JPH096128A - One-component developer carrier and one-component developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a one-component developer carrier and a developing device in which such an image defect as developing ghost and bias leakage does not occur and also which has excellent image density environment stability even at a high temperature and high humidity. SOLUTION: This one-component developer carrier 4 is constituted of a conductive resin layer 4b including carbon black whose surface layer is conductive particulates and graphite whose ash content is <=3.0wt.%. This one- component developing device 3 is provided with the carrier 4 arranged to face oppositely an electrostatic latent image carrier 1, and a developer controlling member 8 forming the thin layer of one-component developer 6 electrified to be of negative polarity on the carrier 4. As the layer 4b, the desirable range of the arithmetic average roughness of surface is 0.8 to 2.5μm, the desirable range of the average higher part interval in ruggedness is 95 to 150μm, and the desirable range of volume resistivity is 2.0×10<-2> to 0.99Ωcm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic copying machine,
The present invention relates to a developing device in an image forming apparatus adopting an electrophotographic method such as a printer and a facsimile. More specifically, the surface layer is made of a conductive resin layer, and the one-component developer carrying member that conveys the developer adhering to the surface to the developing area, and the charged developer is formed on the electrostatic latent image holding member. The present invention relates to a one-component developing device that develops an electrostatic latent image.

[0002]

2. Description of the Related Art In an image forming apparatus employing an electrophotographic system, a method of developing an electrostatic latent image formed on an electrostatic latent image holding member (photoreceptor) depends on the type of developer used and the like. Various methods are conventionally known. Among them, there is a method of developing the developer carried on the developer carrying body by bringing the developer into contact with the photoconductor or non-contactingly flying to the photoconductor, and the surface of the developer carrying body carrying the developer. Various conductive resin layers have been proposed as the layers. For example,
Japanese Patent Laid-Open No. 63-311367 discloses that the volume resistivity (1 × 10 ⁶ to 1 × 10 ¹³ Ωcm) and the thickness are predetermined in order to improve the gradation and the reproducibility of fine lines and halftone dots. A developer carrier having a related outer layer on the surface is disclosed. Further, in Japanese Patent Application Laid-Open No. 4-166864, a thin layer containing positively chargeable resin particles on the surface thereof in order to prevent a decrease in initial image density due to a broad charge amount distribution of a developer at the time of rising of a developing device. And a developer carrier using a negatively charged (one-component) magnetic toner as a developer. Then, JP-A-4-24667.
No. 6, in the case where the same image pattern is repeatedly printed, in order to prevent a phenomenon in which the density of a part of the paper becomes thin along the feeding direction of the paper, a coating layer formed on the surface by polishing treatment A developer carrier is disclosed in which the average spacing Sm of the irregularities and the centerline average roughness Ra are limited.

However, it is difficult to say that any of the conventional developer carriers can sufficiently withstand practically, and there are the following problems. That is, in the developer carrier described in JP-A-63-311367, the resistance of the outer layer is high. Therefore, during development, electric charge remains in the outer layer portion where the developer has transferred to the photoreceptor, and the amount of electric charge in this portion is larger than in other portions, and the newly carried developer is strongly adsorbed to the outer layer. It becomes difficult to transfer to the photoconductor. As a result, the density of the portion of the newly developed toner image corresponding to the previously developed toner image becomes low, so-called development ghost occurs, and the image quality deteriorates. In the developer carrier described in JP-A-4-166864, the dispersion of the positively chargeable resin particles is locally non-uniform and the resistance of the thin layer is non-uniform. Therefore, charges easily flow in the thin layer portion having a low resistance, and a bias leak may occur between this portion and the photoconductor to destroy the surface of the photoconductor. If defects such as pinholes are present on the surface of the photoconductor, the particles of the formed image become coarse and the image quality is degraded. Further, when a negative polarity magnetic toner to which silica or the like having a strong negative polarity is externally added is used as a developer, a development ghost, which is a history of print patterns, is likely to occur on the developer carrier. JP-A-4-24667
In the developer bearing member described in Japanese Patent Laid-Open No. 6, since the average spacing Sm between the surface coating layers is small, the developer particles are fitted in the concave portions of the coating layer and are unlikely to migrate to the photoreceptor. In that case, the developer particles on the embedded developer particles are not sufficiently charged, and the image density is lowered.

