JPH0428106B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for developing an electrostatic image with a magnetic brush, and more specifically, when developing an electrostatic image of magnetic toner with a magnetic brush, the present invention improves the standing of the magnetic brush and effectively triboelectrically charges the magnetic toner. Regarding improvements to be made. The present invention further relates to a magnetic brush developing method that prevents mutual blocking of magnetic toners and eliminates the occurrence of white streaks due to contamination of foreign matter such as paper dust and coarsening of toner particles. Conventionally, as a developer used for magnetic brush development of an electrostatic image, a two-component developer consisting of a mixture of fixable electrostatic powder (toner) and a magnetic carrier;
Two types of one-component magnetic developer are known: a one-component magnetic developer, which is formed by dispersing magnetic powder in a fixing medium and molding it into particles. Among these developers, two-component developers require the toner particles to be charged by friction between the magnetic carrier and the toner, and the mixing ratio of the magnetic carrier and toner must be maintained within a certain range. Otherwise, there is a drawback that good images cannot be obtained.
Further, during long-term use, toner or toner components adhere to and accumulate on the surface of the magnetic carrier (commonly referred to as spent toner), creating the problem that it becomes difficult to charge the toner. On the other hand, a one-component magnetic developer has the advantage that development can be performed without the hassle of using a magnetic carrier, unlike a two-component developer.
When a component-based magnetic developer is used, there is often a drawback that the amount of spikes on the magnetic brush changes considerably due to changes in the environment such as temperature and humidity, making it difficult to maintain a constant amount of spikes. That is, in a one-component magnetic developer, it is the developer itself that forms the ears of the magnetic brush, and the developer particles move on the sleeve as the developing sleeve rotates or as the magnet inside the sleeve rotates. Because brindle formation occurs, when the fluidity of the developer (which changes with environmental changes) changes, the amount of brindle formation also changes. Furthermore, in a one-component magnetic developer, the development threshold is determined by the magnetic attraction force of the developer to the sleeve and the Crohn's force to the electrostatic image, which causes various problems. That is, since the magnetic material is embedded in the resin, the magnetic attraction force to the developing sleeve is weaker than that of a magnetic carrier, which causes the problem that fogging is likely to occur during development, and the fluidity of developer particles is reduced. Therefore, there is a problem in that the particles are not sufficiently charged by friction with each other, resulting in a decrease in image density. Therefore, an object of the present invention is to maintain good standing of the magnetic brush despite environmental changes during magnetic brush development using a one-component magnetic toner, and to effectively triboelectrically charge the toner in the magnetic brush. The purpose of the present invention is to provide a developing method. Another object of the present invention is to provide a developing method in which mutual blocking of magnetic toner particles is prevented, and the occurrence of white streaks due to the mixing of foreign matter such as paper dust into the developer and the coarsening of the particles is also prevented. According to the present invention, there is provided an electrostatic image developing method comprising rubbing a magnetic brush of a developer formed on a developer conveying sleeve with a magnet inside against the surface of a substrate having an electrostatic image. , a spike-promoting component made of granular magnetic material is always held on the sleeve, and a magnetic toner component made of particles of a magnetic powder dispersion is placed in a fixing medium having a particle size of 5 to 50 microns. and the magnetic toner component in a weight ratio of 80:20 to 10:90 to form a magnetic brush on the sleeve with the spike-promoting component and the magnetic toner component, Magnetic brush development of an electrostatic image, characterized in that a concentrated parallel magnetic field region is formed close to the developer introduction side of a spike cutting mechanism made of a non-magnetic material, and the magnetic brush is passed through the parallel magnetic field region on the sleeve. law is provided. The invention will be described in detail below with reference to the accompanying drawings. In FIG. 1 showing an example of the developing device used in the present invention, a drum-shaped support 2 having an electrophotographic photosensitive layer 1 on its surface is rotatably provided, and as the photosensitive layer 1 moves, the whole A developing device indicated by 3 is provided. This developing device 3 is made up of a developer storage chamber 4, a developing roll 5, and a panicle cutting mechanism 6. It consists of a magnet 8 having a pole of . In the present invention, in order to form a concentrated parallel magnetic field region to be described later, it is necessary to keep the magnet 8 fixed in position, and the developer is conveyed by rotation of the sleeve 7. When the magnet 8 is rotated, the magnetic field fluctuates, making it difficult to form a concentrated parallel magnetic field region. Note that the movement of the magnetic brush 9 is performed in the same direction as the rotation direction of the sleeve 7. The developer in the developer storage chamber 5 is attracted and held on the sleeve 7 and stands up at a position corresponding to the magnetic pole N or S to form a magnetic brush 9. At the same time, it is conveyed in a certain direction on the sleeve 7 and rubbed against the photosensitive layer 1,
The electrostatic image on the photosensitive layer 1 is developed. The present invention comprises a spike establishment promoting component 10 consisting of granular magnetic material, and a fixing medium having a particle size of 5 to 50 microns.
