JP2000155465A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a developing device constituted so that the uniform thin layer of developer can be formed without causing printing fogging. SOLUTION: A layer thickness regulation blade 58 is constituted of a conductive member and an electric field is generated between the blade 58 and a developing roller 57 with a power source 91. The direction of the electric field is set so that force for moving normally electrified toner to the roller 57 from the blade 58 acts at a contact part between the blade 58 and the roller 57. Besides, friction coefficient between the contact part of the blade 58 and the toner is set to be larger than that between the surface of the roller 57 and the toner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a developing device for forming a thin layer of developer on a developer carrier by a layer thickness regulating member.

[0002]

2. Description of the Related Art Conventionally, in a developing device using a non-magnetic one-component developer, a layer thickness regulating blade made of rubber or the like is brought into elastic contact with a developing roller, and a thin non-magnetic one-component developer is applied on the developing roller. A method of forming a layer is employed.

For example, Japanese Patent Publication No. Hei 6-52448 discloses that the friction coefficient between the layer thickness regulating blade and the toner is made larger than the friction coefficient between the toners, and the developing roller is made smaller than the friction coefficient between the layer thickness regulating blade and the toner. A method is disclosed in which a thin layer of developer is formed by mechanical force by shearing force by increasing the friction coefficient of the toner.

[0004]

However, the method disclosed in the above publication does not take into account the action of the electrostatic force received by charging the toner. Even weakly charged toner of the opposite polarity is mixed with the normally charged toner and passes through the layer thickness regulating blade with mechanical force,
There is a problem that printing fog occurs.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a developing device capable of forming a uniform thin layer of developer without causing print fog.

[0006]

According to a first aspect of the present invention, there is provided a developing device, wherein a layer thickness regulating member is pressed against a developer carrying member for carrying and transporting a non-magnetic one-component developer. The non-magnetic one-component developer is passed through the pressing portion to form a thin layer of the non-magnetic one-component developer, and the thin layer of the non-magnetic one-component developer is conveyed to a developing area by the developer carrying member and developed. Wherein the layer thickness regulating member is a conductive member, and a coefficient of friction of a contact portion of the pressing portion with the non-magnetic one-component developer is different from a surface of the developer carrier and the non-magnetic one-component developer. An electric field generating means for generating an electric field of a polarity larger than a coefficient of friction with the magnetic one-component developer and for applying a force in a direction from the layer thickness regulating member to the developer carrier to a normally charged developer. It is characterized by.

According to the first aspect of the present invention, the non-magnetic one-component developer supplied to the pressing portion between the developer carrier and the layer thickness regulating member is separated from the developer carrier by the pressing portion. And the frictional force from the layer thickness regulating member. Since the friction coefficient of the contact portion of the layer thickness regulating member with the developer is set to be larger than the friction coefficient between the surface of the developer carrier and the developer, the frictional force acting on the developer is The frictional force from the contact portion of the layer thickness regulating member is larger than the frictional force from the surface of the developer carrier. Therefore, when a force other than a frictional force does not act, the developer prevents passage of the pressing portion between the layer thickness regulating member and the developer carrier by the contact portion of the layer thickness regulating member. Will be done. However, the layer thickness regulating member is a conductive member, and the electric field generating means generates an electric field having a polarity that applies a force in a direction from the layer thickness regulating member to the developer carrier to the normally charged developer. are doing. Therefore, when the normally charged developer is sandwiched between the pressing portions of the layer thickness regulating member, the developer is applied from the contact portion of the layer thickness regulating member by the action of the force received from the electric field. The frictional force received is smaller than the frictional force received from the surface of the developer carrier, and the passage of the pressing portion is not hindered. As a result, the normally charged developer passes through the pressing portion and is formed as a uniform thin layer on the surface of the developer carrier. On the other hand, a developer weakly charged to a polarity opposite to a normally charged developer or an uncharged developer exerts a force in a direction from the layer thickness regulating member toward the developer carrier by the action of the electric field. Since the developer does not receive the developer, the frictional force from the contact portion of the layer thickness regulating member becomes larger than the frictional force received from the surface of the developer carrier, and the developer passes through the pressing portion. Will be hindered. As described above, according to the present invention, only the normally charged developer passes through the pressing portion, and the other developer does not pass through the pressing portion, so that print fog does not occur.

