JPH10104885A - Carrier for developing electrostatic latent image, its production, electrostatic latent image developer and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain low resistance of a coated carrier and to form an image excellent in halftone reproducibility by grafting functional groups of inorg. fine particles to a resin by chemical bond. SOLUTION: This carrier has a coating layer contg. a resin and inorg. fine particles. The core material of this carrier is, e.g. powder of a magnetic metal such as iron or steel or a magnetic oxide such as ferrite or magnetite or glass beads. Functional groups on the surfaces of the inorg. fine particles have been chemically bonded to the terminal functional groups of the resin by graft reaction. The resin is, e.g. polyolefin resin such as PE or PP and the wt. average mol.wt. of the resin is >=5,000, preferably >=7,000. Inorg. fine particles surface- treated by the graft reaction are contained by 10-60wt.% of all the inorg. fine particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic latent image developing carrier used for developing an electrostatic latent image in electrophotography and electrostatic recording, a method for producing the same, and an electrostatic latent image developer. And an image forming method.

[0002]

2. Description of the Related Art Conventionally, in electrophotography, an electrostatic latent image is formed on a photosensitive member or an electrostatic recording member by using various means,
A method is generally employed in which electrostatic fine particles called toner are attached to the electrostatic latent image to develop the electrostatic latent image. In this development, carrier particles, called carriers, are mixed with toner particles and both are triboelectrically charged to impart an appropriate amount of positive or negative charge to the toner. Carriers are generally classified into a coated carrier having a coating layer on the surface and a non-coated carrier having no coating layer on the surface, but in consideration of the life of the developer, the coated carrier is superior. Therefore, various types of coated carriers have been developed and put into practical use.

There are various characteristics required for the coated carrier, but it is necessary to impart appropriate chargeability (charge amount and charge distribution) to the toner and to maintain the appropriate chargeability for a long period of time. For this purpose, it is important that the chargeability of the toner is not changed in response to environmental changes such as impact resistance, friction resistance, and humidity and temperature of the carrier.

Accordingly, nitrogen-containing fluorinated alkyl (meth)
By coating a copolymer of an acrylate and a vinyl monomer or a copolymer of a fluorinated alkyl (meth) acrylate and a nitrogen-containing vinyl monomer on the surface of a carrier core material, a relatively long-life coated carrier is obtained. (JP-A-61-80161, JP-A-61-80161)
80162, JP-A-61-80163).

[0005] Also, a polyamide resin is disclosed in JP-A-1-118150, and a melamine resin is coated on the surface of a carrier core material in JP-A-2-79862.
It has been proposed to obtain a coating carrier with a relatively hard coating. However, these carriers cannot completely prevent the toner component from adhering to and contaminating the carrier surface,
Not satisfactory.

In order to prevent such spent,
It is preferable to use a silicone resin (see JP-A-60-186844) or a fluorine-based resin (see JP-A-64-13560).

On the other hand, the carrier is insulated with the resin film, and the function as a developing electrode is degraded at the time of development, so that solid reproducibility is inferior, for example, an edge effect appears particularly in a solid black portion. In particular, when the subject is a halftone image such as a photograph, an image having extremely poor reproducibility is obtained.

For this reason, a carrier in which a conductive material is dispersed in a coat film has been proposed for the purpose of improving the reproducibility of a solid (JP-A-1-101560 and JP-A-1-105264).

However, the electrical resistance of this coated carrier is
It depends on the probability of contact between the conductive materials dispersed in the coat film, but the dispersion control of the conductive material is unstable, and since there is an isolated conductive material, the dispersion amount of the conductive material is Not enough effect.

In order to improve such instability of dispersion control, there has been proposed a carrier in which fine resin particles having carbon black fixed thereon are coated by a dry coating method (see Japanese Patent Application Laid-Open No. Hei 2-13969). However,
Since the interaction between the binder resin and the conductive material that make up the coat film is weak, the impact strength of the film generally tends to decrease, and the film is scraped off by friction and peeled off from the carrier core, and the toner is appropriately charged. Property (charge amount and charge distribution) cannot be provided, and the charge providing ability cannot be maintained for a long period of time.

