means 70 will be described in more detail with reference to FIG.
FIGS. 3A to 3C are schematic plan views when FIG. 2 is viewed from the direction of the arrow Y in the drawing, and FIGS. It is the figure shown along.
First, FIG. 3A shows a state when the long axis position (A) of the cam disk 73 having the inclined surface 73a comes to the top.
At this time, the contact piece 74 that is in contact with the long axis position (A) of the cam disk 73 is located on the rightmost side in the movable range.
That is, it can be said that the conductive brush 50 in FIG. 3A is in the rightmost position as viewed from the electrophotographic photosensitive member 11 while being urged leftward in the drawing by the spring coil 75.
Next, FIG. 3B illustrates a state when the cam disk 73 rotates 90 ° from the state of FIG. That is, the contact piece 74 is in contact at an intermediate position (B) between the long axis position and the short axis position of the cam disk 73. Therefore, the contact piece 74 is positioned at the center within the movable range.
That is, it can be said that the conductive brush 50 in FIG. 3B is in a state of being positioned at the center of vibration as viewed from the electrophotographic photosensitive member 11 while being urged leftward in the drawing by the spring coil 75.
Next, FIG. 3C illustrates a state where the cam disk 73 is further rotated by 90 ° from the state of FIG. That is, the contact piece 74 is in contact with the short axis position (C) of the cam disk 73. Therefore, the contact piece 74 is positioned on the leftmost side within the movable range.
That is, it can be said that the conductive brush 50 in FIG. 3C shows a state of being leftmost as viewed from the electrophotographic photosensitive member 11 while being urged leftward in the drawing by the spring coil 75.
That is, by continuously performing the series of operations shown in FIGS. 3A to 3C, the conductive brush 50 reciprocates with a predetermined amplitude in the axial direction of the electrophotographic photosensitive member 11. Become.

(2) Angular velocity In the image forming apparatus according to the present invention, when the angular velocity of the reciprocating motion is ω and the angular velocity of the electrophotographic photosensitive member is ω ₁ , the value represented by | ω / ω ₁ | is 0.5. It is characterized by the above.
Here, the influence of the definition of the angular velocity ω and the value of | ω / ω ₁ | on the image characteristics will be described in detail.
First, the angular velocity ω used in the present invention is defined as the angular velocity of circular motion corresponding to reciprocating motion. More specifically, as shown in FIG. 4, a circular orbit of an arbitrary point P on the conductive brush when the reciprocating motion is regarded as a circular motion (constant velocity circular motion) is defined as (A), and the point P When the time change of is a curve (B), the reciprocating motion can be expressed as x = (A / 2) cos (ωt + φ) as position x, amplitude A, angular velocity ω, time t, and initial phase φ.
That is, it can be said that the reciprocating motion of the conductive brush 50 is a motion when the point P on the circular orbit (A) is orthogonally projected.
On the other hand, another angular velocity ω ₁ in the present invention is defined as an angular velocity when the electrophotographic photosensitive member is rotated. That is, it means an angular velocity around the rotation axis when the electrophotographic photosensitive member 11 shown in FIG. 2 or the like rotates in a predetermined direction, and between the linear velocity V (mm / sec) and the electrophotographic photosensitive member. Assuming that the diameter of the body 11 is φ (mm), there is a relationship of V = (φ / 2) × ω ₁ .

Next, the influence of the ratio of the angular velocities | ω / ω ₁ | on the image characteristics will be described.
FIG. 5 is a characteristic diagram showing the adhesion state of particles adhering to the charging means when | ω / ω ₁ | is changed.
In this characteristic diagram, the horizontal axis represents the angular velocity ratio | ω / ω ₁ |, and the vertical axis represents the uniformity of particles adhering to the surface of the charging means.
As can be understood from the characteristic diagram, it can be said that as the angular velocity ratio | ω / ω ₁ | is increased, the particles adhering to the surface of the charging unit are made more uniform. That is, it can be said that as the angular velocity ratio | ω / ω ₁ | is increased, the initial charging potential is stabilized and the obtained image characteristics are improved.
However, when the angular velocity ratio | ω / ω ₁ | is excessively increased, the number of times of contact between the electrophotographic photosensitive member surface and the conductive brush may increase excessively and the photosensitive member surface may be worn.
Furthermore, the gear ratio between the drum gear and the thrust gear may become too large, and an excessive load may be applied mechanically.
Conversely, when the angular velocity ratio | ω / ω ₁ | is reduced, depending on the state of particle adhesion, it may not be sufficiently removed, and particle adhesion unevenness may occur on the charging roller.
Therefore, the range of the angular velocity ratio | ω / ω ₁ | is preferably set to a value in the range of 1.0 to 4.0, and more preferably in the range of 1.5 to 2.5. preferable.

