JP7151289B2 - electrostatic charge image developer - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrostatic image developer, and more specifically, an electrostatic image developer that has sufficient fluidity, improves stability against loads depending on the usage environment and toner coverage, and is capable of forming stable high-quality images. It relates to a charge image developer.

In recent years, in the field of electrophotography, from the viewpoint of energy saving, there is an increasing demand for low-temperature fixability as well as longer life and higher durability of electrophotographic image forming apparatuses. One of the deterioration factors of the constituent materials of the electrophotographic image forming apparatus is load fluctuations such as usage environment and coverage dependence (also referred to as printing area dependence). In particular, an external additive added to a toner for electrostatic image development (hereinafter also simply referred to as "toner") is generally applied for the purpose of adjusting the amount of charge and imparting fluidity. Stability against loads such as various usage environments and coverage dependencies is required.

Materials used as external additives include inorganic oxides such as silica and titania, inorganic compounds such as titanates and silicates, and organic fine particles.

In Patent Document 1, amorphous aluminosilicate is used as an external additive that can provide stability against a coverage-dependent load by suppressing the external additive from being embedded in or detached from the surface of toner base particles. is disclosed. However, it is difficult to obtain sufficient fluidity from the viewpoint of particle size and circularity derived from the manufacturing method of amorphous aluminosilicate. As a result, fogging and dot reproducibility are degraded due to the presence of a low charge amount component that is not sufficiently triboelectrically charged, and there is a problem of stability against coverage dependence.

Patent Document 2 discloses a method of using a mixed oxide of alumina-silica as an external additive. However, the oxide described in Patent Document 2 is not subjected to hydrophobizing treatment with a surface hydrophobizing agent, and sufficient stability against load depending on the usage environment and coverage is not obtained. is the current situation.

Therefore, it is desired to develop a toner for electrostatic charge image development that has sufficient fluidity and improved stability against load depending on usage environment and coverage.

JP 2017-187735 A JP 2009-162957 A

The present invention has been made in view of the above problems and situations, and the problem to be solved is to obtain sufficient fluidity and improve stability against loads depending on the usage environment and coverage. An object of the present invention is to provide an electrostatic image developer capable of obtaining an image quality excellent in fog resistance, image granularity and fixability.

In order to solve the above problems, the present inventors have investigated the causes of the above problems, and found that static toner particles containing toner particles having composite oxide particles composed of hydrophobized silica and alumina as an external additive. The toner for developing the charge image and the electrostatic charge image developer, which is composed of carrier particles, provide sufficient fluidity and improve the stability against load depending on the usage environment and coverage, thereby reducing fogging. The inventors have found that an image quality excellent in durability, image granularity and fixability can be obtained, and have arrived at the present invention.

That is, the above problems related to the present invention are solved by the following means.

1. An electrostatic charge image developer comprising at least a toner for developing an electrostatic charge image containing toner particles having an external additive on the surface of the toner base particles, and carrier particles,
the external additive constituting the toner particles contains at least composite oxide particles mainly composed of alumina and silica;
The composite oxide particles contain alumina in the range of 5 to 50% by mass and silica in the range of 50 to 95% by mass,
The number average particle size of the primary particles of the composite oxide particles is in the range of 7 to 80 nm ,
The composite oxide particles have a hydrophobicity of 40 or more , and
The carrier particles have on their surfaces a resin formed using an alicyclic methacrylate monomer.
An electrostatic charge image developer characterized by:

2. 2. The electrostatic image developer according to claim 1, wherein the composite oxide particles have a structure in which surfaces of silica particles are coated with the alumina.

3. 3. The electrostatic image developer according to item 1 or item 2, wherein the carbon content in the composite oxide particles is in the range of 0.5 to 6.0% by mass.

4. 4. The electrostatic image developer according to any one of items 1 to 3, wherein the number average particle size of the primary particles of the composite oxide particles is in the range of 10 to 50 nm.

5. 5. Any one of items 1 to 4, wherein the content of the composite oxide particles is in the range of 0.1 to 2.0 parts by mass based on 100 parts by mass of the toner particles. 1. The electrostatic image developer according to claim 1 or 1.

6. 6. The electrostatic charge of any one of items 1 to 5, wherein the toner base particles contain a binder resin, and the binder resin contains at least an amorphous polyester resin. image developer.

7. 7. The electrostatic image developer according to item 6, wherein the binder resin further contains a crystalline polyester resin.

8. Item 8. The electrostatic image developer according to Item 7, wherein the content of the crystalline polyester resin is in the range of 0.1 to 20% by mass based on the total mass of the toner particles.
9. 9. The electrostatic image developer according to any one of items 1 to 8, wherein the silica is wet silica.
10. 10. The electrostatic image developer according to any one of items 1 to 9, wherein the composite oxide particles have a surface hydrophobizing agent.

By the above-described means of the present invention, sufficient fluidity is obtained, stability against loads depending on usage environment and coverage is improved, and image quality excellent in fogging resistance, image granularity and fixability is obtained. It is possible to provide an electrostatic charge image developer capable of

Although the expression mechanism or action mechanism of the effects of the present invention has not been clarified, it is speculated as follows.

In the present invention, toner particles having composite oxide particles composed of hydrophobized silica and alumina as external additives and an electrostatic image developer composed of carrier particles provide sufficient fluidity. On top of that, we were able to improve the stability of the usage environment and coverage-dependent load.

In an electrostatic image developer composed of toner particles and carrier particles, as a method of providing sufficient fluidity and improving stability against the load of the usage environment, it is generally added to the toner. A method of making the surface of the external additive particles hydrophobic to reduce the hygroscopicity can be mentioned. By applying a hydrophobic treatment to the external additive particles, the adhesion between toner particles can be reduced and the fluidity can be improved. Mixability with particles is improved, and image quality excellent in fogging resistance, image granularity and fixability can be obtained. Such a hydrophobizing treatment for the external additive particles can exhibit the above-mentioned function by uniformly adhering the hydrophobizing agent to the particle surface. In particular, it was found that by using alumina, which has a large amount of OH groups, on the particle surface, a more uniform hydrophobization treatment can be performed, and the effect of reducing the hygroscopicity and imparting fluidity is large. It is considered that the uniformity of the surface treatment is improved by improving the dispersibility of the primary particles during the surface treatment due to the large number of OH groups.

On the other hand, when alumina is used as an external additive for toner, since the Mohs hardness is high and the difference from the hardness of the toner surface is large, the alumina is gradually buried in the surface of the toner base particles due to the collision force caused by stirring with the carrier. , there was a problem that the original function could not be exhibited. Therefore, by using silica, which has a lower Mohs hardness than alumina and a smaller specific gravity, it was possible to suppress burial during endurance, while maintaining reduced hygroscopicity and fluidity over a long period of time.

In addition, since alumina has a high thermal conductivity, it is presumed that equivalent low-temperature fixability could be obtained without adding a large amount of crystalline polyester that inhibits chargeability as in the above-mentioned Patent Document 2. there is

It should be noted that each of the technical mechanisms described above is merely a guess, and does not limit the technical scope of the present invention.

The electrostatic charge image developer of the present invention is an electrostatic charge image developer composed of a toner for developing an electrostatic charge image containing toner particles having an external additive on the surface of the toner base particles, and carrier particles. The external additive that constitutes the particles contains composite oxide particles mainly composed of alumina and silica, the composite oxide particles contain alumina and silica in a specific range, and the number average particle diameter of the primary particles is 7 80 nm, the degree of hydrophobicity is 40 or more, and the carrier particles have on their surfaces a resin formed using an alicyclic methacrylate monomer . This feature is a technical feature common to or corresponding to each of the following embodiments.

As an embodiment of the present invention, from the viewpoint of manifesting the effects of the present invention, the composite oxide particles have a structure in which the surfaces of silica particles are coated with the alumina, so that the effects of the present invention are more manifested. It is preferable in that it can

In addition, when the carbon content in the composite oxide particles is in the range of 0.5 to 6.0% by mass, the amount of the hydrophobizing agent to be added is in the appropriate range, and the decrease in hygroscopicity and fluidity are reduced. It is preferable in that the imparted effect can be obtained.

Further, when the number average particle diameter of the primary particles of the composite oxide particles is set within the range of 10 to 50 nm, the fluidity can be improved without being buried in the toner, and the stability against coverage dependence can be improved. is preferable in that it is possible to obtain

Further, the content of the composite oxide particles is in the range of 0.1 to 2.0 parts by mass when the toner particles are 100 parts by mass. collision probability becomes low, and burial in the toner can be prevented.

Further, when the toner base particles contain a binder resin and at least an amorphous polyester resin is contained as the binder resin, the mechanical strength of the toner particles can be moderated, and the embedding of the external additive can be suppressed. point is preferable.

Further, the binder resin contains a crystalline polyester resin, and the content of the crystalline polyester resin is in the range of 0.1 to 20% by mass based on the total mass of the toner particles. By suppressing the occurrence of the amount component, it is possible to prevent image deterioration due to occurrence of fogging and deterioration of reproducibility.
Furthermore, it is preferable that the silica is wet silica. Moreover, it is preferable that the composite oxide particles have a surface hydrophobizing agent.

In the present invention, the term "electrostatic charge image developer" refers to one comprising at least a toner for electrostatic charge image development, which is an aggregate of toner particles, and carrier particles.

