JP6862934B2 - Carrier, developer, replenisher developer, image forming apparatus, process cartridge and image forming method - Google Patents

Description

The present invention relates to a carrier, a developer, a replenishing developer, an image forming apparatus, a process cartridge, and an image forming method.

In image formation by the electrophotographic method, an electrostatic latent image is formed on an electrostatic latent image carrier, a toner image is formed on the electrostatic latent image using toner, and then the toner image is used as a recording medium. It is transferred and fixed to make an output image. In recent years, the technology of copiers and printers using the electrophotographic method has been rapidly expanding from monochrome to full color, and the full color market tends to expand.

In full-color image formation, generally, three color toners of yellow, magenta, and cyan, or four color toners in which black is added are laminated to reproduce all colors. Therefore, in order to obtain a clear full-color image with excellent color reproducibility, it is necessary to smooth the surface of the fixed toner image to reduce light scattering. For this reason, many latent image images of conventional full-color copiers and the like achieve high gloss by increasing the amount of toner adhered to the electrostatic latent image in order to achieve smoothness of the toner image. However, due to this, there is a problem of toner spending in which deteriorated toner adheres to the carrier surface during long-term printing.

Among the carrier deterioration caused by tonerspent, the increase in carrier resistance is a particular problem. In the field of production printing, whose market has been expanding in recent years, higher image quality than ever is required. When the carrier resistance is increased by the toner spend, the carrier is transferred onto the electrostatic latent image carrier, so-called carrier adhesion occurs, and there is a problem that the carrier appears as a white spot at the edge or center of the image. , The demand for this issue has become more severe in recent years.

On the other hand, it is conceivable to design the carrier resistance to be a particularly high level at the initial stage and maintain the required level even in long-term use, but in that case, the charge on the carrier surface develops. Immediately after, it does not leak properly, and there is a problem that the edge becomes thin when printing a halftone, for example.

From the above, the initial carrier resistance is low, and maintaining that level is essential for high-quality stabilization. Various attempts have been made to achieve the above technical concept. For example, by using a plurality of resins that are not suitable for the carrier coating resin, the conductive fine particles in the coating layer are unevenly distributed, the spent resistance of the carrier coating resin is utilized, and the carrier resistance is reduced by the conductive fine particles. There is a means (Patent Document 1)

However, in Patent Document 1, as the printing speed is increased, the effect of suppressing the toner spine by the coating resin is not enough, the resistance increases with the number of printed sheets, and the problem of carrier adhesion is unavoidable.

An object of the present invention is to provide a carrier capable of maintaining a desired level of carrier resistance for a long period of time and suppressing carrier adhesion for a long period of time.

In order to solve the above problems, the present invention is a carrier having a core material particles having magnetism and a coating layer for coating the surface thereof, and the coating layer contains a resin and conductive fine particles. The conductive fine particles contain any copper compound selected from copper oxide, copper sulfide, copper sulfate, copper chloride, copper carbonate, copper diversion molybdenum, copper graphite and iron powder, and the average of the coating layer. When the film thickness is h and the volume average particle size of the conductive fine particles is d, 0.5 ≦ d / h ≦ 2.0 is satisfied, and the conductive fine particles with respect to the coating layer obtained by the following measurement method are satisfied. The filling rate of the copper is 50% or more.
[Measuring method]
For 100 carrier particles, the filling ratio of the conductive fine particles with respect to the coating layer is determined from the areas of the conductive fine particles portion and the resin portion obtained by SEM (scanning electron microscope) observation of the carrier cross section.

According to the present invention, it is possible to provide a carrier capable of maintaining the resistance of the carrier at a desired level for a long period of time and suppressing carrier adhesion for a long period of time.

It is a schematic diagram which shows the structure of the carrier resistance measuring apparatus which measures the volume specific resistance of a carrier. It is a schematic explanatory drawing which shows an example of the process cartridge of this invention.

Hereinafter, the carrier, the developer, the replenishing developer, the image forming apparatus, the process cartridge, and the image forming method according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments shown below, and can be modified within the range conceivable by those skilled in the art, such as other embodiments, additions, modifications, and deletions. However, as long as the action and effect of the present invention are exhibited, it is included in the scope of the present invention.

(Career)
The present invention is a carrier having magnetic core material particles and a coating layer for coating the surface thereof. The coating layer contains resin and conductive fine particles, and the conductive fine particles are copper or copper. When the average film thickness of the coating layer is h and the volume average particle size of the conductive fine particles is d, which contains a compound, 0.5 ≦ d / h ≦ 2.0 is satisfied, and the coating layer is described as described above. It is characterized in that the filling rate of the conductive fine particles is 50% or more.

Conventionally, there has been a problem of so-called carrier adhesion, in which carriers are transferred onto an electrostatic latent image carrier due to an increase in carrier resistance due to a toner spend.
In the present invention, the highly conductive fine particles are effectively arranged in the coating layer, and the conductive fine particles function as a conduction circuit even when the toner is spun, and the initial resistance level can be maintained for a long period of time. Carrier adhesion can be suppressed.

Further, the coating layer contains fine particles to form irregularities on the coating layer, but the convex portions are subject to collision in the developing device and are easily scraped. As a result, the toner spine is deposited in the recess. In the present invention, the convex portion of the coating layer can continue to function as a particularly highly conductive point, and the conduction circuit can be formed from that point to the core material particles, so that the carrier resistance can be maintained low even if the coating layer is spun. Is possible. Therefore, the resistance of the carrier can be maintained at a desired level for a long period of time.

The following three points are particularly important points of the present invention.
First, the conductive fine particles in the coating layer contain copper or a copper compound. As described above, the conductive fine particles are required to continue to function as a conduction path, and for that purpose, they preferably have high conductivity, high impact resistance, and affinity with a resin. As a result of diligent studies by the present inventors, it has been found that conductive fine particles containing copper or a copper compound show a very excellent effect.

Second, the d / h satisfies 0.5 ≦ d / h ≦ 2.0. This can be said to be a condition for producing the optimum unevenness on the carrier surface by the conductive fine particles in order to achieve the technical concept. If d / h is less than 0.5, appropriate unevenness is not generated in the coating layer, and the toner spend impairs the function of the conductive fine particles as a conduction path, causing an increase in carrier resistance. Further, when d / h exceeds 2.0, the coating layer cannot retain the conductive fine particles, and as the d / h deteriorates, the conductive fine particles are detached, the core material particles are exposed, and a significant decrease in resistance is caused.

As described above, when d / h deviates from the desired range, the carrier resistance cannot be maintained at a desired level, and problems such as carrier adhesion occur. If d / h is less than 0.5, edge carrier adhesion occurs during long-term printing, and if d / h exceeds 2.0, solid carrier adhesion occurs during long-term printing.

Thirdly, the filling rate of the conductive fine particles with respect to the coating layer is 50% or more. As a result of repeated experiments, it was found that when it was less than 50%, a sufficient convex portion for maintaining the carrier resistance could not be obtained, and the carrier resistance tended to increase. Further, the filling rate is preferably 70% or more, and in this case, the increase in resistance can be suppressed even in a high humidity environment where the toner spend tends to be inferior.

