JP2018054916A - Two-component developer for electrostatic latent image development and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-component developer for electrostatic latent image development that reduces adhesion of carrier to a photoreceptor while reducing white steaks at the rear end of a halftone image when a solid image is printed after the halftone image, and prevents fogging in a high-temperature and high-humidity environment, and an image forming method.SOLUTION: A two-component developer for electrostatic latent image development of the present invention is a two-component developer for electrostatic latent image development containing toner particles and carrier particles. The toner particle has a domain-matrix structure; the matrix contains an amorphous resin; the domain contains a crystalline polyester. The carrier particle contains a carrier core material particle containing strontium (Sr); the carrier core material particle has on its surface a coating layer containing only resin; the carrier particles have a resistance within a range of 1.0×10to 1.5×10Ω cm.SELECTED DRAWING: None

Description

  The present invention relates to a two-component developer for developing an electrostatic latent image and an image forming method. More specifically, the present invention suppresses carrier adhesion to a photoconductor while suppressing a trailing end of a halftone image when printing a solid image after a halftone image, and also prevents fogging in a high temperature and high humidity environment. The present invention relates to a two-component developer for developing an electrostatic latent image and an image forming method.

  In electrophotographic image formation, an electrostatic latent image formed on an image carrier (hereinafter also referred to as a photoconductor) is developed and visualized with toner. As this development method, a developer is conventionally held. Two methods are known depending on the rotation direction of the developing sleeve of the developing device and the photosensitive member. One is a forward development system (see FIG. 1A), and the other is a reverse development system (see FIG. 1B).

1A is a developing method in which the rotation direction W1 of the photosensitive member P and the rotation direction W2 of the developing sleeve S are opposite to each other. In this method, the surface of the photosensitive member and the developer on the developing sleeve are separated. In the developing area that comes into contact, the surface of the photosensitive member and the surface of the developing sleeve are contacted from the same direction and developed.
In the reverse development method shown in FIG. 1B, the rotation direction W1 ′ of the photosensitive member P ′ and the rotation direction W2 ′ of the developing sleeve S ′ are the same direction, and the developer on the surface of the photosensitive member and the developing sleeve is in the developing region. It contacts from the reverse direction.

  In both the forward development method and the reverse development method, a scavenging phenomenon (hereinafter, also simply referred to as “scavenging”), that is, the carrier electrostatically scrapes off the toner developed on the photoreceptor, A phenomenon that disturbs the image occurs. In the forward development method, image defects due to scavenging are particularly noticeable. Specifically, when a document having a solid image adjacent to the trailing edge of the halftone image in the paper feed direction is printed, the halftone image near the boundary between the trailing edge of the halftone image, that is, the solid image is displayed. There is a problem that white is easily missing (hereinafter, also referred to as “half-tone image trailing edge missing” or “lead-off”), and improvement is demanded.

  The cause of scavenging is a difference in the moving speed between the developing sleeve S and the photosensitive member P, and occurs when the moving speed of the developing sleeve S is set higher than the moving speed of the photosensitive member P. More specifically, when a solid image is developed, a large amount of toner is supplied to the photoconductor, so that charges remain on the carrier on the developing sleeve, and the carrier overtakes the solid image portion on the photoconductor, thereby causing a halftone. Scavenging occurs because the toner that forms the halftone image is electrostatically scraped when reaching the image area.

As a method for improving scavenging, a reduction in resistance of carriers has been proposed. By making the carrier have a low resistance, the charge of the carrier generated during solid image development is easily lost, and as a result, the toner is not scraped off and the scavenging is improved.
On the other hand, it is not necessary to lower the resistance of the carrier. If the resistance of the carrier is too low, carrier adhesion to the photoreceptor due to charge injection occurs. Therefore, it is necessary to adjust the carrier resistance to an appropriate range so that the occurrence of scavenging can be suppressed and the carrier adhesion to the photoreceptor can be suppressed.
As a method for adjusting the resistance of the carrier, for example, Patent Document 1 discloses adjusting the resistance of the carrier core particle itself and the thickness of the resin coating layer.

  In order to improve the scavenging, the movement of electrons on the surface of the resin coating layer of the carrier is also important, and it is effective to include a resistance adjusting agent in the resin coating layer. Patent Document 2 discloses that inorganic oxide fine particles are dispersed in a resin coating layer to adjust carrier resistance. However, the particles used as a resistance adjuster are scraped in a form that encloses the resin coating layer with durability, and transfer from the carrier to the toner results in a significant decrease in the charge amount, particularly fogging in a high temperature / high humidity environment. It has become.

JP 2002-139900 A JP 2001-51456 A

  The present invention has been made in view of the above problems and situations, and a solution to the problem is to suppress the trailing edge of the halftone image when printing a solid image adjacent to the trailing edge of the halftone image. Another object of the present invention is to provide a two-component developer for developing an electrostatic latent image and an image forming method that suppress carrier adhesion to a photoreceptor and prevent fogging in a high-temperature and high-humidity environment.

As a result of studying the cause of the above-mentioned problem in order to solve the above-mentioned problems, the present inventor, in the present invention, contains strontium in the carrier core material particles, and the surface of the carrier core material particles is made of only a resin. And a carrier to the photosensitive member while suppressing the trailing edge of the halftone image by using a two-component developer for developing an electrostatic latent image, which is coated with a toner and contains a crystalline polyester in the domain portion of the toner. The present inventors have found that it is possible to provide a two-component developer for developing an electrostatic latent image and an image forming method capable of suppressing adhesion and preventing fogging in a high-temperature and high-humidity environment.
That is, the said subject of this invention is solved by the following means.

1. A two-component developer for electrostatic latent image development containing toner particles and carrier particles,
The toner particles have a domain matrix structure;
The matrix contains an amorphous resin;
The domain contains a crystalline polyester;
The carrier particles contain carrier core particles containing strontium (Sr), and further have a coating layer containing only the resin on the surface of the carrier core particles,
The two-component developer for developing an electrostatic latent image, wherein the resistance of the carrier particles is in a range of 1.0 × 10 ^{8 to} 1.5 × 10 ¹⁰ Ω · cm.

2. The two-component developer for electrostatic latent image development according to item 1, wherein the resistance of the carrier particles is in a range of 1.0 × 10 ^{9 to} 1.5 × 10 ¹⁰ Ω · cm.

  3. 3. The electrostatic latent image development according to claim 1 or 2, wherein the content of strontium (Sr) in the carrier particles is in the range of 25 to 125 in terms of Net intensity by fluorescent X-ray analysis. Two-component developer.

  4). The content of strontium (Sr) in the carrier particles is in the range of 40 to 90 in terms of Net intensity by fluorescent X-ray analysis. Two-component developer for developing an electrostatic latent image.

  5. Item 5. The electrostatic latent image developing according to any one of Items 1 to 4, wherein a shape factor (SF-1) of the carrier core particles is in a range of 110 to 150. Two component developer.

  6). The two-component developer for electrostatic latent image development according to any one of items 1 to 5, wherein the amorphous resin contains a styrene-acrylic resin.

  7). The electrostatic polyester according to any one of items 1 to 6, wherein the crystalline polyester is a hybrid crystalline polyester in which a styrene-acrylic polymer segment is bonded to at least a polyester polymer segment. Two-component developer for developing latent images.

  8). The two-component developer for developing an electrostatic latent image according to item 7, wherein the content of the styrene-acrylic polymer segment in the hybrid crystalline polyester is in the range of 0.5 to 20% by mass.

  9. The static content according to any one of items 1 to 8, wherein a content ratio of the crystalline polyester in a total amount of the resin constituting the toner particles is in a range of 5 to 20% by mass. Two-component developer for developing electrostatic latent images.

  10. Item 10. The electrostatic charge according to any one of Items 1 to 9, wherein the coating layer is a polymerization reaction product of a monomer containing at least an alicyclic (meth) acrylic acid ester compound. Two-component developer for developing latent images.

  11. The electrostatic capacity according to any one of Items 1 to 10, wherein the alicyclic (meth) acrylic acid ester compound has a cycloalkyl group having 5 to 8 carbon atoms. Two-component developer for developing latent images.

  12 The two-component for electrostatic latent image development according to any one of Items 1 to 11, wherein the alicyclic (meth) acrylic acid ester compound is cyclohexyl (meth) acrylate. Developer.

  13. An image forming method using the two-component developer for developing an electrostatic latent image according to any one of items 1 to 12, comprising a charging step, an exposure step, a development step, a transfer step, and a fixing step. An image forming method comprising:

  14 14. The image forming method according to item 13, wherein the developing step is a step of developing by a forward developing method.

15. An image forming method using a two-component developer for developing an electrostatic latent image,
It has a charging process, exposure process, development process, transfer process and fixing process,
The development step is a step of developing by the forward development method,
The electrostatic latent image developing two-component developer contains toner particles and carrier particles,
The toner particles have a domain matrix structure;
The matrix contains an amorphous resin;
The domain contains a crystalline polyester;
The carrier particles contain carrier core particles containing strontium (Sr), and further have a coating layer containing only the resin on the surface of the carrier core particles,
The image forming method according to claim 1, wherein the resistance of the carrier particles is in a range of 1.0 × 10 ^{8 to} 1.5 × 10 ¹⁰ Ω · cm.

  By the above-described means of the present invention, when a solid image is printed after a halftone image, the trailing edge of the halftone image is suppressed, carrier adhesion to the photoconductor is suppressed, and fogging in a high-temperature and high-humidity environment is suppressed. An electrostatic latent image developing two-component developer and an image forming method can be provided.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.
In the present invention, a slight amount of strontium is added to the carrier core material particles to provide a difference in the growth rate of crystals such as ferrite constituting the carrier core material particles. Thereby, carrier core material particle | grains can be deformed, a carrier can be made low resistance, and scavenging can be suppressed.
Specifically, the carrier core material particles have an uneven structure due to the irregular shape of the carrier core material particles, and the coating on the convex portions of the carrier core material particles becomes thin. Alternatively, since the convex portions of the carrier core particles are appropriately exposed on the carrier surface, the resistance on the carrier surface is lowered and the charge is easily lost, so that scavenging can be suppressed. As described above, in the present invention, the carrier core material particles are unevenly shaped to adjust the resistance of the carrier, thereby suppressing the occurrence of scavenging and suppressing the carrier adhesion to the photoreceptor. it can.