Further, "toner particles" refer to those composed of at least toner base particles and an external additive, and aggregates of toner particles are referred to as toner. The term "external additive" refers to a substance composed of at least composite oxide particles mainly composed of alumina and silica, and is preferably subjected to a surface hydrophobizing treatment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention, its constituent elements, and modes and modes for carrying out the present invention will be described below. In the present application, "-" is used to mean that the numerical values before and after it are included as the lower limit and the upper limit.

The electrostatic charge image developer of the present invention is characterized by comprising at least a toner for electrostatic charge image development containing toner particles having an external additive on the surface of toner base particles, and carrier particles. Details of the electrostatic charge image developer of the present invention are described below.

《Toner for electrostatic charge image developer》
The toner for electrostatic charge image development according to the present invention contains toner particles having an external additive on at least the surfaces of the toner base particles.

[External Additive]
Details of the composite oxide particles constituting the external additive according to the present invention will be described below.

[Alumina and silica]
In the present invention, the external additive contains at least composite oxide particles mainly composed of alumina and silica, and the composite oxide particles contain 5 to 50% by mass of alumina and 50 to 95% of silica. One of the characteristics is that it is contained within the range of % by mass.

(Method for producing composite oxide particles from silica and alumina)
Silica and alumina that can be applied to the external additive according to the present invention are not particularly limited. For example, silica used in the alumina-silica composite oxide can be prepared by a known method, and is also commercially available. Among them, wet-process silica is preferable because aggregation of primary particles is suppressed and surface treatment is uniformly performed, although it is easily available.

The composite oxide particles according to the present invention preferably have a structure in which the surfaces of silica particles, specifically silica particles, are coated with alumina. The term “coated with alumina” as used herein means that part of the silica particle surface is island-shaped and is coated with an alumina component, or the entire surface of the silica particle is coated with an alumina component. It may be in a form having a so-called core-shell structure. The content of alumina with respect to the silica particle surface can be determined by a wavelength dispersive X-ray fluorescence spectrometer, which will be described later.

In the present invention, the method of coating the silica particle surface with alumina is not particularly limited, but a wet method is preferred because it enables more uniform coating. For example, when an alumina layer is formed by a sol-gel method, an aluminum hydroxide raw material is added dropwise to a given aqueous dispersion of silica particles in a basic environment, and the system is stirred for a given period of time. As a result, silica particles in which alumina and chemical bonds are formed while fine alumina particles are deposited and formed on the surfaces of the silica particles are obtained. In some cases, the obtained particles may be dried up and calcined, but in order to uniformly disperse the primary particles, it is preferable not to perform the calcination step.

(Alumina and silica content)
One of the characteristics of the composite oxide particles according to the present invention is that they contain alumina in an amount of 5 to 50% by mass, preferably 5 to 30% by mass. If the content of alumina is 5% by mass or more, the surface treatment can be performed uniformly, and the hygroscopicity is increased, so that the charge amount fluctuation under high temperature and high humidity becomes large, and the image quality is deteriorated due to the deterioration of the fluidity. It is possible to suppress deterioration and occurrence of fogging. Further, if it is 50% by mass or less, it becomes difficult for the toner particles to be embedded in the toner particles. point is preferable.

On the other hand, one feature is that the silica content is in the range of 50 to 95 mass %, preferably in the range of 70 to 95 mass %. When the silica content is 50% by mass or more, the composite oxide particles can be prevented from being embedded in the toner particles, and when it is 95% by mass or less, the silica particle surfaces can be stably coated with alumina. can improve the uniformity of the surface treatment.

Further, the composite oxide particles according to the present invention may contain components other than silica/alumina as long as the contents of alumina and silica are within the ranges specified above.

<Method for measuring content>
In the present invention, the contents of alumina and silica in the composite oxide particles can be obtained by the following method.

The content of alumina and silica in the composite oxide can be measured using a wavelength dispersive X-ray fluorescence analyzer "XRF-1700" (manufactured by Shimadzu Corporation).

As a specific measurement method, 3 g of composite oxide particles as a sample were pressurized and pelletized, and qualitative analysis was performed under the following conditions. For the measurement, the Kα peak angle of the element to be measured was determined from the 2θ table and used.

・X-ray generator condition/target Rh
・Tube voltage 40kV
・Tube current 95mA
・Filter None ・Spectral System Condition/Slit Standard ・Attenuator None ・Analyzing Crystal Fe=LiF, Cl=Ge, Ca=LiF
・Detector Fe=SC, Cl=FPC, Ca=FPC
The content of alumina with respect to the composite oxide particles is obtained by dividing the net intensity value of the Al-Si Kα analysis line for alumina/silica alone by the net intensity value of the Al-Si Kα analysis line for the composite oxide. calculated as a value.

(Number average particle diameter of primary particles of composite oxide particles)
One of the characteristics of the present invention is that the number average particle diameter of the primary particles of the composite oxide particles is in the range of 7 to 80 nm, preferably in the range of 10 to 50 nm. When the number average particle diameter of the primary particles of the composite oxide particles is 7 nm or more, they are not buried in the toner, and when it is 80 nm or less, fluidity can be secured and stability against coverage dependence can be obtained. . In addition, the shape of the composite oxide is preferably spherical, disk-like, or needle-like without corners in order to ensure fluidity.

<Method for measuring number average particle size>
The number average particle diameter of the primary particles of the composite oxide particles according to the present invention can be obtained by the following method.

Using a scanning electron microscope (SEM) "JEM-7401F" (manufactured by JEOL Ltd.), an SEM photograph of the composite oxide particles magnified 30,000 times is taken, and the photograph is observed to determine the composite oxide particles. Measure the particle size and determine the average particle size. For particle size measurement, select a region where the total number of relevant particles is about 100 to 200. When the shape of the composite oxide particles is not circular, the projected area of the particles is measured, and the diameter when converted into a circle equivalent area is obtained as the particle size.

(hydrophobicity)
One of the characteristics of the composite oxide particles according to the present invention is that the degree of hydrophobicity is 40 or more, preferably in the range of 50-80. If the degree of hydrophobicity is 40 or more, the effect of making the surface hydrophobic is sufficient, and effects such as reduction of hygroscopicity and provision of fluidity can be obtained.

<Method for measuring degree of hydrophobicity>
The degree of hydrophobicity of the composite oxide particles defined in the present invention can be determined according to the following method.

In a laboratory environment, put a 20 mm long stirrer tip and 60 ml of ion-exchanged water into a 100 mL tall beaker, deaerate by irradiating ultrasonic waves for 5 minutes, and use a powder wettability tester WET-100P (stock (manufactured by the company Lesca). 25 mg of the hydrophobized composite oxide particle sample is floated on the above ion-exchanged water, and immediately after that, a lid and a methanol supply nozzle are set, and measurement is started at the same time as stirring with a stirrer is started. The supply rate of methanol is 1.6 mL/min, and the measurement time is 30 min. The stirring speed of the stirrer is adjusted to 350-450 rpm. The composite oxide particles floated on the surface of the ion-exchanged water immediately after the start of the measurement. Light transmittance is reduced. The wettability is evaluated from the state of this decrease. Specifically, from the obtained data, plot the methanol concentration (% by volume) calculated from Flow (mL) on the horizontal axis and the light transmittance (voltage ratio (%)) on the vertical axis, and the light transmittance is The methanol concentration at the point between the maximum and minimum values was defined as "hydrophobicity".

<Surface hydrophobizing agent>
In the present invention, the method for imparting the desired degree of hydrophobicity to the composite oxide particles is not particularly limited, but a method using a surface hydrophobizing agent (hydrophobicizing agent) containing carbon atoms, which will be described later, is particularly preferred. .

In the present invention, as a surface hydrophobizing agent suitable for obtaining a desired degree of hydrophobization, general coupling agents, silicone oils, fatty acids, fatty acid metal salts, etc. can be used. and silicone oil are preferred.

Examples of silane compounds include chlorosilane-based compounds, alkoxysilane-based compounds, silazane-based compounds, and special silylating agents. Specific compounds include methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane. Silane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N,O-(bistrimethylsilyl) Acetamide, N,N-bis(trimethylsilyl)urea, tert-butyldimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl ) Representative examples include ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-chloropropyltrimethoxysilane, and the like. be able to.

Specific examples of silicone oils include cyclic compounds such as organosiloxane oligomers, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, tetramethylcyclotetrasiloxane, and tetravinyltetramethylcyclotetrasiloxane; Branched or branched organosiloxanes may be mentioned. In addition, highly reactive silicone oil modified at least at the terminals may be used by introducing modifying groups into the side chains, one terminal, both terminals, one side chain terminal, or both side chain terminals. Types of modifying groups include alkoxy, carboxy, carbinol, higher fatty acid modification, phenol, epoxy, methacryl, and amino, but are not particularly limited. It may also be a silicone oil having several modifying groups such as amino/alkoxy modification. In addition, dimethyl silicone oil, these modified silicone oils, and other surface hydrophobizing agents may be mixed or combined. Examples of treatment agents used in combination include silane coupling agents, titanate coupling agents, aluminate coupling agents, various silicone oils, fatty acids, fatty acid metal salts, esters thereof, and rosin acid. .

