JPH11194544A - Electrophotographic developing coat carrier and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image with little fogging or carrier adhesion in a developing process, and provide a high quality image excellent in toner spent resistance and wear resistance, stable over a long period and faithful to an electrostatic latent image by providing a coating layer containing a specified photocatalyst on the surface of a carrier core material. SOLUTION: A coating layer is provided on the surface of a carrier core material. A photocatalyst having an oxidation potential of 1.5 V or more is used in the coating layer. The photocatalyst having the oxidation potential of 1.5 V or more can generate active oxygen in light emission. When a near ultraviolet ray of 250 nm-500 nm is emitted, the active oxygen is generated, and an organic compound present near the photocatalyst is oxidized by the generated active oxygen. Since the organic compound can be finally decomposed into water and carbon dioxide, the organic compound such as a resin adhered to the carrier can be decomposed by the photocatalyst in the coating layer of the carrier and removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic carrier which forms an electrostatic image developer by mixing with a toner,
The present invention relates to an electrophotographic coat carrier in which a functional coating layer is formed on a surface of a core material and an image forming method.

[0002]

2. Description of the Related Art Regarding electrophotography, U.S. Pat.
297, 691, JP-B-42-23910, JP-B-43-24748, and the like, various methods are described. In any of these methods, a photoconductive layer is formed on a photoconductive layer according to an original. An electrostatic latent image is formed by irradiating the image, and then a fine colored powder called a toner having the opposite polarity is attached to the electrostatic latent image to develop the electrostatic latent image. After transferring the toner image onto a transfer material such as paper according to the above, the toner image is fixed by heat, pressure, solvent vapor or the like to obtain a copy.

[0003] Among the above, in the process of developing an electrostatic latent image, toner particles charged to the opposite polarity to the latent image are attracted by electrostatic attraction and adhered to the electrostatic latent image. (In the case of reversal development, a toner having a triboelectric charge of the same polarity as that of the latent image is used.) In general, when such an electrostatic latent image is developed using toner, a small amount of toner is transferred to a medium called a carrier. A method using a so-called two-component developer dispersed is known.

[0004] By the way, the electrophotographic method has almost reached a satisfactory level for document copying, but in recent years, with the development of computers, high-definition televisions and the like, higher definition and full-color image output have been demanded. . In response to such demands, various methods such as digital image processing or application of an alternating electric field during development have been developed. From the material side, improvement of the developer has been particularly attempted. For example, measures have been taken by techniques such as reducing the particle size of the toner constituting the developer or reducing the magnetic force of the carrier. Further improvement in image quality and quality is desired in the future, and it is considered that the importance of the developer as a functional member will further increase.

In general, the carrier constituting such a two-component developer is a conductive carrier typified by iron powder and a so-called insulating carrier whose surface such as iron powder, nickel and ferrite is coated with an insulating resin. It is roughly divided. When a method of applying an alternating electric field is used to improve the image quality, if the resistance of the carrier for the developer is low, the latent image potential leaks through the carrier, and a good image cannot be obtained. As a countermeasure for this, it is necessary that the carrier has a certain resistance or more. In particular, when the carrier core material is conductive, it is preferable to coat the surface of the core material with a resin.

Further, it is preferable to use ferrite having a relatively high resistance as a core material. That is, when viewed as a carrier for high image quality, iron powder has a high magnetic force, and forms a hard developer brush in the developing area, so that a fine image or a rough image is obtained. Can not. Accordingly, ferrite is preferably used from the viewpoint of reducing the magnetic force of the carrier and softening the developer brush to achieve high image quality.

Attempts have also been made to improve various characteristics of the carrier for forming high-quality images. For example, Japanese Patent Application Laid-Open No.
No. 4663 discloses that the saturation magnetization value of a carrier is 50 em.
It is described that by setting the ratio to u / g or less, a good image without nicks can be obtained. However, when a carrier having a gradually reduced saturation magnetization value is used, the reproducibility of the fine line is improved, but the carrier adheres to the electrostatic image carrier (so-called photosensitive drum) as the distance from the magnetic pole increases (hereinafter, referred to as a photosensitive drum). , Carrier adhesion).

As an attempt to improve the image quality by reducing the carrier particle size, Japanese Patent Application Laid-Open No. Sho 60-131549 proposes a method of developing using a finely divided carrier and toner. Here, it is proposed that while achieving high image quality by using a fine particle carrier, the carrier adhesion which is remarkable at that time is cleared by imparting a function of maintaining the insulating property of the carrier even under a high electric field. ing. However, when the carrier is made finer for higher image quality, the amount of toner that can be carried by the carrier increases, so that the toner is liable to be scattered, and the chance of contact between the toner particles increases. The toner of the opposite polarity is likely to be generated, and the image is easily fogged. As described above, although various techniques have been tried to achieve high image quality, a developer carrier that achieves high image quality from the carrier side and satisfies both suppression of fog and carrier adhesion at the same time. At present, there is not enough available yet.

On the other hand, for the purpose of improving the life of the developer, the surface of ferrite or the like is treated with a resin coating or the like,
Although a coating layer is provided on the surface of the core material, especially in long-term durability, the function of the charge applying ability of the carrier is impaired due to the influence of resin powder derived from the coating resin, and stable charging is performed. In some cases, image degradation such as a decrease in image density occurs. In general, as a method for producing such a resin-coated carrier, a method of coating a resin solution on the carrier surface using a fluidized bed coating apparatus is known. As described above, it has been found that it is difficult to form a uniform coating layer without exposing the core material during production, and this may cause image degradation.

For example, in Japanese Patent Application Laid-Open No. 58-202457, a coating liquid is sprayed while a carrier core material is suspended by a fluidized bed method, dried at a high temperature, and spraying and drying of the coating liquid are repeated again. Methods for manufacturing carriers have been proposed. Japanese Patent Application Laid-Open No. Sho 62-153962 discloses a method of spraying or dipping a coating solution while floating or flowing a carrier core material, and forming a coating layer on the surface of the carrier core material while applying shearing force. Has been proposed. Also, Japanese Patent Application Laid-Open No. 3-140969 proposes a method of coating by controlling the air supply temperature of a fluidized bed coating apparatus and the resin concentration of a coating solution. Further, JP-A-5-216284 and JP-A-5-216285 disclose a method of intermittently spraying a coating solution while controlling an ambient temperature in a fluidized bed of a fluidized bed coating apparatus, and a method of fluidized bed. A method has been proposed in which spraying is performed by controlling the temperature of the atmosphere and the amount of flowing air.

On the other hand, a problem in spray coating the surface of the core material while forming a fluidized bed is that, depending on the spraying state or the state of formation of the fluidized bed, carrier particles may be formed or coated during spraying. The resin solution may generate resin powder alone without adhering to the core material surface. Such a tendency becomes remarkable as the amount of the coating resin increases. The presence of these resin powders in the carrier causes image deterioration.

According to the method proposed above,
In any case, it is possible to make the core material surface to a certain degree of resin coating state, but it is difficult to achieve a resin coating having a uniform surface property without hardly exposing the core material, and the coating state is uniform. Even if coating is possible, the yield of the resulting coated carrier tends to be low. In particular, when a thermosetting resin is used as a film-forming material to improve the strength, adhesion, toner spent resistance, and the like of the film, the cohesive force between the carrier particles due to the viscosity of the resin increases as the coating amount increases. Therefore, granulation becomes remarkable,
Obtaining a carrier with a uniform coating layer has been quite difficult. Therefore, a process such as crushing is usually added after coating.

However, the carrier obtained when a crushing step is added to the manufacturing process often exposes the carrier core material to the crushed surface, and a carrier having a coating layer having a uniform surface property can be obtained. There was a disadvantage that there was no. In addition, when a mixed resin of a thermosetting resin and a thermoplastic resin is used as the coating resin, by controlling the mixing ratio of each resin, the resin viscosity at the time of coating is reduced to prevent granulation and prevent spraying. Although application is possible, there is a problem that when heat treatment is performed at the curing temperature of the thermosetting resin after application, granulation occurs due to softening of the thermoplastic resin. In addition, due to the presence of fine powder derived from the coating resin generated in the crushing step, when an image is formed as a developer using the carrier obtained by the above method, fogging and toner scattering easily occur, particularly, In the case of a carrier having a small particle size or a carrier having a low magnetic force, there is a problem that the carrier is easily attached to the photosensitive drum and the image quality is deteriorated.

Further, in the electrophotographic method, the coated magnetic particles for electrophotographic charging used for applying a charge to a member to be charged such as a photoreceptor, a transfer belt or an intermediate transfer member are also coated with a resin on the core material. Layer having a function of providing a charge to the member to be charged as described above, and the same problem as the above-described electrophotographic development coat carrier occurs. There is also.

[0015]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a coated carrier for electrophotographic development capable of obtaining a high quality image. More specifically, in the development process, an image with less fog and carrier adhesion can be obtained, and excellent toner spent and abrasion resistance can be provided. To provide a coated carrier for electrophotography. In particular, in the long-term durability, even if toner spent occurs and image deterioration occurs, the coated carrier for electrophotographic development can recover the function as a carrier with a simple operation, and is further damaged by use. It is an object of the present invention to provide an image forming method capable of recovering the charge imparting ability of a carrier by a simple operation and providing the high-quality image described above. Further, the technical idea of the present invention is extended, and in the coated magnetic particles for electrophotographic charging having the same configuration as the coated carrier for electrophotographic development, even in the long-term durability, even if toner spent occurs and image deterioration occurs. Another object of the present invention is to provide electrophotographic charging coated magnetic particles capable of recovering a charging function by a simple operation. That is, even when a voltage that is not much different from the charging potential is applied to a member to be charged such as a photoreceptor, a transfer belt, or an intermediate transfer member, the member can be charged satisfactorily. Even if it does, it becomes possible to provide coated magnetic particles for electrophotographic charging having good durability without lowering the charging ability.

[0016]

The above object is achieved by the present invention described below. That is, the present invention provides a carrier core material and an oxidation potential provided on the surface of the carrier core material of 1.5 or less.
A coating carrier for electrophotographic development and an image forming method, comprising a coating layer containing a photocatalyst of V or more.

In a preferred embodiment of the present invention, a coated carrier for electrophotographic development having the above-mentioned structure, wherein the coated carrier has a specific resistance of 10 ¹² Ω · cm or more, and is provided on the surface of a core material. The coated carrier for electrophotographic development is characterized in that the carrier particles having a coverage of the coating layer of 90% or more account for 80% by number or more of the whole. Further, when applied to coated magnetic particles for electrophotographic charging, it has a core material composed of magnetic particles and a coating layer provided on the surface of the core material and containing a photocatalyst having an oxidation potential of 1.5 V or more. What is necessary is just to make it the coated magnetic particle of a structure. In a preferred embodiment in this case, the specific resistance of the coated magnetic particles is 10 ⁵ to 10 ¹⁰ Ω · cm or more, or the coating rate of the coating layer provided on the surface of the core material is 9%.
Electromagnetic charging coated magnetic particles in which 0% or more of magnetic particles are 80% by number or more of the whole.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to preferred embodiments. Both the coated carrier for electrophotographic development of the present invention and the coated magnetic particles for electrophotographic charging described above have an oxidation potential of 1.0 on the surface of the core material.
It has a coating layer containing at least a photocatalyst of 5 V or more. By using the coated carrier for electrophotographic development of the present invention or the coated magnetic particles for electrophotographic charging described above, a high-quality image can be stably obtained over a long period of time because the coating layer contains When a photocatalyst having an electric potential of 1.5 V or more is used, when these are used for a long period of time, even when toner spent etc. is generated and the function is deteriorated, the carrier layer or the like is irradiated with light to form a coating layer. Since the photocatalyst contained therein is excited to generate active oxygen, organic substances attached to the carrier surface are easily decomposed and removed, so that the function of the carrier or the like due to long-term use is reduced, for example, to the carrier surface. It is possible to easily recover from a decrease in charging ability caused by toner spent or the like. As a result, stable and favorable development over a long period of time becomes possible. Hereinafter, the coated carrier for electrophotographic development of the present invention or the coated magnetic particles for electrophotographic charging described above will be described.

First, the coated carrier for electrophotographic development of the present invention will be described. As shown in FIG. 1, the coated carrier for electrophotographic development of the present invention is configured by providing a coating layer on the surface of a carrier core material. In the coating layer, a photocatalyst having an oxidation potential of 1.5 V or more is provided. Used. The photocatalyst having an oxidation potential of 1.5 V or more used in the present invention can generate active oxygen at the time of light irradiation, and has a 250 nm
５００500 nm, preferably 290 nm〜500 nm,
More preferably, when near-ultraviolet light of 350 nm to 500 nm is irradiated, active oxygen is generated, and the generated oxygen oxidizes an organic compound near the photocatalyst. Finally, since it is possible to decompose the organic compound into water and carbon dioxide, if a coating layer having the above-described photocatalyst is formed on the carrier surface, the resin adhered to the carrier can be formed. And the like can be decomposed by the photocatalyst in the coating layer of the carrier, and thus can be removed.