In the present invention, it is possible not only to suppress the occurrence of scavenging from the carrier side, but also to suppress the scavenging from the toner side. As the binder resin constituting the toner, a crystalline polyester having a low resistance is used, and the resistance of the crystalline polyester in the domain portion of the toner is low, so that the charge of the toner is easily lost, and the charge of the carrier Therefore, it is assumed that the occurrence of scavenging can be suppressed.
Thus, in order to improve the scavenging from both the toner and the carrier, it is not necessary to add a resistance adjusting agent to the resin coating layer in the present invention. Therefore, it is possible to prevent fogging in a high-temperature and high-humidity environment accompanying a decrease in charge amount due to peeling of the resin coating layer when the above-described resin coating layer contains a resistance adjusting agent.
Further, in the present invention, since the resistance reduction is realized by deforming the carrier core particles, when a resistance modifier is added to the resin coating layer, other than the convex portions of the carrier core particles, That is, leakage also occurs due to the resistance adjusting agent in the resin coated on the recesses of the carrier core particles, and the resistance may be too low depending on the amount of the resistance adjusting agent added. Therefore, in the present invention, using a carrier whose coating layer is composed only of a resin, the resistance value is adjusted to an appropriate range, and the carrier adhesion to the photosensitive member caused by the carrier resistance being too low is suppressed. Can do.

Schematic explaining the rotation direction of the photoconductor and the developing sleeve in the forward developing method Schematic explaining the rotation direction of the photoreceptor and the developing sleeve in the reverse development system Schematic sectional view showing an example of carrier particles Schematic showing an example of the configuration of the image forming apparatus

The two-component developer for developing an electrostatic latent image of the present invention is a two-component developer for developing an electrostatic latent image containing toner particles and carrier particles, and the toner particles have a domain matrix structure. The matrix contains an amorphous resin, the domain contains a crystalline polyester, the carrier particles contain carrier core particles containing strontium (Sr), and the carrier particles It has a coating layer containing only resin on the surface, and the resistance of the carrier particles is in the range of 1.0 × 10 ^{8 to} 1.5 × 10 ¹⁰ Ω · cm.
These features are technical features common to or corresponding to the claimed invention.

Further, the resistance of the carrier particles is in the range of 1.0 × 10 ^{9 to} 1.5 × 10 ¹⁰ Ω · cm, it is possible to suppress the trailing edge missing of the halftone image and to adhere the carrier to the photoreceptor. It is preferable in that the effect of suppressing the above can be further obtained.

  In addition, from the viewpoint of manifesting the effect, the content of strontium (Sr) in the carrier particles is preferably in the range of 25 to 125 in terms of Net intensity by fluorescent X-ray analysis.

  In addition, it is preferable that the content of strontium (Sr) in the carrier particles is in the range of 40 to 90 in terms of Net intensity by fluorescent X-ray analysis, from the viewpoint of further obtaining the effects of the present invention.

  In addition, the shape factor (SF-1) of the carrier core particles is preferably in the range of 110 to 150 from the viewpoint of manifesting the effect.

  Moreover, it is preferable that the amorphous resin contains a styrene-acrylic resin from the viewpoint of suppressing the trailing edge of the halftone image.

  Further, the crystalline polyester is preferably a hybrid crystalline polyester in which a styrene-acrylic polymer segment is bonded to at least a polyester polymer segment from the viewpoint of improving the charging stability of the toner and suppressing fogging.

  In addition, the content of the styrene-acrylic polymer segment in the hybrid crystalline polyester is in the range of 0.5 to 20% by mass from the viewpoint of suppressing the trailing edge loss of the halftone image and suppressing fogging. preferable.

  Further, the content ratio of the crystalline polyester in the total amount of the resin constituting the toner particles is in the range of 5 to 20% by mass, which suppresses the trailing edge missing of the halftone image and facilitates toner preparation. It is preferable from the viewpoint.

  Moreover, it is preferable that the said coating layer is a polymerization reaction material of the monomer containing an alicyclic (meth) acrylic acid ester compound at least from a viewpoint which suppresses the fall of a charge amount and prevents fogging.

  In addition, the alicyclic (meth) acrylic acid ester compound preferably has a cycloalkyl group having 5 to 8 carbon atoms from the viewpoint of further obtaining the effect of suppressing fogging, more preferably (meta ) Cyclohexyl acrylate.

  The two-component developer for developing an electrostatic latent image of the present invention is suitably used for an image forming method having a charging step, an exposure step, a development step, a transfer step, and a fixing step. It is preferable that the development step is a step of developing by a normal development method because the effects of the present invention can be further obtained.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In addition, "-" shown in the following description is used with the meaning which includes the numerical value described before and behind that as a lower limit and an upper limit.

<Two-component developer for electrostatic latent image development>
The two-component developer for developing an electrostatic latent image of the present invention (hereinafter also simply referred to as “two-component developer” or “developer”) contains toner particles and carrier particles, and the toner particles are The surface of carrier core particles having a domain-matrix structure, wherein the matrix contains an amorphous resin, the domain contains crystalline polyester, and the carrier particles contain strontium (Sr) And having a coating layer containing only a resin, and the resistance of the carrier particles is in the range of 1.0 × 10 ^{8 to} 1.5 × 10 ¹⁰ Ω · cm.
Hereinafter, the components of the two-component developer of the present invention will be described in order.

<Carrier particles>
The surface of the carrier core material particles containing strontium (Sr) has a coating layer containing only resin.
FIG. 2 is a schematic cross-sectional view showing an example of carrier particles. As shown in FIG. 2, the carrier particles 100 constituting the two-component developer include carrier core particles 200 containing strontium (Sr), and a coating layer 300 containing only a resin on the surface of the carrier core particles 200. And have. The carrier core material particle 200 has an uneven structure, and a coating layer 300 is formed on the surface of the carrier core material particle 200. The thickness of the coating layer 300 is in accordance with the shape of the carrier core particle 200, so that the convex coating of the carrier core particle 200 is thin and the concave coating is thick. Further, the convex portions of the carrier core particle 200 may be exposed on the surface of the carrier particle 100.

(Carrier core particles)
Examples of carrier core particles (also simply referred to as “core particles” or “magnetic particles”) include magnetite, various ferrite-based particles, or those obtained by dispersing them in a resin. Various ferrite-based particles are preferable. As the ferrite, ferrite containing heavy metals such as copper, zinc, nickel and manganese and light metal ferrite containing alkali metals and / or alkaline earth metals are preferable.
The carrier core particle used in the present invention contains strontium (Sr). By adding a small amount of strontium, by making a difference in the growth rate of the crystals forming the carrier core particles, the carrier core particles are deformed, and low resistance carrier core particles are present in the vicinity of the surface of the carrier. The resistance of the carrier particles can be reduced.

Examples of the method for incorporating strontium into the carrier core material particles include using a compound containing strontium as a raw material in the production of carrier core material particles described later.
The content of strontium in the carrier particles is preferably in the range of 25 to 125, more preferably in the range of 40 to 90 in terms of fluorescent X-ray (Net) intensity by fluorescent X-ray analysis. When the content of strontium is within the above range, it is possible to suppress the trailing edge missing of the halftone image and the carrier adhesion to the photoreceptor, and to prevent the fogging.
The Net intensity of Sr can be measured using, for example, a fluorescent X-ray analyzer “XRF-1700” (manufactured by Shimadzu Corporation). As a specific measurement method, 10 g of carrier is pressurized for 30 seconds with a load of 30 t to be pelletized, and measured by quantitative analysis under the following conditions.
For the measurement, the Kα peak angle of strontium (Sr) is determined from the 2θ table and used.

-X-ray generator condition-
Target: Rh
Tube voltage: 40 kV
Tube current: 95 mA
Filter: None
-Spectroscopic conditions-
Slit: Standard attenuator: None Spectral crystal (S = Ge, C = LiF)
Detector (S = FPC, C = FPC)

The shape factor (SF-1) of the carrier core particles is preferably within the range of 110 to 150. When the shape factor of the carrier core material particles is within the above range, it is possible to suppress the trailing edge of the halftone image and the carrier from adhering to the photoreceptor, and to prevent fogging.
The shape factor of the carrier core particles can be adjusted by changing the composition ratio (strontium content) of the carrier core particles, the degree of pulverization of the raw material, the temperature during firing, and the like.
Hereinafter, a method for measuring the shape factor (SF-1) of the carrier core particles will be described.

The shape factor (SF-1) of the carrier core material particle is a numerical value calculated by the following formula.
(Formula 1): SF-1 = (maximum length of carrier core particle) ² / (projected area of carrier core particle) × (π / 4) × 100
In measuring SF-1 of the carrier core material particles, a carrier is prepared. However, when the carrier is not a single carrier but a developer, preparation is performed.

  Add developer, a small amount of neutral detergent, and pure water to the beaker and mix well. Discard the supernatant while applying a magnet to the bottom of the beaker. Furthermore, pure water is added and the supernatant liquid is discarded, so that only the carrier is separated by removing the toner and neutral detergent. Dry at 40 ° C. to obtain a single carrier. Subsequently, in order to remove the resin coating layer, the coating resin layer is dissolved in a solvent and removed.

  2 g of the carrier is put into a 20 ml glass bottle, and then 15 ml of methyl ethyl ketone is put into the glass bottle, stirred for 10 minutes with a wave rotor, and the coating layer is dissolved with a solvent. The solvent is removed using a magnet, and the carrier core material is washed three times with 10 mL of methyl ethyl ketone. The washed carrier core material is dried to obtain a carrier core material. In the measurement of SF-1 of the carrier core material particles, the carrier core material refers to particles after this pretreatment.

The carrier core material was photographed with a scanning electron microscope at a magnification of 150 at random, and 100 or more particles were photographed. Using the image processing analyzer LUZEX AP (Nireco Corp.) To measure. The number average particle diameter is a value calculated as the average value of the horizontal ferret diameter. The shape factor is a value calculated by the average value of the shape factors SF-1 calculated by Equation 1.
The particle diameter of the carrier core material particles is 10 to 100 μm, preferably 20 to 80 μm, in terms of volume average particle diameter. The volume average particle diameter of the carrier core particles is a volume-based average particle diameter measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by Sympatech) equipped with a wet disperser. Furthermore, the magnetization characteristics of the magnetic particles themselves are preferably 2.5 × 10 ^{−5 to} 15.0 × 10 ⁻⁵ Wb · m / kgG in saturation magnetization. The saturation magnetization is measured by “DC magnetization characteristic automatic recording device 3257-35” (manufactured by Yokogawa Electric Corporation).

(Coating layer)
The coating layer of the carrier used in the present invention contains only a resin. Suitable resins for forming the carrier coating layer include polyolefin resins such as polyethylene, polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene; polyacrylates such as polystyrene and polymethyl methacrylate, polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, and polyvinyl butyral. , Polyvinyl chloride, polyvinyl carbazole, polyvinyl ether, polybiliketone and other polyvinyl and polyvinylidene resins; vinyl chloride-vinyl acetate copolymers and styrene-acrylic acid copolymers; silicone resins comprising organosiloxane bonds Or a modified resin thereof (for example, modified resin by alkyd resin, polyester resin, epoxy resin, polyurethane, etc.); polytetrachloroethylene, polyvinyl fluoride Polyvinylidene fluoride, chloro tri full Lol ethylene and fluorine resins, polyamides, polyesters, polyurethanes, polycarbonates; -; epoxy resins such as urea amino resins such as formaldehyde resin. Preferable is a polyacrylate resin, and in particular, a polymerization reaction product of a monomer containing at least an alicyclic (meth) acrylic ester compound.
By including such a structural unit, the hydrophobicity of the coating layer increases, and the moisture adsorption amount of the carrier particles decreases particularly under high temperature and high humidity. Therefore, a decrease in the charge amount of the carrier under high temperature and high humidity is suppressed, and fogging is also prevented. Moreover, since the said structural unit has a rigid cyclic | annular frame | skeleton, the film | membrane intensity | strength of a coating layer improves and durability of a carrier becomes favorable. Further, a copolymer of an alicyclic (meth) acrylic acid ester compound and methyl methacrylate is more preferable. This is because the film strength is further increased by using methyl methacrylate.

