JP2009069566A - Electrostatic latent image developer carrier, developer and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier giving high image density, having favorable graininess and stable charge imparting ability for a long period of time and capable of suppressing carrier deposition, and to provide a developer using the carrier, and an image forming method, an image forming apparatus and a process cartridge using the developer. <P>SOLUTION: The carrier for electrostatic latent image development includes core particles having magnetism and a coating layer formed on the surface of the core particle, the coating layer containing at least silicone resin and hard particles, wherein the coating layer contains a dispersant that can disperse the hard particles. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a carrier preferably used for electrophotography, electrostatic recording method, electrostatic printing method, and the like, a developer using the carrier, an image forming method using the developer, an image forming apparatus, and a process cartridge. About.

The electrophotographic development system uses a so-called one-component development system consisting mainly of toner, a mixture of glass beads, a magnetic carrier or a coated carrier whose surface is coated with a resin and toner. There are two-component development systems.
The two-component development method is suitable for high-speed printing and is easy to handle non-magnetic toner, and thus is widely used in full-color printing apparatuses. However, the full-color printing apparatus needs to include a plurality of developing devices in the apparatus, and has disadvantages such as an increase in the size and weight of the apparatus as compared with a monochrome machine. In particular, the two-component developing device needs to have a developer storage volume and a stirring mechanism separately from the toner as compared with the one-component developing device. A small amount of is essential.
The carrier in the developer is repeatedly subjected to mechanical friction and impact in the developing device by friction with toner, a sliding friction member such as a sleeve and a blade, a regulating member, and a stirring and conveying member such as a screw and paddle. For this reason, when the amount of the developer is reduced, the friction between the toner and the carrier generated per print increases, the frequency of the carrier passing through the developing portion increases, and the carrier surface in the developing unit becomes contaminated (spent. ) Will progress rapidly.
In order to prevent such a carrier spent, the carrier core material surface is coated with a resin having a low surface energy, specifically, a fluororesin, a silicone resin or the like, thereby extending the life of the carrier. .

For example, a carrier in which the surface of the core particle is coated with two or more layers of silicone resin so that there is no adhesion between the layers (see Patent Document 1), and a carrier in which the core particle surface is sequentially coated with an elastic body and a silicone polymer ( There is known a carrier (see Patent Document 3) in which the surface of a magnetic core material is coated with a film containing a silicone resin, an aminosilane coupling agent and a fluorine-containing silane coupling agent.
However, in recent years, the toner tends to have a smaller particle size in order to improve the image quality, and carrier spent tends to occur. Further, in the case of a developer in which maintenance is facilitated by adding wax to the toner, the amount of contaminated carrier increases, resulting in a decrease in toner charge amount, toner scattering, and background contamination.
In addition, combined with higher printing speed, carrier durability, especially high wear resistance of the coating layer of the carrier, and quick charging over a long period of time while preventing carrier spent by toner and other members. Maintaining has become more important than ever.

JP-A-57-96355 Japanese Patent Publication No. 63-55702 JP 2003-280289 A

  An object of the present invention is to solve various problems in the prior art and achieve the following objects. That is, the present invention provides a carrier having a high image density, good graininess, stable charging ability over a long period of time, and capable of suppressing the occurrence of carrier adhesion, and a developer using the carrier. And an image forming method, an image forming apparatus, and a process cartridge using the developer.

Means for solving the problems are as follows.
(1) In the electrostatic latent image developing carrier comprising a core material particle having magnetism and a coating layer formed on the surface of the core material particle and containing at least a silicone resin and hard particles.
The electrostatic latent image developing carrier, wherein the coating layer contains a dispersant capable of dispersing the hard particles ",
(2) “The carrier for developing an electrostatic latent image according to (1) above, wherein the carrier has a weight average particle diameter of 22 to 32 μm”,
(3) "The electrostatic latent image developing carrier according to item (1) or (2), wherein the dispersant is a polymeric dispersant";
(4) The item (1), wherein the hard particles contain at least one of particles made of an oxide of Si, particles made of an oxide of Ti, and particles made of an oxide of Al. Thru | or the electrostatic latent image developing carrier according to any one of (3),
(5) The above-mentioned items (1) to (4), wherein the content of the hard particles in the coating layer is in the range of 10 to 70% with respect to 100% of the resin solid content weight of the coating layer. ) Carrier for electrostatic latent image development according to any one of items
(6) “The ratio of the weight average particle diameter Dw to the number average particle diameter Dp of the carrier, Dw / Dp is 1.0 <Dw / Dp <1.2,
Items (1) to (1) above, wherein the content of particles having a particle size smaller than 20 μm is 0 to 3% by weight, and the content of particles having a particle size smaller than 36 μm is 92 to 100% by weight. The carrier for developing an electrostatic latent image according to any one of (5) ",
(7) “The magnetization of the core particle when a 1000 oersted magnetic field is applied is 70 to 120 emu / g,” according to any one of the above items (1) to (6). Electrostatic latent image developing carrier ",
(8) The electrostatic latent image according to any one of items (1) to (7), wherein the core particles have a bulk density of 2.35 to 2.50 g / cm ^3. Image development carrier ",
(9) "The electrostatic latent image developing carrier according to any one of (1) to (8) above, wherein the coating layer contains an aminosilane coupling agent";
(10) "Developer comprising the carrier according to any one of (1) to (9) and a toner",
(11) “An electrostatic latent image forming step for forming an electrostatic latent image on a photoconductor, and developing the electrostatic latent image with the developer described in the item (10) to form a visible image. An image forming method comprising at least a developing step for forming, a transferring step for transferring the visible image to a recording medium, and a fixing step for fixing the transferred image transferred to the recording medium.
(12) “At least a photosensitive member and a developing unit that develops the electrostatic latent image formed on the photosensitive member using the developer described in the item (10) to form a visible image; A process cartridge that is detachable from the main body of the image forming apparatus ”.

  As is clear from the following detailed and specific description, according to the present invention, the image density is high, the graininess is good, the charging ability is stable over a long period of time, and the occurrence of carrier adhesion is suppressed. It is possible to provide a carrier capable of performing the above, a developer using the carrier, an image forming method using the developer, an image forming apparatus, and a process cartridge.

Next, the best mode for carrying out the present invention will be described with reference to the drawings.
Note that it is easy for a person skilled in the art to make other embodiments by changing or modifying the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims of the present invention.

The carrier of the present invention is an electrostatic latent image developing carrier comprising a core layer particle having magnetism and a coating layer containing at least a silicone resin and hard particles formed on the surface of the core particle, wherein the coating layer includes the hard particle It contains the dispersing agent which can disperse | distribute.
By including a dispersant capable of dispersing the hard particles, the hard particles can be favorably dispersed in the carrier coating layer coating solution, and the hard particles in the coating layer can be homogenized.
The dispersant can be used without limitation as long as it has a group having an affinity for hard particles and a group having an affinity for the resin contained in the carrier coating layer, but a polymer dispersant is particularly preferable. Used.
Examples of the polymeric dispersant include an affinity for adsorbing to the surface of hard particles such as a tertiary amino group, a quaternary ammonium group, a chlorine ring group having basic nitrogen, and a hydroxy group or a carboxyl group. A polymer compound containing three sites of a chain having a group and a chain having an affinity group compatible with the resin contained in the carrier coating layer is preferably used. Solsperse 2000, 2400, 2600, 2700, 2800 (manufactured by Zeneca), Adiper PB711, PA111, PB811, PW911 (manufactured by Ajinomoto Co.), EFKA-46, 47, 48, 49 (manufactured by EFKA Chemical), Disperbic 160, 162, 163, 166, 170, 180, 182, 184, 190 (Bic Chemie), Floren DOPA-158, 22, 17, G-700, TG-720W, 730W (manufactured by Kyoeisha Chemical Co., Ltd.) It is not limited to these. The content of such a “dispersing agent” is preferably 2% to 40% with respect to the weight of the hard particles. If it is less than 2%, the dispersion effect is small, and if it exceeds 40%, the charging characteristics may deteriorate.

  The carrier coating layer according to the present invention contains hard particles. This makes it possible to reinforce the coating layer. Among these, particles made of a metal oxide are preferably used because they have a high uniformity in particle diameter and a large reinforcing effect on the coating layer. The metal oxide is preferably a Si oxide, a Ti oxide or an Al oxide, and the hard particles can be used alone or in combination of two or more.

  The content of the hard particles in the coating layer is preferably in the range of 5 to 200% by weight, more preferably 10 to 70% by weight, based on the resin solid content weight (100%) of the coating layer weight. The content of the hard particles may be appropriately selected depending on the particle diameter and specific surface area, but if it is less than 5% by weight, the effect of improving the wear resistance of the coating layer may be difficult to be exhibited, and exceeds 200% by weight. In this case, the hard particles are likely to be detached, and the chargeability with time may be reduced.

  In the present invention, the silicone resin used when forming the coating layer has the general formula

で示される繰り返し単位の少なくとも一つを含有することが好ましい。ここで、Ｒ^１は水素原子、ハロゲン基、ヒドロキシル基、メトキシル基、炭素数１〜４の低級アルキル基又はアリール基（フェニル基、トリル基等）であり、Ｒ^２は、炭素数１〜４のアルキレン基又はアリーレン基（フェニレン基等）である。
アリール基の炭素数は、６〜２０であることが好ましく、６〜１４がさらに好ましい。アリール基としては、ベンゼン由来のアリール基（フェニル基）の他、ナフタレン、フェナントレン、アントラセン等の縮合多環式芳香族炭化水素由来のアリール基、ビフェニル、ターフェニル等の鎖状多環式芳香族炭化水素由来のアリール基等が包含される。なお、アリール基は、各種の置換基で置換されていてもよい。
アリーレン基の炭素数は、６〜２０であることが好ましく、６〜１４がさらに好ましい。アリーレン基としては、ベンゼン由来のアリーレン基（フェニレン基）の他、ナフタレン、フェナントレン、アントラセン等の縮合多環式芳香族炭化水素由来のアリーレン基、ビフェニル、ターフェニル等の鎖状多環式芳香族炭化水素由来のアリーレン基等が包含される。なお、アリーレン基は、各種の置換基で置換されていてもよい。