For example, titanium oxide which is a photocatalyst has 25
When irradiated with light having a wavelength of from 0 nm to 400 nm, it absorbs light best and exhibits photocatalytic activity. Accordingly, for example, a coated carrier for electrophotography development of the present invention having a structure in which titanium oxide is contained in a coating layer of a carrier is mixed with a toner to form a two-component developer, and an electrostatic image is formed using the developer. When developed and used for image formation, the following excellent curing is obtained. In other words, even after toner is spent on the surface of the coated carrier after image formation is repeated and the image is deteriorated due to repeated use, even if the image quality is deteriorated, it is 250 nm to 400 nm.
When the light of m is applied to the coat carrier, active oxygen is generated, and organic substances such as a binder resin in the toner are oxidatively decomposed by the oxygen, so that the toner spent can be easily removed by a simple operation. . As a result, the charge imparting function and the like of the coated carrier for electrophotographic development according to the present invention are restored, so that a good image can be formed again.

In order to realize the above state,
This means that the conduction band of the photocatalyst needs to be above the hydrogen generation potential and the valence band needs to be below the oxygen generation potential, as shown by the energy band model of the semiconductor. As a photocatalyst satisfying this condition, for example,
TiO ₂ , SrTiO ₃ , ZnO, SiC, GaP, Cd
S, CdSe, MoS _{3 and the} like. In the present invention, it is more preferable to use one having an oxidation potential of 2.0 V or more, but among the above-mentioned ones, TiO ₂ and ZnO satisfy this condition. Furthermore, in the present invention, it is preferable to use TiO ₂ , particularly from the viewpoint of photocatalytic activity, from the viewpoints of chemical stability, cost, and easiness of production. In the present invention, the photocatalysts listed above may be used alone or in combination of two or more.

[0002] The activity of a photocatalyst is higher as the surface area is increased by making the particles finer.
For example, it is preferable to use a photocatalyst having a particle diameter of 1 to 100 nm, more preferably a particle diameter of 1 to 50 nm. In the present invention, the content of the photocatalyst in the coating layer is preferably 10 to 90 wt%. If it is less than 10 wt%, it is not desirable because sufficient catalytic activity cannot be obtained. On the other hand, if the content is 90 wt% or more, the strength of the coating film formed on the substrate is reduced, and it cannot be used for a long time. In the present invention, the content of the photocatalyst in the coating layer is more preferably 15 to 70 wt%.

The coated carrier for electrophotographic development of the present invention can be obtained by forming a coating layer having a photocatalyst having an oxidation potential of 1.5 V or more on the surface of a carrier core material. State. First, as the core material used in the present invention, iron powder, ferrite powder, and the like, any of those generally used as a carrier core material can be used, but as described above, in the present invention, Preferably, ferrite is used for the core material. Further, the particle size of the core material used in the present invention may be 10 to 1000 μm, preferably 20 to 100 μm.

In the coated carrier for electrophotographic development of the present invention, as a method for forming a coating layer formed on the surface of a core material made of ferrite or the like as described above, for example, the following methods are used. That is, a coating solution is prepared by mixing the specific photocatalyst and the binder component as described above, and the coating solution is applied to the surface of the core material, or the photocatalyst is formed after forming a layer with the binder component. Apply,
Then, a method of fixing the binder component by heat or the like can be used. As a method of applying the coating solution to the surface of the core material used at this time, there are a spray coating method, a roll coating method, a dip coating method, a bar coating method, a blade coating method, and the like. Good. Further, when the coating layer is formed by a plurality of coatings, a plurality of methods can be combined.

In the present invention, the coating layer having a photocatalyst formed on the surface of the core material as described above is 0.5 to 10%.
It is preferable that the film thickness is μm. That is, when the thickness is 0.5 μm or less, the irradiated light is not sufficiently absorbed, and the effect of adding the catalyst cannot be sufficiently obtained. On the other hand, when the thickness is 10 μm or more, the coating layer is too thick, and the magnetic properties and the like of the carrier core material decrease, which is not desirable.

In forming the coating layer of the coated carrier for electrophotographic development of the present invention, the binder component used in combination with the above-mentioned photocatalyst includes, for example, thermosetting SiO ₂ sol, TiO ₂ sol, ZrO ₂ Inorganic glass materials such as sols, thermosetting resins such as phenolic resins and melamine resins, organosiloxane resins, acrylic resins,
Fluororesin or the like can be used. In the present invention,
More preferably, a binder having a bond made of an inorganic compound which is not easily affected by decomposition or the like by a photocatalyst may be used. Specific examples include inorganic glass, polyorganosiloxane, and polysilazane. In the present invention, it is more preferable to use a thermosetting hard coat resin containing a siloxane component, a TiO ₂ sol, or the like.

Here, general methods for producing organopolysiloxanes include those described in JP-B-26-2696 and JP-B-28-6297, as well as in Chemistry and Technology.
ogy of Silicones, Chapter
5, p. 191-(Walter No. 11, Aca
demic Press, Inc. 1968). For example,
It is synthesized by dissolving an organoalkoxysilane or an organohalogenosilane in an organic solvent, polymerizing by dissolving, hydrolyzing, or condensing an acid or a base, and then removing the solvent. Organopolysiloxanes preferably used in the present invention include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as cyclohexanone and hexane, halogen-containing hydrocarbons such as chloroform and chlorobenzene, and alcohols such as ethanol and butanol. It is used by dissolving in a solvent such as

Examples of the monovalent hydrocarbon group directly bonded to a silicon atom in a general organopolysiloxane include the following, and in the present invention, any of them can be preferably used. That is, examples of the linear or branched alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, an amyl group, a hexyl group,
-Ethylhexyl group, dodecyl group, octadecyl group, etc.
Examples of the alkenyl group include an aryl group such as a vinyl group and an allyl group.Examples include a phenyl group and a tolyl group.Examples of the halogenated hydrocarbon group include a trifluoropropyl group, a heptafluoropentyl group, and a nanofluoro group. Examples thereof include halogen-substituted linear or branched saturated hydrocarbon groups such as a fluorohydrocarbon group represented by a hexyl group and the like and a chlorohydrocarbon group such as a chloromethyl group and a chloroethyl group.

