JP2011145388A - Electrophotographic carrier, developer and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developer which, in an image forming method forming a developer in a thin layer, avoids fogging and toner scattering over a long period of time and can give a stable image even in a highly humid environment and an image forming method, and to provide a carrier having a small volume resistivity and capable of suppressing a charge amount reduction and the occurrence of a color stain, a developer including the carrier, a developer container containing the developer, and an image forming method and a process cartridge using the developer. <P>SOLUTION: The carrier has a coating layer including a binder resin and fine particles formed on a surface of a core material particle, wherein the coating layer includes metal oxide conductive particles (I) and another metal oxide and/or a metal salt (II) and includes the metal oxide and/or metal salt (II) in an amount of 100-300 wt.%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a carrier having a coating layer formed on the surface of core material particles, a developer, a container containing a developer, an image forming method, and a process cartridge.

  In electrophotographic image formation, an electrostatic latent image is formed on an electrostatic latent image carrier such as a photoconductive substance, and a charged toner is attached to the electrostatic latent image to form a toner image. After that, the toner image is transferred to a recording medium and fixed to form an output image. In recent years, the technology of copying machines and printers using an electrophotographic system is rapidly expanding from monochrome to full color, and the full color market tends to expand.

  In full-color image formation, generally, color toners of three colors of yellow, magenta, and cyan or four color toners obtained by adding black to this are laminated to reproduce all colors. Therefore, in order to obtain a clear full color image with excellent color reproducibility, it is necessary to smooth the surface of the fixed toner image to reduce light scattering. For these reasons, the image gloss of conventional full-color copying machines and 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. Such a method has high thermal efficiency and enables high-speed fixing, and can give gloss and transparency to the color toner. On the other hand, the surface of the heat-fixing member is brought into contact with the molten toner under pressure. Then, in order to peel off, a so-called offset phenomenon occurs in which a part of the toner image adheres to the surface of the fixing roller and is transferred onto another image.

  In order to prevent such an offset phenomenon, the surface of the fixing roller is made of silicone rubber or fluororesin having excellent releasability, and further, toner fixing prevention oil such as silicone oil is applied to the surface of the fixing roller. This method is generally adopted. However, such a method is extremely effective in preventing toner offset, but requires a device for supplying oil, and there is a problem that the fixing device is increased in size.

  For this reason, in monochrome image formation, an oilless system in which viscoelasticity at the time of melting is large and toner containing a release agent is used so that the melted toner does not break internally, so that no oil is applied to the fixing roller, or There is a tendency to adopt a system in which a small amount of oil is applied.

  On the other hand, in full-color image formation, as in the case of monochrome image formation, an oilless system tends to be employed for the purpose of downsizing the fixing device and simplifying the configuration. However, in full-color image formation, it is necessary to reduce the viscoelasticity of the toner at the time of melting in order to smooth the surface of the fixed toner image. Therefore, offset occurs more than in the case of monochrome image formation without gloss. This makes it difficult to adopt an oilless system. Further, when a toner containing a release agent is used, adhesion of the toner is increased and transferability to a recording medium is decreased. Furthermore, there is a problem in that the durability is lowered due to the occurrence of toner filming and a decrease in chargeability.

  On the other hand, as a carrier, prevention of toner filming, formation of a uniform surface, prevention of surface oxidation, prevention of decrease in moisture sensitivity, extension of developer life, prevention of adhesion to the surface of a photoreceptor, photosensitivity For the purpose of protecting the body from scratches or abrasion, controlling the charge polarity, adjusting the charge amount, etc., a coating layer in which a resin containing carbon black is formed on the surface is known.

  However, a good image can be formed in the initial stage, but there is a problem in that as the number of copies increases, the coating layer is scraped and the image quality decreases. Further, there is a problem that color stains occur due to the coating layer being scraped or the carbon black being detached from the coating layer.

In general, titanium oxide, zinc oxide, and the like are known as alternative materials for carbon black, but the effect of reducing the volume resistivity is insufficient.
Japanese Patent Application Laid-Open No. 11-202560 of Patent Document 1 discloses a carrier in which a coating layer containing antimony-doped tin oxide (ATO) is formed as acicular conductive powder. However, since ATO is bluish in color tone, there is a problem that color stains occur as in the case of carbon black.

  Japanese Patent Laid-Open No. 2006-39357 of Patent Document 2 discloses a carrier in which a coating layer containing conductive particles in which a tin dioxide layer and an indium oxide layer containing tin dioxide are laminated on the surface of a base particle is formed. It is disclosed. However, since such conductive particles contain rare metals, there are problems such as cost and permanent availability.

  In addition, we include first conductive particles having carbon on the surface of tin oxide particles and second conductive particles in which the surfaces of metal oxide particles and / or metal salt particles are subjected to conductive treatment. A carrier having a coating layer has been proposed, and this proposed technique has a certain effect on the decrease in the charging ability of the carrier when the toner is balanced in a large image area. When toner with a large amount of agent was used and continuous paper passing was performed with a large image area, the charge was lowered and the effect was not sufficient.

As described above, the developer used for electrophotographic image formation is roughly divided into two types, ie, a one-component developer and a two-component developer. In particular, a color developer has stable charging characteristics. A two-component developer is advantageous in that it can be secured.
As means for achieving the reduction in the developer layer thickness, typical examples of the two-component developer include the following. As shown in FIG. 6, there are known means for holding the surfaces of the inelastic regulating blade (50) and the developer carrier (28) in a predetermined gap and regulating the developer layer (in the figure, reference numeral (10)). ) Is a photoreceptor.
Among them, a layer in which a thin layer forming method using a rigid rod-shaped magnetic material proposed in Japanese Patent Application Laid-Open No. 2-50184 of Patent Document 3 or a means for pressing a developer layer regulating rod disposed in the developing means is stable. Effective in forming the thickness. However, when this means is used, although there is a merit of forming a stable layer, there is a disadvantage that the developer is subjected to excessive stress. The increase in stress during the formation of the thin layer causes the carrier coating layer to be broken, peeled off, and the like, and has a great adverse effect on the durability of the developer. On the other hand, in recent years, an image forming apparatus to which electrophotography such as a laser printer is applied tends to be miniaturized, and accordingly, a developing device in the image forming apparatus is also miniaturized. However, in a small developing device, the amount of developer is inevitably reduced.

  For this reason, in the two-component developer as described above, it is an important problem how to give an appropriate charge amount at a high speed while the toner is replenished and then moves to the developing region. Conventionally, a negatively chargeable charge control agent has generally been added to a toner in order to improve the charge rising characteristics of a negatively chargeable developer. However, when such a small developing device is used, this alone is not sufficient, and the scattering of the toner and the fog appearing on the image due to the increase of the weakly charged toner are remarkable.

