JP2018146848A - Carrier for electrostatic latent image development, developer, image forming apparatus, process cartridge, and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carrier for electrostatic latent image development that can sufficiently maintain resistance and control charge for image quality required in the field of production printing, can supply a stable amount of developer to a developing area, and can achieve continuous paper feed at a printing density with a high image area ratio and a low image area ratio even in a high-speed machine using a low-temperature fixing toner.SOLUTION: A carrier for electrostatic latent image development comprises a core material particle that has magnetism, and a coating layer that covers the surface of the core material particle. The coating layer contains resin and conductive fine particles; the conductive fine particles are formed of fine particles containing zinc; and the filling factor of the fine particles containing zinc to the resin coating layer is 20% or more and 80% or less (cross-sectional ratio).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a carrier for developing an electrostatic latent image, a developer, an image forming apparatus, a process cartridge, and an image forming method.

  In electrophotographic image formation, an electrostatic latent image is formed on an electrostatic latent image carrier such as a photoconductive substance, and a charged toner is attached to the electrostatic latent image to form a toner image. After that, the toner image is transferred to a recording medium and fixed to form an output image. In recent years, the technology of copying machines and printers using an electrophotographic system is rapidly expanding from monochrome to full color, and the full color market tends to expand.

In full-color image formation, generally, color toners of three colors of yellow, magenta, and cyan or four color toners obtained by adding black to this 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 copying machines or the like realize high gloss by increasing the toner adhesion amount of the electrostatic latent image in order to achieve smoothness of the toner image. For this reason, there is a problem of toner spent in which deteriorated toner adheres to the carrier surface during long-term printing.
Among the carrier deterioration caused by toner spent, problems are an increase in carrier resistance and a decrease in carrier charging ability.

  In the field of production printing, where the market is expanding in recent years, higher image quality than ever has been demanded. The carrier resistance increases due to the toner spent, so that the carrier is transferred onto the electrostatic latent image carrier, so-called carrier adhesion occurs, and a problem that white spots appear at the image edge portion or the central portion occurs. The demand for this problem has become even more severe in recent years.

  On the other hand, in order to prevent carrier adhesion, it is possible to maintain the carrier resistance at a high level by designing the carrier resistance at a high level from the initial stage. For example, when printing a halftone, the end portion becomes thin.

  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 technical concept. For example, in Patent Document 1, by using a plurality of incompatible resins in the carrier coating resin, the conductive fine particles in the coating layer are unevenly distributed, taking advantage of the spent resistance of the carrier coating resin, and the carrier coating by the conductive fine particles. There is a means to achieve low resistance, but with the increase in printing speed, not only the effect of suppressing the toner spent by the coating resin is sufficient, but the resistance increases with the number of printed sheets, and the edge part is printed when halftone is printed. The problem of thinning is inevitable.

  In addition, with respect to a decrease in charging ability due to toner spent, Patent Document 2 discloses that the first conductive particles, which are metal oxide conductive particles, and the surfaces of the metal oxide particles and / or metal salt particles are subjected to conductive treatment. A carrier having a coating layer comprising second conductive particles is disclosed. Patent Document 2 has a certain effect on the reduction of the charging ability of the carrier when the toner is balanced with a high image area. However, in the case of using a toner having a large amount of toner external additives, In the case of continuous paper passing, the charge was lowered and the effect was not sufficient.

  In response, Patent Document 3 and Patent Document 4 disclose carriers in which the coating film contains barium sulfate and the Ba / Si ratio with respect to all elements measured by XPS is 0.01 to 0.08. . Patent Document 5 also describes an example using barium sulfate as a base material. These inventions are effective for reducing the charging ability of the carrier when the toner is balanced in a larger image area.

  However, in recent years, the toner tends to be fixed at a low temperature to reduce power consumption, and in addition to the increase in printing speed, toner spent on the carrier is more likely to occur. Furthermore, toners tend to contain many additives due to demands for higher image quality, and these are spent on the carrier, resulting in a decrease in toner charge amount, a margin for toner scattering and background contamination. Currently. In addition, since the amount of charged fine particles and the like is reduced for fixing the toner at a low temperature, the toner at the time of replenishment is not sufficiently mixed with the developer, so that the toner is not charged and the toner is scattered. Yes.

  With respect to such new problems, fine particles obtained by covering barium sulfate as described above with a substance such as tin oxide have not been sufficiently effective. Similarly, a carrier using zinc oxide is reported in Patent Document 6 as a charging capability and resistance maintenance. However, the amount of zinc oxide reported here cannot exhibit a sufficient effect on toner spent, and cannot exhibit a sufficient effect on resistance stabilization at low resistance and toner scattering.

  The present invention has been made in view of the prior art as described above, and can maintain sufficient resistance and charge control for image quality required in the field of production printing, and can be stably developed in a development region. An electrostatic latent image developing carrier that can supply a continuous amount of paper with a high image area ratio and a low image area ratio even in a high-speed machine using a low-temperature fixing toner. The purpose is to provide.

  In order to achieve such an object, the carrier for developing an electrostatic latent image according to the present invention comprises magnetic core material particles and a coating layer covering the surface of the core material particles, and the coating layer is made of resin and conductive material. The conductive fine particles include fine particles containing zinc, and the filling rate of the fine particles containing zinc in the resin coating layer is 20% or more and 80% or less (cross-sectional area ratio).

  According to the present invention, sufficient resistance maintenance and charge control can be performed for the image quality required in the field of production printing, and a stable developer amount can be supplied to the development area, and low-temperature fixing is possible. It is possible to provide a carrier for developing an electrostatic latent image that enables continuous paper passing at a printing density with a high image area ratio and a low image area ratio even in a high-speed machine using toner.

It is a figure which shows the cell used for the measurement of a carrier resistance value change rate. It is a figure which shows an example of the process cartridge of this invention.

The electrostatic latent image developing carrier of the present invention will be described in detail.
The carrier for developing an electrostatic latent image of the present invention comprises magnetic core material particles and a coating layer covering the surface of the core material particles, the coating layer containing a resin and conductive fine particles, It is comprised by the microparticles | fine-particles containing zinc, and the filling rate of the microparticles | fine-particles containing zinc with respect to the said resin coating layer is 20 to 80% (cross-sectional area ratio).

(Conductive fine particles)
The conductive fine particles of the present invention are composed of fine particles containing zinc. Examples of the fine particles containing zinc include aluminum-doped zinc oxide in which zinc oxide is doped with aluminum, gallium-doped zinc oxide in which zinc oxide is doped with gallium, and aluminum-doped zinc sulfide in which zinc sulfide is doped with aluminum. Is preferred.