Further, a carrier has been proposed in which the surface of carbon black is treated with a silane coupling agent to suppress the shaving of the coating layer (JP-A-62-18275).
No. 9). However, even if the surface of the coupling agent is treated with a low-molecular-weight substance such as a silane coupling agent, the silane coupling agent bonded to the surface functional group and the self-condensate of the silane coupling agent may become entangled in the molecular chain. Since the number of molecular chains having a high degree of freedom to contribute is smaller than that of the resin, the effect of improving the cohesive force cannot be sufficiently obtained.

[0012]

Therefore, in the present invention,
To solve the above problems, to provide a carrier for developing an electrostatic latent image capable of forming an image with excellent halftone reproducibility while maintaining the resistance of a film carrier low, and to provide an image forming method. Is what you do. Further, the present invention is to uniformly disperse the conductive material in the carrier coating layer, increase the cohesive force to the carrier core, improve the impact strength, and maintain a stable charging ability for a long time. An object of the present invention is to provide a carrier for developing an electrostatic latent image. Another object of the present invention is to provide a method for easily producing a carrier for developing an electrostatic latent image having the above characteristics.

[0013]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the carrier for developing an electrostatic latent image, and as a result of study, have succeeded in solving the above-mentioned problems by adopting the following constitution. (1) An electrostatic latent image developing carrier having a coating layer containing a resin and inorganic fine particles, wherein the functional group of the inorganic fine particles and the resin are grafted by a chemical bond. Development carrier. (2) The carrier for developing an electrostatic latent image according to the above (1), wherein the inorganic fine particles are carbon black.

(3) The carrier for developing an electrostatic latent image as described in (1) above, wherein the resin for surface treatment of the inorganic fine particles has a weight average molecular weight of 5,000 or more. (4) The carrier for developing an electrostatic latent image according to the above (1), wherein the resin for surface treatment of the inorganic fine particles is a resin having a critical surface tension of 35 dyn / cm or less.

(5) The carrier for developing an electrostatic latent image according to the above (1), wherein the resin for surface treatment of the inorganic fine particles is a fluorine resin or a silicone resin. (6) The carrier for developing an electrostatic latent image according to (1), wherein the resin for surface treatment of the inorganic fine particles is a nitrogen-containing resin.

(7) A method for producing a carrier for developing an electrostatic latent image provided with a coating layer containing a resin and inorganic fine particles,
The functional group of the inorganic fine particles and the resin are grafted by a chemical bond, the grafted inorganic fine particles and a core material are mixed in a dry system, and then the resin is melted to form a film. The method for producing a carrier for developing an electrostatic latent image according to any one of the above (1) to (6). (8) The method for producing a carrier for developing an electrostatic latent image according to (7), wherein the resin has a glass transition temperature of 120 ° C. or lower.

(9) An electrostatic latent image developer comprising a carrier and a toner having a binder resin and a colorant, wherein the carrier is any one of the above (1) to (6). An electrostatic latent image developer, which is a developing carrier.

(10) forming a latent image on the latent image carrier;
Developing the latent image using a developer, transferring the developed toner image onto a transfer member, and heating and fixing the toner image on the transfer member. An image forming method using the developer according to the above (9) as an agent.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION As the metal powder or carrier core material used in the present invention, iron, steel, nickel,
Examples thereof include magnetic metals such as cobalt, magnetic oxides such as ferrite and magnetite, and glass beads. From the viewpoint of using a magnetic brush method, a magnetic carrier is preferable. The metal powder used for the magnetic material-dispersed carrier preferably has an average particle size in the range of 0.05 to 1 μm, and more preferably 0.1 to 0.6 μm. The average particle size of the carrier core material is 10 to 500 μm.
The range of m is preferably 30 to 150 μm.

In the present invention, the chemical bond between the surface functional group of the inorganic fine particles and the terminal functional group of the resin is based on a graft reaction. There are various types of graft reactions to the inorganic fine particles, and specifically, there are the following three methods. (1) In the presence of inorganic fine particles, the polymerization of a vinyl monomer is carried out using a polymerization initiator, and the terminal functional group of the growing polymer generated in the system is terminated with a functional group on the surface of the inorganic fine particles. Of treating with a growing polymer. (2) A method in which a graft chain is grown from a polymerization initiating group introduced to the surface of the inorganic fine particles, and the surface of the inorganic fine particles is treated with a polymer. (3) A method in which the surface of the inorganic fine particles is treated with a polymer by a polymer reaction between the functional group on the surface of the inorganic fine particles and the functional group at the terminal of the polymer.