[0004]

As described above, in the conventional developer carrier having the surface coated with the conductive resin layer, due to the excess or deficiency of the charge amount of the developer imparted by the triboelectrification,
Alternatively, when using a negative polarity developer added with an external additive that is strongly charged to the negative polarity, or due to discharge generated between the surface of the resin layer and the photoreceptor due to the nonuniform resistance of the resin layer,
There is a problem that development ghost and bias leak occur. Therefore, the present invention is intended to solve the above-mentioned problems and does not cause development ghosts and bias leaks, and at the same time, even when the above-mentioned negative polarity one-component developer is used, development ghosts, etc. Another object of the present invention is to provide a one-component developer carrying member and the developing device capable of forming a good image without the image quality defect. further,
In the present invention, one component having excellent environmental stability of image density even under high temperature and high humidity and low temperature and low humidity, and having excellent durability that does not cause filming such as sticking of developer even after repeated use. An object is to provide a developer carrier and the developing device.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive research to improve image quality in an image forming apparatus equipped with a developer carrying member having a conductive resin layer as a surface layer as a one-component developing device. During the process, I experienced that an image with image quality defect was output. Regarding the cause of this image quality defect, the inventors of the present invention have made diligent efforts to find out that the conductive fine particles in the resin layer are closely related to each other, and finally determine the ash content of graphite. It has been clarified that the cause is, and it has been found that the above object can be achieved by reducing the ash content as much as possible, and the present invention has been accomplished. That is, the one-component developer carrier of the present invention has a surface layer made of a conductive resin layer containing carbon black and graphite which are conductive fine particles, and the graphite has an ash content of 3.0% by weight or less. It is characterized by Further, the one-component developing device of the present invention comprises a developer carrying member arranged so as to face the electrostatic latent image holding member, and a thin layer of the one-component developer charged negatively on the developer carrying member. A developer regulating member to be formed, wherein the surface layer of the developer carrier comprises a conductive resin layer containing carbon black and graphite which are conductive fine particles, and the graphite has an ash content of 3.0% by weight. It is characterized by the following.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
It should be noted that, in order to facilitate understanding of the present invention, the elements of the present invention are denoted by the reference numerals in parentheses corresponding to the elements of the embodiments described below, but the present invention is not limited to the embodiments. .
The conductive resin layer (4b) on the surface of the one-component developer carrying member (4) of the present invention will be described. To form the resin layer (4b) as the surface layer of the developer carrying member (4), a binder resin, carbon black, graphite, a diluent (solvent) and the like are mixed to prepare a coating solution. On this occasion,
It is important to adjust the mixing ratio of the diluent to control the viscosity and film-forming property of the coating solution. Then, the cylindrical substrate (4a)
While rotating, the surface is coated by an air spray method or the like in which a coating liquid is sprayed, and the binder resin is cured at 130 to 250 ° C. As the base material (4a), a conductive member such as aluminum or stainless steel is used. The resin layer (4b) thus formed contains
The conductive carbon black and graphite fine particles are in a dispersed state, and the surface of the resin layer (4b) has fine irregularities in which a part of the conductive fine particles is mainly exposed. Due to the surface structure of the resin layer (4b), a one-component developer carried on the resin layer (4b)
(6) can be stably adsorbed, conveyed, and charged.

Examples of the binder resin include phenol resin, melamine resin, urea resin, alkyd resin, epoxy resin, polyamide, polyimide, polyester, polyurethane, polycarbonate, polyphenylene oxide, polyether sulfone, styrene resin, fluorine resin, and acrylic resin. Resins, silicone resins, etc. are used. In particular, a resin having excellent mechanical strength such as phenol resin, polyamide, polyester, polyurethane or styrene resin, or a resin having excellent releasing property such as fluorine resin or silicone resin is more preferable.
As the diluent, hydrocarbons such as hexane, benzene, toluene and xylene, ketones such as acetone, methyl ethyl ketone and cyclohexanone, methanol,
Examples thereof include alcohols such as ethanol and butanol, ethers such as dibutyl ether, tetrahydrofuran and propylene glycol monomethyl ether, and esters such as ethyl acetate, butyl acetate and ethyl butyrate. These binder resins and diluents may be used alone or in combination of two or more.

The conductive carbon black is dispersed in the resin layer in order to prevent the toner (one-component developer) from being excessively charged, and has a function of discharging an excessive charge. In addition to the function of carbon black, the conductive graphite has a function of preventing toner from adhering to the surface of the resin layer due to surface lubricity. Further, graphite is added so that the resin layer has an appropriate surface roughness and the toner is provided with a sufficient triboelectric charge amount. Graphite usually contains impurities such as various metals including silicon, and it is presumed that some kind of metal exerts an electromagnetic action on the developer carrier, although it has not been confirmed. The content of impurities in the graphite remaining after firing, that is, the ash content is 3.0% by weight or less is used. The preferred ash content is 0.5% by weight or less, and particularly 0.2% by weight or less. When the ash content of graphite is 0.5% by weight or less, there is an effect of preventing a decrease in image density under a low temperature and low humidity environment. Further, when the ash content is 0.2% by weight or less, there is an effect of preventing a decrease in image density even under high temperature and high humidity. In the present invention, the ash content of graphite is set to 3.0% by weight or less, whereby the electromagnetic influence on the developer carrying member can be eliminated as much as possible. Therefore, the charge amount of the toner can be always stabilized.

