JP2009210795A - Electrophotographic carrier, electrophotographic developer, developing device, image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic carrier, capable of suppressing reduction in charging quantity and resistance by suppressing the occurrence of toner spent. <P>SOLUTION: In the electrophotographic carrier including at least a core material particle and a cover layer covering the core material particle, the cover layer comprises at least a binder resin, a solid particle and a carbon nanotube, and the particle size D (μm) of the solid particle satisfies 1<(D/h)<10 wherein h is an average thickness of a resin part in the cover layer (μm). <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic carrier, an electrophotographic developer, a developing device, an image forming apparatus, and an image forming method, and more particularly to an electrophotographic carrier used for forming an electrostatic latent image into a toner image.

  In electrophotographic image formation, an electrostatic latent image is formed by an electrostatic charge on an image carrier such as a photoconductive material, and charged toner particles are attached to the electrostatic latent image to form a visible image. After the toner image is formed, the toner image is transferred to a recording medium such as paper and fixed to form an output image. In recent years, the technology of copiers and printers using an electrophotographic system has been rapidly expanding from monochrome to full color, and the full color market tends to expand. Color image formation by full-color electrophotography generally reproduces all colors by laminating three color toners of three primary colors, yellow, magenta, and cyan, or four color toners with black added thereto. . Therefore, in order to obtain a clear full color image with excellent color reproducibility, it is necessary to smooth the fixed toner image surface to some extent to reduce light scattering. For these reasons, the image gloss of conventional full-color copying machines or the like is often 10 to 50% of medium to high gloss.

  In general, as a method for fixing a dry toner image on a recording medium, a contact heating fixing method in which a roller or belt having a smooth surface is heated and pressed against the toner is frequently used. This method has high thermal efficiency and high-speed fixing, and is advantageous in that it can give gloss and transparency to the color toner. However, the surface of the heat-fixing member is brought into contact with the molten toner under pressure. Since the toner image is peeled off from the surface of the post-heating fixing member, a so-called offset phenomenon occurs in which a part of the toner image adheres to the surface of the heat fixing member and is transferred onto another image. For the purpose of preventing this offset phenomenon, there is a method in which the surface of the heat fixing member is formed of silicone rubber or fluorine resin having excellent releasability, and further, a release oil such as silicone oil is applied to the surface of the heat fixing member. It was generally adopted. However, this method is extremely effective in preventing toner offset, but a device for supplying release oil is necessary, and the fixing device becomes large and unsuitable for downsizing the machine. For this reason, in a monochrome toner, by adjusting the molecular weight distribution of the binder resin so that the melted toner does not break internally, the viscoelasticity at the time of melting of the toner is increased, and a release agent such as wax is further included in the toner. There is a tendency to employ a method in which the release oil is not applied to the fixing roller (oilless) or the amount of oil applied is very small.

  On the other hand, as for color toners, there is a tendency toward oil-less for the purpose of downsizing machines and simplifying the configuration as in monochrome. However, as described above, in order to improve the color reproducibility of the color toner, it is necessary to smooth the surface of the fixed image, so the viscoelasticity at the time of melting must be lowered, and it is easier to offset than the glossy monochrome toner. Therefore, it is more difficult to make the fixing device oil-free and to apply a small amount. In addition, when a release agent is contained in the toner, the adhesion of the toner is increased and the transfer property to the transfer paper is lowered. Further, the release agent in the toner contaminates the frictional charging member such as a carrier to reduce the charging property. This causes a problem that the durability is lowered.

  Regarding the carrier, while the demand for faster and more beautiful image formation is increasing, the stress received by the developer containing the carrier and the toner has increased dramatically with the recent increase in machine speed. Even in a carrier having a long life, a sufficient life cannot be obtained. In order to cope with such a problem, an electrophotographic developer carrier in which the surface of the core material particles is coated with a resin coating layer containing carbon nanotubes has been proposed (see, for example, Patent Documents 1 to 3).

Japanese Patent No. 3887584 JP 2006-091381 A JP 2007-094402 A

  However, those described in Patent Documents 1 to 3 improve the wear resistance of the resin coating layer by including a hard carbon nanotube with excellent wear resistance in the resin coating layer covering the surface of the core particles. However, there is a problem that toner spent is generated, resulting in a decrease in charge amount and a decrease in resistance.

  The present invention has been made in consideration of the above circumstances, and in spite of the fact that carbon nanotubes are contained in the resin coating layer covering the surface of the core material particles, the generation of toner spent is suppressed. An object of the present invention is to provide an electrophotographic carrier, an electrophotographic developer, a developing device, an image forming apparatus, and an image forming method capable of suppressing a decrease in resistance.

In order to solve the above problems, the invention according to claim 1 is an electrophotographic carrier comprising at least core material particles and a coating layer covering the core material particles.
The coating layer includes at least a binder resin, solid particles, and carbon nanotubes,
When the particle size of the solid particles is D (μm) and the average thickness of the resin portion in the coating layer is h (μm), 1 <(D / h) <10 is satisfied.

The invention of claim 2 is the carrier for electrophotography according to claim 1,
The solid particles are alumina particles or silica particles.

The invention of claim 3 is the carrier for electrophotography according to claim 1 or 2,
The solid particles have a particle size D in the range of 0.05 μm to 5 μm.

According to a fourth aspect of the present invention, there is provided the electrophotographic carrier according to any one of the first to third aspects,
The volume resistivity of the solid particles is in the range of 1.0 × 10 ¹² Ω · cm to 1.0 × 10 ¹⁶ Ω · cm.

The invention of claim 5 is the electrophotographic carrier according to any one of claims 1 to 4,
The carbon nanotube is at least one of a single-wall nanotube, a double-wall nanotube, and a multi-wall nanotube.

The invention of claim 6 is the electrophotographic carrier according to any one of claims 1 to 5,
The carbon nanotube has an armchair structure.

The invention of claim 7 is the electrophotographic carrier according to any one of claims 1 to 6,
The carbon nanotube is manufactured by any one of a CVD method, an arc discharge method, and a laser evaporation method.

The invention of claim 8 is an electrophotographic developer obtained by mixing an electrophotographic carrier and a toner.
The electrophotographic carrier according to any one of claims 1 to 7, wherein the electrophotographic carrier is the electrophotographic carrier.

The invention of claim 9 is the electrophotographic developer according to claim 8,
The toner includes at least a binder resin and a colorant.

According to a tenth aspect of the present invention, an electrophotographic carrier and a developer containing toner are accommodated, and the toner is supplied to an electrostatic latent image formed on the electrostatic latent image carrier to form a toner image. In the developing device,
The developer according to claim 8 or 9, wherein the developer is an electrophotographic developer.

According to an eleventh aspect of the present invention, at least the electrostatic latent image carrier and at least a developing device that supplies toner to the electrostatic latent image formed on the electrostatic latent image carrier to form a toner image are integrated. In the process cartridge configured and detachable from the image forming apparatus main body,
The developing device is a developing device according to claim 10.

According to a twelfth aspect of the present invention, there is provided an image forming apparatus comprising: an electrostatic latent image carrier; and a developing device that supplies toner to the electrostatic latent image formed on the electrostatic latent image carrier to form a toner image. In the device
The developing device is a developing device according to claim 10.

According to a thirteenth aspect of the present invention, there is provided an electrostatic latent image forming step of forming an electrostatic latent image on an electrostatic latent image carrier, and developing the electrostatic latent image using an electrophotographic developer. In an image forming method comprising at least a developing step for forming a visible image, a transfer step for transferring the visible image to a recording medium, and a fixing step for fixing the transferred image transferred to the recording medium,
The electrophotographic developer is the electrophotographic developer according to claim 8 or 9.

  According to the present invention, the coating layer includes at least a binder resin, solid particles, and carbon nanotubes, the particle size of the solid particles is D (μm), and the average thickness of the resin portion in the coating layer is h. When (μm) is satisfied, by satisfying 1 <(D / h) <10, the generation of toner spent can be suppressed and the decrease in charge amount and resistance can be suppressed, and electrophotographic carrier A developer, a developing device, an image forming apparatus, and an image forming method can be provided.

