JPH10161355A - Electrophotographic carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin coated carrier excellent in durability as well as to prevent the sticking of the carrier and the deterioration of image quality at high humidity. SOLUTION: Magnetic particles are coated with a resin consisting of one or more kinds of monomers selected from among styrene, n-butyl acrylate, n-butyl methacrylate, methacrylic acid, mono-n-butyl maleate, diethyl maleate and di-n-butyl maleate monomers and acrylamide alkyl sulfonic acid and/or methacrylamide alkyl sulfonic acid represented by the formula (where R1 is H or CH3 and R2 is 1-8C straight chain or branched chain alkyl) and the resultant resin coated particles having >=10<11> Ω.cm electric resistance are surface- treated with electrically conductive fine particles to obtain the objective resin coated carrier having 10<10> -10<14> Ω.cm electric resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier used as a developer for developing an electrostatic image, and more particularly to a resin-coated carrier obtained by coating magnetic particles with a resin.

[0002]

2. Description of the Related Art Conventionally, as a method for developing an electrostatic latent image, toner and a magnetic carrier are mixed to frictionally charge the toner and transfer toner by the carrier.
2. Description of the Related Art A two-component developing system in which an electrostatic latent image is brought into contact with and developed is known. It is known to use magnetic particles such as iron powder or ferrite particles as a carrier used in such a two-component development system. However, the carrier composed of such magnetic particles has low electric resistance and has various drawbacks. Prevention of toner component adhesion (toner spent) to the carrier surface, formation of a uniform surface, and extension of developer life. , For protection from scratches or abrasion by the photoreceptor carrier, control of charging polarity or adjustment of charging amount,
A technique of coating the surface with a suitable resin is known.

In a carrier having such a resin coating layer, various carrier characteristics including electric resistance change by changing the thickness of the resin coating layer. A carrier having a thin resin coating layer has the advantage that the chargeability to the toner is small and the durability is good even when toner is spent, but the carrier adheres to the photoreceptor and an image is formed. The problem of carrier adhesion, which is reproduced in the image, tends to occur, and the problem of a large decrease in image quality at high humidity tends to occur.

On the other hand, when the resin coating layer is thickened,
Although the problems of carrier adhesion and deterioration of image quality at high humidity can be solved, when toner is spent, there is a problem that chargeability to the toner is greatly reduced and durability is poor.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a resin-coated carrier which is excellent in durability while solving the problems of carrier adhesion and image quality deterioration at high humidity. With the goal.

[0006]

That is, the present invention relates to a method for producing a magnetic particle comprising styrene monomer, n-butyl acrylate monomer, n-butyl methacrylate monomer, methacrylic acid monomer and mono-n-butyl maleate. It is composed of at least one monomer selected from a monomer, a diethyl maleate monomer and a di-n-butyl maleate monomer, and acrylamidoalkylsulfonic acid and / or methacrylamidoacrylsulfonic acid (formula 2). Resistance obtained by surface-treating conductive fine particles on the surface of resin-coated particles having an electrical resistance of 10 ¹¹ Ω · cm or more obtained by coating with a copolymer resin.
^The present invention relates to a resin-coated carrier having a resistivity of ¹⁰ to 10 ¹⁴ Ω · cm.
General formula

[0007]

Embedded image (R ₁ ; H, CH ₃ , R ₂ ; linear or branched alkyl group having 1 to 8 carbon atoms) The present inventors have conducted intensive studies on a carrier obtained by coating magnetic particles with a resin, and as a result, Various characteristics of the coated carrier depend on its surface state, that is, the electric resistance of the resin-coated carrier is controlled by the thickness of the resin coating layer, and the thickness of the resin coating layer is small and the electric resistance is 10 ¹⁰ Ω ・ c
m or less, the exposed point of the magnetic particles is increased, and the exposed point of the magnetic particles acts as a charge active point where charge transfer to and from the toner is active. Therefore, even when spent occurs, the charge amount decreases. However, it has been found that such a carrier is liable to cause a problem of carrier adhesion due to a low electric resistance, and is liable to cause a deterioration in image quality at high humidity. Conversely, a carrier having a thick resin coating layer and an electric resistance of 10 ¹¹ Ω · cm or more has a small exposure point of the magnetic particles, so that the toner charge amount is greatly reduced due to spent and a problem occurs in durability. However, they have found that they have excellent characteristics with respect to problems such as carrier adhesion. In view of such findings, it has been found that the above-mentioned problem can be solved by subjecting a resin-coated carrier having a predetermined or higher electric resistance to surface treatment with conductive fine particles and setting the electric resistance within a predetermined range. This has led to the invention.

In the present invention, the electric resistance of the magnetic particles is 10 ¹¹ Ω · cm or more, preferably 10 ¹² Ω · cm.
As described above, a resin coating layer is formed so as to have a resistivity of 10 ¹³ Ω · cm or more, and then a surface treatment is performed with conductive fine particles, so that the electric resistance is 10 ¹⁰ to 10 ¹⁴ Ω · cm, preferably 10 ¹¹ to 10 ¹¹ Ω · cm. Adjust the carrier of 10 ¹³ Ω · cm.

A carrier having such characteristics can solve the problems of carrier adhesion and deterioration of image quality at high humidity, and the presence of conductive fine particles increases the number of charged active sites on the carrier surface. The problem of durability based on a decrease in the amount of charge can also be solved.

The carrier of the present invention comprises at least magnetic particles, a resin coating layer covering the magnetic particles, and conductive fine particles whose surface is treated with the resin coating layer. As the magnetic particles, particles having an average particle size of at least about 30 μm are used in order to prevent carrier adhesion to the electrostatic latent image carrier, and from the viewpoint of preventing deterioration of image quality such as generation of carrier stripes. It is desirable to use one having a size of at most about 60 μm, more preferably one having an average particle size of 40 to 50 μm.

Specific materials for the magnetic particles include those known as two-component carriers for electrophotography, such as metals such as ferrite, magnetite, iron, nickel, and cobalt;
These metals and zinc, antimony, aluminum, lead,
Alloys or mixtures with metals such as tin, bismuth, beryllium, manganese, selenium, tungsten, zirconium, and vanadium; metal oxides such as iron oxide, titanium oxide, and magnesium oxide; nitrides such as chromium nitride and vanadium nitride; and silicon carbide , A mixture with a carbide such as tungsten carbide, ferromagnetic ferrite, and a mixture thereof.

The resin used in the resin coating layer includes styrene monomer, n-butyl acrylate monomer, n-butyl methacrylate monomer, methacrylic acid monomer, mono-n-butyl maleate monomer, and maleic acid. At least one selected from diethyl acrylate monomers and di-n-butyl maleate monomers
It is composed of at least one kind of monomer and acrylamide alkylsulfonic acid and / or methacrylamideacrylsulfonic acid (formula 1).

This is an example of a monomer selected for optimizing an electron energy level in order to improve the rise of charging, but is not limited to this.
Examples of the monomer represented by Chemical Formula 1 include acrylamidoalkylsulfonic acid and / or methacrylamidoacrylsulfonic acid, specifically, acrylamidomethylsulfonic acid, acrylamidoethylsulfonic acid, acrylamido-n-propylsulfonic acid, Acrylamide isopropyl sulfonic acid, acrylamide n-butyl sulfonic acid, acrylamide s-butyl sulfonic acid, acrylamide t-butyl sulfonic acid, acrylamide pentane sulfonic acid, acrylamide hexane sulfonic acid, acrylamide heptane sulfonic acid, acrylamide octane sulfonic acid, methacrylamide methyl sulfonic acid,
Methacrylamide ethyl sulfonic acid, methacrylamide n-propyl sulfonic acid, methacrylamide isopropyl sulfonic acid, methacrylamide n-butyl sulfonic acid, methacrylamide s-butyl sulfonic acid,
Examples include methacrylamide t-butylsulfonic acid, methacrylamidopentanesulfonic acid, methacrylamidohexanesulfonic acid, methacrylamidoheptanesulfonic acid, and methacrylamidooctanesulfonic acid, but are not limited thereto. In forming such a resin coating layer, as described above, the electric resistance of the magnetic particles having the resin coating layer is 10 ¹¹ Ω.
-Formed so as to be at least cm.

In the present invention, as the conductive fine particles for treating the surface of the resin coating layer, one-hundredth of the average particle diameter of the carrier is used.
Fine particles having a particle size of 0 or less can be used, and it is preferable to use fine particles having a particle size of 0.01 to 1.0 μm. The conductive fine particles for treating the surface of the resin coating layer are 0.001 to 10% by weight, preferably 0.01 to 1.0% by weight, more preferably 0.1 to 10% by weight, based on the carrier particles.
It is desirable to use it in the range of 0.5 to 0.3% by weight.

As the conductive fine particles, a substance having a volume resistivity of 10 ¹⁰ Ω · cm or less is preferable, and 10 ⁸ Ω · cm is preferable.
The following substances are more preferred. Specifically, for example, aluminum, zinc, iron, copper, nickel, silver, palladium,
Or metal or metal alloy powder such as stainless steel, fine particles coated with metal such as aluminum coat, nickel coat, silver coat, carbon powder such as acetylene black, Ketjen black, SnO2, ZnO, Sn
Examples include conductive metal oxides such as O 2 —TiO 2 and SnO 2 —BaSO 4, and magnetic powders such as magnetite, γ-hematite, and various ferrites are also used. Among such conductive fine particles, SnO 2 —TiO 2, tin oxide.
Conductive titanium oxide fine particles such as titanium oxide treated with antimony are preferred.

In the present invention, the electric resistance of the finally obtained carrier is adjusted to 10 ¹⁰ to 10 ¹⁴ Ω · cm by subjecting the resin coating layer to a surface treatment with conductive fine particles. The surface treatment of the resin coating layer with the conductive fine particles may be performed, for example, by mechanically mixing and fixing the magnetic particles having the resin coating layer (hereinafter abbreviated as the particles to be processed) and the conductive fine particles. The treatment can be performed by a process of fixing the conductive fine particles by a mechanical impact force, a process of mechanically mixing the particles to be processed and the conductive fine particles, and then heating to fix the conductive particles. As a device for mechanically mixing the particles to be treated and the conductive fine particles, for example, a mechanomill (manufactured by Okada Seiko), a mechanofusion system (manufactured by Hosokawa Micron), a paint conditioner (manufactured by Red Devil) and the like are used. Can be.
As a device for fixing the conductive fine particles to the surface of the particles to be treated by mechanical impact, for example, a hybridizer (manufactured by Nara Machinery Co., Ltd.) or the like can be used. Further, as an apparatus for the heat treatment, a spira coater (manufactured by Okada Seiko Co., Ltd.), a safusing system (manufactured by Nippon Pneumatic Co., Ltd.) or the like can be used.

The toner used as a developer in combination with the carrier of the present invention is not particularly limited, and a known toner can be used. Examples thereof include a suspension polymerization method, a pulverization method, and a microcapsule method. A toner manufactured by a spray drying method, a mechanochemical method, or the like can be used. These toners contain at least a binder resin and a colorant, and various additives such as a charge control agent and an anti-offset agent are used as needed.

The resin used as the binder resin of the toner is
Generally, any resin may be used as long as it is used as a binder resin for toner. For example, polystyrene resin, poly (meth) acrylic resin, polyolefin resin, polyamide resin, polycarbonate resin Thermosetting resin such as bone resin, polyether resin, polysulfone resin, polyester resin, epoxy resin, butadiene resin, or thermosetting of urea resin, urethane resin, urea resin, epoxy resin, etc. Resin, furthermore, copolymers, block polymers, graft polymers, polymer blends, and the like thereof can be used.

The carrier of the present invention is particularly preferred when used in combination with a full-color toner. Carbon black is added to a normal toner as a colorant, and the conductivity of the carbon black prevents charge from being accumulated in the toner, and a stable toner charge amount is obtained. However, since carbon black is not used in the full-color toner, there is a problem that the charge amount of the toner is not stable and gradually increases. However, such a problem is solved by using the carrier in combination with the carrier of the present invention. can do. Further, it is preferable that the toner is also subjected to surface treatment with conductive fine particles. This surface treatment may be performed by mixing toner and conductive fine particles,
It may be performed by fixing conductive fine particles on the toner surface. By performing the surface treatment on the toner, the effect of supplementing the carrier with the conductive fine particles during printing can be expected.

The full color toner has a glass transition point (hereinafter referred to as Tg) of 55 to 70 ° C. as a binder resin.
The softening point is 80 to 150 ° C, the number average molecular weight (hereinafter referred to as Mn) is 2000 to 15000, and the molecular weight distribution (hereinafter referred to as M
It is desirable to use a linear polyester resin having a w / Mn of 3 or less. Further, a linear urethane-modified polyester obtained by reacting a diisocyanate with the linear polyester resin, or a styrene-based, acrylic-based, or aminoacryl-based monomer is modified on the linear polyester resin by graft polymerization, block polymerization, or the like. The resin thus obtained can also be suitably used.

Further, a charge control agent, an anti-offset agent and the like may be further added to the toner. For example, as the positive charge control agent, azine compound nigrosine base EX, Bontron N-01, 02, 04, 05,
07, 09, 10, 13 (manufactured by Orient Chemical Industries)
Oil Black (manufactured by Chuo Gosei Kagaku Co., Ltd.), quaternary ammonium salt P-51, polyamine compound P-52, Sudanch-Schwarz BB (Solvent Black 3: C.I.
I. No. 26150), Fettschwarz HBN
(C.I. No. 26150), Brilliant Spirits Schwarz TN (manufactured by Farben Fabriken Bayer), and further, an alkoxylated amine, an alkylamide,
Molybdate chelate pigments, imidazole compounds and the like can be used.

Examples of the negative charge control agent include chromium complex type azo dyes S-32, 33, 34, 35, 37, 3
8, 40 (manufactured by Orient Chemical Co., Ltd.), Aizen Spiron Black TRH, BHH (manufactured by Hodogaya Chemical Co., Ltd.), Kayaset Black T-22,004 (manufactured by Nippon Kayaku Co., Ltd.), copper phthalocyanine dye S-39 ( Orient Chemical Industry Co., Ltd.), Chromium Complex Salts E-81, 82 (Orient Chemical Industry Co., Ltd.), Zinc Complex Salt E-84 (Orient Chemical Industry Co., Ltd.), Aluminum Complex Salt E-86 (Orient Chemical Industry Co., Ltd.), Calix Allen System compounds and the like can be used.

As for the charge control agent having a large particle diameter, it is desirable to use a charge control agent which has been subjected to a treatment such as pulverization in advance and adjusted to a desired particle diameter. When the charge control agent is dispersed and contained in the toner, the charge control agent is 0.1 to 2 parts by weight based on 100 parts by weight of the binder resin of the toner.
0 parts by weight, preferably 0.1 to 10 parts by weight, and a charge control agent adheres to the surface of the toner.
In the case of fixing, it is desirable to add 0.001 to 10 parts by weight, preferably 0.05 to 2 parts by weight of a charge control agent to 100 parts by weight of the binder resin of the toner.

Further, if necessary, an offset preventing agent may be added to the toner. As an anti-offset agent,
Polyolefin waxes such as low molecular weight polyethylene wax, low molecular weight oxidized polyethylene wax, low molecular weight polypropylene wax, low molecular weight oxidized polypropylene wax, higher fatty acid wax, higher fatty acid ester wax, sasol wax, candelilla wax, carnauba wax, etc. Can be used alone or in combination of two or more. The offset preventing agent may be added in an amount of 1 to 15 parts by weight, preferably 2 to 8 parts by weight, based on 100 parts by weight of the binder resin of the toner.

Further, it is desirable that the toner has a surface on which a fluidizing agent is added, and the adding process of the fluidizing agent is performed by mechanically mixing the toner and the fluidizing agent. As the fluidizing agent, silica fine particles, titanium dioxide fine particles, alumina fine particles, magnesium fluoride fine particles, silicon carbide fine particles, boron carbide fine particles, titanium carbide fine particles, zirconium carbide fine particles, boron nitride fine particles, titanium nitride fine particles, zirconium nitride fine particles, magnetite Fine particles, molybdenum disulfide fine particles, aluminum stearate fine particles, magnesium stearate fine particles, zinc stearate fine particles, fluororesin fine particles,
Acrylic resin fine particles can be used alone or in combination of two or more. The amount of the fluidizing agent added is 0.05 to 2% by weight, preferably 0.1 to 1% by weight based on the toner.
It is. When the amount is less than 0.05% by weight, the fluidity of the toner is insufficient, and when it is more than 2% by weight, the environmental stability is impaired. In particular, the toner is charged when used in a high temperature and high humidity environment. The problem of volume reduction occurs. It is preferable to use a fluidizing agent that has been subjected to a hydrophobizing treatment. As the hydrophobizing agent, a silane coupling agent, a titanium coupling agent, a higher fatty acid, a silicone oil, or the like can be used. For a full-color toner, it is preferable to use two types of the above-mentioned hydrophobizing fluidized agents in combination, and it is preferable to use hydrophobic silica and hydrophobic titanium oxide or hydrophobic silica and hydrophobic aluminum oxide. Is preferred.

Further, the toner may be used as a magnetic toner, and known magnetic fine particles may be dispersed in a binder resin. As the magnetic material, for example, cobalt, iron,
Ferromagnetic metals such as nickel, cobalt, iron, nickel, aluminum, lead, magnesium, zinc, antimony, beryllium, bismuth, cadmium, calcium,
Known magnetic materials such as alloys of metals such as manganese, selenium, titanium, tungsten, and vanadium, mixtures of these metals, oxides, and fired bodies (ferrites) can be used.

The toner suitably used in the present invention has a weight average particle size of 3 to 15 μm, preferably 3 to 9 μm. In addition, the content of particles having a weight twice or more of the weight average particle size is 1%.
It is desirable to use those having a content of particles of not more than 5% by weight and not more than 1/3 of the weight average particle size.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments. The molecular weight of the resin was determined by gel permeation chromatography (GPC) using commercially available monodispersed standard polystyrene as a standard, tetrahydrafuran as a solvent, and a refractometer as a detector. Detector: SHOdex RI SE-31 Solvent: Tetrahydrofuran column: A-80M x 2 + KF-802 Flow rate: 1.2 ml / min Sample: 0.25% THF solution Toner Production Example (Production of Positively Charged Toner A) Ingredient parts by weight ・ Styrene-n-butyl methacrylate resin 100 (softening point: 132 ° C., glass transition point: 60 ° C.) ・ Carbon black 8 (MA # 8: manufactured by Mitsubishi Chemical Corporation) ・ Nigrosine dye 5 (Bontron N-01: Orient・ Low molecular weight polypropylene 3 (High Wax 105P: manufactured by Mitsui Petrochemical Co.) After thoroughly mixing the above materials with a Henschel mixer, 14
The mixture was kneaded by a twin-screw extruder heated to 0 ° C. The kneaded product was allowed to cool, coarsely pulverized, and further finely pulverized by a jet mill. Next, air classification was performed to obtain a toner having an average particle diameter of 13 μm. Then, the hydrophobic silica (R-
972: manufactured by Nippon Aerosil Co., Ltd.) in an amount of 0.1% by weight.
The mixture was mixed with a Waring blender to obtain toner A.

(Manufacture of negatively chargeable toner B) Component parts by weight ・ Styrene-n-butyl methacrylate resin 100 (softening point: 132 ° C., glass transition point: 60 ° C.) ・ Carbon black 5 (MA # 8: manufactured by Mitsubishi Chemical Corporation)・ Chromium-containing dye 3 (Spiron Black TRH: Hodogaya Chemical Co., Ltd.) ・ Low molecular weight polypropylene 3 (High Wax 105P: Mitsui Petrochemical Co., Ltd.) After thoroughly mixing the above materials with a Henschel mixer, 14
The mixture was kneaded by a twin-screw extruder heated to 0 ° C. The kneaded product was allowed to cool, coarsely pulverized, and further finely pulverized by a jet mill. Next, air classification was performed to obtain a toner having an average particle diameter of 11 μm. Then, silica (H-200) is applied to the toner.
0: manufactured by Nippon Aerosil Co., Ltd.) was added in an amount of 0.2% by weight and mixed with a Waring blender to obtain toner B.

(Production of negatively charged magenta toner C) Ingredients: parts by weight ・ Polyester resin 100 (softening point: 130 ° C., glass transition point: 60 ° C., weight average molecular weight: 14000, number average molecular weight: 7000) ・ Lionol Red 6B FG-4213 2.5 (manufactured by Toyo Ink Mfg. Co., Ltd.) Charge control agent 3 (Bontron E-84: manufactured by Orient Chemical Co.) The above materials were sufficiently mixed with a Henschel mixer, and then kneaded with a twin-screw extruder. The kneaded product was allowed to cool, coarsely pulverized, and further finely pulverized by a jet mill. Next, air classification was performed to obtain a toner having an average particle size of 8 μm. Then, 0.3% by weight of hydrophobic silica (H-2000: manufactured by Nippon Aerosil Co., Ltd.) and hydrophobic titanium oxide (T-80) were added to the toner.
5: manufactured by Nippon Aerosil Co., Ltd.) and mixed with a Waring blender to obtain toner C.

COMPARATIVE EXAMPLE 1 A ferrite particle having an average particle size of 45 μm was coated with a styrene / n-butyl acrylate resin so as to have a coating resin amount of 1.5% by weight, and a carrier A having an electric resistance of 10 ⁹ Ω · cm. I got In addition, the electric resistance of the carrier was measured on a metal circular electrode with a thickness of 2 m.
m, a carrier sample is placed using a cell having an electrode area of 9 cm ² , an electrode is placed on the carrier sample, 1 kg of pressure is applied, and a current value one minute after a DC voltage of 100 V is applied is read. It was determined by converting the specific resistance value. The measurement environment was a temperature of 22 ° C. and a relative humidity of 55%. The measurement was repeated five times, and the average was taken.

Comparative Example 2 A carrier B having an electric resistance of 10 ¹¹ Ω · cm was obtained in the same manner as in Comparative Example 1 except that the amount of the coating resin was changed to 2.0% by weight.

Comparative Example 3 A carrier C having an electric resistance of 10 ¹³ Ω · cm was obtained in the same manner as in Comparative Example 1, except that the amount of the coating resin was changed to 2.5% by weight.

(Comparative Example 4) To the carrier C obtained in Comparative Example 3, conductive titanium oxide fine particles (ECTT-1: manufactured by Titanium Industry Co., Ltd.) treated with tin oxide / antimony for surface conductivity were added. 2% by weight added, tumbler-shaker-
Mix for 15 hours with a mixer and have an electrical resistance of 10 ¹¹ Ω · cm
Was obtained. Observation of the obtained carrier with a scanning electron microscope revealed that the conductive titanium oxide fine particles were partially buried and held in the resin coat layer of the carrier.

(Example 1) Styrene (75 parts) / n-butyl acrylate (20 parts) / ferrite particles having an average particle diameter of 45 μm so that the coating resin amount becomes 2.0% by weight.
A carrier having an electric resistance of 10 ¹² Ω · cm was obtained by coating with a resin of metaacramide t-butylsulfonic acid (5 parts).

After adding 0.1% by weight of conductive titanium oxide fine particles (ECTT-1: manufactured by Titanium Industry Co., Ltd.) to the carrier, a heat treatment apparatus (Saffusion System: manufactured by Nippon Pneumatic) was added. The conductive titanium oxide fine particles were fixed on the surface of the resin coat layer of the carrier. Thus, a carrier E having an electric resistance of 10 ¹³ Ω · cm was obtained. Observation of the obtained carrier with a scanning electron microscope revealed that the conductive titanium oxide fine particles were partially buried and held in the resin coat layer of the carrier.

(Example 2) With respect to the carrier E obtained in Example 1, conductive titanium oxide fine particles (ECTT-1:
After adding 0.2% by weight of Titanium Industry Co., Ltd., the conductive titanium oxide fine particles were fixed to the surface of the resin coat layer of the carrier using a surface treatment device (Hybridizer: manufactured by Nara Machinery Co., Ltd.). Thus, the electrical resistance is 10 ¹⁴ Ω
・ Cm carrier F was obtained. Observation of the obtained carrier with a scanning electron microscope revealed that the conductive titanium oxide fine particles were partially buried and held in the resin coat layer of the carrier.

(Example 3) Carrier obtained in Example 1
E is treated with tin oxide and antimony to make the surface conductive.
Conductive titanium oxide fine particles (ECTT-1: Titanium Industry
0.2% by weight) and tumbler shaker-mi
Mix for 15 hours with an electric resistance of 10 ¹²Ω · cm
Carrier G was obtained. The obtained carrier is scanned with a scanning electron microscope.
When observed with a mirror, the conductive resin coating layer on the carrier
The titanium oxide fine particles were partially buried and held.

Example 4 The coating resin was styrene (65
Parts) / n-butyl acrylate (20 parts) / methacrylamide t-butyl sulfonic acid (15 parts) except that the resin had an electrical resistance of 10 ¹¹ Ω in the same manner as in carrier E.
-A carrier H of cm was obtained. Observation of the obtained carrier with a scanning electron microscope revealed that the conductive titanium oxide fine particles were partially buried and held in the resin coat layer of the carrier.

Example 5 The coating resin was styrene (75
Parts) / mono-n-butyl maleate (20 parts) /
Carrier I having an electric resistance of 10 ¹⁰ Ω · cm was obtained in the same manner as in Carrier E, except that the resin was made of metaacramide t-butylsulfonic acid (5 parts). Observation of the obtained carrier with a scanning electron microscope revealed that the conductive titanium oxide fine particles were partially buried and held in the resin coat layer of the carrier.

(Various evaluations) Measurement of charge amount 97 parts by weight of each carrier and toner A or toner B 3
The developer was prepared by putting parts by weight in a 100 ml screw tube. The amounts of charge when this developer was mixed for 1 minute and 60 minutes with a Turbler shaker mixer were defined as (Q1) and (Q60), respectively. Printing durability test Each carrier and toner C were mixed to adjust the developer concentration to 3%, and a printing durability test was performed using a full color copying machine CF-70 (manufactured by Minolta).

The printing durability test was performed at 20 ° C. and 65% RH (N /
The durability of the developer (charge stability, toner fog) was evaluated by performing a 20,000-sheet printing test in the environment of N).
A printing durability test of 10,000 sheets was performed in an environment of 0 ° C. and 85% RH (H / H) to evaluate carrier adhesion and image quality in a high humidity environment.

With respect to the charge amount stability, the charge amount was measured at the initial stage and after printing for 20,000 sheets.
Those smaller than μc / g were evaluated as ○, those with 5 to 10 μc / g were evaluated as Δ, and those larger than 10 μc / g were evaluated as x. Regarding toner fog on the image, toner fog on a white background image was evaluated and ranked. A sample without toner fog was evaluated as ○, a sample with slight toner fog but practically usable was rated as Δ, and a sample with much fog and practically unusable was evaluated as ×.

Regarding the adhesion of the carrier, the adhesion of the carrier around the characters of the image was evaluated and ranked. A sample without carrier adhesion was evaluated as 、, a sample with slight carrier adhesion that was practically usable was rated as Δ, and a sample with a large amount of carrier adhesion that was not practically used was evaluated as ×. Regarding the image evaluation at high humidity, the texture of the solid portion of the image was evaluated and ranked. The ones with good texture in the solid part were evaluated as good, the ones with slightly poor texture but practically usable were evaluated as poor, and those with rough texture that could not be practically used were evaluated as x.
Was evaluated.

[0045]

[Table 1] The carrier of Comparative Example 1 has little change in the charge amount even after copying 20,000 sheets and has good durability without toner fog, but carrier adhesion is observed on the image from the beginning,
Further, in a high humidity environment, the image of the solid portion was noticeable.

The carrier of Comparative Example 2 showed a large change in the charge amount after copying 20,000 sheets, toner fog was observed on the image, and the durability was lower than that of the carrier of Comparative Example 1. However, the carrier adhesion on the image and the image quality under a high humidity environment were improved as compared with the carrier of Comparative Example 1.

The carrier of Comparative Example 3 had a larger change in the charge amount after copying 20,000 sheets than the carrier of Comparative Example 2,
Many toner fogs were observed on the image, and the durability was lower than that of the carrier of Comparative Example 2. However, the carrier adhesion on the image and the image quality under a high humidity environment were improved as compared with the carrier of Comparative Example 1.

The carrier of Comparative Example 4 was inferior in carrier adhesion on an image and image quality in a high humidity environment. The chargeability of both the positively chargeable toner and the negatively chargeable toner was examined. As a result, the carrier of Comparative Example 1 was excellent in chargeability of both, but the carriers of Comparative Examples 2, 3, and 4 were compared. Was inferior in chargeability to positive polarity toner. In contrast, the carriers of Examples 1 to 4
The toner was excellent in negative polarity toner, especially in chargeability for positive polarity, durability, carrier adhesion, and image quality in a high humidity environment.

[0049]

According to the present invention, it is possible to provide a carrier having excellent durability, excellent carrier adhesion and excellent image quality in a high environment.

Claims (1)

[Claims] 1. A magnetic particle comprising a styrene monomer, an n-butyl acrylate monomer, an n-butyl methacrylate monomer, a methacrylic acid monomer, a mono-n-butyl maleate monomer,
Coated with a resin composed of at least one monomer of a maleic acid diethyl monomer and a di-n-butyl maleate monomer and acrylamidoalkylsulfonic acid and / or methacrylamidoacrylsulfonic acid (formula 1) The electric resistance 1 obtained by subjecting the surface of the resin-coated particles having an electric resistance of 10 ¹¹ Ω · cm or more to conductive fine particles is used.
A resin-coated carrier having 0 ¹⁰ to 10 ¹⁴ Ω · cm. General formula (R ₁ ; H, CH ₃ , R ₂ ; a linear or branched alkyl group having 1 to 8 carbon atoms)