JP5459539B2 - Method for producing coating liquid for electrophotographic carrier coating - Google Patents

Description

  The present invention relates to an electrophotographic carrier and an electrophotographic developer, and more particularly to a method for producing a coating liquid for coating a core material of an electrophotographic carrier used for forming an electrostatic latent image into a toner image. .

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

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

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

Regarding the carrier, while the demand for faster and more beautiful image formation is increasing, the stress received by the developer containing the carrier and the toner has increased dramatically with the recent increase in machine speed. Even in a carrier having a long life, a sufficient life cannot be obtained.
Furthermore, in terms of high image quality, with the reduction in toner diameter and carrier diameter, the allowable range in the image quality with respect to the charge amount distribution has become narrower, especially for toner stains (background fogging) in non-image areas. It becomes very easy to become a defective image.

In order to cope with such a problem, for example, in Japanese Patent Application Laid-Open No. 2007-102159 of Patent Document 1 and Japanese Patent Application Laid-Open No. 2008-70837 of Patent Document 2, particles having a diameter larger than the film thickness are included in the coating layer. An electrophotographic carrier has been proposed.
Furthermore, Japanese Patent Application Laid-Open No. 2007-286078 of Patent Document 3 includes two types of particles: toner, first particles having a diameter larger than the film thickness, and second particles having a diameter smaller than the film thickness. There has been proposed a method in which a developing device is replenished with a carrier provided with a coating film on the surface of a core material, and development is performed while discharging an excess developer in the developing device.
Japanese Patent Application Laid-Open No. 11-184167 of Patent Document 4 has a plurality of resin coating layers on a magnetic core, and needle-like or scaly conductive powder is formed on the first coating layer directly above the magnetic core. Describes a carrier for an electrophotographic developer dispersed by a bead mill using glass beads.

However, those described in Patent Documents 1 to 4 have insufficient effects, and are not suitable for carrier adhesion in a solid image portion and toner stain (background fogging) in a non-image portion accompanying a decrease in resistance over time. Enough and problematic.
It has been conventionally known to achieve good dispersion of the powder material in the coating liquid using a bead mill. For example, Japanese Patent Application Laid-Open No. 2007-292298 of Patent Document 5 is not related to a carrier, but in the preparation of a conductive particle-containing coating solution for forming a conductive undercoat layer of a photoreceptor substrate, the particle size is dispersed by dispersion. Since the surface energy increases due to the decrease in the thickness, if the dispersion treatment is performed with a strong shear, the coating solution tends to re-aggregate after the dispersion treatment is completed. Therefore, in order to carry out stable bead mill dispersion, the peripheral speed of the rotating disk of the mill is lowered according to the size (particle size) and specific gravity of the beads used to achieve a low shear force. It is disclosed that. However, the beads used in this disclosed technology are glass beads having a large particle size of 0.8 mm (low specific gravity), and there is no consideration for preventing beads that flow away as the liquid to be treated is discharged. .

  The present invention has been made in consideration of the above-described circumstances, and does not cause carrier adhesion in a solid image portion due to a decrease in resistance over time, and does not cause toner contamination (background fogging) in a non-image portion. It aims at providing the manufacturing method of the coating liquid for coat | covering the core material of a carrier.

That is, the said subject is solved by following (1)-(13) of this invention.
(1) “A method for producing a coating liquid for coating a core material of an electrophotographic carrier, wherein a solution containing at least a binder resin and solid particles is dispersed using beads having a bead diameter of 5 mm or less. has a dispersion step, as disperser in the main dispersion process, using a dispersing machine having a classification mechanism for separating the beads dispersion chamber is intended feeding method of the dispersion is the path system, the A method for producing a coating liquid, wherein the classification mechanism is a centrifuge ”,
(2) “The method for producing a coating liquid according to (1) above, which includes a pre-dispersion step in which the beads are not used before the main dispersion step”;
(3) “The method for producing a coating liquid according to (2) above, which includes a primary sieving step of passing a sieving between the pre-dispersing step and the main dispersing step”;
(4) "The method for producing a coating liquid according to any one of (1) to (3) above, further comprising a secondary sieving step through which a sieve is passed after the main dispersion step" ,
(5) “The method for producing a coating liquid according to any one of (1) to (4) above, wherein the true density of the beads is 2.8 g / cm ³ or more” ,
(6) “The method for producing a coating liquid according to any one of (1) to (5) above, wherein the beads are a single type or a mixture of a plurality of types of beads”,
(7) “After the main dispersion step, the method includes the step of extruding only the coating liquid with the solvent used in the solution, leaving the beads in the dispersion chamber,” The manufacturing method of the coating liquid in any one of (6) term ",
(8) “Coating liquid for covering a core material of an electrophotographic carrier, characterized by being produced by the production method according to any one of (1) to (7)”,
(9) “Coating liquid according to (8) above, which does not contain coarse particles having a particle size of 1 μm or more”,
(10) "Electrophotographic carrier characterized in that it has a coating layer formed on the surface of the core material particles by the coating liquid according to item (8) or (9)",
(11) “The electrophotographic carrier according to item (10), wherein the coating layer does not include coarse particles having a particle diameter of 5 μm or more”,
(12) “Two-component developer for electrophotography, comprising toner and electrophotographic carrier according to item (10) or (11)”,
(13) “Equipped with at least an electrostatic latent image carrier, a means for forming an electrostatic latent image on the image carrier, and a developing means for developing the electrostatic latent image, the developing means An image forming apparatus using the two-component developer according to item (12).

  As will be apparent from the following detailed and specific description, the present invention does not cause carrier adhesion in a solid image portion due to a decrease in resistance over time, and does not cause toner contamination (background fogging) in a non-image portion. This presents an extremely excellent effect that a method for producing a coating liquid for coating the core material of a photographic carrier can be provided.

1 is a schematic diagram illustrating an example of an image forming apparatus of the present invention. It is the schematic which shows the other example of the image forming apparatus of this invention. It is the schematic which shows an example of the further another image forming apparatus (tandem type color image forming apparatus) of this invention. FIG. 4 is a partially enlarged schematic view of the image forming apparatus shown in FIG. 3. In the manufacturing method of the coating liquid for carrier core material coating, it is the schematic which shows an example of the liquid feeding method in this dispersion | distribution process.

Hereinafter, the present invention will be described in more detail.
As a result of continual investigations to solve the above-mentioned problems of the prior art, the present inventors are a method for producing a coating liquid for coating the core material of an electrophotographic carrier, comprising at least a binder resin And a dispersion process in which the solution containing the solid particles is dispersed using beads having a bead diameter of 5 mm or less, and has a classification mechanism for separating the beads in the dispersion chamber as a disperser in the dispersion process. It has been found that the improvement effect is remarkable by using a disperser and using a pass method as a method for feeding the dispersion.

This is because the dispersed state of solid particles in the coating layer is an important requirement for the problem of the present invention, and that stable quality can be obtained by uniformly dispersing in the coating layer. However, it is based on the knowledge that the uniform dispersion of the solid particles in the coating layer is achieved by using a coating liquid produced by a specific production method. That is, by improving the dispersion of the solid particles, it is possible to maintain the same coating layer state at any location of the coating layer, so that the uniformity among the carrier particles is increased. Thus, the charge amount distribution and the wear resistance can be drastically improved.
Furthermore, as a result of using the coating liquid by the specific manufacturing method, the solid particles are uniformly dispersed in the coating layer, so that the surface of the solid particles is surely covered with the resin, so that it is difficult to detach, and a large aggregation state Unlike the case where it exists, the coating film due to the detachment of the solid particles is eliminated, and the core material is prevented from being exposed.
Therefore, it is possible to improve the carrier adhesion in the solid image portion and the toner stain (background fogging) in the non-image portion, which are the problems of the present invention.

As described above, the specific manufacturing method of the coating liquid for achieving the dispersion of the solid particles in the coating resin has been found to be very important for the carrier quality. Sufficient consideration has not been made.
For example, in Japanese Patent Application Laid-Open No. 2007-102159 (Patent Document 1), only a dispersion process is performed in which a raw material is put into a homomixer and dispersed for 10 minutes. As in the present invention, dispersion using beads is performed. No attempt has been made so far to actively disperse solid particles by a method.
Furthermore, since the sand mill described in JP-A-11-184167 (Patent Document 4) has a relatively large bead diameter, it is easy to separate the beads from the dispersion. There is no classifier to separate beads in the dispersion chamber. However, as the bead diameter decreases, the sand mill described here increases the proportion of beads leaking out of the dispersion chamber, and the amount of beads decreases with time, making it substantially impossible to disperse. In addition, when a conventional bead mill is used instead of a sand mill, if a bead having a bead diameter of 5 mm or less is used, a dispersal action cannot be substantially performed as described above. On the other hand, when the bead diameter is increased, the dispersion energy per grain increases, so the surface of the solid particles is excessively activated, causing reaggregation of the solid particles, and decomposing other materials in the dispersion. -Problems such as reaction and further gelation of the dispersion liquid will occur, so that a dispersion liquid having the desired dispersion particle size and without reaggregation cannot be obtained.
In other words, in order to obtain a target dispersed particle size, it is better to use beads with a particle size as small as possible, but it has been difficult to adopt beads with a particle size of 5 mm or less with a conventional disperser.
However, in the present invention, the bead diameter is preferably 1 mm or less, and more preferably 0.5 mm or less. Further, the lower limit value of the bead diameter is not particularly limited as long as this effect is exhibited, but it is preferably 0.01 mm or more in consideration of dispersion efficiency and the like. Furthermore, the specific gravity of the beads is preferably 3 or more, more preferably 5 or more.

FIG. 5 is a schematic view showing an example of a dispersion feeding method in the present dispersion step in the method for producing a coating liquid for coating a core material. As a method for feeding a dispersion liquid to the dispersion apparatus in the dispersion step of the present invention, conventionally, there is a method of circulating the liquid continuously for a fixed time. In this case, in the piping in the circulation path or the dispersion liquid collection tank As the liquid stays inside, there are parts that pass through the dispersing device many times and parts that do not pass at all in the whole liquid, and deviation occurs in the dispersion state in the whole dispersion. The distribution is broad and the desired dispersed particle size cannot be obtained.
In the present invention, the improvement effect is remarkable by adopting the pass method as the liquid feeding method in the dispersion step.
Here, the pass method is a method in which the total amount of the dispersion liquid is completely passed through the present dispersion apparatus, and this is used as one pass, and this liquid total amount dispersion pass is repeated. In the example shown in FIG. 5, the liquid in the circulation tank (2) is passed through a disperser and dispersed, and the total liquid amount is collected in the circulation tank (1) (one pass). Next, the valve provided in the lower part of the circulation tank (1) is opened, the total amount of liquid is transferred to the circulation tank (2), and the second and subsequent dispersions (second and subsequent passes) are repeated. As a result, the number of dispersions of the total amount of the liquid can be made constant, and as a result, the dispersed particle size distribution becomes sharp as the dispersion state of the entire liquid, and the desired dispersed particle size can be obtained.

Furthermore, the improvement effect is remarkable by having the pre-dispersion process which does not use a bead before the dispersion | distribution process using a bead.
This is because the solid particles of the raw material exist as agglomerates of several hundred μm, and as the bead diameter becomes smaller, it becomes difficult to disperse with the beads.
More specifically, in the case of dispersion by beads, since the aggregates are unraveled small by hitting the aggregates, the relationship between the volume and weight of the beads and the size of the aggregates is important. That is, as the bead diameter becomes smaller, the beads become smaller with respect to the size of the aggregate, and the coarse aggregate cannot be dispersed with the beads. Therefore, it has been found that the work of dispersion in the main dispersion step using beads can be reduced by preliminarily dispersing the aggregates by pre-dispersion without using beads.

Thus, the classification mechanism in the present invention may be any method as long as it can separate the dispersion and the beads in the dispersion chamber.
For example, a sieve, a wire screen, a centrifuge, etc. are mentioned.
Among these, sieves and wire screens exist as large agglomerates in the situation where the dispersion of solid particles at the initial stage of dispersion is not progressing. It is easy to cause a problem that the liquid is lost or completely clogged and the dispersion does not flow. On the other hand, classification by the centrifugal separation mechanism has a significantly larger liquid path compared to the bead diameter and the size of the aggregates of solid particles, so clogging does not occur at all, but on the other hand, the beads do not fall out. It is necessary to manage the peripheral speed exactly.
The rotor linear velocity of the bead mill disperser in the present invention is preferably 4 to 20 m / sec, more preferably 4 to 15 m / sec, and particularly preferably 4 to 10 m / sec. The bead filling rate is preferably 10 to 90%, more preferably 20 to 60%, and particularly preferably 30 to 50%.

Furthermore, the improvement effect is remarkable by having a primary sieving step for passing the sieving between the pre-dispersing step and the main dispersing step.
In this case as well, as described in the pre-dispersion section, the dispersion state in the dispersion step using beads is more reduced in the state of aggregation of the solid particles in the dispersion liquid charged into the dispersion step using beads. This is because the workload is small. In addition, by eliminating excessive coarse particles that can be an impediment to dispersion in the dispersion step using beads, an effect of efficiently promoting dispersion can be obtained. The opening size of the sieve is preferably 10 to 100 μm capable of collecting coarse particles.

Furthermore, an improvement effect is remarkable by having the secondary sieving process which makes a sieve pass after this dispersion | distribution process. The main purpose of this is to collect the beads used for dispersion.
Generally, in a disperser using beads, it is difficult to reduce the discharge of beads to the outside of 0%, and this tendency becomes more prominent as the bead diameter becomes smaller.
When the beads are discharged out of the apparatus together with the dispersion liquid, it may cause a failure of the device in the subsequent process or contaminate the carrier product, which is very undesirable. In particular, contamination with carrier products can cause various troubles.
For example, since beads are particles that do not have magnetization, they can be scattered into the electrophotographic equipment, causing failure, or moving to the photoreceptor side, damage to the photoreceptor, damage to the intermediate transfer belt, damage to the fixing roller or fixing belt. May cause a defect image due to carrier adhesion.
Moreover, about the opening of a sieve, in order to be able to repair a bead reliably, it is preferable to make it 1/2 or less of bead diameter.
In addition to collecting beads, it also functions to remove coarse particles (including aggregates) that could not be dispersed in the disperser. In particular, when the beads are dispersed while being circulated, a short pass is unavoidable, and coarse particles (including aggregates) may be mixed into the product. Need to be removed). The opening size of the sieve is preferably 10 to 100 μm capable of collecting beads and coarse particles.

Furthermore, the true density of the beads used for the present dispersion is 2.8 g / cm ³ or more, and the improvement effect is remarkable when used alone or in combination.
This is because the disperser using beads collides with the solid particles that the beads want to disperse, so the dispersion energy increases as the true density of the beads increases, so a high dispersion effect can be obtained. This is because. A more preferable range is 5 g / cm ³ or more.
On the other hand, when it is less than 2.8 g / cm ³ , the density is small, so that a sufficient dispersion effect cannot be obtained.
In addition, in the case of beads such as glass materials, not only the true density is low but also brittle, so cracking occurs during the dispersion treatment, resulting in reduced dispersion efficiency and contamination of the product, which is not preferable. .
Examples of the beads having a true density of 2.8 g / cm ³ or more in the present invention include zirconia, alumina, silicon nitride, steel, and stainless steel. These are not only true density but also brittle (crack) resistant and Although it is very good also about abrasion, it is an illustration to the last and is not limited to these.

Furthermore, the improvement effect is remarkable because the particle size of the beads used for this dispersion is 5 mm or less. This is because beads generally exist up to about 60 mm on the large diameter side, but in the case of an electrophotographic carrier as in the present invention, the solid particles to be dispersed are small and the number of particles is large. However, since the number cannot be increased on the large diameter side, a sufficient dispersion effect cannot be obtained.
Furthermore, since the dispersion energy per grain increases as the diameter increases, the surface of the solid particles is excessively activated, causing reaggregation of the solid particles, and decomposition / reaction of other materials in the dispersion. It is important that the thickness is 5 mm or less because problems such as the occurrence of such problems occur.
Further, it is preferably 1 mm or less, and more preferably 0.5 mm or less. By making this range, the dispersion efficiency can be remarkably improved.

Furthermore, after the main dispersion, by removing the dispersion remaining in the dispersion chamber and the piping, by using the liquid used as the solvent of the dispersion, a step of pushing out only the dispersion while leaving the beads in the dispersion chamber, The improvement effect is remarkable.
This is a method for recovering a dispersion, but in the case of a dispersion method using beads, there is a problem that it is very difficult to separate the dispersion from the beads. This is to solve this problem.
Various methods are considered as candidates for the separation method, but among the candidates, the method of the present invention, in which beads having a large specific gravity are left as they are and only the dispersion liquid portion is driven out with a solvent, is efficiently and in a short time. Can be separated with few side effects.
The minimum amount of solvent used is the sum of the capacity in the dispersion chamber and the capacity of the piping (the amount of dispersion that cannot be discharged and remains), and at the timing when the dispersion in the circulation tank disappears from the circulation tank. By adding this liquid, it is possible to extrude the dispersion without mixing the extrusion amount, which is very preferable.

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

[Binder resin]
The resin for forming the coating layer of the carrier of the present invention is not particularly limited as long as it is generally used for carriers.
For example, silicon resin, fluororesin, acrylic resin, reaction product of acrylic resin and amino resin, epoxy resin, polyurethane resin, fluororesin modified silicone resin, acrylic modified silicone resin, epoxy modified silicone resin, urethane modified silicone resin, etc. However, the present invention is not limited to these. Moreover, coating resin may be used individually by 1 type, may be used by multiple, and may be used in a modified | denatured type.

[Solid particles]
In the present invention, solid particles having a small particle size that can be separated from the dispersing beads by filtration, that is, particles having an average primary particle size of 5 to 500 nm can be preferably used.
For example, fine powders of tin oxide, indium oxide doped tin oxide, conductively treated tin oxide, titanium oxide, zinc oxide, iron suboxide, titanium black, carbon black and the like can be mentioned, but are not limited thereto. It is not a thing.
Needle-like powders (titanium oxide, zinc oxide, etc.) and flake-like powders (graphite, aluminum flakes, copper flakes, metal flakes such as nickel flakes, conductive mica, etc.) can be used. These can be used alone or in combination. Further, a high resistance material such as hydrophobized silica or alumina powder can be used in combination.

[Coating solution]
The coating liquid in the present invention is obtained by dissolving or dispersing 0.02 to 90 parts by weight of a binder resin in 100 parts by weight of a liquid medium. In addition, solid particles and other components (if desired) ( For example, it may contain a resin cross-linking agent, resistance adjusting agent, and the like.
The ratio of the solid particles to the binder resin is preferably in the range of 5/100 to 600/100.
The liquid medium that can dissolve or disperse the binder resin may be a commonly used one. For example, petroleum solvents such as normal hexane and kerosene, halogenated hydrocarbon solvents, benzene, toluene, and xylene. Aromatic solvents such as acetone, methyl ethyl ketone, ketone solvents such as methyl isobutyl ketone, alcohol solvents such as methanol, ethanol and isopropanol, ester solvents such as methyl acetate and ethyl acetate, and diethyl ether Ether solvents, cyclic ethers such as tetrahydrofuran and dioxane, glycol ethers such as ethylene glycol monomethyl ether (methyl cellosolve (registered trademark)), ethylene glycol monoethyl ether (ethyl cellosolve (registered trademark)), dimethylform And nitrogen-containing organic solvent such as an amide, and the like, but not limited thereto.

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

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

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

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

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

As the colorant used in the toner such as the color toner of the present invention, known pigments and dyes capable of obtaining yellow, magenta, cyan, and black toners can be used, and are not limited to those listed here.
Examples of yellow pigments include cadmium yellow, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow GR, Quinoline Yellow Lake, Permanent Yellow NCG and Tartrazine Lake. Can be mentioned.
Examples of the orange pigment include molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK.
Examples of red pigments include Bengala, Cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B.
Examples of purple pigments include fast violet B and methyl violet lake. Examples of blue pigments include cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, and indanthrene blue BC.
Examples of green pigments include chrome green, chromium oxide, pigment green B, and malachite green lake.
Examples of black pigments include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides. Moreover, these colorants can use 1 type (s) or 2 or more types.

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

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

In addition, the combination of hydrophobized silica and hydrophobized titanium oxide increases the amount of hydrophobized titanium oxide externally added compared to the amount of hydrophobized silica externally charged. The toner can also be excellent in stability.
Conventionally used in combination with the above inorganic fine particles, such as silica having a specific surface area of 20 to 50 m ² / g and resin fine particles having an average particle diameter of 1/100 to 1/8 of the average particle diameter of the toner. The durability can be improved by externally adding an external additive having a particle size larger than that of the external additive to the toner.
This is because the metal oxide particles externally added to the toner tend to be embedded in the base toner particles in the process where the toner is mixed and stirred with the carrier in the developing device, charged, and used for development. This is because it is possible to prevent the metal oxide fine particles from being embedded by externally adding an external additive having a particle size larger than that of the oxide fine particles to the toner.

The above-mentioned inorganic fine particles and resin fine particles are included (internally added) in the toner, but the effect is reduced as compared with the case of external addition, but the effect of improving transferability and durability is obtained and the pulverization property of the toner is improved. Can be made.
Further, by using both the external addition and the internal addition, it is possible to suppress embedding of the externally added fine particles, so that excellent transferability can be stably obtained and durability can be improved.

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

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

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

[Image forming apparatus and image forming method]
An embodiment in which the image forming method of the present invention is implemented using an example of the image forming apparatus of the present invention (for example, the image forming apparatus shown in FIGS. 1 to 4) will be described with reference to FIG.
The image forming apparatus (100) of the example shown in FIG. 1 includes a photosensitive drum (10) as an electrostatic latent image carrier (hereinafter referred to as “photosensitive body (10)”), a roller-shaped charging unit (20), An exposure unit (30), a development unit (40), an intermediate transfer member (50), a cleaning unit (60) having a cleaning blade, and a static elimination lamp as a static elimination unit (70).

