JP2000250295A - Developing device and forming device provided with this device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent picture deterioration and density deterioration without generating carrier sticking or the like of a developer carrier by providing a pulse wave of a pulse width equal to or smaller than a specific value in a pulse wave area of a bias to apply between a developer carrier and a developer supplying means so as to allow a DC area to have a prescribed voltage having a time interval equal to or longer than the specific times of that in the pulse wave area. SOLUTION: At the time of carrying toner to a donor roll 21 from a magnetic brush roll 22, the alternate electric field of a rectangular pulse is applied adding on the DC electric field. At the same time, the bias is made a voltage waveform having an area of pulses where voltage applied so as to move the toner from the roll 21 to the roll 22 and voltage applied to move the toner from the roll 22 to the roll 21 are alternately repeated and the pulse width is not larger than 500 μ sec, and a DC area of a prescribed voltage. In this case, the DC area has a prescribed voltage having a time width equal to or longer than 1.5 times of that in a pulse wave area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing method for visualizing a latent image as a developer image by applying a developer carried on a developer carrier to a latent image carrier carrying a latent image. The present invention relates to an apparatus and an image forming apparatus including the developing device.

[0002]

2. Description of the Related Art Conventionally, in such an image forming apparatus,
After uniformly charging the latent image carrier, image exposure is performed by analog exposure or a semiconductor laser or LED, and after forming the electrostatic latent image on the latent image carrier, the electrostatic latent image is developed. After the developer image is visualized as a developer image by a device and the developer image is transferred to a transfer material as a recording medium, the transfer material is separated from the latent image carrier and subjected to a fixing process by a fixing device, so that a fixing process is performed on the transfer material. An image forming apparatus that outputs a developer image as a fixed image is known.

The operation of such a conventional image forming apparatus will be described.

In such an image forming apparatus, for example,
The photosensitive drum includes a photoconductive layer such as OPC or a-Si and is a latent image carrier that is rotated in a predetermined direction.

In such an image forming apparatus, first, the surface of the photosensitive drum is, for example,
It is uniformly charged to 700V.

Next, the surface potential of the exposed portion on the photosensitive drum is reduced by, for example, −20 by image exposure according to the image signal information.
The voltage is attenuated to 0 V, and a latent image corresponding to the image signal of the image is formed on the photosensitive drum. For image exposure, for example, a semiconductor laser or an LED array is used.

Next, the latent image is developed by a developing device as a developing device using a dry type one-component developer, and is visualized as a toner image.

In a conventional developing device, as disclosed in US Pat. No. 4,868,600, a magnetic brush roll serving as a developer supply means includes a two-component developer containing a toner and a carrier. There is known a developing device in which the toner is supplied to a region close to a donor roll as a developer carrier, and toner is supplied from the magnetic brush roll to the donor roll in the close region.

In such a developing device, the donor roll transports the toner to a region facing the latent image carrier. Also, a pair of electrode wires is disposed in the space between the donor roll and the latent image carrier and is electrically biased to separate the toner from the donor roll to form a toner cloud, thereby separating the toner cloud from the toner cloud. The developed toner develops the latent image on the latent image carrier.

In a conventional developing device, as disclosed in US Pat. No. 4,984,019, a developing region is a region where a donor roll and a latent image carrier face each other. 2. Description of the Related Art A developing device having electrode wires arranged adjacent to each other is known.

In such a developing device, the magnetic brush roller transports the developer to the donor roll, and toner is supplied from the magnetic brush roller to the donor roll.

Further, in a conventional developing device, as disclosed in US Pat. No. 5,0101,367,
2. Description of the Related Art A developing device adopting a scavengeless developing system in which a pair of electrode wires is disposed close to a donor roll in a gap between a donor roll and a photosensitive belt serving as a latent image carrier is known.

Such a developing device effectively separates toner from the donor roll by combining an AC voltage applied on the donor roll with an AC voltage applied between the electrode wire and the donor roll, so that the photosensitive belt Is formed in close proximity to the toner cloud.

However, in the conventional developing device as described above, in the case of a certain toner material, an electrode line such as a wire and the like, which is electrically biased and tensioned, vibrates in a state where it is separated from itself and comes into contact with the donor roll. Therefore, uneven development may occur. Further, there is a fear that dust may be instantaneously attached to a wire or the like to cause a streak on the donor roll.

Therefore, it is effective that the electrode wire is not disposed outside the donor roll but is an electrode integrated with the donor roll. S. P. 5172170,
A developing device provided with an electrode-embedded donor roll as disclosed in JP-A-6-3941 has been proposed.

As described above, the hybrid development system, which is a system for developing a latent image on a photoreceptor by supplying only toner in a two-component developer from a magnetic brush roll to a donor roll, has a problem that a carrier adheres to a photoreceptor. This is a technique for reducing This is very effective in preventing the carrier from adhering to the photoreceptor, because the amount of the carrier adhering increases in contradiction with the improvement in the image quality as the diameter of the developer becomes smaller in recent years.

[0017]

However, in such a developing device, when the toner is supplied from the magnetic brush roll to the donor roll, the carrier also slightly adheres to the donor roll. However, there is a possibility that the carrier of the image adheres.

In such a developing device, for example,
U. S. P. 5172170, a developing device having an electrode-embedded donor roll as disclosed in JP-A-6-3941), and a developing device using a wire electrode is free from strobing, wire contamination, etc. Are arranged at predetermined intervals along the peripheral surface of the donor roll in parallel to the
The efficiency of supplying toner from the magnetic brush roll to the donor roll is poor, and there is a possibility that image omission may occur when images having a high image ratio are continuously developed.

Further, in such a developing device, when the toner is supplied from the magnetic brush roll to the donor roll,
If the alternating bias applied to the magnetic brush roll and the donor roll is a conventional rectangular wave or sine wave AC bias, the selectivity (toner particle size, tribo, etc.) of the toner transferred from the magnetic brush roll to the donor roll is high. If the toner particle diameter and the toner component of the toner supplied from the magnetic brush roll to the donor roll change due to the durability, the image quality and the density may be reduced.