3 to 30 carbon black is contained in the resin layer.
It is preferable to contain 10% to 70% by weight of graphite and 10% to 70% by weight of graphite, and it is more preferable to contain 5% to 25% by weight of carbon black and 20% to 60% by weight of graphite. The blending ratio of carbon black and graphite is preferably in the range of 1: 0.5 to 15 by weight, and particularly preferably in the range of 1: 1 to 5. Further, the sum of the blending amounts of carbon black and graphite is preferably contained in the resin layer in the range of 15 to 80% by weight, and more preferably in the range of 20 to 70% by weight. By satisfying the compounding conditions of such carbon black and graphite, a better development process can be carried out.

When the blending ratio in the resin layer is less than 3% by weight of carbon black or less than 10% by weight of graphite, it becomes impossible to escape the excessively charged electric charge of the toner, and the development ghost is likely to occur in the formed image. . On the other hand, when the blending ratio is higher than 30% by weight of carbon black or 70% by weight of graphite, the charge amount of the toner is insufficient and the image density is apt to decrease. Further, if the blending ratio of graphite is lower than 10% by weight, the surface of the resin layer tends to be too smooth and sufficient lubricity cannot be ensured in connection with the average particle size described later. Therefore, the amount of toner conveyed is insufficient and the image density is reduced, and at the same time, toner filming is likely to occur. On the other hand, if the blending ratio of graphite is higher than 70% by weight, the surface roughness of the resin layer becomes too large and the amount of toner conveyed increases, so that sufficient triboelectrification tends not to be obtained. When the compounding ratio of graphite to carbon black is less than 0.5, the charge outflow of toner tends to be large and the charge amount tends to decrease. On the other hand, the mixing ratio is 15
If it exceeds twice, as in the case where the blending ratio of graphite is higher than 70% by weight, the toner tends to be excessively conveyed and the charge amount tends to decrease. Further, if the content of the conductive fine particles in the resin layer is less than 15% by weight, not only sufficient conductivity is not obtained, but also the surface of the resin layer is too smooth and the toner transport amount becomes insufficient. On the other hand, if the blending amount exceeds 80% by weight, it becomes difficult to uniformly mix the conductive fine particles with the binder resin, and it becomes difficult to form a predetermined resin layer.

Carbon black and graphite fine particles having an average particle diameter of 0.01 to 0.2 μm and 1 to 10 μm are preferably used. When the average particle diameter of carbon black is less than 0.01 μm, it requires a high cost to finely pulverize the carbon black, and the conductivity is not improved so much even if the particle diameter of the fine particles is reduced. on the other hand,
When the average particle size is larger than 0.2 μm, the conductivity of the fine particles becomes low, so that the toner is likely to be excessively charged during frictional charging. The average particle size of graphite is 1 μm.
If it becomes smaller, the amount of toner conveyed becomes insufficient and the image density tends to decrease. On the other hand, when the average particle size is larger than 10 μm, the toner conveyance amount becomes too large and the chance of contact between the toner and the surface of the developer carrying member decreases, so that the toner cannot be provided with a sufficient triboelectric charge amount. After all, the image density tends to decrease. The thickness of the conductive resin layer is preferably in the range of 10 to 40 μm, and particularly preferably in the range of 15 to 30 μm. Film thickness is 10μ
When the thickness is smaller than m, the conductive fine particles are exposed to the surface of the resin layer to a large extent, and the surface of the developer carrying member becomes unnecessarily rough. On the other hand, if it is thicker than 40 μm, the coating liquid drips from the cylindrical substrate during curing, and it becomes difficult to form a uniform film thickness.

In the present invention, since the surface of the conductive resin layer has fine irregularities, the amount of toner conveyed and the amount of charge on the developer carrying member are closely related to the surface roughness of the resin layer. Therefore, the surface roughness of the resin layer is an important factor for ensuring an appropriate transport amount and charge amount. Regarding the surface roughness of the resin layer, the arithmetic average roughness Ra is 0.8 to 2.
It is preferable that the range is 5 μm, more preferably 1.0 to 2.2 μm, and the average peak-to-peak spacing Sm of the unevenness is 95 to 150 μm, and further 100 to 140 μm. Here, the arithmetic average roughness Ra and the average peak-to-peak interval Sm mean the surface roughness defined by Japanese Industrial Standards [JISB 0601]. Arithmetic mean roughness Ra is 0.8
When it is less than μm, the surface of the resin layer is too smooth, the amount of toner conveyed is small, and the image density tends to decrease. On the other hand, when the arithmetic mean roughness Ra exceeds 2.5 μm, the toner conveyance amount becomes too large, the toner charge amount becomes low, and as a result, the image density tends to decrease. Further, if the average mountain interval Sm is out of the above range, a development ghost is generated in the formed image, and the image quality tends to be deteriorated. Particularly, when the arithmetic average roughness Ra is in the range of 1.0 to 2.2 μm, a better image is formed. When the average mountain interval Sm is in the range of 100 to 140 μm,
No image development ghost is generated in the formed image, and the image quality is further improved.

