JPH0192779A - Developing method - Google Patents

Abstract

PURPOSE:To thin a developer layer on a developer carrying body without decreasing the adhesion quantity of a non-magnetic particle and to prevent a magnetic particle from adhering to a photosensitive drum by forming the magnetic particle in a shape of an elliptical body and holding it along a line of magnetic force in a state that a long axis of the magnetic particle is roughly parallel to the surface of the outside periphery of the developer carrying body. CONSTITUTION:A magnetic particle 23 of a developer is formed in a shape of an elliptical body, this magnetic particle 23 is carried on the surface of the outside periphery of a developer carrying body 3 opposed to a developing area 4, in a state that a long axis of the magnetic particle 23 is roughly parallel to the surface of the outside periphery of the developer carrying body 3 and the development is executed. Accordingly, the developer 23 in the developing area 4 is carried in a multi-layer state on the surface of the outside periphery of the developer carrying body 3, and not only the surface of the outside periphery is covered completely but also its layer thickness does not become thick. In such a way, the magnetic particle does not adhere to a latent image holding body, and a non-magnetic particle of a necessary and sufficient quantity moves to a developing area, therefore, an image having a stable and high picture quality is obtained extending over a long period of time.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is used in the technical field of non-contact development,
In particular, the present invention relates to a developing method using a developer that is applicable to Victorian color developing devices.

(Prior Art and Problems) The developing sleeve rotates and has a stationary magnetic field generating means inside thereof, and is formed so that the developer is supported on the outer circumferential surface by the magnetic force of the developing sleeve. Then, the magnetic field generating means is positioned so that the magnetic poles of the magnetic field generating means are located in the narrowest area where the developing sleeve is formed facing the photosensitive drum, thereby making the above area a developing area. The lines of magnetic force on the developing sleeve in the developing area are made parallel to the outer peripheral surface of the developing sleeve, and the parallel magnetic lines of force support magnetic particles in a floating state to form a developer layer. The gap (development gap) between the photosensitive drum and the development sleeve in the development area is set to be larger than the thickness of the developer layer.

An alternating electric field is formed in this development gap to restrain the magnetic particles on the outer circumferential surface of the developing sleeve, while causing the particles on the developing side attached and held on the surface of the magnetic particles to fly to the image area and non-image area of the photosensitive drum. Development with the above-mentioned developer was performed by alternately repeating the process and the process of returning excess particles on the developing side to the developing sleeve.

However, in the above-mentioned developer and the developing method using this developer, when the developer is made of a mixture of ordinary spherical magnetic particles and non-magnetic particles, it is difficult to reduce the thickness of the developer layer. The gap must be wide. In this case, there was a problem in that the gap between the electrodes became wide, making it impossible to improve the so-called edge effect.

If the developer layer is simply made thinner in order to reduce this edge effect, a problem arises in that the amount of developer transported is insufficient and the overall density is lowered. Further, since the distance between the regulating member that regulates the layer thickness and the outer circumferential surface of the developing sleeve becomes extremely narrow due to the thinning of the layer, a problem arises in that developer aggregation occurs and white streaks occur. This phenomenon has become a serious problem not only in black and white development, but also in color development, particularly in high-quality development aimed at Victorian color.

Therefore, the particle size of the magnetic particles of the developer is, for example, about several times the particle size of the non-magnetic particles, in other words, 21) to 3
A method has been proposed in which the diameter is reduced to 0.0 l and the developer layer is made thinner to perform development.

However, with this developer and the developing method using this developer, a new problem arises because the particle size of the magnetic particles is small. That is, the magnetic particles tend to be more strongly attracted by the electric field on the photosensitive drum side than by the lines of magnetic force on the developing sleeve side, and thus move toward the photosensitive drum. For this reason, magnetic particles tend to adhere to the photosensitive drum, and if development is continued for a long period of time, the amount of magnetic particles in the developing device decreases significantly, and the harmonious mixing ratio of magnetic particles and non-magnetic particles is disrupted, resulting in so-called land force problems. may occur. Further, since the magnetic particles attached to the photosensitive drum must be removed by a cleaning device, problems such as damage to the photosensitive drum occur.

(Means for Solving the Problems) The present invention solves the above-mentioned problems, and its purpose is to thin the developer layer on the developer carrier without reducing the amount of non-magnetic particles attached. It is an object of the present invention to provide a developing method that makes it possible to prevent strong magnetic particles from adhering to a photosensitive drum and to obtain high-quality images over a long period of time.