notable for forming a magnetic brush 9 on the sleeve 7 with a magnetic toner component 11 consisting of particles of a magnetic powder dispersion and passing the magnetic brush 9 through a concentrated parallel magnetic field region 12 formed on the sleeve 7. It has unique characteristics. First, since the spike-promoting component 10 is composed solely of a magnetic material such as ferrite, the magnetic toner component 1 has magnetic powder dispersed in the fixing medium.
It has superior magnetic properties compared to No. 1, and therefore has the effect of improving the standing of the magnetic brush on the sleeve. In general, magnetic toner contains a fixing medium, so when the temperature rises, its fluidity decreases and may even cause blocking. Such a decrease in fluidity and blocking naturally affect the amount of spikes on the magnetic brush. This results in deterioration of image quality such as blurring and streaks. Such a decrease in fluidity or blocking may similarly occur due to an increase in temperature or dew condensation on the surface of the magnetic toner particles. On the contrary,
When the spike-promoting component of the present invention is combined with a magnetic toner, the spikes of the magnetic brush are always maintained in a good condition regardless of changes in the environment of the magnetic developer, and the image quality is reduced due to the occurrence of scratches, streaks, etc. It becomes possible to suppress the decrease in Furthermore, by using such a spike-promoting component with good magnetic properties in combination with the magnetic toner, a mixing and stirring effect is imparted to the developer when the developer is conveyed on the sleeve, thereby reducing the temperature. There is also the added advantage that the developer components remain in a free-flowing powder state despite environmental changes such as heat and humidity. In the present invention, the magnetic brush 9 made of a mixture of the component 10 made of magnetic particles and the toner component 11 is formed on the developing sleeve 7.
This seems to be similar to a magnetic brush development method using a two-component developer. However, the toner used in the present invention is not only different from that of a normal two-component developer in that it is composed of particles of magnetic powder dispersion in a fixing medium, but also the developing principle is different from that of a two-component developer. It's completely different. That is, the magnetic toner component used in the present invention, like a normal one-component magnetic developer, has a balance between the magnetic attraction force to the sleeve and the electrostatic attraction force (Coulomb force) to the electrostatic image. The development function is also different from that of two-component developers in that the threshold value during development is determined independently of the spike-promoting component and the carrier. Thus, in the developing method according to the present invention, the weight ratio of the spike-promoting component to the toner component is 80:20 to 10:90, particularly
Even when changing the ratio over a wide range of 65:35 to 20:80, the formed image density is maintained at a nearly constant high level, which is one of the important features of the present invention. . Incidentally, high-density images can be obtained without fogging only within a narrow range of toner concentration in a typical two-component developer from 2 to 15% by weight. Furthermore, in the present invention, the above-mentioned spike-up promoting component 10 is always held on the sleeve 7, while only the magnetic toner component 11 is stored in the developer storage chamber 4, and the magnetic toner component 11 is removed from the storage chamber 4. chisel is fed onto the sleeve 7 to form a magnetic brush 9 consisting of a mixture of both. Therefore, according to the present invention, it is possible to handle it in almost the same way as a normal one-component magnetic developer, and there is an advantage that there is no need for troublesome adjustment of toner concentration. In the present invention, in order to form a concentrated parallel magnetic field region 12 on the sleeve 7, a spike-promoting mechanism 13 made of a plate of magnetic material or the like is placed at a small distance from the surface of the sleeve 7 and faces the magnetic pole of the magnet 8. Place it like this. In the specific example shown in Figure 1,
This ear standing promotion mechanism 13 is arranged close to the magnetic brush introduction side of the ear cutting mechanism 6 made of a non-magnetic material, and is connected to the sleeve inner magnetic pole N or S.
