JP2002091089A - Electrophotographic carrier, two-component developer and method for forming image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide new carrier particles having an extremely long life and maintaining the characteristics of the carrier particles for an extremely long time by specifying the range of properties of the carrier particles especially necessary to obtain a long life and to impart sufficient charges to toner particles, maintaining the characteristics of carrier particles for a long time and having a very long life, and to provide a new two-component developer by using the carrier and a new method for forming images by which extremely stable and good image quality for practical use can be obtained for a long time. SOLUTION: In the electrophotographic carrier having a flexible resin layer on the surface of the core having magnetic particles dispersed in a high mol.wt. polymer material, the carrier shows 2 to 16 μm deformation and 50 Knoop hardness when pushed by a Knoop indenter under 29.4 mN force for 5 seconds.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a so-called carrier particle which is a charge imparting member for imparting charge to toner particles by stirring with toner particles, a two-component developer containing at least the toner particles and carrier particles,
Also, the present invention relates to an image forming method for forming an image by an electrophotographic method such as a copying machine, a printer, a facsimile, or an electrostatic recording method using the two-component developer.

[0002]

2. Description of the Related Art Conventionally, in electrophotographic image formation, a latent image is formed by an electrostatic charge on an image carrier such as a photoconductive substance, and charged toner particles adhere to the electrostatic latent image. To form a visible image. The visible image formed by the toner is finally transferred to a transfer medium such as paper, and then fixed on the transfer medium by heat, pressure, a solvent gas, or the like, and becomes an output image. These image forming methods use a method of charging toner particles for visualization, a so-called two-component development method using frictional charging by stirring and mixing of toner particles and carrier particles, and without using carrier particles. It is broadly classified into a so-called one-component development method in which charge is applied to toner particles. The one-component developing system is classified into a magnetic one-component developing system and a non-magnetic one-component developing system depending on whether or not a magnetic force is used to hold toner particles on a developing roller.

Hitherto, in a copying machine or a multifunction machine based on the copying machine which is required to have high speed and image reproducibility, there is a demand for stability of toner particle charging, rising property, and long term stability of image quality. The two-component developing system is often used, and the one-component developing system has been often used in small printers, facsimile machines, and the like, which have great demands for space saving and cost reduction.

[0004] In recent years, in consideration of environmental impact, recycling and reuse of units mainly used in the one-component developing system are being realized. The demand for longer life is increasing.

On the other hand, from the viewpoint of reducing energy consumption, the temperature at which a toner image is fixed is becoming lower. To enable fixing with lower energy, toner particles are easily deformed and fixed at a lower temperature. It has become to.

[0006] The factors of deterioration of the two-component developer are as follows.
(I) wear of the carrier particle surface, (ii) peeling of the carrier surface coat layer, (iii) crushing of the carrier particles, and (iv)
The lowering of the charging performance, the shift from the desired electric resistance, the generation of debris and abrasion powder due to the fixation of the toner particle components to the carrier particles, and the generation of debris and abrasion powder. This causes deterioration of image quality such as generation of fog and resolution, deterioration of an image forming system such as occurrence of physical / electrical scratches on an image carrier, and contamination of a charging member.

[0007] In order to solve the above-mentioned problems, many proposals having a certain effect have been made so far. As a proposal focusing on carrier particles, Japanese Patent Application Laid-Open No. 9-288375 discloses a magnetic carrier having a true specific gravity of 2 to 3.5 and a toner using a toner resin having a melting start temperature of 60 ° C. or more and 100 ° C. or less. Has been shown to reduce the stress on the toner. JP-A-10-198078 discloses that a resin fine particle and a conductive fine particle are dispersed in a matrix resin of a carrier particle coating layer, Patent Document 2 describes that by containing 10% or more of the same resin component as the binder resin of the toner, the toner is less affected by the toner spent on the charging performance.
Japanese Patent No. 874480 discloses a carrier having a core material obtained by dispersing magnetic fine particles in a binder resin and covering the surface of the core material with an insulating resin, wherein the magnetic fine particles are coated with a titanium-based coupling agent. It is described that by the treatment, the dispersibility in the binder resin is improved, and the impact resistance is improved. Japanese Patent Publication No. 8-20774 discloses a resin containing a resin and a magnetic powder. JP-A-11-24323 describes that the mixture is melted and spray-cooled to suppress the surface from becoming porous, thereby increasing the carrier particle strength.
The publication describes that in the presence of a rubber-like polymer, an unsaturated nitrile and an alkyl acrylate are graft-copolymerized, and the glass transition temperature and the weight average molecular weight are specified to improve the charge stability. JP-A-57-78552 describes that the mechanical strength of carrier particles is improved by sequentially coating a core material with an elastic body and a silicone polymer.

[0008] However, in the above-mentioned proposal, a sufficient effect may not be maintained in a situation where the life of the carrier particles is expected to be longer than before, while the fixing temperature is further lowered. For example, Japanese Patent Application Laid-Open No. 9-2883
In Japanese Patent No. 75, the use of a resin carrier is intended to reduce the weight of the carrier, reduce the impact of the collision of the carrier particles, which occurs during stirring with the toner particles, and prevent the destruction of the carrier particles and the fixation of the toner particle components. However, toner particles having a lower fixable energy may not be able to exhibit a sufficient effect of preventing toner components from being fixed. Similarly, when toner particles capable of lowering the fixing temperature are used, in a method as disclosed in Japanese Patent Application Laid-Open No. Hei 10-198078, the same component as the binder resin component of the toner on the carrier surface is fixed to the toner particle component. From the beginning of the stirring, the toner charge amount may be low and unstable.

On the other hand, those disclosed in Japanese Patent No. 2,872,480 and Japanese Patent Publication No. 8-20774 have the effect of improving the impact resistance of the carrier, but the toner sandwiched between the carrier particles by the applied impact force. Local pressure may be applied to the particles, and the toner particle components may adhere from such portions.

[0010] Also, Japanese Patent Application Laid-Open No. 11-24323,
Japanese Unexamined Patent Publication (Kokai) No. 57-78552 discloses that although rubbery components are introduced as a part of the carrier particle composition, any of them can sufficiently absorb impact and prevent the toner particle components from sticking. Not a configuration.

In the two-component developer, the toner particles and the carrier particles are agitated and peeled / triboelectrically charged as described above.
A sufficient amount of electric charge is imparted to the toner particles. For this purpose, it is necessary to stir the developer with a certain degree of strength. It was difficult to achieve both.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems at present, and, from a viewpoint different from the conventional proposals, to extend the life and provide a sufficient amount of toner particle charge. Particularly necessary carrier particle properties are studied, the range is specified, the carrier particle characteristics are maintained for a very long time, very long life new carrier particles, new two-component developer using this, and actual use It is an object of the present invention to provide a novel image forming method capable of obtaining extremely stable and good image quality for a long period of time.

[0013]

As described above, in order to prevent toner particles from adhering to carrier particles while providing sufficient charge to the toner particles, and to prevent crushing and abrasion of the carrier particles, It is important to control the frictional stress when the toner particles and the carrier particles make contact / friction to be in an appropriate range over all contact portions.

That is, the above-mentioned problem is solved by the present invention comprising (1)
"In an electrophotographic carrier in which a flexible resin layer is provided on the surface of a core material in which magnetic particles are dispersed in a high-molecular polymer, the amount of strain caused by indentation of a Knoop indenter when the carrier is applied at 29.4 mN for 5 seconds. Is 2 to 16 μm and the Knoop hardness at this time is 50 or more ”, (2)“ the polymer containing the core material contains polynorbornene and norbornene monomer. Polymer,
And at least one of these derivatives,
And (3) the electrophotographic carrier according to the above (1), wherein the carrier contains at least one oil among naphthenic oils, aroma oils, paraffin oils, and derivatives thereof. (4) “the electrophotographic carrier according to the above (1) or (2), wherein the content of the magnetic particles in the carrier particles is 10 to 40% by volume”; The carrier for electrophotography according to any one of the above items (1) to (3), wherein the true specific gravity of the carrier particles is 1.4 to 4.0 g / cm ³ , (5) The electrophotographic carrier according to any one of (1) to (4), wherein the carrier particles have a weight average diameter of 10 to 80 μm. You.

[0015] The object of the present invention is to provide (6) the present invention, wherein "at least carrier particles and toner particles are mixed, and the carrier particles are formed on the surface of a core material in which magnetic particles are dispersed in a polymer. An electrophotographic carrier provided with a flexible resin layer, wherein the carrier has a strain of 2 to 16 μm due to indentation of a Knoop indenter when applying 29.4 mN for 5 seconds and a Knoop hardness at this time of 50 or more. (2) a two-component developer for electrophotography, wherein the toner particles are toner particles in which a colorant is compatible and / or dispersed in at least a binder resin. Wherein the ratio (Dt / Dc) of the weight average diameter (Dc) of the toner particles to the weight average diameter (Dt) of the toner particles is 0.05 to 0.5. `` Two-component developer for photography '', 8) "the first (6) Electrophotographic two-component developer according to claim, characterized in that the toner particle circularity is 0.95 or more, which is defined by the following equation (1).

[0016]

(Equation 2) Is resolved.

Another object of the present invention is to provide (9) a rotatable substantially cylindrical developing device having a magnetic field generating means inside by frictionally charging toner particles by stirring a two-component developer by a stirring means. In an image forming method for holding a two-component developer containing charged toner particles on a sleeve and developing an electrostatic latent image formed on an image carrier, the two-component developer includes at least carrier particles and toner particles. Wherein the carrier particles are a carrier for electrophotography in which a flexible resin layer is provided on the surface of a core material in which magnetic particles are dispersed in a polymer, and 29.4 mN of the carrier. Distortion due to indentation of Knoop indenter when 5 seconds applied
And image forming, wherein the carrier particles have a Knoop hardness of 50 or more at this time, and the toner particles are toner particles in which a colorant is compatible and / or dispersed in at least a binder resin. Method ".

The inventors of the present invention have conducted intensive studies, and as a result, when the toner particles and the carrier particles are agitated or rubbed, a large pressure may be locally applied to the contact portion between the toner particles and the carrier particles. It was confirmed that this greatly contributed to the occurrence of sticking. Therefore, the present inventors have found that the above-described various problems can be solved by giving the carrier particles appropriate flexibility and preventing local large pressure from being applied at a contact portion between the toner particles and the carrier particles. At times, the range of necessary carrier particle characteristics was specified, and the present invention was completed.

That is, the present invention provides, as a first configuration, an electrophotographic carrier in which a flexible resin layer is provided on the surface of a core material in which magnetic particles are dispersed in a polymer. A carrier for electrophotography, wherein the amount of distortion due to the indentation of the Knoop indenter when applying 4 mN for 5 seconds is 2 to 16 μm, and the Knoop hardness at this time is 50 or more.

The carrier particles of the present invention are, as described above,
By absorbing the local pressure applied during friction by deformation, and by increasing the contact area with the toner particles, it is distributed almost evenly in the surrounding area, thereby preventing a large pressure from being applied to one point. Have.

For the pressure dispersion, the flexibility / easiness of distortion of the carrier particles and the degree of plastic deformation are important. These degrees can be represented by the dynamic characteristics and the Knoop hardness of the indentation amount of the Knoop indenter in the minute region, and as the carrier particles of the present invention, when a load of 29.4 mN (3 gf) is applied for 5 seconds. It is sufficient that the distortion amount due to the indentation of the Knoop indenter is 2 to 16 μm and the Knoop hardness at this time is 50 or more.

When the amount of distortion is less than 2 μm, the contact pressure cannot be sufficiently equalized, and the toner particle component may be fixed. On the other hand, when the distortion amount is 16 μm or more,
The carrier particles themselves become too soft and may be deformed by their own weight when left over time.

In order to more efficiently apply an appropriate frictional / peeling charge as carrier particles, the amount of distortion should be 3
More preferably, it is 12 μm. If the Knoop hardness at this time is less than 50, the amount of plastic deformation of the surface coating layer of the carrier particles is too large, and the toner particles having a small particle diameter are partially buried and do not peel off. May occur.

That is, usually, the hardness of a substance is determined by contacting an indenter typified by a Knoop indenter with an object to be measured, applying a specific load for a certain period of time, pushing in the material, removing the load, and leaving the material on the surface of the object to be measured. The size of the indentation (in the case of a Knoop indenter, the length of the long axis) is measured and calculated. When a load is applied, the measured object is deformed by the indentation of the indenter, and there are irreversible deformation that becomes an indentation after removing the load and reversible deformation that does not contribute to this and does not become an indentation after removing the load. . Conventional carrier particles have been intended to improve durability by increasing mechanical strength. Therefore, carrier particles, particularly, a core material thereof, having a structure and composition that is harder and harder to deform is used. However, when such a core material is used, there is almost no deformation due to the load, if any, up to about 1 μm, and the carrier particle structure is such that a locally applied load can be received only in the applied region. Was. Therefore, in order to improve the durability of the carrier particles, it is necessary to increase the hardness of the surface layer as much as possible.

Unlike the conventional carrier particles, the carrier particles of the present invention are provided with a flexible resin layer on the surface of a core material having a soft polymer as a component. Since the load is dispersed and received by the entire carrier particles, the load is not locally applied. The deformation appears as an amount of distortion due to the indentation of the Knoop indenter, and good dispersion / relaxation of the load is achieved at 2 to 16 μm under specified load application conditions. On the other hand, when the carrier particle surface layer is likely to be plastically deformed, even if the load is dispersed by the deformation of the core material, a large indentation may be formed due to the dispersed load. The generation of such scratches is not preferable because it impairs the durability of the carrier particles. The susceptibility of the surface layer to damage is directly expressed using the hardness as an index, and the Knoop hardness under a specified load application condition is 5%.
When it is 0 or more, carrier particles having good scratch resistance can be obtained.

The Knoop hardness can be measured using a commercially available micro hardness tester, and the amount of distortion can be measured from its dynamic characteristics. A measurement example is roughly as follows.
First, an object to be measured (carrier particles) is attached to a sufficiently rigid flat plate. At this time, an extremely small amount of an adhesive may be used to fix the object to be measured, but an excessively large amount of the adhesive is not preferable because it affects the deformation of the carrier particles. Next, this is set at the measurement position of the microhardness tester, and a load is continuously applied to the Knoop indenter up to the measurement load. After holding the load for a certain period of time, release the application of the load,
The length of the indentation flaw left on the object to be measured is measured, and Knoop hardness is determined. The strain amount in the present invention is a strain amount measured when a load is held for a certain period of time,
The time until the specified load is applied is not included in the load holding time.

The constitution of the present invention is not limited to materials as long as the first constitution range can be taken. For example, as the core material, silicone rubber, fluorine rubber, hydrin rubber,
Rubbers such as nitrile rubber, isoprene rubber, butadiene rubber, polyolefin resin, polyacrylate resin, polymethacrylate resin, polyester resin,
Among resins such as polyether resins, magnetic particles can be used by dispersing them in a polymer having relatively low hardness.

On the other hand, as the magnetic particles, conventionally known magnetic particles can be used, and examples thereof include metals such as iron, cobalt and nickel; alloys and compounds such as magnetite, hematite and ferrite, but are not limited thereto. Not something. Further, these magnetic particles preferably include particles having a size of about 1 to 5 μm.

As the surface coat layer, any material can be used without any limitation as long as it can maintain flexibility. However, from the viewpoint of environmental stability at the surface portion, triboelectricity with toner particles, etc. Examples of the resin forming the coating layer include polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene; polystyrene, acrylic (eg, polymethyl methacrylate), polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral;
Polyvinyl and polyvinylidene resins such as polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, and polybiliketone; vinyl chloride-vinyl acetate copolymers; silicone resins comprising organosiloxane bonds or modified products thereof (eg, alkyd resins, polyester resins, epoxy resins) Perfluoroalkyl ether, polyfluorovinyl, polyvinylidene, polychlorotrifluoroethylene, etc .; polyamide; polyester; polyurethane;
Polycarbonate; amino resins such as urea-formaldehyde resin; epoxy resins; and composite resins thereof. Among them, a silicone resin or a modified product thereof, a fluororesin, particularly a silicone resin or a modified product thereof are preferable as the material for the coating layer from the viewpoint of further preventing the toner component from sticking.

As the silicone resin, any known silicone resin may be used as long as it has Knoop hardness and flexibility as the carrier particles of the present invention, and includes a linear resin containing an organosiloxane represented by the following formula. / A silicone resin obtained by modifying a non-linear silicone resin with alkyd, polyester, epoxy, urethane, or the like.

[0031]

Embedded image (In the above formula, R ₁ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenyl group, R ₂ and R ₃ are a hydrogen group, an alkoxy group having 1 to 4 carbon atoms, a phenyl group, a phenoxy group,
An alkenyl group having 2 to 4 carbon atoms, an alkenyloxy group having 2 to 4 carbon atoms, a hydroxy group, a carboxyl group,
It is an ethylene oxide group, a glycidyl group or a group represented by the following formula.

[0032]

Embedded image In the above formula, R ₄ and R ₅ are a hydroxy group, a carboxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkenyl group having 2 to 4 carbon atoms, and 2 to 2 carbon atoms. 4, alkenyloxy group, phenyl group, phenoxy group, k, l, m, n, o, and p represent an integer of 1 or more. )

Each of the above substituents has, in addition to unsubstituted ones, substituents such as amino, hydroxy, carboxyl, mercapto, alkyl, phenyl, ethylene oxide, glycidyl, and halogen atoms. You may.

The flexible coating layer may contain a low-resistance material for controlling the volume resistivity of the carrier particles. Examples thereof include metals such as iron, gold, and copper; ferrite, magnetite, and the like. Iron oxides; low-resistance / medium-resistance resins based on pigments such as carbon black, polyacetylene-based resins, quaternary ammonium salt-based resins, polyether-based resins, etc., but are not limited thereto. .

These low-resistance materials are used in the coating resin 10.
It is preferably added in an amount of 2 to 30 parts by weight relative to 0 parts by weight, and more preferably 5 to 20 parts by weight. When the low-resistance material is a powder, its particle size is 0.01 to 1 μm.
Are preferred.

In addition, a silane coupling agent, a titanium coupling agent, or the like is added to the core material and / or the coating layer for the purpose of improving the adhesion to the magnetic particles and improving the dispersibility of the conductivity-imparting agent. You may. For example, examples of the silane coupling agent include compounds represented by the following general formula.

[0037]

Embedded image (However, X is a hydrolyzable group bonded to a silicon atom, such as a chloro group, an alkoxy group, an acetoxy group, an alkylamino group, or a propenoxy group. Y is an organic functional group that reacts with an organic matrix and is a vinyl group, Examples include a methacryl group, an epoxy group, a glycidoxy group, an amino group, and a mercapto group. R is an alkyl group or an alkylene group having 1 to 20 carbon atoms.)

Among these silane coupling agents, an aminosilane coupling agent having an amino group in Y is preferable for obtaining a developer having a negative charge property, and an epoxy silane coupling agent having an amino group for Y is preferable for obtaining a developer having a positive charge property. Epoxysilane coupling agents having groups are preferred.

As the method of forming the coating layer, a coating layer forming liquid is sprayed on the surface of the core material particles in the same manner as in the conventionally known method,
What is necessary is just to apply by means, such as an immersion method. However, in order to obtain the distortion amount of the present invention relatively stably, the thickness of the coating layer is 0.1 to
Make it about 2 μm.

The second structure, which exhibits particularly good properties as the core material, is a high-molecular polymer of the core material according to the first structure, wherein the high polymer is polynorbornene, a copolymer containing a norbornene monomer, and An electrophotographic carrier comprising at least one derivative, and at least one oil of a naphthenic oil, an aroma oil, a paraffin oil, and a derivative thereof. By using the second component as a component of the core material, it is possible to reduce the decrease in strength without affecting the charge imparting performance of the carrier particles and also including the oils, Carrier particles in a specified range can be easily obtained.

The norbornene-based polymer can be prepared by an ordinary known method, and can be obtained by ring-opening polymerization of a norbornene monomer or addition polymerization of a norbornene monomer with another polymerization component (and / or a derivative thereof). Can be. Oils may be added during polymerization, or may be added / impregnated after polymerization. Further, the norbornene-based polymer component may have a crosslinked structure.

Particles having a particularly uniform size are mixed with a norbornene monomer or an oligomer thereof, other desired polymer components, oils, a solvent, and the like, and emulsified in a solvent solution incompatible with these. By performing emulsion polymerization. Further, by dispersing the magnetic particles in the emulsion, a carrier core material in which the magnetic particles are dispersed can be obtained simultaneously with the emulsion polymerization. In addition, polymer components other than the above-mentioned polymers may be used in the form of composite /
They may be used in a compatible state.

A third configuration is an electrophotographic carrier according to the first or second configuration, wherein the content of the magnetic particles in the carrier particles is 10 to 40% by volume. Since the amount of the magnetic particles is directly related to the magnetic characteristics of the carrier particles, if the amount is too small, it is difficult to obtain sufficient magnetic characteristics as the carrier particles. The magnetic properties vary greatly depending on the type of the magnetic particles and the like, but preferably occupy at least about 10% by volume of the carrier particles. On the other hand, too many magnetic particles hinder the softness of the carrier particles, which is a feature of the present invention,
The upper limit of the content is about 40% by volume.

The fourth configuration is the same as the first to third configurations, except that the true specific gravity of the carrier particles is 1.4 to 4.0 g / cm.
^3. An electrophotographic carrier, wherein the carrier is 3.
As described above, the carrier particles of the present invention absorb local impact due to agitation by self-reversible deformation, thereby achieving both stability of toner particle charge amount and prevention of adhesion of toner components to carrier particles. However, if the true specific gravity of the carrier particles is too large, the impact of stirring may not be sufficiently absorbed. Therefore, the true specific gravity of the carrier particles is preferably 1.4~4.0g / cm ^3, further preferably 2.0~3.5g / cm ^3.

A fifth configuration is the electrophotographic carrier according to the first to fourth configurations, wherein the weight average diameter of the carrier particles is 10 to 80 μm. As carrier particles, in order to have sufficient charging performance, it is preferable that the carrier particle diameter is small and the specific surface area is large.However, when the carrier particle system is too small, usually, the image portion in the opposite direction to the image portion applied in the non-image portion during development In response to the electric field, carrier particles may adhere to the non-image area. Further, in the magnetic particle-dispersed carrier particles, when the carrier particle diameter is small, the amount of the magnetic particles contained in the individual carrier particles tends to vary, so that the magnetic characteristics of the individual carrier particles vary, Easily adheres to carrier particles. From these facts, the carrier particle diameter in the present invention is preferably 10 to 80 μm in terms of weight average diameter, and more preferably 20 to 60 μm.

In the sixth configuration, at least carrier particles and toner particles are mixed, and the carrier particles are provided with a flexible resin layer on the surface of a core material in which magnetic particles are dispersed in a polymer. A carrier particle having a distortion of 2-16 m and a Knoop hardness of 50 or more at this time when the carrier is pressed at 29.4 mN for 5 seconds, and the Knoop hardness is 50 or more. But,
A two-component developer for electrophotography, comprising toner particles in which a colorant is compatible and / or dispersed in at least a binder resin.

As the toner particles used in the present invention, those usually used as an electrophotographic toner can be used without any particular limitation. For example, examples of the binder resin used for the electrophotographic toner include a homopolymer of styrene such as polystyrene, poly p-chlorostyrene, and polyvinyltoluene and a substituted product thereof; styrene / p-chlorostyrene copolymer. Copolymer, styrene / propylene copolymer, styrene / vinyltoluene copolymer, styrene / vinylnaphthalene copolymer, styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate copolymer Copolymer, styrene / octyl acrylate copolymer, styrene / methyl methacrylate copolymer, styrene / ethyl methacrylate copolymer, styrene / butyl methacrylate copolymer, styrene / α-chloromethyl methacrylate copolymer, Styrene / acrylonitrile copolymer, styrene / vinyl methyl keto Styrene copolymers such as copolymers, styrene / butadiene copolymers, styrene / isoprene copolymers, styrene / maleic acid copolymers; polymethyl acrylate, polybutyl acrylate, polymethyl methacrylate, polymethacryl Acrylate-based homopolymers such as butyl acrylate and copolymers thereof; polyvinyl derivatives such as polyvinyl chloride and polyvinyl acetate; polyester-based polymers, polyurethane-based polymers, polyamide-based polymers, polyimide-based polymers, and polyols Polymer, epoxy polymer, terpene polymer,
Examples thereof include aliphatic or alicyclic hydrocarbon resins and aromatic petroleum resins, which can be used alone or as a mixture, but are not particularly limited thereto. Among them, styrene-acrylic copolymer resin, polyester-based resin, at least one or more selected from polyol-based resin,
It is more preferable in terms of electrical characteristics, cost, and the like.
Furthermore, the use of polyester-based resin and / or polyol-based resin as those having good fixing properties,
More preferred.

As the colorant used in the electrophotographic toner, pigments and dyes conventionally used as toner colorants can be used. Specifically, carbon black, lamp black, iron black and the like can be used. , Ultramarine blue, nigrosine dye, aniline blue, phthalocyanine blue, phthalocyanine green, Hansa Yellow G, rhodamine 6C lake, chaco oil blue, chrome yellow, quinacridone red, benzidine yellow, rose bengal and the like can be used alone or in combination.

Further, if necessary, in order to impart magnetic properties to the toner particles themselves, iron oxides such as ferrite, magnetite and maghematite, metals such as iron, cobalt and nickel, or alloys of these with other metals And the like may be contained alone or in mixture in the toner particles. These components can also be used / used together as colorant components.

Further, in order to use a so-called oilless fixing system in which a releasing agent such as oil is not used at the time of fixing the toner, wax such as polyethylene wax, propylene wax and carnauba wax is contained in the toner particles. This can be achieved by: The amount of these used depends on the type of material used and the fixing method, but is preferably about 0.5 to 10.0% by weight, preferably 3.0% by weight.
It is more preferred to use about 8.0% by weight.

In addition, as the charge control agent for improving the rise of the charge, generally known charge control agents can be used. For example, an amino group-containing vinyl copolymer,
Positive charge control agents such as quaternary ammonium salt compounds, nigrosine dyes, polyamine resins, imidazole compounds, azine dyes, triphenylmethane dyes, guanidine compounds, lake pigments, carboxylic acid derivatives and their metal salts, alkoxylates , An organic metal complex, a chelate compound, or another negatively chargeable charge control agent can be used alone or as a mixture to form a kneaded product and / or additive in the toner particles.

As the additives for improving the fluidity of the toner and the dependence on the environment, generally known additives can be used.
Zinc oxide, tin oxide, aluminum oxide, titanium oxide, silicon oxide, strontium titanate, barium titanate,
Inorganic powders such as calcium titanate, strontium zirconate, calcium zirconate, lanthanum titanate, calcium carbonate, magnesium carbonate, mica, and dolomite, and hydrophobic substances thereof can be used alone or in combination. As other additives, fine particles of fluororesin such as polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer, and polyvinylidene fluoride may be used as a toner surface modifier. These may vary depending on the type of material to be added.
About 0.1 to 10 parts by weight is externally added to 00 parts by weight, and if necessary, mixed with an appropriate mixer to adhere to or adhere to the surface of the toner particles or to be separated at the gap between the toner particles. Can be adjusted and used.

In the method for producing toner particles in a developer according to the present invention, the above-mentioned raw materials are kneaded by a known method such as a twin roll, a twin screw extruder, a single screw extruder or the like, and this is mixed. Well-known pulverization and classification such as a mechanical method or an air flow method can be performed to prepare toner base particles. At the time of kneading, a colorant or a dispersant for controlling the dispersion state of the magnetic substance may be used in combination. Further, the above-mentioned additives may be added to the toner base particles, followed by mixing and surface modification by a mixer or the like.

According to a seventh configuration, in the sixth configuration, the ratio (Dt / Dc) of the weight average diameter (Dc) of the carrier particles to the weight average diameter (Dt) of the toner particles is 0.05 to 0.5. And a two-component developer for electrophotography.

The ratio between the carrier particle diameter and the toner particle diameter affects the charging performance as a developer, and at the same time, when the carrier particles of the present invention are used, the toner particle components adhere to the carrier particles. Also has an effect.

That is, when the toner particle diameter is small and Dt /
If Dc is too small, a force is applied in a very small region between the carrier particles and the toner particles, so that the pressure may not be sufficiently dispersed due to the deformation of the entire carrier particles. In such a case, although the fixation of the toner particle component in the initial stage can be prevented, the fixation component may accumulate over time. On the other hand, when the toner particle diameter is large and Dt
When / Dc is too large, deformation exceeding the flexibility of the surface coat layer may be applied, and carrier particles may be broken. Therefore, Dt / Dc is
It is preferably 0.05 to 0.5, and 0.1 to 0.
More preferably, it is 3.

An eighth configuration is the electrophotographic two-component developer according to the sixth configuration, wherein the toner particle circularity defined by the following equation (1) is 0.95 or more. .

[0058]

(Equation 3)

As described above, the developer of the present invention disperses the local pressure applied to the carrier particles, thereby eliminating the adhesion of the toner particle components. When there is an undesired portion, pressure concentration may occur due to the same reason as in the above-described relationship between the carrier particle diameter and the toner particle diameter, which leads to fixation of toner particle components and destruction of carrier particles. Sometimes. In order to suppress these occurrences, the toner particle circularity defined by the above formula (1) is preferably closer to 1, preferably 0.95 or more, and more preferably 0.98 or more. preferable.

For the measurement of the toner particle circularity, the projected area of each toner particle and the perimeter of the projected image are determined using, for example, a flow type particle image analyzer (FPIA-1000; manufactured by Toa Medical Electronics Co., Ltd.). This can be calculated.

In a ninth configuration, the toner particles are frictionally charged by stirring the two-component developer by the stirring means, and the charged toner is placed on a rotatable substantially cylindrical developing sleeve having a magnetic field generating means inside. In an image forming method for holding a two-component developer containing particles and developing an electrostatic latent image formed on an image carrier, the two-component developer is formed by mixing at least carrier particles and toner particles, Carrier particles are electrophotographic carriers in which a flexible resin layer is provided on the surface of a core material in which magnetic particles are dispersed in a polymer.
29.4 mN of the carrier is a carrier particle having a strain amount of 2 to 16 μm due to indentation of the Knoop indenter when 5 seconds of application is applied and the Knoop hardness at this time is 50 or more, and the toner particles are at least contained in the binder resin. An image forming method, comprising toner particles in which a colorant is compatible and / or dispersed.

The image forming method of the present invention will be described below with reference to the drawings. First, FIG. 1 is a sectional view of an example of the image forming apparatus. Around the drum-shaped image carrier (1), an image carrier charging member (2), an image exposure system (3), a developing mechanism (4), a transfer mechanism (5), a cleaning mechanism (6),
A static elimination lamp (7) is arranged, and an image is formed by the following operation.

A series of processes of image formation will be described by a negative-positive process. An image carrier (1) typified by a photoconductor (OPC) having an organic photoconductive layer is neutralized by a neutralization lamp (7) and is uniformly negatively charged by a charging member (2) such as a charging charger or a charging roller. A latent image is formed (the absolute value of the exposed portion potential is lower than the absolute value of the non-exposed portion potential) with the laser light emitted from the laser optical system (3).

The laser beam is emitted from a semiconductor laser, and scans the surface of the image carrier (1) in the direction of the rotation axis of the image carrier (1) by a polygonal mirror (polygon) or the like rotating at a high speed. The latent image formed in this manner is used as a developing sleeve (4) as a developer carrier in the developing mechanism (4).
1) The toner is developed with a two-component developer composed of a mixture of the toner particles and the carrier particles supplied thereon, and a toner visible image is formed. At the time of developing the latent image, a voltage of an appropriate magnitude or an alternating current between the exposed portion and the non-exposed portion of the image carrier (1) is applied to the developing sleeve (41) from a voltage applying mechanism (not shown). A developing bias on which a voltage is superimposed is applied.

On the other hand, a transfer medium (for example, paper) (9) is fed from a paper feeding mechanism (not shown), and is synchronized with the leading edge of the image by a pair of upper and lower registration rollers (not shown). The toner image is fed between (1) and the transfer member (51), and the toner image is transferred. At this time, it is preferable that a potential having a polarity opposite to the polarity of the toner charge is applied to the transfer member (51) as a transfer bias. Thereafter, the transfer medium (9) is separated from the image carrier (1), and is discharged as an output image via a fixing device (8).

The toner particles remaining on the image carrier are collected by a cleaning member (61) into a toner collecting chamber (62) in the cleaning mechanism (6). The collected toner particles are used as toner recycling means (not shown).
Is transported to the developing section and / or the toner replenishing section by
It may be reused.

FIG. 2 is a schematic structural view of a main part of the developing device of the image forming apparatus. The photosensitive drum (1
The developing mechanism (4) disposed on the side of (2) includes a developing sleeve (41) as a developer carrier and a developer accommodating member (4).
2) It mainly comprises a doctor blade (43) as a regulating member, a support case (44) and the like.

A toner hopper (45) as a toner storage section for storing the toner (10) is joined to a support case (44) having an opening on the photosensitive drum (12) side. A developer container (46), which is adjacent to the toner hopper (45) and stores a developer (11) composed of toner (10) and carrier particles, contains toner particles (1).
0) and a developer stirring mechanism (47) for stirring the carrier particles and imparting friction / separation charge to the toner particles.

Inside the toner hopper (45), a toner agitator (48) as a toner supply means rotated by a driving means (not shown) and a toner supply mechanism (4) are provided.
9) is provided. The toner agitator (48) and the toner replenishing mechanism (49) feed the toner (10) in the toner hopper (45) toward the developer accommodating section (46) while stirring.

A developing sleeve (41) is provided in a space between the photosensitive drum (12) and the toner hopper (45). The developing sleeve (41), which is driven to rotate in the direction of the arrow by a driving means (not shown), is disposed inside the developing sleeve (4) at a fixed position relative to the developing mechanism (4) in order to form a magnetic brush by carrier particles. Further, it has a magnet (not shown) as a magnetic field generating means.

A regulating member (doctor blade) (43) is integrally attached to the side of the developer accommodating member (42) opposite to the side attached to the support case (44). The regulating member (doctor blade) (43)
The developing sleeve (41) is arranged with a certain gap between it and the outer peripheral surface of the developing sleeve (41).

With the above configuration, the toner hopper (45)
The toner (10) sent out from the inside by the toner agitator (48) and the toner replenishing mechanism (49) is carried to the developer accommodating section (46), and is agitated by the developer agitating mechanism (47). A desired frictional / separation charge is provided, and is carried on a developing sleeve (41) as a developer (11) together with carrier particles to be conveyed to a position facing the outer peripheral surface of the photoconductor drum (12). Only the toner image is formed on the photosensitive drum (12) by electrostatically coupling only the electrostatic latent image formed on the photosensitive drum (12).

[0073]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples. Here, "parts" all indicate parts by weight. First, a production example for obtaining carrier particles and toner particles necessary for confirming the effects of the present invention, which are used in Examples, will be described. (Example of core material production)
The mixture was dispersed in a ball mill for 8 hours.
A spray was sprayed into a dry air stream at 50 ° C. under reduced pressure of 0 kPa, and the volatile solvent was removed under reduced pressure to obtain a core material in which magnetic particles were dispersed.

[0074]

[Table 1]

(Example of Carrier Particle Production) To the obtained core material, a separately prepared coating layer solution having the formulation shown in Table 2 was applied in an amount such that the layer thickness after drying was about 1 μm in accordance with the combination shown in Table 3. By heat drying, carrier particles having a coat layer on the surface were obtained.

[0076]

[Table 2]

[0077]

[Table 3]

(Example of Toner Particle Production) 79 parts of polyester resin (Ethylene oxide addition alcohol of bisphenol A, propylene oxide addition alcohol of bisphenol A, condensation polymer of terephthalic acid and trimellitic acid, Mw = about 12000, glass transition point = Carbon black; Mitsubishi Carbon Co., # 44 15 parts Charge control agent; Chromium metal dye; Hodogaya Chemical Co., Ltd. AIZON SPILON BLACK TRH 1 part Carnauba wax; Noda wax 5 parts

The mixture having the above composition was kneaded with a two-roll kneader for 30 minutes, and then pulverized and classified with a mechanical pulverizer / airflow classifier to obtain a weight average diameter of about 5.5 μm and about 10.0 μm.
m of toner base particles were obtained. In addition, toner base particles having a weight average diameter of about 10.0 μm and different circularities were obtained from the above kneaded material by using an airflow pulverizer / airflow classifier. Further, to 100 parts of each toner base particle, 1 part of hydrophobic silica fine particles whose surface was subjected to dimethylsilane treatment was added and mixed by a Henschel mixer for a total of 2 minutes to obtain test toner particles. Tables 4 and 5 show measured values of the characteristics of the obtained carrier particles and toner particles relating to the present invention. Here, the Knoop hardness and strain amount of the carrier are measured using a micro hardness tester DUH-201 (manufactured by Shimadzu Corporation), and the load speed up to the specified load is 9.8 mN / sec.
c (1 g / sec).

[0080]

[Table 4]

[0081]

[Table 5]

Using the carrier particles and the toner particles obtained as described above, the developer of the combination shown in Table 6 was used for an A4 size plate with an image area ratio of 6% using a remodeling machine of Ricoh's copier imagio MF-6550. A continuous image drawing test of 300,000 originals was performed, and a character image, a thin line image, and a band image of a step tone were output at the initial stage and after the continuous outputting, and the image quality was evaluated. As image quality evaluation, toner dust in a character portion, line image reproducibility in a fine line image, gradation and image density stability in a band image, and the presence or absence of other defects in each image were evaluated. Gradation and image density were measured using a Macbeth densitometer (RD-914), and other items were visually evaluated. At the time of image output, the electrostatic image on the image carrier in the image tester has a background portion of -700 V, an image portion of -200 V to -400 V, and a latent image of a gradation image of -5.
Created in 0V increments. A developing bias potential of -500 V was applied to the developing sleeve in a direct current. In addition, 30
After collecting 10,000 images, the developer was sampled, the toner particles adhering to the surface were removed by air blow, a certain amount of the remaining carrier particles were dispersed in toluene, and the supernatant was collected. Then, the amount of the eluted carrier particle toner particle component adhering matter was evaluated. For the evaluation of the amount of fixed matter, using unused carrier particles, in the supernatant liquid collected by the same method, the white-visible light transmittance, and the difference between the white-visible light transmittance of the test sample and the difference in the amount of surface-fixed components. Each sample was caught and evaluated relative. The transmittance was measured using a spectrophotometer TC-1800 (manufactured by Tokyo Denshoku Co., Ltd.) using a C50 light source. Table 7-1 shows the initial evaluation results and Table 7-
2 shows the evaluation results after 100,000 sheets.

Examples 1, 2, 3 and Comparative Examples 1, 5,
When the developer of No. 6 was put in the developing unit and left standing at room temperature for 2 weeks, the developer was agitated again. Stirring was started, but for the developers of Comparative Examples 5 and 6, a large load was applied to the stirring mechanism, and smooth stirring was not performed.

[0084]

[Table 6]

[0085]

[Table 7-1]

[0086]

[Table 7-2] The reproducibility of toner dust and fine lines in Comparative Examples 1, 9, and 10 cannot be evaluated. In Comparative Examples 4, 6, and 7, the carrier core material component was eluted.
Unable to measure toner adhesion

[0087]

As is apparent from the detailed and concrete description, according to the structure of the present invention, Table 7-1 and Table 7-2
As can be seen from the comparison between Examples and Comparative Examples, the adhesion of toner particle components to carrier particles is extremely small over a long period of time,
A carrier for electrophotography and two components for electrophotography that have the characteristics necessary to obtain stable images without image deterioration such as toner dust and background fog, and are also extremely effective in obtaining high-definition, high-resolution, high-quality images. A developer and an image forming method.

[Brief description of the drawings]

FIG. 1 is a sectional view of an example of an image forming apparatus used in the present invention.

FIG. 2 is a schematic configuration diagram of a main part of a developing device of the image forming apparatus used in the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image carrier 2 charging member 3 image exposure system 4 developing mechanism 5 transfer mechanism 6 cleaning mechanism 7 static elimination lamp 8 fixing device 9 transfer medium 10 toner 11 developer 12 photosensitive drum 41 developing sleeve 42 developer accommodating member 43 regulating member ( (Doctor blade) 44 support case 45 toner hopper 46 developer accommodating part 47 developer stirring mechanism 48 toner agitator 49 toner replenishing mechanism 51 transfer member 52 static elimination brush 61 cleaning member 62 toner recovery chamber

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroaki Matsuda 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Naoto Shimoda 1-3-6 Nakamagome, Ota-ku, Tokyo Share Inside Ricoh Company (72) Inventor Akemi Sugiyama 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh Company (72) Kosuke Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh F Term (reference) 2H005 AA21 BA03 BA06 CA02 CA30 EA05 EA07 EA10 FA01

Claims (9)

[Claims] 1. An electrophotographic carrier in which a flexible resin layer is provided on the surface of a core material in which magnetic particles are dispersed in a high-molecular polymer, a Knoop indenter when the carrier is applied at 29.4 mN for 5 seconds. The amount of distortion due to indentation is 2 to 16 μm and
An electrophotographic carrier, wherein the Knoop hardness at this time is 50 or more. 2. The high molecular polymer of the core material contains at least one of polynorbornene, a copolymer containing a norbornene monomer, and a derivative thereof, and is a naphthenic oil, an aroma oil, or paraffin. The electrophotographic carrier according to claim 1, wherein the carrier contains at least one oil selected from a group consisting of a series oil and a derivative thereof. 3. The carrier particles having a magnetic particle content of 1
The electrophotographic carrier according to claim 1, wherein the content is 0 to 40% by volume. 4. The carrier particles have a true specific gravity of 1.4 to 4.
Electrophotographic carrier according to any one of claims 1 to 3, characterized in that it is 0 g / cm ^3. 5. The carrier particles have a weight average diameter of 10-8.
The electrophotographic carrier according to any one of claims 1 to 4, wherein the thickness is 0 µm. 6. An electrophotographic electrophotographic apparatus comprising a mixture of at least carrier particles and toner particles, wherein the carrier particles are provided with a flexible resin layer on a surface of a core material in which magnetic particles are dispersed in a polymer. Carrier, 29.4m of the carrier
N, the amount of distortion caused by pushing the Knoop indenter when 5 seconds was applied was 2
A carrier particle having a Knoop hardness of 50 or more at this time and having a Knoop hardness of 50 or more, wherein the toner particle is a toner particle in which a colorant is compatible and / or dispersed in at least a binder resin. Two-component developer for electrophotography. 7. The ratio (Dt / Dc) of the weight average diameter (Dc) of the carrier particles to the weight average diameter (Dt) of the toner particles is as follows:
The two-component developer for electrophotography according to claim 6, wherein the amount is 0.05 to 0.5. 8. The two-component developer for electrophotography according to claim 6, wherein the circularity of the toner particles defined by the following formula (1) is 0.95 or more. (Equation 1) 9. The toner particles are frictionally charged by stirring the two-component developer by the stirring means, and the charged toner particles are placed on a rotatable substantially cylindrical developing sleeve having a magnetic field generating means therein. In an image forming method for holding a component developer and developing an electrostatic latent image formed on an image carrier, the two-component developer is formed by mixing at least carrier particles and toner particles, and the carrier particles are An electrophotographic carrier in which a flexible resin layer is provided on the surface of a core material in which magnetic particles are dispersed in a high-molecular polymer.
9.4 mN, the amount of distortion due to the indentation of the Knoop indenter when 5 seconds was applied was 2 to 16 μm, and the Knoop hardness at this time was 50 μm.
An image forming method, comprising the carrier particles described above, wherein the toner particles are toner particles in which a colorant is compatible and / or dispersed in at least a binder resin.