Zinc is a substance that is very positively charged and has high chargeability with negatively charged toner, so that the fine particles containing zinc on the surface layer can maintain chargeability even after output over a long and high image area. I can do it.
The filling rate of the fine particles containing zinc with respect to the coating layer is 20% or more and 80% or less, preferably 40 to 70%. By setting the fine particles containing zinc to the above filling rate, the fine particles containing zinc are always exposed on the surface of the carrier coat layer. By doing so, high charging performance can always be maintained by the toner and fine particles containing zinc having high chargeability. Furthermore, by setting the fine particles containing zinc to a high filling rate, highly conductive fine particles are effectively arranged in the coating layer, and the fine particles function as a conduction circuit even when toner spent, and the surface of the carrier coat layer The effect of scraping off the toner spent by the fine particles containing zinc exposed to the surface can be sufficiently exerted, and the initial resistance and charge level can be maintained and long-term printing can be performed.

  However, if the filling rate of the fine particles containing zinc in the coating film exceeds 80%, the resin component for holding the fine particles containing zinc decreases, and the fine particles containing zinc are easily detached from the coating film, which is not preferable. . When the filling rate of the fine particles containing zinc in the coating film is less than 20%, the fine particles containing zinc are not exposed to the surface of the carrier coat layer, and sufficient charging ability cannot be exhibited. Further, in terms of resistance, the conductive circuit and toner spent scraping function when toner spent is lowered, which is not preferable.

  The fine particles containing zinc are present in a convex state with respect to the coating film by setting the aggregate diameter to 150 nm to 1000 nm, more preferably 400 nm to 800 nm. Since the surface of the convex fine particles containing zinc is always stressed by friction with the toner, carrier, development screw, etc. in the developing device, even if toner resin, wax, additives, etc. are temporarily spent Since it is shaved immediately by the stress, the fine particles containing zinc can always be kept exposed.

  On the other hand, toner resin, wax, additives, etc. are spent in the concave portions existing between the convex portions of the fine particles containing zinc. No spent material is deposited. The carrier surface layer that becomes a concave portion due to these spents cannot charge the toner, but because it is a concave portion, the friction probability with the toner is low, and the contribution to the toner charging is small. For this reason, since the site | part where the microparticles | fine-particles containing zinc exist in a convex form determine the charging capability and resistance maintenance capability of a carrier, the charging capability and resistance level stable over the long term can be hold | maintained.

  In addition, since the carrier surface layer has an uneven shape, the bulk density of the carrier is stabilized. Usually, the carrier surface is scraped or the toner component is spent on the carrier surface layer, so the bulk density of the carrier fluctuates and the amount of developer pumped up on the developing sleeve changes, so the amount of developer supplied to the development area changes. As a result, there arises a problem that the developing ability fluctuates. However, when the fine particles containing zinc are contained in the coat layer with an aggregate diameter of 150 nm or more and 1000 nm or less, the spent product accumulates in the recesses, so that the effect that the bulk density fluctuation of the carrier is small can be obtained. In addition, since the coating film strength can be increased by dispersing fine particles containing zinc in the coating layer at high density, the amount of abrasion of the coating layer can be reduced.

  For this reason, fluctuations in bulk density due to spent or scraping hardly occur, and a stable developing ability can be secured over a long period of time. In order to exert the above-described effects, by setting the aggregate diameter of the fine particles containing zinc to 150 nm or more, the convex portion due to the fine particles containing zinc becomes 100 nm or more, and the state where the fine particles containing zinc are always exposed can be maintained. it can. Further, by setting the aggregate diameter of the fine particles containing zinc to 1000 nm or less, it is possible to prevent the fine particles containing zinc from being detached due to stress in the developing device.

(Measuring method of agglomerated diameter, filling rate, convex height d of fine particles containing zinc)
Confirmation of the particle diameter, filling rate, and convex part height d of the fine particles containing zinc can be carried out by a known method, but in the present invention, it was measured by the following method.
That is, it can be performed by cutting the carrier with FIB and observing the cross section with SEM or the like.

A sample is deposited on the carbon tape, and is coated with about 20 nm of osmium for surface protection and conductive treatment. Using an NVision40 manufactured by Carl Zeiss (SII), perform FIB treatment at an acceleration voltage of 2.0 kV, aperture 30 μm, High Current ON, detector SE2, InLens, no conductive treatment, WD 5.0 mm, sample tilt 54 °.
Thermo Fisher Scientific's electronically cooled SDD detector UltraDry (Φ30mm2) and analysis software Thermo Fisher Scientific's NORAN System6 (NSS), acceleration voltage 3.0kV, aperture 120μm, High Current ON, conductive treatment Os, drift correction Yes, WD 10.0mm, measuring method Area Scan, integration time 10sec, integration count 100 times, specimen tilt 54 ° magnification 10000x, SEM observation is taken into TIFF image, Image Cyber Pro made by Media Cybernetics After making an image of only particles, binarization processing was performed, and the resin-coated portion was decomposed into a white portion (fine particle portion) and a black portion (resin portion). Regarding the particle size of the white portion, 10 particles were randomly selected for each carrier particle, and measurement was performed on a carrier of 100 particles.

  Regarding the filling rate, the filling rate of the conductive fine particles to the coating layer was defined from the white and black areas with respect to 100 carriers. Further, regarding the height of the convex portion, the average film thickness of the carrier resin film is calculated from the carrier 100 particles, and the difference between the height of the exposed portion of the fine particles containing zinc and the average film thickness is calculated. Average values were used.

(Aluminum-doped zinc oxide)
The zinc-containing fine particles preferably form conductivity by doping aluminum or the like, and are preferably aluminum-doped zinc oxide. The carrier needs to be appropriately lowered in resistance by fine particles containing zinc present in the coating film. If the resistance is too high, the charge on the carrier surface does not leak properly immediately after development, for example, halftone When printing, there is a problem that the end portion becomes thin.
As the amount of aluminum to be doped, the molar ratio of aluminum to zinc oxide is preferably 1: 400 or more and 1: 5 or less, and more preferably the molar ratio is 1: 300 or more and 1:10 or less. The electrical resistance can be appropriately lowered by increasing the amount of aluminum from 1: 400. Moreover, the enlargement of the particle size of the aluminum dope zinc oxide powder and the increase in bulk density can be prevented by making the amount of aluminum lower than 1: 5. An increase in the particle size and bulk density of the fine particles containing zinc leads to a decrease in the dispersibility of the fine particles containing zinc, leading to uneven distribution of the fine particles containing zinc in the coating film when converted into a carrier.

  The molar ratio measurement of zinc oxide doped with aluminum is obtained from the following. After zinc oxide particles containing aluminum are dissolved with an acid such as nitric acid, the concentration of each element in the solution is analyzed by atomic absorption analysis to calculate the molar ratio. Moreover, as a method for extracting fine particles containing zinc from the carrier according to the present embodiment, the following method is used. A carrier and a coating resin-soluble organic solvent (for example, acetone, chloroform, etc.) are mixed, and ultrasonic waves are applied for 1 hour with an ultrasonic device to peel the coating resin from the core material. Thereafter, a magnet is applied to the bottom of the beaker to recover the organic solvent containing the coating resin and fine particles containing zinc. This operation is repeated three times to completely separate the core particles. The collected organic solvent is centrifuged and the precipitate is dried to extract fine particles containing zinc.

