JPS61176958A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent occurrence of positional deviation in recorded images so as to make efficient image formation, by starting the contact and contact release of a cleaning member with and from an image forming body at the timing other than the image writing at least. CONSTITUTION:At the 1st turn the surface of an image forming body 1 is charged with electricity by means of a charger 2 and an electrostatic image obtained by image exposure 4 is subjected to the 1st development in the developing device containing the toner of the color corresponding to the image exposure 4 out of developing devices 5-8. Such a process is repeated and, before the leading edge of the toner remaining on the image forming body 1 reaches a cleaning blade 14a after the 4th latent image is formed, a cleaning device 14 is actuated and the blade 14a and fur brush 14b are contacted with the image forming body 1. At the moment when the tailing end of the remaining toner passes through the brush 14b, the cleaning device 14 is released and the blade 14a and brush 14b are separated from the image forming body 1.

Description

[Detailed description of the invention] B. Industrial application field The present invention relates to an image forming apparatus.

Conventionally, for example, in order to form a multicolor image by electrophotography,
The copying steps of charging, exposing, developing, and transferring are repeated for each component color, so that toner images of each color are superimposed and transferred onto the copy paper. For example, an electrostatic latent image is formed in each step using separated light of blue, green, red, etc. obtained through a color separation filter, and developed with yellow, magenta, cyan, and if necessary black toner to form a toner image. The toner image is layered on recording paper and transferred to form a multicolor image. However, in such a multicolor image forming method, it is necessary to transfer the image to a transfer body each time the development of each color is completed, which increases the size of the machine, takes a long time to form the image, and There are some drawbacks, such as the need to guarantee positional deviation accuracy.

Therefore, there is a multicolor image forming method that solves the above drawback by superimposing and developing multiple toner images on the same photoreceptor so that the transfer process only needs to be done once. This causes problems such as the color balance of development being disturbed.

In order to avoid such inconvenience, a method is adopted in which a bias with an alternating current component superimposed is applied to the developing device during the second and subsequent development to cause the toner to fly onto the electrostatic latent image formed on the photoreceptor. , a method of forming a multicolor image has been proposed. In this method, the developer layer does not rub the toner image formed up to the previous stage, so that image disturbance does not occur.

The principle of this image forming method will be explained below with reference to the flowchart shown in FIG. FIG. 4 shows changes in the surface potential of the photoreceptor, taking as an example the case where the charging polarity is positive. PH is the exposed area of the photoconductor, DA is the exposed area of the photoconductor, and DUP is the exposure The photoconductor, which rotates at a constant speed, is uniformly charged by a scorotron charger, and is kept constant as shown in (a). becomes a positive surface potential E. Next, the laser
A first image exposure using a cathode ray tube, LED, etc. as an exposure source is applied, and the potential of the exposed portion PH decreases in accordance with the amount of light, as shown in (b). The electrostatic latent image thus formed is attached to the surface potential E toner T in the unexposed area to the exposed area PH having a relatively low potential, and a first toner image T is formed. The potential of the region where the toner image T is formed increases by DUP due to the adhesion of the positively charged toner T, but the potential does not become the same as that of the unexposed area DA. Next, the surface of the photoreceptor on which the first toner image has been formed is charged a second time by a charger, and as a result, the surface potential E becomes uniform regardless of the presence or absence of toner T.

The dirt is shown in (d). A second imagewise exposure is performed on the surface of this photoreceptor to form an electrostatic latent image ((e)), and similarly to (c), a positively charged toner image T' of a color different from that of the toner T is developed. A second toner image is obtained. This is shown in (f). By repeating the above process, a multicolor toner image is obtained on the photoreceptor. A multicolor recorded image can be obtained by transferring this onto recording paper and further fixing it by heating or applying pressure. In this case, the photoreceptor is cleaned of toner and charges remaining on the surface and used for the next multicolor image formation. On the other hand, apart from this, there is also a method of fixing a toner image on a photoreceptor.

In the method illustrated in FIG. 4, it is desirable that at least the developing step (f) be performed without the developer layer coming into contact with the surface of the photoreceptor.

In addition, in the multicolor image forming method, such charging is performed every time g7f! When repeating Lq, a static elimination process by light exposure or corona discharge may be performed before charging. Also,
The exposure sources used for each image exposure may be the same or different.

In the multicolor image forming method, toners of four colors, for example, yellow, magenta, cyan, and black, are often superimposed on a photoreceptor for the following reasons. According to the principle of the subtractive color method, a black image should be obtained by overlapping the three primary colors of yellow, magenta, and cyan, but the toners for the three primary colors that are put into practical use have ideal absorption wavelength ranges. In addition, due to misalignment of the toner images of the three primary colors, it is not only difficult to reproduce the clear black required for characters and lines with only these three primary color toners, but also the density of color images is They tend to run out. Therefore, as described above, a multicolor image is formed using four colors, which are the three primary colors plus black.

In addition to the above-mentioned electrophotographic method, methods for forming latent images for multicolor image formation include a method in which an electrostatic latent image is formed by injecting charges directly onto the image forming body using a multi-needle electrode, and a magnetic method. A method of forming a magnetic latent image using a head can be used.

There are two ways to express various colors using the method described above.

01 A method that does not directly overlap toners of different colors.

■ Method of overlapping toners of different colors.

In (2), colors are reproduced in a pseudo manner on recording paper by distributing toner T IT on one image forming body without overlapping as shown in FIG. 14(A). (3) reproduces colors by superimposing toner of a different color on a toner image of a certain color and developing it.

However, in the case of electrophotography, for example, in case (2), the toner T that has been developed earlier is absorbed and does not reach the photosensitive layer of the image forming member, and a latent image is not completely formed. As shown in the figure, the amount of toner 'F2 developed later tends to decrease. In addition, in (2), it is necessary to precisely align the image exposure so that the toner images of each color do not overlap at the same position, and if the image exposure position is inaccurate as shown in Figure 14 (B), There is a tendency that the toner image T1 partially blocks the image exposure, and the adhesion amount of the toner image T2 developed in the subsequent stage becomes small as shown in FIG. 14(C). This shows that the recording characteristics differ depending on the spectral sensitivity of the image, the spectral characteristics of the light source for image exposure, the spectral transmittance characteristics of the toner, and the order of developing colors.

By the way, when an image is formed on the recording paper as described above, the toner that remains without being transferred to the recording paper adheres to the image forming member (photoreceptor), and this remaining toner is used next time. It is necessary to clean the photoreceptor as this may interfere with image formation. As will be described later, this cleaning method involves bringing a plate and/or a fur brush into contact with the photoreceptor to scrape off residual toner on the photoreceptor.

This cleaning seriously affects the rotational speed of the photoreceptor. That is, when a blade or a fur brush is brought into contact with the photoreceptor, they act like a brake, and the rotational speed of the photoreceptor changes even slightly. Especially, if the rotational speed of the photoreceptor changes even slightly when forming a latent image, The resulting image will have a positional shift for each color.

