JP2937703B2 - Developing device and image forming apparatus provided with the developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device applied to, for example, an electrophotographic apparatus and an image forming apparatus provided with the developing device.

[0002]

2. Description of the Related Art Conventionally, as a developing device of an image forming apparatus for obtaining an image by transferring a toner image obtained by developing an electrostatic latent image to a transfer material such as paper and fixing the toner image, a toner and a carrier have been conventionally used. And a one-component developing device using only toner and a toner are known.

[0003] In recent years, the trend toward downsizing, weighing, and cost reduction of a developing device and a process unit including the developing device has increased, and the one-component developing method has been spotlighted. For example, Tokuho 4
A developing device using a one-component developer disclosed in JP-A-789993 is known.

FIG. 11 is a sectional view showing an example of a conventional one-component developing apparatus of this kind. The developer (toner) 9 stored in the hopper 4 is supplied onto the developer carrier 2 by the rotation of the developer supply member 3 rotating at substantially the same speed as the developer carrier 2. Then, the developer is carried on the developer carrier 2, is pressurized by the regulating member 5 to form a developer layer having a predetermined thickness, is triboelectrically charged, and is statically disposed to face the developer carrier 2. An electrostatic latent image having a surface potential of approximately −20 to −700 V is electrostatically attached to a surface formed on the electrostatic latent image holding member 1 (photoreceptor) and is visualized.

Reference numeral 6 denotes a seal member for preventing the developer 9 from leaking from the inside of the hopper 4. Specifically, the developer carrier 2 is a SUS shaft having a diameter of 8 mm, that is, a thickness of 4 mm and a specific resistance of 1 × 10 ⁵ to 1 × 10 on the developing electrode 7.
After molding a urethane rubber having ⁷ Ωcm and rubber hardness of 35 to 40 ° (JIS-A), the surface is polished to a ten-point surface average roughness Rz of 0.05 to 10 μm, and then a urethane-based The conductive paint is applied in a thickness of 30 to 100 μm.

The developer supply member 3 is provided with a developer carrier 2.
Nip is pressed at 1 mm, and rotates in the direction of the arrow at the same peripheral speed as the developer carrier 2 to supply the developer 9 in the hopper 4 to the developer carrier 2 and precharge the developer. so,
In order to reduce the load applied to the developer carrier 2 at the time of pressing, and to improve the developer conveying force, the shaft 10 serving as a supply bias electrode is worked into a foam roller shape of urethane or the like. The supply member 3 may be provided with a surface treatment of silicon or the like or a coating of EPDM rubber or the like in order to increase the chargeability of the developer.

The regulating member 5 is made of SUS having a thickness of 0.1 mm.
The one side is stopped so that the free length is about 20 mm, and a silicon rubber chip of R1.5 mm is adhered to the free end side. The contact pressure with respect to the developer carrier 2 is set to a linear pressure of 40 g / cm. The developing electrode 7 has-
A DC voltage of 200 V is applied.

The above-mentioned developer 9 is a non-magnetic one-component type developer. A polarity controlling material such as a pigment and a dye such as carbon black is mixed with various thermoplastic resins such as a polyester resin by pulverizing and classifying. Is 13.5 μm in size.

[0009]

In the above-described developing device, even if the toner particle size is not particularly small as compared with the conventional two-component developing system, the toner on the lines around the image and the toner around the halftone dot print pattern is small. A beautiful image with tightness is obtained.

However, the characteristic is maintained only at the initial stage (about 0 to several hundred sheets), and as the printing is continued, the characteristic fades and the toner dust in the developing device on which 1,000 or more sheets have been printed is reduced. Has become noticeable compared to.

Here, FIG. 12 shows the number of prints on the horizontal axis of the graph, and the vertical axis shows the volume average particle diameter of the toner in the hopper 4. As a result, it has been found that the average particle size of the toner in the hopper 4 increases as the number of printed sheets increases, and the size of the toner particles in the dust portion gradually increases.

