JPH09305013A - Non-magnetic one-component developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the lowering of the density not only at the trailing edge of an image but also at the leading edge of the image by controlling a switching means between image forming time when an electrostatic latent image is made visualizable and image non-forming time when the latent image is not made visualizable. SOLUTION: A toner supply roller 6 is obtained by forming a conductive foaming body around a metallic shaft 6a and toner supply bias power sources 25a and 25b are connected to the shaft 6a through a toner supply bias switching means 26. Thus, a toner supply bias value is different from the image forming time and the image non-forming time is impressed. When it is assumed that developing bias voltage impressed on a developing roller 5 is VB and toner supply bias voltage is VSR, VB and VSR have the same polarity, and they satisfy the relation of |VB|<|VSR| at the image forming time and satisfy the relation of |VB|>|VSR| at the image non-forming time, or VB and VSR have the same polarity and satisfy the relation of |VB|<|VSR| at the image forming time and VB and VSR have the reverse polarity at the image non-forming time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-magnetic one-component developing device which constitutes an electrophotographic device or an electrostatic recording device and uses only non-magnetic toner as a developer.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic apparatus mainly uses equipment using dry toner, and has been put into practical use as many copying machines, laser printers, plain paper facsimiles, etc., and has made remarkable progress. This electrophotographic apparatus is an apparatus to which electrophotographic process technology is applied, and visualizes an electrostatic latent image formed on a photoconductor with toner particles.

The structure and operation of the electrophotographic apparatus will be described below with reference to the drawings. FIG. 2 is a block diagram of an electrophotographic apparatus using a conventional non-magnetic one-component developing device. In FIG. 2, reference numeral 1 denotes a photoreceptor, which is made of a metal drum such as aluminum as a base material, and has a photoreceptive layer such as selenium (Se) or an organic photoconductor (hereinafter referred to as OPC) formed on an outer peripheral surface thereof in a thin film form. It is formed by coating. The charger 2 arranged in the vicinity of the photoconductor 1 which is an electrostatic latent image carrier includes a charging wire 2a such as a tungsten wire and a metallic shield plate 2
b and the grid plate 2c. The charging line 2a causes corona discharge to uniformly charge the photoconductor 1 through the grid plate 2c. The exposure light beam 4 emitted from the exposure optical system 3 transmits an image signal to a laser drive circuit (not shown).
Is obtained by light intensity modulation or pulse width modulation by
An electrostatic latent image is formed thereon.

Reference numeral 6 denotes a toner supply roller for supplying the toner 10 stirred and conveyed by the toner stirring member 11 whose both ends are rotatably supported by the developing hopper 9 to the surface of the developing roller 5 which is a toner carrier. The developing roller 5 and the toner supplying roller 6 are made of metal such as stainless steel as a base material, and elastic members such as urethane and silicon are formed in layers on the outer peripheral surfaces thereof, and are rotatably supported at both ends of the developing hopper 9.
5a and 6a are shafts.

The toner 10 supplied by the toner supply roller 6 is triboelectrically charged by the toner regulating blade 7 and forms a thin layer state on the outer peripheral surface of the developing roller 5.
Thereafter, the developing roller 5 is brought into contact with or close to the photoconductor 1, and the bias voltage applied from the developing bias power source 12 causes the toner 10 to be transferred and attached to a portion of the photoconductor 1 where the electrostatic latent image is formed. Visualize the electric latent image.

The toner regulating blade 7 comprises a metal spring plate member 7a and a toner regulating member 7b which contacts the developing roller 5, and the toner regulating member 7b has an elastic member such as silicone or urethane at one end of the metal spring plate member 7a. It is integrally formed. Reference numeral 8 denotes a blade holder for fixing the toner regulation blade 7, which is attached by screwing.

The toner stirring member 11 is a toner supply roller 6
A circular locus is drawn with the rotation of the toner to prevent the toner 10 contained in the developing hopper 9 from aggregating and
To the toner supply roller 6.