A parallel concentrated magnetic field 12 is formed between the two. According to the present invention, the spike-promoting component 10 and the magnetic toner component 11 made of the above-mentioned magnetic particles are provided.
By supplying a mixture of 1 and 2 to the parallel concentrated magnetic field region 12 of the conveying sleeve 7, the density of the mixture in this region 12 is uniformly interpreted as coarse. Since the spike-promoting component 10 and the magnetic toner component 11 are uniformly distributed in a coarse-density state, the spike-promoting component 10 is always held on the sleeve 7, and the magnetic toner component 11 is supplied onto it. Even in the case where the toner particles are mixed and agitated, the toner particles are mixed and stirred extremely effectively, uniformly, and without causing mutual compression of the toner particles, thereby effectively charging the toner particles and preventing blocking of the toner particles. It is possible. Such agitation without compressive force causes the polar magnet inside the sleeve and the magnetic material 13 to
This becomes possible only by passing both components through the parallel concentrated magnetic field region 12 between the two components. In addition, in this parallel concentrated magnetic field region, the spikes are reduced to a coarse and uniform state, so the spikes are uniform over the entire length of the sleeve, and the concentration is uniform, with partial white streaks etc. It becomes possible to form an image without the occurrence of. Furthermore, as shown in the specific example of FIG.
By arranging the spike formation promotion mechanism 13 made of a magnetic material close to the developer introduction side of the magnetic material, the spike formation is uniform and the density of the developer is uniformly coarse, and the non-magnetic spike can be cut immediately. By cutting the magnetic brush with the mechanism 6, it becomes possible to stably and quantitatively supply the magnetic brush of developer over the entire circumference of the sleeve 7. For example, in this embodiment, the magnetic brush 9 is enlarged with a magnetic magnifying glass called the panicle stand promoting mechanism 13, and the enlarged magnetic brush 9 is cut with a non-magnetic panicle cutting plate 6, so that the magnetic brush 9 can be enlarged. This makes it possible to cut the ears with extremely high precision. Therefore, according to this aspect,
It is possible to form an image with uniform and stable density without shading over the entire surface of the photosensitive layer 1. Furthermore, coarse particles generated by the aggregation of toner particles and foreign matter such as paper dust and dirt that entered the developing mechanism from the outside, or hard aggregates of toner particles, are blocked at the tip of the ear cutting mechanism 6. In this case, due to the effect of the above-mentioned panicle stand promoting mechanism 13, a magnetic brush is formed to surround this, and the thickness of the magnetic brush passing through this dammed part is thinner than other parts. This effectively eliminates the occurrence of white streaks. In the present invention, the clearance d ₂ between the magnetic ear standing promoting mechanism 13 and the sleeve 7 is larger than the clearance d ₁ between the ear cutting mechanism 6 and the sleeve 7, and the ratio of d ₂ /d ₁ is generally 1.05 to 1.05. 10, particularly in the range 1.5 to 6.5, is desirable for the purposes of the present invention. That is, whether this ratio is smaller or larger than the above range, it is more difficult to perform the various effects described above than when it is within the above range. Note that the clearance d ₁ may be within a range commonly used for one-component magnetic developers, for example, 0.1 to 1 mm. The panicle establishment promotion mechanism 13 can be made of any magnetic material, such as a soft iron plate, a steel plate, a ferrite sintered plate, a nickel plate, a cobalt plate, etc., and its thickness is set to prevent the waving phenomenon and In order to make the panicle stand well and uniformly, it is desirable that the thickness be sufficient, for example in the range of 0.5 to 5 mm. The ear cutting mechanism 6 can be made of any non-magnetic material, such as brass, phosphor bronze, aluminum, duralumin, non-magnetic stainless steel, various ceramics, glass, plastics, etc. In the present invention, it is preferable that the panicle establishment promoting component 10 is composed of sintered ferrite particles in terms of development efficiency. For example, a known magnetic carrier (commonly called an iron powder carrier) has a magnetic carrier of 10 to 20 e.mu/
The sintered ferrite particles used in the present invention exhibit a remanent magnetization of 0 to 1.0 emu/g and a coercive force of 0 to 50 e, whereas the sintered ferrite particles used in the present invention exhibit a remanent magnetization of 0 to 1.0 emu/g and a coercive force of 0 to 50 e. Thus, in the conventional combination of a magnetic carrier and magnetic toner, the residual magnetization and coercive force of the carrier are large, so that the magnetic toner is difficult to separate from the carrier surface, resulting in poor development efficiency. On the other hand, when sintered ferrite particles are used as the spike-promoting component according to the present invention, the residual magnetization and coercive force are 1/10 of that of conventional magnetic carriers.
