JP2002244355A - Two-component developer - Google Patents

Abstract

(57) [Summary] [PROBLEMS] For a two-component developer having a small particle size that meets the demand for high definition and high image quality, the transportability in a developing device is good, and the resolution, gradation, and fine line are fine. A two-component developer capable of forming an excellent toner image without reproducibility and carrier adhesion is obtained. SOLUTION: This is a two-component developer containing at least a polymerization toner externally added with silica fine particles and titanium oxide fine particles and a carrier, wherein (a) the toner has an average particle diameter of 4 to 8;
and (b) the carrier is a silicone containing a coupling agent containing the surface of spherical composite core particles having an average particle diameter of 10 to 50 μm obtained by combining hard magnetic particle powder and soft magnetic particle powder with a phenol resin as a binder. A coated carrier coated with a resin, (c) the coated carrier has a shape factor SF-1 of 100 to 130, and (d) the coated carrier has a saturation magnetization at 3 kOe of 50 to
90emu / g, (e) the fluidity of the developer is 30-50
(Sec / 50g). There are two other items.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a so-called two-component developer in which a small amount of toner is dispersed in a carrier, and more particularly to a developer having a small particle size.

[0002]

2. Description of the Related Art In recent years, with the widespread use of image forming apparatuses such as electrophotographic copying machines, their uses have been expanded in various ways.
The demand for higher definition and higher image quality is increasing in the market. Therefore, in this technical field, attempts have been made to achieve high image quality by reducing the particle size of the toner. However, as the particle size becomes smaller, the surface area per unit weight increases, and the charge amount of the toner tends to increase. In addition, since the charged amount of the toner is large, the adhesion between the toners is strong, the fluidity is reduced, and problems occur in the stability of toner supply and in the application of tribo to the supplied toner.

A so-called polymerization toner synthesized by suspension polymerization, dispersion polymerization, or the like, has a high fluidity due to its spherical shape, has little variation in individual characteristics of the toner, and is easy to produce a toner having a small particle diameter. Therefore, there is an advantage that high image quality can be achieved. On the other hand, a so-called pulverized toner, which has been widely adopted, is manufactured by melting and kneading a fixing resin such as a styrene-acrylic copolymer with a coloring agent and other additives, and then pulverizing and classifying. This pulverized toner has the disadvantage that the particle size is large and the particle size distribution is wide. Heretofore, some developers have been proposed for the purpose of improving image quality.

Japanese Patent Application Laid-Open No. 51-3244 proposes a non-magnetic toner intended to improve image quality by regulating the particle size distribution. The toner is mainly composed of a toner having a particle size of 8 to 12 μm, and has a relatively large particle size. According to the study by the present inventors, the uniformity of the latent image is poor and the particle size is small. The fact that the diameter distribution is broad also tends to reduce uniformity. In order to form a clear image using toner having such a large particle size and having a broad particle size distribution, a gap between toner particles is filled by thickly overlapping toner particles. It is necessary to increase the apparent image density, and there is also a problem that the amount of toner consumption required to obtain a predetermined image density increases.

As described above, in the technical field, attempts have been made to achieve high image quality by narrowing the particle size distribution of the toner and reducing the particle size. There is a tendency that the surface area per unit weight increases, and the amount of charged electricity of the toner tends to increase. Therefore, by reducing the toner particle size, prevention of image density thinness and durability deterioration, or
Attempts have been made to further reduce the diameter of the carrier for the purpose of improving development efficiency. However, at present, such carriers do not have sufficient quality to cope with changes in the amount of charge due to durability.

First, as an adverse effect caused when the carrier and the toner are reduced in particle size, the fluidity of the developer is reduced, and the developer in the developing device is hardly circulated. As a countermeasure for this, there is a change in apparatus conditions such as increasing the stirring intensity in the developing device, but this is not preferable because it causes a problem such as shortening the durability life of the developer. Therefore, it is important to ensure a certain level of fluidity as a developer. Several means are conceivable for ensuring the fluidity of the developer.

As one of them, it is effective to control the shape of the carrier. That is, the fluidity is improved by increasing the sphericity of the carrier particles. Specifically, Japanese Unexamined Patent Publication No. Hei 8-190224 defines the practical sphericity of a carrier as a carrier, and the effect of the fluidity as a carrier has been confirmed. However, a quality sufficient to cope with a change in the amount of charge due to durability has not been obtained.

Japanese Patent Application Laid-Open No. 1-225962 discloses the fluidity of a carrier. However, when a carrier smaller than the conventional carrier in the present invention described later is used, it is difficult to perform measurement according to JIS-Z2502, and it is difficult to obtain reproducibility. Further, the above publication is limited only to the carrier, and does not include the influence of the chargeability on the toner side and other additives. Therefore, even if the fluidity of the carrier is constant, a good result is not always obtained in reality. For this reason, it is important to pay attention to the developer fluidity including the effect of the chargeability and the toner surface.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has been developed for a two-component developer having a small particle diameter to meet the demand for high definition and high image quality. It is an object of the present invention to provide a two-component developer having good transportability and capable of forming an excellent toner image without resolution, gradation, fine line reproducibility, and carrier adhesion.

