JPH0519152B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a toner coating method for developing an electrostatic latent image with a toner and magnetic particles for toner coating.

Conventionally, various devices have been proposed and put into practical use as dry one-component developing devices. However, in any of the development methods, it is extremely difficult to form a thin layer of dry one-component developer, and for this reason, a developing device has been constructed by forming a relatively thick layer. However, as improvements in the clarity, resolution, etc. of developed images are currently being sought, it is essential to develop a method for forming a thin layer of a dry one-component developer and an apparatus therefor.

As a method of forming a thin layer of a conventionally known dry type one-component developer, Japanese Patent 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. Magnetic developers must have a magnetic material added to them in order to have magnetism, which causes poor fixing properties when heat fixing the developed image transferred to transfer paper, and adding magnetic material to the developer itself. There are problems such as poor color reproduction during color reproduction.

For this reason, as a method for forming a thin layer of non-magnetic developer,
Proposed methods include using a cylindrical brush made of soft beaver hair to apply the developer, and applying the developer to a developing roller with a surface made of fibers such as velvet using a doctor blade. has been done. However, when an elastic blade is used as a doctor blade for the above fiber brush,
Although it is possible to control the amount of developer, uniform application is not achieved, and the developer is simply rubbed against the fiber brush on the developing roller, and no triboelectric charge is imparted to the developer present between the fibers of the brush. Therefore, there was a problem that ghosts and the like were likely to occur. Furthermore, since the device includes a non-magnetic developer, it is difficult to prevent the developer from leaking from the device.

The present invention eliminates the problems of the conventional method described above, and provides a new toner application method in which the developer is formed as a uniform thin layer on the surface of a developer holding member, and is applied with sufficient frictional electrification. It is an object. A further object of the present invention is to prevent the developer from leaking out of the developing device.

Specifically, the present invention provides a developer container that stores non-magnetic toner and magnetic particles for toner application, a toner carrier that conveys the non-magnetic toner to a latent image carrier, and a toner outlet of the developer container. A toner coating method in which a thin layer of non-magnetic toner is formed on the toner carrier by disposing a magnet forming a magnetic brush made of toner coating magnetic particles in contact with the toner carrier on the upstream side of the toner carrier. The present invention relates to a toner application method characterized in that the fluidity of magnetic particles is 10 to 50 sec/50 g.

Furthermore, the present invention provides a developer container that stores non-magnetic toner and magnetic particles for toner application, a toner carrier that conveys the non-magnetic toner to a latent image carrier, and a toner outlet of the developer container on the upstream side of the toner outlet. Magnetic particles for toner application used in a toner application method in which a thin layer of non-magnetic toner is formed on the toner carrier by disposing a magnet forming a magnetic brush of magnetic particles for toner application in contact with the toner carrier. In,
The fluidity of the magnetic particles for toner application is 10 to 50 seconds/
The present invention relates to magnetic particles for toner application, characterized in that the weight is 50 g.

The latent image carrier used in the present invention is a drum-shaped or belt-shaped member having a photoreceptor or an insulating layer, and the magnetic poles are magnetized with magnetic poles of the same polarity or different polarity in the axial direction of a magnetic roller. Alternatively, a plurality of rod-shaped magnets bonded onto a fixed support member may be used. Furthermore, as the rotating developer holding member, it is possible to use a sleeve made of non-magnetic metal such as aluminum, copper, stainless steel, brass, etc. or a synthetic resin material, or an endless belt made of resin or metal, whose circumferential surface is used to convey the toner. A roughened surface or an uneven pattern may be provided in order to improve the electrostatic properties and charging characteristics. In addition, as a regulating member provided on the outlet side of the developer container as necessary,
A blade plate or wall made of a magnetic material such as iron or a non-magnetic material such as aluminum, copper, or resin may be used.

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

FIG. 1 shows a sectional view of a developing device for explaining the developing principle to which the coating method of the present invention is applied.