Since it is as small as 1/20 to 1/20, the spike-promoting component forms a magnetic brush with good spikes, but is not itself magnetized, and therefore good development efficiency can be obtained. When the particle size of the sintered ferrite particles is smaller than 20 microns, it tends to be difficult to make the sintered brush stand up well, while on the other hand, when the particle size is larger than 100 microns, , there is a tendency for scratches called general brush marks to appear on the formed toner image. The sintered ferrite particles used in the present invention are known per se, for example, iron zinc oxide (ZnFe ₂
O ₄ ), iron yttrium oxide (Y ₃ Fe ₅ O ₁₂ ), iron cadmium oxide (CdFe ₂ O ₄ ), iron cadrinium oxide (Gd ₃ Fe ₅ O ₁₂ ), iron and steel oxide (CuFe ₂ O ₄ ), iron lead oxide (PbFe ₁₂ O ₁₉ ), nickel iron oxide (NiFe ₂ O ₄ ), neodymium iron oxide (NdFeO ₃ ), barium iron oxide (BaFe ₁₂ O ₁₉ ), magnesium iron oxide (MgFe ₂
Sintered ferrite particles having a composition of one or more of iron manganese oxide (MnFe _{2 O 4} ), lanthanum iron oxide (LaFeO ₃ ), etc. are used. Particularly suitable for the purposes of the present invention are sintered ferrite particles consisting of iron manganese zinc oxide. There are no particular restrictions on the particle shape, but spherical sintered particles are advantageously used. Of course, sintered particles of irregular shape can also be used for the purpose of the present invention. Furthermore, instead of the sintered ferrite particles, coarse particles produced by solidifying magnetite with a binder, for example particles with a particle size of 75 to 15 μm, can also be used as the ear establishment promoting component. The magnetic toner component used in the present invention is a particle of a magnetic powder dispersion in a fixing medium having a particle size in the range of 5 to 50 microns, and its composition and manufacturing method are known per se for one-component magnetic development. It can be applied in accordance with the drug. The fixing medium used is a resin that exhibits fixing properties under the application of heat or pressure, and can be a thermoplastic resin or an uncured or precondensed thermosetting resin. Useful natural resins include balsam resin, rosin, silica resin, copal, etc., and these natural resins include 1 of the vinyl resins, acrylic resins, alkyd resins, phenolic resins, epoxy resins, oleoresins (oil-based resins), etc. described below. It can be modified with one or more species. Examples of the synthetic resin include vinyl chloride resin, vinylidene chloride resin, vinyl acetate resin, vinyl acetal resin such as polyvinyl butyral, or vinyl resin such as vinyl ether polymer; polyacrylic ester, polymethacrylic ester, acrylic acid copolymer, Acrylic resins such as methacrylic acid copolymers; styrenic resins such as polyethylene, polypropylene, polystyrene, hydrogenated styrene resins, polyvinyltoluene, and styrene copolymers; polyamide resins such as nylon-12, nylon-6, and polymerized fatty acid-modified polyamides. ; polyesters such as polyethylene terephthalate/isophthalate, polytetramethylene terephthalate/isophthalate; alkyd resins such as phthalic acid resins and maleic acid resins; phenol formaldehyde resins; ketone resins; coumaron-indene resins; terpene resins; urea-formaldehyde resins; Amino resins such as melamine-formaldehyde resins; epoxy resins and the like can be used, and these synthetic resins can also be used in combinations of two or more such as phenol-epoxy resins and amino-epoxy resins. The fixing medium may be wax, for example narrow waxes such as carnauba wax, cotton wax, candelilla wax, sugar cane wax, beeswax, wool wax; mineral waxes such as montan wax, paraffin wax, microcrystalline wax; palmitic acid,