Therefore, according to the present invention, the toner particle size, triboelectricity, and the like change due to durability without causing carrier adhesion to the developer carrying member or image omission when images having a high image ratio are continuously developed. It is an object of the present invention to provide a developing device capable of suppressing the selectivity of toner supplied from a developer supply unit to a developer carrier due to the above problem and preventing a decrease in image quality and a decrease in density, and an image forming apparatus including the developing device. I do.

[0021]

According to the present application, the object is to develop a latent image by applying a developer carried on the developer carrier to a latent image carrier carrying a latent image. A developing device that visualizes as a developer image, a rotatable developer carrier that carries a developer, and a rotatable developer that is disposed close to the developer carrier and supplies the developer to the developer carrier. A developing device having a developer supply unit and a bias applied by superimposing an AC voltage on a DC voltage between the developer carrier and the developer supply unit to generate an electric field. The bias applied between the developer carrier and the developer supply means has one cycle of a voltage waveform having a pulse wave region and a DC region, and the pulse wave region is used when the developer is developed from the developer carrier. Voltage and developer applied to move to the agent supply means The voltage applied from the developer supply means to the developer carrier has at least one pulse wave having a pulse width of 500 μsec or less that is alternately repeated based on a predetermined voltage. This is also achieved by the first invention in which the predetermined voltage has a time width 1.5 times or more that of the wave region.

According to the present application, the above object is achieved in the first aspect, wherein the developer carrier has an electrode member that moves along the peripheral surface of the developer carrier with rotation of the developer carrier. The present invention is also achieved by the second invention in which a DC voltage on which an AC voltage is superimposed is applied to the electrode member.

Further, according to the present application, the above object is also achieved by the third invention in which in the first invention or the second invention, the developer is a two-component developer containing a carrier and a toner. Achieved.

Further, according to the present application, the above object is achieved according to the third aspect, in which the developer supply means has a fixed magnet inside, and supplies the two-component developer to move the toner to the developer carrier. This is also achieved by the fourth invention in which a magnetic brush is formed.

Further, according to the present application, the above object is achieved according to any one of the second to fourth inventions, wherein the pulse wave is applied to the electrode member provided on the developer carrier when the developer carrier rotates. The present invention is also achieved by the fifth invention in which the width has at least one pulse within the circumferential width.

Further, according to the present application, the above object is achieved in any one of the first to fifth inventions in that the AC voltage applied from the developer supply means to the developer carrier is a latent image carrier. The invention is also achieved by the sixth invention in which the power is supplied from a power supply for supplying an AC voltage applied between the power supply and the developer carrier.

Further, according to the present application, an object of the present invention is to provide an image forming apparatus for recording an image formed by a series of image forming processes on a recording medium, comprising the developing device of the first invention. The invention is also achieved by the invention of (1).

According to the present application, the above object is achieved according to the seventh aspect, in which the developer carrier has an electrode member which moves along the peripheral surface of the developer carrier with rotation of the developer carrier. The present invention is also achieved by the eighth invention in which a DC voltage on which an AC voltage is superimposed is applied to the electrode member.

Further, according to the present application, the above object is achieved according to the ninth invention in the seventh invention or the eighth invention, wherein the developer is a two-component developer containing a carrier and a toner. Achieved.

Further, according to the present application, the above object is achieved in the ninth aspect of the present invention in that the developer supply means has a fixed magnet inside, and controls the two-component developer to move the toner to the developer carrier. This is also achieved by the ninth invention in which a magnetic brush is formed.

Further, according to the present application, the above object is achieved according to any one of the eighth to tenth aspects, wherein the pulse wave is applied to the electrode member provided on the developer carrier when the developer carrier rotates. This is also achieved by the eleventh invention in which the width has at least one pulse within the circumferential width.

According to the present application, the above object is achieved in any one of the seventh to eleventh aspects of the present invention in that the AC voltage applied from the developer supply means to the developer carrier is a latent image carrier. The invention is also achieved by a twelfth invention in which the power is supplied from a power supply for supplying an AC voltage applied between the body and the developer carrier.

That is, in the first invention according to the present application, a bias whose voltage waveform is optimized is applied between the developer carrier and the developer supply means to generate an electric field.

According to the second aspect of the present invention, a bias for optimizing the voltage waveform is applied between the developer carrier and the developer supply means through the electrode member, and the electric field is reduced. generate.

Further, in the third invention according to the present application, a bias whose voltage waveform is optimized is applied between the developer carrier and the developer supply means to generate an electric field.

According to the fourth aspect of the present invention, a bias for optimizing a voltage waveform is applied between the developer carrier and the developer supply means through an electrode member, and an electric field is generated. At the same time, the fixed magnet forms a magnetic brush to move the toner from the developer supply means to the developer carrier.

Further, in the fifth invention according to the present application, at least one bias pulse whose voltage waveform has been optimized is applied within the width of the electrode member, and the developer carrier and the developer An electric field is generated between the supply means.

In the sixth aspect of the present invention, an AC voltage is supplied to a bias from a power supply for supplying an AC voltage applied between the latent image carrier and the developer carrier. In addition, a bias whose voltage waveform is optimized is applied between the developer carrier and the developer supply unit to generate an electric field.

Further, in the seventh invention according to the present application, a bias whose voltage waveform is optimized is applied between the developer carrier and the developer supply means to generate an electric field.

According to the eighth aspect of the present invention, a bias for optimizing the voltage waveform is applied between the developer carrier and the developer supply means through the electrode member, and the electric field is reduced. generate.

Further, in the ninth invention according to the present application, a bias for optimizing the voltage waveform is applied between the developer carrier and the developer supply means to generate an electric field.

According to the tenth aspect of the present invention, a bias for optimizing the voltage waveform is applied between the developer carrier and the developer supply means through the electrode member, and the electric field is reduced. At the same time, the fixed magnet forms a magnetic brush to move the toner from the developer supply means to the developer carrier.

Further, in the eleventh invention according to the present application, at least one bias pulse for which the voltage waveform is optimized is applied within the width of the electrode member, and the developer carrier is An electric field is generated with the agent supply means.