The intermediate transfer member (50) is an endless belt, and is designed to be movable in the direction of the arrow by three rollers (51) that are arranged on the inner side and stretch the belt.
A part of the three rollers (51) also functions as a transfer bias roller capable of applying a predetermined transfer bias (primary transfer bias) to the intermediate transfer member (50).
A cleaning means (90) having a cleaning blade is disposed in the vicinity of the intermediate transfer member (50), and a developed image (image-forming particle image) is transferred to a transfer paper (95) as a final transfer material. Transfer rollers as transfer means (80) to which a transfer bias for (secondary transfer) can be applied are arranged to face each other.
Around the intermediate transfer member (50), there is a corona charger (58) for applying a charge to the image-forming particle image on the intermediate transfer member (50) in the rotational direction of the intermediate transfer member (50). It is arranged between the contact portion between the photoconductor (10) and the intermediate transfer member (50) and the contact portion between the intermediate transfer member (50) and the transfer paper (95).

The developing means (40) includes a developing belt (41) as a developer carrier, a black developing means (unit) (45K) provided around the developing belt (41), a yellow developing means (unit) (45Y), It is composed of a magenta developing means (unit) (45M) and a cyan developing means (unit) (45C).
The black developing means (45K) includes a developer accommodating portion (42K), a developer supply roller (43K), and a developing roller (44K). The yellow developing means (45Y) is provided with a developer accommodating portion ( 42Y), a developer supply roller (43Y), and a development roller (44Y). The magenta developing means (45M) includes a developer accommodating portion (42M), a developer supply roller (43M), and a development roller (44M). The cyan developing means (45C) includes a developer container (42C), a developer supply roller (43C), and a developing roller (44C).
Further, the developing belt (41) is an endless belt, is rotatably stretched around a plurality of belt rollers, and a part thereof is in contact with the photoreceptor (10).

In the image forming apparatus (100) shown in FIG. 1, for example, the charging means (20) uniformly charges the photosensitive drum (10).
The exposure means (30) performs imagewise exposure on the photosensitive drum (10) to form an electrostatic latent image. The electrostatic latent image formed on the photosensitive drum (10) is developed by supplying image forming particles from the developing means (40) to form a visible image (image forming particle image).
The visible image (image-forming particle image) is transferred (primary transfer) onto the intermediate transfer body (50) by the voltage applied from the roller (51), and further transferred onto the transfer paper (95) (secondary transfer). )
As a result, a transfer image is formed on the transfer paper (95).
The residual image forming particles on the photoreceptor (10) are removed by the cleaning means (60), and the charge on the photoreceptor (10) is once removed by the charge eliminating means (charge eliminating lamp) (70).

Another mode for carrying out the image forming method of the present invention by the image forming apparatus of the present invention will be described with reference to FIG.
The image forming apparatus (100) shown in FIG. 2 does not include the developing belt (41) in the image forming apparatus (100) shown in FIG. 1, and a black developing means (developing unit) (around the photoconductor (10)). 45K), yellow developing means (developing unit) (45Y), magenta developing means (developing unit) (45M) and cyan developing means (developing unit) (45C) are arranged directly opposite to each other, as shown in FIG. The image forming apparatus (100) shown in FIG. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals.

Still another embodiment for carrying out the image forming method of the present invention by the image forming apparatus of the present invention will be described with reference to FIG.
The tandem image forming apparatus shown in FIG. 3 is a tandem type color image forming apparatus. The tandem image forming apparatus includes a copying machine main body (150), a paper feed table (200), a scanner (300), and an automatic document feeder (ADF) (400).
The copying machine main body (150) is provided with an endless belt-like intermediate transfer member (50) at the center. The intermediate transfer member (50) is stretched around the support rollers (14), (15) and (16), and can be rotated clockwise in FIG. An intermediate transfer body cleaning device (17) for removing residual image forming particles on the intermediate transfer body (50) is disposed in the vicinity of the support roller (15).
The intermediate transfer member (50) stretched between the support roller (14) and the support roller (15) has four image forming units (18) of yellow, cyan, magenta, and black along the conveyance direction. A tandem developing means (120) arranged opposite to each other is arranged.
An exposure means (21) is disposed in the vicinity of the tandem developing means (120).
A secondary transfer unit (22) is disposed on the side of the intermediate transfer member (50) opposite to the side on which the tandem type developing unit (120) is disposed. In the secondary transfer means (22), a secondary transfer belt (24), which is an endless belt, is stretched between a pair of rollers (23), and a transfer sheet conveyed on the secondary transfer belt (24); The intermediate transfer member (50) can contact each other. A fixing means (25) is disposed in the vicinity of the secondary transfer means (22). The fixing means (25) includes a fixing belt (26) that is an endless belt, and a pressure roller (27) that is pressed against the fixing belt (26).
In the tandem image forming apparatus, in the vicinity of the secondary transfer means (22) and the fixing means (25), a sheet reversing device (28) for reversing the transfer paper for image formation on both sides of the transfer paper. ) Is arranged.