It preferably contains at least one repeating unit represented by Here, R ¹ is a hydrogen atom, a halogen group, a hydroxyl group, a methoxyl group, a lower alkyl group having 1 to 4 carbon atoms or an aryl group (phenyl group, tolyl group, etc.), and R ² is 1 to 4 carbon atoms. An alkylene group or an arylene group (such as a phenylene group).
The aryl group preferably has 6 to 20 carbon atoms, and more preferably 6 to 14 carbon atoms. As the aryl group, in addition to an aryl group derived from benzene (phenyl group), an aryl group derived from condensed polycyclic aromatic hydrocarbons such as naphthalene, phenanthrene and anthracene, and chain polycyclic aromatics such as biphenyl and terphenyl An aryl group derived from a hydrocarbon is included. The aryl group may be substituted with various substituents.
The carbon number of the arylene group is preferably 6-20, and more preferably 6-14. Arylene groups include benzene-derived arylene groups (phenylene groups), arylene groups derived from condensed polycyclic aromatic hydrocarbons such as naphthalene, phenanthrene, and anthracene, and chain polycyclic aromatics such as biphenyl and terphenyl. A hydrocarbon-derived arylene group and the like are included. The arylene group may be substituted with various substituents.

  In the present invention, a straight silicone resin can be used when forming the coating layer. Examples of the straight silicone resin include KR271, KR272, KR282, KR252, KR255, KR152 (manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400, SR2406, SR2411 (manufactured by Toray Dow Corning Silicone).

  In forming the coating layer, modified silicone resins such as epoxy-modified silicone resins, acrylic-modified silicone resins, phenol-modified silicone resins, urethane-modified silicone resins, polyester-modified silicone resins, and alkyd-modified silicone resins may be used. Examples of the epoxy-modified silicone resin include ES-1001N (manufactured by Shin-Etsu Chemical Co., Ltd.) and SR2115 (manufactured by Toray Dow Corning Silicone Co., Ltd.). Examples of the acrylic-modified silicone resin include KR-5208 (manufactured by Shin-Etsu Chemical Co., Ltd.). ), And the like. Examples of the polyester-modified silicone resin include KR-5203 (manufactured by Shin-Etsu Chemical Co., Ltd.). Examples of the alkyd-modified silicone resin include KR-206 (manufactured by Shin-Etsu Chemical Co., Ltd.), SR2110 (Toray Dow). Corning Silicone Co., Ltd.) and the like, and examples of the urethane-modified silicone resin include KR-305 (Shin-Etsu Chemical Co., Ltd.).

In the present invention, the coating layer includes, in addition to the silicone resin, polystyrene, polychlorostyrene, poly (α-methylstyrene), styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, Styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer) Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylic acid ester copolymer (styrene-methyl methacrylate copolymer, styrene- Ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer Styrene resins such as styrene-phenyl methacrylate copolymer, styrene-α-methyl chloroacrylate copolymer, styrene-acrylonitrile-acrylate ester copolymer, epoxy resin, polyester resin, polyethylene, polypropylene , Ionomer resin, polyurethane resin, ketone resin, acrylic resin, ethylene-ethyl acrylate copolymer, xylene resin, polyamide resin, phenol resin, polycarbonate resin, melamine resin, fluorine resin and the like may be contained. The amount of other silicone resins used is preferably less than 40% of the total resin.
As a method for forming the coating layer on the surface of the core particle, a known method such as a spray drying method, a dipping method, or a powder coating method can be used. In particular, the method using a fluidized bed type coating apparatus is effective for forming a uniform coating layer.

  The thickness of the coating layer on the surface of the core material particles is usually 0.02 to 1 μm, preferably 0.03 to 0.8 μm. Since the film thickness of the coating layer is extremely small compared with the particle diameter of the core particle, the particle diameter of the carrier having the coating layer formed on the surface and the particle of the core material is substantially the same.

  The weight average particle diameter Dw of the carrier of the present invention is preferably 22 to 32 μm, and more preferably 23 μm to 30 μm. When the weight average particle diameter Dw is larger than 32 μm, carrier adhesion hardly occurs, but the toner is not developed faithfully with respect to the latent image, and the variation in the dot diameter may increase and the graininess may decrease. In addition, when the toner concentration is increased, scumming may easily occur. The carrier adhesion indicates a phenomenon in which the carrier adheres to the image portion or the background portion of the electrostatic latent image. At this time, the stronger the applied electric field, the easier the carrier adhesion occurs. In the image area, the electric field is weakened by developing the toner, so that carrier adhesion is less likely to occur compared to the background area. Carrier adhesion is not preferable because it causes inconveniences such as damage to the photoreceptor and the fixing roller. On the other hand, if the ratio Dw / Dp of the number average particle diameter Dp and the weight average particle diameter Dw is larger than 1.20, the ratio of fine particles increases and carrier adhesion resistance may deteriorate.