<Surface hydrophobizing method>
As a method for treating composite oxide particles with a surface hydrophobizing agent, for example, spray drying is performed in which a surface hydrophobizing agent or a solution containing a surface hydrophobizing agent is sprayed on composite oxide particles suspended in a gas phase. wet method in which composite oxide particles are immersed in a solution containing a surface hydrophobizing agent and dried, and a mixing method in which a surface hydrophobizing agent and composite oxide particles are mixed using a mixer. mentioned.

<Content of surface hydrophobizing agent>
In the present invention, a surface hydrophobizing agent, which is an organic compound, is added to the composite oxide particles. It is preferably within the range of ~6.0% by mass. If the carbon content is 0.5% by mass or more, the surface hydrophobizing effect of the surface hydrophobizing agent is sufficient, and effects such as reduction of hygroscopicity and imparting of fluidity can be obtained. In addition, if it is 6.0% by mass or less, the surface hydrophobizing agent does not become excessive, it is possible to prevent uneven surface treatment due to aggregation of the surface hydrophobizing agents, and the surface hydrophobizing agent is applied to the alumina surface. It can be adhered uniformly, and effects such as reduction of hygroscopicity and provision of fluidity can be obtained.

The carbon content in the composite oxide particles can be obtained by the following method.

Using a Soxhlet extractor manufactured by BUCHI, 0.7 g of the composite oxide particle powder after surface modification with a surface hydrophobizing agent (hydrophobizing agent) is placed in a cylindrical filter paper (external size 28 mm × 100 mm). Using n-hexane as an extraction solvent, the free surface hydrophobizing agent is removed from the composite oxide particle powder under conditions of extraction time of 60 minutes and rinsing time of 30 minutes. After that, the amount of carbon in the released surface hydrophobizing agent is quantified using a CHN elemental analyzer (SUMIGRAPH NC-TR22 manufactured by Sumika Chemical Analysis Service) [Content of composite oxide particles]
In the toner particles according to the present invention, the content of the composite oxide particles as an external additive is preferably in the range of 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the toner particles. If the content of the composite oxide particles with respect to the toner particles is 0.1% by mass or more, effects such as reduction in hygroscopicity and provision of fluidity can be obtained. Further, when the content is 2.0 parts by mass or less, the probability that the alumina-coated silica particles, which are composite oxide particles, will receive a collision force with carrier particles can be reduced, and burying in toner particles can be prevented.

[Toner base particles]
The toner particles constituting the electrostatic charge image developing toner according to the present invention are composed of toner base particles having the external additive on their surfaces.

The toner base particles according to the present invention preferably contain at least a binder resin. Specifically, they contain an amorphous polyester resin as the binder resin, and further contain a crystalline polyester resin as the binder resin. In a preferred embodiment, the content of the crystalline polyester resin is within the range of 0.1 to 20% by mass based on the total mass of the toner particles according to the present invention.

In addition to the binder resin, the toner base particles according to the present invention may optionally contain components such as a release agent (wax), a colorant, a charge control agent, and other external additives. good too.

(Binder resin)
<Amorphous resin>
A known amorphous resin can be used as the binder resin constituting the toner base particles. Specific examples thereof include vinyl resins, urethane resins, urea resins and polyester resins. Among them, it is preferable to use a polyester resin in terms of softening the mechanical strength of the toner and suppressing the embedding of the external additive.

From the viewpoint of obtaining excellent fixability, the amorphous polyester resin according to the present invention is preferably contained in the binder resin in an amount of 60 to 90% by mass.

The amorphous polyester resin according to the present invention is a polyester resin that does not have a melting point and has a relatively high glass transition temperature (Tg) when differential scanning calorimetry (DSC) is performed. Further, since the monomers constituting the amorphous polyester resin are different from the monomers constituting the crystalline polyester resin, they can be distinguished from the crystalline polyester resin by analysis such as NMR.

The glass transition temperature (Tg) of the polyester resin is not particularly limited, but is in the range of 30 to 70°C from the viewpoint of reliably obtaining fixability such as low-temperature fixability and heat resistance such as heat-resistant storage stability and blocking resistance. preferably within

The glass transition temperature can be measured according to the method (DSC method) specified in ASTM (American Society for Testing and Materials Standard) D3418-82. For measurement, DSC-7 differential scanning calorimeter (manufactured by PerkinElmer), TAC7/DX thermal analyzer controller (manufactured by PerkinElmer), and the like can be used.

A specific method for producing the amorphous polyester resin according to the present invention is not particularly limited. is produced by a polycondensation reaction in the presence of an appropriate catalyst.

As polyhydric carboxylic acid monomer derivatives, alkyl esters, acid anhydrides and acid chlorides of polyhydric carboxylic acid monomers can be used, and as polyhydric alcohol monomer derivatives, ester compounds of polyhydric alcohol monomers and hydroxycarboxylic acid can be used. Examples of polyvalent carboxylic acid monomers include oxalic acid, succinic acid, maleic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, Fumaric acid, citraconic acid, diglycolic acid, cyclohexane-3,5-diene-1,2-dicarboxylic acid, malic acid, citric acid, hexahydroterephthalic acid, malonic acid, pimelic acid, tartaric acid, mucic acid, phthalic acid , isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylenediacetic acid, m-phenylenediglycolic acid, p-phenylenediglycolic acid, o-phenylenediglycolic acid , diphenylacetic acid, diphenyl-p,p'-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracenedicarboxylic acid, dodecenylsuccinic acid, etc. trivalent carboxylic acids; trivalent or higher carboxylic acids such as trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid.

Among the above polyvalent carboxylic acid monomers, it is preferable to use unsaturated aliphatic dicarboxylic acids such as fumaric acid, maleic acid, and mesaconic acid. It is preferable to use In the present invention, an anhydride of dicarboxylic acid such as maleic anhydride can also be used.

General formula (A): HOOC-(CR ₁ =CR ₂ ) _n -COOH
In general formula (a) above, R ₁ and R ₂ each represent a hydrogen atom, a methyl group or an ethyl group, and may be the same or different. n is an integer of 1 or 2;

Examples of polyhydric alcohol monomers include ethylene glycol, propylene glycol, butanediol, diethylene glycol, hexanediol, cyclohexanediol, octanediol, decanediol, dodecanediol, ethylene oxide adducts of bisphenol A, and propylene oxide adducts of bisphenol A. trihydric alcohols such as glycerin, pentaerythritol, hexamethylolmelamine, hexaethylolmelamine, tetramethylolbenzoguanamine, and trihydric or higher polyols such as tetraethylolbenzoguanamine.

The weight average molecular weight (Mw) of the amorphous polyester resin is preferably 10,000 to 100,000. The method for producing the amorphous polyester resin is not particularly limited. A method of polymerizing by a known polymerization method such as polymerization, solution polymerization, emulsion polymerization, mini-emulsion method, dispersion polymerization method, and the like can be mentioned. Also, for the purpose of adjusting the molecular weight, generally used chain transfer agents can be used. The chain transfer agent is not particularly limited, and examples thereof include alkyl mercaptans such as n-octyl mercaptan and mercapto fatty acid esters.

Further, the binder resin according to the present invention preferably contains the amorphous vinyl resin in the range of 0.1 to 20% by mass, and more preferably in the range of 0.2 to 10% by mass. More preferably, it is contained within the range of 0.3 to 5% by mass. When the amorphous vinyl resin is contained in the range of 0.1% by mass to 20% by mass, the surface of the toner particles becomes moderately hard, so that the toner particles are less likely to be embedded. Moreover, when the amorphous vinyl resin is less than 20% by mass, good low-temperature fixability can be obtained.

The amorphous vinyl resin itself may be contained in the binder resin, or may be contained as a composite resin in which the amorphous vinyl resin component is hybridized.

The vinyl resin is not particularly limited as long as it is obtained by polymerizing a vinyl compound, and examples thereof include (meth)acrylic acid ester resins, styrene-(meth)acrylic acid ester resins, and ethylene-vinyl acetate resins. These may be used individually by 1 type, and may be used in combination of 2 or more type.

Among the above vinyl resins, styrene/(meth)acrylic acid ester resins are preferred in consideration of plasticity during heat fixing.

The styrene/(meth)acrylic resin is formed by addition polymerization of at least a styrene monomer and a (meth)acrylate monomer. The styrene monomer referred to herein includes, in addition to styrene represented by the structural formula of CH ₂ ═CH—C ₆ H ₅ , those having a structure having known side chains and functional groups in the styrene structure.

Further, the (meth)acrylic acid ester monomers referred to herein include, in addition to acrylic acid esters and methacrylic acid esters represented by CH ₂ =CHCOOR (R is an alkyl group), acrylic acid ester derivatives and methacrylic acid ester derivatives. It contains an ester having a known side chain or functional group in the structure such as. In this specification, the term "(meth)acrylic acid ester monomer" collectively refers to "acrylic acid ester monomer" and "methacrylic acid ester monomer".

<Crystalline polyester resin>
It is preferable that the binder resin according to the present invention contains a crystalline polyester resin because the flexibility of the toner base particles is improved and the silica particles are easily fixed. is also preferred. In particular, it is preferable to use a crystalline polyester resin in terms of compatibility with the amorphous resin and manufacturability.

In the present invention, a crystalline resin refers to a resin having a distinct endothermic peak, not a stepwise endothermic change, in differential scanning calorimetry (DSC). A clear endothermic peak specifically means a peak whose half width of the endothermic peak is within 15°C when measured at a temperature increase rate of 10°C/min in differential scanning calorimetry (DSC). do.

