JPH04307560A - Production of magnetic toner - Google Patents

Abstract

PURPOSE:To simply produce a magnetic toner having aggregation preventing property (shelf stability), high flowability and stable electrostatic chargeability and preventing the scattering of fine particles at a low cost as a magnetic toner used in a developing device fitted with an elastically deformable toner support. CONSTITUTION:Fine resin particles 4 of <=1mum size are stuck on the surfaces of core particles 3 contg. a binding resin 1 and a magnetic material 2. Inorg. fine particles 8 of <=0.1mum size are dispersed in a solvent 7 dissolving the fine resin particles 4, this particle dispersed solvent 9 is brought into contact with the fine resin particles 4 on the surfaces of the core particles 3 to dissolve the particles 4 and resin coating layers contg. the inorg. fine particles 8 are formed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing magnetic toner used in an image forming apparatus that performs development using an elastically deformable toner carrier.

0002

[Prior Art] Conventionally, the developing method using magnetic toner is
As disclosed in USP-4121931, a magnetic brush made of one-component magnetic toner is formed on the sleeve using a developing roller having a magnetic roller inside a non-magnetic cylindrical sleeve, and the one-component magnetic toner is transported and developed. One-component magnetic brush development method.

Furthermore, as a developing method that improves the above-mentioned one-component magnetic brush developing method, there is a FEED developing method that improves the image quality of line images and solid images by providing a floating electrode on the developing roller as disclosed in USP-4564285. A developing device has been proposed, as disclosed in US Pat. Generally, the magnetic toner used in these developing methods is made of fine resin powder with a particle size of about 10 μm, to which a magnetic agent, a coloring agent such as a dye or pigment, and a charge control agent are internally added and dispersed.
Products with external additives such as fluidity improvers are used. As an example, US Pat. No. 3,639,245 discloses a magnetic toner in which a ferromagnetic material such as triiron tetroxide, a thermoplastic resin such as an epoxy resin, and a colorant such as carbon black are combined.

[0004] Further, as methods for producing the above-mentioned toner, a kneading and pulverizing method, a suspension polymerization method, a spray drying method, and the like have been proposed, and the toner is generally produced by a kneading and pulverizing method. The kneading and pulverizing method is comprised of the steps of premixing raw material powders, then melting and kneading, coarsely pulverizing, finely pulverizing, classifying, and external addition treatment. Furthermore, in recent years, toners have been required to have higher functionality, and methods have been proposed in which resin layers having various functions are formed on the outer surface of toners. For example, for the purpose of low-energy fixing, a multilayer microcapsule toner (US Pat. No. 3,080,250) in which a high softening point resin is formed on the outer surface of the toner by a polymerization method is used.
No. 59-31066, Japanese Patent Publication No. 1-36934, etc.), and toners having a charge control resin film layer on the outer periphery of the toner for the purpose of charge control using a dry high-speed impact method. JP-A-63-62666
), toners whose surfaces are treated with fine resin powder for the purpose of anti-blocking properties (Japanese Patent Laid-Open No. 105261/1993), and the like. Furthermore, as methods for forming these functional resin layers, spray drying methods, spray granulation methods, and the like have been proposed. Furthermore, as an external addition treatment, it is generally known that, for example, by attaching silica powder to the outer surface of the toner, the cohesiveness and fluidity, which affect toner transport, are improved. Recently, Japanese Patent Publication No. 62-494 discloses coating the surface of a toner with a combination of silica dispersed in polyvinyl alcohol. Further, Japanese Patent Publication No. 61-55108 discloses that fine inorganic particles are attached to the surface of a toner via an adhesive layer made of silicone resin. Further, Japanese Patent Publication No. 60-34104 discloses a developer in which toner particles containing finely divided silica are further mixed with finely divided silica.

