JP2007310063A - Carrier for electrostatic charge image development, electrostatic charge image developer, image forming method, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier for electrostatic charge image development that suppresses deposition of moisture on the carrier and shows stable charging/resistance for a long period of time and can output an image of high picture quality, and to provide an electrostatic charge image developer using the carrier, an image forming method and an image forming apparatus. <P>SOLUTION: The carrier for electrostatic charge image development has a coating resin layer on the surface of a magnetic nucleus particle and is characterized in that the coating resin layer contains carbon black and that the moisture absorption of the carbon black is 1.0 wt.% or less. The electrostatic charge image developer comprises a carrier for electrostatic charge image development and a toner and is characterized in that: the toner comprises toner base particles containing at least a binder resin and a colorant, and an external additive; the external additive shows a moisture absorption of ≥1.0 wt.%; and it is characterized in that the carrier used is the above carrier for electrostatic charge image development. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrostatic charge image developing carrier, an electrostatic charge image developer, an image forming method, and an image forming apparatus used when developing an electrostatic charge image formed by an electrophotographic method, an electrostatic recording method or the like.

A method of visualizing image information through an electrostatic latent image such as electrophotography is currently used in various fields. In electrophotography, an electrostatic latent image formed on a photoreceptor by a charging and exposure process is developed with a developer containing toner, and visualized through a transfer and fixing process. Developers used for development include a two-component developer composed of toner and carrier, and a one-component developer used alone, such as magnetic toner, but the two-component developer includes a carrier whose developer is a developer. Since functions such as agitation, transport, and charging are shared and functions are separated as a developer, it has a feature such as good controllability and is widely used at present. In particular, a developer using a carrier coated with a resin is excellent in charge controllability, and is relatively easy to improve environment dependency and stability over time.
As a developing method, a cascade method has been used in the past, but at present, a magnetic brush method using a magnetic roll as a developer carrier is mainly used.

In recent years, it is necessary to control the resistance of the carrier in order to meet the demand for higher image quality. In many cases, carbon black is used as a carrier resistance control method in terms of handling and cost. When the resistance of the carrier is lowered, there arises a problem of carrier transfer to the photoconductor by charge injection in the developing electric field. In particular, the above problem becomes prominent when it is used under high humidity and a lot of moisture adheres to the carrier, and when it is used for a long time and the exposure of carbon black to the carrier surface increases.
For such problems, a method of controlling the carbon black particle size / carbon black oil absorption amount has been proposed (see, for example, Patent Document 1). However, although this method can surely prevent the carbon black from detaching from the carrier and achieve high image quality, it is difficult to prevent the above problems from occurring under high humidity.

JP 2005-164980 A

  An object of the present invention is to provide a carrier for developing an electrostatic charge image that can suppress moisture adhesion to the carrier, stabilize charging / resistance over a long period of time, and output a high-quality image, and an electrostatic charge image developer using the same. Another object is to provide an image forming method and an image forming apparatus.

The above-described problems of the present invention have been solved by the means described in <1> to <4> below.
<1> A carrier for developing an electrostatic image having a coating resin layer on the surface of magnetic core particles, the coating resin layer containing carbon black, and the moisture absorption amount of the carbon black being 1.0 wt% or less. A carrier for developing an electrostatic image characterized by
<2> An electrostatic image developer having an electrostatic image developing carrier and a toner, wherein the toner comprises toner base particles containing at least a binder resin and a colorant and an external additive. An electrostatic charge image developer, wherein the electrostatic charge image development carrier is the electrostatic charge image development carrier according to <1>, wherein the moisture absorption amount is 1.0 wt% or more;
<3> A latent image forming step of forming an electrostatic latent image on the surface of the latent image holding member, and developing the electrostatic latent image formed on the surface of the latent image holding member with a developer containing toner to form a toner image. An image forming method comprising: a developing step, a transferring step for transferring the toner image formed on the surface of the latent image holding member to the surface of the transfer target, and a fixing step for thermally fixing the toner image transferred to the surface of the transfer target An image forming method, wherein the developer includes the electrostatic image developing carrier according to <1>.
<4> a latent image carrier, charging means for charging the latent image carrier, exposure means for exposing the charged latent image carrier to form an electrostatic latent image on the latent image carrier, An image forming apparatus comprising: a developing unit that develops the electrostatic latent image with a developer to form a toner image; and a transfer unit that transfers the toner image from the latent image carrier to a recording material. An image forming apparatus, wherein the developer comprises the electrostatic charge image developing carrier according to <1>.

  According to the present invention, it is possible to provide a carrier for developing an electrostatic charge image that has stable charge / resistance for a long period of time and can output a high-quality image, a developer using the carrier, an image forming method, and an image forming apparatus.

[Electrostatic charge image development carrier]
The carrier for developing an electrostatic charge image (hereinafter also simply referred to as “carrier”) of the present invention is a carrier for developing an electrostatic charge image having a coating resin layer on the surface of magnetic core particles, and the coating resin layer contains carbon. And the moisture absorption of the carbon black is 1.0 wt% or less.
In the present invention, by setting the moisture absorption amount of the carbon black contained in the carrier coating resin within a specified range, the total number of electric charge paths inside the carrier is reduced, and as a result, by charge injection in a developing electric field or the like. Carrier transfer to the photoreceptor can be prevented. By preventing this carrier transfer, it is possible to further prevent alteration of the surface of the photoreceptor due to the carrier caused by the transfer process and the cleaning process. As a result, an image having no “color point” due to carrier transfer to the photoreceptor can be obtained, and high image quality can be achieved even when used for a long time.

-Carbon black-
In the present invention, the electrostatic charge image developing carrier contains carbon black in the coating resin layer.
In the carrier of the present invention, the moisture absorption of the carbon black contained in the coating resin is 1.0 wt% or less, preferably 0.05 to 0.5 wt%, and 0.05 to 0.2 wt%. It is more preferable.
When the amount of moisture absorption of carbon black exceeds 1.0 wt%, the total number of electric charge paths inside the carrier increases, and carrier transfer to the photoconductor occurs, so that a color point is likely to occur.

In the present invention, the moisture absorption amount of carbon black is measured as follows. First, a flat weighing bottle (height 30 mm, diameter 60 mm, manufactured by ASONE Co., Ltd.) is removed, put into a dryer, and dried at 125 ° C. for 30 minutes. Then, put a flat scale bottle and a stopper into a desiccator, let cool to room temperature, plug the flat scale bottle and weigh accurately to 0.1 mg. A sample of about 2 g is accurately weighed to 0.1 mg, placed in a flat weighing bottle, and left for 24 hours in an environment of 28 ° C. and 85% humidity with the stopper removed. After standing, seal the flat weighing bottle, measure the weight at room temperature, remove the stopper, dry at 125 ° C for 1 hour, place the flat weighing bottle and the stopper in a desiccator, allow to cool to room temperature, Cap the bottle and weigh accurately to 0.1 mg.
The amount of moisture absorption is obtained by the following formula.
Moisture absorption = (m1-m2) / (m2-m0) × 100
m0: Weight of the flat weighing bottle (including stopper) after heating (g)
m1: Flat weighing bottle (including stopper) and sample weight after standing for 24 hours (g)
m2: Weight (g) after heating the flat scale bottle (including the stopper) and the sample

In the present invention, carbon black contained in the coating layer of the electrostatic image developing carrier is added as a conductive powder.
Carbon black preferably has an average primary particle size of 10 to 100 nm, and more preferably 10 to 50 nm. If the average particle diameter exceeds 100 nm, it is not preferable in terms of safety. On the other hand, when the thickness is less than 10 nm, the specific surface area is large, and it is difficult to control the amount of moisture absorption.
The average primary particle diameter can be measured with an electron microscope.

