JPS6042767A - Image formation - Google Patents

Abstract

PURPOSE:To prevent flocculation and fusion and to enable formation of an image having ahigh grade by a nonmagnetic developer by forming a thin layer of the nonmagnetic developer and magnetic particles on a developer holding member spaced at a prescribed distance from a photosensitve body and performing development. CONSTITUTION:A magnet 14 is fixed in a developer holding member 12 provided apart at a distance larger than the thickness of a thin layer from a latent image carrying body 11. A magnetic blade 15 and an iron piece 18 are provided in a vessel 13. When the member 12 rotates in an arrow (b) direction, the circulating motion toward an arrow (C) is generated by the magnetic brush formed by the magnet 14, the effect of gravity and the blade 15, by which the thin layer of magnetic particles and a nonmagnetic developer is formed on the member 12. The development is performed by such thin layer. The magnetic particles which are not transferred are recovered into a cleaning device. The image having a high grade is thus formed by the nonmagnetic developer without flocculation and fustion of said developer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming method using a dry developer. - Conventionally, various proposals have been made for image forming methods using dry developers, and various methods have been put into practice. However, in any of the image forming methods, it is extremely difficult to form a thin layer of dry developer, and therefore images are formed by forming a relatively thick layer.

However, now that improvements in image clarity, resolution, etc. are being sought, a method of forming images by forming a thin layer of dry developer is desired6. A method for forming a thin layer is JP-A-54-4303.
7 has been proposed and put into practical use. However, this concerned the formation of a thin layer of magnetic developer.

In order to make magnetic developers magnetic, it is necessary to add a magnetic substance to the developer. (magnetic materials are usually black), which causes problems such as poor color reproduction.

For this reason, as a method for forming a thin layer of non-magnetic developer, there are methods in which soft bristles such as beaver hair are used as a cylindrical brush and the developer is adhered to the brush, and 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, when an elastic blade is used as a doctor blade for the fiber brush mentioned above, although it is possible to regulate the amount of developer, uniform application is not achieved, and the developer is simply rubbed with the fiber brush of developer a to roller j. Since no triboelectric charge is imparted to the developer present between the fibers of the brush, there is a problem in that fogging is likely to occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for forming an image on a transfer material using a non-magnetic developer, eliminating the drawbacks of the two conventional methods.

According to the invention, a thin developer layer consisting of a non-magnetic developer and magnetic particles is formed on a developer holding member, and the developer holding member holding the thin layer is a distance greater than the thickness of,
The latent image bearing member is made to face a latent image bearing member at a distance, and the latent image on the latent image bearing member is developed with a non-magnetic developer and magnetic particles. An image forming method characterized by forming a developed image consisting of: and then transferring only the non-magnetic developer of this developed image onto a transfer material, thereby forming an image of the non-magnetic developer on the transfer material. , so that an image of a non-magnetic developer can be formed on a transfer material, obviating the drawbacks of two series of conventional methods.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram schematically showing an image forming apparatus that implements the method of the present invention.

In FIG. 1, an apparatus for carrying out the image forming method according to the present invention includes a cylindrical electrophotographic photoreceptor 11 as a latent image carrier.
, an electrostatic image forming device 2 including a charging device and an image exposure device arranged around the electrostatic image forming device, a developing device 3 for developing an electrostatic latent image formed by the electrostatic image forming device, and a developing device 3 for developing an electrostatic latent image formed by the electrostatic image forming device; a corona transfer device 5 that transfers onto the transfer material 4, and
It includes a cleaning device 6 for cleaning the latent image carrier after image transfer. Since a known latent image forming process and a latent image forming apparatus for carrying out the process may be used, a detailed description thereof will be omitted.

