JPH09288420A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain a uniform image having appropriate image density over a long term by easily forming a specified developer layer by applying a specified voltage to a regulating member regulating the quantity of a developer at a specified value and a developer carrier. SOLUTION: A photoreceptor drum 9 is rotated in a clockwise direction and a developing roller 6 and a supplying roller are rotated in a counterclockwise direction by a driving means. At the time of developing, developing bias voltage is impressed on the shaft of the developing roller 6, and supply bias voltage is impressed on the shaft of the supplying roller 7 and blade bias voltage is impressed on the supporting member 10 of a regulating blade 8 by an impressing means 14. The developing roller 6, the supplying roller 7 and the regulating blade 8 possess electrical conductivity, so that surface potential equivalent to bias voltage respectively impressed is impressed on the surfaces of respective members. Toner 2 at the inside of a developing chamber 4 is supplied to the developing roller 6 from the supplying roller 7, and when it passes the regulating blade 8, the uniform thin layer of the toner electrified at specified electrified quantity is formed on the developing roller 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for an image forming apparatus such as a copying machine, a printer or a facsimile,
In particular, it forms a uniform thin layer of developer on the developer carrier.

[0002]

2. Description of the Related Art In order to obtain a high quality image in one-component development using a non-magnetic toner as a developer, a uniform thin layer (layer thickness) of the toner is formed on a developer carrying member (developing roller). It is necessary to stably form (about 1 to 1.5 times the particle diameter of the developer). The image density increases as the toner layer becomes thicker, but since low-charged toner and uncharged toner increase, the toner tends to adhere to non-image areas, resulting in image stains. Adherence increases, the resolution of the image decreases, and the image quality is impaired. Conventional methods for forming a thin layer are as follows: (1) As a regulating member, the flat portion of the antinode of the elastic member is used as a developing roller.
The method of applying a laser (Japanese Patent Laid-Open No. 54-43038). (Fig. 7) (2) Radius of curvature 1 mm to 5 mm formed on the regulating member
A method of applying a curved surface portion consisting of a corner R to a developing roller (configuration of the embodiment of JP-A-3-87759). (FIG. 8) (3) Method of applying a portion near an edge formed on the regulating member to a developing roller (Japanese Patent Laid-Open No. 64-57278, Japanese Patent Laid-Open No. 4-57278)
3189). (FIG. 9) and the like are used. As the material of the regulating member, a rubber material, a leaf spring material made of a metal material, or a combination of both is used.

[0003]

However, in the conventional method of applying the flat portion of the regulating member of (1) or the curved portion of the regulating member of (2), the layer thickness of the toner becomes thick and a thin layer is obtained. Therefore, the pressing force on the developing roller must be increased, and as a result, the problem that the regulating member is worn and the rotating torque of the developing roller is increased, and the stress to the developer is increased, and therefore the developing roller is increased. There is a problem of causing deterioration of the agent.

The method (3) of applying the vicinity of the edge of the regulating member has an advantage that the pressing force of the regulating member can be reduced and the developer is less deteriorated. However, the toner layer becomes too thin, and the image There is a problem that a sufficient concentration cannot be obtained.
As a method of solving this, a radius of curvature of 0.0
By forming a minute corner of about 3 to 0.1 mm (or a round radius), the thickness of the toner layer becomes thicker than the edge, and the radius radius at the edge is effective. However, it is difficult to manufacture a corner having such a small radius of curvature uniformly at the edge portion, and there is a problem that the cost is significantly increased.

The present invention has been made for the purpose of solving the above conventional problems. That is, an object of the present invention is to provide a developing device capable of easily forming a predetermined developer layer and stably obtaining a uniform image having an optimum image density for a long period of time.

[0006]

[Means for Solving the Problems] Claims 1 to 4 of the present invention
In the invention, a regulating member that presses the vicinity of the edge against the developer carrier to regulate the amount of the developer on the carrier to a predetermined value, and a predetermined voltage is applied to the regulator member and the developer carrier. And means. According to the fifth and sixth aspects of the present invention, there is provided a regulating member that presses the vicinity of the edge against the developer carrier to regulate the amount of the developer on the carrier to a predetermined value. It is a predetermined value, and the 23% modulus of the regulating member is 10k.
It is g / cm ² or more and 25 kg / cm ² or less.

