JP2005106923A - Image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method by which expansion of a color gamut and excellent secondary color reproducibility are achieved. <P>SOLUTION: In the image forming method for forming a full color toner image by superposing yellow, magenta, cyan and black toners for electrostatic charge image development on a transfer material, the four color toners for electrostatic charge image development are set to three steps of a low volume-average-particle-diameter (Dv50L) toner, a medium volume-average-particle-diameter (Dv50M) toner and a high volume-average-particle-diameter (Dv50H) toner with respect to particle diameters, the low volume-average-particle-diameter toner is within a range of 3.5 to <7.5 μm, the medium volume-average-particle-diameter toner is within a range of 4.3 to <8.3 μm, the high volume-average-particle-diameter toner is within a range of 5.4 to <8.8 μm, and the difference between the high volume-average-particle-diameter toner and the low volume-average-particle-diameter toner is between 0.7 and 1.4 μm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming method for forming a full-color toner image using toners for developing electrostatic images of four colors of yellow, magenta, cyan and black.

  Initially, full-color image forming methods in electrophotography were mostly used by color photocopies and design contractors.

  However, in recent years, there has been an increasing number of cases where color multifunction machines that also serve as color printers and color copiers are introduced into offices. The background of this is the business of planning documents and reports, etc. by connecting each personal computer and a color multifunction device over the network as the cost of equipment decreases, downsizing and speeding up, and IT progresses in the office. One of the reasons is that documents are now output on color multifunction devices. In addition, small-sized models have speed and ease that can compete with light printing such as offset printing in inkjet systems and high-speed machines. In recent years, by using small-diameter toner typified by polymerized toner, high resolution is achieved. It is possible to perform image formation having Along with such changes, various problems to be newly solved have arisen.

  From the viewpoint of image color reproduction and color gamut expansion, there are the following problems. For example, when full-color image formation is performed, image reproduction is performed mainly using two or more color toners, but high color reproducibility cannot be expected unless the latent image is developed and transferred faithfully. . In particular, it is fatal if there is a difference in how the dots appear when transferring. Further, even in a solid image, if the toners of a plurality of colors do not melt and permeate uniformly, color unevenness occurs and the color gamut tends to be narrow. Further, as the color gamut and color reproducibility faithful to the original image are attempted, the amount of toner consumption tends to increase, and there has been a demand for beautiful full-color image formation without increasing the amount of toner consumption.

  As described above, there is a need for a color toner that expands the color gamut of an output image by full-color electrophotography and improves the color reproducibility of secondary colors.

  Regarding the improvement of the reproducibility of the secondary color described above, for example, image formation by full-color electrophotography in which an image is formed by developing at least three toners of Y (yellow), M (magenta), and C (cyan). In the method, an image support having a spectral reflection characteristic of 95 ≦ R1 when a spectral reflectance of 450 nm is defined as R1% is used as an image support to which three color toner images are transferred and fixed. There has been proposed an image forming method characterized in that a toner image is formed so that a spectral reflectance Ry% at 450 nm of a Y image when a solid Y image is formed on the surface satisfies Ry ≦ 5 (for example, , See Patent Document 1).

However, even if the above technique is applied, neither the color reproducibility of the secondary color nor the expansion of the color gamut is sufficient from the practical point of view, and there is a demand for their solution.
JP-A-11-249377

  An object of the present invention is to provide an image forming method for forming a full-color toner image using toners for developing electrostatic images of four colors of yellow, magenta, cyan, and black. It is to be realized.

  In order to expand the color gamut and improve the secondary color reproducibility, the present inventors need to quickly and sufficiently melt and penetrate the color toner particles superimposed on the transfer material. Therefore, it was considered necessary to place toner particles of each color in a state close to closest packing. Therefore, when the toner particle diameter is changed for each color toner as a means for allowing the four colors of toner to be closely packed with each other without increasing the toner consumption, the color gamut is expanded compared to the conventional one. At the same time, it was found that the reproducibility of secondary colors can be remarkably improved.