In order to achieve the above object, the present invention comprises: a latent image holding member; and a developer carrying member which has a stationary magnetic field generating means inside and carries a developer on its outer peripheral surface by the magnetic force of the magnetic field generating means. The developer carrier is disposed close to the latent image carrier, and the proximate portion is positioned between two adjacent different magnetic poles of the magnetic field generating means to form a development area there, and the magnetic particles and A developer mixed with non-magnetic particles is supported on the outer circumferential surface of the developer carrier by attaching the non-magnetic particles to the surface of the magnetic particles held on the developer carrier by the magnetic force. By applying a bias voltage between the latent image carrier and the developer carrier,
In a method of developing by flying non-magnetic particles onto a latent image carrier.

The magnetic particles are formed into an ellipsoidal shape, and are held along the lines of magnetic force with the long axis of the magnetic particles substantially parallel to the outer circumferential surface of the developer carrier.

It is made up of.

(Embodiment) Hereinafter, an embodiment of the present invention will be described based on FIGS. 1 and 2 of the accompanying drawings.

FIG. 2 shows a general configuration of the entire developing device used in this embodiment. This developing device includes a latent image holding body 1 (
A photosensitive drum (hereinafter referred to as a photosensitive drum) is installed so as to be rotatable in the direction of arrow B. The photosensitive drum 1 includes a back electrode 11 and an electrostatic latent image holder 12, and the electrostatic latent image holder 12 is formed of either an insulating layer or an electrophotographic photosensitive layer. A developer carrier 2 (hereinafter referred to as a developing sleeve) is installed in close proximity to the photosensitive drum 1 so as to be rotatable in the direction of the arrow. Pot ■, preferably 300
〜SOO#L■ Nishishido. The developing sleeve 2 is connected to the container 1
A developing area 4 is formed in the vicinity of the photosensitive drum 1, and a developing area 4 is provided in the opening 14 of the photosensitive drum 1 so as to be close to the photosensitive drum 1 side. It is equipped with a multipolar magnet 3 (hereinafter referred to as magnet).

The magnet 3 has two pairs of magnetic poles: magnetic poles N+, Sl and magnetic poles N,, S, and the center angle θ between the magnetic poles N,, S□ is approximately 4.
5''≦0≦145'. A bias voltage in which the AC power source 6 is added to the DC power source 5 is applied between the developing sleeve 2 and the back electrode 11.

A partition plate 1 having an opening 16 is provided in the middle of the container 13.
5 is provided, and the upper part thereof is used as a stock space for non-magnetic particles T (hereinafter referred to as toner). A toner supply roller 17 having an uneven surface faces the opening 16 of the partition plate 15 . The toner supply roller 17 is configured to be slowly rotated in the direction indicated by the arrow by rotation of a drive gear (not shown) of the developing sleeve 2 that meshes with a drive gear (not shown) of the photosensitive drum l. One end of the elastic member 18 is brought into contact with the lower part of the toner supply roller 17 . The other end of this elastic member 18 is attached to the right side of the partition plate 15 here, and the toner T accumulated in the space above the partition plate 15 is formed below the partition plate 15 by vibration caused by the rotation of the toner supply roller 17. It is set so that it is dropped little by little into the developing chamber 19. Therefore, the container 13
is a bifurcated fork forming a hopper for the developer 7, and in the container 13, there is a regulation for regulating the layer thickness of the developer 7 facing the developing sleeve 2 at a position between the magnetic poles N and S1. A member 20 is provided. The regulating member 20 is made of a non-magnetic material, and the distal end of the regulating member 20 is placed at a distance of approximately 100 to 550 ru, preferably 150 to 450 ru, from the outer peripheral surface of the developing sleeve 2. This regulating member 20 has an AC power supply 6 to the DC power supply 5.
A bias voltage that is superimposed is applied to the developing sleeve 2, so that it is electrically at the same potential as the developing sleeve 2. This regulating member 20
A leveling plate 22 is installed through a mounting member 21. The leveling plate 22 is made of an elastic member such as mylar or urethane rubber, and is formed to uniformize the developer 7 having a regulated layer thickness. Note that the leveling plate 22 can also be omitted.

On the other hand, the developer 7 contains magnetic particles M (hereinafter referred to as carrier).
It is formed by mixing and toner T. The carrier M is formed into an ellipsoid shape, and the average length of the short axis is approximately equal to or less than the average length of the long axis. For example, the short axis length is about 3
If it is 0 liters or more (preferably about 40 to 60 JJ, 2), the length of the major axis will be about 901L or more, which is three times that length. This carrier M contains, for example, 75% magnetic powder of magnetite (Fez04) in a resin whose main component is styrene-acrylic-aminoacrylic copolymer resin.
The above-mentioned ellipsoidal shape can be formed by kneading it, pulverizing it, suspending it in hot air, and colliding it against a cooled metal or the like. Alternatively, a charge control agent such as a pigment or dye may be mixed into the resin so that the toner T has a predetermined polarity and charge amount.