In the carrier of the present invention, the content of particles having a particle size of 0.02 to 20 μm is preferably 7% by weight or less, more preferably 5% by weight or less, and particularly preferably 3% by weight or less. . When the content of the particles is more than 7% by weight, the particle size distribution is widened, and particles having a small magnetic moment are present in the magnetic brush, and carrier adhesion may occur. In addition, the content of the particles is preferably 0.5% by weight or more in order to improve productivity.
Furthermore, in the carrier of the present invention, the content of particles having a particle size of 0.02 to 36 μm is preferably 90% by weight or more, and more preferably 92% by weight or more. Thus, by narrowing the particle size distribution of the carrier whose surface is coated with resin, the distribution of the magnetic moment of each particle can be narrowed, and the occurrence of carrier adhesion can be greatly improved.
In the present invention, the number average particle size Dp and the weight average particle size Dw are calculated based on the particle size distribution (relationship between the number frequency and the particle size) of the particles measured on the basis of the number. It is represented by

ここで、Ｄは、各チャンネルに存在する粒子の代表粒径（μｍ）を示し、ｎは、各チャンネルに存在する粒子数である。なお、チャンネルは、粒径分布図における粒径の範囲を等分に分割するための長さであり、本発明においては、２μｍを採用することができる。また、各チャンネルに存在する粒子の代表粒径としては、各チャンネルの粒径の下限値を採用することができる。粒径分布を測定するための粒度分析計としては、マイクロトラック粒度分析計モデルＨＲＡ９３２０−Ｘ１００（Ｈｏｎｅｗｅｌｌ社製）を用いることができる。

Here, D indicates the representative particle size (μm) of the particles present in each channel, and n is the number of particles present in each channel. The channel is a length for equally dividing the particle size range in the particle size distribution diagram, and 2 μm can be adopted in the present invention. Moreover, the lower limit of the particle size of each channel can be adopted as the representative particle size of the particles present in each channel. As a particle size analyzer for measuring the particle size distribution, a microtrack particle size analyzer model HRA9320-X100 (manufactured by Honeywell) can be used.

In the present invention, crushed particles of a magnetic material can be used as the core material particles. In the case of core particles such as ferrite and magnetite, the primary granulated product before firing is classified, and the fired particles are classified into particle powders having different particle size distribution by classification treatment, and then a plurality of particles. It can be obtained by mixing powder.
As a method of classifying the core particles, known classification methods such as a sieving machine, a gravity classifier, a centrifugal classifier, an inertia classifier, etc. can be used, but productivity is good and the classification point can be easily changed. It is preferable to use an air classifier such as a gravity classifier, a centrifugal classifier, or an inertia classifier.

In the present invention, the magnetization of the core particles when a magnetic field of 1 kOe is applied is preferably 50 to 150 emu / g, and more preferably 70 to 100 emu / g. Thereby, generation | occurrence | production of carrier adhesion can be suppressed. If the magnetization of the core particles is less than 50 emu / g, carrier adhesion may easily occur.
The magnetization of the core particles can be measured as follows using a BH tracer BHU-60 (manufactured by Riken Denshi Co., Ltd.). Fill the cylindrical cell with 1g of core particles, set it in the device, gradually increase the magnetic field to 3kOe, then gradually decrease it to 0 and then gradually increase the opposite magnetic field. 3 kOe. Further, after gradually reducing the magnetic field to zero, the magnetic field is applied in the same direction as the first. In this way, a BH curve diagram is created, and 1 kOe magnetization is calculated from the diagram.
Examples of the core particles used in the present invention include ferromagnetic materials such as iron and cobalt, magnetite, hematite, Li-based ferrite, Mn-Zn-based ferrite, Cu-Zn-based ferrite, Ni-Zn-based ferrite, and Ba-based. Examples thereof include ferrite and Mn-based ferrite.
Ferrite is generally a general formula

で示される焼結体である。ここで、ｘ、ｙ及びｚは、フェライトの組成を表し、Ｍ及びＮとしては、それぞれ独立に、Ｎｉ、Ｃｕ、Ｚｎ、Ｌｉ_２、Ｍｇ、Ｍｎ、Ｓｒ、Ｃａ等が挙げられ、金属酸化物と酸化鉄（ＩＩＩ）との完全混合物から構成されている。

It is a sintered compact shown by. Here, x, y and z represent the composition of ferrite, and M and N are each independently exemplified by Ni, Cu, Zn, Li ₂ , Mg, Mn, Sr, Ca, etc., and metal oxides And a complete mixture of iron (III) oxide.

When the bulk density of the core material particles is small, even if the magnetization (emu / g) is large, the magnetic moment per particle is small, so that carrier adhesion is likely to occur. Factors that reduce the bulk density of the core material particles include the porous structure of the core material particles and the uneven structure of the surface. In addition, if the surface irregularities of the core particles are large, the film thickness distribution of the coating layer may increase, and the charge amount and electrical resistivity are likely to be non-uniform, affecting the carrier adhesion over time. Therefore, it is preferably 2.2 g / cm ³ or more, more preferably 2.35 g / cm ³ or more.
Examples of a method for increasing the bulk density of the core material particles include performing plasma treatment at the time of producing the core material particles and increasing the firing temperature. fused easily, it becomes difficult to crush, preferably to 3.0 g / cm ³ or less, and even more preferably to a 2.5 g / cm ³ or less.

The bulk density of the core particles can be measured as follows according to the metal powder-apparent density test method (JIS-Z-2504). The core particles are naturally allowed to flow out from an orifice having a diameter of 2.5 mm, and the core particles are poured into a 25 cm ³ stainless steel cylindrical container directly below it, and then the container is filled with a nonmagnetic horizontal spatula. Scrape flat along the top edge of the plate in one operation. When the core material particles are difficult to flow out of the orifice having a diameter of 2.5 mm, the core material particles are naturally discharged from the orifice having a diameter of 5 mm. By this operation, the weight of the core particles per cm ³ can be obtained by dividing the weight of the core particles flowing into the container by the volume of the container 25 cm ³ .

