JPS6042777A - Forming device of developer thin layer - Google Patents

Abstract

PURPOSE:To collect a leaked magnetic particle to a developer holding member, and to prevent a bad influence by providing a magnetic particle holding magnetic pole on a prescribed position in the holding member, and setting a distance between the holding member of the magnetic pole position and a photosensitive body to >=1mm. and <=20mm.. CONSTITUTION:In a developer holding member 12, a magnetic particle holding magnetic pole 20 is provided on the downstream side from a position opposed to a photosentive body, and a distance L to the photosensitive body in a position of the magnetic pole 20 is set to >=1mm. and <=20mm.. When a mixture of a magnetic particle and a non-magnetic developer is supplied to the holding member 12 and rotated in the direction as indicated with an arrow (b), a base layer 16 is formed by a magnetic bursh, and a thin layer of a developer is supplied onto the holding member 12, but depending on a condition, sometimes the magnetic particle flows out. In that case, it does not adhere to a photosensitive body 11 since the magnetic pole 20 exists, but is attracted to the member 12 and returned to a vessel 13. Therefore, scattering, etc. of the magnetic particle are prevented, and its bad influence can be prevented effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dry developer thin layer forming apparatus. Furthermore,
The present invention relates to an apparatus for forming a thin layer of non-magnetic developer.

Hitherto, various apparatuses have been proposed and put into practical use as dry developing systems. However, in any of the developing methods, it is extremely difficult to form a thin layer of dry developer, and for this reason, the developing device has been constructed by forming a relatively thick layer. However, now that improvements in the clarity, resolution, etc. of developed images are desired, it is essential to develop a method for forming a thin layer of dry developer and an apparatus therefor.

As a method of forming a thin layer of a conventionally known dry developer, Japanese Patent Application Laid-Open No. 54-43037 has been proposed and has been put into practical use. However, this concerned the formation of a thin layer of magnetic developer. In order to make magnetic developers magnetic, a magnetic material must be added to the developer. Since the body contains a magnetic material (magnetic material is usually black), there is a problem of poor color reproduction when the color is reproduced9.

For this reason, as a method for forming a thin layer of non-magnetic developer, there are two methods: using a cylindrical brush made of soft hair like heather hair, and applying the developer to the brush, or a method where the surface is made of fibers such as velvet. A method has been proposed in which a doctor blade or the like is used to coat the developed roller.

However, if an elastic blade is used as a doctor blade for the fiber brush described in item 1, it is possible to regulate the amount of developer, but uniform application is not achieved, and the fiber brush on the developing roller is simply rubbed. Since the developer present between the fibers is not triboelectrically charged, there is a problem in that fogging is likely to occur.

Emiyu 1 The applicant et al. have developed a new thin layer forming method that is completely different from the conventional method described above, in which a magnetic brush made of magnetic particles is placed upstream of the magnetic particle restraining member in the direction of movement of the surface of the developer holding member. A method and apparatus for forming a thin layer of non-magnetic developer on a developer retaining member using a magnetic brush have already been proposed. However, if the particle size distribution of the magnetic particles is wide-ranging and the magnetic particles contain particles with a diameter smaller than that of the non-magnetic developer, such magnetic particles may be thinned along with the non-magnetic developer. It may be included in the layer. Furthermore, if the fluidity of the developer is improved in order to extend the life of the developer (1), the magnetic particles are less likely to be restrained by the magnetic particle restraining member, resulting in problems such as easy leakage. When magnetic particles are coated in a thin layer together with a non-magnetic developer, these particles may be transferred to the latent image carrier in the developing section, reducing the quality of the developed image or causing local damage to the photoreceptor. An object of the present invention is to provide a developer thin layer forming apparatus that can prevent the adverse effects caused by magnetic particles being included in the thin layer when forming a thin layer of nonmagnetic developer.

According to the present invention, there is provided a developer supply container that monitors the opening, and a cylinder that is provided in the opening and that is movable endlessly inside and outside the container and that faces the latent image carrier in the developing section. a non-magnetic member for holding a developer; a fixed magnetic field generating means provided inside the developer holding member; A developer thin layer forming device having a magnetic particle restraining member for restraining, wherein the developer holding member is measured at a normal line erected on the surface of the developer retaining member at a position of the developer retaining member opposite to the magnetic particle retaining magnetic pole. There is provided a developer thin layer forming apparatus in which the distance 11t&L between the surface of the developer holding member and the surface of the latent image carrier is 1 mm or more and 20 mm or less.

