JPH01204078A - Image forming device - Google Patents

Abstract

PURPOSE:To copy from an identical original in high speed and in low cost by magnetizing a magnetizable magnetic powder image formed on an image carrier which consists of a non-magnetic body, obtaining a master image and forming a magnetic powder image on the master image. CONSTITUTION:When reading an original A is started, an electrostatic latent image responding to image information is formed on a photosensitive body belt 8 which consists of the non-magnetic body. When the obtained electrostatic latent image passes through a first developing unit 21, magnetic developer 23 is electrostatically attached to the electrostatic latent image, and a magnetic powder image which responds to the image is obtained. The developer 23 is composed of magnetic powder which is excellent in magnetic characteristic. The magnetic powder image is fixed by a fixing flash 40 and is permanently magnetized by a magnetizing device 42. Magnetic developer 26 is attached to the magnetized master image by a second developing unit 22, and the magnetic powder image is formed. The magnetic powder image on the master image is transferred onto the recording sheet 33 of a transferring belt 31. Since the master image remains even after the magnetic powder image is transferred, when an identical copying after the first copying is performed, copying from the identical original can be performed many times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an image forming apparatus used as a copying machine or a printer.

(Prior Art) An electronic copying machine or a plate-making/printing device is known as a device for copying a manuscript. Generally, electronic copying machines are
The setup for copying work is simple and the equipment is easy to handle.

In contrast, plate making/printing equipment can create a master plate from a manuscript and use this master plate to repeatedly transfer onto recording paper, so once the master plate is created, it can print at high speed.
There is an advantage that the greater the number of copies made from the same original document, the lower the printing cost.

(Problem to be solved by the invention) Conventional plate making and printing devices can only produce 4 copies from the same original.
For prints of less than one sheet, the original plate accounts for a large proportion of the cost, so the printing cost is higher than that of an electronic copying machine.Moreover, since the process of making the original plate is required, it takes time and effort to set up the work. On the other hand, electronic copying machines repeat processes such as charging, exposure, development, and neutralization each time they copy a single original, so even if the number of copies made from the same original increases, the cost per copy does not decrease. However, the copying speed is considerably slower than that of a printing machine.

To address these problems, electronic copying machines have been put into practical use that can copy at a speed that is closer to that of printing, and that do not require the skilled work and setup required by printing machines.

However, in order to further increase the copying speed, the electric power required for exposing the original, fixing the developer, and charging the document becomes extremely large, making it impossible to use a regular commercial power source.
If an attempt is made to increase the copying speed, there is a problem in that the image quality is sacrificed due to unreasonable development speed, etc.

The present inventor also focused on forming a magnetic latent image on an image carrier and making this magnetic latent image visible using a magnetic developer, as a new type of image forming apparatus that replaces the conventional electronic copying machine. . However, when trying to form a magnetic latent image on an image carrier made of a simple magnetic material, the magnetic head for magnetization is moved at a very small pitch in the width direction of the image carrier, and at a very large number of images over the entire width of the image carrier. This not only makes the structure of the magnetizing device significantly more complex, but also requires high precision, which poses problems such as difficulty in control.

Therefore, it is an object of the present invention to make it possible to make multiple copies from the same original document in the same way as a printing machine with the same simple operation as a conventional electronic copying machine, and to have a structure for a magnetizing device used to obtain a magnetic latent image. An object of the present invention is to provide an image forming apparatus that requires only a simple device.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned object, the image forming apparatus of the present invention provides a first magnetic powder by attaching magnetizable magnetic powder onto an image carrier made of a non-magnetic material. a first magnetic powder image forming means for forming a magnetic powder image; a magnetizing means for obtaining a magnetized master image by magnetizing the magnetic powder image; and a second magnetic powder image forming means for forming a magnetized master image by magnetizing the magnetic powder image; The magnetic powder image forming apparatus includes a second magnetic powder image forming means for forming a magnetic powder image, and a transfer means for transferring the second magnetic powder image on the master image to a transfer member.

