JPH10282727A - Electrostatic charge image developing resin coated carrier, its production and electrostatic charge image developer and image forming method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dry coating carrier having an excellent coating layer even in a fine particle diameter carrier, the producing method and an electrostatic charge image developing method and an image forming method using the same. SOLUTION: The electrostatic charge image developing carrier produced by mixing a magnetic body particle and a resin fine particle and repeatingly imparting mechanical impact force to the mixture to stick the resin fine particle to the surface of the magnetic body particle is obtained by the producing method, to which a process for separating the resin coated carrier 106 from a non-magnetic body particle 105 is added after the resin coated carrier 106 is prepared by repeatingly imparting mechanical impact force to a mixture obtained by adding further the non-magnetic body particle 105 to the magnetic body particle and the resin fine particle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin-coated carrier for developing an electrostatic image, a method for producing the same, an electrostatic image developer, and an image forming method.

[0002]

2. Description of the Related Art Conventionally, as a developer used in electrophotography and the like, a one-component developer composed of only a toner and a two-component developer composed of a toner and a carrier are known. Of these, the two-component developer has a more stable charging property and does not need to contain magnetic particles or the like in the toner, and therefore has a high saturation of a toner image and is suitable for a color image. Accordingly, two-component developers are more commonly used today. Among them, a two-component developer using a carrier in which the surface of magnetic particles is coated with a resin (hereinafter, also referred to as a coating carrier) is particularly preferably used because the carrier has excellent durability and triboelectricity. .

[0003] As a method for producing a coating carrier, fluidized-bed spray coating, dip coating, and sintering coating are known as so-called wet methods.

However, all of the above techniques are coating methods in which a resin coating layer is formed on the surface of magnetic particles using a coating solution prepared by dissolving a coating resin in a solvent. There is an essential problem that granulation (particles in which some magnetic particles are united) easily occurs therein, and the yield is low.

In recent years, in order to improve the image quality of a copied image, a small particle size carrier having an average particle size of 50 μm or less is often required. In this case, the above-mentioned granulation is more likely to be performed, and it is not possible to stably produce a small particle size carrier.

On the other hand, a dry coating for forming a coating layer has also been developed. According to this method, a mixture of magnetic particles and resin fine particles is electrostatically included, then repeatedly subjected to an impact force, and fixed and coated.
87169.

[0007] According to this, a resin coating layer can be formed on the surface of the magnetic particles having a smaller particle diameter. Since dry coating is performed without using a solvent, there is no problem of solvent recovery and incineration. There is also the advantage that the range of choice is widened. However, in the case of dry coating, since the magnetic particles and the resin fine particles are rapidly stirred, a part of the resin fine particles adheres to the inner wall of the mixer and remains as it is, and is mixed into the manufactured carrier.

If this carrier is used as it is, the fine resin particles mixed therein adhere to the latent image forming body (usually a photoconductor, and hence may be referred to as a photoconductor), and a firefly (overhead projector) image is formed on the image. White spots with a diameter of 3 mm or more in the solid image area) may occur, resulting in image defects or accumulation between the surface of the developer carrier (developing sleeve) and the developer layer regulating body, causing white stripes. I do. In addition, the toner accumulates between the photoconductor and the cleaning blade, and may cause damage to the photoconductor.

[0009]

SUMMARY OF THE INVENTION The present invention has been made based on the above circumstances, and an object of the present invention is to provide:
An object of the present invention is to provide a dry coating carrier having a good coating layer even if the carrier has a small particle size, a method for producing the same, and a method for developing an electrostatic image and an image forming method using the same.

[0010]

The object of the present invention is attained by adopting one of the following constitutions.

(1) A carrier for developing an electrostatic charge image produced by mixing magnetic particles and resin fine particles and repeatedly applying a mechanical impact force to the mixture to fix the resin fine particles to the surface of the magnetic particles. In the step of repeatedly applying a mechanical impact force to a mixture of the magnetic particles and the resin fine particles and the non-magnetic particles further added to produce a resin-coated carrier, and then separating the resin-coated carrier and the non-magnetic particles. A resin-coated carrier for developing an electrostatic image, which is obtained by the added manufacturing method.

(2) A carrier for developing an electrostatic charge image produced by mixing magnetic particles and resin fine particles and repeatedly applying a mechanical impact force to the mixture to fix the resin fine particles to the surface of the magnetic particles. In the production method, after mechanically applying a mechanical impact force to a mixture of magnetic particles and resin fine particles further added with non-magnetic particles to produce a resin-coated carrier, the resin-coated carrier and the non-magnetic particles are separated. A process for producing a resin-coated carrier for developing electrostatic images, characterized by adding a step of performing the following.

(3) In an electrostatic image developer comprising a toner and a carrier containing at least a binder resin and a colorant, the carrier is obtained by further adding non-magnetic particles to magnetic particles and resin fine particles. After producing a resin-coated carrier by repeatedly applying a mechanical impact force to the mixture, a process for separating the resin-coated carrier and the non-magnetic material particles was obtained by a method for producing a resin-coated carrier for electrostatic image development. An electrostatic image developer, which is a resin-coated carrier.