  As a means on the carrier side for improving the charge rising characteristics, a positively charged charge control agent is added to the carrier as described in JP-A-2-8860 of Patent Document 4. Examples of positively chargeable charge control agents include quaternary ammonium compounds and patents disclosed in Japanese Patent Application Laid-Open No. 49-51951 in Patent Document 5, Japanese Patent Application Laid-Open No. 52-10141 in Patent Document 6, and the like. Examples include alkylpyridinium compounds and alkylpicolinium compounds (for example, nigrosine SO and nigrosine EX) disclosed in JP-A-56-11461 of Document 7 and JP-A-54-158932 of Patent Document 8. However, these charge control agents are organic compounds having high cohesive strength and poor dispersibility. For this reason, in the coating layer of the carrier, charging failure with the toner is liable to occur due to the ubiquity and release of the charge control agent. In addition, when a so-called spent in which the toner component is fused to the carrier occurs in multi-sheet copying, the charge control agent component existing on the surface is covered with the toner component, so that the charge rising performance cannot be stabilized.

Further, in order to make the developer layer thin and to obtain stable developability, it is necessary to stabilize the developer transport amount. However, the transport amount changes depending on the change in the charge amount of the developer.
Attempts to improve the difference in developer charging environment are disclosed in Japanese Patent Application Laid-Open No. 57-168256 of Patent Document 9, Japanese Patent Application Laid-Open No. 59-228261 of Patent Document 10, and Japanese Patent Application Laid-Open No. Sho 63 of Patent Document 11. As described in JP-A No.-71860 and JP-A-2-110777 of Patent Document 12, the magnetic particles are charged with water absorption by adding inorganic fine particles coated with silicon resin or hydrophobized to the coating layer. It is intended to suppress changes in sex.
However, even in these methods, the hydrophobization is not sufficient when left under a high temperature and high humidity for a long time, and a change in the charging ability of the carrier is observed.

  Further, as means for preventing the chargeability from being changed by toner spent, the purpose of polishing spent toner is disclosed in JP-A-54-21730 and JP-A-58-117555. As described in Japanese Patent Application Laid-Open No. 59-232362 and Japanese Patent Application Laid-Open No. 59-232362, silica is added. However, since the silica used for these is generally spherical, the polishing effect is small. Furthermore, there is a disadvantage that silica is detached in a system with a large stress such as a thin layer forming method. Therefore, although the generation of spent is delayed as compared with a carrier not added with silica, the effect cannot be maintained. After copying a large number of sheets, the silica is completely detached and a large amount of spent is generated, so that a significant change in charge amount occurs, resulting in toner scattering and fogging.

In addition, the coating layer is made of silicon resin to reduce the decrease in charge amount due to moisture absorption when left at high temperature and high humidity, and the coating layer contains alumina particles with a large particle size to provide a polishing effect on the toner spent. A given effect can also be obtained over time. Japanese Patent Laid-Open No. 6-301245 of Patent Document 16 and Japanese Patent Laid-Open No. 7-261465 of Patent Document 17 have a carrier configuration in which magnesium compound particles and a resin are coated, so that magnesium can be used for toner spent. The effect is obtained by using the polishing effect by the compound particles, and the effect is obtained by the positive chargeability of magnesium itself against the decrease in the charge amount when left at high temperature and high humidity.
However, in any of the above-described configurations, the decrease in charge amount when left at high temperature does not become zero, and a configuration in which the decrease in charge amount is smaller is desired in order to reduce the variation in print quality.

Accordingly, an object of the present invention is to provide a stable image even in a high humidity environment without causing fogging or toner scattering over a long period of time in an image forming method in which a developer is formed in a thin layer in view of the above-described problems of the prior art. It is an object to provide a developer and an image forming method that can be obtained.
Further, a carrier having a small volume specific resistance and capable of suppressing a decrease in charge amount and occurrence of color stains, a developer having the carrier, a developer-containing container having the developer, and image formation using the developer It is to provide a method and a process cartridge.

The above-mentioned problems are solved satisfactorily by the following present invention.
(1) “A carrier in which a coating layer containing a binder resin and fine particles is formed on the surface of a core particle, the metal oxide conductive particles (I) and other metal oxides on the coating layer Or a metal salt or both (II), and the metal oxide or metal salt or both (II) is contained in an amount of 100% by weight to 300% by weight ",
(2) “The metal oxide or the metal salt or both (II) contains barium sulfate, and the content thereof is 110 wt% or more and 300 wt% or less with respect to the binder resin. “Carrier described in (1)”,
(3) “The carrier according to (2) above, which contains 100% by weight or more of barium sulfate with respect to the weight of the conductive particles”,
(4) The above-mentioned characteristic that the common logarithm of the specific resistance of the conductive particles (I) is 0.5 [Log (Ω · cm)] or more and 3 [Log (Ω · cm)] or less. The carrier according to (2) or (3) ",
(5) “Inorganic additive containing tin oxide as the conductive particles (I), including the area (A) occupied by the resin in the surface of the coating layer, tin oxide, and all of the metal oxide and metal salt (II) The carrier according to item (1), wherein the ratio (A / B) of the area (B) occupied by the surface exposed portion of the agent is 0.3 or less,
(6) “The metal oxide (II) is at least one selected from the group consisting of aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide and zirconium oxide, and the metal salt (II) is barium sulfate. The carrier according to item (5) above, "
(7) The above-mentioned (5), wherein the tin oxide particles have a common logarithmic value of specific resistance of 0.5 [Log (Ω · cm)] or more and 3 [Log (Ω · cm)] or less. ) Or the carrier according to item (6) ",
(8) The above-mentioned items (1) to (7), wherein the common logarithm of the volume resistivity is 10 [Log (Ω · cm)] or more and 14 [Log (Ω · cm)] or less. The carrier according to any one of the paragraphs ",
(9) "The carrier according to any one of (1) to (8) above, wherein the core material particles have a weight average particle diameter of 20 µm to 65 µm",
(10) "The carrier according to any one of (1) to (9) above, wherein the coating layer has an average film thickness of 0.05 µm to 2 µm";
(11) "The carrier according to any one of (1) to (10), wherein the binder resin contains a silicone resin and / or an acrylic resin",
(12) “The carrier according to any one of (1) to (11) above, wherein the magnetization in a magnetic field of 1 kOe is 40 Am ² / kg or more and 90 Am ² / kg or less”,
(13) "Developer comprising the carrier and toner according to any one of (1) to (12)",
(14) "The developer according to item (13), wherein the toner is a color toner",
(15) "Container with developer, characterized by having the developer according to item (13) or (14)",
(16) “The step of forming an electrostatic latent image on the electrostatic latent image carrier and the electrostatic latent image formed on the electrostatic latent image carrier are described in the item (13) or (14 The toner image is developed with the developer described in the item (1) to form a toner image, the toner image formed on the electrostatic latent image carrier is transferred to a recording medium, and the toner image is transferred to the recording medium. And an image forming method characterized by comprising a step of fixing a toner image ”,
(17) “Developing an electrostatic latent image carrier and an electrostatic latent image formed on the electrostatic latent image carrier using the developer described in the item (13) or (14) The process cartridge is characterized in that the means for supporting is at least integrally supported.