Paper 1 stored in paper cassette 14
The reference numeral 5 designates a half-moon-shaped feed roller 16 from the paper cassette 14.
Then, the sheets are sent one by one to the transport roller 17. The sheet 15, which is the recording sheet that has been sent out, is transported in the direction indicated by arrow A by the transport roller 17. 18 is paper 1
5 is a registration roller for temporarily stopping and waiting the paper 15 in order to make the recording position of the toner image on the recording medium 5 coincide with the toner image formed on the photoconductor 1, and the driven roller 19
Is in contact with The transfer roller 20 is made of a metal such as stainless steel as a base material and has an elastic member formed in a layer on the outer peripheral surface thereof. When the toner image reaches the contact portion between the transfer roller 20 and the photosensitive member 1 as the photoreceptor 1 rotates, the paper 15 also reaches this contact portion at the same timing as the toner image. Transfer bias power supply 24 to metal shaft 20a
A high voltage is applied to the back surface of the paper 15 to apply a charge having a polarity opposite to that of the toner 10, and the toner image on the photoconductor 1 is transferred onto the paper 15. Next, the paper 15 is fed in the direction of arrow A, and the toner image transferred onto the paper 15 is transferred to the heat roller 22 by the fixing device 21 including a heat roller 22 and a pressure roller 23 having a heat source inside. With the pinching rotation with the pressure roller 23, fixing is performed by pressure and heat.

Unlike the two-component developing system, such a non-magnetic one-component developing device does not require a mechanism for mixing with a carrier, stirring, a toner concentration control mechanism, and the like, and is therefore advantageous for downsizing and cost reduction.

[0010]

In the case of the non-magnetic one-component developing device having the above structure, the magnetic force is not used to convey the toner 10 and the electrostatic force and the physical force between the developing roller 5 and the toner 10 are not used. Since a thin layer of the toner 10 is formed on the developing roller 5 with a sufficient force, it is difficult to immediately supply the toner amount used for the development from the toner supplying roller 6 to the developing roller 5 by one rotation of the developing roller 5. Is. When the toner 10 corresponding to the developed toner amount is not supplied,
In the case of a high density image on the entire surface, there arises a problem that the image density at the trailing edge of the image is reduced. Further, since the toner 10 is charged by friction between the toner regulating blade 7 and the toner supply roller 6, when the layer of the toner 10 formed on the developing roller 5 passes through the toner regulating blade 7 a plurality of times without being consumed, each time the toner 10 is charged. Since the charge amount of the toner 10 increases, there is also a problem that the image density at the leading edge of the image decreases.

As a means for solving such a problem, it is known to apply a DC bias voltage to the toner supply roller 6. If the electric field between the developing roller 5 and the toner supplying roller 6 is set so that the toner 10 moves to the developing roller side, it is effective in reducing the image trailing edge density.
If 0 is set to move to the toner supply roller 6 side, the unconsumed toner 10 on the developing roller 5 is completely scraped off by the toner supply roller 6, and the decrease in the image leading edge density can be eliminated. However, according to this solution, the solution conditions for the two problems are contradictory and it is difficult to achieve both at the same time.

Therefore, an object of the present invention is to provide a non-magnetic one-component developing device which can eliminate both the lowering of the image trailing edge density and the lowering of the image leading edge density.

[0013]

In order to solve the above problems, the present invention provides an applying means for applying a DC toner supply bias voltage to a toner supply roller for supplying toner to a developing roller, and a value of the toner supply bias voltage. And a control means for controlling the switching means at the time of image formation for visualizing the electrostatic latent image and at the time of non-image formation in which the electrostatic latent image is not visualized. It is a thing.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a conductive roller for forming a non-magnetic mono-component toner layer on the surface, and a conductive roller for contacting the developing roller and supplying toner to the developing roller. It consists of a toner supply roller composed of a flexible member and a toner regulating blade that regulates the toner on the developing roller to form a thin layer. The toner is attached to the electrostatic latent image on the electrostatic latent image carrier to form a visible image. A non-magnetic mono-component developing device for converting a toner supply roller to a DC toner supply bias voltage, a switching means for switching the toner supply bias voltage value, and an electrostatic latent image visualized. And a control means for controlling the switching means at the time of image formation and at the time of non-image formation in which the electrostatic latent image is not visualized. Different toner supply bias voltage An effect that can be applied to.

