JPS5949578B2 - Electrophotographic development method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic developing method and apparatus.

Powder toner is held uniformly on the circumferential surface of a rotatably arranged donor member formed in the shape of a belt or drum, and the electrostatic latent image bearing surface of the latent image carrier is moved around the circumference of the donor member. the latent image bearing member is moved in a fixed direction along the electrostatic latent image bearing surface, and the donor member is rotated to cyclically move the peripheral surface in one direction. A developing method for visualizing an electrostatic latent image is conventionally known as a touchdown developing method.

In the conventionally known touchdown development method, insulating toner is used, and supply of powder toner to the peripheral surface of the donor member and retention of the toner by the donor member are performed electrically. The following problems arose.

An electrostatic latent image can be created by charging a photoconductive latent image carrier and exposing it to light by irradiating a light image or scanning light according to recorded information, or by exposing a dielectric latent image carrier to a multilayer image. The latent image is formed on the latent image carrier by selectively charging it with a stylus, pinch tube, etc. according to the recorded information.

In order to improve the recording efficiency, it is desirable to perform the formation of the electrostatic latent image and the touch-down development at the same time. However, in this case, the formation of the electrostatic latent image, the supply of the powder toner to the donor member, and the holding by the donor member are all performed electrically, so there is a possibility that these may affect each other. For example, electrical changes associated with the formation of an electrostatic latent image can result in uneven toner delivery to the donor member. Furthermore, during development, a developing bias voltage is applied to the developing section, and toner supply is affected by the presence or absence of this developing bias voltage. This causes uneven retention of the donor member, and
As a result, shading occurs in the recorded image obtained. In a conventional touch-down developing device, the donor member is divided into multiple parts in the direction of movement of the peripheral surface, the parts to be divided are insulated from each other, and the electrical state of each part to be divided is adjusted according to the position of the part to be divided. Although the above-mentioned inconveniences have been avoided by switching, the above-mentioned switching requires timing control, which has the disadvantage that the recording apparatus becomes complicated and expensive.

In addition, the electrostatic latent image bearing surface of the latent image bearing member and the peripheral surface of the donor member are close to each other with a gap of about several tens of microns in the developing section, but the size of the gap changes during development. There was a problem in that the electrostatic latent image bearing surface came into direct contact with the toner on the donor member, resulting in uneven image density of the recorded image.

As a measure to solve the above-mentioned problems, a large air gap is created between the peripheral surface of the donor member and the electrostatic latent image bearing surface, but in this case, toner adhesion becomes insufficient, resulting in a good recorded image. is not obtained.

Otherwise, a new problem arises in that the developing bias voltage must be extremely increased. SUMMARY OF THE INVENTION An object of the present invention is to provide a touch-down type electrophotographic developing method and apparatus that solves the above-mentioned drawbacks and problems.

The present invention will be described below with reference to the drawings.

FIG. 1 schematically shows an example of a recording apparatus to which the present invention is applied. In the figure, reference numeral 1 indicates a latent image holding body.
a photoconductive photoreceptor (common electrophotographic photoreceptors and electrostatic recording dielectrics can be used); 2 is a donor member;
Reference numeral 3 indicates a magnet, reference numeral 4 a sleeve made of a non-magnetic material such as aluminum, and reference numeral 5 a toner container containing toner.

The magnet 3 is an elongated rod-shaped body extending perpendicular to the drawing, magnetized in a direction perpendicular to the length direction, and fixed in the inner space of the donor member 2 with one pole facing the toner container 5. There is. Therefore, regardless of the rotation of the donor member 2, the magnet 3 always maintains the same attitude with respect to the device space. Further, reference numeral 6 is a photoreceptor static elimination section, 7 is a cleaning section, 8 is a charging section, 9 is an exposure section, and 10
shows the transfer section in highly diagrammatic form.