  Hereinafter, the present invention will be described in more detail. As a result of continuing investigations to solve the problems of the prior art, the present inventors have at least a core material particle and an electrophotographic carrier comprising a coating layer covering the core material particle. The coating layer includes at least a binder resin, solid particles, and carbon nanotubes, and the particle diameter D (μm) of the solid particles and the average thickness h (μm) of the resin portion in the coating layer are expressed by the following formula: It was found that the improvement effect was remarkable when 1 <(D / h) <10 was satisfied.

  That is, when the average thickness of the solid particles and the resin portion satisfies the relationship of the above formula, the solid particles become more convex than the resin portion in the coating layer, so by stirring to triboelectrically charge the developer, Contact with a strong impact on the binder resin can be relieved by friction with the toner or friction between the carriers, and it is possible to suppress film abrasion of the binder resin, which is a place where charging occurs.

  In addition, since a large number of solid particles having a particle size larger than that of the coating layer are present on the carrier surface and carrier particles having an uneven surface shape are formed, the spent component of the toner adhering to the carrier surface due to frictional contact between the carriers can be reduced. A cleaning effect that scrapes off efficiently occurs, and toner spent can be prevented.

  Furthermore, since the surface is uneven, the contact area between the toner and the carrier is reduced, and the developer has good fluidity. In addition, the convex shape of the surface allows the toner to be securely held when in contact with the toner, so that the toner can be taken into the developer by sliding the carrier and the toner like a carrier having no irregular shape on the surface. There are few inconveniences such as the absence of toner, and it is possible to efficiently take in the toner replenished in the developer into the developer and start up charging.

  If the (D / h) is 1 or less, the solid particles are likely to be buried in the binder resin, so that the effect may be significantly reduced. Since the contact area with the binder resin is small, sufficient binding force by the binder resin cannot be obtained, and the solid particles may be easily detached. Therefore, the particle diameter D (μm) of the solid particles and the average thickness h (μm) of the resin portion in the coating layer satisfy the above formula, 1 <(D / h) <10, preferably 1 < It is more preferable to satisfy (D / h) <5.

  The particle diameter D of the solid particles is preferably 0.05 μm to 3 μm, and more preferably 0.05 μm to 1 μm. The average thickness h (μm) of the resin portion in the coating layer is preferably 0.04 μm to 2 μm, and more preferably 0.04 μm to 1 μm.

  In this case, the average thickness h of the resin portion in the coating layer is the average thickness of the film existing on the surface of the core particle, and the solid particle portion D is the thickness from the core particle surface to the coating layer surface. It means the average thickness of the removed resin part. Specifically, as shown in FIG. 1, as the thickness of the resin portion E in the coating layer B, the thickness ha of the resin portion E existing between the surface A1 of the core particle A and the solid particles C, There are a thickness hb of the resin part E existing between the solid particles B, a thickness hc of the resin part E on the solid particle B, and a thickness hd of the resin part E on the core particle A.

  The average thickness h of the resin portion E in the coating layer B in the present invention can be measured by observing the cross section of the carrier using, for example, a transmission electron microscope (TEM). Specifically, the thickness of the resin portion E in the coating layer (the thickness ha of the resin portion existing between the surface of the core material particle and the solid particle, between the solid particles at intervals of 0.2 μm along the carrier surface. The thickness hb of the resin portion, the thickness hc of the resin portion on the solid particles, and the thickness hd of the resin portion on the core particles are measured using a transmission electron microscope (TEM), and 50 measurement values are obtained. Thus, the average value of the measured values is defined as the average thickness h of the resin portion E in the coating layer B.

  That is, the value of the average thickness h of the resin portion E in the coating layer B can be obtained as a value obtained by dividing the total value of the measured values by the number of the measured values. The number of measured values is the thickness ha of the resin portion existing between the surface of the core particle and the solid particles, the thickness hb of the resin portion existing between the solid particles, the thickness hc of the resin portion on the solid particles, and The thickness hd of the resin part on the core particle is counted as one each. For example, at the measurement point X in FIG. 1, since the ha and the hc exist, the number of measurement values at the measurement point X is two. Of the 50 measured values, the last measured location was a plurality of measured values (for example, ha and hc) as measured values of the thickness of the resin portion E in the coating layer B. In this case, the value obtained by dividing the total value of the measurement values by the value of “49+ (number of measurement values at the last measurement point)” that is the number of measurement values is the average thickness h of the resin portion in the coating layer. Value.

The volume resistivity of the solid particles is preferably 1.0 × 10 ¹² (Ω · cm) or more, and more preferably 1.0 × 10 ^{12 to} 1.0 × 10 ¹⁶ (Ω · cm). If the volume resistivity is less than 1.0 × 10 ¹² (Ω · cm), the solid particles C are larger than the coating layer B, so that the surfaces of the core material particles A and the coating layer B are separated by one solid particle C. Since a low-resistance region is locally formed and carrier adhesion may occur in the solid portion, it is preferable to set it to 1.0 × 10 ¹² (Ω · cm) or more.

Here, the volume resistivity of the solid particles C can be measured, for example, as follows. A sample (solid particles) is filled in a cylindrical vinyl chloride tube having an inner diameter of 1 inch, and the upper and lower sides are sandwiched between electrodes. A pressure of 15 kg / cm ² is applied to these electrodes with a press machine for 1 minute. Subsequently, in this pressurized state, measurement with an LCR meter is performed to measure resistance (r). The obtained resistivity can be calculated by the following (1) to obtain the volume resistivity.

Volume resistivity (Ω · cm) = [{(2.54 ÷ 2) ² × π} ÷ H] × r (1)
However, in said Formula (1), H represents the thickness of a sample and r represents resistance value.

Examples of the solid particles include solid particles made of a hard inorganic compound having a Mohs hardness of 5 or more, such as alumina (Al ₂ O ₃ ) particles (Mohs hardness: 9) and silica (SiO ₂ ) particles (Mohs hardness: 7). Is mentioned. Among these, the alumina particles not only have good compatibility with the binder resin used for the coating material of the carrier, are excellent in dispersibility and adhesiveness, and have a very high Mohs hardness of 9, so that development is possible. It is particularly preferable because it is difficult to cause wear and cracking against stress in the apparatus, and can exhibit the protective effect of the coating layer and the effect of scraping scrapes over a long period of time.

  The alumina particles preferably have a particle size of 5 μm or less, particularly 0.05 μm to 3 μm, more preferably 0.05 μm to 1 μm, and are preferably not surface-treated or surface-treated such as hydrophobized. Any of those whose surface is subjected to a resistance reduction treatment can be used.

  As the silica, those used for toners and those other than that can be used, and all of those that have not been surface-treated, those that have been subjected to surface treatment such as a hydrophobic treatment, and those whose surface has been subjected to low resistance treatment are used. Can be used.

  10-80 mass% is preferable and, as for content in the coating layer of the said solid particle, 20-60 mass% is more preferable. When the content is less than 10% by mass, since the proportion of solid particles occupies less than the proportion of the binder resin on the surface of the carrier particles, the effect of relaxing contact with a strong impact on the binder resin is achieved. Since it becomes small, sufficient durability may not be obtained. On the other hand, if it exceeds 80% by mass, the proportion of solid particles is too large compared to the proportion of the binder resin on the carrier surface, so that the proportion of the binder resin that is the charge generation location becomes insufficient, and is sufficient. The charging ability may not be demonstrated. Furthermore, since the amount of solid particles is too much compared to the amount of binder resin, the solid particle retention capacity by the binder resin becomes insufficient, the solid particles are easily detached, and the amount of fluctuation such as charge amount and resistance increases. Sufficient durability may not be obtained.

  Here, the content of the solid particles in the coating layer can be calculated by the following equation (2).

  Content of solid particles (mass%) = [content of solid particles ÷ total solid content of material contained in coating layer (solid particles + binder resin solid content + carbon nanotubes + other components)] × 100 (2 )

  In addition, when the carbon nanotube is included in the coating layer, the present inventors not only can appropriately adjust the electric resistance of the carrier due to the good conductivity of the carbon nanotube. It was found that the wear resistance of the coating layer can be further improved by the good wear resistance.