As will be understood from the following detailed and specific description, according to the present invention, a carrier capable of stably maintaining a good charge amount even in a high-temperature and high-humidity environment over a long period of time is provided. A developer having a carrier, a developer-containing container having the developer, an image forming method using the developer, and a process cartridge can be provided.
In addition, according to the present invention, a carrier having a small volume resistivity and capable of suppressing a decrease in charge amount and occurrence of color stains, a developer having the carrier, a developer-containing container having the developer, and the An image forming method using a developer and a process cartridge can be provided.

The figure which is an apparatus which measures the volume specific resistance of electroconductive powder. It is a figure which shows the cell used when measuring the volume specific resistance of a carrier. It is a figure which shows an example of the process cartridge of this invention. 10 is a photograph showing an example of capturing a reflected electron image of a carrier of Example 9. FIG. 10 is a photograph showing an example of capturing a reflected electronic image of a carrier of Comparative Example 4. An example of a developing device having means for regulating the developer layer by holding the non-elastic regulating blade and the surface of the developer carrying member in a predetermined gap is shown.

Next, the form for implementing this invention is demonstrated with drawing.
The carrier of the present invention is a carrier in which a coating layer containing a binder resin and fine particles is formed on the surface of the core particles, the metal oxide conductive particles (I) as fine particles in the coating layer, A metal oxide or metal salt or both (II) other than the above, and the metal oxide or metal salt or both (II) is contained in an amount of 100% by weight to 300% by weight, The carrier of the first category includes barium sulfate particles dispersed in a binder resin as the metal oxide (II). White conductive particles may be included together with the barium sulfate particles.
The carrier of the second category contains tin oxide as the conductive particles (I), the area (A) occupied by the resin in the surface of the coating layer, tin oxide, the metal oxide and the metal salt (II ) The ratio (A / B) of the area (B) occupied by the surface exposed portion of the inorganic additive containing all of (A) is 0.3 or less.

[First category carrier]
The present inventors include conductive fine particles in a resin for coating a core material, and a carrier that can stably maintain a good charge amount even in a high temperature and high humidity environment is a metal oxide or It has been found that the metal salt or both (II) is contained in an amount of 100% by weight or more and 300% by weight or less, and is preferably achieved when the metal oxide is used, particularly when barium sulfate is used. I found out. It is more preferable that white conductive fine particles (I) are contained together with the barium sulfate particles.

[Second category carrier]
Further, as a result of intensive studies, the inventors have found that the charging stability increases as the proportion of the inorganic additive on the surface increases. This is considered to be because the inorganic additive is much harder than the resin, so that the additive contained in the toner becomes difficult to be embedded.

  In order to increase the ratio of the inorganic additive to the surface, first, the amount of the inorganic additive to be added is increased. If the amount is too large, pipe clogging is likely to occur in the process of applying the coating liquid to the core material, and undesired things such as increased inorganic additives that are not held on the carrier surface and are separated and are wasted. However, there was no problem with the quality of the manufactured carrier itself. In addition, it is important that the inorganic additive is dispersed in the coating solution so that it can be dispersed more finely. This is because the surface area of the coated carrier surface naturally increases because the surface area of the inorganic additive increases when finely dispersed even if the amount is the same.

  The coating layer contains tin oxide, contains a metal oxide or a metal salt or both, and the metal oxide is not particularly limited, and examples include aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide, zirconium oxide, Two or more kinds may be used in combination. Moreover, it does not specifically limit as a metal salt, Barium sulfate etc. are mentioned.

  In the carrier of the second category, a coating layer is formed on the surface of the core particle, and the coating layer contains tin oxide as a conductivity imparting agent, and the area occupied by the resin in the surface of the coating layer (A) The ratio (A / B) of the area (B) occupied by the surface exposed portion of the additive including all of tin oxide, metal oxide and metal salt is 0.3 or less.

  These low-conductivity particles have a common logarithmic value of specific resistance of 3 [Log (Ω · cm)] or more, and the ability to reduce the resistance of the coat carrier is not high. Even if these are used alone, they do not provide desirable resistance as a coat carrier.

  Using tin oxide alone can reduce the resistance of the coat carrier, but tin oxide is formulated so that the ratio (A / B) of the area (B) occupied by the surface exposed portion of the additive is 0.3 or less. Then, the resistance falls too much. Causes problems with carrier skipping from the processor. Therefore, it is important to use tin oxide in combination with a metal oxide or metal salt.

Hereinafter, the technical matters common to both categories of carriers will be described. The specific resistance of the conductive particles can be measured as follows. First, 5 g of conductive particles are placed in a cylindrical vinyl chloride tube having an inner diameter of 1 inch (2.54 cm), and the upper and lower sides thereof are sandwiched between electrodes. Next, the resistance r [Ω] is measured using an LCR meter 4216A (manufactured by Yokogawa Hewlett-Packard Company) with a pressure of 10 kg / cm ² applied to these electrodes using a press. The following formula (1)
Log [π (2.54 / 2) ² / H × r] Formula (1)
(In the formula, H is the distance [cm] between the electrodes when measuring resistance.)
From this, the common logarithm value [Log (Ω · cm)] of the specific resistance can be calculated.

  The binder resin is not particularly limited, but is obtained by polymerizing monomers such as polyolefins such as polyethylene and polypropylene or modified products thereof; styrene resins, acrylic resins, acrylonitrile resins; vinyl acetate, vinyl chloride, vinyl carbazole, vinyl ether, and the like. Crosslinkable copolymer; silicone resin; silicone modified alkyd resin, silicone modified polyester, silicone modified acrylic resin, silicone modified epoxy resin, silicone modified polyurethane, silicone modified polyimide and other silicone modified resins; polyamide, polyester, polyurethane, polycarbonate, Examples include urea resin, melamine resin, benzoguanamine resin, epoxy resin, ionomer resin, polyimide and their derivatives. It may be.

  In the present invention, the binder resin preferably contains an acrylic resin because it has strong adhesion to the core particles and conductive particles and has low brittleness. Thereby, scraping and peeling of the coating layer can be suppressed, and the coating layer can be stably maintained. Further, the conductive particles can be held firmly, and particularly when holding conductive particles having a particle size larger than the film thickness of the coating layer, a strong effect can be exhibited.

  The acrylic resin preferably has a glass transition point of 20 to 100 ° C, more preferably 25 to 80 ° C. Thereby, since the binder resin has appropriate elasticity, the impact received by the carrier when the developer is triboelectrically charged can be reduced, and the coating layer can be prevented from being scraped or peeled off.

The binder resin further preferably contains a cross-linked product of an acrylic resin and an amino resin. Thereby, fusion | melting of coating layers can be suppressed, maintaining moderate elasticity.
The amino resin is not particularly limited, but a melamine resin and a benzoguanamine resin are preferable because the charge imparting ability of the carrier can be improved. In addition, when it is necessary to appropriately control the charge imparting ability of the carrier, another amino resin may be used in combination with the melamine resin and / or the benzoguanamine resin.