According to a second aspect of the present invention, there is provided a developing device according to the first aspect, wherein:
The layer thickness regulating member is provided so as to be in surface contact with the developer carrier at the pressing portion.

According to the second aspect of the present invention, the developer comes into contact with the layer thickness regulating member at the pressing portion of the layer thickness regulating member and is given a triboelectric charge. Since the layer thickness regulating member is provided so as to be in surface contact with the developer carrying member at the pressing portion, the contact area is increased, and good frictional charging is achieved. Therefore, the amount of the uncharged developer or the developer charged to the opposite polarity is reduced, and the amount of the developer used for development is further reduced, and print fog is more reliably prevented.

According to a third aspect of the present invention, in order to solve the above-mentioned problem, in the developing apparatus according to the first or second aspect, the layer thickness regulating member is a conductive member having rubber elasticity. There is a feature.

According to the third aspect of the present invention, the developer carrier and the developer are pressed by the layer thickness regulating member at the pressing portion. Since the member has rubber elasticity, the developer hardly deteriorates even when the image forming operation is repeated. That is, since the layer thickness regulating member having rubber elasticity is deformed according to the shape of the external additive composed of fine particles such as silica and titanium oxide attached to the surface of the developer, excessive pressure is applied to the external additive. However, embedding of the external additive in the developer can be significantly reduced. In addition, since a member having rubber elasticity generally has a higher friction coefficient than metal or resin, a developer charged in the opposite polarity or an uncharged developer passes through the pressing portion of the layer thickness regulating member. Can be reliably prevented. Further, since the layer thickness regulating member is a conductive member, the electric field generated by the electric field generating means described above can be reliably generated in the pressing portion, and the passage of the normally charged developer through the pressing portion is excellent. Can be done.

According to a fourth aspect of the present invention, there is provided a developing device according to any one of the first to third aspects, wherein a ten-point average surface of the developer carrier is provided. The roughness is characterized by a value smaller than the average particle diameter of the developer.

According to the fourth aspect of the present invention, the developer is conveyed by the developer carrier, and is in a region facing the pressing portion of the layer thickness regulating member and the photosensitive member. Although the developer is transported to the development area, the ten-point average roughness of the surface of the developer carrier is set to a value smaller than the average particle diameter of the developer. There is no forced transport of the weakly charged developer due to the surface roughness of the developer carrier. Therefore, it is possible to favorably pass only the normally charged developer by the action of the electric field through the pressing portion.

According to a fifth aspect of the present invention, in order to solve the above-mentioned problems, in the developing device according to the first aspect of the present invention, the developer is obtained by polymerization. It is a polymerized toner.

According to the developing device of the present invention, the normally charged developer is subjected to the action of the electric field by the electric field generating means at the pressing portion. Since the obtained polymerized toner has good fluidity, it is easily affected by an electric field, so that only the normally charged developer due to the above-described action of the electric field can be satisfactorily passed through the pressing portion.

[0016]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing a schematic configuration of a laser beam printer 1 as an embodiment of the image forming apparatus of the present invention. In FIG. 1, a laser beam printer 1 is
A feeder unit 10 for feeding paper P as a transfer medium is provided at the bottom of the main body case 2. The feeder unit 10 includes a paper pressing plate 11, a compression spring 12, and a paper feed roller 13.
, The uppermost sheet P is supplied at a predetermined timing.

A pair of registration rollers 14 and 1 are located downstream of the paper feed roller 13 in the transport direction indicated by arrow A.
5 is rotatably supported, and conveys the sheet P to a transfer position formed by the photosensitive drum 20 and the transfer roller 60, which will be described later, at a predetermined timing.

The photosensitive drum 20 as a photosensitive member is made of a positively chargeable material, for example, an organic photosensitive member mainly composed of positively chargeable polycarbonate. More specifically, the photosensitive drum 20 has, for example, a cylindrical aluminum sleeve as a main body, and has a predetermined thickness (for example, about 20 μm) in which a photoconductive resin is dispersed in polycarbonate on an outer peripheral portion thereof. It is composed of a hollow drum on which a conductive layer is formed, and is rotatably supported by the main body case 2 with the cylindrical sleeve grounded. Further, the photosensitive drum 20 is driven to rotate in the direction of arrow B by a driving unit (not shown).

The charger 30 is, for example, a scorotron-type charger for positive charging that generates corona discharge from a charging wire made of tungsten or the like.