The volume resistivity of the carrier of the present invention in which a coating layer is formed on the surface of the core particle is preferably in the range of 1 × 10 ¹⁰ to 1 × 10 ¹⁶ Ω · cm, and in the range of 10 ¹¹ to 10 ¹⁴ Ω · cm. More preferred.
When the volume resistivity of the carrier is lower than 1 × 10 ¹⁰ Ω · cm, when the developing gap (the closest distance between the photosensitive member and the developing sleeve) becomes narrow, charge is induced in the carrier and carrier adhesion occurs. It becomes easy. When the linear velocity of the photosensitive member and the linear velocity of the developing sleeve are large, a tendency of deterioration is observed. In addition, it is remarkable when an AC bias is applied. Usually, a color toner developing carrier is generally used having a low resistance in order to obtain a sufficient toner adhesion amount. It has been found that a sufficient image density can be obtained by using a carrier having the above resistance range under an appropriate toner charge amount.
On the other hand, if the volume resistivity is larger than 1 × 10 ¹⁶ Ω · cm, charges having a polarity opposite to that of the toner are likely to be accumulated, and the carrier is easily charged to cause carrier adhesion.

The volume resistivity of the carrier can be measured by the following method.
As shown in FIG. 1, a cell (101) made of a fluororesin container containing electrodes (102a) and (102b) having a distance between electrodes of 2 mm and a surface area of 2 × 4 cm is filled with a carrier (103), A DC voltage of 1000 V is applied, the DC resistance is measured with a high resistance meter 4329A (4329A + LJK 5HVLVWDQFH OHWHU; manufactured by Yokogawa Hewlett-Packard Co., Ltd.), and the volume resistivity R (Ω · cm) is calculated.
After filling the cell until it overflows into the cell, tapping the entire cell 20 times and then using a horizontal spatula made of non-magnetic top surface of the cell along the top edge of the cell. Scrape flat in one operation.
The volume resistivity of the carrier can be adjusted by adjusting the resistance of the coating layer on the core particles and controlling the thickness of the coating layer.

In the present invention, the coating layer preferably further contains an aminosilane coupling agent. Thereby, a carrier with good durability can be obtained. Examples of the aminosilane coupling agent include the following.
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 NHCH 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
In addition, it is preferable that content of the aminosilane coupling agent in a coating layer is 0.001 to 30 weight%.

The developer of the present invention contains the carrier and toner of the present invention as main components, and in addition, a lubricant derived from the toner such as wax described later, a release agent such as silicon and fluorine-based material, and inorganic fine particles. It may contain a fluidity improver.
As the toner, various known toners containing a binder resin mainly composed of a thermoplastic resin, a colorant, fine particles, a charge control agent, a release agent and the like can be used. The toner can be manufactured using a manufacturing method such as a polymerization method or a granulation method, and an amorphous or spherical toner is obtained. Either magnetic toner or non-magnetic toner can be used.
As binder resin, styrene such as polystyrene and polyvinyltoluene, and homopolymers thereof, styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-acrylic acid Methyl copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, Styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer , Styrene-maleic acid copolymerization , Styrene-maleic acid ester copolymer, polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified Examples thereof include rosin, terpene resin, phenol resin, aliphatic or aliphatic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, and paraffin wax. In addition, these can be used individually or in mixture of 2 or more types.
The polyester resin can lower the melt viscosity while ensuring the stability during storage of the toner, as compared with the styrene resin or the acrylic resin. The polyester resin can be obtained, for example, by a polycondensation reaction between an alcohol component and a carboxylic acid component.
Examples of the alcohol component include polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-propylene glycol, neopentyl glycol, and diols such as 1,4-butenediol, Etherified bisphenols such as 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A, etc., which are saturated or unsaturated with 3 to 22 carbon atoms. Divalent alcohol units substituted with saturated hydrocarbon groups, other divalent alcohol units, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaesitol, dipentaerythritol , Tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, Trivalent or higher alcohol monomers such as trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene and the like can be mentioned.
Carboxylic acid components include monocarboxylic acids such as palmitic acid, stearic acid, oleic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid , Divalent organic acid monomers in which they are substituted with a saturated or unsaturated hydrocarbon group having 3 to 22 carbon atoms, anhydrides of these acids, lower alkyl esters, and dimer acids from linolenic acid, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 3,3-dicarboxymethylbutanoic acid, tetracarboxymethylmethane, 1,2,7,8 Octane tetracarboxylic acid Enboru trimer acid, a trivalent or higher polycarboxylic acid monomers anhydrides of these acids and the like.
As the epoxy resin, a polycondensate of bisphenol A and epichlorohydrin can be used, and specifically, Epomic R362, R364, R365, R366, R367, R369 (Mitsui Petrochemical Industries, Ltd.) , Epototo YD-011, YD-012, YD-014, YD-904, YD-017 (above, manufactured by Tohto Kasei Co., Ltd.), Epocoat 1002, 1004, 1007 (above, manufactured by Shell Chemical Co., Ltd.) Can be mentioned.
Colorants include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, Hansa Yellow G, rhodamine 6G lake, calco oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallyl. Known dyes and pigments such as methane dyes, monoazo dyes and pigments, disazo dyes and pigments can be used singly or as a mixture of two or more.
The magnetic toner contains a magnetic material. Examples of the magnetic material include ferromagnetic materials such as iron and cobalt, magnetite, hematite, Li-based ferrite, Mn-Zn-based ferrite, Cu-Zn-based ferrite, and Ni-Zn-based ferrite. Fine powders such as Ba-based ferrite can be used.