The object of the present invention has been achieved by the following constitution.
(Claim 1)
In an image forming method for forming a full-color toner image by superposing toners for developing electrostatic images of four colors of yellow, magenta, cyan and black on a transfer material, the toner for developing electrostatic images of four colors has a low volume average The particle size is set in three stages: particle size (Dv50L) toner, medium volume average particle size (Dv50M) toner, and high volume average particle size (Dv50H) toner, and the low volume average particle size toner is 3.5 μm or more and 7.5 μm. Less than, medium volume average particle size toner is 4.3 μm or more and less than 8.3 μm, high volume average particle size toner is in the range of 5.4 μm or more and less than 8.8 μm, and high volume average particle size toner and low volume average particle An image forming method, wherein the difference from the diameter toner is between 0.7 μm and 1.4 μm.
(Claim 2)
The low volume average particle size (Dv50L) toner is black toner, the high volume average particle size (Dv50H) toner is yellow toner, the medium volume average particle size (Dv50M) toner is magenta and cyan toner, and the toner. 2. The image forming method according to claim 1, wherein the image is transferred from the photosensitive member to an intermediate transfer member, superposed on the intermediate transfer member, transferred onto a transfer material, and heat-fixed.
(Claim 3)
The low volume average particle diameter (Dv50L) toner is yellow toner, the high volume average particle diameter (Dv50H) toner is black toner, the medium volume average particle diameter (Dv50M) toner is magenta and cyan toner, and the toner 2. The image according to claim 1, wherein the image is superposed on the photoconductor and then transferred onto a transfer material, or the toner of each color is sequentially superposed and transferred from the photoconductor onto the transfer material, and heat fixing. The image forming method described.
(Claim 4)
4. The image forming method according to claim 1, wherein an average value of the circularity of the four color electrostatic image developing toners is 0.94 to 0.99. 5.

  According to the present invention, the toner consumption is increased by setting the volume average particle diameter of the toner for developing electrostatic images of four colors of yellow, magenta, cyan and black used for full-color image formation in three stages. Therefore, the toner of each color can be filled in the most densely on the transfer material. As a result, the color gamut of the color toner image is expanded to enable the formation of a beautiful full-color toner image that exhibits excellent secondary color reproducibility.

  Hereinafter, the present invention will be described in detail.

  The volume average particle diameter (Dv50) refers to a particle diameter that becomes 50% cumulative from the larger particle diameter in the volume-based particle diameter distribution. The method for controlling the volume average particle diameter (Dv50) is exemplified below. For example, in the case of an emulsion association type toner, control is possible by controlling the addition timing of the aggregation terminator during resin particle formation as described later. As shown in the examples described later, the control is performed at the colored particle forming stage, but even when an external additive is added to the toner particles, the particle diameter does not change. Needless to say, when the toner is prepared by the pulverization method, the toner is controlled by the pulverized particle diameter. The volume average particle diameter (Dv50) can be measured with a Coulter Counter TA-II type or Coulter Multisizer (manufactured by Coulter Beckman).

  When fixing each color in an overlapping manner, the toner is greatly melted and deformed in the order closer to the fixing heating member. When the same particle diameter is set for each color, the color close to the heating member becomes strong after fixing. In this case, in the image forming method having one intermediate transfer member, yellow (Y), magenta (M), black (Bk) or yellow (Y), cyan (C), and black (Bk) are transferred in this order. The color becomes stronger (FIG. 4). On the other hand, in the image forming method without using an intermediate transfer member, black (Bk), magenta (M), yellow (Y) or black (Bk), cyan (C), and yellow (Y) are transferred in this order. The taste becomes stronger (Fig. 5).

  According to the present invention, since the particle diameters of the colors are different, the area occupancy ratio of the toners of the respective colors on the transfer material is the same after the fixing even if the difference of the melt deformation is included. That is, secondary color reproduction is good and the color gamut is expanded. Further, the quality of the shadow image is improved, and an image with high resolution can be obtained without losing characters and fine lines (FIGS. 6 and 7).

(Average value of circularity of toner particles)
As for the shape of the toner of the present invention, when 2000 or more toner particles having a particle diameter of 1 μm or more are measured, the average value of circularity (shape factor) represented by the following formula is 0.94 to 0.99, more preferably 0.963 to 0.981. Within this range, the density of the transferred image is increased, the heat conduction between the toner particles is improved, and each color toner is melted and penetrated to expand the color gamut.