[0010]

The above object of the present invention is achieved by the following means. According to the present invention, first,
According to the first aspect, the two-component developer containing a polymerized toner and a carrier in which silica fine particles and titanium oxide fine particles are externally added, and which satisfies the following requirements (a) to (e): It is the main feature. (A) The toner has an average particle size of 4 to 8 μm. (B) The carrier is formed by bonding a hard magnetic particle powder and a soft magnetic particle powder together with a phenolic resin as a binder, and forming a spherical composite core particle having an average particle diameter of 10 to 50 μm. Coated carrier used and coated. (C) The coated carrier has a shape factor SF-1 of 100
~ 130. (D) The coat carrier has a saturation magnetization at 3 kOe of 50 to 90 emu / g. (E) The fluidity of the developer is 30 to 50 (seconds / 50 g).

Secondly, according to a second aspect, in the two-component developer according to the first aspect, the addition ratio (B) / (A) of the silica fine particles (A) and the titanium oxide fine particles (B) is 0.1.
It is characterized by being smaller than 6.

Thirdly, a third aspect of the present invention is the two-component developer according to the first or second aspect, wherein the titanium oxide fine particles are of an anatase type.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The present invention, as described above, limits the average particle size of the toner,
Further, by specifying the ratio of the silica fine particles and the titanium oxide fine particles of the toner externally added fine particles, and further restricting the shape of the magnetic material and the carrier coating material of the carrier, and the shape of the coated carrier, good transportability in the developing device, Another object of the present invention is to provide a two-component developer capable of forming an excellent toner image without resolution, gradation, fine line reproducibility, and carrier adhesion.

The developer of the present invention has a spherical shape and a central particle diameter of 10 to 10.
It consists of a magnetic carrier of 50 μm and a spherical toner having a center particle size of 4 to 8 μm. The flow rate of the developer is 30 to 50 (seconds /
50 g). If the time is longer than 50 seconds, the fluidity is poor, and charging of the supplied toner cannot be performed smoothly, resulting in image deterioration. If the time is shorter than 30 seconds, a phenomenon in which the developer flows as a small lump is observed, causing toner scattering and background soiling.

Further, the magnetic properties of the carrier are affected by the magnet roller incorporated in the developing sleeve, and greatly affect the developing properties and transportability of the developer. The carrier has a saturation magnetization of 50 to 90 emu /
When the value is g, the uniformity of the image and the reproducibility of the gradation are excellent and suitable. If the saturation magnetization exceeds 90 emu / g (applied magnetic field of 3K Oersted), brush-like spikes formed by the carrier and toner on the developing sleeve facing the electrostatic latent image on the photoreceptor at the time of development will occur. The state becomes tight, and the gradation and the reproduction of halftone are deteriorated. Also, 50em
If the ratio is less than u / g, it becomes difficult to hold the toner and the carrier on the developing sleeve satisfactorily, and problems such as deterioration of carrier adhesion and toner scattering are likely to occur. Furthermore, if the residual magnetization and coercive force of the carrier are too high, good transportability of the developer in the developing device is hindered, and image defects such as blurring and uneven density in a solid image are likely to occur. It will be reduced.

The carrier is coated with a silicone resin containing a coupling agent on the surface of spherical composite core particles obtained by binding ferromagnetic iron compound particles and nonmagnetic metal oxide particles using a phenol resin as a binder. The reason for using spherical composite core particles, which are obtained by combining hard magnetic particles and soft magnetic particles with a phenol resin as a binder, is that the required magnetic properties and coercive force can be freely controlled. It is possible to obtain a spherical composite particle powder having high volume resistivity. In addition, when the low-resistance magnetic fine particles are exposed on the carrier surface to cause carrier adhesion, and when the magnetic fine particles are repeatedly used for a long time, the magnetic fine particles may be detached. By applying a silicone resin coat containing a silane coupling agent to prevent this, a highly durable and high quality image can be obtained. Further, the carrier in the present invention has a lower specific gravity than ordinary iron powder or ferrite powder, so that the rubbing force with the photosensitive drum is small,
The resolution is high, and in particular, horizontal fine lines are not blurred, and high image quality can be achieved.

