JP2005091690A - Electrophotographic carrier, developer, method for forming image, storage container, image forming apparatus and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier for a two-component developer having higher durability, to provide a carrier for a two-component developer exhibiting high durability even in combination with toner containing a release agent, and also to provide an image forming apparatus which uses the developer using the carrier. <P>SOLUTION: The carrier having a coating film consisting at least of binder resin and particles is characterized in that: the particle diameter (D) and film thickness (h) of the binder resin are in the relation of 1<[D/h]<10; and the particles are surface treated with a single silicon acrylate compound or two or more kinds of compound expressed by general formula in the figure. In the formula, R1 represents a 1 to 6C alkylene group, each of R2, R3 and R4 represents a hydrogen atom or a 1 to 4C alkyl group, and R5 represents a hydrogen atom or a methyl group. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a carrier, a developer, an image forming method, a storage container, and an image forming apparatus used for developing an electrostatic image in electrophotography, electrostatic recording, electrostatic printing, and the like.

In general, in image forming methods such as electrophotography and electrostatic photography, a developer obtained by stirring and mixing a toner and a carrier in order to develop an electrostatic latent image formed on a latent image carrier. Is used. This developer is required to be a suitably charged mixture.
In general, as a method for developing an electrostatic latent image, a method using a two-component developer obtained by mixing a toner and a carrier and a method using a one-component developer containing no carrier are known. . The former developing method using a two-component developer can provide a relatively stable and good image, but has a drawback that carrier deterioration and fluctuation in the mixing ratio of the toner and the carrier are likely to occur. On the other hand, the latter one-component developer does not have the disadvantages of the former, but has the disadvantage that the chargeability is difficult to stabilize.

Also, when developing a latent electrostatic image repeatedly using a two-component developer, the toner in the developer is consumed and the toner density fluctuates, so it is necessary to obtain a stable image during printing. Therefore, it is necessary to replenish the toner and suppress this fluctuation. In general, as a method for controlling the toner replenishment amount, a copying machine is provided with a permeability detection sensor, a fluidity detection sensor, an image density detection sensor, a bulk density detection sensor, etc., but an image density detection sensor is used. Is the mainstream these days. This sensor is a method for controlling a toner replenishment amount by developing a fixed image pattern on a latent image carrier and detecting an image density from reflected light.
The granular carrier used in such a two-component development system is capable of preventing toner filming on the carrier surface, forming a uniform carrier surface, preventing surface oxidation, preventing moisture sensitivity deterioration, extending the life of the developer, and photosensitive. For the purpose of protecting the body from scratches or abrasion by the carrier, controlling the polarity of the charge, or adjusting the amount of charge, a hard and high-strength coating layer is usually provided by coating with an appropriate resin material. For example, those coated with a specific resin material (Patent Document 1), and further various additives added to the coating layer (Patent Documents 2, 3, 4, 5, 6, 7, 8), There are disclosed one using an additive added to the carrier surface (Patent Document 9), and one using a coating film containing conductive particles larger than the coating film thickness (Patent Document 10). . Patent Document 11 describes the use of a benzoguanamine-n-butyl alcohol-formaldehyde copolymer as a main component for a carrier coating material, and Patent Document 12 describes a carrier coating of a cross-linked product of a melamine resin and an acrylic resin. The use as a material is described.

However, the durability is still inadequate, and there are problems such as spent toner on the carrier surface, associated charge instability, and resistance reduction due to scraping of the coating resin. However, as the number of copies increases, the image quality of the copied image decreases, so improvement is necessary. Therefore, Patent Document 13 reports that these problems can be solved by defining the relationship between the particle diameter and the binder resin film thickness and defining the specific resistance of the particles. Certainly, the effect is remarkable as compared with the conventional ones, but the demand for the durability of the recent developer is further increased, and further improvement is desired. Further, it has been clarified that the combination of the toner containing a release agent and the carrier proposed in Patent Document 14 cannot provide the same effect as the toner containing no release agent. A commercially available digital full-color copying machine described in Patent Document 15 is composed of a toner and a developer that do not contain a release agent.
In recent years, both copying machines and printers have many demands for space saving, and in response to this demand, measures are taken to reduce the fixing portion by omitting the fixing oil or by applying a small amount. In this case, since the toner has a toner configuration including a release agent, there is a great demand for a carrier having high durability even in combination with a toner including a release agent.