The 25% modulus is the tensile stress when the material is stretched by 25% in the tensile test. According to the present invention, a uniform image having an optimum image density can be stably obtained for a long period of time.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the developing device according to the first to fourth aspects of the present invention, there is provided a developer carrying member carrying and carrying a developer, and the vicinity of an edge of the developer carrying member being in pressure contact with the developer carrying member. A regulating member for regulating the amount of the developer on the body to a predetermined value, and an applying means for applying a prescribed voltage to the regulating member and the developer carrying body, and further, the developer on the developer carrying body. It has an applying means for applying a predetermined voltage to the supply member for supplying. When the electric potential of the regulating member is Vk, the electric potential of the supplying member is Vs, and the electric potential of the developing carrier is Vb, 200V ≦ ‖Vk-Vb‖ ≦ 500V and 200V ≦ ‖Vs-Vb‖ ≦ 500V. The regulating member and the supplying member have the same applied voltage. As described above, the structure in which the potential is applied to the regulating member that regulates the layer of the developer by the edge increases the layer thickness of the developer after passing the regulating member, and increases the image density and the uniformity of the density as described later. Has the effect of improving. Further, by applying a voltage to the supply member, a uniform and appropriate developer layer can be easily obtained, so that a uniform image having an optimum density can be easily obtained.
Further, since the pressure contact force of the regulating member can be reduced, there is an effect that a stable image can be obtained for a long period without deterioration of the developer. Further, the layer thickness changes depending on the magnitude of the applied potential, and the image density can be easily adjusted. Further, by making the applied voltage of the regulating member and the applied voltage of the supply member the same, it is possible to simplify the applying means.

According to the fifth and sixth aspects of the present invention, in the developing device, the developer carrying member carrying and carrying the developer and the developer on the carrying member are brought into pressure contact with the developer carrying member in the vicinity of the edge. And a regulating member for regulating the amount of the regulating member to a prescribed value, and the modulus of the regulating member is set to a prescribed value, and preferably the 25% modulus of the regulating member is 10 kg / cm ^2. Above, and 25 kg / cm ² or less, and by setting the modulus to a predetermined value, as will be described later, a suitable thin layer of developer can be formed even with edge contact, and the optimum image density can be obtained. Can be stably obtained. Therefore, by setting the 25% modulus of the regulating member to a predetermined value,
Since the optimum developer layer can be stably obtained, the image density is stable, and the pressure contact force of the regulating member can be reduced, so that a high-quality image having the optimum density can be stably obtained without deterioration of the developer. It has the effect of being able to.
Further, since the layer thickness of the developer changes depending on the magnitude of the modulus, it is possible to easily change the image density.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of a developing device according to an embodiment of the present invention. The developing device includes a developing case 1, a one-component developer (one-component toner) 2, a hopper chamber 3 for accommodating the one-component developer 2, and a developer 2 in the hopper chamber 3.
To a developer carrier (developing roller) 6 for supplying the one-component developer 2 to the developer carrier (supply roller) 7 and a developer for regulating the supplied developer. A regulation member (regulation blade) 8 that forms a uniform thin layer of the developer 2 on the carrier 6, and a developer carrier 6 that carries the developer 2 and rotates.
An electrostatic latent image carrier (photosensitive drum) 9 on which the electrostatic latent image formed on the surface of the control member 8 is visualized.
A charging member for providing a predetermined electrostatic charge to the photosensitive drum 9 as a latent image carrier, and 12 a predetermined electrostatic latent image on the surface of the photosensitive drum 9. Exposure means for forming 13 is a transfer means for transferring a toner image in which the electrostatic latent image on the photosensitive drum 9 is visualized by development to a sheet or the like, 14 is a developer carrier 6 and a supply member 7, It is a voltage applying means for applying a predetermined voltage to the regulating member 8.