As described above, according to the configuration of the present invention, the resistance of the carrier can be maintained at a desired level for a long period of time, and the adhesion of the carrier can be suppressed for a long period of time.
Further, according to the present invention, it is possible to maintain sufficient resistance to the image quality required in the field of production printing over a long period of time, and it is possible to supply a stable amount of developer to the developing region. Further, even in a high-speed machine using low-temperature fixing toner, continuous paper can be passed with a printing density of a high image area ratio. In addition, it has an extremely excellent effect of being able to provide a highly reliable image forming method, an image forming apparatus, and a process cartridge.

<Measurement of average film thickness h of coating layer, volume average particle diameter d of conductive fine particles, and filling rate>
The average film thickness h of the coating layer, the volume average particle size d of the conductive fine particles, and the filling rate can be measured by a known method, but in the present invention, the measurement is performed by the following method. That is, it can be performed by cutting the carrier with a FIB (focused ion beam) and observing the cross section with an SEM (scanning electron microscope) or the like.

The measurement method will be described with an example. First, the sample is adhered to the carbon tape, and osmium is coated with about 20 nm for surface protection and conductive treatment.
Next, for example, the FIB process is performed under the following conditions.

[Condition example]
NVision 40 manufactured by Carl Zeiss (SII)
Acceleration voltage: 2.0kV
Aperture: 30 μm
High Current: ON
Detector: SE2, InLens
Conductive treatment: None W. D: 5.0 mm
Sample tilt: 54 °

Next, SEM observation is performed on the cross section of the carrier under the following conditions, for example.

[Condition example]
Thermo Fisher Scientific Electronic Cooling SDD Detector UltraDry (Φ30mm ² )
Analysis software: NORAN System6 (NSS) manufactured by Thermo Fisher Scientific
Acceleration voltage: 3.0kV
Aperture: 120 μm
High Current: ON
Conductive treatment: 0s
Drift correction: Yes W. D: 10.0mm
Measurement method: Area Scan
Accumulation time: 10 sec
Number of integrations: 100 times Sample tilt: 54 °
Magnification: 10000 times

The result obtained by SEM observation is taken into a TIFF image, and after making an image of only particles using Image-Pro Plus manufactured by Media Cybernetics, binarization treatment is performed, and a white part (conductivity) in the coating layer part is performed. It decomposes into a black part (resin part) and a black part (resin part).

As for the particle size of the white part, 10 particles are randomly selected for each carrier, 100 particles of carriers are measured, and an average value is obtained.
For the black film thickness portion, auxiliary lines are randomly drawn in four directions from the center for each carrier particle, the thickness of the black portion (resin portion) on the auxiliary line is obtained, and the average value of the film thickness is obtained. .. If there are particles on the auxiliary line, only the thickness of the resin portion is calculated, and the average value is calculated. The same film thickness measurement is performed on the carrier 100 particles, and the average value is obtained.

Further, the filling rate of the conductive fine particles in the coating layer is determined from the white and black areas of the carrier 100 particles.

<Constituents of coating layer>
The coating layer of the carrier of the present invention contains a resin and conductive fine particles, and if necessary, contains other components.

<< Conductive fine particles >>
The conductive fine particles contained in the coating layer of the carrier of the present invention include copper or a copper compound.
Examples of the copper include copper powder and the like.
The copper compound may be any compound containing copper, and a compound having a outermost surface layer of copper is preferable. Examples of the copper compound include copper oxide, copper sulfide, copper sulfate, copper chloride, copper carbonate, copper diversion molybdenum, copper graphite, iron powder and the like, and copper oxide is particularly preferable.

The volume average particle diameter of the conductive fine particles is preferably 1.0 μm to 2.0 μm. If it is 1.0 μm or more, the conductive fine particles exert an excellent effect in fulfilling the function of the carrier convex portion regardless of the film thickness of the carrier. Further, if the thickness is 2.0 μm or less, it is particularly advantageous in that there is little separation from the hazard of the developing device. It is considered that this is related to the kinetic energy of the core material particles and the natural vibration, but the exact reason has not been clarified.

The conductive fine particles may contain, for example, tin oxide, alumina, titanium oxide, barium sulfate, etc., in addition to copper or a copper compound. In this case, the content of copper or the copper compound is preferably 20% by mass or more in the conductive fine particles.
In addition to the conductive fine particles containing copper or a copper compound, other conductive fine particles and non-conductive fine particles can also be used in the coating layer (described later).

<< Resin >>
The resin contained in the coating layer preferably contains a heat-treated product of a copolymer having a component A represented by the following general formula (A) and a component B represented by the following general formula (B). .. In this case, the effect of retaining the conductive fine particles in the coating layer is further improved even for long-term printing.

(In the general formula (A) and the general formula (B), R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkyl group having 1 to 4 carbon atoms, and R ³ represents 1 to 8 carbon atoms. Represents an alkyl group or an alkoxy group having 1 to 4 carbon atoms, m represents an integer of 1 to 8, X represents 10 to 90 mol%, and Y represents 10 to 90 mol%.)

The copolymer (1) containing the A component and the B component is shown below.

The copolymer (1) is obtained by radical copolymerizing the monomer component represented by the general formula (A) and the monomer component represented by the general formula (B). The heat-treated product of the copolymer (1) is obtained by hydrolyzing the copolymer (1) to generate a silanol group, cross-linking and coating by condensing with a catalyst, and then heat-treating. Can be done.

In the component A, X is 10 to 90 mol%, more preferably 30 to 70 mol%.
The A component has an atomic group, tris (trimethylsiloxy) silane in which a large number of methyl groups are present in the side chain, and the higher the ratio of the A component to the entire resin, the smaller the surface energy, and the resin component of the toner. , Adhesion of wax components etc. is reduced.

If the A component is less than 10 mol%, the above effect may not be sufficiently obtained and the adhesion of the toner component may increase. On the other hand, if it is more than 90 mol%, the B component and the C component described later may be reduced, the cross-linking may not proceed, and the toughness may be insufficient. Further, the adhesiveness between the core material particles and the coating layer is lowered, and the durability of the carrier coating may be deteriorated.

Examples of the component A include the following tris (trialkylsiloxy) silane compounds and the like. In the following formula, Me is a methyl group, Et is an ethyl group, and Pr is a propyl group.

CH ₂ = CMe-COO-C ₃ H _6- Si (OSiMe ₃ ) ₃
CH ₂ = CH-COO-C ₃ H _6- Si (OSiMe ₃ ) ₃
CH ₂ = CMe-COO-C ₄ H _8- Si (OSiMe ₃ ) ₃
CH ₂ = CMe-COO-C ₃ H _6- Si (OSiEt ₃ ) ₃
CH ₂ = CH-COO-C ₃ H _6- Si (OSiEt ₃ ) ₃
CH ₂ = CME-COO-C ₄ H _8- Si (OSiEt ₃ ) ₃
CH ₂ = CMe-COO-C ₃ H _6- Si (OSiPr ₃ ) ₃
CH ₂ = CH-COO-C ₃ H _6- Si (OSiPr ₃ ) ₃
CH ₂ = CME-COO-C ₄ H _8- Si (OSiPr ₃ ) ₃

The method for producing the component A is not particularly limited, but a method of reacting tris (trialkylsiloxy) silane with allyl acrylate or allyl methacrylate in the presence of a platinum catalyst, or a carboxylic acid described in JP-A-11-217389. Examples thereof include a method of reacting a methacryloxyalkyltrialkoxysilane with a hexaalkyldisiloxane in the presence of an acid and an acid catalyst.

The component B is a radically polymerizable bifunctional or trifunctional silane compound, and Y is 10 to 90 mol%, more preferably 30 to 70 mol%.
If it is less than 10 mol%, sufficient toughness may not be obtained. On the other hand, if it is more than 90 mol%, the film becomes hard and brittle, and film scraping may occur. In addition, environmental characteristics may deteriorate. It is also considered that a large number of hydrolyzed cross-linking components remain as silanol groups, which worsens the environmental characteristics (humidity dependence).

Examples of such B component include 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltriethoxysilane, and 3-methacryloxypropyl. Examples thereof include methyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacrythoxypropyltri (isopropoxy) silane, and 3-acryloxypropyltri (isopropoxy) silane.

Further, in addition to the A component and the B component, the C component (acrylic compound) represented by the following general formula (C) may be contained.

(In the general formula (C), R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkyl group having 1 to 4 carbon atoms, and Z represents 30 to 80 mol%.)

The one to which such a C component is added is represented as the following copolymer (2).

In the copolymer (2), X is preferably 10 to 40 mol%, Y is preferably 10 to 40 mol%, and Z is preferably 30 to 80 mol%. Further, it is preferable that 60 mol% <Y + Z <90 mol%.

The C component can impart flexibility to the coating film and improve the adhesiveness between the core material and the coating film, but if the C component is less than 30 mol%, sufficient adhesiveness may not be obtained. If it is larger than 80 mol%, either the A component or the B component is 10 mol% or less, so that it becomes difficult to achieve both water repellency and hardness of the carrier film and flexibility (film scraping).

As the acrylic compound (monomer) of the C component, an acrylic acid ester and a methacrylic acid ester are preferable, and specific examples thereof include methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, butyl methacrylate and butyl acrylate. Of these, alkyl methacrylate is preferred, and methyl methacrylate is more preferred. Further, one kind of these compounds may be used alone, or a mixture of two or more kinds may be used.

Further, as the C component, 2- (dimethylamino) ethyl methacrylate, 2- (dimethylamino) ethyl acrylate, 3- (dimethylamino) propyl methacrylate, 3- (dimethylamino) propyl acrylate may be used. Further, one kind of these compounds may be used alone, or a mixture of two or more kinds may be used.

The resin in the coating layer preferably contains a heat-treated product of the copolymer (2). Similar to the copolymer (1), the heat-treated product of the copolymer (2) hydrolyzes the copolymer (2) to generate a silanol group, which is crosslinked by condensing with a catalyst. After coating, it can be obtained by heat treatment.

As a high durability technique by cross-linking a coating film, for example, there is Japanese Patent No. 3691115. Patent No. 369115 describes a radical copolymerization of a magnetic particle surface having at least one functional group selected from the group consisting of an organopolysiloxane having a vinyl group at the terminal and a hydroxyl group, an amino group, an amide group and an imide group. It is a carrier for electrostatic charge image development characterized by coating a copolymer with a sex monomer with a thermosetting resin crosslinked with an isocyanate-based compound, but it has sufficient durability in peeling and scraping of the film. The current situation is that it has not been obtained.

The reason for this is not fully clear, but in the case of a thermosetting resin in which the above-mentioned copolymer is crosslinked with an isocyanate-based compound, as can be seen from the structural formula, the isocyanate in the copolymer resin There are few functional groups per unit weight that reacts (crosslinks) with the compound, and it is not possible to form a two-dimensional or three-dimensional dense cross-linked structure at the cross-linking point. Therefore, if it is used for a long time, the coating is likely to be peeled off or scraped (the abrasion resistance of the coating is small), and it is presumed that sufficient durability is not obtained.

When the film is peeled off or scraped, the image quality changes due to a decrease in carrier resistance and carrier adhesion occurs. In addition, peeling / scraping of the film reduces the fluidity of the developer, causes a decrease in the pumping amount, and causes a decrease in image density, background stains due to TC increase, and toner scattering.

The above-mentioned resin is a copolymer resin having a large number of bifunctional or trifunctional crosslinkable functional groups (points) (2 to 3 times more per unit weight) in terms of resin unit weight. Since this is further crosslinked by polycondensation, it is considered that the coating film is extremely tough and difficult to scrape, and high durability is achieved.

Further, since the cross-linking by siloxane bond has a larger binding energy and is more stable against thermal stress than the cross-linking by an isocyanate compound, it is presumed that the stability of the film over time is maintained.

Examples of the resin contained in the coating layer of the carrier include silicone resin, acrylic resin and the like in addition to those described above, or these can also be used in combination.
Above all, it is preferable to use a silicone resin and an acrylic resin together. Acrylic resin has strong adhesiveness and low brittleness, so it has excellent wear resistance. On the other hand, it has high surface energy, so when combined with toner that is easy to spent, toner component spent accumulates. This may cause problems such as a decrease in the amount of charge. In that case, this problem can be solved by using a silicone resin in which the surface energy is low, so that the toner component is less likely to be spinted, and the effect that the spent component is less likely to be accumulated due to the film scraping is obtained.

On the other hand, since silicone resin has weak adhesiveness and high brittleness, it also has a weakness of poor wear resistance. Therefore, it is preferable to obtain the properties of these two types of resins in a well-balanced manner. It is possible to obtain a coating film having a brittleness.

The above-mentioned silicone resin includes all generally known silicone resins, and includes straight silicon resins consisting only of organoshirosan bonds, silicone resins modified with alkyds, polyesters, epoxys, acrylics, urethanes, and the like. However, it is not limited to this. For example, as commercially available straight silicone resins, KR271, KR255, KR152 manufactured by Shin-Etsu Chemical Co., Ltd., SR2400, SR2406, SR2410 manufactured by Toray Dow Corning Silicone Co., Ltd. and the like can be mentioned. In this case, it is possible to use the silicone resin alone, but it is also possible to use other components that undergo a cross-linking reaction, a charge amount adjusting component, and the like at the same time.

Further, as the modified silicone resin, for example, KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical Co., Ltd., SR2115 (epoxy modified) manufactured by Toray Dow Corning Silicon Co., Ltd. ), SR2110 (alkyd modification) and the like.

<< Other ingredients >>
Examples of other components in the coating layer include other conductive fine particles other than conductive fine particles containing copper or a copper compound, non-conductive fine particles, a polycondensation catalyst, a silane coupling agent, and the like.

Other conductive fine particles include, for example, a filler formed of aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide, barium sulfate, zirconium oxide, etc. as a base and tin dioxide, indium oxide, etc. as a layer, carbon black, ITO, PTO, etc. WTO, tin oxide, polyaniline and the like can be used.
As the non-conductive fine particles, for example, a substrate such as aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide, barium sulfate, or zirconium oxide can be used.

Examples of the polycondensation catalyst include titanium-based catalysts, tin-based catalysts, zirconium-based catalysts, and aluminum-based catalysts. Of these, titanium-based catalysts that give excellent results are preferable, and among titanium-based catalysts, titanium diisopropoxybis (ethylacetacetate) is more preferable. It is considered that this is because the effect of promoting the condensation reaction of the silanol group is large and the catalyst is not easily deactivated.

In the present invention, the coating layer composition preferably contains a silane coupling agent. Thereby, the conductive fine particles in the coating layer can be stably dispersed.