Further, the range of amplitude of reciprocation is preferably 1 (mm) or more.
The reason is that as the amplitude is increased, the adhered particles can be made uniform over a wider range, and uneven adhesion on the charging means can be prevented.
However, when the amplitude is set to be excessively large, the number of times of contact between the electrophotographic photosensitive member surface and the conductive brush may increase excessively and the photosensitive member surface may be worn. Furthermore, the movable range of the conductive brush may be too wide, which may hinder downsizing of the device.
Therefore, the range of the amplitude of the reciprocating motion is preferably set to a value in the range of 1.3 to 5.0 (mm), and a value in the range of 1.5 to 3.0 (mm). Is more preferable.

(3) Conductive brush Moreover, the conductive brush used for this invention is provided so that it may be planted in the electroconductive base material 51 which has plate shape, and this electroconductive base material 51, as shown in FIG. The conductive brush fibers 52 are provided with contact pieces 74 and urging means 75 at both ends thereof. The conductive brush 50 configured in this manner is connected to the reciprocating means 70 via the contact piece 74 and reciprocates so that the conductive brush fibers 52 can remove particles adhered to the surface of the electrophotographic photosensitive member. It can be uniformly scattered and uniformized.
In such a conductive brush 50, the material of the conductive brush fiber 52, which is a member in direct contact with the surface of the electrophotographic photoreceptor 11, is preferably a polyamide resin or a polyester resin containing conductive particles.
The reason for this is that by using such a conductive fiber, static electricity due to friction can be efficiently removed, and when a voltage is applied to the uniformizing means, the conductive brush fiber functions as a conductor. This is because the transfer memory can be removed more effectively.
Moreover, in adjusting the yarn resistance of the conductive brush fiber, the conductivity can be easily controlled by adjusting the amount of conductive particles such as carbon.

In addition, when such a conductive brush fiber is used, it is preferable that the resistance of the yarn is 1 × 10 ¹¹ (Ω · cm) or less.
The reason for this is that if the value of the yarn resistance of the conductive brush fiber is excessively high, it is necessary to apply a high voltage to erase the transfer memory, and the contact between the conductive brush fiber and the surface of the photoreceptor is caused. This is because abnormal discharge may occur in the vicinity of the portion and image characteristics may be degraded. Conversely, if the yarn resistance of the conductive brush fibers is excessively lowered, the discharge phenomenon is less likely to occur, and the transfer memory may not be completely erased.
Accordingly, the range of the yarn resistance is preferably a value within the range of 1 × 10 ³ to 1 × 10 ¹⁰ (Ω · cm), and preferably 1 × 10 ⁵ to 1 × 10 ⁹ (Ω · cm). It is more preferable to set the value within the range.

Moreover, it is preferable to make the bristle length in a conductive brush fiber into the value within the range of 2-7 (mm).
The reason for this is that by setting the value within such a range, the curved state of the conductive brush fibers when in contact with the surface of the photoreceptor can be regulated within a predetermined range. This is because the abnormal discharge can be effectively prevented.
In addition, when the length of the bristle is less than 2 (mm), depending on the drum diameter of the photoconductor, a non-contact region is formed at the end of the conductive brush, which may cause abnormal discharge. . On the other hand, when it exceeds 7 (mm), the curved portion of the conductive brush fiber becomes excessively long, which may cause abnormal discharge.
Accordingly, the length of the bristle foot in the conductive brush fiber is more preferably a value in the range of 3 to 6 (mm), and further preferably a value in the range of 4 to 5 (mm).