In the twelfth invention according to the present application, an AC voltage is supplied to a bias from a power supply for supplying an AC voltage applied between the latent image carrier and the developer carrier. Then, a bias whose voltage waveform has been optimized is applied between the developer carrier and the developer supply means to generate an electric field.

[0045]

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

(First Embodiment) First, an image forming apparatus according to a first embodiment of the present invention will be described.

FIG. 1 shows a schematic configuration of an image forming apparatus according to this embodiment.

In the image forming apparatus according to the present embodiment, the process speed is 501 mm / sec and 90 minutes per minute.
This is a single black-and-white digital copying machine, and uses an a-Si drum photoconductor of φ108 as a photoconductor as a latent image carrier. a
-Si drum photoreceptors have relatively high relative dielectric constants compared to organic photoreceptors, so their charging potential is relatively low, so that latent image potential cannot be sufficiently obtained compared to OPC. There is a feature that is suitable for.

In this image forming apparatus, as shown in FIG. 1, after the photosensitive member 1 serving as a latent image carrier is uniformly charged to, for example, +500 V by the charger 3, image exposure 12 is performed at 600 dpi. . The image exposure 12 has a wavelength 68 modulated by the first image signal using a semiconductor laser as a light source.
A first laser beam of 0 nm, the first laser beam is polarized by a polygon mirror (not shown) rotated at a constant rotation speed by a motor, and an imaging lens (not shown).
After being reflected by a folding mirror (not shown),
The photosensitive member 1 is raster-scanned to attenuate the surface potential of the exposed portion to, for example, +100 V to form an image-like latent image.

Thereafter, the latent image is developed as a toner image by a developing device 2 serving as a developing device, and the toner on the photoconductor 1 is negatively charged by a post-charging device 10. Reduces the adsorbing power to facilitate transfer and separation. In the present embodiment, a negative toner having a particle size of 6.5 μm is used as the toner, and regular development is performed.

The post-charger 10 causes a total charge of -100.
FIG. 1 shows a charged toner image to which μA (AC + DC) has flowed.
After being transferred by the transfer charger 4 to the transfer material moving in the direction of the arrow shown in FIG.

Next, the developing device 2 will be described with reference to FIG.

The developing device 2 is a hybrid type developing device. The developing device 2 is a predetermined type with respect to a developer stirring member (not shown), a magnetic brush roll 22 as a developer supply means, and a developer stirring member and the magnetic brush roll 22. And a donor roll 21 which is a developer carrying member and is disposed at intervals.

The magnetic brush roll 22 has a fixed magnet 23 having six magnetic poles inside. The periphery of the fixed magnet 23 is covered with stainless steel 24 (SUS305), which is a non-magnetic and conductive metal. The two-component developer containing toner 26 and carrier 25 is fixed magnet 23
To be coated by the magnetic force.

Further, the developing device 2 has a blade 30 disposed close to the surface of the magnetic brush roll 22 so as to regulate the height and amount of the developer on the magnetic brush roll 22 to a desired level. ing.

The outer peripheral surface of the magnetic brush roll 22 is roughened (Alundum # 400).

The magnetic brush roll 22 transports a predetermined amount of charged toner to the donor roll 21 by an electric bias applied between the donor roll 21 and the magnetic brush roll 22. . A predetermined amount of toner having a predetermined charge on the donor roll 21 conveyed from the magnetic brush roll 22 is supplied to a developing area on the photoconductor 1 facing the donor roll 21, and an electrostatic latent on the photoconductor 1 is charged. The image is developed. In the present embodiment, the rotation directions of the magnetic brush roll 22 and the donor roll 21 are as shown in FIG. 2, but it is preferable to optimize the rotation direction according to the configuration of the developing device.

The developer according to this embodiment has a particle size of 35 μm.
m containing a ferrite-based carrier and a toner in which carbon is dispersed in a polyester resin. The content (weight) of the toner and the carrier in the developer is about 95% to about 99% for the carrier, and about 5% for the toner.
Or about 1%. In the present embodiment, as a set value, the toner content (T / D ratio) in the developer is set to 5%,
The density of the patch formed on the photoconductor 1 is detected by the optical ATR, and the toner density is controlled by changing the toner feeding speed. Note that the toner used in the present embodiment is negatively charged, and the average tribo Q / M of the toner on the donor roll 21 is −26 μC / g.

Next, the configuration of the donor roll 21 will be described.

FIG. 3 is a partial front sectional view of the donor roll 21.

[0061] The donor roll 21 is
1, a dielectric layer 42, an electrode pattern 43 as an electrode member disposed in the circumferential direction of the donor roll 21, and an electrode relaxation permitting layer 44.

The electrode pattern 43 is, as shown in FIG.
The electrode wires are arranged at substantially equal intervals in the circumferential direction of the donor roll 21, and are insulated from the sleeve 41 by the dielectric layer 42. In the present embodiment, the sleeve 41 is made of aluminum (A6063).

The electrode pattern 43 is supplied with an AC (rectangular pulse) bias and a DC bias by applying a power supply bias to the developing nip (developing area) A by the brush 27, and a toner cloud (cloud) is formed on the donor roll 21. ) Is formed, and the electrostatic latent image on the photoconductor 1 is visualized as a toner image and developed.

In the present embodiment, the electrode pattern 43 is composed of a plurality of electrode wires arranged in parallel with the longitudinal direction of the donor roll 21 (the axial direction of the donor roll 21) and over the entire peripheral surface of the donor roll 21. You. The length of each electrode line is preferably not less than the image area and not more than the entire length of the donor roll. In the present embodiment, the length is 305 mm, and the width of the electrode line of the electrode pattern 43 is about 100 μm. Also, the electrode lines of the electrode pattern
The effective depth is preferably about 3 μm to about 20 μm, and in this embodiment, it is 10 μm, and the interval between each electrode wire is 150 μm. The resistance of the electrode pattern 43 is 1
It is about 0 ^-3 Ωcm. The material of the electrode pattern is Ag, C
u, Ni, etc. are preferable, and Cu is used in the present embodiment.