C. Purpose of the Invention The present invention has been made in view of the above circumstances, and there is no risk of the above-mentioned positional deviation occurring in the recorded image obtained, and efficient image formation can be expected. The purpose is to provide an image forming apparatus.

2. Structure of the Invention In other words, the present invention provides a cleaning member in an image forming apparatus that repeatedly performs a process including writing an image on an image forming body and forming a toner image following the writing of the image to superimpose the toner images. According to an image forming apparatus, the start of contact and the start of release of contact with the image forming body are performed at least at a time other than the time of writing the image.

The order in which the rotational speed of the image forming member (photoreceptor) is affected in each process of recording image formation is latent image formation (particularly image writing), development (toner image formation), and charging. is unaffected or only very slightly affected, and retention is not affected at all.

The formation of a latent image will be described as follows. The human eye is sensitive to relative position accuracy, especially first-order differential and second-order differential accuracy. Even in laser printers, it is necessary to suppress the positional accuracy to a fraction of that, preferably to one-tenth or less. According to experiments, it is within ±6 μm at a pitch of 8 dots/nn, and ±8 μm at a pitch of 12 dots/fin.
It is necessary to maintain positional accuracy within ±6 μm at 16 donoto/dragon. When the rotational speed of the photoreceptor changes during latent image formation, a positional shift occurs for each color of the overlapping toner images, and even if this positional shift is slight, it can be recognized with the naked eye. Therefore, the rotational speed of the photoreceptor during latent image formation must be kept constant with high precision.

The development will be described as follows. Since the process of forming a toner image on a latent image is not in an equilibrium state, the density of the toner image is inversely proportional to the peripheral speed of the photoreceptor. Therefore, when the rotational speed of the photoreceptor changes, the density of the recorded image that is obtained changes.

The charging will be described as follows. Charging is not carried out in an equilibrium state, as in the development described above, but depending on the structure of the charger, for example, a corona discharger having an AC component or a scorotron charger, the charging time of the charging potential can be changed. In addition, when development is performed by reversal development, the difference between the potential of the exposed area and the development bias potential becomes the latent image contrast. It is unlikely to affect the image.

Regarding transfer, corona transfer has little speed dependence;
Furthermore, since the recording paper adheres to the photoreceptor and moves due to corona discharge, it follows changes in the rotational speed of the photoreceptor. The transfer roller and adhesive roller may be made to follow the photoreceptor.

Fusing is independent of toner image formation.

For the above reasons, in order to maintain the positional accuracy of the latent image, it is necessary to
In both cases, during latent image formation (particularly image writing), the cleaning member, which changes the rotational speed of the photoreceptor, is prevented from coming into contact with the photoreceptor and from releasing this contact. That is, the cleaning member comes into contact with the photoreceptor at the time when the latent image formation is completed (the time when the rear end of the latent image is located at the latent image forming portion).

In particular, when the latent image forming means and the cleaning member are arranged such that the cleaning section is provided slightly in front of where the leading edge of the latent image is located at the end of latent image formation (where the leading edge of the toner remaining on the photoreceptor after transfer is located). After the final latent image is formed and before the remaining toner reaches the cleaning section, the cleaning member can be brought into contact with the photoreceptor to effectively clean it. After the cleaning is completed, the contact of the cleaning member is released, and formation of a latent image in the next image forming process is then started.

Furthermore, in order to prevent density unevenness in the toner image, it is desirable to bring the cleaning member into contact with the photoreceptor after the final development is completed. Furthermore, in order to prevent unevenness in the charging potential, it is more desirable to complete the release of the cleaning member from contact with the photoreceptor in the previous image forming process before starting charging. In these cases, it is better if the installation position of the cleaning section is determined according to the above-mentioned concept.

E, Example Hereinafter, the present invention will be explained in detail with reference to illustrated examples.

FIG. 2 is a schematic diagram of the configuration of a laser beam scanner for image exposure, FIG. 3 is a partial cross-sectional view of an example of a developing device, and FIG. 2 is a charger that uniformly charges the surface of the image forming body 1; 4 is image exposure for each color of a color image; 5 to 8 are yellow, magenta, Developing units 9 and 10 each use toners of different colors such as cyan and black as developers, and a color image formed by superimposing a plurality of color toner images on the image forming member 1 is transferred to the recording medium. P
11 is a transfer device; 12 is a pre-transfer charger and a pre-transfer exposure lamp provided as necessary to facilitate transfer to
1 is a fixing device for fixing the toner image transferred to the recording medium P; 13 is a static eliminator consisting of one or a combination of a static eliminating lamp and a corona discharger; and 14 is a static eliminator for transferring the color image of the image forming body 1. A cleaning device that includes a cleaning blade 14a and a fur brush 14b that come into contact with the subsequent surface to remove residual toner on the surface and are separated from the surface of the image forming body 1 by the time the first developing surface is reached. It is a device.

The cleaning device 14 is installed so that when the rear end of the latent image is located at the image exposure 4, it is located 10 cm ahead of the leading edge position of the latent image.

Here, the charger 2 is particularly suitable for charging the surface of the image forming body 1 which has already been charged, and for providing stable charging with less influence from the previous charging. The image exposure 4 may be the same as the slit exposure in a normal monochrome electrophotographic copying machine, which is filtered for each color using a filter, but in order to record a clear color image, A laser beam scanner as shown is preferred.

The laser beam scanner shown in FIG. 2 uses an acousto-optic modulator 22 to perform 0N10FF on a laser beam emitted from a laser 21 such as a HeNe laser, and deflects it using a mirror scanner 23 consisting of an octahedral rotating polygonal mirror.
Image exposure 4 is formed by scanning the surface of the image forming body 1 at a constant speed through the -θ lens 24. Note that 25 and 26 are mirrors, and 27 is a lens for enlarging the diameter of the beam incident on the imaging [-θ lens 24] in order to reduce the diameter of the beam on the image forming body 1. If a laser beam scanner like the one shown in FIG. 2 is used to form the image exposure 4, it is possible to easily form electrostatic images of different colors in a shifted manner, as will be described later, and therefore a clear color image can be recorded. be able to. However, the image exposure 4 is not limited to the above-described slit exposure or dot exposure using a laser beam, but may be obtained using, for example, an LED, CRT, liquid crystal, or optical fiber transmission body. In a recording apparatus in which the image forming body can take a flat state such as a belt shape, the image exposure can also be flash exposure.

Furthermore, the developing devices 5 to 8 preferably have a structure as shown in FIG. 3.