  The oil absorption of carbon black is preferably 30 to 250 ml / 100 g, more preferably 50 to 150 ml / 100 g, as the DBP oil absorption. When the DBP oil absorption exceeds 250 ml / 100 g, carbon black dispersion in the carrier coating resin becomes non-uniform, which is not preferable. Moreover, since resistance control is difficult when less than 30 ml / 100g, it is unpreferable.

In the present invention, carbon black is preferably added in an amount of 0.1 to 20% by weight, more preferably 1.0 to 10% by weight, and more preferably 3.0 to 8.0% by weight based on the coating resin layer of the carrier. % Addition is more preferable.
If the amount of carbon black added exceeds 20% by weight, the film strength of the carrier becomes weak, which is not preferable. On the other hand, when the content is less than 0.1% by weight, it is difficult to control resistance.

In the present invention, the resistance of carbon black is preferably 10 ⁻³ to 10 ⁶ Ωcm, and more preferably 10 ⁰ to 10 ³ Ωcm. By setting the resistance of carbon black within the above range, it is preferable because the resistance of the carrier can be controlled within an appropriate range.

-Magnetic core particles-
The electrostatic charge image developing carrier of the present invention is obtained by coating the surface of magnetic core particles with a resin layer.
As the magnetic core particles, in addition to magnetic powders such as iron powder, ferrite powder and magnetite powder, these magnetic powders are melt-kneaded together with a binder resin and a charge control agent, and are pulverized and classified. Suitable resin-dispersed particles and resin-dispersed particles prepared by a polymerization method are preferred. These may be used alone or in combination of two or more.
Among these, it is preferable to use ferrite powder having a relatively low specific gravity and excellent transportability. Various ferrite powders can be used, and there is no particular limitation, but a mixture of several oxides selected from Mn / Mg / Sr / Cu / Zn and the like is used.

  The particle size of the magnetic core particles is preferably 15 to 100 μm, and more preferably 30 to 70 μm in volume average particle size. When the particle size is 15 μm or more, it is preferable because carriers easily migrate onto the latent image carrier and image defects do not occur. Moreover, it is preferable that it is 100 μm or less because the density of the magnetic brush formed on the developer carrying member is good and high image quality can be obtained.

The magnetic core particles preferably have a resistance in the range of 10 ⁶ to 10 ⁹ Ωcm from the viewpoint of controlling the carrier resistance. More preferably, it is in the range of 10 ^6.5 to 10 ^8.5 Ωcm. The resistance of the core particles can be measured by a method similar to the measurement of carrier resistance described later.

-Coating resin layer-
As the resin (coating resin) used for the coating resin layer on the surface of the magnetic core particles of the carrier of the present invention, all general plastic resins can be used. Specifically, styrenes such as styrene, chlorostyrene, and vinylstyrene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate; methyl (meth) acrylate, ethyl (meth) acrylate, Α-methylene aliphatic monocarboxylic acid esters such as butyl (meth) acrylate, dodecyl (meth) acrylate, octyl (meth) acrylate, phenyl (meth) acrylate; vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether Homopolymers or copolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, and the like.

  In particular, typical coating resins include polystyrene, styrene / alkyl acrylate copolymer, styrene / alkyl methacrylate copolymer, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, and styrene / maleic anhydride. A copolymer etc. can be mentioned.

In addition, polyesters, polyurethanes, epoxy resins, silicone resins, polyamides, modified rosins, paraffins, waxes and the like can also be mentioned. Furthermore, a halogen-containing polymer can be mentioned, and specifically, a compound containing fluorine in the side chain is suitable, and in particular, fluorinated alkyl acrylate and fluorinated alkyl methacrylate are mentioned as typical compounds. Furthermore, a fluorinated epoxy resin, a fluorinated polyester resin, a fluorinated silicone resin, or the like can also be used.
These coating resins can be used alone or in combination of two or more.

In the present invention, as the conductive powder added to the coating resin layer, in addition to the above-described carbon black, metal powders such as gold, silver and copper; semiconductive oxides such as titanium oxide and zinc oxide; titanium oxide, A powder surface of zinc oxide, barium sulfate, aluminum borate, potassium titanate or the like coated with tin oxide, carbon black, or metal can be used in combination. Moreover, the specific resistance is preferably 10 ¹⁰ Ωcm or less.

  The conductive powder contained in the coating resin layer should be present on the surface of the coating resin layer of the carrier while having contact with the magnetic core particles of the carrier coated with an insulating resin as a single powder. Can do. For this reason, most of the conductive powder acts as a conductive path in the coating resin layer.

  The average primary particle diameter of the conductive powder used in combination is preferably in the range of 0.02 μm or more and 0.2 μm or less, and can be appropriately selected according to desired charging characteristics. The conductive powder is used for the purpose of resistance control. However, if the addition amount is too large, charge leakage is large, and the charge level is too low, which is not preferable. Moreover, if there is too little addition amount, there will be almost no effect with respect to resistance control. The range of use is preferably in the range of 1 to 25% by weight, more preferably in the range of 3 to 15% by weight, based on the total amount of the above-described carbon black.

  In addition, it is preferable to mix melamine resin fine particles in the carrier coating resin layer because the charge maintenance property is particularly excellent. Like the conductive powder, the melamine resin fine particles can be dispersed in the carrier coating resin layer by adding and mixing in the step of preparing a coating resin layer forming liquid described later. As the melamine resin fine particles used, particles having an average particle diameter in the range of 100 to 500 nm are used. The addition amount is preferably in the range of 0.05 to 1.0% by weight of the carrier weight.

It is also preferable to add a charge control agent incompatible with the resin into the coating resin layer.
Examples of the charge control agent used in the present invention include nigrosine dyes, benzimidazole compounds, quaternary ammonium salt compounds, alkoxylated amines, alkylamides, molybdate chelate pigments, triphenylmethane compounds, and salicylic acid metal salt complexes. Any known azo-chromium complex, copper phthalocyanine, etc. may be used. Particularly preferred are quaternary ammonium salt compounds, alkoxylated amines and alkylamides. These charge control agents are easy to control the dispersion state and have good adhesion to the resin interface, so that desorption of the charge control agent from the carrier resin layer can be suppressed.

  The addition amount of the charge control agent used in the present invention is preferably 0.001 to 5 parts by weight when the magnetic core particle is 100 parts by weight. If the amount is excessive, the strength of the carrier coat film is lowered, and the carrier is easily altered by stress during use. If the amount is too small, the function of the charge control agent cannot be exhibited sufficiently. More preferably, it is 0.01-0.5 weight part.

The coating resin layer is formed by preparing a coating resin or a solution in which the coating resin and various additives are dissolved and dispersed in a solvent (coating resin layer forming solution), and coating the surface of the magnetic core particles with the solution. Then, the coating resin layer forming step of removing the solvent can be performed. As the coating apparatus, a fluidized bed, a spray dryer, a kneader coater, or the like can be used.
The solvent used for the coating resin layer forming solution is not particularly limited as long as it dissolves the coating resin. Examples of the method for dispersing the conductive powder include a sand mill, a dyno mill, and a homomixer.