(Function) The apparatus of the present invention having the above configuration can implement the print mode described below when it is desired to make multiple copies of the same original. First, in the first magnetic powder image forming means, a first magnetic powder image is obtained by developing an electrostatic latent image formed corresponding to the original image with a magnetic developer. This magnetic powder image is fixed on the image carrier by means such as fusing, and is magnetized by a magnetizing means to become a magnetized master image. In this case, since the image carrier is a non-magnetic material and is not affected by magnetic force, a simple magnetizing device with the same polarity in the width direction of the image carrier is used to magnetize the master image. It is possible to magnetize only the master image. A second magnetic powder image is obtained using a magnetic developer using the magnetic force of the thus magnetized master image, and then this magnetic powder image is transferred to a transfer member such as recording paper.

The above-mentioned master image remains on the image carrier as it is even after the magnetic powder image is transferred, so when making the same copy for the second and subsequent copies, the magnetic force of the master image is used again to develop the master image. At the same time, the magnetic powder image is transferred to a transfer member. By repeating the above steps, it is possible to make copies from the same original any number of times. In other words, in this printing mode, once the master image is formed, there is no need to perform the step of forming the first magnetic powder image mentioned above or the step of fixing or magnetizing this magnetic powder image on the image carrier. Not followed. Therefore, when a large number of copies are to be made using this printing mode, power consumption can be saved and the copying speed can be significantly faster than that of conventional electronic copying machines.

(Example) An example of the present invention will be described below with reference to the drawings.

The image forming apparatus 1 shown in FIG. 1 has a document placement table 3 on the upper surface of a housing 2 and an openable/closable document presser 4. The image forming apparatus 1 shown in FIG. The document is read photoelectrically by a document reading means 5 using a scanner or the like.

A drum 7 is rotatably provided inside the housing 2. This drum 7 can be rotated clockwise in the drawing at least at a first speed v1 and a second speed v2 by a drive mechanism (not shown).

The second speed v2 is several times to several tens of times faster than the first speed v1.

A photoreceptor belt 8 as an image carrier made of a non-magnetic material is provided on the outer periphery of the drum 7 . As shown in FIGS. 3 and 4, this photosensitive belt 8 has a photosensitive layer 9 made of normal lead oxide, which is a dielectric material capable of forming an electrostatic latent image, and has a photosensitive layer 9 on the drum 7. It goes around the outer circumference once. Each time a print mode, which will be described later, is performed, the photoreceptor belt 8 is fed out by a new predetermined size from the supply roll 10 onto the drum 7, and the used portion is wound onto the take-up roll 11. ing.

A scorotron type corona charger 13 disposed opposite the outer periphery of the drum 7 uniformly charges the photoreceptor belt 8 with a voltage of -300 to 1,500 volts.

An exposure device 15 equipped with a laser scanner 14 exposes image information read by the reading means 5 and converted into an electrical signal onto the photosensitive layer 9 through an optical system member 16 such as a mirror or a lens. An electrostatic latent image corresponding to image information is formed on the photosensitive layer 9. The charger 13 and the exposure device 15 constitute an electrostatic latent image forming means 17.

Furthermore, a first developing device 21 as a first magnetic powder image forming means and a second developing device 22 as a second magnetic powder image forming means are arranged along the rotational circumferential direction of the drum 7.

The first developing device 21 adopts a so-called conductive magnetic component development method, and uses a first magnetic developer 2 which is a carrierless donor.
3 is accommodated. This magnetic developer 23 is made of fine powder such as barium ferrite having excellent magnetization characteristics or γ-Fe2O3, but in short, any material that can be easily permanently magnetized in the magnetic field produced by the magnetizing device 42 described below is sufficient. , magnetic powders having high magnetization properties other than those described above may also be used. This magnetic developer 23 is attached to a magnetic sleeve 24.
As the image rotates, it is carried to the photoreceptor belt 8 side, and
A positive charge can be applied by frictional charging as the sleeve 24 rotates.

The second developing device 22 accommodates a second magnetic developer 26 . As the magnetic developer 26, a triboelectrically charged magnetic component toner made of magnetic fine powder such as Fe2O4 which has high electric resistance and little permanent magnetization is suitable. The developer 26 is carried toward the photoreceptor belt 8 side as the magnetic sleeve 27 rotates, and can be given a positive charge by frictional charging as the sleeve 27 rotates.