The dielectric layer 42 is applied to the outer peripheral surface of the sleeve 41. The dielectric layer has a total thickness of about 25 μm
To about 75 μm of anodized aluminum or a polymer, and in the present embodiment, a material having a polyamideimide of 50 μm in an amount of 70% to 100% by weight is employed. The dielectric coating is made of various oxides,
It may be an inorganic substance such as ceramics.

The charge relaxation permitting layer 44 is formed of the donor roll 21.
The outermost layer is coated over the entire peripheral surface to prevent an electrical short circuit between the electrode pattern 43 and the magnetic brush roll 22 and between the electrode wires of the electrode pattern 43 and protect the surface of the donor roll 21. It is supposed to. The thickness of the charge relaxation permitting layer 44 is about 5 μm. The permittivity of the charge relaxation permitting layer must be sufficient to dissipate the charge accumulation in a matter of seconds, and the fringe charge must be able to penetrate the coating in less than about a few milliseconds. In the present embodiment, the charge relaxation permitting layer is applied by immersion coating.

Next, the power supply bias will be described.

In the developing area A, a voltage source 3
1 and 32 apply a rectangular pulse + DC bias to the electrode pattern 43. Donor roll 21
Is rotated in the direction of the arrow, the electrode pattern 43 is
The brush 27 comes into contact with the electrode pattern 43 in the developing area A as shown in FIG.
32. As a result, a rectangular pulse + DC electric field is generated between the electrode pattern 43 provided on the donor roll 21 and the photoconductor 1, and the developing area A
By forming a toner cloud on the donor roll 21, the electrostatic latent image on the photoconductor 1 is developed.

Also in the toner supply area B, the brush 28 comes into contact with the donor roll 21 and is connected to the voltage sources 34 and 35. Thus, toner particles are attracted and supplied from the developer on the surface of the magnetic brush roll 22 to the donor roll 21 in the supply area B which is the area where the magnetic brush roll 22 and the donor roll 21 face each other.

The specific specifications of each member of the developing device in this embodiment are as follows: the outer diameter of the donor roll 21 is 32 mm; the outer diameter of the magnetic brush roll 22 is 32 mm.
0 mm The distance between the donor roll 21 and the photoconductor 1 is 0.3 mm. The magnetic force of the magnetic brush roll 22 is 600 G.

The developing device of the hybrid developing method used in the present embodiment is of a type in which an electrode pattern is embedded in a donor roll, and has an advantage that there is no strobing, wire contamination, and the like that occur in a developing device employing a wire electrode method. There is.

However, conventionally, since the electrode portion of the electrode pattern is not continuous in the circumferential direction of the donor roll, there is a possibility that the toner supply from the donor roll to the photoreceptor cannot catch up when the image ratio is high.

In addition, it is difficult to make the interval between the above-mentioned electrode portions in the circumferential direction of the donor roll high from the viewpoint of manufacturing, and if the above-mentioned interval is too small, there is a difficulty that the electrodes become conductive. .

Further, if an AC component (50% duty) is added to make it easy to peel off the toner from the magnetic brush roll, the toner is liable to move, but the carrier adhesion to the donor roll in the endurance increases, and the hybrid There is a possibility that the original merits of development may be lost.

When an AC component having a duty of 50% is applied, selectivity is generated in the toner particles supplied from the magnetic brush roll to the donor roll. There is a possibility that the toner transportability itself may be reduced.

Therefore, in the present embodiment, in consideration of the above-described problem, when conveying the toner from the magnetic brush roll to the donor roll, an alternating electric field of a rectangular pulse is applied in addition to the DC electric field, and the bias is A pulse wave region having a pulse width of 500 μsec or less in which a voltage applied to move toner from the donor roll to the magnetic brush roll and a voltage applied to move toner from the magnetic brush roll to the donor roll are alternately repeated. This is characterized by a voltage waveform having a pulse region (hereinafter, referred to as a pulse region) and a region of a predetermined voltage (hereinafter, referred to as a DC region).

The direction in which the developer is moved from the magnetic brush roll to the donor roll (hereinafter referred to as plus direction)
Also, the direction in which the developer is returned from the donor roll to the magnetic brush roll (hereinafter, referred to as a minus direction) has a voltage of 3
It is preferably at least 00V. In the present embodiment, the voltage is 750 V in both the plus direction and the minus direction.

The time in the DC region of the bias is preferably set to 1.5 times or more the time in the pulse region. In the present embodiment, as shown in FIG. 4, the time in the DC region is set to T3 = 334 μsec.

The reason why the pulse width of the pulse region is preferably 500 μsec or less is because if the pulse width is 500 μsec or more, the application time is long and the effect of the present invention cannot be obtained due to its continuity. Preferably, the pulse width is 200 μsec or less. In this embodiment, as shown in FIG. 4, the pulse width is T1 = 83.5 μsec,
T2 was set to 83.5 μsec.

In this embodiment, the DC component is 1
50 V was applied.

Here, the evaluation of the bias of each duty ratio will be described with reference to FIG. As a comparative example, the highest characteristic of the bias having the duty 50% AC component when the above-described voltage and frequency ranges are all varied, and the D characteristic when the voltage is varied from 0V to 1000V.
It shows the highest characteristic of the bias of only C.

[0082]

[Table 1] Table 1 is a table showing evaluation results of carrier adhesion (initial, durability 100 k sheets), solid black follow-up (toner mobility), and selective transportability (with respect to toner) with respect to bias at each duty ratio.

As shown in Table 1, there is no problem with any bias in the initial stage of carrier adhesion. However, in the case of a 100k-durable sheet, the voltage must be set to 700 V in order to increase the toner transporting property with only the DC component bias. Therefore, under the conditions, Δ is given, and duty 50% AC
If the component bias tries to satisfy the solid black followability, V
Since pp must be 1.0 kV or more, it is x under that condition.