  In the present invention, the resin coating amount of the resin coating layer is preferably in the range of 0.5 to 10 parts by weight with respect to 100 parts by weight of the carrier. If it is less than 0.5 part by weight, the core particles are likely to be exposed on the surface of the carrier, and the electrical resistance of the carrier tends to decrease. When the amount exceeds 10 parts by weight, the fluidity of the carrier is remarkably lowered, and it becomes difficult to uniformly charge the toner.

The carrier resistance is preferably in the range of 1 × 10 ⁸ to 1 × 10 ¹⁶ Ωcm under an electric field of 10 ^3.8 V / cm, but the carrier resistance is the resistance of the magnetic core particle, the thickness of the coating resin layer ( The coating amount) and the amount of conductive powder in the coating resin layer are adjusted. Since the coating resin layer is coated for the purpose of preventing toner adhesion or imparting a charge, it is better that the coating amount of the coating resin is larger in consideration of charge maintenance. However, when the coating amount increases, the resistance of the carrier becomes too large, and a gradation boundary white spot phenomenon and an image covering phenomenon occur. Therefore, in order to increase the coating amount and keep the resistance within a certain range, a method of dispersing conductive powder in the coating resin layer is used.

The resistance (Ωcm) of the carrier can be measured as follows. The measurement environment is a temperature of 20 ° C. and a humidity of 50% RH.
The carrier to be measured is placed flat on the surface of a circular jig having a 20 cm ² electrode plate so as to have a thickness of about 1 to 3 mm to form a carrier layer. A 20 cm ² electrode plate similar to the above is placed on this and the carrier layer is sandwiched. In order to eliminate the gap between the carriers, the thickness (mm) of the carrier layer is measured after a load of 4 kg is applied on the electrode plate placed on the carrier layer. Both electrodes above and below the carrier layer are connected to an electrometer and a high-voltage power generator. The carrier resistance (Ωcm) is calculated by applying a high voltage so that the electric field is 10 ^3.8 V / cm to both electrodes and reading the current value (A) flowing at this time. The calculation formula of the carrier resistance (Ωcm) is as shown in the following formula (2).
R = E × 20 / (I−I ₀ ) / L Formula (2)
In the above formula, R is the carrier resistance (Ωcm), E is the applied voltage (V), I is the current value (A), I ₀ is the current value (A) at an applied voltage of 0 V, and L is the thickness of the carrier layer (mm). Respectively. A coefficient of 20 represents the area (cm ² ) of the electrode plate.

[Toner for electrostatic image development]
In the present invention, an electrostatic charge image developing toner (also simply referred to as a toner) is a toner obtained by externally adding an external additive to toner base particles, and the toner base particles contain at least a binder resin and a colorant. To do.

-Toner base particles-
In the present invention, the toner base particles include at least a binder resin and a colorant. If necessary, a release agent such as wax and an inorganic powder or resin powder for adjusting viscoelasticity can be added as an internal additive.
The toner production method may be any known method, and examples thereof include, but are not limited to, known production methods such as a kneading and pulverizing method, a suspension polymerization method, an emulsion polymerization method, a liquid drying method, and a dispersion polymerization method. It is not something. For the production of the toner, for example, (1) a kneading and pulverizing method in which a binder resin, a colorant, and if necessary, a release agent, a charge control agent and the like are melt-kneaded, pulverized and classified, (2) a kneading and pulverizing method (3) a resin particle dispersion obtained by emulsion polymerization of a binder resin polymerizable monomer, a colorant, and, if necessary, separating the particles obtained in (1) above by mechanical impact force or thermal energy. An emulsion polymerization aggregation method for obtaining toner particles by mixing, aggregating and heat-fusing with a dispersion liquid in which a mold agent, a charge control agent and the like are dispersed, (4) a polymerizable monomer for obtaining a binder resin And a suspension polymerization method in which a solution of a release agent, a charge control agent and the like is suspended in an aqueous solvent for polymerization, and (5) a binder resin and a colorant, and a release agent as required Alternatively, a solution suspension method in which a solution such as a charge control agent is suspended in an aqueous solvent and granulated can be employed. Further, the toner obtained by these methods may be used as a core, and agglomerated particles may be further adhered and heat-fused to obtain a core-shell toner.

In the present invention, the toner base particles contain a binder resin and a colorant, and if necessary, contain other components such as a release agent and a voltage control agent. Each component used in the toner base particles will be described below.
(Binder resin)
As the binder resin for the toner, styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene, and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl acetate; methyl acrylate Acrylates such as ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, and phenyl acrylate; methacrylates such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl methyl ether, vinyl ethyl ether Homopolymers or copolymers of vinyl ethers such as vinyl butyl ether; vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc. As binder resin, polystyrene, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyethylene And polypropylene. Polyester, polyurethane, epoxy resin, silicon resin, polyamide, modified rosin, paraffin wax, and the like can also be used as the binder resin for the toner.

(Coloring agent)
In the present invention, the toner base particles contain a colorant. In the present invention, the colorant used in the toner is not particularly limited as long as it is a known colorant. For example, carbon black such as furnace black, channel black, acetylene black, thermal black, bengara, bitumen, titanium oxide, etc. Inorganic pigments, fast yellow, disazo yellow, pyrazolone red, chelate red, brilliant carmine, para-brown and other azo pigments, copper phthalocyanine, metal-free phthalocyanine and other phthalocyanine pigments, flavantron yellow, dibromoanthrone orange, perylene red, quinacridone red And condensed polycyclic pigments such as dioxazine violet.

  Chrome Yellow, Hansa Yellow, Benzidine Yellow, Slen Yellow, Quinoline Yellow, Permanent Orange GTR, Pyrarozone Orange, Vulcan Orange, Watch Young Red, Permanent Red, Dupont Oil Red, Resol Red, Rhodamine B Lake, Lake Red C, Rose Bengal, aniline blue, ultramarine blue, calco oil blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green, malachite green oxalate, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment 57: 1, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 74, C.I. I. Pigment blue 15: 1, C.I. I. Examples thereof include various pigments such as CI Pigment Blue 15: 3, and these can be used alone or in combination of two or more.

In the present invention, the content of the colorant in the toner is preferably 1 to 20% by weight, more preferably 1 to 10% by weight, more preferably 2 to 2% by weight with respect to 100 parts by weight of the binder resin. It is more preferably 10% by weight, particularly preferably 2 to 7% by weight, and it is preferably as much as possible as long as the smoothness of the image surface after fixing is not impaired. It is also effective to use a surface-treated colorant or a pigment dispersant as necessary. By appropriately selecting the type of the colorant, yellow toner, magenta toner, cyan toner, black toner and the like can be obtained.
When a magnetic material is used as the black colorant, it is added in the range of 30 to 100% by weight, unlike other colorants.

(Release agent)
In the present invention, the toner may contain a release agent. The release agent used is not particularly limited as long as it is a known release agent. For example, natural waxes such as carnauba wax, rice wax, and candelilla wax, low molecular weight polypropylene, low molecular weight polyethylene, sasol wax, Examples include, but are not limited to, synthesis of microcrystalline wax, Fischer-Tropsch wax, paraffin wax, montan wax and the like, and ester wax such as mineral / petroleum wax, fatty acid ester, and montanic acid ester. Moreover, these mold release agents may be used individually by 1 type, and may be used together 2 or more types.

  The melting point of the release agent is preferably 50 ° C. or higher, more preferably 60 ° C. or higher, from the viewpoint of storage stability. Moreover, it is preferable that it is 110 degrees C or less from a viewpoint of offset resistance, and it is more preferable that it is 100 degrees C or less.