In this device, along with the action of a magnetic field generated by a magnetic particle restraining member (magnetic blade) and a fixed magnetic field generating means inside the developer holding member.

Although magnetic particles are substantially prevented from passing through the gap between the magnetic blade and the surface of the developer holding member, even if there is a magnetic particle that happens to pass through the gap and leak out, the magnetic particle will be blocked. In this case, the magnetic particles are prevented from transferring or extending into contact with the latent image carrier by the magnetic particle holding magnetic pole inside the developer holding member, thereby preventing the adverse effects caused by leakage of the magnetic particles. Moreover, this magnetic pole is not located at a position facing the latent image carrier,
It is located downstream from there (in the moving direction of the surface of the developer holding member), and is located on the straight line connecting the magnetic particle holding magnetic pole and the center of the cylindrical developer holding member. The distance between the image carrier surfaces is 1 mm or more2
Since the thickness is set to 0 mm or less, magnetic particles that happen to be transferred to the surface of the latent image carrier can be pulled back from the latent image carrier onto the developer holding member, thereby extremely effectively eliminating the adverse effects of the leaked magnetic particles. It is.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of a method and apparatus for forming a thin layer of nonmagnetic developer according to the present invention.

In Figure 1, 11 is a cylindrical electrophotographic photoreceptor, which serves as a latent image carrier, and moves in the direction of the arrow a. A non-magnetic holding member 12 that holds the developer is provided with a gap between the photoreceptor 11 and, in this embodiment, the electrophotographic photoreceptor has a cylindrical shape, but it can also be used in the form of an endlessly moving web. good. Along with this movement of the photoreceptor 11, the developer holding member 12 is rotated in the direction indicated by the arrow. A developer supply container 13 is used to supply developer to this developer holding member 12.
is provided. The developer supply container 13 has an opening near its lower part, and the developer holding member 12 is provided in the opening. Since a portion of the developer holding member is exposed to the outside through the opening, its surface moves from the inside of the developer supply container to the outside, and then returns to the inside. An enclosure is formed at the lower part of the developer holding container 13 so as to wrap around the lower part of the developer holding member 12 to prevent the developer from leaking to the outside. Further, a magnetic seal member 8 made of a magnetic material is provided to further ensure prevention of this leakage to the outside. A fixed magnetic field generating means for generating a fixed magnetic field, that is, a magnet 14 is fixedly provided inside the developer holding member 12 . Since the magnet 14 is fixed,
Only the developer holding member 12 rotates. This magnet 14 is N
It has magnetic poles of 1, Sl, N2, N2, N3, and N3.

Among the magnetic poles of the magnet 14, the Nl pole moves the magnetic particles to the developer container 1.
3, the S1 pole is a magnetic pole for causing a brush formed by magnetic particles to circulate in accordance with the rotation of the developer holding member, and N2 is a magnetic brush formed by magnetic particles between the magnetic sealing member 8 and the magnetic sealing member 8. This is a magnetic pole to prevent non-magnetic developer from spilling from the developer container.

A magnetic blade 15 made of a magnetic material is disposed near a portion of the opening of the development side supply container 12. The magnetic pole Nl of the magnet 14 is located on the opposite side of the magnetic blade 15 with the developer holding member 12 in between.
It is arranged at an angle of 0 (5 to 50 degrees) shifted at an upstream position in the rotational direction.

The base layer 16 is formed by supplying magnetic particles or a mixture containing magnetic particles and a non-magnetic developer to the developer supply container of the apparatus having such a configuration. The mixture forming the base layer preferably contains about 5 to 70% (by weight) of non-magnetic developer based on the magnetic particles, but it may also contain only magnetic particles. The particle size of the magnetic particles is 30-200, preferably 70-200
It is 150 microns. Each magnetic particle may be made of only magnetic material or may be a combination of magnetic material and non-magnetic material. The magnetic particles in the base layer 16 form a magnetic brush due to the magnetic field generated by the magnet 14, and this magnetic brush performs the circulating action described below. A magnetic brush is formed between the magnetic pole Nl and the magnetic blade 15, which restrains the magnetic particles of the base layer 16 within the developer supply container 13.