On the other hand, in the present embodiment, by applying a pulse-like alternating electric field component, the toner is easily separated from the carrier instantaneously, and the movement from the magnetic brush roll to the donor roll is facilitated. The carrier is prevented from moving to the donor roll by extremely shortening the time of the alternating component applied from the magnetic brush roll to the donor roll. This is because the toner can move with a short electric field because of its small weight compared to the carrier, but the carrier with large inertia cannot move unless an electric field for a sufficient time is given because a time lag occurs to start moving. It is. As described above, in the present embodiment, it is possible to suppress the carrier movement to the donor roll while improving the toner transportability, and to prevent the carrier from adhering on the image even in the durability.

With respect to the solid black followability (toner mobility), a bias of duty 50% including an alternating component is better than a bias of only a DC component, and is even better with a bias consisting of a pulse electric field component and a constant DC value. . still,
As for the pulse width, 50 is required to obtain the effect as described above.
0 μsec or less is preferable. Further, in relation to the width of the electrode on the donor roll, the pulse width of the donor roll is set at the active toner transport unit in order to transport the toner from the magnetic brush to the donor roll with the active electrode. There must be at least one in the electrode in the circumferential direction.

As for the selective transport property, since the toner particle diameter on the magnetic brush roll changes due to durability against the initial toner particle diameter, those having a large change are not preferable because the transport selectivity is large. This is because if the selective transportability is large, a toner group that cannot move to the donor roll due to the coarsening of the toner particle diameter is formed.
That is, the solid black followability is deteriorated. Therefore, the smaller the selective transportability, the better. In the present embodiment, the selective transportability is small with respect to a bias of a normal duty of 50%.
Even in the durability of k sheets, the toner particle size is not so different from the initial toner particle size, so that the toner conveyance is good in the durability. Here, the reason why the present embodiment is better than the normal 50% duty rectangular wave and sine wave bias is that the voltage applied in the direction of moving from the magnetic brush roll to the donor roll by the normal DC bias at the 50% duty bias is as follows. While only the toner of a tribo that is stronger than the voltage returned from the donor roll to the magnetic brush roll and is preferable for flight moves, in the case of the bias composed of the pulsed bias and the DC constant value bias, the time of the DC constant value and the pulsed bias The bias can be adjusted by adjusting the time during which the toner is applied, and selective toner conveyance can be prevented.

Regarding the evaluation criteria in Table 1, the carrier adhesion was evaluated based on the carrier adhesion amount when a solid image was output as an A3 image. , And x was given for 10 mg or more.

The solid black followability is evaluated based on the number of images that can be formed without any white spots when a solid black image (FFH) is continuously copied in A4 size. The score was Δ for 200 to 500 sheets, and ○ for 500 or more sheets.

Further, the selective transport property is evaluated based on the particle size of the toner on the magnetic brush roll. If the toner particle size is large, the transfer to the donor roll is deteriorated. On the other hand, when the degree of coarse powdering was 1.0 μm or less, ○, when 1.0 to 1.5 μm, Δ, and when 1.5 μm or more, ○.

In the present embodiment, the bias applied to the electrode by the brush in the developing section is Vpp 1.60.
kHz, frequency 2.0 kHz, DC component + 250V.

With the configuration described above, in the present embodiment, in the developing device of the hybrid development type having the electrode-embedded donor roll, the carrier does not move from the magnetic brush roll to the donor roll due to the durability.
A developing device capable of outputting a high-quality image without image carrier adhesion can be provided.

In the present embodiment, in the developing device of the hybrid development type having the electrode-embedded donor roll, the toner is transferred from the magnetic brush roll to the donor roll due to the electrodes being arranged at intervals on the donor roll. It is possible to provide a developing device that does not cause a decrease in the moving efficiency or an image omission due to a continuous high image ratio image.

Further, when the toner is moved from the magnetic brush roll to the donor roll, the alternating bias applied to the magnetic brush roll and the donor roll is the conventional AC bias of a rectangular wave and a sine wave, so that the selectivity of the toner (toner Particle size, tribo, etc.), toner particle size, and toner components can be changed to provide a high-speed, high-density and stable developing device without causing deterioration in image quality and density due to durability.

(Second Embodiment) Next, a second embodiment of the present invention will be described. Note that the same components as those of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

The feature of this embodiment is that a plurality of latent images are formed on the photosensitive member while the photosensitive member as the latent image carrier makes one rotation,
The present invention is applied to a two-color image forming apparatus that develops each of the latent images with a plurality of developing devices to form a visible image, and then collectively transfers the visible image to a transfer material.

As described above, the multi-color image forming apparatus which performs the normal multiple transfer resets the potential of the latent image carrier by the pre-exposure device every time the visible image is transferred. Since multiple development is performed on the latent image carrier and then collectively transferred to a transfer material by a transfer device, there is an advantage that productivity is high. The image forming apparatus according to the present embodiment has a process speed of 550 mm / sec.
It is a 102-sheet machine of c.

The developing method using a plurality of colors has a higher image level required for the image forming apparatus than the black and white developing method. In view of the above, the present embodiment employs a hybrid development system having the advantages of two-component development and one-component development using a carrier.

FIG. 5 is a schematic sectional view of the image forming apparatus according to this embodiment.

In FIG. 5, reference numeral 121 denotes an OP which is a latent image carrier capable of transmitting light from the back and moving in the direction of arrow A in the figure.
It is a C-belt photoconductor (hereinafter, referred to as a photoconductor).

After the surface of the photosensitive member 121 is uniformly charged to, for example, -600 V (dark portion potential) by the first charger 122, a first image exposure 123 is performed.

The first image exposure 123 is performed by a first LED of 600 dpi at a wavelength of 670 nm. The image exposure 123 passes through an imaging lens (not shown), and
Irradiated on the belt photoreceptor 121, the surface potential of the exposed portion is attenuated according to the image signal level to form an image-like first latent rubber. For example, it is set to -100 V at the maximum density part.