The volume resistivity of the conductive resin layer is 2.0.
It is preferably in the range of × 10 ^{-2 to} 0.99 Ωcm,
Particularly, the range of 3.0 × 10 ^{-2 to} 0.80 Ωcm is more preferable. When the volume resistivity of the resin layer is lower than 2.0 × 10 ^-2 Ωcm, the charge amount of the toner becomes too low and the image density tends to decrease. On the other hand, when the volume resistivity is higher than 0.99 Ωcm, the charge of the toner is increased to a level where the development ghost is likely to occur, and the development ghost tends to occur.

Further, the one-component developing device (3) of the present invention comprises the above-mentioned developer carrying member (4) and the developer regulating member (8, 8 ') for thinning the toner adhered thereon. A one-component developer having at least the following and being negatively charged as a toner (6)
Is used. When the toner is a magnetic one-component developer, at least a binder resin and a magnetic material are essential components, and when the toner is a non-magnetic one-component developer, at least a binder resin and a colorant are essential components. . A charge control agent, a fluidity promoting agent,
A cleaning aid or the like can be added internally or externally.

As the binder resin, styrenes such as styrene, vinyltoluene and chlorostyrene, vinylnaphthalene, monoolefins such as ethylene, propylene, n-butylene and i-butylene, dienes such as butadiene and isoprene, and fluorine. Vinyl halides such as vinyl chloride, vinyl chloride, vinyl bromide, vinylidene chloride, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl stearate,
Vinyl esters such as vinyl benzoate, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, β-chloroethyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, methacryl Butyl acid, dodecyl methacrylate, acrylic acid amide, acrylonitrile, methacrylonitrile and other derivatives of α-methylene aliphatic monocarboxylic acid, unsaturated poly (methyl maleate), dimethyl maleate, diethyl maleate, dibutyl maleate, etc. Homopolyesters such as divalent carboxylic acid esters, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl propenyl ketone Polymers or copolymers thereof. Furthermore, polyurethane, polyester, polyamide, phenol resin, epoxy resin, furan resin, silicone resin, paraffin wax, modified rosin and the like can be used.

As the magnetic substance, for example, metals such as iron, cobalt, nickel, etc., these metals or various metals (for example, Mg, Al, Ti, V, Mn, Cu, Zn, Sn,
W, Pb, etc.), ferrite, manganese-zinc-containing ferrite, nickel-zinc-containing ferrite, magnetite, hematite, cobalt-added iron oxide, and the like. The average particle size of these magnetic fine particles is 0.
The range of 05 to 1 μm is preferable. The content of the magnetic substance in the magnetic one-component developer is preferably in the range of 20 to 70% by weight, and more preferably 30 to 60% by weight. When the content of the magnetic material is less than 20% by weight, it is difficult to control the charge amount and the resolution, fine line reproducibility and gradation are deteriorated. On the other hand, if it exceeds 70% by weight, the transfer efficiency in a high temperature and high humidity environment is lowered, and it becomes difficult to uniformly disperse the magnetic fine particles in the binder resin. Examples of colorants include carbon black, lamp black, nigrosine dye, aniline blue, calcoil blue, ultramarine blue, methylene blue chloride, phthalocyanine blue, chrome yellow, quinoline yellow, DuPont oil red, rose bengal, malachite green oxalate, etc. Can be illustrated.

In order to impart triboelectric chargeability to the developer, it is preferable to add a positive or negative charge control agent. The negative charge control agent added when the developer is negatively charged is not particularly limited as long as it is a known electron accepting substance, and examples thereof include salicylic acid derivatives such as salicylic acid and alkylsalicylic acid, and chromium. Complexes with transition metals such as azo metal-containing dyes, phenols, carboxylic acids,
Organic acids such as sulfonic acids and chlorinated paraffins are suitable. It is also possible to use the binder resin or other polymer having a carboxy group or a sulfonic acid group introduced into its side chain, or the binder resin itself having an electron-accepting substituent or the triboelectric polarity of an external additive. it can. Further, in order to improve the offset resistance, a releasing agent such as low molecular weight polyethylene, low molecular weight polypropylene, microcrystalline wax, paraffin wax, etc. may be added. Further, for the purpose of improving the durability, fluidity and cleaning property of the developer, inorganic fine powder such as silica, organic fine powder such as fatty acid, metal salt or derivative thereof, styrene resin, fluorine resin, acrylic resin Resin fine powder such as the above can be externally added. In addition, a caking inhibitor may be added externally. The average particle size of such a one-component developer is 5 to 20 μm.
m is preferably in the range.

