JPS6022354B2 - Electrostatic latent image development method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for developing a static latent image in an electrophotographic copying device, an electrostatic recording device, etc., and particularly relates to a method for developing a static latent image using a one-component magnetic toner.

Conventionally, in a developing method using a one-component magnetic toner, a magnetic brush of conductive magnetic toner is formed on a tortoise-conducting sleeve, and the conductive magnetic toner is interposed between the conductive sleeve and the photoreceptor. A known method is to form an electrically conductive path, generate a charge in the magnetic toner by electrostatic induction, and develop an electrostatic latent image on the photoreceptor by the balance between the electrical attraction force and the magnetic force. was.

However, in this method, the amount of charge induced in the magnetic toner changes depending on the time that the magnetic toner is in contact with the photoreceptor, so the time must be controlled, and the application range is very limited. It was narrow. Further, as shown in FIG. 1, a method is known in which a conductive magnetic toner is used and an electric charge is applied to the magnetic toner from the outside. To explain this with respect to the developing device shown in Fig. 1, a sleeve 1 made of a non-magnetic material rotates in a direction of loss and loss, and a magnetic loaf 2 with alternately magnetized N and S poles is fixed inside the sleeve 1. ing. A toner hopper 4 containing one-component magnetic toner 3 is arranged above the sleeve, and as the sleeve 1 rotates, the toner hopper 4
Supply more magnetic toner 3. The magnetic toner 3 discharged from the toner hopper 4 forms a magnetic brush on the sleeve by the magnetic force of the magnetic roller 2. An electrode 5 is provided so as to be in contact with the surface of the magnetic brush, and the magnetic toner is charged to a predetermined polarity by the voltage applied thereto. Next, the magnetic toner in the box is brought into contact with the photoreceptor 6 to develop the electrostatic image formed thereon. By the way, in such a developing device, since the mutually adjacent magnetic poles of the magnetic roller 2 have different polarities as shown in FIG.
A magnetic closed loop is formed between the pole and the south pole, and the one-component magnetic toner forms a chain along the lines of magnetic force.

When the sleeve 1 moves relative to the magnetic roller 2, N poles and S poles appear alternately on the sleeve 1, and as a result, the magnetic toner moves while rotating in the opposite direction to the direction of movement of the magnet. become. Experiments have shown that the magnetic toner rotates half a revolution each time the magnetic pole changes. The magnetic toner on the sleeve 1 is illuminated by the electrode 5. If all the magnetic toner on the sleeve 1 were uniformly charged, there would be no problem even if the magnetic toner rotated, but if the magnetic toner was 5, only the portion in contact with the electrode 5 is charged. Therefore, when the magnetic toner rotates on its own axis as described above, the toner finned by the electrode 6 comes into contact with uncharged or less charged toner around it and leaks sufficient electric charge. Or, during development, uncharged toner or toner with a small amount of charge may appear on the outer surface layer of the magnetic brush. In such a case, the static latent image on the photoreceptor 6 cannot be sufficiently developed, resulting in a low density image.
This results in copies with extremely poor image quality. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a developing method in which the toner is transported and developed without leaking the electric charge of the charged toner. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 3 shows an embodiment of the present invention, in which reference numeral 7 represents a non-magnetic sleeve and 8 represents a permanent magnet.

The non-magnetic sleeve 7 is electrically insulated or made of an insulating material and rotates in all directions. A plurality of permanent magnets 8 are fixed to a support ball 9 within the non-magnetic sleeve 7 . In this embodiment, a six-pole device will be described, but the number of magnetic poles can be selected as appropriate. The magnetic poles of the permanent magnet 8 on the side facing the sleeve 7 are all configured to be the same. A hopper 10 is provided in the upper part of the sleeve 7, and a one-component magnetic toner 11 is stored in the hopper 10.
is stored. When the sleeve 7 rotates, the hopper 1
A predetermined amount of one-component magnetic toner 11 is conveyed from zero to form a magnetic brush on the sleeve 7. At the rear of the hopper 10, a tortoise conductive electrode 12 with an arcuate cross section is arranged on the same 0 circle as the sleeve 7 and with a minute gap of 0.3 to 2 ribs from the sleeve 7. . A voltage is applied to the conductive electrode 12 from an external power source 13 . When the one-component magnetic toner passes between the fin pole 12 and the sleeve 7, it is charged with a fin charge by the electrode 12. The magnetic toner thus removed is then brought into contact with the recording medium 14, which holds the static latent image, and is developed. Now, to explain the conveyance of magnetic toner according to the present invention, as described above, the permanent magnets 8 are arranged so that the N poles appear continuously on the surface of the sleeve 7, and therefore, the magnetic field distribution due to the permanent magnets 8 is This is shown in Figure 4.