The first latent image is, for example, a negatively charged black two-component toner (toner particle size 6 μm, carrier particle system 35 μm).
m) is developed by the first developing device 124 using the developer. For example, a DC bias of −500 V is applied to the first donor roll of φ32 provided in the first developing device 124, and 2000 Hz is applied to the electrode of the second donor roll of φ32 provided in the first developing device 124. Fifteen
A bias voltage in which a DC voltage of -200 V is superimposed on a rectangular wave of 00 Vpp is applied by a brush to reversely develop the first latent image. At this time, the potential of the toner image drops by about -50 V at the maximum density portion due to toner charge, for example, to -150 V.
V. The S-Dgap of the first donor roll is 3
It is designed to perform non-contact development. The S-Dgap of the second donor roll is 25.
The thickness is 0 μm, and non-contact development is performed. Coating amount M / S of toner on first donor roll
Is 1.0 mg / cm, and the toner coating amount M / S on the second donor roll is 0.6 mg / cm. Preferably, as shown in FIG. 6, it is preferable that the toner is scraped off from the donor roll using a scraper member 55 inside the developing device as shown in FIG. still,
The diameter of the magnetic brush roller and the distance between the magnetic brush roller and the donor roll are the same as in the first embodiment.

After the first latent image has been developed by the first developing device 124, the photosensitive member 121 is placed on the back of the photoconductor 121 from the rear. L. Or L
The entire surface is exposed by the ED element 131 or the like, and the first toner image potential at the maximum density portion and the dark portion potential after the first full-surface exposure are reduced by, for example, -50 so as to reduce the potential difference.
V, -200V.

Next, the toner is recharged by the second charger 105. For example, the potential of the toner layer in the maximum density portion is set to -670V, and the potential of the dark portion is set to -700V. That is, the potential of the dark portion is slightly lower than the potential of the toner layer of the maximum density portion, and the potential of the toner layer of the maximum density portion is set to the extent that the second latent image contrast can be obtained.

Next, like the first exposure means 103, the second
Exposure by the second LED modulated by the image signal is performed. It is an LED of 600 dpi equivalent to the first exposure, and the wavelength is 670 nm. The second LED 125 irradiates the photoconductor 121 from the back surface of the photoconductor 121 via an imaging lens. Incidentally, a semiconductor laser element or the like can be used for the exposure apparatus.

The second latent image formed in this manner is a rectangular wave of, for example, 2000 Hz and 2500 Vpp by the second developing device 127 using red toner and a carrier.
By applying a bias in which a DC of -570 V is superimposed on an alternating current of 35%, only the latent image portion is developed without developing the first toner image portion.

Next, the two-color image on the photosensitive member 121 is DC
Toner tribo is optimized by a charger (not shown) to which an AC voltage is superimposed on the voltage, and the transfer material 1 is generally
32 is transferred by the transfer charger 128 to the separation charger 1
The sheet 33 is separated from the photoconductor 121 by the curvature of the photoconductor 121 and is fixed by the fixing unit 129, and then is discharged out of the apparatus as a two-color print. On the other hand, the photoconductor 121
After the residual toner is removed by the cleaning device 130, the cleaning device 130 is used for the next image forming process.

As shown in FIG. 9, the toner conveying bias in this embodiment includes a DC voltage region and a symmetrical pulse region. The symmetrical pulse region has a form in which a very short rectangular pulse is repeated twice. I have.

The voltage in the DC voltage region, that is, the voltage of the DC component of the bias is -580 V, and the pulse amplitude in the minus direction (toner flying direction) of the pulse region is 7V.
The amplitude of the pulse in the plus direction (the direction in which the toner is pulled back) is also 750 V.

The rotation speed of the donor roll was 990 in linear speed.
mm / sec, which is 180% of the speed of the photosensitive belt 121.

In this embodiment, T1 = T2 = T3 = T4
= 41.7 μsec. As described above, the time during which the pulse of the toner transport bias is not applied, that is, the time in the DC voltage region other than the pulse region of the developing bias is preferably 1.5 times or more the time in the pulse region. The effect of the invention becomes remarkable. In the present embodiment, T3 = 334 μsec. The voltage of the DC component was set to 150V.

An AC voltage as shown in FIG. 9 is applied to each developing device as a toner transport bias from the magnetic brush roll to the donor roll.

Table 2 shows the results obtained when this example was implemented.

[0114]

[Table 2] As shown in Table 2, in the same manner as in the first embodiment, the carrier adhesion (initial, durable 100 k sheets), solid black follow-up (toner mobility), and selective transportability were evaluated. As a comparative example, the maximum characteristics when all the above ranges are shifted with a bias of 50% duty and the maximum characteristics when all the above ranges are shifted with a bias of only the DC component are shown.

As a result, in the hybrid developing system having the electrode-embedded donor roll, the carrier does not move from the magnetic brush roll to the donor roll even during the endurance, so that there is no carrier adhesion, and the image with a high image ratio continues because the image continues. It can be seen that there is no detachment, and there is no toner-selective transportability. In particular, as in the present embodiment, the use of a double pulse as short as 12 kHz makes it possible to reduce the degree of carrier adhesion to a level (0.2 mg or less) that hardly exists on the image both in the initial stage and in the durability.

As described above, by implementing this configuration in a multi-color image forming apparatus, there is no carrier adhesion, solid black followability, low selective transportability, It is possible to realize a multicolor image forming apparatus having a high level, a long life and a high durability.

(Third Embodiment) Next, a third embodiment of the present invention will be described. In addition, about the structure similar to 1st Embodiment and 2nd Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

In this embodiment, the developing device is a full-color 2
This is applied to a four-sheet machine.

The image forming apparatus according to the present embodiment has the configuration shown in FIG.
As shown in FIG. 6, four φ60 drums are arranged in a tandem type. In this embodiment, an OPC photosensitive member is used. The OPC photoreceptor is uniformly charged to -700 V by a primary charger at each station, and then writes 800 dpi image information by a semiconductor laser to form a latent image. After that, the latent image is reversely developed with a negatively charged toner by a developing device for each color. The particle size of the negative toner is 9 μm, and the carrier used has a particle size of 50 μm.
m of ferrite particles. Thereafter, the visible image visualized by the developing device is subjected to a transfer and fixing process, and is output as a fixed image.