In FIG. 3, 31 is a developing sleeve made of a non-magnetic material such as aluminum or stainless steel, 32 is a magnet body provided inside the developing sleeve 31 and has a plurality of magnetic poles in the circumferential direction, and 33 is a developing sleeve. A layer thickness regulating blade 34 regulates the thickness of the developer layer formed on the sleeve 31, a scraper blade 34 removes the developed developer layer from the developing sleeve 31, and 35 removes the developer in the developer reservoir 36. 37 is a toner hopper; 38 is a toner replenishment roller that has a recess on its surface into which the toner enters and replenishes toner from the toner hopper 37 to the developer reservoir 36; 3;
Reference numeral 9 applies a bias voltage including an oscillating voltage component to the developing sleeve 31 via the protective resistor 40 to form an electric field for controlling the movement of toner between the developing sleeve 31 and the image forming body 1. Although the figure shows that the developing sleeve 31 and the magnet body 32 rotate in the directions of the arrows, it does not matter whether the developing sleeve 31 is fixed or the magnet body 32 is fixed. Alternatively, the developing sleeve 31 and the magnet body 32 may rotate in the same direction. When the magnet body 32 is fixed, the magnetization is usually strengthened to make the magnetic flux density of the magnetic pole facing the image forming body 1 larger than the magnetic flux density of other magnetic poles.
Two magnetic poles of the same polarity or different polarities are placed close to each other.

In such a developing device, the magnetic pole of the magnet body 32 is usually 500 to 500.
It is magnetized to a magnetic flux density of 1500 Gauss, and the developer in the developer reservoir 36 is attracted to the surface of the developing sleeve 31 by the magnetic force, and the attracted developer is transferred to the layer thickness regulating blade 3.
3 to form a developer layer, and the developer layer moves in the same direction or in the opposite direction (same direction in the figure) as the direction of the rotation arrow of the image forming body 1, and the surface of the developing sleeve 31 is develops the electrostatic image on the image forming body 1 in a developing area facing the surface of the image forming body 1, and the remaining portion is developed by the scraper blade 34.
This allows the surface of the developing sleeve 31 to be removed and returned to the developer reservoir 36. The development is repeated at least for the second and subsequent development to superimpose the color toner images, so that the toner attached to the image forming body 1 in the previous development will not be displaced in the subsequent development. It is preferable to use non-contact jumping development conditions. FIG. 3 shows a state in which development is performed under non-contact jumping development conditions.

Furthermore, the developing units 5 to 8 use non-magnetic toner, which does not require the inclusion of a black or brown magnetic substance in the toner and can provide a toner with a clear color, and can easily control the charging of the toner. It is preferable to use a so-called two-component developer mixed with a magnetic carrier. In particular, when magnetic carriers are used in resins such as styrene resins, vinyl resins, ethyl resins, rosin-modified resins, acrylic resins, polyamide resins, epoxy resins, and boriethral resins, triiron tetroxide, 7-ferric oxide, and Products containing dispersed particles of ferromagnetic or paramagnetic materials such as chromium, manganese oxide, ferrite, and manganese-copper alloys, or materials whose surfaces are coated with the above-mentioned resins. This particle C, which is an insulating carrier with a resistivity of 10" Ωcm or more, preferably 10 Ωcm or more, is injected and the carrier particles tend to adhere to one surface of the image forming body. A problem arises in that not enough is applied.

In particular, when the carrier starts to adhere to the image forming body 1,
Does not adversely affect the tone of color images.

In addition, the resistivity is determined by placing the particles in a container with a cross-sectional area of 0.50 CI and then packing the particles, then on the packed particles],
This value is obtained by reading the current value when applying a load of kg/cat and applying a voltage that generates an electric field of 1000 V/cm between the electrode that also serves as the load and the bottom electrode.

Furthermore, if the average particle size of the carrier is less than 5 μm, the magnetization will be too weak, and if it exceeds 50 μm, the image will not be improved, breakdown or discharge will easily occur, and high voltage will not be able to be applied. Diameter of 5 μm or more 50
It is preferable that it is less than μm.

The toner preferably has an average particle size of 1 to 20 μm, which is made by adding various pigments and, if necessary, a charge control agent to a resin.
The average charge amount is 3 to 300 uc/g, especially 10 to 300 uc/g.
100 μc/g is preferred.

When the average particle size of the toner is less than 1 μm, it becomes difficult to separate from the carrier, and when it exceeds 20 μm, the resolution of the image decreases. If necessary, a fluidizing agent such as hydrophobic silica may be appropriately added as an additive.

When a developer made of a mixture of an insulating carrier and toner as described above is used, the bias voltage applied to the developing sleeve 31 shown in FIG.
Moreover, setting to prevent fogging can be easily performed without the risk of leakage. In order to more effectively control the development movement of the toner by applying such a bias voltage, the structure of the container and developer used for the magnetic carrier may be adjusted to the extent that the color clarity of the toner is not affected. However, the present invention is not limited to this.
Developing devices and developers as described in Japanese Patent Nos. 8656-18659, 56-144452, and 58-116553-116554 may also be used. However, Japanese Patent Application No. 58-57446 and No. 5 filed earlier by the applicant
8-96900 to 96903, 5El-97973
It is preferable to use non-contact jumping development conditions using a two-component developer as described in No. 1 and each specification.

The present invention can be implemented in image formation as shown in FIG. 4 by using the above-described Ip device. In addition, the fourth
The figure shows the stage up to the stage where the development shown in FIG. 2 has been carried out.

In FIG. 4, as mentioned above, the exposed area PH becomes an electrostatic image,
This shows an embodiment of the present invention in which an electrostatic image is formed by an electrostatic image forming method in which an unexposed area DA becomes a background area, and development is performed using toner charged to the same polarity as the background area. According to the recording device shown in FIG.
The surface of the image forming body 1 in the initial state, which has been neutralized by the cleaning device 14 and has a potential of 0, is uniformly charged for the first time by the charger 2 in the first rotation, and the charging A first image exposure is performed on the surface by color-specific image exposure 4 so that the potential of the electrostatic image area becomes approximately 0, and thereby the IM
The electrostatic image thus obtained is first developed by one of the developing devices 5 to 8 that uses a developer of a color toner corresponding to image exposure 4, and the electrostatic image that has risen due to adhesion of toner T is Since the potential is still lower than the background potential, a second charge is uniformly applied again by the charger 2 in the second rotation, and the charger 13 (
Charging may be performed after the surface potential of the image forming body 1 is set to O by uniformly removing the charge using a charge removal lamp (only a charge removal lamp may be used). ), a second image is formed on the charged surface in which the potential of the electrostatic quadrant 1 becomes approximately 0 due to image exposure 4 of a color different from the previous one.
Rotational exposure is carried out, and the obtained electrostatic layer is developed a second time with toner T' using another developer C using a developer of a corresponding color toner, and then a third time is developed in the same manner. The fourth electrostatic image formation and development are repeated until the fourth development is performed and a color image in which color toner images are superimposed is passed through the pre-transfer charger 9. and a pre-transfer exposure lamp 10, and then a transfer device 11 transfers the color image to a recording medium P that is sent in synchronization with the rotation of the image forming body 1, and the transferred color image is transferred to a recording medium P by a fixing device 12. The surface of the image forming body 10, which has been fixed on the recording body P and has transferred the color image, is neutralized by the static eliminator 13 and returned to the initial state by being cleaned by the cleaning device 14, thereby completing one color image recording.
Figure 3 is an embodiment of the invention where a cycle is completed.