The invention as defined in claim 2 is as set forth in claim 1.
In the invention described above, the developing bias voltage applied to the developing roller is applied.
Pressure V_B, Toner supply bias voltage is V_SRAnd then V_B
And V _SRWith the same polarity and the electrostatic latent image is visualized.
Image formation | V_B| <| V_{S R}｜, Visualization of electrostatic latent image
For non-image formation without_B|> | V_SR|
When the image is formed, the toner is transferred to the developing roller side.
When not forming an image, pull the toner to the toner supply roller side.
It has the effect of being able to

According to a third aspect of the invention, in the invention according to the first aspect, the developing bias applied to the developing roller is V.
_B , when the toner supply bias voltage is V _SR , V _B and V _SR have the same polarity when forming an image to visualize an electrostatic latent image, and | V _B | <| V _SR | At the time of non-image formation where the latent image is not visualized, V _B and V _SR are set to have opposite polarities or V _SR = 0, and the same operation as the invention according to claim 2 is obtained.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a block diagram of an electrophotographic apparatus using a non-magnetic one-component developing device according to an embodiment of the present invention. In FIG. 1, the same components as those of the conventional configuration shown in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. The rotation directions of the photoconductor 1, the developing roller 5, and the toner supply roller 6 are in the directions of the arrows shown in FIG. 1, and the respective contact portions are in frictional contact.

The photoreceptor 1 is a negative charging type OPC, and is uniformly charged to -700V by the charger 2.

The developing roller 5 has a resistance value of 10 ⁶ Ω and has a single layer structure in which a metal shaft 5a is used as a base material and a silicone rubber which is a conductive elastic member is formed on the outer peripheral surface thereof. A developing bias power source 12 is connected to the shaft 5 a of the developing roller 5. The developing bias power source 12 is a constant voltage power source of -300V. The developing roller 5 has a rubber hardness of 30.
The range of 60 to 60 degrees is preferable, and the surface roughness is preferably 7 μmRz or less because the higher the surface smoothness is, the more uniform the surface can be in forming the toner thin layer. In this embodiment, the developing roller 5 has a rubber hardness of 40 degrees and a surface roughness of 3 μmRz.

The toner supply roller 6 has a conductive shaft formed around a metal shaft 6a and has a resistance value of 10
^The toner supply bias power supplies 25a and 25b are connected to the shaft 6a via the toner supply bias switching means 26. As a result, different toner supply bias values are applied during image formation and during non-image formation. The toner supply roller 6 has a function of supplying the toner 10 supplied from the development hopper 9 to the development roller 5 and scraping off the toner 10 remaining on the development roller 5 without being developed. The nip width between the toner supply roller 6 and the developing roller 5 is 2 mm.

The toner regulating blade 7 is a stainless steel plate,
An elastic metal spring plate member 7a such as a phosphor bronze plate and urethane elastic rubber having a rubber hardness of 60 degrees, which is an elastic member, is integrally formed at one end thereof as a toner regulating member 7b and is screwed to the blade holder 8. . Toner regulating member 7
“b” presses the developing roller 5 at a linear pressure of 80 g / cm to form a 0.5 mg / cm ² toner layer on the surface of the developing roller 5. In the non-magnetic one-component contact developing method as in this embodiment, the toner layer on the developing roller 5 is 0.3 to 0.6 mg.
The range of / cm ² is preferable.

Toner 10 is a non-magnetic one-component toner, which is a polyester resin in which carbon, wax, a charge control agent, and the like are uniformly dispersed, and a negatively chargeable toner is used.

The transfer roller 20 has a conductive foam formed around the metal shaft 20a and has a resistance value of 10 ⁷ Ω. A transfer bias power source 24 is connected to the metal shaft 20a. The transfer bias power supply 24 is a 4 μA constant current power supply.

The process speed was 76 mm / sec, the peripheral speed of the developing roller 5 was 152 mm / sec, and the peripheral speed of the toner supply roller 6 was 106 mm / sec.

The following printing operation was performed on the electrophotographic apparatus using the non-magnetic one-component developing apparatus constructed as described above. First, the photoconductor 1 is uniformly charged to -700V, and then exposed by the exposure optical system 3 to reduce the surface potential of the photoconductor 1 after exposure to -100V, and the developing bias voltage V _B = -300V is applied to the developing roller 5. A toner image is formed on the photoconductor 1 by applying 4 μA to the paper 15 from the transfer roller 20.
The toner image is transferred by applying the current of (1), and the toner image is fixed on the paper 15 through a fixing step generally known as an electrophotographic process.