The monovalent hydrocarbon group directly bonded to the silicon atom does not necessarily need to be of a single type, and may be appropriately selected according to the improvement of resin properties, the improvement of solubility in a solvent, and the like. For example, it is a well-known fact that when a system in which a methyl group and a phenyl group are mixed is used, the affinity with an organic compound is generally improved as compared with the case where a methyl group is used alone.
In addition, the number of monovalent organic group substitutions per silicon atom in the organopolysiloxane used in the present invention is 1.
It is preferably from 0 to 2.0. That is, when the substitution number of the organic group is 1.5 or less, the composition is close to glass,
The weight loss upon heating is small, and the resulting resin tends to be hard. When the resin weight is 1.0 or less, film formation tends to be difficult.
On the other hand, when the ratio is 1.5 or more, the tendency is opposite. When the ratio is 2.0, the composition becomes polydiorganosiloxane. When the ratio is more than 2.0, the rubbery element becomes too strong, and the hardness of the coating film is lowered. Not suitable for

The use of a fluorohydrocarbon group as a monovalent substituent directly bonded to a silicon atom within the range of the number of substitution of the organic group described above has a remarkable effect on lowering the surface energy of the organopolysiloxane. There is. That is, when a fluorohydrocarbon group is introduced, the surface tension of the silicone resin is reduced due to the effect of fluorine atoms, as in the case of a general polymer. Resin properties change. In the case where a lower surface tension is required for the surface of the coated carrier of the present invention, the silicon units bonded to the fluorohydrocarbon group may be further increased and copolymerized and introduced as appropriate.

In the present invention, the coating layer having the specific photocatalyst formed on the surface of the core material as described above is required to have good adhesion to the carrier core material and high surface hardness in order to withstand long-term durability. Is done. That is, when the electrophotographic image forming apparatus of the present invention is used in an electrophotographic image forming apparatus, in order to prevent the surface from being mechanically deteriorated, a coating layer having a pencil hardness of 4H or more is used. Is preferred. Further, in the present invention, it is possible to disperse and contain conductive fine particles in the coating layer containing the photocatalyst described above. The primary particle size of the conductive fine particles used at this time is 100 nm or less,
More preferably, those having a thickness of 50 nm or less are used. Examples of the conductive fine particles include conductive zinc oxide, conductive titanium oxide, Al, Au, Cu, Ag, Co, Ni, Fe, carbon black, ITO, tin oxide, indium oxide, and indium.

In the coated carrier for electrophotographic development of the present invention, the coating amount of the coating layer formed by the above-mentioned materials and forming method with respect to the carrier core material is 1.0.
It is preferably from 20 to 20% by weight, more preferably from 2.0 to 10.0% by weight. If the coating amount is less than 1.0% by weight, it is difficult to obtain a uniform coating layer.
When the coating amount is not less than% by weight, the effect of the coating does not substantially change, and it is not economical. In addition, adverse effects such as generation of powder due to the coating resin material and granulation become noticeable.

In the present invention, the coating solution at the time of spraying used for forming a coating layer by spray coating the surface of the core material preferably has a solid concentration of 2 to 2.
It is about 20% by weight, more preferably about 5 to 10% by weight. That is, a coating solution having a concentration of less than 2% by weight is not sufficient in terms of production efficiency, and a coating solution having a concentration of 20% by weight or more has a high viscosity. Problems such as easy clogging of the nozzle occur.

When the coating layer of the coated carrier for electrophotographic development of the present invention is formed, a coating solution having a specific photocatalyst is sprayed onto the surface of the carrier core material, and the coating solution is cured at a temperature at which the coating material is cured. Although heat treatment is performed, the temperature at this time depends on the selection of the curable binder to be used, but may be generally in the range of about 100 ° C to 800 ° C. However,
Depending on the addition of a curing agent, curing may be possible even at room temperature, so that the curing temperature is not particularly limited to the above.

Further, the electronic device of the present invention comprising the carrier core material obtained as described above and a coating layer provided on the surface of the carrier core material and containing a photocatalyst having an oxidation potential of 1.5 V or more. photo developing coated carrier, by the manner in which the specific resistance of the carrier so as to be 10 ¹² Ω · cm or more, more, the specific resistance of the carrier 10 ¹² Omega
Cm or more, and the carrier particles having a coverage of the coating layer on the carrier core material surface of 90% or more account for 80% by number or more of the entirety of the carrier core material, so that the conventional carrier for electrophotographic development can be obtained. Even when developing by applying an alternating electric field that can improve the disadvantages that have been obtained and obtain a high-definition image, while achieving high image quality with development faithful to the latent image,
An excellent electrophotographic coated carrier free of fog, carrier adhesion and toner spent.

In particular, the specific resistance of the carrier is 10 ¹² Ω · cm
In the embodiment described above, in which the carrier particles having a coverage of 90% or more are 80% by number or more of the entire carrier, development faithful to the latent image can be performed and a high-definition image can be obtained. The above is considered to be due to the following reasons.
That is, usually, in the development in which an alternating electric field is applied, when the developer brush formed on the developing sleeve is in contact with the photosensitive drum, if the resistance of the carrier used is low, the potential of the latent image on the photosensitive drum is increased. , And as a result, the image may be disturbed. Therefore, it is considered that the leakage of the latent image potential can be suppressed by setting the specific resistance of the carrier high as described above.

Further, as the coated carrier to be used, the coating state of the coating layer of the carrier is 90% or more, and almost the entire surface of the core material is uniformly coated with the coating layer, and the core material is not exposed. When the carrier in the state has a distribution of 80% by number or more of the entire carrier, the leakage of the latent image potential can be remarkably suppressed as compared with the case where a normal coated carrier is used. As a result, it is considered that the image quality can be improved.

That is, in the coated carrier, when the coverage of the coating layer formed on the surface of the core material is reduced, the rate at which the surface of the core material is exposed increases, particularly when a low-resistance carrier core material is used. The degree of disturbing the latent image potential increases. Further, even if a carrier having a high coverage is present, if the carrier does not exist in an amount of more than a certain number%, the latent image potential becomes lower than the resistance of the developer brush which has a low coverage in the developer brush. A conductive path is formed via a low carrier, and leaks from the conductive path, resulting in image disorder.

Further, by increasing the specific resistance of the coated carrier for electrophotography of the present invention to 10 ¹² Ω · cm or more and using a carrier having a high coverage and a high abundance as described above, the occurrence of carrier adhesion can be reduced. Can be reduced.
That is, the cause of the carrier adhesion is considered to be the dominant factor in charge injection from the developing sleeve to the carrier when the developing bias voltage is applied. It is considered that if the resistance is increased, the charge injection from the developing sleeve to the carrier can be suppressed, and the carrier adhesion can be reduced.

The present inventors have found that even if a carrier having a high specific resistance is used in measurement, carrier adhesion may occur in actual development. I thought that it was not planned. In order to confirm this, when the coat state of the coat carrier to which the carrier adheres despite the high measured specific resistance value was analyzed, unevenness was observed in the coat. That is, for this reason, there is a possibility that the microscopic low-resistance portion on the carrier becomes the charge injection site by application of the developing bias voltage. Therefore, the present inventors consider that the point is to control the resistance of the carrier surface at a minute level and to reduce the proportion of the carrier having such coating unevenness in the carrier, and to completely remove the surface of the core material. When a carrier having a uniform and uniform coating state was prepared and used, carrier adhesion was significantly reduced.

As described above, in the present invention, in particular, the coverage of the coating layer formed on the surface of the carrier core material is 9%.
0% or more, and by using a carrier in which such carrier particles are 80% by number or more of the entire carrier,
It has been found that a satisfactory level is achieved in preventing carrier adhesion and providing high quality images. That is, when the surface of a carrier that reached a satisfactory level in preventing carrier adhesion and providing a high-quality image was observed by a scanning electron microscope, a coated carrier having a carrier core material surface almost completely covered was obtained. Met. To summarize the above, it is important that, in the coated carrier for electrophotographic development of the present invention, the resin coverage formed on the carrier core material surface is increased, and the carrier having such a high resin coverage is obtained. The use of a carrier with a high percentage of, enables high image quality to be achieved without disturbing the latent image potential, and at the same time, suppresses charge injection from the developing sleeve to the carrier to prevent carrier adhesion. That is achieved.

Next, electrophotography is used to apply a charge to a member to be charged, such as a photoreceptor, a transfer belt, or an intermediate transfer member, having a structure similar to that of the coated carrier for electrophotographic development of the present invention. The case of the coated magnetic particles for charging will be described. Also in this case, similarly to the electrophotographic developing coat carrier of the present invention described above, the magnetic particle core material and a photocatalyst having an oxidation potential of 1.5 V or more on the surface of the magnetic particle core material were contained. By providing a coating layer, coated magnetic particles for electrophotographic charging are formed. With the configuration described above, even if a voltage that is not much different from the charging potential is applied to the member to be charged, the member can be charged satisfactorily. The coated magnetic particles for electrophotographic charging have good durability without a decrease in performance. In particular, in long-term durability, even if toner spent occurs and image deterioration occurs, it is possible to recover the charging function by a simple operation.

The operation will be described below. First, good chargeability is obtained by applying a voltage because the surface of the core material is covered with a coating layer containing a photocatalyst having a high oxidation potential of 1.5 V or more. This is because the transfer of charges is performed smoothly when it is performed. In particular, when a member to be charged such as a photoreceptor is negatively charged, the oxidation potential is large, so that the member to be charged can be well charged. Furthermore, the coated magnetic particles having the above-described configuration have good charging ability over a long period of time because the coating layer contains a photocatalyst having an oxidation potential of 1.5 V or more. As in the case of the coated carrier for electrophotographic development of the present invention described above, when light is applied to the coated magnetic particles for charging, the photocatalyst is excited to generate active oxygen, and the active oxygen easily removes organic substances attached to the carrier surface. Because it can be decomposed and removed. Therefore, when the coated magnetic particles for electrophotographic charging having such a configuration are used for a long period of time, the deterioration of the coated magnetic particles, for example, the occurrence of toner spent on the surface of the magnetic particles causes the deterioration of the charge imparting function. By irradiating light,
Since the binder resin and the like in the toner can be decomposed, the charge imparting function of the coated magnetic particles can be easily recovered. As a result, if the coated magnetic particles for electrophotographic charging having the above-described configuration are used, good charging can be stably performed over a long period of time, and the provision of a good image can be maintained.

Further, in a preferred embodiment of the coated magnetic particles for electrophotographic charging having the above-described structure, a core material composed of magnetic particles is coated with a coating layer containing a photocatalyst having an oxidation potential of 1.5 V or more. Magnetic particles,
And the specific resistance of the coated magnetic particles is 10 ⁵ to 10 ¹⁰ Ω · cm
Further, the magnetic particles having a coating ratio of 90% or more with respect to the surface of the core material are 80% by number or more of the coated magnetic particles. The above-described electrophotographic charging coated magnetic particles of the present invention improve various drawbacks of conventional electrophotographic charging coated magnetic particles, and have good charging characteristics and do not decrease in charging ability even when contaminated with toner or the like. Good durability can be provided as in the case of the coated carrier of the present invention described above. However, in the case of the coated magnetic particles of the present invention, the specific resistance may be in the range of 10 ⁵ to 10 ¹⁰ Ω · cm.
The reason is considered as follows. That is, 10 ⁵ Ω
If the diameter is less than 1 cm, a large current flows when a pinhole or the like exists in the photoconductor, and the photoconductor may be deteriorated.
When it is larger than 0 ¹⁰ Ω · cm, there is a problem that the charge cannot be sufficiently moved within the charging time, and poor charging easily occurs.

The various measuring methods used in the present invention are described below. The coating rate of the core material surface of the coated carrier or the coated magnetic particles of the present invention is determined by using an image processing analysis device Luz.
Using ex3 (manufactured by Nireco), an image of one carrier particle observed by an electron microscope is two-dimensionally determined to obtain the area of the coated portion and the carrier particle area, respectively, and binarized to perform the two-dimensional carrier particle area. Calculate the area ratio of the covering part to
The coverage was calculated. In the present invention, 30
Zero or more carriers or magnetic particles were extracted and measured.

FIG. 3 shows a schematic diagram of the measurement method for measuring the specific resistance of the coated carrier or coated magnetic particles of the present invention. The electrodes 1 and 2 were arranged so as to be in contact with the filled carrier and the like, a voltage was applied between these electrodes, and a current flowing at that time was measured to obtain a specific resistance. In the above-mentioned measuring method, care must be taken because the powder is used as the carrier, which causes a change in the filling rate, which may change the specific resistance. The conditions for measuring the specific resistance in the present invention are as follows: the contact area S between the filled carrier and the electrode is about 2.3 cm ² , the thickness d is about 1 mm, and the load 2
75 g and an applied voltage of 100 V.

[0047]

Next, the present invention will be described specifically with reference to examples and comparative examples, but the present invention is not limited by the examples. Example 1 A fluidized bed shown in FIG. 2 was obtained by adding a hard coat resin (Vestar Q9-6503, manufactured by Dow Corning) containing 50 wt% of a siloxane component to a titanium oxide sol having an average particle diameter of 10 nm and mixing the same. Using a coating device, average particle size 50 μm, saturation magnetization 20 emu
/ G of spherical ferrite particles of 1.5 kg / g. At this time, the blowing temperature to the fluidized bed room was set to 40 ° C., and the rotation speed of the stirring blade at this time was set to 450 rpm.
And The spray conditions were as follows: the air pressure to the spray nozzle was 3.4 kg / cm ² and the flow rate was 48 l / mi.
n. The supply rate of the coating resin solution is 8.0 ml / mi.
n. It was done as.

