JPH0462393B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a toner application method. 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 developer, and for this reason, development has been performed 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. Conventional methods for forming a thin layer of a dry one-component developer have been proposed in Japanese Patent Laid-Open Nos. 54-43037 and 55-18656, and have been put to practical use. However, this concerned the formation of a thin layer of magnetic developer. Magnetic developers must contain a magnetic substance to make them magnetic, which limits the fixing properties when thermally fixing the developed image transferred to transfer paper and the color reproduction. There are other problems. For this reason, methods for forming a thin layer of non-magnetic developer include using a cylindrical brush made of soft bristles like beaver hair and applying the developer to the brush, or using a brush with a surface made of fibers such as velvet. A method of coating the developing roller with a doctor blade or the like has been proposed. However, if an elastic blade is used as a doctor blade for the above fiber brush,
Although it is possible to regulate the amount of developer, uniform application is not achieved, and the fiber brush on the developing roller is simply rubbed, and no triboelectric charge is imparted to the developer existing between the fibers of the brush. Therefore, there was a problem that ghosts and the like were likely to occur. The present invention eliminates the problems of the conventional method described above, and provides a new method of forming toner as a uniform thin layer on the surface of a toner carrier and applying sufficient frictional electrification, and a magnetic material for toner application for this purpose. The purpose is to provide particles. A further object of the present invention is to prevent developer from leaking out of the developing device. Its features include a developer container that stores toner and magnetic particles for toner application, a toner carrier that conveys the toner to a latent image carrier, and a toner container that is arranged on the upstream side of the toner outlet of the developer container. A toner coating method in which a thin layer of toner is formed on the toner carrier by disposing a magnet having magnetic poles forming a magnetic brush of toner coating magnetic particles in contact with the toner carrier, wherein the toner coating magnetic particles of particles
A method for applying a toner and magnetic particles for applying a toner having a BET specific surface area of 30 to 350 cm ² /g. As the latent image carrier, a drum-shaped or belt-shaped member having a photoreceptor or an insulating layer can be used.
As the magnetic poles, a magnetic roller having magnetic poles of the same polarity or different polarity magnetized in the axial direction, or a plurality of rod-shaped magnets bonded to a fixed support member can be used. Furthermore, as the rotating toner carrier, 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, and the circumferential surface of the sleeve is made of a non-magnetic metal such as aluminum, copper, stainless steel, brass, etc. In order to improve charging characteristics, a roughened surface or an uneven pattern may be provided. Further, as the regulating member provided on the outlet side of the developer container as needed, 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. Hereinafter, the present invention will be explained in more detail 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 corresponding to a latent image carrier, 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 developer 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 screwed to the downstream side of the container 3 in the rotational direction of the sleeve. 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 reality, the effect of the magnetic field created by providing a magnetic pole slightly upstream of the position of the magnetic blade 2 prevents the outflow of magnetic particles.