The melting point Tmc of the crystalline resin is preferably 60° C. or higher from the viewpoint of obtaining sufficient high-temperature storage stability, and preferably 85° C. or lower from the viewpoint of obtaining sufficient low-temperature fixability.

The melting point Tmc of the crystalline resin can be measured by DSC. Specifically, 0.5 mg of a crystalline resin sample is enclosed in an aluminum pan "KITNO.B0143013", set in a sample holder of a thermal analysis device "Diamond DSC" (manufactured by PerkinElmer), and heated and cooled. , the temperature is varied in the order of heating. During the first and second heating, the temperature was raised from 0° C. to 150° C. at a rate of 10° C./min and held at 150° C. for 5 minutes. The temperature is lowered to 0° C. and maintained at 0° C. for 5 minutes. The peak top temperature of the endothermic peak in the endothermic curve obtained during the second heating is measured as the melting point (Tmc) of the crystalline resin.

The content of the crystalline polyester resin is preferably in the range of 0.1 to 20% by weight based on the total weight of the toner particles. If the content is 20% by mass or less, the charge amount can be maintained, and fogging and dot reproducibility deterioration due to low charge amount components can be prevented.

The content of the crystalline polyester resin in the toner particles can be determined by the amount of raw materials charged.

Regarding the content of the crystalline polyester after being produced as toner particles, various analysis methods (TEM observation of stained toner sections, endothermic peak by DSC measurement, solid-state NMR, liquid chromatography, etc.).

Also, the number average molecular weight (Mn) of the crystalline polyester resin is preferably in the range of 2,000 to 10,000, more preferably in the range of 3,000 to 7,000. Within these ranges, the strength of the fixed image is not insufficient, the crystalline resin is pulverized during developer agitation, and the excessive plasticizing effect lowers the glass transition temperature Tg of the toner. The thermal stability is not lowered either. In addition, sharp meltability is exhibited, and low-temperature fixing becomes possible.

The crystalline polyester resin according to the present invention is obtained by a polycondensation reaction between a divalent or higher carboxylic acid (polyvalent carboxylic acid) and a divalent or higher alcohol (polyhydric alcohol). As for the crystalline polyester resin, conventionally known crystalline polyester resins in this technical field can be used.

The crystalline polyester resin can be synthesized by polycondensing (esterifying) the polyhydric carboxylic acid and polyhydric alcohol using a known esterification catalyst.

(Method of Applying External Additive to Toner Base Particles)
A mechanical mixing device can be used for the external addition and mixing treatment of the external additive according to the present invention to the toner base particles. A Henschel mixer, a Nauta mixer, a Turbular mixer, or the like can be used as a mechanical mixer. Among these, a mixing device such as a Henschel mixer that can apply a shearing force to the particles to be treated may be used for mixing treatment such as lengthening the mixing time or increasing the rotation peripheral speed of the stirring blade. In addition to the external additive according to the present invention, when using a plurality of types of external additives described later, all the external additives are mixed together with the toner base particles, or the external additives are mixed together. Depending on the situation, the mixture may be divided into a plurality of times and mixed.

The external additive is mixed by controlling the mixing intensity, that is, the peripheral speed of the stirring blade, the mixing time, or the mixing temperature, etc., using the above-mentioned mechanical mixer. can be controlled.

(Other Additives for Toner Base Particles)
<Release agent>
Various known waxes can be used as release agents for the toner base particles of the present invention. Examples of waxes include polyolefin waxes such as polyethylene wax and polypropylene wax, branched hydrocarbon waxes such as microcrystalline wax, long-chain hydrocarbon waxes such as paraffin wax and Sasol wax, and dialkyl waxes such as distearyl ketone. Ketone wax, carnauba wax, montan wax, behenate behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol diol Examples include ester waxes such as stearate, tristearyl trimellitate and distearyl maleate, and amide waxes such as ethylenediaminebehenylamide and tristearylamide trimellitate. From the viewpoint of fixability, hydrocarbon waxes are preferred. The content of the release agent is preferably 0.1 to 30 parts by mass, more preferably 1 to 10 parts by mass, per 100 parts by mass of the binder resin. These can be used singly or in combination of two or more. Further, the melting point of the release agent is preferably 50 to 95° C. from the viewpoint of the low-temperature fixability and release properties of the toner in electrophotography.

<Coloring agent>
A colorant can be added to the toner base particles according to the present invention.

A known coloring agent can be used as the coloring agent according to the present invention. Specifically, the colorant contained in the yellow toner includes, for example, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Pigment Yellow 14, Pigment Yellow 17, Pigment Yellow 74, Pigment Yellow 93, Pigment Yellow 94, Pigment Yellow 138, Pigment Yellow 155, Pigment Yellow 180, Pigment Yellow 185. These can be used individually by 1 type or in combination of 2 or more types.

Colorants contained in the magenta toner include, for example, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Pigment Red 5, 48:1, 53:1, 57:1, 122, 139, 144, 149, 166, 177, 178 and 222. These can be used individually by 1 type or in combination of 2 or more types.

Colorants contained in the cyan toner include, for example, C.I. I. Pigment Blue 15:3 and the like.

Colorants contained in the black toner include, for example, carbon black, magnetic substances, and titanium black. Examples of carbon black include channel black, furnace black, acetylene black, thermal black and lamp black.

Examples of magnetic materials include ferromagnetic metals such as iron, nickel, and cobalt; alloys containing these ferromagnetic metals; compounds of ferromagnetic metals such as ferrite and magnetite; and the like. Examples of alloys that exhibit ferromagnetism by heat treatment include Heusler alloys such as manganese-copper-aluminum and manganese-copper-tin, and chromium dioxide.

The content of the colorant is preferably in the range of 1 to 10 parts by mass, more preferably in the range of 2 to 9 parts by mass, based on 100 parts by mass of the binder resin.

<Charge control agent>
The charge control agent is not particularly limited as long as it is a substance capable of imparting positive or negative charge by triboelectrification, and various known positive charge control agents and negative charge control agents can be used. Examples include nigrosine dyes, metal salts of naphthenic or higher fatty acids, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, and metal salicylates.

The content of the charge control agent is preferably in the range of 0.01 to 30 parts by mass, more preferably in the range of 0.1 to 10 parts by mass, per 100 parts by mass of the binder resin.

<Other external additives>
The toner particles according to the present invention further contain a known external additive as an external additive in addition to the composite oxide particles composed of alumina and silica according to the present invention, within a range that does not impair the intended effect of the present invention. It's okay. Examples of external additives include inorganic oxide fine particles such as silica single fine particles and titanium oxide fine particles, inorganic stearic acid compound fine particles such as aluminum stearate fine particles and zinc stearate fine particles, or strontium titanate and zinc titanate. and inorganic titanate compound fine particles. These inorganic fine particles are treated with silane coupling agents, titanium coupling agents, higher fatty acids, silicone oil, etc. to improve heat-resistant storage stability and environmental stability. may

Silica single fine particles are particularly preferable from the viewpoint of imparting chargeability, and when silica single fine particles having a number average primary particle diameter of 10 to 60 nm are further included, the fluidity of the toner is improved, and when toner is replenished in the developing machine, the toner is replenished. This is preferable because the toner and carrier are sufficiently mixed and a stable change in charge amount can be obtained. Furthermore, it is preferable to include silica fine particles having a number average primary particle diameter of 80 to 150 nm because it has the effect of softening the impact of the toner and carrier when the developer is agitated in the developing machine during low-coverage printing.

[Particle Size of Toner Base Particles]
In the present invention, the volume average particle diameter of the toner base particles is preferably in the range of 3.5 to 7.0 μm. If the volume-average particle size is 3.5 μm or more, it is suitable for production and easy to control in a copier. Further, when the thickness is 7.0 μm or less, a desired charge amount can be maintained, and image degradation due to low charge amount components can be prevented.

《Carrier particles》
Next, the carrier particles constituting the electrostatic image developer together with the toner particles will be described. Carrier particles have a structure in which the surface of a carrier core material (carrier core) is coated with a coating resin.

(Carrier core material)
Examples of the carrier core material (magnetic particles) used in the present invention include iron powder, magnetite, various ferrite particles, and those dispersed in resin. Magnetite and various ferritic particles are preferred. As the ferrite, ferrite containing heavy metals such as copper, zinc, nickel and manganese, and light metal ferrite containing alkali metals or alkaline earth metals are preferable.

Moreover, it is preferable to contain Sr as a carrier core material. By containing Sr, it is possible to increase the unevenness of the surface of the carrier core material, and even if it is coated with a coating resin, the surface becomes easy to be exposed, making it easy to adjust the resistance of the carrier.

(Average particle diameter of carrier particles)
The volume average particle diameter of the carrier particles is preferably in the range of 10-100 μm, more preferably in the range of 20-80 μm. The volume average particle diameter of the carrier particles can typically be measured by a laser diffraction particle size distribution analyzer "HELOS" (manufactured by SYMPATEC) equipped with a wet disperser.

(Carrier coating resin)
Resins suitable for forming the coating layer of carrier particles include polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene and chlorosulfonated polyethylene; polyacrylates such as polystyrene and polymethylmethacrylate; polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl Polyvinyl and polyvinylidene resins such as butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polyvinyl ketone; copolymers such as vinyl chloride-vinyl acetate copolymers and styrene-acrylic acid copolymers; silicones composed of organosiloxane bonds Resins or modified resins thereof (e.g. alkyd resins, polyester resins, epoxy resins, resins modified by polyurethane, etc.); fluororesins such as polytetrachlorethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrifluoroethylene; polyamides; polyesters; polyurethanes; polycarbonates; amino resins such as urea-formaldehyde resins; epoxy resins and the like.