The developing device used in this embodiment is shown in FIG.
As shown in (1), one developing device is provided with two donor rolls 71 and 72 as developer carriers and a magnetic brush roll 73 as one developer supply unit. This is a system in which the number of times of development is increased even at high speeds, and more stable development can be performed with respect to density and image quality.

This embodiment is characterized in that it is full-color and the AC component of the bias applied to the electrode of the donor roll by the brush in the developing unit and the AC component of the bias used when moving the toner from the magnetic brush roll to the donor roll. Are used to reduce costs by using the same power supply.

The AC bias power supply is expensive, and in an image forming apparatus having four developing units as in this embodiment, a total of 16 AC power supplies or pulsed bias power supplies are required. In order to reduce the frequency by half, in the present embodiment, the configuration is as described above, and a pulse-like alternating electric field is applied to the developing section instead of the normally applied AC component. That is, as shown in FIG. 8, the pulsed alternating components supplied to the brushes 78 and 79 and the brushes 76 and 77 are supplied from the same power supply.

The DC bias applied to the electrode of the donor roll and the DC bias component applied from the magnetic brush to the donor roll are optimized respectively.

As described above, in the full-color image forming apparatus, it is possible to provide a developing device that outputs a high-quality image without causing the carrier to move from the magnetic brush roll to the donor roll and without adhering the image carrier even in durability.
Further, it is possible to provide a high-quality developing device in which the toner transfer efficiency from the magnetic brush roll to the donor roll is reduced and the image with a high image ratio is continued without image omission. It is possible to simultaneously provide a high-speed, high-density and stable developing device without lowering the cost at low cost.

[0125]

As described above, according to the first aspect of the present invention, the bias whose voltage waveform is optimized is applied between the developer carrier and the developer supply means. Since an electric field is generated, the toner particle size and the toner discharge amount due to the endurance are prevented without causing the carrier adherence to the developer carrying member and the image omission when the image having a high image ratio is continuously developed. It is possible to suppress the selectivity of the toner supplied from the developer supply unit to the developer carrying member due to the change of the image quality and the like, and to prevent the image quality and the density from decreasing.

Further, according to the second invention of the present application,
A bias for which the voltage waveform is optimized is applied between the developer carrier and the developer supply means through the electrode member to generate an electric field, so that the carrier adheres to the developer carrier, A toner supplied from a developer supply unit to a developer carrier due to a change in toner particle size, tribo, etc. due to durability without causing image omission when an image having a high image ratio is continuously developed. , The image quality and the density can be prevented from lowering.

Further, according to the third aspect of the present invention, a bias whose voltage waveform is optimized is applied between the developer carrying member and the developer supply means to generate an electric field. Therefore, the toner particle size, tribo, etc. change due to durability without causing carrier adhesion of the developer carrying member or image omission when continuously developing images having a high image ratio. It is possible to suppress the selectivity of the toner supplied from the developer supply unit to the developer carrier, thereby preventing the image quality and the density from decreasing.

According to the fourth invention of the present application,
A bias for adjusting the voltage waveform is applied between the developer carrier and the developer supply unit through the electrode member, and an electric field is generated, and the fixed magnet is moved from the developer supply unit to the developer carrier. Since the magnetic brush is formed so as to move the toner, the toner does not adhere to the carrier of the developer carrier and the image is not missing when the image having a high image ratio is continuously developed. It is possible to suppress the selectivity of the toner supplied from the developer supply unit to the developer carrier due to the change in the particle size, the triboelectricity, and the like, thereby preventing the image quality and the density from decreasing.

Further, according to the fifth aspect of the present invention, at least one bias pulse whose voltage waveform is optimized is applied within the width of the electrode member, and the developer carrier and the developer supply are applied. Since an electric field is generated between the toner particles and the image forming means, the toner particles do not adhere to the developer carrier, and the toner particles do not drop out when the image having a high image ratio is continuously developed. It is possible to suppress the selectivity of the toner supplied from the developer supply unit to the developer carrier due to a change in diameter, tribo, and the like, thereby preventing a decrease in image quality and a decrease in density.

According to the sixth invention of the present application,
An AC voltage is supplied to the bias from a power supply for supplying an AC voltage applied between the latent image carrier and the developer carrier, and a bias for optimizing the voltage waveform is applied to the developer carrier and the developing device. Since it is applied between the developer supply means and generates an electric field, it does not cause carrier adhesion of the developer carrier or image omission when continuously developing an image having a high image ratio. Further, it is possible to suppress the selectivity of the toner supplied from the developer supply unit to the developer carrying member due to the change in the toner particle diameter, the triboelectricity, and the like due to the durability, thereby preventing the image quality and the density from being reduced.

Further, according to the seventh aspect of the present invention, a bias whose voltage waveform is optimized is applied between the developer carrier and the developer supply means so that an electric field is generated. Therefore, the toner particle size, tribo, etc. change due to durability without causing carrier adhesion of the developer carrying member or image omission when continuously developing images having a high image ratio. It is possible to suppress the selectivity of the toner supplied from the developer supply unit to the developer carrier, thereby preventing the image quality and the density from decreasing.

According to the eighth invention of the present application,
A bias for which the voltage waveform is optimized is applied between the developer carrier and the developer supply means through the electrode member to generate an electric field, so that the carrier adheres to the developer carrier, A toner supplied from a developer supply unit to a developer carrier due to a change in toner particle size, tribo, etc. due to durability without causing image omission when an image having a high image ratio is continuously developed. , The image quality and the density can be prevented from lowering.

Further, according to the ninth aspect of the present invention, a bias whose voltage waveform is optimized is applied between the developer carrier and the developer supply means so that an electric field is generated. Therefore, the toner particle size, tribo, etc. change due to durability without causing carrier adhesion of the developer carrying member or image omission when continuously developing images having a high image ratio. It is possible to suppress the selectivity of the toner supplied from the developer supply unit to the developer carrier, thereby preventing the image quality and the density from decreasing.