In the figure, reference numeral 1 denotes an electrophotographic photosensitive drum, which holds a latent image formed by a latent image forming means (not shown), and rotates in the direction of arrow a to pass through a developing position shown in the drawing. A non-magnetic sleeve 2, which is a toner carrier that carries toner, faces the photosensitive drum 1 with a predetermined gap maintained therebetween, and this sleeve 2 rotates in the direction of arrow b. A container 3 made of a non-magnetic material such as resin or aluminum is located above the sleeve 2 and stores a mixture of toner 4 and magnetic particles 5. A magnetic blade 6 is located downstream of the container 3 in the rotational direction of the sleeve. is screwed on.

On the other hand, the sleeve 2 for this magnetic blade 6
A magnet 7 is provided on the opposite side. The installation position of this magnet is determined by the position of the magnetic pole and the magnetic blade 6.
In fact, the effect of the magnetic field created by providing a magnetic pole slightly upstream of the position of the magnetic blade 6 makes it even better in terms of preventing magnetic particles from flowing out and uniformly applying toner. Get results.

In the above configuration, the magnetic particles 5 in the container 3 are
A magnetic brush 8 is formed by the magnetic field generated between the S pole of the magnet 7 and the magnetic blade 6. As the sleeve 2 rotates, the magnetic brush 8
The magnetic particles and toner are stirred and mixed while maintaining the magnetic particles and toner. In this state, on the magnetic blade side of the container 3, due to the presence of the blade 6, the mixture of magnetic particles and toner is prevented from moving by the blade, rises, and circulates in the direction of arrow c.

As a result, the toner is triboelectrically charged by the sleeve 2 or the magnetic particles by mixing with the magnetic particles. The charged toner is uniformly and thinly applied to the surface of the sleeve 2 by a mirror force by a magnetic brush 8 formed near the magnetic blade 6, and reaches a position facing the photoreceptor drum.

By the way, the magnetic particles 5 constituting the magnetic brush 8
By setting the restraining force due to the magnetic field of the magnet 7 to be larger than the conveying force caused by the frictional force,
It does not flow onto the sleeve 2. If there is toner within the area of the magnetic brush 8, the ratio of the magnetic particles of the magnetic brush 8 to this toner remains approximately constant as the sleeve 2 rotates. Thereby, even if the toner on the sleeve is consumed during development, toner is automatically supplied to the area of the magnetic brush 8. Therefore, it is possible to always supply and apply a constant amount of toner onto the sleeve 2.

As is clear from the above description, magnetic particles are particularly important as components in the present invention. The above-mentioned magnetic particles perform the function that magnetic particles had as a carrier material used in two-component developers, which were mixed with the toner in a much larger amount than the toner. Rather than the function of controlling the amount of charge, a magnetic brush must be formed in a system where a large amount of toner exists, apply the toner onto the toner carrier, and control the amount. At the same time, it must also have the function of supplying toner while circulating, and furthermore, it is not preferable for the magnetic particles to pass through the regulating member. In order to fulfill these functions, it is necessary to have an appropriate restraining force generated by the magnetic field, and also to exhibit appropriate circulation, and the brush condition of the formed magnetic brush must be such that it enables uniform application. It must have appropriate hardness and density. For example, relatively sparse brushes tend to cause poorly regulated streaks on the toner carrier, and conversely, dense brushes tend to make the coating layer on the holding member extremely thin. is also not desirable. Furthermore, for example, if the circulation is too good, the coated layer becomes thick and fogging occurs on the image, and if the circulation is poor, ghosts are likely to occur, and various other disadvantages may occur.

The present inventors conducted various studies to ensure that the magnetic particles used in the present invention satisfy the various functions required, and as a result, they found that the fluidity of the magnetic particles has a large influence. For example, if the fluidity of the magnetic particles is poor, the circulation of the brush will be poor, resulting in disadvantages such as the occurrence of ghosts or a decrease in density due to poor application amount (in some cases, some images may come off as white). If the fluidity of the brush is too good, problems such as fogging or leakage of magnetic particles passing through the regulating member may occur due to the circulation of the brush being too fast.
Therefore, there is a preferable range for the fluidity of magnetic particles. The fluidity of the magnetic particles can be determined, for example, by measuring the fluidity as specified in JIS Z-2502.