Particularly preferred is a polyacrylate resin, which contains a resin formed from an alicyclic methacrylate monomer with low hygroscopicity, thereby suppressing fluctuations in the amount of charge due to environmental differences and forming complex oxide particles due to collision between the toner and carrier. It is preferable because burial is suppressed. The alicyclic methacrylate monomer has a cycloalkyl group with 5 to 8 carbon atoms from the viewpoint of mechanical strength, environmental stability of charge amount (small environmental difference in charge amount), ease of polymerization, and availability. is preferred. The alicyclic methacrylate monomer is at least one selected from the group consisting of cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate and cyclooctyl (meth)acrylate. is preferred. Among them, cyclohexyl (meth)acrylate is preferably contained from the viewpoint of mechanical strength and environmental stability of charge amount.

The copolymer ratio of the alicyclic methacrylate monomer is preferably 50% or more, more preferably 75% or more.

(Method for forming resin coating layer)
Specific methods for forming a resin coating layer on the surface of the carrier core include wet coating and dry coating. Each forming method will be described below, but the dry coating method is particularly desirable for application to the present invention.

<Wet coating method>
Wet coating methods include the following.

(1) Fluidized bed type spray coating method A coating liquid obtained by dissolving a coating resin in a solvent is spray-coated onto the surface of magnetic particles, which are carrier core materials, using a fluidized bed, and then dried to form a resin coating layer. How to form.

(2) Immersion coating method A method in which the magnetic particles, which are the carrier core material, are immersed in a coating solution in which a coating resin is dissolved in a solvent, and then dried to form a resin coating layer. Polymerization method The magnetic particles, which are the carrier core material, are immersed in a coating solution in which a reactive compound is dissolved in a solvent, followed by a polymerization reaction by applying heat or the like to form a resin coating layer on the surface of the particles. and the like.

<Dry coating method>
In the dry coating method, the surface of the carrier core material to be coated is coated with resin particles, and then a mechanical impact force is applied to melt or soften the resin particles coated on the carrier core surface to be coated. It is a method of forming a resin coating layer by fixing by pressing.

A carrier core material, a coating resin, low-resistance fine particles, etc. are stirred at high speed using a high-speed stirring mixer capable of imparting mechanical impact force under heating or unheated conditions, and repeatedly imparting impact force to the mixture, In this method, a carrier is produced by dissolving or softening a coating resin on the surface of a carrier core material (magnetic particles) and adhering it thereto.

As for the coating conditions, when heating, the temperature is preferably in the range of 80 to 130° C., and the wind speed that causes impact force is preferably 10 m/s or more during heating, and during cooling, in order to suppress aggregation of carrier particles. 5 m/s or less is preferable. The time for applying the impact force is preferably within the range of 20 to 60 minutes.

A method of exposing the core material by peeling off the resin from the convex portions of the core material by applying stress to the carrier in the process of coating the coating resin or the process after the coating will be described. In the resin coating step of the dry coating method, the resin can be peeled off by lowering the heating temperature to 60° C. or less and setting the wind speed at the time of cooling to high shear. Further, as a step after coating, any device capable of forcible stirring can be used, and examples thereof include stirring and mixing with a turbular, a ball mill, a vibration mill, or the like.

Next, as the above-described method of exposing the core material by applying heat and impact to the coating resin to move the resin on the surface of the convex portion to the concave side, it is possible to take a long time to apply the impact force. becomes valid. Specifically, it is preferable to set the time to one and a half hours or longer.

<<Method for Producing Toner for Developing Electrostatic Charge>>
The method for producing the toner for electrostatic charge image development of the present invention is not particularly limited, and known methods such as kneading pulverization method, suspension polymerization method, emulsion aggregation method, dissolution suspension method, polyester elongation method and dispersion polymerization method. is mentioned. Among these methods, it is preferable to adopt the emulsion aggregation method from the viewpoint of uniformity of particle size and controllability of shape.

(Emulsion aggregation method)
In the emulsion aggregation method, a dispersion liquid of binder resin particles (hereinafter also referred to as "binder resin particles") dispersed with a surfactant or a dispersion stabilizer is added, if necessary, to colorant particles (hereinafter , also referred to as "colorant particles"), aggregated to a desired toner particle size, and further fused between binder resin particles to control the shape of the toner base particles. It is a method of manufacturing. Here, the binder resin particles may optionally contain a release agent, a charge control agent, and the like.

As a preferred method for producing the toner for developing an electrostatic charge image according to the present invention, an example of obtaining toner particles having a core-shell structure using an emulsion aggregation method is shown below.

(1) A step of preparing a colorant particle dispersion in which colorant particles are dispersed in an aqueous medium. (3) mixing the colorant particle dispersion and the core resin particle dispersion to obtain an aggregation resin particle dispersion; A step of aggregating and fusing colorant particles and binder resin particles in the presence of an aggregating agent to form agglomerated particles as core particles (aggregating/fusing step)
(4) A shell layer resin particle dispersion containing binder resin particles for forming a shell layer is added to a dispersion containing core particles to aggregate and fuse the particles for forming a shell layer on the surfaces of the core particles. step of forming core-shell structured toner base particles (aggregation/fusion step)
(5) A step of filtering the toner base particles from the toner base particle dispersion (toner base particle dispersion) to remove the surfactant and the like (washing step).
(6) Step of drying toner base particles (drying step)
(7) A step of adding an external additive to the toner base particles (external additive treatment step).

Toner particles having a core-shell structure are produced by first forming core particles by aggregating and fusing binder resin particles for core particles and colorant particles, and then forming a shell layer in a core particle dispersion. It can be obtained by adding the binder resin particles for forming the shell layer to the surface of the core particles and aggregating and fusing the binder resin particles for forming the shell layer on the surface of the core particles to form a shell layer covering the surface of the core particles. However, for example, in the step (4) above, toner particles formed from a single layer of particles can be similarly produced without adding the resin particle dispersion liquid for the shell.

<<Preparation of electrostatic charge image developer>>
By mixing the electrostatic charge image developing toner according to the present invention with the carrier particles described above, an electrostatic charge image developer such as a two-component developer can be obtained. The mixing device used for mixing the two components is not particularly limited, but examples thereof include a Nauta mixer, a W-cone and a V-shaped mixer.

The content (toner concentration) of the toner component in the electrostatic image developer is not particularly limited, but is preferably in the range of 4.0 to 8.0% by mass.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.

<<Image forming method>>
The electrostatic charge image developer of the present invention can be applied to an electrophotographic image forming method.

Examples of the image forming method applicable to the present invention include a method of forming an image forming layer on a recording medium using the electrostatic image developer (toner) of the present invention.

In the present invention, the image forming method is a method using the toner of the present invention, and can be suitably used for a full-color image forming method. In the full-color image forming method, four types of color developing devices for yellow, magenta, cyan, and black, and one electrostatic image carrier (also referred to as "electrophotographic photoreceptor" or simply "photoreceptor") are used. and a method using a tandem image forming apparatus in which an image forming unit having a color developing device and an electrostatic charge image bearing member for each color is mounted for each color. Any image forming method can be used.

When clear toner is additionally used, a 5-cycle image formation system comprising five types of developing devices for yellow, magenta, cyan, black, and clear, and one electrostatic charge image carrier. An image forming method such as a method using an apparatus or a method using a tandem image forming apparatus in which an image forming unit having a developing device and an electrostatic charge image carrier for each color including clear toner is mounted for each color. can be done.

As the image forming method, an image forming method including a fixing step by a heat pressure fixing system capable of applying pressure and heating is preferably used.

Specifically, in this image forming method, the toner is used to develop, for example, an electrostatic latent image formed on a photoreceptor to obtain a toner image, and the toner image is applied to an image support. After transferring the image, the toner image transferred onto the image support is fixed to the image support by a heat-pressure fixing method, thereby obtaining a print on which a visible image is formed.

The application of pressure and heating in the fixing process are preferably performed simultaneously, or the application of pressure may be performed first, and then the heating may be performed.

Further, the image forming method according to the present invention is preferably used in a heat pressure fixing method. As the heat-pressure fixing device used in the image forming method according to the present invention, various known devices can be employed.

"recoding media"
As a recording medium (also referred to as recording material, recording paper, recording paper, etc.) used for image formation using the electrostatic charge image developer (toner) of the present invention, one commonly used may be used, for example, an image forming apparatus. It is not particularly limited as long as it holds a toner image formed by a known image forming method such as. Usable image supports include, for example, plain paper from thin paper to thick paper, fine paper, art paper, coated printing paper such as coated paper, commercially available Japanese paper and postcard paper, and OHP paper. Examples include plastic films and cloths for packaging, various resin materials used for so-called flexible packaging, resin films formed into films, labels, and the like.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto. In the examples, "parts" or "%" are used, but "mass parts" or "mass%" are indicated unless otherwise specified. Moreover, unless otherwise specified, each operation was performed at room temperature (25° C.).