The laser scanner unit 40 includes a laser generator (not shown) for generating a laser beam L for forming an electrostatic latent image on the photosensitive drum 20, and a polygon mirror (pentahedral mirror) 41 driven to rotate. , A pair of lenses 42 and 4
3 and a pair of reflecting mirrors 44 and 45.

In the developing device 50, a toner accommodating chamber 52 is formed in a case 51. In the toner accommodating chamber 52, an agitator 53 and a toner as a positively chargeable non-magnetic one-component developer having an electrically insulating property are provided. 54 are accommodated. A developing chamber 55 for performing development is provided on the photosensitive drum 20 side of the toner storage chamber 52.
Is formed, and the supply roller 56 and the developing roller 57 are pivotally supported rotatably. The toner 54 on the developing roller 57 is regulated to a predetermined layer thickness by a thin plate-like elastic layer thickness regulating blade 58 and is used for development.

The transfer roller 60 is rotatably pivotally supported,
It is made of a conductive foamed elastic body made of silicon rubber or urethane rubber. The transfer roller 60 is configured to reliably transfer the toner image on the photosensitive drum 20 to the paper P by the applied voltage.

The paper dust removing device 80 includes a paper dust removing roller 82 in a case 81. The paper dust removing roller 82 is
An elastic roller 84 such as a sponge is formed on a metal shaft 83 made of aluminum or the like, and a nonwoven fabric sheet 85 is wound on the elastic roller 84. Below the paper dust removing roller 82, a scraping member 87 formed of a brush supported by a support member 86 on the case 81 is provided so as to contact the paper dust removing roller 82. Note that the paper dust removing roller 82 is rotatably supported by a shaft 83, but in the present embodiment, the rotational driving force is not transmitted to the shaft 83 via a gear or the like as in the related art. Instead, it is configured to rotate following the photosensitive drum 20.

The fixing unit 70 is provided downstream of the photosensitive drum 20 in the transport direction of the sheet P indicated by an arrow A,
A heating roller 71 and a pressing roller 72 are provided. The toner image transferred to the lower surface of the sheet P is pressed while being heated and is fixed on the sheet P.

A pair of transport rollers 73 and a discharge roller 74 for transporting the paper are provided downstream of the fixing unit 70 in the transport direction, respectively, and a discharge tray 75 is provided downstream of the discharge roller 74. Have been.

In the laser beam printer 1 of the present embodiment as described above, the surface of the photosensitive drum 20 is
When the laser beam L modulated according to image information is emitted from the laser scanner unit 40, an electrostatic latent image is formed on the surface of the photosensitive drum 20.
This electrostatic latent image is visualized by the toner 54 by the developing device 50, and the visible image formed on the photosensitive drum 20 is transported by the photosensitive drum 20 to a transfer position. At the transfer position, the paper P is supplied via the feeder unit 10 and the registration rollers 14 and 15, and the visible image is transferred to the paper P by a transfer bias applied by the transfer roller 60. After the transfer, the photosensitive drum 2
The toner remaining on the toner image 0 is collected by the developing device 50 by the developing roller 57 and is again used for development. in this way,
The laser beam printer 1 of the present embodiment employs a so-called cleaner-less developing method.

Next, the paper dust remaining on the photosensitive drum 20 is
The photosensitive drum 20 is removed by a paper dust removing roller 82 which is driven to rotate in the direction of the arrow as the photosensitive drum 20 rotates. At this time, the paper dust removing roller 82 is in contact with the photosensitive drum 20 with a low pressing force by the elastic roller 84, so that filming on the photosensitive drum 20 due to paper dust does not occur. Also,
Since the nonwoven fabric sheet 85 has very fine fibers, paper dust can be reliably removed. Further, a scraping member 87 provided below the paper dust removing roller 82 comes into contact with the paper dust removing roller 82 to remove the paper dust on the paper dust removing roller 82, and the removed paper dust is removed by the scraping member 87. The paper dust removing roller 82 and the photosensitive drum 20 do not catch the paper dust removing roller 82 and the photosensitive drum 20. Therefore, the surface of the photosensitive drum 20 is not damaged by hard pulp fibers, and filming by soft talc can be reliably prevented.

