JP2012177873A - Carrier for electrophotography, developer, process cartridge, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier that simultaneously satisfies the characteristics of: having stable charge application performance for a long period, excellent abrasion resistance (scraping, peeling) of films, less variation in carrier resistance and the amount of pumped-up developer, less variation in charge due to a spent toner composition; and preventing the occurrence of variation in image density, stains on the background, toner scattering, and intra-device contamination and abnormal images due to adhesion of a carrier over a long-time use.SOLUTION: A carrier for electrophotography includes a resin coating layer made of a silicone resin containing conductive fine particles on the surface of a carrier core material coated with a silane coupling agent, and has the average particle diameter of the conductive fine particles of 0.15 to 0.5 μm, which is more than the average thickness b of the resin coating layer.

Description

  The present invention relates to a two-component developer electrophotographic carrier, developer, process cartridge, and image forming method used in electrophotography and electrostatic recording.

In electrophotographic image formation, carrier adhesion and developer pumping amount (development amount of developer due to magnetic force, etc.) when fusing to the carrier surface (hereinafter referred to as toner spent) or coating coating film scrapes or peels off. ) Changes. As a result, there is a possibility that the image density, in particular, the density of the highlight portion changes, and the high image quality cannot be maintained. In addition, color contamination occurs due to the removal of the filler due to the carrier coating film being scraped or peeled (hereinafter, “scraping or peeling” may be simply referred to as “peeling” or “scraping”). With toner, it may be difficult to maintain high image quality.
An electrostatic latent image carrier comprising a surface-coated carrier having a silicone resin-containing coating layer on the surface thereof, wherein a layer containing a silane coupling agent is present on the surface of the carrier core material. The invention is known (see, for example, the claims of Patent Document 1).

Further, in a carrier having at least a coating film made of 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 made of specific silicon. An invention of an electrophotographic carrier characterized in that the surface treatment is carried out with one or two or more acrylate compounds is known (refer to the claims of Patent Document 2).
In the invention of this Patent Document 2, although common in terms of a carrier having a coating film composed of a binder resin and particles, the particles are silica or alumina particles, and the particles are surface-treated with a silicon acrylate compound. In addition, a silicone resin is not substantially used as the binder resin. For this reason, further improvements in spent resistance and carrier resistance are required.

An object of the present invention is to provide a carrier having a stable charge imparting ability over a long period of time and excellent in abrasion resistance (scraping / peeling) of a film.
It is another object of the present invention to provide an electrostatic latent image developer, an electrostatic latent image developing method, a process cartridge, a replenishing developer, and an image forming apparatus using the electrostatic latent image developing carrier.

In order to solve the above-described problems, the present inventors have taken the following solutions.
(1) having a resin coating layer having a silicone resin containing conductive fine particles on the surface of a carrier core material coated with a silane coupling agent;
An electrophotographic carrier having an average particle diameter a of 0.15 to 0.5 μm and an average thickness b of the resin coating layer or more is characterized.
(2) The electrophotographic carrier according to (1), wherein the conductive fine particles have an alumina base and a conductive coating layer containing tin dioxide.
(3) The electrophotographic carrier according to (1) or 2, wherein the conductive fine particles contain tin dioxide in an amount of 4 wt% to 80 wt%.
(4) In the electrophotographic carrier according to any one of (1) to (3), the resin coating layer has an average film thickness of 0.08 μm to 0.3 μm.
(5) The electrophotographic carrier according to any one of (1) to (4), wherein the silane coupling agent is an amino group-containing silane coupling agent.
(6) In the electrophotographic carrier according to any one of (1) to (5), the shape factors SF1 and SF2 are set as follows:
SF1 = (L ² / A) × (π / 4) × 100
And SF2 = (P ² / A) × (1 / 4π) × 100
Then, SF1 of the carrier core material is 100 to 120, and SF2 is 100 to 120.
(7) A developer having the electrophotographic carrier according to any one of (1) to (6) and a toner is characterized.
(8) A replenishment developer containing 2 to 50 parts by mass of toner with respect to 1 part by mass of the carrier, wherein the carrier is an electron according to any one of (1) to (6). It features a developer for replenishment that is a photographic carrier.
(9) The electrostatic latent image carrier, the charging member for charging the surface of the electrostatic latent image carrier, and the electrostatic latent image formed on the electrostatic latent image carrier are the above (7) or (8 And a process cartridge having a developing section that develops the developer using the developer described in (1) and a cleaning member that cleans the electrostatic latent image carrier.
(10) The step of forming an electrostatic latent image on the electrostatic latent image carrier and the electrostatic latent image formed on the electrostatic latent image carrier are described in (7) or (8) above. Developing with a developer to form a toner image, transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and fixing the toner image transferred to the recording medium And an image forming method.

  The present invention can provide a carrier having a stable charge-imparting ability over a long period of time and excellent in abrasion resistance (scraping / peeling) of the film.

FIG. 2 is a schematic diagram for explaining a developing unit of the image forming apparatus according to the embodiment of the present invention. 1 is a cross-sectional view illustrating an example of an image forming apparatus. It is sectional drawing which shows another example of an image forming apparatus. It is a figure which shows one example of the process cartridge concerning embodiment of this invention.

Hereinafter, the present invention will be described with reference to embodiments.
In the carrier of this embodiment, a resin coating layer made of a silicone resin containing conductive fine particles having an average particle diameter a of 0.15 to 0.5 μm is formed on the surface of a carrier core material coated with a silane coupling agent. In addition, when the conductive fine particle diameter and the resin coating layer average thickness b are set so that the average particle diameter a of the conductive fine particles is equal to or larger than the average thickness b of the resin coating layer, the following effects can be obtained. I found it. In addition, as for the measuring method of the particle size of the conductive fine particles, the average primary particle size of the conductive fine particles is determined by observing the cross section of the carrier using a transmission electron microscope (TEM) and conducting particles in the coating layer covering the carrier surface. The diameter was measured and obtained from the average value. Specifically, the short diameter of the conductive fine particles at arbitrary 10 points was measured from the cross section of the carrier, and the average of the measured values was obtained as the average primary particle diameter.
That is, the toner spent on the carrier surface is scraped off by the irregularities on the carrier surface formed by the conductive fine particles, and the toner spent can be suppressed and the decrease in the charge amount due to the toner spent can be suppressed. However, since a force is locally applied to the fine particles forming the convex portion on such a surface, there is a tendency that a part of the resin coating layer formed using the fine particles and the surrounding silicone resin is peeled off integrally. For this reason, it is necessary to firmly fix the fine particles to the surface of the core material. As a result of the investigation, after forming a silane coupling layer on the surface of the core material, a resin coating layer containing a silicone resin containing fine particles is formed. Then, the core material, the resin and the fine particles are firmly bonded. In addition, by coating the surface of the core material with a silane coupling agent, the coating resin of the resin coating layer is uniformly applied with a uniform thickness, and as a result, fine particles are evenly dispersed in the resin coating layer. These effects are considered to contribute to the prevention of peeling between the silicone resin and the fine particles (filler peel resistance). This prevents background stains (background stains) and toner scattering due to a decrease in charge amount as image quality in the actual machine. In addition, a decrease in the amount of pumping to the developing sleeve due to a change in carrier fluidity due to toner spent and a decrease in image density due to this are also suppressed.

  The abrasion resistance of the resin coating layer itself is mainly secured by the mechanical properties such as the hardness and elasticity of the resin coating layer, and the carrier resistance decreases and the carrier adheres because the resin coating layer is thinned and thinned. Cause a malfunction. On the other hand, in the embodiment, in addition to forming a resin coating layer containing a silicone resin containing fine particles and firmly bonding the core material, the resin and the fine particles, the average particle size a of the conductive fine particles is When the average thickness of the coating layer is not less than b, the spacer effect of the convex portion can be used to prevent the resin coating layer from being worn due to the core, and the wear resistance is ensured.

  As the silane coupling agent used in the embodiment, it is particularly effective to contain an appropriate amount (0.001 to 30% by weight) of the aminosilane coupling agent shown below from the viewpoint of adhesiveness and toner charge amount adjustment. is there.

<Aminosilane coupling agent>
H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ MW 179.3
_{H 2 N (CH 2) 3} Si (OC 2 H 5) 3 MW 221.4
_{H 2 N (CH 2) 3} Si (CH 3) 2 (OC 2 H 5) MW 161.3
_{H 2 N (CH 2) 3} Si (CH 3) (OC 2 H 5) 2 MW 191.3
_{H 2 N (CH 2) 2} NHCH 2 Si (OCH 3) 3 MW 194.3
_{H 2 N (CH 2) 2} NH (CH 2) 3 Si (CH 3) (OCH 3) 2 MW 206.4
_{H 2 N (CH 2) 2} NH (CH 2) 3 Si (OCH 3) 3 MW 224.4
_{(CH 3) 2 N (CH} 2) 3 Si (CH 3) (OC 2 H 5) 2 MW 219.4
_{(C 4 H 9) 2 N} (CH 2) 3 Si (OCH 3) 3 MW 291.6
In addition, said MW represents molecular weight.
These silane coupling agents may be contained in the coat resin layer from the viewpoint of adjusting the toner charge amount of the resin coating layer containing a silicone resin, in addition to the coating on the surface of the core material.

In this embodiment, the resin coating layer has a silanol group and / or a functional group capable of generating a silanol group by hydrolysis (for example, an alkoxy group or a negative group such as a halogen group bonded to an Si atom). It is preferable to include a silicone resin.
In the present embodiment, the silicone resin having a silanol group used when forming the resin coating layer and / or a functional group capable of generating a silanol group by hydrolysis is represented by the following general formula (I). It preferably contains at least one of the repeating units shown.

Here, in the above formula (I), A ¹ is a hydrogen atom, a halogen atom, a hydroxy group, a methoxy group, a lower alkyl group having 1 to 4 carbon atoms, or an aryl group (such as a phenyl group or a tolyl group). ² is an alkylene group having 1 to 4 carbon atoms or an arylene group (such as a phenylene group).

  In the aryl group of the above formula, the carbon number thereof is 6 to 20, preferably 6 to 14. This aryl group includes an aryl group derived from benzene (phenyl group), an aryl group derived from a condensed polycyclic aromatic hydrocarbon such as naphthalene, phenanthrene and anthracene, and a chain polycyclic aromatic such as biphenyl and terphenyl. An aryl group derived from a group hydrocarbon is included. The aryl group may be substituted with various substituents.

  In the arylene group of the above formula, the carbon number is 6 to 20, preferably 6 to 14. The arylene group includes an arylene group derived from benzene (phenylene group), an arylene group derived from a condensed polycyclic aromatic hydrocarbon such as naphthalene, phenanthrene, and anthracene, and a chain polycyclic aromatic such as biphenyl and terphenyl. An arylene group derived from a group hydrocarbon is included. The arylene group may be substituted with various substituents.

  A commercially available silicone resin that can be used in the embodiment is not particularly limited, but KR251, KR271, KR272, KR282, KR252, KR255, KR152, KR155, KR211, KR216, KR213 (above, manufactured by Shin-Etsu Silicone), AY42 -170, SR2510, SR2400, SR2406, SR2410, SR2405, SR2411 (manufactured by Toray Dow Corning Co., Ltd.) (manufactured by Toray Silicone).

  As described above, various silicone resins can be used. Among them, methyl silicone resin is particularly preferable because of low toner spent property and small environmental fluctuation of charge amount.

  As a weight average molecular weight of a silicone resin, it is 1000-100,000, Preferably, it is about 1000-30000. When the molecular weight of the resin to be used is greater than 100,000, the viscosity of the coating solution is excessively increased during coating, the coating film uniformity is not sufficiently obtained, and the density of the resin layer may not be sufficiently increased after curing. If it is less than 1000, problems such as brittleness of the cured resin layer tend to occur.

The content ratio of the silicone resin is 5 to 80% by weight, preferably 10 to 60% by weight, based on the total coating resin amount.
If the amount is less than 5% by weight, the effect of improving the spent property and the like cannot be obtained. If the amount is more than 80% by weight, the toughness of the resin layer is insufficient and the film is easily scraped.

  Further, the resin layer composition of the embodiment can also contain a resin other than the silicone resin having the silanol group and / or the hydrolyzable functional group, and such a resin is not particularly limited, but is an acrylic resin. Amino resin, polyvinyl resin, polystyrene resin, halogenated olefin resin, polyester, polycarbonate, polyethylene, polyvinyl fluoride, polyvinylidene fluoride, polytrifluoroethylene, polyhexafluoropropylene, vinylidene fluoride and vinyl fluoride Polymers, fluoroterpolymers such as terpolymers of tetrafluoroethylene, vinylidene fluoride, and non-fluorinated monomers, silicone resins that do not have silanol groups or hydrolyzable functional groups, etc. May be. Among them, an acrylic resin is preferable because it has high adhesion to the core material particles and conductive fine particles and low brittleness.

  The acrylic resin preferably has a glass transition point of 20 to 100 ° C, more preferably 25 to 80 ° C. Since such an acrylic resin has an appropriate elasticity, when the developer is triboelectrically charged, a shock is applied to the resin layer due to the friction between the toner and the carrier or the friction between the carriers. It can be absorbed and deterioration of the resin layer and the conductive fine particles can be prevented.

  The resin layer composition further preferably contains a cross-linked product of an acrylic resin and an amino resin. Thereby, fusion | melting of resin layers can be suppressed, maintaining moderate elasticity. The amino resin is not particularly limited, but a melamine resin and a benzoguanamine resin are preferable because the charge imparting ability of the carrier can be improved. In addition, when it is necessary to appropriately control the charge imparting ability of the carrier, another amino resin may be used in combination with the melamine resin and / or the benzoguanamine resin.

  As the acrylic resin capable of crosslinking with the amino resin, those having a hydroxyl group and / or a carboxyl group are preferable, and those having a hydroxyl group are more preferable. Thereby, adhesiveness with core material particle | grains or electroconductive fine particles can further be improved, and the dispersion stability of electroconductive fine particles can also be improved. In this case, the acrylic resin preferably has a hydroxyl value of 10 mgKOH / g or more, and more preferably 20 mgKOH / g or more.

In addition, titanium-based catalysts, tin-based catalysts, zirconium-based catalysts, and aluminum-based catalysts are used to promote the condensation reaction of crosslinking components in coating resins such as silicone resins having silanol groups and / or hydrolyzable functional groups. it can. Of these various catalysts, titanium alkoxides and titanium chelates are particularly preferred among the titanium-based catalysts that give excellent results.
This is considered to be because the effect of promoting the condensation reaction of the silanol group derived from the crosslinking component B is large and the catalyst is hardly deactivated. An example of a titanium alkoxide catalyst is titanium diisopropoxybis (ethyl acetoacetate) represented by the following structural formula 5, and an example of a titanium chelate catalyst is represented by the following structural formula 6. Titanium diisopropoxybis (triethanolaminate) is mentioned.

The resin layer is composed of a silicone resin having a silanol group and / or a hydrolyzable functional group, a titanium diisopropoxy bis (ethyl acetoacetate) catalyst, and, if necessary, a resin, a resin layer composition containing a solvent. Can be formed.
Specifically, it may be formed by condensing silanol groups while coating the core material particles with the resin layer composition, or after coating the core material particles with the resin layer composition, It may be formed by condensation.
The method of condensing silanol groups while coating the core material particles with the resin layer composition is not particularly limited, but the method of coating the core particles with the resin layer composition while applying heat, light, etc. Etc. Further, the method of condensing the silanol group after coating the core material particles with the resin layer composition is not particularly limited, and examples thereof include a method of heating after coating the core material particles with the resin layer composition. .

Next, the conductive fine particles used in the embodiment will be described.
The carrier of the embodiment includes conductive fine particles for increasing the strength of the resin layer and adjusting the carrier resistance.
According to the study by the present inventors, the conductive fine particles having the conductive coating layer on the surface of the alumina-based substrate, that is, the substrate containing alumina have a high function of adjusting the volume resistivity of the carrier, and the surface energy is small and tough. Combined with the compatibility with various copolymers, carrier resistance and developer pumping amount do not change for a long period of time, change in image density can be prevented, and high-quality images can be formed over a long period of time.

  Further, it is considered that a carrier that is triboelectrically charged with the toner is preferably a substrate having a negative electronegativity from the viewpoint of charging ability. Since silica and titanium oxide, which are toner additives, have a large electronegativity and a large negative chargeability, it is better to use a carrier substrate with a lower electronegativity, because the charging ability is larger and a negatively charged toner is used. Is preferred. When alumina having a low electronegativity is used for the substrate, charging can be stably maintained for a long period of time, and a high-quality image can be formed. On the other hand, when a substrate having a high electronegativity such as titanium oxide other than alumina is used as the substrate, the chargeability cannot be maintained by long-term use even if the charge can be adjusted initially, and the image quality is deteriorated.

As the material used for the alumina-based substrate, any of α-alumina, β-alumina, and γ-alumina can be used, and the specific surface area is 5 to 30 m ² / g.
It is preferable that the conductive coating layer of the conductive fine particles contains tin dioxide or tin dioxide and indium oxide. The conductive coating layer containing tin dioxide or tin dioxide and indium oxide can uniformly coat the surface of the substrate, and good conductivity can be obtained without being affected by the substrate. When tin is tin dioxide, it can be preferably used because it has sufficient resistance adjusting ability and is inexpensive. The particle size of the alumina base substrate can be measured using the same method as the particle size of the conductive fine particles.

In the case where the conductive coating layer is tin dioxide, it is preferable that the entire conductive fine particles contain tin dioxide in an amount of 4 wt% to 80 wt%, and more preferably 30 wt% to 50 wt%.
When the tin dioxide is less than 4% by weight, the volume resistivity of the conductive fine particles is increased, so that the amount of the conductive fine particles is increased, and it is easy to detach from the surface of the carrier particles. The volume resistivity of the conductive fine particles does not decrease so much and the efficiency is low, and it may become non-uniform.
When the conductive coating layer is tin dioxide and indium oxide, the tin dioxide content is 2 wt% or more and 7 wt% or less, and the indium oxide content is 15 wt% or more and 40 wt% or less. It is preferable that

In this embodiment, the volume resistivity of the electrostatic latent image developer carrier is preferably 1 × 10 ⁹ Ω · cm or more and 1 × 10 ¹⁷ Ω · cm or less. By controlling the carrier resistance, it is possible to obtain a high-definition image free from color stains with excellent reproducibility of fine lines such as character portions, with the edge effect suppressed. If the volume resistivity is less than 1 × 10 ⁹ Ω · cm, carrier adhesion may occur in the non-image area, and if it exceeds 1 × 10 ¹⁷ Ω · cm, the edge effect may be at an unacceptable level. is there.
The volume resistivity of the carrier can be controlled by adjusting the resistance of the resin layer on the core particles (addition of conductive fine particles, etc.) and controlling the film thickness. The content of conductive fine particles relative to 100 parts by weight of the resin is 5 It is preferable that it is -200 weight part.
If the amount of the conductive fine particles added is less than 5 parts by weight, the resin layer cannot be sufficiently strengthened, and the carrier resistance may not be sufficiently adjusted. If the amount exceeds 200 parts by weight, the conductive fine particles are detached. In some cases, the volume resistivity of the carrier is likely to change due to use.

In this embodiment, after the resin core composition is coated on the carrier core material, a heat treatment is performed at a temperature lower than the Curie point of the core material particles to be used, preferably at a temperature of 100 to 350 ° C. Promoted. A more preferable heat treatment temperature is 150 to 250 ° C.
When the temperature is lower than 100 ° C., the crosslinking reaction due to condensation does not proceed, and sufficient strength of the resin layer cannot be obtained.
On the other hand, when the temperature is higher than 350 ° C., the resin layer is easily peeled off due to the carbonization of the copolymer.

In the present embodiment, the resin layer (resin coating layer) of the carrier preferably has an average film thickness of 0.08 to 0.3 μm. When the average film thickness is less than 0.08 μm, the resin layer is easily peeled off. When the average film thickness exceeds 0.3 μm, the resin layer is not a magnetic substance, and thus the carrier easily adheres to the image.
The average film thickness of the resin layer was measured by observing the cross section of the carrier using a transmission electron microscope (TEM) and measuring the average film thickness of the resin layer.

  The carrier core particle of the embodiment is not particularly limited as long as it is a magnetic substance, but is not limited to ferromagnetic metals such as iron and cobalt; iron oxides such as magnetite, hematite, and ferrite; various alloys and compounds; Examples thereof include resin particles dispersed in the resin. Of these, Mn-based ferrite, Mn-Mg-based ferrite, Mn-Mg-Sr ferrite, and the like are preferable from the viewpoint of environmental considerations.

In the embodiment, the core particles preferably have a weight average particle diameter Dw of 20 to 65 μm, particularly preferably 20 to 45 μm.
When the weight average particle diameter Dw is larger than the above range, carrier adhesion is less likely to occur, but the toner is not developed faithfully with respect to the latent image, so that the variation in dot diameter increases and the graininess decreases. Further, when the toner concentration is high, the background is easily soiled.
The carrier adhesion indicates a phenomenon in which a carrier adheres to an image portion or a background portion of an electrostatic latent image. The stronger each electric field, the easier the carrier adheres. In the image portion, the electric field is weakened by developing the toner, so that the carrier adhesion is less likely to occur compared to the background portion.

In the embodiment, the weight average particle diameter Dw referred to for the carrier, the carrier core material, and the toner is calculated based on the particle diameter distribution (relationship between the number frequency and the particle diameter) of the particles measured on the basis of the number. .
In this case, the weight average particle diameter Dw is expressed by the following formula.

In the above formula, D represents the representative particle size (μm) of particles present in each channel, and n represents the total number of particles present in each channel. The channel indicates a length for dividing the particle size range in the particle size distribution diagram into measurement width units. In the case of this embodiment, the length is equally divided by 2 μm (particle size distribution width). It was adopted.
Further, as the representative particle size of the particles existing in each channel, the lower limit value of the particle size stored in each channel was adopted.

(Core shape)
As the carrier particle size decreases, the frictional force between the particles increases, the carrier fluidity is poor, and the torque of the developing sleeve increases. Further, when the carrier becomes sphericity and the smoothness of the surface increases, that is, when the shape factor SF1 described below is 100 to 120 and SF2 is 100 to 120, the development torque is reduced and the peeling is reduced. , The decrease in charge amount is reduced.
Sphericalization reduces spent toner and makes it difficult to stain the ground. Therefore, the smaller the particle size, the smaller the shape factors SF1 and SF2. In the particle size range of 20 to 65 μm in the above-described embodiment, when SF1 is larger than 120, the carrier shape is deviated from the true sphere, and when SF2 is larger than 120, the surface unevenness increases and the developing sleeve torque increases. In addition, the amount of toner adhering to the carrier increases, and it tends to cause a decrease in the amount of developer pumped up due to a decrease in developer charge amount and fluidity, a decrease in image density, and background contamination.

In the carrier of the embodiment, it is preferable that the core has a shape close to a true sphere, specifically, the shape factor SF1 is 100 to 120, and SF2 is 100 to 120.
When SF1 and SF2 are 100, the projected shape is a perfect circle shape, and the larger the value is, the more the ball comes off from the true sphere, and the surface has large unevenness or a shape close to an elliptical shape. The closer the core material is to a perfect circle shape, the more uniformly the carrier coat resin (the coating resin of the resin coating layer) is formed in the core material shape, and the conductive fine particles have a uniform distribution. When the core material, particularly the surface irregularities are large, the thickness of the resin coating layer becomes non-uniform, and the distribution of the conductive fine particles also becomes non-uniform.

In particular, when the average particle diameter a of the conductive fine particles is equal to or larger than the average thickness b of the resin coating layer as in the carrier of the embodiment, a large force is easily applied to the conductive fine particles present on the core material convex portion. In addition, a problem that the conductive fine particles peel off from the surface of the core material with a nearby coat layer is likely to occur. As a result, the function of the conductive fine particles, the function of preventing toner spent (toner scraping on the carrier) due to the formation of convex portions, is lost, and the charging due to the toner spent, the background contamination, and the developer pumping amount are reduced. As a result, problems such as a decrease in image density are likely to occur.
This is a phenomenon different from the uniform decrease in the thickness of the coat layer and the decrease in carrier resistance due to wear due to insufficient wear resistance of the coat layer, and the occurrence of carrier adhesion.
The carrier shape factors SF1 and SF2 mean the following.

The shape factors SF1 and SF2 are, for example, 100 sampled carrier particle images magnified 300 times using FE-SEM (S-800) manufactured by Hitachi, Ltd. Analysis is performed by introducing the image into an image analysis apparatus (Luzex AP) manufactured by Nireco Corporation, and the values are calculated from the following formulas (3) and (4), and the obtained values are defined as shape factors SF1 and SF2.
SF1 = (L ² / A) × (π / 4) × 100 (3)
SF2 = (P ² / A) × (1 / 4π) × 100 (4)
In the formula, L represents the absolute maximum length of the particle (the length of the circumscribed circle), P represents the perimeter of the particle, and A represents the projected area of the particle.

In addition, the carrier of the embodiment preferably has a magnetization of 40 to 90 Am ² / kg in a magnetic field of 1 kOe (10 ⁶ / 4π [A / m]). When this magnetization is less than 40 Am ² / kg, the carrier may adhere to the image, and when it exceeds 90 Am ² / kg, the magnetic ear becomes hard and image blurring may occur.

The carrier of the embodiment can be mixed with toner and used as a two-component developer.
The toner used is one in which a colorant, fine particles, a charge control agent, a release agent and the like are contained in a binder resin mainly composed of a thermoplastic resin, and various conventionally known toners are used. Can do. This toner is an indeterminate shape produced by various toner production methods such as a polymerization method and a granulation method, or a toner having the shape factor described above. Further, the toner itself may be either a magnetic toner or a non-magnetic toner.

As the binder resin for the toner, the following can be used alone or in combination.
Styrene binder resin: Styrene such as polystyrene and polyvinyltoluene and its substituted homopolymer, styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-acrylic acid Methyl copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer Polymer, styrene-α-chloromethacrylic acid methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene- Isoprene copolymer, styrene-male Styrenic copolymers such as acid copolymers and styrene-maleic acid ester copolymers; acrylic binders include polymethyl methacrylate and polybutyl methacrylate, and in addition, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene Polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or aliphatic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax, etc. Can be mentioned.
A polyester resin is preferable because it can further reduce the melt viscosity while ensuring the stability of the toner during storage.

  Polyester resins can be preferably used because they can lower the melt viscosity while ensuring the stability during storage of the toner, as compared with styrene and acrylic resins. Such a polyester resin can be obtained, for example, by a polycondensation reaction between an alcohol component and a carboxylic acid component.

  Examples of the alcohol component related to the polyester resin include polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-propylene glycol, neopentyl glycol, 1,4-butenediol, and the like. Diols, 1,4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, etherified bisphenols such as polyoxyethylenated bisphenol A and polyoxypropylenated bisphenol A, these having 3 to 22 carbon atoms Divalent alcohol units substituted with a saturated or unsaturated hydrocarbon group, other divalent alcohol units, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, penta Thritol, dipentaerythritol, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2, Examples include trihydric or higher alcohol monomers such as 4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-trihydroxymethylbenzene.

  Examples of the carboxylic acid component related to the polyester resin include monocarboxylic acids such as palmitic acid, stearic acid, and oleic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, and adipine. Acid, sebacic acid, malonic acid, divalent organic acid monomers in which these are substituted with a saturated or unsaturated hydrocarbon group having 3 to 22 carbon atoms, anhydrides of these acids, lower alkyl esters, and linolenic acid Dimer acid from 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2 , 4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2- List trivalent or higher polyvalent carboxylic acid monomers such as tylene carboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid embol trimer acid, and anhydrides of these acids. Can do.

  Examples of the epoxy resins include polycondensates of bisphenol A and epichlorohydrin, such as EPOMIC R362, R364, R365, R366, R367, R369 (above, manufactured by Mitsui Petrochemical Co., Ltd.), Epototo YD-011. , YD-012, YD-014, YD-904, YD-017 (above, manufactured by Tohto Kasei Co., Ltd.) Epcot 1002, 1004, 1007 (above, manufactured by Shell Chemical Co., Ltd.) It is done.

  Examples of the colorant used in the embodiment include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, Hansa Yellow G, rhodamine 6G lake, calco oil blue, chrome yellow, quinacridone, and benzidine yellow. Conventionally known dyes such as rose bengal, triallylmethane dyes, monoazo dyes, disazo dyes, and dyes can be used alone or in combination.

  Further, the black toner can be made into a magnetic toner by containing a magnetic material. As the magnetic material, ferromagnetic powders such as iron and cobalt, fine powders such as magnetite, hematite, Li-based ferrite, Mn-Zn-based ferrite, Cu-Zn-based ferrite, Ni-Zn ferrite, and Ba ferrite can be used.

For the purpose of sufficiently controlling the triboelectric chargeability of the toner, so-called charge control agents such as metal complex salts of monoazo dyes, nitrohumic acid and its salts, salicylic acid, naphthoic salts, dicarboxylic acid Co, Cr, Fe, etc. , A quaternary ammonium compound, an organic dye, and the like can be contained.
For color toners other than black, white metal salts of salicylic acid derivatives are preferred.

Furthermore, a release agent may be added to the toner used in the embodiment as necessary.
As the release agent material, low molecular weight polypropylene, low molecular weight polyethylene, carnauba wax, microcrystalline wax, jojoba wax, rice wax, montanic acid wax and the like can be used alone or in combination, but are not limited thereto. It is not a thing.

Additives can be added to the toner. In order to obtain a good image, it is important to impart sufficient fluidity to the toner. For this purpose, it is generally effective to externally add hydrophobized metal oxide fine particles and fine particles such as lubricants as fluidity improvers, and metal oxides, organic resin fine particles, metal soaps and the like as additives. It is possible to use. Specific examples of these additives include fluorine resins such as polytetrafluoroethylene, lubricants such as zinc stearate, abrasives such as cerium oxide and silicon carbide; for example, inorganic surfaces such as SiO ₂ and TiO ₂ whose surfaces are hydrophobized. Examples thereof include fluidity-imparting agents such as oxides; those known as anti-caking agents, and surface-treated products thereof. In order to improve the fluidity of the toner, hydrophobic silica is particularly preferably used.

The toner used in the electrostatic latent image developer composed of the toner and the carrier of the embodiment has a weight average particle diameter of 3.0 to 9.0 μm, more preferably 3.0 to 6.0 μm.
The toner particle size was measured using Coulter Multisizer II (manufactured by Coulter Counter).

In addition, the carrier of the embodiment is a developer for replenishment composed of a carrier and a toner, and is applied to an image forming apparatus that forms an image while discharging excess developer in the developing device. Image quality.
That is, the deteriorated carrier in the developing device and the non-deteriorated carrier in the replenishing developer are replaced, and the charge amount is kept stable over a long period of time, so that a stable image can be obtained. This method is particularly effective when printing a large image area. Deterioration at the time of printing a large image area is mainly due to a decrease in carrier charging ability due to toner spent on the carrier. However, using this method, the amount of carrier replenishment increases when the image area is large. The frequency with which the changed carriers are replaced increases. Thereby, a stable image can be obtained for an extremely long period of time.
As described above, the replenishment developer composed of the carrier and the toner according to the embodiment is applied to the image forming apparatus that forms an image while discharging the excess developer in the developing device. Stable image quality can be obtained.

  The mixing ratio of the replenishment developer is 2 to 50 parts by mass, preferably 5 to 12 parts by mass of the toner with respect to 1 part by mass of the carrier. When the amount of toner is less than 2 parts by mass, the amount of replenishment carrier is excessive, the carrier is excessively supplied, and the carrier concentration in the developing device becomes too high, so that the charge amount of the toner tends to increase. Further, when the charge amount of the toner increases, the developing ability decreases and the image density decreases. On the other hand, when the amount exceeds 50 parts by mass, the carrier ratio in the replenishment developer is reduced, so that the replacement of the carrier in the image forming apparatus is reduced, the carrier is deteriorated, and the charge amount of the developer is easily lowered. .

Next, examples of the image forming method and the image forming apparatus of the embodiment will be described in detail with reference to the drawings. However, these examples are for explanation and are not for limiting the present invention.
FIG. 1 is a schematic diagram for explaining the image forming method and the developing unit of the image forming apparatus according to the embodiment, and modifications as described below also belong to the category of the embodiment.
In FIG. 1, a developing device 40 disposed opposite to the photosensitive drum 20 as a latent image carrier includes a developing sleeve 41 as a developer carrier, a developer accommodating member 42, a doctor blade 43 as a regulating member, It is mainly composed of a support case 44 and the like.
To a support case 44 having an opening on the photosensitive drum 20 side, a toner hopper 45 serving as a toner containing portion for containing the toner 21 is joined. The developer container 46 adjacent to the toner hopper 45 and containing the developer composed of the toner 21 and the carrier particles 23 agitates the toner particles 21 and the carrier particles 23 and imparts friction / release charge to the toner particles. For this purpose, a developer stirring mechanism 47 is provided.

Inside the toner hopper 45, a toner agitator 48 and a toner replenishing mechanism 49 are disposed as toner supplying means rotated by a driving means (not shown). The toner agitator 48 and the toner replenishing mechanism 49 send out the toner 21 in the toner hopper 45 toward the developer accommodating portion 46 while stirring.
A developing sleeve 41 is disposed in the space between the photosensitive drum 20 and the toner hopper 45. A developing sleeve 41 that is rotationally driven in the direction of the arrow in the figure by a driving means (not shown) is a magnetic field that is disposed in a relative position with respect to the developing device 40 in order to form a magnetic brush made of carrier particles 23. It has a magnet as a generating means.
On the side of the developer accommodating member 42 facing the side attached to the support case 44, a doctor blade 43 as a regulating member is integrally attached. In this example, the doctor blade 43 serving as a regulating member is disposed in a state where a certain gap is maintained between the tip of the regulating blade 43 and the outer peripheral surface of the developing sleeve 41.

  Using such an apparatus without limitation, the developing method of the embodiment is performed as follows. That is, with the above configuration, the toner 21 sent out from the toner hopper 45 by the toner agitator 48 and the toner replenishing mechanism 49 is conveyed to the developer container 46 and stirred by the developer agitating mechanism 47, so Is applied to the developing sleeve 41 as a developer together with the carrier particles 23 and conveyed to a position facing the outer peripheral surface of the photosensitive drum 20, and only the toner 21 is formed on the photosensitive drum 20. A toner image is formed on the photosensitive drum 20 by electrostatically coupling with the electrostatic latent image thus formed.

  FIG. 2 is a sectional view showing an example of the image forming apparatus. An image carrier charging member 32, an image exposure system 33, a developing device 40, a transfer mechanism 50, a cleaning mechanism 60, and a charge eliminating lamp 70 are disposed around a drum-shaped image carrier, that is, the photosensitive drum 20. In this case, the surface of the image carrier charging member 32 is not in contact with the surface of the photosensitive drum 20 with a gap of about 0.2 mm. When charging the photosensitive drum 20, charging unevenness can be reduced by charging the photosensitive drum 20 with an electric field in which an alternating current component is superimposed on a direct current component by a voltage applying unit (not shown) on the charging member 32. It is effective. The image forming method including the developing method is performed by the following operation.

  A series of image forming processes can be described by a negative-positive process. An image carrier 20 typified by a photoreceptor (OPC) having an organic photoconductive layer is neutralized by a static elimination lamp 70 and uniformly charged negatively by a charging member 32 such as a charging charger or a charging roller. A latent image is formed by the irradiated laser beam (in this example, the absolute value of the exposed portion potential is lower than the absolute value of the non-exposed portion potential).

  Laser light is emitted from a semiconductor laser, and the surface of the image carrier, that is, the photoreceptor 20 is scanned in the direction of the rotation axis of the image carrier 20 by a polygonal polygon mirror (polygon) that rotates at high speed. The latent image formed in this way is developed with a developer composed of a mixture of toner particles and carrier particles supplied onto a developing sleeve 41 which is a developer carrying member in the developing device, developing means or developing device 40. A toner visible image is formed. During the development of the latent image, a voltage of an appropriate magnitude or an AC voltage is superimposed on the developing sleeve 41 from a voltage application mechanism (not shown) between the exposed portion and the non-exposed portion of the image carrier 20. A development bias is applied.

On the other hand, a transfer medium (for example, paper) 80 is fed from a paper feed mechanism (not shown), and the image carrier 20 and the transfer member 50 are synchronized with the leading edge of the image by a pair of upper and lower registration rollers (not shown). And the toner image is transferred. At this time, it is preferable that a potential having a polarity opposite to that of toner charging is applied to the transfer member 50 as a transfer bias. Thereafter, the transfer medium or the intermediate transfer medium 80 is separated from the image carrier 20 to obtain a transfer image.
Further, the toner particles remaining on the image carrier are collected in a toner collection chamber 62 in the cleaning mechanism 60 by a cleaning blade 61 as a cleaning member.
The collected toner particles may be transported to a developing unit and / or a toner replenishing unit by a toner recycling unit (not shown) and reused.
The image forming apparatus may be a device in which a plurality of the developing devices described above are arranged and the toner images are sequentially transferred onto the transfer medium, then sent to the fixing mechanism, and the toner is fixed by heat or the like. It is also possible to use a device that transfers a plurality of toner images to the transfer medium and transfers them all together onto a transfer medium and performs the same fixing.

  FIG. 3 shows another process example using the electrophotographic developing method. The photosensitive member 20 is provided with at least a photosensitive layer on a conductive support, and is driven by driving rollers 24a and 24b, charged by a charging roller 32, image exposure by a light source 33, development by a developing device 40, and a charger 50. The transfer used, the pre-cleaning exposure by the light source 26, the cleaning by the brush-like cleaning means 64 and the cleaning blade 61, and the static elimination by the static elimination light source 70 are repeated. In FIG. 3, the photoconductor 20 (of course, the support is translucent in this case) is irradiated with pre-cleaning exposure light from the support side.

  FIG. 4 shows an example of the process cartridge according to the embodiment. This process cartridge uses the carrier of the above-described embodiment, and includes the photosensitive member 20, the proximity brush-like contact charging unit 32, the developing unit 40 that stores the developer of the embodiment, and the cleaning blade 61 as a cleaning unit. It is a process cartridge that integrally supports at least the cleaning means and is detachable from the main body of the image forming apparatus. In the embodiment, each of the above-described components can be integrally combined as a process cartridge, and the process cartridge can be configured to be detachable from a main body of an image forming apparatus such as a copying machine or a printer.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited to these. “Part” and “%” are based on weight in principle, and are values calculated from the raw material charge at the time of production.

<Manufacture of conductive fine particles>
(Conductive fine particle production example 1)
100 g of aluminum oxide (AKP-30 manufactured by Sumitomo Chemical Co., Ltd.) having an average primary particle size of 0.3 μm was dispersed in 1 liter of water to form a suspension, and heated to 70 ° C. To this suspension, a solution of 100 g of stannic chloride and 3 g of phosphorus pentoxide dissolved in 1 liter of 2N hydrochloric acid and 12 wt% aqueous ammonia was added dropwise over 2 hours so that the pH of the suspension was 7-8. did. After dropping, the cake obtained by filtering and washing the suspension was dried at 110 ° C. Next, this dry powder was treated in a nitrogen stream at 500 ° C. for 1 hour to obtain conductive fine particles 1 containing 37% of tin dioxide.

(Conductive fine particle production example 2)
100 g of aluminum oxide (HIT-70, manufactured by Sumitomo Chemical Co., Ltd.) having an average primary particle size of 0.15 μm was dispersed in 1 liter of water to prepare a suspension and heated to 70 ° C. To this suspension, a solution of 100 g of stannic chloride and 3 g of phosphorus pentoxide dissolved in 1 liter of 2N hydrochloric acid and 12 wt% aqueous ammonia was added dropwise over 2 hours so that the pH of the suspension was 7-8. did. After dropping, the cake obtained by filtering and washing the suspension was dried at 110 ° C. Next, this dry powder was treated in a nitrogen stream at 500 ° C. for 1 hour to obtain conductive fine particles 2 containing 37% of tin dioxide.

(Conductive fine particle production example 3)
100 g of aluminum oxide having a primary particle size of 0.02 μm (AEROXIDE AluC manufactured by DEGUSSA) was dispersed in 1 liter of water to prepare a suspension, and the mixture was heated to 70 ° C. To this suspension, a solution of 100 g of stannic chloride and 3 g of phosphorus pentoxide dissolved in 1 liter of 2N hydrochloric acid and 12 wt% aqueous ammonia was added dropwise over 2 hours so that the pH of the suspension was 7-8. did. After dropping, the cake obtained by filtering and washing the suspension was dried at 110 ° C. Next, this dry powder was treated in a nitrogen stream at 500 ° C. for 1 hour to obtain conductive fine particles 3 containing 37% tin dioxide.

(Conductive fine particle production example 4)
100 g of aluminum oxide having a primary particle size of 0.5 μm (AKP-20 manufactured by Sumitomo Chemical Co., Ltd.) was dispersed in 1 liter of water to form a suspension, and heated to 70 ° C. To this suspension, a solution of 100 g of stannic chloride and 3 g of phosphorus pentoxide dissolved in 1 liter of 2N hydrochloric acid and 12 wt% aqueous ammonia was added dropwise over 2 hours so that the pH of the suspension was 7-8. did. After dropping, the cake obtained by filtering and washing the suspension was dried at 110 ° C. Next, this dry powder was treated in a nitrogen stream at 500 ° C. for 1 hour to obtain conductive fine particles 4 containing 37% tin dioxide.

(Conductive fine particle production example 5)
100 g of aluminum oxide having a primary particle size of 0.3 μm (AKP-30 manufactured by Sumitomo Chemical Co., Ltd.) was dispersed in 1 liter of water to form a suspension, and heated to 70 ° C. To this suspension, a solution obtained by dissolving 7 g of stannic chloride and 0.2 g of phosphorus pentoxide in 1 liter of 2N hydrochloric acid and 12% by weight aqueous ammonia was added over 2 hours so that the pH of the suspension was 7-8. And dripped. After dropping, the cake obtained by filtering and washing the suspension was dried at 110 ° C. Next, this dry powder was treated in a nitrogen stream at 500 ° C. for 1 hour to obtain conductive fine particles 5 containing 4% of tin dioxide.

(Conductive fine particle production example 6)
100 g of aluminum oxide having a primary particle size of 0.3 μm (AKP-30 manufactured by Sumitomo Chemical Co., Ltd.) was dispersed in 1 liter of water to form a suspension, and this liquid was heated to 70 ° C. A solution obtained by dissolving 138 g of stannic chloride and 4 g of phosphorus pentoxide in 1 liter of 2N hydrochloric acid and 12 wt% aqueous ammonia were added dropwise to the suspension over 2 hours so that the pH of the suspension was 7-8. did. After dropping, the cake obtained by filtering and washing the suspension was dried at 110 ° C. Next, this dry powder was treated in a nitrogen stream at 500 ° C. for 1 hour to obtain conductive fine particles 6 containing 44% tin dioxide.

(Conductive fine particle production example 7)
Conductive fine particles 7 not containing tin dioxide (ie, 0%) were obtained from 100 g of aluminum oxide (AKP-30 manufactured by Sumitomo Chemical Co., Ltd.) having a primary particle size of 0.3 μm.

(Conductive fine particle production example 8) 58% + 0.7
100 g of titanium oxide having a primary particle size of 0.7 μm (TA-500 manufactured by Fuji Titanium Industry Co., Ltd.) was dispersed in 1 liter of water to form a suspension and heated to 70 ° C. To this suspension, a solution of 100 g of stannic chloride and 3 g of phosphorus pentoxide dissolved in 1 liter of 2N hydrochloric acid and 12 wt% aqueous ammonia was added dropwise over 2 hours so that the pH of the suspension was 7-8. did. After dropping, the cake obtained by filtering and washing the suspension was dried at 110 ° C. Next, this dry powder was treated in a nitrogen stream at 500 ° C. for 1 hour to obtain conductive fine particles 8 containing 37% tin dioxide.

Next, the carrier will be described. First, the carrier core material will be described.
(Core preparation example 1)
Water was added to 50 mol% Fe ₂ O ₃ , 25 mol% CuO, and 25 mol% ZnO, and the mixture was pulverized to 2 μm or less with a bead mill, and polyvinyl alcohol was added to the resulting slurry to adjust the viscosity. After granulation and drying, the mixture was calcined at 900 ° C. for 5 hours to obtain fine particles. After that, the particles were introduced into a high temperature range of 2000 ° C. to 3000 ° C. made of a mixed gas of acetylene and oxygen, subjected to spheronization treatment, fired at 1150 ° C. to become ferrite, and further equipped with an ultrasonic oscillator. Classification was performed using a vibration sieving machine to obtain a core material production example 1 having a weight average of 35 μm, SF1 = 115, and SF2 = 114.

(Core preparation example 2)
Water was added to 50 mol% Fe ₂ O ₃ , 25 mol% CuO, and 25 mol% ZnO, and the mixture was pulverized to 2 μm or less with a bead mill, and polyvinyl alcohol was added to the resulting slurry to adjust the viscosity. Then, after granulating and drying, it is fired at 1250 ° C. for 5 hours to form a ferrite and then pulverized, and further classified using a vibration sieve equipped with an ultrasonic oscillator, so that the weight average is 35 μm, SF1 = 132. , SF2 = 115 core material production example 2 was obtained.

<Example of carrier production>
(Carrier Production Example 1: C1)
3- (2-Aminoethyl) aminopropyltrimethoxysilane (Toray Dow Corning Z-6020) A 0.3 wt% aqueous solution was added to the core agent of the core agent production example 1 described above using a fluidized bed type coating apparatus. A core material coated with 0.1% by weight of 3- (2-aminoethyl) aminopropyltrimethoxysilane based on the weight of the core material was prepared by spray drying. The temperature in the fluidized bed was controlled at 90 ° C. for coating and drying.
To this core material, a resin solution having a solid content of 10 wt% obtained by diluting 100 parts of silicone resin (SR2411 manufactured by Toray Dow Corning Silicone) and 40 parts of conductive fine particles of Production Example 1 of conductive fine particles with toluene is averaged on the surface of the core material. It applied using the fluid bed type coating device so that a film thickness might be set to 0.2 micrometer. The temperature in the fluidized tank was controlled at 70 ° C. for coating and drying, and the obtained carrier was baked in an electric furnace at 230 ° C. for 2 hours to obtain the carrier of Carrier Production Example 1.

(Carrier Production Example 2: C2)
A carrier was produced under the same conditions as in Carrier Production Example 1 except that the average film thickness of 0.2 μm in Carrier Production Example 1 was changed to 0.3 μm, and a carrier of Carrier Production Example 2 was obtained.

(Carrier Production Example 3: C3)
The same as the carrier production example 1 except that the conductive fine particle production example 1 of the carrier production example 1 is changed to the conductive fine particle production example 2 and then the average film thickness 0.2 μm is changed to the average film thickness 0.1 μm. Carriers were produced under the conditions to obtain the carrier of Carrier Production Example 3.

(Carrier Production Example 4: C4)
Carrier Production Example 1 except that the conductive fine particle production example 1 of the carrier production example 1 is changed to the conductive fine particle production example 2 and then the average film thickness 0.2 μm is changed to the average film thickness 0.08 μm. A carrier was produced under the same conditions as in Example 1 to obtain a carrier of Carrier Production Example 4.

(Carrier Production Example 5: C5)
A carrier was produced under the same conditions as in Carrier Production Example 1 except that Conductive Fine Particle Production Example 1 in Carrier Production Example 1 was changed to Conductive Fine Particle Production Example 5 to obtain a carrier in Carrier Production Example 5.

(Carrier Production Example 6: C6)
A carrier was produced under the same conditions as in Carrier Production Example 1 except that Conductive Particle Production Example 1 in Carrier Production Example 1 was changed to Conductive Fine Particle Production Example 6, and a carrier in Carrier Production Example 6 was obtained.

(Carrier Production Example 7: C7)
A carrier was produced under the same conditions as in Carrier Production Example 1 except that Conductive Particle Production Example 1 in Carrier Production Example 1 was changed to Conductive Fine Particle Production Example 7 to obtain a carrier in Carrier Production Example 7.

(Carrier Production Example 8: C8)
A carrier is produced under the same conditions as in Carrier Production Example 1 except that the core in Carrier Production Example 1 is changed from Core Production Example 1 to Core Production Example 2 to obtain a carrier in Carrier Production Example 8. It was.

(Carrier Production Example 9: C9)
A carrier was produced under the same conditions as in Carrier Production Example 1 except that the conductive fine particles 1 of Carrier Production Example 1 were changed to conductive fine particles 4, and a carrier corresponding to Carrier Production Example 9 (C9 in the table) was obtained. .

(Carrier production comparative example 1: C ratio 1)
The core material coated with 0.1% by weight of 3- (2-aminoethyl) aminopropyltrimethoxysilane of Carrier Production Example 1 is not coated with 3- (2-aminoethyl) aminopropyltrimethoxysilane. A carrier was produced under the same conditions as in Carrier Production Comparative Example 1 except that the carrier was produced in Carrier Production Comparative Example 1.

(Carrier production comparative example 2: C ratio 2)
Under the same conditions as in Carrier Production Example 1 except that the conductive fine particles 1 of Carrier Production Example 1 were changed to conductive fine particles 3 and then the average film thickness was changed to 0.2 μm. A carrier was produced to obtain a carrier of Comparative Example 2 for carrier production.

(Carrier production comparative example 3: C ratio 3)
Carrier production comparative example 1 “silicone resin (SR2411 manufactured by Toray Dow Corning Silicone Co., Ltd.) (100 parts) and conductive fine particles of conductive fine particle production example 1 of 40 parts by weight diluted with toluene” “Silicone resin (SR2411 manufactured by Toledo Corning Silicone Co., Ltd.) (100 parts), conductive fine particles 40 parts of conductive fine particle production example 1, 3- (2-aminoethyl) aminopropyltrimethoxysilane (Toray Dow Corning Z- 6020) A carrier was produced under the same conditions as in Carrier Production Comparative Example 1 except that 1 part was changed to a resin solution having a solid content of 10 wt% diluted with toluene.

(Carrier production comparative example 4: C ratio 4)
A carrier was produced under the same conditions as in Carrier Production Example 1 except that the conductive fine particles 1 of Carrier Production Example 1 were changed to conductive fine particles 2, and a carrier of Carrier Production Comparative Example 4 was obtained.

(Carrier production comparative example 5: C ratio 5)
A carrier was produced under the same conditions as in Carrier Production Example 1 except that the average film thickness of 0.2 μm in Carrier Production Example 1 was changed to 0.4 μm in average film thickness, and the carrier of Carrier Production Comparative Example 5 was obtained. .

(Carrier Production Comparative Example 6: C ratio 6)
The carrier is treated under the same conditions as in Carrier Production Example 1 except that the conductive fine particles 1 of Carrier Production Example 1 are changed to conductive fine particles 4 and the average film thickness is changed to 0.2 μm. The carrier of Comparative Example 6 was obtained.

(Carrier Production Comparative Example 7: C ratio 7)
A carrier was produced under the same conditions as in Carrier Production Example 1 except that the conductive fine particles 1 of Carrier Production Example 1 were changed to conductive fine particles 8, and a carrier corresponding to Carrier Production Comparative Example 7 was obtained.

<Carrier characteristics evaluation>
Hereafter, the evaluation method of a carrier is shown.
[Weight average particle diameter of core particles]
As a particle size analyzer for measuring the particle size distribution in the embodiment, a Microtrac particle size analyzer (model HRA9320-X100: manufactured by Honeywell) was used.
The measurement conditions are as follows.
[1] Particle size range: 100-8 μm
[2] Channel length (channel width): 2 μm
[3] Number of channels: 46
[4] Refractive index: 2.42

[Average thickness of carrier coat resin layer]
Using a transmission electron microscope (TEM), the cross section of 10 carriers was observed (magnification 2000 times), and the average film thickness of the resin layer was measured.

[Dispersion state of power transmission maintenance particles in carrier coat resin layer]
Using a scanning electron microscope (SEM), a cross section of 10 carriers was observed (magnification of 2000 times), and the dispersion state of the convex portions of the conductive fine particles on the carrier surface layer was classified into the following ranks and evaluated.
◯: Convex portions derived from conductive fine particles are uniformly present on the carrier surface layer.
X: The presence of the convex portions derived from the conductive fine particles is biased, and there are portions where the convex portions are connected.

<Example of toner production>
100 parts of polyester resin [weight average molecular weight (Mw) 18,000, number average molecular weight (Mn) 4000, glass transition point (Tg) 59 ° C., softening point; 120 ° C.]
Mold release agent: Carnauba wax 5 parts Carbon black (# 44 manufactured by Mitsubishi Chemical Corporation) 10 parts Fluorine-containing quaternary ammonium salt 4 parts The above components are thoroughly mixed with a Henschel mixer and melt-kneaded with a twin-screw extruder. The kneaded product was rolled and cooled. After cooling, the mixture was coarsely pulverized with a cutter mill, then finely pulverized with a jet airflow fine pulverizer, and further classified with an air classifier to obtain toner base particles having a weight average particle diameter of 7.4 μm.
Further, 1.0 part of hydrophobic silica fine particles (R972: manufactured by Nippon Aerosil Co., Ltd.) were added to 100 parts of the toner base particles, and mixed with a Henschel mixer to obtain toner I.

<Production of developer>
Carrier Production Example To the carrier (93 parts) obtained in the Example and Carrier Production Example Comparative Example, 7.0 parts of the toner 1 (7.2 μm) obtained in the toner production example was added, and 20 minutes by a ball mill. With stirring, developer examples and developer comparative examples were prepared.
Hereinafter, the present invention will be described more specifically with respect to the developers of Examples and Comparative Examples, but the present invention is not limited thereto. “Parts” represents parts by weight.
The thickness b of the resin coating layer was obtained from an average value by observing the cross section of the carrier using a transmission electron microscope (TEM), measuring the thickness of the resin portion of the resin coating layer covering the carrier surface.
Specifically, the distance from the carrier cross section to any 50 core material surfaces and the coating layer surface was measured, and the average of the measured values was obtained as the thickness b (μm) of the resin coating layer.

(Examples and Comparative Examples)
After an initial image was output using the developer examples and developer comparative examples, this developer was mounted on an ImageColor 4000 and stirred for 10 minutes in the single color mode. Thereafter, 100,000 sheets were run using a chart with an image area of 7%. After the test was completed, the image density, the image density of the highlight area, the graininess of the image, dirt on the ground, adhesion of the carrier, An image density variation and toner scattering were evaluated and used as examples and comparative examples.
Further, in Developer Example 4 (C4), instead of the toner of Example 1, a premix toner (replenishment developer) obtained by adding 10 parts of carrier production example 1 to 90 parts of toner of Example 1 Example 4 was performed by running 100,000 sheets in the same manner as in Example 1 except that excess developer was discharged.

(Actual machine quality evaluation)
Characteristic tests such as image quality confirmation and reliability test were made using Ricoh's Imagio Color 4000 (Ricoh's digital color copier / printer multifunction machine) under the following development conditions.
・ Development gap (photosensitive member-developing sleeve): 0.3 mm
・ Doctor gap (developing sleeve-doctor): 0.65mm
-Photoconductor linear velocity: 200 mm / sec
(Development sleeve linear velocity) / (photosensitive member linear velocity): 1.80
-Write density: 600 dpi
・ Charging potential (Vd): -600V
-Potential after exposure of the portion corresponding to the image portion (solid document): -100V
Development bias: DC -500V / AC bias component: 2KHz, -100V to -900V, 50% duty
Quality evaluation was performed on transfer paper. However, carrier adhesion was observed by transferring the state after development and before transfer onto the adhesive tape from the photoreceptor.

(Career evaluation items after actual machine evaluation)
"Changes in developer pumping amount"
Evaluation was performed according to the following formula and rank.
Fluctuation rate (%) of developer pumping amount = {(initial developer pumping amount−developer pumping amount after running 100,000 sheets) / initial developer pumping amount} × 100
However, the developer pumping amount on the developing sleeve = mg / cm ²
Less than ± 5%: ◎ Very good ± 5 to less than ± 10%: ○ Good ± 10 to less than ± 20%: △ Usable ± 20% or more: × Bad

“Amount of spent toner (amount of toner fused to the carrier surface)”
An initial developer (a new developer) and 6 g of a developer running 100,000 sheets are placed in a conductor container (cage) having metal meshes at both ends. The mesh (made of stainless steel) has a mesh size between the toner and the carrier (particle size 20 μm), and is set so that the toner passes between the meshes. When the compressed nitrogen gas (1 kgf / cm ² ) is blown from the nozzle for 60 seconds to eject the toner out of the cage, a carrier having a polarity opposite to the charge of the toner is left in the cage. For the carrier thus recovered, the toner component is extracted with methyl ethyl ketone, and the difference is expressed as the amount of spent toner (expressed in wt% with respect to the carrier weight).
0 or more to less than 0.03 wt%: ◎ very good 0.03 wt% or more to less than 0.07 t%: ○ good
0.07 wt% or more to less than 0.15 Wt%: △ Usable 0.15 wt% or more: X Defect

[Dispersion state of power transmission maintenance particles in carrier coat resin layer]
The initial developer and 6 g of the developer running 100,000 sheets are placed in a conductor container (cage) having metal meshes at both ends. The mesh (made of stainless steel) has a mesh size between the toner and the carrier (particle size 20 μm), and is set so that the toner passes between the meshes. When compressed nitrogen gas (1 kgf / cm ² ) is blown from the nozzle for 60 seconds to cause the toner to jump out of the gauge, a carrier having a polarity opposite to that of the toner charge remains in the cage. For the carrier thus recovered, the toner component is extracted with methyl ethyl ketone, and then the cross section of 10 carriers is observed using a scanning electron microscope (SEM). The degree of presence of (= exposed core material) was classified into the following ranks and evaluated.
○: Coated resin peeled portion (= core material exposed portion) is not seen Δ: Coat resin peeled portion (= core material exposed portion) is confirmed to be less than 10 per carrier particle ×: Coated resin peeled portion (= core 10 or more parts are confirmed per carrier particle).

(Image quality evaluation)
The test methods and evaluation criteria employed for image evaluation in the above image formation are as follows.
Image quality evaluation was carried out on transfer paper. However, the carrier adhesion was observed after transferring the state before transfer from the photosensitive member to the adhesive tape.

"Solid image density"
Under the above development conditions, the center of a solid part (Note 1) of 30 mm × 30 mm was measured at five locations with an X-Rite 938 spectrocolorimeter and the average value was obtained.
Note 1; development potential equivalent to 400V = (exposure portion potential−development bias DC) = − 100V − (− 500V)
1.55 or more: ◎ (very good)
1.50 to 1.55: ○ (good)
1.45 to 1.50: △ (can be used)
Less than 1.45: × (defect)

"Soil dirt"
The background stain was evaluated by visually checking the stain on the background on the image.
A: Very good, O: Good, Δ: Usable ×: Bad

"Carrier adhesion (solid part)"
If carrier adhesion occurs, it may cause damage to the photosensitive drum and the fixing roller, resulting in a decrease in image quality. Even if carrier adhesion occurs on the photoconductor, only a part of the carrier is transferred to the paper, and thus evaluation was made by the following method.
A solid image (30 mm × 30 mm) of IMAGIO COLOR 4000 under the aforementioned development conditions (charge potential (Vd): −600 V, potential after exposure of a portion corresponding to an image portion (solid original): −100 V, development bias: DC −500 V) The number of carriers adhering to () was counted on the photoconductor to evaluate solid carrier adhesion.
A: Very good, O: Good, Δ: Usable, X: Bad.
The evaluation results are shown in Table 1.

DESCRIPTION OF SYMBOLS 11 Cell 12a Electrode 12b Electrode 13 Carrier 20 Photoconductor drum 21 Toner 23 Carrier 24a Drive roller 24b Drive roller 26 Pre-cleaning exposure light source 32 Image carrier charging member 33 Image exposure system 40 Developing device 41 Developer sleeve 42 Developer accommodating member 43 Developer Agent supply restriction member (doctor blade)
44 support case 45 toner hopper 46 developer accommodating portion 47 developer agitating mechanism 48 toner agitator 49 toner replenishing mechanism 50 transfer mechanism 60 cleaning mechanism 61 cleaning blade 62 toner recovery chamber 64 brush-like cleaning means 70 neutralizing lamp 80 intermediate transfer medium

JP 60-0119156 A Japanese Patent Laying-Open No. 2005-091690

Claims (10)

On the surface of the carrier core material coated with the silane coupling agent, has a resin coating layer having a silicone resin containing conductive fine particles,
The electrophotographic carrier according to claim 1, wherein the conductive fine particles have an average particle diameter a of 0.15 to 0.5 μm and an average thickness b of the resin coating layer or more. The conductive fine particles are
An alumina substrate;
The electrophotographic carrier according to claim 1, further comprising a conductive coating layer containing tin dioxide.   The electrophotographic carrier according to claim 1, wherein the conductive fine particles contain tin dioxide in an amount of 4 wt% to 80 wt%.   The electrophotographic carrier according to claim 1, wherein the resin coating layer has an average film thickness of 0.08 μm or more and 0.3 μm or less.   The electrophotographic carrier according to claim 1, wherein the silane coupling agent is an amino group-containing silane coupling agent. The shape factors SF1, SF2 are
SF1 = (L ² / A) × (π / 4) × 100
And SF2 = (P ² / A) × (1 / 4π) × 100
Then, SF1 of the carrier core material is 100 to 120, and SF2 is 100 to 120. The carrier for electrophotography according to any one of claims 1 to 5,   A developer comprising the electrophotographic carrier according to claim 1 and a toner. A developer for replenishment containing 2 to 50 parts by mass of toner with respect to 1 part by mass of the carrier,
A developer for replenishment, wherein the carrier is the electrophotographic carrier according to claim 1.   The developer according to claim 7 or 8, wherein the electrostatic latent image carrier, a charging member for charging the surface of the electrostatic latent image carrier, and the electrostatic latent image formed on the electrostatic latent image carrier. A process cartridge comprising: a developing unit that develops the toner using a toner; and a cleaning member that cleans the electrostatic latent image carrier.   A step of forming an electrostatic latent image on the electrostatic latent image carrier, and an electrostatic latent image formed on the electrostatic latent image carrier are developed using the developer according to claim 7 or 8. Forming a toner image, transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and fixing the toner image transferred to the recording medium. An image forming method.

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