(4) An electrostatic image developer comprising a toner containing at least a binder resin and a colorant and a carrier is coated with a developer layer having a thickness of 20 to 500 μm by a developer regulating member.
In an image forming method for non-contact development of an electrostatic image on a latent image forming body, the carrier repeatedly applies a mechanical impact force to a mixture of magnetic particles and resin fine particles to which non-magnetic particles are further added. A resin-coated carrier obtained by a method for producing a resin-coated carrier for developing an electrostatic image, to which a step of separating the resin-coated carrier and the non-magnetic material particles is added after application and preparation of the resin-coated carrier. Image forming method.

As a result of intensive studies, the present inventors have mixed magnetic particles with resin fine particles, and further mixed nonmagnetic particles with a considerably large particle size, and repeatedly applied a mechanical impact force to the mixture. Later, it was found that this can be achieved by adding a step of separating the resin-coated carrier and the non-magnetic particles, and the present invention has been accomplished.

That is, the present invention has a volume average particle size of 5 as will be understood from the description of Examples and Comparative Examples described later.
With a powder of magnetic particles having a particle size of 0 μm or less, it was difficult to apply a mechanical impact force to the coating resin layer attached to the magnetic particles, and it was difficult to form a good coating layer. However, even when the average particle size is less than 50 μm, the mechanical impact force is repeatedly applied to the mixture of the coating carrier and the non-magnetic material particles, so that the coating resin layer attached to the magnetic material particles can be efficiently mechanically applied. It was found that a high impact force was applied, a good coating layer was formed, and no unattached resin fine particles remained.

When the coating carrier is mixed and agitated with the non-magnetic material particles to give a mechanical impact, a sufficient and uniform mechanical impact and shearing force are applied to the coating resin layer adhered to the coating carrier. Therefore, it is considered that no harmful non-adhered resin fine particles remain, thereby forming a smooth and smooth coating layer on the surface of the magnetic particles.

Since the non-magnetic particles are used, even when the particle size distribution of the coating carrier and the non-magnetic particles overlaps, the coating carrier can be easily separated and recovered by the magnetic separation process. By combining the collected coating carrier with a toner, a developer according to the purpose can be prepared.

FIG. 1 is a conceptual sectional view of a drum type magnetic separator used for separating a coating carrier and non-magnetic particles.
Shown in

In FIG. 1, 101 is a supply gutter, 102 is a rotating drum, 103 is an electromagnet contained in the rotating drum, 104 is a separation / recovery wall, 105 is a non-magnetic particle, and 106 is a coating carrier containing a magnetic component. .

In the present invention, the average particle diameter means a volume average particle diameter measured by a laser diffraction particle size distribution analyzer "HELOS" (manufactured by Nippon Laser Co., Ltd.).

The present invention will be described in more detail.

In the present invention, a wide range of resins is used as the resin used for the resin fine particles. Specifically, a resin such as a styrene resin, an acrylic resin, a styrene-acryl resin, a vinyl halide resin, an ethylene resin, a rosin modified resin, a polyamide resin, a polyester resin, a silicone resin, and a fluorine resin is used. These resins may be used in combination.

Particularly preferred are styrene-acrylic resins, and styrenes such as styrene and α-methylstyrene, and methyl methacrylate, butyl methacrylate, ethyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, methyl acrylate and butyl acrylate. And a copolymer with acrylic acid or methacrylic acid ester such as ethyl acrylate, octyl acrylate and 2-ethylhexyl acrylate.

These resins are used as fine resin particles to form a resin coating by a dry method. In order to form resin fine particles, there are synthetic methods such as an emulsion polymerization method and a suspension polymerization method.

The resin fine particles have a number average primary particle diameter of 0.01 to 1.00 μm, preferably 0.05 to 0.5 μm.
0 μm, and the volume average particle size of the aggregated particles is 1.0 to
It is 5.0 μm, preferably 1.5 to 3.0 μm. That is, in the dry coating method described below, it is necessary to uniformly adhere resin fine particles to the surface of the magnetic particles. For this purpose, uniform adhesion can be achieved by setting the number average primary particle diameter as described above. further,
These resin fine particles need to exist not only as primary particles but also as aggregated particles. This is because the resin coating is more uniformly formed when the core magnetic particles are dry-coated by being present as aggregated particles. Although the reason for this is not clear, mechanical energy is applied to the resin fine particles, and when a resin film is formed, if primary particles are present, the primary particles are extended and the film is accumulated. On the other hand, if it exists as aggregated particles, the aggregated particles themselves are spread and form a film. As a result,
The film formed from the aggregated particles is formed to be uniformly thick as a film as compared with the case formed from the primary particles.
From the viewpoints described above, it is important to exist as aggregated particles.

The number average primary particle diameter is a value observed by a scanning electron microscope, and the volume average particle diameter of the aggregated particles is determined by a laser diffraction method.
OS "(manufactured by SYMPATEC).

Further, since the dry-coated carrier of the present invention is formed by applying a mechanical impact force, it has a polished surface as compared with a resin film formed by a spray drying method or a dipping method. The surface has fine irregularities. Therefore, when friction occurs between the carriers, the friction between the carriers is reduced due to the presence of the unevenness, and the fluidity is improved.

The magnetic particles used in the coating carrier include iron powder, magnetite, various ferrites,
Further, composite magnetic material particles composed of a magnetic material and a resin obtained by a melt-kneading method, a melt spraying method, a polymerization method, or the like (having the same structure as a so-called resin-dispersed carrier) may be used.

Preferred are magnetite, various ferrites, and composite magnetic particles.