The magnetic coated carrier has a shape factor SF-1
Is in the range of 100 to 130 or spherical or substantially spherical. If the SF-1 exceeds 130, the fluidity of the developer decreases, the ability to apply frictional charge to the toner decreases, and the shape of the magnetic brush becomes uneven at the developing pole, so that high-quality images cannot be obtained. . The SF-1 of the carrier particles was measured by randomly extracting 300 or more carrier particles, which were magnified 500 to 5000 times, using a field emission scanning electron microscope S-800 manufactured by Hitachi, Ltd.
This is performed using an image processing / analysis device Luzex3 manufactured by Nireco, and is calculated by the following equation. Shape factor SF-1 = (maximum particle diameter of carrier particles) 2 /
(Projected area of carrier particles) × π / 4 × 100

Further, the present invention provides a toner as an external additive,
One feature is that it contains at least titanium oxide fine particles. In particular, anatase-type titanium oxide fine particles subjected to a surface treatment while hydrolyzing a coupling agent in an aqueous system are extremely effective in terms of stabilizing charging, imparting fluidity, and the like. This has not been achieved with the commonly known hydrophobic silica as a flow improver. The reason for this is that the silica fine particles themselves have strong negative chargeability, whereas the titanium oxide fine particles have almost neutral chargeability. Conventionally, it has been proposed to add hydrophobic titanium oxide. However, titanium oxide fine particles originally have a smaller surface activity than silica, and hydrophobicity has not always been sufficiently achieved. In addition, when a large amount of a treating agent or the like is used or a highly viscous treating agent is used, the degree of hydrophobicity is certainly increased, but coalescence of particles occurs, and the ability to impart fluidity is reduced. The balance between the stabilization and the provision of liquidity has not always been achieved. On the other hand, hydrophobic silica has excellent fluidity-imparting ability,
Conversely, if a large amount is contained, electrostatic aggregation occurs due to its strong chargeability. In this regard, as the amount of titanium oxide increases, the fluidity of the toner improves. The present inventors have conducted intensive studies on the stability of the chargeability of the toner, and as a result, have found that a toner containing anatase-type titanium oxide is extremely effective in terms of stabilizing the charge and imparting fluidity. .

Next, the polymerization toner of the present invention will be described. [Monomer] The polymerizable monomer used for the polymerization is a monomer having a vinyl group, and specific examples thereof include the following monomers. That is, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4
-Styrene such as dimethylstyrene, butylstyrene, and octylstyrene and derivatives thereof, among which styrene monomers are most preferred. Other vinyl monomers include ethylenically unsaturated monoolefins such as propylene, butylene, and isobutylene; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, and vinyl fluoride; vinyl acetate; and vinyl propionate. , Vinyl benzoate, vinyl esters such as vinyl butyrate, methyl acrylate, ethyl acrylate, n-butyl acrylate,
Isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, acrylic acid-2
-Ethylhexyl, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, α-methyl methacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, n-methacrylate Octyl, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, α-methylene aliphatic monocarboxylic esters such as diethylaminoethyl methacrylate, acrylonitrile, methacrylonitrile, acrylic acid such as acrylamide Methacrylic acid derivatives, vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether, vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl Vinyl ketones such as ketone, N-
Examples thereof include N-vinyl compounds such as vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone, and vinylnaphthalene. These monomers can be used alone or in combination.

[Crosslinking Agent] In order to form a crosslinked polymer in the monomer composition, polymerization may be carried out in the presence of the following crosslinking agent. As the crosslinking agent, divinylbenzene, divinylnaphthalene, polyethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-hexane glycol dimethacrylate, neopentyl glycol diacrylate, Dipropylene glycol dimethacrylate,
Polypropylene glycol dimethacrylate, 2,2 '
-Bis (4-methacryloxydiethoxyphenyl) propane, 2,2'-bis (4-acryloxydiethoxyphenyl) propane, trimethylolpropane trimethacrylate, trimethylolmethanetetraacrylate, dibromoneopentylglycol dimethacrylate, And diallyl phthalate. If the amount of the cross-linking agent is too large, the toner is less likely to be melted by heat, and the heat fixing property and the heat pressure fixing property are inferior. If the amount of the cross-linking agent is too small, the properties required for the toner, such as blocking resistance and durability, are reduced, and a part of the toner adheres to the roll surface without being completely fixed to the paper during hot roll fixing. However, a cold offset, ie, transfer to the next paper, occurs. Accordingly, the amount of the crosslinking agent used is 0.001 to 15 parts by weight, preferably 0.1 to 10 parts by weight, based on 100 parts by weight of the polymerizable monomer.

[Release Agent] In order to prevent offset of the obtained toner, a release agent can be contained in the polymer composition. As the release agent, polyolefin such as low molecular weight polyethylene and polypropylene is preferable. This low molecular weight olefin polymer is preferably dispersed in a polymerizable monomer together with a colorant. The release agent is preferably used in an amount of 1 to 15 parts by weight based on 100 parts by weight of the polymerizable monomer. If the amount of the release agent used is less than 1 part by weight, the obtained toner does not have a sufficient release effect and tends to be offset on the roller. Conversely, if the amount used exceeds 15 parts by weight, the release agent from the toner will be spent on the triboelectric charging member. Further, the fluidity of the toner becomes extremely poor.

[Colorant] Examples of the colorant contained in the monomer include conventionally known dyes and pigments such as carbon black and grafted carbon black obtained by coating the surface of carbon black with a resin. Can be used. Other colorants include lamp black, iron black,
Ultramarine, nigrosine dye, aniline blue, phthalocyanine green, hansa yellow G, rhodamine 6G, lake, calco oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallylmethane dye, monoazo dye, disazo dye, etc. There are dyes and pigments. In addition, these colorants can be used in an amount of 0.1 to 30 parts by weight based on 100 parts by weight of the polymerizable monomer.