JP 58-108548 A JP 54-1555048 A JP 57-40267 A JP 58-108549 A JP 59-166968 A Japanese Patent Publication No. 1-19584 Japanese Examined Patent Publication No. 3-628 JP-A-6-202381 JP-A-5-273789 JP-A-9-160304 JP-A-8-6307 Japanese Patent No. 2683624 Japanese Patent Laid-Open No. 2001-188388 Japanese Patent Laid-Open No. 2001-188388 Japanese Patent Laid-Open No. 2001-188388

  In view of the above problems, the present invention provides a more durable two-component developer carrier, and also provides a highly durable two-component developer carrier even in combination with a toner containing a release agent. And Another object of the present invention is to provide an image forming apparatus using a developer using the carrier.

  In order to solve the above-mentioned problems, the present invention according to claim 1 is such that, in a carrier having a coating film composed of at least a binder resin and particles, the particle diameter (D) and the binder resin film thickness (h) are 1. <[D / h] <10, wherein the particles are surface-treated with one or more silicon acrylate compounds represented by the following general formula.

  (Wherein R1 represents an alkylene group having 1 to 6 carbon atoms, R2, R3 and R4 represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R5 represents a hydrogen atom or a methyl group.)

  According to a second aspect of the present invention, there is provided the electrophotographic carrier according to the first aspect, wherein the coating film contains one or more kinds of silicon acrylate compounds.

According to a third aspect of the present invention, in the electrophotographic carrier according to the first aspect, the particles are surface-treated with one or more silicon acrylate compounds, and the coating film is a single silicon acrylate compound. Or it is the carrier for electrophotography characterized by containing 2 or more types.
According to a fourth aspect of the present invention, in the electrophotographic carrier according to any one of the first to third aspects, the specific resistance of the particles is 10 ¹² (Ω · cm) or more. It is a carrier for electrophotography.
According to a fifth aspect of the present invention, there is provided the electrophotographic carrier according to any one of the first to fourth aspects, wherein the particles are alumina and / or silica.
According to a sixth aspect of the present invention, there is provided the electrophotographic carrier according to any one of the first to fifth aspects, wherein the particle content is 40 to 95 wt% of the coating film composition component. Photo carrier.

According to a seventh aspect of the present invention, in the electrophotographic carrier according to any one of the first to sixth aspects, the film thickness of the binder resin is 0.05 μm to 1.00 μm. It is a carrier for photography.
The present invention according to claim 8 is the electrophotographic carrier according to any one of claims 1 to 7, wherein the binder resin is a resin obtained by cross-linking at least an acrylic resin and an amino resin or / and a silicone resin. An electrophotographic carrier characterized by being contained.
The present invention according to claim 9 is the carrier for electrophotography according to any one of claims 1 to 8, wherein the Tg of the resin is 20 to 100 ° C.
The tenth aspect of the present invention is an electrophotographic developer comprising: a toner comprising at least a binder resin and a pigment; and the electrophotographic carrier according to any one of the first to ninth aspects. is there.
The eleventh aspect of the present invention is the electrophotographic developer according to the tenth aspect, wherein the toner contains a release agent.

According to a twelfth aspect of the present invention, there is provided an image forming method using the electrophotographic developer according to the tenth or eleventh aspect.
According to a thirteenth aspect of the present invention, there is provided a multicolor image forming method using the electrophotographic developer according to the tenth or eleventh aspect.
A fourteenth aspect of the present invention is a storage container for storing the electrophotographic developer according to the tenth or eleventh aspect.
According to a fifteenth aspect of the present invention, there is provided an image forming apparatus including a storage container filled with the electrophotographic developer according to the fourteenth aspect.
According to a sixteenth aspect of the present invention, in the process cartridge selected from the photosensitive member, the charging unit, the developing unit, and the cleaning unit, and at least supporting the developing unit integrally, and detachable from the main body of the image forming apparatus, the developing unit Holds a developer, and the developer is the developer according to claim 10 or 11.

  According to the present invention, it is possible to provide a carrier for two-component developer, a developer, an image forming method, a storage container, and an image forming apparatus that are more durable than conventional ones. Further, it is possible to provide a highly durable two-component developer carrier, developer, image forming method, storage container, and image forming apparatus even in combination with a toner containing a release agent.