(Operation of the present invention) According to the one-component developer carrier (4) of the present invention, the conductive resin layer as the surface layer thereof is used.
(4b) contains conductive fine particles of carbon black and graphite. On the surface of the resin layer (4b), a part of the conductive fine particles are exposed to form fine irregularities. Therefore, the amount of the developer (6) conveyed on the carrier (4) and the developer
The charge amount applied to (6) can be adjusted to an appropriate value. Here, the volume resistivity of the resin layer (4b) is 2.0.
When it is set in the range of × 10 ^{-2 to} 0.99 Ωcm, the arithmetic mean roughness Ra of the surface of the resin layer (4b) is in the range of 0.8 to 2.5 μm, and the average peak-to-peak interval Sm is 95 to 150 μm. When the amount is adjusted within the range, the carry amount and the charge amount can be made more appropriate. In the present invention, the ash content of the above graphite is set to 3.0% by weight or less,
The content of impurities (eg, metal) in graphite is reduced as compared with the conventional one. As a result, the developer carrier (4) itself, and by extension, the carrier (4) and the electrostatic latent image carrier.
In the developing area (A) between (1) and (1), impurities hardly affect electromagnetically. Moreover, since the environmental dependence of the carrier (4) due to impurities is also reduced, it is presumed that the charge amount of the one-component developer (6) is always stable. Therefore, not only the proper amount of charge can be uniformly applied to the developer (6), but also development ghost and bias leak can be effectively prevented. Further, since the image density is excellent in environmental stability, the image density can be kept high even under low temperature and low humidity or high temperature and high humidity. In particular, when the ash content of graphite is 0.5% by weight or less, and further 0.2% by weight or less, the above environmental stability is further improved.

Further, according to the one-component developing device (3) of the present invention, on the resin layer (4b) on the surface of the developer carrying member (4) arranged facing the electrostatic latent image holding member (1). Component developer attached to
(6) is thinned by the developer regulating member (8, 8 '). At this time, the developer (6) is negatively charged by friction. Resin layer (4
b) contains carbon black and ash content of 3.0
Because it contains less than wt% graphite,
The carry amount and the charge amount in (6) can be adjusted to appropriate values. Further, for the same reason as described above, not only the image density can be kept high in the environment of low temperature and low humidity and high temperature and high humidity, but also development ghost and bias leak can be effectively prevented.

[0020]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to the following Examples. FIG. 1 and FIG. 2 are explanatory views of a developing device containing a magnetic one-component developer that is negatively charged as a toner. FIG.
In FIG. 1, the electrostatic latent image carrier 1 is a photoconductive drum having an organic photosensitive layer, and after being uniformly charged by a charging unit (not shown), a potential difference caused by irradiating the image light An electrostatic latent image 2 is formed. The surface potential when the electrostatic latent image 2 is formed is, for example, −600 V in the image portion,
The background portion, which serves as a white display portion during image formation, has −120V. The one-component developing device 3 has a developer carrying member 4 arranged to face the electrostatic latent image holding member 1. The hopper 5 of the developing device 3 stores the developer 6 carried on the carrier 4. The hopper 5 accommodates the carrier 4, and the surface of the carrier 4 is opened at a portion facing the holder 1. The carrier 4 and the holder 1 are arranged so as to be partially exposed and close to each other.

The rotation of the developer carrying member 4 conveys the one-component developer 6 attached to the surface thereof. The minimum gap between the carrier 1 and the carrier 4 in the developing area A where the carrier 4 is close to the electrostatic latent image carrier 1 is set to be about 200 μm. Inside the carrier 4, a plurality of magnets are arranged along the peripheral surface, and a magnet roll 7 fixed so as not to rotate is provided. Multiple magnets are S pole and N
A magnetic pattern in which the poles are arranged along the peripheral surface is formed, and the developer 6 can be adsorbed to the surface of the carrier 4 according to the magnetic pattern. The developer carrying member 4 includes a cylindrical aluminum base material 4a having a thickness of 0.7 mm and a conductive resin layer 4b formed on the peripheral surface thereof.
And the magnet roll 7 fixed inside the base material 4a. Conductive carbon black fine particles and conductive graphite fine particles are dispersed in the resin layer 4b. The resin layer 4b is composed of a coating film formed by coating the base material 4a with the coating liquid described below in which carbon black fine particles and graphite fine particles are dispersed in a binder resin and a diluent.

The developer regulating member 8 comprises an elastic member 8a that presses against the surface of the developer carrying member 4 and a leaf spring 8b to which the elastic member 8a is adhered. The other end of the leaf spring 8b is the developing device 3
It is fixedly supported by the body. The pressing portion of the elastic member 8a against the carrier 4 is located on the upstream side in the rotation direction of the carrier 4 with respect to the developing area A. Further, the free end of the leaf spring 8b is attached so as to incline toward the downstream side in the rotation direction of the carrier 4. Elastic member 8a has a width of 15 mm and a thickness of 1.00 m
m, a rubber hardness of 50 °, made of silicone rubber, and the leaf spring 8b has a thickness of 0.1 mm and is made of stainless steel (SUS304C).
SP3 / 4, tensile strength 95 kgf / mm ² ).
In FIG. 2, the developer regulating member 8 ′ is fixed to the upper end of the opening of the hopper 5 and is located right above the carrier 4. The developer regulating member 8'comprising a ferromagnetic blade is provided in non-contact with the developer carrying member 4 so that the gap between the carrying member 4 and the regulating member 8'is smaller than the minimum gap between the carrying member 4 and the holding member 1. Is set to. In this gap, magnetic one-component developer 6
Magnetic brush is formed. Base material 4a of developer carrier 4
And a conductive base material (not shown) of the electrostatic latent image holder 1 connected in series between the high-voltage AC power supply 9 and the DC power supply 10.
A DC superimposed AC voltage, which is a bias voltage, is applied to generate an alternating electric field in the developing area A.