Next, the sheet P is conveyed to the fixing unit 70, and is nipped and conveyed by the heating roller 71 and the pressing roller 72 of the fixing unit 70. The visible image on the sheet P is pressurized and heated. Is established. Then, the sheet P is discharged to the discharge tray 75 above the laser beam printer 1 by the pair of transport rollers 73 and the discharge rollers 74, and the image forming operation is completed.

According to the laser beam printer 1 of the present embodiment, a good image can be formed by such an image forming operation. When a non-magnetic one-component toner is used as the toner 54 as described above, a thin layer of only a toner having a regular charge polarity and charge amount is formed on the developing roller 57.
Has a problem that it is difficult to stably form a uniform layer thickness on the surface of the developing device 50. However, in the present embodiment, since the developing device 50 is configured as follows, such a problem is caused. And a high quality image without density unevenness, insufficient density, or print fog is obtained. Hereinafter, the configuration of the developing device 50 in the present embodiment will be described.

As shown in FIG. 2, in the developing device 50 of the present embodiment, the developing roller 57 as a developer carrier is formed in a cylindrical shape using silicon rubber as a base material, and further has conductive carbon fine particles. And a coat layer of a resin or rubber material containing fluorine on the surface. The base of the developing roller 57 does not necessarily have to be made of silicon rubber, and may be made of urethane rubber. The ten-point average roughness (Rz) of the surface is 3 to 5
μm, which is smaller than the average particle diameter of the toner, 8 μm. Further, a voltage Vb is applied to the developing roller 57 from a power supply 90, so that the developing roller 57 has a predetermined potential difference with the photosensitive drum 20. In this embodiment, the power supply 90 supplies +300 V.
Voltage is applied.

Layer thickness regulating blade 5 as layer thickness regulating member
8 is made of stainless steel or the like,
And a contact portion 58b provided at the tip of the support portion 58a and made of conductive silicon rubber, conductive fluorine-containing rubber, or conductive urethane rubber. ing. The contact portion 58b is pressed against the developing roller 57 by the elastic force of the support portion 58a. As shown in FIG. 2, the shape of the contact portion 58b is formed so that the cross section becomes a substantially half-moon-shaped convex shape. In the present embodiment, the voltage Vbld is also applied to the layer thickness regulating blade 58 by the power supply 91 as the electric field generating means. In the present embodiment, +
A voltage of 500 to +600 V is applied.

The toner 54 is a positively chargeable non-magnetic one-component developer. A well-known coloring agent such as carbon black, a styrene-acrylic resin formed by a suspension polymerization method, and a known coloring agent such as nigrosine and triphenyl Particle size of 6 μm to which a charge control agent such as methane and quaternary ammonium salt is added
It has toner base particles having a particle diameter of 10 μm and an average particle diameter of 8 μm. The toner 54 is configured by adding silica as an external additive to the surface of the toner base particles. Also,
The silica as the external additive is subjected to a well-known hydrophobic treatment with a silane coupling agent or the like, and has an average particle diameter of 10 n.
m, the amount added is 0.6% by weight of the toner base particles. As described above, the toner 54 is a suspension polymerization toner having an extremely spherical shape, and 0.6% by weight of hydrophobically treated silica having an average particle diameter of 10 nm is added as an external additive. Excellent in nature. As a result, a sufficient charge amount can be obtained by frictional charging, so that an image with excellent transfer efficiency and extremely high image quality can be formed.

In the above configuration, the developing device 50 of this embodiment is particularly different from the conventional device in that the friction coefficient between the contact portion 58b of the layer thickness regulating blade 58 and the toner 54 is determined by the surface coefficient of the developing roller 57. Is set to be larger than the friction coefficient between the toner 54 and the toner 54.
The point is that an electric field is generated to move it to the side.

When the friction coefficient between the contact portion 58b of the layer thickness regulating blade 58 and the toner 54 is larger than the friction coefficient between the surface of the developing roller 57 and the toner 54, the contact portion 58b of the layer thickness regulating blade 58 The friction force from the surface of the developing roller 57 and the contact portion 58 of the layer thickness regulating blade 58
b, the frictional force from the contact portion 58b of the layer-thickness regulating blade 58 becomes larger. Therefore, if the action of the electric field is not considered, the toner 54
Is a contact portion 58b of the layer thickness regulating blade 58 and the developing roller 5
7 cannot pass through the gap with the surface.