As the acrylic resin capable of crosslinking with the amino resin, those having a hydroxyl group and / or a carboxyl group are preferable, and those having a hydroxyl group are more preferable. Thereby, adhesiveness with core material particle | grains or electroconductive particle can further be improved, and the dispersion stability of electroconductive particle can also be improved. In this case, the acrylic resin preferably has a hydroxyl value of 10 mgKOH / g or more, and more preferably 20 mgKOH / g or more.
In the present invention, the binder resin preferably contains a silicone resin. Thereby, since the surface energy of the carrier becomes small, filming of the toner can be suppressed, and as a result, the characteristics of the carrier can be maintained over a long period of time. Examples of the structural unit of the silicone resin include methyltrisiloxane, dimethyldisiloxane, and trimethylsiloxane, and two or more kinds may be used in combination. The silicone resin may be mixed with other binder resins, and the coating layer may have a single layer structure or a multilayer structure.

  Since the binder resin can suppress scraping and peeling of the coating layer, a silicone resin having a silanol group and / or a functional group capable of generating a silanol group by hydrolysis (hereinafter referred to as a hydrolyzable functional group) is used. More preferably, it contains a cross-linked product obtained by condensation. Although it does not specifically limit as a hydrolysable functional group, A halosilyl group, an alkoxysilyl group, a hydrosilyl group, an isocyanate silyl group etc. are mentioned, You may use 2 or more types together. Such functional groups are condensed by moisture in the atmosphere or by heating, and the silicone resin is crosslinked.

Examples of commercially available silicone resins include KR271, KR272, KR282, KR252, KR255, KR152 (above, manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400, SR2405, SR2406 (above, manufactured by Toray Dow Corning Silicone). .
Commercially available silicone-modified resins include silicone-modified epoxy resin ES-1001N, silicone-modified acrylic resin KR-5208, X-22-8004, X22-8212, X22-8195X, X-24-798A, silicone-modified polyester. KR-5203, silicone-modified alkyd resin KR-206, silicone-modified polyurethane KR-305 (manufactured by Shin-Etsu Chemical Co., Ltd.), silicone-modified epoxy resin SR2115, silicone-modified alkyd resin SR2110 (manufactured by Toray Dow Corning Silicone) Is mentioned.

  In the present invention, the coating layer preferably further contains a silane coupling agent since the stability of the carrier over time is improved and the durability can be improved. The silane coupling agent is not particularly limited, and examples thereof include methyltrimethoxysilane, methyltriethoxysilane, octyltrimethoxysilane, and the like, but aminosilane is preferable.

The aminosilane is not particularly limited, formula _{H 2 N (CH 2) 3} Si (OCH 3) 3,
H ₂ N (CH ₂ ) ₃ Si (OC ₂ H ₅ ) ₃ ,
H ₂ N (CH ₂ ) ₃ Si (CH ₃ ) ₂ (OC ₂ H ₅ ),
_{H 2 N (CH 2) 3} Si (CH 3) (OC 2 H 5) 2,
H ₂ N (CH ₂ ) ₂ (NH) (CH ₂ ) Si (OCH ₃ ) ₃ ,
H ₂ N (CH ₂ ) ₂ (NH) (CH ₂ ) ₃ Si (CH ₃ ) (OCH ₃ ) ₂ ,
H ₂ N (CH ₂ ) ₂ (NH) (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ,
_{(CH 3) 2 N (CH} 2) 3 Si (CH 3) (OC 2 H 5) 2,
(C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃
The compound represented by these is mentioned.

The content of aminosilane in the coating layer is preferably 0.001 to 30% by mass, and more preferably 0.001 to 15% by mass. When the content is less than 0.001% by mass, the effect of improving the durability of the carrier may be insufficient. When the content exceeds 30% by mass, conductive particles and inorganic particles are retained in the coating layer. May be difficult to do.
In the present invention, the coating layer preferably has an average film thickness of 0.05 to 2 μm. When the average film thickness is less than 0.05 μm, the film peels off due to mechanical stress during use, the core material is exposed, and the initial volume resistivity cannot be maintained, and when it exceeds 2 μm, there are too many resin components. At the time of manufacture, two or more carriers may be fixed and the apparent particle size may increase.

[Resin amount]
The coating amount of the silicone-based resin on the carrier core material is preferably 0.05 to 10.0% by weight, more preferably 0.1 to 7.0% by weight, based on the carrier core material. The coating thickness of the silicone-based resin must be adjusted according to the specific surface area of the carrier core material, and it is necessary to reduce the exposed portion of the carrier core material, which makes it possible to control the resistance, charge amount, and fluidity of the developer. Change can be reduced. The coating thickness is preferably about 0.02 to 2.0 μm.

  In the present invention, the core particle is not particularly limited as long as it is a magnetic substance, but is not limited to ferromagnetic metals such as iron and cobalt; iron oxides such as magnetite, hematite and ferrite; various alloys and compounds; Examples thereof include resin particles dispersed in the resin. Of these, Mn-based ferrite, Mn-Mg-based ferrite, Mn-Mg-Sr ferrite, and the like are preferable from the viewpoint of environmental considerations.

In the present invention, the core particles preferably have a volume average particle size of 20 to 65 μm. When the volume average particle size is less than 20 μm, carrier adhesion may occur. When the volume average particle size exceeds 65 μm, the reproducibility of image details may be reduced, and a fine image may not be formed.
The volume average particle diameter can be measured using a Microtrac particle size distribution model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.).

  The carrier of the present invention preferably has a common logarithmic value of volume resistivity of 10 to 14 [Log (Ω · cm)]. When the common logarithm of the volume resistivity is less than 10 [Log (Ω · cm)], carrier adhesion may occur in the non-image area, and when it exceeds 14 [Log (Ω · cm)], the edge effect May be unacceptable.

The volume resistivity can be measured using the cell shown in FIG. Specifically, first, a carrier (3) is placed in a cell composed of a fluororesin container 2 containing an electrode (1a) and an electrode (1b) having a surface area of 2.5 cm × 4 cm separated by a distance of 0.2 cm. Filling and tapping 10 times with a drop height of 1 cm and a tapping speed of 30 times / minute. Next, a DC voltage of 1000 V is applied between the electrodes (1a) and (1b), and a resistance value r [Ω] after 30 seconds is measured using a high resistance meter 4329A (manufactured by Yokogawa Hewlett-Packard Company). And formula (2)
Log [r × (2.5 × 4) /0.2] Formula (2)
From this, the common logarithmic value [Log (Ω · cm)] of the volume resistivity can be calculated.

The carrier of the present invention preferably has a magnetization of 40 to 90 Am ² / kg in a magnetic field of 1 kOe (10 ⁶ / 4π [A / m]). When this magnetization is less than 40 Am ² / kg, the carrier easily flies away from the developing roll, and when it exceeds 90 Am ² / kg, the carrier ears on the developing roll are crushed and the uniformity of the image may be reduced. .
Magnetization can be measured using VSM-P7-15 (manufactured by Toei Kogyo Co., Ltd.).