(resin)
In the carrier of the present invention, the resin component in the coating layer hydrolyzes the following copolymer (1) obtained by radical copolymerization of the monomer A component and the monomer B component to produce a silanol group, It is preferable that the carrier contains a component obtained by heat treatment after crosslinking and coating by condensation.

In the formula, R ¹ , m, R ² , R ³ , X, and Y are as follows.
R ¹ : hydrogen atom or methyl group (CH ₂ ) m: alkylene group such as methylene group having 1 to 8 carbon atoms, ethylene group, propylene group, butylene group R ² : methyl group having 1 to 4 carbon atoms, An alkyl group R ³ such as an ethyl group, a propyl group, an isopropyl group, and a butyl group: an alkyl group such as a methyl group having 1 to 8 carbon atoms, an ethyl group, a propyl group, an isopropyl group, and a butyl group; 4 alkoxy groups such as methoxy group, ethoxy group, propoxy group, butoxy group

In the previous formula,
R ¹ : hydrogen atom or methyl group (CH ₂ ) m: alkylene group such as methylene group having 1 to 8 carbon atoms, ethylene group, propylene group, butylene group R ² : aliphatic carbonization having 1 to 4 carbon atoms Hydrogen group, methyl group, ethyl group, propyl group, and butyl group

  In A component, it is X = 10-90 mol%, More preferably, it is 30-70 mol%.

  The A component has an atomic group having a large number of methyl groups in the side chain and tris (trimethylsiloxy) silane. When the ratio of the A component to the entire resin increases, the surface energy decreases, and the resin component of the toner. , Adhesion of wax components and the like is reduced. When the A component is less than 10 mol%, a sufficient effect cannot be obtained, and the adhesion of the toner component increases rapidly. On the other hand, if it exceeds 90 mol%, component B and component C decrease, crosslinking does not proceed, toughness is insufficient, adhesion between the core material and the resin layer decreases, and the durability of the carrier coating deteriorates. .

An example of such a monomer component is a tris (trialkylsiloxy) silane compound represented by the following formula.
In the following formulae, 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 production method of 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 It can be obtained by a method of reacting methacryloxyalkyltrialkoxysilane and hexaalkyldisiloxane in the presence of an acid catalyst.

Monomer B is a crosslinking component. In the previous formula,
R ¹ : hydrogen atom or methyl group (CH ₂ ) m: alkylene group such as methylene group having 1 to 8 carbon atoms, ethylene group, propylene group, butylene group R ² : aliphatic carbonization having 1 to 4 carbon atoms A hydrogen group, a methyl group, an ethyl group, a propyl group, and a butyl group R ³ : an alkyl group having 1 to 8 carbon atoms (such as a methyl group, an ethyl group, a propyl group, or a butyl group), or an alkyl group having 1 to 4 carbon atoms Alkoxy group (methoxy group, ethoxy group, propoxy group, butoxy group)

That is, the component B is a radically polymerizable bifunctional or trifunctional silane compound, and Y = 10 to 90 mol%, more preferably 30 to 70 mol%.
If the B component is less than 10 mol%, sufficient toughness cannot be obtained. On the other hand, when it exceeds 90 mol%, the coating becomes hard and brittle, and film scraping tends to occur. Moreover, environmental characteristics deteriorate. It is also conceivable that a large number of hydrolyzed crosslinking components remain as silanol groups, deteriorating environmental characteristics (humidity dependency).

  Examples of such component B include 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltriethoxysilane, and 3-methacryloxypropylmethyl. Examples include dimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltri (isopropoxy) silane, and 3-acryloxypropyltri (isopropoxy) silane.

  In the present invention, the A component and the B component may be added to the acrylic compound (monomer) as a C component. Examples of the copolymer to which such a component C is added include the following copolymers.

(In the formula, R ¹ , m, R ² , R ³ , X, Y, and Z are as follows.)
R ¹ : a hydrogen atom or a methyl group (CH ₂ ) m: an alkylene group having 1 to 8 carbon atoms R ² : an alkyl group having 1 to 4 carbon atoms R ³ is an alkyl group having 1 to 8 carbon atoms, or C1-C4 alkoxy group A component:

X = 10 to 40 mol%.
B component:

Y = 10 to 40 mol%.
C component:

Z = 30 to 80 mol%, and 60 mol% <Y + Z <90 mol%.
The C component imparts flexibility to the coating and improves the adhesion between the core material and the coating. However, if the C component is less than 30 mol%, sufficient adhesion cannot be obtained. If it exceeds 80 mol%, since either the X component or the Y component is 10 mol% or less, it becomes difficult to achieve both water repellency, hardness and flexibility (film scraping) of the carrier coating.

  As the acrylic compound (monomer) of component C, acrylic acid ester and methacrylic acid ester are preferable. Specifically, methyl methacrylate, methyl acrylate, ethyl methacrylate, ethyl acrylate, butyl methacrylate, butyl acrylate, 2- (dimethylamino) ) Ethyl methacrylate, 2- (dimethylamino) ethyl acrylate, 3- (dimethylamino) propyl methacrylate, 3- (dimethylamino) propyl acrylate. Of these, alkyl methacrylate is preferable, and methyl methacrylate is particularly preferable. One of these compounds may be used alone, or a mixture of two or more may be used.

Japanese Patent No. 3691115 is known as a technique for improving durability by crosslinking a coating. Japanese Patent No. 3691115 discloses radical copolymerization of a magnetic particle surface with an organopolysiloxane having at least a terminal vinyl group and at least one functional group selected from the group consisting of hydroxyl group, amino group, amide group and imide group. Is a carrier for developing an electrostatic image characterized in that a copolymer with a photopolymerizable monomer is coated with a thermosetting resin crosslinked with an isocyanate compound. I can't get it.
The reason for this is not clear enough, but in the case of a thermosetting resin obtained by crosslinking the above-mentioned copolymer with an isocyanate compound, the isocyanate in the copolymer resin is understood from the structural formula. There are few functional groups per unit weight which reacts (crosslinks) with the compound, and a two-dimensional or three-dimensional dense crosslinked structure cannot be formed at the crosslinking point. Therefore, if it is used for a long time, the film is easily peeled off or scraped off (the abrasion resistance of the film is small), and it is assumed that sufficient durability is not obtained.
When the film is peeled off or scraped off, the image quality changes due to a decrease in carrier resistance and carrier adhesion occurs. Also, peeling or scraping of the coating reduces the fluidity of the developer and causes a decrease in the amount of pumping, which causes a decrease in image density, contamination when toner is increased, and toner scattering.
The resin of the present invention is a copolymer resin having a large number (two to three times more per unit weight) of bifunctional or trifunctional crosslinkable functional groups (points) than the resin unit weight. Further, since this is further cross-linked by condensation polymerization, it is considered that the coating film is extremely tough and difficult to scrape, and high durability is achieved.
Further, it is presumed that the aging stability of the coating is maintained because the crosslinking by the siloxane bond of the present invention has a higher binding energy and is more stable against heat stress than the crosslinking by the isocyanate compound.