As ferrite, copper, zinc, nickel,
Ferrite containing a heavy metal such as manganese and light metal ferrite containing an alkali metal and / or an alkaline earth metal are preferred, and light metal ferrite containing an alkali metal and / or an alkaline earth metal is particularly preferred.

The composition of the magnetic material contains an alkali metal such as Li and Na and / or an alkaline earth metal such as Mg, Ca, Sr and Ba, and has the following composition.

(M ₂ O) _x (Fe ₂ O ₃ ) _1-x or (M
O) _x (Fe ₂ O ₃ ) _{1 -x} Further, M ₂ O and / or Fe ₂ O ₃ may be partially substituted with an alkaline earth metal oxide. M is an alkali metal such as Li and Na described above and / or M
The alkaline earth metals of g, Ca, Sr, and Ba are shown. Further, x is 30 mol% or less, preferably 18 mol%.
1% or less, and preferably 1 to 10 mol% of the alkaline earth metal and / or alkali metal oxide to be further substituted. More preferably, it is 3 to 15 mol%.

The reason why the light metal ferrite or magnetite is preferable is not limited to the problem of environmental pollution of waste, which has become severe in recent years. This is because, in addition to these, the carrier itself can be reduced in weight, and there is an advantage that stress on the toner can be reduced.

The average particle size of the magnetic particles is 50 μm.
Below, and preferably 8 to 45 μm. 15 to 35
μm is preferred. The saturation magnetization is preferably 20 to 80 emu / g.

The amount of the resin coating may be an amount sufficient to uniformly coat the surface of the magnetic material. The amount of the resin is 0.1 to 6.0% by weight, preferably 0.5 to 4.0% by weight, based on the weight of the magnetic material. When the amount of the resin is small, the effect cannot be exerted. When the amount of the resin is too large, the resin itself is released, which may cause an image defect.

The non-magnetic particles suitable for the present invention include alumina (Al ₂ O ₃ ), zirconia (ZnO ₂ ), silicon nitride (Si ₃ N ₄ ), silicon carbide (S
iC) and zirconia (ZnO ₂ ) / silicone (Si
Ceramic beads obtained by a sintering method or an electrofusion method mainly containing O ₂ ) or the like, or nonmagnetic metal beads mainly containing SUS or the like can be used. In the present invention, the non-magnetic particles refer to particles made of a non-magnetic material and particles that can be separated from the coating carrier by the above-described magnetic separation process even if the particles are somewhat magnetic depending on the conditions.

The average particle size of the nonmagnetic particles is as follows:
More than twice the coating carrier, practically 60 μm
To 1.25 mm. 80
More preferably, the range is from μm to 800 μm,
In particular, the range of 100 μm to 400 μm is preferable.

With respect to the mixing ratio of the magnetic particles and the non-magnetic particles, from the viewpoint of efficiently forming a good coating layer as a coating carrier and increasing the yield,
Magnetic particles and resin fine particles: non-magnetic particles = 50: 50-
90:10 (weight ratio) is preferable, and 50:50 is also preferable.
~ 80: 20 is preferred.

The mixing weight ratio of the magnetic particles to the resin fine particles is 0.1 to 10 parts by weight, preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the magnetic particles of the carrier core material.
Use 5-5 parts by weight.

The electrostatic image developing carrier of the present invention can be produced, for example, by the following method.

That is, magnetic particles having a volume average particle diameter of 10 to 200 μm, and a volume average particle diameter which is １ ／ of those of the magnetic particles.
The resin fine particles having a particle size of less than 00 are mixed and stirred by a usual stirring type mixer or the like, and a uniform mixture is obtained by a mixing step of electrostatically adhering the resin fine particles to the magnetic particle surfaces.

The mixing device in this case is not particularly limited, and examples thereof include a turbulent mixer, a V-type mixer, a Henschel mixer and the like, and a mixing device as shown in FIG. 2 can be used.

Next, non-magnetic particles are added to the mixture,
A resin coating is obtained by a coating step of fixing resin fine particles adhered to the magnetic particles on the surface of the magnetic particles. The non-magnetic particles may be already added in the step of preparing the mixture. As this device, any device that can be stirred at high speed, can apply mechanical energy, and consequently can spread resin fine particles and form a film on the surface of magnetic particles can be used. is there.

For example, there may be mentioned a hybridizer, an ong mill, a mechano mill, a kryptron and the like. Further, it is preferable to use a horizontal stirring type mixing apparatus 1 capable of high speed stirring as shown in FIG. Reference numeral 3 denotes a motor, and 2 denotes a stirring blade. In the mixing apparatus shown in FIG. 2, the above-described adhesion step and film formation step can be performed in the same apparatus by changing the stirring conditions, which is more preferable. In the step for adhering the resin fine particles on the surface of the magnetic particles, the stirring conditions were set such that the peripheral speed of the stirring blade 2 was 4 to 12 m / sec and the stirring time was 3 to 30.
Minutes. Further, in the film forming step, the peripheral speed of the stirring blade is 8 to 15 m / sec, and the stirring time is 10 to 10 m / sec.
Preferably, it is 40 minutes. When the temperature of the mixing device is set to 50 to 120 ° C., the spreading and fixing can be performed more efficiently.

The volume average particle diameter of the toner used together with the carrier is usually about 4 to 15 μm,
Is particularly desirable in terms of obtaining high image quality. As additives other than the colorant and the release agent, for example, a charge control agent, a cleaning property improving agent, a fluidity improving agent, and the like can be used.