Furthermore, along the rotational circumferential direction of the drum 7, a pre-transfer corona charger 29, a paper supply section 30, and an endless transfer belt 31 as a transfer means are arranged. The charger 29 preferably has a negative polarity so that the charge remaining on the photosensitive layer 9 can be erased with light (discharge light). Paper supply section 3
0, the recording paper 33, which is an example of a transfer member stacked on the recording paper storage section 32, is synchronously sent out between the transfer belt 31 and the photoreceptor belt 8 via the guide 34.

The transfer belt 31 is made by laminating a dielectric film such as polyester having a thickness of about 20 to 4 ops on the surface of a belt main body made of a conductive material, and has a corona of about the opposite polarity to that of the pre-transfer corona produced by the charger 29. A bias voltage of 1000 volts is applied. A well-known heat roller type fixing device 36 and a paper discharge table 37 are arranged at the end of the conveyance of the transfer belt 31 .

Note that instead of applying the bias voltage to the transfer belt 31, the recording paper 33 may be charged by corona discharge.

Furthermore, along the rotational circumferential direction of the drum 7, a fixing flash 40 using a xenon lamp or the like as an example of a fixing means, a static elimination lamp 41 for removing residual charges on the photosensitive layer 9, and a magnetizing device 42 are provided. is provided.

Next, the operation of the image forming apparatus 1 having the above configuration will be explained. This apparatus 1 is capable of duplicating the document A in any mode, including a print mode suitable for copying a large number of sheets from the same document, and a copy mode suitable for copying a small number of sheets. First, the print mode will be explained.

When the document reading means 5 starts reading the document A, the drum 7 and the photoreceptor belt 8 are integrated into the first
The photosensitive layer 9 of the photosensitive belt 8 is uniformly negatively charged by the charger 13 as shown in FIG. The image information photoelectrically read by the reading means 5 is converted into a signal by a known means, and the photosensitive layer 9 is irradiated with light as an image signal by the laser scanner 14, so that the electrostatic potential An image is formed (Figure 4).

The electrostatic latent image thus obtained is developed by passing through the first developing device 21 to form a first magnetic powder image.

That is, in this first magnetic powder image forming step, the fifth
As shown in the figure, the positively charged first magnetic developer 23 electrostatically adheres to the negatively charged portions of the photosensitive layer 9, thereby obtaining a magnetic powder image corresponding to the image.

Furthermore, the drum 7 and the photosensitive belt 8 are rotated at a first speed Vl to the fixing flash 40, and are irradiated with heat rays by the fixing flash 40, so that they are instantly fused to the photosensitive layer 9 (the first Figure 6). That is, by going through this fixing step, a master image 45 made of the first magnetic developer 23 is obtained.

The thus fixed master image 45 is moved together with the photosensitive layer 9 to a magnetizing device 42, as shown in FIG. 7, and is permanently magnetized by a magnetic head 46. The magnetic head 46 is provided over the entire effective width of the photoreceptor belt 8. As schematically shown in FIG. 11, the fixed master images 45 are sequentially magnetized in the direction of movement of the photoreceptor belt 8. Since the photosensitive layer 9 itself is a non-magnetic material, it is not magnetized, and only the master image 45 is magnetized. Therefore, this magnetic head 46 is
Since it is only necessary to apply a magnetic field of the same polarity in the width direction of the photoreceptor belt 8, a long one with a simple structure can be used.

As mentioned above, while the drum 7 makes its first rotation,
A magnetization pattern is formed as a magnetized master image or magnetic latent image. The drum 7 continues to be rotated, but from the second rotation onwards, it is rotated at a high speed at the second speed v2, thereby allowing the second developing device 22 to perform development and the recording paper 3.
Transfer to 3 is performed.

That is, when the master image 45 magnetized in the above-described process moves to the second developing device 22, the eighth developing device 22
As shown in the figure, the second magnetic developer 26 is attracted by the magnetic force of the master image 45, and the developer 26 adheres to the surface of the master image 45.

In this way, a second magnetic powder image is formed. This developer 26
is attracted to the master image 45 by magnetic force, so it is not necessarily necessary to apply a charge. After the second development, by receiving a pre-transfer corona discharge by the charger 29,
A negative charge is given (Figure 9).