As the polymerization initiator, an azo polymerization initiator,
Peroxide-based polymerization initiator, n-butyl lithium (n-Bu
An alkyl alkali metal salt such as Li) is used. n
When the surface of carbon black is treated with a resin using -BuLi, n-BuLi extracts hydrogen on the surface of carbon black, and (carbon black) -OL
i, (carbon black)> C- (OLi) (Bu),
(Carbon black) -COOLi, (carbon black) -C- (OLi) ₂ (Bu) and the like are formed and bonded to the surface treatment resin by a graft reaction.

Examples of the resin to be grafted to the surface of the inorganic fine particles by a chemical bond include polyolefin resins such as polyethylene and polypropylene; polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, and polyvinyl chloride. Polyvinyl or polyvinylidene resins such as ethers and polyvinyl ketones; vinyl chloride / vinyl acetate copolymers; styrene / acrylic acid copolymers; straight silicone resins comprising organosiloxane bonds or modified products thereof; fluororesins such as polytetra Fluoroethylene, polyvinyl fluoride,
Polyvinylidene fluoride, polychlorotrifluoroethylene; polyester; polyurethane; polycarbonate;
Phenol resins; amino resins, for example, urea / formaldehyde resins, melamine resins, benzoguanamine resins, urea resins, polyamide resins; epoxy resins; and other known resins can also be used.

The resin to be grafted to the surface of the inorganic fine particles by chemical bonding has a weight average molecular weight of 5,000 or more, preferably 7000 or more. If it is less than 5,000, it is not possible to secure a sufficient cohesive force between the grafted inorganic fine particles and the coating resin. The preferred upper limit of the weight average molecular weight is 500,000.

The carrier for developing an electrostatic latent image of the present invention preferably uses a resin having a critical surface tension of 35 dyn / cm or less in order to suppress contamination of the surface.
More preferably, it is 0 dyn / cm or less. An example of a resin having a critical surface tension of 35 dyn / cm or less that gives a low surface energy is as follows. Polystyrene (γc = 33 dyn / cm), polyethylene (γc = 3
1 dyn / cm), polyvinyl fluoride (γc = 28 dy)
n / cm), polyvinylidene fluoride (γc = 25 dyn)
/ Cm), polytrifluoroethylene (γc = 22 dy)
n / cm), polytetrafluoroethylene (γc = 18
dyn / cm), polyhexafluoropropylene (γc
= 16 dyn / cm), a copolymer of vinylidene fluoride and an acrylic monomer, a copolymer of vinylidene fluoride and vinyl fluoride, tetrafluoroethylene, vinylidene fluoride and a non-fluorinated monomer And terpolymers such as terpolymers.
In particular, a fluorine-containing resin having a critical surface tension of 30 dyn / cm or less and / or a silicone resin are preferable.

The content of the inorganic fine particles in the inorganic fine particles subjected to the surface treatment by grafting is suitably in the range of 10 to 60 wt%, more preferably 10 to 40 wt%. Content is 1
If it is less than 0 wt%, the effect of lowering the electrical resistance is not sufficient, and if it is more than 60 wt%, the adhesion between the grafted inorganic fine particles is not sufficient, and the strength of the coating is greatly reduced. Further, as these inorganic fine particles, conductive or semiconductive ones are preferably used. That is, the volume resistivity of the inorganic fine particles is preferably in the range of 10 ⁻⁴ to 10 ⁹ Ω · cm. The average particle diameter of the inorganic fine particles is 0.005 to 0.005.
A range of 0.5 μm is preferred.

In the present invention, the inorganic fine particles to be subjected to the graft reaction include metals such as gold, silver and copper, carbon black, semiconductive oxides such as titanium oxide and zinc oxide, and titanium oxide. , Zinc oxide, barium sulfate, aluminum borate, potassium titanate powder and the like whose surface is covered with tin oxide, carbon black, and metal. Particularly preferred is carbon black having relatively high conductivity. In addition, these inorganic fine particles are preferably conductive or semiconductive, and specifically, have a volume resistivity of 10 ⁻⁴ to 10 ⁹ Ω ·
A range of cm is suitable. The average particle diameter of the inorganic fine particles is preferably in the range of 0.005 to 0.5 μm.

