JP2023085120A - Magnetic carrier and two-component system developer - Google Patents

Abstract

To provide a magnetic carrier which can output the stable image density even in the use in a very long period of time.SOLUTION: There is provided a magnetic carrier which includes a magnetic core and a coating resin layer that covers a surface of the magnetic core. The coating resin layer contains a cross-linked resin. The cross-linked resin is the resin which is formed by cross-linking reaction between a first molecular chain and a second molecular chain. A partial structure of the first molecular chain has a prescribed SP value.SELECTED DRAWING: None

Description

The present invention relates to a magnetic carrier, a two-component developer, and a developer for replenishment, which are used in an image forming method for visualizing an electrostatic charge image using electrophotography.

Conventionally, in the electrophotographic image forming method, an electrostatic latent image is formed on an electrostatic latent image carrier using various means, and toner is adhered to the electrostatic latent image to form the electrostatic latent image. Developing methods are commonly used. For this development, carrier particles called magnetic carriers are mixed with the toner, triboelectrically charged to impart an appropriate amount of positive or negative charge to the toner, and a two-component development method in which the charge is used as a driving force for development is widely used. Adopted.

In the two-component development method, functions such as agitating, transporting, and charging the developer can be added to the magnetic carrier, so the division of functions with the toner is clear. There is Here, the magnetic carrier often has a structure in which the core is coated with a core for imparting magnetism to acquire transportability and a coating resin for acquiring the ability to impart charge to the toner.

In recent years, due to technological advances in the field of electrophotography, a higher level of longevity of the main body has been demanded, and it is demanded that the carrier maintains its charge-imparting ability even in long-term use. As a method for maintaining the charge-imparting ability, improvement in the stability of the coated film of the carrier-coating resin can be mentioned, and specifically, increasing the strength of the coated film of the carrier-coating resin can be considered. As a method for increasing the coating film strength of a carrier-coated resin, there are examples of cross-linking the molecular chains of the resin (Patent Documents 1 to 4).

However, when the coating film strength of the coating resin is increased by cross-linking, the hardness is improved, but the coating film becomes brittle and may break, resulting in insufficient improvement in the stability of the coating film.

Further, when the coating film strength of the coating resin is increased by cross-linking, the toner component resin, release agent, and external additive adhere to the coating film surface, and the charging ability of the carrier may be lowered.

Therefore, there is an example of a magnetic carrier in which two or more layers are coated so that the surface layer of the carrier is non-crosslinked and the coating layer near the core is crosslinked (Patent Document 5). There is also an example of a magnetic carrier in which the degree of cross-linking is increased from the carrier surface toward the core (Patent Document 6).

With these magnetic carriers, the adherence of the toner components to the carrier is suppressed from the initial to the middle period of use, but the state of the coating changes. etc., and the stability of image quality may be impaired.

Japanese Patent No. 5454228 JP-A-7-160057 JP 2016-018046 A JP-A-2002-169325 Japanese Patent Application Laid-Open No. 2007-322613 Japanese Patent No. 6683032

An object of the present invention is to solve the above-mentioned problems. The coating film strength of the coating resin is increased by cross-linking, the toughness is maintained, and the fixation of toner components is suppressed. It is to provide a carrier that can be output.

A magnetic carrier of the present invention is a magnetic carrier comprising magnetic core particles and a coating resin layer that coats the surface of the magnetic core particles,
The coating resin layer contains a crosslinked resin,
The crosslinked resin is
A partial structure represented by the following formula (1), a partial structure represented by the following formula (2) having a reactive functional group A, and a partial structure represented by the following formula (3) or the following formula ( 4) a first molecular chain having a partial structure represented by
a second molecular chain having a reactive functional group B;
is a resin formed by a cross-linking reaction,
In the crosslinked resin, the first molecular chain and the second is bound to the molecular chain,
When the first molecular chain has a partial structure represented by the following formula (3), the SP value of the portion represented by the following formula (5) is SPa2, and the following formula (5) in the crosslinked resin SPa1 is the SP value of the part other than the part represented,
When the first molecular chain has a partial structure represented by the following formula (4), the SP value of the portion represented by the following formula (6) is SPa2, and the following formula (6) in the crosslinked resin When the SP value of the part other than the part represented is SPa1,
The SPa1 and the SPa2 are
0.5<SPa1−SPa2≦7.0
A magnetic carrier characterized by satisfying

(In the above formula (1),
R ¹ represents H or CH ₃ ,
X represents a phenyl group or COOR ² ,
R ² represents an alicyclic hydrocarbon group having 3 to 12 carbon atoms or a chain alkyl group having 1 to 8 carbon atoms. )

(in the above formula (2),
R ¹ represents H or CH ₃ ,
Z ¹ represents a reactive functional group A having 1-8 carbon atoms. )

(In the above formula (3),
^R3 represents H or _CH3 ,
Y ¹ represents -COO- or -O-,
R ⁴ represents a single bond or a hydrocarbon group having 1 to 10 carbon atoms,
R ⁵ represents a hydrocarbon group having 1 to 10 carbon atoms,
R ⁶ represents CH ₃ or Si(CH ₃ ) ₃ ,
n represents an integer of 5 or more and 50 or less)

(in the above formula (4),
^R3 represents H or _CH3 ,
Y ² represents -COO- or -O-,
R ⁷ represents a single bond or a hydrocarbon group having 2 to 10 carbon atoms,
R ⁸ represents an alkyl group having 8 to 20 carbon atoms, in which at least part of the hydrogen atoms are substituted with fluorine atoms, and part of the remaining hydrogen atoms are halogen atoms other than fluorine atoms and the proportion of fluorine atoms is 5.0 atomic % or more based on the total number of hydrogen atoms, fluorine atoms and halogen atoms other than fluorine atoms contained in the alkyl group, and fluorine The proportion of halogen atoms other than atoms is 40.0 atomic % or less. )

(In the above formula (5),
Y ¹ represents -COO- or -O-,
R ⁴ represents a single bond or a hydrocarbon group having 1 to 10 carbon atoms,
R ⁵ represents a hydrocarbon group having 1 to 10 carbon atoms,
R ⁶ represents CH ₃ or Si(CH ₃ ) ₃ ,
n represents an integer of 5 or more and 50 or less)
—Y ² —R ⁷ —R ⁸ Formula (6)
(In the above formula (6),
Y ² represents -COO- or -O-,
R ⁷ represents a single bond or a hydrocarbon group having 2 to 10 carbon atoms,
R ⁸ represents an alkyl group having 8 to 20 carbon atoms, in which at least part of the hydrogen atoms are substituted with fluorine atoms, and part of the remaining hydrogen atoms are halogen atoms other than fluorine atoms and the proportion of fluorine atoms is 5.0 atomic % or more based on the total number of hydrogen atoms, fluorine atoms and halogen atoms other than fluorine atoms contained in the alkyl group, and fluorine The proportion of halogen atoms other than atoms is 40.0 atomic % or less. )
The present invention also relates to a two-component developer containing the above magnetic carrier and toner.

According to the present invention, there is provided a magnetic carrier capable of outputting a stable image density even when used for a very long period of time.

Further, according to the present invention, there is provided a magnetic carrier capable of suppressing deterioration of the carrier and outputting a stable image density even in a situation with a history of being stored under severe conditions.

1 is a schematic diagram of a preferred image forming apparatus; FIG. 1 is a schematic diagram of an image forming apparatus suitable for full-color image formation; FIG. 1 is a schematic diagram of a surface treatment apparatus suitable for surface treatment of toner; FIG. 1 is a schematic diagram of a device for measuring a specific resistance value; FIG.

In the present invention, unless otherwise specified, the descriptions of "○○ or more and XX or less" and "○○ to XX", which represent numerical ranges, mean numerical ranges including the lower and upper limits that are endpoints.

A magnetic carrier of the present invention is a magnetic carrier comprising magnetic core particles and a coating resin layer that coats the surface of the magnetic core particles,
The coating resin layer contains a crosslinked resin,
The crosslinked resin is
A partial structure represented by the following formula (1), a partial structure represented by the following formula (2) having a reactive functional group A, and a partial structure represented by the following formula (3) or the following formula ( 4) a first molecular chain having a partial structure represented by
a second molecular chain having a reactive functional group B;
is a resin formed by a cross-linking reaction,
In the crosslinked resin, the first molecular chain and the second is bound to the molecular chain,
When the first molecular chain has a partial structure represented by the following formula (3), the SP value of the portion represented by the following formula (5) is SPa2, and the following formula (5) in the crosslinked resin SPa1 is the SP value of the part other than the part represented,
When the first molecular chain has a partial structure represented by the following formula (4), the SP value of the portion represented by the following formula (6) is SPa2, and the following formula (6) in the crosslinked resin When the SP value of the part other than the part represented is SPa1,
The SPa1 and the SPa2 are
0.5<SPa1−SPa2≦7.0
A magnetic carrier characterized by satisfying

(In the above formula (1),
R ¹ represents H or CH ₃ ,
X represents a phenyl group or COOR ² ,
R ² represents an alicyclic hydrocarbon group having 3 to 12 carbon atoms or a chain alkyl group having 1 to 8 carbon atoms. )

(in the above formula (2),
R ¹ represents H or CH ₃ ,
Z ¹ represents a reactive functional group A having 1-8 carbon atoms. )

(In the above formula (3),
^R3 represents H or _CH3 ,
Y ¹ represents -COO- or -O-,
R ⁴ represents a single bond or a hydrocarbon group having 1 to 10 carbon atoms,
R ⁵ represents a hydrocarbon group having 1 to 10 carbon atoms,
R ⁶ represents CH ₃ or Si(CH ₃ ) ₃ ,
n represents an integer of 5 or more and 50 or less)

(in the above formula (4),
^R3 represents H or _CH3 ,
Y ² represents -COO- or -O-,
R ⁷ represents a single bond or a hydrocarbon group having 2 to 10 carbon atoms,
R ⁸ represents an alkyl group having 8 to 20 carbon atoms, in which at least part of the hydrogen atoms are substituted with fluorine atoms, and part of the remaining hydrogen atoms are halogen atoms other than fluorine atoms and the proportion of fluorine atoms is 5.0 atomic % or more based on the total number of hydrogen atoms, fluorine atoms and halogen atoms other than fluorine atoms contained in the alkyl group, and fluorine The proportion of halogen atoms other than atoms is 40.0 atomic % or less. )

(In the above formula (5),
Y ¹ represents -COO- or -O-,
R ⁴ represents a single bond or a hydrocarbon group having 1 to 10 carbon atoms,
R ⁵ represents a hydrocarbon group having 1 to 10 carbon atoms,
R ⁶ represents CH ₃ or Si(CH ₃ ) ₃ ,
n represents an integer of 5 or more and 50 or less)
—Y ² —R ⁷ —R ⁸ Formula (6)
(In the above formula (6),
Y ² represents -COO- or -O-,
R ⁷ represents a single bond or a hydrocarbon group having 2 to 10 carbon atoms,
R ⁸ represents an alkyl group having 8 to 20 carbon atoms, in which at least part of the hydrogen atoms are substituted with fluorine atoms, and part of the remaining hydrogen atoms are halogen atoms other than fluorine atoms and the proportion of fluorine atoms is 5.0 atomic % or more based on the total number of hydrogen atoms, fluorine atoms and halogen atoms other than fluorine atoms contained in the alkyl group, and fluorine The proportion of halogen atoms other than atoms is 40.0 atomic % or less. )

In the carrier of the present invention, the coating resin layer contains a resin in which the first molecular chain and the second molecular chain are crosslinked by a reactive functional group. Furthermore, it is a significant feature that there are graft sites that do not contribute to cross-linking and have a low SP value.