By supplying the non-magnetic developer to the base layer 16, two layers are formed substantially in the vertical direction, that is, on and outside the outer periphery of the developer holding member 12. The developer layer may be formed using a small amount of magnetic particles added to this non-magnetic developer, but even in this case, the magnetic particle content of the developer layer is smaller than that of the base layer 16. Silica particles may be externally added to this non-magnetic developer in order to improve fluidity, and abrasive particles may be externally added in order to polish the photoreceptor 11. The method for forming the two layers is not limited to supplying the two layers in two stages as described above. For example, it is also possible to supply a substantially uniform mixture of magnetic particles and non-magnetic developer for the entire amount of the base layer 16 and developer layer 17. Thereafter, the developer supply container 13 may be vibrated to form two layers due to the difference in specific gravity between the magnetic particles and the non-magnetic developer and the magnetic field of the magnet 14.

Even when a nearly uniform mixture of magnetic particles and non-magnetic developer is supplied without particularly forming two layers,
This is possible as long as it contains a sufficient amount of magnetic particles to form a magnetic brush, but in order to maintain long-term stability of the magnetic brush, it is preferable to use two layers.

When the developer holding member 12 is rotated with the magnetic particles and developer applied in this way, the magnetic particles move in a circular motion as shown by the arrows in FIG. 1 due to the magnetic field and gravity of each magnetic pole. Let's do it. That is, the developer holding member 12
Near the outer surface of the developer supply container 13, the magnetic particles at the bottom of the developer supply container 13 rise along the outer circumference of the developer holding member 12 due to the interaction between the magnetic field of the magnet 14 and the rotation of the developer holding member 12, and at this time, The non-magnetic developer and the surface of the developer holding member 12 come into contact, and the non-magnetic developer in the base layer is electrostatically applied onto the developer holding member 12.

In this embodiment, the non-magnetic developer is charged by friction with the magnetic particles or the developer holding member 12, but preferably there is an oxide film on the surface of the magnetic particles or an oxide film at the same electrostatic level as the non-magnetic developer. The developer holding member 1 is insulated with resin, etc., to reduce tripoding from magnetic particles, and to transfer the necessary charge to the developer holding member 1.
2, it is possible to prevent the influence of deterioration of the magnetic particles and to stabilize the application of the developer to the developer holding member 12.

The magnetic particles rise as the developer holding member 12 rotates, but the gap between the surface of the developer holding member 12 and the tip of the magnetic blade 15 is reduced by the magnetic field formed between the magnetic blade 15 and the magnetic pole Nl. Being prevented from passing. Therefore, the magnetic particles in this area are pushed by the magnetic particles that are sent one after another, rotate as shown in FIG. 2, and then slowly fall due to gravity. During this falling, the non-magnetic developer at the lower part of the developer layer 17 is taken in and returned to the lower part of the developer supply container 13, and this process is repeated.

On the other hand, since the triboelectrically charged developer is non-magnetic, it can pass through without being restrained by the magnetic field that exists in the gap between the tip of the magnetic blade 15 and the surface of the developer holding member 12, and is developed by the magnetic brush section formed on the magnetic blade section. The surface of the developer holding member is coated uniformly and thinly with the action of mirror force, placed on the surface of the developer holding member 120, exits the developer supply container 13, faces the surface of the photoreceptor 11, and is subjected to development. .

However, even with this configuration, depending on the particle size distribution of the magnetic particles, minute magnetic particles may pass through the gap between the surfaces of the magnetic particle restraining member 15 and the developer holding member 12, as shown in FIG. There is a possibility of leakage. The leaked magnetic particles are divided into those that are transferred to the latent image carrier 11 with the development action and those that are not transferred, but some of the former are not transferred to the transfer paper at the development and transfer section.
It reaches the cleaning section and damages the delicate surface of the latent image carrier 11 (photoreceptor) during the cleaning action.

On the other hand, although the latter does not directly damage the latent image carrier 11 (photoreceptor), it does not directly damage the latent image carrier 11 (photoreceptor), but before it returns to the developer supply chamber 13 due to the combined force of centrifugal force and gravity caused by the rotation of the developer holding member 12. It separates from the surface of the developer holding member 12 and falls and scatters as shown by arrow C in FIG. 2, which is the biggest cause of contamination of the copying apparatus.

FIG. 3 shows an embodiment of the invention. Components that are the same as those in FIG. 1 are given the same reference numerals, and a detailed description will be omitted. In FIG. 3, the latent image carrier 1
A magnetic particle holding magnetic pole 20 is provided inside the developer holding member at a position shifted downstream by an angle β in the moving direction of the developer holding member from the position of the developer holding member opposite to the developer holding member 1 . This position is a position of the developer holding member 12 facing the magnetic particle holding magnetic pole 20.
The distance between the surface of the developer holding member 12 and the surface of the latent image carrier 11 measured by the normal line 2 to the outer surface is Lmm or more.
11II11 or less, preferably. The position is such that the distance is 2 mm or more and 10 mm or less.

The magnetic particle holding magnetic pole 20 may be a part of the magnetic pole of the fixed magnetic field generating means 14, or may be a separate magnet. As a result, the magnetic particles leaking through the gap between the surfaces of the magnetic particle restraining member 15 and the developer holding member 12 do not fall and scatter outside the developing device, but remain attracted to the developer holding member 2 in the developer supply container. Returning to i3, the latent image is compatible with the surface of the developer holding member 12 measured at the normal line 2 to the outer surface of the developer holding member 12 at the position of the developer holding member 12 facing the magnetic particle holding magnetic pole 20. Since the distance #L between the surfaces of the body 11 is set as shown in 7, the magnetic particles that happen to be transferred to the latent image carrier are pulled back to the surface of the developer holding member 12 by the magnetic particle holding magnetic pole. In this way, the negative effects of leaked magnetic particles can be prevented.

Here, the angle β formed by the straight line connecting the center of the developer holding member 12 and the center of the latent image carrier and the straight line connecting the magnetic particle restraining magnetic pole 22 and the center of the developer holding member 12 is 8 o II 1 m in diameter of the photoreceptor ii. In an embodiment in which the diameter of the developer holding member is 20 mm, the angle is 10 to 30 degrees, preferably 15 to 20 degrees.

FIG. 4 shows the case where the magnetic particle holding magnetic pole 2o is not placed downstream of the development position but is provided opposite to it (the angle β is
Alternatively, the developer holding member 1 measured at the normal line erected to the outer surface of the developer holding member 12 at the position of the developer holding member 12 facing the magnetic particle holding magnetic pole 2o.
2 is an explanatory diagram when the distance ML between the surface of the latent image 411 and the surface of the latent image 411 carrier 11 is set outside the above range.

In this case, the object of the present invention can be achieved at the initial stage of the developer operation, but as the developer continues to operate, the leaked magnetic particles increase cumulatively near the magnetic particle holding magnetic pole.
When the spikes are formed, there is a possibility that the developer holding member 12 and the latent image carrier 11 are short-circuited through the magnetic particles. When a short circuit occurs, dielectric breakdown occurs in the latent image carrier 11, resulting in pinhole damage. This makes the expensive pH' image 1
The u-holder 11 (photoreceptor) becomes unusable.

On the other hand, if this distance is made too large, the magnetic particles transferred to the photoreceptor cannot be pulled back.

From these points, the above distance is 1 mm or more - 1 = 20 m
+n or less, preferably 2 mm or more and 10 mm or less. Under these conditions, only the non-magnetic developer is applied to the latent image carrier 1.
1, and the magnetic particles that happened to be transferred to the latent image carrier 11 are pulled back onto the developer holding member. Furthermore, a developing device in which leaked magnetic particles do not fall and scatter can be obtained.

The magnetic flux density on the surface of the developer holding member 12 due to the magnetic particle holding magnetic pole 20 is 400 to 70'O Gauss, and the entrainment value l] is 2
A suitable angle is 5 to 50 degrees. Further, the magnetic flux density in the direction perpendicular to the developer holding member 12 at the closest portion between the surface of the latent image carrier 11 and the developer holding member 12 is desirably 200 Gauss or less in order to prevent magnetic particles from staying in this portion. At this intensity, no discharge occurs between the latent image carrier 11 and the surface of the developer holding member 12.