In general, it has been found that in a two-component developing system, the fine powder toner increases as the number of printed sheets increases, but in the case of one component, coarse particles increase due to a completely opposite phenomenon. It is considered that this is because the toner passing through the regulating member has a size smaller than the average particle size, and particles larger than the average size accumulate in the developing device and increase the average particle size.

[0013] Until the past one or two years ago, most of the images formed by printers were mainly composed of characters. However, as the price of graphic software and DTP software became lower and spread, they were used in the field of light printing. As a result, factors for improving the printing quality for halftone images, fine lines, and sharpness of characters have been significantly increased. Therefore, these users cannot satisfy these users with such image characteristics, resulting in a device having no market competitiveness.

Accordingly, an object of the present invention is to provide a developing device capable of obtaining the same stable image quality as in the initial stage without changing the developer particle diameter even when the number of printed sheets increases, and an image forming apparatus provided with the developing device. And

[0015]

According to the present invention, there is provided a developer supply means for performing development by supplying a non-magnetic one-component developer to an image carrier for carrying an electrostatic latent image. , The support and the silicon provided at the tip of the support
Elastic body made of silicon, and the elastic body made of silicon is
Serial pressed against the developing agent supply means, comprising a developer layer forming member for forming a thin layer of the developer on the developing agent supply means,
When the volume average particle diameter of the developer is Dt (μm) and the pressing force of the silicon elastic body of the developer layer forming member against the developer supply means is P (g / cm), Dt <15 The relationship of 20 ≦ P ≦ −16.44 × Dt + 243.5 is satisfied.

An image forming means for forming a latent image on the image carrier; and a developer supply means for performing development by supplying a non-magnetic one-component developer to the latent image formed by the image forming means. And a support provided at the tip of the support.
Said silicon elastic body
And a developer layer forming member that forms a thin layer of the developer on the developer supply unit, wherein the developer has a volume average particle diameter of Dt (μm). Dt <1520 ≦ P ≦ −16.44 × Dt + 243.5 where P (g / cm) is the pressure of the silicon elastic body of the developer layer forming member against the developer supply unit. Meet.

[0017]

The developer has a volume average particle diameter Dt, and the pressing force of the developer layer forming member against the developer supply means is P.
(G / cm), by satisfying the following relationship: Dt <15 20 ≦ P ≦ −16.44 × Dt + 243.5, the toner particle diameter does not change even when the number of printed sheets increases, and the same stable image quality as the initial state is obtained. To be able to get

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 2 shows the internal configuration of the electrophotographic apparatus. In the figure, reference numeral 11A denotes an apparatus main body.
A photosensitive drum 11 as an image carrier that rotates in the direction of arrow a is provided at a central portion in 1. This photosensitive drum 1
Around the periphery of the charging charger 1, a charging charger 1 is provided along the rotation direction.
2, a developing device 13, a transfer roller 14, and a cleaning device (not shown) are provided.

At the lower part of one side of the apparatus main body 1, a paper feed cassette 16 is provided.
The paper P is supplied by the rotation of the roller 17. The supplied paper P is transported along the transport path 18. In the transport path 18, an aligning roller is provided along the transport direction of the paper P.
Roller 19, guide 20, transfer roller 14, guide 2
1, a fixing device 22, a switching gate 23, and a paper discharge roller 24 are provided. Reference numeral 25 denotes a sheet reversing discharge unit.

A laser exposure system 26 as an image forming means is provided on the upper side of the apparatus main body 11.
During image formation, the surface of the photosensitive drum 11 is uniformly charged by the charging charger 12, and the charged surface of the photosensitive drum 11 is exposed to form an electrostatic latent image. The electrostatic latent image is sent to the developing device 13 by the rotation of the photosensitive drum 11 and supplied with a developer to be visualized.