The silane coupling agent is not particularly limited, but is r- (2-aminoethyl) aminopropyltrimethoxysilane, r- (2-aminoethyl) aminopropylmethyldimethoxysilane, r-methacryloxypropyltrimethoxysilane, N. -Β- (N-vinylbenzylaminoethyl) -r-aminopropyltrimethoxysilane hydrochloride, r-glycidoxypropyltrimethoxysilane, r-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, Vinyl triacetoxysilane, r-chloropropyltrimethoxysilane, hexamethyldisilazane, r-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride, r-chlor Propylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, allyltriethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyltrimethoxysilane, dimethyldiethoxysilane, 1,3-divinyltetramethyl Examples thereof include disilazane and methacryloxyethyldimethyl (3-trimethoxysilylpropyl) ammonium chloride, and two or more of them may be used in combination.

Commercially available silane coupling agents include AY43-059, SR6020, SZ6023, SH6026, SZ6032, SZ6050, AY43-310M, SZ6030, SH6040, AY43-026, AY43-031, sh6062, Z-6911, sz6300, sz6075, sz6079, sz6083, sz6070, sz6072, Z-6721, AY43-004, Z-6187, AY43-021, AY43-043, AY43-040, AY43-047, Z-6265, AY43-204M, AY43-048, Z- 6403, AY43-206M, AY43-206E, Z6341, AY43-210MC, AY43-083, AY43-101, AY43-013, AY43-158E, Z-6920, Z-6940 (manufactured by Toray Silicone Co., Ltd.) and the like. ..

The amount of the silane coupling agent added is preferably 0.1 to 10% by mass with respect to the resin in the coating layer. If the amount of the silane coupling agent added is less than 0.1% by mass, the adhesiveness between the core material particles and the conductive fine particles and the resin in the coating layer is lowered, and the coating layer falls off during long-term use. If it exceeds 10% by mass, toner filming may occur during long-term use.

<Core particle>
In the present invention, the core material particles are not particularly limited as long as they have magnetism, but for example, ferromagnetic metals such as iron and cobalt; iron oxides such as magnetite, hematite and ferrite; various alloys and compounds; Examples thereof include resin particles in which a magnetic material is dispersed in a resin. Of these, Mn-based ferrite, Mn-Mg-based ferrite, and Mn-Mg-Sr ferrite are preferable from the viewpoint of the environment.

<Other physical characteristics of the carrier>
The carrier of the present invention preferably has a volume average particle diameter of 28 μm or more and 40 μm or less. If the volume average particle size of the carrier particles is less than 28 μm, carrier adhesion may occur, and if it exceeds 40 μm, the reproducibility of image details may deteriorate and a fine image may not be formed.

The volume average particle size can be measured using, for example, the Microtrack particle size distribution meter model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.).

The carrier of the present invention preferably has a volume specific resistance of 8 to 16 [LogΩ · cm]. If the volume specific resistance is less than 8 [LogΩ · cm], carrier adhesion may occur in the non-image area, and if it exceeds 16 [LogΩ · cm], the edge effect may become an unacceptable level.

The volume specific resistance can be measured using the cell shown in FIG. As a specific example, first, the carrier 13 is filled in a cell made of a fluororesin container 11 in which electrodes 12a and 12b having a surface area of 2.5 cm × 4 cm are housed at a distance of 0.2 cm, and the drop height is increased. Tapping is performed 10 times at 1 cm and a tapping speed of 30 times / minute. Next, a DC voltage of 1000 V was applied between the electrodes 12a and 12b, and the resistance value r [Ω] 30 seconds later was measured using a high resistance meter 4329A (manufactured by Yokogawa Hulett Packard), and the following formula was used. From (1), the volume specific resistance [Ω · cm] can be calculated.

(Developer)
The developer of the present invention has the carrier and toner of the present invention.
The toner contains, for example, a binder resin and a colorant, and may be either a monochrome toner or a color toner. Further, the toner particles may contain a mold release agent in order to apply to an oilless system in which the fixing roller is not coated with the toner sticking prevention oil. Such toners are generally prone to filming, but the carriers of the present invention can suppress filming, so that the developer of the present invention can maintain good quality for a long period of time. it can. Further, color toners, particularly yellow toners, generally have a problem that color stains are generated due to scraping of the coating layer of the carrier, but the developer of the present invention can suppress the occurrence of color stains.

The toner can be produced by using a known method such as a pulverization method or a polymerization method. For example, when a toner is produced by using a pulverization method, first, the melt-kneaded product obtained by kneading the toner material is cooled, then pulverized and classified to produce parent particles. Next, in order to further improve the transferability and durability, an external additive is added to the parent particles to prepare a toner.

At this time, the apparatus for kneading the toner material is not particularly limited, but is a batch type two-roll; Banbury mixer; KTK type twin-screw extruder (manufactured by Kobe Steel Co., Ltd.), TEM type twin-screw extruder (Toshiba Machine Co., Ltd.) Continuous twin-screw extruder such as twin-screw extruder (manufactured by KCK), PCM-type twin-screw extruder (manufactured by Ikekai Iron Works), KEX-type twin-screw extruder (manufactured by Kurimoto Iron Works); Examples thereof include a continuous type uniaxial kneader such as Ko Nida (manufactured by Buss).

When crushing the cooled melt-kneaded product, it is roughly crushed using a hammer mill, a rotoplex, or the like, and then finely pulverized using a pulverizer using a jet stream, a mechanical pulverizer, or the like. be able to. It is preferable to grind so that the average particle size is 3 to 15 μm.

Further, when classifying the crushed molten kneaded product, a wind classifier or the like can be used. It is preferable to classify the matrix particles so that the average particle size is 5 to 20 μm.
Further, when the external additive is added to the matrix particles, the external additive is crushed and adheres to the surface of the matrix particles by mixing and stirring using mixers.

The binder resin is not particularly limited, but is a homopolymer of styrene such as polystyrene, polyp-styrene, polyvinyltoluene and its substitution product; styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene. -Vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-methacrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer , Styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinylmethyl ether copolymer, styrene-vinylmethylketone copolymer, styrene-butadiene Styrene-based copolymers such as copolymers, styrene-isoprene copolymers, styrene-maleic acid ester copolymers; polymethylmethacrylate, butylpolymethacrylate, vinyl chloride, vinylacetate, polyethylene, polyester, polyurethane , Epoxy resin, polyvinyl butyral, polyacrylic acid, rosin, modified rosin, terpen resin, phenol resin, aliphatic or aromatic hydrocarbon resin, aromatic petroleum resin and the like, and two or more of them may be used in combination.

The binder resin for pressure fixing is not particularly limited, but is a polyolefin such as low molecular weight polyethylene and low molecular weight polypropylene; ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, and styrene-methacrylic acid copolymer. , Ethylene-methacrylic acid ester copolymer, ethylene-vinyl chloride copolymer, ethylene-vinyl acetate copolymer, olefin copolymer such as ionomer resin; epoxy resin, polyester, styrene-butadiene copolymer, polyvinylpyrrolidone, Examples thereof include a methyl vinyl ether-maleic anhydride copolymer, a maleic acid-modified phenol resin, and a phenol-modified terpene resin, and two or more of them may be used in combination.