  As the carrier coating resin, silicon resin, acrylic resin, or a combination thereof can be used. This is because acrylic resin has a very excellent property of abrasion resistance due to its strong adhesiveness and low brittleness, but on the other hand, since the surface energy is high, the toner component spent in combination with easily spent toner Problems such as a decrease in charge amount due to accumulation may occur. In this case, this problem can be solved by using together a silicon resin that has an effect that it is difficult to spend the toner component due to the low surface energy and the accumulation of the spent component is difficult to progress due to film scraping. However, since silicon resin has weak adhesiveness and high brittleness, it also has a weak point that it has poor wear resistance. Therefore, it is important to obtain a good balance between the properties of these two types of resins, which makes it difficult to spend. It is possible to obtain a coating film having wear characteristics. Therefore, the improvement effect is remarkable. This is because the silicone resin has a low surface energy, so that it is difficult for the toner component to be spent and the accumulation of the spent component due to film scraping is difficult to obtain.

As used herein, the term “silicon resin” refers to all commonly known silicon resins, such as straight silicon consisting only of organosilosan bonds, and silicon resins modified with alkyd, polyester, epoxy, acrylic, urethane, etc. However, it is not limited to this.
Examples of commercially available products include KR271, KR255, and KR152 manufactured by Shin-Etsu Chemical, SR2400, SR2406, and SR2410 manufactured by Toray Dow Corning Silicon Co., Ltd. as straight silicon resins. In this case, it is possible to use the silicon resin alone, but it is also possible to simultaneously use other components that undergo a crosslinking reaction, charge amount adjusting components, and the like. Further, as modified silicone resin, KR206 (alkyd modified), KR5208 (acryl modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical, SR2115 (epoxy modified) manufactured by Toray Dow Corning Silicon Co., Ltd. , SR2110 (alkyd modified) and the like.

(Conductive fine particles other than the above)
The coating layer of the present invention preferably contains conductive fine particles other than the fine particles containing zinc in order to adjust the volume resistivity of the carrier. Although it does not specifically limit as electroconductive fine particles, Conductive polymers, such as carbon black, ITO, PTO, WTO, a tin oxide, barium sulfate, polyaniline, are mentioned, You may use together 2 or more types.

The carrier of the present invention preferably has a volume average particle size of 28 μm or more and 40 μm or less. When the volume average particle diameter of the carrier particles is less than 28 μm, carrier adhesion may occur. When the volume average particle diameter exceeds 40 μm, the reproducibility of image details may be reduced, and a fine image may not be formed.
The volume average particle diameter can be measured using, for example, a Microtrac particle size distribution model HRA9320-X100 (manufactured by Nikkiso Co., Ltd.).

  The carrier of the present invention preferably has a volume resistivity of 8 to 16 (LogΩ · cm). If the volume resistivity is less than 8 (Log Ω · cm), carrier adhesion may occur in the non-image area, and if it exceeds 16 (Log Ω · cm), the edge effect may be at an unacceptable level.

  Examples of the condensation polymerization catalyst used in the present invention include titanium-based catalysts, tin-based catalysts, zirconium-based catalysts, and aluminum-based catalysts. In the present invention, among these various catalysts, titanium-based catalysts that give excellent results. Among the catalysts, titanium diisopropoxybis (ethyl acetoacetate) is most preferable as the catalyst. This is considered to be because the effect of promoting the condensation reaction of the silanol group is large and the catalyst is hardly deactivated.

  In the present invention, the coating layer has no film defects, and the average film thickness is preferably 0.80 to 1.50 μm. When the average film thickness is less than 0.80 μm, it is difficult to sufficiently retain the fine particles containing zinc, and the fine particles containing zinc are easily detached from the film. On the other hand, if it exceeds 1.50 μm, zinc-containing fine particles are taken into the resin layer, making it difficult to exhibit sufficient charging ability.

(Core particles)
In the present invention, the core particle 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.

(Developer)
The developer of the present invention has the carrier and toner of the present invention.
The toner contains a binder resin and a colorant, and may be a monochrome toner or a color toner. Further, the toner particles may contain a release agent in order to be applied to an oilless system in which toner fixing prevention oil is not applied to the fixing roller. Such toner generally tends to cause filming. However, since the carrier of the present invention can suppress filming, the developer of the present invention maintains good quality for a long time. Can do. Further, color toners, particularly yellow toners, generally have a problem that color stains occur due to scraping of the coating layer of the carrier, but the developer of the present invention can suppress the occurrence of color stains.

(toner)
The toner can be produced using a known method such as a pulverization method or a polymerization method. For example, when a toner is manufactured using a pulverization method, first, a melt-kneaded product obtained by kneading a toner material is cooled, pulverized, and classified to prepare base particles. Next, in order to further improve transferability and durability, an external additive is added to the base particles to produce a toner.
At this time, the apparatus for kneading the toner material is not particularly limited, but a batch type two roll; Banbury mixer; KTK type twin screw extruder (manufactured by Kobe Steel), TEM type twin screw extruder (Toshiba Machine) A continuous twin screw extruder such as a twin screw extruder (manufactured by KCK), a PCM type twin screw extruder (manufactured by Ikegai Iron Works), a KEX type twin screw extruder (manufactured by Kurimoto Iron Works); Examples thereof include a continuous single-shaft kneader such as Ko Nida (manufactured by Buss).
Further, when the cooled melt-kneaded product is pulverized, it is roughly pulverized using a hammer mill, a rotoplex, etc., and then finely pulverized using a fine pulverizer using a jet stream, a mechanical pulverizer or the like. be able to. In addition, it is preferable to grind | pulverize so that an average particle diameter may be set to 3-15 micrometers.
Furthermore, when classifying the crushed melt-kneaded material, a wind classifier or the like can be used. In addition, it is preferable to classify so that the average particle diameter of the base particles is 5 to 20 μm.
In addition, when an external additive is added to the base particle, the external additive adheres to the surface of the base particle while being pulverized by mixing and stirring using a mixer.

  The binder resin used as the toner raw material is not particularly limited, but is a homopolymer of styrene such as polystyrene, poly-p-styrene, polyvinyltoluene and the like; a styrene-p-chlorostyrene copolymer, and styrene-propylene. Copolymer, Styrene-vinyltoluene copolymer, Styrene-methyl acrylate copolymer, Styrene-ethyl acrylate copolymer, Styrene-methacrylic acid copolymer, Styrene-methyl methacrylate copolymer, Styrene-methacrylic Ethyl acid copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer Coalescence, styrene-butadiene copolymer, Styrene copolymers such as tylene-isoprene copolymer and styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polyester, polyurethane, epoxy resin, Examples include polyvinyl butyral, polyacrylic acid, rosin, modified rosin, terpene resin, phenol resin, aliphatic or aromatic hydrocarbon resin, aromatic petroleum resin, and the like.

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

  Although it does not specifically limit as a coloring agent (pigment or dye), Cadmium yellow, mineral fast yellow, nickel titanium yellow, Navels yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow GR, quinoline 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, indanthrene brilliant orange RK, benzidine orange G, indanthrene brilliant orange GK; bengara, cadmium Red, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red Calcium Salt, Lake Red D, Brilliant Carmine Red pigments such as B, eosin lake, rhodamine lake B, alizarin lake, brilliant carmine 3B; purple pigments such as fast violet B, methyl violet lake; cobalt blue, alkali blue, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, Blue pigments such as phthalocyanine blue partially chlorinated, First Sky Blue, Indanthrene Blue BC; Green pigments such as Chrome Green, Chrome Oxide, Pigment Green B, Malachite Green Lake; Carbon Black, Oil Furnace Black, Channel Black, Lamp Black Azine dyes such as acetylene black and aniline black, black pigments such as metal salt azo dyes, metal oxides and composite metal oxides, etc. It may be.

  The release agent is not particularly limited, but includes polyolefins such as polyethylene and polypropylene, fatty acid metal salts, fatty acid esters, paraffin wax, amide wax, polyhydric alcohol wax, silicone varnish, carnauba wax, ester wax and the like. Two or more kinds may be used in combination.

  The toner may further contain a charge control agent. The charge control agent is not particularly limited, but nigrosine; an azine dye having an alkyl group having 2 to 16 carbon atoms (see Japanese Patent Publication No. 42-1627); I. Basic Yellow 2 (C.I. 41000), C.I. I. Basic Yellow 3, C.I. I. Basic Red 1 (C.I. 45160), C.I. I. Basic Red 9 (C.I. 42500), C.I. I. Basic Violet 1 (C.I. 42535), C.I. I. Basic Violet 3 (C.I. 42555), C.I. I. Basic Violet 10 (C.I. 45170), C.I. I. Basic Violet 14 (C.I. 42510), C.I. I. Basic Blue 1 (C.I. 42025), C.I. I. Basic Blue 3 (C.I. 51005), C.I. I. Basic Blue 5 (C.I. 42140), C.I. I. Basic Blue 7 (C.I. 42595), C.I. I. Basic Blue 9 (C.I. 52015), C.I. I. Basic Blue 24 (C.I. 52030), C.I. I. Basic Blue 25 (C.I. 52025), C.I. I. Basic Blue 26 (C.I. 44045), C.I. I. Basic Green 1 (C.I. 42040), C.I. I. Basic dyes such as Basic Green 4 (C.I. 42000); lake pigments of these basic dyes; I. Solvent Black 8 (C.I. 26150), quaternary ammonium salts such as benzoylmethylhexadecyl ammonium chloride and decyltrimethyl chloride; dialkyltin compounds such as dibutyl and dioctyl; dialkyltin borate compounds; guanidine derivatives; vinyl having an amino group Polyamine resins such as polycondensation polymers and condensation polymers having amino groups; described in JP-B-41-20153, JP-B-43-27596, JP-B-44-6397, and JP-B-45-26478 Metal complex salts of monoazo dyes; salicylic acids described in JP-B-55-42752 and JP-B-59-7385; dialkylsalicylic acid, naphthoic acid, dicarboxylic acid Zn, Al, Co, Cr, Fe, etc. Metal complexes of Examples thereof include honed copper phthalocyanine pigments; organic boron salts; fluorine-containing quaternary ammonium salts; calixarene compounds, and the like. For color toners other than black, white metal salts of salicylic acid derivatives are preferred.

  The external additive is not particularly limited, but inorganic particles such as silica, titanium oxide, alumina, silicon carbide, silicon nitride, boron nitride, etc .; 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 kinds may be used in combination. Among these, metal oxide particles such as silica and titanium oxide whose surfaces are hydrophobized are preferable. Furthermore, by using a combination of hydrophobized silica and hydrophobized titanium oxide, the amount of added hydrophobized titanium oxide is higher than that of hydrophobized silica. A toner having excellent charging stability can be obtained.

(Replenishment developer)
By using the carrier of the present invention as a replenishment developer composed of a carrier and toner, and applying it to an image forming apparatus that forms an image while discharging excess developer in the developing device, a stable image can be obtained over a very long period of time. Quality is obtained. 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. When printing a large image area, carrier charge deterioration due to toner spent on the carrier is the main carrier deterioration. However, when this method is used, the carrier replenishment amount increases when the image area is large, and the deteriorated carrier is replaced. Increases frequency. Thereby, a stable image can be obtained for an extremely long period of time.

  The mixing ratio of the replenishment 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 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 developer tends to increase. Further, when the developer charge amount increases, the developing ability decreases and the image density decreases. On the other hand, if the amount exceeds 50 parts by mass, the carrier ratio in the replenishment developer decreases, so that the replacement of carriers in the image forming apparatus decreases, and the effect on carrier deterioration cannot be expected.

(Image forming apparatus, image forming method and process cartridge)
The image forming apparatus of the present invention includes an electrostatic latent image carrier, a charging unit that charges the electrostatic latent image carrier, an exposure unit that forms an electrostatic latent image on the electrostatic latent image carrier, Developing means for developing the electrostatic latent image formed on the electrostatic latent image carrier using the developer of the present invention to form a toner image, and toner formed on the electrostatic latent image carrier The image forming apparatus includes a transfer unit that transfers an image to a recording medium, and a fixing unit that fixes the toner image transferred onto the recording medium. Means, recycling means, control means and the like.
The image forming method of the present invention comprises a 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 with the developer of the present invention. Developing the toner image to form a toner image; transferring the toner image formed on the electrostatic latent image carrier to a recording medium; fixing the toner image transferred to the recording medium; Have
Note that the configuration of the image forming apparatus and method used in the present invention is not limited to the above-described embodiment, and an image forming apparatus and method having other configurations can be used as long as they have similar functions. It is also possible to adopt.

  FIG. 2 shows an example of the process cartridge of the present invention. The process cartridge (10) comprises a photoreceptor (11), a charging device (12) for charging the photoreceptor (11), and an electrostatic latent image formed on the photoreceptor (11) using the developer of the present invention. A developing device (13) for developing and forming a toner image and a cleaning device (for removing toner remaining on the photosensitive member (11) after transferring the toner image formed on the photosensitive member (11) to a recording medium. 14) is integrally supported, and the process cartridge (10) is detachable from the main body of an image forming apparatus such as a copying machine or a printer.

  Hereinafter, a method for forming an image using the image forming apparatus equipped with the process cartridge (10) will be described. First, the photosensitive member (11) is rotationally driven at a predetermined peripheral speed, and the charging device (12) uniformly charges the peripheral surface of the photosensitive member (11) to a predetermined positive or negative potential. Next, exposure light is irradiated onto the peripheral surface of the photoreceptor (11) from an exposure apparatus (not shown) such as a slit exposure type exposure apparatus or an exposure apparatus that performs scanning exposure with a laser beam, and electrostatic latent images are sequentially formed. The Further, the electrostatic latent image formed on the peripheral surface of the photoconductor (11) is developed by the developing device (13) using the developer of the present invention to form a toner image. Next, the toner image formed on the peripheral surface of the photoconductor (11) is synchronized with the rotation of the photoconductor (11), and the photoconductor (11) and the transfer device (not shown) are fed from the paper feed unit (not shown). ) Are sequentially transferred onto the transfer paper fed during (). Further, the transfer paper onto which the toner image has been transferred is separated from the peripheral surface of the photoreceptor (11), introduced into a fixing device (not shown) and fixed, and then copied as a copy (copy) of the image forming apparatus. Printed out. On the other hand, after the toner image is transferred, the surface of the photoconductor (11) is cleaned by the cleaning device (14) to remove the remaining toner, and then the charge is removed by a static eliminator (not shown). Used for image formation.

  Hereinafter, although an example and a comparative example are given and the present invention is explained still more concretely, the present invention is not limited to these. “Part” means part by weight unless otherwise specified.

(Resin synthesis example 1)
300 g of toluene was charged into a flask equipped with a stirrer, and the temperature was raised to 90 ° C. under a nitrogen gas stream.
Then this
_{CH 2 = CMe-COO-C} 3 H 6 -Si (OSiMe 3) 3 ( wherein, Me is a methyl group.) 3-methacryloxypropyl tris (trimethylsiloxy) silane 84.4 g (200 mmol represented by : Silaplane TM-0701T / manufactured by Chisso Corporation), 3-methacryloxypropylmethyldiethoxysilane 39 g (150 mmol), methyl methacrylate 65.0 g (650 mmol), and 2,2′-azobis-2- A mixture of 0.58 g (3 mmol) of methylbutyronitrile was added dropwise over 1 hour.
After completion of the dropwise addition, 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 The total amount of nitriles (0.64 g = 3.3 mmol) was mixed at 90 to 100 ° C. for 3 hours for radical copolymerization to obtain a methacrylic copolymer having a weight average molecular weight of 35,000.

(Carrier Production Example 1)
Methacrylic copolymer having a weight average molecular weight of 35,000 obtained in Resin Synthesis Example 1 [solid content 100% by weight]: 20 parts, silicon resin solution [solid content 20% by weight]: 100 parts, aminosilane [solid content 100 % By weight]: 3.0 parts, aluminum-doped zinc oxide fine particles as fine particles (aluminum: zinc oxide molar ratio 1:20 manufactured by Hux Itec Corp.): 176 parts were diluted with toluene to obtain a resin solution having a solid content of 20 wt%. .
The resin solution was mixed with a homogenizer [manufactured by PRIMIX; K. After carrying out a dispersion treatment at 10000 rpm for 3 minutes using a homomixer MARKII], 2 parts of titanium diisopropoxybis (ethylacetoacetate) TC-750 (manufactured by Matsumoto Fine Chemical Co., Ltd.) was added as a catalyst, did.
Using Mn ferrite particles with a weight average particle size of 35 μm as the core material, and using a atomizing nozzle in the fluidized bed type coating device so that the average film thickness is 1.00 μm on the surface of the core material, The coating was dried at a temperature controlled to 60 ° C. The obtained carrier was baked in an electric furnace at 210 ° C./1 hour to obtain carrier 1.

(Carrier Production Example 2)
A carrier 2 corresponding to the carrier production example 2 was obtained by the same method as the carrier production example 1 except that the aluminum-doped zinc oxide fine particles were changed to 234 parts.

(Carrier Production Example 3)
Example of carrier production, except that aluminum doped zinc oxide fine particles were changed to 59 parts and carbon (made by Ketjen Black Lion) 3 parts was added at the same timing as aluminum doped zinc oxide was added for the purpose of reducing resistance. In the same manner as in Example 1, Carrier 3 corresponding to Carrier Production Example 3 was obtained.

(Carrier Production Example 4)
Carrier 4 corresponding to carrier production example 4 was obtained in exactly the same manner as carrier production example 1 except that the dispersion time in the homogenizer was changed to 15 minutes.

(Carrier Production Example 5)
Carrier 5 corresponding to carrier production example 5 was obtained in exactly the same manner as carrier production example 1, except that the dispersion time in the homogenizer was changed to 20 minutes.

(Carrier Production Example 6)
Carrier 6 corresponding to carrier production example 6 was obtained in exactly the same manner as carrier production example 1, except that the dispersion time in the homogenizer was changed to 1 minute.

(Carrier Production Example 7)
A carrier 7 corresponding to the carrier production example 7 was obtained by the same method as the carrier production example 1 except that the dispersion with a homogenizer was not carried out.

(Carrier Production Example 8)
The aluminum-doped zinc oxide fine particles are changed to 88 parts, and 3 parts of carbon (Ketjen Black) is added at the same timing as the aluminum-doped zinc oxide is added for the purpose of reducing the resistance. Carrier 8 corresponding to carrier production example 8 was obtained in exactly the same manner as carrier production example 4, except that the above-mentioned change in formulation and the dispersion time with a homogenizer were set to 15 minutes.

(Carrier Production Example 9)
Carrier 9 corresponding to carrier production example 9 was obtained in exactly the same manner as carrier production example 1, except that the aluminum: zinc oxide molar ratio of the aluminum-doped zinc oxide fine particles was changed to 1: 400.

(Carrier Production Example 10)
Carrier 10 corresponding to carrier production example 10 was obtained in exactly the same manner as carrier production example 1, except that the aluminum: zinc oxide molar ratio of the aluminum-doped zinc oxide fine particles was changed to 1: 450.

(Carrier Production Example 11)
Carrier 11 corresponding to carrier production example 11 was obtained in exactly the same manner as carrier production example 1 except that the aluminum: zinc oxide molar ratio of the aluminum-doped zinc oxide fine particles was changed to 1: 5.

(Carrier Production Example 12)
Carrier 12 corresponding to carrier production example 12 was obtained in exactly the same manner as carrier production example 1, except that the aluminum: zinc oxide molar ratio of the aluminum-doped zinc oxide fine particles was changed to 1: 4.

(Carrier Production Comparative Example 1)
A carrier 13 corresponding to Carrier Production Comparative Example 1 was obtained in exactly the same manner as Carrier Production Example 1 except that the aluminum-doped zinc oxide fine particles were changed to 249 parts.

(Carrier Production Comparative Example 2)
Except for changing the aluminum-doped zinc oxide fine particles to 44 parts and introducing 3 parts of carbon (Ketjen Black) at the same timing as the introduction of the aluminum-doped zinc oxide for the purpose of lowering the resistance, exactly the same as in carrier production example 1 By the same method, a carrier 14 corresponding to Carrier Production Comparative Example 2 was obtained.