and even better results in terms of uniform toner application. In the above configuration, the magnetic particles 5 in the container 3 are
The magnetic field generated between the S pole of the magnet 7 and the magnetic blade 6 forms a magnetic brush 8 that comes into contact with the toner retaining member. As the sleeve 2 rotates, the magnetic particles and toner are stirred and mixed while the magnetic brush 8 remains formed. In this state, on the magnetic blade side of the container 3, due to the presence of the blade 6, the mixture of toner and magnetic particles 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. 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. As a result, even if the toner on the sleeve is consumed during development, developer 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. In addition, in the above explanation of the principle, a magnetic blade is used as the regulating member, but the non-magnetic blade or the wall of non-magnetic material such as resin or aluminum that constitutes the container can be
It can also be used as this regulating member. However, in this case, to prevent the outflow of magnetic particles,
It is necessary to make the gap between the sleeve and the regulating member even smaller than when using a magnetic blade. Further, when a magnetic blade is used, it is preferable in that a magnetic brush can be stably formed at the toner exit portion by the magnetic field between the blade and the magnetic pole. As toners that can be used here, toners conventionally used in electrophotography, such as those obtained by kneading pigments or dyes with resin and pulverizing or encapsulating the mixture, can be used. 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 controlling the amount of charge, a magnetic brush must be formed in a system where a large amount of toner exists to apply the toner onto the toner carrier and to 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. 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 tend to occur. The inventors of the present invention conducted various studies in order to satisfy the various functions required by the magnetic particles used in the present invention, and as a result, they found that the magnetic particles for toner coating have a large influence. That is, when the specific surface area of the magnetic particles is smaller than 30 cm ² /g, the rotation of the sleeve 2 causes the magnetic brush 8, which is a mixture of toner particles and magnetic particles, to circulate, and the downstream side of the blade 6 When only toner is applied onto the sleeve, the applied amount is larger than the appropriate value, and the uniformity of the applied surface is also poor, which tends to lead to streaks and unevenness. As a result, when a latent image is developed using such a coating layer, fogging is likely to occur. On the other hand, when the specific surface area of the magnetic particles is large, it is desirable that the coating layer is uniform, relatively thin, and has a good coating state with no fog. However, the specific surface area is 350
When magnetic particles larger than cm ² /g are used, the uniformity of the coated surface is good and fogging is less likely, but the coating amount is small and the image density is low. Also,
If the circulation movement of the sleeve is repeated over a long period of time, the speed at which toner is supplied to the inside of the magnetic brush becomes slow, which may result in problems such as a partial decrease in density and, in some cases, parts of the image appearing white. be. That is, in the coating method of the present invention, magnetic particles having a specific surface area of 30 to 350 cm ² /g are used,
As shown in the examples, more preferably 50 to 320 cm ² /
The g range is good. Furthermore, a range of 70 to 280 cm ² /g is optimal. In the conventional two-component magnetic brush development method for electrophotography, an improvement proposal in which the surface area of the carrier particles was increased was proposed in Japanese Patent Application Laid-Open No. 51-3238. The toner concentration can be increased without reducing the amount of toner per unit surface area, and as a result,
This is aimed at preventing fogging when the toner carried on the carrier is developed in contact with the latent image surface, and by circulating a magnetic brush inside the container as in the present invention,
The coating layer of the toner coating layer on the sleeve surface outside the container and the amount of coating that makes the coating state appropriate are different in concept. In the present invention, the specific surface area is a value obtained by the known BET specific surface area measurement method. As the magnetic particles for toner application used in the present invention, for example, surface-oxidized or unoxidized metals such as iron, nickel, cobalt, manganese, chromium, rare earths, and their alloys or oxides can be used. The surface may be coated with a resin or a suitable treatment agent. Moreover, there are no special restrictions on the manufacturing method. As the binder resin for the toner, monopolymers of styrene and its substituted products such as polystyrene, polyP-chlorostyrene, and polyvinyltoluene; styrene-P-chlorostyrene copolymers, styrene-propylene copolymers, and styrene-vinyl Toluene copolymer, styrene-vinylnaphthalene copolymer, styrene-butyl acrylate copolymer, styrene-
Octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-alpha chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer combination, styrene-vinyl methyl ether copolymer,
Styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-
Styrenic copolymers such as butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer, styrene-maleic acid copolymer, and styrene-maleic ester copolymer; polymethyl methacrylate, Butyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, polyamide, epoxy resin, polyvinyl butyral, polyacrylic resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic carbonized Hydrogen resin, aromatic petroleum resin, chlorinated paraffin, fluffin 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, benzidine, and 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, desyltrimethylammonium chloride, nigrosine base, nigrosine hydrochloride, safranin γ and Crystal violet, metal-containing dyes, salicylic metal-containing compounds, etc. may be added. The above-mentioned toner structure may be used in a developer produced by the commonly used mixing and pulverization method, or may be used as a wall material or a core material or both of them in 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. [Example 1] An example of the present invention will be described with reference to FIG. In the figure, the same members as in FIG. 1 are given the same reference numerals. In the embodiment device, the photoreceptor drum 1 is indicated by arrow a.