Solid higher fatty acids having 16 to 22 carbon atoms such as stearic acid, hydroxystearic acid, and behenic acid; oleic acid amide, stearic acid amide, palmitic acid amide, N-hydroxyethyl-hydroxystearamide, N,N'-ethylene- Higher carbon atoms having 16 to 22 carbon atoms such as bis-stearamide, N,N'-ethylene-bis-ricinolamide, N,N'-ethylene-bis-hydroxystearylamide (hereinafter, the term higher refers to the above-mentioned carbon atoms having 16 to 22 carbon atoms)
Amides of fatty acids; for example, alkali metal salts, alkaline earth metal salts, zinc salts, and aluminum salts of higher fatty acids such as calcium stearate, aluminum stearate, magnesium stearate, and calcium palmitate. Metal salts such as palmitic acid hydrazide,
Higher fatty acid hydrazides such as stearic acid hydrazide; p-hydroxyanilide of myristic acid;
p-hydroxyanilides of higher fatty acids such as p-hydroxyanilide of stearic acid; β-diethylaminoethyl ester hydrochloride of higher fatty acids such as β-diethylaminoethyl ester hydrochloride of lauric acid, β-diethylaminoethyl ester hydrochloride of stearic acid; ; higher fatty acid amide-formaldehyde condensates such as stearic acid amide-formaldehyde condensates and palmitic acid amide-formaldehyde condensates; combinations of dyes or dye bases having amino groups and higher fatty acids in an amount of 4 times or more by mole per said dye or dye base; Salt-forming reaction products, such as salt-forming products of stearic acid, palmitic acid, or myristic acid and dyes or dye bases; hardened oils such as hardened castor oil and hardened tallow oil; polyethylene wax, polypropylene wax, oxidized polyethylene, etc. . Magnetic powders include magnetite (Fe ₃ O ₄ ),
In addition to γ-iron sesquioxide (γ-Fe ₂ O ₃ ), the above-mentioned spike-promoting components are used, but the amount of magnetic powder in the developer component particles depends on the fixing medium and magnetic powder. The amount is preferably in the range of 40 to 75% by weight based on the total amount. The magnetic toner component of the present invention can be used in the form of a so-called conductive magnetic developer, and in this case, the electrical resistance of the developer component is in the range of 10 ⁴ Ω-cm to 10 ¹² Ω-cm. A conductive agent such as carbon black is contained in the particles of the developer component, or a conductive agent such as carbon black is attached to the surface of the developer component particles by a matrix, or is further embedded. In this conductive developer component, developer component particles are charged by dielectric polarization and development is performed. Further, this magnetic toner component can be used in the form of a so-called insulating magnetic developer. In this case,
The electrical resistance of the developer component is 10 ¹³ Ω-cm or more.
In this developer, a known negative or positive charge control agent may be blended, if desired, in order to control the triboelectric charge to a constant polarity. In any of these types of toner ingredients,
Granulation can be easily carried out by melt-kneading the above ingredients, cooling and then pulverizing the mixture.
Furthermore, granules can also be obtained by dispersing magnetic powder in a resin solution and then spray granulating it. The shape of the particles may be spherical, irregular, or irregular with slightly rounded corners. In the present invention, as described above, the ear stand promoting component and the magnetic toner component may be present on the sleeve in a weight ratio of 80:20 to 10:90, particularly in a weight ratio of 65:35 to 20:80. can. In the present invention, it is desirable that the ear establishment promoting component is always retained on the sleeve without detaching.
