JPS6368869A - Magnetic transfer device - Google Patents

Abstract

PURPOSE:To perform sufficient transfer with relatively small magnetic force by magnetizing a magnetic belt from the opposite surface side from a photosensitive drum and making its magnetic force easy to affect magnetic toner. CONSTITUTION:The magnetic belt 21 as a magnetic operating body is conveyed repeatedly to a transfer part 13 and magnetized halfway by a magnetizing means 23 to attract magnetic toner on a recording medium across a transfer body 14 when reaching the transfer part 13, and thus the magnetic toner on the recording medium 4 is attracted and transferred to the transfer body side. The magnetic belt 21 is magnetized from the opposite surface side from the recording medium 4 and has its opposite surface magnetized to operate on the magnetic toner only across the transfer body, so the developing toner is attracted sufficiently for the transfer even through weak magnetic operation when the belt faces the recording medium 4.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention involves sandwiching a transferred material between a recording medium and a magnetically acting body, and transferring magnetic toner on the recording medium to the transferred material by the magnetic action of the magnetically acting body. It relates to a magnetic transfer device for transferring, and is used, for example, in an electrophotographic copying mechanism for obtaining a positive copy image from a negative or positive image in a reader printer.

(Prior Art) A general method for exposing a negative or positive image onto a photoreceptor and developing it for a positive image by operating a single switch is to use a bipolar photoreceptor or to develop a positive image using a developing device. It is currently being done to use two types of.

However, in the case of the former, there are only a few types of photoreceptor materials, and the degree of freedom is poor in terms of sensitivity and cost. In the latter case, one copying mechanism must be provided with two developing units, and a mechanism for selectively operating them is also required, resulting in a complicated structure and an increase in the size of the apparatus.

On the other hand, as a method that achieves bipolar polarity with a single photoreceptor and a single developing device and does not have the above-mentioned drawbacks, high-resistance magnetic toner or conductive magnetic toner is used, and the development bias can be adjusted to produce negative or It has also been proposed to perform bipolar development to obtain a copy of a positive image from a positive image.

In this method of using high-resistance magnetic toner or conductive magnetic toner, electrostatic transfer is affected by the environment, such as temperature and humidity, and charges due to corona discharge tend to flow through the copy paper to the toner. Transfer cannot be performed well.

A magnetic transfer device described in Japanese Unexamined Patent Publication No. 52-20036 is known as a device that makes this possible. In this device, a permanent magnet is housed in a non-magnetic rotating sleeve that presses the transfer material against the recording medium and indirectly faces the recording medium to attract magnetic toner from the recording medium and transfer it to the transfer material. There is.

(Problem to be solved by the invention) However, the permanent magnet exerts magnetic action indirectly through the non-magnetic rotating sleeve, and there is also a gear between it and the non-magnetic rotating sleeve to rotate it. Therefore, it is necessary to have a strong magnetic force that does not easily exert a magnetic effect on the toner on the recording medium.

In addition, the magnetic action from the permanent magnet is applied either on a localized surface or on an arcuate surface, and the magnetic field is generated either concentratedly or radially, which tends to disturb the toner while attracting and transferring the toner on the recording medium to the transfer object. Good transfer is difficult.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention inserts a transfer material between a recording medium and a magnetically acting body, and the magnetic toner on the recording medium is transferred to the magnetically acting body. In a magnetic transfer device that transfers images onto a transfer material by the magnetic action of a magnetic belt, the magnetic effect member is a magnetic belt that is repeatedly transferred to the transfer section, and a heald guide that keeps the magnetic heald substantially flat in the transfer section; The device is characterized in that it is provided with a magnetizing means that faces the side facing the recording medium and magnetizes the magnetic heald from the side facing the recording medium so that the facing side becomes the same polarity.

(Function) The magnetic belt, which serves as a magnetic effecting body, is repeatedly transported to the transfer section and is magnetized by magnetizing means on the way, so that when it reaches the transfer section, it is attracted to the magnetic I/N of the recording medium through the transfer material. It can act to attract the magnetic toner on the recording medium and transfer it to the transfer object.

The magnetic belt receives the magnetization effect from the surface facing the recording medium, and the opposite surface is magnetized and acts on the magnetic toner only through the transferred material, so even a weak magnetic effect can cause the developed toner to be absorbed when facing the recording medium. A sufficient suction effect can be exerted on the transfer.

In addition, the magnetic heald is kept flat by a belt guide at the transfer section, and a parallel magnetic field is generated at the section facing the recording medium, so that transfer can be performed without disturbing or misaligning the magnetic toner.

In addition, while the magnetic heald is moving, the surface facing the recording medium is uniformly magnetized by the magnetization means so that the surface facing the recording medium has the same polarity, so there is no unevenness in the magnetic action during transfer, and there is no influence from the magnetic pole boundary, and the transferred image is uneven. Uniform transfer can be performed without creating streaks or streaks.

(Example) An example of the present invention shown in FIGS. 1 to 3 will be described. This embodiment shows a case where it is applied to a copying mechanism in a reader printer, and as shown in FIG. 2, an image of an illumination Sarel film F is projected onto a screen 3 by a projection lens 2 using a condenser system 1 for viewing. , the photosensitive drum (recording medium) 4 is exposed and used for copying.

Projection onto the screen 3 is performed by directing the light beam from the projection lens 2 toward the screen 3 using the first mirror 5 and the movable mirror 6. Exposure to the photoreceptor drum 4 is performed by moving the movable mirror 6 upward and retracting, and directing the light beam from the projection lens 2 to the photoreceptor drum 4 using the first scan mirror 8 and the second scan mirror 9. Therefore, the reader state or the printing state can be switched by placing the movable mirror 6 in the downward moving position or in the upward moving retracted position.

A charger 10, a developer 1), a cleaning device 12, etc. are provided around the photoreceptor drum 4, and the exposure forms an electrostatic latent image on the photoreceptor drum 4 and develops it with toner. 1) and the cleaning device 12, the transfer sheet 14(
The toner image is transferred onto the paper (Fig. 1).

The developing device 1) uses high resistance or conductive magnetic toner, and a sleeve 25 is connected to a bias power source 2 as shown in FIG.
Development is performed by applying a predetermined bias from 6 to inject charge into the toner. In this developing system, normal development or reversal development can be selectively performed depending on the magnitude of the applied bias. Thereby, development is possible when obtaining a positive copy image from either a negative image or a positive image.

Magnetic transfer is used to transfer toner images developed with such high resistance or conductive magnetic toner. For this magnetic transfer, a transfer portion 13 on the surface of the photoreceptor drum 4
A magnetic belt 21 is pressed into position. The magnetic heald 21 feeds the transfer sheet 14 supplied from the paper feed section 15 to the transfer section 13 in synchronization with the toner image on the photoreceptor drum 4, and further transfers the transferred transfer sheet 14 to the flash fixing device 16. It also serves as a conveyor for discharging paper through the paper discharge port 17, and is stretched by a driving roller 18 and a driven roller 19. A backup roller 20 is provided at the position of the transfer section 13 on the back surface of the magnetic heald 21,
The magnetic belt 21 is brought into pressure contact with the photosensitive drum 4. Further, the driving roller 18, the driven roller 19, and the hack-up roller 20 serve as belt guides to make the magnetic heel 1-21 flat at least at the transfer portion 13.

The magnetic belt 21 is made of a magnetic rubber material, and can easily bring the transfer sheet 14 into pressure contact with the photoreceptor drum 4 at the transfer section 13. As shown in FIG. 1, a magnetic sensor 22 and a magnetizing head (magnetizing means) 23 are provided around the driven roller 19 of the magnetic belt 2 at the front and rear facing the driving direction of the magnetic belt 21. The control circuit 24 receives the output and operates the magnetizing head 23 only when a decrease in the surface magnetic force of the magnetic heald 21 is detected.