The mixing ratio with the carrier is preferably such that the toner concentration is 1 to 15% by weight.

A Coulter counter is usually used for measuring the volume average particle size of the toner. Coulter counter is, for example, Coulter TA-II (manufactured by Coulter Inc.)
Is used. The measurement was conducted using a toner solution ISOTONE-II.
(Manufactured by Nikkaki Co., Ltd.), and the mixture was dispersed in a coulter counter described above. The measurement may be performed two to three times in order to increase the accuracy.

The binder resin constituting the toner is not particularly limited, and resins conventionally used for this type of application can be used. Specifically, for example, a styrene resin, a styrene-acrylic resin, a styrene-butadiene resin, an ester resin, and an epoxy resin can be used. Among them, an ester-based resin and a styrene-acrylic-based resin can be preferably used as those having a stable triboelectric charging property. These resins are used alone or as a mixture of two or more.

The coloring agent is not particularly limited, and many dyes and pigments such as carbon black, phthalocyanine blue, Pigment Green B and Solvent Red 49 conventionally used for this kind of application can be used. For example, as a black toner, carbon black, a nigrosine dye, or the like is used, and as a pigment required for yellow, magenta, and cyan toners, C.I. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 6, C.I. I. Pigment Blue 6
8, C.I. I. Pigment Red 48-3, C.I. I. Pigment Red 122, C.I. I. Pigment Red 21
2, C.I. I. Pigment Red 57-1, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow 8
1, C.I. I. Pigment Yellow 154 and the like can be suitably used.

As the release agent, for example, low molecular weight polyolefin, aliphatic ester and aliphatic ester wax, carnauba wax and the like can be used. As the charge control agent, for example, a nigrosine dye, a metal complex dye, or the like can be used.

The method for producing the toner includes a binder resin, a colorant,
The release agent is mixed with a Henschel mixer, etc., and kneaded while dispersing the colorant and the release agent into a predetermined dispersion diameter under various conditions, and thereafter, through the respective steps of pulverization and classification, and further, in some cases, cleaning. A fluidity improver, a fluidity improver and the like can be externally added and mixed.

As another toner production method, a polymerization method can be applied.

Specific examples of the polymerization method include a suspension polymerization method, an emulsion polymerization / granulation method, and a similar method thereof. The starting material is a polymerizable monomer, and the pulverizing / classifying process can be eliminated or simplified.

The melt-kneading and pulverizing method has an essential problem that the production cost is drastically increased because the load on the pulverizing / classifying step increases as the toner particle diameter decreases. On the other hand, in the polymerization method, the toner particle size hardly correlates with the manufacturing cost. Therefore, the polymerization method is a toner manufacturing method suitable for reducing the toner particle size and sharpening the particle size distribution with higher precision of an image. .

As an example of the suspension polymerization method, a colorant and other additives are dispersed in a monomer (dispersion step), a monomer droplet is formed by primary stirring in an aqueous phase, and a monomer droplet is formed by secondary stirring. Droplets are polymerized to obtain a toner (polymerization step).

The shape is characterized by a true sphere and a sphere. Further, the particle size and the particle size distribution depend on the concentration of the suspension stabilizer and the dispersant, the stirring speed of primary and secondary stirring, time, and temperature.

As an example of the emulsion polymerization method, monomers are polymerized in an aqueous solvent to obtain primary particles having a submicron diameter (polymerization step). Next, a coloring agent and other additives are added and adsorbed on the surface of the primary particles and then associated to form secondary particles of several μm (dispersion / association step). Further, the secondary particles are agglomerated in a dispersion medium (granulation step), heated to a temperature equal to or higher than the glass transition temperature of the polymer, and the interface between the secondary particles is fused to form toner particles (ripening step).

Further, the monomer is polymerized in the presence of a colorant and other additives to obtain colorant-containing primary particles having a submicron diameter (polymerization step), and the primary particles are associated in the presence of an aggregating agent ( It is also possible to heat the polymer to a temperature equal to or higher than the glass transition temperature of the polymer and fuse the interface between the primary particles to form toner particles (aging process).

In the emulsion polymerization / association method, the shape of the toner can be controlled in a wide range from spherical to irregular.

The toner obtained by the polymerization method is dried after washing, and if necessary, a cleaning improver, a fluidity improver and the like can be externally added and mixed.

As the cleaning improver externally added to the toner, for example, aliphatic metal salts such as zinc stearate and lithium stearate, and fine polymer particles such as a fluorine-based polymer and a styrene-acrylic polymer may be used. it can. As the fluidity improver, for example, inorganic fine particles are used, such as silica, alumina, titanium oxide, titanate, zinc oxide, silicon carbide, silicon nitride, chromium oxide, zirconium oxide, magnesium oxide, barium carbonate, barium sulfate, and the like. Inorganic oxide fine particles are preferably used. These inorganic oxide fine particles are preferably subjected to a hydrophobic treatment with a silane coupling agent or the like.

The developing method according to the present invention is preferably a so-called non-contact developing method in which a gap is provided between the developer layer on the developing sleeve and the latent image forming member during development. in this case,
The layer thickness of the developer layer on the developing sleeve is generally thinner than that of the contact developing method, and is suitably 20 to 500 μm.