<<Preparation of toner base particles>>
[Preparation of Materials Used for Preparation of Toner Base Particles]
[1: Preparation of amorphous polyester resin particle dispersion]
(Preparation of amorphous polyester resin particle dispersion (a1))
First, an amorphous polyester resin (A1) was prepared according to the following method.

Bisphenol A ethylene oxide 2.2 mol adduct 40 mol parts Bisphenol A propylene oxide 2.2 mol adduct 60 mol parts Dimethyl terephthalate 60 mol parts Dimethyl fumarate 15 mol parts Dodecenylsuccinic anhydride 20 mol parts Trimellitic anhydride 5 mol parts Into a reaction vessel equipped with a stirrer, a thermometer, a condenser and a nitrogen gas inlet tube, among the above monomers, monomers other than dimethyl fumarate and trimellitic anhydride, and tin dioctate are added to the above monomers. 0.25 parts by mass was added to a total of 100 parts by mass.

Then, after reacting at 235° C. for 6 hours under nitrogen gas stream, the temperature was lowered to 200° C., dimethyl fumarate and trimellitic anhydride were added, and reacted for 1 hour. The temperature was raised to 220° C. over 5 hours, and polymerization was carried out under a pressure of 10 kPa until the molecular weight below was reached to obtain a pale yellow transparent amorphous polyester resin (A1).

The amorphous polyester resin (A1) had a weight average molecular weight of 35,000, a number average molecular weight of 8,000, and a glass transition temperature (Tg) of 56°C.

Next, 200 parts by mass of the amorphous polyester resin (A1) prepared above, 100 parts by mass of methyl ethyl ketone, 35 parts by mass of isopropyl alcohol, and 7.0 parts by mass of a 10% by mass aqueous ammonia solution are placed in a separable flask and sufficiently After mixing and dissolving, ion-exchanged water is added dropwise at a liquid sending rate of 8 g/min using a liquid sending pump while being heated and stirred at 40 ° C. Dropping is stopped when the liquid sending amount reaches 580 parts by mass. rice field. Thereafter, the solvent was removed under reduced pressure to obtain an amorphous polyester resin particle dispersion. Ion-exchanged water was added to the dispersion to adjust the solid content to 25% by mass, thereby preparing an amorphous polyester resin particle dispersion (a1). The volume-based median diameter (d ₅₀ ) of this dispersion was measured with Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 156 nm.

(Preparation of amorphous vinyl resin particle dispersion (b1))
5.0 parts by mass of an anionic surfactant (Dowfax manufactured by Dow Chemical Co.) and 2500 parts by mass of ion-exchanged water were added to a 5 L reaction vessel equipped with a stirring device, a temperature sensor, a cooling pipe and a nitrogen introducing device. After charging, the internal temperature was raised to 75° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

Next, a solution obtained by dissolving 18.0 parts by mass of potassium persulfate (KPS) in 342 parts by mass of ion-exchanged water was added, and the liquid temperature was adjusted to 75°C. Furthermore, 903.0 parts by mass of styrene (St), 282.0 parts by mass of n-butyl acrylate (BA), 12.0 parts by mass of acrylic acid (AA), and 3.0 parts by mass of 1,10-decanediol diacrylate were added to the above solution. A monomer mixture containing 0 parts by mass and 8.1 parts by mass of dodecanethiol was added dropwise over 2 hours.

After completion of the dropwise addition, polymerization was performed by heating and stirring at 75° C. for 2 hours to obtain an amorphous vinyl resin particle dispersion. Amorphous vinyl resin (B1) particle dispersion (b1) was prepared by adding ion-exchanged water to the above dispersion to adjust the solid content to 25% by mass. The volume-based median diameter (d ₅₀ ) of this dispersion was measured with Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 160 nm.

The amorphous vinyl resin (B1) had a glass transition temperature (Tg) of 52°C, a weight average molecular weight (Mw) of 38,000, and a number average molecular weight (Mn) of 15,000.

[2: Preparation of crystalline polyester resin particle dispersion]
[Preparation of crystalline polyester resin particle dispersion (c1)]
First, a crystalline polyester resin (C1) was prepared according to the following method.

Dodecanedioic acid 50 mol parts 1,6-Hexanediol 50 mol parts The above monomers were placed in a reaction vessel equipped with a stirrer, a thermometer, a condenser and a nitrogen gas inlet tube, and the inside of the reaction vessel was purged with dry nitrogen gas. Next, titanium tetrabutoxide (Ti(On-Bu) ₄ ) was added in an amount of 0.25 parts by mass with respect to a total of 100 parts by mass of the above monomers. After stirring and reacting at 170° C. for 3 hours under a nitrogen gas stream, the temperature was further raised to 210° C. over 1 hour, the pressure in the reaction vessel was reduced to 3 kPa, and the reaction was stirred for 13 hours under reduced pressure. , to obtain a crystalline polyester resin (C1).

The crystalline polyester resin (C1) had a weight average molecular weight of 25,000, a number average molecular weight of 8,500, and a melting point of 71.8°C.

Next, 200 parts by mass of the crystalline polyester resin (C1) prepared above, 120 parts by mass of methyl ethyl ketone, and 30 parts by mass of isopropyl alcohol are placed in a separable flask, and the mixture is sufficiently mixed and dissolved at 60°C. 8 parts by mass of an aqueous ammonia solution was added dropwise. The heating temperature of the resin solution is lowered to 67° C., and while stirring, ion-exchanged water is added dropwise using a liquid-sending pump at a liquid-sending rate of 8 g/min. stopped dripping. Thereafter, the solvent was removed under reduced pressure to obtain a crystalline polyester resin particle dispersion. Ion-exchanged water was added to the dispersion to adjust the solid content to 25% by mass to prepare a crystalline polyester resin particle dispersion (c1). The volume-based median diameter (D ₅₀ ) of this dispersion was measured with Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 198 nm.

[3: Preparation of Release Agent Particle Dispersion (W1)]
Release agent: paraffin wax (HNP0190 manufactured by Nippon Seiro, melting temperature 85°C)
270 parts by mass anionic surfactant (Daiichi Kogyo Seiyaku Neogen RK)
13.5 parts by mass (60% active ingredient, 3% relative to release agent)
Ion-exchanged water 21.6 parts by mass After mixing the above constituent materials and dissolving the release agent at an internal liquid temperature of 120 ° C. with a pressure discharge homogenizer (Golin Homogenizer manufactured by Gaulin Co.), the dispersion pressure was 120 at a dispersion pressure of 5 MPa. minutes, followed by continuous dispersion treatment at 40 MPa for 360 minutes, followed by cooling to obtain a dispersion liquid. Ion-exchanged water was added to adjust the solid content to 20% by mass, and this was used as release agent particle dispersion (W1). The volume average particle size of the release agent particles in the release agent particle dispersion (W1) was 215 nm.

[4: Preparation of colorant particle dispersion]
(Preparation of black colorant particle dispersion (1))
Carbon black (Regal (registered trademark) 330 manufactured by Cabot Corporation) 100 parts by mass Anionic surfactant (Neogen SC manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 15 parts by mass Ion-exchanged water 400 parts by mass Lux, manufactured by IKA) for 10 minutes, followed by dispersion treatment for 30 minutes at a pressure of 245 MPa using a high pressure impact type disperser Ultimizer (manufactured by Sugino Machine) to obtain black colorant particles. was obtained. A black colorant particle dispersion (1) was prepared by adding ion-exchanged water to the resulting dispersion to adjust the solid content to 15% by mass. The volume-based median diameter (D ₅₀ ) of the colorant particles in this dispersion was 110 nm when measured using Microtrac UPA-150 (manufactured by Nikkiso Co., Ltd.).

[Preparation of toner base particles (1) to (4)]
[Preparation of toner base particles (1)]
(aggregation/fusion process and aging process)
Amorphous polyester resin particle dispersion (a1) 1040 parts by mass Crystalline polyester resin particle dispersion (c1) 160 parts by mass Release agent particle dispersion (W1) 200 parts by mass Black colorant particle dispersion (1) 187 parts by mass Part Anionic surfactant (Dowfax2A1 20% by mass aqueous solution manufactured by Dow Chemical Co.) 40 parts by mass Ion-exchanged water 1500 parts by mass Into a 4-liter reaction vessel equipped with a thermometer, a pH meter and a stirrer, each of the above constituent materials was added. was added, and 1.0% nitric acid was added at a temperature of 25° C. to adjust the pH to 3.0. After that, 100 parts by mass of an aqueous solution of aluminum sulfate (coagulant) having a concentration of 2% by mass was added over 30 minutes while dispersing at 3000 rpm with a homogenizer (Ultra Turrax T50 manufactured by IKA). After the dropwise addition was completed, the mixture was stirred for 10 minutes to sufficiently mix the raw material and the flocculant to prepare a slurry 1 .

Next, a stirrer and a mantle heater were installed in the reaction vessel, and the rotation speed of the stirrer was adjusted so that the slurry was sufficiently stirred. After exceeding °C, the temperature was raised at a heating rate of 0.05 °C/min, and the particle size was measured with a Coulter Multisizer 3 (aperture diameter 100 µm, manufactured by Beckman Coulter) every 10 minutes. When the volume-based median diameter reached 3.9 μm, the temperature was maintained, and the premixed liquid mixture 1 described below was added over 20 minutes.