In the present invention, measurements were performed using a powder rheometer manufactured by the Institute of Production Development Science, according to the operating method specified in JIS Z-2502, and the flow rate was 10.
Magnetic particles exhibiting a rate of ~50 sec/50 g can be preferably used, and a range of 10~40 sec/50 g is more preferred. (The correction coefficient for correcting variations between models was set to 1.035 after measuring a standard sample specified by the manufacturer.) The magnetic particles for toner application used in the present invention include, for example, surface oxidized or unoxidized iron, nickel, etc. , cobalt, manganese, chromium, rare earth metals, and alloys or oxides thereof, and the surface thereof may be coated with a resin or a suitable treatment agent. Moreover, there are no special restrictions on the manufacturing method.

On the other hand, as the binder resin of the toner used in the present invention, monopolymers of styrene and its substituted products such as polystyrene, polyP-chlorostyrene, and polyvinyltoluene; styrene-P-chlorostyrene copolymers, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer,
Styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-acrylic-aminoacrylic copolymer, styrene-amino Acrylic copolymer, styrene-alpha chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinylethyl ether copolymer,
Styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer, etc. Styrenic copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene,
Polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin,
Aromatic petroleum resins, chlorinated paraffin, paraffin wax, etc. can be used alone or in combination.

Any suitable pigment or dye can be used as a colorant in the toner. For example, carbon black, iron black, phthalocyanine blue, ultramarine blue,
There are known dyes and pigments such as quinacridone and benzidine yellow.

In addition, as a charge control agent, amino compounds, quaternary ammonium compounds, organic dyes, especially basic dyes and their salts, benzyldimethyl-hexadecyl ammonium chloride, decyl-trimethylammonium chloride, nigrosine base, nigrosine hydrochloride, safranin γ and Crystal violet, metal-containing dyes, salicylic acid metal-containing compounds, etc. may be added.

The toner structure described above may be used in a developer produced by a commonly used mixing-pulverization method, or may be used as a wall material or a core material, or both, of a microcapsule developer.

The present invention will be explained in more detail with reference to Examples below. The parts given in the examples are parts by weight.

Embodiment 1 In FIG. 2, the same members as in FIG. 1 are given the same reference numerals. In the embodiment apparatus, the photosensitive drum 1 rotates in the direction of arrow a at a circumferential speed of 60 mm/sec.
2 is a stainless steel (SUS304) sleeve with an outer diameter of 32 mm and a thickness of 0.8 mm that rotates in the direction of arrow b at a circumferential speed of 66 mm/sec, and its surface is amorphous sandblasted using #600 alundum abrasive grains. The roughness of the circumferential surface was set to 0.8 μm (R _z =).

On the other hand, a sintered ferrite type magnet 7 is fixedly disposed inside the rotating sleeve 2, and the N pole of the first magnetic pole is opposite to the magnetic blade 6.
The blade is set at an angle of 30 degrees (θ in the figure) from the line connecting the center O of the blade and the tip of the blade.

The magnetic blade 6 is made of iron and has a nickel plated surface to prevent rust. The distance between the blade 6 and the surface of the sleeve 2 was set to 200 μm.

The magnetic particles 5 have a particle size of 70 to 100μ and a fluidity.
100g of sponge iron powder of 14.8sec/50g was used.

On the other hand, as toner 4, polyester resin
Average particle size when 100 parts are internally added with 10 parts of copper phthalocyanine pigment, 5 parts of negative charge control material (alkyl salicylic acid metal complex), and 0.5% of silica is externally added.
200 g of cyan powder charged with negative (-) polarity of 12 μm was prepared. After the toner and magnetic particles are thoroughly mixed, they are placed in the container 3. The mixture of toner and magnetic particles in the container 3 could be observed to move in circulation as the magnetic particles were conveyed by the sleeve under a magnetic field, especially when the amount of developer was running low.

In the developing device having the above configuration, as the sleeve rotates, the surface of the sleeve 2 has approximately
A thin layer of only toner with a thickness of 40 μm could be formed.
When the charging potential of this developer layer was measured by a blow-off method, it was confirmed that the developer layer was uniformly charged with a potential of -7.1 μc/g.