[Dispersion stabilizer] The following can be used as the dispersion stabilizer. That is, water-soluble polymers such as polyvinyl alcohol, starch, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, sodium polyacrylate, sodium polymethacrylate, barium sulfate, calcium sulfate, barium carbonate, magnesium carbonate, calcium phosphate, talc, clay, and silica Sodium, metal oxide powder and the like are used. These are preferably used in the range of 0.1 to 10% by weight based on water.

[Polymerization Initiator] In the present invention, the polymerization initiator may be added to the dispersion containing the monomer composition after granulation, but it is uniformly polymerized into individual monomer composition particles. From the viewpoint of providing an initiator, it is desirable to include the initiator in the monomer composition before granulation. As such a polymerization initiator,
2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,
Azo or diazo polymerization initiators such as 1'-azobis- (cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisbutyronitrile And peroxide-based polymerization initiators such as benzoyl peroxide, methyl ethyl ketone peroxide, isopropyl peroxide, 2,4-dichlorobenzoyl peroxide and lauryl peroxide.

As the silica fine particles to be added to the polymerized toner particles, various conventionally known materials can be used. In particular, silica-based surface treating agents containing hydrophobic silica fine particles, for example, ultrafine anhydrous silica and colloidal silica Etc. are preferably used.

Next, the magnetic coated carrier of the present invention will be described. (Resin) As the silicone resin used in the present invention,
Any conventionally known silicone resin may be used, and examples thereof include a straight silicone resin and a silicone resin modified with alkyd, polyester, epoxy, urethane, or the like. For example, as a commercial product, straight silicone resin is KR271, KR2 manufactured by Shin-Etsu Chemical Co., Ltd.
55, KR152, SR2400, SR2405 manufactured by Toray Dow Corning Silicone Co., Ltd., and modified silicone resins are KR206 alkyd modified by Shin-Etsu Chemical Co., Ltd., KR5208 (acrylic modified), ES1001N
(Epoxy modification), KR305 (urethane modification), SR2115 (epoxy modification) and SR2110 (alkyd modification) manufactured by Toray Dow Corning Silicone Co., Ltd.

[Additives] As the conductive substance used as a carrier resistance regulator in the present invention, any known substances may be used, but from the viewpoint of an inexpensive conductive substance. It is preferable to use carbon black. Moreover, the BET is 80 for carbon black.
0 m ² / g, preferably 1000 m ² / g or more, DBP
Oil absorption 200ml / 100g, preferably 250ml
/ 100 g or more of carbon black is most preferable. Since the above-mentioned carbon black has a surface area several times that of ordinary carbon black, it is possible to obtain a desired resistance value with a small amount when contained in the carrier coating layer. In general, since the conductive substance is easily affected by the environment, it is desirable that the content thereof is small. Therefore, the content of such carbon black can be reduced, so that the environmental stability of the carrier can be further improved as compared with a normal conductive substance. Commercial products of such carbon black include BLOT manufactured by Cabot Corporation.
ack Pearls 2000, Degussa Pri
ntex XE2, # 3600B manufactured by Mitsubishi Kasei, Ketjen Black ECDJ-600 manufactured by Lion Aguso
And the like.

When color contamination is a problem in a color carrier or the like, it is preferable to use a white metal oxide. Examples of the white metal oxide include titanium oxide-based, zinc oxide-based, and tin oxide-based particles. Commercial products include the following. ECT-52 (manufactured by Titanium Industry), KV400 (manufactured by Titanium Industry), ECR-
72 (manufactured by Titanium Industry), ECTR-82 (manufactured by Titanium Industry), 500 W (manufactured by Ishihara Sangyo), 300 W (manufactured by Ishihara Sangyo), S-1 (manufactured by Ishihara Sangyo), W-1 (Mitsubishi Metals) 23K (manufactured by Hakusui Chemical), MEC300 ・ 50
0 (manufactured by Teikoku Kakosha)

[Coupling Agent] The silane coupling agent preferably used in the present invention includes, for example,
γ- (2-aminoethyl) aminopropyltrimethoxysilane, γ- (2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β- (N-vinylbenzylaminoethyl)- γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxysilane, γ
-Mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethyldisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyl Dimethyl [3- (trimethoxysilyl) propyl] ammonium chloride, γ-chloropropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane
Toray Silicon), allyltriethoxysilane,
3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1.3-divinyltetramethyldisilazane, methacryloxyethyldimethyl (3-trimethoxysilylpropyl) ammonium chloride (Chisso Corporation) Made)
And the like. The amount of the silane coupling agent used in the present invention is 1 to 1 with respect to the solid content of the silicone resin.
25 wt% is preferred. When the content of the silane coupling agent is less than 1% by weight, the effect is not exhibited, and the adhesion between the core particles and the silicone coating layer is inferior. On the other hand, if the content exceeds 25% by weight, the spent resistance of the silicone is deteriorated, and the spent toner is caused after long-term use.