[0005]

[Problems to be Solved by the Invention] However, in the conventional magnetic toner described above, the magnetic agent is exposed on the toner surface, and the exposed magnetic agent causes a decrease in the amount of charge, a decrease in environmental resistance characteristics, and the generation of toner of opposite polarity. It has the following disadvantages. Furthermore, in a method in which development is carried out by pressing an elastically deformable toner carrier against a latent image carrier, the drawbacks of the magnetic toner greatly affect the image quality, resulting in uneven density due to variations in the amount of charge, and the occurrence of toner with opposite polarity. However, there is a problem in that image deterioration such as background fog occurs. Furthermore, in the conventional external addition method, the adhesion force of fine particles attached to the surface is weak, and they peel off from the toner surface during toner transportation and development, and agglomeration easily occurs depending on the operating ambient temperature, resulting in blocking and caking, which causes toner development characteristics. It has the disadvantage of decreasing. Furthermore, the peeled off particles contaminate the inside of the apparatus, resulting in negative effects such as image deterioration and mechanical failure. Furthermore, when SiO2 particles are immobilized by a polymerization method, there is a drawback that material selectivity becomes extremely narrow. Furthermore, each toner has a different amount of charge depending on the amount of fine particles attached to its surface, which has a disadvantage in that it adversely affects image quality.

SUMMARY OF THE INVENTION The present invention aims to solve these problems, and its object is to provide a developing device for developing a latent image carrier using an elastically deformable toner carrier. To provide a simple, low-cost method for manufacturing magnetic toner that has anti-agglomeration (storability), high fluidity, prevention of fine particle scattering, stable charging properties, and forms high-resolution, high-quality images. That's a thing.

[0007]

[Means for Solving the Problems] The method for producing magnetic toner of the present invention is a magnetic toner used in a developing device that conveys magnetic toner and develops a latent image carrier using an elastically deformable toner carrier. Yes, the outer surface of the magnetic toner is treated with a solvent after the resin coating layer is formed of at least resin fine particles and inorganic fine particles, and the resin fine particles are attached to the outer surface of the inner core particles consisting of at least a binder resin and a magnetic agent. In the method for producing the resin, the method includes a step of attaching at least resin fine particles to the outer surface of the inner core particles, then dispersing at least inorganic fine particles in a solvent that dissolves the resin particles, and adhering the mixed solvent to the outer surface of the inner core particles. It is characterized by a process of contacting and dissolving fine particles to form a resin coating layer. Further, the particle size of the inorganic fine particles is 0.1
μm or less, characterized in that the particle size of the resin fine particles is 1 μm or less.

[0008]

[Function] According to the structure of the present invention, by coating the surface of the inner core particle with the magnetic agent exposed on the surface with resin and inorganic fine particles, a reverse charge is generated due to frictional electrification of the magnetic agent.
It is also possible to prevent minute static elimination effects, and to have the electrical characteristics of only a high-resistance resin. This results in
In a pressure-contact development method using an elastically deformable toner carrier with a large developing electrode effect, there is no generation of toner of opposite polarity, and a thin toner layer with a uniform charge amount can be stably formed. This makes it possible to reduce density unevenness due to variations in toner layer thickness, toner scattering due to toner of opposite polarity, and background fog. Further, it is generally known that the fluidity of toner is improved by attaching silica or the like to the toner surface, but the detailed causes of this are still unclear. We conducted extensive research on this point and found that when resin fine particles with a smaller particle size than the inner core particles are mixed with the inner core particles and treated, the resin fine particles exert an electrostatic force on the surface of the inner core particles.
Adheres uniformly due to chemical adsorption, physical adsorption, etc. Next, by bringing the mixed solvent that dissolves the resin particles in which inorganic particles are dispersed into contact with the resin particles attached to the surface of the inner core particles, the inorganic particle dispersion solvent penetrates the gaps between the resin particles, and the resin particles surface. Inorganic fine particles are attached to the surface, and resin fine particles are dissolved by a solvent to form a film. As a result, the inorganic fine particles are exposed not only inside but also on the surface, and furthermore, the inorganic fine particles are firmly fixed by the resin. The coating state at this time is controlled by controlling the type of solvent and the contact time.

Furthermore, at this time, the particle size of the resin fine particles is set to 1.
When the thickness exceeds μm, the thickness of the coating layer becomes large, the inorganic fine particles become unevenly dispersed, and the fluidity deteriorates. Furthermore,
Similar results are obtained when the particle size of the inorganic fine particles is larger than 0.1 μm. In this way, since a coating layer mainly composed of resin is formed on the surface of the inner core particle, the inner core particle is not affected by the solvent, and even if the inner core particle has a lower softening point and is softer than the fine resin particles, the coating layer can be formed on the surface of the inner core particle. It can be formed reliably.

The present invention will be explained in detail below with reference to Examples.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a flowchart of the toner manufacturing method of the present invention. Inner core particles 3 are produced by a kneading and pulverizing method, a spray drying method, a polymerization method, etc. using raw materials consisting of a binder resin 1, a magnetic agent 2, and the like. Next, resin fine particles 4 are added to the inner core particles 3.
External addition treatment 5 is performed to attach resin fine particles to externally added inner core particles 6. Next, an inorganic fine particle dispersion solvent 9 in which inorganic fine particles 8 are mixed and dispersed in a solvent 7 for dissolving the resin fine particles 4 is brought into contact with the resin fine particle externally added inner core particles 6 for coating treatment 10.
A resin-coated magnetic toner 11 containing inorganic fine particles is prepared.

[0012] As a method for adhering the fine resin particles to the surface of the inner core particles, a conventional mixer such as a ball mill or a V-type mixer can be used, but it is preferable to use a so-called high-speed fluidized stirrer. As the high-speed fluidized stirrer, a so-called Henschel mixer, Mechano Fusion System (Hosokawa Micron), Nara Hybridization System (Nara Kikai Seisakusho), Mechano Mill (Okada Seiko), etc. are used. However, the device for fixing the resin fine particles to the surface of the inner core particles is by no means limited to these. Other adhesion methods include a heterocoagulation method that utilizes electrostatic adhesion due to the zeta potential difference between the surface of the inner core particle and the surface of the resin fine particle, a wet milling method that involves milling a mixed dispersion using a ball mill, etc., and a method of attaching the inner core particle to the coupling agent. It is also possible to apply a coupling agent method in which the resin is treated with resin particles, and then mixed with resin particles and treated with adhesion. Next, methods for treating the solvent include spray drying, immersion, and the like, but any method may be used as long as the contact time can be controlled. Preferably a powder coating device, for example, Dispercoat (Nissin Seifun)
, use Coatmizer (Freund Sangyo), etc.

[0013] Furthermore, the solvent brought into contact with the particles is rapidly evaporated by heat or the like and removed from the particles, thereby preventing the particles from coagulating with each other. The solvent 7 for treating particles with fine resin particles attached to the surface of the inner core particles is determined depending on the materials of the inner core particles and the fine resin particles. For this reason, water-based, organic solvent-based, etc. can be used. For example, organic solvents include halogenated hydrocarbons such as dichloromethane, chloroform, carbon tetrachloride, dichloroethane, and chlorobenzene, alcohols such as methanol, methyl cellosolve, and benzyl alcohol, dioxane, tetrahydrofuran,
Ethers such as benzyl ether, esters such as ethyl acetate, butyl acetate, ketones such as furfural, acetone, methyl ethyl ketone, cyclohexane, aromatics such as benzene, toluene, xylene, nitrobenzene, acetonitrile, diethylamine, aniline, dimethyl Nitrogen compounds such as formamide and pyrrolidone can be used.

The inner core particles 3 are composed of a binder resin 1, a magnetic agent 2, a coloring agent, a mold release agent, and the like. However, the composition of the inner core particles is not limited to these, and various types can be used. Examples of the binder resin 1 include polystyrene and copolymers, such as hydrogenated styrene resins, styrene-isobutylene copolymers, ABS resins, and ABS resins.
SA resin, AS resin, AAS resin, ACS resin, AES
Resin, styrene/P-chlorostyrene copolymer, styrene/propylene copolymer, styrene/butadiene crosslinked polymer, styrene/butadiene/chlorinated paraffin copolymer, styrene/allyl/alcohol copolymer, styrene/butadiene rubber emulsion, Styrene maleate copolymers, styrene/isobutylene copolymers, styrene/maleic anhydride copolymers, acrylate resins or methacrylate resins and their copolymers, styrene/acrylic resins and their copolymers, e.g. , styrene/acrylic copolymer, styrene/diethylamino/ethyl methacrylate copolymer, styrene/butadiene/acrylic ester copolymer, styrene/methyl methacrylate copolymer, styrene/n-butyl methacrylate copolymer, Styrene/diethylamino/ethyl methacrylate copolymer, styrene/methyl methacrylate/n-butyl acrylate copolymer, styrene/methyl methacrylate/butyl arylate/N
-(Ethoxymethyl)acrylamide copolymer, styrene/glycidyl methacrylate copolymer, styrene/
Butadiene/dimethyl/aminoethyl methacrylate copolymer, styrene/acrylic acid ester/maleic ester copolymer, styrene/methyl methacrylate/
2-ethylhexyl acrylate copolymer, styrene/N
-Butyl arylate/ethyl glycol methacrylate copolymer, styrene/n-butyl methacrylate/
Acrylic acid copolymer, styrene/n-butyl methacrylate/maleic anhydride copolymer, styrene/butyl acrylate/isobutyl maleic acid half ester/divinylbenzene copolymer, polyester and its copolymer, polyethylene and its copolymer One type or a blend of two or more types of resins such as epoxy resins, silicone resins, polypropylene and their copolymers, fluorocarbon resins, polyamide resins, polyvinyl alcohol resins, polyurethane resins, and polyvinyl butyral resins can be used. .

[0015] As waxy substances, plant-based natural waxes such as candelilla wax, carnauba wax, and rice wax; animal-based natural waxes such as beeswax and lanolin; mineral-based natural waxes such as montan wax and ozokerite; paraffin wax; Microcrystalline wax, natural petroleum wax such as petrolatum,
Synthetic hydrocarbon waxes such as polyethylene wax and Fischer-Tropsch wax, modified waxes such as montan wax derivatives and paraffin wax derivatives, hydrogenated waxes such as hydrogenated castor oil and hydrogenated castor oil derivatives, waxes such as synthetic waxes, stearic acid, palmitin Higher fatty acids such as acids, polyolefins such as low molecular weight polyethylene, polyethylene oxide, polypropylene, olefin copolymers such as ethylene/acrylic acid copolymers, ethylene/acrylic acid ester copolymers, ethylene/vinyl acetate copolymers, etc. A toner for low-temperature, low-pressure fixing containing one or more of them can also be used as the inner core particles.

The magnetic agent 2 is preferably fine particles that are chemically stable when dispersed in the binder resin 1 and have a particle size of 5 μm or less. For example, metal powders such as Fe, Co, Ni, Cr, and Mn, metal oxides such as Fe3O4, Fe2O3, Cr2O3, and ferrite, and alloys that exhibit ferromagnetism through heat treatment such as alloys containing manganese and copper can be used. ,
A preliminary treatment such as a coupling agent may be applied in advance.

The amount of magnetic agent is preferably 70% or less in consideration of fixing properties and the like, and can be set arbitrarily depending on the magnetic force of the toner carrier. As the coloring agent, black dyes and pigments such as carbon black, graphite, black titanium oxide, spirit black, and nigrosine are used. For color use, phthalocyanine, rhodamine B
Dyes such as Lake, Solar Pure Yellow 8G, quinacridone, polytungstophosphoric acid, industhrene blue, sulfonamide derivatives, etc. can be used. Further, as a mold release agent, waxes, particularly polyethylene wax, polypropylene wax, etc., can be used to prevent offset to the heat roller. Furthermore, as other additives, metal soaps, dispersants such as polyethylene glycol, electron-accepting metal complexes as charge control agents, chlorinated polyesters, nitrofumic acids, quaternary ammonium salts,
Pyridinyl salts and the like can be added.

As the resin particles 4, resin particles having the same composition as the binder resin 1 used for the inner core particles 3 are used. Preferably polymethyl methacrylate, polyethyl methacrylate, poly n-butyl methacrylate, polyester, (styrene-butadiene) copolymer, (PV
C, PVA, PVAc) copolymer, polyγ-methyl-glutamate, fluororesin, vinylidene fluoride resin, benzoquanamine resin, silicone resin, epoxy resin,
Nylon 66/6, nylon 11, nylon 12, polystyrene resin, crosslinked polystyrene resin, phenol resin, melamine resin, polyolefin resin, polyethylene resin, cellulose, etc. are used. In addition, the inorganic fine particles 8 to be dispersed in the above solvent include Si02, TiO2, (rutile, anatase), Zn0, Al2O3 (α type, β type), TiON, TiBaO3, MgO, ZrO2, Ca
Fine particles of CO3, NiO, SnO, clay, talc, silica sand, mica, SiN, SiC, Ba2SO4, carbon black, etc. can be used.

Using the raw materials and methods described above, a resin coating layer containing inorganic fine particles can be formed on the surface of the magnetic fixing core particles. This example will be explained in more detail below.

(Example 1) [Preparation of inner core particles] Polyester resin 5
9 parts by weight Fe3O4
40 parts by weight carbon black
Using 1 part by weight of raw materials having the above composition, they are kneaded in a screw extruder, cooled, and coarsely ground. Next, it is finely pulverized with a jet pulverizer and classified into 5 to 20
Inner core particles of μm (average particle diameter 10 μm) were produced.

[External addition of resin fine particles] Polybutyl methacrylate (PBMA) is added to the inner core particles as resin fine particles.
was used. The PBMA used had a particle size of 0.4 μm and a glass transition point of 83°C. The fine resin particles and the inner core particles were mixed to have the composition shown below, and the mixture was attached to the surface of the inner core particles using a mechanofusion system (manufactured by Hosokawa Micron). The composition and conditions are shown below.

PBMA fine particles: 20 parts by weight Inner core particles: 80 parts by weight The mechano conditions were a rotation speed of 1500 rpm and a processing time of 30 minutes. Observation with an electron microscope revealed that the PBMA particles of the obtained powder adhered to the surface of the inner core particles without peeling off. Further, when the cross section was observed using an electron microscope, it was observed that the PBMA particles remained spherical and were slightly embedded in the surface of the inner core particles.

[Solvent treatment for dispersing inorganic fine particles] The inner core particles to which the resin fine particles prepared by the above method were attached were subjected to a solvent treatment. Acetone was used as the solvent. In this solvent, 3% by weight of SiO2 having a particle size of 0.02 μm was mixed and dispersed as inorganic fine particles. This inorganic fine particle dispersion solvent was brought into contact with the externally added inner core particles of the resin fine particles for 1.0 seconds, and then spray-dried at a drying temperature of 60° C. to evaporate acetone. The particles obtained by this solvent treatment have no binding between particles,
Each particle was a collection of independent particles. Also,
When the cross section of the particles produced in this example was observed using an electron microscope, it was found that a resin coating layer of 0.2 to 0.3 μm was formed on the surface of the inner core particle. Furthermore, it was confirmed that SiO2 was uniformly dispersed in the resin layer and that SiO2 was also exposed on the surface of the coating layer. Further, the specific resistance of the obtained toner was 10
It was 15 Ωcm or more, and was able to have a sufficiently high resistance. (The specific resistance was measured by the pressure cell method. That is,
A sample was placed between two electrodes, and a pressure of 15 kg/cm2 was applied to measure the resistance. ) Next, as a guideline for liquidity,
When the angle of repose was measured using an electromagnetic vibration type angle of repose measuring device, it showed high fluidity of around 30 degrees.

Next, an image was formed using the magnetic toner prepared in this example. FIG. 2 shows a cross-sectional overview of the image forming apparatus used in this example. The latent image carrier 21 is
A photosensitive layer 23 having organic or inorganic photoconductivity is coated on a conductive support portion 22, and the photosensitive layer 23
After charging using a charger 24 such as a corona charger or a charging roller, light emitted from a light source 25 such as a laser or LED is selectively irradiated onto the photosensitive layer 23 according to the image through an imaging optical system 26. to obtain potential contrast and form an electrostatic latent image. On the other hand, the developing device 27 conveys and develops the magnetic toner 28, and the developing roller 29 that conveys the toner 28 has an elastic layer 31 and a magnetic field generating layer 32 arranged concentrically around the outer periphery of the shaft 30. I did it,
The magnetic toner 2 is caused by the leakage magnetic flux around the outer periphery of the magnetic field generation layer 32.
8 is directly held on the developing roller 29, and the developing roller 29 is rotated to convey a thin layer of toner 28 while regulating the appropriate amount with a plate-shaped elastic blade 33 made of non-magnetic or magnetic metal or resin. It is something to do. Developing roller 2
9 is in pressure contact with the latent image carrier 21 at a predetermined pressure, and when the toner 28 on the developing roller 29 is conveyed to the pressure contact portion, the potential contrast of the latent image carrier 21 and the developing electric field by the developing bias applying means 34 are applied. Toner 2 charged according to
8 adheres to the latent image carrier 21, and the electrostatic latent image is visualized. Further, a toner image is transferred onto a recording paper 36 using a transfer device 35 such as a corona transfer device or a transfer roller, and the toner is fixed on the recording paper using heat or pressure to obtain a desired image on the recording paper. It is. When 10,000 sheets of 600 [DPI] line images, character images, and solid images were continuously formed using the image forming apparatus shown in FIG. 2, the 600 [DPI] line images were stable without line thickening. It is possible to stably form a high-density solid image with an OD value of 1.5 or more without trailing or background fog on the image edges, and of course there is no background fog on the recording paper. There was no background fog on the image carrier, and the amount of waste toner could be significantly reduced.