The colorant (pigment or dye) is not particularly limited, but Cadmium Yellow, Mineral Fast Yellow, Nickel Titanium Yellow, Nabres Yellow, Naftor Yellow S, Hansa Yellow G, Hansa Yellow 10G, Benzidine Yellow GR, Kinolin Yellow Lake, Yellow pigments such as permanent yellow NCG and tartrazine lake; orange pigments such as molybdenum orange, permanent orange GTR, pyrazolone orange, vulcan orange, indance lem brilliant orange RK, benzidine orange G, indance lem brilliant orange GK; red iron oxide, cadmium Red pigments such as Red, Permanent Red 4R, Resole Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamin Lake B, Alizarin Lake, Brilliant Carmine 3B; Fast Violet B, Methyl Violet Lake Purple pigments such as cobalt blue, alkaline blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue partially chlorinated, first sky blue, indanslen blue BC and other blue pigments; chrome green, chromium oxide, pigment Green pigments such as Green B and Malakite Green Lake; azine pigments such as carbon black, oil furnace black, channel black, lamp black, acetylene black and aniline black, metal salt azo pigments, metal oxides, composite metal oxides, etc. Examples include black pigments, and two or more of them may be used in combination.

The release agent is not particularly limited, and examples thereof include polyolefins such as polyethylene and polypropylene, fatty acid metal salts, fatty acid esters, paraffin wax, amide wax, polyhydric alcohol wax, silicone varnish, carnauba wax, and ester wax. , Two or more types may be used together.

In addition, the toner may further contain a charge control agent. The charge control agent is not particularly limited, but is niglosin; an azine dye having an alkyl group having 2 to 16 carbon atoms (see Japanese Patent Publication No. 42-1627); I. Basic Yellow 2 (CI 41000), C.I. I. Basic Yellow 3, C.I. I. Basic Red 1 (CI 45160), C.I. I. Basic Red 9 (CI 42500), C.I. I. Basic Violet 1 (CI 42535), C.I. I. Basic Violet 3 (CI 42555), C.I. I. Basic Violet 10 (CI 45170), C.I. I. Basic Violet 14 (CI 42510), C.I. I. Basic Blue 1 (CI 42025), C.I. I. Basic Blue 3 (CI 51005), C.I. I. Basic Blue 5 (CI 42140), C.I. I. Basic Blue 7 (CI 42595), C.I. I. Basic Blue 9 (CI 52015), C.I. I. Basic Blue 24 (CI 52030), C.I. I. Basic Blue25 (CI52025), C.I. I. Basic Blue 26 (CI44045), C.I. I. Basic Green 1 (CI 42040), C.I. I. Basic dyes such as Basic Green 4 (CI 42000); rake pigments of these basic dyes; C.I. I. Quadruple ammonium salts such as Solvent Black 8 (CI 26150), benzoylmethylhexadecylammonium chloride, decyltrimethyl chloride; dialkyltin compounds such as dibutyl and dioctyl; dialkyltinborate compounds; guanidine derivatives; vinyls with amino groups Polyamine resins such as based polymers and condensed polymers having an amino group; described in Japanese Patent Publication No. 41-20153, Japanese Patent Publication No. 43-27596, Japanese Patent Publication No. 44-6397, and Japanese Patent Publication No. 45-26478. Metal complex salts of monoazo dyes; Sartylic acid described in Japanese Patent Publication No. 55-42752, Japanese Patent Publication No. 59-7385; Zn, Al, Co, Cr, Fe, etc. of dialkylsartylic acid, naphthoic acid, dicarboxylic acid, etc. Metal complexes; sulfonated copper phthalocyanine pigments; organic boron salts; fluorine-containing quaternary ammonium salts; calix-allene compounds and the like, but two or more of them may be used in combination. For color toners other than black, a metal salt of a white salicylic acid derivative or the like is preferable.

The external additive is not particularly limited, but is an inorganic particle such as silica, titanium oxide, alumina, silicon carbide, silicon nitride, or boron nitride; a poly having an average particle size of 0.05 to 1 μm obtained by a soap-free emulsion polymerization method. Examples thereof include resin particles such as methyl methacrylate particles and polystyrene particles, and two or more of them may be used in combination. Of these, metal oxide particles such as silica and titanium oxide whose surface is hydrophobized are preferable. Furthermore, by using the hydrophobized silica and the hydrophobized titanium oxide in combination and increasing the amount of the hydrophobized titanium oxide added as compared with the hydrophobized silica, the amount of the hydrophobized titanium oxide is increased with respect to the humidity. A toner having excellent charge stability can be obtained.

By using the carrier of the present invention as a replenishing developer composed of a carrier and toner and applying it to an image forming apparatus that forms an image while discharging excess developing agent in the developing apparatus, stable image quality can be obtained for an extremely long period of time. can get. That is, the deteriorated carriers in the developing apparatus and the non-deteriorated carriers in the replenishing developing agent are replaced to keep the charge amount stable for a long period of time, and a stable image can be obtained. This method is particularly effective when printing a high image area.

When printing a high image area, the carrier charge deterioration due to the toner spent on the carrier is the main carrier deterioration. However, by using this method, the carrier replenishment amount increases when the image area is high, so that the deteriorated carriers are replaced. The frequency goes up. As a result, a stable image can be obtained for an extremely long period of time.

The mixing ratio of the replenishing developer is preferably 2 to 50 parts by mass of 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 replenished carriers is too large, the carrier supply is excessive, and the carrier concentration in the developing apparatus becomes too high, so that the charged amount of the developer tends to increase. Further, as the amount of charge of the developer increases, the developing ability decreases and the image density decreases. If it exceeds 50 parts by mass, the carrier ratio in the replenishing developer is reduced, so that the carriers in the image forming apparatus are less replaced, and the effect on carrier deterioration cannot be expected.

(Image formation method)
In the image forming method of the present invention, 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 subjected to the developer of the present invention. It includes a step of developing and forming a toner image, a step of transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and a step of fixing the toner image transferred to the recording medium. Further, it has other steps appropriately selected as necessary, such as a static elimination step, a cleaning step, a recycling step, a control step and the like.

(Process cartridge)
The process cartridge of the present invention uses an electrostatic latent image carrier, a charging means for charging the electrostatic latent image carrier, and an electrostatic latent image formed on the electrostatic latent image carrier with the developer of the present invention. It has a developing means for developing using and a cleaning means for cleaning the electrostatic latent image carrier.

FIG. 2 shows an example of the process cartridge of the present invention. In the process cartridge of the present embodiment, the photoconductor 101 (electrostatic latent image carrier), the charging device 102 for charging the photoconductor 101, and the electrostatic latent image formed on the photoconductor 101 are used with the developer of the present invention. A developing device 104 that develops to form a toner image and a cleaning device 107 that removes the toner remaining on the photoconductor 101 after transferring the toner image formed on the photoconductor 101 to a recording medium 105 are integrally supported. Has been done. The process cartridge of this embodiment can be attached to and detached from the main body of an image forming apparatus such as a copying machine or a printer.

Hereinafter, a method of forming an image using an image forming apparatus equipped with the process cartridge of the present embodiment will be described. First, the photoconductor 101 is rotationally driven at a predetermined peripheral speed, and the peripheral surface of the photoconductor 101 is uniformly charged to a predetermined positive or negative potential by the charging device 102. Next, the peripheral surface of the photoconductor 101 is irradiated with the exposure light 103 from an exposure device such as a slit exposure type exposure device or an exposure device that scans and exposes with a laser beam, and an electrostatic latent image is sequentially formed.

