JPS6088974A - Developing device - Google Patents

Abstract

PURPOSE:To coat a developer carrier with a single-component nonmagnetic developer uniformly while triboelectrifying sufficiently by providing numbers of specific magnetic particles which are chained in a brush shape while restrained by a magnetic field and circulated and stirred. CONSTITUTION:A developer container 2 contains toner 3 and magnetic particles 6 are put in the container 2 closely to a magnet 4; and the magnetic particles 6 covered with resin containing conductive particulates gather to form a brush at the upstream side of the specifying blade 5 by the magnetic field of the magnet 4. The brush of the magnetic particles is circulated near the specifying blade 5 accoring to the rotation of a sleeve 1. This circulation mixes the toner 3 with the brush and circulates and stirs them, so that the toner 3 and magnetic particle brush are triboelectrified. The toner 3 sticking to the brush 6 is applied uniformly over the sleeve 1 and conveyed according to the rotation of the sleeve. The magnetic particles 6 forming the brush, on the other hand, are given restrain by the magnetic field of the magnet 4 larger than the conveyance force depending upon the electrostatic sticking force and mechanical friction force of the sleeve 1 and magnetic particles 6, so the particles are applied over the sleeve 1 together with the toner 3 and stay in the container 2 without being conveyed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an image forming apparatus using a powder developer, such as an electrophotographic copying machine, in which a developer, particularly a -component, is placed on a developer carrier that supplies the developer to a latent image carrier. The present invention relates to a developing device that applies a non-magnetic developer.

In an image forming apparatus using a powder developer, for example, an electrophotographic copying machine, a latent image carrier (photosensitive drum) 314rl&J
l17r4+7. L, +! ,! ml1b+P-Work day no 1
7+, J--"/-JirAls&, to apply the developer to an endlessly rotating developer carrier (developing roller) disposed in close proximity to the surface in order to supply the developer to the surface. will be carried out.

Conventionally, a development method in which a magnetic toner is used all around as a component developer has been put into practical use, but the fixing performance when thermally fixing a toner image transferred to a developer transfer paper is poor. Because it contains , it has disadvantages such as poor color toner.

For this reason, a developing method using non-magnetic toner has been considered, and in order to apply the toner to the developer carrier, the developer is applied to the developer carrier, which is made of a cylindrical brush made of soft beaver hair. A method in which the developer is applied by adhesion, and a method in which the developer is applied using a doctor blade or the like to a developing roller whose surface is made of a fiber brush such as Velpet have been proposed.

However, if an elastic blade is used as a tractor blade for the above-mentioned fiber brush, it is possible to control the amount of toner, but uniform application is not achieved, and the fiber brush on the developing roller still simply rubs. However, since the toner present between the fibers of the brush is not triboelectrically charged, ghosts and the like are likely to occur.

An object of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods and to provide a new developing device capable of uniformly applying a -component non-magnetic developer to a developer carrier while imparting sufficient triboelectric charging. There is.

The developing device of the present invention includes a container containing toner, a toner carrier (preferably a non-magnetic toner carrier) that moves (preferably moves endlessly) in contact with the toner, and the toner carrier 3Ji Bt agitation which is in contact with the toner in the container, is chained in a brush shape by being restrained by the magnetic field generated by the magnetic field generating means, and is circulated by the movement of the toner carrier. Equipped with a large number of moving magnetic particles,
The symptom is that each of the magnetic particles is made of resin containing conductive fine powder.

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

In Fig. 41, numeral 1 denotes a developing sleeve as a developer carrier, which is made of a non-magnetic material and rotates in the direction of arrow a. A developer container 2 has an open bottom and partially surrounds the developing sleeve 1, and a developer (toner) 3 is stored therein. Reference numeral 4 indicates a stationary magnet disposed within the developing sleeve 1, and reference numeral 5 indicates a regulating blade made of a magnetic material screwed onto one side of the container 2. Magnetic particles 6 are placed in the container 2 near the magnet 4.
Due to the magnetic field, the magnetic particles 6 gather on the upstream side of the regulating blade 5 to form a brush. This magnetic particle brush moves in a circular motion around regulation grade 5 due to the rotation of the sleeve 1, and due to this circular motion, the toner 3 is mixed with the brush,
The toner 3 and the magnetic particle brush are triboelectrically charged by the circulation and agitation. The toner 3 adhering to the brush 6 is uniformly applied onto the sleeve 1 by the reflection force with the sleeve 1, and is conveyed through the gap below the regulating blade 5 as the sleeve rotates. On the other hand, the magnetic particles 6 constituting the brush are set so that the binding force due to the magnetic field of the Fugunet 4 is greater than the conveying force that depends on the electrostatic adhesion force and mechanical friction between the sleeve 1 and the magnetic particles 6. Therefore, the toner remains in the container 2 without being applied onto the sleeve 1 together with the toner 3 and transported.