(Carrier Production Comparative Example 3)
Carrier is changed except that aluminum doped zinc oxide fine particles are changed to alumina fine particles (AA-03 manufactured by Sumitomo Chemical Co., Ltd.) and 3 parts of carbon (Ketjen Black) is charged at the same timing as alumina is charged for the purpose of reducing resistance. A carrier 15 corresponding to Carrier Production Comparative Example 3 was obtained in exactly the same manner as in Production Example 1.

The obtained carrier characteristics are shown in Table 1.
In addition, the average value of the aggregate diameter of zinc and the height d of the exposed part was measured by the method described above.

<Example of toner production>
-Synthesis of polyester resin A-
Into a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, 65 parts of 2-molar addition product of ethylene oxide of bisphenol A, 86 parts of 3-mole addition product of propion oxide of bisphenol A, 274 parts of terephthalic acid and 2 parts of dibutyltin oxide And allowed to react at 230 ° C. for 15 hours under normal pressure. Next, it was made to react under reduced pressure of 5-10 mmHg for 6 hours, and the polyester resin was synthesize | combined. 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 value of It was 35 mgKOH / g.

-Synthesis of prepolymer (polymer capable of reacting with active hydrogen group-containing compound)-
In a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, 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 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. Subsequently, it was made to react under reduced pressure of 10-15mHg for 5 hours, and the intermediate polyester was synthesize | combined.
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 of 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 are 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. Thus, a prepolymer (polymer capable of reacting with the 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 ketimine (the active hydrogen group-containing compound)-
In a reaction vessel equipped with a stir bar and a thermometer, 30 parts by mass of isophoronediamine and 70 parts by mass of methyl ethyl ketone were charged and reacted at 50 ° C. for 5 hours to synthesize a ketimine compound (the active hydrogen group-containing compound). The amine value of the obtained ketimine compound (the active hydrogen machine-containing compound) was 423.

-Preparation of master batch-
1,000 parts of water, 540 parts of carbon black Printex 35 (manufactured by Degussa) having a DBP oil absorption of 42 mL / 100 g and a pH of 9.5, and 1,200 parts of polyester resin A, Henschel mixer (manufactured by Mitsui Mining) And mixed. Next, the obtained mixture was kneaded at 150 ° C. for 30 minutes using two rolls, then rolled and cooled, and pulverized with a pulverizer (manufactured by Hosokawa Micron Corporation) to prepare a master batch.

-Preparation of aqueous medium-
An aqueous medium was prepared by mixing and stirring 306 parts of ion-exchanged water, 265 parts of a 10% by mass suspension of tricalcium phosphate, and 1.0 part of sodium dodecylbenzenesulfonate, and uniformly dissolving them.

-Measurement of critical micelle concentration-
The critical micelle concentration of the surfactant was measured by the following method. Using a surface tension meter Sigma (manufactured by KSV Instruments), analysis was performed using an analysis program in the Sigma system. Surfactant was added dropwise by 0.01 wt% with respect to the aqueous medium, and the interfacial tension after stirring and standing was measured. From the obtained surface tension curve, the surfactant concentration at which the interfacial tension did not decrease even when the surfactant was 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 wt% with respect to the weight of the aqueous medium.

-Adjustment of toner material liquid-
In a beaker, 70 parts of polyester resin A, 10 parts by mass of prepolymer and 100 parts of ethyl acetate were added and dissolved by stirring. As a release agent, 5 parts of paraffin wax (HNP-9, melting point 75 ° C., manufactured by Nippon Seiki Co., Ltd.), 2 parts of MEK-ST (Nissan Chemical Industry Co., Ltd.), and 10 parts of masterbatch were added. After 3 passes under the condition that the liquid feeding speed is 1 kg / hour, the peripheral speed of the disk is 6 m / second, and 80% by volume of zirconia beads having a particle diameter of 0.5 mm are filled, the ketimine 2.7 is used. A part by mass was added and dissolved to prepare a toner material solution.

―Preparation of emulsion or dispersion―
150 parts by mass of the aqueous medium phase is placed in a container, and stirred at a rotational speed of 12,000 rpm using a TK homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), and 100 parts by mass of the solution or dispersion of the toner material is added thereto. The mixture was added and mixed for 10 minutes to prepare an emulsified dispersion (emulsified slurry).

―Removal of organic solvent―
100 parts by mass of the emulsified slurry was charged into a Kolben equipped 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.

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

-Surfactant adjustment-
To the filter cake obtained by the above washing, 300 parts by mass of ion-exchanged water was added, and the electrical conductivity of the toner dispersion was measured by mixing with a TK homomixer (10 minutes at 12,000 rpm). The surfactant concentration of the toner dispersion was calculated from a calibration curve for surfactant concentration prepared in advance. From this value, ion-exchanged water was added so that the surfactant concentration was the target surfactant concentration of 0.05 wt%, and a toner dispersion was obtained.

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

―Dry―
The obtained final filter cake was dried with a circulating dryer at 45 ° C. for 48 hours, and sieved with an opening of 75 μm mesh to obtain toner base particles 1.

―External treatment―
Further, with respect to 100 parts by weight of toner base particle 1, 3.0 parts by weight of hydrophobic silica having an average particle diameter of 100 nm, 1.0 part by weight of titanium oxide having an average particle diameter of 20 nm, and hydrophobicity having an average particle diameter of 15 nm. 1.5 parts of silica fine powder was mixed with a Henschel mixer to obtain [Toner 1].

<Production of developer>
[Carrier 1] to [Carrier 15] (930 parts by mass) and toner 1 (70 parts by mass) obtained in Examples and Comparative Examples were mixed, and stirred at 81 rpm for 5 minutes using a Turbuler mixer, and evaluated. [Developer 1] to [Developer 15] were prepared. The replenishment developer was prepared using the carrier and the toner so that the toner concentration became 95% by weight.

<Developer characteristics evaluation>
Using Ricoh's RICOH Pro C7110S (Ricoh Digital Color Copier / Printer Combined Machine) with Developers 1 to 15 and Toner 1 of Examples and Comparative Examples, 1 million sheets at an initial image area ratio of 80% The charge amount and resistance of the carrier after running were measured, and the change rate of the charge amount and resistance (evaluation of charging stability and resistance stability) was calculated. Further, toner scattering, background fogging, and inter-page density fluctuation (evaluation of inter-page density variation) after running 1 million sheets were evaluated.

<Charging stability>
The charge amount (Q1) of the initial carrier was determined by using a blow-off device TB-200 (manufactured by Toshiba Chemical Co., Ltd.) for a sample obtained by mixing carriers 1 to 15 and toner 1 at a mass ratio of 93: 7 and frictionally charging the sample. Measured. The charge amount (Q2) of the carrier after running 1 million sheets was measured in the same manner as described above except that the carrier from which the toner of each color in the developer after running was removed using a blow-off device. The change rate of the charge amount was defined as an absolute value of (Q1-Q2) / Q1 × 100. The evaluation criteria for charging stability based on the rate of change of the charge amount are shown below.

