JPH11327291A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which, even in the use of non- magnetic one-component developer, prevents such toner deterioration that an added agent fills a toner base-particle, and, at the same time, obtains a sufficient amount of electrification and a sufficient amount of carrying and also causes no ghost phenomena. SOLUTION: As the non-magnetic one-component developer, the toner T obtained by suspension polymerization is used, and a supply roller 28 is disposed apart from a developing roller 27 so as to have a prescribed distance (d) between them. Also, a layer-thickness regulation blade 32 is composed of a support part 32 formed of stainless steel or the like, and a contact part 32b formed of conductive silicone rubber, conductive fluorine-containing rubber, or resin. A voltage higher than the voltage that is applied to the developing roller 27 by a power source 40 is applied to the layer-thickness regulation blade 32 by a power source 41.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a charged nonmagnetic 1
The invention belongs to the technical field of an image forming apparatus for forming an image with a component developer.

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image carrier, such as a photosensitive drum, on which an electrostatic latent image is formed, and a developer, such as toner, conveyed to the surface of the electrostatic latent image carrier, have been described. 2. Related Art An image forming apparatus including a developing unit that develops an electrostatic latent image and a supply unit that supplies a developer to the developing unit is known.

In this type of image forming apparatus, a developer supplied from a supply unit to a developing unit is transported by the developing unit to a developing region where the developing unit and the electrostatic latent image carrier face each other. The electrostatic latent image is developed by moving a developer from a developing unit to a surface of the electrostatic latent image carrier on which the electrostatic latent image is formed.

As the developer, a two-component developer containing a toner and a carrier, and a one-component developer containing no carrier are known. In recent years, a one-component developer has been increasingly used in place of a two-component developer because of easy maintenance and miniaturization of the image forming apparatus. In the case of a one-component developer, when a magnetic force is used to transport the toner, the toner contains a magnetic material.
However, since the magnetic material is opaque, it is appropriate to use a non-magnetic developer especially in color development. Therefore, in recent years, a non-magnetic one-component developer has been generally used in a so-called electrophotographic image forming apparatus that forms an image by transferring a developer such as a toner onto a recording medium.

In order to move the non-magnetic one-component developer from the developing means to the electrostatic latent image carrier on which the electrostatic latent image is formed, the non-magnetic one-component developer is positively charged by friction charging or the like. Alternatively, it is necessary to negatively charge and use electrostatic attraction. Not only for such development, but also for transporting the non-magnetic one-component developer to the development area by the developing means, the non-magnetic one-component developer is positively or negatively charged by friction charging or the like, It is necessary to carry the toner on the developing means by utilizing electrostatic attraction.

Therefore, conventionally, a supply roller formed of a foamed elastic material such as a conductive sponge is used as a supply means, and both rollers are simultaneously rotated while pressing the supply roller against a development roller as a development means. Has been adopted. With such a configuration, the non-magnetic one-component developer is charged by being rubbed by the pressing portions of both rollers, and adheres to the surface of the developing roller by electrostatic attraction. Then, it is transported to the developing area by the developing roller.

However, in such a configuration in which the supply roller is directly pressed against the developing roller, the non-magnetic one-component developer may be deteriorated. For example, when a toner is used as the non-magnetic one-component developer, the toner and the external additive attached to the toner are rubbed by the pressing portion,
There is a problem that the external additive may be buried in the toner base particles, and the toner may be deteriorated in a long-term use. In particular, since four color toners are fixed at the same time, a toner that is softer than usual is often used, and the burying is likely to occur.

Therefore, a method of supplying toner by using a cylindrical or polygonal column made of metal or resin as the supply roller, disposing the supply roller in non-contact with the developing roller, and rotating near the developing roller is used. was suggested. According to this configuration, the amount of frictional charge of the toner at the pressing portion is reduced as compared with the case where the supply roller is pressed against the development roller, but the toner and the development roller or the toner and the supply roller are opposed to each other in the area where the supply roller and the development roller are opposed. Rub against each other, so that a sufficient amount of triboelectric charge can be obtained for the toner to adhere to the developing roller.

[0009]

However, in the conventional method, a layer thickness regulating blade pressed against the developing roller with a predetermined pressing force is used in order to keep the toner layer thickness on the developing roller constant. Since a metal blade harder than the toner is used for the layer thickness regulating blade, there is a problem that the toner is deteriorated by the layer thickness regulating blade.

Therefore, in order to solve such a problem, a method has been proposed in which the layer thickness regulating blade uses a member such as rubber or resin that is softer or at least equivalent to the toner at least in a portion that rubs against the toner.

In the method in which the supply roller is disposed in non-contact with the developing roller as described above, the amount of frictional charge that causes the toner to adhere to the developing roller is obtained, but the frictional charge for developing the electrostatic latent image is obtained. The charge amount becomes insufficient.

In view of the above, a method has been proposed in which a member such as rubber or resin, which can satisfactorily charge the toner, is used at least in a portion of the layer thickness regulating blade that rubs against the toner. Examples of such a member include silicone rubber, and a positively charged toner containing fluorine.

However, when the toner charging performance of the layer-thickness regulating blade is improved as described above, charges having the opposite polarity to the toner accumulate in the layer-thickness regulating blade by charging the toner, and are charged by the charges of the opposite polarity. There has been a problem that it is difficult for the toner to pass through the layer thickness regulating blade, and the transport amount of the toner on the developing roller is reduced. As a result, the charging of the toner becomes unstable, fogging may occur, and the image quality of a solid black image may deteriorate. Further, after printing an image in which black solid areas and white solid areas are alternately arranged, there is a problem that a remarkable difference occurs in the charge amount of the toner on the developing roller and ghost occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a configuration in which a supply roller is disposed in non-contact with a developing roller, and a rubber or resin or the like is provided at least in a portion of a layer thickness regulating blade that rubs against toner. It is another object of the present invention to provide an image forming apparatus which does not charge the layer thickness regulating blade to the opposite polarity to the toner, even when using a member capable of charging the toner satisfactorily.