In the thin-layer non-contact developing system, the developing area is preferably 20 to 50 on the surface of the developer carrier.
A 0 μm developer layer is formed. Particularly preferably 50 to 3
A developer layer of 00 μm is formed. In order to form the thin layer, there are a magnetic blade using a magnetic force, a method of pressing a developer layer regulating rod against the surface of a developer carrying member, and the like. Further, there is a method in which a urethane blade, a phosphor bronze plate or the like is brought into contact with the surface of the developer carrier to regulate the developer layer.

As the developer carrying member, a developing device having a magnet built in the carrying member is used, and as the material constituting the surface of the developer carrying member, aluminum or aluminum or stainless steel whose surface is oxidized is used. Can be

The pressing force of the pressing regulating member is 1 to 15 g.
f / mm is preferred. When the pressing force is small, the conveyance becomes unstable due to insufficient regulating force. On the other hand, when the pressing force is large, the stress on the developer increases, and the durability of the developer decreases. The preferred range is 3 to 1.
0 gf / mm.

The gap between the developer carrier and the surface of the photoreceptor needs to be larger than the developer layer.
It is preferable that the width is 0 μm or more. In particular, a preferable range in which the gap is wider than that of the developer layer is 15 to 200 μm. Further, it is preferable to apply an AC bias as an alternating electric field in addition to a DC component as a developing bias. The alternating electric field is 1000 to 3000 Hz, and the voltage is 500 to 200 in absolute value from peak to peak (Vp-p).
0V is a suitable range.

The size of the developer carrier is 10 mm in diameter.
Those having a size of ４０40 mm are preferred. When the diameter is small, the mixing of the developer is insufficient, and it is difficult to secure sufficient mixing to perform charging to the toner, and when the diameter is too large, the centrifugal force on the developer becomes large, A problem of toner scattering occurs.

FIG. 3 is a sectional view showing an example of a developing device (developing device) used in the image forming method according to the present invention. In this figure, reference numeral 41 denotes a developing sleeve which is a developer carrying body having a fixed magnet 42 therein; 46, a regulating rod which is a developer carrying amount regulating body; 47, a scraper which is a developer scraping member; A stirring roller which is a developer stirring member,
49 is a casing of the developing device, 50 is a two-component developer composed of toner T and carrier C, 51 is a power supply as a bias applying means, and 10 is a latent image forming body having the photosensitive layer 12 formed on the conductive substrate 11. The photoconductor drum D ₁ indicates the closest distance between the photoconductor drum 10 and the developing sleeve 41, and the arrow in FIG. 10 indicates the rotation direction of the photoconductor drum 10 and the developing sleeve 41.

The developing sleeve 41 is made of, for example, aluminum,
It is a cylinder of 0.5 to 3 cm in diameter made of non-magnetic and conductive metal such as stainless steel, and has a surface roughness (Rz) of 1 to 3.
It is processed to be 30 μm. Inside the developing sleeve 41, 4 to 12 magnetized to the N pole or the S pole
A magnet body 42 such as a columnar or split chopstick-shaped (column-shaped) aggregate having magnetic poles is fixedly provided, and the developing sleeve 41 is rotatable with respect to the magnet body 42.

The casing 49 is a casing made of, for example, an insulating resin such as acryl or polycarbonate. Inside the casing 49, the developing sleeve 41 including the fixed magnet body 42, the supply roller 45, and the scraper 4 are provided.
7 and the stirring roller 48 are disposed,
A regulating rod 46 is disposed at the outlet of the control rod.

A two-component developer 50 composed of a toner T and a carrier C is stored inside the casing 49. The two-component developer 50 is stirred and mixed by the stirring roller 48 and is supplied by the supply roller 45 and adheres to the developing sleeve 41 to form a magnetic brush. The magnetic brush is transported while the transport amount is regulated by the regulating rod 46 as the developing sleeve 41 rotates.

An AC voltage having a DC component from the power supply 51 is applied to the developing sleeve 41.
A strong oscillating electric field is formed in the gap between the photosensitive drum 10 and the photosensitive drum 10. Due to the strong oscillating electric field, the toner T flies away from the carrier C, and a toner cloud is generated. As a result, a flight toward the latent image on the photosensitive drum 10 occurs, and a toner image is formed on the photosensitive drum 10.

FIG. 4 is a block diagram showing an example of the image forming apparatus of the present invention. In the figure, reference numeral 10 denotes a photosensitive drum as an image forming body, 20 denotes a scorotron charger as charging means,
25 is an image reading unit, 30 is an image writing unit using a laser beam as exposure means, 40A, 40B, 40
Reference numerals C and 40D denote developing devices shown in FIG. 3 containing two-component developers of different colors, 60 denotes a paper feeding unit including a first paper feeding roller 61 and a second paper feeding roller 62, and 70 denotes a transfer unit. A corona charger for transfer; 75, a corona charger for separation as separation means; 80, a transport unit; 85, a fixing unit; 90, a cleaning device including a cleaning blade 91;
Reference numeral 95 denotes a pre-charging exposure lamp. Arrows in the drawing indicate the rotation direction of the photosensitive drum 10.