Further, reference numeral 11 indicates a transfer paper set to move in the gap between the photoreceptor 1 and the transfer unit 10, and reference numeral 12
Reference numeral 13 indicates a toner charging section disposed close to the circumferential surface of the donor member 2, and reference numeral 13 indicates a toner charging section disposed close to the circumferential surface of the donor member 2 at a distance from the charging section 12. Each figure shows a static eliminator.

A plurality of (four in the illustrated example) magnets 14 are arranged inside the sleeve 4 .

Each of these magnets 14 is a rod-shaped body whose longitudinal direction is perpendicular to the drawing, and is magnetized in the direction perpendicular to the longitudinal direction.
One of the magnetic poles is exposed to the inner peripheral surface of the sleeve 4, and the other is
It is arranged near the central axis of the sleeve 4. The arrangement of magnetic poles is reversed between adjacent ones. These magnets 14 are fixed in the device space, and one of them
The magnet 3 faces the magnet 3. And the magnetic pole of magnet 3,
The magnetic poles of the magnet 14 facing this are selected so as not to repel each other. Now, an outline of image recording by the recording apparatus according to the present invention is as follows.

During recording, the drum-shaped photoreceptor 1 rotates in the direction of the arrow, and its circumferential surface is uniformly charged by the charging section 8, and then exposed to light by the exposure section 9 to remove the electrostatic latent. An image is formed.

The formed electrostatic latent image is visualized by the powder toner T held on the donor member 2 in the developing process section 15 where the donor member 2 and the photoreceptor 1 face each other, and the electrostatic latent image is visualized by the powder toner T held on the donor member 2 and transferred to the photoreceptor 1. A visible image is formed on top. This visible image is then electrostatically transferred onto transfer paper 11 by transfer section 10 . The transferred visible image is fixed onto the transfer paper 11 by a fixing section (not shown), and then discharged to the apparatus. After the visible image has been transferred, the photoreceptor 1 is neutralized by a photoreceptor static eliminator 6, and then residual toner is removed by a photoreceptor cleaner 7. Now, the features of the present invention include a developing method for visualizing an electrostatic latent image on a photoreceptor, and in detail, physical properties of toner T, donor member 2, etc.
The fine structure of the peripheral surface of the donor member and the method of supplying the toner T to the donor member.

Hereinafter, these will be explained in detail based on the example of the apparatus shown in FIG.

Toner-T has an average particle size in the range of 1 to 300 Itm,
More preferably fine particles in the range of 2 to 30 μm,
It constitutes a powdery aggregate.

Hereinafter, this powdery aggregate will also be referred to as a toner, and in particular, when a single fine particle is concerned, it will be referred to as a toner particle.

First of all, the toner used in carrying out the present invention has magnetic properties.

The fact that the toner T is magnetic means that the toner particles are magnetically attracted to each other. The toner particles are given this property by containing powder particles of a magnetically attractable metal, such as magnetite. Second, Toner-T is electrically non-conducting and has a resistivity of 1010 in an electric field of 200V/cfrL.
Ω・? Above, preferably 1012Ω・? It has been prepared to meet the above requirements. The donor member 2 includes a support sleeve 201 made of any material such as aluminum, copper, iron, plastic, rubber, ceramic, glass, etc., and a surface layer 202 formed on the peripheral surface of the support sleeve 201. It consists of

The surface layer 202 is formed by fixing minute protrusions having both conductivity and ferromagnetism to the circumferential surface of the support sleeve 201, and its form is shown in FIGS. 2 to 5. In addition,
As the material of the convex piece, cobalt, nickel, iron, or an alloy containing these as main ingredients is used. In the example shown in FIG. 2, the respective convex pieces D constituting the surface layer 202 are spaced apart from each other, and the surface layer 202 forms fine irregularities.

In the example shown in FIG. 3, the convex pieces D are in close contact with each other. however,
Since the top of the convex piece D is rounded, the surface layer 202 forms fine irregularities. In the example shown in FIG. 4, a non-magnetic material indicated by reference numeral 16 is filled with the top of the convex piece D, which is constructed in the same manner as in the example shown in FIG. 3, left intact.