The content of the release agent is preferably in the range of 1 to 30 parts by weight and more preferably in the range of 2 to 20 parts by weight with respect to 100 parts by weight of the binder resin. When the content of the release agent is within the above range, the effect of adding the release agent can be obtained, and hot offset at high temperature is not caused, which is preferable. Furthermore, the charging property is not adversely affected, and the mechanical strength of the toner is not lowered. Also when used as a color toner, it is preferable because no domain remains in the fixed image and good OHP transparency is obtained.
In the present invention, a toner containing no release agent may be used.

(Other additives)
In addition to the above-described components, various components such as an internal additive, a charge control agent, inorganic powder (inorganic fine particles), and organic fine particles can be added to the toner of the present invention as necessary. .

  Examples of the internal additive include metals such as ferrite, magnetite, reduced iron, cobalt, nickel and manganese, alloys, and magnetic materials such as compounds containing these metals.

  Examples of the charge control agent include quaternary ammonium salt compounds, nigrosine compounds, dyes composed of complexes of aluminum, iron, chromium, and triphenylmethane pigments. Inorganic powder is added mainly for the purpose of adjusting the viscoelasticity of the toner. For example, silica, alumina, titania, calcium carbonate, magnesium carbonate, calcium phosphate, cerium oxide, etc. are usually used as external additives on the toner surface. And all inorganic fine particles to be used.

-Toner production method-
As described above, the method for producing the toner of the present invention is not particularly limited, but it is preferably produced by a wet granulation method. Examples of the wet granulation method include known melt suspension methods, emulsion aggregation methods, and dissolution suspension methods. Among these methods, the emulsion aggregation method is preferably used in the present invention.
When using the emulsion aggregation method, it is preferable to include at least an emulsification step of preparing a dispersion containing at least binder resin particles, and an aggregation step of forming aggregated particles including the binder resin in the dispersion. More preferably, it includes a fusing step of fusing the aggregated particles by heating. Hereinafter, each step will be described in detail.

-Emulsification process-
In the emulsification step, the raw material dispersion is a solution in which a binder resin emulsified particle (hereinafter abbreviated as “resin particle”) is mixed with an aqueous medium and, if necessary, a dispersion containing a colorant and a release agent. Is formed by applying a shearing force. Therefore, the binder resin needs to be dispersed in advance as resin particles in the raw material dispersion.

  The volume average particle size of the resin particles is preferably 1 μm or less, and more preferably 0.01 to 1 μm. When the volume average particle size is within the above range, the particle size distribution of the finally obtained electrostatic latent image developing toner is narrow, and free particles are not generated, so the performance and reliability are improved. This is preferable. Further, the uneven distribution between the toners is reduced, the dispersion in the toners is improved, and the variation in performance and reliability is advantageous. The volume average particle diameter can be measured using, for example, a Coulter counter.

  Examples of the dispersion medium in the dispersion include an aqueous medium and an organic solvent. Examples of the aqueous medium include water such as distilled water and ion exchange water, and alcohols. These may be used individually by 1 type and may use 2 or more types together. In the present invention, it is preferable to add and mix a surfactant in the aqueous medium. Although it does not specifically limit as surfactant, For example, anionic surfactants, such as a sulfate ester type, a sulfonate type, a phosphate ester type, soap type; Nonionic surfactants such as polyethylene glycol-based, alkylphenol ethylene oxide adduct-based, polyhydric alcohol-based, and the like. Among these, anionic surfactants and cationic surfactants are preferable. The nonionic surfactant is preferably used in combination with the anionic surfactant or the cationic surfactant. The said surfactant may be used individually by 1 type, and may use 2 or more types together.

  Specific examples of the anionic surfactant include sodium dodecylbenzenesulfonate, sodium dodecylsulfate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate and the like. Specific examples of the cationic surfactant include alkylbenzene dimethyl ammonium chloride, alkyl trimethyl ammonium chloride, distearyl ammonium chloride and the like. Among these, ionic surfactants such as anionic surfactants and cationic surfactants are preferable. Examples of the organic solvent include ethyl acetate and toluene, which are appropriately selected according to the binder resin.

  When the resin particle is a homopolymer or copolymer (vinyl resin) of a vinyl monomer such as the ester having a vinyl group, the vinyl nitrile, the vinyl ether, or the vinyl ketone. By conducting emulsion polymerization or seed polymerization of the vinyl monomer in an ionic surfactant, resin particles made of a vinyl monomer homopolymer or copolymer (vinyl resin) are made ionic. A dispersion obtained by dispersing in a surfactant is prepared.

When the resin particle is a resin other than a homopolymer or a copolymer of the vinyl monomer, the resin can be dissolved in an oily solvent having a relatively low solubility in water. The resin is dissolved in the oily solvent, and this solution is dispersed in water together with an ionic surfactant and polymer electrolyte using a disperser such as a homogenizer, and then the oily solvent is evaporated by heating or decompression. Thus, a dispersion liquid in which resin particles made of resin other than vinyl resin are dispersed in an ionic surfactant is prepared.

  On the other hand, when the resin particle is a crystalline polyester and an amorphous polyester resin, it contains a functional group that can become an anionic type by neutralization, and has a self-water dispersibility. A stable aqueous dispersion can be formed under the action of an aqueous medium, all neutralized with a base. In the crystalline polyester and the amorphous polyester resin, the functional group that can become a hydrophilic group by neutralization is an acidic group such as a carboxyl group or a sulfone group. As the neutralizing agent, for example, sodium hydroxide, potassium hydroxide, water Examples thereof include inorganic bases such as lithium oxide, calcium hydroxide, sodium carbonate and ammonia, and organic bases such as diethylamine, triethylamine and isopropylamine.

  Further, when a polyester resin that does not disperse in water, that is, does not have self-water dispersibility, is used as a binder resin, the resin solution and / or an aqueous medium mixed with the resin solution, as described later, Disperse with a polymer electrolyte such as a surfactant, polymer acid, polymer base, etc., heat to a glass transition point or higher than the melting point, and treat using a homogenizer or pressure discharge type disperser capable of applying a strong shear force Can be easily made into fine particles of 1 μm or less. When this ionic surfactant or polymer electrolyte is used, it is appropriate that the concentration in the aqueous medium is about 0.5 to 5 wt%.

As the colorant mixed with the resin dispersion in the emulsification step, the colorants described above can be used. As a method of dispersing the colorant, any method such as a general dispersion method such as a rotary shearing homogenizer, a ball mill having a medium, a sand mill, or a dyno mill can be used, and the method is not limited at all. If necessary, an aqueous dispersion of these colorants can be prepared using a surfactant, or an organic solvent dispersion of these colorants can be prepared using a dispersant. As the surfactant and the dispersing agent used for dispersion, the same dispersing agents that can be used when dispersing the binder resin can be used.
These colorants may be added to the mixed solvent at the same time as other fine particle components, or may be divided and added in multiple stages.

  As the release agent mixed with the resin dispersion in the emulsification step, the release agent described above can be used. As with the case of emulsifying and dispersing a polyester resin that does not have self-water dispersibility, the release agent is dispersed together with an ionic surfactant or the like in water, heated above the melting point, and can be applied with a strong shearing force. Using a pressure discharge type disperser, the dispersed fine particle diameter is adjusted to 1 μm or less. As the dispersion medium in the release agent dispersion, the same dispersion medium as that for the binder resin can be used.