[0015]

According to a first aspect of the present invention, in the image forming apparatus, a non-magnetic one-component developer obtained by developing an electrostatic latent image is transferred to a recording medium. An image forming apparatus for forming an image, comprising: an electrostatic latent image carrier on which an electrostatic latent image is formed, and a non-magnetic one-component developer charged on the surface of the electrostatic latent image carrier. A developer carrier that develops the electrostatic latent image, and a developer carrier that is rotatably disposed at a position near the developer carrier in a non-contact manner with the developer carrier, so that the nonmagnetic one-component developer is developed. Supply means for supplying to the developer carrier, pressure contact of the non-magnetic one-component developer on the developer carrier, which is pressed against the developer carrier, and which is supplied by the supply means, contacts the developer carrier. Contact at the position,
A layer thickness regulating means for regulating a layer thickness of the non-magnetic one-component developer, wherein the layer thickness regulating means is such that at least a contact portion with the non-magnetic one-component developer is formed of conductive rubber or resin. It is characterized by having been done.

According to the image forming apparatus of the first aspect,
The non-magnetic one-component developer is supplied to the developer carrier by the supply unit, and the supply unit is rotatably disposed at a position near the developer carrier without contact with the developer carrier. Therefore, toner deterioration such as embedding of the external additive into the base particles of the toner due to the pressing of the supply means does not occur. The non-magnetic one-component developer supplied to the developer carrier as described above is charged to a predetermined charge amount by friction charging in a supply process or the like, and the non-magnetic one-component developer is in contact with the electrostatic latent image carrier by the developer carrier. It will be transported to the facing area. Furthermore,
In this transporting process, the layer contacts the layer thickness regulating means provided so as to be in pressure contact with the developer carrying member, and the layer thickness is regulated, and the layer is triboelectrically charged to a sufficient charge amount. In addition, the layer thickness regulating means includes at least a non-magnetic layer.
Since the contact portion with the component developer is formed of conductive rubber or resin, the toner is satisfactorily charged without causing toner deterioration such as embedding of the external additive into the toner base particles due to the contact. In addition, a charge having a polarity opposite to that of the toner generated by the contact with the toner is reliably removed by a conductive rubber or resin. Accordingly, no electric field having a polarity that hinders the toner conveyance is generated in the opposing portion between the layer thickness regulating means for regulating the layer thickness and the developer carrying member, and the toner can be satisfactorily conveyed. As a result, a sufficient amount of charged toner is conveyed to the opposing portion between the electrostatic latent image carrier and the developer carrier, and the toner is formed on the electrostatic latent image carrier. The developed electrostatic latent image is satisfactorily developed and transferred to a recording medium to form a good image.

According to a second aspect of the present invention, there is provided an image forming apparatus according to the first aspect, wherein a voltage is applied to the developer carrier in the image forming apparatus according to the first aspect.
A voltage applying unit configured to apply a voltage to the layer thickness regulating unit, wherein the second voltage applying unit is configured to perform the developing by the first voltage applying unit at least during execution of development. A voltage having an absolute value equal to or greater than the absolute value of the voltage applied to the agent carrier is applied to the layer thickness regulating means.

According to the image forming apparatus of the second aspect,
At least during development, a voltage is applied to the layer thickness regulating means by the second voltage applying means, and the absolute value of this voltage is the absolute value of the voltage applied to the developer carrier by the first voltage applying means. It has an absolute value greater than or equal to the value. Therefore, the charge of the opposite polarity to the developer generated in the layer thickness regulating portion of the developer by the layer thickness regulating means is reliably removed, and
The developer can be reliably used for development without being held in the layer thickness regulating portion of the layer thickness regulating means by the action of the electric field.

According to a third aspect of the present invention, there is provided an image forming apparatus according to the first or second aspect, wherein the contact portion of the layer thickness regulating means is electrically conductive. It is characterized by being formed of silicone rubber.

According to the image forming apparatus of the third aspect,
Since the contact portion of the layer thickness regulating means with the developer is formed of conductive silicone rubber, the contact portion does not cause toner deterioration such as embedding of the external additive into the mother particles of the toner, In addition, it is possible to reliably remove charges having a polarity opposite to that of the developer generated at the contact portion.

According to a fourth aspect of the present invention, there is provided an image forming apparatus according to the first or second aspect, wherein the contact portion of the layer thickness regulating means is electrically conductive. Characterized by being made of a fluorine-containing rubber or a conductive fluorine-containing resin.

According to the image forming apparatus of the fourth aspect,
Since the contact portion of the layer thickness controlling means with the developer is formed of conductive fluorine-containing rubber or conductive fluorine-containing resin, the external additive may be embedded in the mother particles of the toner at the contact portion. Without causing toner deterioration, and
The charge of the polarity opposite to that of the developer generated at the contact portion can be reliably removed.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the non-magnetic one-component developer comprises: , A polymerized toner obtained by polymerization.

According to the image forming apparatus of the fifth aspect,
Since the non-magnetic one-component developer is a polymerized toner obtained by polymerization, the mechanical strength is weak, and toner deterioration such as embedding of an external additive in toner base particles easily occurs. Is rotatably arranged at a position near the developer carrying member without contact with the developer carrying member, so that such toner deterioration can be prevented. Moreover, even when the supply means is arranged in non-contact with the developer carrier,
Due to the high fluidity, good frictional charging can be performed without lowering the toner transport amount. Further, although the polymerized toner is easily affected by an electric field, as described above, the electric charge of the opposite polarity to the toner in the layer thickness regulating section by the layer thickness regulating means is reliably removed by the conductive rubber or resin, so that the toner is conveyed. Is not disturbed.

According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, in order to solve the above-mentioned problem, the developer carrier has a surface. Is characterized in that the ten-point average roughness (Rz) is smaller than the average particle diameter of the toner contained in the non-magnetic one-component developer.

According to the image forming apparatus of the sixth aspect,
The developer carrier has a ten-point average roughness (Rz) on its surface,
Since the average particle diameter of the toner contained in the non-magnetic one-component developer is smaller than the average particle diameter of the toner, even if there is insufficiently charged toner in the layer thickness regulating portion formed between the layer thickness regulating means and the Such a phenomenon that the toner is buried in the concave portion on the surface of the developer carrier and conveyed can be substantially eliminated, and only the toner having a sufficient charge amount can be used for development.

According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, in order to solve the above-mentioned problem, the contact of the layer thickness regulating means is controlled by the contact of the layer thickness regulating means. The section is characterized in that the cross section is formed in a substantially half-moon-like convex shape.