  Hereinafter, the present invention will be described in more detail. As a result of continuous studies to solve the above-described problems of the prior art, the present inventors have determined that the particle diameter (D) and the binder resin film thickness in a carrier having a coating film having at least a binder resin and particles. When (h) is 1 <[D / h] <10 and the particles are surface-treated with one or more silicon acrylate compounds represented by the following general formula, the improvement effect may be remarkable. all right.

  (Wherein R1 represents an alkylene group having 1 to 6 carbon atoms, R2, R3 and R4 represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R5 represents a hydrogen atom or a methyl group.)

This is because the particles are more convex than the coating film, so the contact with the strong impact on the binder resin is reduced by the friction with the toner or the friction between the carriers by agitation to frictionally charge the developer. can do. As a result, it is possible to prevent the toner spent on the carrier and to prevent the binder resin film from being charged.
However, the convex portion, that is, the particle portion relaxes the contact with a strong impact on the binder resin, so that the particle itself is always easily detached from the coating film. In order to cope with further high durability, it is necessary to suppress the detachment of the particles. According to the present inventors, the particles can be treated by surface-treating the general formula alone or in combination of two or more thereof. Can be suppressed. This is because the detachment of the particles is suppressed by increasing the adhesion between the particles and the binder resin in the coating film. In the case of a toner containing a release agent, the release of the particles was accelerated mainly by the release agent. However, the adhesive between the particles and the binder resin in the coating film increased, so The same effect as in the case of the toner containing is obtained.

  Moreover, according to the present inventors, it has become clear that there is a specific range for [D / h]. When [D / h] is 1 or less, the particles are buried in the binder resin, which is not preferable because the effect is remarkably lowered. Conventionally, when [D / h] is 5 or more, the contact area between the particles and the binder resin is small, so that a sufficient restraining force cannot be obtained and the particles are easily detached. Is surface treated with a single or two or more types of silicon acrylate compounds represented by the general formula, thereby increasing the adhesion to the binder resin, and particles are not detached even when the number is 5 or more and 10 or less. It became possible to obtain film convexity.

There are two surface treatment methods used in the present invention, wet and dry. In the wet process, the particles and the silicon acrylate compound represented by the general formula are dispersed in a solvent, and the silicon acrylate compound is adhered to the particle surface. As the dispersing means, general dispersing means such as a ball mill and a sand mill can be used. Next, after this dispersion solution is dried by a dryer to remove the solvent, heat treatment is further performed to fix the silicon acrylate compound to the particle surface. If necessary, the treated particles may be pulverized.
In the dry process, the silicon acrylate compound and the conductive metal oxide fine particles are mixed and kneaded without using a solvent to adhere the silicon acrylate compound to the surface of the fine particles. Thereafter, heat treatment, pulverization treatment, and the like are performed in the same manner as the wet treatment to complete the surface treatment.

The ratio of the silicon acrylate compound to the particles in the present invention is affected by the particle size of the particles, but is preferably 0.01 to 100% by weight, particularly 3% with respect to the total weight of the surface-treated particles. It is preferable that the content is ˜40% by weight. In addition, the silicon acrylate compound was not only subjected to surface treatment on the particles, but the same effect was obtained even when contained alone or in combination of two or more in the coating film.
In addition, when these were surface-treated with particles and when they were contained in the coat film, the effect was more prominent.
Moreover, although these quantities depend on the particle diameter of a particle | grain and the structure of a silicon acrylate compound, it is desirable that it is 0.01-50 weight part with respect to 100 weight part of particle | grains. More preferably 0.05 to 40 parts by weight Silicon acrylate compound represented by the general formula: γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltrihydroxysilane, and γ-acryloxypropylethoxysilane.

Further, according to the present invention, it is effective that the specific resistance of the particles is 10 ¹² (Ω · cm) or more in order to suppress a decrease in charge amount during storage of the developer for a long period of time. This is because even if the particles are exposed on the surface while having contact with the core material, charge leakage can be suppressed, so that stable chargeability can be obtained. On the other hand, when the specific resistance of the particles is less than 10 ¹² (Ω · cm), since charge leakage cannot be suppressed, stable chargeability cannot be obtained, which is not preferable. In addition, as mentioned in the prior art, as a difference from the technique similar to the present invention in which conductive particles larger than the coating resin film thickness are contained in the coating film (for example, Patent Document 10), In the present invention, the particles are not used as a resistance adjusting material as in the prior art, but are characterized by being used as a protective material for the coating film resin and a surface shape adjusting material. Furthermore, the silicon acrylate compound represented by the general formula is essential for suppressing the detachment of the particles.

  Further, the effect is remarkable when the particles are alumina and the content thereof is in the range of 50 to 95 wt% of the coating film composition component, preferably 70 to 90 wt%. Furthermore, the effect is remarkable when the particles are silica and the content thereof is in the range of 50 to 95 wt% of the coating film composition component, preferably 70 to 90 wt%. A mixture of alumina and silica may also be used. When the content ratio of the particles is less than 50 wt%, since the proportion of the particles is smaller than the proportion of the binder resin on the surface of the carrier particles, the contact with a strong impact on the binder resin is reduced. Since the effect is small, sufficient durability cannot be obtained, which is not preferable. On the other hand, if the amount is more than 95 wt%, the proportion of particles is too large compared to the proportion of the binder resin on the carrier surface, so the proportion of the binder resin that is a charging occurrence point is insufficient, The charging ability cannot be demonstrated. In addition, since the amount of particles is too much compared to the amount of binder resin, the ability to hold particles by the binder resin becomes insufficient, and the particles are liable to be detached, so that sufficient durability cannot be obtained, which is not preferable. In addition, the invention described in Patent Document 10 is different from the present invention in terms of the content range of the particles, "0.01 to 50% by weight of the coating resin", that is, when converted into the content calculation method of the present invention “0.01 to 33.33 wt% of the coating film composition component”. In this case, the durability is improved as compared to the conventional case, but as described above, the ratio of the binder resin to the surface of the carrier particles is In comparison, since the proportion of particles is small, the effect of relaxing contact with a strong impact on the binder resin is small, and sufficient durability cannot be obtained.

According to the present invention, it is important that the binder resin contains a resin obtained by crosslinking an acrylic resin and an amino resin or / and a silicone resin.
As this amino resin, a conventionally known amino resin can be used. However, the use of guanamine or melamine remarkably improves the charge imparting ability.
Further, as the silicone resin, conventionally known silicone resins can be used.
In addition to the resins listed here, resins generally used as carrier coating resins can be used, and of course, they may be used in combination with the above resins. For example, polystyrene resin, poly (meth) acrylic resin, polyolefin resin, polyamide resin, polycarbonate resin, polyether resin, polysulfinic acid resin, polyester resin, epoxy resin, polybutyral resin, urea Resins, urethane / urea resins, polyethylene resins, Teflon (registered trademark) resins, and other thermoplastic resins and thermosetting resins, and mixtures thereof, as well as copolymers, block polymers, and graft weights of these resins Examples include, but are not limited to, coalescence and polymer blends.

According to the present invention, these resins should have a Tg of 20-100 ° C, preferably 25-80 ° C. When the Tg of the resin is within this range, the resin has an appropriate elasticity, and the friction between the toner and the carrier or the friction between the carriers in the stirring for frictionally charging the developer causes the resin to be bonded to the binder resin. In the case of contact with a strong impact, the impact can be absorbed and the coating film can be maintained without being damaged. Moreover, when Tg is 20 ° C. or lower, the binder resin is blocked even at room temperature, which is not preferable because the storage stability is poor and it cannot be used practically. On the other hand, when Tg is 100 ° C. or higher, the binder resin is hard and brittle, and the impact cannot be absorbed, and the binder resin is scraped from the brittleness and particles cannot be retained. , Because it is easy to desorb.
The carrier core material is at least 20 μm (average particle size) from the viewpoint of preventing carrier adhesion (scattering) to the electrostatic latent image carrier, and prevents the generation of carrier streaks etc. From the standpoint of preventing the decrease, the one having a maximum of 100 μm is used. Specific materials that are known as two-component carriers for electrophotography, such as ferrite, magnetite, iron, nickel, etc., may be appropriately selected according to the use and purpose of use of the carrier.

In order to obtain a desired resistance, carbon black, acidic catalyst, zinc oxide, titanium oxide, tin oxide, indium oxide, bismuth oxide, indium oxide doped with tin, tin oxide doped with antimony, zirconium oxide Ultrafine particles such as can be used. These resistance modifiers are used alone or in combination. When two or more types are mixed, they may take the form of a solid solution or fusion.
Any carbon black that is commonly used for carriers or toners can be used. As the acidic catalyst, one having a catalytic action can be used. For example, it has a reactive group such as a fully alkylated type, a methylol group type, an imino group type, and a methylol / imino group type, but is not limited thereto.
The carrier of the present invention is used as a two-component developer composed of toner, but the composed toner may be black toner or multicolor toner used in the multicolor image forming method.

The image forming apparatus of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of an image forming apparatus on which a container filled with a developer using the electrophotographic carrier of the present invention is mounted, and a developing unit 1 mounted in the main body of the image forming apparatus. And a developer storage container 2 filled with a developer using the electrophotographic carrier of the present invention replenished to the developing section 1, and a developer cross-sectional view showing a developer flow means 3 for connecting the two. .
In FIG. 1, a developing section 1 includes a developing housing 4 filled with a developer using the electrophotographic carrier of the present invention containing a liquid two-component developer D obtained by mixing a toner and a carrier, The first and second agitating screws 5 and 6 for agitating and mixing the developer D and a developing roller 7 are provided, and the developing roller 7 is disposed to face the photosensitive member 8 of the latent image carrier. ing. The photoreceptor 8 is driven to rotate in the direction indicated by the arrow, and an electrostatic latent image is formed on the surface thereof. Reference numeral 26 in the drawing is a cap fitted on the connecting member 24 with or without the filter 25. Around the photosensitive member 8, other known units such as a charging unit, an exposure unit, a transfer unit, a charge removing unit, and a cleaning unit (not shown) are arranged.

  As the first and second agitating screws 5 and 6 rotate, the developer D in the developing housing 4 is agitated, and the toner is frictionally charged with the carrier having opposite polarities. The developer D is supplied to the peripheral surface of the developing roller 7 that is rotationally driven in the direction of the arrow, and the supplied developer is carried on the peripheral surface of the developing roller 7, and the developer roller 7 is rotated by the rotation of the developing roller 7. Conveyed in the direction. Next, the amount of the conveyed developer is regulated by the doctor blade 9, and the regulated developer is conveyed to the development area between the photoconductor 8 and the developing roller 7, where the toner in the developer is removed. The electrostatic latent image on the surface of the photoreceptor is electrostatically transferred, and the electrostatic latent image is visualized as a toner image.

EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these.
Toner production example 1
<Toner Production Example 1>
Black toner 1
Water 1200 parts Phthalocyanine green water-containing cake (solid content 30%) 200 parts Carbon black (MA60, manufactured by Mitsubishi Chemical Corporation) 540 parts is thoroughly stirred with a flasher. To this, 1200 parts of epoxy resin (Mn; 3500) was added, kneaded at 150 ° C. for 30 minutes, 1000 parts of xylene were added, kneaded for 1 hour, water and xylene were removed, rolled and cooled, pulverized with a pulverizer, master batch pigment Got.
Epoxy resin (Mn; 3500) 100 parts Master batch 5 parts Zinc salicylate derivative 4 parts (Bontron E84, Orient Chemical)
The above materials were mixed with a mixer and then melt-kneaded with a two-roll mill, and the kneaded product was rolled and cooled. Thereafter, pulverization and classification were performed to obtain a toner having a weight average particle diameter of 7.8 μm. Further, as in the case of the yellow toner 1, additives were added and mixed with a Henschel mixer to obtain a black toner 1.

<Toner Production Example 2>
Black toner 2
Except for adding 5 parts of carnauba wax to Toner Production Example 1, all were produced in the same manner as in Production Example 1.

<Surface treatment particle production example 1>
Alumina particles 1
Alumina (0.3 μm, specific resistance 10 ¹⁴ Ω · cm) particles 50 in a solution composed of 5 parts by weight of γ-methacryloxypropyltrimethoxysilane (trade name KBM-503, manufactured by Shin-Etsu Chemical Co., Ltd.) and 495 parts by weight of acetone Part by weight was added and stirred for 2 hours, followed by filtration to remove the solvent, followed by drying at 120 ° C. for 2 hours to obtain alumina particles 1 surface-treated with γ-methacryloxypropyltrimethoxysilane.

<Surface treatment particle production example 2>
Alumina particles 2
50 parts by weight of alumina (0.3 μm, specific resistance 10 ¹⁴ Ω · cm) particles were added to a solution consisting of 5 parts by weight of γ-methacryloxypropyltriethoxysilane and 495 parts by weight of acetone, followed by stirring for 2 hours, followed by filtration and solvent. Then, drying was performed at 120 ° C. for 2 hours to obtain alumina particles 2 surface-treated with γ-methacryloxypropyltriethoxysilane.

<Carrier production example 1>
Career 1
Acrylic resin solution (solid content 50% by weight) 56.0 parts Guanamin solution (solid content 77% by weight) 15.6 parts Alumina particles 1 160.0 parts Toluene 900 parts Butyl cellosolve 900 parts are dispersed with a homomixer for 10 minutes, A film-forming solution was prepared. A sintered ferrite powder [F-300: average particle size; 50 μm (manufactured by Powdertech)] is used as a core material, and the above-mentioned coating film forming solution is spiral coater (Okada so that the core material surface has a film thickness of 0.15 μm. Applied and dried. The obtained carrier was baked in an electric furnace at 300 ° C. for 2 hours. After cooling, the ferrite powder bulk was pulverized using a sieve having an opening of 100 μm, and carrier 1 was obtained. The measurement of the binder resin film thickness was performed by observing the cross section of the carrier with a transmission electron microscope so that the coating film covering the carrier surface could be observed.

<Carrier production example 2>
Career 2
All were produced in the same manner as in Carrier Production Example 1 except that the alumina particles 1 in Carrier Production Example 1 were changed to alumina particles 2.

<Carrier Production Example 3>
Career 3
Acrylic resin solution (solid content 50% by weight) 56.0 parts Guanamine solution (solid content 77% by weight) 15.6 parts Alumina particles (0.3 μm, specific resistance 10 ¹⁴ Ω · cm) 160.0 parts γ-methacryloxy Propyltrimethoxysilane 1.0 part Toluene 900 parts Butyl cellosolve 900 parts All were produced in the same manner as in Charaly Production Example 1 except that the above formulation was changed.

<Carrier Production Example 4>
Carrier 4
All were produced in the same manner as in Carrier Production Example 3 except that γ-methacryloxypropyltrimethoxysilane in Carrier Production Example 3 was changed to γ-methacryloxypropyltriethoxysilane.

<Carrier Production Example 5>
Carrier 5
All were produced in the same manner as in Carrier Production Example 3 except that the alumina particles in Carrier Production Example 3 were changed to alumina particles 1.

<Carrier Production Example 6>
Career 6
Acrylic resin solution (solid content 50% by weight) 56.0 parts Guanamin solution (solid content 77% by weight) 15.6 parts Alumina particles (0.3 μm, specific resistance 10 ¹⁴ Ω · cm) 160.0 parts Toluene 900 parts Butyl cellosolve 900 parts All were produced in the same manner as in Carrier Production Example 1 except that the prescription was changed.

<Example 1>
The carrier 1 and the black toner 1 thus obtained were placed in a ball mill and mixed for 10 minutes so that the toner concentration was 5% to obtain a developer. This developer and black toner 1 were set in a commercially available digital full-color copying machine (imageColor 2800 manufactured by Ricoh), and 600,000 sheets were evaluated for running. Tables 1 and 2 show the results of determining the charge reduction amount and resistance reduction amount of the carrier after the running.
The amount of charge reduction referred to here is a 95% by weight of the initial carrier mixed with a toner at a ratio of 5% by weight and triboelectrically charged to a general blow-off method [manufactured by Toshiba Chemical Co., Ltd .: TB- 200] is subtracted from the charge amount (Q2) measured by the same method as described above, from the carrier from which the toner in the developer after running has been removed by the blow-off device. The target value is 7.0 (μc / g) or less. Further, since the cause of the decrease in the charge amount is the toner spent on the carrier surface, the decrease in the charge amount can be suppressed by reducing the toner spent. The amount of resistance decrease is a value obtained by converting an initial carrier into a resistance measurement parallel electrode: an electrode having a gap of 2 mm, applying a DC 200V and measuring a resistance value after 30 seconds with a high resist meter into a volume resistivity ( R1) is the amount obtained by subtracting the value (R2) measured by the same method as the resistance measuring method from the carrier that can remove the toner in the developer after running by the blow-off device. The value is 2.0 [Log (Ω · cm)] or less. In addition, since the cause of the resistance reduction is scraping of the binder resin film of the carrier, the resistance reduction amount can be suppressed by reducing the film scraping.

<Example 2>
Evaluations were made in the same manner as in Example 1 except that the black toner 1 of Example 1 was changed to black toner 2. The evaluation results are shown in Tables 1 and 2.

<Example 3>
Evaluations were made in the same manner as in Example 2 except that carrier 1 in Example 2 was changed to carrier 2. The evaluation results are shown in Tables 1 and 2.

<Example 4>
Evaluations were made in the same manner as in Example 2 except that the carrier 1 in Example 2 was changed to the carrier 3. The evaluation results are shown in Tables 1 and 2.

<Example 5>
Evaluations were made in the same manner as in Example 2 except that the carrier 1 in Example 2 was changed to the carrier 4. The evaluation results are shown in Tables 1 and 2.

<Example 6>
Evaluations were made in the same manner as in Example 2 except that the carrier 1 in Example 2 was changed to the carrier 5. The evaluation results are shown in Tables 1 and 2.

<Comparative Example 1>
Evaluation was performed in the same manner as in Example 1 except that the carrier 1 in Example 1 was changed to the carrier 8. The evaluation results are shown in Tables 1 and 2.

<Comparative example 2>
Evaluations were made in the same manner as in Example 1 except that the carrier 2 in Example 2 was changed to the carrier 8. The evaluation results are shown in Tables 1 and 2.

  From Tables 1 and 2, by using the carrier of the present invention, an effect more than double that of the conventional durability can be obtained. Further, in the combination with a toner containing a release agent, a higher durability effect can be obtained as compared with the conventional result.

1 is a view showing a container filled with an electrophotographic developer according to the present invention and an image forming apparatus equipped with the container.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Developing part 2 Developer container 3 Developer delivery means 4 Developing housing 5 Stir screw 6 Stir screw 7 Developing roller 8 Photoconductor 9 Doctor blade 24 Connection member 25 Filter 26 Cap D Developer

Claims (16)

In a carrier having a coating film composed of at least a binder resin and particles,
The particle diameter (D) and the binder resin film thickness (h) are 1 <[D / h] <10, and the particles are surface-treated with one or more silicon acrylate compounds represented by the following general formula. An electrophotographic carrier characterized by comprising:

(Wherein R1 represents an alkylene group having 1 to 6 carbon atoms, R2, R3 and R4 represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R5 represents a hydrogen atom or a methyl group.) The electrophotographic carrier according to claim 1,
An electrophotographic carrier, wherein the coating film contains one or more silicon acrylate compounds. The electrophotographic carrier according to claim 1,
A carrier for electrophotography, wherein the particles are surface-treated with one or more kinds of silicon acrylate compounds, and the coating film contains one or more kinds of silicon acrylate compounds. The electrophotographic carrier according to any one of claims 1 to 3,
The electrophotographic carrier according to claim 1, wherein the specific resistance of the particles is 10 ¹² (Ω · cm) or more. The electrophotographic carrier according to any one of claims 1 to 4,
A carrier for electrophotography, wherein the particles are alumina and / or silica. The electrophotographic carrier according to any one of claims 1 to 5,
A carrier for electrophotography, wherein the content of particles is 40 to 95 wt% of the coating film composition component. The electrophotographic carrier according to any one of claims 1 to 6,
An electrophotographic carrier, wherein the thickness of the binder resin is 0.05 μm to 1.00 μm. The electrophotographic carrier according to any one of claims 1 to 7,
A carrier for electrophotography, wherein the binder resin contains at least a resin obtained by cross-linking an acrylic resin and an amino resin or / and a silicone resin. The electrophotographic carrier according to any one of claims 1 to 8,
An electrophotographic carrier, wherein the Tg of the resin is 20 to 100 ° C. An electrophotographic developer comprising: a toner comprising at least a binder resin and a pigment; and the electrophotographic carrier according to claim 1. The electrophotographic developer according to claim 10,
An electrophotographic developer, wherein the toner contains a release agent. An image forming method using the electrophotographic developer according to claim 10. A multicolor image forming method using the electrophotographic developer according to claim 10. 12. A storage container for storing the electrophotographic developer according to claim 10 or 11. An image forming apparatus comprising a storage container filled with the electrophotographic developer according to claim 14. In a process cartridge that is selected from a photoconductor, a charging unit, a developing unit, and a cleaning unit, that supports at least the developing unit integrally, and is detachable from the main body of the image forming apparatus.
12. The process cartridge according to claim 10, wherein the developing means holds the developer, and the developer is the developer according to claim 10.

Images