In this cleaning, after the completion of the fourth latent image formation, the leading edge of the toner remaining on the image forming body 1 is removed by the cleaning blade 1.
4a, the cleaning device 14 is activated (the cleaning blade 14a and the fur brush 14b come into contact with the image forming body 1), and the cleaning device 14 is released when the rear end of the residual toner passes the fur brush 14b. The cleaning device 14 is controlled to move the cleaning blade +43 and the fur brush 14b away from the image forming body 1. Also, the first image in the next image process
The laser beam scanner shown in FIG. 2 is controlled so that the latent image formation starts immediately after the cleaning device 14 is released.

Charging for each electrostatic image formation is performed by the charger 2, and the image exposure is also performed using, for example, the same slit equipped with filter switching means. Since this is done by the same exposure device made by the 8-light device or the laser beam scanner shown in Figure 2, there is no need for a separate image exposure device for each electrostatic image formation, making the recording device compact and inexpensive. This allows for easy synchronization control of electrostatic image formation each time. Note that the charge removal by the charge remover 13 between the previous development and the next charge can be omitted.

In order to avoid color mixing, it is preferable to set the DC bias during development to a higher value in later stages, or to reduce the amplitude of the AC component.

Correspondingly, the charging potential may also be set higher in sequence.

Details of the image forming conditions in this example are as follows.

The image forming body 1 had a CdS photoreceptor surface layer, and its peripheral speed was 180+n/sec. The surface of this image forming body 1 was charged to -500V using a charger using a scorotron corona discharger.1. The charged surface was exposed to laser light corresponding to the blue component of the image.

As a result, the image forming body 1 has an electrostatic image potential of −5 at the exposed portion PH.
A background portion was formed in which the potential of the non-exposed portion was 1500 cm with respect to 0V. This electrostatic image is transferred to a developing device 5 as shown in FIG.
The image was developed for the first time.

The developing device 5 contains 50wt% of magnetophyte dispersed in the resin, which has an average particle size of 20μm and a magnetization of 30emμ/g.
, a carrier having a resistivity of IOΩcm or more, a styrene-acrylic resin, 10 parts by weight of a benzine derivative as a yellow pigment, and other charge control agents, and an average particle size of 10 μm.
A developer consisting of negatively charged non-magnetic toner was used under conditions such that the ratio of toner to carrier was 25-t%.

Further, the outer diameter of the developing sleeve 31 is 30 mm, its rotation speed is 1100 rpm, and the magnetic flux density of the N and S magnetic poles of the magnet body 32 is 1.
000 Gauss, rotation speed is lo00 rpm, developer layer thickness Q in the developing area, 7u+, developing sleeve 31 and image forming body 1
Gap between 0.81111. 140 for the developing sleeve 31
A non-contact jumping development condition was used in which a superimposed voltage of 0V DC voltage and 3V, 100OV AC voltage was applied.

While the electrostatic image is being developed in the developing unit 5, the other
Developing units 6 to 8 as shown in the figure were kept in a non-developing state. This is achieved by disconnecting the developing sleeve 31 from the power source 39 and placing it in a floating state, or by grounding it, or by actively applying a DC bias voltage of opposite polarity to the toner charging to the developing sleeve 31. Among these, it is preferable to apply a DC bias voltage. The developing units 6 to 8 are also assumed to perform development under non-contact jumping development conditions like the developing unit 5, but it is possible to remove the developer layer on the developing sleeve 31 or separate the developing sleeve from the image forming body. Even better. This developer 6
In this example, a developer is used in which the toner in the developing device 5 is changed to a toner containing polytungstophosphoric acid as a magenta pigment instead of a yellow pigment, and the toner in the developing device 7 is also changed to a toner containing polytungstophosphoric acid as a cyan pigment. A developer with a changed composition to a toner containing was used.

Of course, color toners based on other pigments or dyes can be used, and the order of the colors to be developed and the order of the developing devices can also be appropriately selected.

The static eliminator 13 and the charger 2 act on the surface of the image forming body 1 that has undergone the first development to re-charge it to -600 cm, but the static eliminator does not need to be operated. ) A second image exposure is performed on the charged surface by laser exposure corresponding to the green component of the image.
A second development of the magenta toner was carried out using the developing device 6 under non-contact jumping development conditions in which a superimposed voltage of a DC voltage of (2) and an AC voltage of 3 KHz, 1000 V was applied. Similarly, laser exposure and third development of cyan toner by the developer 7 were repeated in accordance with the charging and the red component of the image. In the development after the second development, the DC bias component or AC component of the voltage applied to the developing sleeve 31 is adjusted appropriately depending on the change in the surface potential of the image forming body 1, the development characteristics, and the color reproducibility. The amplitude, frequency, selection time of time selection conversion, etc. can be changed. In particular, gradually increasing the charge potential and increasing the DC bias has the effect of preventing color mixing of toner.

When the third development is performed and a four-color image is formed on the image forming body 1, it is easily transferred by the pre-transfer charger 9 and the pre-transfer exposure lamp 10, and then the image is recorded by the transfer device 11. body P
The image was transferred to the computer and fixed by the fixing device 12. The image forming body 1 to which the color image has been transferred is charged by a static eliminator 13,
As described above, residual toner is removed from the surface by the contact of the cleaning blade 14a and the fur brush 14b of the cleaning device 14, and when the surface on which the color image has been formed passes through the cleaning device 13, a color image is completely formed. One cycle of recording has been completed.

In the color images repeatedly recorded in the above manner, each color showed sufficient density and was clear, and the positional deviation of each color could not be discerned with the naked eye.

Further details of the developer used in the present invention are as follows.

That is, Japanese Patent Application No. 183152/1989, which the applicant had already proposed.
No. 58-184381, No. 58-187000, and No. 58-57446, it is desirable that the carrier and toner satisfy the following conditions.

First, regarding the carrier, the fact that the magnetic carrier particles are spherical improves the agitation performance of the toner and carrier and the II transport performance of the developer, and also improves the charge controllability of the toner, which allows the toner particles to form a spherical shape. and to prevent aggregation of toner particles and carrier particles from occurring. However, in the present invention, if the average particle size of the magnetic carrier particles is large, (1) the condition of the ears of the magnetic brush formed on the developer transport carrier is rough, and the electrostatic image is developed while being vibrated by an electric field; too,
Problems such as unevenness easily appearing in the toner image and high density development not being carried out because the toner density in the ears becomes low may occur. In order to solve this problem (2), the average particle size of the carrier particles can be reduced, and as a result of experiments, the effect begins to appear when the average particle size is 50 μm or less, and especially when the particle size is 30 μm or less, the problem (2) actually occurs. It was found that this no longer occurs. Further, the @ problem is solved by making the magnetic carrier particles finer than the problem (■), and the toner concentration in the spike increases, allowing high-density development to be performed. However, if the carrier particles are too fine, they may adhere to the surface of the image carrier together with the toner particles, or they may easily scatter. These phenomena are also related to the strength of the magnetic field acting on the carrier particles and the resulting magnetization strength of the carrier particles, but according to experiments, when the average particle size of the carrier particles is 15μ
When it becomes less than m, the next limit m starts to appear, and it becomes noticeable when it is less than 5 μm. The carrier particles attached to the surface of the image carrier (photoreceptor) usually have a dark colored color.
A portion of the toner migrates onto recording paper, etc., and has a serious adverse effect on color images.