The operation of the one-component developing device of this embodiment is as follows. Magnetic one-component developer 6 in hopper 5
Adheres to the surface of the rotating developer carrier 4 and is rubbed by the elastic member 8a of the developer regulating member 8 and the conductive resin layer 4b having fine irregularities on the surface in the developing device 3 shown in FIG. It In this case, some of the carbon black fine particles and graphite fine particles dispersed in the resin layer 4b are exposed on the surface of the resin layer 4b, and the carrier 4 is adjusted to have an appropriate surface roughness. Thereby, when developing the electrostatic latent image 2 formed on the electrostatic latent image holder 1, a sufficient layer thickness of the developer 6 can be formed on the carrier 4. At the same time
Graphite having an ash content of 3.0% by weight, which is shown in each of the following examples, is dispersed or partially exposed in the resin layer 4b, so that a uniform and sufficient negative triboelectric charge is imparted to the developer 6. be able to. The thinned developer 6 is conveyed to the development area A as the carrier 4 rotates, and is negatively charged in the alternating electric field generated in the gap between the carrier 4 and the holder 1. 6 particles of the agent fly and reciprocate. Also,
Due to this reciprocating motion, the particles of the developer 6 collide with each other and the entire developer 6 becomes cloud-shaped. The cloud of the developer 6 is attracted to the electrostatic latent image 2 portion of the holder 1 by the DC component of the bias voltage, and the development is completed.

In the developing device 3 shown in FIG. 2, the magnetic brush of the developer 6 formed in the gap between the carrier 4 and the developer regulating member 8'is regulated in the layer thickness by the rotation of the carrier 4, and the developing process is performed. The agent 6 is thinned. The developer 6 adjusted to a predetermined amount from the gap is conveyed to the developing area A by the rotation of the carrier 4, and the electrostatic latent image formed on the electrostatic latent image holder 1 is formed in the same manner as the developing device 3 shown in FIG. The latent image 2 is developed. A print test was carried out by operating each one-component developing device 3 shown in FIGS. 1 and 2, and the former developing device provided good results. In the triboelectric charging method of the developing device 3 shown in FIG. 1, the developer 6 is pressed by the developer regulating member 8 against the surface of the resin layer 4b having a fine uneven shape.
Is because it becomes possible to make more efficient frictional contact with the resin layer 4b. Therefore, in the example below, FIG.
Specific examples of the method of forming the conductive resin layer 4b in the developing device 3 and the print test by the developing device 3 will be described.

Example 1 A method for forming the conductive resin layer (4b) is shown below. Binder resin Phenolic resin (molecular weight 1000 to 3000) 100 parts by weight Conductive fine particles Carbon black (XC-72R: made by Cabot Co.) 20 parts by weight Graphite (made by Nippon Graphite Co., Ltd.) 50 parts by weight Ash content 3.0 wt%; acid Alkali treatment Diluent Propylene glycol monomethyl ether-ethanol (2: 1 mixture) 100 parts by weight The conductive fine particles in the above composition are dispersed by a bead mill, and the obtained coating liquid is applied onto an aluminum substrate (4a). After spraying and applying, it was heated and cured at 160 ° C. for 30 minutes in a hot air drying oven to form a conductive resin layer (4b). This resin layer (4b) has a surface arithmetic average roughness Ra value of 1.50 μm.
m, average peak-to-peak interval Sm value 100 μm, film thickness 20
μm. The volume resistivity of the resin layer (4b) was 8.0 × 10 ^-2 Ωcm. One-component developing device in which the magnet roll (7) is fixed inside the base material (4a), and the developer carrying member (4) thus produced is shown in FIG.
The developing device (3) of the present embodiment was mounted on (3).

Thereafter, in the same manner as in Example 1, Examples 2 to 1
A one-component developing device (3) of Comparative Example 1 and Comparative Examples 1 and 2 was produced. In each of the examples and comparative examples, the ash content of graphite, the method for forming the conductive resin layer (4b) and the above-mentioned physical property values are shown. Example 2 A conductive resin layer was formed in the same manner as in Example 1 except that graphite was changed to one having an ash content of 2.0% by weight (wt). The arithmetic average roughness Ra value of this resin layer surface is 1.
40 μm, the average peak-to-peak interval Sm value is 110 μm, the film thickness is 22 μm, and the volume resistivity of the resin layer is 8.0 ×.
It was 10 ^-2 Ωcm.