Recording paper 33 is fed out one by one from the paper supply section 30
is sandwiched between the photoreceptor belt 8 and the transfer belt 31 while being transferred by the transfer belt 31 in synchronization with the rotational direction of the drum 7 . Since a bias voltage having a polarity opposite to that of the pre-transfer corona is applied to the transfer belt 31, the second developer 26 is electrostatically transferred one after another onto the recording paper 33 side. The recording paper 33 after the transfer is sent to a heat roller type fixing device 36 as the transfer belt 31 runs, and the image is fixed by being heated and pressurized at the same time. is discharged to the top.

Note that if the second developer 26 is a triboelectrically charged toner and can be sufficiently charged during development, the pre-transfer corona discharge by the charger 29 can be omitted. However, in order to ensure electrostatic transfer in a short time, such as when high-speed transfer is required, it is preferable to apply a sufficient charge to the developer 26 by performing corona discharge before transfer.

To continue to make second and subsequent copies from the same original in this printing mode, the second magnetic powder image formation step (Fig. 8), the pre-transfer corona discharge (Fig. 9), and the transfer step (first
By repeating (Figure 0) at the second speed v2, it is possible to make any number of copies with the same content. That is, after the master image 45 is formed and magnetized, a charging process (Fig. 3), an exposure process (Fig. 4), a first magnetic powder image forming process (Fig. 5), a fixing process ( Fig. 6) One magnetization step (Fig. 7) does not require pro-eutectoid analysis. Then, the power required for charging, image exposure, etc. can be applied to the fixing device 36.

Therefore, not only power saving can be achieved, but also the printing mode can be performed at a high rotational speed v2 after the master image is formed, so that the copying speed can be significantly increased. Furthermore, the greater the number of copies made from the same document, the lower the cost per copy.

Note that in order to prevent the photosensitive layer 9 from being charged due to residual charges after the second rotation of the drum 7 in the above printing mode, it is preferable to leave the static elimination lamp 41 on. When the copying of one document is completed in print mode, the photoreceptor belt 8 is wound around the take-up roll 11 by the size of the master image 45 fixed thereon, and a new unused length is taken up by the take-up roll 11. It is fed out onto the drum 7.

Next, a copy mode suitable for copying a small number of sheets will be explained.

The copy mode differs from the print mode described above in that a master image is not formed. In this copy mode, drum 7
is rotated at the aforementioned first speed Vl, or at a third speed v3 faster than the first speed v1. However, v3 is the second speed v2 in print mode.
It's slower than that.

As in the print mode, when the reading unit 5 starts reading the document A, the drum 7 and the photoreceptor belt 8
are combined to achieve the third speed v3 (or the first speed vl
), and the photosensitive layer 9 is uniformly charged by the charger 13 as shown in FIG.

Note that the voltage of the charger 13 and the like are adjusted according to the rotational speed of the drum 7 so that a predetermined potential can be obtained even if the rotational speed v3 of the drum 7 is faster than vl.

The image information read by the reading means 5 is converted into a signal, and the laser scanner 14 irradiates the photosensitive layer 9 with light as an image signal, thereby forming electrostatic latent images one after another (FIG. 4). The electrostatic latent image thus obtained is visualized by passing through the second developing device 22. Since development using magnetic force cannot be performed in this copying mode, the second magnetic developer 26, which has been positively charged by frictional charging or the like, is used to remove the negative charges on the photosensitive layer 9, as shown in FIG. A magnetic powder image corresponding to the image is obtained by electrostatically attaching the powder to the location.

Subsequently, the drum 7 is rotated, and as shown in FIG. 13, the charger 29 receives a pre-transfer corona discharge and gives an electric charge, and then the developer 26 is sequentially applied to the recording paper 33 as shown in FIG. transcribed.

After the transfer, the recording paper 33 is fixed by the heat roller type fixing device 36 as in the print mode, and then is discharged onto the paper discharge table 37.

Note that if a voltage is applied to the transfer belt 31 with a polarity such that the recording paper 33 is negatively charged as shown in FIG. 15, or if corona discharge is performed, the pre-transfer corona discharge (FIG. 13) can be avoided. The developer 26 can be transferred onto the recording paper 33.