Circularity = (perimeter of equivalent circle) / (perimeter of toner particle projection image)
= 2π × (particle projected area / π) ^1/2 / (periphery length of toner particle projected image)
Here, the equivalent circle is a circle having the same area as the toner particle projection image, and the equivalent circle diameter is the diameter of the equivalent circle.

  In addition, as a measuring method of the said circularity, it can measure by FPIA-1000 (made by Sysmec). At this time, the equivalent circle diameter is defined by the following equation.

Equivalent circle diameter = 2 × (projected area of particle / π) ^1/2
<< Method for producing toner for developing electrostatic image >>
A method for producing the toner for developing an electrostatic charge image of the present invention will be described.

  The toner of the present invention forms composite resin particles in the absence of a colorant, adds a dispersion of colorant particles to a dispersion of the composite resin particles, and salting out the composite resin particles and the colorant particles. Those prepared by agglomeration and fusion are preferred. Thus, the polymerization reaction for obtaining the composite resin particles is not inhibited by preparing the composite resin particles in a system in which no colorant is present.

  Further, as a result of the polymerization reaction for obtaining the composite resin particles being reliably performed, no monomer or oligomer remains in the resulting colored particles, and the heat fixing step of the image forming method using the toner , The generation of off-flavors can be prevented or reduced. Furthermore, since the surface characteristics of the obtained toner particles are uniform and the charge amount distribution is sharp, an image with excellent sharpness can be formed over a long period of time.

  The “composite resin particle” constituting the toner of the present invention is one or more composed of a resin having a different molecular weight and / or composition from the resin forming the core particle so as to cover the surface of the core particle composed of the resin. The resin particles having a multilayer structure in which the coating layer is formed. The “central part (core)” of the composite resin particle refers to “core particle” constituting the composite resin particle. The “outer layer (shell)” of the composite resin particle refers to the outermost layer among “one or more coating layers” constituting the composite resin particle. The “intermediate layer” of the composite resin particles refers to a coating layer formed between the central portion (core) and the outer layer (shell).

  In the present invention, it is preferable to use the “multistage polymerization method” to obtain composite resin particles from the viewpoint of controlling the molecular weight distribution, that is, from the viewpoint of securing the fixing strength and the offset resistance. In the present invention, the “multi-stage polymerization method” for obtaining composite resin particles means a single amount in the presence of resin particles (n) obtained by polymerizing monomer (n) (n-th stage). Polymer (n + 1) is polymerized (n + 1 stage), and the polymer of monomer (n + 1) is dispersed and / or composition on the surface of the resin particle (n). A method of forming a coating layer (n + 1) made of different resins). When the resin particle (n) is a core particle (n = 1), the “two-stage polymerization method” is used. When the resin particle (n) is a composite resin particle (n ≧ 2), three or more stages are used. The multistage polymerization method.

  A plurality of resins having different compositions and / or molecular weights are present in the composite resin particles obtained by the multistage polymerization method. Therefore, the colored particles obtained by salting out, aggregating, and fusing the composite resin particles and the colorant particles exhibit characteristics that the variation in composition, molecular weight, and surface characteristics is extremely small among the colored particles. According to such a toner having a uniform composition, molecular weight, and surface characteristics between toner particles, an image forming method including a fixing process using a contact heating method maintains good adhesion (high fixing strength) to an image support. However, it is possible to improve the anti-offset property and the anti-winding property, and an image having an appropriate gloss can be obtained.

An example of the method for producing the toner for developing an electrostatic charge image of the present invention is specifically shown as follows:
(1) Multistage polymerization step (I) for obtaining composite resin particles prepared so that the release agent and / or crystalline polyester is contained in a region (center portion or intermediate layer) other than the outermost layer,
(2) Step (II) of salting out, agglomerating and fusing the composite resin particles and the colorant particles to obtain colored particles by salting out, agglomerating and fusing.
(3) Filtration and washing process for separating the toner particles from the dispersion system of the colored particles and removing the surfactant from the colored particles;
(4) A drying step of drying the washed colored particles,
(5) It comprises a step of adding an external additive to the dried colored particles.

  Hereinafter, each step will be described.