On the surface of the photoreceptor drum 1 facing the sleeve 2, an electrostatic latent image is formed with a dark area of +600V and a bright area of +150V.
to form a charge pattern and increase the distance from the sleeve surface.
It was set to 300μm. Then, the frequency of 800Hz and the peak-to-peak value was set to the above sleeve by power source E.
When we applied a voltage of 1.4KV with a center value of +300V, we were able to obtain a high-quality, clear blue developed image with no uneven development, ghost images, or fog.

Furthermore, regarding the mixture in container 3, only the toner was consumed for development, with almost no magnetic particles being consumed. Further, the developing function remained unchanged until almost all of the toner was consumed.
After the toner was consumed, the developing device was removed from the main body and the lower part of the sleeve 2 was looked at, and it was found that not only were there no magnetic particles, but almost no toner had leaked there.

Example 2 The distance between the blade 6 and the sleeve 2 is 100μ,
As the magnetic particles 5, iron powder having a fluidity of 18.1 sec/50 g and whose surface was coated with a fluorocarbon resin was used.
Furthermore, styrene acrylic resin is used as toner 4.
Colloidal silica is added to a toner consisting of 100 parts, 10 parts of azo pigment, and 5 parts of aminoacrylic resin.
Using a material with 0.5% external addition, photosensitive plate drum 1 was
An OPC photoreceptor was used. When the experiment was carried out in the same manner as in Example 1 with the above configuration, the circulation of the magnetic particles was appropriate, and a thin layer made only of toner could be formed on the surface of the sleeve 2. Furthermore, when the electrostatic charge image on the photosensitive plate drum 1 was developed using this thin layer of toner, an extremely good red developed image was obtained. Further, the developing function remained stable until the toner 4 was almost consumed, and there was no leakage to the lower part of the sleeve 2, which was good.

Example 3 The distance between the blade 6 and the sleeve 2 is 250μ,
The same procedure as in Example 2 was carried out except that ferrite particles having a fluidity of 28.2 sec/50 g were used as the magnetic particles 5, and good results were obtained.

Example 4 Good results were obtained in almost the same manner as in Example 2 except that slightly flat iron powder with a fluidity of 38.6 sec/50 g was used as the magnetic particles 5.

Comparative Example 1 The same procedure as in Example 4 was carried out except that flat iron powder with a fluidity of 52.1 sec/50 g was used as the magnetic particles 5, but the uniformity of the coating layer on the surface of the sleeve 2 was poor and the concentration was partially reduced. This occurred and leakage of magnetic particles was observed at the lower part of the sleeve 2.

In this example, a non-magnetic developer was used as the toner, but it has significantly weaker magnetism than magnetic particles, and a magnetic developer can also be used if it can be tribocharged.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developing device for explaining the principle of the present invention, and FIG. 2 is a sectional view of a developing device used in an embodiment of the present invention. In the figure, 1 is a photosensitive drum which is a latent image holding member, 2 is a sleeve which is a toner carrier, 3 is a container, 4 is a toner, 5 is a magnetic particle, 6 is a magnetic blade which is a regulating member, and 7 is a magnet.

Claims (1)

[Scope of Claims] 1. A developer container that stores non-magnetic toner and magnetic particles for toner application, a toner carrier that conveys the non-magnetic toner to a latent image carrier, and an upstream side of the toner outlet of the developer container. A toner coating method in which a thin layer of non-magnetic toner is formed on the toner carrier by disposing a magnet forming a magnetic brush of toner coating magnetic particles in contact with the toner carrier on the side, the magnetic particles A toner application method characterized by having a flow rate of 10 to 50 seconds/50g. 2. A developer container that stores non-magnetic toner and magnetic particles for toner application, a toner carrier that conveys the non-magnetic toner to the latent image carrier, and a toner carrier that is located upstream of the toner outlet of the developer container. A toner coating method for forming a thin layer of non-magnetic toner on the toner carrier by disposing a magnet forming a magnetic brush made of toner coating magnetic particles in contact with the toner coating magnetic particles. Magnetic particles for toner coating, characterized in that the magnetic particles for coating have a fluidity of 10 to 50 sec/50g.