JPH0926675A - Photographic carrier and its production and electrostatic charge imparting member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carrier with which image quality including excellent electrostatic charge maintainability, environmental stability and image maintainability and excellent image reproducibility of low-potential latent images free from unequal densities and surface staining of images is obtainable by using plural resins incompatible with each other, dispersing conductive powder only in the one kind of the resin thereof and coating core materials with these resins, thereby forming resin layers. SOLUTION: At least two kinds of the resins incompatible with each other are used and the conductive powder is dispersed only in the one kind of the resin thereof. The core materials are then coated with these resins, by which the resin layers are formed. Both thermoplastic and thermosetting resins are usable as the coating resins to be used and are not particularly restricted, insofar as the resins are the combination of the incompatible resins. The more adequate resins among these resins include a copolymer of a nitrogen-contained vinyl monomer and styrene, etc., for the coating resins for controlling electric charge which are not dispersed with the conductive powder and the resins for dispersing the conductive powder include polyamide, melamine, etc., having high polarity. The conductive powder to be used is not particularly limited, insofar as the powder are inorg. particles exhibiting electrical conductivity.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrostatic charge image developing carrier used for developing an electrostatic charge image formed by an electrophotographic method, an electrostatic recording method or the like with a two-component developer, and a method for producing the same. The present invention relates to the charge imparting member.

[0002]

2. Description of the Related Art Methods for visualizing image information via an electrostatic image, such as electrophotography, are currently used in various fields. In the electrophotographic method, an electrostatic latent image is formed on a photoreceptor in a charging and exposing step, the electrostatic latent image is developed with a developer containing a toner, and visualized through a transfer and fixing step. The developer used here is a two-component developer including a toner and a carrier,
There is a one-component developer that can be used alone, such as magnetic toner, but in a two-component developer, the carrier shares functions such as stirring, carrying, and charging of the developer, and the functions are separated as the developer. Currently, it is widely used because of its good controllability.

In particular, a developer using a resin-coated carrier is excellent in charge controllability, and it is relatively easy to improve environmental dependency and stability over time. Further, as a developing method, a cascade method or the like has been used in the past, but a magnetic brush method using a magnetic roll as a developer carrier is mainly used at present. Further, also in the developing method using a one-component developer, a specific resin and a charge control agent are contained in a charge imparting member such as a developing roll, a toner supply roll, and a charging blade to improve image quality and maintainability.

[0004] The magnetic brush method using a two-component developer includes:
Image density drop due to deterioration of developer charge, remarkable background stain, image roughening due to carrier adhesion to image,
In addition, there are problems such as consumption of carriers and occurrence of uneven image density. Further, due to electrostatic charge deterioration of the developer, background stains and the like tend to occur when the environment changes such as humidity and temperature, or when toner is added or when the toner concentration is high.

It has been proposed to lower the resistance of the carrier in order to accelerate the rise of charging during development, to prevent the occurrence of carrier adhesion, and to improve the reproducibility of halftone. For example,
Carbon black is added to the surface of magnetic particles coated with a silicone resin or the like to lower the resistance of the carrier or the like (Japanese Patent Laid-Open No. Hei 6).
No. 148952), the magnetic particles are coated with a mixture of a dispersion of fluorine-based polymer particles and a dispersion liquid of carbon black to achieve reproducibility of halftone and prevention of carrier adhesion (Japanese Patent Laid-Open No. 5-34993). Japanese Patent Laid-Open No. 6-202382) has been proposed to suppress the detachment of the carrier-added carbon black from the carrier to reduce the resistance of the carrier (see JP-A-6-202382). But,
When the electric resistance of the carrier is reduced by these methods, the amount of charge is reduced, and there is a problem that the image quality maintenance is deteriorated.

