JP2007206481A - Carrier for electrophotography, two-component developer, and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier for electrophotography, having an image carrier of an amorphous silicon photoreceptor of which volume resistivity of its surface layer is 10<SP>9</SP>-10<SP>14</SP>Ω cm, and which is superior in developability, even when development is carried out under the alternation electric field, and can suppress the leakage of charge and the adhesion of carrier to the photoreceptor. <P>SOLUTION: The carrier for electrophotography is comprises formed of a first resin coating layer composed of a nitrogen-containing resin and a second resin coating layer, containing conductive particles on the first resin coating layer on magnetic carrier core particles containing binder resin and magnetic particles. The magnetic carrier core particles contain 70-95% by mass of magnetic particles. The carrier for electrophotography is such that (1) the magnetization strength in 79.6 kA/m is 40-70 Am<SP>2</SP>/kg, and (2) the volume resistance (R1), when 5×10<SP>5</SP>V/m is applied is in the range of 1.0×10<SP>10</SP>-1.0×10<SP>13</SP>Ω cm, and the volume resistance (R2), when 2×10<SP>5</SP>V/m is applied is in the range of 1.0×10<SP>13</SP>-1.0×10<SP>16</SP>Ω cm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic carrier that can be used in a wide range of output devices such as a copying machine, a printer, a facsimile, and a light printing system using an image forming method such as electrophotography and electrostatic recording. The present invention relates to a component developer and an image forming method.

  In electrophotography, an electrostatic latent image formed on a latent image carrier is developed with toner, and then transferred and fixed on transfer paper. As a developing method in this case, currently, a two-component developing method using a two-component developer using a two-component developer composed of a toner and a magnetic carrier as a developer, or a one-component developer not using a magnetic carrier. There is known a one-component development system using In the case of a full-color copying machine or printer that requires higher image quality, a two-component development system is preferably used.

  As magnetic carriers used in the two-component developer system, iron powder carriers, ferrite carriers, and magnetic material dispersion type carriers are conventionally known.

In iron powder carrier, the specific gravity is of the order of 7-8, for bulk density as high as ^{3g / cm 3 ~4g / cm 3} , require a large driving force in order to stir in the developing machine, the machine The toner tends to be worn out, and the toner tends to become spent, the chargeability of the carrier itself deteriorates and the photoreceptor is easily damaged. In addition, since the volume resistivity is relatively low at 10 ⁶ Ωcm or less, carriers are attached to the image portion of the photosensitive member by charge injection from the sleeve, or latent image charges escape through the carriers and the latent image is disturbed. There are problems such as image loss.

  Even when a ferrite carrier having a relatively high volume resistance is used, particularly in a developing method in which an alternating electric field is applied, there may be a case where charge leakage of an electrostatic charge image through the ferrite carrier cannot be prevented. Since these have a large saturation magnetization, the magnetic brush becomes stiff, and the toner image may have a magnetic brush sweep.

  In order to solve such a problem, a magnetic material-dispersed resin carrier in which magnetic fine particles are dispersed in a binder resin has been proposed. The magnetic material dispersion type resin carrier has a relatively high volume resistance, a small saturation magnetization, and a small true specific gravity compared to the ferrite carrier, so that the magnetic brush by the carrier does not become stiff, and a good toner image without sweeping. Can be formed.

  Specifically, a binder type carrier in which the carrier surface is coated with a resin to increase the electric resistance of the carrier has been proposed (Patent Documents 1 and 2).

However, since these resins are insulators, the electric resistance of the carrier itself is likely to be higher than 10 ¹⁵ Ωcm, the carrier charge is difficult to leak, and the charge amount of the toner is also increased, resulting in an image obtained as a result. Although an image with an edge is effective, on the other hand, there is a problem that the image density in the central portion becomes very thin on a large area image surface.

For these reasons, although a relatively high electric resistance value is required as a carrier, an electric resistance value that is too high tends to cause problems in image formation. Specifically, the volume resistivity value is 10 ⁹ to 10 ¹² Ωcm. A degree is required.

  On the other hand, in the conventional two-component developer, a part of the toner is physically attached to the surface of the magnetic carrier due to mechanical collision such as collision between particles and collision between the particle and the developer, or heat generated by these collisions. As a result, so-called “spenting” may occur.

  In such a situation, a film due to the toner component gradually accumulates on the surface of the magnetic carrier, and the frictional charge between the toner and the magnetic carrier is replaced with the frictional charge between the toners. As a result, the triboelectric charge characteristic deteriorates, and as a result, a so-called “background stain” phenomenon occurs in which a large amount of toner adheres to the background portion of the copy image, resulting in a decrease in copy quality.

  Further, when the toner component film is formed on the surface of the magnetic carrier, the entire developer has to be replaced, resulting in an increase in cost.

  On the other hand, the above-mentioned magnetic material dispersion type resin carrier has a small saturation magnetization and a small true specific gravity, which is advantageous for such a spent state. There is also an advantage that can be lightened.

  Furthermore, the magnetic material-dispersed resin carrier has excellent fluidity because it is relatively easy to form a spherical shape with little particle distortion and high particle strength. Furthermore, since the particle size can be controlled over a wide range, it is expected to be applied to a high-speed copying machine or a high-speed laser beam printer.

  However, magnetic dispersion resin carriers, when trying to cope with higher speeds such as high-speed copying machines and high-speed laser beam printers, cause the carrier to adhere to the photoconductor because of its low magnetic force, thus disturbing image quality. I had to do it.

  In addition, in the magnetic material dispersion type resin carrier, magnetite is often used as a magnetic material from the viewpoint of versatility and cost. However, if the magnetite content is increased in order to increase the magnetic force, the resistance is reduced. Since low magnetite tends to exist on the surface of the carrier particles, the resistance value necessary for obtaining good image quality may not be obtained.

  In view of the above, it can be seen that it is important to provide a stable developer without deteriorating the image quality because the magnetic dispersion resin carrier has high development characteristics.

  On the other hand, with the progress of color shift of output devices as mentioned above, the demand for higher image quality, higher speed, and higher stability of output images has further increased, and in the future the light printing market for copiers and various printers The advance to is expected.

  In order to break into the printing market with the electrophotographic method generally used in copying machines and various printers, high image quality and high stability are the minimum issues. Conventionally, selenium-based photoconductors, amorphous silicon photoconductors, organic photoconductors, etc. have been put to practical use as photoconductors used in the electrophotographic process. Among them, amorphous silicon photoconductors are particularly excellent in image quality and durability. It is known to have

Japanese Patent Laid-Open No. 47-13554 JP-A-54-660

However, when an amorphous silicon drum is used as the photosensitive drum, the volume resistivity of the surface layer of the photosensitive member is 10 ⁹ to 10 ¹⁴ Ω · cm, so that fog occurs in the image and the output image density is low. It was not obtained. The fogging and the reduction in image density were developed under an alternating electric field using a two-component developer on a photosensitive drum having a surface layer volume resistivity of 10 ⁹ to 10 ¹⁴ Ω · cm as described later. It was found to occur. Various studies were conducted on the above-described fogging and the phenomenon in which the image density was lowered. As a result, it has been found that these phenomena occur when charges are injected from a magnetic carrier during development on a photosensitive drum having a surface layer volume resistivity of about 10 ⁹ to 10 ¹⁴ Ω · cm.

For a photosensitive drum having a surface layer with a volume resistivity of about 10 ⁹ to 10 ¹⁴ Ω · cm, particles such as ferrite with a volume resistivity of 10 ¹⁰ Ω · cm or less (preferably a particle size of about 100 μm or less, preferably 15 The photosensitive drum can be charged by carrying a developing bias while carrying the magnetic particles (˜50 μm) on a charging sleeve containing a magnet and sliding on the photosensitive drum adjusted to the above-mentioned surface resistivity. . Such a charging method is called an injection charging method, and the same thing as this injection charging is the development using a magnetic carrier having a volume resistivity of about 10 ⁶ to 10 ¹⁰ Ω · cm. It has been found that this also occurs when two-component development in contact with the drum is performed.

  Furthermore, in injection charging, it has also been confirmed that charging efficiency is improved when an alternating electric field having a frequency of 100 to 6000 Hz, preferably 500 to 2000 Hz is superimposed. For this reason, also in the development method shown in the conventional example, the two-component development using the magnetic carrier, which was adopted for improving the development efficiency and the image quality, was added, and the alternating electric field having a frequency of 2000 Hz applied in the conventional example was superimposed. It is considered that the same thing occurred during development due to the development bias.

That is, a photosensitive drum in which the volume resistivity of the surface layer for injection charging is adjusted to about 10 ⁹ to 10 ¹⁴ Ω · cm and a magnetic carrier having a volume resistivity of about 10 ⁶ to 10 ¹⁰ Ω · cm are used. When reversal development is performed by superimposing an alternating electric field having a frequency of about 100 to 6000 Hz on the component developer, charge is injected from the magnetic carrier for development to the photosensitive drum in the developing unit, and thus the white background portion (photosensitive portion) The portion where the drum is uniformly charged and not exposed) and the black portion (the portion where the photosensitive drum is uniformly charged and then exposed) appear to converge to the DC component of the voltage applied to the developing sleeve. become. For this reason, it has been found that the potential difference between the white background portion and the developing sleeve decreases, fogging occurs, and the potential difference between the black character portion and the developing sleeve also decreases, resulting in a decrease in image density.

  In the above description of the conventional example, only the reversal development method has been described as the development method. However, such a problem is not unique to the reversal development method, and may occur in the same manner when the regular development method is used. It became clear by research of the present inventors.

Therefore, an object of the present invention is to develop an image carrier having an image carrier whose surface layer has a volume resistivity adjusted to about 10 ⁹ to 10 ¹⁴ Ω · cm, such as an amorphous silicon drum, under an alternating electric field. In particular, an object of the present invention is to provide an electrophotographic carrier that has excellent developability, can prevent charge leakage, and can suppress carrier adhesion to a photoreceptor. It is another object of the present invention to provide a two-component developer using the same and an image forming method capable of forming a good image without causing fogging and a decrease in image density.

  The above object can be achieved by the following configuration of the present invention.

The present invention provides a magnetic carrier core particle containing at least a binder resin and magnetic particles, a first resin coating layer made of a nitrogen-containing resin, and a second resin coating containing conductive particles on the first resin coating layer. An electrophotographic carrier comprising a layer, wherein the magnetic carrier core particles contain 70 to 95% by mass of magnetic particles,
The electrophotographic carrier is
1) The magnetization intensity (M) at 79.6 kA / m is 40 to 70 Am ² / kg,
2) Volume resistance (R1) at the time of application of 5 × 10 ⁵ V / m is 1.0 × 10 ^{10 to} 1.0 × 1
0 ¹³ Ωcm,
Volume resistance (R2) at the time of 2 * 10 < ⁵ > V / m application is 1.0 * 10 < ¹³ > -1.0 * 1
0 ¹⁶ Ωcm
It is an object of the present invention to provide an electrophotographic carrier characterized by being in the range described above.

  In the present invention, the carrier is characterized in that the nitrogen-containing resin is a melamine resin, and the conductive fine particles contained in the second resin coating layer are carbon black. The present invention provides a two-component developer constituted, and further provides an image forming method for visualizing a latent image formed on an amorphous silicon drum using the two-component developer. .

  That is, the present invention uses a photosensitive drum having a high charge capacity, such as an amorphous silicon drum, as a photosensitive drum for high image quality and high stability. It is summarized that a high-quality image without fog is obtained by using a developer.

  For this reason, the volume resistance value of the magnetic carrier in the present invention is not so high. Using a high-resistance carrier can suppress fogging and thinning due to charge injection that occurs in the developing section, but on the other hand, there is no counter electrode for the latent image potential on the photosensitive drum, and edge enhancement occurs. Because it will do.

  According to the configuration of the present invention, there is a relatively medium magnetic resistance magnetic carrier in the vicinity of the latent image portion formed on the photoconductor, and as a result, this carrier can be a counter electrode. Accordingly, it is possible to realize high image quality over a long period of time without causing fogging or low density and without edge enhancement.

  According to the present invention, a two-component development that does not impair developability in providing a high-resistance developer without charge injection or the like in the developing portion of a photoreceptor having a large electrostatic capacity such as an amorphous silicon photoreceptor. It has become possible to provide a high-quality visible image with little fogging and rust.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments of the present invention.

The present invention relates to a two-component developer suitably used for an image forming method using a photosensitive drum having a large electrostatic capacity such as an amorphous silicon drum, and further relates to a magnetic carrier used therefor.
The magnetic carrier core particle containing at least a binder resin and magnetic particles is composed of two resin layers, the first resin layer is made of a nitrogen-containing resin, and the second resin layer is electrically conductive. It consists of a resin layer containing conductive fine particles.

Further, the magnetic carrier core particles contain 70 to 95% by mass of magnetic particles, and the magnetic carrier having the resin layer,
1) The magnetization intensity (M) at 79.6 kA / m is 40 to 70 Am ² / kg,
2) Volume resistance (R1) at the time of application of 5 × 10 ⁵ V / m is 1.0 × 10 ^{10 to} 1.0 × 1
0 ¹³ Ωcm,
Volume resistance (R2) when applied with 2 × 10 ⁵ V / m is 1.0 × 10 ¹³ to 1.0 × 10 ¹⁶ Ωcm
It is the range of these.

  As a result of intensive studies by the present inventors, in order to provide a stable two-component developer having high development characteristics in an image forming method using an amorphous silicon drum, development characteristics and carrier resistance in the two-component developer are provided. We found that the properties have a very close correlation.

  In general, it has been confirmed that the development characteristics decrease as the volume resistance of the magnetic carrier increases, and conversely, the development characteristics improve as the volume resistance decreases. It is also known that it largely depends on the volume resistance of the carrier.

  The above tendency can be explained by an electrode effect model between the sleeve and the photosensitive drum in the electrophotographic process.

  If the two-component developer is held on the sleeve and the resistance value of the magnetic carrier is low at the developing nip portion with the photosensitive drum, the electric field strength between the photosensitive drum surface and the tip of the developer head becomes high, and the bias High developability can be created by application.

  On the other hand, if the volume resistance of the magnetic carrier is high, the electric field strength between the surface of the photosensitive drum and the tip of the developer head becomes low and it becomes difficult to maintain high developability.

  Thus, it can be said that the developability itself is likely to depend on the resistance characteristics of the magnetic carrier based on the idea of the electrode effect model, etc., but these can be replaced with dielectric characteristics (dielectric constant). That is, the lower the resistance characteristic, the higher the dielectric constant, and conversely, the higher the resistance characteristic, the lower the dielectric constant.

For this reason, it is possible to design the magnetic carrier volume resistance in the direction of low volume resistance only by improving the developability. However, as described above, the amorphous silicon drum is used as the photosensitive drum. , The volume resistivity of the surface layer of the photoconductor is 10 ⁹ to 10 ¹⁴ Ω · cm, so that fog is generated in the image and only the output image density is low. The fog and the decrease in image density occur when a two-component developer is used for a photosensitive drum having a surface layer volume resistivity of 10 ⁹ to 10 ¹⁴ Ω · cm and development is performed under an alternating electric field. I understood it.

As a result of various studies on the above-described fogging and the phenomenon in which the image density is lowered, these phenomena are developed on a photosensitive drum having a surface layer volume resistivity of about 10 ⁹ to 10 ¹⁴ Ω · cm. Occasionally, it has been found that charge is injected from a magnetic carrier.

  As a result of intensive studies in view of the above, the present inventors have developed a problem that has been a problem by providing a polymer layer made of a nitrogen-containing resin with a high volume resistance on a magnetic carrier core particle with a low volume resistance. It is possible to maintain the high development characteristics obtained by the electrode effect by reducing the volume resistance of the magnetic carrier core particles and increasing the dielectric properties while preventing the charge injection from the magnetic carrier at the time Was found.

  The magnetic carrier core particles (hereinafter abbreviated as “core particles”) in the present invention preferably contain 70 to 95% by mass of magnetic particles with respect to the entire core particles. In order to enhance the dielectric properties and obtain a high electrode effect at the development site, it is preferable that the volume resistance of the core particles is low.

  Commonly known magnetic material dispersion type resin carriers often contain non-magnetic particles (eg, hematite) in addition to the binder resin component and magnetic particles, and are used by adjusting the volume resistance of the core particles themselves. In addition, since the content of the magnetic particles also decreased, the volume resistance was increased.

  The core particles used in the present invention increase the electrode effect in the development process by lowering the volume resistance. Therefore, it is important that a large amount of magnetic particles are present. It has been found that it is preferable to contain the magnetic particles.

  When the amount of magnetic particles contained in the core particles is less than 70% by mass, an appropriate specific gravity cannot be obtained, so that the miscibility with the toner is deteriorated and it is difficult to obtain uniform charging. In addition, since the volume resistance is increased, high-definition images can be reproduced for delicate images such as dots and fine lines, while white images, uniformity of density, and insufficient density in solid images. Defects are likely to occur and carrier adhesion to the photosensitive drum is likely to occur, although this is related to the magnetic characteristics. In addition, since the volume resistance of the core particles tends to increase and the dielectric properties and the like do not increase, it becomes difficult to improve developability (development efficiency) in the electrophotographic development process.

  On the other hand, when the content of magnetic particles exceeds 95%, the latent image formed on the photoreceptor as a latent image holding member is easily filled with the charge of the toner, and image defects such as white spots are difficult to occur. On the other hand, not only the strength of the core particles themselves is lowered and the durability characteristics are remarkably deteriorated, but there is a possibility that many irregular particles exist due to cracks and the like, and the charge on the surface of the photosensitive drum tends to be disturbed. The reproducibility will be poor.

  It is possible to use the core particles with low volume resistance as described above, then apply a general resin coat and use it as the final magnetic carrier, just by improving the development characteristics as described above, but with high image quality and high stability. For example, in a system using an amorphous silicon drum having a large electrostatic capacity as a photosensitive drum, or a system in which an alternating electric field is further applied, a charge is injected from a magnetic carrier during development. There are concerns.

  In the present invention, in order to prevent charge injection during such development while maintaining high development characteristics, a polymerized layer is formed using a nitrogen-containing resin as the first resin coating layer on the core particle surface. In order to prevent charge injection during development, the electric resistance of the outermost layer is high, and the volume resistance of the core particles existing inside is low so as to improve the developability by utilizing the electrode effect. They found that it can be resolved.

  As the electrostatic capacity of the photosensitive drum increases, the developer needs to fill the latent image with more charge. Therefore, the charge amount of the developer must be high, and in the present invention, a nitrogen-containing resin that can further improve the negative chargeability is required.

  As the nitrogen-containing compound according to the nitrogen-containing resin of the present invention, at least one nitrogen-containing compound selected from the group consisting of an aromatic amine compound having at least one active hydrogen bonded to a nitrogen atom, an amide compound, and a thioamide compound is used. Isocyanates such as resin, urea, thiourea, melamine, guanidine, guanamine, dicyandiamide and cyanuric acid, aromatic isocyanate, aliphatic isocyanate, for example, diphenylmethane-4,4′-diisocyanate, polyphenylene polyphenyl polyisocyanate, hexamethylene diisocyanate , Imidazoles, quaternary ammonium salts, acrylonitrile and the like, and one kind or two or more kinds can be used.

  Among them, the present inventors have found that it is particularly preferable to provide a coating layer on the surface of the core particle by a polymerization method using a melamine resin.

  This is because the volume resistance of melamine itself is relatively high. The melamine resin is a thermosetting resin obtained from melamine and formaldehyde, and forms a very hard film by forming a three-dimensional crosslink. This is because it will continue to extend the service life.

  In this way, the core particle surface is polymerized and coated with melamine resin as the first coating resin layer, so that the core particle has a low volume resistance and the surface resistance of the first coating resin layer is increased. It has been found that prevention of charge injection at the time and high developability due to the electrode effect are obtained.

  Further, since the melamine resin is polymerized on the surface of the core particle, the uniformity of the resin coating can be obtained, and as a result, it is hardly affected by the resistance of the core particle as a factor relating to charge injection.

  As the binder resin that controls the core particles used in the present invention, a thermosetting resin is preferable. Further, it is preferably a thermosetting resin containing a resin partially or wholly crosslinked three-dimensionally, such as a phenol resin. By using this resin, the dispersed metal compound particles can be strongly bound, so that the strength of the carrier can be increased, and the metal compound particles are hardly detached even in a large number of copies.

  As the monomer used in the binder resin, a radical polymerizable monomer polymerizable monomer can be used. For example, styrene; styrene derivatives such as o-methylstyrene, m-methylstyrene, p-methoxystyrene, p-ethylstyrene, p-tertiarybutylstyrene; acrylic acid, methyl acrylate, ethyl acrylate, acrylic acid-n- Acrylic acid esters such as butyl, acrylate-n-propyl, isobutyl acrylate, octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate; methacrylic acid , Methyl methacrylate, ethyl methacrylate, methacrylate-n-propyl, methacrylate-n-butyl, isobutyl methacrylate, methacrylate-n-octyl, dodecyl methacrylate, 2-ethylhexyl methacrylate, methacrylic acid Methacrylic acid esters such as thearyl, methacrylic acid difference phenyl, dimethylaminomethyl methacrylate, diethylaminoethyl methacrylate, benzyl methacrylate; 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate; acrylonitrile, methacrylonitrile, acrylamide; methyl vinyl ether , Ethyl vinyl ether, propyl vinyl ether, n-butyl ether, isobutyl ether, β-chloroethyl vinyl ether, phenyl vinyl ether, p-methylphenyl ether, p-chlorophenyl ether, p-bromophenyl ether, p-nitrophenyl vinyl ether, p-methoxy Mention may be made of vinyl ethers such as phenyl vinyl ether; diene compounds such as butadiene.

  These monomers can be used alone or in combination, and a suitable polymer composition can be selected so that preferable characteristics can be obtained.

  Other binder resin monomers include epoxy resin starting materials bisphenols and epichlorohydrin; phenolic resin starting materials phenols and aldehydes; urea resin starting materials urea and aldehydes, melamine resin starting materials Examples of the raw material include melamine and aldehydes. As described above, the most preferable binder resin according to the present invention is a phenol resin.

  Examples of the starting material include phenol compounds such as phenol, m-cresol, 3,5-xylenol, p-alkylphenol, resorcil, and p-tert-butylphenol, and aldehyde compounds such as formalin, paraformaldehyde, and furfural. A combination of phenol and formalin is particularly preferable.

  The phenol resin can be obtained by reacting phenols and aldehydes in the presence of a basic catalyst.

  As phenols used in the present invention, in addition to phenol itself, alkylphenols such as m-cresol, p-tert-butylphenol, o-propylphenol, resorcinol, and bisphenol A, and a part or all of benzene nucleus or alkyl group are included. Although compounds having a phenolic hydroxyl group such as halogenated phenols substituted with a chlorine atom or a bromine atom are exemplified, phenol is most preferred. When a material other than phenols is used, particles may be difficult to produce, or even if particles are produced, they may have an indefinite shape.

  Examples of aldehydes used in the present invention include formaldehyde and furfural in the form of either formalin or paraaldehyde, and formaldehyde is particularly preferable.

  The molar ratio of aldehydes to phenols is preferably 1 to 4, particularly preferably 1.2 to 3. If the molar ratio of aldehydes to phenols is less than 1, particles are difficult to produce, and even if they are produced, the resin is difficult to cure, and the strength of the particles produced tends to be weak. On the other hand, when the molar ratio of aldehydes to phenols is larger than 4, unreacted aldehydes remaining in the aqueous medium after the reaction tend to increase.

  As a basic catalyst used for this invention, what is used for normal resole resin manufacture, For example, alkylamines, such as aqueous ammonia, hexamethylenetetramine, dimethylamine, diethyltriamine, polyethyleneimine, are mentioned. The molar ratio of these basic catalysts to phenols is preferably 0.02 to 0.3.

  In the present invention, other resins can be used as the binder resin in accordance with the phenol resin to the extent that the effects of the present invention are not impaired.

  Next, the manufacturing method of the core particle in this invention is demonstrated.

  As a method for producing core particles, there is a method in which a monomer of binder resin and magnetic particles are mixed and the monomer is polymerized to obtain core particles.

  At this time, as monomers used for polymerization, in addition to the above-mentioned vinyl monomers, bisphenols and epichlorohydrin for forming epoxy resins; phenols and aldehydes for forming phenol resins; urea resins are formed. For this purpose, urea and aldehydes, melamine and aldehydes are used.

  For example, as a method for producing core particles using a curable phenolic resin, a magnetic material is put in an aqueous medium, and phenols and aldehydes are polymerized in the presence of a basic catalyst in the aqueous medium to obtain core particles. There is a way.

  As another method for producing the core particles, a vinyl-type or non-vinyl-type thermoplastic resin, magnetic particles, and other additives are sufficiently mixed by a mixer, and then a kneader such as a heating roll, a kneader, or an extruder. There is a method in which the core particles are obtained by melting and kneading using, then cooling and then pulverizing and classifying. At this time, it is preferable that the obtained core particles are spheroidized thermally or mechanically and used as the core particles for the magnetic carrier.

  Among the binder resins described above, thermosetting resins such as phenol resins, melamine resins, and epoxy resins are preferable in terms of excellent durability, impact resistance, and heat resistance. The binder resin is more preferably a phenol resin in order to more suitably express the characteristics of the present invention.

  The magnetic carrier of the present invention comprises core particles as nuclei and a coating layer formed by coating the core particles with a resin coating material as necessary.

  The core particles used in the magnetic carrier of the present invention are a resin (binder resin), dispersed in the resin, for example, oxidized or unoxidized iron powder, or iron, lithium, calcium, magnesium, nickel, Magnetic particle-dispersed resin carrier containing metal particles such as copper, zinc, cobalt, manganese, chromium, rare earth elements, alloy particles thereof, or magnetic particles such as oxide particles, magnetite, or ferrite containing these elements This is a so-called resin carrier.

  The number average particle size of the magnetic particles to be used is about 20 to 800 nm (more preferably 50 to 300 nm), preventing the magnetic particles from being detached from the binder resin, increasing the carrier strength, and further providing a recess on the carrier surface. This is preferable in order to prevent the presence of irregularly shaped particles.

The shape may be granular, spherical, or needle-shaped. The saturation magnetization σs of the magnetic particles is preferably not less than 20 Am ² / kg, and more preferably 30 Am ² / kg or more.

On the other hand, as magnetic characteristics of the magnetic particles, the magnetization intensity (M) at 79.6 kA / m is 40 to 70 Am ² / kg, preferably 50 to 70 Am ² / kg. When the strength (M) of magnetization exceeds 70 Am ² / kg, the transportability by the magnetic force of the carrier increases, and the mechanical force relating to the toner increases and the toner may be crushed. Further, when the magnetization intensity (M) is less than 40 Am ² /, the carrier is detached from the surface of the developing sleeve during the conveyance of the developer, and adheres to the surface of the photosensitive member to cause a defect in the image.

The magnetic properties of the carrier can be measured using, for example, an oscillating magnetic field type magnetic property automatic recording device BHV-35 manufactured by Riken Denshi Co., Ltd. As measurement conditions when using this apparatus, an external magnetic field of 1000 / 4π (kA / m) is created, and on the other hand, the carrier particles do not move in the cylindrical plastic container of the magnetic material-dispersed resin carrier of the present invention. In this state, the magnetizing moment is measured, the actual weight when the sample is put is measured, and the magnetization strength (Am ² / kg) is obtained. .

  As described above, the amount of the magnetic particles used for the core particles is 70 to 95% by mass (more preferably 80 to 90% by mass) with respect to the entire magnetic carrier, thereby reducing the true specific gravity of the magnetic carrier and increasing the magnetic properties. This is preferable for sufficiently securing the mechanical strength of the carrier. It is also preferable for suppressing the presence of a magnetic carrier having a concave portion on the surface.

  Furthermore, in order to change the magnetic properties and volume resistance of the magnetic carrier, in the present invention, a nonmagnetic inorganic compound may be contained in the core particle in addition to the magnetic particle as long as the content of the magnetic particle is not impaired.

  Further, when the nonmagnetic inorganic compound is used in combination with the above magnetic particles, the content of the magnetic particles may be adjusted so that the magnetic particles are contained in an amount of 50 to 95% by mass based on the total amount of the magnetic particles and the nonmagnetic inorganic compound. It is preferable to adjust the magnetization strength of the magnetic carrier to prevent carrier adhesion and further to adjust the volume resistance value of the magnetic carrier.

The nonmagnetic inorganic compound particles have a volume resistance of 10 ¹⁰ Ωcm or more, preferably 10 ¹¹ Ωcm or more, and examples thereof include titanium oxide, silica, alumina, zinc oxide, magnesium oxide, hematite, goethite, and ilmenite. Metal oxide fine particles, silicon carbide, aluminum nitride, boron nitride and the like can be used.

  Those having a specific gravity difference from the ferromagnetic compound particles, hematite, zinc oxide, titanium oxide and the like are more preferable. The particle size of the non-magnetic inorganic compound particles used for the production of the magnetic carrier core material is preferably 0.05 to 5 μm. If the dispersion in the aqueous medium and the strength of the resulting composite particles are taken into account, the particle size is 0.1. More preferably, it is ˜3 μm.

In addition, the nonmagnetic inorganic compound preferably has a saturation magnetization σs of 10 Am ² / kg or less, and more preferably 5 Am ² / kg or less. On the other hand, the particle size of the nonmagnetic inorganic compound particles used for the coating layer in the present invention is 1 μm or less, preferably 0.5 μm or less, considering the thickness of the coating layer. The shape may be any of granular, spherical and acicular.

  The magnetic particles and non-magnetic inorganic compound particles in the present invention can be used as they are without being surface-treated, but may be subjected to a lipophilic treatment in advance. In addition, when using magnetic particles and non-magnetic inorganic compound particles that have not been subjected to lipophilic treatment, as suspension stabilizers, hydrophilic organic compounds such as carboxymethyl cellulose and polyvinyl alcohol, fluorine compounds such as calcium fluoride, etc. It becomes easy to produce spherical particles by adding.

  The oleophilic treatment is a method in which a coupling agent such as a silane coupling agent or titanate coupling agent is added to and mixed with the ferromagnetic compound particles, or a magnetic particle or the like in an aqueous solvent containing a surfactant. There is a method of dispersing a surfactant and adsorbing a surfactant on the particle surface.

  Silane coupling agents include those having a hydrophobic group, amino group, and epoxy group, and silane coupling agents having a hydrophobic group include vinyltrichlorosilane, vinyltriethoxysilane, vinyl tris (β -Methoxy) silane and the like.

  Examples of the silane coupling agent having an amino group include γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, and N-β- (aminoethyl) -γ-aminopropylmethyl. Examples include dimethoxysilane and N-phenyl-γ-aminopropyltrimethoxysilane.

  Examples of the silane coupling agent having an epoxy group include γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) trimethoxysilane, and the like.

  Examples of titanate coupling agents include isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, and isopropyl tris (dioctyl pyrophosphate) titanate.

  As the surfactant, commercially available surfactants can be used, and those having a functional group capable of bonding to a hydroxyl group present on the surface of the magnetic particle, nonmagnetic inorganic compound particle or particle are desirable, and can be said to be ionic. If it is cationic or anionic, it is preferable.

  The object of the present invention can be achieved by any of the above treatment methods, but treatment with a silane coupling agent having an amino group or an epoxy group is preferable in view of the adhesiveness with a phenol resin.

  In the present invention, an example of means for polymerizing and coating the surface of the core particles with a melamine resin as a first coating layer will be specifically shown.

  Phenols containing melamine, formalins, water and core particles are charged into a reaction kettle and stirred thoroughly, then heated with stirring by adding ammonia, the reaction temperature is adjusted to 70-90 ° C., and phenol resin is added. Harden. The cured reaction product is cooled to 40 ° C. or less, and the resulting aqueous dispersion is separated into solid and liquid according to conventional methods such as filtration and centrifugation. Magnetic carrier particles having a layer made of polymerized phenol resin are obtained. At that time, in order to sufficiently cure the resin, for example, it is necessary to sufficiently cure the resin at a temperature of about 100 to 350 ° C., and to prevent oxidation of the core particles, for example, in an inert atmosphere, for example, It is desirable to perform the treatment while flowing an inert gas such as helium, argon, or nitrogen. The heat treatment lamp may be either a fixed type or a rotary type, but a rotary type is desirable in order to prevent aggregation of particles.

  At this time, the preferable amount of melamine is preferably 0.1 to 1.5% by mass with respect to the core particles. If it is less than 0.1% by mass, it is difficult to obtain a stable resin coating layer, and there are problems such as variations in electric resistance values. On the other hand, when it is more than 1.5% by mass, it is possible to obtain a stable electric resistance value, but it becomes easy for the core particles to coalesce during the polymerization reaction. For this reason, there is a possibility that fluidity as a magnetic carrier may be impaired, and problems such as a poor mixing of toner and magnetic carrier which are fatal as a two-component developer are likely to occur.

  Up to now, as an example of containing a nitrogen-containing resin, for example, a binder resin carrier using melamine has been described in JP-A-8-160671. In other words, the effect of stabilizing the charging over a long period of time cannot be achieved.

  In the present invention, it is further one of the features that a second resin coating layer containing conductive particles is formed on the first resin coating layer.

  The resin coating amount is 0.01 to 5% by mass, preferably 0.05 to 3% by mass with respect to the core particles. When the amount of the resin to be coated is less than 0.01% by mass, a sufficient coating effect cannot be obtained, and when it exceeds 5% by mass, the coalescence of particles tends to occur.