The fiber density of the conductive brush fibers in the conductive brush is preferably set to a value of 180 kF / inch ² (≈28 kF / cm ² ) or less.
The reason for this is that by setting the value within such a range, the contact state between the conductive brush fibers can be defined, and abnormal discharge resulting from uneven contact between the conductive brush fibers can be prevented. is there.

Moreover, when prescribing the thickness of the conductive brush fibers constituting the conductive brush, it is preferable to set the single yarn fineness of the brush fibers to a value of 6 (denier) or more.
The reason for this is that by setting the value within such a range, the contact area between the conductive brush fiber and the photosensitive member can be made a predetermined value or more, and the occurrence of abnormal discharge can be effectively prevented. Because. Moreover, it is because the value of the yarn yarn resistance of the brush fiber can be controlled using the value of the single yarn fineness, and the resistance value of the brush fiber can be controlled with higher accuracy.

(4) Conductive substrate The conductive substrate according to the present invention is not particularly limited as long as it has conductivity and sufficient mechanical strength. For example, stainless steel, copper, Further, it is preferable to use a metal plate such as aluminum, and a stainless steel plate is particularly preferable.
The reason for this is that a stainless steel plate is particularly excellent in conductivity and mechanical strength, so that the conductive brush can be prevented from being deformed and a stable uniform effect can be obtained over a long period of time.

(5) Charging characteristics Next, as an additional function of the homogenizing means 2, as described above, the homogenizing means 2 is made of a conductive material. A function as a means can be added.
As shown in FIG. 1, it is preferable that a voltage applying means 61 for applying a predetermined voltage is connected to the uniformizing means 2 as shown in FIG.
More specifically, the voltage applying means 61 is electrically connected to the conductive base 51 constituting the conductive brush 50 so that the conductive brush 50 side becomes a positive electrode, and the transfer means 15 The reverse polarity is applied.
Further, the voltage applying means 61 can apply only a direct current component (DC) in accordance with the mode of the homogenizing means 2, and further, in order to obtain a stable charging characteristic by expanding the charging saturation region. A superimposed voltage obtained by superimposing an alternating current component (AC) on the direct current component can also be used.

Further, in the uniformizing means 2, a predetermined amount of charge is applied to the surface of the electrophotographic photosensitive member via the conductive brush fibers 51 by applying a predetermined voltage to the conductive brush 50 using the voltage applying means 61. The transfer memory generated by the transfer means can be erased.
At this time, as an application condition applied to the uniformizing means 2, the current density (I _b ) of the current flowing from the conductive brush 50 to the photoconductor 11 can be set to a value of 700 (μA / m ² ) or more. .
Here, FIG. 6 shows the current density (I _b ) of the current injected from the conductive brush and the transfer memory potential (V _t ) when a positively charged electrophotographic photosensitive member is used as the photosensitive member. The characteristic figure showing a relationship is shown.
In FIG. 6, the horizontal axis represents the current density (I _b ) of the current injected from the conductive brush, and the vertical axis represents the transfer memory potential (V _t ).
That is, in the vertical axis, the upper part means that the transfer memory is erased by the uniformizing means, and the lower part means that the transfer memory is not sufficiently erased by the uniformizing means. is doing.
Further, curves (A) to (D) in FIG. 6 are characteristic curves when conductive brush fibers having different yarn resistances are used. More specifically, the curves at 1 × 10 ^12.5 (Ω · cm), 1 × 10 ^10.5 (Ω · cm), 1 × 10 ^8.5 (Ω · cm), and 1 × 10 ^6.5 (Ω · cm) in this order. Represents.
In the present invention, the transfer memory potential (V _t ) is defined as the amount of change in the surface potential of the photoreceptor surface at the development position when continuous printing is performed.
More specifically, when a blank paper image is printed by continuously rotating the photoconductor, the surface potential of the photoconductor surface at the development position at the first round is set to (V ₁ ), and the third round the surface potential of the photosensitive member surface at the developing position when the when the _{(V 3), (V 1} ) - is defined as a value expressed by (V _3).