However, in practice, when the normally positively charged toner 54 is conveyed to the gap, the action of the electric field acts. A force acts in a direction away from the contact portion 58b side of the thickness regulating blade 58 toward the surface of the developing roller 57. Therefore, the frictional force acting on the toner 54 from the contact portion 58b is smaller than when the action of the electric field is not considered as described above, and the contact portion 58b of the layer thickness regulating blade 58 and the developing roller 57 And a toner thin layer having a uniform thickness is formed.

On the other hand, the developing device 50
Depending on the agitation state or the like, there may be uncharged toner or weakly charged toner having the opposite polarity to the normally charged toner. However, the uncharged toner or the weakly-charged toner having the opposite polarity is not applied to the contact portion 58 of the layer thickness regulating blade 58.
b and the developing roller 57, the electric field causes the contact portion 5 of the layer thickness regulating blade 58.
8b, no force is applied in the direction toward the surface of the developing roller 57. Therefore, the frictional force from the contact portion 58b acts more on the uncharged toner and the weakly charged toner having the opposite polarity than the frictional force from the surface of the developing roller 57, and the uncharged toner and the reversely charged toner have the opposite polarity. Polar weakly charged toner does not pass through the gap between the contact portion 58b of the layer thickness regulating blade 58 and the surface of the developing roller 57.

In particular, since the toner 54 of the present embodiment is a polymerized toner having better fluidity than the pulverized toner, it is easily affected by an electric field, and the above-described action by the electric field can be surely exhibited.

As described above, the developing device 50 of this embodiment
According to this, only the normally charged toner passes through the gap between the contact portion 58b of the layer thickness regulating blade 58 and the surface of the developing roller 57, and the uncharged toner and the weakly charged toner having the opposite polarity pass through the gap. Therefore, unfed toner or weakly charged toner having the opposite polarity is not used for development, and the occurrence of print fog can be reliably prevented.

On the other hand, Japanese Patent Publication No. 6-52448 discloses a configuration in which the friction coefficient of the developing roller with respect to the toner is set to be larger than the friction coefficient of the layer thickness regulating blade with respect to the toner. In this case, the uncharged toner and the weakly charged toner having the opposite polarity may pass through the layer thickness regulating portion between the layer thickness regulating blade and the developing roller, and may cause print fog.

Accordingly, it can be seen that the developing device of the present embodiment has an extremely excellent effect that high-quality development without print fog can be performed as compared with the conventional device.

Here, a method of determining the magnitude of the coefficient of friction between the developing roller 57 and the layer thickness regulating blade 58 in this embodiment will be described. In the present embodiment, the frictional force between the developing roller 57 and the layer thickness regulating blade 58 against the stainless steel foil is measured, and the magnitude of the frictional coefficient is determined based on the frictional force. A method as shown in FIG. 3 was used for measuring the frictional force. First, as shown in FIG. 3, a member to be measured, for example, a developing roller 57 is formed in a roller shape as it is, and is horizontally supported so as not to rotate. The reason why the roller shape is maintained is that the method in which the member to be measured is made flat and measured is affected by the difference in the surface state due to the polishing method. Next, a 100g weight 1 on one end
A stainless steel foil 101 having a thickness of 0.03 mm and a width of 30 mm and having a thickness of 00 is wound around the developing roller 57 so that the weight 1
The 00 side is dropped vertically downward, and the other end is connected to the digital force gauge 102, and is gradually pulled in the direction of the arrow, and the force required for the pull is read by the gauge 102.

In the measurement of the layer thickness regulating blade 58, a plate-like sample made of the same material as the contact portion 58b of the layer thickness regulating blade 58 is prepared.
As shown in FIG. 4A, the developing roller 57 is bent in accordance with the curvature of the developing roller 57, or as shown in FIG.
A sample having the curvature is prepared using a mold corresponding to the curvature of No. 7, and is placed at the position of the developing roller 57 in FIG. 3 and measured in the same manner as described above.