(Charging stability evaluation)
0 or more to less than 5: ◎ (very good)
5 or more and less than 10: ○ (good)
10 or more and less than 20: △ (can be used)
20 or more: × (defect)

<Resistance stability>
The carrier resistance value change rate was measured by the following method.
FIG. 1 is a diagram showing a cell used for measurement of the rate of change in carrier resistance value in this example.
The carrier is put into the cell 31 made of a fluororesin container containing the electrode 32a and the electrode 32b having a distance of 2 mm between the electrodes (32a) and (32b) of the resistance measurement parallel electrodes and a surface area of 2 × 4 cm, and DC 1000 V is applied. The resistance value after 30 seconds was measured with a high resist meter.
A value obtained by converting the obtained value into a volume resistivity is defined as an initial resistance value (R1). Next, the toner in the developer after running is removed with a blow-off device, and resistance measurement is performed on the obtained carrier by the same method as the resistance measurement method, and the obtained value is converted into volume resistivity. Conversion is made into a deterioration resistance value (R2).
The carrier resistance value change rate was defined by the following equation.
| (R1-R2) | / R1 × 100
The evaluation criteria of resistance stability based on the resistance value change rate are shown below.

(Resistance stability evaluation)
0 or more to less than 3: ◎ (very good)
3 to less than 6: ○ (good)
6 or more and less than 10: △ (can be used)
10 or more: × (defect)

<Toner scattering>
After running 1 million sheets, the amount of toner collected at the bottom of the developer carrying member was sucked and collected, and the toner weight was measured. The evaluation criteria of toner scattering based on the toner weight are shown below.

(Evaluation of toner scattering)
0 mg to less than 50 mg: ◎ (very good)
50 mg to less than 100 mg: ○ (good)
100 mg or more and less than 250 mg: Δ (can be used)
250 mg or more: × (defect)

<Skin cover>
After running 1 million sheets, the blank image is stopped during development, the toner on the photoconductor after development is transferred to tape, and the difference (ΔID) from the image density of the untransferred tape is measured by 938 Spectrodensitometer (X-Rite) The measurement was carried out by the company).
The evaluation criteria for the background fog based on the image density difference are shown below.

(Skin cover evaluation)
0 or more and less than 0.005: ◎ (very good)
0.005 or more to less than 0.01: ○ (good)
0.01 or more and less than 0.02: Δ (can be used)
0.02 or more: × (defect)

<Concentration variation between pages>
100 million A3 solid images are output continuously after running 1 million sheets, and the first, 50th, and 100th solid images are measured with a 938 Spectrodensitometer (manufactured by X-Rite). went. The measurement was carried out on a single sheet at a total of 6 locations, 3 locations in the paper passing direction and 2 locations in the longitudinal direction, and the average value of the density was adopted as the ID. The maximum value of the difference between the IDs of the first, 50th, and 100th sheets was evaluated as ΔID.
Evaluation criteria for inter-page density variation based on the ID difference are shown below.

(Evaluation of variation in concentration between pages)
0 or more to less than 0.05: ◎ (very good)
0.05 or more and less than 0.1: ○ (good)
0.1 or more and less than 0.2: △ (can be used)
0.2 or more: x (defect)

  In addition, using RICOH Pro C7110S (Ricoh Digital Color Copier / Printer Combined Machine) manufactured by Ricoh, the developer 1 to 15 of Examples and Comparative Examples and the toner 1 were used, and the image area ratio was 0.5%. 1 million sheets were run, and the developer amount stability, charging stability, resistance stability, and density variation between pages were evaluated. The charging stability, resistance stability, and inter-page density variation were evaluated using the same method as described above. The evaluation method of developer amount stability is as follows.

<Developer amount stability>
The developer amount after passing through the developing doctor of the developing device is collected using a measuring jig (a jig capable of collecting 1 cm ² of developer), and the weight is measured. Three points were measured in the longitudinal direction of the developing sleeve, and the average value was taken as the developer amount on the sleeve. This was measured after the initial time and after running 1 million sheets, and evaluated by the absolute value of the difference. The evaluation criteria are shown below.
(Developer amount stability)
0 mg to less than 1 mg: ◎ (very good)
1 mg to less than 2 mg: ○ (good)
2 mg to less than 4 mg: Δ (available)
4mg or more: x (defect)

  Table 2 shows the results of the image evaluation.

31 cell 32, 32b electrode 33 carrier

Japanese Patent No. 2714590 JP 2010-117519 A Japanese Patent No. 5534409 JP 2011-209678 A JP 2006-079022 A JP 2012-058418 A

Claims (10)

Consisting of core material particles having magnetism and a coating layer covering the surface of the core material particles,
The coating layer contains a resin and conductive fine particles,
For developing an electrostatic latent image, wherein the conductive fine particles are composed of fine particles containing zinc, and a filling ratio of the fine particles containing zinc to the resin coating layer is 20% or more and 80% or less (cross-sectional area ratio). Career.   2. The electrostatic latent image developing carrier according to claim 1, wherein the fine particles containing zinc have an aggregation diameter in a resin coating film of 150 nm or more and 1000 nm or less. Fine particles containing zinc are exposed on the surface of the resin coating layer,
The exposed portion of the fine particles containing zinc is convex with respect to the surface layer of the resin coating layer that is not exposed, and the average value of the height d is 100 nm or more. The carrier for developing an electrostatic latent image.   The fine particles containing zinc are made of zinc oxide doped with aluminum, and the molar ratio of aluminum to zinc oxide is 1: 400 or more and 1: 5 or less. The electrostatic latent image developing carrier according to claim 1.   A developer comprising the carrier and the toner according to claim 1.   The developer according to claim 5, wherein the toner is a color toner.   A replenishment developer containing a carrier and a toner, the toner being contained in an amount of 2 to 50 parts by weight with respect to 1 part by mass of the carrier, wherein the carrier is the carrier according to any one of claims 1 to 4. A developer for replenishment.   An electrostatic latent image carrier, a charging unit for charging the latent image carrier, an exposure unit for forming an electrostatic latent image on the latent image carrier, and an electrostatic latent image carrier formed on the electrostatic latent image carrier. A developing unit that develops the electrostatic latent image using the developer according to claim 5 to form a toner image, and transfers the toner image formed on the electrostatic latent image carrier onto a recording medium. An image forming apparatus comprising: a transfer unit that fixes the toner image transferred to the recording medium.   An electrostatic latent image carrier, a charging member for charging the surface of the photosensitive member, and an electrostatic latent image formed on the electrostatic latent image carrier are developed using the developer according to claim 5 or 6. A process cartridge comprising: a developing unit that performs cleaning; and a cleaning member that cleans the electrostatic latent image carrier.   A process 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 5 or 6. 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.