As can be understood from FIG. 6, regardless of the value of the yarn resistance of the conductive brush fiber, the higher the current density (I _b ), the smaller the remaining transfer memory potential becomes, particularly 700 (μA). / M ² ) or more, it can be said that erasure is stable.
Conversely, when the current density (I _b ) is excessively high, abnormal discharge may occur in the vicinity of the contact portion between the conductive brush and the surface of the photoreceptor, which may cause a problem in charging characteristics.
Therefore, the range of the current density (I _b ) is preferably a value in the range of 700 to 2000 (μA / m ² ), and a value in the range of 1000 to 1500 (μA / m ² ). It is more preferable.
In the present invention, the current density means a value obtained by dividing a current value by an application area per second. That is, when the current having the current value I (A) flows to the photosensitive member rotating at the shaft length L (mm) and the outer peripheral speed D (mm / sec), the current density is I / (L × D ) (ΜA / m ² ).

FIG. 7 is a characteristic diagram showing the relationship between the voltage applied to the conductive brush (V _b ) and the transfer memory potential (V _t ).
In this characteristic diagram, the horizontal axis represents the applied voltage (V _b ) to the conductive brush, and the vertical axis represents the transfer memory potential (V _t ).
That is, FIG. 7 corresponds to the current density (I _b ) in FIG. 6 converted to a voltage using the respective yarn resistance values of the characteristic curves (A) to (D).
As can be understood from FIG. 7, it can be said that the higher the value of the yarn resistance of the conductive brush, the higher the voltage that needs to be applied to erase the transfer memory. In particular, when compared with the same applied voltage, it can be seen that when the yarn resistance of the conductive brush fiber exceeds 1 × 10 ¹¹ (Ω · cm), erasing of the transfer memory potential becomes extremely insufficient.
Accordingly, the range of the yarn resistance is preferably a value within the range of 1 × 10 ³ to 1 × 10 ¹⁰ (Ω · cm), and preferably 1 × 10 ⁵ to 1 × 10 ⁹ (Ω · cm). It is more preferable to set the value within the range.

Moreover, it is preferable that the applied voltage (V _b ) to the conductive brush is a DC voltage of 1100 (V) or more. This is because, as shown in FIG. 7, the transfer memory potential (V _t ) can be lowered regardless of the specific resistance value of the conductive brush.
On the other hand, when the applied voltage (V _b ) is excessively increased, abnormal discharge may occur between the conductive brush and the photosensitive member, which may adversely affect the charging characteristics.
Therefore, the applied voltage (V _b ) is preferably set to a value within the range of 1100 to 3000 (V), and more preferably set to a value within the range of 1100 to 2000 (V).

When the current density of current injected from the conductive brush is I _b (μA / m ² ) and the current density of current injected from the transfer means is I _t (μA / m ² ), | I _The value represented by _b / I _t | is preferably 2 or more.
Here, FIG. 8 shows the current density (I _b ) of the current injected from the conductive brush and the transfer memory potential (V) when a conductive brush fiber having a predetermined yarn resistance is used as the conductive brush. and _t), the relationship shows a current density (I _t) characteristic diagram showing each of the current injected from the transfer means 15. The curve in FIG. 8 (E) ~ (G), the current density of the current injected from the transfer means (I _t) is ^{sequentially, -395 (μA / m 2)} , - 316 (μA / m 2 ), −237 (μA / m ² ).
FIG. 9 is a characteristic diagram in which the horizontal axis in FIG. 8 is converted to | I _b / I _t |.
As can be understood from these characteristic diagrams, the larger the absolute value of the current density (I _t ) of the current injected from the transfer means, the higher the transfer memory potential (V _t ), and more specifically, | I _b / I It can be seen that when the value represented by _t | is 2 or more, the transfer memory potential (V _t ) is sufficiently lowered.
That is, in the characteristic curve (E), when the absolute value of the current density (I _b ) of the current injected from the conductive brush is 790 or more, the transfer memory potential is lowered. In addition, the absolute value of I _b is 632 or more in the characteristic curve (F), and the absolute value of I _b is 474 or more in the characteristic curve (G).
Conversely, when the current density (I _b ) is excessively high, abnormal discharge may occur in the vicinity of the contact portion between the conductive brush and the surface of the photoreceptor, which may cause a problem in charging characteristics.
Therefore, the value represented by | I _b / I _t | is preferably set to a value in the range of 2.5 to 8.0, and more preferably set to a value in the range of 3.0 to 6.0. preferable.