(Example 2) A toner was prepared using the same inner core particles, inorganic fine particles SiO2, and resin fine particles PBMA as in Example 1, and by changing the particle sizes of the inorganic fine particles and the resin fine particles. Tables 1 and 2 show the relationship between experiment number and particle size. Table 1 shows the PBMA used in Example 1 as resin fine particles: 0
．． 4 μm, and the particle size of the SiO2 particles was changed. In Table 2, SiO2 used in Example 1 (0.02 μm) was used as the inorganic fine particles, and the particle size of the resin fine particles was changed.

[0026]

[Table 1]

*All resin fine particles are PBMA: 0.4 μm

[0028]

[Table 2]

*All inorganic fine particles are SiO2: 0.02
μm Next, in the same manner as in Example 1, [external addition of resin fine particles] and [inorganic fine particle dispersion solvent treatment] were performed. However, the contact time was changed depending on the particle size. Table 3 shows the results of toners produced using the above materials. Furthermore, images were formed using these toners in the same manner as in Example 1, and the images were evaluated. The results are shown in Table 4.

[0030]

[Table 3]

[0031]

[Table 4]

The definition of 'clear' is an image with no background fog and an image density of 1.5 or more.

According to this example, the particle size of the inorganic fine particles is 0.
If it is larger than 1 μm, the particle size of the resin fine particles is 1.0 μm.
It has become clear that when it is larger than m, the fluidity deteriorates and clear images cannot be obtained.

(Example 3) In this example, inner core particles having the composition shown below were used.

[Composition of inner core particles] Styrene/acrylic copolymer 58 parts by weight F
e3O4
30 parts by weight polyethylene wax
4 parts by weight Nigrosine
5 parts by weight charge control agent
3 parts by weight Next, in the same manner as in Example 1, [preparation of inner core particles], [external addition of fine resin particles], and [dispersion treatment of inorganic fine particles] were carried out to prepare a magnetic toner. However, polymethyl methacrylate (PMMA) was used as the resin fine particles. Next, Figure 3
Image formation was performed using the image forming apparatus shown in the cross-sectional overview diagram. Components having substantially the same functions and names as those in FIG. 2 are given the same numbers, and descriptions thereof will be omitted. The developing device 41 stores magnetic toner 28
The developing roller 42 that conveys the toner 28 includes a driving roller 43 that is rotatably driven and has a friction portion on its outer periphery, and a cylindrical roller that is sheathed with an extra length left on the outer periphery of the driving roller 43. A magnetic field generating layer 45 is disposed on the cylindrical thin film member 44, and the magnetic toner 28 is held directly on the developing roller 42 by the leakage magnetic flux around the outer periphery of the magnetic field generating layer 45. Plate-shaped elastic blade 3 made of magnetic or magnetic metal or resin
3, the developing roller 42 is rotated to convey a thin layer of toner 28 with the amount regulated to an appropriate amount. The developing roller 43 is pressed against the latent image carrier 21 with a predetermined pressure, and when the toner 28 on the developing roller 42 is conveyed to the pressure contact portion, the potential contrast of the latent image carrier 21 and the developing bias applying means 34 are applied. Toner 28 charged according to the developing electric field adheres to the latent image carrier 21, and the electrostatic latent image is visualized. When an image was formed in the same manner as in Example 1 using the image forming apparatus shown in FIG. 3, an image similar to that in Example 1 could be formed.