Conventional coating resins having a crosslinked structure have the following characteristics: (i) linear molecular chains are crosslinked by reactive functional groups; (ii) reactive functional groups are present at graft sites; or (iii) a reactive functional group is present in both the main chain and the graft site, and the main chain and the graft site are crosslinked. Although this increases the strength of the crosslinked portion, the degree of freedom of the molecular chains decreases, and the portions between the molecular chains that are not crosslinked become brittle. As a result, there is concern that a slight mechanical impact may cause cracks in the coating resin layer, which may lead to destruction of the resin coating layer.

However, when the reactive functional groups of the main chain are crosslinked as in the present invention and there is a graft site that does not contribute to crosslinking, the degree of freedom of the molecular chain is increased, the brittleness due to crosslinking is improved, and the toughness is improved. Furthermore, since the SP value of the grafted portion is separated from the SP values of other partial structures, the degree of freedom of the grafted portion is further increased, and the toughness is further improved.

Furthermore, the SP value of the graft site is characterized by being smaller than the SP values of other partial structures. By orienting the grafted portion with a low SP value toward the carrier surface side, the toughness of the carrier surface layer, which is susceptible to mechanical impact, can be improved. In addition, since the graft sites with low SP values are oriented on the carrier surface side, the surface free energy is lowered, and it is possible to suppress the fixation of toner components to the carrier.

In addition, the carrier of the present invention can suppress deterioration even in a situation where the carrier has a history of being stored under severe conditions. Although the details are not clear about this, not all reactive functional groups are reacted in cross-linking, and some remain as they are. It is thought that when the carrier is stored in an environment with high humidity, the remaining reactive functional groups change, causing deterioration of the resin coating layer of the carrier. However, in the carrier of the present invention, the surface free energy of the carrier surface is low, and the graft sites that do not contribute to the reaction are oriented on the surface. they think.

The carrier of the present invention is the SP value of the portion represented by formula (5) in the partial structure represented by formula (3), or the following formula (6) in the partial structure represented by formula (4) When the SP value of the portion represented by SPa2 and the SP value of the portion other than the portion represented by formula (5) or formula (6) in the crosslinked resin is SPa1, the SPa1 and SPa2 are:
0.5≦SPa1−SPa2≦7.0
meet. More preferably
1.0≦SPa1−SPa2≦6.5
and particularly preferably
1.5≦SPa1−SPa2≦6.0
meet.

When SPa1-SPa2 is within the above range, the coating film strength and toughness of the coating resin are improved, and stable image density can be output even in very long-term use. In addition, it is possible to satisfactorily suppress adhesion of toner components.

As a method of adjusting SPa1-SPa2 to the above range, adjustment can be made by optimizing the structure and addition ratio after grasping the SP value of each monomer.

The SP value is calculated from the following formula.
SP value = √(Ev/v) = √(ΣΔei/ΣΔvi)
(Ev: evaporation energy (J/mol)
v: molar volume (cm ³ /mol)
Δei: evaporation energy of each atom or atomic group Δvi: molar volume of each atom or atomic group)

<Coating resin>
The magnetic carrier of the present invention has a coating resin layer on the surface of magnetic carrier particles, and the coating resin layer contains a crosslinked resin. The crosslinked resin is a resin formed by a crosslink reaction between the first molecular chain and the second molecular chain.

and the first molecular chain is
(i) a partial structure represented by the following formula (1);
(ii) a partial structure represented by the following formula (2) having a reactive functional group A;
and further
(iii) a partial structure represented by the following formula (3) or a partial structure represented by the following formula (4);

The partial structure represented by formula (3) is a structure having a silicone unit (partial structure of formula (5)) as a graft site, and the partial structure represented by formula (4) is a structure having a fluorinated alkyl unit (formula (6) partial structure) as a graft site.

(In the above formula (1),
R ¹ represents H or CH ₃ ,
X represents a phenyl group or COOR ² ,
R ² represents an alicyclic hydrocarbon group having 3 to 12 carbon atoms or a chain alkyl group having 1 to 8 carbon atoms. )
The partial structure of formula (1) can be introduced, for example, by copolymerizing the following monomers. Methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, cyclobutyl acrylate, cyclohexyl acrylate, cyclopentyl acrylate, cyclooctyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacryl Butyl acid, hexyl methacrylate, cyclobutyl methacrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, cyclooctyl methacrylate, styrene, and the like. One or two or more of the above monomers may be copolymerized.

(in the above formula (2),
R ¹ represents H or CH ₃ ,
Z ¹ represents a reactive functional group A having 1-8 carbon atoms. )
Examples of the reactive functional group A in formula (2) include a carboxy group, a hydroxy group, an epoxy group, an amide group, and an amino group.

The partial structure of formula (2) can be introduced, for example, by copolymerizing the following monomers. acrylic acid, methacrylic acid, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, acrylic acid amide, methacrylic acid amide, glycidyl acrylate, glycidyl methacrylate, etc. .

(In the above formula (3),
^R3 represents H or _CH3 ,
Y ¹ represents -COO- or -O-,
R ⁴ represents a single bond or a hydrocarbon group having 1 to 10 carbon atoms,
R ⁵ represents a hydrocarbon group having 1 to 10 carbon atoms,
R ⁶ represents CH ₃ or Si(CH ₃ ) ₃ ,
n represents an integer of 5 or more and 50 or less. )
When n is an integer of 5 or more and 50 or less, the effect of suppressing fixation of toner components is high, and deterioration of the carrier can be suppressed even when the toner has a history of being stored under severe conditions, and stable image density can be obtained. can be output.

(in the above formula (4),
^R3 represents H or _CH3 ,
Y ² represents -COO- or -O-,
R ⁷ represents a single bond or a hydrocarbon group having 2 to 10 carbon atoms,
R ⁸ represents an alkyl group having 8 to 20 carbon atoms, in which at least part of the hydrogen atoms are substituted with fluorine atoms, and part of the remaining hydrogen atoms are halogen atoms other than fluorine atoms and the proportion of fluorine atoms is 5.0 atomic % or more based on the total number of hydrogen atoms, fluorine atoms and halogen atoms other than fluorine atoms contained in the alkyl group, and fluorine The proportion of halogen atoms other than atoms is 40.0 atomic % or less. )
With the above configuration, the effect of suppressing the fixation of the toner component is high, and deterioration of the carrier can be suppressed even when the toner has a history of being stored under severe conditions, and stable image density can be output.

Next, the second molecular chain is the molecular chain having the reactive functional group B. Here, the second molecular chain may be the same as or different from the first molecular chain.

When the second molecular chain and the first molecular chain are the same, the reactive functional group A and the reactive functional group B are also the same. In this case, the reactive functional group A and the reactive functional group B are bonded by a bond formed by reaction via a cross-linking agent.

When the reactive functional group A and the reactive functional group B are carboxy groups, the cross-linking agent may be an ammonium salt (such as a methylolated cross-linking agent), an isocyanate compound, a polyfunctional epoxy compound, or a polyvalent metal salt of Ca, Zn, or Al. metal oxides, and the like.

Examples of isocyanate compounds include isophorone diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, triene diisocyanate, polymeric MDI, naphthalene diisocyanate, tetramethylxylylene diisocyanate, trimethylhexamethylene diisocyanate and the like.

Examples of polyfunctional epoxy compounds include 2,2-bis(4-hydroxyphenyl)propane diglycidyl ether (bisphenol A diglycidyl ether), ethylene glycol diglycidyl ether, triglycidyl isocyanurate, bisphenol A type epoxy resin, benzoguanamine. Resins, oxazoline group-containing resins, and the like can be mentioned.

When the reactive functional group A and the reactive functional group B are hydroxyl groups, examples of cross-linking agents include urea, melamine resins, and acrolein.

When the reactive functional group A and the reactive functional group B are epoxy groups, examples of cross-linking agents include polyvalent carboxylic acid compounds, primary amines, secondary amines, benzoguanamine, and the like.

Specific examples of polycarboxylic acid compounds include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, terephthalic acid, and isophthalic acid.

Primary amines and secondary amines include hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, 2-methyl-1,5-diaminopentane, 3,3-dimethylbutane-1,2-diamine, 4-methylpentane-1,2-diamine, 2,2,4,4-tetramethylcyclobutane, 2-methylcyclohexane-1,3-diamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2, 6-diaminotoluene, 3,4-diaminotoluene, 2,3-diaminotoluene, 2,5-dimethylbenzene-1,2-diamine, 3,4-dimethylbenzene-1,2-diamine and the like.

When the second molecular chain and the first molecular chain are different, the reactive functional group A and the reactive functional group B may be the same or different. When the reactive functional group A and the reactive functional group B are also the same, they have a bond formed by reacting through a cross-linking agent in the same manner as described above.

When the reactive functional group A and the reactive functional group B are different, the reactive functional group A and the reactive functional group B can be reacted to form a bond without using a cross-linking agent.

In the crosslinked resin, (i) when the first molecular chain has a partial structure represented by the formula (3), the content of the portion represented by the formula (5) is 1 based on the crosslinked resin. It is preferably ~50% by mass. Further, (ii) when the first molecular chain has a partial structure represented by formula (4), the content of the moiety represented by formula (6) is preferably 1 to 50% by mass. . In any case, it is more preferably 5 to 49% by mass. Within the above range, the coating film strength and toughness of the coating resin are improved, and stable image density can be output even in very long-term use. In addition, the effect of suppressing fixation of toner components is improved.

The total amount of the crosslinked resin is preferably 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the magnetic core particles. Within the above range, the coating film strength and toughness of the coating resin are improved, and stable image density can be output even in very long-term use. In addition, the effect of suppressing fixation of toner components is improved.

Furthermore, the coating resin layer can also contain conductive fine particles. The conductive fine particles can appropriately control the specific resistance of the carrier. The content of the conductive fine particles added to the coating resin is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the coating resin. Examples of conductive fine particles include carbon black, titanium oxide, and silver.

Further, fine particles other than the conductive fine particles may be contained in the coating resin for the purpose of enhancing the ability to impart charge to the toner and improving releasability. These fine particles may be fine particles of either an organic material or an inorganic material, but are preferably crosslinked resin fine particles or inorganic fine particles that have a strength capable of retaining the shape of the fine particles when coated. . Crosslinked resins forming the crosslinked resin fine particles include crosslinked polymethyl methacrylate resins, crosslinked polystyrene resins, melamine resins, guanamine resins, urea resins, phenol resins and nylon resins. Moreover, silica, an alumina, a titania etc. are mentioned as an inorganic fine particle.

The content of fine particles in the coating resin layer is preferably 0.1 to 20 parts by mass with respect to 100 parts by mass of the coating resin.

The first molecular chain and the second molecular chain are produced by known polymerization methods. Specific examples include a bulk polymerization method, a solution polymerization method, a suspension polymerization method, and the like.

<Magnetic core particles and method for producing the same>
As the magnetic core particles (carrier core particles), known magnetic particles such as magnetite particles, ferrite particles, magnetic material-dispersed resin particles, and resin-filled porous magnetic particles can be used. Among them, resin-filled porous magnetic particles or magnetic material-dispersed resin particles are preferable from the viewpoint of prolonging the life of the magnetic carrier, because the specific gravity of the magnetic carrier can be reduced.