  The alicyclic (meth) acrylic acid ester compound is a cyclohexane having 5 to 8 carbon atoms from the viewpoint of mechanical strength, environmental stability of charge amount (small environmental difference of charge amount), ease of polymerization and availability. It preferably has an alkyl group. The alicyclic (meth) acrylic acid ester compound is at least one selected from the group consisting of cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, and cyclooctyl (meth) acrylate. It is preferable that Among these, from the viewpoint of the mechanical strength and the environmental stability of the charge amount, it is preferable to contain cyclohexyl (meth) acrylate.

In the resin, the content of the structural unit derived from the alicyclic (meth) acrylic acid ester compound is preferably 10 to 100% by mass, and more preferably 20 to 100% by mass. Within such a range, the environmental stability and durability of the charge amount of the carrier are further improved.
The number of parts of the resin added to 100 parts by mass of the carrier core particles is preferably 1 part by mass or more and 5 parts by mass or less. The amount is more preferably 1.5 parts by mass or more and 4 parts by mass or less. When the number of added parts is within the range, it is possible to easily maintain the charge amount and suppress the resistance from becoming too high.

(Characteristics of carrier)
The resistance of the carrier particles is in the range of 1.0 × 10 ^{8 to} 1.5 × 10 ¹⁰ Ω · cm, more preferably in the range of 1.0 × 10 ^{9 to} 1.5 × 10 ¹⁰ Ω · cm. Is within. When the resistance of the carrier particles is within the above range, it is possible to suppress the adhesion of the carrier to the photoconductor while suppressing the trailing edge missing of the halftone image.
The carrier resistance of the present invention indicates the resistance of the initial carrier, and is the resistance of the carrier from which the toner is separated from the developer at the start of use of the carrier. Resistance measurement is performed by the following resistance measurement method.
The carrier resistance in the present invention is a resistance that is dynamically measured under developing conditions with a magnetic brush. An aluminum electrode drum having the same dimensions as the photosensitive drum is replaced with a photosensitive drum, and carrier particles are supplied onto the developing sleeve to form a magnetic brush. By sliding the magnetic brush against the electrode drum, applying a voltage (500 V) between the sleeve and the drum, and measuring the current flowing between the two, the resistance of the carrier particles can be obtained by the following equation 2. it can.

(Formula 2): DVR (ΩCM) = (V / I) × (N × L / DSD)
DVR: Carrier resistance (Ωcm)
V: Voltage between developing sleeve and drum (V)
I: Measurement current value (A)
N: Development nip width (cm)
L: Development sleeve length (cm)
DSD: Distance between developing sleeve and drum (cm)

In the present invention, the measurement is performed at V = 500 V, N = 1 cm, L = 6 cm, and DSD = 0.6 mm.
The volume average particle diameter of the carrier particles is preferably 10 to 100 μm, more preferably 20 to 80 μm. The volume average particle diameter of the carrier particles can be typically measured by a laser diffraction type particle size distribution measuring apparatus “HELOS” (manufactured by Sympathec) equipped with a wet disperser.

<Carrier manufacturing method>
(Preparation of carrier core particles)
An appropriate amount of raw material is weighed and then pulverized and mixed in a wet media mill, ball mill, vibration mill or the like, preferably for 0.5 hour or more, more preferably for 1 to 20 hours. Among the raw materials are compounds containing strontium. The pulverized product thus obtained is pelletized using a pressure molding machine or the like, and then calcined at a temperature of preferably 700 to 1200 ° C., preferably for 0.5 to 5 hours.

After pulverizing without using a pressure molding machine, water may be added to form a slurry, and granulated using a spray dryer. After preliminary calcination, after further pulverizing with a ball mill or vibration mill, etc., water and, if necessary, a dispersant, a binder such as polyvinyl alcohol (PVA), etc. are added to adjust the viscosity, and granulation is performed. Done. The firing temperature is preferably 1000 to 1500 ° C., and the firing time is preferably 1 to 24 hours. When pulverizing after calcination, water may be added and pulverized with a wet ball mill, a wet vibration mill or the like.
The pulverizer such as the above-mentioned ball mill or vibration mill is not particularly limited, but it is preferable to use fine beads having a particle diameter of 1 cm or less for the medium to be used in order to disperse the raw materials effectively and uniformly. Further, the degree of grinding can be controlled by adjusting the diameter, composition and grinding time of the beads used.

The fired product thus obtained is pulverized and classified. As a classification method, the particle size is adjusted to a desired particle size using an existing air classification method, mesh filtration method, sedimentation method, or the like.
Thereafter, if necessary, the surface can be heated at a low temperature to perform an oxide film treatment to adjust the resistance. The oxide film treatment can be performed by heat treatment at, for example, 300 to 700 ° C. using a general rotary electric furnace, batch electric furnace or the like. The thickness of the oxide film formed by this treatment is preferably in the range of 0.1 nm to 5 μm. By making the thickness of the oxide film within the above range, the effect of the oxide film layer can be obtained, and it is easy to obtain desired characteristics without becoming too high resistance. If necessary, reduction may be performed before the oxide film treatment. In addition, after classification, low-magnetism products may be further classified by magnetic separation.

(Preparation of coating layer)
Specific methods for producing the coating layer include a wet coating method and a dry coating method. Each method will be described below. The dry coating method is a particularly desirable method to be applied to the present invention, and will be described in detail.

(Wet coating method)
(1) Fluidized bed type spray coating method A coating solution in which a coating resin is dissolved in a solvent is spray coated on the surface of magnetic particles using a fluidized bed, and then dried to produce a coated layer. (2) Immersion Formula Coating Method A method in which magnetic particles are immersed in a coating solution in which a coating resin is dissolved in a solvent and then coated, and then dried to prepare a coating layer. (3) Polymerization Method A reactive compound is dissolved in a solvent. A method for producing a coating layer by immersing magnetic particles in a coating solution, followed by a coating treatment by applying heat and the like.

(Dry coat method)
A method in which resin particles are deposited on the surface of particles to be coated, and then a mechanical impact force is applied to melt or soften the resin particles deposited on the surface of the particles to be coated to fix the coated layer. It is.
Using a high-speed stirring mixer that can apply mechanical impact force to the carrier core material and resin without heating or under heating, the impact force is repeatedly applied to the mixture by high-speed stirring and dissolved on the surface of the magnetic particles. Alternatively, the carrier is softened and fixed.
The coating conditions are preferably 80 to 130 ° C. when heating, and the wind speed causing the impact force is preferably 10 m / s or more during heating and 5 m / s or less in order to suppress aggregation of carrier particles during cooling. Is preferred. The time for applying the impact force is preferably 20 to 60 minutes.

In the resin coating process or the process after coating, a technique for peeling the resin on the convex portion of the core material by applying stress to the carrier and exposing the core material will be described. In the resin coating process by the dry coating method, the resin can be peeled off by setting the wind speed during cooling to high-speed shear while lowering the heating temperature to 60 ° C. or lower.
Further, as the step after coating, any device capable of forced stirring can be used, and examples thereof include stirring and mixing with a turbuler, ball mill, vibration mill or the like.
Next, as a method of exposing the core material by applying the heat and impact to the coating resin to move the resin on the surface of the convex portion to the concave portion side, it is effective to take a long time to apply the impact force. Specifically, it is preferable to set it to 1 hour and a half or more.

<toner>
In the present invention, “toner” refers to an aggregate of “toner particles”. The toner particles contain at least toner base particles, and the toner particles refer to toner base particles themselves or those obtained by adding at least an external additive to the toner base particles.

(Toner base particles)
The toner base particles constituting the toner particles include an amorphous resin and a crystalline polyester as a binder resin (binder resin). The toner base particles have a domain / matrix structure in which a domain phase containing a crystalline resin is dispersed in a matrix phase containing an amorphous resin.
The “domain matrix structure” means a structure in which a domain phase having a closed interface (a boundary between phases) exists in a continuous matrix phase. In the domain matrix structure according to the present invention, the matrix contains an amorphous resin, and the domain contains a crystalline polyester. The toner base particles have a structure in which there is a portion in which the crystalline polyester is introduced incompatible with the amorphous resin.
In addition, this structure can observe the cross section of the toner base particle dye | stained by the osmium by a usual method using a transmission electron microscope. In the case of cutting a section with an ultramicrotome, the thickness of the section is set to 100 nm. In addition to the crystalline polyester, wax or the like may be added in the domain.
The toner base particles may contain an internal additive such as a colorant, a release agent, and a charge control agent, if necessary. The toner base particles may be dry, but a wet manufacturing method (for example, an emulsion aggregation method) prepared in an aqueous medium is more preferable.

(Amorphous resin)
There is no particular limitation on the amorphous resin constituting the matrix phase, and a conventionally known amorphous resin in this technical field can be used. Among them, the amorphous resin may contain an amorphous vinyl resin. preferable. Particularly preferred is a styrene-acrylic copolymer resin formed using a styrene monomer, a (meth) acrylic acid ester monomer or acrylic acid.
By emulsifying and aggregating styrene-acrylic resin into a toner, the amount of water in the toner becomes moderately high, the adhesion of the toner to the photoreceptor increases, the toner becomes difficult to detach from the photoreceptor, and scavenging occurs. Can be suppressed.
As the vinyl monomer that forms the amorphous vinyl resin, one or more selected from the following may be used.

(1) Styrene monomer Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert -Butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, and derivatives thereof.

(2) (meth) acrylic acid ester monomer (meth) methyl acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isopropyl (meth) acrylate, isobutyl (meth) acrylate, T-butyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, phenyl (meth) acrylate, (meth ) Diethylaminoethyl acrylate, dimethylaminoethyl (meth) acrylate, and derivatives thereof.

(3) Vinyl esters Vinyl propionate, vinyl acetate, vinyl benzoate and the like.
(4) Vinyl ethers Vinyl methyl ether, vinyl ethyl ether and the like.
(5) Vinyl ketones Vinyl methyl ketone, vinyl ethyl ketone, vinyl hexyl ketone and the like.
(6) N-vinyl compounds N-vinylcarbazole, N-vinylindole, N-vinylpyrrolidone and the like.

(7) Others Vinyl compounds such as vinyl naphthalene and vinyl pyridine, acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile and acrylamide.
Moreover, as a vinyl-type monomer, it is preferable to use the monomer which has ionic dissociation groups, such as a carboxy group, a sulfonic acid group, and a phosphoric acid group, for example. Specifically, there are the following.
Examples of the monomer having a carboxy group include acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, and the like. Examples of the monomer having a sulfonic acid group include styrene sulfonic acid, allyl sulfosuccinic acid, and 2-acrylamido-2-methylpropane sulfonic acid. Furthermore, examples of the monomer having a phosphate group include acid phosphooxyethyl methacrylate.

Furthermore, polyfunctional vinyls can be used as the vinyl monomer, and the amorphous vinyl resin can have a crosslinked structure. Polyfunctional vinyls include divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol Examples include diacrylate.
As described above, the vinyl resin has been described in detail as a preferred form of the amorphous resin, but an amorphous polyester resin or the like may be used as the amorphous resin.

(Crystalline polyester)
In the present invention, the domain phase of the toner contains a crystalline polyester. There is no restriction | limiting in particular also about the crystalline polyester which comprises a domain phase, The conventionally well-known amorphous resin in this technical field can be used.
“Crystalline polyester” means a differential scanning calorific value among known polyester resins obtained by polycondensation reaction of a divalent or higher carboxylic acid (polyvalent carboxylic acid) and a divalent or higher alcohol (polyhydric alcohol). In measurement (DSC), it refers to a resin having a clear endothermic peak rather than a stepwise endothermic change.
The clear endothermic peak specifically means a peak in which the half-value width of the endothermic peak is within 15 ° C. when measured at a rate of temperature increase of 10 ° C./min in differential scanning calorimetry (DSC). To do.

  The polyvalent carboxylic acid is a compound containing two or more carboxy groups in one molecule. Specifically, for example, oxalic acid, malonic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, n-dodecyl succinic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, decanedicarboxylic acid, dodecanedicarboxylic acid Saturated aliphatic dicarboxylic acids such as alicyclics; cycloaliphatic dicarboxylic acids such as cycloaliphatic dicarboxylic acids; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid; and trivalent or higher polyvalents such as trimellitic acid and pyromellitic acid Carboxylic acid; and anhydrides of these carboxylic acid compounds, or alkyl esters having 1 to 3 carbon atoms. These may be used individually by 1 type and may be used in combination of 2 or more type.

  A polyhydric alcohol is a compound containing two or more hydroxyl groups in one molecule. Specifically, for example, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol , 1,8-octanediol, 1,9-nonanediol, dodecanediol, neopentylglycol, 1,4-butenediol and other aliphatic diols; glycerin, pentaerythritol, trimethylolpropane, sorbitol A polyhydric alcohol etc. are mentioned. These may be used individually by 1 type and may be used in combination of 2 or more type.

In the present invention, from the viewpoint of the size of the crystalline polyester domain, the number of carbons in the main chain of the structural unit derived from the polyhydric alcohol for forming the crystalline polyester resin is Calcohol, and the crystalline polyester resin is formed. When the number of carbons in the main chain of the structural unit derived from the polycarboxylic acid is Cacid, it is preferable to satisfy the following relational expression (1).
Relational expression (1): 5 ≦ | Cacid-Calcol | ≦ 12
Relational expression (2): Cacid> Calcohol
When the alkyl chains of alcohol and acid are different, non-uniform crystalline polyester is formed, and the crystalline polyester is difficult to aggregate.
By satisfying the relational expression (1) and the relational expression (2), the domain becomes an appropriate size, charges can be diffused appropriately, and scavenging can be suppressed.

In the present invention, the melting point of the crystalline polyester is a value measured as follows. That is, using a differential scanning calorimeter “Diamond DSC” (manufactured by PerkinElmer Co., Ltd.), a first temperature raising process in which the temperature is raised from 0 ° C. to 200 ° C. at an elevation rate of 10 ° C./min, and a cooling rate of 10 ° C./min is 200 ° C. It is measured by the measurement conditions (temperature increase / cooling conditions) that pass through the cooling process for cooling from 0 to 0 ° C. and the second temperature increasing process for increasing the temperature from 0 ° C. to 200 ° C. at a rate of 10 ° C./min. Yes, based on the DSC curve obtained by this measurement, the endothermic peak top temperature derived from the crystalline polyester in the first temperature raising process is defined as the melting point (Tm).
As a measurement procedure, 3.0 mg of a measurement sample (crystalline polyester resin) is sealed in an aluminum pan and set in a diamond DSC sample holder. The reference uses an empty aluminum pan.

The content of the crystalline polyester is preferably in the range of 5 to 20% by mass with respect to the total amount of the resin constituting the toner particles. When the content of the crystalline polyester is within the range, the effect of suppressing the trailing edge missing of the halftone image is easily obtained, and the toner is easily manufactured.
The crystalline polyester forming the domain is preferably a hybrid crystalline polyester in which a styrene-acrylic polymer segment is bonded to a polyester polymer segment. At this time, it is preferable that the styrene-acrylic polymer segment and the polyester polymer segment are a hybrid crystalline polyester in which both reactive monomers are bonded. By hybridizing crystalline polyester with styrene-acrylic resin, the styrene-acrylic resin in the hybrid part firmly binds the domain and the matrix. By being hybridized, the strength is increased at the interface between the domain and the matrix, so that the durability is increased and the toner is hardly broken.

  The styrene-acrylic polymer segment constituting the hybrid crystalline polyester is composed of a styrene-acrylic resin obtained by polymerizing a vinyl monomer. Here, since it is as having mentioned above as a vinyl-type monomer, detailed description is abbreviate | omitted here. In addition, it is preferable that the content rate of the styrene-acryl polymerization segment in a hybrid crystalline polyester exists in the range of 0.5-20 mass%. When the content ratio of the styrene-acrylic polymer segment is within the numerical range, an effect of preventing fogging is easily obtained, and an effect of suppressing the trailing edge omission of the halftone image is easily obtained.

  The polyester polymerization segment constituting the hybrid resin is composed of a crystalline polyester produced by performing a polycondensation reaction between a polyvalent carboxylic acid and a polyhydric alcohol in the presence of a catalyst. Here, the specific types of the polyvalent carboxylic acid and the polyhydric alcohol are as described above, and thus detailed description thereof is omitted here.

  The “both reactive monomers” is a monomer that binds a polyester polymer segment and a styrene-acryl polymer segment. In the molecule, a hydroxy group, a carboxy group, an epoxy group, a first group that forms a polyester polymer segment. It is a monomer having both a group selected from a primary amino group and a secondary amino group and an ethylenically unsaturated group that forms a vinyl polymerized segment. Both reactive monomers are preferably monomers having a hydroxy group or a carboxy group and an ethylenically unsaturated group. More preferably, it is a monomer having a carboxy group and an ethylenically unsaturated group. That is, it is preferably a vinyl carboxylic acid.

Specific examples of the both reactive monomers include, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid and the like, and even these hydroxyalkyl (1 to 3 carbon atoms) esters. Acrylic acid, methacrylic acid or fumaric acid is preferred from the viewpoint of reactivity. The polyester polymer segment and the styrene-acryl polymer segment are bonded through the both reactive monomers.
From the viewpoint of improving the low-temperature fixability, high-temperature offset resistance and durability of the toner, the amount of both reactive monomers used is 100 parts by weight based on the total amount of vinyl monomers constituting the styrene-acrylic polymer segment. 1 to 10 parts by mass is preferable, and 4 to 8 parts by mass is more preferable.
As a method for producing the hybrid resin, an existing general scheme can be used. The following three methods are listed as typical methods.

(1) A polyester polymerization segment is preliminarily polymerized, and the polyester polymerization segment is reacted with both reactive monomers, and further, an aromatic vinyl monomer for forming a vinyl polymerization segment and (meth) A method of forming a hybrid resin by reacting an acrylate monomer.
(2) A vinyl polymer segment is polymerized in advance, the vinyl polymer segment is reacted with both reactive monomers, and a polyvalent carboxylic acid and a polyhydric alcohol for forming a polyester polymer segment are further reacted. A method for forming a polyester polymer segment by causing the polyester polymer segment to form.
(3) A method in which a polyester polymer segment and a vinyl polymer segment are polymerized in advance, and both are reacted with each other to react them.

In the present invention, any of the above production methods can be used, but the method of the above item (2) is preferred. Specifically, the polyhydric carboxylic acid and polyhydric alcohol forming the polyester polymerization segment, the vinyl monomer forming the vinyl polymerization segment and the both reactive monomers are mixed, and a polymerization initiator is added. It is preferable to carry out a polycondensation reaction by adding an esterification catalyst after addition polymerization of a vinyl monomer and an amphoteric monomer to form a styrene-acrylic polymer segment.
Here, as a catalyst for synthesizing the polyester polymerization segment, various conventionally known catalysts can be used. In addition, examples of the esterification catalyst include tin compounds such as dibutyltin oxide and tin (II) 2-ethylhexanoate, and titanium compounds such as titanium diisopropylate bistriethanolamate. An acid etc. are mentioned.

(External additive)
The toner base particles can be used as toner particles as they are, but from the viewpoint of improving charging performance, fluidity, or cleaning properties as toner, particles such as known inorganic fine particles and organic fine particles on the surface thereof, A lubricant can be added as an external additive.
As the external additive, conventionally known metal oxide particles can be used. For example, silica particles, titania particles, alumina particles, zirconia particles, zinc oxide particles, chromium oxide particles, cerium oxide particles, antimony oxide particles, Examples include tungsten oxide particles, tin oxide particles, tellurium oxide particles, manganese oxide particles, and boron oxide particles. These may be used alone or in combination of two or more.

[Lubricant]
In order to further improve the cleaning property and transfer property, it is possible to use a lubricant as an external additive. For example, the following salts of zinc stearate, aluminum, copper, magnesium, calcium, etc., zinc oleate, manganese, iron, copper, magnesium, etc., zinc palmitate, salts of copper, magnesium, calcium, etc., Examples thereof include metal salts of higher fatty acids such as zinc linoleic acid, salts such as calcium, and zinc ricinoleic acid, such as zinc and calcium.
The total amount of these external additives is preferably in the range of 0.1 to 10% by mass, more preferably in the range of 1 to 5% by mass with respect to the total toner.

[Internal additive]
Examples of the internal additive used in the present invention include a release agent, a charge control agent, a colorant, and the like, and the details will be described.

[Release agent]
The toner particles may contain a release agent. Here, the release agent is not particularly limited. For example, hydrocarbon waxes such as polyethylene wax, oxidized polyethylene wax, polypropylene wax, oxidized polypropylene wax, carnauba wax, fatty acid ester wax, sacrificial wax. Examples include sol wax, rice wax, candelilla wax, jojoba oil wax, and beeswax wax.
The content of the release agent in the toner particles is preferably in the range of 1 to 30 parts by mass, more preferably in the range of 5 to 20 parts by mass with respect to 100 parts by mass of the binder resin. .