On the other hand, at this time, the paper P is supplied from a paper feed cassette 16 (not shown) by rotation of a paper feed roller 17, the paper P is aligned by a registration roller 19, and then transferred to the photosensitive drum 11. It is sent between the rollers 14. Here, the visible image on the photosensitive drum 11 is transferred to the transfer roller 14.
Is transferred to the paper P by the action of, and after this transfer, it is separated from the photosensitive drum 11 and sent to the fixing device 22, where the image is fixed and discharged.

The developing device 13 is configured as shown in FIG. That is, the developing device 13 is a non-magnetic one-component developing device and has a developing roller 32 as a developer supply unit having conductivity and elasticity. A thin layer of non-magnetic toner is formed on the surface of the developing roller 32. The developing device is developed by bringing it into contact with the surface of the photosensitive drum 11, and does not require a carrier, a magnet roller, a toner concentration control device, and the like, and is a developing device that can be reduced in size and cost.

The non-magnetic toner 39 in the developing container 34 is sent to a supply member (hereinafter referred to as a supply roller) 33 by an agitator 36 which agitates and supplies while rotating in the direction of the arrow. After the toner 39 is conveyed and supplied from the supply roller 33 to the developing roller 32, the toner 39 is temporarily charged by the friction between the supply roller 33 and the surface of the developing roller 32 at the contact portion between the supplying roller 33 and the developing roller 32. It is transported by suction. Thereafter, the amount of toner 39 on the developing roller 32 is regulated by the developing blade 35, which is a developer thin layer forming member, to a uniform thin layer, and at the same time, the developing roller 3
2 and the developing blade 35 perform full-scale triboelectric charging of the toner to be a negatively charged toner. Then, the electrostatic latent image on the photoconductor 1 is developed by being transported to the developing section of the photosensitive drum 11. At this time, the undeveloped toner which has not contributed to the development, for example, a portion on the developing roller 32 corresponding to a white background portion of the image, slips through the recovery blade 31 and returns to the inside of the toner container 34 again.

In this embodiment, a reversal developing method using a negative photosensitive drum 11 is employed, and the toner has a negative polarity. The photosensitive drum 11 is an OPC having sensitivity to a semiconductor laser having a diameter of 30 mm, and the surface potential is set to -500V. The developing bias applied to the developing roller 32 is -200 V and is supplied from the metal shaft 32a of the developing roller 32. The rotation speed of the photosensitive drum 11 is 80 mm / sec, and the developing roller 32 is 160 mm / sec.
It is rotating in the direction of the arrow in FIG. The developing roller 32 is pressed against the photosensitive drum 11 with a constant load of 50 g / cm by a force urged against the developing device when the developing roller 32 is mounted in the apparatus main body 11 with respect to the photosensitive drum 11. Contact is made at a nip of about 2 mm.

As described above, the toner supply roller 33 plays a role of supplying the toner to the developing roller 32, applying a charge to the toner by frictional charging, and scraping off the toner on the developing roller 32 after the development. Therefore, the supply roller 33 uses a conductive soft urethane foam having a metal shaft 33a as a core metal. Developing roller 32
Is set to about 0.75 mm.

Next, the developing roller 32 will be described. In this embodiment, a roller having a structure as shown in the perspective sectional view of FIG. 3 is used. The elastic layer 32b has a rubber hardness of 3
5 degree (JIS-A), a urethane rubber having a resistance value of 5 × 10 ⁵ Ωcm is used, and the surface layer 32 c is made of a conductive polyurethane paint (product name Nihon Milactran Co., Ltd., Sparex).
A surface layer having a resistance value of 5 × 10 ³ Ωcm was used as a surface layer of about 70 μm. The rubber hardness of the formed developing roller 32 as a whole is about 40 degrees, and the surface resistance with the shaft 32a is about 100 degrees.
KΩ and surface roughness of about 3 μm.

As shown in FIG. 4, the developing blade 35 is provided at the tip of a 1.5 mm-thick phosphor bronze leaf spring 41 serving as a supporting member, and has an R1.5 mm arc-shaped silicone rubber elastic section as shown in FIG. The one to which the body 42 is adhered is used. The silicon rubber elastic body 42 is pressed against the developing roller 32 by using the elasticity of the leaf spring 41.