  As a coating method, any conventionally known resin coating method of a carrier such as a method of dissolving or suspending a coating material such as a resin in a solvent and applying it to a carrier and a method of simply mixing with a powder can be applied. .

  One of the features of the present invention is that the second resin coating layer contains conductive particles. Examples of the conductive fine particles include metals or alloys such as copper, nickel, silver, and aluminum. Examples thereof include powders, metal oxides such as antimony oxide, indium oxide, tin oxide, and titanium oxide, and carbon-based conductive fine particles such as carbon fiber, carbon black, and graphite.

  As the conductive fine particles used in the present invention, carbon black is preferably used, and conductive carbon black is particularly preferable.

  Conductive carbon black is excellent in electrical conductivity, and can be given conductivity by adding a small amount compared to other substances. It can be used to a certain degree by controlling the amount added, so it can be used suitably. It is done.

  As the conductivity index, the DBP oil absorption amount in carbon black is generally used, and the higher the value, the higher the conductivity.

Generally the carbon black itself even in the raw material level, relatively conductive is entering the high classification, as the known technology in the electrophotographic method, in general, frequently used those 30~170cm ³ / 100g as DBP absorption whereas is, it is preferable in particular conductive carbon black contained in the second resin coating layer according to the present invention is a DBP oil absorption 200 cm ^3/100 g or more.

  In particular, in the present invention, as described above, it is characterized by having the first coating layer obtained by polymerizing the melamine resin on the core particles. However, since it is a nitrogen compound, the positive chargeability tends to be strong. is there. Depending on the type of usage when used in a two-component developer, the toner tends to be excessively charged negatively by friction mixing, and is the outermost layer in order to derive stable charging characteristics. By containing highly conductive carbon black in the second resin coating layer, an effect of releasing excess charge accumulated in the carrier (leakage) can be obtained. In addition, since the conductivity is high, a portion having a low resistance is present, and the effect of increasing the developability can also be obtained.

  In this invention, it is preferable that the quantity of the conductive carbon black contained in a 2nd resin coating layer is 1-20 mass% with respect to a 2nd resin coating layer.

  When the content is less than 1% by mass, charge-up or the like is likely to occur, and image quality such as a significant decrease in image density is deteriorated. On the other hand, when the content is more than 20% by mass, the surface resistance of the carrier may be abruptly lowered, and adverse effects such as charge injection during development are likely to occur.

  The resin used for the second resin coating layer varies depending on the toner material used as the two-component developer, but either a thermosetting resin or a thermoplastic resin can be used without particular limitation.

  For example, polytetrafluoroethylene, monochlorotrifluoroethylene polymer, polyvinylidene fluoride, silicone resin, polyester resin, metal compound of ditertiary butyl salicylic acid, styrenic resin, acrylic resin, polyamide, polyvinyl butyral, nigrosine, aminoacrylate resin, base Dyes and lakes thereof, fine silica powder, fine alumina powder. These may be used alone or in combination.

  As a particularly preferred form, the surface of the core particle having the first resin coating layer is formed by combining (i) a fluorine resin and a styrene resin (for example, a combination of poly (vinylidene fluoride) and a styrene-methyl methacrylate resin, A combination of tetrafluoroethylene and styrene-methyl methacrylate resin, a combination of fluorine-based copolymer and styrene-based copolymer), preferably 90:10 to 20:80, more preferably 70:30 to 30: A carrier mixed at a ratio of 70, or (ii) a carrier coated with a silicone resin, preferably 0.01 to 5% by mass, more preferably 0.1 to 3% by mass.

  Examples of the fluorine-based copolymer include vinylidene fluoride-tetrafluoroethylene copolymers (10:90 to 90:10). As the styrene-based copolymer, styrene-acrylic acid 2-ethylhexyl copolymer (20: 80-80: 20), styrene-acrylic acid 2-ethylhexyl-methyl methacrylate copolymer (20-60: 5-30: 10-50).

  Further, other resin particles or inorganic compound particles may be contained in the coating resin. Furthermore, it is more preferable to modify the surface with another material such as a reactive coupling agent before coating the resin. By performing the surface modification, the adhesion between the resin layer and the core particles is improved, and more excellent durability can be obtained.

  In addition, the resin coating amount of the magnetic carrier in the present invention can be determined from the mass reduction rate using a thermobalance (TGA-7: manufactured by Perkin Elmer).

  Thus, the configuration of the magnetic carrier in the present invention will be described with reference to an image diagram as shown in FIG.

As the volume resistance of the electrophotographic carrier according to the present invention, the volume resistance (R1) when 5 × 10 ⁵ V / m is applied is 1.0 × 10 ^{10 to} 1.0 × 10 ¹³ Ωcm, and 2 × 10. The volume resistance (R2) when ⁵ V / m is applied is preferably 1.0 × 10 ^{13 to} 1.0 × 10 ¹⁶ Ωcm.

When (R1) is less than 1.0 × 10 ¹⁰ Ωcm, the charge on the electrostatic latent image tends to flow through the carriers (so-called charge injection occurs), and the image is easily disturbed or missing. Become. When (R2) exceeds 5.0 × 10 ¹⁶ Ωcm, there is a problem that carrier charge leakage is less likely to occur, the toner charge amount is increased, and the image density becomes very thin at the center of the black solid portion. Arise.

As a more preferable volume resistance, the volume resistance (R1) when applying 5 × 10 ⁵ V / m is 1.0 × 10 ^{10 to} 1.0 × 10 ¹² Ωcm, and when applying 2 × 10 ⁵ V / m. The volume resistance (R2) is preferably 1.0 × 10 ^{13 to} 1.0 × 10 ¹⁵ Ωcm. High electrical resistance within the above range makes it possible to maintain high development characteristics while preventing charges from being injected from the magnetic carrier during development.

  The electrophotographic carrier of the present invention preferably has a volume average particle size (Dv) of 15 to 60 μm, more preferably 20 to 50 μm.

  In the present invention, the volume average particle size of the carrier particles is a median value in the particle size distribution based on the volume distribution. For example, a value at which the cumulative distribution value in the particle size distribution is 50%, or a particle size measurement range. Is an arithmetic average value of a section including a cumulative distribution value of 50% when appropriately dividing.

  When the volume average particle diameter of the carrier particles is 15 μm or less, the carrier adhesion to the non-image area by the particles on the fine particle side in the particle size distribution of the carrier particles may not be satisfactorily prevented. In particular, when a high magnetic force as in the present invention is to be achieved, it is difficult to obtain a sufficient resistance. When the volume average particle diameter of the carrier particles is larger than 60 μm, the density of the magnetic brush is liable to be impaired, and image unevenness may occur.

  Moreover, as a particle size distribution of the electrophotographic carrier of the present invention, the content of carrier particles of 20 μm or less by the mesh method is 0.01 to 10% by mass, and the content of 74 μm or more is 0.1 to 20% by mass. It is desirable to be.

  When the content of carrier particles of 20 μm or less is less than 0.01% by mass, the developer tends to be densely clogged, and the agent is liable to deteriorate. When the content of carrier particles of 20 μm or less is more than 10% by mass, carrier adhesion due to carrier particle fine powder tends to occur. Even when the content of carrier particles of 74 μm or more is less than 0.1% by mass, agent deterioration due to high density is likely to occur, and when it is 20% by mass or more, an appropriate charge amount is given to the toner. Therefore, a sufficient surface area may not be obtained.

Further, the magnetic property σ1000 at 1000 / 4π (kA / m) of carrier particles of 20 μm or less by mesh method is preferably 30 to 80 Am ² / kg from the viewpoint of carrier adhesion.

  The volume average particle size and particle size distribution can be adjusted by the production conditions of carrier particles, classification of carrier particles by sieving or various classifiers, and mixing of classified products.

True specific gravity of the electrophotographic carrier of the present invention is 3.0g / cm ³ ~4.5g / cm ³ are preferred. If the true specific gravity is less than 3.0 g / cm ^3, it is related to the magnetic properties of the carrier particles, but not only the carrier adhesion is likely to occur, but also the miscibility with the toner is deteriorated and uniform charging can be obtained. It becomes difficult. On the other hand, when the true specific gravity exceeds 4.5 g / cm ³ , the share in the developer increases, and the spent by the toner or the coating resin peeling off on the carrier particles tends to occur.

  The electrophotographic carrier according to the present invention can be mixed with toner and used as a two-component developer, so that the characteristics according to the present invention can be exhibited.

  In this case, various toners such as those produced by a pulverization method and those produced by a polymerization method are used as the toner to be used. However, the toner is not particularly limited. Show.

  Next, the toner used with the carrier will be described in detail.

  When the toner of the present invention is produced by a pulverization method, a known method can be used. Known methods include, for example, a binder resin, a magnetic material, a release agent, a charge control agent, and in some cases, a component such as a colorant and other additives necessary for the toner and other additives, etc., a mixer such as a Henschel mixer or a ball mill. After thoroughly mixing, melt or knead using a heat kneader such as a heating roll, kneader, extruder, etc. to disperse other toner materials such as a magnetic substance in the resin or the like. After dissolution, cooling and solidification, and pulverization, classification and surface treatment as necessary are performed to obtain toner particles. If necessary, a fine powder or the like is added and mixed to obtain a developer. Either the classification or the surface treatment may be performed first. In the classification step, it is preferable to use a multi-division classifier from the viewpoint of production efficiency.

  The pulverization step can be performed using a known pulverizer such as a mechanical impact type or a jet type. Moreover, you may grind | pulverize with a heat | fever and may perform the process which adds a mechanical impact auxiliary. Furthermore, a hot water bath method in which finely pulverized (classified as necessary) toner particles are dispersed in hot water, a method of passing in a hot air stream, or the like may be used.

  As a method of applying a mechanical impact force, for example, there is a method using a mechanical impact type pulverizer such as a kryptron system manufactured by Kawasaki Heavy Industries, Ltd. or a turbo mill manufactured by Turbo Industry. In addition, like devices such as the Mechano-Fusion System manufactured by Hosokawa Micron Co., Ltd. and the hybridization system manufactured by Nara Machinery Co., Ltd., the toner is pressed against the inside of the casing by centrifugal force with high-speed rotating blades, and the force of compression force, friction force, etc. A method of applying a mechanical impact force to the toner may be used.

  In the case of performing a process of applying mechanical impact, the atmosphere temperature during the process is set to a temperature near the glass transition point Tg of the toner (that is, a temperature in the range of ± 30 ° C. of the glass transition point Tg) to prevent aggregation. From the viewpoint of productivity. More preferably, the treatment at a temperature in the range of ± 20 ° C. of the glass transition point Tg of the toner is particularly effective for improving the transfer efficiency.

  Furthermore, the toner of the present invention is a method for obtaining a spherical toner by atomizing a molten mixture into air using a disk or a multi-fluid nozzle described in JP-B-56-13945, etc. Represented by a dispersion polymerization method in which a toner is directly produced using an aqueous organic solvent in which the polymer obtained in 1 is insoluble, or a soap-free polymerization method in which a toner is produced by direct polymerization in the presence of a water-soluble polar polymerization initiator. The toner can also be produced by a method of producing toner using an emulsion polymerization method or the like.