Next, the main components of the developing device having the above structure will be described. The developer carrying member (developing roller) 6 is
A NBR rubber having a hardness of 40 degrees (JISA) having conductivity is provided as an electrically conductive layer on the outer periphery of a metal shaft.
The diameter of the shaft is 10mm, and the diameter of the rubber roller is 18mm.
mm, resistance between metal shaft and rubber surface is 2 × 10
⁶ Ω, the roughness of the rubber surface is Rz 10 microns. The conductive layer is not limited to NBR rubber, but may be rubber such as urethane, silicon, chloroprene, and EPDM, or foamed sponge or resin instead of rubber. Alternatively, a metal such as aluminum or stainless steel may be used. Further, the surface of the conductive layer may be further coated with fluorine resin, silicon resin, or the like.

The supply member (supply roller) 7 is a metal shaft provided with a urethane sponge having a conductivity of 70 degrees (Asuka F) as a conductive layer on the outer periphery thereof. The diameter of the shaft is 6 mm, the diameter of the sponge roller is 13 mm, and the resistance value between the metal shaft and the surface of the sponge is 7 × 10 ⁴ Ω. Not limited to urethane, sponge such as silicon, NBR, chloroprene, or rubber may be used.

The regulating member (regulating blade) 8 is made of urethane rubber having conductivity and is supported by a metal supporting member 10. One end of the tip of the regulating blade 8 is connected to the developing roller 6. It is provided so as to make pressure contact. Regulation Blade 8
There is continuity between the support member 10 and the support member 10, and the resistance value between the tip of the regulation blade 8 and the support member 10 is 5 × 10 ⁴ Ω.
The regulating member 8 is not limited to urethane, but silicon or N
BR or the like may be used, or a metal plate having a spring property such as stainless steel or phosphor bronze may be used, or a metal plate provided with rubber or resin may of course be used. In any case, the regulating member 8 may be configured so that it has conductivity, an edge is formed, and the edge is pressed against the developer carrying member 6. In this embodiment, the rubber blade is pressed against the developing roller 6 in the counter direction, but it may be in the trading direction or any other method.

As the developer 2, a styrene-acrylic resin in which carbon, CCA or the like is dispersed, and a negatively charged non-magnetic one-component toner having an average particle size of about 7 microns was used. Next, the image forming process of this embodiment will be described. The photosensitive drum 9 is rotated clockwise by the driving means (not shown in FIG. 1), the developing roller 6 and the supply roller 7 are rotated counterclockwise, and the peripheral speed of the photosensitive drum 9 is 40 mm.
/ S, the peripheral speed of the developing roller 6 is 100 mm / s, which is 2.5 times the peripheral speed of the photosensitive drum 9, and the peripheral speed of the supply roller 7 is 5.
It is set to 0 mm / s. Further, at the time of development, application means 1
4, the developing bias voltage Vb (-200V) is applied to the shaft of the developing roller 6, the supplying bias voltage Vs (-550V) is applied to the shaft of the supplying roller 7, and the supporting member 10 of the regulating blade 8 is moved to a different position. -Dbias voltage Vk (-550
V) is applied. As described above, since the developing roller 6, the supplying roller 7 and the regulating blade 8 have conductivity, the bias voltages Vb, Vs and Vk applied respectively.
Is applied to the surface of each member. The toner-2 in the developing chamber 4 is supplied from the supply roller 7 to the developing roller 6 and, after passing through the regulation blade 8, a uniform toner charged to a predetermined charge amount (negative charge). A thin layer of-is formed on the developing roller-6.

In the image forming process, the surface of the photosensitive drum 9 is charged to -700V by the charging means 11 and the portion corresponding to the image portion is exposed by the exposing means 12 to change the surface potential of the exposed portion from -700V to -50V. As a result, the electrostatic latent image is formed on the photosensitive drum 9. In the developing device 1, the negatively charged toner-2 on the developing roller 6 to which the developing bias voltage Vb (-200V) is applied by the applying means 14 is the developing roller 6 of the photosensitive drum 9. The toner adheres to the exposed portion (surface potential -50V) having a higher potential and does not adhere to the non-exposed portion having a lower potential (surface potential -700V).
A visible image by 2 is formed. After that, the toner image on the photosensitive drum 9 is transferred onto the paper by the transfer means 13,
An image is formed on the paper. The developing roller 6 after the development again passes through the supplying roller 7 and the regulating blade 8 to supply the toner on the developing roller 6 and to form the toner layer.
A thin layer of uniform toner is formed and redeveloped.