Example 3 A conductive resin layer was formed in the same manner as in Example 1 except that graphite was changed to one having an ash content of 1.0 wt%. The arithmetic average roughness Ra value of this resin layer surface is 1.35 μ.
m, average peak-to-peak interval Sm value is 120 μm, film thickness is 24
and the volume resistivity of the resin layer was 0.12 Ωcm. Example 4 A conductive resin layer was formed in the same manner as in Example 1 except that graphite was changed to one having an ash content of 1.0 wt%. However, in Example 1, the number of revolutions of the spray device, the discharge amount, and the distance between the gun and the substrate were changed. The arithmetic average roughness Ra value of the formed resin layer surface was 1.20 μm, the average peak-to-peak interval Sm value was 115 μm, the film thickness was 24 μm, and the volume resistivity of the resin layer was 0.11 Ωcm. Example 5 A conductive resin layer was formed in the same manner as in Example 1 except that graphite was changed to one having an ash content of 1.0 wt%. However, in Examples 1 and 4, the number of revolutions of the spray device, the discharge amount, and the distance between the gun and the substrate were changed. The arithmetic mean roughness Ra value of the formed resin layer surface is 0.80 μm,
The average peak-to-peak interval Sm value is 105 μm, and the film thickness is 23 μm
And the volume resistivity of the resin layer is 9.0 × 10 ^-2 Ωcm.
Met.

Example 6 A conductive resin layer was formed in the same manner as in Example 1 except that graphite was changed to one having an ash content of 0.5 wt%. The arithmetic average roughness Ra value of this resin layer surface is 1.30 μ.
m, average peak-to-peak interval Sm value is 105 μm, film thickness is 21
and the volume resistivity of the resin layer was 0.10 Ωcm. Example 7 A conductive resin layer was formed in the same manner as in Example 1 except that graphite was changed to one having an ash content of 0.5 wt%. However, in Example 1, the number of revolutions of the spray device, the discharge amount, and the distance between the gun and the substrate were changed. The arithmetic average roughness Ra value of the formed resin layer surface is 1.70 μm, the average peak-to-peak interval Sm value is 135 μm, the film thickness is 22 μm, and the volume resistivity of the resin layer is 9.0 × 10 ^−2. It was Ωcm. Example 8 A conductive resin layer was formed in the same manner as in Example 1 except that graphite was changed to one having an ash content of 0.5 wt%. However, in Examples 1 and 7, the number of revolutions of the spray device, the discharge amount, and the distance between the gun and the substrate were changed. The arithmetic mean roughness Ra value of the formed resin layer surface is 0.80 μm,
Average peak-to-peak spacing Sm value is 103 μm, film thickness is 20 μm
The volume resistivity of the resin layer was 0.11 Ωcm.

Example 9 A conductive resin layer was formed in the same manner as in Example 1 except that graphite was changed to one having an ash content of 0.2 wt%. The arithmetic average roughness Ra value of this resin layer surface is 1.60 μm.
m, average peak-to-peak interval Sm value of 125 μm, film thickness 21
and the volume resistivity of the resin layer was 0.14 Ωcm. Example 10 A conductive resin layer was formed in the same manner as in Example 1 except that graphite was changed to one having an ash content of 0.2 wt%. However, in Example 1, the number of revolutions of the spray device, the discharge amount, and the distance between the gun and the substrate were changed. The arithmetic average roughness Ra value on the surface of the formed resin layer was 1.15 μm, the average peak-to-peak interval Sm value was 123 μm, the film thickness was 19 μm, and the volume resistivity of the resin layer was 0.10 Ωcm. Example 11 A conductive resin layer was formed in the same manner as in Example 1 except that graphite was changed to one having an ash content of 0.2 wt%. However, in Examples 1 and 10, the number of rotations of the spray device, the discharge amount, and the distance between the gun and the substrate were changed. The arithmetic mean roughness Ra value of the formed resin layer surface is 0.78 μm,
The average peak-to-peak interval Sm value is 100 μm, and the film thickness is 20 μm
The volume resistivity of the resin layer was 0.15 Ωcm.

Comparative Example 1 A conductive resin layer was formed in the same manner as in Example 1 except that graphite was changed to one having an ash content of 4.0 wt%. The arithmetic average roughness Ra value of this resin layer surface is 1.40 μm.
m, average peak-to-peak interval Sm value is 125 μm, film thickness is 18
μm, and the volume resistivity of the resin layer is 1.9 × 10 ^-2
Ωcm. Comparative Example 2 A conductive resin layer was formed in the same manner as in Example 1 except that graphite was changed to one having an ash content of 4.0 wt%. However, in Example 1, the number of revolutions of the spray device, the discharge amount, and the distance between the gun and the substrate were changed. The arithmetic average roughness Ra value of the formed resin layer surface is 0.80 μm, the average crest interval Sm value of the irregularities is 100 μm, the film thickness is 21 μm, and the volume resistivity of the resin layer is 1.8 × 10 ^−2. It was Ωcm.

