JP2607426B2 - Multicolor image forming 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 multicolor image forming apparatus, and more particularly to a multicolor image forming apparatus which is particularly suitable for obtaining a multicolor image by sequentially forming toner images of different colors on an image carrier.

[0002]

2. Description of the Related Art A typical multi-color image forming apparatus as described above is a multi-color image forming apparatus. The multi-color image forming apparatus is configured to sequentially transfer toner images one by one to recording paper to record a multi-color image, and to sequentially develop one color at a time on an image carrier, and then perform transfer to form a multi-color image. May be recorded. In these multicolor image forming apparatuses and the like, an electrostatic latent image formed on an image carrier is developed by one of a plurality of developing devices, and other developing devices are not subjected to development during the development. Like that. In such an image forming apparatus, there is a problem that toner particles constituting a toner image formed on an image carrier are mixed into a developing device containing another toner, or the toner is not transferred from another developing device on a latent image. Is mixed in. This problem causes color smearing in an image forming apparatus that sequentially develops one color at a time on an image carrier to form a multicolor image.

The above problem will be further described.

As a typical method for developing a latent image, an image carrier is rubbed with a developer layer formed on a developer carrier,
There is a magnetic brush development method in which toner particles are attached to a latent image, and a non-contact development method in which a developer layer is placed in a state where it is not in contact with an image forming body, and toner particles fly from the developer layer and adhere to the latent image. .

In the magnetic brush developing method, the magnetic brush of a developing device that is not used for developing the formed toner image is scraped off, and the image is significantly deteriorated, and another kind of toner is mixed into the developing device. Therefore, in the magnetic brush developing method, it is necessary to remove the magnetic brush of the developing device that is not used for development from the developer carrier or to prevent the magnetic brush from coming into contact with the image carrier.

In the non-contact developing method, an AC voltage is applied to the developer carrier in order to cause toner particles to fly from the non-contact developer layer and sufficiently adhere to the latent image on the image carrier. Although the formed toner image is not scraped off as in the case of the magnetic brush developing method, different kinds of toners are still developed due to the force of transferring the toner particles generated by the AC voltage to the developer carrier. Mix in equipment. For this reason, the above-described AC voltage is not applied to a developing device that is not used for development. However, the fact is that the mixing of different types of toner is not completely prevented. In fact, it does not prevent the toner from being attracted and attached to the latent image potential. Furthermore, in the non-contact development method, since toner particles fly, the toner particles are relatively scattered, and the scattered and floating toner may be mixed into another developing device.

In the conventional color image recording apparatus, (1) the transport of the developer layer on the developer transport carrier is stopped with respect to the developing device that is not performing development, and (2) the developer transport carrier is connected to the image carrier. (3) The developer layer on the developer carrier is scraped off. However, these methods have not been able to sufficiently eliminate toner particles or flying toner particles transferred by an AC voltage from being mixed into a developing device and adhesion of toner from another developing device to a latent image. In addition, the above (2),
The method of (3) has a problem that the device is complicated because a mechanical operation is required, and the burden is increased.

Further, when the transfer of the toner image to the recording paper is completed, the image carrier is neutralized, and then the remaining toner that has not been transferred is scraped off and cleaned to prepare for the next image formation. However, it is extremely difficult to completely remove the static electricity from the image carrier by static elimination, so that a small amount of toner may adhere to the image carrier that has been cleaned before the next latent image is formed. Such a problem occurs not only in a multi-color image forming apparatus but also in a mono-color image forming apparatus (the number of developing devices is one).

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been developed in which a developing device which is not used for development among a plurality of developing devices is already provided on an image carrier. To effectively prevent the toner particles forming the toner particles or toner particles from other developing devices from being mixed in, or the toner from the developing device whose development is stopped to adhere to the image carrier. It is an object to provide a color image forming apparatus.

[0010]

According to the present invention, there is provided an image carrier,
Charging means for uniformly charging the image carrier, latent image forming means for forming a latent image on the image carrier, and non-contact between the image carrier and the developer layer on the developer carrier in the developing area A developing device that performs reversal development by causing the toner to fly under a bias voltage while facing each other, and repeating charging, latent image formation, and reversal development by superimposing a plurality of toner images of different colors on the image carrier. Then, in a multicolor image forming apparatus for transferring to a transfer material, a latent image for developer consumption is formed before and after the latent image in the image area, and when the latent image for developer consumption passes through the development area, the developer is conveyed. Stopping the transport of the developer on the carrier, and applying a bias voltage having the same polarity as that of the toner for causing the toner to flow on the developer-consumption latent image to the developer transport carrier, thereby forming an image portion latent image of another color. When the developer passes through the developing area, the current It stops the conveyance of the material, according to the multi-color image forming apparatus characterized by applying a bias voltage of the same polarity as the toner in the developer transport carrier.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described with reference to the illustrated examples.

FIG. 1 is a schematic configuration diagram showing an example of a multicolor image forming apparatus for sequentially transferring a developer (toner) image to recording paper to form a multicolor image, and FIG. 2 is a portion showing an example of the developing device. Sectional view,
FIG. 3 is a timing chart of forming a multicolor image in the multicolor image forming apparatus of FIG. 1, and FIG. 4 is a schematic diagram illustrating an example of a multicolor image forming apparatus that sequentially forms a toner image on an image carrier to obtain a multicolor image. FIG. 5 is a timing chart of multicolor image formation in the multicolor image forming apparatus of FIG.