After completion of the spraying, the obtained carrier was introduced into a fluidized bed room, and kept at a temperature of 150 ° C. for 40 minutes to be cured to obtain a coated carrier. The thickness of the surface coating layer containing the obtained photocatalyst was about 2 μm. Separately,
The pencil hardness of the film formed from the above coating resin solution was 6H. In the carrier taken out of the fluidized bed room, no granulation was observed, and no fine powder of the coating resin component was observed. When the coating amount of the surface coating layer of the obtained coated carrier was measured, it was 2.0% by weight based on the carrier core material. Further, when the surface of the coated carrier particles was observed with a scanning electron microscope, it was found that the coating layer was formed in a state where the surface of the carrier core material was almost completely covered. At this time, the specific resistance of the coated carrier was 2.9 × 10 ¹³ Ω · cm, and the coverage was 94%.

On the other hand, a toner was prepared as follows. First, the following components were sufficiently premixed, melt-kneaded, cooled, and coarsely pulverized using a hammer mill to a particle size of about 1 to 2 mm. Next, the mixture is finely pulverized with a fine pulverizer using an air jet method, and the obtained finely pulverized material is classified using an elbow jet classifier to have a weight average particle size of 8.3.
A negatively-chargeable cyan fine powder of μm was obtained. 100 parts by weight of polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 5 parts by weight of copper phthalocyanine pigment 4 parts by weight of chromium complex salt of di-tert-butylsalicylic acid

To 100 parts by weight of the cyan fine powder obtained as described above, 0.5 parts by weight of silica fine powder hydrophobized with hexamethyldisilazane and 0.3 parts by weight of alumina fine powder were added. In addition, the mixture was mixed with a Henschel mixer to prepare a cyan toner used in this example.

The two-component developer was obtained by mixing the above-obtained coated carrier and the toner so that the toner concentration was 5.0% by weight. This developer was mounted on a modified full-color laser copying machine CLC-500 manufactured by Canon Inc., and an image output durability test of 10,000 sheets was performed. At this time, the distance between the developer carrying member (developing sleeve) of the developing device and the developer regulating member (magnetic blade) was 600 μm, and the distance between the developing sleeve and the electrostatic latent image carrying member (photosensitive drum) was 450 μm.
The peripheral speed ratio between the developing sleeve and the photosensitive drum is 1.3:
1. The magnetic field of the developing pole of the developing sleeve was set to 1,000 gauss. Further, the developing conditions were set such that the alternating electric field was 1,800 V _PP and the frequency was 2,000 Hz.

As a result, from the initial stage to 5,000 sheets, the density of the solid image is stably high at 1.5 to 1.6, there is no fog, the reproducibility of the halftone portion, the line image An image having good reproducibility was obtained. In addition, no carrier adhered on the image, and no toner scattering during development was observed. Also, after 5,000 sheets of images have been output, the developer is taken out of the developing device, and the scanning electron microscope (FE-SE) is used.
When the carrier surface was observed in M), no spent toner and no peeling of the coating layer were observed.

Further, when an image endurance test was performed on up to 20,000 sheets, the image density of the solid image was reduced to 1.0 to 1.1. After the durability test, the developer was taken out of the developing device and the carrier surface was observed with a scanning electron microscope (FE-SEM). As a result, spent toner was observed.
Therefore, while stirring the developer having the coated carrier of the present example provided with the coating layer having the photocatalyst, 10
It was irradiated with a high-pressure mercury lamp of W / cm ² for 3 hours. Then, the scanning electron microscope (FE-
When the carrier surface was observed by SEM), the spent of the toner was removed. When an image forming test was performed again using this developer, the image density of the solid image was 1.
The reproducibility of the halftone portion and the reproducibility of the line image were also good, stably high at 5 to 1.6, without fog.

Example 2 This example was carried out in the same manner as in Example 1 except that 1.5 kg of the carrier core material used in Example 1 was used, and the spraying conditions and the coating resin solution used were as follows. Was prepared. The coating resin solution has an average particle size of 20 n.
m anatase-type titanium oxide and 70 wt% hard coat resin (Vestar Q9- manufactured by Dow Corning)
6503) was used. The spray conditions of the coating resin solution are as follows: air pressure to the spray nozzle is 3.8 kg / cm ² , and flow rate is 45 liter / mi.
n. And the solution supply rate was 6.0 ml / min. And
After the spraying, the carrier was set at a temperature of 540 ° C. to the fluidized bed room, cured for 30 minutes, and then air-cooled. When the temperature of the fluidized bed room became 50 ° C., the carrier was taken out to remove the coated carrier. Obtained.

The carrier taken out of the fluidized bed room had almost no granulation, and no generation of fine powder was observed. When the coating amount of the coating layer of the obtained coated carrier was quantified, it was 3.14% by weight based on the carrier core material. In addition, the surface of the carrier is scanned with a scanning electron microscope (FE).
-SEM), the carrier core material was hardly exposed, and was uniformly coated.
7%. The specific resistance of the obtained coated carrier was 6.2 × 10 ¹³ Ω · cm.

A two-component developer was prepared using this carrier and the same toner as used in Example 1, and an image durability test was performed in the same manner as in Example 1. As a result, the density of the solid image was 1.5 to
The obtained image was stable and sufficiently high at 1.6, was free of fog, and had good reproducibility of the halftone portion and reproducibility of the line image. In addition, no carrier adhered to the image, and no toner scattering during development was observed. Further, after 10,000 images were output, the developer was taken out of the developing device and the carrier surface was observed with a scanning electron microscope (FE-SEM). As a result, no spent toner and no peeling of the coating layer were observed.

Further, when an image output durability test was performed on up to 30,000 sheets, the image density of the solid image was reduced to 1.0 to 1.1. After the durability test, the developer was taken out of the developing device and the carrier surface was observed with a scanning electron microscope (FE-SEM). As a result, spent toner was observed. Therefore,
While stirring the developer containing the coated carrier of the present example provided with the coating layer having a photocatalyst, 10 W / c
Irradiated with a high pressure mercury lamp of m ² for 3 hours. After the irradiation is completed, the carrier is scanned with a scanning electron microscope (FE-SE).
Observation of the carrier surface in M) revealed that spent toner was removed. Further, when an image output durability test was performed again using this developer, the density of the solid image was 1.5%.
It was stable and high at ~ 1.6, there was no fog, and the reproducibility of the halftone portion and the reproducibility of the line image were good.

Comparative Example 1 The same 1.5 kg carrier core material as used in Example 1 was used.
A carrier was produced in the same manner as in Example 1 except that the following was used as the coating resin solution. Hard coat resin similar to that used in Example 1 (manufactured by Dow Corning,
Vestar Q9-6503) was prepared, and the solution was sprayed under the conditions of an air pressure of 3.8 kg / cm ² to the spray nozzle, a flow rate of 45 liter / min. Solution supply rate 6.0 ml / min.
Then, it was applied to the carrier core material. After the spraying, the carrier is introduced into the fluidized bed room, the blast temperature is set to 540 ° C., and the mixture is cured by holding for 30 minutes. A coated carrier for comparison was obtained. The carrier removed from the fluidized bed room had almost no granulation, and no generation of fine powder was observed. When the coating amount of the coating layer of the obtained carrier was determined, it was 2.8% by weight based on the carrier core material. Further, when the surface of the carrier was observed with a scanning electron microscope (FE-SEM), almost no exposure of the carrier core material was recognized, and the carrier was uniformly coated. The specific resistance of the obtained coated carrier is 2.6 × 10 ¹⁴ Ω · cm.
And the coverage was 97%.

Using the coated carrier obtained above, an image durability test was performed in the same manner as in Example 1. As a result, from the initial stage to 10,000 sheets, the density of the solid image is
The reproducibility of the halftone portion and the reproducibility of the line image were good, stably and sufficiently high at 1.5 to 1.6, without fog. In addition, no carrier adhered to the image, and no toner scattering during development was observed. Also, after 10,000 images were output, the developer was taken out of the developing device and the surface of the carrier was observed with a scanning electron microscope (FE-SEM). As a result, no spent toner and no peeling of the coating layer were observed.

Further, when an image endurance test was performed on up to 30,000 sheets, the image density of the solid image was reduced to 1.0 to 1.1. At this time, when the developer was taken out of the developing device and the carrier surface was observed with a scanning electron microscope (FE-SEM), spent toner was observed. Then, while stirring the developer containing the coat carrier of the present comparative example obtained above, a high-pressure mercury lamp of 10 W / cm ²
Scanning electron microscope (FE-S)
When the carrier surface was observed by EM), the spent of the toner was not removed. Further, the image formation test was performed again, but the image density was still reduced.

Example 3 Spherical magnetite of 50 μm was used as a carrier core material, and the spraying conditions were 4.0 kg / cm ² air pressure and 5 flow rates.
0 liter / min. 8.2 ml of coating solution supply speed
/ Min. A coated carrier of this example was manufactured in the same manner as in Example 2 except that The obtained carrier was not granulated, and no generation of fine powder was observed.
Further, the amount of the coating layer of the obtained coated carrier was determined to be 3.8% by weight. When the surface of the carrier was observed with a scanning electron microscope, no exposure of the carrier core material was observed at all, and it was found that a uniform coating was formed. The specific resistance of the coated carrier of this example was 8.7 × 10 ¹³ Ω · cm, and the coverage was 98%.

The coated carrier obtained above and Example 1
A two-component developer was prepared in the same manner as in Example 1 by using the toner used in Example 1, and an image output test was performed using this developer. As a result, from the initial stage to the 10,000 sheets, the solid image density was stable and sufficiently high at 1.6 to 1.7, and the reproducibility of the halftone portion and the line image was good. There was no fogging or carrier adhesion on the image, and no toner scattering. Further, after the completion of image output on 10,000 sheets, the developer was taken out of the developing device and the carrier surface was observed with a scanning electron microscope. As a result, no spent toner and no peeling of the coating layer were observed.

Further, when an image endurance test was performed on up to 30,000 sheets, the density of the solid image was reduced to about 1.0 to 1.1. The developer was taken out of the developing device and the carrier surface was observed with a scanning electron microscope (FE-SEM). As a result, spent toner was observed. Thus, a scanning electron microscope (F) was used for irradiation with a high-pressure mercury lamp of 10 W / cm ² for 3 hours while stirring the developer containing the coat carrier of the present example provided with the coating layer having a photocatalyst.
When the carrier surface was observed by E-SEM), the spent of the toner was removed. Further, when the image was reproduced again, the density of the solid image was stably high at 1.5 to 1.6, there was no fog, and the reproducibility of the halftone portion and the reproducibility of the line image were good. Was.

Reference Example 1 Ferrite core material having a volume resistance of 9.2 × 10 ⁶ Ω · cm
Coating magnetic particles for charging were produced in the same manner as in Example 1 except that the following coating materials were used for 5 kg, and the apparatus conditions were set as follows. 50 wt% of hard coat resin (manufactured by Dow Corning, Vestar Q9-6503) and 20 wt% of titanium oxide sol having an average particle diameter of 10 nm
% Of the conductive tin oxide was added and mixed to prepare a coating resin solution. The spraying conditions of this solution include an air pressure of 3.8 kg / cm ² to the spray nozzle, a flow rate of 50 liter / min. , Solution supply rate for coating 6.0 ml / min
Was applied. After the spraying is completed, the blast temperature to the fluidized bed room is kept at 150 ° C. and kept for 60 minutes to cure.
It was air-cooled and taken out when the fluidized bed chamber reached 40 ° C. to obtain coated magnetic particles.

The coated magnetic particles taken out of the fluidized bed room were hardly granulated, and no generation of fine powder of the coating resin was observed. When the coating amount of the coating layer of the obtained coated magnetic particles was quantified, it was 3.4 to the carrier core material.
% By weight. In addition, when the surface of the coated magnetic particles was observed with a scanning electron microscope (FE-SEM), almost no exposure of the core material was recognized, and the particles were uniformly coated with the resin. The specific resistance of the obtained coated magnetic particles was 6.7 × 1.
0 ⁷ Ω · cm, and the coverage was 95%. The thickness of the surface coating layer containing the photocatalyst of the obtained coated magnetic particles was about 2 μm. The surface had a pencil hardness of 4H.

When the charging coated magnetic particles were brought into contact with the amorphous silicon photosensitive member while rotating counter while applying a voltage of -700 V as a magnetic brush, the surface potential of the photosensitive member became negative during one rotation of the photosensitive member. 700V
Was charged well. Further, when the magnetic brush charger and the photosensitive member were attached to a digital copier GP55 manufactured by Canon Inc. to perform image output, a good image was obtained even on 5,000 sheets. Further, when an image output durability test was performed on up to 20,000 sheets, fogging due to poor charging occurred.