According to the image forming apparatus of the seventh aspect,
Since the contact portion of the layer thickness regulating means is formed in a convex shape having a substantially half-moon cross section, the regulating force is improved, for example, as compared with a case where the contact portion is formed in a plate shape, and the charge amount is reduced. The phenomenon that insufficient toner passes through the layer thickness regulating portion can be almost eliminated. Therefore, only a toner having a sufficient charge amount can be used for development.

According to an eighth aspect of the present invention, there is provided an image forming apparatus according to any one of the first to seventh aspects, wherein the supply unit comprises the developer. The closest distance to the carrier is about 2 mm or less.

According to the image forming apparatus of the present invention,
Since the supply unit has a closest distance to the developer carrier of about 2 mm or less, it is possible to secure a sufficient charge amount and a sufficient conveyance amount while reliably preventing the external additive from being embedded in the toner base particles. it can.

[0031]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of main components of a laser printer as an image forming apparatus to which the present invention is applied, and FIG. 2 is a schematic sectional side view of the laser printer.

The main body case 1 of the laser printer according to this embodiment is formed of a synthetic resin, and as shown in FIG. 1, a main frame 1a and the main frame 1a.
And a main cover 1b that covers the outer surfaces of the four circumferences (both front and rear and right and left sides). The main frame 1a and the main cover 1b are integrally formed by injection molding or the like.

On the main frame 1a, a scanner unit 2 as an exposure unit, a process cartridge 3 as an image forming unit, a fixing unit 4 as a fixing unit, and a sheet feeding unit 5 are mounted from the top.

The drive system unit 6 including the drive motor and the gear train is housed in the main body case 1d in the storage recess 1d between the left inner surface of the main cover 1b in FIG. 1 and the left side of the main frame 1a adjacent thereto. 1 is inserted and fixed from below. Further, a top cover 7 as a main body cover made of synthetic resin for covering the upper surfaces of the main frame 1a and the main cover body 1b has a hole 7a through which an operation panel portion 1c projecting upward to the right side of the main frame 1a.
And a hole 7b for penetrating the base of the sheet feeding unit 5. The base of the paper discharge tray 8 is attached to brackets 9 (only one is shown in FIG. 1) protruding from the left and right sides of the front end of the top cover 7 so as to be vertically swingable. 8 can be folded and covered on the upper surface side of the top cover 7.

In the feeder unit case 5a of the paper feeding unit 5, recording papers P as recording media are set in a stacked state. As shown in FIG. 2, the leading end side of the recording paper P is pressed toward the paper feed roller 11 by a support plate 10 urged by a spring 10a in the feeder case 5a. Therefore, the recording paper P can be separated one by one and sent to the pair of upper and lower registration rollers 13 and 14 by the paper feed roller 11 and the separation pad 12 which are rotated by the power transmitted from the drive system unit 6. .

The process cartridge 3 forms an image with the toner T (FIG. 3) on the surface of the separated recording paper P fed by the registration rollers 13 and 14. Further, the fixing unit 4 heats the recording paper P on which the image of the toner T is formed by nipping the recording paper P between the heating roller 15 and the pressing roller 16 to fix the toner image on the recording paper P. A paper discharge unit including a paper discharge roller 17 and a pinch roller 18 disposed downstream in the case of the fixing unit 4 feeds the recording paper P on which the toner image has been fixed to a paper discharge tray 8.
To be discharged. The section from the paper feed roller 11 to the paper discharge section is a recording medium transport route. The paper feeding unit 5 is provided with a manual insertion opening 5b that opens diagonally upward, and a recording paper different from the recording paper P in the feeder unit case 5a can be inserted into the recording medium transport route and printed. It has been like that.

An upper support plate 2a of the scanner unit 2 is provided with a bottom plate of the main frame 1a at a position below the process cartridge 3, which is disposed substantially at the center of the main frame 1a having an open top in the main body case 1 in plan view. It is fixed to a stay part integrally formed on the upper surface side of the part with screws or the like. And a scanner unit 2 as an exposure unit
A laser emission unit (not shown), a polygon mirror 20, a lens 21,
The reflection mirror 22 and the like are arranged. The upper support plate 2a is provided with a glass plate 24 for covering a horizontally long scanner hole formed so as to extend along the axis of the photosensitive drum 23 as an electrostatic latent image carrier. The laser beam L emitted from the laser emitting section is reflected by the polygon mirror 20, the reflecting mirror 22,
The light is irradiated on the outer peripheral surface of the photosensitive drum 23 in the process cartridge 3 via the lens 21 and the glass plate 24.

As shown in FIGS. 2 and 3, the process cartridge 3 includes a photosensitive drum 23 and a transfer roller 25 in contact with the photosensitive drum 23, and a developing unit disposed upstream of the photosensitive drum 23 in the sheet feeding direction. Developing roller 27,
And a developing device having a supply roller 28 as supply means disposed further upstream thereof, a toner cartridge 29 which can be attached to and detached from a developer supply section, that is, a process cartridge 3 disposed further upstream thereof, and a photosensitive drum 23 The cleaning roller 30 and the like are disposed downstream of the cleaning roller 30. The process cartridge 3 is made into a cartridge by incorporating these components into a case 34 made of a synthetic resin.
It is detachably attached to. The photosensitive drum 23,
Both the developing roller 27 and the supply roller 28 rotate clockwise in FIG.

Process cartridge 3 and fixing unit 4
A charge removing lamp 30a for removing charges from the photosensitive drum 23 is provided between the discharge lamps 30a and 30b. Further, a charger 26 is provided below the photosensitive drum 23. The charger 26 is formed of a discharge wire 26a and a grid electrode 2 made of tungsten or the like.
6b, and is a well-known scorotron-type charger for positive charging, and is integrally provided on the upper surface of the upper support plate 2a of the scanner unit 2.