<Mixed liquid 1>
Amorphous polyester resin particle dispersion (a1) 400 parts by mass Anionic surfactant (Dowfax2A1 20% by mass aqueous solution manufactured by Dow Chemical Company) 15 parts by mass Next, after holding at 50°C for 30 minutes, EDTA was added to a reaction vessel. After adding 8 parts of a 20% by mass (ethylenediaminetetraacetic acid) liquid, a 1 mol/L sodium hydroxide aqueous solution was added to control the pH of the raw material dispersion at 9.0. Thereafter, while adjusting the pH to 9.0 every 5°C, the temperature was raised to 85°C at a heating rate of 1°C/min and maintained at 85°C.

(Cooling process)
After that, a particle image analysis is performed using a flow type particle image analyzer FPIA-3000 (manufactured by Sysmex Corporation). When the shape factor reaches 0.970, the particles are cooled at a cooling rate of 10° C./min to disperse the toner base particles. A liquid (1) was obtained.

(Filtration/washing process and drying process)
After that, the toner base particle dispersion (1) was filtered and thoroughly washed with ion-exchanged water. Then, it was dried at 40° C. to obtain toner base particles (1). The obtained toner base particles (1) had a volume-based median diameter of 6.0 μm and an average circularity of 0.972. Further, the content of the crystalline polyester resin in the toner base particles (1) is 10% by mass.

[Preparation of toner base particles (2)]
In the preparation of the toner base particles (1), the added amount of the amorphous polyester resin particle dispersion (a1) was changed to 880 parts by mass, and the added amount of the crystalline polyester resin particle dispersion (c1) was changed to 320 parts by mass. Toner base particles (2) were prepared in the same manner as described above. The obtained toner base particles (2) had a volume-based median diameter of 5.5 μm and an average circularity of 0.973. Also, the content of the crystalline polyester resin in the toner base particles (2) is 20% by mass.

[Preparation of toner base particles (3)]
In the preparation of the toner base particles (1), the addition amount of the amorphous polyester resin particle dispersion (a1) is changed to 1200 parts by mass, and the crystalline polyester resin particle dispersion (c1) is not added. Toner base particles (3) were prepared. The obtained toner base particles (3) had a volume-based median diameter of 5.8 μm and an average circularity of 0.968.

[Preparation of toner base particles (4)]
Toner base particles (4) were prepared in the same manner as in the production of toner base particles (1), except that the structure of slurry 1 used in the aggregation/fusion step and aging step was changed as follows.

Amorphous polyester resin particle dispersion (a1) 1008 parts by mass Amorphous vinyl resin particle dispersion (b1) 32 parts by mass Crystalline polyester resin particle dispersion (c1) 160 parts by mass Release agent particle dispersion (W1) 200 parts by mass Black colorant dispersion (1) 187 parts by mass Anionic surfactant (Dowfax2A1, 20% by mass aqueous solution, manufactured by Dow Chemical Company) 40 parts by mass Ion-exchanged water 1500 parts by mass The resulting toner base particles (4) are , the volume-based median diameter was 5.5 μm, and the average circularity was 0.970.

<<Preparation of external additives>>
According to the following method, external additives 1 to 14 were prepared which were composed of alumina-coated silica particles and whose surfaces were subjected to a hydrophobic treatment.

[Preparation of External Additive 1]
(Preparation of alumina-coated silica particles)
945 parts by mass of methanol, 45 parts by mass of 28% aqueous ammonia, and 135 parts by mass of water were added and mixed in a 3-liter reactor equipped with a stirrer, dropping funnel and thermometer. The temperature of this solution was adjusted to 35° C., and 405 parts by mass of tetramethoxysilane was added dropwise over 6 hours while stirring. After the dropwise addition, stirring was continued for 1 hour for hydrolysis to disperse the silica particles. A liquid was prepared.

While this dispersion is heated and maintained at 70° C., a 5 mol/L sodium hydroxide aqueous solution is added dropwise so that the pH becomes 8.0, and sodium aluminate is 30% by mass as alumina with respect to the silica mass. After preparing a slurry containing alumina-coated silica particles by adding a corresponding amount, the pH of the slurry was neutralized to 5.0 and kept at a temperature of 80° C. for 30 minutes with stirring for aging. After this slurry was distilled under reduced pressure and dried, fine particles were pulverized to prepare external additive particles 1 . The number average primary particle diameter (D ₅₀ ) of the external additive particles 1 obtained by the above method was measured and found to be 20 nm.

(Surface hydrophobic treatment)
The external additive particles 1 obtained above were placed in a reaction vessel, and octyltriethoxy was added as a hydrophobizing agent to 100 g of the external additive particles 1 powder in a nitrogen atmosphere while stirring the powder with a rotating blade. A solution obtained by diluting 20 g of silane with 60 g of hexane was added, heated and stirred at 200° C. for 120 minutes, cooled with cooling water, and dried under reduced pressure to obtain an external additive 1 .

The carbon content of the external additive 1 after the surface hydrophobizing treatment was 4.0% by mass. Moreover, the degree of hydrophobicity of external additive 1 (alumina-coated silica particles) was 65 as measured by the following method.

<Measurement of hydrophobicity of external additive 1>
Put a 20 mm long stirrer tip and 60 mL of ion-exchanged water in a 100 mL tall beaker, deaerate by irradiating with ultrasonic waves for 5 minutes, and then transfer to a powder wettability tester WET-100P (manufactured by Resca Co., Ltd.). set.

Next, 25 mg of the external additive 1 sample was floated on the ion-exchanged water, and then, immediately after that, the lid and the methanol supply nozzle were set, and measurement was started simultaneously with the start of stirring with the stirrer. The supply rate of methanol was 1.6 mL/min, and the measurement time was 30 min. The stirring speed of the stirrer was adjusted to 350-450 rpm. The external additive initially floats on the interface of the ion-exchanged water, but as the methanol concentration rises, it gradually gets wet with the mixture of ion-exchanged water and methanol and disperses in the liquid, resulting in a decrease in the light transmittance of the liquid. . The wettability is evaluated from the state of this decrease. Specifically, from the obtained data, plot the methanol concentration (vol%) calculated from Flow (mL) on the horizontal axis and the light transmittance (voltage ratio (%)) on the vertical axis. The methanol concentration at the point between the maximum and minimum values was obtained as the "hydrophobicity".

[Preparation of external additives 2 to 14]
In the preparation of the external additive 1 in which the surface of the alumina-coated silica particles is subjected to a hydrophobic treatment, the mass ratio of tetramethoxysilane, ammonia, alcohol and water, reaction temperature, stirring speed, and supply speed in the hydrolysis and polycondensation steps By appropriately controlling the number average particle diameter described in Table I, furthermore, the alumina content ratio, the type and treatment amount of the surface hydrophobizing agent, the carbon content, and the degree of hydrophobization are set to the conditions described in Table I. External additives 2 to 14 were prepared by appropriately changing the

<<Preparation of electrostatic charge image developer>>
[Preparation of electrostatic charge image developer 1]
[Preparation of Toner Particles]
[Preparation of Toner Particles 1]
(External additive addition step)
0.8 parts by mass of external additive 1 and 0.5 parts by mass of hydrophobic silica 1 (RY50 manufactured by Nippon Aerosil Co., Ltd.) are added to the prepared toner base particles 1 (volume-based median diameter 6.0 μm). Then, the toner particles 1 were produced by mixing for 20 minutes with a Henschel mixer.

(Preparation of Toner Particles 2 to 23)
In the preparation of toner particles 1, as shown in Table 2, the type and amount of the external additive added, the amount of hydrophobic silica 1 added, the presence or absence of addition of hydrophobic silica 2, and the presence or absence of addition of alumina were changed. Toner particles 2 to 23 were produced in the same manner as above.

Hydrophobic silica 1: AEROSIL RY50 (primary particle size: 40 nm, manufactured by Nippon Aerosil Co., Ltd.),
Hydrophobic silica 2: X-24-9163A (sol-gel silica spherical fine particles manufactured by Shin-Etsu Chemical Co., Ltd.)
Alumina: AEROXIDE AluC (manufactured by Nippon Aerosil Co., Ltd.)
[Preparation of carrier particles]
(Preparation of core particles)
MnO: 35 mol%, MgO: 14.5 mol%, Fe ₂ O ₃ : 50 mol%, and SrO: 0.5 mol% were each weighed, mixed with water, and pulverized for 5 hours in a wet media mill. to obtain a slurry.

The resulting slurry was dried with a spray dryer to obtain spherical particles. After adjusting the particle size of the particles, the particles were heated at 950° C. for 2 hours and calcined in a rotary kiln. After pulverizing with a dry ball mill for 1 hour using stainless steel beads with a diameter of 0.3 cm, 0.8% by mass of polyvinyl alcohol is added as a binder to the solid content, water and a dispersant are added, and a diameter of 0.5 cm is added. of zirconia beads for 25 hours. Then, the mixture was granulated and dried using a spray dryer, and was fired in an electric furnace at a temperature of 1050° C. for 20 hours.

After that, the material was pulverized, further classified to adjust the particle size, and then the low magnetic force products were separated by magnetic separation to obtain core material particles. The volume average particle diameter of the core particles was 28.0 μm.