In the present invention, a carrier film may be formed by simultaneously using one or more kinds of resin and / or crosslinked resin particles on the inorganic fine particles surface-treated by grafting with the chemical bond. When the core material can be sufficiently covered only with a resin that is grafted to the surface of the inorganic fine particles by a chemical bond, it is not essential to use these resins for forming a carrier film. Examples of the film-forming resin include polyolefin resins such as polyethylene and polypropylene; polyvinyls such as polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, and polyvinyl ketone. -Based or polyvinylidene-based resin; vinyl chloride-vinyl acetate copolymer; styrene-acrylic acid copolymer; straight silicone resin comprising organosiloxane bond or a modified product thereof; polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, Fluororesins such as polychlorotrifluoroethylene; polyesters; polyurethanes; polycarbonates; phenolic resins; urea / formaldehyde resins, melamine resins, There may be mentioned an epoxy resin; Nzoguanamin resin, urea resin, amino resin such as a polyamide resin
Known resins other than these can also be used.

Further, as the above-mentioned crosslinked resin particles,
Solvent-insoluble resin fine particles such as silicone, melamine, polyvinylidene fluoride, and styrene acryl can be used. Known resin particles other than these can also be used. The average particle size of the resin particles is preferably in the range of 0.1 to 2 μm, more preferably in the range of 0.2 to 1 μm. 0.1
If it is smaller than 2 μm, dispersion in the coating layer is very poor,
If it is larger, it will easily fall off from the coating layer, and the original function cannot be maintained.

As a method of forming the resin coating layer on the surface of the carrier core material, for example, an immersion method in which powder of the carrier core material is immersed in a solution for forming a film, or a solution for forming a film is sprayed on the surface of the carrier core material. Spraying method, fluidized bed method of spraying coating solution while suspending carrier core material with flowing air, kneader coater method of mixing carrier core material and coating forming solution in kneader coater and removing solvent Examples of the wet coating method include a dry coating method in which a core material and a film-forming material are mixed in a gaseous phase and heated and melted to form a resin film, using almost no solvent.

The method of forming the resin coating layer on the carrier core material in the present invention may be selected in consideration of the properties of the coating resin and the resin for surface treating the inorganic fine particles. A method that can be dispersed in the coating layer with energy is preferred.

In the wet coating method, the affinity of the graft inorganic fine particles for the solvent is improved, and the pot life can be extended. In addition, the dry coating method can easily and uniformly disperse the inorganic fine particles surface-treated with the resin by the graft reaction, and can omit the step of dispersing the inorganic fine particles in the solvent. Since it is not discharged into the environment, it does not pollute the environment. In addition, since there is no restriction on the solubility of the resin forming the film in the solvent, for example, a solvent-insoluble resin or resin particles can be used. Further, in the dry coating method, it is possible to avoid a state in which two or more kinds of resins are melted and mixed with each other, rather than to form a film using a solvent, so that individual functions can be provided in a coating surface direction. For example, it is relatively easy to appropriately coexist a surface for controlling resistance and a surface for controlling charging.

In the dry coating method, the resin to be coated is melted by applying heat or mechanical shear to form a resin film on the surface of the carrier core material. Therefore, the Tg of the coating resin
(Glass transition temperature) is generally preferably low from the viewpoint of energy saving. The Tg of the resin of the grafted inorganic particles is 4
The range is 0 to 120 ° C, preferably 50 to 100 ° C. When Tg is less than 40 ° C., thermal preservability as a carrier cannot be obtained, and for example, blocking occurs. Also,
If the Tg is higher than 120 ° C, a good coating cannot be obtained unless the heating temperature during the dry coating is set to 300 ° C or higher. For example, when manufactured at 200 ° C., the coating amount is clearly lower than the charged amount of the raw material, and the carrier core material is easily exposed.

The total coating amount on the carrier core material is affected by the average particle size, specific gravity, and shape of the core material.
The range of wt%, preferably the range of 1-3 wt% is good.
When the total coating amount is less than 0.5 wt%, exposure of the carrier core material is clearly recognized, and carrier contamination is likely to occur. On the other hand, if the content is more than 6 wt%, the adhesion between carriers during coating becomes excessive, aggregates increase, and the production yield decreases.

When the carrier is stirred in the developing machine,
Since the collision with the toner and each part constituting the housing in the developing machine is repeated, it is important to maintain the film of the resin-coated carrier. When the conventional inorganic fine particles are simply dispersed in the coating layer, the bonding force between the inorganic fine particles and the resin is small, and the coating strength of the carrier is weak, so that the coating is easily worn or cracked. It is difficult to maintain the characteristics.