At this time, the difference in density between the leading edge and the trailing edge of the image when the toner supply bias voltage was changed during image formation and during non-image formation was evaluated. The image has a high front density, and the measurement results of the front density and the rear density and the visual evaluation results of the density difference are shown in (Table 1). Toner supply bias voltage is V during image formation
_SR1 and V _SR2 during non-image formation, and the density difference evaluation is ○,
A three-level evaluation of Δ and × was made.

[0027]

[Table 1]

As is clear from (Table 1), V _B and V _SR
Have the same polarity and satisfy the relationship of | V _B | <| V _SR | during image formation, and the relationship of | V _B |> | V _SR | during non-image formation, or V _B and V _SR during image formation. If the relationship of the same polarity and | V _B | <| V _SR | is satisfied and V _B and V _SR have opposite polarities during non-image formation or V _SR = 0, no difference in density between the front and rear edges of the image is observed. It was

In this embodiment, the bias voltage is changed by the toner supply bias switching means 26 by using the two bias power supplies of the toner supply bias power supplies 25a and 25b, but the output is electrically changed by one bias power supply. May be. In addition, a negatively charged photoreceptor as in this embodiment,
Not a system with negatively charged toner, but a positively charged photoreceptor,
The same applies to positively charged toner. Also,
Urethane rubber, which is an elastic member, is used as the toner regulating member 7b, but other various rubber materials such as silicon rubber, fluorine rubber, acrylic rubber, butadiene rubber, EPDM rubber, various resin materials that are rigid members, and metal members. May be used. However, in order to prevent the amount of toner 10 deposited on the developing roller 5 from changing with time, it is preferable that the abrasion resistance is excellent. Further, the developing roller 5 is not limited to the elastic roller, and may be a metal roller or a resin roller. Further, the developing roller 5 and the photoconductor 1 may not be in contact with each other.

As described above, in the present embodiment, the toner supply bias switching means 26 is provided, V _B and V _SR have the same polarity, and the relationship of | V _B | <| V _SR | during formation | V _B |> | satisfy the relationship, or V _B and V _SR is at the time of image formation is the same polarity and _{| | V SR V B | <} | V SR | during satisfies the relationship unimaged V _B
By setting the opposite polarities of V _SR and V _SR or setting V _SR = 0, it is possible to eliminate both the lowering of the image trailing edge density and the lowering of the image leading edge density.

[0031]

As described above, according to the present invention, the toner is moved to the developing roller side during image formation, and the electric field is generated so that the toner is moved toward the toner supply roller side during non-image formation. It is possible to eliminate both the decrease in the density and the decrease in the image leading edge density to obtain a high quality image.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an electrophotographic apparatus using a non-magnetic one-component developing device according to an embodiment of the present invention.

FIG. 2 is a block diagram of an electrophotographic apparatus using a conventional non-magnetic one-component developing device.

[Explanation of symbols]

 5 developing roller 6 toner supply rollers 25a, 25b toner supply bias power source 26 toner supply bias switching means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Noda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Hiroki Taguchi, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A developing roller having a non-magnetic one-component toner layer formed on its surface, a toner supplying roller which is arranged in contact with the developing roller and supplies a toner to the developing roller, and the developing roller. A non-magnetic single-component developing device comprising a toner regulating blade that regulates the toner on the roller to form a thin layer, and that makes toner visible on the electrostatic latent image on the electrostatic latent image carrier, An application unit that applies a DC toner supply bias voltage to the toner supply roller, a switching unit that switches the value of the toner supply bias voltage, an image forming time for forming an electrostatic latent image into a visible image, and an electrostatic latent image A non-magnetic one-component developing device comprising: a control unit that controls the switching unit when a non-image is formed without visualizing. 2. When the developing bias voltage applied to the developing roller is V _B and the toner supply bias voltage is V _SR , V _B and V _SR have the same polarity and the electrostatic latent image is visualized. │V _B │ <│V _SR │ for image formation, and │V _B │> │V _SR │ for non-image formation without visualizing the electrostatic latent image.
The non-magnetic one-component developing device according to claim 1, wherein 3. When the developing bias voltage applied to the developing roller is V _B and the toner supply bias voltage is V _SR , V _B and V _SR are applied during image formation for visualizing an electrostatic latent image.
Have the same polarity, and | V _B | <| V _SR |, and V _B and V _SR have opposite polarities or V _SR = 0 when non-image formation is performed without visualizing the electrostatic latent image. The non-magnetic one-component developing device according to claim 1.