<< Multistage polymerization process (I) >>
The multistage polymerization step (I) is a step of producing composite resin particles by a multistage polymerization method in which a coating layer (n + 1) made of a polymer of the monomer (n + 1) is formed on the surface of the resin particles (n). . Here, it is preferable to employ a multi-stage polymerization method of three-stage polymerization or more from the viewpoint of production stability and crushing strength of the obtained toner.

  Hereinafter, a two-stage polymerization method and a three-stage polymerization method, which are representative examples of the multistage polymerization method, will be described.

<Description of the two-stage polymerization method>
The two-stage polymerization method is a method for producing composite resin particles composed of a central portion (core) formed from a high molecular weight resin containing a release agent and an outer layer (shell) formed from a low molecular weight resin. is there. That is, the composite resin particles obtained by the two-stage polymerization method are composed of a core and a single coating layer.

  This method will be described in detail. First, a monomer solution obtained by dissolving a release agent in a monomer (H) is dispersed in oil droplets in an aqueous medium (an aqueous solution of a surfactant). By subjecting this system to a polymerization treatment (first stage polymerization), a dispersion of high molecular weight resin particles (H) containing a release agent is prepared. Next, a polymerization initiator and a monomer (L) for obtaining a low molecular weight resin are added to the dispersion of the resin particles (H), and the monomer (L) is added in the presence of the resin particles (H). ) Is polymerized (second-stage polymerization) to form a coating layer (L) made of a low molecular weight resin (polymer of monomer (L)) on the surface of the resin particles (H).

<Description of three-stage polymerization method>
In the three-stage polymerization method, composite resin particles composed of a central portion (core) formed from a high molecular weight resin, an intermediate layer containing a release agent, and an outer layer (shell) formed from a low molecular weight resin are formed. It is a manufacturing method. That is, the composite resin particles obtained by the three-stage polymerization method are composed of a nucleus and two coating layers.

  This method will be described in detail. First, a dispersion of resin particles (H) obtained by a conventional polymerization process (first stage polymerization) is added to an aqueous medium (an aqueous solution of a surfactant). In addition, by dispersing oil droplets of a monomer solution obtained by dissolving a release agent in the monomer (M) in the aqueous medium, this system is polymerized (second-stage polymerization), A composite resin obtained by forming a coating layer (M) (intermediate layer) made of a resin (monomer (M) polymer) containing a release agent on the surface of the resin particles (H) (core particles). A dispersion of particles [high molecular weight resin (H) -intermediate molecular weight resin (M)] is prepared. Next, a polymerization initiator and a monomer (L) for obtaining a low molecular weight resin are added to the resulting dispersion of composite resin particles, and the monomer (L) is added in the presence of the composite resin particles. Is subjected to polymerization treatment (third-stage polymerization) to form a coating layer (L) made of a low molecular weight resin (polymer of monomer (L)) on the surface of the composite resin particles.

  In this three-stage polymerization method, when the coating layer (M) is formed on the surface of the resin particles (H), the dispersion of the resin particles (H) is added to an aqueous medium (an aqueous solution of a surfactant) Employing a method in which a monomer solution obtained by dissolving a release agent in the monomer (M) is dispersed in oil droplets in the aqueous medium, and then this system is polymerized (second stage polymerization). Thus, the release agent can be finely and uniformly dispersed.

  In addition, as for the addition treatment of the dispersion of the resin particles (H) and the oil droplet dispersion treatment of the monomer solution, either may be performed in advance as described below, or may be performed simultaneously. .

(A) When forming the intermediate layer constituting the composite resin particles, after adding the resin particles to be the central part (core) of the composite resin particles into the aqueous solution of the surfactant, the release agent is added to the aqueous solution. A mode in which a monomer composition containing a crystalline polyester is dispersed and this system is polymerized.
(B) When forming the intermediate layer constituting the composite resin particles, after dispersing the monomer composition containing the release agent / crystalline polyester in an aqueous solution of a surfactant, in the aqueous solution, A mode in which resin particles to be the central part (core) of the composite resin particles are added and this system is polymerized,
(C) When forming the intermediate layer constituting the composite resin particles, the resin particles to be the central part (core) of the composite resin particles are added to the aqueous solution of the surfactant, and at the same time, the release agent is added to the aqueous solution. / A mode in which a monomer composition containing a crystalline polyester is dispersed and this system is polymerized is included.