However, in the resin-coated carrier using the grafted inorganic fine particles of the present invention, the functional group on the surface of the inorganic fine particles in the coating is chemically bonded to the functional group of the resin by a graft reaction. Has an extremely high adhesive strength. As a result, since the inorganic fine particles can be maintained in the initial film, it is possible to impart appropriate chargeability (charge amount and charge distribution) to the toner, maintain the appropriate chargeability for a long time, and Since the change in the state of the coating is small, the change in the electric resistance is also small. Further, as compared with a carrier coated with inorganic fine particles by conventional physical adsorption, the above-mentioned carrier has improved durability and the inorganic fine particles do not detach from the carrier surface, so that impaction on the photoreceptor does not occur.

The toner used in the developer of the present invention contains a binder resin and a colorant. The coloring agents include carbon black, nigrosine, aniline blue, calcoil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal,
C. I. Pigment Red 48: 1, C.I. I. Pigment Red 122, C.I. I. Pigment Red 5
7: 1, C.I. I. Pigment Yellow 97, C.I. I.
Pigment Yellow 12, C.I. I. Pigment Blue 15: 1, C.I. I. Pigment Blue 15: 3 and the like can be exemplified.

Examples of the binder resin include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isoprene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl acetate; Methyl acrylate, ethyl acrylate,
Α-methylene aliphatic monocarboxylic esters such as butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate; vinyl methyl ether, vinyl ethyl ether And vinyl ethers such as vinyl butyl ether; homopolymers such as vinyl methyl ketone, vinyl hexyl ketone, and vinyl ketone such as vinyl isopropenyl ketone; and copolymers thereof.

In particular, typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene Examples include a maleic anhydride copolymer, polyethylene, and polypropylene. Further, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin, waxes and the like can be mentioned. Among these, polyester is particularly suitable as the binder resin. For example,
A linear polyester resin comprising a polycondensate containing bisphenol A and a polyvalent aromatic carboxylic acid as main monomer components is preferred.

Further, the softening point is 90 to 150 ° C., the glass transition point is 50 to 70 ° C., the number average molecular weight is 2,000 to 6,000, the weight average molecular weight is 8,000 to 150,000, the acid value is 5 to 30,
A resin having a hydroxyl value of 5 to 40 can be particularly preferably used. These toner particles may optionally contain known additives such as a charge control agent and a fixing aid.

[0040]

【Example】

[Production of Grafted Inorganic Particles] (Grafted Inorganic Particles 1) 4,4-azobis (4-cyanopentanoic acid) and diamine-type polydimethylsiloxane (M
An azo polymer was synthesized by a polycondensation reaction with w = 4.2 × 10 ³ ). The azo polymer had a critical surface energy of 29 dyn / cm and a Tg of 56 ° C.

Next, carbon black [Neospectra II, manufactured by Columbia Carbon Co., Ltd.] was placed in a 300 ml flask.
(Average particle size 0.013 μm, volume resistivity 10 ⁻² Ω · c
m)] 1 g, 10 g of the above azo polymer and toluene 6
0 ml was added, and the mixture was reacted at 100 ° C. for 1 hour while stirring with a magnetic stirrer under a nitrogen atmosphere. Thereafter, about 60 ml of toluene was added to the reaction system for dilution, and the reaction was stopped by cooling to room temperature. And
The toluene solution was centrifuged from the reaction product, carbon black was completely settled, and the carbon black was dried by heating, followed by Soxhlet extraction using tetrahydrofuran as a solvent to remove the non-grafted polymer. The carbon black content of the polymer graft carbon black thus obtained was 20.3% by weight, and the weight average molecular weight of the grafted polymer was 8.2 × 10 ³ . In addition, the content of carbon black was measured using a pyrolyzer (TGA-50, a pyrolyzer for Shimadzu gas chromatograph).
The weight loss was measured and calculated in a nitrogen atmosphere.