The spherical composite particles according to the present invention are prepared by coexisting phenols and aldehydes in an aqueous medium with hard magnetic particles and soft magnetic particles in the presence of a basic catalyst. It can be obtained by reacting with aldehydes.

[Phenols] Phenols, m-cresol,
Alkylphenols such as p-tert-butylphenol, o-propylphenol, resorcinol and bisphenol A, and phenolic hydroxyl groups such as halogenated phenols in which part or all of a benzene nucleus or an alkyl group is substituted with a chlorine atom or a bromine atom Among these, phenol is most preferred. When a compound other than phenol is used as the phenol, particles may be difficult to form, or even if particles are formed, the particles may have an irregular shape. Therefore, phenol is most preferable in consideration of shape.

[Aldehydes] Examples of those preferably used in the present invention include formaldehyde and furfural in the form of either formalin or paraaldehyde, with formaldehyde being particularly preferred. The molar ratio of aldehydes to phenols is preferably from 1 to 4, particularly preferably from 1.2 to 3. If the molar ratio of the aldehydes to the phenols is less than 1, particles are difficult to form, or even if they are formed, the curing of the resin is difficult to progress, and the strength of the particles to be formed tends to be weak. When the molar ratio of aldehydes to phenols is greater than 4, unreacted aldehydes remaining in the aqueous medium after the reaction tend to increase.

[Basic catalyst] As a catalyst preferably used in the present invention, a basic catalyst used in the production of ordinary resol resins is used. Examples thereof include aqueous ammonia, hexamethylenetetramine, and alkylamines such as dimethylamine, diethyltriamine, and polyethyleneimine. The molar ratio of these basic catalysts to phenols is preferably from 0.02 to 0.3. If it is less than 0.02, curing will not proceed sufficiently and granulation will not occur. 0.
If it exceeds 3, the granulation property is deteriorated because it affects the structure of the phenolic resin, and a large particle size cannot be obtained.

[Hard Magnetic Particles] The hard magnetic particle powder used in the present invention is represented by MFe ₁₂ O ₁₉ (where M is one or more elements selected from strontium, barium, calcium and lead). Magnetoplumbite type magnetic particle powder, fine particle powder of iron and its alloys having an oxide layer on the surface, and the like can be used. Preferably, it is a magnetoplumbite type magnetic particle powder. The particle shape may be any of a plate shape, a granular shape, a spherical shape, and a needle shape. The average particle size of the hard magnetic particles constituting the hard magnetic particle powder is preferably 0.1 to 5 μm. The coercive force of the hard magnetic particle powder is preferably 1000 to 4000 Oe. The volume resistivity of the hard magnetic particle powder is preferably 10 ¹⁰ to 1.
0 ¹³ Ωcm.

[Soft Magnetic Particles] As the soft magnetic particle powder,
Magnetite particle powder, maghemite particle powder, spinel-type ferrite particle powder containing one or more metals (Mn, Ni, Zn, Mg, Cu, etc.) other than iron can be used. Preferably, it is a spinel type magnetic particle powder. The particle shape may be spherical, granular, needle-like, or plate-like. The average particle size of the soft magnetic particles constituting the soft magnetic particle powder is preferably 0.05 to 3 μm. The relationship with the average particle size of the hard magnetic particles is such that the hard magnetic particles are larger than the soft magnetic particles. When the soft magnetic particle powder is larger than the hard magnetic particles, soft magnetic particles having a relatively low volume resistivity tend to appear on the surface of the spherical composite particles, so that the volume resistivity of the spherical composite particle powder is low. . The coercive force of the soft magnetic particle powder is preferably 1 to 300 Oe. The volume resistivity of the soft magnetic particle powder is preferably 10 ⁷ to 10 ¹¹ Ωcm. The volume resistivity of the hard magnetic particle powder is higher than that of the soft magnetic particle powder.

It is preferable that both the hard magnetic particles and the soft magnetic particles used in the present invention have been subjected to lipophilic treatment in advance, and the hard magnetic particles or the soft magnetic particles which have not been subjected to the lipophilic treatment. When the particle powder is used, it may be difficult to obtain composite particles having a spherical shape.
The developer of the present invention is a two-component developer obtained by mixing the above magnetic carrier and spherical toner. The toner concentration in this developer can be used in a wide range of 5 to 12% by weight.