(Print Test) The one-component developing device (3) produced in Examples 1 to 11 and Comparative Examples 1 and 2 was incorporated into a laser printer (FX4109: manufactured by Fuji Xerox Co., Ltd.), and the following was placed in the developing device (3). Filled with one-component developer (6), normal temperature and normal humidity (23 ° C, RH 60%), low temperature and low humidity (1
0 ℃, RH30%) and high temperature and high humidity (28 ℃, RH85
%), And the print test was performed. The average particle size of the used developer (6) is 7 to 9 μm and has the following composition. Binder resin 100 parts by weight Styrene-n-butyl acrylate copolymer (80:20) Magnetic powder: magnetite 100 parts by weight Charge control agent: TRH 1 part by weight Wax: low molecular weight polypropylene 3 parts by weight External additive: hydrophobic 1 part by weight of silica

In the print sample, the image density is measured by a densitometer (Model 404A: manufactured by X-Rite).
The development ghost and the bias leak were evaluated by the following visual criteria. Table 1 shows the results. Evaluation Criteria for Image Density and Development Ghost and Bias Leak ◎ Density 1.50 or higher No image quality defect is observed ○ Density 1.40 or higher but less than 1.50 Almost no image quality defect is observed △ Density 1.30 or higher 1.40 Less than some image quality defects are seen, but there is no problem in practical use x Density less than 1.30 Clear image quality defects are seen

[0033]

[Table 1]

As is clear from Table 1, in Example 1 in which the ash content of graphite was 3.0 wt%, practically no problem was obtained. The above ash content is 2.0 wt%
In Example 2 of No. 3, good results were obtained for both the development ghost and the bias leak. In Examples 3 to 5 in which the ash content was 1.0 wt%, good results were obtained in each environment in terms of image density, development ghost, and bias leak.
In Examples 6 to 8 having the same ash content of 0.5 wt%, the decrease in image density was prevented not only under normal temperature and normal humidity but also under low temperature and low humidity. Furthermore, the ash content is 0.2 wt.
%, In Examples 9 to 11, very excellent results were obtained with respect to the image density under high temperature and high humidity which is a stress condition. On the other hand, the ash content of graphite is 4.0 wt%
In Comparative Examples 1 and 2, the image density under high temperature and high humidity was remarkably low. Thus, the lower the ash content of graphite in the conductive resin layer, the higher the image density, and the image density is significantly improved even under high temperature and high humidity.
Further, development ghost and bias leak hardly occur. Furthermore, when a 10,000-sheet durability test was conducted, filming due to the adherence of the developer did not occur in each of the examples.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, but various modifications can be made within the scope of the claims.
For example, conductive fine powders other than carbon black and graphite may be dispersed in the resin layer so that the total amount of the fine particles mixed is within the range of the above upper limit. Further, depending on the type and polarity of the developer, for example, for the positive magnetic one-component developer and the non-magnetic one-component developer, the developer carrier of the present invention is applied by adopting various developing methods. It is possible. As an example, when the developer is a non-magnetic one-component developer, a thin developer layer is added to the electrostatic latent image carrier instead of the developer regulating member shown in FIGS. A doctor blade system in which pressure is applied for development can be adopted. Further, a developing system (NSP) may be adopted in which the developer regulating member is changed to a magnetic blade having elasticity and the developer supply roll is rotated in contact with the developer carrying member.

[0036]

According to the one-component developer carrier and the one-component developing device of the present invention, the ash content of graphite contained together with carbon black in the conductive resin layer on the surface of the developer carrier is 3.0% by weight or less. By doing so, an appropriate amount of charge can be uniformly applied to the one-component developer. As a result, it has excellent image density environmental stability that it is possible to effectively prevent development ghosts and bias leaks, and to maintain high image density under high temperature and high humidity. Therefore, according to the one-component developer carrier and the one-component developing device of the present invention, it is possible to form a good image that is excellent in environmental stability of image density and does not cause image defects such as development ghost and bias leak. .

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a one-component developing device shown as an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a one-component developing device shown as another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electrostatic latent image holder, 3 ... One-component developing device, 4 ... Developer carrying body, 4b ... Conductive resin layer, 6 ... One-component developer, 8,
8 '... Developer regulating member.

Claims (6)

[Claims] 1. A one-component development wherein the surface layer is composed of a conductive resin layer containing carbon black which is conductive fine particles and graphite, and the ash content of the graphite is 3.0% by weight or less. Agent carrier. 2. The ash content of the graphite is 0.5.
The one-component developer carrying member according to claim 1, which is not more than wt%. 3. The ash content of the graphite is 0.2
3. The one-component developer carrying member according to claim 2, which is not more than wt%. 4. The component according to claim 1, wherein the arithmetic average roughness of the surface of the conductive resin layer is in the range of 0.8 to 2.5 μm, and the average pitch of the irregularities is in the range of 95 to 150 μm. Developer carrier. 5. The one-component developer carrier according to claim 1, wherein the volume resistivity of the conductive resin layer is in the range of 2.0 × 10 ^{−2 to} 0.99 Ωcm. 6. A developer carrying member arranged to face the electrostatic latent image carrying member, and a developer regulating member for forming a thin layer of a negatively charged one-component developer on the developer carrying member. With and
One component characterized in that the surface layer of the developer carrier comprises a conductive resin layer containing carbon black and graphite which are conductive fine particles, and the ash content of the graphite is 3.0% by weight or less. Development device.