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

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

Each image information of black, yellow, magenta and cyan is stored in each image forming means (18) (black image forming means, yellow image forming means, magenta image forming means and cyan) in the tandem developing means (120). Image forming means), and image forming particle images of black, yellow, magenta and cyan are formed in each image forming means.
That is, each image forming means (18) (black image forming means, yellow image forming means, magenta image forming means, and cyan image forming means) in the tandem developing means (120) is partially enlarged in FIG. As shown in FIG. 4, which is a schematic diagram, the photoreceptor (10) (the photoreceptor for black (10K), the photoreceptor for yellow (10Y), the photoreceptor for magenta (10M), and the photoreceptor for cyan (10C), respectively. ), Charging means (59) for uniformly charging the photosensitive member, and based on each color image information, the photosensitive member is exposed (L in FIG. 4) for each color image corresponding image, and the photosensitive member is exposed. Exposure means for forming an electrostatic latent image corresponding to each color image on the body, and each color developer of the present invention (black developer, yellow developer, magenta developer and cyan developer) Develop with each A developing means (61) for forming a toner image with a color developer, a transfer charger (62) for transferring the developed toner image onto the intermediate transfer body (50), and a photoreceptor cleaning means (63). And a static eliminator (64), and each monochrome image (black image, yellow image, magenta image, and cyan image) can be formed based on the image information of each color.
The black image, the yellow image, the magenta image, and the cyan image thus formed are transferred onto the intermediate transfer member (50) that is rotationally moved by the support rollers (14), (15), and (16) in FIG. The black image formed on the black photoconductor (10K), the yellow image formed on the yellow photoconductor (10Y), the magenta image formed on the magenta photoconductor (10M), and the cyan photoconductor, respectively. The cyan image formed on the body (10C) is sequentially transferred (primary transfer).
Then, the black image, the yellow image, the magenta image, and the cyan image are superimposed on the intermediate transfer member (50) to form a composite color image (color transfer image).

On the other hand, in the paper feed table (200), one of the paper feed rollers (142) is selectively rotated so that the sheet (recording paper) is fed from one of the paper feed cassettes (144) provided in the paper bank (143). ), Separated one by one by the separation roller (145), sent to the paper feed path (146), and conveyed by the conveyance roller (147) to the paper feed path (148) in the copier body (150). Guide and stop against the registration roller (49).
Alternatively, the sheet feed roller (142) is rotated to feed out the sheets (recording paper) on the manual feed tray (54), separated one by one by the separation roller (52), and put into the manual feed path (53). Stop against the registration roller (49). The registration roller (49) is generally used while being grounded, but may be used in a state where a bias is applied to remove paper dust from the sheet.
Then, the registration roller (49) is rotated in synchronism with the synthesized color image (color transfer image) in which the respective toners are synthesized on the intermediate transfer member (50), and the intermediate transfer member (50) and the secondary transfer means ( 22), a sheet (recording paper) is sent to the sheet (recording paper), and the composite color image (color transfer image) is transferred (secondary transfer) onto the sheet (recording paper) by the secondary transfer means (22). A color image is transferred and formed on the sheet (recording paper). The residual toner on the intermediate transfer member (50) after the image transfer is cleaned by the intermediate transfer member cleaning device (17).

The sheet (recording paper) on which the color image has been transferred is transported by the secondary transfer means (22) and sent to the fixing means (25). The fixing means (25) generates heat and pressure. The composite color image (color transfer image) is fixed on the sheet (recording paper).
Thereafter, the sheet (recording paper) is switched by the switching claw (55) and discharged by the discharge roller (56) and stacked on the discharge tray (57), or switched by the switching claw (55) and the sheet is reversed. The image is reversed by the device (28) and guided again to the transfer position, and an image is recorded also on the back surface. Then, the image is discharged by the discharge roller (56) and stacked on the discharge tray (57).

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

・ Acrylic resin solution (solid fraction: 50 mass%) 80 mass parts ・ Guanamine solution (solid fraction; 70 mass%) 25 mass parts ・ Acid catalyst (solid fraction; 40 mass%) 1 mass part ・ Silicone resin solution (Solid fraction: 20% by mass) 250 parts by mass. Aminosilane (solid fraction: 100% by mass) 2 parts by mass. Conductive-treated titanium oxide particles (surface: ITO treatment, primary particle size: 70 nm, volume resistivity: 1 0.0 × 10 ² Ω · cm) 170 parts by mass / 800 parts by mass of toluene were put into a circulation tank and subjected to dispersion treatment under the following dispersion conditions to obtain a coating film forming solution.
・ Bead mill disperser: Nanogetter (DMR-L110 type) [manufactured by Ashizawa Finetech Co., Ltd., has a bead classification mechanism in the dispersion chamber]
-Beads: zirconia (true density; 6.0 g / cm ³ ) /0.1 mm
・ Bead filling rate (bulk): 50%
・ Rotater speed: 10m / sec
・ Dispersion liquid feeding method: Pass method / Number of passes: Three times ・ Dispersion discharge: Toluene extrusion Next, average particle size as core material particles: 35 μm calcined ferrite powder [DFC-400M (Mn ferrite, DOWA IP Creation Co., Ltd.) The coating film forming solution was applied onto the surface of the core material particles so as to have a film thickness of 0.2 μm at a coater internal temperature of 40 ° C. and dried. The obtained carrier was baked by standing in an electric furnace at 150 ° C. for 1 hour. After cooling, the ferrite powder bulk was pulverized using a sieve having an aperture of 63 μm, and the charge amount: 32.1 (−μc / g), volume resistivity: 11.7 [Log (Ω · cm)] [carrier 1 ]
On the other hand, toner
Binder resin: 100 parts by weight of polyester resin Release agent: 7 parts by weight of carnauba wax Charge control agent: E-84 [manufactured by Orient Chemical Co., Ltd.] 1 part by weight Colorant: C.I. I. P. Y. 180 6 parts by mass Of the above materials, the colorant, the binder resin, and pure water were mixed at a ratio of 1: 1: 0.5 and kneaded by two rolls. Kneading was performed at 70 ° C., and then the roll temperature was raised to 120 ° C. to evaporate water and prepare a master batch in advance. Using the master batch obtained in this way, weigh the materials so that they are the same as the above recipe, mix with a Henschel mixer, melt knead for 40 minutes at 120 ° C. with two rolls, cool, and then coarsely pulverize with a hammer mill Thereafter, fine powder obtained by fine pulverization with an air jet pulverizer was classified to prepare toner base particles having a weight average particle diameter of 5 μm. Further, to 100 parts of the toner base material, 1 part of silica whose surface was hydrophobized and 1 part of titanium oxide whose surface was hydrophobized were added and mixed with a Henschel mixer to obtain yellow toner [Toner 1 ] Was obtained.
7 parts of [Toner 1] thus obtained and 93 parts of [Carrier 1] were mixed and stirred to prepare a developer having a toner concentration of 7 wt%.