To control the triboelectric chargeability, the toner is composed of a metal complex salt of monoazo dye, nitrohumic acid and its salt, salicylic acid, naphthoic salt, dicarboxylic acid such as Co, Cr, Fe, etc. You may contain charge control agents, such as dye.
Further, the toner may contain a release agent as necessary. As the mold release agent, low molecular weight polypropylene, low molecular weight polyethylene, carnauba wax, microcrystalline wax, jojoba wax, rice wax, montanic acid wax and the like can be used alone or in combination.
The toner may contain other additives. In order to obtain a good image, it is preferable to impart fluidity to the toner. For this purpose, it is generally effective to add hydrophobized metal oxide particles and lubricant particles as fluidity improvers, and metal oxide, resin, metal soap and other particles as additives. Can be used. Specific examples of additives include fluororesins such as polytetrafluoroethylene, lubricants such as zinc stearate, abrasives such as cerium oxide and silicon carbide, inorganic oxides such as SiO ₂ and TiO ₂ having a hydrophobic surface, etc. Fluidity-imparting agents, known anti-caking agents and surface treated products thereof. In order to improve the fluidity of the toner, hydrophobic silica is particularly preferably used.
The weight average particle diameter of the toner is preferably 3.0 to 9.0 μm, and more preferably 3.5 to 7.5 μm. The particle size of the toner can be measured using a Coulter counter (manufactured by Coulter Counter).

  The image forming method of the present invention comprises a developing step of developing an electrostatic latent image formed on the surface of a photoreceptor with the developer of the present invention, and a transferring step of transferring the image developed on the photoreceptor to an image recording medium. And a cleaning step for cleaning the developer remaining on the surface of the photoconductor after the transfer.

The process cartridge of the present invention at least integrally supports a photoconductor and a developing device that develops the electrostatic latent image formed on the surface of the photoconductor with the developer of the present invention, and is detachable from the image forming apparatus main body. In addition to the above, the process cartridge further integrally supports a charging device such as a charging brush for charging the surface of the photoreceptor and a cleaning device such as a blade for wiping off the developer remaining on the surface of the photoreceptor. Also good.
FIG. 2 shows an example of the process cartridge of the present invention. This process cartridge is formed by integrally coupling a photoconductor (35), a charging device (34), a developing device (30), and a cleaning device (37) to a case (32), and image forming such as a copying machine and a printer. It is configured to be detachable from the apparatus main body. At this time, in the developing device, development is performed using the developer of the present invention.

  Hereinafter, the present invention will be specifically described by way of examples. In addition, this invention is not limited to the Example illustrated here. However, a part represents a weight part.

Example 1
A mixture containing Fe ₂ O ₃ , CuO, and ZnO in the following quantitative ratio was pulverized using a wet ball mill so that the particle size of the pulverized product was 1 μm or less. Polyvinyl alcohol was added to the pulverized product thus obtained, and then granulated by a spray dryer. After this granulated material was baked in an electric furnace, it was crushed and classified, and the particle size was adjusted to obtain [Core 1]. When component analysis of this [core material 1] was performed, it was confirmed that Fe ₂ O ₃ was 46 mol%, CuO was 27 mol%, and ZnO was 27 mol%.
Next, with respect to the silicone resin (SR2411, manufactured by Toray Dow Corning Silicone), alumina particles having an average particle size of 0.3 μm and a polymer dispersant (Floren G-700, manufactured by Kyoeisha Chemical Co., Ltd.) The liquids prepared so as to be 40% by weight and 5% by weight, respectively, were dispersed for 30 minutes using a homogenizer. The obtained dispersion is diluted so that the solid content becomes 10% by mass.

で表されるアミノシランカップリング剤をシリコーン樹脂の固形分に対して３質量％添加して混合し、被覆層塗布液を得た。
次に、芯材１に対して被覆層塗布液を、流動床型コーティング装置を用いて、１００℃の雰囲気下で、５０ｇ／分の割合で塗布した。更に、２５０℃で２時間加熱して、表１に示す特性を有する、平均被覆層厚みが０．６μｍの［キャリア１］を作製した。

Was added and mixed with the solid content of the silicone resin to obtain a coating layer coating solution.
Next, the coating layer coating solution was applied to the core material 1 at a rate of 50 g / min in an atmosphere at 100 ° C. using a fluid bed type coating apparatus. Furthermore, it heated at 250 degreeC for 2 hours, and produced the [carrier 1] which has the characteristic shown in Table 1 and whose average coating layer thickness is 0.6 micrometer.

(Manufacture of toner)
100 parts of a polyester resin, 3.5 parts of a quinacridone-based magenta pigment and 4 parts of a fluorine-containing quaternary ammonium salt were sufficiently mixed with a blender, and then melt-kneaded with a twin-screw extruder and allowed to cool. Next, coarsely pulverized with a cutter mill, finely pulverized with a jet airflow fine pulverizer, and further classified with an air classifier to obtain toner base particles having a weight average particle diameter of 6.8 μm and a true specific gravity of 1.20. It was.
Further, 0.8 part of hydrophobic silica particles R972 (manufactured by Nippon Aerosil Co., Ltd.) was added to 100 parts of toner base particles, and mixed with a Henschel mixer to obtain a toner.
To 100 parts of [Carrier 1], 8 parts of toner prepared in the manufacture of toner was added and stirred for 20 minutes with a ball mill to prepare a developer.

Comparative Example 1
[Carrier 2] was produced in exactly the same manner as in [Carrier 1] in Example 1, except that no polymer dispersant was added.
A developer was prepared in the same manner as in Example 1 except that [Carrier 2] was used instead of [Carrier 1] in Example 1.

Example 2
In the production of [Carrier 1] of Example 1, the [Character 1] having the characteristics shown in Table 1 was obtained in the same manner as in the production of [Carrier 1], except that [Core 2] with different classification and particle size adjustment conditions was used. [Carrier 3] having an average coating layer thickness of 0.6 μm was produced.
A developer was prepared in the same manner as in Example 1 except that [Carrier 3] was used instead of [Carrier 1] in Example 1.

Example 3
[Carrier 4] was produced in the same manner as in [Carrier 1] in Example 1, except that silica having a particle diameter of 0.03 μm was added instead of alumina particles having an average particle diameter of 0.3 μm.
A developer was prepared in the same manner as in Example 1 except that [Carrier 4] was used instead of [Carrier 1] in Example 1.

Example 4
[Carrier 5] was produced in the same manner as in [Carrier 1] in Example 1, except that titanium oxide having a particle diameter of 0.03 μm was added instead of alumina particles having an average particle diameter of 0.3 μm.
A developer was prepared in the same manner as in Example 1 except that [Carrier 5] was used instead of [Carrier 1] in Example 1.

Example 5
In the production of [Carrier 1] of Example 1, 5 wt.% Each of alumina particles having an average particle diameter of 0.3 μm and a polymer dispersant (Floren G-700, manufactured by Kyoeisha Chemical Co., Ltd.) with respect to the solid content of the silicone resin. [Carrier 6] was prepared in exactly the same manner except that the amount was 1% by weight and 1% by weight.
A developer was prepared in the same manner as in Example 1 except that [Carrier 6] was used instead of [Carrier 1] in Example 1.

Example 6
In the production of [Carrier 1] in Example 1, 20 wt.% Each of alumina particles having an average particle size of 0.3 μm and a polymer dispersant (Floren G-700, manufactured by Kyoeisha Chemical Co., Ltd.) with respect to the solid content of the silicone resin [Carrier 7] was produced in exactly the same manner except that the content was adjusted to be 2.5% and 2.5% by weight.
A developer was prepared in the same manner as in Example 1 except that [Carrier 7] was used instead of [Carrier 1] in Example 1.

Example 7
In the production of [Carrier 1] of Example 1, 60 wt.% Each of alumina particles having an average particle diameter of 0.3 μm and a polymer dispersant (Floren G-700, manufactured by Kyoeisha Chemical Co., Ltd.) with respect to the solid content of the silicone resin [Carrier 8] was produced in exactly the same manner except that it was adjusted to be 7.5% and 7.5% by weight.
A developer was prepared in the same manner as in Example 1 except that [Carrier 8] was used instead of [Carrier 1] in Example 1.

Example 8
In the production of [Carrier 1] of Example 1, 100 weights each of alumina particles having an average particle diameter of 0.3 μm and a polymer dispersant (Floren G-700, manufactured by Kyoeisha Chemical Co., Ltd.) with respect to the solid content of the silicone resin were used. [Carrier 9] was produced in exactly the same manner except that it was adjusted to be 7.5% and 7.5% by weight.
A developer was prepared in the same manner as in Example 1 except that [Carrier 9] was used instead of [Carrier 1] in Example 1.

Example 9
In the production of [Carrier 1] of Example 1, the [Character 1] having the characteristics shown in Table 1 was produced in the same manner as in the production of [Carrier 1], except that [Core material 3] with different classification and particle size adjustment conditions was used. [Carrier 10] having an average coating layer thickness of 0.6 μm was produced.
A developer was prepared in the same manner as in Example 1 except that [Carrier 10] was used instead of [Carrier 1] in Example 1.

Example 10
Fe ₂ O ₃ was pulverized using a wet ball mill so that the particle size of the pulverized product was 1 μm or less. Polyvinyl alcohol was added to the pulverized product thus obtained, and granulated by a spray dryer. This granulated material was fired in an electric furnace, and then crushed, classified, and adjusted in particle size to obtain [Core 4]. A coating layer was provided on [Core 4] in the same manner as in Example 1, and [Carrier 11] having the characteristics shown in Table 1 and an average coating layer thickness of 0.6 μm was produced.
A developer was prepared in the same manner as in Example 1 except that [Carrier 11] was used instead of [Carrier 1] in Example 1.