For the above reasons, the average particle size of the magnetic carrier is 5.
The proper condition is 0 μm or less, particularly preferably 30 μm or less, 5 μm or more, and even more preferably 15 μm or more, and it is preferable that the particle size is spherical. In addition, the above average particle diameter is
This is the weight average particle diameter determined using a Cole Counter (manufactured by Cole Co., Ltd.).

Such magnetic carrier particles are made of metals such as iron, chromium, nickel, cobalt, etc., or compounds or alloys thereof, as in conventional magnetic carrier particles.
For example, triiron tetroxide, γ-ferric oxide, chromium dioxide,
Particles of ferromagnetic or paramagnetic substances such as manganese oxide, ferrite, and manganese-copper alloys are made fine, preferably spherical, or the surfaces of these magnetic particles are preferably coated with styrene resin or vinyl resin. , spherically coated with resin such as ethyl resin, rosin modified resin, acrylic resin, polyamide resin, epoxy resin, polyester resin, or fatty acid wax such as palmitic acid or stearic acid, or more preferably magnetically or spherically. It can be obtained by preparing particles and sorting the obtained particles by a conventionally known means for determining the average particle size.

In addition to the above-mentioned effects, forming the carrier particles into a spherical shape using a resin or the like as described above makes the developer layer formed on the developer transport carrier uniform, and also increases the It also has the effect of making it possible to apply a bias voltage.

That is, the fact that the carrier particles are made spherical by resin etc. is because (1) Generally, carrier particles tend to be magnetized and attracted in the long axis direction, but by sphericalization, this directionality is lost, and therefore the developer layer is uniform. (2) As the resistance of carrier particles becomes higher, the edge portions seen in conventional carrier particles are eliminated, which prevents the occurrence of locally low resistance regions and uneven layer thickness. As a result, even if a high bias voltage is applied to the developer transport carrier, the electrostatic latent image may be disturbed due to discharge on the image forming body surface, or the bias voltage may break down. It gives the effect that nothing will happen. The fact that this high bias voltage can be applied means that when development under an oscillating electric field in a preferred embodiment of the present invention is performed by applying an oscillating bias voltage, the effects described below can be sufficiently achieved. This means that you can make the most of it. As mentioned above, wax can also be used as the carrier particles that produce the above-mentioned effects, but from the viewpoint of the durability of the carrier, it is preferable to use resins as mentioned above, and furthermore, the resistivity of the carrier particles should be low. 108
It is preferable to form insulating magnetic particles so that the resistance is Ω or more, particularly 10 Ω or more. This resistivity is calculated by placing the particles in a container with a cross-sectional area of 0.50 cal and tapping, then l kg/cnf on the packed particles.
A load of 1000 V is applied between the load and the bottom electrode.
This value is obtained by reading the current value when applying a voltage that generates an electric field of / cm. If this resistivity is low, when a bias voltage is applied to the developer transport carrier, charges will be injected into the carrier particles. As a result, carrier particles tend to adhere to the surface of the image carrier, or breakdown of the bias voltage tends to occur.

In summary, the magnetic carrier particles are spherical so that the ratio of the major axis to the minor axis is at least 3 times or less,
There are no protrusions such as needles or edges, and the resistivity is 108ΩG.
The appropriate condition is preferably 10 9 cm or more. For such magnetic carrier particles, spherical magnetic particles with high resistance or resin-coated carriers are produced by selecting magnetic particles as spherical as possible and coating them with resin, and by using a magnetic fine particle dispersion system. The carrier is manufactured by using fine particles of magnetic material as much as possible, by performing a spheroidization treatment after forming dispersed resin particles, or by obtaining dispersed resin particles by a spray drying method.

Next, regarding toner, as the average particle size of the toner particles in a two-component paste becomes smaller, the amount of charge qualitatively decreases in proportion to the square of the particle size, which is relatively similar to the van der Waals force. The adhesion force increases, making it difficult for the toner particles to separate from the carrier particles, and once the toner particles adhere to the non-image area of the image bearing surface, they cannot be easily removed by rubbing with a conventional magnetic brush. It starts to cause a dizziness. In the conventional magnetic brush development method, such problems became noticeable when the average particle size of toner particles was 10 μm or less. The present invention a*wlp
This problem is solved by performing development using a developer, a so-called magnetic brush, under an oscillating electric field. That is,
The toner particles adhering to the developer layer are easily moved away from the developer layer and transferred to the image area and non-image area on the image carrier surface by the electrically applied vibrations, and are also easily separated from the developer layer.

Toner particles with a low charge amount hardly migrate to the image area or non-image area, and since they are not rubbed against the surface of the image carrier, they are no longer attached to the image carrier due to frictional charging. Toner particles with a particle size of about 1 μm have come to be used. Therefore, it is possible to obtain a clear toner image with good reproducibility in which the electrostatic latent image is faithfully developed. Furthermore, since the oscillating electric field weakens the bond between toner particles and carrier particles, adhesion of carrier particles accompanying toner particles to the image bearing surface is also reduced. In the image area and non-image area, toner particles with a large amount of charge vibrate under an oscillating electric field, and depending on the strength of the electric field, carrier particles also vibrate, so that the toner particles selectively move to the image area on the image carrier surface. , the adhesion of carrier particles to the surface of the image carrier is significantly reduced.

On the other hand, as the average particle size of the toner increases, as described above, the roughness of the image becomes noticeable.

Normally, toner with an average particle size of about 20 μm has no practical problem for developing fine lines lined up in a pinch of about 10 lines/dragon, but if fine particles with an average particle size of 10 μm or less are used, The resolution has been significantly improved, and it is now possible to produce clear, high-quality images that faithfully reproduce the differences in shading. For the above reasons, it is appropriate that the average particle size of the toner be 20 μm or less, preferably 10 μm or less. Also,
In order for the toner particles to follow the electric field, the charge amount of the toner particles is greater than 1 to 3 μc/g (preferably 3 to 1 μc/g).
00 μc/g) is desirable. Particularly when the particle size is small, a high amount of charge is required. Also, the resistivity is lOdayΩcm
More preferably, the length is 100 cm or more.