FIG. 2 shows a developing device embodying the method of the invention. In the figure, the latent image carrier 11 moves in the direction of the arrow a. A non-magnetic holding member 12 for holding the developer is provided with a gap between the latent image carrier 11, and in this embodiment, this holding member 12 is cylindrical, but it is shaped like an endlessly moving web. Also good. The same applies to the latent image carrier 11. As the latent image carrier 11 moves, the developer holding member 1
Rotate 2 in the direction of the arrow. A developer supply container 13 is provided to supply developer to the developer holding member 12 . 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 part of the developer holding member 12 is exposed to the outside from the opening I, its surface moves from the inside of the developer supply container 13 to the outside, and then returns to the inside of the developer supply container 13. An enclosure is formed at the lower part of the developer holding member 12 so as to wrap around the lower part of the developer holding member 12 to prevent the developer from leaking outside. A magnetic field generating means, that is, a magnet 14 is fixedly provided.Since the magnet 14 is fixed, only the developer holding member 12 rotates.This magnet 14
has a particle regulating magnetic pole 20 and a dityl magnetic pole 22, which will be described later.

A magnetic blade 15 made of a magnetic material is arranged near the opening of the developer supply container 12 . There is a particle regulating magnetic pole 20 of the magnet 14 on the opposite side of the magnetic blade 15 with the developer holding member 12 in between. The angle θ (5
~50 degrees). Developer holding member I2
On the downstream side of the magnetic blade 15 with respect to the rotational direction of ? The magnetic pole may be provided on the upstream side of the position facing the II image carrier 11 . However, if a magnetic pole is provided at the development position, a magnetic brush is formed by magnetic particles at that part and a short circuit phenomenon occurs, which is undesirable.Also, even if the magnetic blade 15 is magnetized to the opposite polarity to the magnetic pole 20, good.

An iron piece 18 made of a magnetic material is provided on the inner wall of the developer supply container 13 facing the sealing magnetic pole 21, and a magnetic brush formed between these pieces seals the lower part of the container 13 and prevents the circulation of magnetic particles. It also improves. iron piece 18
In addition to metals such as iron, the magnet may be a magnet that faces the sealing magnetic pole 21 in a reverse polarity relationship. These magnetic members may be attached to the wall of the container 13 facing the sealing magnetic pole 21, or a part of the container itself may be made of a magnetic material such as iron, and the wall of the container facing the sealing magnetic pole 21 may be used to hold the developer. It may be configured close to the member 12.

The mixture layer 16 is formed by supplying a mixture containing magnetic particles and non-magnetic developer to the developer supply container of the apparatus having such a configuration. The mixture forming this mixture layer preferably contains about 5 to 70% (flat stitch) non-magnetic developer based on the magnetic particles. The particle size of the magnetic particles is between 5 and 50 microns, preferably between 10 and 30 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 mixture layer 16 form a magnetic brush due to the magnetic field generated by the magnet 14, and this magnetic brush performs a circulating action as described below. A magnetic brush is also formed between the particle regulating magnetic pole 20 and the magnetic blade 15, which is connected to the mixture layer 1.
The magnetic particles and non-magnetic developer particles of No. 6 are restrained inside the developer supply container 13.

When the developer holding member 12 is rotated with the magnetic particles and developer applied in this manner, the magnetic particles and non-magnetic developer particles are moved as shown in FIG. Make a circular motion as shown by arrow C. That is, near the outer surface of the developer holding member 12, the magnetic particles in the lower part of the developer supply container 13 are attached to the magnet 1.
4 and the phase V of the rotation of the developer holding member 12, the non-magnetic developer and the surface of the developer holding member 12 come into contact with each other. The non-magnetic developer in the mixture layer is electrostatically applied to the developer holding member 12''.

The magnetic particles and non-magnetic developer particles are stored in the developer holding member 12.
As the developer rotates, the developer rises, but the thickness is regulated by the magnetic field formed between the magnetic blade 15 and the particle regulating magnetic pole 20, and the developer is coated as a thin layer on the developer holding member 124. It exits the supply container 13. On the other hand, due to this regulating action, the magnetic particles and non-magnetic developer particles retained in the developer supply container 13 are pushed by the magnetic particles that are sent in one after another, as shown by the arrows in FIG. It spins and flips around, then slowly falls back to the bottom due to gravity, and repeats this process.