Here, printing was performed on 3,000 sheets each by changing the volume average particle diameter of the toner and the pressure of the developing blade 35. FIG. 10 is a graph showing the results.

The horizontal axis represents the linear pressure (g / c) of the developing blade 35.
m), and the vertical axis represents the ratio R of the volume average particle size of the toner to the initial volume average particle size at 3,000 sheets (that is, the ratio of how much the particle size has changed from the initial value). It is. The toner has a volume average particle size of 7.5 μm, 9
μm, 10 μm, 12 μm and 13.5 μm were made of polyester resin and used.

As can be seen from FIG.
When the linear pressure becomes a certain value or more, the particle diameter of the toner in the developing container 34 changes together with the printing, and when the linear pressure is less than a certain value, the particle diameter of the toner remains almost constant even if the number of prints and the number of prints increase. And the developing blade 3 where this change starts
The linear pressure of No. 5 differs depending on the initial volume average particle diameter of the toner. The starting point of the particle diameter change is defined as a limit point, the initial volume average particle diameter of the toner is plotted on the horizontal axis, and the linear pressure of the developing blade 35 at this time is plotted on the vertical axis. Become like Then, the following relationship was derived from these plot points.

Developing blade linear pressure = P (g / cm) Toner volume average particle diameter = Dt (μm) P ≦ −16.44 × Dt + 243.5 However, if the toner particle diameter is 15 μm or more, the sharpness of the fine line becomes smaller than the initial stage. Bad, Chile is not noticeable and not practical due to poor quality.

If the linear pressure of the developing blade is less than 20 g / cm, the toner is not sufficiently charged, so that some uncharged toner is formed and the image is fogged. That is, Dt <15 (1) 20 ≦ P ≦ −16.44 × Dt + 243.5 (2) As described above, satisfying this relationship is a necessary and sufficient condition for maintaining an image in which dust and blemishes such as halftone dots and thin lines remain unchanged from the initial state to the end regardless of the number of prints.

FIG. 8 shows another embodiment of the present invention.
It is sectional drawing of the whole apparatus. In this embodiment, the path of the transfer paper is set to the photosensitive member 51 in consideration of miniaturization of the apparatus that requires face-down (discharge with the print surface facing down), the scattering of the developer on the paper path, and the prevention of spillage. It is arranged above.

FIG. 9 is a sectional view of the process unit used in FIG. In this process unit, a photosensitive member 51, a cleaner 52, and a charging charger 53 are integrated with a developing device 54 to facilitate replacement of consumables.

Here, the developing section of the embodiment includes a transfer, a cleaner,
Due to the arrangement of the charging and exposure positions, the silicon elastic body 56 at the tip of the developing blade 55 contacts the developing roller 57 upward and is located below the developing unit. Therefore, when the rotation direction of the developing roller 57 and the supply roller 58 is set to the same direction as in the above embodiment, the pressure of the toner near the developing blade 55 increases, and the silicon elastic body 56 at the tip of the developing blade 55
The supply roller 58 is rotating in the opposite direction to the developing roller 57 because the image is scattered and the image is scattered.

The apparatus of this embodiment employs a reversal development system using a negative photosensitive member 51 as in the above embodiment, and the polarity of the toner is negative. The surface potential of the photoconductor 51 is −
450V, development bias -200V, rubber hardness 35
Is supplied to the metal shaft 57a of the developing roller 57 made of conductive silicone rubber. Developing blade 55
The R of the silicon elastic body 56 at the tip of is 2.0 mm.
Here, the developing roller 57 is different from the above-described embodiment in that the photosensitive member 51
And the axis of the developing roller 57 are fixed at a fixed value, and the bite is 0.2 mm. The peripheral speed of the photoconductor 51 is 30
mm / sec, and the peripheral speed of the developing roller 57 is 54 mm / sec.
It rotates in the direction of the arrow in the figure at c.