In the multicolor image forming apparatus shown in FIG. 1, reference numeral 1 denotes a drum-shaped image carrier having a photosensitive layer having a conductive layer and a photoconductive layer. A document to be copied is placed on a platen glass 2 and irradiated by an exposure lamp 3. Light reflected from the document surface is incident on the image carrier surface via mirrors 4 to 7, imaging lens 8 and color separation means 9. Image carrier 1
Is rotated in the direction of the arrow, the surface of the filter is uniformly charged by the charger 10, and the light passing through the above-described color separation means 9 is incident on the charged surface, and is inserted into the optical path of the color separation means 9. Is formed for each color. That is, the projection of the original image onto the image carrier 1 is performed in proportion to the surface speed of the image carrier 1 on the original platen glass 2 or the exposure lamp 3 of the exposure optical system and the original surface on which the mirrors 4 and 5 and 6 move. This is performed by exposure scanning, and the color separation means 9 includes blue, green, and red filters, and selects one of the color filters and inserts it into the optical path during one exposure scanning. The formed electrostatic latent image is developed by any one of the plurality of developing devices 11A to 11C, preferably a developing device that stores a color toner having a complementary color relationship with the used color separation filter. That is, the plurality of developing devices 11A to 11C use yellow, magenta, and cyan color toner particles as developers for the blue, green, and red filters of the color separation unit 9, respectively. 12
Is a bias power source for applying a bias voltage to the developing devices 11A to 11C.

On the other hand, the recording paper P is fed into a drum-shaped transfer unit 13 by feeding means (not shown), and moves with the rotation of the gripper 13 in the direction of the arrow.

The developed toner image is transferred onto a recording sheet P by a transfer unit 15 provided in the transfer unit 13. In the case of a single-color image copy, the recording paper P is
By the operation of, the leading end is gripped by the transfer unit, separated from the transfer unit, sent to the heat fixing roller 17 to fix the toner image, and then discharged out of the apparatus.
In the case of copying a multicolor image of two or more colors, the separation claw 16 does not operate, and the recording paper P rotates while being held by the transfer unit 13.

The surface of the image carrier on which the toner image has been transferred is cleaned of residual toner by a cleaning device 18 to prepare for the next image forming step. Then, in the case of multicolor image transfer of two or more colors, the same image exposure as the previous time is made incident on the surface charged by the charger 10 by changing the filter of the color separation means 9,
Form electrostatic latent images of different color separations. The electrostatic latent image is developed into a toner image by a corresponding developing device different from that before, and the toner image is transferred onto the recording paper P held by the transfer unit 13 at a position above the toner image. As a result, a two-color image is formed on the recording paper P. In the case of two-color image copying, the separating claw 16 is actuated at this time to separate the recording paper P from the transfer unit 13, and thereafter, a monochrome image is formed. The toner image is fixed and discharged in the same manner as in the above case. In the case of three-color image copying, the separation claw 16 has not yet been operated, and the formation of an electrostatic latent image of a different color separation on the image carrier 1 and the development by another developing device are performed as before. The separation claw 16 operates only when the toner image is transferred onto the recording paper P in the same manner as before. After that, as in the case of single color or two colors, the recording paper P
Is discharged after the toner image is fixed.

The developing devices 11A to 11C use a developing operation having a basic configuration as shown in FIG. This developing device
The non-magnetic developing sleeve 21, which is a developer carrier, rotates counterclockwise, and the internal magnet body 22 rotates clockwise to attract the developer in the developer pool 23 to the surface of the developing sleeve 21 and rotate the magnet body 22. It is transported in the opposite direction. The thickness of the developer conveyed onto the developing sleeve 21 is regulated on the way by the layer thickness regulating blade 24 to form a developer layer.

When the development is performed, a DC bias voltage and / or an AC voltage are applied to the developing sleeve 21 by the bias power supply 12 as necessary. As a result, development is performed in the developing region E, and the developer layer that has passed through the developing region E is removed from the developing sleeve 21 by the cleaning blade 25 and is reduced to the developer reservoir 23. The developer reservoir 23 is supplied with toner. Toner reservoir 23 is supplied with toner from toner hopper 27 by toner supply roller 26. Further, the developer in the developer reservoir 23 is uniformly stirred by the stirring means 28, and a sufficient charge is given to the toner particles.

In the above description, the transport of the developer layer may be performed while the developing sleeve 21 is stationary or clockwise, or the magnet body 22 may be rotated counterclockwise or stationary.

As the developer, a one-component developer composed of magnetic toner particles can be used. However, a two-component developer in which magnetic carrier particles and non-magnetic toner particles are mixed is used to provide color clarity and toner charge control. It is preferably used from the viewpoint of. Details of a suitable developer will be described later.

Further, in the case of the non-contact developing method, in order to effectively control the flying of the toner by applying a bias voltage to the developing sleeve 21, the gap between the image carrier 1 and the developing sleeve 21 must be several tens to 2000 mm. And therefore the thickness regulating blade
It is preferable to make the layer thickness of the developer regulated by 24 smaller. If the gap in the development area is made too narrow, the thickness of the developer layer must be extremely thin, so that a uniform layer thickness cannot be obtained. Therefore, it is necessary to supply toner particles stably to the development area. Not only cannot
Discharge is easily caused between the developing sleeve 21 and the image carrier 1, so that the developer is easily damaged and toner particles are easily scattered. On the other hand, if the gap in the developing area is too wide, it becomes difficult to control the scattering of toner by vibrating electrolysis.

By using the above preferable conditions for the developing devices 11A to 11C, the respective developing devices 11A to 11C
The development of the electrostatic latent image for each color can be performed sharply without fogging. Therefore, a clear monochromatic image or a multicolor image is recorded on the recording paper P.

In the present invention, when the development is stopped, the rotation of the developer carrier (sleeve 21) is stopped, and then the rotation of the magnet carrier (sleeve 21) is stopped.
(If the image is rotating, stop this operation.) The developer on the sleeve 21 in the development area E is reduced. The method described below is effective for reducing the developer.

The electrostatic latent image in this example includes a developer consuming latent image (having a width of several cm parallel to the axis of the drum-shaped image carrier).
And a latent image formed by scanning exposure of a document (hereinafter, referred to as an image portion latent image). When the development is stopped, the rotation of the sleeve 21 is stopped, and the latent image for developer consumption formed in advance on the image carrier 1 is developed. As a result, the developer is not consumed on the sleeve 21 in the developing area E.
Therefore, even if the image area latent image comes to the development area E thereafter, the developer does not adhere to this.

As described above, the stop of the development can be realized by stopping the transport of the developer and subsequently consuming the developer. The developer consumption latent image may be formed close to the rear side of the image latent image on the image carrier 1 or may be formed close to the front side of the next image latent image.

In the above, the developer consuming latent image is developed while the bias voltage for developing the image portion latent image is applied as it is, and the developer is consumed. Further, the bias power supply of the developing device does not need to be turned on and off, and a common bias power supply can be used. That is, since the developer has already been consumed from the developer carrying carrier of the developing device that is not used for development, the development stop means (AC bias power supply) by changing the developing bias to prevent the developer from transferring to the image carrier. , Application of only a DC bias, floating of the developing device or the sleeve 21, grounding of the sleeve 21, etc.) are not always necessary. Further, in the non-contact development, the developing bias is changed when the developer is consumed by using the fact that the developing bias has a large effect on the developability (the AC voltage is increased, the frequency is reduced, and the DC component is changed). Thereby, the amount of the consumed developer can be increased.

In addition to the above-described control of the consumption of the developer in the non-image area, when used in combination with the development stopping means by changing the developing bias thereafter, it is more effective to prevent the mixing of the developer and the flying as described above. It is a target.

In the multicolor image forming apparatus shown in FIG. 1, in order to prevent the developed or scattered toner from being mixed into another developing apparatus, the bias power supply 12 is used for the image forming step of performing the development in the upstream developing apparatus 11A. In this case, not only is the developing bias voltage applied to the developing device 11A for developing, but also the toner particles are formed in the downstream developing devices 11B and 11C until the toner image formed by the upstream developing device 11A passes. A bias voltage for preventing the flight of the airplane is applied.

FIG. 3 shows three Os in charging and image exposure.
7 is a timing chart showing an example of three-color image formation in which electrostatic latent images of respective colors are formed by N and are developed by the non-contact developing methods by the developing devices 11A to 11C, respectively. In this example, the development-consumption latent image is provided behind the image portion latent image. Further, in this example, a bias voltage in which an AC bias of an AC voltage and a DC bias of a DC voltage are superimposed is applied to the developing sleeve 21 of the developing device for performing development.
At the same time, the developer layer carrying rotation of the magnet body 22 as the developing sleeve 21 is performed. The DC bias at the time of development is a DC voltage for preventing fog of the opposite polarity to the charging of the toner particles, and the AC bias and the DC bias voltage are changed at the beginning and end of the development because of the developer consuming portion. This is to ensure developer consumption. Further, while the developer consuming latent image is passing through the developing area E, the driving of the developing device is stopped.

Further, for example, in the image forming step of developing with the developing device 11A, while the toner image formed by the developing device 11A also passes through the developing sleeves 21 of the other developing devices 11B and 11C, the charging of the toner particles is performed. May be applied as a bias voltage. As a result, the toner particles of the developing device 11A do not enter the developing devices 11B and 11C, and a clear multicolor image can be formed forever without the toner flying due to the AC bias.

The above-described example is an example in which development is performed by so-called regular development in which toner particles are adhered to unexposed portions. In the case of so-called reversal development in which toner particles are adhered to exposed portions, developer consumption is reduced. The latent image is formed by performing exposure, and the exposed portion is reversely developed to consume the developer.

The developing device shown in FIG. 4 is a multi-color image recording device for forming a multi-color image by sequentially developing the image on the image carrier 1, and the same reference numerals as those in FIG. 1 denote the same functional members.

In this recording apparatus, the charged surface of the image carrier 1
An image exposure 41 is incident from a laser beam scanner (not shown) including a Ne laser light source, an acousto-optic modulator, a lens device, a rotating polygon mirror, etc. to form an electrostatic latent image having a low-potential dot configuration, and then developed. Is performed by reversal development. In the case of three-color image recording, first, for example,
The toner image developed by the cleaning device 18 is passed through the cleaning device 18 which has been released without being transferred to the recording paper, and the toner image forming surface is further charged by the charger 10 if necessary, and the surface is exposed again by the image exposure 41. To form an electrostatic latent image related to another color, and newly develop it on the toner image previously formed by the developing device 11B. Similarly, formation of the electrostatic latent image and development by the developing device 11C To form a three-color toner image on the image forming body 1, charge the three-color toner image by the pre-transfer charger 42, and transfer the three-color toner image to the recording paper P at once by the transfer device 15. It is. The recording paper P onto which the toner image has been transferred is separated by the separator 43 into the image carrier 1.
And the toner image is fixed by a fixing device (not shown). Further, the surface of the image carrier 1 on which the toner image has been transferred is neutralized by the neutralizer 44 and cleaned by the pressed cleaning device 18 to be ready for the next image forming and fixing.