(Graft inorganic particles 2) 1 g of carbon black (Neospectra II used in the graft inorganic particles 1) and a styrene / methyl methacrylate copolymer having a glycidyl group introduced therein (copolymerization ratio: 300 ml)
1: 1, Mw = 5.5 × 10 ³ , critical surface energy =
10 g of 35 dyn / cm, Tg = 59 ° C.) and 60 ml of toluene were added, and reacted at 100 ° C. for 1 hour while stirring with a magnetic stirrer under a nitrogen atmosphere.
Thereafter, about 60 ml of toluene was added to the reaction system for dilution, and the reaction was stopped by cooling to room temperature. Then, the toluene solution was centrifuged from the reaction product, carbon black was completely settled, and the carbon black was heated and dried, and then subjected to Soxhlet extraction using tetrahydrofuran as a solvent to remove the non-grafted polymer. The carbon black content of the polymer graft carbon black thus obtained was 15.5 wt%, and the weight average molecular weight of the grafted polymer was 7.6 × 10 ³ .

(Graft inorganic particles 3) 1 g of carbon black (Neospectra II used for the graft inorganic particles 1) and a styrene-perfluorooctylethyl methacrylate copolymer having a glycidyl group introduced therein (copolymerization ratio 1: 1) were placed in a 300 ml flask. 1, Mw = 4.5 × 10 ³ , critical surface energy = 25 dyn / cm, Tg = 60 ° C.)
0 g and 60 ml of toluene were added, and stirred at 100 ° C. while stirring with a magnetic stirrer under a nitrogen atmosphere.
Allowed to react for hours. Thereafter, about 60 ml of toluene was added to the reaction system for dilution, and the reaction was stopped by cooling to room temperature. Then, the toluene solution of the reaction product was centrifuged to completely settle the carbon black, and the carbon black was dried by heating, and then subjected to Soxhlet extraction using tetrahydrofuran as a solvent to remove the non-grafted polymer. The carbon black content of the polymer graft carbon black thus obtained is 30.0 wt.
%, The weight average molecular weight of the grafted polymer is 6.6 ×
It was 10 ^3.

(Graft inorganic particles 4) 1 g of carbon black (Neospectra II used for the graft inorganic particles 1), a methyl methacrylate resin introduced with a glycidyl group (Mw = 7.5 × 10 ³ , critical surface energy) in a 300 ml flask = 20 dyn / cm, Tg = 60 ° C) 1
0 g and 60 ml of toluene were added, and stirred at 100 ° C. while stirring with a magnetic stirrer under a nitrogen atmosphere.
Allowed to react for hours. Thereafter, about 60 ml of toluene was added to the reaction system for dilution, and the reaction was stopped by cooling to room temperature. Then, the toluene solution of the reaction product was centrifuged to completely settle the carbon black, and the carbon black was dried by heating, and then subjected to Soxhlet extraction using tetrahydrofuran as a solvent to remove the non-grafted polymer. The carbon black content of the polymer graft carbon black thus obtained is 30.0 wt.
%, The weight average molecular weight of the grafted polymer is 9.6 ×
It was 10 ^3.

(Carbon Black Dispersed Resin Particles) 100 parts by weight of styrene / methyl methacrylate copolymer (copolymerization ratio 1: 1, critical surface energy = 33 dyn / cm, Tg = 67 ° C.) Neospectra II) 20 parts by weight The above resin and carbon black were mixed in a V-type blender, the mixture was kneaded with an extruder, pulverized by a jet mill, and then coarse powder was cut by a wind-type classifier.
A carbon black dispersion resin having an average of 3 μm was obtained.

(Silane-Coupled Inorganic Fine Particles) 1 g of carbon black (Neospectra II used in grafted inorganic particles 1), propyltriethoxysilane 10
g and toluene 150 g were dispersed and mixed with a homomixer for 30 minutes to treat the surface of the carbon black. This carbon black was filtered, sufficiently washed with toluene, and an excess silane coupling agent was removed to obtain inorganic fine particles treated with the silane coupling agent.

[Manufacture of Carrier] (Example 1) Ferrite particles (average diameter = 50 μm) 100 parts by weight Grafted inorganic fine particles 1 2 parts by weight Ferrite particles and grafted inorganic fine particles 1 were mixed in a V-type blender. Liter in a horizontal kneader and stirred at a jacket set temperature of 200 ° C for 60 minutes.
The mixture was allowed to cool for 60 minutes with further stirring. Then, the mixture was sieved with a sieve having an opening of 75 μm to obtain a carrier A.

(Example 2) Ferrite particles (average diameter = 50 μm) 100 parts by weight Grafted inorganic fine particles 2 2 parts by weight Ferrite particles and grafted inorganic fine particles 1 were mixed in a V-type blender, and the mixture was placed in a 1 liter horizontal kneader. After stirring at a jacket set temperature of 200 ° C. for 60 minutes,
The mixture was allowed to cool for 60 minutes with further stirring. Then, the mixture was sieved with a sieve having an opening of 75 μm to obtain a carrier B.

(Example 3) Ferrite particles (average diameter = 40 μm) 100 parts by weight Grafted inorganic fine particles 3 1 part by weight Polystyrene particles (average particle diameter = 0.4 μm) 1 parts by weight Ferrite particles, grafted inorganic fine particles 3 and polystyrene particles Was mixed in a 1-liter horizontal kneader, stirred at a jacket set temperature of 200 ° C. for 60 minutes, and allowed to cool for 60 minutes with further stirring. Then, the mixture is sieved with a sieve having an opening of 75 μm and
I got

(Example 4) Ferrite particles (average diameter = 35 μm) 100 parts by weight Grafted inorganic fine particles 1 1.6 parts by weight Melamine particles (average particle diameter = 0.3 μm) 0.2 parts by weight Ferrite particles, grafted inorganic fine particles 1 and melamine particles were mixed in a V-type blender, and the mixture was placed in a 1-liter horizontal kneader, and heated at a jacket set temperature of 200 ° C. for 60 minutes.
After stirring for minutes, the mixture was allowed to cool for 60 minutes with further stirring.
Then, the mixture was sieved with a sieve having an opening of 75 μm to obtain a carrier D.

Example 5 Ferrite particles (average diameter = 50 μm) 100 parts by weight Toluene 14 parts by weight Styrene / perfluorooctylethyl methacrylate copolymer (copolymerization ratio 1: 1) 1.6 parts by weight Crosslinked melamine resin particles (Average particle size = 0.3 µm) 0.25 parts by weight Grafted inorganic fine particles 3 0.12 parts by weight Except for the ferrite particles, the above components are dispersed with a stirrer for 10 minutes to prepare a film forming solution. After the particles were placed in a vacuum deaeration kneader and stirred at a temperature of 60 ° C. for 30 minutes, the pressure was reduced and the toluene was distilled off to form a coating layer, which was sieved with a 75 μm mesh sieve to obtain Carrier E. (However, the grafted inorganic fine particles 4 were added to a styrene / perfluorooctylethyl methacrylate copolymer as a coating resin, diluted with toluene, and dispersed in advance by a sand mill to obtain a coating forming liquid.)

(Example 6) Ferrite particles (average diameter = 50 μm) 100 parts by weight Toluene 14 parts by weight Silicone resin (KR251, manufactured by Shin-Etsu Silicone Co., Ltd.) 2 parts by weight Grafted inorganic fine particles 4 0.12 parts by weight A film forming solution is prepared by dispersing with a stirrer, and the film forming solution and ferrite particles are placed in a vacuum degassing kneader and stirred at a temperature of 60 ° C. for 30 minutes, and then toluene is distilled off under reduced pressure to form a coating layer. Carrier F was obtained by sieving with a sieve having an opening of 75 μm. (However, the graft inorganic fine particles 4 were added to a silicone resin as a coating resin, diluted with toluene, and dispersed in advance by a sand mill to obtain a coating forming liquid.)

Comparative Example 1 Ferrite particles (average diameter = 50 μm) 100 parts by weight Carbon black-dispersed resin particles 2 parts by weight Ferrite particles and carbon black-dispersed resin particles were mixed in a V-type blender, and this mixture was mixed with 1 liter horizontal type. The mixture was placed in a kneader and stirred at a jacket set temperature of 200 ° C. for 60 minutes. The mixture was allowed to cool for 60 minutes with further stirring. Aperture 7
The carrier G was obtained by sieving with a 5μ sieve.

Comparative Example 2 A carrier H was prepared in the same manner as in Example 1 except that the graft inorganic fine particles 1 were omitted.

Comparative Example 3 Ferrite particles (average diameter = 50 μm) 100 parts by weight Toluene 14 parts by weight Silicone resin (KR251 manufactured by Shin-Etsu Silicone Co., Ltd.) 2 parts by weight Carbon black (VXC72 manufactured by Cabot Corporation) 0.12 parts by weight A film-forming solution comprising the above components is prepared, and the film-forming solution and ferrite particles are placed in a vacuum degassing kneader and heated at a temperature of 6 ° C.
After stirring at 0 ° C. for 30 minutes, toluene was distilled off under reduced pressure to form a coating layer, which was sieved with a sieve having openings of 75 μ to obtain Carrier I. (However, carbon black was added to a straight silicone resin (KR251) as a coating resin, diluted with toluene, and dispersed in advance by a sand mill to obtain a coating forming liquid.)

