JP2002287430A - Electrophotographic developer, image forming method and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide electrophotographic developer that substantially prevents a change in developer characteristic with time, retains a high quality image for a very long period of time, is capable of fixing with low fixing energy, retains a high quality image even in use of toner capable of being fixed with saved energy and has a very high function. SOLUTION: The electrophotographic developer comprises a mixture of toner and carrier. The toner is formed by adding two or more kinds of fine particles to a host toner particle composed of at least a coloring agent and a binding resin. In the added fine particles of the toner, the average primary particle diameter of the fine particles, which have the smallest average primary fine particle diameter, is 5 to 50 nm. The carrier particle is obtained in such a manner that a coat layer containing a resin layer is formed on the surface of a core material composed of at least a magnetic substance. The area where a height difference between an arbitrary projection and its adjacent recess of the surface of the carrier particle is 5 nm or less occupies 60% or more of the surface of the carrier particle.

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 electric charge to toner particles by stirring with toner particles, a two-component developer containing at least the toner particles, and More particularly, the present invention relates to an image forming method having a so-called recycle mechanism for reusing toner remaining on an image carrier for development, and an electrophotographic developer suitable for the method.

[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, and use a so-called two-component developing method using frictional charging by stirring and mixing of toner particles and carrier particles, without using carrier particles. It is broadly classified into a so-called one-component development system 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 a magnetic force is used to hold toner particles on a developing roller.
Until now, in copying machines that require high speed and image reproducibility, and in multifunction machines based on this, due to demands such as stability of toner particle charging, rising performance, and long-term stability of image quality,
The two-component developing method is often used, and the one-component developing method is often used in small printers, facsimile machines, and the like, for which there is a great demand for space saving and cost reduction. In recent years, in consideration of environmental impact, recycling and reuse of units mainly used in the one-component developing system are being realized, and at the same time, the life of the developer is further extended in the two-component developing system. Demands are growing.

Further, with the recent trend of energy saving, the fixing energy of toner in image formation has been reduced, and therefore, a resin which softens with lower thermal energy than before has been adopted as a binder resin for toner. Tend to These resins tend to have high tackiness even at room temperature, and therefore, to ensure toner fluidity by preventing binding of toner particles at room temperature, and to fix toner base particle composition components to the surface of carrier particles. In order to prevent (so-called toner spent), a large amount of externally added fine particles tend to be contained as a fluidity improver. However, in such a toner, although the fixation of the toner base particle composition component to the surface of the carrier particles is suppressed, a part of the externally added fine particles often contained in the toner is often in a free state. May strongly adhere to the surface of the carrier particles due to the action of an external force such as stirring, which may cause fluctuations in developer characteristics such as fluctuations in the charge imparting ability of the carrier particles.

On the other hand, from the viewpoint of resource saving, a so-called transfer residual toner remaining on the image carrier after transferring the toner from the image carrier to an image transfer medium such as paper, for reusing the toner in the apparatus. An image forming method including a recycling step is becoming common. In the image forming method including the toner recycling step, externally added fine particles in the toner may be buried in the toner base particles in the toner recycling step. In order to suppress the fluctuation of toner fluidity accompanying this, more externally added fine particles are used, and therefore, the amount of free externally added fine particles in the toner is increased. In the case of the developer, the variation with time of the developer characteristics appeared more remarkably. these,
When the developer characteristics fluctuate, deterioration in image quality such as a decrease in image density, generation of background fog, and decrease in resolution appears as a change with time, and further, generation of physical / electrical scratches on the image carrier. Also, the deterioration of the image forming system such as contamination of the charging member may be caused, and the life of the image forming apparatus itself is shortened.

Therefore, in order to obtain a stable and good quality image over a long period of time, and further to maintain the life of the image forming apparatus, the characteristics of the developer do not fluctuate depending on the use period and are stable. It has become important, and various proposals have been made so far focusing on suppression of carrier particle aging. An example of such a proposal is to use a carrier having an uneven structure on the surface and a carrier having an uneven structure on the surface at the same time, thereby preventing toner spent and improving the rise of charging (Japanese Patent Laid-Open No.
No. 43686), a magnetic carrier having a central particle diameter of 60 to 100 μm having fine irregularities on the surface, and a central particle diameter of 5 to 8 μm.
The use of a spherical toner having a large surface area allows the toner to be charged even if the fine powder toner adheres to the surface of the carrier (Japanese Patent Application Laid-Open No. 8-190224).
No.), an average sphericity of 1.1 or more and 1.5 or less and having a sphericity of less than 1.3 and 70% by number or more suppresses carrier surface irregularities of the degree of sphericity, Preventing spent of toner fine powder (Japanese Unexamined Patent Publication No.
No. 244301). However, these proposals focus on the fixation of the toner base composition component to the surface of the carrier particles, and in order to further extend the life of the developer and save resources, the above-described toner is used. An electrophotographic developer, an image forming method, and an image forming apparatus having sufficiently stable developer characteristics by preventing the added fine particles therein from being fixed to the carrier particle surface have not been studied at all.

On the other hand, the characteristics of the additives contained in the toner are intended to maintain the image quality by suppressing the temporal fluctuation of the state of the toner itself, to prevent the toner filming on the surface of the photoreceptor, and to improve the environmental stability. About the type and the type, Japanese Patent No. 2704789 and Japanese Patent No. 275461
No. 8, JP-B-8-16802, JP-A-61-1769
No. 46, JP-A-1-126660, JP-A-6-167
No. 827, JP-A-6-258882, JP-A-6-33
2236, JP-A-7-84406, JP-A-7-19
9539, JP-A-7-261446, JP-A-10-
10773, JP-A-10-186723, JP-A-1
1-1143118, JP-A-11-174731, JP-A-11-184145, JP-A-11-327301
No. 2000-56511, 2000-56595, etc., and many other proposals have been made. However, even in these proposals, no study has been made on the attachment and fixation of the added fine particles on the surface of the carrier particles.
No mention is made of the variation over time in developer quality caused by this. That is, according to these proposals, although the state of the toner itself can be maintained, the adhesion of the externally added fine particles in the toner to the surface of the carrier particles as described above can be prevented.
The immobilization is not improved at all, and the variation over time of the developer quality due to the variation in the characteristics of the carrier particles is not improved. As described above, in a two-component developer, a proposal for suppressing the fluctuation of the developer characteristics for a longer period of time, particularly a proposal for suppressing the fixation of the added fine particles in the toner to the carrier particle surface, has not yet been made. It has been a very difficult task to stably obtain high-quality images without replacing the developer.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems, the present invention suppresses the aging fluctuation of the developer characteristics to a substantially negligible level, and provides a high-quality image for an extremely long time. It is an object of the present invention to provide an electrophotographic developer having an extremely high function, which can maintain a high quality image even with an energy-saving fixable toner that can be held and fixed with lower fixing energy. Another object of the present invention is to provide an image forming method and an image forming apparatus which can substantially reduce the amount of waste toner and have an extremely small effect on the environment.

[0008]

In order to suppress the fluctuation of the developer characteristics, it is important to suppress the fluctuation over time of the surface characteristics of the carrier particles as a frictional charge imparting member. It is particularly important to suppress the variation in the applied characteristics. The main cause of the variation in the charge imparting characteristics on the carrier particle surface is that the toner component migrates to and adheres to the carrier particle surface due to the impact force at the time of stirring and friction with the toner, thereby contaminating the carrier particle surface. Accordingly, by suppressing the occurrence of such a phenomenon, it is possible to extremely reduce the variation in the charge imparting characteristics of the carrier particles. In addition, while the influence of the toner base particle component sticking to the time-dependent fluctuation of the charge imparting property is described above, the transfer of the added fine particles onto the carrier particle surface and the sticking of the added fine particles to the toner and the carrier particle surface substantially reduce the variation. The effect of homogenization is extremely large. That is, it is necessary to maintain sufficient toner fluidity and to keep the replenishment toner from rapidly diffusing into the developer while minimizing the migration of the added fine particles contained in the toner to the surface of the carrier particles. It is important to control. The present inventors have conducted intensive studies and found that there are fine irregularities on the surface of the carrier particles and a primary particle diameter range of the added fine particles contained in the toner, which can significantly suppress the adhesion of the added fine particles to the surface of the carrier particles. By specifying these conditions and ranges, they have found that the initial developer characteristics can be maintained for an extremely long period of time while maintaining the toner fluidity, and the present invention has been accomplished based on this finding.

That is, a first aspect of the present invention is an electrophotographic developing method comprising mixing toner particles obtained by externally adding two or more kinds of fine particles to toner base particles comprising at least a colorant and a binder resin, and carrier particles. Agent having the smallest average primary particle diameter among two or more kinds of added fine particles in the toner.
The seed particles have an average primary particle diameter of 5 to 50 nm, and the carrier particles are particles obtained by providing a coating layer containing a resin phase on at least the surface of a core material made of a magnetic material. A region in which the difference in height between an arbitrary convex portion and a concave portion adjacent to the convex portion is 5 nm or less occupies 60% or more of the surface of the carrier particles. The second aspect of the present invention is that a surface roughness R in a 100 nm × 100 nm region of the surface of the carrier particles is provided.
2. The toner according to claim 1, wherein z and an average primary particle diameter Dmin of one type of additional fine particle having a minimum average primary particle diameter among two or more types of additional fine particles in the toner satisfy the following expression (1). It is an electrophotographic developer.

2.3 × Rz <Dmin (1) A third aspect of the present invention is that the resin forming the core material particles of the carrier particles and / or the surface coat layer is a silicone resin or a modified product thereof or a fluorine resin. an electrophotographic developer of claim 1 or 2, wherein. The fourth aspect of the present invention is the electrophotographic developer according to claim 1, wherein the carrier particle surface coat layer contains a compound having a siloxane bond skeleton in a main chain and / or a side chain. The fifth aspect of the present invention is that the ratio of the added fine particles in the toner to the toner base particles is 0.1%.
The electrophotographic developer according to claim 1, wherein the amount is 5 to 5% by weight. The sixth aspect of the present invention is that the toner having a thickness of 4.0 μm
The electrophotographic developer according to any one of claims 1 to 5, wherein the following toner particles are 50% by number or less. A seventh aspect of the present invention is the electrophotographic developer according to any one of claims 1 to 6, wherein the core material and / or the coat layer of the carrier particles contain a silane coupling agent and / or a titanium coupling agent. is there. According to an eighth aspect of the present invention, there is provided an image forming method for developing an electrostatic latent image formed on an image bearing member with an electrophotographic developer comprising toner and carrier particles, wherein the electrophotographic developer comprises An image forming method according to any one of the above.
A ninth aspect of the present invention is the image forming method according to claim 8, wherein the image carrier is cleaned in a cleaning step, and the toner collected in the cleaning step is reused in a developing step. According to a tenth aspect of the present invention, there is provided an image forming apparatus for developing an electrostatic latent image formed on an image carrier with an electrophotographic developer including toner and carrier particles. An image forming apparatus according to any one of the preceding claims. According to an eleventh aspect of the present invention, there is provided a toner recycling mechanism including at least a cleaning mechanism for cleaning the image carrier and a transport mechanism for transporting the toner collected by the cleaning mechanism to the developing mechanism, and the collected toner is reused. An image forming apparatus according to any one of the preceding claims.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The fine particles added to the toner and the surface structure of the carrier particles according to the first aspect of the present invention allow the developer to exhibit extremely good stability over time of the developer characteristics. become. That is, in the present invention,
Fine irregularities on the surface of carrier particles (60% or more
nm or less) is smaller than or equal to the scale of the added fine particles, and especially the scale of the added fine particles having the smallest average particle diameter (5 to 50 n).
m) or less, even if each of the added fine particles formed of two or more types once migrates to the surface of the carrier particles, the particles rapidly roll without remaining at a certain position. As a result, the toner-added fine particles hardly adhere to the surface of the carrier particles, and the change in the surface of the carrier particles can be suppressed over a long period of time as compared with the carrier particles whose surface shape is not controlled. Agent properties can be developed. When the height difference of the concavo-convex portion occupying most of the carrier particle surface is more than 5 nm, the fine concavo-convex scale on the surface of the carrier particle is substantially the same as at least one of the added fine-particle scales, and thus the amount of liberated added fine particles is large. In the case where the toner particles are imparted with fluidity in the presence, the added fine particles are stuck in the fine recesses on the surface of the carrier particles and cannot be desorbed, thereby changing the surface characteristics of the carrier particles. . Further, this portion becomes a nucleus, and further increases the fixation of the toner composition component. Further, such selective fixation of the specific added fine particles leads to a change in the toner composition, which tends to be disadvantageous in terms of the quality with time. The region where the height difference of the fine unevenness is 5 nm or less needs to occupy 60% or more of the surface of the carrier particle, and more preferably 70% or more. In the case of an occupied area smaller than this, the influence of the carrier particle surface characteristic fluctuation due to the fixation of the added fine particles to the region outside the specified range becomes large, and it is practically difficult to exert the characteristic stabilizing effect by suppressing the added fine particle fixation Becomes

Here, the fine structure of the carrier particle surface is as follows:
An outline can be obtained as follows. First, the carrier particles provided with the surface coat layer are fixed to a sufficiently rigid support. At this time, a double-sided tape, an adhesive, or the like may be used as necessary for fixing. Next, the sample on which the particles are fixed is set at a measurement site of a scanning probe microscope (SPM) under an environment of room temperature and normal pressure. Subsequently, the measurement site scans the sample surface while oscillating the measurement probe at the resonance frequency in a scan range of about 0.5 to 10 μm,
Performing a so-called tapping mode scanning. At this time, the radius of curvature of the probe tip is preferably about 5 to 20 nm, and the tapping frequency is preferably about 150 to 450 kHz.
By performing tapping mode scanning under the above conditions, a fine surface shape can be observed.

The material of the carrier particles used in the developer of the present invention is not particularly limited as long as it can satisfy the first constitutional range of the present invention, and conventionally known materials can be used. Examples of inorganic / metal magnetic particles that can be used as the core material of the particles include metals such as iron, cobalt, and nickel; alloys and compounds such as magnetite, hematite, and ferrite, but are not limited thereto. Absent. These magnetic particles may be used in any core material form such as single crystal / amorphous particles, single / composite sintered body, and particles in which single / composite particles are dispersed in a polymer such as resin. Good. In addition, in the case of magnetic particles dispersed in a polymer, in order to achieve both the magnetic properties of the carrier particles and the dispersibility of the magnetic particles, these magnetic particles include particles having a size of about 0.5 to 10 μm. Is preferred.

Next, examples of the resin forming the core material particles and / or the surface coat layer of the carrier particles include polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene and chlorosulfonated polyethylene; polystyrene and acrylic resins (for example, Polymethyl methacrylate), polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polyvinyl ketone, and other polyvinyl resins and polyvinylidene resins; vinyl chloride-vinyl acetate copolymers; organosiloxanes Bonded silicone resin or modified product thereof (for example, modified by alkyd resin, polyester, epoxy resin, polyurethane, etc.); perhydropolysilazane or Modified products (including partial oxides); fluorine resins such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, and polychlorotrifluoroethylene; polyamides; polyesters; polyurethanes; polycarbonates; urea resins; Benzoguanamine resin; epoxy resin and the like; among them, preferred examples of the coating layer material include a silicone resin or a modified product thereof and a fluorine resin, particularly a silicone resin or a modified product thereof. The silicone resin or a modified product thereof is not particularly limited, but is preferably a straight silicone consisting of only an organosiloxane bond represented by the following general formula, or an alkyd resin, a polyester, an epoxy resin, or a silicone resin modified with a polyurethane. No.

[0014]

Embedded image In the above formula, R1 is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or a phenyl group, R2 and R3 are a hydrogen atom, an alkoxy group having 1 to 4 carbon atoms, a phenyl group, a phenoxy group, and an alkenyl having 2 to 4 carbon atoms. A alkenyloxy group having 2 to 4 carbon atoms, a hydroxy group, a carboxyl group, an ethylene oxide group, a glycidyl group or a group represented by the following formula.

Embedded image In the above formula, R4 and R5 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, an alkenyloxy group having 2 to 4 carbon atoms, a phenyl group, a phenoxy group, k, l,
m, n, o, and p represent an integer of 1 or more. Each of the above substituents is unsubstituted, for example, an amino group, a hydroxy group,
It may have a substituent such as a carboxyl group, a mercapto group, an alkyl group, a phenyl group, an ethylene oxide group, a glycidyl group, and a halogen atom.

As described above, the material used for controlling the electric resistance of the carrier core material particles and / or the coating layer by the dispersion of the low-resistance material particles may be a conventionally known material. And iron oxides such as ferrite and magnetite; and pigments such as carbon black. Among them, a mixture of furnace black and acetylene black, one of carbon blacks, is a small amount of low-resistance fine powder. Is preferred because conductivity can be effectively adjusted. These low-resistance fine powders preferably have a particle size of about 0.01 to 10 μm, and are preferably added in an amount of 2 to 30 parts by weight based on 100 parts by weight of the core material particles or the coat layer resin, and more preferably 5 to 20 parts by weight. It is even more preferred to add parts by weight. It is preferable that these low-resistance fine powders are not exposed to the surface of the coat layer as much as possible in order to suppress the formation of fine irregularities on the surface of the carrier particles.

The carrier core material particles and / or the coating layer may have a coupling agent such as a silane coupling agent or a titanium coupling agent for the purpose of improving their adhesion or dispersibility of the resistance controlling material. May be contained as an auxiliary. Use of these coupling agents is also effective in suppressing the surface exposure of the low-resistance fine powder described above. Examples of the silane coupling agent include a compound represented by the following general formula.

Embedded image YRSix₃  In the above formula, X is a hydrolyzable group bonded to a silicon atom.
For example, a chloro group, an alkoxy group, an acetoxy group,
Examples thereof include a alkylamino group and a propenoxy group. Also, Y
Is an organic functional group that reacts with the organic matrix.
Nyl group, methacryl group, epoxy group, glycidoxy group,
Examples include an amino group and a mercapto group. R is the number of carbon atoms
1 to 20 alkylene groups. This silane coupling
To obtain a developer having a particularly negative charge property
Aminosilane coupling agents in which Y is an amino group are preferred
In order to obtain a positively charged developer, Y is an epoxy group.
Are preferred.

The method of forming the coat layer is the same as in the prior art.
The coating liquid for forming a coat layer may be applied to the surface of the core material particles by a method such as a spraying method and a dipping method. The thickness of the coating layer is 0.1-20
μm is preferred.

On the other hand, the toner used in the developer of the present invention is also provided as long as the first constitution range of the present invention can be taken.
The material is not limited, and a material usually used as an electrophotographic toner can be used without any particular limitation. For example, examples of the binder resin used for the toner base particles include polystyrene, poly-p-chlorostyrene, a homopolymer of styrene such as polyvinyltoluene or a substituted product thereof; a styrene / p-chlorostyrene copolymer,
Styrene / propylene copolymer, styrene / vinyltoluene copolymer, styrene / vinylnaphthalene copolymer,
Styrene / methyl acrylate copolymer, styrene / ethyl acrylate copolymer, styrene / butyl acrylate 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 ketone copolymer, styrene / butadiene copolymer, styrene / Styrene-based copolymers such as isoprene copolymer and styrene / maleic acid copolymer; acrylate-based homopolymers such as polymethyl acrylate, polybutyl acrylate, polymethyl methacrylate, and polybutyl methacrylate; Copolymers such as polyvinyl chloride and polyvinyl acetate Livinyl derivative; polyester-based polymer, polyurethane-based polymer, polyamide-based polymer, polyimide-based polymer, polyol-based polymer, epoxy-based polymer, terpene-based polymer, aliphatic or alicyclic hydrocarbon resin, aromatic And the like. These can be used alone or as a mixture, but are not particularly limited thereto. Among these, at least one selected from styrene-acrylic copolymer resins, polyester resins and polyol resins is preferable in view of electrical characteristics, cost, and the like. And / or polyol resins are more preferred.

As the colorant used for the toner base particles, pigments and dyes conventionally used as toner colorants can be used.
Carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue,
Phthalocyanine Green, Hansa Yellow G, Rhodamine 6C Lake, Calco Oil Blue, Chrome Yellow,
Examples thereof include quinacridone red, benzidine yellow, and rose bengal, and these are used alone or in combination.

If necessary, the magnetic properties of the toner particles can be adjusted by using 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, a so-called oil-less fixing system that does not use a release agent such as oil at the time of fixing the toner can be realized by including waxes such as polyethylene wax, propylene wax and carnauba wax in the toner particles. . The content of these waxes is preferably in the range of 0.5 to 10.0% by weight, and more preferably in the range of 3.0 to 8.0% by weight, depending on the type and fixing method.

Further, the toner base particles may contain a charge control agent for improving the rise of the charge. As the charge control agent, those generally known, for example, an amino group-containing vinyl copolymer, a quaternary ammonium salt compound, a nigrosine dye, a polyamine resin, an imidazole compound, an azine dye, a triphenylmethane dye, a guanidine compound, Positively chargeable charge control agents such as lake pigments and negatively chargeable charge control agents such as carboxylic acid derivatives and their metal salts, alkoxylates, organometallic complexes and chelate compounds, alone or in combination, are added to the toner particles. Can be used as a kneaded product and / or additive. When these charge control agents are used in a dispersed state,
For interaction with the surface of the carrier particles occurs substantially uniformly, the dispersion diameter is more preferably preferably at 2.0μm or less, and 1.0μm or less.

Known additives can be used as additives for improving the fluidity of the toner and for stabilizing the environmental dependency while suppressing the coalescence of the toner base particles. Zinc oxide, tin oxide, aluminum oxide, titanium oxide, silicon oxide, strontium titanate,
Inorganic powders such as barium titanate, calcium titanate, strontium zirconate, calcium zirconate, lanthanum titanate, calcium carbonate, magnesium carbonate, mica, and dolomite, and hydrophobic substances thereof can be used. As other additives, fine particles of fluororesin such as polytetrafluoroethylene, tetrafluoroethylene hexafluoropropylene copolymer, and polyvinylidene fluoride may be used as a toner surface modifier. The addition fine particles may be selected by using two or more components from the fine particles represented above. This selection includes, for example, a case where two or more kinds of the same type of compositions having different particle size distributions are selected.

In order to produce the toner in the developer of the present invention, the above-mentioned raw materials are first kneaded by a known method using a twin roll, a twin screw kneader, a single screw kneader or the like. This is crushed by a known method such as a mechanical method or an air flow method,
Classification is performed to prepare toner base particles. During the kneading, a colorant or a dispersant for controlling the dispersion state of the magnetic material may be used in combination. Next, the above-mentioned added fine particles are added to the toner base particles, and they are mixed by a mixer or the like to perform surface modification. Thus, a toner is manufactured.

The charge amount of the toner varies depending on the actual use process, and thus cannot be determined unconditionally. However, in general, in combination with the carrier particles according to the constitution of the present invention, the toner has an absolute value of 3 to 80 μC / g. About 50 to 50 μm.
More preferably, the saturated charge amount is about C / g.
It is even more preferable that the saturation charge amount is about 0 to 40 μC / g.

In the developer of the present invention, the surface roughness Rz within a 100 nm × 100 nm region of the carrier particle surface is used.
And the average primary particle diameter Dmin of the added fine particles having the minimum average primary particle diameter among the added fine particles in the toner preferably satisfy the following expression (1). In the case of deviating from 1, the rolling of the added fine particles on the surface of the carrier particles in the region becomes difficult to occur, and depending on the stirring conditions of the developer, the generation of the added fine particles may not be sufficiently suppressed. Is not preferred.

2.3 × Rz <Dmin (1) By adding a compound having a siloxane bond skeleton in the main chain and / or the side chain to the carrier particle surface coat layer, the surface energy of the carrier particle can be reduced. In addition, the immobilization of the added fine particles on the surface of the carrier particles is more reliably suppressed.

The ratio of the added fine particles to the toner base particles depends on the type of the material to be added, but the total amount is about 0.5 to 5% by weight, and the amount of the externally added fine particles having the smallest average primary particle diameter is about 0%. It is preferably from 3 to 2% by weight. Further, these added fine particles can be mixed and mixed with an appropriate mixer so as to be adhered to or adhered to the surface of the toner particles or to be released in a small amount of toner particles before use. The total amount of added fine particles is 0.5% by weight
If the ratio is less than 0.1%, the surface of the toner base particles is insufficiently covered with the added fine particles, and the toner base particles may be united with each other. A large amount of added fine particles may be easily generated from the toner, and the amount of the free fine particles may change with time, which may result in insufficient fluctuation of the properties of the toner itself as a developer. The ratio of the added fine particles was 0.7 in total amount with respect to the toner base particles.
If it is about 3% by weight, it is more preferable. When mixing these added fine particles, the added fine particles may be added to the mixer together with the toner base particles at a time, followed by stirring and mixing, or they may be sequentially charged and stirred and mixed.

If the difference between the average primary particle diameters of the added fine particles is too large, the other added fine particles adhere to the surface of the added fine particles having a large average primary particle diameter, and the desired effect of adding the fine particles is obtained. In some cases, the maximum average primary particle diameter of the added fine particles is preferably about 100 times or less, more preferably about 50 times or less, the minimum average primary particle diameter. Further, when too much fine toner particles are contained in the toner used for the developer of the present invention, the fine toner particles themselves adhere to the surface of the carrier particles and deteriorate the surface of the carrier particles. It is not preferable because it may cause Such an effect is peculiar to particles having a small particle diameter. In particular, by restricting the amount of fine particles having a size of about 4.0 μm, the developer can be further stably prolonged in life. Therefore, in the electrophotographic developer according to the configuration of the present invention, it is preferable that the number of toner particles having such a small particle size is as small as possible, specifically, 4.0 μm.
The following minute toner particles are preferably 50% by number or less, more preferably 35% by number or less.

In an image forming method for developing an electrostatic latent image formed on an image carrier with an electrophotographic developer comprising toner and carrier particles, the developer of the present invention is used as the electrophotographic developer. By using this, a stable high-quality image can be obtained over a long period of time. further,
The image carrier is cleaned in the cleaning process, and the toner collected in the cleaning process has a characteristic of forming a stable high-quality image for a long period of time as described above. In addition, resource saving of toner is achieved.

Further, as a specific image forming apparatus for performing these image forming methods, there is an image forming apparatus which develops an electrostatic latent image formed on an image carrier with an electrophotographic developer comprising toner and carrier particles. In the forming apparatus, there is an electrophotographic developer using the developer of the present invention. Further, in such an image forming apparatus,
It is preferable to provide a toner recycling mechanism including at least a cleaning mechanism for cleaning the image carrier and a transport mechanism for transporting the toner collected by the cleaning mechanism to the developing mechanism, so that the collected toner is reused.

The image forming method and apparatus 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. An image carrier charging member 2, an image exposure system 3, a developing mechanism 4, a transfer mechanism 5, a cleaning mechanism 6, and a static elimination lamp 7 are arranged around a drum-shaped image carrier 1. Image formation is performed by the following operation. I do.

A series of image forming processes will be described by taking a negative-positive process as an example. The image carrier 1 typified by a photoconductor (OPC) having an organic photoconductive layer is neutralized by a neutralization lamp 7, is uniformly negatively charged by a charging member 2 such as a charging charger or a charging roller, and is irradiated by a laser optical system 3. 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. The laser light 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 using a polygonal polygonal mirror or the like that rotates at a high speed. The latent image formed in this manner is developed by a two-component developer composed of a mixture of toner particles and carrier particles supplied onto a developing sleeve 41 which is a developer carrier in the developing mechanism 4, and a toner visible image is formed. An image is formed. At the time of developing the latent image, a voltage of an appropriate magnitude between the exposed portion and the non-exposed portion of the image carrier 1 or an AC voltage is superposed on the developing sleeve 41 from a voltage applying mechanism (not shown). A development bias 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).
, And the toner image is transferred. At this time, the transfer member 51
Preferably, a potential having a polarity opposite to the polarity of the toner charge is applied. Thereafter, the transfer medium 9 is separated from the image carrier 1 and discharged as an output image via the fixing device 8. Further, the toner particles remaining on the image carrier are removed by the cleaning member 61 into the toner collecting chamber 6 in the cleaning mechanism 6.
Collected to 2. The collected toner particles may be conveyed to a developing unit and / or a toner replenishing unit by a toner recycling unit (not shown) and reused.

FIG. 2 is a schematic view of a main part of the developing device of the image forming apparatus. The developing mechanism disposed on the side of the image carrier (photosensitive drum) 1 includes a developing sleeve 41 as a developer carrier, a developer accommodating member 42, a doctor blade 43 as a regulating member, a support case 44, and the like. It is mainly composed. A toner hopper 45 serving as a toner storage unit for storing the toner 10 therein is joined to a support case 44 having an opening on the image carrier (photoconductor drum) 1 side.
A developer accommodating portion adjacent to the toner hopper for accommodating the developer including the toner and the carrier particles;
, The stirred toner 10 and carrier particles, for imparting friction / peel charge to the toner particles, a developer stirring mechanism 4
7 are provided. Inside the toner hopper 45,
Toner agitator 48 and toner supplying mechanism 49 as a toner supply means which is rotated by an unillustrated driving means
Are arranged. 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.

In the space between the image carrier (photosensitive drum) 1 and the toner hopper 45, a developing sleeve 41 is provided. A developing sleeve 41, which is rotationally driven by a driving unit (not shown) in the direction of the arrow in the figure, has a magnetic field generating unit disposed inside thereof at a fixed position relative to the developing mechanism in order to form a magnetic brush by carrier particles. (Not shown). A regulating member (doctor blade) 43 is integrally attached to a side of the developer accommodating member 42 opposite to the side attached to the support case 44. The regulating member (doctor blade) 43 is disposed with a certain gap kept between its tip and the outer peripheral surface of the developing sleeve 41. With the above-described configuration, the toner 10 sent out from the inside of the toner hopper 45 by the toner agitator 48 and the toner replenishing mechanism 49 is conveyed to the developer accommodating section 46 and is agitated by the developer agitating mechanism 47 so as to have a desired friction. The carrier 11 is provided with a peeling charge, is carried on the developing sleeve 41 as the developer 11 together with the carrier particles, and is transported to a position facing the outer peripheral surface of the image carrier (photosensitive drum) 1, and only the toner 10 is transferred to the image carrier ( The toner image is formed on the image carrier (photosensitive drum) 1 by being electrostatically coupled with the electrostatic latent image formed on the photosensitive drum 1.

[0036]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Here, "parts" all indicate parts by weight.

Production Example 1 [Production of carrier particles (C1)] Polyethyleneimine / silicone resin (= 50/50) graft polymer solution (solid content = 10% equivalent) 500 parts Tetraethoxysilane 25 parts Ethyl alcohol 475 parts The components of the formulation were mixed and stirred with a stirrer to prepare a coating solution for forming a coat layer. This was coated on the surface of 5000 parts of spherical ferrite particles having a weight average particle diameter of 50 μm by a fluidized bed spray coater, and then heated at 160 ° C. for 2 hours to react each of the resin phase compositions, thereby forming a coat layer on the surface. The obtained carrier particles (C1) were obtained. Here, the shape observation of the carrier particle surface coat layer was performed using a scanning probe microscope Nanoscope II manufactured by Digital Instruments.
This was performed using Ia, Dimension 3100. The carrier particles as a measurement sample were fixed on an aluminum flat plate with a thinly applied adhesive. Scan range is 5
Each sample was observed at three independent locations. Based on these surface shape observation data, the ratio of the area where the height difference of the fine irregularities on the surface of the carrier particle was 5 nm or less and the scan profile were 1%.
The surface roughness (Rz) in the 00 nm × 100 nm region was calculated. Table 1 shows the carrier particle surface observation results.

[Table 1]

Production Example 2 [Production of Toner (T1)] 79 parts of polyester resin (condensation polymer of ethylene oxide addition alcohol of bisphenol A, propylene oxide addition alcohol of bisphenol A, terephthalic acid and trimellitic acid; Mw = 12000, (Glass transition point = 61 ° C) Carbon black; Mitsubishi Carbon Co., Ltd. # 44 15 parts Charge control agent; AIZON SPILON BLACK TRH (Hodogaya Chemical Co., Ltd., chromium-containing metal dye) 1 part Carnauba wax; Noda wax company 5 Part The mixture of the above formulation was kneaded with a two-roll kneader for 30 minutes, and then pulverized and classified while adjusting the pulverization and classification conditions with a mechanical pulverizer / air flow type classifier to obtain toner base particles 1. . Further, based on the toner base particles 1, 1.0% by weight of hydrophobic silica fine particles (average primary particle diameter = 25 nm) and hydrophobic titanium oxide fine particles (average primary particle diameter = 15 nm) each having a surface treated with dimethylsilane were 1.0% by weight. And 0.5
% By weight, and mixed for 2 minutes by a Henschel mixer to obtain a toner (T1). Toner (T
When the particle size distribution of 1) was measured by a Coulter counter TA2, the weight average diameter D4 was 6.0 μm, and
The number of toner particles of 0 μm or less was 45% by number.

Example 1 1000 parts of carrier particles (C1) and toner (T1) 5
By mixing 0 parts, an electrophotographic developer was prepared, and a modified Ricoh's copying machine, imageio MF-6550, was used.
A4 size, image area ratio 6% while recycling toner
A continuous image drawing test of 600,000 documents was performed, and character images and solid images at the initial stage and after continuous drawing were output to evaluate the image quality. The image quality was evaluated based on the background fog in the character portion, the stability of the image density in the solid image, and the presence or absence of other defects in each image. The image density was measured using a Macbeth densitometer (RD-914), and the other items were visually evaluated. The electrostatic charge image on the image carrier at the time of image output was set to -700 V for the background portion and -200 V for the image portion. Further, a DC developing bias potential was applied to the developing sleeve. After the 600,000-sheet continuous image drawing test is completed, the developer is collected, the toner particles adhering to the surface are removed by air blowing, and the remaining carrier particles are given an electric charge-imparting ability. The ability was compared and evaluated. The measurement of the charge amount is performed by a normal blow-off method,
The same toner as that used in the continuous image drawing test was used as the toner. Tables 2 and 3 show the evaluation results at the initial stage and after 600,000 sheets. Similarly, a 1,000,000-sheet continuous image drawing test was performed. As a result, a high-definition and high-resolution image comparable to the initial image was obtained.

Production Example 3 [Production of Toner (T2)] Toner base particles 1 obtained in the same manner as in Production Example 2 were treated with dimethylsilane-treated hydrophobic silica fine particles (average primary particle diameter = 15 n).
m) and hydrophobic titanium oxide fine particles (average primary particle size =
30 nm) at a ratio of 0.8% by weight, respectively, and mixed with a Henschel mixer for a total of 2 minutes to obtain a toner (T2).

Example 2 A developer was prepared and tested in the same manner as in Example 1 except that (T2) was used as the toner, and evaluation was performed. The results are shown in Tables 2 and 3.

Production Example 4 [Production of Toner (T3)] Toner base particles 1 obtained in the same manner as in Production Example 2 were treated with dimethylsilane-treated hydrophobic silica fine particles (average primary particle diameter = 60 n).
m) and silica particles (average primary particle size = 15 nm) subjected to the same hydrophobization treatment at 2.0% by weight and 0.5% by weight, respectively, and mixed with a Henschel mixer for a total of 2 minutes to form a toner ( T3) was obtained.

Example 3 A developer was prepared and tested in the same manner as in Example 1 except that (T3) was used as the toner, and evaluation was performed. The results are shown in Tables 2 and 3.

Production Example 5 [Production of carrier particles (C2)] Polyethyleneimine / silicone resin (= 50/50) graft polymer solution (solid content = 10%) 500 parts Tetraethoxysilane 50 parts Ethyl alcohol 450 parts Carrier particles (C2) were obtained in the same manner as in Production Example 1 except that the components of the formulation were used. Table 1 shows the carrier particle surface observation results.

Example 4 A developer was prepared in the same manner as in Example 1 except that the carrier particles (C2) were used, and a test was conducted to evaluate the developer. The results are shown in Tables 2 and 3.

Production Example 6 [Production of Toner (T4)] Using the toner formulation of Production Example 2, the pulverization and classification conditions were adjusted to obtain toner base particles 2 containing a large amount of toner particles of 4.0 μm or less. Further, with respect to the toner base particles 2, hydrophobic silica fine particles (average primary particle diameter = 60 nm) and hydrophobic titanium oxide fine particles (average primary particle diameter = 30 n
m) was added at a ratio of 2.0% by weight and 0.5% by weight, respectively, and mixed by a Henschel mixer for a total of 2 minutes to obtain a toner (T4). When the particle size distribution of the toner (T4) was measured by a Coulter counter TA2, the weight average diameter D4 was 5.8 μm, and the number of toner particles having a particle size of 4.0 μm or less was 60% by number.

Example 5 A developer was prepared and tested in the same manner as in Example 1 except that the toner (T4) was used, and the evaluation was performed. The results are shown in Tables 2 and 3.

Production Example 7 [Production of Toner (T5)] Toner base particles 1 obtained in the same manner as in Production Example 2 were treated with dimethylsilane-treated hydrophobic silica fine particles (average primary particle diameter = 25 n).
m) and hydrophobic titanium oxide fine particles (average primary particle size =
15 nm) at a ratio of 0.3% by weight and 0.1% by weight, respectively, and a total of 2
The mixture was mixed for minutes to obtain a toner (T5).

Example 6 A developer was prepared and tested in the same manner as in Example 1 except that the toner (T5) was used, and the evaluation was performed. The results are shown in Tables 2 and 3.

Production Example 8 [Production of Toner (T6)] Toner base particles 1 obtained in the same manner as in Production Example 2 were treated with dimethylsilane-treated hydrophobic silica fine particles (average primary particle diameter = 25 n).
m) and hydrophobic titanium oxide fine particles (average primary particle size =
15 nm) at a ratio of 3.0% by weight, respectively, and mixed with a Henschel mixer for a total of 2 minutes to obtain a toner (T6).

Example 7 A developer was prepared and tested in the same manner as in Example 1 except that the toner (T6) was used, and the evaluation was performed. The results are shown in Tables 2 and 3.

Production Example 9 [Production of Toner (T7)] Toner base particles 1 obtained in the same manner as in Production Example 4 were treated with dimethylsilane-treated hydrophobic silica fine particles (average primary particle diameter = 25 n).
m) and hydrophobic titanium oxide fine particles (average primary particle size =
15 nm) at a ratio of 3.0% by weight, respectively, and mixed with a Henschel mixer for a total of 2 minutes to obtain a toner (T7).

Example 8 A developer was prepared and tested in the same manner as in Example 1 except that (T7) was used as the toner, and evaluation was performed. The results are shown in Tables 2 and 3.

Production Example 10 [Production of carrier particles (C3)] Weight average particle diameter 50 μm
5000 parts of spherical ferrite particles and 50 parts of polyethylene powder were put into a batch mixer, and 90 ± 10 ° C.
After heating and shear mixing for 2 hours, the mixture was allowed to cool at room temperature to obtain carrier particles (C3) surface-modified with a polyethylene film. Table 1 shows the carrier particle surface observation results.

Example 9 A developer was prepared and tested in the same manner as in Example 1 except that (C3) was used as the carrier particles, and evaluation was performed. The results are shown in Tables 2 and 3.

Example 10 (C2) was used as carrier particles, and (T
A developer was prepared and tested in the same manner as in Example 1 except that 2) was used, and the evaluation was performed. Table 2 shows the results.
It is shown in Table 3.

Example 11 (C3) was used as carrier particles, and (T
A developer was prepared and tested in the same manner as in Example 1 except that 7) was used, and the evaluation was performed. The results are shown in Tables 2 and 3.

Comparative Example 1 Polyethylene imine / silicone resin (= 50/50) graft polymer solution (solid content = equivalent to 10%) 500 parts Tetraethoxysilane 100 parts Ethyl alcohol 400 parts The above-mentioned coating liquid for forming a coating layer was used. Carrier particles (C4) were obtained in the same manner as in Production Example 1 except that the formulation was used. Table 1 shows the carrier particle surface observation results. A developer was prepared and tested in the same manner as in Example 1 except that (C4) was used as the carrier particles, and evaluation was performed. The results are shown in Tables 2 and 3.

Production Example 11 [Production of Toner (T8)] Hydrophobic silica fine particles whose surface was treated with dimethylsilane (average primary particle diameter = 4 nm) with respect to toner base particles 1 obtained in the same manner as Production Example 2.
And hydrophobic titanium oxide fine particles (average primary particle size = 15
nm) at a ratio of 1.0% by weight and 0.5% by weight, respectively, and mixed with a Henschel mixer for a total of 2 minutes to obtain a toner (T8).

Comparative Example 2 A developer was prepared and tested in the same manner as in Example 1 except that the toner (T8) was used, and the evaluation was performed. The results are shown in Tables 2 and 3.

Production Example 12 [Production of Toner (T9)] With respect to the toner base particles 1 obtained in the same manner as in Production Example 2, hydrophobic silica fine particles whose surfaces were treated with dimethylsilane (average primary particle diameter = 60 n)
m) and hydrophobic titanium oxide fine particles (average primary particle size =
60 nm) at a ratio of 1.0% by weight, respectively, and mixed with a Henschel mixer for a total of 2 minutes to obtain a toner (T9).

Comparative Example 3 A developer was prepared and tested in the same manner as in Example 1 except that the toner (T9) was used, and the evaluation was performed. The results are shown in Tables 2 and 3.

[0063]

[Table 2]

[0064]

[Table 3]

[0065]

According to the constitution of the present invention, the relationship between the surface shape of the carrier particles and the primary particle diameter of the fine particles added to the toner in Table 1 and the comparison between the examples and comparative examples shown in Tables 2 and 3 are shown. As is evident, it has the characteristics necessary to obtain a stable image with no image deterioration due to deterioration of the developer or image deterioration such as toner dust and background fog, and at the same time, high quality images with high definition and high resolution Is an extremely effective two-component developer for electrophotography to obtain over a long period of time, and at the same time, an effective two-component developer for electrophotography and an image forming method for resource saving. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of an image forming apparatus.

FIG. 2 is a schematic diagram of a main part of a developing device of the image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive drum) 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 41 Developing sleeve 42 Developer storing member 43 Regulatory member (Doctor blade) 44 Support case 45 Toner hopper 46 Developer storage unit 47 Developer stirring mechanism 48 Toner agitator 49 Toner supply mechanism 51 Transfer member 52 Static elimination brush 61 Cleaning member 62 Toner recovery chamber

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 21/10 G03G 9/10 354 362 15/08 507D 21/00 326 (72) Inventor Yoichiro Watanabe Tokyo 1-3-6 Nakamagome, Ota-ku, Ricoh Co., Ltd. (72) Inventor Akihiro Ban 1-3-6, Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Inventor Mitsuteru Kato Naka, Ota-ku, Tokyo 1-3-6, Magome, Ricoh Co., Ltd. (72) Keiko Shiraishi, Inventor Keiko Shiraishi 1-3-6, Nakamagome, Ota-ku, Tokyo (72) Inventor Toshiki Sawada, 1-3-3 Nakamagome, Ota-ku, Tokyo No. 6 F-term in Ricoh Co., Ltd. (reference) 2H005 AA08 BA06 BA07 BA15 CA11 CA12 CA25 CA26 EA05 EA07 2H077 AA37 AC16 EA03 EA21 2H134 GA01 GB02 JA01 JA11 KG0 7 KH17

Claims (11)

[Claims] 1. An electrophotographic developer obtained by mixing toner particles obtained by externally adding two or more kinds of fine particles to toner base particles comprising at least a colorant and a binder resin, and carrier particles, wherein Among the two or more types of added fine particles, one type of added fine particles having the smallest average primary particle size has an average primary particle size of 5 to 50 nm, and the carrier particles have a resin phase on at least the surface of a core material made of a magnetic material. And a height difference between an arbitrary convex portion present on the surface of the carrier particle and a concave portion adjacent to the convex portion is 5 nm.
An electrophotographic developer, wherein the following region occupies 60% or more of the surface of the carrier particles. 2. 100 nm × 100 on the surface of carrier particles
The surface roughness Rz in the nm region and the average primary particle diameter Dmin of one type of additional fine particle having the smallest average primary particle diameter among the two or more types of additional fine particles in the toner are represented by the following equation (1).
The electrophotographic developer according to claim 1, which satisfies the following. ## EQU1 ## 2.3 × Rz <Dmin (1) 3. The electrophotographic developer according to claim 1, wherein the resin forming the surface coat layer of the carrier particles is a silicone resin or a modified product thereof or a fluorine resin. 4. The electrophotographic developer according to claim 1, wherein the carrier particle surface coat layer contains a compound having a siloxane bond skeleton in a main chain and / or a side chain. 5. The electrophotographic developer according to claim 1, wherein the ratio of the added fine particles in the toner to the toner base particles is 0.5 to 5% by weight. 6. The electrophotographic developer according to claim 1, wherein the number of toner particles having a size of 4.0 μm or less in the toner is 50% by number or less. 7. The electrophotographic developer according to claim 1, wherein the core material and / or the coating layer of the carrier particles contain a silane coupling agent and / or a titanium coupling agent. 8. An image forming method for developing an electrostatic latent image formed on an image carrier with an electrophotographic developer comprising toner and carrier particles, wherein the electrophotographic developer is any one of claims 1 to 7. An image forming method according to any one of claims 1 to 3. 9. The image forming method according to claim 8, wherein the image carrier is cleaned in a cleaning step, and the toner collected in the cleaning step is reused in a developing step. 10. An image forming apparatus for developing an electrostatic latent image formed on an image carrier with an electrophotographic developer comprising toner and carrier particles, wherein the electrophotographic developer is any one of claims 1 to 7. An image forming apparatus according to any one of claims 1 to 3. 11. The image according to claim 10, further comprising a toner recycling mechanism including a cleaning mechanism for cleaning at least the image carrier and a transport mechanism for transporting the toner collected by the cleaning mechanism to the developing mechanism, wherein the collected toner is reused. Forming equipment.