(6) Charging means In the present invention, the charging means for charging the surface of the photosensitive member to a predetermined potential is a contact-type charging means.
This contact-type charging means is smaller than the case where a non-contact charging type such as corona charging is adopted, and does not generate harmful substances such as ozone generated during corona charging. It is a charging means with excellent environmental properties.
However, since it is configured to be in direct contact with the surface of the electrophotographic photosensitive member, a developer component that remains unevenly on the surface of the electrophotographic photosensitive member after printing, for example, an external additive such as titanium oxide is charged by the charging member. May adhere unevenly to the surface of the film and cause uneven charging.
Therefore, in the present invention, by providing a uniformizing means that reciprocates at a predetermined angular velocity, even when a contact-type charging means is used as the charging means, it remains non-uniformly in the previous stage of the charging means. Particles can be evenly distributed, and the occurrence of uneven charging can be suppressed.
The electrophotographic photosensitive member used in the present invention may be either a single layer type or a laminated type, but is preferably a single layer type electrophotographic photosensitive member.
This is because the manufacturing process can be simplified as compared with the laminated type. In addition, even when a positive charging method that charges the surface of the photosensitive member to a positive polarity is adopted as the charging method, the problem of narrowing the charging saturation region that occurs when a superimposed voltage is used as the charging applied voltage is solved. This is because the surface of the electrophotographic photosensitive member can be stably charged.

The initial charging potential of the electrophotographic photosensitive member by this charging means is preferably set to a value of 400 (V) or more.
This is because by setting the initial charging potential to a predetermined value or more, a desired image density can be obtained while suppressing image unevenness.

Further, in the charging unit, it is preferable to use conductive rubber or conductive sponge as a member of the contact portion with the surface of the photoreceptor.
More specifically, an ionic conductive agent is added to semi-conductive polar rubber (ionic conductive rubber) such as epichlorohydrin rubber and acrylonitrile-butadiene copolymer (NBR), urethane rubber, acrylic rubber, silicone rubber, etc. Thus, ion conductive rubber or the like imparted with semiconductivity can be used. At this time, the volume resistivity is preferably set to a value in the range of 1 × 10 ³ to 1 × 10 ¹⁰ (Ω · cm).

(7) Moving Means Further, the uniformizing means 2 is preferably provided with a moving means capable of changing the distance between the conductive brush 50 and the surface of the electrophotographic photosensitive member 11. The reason for this is that by using such a moving means, the pressing force between the conductive brush and the surface of the photosensitive member can be adjusted, and the conductive brush and the electrophotographic photosensitive member can be adjusted according to the adhesion state of the particles. This is because the contact state can be appropriately adjusted.
At this time, the pressing force of the conductive brush against the surface of the photosensitive member is preferably set to a value within the range of 0.1 to 100 (kgf / cm ² ). If the value is within such a range, the adhered particles can be effectively made uniform without imposing an excessive load on the driving of the photoreceptor.

