JP2007033631A - Carrier and two-component developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier and a two-component developer having excellent durability and environmental stability. <P>SOLUTION: The carrier has a core material coated with a coating resin, wherein the coating resin is applied on the core material in an amount of 5-20 wt.% based on the weight of the core material so as to improve the durability. Further, the coating resin contains titanium oxide fine powder in order to improve environmental stability. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a two-component developer comprising a toner and a carrier and the carrier.

  As an image forming method using a developer, an electrophotographic method using a Carlson process is widely used. An image forming apparatus using an electrophotographic system forms an image by a charging process, an exposure process, a development process, a transfer process, a cleaning process, a fixing process, and the like. In the charging step, the surface of the photoreceptor is uniformly charged in a dark place. In the exposure step, the original image is projected onto the charged photoconductor, so that the charged portion is removed and an electrostatic latent image is formed on the surface of the photoconductor. In the developing step, a visible toner image is formed by attaching a developer toner to the electrostatic latent image formed on the surface of the photoreceptor. In the transfer process, a recording medium such as paper or sheet is brought into contact with the visible image formed on the surface of the photoreceptor, and corona discharge is performed from the side opposite to the surface of the recording medium that is in contact with the visible image. Transfers a visible image to a recording medium by applying a charge of opposite polarity to the recording medium. In the fixing step, the visible image transferred to the recording medium is fixed by means such as heating and pressing. In the cleaning process, the toner remaining on the surface of the photoreceptor without being transferred to the recording medium is collected. By repeating the above steps, an image forming apparatus using an electrophotographic process forms a desired image on a recording medium.

  Conventionally, it is known that a developer used in an image forming apparatus using an electrophotographic system includes a toner manufactured by a pulverization method, a polymerization method, or the like. The pulverization method is to melt and knead a thermoplastic resin, a colorant, a charge control agent and a wax as an anti-offset agent, then cool and solidify to prepare a melt-kneaded product, and pulverize and classify the melt-kneaded product. This is a method for preparing a toner. The polymerization method is a method for preparing toner by suspension polymerization method or emulsion polymerization method.

  Currently, image forming apparatuses such as copying machines and printers have been increased in speed and size, and in order to obtain high-quality images for a long period of time, development of a developer having excellent durability and environmental stability is required. It has been.

  If the developer is a two-component developer consisting of a toner and a carrier, in order to develop a developer having excellent durability and environmental stability, in order to stably charge the developer in the image forming apparatus The development of a carrier, such as optimization of the type of core material, the type of coat resin, and the amount of coat resin, is important along with the development of toner.

  A typical conventional technique for carrier development is described in US Pat. The color developer of Patent Document 1 is a developer composed of a toner and a carrier, and the carrier is 0.1 to 5.0% by weight of a predetermined resin (coat resin) with respect to the weight of the carrier core material (core material). It is a color developer that is coated.

  Another conventional technique is described in Patent Document 2. The two-component developer for electrophotography of Patent Document 2 is composed of a carrier having a coating amount of 5.0% by weight or more with respect to the core material, and a toner to which an external additive is added. A two-component developer for electrophotography.

JP-A-4-177369 JP 2004-144777 A

  The developer needs to have appropriate fluidity and chargeability so that the developer toner can smoothly adhere to the electrostatic latent image formed on the surface of the photoreceptor. The flowability and chargeability of the developer vary depending on the carrier composition.

  According to the color developer disclosed in Patent Document 1, the carrier core material is coated with a carrier that is coated with a predetermined resin in an amount of 0.1 to 5.0% by weight with respect to the weight of the carrier core material. By using it, contamination such as toner forming a thin film on the surface of the carrier can be prevented, and the developer is excellent in durability and environmental stability. However, in recent years, image forming apparatuses have been speeded up and miniaturized, and when an image is formed using such an image forming apparatus, the stress applied to the developer is larger than the previous image forming apparatus. If the toner is used as it is for a long time, the resin peels off from the carrier core and the carrier core is exposed on the surface. In other words, in the case of forming an image using a high-speed and downsized image forming apparatus, the developer is insufficient in durability that cannot maintain the initial carrier characteristics, and the obtained image has an image density. It may cause a decline.

  Further, as disclosed in Patent Document 2, the inventors of the present application have sufficient carrier characteristics that the carrier is difficult to be exposed on the surface even when used in an image forming apparatus that is further increased in speed and size. In order to obtain a developer with higher durability that can be maintained at a high level, it has been proposed to use a carrier coated with a coating resin so that the carrier coating amount is 5.0% by weight or more based on the core material. . At that time, if a large amount of the coating resin is coated on the carrier, depending on the type of the coating resin, the carrier characteristics such as environmental characteristics cannot be secured, and the toner concentration in the developer under high temperature and high humidity during image formation. The problem is that the developer may be inferior in environmental stability, causing toner scattering, white background fogging, etc., and using toner added with external additives, and further defining the toner concentration It was found that a developer having excellent durability and environmental stability can be obtained.

  Furthermore, the inventors of the present application have found that it is very effective to contain a fine powder of titanium oxide in the coating resin covering the carrier in order to obtain a developer having excellent durability and environmental stability. .

  An object of the present invention is to provide a carrier and a two-component developer that are more excellent in durability and environmental stability.

The present invention is a carrier constituting a two-component developer,
The core material is coated with a coating resin,
The coating resin is 5% by weight or more and 20% by weight or less based on the weight of the core material,
A carrier comprising barium titanate fine powder in a coating resin.

  The present invention is also characterized in that the content of the barium titanate fine powder in the coating resin is 3 wt% or more and 50 wt% or less.

Further, the present invention is a two-component developer comprising a toner and a carrier,
A two-component developer, wherein the carrier is the carrier described above.

  According to the present invention, the carrier has a core material coated with a coating resin. The coating resin is 5% by weight or more and 20% by weight or less based on the weight of the core material, and the coating resin contains barium titanate fine powder.

  In order to achieve environmental stability, it is necessary to set the toner charge amount as high as possible. However, when the toner charge amount is increased, the required image density cannot be obtained, and it is difficult to achieve compatibility with the conventional carrier design.

  Therefore, by adding barium titanate fine powder, which is a ferroelectric substance, to the coating resin, the dielectric constant of the developer is increased, the electric field strength between the developing sleeve and the photosensitive member is increased, and high developability is achieved even at high charge amount. Can be secured.

  By coating the coating resin so that it is 5% by weight or more based on the weight of the core material, it becomes a carrier having excellent durability, and further, by containing barium titanate fine powder in the coating resin, environmental stability is achieved. It becomes a carrier with excellent properties.

  Further, according to the present invention, by containing the barium titanate fine powder in the coat resin so as to be 3% by weight or more and 50% by weight or less, the carrier is more excellent in environmental stability.

  Further, according to the present invention, the two-component developer includes a toner and a carrier, and the carrier is a two-component developer using the carrier. Since the carrier is excellent in durability and environmental stability, it is a two-component developer excellent in durability and environmental stability.

  The present invention is a carrier obtained by coating a core material with a coating resin containing barium titanate fine powder and a two-component developer containing the carrier.

[Career]
The carrier according to the present invention is constituted by coating a core resin with a coating resin. The carrier has factors such as powder characteristics, electrical characteristics, and magnetic characteristics, and requires performance that matches the development system. In recent years, a carrier in which a core material is coated with a coating resin has been widely used in order to improve frictional charging, environmental stability, and durability.

(Coat resin)
The carrier includes a coating resin containing fine barium titanate powder. As the coating resin, a known resin can be used, and examples thereof include a polyester resin, a fluorine resin, an acrylic resin, and a silicone resin. The coating resin is coated on the core material by a method such as spraying or dipping. The coating resin is preferably 5% by weight or more and 20% by weight or less, and more preferably 5% by weight or more and 10% by weight or less, based on the weight of the core material. When the amount is less than 5% by weight, the coating resin is easily peeled off and becomes a carrier having poor durability, and when the amount is more than 20% by weight, the carrier has poor environmental stability. Carbon black may be added to the coating resin. By doing so, an increase in charge amount can be suppressed and a stable image density can be maintained.

(Barium titanate fine powder)
The coating resin contains barium titanate fine powder. By containing the fine powder of barium titanate in the coating resin, it becomes a carrier having excellent environmental stability. Barium titanate fine powder is tetragonal at room temperature. It also has ferroelectricity because it has a dipole moment that can be reversed by an external electric field. Therefore, it is known that barium titanate is used alone as a barium titanate ceramic as a capacitor material, a pyroelectric body, or a piezoelectric body by utilizing its dielectric property.

  The fine powder of barium titanate is preferably obtained by hydrophobizing the surface of the fine powder. Examples of the hydrophobizing treatment include treatment with a silane coupling agent such as dimethyldichlorosilane and amylosilane, treatment with silicone oil, treatment with a fluorine-containing component, and the like.

  Inclusion of fine titanium oxide powder in the coating resin is also an effective means for obtaining a carrier with excellent environmental stability. However, when fine barium titanate powder is added, environmental stability is improved. The effect is greater, and the same effect can be achieved with a small amount of addition. Specifically, only 3% by weight of barium titanate fine powder is added to the coating resin, and a sufficient effect on environmental stability is exhibited. However, when 50 wt% or more of barium titanate fine powder was added to the coating resin, the image density was lowered, causing problems other than environmental stability. As a result, the barium titanate fine powder content in the carrier coat resin is preferably 3% by weight to 50% by weight, and more preferably 3% by weight to 40% by weight. The average particle diameter of the barium titanate fine powder is preferably 10 nm or more and 1.0 μm or less.

(Core material)
The carrier is configured to include a core material. A well-known thing can be used for a core material, and iron powder, a ferrite, etc. can be mentioned. The shape can be from irregular to spherical. Furthermore, an average particle diameter of 10 μm or more and 1000 μm or less can be used, and more preferably 40 μm or more and 100 μm or less. If it is less than 40 μm, a phenomenon that the carrier adheres to the photoreceptor and flows out, that is, a so-called carrier rise is caused, and the toner amount in the developer cannot be controlled well by gradually decreasing the developer amount. The possibility increases. Further, when the carrier rise becomes remarkable, the developer appears on the recording material. On the other hand, if it is larger than 100 μm, when the toner of the developer is moved from the developing roller to the photoreceptor, the two-component developer has a rough edge (magnetic brush), which makes it difficult to supply a stable image quality. This may cause a phenomenon that the component developer spills from the developing tank.

  Moreover, a well-known thing can be used for iron powder, and reduced iron powder, atomized iron powder, iron nitride powder, etc. can be mentioned. Since the reduced iron powder and the iron nitride powder are indefinite, they may be spheroidized. A well-known thing can be used for a ferrite carrier, and ferrite powders, such as copper, nickel, zinc, cobalt, manganese, and calcium, can be mentioned. Since the ferrite carrier is spherical, has good fluidity and is chemically stable, it is preferably used for high image quality and long life.

[toner]
The toner constituting the two-component developer according to the present invention is constituted by adding an external additive to toner base particles containing a binder resin, a colorant, a release agent, a charge control agent and the like.

(Binder resin)
The toner base particles include a binder resin. As the binder resin, known resins can be used. For example, polystyrene, styrene-acrylic copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, styrene-acrylic-maleic anhydride copolymer. Examples thereof include polymers, polyvinyl chloride, polyolefin resins, epoxy resins, silicone resins, polyamide resins, polyurethane resins, urethane-modified polyester resins, and acrylic resins. Said resin may be used independently and may be used with a several mixture. The copolymer may be a block copolymer or a graft copolymer. The molecular weight distribution may be one peak or two peaks.

  Moreover, as a thermal property, it is preferable that a glass transition point (Tg) is 40 degreeC or more and 70 degrees C or less. When the temperature is lower than 40 ° C., when the temperature in the image forming apparatus rises, the toner melts and aggregation between the toners occurs. On the other hand, when the temperature is higher than 70 ° C., the fixing property is inferior and the practicality is poor.

(Coloring agent)
The toner base particles include a colorant. As the colorant, known ones can be used, and examples thereof include carbon black, iron black, alloy azo dyes, oil-soluble dyes and pigments. The colorant is preferably 1 to 10 parts by weight, more preferably 3 to 8 parts by weight, based on 100 parts by weight of the binder resin. If the amount is less than 1 part by weight, a sufficient image density cannot be secured. If the amount is more than 10 parts by weight, the colorant cannot be uniformly dispersed in the resin, so that a high-quality image cannot be obtained.

(Release agent)
The toner base particles include a wax as a release agent. As the wax, known ones can be used, and examples thereof include at least one wax selected from polyethylene, polypropylene, ethylene-propylene copolymer, polyolefin and the like. The wax is preferably 1 to 10 parts by weight, more preferably 2 to 5 parts by weight, based on 100 parts by weight of the binder resin. If the amount is less than 1 part by weight, offset tends to occur. When the amount is more than 10 parts by weight, filming tends to occur.

(Charge control agent)
The toner base particles include a charge control agent. There are two types of charge control agents: positive charge control charge control agents and negative charge control charge control agents, and examples include azo dyes, carboxylic acid metal complexes, quaternary ammonium compounds, and nigrosine dyes. . The charge control agent is preferably 0.1 to 5 parts by weight, more preferably 0.5 to 2 parts by weight, based on 100 parts by weight of the resin. When the amount is less than 0.1 part by weight, sufficient charging property cannot be imparted. When the amount is more than 5 parts by weight, the charge control agent cannot be mixed uniformly in the resin.

(External additive)
The toner is constituted by adding an external additive to toner base particles. As the external additive, known ones can be used, and examples thereof include fine powders of metal oxide fine particles such as silica, titanium, alumina, magnetite and ferrite, and metal nitride fine particles such as silicon nitride and boron nitride. it can. Furthermore, the surface of the fine powder is preferably hydrophobized. Examples of the hydrophobizing treatment include treatment with a silane coupling agent such as dimethyldichlorosilane and amylosilane, treatment with silicone oil, treatment with a fluorine-containing component, and the like. One kind of the above external additives may be used, or two or more kinds may be used. Moreover, as an external additive, a silica is more preferable. Even if only fine particles other than silica are externally added, charging may not be sufficient in the contact between the toner and the carrier. Further, since silica acts as a fluidizing agent for the toner, the amount of toner supply can be stabilized. It can be made.

(Production method)
A binder resin, a colorant, a release agent, a charge control agent, and the like are sufficiently mixed by a mixer such as a Henschel mixer or a supermixer, and the obtained mixture is melt-kneaded by a twin-screw kneader. The kneaded product is pulverized by a jet pulverizer and then classified to obtain toner base particles having a volume average particle diameter of about 5 μm to 15 μm. Further, the toner is manufactured by adding inorganic fine particles to the toner base particles and adhering and uniformly dispersing them with a mixer such as a Henschel mixer or a super mixer.

[Two-component developer]
The two-component developer according to the present invention can be produced by mixing the toner and the carrier as described above with a mixer so as to have a prescribed toner concentration. As a mixer, a well-known thing can be used and a Nauta mixer (The Hosokawa Micron Corporation make: VL-0) can be mentioned.

  The present invention will be specifically described below with reference to examples and comparative examples, but is not limited to the examples.

[Example A]
In Example A, the influence of the carrier coat amount of the carrier constituting the two-component developer (weight% of the coat resin with respect to the weight of the core material) was examined.

(Example of toner production)
For 100 parts by weight of the polyester resin, 1.0 part of polyethylene (manufactured by Clariant Japan: PE130) and 1.5 parts of polypropylene (manufactured by Mitsui Chemicals: NP-505) as a wax, carbon black (manufactured by Cabot Corporation: 330R) 5 parts, charge control agent (Hodogaya Chemical Co., Ltd .: S-34) 1 part, magnetite (Kanto Denka Co., Ltd .: KBC-100) 1.5 parts, super mixer (Kawada Co., Ltd .: V-20) ), And the resulting mixture was melt-kneaded by a biaxial kneader (Ikegai Iron Works Co., Ltd .: PCM-30). The kneaded product was pulverized with a jet type pulverizer (manufactured by Nippon Pneumatic Industrial Co., Ltd .: IDS-2) and classified to obtain toner base particles having a volume average particle size of 7.5 μm. Toner was obtained by externally adding 0.3 part of silica fine particles (manufactured by Nippon Aerosil Co., Ltd .: R972) to the toner base particles.

(Example of carrier production)
Silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd .: KR-255) is used as a coating resin, 20% by weight of barium titanate fine powder (manufactured by Fuji Titanium Industry Co., Ltd.) having a particle size of 100 nm, carbon black (manufactured by Lion Corporation: Ketjen Black) EC) was added to 5.0 wt% and they were dispersed in toluene. A carrier obtained by applying a dispersion obtained by using a fluidized bed coating apparatus to a ferrite core material having a particle size of 90 μm, heating at 250 ° C. for 2 hours, and curing the applied coating resin. .

Example 1
A toner obtained by the above manufacturing method and a ferrite carrier coated with a coating resin so that the carrier coating amount is 8.0% as shown in Table 1, and a Nauta mixer so that the toner concentration is 5%. A two-component developer was produced by stirring for 20 minutes (manufactured by Hosokawa Micron Corporation: VL-0).

(Example 2)
A two-component developer was produced in the same manner as in Example 1 except that the carrier coat amount of the carrier was 5.0%.

(Comparative Example 1)
A two-component developer was produced in the same manner as in Example 1 except that the carrier coat amount of the carrier was 4.1%.

(Comparative Example 2)
A two-component developer was produced in the same manner as in Example 1 except that the carrier coat amount of the carrier was 2.2%.

[Evaluation methods]
Using the two-component developer obtained by the above production method, an original with a printing rate of 5% was printed by a monochrome copying machine (manufactured by Sharp Corporation: AR-450).

  For Examples 1 and 2 and Comparative Examples 1 and 2, image density change evaluation was performed as follows. The physical properties of the two-component developer produced by the above method are evaluated by the following evaluation methods, and the results are shown in Table 1. Note that symbols such as “◯” and “x” described in the description of the evaluation items are symbols indicating the evaluation results used in Table 1. “◯” indicates superiority, and “X” indicates that practical use is difficult.

(Image density)
The image density of an image printed using the developer in the initial state (initial image density) and the image density of an image printed after printing 100,000 sheets of 5% originals intermittently (image density after printing 100,000 sheets) ) Was measured with a Macbeth reflection densitometer (manufactured by Macbeth: RD-914). The image density after printing 100,000 sheets was evaluated based on the following criteria.
○: Image density is 1.30 or more and less than 1.32.
X: The image density is less than 1.30.

Table 1 shows the relationship between the carrier coat amount and the image density with respect to the core material.
Using the toner obtained by the above production method and a developer composed of a carrier having a different carrier coat amount, printing is performed using a commercially available monochrome copying machine (manufactured by Sharp Corporation: AR-450). The image density after printing 100,000 sheets of 5% originals intermittently was compared.

  As can be seen from Table 1, the developer (Examples 1 and 2) in which the coating resin used a carrier of 5% by weight or more based on the weight of the core material had an image density even after printing 100,000 sheets. It was a developer with excellent durability that could be maintained. However, the developer (Comparative Examples 1 and 2) using a carrier whose coating material is less than 5% by weight with respect to the weight of the core material has greatly reduced the image density after printing 100,000 sheets.

[Example B]
In Example B, the influence of the addition amount of the barium titanate fine powder in the coating resin coated on the carrier was examined.

(Example 3)
In Examples 1 and 2 and Comparative Examples 1 and 2 described above, except for changing the pulverization conditions such as the pressure of air when the kneaded material is pulverized by a jet pulverizer (manufactured by Nippon Pneumatic Industry Co., Ltd .: IDS-2). The toner was manufactured in the same manner as the toner used. Toner base particles having a volume average particle diameter of 8.5 μm were obtained, and a toner was obtained by externally adding 0.3 part of silica fine particles (manufactured by Nippon Aerosil Co., Ltd .: R972).

  Silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd .: KR-255) is used as the coating resin, 30% by weight of barium titanate fine powder (manufactured by Fuji Titanium Industry Co., Ltd.) having a particle size of 100 nm and carbon black (manufactured by Lion Corporation: Ketjen Black) EC) was added to 5.0 wt% and they were dispersed in toluene. The dispersion obtained by using a fluidized bed coating apparatus is applied to a ferrite core material having a particle size of 90 μm so that the carrier coat amount is 6.0%, and heated at 250 ° C. for 2 hours to be applied. A carrier was obtained by curing the coated resin.

  The obtained toner and carrier were stirred for 20 minutes in a Nauta mixer (manufactured by Hosokawa Micron Corporation: VL-0) so that the toner concentration was 5%, thereby producing a two-component developer.

Example 4
A two-component developer was produced in the same manner as in Example 3 except that the barium titanate fine powder in the coating resin was added so as to be 2% by weight so as to be 30% by weight.

(Example 5)
A two-component developer was produced in the same manner as in Example 3 except that the barium titanate fine powder in the coating resin was added so as to be 3% by weight so as to be 30% by weight.

(Example 6)
A two-component developer was produced in the same manner as in Example 3 except that the barium titanate fine powder in the coating resin was added so as to be 30% by weight and 50% by weight.

(Example 7)
A two-component developer was produced in the same manner as in Example 3 except that the barium titanate fine powder in the coating resin was added so as to be 30% by weight and 55% by weight.

(Comparative Example 3)
A two-component developer was produced in the same manner as in Example 3 except that the barium titanate fine powder was not added to the coating resin.

[Evaluation methods]
Regarding Examples 3 to 7 and Comparative Example 3 in Table 2, the following environmental stability evaluation and image density evaluation were performed. The physical properties of the two-component developer produced by the above method are evaluated by the following evaluation methods, and the results are shown in Table 2. Note that symbols such as “◎”, “◯”, “Δ”, and “x” described in the description of the evaluation items are symbols indicating evaluation results used in Table 2. “◎” indicates very good, “○” indicates excellent, “△” indicates that it is practical, and “×” indicates that practical use is difficult. Indicates. However, in the comprehensive evaluation, “◯” indicates that practical use is possible, and “×” indicates that practical use is difficult.

(Environmental stability)
After setting the two-component developer, the toner replenishment time after being left for 17 hours under high temperature and high humidity (35 ° C., 85%) is measured, and the white background fog of the printed image after being left for 17 hours is measured with a Hunter whiteness meter ( Nippon Denshoku Industries Co., Ltd.) and the measurement results were evaluated based on the following criteria.
A: The value of white background fog is less than 0.5.
◯: The value of white background fog is 0.5 or more and less than 1.0.
X: The value of white background fog is 1.0 or more.

  The toner replenishment time is the time from the time when the two-component developer starts to be stirred until the time when the toner of the two-component developer is attached to the photoreceptor, the so-called toner supply time. This is because the fluidity and chargeability are changed by leaving the developer for a long time under high temperature and high humidity.

(Image density)
The initial image density was measured by the same method as the above image density change evaluation, and the measured image density was evaluated based on the following criteria.
A: Image density is 1.35 or more.
○: Image density is 1.30 or more and less than 1.35.
X: The image density is less than 1.30.

  As can be seen from Table 2, when fine powder of barium titanate was contained in the coating resin (Examples 3 to 7), it was a two-component developer excellent in environmental stability and image density. Furthermore, when the content of the barium titanate fine powder is 3 to 50% by weight (Examples 3, 5 and 6) which is a preferred range (Examples 3, 5 and 6), it is a two-component developer with better environmental stability. there were.

  Further, if the coating resin does not contain fine barium titanate powder (Comparative Example 3), the carrier coating amount is 5% by weight or more, so that it is a two-component developer having an excellent image density. Since the resin does not contain barium titanate fine powder, it was a two-component developer with poor environmental stability.

  As a result, when the barium titanate fine powder was added, the environmental characteristics were greatly improved. However, when the addition amount of the barium titanate fine powder is less than 3% by weight, the effect is small. On the contrary, when the addition amount exceeds 50% by weight, the image density is lowered and other adverse effects occur. .

[Example C]
In Example C, the influence of the type of fine powder contained in the coating resin was examined. The case where 2% by weight of barium titanate fine powder was contained in the coating resin and the case of containing 3% by weight of titanium oxide fine powder in the coating resin were examined.

(Comparative Example 4)
Example 4 except that the fine powder of barium titanate is added to the coating resin so as to be 2% by weight, except that the fine powder of titanium oxide (Ishihara Sangyo Co., Ltd .: TTO-D1) is added to be 3% by weight. It is the same.

[Evaluation methods]
For Example 4 and Comparative Example 4 in Table 3, environmental stability evaluation and image density evaluation were performed. Table 3 shows the evaluation results of the physical property evaluation of the two-component developer produced by the above method.

  As can be seen from Table 3, when the coating resin contains 2% by weight of barium titanate fine powder (Example 4) and when the coating resin contains 3% by weight of titanium oxide fine powder ( When compared with Comparative Example 4), both image densities were 1.38. The toner replenishment time was 14 seconds in Example 4, 18 seconds in Comparative Example 4, and the white background fog was 0.62 in Example 4 and 0.67 in Comparative Example 4. As described above, it was also found that the barium titanate fine powder has the same or better effect on the environmental characteristics than the titanium oxide fine powder in a small amount.

Claims (3)

A carrier constituting a two-component developer,
The core material is coated with a coating resin,
The coating resin is 5% by weight or more and 20% by weight or less based on the weight of the core material,
A carrier comprising barium titanate fine powder in a coating resin.   The carrier according to claim 1, wherein the content of the barium titanate fine powder in the coating resin is 3 wt% or more and 50 wt% or less. A two-component developer comprising a toner and a carrier,
A two-component developer, wherein the carrier is the carrier according to claim 1 or 2.