A charger 26 is provided on the outer peripheral surface of the photosensitive drum 23.
An electrostatic latent image is formed by scanning the laser beam L modulated in accordance with image information by the scanner unit 2 on the photosensitive layer charged by (1). That is, the scanner unit 2 corresponds to an electrostatic latent image forming unit. As shown in the enlarged view of FIG. 3, the toner T as the developer stored in the toner cartridge 29 is agitated by the agitator 31 and released, and then is supplied to the outer periphery of the developing roller 27 via the supply roller 28. The thickness of the layer on the outer peripheral surface of the developing roller 27 is regulated by the layer thickness regulating blade 32. The electrostatic latent image on the photosensitive drum 23 is
Is developed (developed) by being adhered. The configuration of the toner T, the developing mechanism, and the like will be described later in detail.

An image (toner image) formed on the photosensitive drum 23 by the toner T is formed on a recording paper passing between the transfer roller 25 to which a transfer bias having a potential opposite to the potential of the photosensitive drum 23 is applied and the photosensitive drum 23. The toner image is transferred to P to form a toner image. Then, the toner T remaining on the photosensitive drum 23 after the transfer is temporarily collected by the cleaning roller 30, returned to the photosensitive drum 23 at a predetermined timing, and collected in the process cartridge 3 by the developing roller 27.

Incidentally, the upper support portion 2a of the scanner unit 2
(FIG. 2), a toner sensor 33 projecting upward is provided, and the toner sensor 33 including a pair of a light emitting unit and a light receiving unit is attached to the toner cartridge 2 of the process cartridge 3.
9, the presence or absence of the toner T in the toner cartridge 29 can be detected.

Returning to FIG. 2, a storage section 36 for storing the cooling fan 35 and a storage section 36 for the recording paper P are provided on the lower surface side of the continuous section between the front section of the main frame 1a and the front section of the main cover 1b. A ventilation duct 37 extending in the left-right direction perpendicular to the passing direction is formed to communicate with each other. And ventilation duct 3
7, the upper plate 37a is formed in a downward V-shaped cross section, and the upper plate 37a is located between the process cartridge 3 and the fixing unit 4 so that the heat generated from the heating roller 15 in the fixing unit 4 causes the process. It shuts off so that it is not directly transmitted to the cartridge 3 side.

The cooling air generated by the cooling fan 35 passes through the inside of the ventilation duct 37 and along the lower surface of one side of the main frame 1a to cool the power supply unit 39 and the drive motor of the drive system unit 6, while cooling the drive motor. The cooling air is blown out from a plurality of slit holes opened on the side of the process cartridge 3 in the face plate portion 37 a, and the cooling air passes through the space between the process cartridge 3 and the fixing unit 4 and rises.
The air is exhausted out of the apparatus through exhaust holes 40 (FIG. 1) formed in a plurality of holes.

(First Embodiment of Developing Mechanism) Next, a first embodiment of the developing mechanism for the toner image will be described.

The photosensitive drum 23 as the electrostatic latent image carrier of the present embodiment is made of polycarbonate or the like. For example, a photoconductive resin is dispersed in polycarbonate around the outer periphery of a grounded aluminum cylindrical sleeve. A photoconductive layer is formed.

The developing roller 27 as a developer carrier is
It is formed in a columnar shape using silicon rubber as a base material, and further includes fine particles of conductive carbon, and has a coating layer of a resin or rubber material containing fluorine on the surface. The base of the developing roller 27 does not necessarily have to be made of silicon rubber, and may be made of urethane rubber. The surface has a ten-point average roughness (Rz) of 5 μm.
m, which is 9 μm, which is the average particle size of the toner.
It is configured to be smaller than that. Further, a predetermined voltage is applied to the developing roller 27 by a power supply 40 as first voltage applying means, and the developing roller 27 is configured to have a predetermined potential difference between the developing roller 27 and the photosensitive drum 23. In the present embodiment, a voltage of 300 V is applied by the power supply 40.

The supply roller 28 serving as a supply means is made of a metal such as stainless steel or nickel-plated iron and has a smooth cylindrical surface, and is arranged in non-contact with the developing roller 27. It was set to 0.5 mm.

Layer thickness regulating blade 3 as layer thickness regulating means
Reference numeral 2 denotes a support portion 32a formed of stainless steel or the like, the base end of which is fixed to the case 34 of the process cartridge 3.
A contact portion 32b provided at the tip of the support portion 32a and made of conductive silicon rubber or conductive fluorine-containing rubber or resin is provided. The contact part 32b is the support part 3
It is pressed against the developing roller 27 by the elastic force of 2a. As shown in FIG. 3, the shape of the contact portion 32b is formed such that the cross section is a substantially half-moon-shaped convex shape. In the present embodiment, a predetermined voltage is also applied to the layer thickness regulating blade 32 by the power supply 41 as the second voltage applying unit. In the present embodiment, 300 V
A voltage of up to 500 V is applied.

With the above configuration, the developing roller 27
At the opposing portion of the photosensitive drum 23
The positively charged toner T can be favorably developed by the reversal developing method with respect to the positive latent (positively charged) electrostatic latent image formed thereon.

Next, the components of the developing mechanism of the present embodiment configured as described above will be described in detail.

First, the toner T stored in the toner cartridge 29 is a positively chargeable non-magnetic one-component developer.
Average particle size obtained by adding a well-known coloring agent such as carbon black and a charge control agent such as nigrosine, triphenylmethane, and quaternary ammonium salt to a styrene-acrylic resin formed into a spherical shape by suspension polymerization. It has 9 μm toner base particles. The toner T is configured by adding silica as an external additive to the surface of the toner base particles. The silica as the external additive is subjected to a well-known hydrophobic treatment using a silane coupling agent or the like, has an average particle diameter of 10 nm, and has an addition amount of 0.6 nm of the toner base particles.
% By weight.

As described above, the toner T is an extremely spherical suspension polymerization toner, and 0.6% by weight of hydrophobically treated silica having an average particle diameter of 10 nm is added as an external additive. , Extremely excellent in fluidity. 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.

However, suspension-polymerized toners are known for their low mechanical strength. An external additive having an average particle diameter of 30 nm or less enhances the fluidity of the non-magnetic one-component developer to enable extremely high-quality image formation, but is embedded in the toner base particles when pressure is applied. It is known for its ease of entry. Therefore, the toner T of the present embodiment in which an external additive having an average particle diameter of 10 nm is externally added to the suspension-polymerized toner tends to cause deterioration of the toner, particularly, deterioration due to the external additive being embedded in the toner base particles. .