In this image forming apparatus, it is desirable to use a non-contact developing method that does not destroy the previously formed toner image. As the developing devices 11A to 11C, a developing device having a structure as shown in FIG. 2 is used while keeping the image forming body and the developer layer in non-contact. Then, charging is ON during rotation of the image carrier.
In order to prevent toner particles from entering from other developing devices, a common developing bias voltage is applied to a developing device that performs development by a bias power supply 12, while a developing device that does not perform development is: In a state where the transport of the developer is stopped in advance, the developer consuming latent image is developed to consume the developer. In this way, the driving of the developing device is turned ON-
ON-OFF of development is performed only by turning OFF.

FIG. 5 is a timing chart showing an example of the three-color image formation. In this example, in the formation of the electrostatic latent image for each color, the charging is continuously performed by the charger 10 every time, and the developing sleeves 21 of the developing devices 11A to 11C for performing the developing are applied with a DC voltage having the same polarity as the charging of the toner particles. And an AC voltage are superimposed. Also, a common AC bias voltage is applied to the developing sleeve 21 of the developing device that does not perform the development while the toner image formed by the other developing device passes. The developer layer transport rotation of the developing sleeve 21 is performed only in each image portion, as in the example of FIG.
It stops at the latent image portion for developer consumption.

In the image forming apparatus of FIG. 4, as in the case of the image forming apparatus of FIG. 1, it goes without saying that a monochromatic image or a two-color image can be recorded.

Next, the two-component developer for non-contact development suitable for use in the image forming apparatus of the present invention will be described.

First, regarding the carrier, an unstable or spherical magnetic carrier is used. In particular, the spherical shape of the magnetic carrier particles improves the agitating property of the toner and the carrier and the transportability of the developer, further improves the charge control property of the toner, and improves the toner particles and the toner particles and the carrier particles. Aggregation is less likely to occur. However, in the present invention, if the average particle size of the magnetic carrier particles is large, the state of the ears of the magnetic brush formed on the developer carrier is rough, so that the electrostatic image can be developed while applying vibration by an electric field. In addition, unevenness tends to appear in the toner image, and the toner density in the ears becomes low, so that a problem such as that high-density development is not performed may occur. To solve this problem, the average particle size of the carrier particles may be reduced, and as a result of the experiment, the effect starts to appear at an average particle size of 50 μm or less,
It has been found that when the thickness is less than μm, no substantial problem occurs. In addition, the problem described in (1) above is solved by increasing the toner concentration in the spikes by developing the magnetic carrier into fine particles.
However, if the carrier particles are too fine, they may adhere to the surface of the image bearing member together with the toner particles or may be easily scattered. These developments are also related to the strength of the magnetic field acting on the carrier particles and the resulting magnetic strength of the carrier particles.According to experiments, when the average particle size of the carrier particles becomes 15 μm or less, the tendency gradually starts to appear, It appears remarkably at 5 μm or less. The carrier particles adhering to the surface of the image forming body are usually dark and colored, and part of the carrier particles are transferred onto the recording paper together with the toner, and have a significant effect on the color image.

As described above, the average particle diameter of the magnetic carrier particles is preferably 50 μm or less, more preferably 30 μm or less, and 5 μm or less.
Above, particularly preferably 15 μm or more is an appropriate condition, and it is preferable that the particles are spherical. The average particle size is a weight average particle size, which is a weight average particle size obtained using a Coulter Counter (manufactured by Coulter) and Omnicon Alpha (manufactured by Bausch & Lomb). Such magnetic carrier particles,
As in the conventional magnetic carrier particles as a magnetic material, iron, chromium, nickel, metals such as cobalt, or compounds or alloys thereof, for example, ferric oxide, γ-ferric oxide, chromium dioxide, manganese oxide, Ferrite, manganese-ferromagnetic or paramagnetic particles such as copper-based alloy particles finer, preferably spherical, or preferably the surface of the magnetic particles styrene resin, vinyl resin, ethyl resin, Rosin modified resin, acrylic resin,
The resin is coated spherically with a resin such as polyamide resin, epoxy resin or polyester resin or a fatty acid wax such as palmitic acid or stearic acid, or more preferably a resin or fatty acid wax containing dispersed magnetic fine particles is powdered. Particles obtained by pulverizing or granulating and polymerizing, preferably, spherical particles are obtained by selecting the particle size by means of a conventionally known average particle size.