The toner T is formed as particles having a volume average particle size of about 51 Lm, for example, mainly composed of a thermoplastic resin (polystyrene), and is set to be negatively charged with respect to the carrier M.

The number average particle diameter DT of the toner T is set within the range of D7≦D and ≦30D with respect to the number average particle diameter D2 of the carrier M so that a stable high-quality image can be obtained. There is.

Further, the mixing ratio of toner T and carrier M is, for example, 10wt.
It can be selected within a wide range of 1 to 40 wt$, and is set to facilitate the control of toner density and to obtain images with high developed density without blurring.

After the toner T falls from the upper part of the container 13 into the developing chamber 19, as the developing sleeve 2 rotates in the direction of the arrow A, the toner T moves in the direction of the arrow C, is mixed with the carrier M, and is mixed with the developer 7.
is formed. The toner T adheres to the surface of the carrier M due to the electrostatic force generated by friction during this mixing.

Next, a developing method using the above-mentioned developer 7 will be described.

The carrier M to which the toner T has adhered is moved to the magnetic pole S2. It is supported on the outer circumferential surface of the developing sleeve 2 by the lines of magnetic force acting between N2 and transported to the developing area 4.

When the carrier M has the toner T attached thereto, as shown in FIG.
It is supported by a plurality of lines of magnetic force 23 between St. In that case, the ellipsoidal carrier M has its long axis or the magnetic field line 23
The child begins to take a sleeping position along the lines.

Even if the carrier M supported in this way has a predetermined mass and forms the developer layer 7 in a multi-layered state, the layer becomes thin, and as a result, the carrier M moves onto the developing sleeve 2 and forms the magnetic field lines 23. Even if it is not strongly restrained by the photosensitive drum l side, it is not affected much by the electric field on the photosensitive drum l side and does not fly toward the photosensitive drum l side. Furthermore, since the carrier M has an ellipsoidal shape, its surface area can be secured to a predetermined value, and a sufficient amount of toner T can be deposited on the carrier M.

Thus, the outer peripheral surface of the developing sleeve 2 in the developing area 4 is completely covered with the S layer and a sufficient amount of the developer 7. For this reason, unnecessary toner T is not attracted to the photosensitive tram l side and is not developed, so that no ground force blur occurs.

Further, since a sufficient amount of toner T is carried, so-called solid black density is good.

(Effects of the Invention) The present invention forms magnetic particles of a developer into an ellipsoidal shape, and places the magnetic particles on the outer circumferential surface of a developer carrier facing the development area so that the long axis of the magnetic particles is aligned with the developer carrier. Since we decided to develop the film by supporting it almost parallel to the outer circumferential surface of the body,
The developer in the development area is distributed on the outer peripheral surface of the developer carrier.
It is supported in a multi-layered (laminated) state, and not only the outer circumferential surface is completely covered, but the layer thickness does not increase.

As a result, magnetic particles do not adhere to the latent image carrier, and only a necessary and sufficient amount of non-magnetic particles move to the development area, so that stable, high-quality images can be obtained over a long period of time. In particular, with Victorian color, high quality images can be obtained and the reliability of the developing device can be improved.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing a developing section showing a developing method as an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view showing the essential structure of a developing device having the developing section shown in FIG. 1-----...Latent image holder (photosensitive drum) 2...
...Developer carrier (development sleeve) 7...
...Developer S...Carrier T...Toner patent applicant Canon Co., Ltd. Agent Patent attorney Toru Fujioka Figure 1

Claims (1)

[Scope of Claims] A latent image holding member, a developer carrying member having a magnetic field generating means stationary therein and carrying a developer on its outer circumferential surface by the magnetic force of the magnetic field generating means, A carrier is disposed close to the latent image carrier, and the proximate portion is positioned between two adjacent different magnetic poles of the magnetic field generating means to form a development region there, and to form a development area therein, to form a development area where magnetic particles and non-magnetic particles are separated. The mixed developer is supported on the outer peripheral surface of the developer carrier by attaching the non-magnetic particles to the surface of the magnetic particles held on the developer carrier by the magnetic force, thereby retaining the latent image. Due to the bias voltage between the body and the developer carrier,
In a method of developing by flying non-magnetic particles onto a latent image carrier, the magnetic particles are formed into an ellipsoidal shape, and lines of magnetic force are formed in a state where the long axis of the magnetic particles is substantially parallel to the outer peripheral surface of the developer carrier. A developing method characterized by: being maintained along.