Further, according to the tenth aspect of the present invention,
A bias for adjusting the voltage waveform is applied between the developer carrier and the developer supply unit through the electrode member, and an electric field is generated, and the fixed magnet is moved from the developer supply unit to the developer carrier. Since the magnetic brush is formed so as to move the toner, the toner does not adhere to the carrier of the developer carrier and the image is not missing when the image having a high image ratio is continuously developed. It is possible to suppress the selectivity of the toner supplied from the developer supply unit to the developer carrier due to the change in the particle size, the triboelectricity, and the like, thereby preventing the image quality and the density from decreasing.

Further, according to the eleventh aspect of the present invention, at least one bias pulse whose voltage waveform is optimized is applied within the width of the electrode member, and the developer carrier and the developer Since an electric field is generated between the toner supply means and the toner supply means, there is no toner adhesion due to carrier adhesion of the developer carrier or image omission when continuously developing an image having a high image ratio. It is possible to suppress the selectivity of the toner supplied from the developer supply unit to the developer carrier due to the change in the particle diameter, the triboelectricity, and the like, thereby preventing the image quality and the density from decreasing.

According to the twelfth aspect of the present invention, the AC voltage is supplied to the bias from the power supply for supplying the AC voltage applied between the latent image carrier and the developer carrier. In addition, since a bias for optimizing the voltage waveform is applied between the developer carrier and the developer supply means to generate an electric field, carrier adhesion of the developer carrier and image ratio Of toner supplied from the developer supply means to the developer carrier due to the change in toner particle size, tribo, etc. due to durability without causing image omission when continuously developing images with high And the image quality and the density can be prevented from lowering.

[Brief description of the drawings]

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

FIG. 2 is a schematic sectional view showing a schematic configuration of a developing device provided in the image forming apparatus of FIG.

FIG. 3 is a cross-sectional view illustrating a surface of a donor roll provided in the developing device of FIG. 2;

FIG. 4 is a diagram for explaining an AC component of a bias for toner conveyance in the developing device of FIG. 2;

FIG. 5 is a schematic sectional view showing a schematic configuration of an image forming apparatus according to a second embodiment of the present invention.

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

FIG. 7 is a schematic sectional view illustrating a schematic configuration of an image forming apparatus according to a third embodiment of the present invention.

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

FIG. 9 is a diagram for explaining an AC component of a bias for conveying toner in the developing device according to the first embodiment and the second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor (latent image carrier) 2 Developing device (developing device) 21 Donor roll (developer carrier) 22 Magnetic brush roll (developer supply means) 23 Fixed magnet 25 Carrier 26 Toner 31, 34 Power supply 43 Electrode pattern ( Electrode member) 59 Power supply 71, 72 Donor roll (developer carrier) 73 Magnetic brush roll (developer supply means) 121 OPC belt photoconductor (latent image carrier) 127 Developing device (developing device)

Continued on the front page F term (reference) 2H031 AC03 AC07 AC30 AD03 AD09 BA05 BA09 CA01 CA15 DA01 FA01 2H073 AA05 BA04 BA13 BA41 BA45 CA03 CA22 2H077 AC04 AC12 AD02 AD06 AD13 AD36

Claims (12)

[Claims] 1. A developing device for visualizing a latent image as a developer image by applying a developer carried on a developer carrier to a latent image carrier carrying a latent image, the developer comprising: A developer carrier having a rotatable developer carrier for carrying, and a rotatable developer supply unit disposed in close proximity to the developer carrier for supplying a developer to the developer carrier; Between the developer carrier and the developer supply means in a developing device that generates an electric field by applying a bias in which an AC voltage is superimposed on a DC voltage between the developer supply means and the developer supply means. The bias to be applied has a voltage waveform having a pulse wave region and a DC region as one cycle, and the pulse wave region is
The voltage applied to move the developer from the developer carrier to the developer supply unit and the voltage applied to move the developer from the developer supply unit to the developer carrier alternately with respect to a predetermined voltage. Developing at least one pulse wave having a pulse width of 500 μsec or less which is repeated, and wherein the DC region is the predetermined voltage having a time width 1.5 times or more of the pulse wave region. apparatus. The developer carrier has an electrode member that moves along the peripheral surface of the developer carrier with rotation of the developer carrier, and a DC voltage on which an AC voltage is superimposed is applied to the electrode member. The developing device according to claim 1, wherein 3. The developer according to claim 1, wherein the developer is a two-component developer containing a carrier and a toner.
3. The developing device according to claim 1. 4. The developer supply means has a fixed magnet inside, and forms a magnetic brush of a two-component developer so as to move the toner to the developer carrier. 3. The developing device according to claim 1. 5. The pulse wave has a width such that at least one pulse is present within a circumferential width of an electrode member provided on the developer carrier when the developer carrier is rotated. The developing device according to claim 4. 6. An AC voltage applied from the developer supply means to the developer carrier is supplied from a power supply for supplying an AC voltage applied between the latent image carrier and the developer carrier. The developing device according to any one of claims 1 to 5, wherein the developing device is configured as follows. 7. An image forming apparatus for recording an image formed by a series of image forming processes on a recording medium,
An image forming apparatus comprising the developing device according to claim 1. 8. The developer carrier has an electrode member that moves along the peripheral surface of the developer carrier as the developer carrier rotates, and a DC voltage on which an AC voltage is superimposed is applied to the electrode member. The image forming apparatus according to claim 7, wherein: 9. The developer according to claim 7, wherein the developer is a two-component developer containing a carrier and a toner.
An image forming apparatus according to claim 1. 10. The developer supply means has a fixed magnet inside, and forms a magnetic brush of a two-component developer so as to move the toner to the developer carrier. 4. The image forming apparatus according to claim 1. 11. The pulse wave has a width such that at least one pulse is present within a circumferential width of an electrode member provided on the developer carrier when the developer carrier is rotated. The image forming apparatus according to claim 10. 12. An AC voltage applied from the developer supply means to the developer carrier is supplied from a power supply for supplying an AC voltage applied between the latent image carrier and the developer carrier. Claim 7 to Claim 1
The image forming apparatus according to claim 1.