FIG. 2 shows the developing bias Vb and the image density ID.
The relationship with (reflection density) is shown. From Figure 2, development bias V
When b is high, the image density is low, and as Vb is low, the image density increases, and when Vb is −200 V or less, the image density becomes a constant value (ID1.5). The reason for this is the development bias V
The lower b is, the developing bias Vb and the potential of the exposed portion (-50
This is because the potential difference between V) becomes large, the electric field formed between the developing roller 6 and the exposed portion on the photosensitive drum 9 becomes large, and the amount of toner adhering to the exposed portion increases. .
When the toner on the developing roller 6 is 100% developed, the toner amount developed is constant and the image density is saturated and constant.

3 and 4 show the relationship with the image density ID when the supply bias Vs is changed. At this time, the developing bias Vb is -200V, and the blade bias Vk is
Is constant at 0 V in FIG. 3 and −600 V in FIG. 3 and 4, the lower the supply bias Vs, the higher the image density, and the smaller the density difference between the image leading end and the latter half. In particular, in FIG. 4 in which the blade bias Vk is -600 V, the density difference between the first half and the second half of the image disappears and a uniform image can be obtained. That is, by applying the blade bias Vk and then the supply bias, the image density is increased and the uniformity of the density is improved. The reason for this is that the regulation bias depends on the application of the blade bias Vk and the supply bias Vs.
Electric fields are formed between the developing roller 6 and the developing roller 6 and between the supplying roller 7 and the developing roller 6, respectively, and the regulation blur is generated.
This is because the toner passing through the door 6 is increased and the toner layer is stabilized.

FIG. 5 shows the relationship with the image density ID when the blade bias Vk is changed. At this time, the developing bias Vb was -200 V and the supply bias Vs was always the same potential as the blade bias Vk. After all blade bias V
The potential difference between k and the developing bias Vb is large (Vk is low).
As the image density increases, the density uniformity improves. In FIG. 5, the reason why the concentration decreases when the blade bias Vk becomes −650 V is that the potential difference is too large and the current leaks.

As described above, it was found that a uniform and high-density image can be obtained by applying the bias voltage to the regulation blade 8 and the supply roller 7. Further, the image density can be easily changed by changing the applied voltage. Also, since the pressing force of the regulation blade 8 is small, the toner
The mechanical stress applied to the surface is small, and a stable image without toner deterioration can be obtained for a long period of time. 3 and 4,
From FIG. 5, the potential difference between the supply bias Vk and the developing bias Vb and the potential difference between the blade bias Vs and the developing bias Vb are preferably 200 to 500 V, more preferably 300.
~ 400V. In this embodiment, the developer carrier 6
The voltage is applied to the regulating member 8 and the supplying member 7, but not limited to this, there is a potential difference between the developer carrying member 6 and the regulating member 8, and more preferably, the developing carrier 6 and the supplying member 8. Any configuration may be used as long as there is a potential difference between them. Further, the voltage application means can be simplified by making the applied voltages of the regulating member 8 and the supply member 7 the same.

FIG. 6 shows the relationship between the modulus and the image density when the regulation blade 8 having a different 25% modulus is used in this embodiment. As shown in FIG. 6, there is a clear correlation between the modulus and the image density. The smaller the modulus, the thicker the toner layer and the higher the image density, but if the modulus is too small, the toner layer becomes too thick and image fog occurs. Conversely, if the modulus is too large, the image density will decrease. Therefore, in order to stabilize the image density, it is understood that it is necessary to use a regulating member whose modulus is in an appropriate range. From FIG. 3, the 25% modulus of the regulating member is 10 kg / cm ² or more and 25 kg / cm ² or less in an appropriate range, and more preferably 12 kg / cm ² or more and 18 kg / cm ² or less. The inventors also examined the relationship between rubber hardness and Young's modulus, which have been often used in the past, and image density.
No clear and significant correlation was found between rubber hardness or Young's modulus and image density as compared with 25% modulus. Therefore, it was found that the 25% modulus, which is the material characteristic of the regulation blade 8, is an important factor that affects the toner layer thickness and the image density. The reason for this is that the toner layer thickness changes depending on the pressing force of the regulation blade against the developing roller, so that the modulus is more accurate and sensitive than the hardness and Young's modulus especially in a non-linear elastic body such as rubber. It is considered that this is because the pressing force is affected.