Such toner can be obtained in the same manner as conventional toner. That is, it is possible to use a toner in which spherical or irregularly shaped non-magnetic or magnetic toner particles in conventional toners are sorted by an average particle size sorting means. Among these, it is preferable that the toner particles are magnetic particles containing magnetic particles, particularly when the amount of magnetic fine particles is 60 wt.
It is preferable that the amount does not exceed 30-1%, but in order to obtain color clarity, a small amount of 30-1% or less is preferable. When the toner particles contain magnetic particles, the toner particles are influenced by the magnetic force π of the magnet included in the developer transport carrier, so that the uniform formation of the magnetic brush is further improved. ,
The occurrence of fogging is prevented, and furthermore, toner particles are less likely to scatter. However, if the amount of magnetic material contained is too large, the magnetic force between it and the carrier particles becomes too large, making it impossible to obtain a sufficient development density, and
As mentioned above about the carrier, fine magnetic particles appear on the surface of the toner particles, making it difficult to control triboelectrification, making the toner particles more likely to be damaged, and causing aggregation between the particles and the carrier particles. Average particles can be produced by a method similar to a conventionally known method for producing toner particles by using fine particles of a resin and a magnetic material, and adding a coloring component such as carbon and a charge control agent as necessary. A developer in which spherical carrier particles having a diameter of 20 μm or less, particularly preferably 10 μm or less and toner particles are mixed in the same ratio as in a conventional two-component developer is preferably used. Further, if necessary, a fluidizing agent for improving the fluidity and sliding of particles and a cleaning agent for cleaning the surface of the image bearing member are mixed. As a fluidizing agent, colloidal silica, silicone varnish,
Metal stone! Alternatively, a nonionic surfactant or the like can be used, and as the cleaning agent, a surfactant such as fatty acid metal salt, organic group-substituted silicon, or fluorine can be used.

The above are the conditions for the developer, and such a developer can prevent color turbidity of each color. Next, conditions regarding a developer transporting carrier that forms a developing layer with such a developer to develop an electrostatic image on an image carrier will be described.

A developer (shell carrier) similar to that used in conventional development methods in which a bias voltage can be applied is used, but especially inside the sleeve where a developer layer is formed on the surface. A structure in which a rotating magnet body having a plurality of magnetic poles is provided is preferably used. In such a developer transport carrier, the developer layer formed on the surface of the sleeve by the rotation of the rotating magnet body is preferably used. As the developer moves in a wave-like manner, new developer is supplied one after another, and even if the developer layer on the sleeve surface has some uneven thickness,
This effect is sufficiently covered by the above-mentioned wave-like undulations so that it does not become a problem in practice. The developer transport speed due to the rotation of the rotating magnet and the rotation of the sleeve is
It is preferable that the moving speed is almost the same as or faster than the moving speed of the image carrier.

Further, it is preferable that the rotation of the rotating magnet and the rotation of the sleeve are carried in the same direction. Image reproducibility is better in the same direction than in the opposite direction. However, it is not limited to these.

In addition, the thickness of the developer layer formed on the developer transport carrier is
The thickness is preferably such that the adhered developer is sufficiently scraped off by the thickness regulating blade to form a uniform layer, and the gap between the developer transport carrier and the image carrier is several lO.
~2000 μm is preferred.

If the surface gap between the developer transport carrier and the image carrier becomes narrower than several tens of micrometers, it will be difficult to form magnetic brush ears that will uniformly develop the gap, and it will also be difficult to transfer sufficient toner particles to the developing area. If the gap is 2000 μm, stable development will not be possible.
If m is greatly exceeded, the counter electrode effect will be reduced and sufficient development density will not be obtained. in this way,
It becomes impossible to form a developer layer, but the gap is several tens of μm.
In the range of 2000 μm to 2000 μm, the developer layer can be formed with an appropriate thickness. Therefore, the gap and the thickness of the developer layer should be adjusted such that the tip of the magnetic brush does not come into contact with the surface of the image carrier with a gap of 10 to 500 μm and is close to the surface of the image carrier under the condition that no oscillating electric field is applied. It is particularly preferable to set the conditions.

This is because the toner development of the latent image is prevented from having scratches or fog caused by the rubbing of the magnetic brush.

Furthermore, development under an oscillating electric field is preferably carried out by applying an oscillating bias voltage to the sleeve of the developer transport carrier. Further, it is preferable to use a bias voltage that is a combination of a direct current voltage that prevents toner particles from adhering to non-image areas and an alternating current voltage that makes it easier for toner particles to separate from carrier particles. However, the present invention is not limited to the method of applying an oscillating voltage to the sleeve or the method of applying a superimposed voltage of DC and AC.

1 flat aim I In this example, in place of the charger 2 of the image forming apparatus shown in FIG.
As shown in FIG. 5, there are two chargers: a primary charger 102 consisting of a combination of a lamp 102a that irradiates the surface of the image forming body 1 and a corona discharger 102b, and a secondary charger 103 consisting of a corona discharger. This is an example using . Note that, as shown in FIG. 6, the image forming body 1 is made of a conductive substrate la made of aluminum, nickel, or the like, coated with S e and Cd S %.
A photoconductive photosensitive layer 1b made of Si or the like is provided, a transparent insulating surface layer 1C made of a transparent resin or the like is provided thereon, and a conductive substrate 1a is grounded. The rest is the same as in the first embodiment.

Here, the negative electric current generator 102 is the light of the image forming body 1.

When the conductive photosensitive layer 1b has a semiconductor property that exhibits a rectifying effect such that charge can be injected from the base 1a, it does not necessarily include the lamp 102a, and 102 is the lamp 10.
When a corona discharge is performed using the corona discharge W102b while irradiating the surface of the image forming body 1 with the lamp 2a (as mentioned earlier, the lamp 102a may not be necessary), the image forming body 1
The surfaces of the photoconductive photosensitive layer 1b and the transparent insulating surface layer 1c are charged as shown in FIG. 7A. When the secondary charger 103 performs corona discharge on the surface of the charged image forming body 1, the charge on the surface of the transparent insulating surface layer 1c decreases because the photoconductive photosensitive layer 1b is insulating. As a result, the charge on the image forming member 1 changes as shown in FIG. 7B. When the image exposure light 4 is incident on the surface of this secondarily charged image forming body 1,
The surface charge of the photoconductive photosensitive member 751b in the exposed area PH decreases, and the charge remains as it was in the non-exposed area DA, so that the charging of the image forming member 1 becomes as shown in FIG. 7C. Change. FIG. 8 shows the changes in the surface potential of the image forming body 1 during this period, and the potentials in states A, B, and C in FIG. 8 are the same as those in states A, B, and C in FIG. correspond to the state. That is, the potential of the exposed area PH where the imagewise exposure light 4 is incident is the surface potential shown by C(PH) in FIG. Since C(DA) is approximately the same as the surface potential shown by B in the figure, an electrostatic image with a surface potential shown by C(PH) is formed by image exposure 4 with respect to this background potential. This electrostatic image is
As in a normal electrophotographic copying machine, the exposed area PH can be developed with a developer charged to the opposite polarity to that of the latent image, and this development is carried out by the developer corresponding to the image exposure 4 that formed the electrostatic image. This is done using a developing device of any color from 5 to 8. When development is performed and toner adheres, the potential of the electrostatic image decreases in accordance with the amount of toner adhering that is charged to the opposite polarity.

However, the charge in the non-exposed area DA of the image forming body 1 where the image exposure light 4 was not incident is still in the state shown by DA in C, which is the same as in FIG. 7B, and the surface potential of that area has no dark decay. However, since the potential is C (DA) which is approximately the same as B in FIG. When made incident, an electrostatic image can be formed as in the previous case without performing the above-mentioned primary charging and secondary charging. In this way, forming the second and subsequent electrostatic images using the first primary charging and secondary charging is a development process in which a developer charged with the opposite polarity is attached to the latent image. By law, and
This is easily achieved when non-contact jumping development conditions are used. This is because toner can be easily attached to an electrostatic image compared to a developing method in which a developer charged with the same polarity is attached. Therefore, the charged state of the image forming body 1 is maintained stably.Furthermore, the non-contact jumping development condition allows the developer layer of the developing device to come into contact with the surface of the image forming body 1. Therefore, the charged state of the image forming body 1 is maintained stably. In addition, in order to form electrostatic images for each color, shifting the position of the image exposure 4 with respect to the tlN light 4 as described above is similar to the rule in FIG. 2 described earlier for forming the image exposure 4. - This can be easily done by using a laser beam scanner or the like.

The present invention utilizes the first primary charging and the secondary charging to generate the second
This is not limited to the case where electrostatic image formation is performed from the second time onwards, but generally, even if primary charging and secondary charging are performed again each time when electrostatic image formation is performed from the second time onwards, the It is also possible to eliminate the previous charge using the static eliminator 13, or to apply only secondary charging to compensate for the erasure and dark decay of the previous electrostatic image. Especially when primary charging and secondary charging are performed again without removing the previous charge, or when only secondary charging is performed, the previous charge may be transferred to the corona discharger of the negative charger 102 or the secondary charger 103. It is preferable to use a scorotron corona discharger, which can perform stable charging even if there is a scorotron corona discharger. It is particularly desirable to perform primary charging and secondary charging again each time an electrostatic image is formed, when emphasis is placed on gradation reproducibility, or when image exposure 4 is slit exposure or Franche exposure. In addition, NP and KI which form an electrostatic image by carrying out image exposure at the same time as secondary charging and then exposing the entire surface after the negative charge
P method can also be adopted. In some of the methods described above, the electrostatic image potential can be controlled so that the exposed and non-exposed areas have the same or opposite polarity depending on the relative strengths of the negative charge and the secondary charge. Considering the ease of development, it is preferable that the potentials of the exposed area and the non-exposed area are opposite in polarity.

The electrostatic image formed in the second rotation as described above is developed by a developing device of a different color from the previous one among the developing devices 5 to 8 corresponding to the image exposure 4 that formed it. °Similarly, during the three rotations of the image forming body 1, an electrostatic image is formed and development is performed using a different developing device corresponding to the electrostatic image, so that different colors are formed on the image forming body 1. A color image is formed by superimposing the toner images. Then, the surface of the image forming body 1 that has been subjected to the final development is charged with a toner image by a corona discharger 9 as necessary, and is further irradiated with a pre-transfer lamp 10, whereby a transfer device 11 The color image is easily transferred to the recording medium P, and the color image transferred to the recording medium P is fixed on the recording medium P by the fixing device 12. The surface of the image forming body 1 to which the color image has been transferred is neutralized by the static eliminator 13, and the cleaning blade 14a and fur brush 14b of the cleaning device 14, which had been separated until then, come into contact with the surface, thereby removing any residual after the transfer. Toner is removed. Then, when the surface portion of the image forming body 1 on which the color image has been formed passes through the cleaning device 14, the cleaning blade 14a and the fur brush 14b are separated from the surface of the image forming body 1, so that one part of the color image is recorded.
The cycle ends.

FIG. 9 is a flowchart of changes in the surface potential of the image forming body, showing an example of the present invention in which an electrostatic image is formed by image exposure each time using the initial primary charging and secondary charging. As shown, an example of the present invention of electrostatic imaging is shown in which an electrostatic image is formed in the image exposure area and toner is deposited thereon.

Details of the image forming conditions in this example are as follows.

The image forming body 1 has a thickness of 20 μm on a CdS photosensitive layer of 30 μm thickness.
It has a transparent insulating layer with a thickness of 18 μm, and its circumferential speed is 18
01■/sec. A primary charger 1 is attached to this image forming body 1.
While performing uniform exposure using a No. 02 lamp 102a, the image forming member 1 was charged to a surface potential of +1000 V using a DC scorotron corona discharger 102b. Next, the image forming member 1 was charged with a secondary charger 103 consisting of a scorotron corona discharger having an alternating current component so that the surface potential of the image forming member 1 was 1100 cm. Writing exposure was performed on this charged surface using a laser beam scanner using a He-Ne laser as shown in Fig. 2 at a density of 16 dosoto/dragon, and the potential of the exposed area was +300V with respect to the background area potential of -100V. An electrostatic image was formed. This electrostatic image was developed using a developing device 5 as shown in FIG.

The developing device 5 contains 50-t% magnetite dispersed in the resin, an average particle size of 30 μm, and a magnetization of 30 emu/g.
, a carrier with a resistivity of 10"00 or more, and a benzidine derivative 10 as a yellow pigment on a styrene-acrylic resin.
Average particle size including parts by weight and other charge control agents is 10μ
A developer consisting of m negatively charged non-magnetic toner was used under conditions such that the ratio of toner to carrier was 20-t%. Further, the outer diameter of the developing sleeve 31 is 30 fins, its rotation speed is 1100 J7rp, the magnetic flux density of the N and S magnetic poles of the magnet body 32 is 900 Gauss, the rotation speed is 11000 rpm, and the thickness of the developer layer in the developing area is 0. 7 m, the gap between the developing sleeve 31 and the image forming body 1 is 0.8 m, and the developing sleeve 31 has a gap of 15 m.
Non-contact jumping development conditions were used in which a superimposed voltage of 0 V DC voltage and 2.5 KH AC voltage of 2000 V was applied.

Incidentally, while the electrostatic image was being developed by the developing device 5, the other developing devices 6 to 8 shown in FIG. 3 were kept in a non-developing state. This can be done by separating the developing sleeve 31 from the power supply 39 and leaving it in a floating state, or by grounding it, or by actively applying a DC bias voltage of the same polarity as the electrostatic image, that is, the opposite polarity to the toner charging, to the developing sleeve 31. Among these, it is preferable to apply a DC bias voltage. Developers 6 to 8 are also developer 5
Since the development is performed under the same non-contact jumping development conditions as described above, the developer layer on the development sleeve 5 does not need to be removed. This developing device 6 uses a developer in which the toner in the developer in the developing device 5 is changed to a toner containing polytanguez 1-phosphoric acid as a magenta pigment instead of a yellow pigment, and the developing device 7 also contains toner. A developer was used in which the toner was changed to a toner containing a copper phthalocyanine derivative as a cyan pigment, and a developer in which the toner was changed to a toner containing a carbon blank as a black pigment was used in the developing device 8. Of course, color toners based on other pigments or dyes can be used, and the order of developing colors can be appropriately determined so as to obtain clear color images.