The developing method used here is Special Publication No. 58-3237
The method described in 5 is preferred. A voltage is applied between the electrophotographic photoreceptor 11 and the developer holding member 12 by a bias power supply 19 . The bias power supply 19 may be an alternating current or a direct current, but preferably one in which alternating current and direct current are superimposed. The developer provided by the development is supplied from the base layer 16 to the developer holding member 12, and the insufficient amount in the base layer 16 is supplied from the developer layer 17 by the above-mentioned circulation movement. The base layer 16 is formed near the outer surface of the developer holding member 12 from the beginning,
Furthermore, since the developer layer 17 contains no magnetic particles or only a small amount to compensate for the loss of magnetic particles that inevitably occurs with the use of the device, the state of the magnetic brush in the base layer 16 is It remains almost constant and does not change even if it continues for a long time. In this sense, the magnetic particles in base layer 16 are part of the development apparatus rather than the developer material or part thereof.

In addition, in the above explanation of the principle, a magnetic blade made of a magnetic material such as iron is used as the regulating member, but a non-magnetic blade made of a non-magnetic material such as aluminum, copper, or resin or a non-magnetic blade made of a non-magnetic material such as resin or aluminum constituting the container is used. A magnetic wall can also be used as this regulating member. However, in this case, in order to prevent the magnetic particles from flowing out, it is necessary to make the gap between the sleeve and the regulating member more narrow than when using a magnetic blade. Further, when a magnetic blade is used, it is preferable because a magnetic brush can be stably formed at the developer outlet by the magnetic field between the blade and the magnetic pole.

Based on the method described above, good results were obtained using a developer having the following composition.

In order to subject the non-magnetic developer coating layer formed by the developer thin layer forming apparatus of the present invention to a developing action, the electrophotographic photoreceptor 11 having a dark area of +500V and a bright area of -150V as an electrostatic latent image is placed on the surface of the cylinder. A voltage of 800 Hz, a peak-to-peak value of 1.8 KV, and a center value of +100 V is applied between the cylindrical developer holding member 12 and the electrophotographic photosensitive member by a power source 19, with a spacing of 300 lm between the surfaces of the cylindrical developer holding member 12. In addition, good clear images without ghosts or fog were obtained using the Canon NP2O0J copier.

Further, after copying about 3,000 sheets, there was no change in image density until the non-magnetic developer layer was almost consumed, and no magnetic particles were used for development.

According to the present invention, the magnetic particle holding magnetic pole 20 is provided, and the magnetic pole 20 is connected to the latent image carrier 1.
1, the magnetic particles carried to the development site due to leakage are prevented from damaging the latent image carrier 11 or contaminating the inside and outside of the copying machine, and also prevents the magnetic particles from causing damage to the latent image carrier 11 or contaminating the inside and outside of the copying machine. The magnetic particles transferred to the carrier can be pulled back onto the surface of the developer holding member.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a non-magnetic developer thin forming device which is the basis of the present invention, FIG. 2 is an explanatory diagram of the device shown in FIG. 1 which is not based on the present invention, and FIG. FIG. 4 is a sectional view illustrating the state when the magnetic particle restraining magnetic poles are shifted. Explanation of symbols 11: Latent image carrier 12: Developer holding member 13: Developer supply container 14: Magnet 15: Magnetic particle restraining member

Claims (1)

[Scope of Claims] A developer supply container having an opening;
A non-magnetic member for holding developer facing the latent image bearing member, fixed magnetic field generating means provided inside the developer holding member; Together with the fixed magnetic field generating means, there is also a magnetic particle restraining member for restraining the magnetic particles in the developer supply container 4, and a magnetic particle restraining member for restraining the magnetic particles in the developer supply container before the development autopsy inside the developer holding member. Part or latent image J
Positional force 1 facing the FI holder, backward development] has a magnetic particle holding magnetic pole provided at a position on the downstream side in the moving direction of the front member, and the magnetic particle holding magnetic pole is opposed to the magnetic particle holding magnetic pole. The distance between the surface of the developer holding member and the surface of the latent image carrier measured at the position of the developer holding member at the normal line to the surface of the developer holding member is 1 mm or more.
A developing material thin layer forming device characterized in that the thickness is 120 mm or less.