The developer of the present invention has the carrier and toner of the present invention.
The toner contains a binder resin and a colorant, and may be a monochrome toner or a color toner. In addition, the toner may contain a release agent for application to an oilless system in which toner fixing prevention oil is not applied to the fixing roller. Such toner generally tends to cause filming. However, since the carrier of the present invention can suppress filming, the developer of the present invention maintains good quality for a long time. Can do. Furthermore, color toners, particularly yellow toners, generally have a problem that color stains occur due to scraping of the coating layer of the carrier. However, the developer of the present invention contains white color barium sulfate, which causes color stains. Occurrence can be suppressed.

  The toner can be produced using a known method such as a pulverization method or a polymerization method. For example, when a toner is manufactured using a pulverization method, first, a melt-kneaded product obtained by kneading a toner material is cooled, pulverized, and classified to prepare base particles. Next, in order to further improve transferability and durability, an external additive is added to the base particles to produce a toner.

At this time, the apparatus for kneading the toner material is not particularly limited, but a batch type two roll; Banbury mixer; KTK type twin screw extruder (manufactured by Kobe Steel), TEM type twin screw extruder (Toshiba Machine) A continuous twin screw extruder such as a twin screw extruder (manufactured by KCK), a PCM type twin screw extruder (manufactured by Ikegai Iron Works), a KEX type twin screw extruder (manufactured by Kurimoto Iron Works); Examples thereof include a continuous single-shaft kneader such as Ko Nida (manufactured by Buss).
Further, when the cooled melt-kneaded product is pulverized, it is roughly pulverized using a hammer mill, a rotoplex, etc., and then finely pulverized using a fine pulverizer using a jet stream, a mechanical pulverizer or the like. be able to. In addition, it is preferable to grind | pulverize so that an average particle diameter may be set to 3-15 micrometers.

Furthermore, when classifying the crushed melt-kneaded material, a wind classifier or the like can be used. In addition, it is preferable to classify so that the average particle diameter of the base particles is 5 to 20 μm.
In addition, when an external additive is added to the base particle, the external additive adheres to the surface of the base particle while being pulverized by mixing and stirring using a mixer.

  The binder resin is not particularly limited, but is a homopolymer of styrene such as polystyrene, poly-p-styrene, polyvinyltoluene and the like; and a styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene. -Vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylic acid copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer Styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene Copolymer, styrene-isoprene copolymer Styrene copolymers such as styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid Rosin, modified rosin, terpene resin, phenol resin, aliphatic or aromatic hydrocarbon resin, aromatic petroleum resin and the like, and two or more of them may be used in combination.

  The binder resin for pressure fixing is not particularly limited, but polyolefins such as low molecular weight polyethylene and low molecular weight polypropylene; ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, styrene-methacrylic acid copolymer. Olefin copolymers such as ethylene-methacrylate copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, ionomer resin; epoxy resin, polyester, styrene-butadiene copolymer, polyvinylpyrrolidone, Examples thereof include methyl vinyl ether-maleic anhydride copolymer, maleic acid-modified phenol resin, phenol-modified terpene resin, and the like, and two or more of them may be used in combination.

  Although it does not specifically limit as a coloring agent (pigment or dye), Cadmium yellow, mineral fast yellow, nickel titanium yellow, Navels yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow GR, quinoline yellow lake, Yellow pigments such as permanent yellow NCG and tartrazine lake; orange pigments such as molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK; bengara, cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine Red pigments such as B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B; purple pigments such as fast violet B, methyl violet lake; cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, Blue pigments such as phthalocyanine blue partially chlorinated, First Sky Blue, Indanthrene Blue BC; Green pigments such as Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Lake; Carbon Black, Oil Furnace Black, Channel Black, Lamp Black Azine dyes such as acetylene black and aniline black, black pigments such as metal salt azo dyes, metal oxides and composite metal oxides, etc. It may be.

  The release agent is not particularly limited, but includes polyolefins such as polyethylene and polypropylene, fatty acid metal salts, fatty acid esters, paraffin wax, amide wax, polyhydric alcohol wax, silicone varnish, carnauba wax, ester wax and the like. Two or more kinds may be used in combination.

  The toner may further contain a charge control agent. The charge control agent is not particularly limited, but nigrosine; an azine dye having an alkyl group having 2 to 16 carbon atoms (see Japanese Patent Publication No. 42-1627); I. Basic Yellow 2 (C.I. 41000), C.I. I. Basic Yellow 3, C.I. I. Basic Red 1 (C.I. 45160), C.I. I. Basic Red 9 (C.I. 42500), C.I. I. Basic Violet 1 (C.I. 42535), C.I. I. Basic Violet 3 (C.I. 42555), C.I. I. Basic Violet 10 (C.I. 45170), C.I. I. Basic Violet 14 (C.I. 42510), C.I. I. Basic Blue 1 (C.I. 42025), C.I. I. Basic Blue 3 (C.I. 51005), C.I. I. Basic Blue 5 (C.I. 42140), C.I. I. Basic Blue 7 (C.I. 42595), C.I. I. Basic Blue 9 (C.I. 52015), C.I. I. Basic Blue 24 (C.I. 52030), C.I. I. Basic Blue 25 (C.I. 52025), C.I. I. Basic Blue 26 (C.I. 44045), C.I. I. Basic Green 1 (C.I. 42040), C.I. I. Basic dyes such as Basic Green 4 (C.I. 42000); lake pigments of these basic dyes; I. Solvent Black 8 (C.I. 26150), quaternary ammonium salts such as benzoylmethylhexadecyl ammonium chloride and decyltrimethyl chloride; dialkyltin compounds such as dibutyl and dioctyl; dialkyltin borate compounds; guanidine derivatives; vinyl having an amino group Polyamine resins such as polycondensation polymers and condensation polymers having amino groups; described in JP-B-41-20153, JP-B-43-27596, JP-B-44-6397, and JP-B-45-26478 Metal complex salts of monoazo dyes; salicylic acids described in JP-B-55-42752 and JP-B-59-7385; dialkylsalicylic acid, naphthoic acid, dicarboxylic acid Zn, Al, Co, Cr, Fe, etc. Metal complexes of Examples thereof include honed copper phthalocyanine pigments; organic boron salts; fluorine-containing quaternary ammonium salts; calixarene compounds, and the like. For color toners other than black, white metal salts of salicylic acid derivatives are preferred.

  The external additive is not particularly limited, but inorganic particles such as silica, titanium oxide, alumina, silicon carbide, silicon nitride, boron nitride, etc .; poly having an average particle size of 0.05 to 1 μm obtained by a soap-free emulsion polymerization method Examples thereof include resin particles such as methyl methacrylate particles and polystyrene particles, and two or more kinds may be used in combination. Among these, metal oxide particles such as silica and titanium oxide whose surfaces are hydrophobized are preferable. Furthermore, by using a combination of hydrophobized silica and hydrophobized titanium oxide, the amount of added hydrophobized titanium oxide is higher than that of hydrophobized silica. A toner having excellent charging stability can be obtained.