  In the present invention, as an apparatus for mixing and dispersing the binder resin and the release agent with an aqueous medium, for example, a homomixer (Special Machine Industries Co., Ltd.), a slasher (Mitsui Mine Co., Ltd.), Cavitron (stock) Examples include continuous emulsifying and dispersing machines such as Eurofluid Co., Ltd., Microfluidizer (Mizuho Industrial Co., Ltd.), Menton Gorin homogenizer (Gorin Inc.), Nanomizer (Nanomizer Inc.), Static Mixer (Noritake Company), and the like.

  The content of the resin particles contained in the binder resin dispersion in the emulsification step and the content of each of the colorant and the release agent in the dispersion of the colorant and the release agent are preferably 5 to 50% by weight, More preferably, it is 10 to 40% by weight. It is preferable for the content to be in the above range because the particle size distribution is narrow and good characteristics are obtained.

  In the present invention, other components such as an internal additive, a charge control agent, and an inorganic powder as described above may be dispersed in the binder resin dispersion according to the purpose. The charge control agent in the present invention is preferably made of a material that is difficult to dissolve in water in terms of controlling ionic strength that affects the stability of the aggregation process and the fusion process and reducing wastewater contamination.

  The volume average particle size of the other components is preferably 1 μm or less, and more preferably 0.01 to 1 μm. When the volume average particle size is within the above range, the particle size distribution of the finally obtained electrostatic latent image developing toner is narrow, and free particles are not generated, so that good performance and reliability are obtained. This is preferable. Further, it is advantageous in that uneven distribution between toners is reduced, dispersion in the toner is good, and variations in performance and reliability are reduced.

-Aggregation process-
In the aggregation step, the resin particles obtained in the emulsification step, and the colorant and release agent dispersion are mixed (hereinafter this mixture is referred to as “raw material dispersion”), and the glass transition point of the binder resin or Aggregated particles are formed by agglomerating the respective dispersed particles by heating at a temperature near the melting point and at a glass transition point or lower than the melting point.

  Agglomerated particles are formed by adding a flocculant at room temperature under stirring with a rotary shearing homogenizer to make the pH of the raw material dispersion acidic. The pH is preferably 3.5 to 6 and more preferably 4 to 6 when a vinyl copolymer is used as the amorphous polymer of the binder resin.

  As the aggregating agent used in the aggregating step, a surfactant having a polarity opposite to that of the surfactant used for the dispersant, an inorganic metal salt, and a divalent or higher-valent metal complex can be preferably used. The use of a metal complex is particularly preferred because the amount of surfactant used can be reduced and charging characteristics are improved.

Examples of the inorganic metal salt include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, and polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. Examples thereof include inorganic metal salt polymers. Among these, an aluminum salt and a polymer thereof are particularly preferable. In order to obtain a sharper particle size distribution, the valence of the inorganic metal salt is bivalent than monovalent, trivalent than bivalent, trivalent than trivalent, and tetravalent than trivalent. The inorganic metal salt polymer is more suitable.
Further, in the aggregation process, in order to suppress rapid aggregation due to heating, it is preferable to adjust pH at the stage of stirring and mixing at room temperature, and to add a dispersion stabilizer as necessary (hereinafter, this stage is referred to as “ Called pre-aggregation step). As the dispersion stabilizer used in this pre-aggregation step, it is preferable to add 1 to 3% of a known nonionic surfactant so as not to change the polarity. It is preferable to add a dispersion stabilizer because the fine particles of the raw material particles can be taken in well in the heat aggregation step, and as a result, a narrow particle size distribution can be obtained. Further, it is effective to add the dispersion stabilizer separately in both the pre-aggregation step and the heat aggregation step.

-Adhesion process-
In the attaching step, the coating layer can also be formed by further attaching a bond to the surface of the agglomerated particles formed through the aggregating step (hereinafter abbreviated as “core agglomerated particles”). This can be performed by additionally adding a dispersion liquid containing a binder resin to the dispersion liquid in which the core aggregated particles are formed in the aggregation process, and other components may be additionally added as necessary. Also in the attaching step, the pH and the aggregating agent are selected in the same manner as in the aggregating step depending on the resin used, and the binder resin having the lowest glass transition point or melting point among the two or more types of binder resins contained in the agglomerated particles. Aggregated particles can be obtained by heating at a temperature below the glass transition point or the melting point. This adhesion process is also effective in leading the raw material fine particles that have not been taken into the aggregated particles at the pre-aggregation stage.

-Fusion process-
In the fusion step, under the same agitation as in the agglomeration step, the pH of the suspension of the agglomerated particles is set in the range of 6.5 to 8.5 to stop the agglomeration, and then the binder resin glass The aggregated particles are fused by heating at a temperature above the transition point or melting point. Although depending on the liquid property of the dispersion containing aggregated particles, if the pH at which aggregation is stopped is not an appropriate pH, the aggregated particles are dispersed in the temperature raising process for fusing, resulting in a poor yield. Moreover, you may implement a fusion process, after obtaining an aggregation process as needed.

  There is no problem if the heating temperature at the time of fusion is not less than the glass transition point or melting point of the binder resin contained in the aggregated particles. The heating time may be performed so that the fusion is sufficiently performed, and may be performed for about 0.5 to 1.5 hours. If it takes more time, the binder resin contained in the core aggregated particles is likely to be exposed on the toner surface. Therefore, although it is effective for fixing property and document storage property, it is not preferable to heat for a long time because it adversely affects charging property.

  In the fusion step, a crosslinking reaction may be performed when the binder resin is heated to a glass transition point or a melting point or higher, or after the fusion is completed. In addition, a crosslinking reaction can be performed simultaneously with the fusion. When the crosslinking reaction is performed, for example, an unsaturated sulfonated crystalline polyester resin obtained by copolymerizing a double bond component as a binder resin is used, and a radical reaction is caused to the resin to introduce a crosslinked structure. . At this time, the following polymerization initiator can be used.

  Examples of the polymerization initiator include t-butyl peroxy-2-ethylhexanoate, cumyl perpivalate, t-butyl peroxylaurate, benzoyl peroxide, lauroyl peroxide, octanoyl peroxide, di-t. -Butyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, 2,2'-azobisisobutyronitrile, 2,2'-azobis (2-methylbutyronitrile), 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane 1,1-bis (t-butylperoxy) cyclohexane, 1,4-bis (t-butylperoxyca) Bonyl) cyclohexane, 2,2-bis (t-butylperoxy) octane, n-butyl 4,4-bis (t-butylperoxy) valerate, 2,2-bis (t-butylperoxy) butane, , 3-bis (t-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylper) Oxy) hexane, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, di-t-butyldiperoxyisophthalate, 2,2-bis (4,4-di-t-butylperoxy) (Cyclohexyl) propane, di-t-butylperoxy α-methylsuccinate, di-t-butylperoxydimethylglutarate, di-t-butylperoxyhexahydrotereph Tartrate, di-t-butylperoxyazelate, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, diethylene glycol-bis (t-butylperoxycarbonate), di-t-butylper Oxytrimethyl adipate, tris (t-butylperoxy) triazine, vinyltris (t-butylperoxy) silane, 2,2'-azobis (2-methylpropionamidine dihydrochloride), 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine], 4,4′-azobis (4-cyanovaleric acid) and the like.

  These polymerization initiators can be used alone or in combination of two or more. The amount and type of the polymerization initiator are selected depending on the amount of unsaturated sites in the polymer and the type and amount of the coexisting colorant. The polymerization initiator may be mixed with the polymer in advance before the emulsification step, or may be incorporated into the aggregate in the aggregation step. Further, it may be introduced after the fusion step or after the fusion step. In the case of introduction after the aggregation step, the adhesion step, the fusion step, or the fusion step, a solution in which the polymerization initiator is dissolved or emulsified is added to the particle dispersion (resin particle dispersion or the like). These polymerization initiators may be added with known crosslinking agents, chain transfer agents, polymerization inhibitors and the like for the purpose of controlling the degree of polymerization.