In FIG. 4, the lines of magnetic force from one magnet 8 and the lines of magnetic force from the other magnet 82 do not form a closed loop. The magnetic toner on the sleeve 7 forms a magnetic brush in different chains along the lines of magnetic force of the magnets 8, 82, but even when the sleeve 7 rotates, the magnetic toner does not rotate. That is, the magnetic toner charged by the conductive electrode 12 is held on the surface layer of the magnetic brush so as not to rotate while being conveyed to the developing section by the sleeve 7. As a result, insufficiently charged magnetic toner in the intermediate layer portion and almost uncharged magnetic toner on the sleeve 7 side do not appear on the surface layer portion during development, so that sufficient development can be performed. Therefore, the area where the magnetic toner is not allowed to rotate should be at least the range from when the magnetic brush comes into contact with the crab-conducting electrode 12 until it finishes passing through the developing section. In FIG. 3, the magnetic toner is configured not to rotate over the entire surface of the sleeve 7, but this is not necessarily necessary. It is also possible to use a type in which the sleeve 7 is fixed and the magnet 8 is rotated, or both are rotated, but in this case, the magnetic poles of the magnet 8 are approximately equally spaced and all have the same magnetic pole. Of course it has to be.

Next, an example of charging the one-component magnetic toner 11 will be described.

When the magnetic toner has a relatively low resistance value of 1010 to 1000, the voltage applied to the electrode 12 is approximately several IW to 20
It should be as low as about 0V. On the other hand, when the resistance value is as high as 10130 or more, a voltage of 300 V or more must be applied to the electrode 12 because charge injection or discharge is the main problem with magnetic materials.

FIG. 5 shows another embodiment of the present invention, in which reference numeral 15 is a photosensitive drum on which an electrostatic latent image is formed, and is rotating in the direction of the arrow.

A developing device 16 is provided in an upwardly moving portion of the photosensitive drum 15. This developing machine 16 includes a non-magnetic sleeve 17 and a magnetic roller 1 disposed inside the sleeve 17.
8 and a hopper 19 provided on the upper part of the sleeve 17. The sleeve 17 is rotated so that its surface moves in the same direction as the surface of the photosensitive drum 15, and its surface is coated with an electrically insulating material.
For example, in the case of an aluminum sleeve, alumite treatment (oxidation treatment) or coating with an insulating resin such as Mylar may be considered. The magnetic roller 18 fixed within the sleeve 17 is
A roller is used whose outer circumferential surface is all magnetized to the S pole and the inner circumferential surface is magnetized to the N pole. Of course, a magnetic roller device as shown in FIG. 3 may also be used. The one-component magnetic toner 20 supplied from the hopper 19 to the sleeve 17 is
A magnetic brush is formed on the sleeve 17 and is conveyed in the same rotational direction as the sleeve 17. Between the hopper 19 and the developing section A, two conductive electrodes 21 and 22 are arranged on the left side of the sleeve 17 so as to be in contact with the magnetic brush on the sleeve 17. The two electrodes 21 and 22 have a potential difference between them, the electrode 21 is grounded via a switch 23, and the electrode 22 is connected to the positive side of a power source 24.