The toner according to the other embodiment described above was used to prepare a toner having a volume average particle diameter of 7.5 μm, 9 μm, 10 μm, 12 μm,
13.5 μm was made of styrene acrylic resin, and the same test was performed as in the above example. The same result was obtained. Did not change. FIG. 10 shows one result of this embodiment, in which the change in the toner particle diameter in the developing unit when the number of prints increases when the initial toner particle diameter is 10 μm shows the difference when the linear pressure of the developing blade 55 is changed. It is shown. Note that the above-described embodiment uses the developing roller 3
Although the photoconductors 2 and 37 contact the photoconductors 11 and 51, the photoconductors 11 and 51 may have an interval.

[0038]

As described above, the present invention is based on the case where the volume average particle diameter of the developer is Dt (μm) and the pressing force of the developer layer forming member against the developer supply means is P (g / cm). Dt <15 20 ≦ P ≦ −16.44 × Dt + 243.5, so that the pressure of the developer layer forming member can be optimized with respect to the developer particle diameter, and the change in the developer particle diameter can be reduced. Even if the number of prints increases, it does not change from the initial. Therefore, even if the number of printed sheets is increased, there is no increase in toner dust around the print pattern such as fine halftone dots and fine lines on the image, so that a beautiful uniform image which is the same as the initial one can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a configuration diagram illustrating an image forming apparatus including the developing device of FIG. 1;

FIG. 3 is a perspective view showing a developing roller of the developing device of FIG. 1 with a part cut away.

FIG. 4 is a perspective view showing a developing blade of the developing device of FIG. 1;

FIG. 5 is a side view showing the developing blade of FIG. 4;

FIG. 6 is a graph showing a relationship between a linear pressure of a developing blade and a toner particle diameter change ratio in the developing device of FIG. 1;

FIG. 7 is a graph showing a relationship between an average toner particle diameter and a linear pressure of a developing blade in the developing device of FIG. 1;

FIG. 8 is a configuration diagram illustrating an image forming apparatus according to another embodiment of the present invention.

FIG. 9 is a configuration diagram illustrating a process unit of the image forming apparatus of FIG. 8;

FIG. 10 is a graph showing the relationship between the number of prints and the toner volume average particle diameter in the image forming apparatus of FIG. 8;

FIG. 11 is a configuration diagram showing a conventional developing device.

FIG. 12 is a graph showing the relationship between the number of prints and the toner volume average particle diameter in the developing device of FIG. 11;

[Explanation of symbols]

11, 51: photoconductor (image carrier), 32, 57: developing roller (developer supply means), 35, 55: developing blade (developer layer forming member).

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 15/08-15/09

Claims (2)

(57) [Claims] 1. A developer supply means for performing development by supplying a non-magnetic one-component developer to an image carrier for carrying an electrostatic latent image, a support, and a support provided at a front end of the support. Made of silicon
A developer layer-forming member comprising an elastic body, wherein the silicon-made elastic body is pressed against the developer supply means, and a thin layer of the developer is formed on the developer supply means. When the volume average particle diameter of the developer is Dt (μm) and the pressing force of the silicon elastic body of the developer layer forming member against the developer supply means is P (g / cm), Dt <15 20 A developing device that satisfies the relationship: ≤P≤-16.44 x Dt + 243.5. 2. An image forming means for forming a latent image on an image carrier, and a developer supply means for performing development by supplying a non-magnetic one-component developer to the latent image formed by the image forming means. , A support and a silicon-made support provided at the tip of the support.
A developer layer forming member comprising an elastic body, wherein the silicon elastic body is brought into contact with the developer supply unit, and a thin layer of the developer is formed on the developer supply unit. When the volume average particle diameter of the developer is Dt, and the pressing force of the silicone elastic body of the developer layer forming member against the developer supply means is P (g / cm), Dt <15 20 ≦ P ≦ An image forming apparatus which satisfies a relationship of −16.44 × Dt + 243.5.