Therefore, in the present embodiment, in order to prevent such deterioration of the toner, the supply roller 28 is
The surface was formed into a cylindrical shape having a smooth surface by a metal such as stainless steel or nickel-plated iron, and was arranged in non-contact with the developing roller 27, and the interval d was set to 0.5 mm.

As described above, in this embodiment, since the supply roller 28 is not directly pressed against the developing roller 27,
Even when the toner T having a suspension polymerization toner having a low mechanical strength and an external additive having an average particle diameter of 10 nm which is easily embedded in the toner base particles is used, the supply roller 28 and the developing roller 2
7, the deterioration of the toner, such as the embedding of the external additive in the toner base particles, around the area facing the toner matrix 7 can be reliably prevented.

However, the supply roller 2 as described above
The toner T supplied onto the developing roller 27 by the roller 8 has a constant layer thickness on the developing roller 27 by a layer thickness regulating blade downstream of the area where the supply roller 28 and the developing roller 27 face each other in the rotation direction of the developing roller 27. And the pressing force from the layer thickness regulating blade may cause the deterioration of the toner such as the embedding of the external additive in the toner base particles described above. In particular, when a metal layer thickness regulating blade, which is much harder than the toner, is used as in the related art, such toner deterioration is likely to occur.

Therefore, in the present embodiment, as shown in FIG. 3, a contact portion 32b made of rubber or resin is provided on a support portion 32a made of stainless steel or the like in which the thickness regulating blade 32 is made of stainless steel. The contact portion 32b is the developing roller 2
7 so as to be in contact with the toner T.

As described above, in the present embodiment, the layer thickness regulating blade 32 is formed by using a member such as rubber or resin that is softer or equivalent to the toner, at least in the portion of the layer thickness regulating blade 32 that rubs against the toner. In the vicinity of the area where the developing roller 27 and the developing roller 32 face each other, deterioration of the toner such as embedding of the external additive into the toner base particles is reliably prevented.

However, the member provided at least at the portion of the layer thickness regulating blade 32 that rubs against the toner is not limited to a member that is softer or equivalent to the toner such as rubber or resin. Needs to be This is because the effect of charging the toner by the supply roller 28 is weak when the supply roller 28 is disposed in non-contact with the developing roller 27 as described above.

Therefore, in the present embodiment, silicon rubber or fluorine-containing rubber or resin is used as the rubber or resin for the contact portion 32b of the layer thickness regulating blade 32. Silicone rubber shows good chargeability for both positively charged toner and negatively charged toner, and fluorine-containing rubber or resin shows good chargeability especially for positively charged toner.

However, simply by improving the toner charging performance of the layer thickness regulating blade, when printing an image consuming a large amount of toner such as a solid black image, the layer thickness regulating blade is charged by charging the toner. The charge of the opposite polarity to that of the toner accumulates, and the charge of the opposite polarity makes it difficult for the well-charged toner to pass through the layer thickness regulating blade, so that the amount of toner transported on the developing roller 27 decreases.
In particular, when a suspension polymerization toner having a high fluidity and easily affected by an electric field is used as in the present embodiment, the opposing portion between the developing roller and the layer thickness regulating blade having the opposite polarity to the toner is charged. This makes it difficult for the collected toner to pass through, and causes image defects such as ghosts. As shown in FIG. 4, this ghost phenomenon is caused by solid black image areas and white solid image areas alternately arranged in the width direction of the recording paper P, and further by 600 d below.
This can be confirmed by printing a test image having a so-called zip pattern in which a line for one dot and a space for two dots are alternately arranged at a resolution of pi along the transport direction of the recording paper P.

This is for the following reason. Most of the toner on the developing roller 27 in the area corresponding to the solid black image area is consumed for development after developing the solid black image, while the toner on the developing roller 27 in the area corresponding to the solid white image area is used. The toner is not provided for development. Then, new toner is supplied onto the developing roller 27 by the supply roller 28. In a region corresponding to the solid black image region, the corresponding portion of the layer thickness regulating blade has the opposite polarity as described above. Since the toner is charged, it becomes difficult for the well-charged toner to pass through the layer thickness regulating blade, and the amount of toner transported on the developing roller 27 decreases. On the other hand, the toner on the developing roller 27 in the area corresponding to the solid white image area is not consumed and is further charged by the layer thickness regulating blade.
In this manner, the toner on the developing roller 27 in the area corresponding to the solid black image area has a reduced charge amount per unit mass of the toner, Q / m, and the developing roller in the area corresponding to the solid white image area. The toner on 27 has a high Q / m.
The amount of toner used for development, that is, the amount of toner transferred to the photosensitive drum 23 side is determined by the amount of electric charge stored on the photosensitive drum 23. The amount of electric charge is determined by the potential between the photosensitive drum 23 and the developing roller 27 and the amount of the photosensitive drum. The upper limit is the value determined by the 23 capacitors. Therefore, in the region where the Q / m is low, more toner is subjected to development, while in the region where the Q / m is high, less toner is subjected to development. As a result, the zip pattern developed by the area corresponding to the solid black image area on the developing roller 27 has a high density, and the zip pattern developed by the area corresponding to the solid white image area has a low density. . In this way, the zip pattern shown in FIG. 4 becomes an image with shading under the influence of the solid black image and the solid white image printed immediately before the zip pattern, and a phenomenon called a ghost occurs.

Therefore, in the present embodiment, in order to reliably prevent such a ghost phenomenon, the contact portion 32b of the layer thickness regulating blade 32 is not simply made of silicon rubber or fluorine-containing rubber or resin. And made of conductive silicon rubber or conductive fluorine-containing rubber or resin. As a result, even when the toner is charged by the layer thickness regulating blade 32, the charge having the opposite polarity to the toner does not accumulate on the layer thickness regulating blade 32 as described above, and the charged toner can be satisfactorily charged. 32, so that the toner transport amount is not reduced. Therefore, even after the development of the solid black image and the solid white image as shown in FIG.
Since there is no area where electric charges of the opposite polarity accumulate, there is no difference in Q / m of the toner on the developing roller 27 after passing through the contact portion 32b, and the ghost phenomenon as described above is reliably prevented. be able to.