The basic operation of the multicolor image forming process according to the present embodiment is as follows. First, a copy start command is sent from an operation unit (not shown) to a control unit (not shown), and the photosensitive drum 10 starts rotating. As the photosensitive drum 10 rotates, its peripheral surface is uniformly charged by the scorotron charger 20. In the image reading unit 25, optical information from the document is converted into an electric signal. The electric signal is subjected to image processing and then input to the image writing unit 30. The charged photosensitive drum 10 is irradiated with a laser beam from the image writing unit 30 to form a latent image on the photosensitive drum 10. The latent image on the photosensitive drum 10 is
The toner is developed on any one of the developing devices 40A, 40B, 40C, and 40D, and a toner image is formed on the photosensitive drum 10.

The photosensitive drum 1 on which the toner image is formed
0 is uniformly charged again by the scorotron charger 20 and is irradiated with a laser beam by the image writing section 30 to form the next latent image. The latent images on the photosensitive drum 10 are stored in the developing devices 40A, 40B, 40C.
Or 40D, and the next toner image is superimposed on the photosensitive drum 10.

In this embodiment, the latent image forming process described above
The development process is repeated four times, and four color toner images are superimposed on the photosensitive drum 10.

The paper supply unit 60 stores recording paper as a transfer material, and includes a first paper supply roller 61 and a second paper supply roller 6.
2, the toner image is sent to the transfer corona charger 70 in synchronization with the toner image superimposed on the photosensitive drum 10.
The toner image superimposed on the photosensitive drum 10 is transferred onto recording paper by the transfer corona charger 70,
The recording paper is separated from the photosensitive drum 10 by a separating corona charger 75. The recording paper onto which the toner image has been transferred is conveyed to the fixing unit 85 via the conveying unit 80, and is fused and pressed and then discharged out of the apparatus.

On the other hand, the toner remaining on the photosensitive drum 10 without being transferred to the recording paper is cleaned by a cleaning blade 9 which is pressed onto the photosensitive drum 10 at a proper timing.
1 is scraped off by a cleaning device 90 having
After the residual potential is removed by the pre-charging exposure lamp 95,
Enter the next image forming process.

In the development in the present invention, non-contact development is performed by applying an AC voltage.
0 to 50,000 Hz is desirable, and the development electric field in the development region is preferably 0.5 Mv / m or more and 20 Mv / m or less.

Here, the order of superimposing the yellow, magenta, cyan, black, and other color images formed on the photoreceptor surface may be any order, but the thickness of the developer layer on the developing sleeve is Dsd ( (The closest distance between the photoconductor and the developing sleeve).

[0082]

EXAMPLES The present invention will be described below in detail with reference to examples, but embodiments of the present invention are not limited thereto.

Production of Composite Magnetic Particles: (A) Phenol 20 was placed in a 4-liter three-necked flask.
0 g, 37% formalin 260 g, spherical magnetite (average particle diameter 240 nm) 1.6 kg, 28% ammonia water 31.2 g, calcium fluoride 4.0 g, water 500
g was added with stirring, the temperature was raised to 85 ° C. at about 1 ° C./min, and stirring was continued at 85 ° C. for about 3 hours to produce composite particles composed of spherical magnetite and cured phenolic resin.

Then, the content in the flask was cooled to room temperature, 2 liters of water was added, the supernatant was removed, and the composite particles remaining in the flask were washed with water. It was separated and collected by filtration, and left to dry. Further, the composite magnetic particles A were dried at 60 ° C. under reduced pressure.
I got The average particle size of the composite magnetic particles A was 14 μm.

(B) In a 4-liter three-necked flask, 200 g of phenol, 260 g of 37% formalin, 1.6 kg of spherical magnetite (average particle size 240 nm), 28 kg
% Ammonia water 31.2 g, calcium fluoride 4.0
g and 400 g of water were added with stirring, the temperature was raised to 85 ° C. at a rate of about 1 ° C. per minute, and stirring was continued at 85 ° C. for about 3 hours to produce composite particles composed of spherical magnetite and a cured phenol resin. .

Next, the content in the flask was cooled to room temperature, 2 liters of water was added, the supernatant was removed, and the composite particles remaining in the flask were washed with water. It was separated and collected by filtration, and left to dry. Further, the composite magnetic material particles B were dried at 60 ° C. under reduced pressure.
I got The average particle size of the composite magnetic particles B was 19 μm.

(C) In a 4-liter three-necked flask, 200 g of phenol, 260 g of 37% formalin, 1.6 kg of spherical magnetite (average particle diameter 240 nm), 28 kg
% Ammonia water 31.2 g, calcium fluoride 4.0
g and 300 g of water were added with stirring, the temperature was raised to 85 ° C. at a rate of about 1 ° C. per minute, and stirring was continued at 85 ° C. for about 3 hours to produce composite particles composed of spherical magnetite and a cured phenol resin. .

Next, the content in the flask was cooled to room temperature, 2 liters of water was added, the supernatant was removed, and the composite particles remaining in the flask were washed with water. It was separated and collected by filtration, and left to dry. Further, the composite magnetic particles C were dried at 60 ° C. under reduced pressure.
I got The average particle size of the composite magnetic particles C was 34 μm.

Production of carrier: (1) Composite magnetic particles A: 100 parts by weight Resin fine particles: 7 parts by weight (composition: methyl methacrylate / styrene = 6/4 (weight ratio), number average primary particle diameter: 65 nm, Volume average diameter of aggregated particles: 1.9 μm) Zirconia beads: 100 parts by weight (average particle diameter 205 μm)
m) was charged into the horizontal stirring type mixer shown in FIG. 2, and at 30 ° C. under the condition that the stirring peripheral speed of the horizontal stirring blade was 10.5 m / s.
After stirring for 5 minutes, resin fine particles were adhered to the surfaces of the composite magnetic material particles A.