  As a method of forming resin particles (core particles) or coating layer (intermediate layer) containing a release agent, the release agent is dissolved in a monomer, and the resulting monomer solution is oil-dropped in an aqueous medium. A method of obtaining latex particles by dispersing and polymerizing this system can be employed.

  Here, the “aqueous medium” refers to a medium composed of 50 to 100% by mass of water and 0 to 50% by mass of a water-soluble organic solvent. Examples of the water-soluble organic solvent include methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran, and alcohol-based organic solvents that do not dissolve the resulting resin are preferable.

  As a suitable polymerization method for forming resin particles or a coating layer containing a release agent, a release agent is used as a monomer in an aqueous medium in which a surfactant having a concentration equal to or lower than the critical micelle concentration is dissolved. The monomer solution is dissolved in oil droplets using mechanical energy to prepare a dispersion liquid, and a water-soluble polymerization initiator is added to the obtained dispersion liquid to generate radicals in the oil droplets. Examples thereof include a polymerization method (hereinafter referred to as “miniemulsion method”). Instead of adding a water-soluble polymerization initiator, or while adding the water-soluble polymerization initiator, an oil-soluble polymerization initiator may be added to the monomer solution.

  According to the mini-emulsion method that mechanically forms oil droplets, unlike the usual emulsion polymerization method, the release agent dissolved in the oil phase is not detached, and the resin particles or the coating layer is formed. A sufficient amount of the release agent can be introduced.

  Here, the disperser for dispersing oil droplets by mechanical energy is not particularly limited, and a stirring device “CLEARMIX” equipped with a rotor that rotates at a high speed (M Technique Co., Ltd.) Product), an ultrasonic disperser, a mechanical homogenizer, a manton gourin, a pressure homogenizer, and the like. The dispersed particle size is 10 to 1000 nm, preferably 50 to 1000 nm, and more preferably 30 to 300 nm.

  A known method such as an emulsion polymerization method, a suspension polymerization method, or a seed polymerization method can also be employed as a polymerization method for forming resin particles or a coating layer containing a release agent. These polymerization methods can also be employed to obtain resin particles (core particles) or coating layers constituting the composite resin particles that do not contain a release agent and crystalline polyester.

  The particle diameter of the composite resin particles obtained in the polymerization step (I) is in the range of 10 to 1000 nm as a weight average particle diameter measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.). It is preferable that it exists in. Moreover, it is preferable that the glass transition temperature (Tg) of a composite resin particle exists in the range of 48-74 degreeC, More preferably, it is 52-64 degreeC. The softening point of the composite resin particles is preferably in the range of 95 to 140 ° C.

<< Step of salting out, agglomerating and fusing (II) >>
In the step (II) of salting out, agglomerating and fusing, the composite resin particles and the colorant particles obtained in the multistage polymerization step (I) are salted out, agglomerated and fused (salting out and fusing). This is a step of obtaining irregular (non-spherical) toner particles by causing them to occur simultaneously. In the salting-out, agglomeration and fusion process (II), the additive resin particles (fine particles having a number average primary particle size of about 10 nm to 1000 nm) are salted together with the composite resin particles and the colorant particles. It may be deposited, agglomerated or fused.

  The colorant particles may be surface modified. A conventionally well-known thing can be used here as a surface modifier.

  The colorant particles are subjected to salting out, aggregation, and fusion treatment in a state of being dispersed in an aqueous medium. Examples of the aqueous medium in which the colorant particles are dispersed include an aqueous solution in which the surfactant is dissolved at a concentration equal to or higher than the critical micelle concentration (CMC). As the surfactant, the same surfactant as that used in the multistage polymerization step (I) can be used.

  The disperser used for the dispersion treatment of the colorant particles is not particularly limited, but preferably a stirring device “CLEARMIX” (manufactured by M Technique Co., Ltd.) equipped with a rotor that rotates at high speed, an ultrasonic disperser, Examples thereof include a pressure disperser such as a mechanical homogenizer, a manton gourin, and a pressure homogenizer, and a medium disperser such as a Getzman mill and a diamond fine mill.