[Charge control agent]
The toner particles may contain a charge control agent. Examples thereof include metal complexes (salicylic acid metal complexes) of salicylic acid derivatives such as zinc and aluminum, calixarene compounds, organic boron compounds, and fluorine-containing quaternary ammonium salt compounds.
The content ratio of the charge control agent in the toner particles is preferably in the range of 0.1 to 5 parts by mass with respect to 100 parts by mass of the binder resin.

[Colorant]
The toner particles may further contain a colorant to form a color toner.
Colorants that can be used include known inorganic or organic colorants. Hereinafter, specific colorants are shown.
Examples of the black colorant include carbon black such as furnace black, channel black, acetylene black, thermal black and lamp black, and magnetic powder such as magnetite and ferrite.

  Examples of the colorant for magenta or red include C.I. I. Pigment Red 2, 3, 5, 6, 7, 15, 15, 48: 1, 53: 1, 57: 1, 60, 63, 64, 68, the same 81, 83, 87, 88, 89, 90, 112, 114, 122, 123, 139, 144, 149, 150, 163, 166, 170, 177, 178, 184, 202, 206, 207, 209, 222, 238, 269, and the like.

Examples of the colorant for orange or yellow include C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment yellow 12, 14, 15, 17, 74, 83, 93, 94, 138, 155, 162, 180, 185, and the like.
Further, examples of the colorant for green or cyan include C.I. I. Pigment Blue 2, 3, 15, 15, 15: 2, 15: 3, 15: 4, 16, 17, 17, 60, 62, 66, C.I. I. And CI Pigment Green 7.

  Examples of the dye include C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 2, 6, 14, 15, 16, 19, 21, 21, 33, 44, 56, 61, 77, 79, 80, 81, 82, the same 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95 and the like.

These colorants can be used alone or in combination of two or more as required. When the colorant is used, the addition amount is preferably in the range of 1 to 30% by mass and more preferably in the range of 2 to 20% by mass with respect to the whole toner.
As the colorant, a surface-modified one can also be used. As the surface modifier, conventionally known ones can be used, and specifically, silane coupling agents, titanium coupling agents, aluminum coupling agents and the like can be preferably used.

(Volume average particle diameter of toner particles)
The volume average particle size of the toner particles, that is, the particles after the external additive is added, is preferably 4.0 μm or more and 10.0 μm or less. When the volume average particle size is in the numerical range, the fluidity of the toner particles is improved, and the rise in the charge amount of the toner particles and the deterioration in image quality can be suppressed. The volume average particle size of the toner particles is more preferably 4.5 μm or more and 8.0 μm or less, and further preferably 5.0 μm or more and 7.5 μm or less.
As the volume average particle diameter of the toner particles, specifically, a volume-based median diameter (D50) measured by the following method is adopted.

≪Measurement method≫
The volume-based median diameter (D50) of the toner particles can be measured and calculated using an apparatus in which a computer system for data processing is connected to “Multisizer 3 (manufactured by Beckman Coulter)”.
As a measurement procedure, 0.02 g of toner particles are added with 20 mL of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing toner particles). After being blended, ultrasonic dispersion is performed for 1 minute to prepare a toner particle dispersion.
This toner particle dispersion is poured into a beaker containing ISOTON II (manufactured by Beckman Coulter) in a sample stand with a pipette until the measured concentration falls within a range of 5 to 10%. Set to and measure.

The aperture size of the multisizer 3 is 100 μm. The frequency number obtained by dividing the measurement range of 1 to 30 μm into 256 parts is calculated, and the particle diameter of 50% from the larger volume integrated fraction is defined as the volume-based median diameter (D50).
The volume average particle diameter of the toner particles can be controlled by controlling the concentration of the aggregating agent, the amount of the organic solvent added, the fusing time, and the like in the above production method.

(Average circularity of toner particles)
The average circularity of the toner particles is preferably 0.98 or less, more preferably 0.97 or less, and further preferably in the range of 0.93 to 0.97. If the average circularity is in such a range, the toner particles are more easily charged.
The average circularity can be measured using, for example, a flow type particle image analyzer “FPIA-3000” (manufactured by Sysmex), and specifically can be measured by the following method.

≪Measurement method≫
The toner particles are moistened with an aqueous surfactant solution and subjected to ultrasonic dispersion for 1 minute. After dispersion, the number of HPF detections is 3000 to 10,000 in the measurement condition HPF (high magnification imaging) mode using “FPIA-3000”. Measure at an appropriate concentration within the range. Within this range, reproducible measurement values can be obtained. The circularity is calculated by the following formula 3.
(Expression 3): Circularity = (perimeter of a circle having the same projection area as the particle image) / (perimeter of the particle projection image)
The average circularity is an arithmetic average value obtained by adding the circularity of each particle and dividing by the total number of particles measured.
The average circularity of the toner particles can be controlled by controlling the temperature, time, etc. during the aging process in the above-described production method.

<Toner production method>
(Method for producing toner base particles)
The toner base particles, that is, the particles before the addition of the external additive can be manufactured by a known toner manufacturing method. That is, a toner by a so-called pulverization method in which toner base particles are produced through a kneading, pulverization, and classification process, or a so-called polymerization method in which a polymerizable monomer is polymerized and at the same time particle formation is performed while controlling the shape and size. A manufacturing method is mentioned.
Among these, the toner production method using the polymerization method can form particles while controlling the size and shape, which is advantageous for producing small-sized toner particles for forming high-quality images such as fine dot images and fine line images. Can be said. The toner manufacturing method using a polymerization method is, for example, for producing toner base particles through a step of forming resin particles by a polymerization reaction such as suspension polymerization or emulsion polymerization.

  Among the polymerization methods, a toner production method of a polymerization method having an association step in which resin particles of about 100 nm, for example, are produced by a polymerization reaction and the toner particles are aggregated and fused to produce toner base particles is particularly preferable. . By providing this association step, for example, resin particles having a low glass transition temperature contributing to low-temperature fixing are aggregated to produce core particles, and then, resin particles having a high glass transition temperature are attached to the surface of the core particles. It is also possible to produce toner particles having a core-shell structure by agglomeration.

In the emulsion association method, first, resin particles of a binder resin of about 100 nm are formed in advance by an emulsion polymerization method or a suspension polymerization method, and the toner particles are aggregated and fused to form toner base particles.
More specifically, the binder resin particles (dispersion liquid) are obtained by charging and dispersing the monomer constituting the binder resin in an aqueous medium and polymerizing these polymerizable monomers with a polymerization initiator. Is made. Moreover, when it contains a coloring agent, a coloring agent is separately disperse | distributed in an aqueous medium, and a coloring agent particle dispersion liquid is produced. The volume-based median diameter (D50) of the colorant particles in the dispersion is preferably in the range of 80 to 200 nm. The volume-based median diameter of the colorant particles in the dispersion can be measured, for example, using a Microtrac particle size distribution analyzer UPA-150 manufactured by Nikkiso Co., Ltd.

  Next, the above-mentioned resin particles and, if necessary, the colorant particles are aggregated in an aqueous medium, and at the same time, these particles are fused to produce toner base particles. That is, after adding an alkali metal salt or a salt of a Group 2 element as an aggregating agent to an aqueous medium obtained by mixing the resin particle dispersion and the colorant particle dispersion, the resin particles have a glass transition temperature or higher. Aggregation is advanced by heating at a temperature, and at the same time, the resin particles are fused. When the size of the toner base particles reaches a target size, salt is added to stop aggregation. Thereafter, the reaction system is heated to age the toner base particles to a desired shape, thereby completing the toner base particles.

When aggregating, the time for which the dispersion is allowed to stand after adding the aggregating agent (time until heating is started) is shortened as much as possible, and heating is started as quickly as possible, and the glass transition temperature of the binder resin is exceeded. It is preferable to do.
The standing time is usually within 30 minutes, preferably within 10 minutes. The temperature at which the flocculant is added is not particularly limited, but is preferably not higher than the glass transition temperature of the binder resin.
Thereafter, the temperature is preferably raised quickly by heating, and the rate of temperature rise is preferably 0.5 ° C./min or more.

The upper limit of the heating rate is not particularly limited, but is preferably 15 ° C./min or less from the viewpoint of suppressing the generation of coarse particles due to rapid progress of fusion.
Furthermore, after the dispersion liquid for aggregation reaches a temperature equal to or higher than the glass transition temperature, the fusion is continued by maintaining the temperature of the dispersion liquid for a certain period of time. Thereby, the growth of the toner base particles (aggregation of the binder resin particles and the colorant particles) and the fusion (disappearance of the interface between the particles) can be effectively advanced.
More specifically, a base such as an aqueous sodium hydroxide solution is added to the dispersion of colorant particles and binder resin particles in advance to impart cohesion, and the pH is adjusted within the range of 9-12. Is preferred.

Next, an aggregating agent such as an aqueous magnesium chloride solution is added to the dispersion containing the binder resin particles and the colorant particles with stirring within a range of 25 to 35 ° C. for 5 to 15 minutes.
The amount of the flocculant used is suitably in the range of 5 to 20% by mass with respect to the total solid content of the binder resin particles and the colorant particles.
Thereafter, the mixture is allowed to stand for 1 to 6 minutes, and the temperature is raised to a range of 70 to 95 ° C. over 30 to 90 minutes, so that the aggregated resin particles and colorant particles can be fused. At this time, the volume-based median diameter of the fused toner base particles is measured, and when it falls within the range of 3 to 5 μm, an aqueous sodium chloride solution or the like is added to stop particle growth.
Further, as the aging treatment, the liquid temperature can be set within the range of 80 to 100 ° C., and the mixture can be heated and stirred, and the particles can be fused until the average circularity becomes within the range of 0.900 to 0.980.

<Flocculant>
Although the flocculant which can be used by this invention is not specifically limited, What is selected from a metal salt is used suitably. For example, monovalent metal salts such as alkali metal salts such as sodium, potassium and lithium; divalent metal salts such as calcium, magnesium, manganese and copper; salts of trivalent metals such as iron and aluminum There is.
Specific examples of the salt include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, and manganese sulfate. Among these, divalent metal is particularly preferable. It is salt. When a divalent metal salt is used, agglomeration can be promoted with a smaller amount. These may be used alone or in combination of two or more.

<Other additives>
The dispersion liquid in the aggregation step may contain the above-described release agent, charge control agent, and further known additives such as a dispersion stabilizer and a surfactant. These additives may be added to the aggregation process as a dispersion of the additive, or may be contained in the dispersion of the colorant particles or the dispersion of the binder resin.
The toner base particles grown to a desired size by the method described above are filtered and dried. Examples of the filtration method include a centrifugal separation method, a vacuum filtration method using Nutsche and the like, and a filtration method using a filter press and the like, and are not particularly limited. Next, the toner base particles (cake-like aggregate) separated by filtration are washed with ion-exchanged water to remove deposits such as a surfactant and an aggregating agent. In the washing treatment, the washing treatment is performed until the electrical conductivity of the filtrate reaches a level of, for example, 3 to 10 μS / cm.