  A carbon nanotube is a material in which a six-membered ring network made of carbon is formed into a single-layer or multi-layer coaxial tube, and has a structure in which uniform plane graphite (graphene sheet) is rolled into a cylindrical shape. It is a substance that may be classified as a kind of fullerene in an allotrope of carbon. In addition, a cylindrical tube may have a plurality of concentric cylindrical layers. A single-walled tube is a single-wall nanotube (SWNT), a double-walled tube is a double-walled nanotube (DWNT), and a multi-walled tube is used. It is called a multi-wall nanotube (MWNT). As for the structure (how to wind), there are armchair type, zigzag type, chiral (spiral) type, etc., and zigzag type, chiral (spiral) type is a semiconductor, but armchair type shows the characteristics of conductor, In the present invention, the above effects can be remarkably exhibited by using the armchair type carbon nanotube.

  There are various advantages of carbon nanotubes, and it is said that there is a possibility that the advantages can be obtained even in an unconfirmed region. It has excellent electrical conductivity, high strength and high elasticity, such as having properties, 20 times the strength of steel, and extremely flexible elasticity. This is a very useful characteristic as a conductive material, and can obtain an effect different from that of carbon black conventionally used as a resistance control agent.

  That is, the point which is excellent in electrical conductivity provides resistance controllability far exceeding that of conventional carbon black in the coating layer. In addition, the excellent strength and elasticity are that the release from the coating layer is suppressed, and that the carbon nanotubes themselves are not easily chipped or cracked, so that a very good level of color stain characteristics can be obtained. . Also, regarding the detachment from the coating layer, since the carbon nanotube has a shape having a certain length with respect to the diameter, the adhesion area with the coating resin can be increased, so even if an external force is applied to the carbon nanotube. , Very difficult to detach. Thus, carbon nanotubes are materials that can exhibit completely different effects from conventional carbon black. In addition, the carbon nanotubes referred to in the present invention are not particularly limited as long as they are carbon nanotubes, and those generally used can be used.

  Here, the usefulness of using carbon nanotubes will be described. Similar to carbon black, carbon nanotubes are used as a resistance adjusting agent that lowers the resistance when the resistance of the carrier is high, and the effect is very large. In general, when a carrier having a high resistance is used as a developer, the image density of a large-area copy image has a very thin image density at the center, and only the edges are expressed deeply. It becomes the image that was. In addition, when the image is a character or a thin line, the image is clear due to the edge effect. However, when the image is halftone, there is a defect that the image is very reproducible. Such a defect can be appropriately improved by mixing carbon nanotubes into the coating layer of the carrier using a resistance adjusting agent.

  Furthermore, carbon nanotubes, unlike carbon black, have the effect of increasing the strength of the coating layer by tangling the carbon nanotubes in the coating layer when the length is long relative to the diameter. An effect of improving the wear resistance can also be obtained. Therefore, an excellent image can be obtained by using carbon nanotubes appropriately.

  It should be noted here that there is a large difference between the conventional color stain level and the color stain level referred to in the present invention. Specifically, as described above, the stress applied to the developer has increased dramatically with the recent increase in speed, but even with carriers that have conventionally allowed color stains, Since the amount of shaving increases, the color smear becomes an unacceptable level.

  Furthermore, since the carbon nanotube is a single-wall single-wall nanotube, a double-wall double-wall nanotube, or a multi-wall multi-wall nanotube, the improvement effect is remarkable. This is a structure in which carbon nanotubes are formed by rolling uniform graphite (graphene sheet) into a cylindrical shape, but multiple layers of carbon nanotubes on concentric circles with different diameters are formed. This is because when the plurality of layers are formed, the carbon nanotubes are densely formed, so that the resistance decreases as the number of layers increases, and the resistance adjustment effect can be made more efficient. The carbon nanotubes appropriately used in the present invention may be at least one of single-wall nanotubes, double-wall nanotubes, and multi-wall nanotubes, and these types of carbon nanotubes may be mixed and used.

  Furthermore, the structure (winding method) of the carbon nanotube used in the present invention is an armchair type, which is preferable because the improvement effect is remarkable. Carbon nanotubes have armchair type, zigzag type, chiral (helical) type, etc. in terms of structure (winding), but zigzag type, chiral (helical) type has the resistance value of the semiconductor region. The resistance adjustment effect cannot be exhibited efficiently. However, since the armchair type has the resistance value of the conductor region, the resistance control effect can be efficiently exhibited.

  Furthermore, the improvement effect is remarkable because the manufacturing method of the carbon nanotube is a CVD method, an arc discharge method, or a laser evaporation method. There are various methods for producing carbon nanotubes currently being investigated. Besides these, there are, for example, the HiPCO method and the super-growth CVD method. This is because the effect is excellent.

  The resin for forming the coating layer of the carrier of the present invention is not particularly limited as long as it is generally used for carriers. For example, a silicon resin, a fluororesin, an acrylic resin, and the like can be given, but the present invention is not limited to these. Moreover, coating resin may be used individually by 1 type, may be used by multiple, and may be used in a modified | denatured type.

  The core particles for the carrier of the present invention include those known as two-component carriers for electrophotography, such as iron, ferrite, magnetite, hematite, cobalt, iron-based, magnetite-based, Mn-Mg-Sr-based ferrite, Mn-based. Ferrite, Mn—Mg ferrite, Li ferrite, Mn—Zn ferrite, Cu—Zn ferrite, Ni—Zn ferrite, Ba ferrite, etc. It is not limited to the above example.

  The term “for color” as used in the present invention includes not only a color toner generally used for a single color, but also black toner in addition to yellow, magenta, cyan, red, green, blue and the like used for full color. Furthermore, the toner referred to in the present invention may be a general toner regardless of whether it is a monochrome toner, a color toner, or a full color toner. For example, conventionally kneaded and pulverized toners and various polymerized toners that have been used in recent years can be used.

  Furthermore, a toner containing a release agent, so-called oilless toner can also be used. In general, oilless toner contains a release agent, so that the release agent is likely to be transferred to the carrier surface, and so-called spent is likely to occur. Quality can be maintained. In particular, oilless full color toners are generally said to be spent easily because the binder resin is soft, but it can be said that the carrier of the present invention is very suitable.

  As the binder resin used in the toner of the present invention, known resins can be used. For example, styrene such as polystyrene, poly-p-styrene, and polyvinyltoluene, and homopolymers thereof, styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene- Methyl acrylate copolymer, Styrene-ethyl acrylate copolymer, Styrene-methacrylic acid copolymer Corp., Styrene-methyl acrylate copolymer, Styrene-ethyl acrylate copolymer, Styrene-methacrylic acid Butyl copolymer, styrene-α-chloromethacrylic acid methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, Styrene-isopropyl copolymer, styrene-male Styrene copolymers such as acid ester copolymer, polythyme methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified Rosin, terpene resin, phenol resin, aliphatic or aromatic hydrocarbon resin, aromatic petroleum resin, or the like can be used alone or in combination.

  Furthermore, as the pressure fixing binder resin, known resins can be mixed and used. For example, polyolefin such as low molecular weight polyethylene and low molecular weight polypropylene, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, styrene-methacrylic acid copolymer, ethylene-methacrylic acid ester copolymer, ethylene-chlorinated Vinyl copolymer, ethylene-vinyl acetate copolymer, olefin copolymer such as ionomer resin, epoxy resin, polyester resin, styrene-butadiene copolymer, polyvinylpyrrolidone, methyl vinyl ether-maleic anhydride, maleic acid modified phenol resin Phenol-modified terpene resins and the like can be used alone or in combination, but are not limited thereto.

  The toner used in the present invention may contain a fixing aid in addition to the binder resin, the colorant, and the charge control agent. Accordingly, it can be used in a fixing system in which toner fixing prevention oil is not applied to the fixing roll, so-called oilless system. Known fixing aids can be used. For example, polyolefins such as polyethylene and polypropylene, fatty acid metal salts, fatty acid esters, paraffin waxes, amide waxes, polyhydric alcohol waxes, silicone varnishes, carnauba waxes and ester waxes can be used, but are not limited thereto.

  As the colorant used in the toner such as the color toner of the present invention, known pigments and dyes capable of obtaining yellow, magenta, cyan, and black toners can be used, and are not limited to those listed here. Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG, and Tartrazine Lake. Can be mentioned.

  Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK.

  Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B.

Examples of purple pigments include fast violet B and methyl violet lake. Examples of blue pigments include cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, fast sky blue, and indanthrene blue BC.
Examples of green pigments include chrome green, chromium oxide, pigment green B, and malachite green lake.

  Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides. Moreover, these colorants can use 1 type (s) or 2 or more types.

The toner such as the color toner of the present invention may contain a charge control agent in the toner as necessary. For example, the color toner of the present invention can contain a charge control agent in the toner as needed. For example, nigrosine, an azine dye containing an alkyl group having 2 to 16 carbon atoms (see Japanese Patent Publication No. 42-1627), a basic dye (for example, CI Basic Yellow 2 (C.I. 41000), C.I. I. Basic Yellow 3, C. I. Basic Red 1 (C.I. 45160), C. I. Basic Red 9 (C.I. 42500), C. I. Basic Violet 1 (C.I. 42535), CI Basic Violet 3 (C.I. 42555), C.I.Basic Violet 10 (C.I.45170), C.I.Basic Violet 14 (C.I. 42510), C.I.Basic Violet Blue 1 (C.I.42025), C.I.Basic Blue 3 (C.I.51005), C.I.Basic Blue 5 (C.I. 42140), C.I.Basic Blue 7 (C.I.42595), C.I.Basic Blue 9 (C.I.52015), C.I.Basic Blue 24 (C.I. I.52030), C.I.Basic Blue 25 (C.I.52025), C.I.Basic Blue 26 (C.I.44045), C.I.Basic Green 1 (C.I.42040), C.I. Lake basic pigment lake pigments such as CI Basic Green 4 (CI 42000), CI Solvent Black 8 (CI 26150), benzoylmethyl hexadecyl ammonium chloride, decyl trimethyl chloride, Quaternary ammonium salts such as dialkyl tin such as dibutyl or dioctyl Compound, dialkyltin borate compound, guanidine derivative, vinyl polymer containing amino group, polyamine resin such as condensation polymer containing amino group, JP-B-41-20153, JP-B-43-27596, Metal complex salts of monoazo dyes described in JP-B-44-6397 and JP-B-45-26478, salicylic acid and dialkylsartyl described in JP-B-55-42752, JP-B-59-7385 Acid, naphthoic acid, dicarboxylic acid Zn, Al
Metal complexes such as Co, Cr and Fe, sulfonated copper phthalocyanine pigments, organic boron salts, fluorine-containing quaternary ammonium salts, calixarene compounds, and the like. Naturally, color toners other than black should avoid the use of charge control agents that impair the target color, and white metal salts of salicylic acid derivatives are preferably used.

  As for the external additive, transferability and durability are further improved by externally adding inorganic fine particles such as silica, titanium oxide, alumina, silicon carbide, silicon nitride, boron nitride and resin fine particles to the base toner particles. This effect can be obtained by covering the wax that lowers transferability and durability with these external additives and reducing the contact area due to the toner surface being covered with fine particles. The surface of these inorganic fine particles is preferably subjected to a hydrophobic treatment, and metal oxide fine particles such as silica and titanium oxide subjected to the hydrophobic treatment are preferably used. As the resin fine particles, polymethyl methacrylate or polystyrene fine particles having an average particle size of about 0.05 to 1 μm obtained by a soap-free emulsion polymerization method are suitably used.

In addition, the combination of hydrophobized silica and hydrophobized titanium oxide increases the amount of hydrophobized titanium oxide externally added compared to the amount of hydrophobized silica externally charged. The toner can also be excellent in stability. In combination with the above-mentioned inorganic fine particles, silica having a specific surface area of 20 to 50 m ² / g and resin fine particles having an average particle diameter of 1/100 to 1/8 of the average particle diameter of the toner are conventionally used. The durability can be improved by externally adding an external additive having a particle size larger than that of the additive to the toner.

  This is because the metal oxide particles externally added to the toner tend to be embedded in the base toner particles in the process where the toner is mixed and stirred with the carrier in the developing device, charged, and used for development. This is because it is possible to prevent the metal oxide fine particles from being embedded by externally adding an external additive having a particle size larger than that of the oxide fine particles to the toner.

  The above-mentioned inorganic fine particles and resin fine particles are contained (internally added) in the toner, but the effect is reduced as compared with the case of external addition, but the effect of improving transferability and durability can be obtained and the pulverization property of the toner can be improved. Can do. In addition, since external addition and internal addition can be used together to suppress embedding of externally added fine particles, excellent transferability can be stably obtained and durability can be improved.

  In addition, the following are mentioned as a typical example of the hydrophobization processing agent used here. Dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, allyldimethyldichlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, p-chloroethyltrichlorosilane, Chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, p-chlorophenyltrichlorosilane, 3-chloropropyltrichlorosilane, 3-chloropropyltrimethoxysilane, vinyltriethoxysilane, vinylmethoxysilane, vinyl-tris (β-methoxyethoxy) ) Silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, divinyldichlorosilane, dimethylvinylchlorosilane, octyl Trichlorosilane, decyl-trichlorosilane, nonyl-trichlorosilane, (4-t-propylphenyl) -trichlorosilane, (4-t-butylphenyl) -trichlorosilane, diventyl-dichlorosilane, dihexyl-dichlorosilane, dioctyl-dichlorosilane, dinonyl -Dichlorosilane, didecyl-dichlorosilane, didodecyl-dichlorosilane, dihexadecyl-dichlorosilane, (4-t-butylphenyl) -octyl-dichlorosilane, dioctyl-dichlorosilane, didecenyl-dichlorosilane, dinonenyl-dichlorosilane, di-2-ethylhexyl-dichlorosilane, di- 3,3-dimethylbenthyl-dichlorosilane, trihexyl-chlorosilane, trioctyl-chlorosilane, tridecyl-chlorosilane Dioctyl-methyl-chlorosilane, octyl-dimethyl-chlorosilane, (4-t-propylphenyl) -diethyl-chlorosilane, octyltrimethoxysilane, hexamethyldisilazane, hexaethyldisilazane, diethyltetramethyldisilazane, hexaphenyldisilazane , Hexatolyl disilazane and the like. In addition, titanate coupling agents and aluminum coupling agents can also be used. In addition, as an external additive for the purpose of improving cleaning properties, a lubricant such as a fatty acid metal salt or a fine particle of polyvinylidene fluoride can be used in combination.

  A conventionally known method such as a pulverization method or a polymerization method can be applied to the production of the toner in the present invention. For example, in the case of the pulverization method, as a device for kneading the toner, a batch type two roll, a Banbury mixer or a continuous twin screw extruder, for example, KTK type twin screw extruder manufactured by Kobe Steel, TEM manufactured by Toshiba Machine Co., Ltd. Type twin screw extruder, KCK twin screw extruder, Ikegai Iron Works PCM type twin screw extruder, Kurimoto Iron Works KEX type twin screw extruder, continuous single screw kneader, for example Buss Co-kneader is preferably used. The melt-kneaded product obtained as described above is cooled and then pulverized. For pulverization, for example, coarsely pulverized using a hammer mill, a funnel plex or the like, and further, a fine pulverizer using a jet stream or mechanical pulverization A machine can be used. The pulverization is desirably performed so that the average particle diameter is 3 to 15 μm. Furthermore, it is preferable that the particle size of the pulverized product is adjusted to 5 to 20 μm by a wind classifier or the like.

  Subsequently, the external additive is externally added to the base toner. The base toner and the external additive are mixed and stirred using a mixer, and the external additive is crushed and coated on the toner surface. At this time, it is important in terms of durability that external additives such as inorganic fine particles and resin fine particles are uniformly and firmly attached to the base toner. The above is only an example, and the present invention is not limited to this.

  Next, an image forming apparatus using the electrophotographic carrier and developer according to the present invention will be described with reference to the drawings.

  FIG. 2 is a cross-sectional view showing a schematic configuration showing an example of a developing device equipped with a container filled with a developer using an electrophotographic carrier according to the present invention. In the figure, reference numeral 1 denotes a developing unit that supplies toner to the photoconductor 10 to convert the electrostatic latent image on the photoconductor 10 into a toner image, and reference numeral 2 denotes the developing unit 1 that is replenished to the developing unit 1. Reference numeral 3 denotes a developer storage container filled with a developer using an electrophotographic carrier. Reference numeral 3 denotes a developer flow means for connecting the developing unit 1 and the developer storage container 2.