(Preparation of coating resin)
100 parts by mass of cyclohexyl methacrylate monomer and 1 part by mass of dodecanethiol were mixed and dissolved, and 0.5 parts by mass of an anionic surfactant (Neogen SC manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was dissolved in 400 parts by mass of deionized water. The solution was added to a flask containing the solution to cause emulsion polymerization, and 50 parts by mass of deionized water in which 0.5 parts by mass of ammonium persulfate was dissolved as an initiator was added thereto while slowly mixing for 10 minutes. After purging with nitrogen, 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 to obtain a resin dispersion. Thereafter, the resin dispersion was dried by spray drying to obtain a coating resin. The weight average molecular weight of the resin particles for coating layer formation was 350,000.

(Preparation of carrier particles)
100 parts by mass of the core particles prepared above and 4.5 parts by mass of the coating resin prepared above were added to a high-speed stirring mixer equipped with horizontal stirring blades, and the peripheral speed of the horizontal rotary blades was 8 m / sec. After mixing and stirring for 15 minutes at 22° C. under the following conditions, the mixture is mixed at 120° C. for 50 minutes to coat the surface of the core material particles with the coating resin by the action of mechanical impact force (mechanochemical method). to produce carrier particles.

[Preparation of electrostatic charge image developer]
Toner particles 1 and carrier particles prepared as described above were mixed so that the toner particle concentration was 9 mass %, and electrostatic charge image developer 1 was prepared. The mixer used for mixing was a V-type mixer (manufactured by Tokuju Kosakusho Co., Ltd.), and the mixture was mixed at 25° C. for 30 minutes.

[Preparation of electrostatic charge image developers 2 to 23]
Electrostatic charge image developers 2 to 23 were prepared in the same manner as in the preparation of electrostatic charge image developer 1, except that toner particles 2 to 23 were used instead of toner particles 1.

<<Evaluation of Electrostatic Charge Image Developer>>
Each electrostatic charge image developer prepared above was evaluated as follows.

[Evaluation of Image Density]
(Printing of evaluation image)
A commercially available color multifunction machine "bizhub PRO C6500" (manufactured by Konica Minolta, Inc.) was filled with each electrostatic image developer prepared above.

First, in a normal temperature and normal humidity environment (temperature 20°C, humidity 50% RH, indicated as "NN"), as a test image, a belt-shaped solid image with a printing rate of 5% was printed on A4-size high-quality paper (65 g/m ² ). One thousand prints were made to form the image. In Table III, it is labeled "initial (NN)" and is referred to as evaluation step 1.

Then, under a high-temperature and high-humidity environment (temperature of 30° C., humidity of 80% RH, indicated as “HH”), 70,000 sheets of test images were printed to form a band-shaped solid image with a print rate of 5%. A total of 100,000 sheets, ie, 30,000 sheets, were printed to form a band-shaped solid image with a printing rate of 40%. Table III is labeled "100 kp (HH)" and is referred to as Evaluation Step 2.

Finally, under a low temperature and low humidity environment (Temperature 10°C, Humidity 20% RH, indicated as "LL"), 70,000 copies were similarly printed to form a band-shaped solid image with a print rate of 5% as a test image. Then, 30,000 sheets were printed to form a band-shaped solid image with a coverage rate of 40%, for a total of 100,000 sheets, and a total of 200,000 sheets were printed. Table III is labeled "200 kp (LL)" and is referred to as Evaluation Step 3.

(Measurement of image density)
After printing 1,000 sheets of continuous printing (NN, evaluation step 1), after printing 100,000 sheets (HH, evaluation step 2), and after printing 200,000 sheets (LL, evaluation step 3), each of A4 size A solid patch image was printed on high-quality paper (65 g/m ² ), and the density was measured with a reflection densitometer "RD-918" manufactured by Macbeth. Image density is absolute density.

[Evaluation of fog resistance]
Using a Macbeth reflection densitometer “RD-918”, the absolute image densities of 20 points on an unused blank sheet without printing were measured and averaged to obtain the blank sheet density.

Next, the 1,000th image print sample in the evaluation step 1 (NN), the 100,000th image print sample in the evaluation step 2 (HH), and the 200,000th image print sample in the evaluation step 3 (LL) Absolute image densities were measured at 20 locations on the white background portion other than the image printed portion and averaged. For the high level, the fogging resistance was evaluated according to the evaluation criteria below.

◯: Fogging density of less than 0.007 Δ: Fogging density of 0.007 or more and less than 0.010 ×: Fogging density of 0.010 or more [Evaluation of Image Granularity]
After printing 1,000 sheets of continuous printing (NN, evaluation step 1), after printing 100,000 sheets (HH, evaluation step 2), and after printing 200,000 sheets (LL, evaluation step 3), the quality of A4 A gradation pattern with a gradation rate of 32 steps is output on paper (65 g/m ² ), and the value read by the CCD is subjected to Fourier transform processing in consideration of MTF (Modulation Transfer Function) correction. The GI value (Graininess Index) was measured in accordance with the relative luminosity of , and the maximum GI value (GIi) was obtained. The smaller the GIi value, the better, and the smaller the GIi value, the less grainy the image. This GI value is the value published in Journal of Imaging Society of Japan, 39(2), 84-93 (2000). The image graininess of the gradation pattern in the image was evaluated according to the following evaluation criteria for the highest level of the maximum GI value (GIi) among the above evaluation steps.

○: The maximum GI value (GIi) in the image is less than 0.170 △: The maximum GI value (GIi) in the image is 0.170 or more and less than 0.180 ×: The maximum GI value (GIi) in the image is 0.180 or more [Evaluation of fixability]
A commercially available full-color copier "bizhub PRO C6500" (manufactured by Konica Minolta) was modified so that the surface temperature of the fixing heat roller could be changed within the range of 100 to 210°C. A fixing test was performed by filling each electrostatic charge image developer prepared above and fixing a solid image with an adhesion amount of 5 mg/10 cm ² on A4 plain paper (basis weight 80 g/m ² ) at a set fixing temperature. 100° C., 105° C., . . . in 5° C. increments.

The printed matter obtained in the fixing experiment at each fixing temperature was folded with a folding machine so as to apply a load to the solid image, and compressed air of 0.35 MPa was blown to the fold, and the crease was made according to the following evaluation criteria. ranked to.

Rank 5: No peeling along the crease Rank 4: Fine peeling along the crease Rank 3: Fine linear peeling along the crease Rank 2: Thick linear delamination along the crease Rank 1: Excessive peeling that cannot be used for practical use Next, the fixing temperature in the fixing experiment that gave Rank 3 in the above ranking evaluation was determined, and this was taken as the lower limit fixing temperature, and fixability was evaluated according to the following criteria. .

◎: Minimum fixing temperature is less than 165°C ○: Minimum fixing temperature is 165°C or more and less than 170°C △: Minimum fixing temperature is 170°C or more and less than 175°C ×: Minimum fixing temperature is 175 The results obtained above are shown in Table III.

As is clear from the results shown in Table III, the electrostatic charge image developer of the present invention was superior in image density, fogging resistance after continuous printing, image granularity and fixation when printing under each environment, compared to the comparative examples. It can be seen that it is superior in quality.

Further, the shape of the toner particles after the above evaluation of the toner particles 1 and 15 of the present invention and the toner particles 23 of the comparative example was examined using a scanning electron microscope (SEM) "JEM-7401F" (manufactured by JEOL Ltd.). As a result of observing the embedding state of the external additive in the toner particles by taking an SEM photograph magnified 30,000 times, it was found that the external additive was significantly embedded in the toner particles 23 of the comparative example, and the toner particles of the present invention. In No. 1 and Toner Particle 15, the embedding of the external additive was small, and the order of embedding degree was (large) Toner Particle 23 >> Toner Particle 1 > Toner Particle 15 .

Claims (10)

An electrostatic charge image developer comprising at least a toner for developing an electrostatic charge image containing toner particles having an external additive on the surface of toner base particles, and carrier particles,
the external additive constituting the toner particles contains at least composite oxide particles mainly composed of alumina and silica;
The composite oxide particles contain alumina in the range of 5 to 50% by mass and silica in the range of 50 to 95% by mass,
The number average particle size of the primary particles of the composite oxide particles is in the range of 7 to 80 nm ,
The composite oxide particles have a hydrophobicity of 40 or more , and
The carrier particles have on their surfaces a resin formed using an alicyclic methacrylate monomer.
An electrostatic charge image developer characterized by: 2. The electrostatic image developer according to claim 1, wherein said composite oxide particles have a structure in which surfaces of silica particles are coated with said alumina. 3. The electrostatic image developer according to claim 1, wherein the carbon content in said composite oxide particles is in the range of 0.5 to 6.0 mass %. The electrostatic image developer according to any one of claims 1 to 3, wherein the number average particle diameter of primary particles of the composite oxide particles is in the range of 10 to 50 nm. 5. Any one of claims 1 to 4, wherein the content of the composite oxide particles is in the range of 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the toner particles. 1. The electrostatic image developer according to claim 1 or 1. 6. The electrostatic charge according to any one of claims 1 to 5, wherein the toner base particles contain a binder resin, and the binder resin contains at least an amorphous polyester resin. image developer. 7. The electrostatic image developer according to claim 6, wherein said binder resin further contains a crystalline polyester resin. 8. The electrostatic image developer according to claim 7, wherein the content of said crystalline polyester resin is in the range of 0.1 to 20% by mass of the total mass of said toner particles. 9. The electrostatic image developer according to any one of claims 1 to 8, wherein said silica is wet silica. 10. The electrostatic image developer according to any one of Claims 1 to 9, wherein the composite oxide particles have a surface hydrophobizing agent.