Drying is not particularly limited as long as the washed toner base particles can be dried. Examples of the dryer include known dryers such as a spray dryer, a vacuum freeze dryer, and a vacuum dryer. It is possible to use a mobile shelf dryer, a fluidized bed dryer, a rotary dryer, a stirring dryer, an airflow dryer, and the like. The amount of water contained in the dried toner base particles is preferably 5% by mass or less, and more preferably 2% by mass or less.
Further, when the dried toner base particles are aggregated with a weak interparticle attractive force, the aggregate may be crushed. Here, as the crushing treatment device, a mechanical crushing device such as a jet mill, a Henschel mixer, a coffee mill, a food processor, or the like can be used.

(How to add external additives)
External additives are added to the obtained dried toner base particles by a dry method in which the following external additives are added in powder form and mixed, whereby the toner particles according to the present invention are produced. As a mixing device for the external additive, various known mixing devices such as a Turbuler mixer, a Henschel mixer, a Nauter mixer, and a V-type mixer can be used. For example, when a Henschel mixer is used, the peripheral speed at the tip of the stirring blade is preferably in the range of 30 to 80 m / s, and the mixture is stirred and mixed at 20 to 50 ° C. for about 10 to 30 minutes.

<Method for producing two-component developer>
Carrier particles and toner particles are mixed to prepare a two-component developer. Examples of the mixing apparatus used for mixing the carrier particles and the toner particles include a Henschel mixer, a Nauter mixer, and a V-type mixer. The mixing amount of the toner particles is preferably in the range of 1 to 10% by mass with respect to the entire two-component developer.

<Image forming method>
The two-component developer of the present invention can be used in various known electrophotographic image forming methods, for example, a monochrome image forming method or a full color image forming method. In the full-color image forming method, four types of color developing devices for yellow, magenta, cyan, and black, respectively, and one electrostatic latent image carrier (also referred to as “electrophotographic photosensitive member” or simply “photosensitive member”). 4 cycle type image forming method, and a tandem type image forming method in which an image forming unit having a color developing device and an electrostatic latent image carrier for each color is mounted for each color, etc. The image forming method can also be used.

  As an electrophotographic image forming method, specifically, by using the two-component developer of the present invention, for example, charging (charging process) on an electrostatic latent image carrier with a charging device and image exposure. The electrostatic latent image (exposure process) formed electrostatically is developed by charging the toner particles with the carrier particles in the two-component developer of the present invention in the developing device, and developing the toner image. To obtain (development process). Then, the toner image is transferred to a sheet through an intermediate transfer member as necessary (transfer process), and then the toner image transferred onto the sheet is fixed on the sheet by a fixing process such as a contact heating method (fixing process). ) To obtain a visible image.

The development process may be either a development process using the forward development system or a development process using the reverse development system, but the two-component developer of the present invention is particularly suitable for image formation having a development process using the forward development system. It is suitably used for the method.
The forward rotation developing method is a developing method in which the rotation direction W1 of the photosensitive member P and the rotation direction W2 of the developing sleeve S are opposite to each other as shown in FIG. 1A. In this method, in the development region where the surface of the photosensitive member and the developer on the developing sleeve are in contact, development is performed by contacting the surface of the photosensitive member and the surface of the developing sleeve from the same direction.
On the other hand, as shown in FIG. 1B, the reverse developing method is a developing method in which the rotation direction W1 ′ of the photosensitive member P ′ and the rotation direction W2 ′ of the developing sleeve S ′ are the same direction. In this method, in the development region where the surface of the photosensitive member and the developer on the developing sleeve are in contact, development is performed by contacting the surface of the photosensitive member and the surface of the developing sleeve from opposite directions.

The scavenging phenomenon, that is, the phenomenon in which the carrier electrostatically scrapes off the toner developed on the photosensitive member and disturbs the image occurs in both the forward developing method and the reverse developing method. This is particularly noticeable when the forward developing method is adopted, and occurs when the peripheral speed Vs of the developing sleeve S is larger than the peripheral speed Vp of the photosensitive member P.
The two-component developer of the present invention is preferably used in an image forming method having a developing process by a forward rotation developing system in that the effect of the present invention can be further obtained.
In the following, first, an image forming apparatus used in the image forming method of the present invention will be described. However, the image forming apparatus used in the image forming method of the present invention is not limited to the following forms and illustrated examples.

<Image forming device>
FIG. 3 is a schematic diagram illustrating an example of the configuration of the image forming apparatus. In the illustrated example, an image forming apparatus adopting a forward developing method is shown. When the reverse development method is employed, the rotation direction of the photoconductor and the rotation direction of the developing sleeve are changed as shown in FIG. 1B.
This image forming apparatus includes a photosensitive member P that is a rotating image forming member, and a charging unit 11, an exposing unit 12, and a developing unit 13 that are arranged on the peripheral surface of the photosensitive member P along the rotation direction W 1 of the photosensitive member P. The image forming apparatus includes a transfer unit 14, a charge eliminating unit 15, and a cleaning unit 16, and further includes a fixing unit (not shown).

The photoreceptor P is made of an organic photoreceptor in which a photosensitive layer made of a resin containing an organic photoconductor is formed on the outer peripheral surface of a drum-shaped metal substrate, and is charged to the same polarity as the toner by the charging unit 11. Is done.
The exposure unit 12 includes a beam emission source such as a laser diode, and the charged surface of the photosensitive member P is irradiated with beam light so that the charge of the irradiated portion disappears. An electrostatic latent image is formed.
The developing unit 13 includes a developing sleeve S disposed so as to face the photosensitive member P with the developing region R interposed therebetween. The developing sleeve S rotates so that the peripheral surface thereof is moved in the forward direction with the rotation direction W1 of the photosensitive member P at a position facing the photosensitive member P, and carries and conveys a two-component developer described later in the developing region R. Then, the electrostatic latent image on the photoreceptor P is developed.

The circumferential speed Vs of the developing sleeve S is, for example, 10 mm / sec to 2400 mm / sec, and the circumferential speed Vp of the photosensitive member P is, for example, 10 mm / sec to 800 mm / sec. As described above, the scavenging phenomenon occurs when the peripheral speed Vs of the developing sleeve S is faster than the peripheral speed Vp of the photosensitive member P, and the peripheral speed ratio between the developing sleeve S and the photosensitive member P ( Vs / Vp) is preferred when it is in the range of 1.2-3.
Since the peripheral speed ratio is within the range, the amount of the developer guided to the photosensitive member P by the developing unit 13 is reduced, and the toner supplied from the developing unit 13 to the photosensitive member P is not short. Thus, an image having a sufficient image density is easily obtained. In addition, the effect of suppressing the trailing edge loss of the halftone image due to the scavenging phenomenon can be sufficiently obtained.
Further, the size of the closest distance between the developing sleeve S and the photoreceptor P in the developing region R is preferably in the range of 0.25 to 0.35 mm, for example. The developing sleeve S is made of a metal such as aluminum or SUS, and has a magnet body (not shown) fixedly provided therein. On the developing sleeve S, an AC voltage from an AC power source and a DC voltage from a DC power source are superimposed as a developing bias.

The transfer unit 14 faces the photoconductor P through the transfer material T, and transfers a toner image based on the electrostatic latent image to the transfer material T.
The neutralization unit 15 performs neutralization on the photoreceptor P after the toner image is transferred.
A fixing unit (not shown) applies a fixing process by applying heat, pressure, or the like to fix the image on the transfer material T.
The cleaning unit 16 includes a blade B, and the blade B cleans the surface of the photoconductor P to remove the developer remaining on the surface of the photoconductor P.

<Image forming operation>
In the above image forming apparatus, for example, an image forming operation is performed as follows.
That is, first, the photoconductor P is rotated in the direction indicated by the arrow W1 in FIG. 1, and the surface of the photoconductor P is sequentially charged to a predetermined polarity (for example, the same polarity as the toner) by the charging unit 11, and a predetermined potential is applied. After that, the surface of the photosensitive member P is exposed by the exposure unit 12 to form an electrostatic latent image corresponding to the image data.
On the other hand, the developing sleeve S is rotated so that the peripheral surface thereof is moved in the forward direction in the developing region R (the direction indicated by the arrow W2), and is charged with the same polarity as the surface potential of the photosensitive member P. In a state where the transport amount is regulated by a developer amount regulating member (not shown), the developer containing the toner is developed while forming a magnetic brush by the magnetic force of the magnet body arranged inside the developing sleeve S. It is carried and transported to the region R. Then, the toner on the developing sleeve S adheres to the exposed portion of the photoreceptor P and development is performed, whereby a toner image is formed on the photoreceptor P.

The toner image formed on the photoreceptor P is transferred by the transfer unit 14 onto the transfer material T conveyed in synchronization with the transfer unit 14, and then the toner image is transferred by the charge eliminating unit 15. The subsequent charge removal on the photoreceptor P is performed. The transfer material T onto which the toner image has been transferred is conveyed to a fixing unit (not shown), and a fixing process is performed by the fixing unit to fix the visible image on the transfer material T.
On the other hand, the untransferred toner remaining on the photoreceptor P is removed by the blade B of the cleaning unit 16.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" is used in an Example, all represent "mass part".

[Preparation of core particles]
(Preparation of core particle 1)
19.0 mol% in terms of MnO, 2.8 mol% in terms of MgO, 1.5 mol% in terms of SrO, and appropriate amount of each raw material to be 75.0 mol% in terms _{of Fe} 2 _{O 3.} Water was added, and the mixture was pulverized, mixed and dried for 10 hours in a wet ball mill, held at 950 ° C. for 4 hours, and then the slurry pulverized for 24 hours in a wet ball mill was granulated and dried. Next, 50% of the volume was added into a firing furnace with a built-in stirring device, held at a peripheral speed of 10 m / s, and 1300 ° C. for 4 hours, and then crushed to adjust the particle size to a particle size of 35 mm. Core material particles 1 were obtained. Moreover, the shape factor SF-1 of the carrier core material particles of the obtained core material particles 1 was 129.

(Preparation of core particle 2-10)
In the production of the core material particles 1, core material particles 2 to 10 were obtained in the same manner as the production method of the core material particles 1 except that the addition amount of SrO and the firing temperature were changed as shown in Table 1.

<Creation of carrier>
<< Production of Carrier 1 >>
100 parts by mass of the core material particles 1 produced above and 2.5 parts by mass of copolymer resin fine particles of cyclohexyl methacrylate / methyl methacrylate (copolymerization ratio 5/5), a high-speed mixer with stirring blades It was thrown into. After stirring and mixing at 125 ° C. for 45 minutes at a wind speed of 10 m / s and forming a resin coating layer on the surface of the core particles by the action of mechanical impact force, cooling is performed by lowering the wind speed to 2 m / s and coating with resin. “Carrier 1” was prepared.
As described above, the Net intensity of Sr was measured by fluorescent X-ray analysis and found to be 73.3. Further, when the resistance of the carrier was measured as described above, it was 5.1 × 10 ⁹ Ω · cm.