  The fused particles obtained by fusing can be made into toner particles through a solid-liquid separation process such as filtration and, if necessary, a washing process and a drying process. In this case, in order to ensure sufficient charging characteristics and reliability as a toner, it is preferable to sufficiently wash in the washing step.

  In the drying process, an arbitrary method such as a normal vibration type fluidized drying method, a spray drying method, a freeze drying method, or a flash jet method can be adopted. The toner particles should have a moisture content after drying of preferably 1.0% or less, and more preferably 0.5% or less.

In the present invention, the cumulative volume average particle diameter D ₅₀ of the toner is preferably in the range of 3.0 to 9.0 μm, more preferably in the range of 3.0 to 5.0 μm. When D ₅₀ is 3.0 μm or more, the adhesive force is appropriate and the developability is good, which is preferable. Moreover, it is excellent in the resolution of an image as it is 9.0 micrometers or less, and preferable.

  Further, the volume average particle size distribution index GSDv of the obtained toner is preferably 1.30 or less. It is preferable that GSDv is 1.30 or less because image resolution is excellent and image defects such as toner scattering and fog do not occur.

Here, the cumulative volume average particle size D ₅₀ and the average particle size distribution index are, for example, the particle size distribution measured by a measuring instrument such as Coulter Counter TAII (manufactured by Nikka Kisha Co., Ltd.), Multisizer II (manufactured by Nikka Kisha Co., Ltd.), or the like. The particle size range (channel) divided based on the volume and number are cumulative distributions starting from the small diameter side, and the particle size that is 16% cumulative is the volume D _16v , the number D _16P , and the particle that is 50% cumulative The diameter is _defined as a volume D _50v and a number D _50P , and the particle diameter at a cumulative 84% is defined as a volume D _84v and a number D _84P . Using these, the volume average particle size distribution index (GSDv) is calculated as (D _84v / D _16V ) ^1/2 and the number average particle size distribution index (GSDp) is calculated as (D _84P / D _16P ) ^1/2 .

The shape factor SF1 of the obtained toner is preferably from 100 to 140, more preferably from 110 to 135, from the viewpoint of image formability.
The shape factor SF1 is digitized mainly by analyzing a microscope image or a scanning electron microscope image with an image analyzer, and is obtained as follows, for example. In measuring the shape factor SF1, first, an optical microscope image of the toner spread on the slide glass is taken into a Luzex image analyzer through a video camera, and SF1 of the following formula is calculated for 50 or more toners to obtain an average value. Can be obtained.

ここでＭＬはトナー粒子の絶対最大長、Ａはトナー粒子の投影面積である。

Here, ML is the absolute maximum length of the toner particles, and A is the projected area of the toner particles.

Toner particles granulated through the drying process as described above can be added with various known external additives such as inorganic fine particles and organic fine particles, which will be described later, depending on the purpose.
The external additives added to the toner base particles will be described below.
-External additive-
In the present invention, the moisture absorption amount of the external additive is preferably 1.0 wt% or more, more preferably 1.5 to 10.0 wt%, and further preferably 2.0 to 5.0 wt%. preferable.
It is preferable that the moisture absorption amount of the external additive is 1.0 wt% or more because carrier contamination can be prevented.
The moisture absorption amount of the external additive can be measured in the same manner as the moisture absorption amount of the carbon black described above.
By increasing the moisture absorption of the external additive and designing the moisture absorption of the carbon black in the carrier coating resin to be low, the affinity between the external additive and the carrier is reduced, preventing contamination of the external additive to the carrier. It is considered possible.

The external additive is added to the surface of the toner base particles for the purpose of improving fluidity, and various resin powders and inorganic compounds can be added as external additives. As the resin powder, spherical particles such as PMMA, nylon, melamine, benzoguanamine, and fluorine resin can be used. Examples of various known inorganic compounds include SiO ₂ , TiO ₂ , Al ₂ O ₃ , MgO, CuO, ZnO, SnO ₂ , CeO ₂ , Fe ₂ O ₃ , BaO, CaO, K ₂ O, and Na ₂ O. , ZrO ₂ , CaO · SiO ₂ , CaCO ₃ , K ₂ O (TiO ₂ ) _n , MgCO ₃ , Al ₂ O ₃ · 2SiO ₂ , BaSO ₄ , MgSO _4, etc., preferably SiO ₂ , Examples thereof include TiO ₂ and Al ₂ O _3, but are not limited to these, and one or more of these may be used in combination.

Further, the toner of the present invention is preferably used by mixing inorganic particles such as a fluidity improver as an external additive.
As said inorganic particle used in this invention, it is preferable that a primary particle diameter is 5 nm-2 micrometers, More preferably, it is 5 nm-500 nm. Moreover, it is preferable that the specific surface area by BET method is 20-500 m < ² > / g.
The proportion mixed with the toner is preferably 0.01 to 5% by weight, more preferably 0.01 to 2.0% by weight.
Examples of such inorganic particles include silica powder, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, Examples thereof include chromium oxide, cerium oxide, bengara, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, and silicon nitride, and silica powder is particularly preferable.
The silica powder here is a powder having a Si—O—Si bond, and includes both those produced by a dry method and a wet method. In addition to anhydrous silicon dioxide, any of aluminum silicate, sodium silicate, potassium silicate, magnesium silicate, zinc silicate and the like may be used, but those containing SiO _{2 in an amount} of 85% by weight or more are preferable.
Specific examples of these silica powders include various commercially available silicas, but those having a hydrophobic group on the surface are preferable. For example, AEROSIL R-972, R-974, R-805, R-812 (manufactured by Aerosil Co., Ltd.) ), Thalax 500 (manufactured by Tarco) and the like. In addition, silica powder treated with a silane coupling agent, a titanium coupling agent, silicon oil, silicon oil having an amine in the side chain, or the like can be used.

  The mixing ratio (weight ratio) of the toner and the carrier in the two-component developer is preferably in the range of toner: carrier = 1: 100 to 30: 100, and in the range of 3: 100 to 20: 100. Is more preferable.

[Image forming method]
The electrostatic image developing carrier and electrostatic image developer of the present invention can be used in an image forming method of a normal electrostatic image developing system (electrophotographic system).
The image forming method of the present invention includes a latent image forming step of forming an electrostatic latent image on the surface of the latent image holding member, and developing the electrostatic latent image formed on the surface of the latent image holding member with a developer containing toner. A developing step for forming a toner image, a transfer step for transferring the toner image formed on the surface of the latent image holding member to the surface of the transfer target, and a fixing step for thermally fixing the toner image transferred to the surface of the transfer target. The developer includes the carrier for developing an electrostatic image of the present invention.
For each of the above steps, a known step can be used in the image forming method, and are described in, for example, JP-A-56-40868 and JP-A-49-91231.
Further, the image forming method of the present invention may include steps other than the above-described steps. For example, a cleaning step for removing the electrostatic charge image developer remaining on the electrostatic latent image carrier is preferable. Can be mentioned. In the image forming method of the present invention, an embodiment that further includes a recycling step is preferable. The recycling step is a step of transferring the electrostatic charge image developing toner collected in the cleaning step to a developer layer. The image forming method including the recycling step can be performed using an image forming apparatus such as a toner recycling system type copying machine or facsimile machine. The present invention can also be applied to a recycling system in which the cleaning process is omitted and toner is collected simultaneously with development.