The magnitude of the coefficient of friction of the developing roller 57 and the layer thickness regulating blade 58 with respect to the stainless steel foil thus determined is determined, and the contact portion 58b of the layer thickness regulating blade 58 is determined.
The material of the contact portion 58b of the layer thickness regulating blade 58 and the material of the developing roller 57 were selected such that the coefficient of friction was larger than that of the developing roller 57. Specifically, in order to reduce the friction coefficient of the developing roller 57, a coating layer containing fluorine is provided on the surface, or a contact portion 58b of the layer thickness regulating blade 58 is provided.
It is effective to use a material having rubber elasticity.
The friction coefficient can be increased by roughening the surface of the contact portion 58b of the layer thickness regulating blade 58. However, an external additive such as silica added to the toner 54 is used as an abrasive. By working, the surface of the contact portion 58b of the layer-thickness regulating blade 58 is gradually scraped, so that the surface roughness is reduced, and there is no point in roughening the surface. In particular, when a material having rubber elasticity is used for the contact portion 58b of the layer thickness regulating blade 58, the surface is remarkably shaved. Therefore, it is more important to increase the friction coefficient of the material itself than to roughen the surface. It is.

The reason why such a measuring method is adopted is that it is difficult to measure the coefficient of friction between the toner 54 and the contact portion 58b of the developing roller 57 or the layer thickness regulating blade 58. On the other hand, Japanese Patent Publication No. 6-52448 discloses a method for measuring the friction coefficient between the toner and the developing roller or between the toner and the layer thickness regulating blade. Since the toner adheres to the regulating blade, the measured value is greatly affected by the friction coefficient between the toners unless the toner scraping member is provided on the developing roller or the layer thickness regulating blade. on the other hand,
When the scraping member is provided, accurate measurement is difficult because the scraping member is affected by a coefficient of friction between the scraping member and the developing roller or the layer thickness regulating blade.

On the other hand, by using the measuring method of the present embodiment, it is possible to accurately determine the magnitude relationship between the friction coefficient of the developing roller 57 and the contact portion 58b of the layer thickness regulating blade 58.

Further, Japanese Patent Publication No. 6-52448 discloses a method of measuring the friction coefficient between toners. However, in reality, the toners are charged and repulsive forces are generated. The coefficient of friction is smaller than that of a developing roller or a layer thickness regulating blade.

Therefore, in this embodiment, the friction coefficient between the toners is neglected, and the layer thickness in the developing device 50 is determined by using the magnitude relationship between the friction coefficient of the developing roller 57 and the contact portion 58b of the layer thickness regulating blade 58. Defined the structure of the regulatory department.

In this embodiment, the surface roughness Rz of the developing roller 57 is 3 to 5 μm as a result of the above-described measurement and roughening.
m, surface roughness R of the contact portion 58b of the layer thickness regulating blade 58
z was 5 to 6 μm. The average particle size of the toner 54 is 8 μm, which is larger than the surface roughness of the developing roller 57. This is because, when the average particle diameter of the toner is smaller than the surface roughness of the developing roller 57, the toner is trapped in the concave portion on the surface of the developing roller 57 regardless of the charging polarity and the charging amount. In this case, and may pass between the contact surface 58b and the contact portion 58b of the layer thickness regulating blade 58.

Although the value of the bias voltage Vbld applied to the layer thickness regulating blade 58 is not particularly limited to the above-described value, it is necessary to set the potential difference between the developing roller and the developing roller to be lower than the discharge starting voltage. is there.

Although stainless steel foil was used in the above-described measurement of frictional force, the present invention is not limited to this, and measurement may be made using a member such as paper instead of stainless steel foil.

Further, in the above embodiment, the layer thickness regulating blade 58 is provided with the convex contact portion 58b on the support portion 58a, but the present invention is not limited to this.
As shown in FIG. 5, one end of a contact portion 58b 'made of conductive plate-like silicon rubber or the like is attached to a support portion 58a' made of aluminum or the like.
A configuration may be adopted in which the free end of the contact portion 58b 'is elastically brought into surface contact with the developing roller 57 by attaching 8a' to the case 51 of the developing device 50. With this configuration, uncharged toner and weakly charged toner of opposite polarity can be significantly reduced, so that uncharged toner and weakly charged toner of opposite polarity can be more reliably prevented from being used for development. can do.

[0053]

According to the first aspect of the present invention, the layer thickness regulating member is a conductive member, and the friction coefficient of the contact portion of the pressing portion against the developer carrier with the non-magnetic one-component developer is determined by: The friction coefficient between the surface of the developer carrier and the non-magnetic one-component developer is set to be larger than that of the non-magnetic one-component developer. Since an electric field of a polarity that gives a force is generated, the normally charged developer is formed as a uniform thin layer on the surface of the developer carrying member without being obstructed from passing through the pressing portion. On the other hand, the developer weakly charged to the opposite polarity to the normally charged developer or the uncharged developer is prevented from passing through the pressing portion due to the frictional force from the contact portion of the layer thickness regulating member. As described above, according to the present invention, a developer thin layer having a uniform layer thickness can be formed while restricting the passage of the pressing portion to only a normally charged developer. No good development can be performed.