As described above, the layer thickness regulating blade 32 of the present embodiment, as shown in FIG. 4, has a support portion 32a made of stainless steel, etc. A contact portion 32b made of fluorine-containing rubber or resin is provided, and the contact portion 32b is configured to contact the toner T on the developing roller 27. In the present embodiment, conductivity is achieved by dispersing carbon in silicon rubber, fluorine-containing rubber or resin, and the resistance value is set to 10 ⁷ Ω or less. Also, the contact part 3
The method for forming 2b may be such that conductive silicon rubber or conductive fluorine-containing rubber or resin is formed in a convex shape as shown in FIG. 3 and then bonded to the support portion 32a with an adhesive. Alternatively, insert molding may be used in which conductive silicon rubber or conductive fluorine-containing rubber or resin is placed in a mold provided with the support portion 32a and molded.

With such a configuration, the supply roller 28 is arranged in non-contact with the developing roller 27, and the suspension polymer toner having low mechanical strength and the average which is easily embedded in the toner base particles. Even when the toner T having an external additive having a particle diameter of 10 nm is used, deterioration of the toner such as embedding of the external additive in the toner base particles can be reliably prevented. In addition, even when the supply roller 28 is disposed in non-contact with the developing roller 27, at least the contact portion 32b of the layer thickness regulating blade 32 with the toner is formed of silicon rubber, fluorine-containing rubber or resin, and thus the toner is formed. In addition to being capable of being sufficiently charged, the silicon rubber or fluorine-containing rubber or resin is made of conductive silicon rubber or fluorine-containing rubber or resin. The ghost phenomenon can be reliably prevented without the electric charge of the opposite polarity of the toner being accumulated in the contact portion 32b of the regulating blade 32. Therefore, according to the image forming apparatus of the present embodiment, it is possible to form an extremely high-quality image with high transfer efficiency and no density unevenness over a long period of time.

Further, in this embodiment, in order to further exhibit the effect of forming the contact portion 32b of the layer thickness regulating blade 32 with conductive silicon rubber or fluorine-containing rubber or resin, at least a printing operation is performed. , A voltage having an absolute value equal to or higher than that of the developing roller 27 is applied to the layer thickness regulating blade 32 by the power supply 41. In the present embodiment, a bias voltage of 300 V is applied to the developing roller 27, and 300 V to 500 V is applied to the layer thickness regulating blade 32.
It is configured to apply a voltage of V. With this configuration, it is possible to reliably remove the electric charge having the opposite polarity to the toner T generated in the silicon rubber or fluorine-containing rubber or resin, and to prevent the layer thickness regulating blade 32 and the developing roller 27 from facing each other. Can be more reliably conveyed to the developing roller 27 side for development, and the ghost phenomenon can be more reliably prevented. Further, it becomes difficult for the defective toner charged to the opposite polarity to pass through the layer thickness regulating blade 32, and it is also possible to prevent image defects such as fog due to adhesion of the opposite polarity toner.

Further, the developing roller 27 of the present embodiment is formed in a columnar shape using silicon rubber as a base material, and further has a coating layer made of a resin or rubber material containing fluorine on the surface while containing fine carbon particles. ing. The ten-point average roughness (Rz) of the surface is set to 5 μm or less, and is configured to be smaller than the average particle diameter of the toner of 9 μm. Further, as shown in FIG. 3, the shape of the contact portion 32b of the layer thickness regulating blade 32 is formed in a convex shape having a substantially half-moon cross section.

With this configuration, in the area where the layer thickness regulating blade 32 and the developing roller 27 face each other,
The ability to scrape off the toner T having an insufficient charge amount is improved, and the thickness of the toner layer on the developing roller 27 can always be kept constant. Therefore, in the development area,
Only sufficiently charged toner T can be transported with a constant layer thickness, and high-quality development is possible. In particular, since the layer thickness regulating blade 32 comes into contact with the toner on the developing roller 27 at the tip of the linear contact portion by the convex portion, the scraping ability is less than the toner of the developing roller 27. It is higher than the stomach contact method that contacts on a wide surface. Also, since the ten-point average roughness (Rz) of the surface of the developing roller 27 is set smaller than the average particle diameter of the toner, the toner is conveyed by the developing roller 27 despite the insufficient charge amount of the toner T. It is possible to solve the problem described above, and in combination with the configuration of the layer thickness regulating blade 32, it is possible to convey only the sufficiently charged toner T to the developing area.

If the configuration in which the supply roller 28 is arranged so as to be in non-contact with the developing roller 27 as described above, the transportability of the toner T tends to decrease. However,
In the present embodiment, the developing roller 27 and the supply roller 2
8 is relatively narrow, 0.5 mm (1 of toner T).
Since the supply roller 28 has the cylindrical shape, the conveyance force of the toner T is very well secured. In addition, the use of the suspension polymerization toner having extremely excellent fluidity as described above also ensures a good toner T transport force. Therefore, in the laser printer of the present embodiment, it is possible to suppress deterioration of the toner T and prevent a shortage of the toner T to form an extremely good image.

The distance d between the developing roller 27 and the supply roller 28 can be set to various values as long as it is about 2 mm or less. However, the distance d is 1 of the toner.
If it is opened by the number of layers or more, the deterioration can be sufficiently suppressed. In order to both prevent the deterioration of the toner T and secure a good conveying force, the distance d is desirably 0.1 to 0.5 mm.

According to the present embodiment, with the above-described configuration, first, the supply roller 28 and the developing roller 27 rotate in the above-described direction at positions separated from each other, and when the toner T rubs between the two, the toner T Is easily and reliably positively charged positively without causing the external additive to be embedded in the toner base particles. The surface of the developing roller 27 has the toner T
Has a ten-point average roughness (Rz) smaller than the average particle size of the toner, and the positively charged toner T adheres to the surface of the developing roller 27 by a mirror image force. Similarly, the supply roller 28 also has a smooth cylindrical shape made of metal, so that the toner T adheres to the surface of the supply roller 28 by a strong mirror image force. Therefore, the supply roller 28
Further, the toner T is positively charged by the developing roller 27 and is conveyed to the surface of the photosensitive drum 23 easily and satisfactorily. In addition, a sufficient flowability of the toner is ensured by the good fluidity of the suspension polymerization toner.