Forming the carrier particles into a spherical shape using a resin or the like as described above, in addition to the above-described effects, makes the developer layer formed on the developer carrying carrier uniform, This also has the effect that a high bias voltage can be applied to the carrier. That is, the fact that the carrier particles are made spherical by a resin or the like is based on (1)
In general, carrier particles are easily magnetized and adsorbed in the major axis direction, but their directionality is lost due to spheroidization, so that the developer layer is formed uniformly, causing local low resistance areas and uneven thickness. (2) With the increase in the resistance of the carrier particles, the edge portion as seen in the conventional carrier particles is eliminated, and the concentration of the electric field on the edge portion does not occur. As a result, a high bias is applied to the developer carrier. Even when a voltage is applied, the electrostatic latent image is not disturbed by being left on the surface of the image forming member, and the bias voltage does not break down. The fact that the high bias voltage can be applied means that in the preferred embodiment of the present invention, when the development under the oscillating electric field is performed by the application of the oscillating bias voltage, the effect described later can be sufficiently exhibited. It is possible to do.
As described above, wax is also used for the carrier particles having the above-described effects. However, from the viewpoint of the durability of the carrier, the use of the above-described resin is preferable. Is 10 ⁸ Ωcm or more, especially 1
It is preferable that insulating magnetic particles are formed so as to have a diameter of 0 ¹³ Ωcm or more. The resistivity, the electric field of 1000V / cm between the after tapping in a container having a 0.50 cm ² cross-sectional area of the particles, applying a load of 1 kg / cm ² on packed particles, the load and a bottom electrode Is a value obtained by reading the current value when a voltage is applied, and if this resistivity is low, when a bias voltage is applied to the developer carrier, charges are injected into the carrier particles and the image is Carrier particles tend to adhere to the surface of the carrier, or breakdown of the bias voltage tends to occur.

In consideration of the above, the magnetic carrier particles are spherical so that the ratio of the major axis to the minor axis is at least three times or less, have no protrusions such as needle-like parts and edge parts, and have a resistivity. Is at least 10 ⁸ Ωcm, preferably at least 10 ¹³ Ωcm. For such magnetic carrier particles, in the case of high-resistance spherical magnetic particles or resin-coated carriers, magnetic particles are selected as spherical as possible and subjected to a resin coating treatment. The carrier is manufactured by performing spheroidizing treatment after forming dispersed resin particles using magnetic fine particles as much as possible, or obtaining dispersed resin particles by a spray drying method.

Next, the toner will be described. Generally, when the average particle size of the toner particles of the two-component developer is reduced, the charge amount is qualitatively reduced in proportion to the square of the particle size, and the van der Waals force is relatively reduced. And the toner particles become difficult to separate from the carrier particles, or once the toner particles adhere to the non-image area on the surface of the image carrier, they are easily rubbed with a conventional magnetic brush. It will cause fogging without being removed. In the magnetic brush developing method, when the average particle diameter of the toner particles is 10 μm or less, such a problem becomes remarkable. The non-contact development method solves the above-mentioned problem by performing development using a developer layer, a so-called magnetic brush, under an oscillating electric field. That is, the toner particles adhering to the developer layer are easily separated from the developer layer by the vibration applied electrically, and are easily transferred to the image portion and the non-image portion on the surface of the image bearing member. Then, the toner particles having a low charge amount hardly migrate to the image portion or the non-image portion, and also do not adhere to the image carrier due to triboelectric charging because they are not rubbed with the image carrier surface, Even toner particles of about 1 μm can be used. Accordingly, a clear toner image with good reproducibility, which is obtained by faithfully developing the electrostatic latent image, can be obtained. further,
Since the oscillating electric field weakens the binding of the carrier particles associated with the toner particles, the adhesion of the carrier particles associated with the toner particles to the surface of the image carrier is also reduced. In the image part and the non-image part area,
The toner particles having a large charge amount vibrate under an oscillating electric field,
Depending on the strength of the electric field, the carrier particles also oscillate, causing the toner particles to selectively move to the image portion on the image carrier surface, so that the adhesion of the carrier particles to the image carrier surface is greatly reduced.

On the other hand, when the average particle size of the toner becomes large,
As described above, the roughness of the image becomes conspicuous.
Normally, for development with a resolution of fine lines arranged at a pitch of about 10 lines / mm, a toner having an average particle diameter of about 20 μm is not a problem in practical use. However, when a finely divided toner having an average particle diameter of 10 μm or less is used, The resolving power is remarkably improved, and a clear, high-quality image with faithful reproduction of shades and the like is provided.
For the above reasons, the average particle diameter of the toner is 20 μm or less,
Preferably, the appropriate condition is 10 μm or less. Further, since the toner particles follow the electric field, the charge amount of the toner particles becomes 1
よ り 大 き い 3 μc / g (preferably 2-100 μc / g)
g) is desirable. In particular, when the particle size is small, a high charge amount is required. The resistivity is 10 ⁸ Ωcm or more, preferably 1
0 ¹³ Ωcm or more is preferable.

Then, such a toner is obtained by the same method as the conventional toner. That is, a toner in which spherical or irregular non-magnetic or magnetic toner particles in a conventional toner are selected by an average particle size selecting means can be used. Among them, it is preferable that the toner particles are magnetic particles containing magnetic particles, and particularly the amount of the magnetic particles is 60%.
In order to obtain color clarity that does not exceed wt%, a small amount of 30 wt% or less is preferred. If the toner particles contain magnetic particles, the toner particles will be affected by the magnetic force of the magnet included in the developer carrier,
The uniformity of the magnetic brush is further improved, fogging is prevented, and toner particles are less likely to scatter. However, if the amount of the magnetic substance contained is too large, the magnetic force between the carrier particles becomes too large,
Sufficient development density cannot be obtained, and magnetic fine particles also appear on the surface of the toner particles, making it difficult to control triboelectric charging, making the toner particles easily breakable, Between them.