The two military poles 21 and 22 are spaced apart from each other by a small distance, for example, close to each other by two or less ribs. When switch 23 is actuated by a copier control signal to close the circuit, current from power source 24 flows through the magnetic toner on electrode 22 and sleeve 17 to electrode 21. As a result, the magnetic toner that is in contact with the electrodes 21 and 22 on the surface layer of the magnetic brush is mainly charged. As described above, the magnetic brush does not rotate in conjunction with the rotation of the magnetic toner because the magnetic poles appearing on the sleeve 17 of the magnetic roller 18 are all the same, so the charged magnetic toner remains as it is on the surface of the magnetic brush. The image is transported to the developing section A while remaining in the image. Then, the static fly bath image on the photosensitive drum 15 is developed. developed toner
The image is transferred onto transfer paper by a transfer device (not shown). In this case, since the surface of the sleeve 17 is insulated, the current from the electrode 22 does not flow to the sleeve 17, but instead flows to one electrode 21 via the magnetic toner, making it possible to efficiently charge the toner. I can do it.

By the way, when the sleeve 17 stops rotating during non-development or non-copying operation, the switch 23 is opened and the electrode 21
, 22.

This is because when the sleeve 17 stops, current always flows only to the magnetic toner near the electrodes 21 and 22 on the sleeve 17, which prevents the toner from generating heat due to its own resistance and from sticking. It's for a reason. In order to make the toner charged by the electrodes effectively act on the developing section, it is desirable that the crab poles 21 and 22 be as close to the developing section A as possible. It is also possible to arrange the electrodes 21 and 22 below the sleeve 17.

The voltage applied between the electrodes 21 and 22 may be appropriately selected depending on the resistance value of the magnetic toner used, as described above.

Although the above embodiment has been explained in the case of an electrophotographic copying device, the same device can also be used in an electrostatic recording device in which a static box image is directly formed on a dielectric material instead of a photoreceptor by a multi-stylus or the like. It is possible to implement

Furthermore, in each of the embodiments, the magnet or magnetic roller has the same magnetic pole all around the circumference, but as shown in FIG. The magnetic poles of both should be the same.

Components that have the same functions and effects as those of the above-described embodiments will be described using the same reference numerals. In FIG. 6, six poles of magnets 25 are arranged in the sleeve 7, and the hopper 1
The magnetic pole of the magnet 25 facing 0 is the S pole, the two magnets 252 and 253 facing the conductive electrode 12 are both the N pole, and the magnet 254 facing the photoreceptor 14 is also the N pole. The other two magnets 255 and 256 have south and north poles, respectively. That is, the polarity is set so that the toner does not rotate after the magnetic brush on the sleeve 7 contacts the electrode 12 until it reaches the developing section A, and before and after that, the polarity is set so that the toner does not rotate.
~256, 25 and ~252 are alternately N and S poles. - As described above, according to the present invention, the charge on the magnetic toner charged by the electrode is prevented from disappearing, or the charged toner is transported to the developing section while being kept on the surface layer of the magnetic brush. , efficient development can be performed.

Further, it is possible to obtain a developed image with excellent low contrast reproducibility and a wide exposure latitude.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining a conventional developing device, FIG. 3 is a sectional view of a developing device showing an embodiment of the present invention, and FIG. 4 is a diagram for explaining the principle of the present invention. , 5 and 6 are sectional views of a developing device showing another embodiment of the present invention. 7, 17... Sleeve, 8, 25, ~ 256... Magnet, 10, 19... Hopper, 1 1, 20.
...One-component magnetic toner, 12, 21, 22...
...Guiding fin electrode, 13,24...Power supply. Figure Rare 2 Figures Rough 3 Figures Fine 4 Figures 5 Cans 6 Figures

Claims (1)

[Claims] 1. A magnetic brush forming means comprising a magnet for forming a magnetic brush of one-component magnetic toner on a non-magnetic sleeve that is electrically insulated or made of an electrically insulating material; In a developing device for developing an electrostatic latent image on an electrostatic latent image carrier, the developing device has a conductive electrode to which a predetermined voltage is applied to apply a charge to the electrostatic latent image carrier, at least the magnetic brush is connected to the electrostatic latent image from the conductive electrode to the electrostatic latent image carrier. While reaching the latent image carrier, the magnetic poles of the magnet on the side facing the non-magnetic sleeve are made to have the same polarity, and the one-component magnetic toner charged by the conductive electrode is kept static on the surface layer of the magnetic brush. A method for developing an electrostatic latent image, characterized in that the electrostatic latent image is brought into contact with the electrostatic latent image.