(Production of carriers 2 to 13 and carriers 17 to 19)
Carriers 2 to 13 and carriers 17 to 19 were obtained in the same manner as the carrier 1 except that the amount of the core particles and the coating layer used was changed as shown in Table 2 in the production of the carrier 1.

(Preparation of carrier 14)
Carrier 14 was obtained in the same manner as Carrier 1 except that “cyclohexyl methacrylate” was changed to “cyclopentyl methacrylate” in preparation of carrier 1.

(Preparation of carrier 15)
Carrier 15 was obtained in the same manner as Carrier 1 except that “cyclohexyl methacrylate” was changed to “cyclooctyl methacrylate” in the production of carrier 1.

(Preparation of carrier 16)
A resin solution having a solid content of 10% by mass was prepared by diluting 100 parts of a silicone resin (SR2411 solid content: 20% by mass, manufactured by Toray Dow Corning Silicone) with toluene. The obtained resin solution was applied to 100 parts by mass of the core material particles 1 and dried by using a fluidized bed coating apparatus so as to be equivalent to 2.5 parts by solid content. Coating and drying were performed while controlling at 70 ° C. to obtain a carrier 16.

(Preparation of carrier 20)
100 parts by mass of the core material particles 1 produced above, 2.5 parts by mass of copolymer resin fine particles of cyclohexyl methacrylate / methyl methacrylate (copolymerization ratio 5/5), and carbon black (CB) particles ( 1.0 part of the volume average particle size 80 nm) was charged into a high-speed mixer equipped with stirring blades. After stirring and mixing at 125 ° C. for 45 minutes at a wind speed of 10 m / s and forming a coating layer on the surface of the core particles by the action of mechanical impact force, cooling is performed by lowering the wind speed to 2 m / s and coating with resin. “Carrier 20” was produced.

<Production of toner particles>
[Preparation of colorant particle dispersion]
While stirring a solution obtained by dissolving 90 parts by mass of sodium dodecyl sulfate in 1600 parts by mass of ion-exchanged water, 420 parts by mass of carbon black “Mogal L” (manufactured by Cabot) was gradually added. Next, a “colorant fine particle dispersion [Bk]” was prepared by performing a dispersion treatment using a stirrer “Clearmix (registered trademark)” (manufactured by M Technique Co., Ltd.).

[Preparation of crystalline polyester dispersion]
(Synthesis of crystalline polyester resin 1)
281 parts by mass of tetradecanedioic acid as a polyvalent carboxylic acid compound and 283 parts by mass of 1,6-hexanediol as a polyhydric alcohol compound were placed in a reaction vessel equipped with a nitrogen introduction tube, a dehydration tube, a stirrer and a thermocouple. The mixture was heated to 160 ° C. and dissolved. 2.5 parts of tin (II) 2-ethylhexanoate and 0.2 part of gallic acid were added, the temperature was raised to 210 ° C., and the reaction was performed for 8 hours. Furthermore, reaction was performed at 8.3 kPa for 1 hour to obtain a crystalline resin 1 made of a polyester resin. The weight after drying was equivalent to 562 parts.
About the obtained crystalline resin 1, using the differential scanning calorimeter “Diamond DSC” (manufactured by PerkinElmer Co., Ltd.) as described above, a DSC curve was obtained under the condition of a heating rate of 10 ° C./min. It was 67 degreeC when melting | fusing point (Tm) was measured by the method of measuring a peak top temperature. Further, when the molecular weight was measured by GPC “HLC-8120GPC” (manufactured by Tosoh Corporation), Mw in terms of standard styrene was 28000.

(Synthesis of crystalline polyester resin 2)
281 parts by mass of tetradecanedioic acid as a polyvalent carboxylic acid compound as a material of the polyester polymerization segment and 283 parts by mass of 1,6-hexanediol as a polyhydric alcohol compound were mixed with a nitrogen introduction tube, a dehydration tube, a stirrer, and a thermocouple. Was heated to 160 ° C. and dissolved. On the other hand, 4.5 parts of styrene, 1.2 parts of n-butyl acrylate, 2.5 parts of dicumyl peroxide, and 2 parts of acrylic acid as both reactive monomers, which are materials of the vinyl polymer segment premixed The solution was added dropwise using a dropping funnel over 1 hour. Stirring was continued for 1 hour while maintaining at 170 ° C., and after polymerizing styrene, n-butyl acrylate and acrylic acid, 2.5 parts of tin (II) 2-ethylhexanoate and 0.2 part of gallic acid were added. The temperature was raised to 210 ° C. and the reaction was carried out for 8 hours. Furthermore, reaction was performed at 8.3 kPa for 1 hour, and the hybridized crystalline polyester resin 2 was obtained. The amount of introduction of the hybrid part was 1.0% by mass.

(Synthesis of crystalline polyester resin 3)
In the production method of the crystalline polyester resin 2, except that 23.5 parts of styrene, 6.5 parts of n-butyl acrylate, 2.5 parts of dicumyl peroxide, and 2 parts of acrylic acid as both reactive monomers In the same manner, a hybridized crystalline polyester resin 3 was obtained. The amount of introduction of the hybrid part was 5.0% by mass.

(Synthesis of crystalline polyester resin 4)
In the production method of the crystalline polyester resin 2, a hybrid was similarly produced except that 110 parts of styrene, 31 parts of n-butyl acrylate, 12 parts of dicumyl peroxide and 9 parts of acrylic acid as both reactive monomers were used. Crystalline polyester resin 4 was obtained. The amount of introduction of the hybrid part was 20% by mass.

(Synthesis of crystalline polyester resin 5)
In the preparation method of the crystalline polyester resin 2, a hybrid was similarly produced except that styrene 146 parts, n-butyl acrylate 41 parts, dicumyl peroxide 16 parts, and both reactive monomers were 12 parts acrylic acid. Crystalline polyester resin 5 was obtained. The introduction amount of the hybrid part was 25% by mass.

(Synthesis of crystalline polyester resin 6)
Crystalline polyester resin 6 was prepared in the same manner as in preparation of crystalline polyester resin 1 except that 1,9-nonanediol was used instead of 1,6-hexanediol.

(Synthesis of crystalline polyester resin 7)
Crystalline polyester resin 7 was prepared in the same manner as in preparation of crystalline polyester resin 1 except that 1,3-propanediol was used instead of 1,6-hexanediol.

(Synthesis of crystalline polyester resin 8)
In the preparation of the crystalline polyester resin 1, a crystalline polyester resin was prepared in the same manner except that dodecanedioic acid was used instead of tetradecanedioic acid and 1,9-nonanediol was used instead of 1,6-hexanediol. 8 was prepared.

(Synthesis of crystalline polyester resin 9)
In the preparation of the crystalline polyester resin 1, a crystalline polyester resin was prepared in the same manner except that octadecanedioic acid was used instead of tetradecanedioic acid and 1,4-butanediol was used instead of 1,6-hexanediol. 9 was prepared.

[Preparation of crystalline polyester resin fine particle dispersion]
(Preparation of crystalline polyester resin fine particle dispersion 1)
100 parts of the “crystalline polyester resin 1” obtained above was dissolved in 400 parts of ethyl acetate. Next, 25 parts of a 5.0% aqueous sodium hydroxide solution was added to prepare a crystalline polyester resin solution. While the crystalline polyester resin solution was put into a container having a stirring device and stirred, 638 parts of a 0.26% aqueous sodium lauryl sulfate solution was dropped and mixed over 30 minutes. During the dropwise addition of the sodium lauryl sulfate aqueous solution, the liquid in the reaction vessel became cloudy, and after adding the entire amount of the sodium lauryl sulfate aqueous solution, an emulsion was prepared in which amorphous resin fine particles were uniformly dispersed.
Next, the emulsion is heated to 40 ° C., and ethyl acetate is distilled off under a reduced pressure of 150 hPa using a diaphragm vacuum pump “V-700” (manufactured by BUCHI) to produce crystals made of a polyester resin. A crystalline polyester resin fine particle dispersion 1 in which the fine resin fine particles are dispersed was obtained.

(Preparation of crystalline polyester resin fine particle dispersions 2 to 9)
In the preparation of the crystalline polyester resin fine particle dispersion 1, the “crystalline polyester resin 1” was changed to “crystalline polyester resins 2 to 9”, respectively. Similarly, crystalline polyester resin fine particle dispersions 2 to 9 were obtained.

[Preparation of Amorphous Resin Fine Particle Dispersion 1]
(Preparation of amorphous resin fine particle dispersion 1)
<First stage polymerization>
A reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen introducing device was charged with a solution of 4 parts of sodium polyoxyethylene (2) sodium dodecyl ether sulfate in 3000 parts of ion-exchanged water, and 230 rpm under a nitrogen stream. The internal temperature was raised to 80 ° C. while stirring at a stirring speed. After heating, 10 parts of potassium persulfate dissolved in 200 parts of ion-exchanged water was added to a liquid temperature of 75 ° C., and a monomer mixture consisting of styrene, n-butyl acrylate and methacrylic acid in the following amounts was added. The solution was added dropwise over 1 hour. Thereafter, polymerization was carried out while heating and stirring at 75 ° C. for 2 hours to prepare a dispersion of resin fine particles [b1].
-Styrene 584 parts by mass-N-butyl acrylate 160 parts by mass-Methacrylic acid 56 parts by mass

<Second stage polymerization>
A reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen introducing device was charged with a solution of 2 parts of polyoxyethylene (2) sodium dodecyl ether sulfate in 3000 parts of ion-exchanged water, and the internal temperature was 80 ° C. The temperature was raised to.
Next, 42 parts of the dispersion of resin fine particles [b1] obtained above (in terms of solid content) and 70 parts of microcrystalline wax “HNP-0190” (manufactured by Nippon Seiwa Co., Ltd.) were added to the following amounts of styrene and acrylic acid n -A solution dissolved at 80 ° C in a monomer mixture consisting of butyl, methacrylic acid and n-octyl mercaptan was added. A dispersion containing emulsified particles (oil droplets) was prepared by mixing and dispersing for 1 hour using a mechanical disperser “CLEARMIX” (manufactured by M Technique) having a circulation path.
・ Styrene 239 mass parts ・ N-butyl acrylate 111 mass parts ・ Methacrylic acid 26 mass parts ・ n-octyl mercaptan 3 mass parts

  Next, an initiator solution in which 5 parts of potassium persulfate is dissolved in 100 parts of ion-exchanged water is added to this dispersion, and this system is heated and stirred at 80 ° C. for 1 hour to perform polymerization. A dispersion of fine particles [b2] was prepared.