  In order to salt out, agglomerate, and fuse the composite resin particles and the colorant particles, in the dispersion in which the composite resin particles and the colorant particles are dispersed, a flocculant having a critical aggregation concentration or more is added, It is preferable to heat this dispersion to a glass transition temperature (Tg) or higher of the composite resin particles. More preferably, a coagulation terminator is used when the composite resin particles reach a desired particle size by the coagulant. As the aggregation terminator, a monovalent metal salt, particularly sodium chloride is preferably used.

  The temperature range suitable for salting out, agglomerating, and fusing is (Tg + 10 ° C.) to (Tg + 50 ° C.), particularly preferably (Tg + 15 ° C.) to (Tg + 40 ° C.). In addition, an organic solvent that is infinitely soluble in water may be added in order to effectively perform fusion.

  Here, examples of the “flocculating agent” used in salting out, agglomeration, and fusion include alkali metal salts and alkaline earth metal salts as described above.

  The salting out and aggregation used in the present invention will be described.

  In the present invention, “salting out, agglomeration, fusion” means that salting out (aggregation of particles) and fusion (disappearance of the interface between particles) occur simultaneously, or salting out and fusion occur simultaneously. An act. In order to perform salting out and fusion at the same time, particles (composite resin particles, colorant particles) are aggregated under a temperature condition equal to or higher than the glass transition temperature (Tg) of the resin constituting the composite resin particles. preferable.

  The release agent used for the toner of the present invention will be described.

  The content of the release agent constituting the toner for developing an electrostatic charge image of the present invention is usually 1 to 30% by mass, preferably 2 to 20% by mass, more preferably 3 to 15% by mass. .

  As the release agent, low molecular weight polypropylene (number average molecular weight = 1500 to 9000), low molecular weight polyethylene or the like may be added, and a preferable release agent is preferably an ester compound represented by the following general formula.

General formula R _1- (OCO-R ₂ ) _n
In the formula, n represents an integer of 1 to 4, preferably 2 to 4, more preferably 3 to 4, and particularly preferably 4.

R ₁ and R ₂ represent a hydrocarbon group which may have a substituent.

R ₁ : carbon number = 1-40, preferably 1-20, more preferably 2-5
R ₂ : carbon number = 1-40, preferably 16-30, more preferably 18-26
Although the specific example of the ester compound represented by the said general formula is shown below, this invention is not limited to these.

  The preferred molecular weight, molecular weight range, peak molecular weight, etc. of the resin component constituting the toner for developing an electrostatic charge image of the present invention will be described.

  The toner of the present invention preferably has a peak or shoulder at 100,000 to 1,000,000 and 1,000 to 50,000. The molecular weight of the toner resin has a high molecular weight component having a peak or shoulder in the region of 100,000 to 1,000,000 and a peak or shoulder in the region of 1,000 to less than 50,000. A resin containing at least both low molecular weight components is preferred.

  The molecular weight is measured using GPC (gel permeation chromatography) using THF (tetrahydrofuran) as a column solvent. Specifically, 1 ml of THF is added to 1 mg of a measurement sample, and the mixture is sufficiently dissolved by stirring using a magnetic stirrer at room temperature. Subsequently, after processing with a membrane filter having a pore size of 0.45 to 0.50 μm, the solution is injected into GPC. The measurement conditions of GPC are that the column is stabilized at 40 ° C., THF is flowed at a flow rate of 1 ml / min, and about 100 μl of a sample having a concentration of 1 mg / ml is injected for measurement. As the column, it is preferable to use a combination of commercially available polystyrene gel columns. For example, Shodex GPC KF-801, 802, 803, 804, 805, 806, 807 made by Showa Denko KK, TSKgel G1000H, G2000H, G3000H, G4000H, G5000H, G6000H, G7000H, TSK guard column made by Tosoh Combinations can be mentioned.

  As the detector, a refractive index detector (IR detector) or a UV detector is preferably used. In the measurement of the molecular weight of a sample, the molecular weight distribution of the sample is calculated using a calibration curve created using monodisperse polystyrene standard particles. About 10 points are preferably used as polystyrene for preparing a calibration curve.

  The filtration / washing process relating to the production of the electrostatic image developing toner will be described.

  In this filtration / washing step, a filtration treatment for filtering the colored particles from the dispersion system of the colored particles obtained in the above step, and a surfactant and a flocculant from the filtered colored particles (cake-like aggregate). And a cleaning process for removing deposits. Here, the filtration method is not particularly limited, such as a centrifugal separation method, a vacuum filtration method using Nutsche or the like, a filtration method using a filter press or the like.

<< Drying process >>
This step is a step for drying the washed colored particles. Examples of dryers used in this process include spray dryers, vacuum freeze dryers, vacuum dryers, etc., stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, rotary dryers It is preferable to use a stirring dryer or the like. The water content of the dried colored particles is preferably 5% by mass or less, more preferably 2% by mass or less.

  In addition, when the dried colored particles are aggregated by weak interparticle attractive force, the aggregate may be crushed. Here, as the crushing treatment apparatus, a mechanical crushing apparatus such as a jet mill, a Henschel mixer, a coffee mill, or a food processor can be used.

  The polymerizable monomer according to the present invention will be described.

(1) Hydrophobic monomer As a hydrophobic monomer which comprises a monomer component, it does not specifically limit and a conventionally well-known monomer can be used. Moreover, it can be used combining 1 type (s) or 2 or more types so that the required characteristic may be satisfy | filled.

  Specifically, monovinyl aromatic monomers, (meth) acrylic acid ester monomers, vinyl ester monomers, vinyl ether monomers, monoolefin monomers, diolefin monomers , Halogenated olefin monomers and the like can be used.

  Examples of vinyl aromatic monomers include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, p-ethyl styrene, p. -N-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2, Examples thereof include styrene monomers such as 4-dimethylstyrene and 3,4-dichlorostyrene and derivatives thereof.

  Examples of acrylic monomers include acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, methyl methacrylate, methacrylic acid. Examples include butyl acid, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and the like. Examples of vinyl ester monomers include vinyl acetate, vinyl propionate, and vinyl benzoate. Examples of the vinyl ether monomer include vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyl phenyl ether and the like.

  Examples of the monoolefin monomer include ethylene, propylene, isobutylene, 1-butene, 1-pentene, 4-methyl-1-pentene and the like. Examples of the diolefin monomer include butadiene, isoprene, chloroprene and the like.

(2) Crosslinkable monomer A crosslinkable monomer may be added to improve the properties of the resin particles. Examples of the crosslinkable monomer include those having two or more unsaturated bonds such as divinylbenzene, divinylnaphthalene, divinyl ether, diethylene glycol methacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, and diallyl phthalate.

(3) Monomer having an acidic polar group Monomers having an acidic polar group include (a) an α, β-ethylenically unsaturated compound having a carboxyl group (—COOH) and (b) a sulfone group (— Mention may be made of α, β-ethylenically unsaturated compounds having SO ₃ H).

Examples of the α, β-ethylenically unsaturated compound (a) having a —COO group include acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, cinnamic acid, maleic acid monobutyl ester, maleic acid. Examples thereof include acid monooctyl esters and metal salts thereof such as Na and Zn. (B) Examples of α, β-ethylenically unsaturated compounds having a sulfo group (—SO ₃ H group) include sulfonated styrene, its Na salt, allylsulfosuccinic acid, allylsulfosuccinic acid octyl, its Na salt and the like. Can be mentioned.

  The initiator (also referred to as polymerization initiator) used for the polymerization of the polymerizable monomer according to the present invention will be described.

  The polymerization initiator used in the present invention can be appropriately used as long as it is water-soluble. For example, persulfates (potassium persulfate, ammonium persulfate, etc.), azo compounds (4,4′-azobis-4-cyanovaleric acid and its salts, 2,2′-azobis (2-amidinopropane) salts, etc.), Examples thereof include peroxide compounds such as hydrogen peroxide and benzoyl peroxide. Furthermore, the said polymerization initiator can be combined with a reducing agent as needed to make a redox initiator. By using a redox initiator, the polymerization activity is increased, the polymerization temperature can be lowered, and the polymerization time can be further shortened.

  The polymerization temperature may be any temperature as long as it is equal to or higher than the lowest radical generation temperature of the polymerization initiator. For example, a range of 50 ° C. to 80 ° C. is used. It is also possible to polymerize at or near room temperature by using a polymerization initiator that starts at room temperature, for example, a combination of hydrogen peroxide-reducing agent (such as ascorbic acid).

  The chain transfer agent used in the present invention will be described.