By lowering the specific gravity of the magnetic carrier, the load on the toner in the developing device can be reduced, and the adhesion of toner components to the surface of the magnetic carrier can be prevented. Moreover, since the load between the carriers is reduced, peeling, chipping, and scraping of the coating resin layer can be suppressed. In addition, dot reproducibility can be improved, and high-definition images can be obtained.

As the resin to be contained in the pores of the porous magnetic particles, the copolymer resin used as the coating resin can be used, but not limited to this, any known resin can be used. Examples of thermoplastic resins include polystyrene, polymethyl methacrylate, styrene-acrylate copolymer, styrene-methacrylate copolymer, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, and polyvinyl chloride. , polyvinyl acetate, polyvinylidene fluoride resin, fluorocarbon resin, perfluorocarbon resin, solvent-soluble perfluorocarbon resin, polyvinylpyrrolidone, petroleum resin, novolac resin, saturated alkyl polyester resin, polyethylene terephthalate, polybutylene terephthalate, aromatic polyester such as polyarylate , polyamide, polyacetal, polycarbonate, polyethersulfone, polysulfone, polyphenylene sulfide, polyetherketone.

Examples of thermosetting resins include phenolic resins, modified phenolic resins, maleic resins, alkyd resins, epoxy resins, acrylic resins, unsaturated polyesters obtained by polycondensation of maleic anhydride, terephthalic acid and polyhydric alcohols, and urea. Resins, melamine resins, urea-melamine resins, xylene resins, toluene resins, guanamine resins, melamine-guanamine resins, acetoguanamine resins, glyptal resins, furan resins, silicone resins, polyimides, polyamideimides, polyetherimides, and polyurethanes. .

As a method of filling the voids of the porous magnetic particles with the resin component, there is a method of diluting the resin component with a solvent and adding the diluted solution to the porous magnetic particles. Any solvent may be used as long as it can dissolve each resin component. When the resin is soluble in an organic solvent, organic solvents such as toluene, xylene, cellosolve butyl acetate, methyl ethyl ketone, methyl isobutyl ketone and methanol may be used. In the case of a water-soluble resin component or an emulsion-type resin component, water may be used. As a method for adding the resin component diluted with a solvent into the inside of the porous magnetic core particles, the resin component is impregnated by a coating method such as a dipping method, a spray method, a brush coating method, a fluidized bed method, and a kneading method, Then, the method of volatilizing a solvent is mentioned. In the case of filling with a thermosetting resin, after the solvent is volatilized, the temperature is raised to the temperature at which the resin used is cured to cause a curing reaction.

On the other hand, as a specific method for producing the magnetic material-dispersed resin particles, the following method can be mentioned. For example, submicron magnetic materials such as iron powder, magnetite particles, and ferrite particles are kneaded so as to be dispersed in a thermoplastic resin, pulverized to a desired carrier particle size, and, if necessary, subjected to thermal or mechanical spheroidization. It can be obtained by applying a chemical treatment. It is also possible to manufacture by dispersing the above magnetic material in a monomer and polymerizing the monomer to form a resin.

Resins in this case include vinyl resins, polyesters, epoxy resins, phenolic resins, urea resins, polyurethanes, polyimides, cellulose resins, silicone resins, acrylic resins and polyethers. The resin may be of one type or a mixed resin of two or more types. Phenolic resins are particularly preferred in that they increase the strength of the magnetic core particles. The true density and specific resistance can be adjusted by adjusting the amount of magnetic material. Specifically, in the case of magnetic particles, it is preferable to add 70 to 95% by mass based on the mass of the magnetic carrier.

The magnetic core particles should have a 50% particle diameter (D50) of 20 to 80 μm based on volume distribution so that the coating resin can be uniformly coated, and the density of the developer magnetic brush for preventing carrier adhesion and obtaining high-quality images can be increased. It is preferable to make it moderate.

Good developability can be obtained when the specific resistance of the magnetic core particles is 1.0×10 ⁵ to 1.0×10 ¹⁴ Ω·cm at an electric field strength of 1000 (V/cm). Therefore, it is preferable.

<Coating method of coating resin>
The method for coating the surface of the magnetic core particles with the coating resin is not particularly limited, and any known method can be used. For example, there is a so-called immersion method in which the magnetic core particles and the coating resin solution are stirred while the solvent is volatilized to coat the surfaces of the magnetic core particles with the coating resin. Specific examples thereof include a universal mixing stirrer (manufactured by Fuji Paudal Co., Ltd.), Nauta Mixer (manufactured by Hosokawa Micron Co., Ltd.), and the like. There is also a method of spraying a coating resin solution from a spray nozzle while forming a fluidized bed to coat the surface of the magnetic core particles with the coating resin. Specific examples include Spiracoater (manufactured by Okada Seiko) and Spiraflow (manufactured by Freund Corporation). There is also a method of dry-coating the magnetic carrier core with the coating resin in the form of particles. Specifically, processing methods using devices such as Hybridizer (manufactured by Nara Machinery Works), Mechanofusion (manufactured by Hosokawa Micron), Hiflex Gral (manufactured by Fukae Powtech), Theta Composer (manufactured by Tokuju Kosakusho), etc. can be mentioned.

<Magnetic carrier>
Next, the magnetic carrier will be explained.

The magnetic carrier preferably has a magnetization strength of 40 to 80 Am ² /kg under a magnetic field of 5000/4π (kA/m). When the strength of magnetization of the magnetic carrier is within the above range, the magnetic binding force to the developing sleeve is moderate, so the occurrence of carrier adhesion can be suppressed more satisfactorily. Moreover, since the stress applied to the toner in the magnetic brush can be reduced, deterioration of the toner and adhesion to other members can be suppressed satisfactorily.

In addition, the strength of magnetization of the magnetic carrier can be appropriately adjusted by the amount of resin contained. The residual magnetization of the magnetic carrier is preferably 20.0 Am ² /kg or less, more preferably 10.0 Am ² /kg or less. When the residual magnetization of the magnetic carrier is within the above range, particularly good fluidity as a developer can be obtained, and good dot reproducibility can be obtained.

The magnetic carrier preferably has a true density of 2.5 to 5.5 g/cm ³ , more preferably 3.0 to 5.0 g/cm ³ . A two-component developer containing a magnetic carrier having a true density within this range imposes less load on the toner and suppresses adhesion of toner components to the magnetic carrier. Further, the true density in this range is preferable for the magnetic carrier in order to achieve both good developability in a low electric field strength and prevention of carrier adhesion.

The magnetic carrier preferably has a volume-average particle size (D50) of 21 to 81 μm from the viewpoint of charging the toner, suppressing adhesion of the carrier to the image area, and improving image quality. More preferably, it is 25 to 60 μm.

Next, methods for measuring various physical properties of the carrier will be described.

<Method for measuring 50% particle size (D50) based on volume distribution of magnetic carrier>
The particle size distribution was measured using a laser diffraction/scattering type particle size distribution analyzer “Microtrac MT3300EX” (manufactured by Nikkiso Co., Ltd.).

The 50% particle diameter (D50) based on the volume distribution of the magnetic carrier was measured using a sample feeder for dry measurement "One-shot dry sample conditioner Turbotrac" (manufactured by Nikkiso Co., Ltd.). Turbotrac was supplied with a dust collector as a vacuum source, an air volume of about 33 l/sec, and a pressure of about 17 kPa. Control is performed automatically on software. As for the particle size, a 50% particle size (D50), which is a cumulative value based on volume distribution, is obtained. Control and analysis are performed using attached software (version 10.3.3-202D). The measurement conditions are as follows.
SetZero time: 10 seconds Measurement time: 10 seconds Number of measurements: 1 Particle refractive index: 1.81%
Particle shape: non-spherical measurement upper limit: 1408 μm
Measurement lower limit: 0.243 μm
Measurement environment: 23°C, 50% RH
<Measurement of resistivity of magnetic carrier>
The specific resistance value of the magnetic carrier is measured using the measuring device shown in FIG.

The specific resistance is measured by filling a cell E with a carrier, arranging a lower electrode and an upper electrode so as to be in contact with the carrier particles 1, applying a voltage between these electrodes, and measuring the current flowing at that time. Use the method of obtaining the resistivity by The specific resistance measurement conditions in the present invention are as follows: contact area S between filled carrier and electrode = about 2.4 cm ² , sample thickness d = about 0.2 cm, and upper electrode load of 240 g (2.35 N). Voltage application conditions are applied in the order of application conditions (I), (II), and (III), and the current at the applied voltage under application condition (III) is measured. After that, the thickness d of the sample was accurately measured, and the specific resistance (Ω cm) at each electric field strength (V/cm) was calculated. resisted.
Application condition (I): (changed from 0 V to 1000 V: increased stepwise by 200 V every 30 seconds)
(II): (Hold at 1000V for 30 seconds)
(III): (Changed from 1000 V to 0 V: Decrease stepwise by 200 V every 30 seconds)
Specific resistance of magnetic carrier (Ω cm)
= (applied voltage (V)/measured current (A)) x S (cm ² )/d (cm)
Electric field strength (V/cm) = applied voltage (V)/d (cm)
The specific resistance of the magnetite fine particles used in the magnetic substance dispersed resin carrier was also measured in the same manner.

<Method for Measuring Magnetization Strength of Magnetic Core Particles>
The strength of magnetization of the magnetic core particles can be determined by a vibrating magnetic field type magnetic property measuring device (Vibrating sample magnetometer) or a direct current magnetic property recording device (BH tracer). In the examples described later, measurements are carried out using an oscillating magnetic field type magnetic property measuring apparatus BHV-30 (manufactured by Riken Denshi Co., Ltd.) according to the following procedure.

The sample is a cylindrical plastic container filled with sufficiently dense magnetic core particles. Measure the actual mass of the sample filled in the container. After that, the sample in the plastic container is adhered with an instant adhesive so that the sample does not move.

A standard sample is used to calibrate the external magnetic field axis and magnetization moment axis at 5000/4π (kA/m).

The intensity of magnetization was measured from a loop of magnetization moment applied with an external magnetic field of 5000/4π (kA/m) at a sweep speed of 5 (min/roop). From these, the magnetization intensity (Am ² /kg) of the magnetic core particles is obtained by dividing by the sample weight.

<Measurement of true specific gravity of magnetic core particles>
The true specific gravity of the magnetic core particles can be determined by a dry automatic densitometer autopycnometer.

<Quantification of coating amount of coating resin>
As a measuring device, an automatic sample burning device AQF-100 type (manufactured by Mitsubishi Chemical Corporation) and an ion chromatography ICS-2000 (manufactured by Dionex Corporation) are used. The principle of the measurement is to burn the sample with an automatic sample burner, use hydrogen peroxide water (H ₂ O ₂ ) as the absorption liquid, make the fluorine element in the fluororesin exist as F ⁻ , and PO ₄ ³⁻ inside. It is used as a standard substance and quantified by ion chromatography.

The measurement conditions of the automatic sample combustion device AQF-100 type (manufactured by Mitsubishi Chemical Corporation) are as follows.
Inlet Temp. : 900°C
Outlet Temp. : 1000℃
Ar/ _O2 : 200ml/min
_O2 : 400ml/min
1st position: 150mm/60s
End Time: 360s
Cool Time: 30s
Boat Speed: 10mm/s
Measurement conditions for ion chromatography ICS-2000 (manufactured by Dionex Co.) are as follows.
Separation column: AG12A/AS12A
Injection volume: 25 μl
Eluent: 1 mM→40 mM (20 min)
A gradient elution method is used with an eluent generator.
Flow rate: 1.0ml/min
Column oven: 35°C

<Toner>
Next, in the two-component developer, the configuration of the toner used together with the magnetic carrier will be described in detail below.