Then, the magnetic particles coated with the charge were taken out of the charger and the surface was observed with a scanning electron microscope (FE-SEM). As a result, spent toner was observed. Therefore, while stirring the coated magnetic particles for charging, 10 W
/ Cm ² for 3 hours. And what was irradiated with light was a scanning electron microscope (FE-SEM).
When the surface of the carrier was observed, the spent of the toner was removed and the magnetic particles coated with the charging magnetic particles were returned to the charger, and an image was formed again. As a result, a good image was obtained.

Reference Comparative Example 2 Coating magnetic particles for charging were produced in the same manner as in Reference Example 1 except that the following resin solution for coating was used for 1.5 kg of the core material used in Reference Example 1. 60 wt% hard coat resin (Vestar Q, manufactured by Dow Corning)
9-6503) and 40 wt% of conductive tin oxide were added and mixed to obtain a coating resin solution. After the spraying, the particles were introduced into the fluidized bed chamber, and the resin was cured by maintaining the blowing temperature at 150 ° C. for 60 minutes, and then air-cooled and taken out when the fluidized bed chamber reached 40 ° C. for comparison. To obtain coated magnetic particles.

The coated magnetic particles taken out of the fluidized bed room were hardly granulated, and no generation of coated resin powder was observed. When the coating amount of the obtained coated magnetic particles was quantified, it was 2.9% by weight based on the core material.
In addition, the surface of the coated magnetic particles is scanned with a scanning electron microscope (FE-
When observed by SEM), almost no exposure of the core material was observed, and the core material was uniformly covered with the resin. The specific resistance of the coated magnetic particles is 1.1 × 10 ⁸ Ω · cm, and the coverage is 9
1%. The thickness of the obtained surface coating layer was about 3 μm. The pencil hardness of the surface was 7H.

The charging coated magnetic particles were used as a magnetic brush to make contact with the amorphous silicon photoreceptor while applying a voltage of -700 V while rotating the counter counterclockwise. 700V
Was charged well. Further, when the magnetic brush charger and the photosensitive member were attached to a digital copier GP55 manufactured by Canon Inc. to perform image output, a good image was obtained even on 5,000 sheets. Further, when the image output durability was performed up to 20,000 sheets, fogging due to poor charging occurred.

The charge carrier was taken out of the charger and the carrier surface was observed with a scanning electron microscope (FE-SEM). As a result, spent toner was observed. The carrier was irradiated with a high-pressure mercury lamp of 10 W / cm ² for 3 hours while stirring the carrier, and a scanning electron microscope (FE-SE) was used.
Observation of the carrier surface in M) revealed that the spent toner was not removed and image formation was performed again, but fog was not improved.

[0072]

As described above, the photocatalyst of the present invention is included.
Electrophotographic coated carrier having a coating layer
According to a, by using this, good image output
Can be performed stably for a long time. Good durability
Having good coat carrier for development and good chargeability
It is possible to obtain a coated carrier with good durability.
Noh. The coated carrier for electrophotographic development of the present invention
Waste can be reduced while reducing costs due to repeated use
And reduce the burden on the environment.
is there. As described above, according to the present invention, a high-quality image
Electrophotography that can stably obtain images over a long period of time
Provided is a coat carrier for development and an image forming method.
You. That is, according to the present invention, in long-term durability, toner
Easy operation even if the image is deteriorated due to spent
It is possible to recover the function as a career with the work
Therefore, stable image formation over a long period of time is possible.
Become. In addition, according to a preferred embodiment of the present invention,
Image with little fog and carrier adhesion
Excellent spent and abrasion resistance, stable and static for a long time
It is possible to provide high-definition, high-quality images that are faithful to
To Also, a configuration similar to the electrophotographic coated carrier of the present invention.
Forming a magnetic brush and applying a voltage
To charge a member to be charged such as a photoreceptor.
Of the magnetic particles for electrophotographic charging
Charging is applied in the same way as the coated carrier for electrophotography
Power that can maintain stability over a long period of time.
Coated magnetic particles for photolithography can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic view of a cross section of a coated carrier for electrophotographic development of the present invention.

FIG. 2 is a schematic view of an apparatus for producing a coated carrier for electrophotography according to the present invention.

FIG. 3 is a schematic view showing a method for measuring the specific resistance of a carrier or the like.

[Explanation of symbols]

 1: Air supply blower 2: Fluidized bed room 3: Carrier core 4: Rotating disk 5: Stirring blade 6: Spray nozzle 7: Compressed air 8: Bag filter 9: Exhaust blower 10: Heater 11: Resin solution for coating 12 : Mesh 13: Tube 31: Lower electrode 32: Upper electrode 33: Insulator 34: Ammeter 35: Voltmeter 36: Constant voltage device 37: Carrier 38: Guide ring d: Thickness of measurement sample E: Resistance measurement cell

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Keiko Hiraoka 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (8)

[Claims] 1. A coated carrier for electrophotographic development, comprising: a carrier core material; and a coating layer provided on the surface of the carrier core material and containing a photocatalyst having an oxidation potential of 1.5 V or more. 2. The coated carrier having a specific resistance of 1 × 10 ¹²
2. The coated carrier for electrophotographic development according to claim 1, which has an Ω · cm or more. 3. The coating rate on the carrier core material surface is 90.
2. The coated carrier for electrophotographic development according to claim 1, wherein at least 80% by weight of the carrier particles are at least 80% by number. 4. The coated carrier for electrophotographic development according to claim 1, wherein the photocatalyst is an anatase type titanium oxide. 5. An image forming method comprising: a developing step of developing an electrostatic image carried on an electrostatic image carrier using a two-component developer having a toner and a carrier. After developing with a two-component developer using a coated carrier having a coating layer containing a photocatalyst having an oxidation potential of 1.5 V or more provided on the surface of the carrier core material to form an image, the two-component developer is used. An image forming method comprising irradiating a developer with near-ultraviolet light having a wavelength of 250 nm to 500 nm, mixing the mixture, and performing image formation again using the mixed two-component developer. 6. The coated carrier having a specific resistance of 1 × 10 ¹²
The image forming method according to claim 5, wherein the resistance is Ω · cm or more. 7. The coating rate on the carrier core material surface is 90.
The image forming method according to claim 5, wherein the percentage of the carrier particles is 80% by number or more of the whole. 8. The image forming method according to claim 5, wherein the photocatalyst is an anatase type titanium oxide.