As a method of changing the modulus of the regulating blade 8, if the regulating member is rubber, a method of changing the ratio of a rubber material, an additive compounded in the rubber, a cross-linking agent, or the like,
If carbon is included for conductivity, there is a method of changing the ratio of carbon. In this embodiment, the modulus of the regulation blade 8 is optimized by changing the ratio of the cross-linking agent compounded in the rubber. Therefore, it is easy to change the modulus, and it is possible to obtain the optimum toner layer thickness and image density by optimizing the modulus value. On the contrary, if the modulus of the regulation blade 8 is large, the variation of the image density is large, and if the modulus is not a predetermined value, an appropriate image density cannot be obtained. Therefore, it is important to optimize the modulus of the regulation member. In this embodiment,
Control blade 8 thickness 1.2 mm, free length 10 mm
Was used. Of course, the thickness and free length of the regulation blade 8, the amount of bite into the developing roller, and the developing roller.
It goes without saying that the shape characteristics such as the angle formed by and the toner are factors that determine the image density. Then, by setting the modulus to a predetermined value as in the present invention, a stable image can always be obtained.

[0022]

INDUSTRIAL APPLICABILITY As described above, according to the present invention, a high-quality image having an optimum density, a uniform density, and a high resolution can be obtained at all times, and a stable image can be obtained for a long period with little deterioration of the developer. The effect of being able to do is obtained.
The image density can be set to an arbitrary density by changing the applied voltage and the modulus of the regulating member.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a developing device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a developing bias Vb and an image density ID in the developing device according to the embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a supply bias Vs and an image density ID in the developing device according to the embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a supply bias Vs and an image density ID in the developing device according to the embodiment of the present invention.

FIG. 5 is a diagram showing a relationship between a blade bias Vk and an image density ID in the developing device according to the embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between the 25% modulus of the regulating member and the image density ID in the developing device according to the embodiment of the present invention.

FIG. 7 is a configuration diagram of a developer regulating member in a developing device of Conventional Example (1).

FIG. 8 is a configuration diagram of a developer regulating member in a developing device of a conventional example (2).

FIG. 9 is a configuration diagram of a developer regulating member in a developing device of a conventional example (3).

[Explanation of symbols]

 2 developer 6 developer carrier 8 regulating member

Claims (6)

[Claims] 1. A developer carrying member carrying and carrying a developer, and a regulating member for pressing the developer carrying member near the edge to press the developer carrying member to a predetermined value. A developing device having a regulating member and an application unit for applying a predetermined voltage to the developer carrying member. 2. The developing device according to claim 1, further comprising a supply member for supplying the developer to the developer carrying member, and an application unit for applying a predetermined voltage to the supply member. 3. When the potential of the developing carrier is Vb, the potential of the regulating member is Vk, and the potential of the supply member is Vs, 200V ≦ ‖Vk−Vb‖ ≦ 500V and 200V ≦ ‖Vs-Vb‖ ≦ 500V. The developing device according to claim 2. 4. The developing device according to claim 2, wherein the regulating member and the supply member have the same applied voltage. 5. A developer carrying body carrying and carrying a developer, and a regulating member for pressing the developer carrying body in the vicinity of an edge thereof in pressure contact with the developer carrying body to regulate the amount of the developer in the developer carrying body to a predetermined value. And a developing device having a modulus of the regulating member as a predetermined value. 6. The 25% modulus of the regulating member is 10 k.
The developing device according to claim 5, wherein the developing device has a g / cm ² or more and 25 kg / cm ² or less.