  When the toner of the present invention is produced by a pulverization method, the binder resin may be a styrene such as polystyrene or polyvinyltoluene or a homopolymer of a substituted product thereof; a styrene-propylene copolymer, a styrene-vinyltoluene copolymer, or styrene. -Vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate Copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether Copolymer, styrene-vinyl ethyl acetate Styrene copolymer such as styrene copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer Combined; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, fat Aromatic or alicyclic hydrocarbon resins, aromatic petroleum resins, paraffin waxes and carnauba waxes can be used alone or in combination. In particular, a styrene copolymer and a polyester resin are preferable in terms of development characteristics, fixing properties, and the like.

  Examples of the release agent used in the present invention include aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, low molecular weight olefin copolymers, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax; Oxides of aliphatic hydrocarbon waxes such as: waxes based on fatty acid esters such as aliphatic hydrocarbon ester waxes; and fatty acid esters such as deoxidized carnauba wax that have been partially or wholly deoxidized. It is done. Furthermore, a partially esterified product of a fatty acid such as behenic acid monoglyceride and a polyhydric alcohol; a methyl ester compound having a hydroxyl group obtained by hydrogenating vegetable oils and the like. Particularly preferred waxes are aliphatic hydrocarbon waxes such as paraffin wax, polyethylene wax, and Fischer-Tropsch wax, which have a short molecular chain and little steric hindrance and excellent mobility.

  In the toner used in the present invention, a toner used for oilless fixing having a binder resin, a colorant, a release agent, and inorganic fine particles is preferable. The binder resin contains a polyester unit, and the release agent is a hydrocarbon. The endothermic curve in the differential thermal analysis measurement of the toner has one or more endothermic peaks in the temperature range of 30 to 200 ° C., and the maximum endothermic peak temperature is 65. A toner having a temperature of from 110 ° C. to 110 ° C. can be preferably used because the degree of aggregation of the toner is appropriately increased to improve transferability and image defects such as white spots can be improved.

  The release agent used in the present invention preferably has a content of 1 to 10 parts by mass, and more preferably 2 to 8 parts by mass with respect to 100 parts by mass of the binder resin. If the content is less than 1 part by mass, the releasability may not be exhibited well at the time of oilless fixing, or the low-temperature fixing property may not be satisfied. When the amount exceeds 10 parts by mass, the release agent tends to exude to the toner surface, and white spots may be deteriorated.

  The toner of the present invention can be used in combination with a known charge control agent. Examples of such charge control agents include organometallic complexes, metal salts, and chelate compounds, such as monoazo metal complexes, acetylacetone metal complexes, hydroxycarboxylic acid metal complexes, polycarboxylic acid metal complexes, and polyol metal complexes. In addition, carboxylic acid derivatives such as metal salts of carboxylic acids, carboxylic acid anhydrides and esters, and condensates of aromatic compounds are also included. As the charge control agent, phenol derivatives such as bisphenols and calixarenes are also used. In the present invention, it is preferable to use a metal compound of an aromatic carboxylic acid in order to improve the rising of charging.

  In the present invention, the charge control agent preferably has a content of 0.1 to 10 parts by mass, more preferably 0.2 to 5 parts by mass with respect to 100 parts by mass of the binder resin. If the amount is less than 0.1 parts by mass, the change in the toner charge amount in an environment from high temperature and high humidity to low temperature and low humidity may become large. If the amount is more than 10 parts by mass, the toner may be inferior in low-temperature fixability.

  As the colorant used in the present invention, known pigments and dyes can be used alone or in combination. For example, as the dye, C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Modern Tread 30, C.I. I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Modern Blue 7, C.I. I. Direct Green 6, C.I. I. Basic Green 4, C.I. I. Basic green 6 etc. are mentioned.

  As pigments, mineral fast yellow, navel yellow, naphthol yellow S, hansa yellow G, permanent yellow NCG, tartrazine lake, molybdenum orange, permanent orange GTR, pyrazolone orange, benzidine orange G, permanent red 4R, watch red red calcium salt , Eosin Lake, Brilliant Carmine 3B, Manganese Purple, Fast Violet B, Methyl Violet Lake, Cobalt Blue, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Fast Sky Blue, Indanthrene Blue BC, Chrome Green, Pigment Green B, Malachite green lake, final yellow green G, etc. are mentioned.

  When used as a full-color image forming toner, the magenta color pigment includes C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 163, 202, 206, 207, 209, 238, C.I. I. Pigment violet 19, C.I. I. Bat red 1, 2, 10, 13, 15, 23, 29, 35, etc. are mentioned.

  Although such a pigment may be used alone, it is more preferable from the viewpoint of the image quality of a full-color image to improve the sharpness by using a dye and a pigment together. Examples of the magenta dye include C.I. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 49, 81, 82, 83, 84, 100, 109, 121, C.I. I. Disper thread 9, C.I. I. Solvent Violet 8, 13, 14, 21, 27, C.I. I. Oil-soluble dyes such as Disperse Violet 1; I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18, 22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40, C.I. I. Basic dyes such as basic violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27, and 28 may be mentioned.

  Examples of the color pigment for cyan include C.I. I. Pigment blue 2, 3, 15, 16, 17; I. Acid Blue 6; I. Examples thereof include Acid Blue 45 or a copper phthalocyanine pigment in which 1 to 5 phthalimidomethyl groups are substituted on the phthalocyanine skeleton.

  Examples of the color pigment for yellow include C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 65, 73, 74, 83, 93, 97, 155, 180, 185C. I. Bat yellow 1, 3, 20 etc. are mentioned.

  The amount of the colorant used is preferably 1 to 15 parts by mass, more preferably 3 to 12 parts by mass, and still more preferably 4 to 10 parts by mass with respect to 100 parts by mass of the binder resin. .

  When the content of the colorant is more than 15 parts by mass, the transparency is lowered, and in addition, the reproducibility of intermediate colors as typified by human skin color is likely to be lowered, and further, the charging property of the toner is stabilized. And the low-temperature fixability becomes difficult to obtain. When the content of the colorant is less than 1 part by mass, the coloring power is low, so that a large amount of toner must be used to obtain the density, the dot reproducibility is easily impaired, and a high-quality image with a high image density. Is difficult to obtain.

  For the purpose of improving fluidity, transferability, particularly toner separation, and improving white spots, toner is added with fine particles. One of the external additives externally added to the toner surface is inorganic fine particles, and at least one of titanium oxide, alumina oxide and silica is used. The average particle size (number distribution) of the inorganic fine particles is used. Is preferably 80 nm or more and 200 nm or less in order to function as spacer particles for improving toner separation from the carrier. The external additive is preferably used in combination with fine particles having an average particle diameter (peak value of the number distribution) of 50 nm or less in order to improve toner fluidity.

  The photoreceptor used in the present invention will be described below.

  The organic photoreceptor and the amorphous silicon drum are not limited at all in terms of exhibiting the carrier characteristics according to the present invention.

[Organic photoconductor: OPC-1]
Examples of the conductive substrate include metals such as aluminum and stainless steel, plastics having a coating layer made of aluminum alloy, indium oxide-tin oxide alloy, paper / plastic impregnated with conductive particles, plastics having a conductive polymer, etc. Cylindrical cylinders and films are used.

  On these conductive substrates, the purpose is to improve the adhesion of the photosensitive layer, improve coating properties, protect the substrate, cover defects on the substrate, improve charge injection from the substrate, and protect against electrical breakdown of the photosensitive layer. An undercoat layer may be provided. Undercoat layer is polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, casein, polyamide, copolymer nylon, glue, gelatin, polyurethane -It is made of a material such as aluminum oxide. The film thickness is usually about 0.1 to 10 μm, preferably about 0.1 to 3 μm.

  The charge generation layer is made of azo pigments, phthalocyanine pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethane dyes, selenium, amorphous silicon, etc. A charge generating material such as an inorganic material is dispersed in a suitable binder and applied, or vapor deposition is used. Of these, phthalocyanine pigments are preferred for adjusting the sensitivity of the photoreceptor to a sensitivity suitable for the present invention. The binder can be selected from a wide range of binder resins, such as polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacrylic resin, phenol resin, silicone resin, epoxy resin, vinyl acetate resin, etc. Is mentioned. The amount of the binder contained in the charge generation layer is selected to be 80% by mass or less, preferably 0 to 40% by mass. The thickness of the charge generation layer is preferably 5 μm or less, and particularly preferably 0.05 to 2 μm.

  The charge transport layer has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them. The charge transport layer is formed by dissolving a charge transport material in a solvent together with a binder resin as required, and coating, and the film thickness is generally 5 to 40 μm. Examples of the charge transport material include polycyclic aromatic compounds having a structure such as biphenylene, anthracene, pyrene, phenanthrene in the main chain or side chain, nitrogen-containing cyclic compounds such as indole, carbazole, oxadiazole, pyrazoline, hydrazone compounds, Examples include styryl compounds, selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide.

  Examples of binder resins for dispersing these charge transport materials include polycarbonate resins, polyester resins, polymethacrylate esters, polystyrene resins, acrylic resins, polyamide resins, and other organic photoconductive materials such as poly-N-vinylcarbazole and polyvinylanthracene. Include a functional polymer.

  Moreover, you may provide a protective layer as a surface layer. As the resin for the protective layer, polyester, polycarbonate, acrylic resin, epoxy resin, phenol resin, or a curing agent for these resins may be used alone or in combination of two or more.

  Moreover, you may disperse | distribute electroconductive fine particles in resin of a protective layer. Examples of the conductive fine particles include metals and metal oxides, preferably zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin oxide coated titanium oxide, tin coated indium oxide, There are ultrafine particles such as antimony-coated tin oxide and zirconium oxide. These may be used alone or in combination of two or more. In general, when particles are dispersed in a protective layer, it is necessary that the particle diameter of the particles is smaller than the wavelength of the incident light in order to prevent scattering of incident light by the dispersed particles. The particle size of the conductive and insulating particles to be used is preferably 0.5 μm or less. Moreover, 2-90 mass% is preferable with respect to the protective layer total weight, and, as for content in a protective layer, 5-80 mass% is more preferable. The thickness of the protective layer is preferably from 0.1 to 10 μm, more preferably from 1 to 7 μm.

  The surface layer can be applied by spray coating, beam coating or penetration (dipping) coating of the resin dispersion.

[Inorganic photoconductor: amorphous silicon photoconductor (a-Si) -1)]
In general, a photoreceptor for an image forming apparatus using a-Si: H is obtained by heating a conductive support to 50 ° C. to 400 ° C., and vacuum deposition, sputtering, ion plating on the support. A photoconductive layer made of a-Si is formed by a film forming method such as a CVD method, a thermal CVD method, a photo CVD method, or a plasma CVD method (hereinafter referred to as “PCVD method”). Among them, the PCVD method, that is, the method of decomposing the raw material gas by direct current, high frequency or microwave glow discharge and sequentially forming the a-Si deposited film on the support has been put into practical use.

{Support}
The support used in the present invention may be conductive or electrically insulating. Examples of the conductive support include well-known metals such as Al and Fe, and alloys thereof such as stainless steel. Further, it is also possible to use a support obtained by conducting a conductive treatment on at least the surface on which the photosensitive layer is formed of an electrically insulating support such as a synthetic resin film or sheet, glass or ceramic.

  In addition, as another method for more effectively eliminating the image defect due to the interference fringe pattern when using coherent light such as laser light, a plurality of charge carriers on the surface of the support in a range in which there is substantially no decrease in charge carriers. An uneven shape by a spherical trace depression may be provided, or an interference preventing layer or region such as a light absorption layer may be provided below the photosensitive layer.

{Photoconductive layer}
In the present invention, in order to effectively achieve the object, the photoconductive layer which is formed on the support and, if necessary, on the undercoat layer and constitutes a part of the photosensitive layer is desired by the vacuum deposition film forming method. In order to obtain the characteristics, the film forming parameters are appropriately set with numerical conditions.

  In order to form the photoconductive layer by the glow discharge method, basically, a source gas for supplying Si that can supply silicon atoms (Si) and a source gas for supplying H that can supply hydrogen atoms (H) or / And a source gas for X supply capable of supplying halogen atoms (X) is introduced in a desired gas state into a reaction vessel whose inside can be depressurized to cause glow discharge in the reaction vessel, What is necessary is just to form the layer which consists of a-Si: H, X on the predetermined support body installed in the position.

  Examples of atoms that control conductivity include so-called impurities in the semiconductor field. As is well known, atoms belonging to group IIIb of the periodic table (group IIIb atoms) or n-type conductivity that give p-type conduction characteristics. An atom (group Vb atom) belonging to group Vb of the periodic table giving characteristics can be used.

  In the present invention, the layer thickness of the photoconductive layer is appropriately determined as desired from the viewpoints of obtaining desired electrophotographic characteristics and economic effects, etc., preferably 20-50 μm, more preferably 23-45 μm, optimally Is preferably 25 to 40 μm.

  In order to achieve the object of the present invention and form a photoconductive layer having desired film characteristics, the mixing ratio of Si supply gas and dilution gas, the gas pressure in the reaction vessel, the discharge power and the support temperature are set. It can be set appropriately.

{Surface layer}
In the present invention, it is preferable to further form a surface layer on the photoconductive layer formed on the support as described above. This surface layer has a free surface and is provided to achieve the object of the present invention mainly in moisture resistance, continuous repeated use characteristics, electrical pressure resistance, use environment characteristics, and durability.

  The surface layer contains an amorphous silicon (a-Si) -based material, for example, an amorphous silicon containing hydrogen atoms (H) and / or halogen atoms (X) and further containing carbon atoms (hereinafter referred to as “a-SiC: H, X ”), amorphous silicon containing hydrogen atoms (H) and / or halogen atoms (X) and further containing oxygen atoms (hereinafter referred to as“ a-SiO: H, X ”), Amorphous silicon containing hydrogen atoms (H) and / or halogen atoms (X) and further containing nitrogen atoms (hereinafter referred to as “a-SiN: H, X”), hydrogen atoms (H) and / or halogens Amorphous silicon (hereinafter referred to as “a-SiCON: H, X”) containing an atom (X) and further containing at least one of a carbon atom, an oxygen atom and a nitrogen atom, or amorphous Carbon (a-C: H, X) material or the like is preferably used.

  The amount of carbon when the surface layer is composed mainly of a-SiC is preferably in the range of 30% to 90% with respect to the sum of silicon atoms and carbon atoms.

  The layer thickness of the surface layer in the present invention is usually 0.01 to 3 μm, preferably 0.05 to 2 μm, and most preferably 0.1 to 1 μm. When the layer thickness is less than 0.01 μm, the surface layer is lost due to wear or the like during use of the photoreceptor, and when it exceeds 3 μm, electrophotographic characteristics such as an increase in residual potential are observed.

  Furthermore, in the present invention, it is also possible to provide a blocking layer (lower surface layer) in which the content of carbon atoms, oxygen atoms and nitrogen atoms is reduced from the surface layer between the photoconductive layer and the surface layer. It is effective for further improvement.

{Charge injection blocking layer}
In the photoreceptor for an image forming apparatus of the present invention, it is more effective to provide a charge injection blocking layer that functions to block charge injection from the conductive support side between the conductive support and the photoconductive layer. Is.

  Examples of the atoms that control the conductivity contained in the charge injection blocking layer include so-called impurities in the semiconductor field, which provide Group III atoms in the periodic table that give p-type conduction characteristics or n-type conduction characteristics. Periodic table group V atoms can be used.

  Furthermore, the charge injection blocking layer contains at least one of carbon atom, nitrogen atom and oxygen atom, thereby improving the adhesion with other layers provided in direct contact with the charge injection blocking layer. You can plan even more.

  In addition, hydrogen atoms and / or halogen atoms contained in the charge injection blocking layer in the present invention compensate for dangling bonds present in the layer, and are effective in improving the film quality.

  In the present invention, the layer thickness of the charge injection blocking layer is preferably from 0.1 to 5 μm, more preferably from 0.3 to 4 μm, optimally from the viewpoint of obtaining desired electrophotographic characteristics and economic effects. It is desirable to be 0.5 to 3 μm.

In the image forming apparatus photoconductor of the present invention, for the purpose of further improving the adhesion between the support and the photoconductive layer or the charge injection blocking layer, for example, Si ₃ N ₄ , SiO ₂ , You may provide the contact | adherence layer comprised by the amorphous material etc. which use SiO or a silicon atom as a base | substrate, and contain a hydrogen atom and / or a halogen atom, and a carbon atom and / or an oxygen atom and / or a nitrogen atom. Furthermore, as described above, a light absorption layer for preventing the generation of interference patterns due to the reflected light from the support may be provided.

In the image forming method of the present invention, it is preferable to use an electrophotographic photosensitive member having a charge capacity of 1.0 to 8.0 μF / m ² . When the charge capacity is smaller than 1.5 μF / m ² , there is no problem in an image with a low resolution, but as a result, the fidelity of dots decreases as the resolution increases. When the charge capacity is larger than 8.0 μF / m ² , the dot fidelity is high, but the toner charge filling the photoreceptor increases, and the charge cannot be fully filled. It becomes easier to pick up defects. Further, it is more preferable to use an electrophotographic photosensitive member having a charge capacity of 1.5 to 6.0 μF / m ² . In order to change the charge capacity, it is possible to produce a photoconductor having an arbitrary charge capacity by changing the material of the photoconductor, adjusting the dielectric constant of the photoconductor, and changing the film thickness of the charge holding region.

  Next, the image forming method of the present invention will be described with reference to the drawings.

  FIG. 2 is a schematic configuration diagram of an electrophotographic full-color machine which is an image forming apparatus embodying the present invention.

  In FIG. 2, each ABCD station forms a full-color image of yellow, magenta, cyan, and black, but the station color order does not matter at all. In the following description, for example, the primary charger 21 refers to the primary chargers 21A, 21B, 21C, and 21D in each ABCD station.

  In each station, image formation is performed as follows.

  First, a photosensitive drum 4 as an image carrier is rotatably provided, and the photosensitive drum 4 is uniformly charged by a primary charger 21, and then an information signal is exposed by a light emitting element 22 such as a laser to statically. An electrostatic latent image is formed and visualized by the developing device 9. Next, the visible image is transferred to the transfer paper 24 conveyed by the transfer paper conveyance sheet 27 by the transfer charger 23.

  On the transfer paper 24, a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are sequentially superimposed and transferred at each station.

  The transfer paper 24 on which the toner images of the four colors are laminated is mixed and fixed by heat and pressure in the fixing device 25, and is discharged out of the device as a full color image.

  The measurement method in the present invention will be described below.

1. Method for measuring volume average particle size of magnetic carrier:
The volume average particle diameter of the magnetic carrier can be measured by, for example, a laser diffraction particle size distribution meter (manufactured by Horiba, Ltd.).

  For the measurement of the fine powder amount of 20 μm or less and the coarse powder amount of 74 μm or more by the mesh method, a mesh of each mesh is prepared and, for example, an electromagnetic experimental sieve shaker (Fritche Japan Analyset Type 3) is used. Can be measured. As a measurement method when this shaker is used, Timer = 5 min, Amplitude intensity = 2, and 200 g of the sample is used.

2. Method for measuring the amount of magnetization of a magnetic carrier:
The strength (amount) of magnetization of the magnetic carrier is obtained from the magnetic properties of the magnetic carrier and the true specific gravity of the magnetic carrier. The magnetic characteristics of the magnetic carrier can be measured by using an oscillating magnetic field type magnetic characteristic automatic recording apparatus BHV-30 manufactured by Riken Denshi Co., Ltd. As a measuring method, a cylindrical plastic container is filled with a magnetic carrier so as to be sufficiently dense, while an external magnetic field of 1 kilo-Oersted (79.6 kA / m) is formed, and in this state, the magnetic material filled in the container is filled. Measure the magnetization moment of the carrier. Further, the actual mass of the magnetic carrier filled in the container is measured to determine the magnetization strength (Am ² / kg) of the magnetic carrier.

3. Measuring method of resistance of magnetic carrier:
The volume resistance value of the magnetic carrier is measured using the measuring apparatus shown in FIG. The cell E is filled with carrier particles, the lower electrode 11 and the upper electrode 12 are arranged so as to be in contact with the filled carrier particles, a voltage is applied between these electrodes, and the current flowing at that time is measured to measure the volume. A method for obtaining resistance is used. The measurement conditions of the volume resistance in the present invention are as follows: the contact area S between the filled carrier particles and the electrode is about 2.3 cm ² , the thickness d is about 0.5 mm, and the load of the upper electrode 12 is 41.76 N (180 g).

4). Measuring method of true specific gravity of magnetic carrier:
The true specific gravity of the magnetic carrier particles can be measured by, for example, a dry automatic densitometer Accupic 1330 (manufactured by Shimadzu Corporation).

5). Measurement of toner particle or toner particle size distribution:
As a measuring device, Coulter Counter TA-II or Coulter Multisizer II (manufactured by Coulter Inc.) is used. As the electrolytic solution, an about 1% NaCl aqueous solution is used. As the electrolytic solution, an electrolytic solution prepared using primary sodium chloride or, for example, ISOTON (registered trademark) -II (manufactured by Coulter Scientific Japan) can be used.

  As a measurement method, 0.1 to 5 ml of a surfactant (preferably alkylbenzenesulfone hydrochloride) is added as a dispersant to 100 to 150 ml of the electrolytic aqueous solution, and 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and the volume and number of the sample are measured for each channel by the measuring device using a 100 μm aperture as the aperture. The volume distribution and the number distribution are calculated. From these obtained distributions, the weight average particle diameter of the sample is determined.

  As channels, 2.00 to 2.52 μm; 2.52 to 3.17 μm; 3.17 to 4.00 μm; 4.00 to 5.04 μm; 5.04 to 6.35 μm; 6.35 to 8. 00 μm; 8.00 to 10.08 μm; 10.08 to 12.70 μm; 12.70 to 16.00 μm; 16.00 to 20.20 μm; 20.20 to 25.40 μm; 25.40 to 32.00 μm; 13 channels of 32-40.30 μm are used.

6). Measurement of toner triboelectric charge:
The triboelectric charge amount of the toner of the present invention can be determined by the following method. First, the toner and the magnetic carrier are mixed so that the toner mass becomes 5% by mass, and then mixed for 120 seconds with a turbula mixer. This developer is put in a metal container with a 635 mesh conductive screen at the bottom, sucked with a suction machine, and the mass difference before and after suction and the potential accumulated in a capacitor connected to the container are measured. To do. At this time, the suction pressure is set to 250 mmH ₂ O. From the mass difference, the stored potential, and the capacitor capacity, the triboelectric charge amount of the toner is calculated using the following formula. FIG. 4 is an explanatory diagram of an apparatus for measuring the triboelectric charge amount of toner. First, in a metal measuring container 2 having a 500 mesh screen 1 at the bottom, 50 g of a 1:19 weight ratio mixture of toner and carrier to be measured for triboelectric charge is placed in a polyethylene bottle of 50 to 1000 ml capacity. , 30 times and 500 times by hand, about 0.5 to 0.9 g of the mixture (developer) is put into a metal lid 3. The total mass of the measurement container 2 at this time is weighed and is defined as W1 (g). Next, in the suction device 4 (at least the insulator is in contact with the measurement container 2), suction is performed from the suction port 5 and the air volume control valve 6 is adjusted so that the pressure of the vacuum gauge 7 is 250 mmAq. In this state, the toner is sucked and removed by suction for about 2 minutes. The potential of the electrometer 8 at this time is set to V (volt). Here, 9 is a capacitor, and the capacity is C (μF). Moreover, the mass of the whole measurement container after suction is weighed and is defined as W2 (g). The triboelectric charge amount (μC / g) of the toner is calculated by the following equation.
Toner triboelectric charge amount (μC / g) = C × V / (W1−W2)

7). Measurement of maximum endothermic peak of release agent and toner:
The maximum endothermic peak of the release agent and toner can be measured according to ASTM D3418-82 using a differential thermal analyzer (DSC measuring device) and DSC2920 (TA Instruments Japan).

  As a measuring method, 5 to 20 mg, preferably 10 mg of a measurement sample is accurately weighed. This is put into an aluminum pan, and an empty aluminum pan is used as a reference, and measurement is performed at a temperature rise rate of 10 ° C./min and normal temperature and humidity in a measurement temperature range of 30 to 200 ° C. In this temperature rising process, an endothermic peak in the temperature range of 30 to 200 ° C. is obtained. When there are a plurality of peaks, the highest endothermic peak is the one having the highest height from the baseline in the region above the endothermic peak due to the resin.

8). Measurement of particle size of toner fine particles and external additives:
Regarding the particle size of the inorganic fine particles and the external additive on the toner surface, 500 or more particles having a particle size of 0.001 μm or more are randomly extracted by a scanning electron microscope (50,000 times), and the major axis and the minor axis are digitized. The average value is the particle size, and the peak value in the range of 0.001 to 0.06 μm is the number average particle size of the external additive, with the particle size becoming the peak of the particle size distribution of 500 or more particles. The diameter is calculated as the number average particle diameter of the inorganic fine particles with the peak value in the range of 0.06 or more.

  Examples of the present invention will be specifically described below, but the present invention is not limited thereto.

● Production example of carrier 1 for electrophotography (i) 7.5 parts by mass of phenol (ii) 11.25 parts by mass of formalin solution (about 40% formaldehyde, about 10% methanol, the rest is water)
(Iii) 100 parts by mass of magnetite fine particles lipophilically treated with 1.0% by mass of γ-glycidoxypropyltrimethoxysilane (average particle size 0.35 μm, volume resistance 5.3 × 10 ⁵ Ωcm)
The above materials and 11 parts by mass of water were mixed for 1 hour while maintaining the temperature at 40 ° C. Here, the lipophilic treatment of the above magnetite is performed by adding 1.0 part by mass of γ-glycidoxypropyltrimethoxysilane to 100 parts by mass of magnetite, and premixing and stirring at 100 ° C. for 30 minutes in a Henschel mixer. Went by.

To this slurry, 2.0 parts by mass of 28% by mass ammonia water as a basic catalyst and 11 parts by mass of water were added, and the temperature was raised to 85 ° C. for 40 minutes while stirring and mixing, followed by reaction for 3 hours. A resin was produced and cured. Then, after cooling to 30 degreeC and adding 100 mass parts water, the supernatant liquid was removed, the deposit was washed with water, and air-dried. Next, this was dried at 160 ° C. under reduced pressure (5 mmHg (6.7 × 10 ² Pa) or less) to obtain magnetite fine particle-containing spherical magnetic carrier core particles A using a phenol resin as a binder resin.

(Formation of first resin coating layer)
Next, (i) melamine 5.5 parts by mass (ii) formalin solution 10.75 parts by mass (formaldehyde about 40%, methanol about 10%, the rest is water)
(Iii) Magnetic carrier core particle A 160 parts by mass (iv) Calcium fluoride 0.5 part by mass The above materials and 200 parts by mass of water are added, and the solution pH is adjusted to 8.5 with sodium hydroxide while stirring. Raise to 85 ° C. in minutes and allow to react for 15 minutes at this temperature. After completion of the reaction, cool to 30 ° C,
(V) 30% by mass of 5% ammonium solution was added, the temperature was raised to 85 ° C. over 60 minutes, and the reaction and curing were performed at the temperature for 90 minutes.

  After completion of the reaction and curing, the contents in the flask are cooled to 30 ° C., washed several times with water, air-dried, and dried under reduced pressure at 60 ° C. (5 mmHg or less) to coat with a melamine resin. Particle A was obtained.

  The dried core particles are passed through a 60-mesh and 100-mesh sieve to remove coarse particles, and then a multi-division wind classifier using the Coanda effect (Ebbo Jet Lab EJ-L-3, manufactured by Nittetsu Mining) Were used to remove fine powder and coarse powder to obtain carrier core particles having a volume average particle diameter of 37 μm.

(Formation of second resin coating layer)
The obtained carrier core particles were put into a coater, and a methyl methacrylate copolymer having a methyl methacrylate and a perfluoroalkyl group (m = 7) (copolymerization ratio 8: 1 weight average molecular weight 45,000) was used as a coating material. ) To the carrier core while volatilizing the solvent at 70 ° C. while continuously applying a shear stress to the coating solution so as to be 10% by mass in a mixed solvent of methyl ethyl ketone and toluene so as to be 2 parts by mass. Then, resin coating was performed on the surface of the magnetic carrier core particle A.

The resin-coated magnetic carrier particles were heat-treated with stirring at 100 ° C. for 2 hours, cooled, crushed, classified by a 200 mesh sieve, and number-average particle diameter 32 μm, true specific gravity 3.53 g / cm ^3. A carrier 1 having a magnetization strength of 51.7 Am ² / kg was obtained. The physical properties of the obtained carrier 1 are shown in Table 1.

Production Examples of Carriers 2 to 15 Carriers 2 to 15 were prepared according to the same production method as that of the production example of Carrier 1. Table 1 shows the physical properties of the obtained carriers.

● Example of toner production <Production method of hybrid resin>
As a vinyl copolymer, 1.9 mol of styrene, 0.21 mol of 2-ethylhexyl acrylate, 0.15 mol of fumaric acid, 0.03 mol of α-methylstyrene dimer, and 0.05 mol of dicumyl peroxide are put into a dropping funnel. . In addition, 7.0 mol of polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2.2) -2,2-bis (4-hydroxyphenyl) propane; Put 0 mol, 3.0 mol of succinic acid, 2.0 mol of trimellitic anhydride, 5.0 mol of fumaric acid and 0.2 g of dibutyltin oxide in a 4-liter 4-neck flask made of glass, thermometer, stir bar, condenser and nitrogen The introduction tube was installed and placed in a mantle heater. Next, after the inside of the flask was replaced with nitrogen gas, the temperature was gradually increased while stirring, and while stirring at a temperature of 145 ° C., the monomer of the vinyl resin, the crosslinking agent and the polymerization initiator were added from the previous dropping funnel. It was dripped over 4 hours. Subsequently, the temperature was raised to 200 ° C. and reacted for 4 hours to obtain a hybrid resin (1).

<Toner 1>
A cyan toner (toner 1) was prepared by the following method.

・ Hybrid resin resin (1) 60 mass parts ・ First paste form with a solid content of 40 mass% obtained by removing water from the pigment slurry to some extent from the Cu phthalocyanine filtration step and without passing through the drying step. 100 parts by weight of pigment (the remaining 60% by weight is water)

(First kneading step)
First, the above raw materials are charged into a kneader type mixer according to the above formulation, and the temperature is raised under no pressure while mixing. When the maximum temperature (necessarily determined by the boiling point of the solvent in the paste. In this case, about 90 to 100 ° C.) is reached, the pigment in the aqueous phase is distributed or transferred to the molten resin phase, and this is confirmed. After that, the mixture is further melted and kneaded for 30 minutes to sufficiently transfer the pigment in the paste. Then, once the mixer was stopped and the hot water was discharged, the temperature was further raised to 130 ° C., heated and kneaded for about 30 minutes, the pigment was dispersed and the water was distilled off, and the process was completed. The kneaded product was taken out and cooled to obtain a first kneaded product. The water content of the first kneaded product was about 0.5% by mass.

  Next, toner 1 was prepared by the following method.

Hybrid resin (1) 92.5 parts by mass The first kneaded product (pigment particle content 40% by mass) 12.5 parts by mass Wax A (paraffin Tg = 68 ° C) 5 parts by mass 0.2 parts by mass of an aluminum compound of butyl salicylic acid (charge control agent)

(Second kneading step)
After mixing the ingredients of the above formulation with a Henschel mixer (FM-75 type, manufactured by Mitsui Miike Chemical Co., Ltd.), a twin-screw kneader (PCM-30 type, Ikegai Iron Works Co., Ltd.) set at a temperature of 130 ° C. Kneaded). The obtained kneaded material was cooled and coarsely pulverized to 1 mm or less with a hammer mill to obtain a coarsely pulverized material. The obtained coarsely pulverized toner was pulverized using a collision-type airflow pulverizer using high-pressure gas. The obtained finely pulverized product had a weight average diameter of 4.8 m. Next, the finely pulverized product thus obtained was strictly and finely removed simultaneously with a multi-division classifier to obtain a cyan classified product.

  To 100 parts by mass of the obtained cyan classified product, 1.0 part by mass of hydrophobized titanium oxide having an average particle diameter of 40 nm and 1.5 parts by mass of amorphous silica having an average particle diameter of 110 nm are externally added and mixed. (Toner 1) was obtained. The obtained toner 1 had a weight average particle diameter of 5.5 μm and a number average particle diameter of 4.9 μm.

<Toner 2>
A 0.1 mol / liter-Na ₃ PO ₄ aqueous solution and a 1.0 mol / liter-CaCl ₂ aqueous solution are prepared. 710 parts by mass of ion-exchanged water and 550 parts by mass of 0.1 mol / liter-Na ₃ PO ₄ aqueous solution were added to a 2-liter four-necked flask equipped with a TK homomixer (Special Machine Industries Co., Ltd.) and rotated. The number was adjusted to 10,000 revolutions and warmed to 65 ° C. To this, 68 parts by mass of a 1.0 mol / liter-CaCl ₂ aqueous solution was gradually added to prepare a dispersion medium system containing a fine water-soluble water-soluble dispersant Ca ₃ (PO ₄ ) ₂ .

On the other hand, the dispersoid system is
-Styrene 160 parts by mass-n-butyl acrylate 40 parts by mass-Colorant (phthalocyanine pigment) 6 parts by mass-Saturated polyester 10 parts by mass (terephthalic acid-propylene oxide modified bisphenol A)
-Aluminum compound of di-tert-butylsalicylic acid 3 parts by mass-Wax B 20 parts by mass After the above mixture was dispersed for 3 hours using an attritor, 2,2'-azobis (2,4-dimethyl) which is a polymerization initiator A dispersion to which 2 parts of valeronitrile) was added was prepared.