In particular, when the image exposure positions overlap, the order in which the colors are developed has a large effect on the clarity of the color image.
Decisions need to be made carefully.

The surface of the image forming body 1 developed by the developing device 5 is transferred to a corona discharger 9 and a pre-transfer lamp 10, which are unnecessary until the final transfer is performed, and a static eliminator 13 which is also placed in an inactive state. The cleaning device 14 and the primary charger 1 that enters a dormant state after completing the above-mentioned primary charging and secondary charging operations.
02 and is recharged by a secondary charger 103.
When reaching the position to receive image exposure 4 again, a second writing was performed with the same dot density using the same laser beam scanner as the previous time, with the dot position shifted.

The potential of the electrostatic image obtained in this way is -100
V, it was +300 V. This electrostatic image is transferred to the developing sleeve 31 with a DC component of -50V and an AC component of 2.5K.
Developing was carried out in developer 6 under the same conditions as in developer 5 except that a voltage of 2000 V was applied.

Similarly, in the third rotation of the image forming body 1, writing is performed using a laser beam scanner in the same manner, and an electrostatic image of +300V is formed against the background area of -100V. This electrostatic image is transferred to the developing sleeve 31. DC component -50V, AC component 2.5K
Developing was carried out in developer 7 under the same conditions as in developer 5, except that a voltage of 2000 V was applied. Similarly, for the fourth rotation of the image forming body 1, writing is performed using a laser beam scanner with the light intensity doubled at first, and the background area -1
00 V, an electrostatic image of +soo v is formed, and this electrostatic image is applied to the developing sleeve 31 with a DC component of 200 V,
Developing was carried out in developing unit 8 under the same conditions as in developing unit 5 except that an alternating current component of 2.5 KHz and a voltage of 2000 V was applied.

When this fourth development is performed and a four-color image is formed on the image forming body 1, the corona discharger 9 and the pre-transfer lamp 10 are activated, thereby transferring the color image. The image was transferred onto the recording medium P by the transfer device 11 and fixed by the fixing device 12.

The image forming body 1 to which the color image was transferred was neutralized by the static eliminator 13, residual toner was removed from the surface by contact with the cleaning blade 14a and the fur brush 14b of the cleaning device 14, and the cycling process was completed.

In the color images repeatedly recorded in the above manner, each color showed sufficient density and was clear, and the positional deviation of each color could not be discerned with the naked eye.

Regarding Examples 1 and 2, when the installation position of the cleaning device 14 was changed and the contact with the cleaning plate was released immediately before the first charging, the positional deviation of each color of the recorded color image was as follows. No discrimination was observed, and no change in image density was observed, resulting in a higher quality color image.

Taking Example 1 as an example, the image forming process is shown in a timing chart as shown in FIG.

In the figure, a line a indicating cleaning indicates an example in which the operation of the cleaning device was started immediately after the final latent image formation, and an example in which the operation was canceled immediately before the first charging.

The image forming process is as described above (Fig. 4, 9).
Contrary to Figure 11, as shown in Figure 11, a latent image is formed by an electrostatic image forming method in which the exposed area PH is the background area and the unexposed area DA is the electrostatic image. , the cleaning member is released from contact with the image forming body,
In the timing chart of FIG. 12, as shown by the solid line a, this is performed before the first image writing for forming the next recorded image, and also after the image writing for the next recorded image formation and the next time, as shown by the broken line. This may be performed between the image writing and the image writing. Furthermore, as shown in FIG. 13, development is performed between the image writing and the next image writing, and the cleaning member is released from contact with the image forming body in the same manner as in FIG. 12. As shown by the solid line a, the image writing for the next recorded image formation is performed before the first image writing, or as shown by the broken line, the image writing for the next recorded image formation and the next image writing are performed. It can also be done in between.

In addition, in FIGS. 10, 12, and 13, three of the developing devices 5, 6, 7, and 8 shown in FIGS. 1 and 5 are used, but three developing devices are sufficient. ) is developed with yellow, magenta, and cyan toner, and black is produced by combining these three colors, but if black toner is also used and all four developing devices are used, the black will be even clearer. I can put it out. In this case, the image forming body 1 rotates four times per cycle to obtain a recorded image.

In this way, in the above example, all recorded images obtained are clear with sufficient density, there is no positional shift for each color, and image formation is not performed until all processes except cleaning are completed. There is no need for extra time during continuous recording image formation, such as rotating the image forming body only for cleaning.

As described in detail above, since the present invention has the above-described configuration, the image forming apparatus based on the present invention can produce high-quality color images without the risk of positional deviation for each color. However, efficient connection is possible.

[Brief explanation of drawings]

1 to 13 show embodiments of the present invention. FIGS. 1 and 5 are schematic diagrams showing the main parts of an image forming apparatus, and FIG. 2 is a schematic diagram showing the main parts of a laser beam scanner. FIG. 3 is a sectional view of the developing device; FIGS. 4, 9 and 11 are flowcharts of the image forming process; FIG. 6 is a sectional view showing an example of the structure of the image forming body; The figure is a charging state change diagram schematically showing an example of the electrostatic image forming process. FIG. 13 is a timing chart showing the operation of each part of the image forming apparatus. 14 to 16 show a conventional example, and FIGS. 14(A), 14(B), and 14(C) are cross-sectional views showing toner adhesion during image formation, and FIGS. 15 and 16 show a conventional example. FIG. 16 is a cross-sectional view showing the state of toner adhesion during other image formation. In addition, in the symbols shown in the drawings, 1... Image forming body 2, 102, 103... Charger 4...
......Image exposure 5.6.7.8...Developer 9...
...Pre-transfer charger 10... Pre-transfer exposure lamp 11...
......Transfer device 12...Fixing device 13...Static eliminator 14...Cleaning device 14a...
...Cleaning blade 14b...
Fur brush P... Recorded object (recording paper) T, T... Toner 731... Toner conveying sleeve 32.・
. . . Magnet body 39 . . . Power source.

Claims (1)

[Scope of Claims] 1. In an image forming apparatus in which the toner images are superimposed by repeating a process including writing an image on an image forming body and forming a toner image following the writing of the image, the forming of the image on the cleaning member An image forming apparatus characterized in that the start of contact and the start of release of contact with the body are performed at least at a time other than the image writing time. 2. A transferred image in which a toner image is transferred to a recording medium, in which a cleaning member is brought into contact with the image forming body after the final image writing for forming this transferred image is completed, and the cleaning member is brought into contact with the image forming body to form the next transferred image. 2. The image forming apparatus according to claim 1, wherein the cleaning member starts to be released from contact with the image forming body at a time when image writing is not being performed. 3. The cleaning member is brought into contact with the image forming body after the final image writing is completed, and the cleaning member is released from the contact with the image forming body at the beginning of the first image writing for forming the next toner image. An image forming apparatus according to claim 1 or 2, which is performed before the image forming apparatus.