The method for measuring the characteristic value of the developer of the present invention will be described below. (1) Magnetic properties of carrier: BHU-60
Type magnetization measurement device (manufactured by RIKEN) is used. Specifically, about 1.0 g of a measurement sample was weighed, the inner diameter was 7 mm, and the height was 1
The cell is packed in a 0 mm cell and set in the above-mentioned device. In the measurement, an applied magnetic field is gradually applied to change the maximum to 3,000 Oe. Next, the applied magnetic field is decreased, and finally a hysteresis curve of the sample is obtained on the recording paper. Than this,
Obtain the saturation magnetization, residual magnetization, and coercive force. (2) Measurement of the particle size distribution of the carrier: The measurement was performed using an SRA type Microtrac particle size analyzer (Nikkiso Co., Ltd.) with a range setting of 0.7 to 125 μm. (3) Developer Fluidity Measurement Method: In this experiment, the developer fluidity was measured as follows. That is, the toner and the carrier are actually used at the toner concentration (5 to 12%),
Mix in an environment at a temperature of 23 ° C. ± 2 ° C. and a humidity of 60% ± 3%, leave for 1 hour, and measure. Measurement method is JIS-Z
2502. Here, the measuring device is as shown in FIG. 1, but FIG. 2 is a sectional view. A modified funnel is used. (4) Measuring method of toner particle size: Electrolyte solution 10 described above
0.1 to 5 ml of a surfactant (alkylbenzene sulfonate) is added to 0 to 150 ml, and the measurement sample is
Add ~ 20 mg. An electrolytic solution in which a sample is suspended is subjected to a dispersion treatment by an ultrasonic disperser for 1 to 3 minutes, and a particle size distribution or the like of 2 to 40 μm is measured using a 100 μm aperture with a Coulter counter TAII as described above based on volume. And

(Example) Next, the two-component developer of the present invention will be described with reference to examples and comparative examples. However, the present invention is not limited by the following examples. Example 1 (1) Preparation of Magnetic Carrier After 150 g of strontium ferrite particles were charged into a Henschel mixer and sufficiently stirred, 1.8 g of a silane coupling agent was added, and the temperature was raised to about 100 ° C. and good for 30 minutes. By mixing and stirring, barium ferrite particle powder (hard magnetic particle powder) coated with the coupling agent was obtained. Similarly, after 250 g of magnetite particle powder is charged into a Henschel mixer and sufficiently stirred, 3.75 g of a silane coupling agent is added and treated, and magnetite particle powder coated with the coupling agent (soft magnetic particle powder) I got Separately, 47 g of phenol, 37% formalin 57 were placed in a 1 l four-necked flask.
g, a total amount of 400 g of the lipophilic hard magnetic particle powder and the lipophilic soft magnetic particle powder, 15 g of 28% ammonia water, and 60 g of water, and 4
Raise the temperature to 85 ° C in 0 minutes and react at the same temperature for 180 minutes.
After curing, composite particles composed of the hard magnetic particle powder, the soft magnetic particle powder, and the cured phenol resin were produced. Next, after adding 0.5 l of water, the supernatant was removed, and the lower layer of the precipitate composed of the composite particles was washed with water and dried under reduced pressure to obtain a spherical composite particle powder. Was. Next, 440 g (solid content: 20%) of a silicone resin solution, 5 g of carbon black, 220 g of toluene and γ- (2
-Aminoethyl) aminopropyltrimethoxysilane 5
g was dispersed with a homomixer for 20 minutes to prepare a coating layer forming liquid. The coating liquid for forming a coating layer was coated on the surface of 5000 g of the spherical composite particle powder using a fluidized bed type coating apparatus to obtain a magnetic coated carrier (I). The obtained magnetic coated carrier has a center particle diameter of 37 μm, a shape factor SF-1 of 121, and a saturation magnetization of 61.
emu / g.

(2) Preparation of Spherical Toner In a 500 ml four-necked flask equipped with a stirring blade and a condenser, 3.5 parts by weight of a methyl vinyl ether-mannic anhydride copolymer (molecular weight: 40000) and methanol 100
The mixture was stirred at 60 ° C. for 2 hours to completely dissolve the methyl vinyl ether-mannic anhydride copolymer to prepare a dispersion stabilizer. Then, it cooled to room temperature and prepared the following. Styrene 60 parts by weight Methyl methacrylate 40 parts by weight t-dodecyl mercaptan 0.06 parts by weight 1,3-butanediol dimethacrylate 0.5 parts by weight While stirring these, the flask was purged with nitrogen gas, and The stirring (1000 rpm) was continued gently for about 1 hour until the residual oxygen concentration reached 0.1%. afterwards,
After raising the temperature of the thermostat to 60 ° C., polymerization was continued for 24 hours using 0.2 parts by weight of 2,2′-azobisisobutyronitrile as an initiator. When the obtained dispersion was cooled and centrifuged at 2,000 rpm in a centrifuge, the polymer particles were completely precipitated and the upper liquid was transparent. The supernatant was removed, and 200 g of methanol was newly added, followed by washing with stirring for 1 hour. The operation of centrifuging and washing with methanol was repeated and filtered. The filtered product was dried under reduced pressure at 50 ° C. for 24 hours to obtain white resin particles in a yield of 90%. The obtained particles had a volume average particle size of 5.44 μm. Next, 2 parts by weight of oil black was dissolved in 100 parts by weight of methanol by heating, cooled, and filtered with a filter of about 1 μm to prepare a dye solution. Next, 30 parts by weight of the resin particles of the white powder were added to the filtrate and dispersed, and the mixture was stirred and heated at 50 ° C. for 1 hour. Thereafter, the dispersion was cooled to room temperature and filtered to obtain a colored resin particle dispersion. Subsequently, a compound represented by the following formula 1 was added as a charge control agent to water / methanol (1).
/ 1) Dissolved in a mixed solvent and added 2 parts by weight to 100 parts by weight of colored resin particles. After stirring for 1 hour, the mixture was filtered and dried to obtain toner (a).