According to the second aspect of the present invention, since the layer thickness regulating member is provided so as to be in surface contact with the developer carrier at the pressing portion, the contact area with the developer increases. In addition, the developer can be favorably charged by friction. As a result, the amount of the uncharged developer and the developer charged to the opposite polarity can be significantly reduced, and this developer is further reduced from being subjected to development, and the printing fog can be more reliably reduced. Can be prevented.

According to the third aspect of the present invention, since the layer thickness regulating member is a conductive member having rubber elasticity, the developer hardly deteriorates even when the image forming operation is repeated. That is, since the layer thickness regulating member having rubber elasticity is deformed according to the shape of the external additive composed of fine particles such as silica and titanium oxide attached to the surface of the developer, excessive pressure is applied to the external additive. However, embedding of the external additive in the developer can be significantly reduced. In addition, since a member having rubber elasticity generally has a higher friction coefficient than metal or resin, a developer charged in the opposite polarity or an uncharged developer passes through the pressing portion of the layer thickness regulating member. Can be reliably prevented. Further, since the layer thickness regulating member is a conductive member, the electric field generated by the electric field generating means described above can be reliably generated in the pressing portion, and the passage of the normally charged developer through the pressing portion is excellent. Can be done.

According to the fourth aspect of the present invention, the ten-point average roughness of the surface of the developer carrier is set to a value smaller than the average particle diameter of the developer, so that the uncharged developer or the reverse polarity Is not forcibly conveyed due to the roughness of the surface of the developer carrying member. Therefore, it is possible to favorably pass only the normally charged developer by the action of the electric field through the pressing portion.

According to the developing device of the present invention, since the developer is a polymerized toner obtained by polymerization, the developer is easily subjected to the above-described electric field due to good fluidity, and is normally charged. Only the developer can be satisfactorily passed through the pressing portion.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of a developing device in the image forming apparatus of FIG.

FIG. 3 is a perspective view for explaining a method of measuring a frictional force between a developing roller and a layer thickness regulating blade in one embodiment of the present invention.

4A is a diagram showing a sample shape of a layer thickness regulating blade applicable to the measuring method of FIG. 3; FIG. 4A is a diagram showing a member made of the same material as the layer thickness regulating blade formed in a plate shape; FIG. 6B is a diagram showing the shape of a sample bent to a curvature, and FIG. 8B shows the shape of a sample formed of a member having the same material as the layer thickness regulating blade using a mold having a curved surface with the same curvature as the developing roller.

FIG. 5 is a view showing another embodiment of a layer thickness regulating blade applicable to the present invention.

[Explanation of symbols]

 Reference Signs List 50 developing device 54 toner 57 developing roller 58 layer thickness regulating blade 91 electric field generating means

Claims (5)

[Claims] 1. A layer-thickness regulating member is pressed against a developer carrying member which carries and conveys a non-magnetic one-component developer, and the non-magnetic one-component developer is passed through the pressing portion to reduce the thickness of the non-magnetic one-component developer. A developing device for forming a layer and transporting a thin layer of the non-magnetic one-component developer to a development area by the developer carrier to perform development, wherein the layer thickness regulating member is a conductive member; The coefficient of friction at the contact portion of the pressing portion with the non-magnetic one-component developer is larger than the friction coefficient between the surface of the developer carrier and the non-magnetic one-component developer. A developing device comprising: an electric field generating unit that generates an electric field of a polarity that applies a force in a direction from the regulating member toward the developer carrier. 2. The developing device according to claim 1, wherein the layer thickness regulating member is provided so as to be in surface contact with the developer carrier at the pressing portion. 3. The developing device according to claim 1, wherein the layer thickness regulating member is a conductive member having rubber elasticity. 4. The method according to claim 1, wherein the ten-point average roughness of the surface of the developer carrier is smaller than the average particle diameter of the developer. Developing device. 5. The developer according to claim 1, wherein the developer is a polymerized toner obtained by polymerization.
The developing device according to claim 1.