  The image forming method of the present invention uses the developer of the present invention to form an electrostatic latent image on the electrostatic latent image carrier and the electrostatic latent image formed on the electrostatic latent image carrier. Development to form a toner image, a step of transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and a step of fixing the toner image transferred to the recording medium.

  FIG. 3 shows an example of the process cartridge of the present invention. The process cartridge (10) comprises a photoreceptor (11), a charging device (12) for charging the photoreceptor (11), and an electrostatic latent image formed on the photoreceptor (11) using the developer of the present invention. A developing device (13) for developing and forming a toner image and a cleaning device (after removing the toner remaining on the photoconductor (11) after transferring the toner image formed on the photoconductor (11) to a recording medium. 14) is integrally supported, and the process cartridge (10) is detachable from the main body of an image forming apparatus such as a copying machine or a printer.

  Hereinafter, a method for forming an image using the image forming apparatus equipped with the process cartridge (10) will be described. First, the photosensitive member (11) is rotationally driven at a predetermined peripheral speed, and the charging device (12) uniformly charges the peripheral surface of the photosensitive member (11) to a predetermined positive or negative potential. Next, exposure light is irradiated onto the peripheral surface of the photoreceptor (11) from an exposure apparatus (not shown) such as a slit exposure type exposure apparatus or an exposure apparatus that performs scanning exposure with a laser beam, and electrostatic latent images are sequentially formed. The Further, the electrostatic latent image formed on the peripheral surface of the photoconductor (11) is developed by the developing device (13) using the developer of the present invention to form a toner image. Next, the toner image formed on the peripheral surface of the photoconductor (11) is synchronized with the rotation of the photoconductor (11), and the photoconductor (11) and the transfer device (not shown) are fed from the paper feed unit (not shown). ) Are sequentially transferred onto the transfer paper fed during (). Further, the transfer paper onto which the toner image has been transferred is separated from the peripheral surface of the photoreceptor (11), introduced into a fixing device (not shown) and fixed, and then copied as a copy (copy) of the image forming apparatus. Printed out. On the other hand, after the toner image is transferred, the surface of the photoconductor (11) is cleaned by the cleaning device (14) to remove the remaining toner, and then the charge is removed by a static eliminator (not shown). Used for image formation.

  Next, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these. In addition, a part is a mass reference | standard.

  26 parts of acrylic resin “Hitaroid 3001 (manufactured by Hitachi Chemical Co., Ltd.)” with a solid content of 50% by mass, 10 parts of guanamine resin Mycoat 106 (manufactured by Mitsui Cytec Co., Ltd.) with a solid content of 70% by mass, and 40% by mass of solid content Acid catalyst catalyst 4040 (manufactured by Mitsui Cytec Co., Ltd.), silicone resin SR2410 (manufactured by Toray Dow Corning Co., Ltd.) 354 parts, solid content 15 mass% aminosilane SH6020 (Toray 0.42 parts manufactured by Dow Corning Co., Ltd. Tin oxide S2000 (manufactured by Mitsubishi Materials Corp.) having an average primary particle size of 30 nm and a common logarithm of specific resistance of 2.1 [Log (Ω · cm)] as the second conductive particles 150 parts, 160 parts of barium sulfate BF10 (manufactured by Sakai Chemical Industry Co., Ltd.), and 800 parts of toluene were dispersed for 10 minutes using a homomixer. To obtain a covering layer coating solution.

Using Spiracoater SP-40 (Okada Seiko Co., Ltd.), the temperature in the coater was set to 50 ° C., and the coating liquid for coating layer was 5,000 parts of sintered ferrite powder having a volume average particle size of 35 μm (DOWAIP Creation) Applied) and dried. Next, it was fired in an electric furnace at 200 ° C. for 1 hour, cooled, and then crushed using a sieve having an opening of 63 μm to obtain a carrier.
The solid content of the resin calculated with this carrier is 91.7 parts, and the prescribed amount of barium sulfate is within the scope of the present invention.

  A carrier was obtained in the same manner as in Example 1 except that 200 parts of barium sulfate BF10 (manufactured by Sakai Chemical Industry Co., Ltd.) was used.

  A carrier was obtained in the same manner as in Example 1 except that 250 parts of tin oxide S2000 (manufactured by Mitsubishi Materials) and 260 parts of barium sulfate BF10 (manufactured by Sakai Chemical Industry Co., Ltd.) were used.

  A carrier was obtained in the same manner as in Example 1 except that 100 parts of tin oxide S2000 (manufactured by Mitsubishi Materials) and 150 parts of barium sulfate BF10 (manufactured by Sakai Chemical Industry Co., Ltd.) were used.

  A carrier was obtained in the same manner as in Example 1 except that 200 parts of tin oxide S2000 (manufactured by Mitsubishi Materials) and 220 parts of barium sulfate BF10 (manufactured by Sakai Chemical Industry Co., Ltd.) were used.

  Example 1 except that 120 parts of tin oxide S2000 (manufactured by Mitsubishi Materials), 120 parts of ITO-treated alumina EC-700 (manufactured by Titanium Industry) and 160 parts of barium sulfate BF10 (manufactured by Sakai Chemical Industry Co., Ltd.) were used. , Got a career.

  Example 1 except that 160 parts of tin oxide S2000 (manufactured by Mitsubishi Materials), 160 parts of ITO-treated alumina EC-700 (manufactured by Titanium Industry), and 180 parts of barium sulfate BF10 (manufactured by Sakai Chemical Industry Co., Ltd.) were used. , Got a career.

  A carrier was obtained in the same manner as in Example 1 except that 150 parts of tin oxide S2000 (manufactured by Mitsubishi Materials) and 200 parts of barium sulfate BF21 (manufactured by Sakai Chemical Industry Co., Ltd.) were used.

[Comparative Example 1]
A carrier was obtained in the same manner as in Example 1 except that 250 parts of tin oxide S2000 (manufactured by Mitsubishi Materials) and 200 parts of barium sulfate BF10 (manufactured by Sakai Chemical Industry Co., Ltd.) were used.

[Comparative Example 2]
A carrier was obtained in the same manner as in Example 1 except that 150 parts of tin oxide S2000 (manufactured by Mitsubishi Materials) and 100 parts of barium sulfate BF10 (manufactured by Sakai Chemical Industry Co., Ltd.) were used.

[Comparative Example 3]
A carrier was obtained in the same manner as in Example 1 except that 150 parts of tin oxide S2000 (manufactured by Mitsubishi Materials) and 300 parts of barium sulfate BF10 (manufactured by Sakai Chemical Industry Co., Ltd.) were used.
Hereinafter, evaluation methods of carrier characteristics and charging stability will be described.