(Example 4) In this example, particles containing wax as a main component were used as the inner core particles. In other respects, the same procedure as in Example 1 was carried out.

[Preparation of inner core particles] Paraffin wax 30
wt% polyethylene wax
30wt%Fe3O4
38wt% carbon black
Using raw materials having the above composition of 2 wt%, they are kneaded in a batch kneader, cooled and coarsely pulverized. Next, it was finely pulverized using a jet pulverizer, and then classified to produce inner core particles with an average particle size of 10 microns and a distribution of 5 to 25 μm.

[External addition of resin fine particles] Same P as in Example 1
BMA was used under similar mixing conditions. However, as the mechano conditions, the rotation speed is 80 because the inner core particles are soft.
The processing was performed at 0 rpm and for 15 minutes. The obtained powder is P
Electron microscopic observation of the surface revealed that the BMA particles were not peeled off from the surface of the inner core particle but were attached to it. Further, when the cross section was observed using an electron microscope, it was observed that the PBMA particles remained spherical and were embedded in the surface of the inner core particles.

[Solvent treatment for dispersing inorganic fine particles] The inner core particles to which the resin fine particles produced by the above method were attached were subjected to a solvent treatment. Xylene was used as the solvent. In this solvent, 5% by weight of SiO2 having a particle size of 0.02 μm was mixed and dispersed as inorganic fine particles. This inorganic fine particle dispersion solvent was brought into contact with the externally added inner core particles of the resin fine particles for 1.0 seconds, and then spray-dried at a drying temperature of 60° C. to evaporate xylene. The particles obtained by this solvent treatment have no binding between particles,
Each particle was a collection of independent particles. Also,
When the cross section of the particles produced in this example was observed using an electron microscope, it was found that a resin coating layer of 0.2 to 0.3 μm was formed on the surface of the inner core particle. Furthermore, it was confirmed that SiO2 was uniformly dispersed in the resin layer and that SiO2 was also exposed on the surface of the coating layer. Further, the specific resistance of the obtained toner was 10
It was 15 Ωcm or more, and was able to have a sufficiently high resistance. (The specific resistance was measured by the pressure cell method. That is,
A sample was placed between two electrodes, and a pressure of 15 kg/cm2 was applied to measure the resistance. ) Next, as a guideline for liquidity,
When the angle of repose was measured using an electromagnetic vibration type angle of repose measuring device, it was found to be around 32 degrees, indicating high fluidity.

Next, when an image was formed using the above-prepared toner in the same manner as in Example 1, it was possible to form an image similar to that in Example 1. Furthermore, it was possible to fix a clear image at a low fixing temperature of 120°C.

(Example 5) Inner core particles manufactured using the following composition and manufacturing method were used.

Microcrystalline wax 20 parts by weight Carnauba wax 20 parts by weight Ethylene/vinyl acetate copolymer 18 parts by weight Fe3O4
40 parts by weight carbon black
2 parts by weight of raw materials having the above composition are kneaded in a batch kneader, cooled and coarsely pulverized. Next, the mixture was finely pulverized using a jet pulverizer, and then classified to produce inner core particles with an average particle diameter of 10 μm and a distribution of 5 to 25 μm. Hereinafter, the steps of [external addition of resin fine particles] and [inorganic fine particle dispersion solvent treatment] were performed in the same manner as in Example 4. When an image was formed on the obtained toner in the same manner as in Example 4, the same results as in Example 4 could be obtained.