Further, the electrostatic latent image formed on the peripheral surface of the photoconductor 101 is developed by the developing apparatus 104 using the developing agent of the present invention to form a toner image.
Next, the toner image formed on the peripheral surface of the photoconductor 101 is sequentially transferred from the paper feed unit to the transfer paper fed between the photoconductor 101 and the transfer device in synchronization with the rotation of the photoconductor 101. Will be done. Further, the transfer paper on which the toner image is transferred is separated from the peripheral surface of the photoconductor 101, introduced into the fixing device 106 and fixed, and then printed out as a copy to the outside of the image forming device. Toner.
On the other hand, the surface of the photoconductor 101 after the toner image is transferred is cleaned by removing the residual toner by the cleaning device 107, and then statically removed by the static eliminator, and is repeatedly used for image formation.

(Image forming device)
The image forming apparatus of the present invention includes an electrostatic latent image carrier, a charging means for charging the electrostatic latent image carrier, an exposure means for forming an electrostatic latent image on the electrostatic latent image carrier, and electrostatic. A developing means for developing a latent image formed on a latent image carrier by using the developer of the present invention to form a toner image, and recording a toner image formed on the latent image carrier are recorded. It has a transfer means for transferring to a medium and a fixing means for fixing a toner image transferred to a recording medium. Further, it has other means appropriately selected as necessary, such as static elimination means, cleaning means, recycling means, control means and the like.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples. In addition, hereinafter, "part" means "mass part". Further, Example 15 is Reference Example 15 which is not included in the present invention.

(Example of resin synthesis)
300 g of toluene was put into a flask equipped with a stirrer, and the temperature was raised to 90 ° C. under a nitrogen gas stream. Next, _{3-methacryloxypropyltris (trimethylsiloxy) silane represented by CH 2} = CMe-COO-C ₃ H _6- Si (OSiMe ₃ ) ₃ (Me is a methyl group in the formula) 84. 4 g (200 mmol: Cyraplane TM-0701T / manufactured by Chisso), 39 g (150 mmol) of 3-methacryloxypropylmethyldiethoxysilane, 65.0 g (650 mmol) of methyl methacrylate, and 2,2'-azobis-2- A mixture of 0.58 g (3 mmol) of methylbutyronitrile was added dropwise over 1 hour. As a result, the copolymer R1 was obtained.
After completion of the dropping, a solution prepared by dissolving 0.06 g (0.3 mmol) of 2,2'-azobis-2-methylbutyronitrile in 15 g of toluene was further added (2,2'-azobis-2-methylbutyro). A total amount of nitrile of 0.64 g = 3.3 mmol) was mixed at 90 to 100 ° C. for 3 hours to obtain a [R1 resin solution] (heat-treated product of copolymer R1).

(Production example of conductive fine particles)
Using several grades of copper oxide particles (manufactured by DOWA Electronics Co., Ltd.), the particles were adjusted to a desired particle size by airflow classification to obtain [particles 1] to [particles 8].
Alumina (AA-1.5 manufactured by Sumitomo Chemical Co., Ltd.) was used as [particle 9], barium sulfate (W-1 manufactured by Takehara Chemical Co., Ltd.) was used as [particle 10], and carbon black (particle 11) was used as [particle 11]. ECP600JD manufactured by Lion Specialty Chemicals Co., Ltd.) was used.
Further, copper particles (manufactured by FUKUDA) were used as [particles 12], and copper sulfate (manufactured by FPC Connect) was used as [particles 13], and the particle size was adjusted to a desired value by airflow classification.

Table 1 shows the types of particles obtained and the volume average particle diameter.

(Example of core material manufacturing)
MnCO ₃ , Mg (OH) ₂ , Fe ₂ O ₃ and SrCO ₃ powders were weighed and mixed to obtain a mixed powder. This mixed powder was calcined in an air atmosphere at 800 ° C. for 2 hours in a heating furnace, and the obtained calcined product was cooled and then pulverized to obtain a powder having a particle size of 3 μm or less. This powder was added with 1% by mass of a dispersant together with water to form a slurry, and this slurry was supplied to a spray dryer for granulation to obtain a granulated product having an average particle size of about 40 μm. This granulated product was loaded into a baking furnace and baked in a nitrogen atmosphere at 1120 ° C. for 4 hours.
After crushing the obtained fired product with a crusher, the particle size was adjusted by sieving to obtain spherical ferrite particles having a volume average particle size of about 35 μm and a BET specific surface area of 0.18 m ^{2 / g.}

(Toner manufacturing example)
<Synthesis of polyester resin A>
65 parts of ethylene oxide 2 mol adduct of bisphenol A, 86 parts of propion oxide 3 mol adduct of bisphenol A, 274 parts of terephthalic acid and 2 parts of dibutyltin oxide are put into a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube. Then, the reaction was carried out at 230 ° C. for 15 hours under normal pressure. Next, the reaction was carried out under reduced pressure of 5 to 10 mmHg for 6 hours to synthesize [polyester resin A]. The obtained [polyester resin A] has a number average molecular weight (Mn) of 2,300, a weight average molecular weight (Mw) of 8,000, a glass transition temperature (Tg) of 58 ° C., an acid value of 25 mgKOH / g, and a hydroxyl group. The value was 35 mgKOH / g.

<Styrene-Acrylic Resin A Synthesis>
300 parts of ethyl acetate, 185 parts of styrene, 115 parts of acrylic monomer and 5 parts of azobisisobutynitrile were put into a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, and the temperature was 65 ° C. (normal pressure) under a nitrogen atmosphere. ) For 8 hours. Next, 200 parts of methanol was added, and the mixture was stirred for 1 hour, the supernatant was removed, and the mixture was dried under reduced pressure to synthesize [styrene-acrylic resin A]. The obtained [styrene-acrylic resin A] had a Mw of 20,000 and a Tg of 58 ° C.

<Synthesis of prepolymer (polymer capable of reacting with active hydrogen group-containing compound)>
682 parts by mass of bisphenol A ethylene oxide 2 mol adduct, 81 parts by mass of bisphenol A propylene oxide 2 mol adduct, 283 parts by mass of terephthalic acid, trimellitic anhydride in a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube. 22 parts by mass and 2 parts by mass of dibutyltin oxide were charged and reacted at 230 ° C. for 8 hours under normal pressure. Then, the reaction was carried out under reduced pressure of 10 to 15 mHg for 5 hours to synthesize an intermediate polyester.
The obtained intermediate polyester has a number average molecular weight (Mn) of 2,100, a weight average molecular weight (Mw) of 9,600, a glass transition temperature (Tg) of 55 ° C., an acid value of 0.5, and a hydroxyl value. It was 49.
Next, 411 parts by mass of the intermediate polyester, 89 parts by mass of isophorone diisocyanate, and 500 parts by mass of ethyl acetate were charged in a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, and reacted at 100 ° C. for 5 hours. [Prepolymer] (a polymer capable of reacting with an active hydrogen group-containing compound) was synthesized.
The free isocyanate content of the obtained [prepolymer] was 1.60% by mass, and the solid content concentration of the prepolymer (after standing at 150 ° C. for 45 minutes) was 50% by mass.

<Synthesis of ketimin (active hydrogen group-containing compound)>
30 parts by mass of isophoronediamine and 70 parts by mass of methylethylketone were placed in a reaction vessel in which a stirring rod and a thermometer were set, and the reaction was carried out at 50 ° C. for 5 hours to synthesize a [ketimine compound] (active hydrogen group-containing compound). .. The amine value of the obtained [ketimine compound] (active hydrogen machine-containing compound) was 423.

<Making a masterbatch>
Henschel mixer (manufactured by Mitsui Mining Co., Ltd.) with 1,000 parts of water, 540 parts of carbon black Printex35 (manufactured by Degussa) with DBP oil absorption of 42 mL / 100 g and pH of 9.5, and 1,200 parts of [polyester resin A]. ) Was used for mixing. Next, using two rolls, the obtained mixture was kneaded at 150 ° C. for 30 minutes, rolled and cooled, and pulverized with a palperizer (manufactured by Hosokawa Micron Co., Ltd.) to prepare a [master batch].

<Preparation of aqueous medium>
306 parts of ion-exchanged water, 265 parts of a 10 mass% suspension of tricalcium phosphate and 1.0 part of sodium dodecylbenzenesulfonate were mixed and stirred to uniformly dissolve them to prepare an [aqueous medium].

-Measurement of critical micelle concentration-
The critical micelle concentration of the surfactant was measured by the following method. Analysis was performed using an analysis program in the Sigma system using a surface tension meter Sigma (manufactured by KSV Instruments). The surfactant was added dropwise to the [aqueous medium] in an amount of 0.01% by mass, and the interfacial tension after stirring and standing was measured. From the obtained surface tension curve, the concentration of the surfactant at which the surfactant does not decrease even when the surfactant is dropped was calculated as the critical micelle concentration. When the critical micelle concentration of sodium dodecylbenzenesulfonate with respect to the aqueous medium was measured with a surface tension meter Sigma, it was 0.05% by mass with respect to the weight of the aqueous medium.

<Dissolution of toner material or preparation of dispersion>
70 parts of [Polyester resin A], 10 parts by mass of [Prepolymer] and 100 parts of ethyl acetate were placed in a beaker and dissolved by stirring. Add 5 parts of paraffin wax (HNP-9 manufactured by Nippon Seiko Co., Ltd., melting point 75 ° C.), 2 parts of MEK-ST (manufactured by Nissan Chemical Industries, Ltd.), and 10 parts of [Masterbatch] as a mold release agent. Using a Viscomill (manufactured by Imex), after 3 passes under the condition that the liquid feeding speed is 1 kg / hour, the peripheral speed of the disc is 6 m / sec, and 80% by mass of zirconia beads having a particle size of 0.5 mm is filled, then [Ketimin] ] 2.7 parts by mass was added and dissolved to prepare a [dissolved or dispersion] of the toner material.

<Emulsification or preparation of dispersion>
[Aqueous medium] 150 parts by mass is placed in a container, and a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) is used to stir at a rotation speed of 12,000 rpm. Parts were added and mixed for 10 minutes to prepare an [emulsified or dispersion] (emulsified slurry).

<Removal of organic solvent>
100 parts by mass of [emulsified or dispersed liquid] (emulsified slurry) was charged into a corben set with a stirrer and a thermometer, and the solvent was removed at 30 ° C. for 12 hours while stirring at a stirring peripheral speed of 20 m / min to obtain a dispersed slurry. It was.

<Washing>
After 100 parts by mass of the dispersed slurry was filtered under reduced pressure, 100 parts by mass of ion-exchanged water was added to the filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered. 300 parts by mass of ion-exchanged water was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered twice. To the obtained filtered cake, 20 parts by mass of a 10 mass% sodium hydroxide aqueous solution was added, mixed with a TK homomixer (rotation speed 12,000 rpm for 30 minutes), and then filtered under reduced pressure. 300 parts by mass of ion-exchanged water was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered. 300 parts by mass of ion-exchanged water was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered twice. Further, 20 parts by mass of 10% by mass hydrochloric acid was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered.

<Adjusting the amount of surfactant>
300 parts by mass of ion-exchanged water was added to the filtered cake obtained by the above washing, and the electric conductivity of the toner dispersion liquid when mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes) was measured. , The surfactant concentration of the toner dispersion was calculated from the calibration curve of the surfactant concentration prepared in advance. From that value, ion-exchanged water was added so that the surfactant concentration became the target surfactant concentration of 0.05% by mass, and a toner dispersion liquid was obtained.

<Surface treatment process>
The toner dispersion liquid adjusted to the predetermined surfactant concentration was heated in a water bath at a heating temperature of T1 = 55 ° C. for 10 hours while mixing with a TK homomixer at 5000 rpm. Then, the toner dispersion was cooled to 25 ° C. and filtered. Further, 300 parts by mass of ion-exchanged water was added to the obtained filtered cake, mixed with a TK homomixer (rotation speed 12,000 rpm for 10 minutes), and then filtered.

<Drying>
The obtained final filtered cake was dried at 45 ° C. for 48 hours in a circulation dryer and sieved with a mesh having a mesh size of 75 μm to obtain [Toner Mother Particle 1].

<External processing>
Further, with respect to 100 parts by mass of [Toner matrix particles 1], 3.0 parts by mass of hydrophobic silica having an average particle size of 100 nm, 1.0 part by mass of titanium oxide having an average particle size of 20 nm, and an average particle size of 15 nm. Hydrophobic silica fine powder was mixed with 1.5 parts by mass with a Henshell mixer to obtain [Toner 1].

(Example 1)
Silicone resin solution (solid content 20% by mass) 646 parts by mass, aminosilane (solid content 100% by mass) 12 parts, conductive fine particles [particle 1] 460 parts by mass, titanium diisopropoxybis (ethylacetoacetate) TC as a catalyst A resin solution was obtained by diluting 31 parts by mass of −750 (manufactured by Matsumoto Fine Chemicals Co., Ltd.) with 750 parts by mass of toluene.
Using the ferrite particles obtained in the above core material production example as the core material particles, a atomizing nozzle was used in the fluidized bed coating device, and the temperature inside the fluidized bed was controlled to 65 ° C. for coating and drying. .. The obtained carrier was calcined in an electric furnace at 250 ° C. for 1 hour to obtain [Carrier 1]. 930 parts by mass of the obtained [Carrier 1] and 70 parts by mass of [Toner 1] were mixed and stirred at 81 rpm for 4 minutes using a turbuler mixer to prepare a developer for evaluation. The replenishing developer was produced by using the carrier and the toner so that the toner concentration was 95% by mass (19 parts by mass of the toner with respect to 1 part by mass of the carrier).

(Examples 2 to 16, Comparative Examples 1 to 8)
The manufacturing method was the same as in Example 1, and the materials used and the number of copies were changed as shown in Table 2 to prepare carriers. Further, a developer was prepared in the same manner as in Example 1.
In Example 14, the conductive fine particles were [particle 1] 300 parts by mass and [particle 9] 238 parts by mass.

(Measurement and evaluation)
The obtained carrier characteristics were measured and evaluated as follows. The results are shown in Tables 3 and 4.

<Measurement of average film thickness h of coating layer, volume average particle diameter d of conductive fine particles, and filling rate>
For the obtained carriers, d / h and filling rate were determined as follows. The carrier is cut with a FIB (focused ion beam), and the cross section thereof is observed with an SEM. First, the sample was adhered on the carbon tape, and osmium was coated at about 20 nm for surface protection and conductive treatment. Next, the FIB treatment was performed under the following conditions.