  In FIG. 2, the developing unit 1 includes a developing housing 4 containing a two-component developer T obtained by mixing toner and a carrier, and first and second stirring screws 5 and 6 for stirring and mixing the developer T. And the developing roller 7, and the developing roller 7 is disposed to face the photosensitive member 10 of the latent image carrier. The photoconductor 10 is rotationally driven in the direction indicated by the arrow, and an electrostatic latent image is formed on the surface thereof. In the drawing, reference numeral 126 denotes a cap fitted on the connecting member 124 with or without the filter 125.

  As the first and second agitating screws 5 and 6 rotate, the developer T in the developing housing 4 is agitated, and the toner and the carrier are frictionally charged with opposite polarities. The developer T is supplied to the peripheral surface of the developing roller 7 that is rotationally driven in the direction of the arrow, and the supplied developer is carried on the peripheral surface of the developing roller 7, and the rotation is performed by the rotation of the developing roller 7. Conveyed in the direction. Next, the amount of the conveyed developer is regulated by the doctor blade 9, and the regulated developer is conveyed to the development area between the photoconductor 10 and the developing roller 7, where the toner in the developer is removed. The electrostatic latent image on the surface of the photoreceptor is electrostatically transferred, and the electrostatic latent image is visualized as a toner image.

Next, an embodiment (first embodiment) of an image forming apparatus using an electrophotographic carrier according to the present invention will be described with reference to FIG.
The image forming apparatus 100 in the example shown in FIG. 3 includes a drum-shaped photosensitive member 10 as an electrostatic latent image carrier, a roller charging unit 20, an exposure unit 30, a developing device 40, and an endless belt. An intermediate transfer member 50, a cleaning unit 60 having a cleaning blade, and a static elimination lamp as a static elimination unit 70 are provided.

  The intermediate transfer member 50 is an endless belt, and is designed to be movable in the direction of an arrow by three rollers 51 that are arranged on the inner side and stretch the belt. Part of the three rollers 51 also functions as a transfer bias roller that can apply a predetermined transfer bias (primary transfer bias) to the intermediate transfer member 50. The intermediate transfer body 50 is provided with a cleaning means 90 having a cleaning blade in the vicinity thereof, and for transferring (secondary transfer) a developed image (toner image) onto a transfer paper P as a final transfer material. Transfer rollers as transfer means 80 to which a transfer bias can be applied are arranged to face each other. Around the intermediate transfer member 50, a corona charger 58 for applying a charge to the toner image on the intermediate transfer member 50 is arranged between the photosensitive member 10 and the intermediate transfer member 50 in the rotation direction of the intermediate transfer member 50. It is disposed between the contact portion and the contact portion between the intermediate transfer member 50 and the transfer paper P.

  The developing device 40 includes a developing belt 41 as a developer carrying member, a black developing unit (unit) 45K, a yellow developing unit (unit) 45Y, a magenta developing unit (unit) 45M, and a cyan developing unit provided around the developing belt 41. Means (unit) 45C. In this embodiment, the black developing means 45K includes a developer accommodating portion 42K, a developer supplying roller 43K, and a developing roller 44K, and the yellow developing means 45Y includes a developer accommodating portion 42Y and a developer supplying roller 43Y. And a developing roller 44Y. The magenta developing unit 45M includes a developer accommodating portion 42M, a developer supplying roller 43M, and a developing roller 44M. The cyan developing unit 45C includes a developer accommodating portion 42C and a developing roller. An agent supply roller 43C and a developing roller 44C are provided. The developing belt 41 is an endless belt, is rotatably stretched around a plurality of belt rollers, and a part thereof is in contact with the photoconductor 10.

  In the image forming apparatus 100 shown in FIG. 3, for example, the charging unit 20 charges the photosensitive drum 10 uniformly. The exposure means 30 exposes the image on the photosensitive drum 10 imagewise to form an electrostatic latent image. The electrostatic latent image formed on the photosensitive drum 10 is developed by supplying toner from the developing means 40 to form a visible image (toner image). The visible image is transferred (primary transfer) onto the intermediate transfer member 50 by the voltage applied from the roller 51 and further transferred (secondary transfer) onto the transfer paper P. As a result, a transfer image is formed on the transfer paper P. The residual toner on the photoconductor 10 is removed by the cleaning unit 60, and the charge on the photoconductor 10 is once removed by the static elimination unit (static elimination lamp) 70.

  An image forming apparatus (second embodiment) according to another embodiment of the present invention will be described with reference to FIG. The image forming apparatus 100 illustrated in FIG. 4 does not include the developing belt 41 in the image forming apparatus 100 illustrated in FIG. 3, and the black toner that stores toner of each color having the structure illustrated in FIG. 3 except that the developing device (developing unit) 46K, the yellow developing device (developing unit) 46Y, the magenta developing device (developing unit) 46M, and the cyan developing device (developing unit) 46C are directly opposed to each other. The image forming apparatus 100 has the same configuration as that of the illustrated image forming apparatus 100 and exhibits the same function and effect. In FIG. 4, the same components as those in FIG. 2 are denoted by the same reference numerals.

  An image forming apparatus (third embodiment) according to another embodiment of the present invention will be described with reference to FIG. A tandem image forming apparatus 120 shown in FIG. 5 is a tandem color image forming apparatus. The tandem image forming apparatus 120 includes a copying apparatus main body 150, a paper feed table 200, a scanner 300, and an automatic document feeder (ADF) 400. The copying apparatus main body 150 is provided with an endless belt-like intermediate transfer member 50 at the center. The intermediate transfer member 50 is stretched around the support rollers 14, 15 and 16, and can be rotated clockwise in FIG. 5. An intermediate transfer body cleaning device 17 for removing residual image toner on the intermediate transfer body 50 is disposed in the vicinity of the support roller 15. The intermediate transfer body 50 stretched by the support roller 14 and the support roller 15 is a tandem type in which four image forming means 18 of yellow, cyan, magenta, and black are arranged in parallel and facing each other along the conveyance direction. Developing means 120 is arranged. An exposure unit 21 is disposed in the vicinity of the tandem developing unit 120. On the opposite side of the intermediate transfer member 50 from the side on which the tandem developing unit 120 is disposed, the secondary transfer unit 22 is disposed.

  In the secondary transfer unit 22, a secondary transfer belt 24, which is an endless belt, is stretched around a pair of rollers 231 and 232, and the transfer paper P and the intermediate transfer member 50 conveyed on the secondary transfer belt 24 are provided. Can touch each other. A fixing unit 25 is disposed in the vicinity of the secondary transfer unit 22. The fixing unit 25 includes a fixing belt 26 that is an endless belt, and a pressure roller 27 that is pressed against the fixing belt 26. In the tandem image forming apparatus 120, a sheet reversing device 28 for reversing the transfer paper P in order to form an image on both sides of the transfer paper P is disposed in the vicinity of the secondary transfer means 22 and the fixing means 25. Has been.

  Next, full color image formation (color copy) using the tandem type image forming apparatus 120 will be described. That is, first, a document is set on the document table 130 of the automatic document feeder (ADF) 400, or the automatic document feeder 400 is opened and the document is set on the contact glass 32 of the scanner 300. 400 is closed.

  When a start switch (not shown) is pressed, when the document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 32, and then the document is set on the contact glass 32. Immediately after that, the scanner 300 is driven, and the first traveling body 33 and the second traveling body 34 travel. At this time, light from the light source is irradiated by the first traveling body 33 and reflected light from the document surface is reflected by the mirror in the second traveling body 34 and is received by the reading sensor 36 through the imaging lens 35 to be color. An original (color image) is read and used as black, yellow, magenta, and cyan image information.

  The image information of black, yellow, magenta, and cyan is stored in each image forming unit (black image forming unit 18K, yellow image forming unit 18Y, magenta image forming unit 18M, and cyan) in the tandem type image forming apparatus 120. Each of the image forming units forms a toner image of each color of black, yellow, magenta, and cyan. That is, each of the image forming units 18K, 18Y, 18M, and 18C in the tandem type image forming apparatus 120 has a photoconductor (black photoconductor (10K) as shown in FIG. 6 which is a partially enlarged schematic view of FIG. ), A yellow photoconductor (10Y), a magenta photoconductor (10M) and a cyan photoconductor (10C)), a charging roller 59 for uniformly charging the photoconductor, and each color image information based on each color image information. Exposure means 21 for exposing the photoconductor to an image corresponding to a color image (L in FIG. 6) to form an electrostatic latent image corresponding to each color image on the photoconductors 10K, 10Y, 10M, and 10C; The electrostatic latent image corresponding to each color is developed using each color developer (black developer, yellow developer, magenta developer, and cyan developer) according to the present invention to form a toner image by each color developer. Image devices 46K, 46Y, 46M, and 46C, a transfer charger 62 for transferring the developed toner image onto the intermediate transfer member 50, a photoconductor cleaning device 63, and a static eliminator 64, respectively. Each single color toner image (black image, yellow image, magenta image, and cyan image) is formed on the photoreceptors 10K, 10Y, 10M, and 10C based on the color image information. In this case, the developing devices 46K, 46Y, 46M, and 46C have the same configuration as the developing device shown in FIG. 2, and the same components as those in FIG. Is omitted.

  The photosensitive member cleaning device 63 removes residual toner on the surface of the photosensitive member 10 after the toner image on the photosensitive member 10 is transferred onto the intermediate transfer member 50, and includes a cleaning unit 60 including a cleaning blade, And a brush roller 76. The toner removed from the surface of the photoconductor 10 by the cleaning blade 60 and the brush roller 76 is transported out of the system by the transport screw 79. In FIG. 6, reference numeral 77 denotes a cleaning roller that cleans the surface of the brush roller 76, and reference numeral 78 denotes a cleaning blade that scrapes off toner adhering to the surface of the cleaning roller 77.

  The black image, the yellow image, the magenta image, and the cyan image thus formed are respectively transferred onto the black photoconductor 10K on the intermediate transfer member 50 that is rotated by the support rollers 14, 15 and 16 in FIG. A black toner image formed on the yellow photosensitive member 10Y, a yellow toner image formed on the yellow photosensitive member 10Y, a magenta toner image formed on the magenta photosensitive member 10M, and a cyan toner image formed on the cyan photosensitive member 10C. Then, sequential transfer (primary transfer) is performed. Then, the black toner image, the yellow toner image, the magenta toner image, and the cyan toner image are superimposed on the intermediate transfer member 50 to form a composite color image (color transfer image).

  On the other hand, in the paper feed table 200, one of the paper feed rollers 142 is selectively rotated to feed out the sheet-like recording paper P from one of the paper feed cassettes 144 provided in multiple stages in the paper bank 143, and the separation roller 145. The sheet is separated one by one and sent to the sheet feeding path 146, conveyed by the conveying roller 147, guided to the sheet feeding path 148 in the copying machine main body 150, and abutted against the registration roller 49 and stopped. Alternatively, the paper feed roller 142 is rotated to feed out the recording paper P on the manual feed tray 54, separated one by one by the separation roller 52, put into the manual feed path 53, and abutted against the registration roller 49 and stopped. The registration roller 49 is generally used while being grounded, but may be used in a state where a bias is applied to remove paper dust from the sheet.

  Then, the registration roller 49 is rotated in synchronism with a synthesized color image (color transfer image) obtained by synthesizing each toner on the intermediate transfer member 50, and the recording paper is interposed between the intermediate transfer member 50 and the secondary transfer unit 22. P is sent out, and the composite color image (color transfer image) is transferred (secondary transfer) onto the recording paper P by the secondary transfer means 22, whereby a color image is transferred and formed on the recording paper P. The residual toner on the intermediate transfer member 50 after image transfer is cleaned by the intermediate transfer member cleaning device 17.

  The recording paper P on which the color image has been transferred is conveyed by the secondary transfer means 22 and sent to the fixing means 25, where the combined color image (color transfer image) is generated by heat and pressure. Is fixed on the recording paper P. Thereafter, the recording paper P is switched by the switching claw 55 and discharged by the discharge roller 56 and stacked on the paper discharge tray 57. Alternatively, the recording paper P is switched by the switching claw 55 and reversed by the sheet reversing device 28 to return to the transfer position. After guiding and recording an image on the back side, the image is discharged by the discharge roller 56 and stacked on the discharge tray 57.

  In the image forming apparatus according to the third embodiment, the developing device 46, the charging roller 59, and the cleaning unit 63 are integrally formed around each photoconductor 10 to form a process cartridge. Accordingly, when performing maintenance, inspection, replacement, etc. of the developing device 46, the charging roller 59, and the cleaning means 63, it is easy to check and replace these devices and parts by detaching the process cartridge from the image forming apparatus. It is possible to do.

  FIG. 7 specifically shows a schematic diagram of an image forming apparatus equipped with a process cartridge according to an embodiment of the present invention. In FIG. 7, reference numeral 101 denotes the entire process cartridge, reference numeral 7 denotes a developing roller, reference numeral 10 denotes a photosensitive member, reference numeral 20 denotes a charging unit, reference numeral 46 denotes a developing device, reference numeral 60 denotes a cleaning unit, and reference numeral 63 denotes a cleaning device. .

  In the present invention, among the above-described components such as the photosensitive member 10, the charging unit 20, the developing device 46, and the cleaning device 63, the process cartridge including at least the photosensitive member 10 and the developing device 46 is integrally coupled. The process cartridge is configured to be detachable from a main body of an image forming apparatus such as a copying machine or a printer. In this case, a process cartridge having an integral structure including the charging unit 20 and / or the cleaning device 63 in addition to the photosensitive member 10 and the developing device 46 may be used.

  In the image forming apparatus having the process cartridge of the present invention, the photosensitive member 10 is rotationally driven at a predetermined peripheral speed. In the rotating process, the photosensitive member 10 is uniformly charged at a predetermined positive or negative potential on the peripheral surface thereof by the charging unit 20, and then from the image exposure unit 30 (see FIG. 5) such as slit exposure or laser beam scanning exposure. In response to the image exposure light, electrostatic latent images are sequentially formed on the peripheral surface of the photoreceptor 10. The formed electrostatic latent image is then developed with toner by the developing means 46, and the developed toner image is synchronized with the rotation of the photoconductor 10 between the photoconductor 10 and the transfer means 62 (see FIG. 5). The toner image is transferred to the fed intermediate transfer member 50 (see FIG. 5), and transferred from the intermediate transfer member 50 to the transfer paper P by the secondary transfer unit 22. The transfer paper P that has received the transfer of the toner image is introduced into the fixing means 25, the toner image is fixed on the transfer paper P, and printed out as a copy (copy). After the toner image is transferred, the surface of the photoreceptor 10 is cleaned by the cleaning device 63 after the transfer residual toner is removed, and after being further discharged, it is repeatedly used for image formation.

  Next, the electrophotographic carrier according to the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited thereto.

[Example 1]
Acrylic resin solution (solid content: 50% by mass) 85 parts by mass Guanamine solution (solid content: 70% by mass) 26 parts by mass Acid catalyst (solid content: 40% by mass) 1 part by mass Silicon resin solution (Solid fraction: 20% by mass) 290 parts by mass Aminosilane (solid fraction: 100% by mass) 2 parts by mass Alumina particles (volume average particle diameter (D); 0.35 μm, volume resistivity: 1.0 × 10 ¹⁴ Ω · cm) 185 parts by mass Carbon nanotubes (single wall nanotube, armchair type, production method: CVD method, diameter: 51 nm, length: 150 nm) 3 parts by mass Disperse 1300 parts by mass of toluene with a homomixer for 10 minutes Thus, a coating film forming solution was obtained. Average particle diameter: 35 μm calcined ferrite powder [DFC-400M (Mn ferrite, manufactured by DOWA IP Creation Co., Ltd.)] is used as the core particle, and the coating film forming solution has a film thickness of 0.2 μm on the surface of the core particle. As described above, the coating was carried out by a Spira coater (Okada Seiko Co., Ltd.) at a coater temperature of 40 ° C. and dried. The obtained carrier was baked by standing in an electric furnace at 150 ° C. for 1 hour. After cooling, the ferrite powder bulk was pulverized using a sieve having an aperture of 63 μm, and the charge amount: 39.3 (−μc / g), volume resistivity: 13.2 [Log (Ω · cm)] [carrier 1 ]

On the other hand, toner
Binder resin: 100 parts by weight of polyester resin Release agent: 5 parts by weight of carnauba wax Charge control agent: E-84 [manufactured by Orient Chemical Co., Ltd.] 1 part by weight Colorant: C.I. I. P. Y. 180 8 parts by mass Of the above materials, the colorant, the binder resin, and pure water were mixed at a ratio of 1: 1: 0.5 and kneaded by two rolls. Kneading was performed at 70 ° C., and then the roll temperature was raised to 120 ° C. to evaporate water and prepare a master batch in advance. Using the master batch obtained in this way, weigh the materials so that they are the same as the above recipe, mix with a Henschel mixer, melt knead for 40 minutes at 120 ° C. with two rolls, cool, and then coarsely pulverize with a hammer mill Thereafter, fine powder obtained by fine pulverization with an air jet pulverizer was classified to prepare toner base particles having a weight average particle diameter of 5 μm. Further, to 100 parts of the toner base material, 1 part of silica whose surface was hydrophobized and 1 part of titanium oxide whose surface was hydrophobized were added and mixed with a Henschel mixer to obtain yellow toner [Toner 1 ] Was obtained.

  7 parts of [Toner 1] thus obtained and 93 parts of [Carrier 1] were mixed and stirred to prepare a developer having a toner concentration of 7 wt%.

[Example 2]
In Example 1, the carbon nanotube was changed into a carbon nanotube (double wall nanotube, armchair type, CVD method, diameter: 53 nm, length: 148 nm) in the same manner as in the case of the carrier, and the charge amount: 38.0 (-Μc / g), [Carrier 2] having a volume resistivity of 12.6 [Log (Ω · cm)] was obtained. A developer was prepared from [Carrier 2] and [Toner 1] thus obtained in the same manner as in Example 1.

Example 3
In Example 1, the carbon nanotubes were changed into carbon nanotubes (triple wall nanotubes, armchair type, CVD method, diameter: 55 nm, length: 151 nm) in the same manner as in the case of carriers. Thus, [Carrier 3] having a volume resistivity of 12.0 [Log (Ω · cm)] was obtained. A developer was prepared from [Carrier 3] and [Toner 1] thus obtained in the same manner as in Example 1.

Example 4
In Example 1, the carbon nanotubes were changed to carbon nanotubes (single wall nanotubes, armchair type, arc discharge method, diameter: 52 nm, length: 151 nm) in the same manner as in the case of carriers, and the charge amount: 39 0.1 (-μc / g), volume resistivity: 13.0 [Log (Ω · cm)] [Carrier 4] was obtained. A developer was prepared from [Carrier 4] and [Toner 1] thus obtained by the same method as in Example 1.

Example 5
In Example 1, it was converted into a carbon nanotube as a carbon nanotube (single wall nanotube, armchair type, laser evaporation method, diameter: 50 nm, length: 149 nm). [Carrier 5] of 1.5 (−μc / g) and volume resistivity: 13.1 [Log (Ω · cm)] was obtained. A developer was prepared from [Carrier 5] and [Toner 1] thus obtained in the same manner as in Example 1.

Example 6
In Example 1, it was converted into a carbon nanotube as a carbon nanotube (single wall nanotube, zigzag type, CVD method, diameter: 53 nm, length: 150 nm). (-Μc / g), [Carrier 6] having a volume resistivity of 14.4 [Log (Ω · cm)] was obtained. A developer was prepared from [Carrier 6] and [Toner 1] thus obtained in the same manner as in Example 1.

Example 7
In Example 1, except that the carbon nanotube was changed to a carbon nanotube (single wall nanotube, chiral type, CVD method, diameter: 52 nm, length: 152 nm), it was converted into a carrier, and the charge amount: 41.9. (-Μc / g), [Carrier 7] having a volume resistivity of 14.3 [Log (Ω · cm)] was obtained. A developer was prepared from [Carrier 7] and [Toner 1] thus obtained in the same manner as in Example 1.

[Comparative Example 1]
In Example 1, except that the coating film forming solution was changed to the following, it was converted into a carrier in the same manner, the charge amount: 36.8 (-μc / g), the volume resistivity: 12.1 [Log (Ω · cm) [Carrier 8] was obtained. A developer was prepared from [Carrier 8] and [Toner 1] thus obtained by the same method as in Example 1.

Acrylic resin solution (solid content: 50% by mass) 85 parts by mass Guanamine solution (solid content: 70% by mass) 26 parts by mass Acid catalyst (solid content: 40% by mass) 1 part by mass Silicon resin solution (Solid fraction: 20% by mass) 290 parts by mass Aminosilane (solid fraction: 100% by mass) 2 parts by mass Carbon nanotubes (single wall nanotube, armchair type, CVD method, diameter: 51 nm, length: 150 nm) 3 parts by mass-1300 parts by mass of toluene

[Comparative Example 2]
In Example 1, except that the coating film forming solution was changed to the following, it was converted into a carrier in the same manner, the charge amount: 44.1 (−μc / g), the volume resistivity: 16.1 [Log (Ω · cm) [Carrier 9] was obtained. A developer was prepared from [Carrier 9] and [Toner 1] thus obtained in the same manner as in Example 1.

Acrylic resin solution (solid content: 50% by mass) 85 parts by mass Guanamine solution (solid content: 70% by mass) 26 parts by mass Acid catalyst (solid content: 40% by mass) 1 part by mass Silicon resin solution (Solid fraction: 20% by mass) 290 parts by mass Aminosilane (solid fraction: 100% by mass) 2 parts by mass Alumina particles (volume average particle size: 0.35 μm, volume resistivity: 1.0 × 10 ¹⁴ Ω)・ Cm) 185 mass parts ・ carbon black (BP-2000; manufactured by Cabot Corporation) 3 mass parts ・ toluene 1300 mass parts

[Comparative Example 3]
In Example 1, except that the coating film forming solution was changed to the following, it was converted into a carrier, and the charge amount: 39.1 (-μc / g), volume specific resistance: 13.4 [Log (Ω · cm) ] [Carrier 10] was obtained. A developer was prepared from [Carrier 10] and [Toner 1] thus obtained in the same manner as in Example 1.

Acrylic resin solution (solid content: 50% by mass) 85 parts by mass Guanamine solution (solid content: 70% by mass) 26 parts by mass Acid catalyst (solid content: 40% by mass) 1 part by mass Silicon resin solution (Solid fraction: 20% by mass) 290 parts by mass Aminosilane (solid fraction: 100% by mass) 2 parts by mass Alumina particles (volume average particle size: 0.35 μm, volume resistivity: 1.0 × 10 ¹⁴ Ω) -Cm) 185 parts by mass-Carbon black (BP-2000; manufactured by Cabot Corporation) 26 parts by mass-Toluene 1300 parts by mass

  Using the developers prepared in Examples 1 to 7 and Comparative Examples 1 to 3, the amount of charge reduction, the amount of resistance reduction, color stain, and the edge effect were evaluated. The evaluation results are shown in FIG. In addition, the measurement method and evaluation method regarding the said evaluation item followed the following.

[Method for measuring average particle diameter of core particles]
For the average particle size measurement of the core particles, an SRA type of Microtrac particle size analyzer (manufactured by Nikkiso Co., Ltd.) was used, and the measurement was performed with a range setting of 0.7 [μm] or more and 125 [μm] or less. Using.

(Volume resistivity method)
The volume resistivity of the carrier shown in the above examples and comparative examples is that the carrier is injected between parallel electrodes separated by a gap of 2 mm, tapped, then DC 1000 V is applied between both electrodes, and the resistance value after 30 sec is measured with a high resist meter. The value measured in (1) was obtained by converting into volume resistivity. In addition, when it fell below the measurable lower limit of the high resist meter, the volume specific resistance value was not substantially obtained, and it was handled as a breakdown.

[Evaluation method of charge reduction / resistance reduction]
A developer was set on a commercially available digital full-color printer (made by Ricoh Co., Ltd., imgio MP C7500), and a running evaluation of 300,000 sheets in a single color was performed. Then, the amount of decrease in charge amount and the amount of decrease in resistance of the carrier after the running was evaluated.

  The amount of charge reduction was measured by a general blow-off method (TB-200, manufactured by Toshiba Chemical Co., Ltd.) on a sample that had been mixed and frictionally charged at a ratio of 7% by mass of toner to 93% by mass of the initial carrier. The carrier obtained by removing the toner in the developer after running with the blow-off device was calculated by subtracting the charge amount (Q2) measured by the same method as described above from the obtained charge amount (Q1). The target charge reduction amount is within 8.0 μc / g. Further, since the cause of the decrease in the charge amount is the toner spent on the carrier surface, the decrease in the charge amount can be suppressed by reducing the toner spent.

  The amount of decrease in resistance was measured by putting initial carriers between the electrodes of the resistance measurement parallel electrodes (gap 2 mm), applying DC 1000V, and measuring the resistance value after 30 seconds with a high resist meter. The value obtained by converting the obtained value into the volume resistivity (R1), and measuring the carrier obtained by removing the toner in the developer after running with the blow-off device by the same method as the resistance measuring method. It was calculated as an amount obtained by subtracting (R2). The target resistance reduction amount is within 2.0 [Log (Ω · cm)] in absolute value. Further, the cause of the resistance change is scraping of the carrier coating layer, spent toner component, detachment of solid particles in the carrier coating layer, and the like. By reducing these, the resistance reduction amount can be suppressed.

[Color stain evaluation method]
The developer prepared in each of the above Examples and Comparative Example 1 was set in a developing unit of a commercially available digital full color printer (image MP MP7500, manufactured by Ricoh Co., Ltd.), and the developing unit alone was stirred for 1 hour. The developer thus obtained was developed and fixed, and the L * 1, a * 1, and b * 1 values of the CIE color system at the location where the image density was 1.5 were determined. On the other hand, in order to obtain an image free from color stains, an image formed with toner alone (including fixing) without being brought into contact with the carrier is prepared, and the CIE table of the portion where the image density is 1.5 as described above. L * 0, a * 0, and b * 0 values of the color system were obtained. The color difference ΔE between the two images thus obtained is obtained by the following equation (3). If ΔE ≦ 3.0, there is no problem in actual use, but ΔE> 3.0 causes a problem in actual use.

ΔE = √ [(L * 0−L * 1) ² + (a * 0−a * 1) ² + (b * 0−b * 1) ² ] (3)

[Edge effect evaluation method]
Developers prepared in the above Examples and Comparative Example 1 were set in a commercially available digital full color printer (IPSiO CX 9000 manufactured by Ricoh Co., Ltd.), and a test pattern having a large area image was output. The difference between the thinness of the image density at the central portion of the image pattern thus obtained and the darkness of the edge portion was ranked as follows. The evaluation was evaluated as “A” when there was no difference, “B” when there was a slight difference, and “B” when the difference occurred to an unacceptable level.

  From the evaluation results shown in FIG. 8, the developers according to Examples 1 to 7 containing the solid particles according to the present invention in the coating layer of the carrier are compared with those of Comparative Example 1 which does not contain the solid particles in the coating layer of the carrier. It is clear that the amount of charge reduction and the amount of resistance reduction are small, and the occurrence of toner spent on the carrier is suppressed.

  In addition, the developer containing the carrier using the carbon nanotubes of Examples 1 to 7 has less color stains and edge effect compared to those using carbon black as the conductive material shown in Comparative Examples 2 and 3. It is clear that also shows good results.

  Furthermore, what used the armchair type carbon nanotube shown in Examples 1-5 compared with the case where the zigzag type carbon nanotube shown in Example 6 is used, and the case where the chiral type carbon nanotube shown in Example 7 is used. It is clear that the edge effect is good both in the charge reduction amount and the resistance reduction amount.

1 is a schematic cross-sectional view in which a part of an electrophotographic carrier according to an embodiment of the present invention is cut away. 1 is a cross-sectional view illustrating a schematic configuration of a developing device according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to a first embodiment of the present invention. It is sectional drawing which shows schematic structure of the image forming apparatus of 2nd Embodiment by this invention. It is sectional drawing which shows schematic structure of the image forming apparatus of 3rd Embodiment by this invention. FIG. 6 is an enlarged cross-sectional view illustrating a schematic configuration of an image forming unit of the image forming apparatus illustrated in FIG. 5. It is a typical sectional view showing a schematic structure of a process cartridge of one embodiment by the present invention. It is a table | surface figure which shows the evaluation result of the charge amount fall amount, resistance fall amount, color stain, and edge effect with respect to the developer of each Example and Comparative Example 1 according to the present invention.

Explanation of symbols

A core material particle B coating layer C solid particle E resin part T developer 1 developing part 2 developer storage container 4 developing housing 5, 6 conveying screw 7 developing roller 9 doctor blade 10, 10Y, 10C, 10M, 10K photoconductor 20 Charging means 22 Secondary transfer means 25 Fixing means 30 Exposure means 40, 46, 46Y, 46C, 46M, 46K Developing device 50 Intermediate transfer member 60 Cleaning means 63 Cleaning device

Claims (13)

In an electrophotographic carrier comprising at least core material particles and a coating layer covering the core material particles,
The coating layer includes at least a binder resin, solid particles, and carbon nanotubes,
Electrophotographic carrier characterized by satisfying 1 <(D / h) <10, where D (μm) is the particle size of the solid particles and h (μm) is the average thickness of the resin portion in the coating layer. . The electrophotographic carrier according to claim 1,
The carrier for electrophotography, wherein the solid particles are alumina particles or silica particles. The electrophotographic carrier according to claim 1 or 2,
The electrophotographic carrier according to claim 1, wherein the particle size D of the solid particles is in the range of 0.05 μm to 5 μm. The carrier for electrophotography according to any one of claims 1 to 3,
The volume resistivity of the solid particles is in the range of 1.0 × 10 ¹² Ω · cm to 1.0 × 10 ¹⁶ Ω · cm. The electrophotographic carrier according to any one of claims 1 to 4,
The carrier for electrophotography, wherein the carbon nanotube is at least one of a single-wall nanotube, a double-wall nanotube, and a multi-wall nanotube. The electrophotographic carrier according to any one of claims 1 to 5,
The carrier for electrophotography, wherein the carbon nanotube has an armchair structure. The electrophotographic carrier according to any one of claims 1 to 6,
The electrophotographic carrier according to claim 1, wherein the carbon nanotube is manufactured by any one of a CVD method, an arc discharge method, and a laser evaporation method. In an electrophotographic developer formed by mixing an electrophotographic carrier and a toner,
The electrophotographic developer according to claim 1, wherein the electrophotographic carrier is the electrophotographic carrier according to claim 1. The developer for electrophotography according to claim 8,
An electrophotographic developer, wherein the toner contains at least a binder resin and a colorant. In a developing device that contains a developer including an electrophotographic carrier and a toner and supplies the toner to an electrostatic latent image formed on an electrostatic latent image carrier to form a toner image.
10. The developing device according to claim 8, wherein the developer is an electrophotographic developer according to claim 8 or 9. At least the electrostatic latent image carrier and at least a developing device for supplying toner to the electrostatic latent image formed on the electrostatic latent image carrier to form a toner image are integrated into and detached from the image forming apparatus main body. In a flexible process cartridge,
A process cartridge according to claim 10, wherein the developing device is a developing device according to claim 10. An image forming apparatus comprising: an electrostatic latent image carrier; and a developing device that supplies toner to the electrostatic latent image formed on the electrostatic latent image carrier to form a toner image.
The image forming apparatus according to claim 10, wherein the developing apparatus is a developing apparatus according to claim 10. An electrostatic latent image forming step of forming an electrostatic latent image on the electrostatic latent image carrier, and a developing step of developing the electrostatic latent image using an electrophotographic developer to make a visible image; In the image forming method, comprising at least a transfer step of transferring the visible image to a recording medium, and a fixing step of fixing the transfer image transferred to the recording medium.
The image forming method according to claim 8, wherein the electrophotographic developer is the electrophotographic developer according to claim 8.

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