WO1998026332A1

WO1998026332A1 - Carrier for electrophotography and developer using the carrier

Info

Publication number: WO1998026332A1
Application number: PCT/JP1997/004563
Authority: WO
Inventors: Shigeo Matsuzaki; Takashi Arakane; Kazuo Murakata; Susumu Kikuchi
Original assignee: Idemitsu Kosan Co., Ltd.; Kyocera Corporation
Priority date: 1996-12-11
Filing date: 1997-12-11
Publication date: 1998-06-18
Also published as: JPH10171168A; DE69724592D1; TW384418B; DE69724592T2

Abstract

A carrier for electrophotography making the most of excellent characteristics of a carrier having a polyolefinic resin coating, being freely adjustable of its charge quantity and its static resistance, being also obtainable of an image having a stable density and being able to effectively prevent external additives from being spent due to adhesion of the external additives, and a developer for electrophotography using this carrier. In a carrier for electrophotography including a carrier core material having magnetism and a coating layer consisting of a high molecular weight polyethylene resin covering the surface of the carrier core material, the coating layer consisting of the high molecular weight polyethylene resin includes, at least as the outermost layer, a layer containing magnetic powder the cubic shape of which is a convexed polyheral body encompassed by at least six flat and/or curved surfaces, or a layer containing this magnetic powder, silica and/or a fine particle resin.

Description

Description Electrophotographic carrier and electrophotographic developer using the same

The present invention relates to an electrophotographic carrier and an electrophotographic developer using the same. More specifically, the present invention relates to an electrophotographic carrier used for developing an electrostatic latent image in an image forming method using electrophotography, and an electrophotographic developer using the same. Background art

Conventionally, the electrostatic latent image developing method for electrophotography has been developed as a one-component magnetic jumping developing method, a one-component non-magnetic contact developing method, or by mixing an insulating non-magnetic toner with magnetic carrier particles to rub the toner. There is known a two-component developing system in which a developer is conveyed while being charged, and is developed by being brought into contact with an electrostatic latent image.

In particular, the application of the two-component developing method to a color printer is being reviewed as a future development.

The granular carrier used in such a two-component developing system prevents toner filming on the carrier surface, forms a uniform carrier surface, extends the life of the developer, adjusts the amount of damage or charge on the photoreceptor carrier, etc. For this purpose, it is customary to coat a magnetic carrier core material with a suitable material.

However, the conventional resin-coated carrier is not satisfactory in terms of durability because the coating easily peels off due to impacts such as stirring during use.

As a method for solving such a problem, the present inventor has conducted polymerization of an olefin monomer directly on carrier core particles such as ferrite. A technology for forming a olefin resin-based coating was developed and proposed earlier (for example, Japanese Patent Application Laid-Open No. Hei 2-18771). Polyolefin resin-coated carriers obtained by this method have a strong coating between the core material and the coating, because the coating is formed directly on the carrier core particles, and the image quality deteriorates even after long-term continuous copying. And has excellent durability and spent resistance.

However, on the other hand, this polyolefin-based resin-coated carrier cannot control the charge polarity and adjust the charge amount, etc., and also causes the external additive to be spent due to the adhesion of the toner external additive. However, it did not necessarily have sufficient durability, for example, due to problems such as the occurrence of problems.

In addition, it did not always have satisfactory performance with regard to fine adjustment of resistance value and adjustment of image density.

As a method for solving the above-mentioned problem, Japanese Patent Application Laid-Open No. 53-10042 discloses a method in which a carrier coating resin contains a nigricin to improve the negative charge amount. In addition, Japanese Patent Application Laid-Open No. 61-9661 discloses an example in which a fluidity improving agent is added to improve the fluidity. Furthermore, Japanese Patent Application Laid-Open No. 2-210365 discloses a technique in which one of conductive particles, inorganic filler particles, and a charge controlling agent is added to prevent uniform chargeability and prevent spent. I have.

However, all of these technologies take advantage of the excellent properties of the above-mentioned polyolefin resin-coated carrier to freely control the charge polarity, adjust the charge amount, and adjust the resistance. Preventing both could not be satisfied.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and makes it possible to freely adjust a charge amount and a static resistance while taking advantage of the excellent characteristics of a carrier having a polyolefin-based resin coating, and to achieve stable density. An object of the present invention is to provide an electrophotographic carrier and an electrophotographic developer using the same, which can obtain an image and effectively prevent the external additive from being spent on the toner due to adhesion of the external additive. And Disclosure of the invention

In order to achieve the above object, according to the present invention, there is provided an electrophotographic carrier having a carrier core having magnetism and a coating layer made of a high molecular weight polyethylene resin covering the surface of the carrier core;

A coating layer made of a high-molecular-weight polyethylene resin is used as at least the outermost shell layer, a layer containing a magnetic powder that is a convex polyhedron whose three-dimensional shape is surrounded by six or more planes and / or curved surfaces, or this magnetic powder and silica And an electrophotographic carrier characterized by having a layer containing fine particle resin.

In a preferred embodiment, the carrier for electrophotography according to claim 1, wherein the average particle size of the magnetic powder is in the range of 0.1 to 1 μm.

Further, as a preferred embodiment, the resistance value is 1 0 ² to 1 0 "electrophotographic carrier which is a Omega · cm is provided.

Further, as a preferred embodiment thereof, the electrophotographic carrier is 2 to 40% by weight based on the total amount of the carrier and the toner. The present invention provides an electrophotographic developer comprising a toner mixed at a ratio of / ₀ . BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an explanatory diagram showing the dependence of the image density on the magnetic field potential in Application Example 1 of the present invention.

FIG. 2 is an explanatory diagram showing the results of continuous printing evaluation in Application Example 2 of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the electrophotographic carrier of the present invention and an electrophotographic developer using the same will be specifically described.

I. Carrier for electrophotography The electrophotographic carrier of the present invention has a carrier core material and a coating layer made of a high molecular weight polyethylene resin that coats the surface of the carrier core material, and at least the coating layer made of the high molecular weight polyethylene resin has The outermost shell layer has a layer containing magnetic powder which is a convex polyhedron surrounded by planes or curves having three or more three-dimensional shapes, or a layer containing this magnetic powder and silica and / or fine particle resin. I have.

Hereinafter, each component will be specifically described.

1. Carrier core material

(1) Material

The carrier core material used in the present invention is not particularly limited, and those known as two-component carriers for electronic photography, such as ferrite, magnetite, and metals such as iron, nickel, and cobalt; Alloys or mixtures of these metals with metals such as copper, zinc, antimony, aluminum, lead, tin, bismuth, beryllium, manganese, magnesium, selenium, tungsten, di / recombium, and vanadium; A mixture of the ferrite or the like, a metal oxide such as iron oxide, titanium oxide, or magnesium oxide; a nitride such as chromium nitride or vanadium nitride; or a carbide such as silicon carbide or tungsten carbide; , And (1) a mixture thereof.

(2) Shape and particle size

The shape is not particularly limited, and may be spherical or irregular. Although there is no particular limitation on the particle size, for example, those having a particle size of 20 to 100 / m can be suitably used. If it is less than 20 // m, the carrier may adhere (scatter) to the electrostatic latent image carrier (generally the photoreceptor). If it exceeds 1 OO / zm, carrier streaks etc. will occur, May decrease. (3) Composition ratio

The composition ratio of the carrier core material is set to 90% by weight or more, preferably 95% by weight or more of the entire carrier. This composition ratio indirectly defines the thickness of the resin coating layer of the carrier. If the composition ratio is less than 90% by weight, the coating layer becomes too thick, and even if the coating layer is actually applied to the developer, the coating layer peels off, the charge amount increases, and the durability required for the developer is reduced. Charging stability cannot be satisfied. In addition, fine line reproducibility is inferior in image quality, and problems such as a decrease in image density occur. There is no particular upper limit, but the upper limit is such that the coating resin layer completely covers the surface of the carrier core material. This value varies depending on the physical properties of the carrier core material and the coating method.

(4) Conductive layer

A conductive layer may be provided on the carrier core particles, if necessary, prior to coating with a high molecular weight polyethylene resin.

As the conductive layer formed on the carrier core particles, for example, a layer in which conductive fine particles are dispersed in an appropriate binder resin can be used. The formation of such a conductive layer is effective in enhancing the developability and obtaining a high-contrast clear image with high image density. This is probably because the presence of the conductive layer causes the electrical resistance of the carrier to be reduced appropriately, and the charge to be leaked and accumulated in a well-balanced manner.

As the conductive fine particles to be added to the conductive layer, include carbon black, the force one carbon black such Asechi Ren black, carbide such as S i C, magnetic powder such as Maguneta wells, the S N_〇 _2, and titanium black be able to. Examples of the binder resin for the conductive layer include a polystyrene resin, a poly (meth) acrylic resin, a polyolefin resin, a polyamide resin, a polycarbonate resin, a polyether resin, a polysulfonic acid resin, and a polyester resin. , Epoxy-based resins, polybutyral-based resins, urea-based resins, urethane / urea-based resins, silicon-based resins, Teflon-based resins and other thermoplastic resins and thermosetting resins, and mixtures thereof. Resin copolymers, block polymers, graft polymers, polymer blends, and the like.

The conductive layer can be formed by applying a solution in which the conductive fine particles are dispersed in the above-described appropriate binder resin to the surface of the carrier core material particles by a spray coating method, a diving method, or the like. It can also be formed by melting, kneading and pulverizing core particles, conductive fine particles and binder resin. Further, it can also be formed by polymerizing a polymerizable monomer on the surface of the core particles in the presence of the conductive fine particles. The size and amount of the conductive fine particles are not particularly limited as long as they satisfy various characteristics such as electric resistance of the finally obtained carrier of the present invention. Particle size that can be uniformly dispersed in the resin solution, specifically, average particle size of 2 to 0.01 // m, preferably:! ~ 0.01 μm is enough. Although the amount of the conductive fine particles to be added cannot be specified strictly depending on the type or the like, the amount is 0.1% by weight to 60% by weight with respect to the binder resin of the conductive layer. / ₀ , preferably from 0.1 to 40% by weight. / ₀ is appropriate. Especially the carrier filling rate is 90 weight. / _0, and the thickness of the coating layer is relatively thick, the continuous reproducibility of fine lines using such a carrier causes a problem of reduced reproducibility. The problem is solved by the addition of the conductive fine particles.

Hereinafter, those in which a functional layer such as a conductive layer is formed on the carrier core particles will be simply referred to as carrier core particles without misunderstanding.

2. Coating layer composed of high molecular weight polyethylene resin

(1) Molecular weight of resin

The high-molecular-weight polyethylene resin is usually simply referred to as polyethylene. In the present invention, a resin having a number-average molecular weight of 10,000 or more or a weight-average molecular weight of 50,000 or more is particularly preferable. In general, the number average molecular weight is less than 10,000. For example, polyethylene wax (Mitsui High Wax (Mitsui Petrochemical), Dialen 30 (Mitsubishi Chemical), Stone Rexpol (manufactured by Nippon Oil Co., Ltd.), Sunwax (manufactured by Sanyo Chemical Co., Ltd.), Poly Let's (manufactured by Chusei Wax Polymer Co., Ltd.), Neowax (manufactured by Yasuhara Chemical Co., Ltd.), AC Polyethylene (manufactured by Allied Chemical Co., Ltd.) ), Epolen (Eastman's Kodak), Hex Wax (Hexto), A-Wax (BASF), Polywax (Petrolite), Escoma (Exon) Chemical Co., Ltd.) is distinguished from the high molecular weight polyethylene resin used in the present invention. Polyethylene wax can be coated by ordinary dipping or spraying by dissolving it in hot toluene or the like.However, due to the low mechanical strength of the resin, the It is peeled off from the core material due to shear and the like.

In addition, one or more kinds of functional fine particles such as the conductive fine particles and the fine particles having charge control ability described later may be added to the coating layer made of the high molecular weight polyethylene resin.

(2) Coating layer formation method

The method for forming the coating layer used in the present invention is not particularly limited, and known methods such as dipping method, fluidized bed, dry method, spray drying, polymerization method, etc. S, polyethylene resin The following polymerization method is preferred for the coating of (1) because the resin coating strength is high and the resin is hardly peeled off.

①Polymerization method

The polymerization method refers to a method in which the surface of a carrier core material is treated with an ethylene polymerization catalyst to produce a polyethylene resin-coated carrier while polymerizing (generating) ethylene directly on the surface. Examples of the method include the methods described in Japanese Patent Application Laid-Open No. 10-68080 and Japanese Patent Application Laid-Open No. 2-187770. That is, the polyethylene resin coating layer is prepared by pre-contacting a carrier core material with a highly active catalyst component containing titanium and / or zirconium and soluble in a hydrocarbon solvent (eg, hexane, heptane, etc.). Using the resulting product, and an organoaluminum compound, It can be formed by suspending in a hydride solvent, supplying an ethylene monomer, and polymerizing on the surface of the carrier core material. Further, when the fine particles having the charge imparting function or the conductive fine particles are added, they may be added and present at the time of forming the high molecular weight polyethylene resin coating layer.

In this production method, the polyethylene coating layer is formed directly on the surface of the carrier core material, so that the resulting coating has excellent strength and durability.

As described above, if functional fine particles such as conductive fine particles and fine particles having charge control ability are dispersed and coexisted in the polymerization system, when a high molecular weight polyethylene resin coating is grown and formed by polymerization, The functional fine particles are taken into this coating, and a high molecular weight polyethylene resin coating containing the functional fine particles is formed.

The high molecular weight polyethylene resin coating is preferably formed so that the weight ratio of [carrier core material particles] / [high molecular weight polyethylene resin coating] = 99.5 / 0.5 to 90 ° 10. And more preferably 991 to 95/5.

③ Addition and loading of functional fine particles

In the high molecular weight polyethylene resin coating, one or more kinds of functional fine particles such as conductive fine particles and fine particles having charge control ability can be added and supported as described above to modify the high molecular weight polyethylene resin coating.

As the conductive fine particles to be added and supported in the high molecular weight polyethylene resin coating, all conventionally known conductive fine particles can be used, for example, the above-mentioned conductive materials such as carbon black, carbide such as SiC, and magnetite. magnetic powder, S n 0 _2, it is possible to use a titanium black. The average particle size of the conductive fine particles is preferably from 0.01 to 5.0 μm. (3) Outer shell layer

The coating layer is a layer containing a magnetic powder which is a convex polyhedron surrounded by a plane or curved surface having a three-dimensional shape of at least 6 as its outermost shell layer, or a layer containing the magnetic powder and silica and And / or a layer containing fine particle resin.

① Magnetic powder

Examples of the material of the magnetic powder used in the present invention include magnetite, ferrite, iron powder and the like.

The three-dimensional shape of the magnetic powder is a convex polyhedron surrounded by six or more planes and / or curved surfaces. Usually, a polyhedron means a solid surrounded only by a plane, but the present invention also includes a solid body in which all or some of the surfaces are curved. It is important that ridges and vertices formed by such a plane or a curved surface exist.

With such a polyhedron, the conductive efficiency is improved by changing from a conductive mechanism at the surface to a conductive mechanism at a point at the convex portion of the polyhedron.

The polyhedron may be a single kind or a combination of plural kinds. The average particle size is preferably from 0.1 to 1 / m, more preferably from 0.2 to 0.7 // m. If it is less than 0. 1 m, the effect as a spacer is lost, and if it exceeds l / m, it may not be possible to add it to the outermost shell layer.

The resistance is preferably 1E + 7 to: IE + 10Ω · cm, and more preferably 1E + 7 to: 1Ε + 9Ω · c. If it is less than 1 E + 7 Ω.cm, the chargeability may be impaired. If it exceeds 1 E + 10 Ω · cm, the resistance cannot be adjusted, and the function as a magnetic powder may not be achieved.

Commercially available products include Magnetite MG-1306 (octahedron) and Magnetite MG-9300 (polyhedron) manufactured by Mitsui Kinzoku Co., Ltd. ②Silica

Examples of the silica used in the present invention include those obtained by subjecting silica to a surface beading treatment so as to be positively or negatively chargeable. The primary particle size is preferably 40 nm or less, more preferably 10 to 30 nm. If it exceeds 40 nm, the gap between the silica particles becomes large and irregularities occur on the carrier surface.

Commercially available products include RA 200 HS manufactured by Nippon Aerosil and 2015 EP and 2050 EP manufactured by Pecker Chemicals as positively chargeable silica, and Nippon Aerosil Co., Ltd. as negatively chargeable silica. R812, RY200, 2000, 20004 manufactured by Pecker Chemicals, and the like.

It is preferable to add negatively chargeable silica to the positively charged toner, and to add positively chargeable silica to the negatively charged toner.

③ Fine particle resin

Examples of the fine particle resin used in the present invention include the following negatively chargeable resin (A) and positively chargeable resin (B).

(A) Negatively chargeable resin

Fluorine-based resins (eg, vinylidene fluoride resin, tetrafluoroethylene resin, ethylene trifluoride ethylene resin, tetrafluoroethylene-hexylene propylene copolymer resin, etc.), vinyl chloride resin, celluloid

(B) Positive charging resin

Acrylic resin, polyamide resin (eg, nylon-6, nylon-6, nylon-11, etc.), styrene resin (polystyrene, ABS, AS, AAS, etc.), vinylidene chloride resin, polyester resin (Eg, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyatalylate, polyoxybenzoyl, polycarbonate, etc.), polyether-based resin (polyacetal, polyphenylene) Ethylene resin (EVE, E EA, EAA, EMA A, EA AM, EMMA, etc.)

It is preferable that a negatively chargeable resin be added to the positively charged toner, and a positively chargeable resin be added to the negatively charged toner.

Further, both the silica and the fine particle resin may be contained, or only one of them may be contained. Further, the silica and the fine particle resin may each be a single kind or a plurality of kinds.

The layer thickness of the outermost shell is preferably 0.1 to 6 tm. If it is less than _0. 1 μ Γ η, the coating is incomplete, when it exceeds 6 Myuiotaita, there is a risk that peeling of the outermost layer by mechanical impact such as friction from the outside occurs.

方法 Method of forming and fixing outermost shell layer

The method of forming and fixing the outermost shell layer used in the present invention is based on the particle size and shape of the magnetic powder to be used and the physical properties of the silica type and silica or resin (particle size, solubility in organic solvents, melting point, hardness, etc.). ), Can be selected from the following two types and used alone or in combination.

(i) Fixing by mechanical impact

Using a crusher such as a Henschel mixer (Mitsui Miike Koki Co., Ltd., FM10L type), a core material coated with a high molecular weight polyethylene resin and an appropriate amount of magnetic powder, or magnetic powder and silica and / or fine particle resin The outermost layer is formed by a mixture of the above. At this time, the amount of the magnetic powder or the mixture of the magnetic powder and the silica or Z or fine particle resin is determined by the resistance value to be changed, the absolute value of the charge amount, and the stability of the density of the actual printed image.

Specifically, 0.1 to 50 phr (% by weight of the additive to the coating resin) based on the coated polyethylene amount of the high molecular weight polyethylene coated carrier is used. Usually, it is added in a ratio, but considering durability, resistance change due to formation of the outermost layer, and production stability, an appropriate amount is about 20 to 30 phr. The treatment with the Henschel mixer is performed in a treatment amount of 1 to 5 kg at a low rotation speed at which the added magnetic powder, silica, and particulate resin are not scattered.

The treatment time varies depending on the amount of the magnetic powder to be added, the amount of silica and / or fine particle resin, the amount of the coated high molecular weight polyethylene, and the like, but should be about 0.5 to 5 hours. In fixing magnetic powder, silica, Z or fine particle resin by mechanical shock, dust (various fine powder, etc.) is generated, so classification must be performed sufficiently.

(ii) Thermal fixation by heating

Using a heat-sphering machine (Hosokawa Micron Co., Ltd., thermo-sphering machine), etc., a high-molecular-weight polyethylene resin-coated carrier and an appropriate amount of magnetic powder, or a magnetic powder and silica and / or fine particles are used. The outermost shell layer is formed by the mixture. The amount of the magnetic powder, silica, Z or fine particle resin added at this time is determined by the absolute value of the charge amount to be changed and the stability of the actual printed image.

Specifically, it is usually added at a rate of 0.1 to 50 phr to the amount of coated polyethylene of the high molecular weight polyethylene-coated carrier, but durability, resistance change due to outermost shell layer formation, and production stability Considering the nature, 20 to 30 phr is appropriate.

In the thermal sphering treatment, it is necessary to uniformly adhere magnetic powder, silica and Z or fine particle resin to the surface of the high molecular weight polyethylene resin-coated carrier before the treatment. Therefore, in addition to ball milling, V blender processing, etc., mixing processing such as Henschel mixer processing (about 1 minute) is performed, and magnetic powder and fine powder of silica, silica, or fine particle resin are electrostatically or mechanically subjected to high molecular weight polyethylene. Attach to resin-coated carrier surface. It is immobilized by instantaneous heating while uniformly attached to the surface of a high molecular weight polyethylene resin-coated carrier, forming an outermost shell layer. 3. Carrier conductive properties

The conductive properties of Canon rear, optimum for the system developer using Kiyaria is vary, generally, the resistance measurement is an indication of the value of ^{^{1 0 2 ~ 1 0 14 (}} Ω · cm) preferable.

1 Kiyaria development and to be less than 0 ² Ω · cm, there is Re emesis that fogging occurs, 1 ◦ "exceeds Omega · cm when there fear force in image density decrease or the like image quality deterioration.

The resistance value was determined by applying a voltage of 1 to 500 V to the upper and lower electrodes by providing a carrier layer with a thickness of 0.5 cm under a load of 1 kg with an electrode area of 5 cm, and applying the current to the bottom. Was measured and converted.

I I. Electrophotographic developer

The electrophotographic developer of the present invention can be obtained by mixing the carrier with various toners. 1. Toner

As the toner used in the present invention, a toner produced by a known method, for example, a toner produced by a suspension polymerization method, a pulverization method, a microcapsule method, a spray drying method, or a mechanochemical method can be used. In addition, a binder resin, a colorant, and, if necessary, other additives such as a charge controlling agent, a lubricant, an offset preventing agent, and a fixing improving auxiliary can be blended. A magnetic material can be added to form a magnetic toner, which is effective for improving development characteristics and preventing toner from scattering inside the machine. Further, a fluidizing agent may be externally mixed to improve the fluidity. Examples of the binder resin include polystyrene resins such as polystyrene, styrene / butadiene copolymer, and styrene / acrylic copolymer, polyethylene, ethylene / butyl acetate copolymer, and ethylene / butyl alcohol copolymer. Ethylene copolymer, epoxy resin, phenolic resin, acrylic phthalate resin, polyamide resin Fats, polyester resins, maleic resins, and the like can be used. As the colorant, known dyes and pigments such as carbon black, Futaroshia Ninbunore, Indasurenpuru one, Peacock pull one, Nono ⁰ - Manentoretsu de, red iron oxide, Arizari Nreki, chrome green, Maracay Toguri Nreki, methylcarbamoyl Honoré bio Re' Toreki, Nono Nzai Yellow, no- ^zero —mant yellow, titanium oxide; positive charge control agents such as egrosin, nigrosine base, triphenylmethane compound, polybierpyridine, and quaternary ammonium salt as charge control agents A metal complex salt of an alkyl-substituted salicylic acid (for example, a chromium complex salt or a zinc complex salt of di-tert-butylsalicylic acid); and a lubricant such as Teflon, zinc stearate, and polyvinylidene fluoride; Anti-offset agent, fixation aid Polyolefin wax such as low molecular weight polypropylene or a modified product thereof; magnetite, ferrite, iron, nickel, etc. as magnetic material; silica, titanium oxide, aluminum oxide, etc. as fluidizing agent. Can be.

The average particle size of the toner is preferably 20 // m or less, more preferably 5 to 15 zm.

2. Mixing ratio

The mixing ratio of the toner in the present invention is 2 to 40% by weight of the total amount of the carrier and the toner. / ₀ , preferably 3 to 30% by weight, more preferably 4 to 25% by weight. If the mixing ratio of the toner is less than 2% by weight, the toner charge becomes too high to obtain a sufficient image density, and if it exceeds 40% by weight, a sufficient charge cannot be obtained. Scattered from the developing machine, contaminating the inside of the copier and toner capri on the image.

3. Applications

The developer of the present invention is a two-component or 1.5-component developing electrophotographic system such as a copier (analog, digital, monochrome, color), Used for linters (monochrome, color), fax, etc. Particularly, it is optimally used in high-speed / ultra-high-speed copiers and printers in which the stress applied to the developer in the developing machine is large. There are no particular restrictions on the image forming method, exposure method, developing method (apparatus), and various control methods (for example, toner concentration control method in the developing machine). The optimum carrier and toner resistance, particle size, and particle size depend on the system. The diameter distribution, magnetic force, charge amount, etc. may be adjusted. Example

Hereinafter, the present invention will be described more specifically with reference to examples.

(1) Preparation of catalyst component containing titanium

200 ml of dehydrated n-heptane at room temperature and 15 g (25 mmol) of magnesium stearate, which had been dehydrated at 120 ° C under reduced pressure (2 mmHg), were placed in a 500 ml flask with an inner volume replaced with argon. Into a slurry. After stirring, 0.44 g (2.3 mmol) of titanium tetrachloride was added dropwise, and the temperature was raised. The mixture was reacted under reflux for 1 hour, and a viscous transparent titanium-containing catalyst (active catalyst) solution was added. Obtained.

(2) Activity evaluation of titanium-containing catalyst components

Dehydrated hexane is added to a 1-liter autoclave with an inner volume replaced with argon.

400 ml, 0.8 mol of triethynolealuminum, 0.8 mmol of getinoleanolenedium chloride and 0.004 mmol of titanium containing the titanium-containing catalyst obtained in (1) above as a titanium atom. It was charged and heated to 90 ° C. At this time, the internal pressure was 1.5 kg / cm ² G. Then by supplying hydrogen, 5. After boosting to 5 kg / cm ² G, and continuously feeding ethylene to maintain the total pressure ^{9. 5 kg / cm 2 G,} 1 hour Polymerization Was performed to obtain 70 g of a polymer. The polymerization activity is 365 kg / g-Ti / Hr, and the MFR of the obtained polymer (190 ° C, load 2.16 k The melt flowability in g; JISK7210) was 40.

(3) Manufacture of polyethylene-coated carrier

960 g of sintered ferrite powder F_300 (manufactured by Padertec Co., Ltd., average particle size 50 / m) was placed in a 2-liter autoclave with argon replacement, and the temperature was raised to 80 ° C. Drying was performed for 1 hour under reduced pressure (10 mmHg). Thereafter, the temperature was lowered to 40 ° C., and dehydrated hexane 8 O Oml was added thereto, and stirring was started. Next, 5.0 millimol of getyl aluminum chloride and 0.05 millimol of the titanium-containing catalyst component (1) as a titanium atom were added, and the mixture was reacted for 30 minutes. Thereafter, the temperature was raised to 90 ° C, and 4 g of ethylene was introduced. At this time, the internal pressure was 3.0 kg / cm ² G. Then, hydrogen was supplied and the pressure was increased to 3.2 kg / cm ² G. Triethylaluminum 5.0 mmol was added and polymerization was started.The system pressure was 2.3 kg / cm ^{2 in} about 5 minutes. It decreased to G and stabilized. Then, 5.5 g of carbon black (manufactured by Mitsubishi Chemical Corporation; MA-100) was slurried with 100 ml of dehydrated hexane, and then the internal pressure was increased to 4.3 kg / cm ² G. 45 minutes while continuously supplying ethylene to maintain the temperature (stop the introduction when a total of 40 g of ethylene was introduced into the system) Polymerization was carried out, and 100 5.5 g of carbon black was contained in total. A ferrite coated with a polyethylene resin was obtained. The dried powder was uniformly black, and electron microscopy showed that the ferrite surface was thinly covered with polyethylene and that carbon black was uniformly dispersed in the polyethylene. When this composition was measured by TGA (thermal balance), the composition ratio of ferrite, carbon black, and polyethylene was 95.5: 0.5: 4.0 (weight ratio).

The intermediate stage carrier obtained through this step is called a carrier. The weight average molecular weight of the coated polyethylene was measured by GPC and found to be 206,000.

Next, the carrier was classified with a 125 μm sieve to remove particles having a large particle size of 125 / m or more. After classifying the carrier, the fluidized bed The carrier was placed in a flow classifier, and air (115 ° C) heated so that the airflow linear velocity of the classifier body became 20 (cmZs), and the carrier was allowed to flow for 10 hours. The resulting carrier and the carrier A _2.

[Example 1]

Carrier A ₂ 1 0 0 0 g capacity 1 0 Li Tsu Torr to the Nshienoremikisa: placed in (Mitsui Miike Engineering Corporation FM 1 0 L-type), career by stirring for 1 hour giving a mechanical impact by smoothing the surface of the a _2. Then the magnetic powder

(Mitsui Metals: Magnetite MG1306 (octahedral)) was mixed in an amount of 8 g, and a mechanical shock was further applied for 1 hour using a Henschel mixer to form a magnetic powder-containing outermost shell layer. For the purpose of removing magnetic powder that is not immobilized and exists in a free state, a large-diameter carrier and agglomerated magnetic powder were removed by sieving. In addition, in order to remove magnetic powder and the like that had not been fixed, treatment was performed at a linear velocity of 20 cm for 2 hours using a fluidized bed type air classifier. As a result, carrier B was obtained.

[Example 2]

Example 1 was the same as Example 1 except that the amount of magnetic powder mixed was changed from 8 g to 20 g. As a result, carrier C was obtained.

[Example 3]

Carrier A ₂ 1 OOO g is placed in a 10 liter Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd .: FM10L type), and stirred for 1 hour to give a mechanical shock to carrier A ₂ . The surface was smoothed. Then the magnetic powder

(Mitsui Metals: Magnetite MG 1306 (octahedral)) was mixed in an amount of 8 g, and a mechanical shock was applied with a Henschel mixer for an additional hour, followed by silica (Aerosil, Japan: R812). The mixture was mixed with 12 g, and further subjected to a mechanical shock with a Henschel mixer for 1 hour to form an outermost layer of a mixture of magnetic powder and silica. To remove magnetic powder and silica that are not immobilized and exist in a free state A large particle size carrier, agglomerated magnetic powder, and agglomerated silica were removed by sieving. In order to remove magnetic powder, silica fine particles, and the like that were not immobilized, treatment was performed for 2 hours at a linear velocity of 20 cm using a fluidized bed type air classifier. As a result, Carrier D was obtained.

[Example 4]

Carrier A ₂ 1 OOO g is placed in a 10 liter Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd .: FM10 L type), and magnetic powder (Mitsui Metals: magnetite MG 13 06 ( octahedron)) to 8 g and particulate resin (Soken chemical Co., Ltd.: MP 2 7 0 1) of 8 g were mixed and stirred to adhere electrostatically or mechanically on the carrier a ₂ surface 1 minute. After that, heat treatment with hot air of 200 ° C was performed by a heat sphering machine (Hosokawa Mikuguchi Co., Ltd .: heat sphering machine) to melt and fix the magnetic powder and fine particle resin in the coated polyethylene resin. The outermost layer of the resin mixture was formed. For the purpose of removing magnetic powder and resin which are not immobilized and exist in a free state, a large particle size carrier, agglomerated magnetic powder, and agglomerated resin were removed by sieving. In addition, in order to remove the non-immobilized magnetic powder, fine particle resin, and the like, treatment was performed at a linear velocity of 20 cm for 2 hours using a fluidized bed type air flow classifier. As a result, carrier E was obtained.

[Example 5]

Example 1 was the same as Example 1 except that the magnetic powder type was changed from Mitsui Kinzoku's magnetite MG 13 06 to Magnetite MG 9300 (polyhedron). As a result, carrier F was obtained.

[Comparative Example 1]

It was not subjected to any treatment to carrier A ₂ obtained in Production Example of Kiyaria. [Comparative Example 2]

In Example 1, the magnetic powder (manufactured by Mitsui Kinzoku Co., Ltd .: magnetite MG130) 6 (octahedron)) was replaced by magnetic powder (DFC450, 25 μm, manufactured by Dowa Iron Powder Co., Ltd.). The particle size of this magnetic powder was too large to be fixed.

[Comparative Example 3]

Example 2 was the same as Example 1 except that the magnetic powder was changed from a magnet MG1306 manufactured by Mitsui Kinzoku Co., Ltd. to a ferrite MG8200 (spherical) manufactured by Mitsui Kinzoku. As a result, carrier G was obtained.

[Application 1]

For, respectively carrier A ₂ ~ G it obtained in Examples 1 5 and Comparative Example 1, 3, it was carried out actual printing evaluation with toner A, the B. The actual print evaluation was performed using a modified version of Ekosys 3.550 (manufactured by Kyocera Corporation). The remodeling point was that amorphous silicon was used for the photoconductor when evaluating the positively chargeable toner, and organic electrophotographic photoreceptor was used when the negatively chargeable toner was evaluated. The photoconductor surface potential and magnet roller bias potential have been modified so that they can be adjusted. Table 1 shows the results of the actual printing evaluation, the charge amount, and the static resistance value. The following toner A and toner B were used.

Toner A: Styrene-n-butyl methacrylate copolymer resin

100 parts by weight carbon black (manufactured by Mitsubishi Chemical Corporation, MA # 8)

5 parts by weight dye (manufactured by Orient Chemical Industries, NO 7)

5 parts by weight The above materials were sufficiently mixed by a ball mill, and kneaded on a three-roll heated to 140 ° C. After allowing the mixture to cool, the mixture was coarsely pulverized using a feather mill and further finely pulverized using a dit mill to obtain toner A.

Toner B: Bisphenol A polyester resin 00 parts by weight carbon black (Cabot, BPL)

8 parts by weight dye (E-84, manufactured by Orient Chemical Co., Ltd.)

5 parts by weight After the above materials were sufficiently mixed by a ball mill, they were kneaded on a _three- roll heated to 140 ° C. After allowing the mixture to cool, the mixture was roughly pulverized using a feather mill and finely pulverized using a jet mill to obtain toner B.

In actual printing evaluation, actual printing was performed while changing the bias potential, and the density of the solid portion was evaluated by Macbeth. At the same time, the static resistance value and the charge amount were measured. The measurement of the charge amount was performed using a charge amount measuring device (Toshiba Chemical Co., Ltd .: type 8-200). Measurement conditions at this time, by mixing the toner 0. 5 g and the carrier 9. 5 g, placed in a 50 m 1 plastic bottle, stirring for 1 hour the baud mill, a blow pressure 0. 8 kg / cm ^2, blow The test was performed for 50 seconds using a 500 mesh stainless steel wire mesh.

Carrier type obi (C / g)

(IJ¾l of each power supply ίίτ ') Toner-A Toner-B (Ωcm) 150V 200V 250V 300V 350V Carrier A ₂ + 11.2 1 13.5 3.1E + 11 1.17 1.23 1.30 1.32 1.33 Carrier B + 10.9 -13.1 1. 1E + 10 1.19 1.27 1.35 1.44 1.53

+

Carrier C + 11.0 -12.9 8.9E + 08 Carrier D-7.2 7.8E + 12 Carrier E + 7.5 -19.3 Carrier F + 11.2 -13.3 2.7E + 11 Carrier G + 10.8 -13.4 2.5E + 10 1.21 1.24 1.29 1.32 1.34

Figure 1 shows the dependence of the image density on magnet roller bias potential in Application Example 1.

As is clear from the above, by making the shape of the magnetic powder added to the outermost layer of the electrophotographic carrier used in the electrophotographic developer into an octahedron or the like, the image density with respect to the bias potential is reduced. There is a proportional relationship, and even in a high bias potential region, the increase rate of the image density increases without lowering, so that a clear print density and a stable image can be obtained.

[Application 2]

Example 1, Carrier B was obtained in Comparative Example 1 and Comparative Example 3, A _2, Great and G Kyocera Corp. toner (trade name: We co tones) and formulated into the toner concentration T / C = 5% by weight After the agitation treatment, the printer was mounted on an Ekosys printer FS355 manufactured by Kyocera Corporation to evaluate continuous printing. Figure 2 shows the results. Industrial applicability

As described above, according to the present invention, not only the durability and the chargeability are excellent, but also the print density in actual printing is clarified as compared with the conventional one, and the delicate static resistance adjustment and the adjustment of the charge amount are performed. It is possible to provide an electrophotographic carrier and an electrophotographic developer using the same, which can be freely performed.

Claims

The scope of the claims

1. An electrophotographic carrier having a carrier core material having magnetism and a coating layer made of a high molecular weight polyethylene resin covering the surface of the carrier core material.

A coating layer made of a high-molecular-weight polyethylene resin is used as at least an outermost shell layer containing a magnetic powder that is a convex polyhedron surrounded by six or more planes and / or curved surfaces, or a layer containing the magnetic powder. An electrophotographic carrier characterized by having a layer containing silience and fine particles resin.

2. The carrier for electrophotography according to claim 1, wherein the average particle size of the magnetic powder is in the range of 0.1 to 1 / m.

3. Its ^{resistance, 1 0 2 ~ 1 0 "} Ω · cm in Claims paragraph 1 or electrophotographic Kiyaria of the second term, wherein it is.

4. The electrophotographic carrier according to any one of claims 1 to 3, and 2 to 40 weight of the total amount of the carrier and toner. An electrophotographic developer comprising a toner mixed at a ratio of / ₀ .