Comparative Example 4 Ferrite particles (average diameter = 50 μm) 100 parts by weight Toluene 14 parts by weight Silicone resin (KR251, manufactured by Shin-Etsu Silicone Co., Ltd.) 2 parts by weight 0.12 parts by weight of the above-mentioned silane-coupled inorganic fine particles 0.12 parts by weight Is prepared, and the film forming solution and ferrite particles are put into a vacuum degassing type kneader and heated at a temperature of 6 ° C.
After stirring at 0 ° C. for 30 minutes, the pressure was reduced to remove the Toern, and a coating layer was formed. The coated layer was sieved with a 75 μm sieve to obtain Carrier J. (However, carbon black was added to straight silicone resin as a coating resin, diluted with toluene, and dispersed in advance by a sand mill to obtain a coating forming liquid.)

(Production of Toner) Linear polyester resin 100% by weight (Linear polyester obtained from terephthalic acid / bisphenol A ethylene oxide adduct / cyclohexane dimethanol; Tg = 62 ° C., Mn = 4,000, Mw = 35,000, acid value = 12, hydroxyl value = 25) Magenta pigment (CI Pigment Red 57) 3% by weight The above mixture was kneaded with an extruder, pulverized with a jet mill, and then with an air classifier. After classification, magenta toner particles having d ₅₀ = 8 μm were obtained.

(Preparation of Developer) The carriers of Examples 1 to 6 and Comparative Examples 1 to 4 were each added to 100 parts by weight of
Six kinds of developers were prepared by mixing with 6 parts by weight of the magenta toner. The respective developers are referred to as developers 1 to 10.

(Copy Test) An electrophotographic copying machine (A-Col, manufactured by Fuji Xerox Co., Ltd.)
or 630). Table 1 shows the results.
It was shown to. Note that the charge amount in Table 1 is a value obtained by image analysis of CSG (charge spectrograph method).

In the case of the developers using the carriers of Examples 1 to 6, images having no edge effect were obtained as shown in Table 1. Further, the image density was stable at 1 to 1.2, and the toner charge amount was stable even after 10,000 copies. On the other hand, in the case of the developers using the carriers of Comparative Examples 1, 3, and 4, an image having no edge effect was obtained at the initial stage.
The charge amount of the toner after printing was clearly reduced, and a low-quality image with fog was obtained. Observation of the surface of these carriers by SEM photograph revealed that many exposures of the carrier core material, which are considered to be caused by abrasion of the coating layer, were observed. In the case of the developer using the carrier of Comparative Example 2, an edge effect was clearly observed.

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[Table 1]

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According to the present invention, a carrier for a two-component developer is
With the above configuration, the resistance of the developer does not increase,
An image with excellent halftone reproducibility can be obtained, and even when used continuously for a long period of time, good charging ability is maintained.

Claims (5)

[Claims] 1. A carrier for developing an electrostatic latent image provided with a coating layer containing a resin and inorganic fine particles, wherein the functional group of the inorganic fine particles and the resin are grafted by a chemical bond. Latent image development carrier. 2. A method for producing a carrier for developing an electrostatic latent image provided with a coating layer containing a resin and inorganic fine particles, wherein the functional group of the inorganic fine particles and the resin are grafted by a chemical bond. A method for producing a carrier for developing an electrostatic latent image, comprising mixing inorganic fine particles and a core material in a dry manner, and then melting the resin to form a coating. 3. The method for producing a carrier for developing an electrostatic latent image according to claim 2, wherein the resin has a glass transition temperature of 120 ° C. or lower. 4. An electrostatic latent image developer comprising a toner containing a binder resin and a colorant and a carrier, wherein the carrier is the carrier for developing an electrostatic latent image according to claim 1. Electrostatic latent image developer. 5. A step of forming a latent image on a latent image carrier, a step of developing the latent image using a developer, a step of transferring the developed toner image onto a transfer body, and a step of transferring the latent image 5. An image forming method comprising a step of heating and fixing the above toner image, wherein the developer according to claim 4 is used as the developer.