[Second Embodiment]
Another aspect of the present invention is an image forming method using an image forming apparatus in which a charging unit, a developing unit, a transfer unit, and a charge eliminating unit are sequentially arranged around an electrophotographic photosensitive member. The charging means is a contact-type charging means, and a uniformizing means for leveling the particles on the surface of the electrophotographic photosensitive member is disposed between the charging means and the charge eliminating means. The uniformizing means is an electrophotographic photosensitive member. A conductive brush in contact with the body surface, and reciprocating means for reciprocating the conductive brush in a direction orthogonal to the rotation direction of the electrophotographic photosensitive member, and having a circular motion corresponding to the reciprocating motion An image forming method characterized in that the value represented by | ω / ω ₁ | is 0.5 or more, where ω is the angular velocity and ω ₁ is the angular velocity when the electrophotographic photosensitive member is rotated. is there.
Hereinafter, the contents already described in the first embodiment will be omitted, and the second embodiment will be described focusing on differences from the first embodiment.
In carrying out the image forming method of the second embodiment, an image forming apparatus 10 as shown in FIG. 1 can be suitably used.
Here, FIG. 1 is a schematic diagram showing the overall configuration of the image forming apparatus. Hereinafter, the operation will be described in order.
First, the photoconductor 11 of the image forming apparatus 10 is rotated at a predetermined process speed (circumferential speed) in the direction indicated by the arrow A, and then the surface is charged to a predetermined potential by the charging unit 12.
Next, the exposure unit 13 exposes the surface of the photoconductor 11 through a reflection mirror or the like while being optically modulated in accordance with image information. By this exposure, an electrostatic latent image is formed on the surface of the photoreceptor 11.
Next, based on the electrostatic latent image, latent image development is performed by the developing unit 14. The developing means 14 contains toner, and the toner adheres corresponding to the electrostatic latent image on the surface of the photoconductor 11 to form a toner image.
Further, the recording paper 20 is conveyed to the lower part of the photoconductor along a predetermined transfer conveyance path. At this time, a toner image can be transferred onto the recording material 20 by applying a predetermined transfer bias between the photoconductor 11 and the transfer means 15.

Next, the recording paper 20 on which the toner image has been transferred is separated from the surface of the photoconductor 11 by a separating unit (not shown) and conveyed to a fixing device by a conveying belt. Next, the toner image is fixed on the surface by being heated and pressed by the fixing device, and then discharged to the outside of the image forming apparatus 10 by a discharge roller.
On the other hand, the photoconductor 11 after the toner image is transferred continues to rotate, and residual toner (adhered matter) that has not been transferred to the recording paper 20 at the time of transfer is removed from the surface of the photoconductor 11 by the cleaning device 17 of the present invention. .
Further, particles that could not be removed by the cleaning device 17, for example, inorganic fine particles as external additives such as titanium oxide, are made uniform and flattened by the homogenizing means 2.
Further, the charge remaining on the surface of the photoconductor 11 is completely erased by the discharge of the charge removal light from the charge remover 18 and is used for the next image formation.
Therefore, by using the image forming apparatus of the present invention, even when the contact charging method is adopted as the charging means, the uniformizing means that reciprocates at a predetermined angular velocity is used to non-uniformly adhere to the surface of the photoreceptor. It is possible to maintain excellent image characteristics over a long period of time by uniformizing the particles being processed.

[Example 1]
1. Preparation of electrophotographic photosensitive member 2.7 parts by weight of X-type metal-free phthalocyanine as a charge generating substance, 50 parts by weight of a stilbene amine compound as a hole transporting agent, 35 parts by weight of an azoquinone compound as an electron transporting agent, and a binder resin As follows, 100 parts by weight of bisphenol Z-type polycarbonate resin having an average molecular weight of 30000 and 700 parts by weight of tetrahydrofuran were placed in a stirring vessel, and then mixed and dispersed by a ball mill for 50 hours to prepare a coating solution. Next, the obtained coating solution was applied on a conductive support composed of an alumite tube by a dip coating method, and then dried with hot air under conditions of 130 ° C. for 45 minutes, and a single layer type having a film thickness of 30 μm and a diameter of 30 mm An electrophotographic photoreceptor was obtained.

2. Creation of a conductive brush In addition, as a conductive brush fiber, a conductive nylon brush (single yarn fineness 6.2 (denier), hair length 3 mm, yarn resistance 1 × 10 ^8.5 (Ω · cm)) is used. A stainless steel plate was used as the conductive substrate.