(Example 6) Using the inner core particles produced in Example 1, the step of [external addition of resin fine particles] was carried out in the following manner. In this example, methyl methacrylate to butyl methacrylate copolymer was used as the resin fine particles. The resin fine particles (particle size 0.4 μm) were dispersed in an aqueous solution, and 5%
An aqueous dispersion solution was prepared. Next, the inner core particles produced in Example 1 were mixed with this aqueous solution, and an adhesion treatment was carried out by wet milling in a ball mill, followed by drying with a spray dryer to produce inner core particles with fine resin particles attached. Observation using an electron microscope revealed that the resin fine particles of the obtained powder adhered to the surface of the inner core particles without being peeled off. Furthermore,
[Inorganic fine particle dispersion solvent treatment] The process was carried out in the same manner as in Example 1, and the obtained toner was subjected to image formation using the same image forming apparatus as in Example 1. As in Example 1, there was no background fog. I was able to form a clear image. (Example 7) The inner core particles of Example 1 were prepared by a spray drying method. Using the raw material used for producing the inner core particles in Example 1, this was dissolved and dispersed in tetrahydrofuran so that the solid content was 15%. This dispersion was sprayed and granulated using a spray dryer to produce inner core particles. A two-fluid nozzle was used for the spraying method. The spray conditions are pressure 2kg/
cm2, and the drying temperature was 40°C. The obtained particles were adjusted to 5 to 20 μm (average particle size 10 μm) by classification,
It was used as the core particle of magnetic toner. [External addition of fine resin particles] The following procedure was carried out in the same manner as in Example 1 using the inner core particles. As a result, a magnetic toner similar to that in Example 1 could be obtained, and when image formation was performed in the same manner as in Example 1, a clear image similar to that in Example 1 could be formed.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments.

[0045]

[Effects of the Invention] As explained above, magnetic particles are formed by attaching resin particles to the outer surface of the inner core particle containing a magnetic agent, and then dissolving the resin particles using a mixed solvent in which inorganic particles are dispersed to form a resin coating layer. According to the toner manufacturing method,
Since a resin coating layer with fixed inorganic fine particles can be formed, the produced magnetic toner hardly aggregates, and furthermore, since the inorganic fine particles fixed on the toner surface are not peeled off, there is no contamination inside the device. In addition, the development gap is reduced, the development electrode effect is enhanced, and even in pressure contact and contact development, which can form the highest resolution images, there is no image deterioration due to background fog or trailing due to reversely charged toner. It is possible to provide a high-resistance magnetic toner that does not reduce the amount of charge regardless of contact, has stable triboelectric charging characteristics, and has excellent environmental resistance characteristics. This has the great effect of providing clearer, higher quality images than ever before. Also,
Regardless of the material properties of the inner core particles, a highly fluid magnetic toner having a uniform resin coating layer can be easily produced by controlling various materials to have an arbitrary film thickness. In other words, it has the great effect of being able to provide a magnetic toner that can form high-quality images at a lower cost than ever before. Furthermore, the toner manufacturing method of the present invention can be widely applied to copying machines, printers, facsimile machines, etc.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a flowchart of a method for producing magnetic toner of the present invention.

FIG. 2 is a cross-sectional schematic diagram of an image forming apparatus using the magnetic toner of the present invention.

FIG. 3 is a cross-sectional schematic diagram of an image forming apparatus used in another embodiment of the present invention.

[Explanation of symbols]

1 Binder resin 2 Magnetic agent 3 Inner core particles 4 Resin fine particles 5 External addition treatment 6 Resin fine particles externally added inner core particles 7 Solvent 8 Inorganic fine particles 9 Inorganic fine particle dispersion solvent 10 Coating treatment 11 Resin-coated magnetic toner containing inorganic fine particles 21
Latent image carrier 22 Conductive support 23 Photosensitive layer 24 Charger 25 Light source 26 Imaging optical system 27 Developing device 28 Toner 29 Developing roller 30 Shaft 31 Elastic layer 32 Magnetic field generating layer 33 Elastic blade 34 Developing bias applying means 35 Transfer Container 36 Recording paper 41 Developing device 42 Developing roller 43 Drive roller 44 Thin film member 45 Magnetic field generation layer

Claims (2)

[Claims] 1. A magnetic toner used in a developing device that conveys magnetic toner and develops a latent image carrier using an elastically deformable toner carrier, the outer surface of the magnetic toner being composed of at least resin fine particles and inorganic matter. A method of manufacturing a resin coating layer composed of fine particles by attaching resin fine particles to the outer surface of an inner core particle made of at least a binder resin and a magnetic agent, and then treating with a solvent. A step of attaching fine particles, then a step of dispersing at least inorganic fine particles in a solvent that dissolves the resin fine particles, and bringing the mixed solvent into contact with and dissolving the resin fine particles adhered to the outer surface of the inner core particles to form a resin coating layer. A method for producing a magnetic toner comprising: Claim 2: The particle size of the inorganic fine particles is 0.1 μm.
2. The method for producing a magnetic toner according to claim 1, wherein the resin fine particles have a particle size of 1 μm or less.