[0040]

Embedded image To 100 parts of the toner (a), 0.3 part of titanium oxide fine particles and 0.7 part of silica fine particles were mixed with a Henschel mixer to obtain a toner (A).

(3) Preparation of Developer The magnetic carrier (I) obtained above and the toner (A) were mixed at a toner concentration of 7% to obtain a developer. The fluidity of this developer was 40 (sec / 50 g). This developer is used in an electrophotographic copying machine [imagioMF manufactured by Ricoh Co., Ltd.
2700] using a copier modified from the above. The developing condition was such that the photosensitive drum was rotated at a peripheral speed of 160 mm / sec and the gap between the photosensitive drum and the magnetic roll was set to 0.06 cm. The resulting copy images were evaluated for initial image quality and image quality after 10,000 copies. Table 1 shows the results.

Example 2 (1) Preparation of magnetic carrier Barium ferrite particle powder 6 in a Henschel mixer
After adding 0 g and stirring sufficiently, 1.0 g of a silane coupling agent was added, the temperature was raised to about 100 ° C., and the mixture was thoroughly mixed and stirred for 30 minutes to obtain a barium ferrite particle powder coated with the coupling agent ( Hard magnetic particles). Similarly, after charging 350 g of magnetite particle powder in a Henschel mixer and stirring sufficiently well,
7.0 g of a silane coupling agent was added to obtain a magnetite particle powder (soft magnetic particle powder) coated with the coupling agent. Separately, in a 1 l four-necked flask,
Phenol 45 g, 37% formalin 55 g, the total amount of the lipophilic hard magnetic particle powder and the lipophilic soft magnetic particle powder 400 g, 28% ammonia water 1
5 g and water 50 g were mixed and stirred for 85 minutes in 40 minutes.
C., and reacted and cured at the same temperature for 180 minutes to produce composite particles composed of hard magnetic particles, soft magnetic particles, and a cured phenol resin. Next, 0.5
After the addition of 1 l of water, the supernatant was removed, and the lower layer of the precipitate composed of the composite particles was washed with water and dried under reduced pressure to obtain spherical composite particle powder. Next, the surface was coated in the same manner as in Example 1 to obtain a magnetic coated carrier (II). The obtained magnetic coated carrier had a center particle diameter of 46 μm, a shape factor SF-1 of 114, and a saturation magnetization of 78 emu / g.

(2) Preparation of Developer The magnetic coat carrier (II) obtained above and the toner (A) of Example 1 were mixed at a toner concentration of 7% to obtain a developer. The fluidity of this developer was 37 (sec / 50 g). This developer is used in an electrophotographic copying machine [Ricoh Co., Ltd.
imageioMF2700] using a modified copier. The developing condition was such that the photosensitive drum was rotated at a peripheral speed of 160 mm / sec and the gap between the photosensitive drum and the magnetic roll was set to 0.06 cm. The resulting copy images were evaluated for initial image quality and image quality after 10,000 copies. Table 1 shows the results.

Example 3 (1) Production of Spherical Toner To 100 parts of the toner (a) of Example 1, 0.6 part of titanium oxide fine particles and 0.5 part of silica fine particles were mixed with a Henschel mixer to obtain a toner (B). ) Got. (2) Preparation of Developer The magnetic carrier (I) of Example 1 and the toner (B) obtained above were mixed at a toner concentration of 7% to obtain a developer. The fluidity of this developer was 39 (sec / 50 g).
This developer was used in an electrophotographic copying machine [ima, manufactured by Ricoh Co., Ltd.
[GioMF2700] was used to perform a copy operation. The development condition is that the photosensitive drum is rotated at a peripheral speed of 160.
The rotation was performed at a moving speed of mm / sec, and the gap between the photosensitive drum and the magnetic roll was set to 0.06 cm. The resulting copy images were evaluated for initial image quality and image quality after 10,000 copies. Table 1 shows the results.