As is well known, the toner conveyed to the wall cloth adheres to a photosensitive drum (not shown) closely facing the developing sleeve 1 for development and is consumed. However, if there is enough toner on the brush part in the container 2, the ratio of toner particles to magnetic particles in the brush part will always be a constant value, so as the toner is used and consumed for development, it will automatically Since the toner 3 is supplied to the brush portion at the same time, it is possible to always apply a constant amount of toner.

In order to stably perform the action based on the above-described magnetic particle brush restrained on the sleeve and circulated, there are some desirable conditions, which will be explained in more detail below.

In order to stably restrain the brush of magnetic particles near the regulating blade 5 and to make it circulate, the regulating blade 5 must be
may be a non-magnetic material, but is preferably a magnetic material.

In addition, as shown in FIG. 1, the magnetic field generating means has an angle of 0
Write only one item. A value of 0 means that when there is no magnetic material such as magnetic particles 6 or magnetic regulating blade 5 near the magnet 4, the magnetic flux density due to the magnet 4 at the position facing the regulating blade on the surface of the sleeve 7 is the maximum magnetic flux on the sleeve surface. density(
It is best to select a position that is 30 to 90% of the magnetic pole opposing position.

When the regulation blade 5 and the digit 1 convex 113111 of the magnet 4 are selected as the values listed below, the magnetic particles 6 in the blade 5 part
The shape of the brush is as shown in Fig. 282(b), and most of the lines of magnetic force from the magnet 4 (indicated by broken lines) exist on the upstream side of the regulating blade 5, so the magnetic particles 6 are restrained there. .

If the pole position of the magnet is on the downstream side of the regulating blade 5 as shown in Figure 2 (,), the magnetic particles will not be restrained, and the circulating movement of the magnetic particle brush on the downstream side of the regulating blade will also be difficult to occur. Become.

Furthermore, even if the positional relationship between the magnet 4 and the regulating blade 5 is as shown in FIG. He is restrained in a protruding state. Although it is not impossible to apply toner under such conditions, streaks are likely to occur in the toner coating because the magnetic particles on the downstream side of the regulating blade 5 cannot circulate.

Note that the magnetic field for fully restraining the magnetic particles is preferably 400 Gauss or more at the position where the magnetic poles face each other on the sleeve surface (the maximum position of the magnetic flux density distribution).

It is desirable that the magnetic particles have an average particle size of 1 to 30 times the average particle size of the toner particles. If the particle size of the magnetic particles is significantly smaller than that of the toner particles, the toner and magnetic particles tend to adhere to each other and be coated onto the sleeve.On the other hand, if the magnetic particles are significantly larger than the toner particles, the toner may enter the brush. As the amount of toner particles decreases, stirring of the toner and magnetic particles at the brush portion becomes poor, and streaks are likely to occur in the resulting toner coating.

As the magnetic particles 6, those widely known as carriers in two-component development methods, such as iron balls and ferrite particles, can be used.

3=The surface of the magnetic particles 6 in the invention is assumed to be insulating to some extent, so that they have a slight electrostatic force on the surface of the sleeve, and are caused to adhere to the surface by this force. However, if the magnetic particles are completely conductive, the magnetic particles near the sleeve surface cannot push away the magnetic particles in the upper layer of the sleeve, making it difficult for the magnetic particles to circulate in the regulating member portion. Various methods can be used to make the surface of magnetic particles insulating, but among them, a method of coating the particles with resin is common and effective. However, when such insulated magnetic particles are used, image density may decrease under low humidity conditions due to charge accumulation in the magnetic particles. Therefore, in the present invention, in order to eliminate excessive charging of the toner under low humidity, image density is stabilized by adding an appropriate amount of conductive fine powder to the resin. however,
If a large amount of conductive fine powder is added, the conductivity of the magnetic particles on the surface of the resin cord will be too high, which will impede the circulation movement of the magnetic particles in the regulation blade 5'fA under high humidity and humidity. Therefore, the conductive fine powder is 0.01% to 50%,
Preferably, it is added in an amount of 0.01% to 30%.

As for the amount of magnetic particles, it is desirable that the amount be sufficient to be held by the magnet in the regulating blade portion and to generate a circular movement. If the number of piles is small, the circulating movement of the magnetic particles will not occur, and the magnetic particles will remain stationary and rub against the sleeve surface, making it easy for the toner coating to become streaky and uneven.

Further, it is preferable that the sleeve surface has a surface roughness of about 0.5 to 5 .mu.m so that the toner can easily contact and be transported.

The distance between the sleeve 1 and the regulating blade 5, marked as d in Figure 1, is 0.9 to 20 times the diameter of the magnetic particles 6.
It is desirable to be in the twice range. If this distance is less than 0.9 times the magnetic particle diameter, the magnetic particles will easily get stuck between the IJ-sphere and the regulation blade, and if it is significantly larger than 20 times, the magnetic particles will not be retained. I can't.