[0006]

Therefore, the present invention solves the above problems and provides an electrophotographic carrier and a method of manufacturing the same, and an electrophotographic charging member having the following features. It is a thing. High image quality can be secured even during long-term use. To improve background contamination when toner is added and to extend the life of the developer and the charging member. Improving image quality retention against changes in charging due to environmental changes. It should be possible to provide excellent image quality for reproducing solid black and fine lines. To be able to develop low potential latent images efficiently.

[0007]

Means for Solving the Problems The inventors of the present invention have diligently studied a resin-coated carrier in which a conductive powder is dispersed and a charging property-imparting member. As a result, at least two resins which are incompatible with each other are used. It has been found that the problems of the invention can be solved by dispersing the conductive powder in only one of the resins and coating the core material with the resin to form a resin layer. That is, the present invention uses two or more types of resins that are incompatible with each other as the resin layer that coats the core material.
By dispersing the conductive powder in one, it is possible to form an effective conductive path with a small amount of the conductive powder, the resin layer in which the conductive powder is not dispersed, it is possible to maintain the chargeability, the problems of the invention described above. I was able to solve it. That is, the present invention has the following configurations.

(1) In an electrophotographic carrier having a core material coated with a resin, the resin is composed of at least two kinds of resins which are incompatible with each other, and conductive powder is dispersed in one resin. An electrophotographic carrier characterized by the following.

(2) A method for producing a carrier for electrophotography, which comprises a step of dispersing conductive powder in a resin, and a step of coating a core material with the dispersion and a resin incompatible with the resin. .

(3) In a charging member for electrophotography, which comprises a core material coated with a resin, the resin is composed of at least two kinds of resins which are incompatible with each other, and conductive powder is dispersed in one resin. A charging member for electrophotography, comprising:

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As the coating resin used in the present invention, any thermoplastic or thermosetting resin can be used as long as it is a combination of incompatible resins, and is not particularly limited. Specifically, the following resins can be used. Copolymers of vinylic fluorine-containing monomers such as vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, monochlorotrifluoroethylene, monochloroethylene, trifluoroethylene; styrenes such as styrene, chlorostyrene, methylstyrene; methyl methacrylate, Α-methylene aliphatic monocarboxylic acids such as methyl acrylate, propyl acrylate, lauryl acrylate, methacrylic acid, acrylic acid, butyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate and ethyl methacrylate; nitrogen-containing acrylics such as dimethylaminoethyl methacrylate; Nitriles such as acrylonitrile and methacrylonitrile; vinyl pyridines such as 2-vinylpyridine and 4-vinylpyridine; vinyl ethers; vinyl Ton type: ethylene, propylene, olefins such as butadiene, polyamides,
Main chain nitrogen-containing resins such as polyimide and melamine; silicones such as methylsilicon and methylphenylsilicon; polyesters including bisphenol, glycol and the like; homopolymers or copolymers thereof can be used.

Among the above, preferred ones are vinylidene fluoride homopolymers, methyl methacrylate homopolymers, acrylonitrile, dimethylaminoethyl methacrylate, and other nitrogen-containing vinyl monomers and styrene as charge control coating resins that do not disperse conductive powder. Examples thereof include polymers. Examples of the conductive powder dispersion resin include highly polar polyamide, melamine, polyimide, polyester and the like. The incompatibility can be easily confirmed by observing the cross section of the carrier with a transmission electron microscope (hereinafter referred to as TEM) and determining whether or not an interface exists in the coating resin. Further, as the incompatible resin, those having different SP values (solubility parameters) may be selected.

As the core particles used in the present invention, iron particles, ferrite particles, granulated magnetite particles having a substantially spherical shape are suitable. Normal average particle size is 20
The thickness of about 120 μm is used.

The amount of coating resin blended is such that image quality, secondary obstacles (decrease in fluidity due to high coating amount, poor conveyance of developer, carrier adhesion to photoreceptor due to high electrification, and low resistance carrier due to low coating amount). Generation, leakage to the photoconductor, carrier scattering due to charge injection, etc. and chargeability,
0.1 to 10% by weight in total with respect to carrier core particles,
Preferably 0.5 to 7% by weight, more preferably 1 to 6
A weight percent range is suitable. The mixing ratio of the resin for dispersing the conductive powder is 1 to 99% by weight, preferably 3 to 97% by weight, more preferably 5 to 9% by weight based on the total amount of the coating resin.
A range of 5% by weight is suitable. If the amount is less than 1% by weight, the conductive path cannot be reliably formed. If the amount is more than 99% by weight, the conductive powder is dispersed in the entire coating layer, so that the charge amount is reduced.

The conductive powder used in the present invention is not particularly limited as long as it is an inorganic fine particle exhibiting conductivity. Specific examples include carbon black, various metal powders, titanium oxide, tin oxide, magnetite, ferrite and other metals. An oxide can be illustrated. Among these, carbon black is easily dispersed in a resin having high polarity and is suitable for being selectively dispersed in one resin layer. The conductive powder can be selectively dispersed in one resin layer after being coated on the core particle surface by being dispersed in the resin having the highest polarity among two or more incompatible resins. . That is, when dispersed in a resin having a low polarity and then mixed with a resin having a high polarity, carbon black shifts to a resin having a high polarity.

The amount of the conductive powder added is appropriately in the range of 1 to 100 parts by weight, preferably 2 to 80 parts by weight, more preferably 5 to 60 parts by weight, based on the total amount of the coating resin. If the addition amount is less than 1 part by weight, the conductivity cannot be exhibited, and if it exceeds 100 parts by weight, it is difficult to disperse the conductive powder.

In the method for producing a carrier of the present invention, two or more types of incompatible coating resin and conductive powder are simultaneously mixed with a solution and mixed with a stirrer such as a ball mill, or the coating resin and conductive powder having the highest polarity are mixed. After mixing with other coating resin, mixed with the core particles, heated under reduced pressure, kneading to volatilize the solvent, to coat the core particles, or without using a solvent After mixing the coating resin and the core particles, the coating resin is melted by heating and kneading at a temperature not lower than the melting point of the coating resin to coat the core particles. As a manufacturing apparatus used for coating, a heating type kneader, a heating type Henschel mixer, a UM mixer, a planetary mixer and the like can be mentioned.

As a method of dispersing the conductive powder, when coating with a solvent solution, the conductive powder can be added to the resin solution for dispersing the conductive powder and dispersed by a ball mill, a sand mill or the like. When the resin is melt-coated, the conductive powder-dispersed resin and the conductive powder may be melt-kneaded by a roll mill, a Banver mixer, an extruder, a pressure kneader, or the like, and then, pulverized as needed before use.

The carrier of the present invention is mixed with a toner and used as a two-component developer. The toner is a binder resin in which a colorant or the like is dispersed, and examples of the binder resin used in the toner include styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl (meth) acrylate, Ethyl (meth) acrylate, n (meth) acrylate
Α-methylene aliphatic monocarboxylic esters such as -propyl, lauryl (meth) acrylate and 2-ethylhexyl (meth) acrylate; vinyl nitriles such as (meth) acrylonitrile; 2-vinylpyridine, 4-vinylpyridine Vinyl pyridines such as vinyl methyl ether and vinyl isobutyl ether; vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone: ethylene, propylene,
Polymers of monomers such as unsaturated hydrocarbons such as isoprene and butadiene and their halides, halogenated unsaturated hydrocarbons such as chloroprene, or copolymers obtained by combining two or more of these monomers Polymers, further mixtures thereof, non-vinyl condensation resins such as rosin-modified phenol formalin resin, epoxy resin, polyester resin, polyurethane resin, polyamide resin, cellulose resin, polyether resin, or these and the above A mixture with a vinyl resin can be mentioned.

Examples of the colorant used in the toner include carbon black, nigrosine dye, aniline blue, calcoil blue, chrome yellow, ultramarine blue, methylene blue, rose bengal, phthalocyanine blue, or a mixture thereof.

As the toner component other than the colorant, there are a charge control agent, an offset preventive agent, a fluidity improving agent and the like, and a magnetic fine powder may be contained if necessary. The particle size of the toner is preferably small in order to improve the image quality,
Toners having an average particle size of microns, preferably 5-10 microns are good.

[0022]

The present invention will now be described by way of examples, which should not be construed as limiting the invention. In the examples, “part” means part by weight. [Example 1] Nylon-12 (Toray Industries, Inc., Rilsan AMNO) 10 parts Ketjen Black (Lion Akzo, EC-DJ500) 2 parts The above materials were kneaded for 20 minutes by a roll mill heated to 200 ° C and cooled. . Cu-Zn ferrite (manufactured by Powder Tech Co., average particle size 50μ) 1000 parts The above kneaded material 12 parts Styrene / acrylonitrile copolymer (copolymerization ratio 7: 3) 20 parts The above materials are 1L small kneader equipped with a heater. Inside, the temperature of the heat medium was raised to 250 ° C., and the mixture was stirred and kneaded for 60 minutes, then the heater was turned off, and the mixture was cooled for 1 hour while stirring. Then, it was sieved with a 105 μm sieve to obtain the carrier of Example 1. When the coating layer of the obtained carrier was observed with a transmission electron microscope, the interface between two types of resin could be confirmed. It was also observed that carbon black was dispersed in nylon-12.

Example 2 Polyester consisting of bisphenol A / ethylene oxide adduct and terephthalic acid (acid value 14) 20 parts Ketjen Black (EC-DJ500, manufactured by Lion Akzo Co.) 6 parts Toluene 174 parts The above materials are stainless steel. The balls were dispersed for 15 hours with a ball mill used as a medium. Cu-Zn ferrite (manufactured by Powder Tech Co., average particle size 50μ) 1000 parts Dispersion 150 parts Polymethylmethacrylate toluene solution (solid content 10% by weight) 150 parts Toluene 300 parts Decompression device and heater In a 1 L small kneader equipped with, the heating medium temperature was raised to 100 ° C., and the solvent was removed by stirring while heating and depressurizing. Then 105μ
The carrier of Example 2 was obtained by sieving with a m sieve. When the coating layer of the obtained carrier is observed with a transmission electron microscope, it is 2
It was possible to confirm the interfaces of the types of resin. It was also observed that carbon black was dispersed in the polyester.

[Comparative Example 1] Cu-Zn ferrite (manufactured by Powdertec Co., average particle size: 50 µ) 1000 parts Nylon-12 (manufactured by Toray, Rilsan AMNO) 10 parts Styrene-acrylonitrile copolymer (copolymerization ratio 7: 3) 20 parts The above material was treated in the same manner as in weight% 1 to obtain a carrier of Comparative Example 1.

Comparative Example 2 Polymethylmethacrylate Toluene Solution (Solid Content 10% by Weight) 200 parts Ketjen Black (EC-DJ500 manufactured by Lion Akzo Co., Ltd.) 6 parts A ball mill using the above materials as stainless balls as media. Dispersed for 15 hours. Cu-Zn ferrite (manufactured by Powdertec Co., average particle size 50μ) 1000 parts Dispersion 154.5 parts Polymethylmethacrylate toluene solution (solid content 10% by weight) 150 parts Toluene 300 parts The carrier of Comparative Example 2 was obtained by treating in the same manner. When the coating layer of the obtained carrier was observed with a transmission electron microscope, the resin interface could not be confirmed, and it was uniform.

(Toner Production Example 1) Styrene / n-butyl acrylate resin 87 parts Carbon black (manufactured by Cabot, BPL) 8 parts Charge control agent (TRH manufactured by Hodogaya Chemical Co., Ltd.) 1 part Polypropylene wax (manufactured by Sanyo Kasei Co., Ltd., 660P) 4 parts Toner particles having an average particle size of 7.5 μm were obtained by a kneading and pulverizing method using the above materials. To 100 parts of the toner particles, 1 part of colloidal silica (R972 manufactured by Nippon Aerosil Co., Ltd.) was added and mixed with a Henschel mixer to obtain a toner for evaluation.

(Evaluation of Image Quality) Examples 1 and 2 and Comparative Example 1,
The carrier obtained in 2 was mixed with the toner of Toner Production Example 1 so as to have a toner concentration of 5% to prepare a developer for evaluation. With respect to these developers, the dark potential of the photoconductor was set to 4 by using a modified Able1301α machine manufactured by Fuji Xerox.
00V, exposed portion potential 100V, developing bias potential 350
The image quality was evaluated by setting the developing conditions so that V was obtained.
The results are shown in Table 1. Compared to Comparative Examples 1 and 2, the carriers of Examples 1 and 2 are excellent in charge maintaining property and environmental stability,
The low potential latent image developability was good, and good image quality could be obtained.

[0028]

[Table 1]

[Example 3] Nylon-12 (Toray Industries, Inc., Rilsan AMNO) 10 parts Ketjen Black (Lion Akzo, EC-DJ500) 2 parts The above materials were kneaded for 20 minutes by a roll mill heated to 200 ° C. , Cooled. The above kneaded material 12 parts Styrene / acrylonitrile copolymer (copolymerization ratio 7: 3) 20 parts The above materials are heated and melted at 250 ° C., and 50 g on the surface of a developing roll sleeve (stainless steel) for Fuji Xerox laser printer 4105. / M ² thickness,
The charging member of Example 3 was obtained. When the coating layer of the obtained charge imparting member was observed with a transmission electron microscope, the interface between the two kinds of resins could be confirmed. Also, nylon-12
It was observed that carbon black was dispersed in it.

Comparative Example 3 A developing roll sleeve (made of stainless steel) for a laser printer 4105 manufactured by Fuji Xerox Co., Ltd. was used as it was.

(Toner Production Example 2) Styrene / n-butyl acrylate resin 44 parts Magnetite (manufactured by Toda Kogyo Co., Ltd., EPT-1000) 50 parts Charge control agent (TRH manufactured by Hodogaya Chemical Co., Ltd.) 2 parts Polypropylene wax (Sanyo Kasei Co., Ltd.) Manufactured 660P) 4 parts Toner particles having an average particle size of 7.5 μm were obtained by a kneading and pulverizing method using the above materials. To 100 parts of the above toner particles, 0.8 part of colloidal silica (R972 manufactured by Nippon Aerosil Co., Ltd.) was added and mixed with a Henschel mixer to obtain a toner for evaluation.

(Evaluation of Image Quality) The sleeves obtained in Example 3 and Comparative Example 3 were used as laser printers 41 manufactured by Fuji Xerox Co., Ltd.
The toner of Example 5 was used to evaluate the image quality. The results are shown in Table 2. The charge imparting member of Example 3 was excellent in image quality stability as compared with Comparative Example 3.

[0033]

[Table 2]

[0034]

According to the present invention, by adopting the above-mentioned constitution, the charge maintaining property, environmental stability and image quality maintaining property can be greatly improved, and the image is free from uneven density and scumming, and is low. The reproducibility of the potential latent image is good, and it has become possible to obtain excellent image quality.

Claims (3)

[Claims] 1. An electrophotographic carrier comprising a core material coated with a resin, wherein the resin is composed of at least two kinds of resins which are incompatible with each other, and conductive powder is dispersed in one resin. A carrier for electrophotography, which is characterized in that 2. A method of manufacturing a carrier for electrophotography, comprising: a step of dispersing conductive powder in a resin; and a step of coating a core material with the dispersion and a resin incompatible with the resin. 3. A charge imparting member for electrophotography, comprising a core material coated with a resin, wherein the resin comprises at least two kinds of resins which are incompatible with each other, and conductive powder is dispersed in one resin. A charge imparting member for electrophotography, characterized by comprising: