JP2007271864A - Carrier for electrophotographic development, method for manufacturing the same and two-component developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier for electrophotographic development capable of retaining good properties when used in various environments, and capable of sustaining high-quality image formation in long-term electrophotographic development. <P>SOLUTION: The surface of a carrier core material 1 is coated with a mixture of a hydrophilic resin 4 and a hydrophobic resin 2 into which conductive fine particles 3 have been incorporated up to saturation, whereby conductive fine particles contained in the hydrophilic resin 4 are deposited/accumulated at the interfaces between the hydrophilic resin 4 and the hydrophobic resin 2 to form conductive pathways 5. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a carrier for electrophotographic development used for a two-component developer, and in particular, a carrier for electrophotographic development in which a resin coating containing conductive fine powder is applied on the surface of a carrier core material such as ferrite. And a manufacturing method thereof, and a two-component developer.

  The two-component developer for electrophotographic development contains a toner and a carrier for electrophotographic development (hereinafter sometimes simply referred to as “carrier”). The electrophotographic development carrier is required to have various characteristics such as electrical characteristics, tribocharging, durability, and fluidity. In addition, it prevents the toner component from fusing (spenting) to the carrier surface due to collisions between the carriers due to stirring during electrophotographic development, friction between the developing unit and the carrier, and the like to prevent charging failure. For this reason, a resin coating may be applied to the surface of the carrier.

  In the so-called resin-coated carrier with the resin coating as described above, the coating resin on the surface of the carrier may be peeled off due to collision between carriers caused by stirring, friction between the developing unit and the carrier, or the like. When the peeling occurs, the toner component is fused to the carrier surface and charging failure occurs. Therefore, it is required not to cause the peeling, and the desired charging characteristics must be constantly obtained in various environments. Has been.

  Further, in the conventional two-component developer having the resin coating on the surface of the carrier in this way, the charge amount is reduced under high temperature and high humidity due to the change in environment at the time of printing, and toner scattering, image fogging, There is a problem such as pulling, and the charge amount increases at low temperatures and low humidity, resulting in a problem that the image density is insufficient. As a result, there is a problem that the life of the developer is shortened.

  Recently, in order to reduce power consumption, as a main binder resin for toner, a polyester resin having a relatively low melt viscosity among various resins, a negative chargeability, and an easily adjustable charge level by an acid value. Often used. However, when a polyester resin is used, there is a problem that the fluidity of the toner is deteriorated and the toner is easily absorbed in a high-temperature and high-humidity environment, and the charge amount is reduced.

  In order to solve such a problem, there is a method of adjusting the charge amount by combining various resins so that the charge amount is increased on the surface of the carrier coating layer. However, the surface coating layer adjusted to have a high charge amount in this way has an increased charge due to changes in the surface thickness of the carrier due to surface wear, peeling, etc., while being used for a long period of time. Therefore, there is a problem that the image density is lowered and the life of the developer is shortened.

  Here, as a carrier that can withstand high speed and high image quality without causing toner scattering and toner contamination, the resin coating layer on the surface of the carrier core material contains carbon black, and the contained carbon black is coated. Patent Document 1 proposes a carrier having a concentration gradient in the thickness direction of the layer.

  In addition, the surface of the carrier core material is coated with a resin in which graphite powder and carbon black powder having a specific particle size are dispersed in order to prevent the toner from becoming spent and to provide a high quality image for a long time. Another carrier is proposed in Patent Document 2.

JP-A-8-179570 Japanese Patent No. 2824778

  However, according to the study by the present inventors, the technique described in Patent Document 1 has a concentration gradient of carbon black in the thickness direction in the resin coating, so that the rising rate of the charge amount without changing the carrier resistance. Can be adjusted. However, when the resin coating layer is worn, the dielectric constant also changes due to the concentration gradient in the thickness direction of the carbon black, and as a result, the charge amount also changes.

  Further, in the technique described in Patent Document 2, when used in a developing tank having a large stirring stress, as the coating layer wears, the graphite powder having a relatively large particle size peels off from the coating layer. The toner tends to become spent, the stability of the charge amount is lowered, and it is difficult to maintain a high-quality image in electrophotographic development over a long period of time.

  The present invention has been made in the context of the above-mentioned situation. In use in various environments including low-temperature and low-humidity environments and high-temperature and high-humidity environments, the present invention can maintain good characteristics and can be used for long-term electrophotographic development. It is an object of the present invention to provide a carrier for electrophotographic development capable of maintaining high-quality image formation, a method for producing the same, and a two-component developer.

  Conventionally, the surface of the carrier core material is coated with a silane coupling agent as a coupling agent, and further coated with a coating resin such as a silicone resin or an epoxy resin, and conductive fine powder is formed in the coating resin. The amount of charge has been adjusted by adding it, but when conductive fine powder is dispersed in the coating resin layer, it is coated when the coating layer is worn unless it is an ideal uniform dispersion. Since the conductivity changes depending on the thickness of the layer, a stable effect cannot be obtained in the long-term printing durability and durability.

As a result of intensive studies conducted by the present inventors, the following (1) and (2) were adopted as means for solving the problem.
(1) Resin in which the dispersibility of the fine particles is set relatively low so that the fine particles are aggregated to some extent even when the conductive fine particles are in a non-uniform dispersion state, and a continuous conductive path is always formed from the core surface to the coating layer. Was used as a coating layer.
(2) In order to make it possible to adjust the conductivity of the entire coating layer, a state in which the conductive fine powder is uniformly dispersed is also present, and a coating layer in which two different dispersed states are present simultaneously is formed.

That is, the first means for solving the problem is that the surface of the carrier core material is coated with a mixture of a hydrophilic resin and a hydrophobic resin each containing conductive fine particles. Is a career.
The electrophotographic developing carrier having the above configuration maintained a constant conductivity and stable carrier resistance even when the coating layer was worn.

The second means is the electrophotographic developer carrier according to the first means, wherein at least the hydrophobic resin contains conductive fine particles until saturation.
A stable conductive path was formed in the carrier for electrophotographic development having this configuration.

  A third means is the electrophotographic developer carrier according to the first or second means, wherein the conductive fine particles are carbon black, and the average particle diameter is 80 nm or more and 1 μm or less. .

  Any one of the first to third means is characterized in that the hydrophobic resin has a surface tension of 30 mN / m or less and the hydrophilic resin has a surface tension of 36 mN / m or more. The carrier for electrophotographic development described in 1.

  A fifth means is a carrier for electrophotographic development according to any one of the first to fourth means, wherein the carrier core material contains soft ferrite.

  Sixth means is a two-component developer comprising a toner containing a polyester resin as a main component and the electrophotographic developing carrier according to any one of the first to fifth means. .

  The seventh means is to coat the interface between the hydrophilic resin and the hydrophobic resin by coating the surface of the carrier core material with a mixture of a hydrophilic resin and a hydrophobic resin each containing conductive fine particles until they become saturated. And a method for producing a carrier for electrophotographic development, wherein the conductive fine particles contained in the hydrophilic resin are deposited and accumulated.

  According to the present invention, a stable charge amount can be maintained in various environments including long-term electrophotographic development and low temperature and low humidity environments and high temperature and high humidity environments. In addition, even when used for a long period of time in various environments including long-term electrophotographic development and low-temperature and low-humidity environments and high-temperature and high-humidity environments, sharp images without image fog or toner scattering could be obtained.

The electrophotographic development carrier of the embodiment of the present invention is obtained by coating the surface of a carrier core material with a mixture of a hydrophilic resin and a hydrophobic resin each containing conductive fine particles. In addition, the conductive fine particles are contained until saturated.
In the present invention, the state in which the conductive fine particles are saturated in the resin means that when the amount of the conductive fine particles dispersed in the resin is increased, a larger amount cannot be dispersed. The state that begins to flow out.

  As the conductive fine particles, it is preferable to use carbon black having an average particle size of 80 nm or more and 1 μm or less. Further, it is preferable to use a hydrophobic resin having a surface tension of 30 mN / m or less, more preferably 26 mN / m or less, and a hydrophilic resin having a surface tension of 36 mN / m or more, more preferably It is good to use a thing of 42 mN / m or more. Further, it is preferable to use a carrier core material containing soft ferrite. In the case of constituting a two-component developer, a toner containing a polyester resin as a main component and the carrier of this embodiment are included.

  When the carrier of this embodiment is manufactured, the surface of the carrier core material is coated with a mixture of a hydrophilic resin and a hydrophobic resin each containing conductive fine particles until saturated. Thereby, conductive fine particles contained in the hydrophilic resin are deposited and accumulated in the hydrophilic resin layer at the interface portion between the hydrophilic resin and the hydrophobic resin to form a conductive path.

The formation of the conductive path will be described with reference to FIG.
FIG. 1 is a schematic cross-sectional view of a resin coat portion formed on the surface of a carrier core material, which is a carrier according to the present embodiment.
As shown in FIG. 1, the carrier according to this embodiment is such that the surface of the carrier core material 1 is covered with a coupling layer 6, and the conductive fine particles 3 are saturated on the coupling layer 6. A mixture of the hydrophilic resin 4 and the hydrophobic resin 2 contained is covered. The hydrophilic resin 4 and the hydrophobic resin 2 exist without being mixed with each other, the hydrophobic resin 2 takes a foam shape, and the hydrophilic resin 4 exists around the hydrophobic resin 2 having a foam shape. It is thought that.

  On the other hand, as described above, carbon powder is added as the conductive fine powder 3 to the hydrophilic resin 4 and the hydrophobic resin 2, respectively. The conductive fine powder 3 does not conform to the hydrophilic resin 4 and has a property to conform to the hydrophobic resin 2. For this reason, the conductive fine powder 2 added to the hydrophilic resin 4 is excluded from the center of the hydrophilic resin 4 and is accumulated near the boundary with the hydrophobic resin 2. However, since the conductive fine powder 3 already exists in the hydrophobic resin 2, it cannot freely penetrate into the hydrophobic resin 3, and accumulates near the boundary with the hydrophobic resin 2. Thus, it is considered that the conductive path 5 is formed. This effect becomes more prominent and preferable by keeping the abundance of the conductive fine powder 3 in the hydrophobic resin 2 in a saturated state, and further in a supersaturated state.

  Accordingly, the conductive path 5 always forms a continuous conductive path from the core surface into the coating layer in a mesh shape along the boundary between the hydrophilic resin 4 and the hydrophobic resin 2. By securing the mesh-like conductive path, it is considered that even if the coating layer is worn, the remaining coating layer maintains a certain conductivity and the carrier resistance is stable.

  Here, as specific examples of the conductive fine particles, for example, VULCAN XC72R, REGAL330R, MONARCH120 (manufactured by Cabot Corporation), # 2700, MA100, MA7, # 52 (manufactured by Mitsubishi Chemical Corporation) and the like can be used.

  Moreover, as an example of the silicone resin used as the hydrophobic resin, a straight silicon type can be preferably used, and a dimethyl type is more preferable. Specifically, for example, SR2410, SR2411, SH804, SH805, SH806A, SH8404 (made by Toray Dow Corning Silicone Co., Ltd.), X-40-2151, KR350 (made by Shin-Etsu Chemical Co., Ltd.), TSR116, TSR144, TSR102 , TSR127B (GE Toshiba Silicone) and the like can be suitably used.

  Moreover, as an example of the epoxy resin used as the hydrophobic resin, not only the so-called BPA type, for example, Adeka Resin EP4100 (manufactured by Asahi Denka), novolak type, but also a silicon-modified type (epoxy-modified silicone resin) can be preferably used. Specifically, for example, SR2115, SR2145 (manufactured by Toray Dow Corning Silicone Co., Ltd.), TSR194 (GE Toshiba Silicone) and the like can be suitably used.

  Moreover, as a melamine resin used as a hydrophilic resin, the thing of types, such as methylated melamine and butylated melamine, can be used preferably. For example, MW-30HM (manufactured by Sanwa Chemical), J-820-60 (manufactured by Dainippon Ink), Cymel 300 (Mitsui Cytec) and the like can be suitably used.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
Using Mn-Mg based ferrite fired in a nitrogen atmosphere with an average particle diameter of 50 μm as the core material, mixing aminosilane and glycidoxylsilane in a ratio of 1: 1 as a coupling treatment and dissolving for a certain period in an organic solvent The solvent was removed by heating and stirring so that the total weight ratio to the core material was 0.3%.
Thereafter, a solution containing 2 parts of carbon black with respect to 100 parts of silicone resin (solid content 20%) was prepared, and separately 5 parts of carbon black was added to 100 parts of melamine resin (solid content 50%) to prepare a solution. And 2 types of solutions were mixed in the ratio of 100 parts and 20 parts, and the solution for forming a coating layer was prepared.
Therefore, when converted into a 100% resin content obtained by repeating the solid content in the solution for forming the coating layer, 2000 parts of silicone resin, 1000 parts of melamine resin, and carbon black 200 in silicone resin (hydrophobic resin). Part, 100 parts of carbon black in melamine resin (hydrophilic resin). In this embodiment, the carbon black in the silicone resin (hydrophobic resin) is in a saturated state.
This was added to the ferrite particles after the coupling treatment using an immersion method so that the weight ratio of the coat layer to the particle surface was 3.0%, and the mixture was heated and stirred to remove the solvent.
The coated particles were cured at 250 ° C. to obtain a carrier.
This carrier and a toner mainly composed of commercially available polyester were mixed at a carrier: toner ratio of 94: 6 to produce an electrophotographic developer according to Example 1. When an image was output with an actual machine using the electrophotographic developer, a stable image was obtained without any change in resistance.

Example 2
Using Mn-Mg based ferrite fired in a nitrogen atmosphere with an average particle diameter of 50 μm as the core material, mixing aminosilane and glycidoxylsilane in a ratio of 1: 1 as a coupling treatment and dissolving for a certain period in an organic solvent The solvent was removed by heating and stirring so that the total weight ratio to the core material was 0.3%.
Thereafter, a solution containing 5 parts of carbon black per 100 parts of silicone resin (solid content 20%) was prepared, and 5 parts of carbon black was separately added to 100 parts of melamine resin (solid content 50%) to prepare a solution. And 2 types of solutions were mixed in 100 parts and 20 parts, and the solution for forming a coating layer was prepared.
Therefore, when converted into a 100% resin content obtained by repeating the solid content in the solution for forming the coating layer, 2000 parts of silicone resin, 1000 parts of melamine resin, and carbon black 500 in silicone resin (hydrophobic resin). Part, 100 parts of carbon black in melamine resin (hydrophilic resin). In this embodiment, carbon black in the silicone resin (hydrophobic resin) is in a supersaturated state.
This was added to the ferrite particles after the coupling treatment using an immersion method so that the weight ratio of the coat layer to the particle surface was 3.0%, and the mixture was heated and stirred to remove the solvent.
The coated particles were cured at 250 ° C. to obtain a carrier.
Using this carrier, the electrophotographic developer according to Example 2 was produced in the same manner as in Example 1, and an image was output with an actual machine. As a result, a stable image without change in resistance could be obtained.

Example 3
Using Mn-Mg based ferrite fired in a nitrogen atmosphere with an average particle diameter of 50 μm as the core material, mixing aminosilane and glycidoxylsilane in a ratio of 1: 1 as a coupling treatment and dissolving for a certain period in an organic solvent The solvent was removed by heating and stirring so that the total weight ratio to the core material was 0.3%.
Thereafter, a solution containing 2 parts of carbon black with respect to 100 parts of silicone resin (solid content 20%) was prepared, and separately 10 parts of carbon black was added to 100 parts of melamine resin (solid content 50%) to prepare a solution. Then, two kinds of solutions were mixed in 100 parts and 20 parts to prepare a solution for forming a coat layer.
Therefore, when converted into a 100% resin content obtained by repeating the solid content in the solution for forming the coating layer, 2000 parts of silicone resin, 1000 parts of melamine resin, and carbon black 200 in silicone resin (hydrophobic resin). Part, 200 parts of carbon black in melamine resin (hydrophilic resin). In this embodiment, the carbon black in the silicone resin (hydrophobic resin) is in a saturated state.
This was added to the ferrite particles after the coupling treatment using an immersion method so that the weight ratio of the coat layer to the particle surface was 3.0%, and the mixture was heated and stirred to remove the solvent.
The coated particles were cured at 250 ° C. to obtain a carrier.
Using this carrier, the electrophotographic developer according to Example 3 was produced in the same manner as in Example 1, and an image was output with an actual machine. As a result, a stable image without change in resistance could be obtained.

Example 4
Using Mn-Mg based ferrite fired in a nitrogen atmosphere with an average particle size of 50 μm as the core material, mixing aminosilane and glycidoxylsilane in a ratio of 1: 1 as a coupling treatment, and stirring for a certain period of time was dissolved in an organic solvent. The solvent was removed by heating and stirring so that the total weight ratio to the core material was 0.3%.
Thereafter, a solution containing 2 parts of carbon black with respect to 50 parts of a silicone resin (solid content 20%) and 50 parts of an epoxy resin (solid content 20%) was prepared, and carbon was separately added to 100 parts of a melamine resin (solid content 50%). A solution was prepared by adding 5 parts of black. Then, two kinds of solutions were mixed in 100 parts and 20 parts to prepare a solution for forming a coat layer.
Therefore, when converted into 100% resin content obtained by repeating the solid content in the solution for forming the coating layer, 1000 parts of silicone resin, 1000 parts of epoxy resin, 1000 parts of melamine resin, silicone resin and epoxy resin (hydrophobic 200 parts of carbon black in the hydrophilic resin) and 100 parts of carbon black in the melamine resin (hydrophilic resin). In this embodiment, the carbon black in the silicone resin and epoxy resin (hydrophobic resin) is in a saturated state.
This was added to the ferrite particles after the coupling treatment using an immersion method so that the weight ratio of the coat layer to the particle surface was 3.0%, and the mixture was heated and stirred to remove the solvent.
The coated particles were cured at 250 ° C. to obtain a carrier.
Using this carrier, the electrophotographic developer according to Example 4 was produced in the same manner as in Example 1, and an image was output with an actual machine. As a result, a stable image without change in resistance could be obtained.

Example 5
Using Mn-Mg based ferrite fired in a nitrogen atmosphere with an average particle diameter of 50 μm as the core material, mixing aminosilane and glycidoxylsilane in a ratio of 1: 1 as a coupling treatment and dissolving for a certain period in an organic solvent The solvent was removed by heating and stirring so that the total weight ratio to the core material was 0.3%.
Thereafter, a solution containing 2 parts of carbon black with respect to 100 parts of epoxy resin (solid content 20%) was prepared, and 5 parts of carbon black was separately added to 100 parts of melamine resin (solid content 50%) to prepare a solution. Then, two kinds of solutions were mixed in 100 parts and 20 parts to prepare a solution for forming a coat layer.
Therefore, when converted into a 100% resin content obtained by repeating the solid content in the solution for forming the coating layer, 2000 parts of epoxy resin, 1000 parts of melamine resin, and carbon black 200 in epoxy resin (hydrophobic resin). Part, 100 parts of carbon black in melamine resin (hydrophilic resin). In this embodiment, the carbon black in the epoxy resin (hydrophobic resin) is in a saturated state.
This was added to the ferrite particles after the coupling treatment using an immersion method so that the weight ratio of the coat layer to the particle surface was 3.0%, and the mixture was heated and stirred to remove the solvent.
The coated particles were cured at 250 ° C. to obtain a carrier.
Using this carrier, an electrophotographic developer according to Example 5 was produced in the same manner as in Example 1, and an image was output using an actual machine. The change in charge amount was slightly large, but there was no change in resistance, and the image was stable. I was able to get an image.

<< Comparative Example 1 >>
Using Mn-Mg based ferrite fired in a nitrogen atmosphere with an average particle diameter of 50 μm as the core material, mixing aminosilane and glycidoxylsilane in a ratio of 1: 1 as a coupling treatment and dissolving for a certain period in an organic solvent The solvent was removed by heating and stirring so that the total weight ratio to the core material was 0.3%.
Thereafter, a solution containing 1 part of carbon black with respect to 100 parts of silicone resin (solid content 20%) was prepared, and 2 parts of carbon black was added to 100 parts of epoxy resin (solid content 20%) to prepare a solution. Then, two solutions were mixed in 100 parts and 50 parts to prepare a solution for forming a coat layer.
Therefore, in the solution for forming the coating layer, when converted into a resin content of 100% obtained by repeating the solid content, in 2000 parts of silicone resin, 1000 parts of epoxy resin, silicone resin and epoxy resin (hydrophobic resin) It becomes 200 parts of carbon black.
This was added to the ferrite particles after the coupling treatment using an immersion method so that the weight ratio of the coat layer to the particle surface was 3.0%, and the mixture was heated and stirred to remove the solvent.
The coated particles were cured at 250 ° C. to obtain a carrier.
Using this carrier, the electrophotographic developer according to Comparative Example 1 was produced in the same manner as in Example 1, and an image was output with an actual machine. As a result, the resistance in life decreased and an image with much fog was obtained.

<< Comparative Example 2 >>
Using Mn-Mg based ferrite fired in a nitrogen atmosphere with an average particle diameter of 50 μm as the core material, mixing aminosilane and glycidoxylsilane in a ratio of 1: 1 as a coupling treatment and dissolving for a certain period in an organic solvent The solvent was removed by heating and stirring so that the total weight ratio to the core material was 0.3%.
Thereafter, a solution containing 2 parts of carbon black with respect to 100 parts of silicone resin (solid content 20%) was prepared.
Therefore, in the solution for forming the coating layer, when converted to 100% resin content obtained by breaking the solid content, 2000 parts of silicone resin and 200 parts of carbon black in the silicone resin (hydrophobic resin) are obtained. In this comparative example, the carbon black in the silicone resin (hydrophobic resin) is in a saturated state.
This was added to the ferrite particles after the coupling treatment using an immersion method so that the weight ratio of the coat layer to the particle surface was 2.0%, and the mixture was heated and stirred to remove the solvent.
The coated particles were cured at 250 ° C. to obtain a carrier.
Using this carrier, the electrophotographic developer according to Comparative Example 2 was produced in the same manner as in Example 1, and an image was output with an actual machine. As a result, the life resistance was reduced and an image with much fog was obtained.

<< Comparative Example 3 >>
Using Mn-Mg based ferrite fired in a nitrogen atmosphere with an average particle size of 50 μm as the core material, mixing aminosilane and glycidoxylsilane in a ratio of 1: 1 as a coupling treatment, and stirring for a certain period of time was dissolved in an organic solvent. The solvent was removed by heating and stirring so that the total weight ratio to the core material was 0.3%.
Thereafter, a solution containing 2 parts of carbon black with respect to 100 parts of a silicone resin (solid content 20%) is prepared, and the ratio is 100 parts and 20 parts of melamine resin (solid content 50%) to form a coat layer. A solution was prepared.
Therefore, when converted into a 100% resin content obtained by repeating the solid content in the solution for forming the coating layer, 2000 parts of silicone resin, 1000 parts of melamine resin, and carbon black 200 in silicone resin (hydrophobic resin). Part. In this comparative example, the carbon black in the silicone resin (hydrophobic resin) is in a saturated state.
This was added to the ferrite particles after the coupling treatment using an immersion method so that the weight ratio of the coat layer to the particle surface was 3.0%, and the mixture was heated and stirred to remove the solvent.
The coated particles were cured at 250 ° C. to obtain a carrier.
Using this carrier, an electrophotographic developer according to Comparative Example 3 was produced in the same manner as in Example 1 and an image was output with an actual machine. As a result, an image having an excessively high charge amount and insufficient image density was obtained.

<< Comparative Example 4 >>
Using Mn-Mg based ferrite fired in a nitrogen atmosphere with an average particle diameter of 50 μm as the core material, mixing aminosilane and glycidoxylsilane in a ratio of 1: 1 as a coupling treatment and dissolving for a certain period in an organic solvent The solvent was removed by heating and stirring so that the total weight ratio to the core material was 0.3%.
Then, a solution mixed with 50 parts of a silicone resin (solid content 20%) and 50 parts of an epoxy resin (solid content 20%) is prepared and mixed at a ratio of 20 parts and 100 parts of another melamine resin (solid content 50%). Then, a solution for forming a coating layer was prepared.
Therefore, in the solution for forming the coating layer, when converted into a resin content of 100% obtained by repeating the solid content, 1000 parts of silicone resin, 1000 parts of epoxy resin, and 1000 parts of melamine resin are obtained.
This was added to the ferrite particles after the coupling treatment using an immersion method so that the weight ratio of the coat layer to the particle surface was 3.0%, and the mixture was heated and stirred to remove the solvent.
The coated particles were cured at 250 ° C. to obtain a carrier.
Using this carrier, the electrophotographic developer according to Comparative Example 4 was produced in the same manner as in Example 1, and an image was output with an actual machine. As a result, the image was insufficient in image density with a large increase in charge amount.

Table 1 shows the characteristics and compositions of the samples according to Examples and Comparative Examples as a list.
As the characteristic value of the sample, the static resistance value, the surface tension of the hydrophobic resin, and the surface tension of the hydrophilic resin were measured. Furthermore, using an electrophotographic developer, 10000 (10K) sheets of electrophotographic development is performed with an actual machine, the initial development time is set to 10K, and the first 10000 (10K) development time is set to 10K. It was measured.

Table 2 shows the actual machine evaluation results of the samples according to the example and the comparative example as a list.
In the actual machine evaluation, an electrophotographic developer was produced using the samples according to Examples and Comparative Examples, and 10,000 (10K) electrophotographic developments were performed using the electrophotographic developer using the actual machine.
The evaluation items were the items of image density, image fog, charge amount environment fluctuation, toner scattering, and carrier adhesion. In the actual machine evaluation, the actual machine was installed in a high-temperature and high-humidity environment or a low-temperature and low-humidity environment, and electrophotographic development was performed.
In the evaluation item, the development result of the first sheet is initial, the development result of the 10,000th (10K) sheet is 10K, ◎ if the level is very good, ◯ if the level is good, and if the level is usable. △, in the case of the level which cannot be used, it evaluated as x.

It is a stylized sectional view of a resin coat portion of a carrier according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carrier core material 2 Hydrophobic resin 3 Conductive fine powder 4 Hydrophilic resin 5 Conductive path 6 Coupling layer

Claims (7)

  A carrier for electrophotographic development, wherein the surface of the carrier core material is coated with a mixture of a hydrophilic resin and a hydrophobic resin each containing conductive fine particles.   The carrier for electrophotographic development according to claim 1, wherein the conductive fine particles are contained in at least the hydrophobic resin until the conductive fine particles are saturated.   The carrier for electrophotographic development according to claim 1 or 2, wherein the conductive fine particles are carbon black, and an average particle diameter thereof is 80 nm or more and 1 µm or less.   4. The electrophotographic developer carrier according to claim 1, wherein the hydrophobic resin has a surface tension of 30 mN / m or less and the hydrophilic resin has a surface tension of 36 mN / m or more. .   The carrier for electrophotographic development according to any one of claims 1 to 4, wherein the carrier core material contains soft ferrite.   A two-component developer comprising: a toner containing a polyester resin as a main component; and the electrophotographic developing carrier according to claim 1.   By coating the surface of the carrier core material with a mixture of a hydrophilic resin and a hydrophobic resin each containing conductive fine particles until saturation, the hydrophilic resin and the hydrophobic resin are bonded to the hydrophilic resin. A method for producing an electrophotographic developing carrier, comprising depositing and accumulating conductive fine particles contained therein.

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