Comparative Example 1 (1) Preparation of Magnetic Carrier Styrene-butyl acrylate copolymer 30 parts by weight Magnetite 40 parts by weight α-Fe2O3 30 parts by weight The mixture was melt-kneaded twice with a roll mill, cooled, and coarsely ground to a particle size of about 2 mm using a hammer mill. Then, with an air jet type pulverizer, the average particle size is about 33.
Milled to μm. Next, fine powder and coarse powder were cut using an elbow jet classifier. The obtained carrier (III) was coated on the surface in the same manner as in Example 1,
A magnetic coated carrier (IV) was obtained. The magnetic coated carrier (IV) has a center particle diameter of 35 μm and a shape factor SF−
1 was 96, and the saturation magnetization was 46 emu / g. (2) Preparation of Developer The magnetic carrier (IV) and the toner (A) obtained in Example 1 were mixed at a toner concentration of 7% to obtain a developer. The fluidity of this developer was 56 (sec / 50 g).
This developer was used in an electrophotographic copying machine [ima, manufactured by Ricoh Co., Ltd.
[GioMF2700] was used to perform a copy operation. The development condition is that the photosensitive drum is rotated at a peripheral speed of 160.
The rotation was performed at a moving speed of mm / sec, and the gap between the photosensitive drum and the magnetic roll was set to 0.06 cm. The resulting copy images were evaluated for initial image quality and image quality after 10,000 copies. Table 1 shows the results.

Comparative Example 2 (1) Preparation of Magnetic Carrier The magnetic coated carrier (III) obtained in Comparative Example 1 was charged into Mechanomill MM-10 and mechanically made spherical. Carrier (V) without coating the obtained carrier
Used as Obtained magnetic coated carrier (V)
Has a central particle size of 35 μm and a shape factor SF-1 of 1
26, and the saturation magnetization was 47 emu / g. (2) Preparation of Developer The magnetic carrier (V) described above and the toner (A) obtained in Example 1 were mixed at a toner concentration of 7% to obtain a developer. The fluidity of this developer was 45 (sec / 50 g).
This developer was used in an electrophotographic copying machine [ima, manufactured by Ricoh Co., Ltd.
[GioMF2700] was used to perform a copy operation. The development condition is that the photosensitive drum is rotated at a peripheral speed of 160.
The rotation was performed at a moving speed of mm / sec, and the gap between the photosensitive drum and the magnetic roll was set to 0.06 cm. The resulting copy images were evaluated for initial image quality and image quality after 10,000 copies. Table 1 shows the results.

Comparative Example 3 (1) Production of Spherical Toner To 100 parts of the toner (a) of Example 1, only 1.0 part of silica fine particles was mixed with a Henschel mixer to obtain a toner (C). (2) Preparation of Developer The magnetic carrier (I) of Example 1 and the toner (C) obtained above were mixed at a toner concentration of 7% to obtain a developer. The fluidity of this developer was 36 (sec / 50 g).
This developer was used in an electrophotographic copying machine [ima
[GioMF2700] was used to perform a copy operation. The development condition is that the photosensitive drum is rotated at a peripheral speed of 160.
The rotation was performed at a moving speed of mm / sec, and the gap between the photosensitive drum and the magnetic roll was set to 0.06 cm. The resulting copy images were evaluated for initial image quality and image quality after 10,000 copies. Table 1 shows the results.

[0048]

[Table 1]

[0049]

As described above, according to the two-component developer of the first aspect, a two-component developer having good transportability in the developing device can be obtained, the image density is high, and the background stain and It is possible to obtain a toner image having no carrier adhesion and excellent in resolution, gradation and fine line reproducibility.

According to the two-component developer of the second aspect, since the addition ratio (B) / (A) of the fine titanium oxide particles (B) and the fine silica particles (A) is smaller than 0.6, excellent toner properties are obtained. Charge stabilization and fluidity can be imparted, and when the ratio is higher than this, the effect of reducing dot reproducibility and preventing background contamination can be seen.

According to the two-component developer of the third aspect, since the titanium oxide fine particles are of an anatase type, they are extremely effective in stabilizing charging and imparting fluidity.

[Brief description of the drawings]

FIG. 1 is a side view of a developer fluidity measuring device used in the present invention.

FIG. 2 is a sectional view of a funnel portion of the flow rate measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Funnel 2 Funnel support 3 Support rod 4 Support base

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroshi Nakai 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Minoru Masuda 1-3-6 Nakamagome, Ota-ku, Tokyo Share F-term in Ricoh Company (reference) 2H005 AA08 BA03 BA15 CA15 CB03 CB04 CB07 CB13 EA02 EA05 EA07

Claims (3)

[Claims] 1. A two-component developer containing at least a polymerized toner externally added with silica fine particles and titanium oxide fine particles and a carrier, wherein the following requirements (a) to (e) are satisfied. Component developer. (A) The toner has an average particle size of 4 to 8 μm. (B) The carrier is formed by bonding a hard magnetic particle powder and a soft magnetic particle powder together with a phenolic resin as a binder, and forming a spherical composite core particle having an average particle diameter of 10 to 50 μm. Coated carrier used and coated. (C) The coated carrier has a shape factor SF-1 of 100
~ 130. (D) The coat carrier has a saturation magnetization at 3 kOe of 50 to 90 emu / g. (E) The fluidity of the developer is 30 to 50 (seconds / 50 g). 2. The two-component developer according to claim 1, wherein
A two-component developer, wherein the addition ratio (B) / (A) of the silica fine particles (A) and the titanium oxide fine particles (B) is smaller than 0.6. 3. The two-component developer according to claim 1, wherein said titanium oxide fine particles are of an anatase type.