<Third stage polymerization>
A solution obtained by dissolving 10 parts of potassium persulfate in 200 parts of ion-exchanged water is added to the dispersion of the resin fine particles [b2] obtained above, and the following amounts of styrene and acrylic acid are added under a temperature condition of 80 ° C. A monomer mixture consisting of n-butyl, methacrylic acid and n-octyl mercaptan was added dropwise over 1 hour. After completion of the dropwise addition, polymerization was carried out by heating and stirring for 2 hours, and then cooled to 28 ° C. to prepare amorphous resin fine particle dispersion 1.
-Styrene 380 parts by mass-N-butyl acrylate 132 parts by mass-Methacrylic acid 39 parts by mass-N-octyl mercaptan 6 parts by mass

(Preparation of Toner 1)
<Aggregation / fusion process>
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device, 300 parts of amorphous resin fine particle dispersion 1 (in terms of solid content) and 34 parts of solid crystalline polyester resin fine particle dispersion 1 (in solid content) Conversion), 1100 parts of ion-exchanged water, and 40 parts of the colorant fine particle dispersion [Bk] (solid content conversion) were charged, the liquid temperature was adjusted to 30 ° C., and then 5N sodium hydroxide aqueous solution was added to adjust the pH. Adjusted to 10.

  Next, an aqueous solution obtained by dissolving 60 parts of magnesium chloride in 60 parts of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. The temperature was raised after holding for 3 minutes, and the temperature of the system was raised to 85 ° C. over 60 minutes, agglomerating while maintaining 85 ° C., and the particle growth reaction was continued. In this state, the particle size of the aggregated particles was measured with “Coulter Multisizer 3” (manufactured by Beckman Coulter), and when the volume-based median diameter reached 6 μm, 40 parts of sodium chloride was added to ion-exchanged water 160 The aqueous solution dissolved in the part is added to stop the particle growth, and further, as a ripening step, the mixture is heated and stirred at a liquid temperature of 80 ° C. for 1 hour to promote fusion between the particles. A dispersion was prepared.

<Washing and drying process>
The dispersion of toner base particles 1 prepared as described above was subjected to solid-liquid separation with a basket-type centrifuge “MARK III model number 60 × 40 + M” (manufactured by Matsumoto Kikai Co., Ltd.) to form a wet cake of toner base particles. The wet cake was washed with ion exchange water at 40 ° C. using the basket type centrifuge until the electric conductivity of the filtrate reached 5 μS / cm, and then the “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.). The toner base particles 1 were prepared by transferring and drying until the water content became 0.5%. When the cross section of the toner base particle 1 dyed with osmium was observed by a conventional method using a transmission electron microscope, a domain of crystalline polyester was confirmed.

<External additive addition process>
1 part of hydrophobic silica (volume-based median diameter = 12 nm) and 0.3 part of hydrophobic titania (volume-based median diameter = 20 nm) are added to 100 parts of toner base particles 1 and mixed by a Henschel mixer. Thus, Toner 1 was produced.

(Preparation of toners 2 to 13)
In the production of the toner 1, toners 2 to 13 were obtained in the same manner as in the production method of the toner 1 except that the type and amount of the crystalline polyester resin used were changed as shown in Table 3.

(Preparation of Toner 14)
A toner 14 was obtained in the same manner as in the preparation of the toner 1 except that the crystalline polyester resin fine particle dispersion 1 was not used in the preparation of the toner 1.

[Preparation of two-component developer 1]
95 parts by weight of “Carrier 1” and 5 parts by weight of “Toner 1” were blended to prepare “Two-Component Developer 1”. The two-component developer was produced by mixing toner particles and carrier particles using a V blender in an environment of normal temperature and normal humidity (temperature 20 ° C., relative humidity 50% RH). The V blender was rotated at a rotational speed of 20 rpm and a stirring time of 20 minutes, and the mixture was further sieved with a mesh having an opening of 125 μm.

[Preparation of two-component developers 2-33]
In the preparation of the two-component developer 1, “two-component developers 2-33” are obtained in the same manner as the preparation method of the two-component developer 1 except that the combination of the carrier and the toner is changed as shown in Table 4. It was.

〔Evaluation method〕
Using the commercially available multifunction device “bizhub Pro C500 (manufactured by Konica Minolta Business Technologies)”, the two-component developer prepared above was sequentially loaded, developed by the forward development method, and the following evaluation was performed. .
In addition, the developing sleeve of the bizhub Pro C500 and the peripheral speed of the photosensitive member were changed so that they could be used under the following conditions.
Development sleeve peripheral speed (Vs): 800 mm / sec
Photoconductor peripheral speed (Vp): 400 mm / sec
Peripheral speed ratio (Vs / Vp): 2
In addition, the following evaluation was performed using a black toner, the result of which is most apparent. The evaluation results are shown in Table 4.

[Occurrence of trailing edge (lead-off) of halftone image due to scavenging]
An image chart in which a solid image having an image density of 1.2 to 1.3 is printed at the rear of a halftone image having a density of 0.5 with black toner on A4 quality fine paper (64 g / m ² ) is printed. The degree of occurrence of scavenging at the boundary between the solid image and the halftone image was visually evaluated. A to D were accepted.
A: No half-tone image trailing edge omission has occurred.
B: Almost no trailing edge of halftone image occurs.
C: The trailing edge of the halftone image is slightly missing but not noticeable.
D: Although there is a trailing end of the halftone image, it is a level that can be regarded as being within the practical range.
E: The trailing edge of the halftone image is clearly missing, and there is a problem in practical use.

[Carrier adhesion]
The carrier adheres to the photoconductor in a printing environment of normal temperature and normal humidity (20 ° C., 50% RH), and after printing 200,000 character images with a printing rate of 5%, a solid image (100 mm × 100 mm) is printed. The number of carrier particles adhered on the solid image was visually counted using a magnifying glass and evaluated. In addition, carrier adhesion makes 40 or less pass.

[Fog]
The fog is printed in a high-temperature, high-humidity (30 ° C, 80% RH) environment after printing 500,000 prints of a character image with a printing rate of 5%, and then the white paper density of the transfer material after printing 500,000 copies. evaluated. The density at 20 locations on the A4 size transfer material is measured, and the average value is defined as the blank paper density. Density measurement was performed using a reflection densitometer “RD-918” (manufactured by Macbeth). If the white paper density is 0.01 or less, it is considered acceptable.

As shown in Table 4, the “two-component developer 1 to 27” of the present invention prevents the trailing edge of the halftone image from falling off when the solid image is printed after the halftone image, and adheres to the photoconductor. And fogging in a high-temperature and high-humidity environment was confirmed, and it was confirmed that the effects of the present invention were exhibited.
This is because the carrier core particles contain strontium and the toner domain contains crystalline polyester to adjust the carrier resistance and suppress the occurrence of scavenging and carrier adhesion. Furthermore, it is presumed that fogging in a high temperature and high humidity environment could be suppressed by using a coating layer containing only resin.

On the other hand, in the “two-component developers 28 to 33” of the comparative example, it was confirmed that there was a problem with any of the above evaluation items and the effects of the present invention were not achieved.
As described above, according to the present invention, in the case of printing a solid image after a halftone image, it is possible to suppress carrier adhesion to the photoconductor while suppressing the trailing end of the halftone image, and in a high temperature and high humidity environment. It is possible to provide a two-component developer for developing an electrostatic latent image and an image forming method that prevent fogging.

P, P ′ Photoconductors W1, W1 ′ Photoconductor rotation direction S, S ′ Development sleeve W2, W2 ′ Development sleeve rotation direction 11 Charging unit 12 Exposure unit 13 Development unit 14 Transfer unit 15 Static elimination unit 16 Cleaning unit R Development region T Transfer material B Blade 100 Carrier particle 200 Carrier core material particle 300 Coating layer

Claims (15)

A two-component developer for electrostatic latent image development containing toner particles and carrier particles,
The toner particles have a domain matrix structure;
The matrix contains an amorphous resin;
The domain contains a crystalline polyester;
The carrier particles contain carrier core particles containing strontium (Sr), and further have a coating layer containing only the resin on the surface of the carrier core particles,
The two-component developer for developing an electrostatic latent image, wherein the resistance of the carrier particles is in a range of 1.0 × 10 ^{8 to} 1.5 × 10 ¹⁰ Ω · cm. 2. The two-component developer for developing an electrostatic latent image according to claim 1, wherein the resistance of the carrier particles is in the range of 1.0 × 10 ^{9 to} 1.5 × 10 ¹⁰ Ω · cm.   3. The electrostatic latent image development according to claim 1, wherein the content of strontium (Sr) in the carrier particles is in the range of 25 to 125 in terms of Net intensity by fluorescent X-ray analysis. Two-component developer.   4. The content of strontium (Sr) in the carrier particles is in the range of 40 to 90 in terms of Net intensity by fluorescent X-ray analysis. 5. Two-component developer for developing an electrostatic latent image.   5. The electrostatic latent image developing according to claim 1, wherein a shape factor (SF-1) of the carrier core particles is within a range of 110 to 150. 5. Two component developer.   The two-component developer for developing an electrostatic latent image according to any one of claims 1 to 5, wherein the amorphous resin contains a styrene-acrylic resin.   The electrostatic polyester according to any one of claims 1 to 6, wherein the crystalline polyester is a hybrid crystalline polyester in which a styrene-acrylic polymer segment is bonded to at least a polyester polymer segment. Two-component developer for developing latent images.   The two-component developer for developing an electrostatic latent image according to claim 7, wherein the content ratio of the styrene-acrylic polymer segment in the hybrid crystalline polyester is in the range of 0.5 to 20% by mass.   The static content according to any one of claims 1 to 8, wherein a content ratio of the crystalline polyester in a total amount of the resin constituting the toner particles is in a range of 5 to 20 mass%. Two-component developer for developing electrostatic latent images.   10. The electrostatic according to claim 1, wherein the coating layer is a polymerization reaction product of a monomer containing at least an alicyclic (meth) acrylic acid ester compound. 11. Two-component developer for developing latent images.   The said alicyclic (meth) acrylic acid ester compound has a C5-C8 cycloalkyl group, The electrostatic as described in any one of Claim 1- Claim 10 characterized by the above-mentioned. Two-component developer for developing latent images.   The two-component for electrostatic latent image development according to any one of claims 1 to 11, wherein the alicyclic (meth) acrylic acid ester compound is cyclohexyl (meth) acrylate. Developer.   An image forming method using the two-component developer for developing an electrostatic latent image according to any one of claims 1 to 12, comprising a charging step, an exposure step, a development step, a transfer step, and a fixing step. An image forming method comprising:   The image forming method according to claim 13, wherein the developing step is a step of developing by a forward developing method. An image forming method using a two-component developer for developing an electrostatic latent image,
It has a charging process, exposure process, development process, transfer process and fixing process,
The development step is a step of developing by the forward development method,
The electrostatic latent image developing two-component developer contains toner particles and carrier particles,
The toner particles have a domain matrix structure;
The matrix contains an amorphous resin;
The domain contains a crystalline polyester;
The carrier particles contain carrier core particles containing strontium (Sr), and further have a coating layer containing only the resin on the surface of the carrier core particles,
The image forming method according to claim 1, wherein the resistance of the carrier particles is in a range of 1.0 × 10 ^{8 to} 1.5 × 10 ¹⁰ Ω · cm.

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