As the nuclide resin of the magnetic particles 6 in the present invention, many kinds including known materials can be used. Typical examples are ζ fluororesin, various fluoropolymers, melanin resin,
Xylene epoxy resin, polyphenylene oxide resin, silicone resin, polyester resin, polyamide resin, styrene-vinyl chloride copolymer resin, styrene-methyl methacrylate copolymer resin, styrene-methacrylic acid-
Butyl copolymerized filtrate, styrene-butatsuene copolymerized resin, etc. are used.

As the conductive fine powder to be added to the coating resin of the magnetic particles in the present invention, a large number of materials including known materials can be used. Metal oxide fine powder, conductive carbon bra from various companies,
Coordination polymers including carbon fiber or j+:il 1 nickel, cobalt, etc. may be used.

The method for producing the #L agricultural magnetic particles in the present invention is not limited to the following method, but it is possible to use a solvent (toluene, xylene, MEK,
), etc., and magnetic particles are mixed with this dispersion liquid.
Dryer Method % Magnetic particles may be coated, dried, granulated, and sieved by an EL mobilization bed method or the like, and the magnetic particles may be taken out as one magnetic particle that does not pass through.

A specific embodiment of the present invention will be explained with reference to FIG.

In Fig. 3, 2 is a developing sleeve made of SUS 304 with a diameter of 30 m, and the entire surface is cine-shaped sandblasted with ≠ 600 alundum abrasive grains to obtain a surface roughness f Rz:
It is set to 0.8 μm. A ferrite sintered type roll-shaped magnet 4 is contained within this developing sleeve l.
As shown in the figure, the magnetic pole position is fixed. The angle θ formed between the S pole position of this magnet and the regulating blade 5 was set to 20°. The regulating blade 5 is made of iron and has a nickel plated surface. The maximum magnetic flux on the sleeve surface of the magnet is 800 Gauss, and the regulating blade 5
At the position , the pressure is 600 Gauss when the regulating blade is removed. As magnetic particles 6, iron powder with an average particle size of 90 μm, styrene methyl methacrylate copolymer, and iron powder kO,05w were used.
Using about 1009, which was mixed with t%, three? Distance d between "l" and regulating blade 5 (i7300μm
The toner was coated as a.

Toner 3 was a negative cyan toner in which 3 parts of a copper phthalocyanine pigment and 5 parts of a negative charge control agent were internally added to 100 parts of a polyester resin, and 200 g of it was supplied into the container 2.

When sleeve ■ was rotated in this state, sleeve 1
As the toner rotated to 0, the toner was stirred and circulated together with the magnetic particle brush, and a uniform toner coating layer of about 120 .mu.m and a 117 charge of 17 .mu.C/g as measured by the blow-off method was obtained on the sleeve.

In FIG. 3, reference numeral 9 is a polyethylene terephthalate sheet with a J wrinkle of 200 μm, and the toner coating layer obtained on the sleeve 1 in this manner prevents the toner from falling and spilling from this part. In order to subject the photosensitive drum 10 to the developing action, the photosensitive drum 10, which has an electrostatic latent image of -500V in the dark part and -50V in the light part, is grounded with a distance of 300 μm between the sleeve 1 and the sleeve 1. Connect power supply 7 and set frequency to 800
Hz, peak-to-peak value 1.6 kV, center value -
When a voltage of 200 V was applied, a good developed image without ghost fog was obtained, and after copying about 3 QOO sheets, there was no change in the image fa degree until the toner was almost consumed, and the magnetic particles 6 remained on the photosensitive drum. It was not even supplied to the government.

As explained above, according to the present invention, it is possible to use a one-component non-magnetic toner without using a magnetic toner that has an adverse effect on heat fixability or image color, and moreover, the toner can be transferred to a developer carrier ( It is possible to uniformly apply and convey a sufficient amount of frictional charge to the developing sleeve (developing sleeve) at a constant supply amount.

Furthermore, since the magnetic particles used in the present invention are coated with a moderately insulating coating, they adhere to the sleeve surface with a slight electrostatic force, improving circulation and toner application effects. , there is no excessive charging under low humidity (image density can be stabilized).

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of embroidery of the present invention, Fig. 2(a)
, (b) is the gift FA of its action, i q 1IX
l rA・t u mark y 1lSl showing a specific example
01... Developing sleeve 2... Toner container 3... Toner 4... Magnet 5... Regulating blade 6... Magnetic particles 9... Dropout prevention sheet IO... photosensitive drum. I 桔゛1(- Tadashi Kishida, (,1U: Figure 3)

Claims (1)

[Claims] A container containing toner, a toner carrier that moves in contact with the toner, a magnetic field generating means disposed inside the toner carrier, and a magnetic field generating means that is in contact with the toner in the accumulator and is in contact with the magnetic field generated by the magnetic field generating means. A large number of magnetic particles are bound and chained in a brush-like manner and perform a circular agitation motion due to the movement of the toner carrier, each of the magnetic particles being coated with a resin containing conductive fine powder. A developing device characterized by: