JP2000098666A - Coated carrier for development of electrostatic latent image, developer for electrostatic latent image and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coated carrier for development of electrostatic latent images which has excellent electrification stability and holding property against temp. and humidity changes and with which images without image defects can be stably obtd., to obtain an electrostatic latent image developer containing that carrier, and to obtain an image forming method using the carrier and developer. SOLUTION: In the coated carrier for development of electrostatic latent images having a coating layer on the core, the coating layer contains at least metal oxide powder having <=106 [Ωcm] electric resistivity and inorg. oxide fine particles having >=108 [Ωcm] electric resistivity. The electrostatic latent image developer contains the coated carrier for development of electrostatic latent images. In the image forming method, the above-described electrostatic latent image developer is used to develop latent images formed on a latent image holding body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated carrier for developing an electrostatic latent image used for developing an electrostatic image in electrophotography and electrostatic recording, an electrostatic latent image developer containing the same, and an electrostatic latent image developer containing the same. The present invention relates to an image forming method using an electrostatic latent image developer.

[0002]

2. Description of the Related Art In recent years, image forming methods for visualizing image information via an electrostatic image have been used in various fields such as electrophotography. In the electrophotographic method, an electrostatic latent image is formed on a latent image carrier (photoreceptor) in a charging and exposing step, and the electrostatic latent image is developed with a developer containing toner, and then transferred and fixed. Is visualized (imaged) through. The developer used here includes a two-component developer composed of a toner and a carrier,
There are two types: a one-component developer consisting of a single toner, such as a magnetic toner. In a two-component developer, the carrier plays a role of stirring, transporting, charging, etc. the developer, and has controllability as a developer. Is widely used at present because of its high cost.

Further, as a developing method, a
Although a magnetic brush method has been used, a magnetic brush method using a magnetic roll as a developer transporting carrier is mainly used at present. In particular, in the two-component magnetic brush development, a conductive magnetic brush (CMB) development using a conductive carrier and an insulating magnetic brush (IMB) development using an insulating carrier are known. Among them, in CMB development, electric charge is injected from a magnetic roll due to the low electric resistance of the carrier, and the carrier in the vicinity of the photoreceptor acts as a development electrode, effectively increasing the electric field during the development process and effectively transferring the toner. Therefore, it has a feature that the reproducibility of the solid image is excellent.

On the other hand, there is a problem that an image defect is apt to occur due to a white line called a brush mark or a carrier called a carrier over adhered to a photoreceptor caused by charge injection from a magnetic roll.

[0005] Further, as the colorization of an image is rapidly progressing, the required level of the image quality is increasing more and more. In this color image, in particular, quality improvement of a solid image is important, and a CM including a durability such as a long life is included.
Further improvement in the performance of the carrier for B development is strongly desired.

In order to enhance the durability of the carrier, a resin-dispersed carrier having a small specific gravity of a magnetic carrier, a resin-coated carrier using a low surface energy material, and the like have been proposed. Various characteristics are required for the resin-coated carrier, and in particular, the resin-coated carrier has a property capable of imparting appropriate chargeability to toner particles and maintaining appropriate chargeability of toner particles for a long period of time. It is necessary to be. Further, in addition to impact resistance and abrasion resistance, it is necessary to have the ability to stably maintain the chargeability of toner particles against environmental changes such as humidity and temperature. Various studies on the point have been performed, and various resin-coated carriers have been proposed.

As a method of adjusting the electric resistance of the coating resin layer provided on the resin-coated carrier, a technique of adjusting the electric resistance by dispersing conductive powder in a resin component is known. As the conductive powder used here, carbon black, metal powder, metal oxide powder and the like have been proposed. In particular, carbon black is inexpensive and used for general purposes because its electrical resistance can be easily adjusted with a small amount of addition. There is a problem in the point.

On the other hand, in the case where a carrier provided with a carbon black resin coating layer is used, if the carbon black resin coating layer is peeled off due to a mixing impact generated between the toner and the toner in a developing machine, toner is not generated during development. Together with the image portion or the non-image portion to cause image quality contamination. This is an important problem particularly when outputting a color image.

Further, carbon black itself has a low electric resistance, and therefore has a drawback that bias leakage tends to occur particularly in CMB development, and as a result, image defects such as brush marks tend to occur.

When another conductive powder is used, the electric resistance is higher by two orders of magnitude or more than that of the above-mentioned carbon black. To obtain a carrier having a desired electric resistance, a large amount of conductive powder is added to the resin to be coated. Therefore, it becomes difficult to prepare a coating solution for a coating layer having excellent dispersion stability. In addition, when the amount of the conductive powder added is large, the formed coating layer itself becomes brittle, causing the coating layer to be dropped and causing a change in the electric resistance of the carrier. Further, there are various problems that the conductive powder is easily exposed on the surface of the coating resin layer, and the influence of the conductive powder on the frictional charging of the toner cannot be ignored. As described above, it is extremely difficult to easily and appropriately control and adjust the triboelectric charge applied to the toner particles by adding only the conductive powder to the coating resin layer.

However, in the field of recent digital full color copying machines, printers, etc., with the rapid spread thereof,
It has been desired to further stabilize the image quality, increase the image quality, and reduce the cost per copy. To meet these demands, for example, JP-A-4-33738 and JP-A-6-33738.
No. 75430 proposes to use a color toner having a small particle size for the purpose of improving the image quality of a color copy and improving image reproducibility.

However, the smaller the toner particles, the smaller the diameter.
The development, transfer, and cleaning characteristics deteriorate, and the stability and maintainability of the image quality deteriorate. In addition, the frictional charging characteristics with the carrier tend to deteriorate, and the environmental charging characteristics also tend to deteriorate.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to provide a stable and free image defect by providing a coating layer having excellent charge stability and charge retention against changes in temperature and humidity environments and having a high strength. Long-life electrostatic latent image developing coated carrier capable of obtaining an image, electrostatic latent image developer containing this electrostatic latent image developing coated carrier, and image forming method using this electrostatic latent image developer Is to provide.

[0014]

Means for Solving the Problems The present inventors have paid attention to the components constituting the coating layer of the coating carrier for developing an electrostatic latent image used in a two-component developer, and have conducted intensive studies. By simultaneously using the specific metal oxide powder and the specific inorganic oxide fine particles in the resin component of the layer, it is possible to impart an appropriate charge to the toner particles, and to maintain the applied charge for a long time, The inventors have found that the film strength of the coating layer itself can be increased, and have completed the present invention. That is, the above object is achieved by the following coated carrier for developing an electrostatic latent image, an electrostatic latent image developer and an image forming method of the present invention. <1> In a coated carrier for developing an electrostatic latent image having a coating layer on a core material, the coating layer includes at least a metal oxide powder having an electric resistance of 10 ⁶ [Ωcm] or less, and an electric resistance of 10 ⁸ [Ωcm] or less. A coated carrier for developing an electrostatic latent image, which is a resin layer containing inorganic oxide fine particles of [Ωcm] or more.

<2> A two-component electrostatic latent image developer comprising the electrostatic latent image developing coated carrier according to <1> and a toner.

<3> A charging step of charging the latent image carrier, an exposure step of forming a latent image on the latent image carrier, and a developing step of developing the latent image with a developer containing a toner and a carrier A step of transferring the developed toner image to a transfer member, and a fixing step of heat-fixing the toner image on the transfer member. An image forming method, comprising: an electrostatic latent image developer according to (1).

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The coated carrier for developing an electrostatic latent image of the present invention comprises a metal oxide powder having an electric resistance of 10 ⁶ [Ωcm] or less in a resin component constituting a coating layer provided on a core material thereof. And inorganic oxide fine particles having an electric resistance of 10 ⁸ [Ωcm] or more. By forming a specific coating layer containing these on the core material, 10 ⁴ [V / cm]
Under an electric field of 10 to 10 to 10
⁸ [Ωcm] coated carrier for electrostatic latent image development with a dynamic electric resistance in the range, improving the charge control characteristics of the toner and its retention characteristics, and having high film strength to achieve high image quality To achieve a longer life of the carrier.

In order to obtain a good solid image free from image defects such as brush marks, carrier overs and fog in the image, it is necessary that the electric resistance of the carrier used is within a desired range. In order to achieve this, in the present invention, a conductive specific metal oxide powder and a high-resistance specific inorganic oxide fine particle are simultaneously used as a resistance adjusting agent in the coating layer covering the core material.

The metal oxide powder used as a resistance adjusting agent in the coating layer according to the present invention is indispensable for adjusting the dynamic electric resistance of the carrier to a desired region. It is difficult to control the toner particles to a desired charge amount, and to maintain the charge for a long period of time. Also, since the electric resistance is small, the amount that can be added is small, so that a desired filler effect on the resin cannot be expected. ,
Sufficient film strength cannot be obtained.

Therefore, the coating layer of the coated carrier for developing an electrostatic latent image of the present invention contains the metal oxide powder described above,
By containing the inorganic oxide fine particles having higher electric resistance than the core material, the carrier can be adjusted to a desired dynamic electric resistance. As a result, the charge of the toner is controlled and the charge is kept stable. It becomes possible. Further, since the inorganic oxide fine particles are fine particle substances, a sufficient filler effect can be obtained by adding the inorganic oxide fine particles, and the film strength of the coating layer can be improved.

More specifically, metal oxide powder having an electric resistance of 10 ⁶ [Ωcm] or less and inorganic oxide fine particles having an electric resistance of 10 ⁸ [Ωcm] or more are used as the metal oxide powder. Thereby, the effects of the present invention described above can be achieved. In particular, by using the metal oxide powder and the inorganic oxide fine particles in combination at an appropriate mixing ratio to form a carrier having a dynamic electric resistance in a range suitable for use and using the carrier together with the toner particles, Since the charge imparting ability is obtained and the film strength can be improved at the same time, the toner can be stably charged for a long time. As a result, the shelf life of the developer is improved. Therefore, by using the electrostatic latent image developing coated carrier of the present invention, a high quality image can be stably obtained.

Metal oxide powder is dispersed and used as a resistance adjusting agent in the coating layer. The metal oxide powder is a conductive particle and preferably has an electric resistance of 10 ⁶ Ωcm or less, more preferably at least 10 ⁻¹ Ωcm or more.

The metal oxide powder is not particularly limited as long as it can impart a desired electric resistance to the coating layer, and may have various particle shapes such as spherical, fiber (needle), and scale. Can be used. The size of the particles is regulated by the size of the core particles used, the smoothness and uniformity of the surface of the coating layer, the film strength of the coating layer, the dispersion stability at the time of production, and the like. Is preferably 3 μm or less, more preferably 1 μm or less.

Examples of the material of the metal oxide powder include simple substances such as zinc oxide, tin oxide, titanium oxide, iron oxide, and titanium black; and titanium oxide, zinc oxide, aluminum borate or potassium titanate, and barium sulfate. A composite material in which the surface of the fine particles is coated with a conductive metal oxide is exemplified, and among them, titanium oxide having a core material whose surface is coated with a conductive metal oxide, titanium black, zinc oxide and the like are preferable. When used in the present invention, each of the electric resistance values needs to be 10 ⁶ Ωcm or less, and these may be used alone or in combination of two or more within this range.

Examples of the conductive metal oxide used for coating the surface of the fine particles include metal oxides doped with antimony such as antimony-type tin oxide and oxygen-deficient metal oxides such as oxygen-deficient tin oxide. However, in the case of oxygen-deficient metal oxides, it is preferable to use antimony-type metal oxides because moisture can be relatively easily adsorbed to the oxygen-deficient portions.

The amount of the metal oxide powder used in the coating layer formed on the surface of the core material particles is appropriately selected and used to make the carrier resistance have a desired electric resistance value. In this case, the metal oxide powder is selectively used in view of the specific gravity, electric resistance, and orientation in the coating layer. Among them, it is preferably used in the range of 10 to 50% by weight of the solid content of the coating layer. Preferably, it is more preferably used in the range of 20 to 50% by weight. If the amount used is less than 10% by weight, the electric resistance of the coating layer does not decrease to a desired value, and even if it is added in excess of 50% by weight, the electric resistance does not decrease, but rather the coating layer tends to become brittle. When producing a coating liquid for a layer, it is not preferable because the metal oxide powder cannot be uniformly dispersed and its dispersion stability cannot be ensured.

In the coating layer, specific inorganic oxide fine particles are dispersed and used as a resistance adjusting agent in addition to the above-mentioned metal oxide powder. As the inorganic oxide fine particles, the electric resistance is 1
While using the 0 ⁸ [Omega] cm or more of, even if the surface treatment is performed on the particle surface, or may be unprocessed. Among them, the inorganic oxide fine particles are 10 ⁸ to
Those having an electric resistance in the range of 10 ¹⁶ Ωcm are preferred. Further, the electric resistance of the inorganic oxide fine particles, the lower limit of any of the above numerical range or any value of the electric resistance of the inorganic oxide fine particles adopted in the examples described below as a lower limit, any of the above numerical range It is also preferable that the upper limit of the above or the numerical range having the upper limit of any one of the electric resistances of the inorganic oxide fine particles employed in Examples described later as an upper limit.

Examples of the above-mentioned inorganic oxide fine particles include silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, zinc oxide and molybdenum oxide.
Among them, titanium oxide, silicon oxide and zirconium oxide are preferable. When used in the present invention, each electric resistance value needs to be within the above range, and within this range, these may be used alone or in combination of two or more.

The primary particle size of these particles is 3
It is preferable to use one having a size of 1 μm or less, more preferably one having a size of 1 μm or less.

Further, in order to maintain the film strength for a longer period of time and to obtain a stable image quality by preventing the destruction and contamination of the surface of the coating layer, the inorganic oxide fine particles used in the present invention are preferably provided with a hydrophobic surface. It is preferable that the oxide fine particles have been subjected to a chemical treatment. By dispersing the extremely hydrophobic fine particles subjected to the hydrophobizing treatment in the resin, the amount of water adsorbed on the particle surface is suppressed,
A change in electrical resistance due to a change in temperature and humidity environment can be relatively suppressed. Accordingly, the charge amount of the toner particles to which the charge is applied and maintained by the carrier is stably maintained, and a high quality image can always be obtained stably without being affected by the environment.

As the hydrophobizing agent used in the hydrophobizing treatment, a silane coupling agent, a titanate coupling agent, an aluminate coupling agent, a zirconium coupling agent, a silicone oil, etc. can be preferably used. It is preferable to use a silane coupling agent or a silicone oil represented by the following chemical formulas (1) to (3). R _4-x Si (NCO) _x (1) R _4-x Si (OR ¹ ) _x (2) R _4-x SiCl _x (3)

[In the formula, x represents an integer of 1 to 3, R represents an alkyl group having 1 to 16 carbon atoms or a perfluoroalkyl group, and OR ¹ represents an alkoxy group such as a methoxy group or an ethoxy group. ]

A specific example of the above chemical formula is (CH ₃ )
₂ Si (NCO) ₂ , CH ₃ Si (NCO) ₃ , CH ₃
Si (OCH ₃ ) ₃ , C ₁₀ H ₂₁ Si (OCH ₃ ) ₃ , C
F ₃ Si (OCH ₃ ) ₃ , CH ₃ Si (OC ₂ H ₅ ) ₃
And the like. Among them, those having x = 3 are particularly preferable from the viewpoint of increasing the charge amount. For the same reason, R is preferably an alkyl group having 7 to 16 carbon atoms or a perfluoroalkyl group.

Examples of the silicone oil include dimethyl silicone oil, methylphenyl silicone oil, monomethyl silicone oil, modified silicone oil, and the like. Among them, dimethyl silicone oil,
Modified silicone oils and the like are preferred.

As the hydrophobizing agent used in these hydrophobizing treatments, 5 wt.
0% by weight or less, preferably 0.1 to 30% by weight.
More preferably, it is used in the range of 0.5% by weight.
Most preferably, it is used in the range of 10 to 10. If it is less than 0.1, it is not possible to obtain a sufficient hydrophobic effect against changes in the temperature and humidity environment. If it exceeds 50% by weight, the particles aggregate, making it difficult to disintegrate, and the particles tend to become large. Not preferred.

The hydrophobizing treatment can be performed by a conventionally known wet or dry method. The wet method is, for example, a method in which a treating agent is added while dispersing the particles in a solvent, the particles are adsorbed on the particles, separated, dried, and further subjected to a heat treatment. The dry method is, for example, a method in which a treatment liquid is sprayed while particles are suspended and fluidized, and heated and dried.

The above-mentioned inorganic oxide fine particles are appropriately selected and determined from the relationship between the electric resistance value of the above-mentioned metal oxide powder and the used amount thereof so that the resistance of the carrier becomes a desired electric resistance value. Addition of an excessive amount of inorganic oxide fine particles
It is not preferable because the viscosity of the coating liquid after dispersion is increased. Therefore, the addition amount is determined and limited in consideration of the viscosity of the coating liquid for the coating layer, but it is particularly preferably used in the range of 1 to 20% by weight based on the weight of the resin contained in the coating layer. More preferably, it is used in the range of 10 to 10% by weight. If the amount is less than 1% by weight, the effect of imparting charge to the toner particles is poor, and sufficient film strength cannot be obtained. It is not preferable because the viscosity of the liquid increases and the dispersibility and stability of the additive tend to decrease.

The combination of the metal oxide powder and the inorganic oxide fine particles is adjusted in consideration of the dynamic electric resistance of the carrier after the formation of the coating layer and the charge state of the carrier from the frictional charge with the toner used. In particular, the mixing ratio (a: b, weight ratio) of the metal oxide powder (a) and the inorganic oxide fine particles (b) is as follows:
It is preferably determined in the range of 1: 9 to 9: 1,
More preferably, it is determined in the range of 3: 7 to 7: 3.

The combination of the above-mentioned metal oxide powder and inorganic oxide fine particles includes the combination of (a-1) a conductive tin oxide-coated titanium oxide composite powder and (b-1) hydrophobic silica. Combination of (a-2) tin oxide and (b-2) hydrophobic silica, (a-3) combination of conductive tin oxide-coated barium sulfate composite powder and (b-3) hydrophobic silica Are preferred. In this case they are 1: 9 to 9: 1
Compounding ratio in the range of (a-1: b-1), 1: 9 to 9: 1
(A-2: b-2) compounding ratio in the range, or 1: 9 to
The use of a compounding ratio in the range of 9: 1 (a-3: b-3) is preferable in that the effects of the present invention can be sufficiently achieved.

In the coating layer, a resin is used as a binder in addition to the metal oxide powder and the inorganic oxide fine particles. This resin is preferably used in an amount of 20% by weight or less of the total solid content of the coating layer, and more preferably in the range of 3 to 15% by weight. If the amount is less than 3% by weight, the desired strength cannot be obtained. If the amount exceeds 20% by weight, the metal oxide powder and the inorganic oxide fine particles to be added are uniformly dispersed when producing the coating solution for the coating layer. In addition, it is difficult to secure the dispersion stability, which is not preferable.

As the resin used for the coating layer, any of generally known thermoplastic resins can be used. For example, polyolefin resins such as polyethylene and polypropylene; polyvinyl resins such as polystyrene, acrylic resin, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, polyvinyl ether and polyvinyl ketone Or polyvinylidene resin; vinyl chloride-vinyl acetate copolymer; styrene-acrylate copolymer; straight silicone resin comprising organosiloxane bond or a modified product thereof; polytetrafluoroethylene, polyvinyl fluoride,
Fluorine resins such as polyvinylidene fluoride or polychlorotrifluoroethylene; polyester resins; polyurethane resins; polycarbonate resins; amino resins such as urea-formaldehyde resins; and epoxy resins.
These may be used alone or a plurality of resins may be mixed. Further, a thermoplastic resin may be mixed with a curing agent or the like and cured to be used.

In the coated carrier for developing an electrostatic latent image of the present invention, the method for coating the above resin on the surface of the core particles is as follows.
For example, (1) a dipping method in which the core particles are immersed in a solution for the coating layer, (2) a spray method in which the solution for the coating layer is sprayed on the surface of the core particles, and (3) the core particles are suspended by flowing air. In the state, the fluidized bed method of spraying the coating layer solution, (4) While mixing the core particles and the coating layer solution in a kneader coater,
It can be performed by a known method such as a kneader coater method for removing a solvent.

As the solvent used in the coating layer solution, any solvent can be used as long as it can dissolve the resin usable in the coating layer. For example, aromatic hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, and ethers such as tetrahydrofuran and dioxane can be used. Further, a mixed solution of these solvents may be used.

The thickness of the coating layer of the coated carrier for developing an electrostatic latent image of the present invention is preferably in the range of 0.3 to 5 μm, more preferably in the range of 0.5 to 3 μm. Further, the thickness of the coating layer, the lower limit of any of the above numerical range or any value of the electrical resistance of the inorganic oxide fine particles adopted in the examples described below as a lower limit, any upper limit of the above numerical range Alternatively, a numerical range having an upper limit of any value of the thickness of the coating layer employed in Examples described later is also preferable. If the thickness of the coating layer is less than 0.3 μm, it is difficult to form a uniform coating layer on the surface of the core material, and if it is more than 5 μm, the drying time becomes long and it is not economical, and the ratio of the remaining solvent is large. This is not preferable because toner contamination easily occurs.

The average particle size of the coated carrier for developing an electrostatic latent image of the present invention having a coating layer formed on a core material is preferably in the range of 10 to 80 μm, more preferably 20 to 60 μm. Those having a range of 30 to 55 μm are most preferred. Further, the thickness of the coating layer, the lower limit of any of the above numerical range or any value of the electrical resistance of the inorganic oxide fine particles adopted in the examples described below as a lower limit, any upper limit of the above numerical range Alternatively, a numerical range having an upper limit of any value of the thickness of the coating layer employed in Examples described later is also preferable. The particle diameter of the coated carrier for electrostatic latent image development of the present invention,
If the thickness is less than 10 μm, coating defects may occur, making it difficult to coat the surface uniformly, and the developer may be easily scattered in the developing device, and the carrier may adversely affect the image during development, which is not preferable. Further, when the thickness exceeds 80 μm, the effect on the image quality is large, and in particular, the reproducibility of fine lines and the reproducibility of dots may be undesirably reduced.

As the core material of the coated carrier for developing an electrostatic latent image according to the present invention, any known materials can be used. Among them, ferrite or magnetic powder-dispersed resin having low electric resistance is preferable.

In particular, in the case of ferrite, the electric resistance of the ferrite can be easily changed after firing, for example, by appropriately controlling the reduction time or the like in a hydrogen atmosphere at an appropriate temperature. Is particularly preferred in that it can be easily obtained. As other core materials, for example, iron powder and magnetite are known, but in the case of iron powder, toner and external additives are liable to adhere to the powder due to its large specific gravity, and its stability is inferior to ferrite. In the case of magnetite,
Resistance control is difficult, and there is a problem that the latitude of the electric resistance is narrow. Therefore, in any case, it is not preferable in use.

The volume average particle diameter of the core particles composed of magnetic particles such as ferrite is preferably 10 to 100 μm, more preferably 20 to 80 μm. When the volume average particle diameter is less than 10 μm, the developer in the developing device is liable to be scattered, and is also developed together with toner during development, which adversely affects the image.
If it exceeds μm, toner cannot be supplied faithfully with respect to the developing potential on the photoreceptor, and a high-quality image cannot be obtained.

The above magnetic powder-dispersed resin includes ferrite,
Powders of magnetic particles such as iron powder and magnetite are dispersed in a thermoplastic resin or a thermosetting resin. Examples of the thermoplastic resin and the thermosetting resin used here include a polyolefin resin, a polyester resin, a polyurethane resin, a polycarbonate resin, a melamine resin, and a phenol resin.

Further, the particle diameter of the magnetic particles is preferably in the range of 0.
It is preferably in the range of 01 to 10 μm, and 0.05
Those having a range of from 5 to 5 μm are more preferable. The volume average particle diameter of the magnetic powder-dispersed resin in which these are dispersed in a resin is the same as the above-mentioned magnetic particles, preferably in the range of 10 to 100 μm, more preferably in the range of 20 to 80 μm.

The coated carrier for developing an electrostatic latent image of the present invention having a coating layer obtained in the above manner is 10 ⁴
Under an electric field of V / cm, 10 to 10
Those having a dynamic electric resistance in the range of ⁸ Ωcm are preferable, and those having a dynamic electric resistance in the range of 10 ³ to 10 ⁶ Ωcm are more preferable. Further, the dynamic electric resistance is a lower limit of any one of the above numerical ranges or any value of the electric resistance of the inorganic oxide fine particles employed in Examples described later, and an upper limit of any one of the above numerical ranges. It is also preferable that the upper limit be a value or any of the values of the dynamic electric resistance employed in the examples described later. The dynamic resistance of the carrier is
When the value is not within the range of 10 to 10 ⁸ Ωcm, it is difficult to impart an appropriate charge to the toner particles, and the solid image and the line image cannot be faithfully reproduced.

The dynamic electric resistance of the coated carrier for developing an electrostatic latent image of the present invention can be determined as follows. Le, a plate electrode with an area of 3 cm ² are opposed at a spacing of 2.5 mm, the magnetic b facing the carrier in a flat plate electrode - - diameter 4 cm, magnetic Hollow axial length 10cm magnetic brush put on Le Form. At this time, the weight of the carrier per unit area was adjusted to about 40 mg / cm ² . 12
A voltage is applied between the magnetic roll and the plate electrode while rotating the magnetic roll at a rotation speed of 0 rpm, and the current flowing at that time is measured. From the obtained current-voltage characteristics, the electrical resistance is obtained by using the relational expression of Ohm's law.

In general, there is a relation of logJ∝E1 / 2 between the applied voltage E and the current density J at this time, as described in “Japanese Journal of Ap.
plied Physics "(Vol. 19, No. 12, p.
2413) and are well known.

Also in the case of the coated carrier for developing an electrostatic latent image of the present invention, when the electric resistance is low, a large current flows under a high electric field of 1000 v / cm or more, so that the measurement may not be performed. In such a case, three or more points are measured under a low electric field, and 10 ⁴ v /
Extrapolated to an electric field of cm.

Further, in the present invention, the above-mentioned carrier core particles may be provided with a thin resin coating layer on the surface thereof. In this case, it is preferable to use a coupling agent such as a silane coupling agent or a titanate coupling agent between the core particles and the coating layer. Examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, tris- (β-methoxyethoxy) vinylsilane, vinyl and riacetoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyl Trimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, β-mercaptoethyltrimethoxysilane, γ-chloropropyltrimethoxysilane, and the like,

Examples of the titanate coupling agent include known compounds such as isopropyl tristearoyl titanate and isopropyl methacryl isostearyl titanate.

The toner used together with the carrier contains a binder resin and a coloring agent such as a pigment. Examples of the binder resin used in the toner used with the coated carrier for developing an electrostatic latent image of the present invention include styrenes such as styrene and chlorostyrene; monoolefins such as ethylene, propylene, butylene and isoprene; vinyl acetate and propionic acid Vinyl esters such as vinyl and vinyl benzoate; methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate Etc. α
-Methylene fatty acid monocarboxylic acid esters; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; homopolymers or copolymers such as vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone; Can be mentioned.

Among the above homopolymers or copolymers,
Particularly typical binder resins include polystyrene, styrene-acrylate copolymer, styrene-methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, and styrene-maleic anhydride. Copolymers, polyethylene, polypropylene, polyester resin, polyurethane resin, epoxy resin, silicone resin, polyamide resin, modified rosin, paraffin, waxes and the like can be mentioned.

Among them, a polyester resin is particularly preferable, and a polyester resin comprising a polycondensate containing bisphenol A and a polyvalent aromatic carboxylic acid as main monomer components is more preferable. Further, among the above binder resins, the softening point is 8
In the range of 0 to 150 ° C. and a glass transition point (Tg) of 5
Those in the range of 0 to 80 ° C are particularly preferred.

The coloring agents include carbon black, titanium black, nigrosine, aniline blue, calcoil blue, chrome yellow, ultramarine blue, and
Pon Oil Red, Quinoline Yellow, Methylene Blue Chloride, Phthalocyanine Blue, Malachite Green Oxalate, Lamp Black, Rose Bengal,
C. I. Pigment Red 48: 1, C.I. I. Pigment Red 57-1, C.I. I. Pigment Red 1
22, C.I. I. Pigment Red 238, C.I. I. Pigment Yellow 13, C.I. I. Pigment Yellow 17, C.I. I. Pigment yellow 154, C.I.
I. Pigment Yellow 180, C.I. I. Pigment Yellow 185, C.I. I. Pigment Yellow 9
7, C.I. I. Pigment Blue 15, C.I. I. Pigment Blue 15: 1, C.I. I. Pigment Blue 1
5: 3 and the like can be cited as typical examples.

The toner may contain additives such as a quaternary ammonium salt, a charge controlling agent having an organometallic complex or various salt structures, and a fixing aid such as polyethylene wax, if necessary.

The average particle diameter of the toner particles is 30 μm.
m or less, more preferably 2 to 15 μm.

The electrostatic latent image developer of the present invention is a two-component developer in which the coated carrier for developing an electrostatic latent image of the present invention and a toner are mixed, and the amount of toner contained in the developer is as follows. Is preferably used in the range of 0.3 to 30% by weight, more preferably 3 to 10% by weight, based on the total weight of the toner.

The electrostatic latent image developer of the present invention is used as a color developer by appropriately using the above-mentioned coloring agent. Color toners and black toners used in electrostatic latent image developers are used for the purpose of improving fluidity of toner powder, developing property, transferability, and controlling frictional charging between toner and carrier. External additives need to be added.

As the external additive, any known ones such as titanium oxide, silica, and alumina can be used. Among them, titanium oxide fine particles, silica fine particles, or particles whose surface is treated with a hydrophobizing agent. Hydrophobic titanium oxide fine particles and hydrophobic silica fine particles are preferred.

As the above-mentioned hydrophobizing agent, known ones can be used. In particular, it is preferable to use the same hydrophobizing agent as used in the above-mentioned hydrophobizing treatment of the surface of the inorganic oxide fine particles. it can.

When externally added to various color toners used in the electrostatic latent image developer of the present invention, the hydrophobic fine particles are added in an amount of 0.2 to 5% by weight based on the total weight of the toner. It is more preferable to add in the range of 0.3 to 3% by weight. However, the optimum amount is determined by the fluidity and charging characteristics of the toner powder.

The average particle diameter of the hydrophobic fine particles is as follows:
Those having a range of 5 to 500 nm are used.

The external additive can be attached to the toner particle surface by using, for example, a high-speed mixer. Specifically, the toner particles and the external additive can be attached by using a Henschel mixer, a V-type blender, or the like to mix the toner particles. Further, as a method of firmly adhering or sticking, a hybridizer (manufactured by Nara Machinery Co., Ltd.), Angmill (manufactured by Hosokawa Micron Corporation), or the like can be used.

As the coated carrier for developing an electrostatic latent image of the present invention and an apparatus used for forming an image using an electrostatic latent image developer using the same, a known electrostatic latent image recording apparatus can be used. it can. An image forming method for forming an image using the electrostatic latent image developer containing the coated carrier for developing an electrostatic latent image of the present invention and a toner is described with reference to the image forming apparatus shown in FIG. This will be described below. In FIG.
Reference numeral 1 denotes a photosensitive drum serving as a latent image carrier. The photosensitive drum 1 is formed by forming a thin photosensitive layer 1b on the surface of a cylindrical member 1a made of a conductive material. Around the photoconductor drum 1, along a rotation direction thereof, a charger 2, an exposure unit 3, and a developing device 4 in which a developer carrier 11 formed of a cylindrical member is fixed to face the photoconductor drum 1, Corotron 6 before transfer, peeling corotron 7, and cleaner 8
, And an electrophotographic recording means comprising a light neutralizer 9. Reference numeral 10 denotes a recording sheet.

In this image recording apparatus, the photosensitive drum 1 is driven to rotate in the direction of the arrow by driving means (not shown). Next, an image forming method using this apparatus will be described. First, the surface of the photosensitive drum 1 is uniformly charged by the neutralizer 2. Subsequently, the image portion is exposed by a laser beam to form an electrostatic latent image on the photosensitive drum 1, and the developing device 4 develops the latent image into toner by developing the toner. At this time, a developing bias voltage is applied to the developer carrier 11 by a developing bias power supply (not shown). Further, the toner image formed on the photosensitive drum 1 is transferred onto the recording paper 10 by charging by the transfer corotron 6. Thereafter, the recording paper 10 is peeled off from the surface of the photosensitive drum 1 by charging of the peeling corotron 7, and is conveyed to a fixing device (not shown). When the fixing of the toner image on the recording paper 10 is completed, the image recording is completed.
After the transfer of the toner image and the peeling process of the recording paper 10 are completed, the surface of the photosensitive drum 1 is cleaned by a cleaner 8 to remove residual toner, and then the residual charge is removed by exposure from an optical charge remover 9. Prepare for the image recording step.

The developing device 4 has the structure shown in FIG. That is, the developing device 4 has a structure in which a developing opening 16 is provided at a portion of the developing housing 15 in which the developer is stored, facing the photosensitive drum 1, and the developing roll 12 is disposed facing the developing opening 16. The developing roll 12 includes the developer carrier 11 that rotates in the direction of the arrow, and shafts at both ends (not shown).

As one of the full-color image forming methods of the present invention, an electrostatic latent image is developed on a photoreceptor using various color toners and / or black toner, and the toner image is formed on paper or the like. It is formed by superimposing at least a cyan color toner image, a magenta color toner image and a yellow color toner image, and / or a black toner image on a support. As the color toner and black toner, the above-mentioned color toner and black toner used for the electrostatic latent image developer are used.

[0074]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited by these examples. In the following, “parts” in the examples means “parts by weight”.

<Preparation of Hydrophobic Inorganic Oxide Fine Particles> (Hydrophobic Titanium Oxide A-1) 10 g of titanium oxide (trade name: MT150A, manufactured by Teica) having an average particle diameter of 15 nm was added to 1.5 g of decyltrimethoxysilane. Methano
Into the solution, and apply 3
Dispersed for 0 minutes. Next, the dispersion medium was removed with an evaporator and dried, then cured at a temperature of 120 ° C., and crushed in a mortar to obtain hydrophobic titanium oxide A-1.

(Hydrophobic Titanium Oxide A-2) Produced by a dry method in which titanium tetrachloride is vaporized and reacted with water.
Hydrophobized titanium oxide A-2 (trade name: T805, manufactured by Nippon Aerosil Co., Ltd.) obtained by hydrophobizing titanium oxide having an average particle diameter of 30 nm with octyltrimethoxysilane.

(Hydrophobic silicon oxide B-1) Average particle diameter 40
10 g of silicon oxide (trade name: OX50, manufactured by Nippon Aerosil Co., Ltd.) was added to a methanol solution to which 1.5 g of decyltrimethoxysilane was added, and dispersed with a stirrer for 30 minutes while applying ultrasonic waves. . Next, the evaporator
After removing the dispersion medium and drying, the mixture is cured at a temperature of 120 ° C., crushed in a mortar, and subjected to hydrophobic silicon oxide B-
1 was obtained.

(Hydrophobic Silicon Oxide B-2) Average Particle Size 40
10 g of silicon oxide (trade name: OX50, manufactured by Nippon Aerosil Co., Ltd.) with a thickness of 3,3,3-trifluoropropyltrimethoxysilane was added to a methanol solution to which 1 g of 3,3,3-trifluoropropyltrimethoxysilane was added.
The mixture was dispersed with a stirrer for 30 minutes while applying ultrasonic waves. Next, the dispersion medium was removed with an evaporator and dried, followed by curing at a temperature of 120 ° C. and crushing in a mortar to obtain hydrophobic silicon oxide B-2.

<Synthesis of Resin for Coating Layer> 85.0 g (850 mmol) of methyl methacrylate was added to toluene 3
Of the polymerization initiator AIBN (10.
mmol) and reacted under a nitrogen stream at a temperature of 60 ° C. for 40 hours. After the completion of the reaction, precipitated in methanol,
After being collected by filtration, it was dried under vacuum to obtain a resin P for a coating layer. When the molecular weight of the obtained resin P was measured by gel permeation chromatography, the weight average molecular weight Mw was 320.
00.

<Preparation of Binder Resin T for Toner> A mixture having the following composition was placed in a two-liter glass four-necked flask, and a stirring rod, a condenser, a nitrogen gas inlet tube, and a thermometer were set. Set to After the inside of the reaction vessel was replaced with nitrogen gas, 1 g of dibutyltin oxide was added, and the reaction was carried out at about 180 ° C. in the first half of the reaction and under reduced pressure at 220 ° C. in the second half of the reaction while heating with a mantle heater under a nitrogen stream. While reacting.・ Polyoxyethylene (2,2) -2,2-... 0.7 mol bis (4-hydroxyphenyl) propane ・ Polyoxypropylene (2.2) -2,2-... 1.6 mol Bis ( 4-Hydroxyphenyl) propane ・ terephthalic acid ・ ・ ・ 1.4mol ・ n-dodecenylsuccinic acid ・ ・ ・ 0.7mol ・ trimellitic acid ・ ・ ・ 0.2mol The polymerization degree is determined by the ring and ball softening point measurement method (JIS-K2531). The softening point is 130 ° C. while following the softening point
When the reaction reached, the reaction was terminated. After the completion of the reaction, the mixture was allowed to cool to room temperature to obtain a binder resin T for toner. The glass transition point Tg of the obtained binder resin T was 67 ° C.

<Preparation of Cyan Pigment> To 100 parts of the above binder resin T for toner, 60 parts of a cyan pigment (CI Pigmentable-15: 3) having a water content of 30% by weight was added. 1 kgf /
The rotor was rotated at 20 cm / sec while pressurizing to ² cm ² , and melt kneading and water removal were repeated to obtain a pigment content of 30 cm ^2.
% By weight of a flushing cyan pigment was obtained.

<Preparation of Magenta Pigment> To 100 parts of the above binder resin T for toner, 60 parts of a magenta pigment (CI Pigment Red 57: 1) having a water content of 30% by weight was added and heated to about 120 ° C. 1 kgf /
The rotor was rotated at 20 cm / sec while pressurizing to ² cm ² , and melt kneading and water removal were repeated to obtain a pigment content of 30 cm ^2.
% By weight of a flushing magenta pigment was obtained.

<Preparation of Yellow Pigment> To 100 parts of the binder resin T for toner described above, 60 parts of a yellow pigment (CI pigment yellow-17) having a water content of 30% by weight was added, and the mixture was heated to about 120 ° C. 1 kgf /
The rotor was rotated at 20 cm / sec while pressurizing to ² cm ² , and melt kneading and water removal were repeated to obtain a pigment content of 30 cm ^2.
% By weight of a flushing yellow pigment was obtained.

<Preparation of Externally Added Cyan Toner> 16.7 parts of the above flushing cyan pigment and binder resin T8 for toner
3.7 parts were previously mixed and melt-kneaded with an extruder. Next, after cooling and coarse pulverization, the mixture was further pulverized by a jet mill and classified to obtain cyan toner having a cyan pigment content of 4% by weight. The obtained cyan toner was measured for 50% volume average particle diameter using a particle size analyzer (Coulter Counter II, manufactured by Coulter Corporation) to find that it was 6.8 μm. In addition, the volume particle size distribution D16
(Vol) / D84 (vol) was 1.6.

Further, 100 parts of the above cyan toner, 1 part of the above-mentioned hydrophobic titanium oxide A-1 and 1 part of a hydrophobic silicon oxide (trade name: R972, manufactured by Nippon Aerosil Co., Ltd.) were mixed with a Henschel mixer. An additional cyan toner was prepared.

In the same manner as described above, an externally added magenta toner and an externally added yellow toner were produced using the magenta pigment and the yellow pigment obtained above.

Example 1 A mixture having the following composition was placed in a sand mill, and after dispersion, the medium mill was removed to prepare a dispersion (I). <Dispersion (I)>-Toluene 100 parts-Resin P for coating layer 9 parts-Tin oxide metal powder (metal oxide powder) 27 parts (43% by weight) (Product name: Pastoran Type-IV, electric resistance 1 × 10 ⁴ Ωcm, volume average particle diameter 100 nm; manufactured by Mitsui Kinzoku Co., Ltd. ・ The above-mentioned hydrophobic silicon oxide B-2: 3 parts (13.5% by weight) (electric resistance) 1 × 10 ¹³ Ωcm, average volume particle size 40 nm) ・ Bead for media mill (diameter 1 mm) ・ ・ ・ 200 parts

18.8 parts of the above dispersion (I) and magnetite (trade name: MX030A, volume average particle diameter 50 μm)
m; manufactured by Fuji Electric Chemical Co., Ltd.)
And put it in a tank and reduce
The mixture was stirred for 1 minute, and the coating was performed while the solvent was gradually removed to obtain a coated carrier (I) for developing an electrostatic latent image of the present invention.

The thickness of the coating layer of the obtained carrier (I) for developing an electrostatic latent image is determined by embedding the carrier in an epoxy resin, polishing the carrier with an abrasive to form a cross section of the carrier, Observation and measurement were performed with a microscope (XL30, manufactured by Philips). As a result of the measurement, the thickness of the coating layer was about 0.8 μm. The electric resistance of the obtained electrostatic latent image developing coated carrier (I) was measured in the state of a magnetic brush by the method described above, and the electric resistance when extrapolated to an electric field of 10 ⁴ V / cm was measured. The value was 8 × 10 ⁶ Ωcm.

6 parts of the external cyan toner thus obtained and 100 parts of the coated carrier (I) for developing an electrostatic latent image were
The mixture was dispersed and mixed with a blender for about 30 minutes to prepare a cyan electrostatic latent image developer A of the present invention. This cyan electrostatic latent image developer A was loaded into a modified A Color 635, and a solid image having an image density of 30% to 100% was created under a normal temperature and normal humidity environment.

<Evaluation of Image> The formed cyan image was visually evaluated according to the following criteria. Rank A: Uniform and highly reproducible image quality free of image defects such as brush marks is obtained over the entire surface including the edge portion of the solid. Rank B: Image defects such as brush mark and image omission are slightly observed, but are not conspicuous and have no problem in practical use. Rank C: Image defects such as brush marks and image omissions are conspicuous, the image has a rough image quality, and cannot be used.

<Evaluation of Charging Characteristics> The above-mentioned external color toner
6 parts and 100 parts of the carrier (I) are weighed and placed in a glass reagent bottle, and the opening is kept open for one day and night under a low temperature and low humidity environment (10 ° C., 20% RH), and a high temperature and high humidity environment. Each was seasoned under (30 ° C., 80% RH). Then, it was covered and dispersed and mixed for 30 minutes with a table mill to measure blow-off tribo. The environmental charge ratio was calculated by using the obtained values to determine the environmental charge ratio characteristics. These values were used as indices for evaluating the charging characteristics [μq / g]. (Blow-off tribo) ○: 20 to 35 μq / g ×: Other than the above range (Environmental charging ratio characteristics: B / A) B / A = (Charging characteristics under low temperature and low humidity) / (Charging characteristics under high temperature and high humidity) ): 0.5 to 1.0 Δ: 0.4 to 0.5 ×: Other than the above range The results obtained above are shown in Table 1 below.

(Example 2) 27 parts (43% by weight) of the tin oxide-based metal powder used in the dispersion liquid (I) of Example 1 was prepared by using acicular conductive titanium oxide (FT1000, electric resistance 3Ωcm, Ishihara Sangyo Co., Ltd.) Co., Ltd.) 24 parts (40% by weight), and the hydrophobic silicon oxide B-2 was replaced with the hydrophobic silicon oxide B-1.
(Electric resistance 6 × 10 ¹⁵ Ωcm) A dispersion liquid (II) was prepared in the same manner as in Example 1, except that 4 parts (17% by weight) were used.

20 parts of the above dispersion (II) and magnetite (trade name: MX030A, volume average particle diameter 50 μm;
100 parts by vacuum degassing type kneader (Fuji Electric Chemical Co., Ltd.)
, And the mixture was stirred for 30 minutes under reduced pressure at a tank temperature of about 50 ° C., and coated while gradually removing the solvent to obtain a coated carrier (II) for developing an electrostatic latent image of the present invention. . The thickness of the coating layer of the obtained coating carrier (II) for developing an electrostatic latent image was measured in the same manner as in Example 1.
μm. The electrical resistance was measured in the state of the magnetic brush in the same manner as in Example 1. As a result, the electrical resistance when extrapolated to an electric field of 10 ⁴ V / cm was 5 × 10 ³ Ωcm.

Further, the present invention was carried out in the same manner as in Example 1 except that the electrostatic latent image developing coated carrier (I) used in Example 1 was replaced with the electrostatic latent image developing coated carrier (II). And a solid image having an image density of 30% to 100% was prepared in the same manner as in Example 1.

The image quality characteristics and the charging characteristics of the formed solid image were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1 below together with the results of Example 1.

Example 3 27 parts (43% by weight) of tin oxide-based metal powder used in the dispersion liquid (I) of Example 1 was replaced with 15 parts (24% by weight) of the same tin oxide-based metal powder. And the hydrophobic silicon oxide B-2, and the hydrophobic titanium oxide A-1.
(Electric resistance 6 × 10 ¹² Ωcm) A dispersion liquid (III) was prepared in the same manner as in Example 1, except that 3 parts (7.7% by weight) were used.

18.8 parts of the above dispersion (III) and magnetite (trade name: MX030A, volume average particle diameter 50 μm)
m; manufactured by Fuji Electric Chemical Co., Ltd.)
And put it in a tank and reduce
The mixture was stirred for minutes, and the coating was performed while the solvent was gradually removed to obtain a coated carrier (III) for developing an electrostatic latent image of the present invention. The thickness of the coating layer of the obtained coating carrier (III) for electrostatic latent image development was measured in the same manner as in Example 1, and it was about 0.8 μm. Further, the electric resistance was measured in the state of the magnetic brush in the same manner as in Example 1, and as a result, 10 ⁴ V / c
The electric resistance value when extrapolated to an electric field of m is 8 × 10 ⁷ Ω
cm.

Further, the present invention was carried out in the same manner as in Example 1 except that the electrostatic latent image developing coated carrier (I) used in Example 1 was replaced with the electrostatic latent image developing coated carrier (III). And a solid image having an image density of 30% to 100% was prepared in the same manner as in Example 1.

The image quality characteristics and the charging characteristics of the formed solid image were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1 below together with the results of Example 1.

Example 4 27 parts (43% by weight) of the tin oxide-based metal powder used in the dispersion liquid (I) of Example 1 was converted to acicular conductive titanium oxide (FT1000, electric resistance 3 Ωcm, Ishihara Sangyo Co., Ltd.). 24 parts (40% by weight) and carbon black (trade name: VXC72, electric resistance 10 ^-1 Ωc)
m, manufactured by Cabot Corporation) and 0.1 parts (2% by weight) of hydrophobic silicon oxide B used in dispersion (I) of Example 1.
-2 as the hydrophobic titanium oxide A-2 (electrical resistance 3 × 1
0 ¹³ Ωcm) to prepare a dispersion (IV) in the same manner as in Example 1, except that 4 parts (10% by weight) were used.

20 parts of the above dispersion (IV) and magnetite (trade name: MX030A, volume average particle diameter 50 μm;
100 parts by vacuum degassing type kneader (Fuji Electric Chemical Co., Ltd.)
And the mixture was stirred under reduced pressure at a temperature of about 50 ° C. for 30 minutes under reduced pressure, and the coating was performed while gradually removing the solvent to obtain a coated carrier (IV) for electrostatic latent image development of the present invention. . The thickness of the coating layer of the obtained electrostatic latent image developing coating carrier (IV) was measured in the same manner as in Example 1.
μm. The electrical resistance was measured in the state of the magnetic brush in the same manner as in Example 1. As a result, the electrical resistance when extrapolated to an electric field of 10 ⁴ V / cm was 20 Ωcm.

Further, the present invention was carried out in the same manner as in Example 1 except that the electrostatic latent image developing coated carrier (I) used in Example 1 was replaced with the electrostatic latent image developing coated carrier (IV). And a solid image having an image density of 30% to 100% was prepared in the same manner as in Example 1.

The image quality characteristics and charging characteristics of the formed solid image were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1 below together with the results of Example 1.

(Comparative Example 1) 27 parts (43% by weight) of the tin oxide-based metal powder used in the dispersion liquid (I) of Example 1 was mixed with carbon black (trade name: VXC72, electric resistance 10 ^-1 Ωc).
m, manufactured by Cabot Corporation), and 3 parts (2% by weight) of hydrophobic silicon oxide B-2 used in the dispersion liquid (I) of Example 1.
A dispersion liquid (V) was prepared in the same manner as in Example 1 except that no dispersion was used.

18.8 parts of the above dispersion (V) and ferrite (trade name: EFC-50B, volume average particle diameter 50 μm)
m; manufactured by Powder Tech Co.) 100 parts were placed in a vacuum degassing type kneader, mixed and stirred for 30 minutes under reduced pressure at a temperature of about 50 ° C. in the tank, and coating was performed while gradually removing the solvent. Thus, a coated carrier (V) for developing an electrostatic latent image of the present invention was obtained. The thickness of the coating layer of the obtained coated carrier for electrostatic latent image development (V) was measured in the same manner as in Example 1, and it was about 1.2 μm. Further, the electric resistance was measured in the state of the magnetic brush in the same manner as in Example 1, and as a result, 10 ⁴ V / c
The electric resistance value when extrapolated to an electric field of m is 3 × 10 ⁴ Ω
cm.

Further, the present invention was carried out in the same manner as in Example 1 except that the electrostatic latent image developing coated carrier (I) used in Example 1 was replaced with the electrostatic latent image developing coated carrier (V). And a solid image having an image density of 30% to 100% was prepared in the same manner as in Example 1.

The image quality characteristics and charging characteristics of the formed solid image were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1 below together with the results of Example 1.

Comparative Example 2 A dispersion liquid (VI) was prepared in the same manner as in Example 1 except that the hydrophobic silicon oxide B-2 used in the dispersion liquid (I) of Example 1 was not used.

18.8 parts of the above dispersion (VI) and magnetite (trade name: MX030A, volume average particle diameter 50 μm)
m; manufactured by Fuji Electric Chemical Co., Ltd.)
And put it in a tank and reduce
The mixture was stirred for minutes, and the coating was performed while the solvent was gradually removed to obtain a coated carrier (VI) for electrostatic latent image development of the present invention. The thickness of the coating layer of the obtained coated carrier for developing an electrostatic latent image (VI) was measured in the same manner as in Example 1, and it was about 0.8 μm. Further, the electric resistance was measured in the state of the magnetic brush in the same manner as in Example 1, and as a result, 10 ⁴ V / c
The electric resistance value when extrapolated to an electric field of m is 5 × 10 ⁶ Ω
cm.

Further, the present invention was carried out in the same manner as in Example 1 except that the electrostatic latent image developing coated carrier (I) used in Example 1 was replaced with the electrostatic latent image developing coated carrier (VI). And a solid image having an image density of 30% to 100% was prepared in the same manner as in Example 1.

The image quality characteristics and the charging characteristics of the formed solid image were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1 below together with the results of Example 1.

(Comparative Example 3) 27 parts (43% by weight) of the tin oxide-based metal powder used in the dispersion liquid (I) of Example 1 was mixed with a metal oxide powder (trade name: Pastoran TYPE-IV: 4350-1).
0, electrical resistance 2.4 × 10 ⁶ Ωcm, Mitsui Kinzoku Co., Ltd.
(VII) was prepared in the same manner as in Example 1, except that 32 parts (50% by weight) were used.

20 parts of the above dispersion (VII) and ferrite (trade name: EFC-50B, volume average particle diameter 50 μm;
100 parts was placed in a vacuum degassing type kneader, and the mixture was stirred for 30 minutes while reducing the pressure at a temperature of about 50 ° C. in the tank, and the coating was performed while gradually removing the solvent.
A coated carrier (VII) for developing an electrostatic latent image according to the present invention was obtained. The thickness of the coating layer of the obtained coating carrier (VII) for electrostatic latent image development was measured in the same manner as in Example 1.
m. Further, the electric resistance was measured in the state of the magnetic brush in the same manner as in Example 1. As a result, the electric resistance when extrapolated to an electric field of 10 ⁴ V / cm was 3 × 10 ⁷ Ωcm.

Further, the present invention was carried out in the same manner as in Example 1 except that the electrostatic latent image developing coated carrier (I) used in Example 1 was replaced with the electrostatic latent image developing coated carrier (VII). And a solid image having an image density of 30% to 100% was prepared in the same manner as in Example 1.

The image quality characteristics and the charging characteristics of the formed solid image were evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1 below together with the results of Example 1.

Comparative Example 4 The hydrophobic silicon oxide B-2 used in the dispersion liquid (I) of Example 1 was replaced with inorganic oxide fine particles ZnO
Example 1 except that 5 parts (24% by weight) of (Al) diameter (trade name: Pastoran TYPE-II, electric resistance 10 Ωcm, volume average particle diameter 200 nm, manufactured by Mitsui Kinzoku Co., Ltd.) were used.
A dispersion liquid (VIII) was prepared in the same manner as described above.

20 parts of the above dispersion (VIII) and magnetite (trade name: MX030A, volume average particle diameter 50 μm)
m; manufactured by Fuji Electric Chemical Co., Ltd.)
And put it in a tank and reduce
The mixture was stirred for minutes, and the coating was performed while the solvent was gradually removed to obtain a coated carrier (VIII) for electrostatic latent image development of the present invention. When the thickness of the coating layer of the obtained coating carrier (VIII) for electrostatic latent image development was measured in the same manner as in Example 1,
It was about 1 μm. As a result of measuring the electrical resistance in the state of the magnetic brush in the same manner as in Example 1, 10 ⁴ V / cm
The electric resistance value when extrapolated to the electric field of 4 × 10 ⁴ Ωc
m.

Further, the present invention was carried out in the same manner as in Example 1 except that the electrostatic latent image developing coated carrier (I) used in Example 1 was replaced with the electrostatic latent image developing coated carrier (VIII). And a solid image having an image density of 30% to 100% was prepared in the same manner as in Example 1.

Further, the image quality characteristics and the charging characteristics of the formed solid image were evaluated by the same method as that shown in Example 1. The evaluation results are shown in Table 1 below together with the results of Example 1.

[0121]

[Table 1]

(Examples 5 to 8, Comparative Examples 5 to 8) Using the externally added cyan toner, externally added magenta toner and externally added yellow toner obtained above, the above Examples 1-4 and Comparative Examples 1-4. In each case, in the same manner as
A color electrostatic latent image developer (cyan, magenta, and yellow) was prepared, loaded into an A Color 635 modified machine (manufactured by Fuji Xerox Co., Ltd.), and a test of forming 50,000 continuous full-color images was performed.

<Evaluation of Image Stability> After processing a certain number of sheets (1000 sheets, 5000 sheets, 10,000 sheets, and 50,000 sheets), the image quality of the formed images and the image stability by multiple processing were evaluated. . The evaluation was carried out by visual sensory evaluation according to the following criteria. The evaluation results are shown in Table 2 below. ：: A stable image with no fog on the background and no image defects. Δ: Some fog on the background was observed, but there was no problem in practical use. ×: Fogging on the background was remarkable, and image defects such as rubbing were observed, and the image could not be used.

[0124]

[Table 2]

As is clear from Table 1, the coating layer on the surface of the core particles contains the coated carrier for developing an electrostatic latent image of the present invention using the specific metal oxide powder and the specific inorganic oxide fine particles. In Examples 1 to 4 in which images were formed using the latent image developers A to D, high-quality images without image defects could be obtained. When the coated carrier for developing an electrostatic latent image of the present invention (I) to (IV) was contained, the change in charging characteristics in a low-temperature low-humidity environment or a high-temperature high-humidity environment was small, and the charging characteristics were stable. On the other hand, when using a coated carrier for developing an electrostatic latent image that does not contain the specific metal oxide powder and the specific inorganic oxide fine particles specified in the present invention in the coating layer,
It was not possible to simultaneously satisfy both the image quality and the charging characteristics of the formed image.

Further, as is apparent from Table 2, the electrostatic latent image containing the coated carrier for developing an electrostatic latent image of the present invention using the specific metal oxide powder and the specific inorganic oxide fine particles in the coating layer. In Examples 5 to 8 in which a full-color image was formed using a developer, fog and image defects did not occur.
A stable image could be formed. On the other hand, a full-color image using an electrostatic latent image developer containing a coating carrier for developing an electrostatic latent image which does not contain the specific metal oxide powder and the specific inorganic oxide fine particles defined in the present invention in the coating layer is used. In Comparative Examples 5 to 8 in which the pattern was formed, as the number of processed sheets increased, fogging and image defects gradually occurred, and a stable image could not be formed.

[0127]

The coated carrier for developing an electrostatic latent image of the present invention and the electrostatic latent image developer containing the same are excellent in charge stability and charge retention which are not affected by changes in the temperature and humidity environment. As a result, a stable high-quality image can always be obtained. Further, according to the image forming method of the present invention, a high-quality image can be stably formed for a long period of time.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an electrostatic latent image recording device used in an image forming method of the present invention.

FIG. 2 is a schematic sectional view of a developing device provided in the electrostatic latent image recording device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Latent image carrier 1a Conductive cylindrical member 1b Photoreceptor layer 2 Charger 3 Exposure means 4 Developing device 6 Pre-transfer corotron 7 Peeling corotron 8 Cleaner 9 Optical neutralizer 10 Recording paper 11 Developer carrier 12 Developing roll 13 Layer regulation Member 14 Developer 15 Development housing 16 Development opening

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kaneishi 1600 Takematsu, Minamiashigara-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. Reference) 2H005 BA07 CA26 CB07 CB13 DA08 EA01 FA02

Claims (3)

[Claims] 1. A coated carrier for developing an electrostatic latent image having a coating layer on a core material, wherein the coating layer has an electric resistance of at least 10 ⁶ [Ωcm].
A coated carrier for developing an electrostatic latent image, comprising a resin layer containing the following metal oxide powder and inorganic oxide fine particles having an electric resistance of 10 ⁸ [Ωcm] or more. 2. A two-component electrostatic latent image developer comprising the electrostatic latent image developing coated carrier according to claim 1 and a toner. 3. A charging step of charging the latent image carrier,
An exposure step of forming a latent image on the latent image carrier, a development step of developing the latent image with a developer containing toner and a carrier, and a transfer step of transferring the developed toner image to a transfer body A fixing step of heating and fixing the toner image on the transfer member, wherein the developer is the electrostatic latent image developer according to claim 2.