As the non-magnetic material 16, aluminum, copper, plastic, rubber, ceramic, etc. are used. In the example shown in FIG. 5, the surface of the support sleeve 201 itself is manufactured with a large number of concavities and convexities, and these concave and convex surfaces are made of a substance 17 made of the same material as the convex piece DD and have a uniform thickness. , forming a surface layer 202 consisting of a large number of mountain-shaped unevenness. The unevenness of each surface layer 202 shown in FIGS. 2 to 5 above has a lattice shape.

Further, the forming method includes a mechanical processing method, a chemical corrosion processing method, an electrical surface treatment method, etc., and it is produced by these known techniques. The depth of the concave portion and the interval between the convex portions are manufactured to be in the range of about 1 to 300 μm, more preferably in the range of about 3 to 100 μm. The development process performed using the toner T and donor member 2 having such characteristics is as follows.

1. (Supplying Toner to Sleeve) Toner T is stored in the toner container 5 in an amount sufficient to fill the lower part of the sleeve 4, and the sleeve 4 is rotated in the direction of the arrow.

Toner particles that have non-uniformly adhered to the circumferential surface of the sleeve due to the magnetic attraction of the magnet 14 are scraped off by the blade 18 as the sleeve 4 rotates, resulting in a toner layer with a uniform thickness that is attached to the magnet. 3 and the magnet 14 are opposed to each other. Here, the magnet 3, sleeve 4, magnet 14, etc. are means for supplying toner T to the donor member 2, as described below, and are therefore referred to as toner supply means.

2, (Supplying toner to donor part) Donor member 2 is rotating in the direction of the arrow.

Along with this rotation, when the surface layer 201 passes through the opposing part of the magnet 3 and the magnet 14, the magnetic field is increased due to the action of many minute non-uniform magnetic fields formed in the minute unevenness of the surface layer 201. Toner particles adhering to the sleeve 4 are intensively transferred and adhered to particularly strong convex portions by the magnetic attraction force. (See Figure 2). The coating of toner particles onto the donor member 2 performed in this manner allows the thickness of the coating layer to be
It can be controlled relatively easily by adjusting the surface structure of the donor member, the external magnetic field, the magnetic properties of the toner, the particle size, etc.
For example, under certain conditions, the thickness of the toner coating layer could be macroscopically uniformly set to 4 to 5 toner particles. Further, under other specific conditions, the number of toner particles could be set to 20 to 25 particles. In view of these results, the toner coating on the donor member according to the present invention makes the toner coating layer thinner and macroscopically thinner than other electrical methods or mechanical methods using a blade. can be uniformly adjusted. 3. (Charging of Toner) Next, while passing through the toner charging section 12, the toner that has uniformly covered the surface of the donor member 2 has a polarity opposite to that of the electrostatic latent image formed on the photoreceptor 1. charged.

4. (Development) The toner uniformly charged with a polarity opposite to the polarity of the electrostatic latent image on the photoconductor 1 is applied with an electric attraction force to the electrostatic latent image on the photoconductor in the development process section 15. The electrostatic latent image is made visible by the electrostatic latent image.

Here, the air gap t between the top of the toner layer in the developing section 15 and the circumferential surface of the photoreceptor 1 is maintained at a constant value in the range of several μm to several 100 μm.

This is possible due to the uniform thickness of the toner layer covering the donor member 2. The image visualized in this way on the photoreceptor 1 is transferred to the transfer section 1 as described above.
0 onto the transfer paper 11.

5. (Static charge removal of toner) After passing through the developing process section 15, the toner remaining in the donor member 2 is charge-free when passing through the toner charge removal section 13.
It is prepared for the cyclical charging and developing steps.

The contents described in each section 1 to 5 above are the development process.

Here, the electrophotographic development method according to the present invention will be considered in conjunction with the drawbacks or problems in the prior art.