The toner contains toner particles containing a binder resin.

<Binder resin>
As the binder resin, the following polymers and the like can be used. Homopolymers of styrene and substituted products thereof such as polystyrene, poly-p-chlorostyrene and polyvinyltoluene; styrene-p-chlorostyrene copolymers, styrene-vinyltoluene copolymers, styrene-vinylnaphthalene copolymers, styrene -Styrenic copolymers such as acrylic acid ester copolymers and styrene-methacrylic acid ester copolymers; polyesters; hybrid resins in which polyester and vinyl resins are partially reacted; polyvinyl chloride, phenolic resins, naturally modified phenols Resins, natural resin-modified maleic acid resins, acrylic resins, methacrylic resins, polyvinyl acetate, silicone resins, polyesters, polyurethanes, polyamides, furan resins, epoxy resins, xylene resins, polyethylene, polypropylene and the like. Among them, it is preferable to use polyester as the main component from the viewpoint of low-temperature fixability.

Monomers used for polyester synthesis include polyhydric alcohols (dihydric or trihydric or higher alcohols), polyhydric carboxylic acids (dihydric or trihydric or higher carboxylic acids), their acid anhydrides or their lower alkyl esters. and are used. Here, in order to express "strain hardening" and to create a branched polymer, it is effective to partially crosslink within the molecule of the amorphous resin. is preferably used. Therefore, it is preferable that a carboxylic acid having a valence of 3 or higher, an acid anhydride thereof or a lower alkyl ester thereof, and/or an alcohol having a valence of 3 or higher are included as raw material monomers for the polyester.

The following polyhydric alcohol monomers can be used as polyhydric alcohol monomers used for polyester synthesis.

Dihydric alcohol components include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1, 6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, hydrogenated bisphenol A can be mentioned.

Also, bisphenol represented by formula (A) and derivatives thereof:

(Wherein, R is an ethylene or propylene group, x and y are each an integer of 0 or more, and the average value of x + y is 0 or more and 10 or less.);
Diols represented by formula (B):

(wherein R' is -CH ₂ CH ₃ - or

or

where x' and y' are integers of 0 or more, and the average value of x'+y' is 0 or more and 10 or less. )
is mentioned.

Examples of trihydric or higher alcohol components include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, and 1,2,4-butanetriol. , 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene mentioned. Among these, glycerol, trimethylolpropane, and pentaerythritol are preferably used. These dihydric alcohols and trihydric or higher alcohols may be used alone or in combination.

The following polyvalent carboxylic acid monomers can be mentioned as the polyvalent carboxylic acid monomers used in the synthesis of the polyester.

Examples of divalent carboxylic acid components include maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid, n-dodecenylsuccinic acid, isododecenylsuccinic acid, n-dodecylsuccinic acid, isododecylsuccinic acid, n-octenylsuccinic acid, n-octylsuccinic acid, isooctenylsuccinic acid, isooctylsuccinic acid, anhydrides of these acids and Lower alkyl esters of these are included. Among these, maleic acid, fumaric acid, terephthalic acid and n-dodecenylsuccinic acid are preferably used.

Trivalent or higher carboxylic acids, their acid anhydrides or their lower alkyl esters include, for example, 1,2,4-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid and 1,2,4-naphthalenetricarboxylic acid. , 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra( methylenecarboxyl)methane, 1,2,7,8-octanetetracarboxylic acid, pyromellitic acid, empol trimer acid, their acid anhydrides or their lower alkyl esters. Among these, 1,2,4-benzenetricarboxylic acid, ie, trimellitic acid or derivatives thereof, is particularly preferred because it is inexpensive and reaction control is easy. These bivalent carboxylic acids and trivalent or higher carboxylic acids may be used alone or in combination.

The method for producing the polyester is not particularly limited, and known methods can be used. For example, the above alcohol monomer and carboxylic acid monomer are charged at the same time, polymerized through an esterification reaction or a transesterification reaction, and a condensation reaction to produce a polyester. Moreover, although the polymerization temperature is not particularly limited, it is preferably in the range of 180 to 290°C. Polymerization catalysts such as titanium-based catalysts, tin-based catalysts, zinc acetate, antimony trioxide, and germanium dioxide can be used in the polymerization of polyester. In particular, the binder resin of the present invention is more preferably polyester polymerized using a tin-based catalyst.

In addition, the polyester has an acid value of 5 to 20 mgKOH/g and a hydroxyl value of 20 to 70 mgKOH/g, which suppresses the amount of water adsorption in a high-temperature and high-humidity environment and suppresses the non-electrostatic adhesion force. Therefore, it is preferable from the viewpoint of fog resistance.

Also, the binder resin may be a mixture of a low-molecular-weight resin and a high-molecular-weight resin.

<Wax>
The toner may contain wax. Examples of wax include the following. Hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, alkylene copolymers, microcrystalline wax, paraffin wax and Fischer-Tropsch wax; oxides of hydrocarbon waxes such as oxidized polyethylene wax or block copolymers thereof; Waxes containing fatty acid ester as a main component such as carnauba wax; partially or wholly deoxidized fatty acid ester such as deoxidized carnauba wax. Furthermore, the following are mentioned. saturated straight-chain fatty acids such as palmitic acid, stearic acid and montanic acid; unsaturated fatty acids such as brassic acid, eleostearic acid and valinaric acid; saturated alcohols such as silalcohol; polyhydric alcohols such as sorbitol; fatty acids such as palmitic acid, stearic acid, behenic acid and montanic acid; Esters with alcohols such as silalcohol; Fatty acid amides such as linoleic acid amide, oleic acid amide and lauric acid amide; saturated fatty acid bisamides such as acid amides; unsaturated fatty acid amides such as ethylenebisoleic acid amide, hexamethylenebisoleic acid amide, N,N'dioleyladipic acid amide, N,N'dioleylsebacic acid amide; - aromatic bisamides such as xylene bisstearic acid amide and N,N' distearyl isophthalic acid amide; aliphatic metal salts such as calcium stearate, calcium laurate, zinc stearate and magnesium stearate (generally called metal soap) waxes obtained by grafting vinyl monomers such as styrene and acrylic acid to aliphatic hydrocarbon waxes; partial esters of fatty acids and polyhydric alcohols such as behenic acid monoglyceride; hydrogen of vegetable oils and fats A methyl ester compound having a hydroxyl group obtained by addition.

Among these waxes, hydrocarbon waxes such as paraffin wax and Fischer-Tropsch wax, or fatty acid ester waxes such as carnauba wax are preferred from the viewpoint of improving low-temperature fixability and fixability. In the present invention, hydrocarbon waxes are more preferable in terms of further improving hot offset resistance.

The wax is preferably used in an amount of 3 to 8 parts by weight per 100 parts by weight of the binder resin.

Further, in an endothermic curve measured with a differential scanning calorimeter (DSC) device, the peak temperature of the maximum endothermic peak of the wax is preferably 45 to 140°C. When the peak temperature of the maximum endothermic peak of the wax is within the above range, the storage stability and hot offset resistance of the toner can be compatible, which is preferable.

<Colorant>
The toner particles may contain a colorant. Colorants include the following.

Examples of black colorants include those toned black using carbon black; a yellow colorant, a magenta colorant and a cyan colorant. A pigment may be used alone as a coloring agent, but it is more preferable to use a dye and a pigment in combination to improve the definition from the viewpoint of image quality of a full-color image.

Examples of magenta toner pigments include the following. C. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48:2, 48:3, 48:4, 49, 50, 51, 52, 53, 54, 55, 57:1, 58, 60, 63, 64, 68, 81: 1, 83, 87, 88, 89, 90, 112, 114, 122, 123, 146, 147, 150, 163, 184, 202, 206, 207, 209, 238, 269, 282; I. Pigment Violet 19; C.I. I. Bat Red 1, 2, 10, 13, 15, 23, 29, 35.

Dyes for magenta toner include the following. C. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121; C.I. I. disperse thread 9;C. I. Solvent Violet 8, 13, 14, 21, 27; C.I. I. Oil-soluble dyes such as Disper Violet 1, C.I. I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40; C.I. I. Basic dyes such as Basic Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, 28.

Examples of cyan toner pigments include the following. C. I. Pigment Blue 2, 3, 15:2, 15:3, 15:4, 16, 17; C.I. I. Bat Blue 6; C.I. I. Acid Blue 45, a copper phthalocyanine pigment having a phthalocyanine skeleton substituted with 1 to 5 phthalimidomethyl groups.

As dyes for cyan toners, C.I. I. Solvent Blue 70 can be mentioned.

Examples of yellow toner pigments include the following. C. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 62, 65, 73, 74, 83, 93, 94, 95, 97, 109, 110, 111, 120, 127, 128, 129, 147, 151, 154, 155, 168, 174, 175, 176, 180, 181, 185; I. Bat Yellow 1, 3, 20.

As a yellow toner dye, C.I. I. Solvent Yellow 162 is mentioned.

These colorants can be used singly or in combination, or in the form of a solid solution. Colorants are selected in terms of hue angle, chroma, brightness, lightfastness, OHP transparency, and dispersibility in toner.

The content of the coloring agent is preferably 0.1 to 30.0 parts by mass with respect to 100 parts by mass of the binder resin.

<Inorganic fine particles>
The toner preferably contains inorganic fine particles for the main purpose of improving fluidity and chargeability, and is preferably in the form of adhering to the surface of the toner.

Silica particles having a maximum peak particle diameter of 80 to 200 nm based on the number distribution are preferable as the inorganic fine particles as spacer particles for enhancing the releasability between the toner and the carrier. It is more preferably 100 to 150 nm in order to better suppress detachment from the toner while functioning as spacer particles.

In addition, in order to improve the fluidity of the toner, it is preferable to incorporate inorganic fine particles having a maximum peak particle size of 20 to 50 nm based on the number distribution, and it is also preferable to use them together with the silica particles.

Furthermore, other external additives may be added to the toner particles with the aim of improving fluidity and transferability. The external additive externally added to the surface of the toner particles preferably contains inorganic fine particles such as titanium oxide, alumina oxide and silica, and a plurality of types may be used in combination.

The total content of the external additive is preferably 0.3 to 5.0 parts by mass, more preferably 0.8 to 4.0 parts by mass, with respect to 100 parts by mass of the toner particles. Among them, the content of silica particles having a maximum peak particle size of 80 to 200 nm based on number distribution is 0.1 to 2.5 parts by mass, more preferably 0.5 to 2.0 parts by mass. Within this range, the effect of spacer particles becomes more pronounced.

In addition, it is preferable that the surfaces of the silica particles and the inorganic fine particles used as the external additive are subjected to a hydrophobic treatment. The hydrophobizing treatment is preferably carried out with coupling agents such as various titanium coupling agents and silane coupling agents; fatty acids and metal salts thereof; silicone oils; or combinations thereof.

Examples of titanium coupling agents include the following. Tetrabutyl titanate, tetraoctyl titanate, isopropyl triisostearoyl titanate, isopropyl tridecylbenzenesulfonyl titanate, bis(dioctyl pyrophosphate) oxyacetate titanate.

Moreover, as a silane coupling agent, the following are mentioned, for example. γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β-(N-vinylbenzylaminoethyl)γ - aminopropyltrimethoxysilane hydrochloride, hexamethyldisilazane, methyltrimethoxysilane, butyltrimethoxysilane, isobutyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, decyltrimethoxysilane, dodecyltrimethoxysilane, phenyl trimethoxysilane, o-methylphenyltrimethoxysilane, p-methylphenyltrimethoxysilane.