As the latent image holding member, for example, an electrophotographic photosensitive member and a dielectric recording member can be used.
In the case of an electrophotographic photosensitive member, the surface of the electrophotographic photosensitive member is uniformly charged by a corotron charger, a contact charger or the like and then exposed to form an electrostatic latent image (latent image forming step). Next, the toner particles are attached to the electrostatic latent image by contacting or approaching a developing roll having a developer layer formed on the surface, thereby forming a toner image on the electrophotographic photosensitive member (developing step). The formed toner image is transferred onto the surface of a transfer medium such as paper using a corotron charger or the like (transfer process). Further, the toner image transferred onto the surface of the transfer medium is thermally fixed by a fixing device (fixing step), and a final toner image is formed.
In the heat fixing by the fixing device, a release agent is usually supplied to a fixing member in the fixing device in order to prevent offset and the like.

[Image forming apparatus]
The image forming apparatus of the present invention comprises an electrostatic latent image carrier (latent image carrier), a charging means for charging the surface of the electrostatic latent image carrier, and the carrier charged by the charging means. An exposure unit that forms an electrostatic latent image by exposing the surface according to image information; a developing unit that develops the electrostatic latent image with toner to form a toner image; and the toner image that carries the image A transfer unit that transfers the image from the body to the recording material, and a fixing unit that fixes the toner image on the fixing base as necessary. In the transfer unit, the transfer may be performed twice or more using an intermediate transfer member.

As the electrostatic latent image carrier and each of the above-described means, the configurations described in the respective steps of the image forming method can be preferably used.
Any of the above-described means can be a known means in the image forming apparatus. Further, the image forming apparatus used in the present invention may include means and devices other than the above-described configuration. Further, the image forming apparatus used in the present invention may simultaneously perform a plurality of the above-described means.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all. In addition, unless otherwise indicated, the part in an Example shows a weight part altogether.
Example 1
[Production of Cyan Toner A]
-Preparation of resin particle dispersion-
Styrene 370 parts n-Butyl acrylate 30 parts Acrylic acid 8 parts Dodecanethiol 24 parts Carbon tetrabromide 4 parts A nonionic surfactant (Nonipol 400: Sanyo Chemical Co., Ltd.) was prepared by mixing and dissolving the above ingredients. 6 parts) and 10 parts of an anionic surfactant (Neogen SC: manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) were dissolved in 550 parts of ion-exchanged water and subjected to emulsion polymerization. 50 parts of ion-exchanged water in which 4 parts of ammonium persulfate was dissolved was added. After carrying out nitrogen substitution, the inside of the flask was stirred and heated in an oil bath until the content reached 70 ° C., and emulsion polymerization was continued for 5 hours. As a result, a resin particle dispersion in which resin particles having a volume average particle size of 150 nm, Tg = 58 ° C., and weight average molecular weight Mw = 11,500 was obtained. The solid content concentration of this dispersion was 40% by weight.

-Preparation of colorant dispersion-
Cyan pigment (CI Pigment Blue 15: 3) 60 parts Nonionic surfactant (Nonipol 400: manufactured by Sanyo Chemical Co., Ltd.) 5 parts Ion-exchanged water 240 parts The above ingredients are mixed and dissolved, homogenizer ( The mixture was stirred for 10 minutes using Ultra Turrax T50 (manufactured by IKA), and then dispersed for 10 minutes with an optimizer to prepare a colorant dispersion in which colorant particles having an average particle diameter of 250 nm were dispersed. .

-Preparation of release agent dispersion-
100 parts of paraffin wax (HNP0190: manufactured by Nippon Seiwa Co., Ltd., melting point 85 ° C.)
Cationic surfactant (Sanisol B50: manufactured by Kao Co., Ltd.) 5 parts Ion-exchanged water 240 parts The above ingredients were mixed in a round stainless steel flask using a homogenizer (Ultra Turrax T50: manufactured by IKA). After being dispersed for a minute, it was dispersed with a pressure discharge type homogenizer to prepare a release agent dispersion in which release agent particles having an average particle diameter of 350 nm were dispersed.

-Preparation of cyan toner A-
Resin particle dispersion 234 parts Colorant dispersion 30 parts Release agent dispersion 40 parts Polyaluminum chloride (PAC100W, manufactured by Asada Chemical Co., Ltd.) 1.8 parts Ion-exchanged water 600 parts In a round stainless steel flask Were mixed and dispersed using a homogenizer (Ultra Turrax T50: manufactured by IKA), and then heated to 52 ° C. while stirring the inside of the flask in an oil bath for heating. After holding at 52 ° C. for 120 minutes, it was confirmed that aggregated particles having a volume average particle diameter D ₅₀ of 4.8 μm were formed. Thereafter, 32 parts by weight of a resin particle dispersion was added to the dispersion containing the aggregate particles, and then the temperature of the heating oil bath was raised to 53 ° C. and held for 30 minutes. The dispersion containing the aggregated particles is added with 1N sodium hydroxide to adjust the pH of the system to 5.0, and then the stainless steel flask is sealed and heated to 95 ° C. while stirring with a magnetic seal. And held for 6 hours. After cooling, the toner base particles were separated by filtration, washed four times with ion exchange water, and then freeze-dried to obtain cyan toner A. The cyan toner A had a cumulative volume average particle diameter D ₅₀ of 5.5 μm and a volume average particle size distribution index GSDv of 1.16.

<Measurement of D ₅₀ and GSDv>
Using a multisizer (manufactured by Nikka Machine Co., Ltd.), measurement was performed with an aperture diameter of 100 μm. The cumulative volume average particle size (D ₅₀ ) refers to the particle size at which the cumulative distribution is drawn from the coarse powder side in the volume distribution and becomes 50%. Further, the volume average particle size distribution index (GSDv) was obtained from the ratio of particle diameters (D ₁₆ / D ₈₄ ) where the cumulative distribution was drawn from the coarse powder side in the volume distribution and became 16% and 84%.

[Manufacture of external additive toner A]
Cyan toner A 100 parts Rutile type titanium oxide 0.8 parts (particle size 20 nm, 0.05% vinyltrimethoxysilane treatment, moisture absorption 2.5 wt%)
Silica 1.0 part (particle size 40 nm, 0.05% 3-acryloxypropyltrimethoxysilane treatment, moisture absorption 1.3 wt%)
The above components were mixed using a Henschel mixer to obtain externally added toner A.