Rotates in the direction at a peripheral speed of 60mm/sec. 2 is arrow b
It is a stainless steel (SUS304) sleeve with an outer diameter of 32 mm and a thickness of 0.8 mm that rotates at a circumferential speed of 66 mm/sec in the circumferential direction. The surface roughness was set to 0.8 μm (Rz=). On the other hand, a ferrite sintered type magnet 7c is fixedly disposed inside the rotating sleeve 2, and the first
The north pole of the magnetic pole is set at an angle of 30 degrees (θ in the figure) with respect to the magnetic blade 6 from a line connecting the center O of the sleeve 2 and the tip of the blade. S of one second magnetic pole
The pole is located opposite to an iron piece 10, which is a magnetic member, provided on the sleeve inlet side of the container. 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. As the magnetic particles 5, 50 g of sponge iron powder (BET specific surface area: 180 cm ² /g) with a particle size of 70 to 100 μm was used. On the other hand, as toner 4, polyester resin
10 parts of the same phthalocyanine pigment per 100μ parts,
Average particle size with built-in 5 parts of negative charge control agent (alkyl salicylate metal complex) and external addition of 0.5% silica
A 12 μm cyan powder charged with negative (-) polarity was used. After thoroughly mixing 5 g of the toner powder with 50 g of the powder, the mixture is placed in a container 3. In the magnetic brush thus formed, it was observed that the magnetic particles in particular moved in circulation as they were conveyed by the sleeve under the magnetic field. 150 g of toner particles were placed on top of this magnetic brush. In the coating device having the above configuration, as the sleeve rotates, the surface of the sleeve 2 is coated with approximately
A thin layer of 80 μm consisting only of toner could be formed. When the charging potential of this toner was measured by a blow-off method, it was confirmed that the toner was uniformly charged with a potential of -7.8 μ/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 at 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 1.4V with a center value of +300V, we were able to obtain a high-quality, clear blue developed image without 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 stable 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,
The magnetic particles 5 have a particle size of 20 to 80 μ and a specific surface area of
Flat iron powder particles of 300 cm ² /g were used. Toner 4 is a toner consisting of 100 parts of styrene acrylic resin, 10 parts of azo pigment, and 5 parts of amino acrylic resin, to which 0.5% colloidal silica is externally added, and photosensitive plate drum 1 is an OPC photosensitive member. It 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. When the electrostatic charge image on the photosensitive 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. [Examples 3 to 16] Using the same apparatus as in Examples, magnetic particles having various specific surface areas were used, and the results are shown in the table below. The toner used and developing conditions were the same as in Example 1.

[Table] Note that although a non-magnetic developer was used as the toner in this example, it has significantly weaker magnetism than magnetic particles, and a magnetic developer can also be used as long as 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. 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 bearing member, 2 is a sleeve which is a toner carrier, 3 is a developer container, 4 is a toner, 5 is a magnetic particle, 6 is a magnetic blade that is a regulating member, 7 is a magnet.

Claims (1)

[Scope of Claims] 1. A developer container that stores toner and magnetic particles for toner application, a toner carrier that conveys the toner to a latent image carrier, and a developer container that stores the toner on the upstream side of a toner outlet of the developer container. A toner coating method in which a thin layer of toner is formed on the toner carrier by arranging a magnet having a magnetic pole forming a magnetic brush of toner coating magnetic particles in contact with the toner carrier, wherein the toner coating magnetic particles BET specific surface area of 30~350
A toner application method characterized by cm ² /g. 2. A developer container that stores toner and magnetic particles for toner application, a toner carrier that conveys the toner to the latent image carrier, and a toner that contacts the toner carrier on the upstream side of the toner outlet of the developer container. Toner coating magnetic particles used in a toner coating method in which a thin layer of toner is formed on the toner carrier by arranging a magnet forming a magnetic brush of coating magnetic particles, the magnetic particles having a BET specific surface area of 30 to 30. Magnetic particles for toner application with a density of 350 cm ² /g.