Further, mechanical energy was repeatedly applied by stirring at 110 ° C. for 40 minutes to form a resin coating layer on the surfaces of the composite magnetic particles. Next, the zirconia beads were separated using a drum-type magnetic separator to obtain resin-coated composite magnetic particles (carrier-1).

(2) Composite magnetic particles B: 100 parts by weight Resin fine particles: 6 parts by weight (composition: methyl methacrylate / styrene = 6/4 (weight ratio), number average primary particle diameter: 90 nm, volume average of aggregated particles) Diameter: 1.9 μm) Zirconia beads: 100 parts by weight (average particle size 310 μm)
m) was charged into the horizontal stirring type mixer shown in FIG. 2, and at 30 ° C. under the condition that the stirring peripheral speed of the horizontal stirring blade was 10.5 m / s.
After stirring for 5 minutes, resin fine particles were adhered to the surfaces of the composite magnetic particles B.

Further, mechanical energy was repeatedly applied by stirring at 110 ° C. for 40 minutes to form a resin coating layer on the surfaces of the composite magnetic particles. Next, the zirconia beads were separated using the drum-type magnetic separator shown in FIG. 1 to obtain resin-coated composite magnetic material particles (carrier-2).

(3) Composite magnetic particles C: 100 parts by weight Resin fine particles: 5 parts by weight (composition: methyl methacrylate / cyclohexyl methacrylate = 5/5 (weight ratio), number average primary particle diameter: 95 nm, volume of aggregated particles) (Average diameter: 2.0 μm) ZnO ₂ / SiO ₂ electrofused beads: 100 parts by weight (average particle diameter: 100 μm) were charged into the horizontal stirring type mixer shown in FIG. 15 at 30 ° C under the condition of 5m / s
After stirring for a minute, the resin fine particles were adhered to the surfaces of the composite magnetic particles C.

Further, mechanical energy was repeatedly applied by stirring at 120 ° C. for 30 minutes to form a resin coating layer on the surfaces of the composite magnetic particles. Next, using a drum-type magnetic separator, the fused ZnO ₂ / SiO ₂ beads were separated to obtain resin-coated composite magnetic material particles (carrier-3).

(4) Resin-coated composite magnetic particles (carrier-4) were obtained in the same manner as in (1) except that zirconia beads were not added.

(5) Resin-coated composite magnetic particles (Carrier-5) were obtained in the same manner as in (2) except that no zirconia beads were added.

(6) Resin-coated composite magnetic material particles (Carrier-6) were obtained in the same manner as in (3) except that ZnO ₂ / SiO ₂ electrofused beads were not added.

Production of toner: C.I. I. Pigment. Bl
ue15-3 (KEY-BLUE104; manufactured by Dainippon Ink and Chemicals), 5 g of sodium dodecyl sulfate, and 1 g of pure water
An aqueous dispersion of the cyan colorant was prepared in advance by adding the mixture to a solution dissolved in 20 ml and applying stirring and ultrasonic waves. In addition, low molecular weight polypropylene (number average molecular weight = 3
Emulsion dispersion was prepared in advance by emulsifying water in water so as to obtain a solid content concentration of 30% by weight while adding heat.

60 g of a low molecular weight polypropylene emulsified dispersion was mixed with the cyan colorant dispersion, and 220 g of a styrene monomer and 40 g of an n-butyl acrylate monomer were further added.
g, methacrylic acid monomer 12 g, t-dodecyl mercaptan 5.4 g as a chain transfer agent, degassed pure water 2
After adding 100 ml, the temperature was raised to 70 ° C. while stirring under a nitrogen stream. Next, 4.3 g of potassium persulfate dissolved as a polymerization initiator in 440 ml of pure water was added, and the mixture was maintained at 70 ° C. for 3 hours to perform emulsion polymerization. The dispersion liquid of the cyan pigment-containing resin particles thus obtained is referred to as “polymerization liquid 1”.

Sodium hydroxide was added to 1000 ml of the “polymerization liquid 1” to adjust the pH to 7.0, and then
270 ml of a 2.7 mol% aqueous potassium chloride solution is added, and 160 ml of isopropyl alcohol and 9.0 g of polyoxyethylene octyl phenyl ether having an average degree of polymerization of ethylene oxide of 10 are dissolved in 67 ml of pure water, and the mixture is maintained at 75 ° C. Then, the mixture was stirred and reacted for 6 hours. The resulting reaction solution was filtered, washed with water, dried and crushed to obtain colored particles. 3.0% by weight of hydrophobic silica particles were added to the colored particles, and the average particle diameter was 5.4 μm.
Was manufactured.

Preparation of developer: A carrier and a toner were mixed in the composition shown in Table 1 to prepare a two-component developer.

Evaluation: When it was necessary to use a copying machine for evaluation, a Konica 9028 color copying machine manufactured by Konica was modified and used. The conditions are as shown below. A laminated organic photoreceptor was used as the photoreceptor.