In the above-described transport process, the contact portion 32b is formed of a conductive silicon rubber, a conductive fluorine-containing rubber or a resin by the layer thickness regulating blade 32, and the toner T is used as an external additive toner. Since the contact portion 32b is not charged to the opposite polarity to that of the toner without causing embedding or the like in the base particles, a sufficient amount of the well-charged toner can be supplied to the layer thickness regulating blade 32. , And only the sufficiently charged toner T is transported while being regulated to a constant layer thickness by the convex shape of the layer thickness regulating blade 32 and the predetermined surface roughness of the developing roller 27. Become.

On the other hand, an electrostatic latent image having a positive polarity (positive charge) is formed on the photoconductive layer of the photosensitive drum 23, and is charged to a favorable positive charge amount as described above to have a constant layer thickness. When the regulated toner T is conveyed to the developing area where the photosensitive drum 23 and the developing roller 27 are opposed to each other, the potential difference between the photosensitive drum 23 and the developing roller 27 formed by the power supply 40 makes it possible to favorably perform the reversal developing method. Development takes place. By transferring the toner image thus developed onto the recording paper P at a position facing the transfer roller 25 as described above, an extremely high quality image can be stably formed on the recording paper P. it can.

As described above, according to this embodiment, even when the suspension polymerization toner is used as the non-magnetic one-component developer, the toner deterioration such as the embedding of the external additive into the toner base particles occurs. Without this, it is possible to secure a sufficient charge amount and transport amount of the toner, and to form an extremely high-quality image without a ghost phenomenon.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 5 is an enlarged view showing the structure of the process cartridge 3 according to the second embodiment of the present invention. In the process cartridge 3 of the laser printer illustrated in FIG. 5, instead of the supply roller 28, a supply roller 128 formed of a regular hexagonal prism made of a synthetic resin such as ABS is used. In this laser printer, the supply roller 128
The closest distance d to the developing roller 27 was 0.5 mm. Even in the laser printer configured as described above, since the developing roller 27 and the supply roller 128 rotate at positions separated from each other, the deterioration of the toner T can be prevented well. Further, since the supply roller 128 has a shortest distance to the developing roller 27 of less than 2 mm and has a prismatic shape, the toner T can be conveyed in such a manner that the toner T is pushed in by a hexagonal corner. In addition, the toner T has excellent fluidity as described above. For this reason, the conveyance force of the toner T is very well secured.

In this embodiment, the contact portions 3
2b is provided with a layer-thickness regulating blade 32 made of conductive silicon rubber, conductive fluorine-containing rubber, or resin.
It was configured to apply a voltage of ~ 500V. Therefore,
It is possible to prevent the toner T from deteriorating and prevent the layer thickness regulating blade 32 from being charged with a polarity opposite to that of the toner T, so that the toner T can be charged favorably, and an extremely high-quality image can be stably formed. Can be.

The supply roller 128 may be formed in a prismatic shape having another polygonal cross section, but a triangular prism or a quadrangular prism has a significant variation in the amount of toner T transported. Further, in the case of a heptagon or more, the pushing force is reduced. Therefore, it is desirable that the supply roller 128 is configured as a pentagonal or hexagonal prism. In addition, in the case of constructing more than a seven-sided prism,
It is desirable to use a conductive material such as a metal so that the mirror image works well.

The present invention is not limited to the above-described embodiment, and can be implemented in various forms without departing from the gist of the present invention. For example, as the external additive, in addition to the silica, alumina, titanium oxide, etc.
Various external additives can be used, and the average particle diameter of the external additives may be 30 nm or less, and 0.5% by weight or more may be added.

Further, an external additive having an average particle diameter of 30 nm or more (preferably 40 nm or more) may be added to the toner T by mixing with 0.8% by weight or less of the toner base particles and the above-mentioned external additive. If this kind of external additive is excessively added, it will rather impair the fluidity of the toner T, but a small external additive (for example, an external additive having an average particle diameter of 30 nm or less) is buried in the toner mother particles. Can be suppressed. By mixing and adding these large and small external additives, the fluidity of the toner T is further ensured, and a better image can be formed more stably. The average particle size of the toner base particles is
It may be changed in the range of 6 μm to 10 μm.

Further, the present invention relates to an image forming apparatus such as a copying machine for forming an electrostatic latent image by using a laser beam L reflected on an original, and furthermore, the present invention relates to an image forming apparatus other than a suspension polymerization toner. The present invention can be similarly applied to an image forming apparatus using a magnetic one-component developer, for example, an image forming apparatus using another polymerized toner obtained by emulsion polymerization or the like. Even when the toner T has such a configuration, relatively good fluidity can be obtained, and similar effects can be obtained although the toner T is slightly inferior.

[0083]

As described above, according to the image forming apparatus of the first aspect, an image is formed by transferring a non-magnetic one-component developer having developed an electrostatic latent image to a recording medium. In the image forming apparatus, the supply unit is rotatably arranged at a position near the developer carrier in a non-contact manner with the developer carrier, and a contact portion of the layer thickness regulating unit with at least the non-magnetic one-component developer is provided. Since it is formed of conductive rubber or resin, the non-magnetic one-component developer is sufficiently charged while reliably preventing deterioration such as embedding of the external additive in the toner base particles in the non-magnetic one-component developer, In addition, it is possible to reliably remove the electric charge having the polarity opposite to that of the non-magnetic one-component developer generated at the contact portion of the layer thickness regulating means. Therefore, the non-magnetic one-component developer can be supplied to the developing area with a sufficient amount of charge and a sufficient amount of conveyance without deteriorating, and an extremely high-quality image can be formed without a ghost phenomenon.

According to the image forming apparatus of the second aspect,
At least during development, a voltage is applied to the layer thickness regulating means by the second voltage applying means, and the absolute value of this voltage is determined by the absolute value of the voltage applied to the developer carrier by the first voltage applying means. Since it is configured so as to have the above absolute value, it is possible to reliably remove the charge of the opposite polarity to the developer generated in the layer thickness regulating portion of the developer by the layer thickness regulating means, and to apply the electric field to the layer of the developer. It is possible to prevent the phenomenon of being held by the layer thickness regulating portion of the thickness regulating means. Therefore, the developer can be supplied to the developing area with a sufficient charge amount and a sufficient transport amount, and an extremely high quality image can be formed without a ghost phenomenon.