In this embodiment, the non-magnetic developer is charged primarily by friction with the developer holding member 12, although it is also charged by friction with magnetic particles. Preferably, the surface of the magnetic particles is insulated with an oxide film or a resin that is at the same electrostatic level as the non-magnetic developer, or the magnetic particles are made conductive to prevent the magnetic particles themselves from being charged up. By reducing the amount of tripo imparted by the magnetic particles so that the necessary charge is received from the developer holding member, 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. .

Thus, in order to coat both magnetic particles and non-magnetic developer particles as a thin layer, the particle size of the magnetic particles should be approximately equal to the particle size of the non-magnetic developer particles, or the particle size of the magnetic particles should be approximately equal to the particle size of the non-magnetic developer particles.
It is desirable to approximately double the amount. If the particle size of the magnetic particles is too large, the magnetic particles tend to be restrained within the developer supply container 13 by the action of the magnetic pole 20 and the magnetic plate 15, and a thin layer of only magnetic developer particles is formed. Become so. Even if only the non-magnetic developer particles are completely coated on the developer-holding member 12, the non-magnetic developer is sufficiently charged due to frictional electrification with the surface of the developer-holding member, as described above, so that it can be used for the developing action. However, problems may occur depending on the type of nonmagnetic developer. That is, in a developer that tends to agglomerate or fuse under mechanical pressure, especially in a pressure fixing developer, the magnetic particles that are completely bound to the magnetic blade 15 fuse together due to the pressure when they pass through the magnetic brush. there is a possibility. In the present invention, since magnetic particles are also applied onto the developer holding member, pressure does not increase, so even if the developer is used, there is no fusion or aggregation.

Furthermore, in order to make it easier for the magnetic particles to be coated onto the developer holding member 12, instead of reducing the particle size of the magnetic particles, particles made by adding a non-magnetic substance to a magnetic substance, for example, magnetic particles, are mixed with a synthetic resin binder. It may be tied with In the present invention, since the non-magnetic developer and magnetic particles are supplied to the image carrier at a constant ratio from the developer supply container 13, the ratio in the developer supply container can be maintained constant without the need for special means. It is maintained.

The developing method used here is Special Publication No. 58-3237
The method described in 5 is preferred. A voltage is applied between the latent image carrier 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. Here, not only the non-magnetic developer particles but also the magnetic particles interact with the latent image carrier.
It is thought that the reason why the magnetic particles reciprocate between the magnetic particles and the developer holding member 12- is that electric charges are induced in the magnetic particles by electrostatic induction due to the electric field formed between them.

Next, a specific example of the present invention will be explained. In the specific example device, the latent image carrier 11 as the latent image carrier has 6
It rotates at a circumferential speed of 6/sec, and the developer holding member 12 is 60 m long.
It rotates at a circumferential speed of m/s. The developer holding member 12 is made of stainless steel (SUS304) with an outer diameter of 32 mm and a thickness of 0.8 mm.
). The surface was subjected to amorphous sandblasting using #600 alundum abrasive grains, and the roughness of the circumferential surface was made 0.8 microns (RZ=0.83).

On the other hand, a sintered ferrite type magnet 14 is fixedly disposed inside the rotating developer holding member 12 , and the N pole, which is the magnetic particle regulating magnetic pole 20 , is connected to the developer holding member 12 with respect to the magnetic blade 15 . The magnetic blade 15, which is set at an angle of 25 degrees from the line connecting the center 0 and the tip of the magnetic blade 15, is made of iron, and its surface is nickel-plated to prevent rust. This magnetic +! L plate 15
The distance between the developer holding member 12 and the surface of the developer holding member 12 was set to 200 microns.

The magnetic particles have a particle size of 10 to 30 microns and a maximum magnetization of 6.
100 g of 0 e mu / g spherical ferrite (manufactured by TDK) was used. Here, it is preferable that the ferrite has a conductivity of 1-4±4±, preferably 1010ΩCl11 or less. On the other hand, as a non-magnetic developer, 100 parts of PoIJ ethylene wax, 10 parts of copper phthalocyanine pigment, and 1 part of negative charge control agent (alkyl saltylated with an average particle diameter of 12 microns and a negative (-) polarity number) are used. 200g of cyan powder (pressure fixing toner) was prepared.Then, the non-magnetic developer and magnetic particles were thoroughly mixed and then placed in the developer supply container 13.''-Developer supply container Within 13 days (
It was observed that the mixture of magnetic developer and magnetic particles was conveyed by the developer holding member 12 under a magnetic field and moved in circulation when the amount of developer decreased.

In the developing device 1 having this configuration, a developing device 1 holding member 1 is provided.
2, the surface of the λ developer holding member 12 has the following properties:
A thin layer approximately 120 microns thick could be formed. When this developer thin layer was charged to Jll+ by the mesh method, it was confirmed that it was uniformly charged at a potential of -7 microtrons/g. A thin non-magnetic layer formed on the developer holding member! The ratio of L developer R to magnetic particles was 2:1 in terms of gravity ratio.

On the surface of the donor body 11 facing the developer holding member 12, there is an electrostatic latent image with a dark area of +600V and a bright area of +150V.
A charge pattern of V was formed, and the distance from the surface of the developer holding member 12 was set to 300 microns and ε9. Then, a frequency of 800 is applied to developer holding member No. 12 by power supply 19.
Hz, peak-to-peak value is 1.4 kV, center value is +
When a voltage of 300 V was applied, it was possible to obtain a high-quality developed image free from uneven development, ghost images, and IF fog. In addition, the developed image on the latent image carrier ll is
In particular, adhesion of magnetic particles was observed in the bright areas.

On the other hand, no magnetic particles were observed on the transfer material after the developed image was transferred by the corona transfer device. This is thought to be due to the fact that the magnetic particles are charged with a polarity opposite to that of the non-magnetic developer.

Next, when spherical iron having a particle diameter of 10 to 30 microns and a maximum magnetization of 200 emu/g was used as the magnetic particles, an example was carried out in the same manner as in the above specific example, and good images were obtained as in the above specific example. Iron particles that were not transferred were collected in the cleaning device.

It is thought that the iron particles are reduced iron and are almost pure iron, and are not transferred during corona transfer due to their conductivity.

Furthermore, as magnetic particles, styrene acrylic resin 10
0 parts and 100 parts of magnetite are kneaded and crushed to obtain a particle size of 10 to 2.
0 micron insulating particles, 100 parts of styrene resin,
10 parts of conductive carbon black and magnetite +-i o
Similar results were obtained using conductive particles obtained by kneading and pulverizing part o.

In either case, if there is a strong magnetic field at the closest point between the latent image carrier 11 and the image holding member 12, the magnetic particles will become brush-like and cause an electrical short circuit between them, which is undesirable.
It is better to make the magnetic field as weak as possible, preferably to eliminate it altogether.

Difference in Color and Gloss] As explained above, according to the present invention, developer agglomeration and
Image formation using a non-magnetic developer is possible without fusion occurring.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an image forming apparatus embodying the present invention; FIG. 2 is a sectional view of a developing device embodying the image forming method according to the present invention; Explanation of symbols: latent image carrier 12: Developer holding member 13: Developer supply container 14: Fixed magnetic field generating means 16: Mixture layer 20: Particle regulating magnetic pole □l

Claims (1)

[Claims] A developer thin layer consisting of a non-magnetic developer and magnetic particles is formed on a developer holding member -1 m, and the developer holding members holding the thin layer are separated by a distance greater than the thickness of the thin layer. The latent image carrier is made to face a latent image carrier, and the latent image on the latent image carrier is developed with a non-magnetic developer and magnetic particles. An image forming method comprising forming a developed image and then transferring only the non-magnetic developer of the developed image onto a transfer material, thereby forming an image of the non-magnetic developer on the transfer material.