While the magnetizing head 23 is in operation, it continuously magnetizes the magnetic belt 21 so that the surface side facing the photosensitive drum 4 has the same polarity. When the magnetic heald 21 is formed of a material whose saturation magnetic force matches a predetermined magnetic force necessary for transfer, the magnetizing head 23
It is possible to maintain a constant magnetic force even when the magnet is turned on. In this case, the magnetic sensor 22 is not required.

A cleaning device 28 is provided at one location around the drive roller 18 portion of the magnetic belt 21 . Cleaning device 2
8 indicates a blade type, but is not limited thereto. For example, magnetic cleaning, solvent cleaning, or web cleaning may be used.

Reference numeral 27 in FIG. 1 indicates a charger power source of the charger 10. As shown in FIG.

In FIG. 1, the high asuka 9wA of the developing device 1) is adjusted depending on the mode setting of whether a negative image or a positive image is exposed on the photosensitive drum 4. As a result, the developing device 1) performs normal development or reversal development, and develops the electrostatic latent image formed on the photoreceptor drum 4, corresponding to whether it is a negative image or a positive image, so that a positive toner image is obtained. The developed toner image reaches the transfer section 13 and is transferred to the transfer paper 14 which is supplied to the transfer section 13 by the magnetic belt 21.
come into contact with At this time, the magnetic belt 21 presses the transfer sheet 14 against the photoreceptor drum 4 by its own tension and the pressure from the backup roller 20, and while the transfer sheet 14 and the magnetic toner on the photoreceptor drum 4 are in close contact with each other, the magnetic toner is transferred to the magnetic toner. is always attracted with a predetermined magnetic force to ensure transfer to the transfer sheet 14 side.

Moreover, since the magnetic belt 21 is kept flat at least in the transfer section 13, a parallel magnetic field is formed between it and the photoreceptor drum 4, and the transfer is performed without causing any disturbance or positional shift in the magnetic toner. Let it happen.

Furthermore, the magnetic belt 21 is magnetized from the side facing the photoreceptor drum 4, and the resulting magnetic force is easily exerted on the magnetic toner. Therefore, sufficient transfer can be performed with a relatively small magnetic force, and the magnetization is Since the transfer is performed uniformly so that the surface facing the photosensitive drum 4 has the same polarity, the transfer is performed without disturbing the magnetic toner.

As described above, the transfer in the transfer section 13 is performed satisfactorily.

After the transfer, the transfer sheet 14 is sent by the magnetic belt 21 to a flash fixing device 16, where the transferred toner image is fixed. The magnetic belt 21 continues to exert the uniform magnetic action on the toner image on the transfer sheet 14-H even during this conveyance, and prevents the toner image from being disturbed before it reaches the fixing device 16.

Here, the fixing device 16 fixes the toner on the transfer sheet 141 to the extent that it is not disturbed, and finally fixes it with another fixing device in a part away from the magnetic acting body such as the magnetic belt 21. You can also do that.

(Effects of the Invention) According to the present invention, since it has the above-described structure and operation, sufficient transfer can be achieved with weak magnetization of the magnetic belt, and the transfer can be prevented by toner disturbance, positional deviation, or the influence of magnetic poles. It can be done well without stripes or the like.

[Brief explanation of the drawing]

Fig. 1 is a side view of an image forming mechanism showing an embodiment of the present invention applied to a reader printer, Fig. 2 is a schematic side view of the internal structure of the entire reader printer, and Fig. 3 is a magnetic belt attachment. It is an explanatory view showing a magnetic state.

Claims (1)

[Claims] (1) In a magnetic transfer device in which a transfer material is sandwiched between a recording medium and a magnetic action body and magnetic toner on the recording medium is transferred to the transfer material by the magnetic action of the magnetic action body, the magnetic action body is transferred to the transfer portion. a magnetic belt that is repeatedly transferred, a belt guide that keeps the magnetic belt substantially flat in the transfer section, and a belt guide that faces a side of the magnetic belt that faces a recording medium, and a side that faces the magnetic belt that faces the recording medium. and magnetizing means for magnetizing the opposing surfaces so that the opposite surfaces thereof have the same polarity.