Examples of fatty acids include the following. Long-chain fatty acids such as undecylic acid, lauric acid, tridecylic acid, dodecylic acid, myristic acid, palmitic acid, pentadecylic acid, stearic acid, heptadecylic acid, arachidic acid, montanic acid, oleic acid, linoleic acid, arachidonic acid. Metals of these fatty acid metal salts include, for example, zinc, iron, magnesium, aluminum, calcium, sodium, and lithium.

Examples of silicone oils include dimethylsilicone oil, methylphenylsilicone oil, and amino-modified silicone oil.

The hydrophobizing treatment is performed by adding a hydrophobizing agent to the particles to be treated in an amount of 1 to 30% by mass (more preferably 3 to 7% by mass) relative to the particles to be treated and coating the particles to be treated. is preferred.

The degree of hydrophobization of the hydrophobized external additive is not particularly limited. Hydrophobicity indicates the wettability of a sample to methanol, and is an index of hydrophobicity.

When the toner of the present invention is mixed with a magnetic carrier and used as a two-component developer, the carrier mixing ratio at that time is preferably 2 to 15% by mass in terms of toner concentration in the developer, and more preferably. Good results are usually obtained when the content is 4 to 13% by weight. If the toner concentration is less than 2% by mass, the image density tends to decrease, and if it exceeds 15% by mass, fogging and in-machine scattering tend to occur.

Further, in the replenishing developer for replenishing the developing device according to the decrease in the toner density of the two-component developer in the developing device, the toner amount is 2 to 50 parts by mass with respect to 1 part by mass of the replenishing magnetic carrier. be.

Next, an image forming apparatus equipped with a developing device using a magnetic carrier, a two-component developer, and a replenishing developer will be described as an example, but the present invention is not limited to this.

<Image forming method>
In FIG. 1, an electrostatic latent image carrier 1 rotates in the direction of the arrow in the figure. The electrostatic latent image carrier 1 is charged by a charger 2 as charging means, and the surface of the charged electrostatic latent image carrier 1 is exposed by an exposure device 3 as electrostatic latent image forming means to generate an electrostatic latent image. form an image. The developing device 4 has a developing container 5 containing a two-component developer. 7 is included. At least one of the magnets 7 is installed so as to face the latent image carrier. The two-component developer is held on the developer carrier 6 by the magnetic field of the magnet 7 , and the amount of the two-component developer is regulated by the regulating member 8 . be transported. In the developing section, the magnetic field generated by the magnet 7 forms a magnetic brush. After that, the electrostatic latent image is visualized as a toner image by applying a developing bias obtained by superimposing an alternating electric field on a DC electric field. A toner image formed on the electrostatic latent image carrier 1 is electrostatically transferred to a recording medium (transfer material) 12 by a transfer charger 11 . Here, as shown in FIG. 2, the image may be transferred once from the electrostatic latent image carrier 1 to the intermediate transfer member 9 and then electrostatically transferred to the recording medium 12 .

After that, the recording medium 12 is conveyed to a fixing device 13 where the toner is fixed on the recording medium 12 by being heated and pressurized. After that, the recording medium 12 is discharged outside the apparatus as an output image. Toner remaining on the electrostatic latent image carrier 1 is removed by a cleaner 15 after the transfer process. After that, the electrostatic latent image carrier 1 cleaned by the cleaner 15 is electrically initialized by light irradiation from the pre-exposure 16, and the above image forming operation is repeated.

FIG. 2 shows an example of a schematic diagram in which the image forming method of the present invention is applied to a full-color image forming apparatus.

Arrows indicating the arrangement of image forming units such as K, Y, C, and M in the drawing and the direction of rotation are not limited to these. K stands for black, Y for yellow, C for cyan, and M for magenta. In FIG. 2, electrostatic latent image carriers 1K, 1Y, 1C and 1M rotate in the direction of the arrows in the figure. Each electrostatic latent image carrier is charged by chargers 2K, 2Y, 2C and 2M, which are charging means. It is exposed by 3Y, 3C and 3M to form an electrostatic latent image. After that, the electrostatic latent image is formed into a toner image by a two-component developer carried on developer carriers 6K, 6Y, 6C, and 6M provided in developing devices 4K, 4Y, 4C, and 4M, which are developing means. visualized. Further, the toner image is transferred onto an intermediate transfer member 9 by intermediate transfer chargers 10K, 10Y, 10C, and 10M, which are transfer means. Further, the image is transferred onto a recording medium 12 by a transfer charger 11, which is a transfer means, and the recording medium 12 is heated and pressure-fixed by a fixing device 13, which is a fixing means, and output as an image. An intermediate transfer member cleaner 14, which is a cleaning member for the intermediate transfer member 9, collects transfer residual toner and the like. Specifically, in the developing method of the present invention, an alternating voltage is applied to the developer carrier to form an alternating electric field in the developing region, and development is performed in a state in which the magnetic brush is in contact with the photosensitive member. is preferred. A distance (SD distance) between the developer bearing member (development sleeve) 6 and the photosensitive drum is preferably 100 to 1000 μm for preventing carrier adhesion and improving dot reproducibility. If it is narrower than 100 μm, the supply of developer tends to be insufficient, resulting in low image density. If it exceeds 1000 μm, the magnetic line of force from the magnetic pole S1 spreads, the density of the magnetic brush becomes low, the dot reproducibility is deteriorated, and the force to bind the magnetic coat carrier is weakened, which tends to cause carrier adhesion.

The peak-to-peak voltage (Vpp) of the alternating electric field is 300-3000V, preferably 500-1800V. The frequency is 500 to 10,000 Hz, preferably 1,000 to 7,000 Hz, which can be appropriately selected depending on the process. In this case, the AC bias waveform for forming the alternating electric field includes a triangular wave, a rectangular wave, a sine wave, or a waveform with a different duty ratio. Sometimes, in order to cope with changes in the toner image forming speed, it is preferable to apply a development bias voltage having a discontinuous AC bias voltage (intermittent alternating voltage) to the developer carrying member for development. . If the applied voltage is lower than 300 V, it may be difficult to obtain a sufficient image density, and the fog toner in the non-image areas may not be recovered satisfactorily. Moreover, when the voltage exceeds 3000 V, the latent image is disturbed via the magnetic brush, and the image quality may be deteriorated.

By using a two-component developer with well-charged toner, the fog removal voltage (Vback) can be lowered, and the primary charging of the photoreceptor can be lowered, thereby extending the life of the photoreceptor. can. Vback is preferably 200 V or less, more preferably 150 V or less, depending on the development system. A contrast potential of 100 to 400 V is preferably used so as to obtain a sufficient image density.

Further, if the frequency is lower than 500 Hz, the structure of the electrostatic latent image-carrying photoreceptor may be the same as that of a photoreceptor normally used in an image forming apparatus, although this affects the process speed. For example, a photoreceptor having a structure in which a conductive layer, an undercoat layer, a charge generation layer, a charge transport layer and, if necessary, a charge injection layer are provided in order on a conductive substrate such as aluminum or SUS.

The conductive layer, undercoat layer, charge generation layer, and charge transport layer may be those commonly used in photoreceptors. As the outermost layer of the photoreceptor, for example, a charge injection layer or a protective layer may be used.

<Toner manufacturing method>
A method for producing toner particles is not particularly limited, but a pulverization method is preferable from the viewpoint of dispersing a releasing agent or a polymer obtained by graft polymerization of a styrene-acrylic polymer to a polyolefin. The reason for this is that when toner particles are produced in an aqueous medium, highly hydrophobic release agents and polymers obtained by graft polymerization of styrene-acrylic polymers to polyolefin tend to be localized inside the toner particles. Therefore, it becomes difficult to form a core-shell structure by the heat treatment apparatus described above.

The procedure for manufacturing toner by the pulverization method will be described below.

In the raw material mixing step, predetermined amounts of other components such as a binder resin, a release agent, a colorant, a crystalline polyester, and, if necessary, a charge control agent are weighed and blended as materials constituting the toner particles. , to mix. Examples of the mixing device include a double-con mixer, a V-type mixer, a drum-type mixer, a super mixer, a Henschel mixer, a Nauta mixer, and a Mechanohybrid (manufactured by Nippon Coke Kogyo Co., Ltd.).

Next, the mixed materials are melt-kneaded to disperse wax and the like in the binder resin. In the melt-kneading process, a batch-type kneader such as a pressure kneader or a Banbury mixer, or a continuous kneader can be used, and single-screw or twin-screw extruders are the mainstream because of their superiority in continuous production. ing. For example, KTK type twin-screw extruder (manufactured by Kobe Steel, Ltd.), TEM type twin-screw extruder (manufactured by Toshiba Machine Co., Ltd.), PCM kneader (manufactured by Ikegai Iron Works), twin-screw extruder (manufactured by K.C.K. ), Co-Kneader (manufactured by Buss Co., Ltd.), Kneedex (manufactured by Nippon Coke Industry Co., Ltd.), and the like. Further, the resin composition obtained by melt-kneading may be rolled with two rolls or the like and cooled with water or the like in the cooling step.

The cooled resin composition is then pulverized to a desired particle size in a pulverization step. In the pulverization step, for example, after coarse pulverization with a pulverizer such as a crusher, hammer mill, or feather mill, further, for example, Kryptron System (manufactured by Kawasaki Heavy Industries, Ltd.), Super Rotor (manufactured by Nisshin Engineering Co., Ltd.), Turbo Mill (manufactured by Turbo Kogyo Co., Ltd.) or a fine pulverizer using an air jet method.

After that, classification such as inertial classification Elbow Jet (manufactured by Nittetsu Mining Co., Ltd.), centrifugal force classification system Turboplex (manufactured by Hosokawa Micron Corporation), TSP Separator (manufactured by Hosokawa Micron Corporation), and Faculty (manufactured by Hosokawa Micron Corporation) as necessary. Classify using a sieving machine or sieving machine.

Thereafter, the toner particles are surface-treated by heating to increase the circularity of the toner. For example, a surface treatment apparatus shown in FIG. 3 can be used to perform surface treatment with hot air.

The mixture supplied by the raw material constant supply means 31 is guided by the compressed gas adjusted by the compressed gas adjustment means 32 to the introduction pipe 33 installed on the vertical line of the raw material supply means. The mixture that has passed through the introduction pipe is uniformly dispersed by a conical protruding member 4 provided in the central portion of the raw material supply means, is led to a supply pipe 35 extending radially in eight directions, and enters the processing chamber where heat treatment is performed. be introduced.

At this time, the flow of the mixture supplied to the processing chamber is regulated by regulation means 39 provided in the processing chamber for regulating the flow of the mixture. Therefore, the mixture supplied to the processing chamber is heat-treated while swirling in the processing chamber, and then cooled.

Hot air for heat-treating the supplied mixture is supplied from the hot air supply means 37, and is helically swirled and introduced into the processing chamber by a swirling member 43 for swirling the hot air. As for the configuration, the swirling member 43 for swirling the hot air has a plurality of blades, and the swirling of the hot air can be controlled by the number and angle of the blades. The hot air supplied into the processing chamber preferably has a temperature of 100 to 300° C. at the outlet of the hot air supply means 37 . If the temperature at the outlet of the hot air supply means is within the above range, it is possible to uniformly spheroidize the toner particles while preventing fusion and coalescence of the toner particles due to excessive heating of the mixture. Become.

Further, the heat-treated toner particles are cooled by cold air supplied from the cold air supply means 38, and the temperature of the air supplied from the cold air supply means 38 is preferably -20 to 30°C. If the temperature of the cold air is within the above range, the heat-treated toner particles can be efficiently cooled, and fusion and coalescence of the heat-treated toner particles can be prevented without impeding the uniform spheroidizing treatment of the mixture. be able to. The absolute water content of cold air is preferably 0.5 to 15.0 g/m ³ .

The cooled, heat-treated toner particles are then collected by collection means 40 at the lower end of the processing chamber. A blower (not shown) is provided at the end of the recovering means, so that the particles are sucked and conveyed.

The powder particle supply port 44 is provided so that the swirling direction of the supplied mixture and the swirling direction of the hot air are the same. It is provided on the outer periphery of the processing chamber so as to maintain the turning direction. Furthermore, the cold air supplied from the cold air supply means 38 is configured to be supplied horizontally and tangentially from the outer peripheral portion of the apparatus to the inner peripheral surface of the processing chamber. The swirling direction of the toner supplied from the powder supply port, the swirling direction of the cool air supplied from the cool air supplying means, and the swirling direction of the hot air supplied from the hot air supplying means are all the same direction. As a result, turbulence does not occur in the processing chamber, the swirling flow in the device is strengthened, and a strong centrifugal force is applied to the toner, which further improves the dispersibility of the toner. can be obtained.

Next, a desired amount of fine silica particles A is externally added to the surface of each of the heat-treated toner particles. As a method for external addition treatment, a mixing device such as a double-con mixer, V-type mixer, drum-type mixer, super mixer, Henschel mixer, Nauta mixer, Mechanohybrid (manufactured by Nippon Coke Industry Co., Ltd.), Nobilta (manufactured by Hosokawa Micron Co., Ltd.), etc. is used as an external addition device to stir and mix. At that time, if necessary, an external additive other than silica fine particles, such as a fluidizing agent, may be externally added.

Next, methods for measuring various physical properties of toner and raw materials will be described below.

<Method for Measuring Weight Average Particle Diameter (D4) and Number Average Particle Diameter (D1) of Toner>
The weight-average particle diameter (D4) and number-average particle diameter (D1) of the toner were measured by a precision particle size distribution measuring device "Coulter Counter Multisizer 3" (registered trademark, Beckman Co., Ltd.) by the pore electrical resistance method equipped with a 100 μm aperture tube. Beckman Coulter Co., Ltd.) and attached dedicated software "Beckman Coulter Multisizer 3 Version 3.51" (Beckman Coulter Co., Ltd.) for setting measurement conditions and analyzing measurement data. Measurement was performed with 25,000 effective measurement channels, and the measurement data was analyzed and calculated.

As the electrolytic aqueous solution used for measurement, a solution obtained by dissolving special grade sodium chloride in ion-exchanged water to a concentration of about 1% by mass, for example, "ISOTON II" (manufactured by Beckman Coulter, Inc.) can be used.

Before performing the measurement and analysis, the dedicated software was set as follows.

In the "change standard measurement method (SOM) screen" of the dedicated software, set the total number of counts in control mode to 50000 particles, set the number of measurements to 1, and set the Kd value to "standard particle 10.0 μm" (Beckman Coulter Co., Ltd. (manufactured) to set the value obtained using By pressing the threshold/noise level measurement button, the threshold and noise level are automatically set. Also, set the current to 1600 μA, the gain to 2, the electrolyte to ISOTON II, and check the flash of aperture tube after measurement.

In the "pulse-to-particle size conversion setting screen" of the dedicated software, set the bin interval to logarithmic particle size, the particle size bin to 256 particle size bins, and the particle size range from 2 μm to 60 μm.

A specific measuring method is as follows.
(1) About 200 ml of the electrolytic aqueous solution is placed in a 250 ml round-bottom glass beaker exclusively for Multisizer 3, set on a sample stand, and stirred with a stirrer rod counterclockwise at 24 rotations/second. Then, use the analysis software's "flush aperture" function to remove dirt and air bubbles inside the aperture tube.
(2) About 30 ml of the electrolytic aqueous solution is placed in a 100 ml flat-bottom glass beaker. As a dispersant, "Contaminon N" (a 10% by mass aqueous solution of a neutral detergent for cleaning precision measuring instruments at pH 7 consisting of a nonionic surfactant, an anionic surfactant, and an organic builder, manufactured by Wako Pure Chemical Industries, Ltd.) was used as a dispersant. ) is diluted with ion-exchanged water to 3 times the mass, and about 0.3 ml of the diluted solution is added.
(3) Two oscillators with an oscillation frequency of 50 kHz are built in with a phase shift of 180 degrees, and placed in a water tank of an ultrasonic disperser with an electrical output of 120 W "Ultrasonic Dispersion System Tetora 150" (manufactured by Nikkaki Bios Co., Ltd.). Add a certain amount of deionized water. About 2 ml of the contaminon N is added to this water bath.
(4) The beaker of (2) is set in the beaker fixing hole of the ultrasonic disperser, and the ultrasonic disperser is operated. Then, the height position of the beaker is adjusted so that the resonance state of the liquid level of the electrolytic aqueous solution in the beaker is maximized.
(5) While the electrolytic aqueous solution in the beaker in (4) above is being irradiated with ultrasonic waves, about 10 mg of toner is added little by little to the electrolytic aqueous solution and dispersed. Then, the ultrasonic dispersion treatment is continued for another 60 seconds. In the ultrasonic dispersion, the temperature of the water in the water bath is appropriately adjusted to 10 to 40°C.
(6) Using a pipette, drop the electrolytic aqueous solution of (5) in which the toner is dispersed into the round-bottomed beaker of (1) set in the sample stand, and adjust the measured concentration to about 5%. . The measurement is continued until the number of measured particles reaches 50,000.
(7) Analyze the measurement data with the dedicated software attached to the apparatus, and calculate the weight average particle size (D4) and the number average particle size (D1). In addition, when the graph/volume% is set with the dedicated software, the "average diameter" on the analysis/volume statistics (arithmetic mean) screen is the weight average particle size (D4), and the graph/number% is set with the dedicated software. The "average diameter" on the analysis/number statistical value (arithmetic mean) screen is the number average particle diameter (D1).

Different types of magnetic core particles (magnetic carrier cores) were prepared as follows.

<Production Example of Magnetic Carrier Core 1 (Porous Magnetic Core Particles)>
Step 1 (weighing and mixing step)
_{Fe2O3 67.5} % by mass
_MnCO3 29.2% by mass
Mg(OH) ₂ 2.0% by mass
_SrCO3 1.3% by mass
The ferrite raw material was weighed, and 20 parts by mass of water was added to 80 parts by mass of the ferrite raw material and pulverized to prepare a slurry. The solid content concentration of the slurry was set to 80% by mass.

Step 2 (temporary firing step)
After drying the obtained slurry with a spray dryer (manufactured by Okawara Kakoki Co., Ltd.), it is fired in a batch type electric furnace under a nitrogen atmosphere (oxygen concentration 1.0% by volume) at a temperature of 1030 ° C. for 3.0 hours. Baked ferrite was produced.

Step 3 (pulverization step)
After crushing the obtained calcined ferrite to about 0.5 mm with a crusher, water was added to prepare a slurry. The solid content concentration of the slurry was set to 70% by mass. The slurry was pulverized for 3 hours with a wet ball mill using stainless steel beads with a diameter of 1/8 inch, and further pulverized for 4 hours with a wet bead mill using zirconia with a diameter of 1 mm, and the 50% volume-based particle diameter (D50) was A 1.3 μm calcined ferrite slurry was obtained.

Step 4 (granulation step)
To the calcined ferrite slurry, 1.0 parts by weight of ammonium polycarboxylate as a dispersant and 1.5 parts by weight of polyvinyl alcohol as a binder are added to 100 parts by weight of calcined ferrite. company) to form spherical particles and dried. After adjusting the particle size of the obtained granules, they were heated at 750° C. for 2 hours using a rotary electric furnace to remove organic substances such as dispersants and binders.

Step 5 (Baking step)
In a nitrogen atmosphere (oxygen concentration of 1.0% by volume), the time from room temperature to the firing temperature (1100° C.) was set to 2 hours, and the temperature was kept at 1100° C. for 4 hours and fired. After that, the temperature was lowered to 60° C. over 8 hours, the nitrogen atmosphere was returned to the air, and the temperature was 40° C. or less and taken out.

Step 6 (sorting step)
After crushing the aggregated particles, sieving with a sieve with an opening of 150 μm to remove coarse particles, air classification to remove fine powder, and magnetic separation to remove low magnetic force components to remove ferritic core particles. got The obtained ferritic core particles were porous and had pores.

Step 7 (filling step)
100 parts by mass of the obtained ferritic core particles are placed in a stirring vessel of a mixing stirrer (universal stirrer NDMV type manufactured by Dalton), the temperature is maintained at 60° C., and nitrogen is introduced while reducing the pressure to 2.3 kPa. bottom. Then, 50 parts by mass of methylphenyl silicone resin and 50 parts by mass of toluene were mixed with a multi-blender mixer for 10 minutes, and the resulting mixture was added dropwise to the ferritic core particles. The dropping amount was adjusted so that the solid content of the resin component was 5.0 parts by mass with respect to 100 parts by mass of the ferritic core particles.

After the dropping was completed, stirring was continued for 2.5 hours, the temperature was raised to 70° C., the solvent was removed under reduced pressure, and the resin composition was filled into the ferritic core particles.

After cooling, the obtained ferrite-based core particles were placed in a rotatable mixing vessel and transferred to a mixer with spiral blades (Drum Mixer UD-AT manufactured by Sugiyama Heavy Industries Co., Ltd.), and heated at 2° C./ The set temperature of the stirrer was raised to 220° C. at a heating rate of 100 minutes. Heating and stirring were performed at this temperature for 1.0 hour to cure the resin, and the stirring was continued while maintaining the temperature at 200° C. for another 1.0 hour.

After cooling to room temperature, the resin-filled and hardened ferritic core particles were taken out, and non-magnetic substances were removed using a magnetic separator. Furthermore, a magnetic carrier core 1 filled with resin was obtained by removing coarse particles with a vibrating sieve. The 50% particle diameter (D50) based on volume distribution of the magnetic carrier core 1 was 37.7 μm. Table 1 shows the physical properties of the magnetic carrier core 1 thus obtained.

<Production Example of Magnetic Carrier Core 2 (Ferrite Core Particle)>
Step 1 (weighing/mixing step)
_{Fe2O3 61.7} % by mass
_MnCO3 34.2% by mass
Mg(OH) ₂ 3.0% by mass
_SrCO3 1.1% by mass
The ferrite raw material was weighed so that

After that, it was pulverized and mixed for 2 hours in a dry ball mill using zirconia (φ10 mm) balls.

Step 2 (temporary firing step)
After pulverizing and mixing, the powder was fired in the atmosphere at 1000° C. for 2 hours using a burner type firing furnace to prepare calcined ferrite. The composition of ferrite is as follows.
( _MnO )a(MgO)b(SrO)c( _Fe2O3 )d
In the above formula, a = 0.40, b = 0.07, c = 0.01, d = 0.52
Step 3 (pulverization step)
After pulverizing to about 0.5 mm with a crusher, 30 parts by mass of water was added to 100 parts by mass of calcined ferrite using stainless balls (φ10 mm), and pulverized with a wet ball mill for 2 hours. After the balls were separated, they were pulverized in a wet bead mill for 3 hours using stainless steel balls (φ10 mm) to obtain a ferrite slurry.