3. Evaluation of adhesion unevenness on the charging roller The obtained photoreceptor is mounted on a modified printer KM 1500 manufactured by Kyocera Mita Co., Ltd., and the conductive brush has a nip width of 5 mm and a tip bite amount of 0.5 mm with respect to the surface of the photoreceptor. It was made to press.
Next, the electrophotographic photosensitive member is rotated at a peripheral speed of 110 (mm / sec) (angular speed ω ₁ = 7.3 (rad / sec)), and then 1200 between the surface of the photoconductor and the charging unit. A DC voltage of (V) was applied to charge the surface of the photoreceptor to about 400 (V).
Next, a direct current voltage is applied between the transfer unit and the surface of the photosensitive member, and the current density (I _t ) of the current injected from the transfer unit is −316 (μA / m ² ) (current value conversion: −8 (ΜA)).
Finally, a voltage of 1000 (V) is applied to the conductive brush, the amplitude is 2 (mm), the angular velocity ω is 3.7 (rad / sec), and the angular velocity ratio | ω / ω ₁ | = 0.5. The paper was printed by passing 50000 sheets of recording paper while continuously reciprocating. Further, after printing, the adhesion unevenness to the charging roller was visually confirmed and evaluated according to the following criteria. The obtained results are shown in Table 1.
○: No adhesion unevenness on the charging roller is observed.
Δ: Some uneven adhesion on the charging roller is seen, but there is no problem in actual use.
X: Adhesion unevenness on the charging roller is noticeable.

4). Evaluation of image unevenness Further, the occurrence of density unevenness was confirmed for a gray image obtained by passing through 50000 recording sheets and printed, and evaluated according to the following criteria. The obtained results are shown in Table 1.
○: No density unevenness is observed in the gray image.
Δ: Density unevenness in the gray image is slightly seen, but there is no problem in actual use.
X: Density unevenness in the gray image is noticeable.

[Examples 2 to 7]
In Examples 2 to 7, an electrophotographic photosensitive member and a conductive brush were prepared and evaluated under the same conditions as in Example 1 except that the angular velocity ratio | ω / ω ₁ | was changed to 0.66 to 4.0. did. The obtained results are shown in Table 1.
At this time, the angular velocity ω _{1 of the} electrophotographic photosensitive member remains fixed at 7.3 (rad / sec), and the angular velocity ω of the conductive brush reciprocating is 4.8 to 29.2 (rad / sec). Changed to

[Comparative Example 1]
In Comparative Example 1, an electrophotographic photosensitive member and a conductive brush were prepared and evaluated under the same conditions as in Example 1 except that the reciprocation of the conductive brush was stopped. The obtained results are shown in Table 1.

[Comparative Example 2]
In Comparative Example 2, an electrophotographic photosensitive member and a conductive brush were prepared and evaluated under the same conditions as in Example 1 except that the angular velocity ratio | ω / ω ₁ | of the conductive brush was 0.2. The obtained results are shown in Table 1.

As understood from the results shown in Table 1, in Examples 1 to 7, since the conditions suitable for the present invention were used, good results were obtained in the evaluation of adhesion unevenness and image unevenness on the charging roller. It was.
Further, in Comparative Example 1, since the conductive brush was not reciprocated, the particles remaining unevenly on the surface of the electrophotographic photosensitive member adhered to the surface of the charging means while remaining uneven. In the image evaluation, defects were seen.
In Comparative Example 2, since the angular velocity ratio | ω / ω ₁ | of the conductive brush was small, the particles remaining unevenly on the surface of the electrophotographic photosensitive member were not sufficiently uniformed and remained nonuniform. Since it adhered to the surface of the charging means, a defect was observed in the image evaluation.

According to the image forming apparatus and the image forming method using the same according to the present invention, the conductive brush can reciprocate at a predetermined angular velocity, and the particles attached to the surface of the electrophotographic photosensitive member can be made uniform. For this reason, in the subsequent charging means, the uniformized particles adhere to the surface of the charging means, so that the occurrence of uneven charging is small and excellent charging characteristics can be maintained.
Therefore, the image forming apparatus and the image forming method using the same according to the present invention are expected to contribute to high image quality and downsizing of the image forming apparatus.