If desired, it may be temporarily removed from the sleeve and then supplied onto the sleeve again. In the former case, it is only necessary to fill the developer container with toner components and supply this toner component to the sleeve, and the developer supply operation is the same as for ordinary one-component magnetic developers. is quite simple. In the latter case, even in the developer container,
Since the spike-promoting component and the magnetic toner component are mixed, fluidity is improved and blocking is more completely prevented. The invention is illustrated by the following example. Preparation of panicle establishment promoting component (1) Iron manganese zinc oxide sintered ferrite particles (average particle size 40 μm; particle size distribution 23-53 μm; TDK
(2) Prescription Priorite VTL 27 parts by weight (vinyl toluene-butadiene copolymer manufactured by Gutdeyer) Viscol 550P 3 (manufactured by Sanyo Kasei Co., Ltd. Polypropylene wax) ) Printex L 0.1 〃 (Carbon black manufactured by Degussa) Iron black B6 70 〃 (Triiron tetroxide manufactured by Toyo Shiki Co., Ltd.) Manufacturing method The above prescription materials are melted and kneaded in a pressure kneader, dispersed, cooled, and manufactured by Alpine. Grind with a pin mill.
The crushed product was classified into 75-150 μm particles using a vibrating sieve machine to obtain panicle establishment promoting particles (). Prescription and manufacturing method of magnetic developer components (a) Prescription Priorite ACL 14 parts by weight (Styrene-acrylic copolymer manufactured by Gutdeyer Co., Ltd.) Hi Wax200P 31 〃 (Polyethylene wax manufactured by Mitsui Polychemical Co., Ltd.) Magnetic iron oxide RB. BL 55 〃 (Triiron tetroxide manufactured by Titan Industries Co., Ltd.) The above prescription materials are mixed, melted and kneaded using a heated three-roll mill, and after cooling, pulverized using a jet mill. Particles of 5-15 μm were obtained using an Alpine wind classifier. 5~ obtained by classification
Put 2000 parts by weight of 15 μm fixable magnetic particles and 100 parts by weight of RB/BL (triiron tetroxide manufactured by Titanium Industries Co., Ltd.) into a Henschel mixer, and stir at 1500 rpm for 30 minutes while keeping the inside at 50°C. Triiron tetroxide particles were embedded on the surface of the fixable magnetic particles. Next, the mixer was cooled, and 80 parts by weight of triiron tetroxide and 10 parts by weight of Erosil R972 were stirred and mixed at a rotational speed of 1000 rpm for 5 minutes to obtain a self-charging pressure-fixable magnetic particle toner (1). (b) Prescription Alcon P-125 45 parts by weight (Hydrogenated styrene resin manufactured by Arakawa Hayashi Chemical Industry KK) Nigrosine stearate 10 〃 (Salt of nigrosine base and stearic acid 1:4 parts by weight) Amide AP-1 25 〃 (Nippon Kasei Co., Ltd., fatty acid amide mp98℃) Evaflex 420 20 (Ethylene-vinyl acetate copolymer, Mitsui Polychemical Co., Ltd.) Special Black N 12 (Degussa carbon black) Iron black B6 250 parts by weight (Toyo Shiki) (manufactured by Triiron Tetroxide, Inc.) The above prescription materials are added to 1000 parts by weight of heated toluene with stirring, and dissolved and dispersed for 30 minutes using a homomixer. This dispersion was kept at 70°C and sprayed into hot air at 150°C to obtain spherical dry fine particles. The particles were classified into particle sizes of 5 to 15μ. A conductive toner (2) was obtained by uniformly mixing 0.5 parts by weight of Printek L (carbon black) and 0.3 parts by weight of Erosil R972 (fine silica powder) with 100 parts by weight of the classified particles using a Henschel mixer. The volume electrical resistance of the toner particles was 10 ⁸ Ω·cm. (c) Prescription Priorite ACL 40 parts by weight Viscole 550P 5 Iron black B6 55 The above ingredients are mixed, melt-kneaded using a heated three-roll mill, and after cooling, pulverized using a jet mill. Particles of 5-15μ were obtained using an Alpine wind classifier. 2000 parts by weight of the 5-15μ fixable magnetic particles obtained by classification and 60 parts by weight of RB/BL (triiron tetroxide) are placed in a Henschel mixer and stirred at 2000 rpm for 10 minutes while keeping the inside at 40°C. A mixture was prepared in which a portion of triiron tetroxide was embedded in the surface of the fixable magnetic particles. Next, the Henschel mixer was cooled, 10 parts by weight of Erosil R972 was added, and the mixture was stirred and mixed at a rotational speed of 1000 rpm for 5 minutes to obtain a self-charging heat-fixable magnetic particle toner (3). Example 1 Using a sleeve/magnet dual-rotation type developing device shown in FIG. 1 in which a magnetic plate is attached to the toner hopper side of a non-magnetic ear cutting plate, spike-promoting particles () made of sintered ferrite particles are placed on the sleeve. After making 5g evenly stand, add 100g of magnetic toner (a) and paper powder.