  In Example 1, before the bead mill dispersion treatment, a homogenizer [manufactured by PRIMIX; K. In the same manner except that pre-dispersion treatment was performed at 10000 rpm for 10 minutes with a homomixer MARKII], the charge amount was 35.5 (-μc / g), the volume resistivity was 13.2 [Log ( [Carrier 2] of [Ω · cm)]. Developers were produced from [Carrier 2] and [Toner 1] thus obtained in the same manner as in Example 1.

  In Example 2, a carrier was formed in the same manner except that a sieving process with an aperture of 63 μm was performed between the pre-dispersion process and the bead mill dispersion process, and the charge amount: 37.1 (−μc / g), specific volume Resistance: [Carrier 3] of 13.7 [Log (Ω · cm)] was obtained. A developer was produced from [Carrier 3] and [Toner 1] thus obtained in the same manner as in Example 1.

  In Example 3, after carrying out the bead mill dispersion treatment, a carrier was formed in the same manner except that a sieve treatment with an opening of 26 μm was carried out, and the charge amount: 38.3 (−μc / g), volume specific resistance: 14.1 [Carrier 4] of [Log (Ω · cm)] was obtained. Developers were produced from [Carrier 4] and [Toner 1] thus obtained in the same manner as in Example 1.

In Example 4, the bead material is silicon nitride and the carrier is changed in the same manner except that the bead has a true specific gravity of 3.2 g / cm ^{3. The} charge amount is 35.7 (−μc / g). , Volume resistivity: 13.1 [Log (Ω · cm)] [Carrier 5] was obtained. Developers were produced from [Carrier 5] and [Toner 1] thus obtained by the same method as in Example 1.

In Example 4, the bead material is glass, and the carrier is similarly changed to a bead having a true specific gravity of 2.4 g / cm ³ , and the charge amount is 33.8 (−μc / g), [Carrier 6] having a volume resistivity of 12.5 [Log (Ω · cm)] was obtained. Developers were produced from [Carrier 6] and [Toner 1] thus obtained in the same manner as in Example 1.

  In Example 4, a carrier was formed in the same manner except that the bead diameter became 5 mm, and the charge amount was 32.4 (−μc / g), and the volume resistivity was 11.9 [Log (Ω · cm)]. [Carrier 7] was obtained. Developers were produced from [Carrier 7] and [Toner 1] thus obtained by the same method as in Example 1.

[Comparative Example 1]
In Example 1, the dispersion liquid feeding method is set to the circulation method instead of the pass method / number of passes: 3 times, and the circulation time is set by converting to the time of circulating the same liquid volume as the pass method / three times pass. Except for the above, it was converted into a carrier in the same manner to obtain [Carrier 8] having a charge amount of 32.0 (−μc / g) and a volume resistivity of 10.9 [Log (Ω · cm)]. Developers were produced from the thus obtained [Carrier 8] and [Toner 1] in the same manner as in Example 1.

  Using the solid particle size distribution in the dispersions dispersed in Examples 1 to 7 and Comparative Example 1 above and the developers prepared in Examples 1 to 7 and Comparative Example 1, background fogging, adherence of solid carrier over time Evaluation was conducted. The evaluation results are shown in Table 1. The measurement method and evaluation method for the above evaluation items were as follows.

[Dispersion particle size distribution measurement method]
For measurement of the particle size distribution of the dispersion, LA-950V2 (Horiba Seisakusho, laser diffraction type) was used, and the batch cell method was used, and the software version: Ver. 5 and sample refractive index: 2.244, dispersion medium refractive index: 1.4962, particle diameter standard: volume.

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

[Charging amount measurement method]
The charge amount was measured using a blow-off device TB-200 (manufactured by Toshiba Chemical Co., Ltd.)], which was mixed at a ratio of 7% by weight of toner with respect to 93% by weight of carrier and frictionally charged.

(Volume resistivity measurement method)
Volume resistivity is calculated by applying a carrier between parallel electrodes with a gap of 2 mm and tapping, then applying DC 1000 V between both electrodes, and converting the resistance value measured after 30 seconds with a high resist meter into volume resistivity. And asked. In addition, when it fell below the measurable lower limit of the high resist meter, the volume specific resistance value was not substantially obtained, and it was handled as a breakdown.

[Skin cover evaluation method]
A developer is set on a commercially available digital full color printer (Imagio MP C5000, manufactured by Ricoh Co., Ltd.), A5 images with an image area of 5% are output by 1 sheet / 1000 JOB, and then an A3 image with an image area of 0%. , And observing the toner fog state of the background portion, ◎ for those that do not have any toner fog, ◯ for those that are almost unknown, △ for those that are slightly visible, and × for those that are clearly visible, ◎, ○ and △ were accepted and x was rejected.