Photoconductor surface potential = -650 V DC bias = -250 V AC bias = Vp-p: -50 to -450 V Alternating electric field frequency = 2500 Hz Rejection between current sleeve and photoconductor = 300 μm Pressing force = 10 gf / mm Pressing Control rod = SUS416 (magnetic stainless steel) /
Diameter 3 mm Developer layer thickness = 150 μm Developing sleeve = diameter 20 mm (a) Measurement of white powder amount Place 10 g of carrier in a 20 ml sample tube, and add 10 m of 2% aqueous solution of sodium dodecylbenzenesulfonate.
and mix by a wave rotor (manufactured by Tokyo Thermonics) at 46 rpm for 3 minutes. Thereafter, the transmittance of the supernatant is measured with a spectrophotometer (wavelength 522 nm). The amount of white powder was measured from a calibration curve of the concentration of the standard solution previously adjusted by changing the amount of the resin particles and the transmittance of the spectrophotometer.

(B) Evaluation of Image Quality OHP Image Defect (Firefly) Using an OHP sheet, thirty continuous solid images were passed, and the occurrence of fireflies was visually evaluated. The case where the number of fireflies with a diameter of 3 mm or more was 1 or less / sheet was "O", and the case where the number of fireflies with a diameter of 3 mm or more was 2 or more / sheet was "x".

At the same time, white streaks on the image were also visually confirmed.

(C) Evaluation of photoreceptor surface properties The state of scratches and abrasion on the photoreceptor surface after the end of the actual test was visually evaluated. "○" indicates a very good condition with no occurrence of scratches or abrasion, "を" indicates a good condition with almost no occurrence,
The case where it was impractical was marked as “×”.

[0107]

[Table 1]

As is clear from Table 1, Examples 1 to 3 in the present invention have no problem in any of the characteristics, while Comparative Examples 1 to 3 outside the present invention have a problem in practice. .

[0109]

According to the present invention, it is possible to provide a dry coating carrier having a good coating layer even if the carrier has a small particle size, a method for producing the same, an electrostatic image developing method and an image forming method using the same. Can be done.

[Brief description of the drawings]

FIG. 1 is a conceptual sectional view of a drum type magnetic separator.

FIG. 2 is a schematic sectional view of a horizontal stirring type mixing apparatus.

FIG. 3 is a sectional view showing an example of a developing device according to the present invention.

FIG. 4 is a configuration diagram illustrating an example of an image forming apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Horizontal stirring type mixing apparatus 2 Stirring blade 3 Motor 10 Photoconductor drum (image forming body) 11 Conductive substrate 12 Photosensitive layer 20 Scorotron charger 25 Image reading part 30 Image writing part 40A, 40B, 40C, 40D Development Apparatus (developing device) 41 Developing sleeve (developer conveying body) 42 Magnet 45 Supply roller 46 Regulator rod 47 Scraper 48 Stirring roller 49 Casing 50 Two-component developer 51 Power supply 60 Paper feed unit 61 First paper feed roller 62 Second Paper feed roller 70 Corona charger for transfer 75 Corona charger for separation 80 Conveyor unit 85 Fixing unit 90 Cleaning device 91 Cleaning blade 95 Exposure lamp before charging 101 Supply gutter 102 Rotating drum 103 Electromagnet contained in rotating drum 104 Separation / recovery wall 105 Non-magnetic particles 106 Magnetic components Coating the carrier that

Claims (4)

[Claims] 1. A carrier for developing an electrostatic charge image produced by mixing magnetic particles and resin fine particles and repeatedly applying a mechanical impact force to the mixture to fix the resin fine particles to the surface of the magnetic particles. A step of repeatedly applying a mechanical impact force to a mixture of magnetic particles and resin fine particles to which non-magnetic particles are added to prepare a resin-coated carrier, and then adding a step of separating the resin-coated carrier and the non-magnetic particles A resin-coated carrier for developing an electrostatic image, obtained by the above-mentioned production method. 2. An electrostatic image developing carrier manufactured by mixing magnetic particles and resin fine particles and repeatedly applying a mechanical impact force to the mixture to fix the resin fine particles to the surface of the magnetic particles. In the production method, a resin-coated carrier is produced by repeatedly applying a mechanical impact force to a mixture obtained by adding non-magnetic particles to magnetic particles and resin fine particles, and then separating the resin-coated carrier and the non-magnetic particles. A method for producing a resin-coated carrier for developing an electrostatic image, characterized by adding a step. 3. An electrostatic image developer comprising a toner and a carrier containing at least a binder resin and a colorant, wherein the carrier is a mixture of magnetic particles and resin fine particles further added with non-magnetic particles. A resin obtained by a method for producing a resin-coated carrier for electrostatic charge image development, wherein a step of separating the resin-coated carrier from the non-magnetic material particles is added after repeatedly applying a mechanical impact force to the resin-coated carrier. An electrostatic image developer, which is a coated carrier. 4. An electrostatic image developer comprising a toner containing at least a binder resin and a colorant and a carrier is thinned to a developer layer thickness of 20 to 500 μm by a developer regulating member to form a latent image. In an image forming method in which an electrostatic image on a body is developed in a non-contact manner, a resin-coated carrier is produced by repeatedly applying a mechanical impact force to a mixture of the magnetic particles and resin fine particles to which non-magnetic particles are further added. An image forming method, which is a resin-coated carrier obtained by a method for producing a resin-coated carrier for developing an electrostatic image, to which a step of separating the resin-coated carrier and the nonmagnetic particles is added.