Step 4 (granulation step)
To the ferrite slurry, 1.5 parts by mass of polyvinyl alcohol was added as a binder to 100 parts by mass of calcined ferrite, and the mixture was granulated into spherical particles of 36 μm with a spray dryer (manufacturer: Ogawara Kakoki).

Step 5 (main firing step)
In order to control the firing atmosphere, firing was performed at 1200° C. for 6 hours in an electric furnace under a nitrogen atmosphere (oxygen concentration of 0.6% by volume).

Step 6 (sorting step)
After the agglomerated particles were pulverized, the particles were sieved through a sieve with an opening of 250 μm to remove coarse particles, and a magnetic carrier core 2 was obtained. Table 1 shows the physical properties of the obtained magnetic carrier core 2 .

<Preparation of magnetic particles A>
26.7 L of an aqueous solution of ferrous sulfate containing 1.5 mol/L of Fe ²⁺ and silicic acid containing 0.2 mol/L of Si ⁴⁺ while passing nitrogen gas through a reaction vessel having a gas inlet pipe at 20 L/min. 1.0 L of Soda No. 3 aqueous solution was added to 22.3 L of 3.4 mol/L sodium hydroxide aqueous solution, and the pH was raised to 6.8 and the temperature was raised to 90°C. Add another 1.2 L of 3.5 mol/L aqueous sodium hydroxide solution to adjust the pH to 8.5, continue to stir, change the gas to air, and aerate at 100 L/min for 90 minutes. Using dilute sulfuric acid, neutralization was carried out to pH 7, and the produced particles were washed with water, filtered, dried and pulverized to obtain magnetic particles A having a number average particle diameter of 0.30 μm.

The obtained magnetic particles A and a silane-based coupling agent (3-glycidoxypropylmethyldimethoxysilane) (1.2 parts by mass per 100 parts by mass of the magnetite fine particles) were introduced into a container. Then, the magnetic particles A were surface-treated by high-speed mixing and stirring at 100° C. for 1 hour in the vessel.

<Preparation of magnetic particles B>
Magnetic particles A and 1.2 parts by mass of a silane-based coupling agent (3-(2-aminoethylamino)propyltrimethoxysilane) per 100 parts by mass of spherical hematite particles having a number average particle diameter of 0.40 μm. Surface treated in the same way.

<Production Example of Magnetic Carrier Core 3 (Magnetic Material Dispersed Resin Core Particles)>
Phenol 10.0 parts by mass Formaldehyde solution (37% by mass formaldehyde aqueous solution) 15.0 parts by mass Surface-treated magnetic particles A 90.0 parts by mass Surface-treated magnetic particles B 10.0 parts by mass 25 Mass % aqueous ammonia 3.5 parts by mass Water 15.0 parts by mass

The above materials were introduced into the reaction kettle and brought to a temperature of 40° C. and mixed well. Thereafter, the mixture was heated to a temperature of 85° C. at an average heating rate of 1.5° C./min while stirring, maintained at a temperature of 85° C., and polymerized for 3 hours for curing. The peripheral speed of the stirring blade at this time was 1.96 m/sec.

After the polymerization reaction, the temperature was cooled to 30° C. and water was added. The precipitate obtained by removing the supernatant was washed with water and air-dried. The resulting air-dried product was dried at 180° C. for 5 hours under reduced pressure (5 mmHg or less) to obtain magnetic carrier cores 3, which are magnetic material-dispersed resin particles. Table 1 shows the physical properties of the obtained magnetic carrier core 3 .

<Production Examples of Resins A-1 to A-22 and A-24>
Add an acrylic monomer corresponding to the repeating units shown in Tables 2-1 to 2-4 in the parts by mass shown in Table 2, and a reflux condenser, a thermometer, a nitrogen suction pipe, and a four-necked stirrer equipped with a grind-type stirrer. added to the flask. Further, 100 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.0 parts by mass of azobisisovaleronitrile were added. The obtained mixture was kept at 75° C. for 10 hours under nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain resins A-1 to A-22 and A-24 (solid content: 30 mass %).

<Production Example of Resin A-23>
Resin A-23 was obtained by stirring 100 parts by mass of monomers corresponding to repeating units shown in Tables 2-3 to 2-4, 90 parts by mass of toluene, and 4 parts by mass of tetraisopropyl titanate in a multi-blender mixer for 10 minutes. .

<Production Examples of Resins B-1 to B-13, B-16, B-18, and B-19>
An acrylic monomer corresponding to the repeating units shown in Tables 3-1 to 3-3 is added in the parts by mass shown in Table 3, and a reflux condenser, a thermometer, a nitrogen suction pipe, and a four-necked stirrer equipped with a grind-type stirrer. added to the flask. Further, 100 parts by mass of toluene, 100 parts by mass of methyl ethyl ketone, and 2.0 parts by mass of azobisisovaleronitrile were added. The resulting mixture was held at 75° C. for 10 hours under a nitrogen stream, and after completion of the polymerization reaction, washing was repeated to obtain resins B-1 to B-13, B-16, B-18, and B-19 (solid content: 30 mass %) was obtained.

<Production Examples of Resins B-14, B-15, and B-17>
100 parts by mass of monomers corresponding to the repeating units shown in Tables 3-1 to 3-2, 90 parts by mass of toluene, and 4 parts by mass of tetraisopropyl titanate were stirred for 10 minutes in a multi-blender mixer Resins B-14 and B-15 , B-17.

<Manufacturing Example of Magnetic Carrier 1>
Resin A-1 50 parts by mass (solid content)
Resin B-1 50 parts by mass (solid content)
Triglycidyl isocyanate (crosslinking agent) 5 parts by mass Toluene 400 parts by mass The above materials were mixed and stirred for 10 minutes in a multi-blender mixer to prepare a resin solution.

Next, under reduced pressure (1.5 kPa), a planetary motion mixer (Nauta Mixer VN type manufactured by Hosokawa Micron Corporation) maintained at a temperature of 60° C. is added to 100 parts by mass of the magnetic carrier core 1 to solidify the resin component. The resin solution was added so as to be 2.2 parts by mass per minute. Solvent removal and application were performed at a temperature of 100° C. for 50 minutes after charging.

Thereafter, the magnetic carrier coated with the coating resin composition was placed in a rotatable mixing container and transferred to a mixer having spiral blades (Drum Mixer UD-AT manufactured by Sugiyama Heavy Industries, Ltd.). Heat treatment was performed at a temperature of 120° C. for 2 hours in a nitrogen atmosphere while the mixing vessel was rotated 10 times per minute and stirred. The obtained magnetic carrier particles were separated into low magnetic particles by magnetic separation, passed through a sieve with an opening of 150 μm, and then classified by an air classifier to obtain a magnetic carrier 1 .

<Manufacturing Examples of Magnetic Carriers 2 to 26>
Magnetic carrier 1 above except that the types of magnetic carrier core, resin A, resin B and cross-linking agent, the ratio of resin A and resin B, and the amount of coating resin are changed as described in Tables 4-1 and 4-2. Magnetic carriers 2 to 19, 22, 24 and 26 were obtained in the same manner as in the production example of .

Further, magnetic carriers 20, 21, 23 and 25 were obtained in the same manner as in the manufacturing example of magnetic carrier 1 except that they were heat-treated at a temperature of 180° C. for 3 hours in a nitrogen atmosphere using a mixer having spiral blades.

<Production Example of Toner 1>
・Polyester resin 100 parts by mass ・Fischer-Tropsch wax (maximum endothermic peak peak temperature 90°C)
4 parts by mass · 3,5-di-t-butylsalicylic acid aluminum compound (Bontron E88 manufactured by Orient Chemical Industry Co., Ltd.) 0.1 part by mass · C.I. I. Pigment Blue 15:3 4.5 parts by mass The above materials were mixed using a Henschel mixer (FM-75 type, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 1500 rpm and a rotation time of 5 minutes, and then the temperature was set to 130 ° C. The mixture was kneaded with a twin-screw kneader (Model PCM-30, manufactured by Ikegai Co., Ltd.). The resulting kneaded product was cooled and coarsely pulverized to 1 mm or less with a hammer mill to obtain a coarsely pulverized product. The coarsely crushed product obtained was finely pulverized with a mechanical pulverizer (T-250, manufactured by Turbo Kogyo Co., Ltd.). Further, classification was performed using Faculty (F-300, manufactured by Hosokawa Micron Corporation) at a classification rotor rotation speed of 11000 rpm and a dispersion rotor rotation speed of 7200 rpm to obtain toner base particles 1 .
・Toner base particles 1 100 parts by mass ・Silica fine particles A (number average particle diameter (D1) is 120 nm) 2.0 parts by mass

The above materials are mixed using a Henschel mixer (FM-10C model, manufactured by Mitsui Mining Co., Ltd.) at a rotation speed of 1900 rpm for a rotation time of 3 minutes, and then heat-treated by the surface treatment apparatus shown in FIG. Obtained. The operating conditions were feed rate = 5 kg/hr, hot air temperature = 160°C, hot air flow rate = 6 m ³ /min, cold air temperature = -5°C, cold air flow rate = 4 m ³ /min, blower air flow rate = 20 m ³ /min, injection air. The flow rate was set at 1 m ³ /min.

The heat-treated toner particles thus obtained were classified using an inertial classification type elbow jet (manufactured by Nittetsu Mining Co., Ltd.).
・Heat-treated toner particles 1 100 parts by mass ・Silica fine particles B (number average particle diameter (D1) is 20 nm) 0.6 parts by mass The above materials are rotated in a Henschel mixer (FM-75 model, manufactured by Mitsui Miike Kakoki Co., Ltd.). Mixing was carried out at several 1900 rpm for a rotation time of 3 minutes to obtain Toner 1 (weight average particle diameter 6.0 μm).

[Example 1]
9 parts by mass of toner 1 was added to 91 parts by mass of magnetic carrier 1, and the mixture was shaken with a shaker (YS-8D type: manufactured by Yayoi Co., Ltd.) to prepare 320 g of two-component developer 1. . The amplitude condition of the shaker was 150 rpm for 2 minutes.

On the other hand, 90 parts by mass of toner 1 was added to 10 parts by mass of magnetic carrier 1, and mixed for 5 minutes with a V-type mixer in an environment of normal temperature and humidity of 23° C. and 50% RH to obtain replenishing developer 1. rice field.

[Examples 2 to 20, Comparative Examples 1 to 6]
Two-component developers 2 to 26 and replenishment developers 2 to 26 were prepared in the same manner as in Example 1 except that magnetic carriers 2 to 26 were used.

〔evaluation〕
Using the prepared two-component developer and replenishment developer, the following evaluations were carried out. Evaluation results are shown in Table 5.

A modified imagePRESS C800 (manufactured by Canon) was used as the image forming apparatus. As modifications, the DC voltage VDC of the developer carrier, the charging voltage VD of the electrostatic latent image carrier, the laser power, and the total amount of discharge current of the charger were changed so that they could be freely set.

In the image output evaluation, an FFH image (solid image) with a desired image ratio is output, and the VDC, VD, and laser power are adjusted so that the toner amount of the FFH image is desired, and the evaluation described later is performed. rice field. FFH is a value representing 256 gradations in hexadecimal, 00H is the 1st gradation (white background portion) of 256 gradations, and FFH is the 256th gradation (solid portion) of 256 gradations. .