According to the image forming apparatus of the third aspect,
Since the contact portion of the layer thickness regulating means with the developer is formed of conductive silicone rubber, the contact portion does not cause toner deterioration such as embedding of the external additive into the base particles of the toner, and The charge of the polarity opposite to that of the developer generated at the contact portion can be reliably removed. Further, by using silicone rubber, the toner can be favorably charged irrespective of the charge polarity of the toner as compared with other rubber materials.
Therefore, the developer can be supplied to the developing area with a sufficient charge amount and a sufficient transport amount, and an extremely high quality image can be formed without a ghost phenomenon.

According to the image forming apparatus of the fourth aspect,
Since the contact portion with the developer of the layer thickness regulating means was formed of conductive fluorine-containing rubber or conductive fluorine-containing resin,
The deterioration of the toner such as the embedding of the external additive in the base particles of the toner at the contact portion does not occur, and the charge of the opposite polarity to the developer generated at the contact portion can be reliably removed. Further, the toner can be favorably charged to a positive polarity by the fluorine-containing rubber or resin. Therefore, the developer can be supplied to the developing area with a sufficient charge amount and a sufficient transport amount, and an extremely high quality image can be formed without a ghost phenomenon.

According to the image forming apparatus of the fifth aspect,
Since the polymerized toner obtained by polymerization is used as the non-magnetic one-component developer, a sufficient charge amount can be obtained without lowering the toner conveyance amount due to its high fluidity. Moreover, with the above-described configuration,
Such a polymerized toner can be satisfactorily conveyed to the development area, and an extremely high-quality image can be formed.

According to the image forming apparatus of the sixth aspect,
The developer carrier has a ten-point average roughness (Rz) on the surface,
Since the toner is configured to be smaller than the average particle diameter of the toner contained in the non-magnetic one-component developer, insufficiently charged toner is present in the layer thickness regulating portion formed between the nonmagnetic one-component developer and the layer thickness regulating means. Even in such a case, such a phenomenon that the toner is buried in the concave portion on the surface of the developer carrying member and conveyed can be substantially eliminated, and only the toner having a sufficient charge amount can be used for development. Therefore, the developer can be supplied to the developing area with a sufficient charge amount and a sufficient transport amount, and an extremely high quality image can be formed without a ghost phenomenon.

According to the image forming apparatus of the seventh aspect,
Since the contact portion of the layer thickness regulating means is formed in a convex shape having a substantially half-moon cross section, the regulating force can be improved as compared with, for example, a case where the contact portion is formed in a plate shape, and the charge amount can be improved. The phenomenon that insufficient toner passes through the layer thickness regulating portion can be almost eliminated. Therefore, the developer can be supplied to the developing area with a sufficient charge amount and a sufficient transport amount, and an extremely high quality image can be formed without a ghost phenomenon.

According to the image forming apparatus of the present invention,
The closest distance between the supply means and the developer carrier is about 2
Since it is set to be equal to or less than mm, it is possible to ensure a sufficient charge amount and a sufficient transport amount while reliably preventing the external additive from being embedded in the toner base particles. Therefore, the developer can be supplied to the developing area with a sufficient charge amount and a sufficient transport amount, and an extremely high quality image can be formed without a ghost phenomenon.

[Brief description of the drawings]

FIG. 1 is a perspective view of main components of a laser beam printer according to an embodiment of the present invention.

FIG. 2 is a schematic side sectional view of the laser beam printer of FIG.

FIG. 3 is a side sectional view showing a configuration of a first embodiment of a developing mechanism in the laser beam printer of FIG. 1;

FIG. 4 is a diagram showing an image as a result of image evaluation performed by a conventional laser beam printer.

FIG. 5 is a side sectional view showing a configuration of a second embodiment of a developing mechanism in the laser beam printer of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Laser beam printer 3 ... Process cartridge 23 ... Photosensitive drum 27 ... Developing roller 28,128 ... Supply roller 32 ... Layer thickness regulating blade 32a ... Support part 32b ... Contact part 40, 41 ... Power supply

Claims (8)

[Claims] An image forming apparatus for forming an image by transferring a non-magnetic one-component developer obtained by developing an electrostatic latent image to a recording medium, wherein the electrostatic latent image is formed on a surface of the image forming apparatus. A latent image carrier, a developer carrier that transports a charged non-magnetic one-component developer on the surface of the electrostatic latent image carrier, and develops the electrostatic latent image; and a position near the developer carrier. A supply unit that is rotatably arranged in a non-contact manner with the developer carrier and supplies the non-magnetic one-component developer to the developer carrier; Layer thickness regulating means for contacting the supplied non-magnetic one-component developer on the developer carrier at a pressure contact position with the developer carrier to regulate the layer thickness of the non-magnetic one-component developer. Wherein the layer thickness regulating means is configured such that at least a contact portion with the non-magnetic one-component developer is a conductive rubber. Or is formed of a resin, the image forming apparatus characterized by. 2. The apparatus according to claim 1, further comprising: first voltage applying means for applying a voltage to said developer carrier; and second voltage applying means for applying a voltage to said layer thickness regulating means. The application unit applies a voltage having an absolute value equal to or greater than the absolute value of the voltage applied to the developer carrier by the first voltage application unit to the layer thickness regulating unit at least during development. The image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 1, wherein said contact portion of said layer thickness regulating means is formed of conductive silicone rubber. 4. The device according to claim 1, wherein said contact portion of said layer thickness regulating means is formed of conductive fluorine-containing rubber or conductive fluorine-containing resin.
An image forming apparatus according to claim 1. 5. The method according to claim 1, wherein the non-magnetic one-component developer is a polymerized toner obtained by polymerization.
The image forming apparatus according to claim 4. 6. The developer carrier according to claim 1, wherein the ten-point average roughness (Rz) of the surface is smaller than the average particle diameter of the toner contained in the non-magnetic one-component developer. The image forming apparatus according to claim 4. 7. The image according to claim 1, wherein said contact portion of said layer thickness regulating means is formed in a convex shape having a substantially semicircular cross section. Forming equipment. 8. The image forming apparatus according to claim 1, wherein the supply unit has a closest distance to the developer carrier of about 2 mm or less.