In summary, the toner preferred in the present invention uses the resin described above for the carrier and also fine particles of a magnetic substance, and adds a coloring component such as carbon and, if necessary, a charge controlling agent and the like. The toner particles have an average particle size of 20 μm or less, particularly preferably 10 μm or less, which can be produced by a method similar to a conventionally known method for producing toner particles.

In the image forming apparatus of the present invention, a developer in which fine and spherical carrier particles and toner particles as described above are mixed at the same ratio as in a conventional two-component developer is preferably used. In addition, if necessary, a fluidizing agent for improving the fluid sliding of the particles, a cleaning agent useful for cleaning the surface of the image carrier, and the like are mixed. As the fluidizing agent, colloidal silica, silicon varnish, metal soap or nonionic surfactant can be used. As the cleaning agent, a surfactant such as fatty acid metal salt, organic group-substituted silicon or fluorine can be used. Can be.

Next, the present invention will be described with reference to more specific examples.

Example 1 (i) Preliminary Experiment In the developing device shown in FIG.
The magnetic body 22 has magnetic poles N and S of 800 gauss alternately arranged on the circumference, the gap between the layer thickness regulating blade 24 and the developing sleeve 21 is 0.3 mm, and a two-component developer is used. The magnetic pole positions of the layer thickness regulating blade 24 and the magnet body 22 were defined, and after the developing sleeve 21 was rotated, it was stopped. Thus, a developer layer was formed on the developing sleeve 21.

The developer layer thickness does not change depending on the position on the magnet body facing the layer thickness regulating blade, and the relationship between the two is that the thickness of the developer on the developing sleeve that has passed through the layer thickness regulating blade is determined on the magnetic pole. The measurement was as shown in FIG. FIG.
7, A is the height of the ear on the magnetic pole N (or S) in the developing section as shown in FIG. 7, and B is the central ear between the magnetic poles N and S in the developing section as shown in FIG. The height of each is shown.

The developer layer is extremely thin in the state (B) of FIG. 6 and has a sufficient thickness for development in the state (A) of FIG. Further, when a layer thickness regulating blade made of a magnetic material is used, the developer layer can be formed thinner than in FIGS. 6 and 7 described above. In particular, in FIG. 6, the development is performed without the magnetic pole corresponding to the development area during non-development. By laying down the ears of the developer, the height of the ears of the developer during non-development can be further reduced.

From the above results, if the magnetic poles in the developing area are stopped as shown in FIG. 6 while the driving of the developing device is stopped, the developing is smoothly performed during the developing, and the developing as described above is performed during the non-developing. It can be understood that mixing of the agent and fogging are prevented, which is extremely advantageous.

A drum-shaped image carrier having a selenium photoreceptor layer was used, rotated at a peripheral speed of 120 mm / sec, charged to 1000 V, exposed, and exposed to a light having a width of 10 mm in parallel with the rotation axis.
A solid latent image of cm (a latent image for developer consumption) was formed.

Next, the above latent image was formed by using a two-component developer obtained by mixing ferrite particles with a resin having an average particle diameter of 30 μm as a carrier and a toner having an average particle diameter of 10 μm at a weight ratio of 4: 1. Developed. The toner charge amount is -15μc / g
It is. As development bias, frequency 2.0kHz, amplitude 2.0k
A V AC component and a +100 V DC component were applied. The gap between the image bearing member 1 and the sleeve 21 in the developing area E is 1.0 mm, and the thickness of the developer layer is 0.8 mm.

When the change in the amount of adhered toner depending on the position in the rotation direction of the image carrier 1 was examined, the result shown in FIG. 9 was obtained. In the figure, A shows the case where the magnetic pole faces the development area E (the state of FIG. 7), and B shows the case where the center between the magnetic poles faces the development area E (the state of FIG. 6). I have. From the figure,
The toner adheres to the image carrier within a range of a width of 2 to 3 cm. Therefore, in a rotation of 2 to 3 cm on the image carrier, the developer is substantially deposited on the sleeve 21 in the developing zone E. You can see that it is gone. FIG. 7 shows the development of the latent image for developer consumption.
When the latent image for developer consumption passes through the development area E, the state shown in FIG.

(Ii) Embodiment A three-color image is recorded by the recording apparatus of FIG. 1 equipped with a developing device for rotating both the magnet and the developing sleeve as shown in FIG. 2 in accordance with the timing chart shown in FIG. went.

The image carrier 1 has a selenium photosensitive layer as a photoconductive layer.
The surface is charged to 600 V by 10 and the image exposure of each color is incident to form an electrostatic latent image with a background potential of 50 V, and black on the back of the white platen near the rear end of the original Patches are provided, and a 10 cm wide electrostatic latent image for developer consumption is formed by light exposure of the white and black patches on the back of the document table. FIG. 10 is a perspective view schematically showing a state in which an image portion latent image 31 and a developer consumption latent image 32 are formed on the image carrier 1.