The process speed was set to 357 mm/s, and the total discharge current of the charger was set to 100 μA. CS-680 (68.0 g/m ² ) (available from Canon Marketing Japan Inc.) was used for the evaluation.

[Evaluation X: Image density in-plane stability after long-term use]
Ten sheets of "96H output chart (A4 full-surface halftone image) X1 with an image ratio of 100%" were output at 32° C. and a humidity of 80% RH (hereinafter referred to as H/H environment).

Next, in the same environment (H/H environment), 10,000 charts with an image area ratio of 30% FFH output were output per day, and a total of 600,000 charts were output for 60 days.

After that, it was left in the same environment for 24 hours, and after leaving, 10 sheets of "96H output chart (A4 full-surface halftone image X2) with an image ratio of 100%" were output.

For the obtained image, the following 12 image densities were measured using a spectral densitometer 500 series (manufactured by X-Rite).
Three points of 5.0 cm, 15.0 cm, and 25.0 cm from the left edge of the image (the side printed first) at a position 0.5 cm from the tip of the image (the side printed first);
Three points, 7.0 cm from the tip of the image and 5.0 cm, 15.0 cm, and 25.0 cm from the left end of the image;
Three points at 14.0 cm from the tip of the image and 5.0 cm, 15.0 cm, and 25.0 cm from the left end of the image;
Three points, 20.0 cm from the tip of the image and 5.0 cm, 15.0 cm, and 25.0 cm from the left edge of the image.

The difference between the average value of the image density of X1 and the average value of the image density of X2 was obtained. Evaluation criteria are as follows.

A (10 points): less than 0.040 B (9 points): 0.040 or more and less than 0.050 C (8 points): 0.050 or more and less than 0.060 D (7 points): 0.060 or more and 0.060 Less than 070 E (6 points): 0.070 or more and less than 0.080 F (5 points): 0.080 or more and less than 0.090 G (4 points): 0.090 or more and less than 0.100 H (3 points): 0.100 or more and less than 0.110 I (2 points): 0.110 or more and less than 0.120 J (1 point): 0.120 or more In the evaluation X, 7 points or more was taken as a passing score.

[Evaluation Y: Carrier coat stability after long-term use]
An FFH image with a size of 50 mm×50 mm was output at the center of the paper at 23° C. and 50% RH (hereinafter referred to as N/N environment). At this time, Vi (V) was defined as the development contrast when the amount of toner laid on paper was 0.35 mg/cm ² .

Next, 20,000 sheets of a chart with an image area ratio of 2% FFH output were output per day in an N/N environment, and a total of 1,200,000 sheets were output for 60 days.

Left in an N/N environment for 24 hours. After leaving in the same environment, an FFH image of 50 mm x 50 mm was output to the center of the paper, and developed when the amount of toner on the paper was 0.35 mg/cm ² . The contrast was set to Vf(V).

The difference in development contrast (absolute value of Vi-Vf) was calculated and evaluated according to the following criteria. The results are shown in the table.

A (10 points): less than 30 V B (9 points): 30 V or more and less than 35 V C (8 points): 35 V or more and less than 40 V D (7 points): 40 V or more and less than 45 V E (6 points): 45 V or more and less than 50 V F ( 5 points): 50 V or more and less than 55 V G (4 points): 55 V or more and less than 60 V H (3 points): 60 V or more and less than 65 V I (2 points): 65 V or more In the evaluation Y, 6 points or more were accepted.

[Evaluation Z: Temporal stability of carrier stored in harsh environment]
Ten sheets of "96H output chart (A4 full-surface halftone image Z1) with an image ratio of 100%" were output in an N/N environment.

Separately, a magnetic carrier stored in a container for 60 days at 40° C., 95% RH, and a load of 100 N/cm ² (container area: 100 cm ² ) was prepared. 9 parts by mass of toner 1 was added to 91 parts by mass of the magnetic carrier, and the mixture was shaken with a shaker (YS-8D type: manufactured by Yayoi Co., Ltd.) to prepare 320 g of two-component developer 1R.

Using the two-component developer 1R, 10 sheets of "96H output chart (A4 full-surface halftone image Z2) with an image ratio of 100%" were output in an N/N environment.

The measurement site was the same position as the evaluation X, and the difference between the average value of the image density of Z1 and the average value of the image density of Z2 was obtained. Evaluation criteria are as follows.

A (10 points): less than 0.030 B (9 points): 0.030 or more and less than 0.040 C (8 points): 0.040 or more and less than 0.050 D (7 points): 0.050 or more and 0.050 Less than 060 E (6 points): 0.060 or more and less than 0.070 F (5 points): 0.070 or more and less than 0.080 G (4 points): 0.080 or more and less than 0.090 H (3 points): 0.090 or more and less than 0.100 I (2 points): 0.100 or more and less than 0.110 J (1 point): 0.110 or more In the evaluation Z, 8 points or more were taken as a passing score.

Claims (9)

A magnetic carrier having a magnetic core particle and a coating resin layer coating the surface of the magnetic core particle,
The coating resin layer contains a crosslinked resin,
The crosslinked resin is
A partial structure represented by the following formula (1), a partial structure represented by the following formula (2) having a reactive functional group A, and a partial structure represented by the following formula (3) or the following formula ( 4) a first molecular chain having a partial structure represented by
a second molecular chain having a reactive functional group B;
is a resin formed by a cross-linking reaction,
In the crosslinked resin, the first molecular chain and the second molecular chains are bound together,
When the first molecular chain has a partial structure represented by the following formula (3), the SP value of the portion represented by the following formula (5) is SPa2, and the following formula (5) in the crosslinked resin SPa1 is the SP value of the part other than the part represented,
When the first molecular chain has a partial structure represented by the following formula (4), the SP value of the portion represented by the following formula (6) is SPa2, and the following formula (6) in the crosslinked resin When the SP value of the part other than the part represented is SPa1,
The SPa1 and the SPa2 are
0.5≦SPa1−SPa2≦7.0
A magnetic carrier characterized by satisfying

(In the above formula (1),
R ¹ represents H or CH ₃ ,
X represents a phenyl group or COOR ² ,
R ² represents an alicyclic hydrocarbon group having 3 to 12 carbon atoms or a chain alkyl group having 1 to 8 carbon atoms. )

(in the above formula (2),
R ¹ represents H or CH ₃ ,
Z ¹ represents a reactive functional group A having 1-8 carbon atoms. )

(In the above formula (3),
^R3 represents H or _CH3 ,
Y ¹ represents -COO- or -O-,
R ⁴ represents a single bond or a hydrocarbon group having 1 to 10 carbon atoms,
R ⁵ represents a hydrocarbon group having 1 to 10 carbon atoms,
R ⁶ represents CH ₃ or Si(CH ₃ ) ₃ ,
n represents an integer of 5 or more and 50 or less. )

(in the above formula (4),
^R3 represents H or _CH3 ,
Y ² represents -COO- or -O-,
R ⁷ represents a single bond or a hydrocarbon group having 2 to 10 carbon atoms,
R ⁸ represents an alkyl group having 8 to 20 carbon atoms, in which at least part of the hydrogen atoms are substituted with fluorine atoms, and part of the remaining hydrogen atoms are halogen atoms other than fluorine atoms and the proportion of fluorine atoms is 5.0 atomic % or more based on the total number of hydrogen atoms, fluorine atoms and halogen atoms other than fluorine atoms contained in the alkyl group, and fluorine The proportion of halogen atoms other than atoms is 40.0 atomic % or less. )

(In the above formula (5),
Y ¹ represents -COO- or -O-,
R ⁴ represents a single bond or a hydrocarbon group having 1 to 10 carbon atoms,
R ⁵ represents a hydrocarbon group having 1 to 10 carbon atoms,
R ⁶ represents CH ₃ or Si(CH ₃ ) ₃ ,
n represents an integer of 5 or more and 50 or less)
—Y ² —R ⁷ —R ⁸ Formula (6)
(In the above formula (6),
Y ² represents -COO- or -O-,
R ⁷ represents a single bond or a hydrocarbon group having 2 to 10 carbon atoms,
R ⁸ represents an alkyl group having 8 to 20 carbon atoms, in which at least part of the hydrogen atoms are substituted with fluorine atoms, and part of the remaining hydrogen atoms are halogen atoms other than fluorine atoms and the proportion of fluorine atoms is 5.0 atomic % or more based on the total number of hydrogen atoms, fluorine atoms and halogen atoms other than fluorine atoms contained in the alkyl group, and fluorine The proportion of halogen atoms other than atoms is 40.0 atomic % or less. ) 2. The magnetic carrier according to claim 1, wherein the second molecular chain has a partial structure represented by the following formula (1) and a partial structure represented by the following formula (7).

(In the above formula (1),
R ¹ represents H or CH ₃ ,
X represents a phenyl group or COOR ² ,
R ² represents an alicyclic hydrocarbon group having 3 to 12 carbon atoms or a chain alkyl group having 1 to 8 carbon atoms. )

(in the above formula (7),
R ¹ represents H or CH ₃ ,
Z ² represents a reactive functional group B having 1 to 8 carbon atoms) 3. The magnetic carrier according to claim 2, wherein the second molecular chain further has a partial structure represented by the following formula (3) or a partial structure represented by the following formula (4).

(In the above formula (3),
^R3 represents H or _CH3 ,
Y ¹ represents -COO- or -O-,
R ⁴ represents a single bond or a hydrocarbon group having 1 to 10 carbon atoms,
R ⁵ represents a hydrocarbon group having 1 to 10 carbon atoms,
R ⁶ represents CH ₃ or Si(CH ₃ ) ₃ ,
n represents an integer of 5 or more and 50 or less)

(in the above formula (4),
^R3 represents H or _CH3 ,
Y ² represents -COO- or -O-,
R ⁷ represents a single bond or a hydrocarbon group having 2 to 10 carbon atoms,
R ⁸ represents an alkyl group having 8 to 20 carbon atoms, in which at least part of the hydrogen atoms are substituted with fluorine atoms, and part of the remaining hydrogen atoms are halogen atoms other than fluorine atoms and the proportion of fluorine atoms is 5.0 atomic % or more based on the total number of hydrogen atoms, fluorine atoms and halogen atoms other than fluorine atoms contained in the alkyl group, and fluorine The proportion of halogen atoms other than atoms is 40.0 atomic % or less. ) In the cross-linked resin, the first molecular chain and the second molecular chain are bonded by a bond formed by reacting the reactive functional group A and the reactive functional group B via a cross-linking agent. The magnetic carrier according to any one of claims 1 to 3. In the crosslinked resin, the first molecular chain and the second molecular chain are bonded by a bond formed by the reaction of the reactive functional group A and the reactive functional group B without a cross-linking agent. The magnetic carrier according to any one of claims 1 to 3, which is bonded. The SPa1 and the SPa2 are
1.5≦SPa1−SPa2≦6.0
The magnetic carrier according to any one of claims 1 to 5, satisfying: The crosslinked resin is based on the crosslinked resin,
(i) when the first molecular chain has a partial structure represented by the following formula (3), the content of the portion represented by the following formula (5) is 1 to 50% by mass;
(ii) when the first molecular chain has a partial structure represented by the following formula (4), the content of the portion represented by the following formula (6) is 1 to 50% by mass;
The magnetic carrier according to any one of claims 1-6. The magnetic carrier according to any one of claims 1 to 7, wherein the total amount of the crosslinked resin is 0.5 to 5.0 parts by mass with respect to 100 parts by mass of the magnetic core particles. A two-component developer containing the magnetic carrier according to any one of claims 1 to 8 and a toner.

Images