[Evaluation method for adhesion of solid carrier over time]
The developer was set on a commercially available digital full-color printer (Imagio MP C5000, manufactured by Ricoh Co., Ltd.), and a running evaluation of 300,000 sheets in a single color was performed. Then, the solid carrier adhesion of the developer after the running was evaluated.
The solid image carrier adhesion evaluation method was evaluated by fixing the background potential to 150 V using the copying machine, developing a solid image on A3 size paper, and observing with a magnifying glass. ◎ when the number of white spots on the image and the total number of carriers actually attached are 0, ◯ when 1-5, △, 11 when 6-10 The case of more than one was determined as x, ×, ○, △ were accepted, and x was rejected.

  From the evaluation results shown in Table 1, the solid particle size distribution in the dispersions according to Examples 1 to 7 according to the present invention is a sharper distribution compared to Comparative Example 1, and the developer prepared using this dispersion is Compared with Comparative Example 1, it is clear that the background fogging and temporal solid carrier adhesion are suppressed.

(FIGS. 1 to 4)
L Exposure 10 Photoconductor (Photoconductor drum)
10K black photoreceptor 10Y yellow photoreceptor 10M magenta photoreceptor 10C cyan photoreceptor 14 support roller 15 support roller 16 support roller 17 intermediate transfer cleaning device 18 image forming means 20 roller-shaped charging means 21 exposure means 22 secondary transfer Means 23 Roller 24 Secondary transfer belt 25 Fixing means 26 Fixing belt 27 Pressure belt 28 Sheet reversing device 30 Exposure means 32 Contact glass 33 First traveling body 34 Second traveling body 35 Imaging lens 36 Reading sensor 40 Developing means 41 Developing Belt 42K Developer container 42Y Developer container 42M Developer container 42C Developer container 43K Developer supply roller 43Y Developer supply roller 43M Developer supply roller 43C Developer supply roller 44K Developer roller 44Y Developer roller 44M Developer roller 44C development Over La 45K black developing means (developing unit)
45Y yellow development means (development unit)
45M Magenta development means (development unit)
45C Cyan development means (development unit)
49 Registration roller 50 Intermediate transfer member 51 Roller 52 Separation roller 53 Manual feed path 54 Manual feed tray 55 Switching claw 56 Discharge roller 57 Discharge tray 58 Corona charger 59 Charging means 60 Cleaning means 61 Developing means 62 Transfer charger 63 Photoconductor cleaning Means 64 Static eliminator 65 Developing roller 66 Developing unit 67 Developing unit lid 68 Stir screw 69 Isolation wall 70 Static eliminating means (static elimination lamp)
71 toner density sensor 72 magnet 73 developer pumping amount adjusting plate 75 mylar 76 cleaning roller 77 scraping roller 78 regulating plate 79 conveying screw 80 transfer roller (transfer means)
90 Cleaning means 95 Transfer paper 100 Image forming apparatus 120 Tandem developing means 130 Document table 142 Paper feed roller 143 Paper bank 144 Paper feed cassette 145 Separating roller 146 Paper feed path 147 Carrying roller 148 Paper feed path 150 Copying apparatus main body 200 Paper feed Table 300 Scanner 400 Automatic document feeder (ADF)

JP 2007-102159 A JP 2008-70837 A JP 2007-286078 A JP-A-11-184167 JP 2007-292298 A

Claims (13)

A method for producing a coating liquid for coating the core material of an electrophotographic carrier, comprising a main dispersion step of dispersing a solution containing at least a binder resin and solid particles using beads having a bead diameter of 5 mm or less. In this dispersion step, a disperser having a classification mechanism for separating the beads in a dispersion chamber is used, and the dispersion liquid feeding method is a pass system , and the classification mechanism is a centrifugal separator. A method for producing a coating liquid, which is a separator .
  The method for producing a coating liquid according to claim 1, further comprising a pre-dispersion step in which the beads are not used before the main dispersion step.   The method for producing a coating liquid according to claim 2, further comprising a primary sieving step of passing a sieving between the pre-dispersing step and the main dispersing step.   The method for producing a coating liquid according to any one of claims 1 to 3, further comprising a secondary sieving step of passing the sieving after the main dispersion step. The method for producing a coating liquid according to claim 1, wherein the true density of the beads is 2.8 g / cm ³ or more.   The method for producing a coating liquid according to any one of claims 1 to 5, wherein the beads are a single type or a mixture of a plurality of types of beads.   The method according to any one of claims 1 to 6, further comprising a step of extruding only the coating liquid with the solvent used in the solution after the main dispersion step, while leaving the beads in the dispersion chamber. Manufacturing method of coating liquid.   A coating liquid for coating a core material of an electrophotographic carrier, which is produced by the production method according to claim 1.   The coating liquid according to claim 8, wherein the coating liquid does not include coarse particles having a particle diameter of 1 μm or more.   An electrophotographic carrier comprising a coating layer formed of the coating liquid according to claim 8 or 9 on the surface of core material particles.   The electrophotographic carrier according to claim 10, wherein the coating layer does not contain coarse particles having a particle diameter of 5 μm or more.   An electrophotographic two-component developer comprising a toner and the electrophotographic carrier according to claim 10.   An electrostatic latent image carrier, at least a means for forming an electrostatic latent image on the image carrier, and a developing means for developing the electrostatic latent image, the developing means according to claim 12. An image forming apparatus using the two-component developer described above.

Images