In each of the developing devices 11A to 11C, the gap between the developing area E of the developing sleeve 21 and the image carrier 1 is set to 1.0 mm, and the average particle diameter of a magnetic material dispersed in a resin is set as a developer. 30μm, magnetization 50emu / g, resistivity 10 ¹⁴ Ωcm or more spherical carrier particles, thermoplastic resin 90wt%, pigment 10wt%, a small amount of charge control agent was added and kneaded and pulverized. The average particle size was 10μm.
And the toner particles were mixed at a weight ratio of 4: 1. As the pigment of the toner particles, yellow, magenta, and cyan pigments are used by the developing devices 11A to 11C. Each of the toner particles is charged in the developer pool 23 to an average charge of both −20 μc / g. Each developing device 11A
-11C, the frequency 1.
An AC component of 5 kHz and an amplitude of 1.5 kV and a DC component of +100 V were applied to form a developer layer having a thickness of about 0.6 mm on the developing sleeve 21. Therefore, development is performed by a non-contact development method in which the developer layer does not rub the surface of the image carrier 1.
For this reason, the layer thickness regulating blade 24 made of a magnetic material is installed at a position where the layer thickness of the developer layer is regulated to 0.6 mm. Immediately after the development of the image portion latent image is completed, as shown in FIG. 6, the sleeve 21 is stopped and the magnetic pole of the magnet body 22 (N or S may be used).
Is made to face the layer thickness regulating blade 24, and the magnet body 22 is stopped. In this state, the central portion between the magnetic poles is located in the development area E.
Therefore, it is effective that the thickness regulating blade 24 is made of an iron-based alloy such as steel or other magnetic material. In the above control of the magnet body 22, the magnet body 22 attracts the layer thickness regulating blade 24 by magnetic force, and naturally stops at the opposing position. Alternatively, in addition to the electric control, a simple mechanism such as a cam or a clutch can be used. When the development is performed only by rotating the developing sleeve 21 with the magnet body 22 fixed, the magnetic pole is opposed to the development area at the time of development (the state shown in FIG. 7), and during the non-development, particularly the passage of the latent image for developer consumption. Later, the magnetic pole may not be opposed to the development area (the state of FIG. 6).

In this state, the developer consuming electrostatic latent image is developed, and the developing ability can be eliminated. The developer on the developing sleeve 21 of the developing device that does not perform the development was substantially free of toner. At the time of developing the latent image for developer consumption, the developing sleeve 21 is provided with -50 for actively consuming toner.
A DC voltage of 0 V is changed and applied together with an AC voltage as a developing bias. In both rotations of the developing sleeve 21 and the magnet body 22, the developer is conveyed when the image portion electrostatic latent image reaches the developing device, and stopped before the development of the developer consuming latent image passes. So that At the timing when the toner image formed by the upstream developing device 11A passes through the downstream developing devices 11B and 11C, a DC voltage of -50 V is applied to the developing sleeve 21 of the downstream developing devices 11B and 11C that do not perform development. Is applied as a mixing prevention bias. In addition to the DC bias, the developing sleeve 21 may be grounded, and may be a bias having the same polarity or a different polarity as the developer. Further, the developing sleeve 21 may be in a floating state.

FIG. 11 shows a state immediately after the development of the image portion and the developer-consumption latent image. The consumed toner T32 adheres to the image carrier 1 following the image toner T31, and the toner is conveyed to the development area E of the sleeve 21. No toner is newly attached to the opposing portion, and even if the next image portion latent image 31 indicated by the imaginary line comes to the development area E, the toner does not adhere to it.

FIG. 12 is an enlarged cross-sectional view schematically showing the adhesion state of the three color toners adhered to the developer consumption latent image by the apparatus of FIG. 4, and the consumed toner T32 composed of these toners TY, YM, YC. Is removed from the image carrier 1 by the cleaning device 18 shown in FIG. 1 at the end of one cycle of image formation.

Although a large number of recording papers were obtained under the above conditions, the recorded three-color image was a clear color image without color mixture, which did not change from the beginning to the end.

Embodiment 2 The magnet body 22 in Embodiment 1 was kept stationary during both development and non-development, and during non-development, the developer layer thickness in the development area E was reduced as shown in FIG. At the time of development of the image portion and the latent image for developer consumption, as shown in FIG. 7, the magnetic poles were opposed to each other so that the thickness of the developer layer was sufficient for development. The developing sleeve 21 rotates only when passing through the image area. Others are the same as in the first embodiment.

The three-color image obtained as described above was of high quality as in the first embodiment.

Example 3 A developing device as shown in FIG.
The image forming apparatus shown in FIG. 4 records three color images in accordance with the timing chart shown in FIG. Image carrier 1 has a diameter of 120 mm
During the formation of an electrostatic latent image by the scorotron charger 10 while rotating at a peripheral speed of 120 mm / sec,
It is always charged to about 600 V, and a 0 V dot-constituting image portion and an electrostatic latent image for developer consumption are formed on the charged surface by the image exposure 41. The gap between the image carrier 1 and the developing sleeves 21 of the developing devices 11A to 11C is set to 1.0 mm.
The same developer as in Example 1 is used as the 1C developer except that the charge control agent of the toner particles is different and the toner particles are charged to 20 μc / g. The layer thickness regulating blade 24 is set so that a developer layer having a layer thickness of 0.7 mm is formed on the developing sleeve 21. Each of the developing devices 11A to 11C superimposes an AC partial pressure having a frequency of 2 kHz and an amplitude of 1.2 kV and a DC voltage of 500 V on the developing sleeve 21 and applies a developing bias thereto. On the other hand, the same bias is applied during non-development. Developing sleeve
The developer layer transport rotation 21 is performed only in the image area, and the developer layer is not transported during the development and non-development of the developer consumption latent image.

As shown in FIG.
The central portion between the magnetic poles N and S is located at the developing area E and is stationary.

Although a large number of recording papers were obtained under the above conditions, the recorded three-color image was a clear color image without color mixture, which did not change from the beginning to the end.