[Production of carbon black A]
10 parts by weight of hexamethyldisilazane is added to 100 parts by weight of ethanol and spray-coated on 100 parts by weight of carbon black (trade name R330R; manufactured by Cabot, average primary particle size 25 nm, DBP oil absorption 70 mL / 100 g). After desolvation, heat treatment was performed at 130 ° C. for 2 hours. Further, while stirring 100 parts by weight of the treated carbon black, 20 parts by weight of dimethyl silicone oil (KF96, 100CS, manufactured by Shin-Etsu Chemical Co., Ltd.) is sprayed and heat treated at 150 ° C. for 5 hours to obtain carbon black A. Obtained.
The obtained carbon black A was measured for moisture absorption as follows.
First, a flat weighing bottle (height 30 mm, diameter 60 mm, manufactured by ASONE Co., Ltd.) was removed, put into a dryer, and dried at 125 ° C. for 30 minutes. Thereafter, a flat weighing bottle and a stopper were placed in a desiccator, allowed to cool to room temperature, and then the flat weighing bottle was stoppered and accurately weighed to 0.1 mg. About 2 g of carbon black A was correctly weighed to 0.1 mg, put in a flat weighing bottle, and then left for 24 hours in an environment of temperature 28 ° C. and humidity 85% with the stopper removed. After standing, seal the flat weighing bottle, measure the weight at room temperature, remove the stopper, dry at 125 ° C for 1 hour, place the flat weighing bottle and the stopper in a desiccator, allow to cool to room temperature, The bottle was capped and accurately weighed to 0.1 mg.
The amount of moisture absorption is obtained by the following formula.
Moisture absorption = (m1-m2) / (m2-m0) × 100
m0: Weight of the flat weighing bottle (including stopper) after heating (g)
m1: Weight (g) of flat scale bottle (including stopper) and carbon black A after 24 hours
m2: Weight (g) after heating of flat scale bottle (including stopper) and carbon black A.
The moisture absorption of carbon black A was 0.1 wt%.

[Preparation of Carrier A]
Mn—Mg—Sr ferrite particles (average particle size 40 μm) 100 parts Toluene 14 parts Styrene / methyl methacrylate copolymer 2.0 parts (copolymerization ratio 2: 8, Mw 100,000)
Carbon black A 0.12 parts The above components excluding ferrite particles and glass beads (φ1 mm, equivalent to toluene) were stirred at 1,200 ppm for 30 min using a sand mill manufactured by Kansai Paint Co., Ltd., to obtain a resin coating layer forming solution. . Further, the resin coating layer forming solution and ferrite particles were placed in a vacuum degassing kneader and stirred for 10 minutes while maintaining a temperature of 60 ° C., and then the pressure was reduced and toluene was distilled off to form a resin coating layer. This was sieved with a 75 μm mesh to obtain carrier A.

[Preparation of Developer A]
8 parts of external toner A and 100 parts of carrier A were stirred with a V-blender at 40 rpm for 20 minutes and sieved with a sieve having an opening of 212 μm to obtain developer A.

(Example 2)
A developer B was obtained in the same manner as in Example 1 except that the externally added toner A was changed to the externally added toner B in Example 1. A method for manufacturing the external toner B will be described below.
[Manufacture of external additive toner B]
Cyan toner A 100 parts Rutile type titanium oxide 0.8 parts (particle size 20 nm, 15% silicone oil treatment, moisture absorption 0.9 wt%)
Silica 1.0 part (particle size 40nm, 15% silicone oil treatment, moisture absorption 0.8wt%)
The above components were mixed with a Henschel mixer to obtain externally added toner B.

(Example 3)
A developer C was obtained in the same manner as in Example 1 except that the carbon black A was changed to the carbon black B in Example 1. The manufacturing method of carbon black B is shown below.
[Production of carbon black B]
Carbon black B was obtained in the same manner as carbon black A except that the amount of dimethyl silicone oil was changed from 20 parts by weight to 5 parts by weight in the production of carbon black A.

(Comparative Example 1)
[Manufacture of carrier D]
Carrier D was obtained in the same manner as in Example 1 except that carbon black A was changed to R330R (manufactured by Cabot, moisture absorption 1.95 wt%) in the production of carrier A.

[Preparation of developer D]
8 parts of external toner B and 100 parts of carrier B were stirred with a V-blender at 40 rpm × 20 minutes, and sieved with a sieve having an opening of 212 μm to obtain developer D.

(Comparative Example 2)
A developer E was obtained in the same manner as in Comparative Example 1 except that the externally added toner B was changed to the externally added toner A in Comparative Example 1.

(Comparative Example 3)
A developer F was obtained in the same manner as in Example 1 except that the carbon black A was changed to carbon black C in Example 1. The manufacturing method of carbon black C is shown below.
[Production of carbon black C]
Carbon black C was obtained in the same manner as carbon black A except that the amount of dimethyl silicone oil was changed from 20 parts by weight to 3 parts by weight in the production of carbon black A.

Using the developer thus obtained, the following copy test was carried out at a sleeve peripheral speed of 250 mm / sec with a modified machine of DocuPrint C1616 manufactured by Fuji Xerox.
This copy test was performed by copying 30,000 copies at room temperature and high humidity (22 ° C, 95% RH) with an area coverage of 5%, after 10 copies (initial) and after 30,000 copies. The items of image density, fog, and color point were evaluated by the following evaluation methods.

(Concentration evaluation method)
An image of 2 cm × 5 cm was output, and the image density after printing 10 sheets and the image density after 30,000 printing were measured by X-rite 938. Table 1 shows the results of measuring the image density after printing 10 sheets and after printing 30,000.
Judgment criteria are as follows.
A: Density after 30,000 sheets / 10 density after 10 sheets: 97% or more O: Density after 30,000 sheets / 10 density after 10 sheets: 95% or more Δ: Density after 30,000 sheets / 10 density after 10 sheets: 90% X: Density after 30,000 sheets / 10 density after 10 sheets: less than 90%

(Cover evaluation method)
For the white background portion of the image, the number of toners per 100 cm ² was counted.
The evaluation criteria are as follows, and ◎ and ○ are practical levels.
◎: No toner ○: Less than 3 △: 3 or more and less than 5 ×: 5 or more

(Color point evaluation method)
A4 blank paper was output and the number of color points was counted.
The evaluation criteria are as follows, and ◎ and ○ are practical levels.
◎: No color point ○: Total less than 5 △: Total 5 or more and less than 10 ×: Total 10 or more

(Comprehensive evaluation)
Evaluation items for density, fogging, and color point were evaluated by addition values when ◎ 0 point, ◯ 1 point, △ 2 point, and × 3 point. Judgment criteria are as follows, and ◎ and ○ are practical levels.
◎: Addition value is 2 points or less ○: Addition value is 3 points to 5 points △: Addition value is 6 points to 8 points ×: Addition value is 9 points or more The obtained evaluation results are shown in the following table.

Claims (4)

An electrostatic charge image developing carrier having a coating resin layer on the surface of magnetic core particles,
The coating resin layer contains carbon black,
A carrier for developing an electrostatic image, wherein the carbon black has a moisture absorption of 1.0 wt% or less. An electrostatic image developer having an electrostatic image developing carrier and a toner,
The toner comprises toner base particles containing at least a binder resin and a colorant and an external additive,
The moisture absorption amount of the external additive is 1.0 wt% or more,
The electrostatic charge image developing carrier according to claim 1, wherein the electrostatic charge image developing carrier is the electrostatic charge image developing carrier according to claim 1. A latent image forming step for forming an electrostatic latent image on the surface of the latent image holding member;
A developing step of developing the electrostatic latent image formed on the surface of the latent image holding member with a developer containing toner to form a toner image;
A transfer step of transferring the toner image formed on the surface of the latent image holding member to the surface of the transfer target; and
An image forming method comprising a fixing step of thermally fixing the toner image transferred to the surface of the transfer material,
An image forming method, wherein the developer comprises the electrostatic image developing carrier according to claim 1. A latent image carrier;
Charging means for charging the latent image carrier;
Exposure means for exposing the charged latent image carrier to form an electrostatic latent image on the latent image carrier;
Developing means for developing the electrostatic latent image with a developer to form a toner image;
Transfer means for transferring the toner image from the latent image carrier to a recording material, and an image forming apparatus comprising:
An image forming apparatus, wherein the developer includes the electrostatic image developing carrier according to claim 1.