  This was put into the dispersion medium and granulated for 8 minutes while maintaining the rotation speed. Then, the stirrer was changed from a high-speed stirrer to a propeller stirring blade, and while stirring at 50 revolutions, the internal temperature was increased to 60 ° C. for 4 hours, and then the temperature was raised to 80 ° C. and polymerization was continued for 4 hours for a total of 8 hours. After completion of the polymerization, the slurry was cooled, diluted hydrochloric acid was added to remove the dispersant, and a nonmagnetic toner was obtained.

For 100 parts by mass of the non-magnetic toner, 0.7 parts by mass of hydrophobic titanium oxide fine particles having a BET specific surface area of 100 m ² / g and 0.7 parts by mass of hydrophobic silica fine particles having a BET specific surface area of 40 m ² / g Mixing with a Henschel mixer gave a cyan-classified product.

  The obtained cyan classified product was subjected to the same external additive mixing as that of toner 1 to obtain a cyan toner (toner 2). The obtained toner 2 had a weight average particle diameter of 6.2 μm and a number average particle diameter of 5.1 μm.

<Example 1>
92 parts by mass of carrier 1 obtained above and 8 parts by mass of toner 1 were added and mixed with a V-type mixer or the like to obtain a start developer.

Using this developer, Canon's full color copier CLC5000 remodeled machine (with a reduced laser spot diameter and a structure that can be fitted with a secondary transfer mechanism, can output at 600 dpi, change the surface of the fixing roller of the fixing unit to a PFA tube, oil The image formation evaluation was performed using a device with the coating mechanism removed and a modified CLC5000. The developing condition is that the developing sleeve and the photosensitive member are rotated in the forward direction in the developing region, the developing sleeve is 1.85 times the photosensitive member, Vd-600 V, Vl-110 V, Vdc-450 V, Vpp 2 kV, frequency 1 8 kHz. The photoconductor used here was an amorphous silicon photoconductor 1) having a surface resistance of 2.6 × 10 ¹⁴ Ωcm.

  These evaluation results are shown in Table 2. The image evaluation items and evaluation criteria are shown below.

  Furthermore, a printing durability test of 50,000 sheets was performed under the above-described process conditions under a normal environment (23 ° C./60%), and the results were satisfactory without significant image quality degradation. Similarly, the evaluation results are shown in Table 2, and the evaluation criteria are shown below.

(1) Development injectability A full-color copying machine CLC5000 made by Canon is used and a photoconductor used in this embodiment is disposed.

Only the carrier was put in the developing device, and the amount of the carrier on the developing roller was adjusted with a regulating blade so as to be 30 mg / cm ² . Further, the distance between the developing roller and the photosensitive member was adjusted to be 400 μm.

  In addition, a 650 nm semiconductor laser was used as the laser, the spot diameter was reduced, and output was possible at 600 dpi.

  When there was no potential setting carrier, when using an amorphous silicon photoconductor, the non-exposed portion potential: −450 V, the exposed portion potential: −50 V, the bias potential was set to DC: −300 V, and AC: body setting.

  When using the OPC photosensitive member, the non-exposed portion potential: -700 V, the exposed portion potential: -150 V, the bias potential was set to DC: -500 V, and AC: main body setting.

  A potential sensor (Model 344 manufactured by Trek) was disposed immediately after the developing device, and the potential difference between when the carrier was present and when it was absent was determined.

(2) Development efficiency and transfer efficiency As an evaluation means for showing the development characteristics in the present invention, it is useful to substitute the following measurement method.

  It is appropriate that the development characteristics are expressed as development efficiency. As a measuring means, first, the two-component developer according to the present invention is used, and a Canon full-color copier CLC5000 remodeled machine that is also used in the examples described later. Then, the entire solid image is developed.

  In that case, the developer amount per unit area of the developer carried on the developing sleeve is measured in advance (D1). Thereafter, as described above, the entire solid image is developed on the photosensitive drum, and the photosensitive drum is stopped at a stage before being transferred to the intermediate transfer member or the like. The toner layer developed on the stopped photosensitive drum is subjected to suction sampling, and the toner amount (D2) per unit area is measured in the same manner as on the sleeve.

  Finally, the development efficiency is calculated from the ratio between the developer amount on the sleeve (D1) and the toner amount (D2) developed on the photosensitive drum.

In the case of transfer efficiency, the main body is stopped in the sequence before the fixing machine enters the image pattern, an unfixed image on the transfer medium is sucked and collected, and the toner amount (D3) is calculated. Thereafter, the transfer efficiency is calculated from the ratio between the toner amount (D2) developed on the photosensitive drum and the collected toner amount (D3), as in the development efficiency measurement.
A: When developing (transfer) efficiency of 95% or more B: When developing (transfer) efficiency of 90% or more C: When developing (transfer) efficiency of 85% or more D: 80% or more E: When development (transfer) efficiency is 80% or less

(3) Scattering Evaluation of image scattering was carried out by using the above-described imaging tester to evaluate image scattering of a horizontal line pattern in which 4-dot horizontal lines were printed every 176 dot spaces.
A: Image with little image scattering even by magnified observation B: Image with little image scattering even by magnified observation C: Unevenness in line thickness due to scattering D: Some fine characters are crushed due to scattering Seen

(4) Graininess and HT uniformity of HT portion An HT image (30H image) is formed using the toner and the remodeling machine, and this image is observed with eyes. The graininess and uniformity of the image are as follows. Based on the criteria of The 30H image is a halftone image when 256 gradations are displayed in hexadecimal, 00H is solid white, and FFH is solid black (entire image).
The evaluation level of HT granularity is as follows.
A: Smooth and smooth.
B: I don't feel a lot of rustling.
C: Although there is a slight feeling of roughness, it is at a level where there is no practical problem.
D: There is a feeling of roughness and is a problem.
E: There is a very rough feeling.

The evaluation level of HT uniformity is as follows. The image density was evaluated using a reflection densitometer 500 Series Spectrodensitometer manufactured by X-rite.
A: The concentration is uniform over the entire surface.
B: The density difference at the front end of the image is within 0.3, and there is no practical problem.
C: The density difference at the leading edge of the image is within 0.3 to 0.5, and the density difference is noticeable.
D: The density difference at the front end of the image is 0.5 or more, which is a problem.

(5) Evaluation criteria A by printing durability test : Good without impairing image quality.
B: Some unevenness was confirmed with respect to density uniformity in the HT portion.
C: The image quality is drastically reduced due to low density from the beginning and scattering from the middle of the printing durability.
D: The printing durability test was canceled due to the occurrence of abrasion on the photosensitive drum surface.

<Examples 2 to 4>
A developer was prepared using Carriers 2 to 4 instead of Carrier 1 used in Example 1. After that, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 2.

<Comparative Examples 1-6>
A developer was prepared using Carriers 5 to 10 instead of Carrier 1 used in Example 1. After that, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 2.

<Examples 5-7>
A developer was prepared using Carriers 11 to 13 instead of Carrier 1 used in Example 1. After that, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 2.

<Comparative Examples 7-8>
A developer was prepared using Carriers 14 to 15 instead of Carrier 1 used in Example 1. After that, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 2.

<Example 8>
The same evaluation as in Example 1 was performed except that toner 2 was used instead of toner 1 used in Example 1. The evaluation results are shown in Table 2.

<Comparative Example 9>
The same evaluation as in Comparative Example 1 was performed except that Toner 2 was used instead of Toner 1 used in Comparative Example 1. The evaluation results are shown in Table 2.

<Examples 9 to 10>
A developer was prepared using the OPC photoreceptor 1) instead of the a-Si photoreceptor 1) used in Example 8, and using the carrier 3 and the carrier 4 instead of the carrier 1. After that, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 2.

<Examples 11 to 12>
A developer was prepared in the same manner except that toner 1 was used instead of toner 2 used in Examples 9 and 10. After that, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 2.

<Comparative Examples 10-11>
Developers were similarly prepared except that Carrier 8 and Carrier 9 were used instead of Carrier 3 and Carrier 4 used in Examples 11 and 12, respectively. After that, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 2.

<Comparative Examples 12-13>
A developer was prepared in the same manner except that toner 2 was used instead of toner 1 used in Comparative Examples 10 and 11. After that, the same evaluation as in Example 1 was performed. The evaluation results are shown in Table 2.

It is an image figure which shows the structure of the magnetic carrier in this invention. FIG. 2 is a diagram illustrating an image forming apparatus using a developing device having a plurality of developer holders, which represents the present invention. It is a schematic sectional drawing of the apparatus which measures the volume resistance of the magnetic carrier of this invention, a magnetic body, and a nonmagnetic inorganic compound. FIG. 6 is an explanatory diagram of an apparatus for measuring the triboelectric charge amount of toner.

Explanation of symbols

11: Lower electrode 12: Upper electrode 13: Insulator 14: Ammeter 15: Voltmeter 16: Constant voltage device 17: Carrier 18: Guide ring d: Sample thickness E: Resistance measurement cell

Claims (10)

A first resin coating layer made of a nitrogen-containing resin and a second resin coating layer containing conductive particles are formed on the magnetic carrier core particles containing at least a binder resin and magnetic particles. An electrophotographic carrier comprising the magnetic carrier core particles containing 70 to 95% by mass of magnetic particles,
The electrophotographic carrier is
1) The magnetization intensity (M) at 79.6 kA / m is 40 to 70 Am ² / kg,
2) Volume resistance (R1) when 5 × 10 ⁵ V / m is applied is 1.0 × 10 ¹⁰ to 1.0 × 10 ¹³ Ωcm,
Volume resistance (R2) when applied with 2 × 10 ⁵ V / m is 1.0 × 10 ¹³ to 1.0 × 10 ¹⁶ Ωcm
An electrophotographic carrier characterized by being in the range.   The electrophotographic carrier according to claim 1, wherein the nitrogen-containing resin is a melamine resin.   3. The electrophotographic carrier according to claim 1, wherein the magnetic carrier core particle is coated with a nitrogen-containing resin in a range of 0.1 to 1.5 mass%.   The electrophotographic carrier according to claim 1, wherein the conductive particles contained in the second resin coating layer are carbon black.   5. The electrophotographic carrier according to claim 4, wherein a content of the carbon black is 1 to 20% by mass with respect to a resin forming the second resin coating layer. The electrophotographic carrier according to claim 1, wherein the true specific gravity of the electrophotographic carrier is 3.0 g / cm ³ or more and 4.5 g / cm ³ or less. The volume resistance (R1) when an electrophotographic carrier is applied with 5 × 10 ⁵ V / m is 1.0 × 10 ^{10 to} 5.0 × 10 ¹² Ωcm, and the volume resistance when applying 2 × 10 ⁵ V / m (R2). ) Is in the range of 1.0 × 10 ^{13 to} 1.0 × 10 ¹⁵ Ωcm, The electrophotographic carrier according to claim 1.   8. The electrophotographic carrier according to claim 1, wherein the resin forming the second resin coating layer is a thermoplastic resin.   A two-component developer comprising a toner containing at least a binder resin and a colorant and the electrophotographic carrier according to any one of claims 1 to 8.   An image forming method comprising developing a latent image formed on an amorphous silicon photoreceptor using the two-component developer according to claim 9.

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