(Developer evaluation)
An image was formed using the developer described above, and the image quality was evaluated. In forming an image, a digital color copier / printer combined machine Imagio Color 5000 (manufactured by Ricoh) was used.
The adopted evaluation method is as follows.
(1) Granularity Granularity (brightness range: 50 to 80) defined by the following formula was measured, and the numerical values were: ◎ (very good): 0 or more and less than 0.1, ○ (good): 0.1 More than 0.2, Δ (usable): 0.2 or more and less than 0.3, × (unusable): evaluated by replacing with a rank of 0.3 or more.

Ｌ：平均明度
ｆ：空間周波数（ｃｙｃｌｅ／ｍｍ）
ＷＳ（ｆ）：明度変動のパワースペクトラム
ＶＴＦ（ｆ）：視覚の空間周波数特性
ａ、ｂ：係数
（２）地汚れ
画像上の地肌部の汚れを目視で評価し、◎：大変良好、○：良好、△：使用可能、×：不良（許容不可のレベル）として、判定した。
（３）キャリア付着
キャリア付着が発生しても一部のキャリアしか紙に転写してこないため、感光体上から粘着テープで転写して評価した。具体的には、帯電電位（Ｖｄ）を−７５０Ｖ、現像バイアス（Ｖｂ）をＤＣ−４００Ｖに固定し、地肌部（未露光部）を現像し、感光体上の３０ｃｍ^２に付着したキャリアの個数を直接カウントしてキャリア付着の評価を行い、◎：大変良好、○：良好、△：使用可能、×：不良（許容不可のレベル）として、判定した。
（４）１万枚ラン後のキャリア付着
トナーを補給しながら画像面積率６％の文字画像チャートで１万枚の通紙ランニングを行い、（３）と同じ方法でキャリア付着を評価した。
評価結果を表２に示す。

L: Average brightness f: Spatial frequency (cycle / mm)
WS (f): power spectrum of lightness fluctuation VTF (f): visual spatial frequency characteristics a, b: coefficient (2) background stain The stain on the background of the image is visually evaluated, ◎: very good, ○: It was judged as good, Δ: usable, ×: bad (unacceptable level).
(3) Carrier adhesion Since only a part of the carrier is transferred to the paper even if the carrier adhesion occurs, it was evaluated by transferring it from the photosensitive member with an adhesive tape. Specifically, the number of carriers adhering to 30 cm ² on the photosensitive member, with the charging potential (Vd) fixed at −750 V, the developing bias (Vb) fixed at DC-400 V, the background portion (unexposed portion) developed. Was directly counted and evaluated for carrier adhesion, and judged as ◎: very good, ◯: good, △: usable, ×: defective (unacceptable level).
(4) Carrier Adhesion after Run of 10,000 Sheets 10,000 sheets were run on a character image chart with an image area ratio of 6% while supplying toner, and the carrier adhesion was evaluated by the same method as (3).
The evaluation results are shown in Table 2.

It is a perspective view of the resistance measurement cell used for the measurement of the resistivity of a carrier. It is the figure which showed an example of the process cartridge of this invention.

Explanation of symbols

21 Cell 22a Electrode 22b Electrode 23 Carrier 30 Developing device 32 Case 34 Charging device 35 Photoconductor 37 Cleaning device

Claims (12)

In an electrostatic latent image developing carrier comprising magnetic core material particles and a coating layer formed on the surface of the core material particles and including at least a silicone resin and hard particles,
The carrier for electrostatic latent image development, wherein the coating layer contains a dispersant capable of dispersing the hard particles.   The carrier for developing an electrostatic latent image according to claim 1, wherein the carrier has a weight average particle diameter of 22 to 32 μm.   3. The electrostatic latent image developing carrier according to claim 1, wherein the dispersant is a polymer-based dispersant.   The hard particle contains at least one of particles made of Si oxide, particles made of Ti oxide, and particles made of Al oxide. Carrier for electrostatic latent image development.   5. The electrostatic latent image according to claim 1, wherein the content of hard particles in the coating layer is in the range of 10 to 70% with respect to 100% of the resin solid content weight of the coating layer. Image development carrier. The ratio of the weight average particle diameter Dw to the number average particle diameter Dp of the carrier, Dw / Dp, is 1.0 <Dw / Dp <1. 2
6. The content of particles having a particle size of less than 20 μm is 0 to 3% by weight, and the content of particles having a particle size of less than 36 μm is 92 to 100% by weight. The carrier for developing an electrostatic latent image described in 1.   7. The electrostatic latent image developing carrier according to claim 1, wherein the core particles have a magnetization of 70 to 120 emu / g when a magnetic field of 1000 oersted is applied. 8. The electrostatic latent image developing carrier according to claim 1, wherein the core particles have a bulk density of 2.35 to 2.50 g / cm ³ .   9. The electrostatic latent image developing carrier according to claim 1, wherein the coating layer contains an aminosilane coupling agent.   A developer comprising the carrier according to claim 1 and a toner.   An electrostatic latent image forming step of forming an electrostatic latent image on a photoreceptor, a developing step of developing the electrostatic latent image using the developer according to claim 10 to form a visible image, and An image forming method comprising at least a transfer step of transferring a visible image to a recording medium and a fixing step of fixing the transferred image transferred to the recording medium.   It has at least developing means for developing a latent image formed on the photosensitive member using the developer according to claim 10 to form a visible image, and is detachable from the main body of the image forming apparatus. Process cartridge characterized by being.

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