1 is a schematic view of an image forming apparatus according to the present invention. It is a schematic perspective view of the uniformization means and conductive brush concerning the present invention. (A)-(c) is sectional drawing for demonstrating the operating principle of a uniformization means. It is a schematic diagram for demonstrating angular velocity (omega) of reciprocation. It is a characteristic view showing the relationship between the angular velocity ratio and the uniformity of particles attached to the charging means. FIG. 6 is a characteristic diagram showing a relationship between a current density (I _b ) of a current flowing from the conductive brush to the surface of the photosensitive member and a transfer memory potential (V _t ). It is a characteristic view showing the relationship between the applied voltage (V _b ) applied to the conductive brush and the transfer memory potential (V _t ). FIG. 6 is a characteristic diagram showing the relationship between the current density (I _t ) of the current flowing from the transfer means to the photoreceptor surface and the transfer memory potential (V _t ). FIG. 6 is a characteristic diagram showing a relationship between a current density ratio | I _b / I _t | and a transfer memory potential (V _t ). It is a figure provided in order to demonstrate the structure of the conventional image forming apparatus.

Explanation of symbols

2: uniformizing means, 10: image forming apparatus, 11: electrophotographic photosensitive member, 12: charging means, 13: exposure means, 14: developing means, 15: transfer means, 17: cleaning device, 20: recording paper, 50 : Conductive brush, 51 conductive substrate, 52: conductive brush fiber, 70: reciprocating means, 71: drum gear, 72: thrust gear, 73: cam disk, 73a: inclined surface, 74 contact piece, 75: Energizing means

Claims (8)

In an image forming apparatus in which a charging unit, a developing unit, a transfer unit, and a charge eliminating unit are sequentially arranged around an electrophotographic photosensitive member.
The charging means is a contact-type charging means, and a uniformizing means for leveling particles on the surface of the electrophotographic photosensitive member is disposed between the charging means and the charge eliminating means.
The uniformizing means includes a conductive brush in contact with the surface of the electrophotographic photosensitive member, and a reciprocating means for reciprocating the conductive brush in a direction perpendicular to the rotation direction of the electrophotographic photosensitive member. When the angular velocity of the circular motion corresponding to the reciprocating motion is ω and the angular velocity when the electrophotographic photosensitive member is rotated is ω ₁ , a value represented by | ω / ω ₁ | is 0.5. An image forming apparatus characterized by the above.   The reciprocating means has a drum gear concentrically coupled to the end of the electrophotographic photosensitive member, a thrust gear meshing with the drum gear, and a concentric coupling with the thrust gear and an inclined surface on the outer side surface. A cam disk, biasing means provided at one end of the conductive brush and biasing the conductive brush toward the cam disk, one end abutting the inclined surface and the other end of the conductive brush The image forming apparatus according to claim 1, further comprising a contact piece fixed to the surface.   The conductive brush is composed of a conductive base material and conductive brush fibers, and the conductive base material is connected to a voltage applying means for applying a predetermined voltage to the electrophotographic photosensitive member. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. 4. The image forming apparatus according to claim 3, wherein the yarn resistance of the conductive brush fiber is set to a value of 1 × 10 ¹¹ (Ω · cm) or less.   The image forming apparatus according to claim 3, wherein a stainless steel plate is used as the conductive base material.   6. The image forming apparatus according to claim 1, wherein the electrophotographic photosensitive member is a single layer type electrophotographic photosensitive member.   The image forming apparatus according to claim 1, wherein an initial charging potential of the electrophotographic photosensitive member by the charging unit is set to a value of 400 (V) or more. In an image forming method using an image forming apparatus in which a charging unit, a developing unit, a transfer unit, and a charge eliminating unit are sequentially arranged around an electrophotographic photosensitive member.
The charging means is a contact-type charging means, and a uniformizing means for leveling particles on the surface of the electrophotographic photosensitive member is disposed between the charging means and the charge eliminating means,
The uniformizing means includes a conductive brush in contact with the surface of the electrophotographic photosensitive member, and a reciprocating means for reciprocating the conductive brush in a direction perpendicular to the rotation direction of the electrophotographic photosensitive member. When the angular velocity of the circular motion corresponding to the reciprocating motion is ω and the angular velocity when the electrophotographic photosensitive member is rotated is ω ₁ , a value represented by | ω / ω ₁ | is 0.5. An image forming method as described above.

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