[Specific resistance of conductive particles]
The specific resistance of the conductive particles was measured as follows. First, 5 g of conductive particles were put in a cylindrical vinyl chloride tube having an inner diameter of 1 inch (2.54 cm), and the upper and lower sides thereof were sandwiched between electrodes. Next, the resistance r [Ω] is measured using an LCR meter 4216A (manufactured by Yokogawa Hewlett-Packard Company) with a pressure of 10 kg / cm ² applied to these electrodes using a press. Formula (1)
Log [π (2.54 / 2) ² / H × r] Formula (1)
(In the formula, H is the distance [cm] between the electrodes when measuring resistance.)
From the above, the common logarithm value [Log (Ω · cm)] of the specific resistance was calculated.

[Volume average particle diameter of core particles]
The particle size distribution of the core particles was measured using a Microtrac particle size distribution model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.).

[Average film thickness of coating layer]
Using a transmission electron microscope (TEM), the cross section of the carrier was observed, and the average film thickness of the coating layer was measured.

[Volume resistivity]
The volume resistivity was measured using the cell shown in FIG. Specifically, first, a carrier 3 is filled in a cell composed of a fluororesin container 2 containing electrodes 1a and 1b having a surface area of 2.5 cm × 4 cm with a distance of 0.2 cm, and the drop height is set. Tapping was performed 10 times at 1 cm and a tapping speed of 30 times / minute. Next, a resistance value r [Ω] 30 seconds after applying a DC voltage of 1000 V between the electrodes 1a and 1b was measured using a high resistance meter 4329A (manufactured by Yokogawa Hewlett-Packard Company), and the following formula (2)
Log [r × (2.5 × 4) /0.2] Formula (2)
From the above, the common logarithmic value [Log (Ω · cm)] of the volume resistivity was calculated.

[Magnetization in a magnetic field of 1 kOe]
About 0.15 g of carrier is filled in a cell with an inner diameter of 2.4 mm and a height of 8.5 mm, and then magnetization is measured in a magnetic field of 1 kOe using VSM-P7-15 (manufactured by Toei Kogyo Co., Ltd.). did.

[Charging stability]
100 parts of polyester having a number average molecular weight of 3800, a weight average molecular weight of 20000, a glass transition point of 60 ° C. and a softening point of 122 ° C., 5 parts of an azo yellow pigment C.I. I. P. Y. 180 parts, 2 parts of zinc salicylate and 3 parts of carnauba wax having a melting point of 82 ° C. were mixed using a Henschel mixer and then melt-kneaded for 40 minutes at 120 ° C. using two rolls. Next, after cooling, it was coarsely pulverized using a hammer mill and finely pulverized using an air jet pulverizer. The obtained fine powder was classified to obtain base particles having a weight average particle diameter of 5 μm.

Next, 1 part of silica whose surface was hydrophobized and 1 part of titanium oxide prepared by a wet method were added to 100 parts of the base particles and mixed using a Henschel mixer to obtain a yellow toner.
Further, 93 parts of the carrier of Example or Comparative Example and 7 parts of toner were mixed and stirred for 5 minutes with a shaker mixer T10B (manufactured by Bachofen) to obtain a developer.

  The toner charge amount of the developer was measured with a blow-off device TB-200 (manufactured by Toshiba Chemical Corporation). Let this charge amount be Q1.

  After being left in an environment of 27 ° C. and 80% for 12 hours, the toner charge amount was measured with a blow-off device. Let this charge amount be Q2.

Set the developer to a modified machine of a digital full-color printer IPSiO CX 8200 (manufactured by Ricoh Company, Ltd.), to measure the charge amount Q3 of the carrier after 3000 sheets are continuously in charge amount _{Q 1} and the image area ratio of 20% of the initial carrier .

The running developer was left in an environment of 27 ° C. and 80% for 12 hours, and then the toner charge amount was measured with a blow-off device. Let this charge amount be Q4.
A charge amount of about -30 μC / g to 40 μC / g is particularly desirable in terms of quality. When the absolute value is reduced to 15 μC / g or less, problems such as background contamination and in-machine contamination due to toner scattering occur.
In addition, if the rate of decrease in charge amount upon standing is large, the charge amount variation tends to increase during re-stirring, and the image density variation tends to increase. It is preferable that the amount of fluctuation W1 = | (Q1-Q2) / Q1 | and W2 = | (Q3-Q4) / Q3 |
Tables 1 and 2 show the evaluation results of the carrier characteristics and charging stability of the examples and comparative examples.

From Tables 1 and 2, it can be seen that the carriers of Examples 1 to 8 do not have an absolute value of charge of 15 μC / g or less, and have sufficient charging ability even before and after use and in the environment. Further, since the amount of change in charge amount is small, it can be seen that the variation in image density will be small even when continuously used after being left.
On the other hand, the carriers of Comparative Examples 1 and 2 have a charge amount after standing of 15 μC / g or less, and if the prescription amount of barium sulfate is small with respect to the conductive particles, the carrier is charged after leaving at high temperature and high humidity after using the copy. It can be seen that the amount tends to decrease.
Further, the carrier of Comparative Example 3 has a charge amount decrease rate W1 of more than 0.5, and when the prescribed amount of barium sulfate exceeds 300% of the solid content of the resin,

58 parts by weight of acrylic resin (Hitaroid 3001: made by Hitachi Chemical Co., Ltd.) with a solid content of 50% by mass, 16 parts by weight of guanamine resin (My Coat 106: made by Mitsui Cytec Co., Ltd.) with 77% by mass, and 20% by mass of solid content 204 parts of silicone resin SR2410 (manufactured by Dow Corning Toray), 2.5 parts of aminosilane SH6020 (manufactured by Dow Corning Toray), oxygen-deficient tin oxide-coated barium sulfate particles “Pastran 4310” (manufactured by Mitsui Metals) as an inorganic additive ) 300 copies
The above coating layer raw materials were dispersed for 1 hour with a paint shaker together with 1000 parts of 1 mm Zr beads to obtain a coating solution for coating layer.

  Using a Spira coater (manufactured by Okada Seiko Co., Ltd.), the temperature in the coater was set to 40 ° C., and the coating layer coating solution was applied to 5000 parts of sintered ferrite powder having a weight average particle size of 35 μm and dried. Next, it was fired in an electric furnace at 300 ° C. for 1 hour, cooled, and then crushed using a sieve having an opening of 63 μm to obtain a carrier.

  The carrier was the same as in Example 9, except that 200 parts of “Pastran 4310” of Example 9 and 100 parts of conductive processed alumina “EC-700” (manufactured by Titanium Industry) were used as the inorganic additive. Got.

  Example 9 except that 100 parts of oxygen-deficient tin oxide S-2000 (manufactured by Mitsubishi Materials) and 100 parts of conductive processed alumina “EC-700” (manufactured by Titanium Industry) were used as the inorganic additive. Just got a career.

  The carrier was obtained in the same manner as in Example 9, except that 200 parts of “Pastlan 4310” in Example 9 and 100 parts of oxygen-deficient tin oxide S-2000 (manufactured by Mitsubishi Materials) were used as the inorganic additive. It was.