The developer 26 remaining on the photosensitive layer 9 after the transfer is neutralized by the static eliminating lamp 41, and is then brushed off by the magnetic brush effect in the second developing device 22 while the drum 7 makes one more revolution. The toner is collected in the second developing device 22. In other words, the copying mode of the present apparatus 1 is a two-rotation/one-copy method using magnetic brush cleaning, and one of the drums 7
Steps such as formation, development, and transfer of an electrostatic latent image are performed in the second rotation, and cleaning of the photosensitive layer 9 is performed in the second rotation.

In this copying mode, the same photosensitive surface of the photoreceptor belt 8 is used repeatedly, for example, about 1000 times, and when a predetermined number of times is reached, the photoreceptor belt 8 is wound up by a predetermined length onto the take-up roll 11, and an unused new size The portions are dispensed onto the drum 7 and ready for use.

As described above, in the apparatus 1 of this embodiment, the first developer 23 having conductivity and the second developer 26 having insulation properties are used. The reason why conductive toner is used for the first developer 23 is that by using conductive toner when creating a master image in print mode, edge effects are suppressed and a master image of extremely high quality can be obtained. be. Since this developer 23 is used to obtain a master image and has no relation to the actual copy color, it does not matter what color it is. Therefore, it is easy to select a material that is easily magnetized.

On the other hand, the reason why insulating toner is used as the second developer 26 is to transfer the developer 26 to the recording paper 33 by electrostatic transfer. It is necessary to use it.

Note that, depending on the image quality, it may not be necessary to use conductive toner for the first developer 23, so the developer 2
It is possible to reduce costs by combining 1.22 into one and using a common developer. When using a common developer, it is preferable to use an insulating magnetic toner with triboelectric charging properties.

Further, in the above embodiment, zinc oxide is used for the photoreceptor belt 8, but the material is not limited to this, and various dielectrics such as other photoreceptor materials and dielectric belts for electrostatic recording can be used. Furthermore, the apparatus of the present invention exposes the photosensitive layer of the image carrier with reflected light or transmitted light from the document obtained by irradiating the document with illumination light through an optical system member, instead of exposing the document with the laser scanner 14. It can be in a format like this.

The apparatus of the present invention can of course be used as a copying machine, but it is also extremely effective when making large numbers of copies using, for example, a laser printer.

[Effects of the Invention] As described above, according to the present invention, by switching to the print mode when a large number of copies are to be made, it is possible to make copies from the same document at high speed and at low cost. Furthermore, a magnetizing device with a simple structure can be used.

[Brief explanation of the drawing]

1 to 14 show one embodiment of the present invention, and the first
The figure is a cross-sectional view schematically showing the internal structure of the image forming apparatus, Figure 2 is an enlarged view of the vicinity of the drum in Figure 1, and Figures 3 to 10 each show the image forming process in print mode in order of process. FIG. 11 is a side view, FIG. 11 is a plan view showing a part of the magnetizing device and a master image, and FIGS. 12 to 14 are
Each figure is a side view showing a part of the image forming process in the copying mode in the order of steps, and FIG. 15 is a side view when the polarity of the transfer belt is changed. DESCRIPTION OF SYMBOLS 1... Image forming device, 5... Original reading means, 7...
・Drum, 8... Photoreceptor belt (image carrier), 9...
・Photosensitive layer, 13... Charger, 15... Exposure device, 1
7... Electrostatic latent image forming means, 21... First developing device (first magnetic powder image forming means), 22... Second developing device (second developing device).
magnetic powder image forming means), 23... first magnetic developer,
26... Second magnetic developer, 29... Pre-transfer corona charger, 31... Transfer belt (transfer means), 33...
Recording paper (transfer member), 40... Fixing flash (fixing means), 42... Magnetizing device, 45... Master image, 46... Head of magnetizing device. Applicant's representative Patent attorney Takehiko Suzue Figure 2 1. Correct 7 Fig. 3 Fig. 4 Fig. 5 Fig. 6Il￥] No. 7U: Fig. 8 No. 9U, 1 Fig. 10 No. 11 r;j

Claims (1)

[Claims] a first magnetic powder image forming means for forming a first magnetic powder image by attaching magnetizable magnetic powder onto an image carrier made of a non-magnetic material; a second magnetic powder image forming means for forming a second magnetic powder image using a magnetic developer on the master image; and a second magnetic powder image on the master image. An image forming apparatus comprising: a transfer means for transferring the image to a transfer member.