[Condition example]
NVision 40 manufactured by Carl Zeiss (SII)
Acceleration voltage: 2.0kV
Aperture: 30 μm
High Current: ON
Detector: SE2, InLens
Conductive treatment: None W. D: 5.0 mm
Sample tilt: 54 °

Next, SEM observation was performed on the carrier cross section under the following conditions.

[Condition example]
Thermo Fisher Scientific Electronic Cooling SDD Detector UltraDry (Φ30mm ² )
Analysis software: NORAN System6 (NSS) manufactured by Thermo Fisher Scientific
Acceleration voltage: 3.0kV
Aperture: 120 μm
High Current: ON
Conductive treatment: 0s
Drift correction: Yes W. D: 10.0mm
Measurement method: Area Scan
Accumulation time: 10 sec
Number of integrations: 100 times Sample tilt: 54 °
Magnification: 10000 times

The result obtained by SEM observation is taken into a TIFF image, and after making an image of only particles using Image-Pro Plus manufactured by Media Cybernetics, binarization treatment is performed, and a white part (fine particles) in the resin-coated part is performed. It was decomposed into a black part (resin part) and a black part (resin part).

As for the particle size of the white part, 10 particles were randomly selected for each carrier, and 100 particles of carriers were measured.
For the black film thickness portion, auxiliary lines are randomly drawn in four directions from the center of each carrier particle to obtain the thickness of the black portion (resin portion) on the auxiliary line, and the average value of the film thickness is calculated. I asked. When there were particles on the auxiliary line, only the thickness of the resin portion was calculated, and the average value was calculated. The same film thickness measurement was performed on the carrier 100 particles.
Further, the filling rate of the conductive fine particles with respect to the coating layer was determined from the white and black areas with respect to the carrier 100 particles.

The measurement results are shown in Table 3.

<Developer characteristic evaluation>
Using the obtained developer, image evaluation was carried out using RICOH Pro C7110S manufactured by Ricoh Co., Ltd. (digital color copier / printer multifunction device manufactured by Ricoh Co., Ltd.). Specifically, the machine is placed in an environmental evaluation room (25 ° C., 55% normal temperature and humidity environment) and left for one day, and then evaluated using the developing agents of Examples and Comparative Examples and [Toner 1]. did.

<Carrier adhesion evaluation>
Next, carrier adhesion evaluation was carried out. Using the developer of Examples and Comparative Examples and [Toner 1] on Ricoh's RICOH Pro C7110S (Ricoh's digital color copier / printer multifunction device), 100,000 sheets with an image area ratio of 2.5% 200,000 sheets were run, and after running, the solid carrier adhesion and edge carrier adhesion shown below were evaluated.

<< Solid carrier adhesion >>
After running the predetermined number of sheets, a solid image is imaged under predetermined development conditions (charging potential (Vd): -600V, potential after exposure of the portion corresponding to the image portion (solid original): -100V, development bias: DC-500V). The image formation was interrupted by a method such as turning off the power inside, and the number of carriers attached to the photoconductor after transfer was counted and evaluated. The region to be evaluated was a region of 10 mm × 100 mm on the photoconductor.
The evaluation criteria are shown below. Ranks A to D were accepted, and ranks E and F were rejected.

[Evaluation criteria]
A: The number of carriers attached is 0 B: The number of carriers attached is 1 to 3 C: The number of carriers attached is 4 to 6 D: The number of carriers attached is 7 to 10 E: The number of carriers attached is 11 ~ 15 F: Number of carriers attached is 16 or more

<< Edge carrier adhesion >>
The same conditions were used except that the solid image of the solid carrier adhesion evaluation was changed to a 2-dot line (100 lpi / inch) image in the sub-scanning direction on the photoconductor. Next, the 2-dot lines developed on the photoconductor ^{were transferred with an adhesive tape (area 100 cm 2} ), and the number of them was counted to evaluate the carrier adhesion.
The evaluation criteria are shown below. Ranks A to D were accepted, and ranks E and F were rejected.

[Evaluation criteria]
A: The number of carriers attached is 0 B: The number of carriers attached is 1 to 3 C: The number of carriers attached is 4 to 6 D: The number of carriers attached is 7 to 8 E: The number of carriers attached is 9 ~ 11 F: Number of carriers attached is 12 or more

The evaluation results are shown in Table 4.

11 Fluororesin container 12a Electrode 12b Electrode 13 Carrier 101 Photoreceptor 102 Charging device 103 Exposure light 104 Developing device 105 Recording medium 106 Fixing device 107 Cleaning device

Japanese Patent No. 2714590

Claims (9)

A carrier having a magnetic core material particle and a coating layer covering the surface thereof.
The coating layer contains a resin and conductive fine particles, and contains
The conductive fine particles contain any copper compound selected from copper oxide, copper sulfide, copper sulfate, copper chloride, copper carbonate, copper diversion molybdenum, copper graphite and iron powder.
When the average film thickness of the coating layer is h and the volume average particle size of the conductive fine particles is d,
0.5 ≦ d / h ≦ 2.0
A carrier characterized in that the filling rate of the conductive fine particles with respect to the coating layer determined by the following measuring method is 50% or more.
[Measuring method]
For 100 carrier particles, the filling ratio of the conductive fine particles with respect to the coating layer is determined from the areas of the conductive fine particles portion and the resin portion obtained by SEM (scanning electron microscope) observation of the carrier cross section. The carrier according to claim 1, wherein the conductive fine particles have a volume average particle size of 1.0 to 2.0 μm. 1. The resin comprises a heat-treated product of a copolymer having a component A represented by the following general formula (A) and a component B represented by the following general formula (B). Or the carrier according to 2.

(In the general formula (A) and the general formula (B), R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkyl group having 1 to 4 carbon atoms, and R ³ represents 1 to 8 carbon atoms. Represents an alkyl group or an alkoxy group having 1 to 4 carbon atoms, m represents an integer of 1 to 8, X represents 10 to 90 mol%, and Y represents 10 to 90 mol%.) A developer having the carrier and toner according to any one of claims 1 to 3. The developer according to claim 4, wherein the toner is a color toner. A replenishing developer having the carrier and toner according to any one of claims 1 to 3.
A replenishing developer characterized by containing 2 to 50 parts by mass of the toner with respect to 1 part by mass of the carrier. Electrostatic latent image carrier and
A charging means for charging the electrostatic latent image carrier and
An exposure means for forming an electrostatic latent image on the electrostatic latent image carrier,
A developing means for forming a toner image by developing an electrostatic latent image formed on the electrostatic latent image carrier with the developer according to claim 4 or 5.
A transfer means for transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and
A fixing means for fixing the toner image transferred to the recording medium, and
An image forming apparatus characterized by having. Electrostatic latent image carrier and
A charging means for charging the electrostatic latent image carrier and
A developing means for developing an electrostatic latent image formed on the electrostatic latent image carrier using the developer according to claim 4 or 5.
A cleaning means for cleaning the electrostatic latent image carrier, and
A process cartridge characterized by having. The process of forming an electrostatic latent image on the electrostatic latent image carrier,
A step of developing an electrostatic latent image formed on the electrostatic latent image carrier with the developer according to claim 4 or 5 to form a toner image.
A step of transferring the toner image formed on the electrostatic latent image carrier to a recording medium, and
The step of fixing the toner image transferred to the recording medium and
An image forming method characterized by having.

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