[Comparative Example 4]
In Example 9, a carrier was obtained in the same manner as in Example 9, except that the amount of “Pastran 4310” was 200 parts.

[Comparative Example 5]
In Example 9, a carrier was obtained in the same manner as in Example 9, except that the coating layer raw material was stirred with a homomixer for 10 minutes without using beads to obtain a coating layer coating solution.

[Comparative Example 6]
In Comparative Example 5, instead of “Pastran 4310”, 200 parts of oxygen-deficient tin oxide S2000 (manufactured by Mitsubishi Materials) and 100 of electrically conductive treated alumina “EC-700” (manufactured by Titanium Industry) were used as the inorganic additive. A carrier was obtained in the same manner as in Comparative Example 5 except that a part of the carrier was used.
The specific characteristics of the conductive particles, the volume resistivity, the charging stability, the magnetization in the magnetic field of 1 kOe, the characteristics of the carrier such as the charging stability, and the evaluation methods of the charging stability are the same as in Examples 1-8 and Comparative Examples 1-3. Measurements were made as in the case.
Further, the following remaining characteristics were measured.

[Weight average particle diameter of core particles]
The particle size distribution of the core particles was measured using a Microtrac particle size distribution model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.).

[Average film thickness of coating layer]
Using a transmission electron microscope (TEM), the cross section of the carrier was observed, and the average film thickness of the coating layer was measured.

Further, 93 parts of the carrier of Example or Comparative Example and 7 parts of toner were mixed and stirred to obtain a developer.
Set the developer to a modified machine of a digital full-color printer IPSiO CX 8200 (manufactured by Ricoh Company, Ltd.), measuring the charge amount _{Q 2} of the carrier after 3000 sheets are continuously in charge amount _{Q 1} and the image area ratio of 20% of the initial carrier did.

The charge amount of the initial carrier was measured using a blow-off device TB-200 (manufactured by Toshiba Chemical Co., Ltd.) for a sample in which the carrier and toner were mixed at a mass ratio of 93: 7 and frictionally charged. Further, the charge amount of the carrier after running was measured in the same manner as described above, except that the carrier from which the toner in the developer after running was removed using a blow-off device TB-200 (manufactured by Toshiba Chemical Co., Ltd.). did.
Charge at least, _{Q 1} also _{Q 2} also 20 [μC / g] or more.

[Exposed area of resin / Exposed area of additive]
Regarding the exposed area of the resin / the exposed area of the additive, the carrier from which the toner was removed after measuring the initial charge amount of the carrier was observed with a thermal field emission scanning electron microscope, and the carrier having a particle diameter of 10 μm or more. 30 are extracted at random, and a backscattered electron image of each carrier center is taken at a magnification of 10,000 times. In the reflected electronic image, the coat resin portion is dark and the filler portion used in the present invention is photographed brightly. The obtained image sample is introduced into image analysis software (for example, Photoshop C2 manufactured by Adobe Systems), and the black / white ratio after binarization based on an appropriate binarization standard is calculated by using the resin exposed area / additive exposure. The area.
Incidentally, the specific resistance measurement results of the powders used are shown in Table 3, and the measurement results for the carriers of Examples and Comparative Examples are shown in Table 4, respectively. In addition, as an example of taking a reflected electronic image, the example 9 is shown in FIG. 4, and the comparative example 4 is shown in FIG.

DESCRIPTION OF SYMBOLS 10 Process cartridge 11 Photoconductor 12 Charging apparatus 13 Developing apparatus 14 Cleaning apparatus (About FIG. 6)
10 Photosensitive member 28 Developer carrier 50 Inelastic regulating blade

JP-A-11-202560 JP 2006-39357 A JP-A-2-50184 Japanese Patent Laid-Open No. 2-8860 JP 49-51951 A JP-A-52-10141 JP-A-56-11461 JP 54-158932 A JP-A-57-168256 JP 59-228261 A JP-A-63-71860 Japanese Patent Laid-Open No. 2-110577 Japanese Patent Laid-Open No. 54-21730 JP 58-117555 A JP 59-232362 A JP-A-6-301245 JP 7-261465 A

Claims (17)

  A carrier in which a coating layer containing a binder resin and fine particles is formed on the surface of core material particles, the metal oxide conductive particles (I) and other metal oxide or metal salt in the coating layer Or a carrier containing both (II) and containing 100 wt% or more and 300 wt% or less of the metal oxide or metal salt or both (II).   The metal oxide or metal salt or both (II) contains barium sulfate, and the content thereof is 110% by weight or more and 300% by weight or less based on the binder resin. Career.   The carrier according to claim 2, comprising 100% by weight or more of barium sulfate based on the weight of the conductive particles.   The common logarithmic value of the specific resistance of the conductive particles (I) is 0.5 [Log (Ω · cm)] or more and 3 [Log (Ω · cm)] or less, according to claim 2 or 3 The listed carrier.   Surface exposure of an inorganic additive containing tin oxide as the conductive particles (I) and including all of the area (A) of the resin on the surface of the coating layer, tin oxide, and the metal oxide and metal salt (II) The carrier according to claim 1, wherein the ratio (A / B) of the area (B) occupied by the portion is 0.3 or less.   The metal oxide (II) is at least one selected from the group consisting of aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide and zirconium oxide, and the metal salt (II) is barium sulfate. The carrier according to claim 5.   The said tin oxide particle is 0.5 [Log (ohm * cm)] or more and 3 [Log (ohm * cm)] or less in the common logarithm value of a specific resistance, The Claim 5 or 6 characterized by the above-mentioned. Career.   The carrier according to claim 1, wherein a common logarithmic value of the volume resistivity is 10 [Log (Ω · cm)] or more and 14 [Log (Ω · cm)] or less.   The carrier according to any one of claims 1 to 8, wherein the core particles have a weight average particle diameter of 20 µm or more and 65 µm or less.   The carrier according to claim 1, wherein the coating layer has an average film thickness of 0.05 μm to 2 μm.   The carrier according to any one of claims 1 to 10, wherein the binder resin contains a silicone resin and / or an acrylic resin. The carrier according to any one of claims 1 to 11, wherein magnetization in a magnetic field of 1 kOe is 40 Am ² / kg or more and 90 Am ² / kg or less.   A developer comprising the carrier and the toner according to claim 1.   The developer according to claim 13, wherein the toner is a color toner.   A developer-containing container comprising the developer according to claim 13 or 14. Forming an electrostatic latent image on the electrostatic latent image carrier;
Developing the electrostatic latent image formed on the electrostatic latent image carrier using the developer according to claim 13 or 14 to form a toner image;
Transferring the toner image formed on the electrostatic latent image carrier to a recording medium;
And a step of fixing the toner image transferred to the recording medium.   The electrostatic latent image carrier and the means for developing the electrostatic latent image formed on the electrostatic latent image carrier using the developer according to claim 13 or 14 are at least integrally supported. Process cartridge characterized by.

Images