First, since the present invention uses a magnetic field rather than an electric field to coat the donor member with toner, there is no electrical influence during the development process; , when a bias voltage that assists development is applied to the photoreceptor 1, this has no effect on the toner coating on the donor member, so it has electrical conductivity and ferromagnetism as in the prior art. There is no need to divide the surface portion of the donor member into multiple parts for each process and to electrically insulate each of the divided parts from each other.

Second, the toner coating on the donor member according to the present invention allows the thickness of the toner coating layer to be adjusted to be thinner and macroscopically uniform compared to other electrical methods or mechanical methods using a blade. As a result, the air gap between the electrostatic latent image bearing surface and the electrostatic latent image bearing surface does not vary, thereby solving the problem of uneven image density of the recorded image.

Third, the reproducibility of halftones has been improved.

The reason for this is that according to the present invention, toner T adheres to the convex portions on the surface of the donor member in the form of mountain-like aggregates as shown in FIG. Therefore, of the electrostatic latent image formed on the photoreceptor 1, most of the area from the bottom to the top of the mountain-like aggregate of the toners is transferred to the area where the potential of the latent image is high; This is thought to be because only the toner particles at the top of the mountain-like aggregate are transferred to the area where the image potential is low, and in this way, the amount of toner transfer is controlled by the latent image potential.
Below, specific experimental examples of the recording method according to the present invention will be described. (Experimental Example) An apparatus having the configuration shown in FIG. 1 was used.

As the donor member, one having the configuration shown in Fig. 2 was used,
The support sleeve 201 was made of aluminum, and the surface layer 202 was made of nickel. Also, the air gap t is 5
When recording was performed with the setting at 0 μm, a high-density toner image with no background smear could be obtained on plain paper.

[Brief explanation of the drawing]

FIG. 1 is a front view illustrating an example of a recording device to which the present invention is applied, and FIGS. 2 to 5 are diagrams showing examples of a fine uneven structure on the peripheral surface of a donor member. 1... Photoreceptor (as a latent image carrier), 2...
... Donor member, T ... Toner.

Claims (1)

[Claims] 1. Powder toner is uniformly held on the circumferential surface of a rotatably disposed donor member formed in the shape of a belt or a drum, and the electrostatic latent image of the latent image carrier is supported. a surface close to the peripheral surface of the donor member, the latent image carrier is moved in a fixed direction along the electrostatic latent image bearing surface, and the donor member is rotated to circulate the peripheral surface in one direction. In an electrophotographic development method in which the electrostatic latent image on the latent image carrier is visualized by moving the latent image carrier, a toner supply means is provided on the surface of the donor member to supply a door using magnetic attraction force, and the developing Prior to the process, a donor member made of a material having both electrical conductivity and ferromagnetism at least on the surface and with many fine irregularities is placed in a magnetic field, and a large number of A small non-uniform magnetic field is formed to selectively attach the magnetic but non-conductive toner to the convex portion of the donor member using magnetic attraction, and then the toner attached to the donor member is selectively attached to the convex portion of the donor member. The toner is uniformly charged, and then the toner on the uniformly charged donor member is electrostatically charged in a developing process section configured such that the latent image carrier and the donor member are closely opposed to each other. 1. An electrophotographic development method characterized in that an electrostatic latent image on a latent image carrier is visualized by transferring the electrostatic latent image onto a latent image carrier using electric attraction force. 2. Powder toner is held uniformly on the circumferential surface of a rotatably arranged donor member formed in the shape of a belt or drum, and the electrostatic latent image bearing surface of the latent image bearing member is aligned with the surface of the donor member. The latent image carrier is brought close to the peripheral surface and moved in a fixed direction along the electrostatic latent image bearing surface, and the donor member is rotated to move the peripheral surface cyclically in one direction, so that the latent image carrier is In an electrophotographic development method for visualizing an electrostatic latent image on an image carrier, a donor member is made of a material having both conductivity and ferromagnetism at least on its surface and is provided with a large number of fine irregularities. and a toner supply means for supplying toner to the surface of the donor member using magnetic attraction force.