0.1 g of the mixture was placed in a hopper and a developing device was set in a pressure fixing copying machine to make continuous copies. After making 10,000 copies and comparing the image density, ground fog, and uniformity of image quality with the starting image, stable images were obtained with no changes. Comparative Example 1 Using the same developing device as in Example 1 without a magnetic plate, an example was carried out using 5 g of spike-up promoting particles (), 100 g of magnetic toner (a), and 0.1 g of paper powder mixed well in advance. When I conducted a copy test using the same method as in step 1, the image quality became inconsistent after the 1000th copy. In other words, so-called white streaks occur in the copy paper conveyance direction of the copy, and when checking the spikes of toner on the sleeve, it is found that there are some areas where the spikes do not appear and these streaks form. Upon investigation, it was discovered that the short fibers of paper powder and toner had become entangled with each other to form large particles that were clogging the cutting board, preventing the toner from being transported. Comparative Example 2 Using the same developing device and copying machine as in Example 1,
When I performed a copy test by putting 100 g of magnetic toner (a) and 0.1 g of paper powder into the hopper without using spike-promoting particles, white streaks appeared on the image from around the 2300th page. did. Upon inspection, it was discovered that the tip plate was clogged with paper dust agglomerates, which prevented toner transport and caused streaks on the sleeve with no tips. The image density of the copies in Example 1 and Comparative Examples 1 and 2 (density of the image area corresponding to the solid black area of a square with one side of 2 cm on the original) and the fog density (density corresponding to the non-image area of the original) Shown in Table 1. The concentration was measured using SAKURA densitometer PDA65 (manufactured by Konishiroku Photo Industry Co., Ltd.).

[Table] However, although not parallel white streaks, streak-like shading appears, resulting in a significant increase in image density.
A sharp decline had occurred.

[Brief explanation of drawings]

FIG. 1 is a side layout diagram showing an example of a developing device used in the present invention. 1 is a photosensitive layer, 4 is a developer storage chamber, 7 is a sleeve, 8 is a magnet, 9 is a magnet, 10 is a spike-up promoting component,
11 is a magnetic toner component, 12 is a concentrated parallel magnetic field region,
13 is the panicle establishment promotion mechanism.

Claims (1)

[Claims] 1. A method for developing an electrostatic image, which comprises rubbing the surface of a substrate having an electrostatic image with a magnetic brush of developer formed on a developer conveying sleeve equipped with a magnet inside. In this step, a spike-promoting component made of granular magnetic material is always held on the sleeve, and a magnetic toner component made of particles of a magnetic powder dispersion in a fixing medium having a particle size of 5 to 50 microns is applied to the spike-promoting component. Supplied onto the sleeve so that the weight ratio of the components and the magnetic toner component is 80:20 to 10:90, and the spike-promoting component and the magnetic toner component form a magnetic brush on the sleeve. , a magnetic brush for an electrostatic image, characterized in that a concentrated parallel magnetic field region is formed close to the developer introduction side of a spike cutting mechanism made of a non-magnetic material, and the magnetic brush is passed through the parallel magnetic field region on the sleeve. Development method. 2. The developing method according to claim 1, wherein the panicle-promoting component comprises sintered ferrite particles having a particle size of 20 to 100 microns.