The stop of the transport of the developer may be performed before the latent image for consuming the developer reaches the developing area, or while the latent image for consuming the developer passes through the developing area. Further, the developer consuming latent image may be provided earlier than the image portion latent image. That is, under a state in which the developing bias is applied (the developer carrying carrier is stopped), the developer consuming latent image is sent to the developing area before the image section latent image, and The developer used for the development and on the stopped developer carrier can be consumed. Further, a developer consumption latent image before and after the image portion latent image may be provided. Further, the present invention is not limited to the method of removing the toner to the photoconductor side as in the above-described embodiment, and other removal methods may be employed.

The present invention can be similarly applied to non-contact development using a one-component developer. In the two-component developer, only the toner is consumed, whereas in the one-component developer, since only the toner is used, most of the developer on the developer transport carrier in the developing area is consumed.

[0069]

As described above, in the multicolor image forming apparatus according to the present invention, the image carrier and the band are uniformly formed on the image carrier.
Charging means for charging, a latent image forming means for forming a latent image on the image carrier, and a non-contact opposition of the image carrier and the developer layer on the developer carrying carrier in a developing area to apply toner under a bias voltage. in to fly and a developing device for performing reversal development, strips
After superposing a plurality of toner images having different colors on electrostatic and latent image formation repeated reversal development the image bearing member, in the multi-color image forming apparatus for transferring a transfer material, before and after the image portion latent <br Forming a latent image for developer consumption, when the latent image for developer consumption passes through the development area, stopping the transport of the developer on the developer transport carrier, and transferring the developer to the developer transport carrier; A bias voltage having the same polarity as that of the toner that causes the toner to fly to the developer consumption latent image is applied, and when an image portion latent image of another color passes through the development area, the developer on the developer transport carrier Since the conveyance is stopped and a bias voltage having the same polarity as that of the toner is applied to the developer conveyance carrier, the following specific effects can be obtained.

In a developing device which is not used for development, since the amount of the developer at a predetermined position is reduced while the transport of the developer is stopped, at least a position close to the image carrier on the developer transporting carrier (accordingly, In a desired required portion), the amount of the developer is surely reduced, and the burden on the means for reducing the developer is greatly reduced. Therefore, while the development is stopped, undesired movement of the developer such as transfer of the developer from the developing device to the image carrier or transfer of the developer from the image carrier to the developing device is sufficiently and easily prevented. Is done.

Therefore, even if continuous recording is performed many times, a clear, high-quality recorded image without color turbidity can be obtained. Such an effect is particularly great in forming a multicolor image. Moreover,
The structure of the device is not complicated and large.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a multicolor image forming apparatus of the present invention that forms a multicolor image by transferring a toner image one color at a time onto recording paper.

FIG. 2 is a sectional view of a main part of the developing device.

FIG. 3 is a timing chart of image formation in the multicolor image forming apparatus of FIG.

FIG. 4 is a schematic configuration diagram of a multicolor image forming apparatus that sequentially forms a multicolor image on an image carrier as development.

FIG. 5 is a timing chart of image formation in the multicolor image forming apparatus of FIG. 4;

FIG. 6 is a partial cross-sectional view of the developing device when development is stopped.

FIG. 7 is a partial cross-sectional view of the developing device when development is stopped.

FIG. 8 is a graph showing a relationship between a position of a magnet body with respect to a layer thickness regulating blade made of a magnetic material in a preliminary experiment and a developer layer thickness in a development area of a formed developer layer.

FIG. 9 is a graph showing a relationship between magnetism of a magnet body and a developer layer thickness in a development region in a preliminary experiment.

FIG. 10 is a perspective view of an image carrier showing a positional relationship between a developer consumption latent image and an image portion latent image.

FIG. 11 is a partial cross-sectional view of the developing device immediately after a developer consuming latent image has been developed.

FIG. 12 is an enlarged cross-sectional view of the attached toner, schematically illustrating a state in which the developer consumption latent image has been developed.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Image carrier 9 Color separation means 10 Charger 11A, 11B, 11C Developing device 12 Bias power supply 18 Cleaning device 21 Developing sleeve (developer carrier) 22 Magnet 23 Developer reservoir 24 Layer thickness regulating blade 31 Image latent image 32 Latent image for developer consumption E Development area P Transfer material (recording paper) TY Yellow toner TM Magenta toner TC Cyan toner T31 Image toner T3a Consumed toner

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location G03G 15/08 507 G03G 15/08 507H 15/09 15/09 Z

Claims (1)

(57) [Claims] An image bearing member and an image bearing member are charged uniformly.
A charging unit, a latent image forming unit for forming a latent image on the image carrier, and a non-contact facing of the image carrier and the developer layer on the developer carrier in the developing area to fly toner under a bias voltage A multicolor image to be transferred to a transfer material after a plurality of toner images having different colors are superimposed on the image carrier by repeating charging, latent image formation, and reversal development. In the forming apparatus, a developer consumption latent image is formed before and after the image portion latent image, and when the developer consumption latent image passes through the development area, the transport of the developer on the developer transport carrier is stopped. A bias voltage having the same polarity as that of the toner for causing the toner to fly on the developer consumption latent image is applied to the developer transporting carrier, and when the image portion latent image of another color passes through the development area, the developing is performed. Stop the transport of the developer on the developer carrier A multicolor image forming apparatus, wherein a bias voltage having the same polarity as that of the toner is applied to the developer carrier.