  In the present invention, conventionally known generally used chain transfer agents can be used for the purpose of adjusting the molecular weight of the resin particles produced by polymerization of the polymerizable monomer.

  The chain transfer agent is not particularly limited. In particular, a compound having a mercapto group is preferably used because a toner having a sharp molecular weight distribution can be obtained and storage stability, fixing strength, and offset resistance are excellent. For example, a compound having a mercapto group such as octanethiol, dodecanethiol, and tert-dodecanethiol is used. Preferred examples include ethyl thioglycolate, propyl thioglycolate, butyl thioglycolate, t-butyl thioglycolate, 2-ethylhexyl thioglycolate, octyl thioglycolate, decyl thioglycolate, thioglycol Examples include dodecyl acid, thioglycolic acid ester of ethylene glycol, thioglycolic acid ester of neopentyl glycol, and thioglycolic acid ester of pentaerythritol. Among these, n-octyl-3-mercaptopropionic acid ester is preferably used from the viewpoint of suppressing odor during toner heat fixing.

《Colorant》
The colorant according to the present invention will be described.

  The colorant according to the toner for developing electrostatic images of each of the four colors of yellow, magenta, cyan and black according to the present invention is a salt of the above composite resin particles at the time of toner production from the viewpoint of improving the uniformity of toner charge. It is preferably salted out, agglomerated and fused together with the resin particles at the time of precipitation, aggregation and fusion, and contained in the colored particles.

  Examples of the colorant constituting the toner of the present invention (colorant particles used for salting out, agglomeration, and fusion with composite resin particles) include various inorganic pigments, organic pigments, dyes, and the like. Examples of inorganic pigments include conventionally known black pigments and magnetic powders.

  Examples of the black pigment used for the preparation of the black toner include carbon black such as furnace black, channel black, acetylene black, thermal black, and lamp black, and examples of the magnetic powder include magnetite and ferrite.

  These inorganic pigments can be used alone or in combination as required. The content of the inorganic pigment in the toner is preferably in the range of 2 to 20% by mass, more preferably in the range of 3 to 15% by mass.

  When used as a magnetic toner, the above-mentioned magnetite can be added. In this case, from the viewpoint of imparting predetermined magnetic properties, the content in the toner is preferably 20 to 120% by mass.

  Conventionally known organic pigments and dyes can also be used. Specific organic pigments and dyes are exemplified below.

  Examples of organic pigments for magenta or red used for preparing magenta toner include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of organic pigments for orange or yellow used for the preparation of yellow toner include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 185, C.I. I. Pigment yellow 155, C.I. I. And CI Pigment Yellow 156.

  Examples of organic pigments for green or cyan used for preparing cyan toner include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  As the dye, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95 and the like. These dyes may be used alone or as a mixture of a plurality of dyes.

  Furthermore, these organic pigments and dyes can be used alone or in combination as desired. The content of the organic pigment or dye in the toner is preferably in the range of 2 to 20% by mass, more preferably in the range of 3 to 15% by mass.

  The colorant (colorant particles) according to the present invention may be surface-modified. 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.

  Silane coupling agents include: methyltrimethoxysilane, phenyltrimethoxysilane, methylphenyldimethoxysilane, alkoxysilane such as diphenyldimethoxysilane, siloxane such as hexamethyldisiloxane, γ-chloropropyltrimethoxysilane, vinyltrichlorosilane, Vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-ureidopropyltri An ethoxysilane etc. are mentioned.

  Examples of titanium coupling agents include TTS, 9S, 38S, 41B, 46B, 55, 138S, and 238S, which are commercially available under the trade name “Plenact” manufactured by Ajinomoto Co., Inc., and commercial products A manufactured by Nippon Soda Co., Ltd. -1, B-1, TOT, TST, TAA, TAT, TLA, TOG, TBSTA, A-10, TBT, B-2, B-4, B-7, B-10, TBSTA-400, TTS, TOA -30, TSDMA, TTAB, TTOP and the like.

  Examples of the aluminum coupling agent include “Plenact AL-M” manufactured by Ajinomoto Co., Inc.

  The addition amount of these surface modifiers is preferably in the range of 0.01 to 20% by mass, more preferably 0.1 to 5% by mass with respect to the colorant.

  Examples of the method for modifying the surface of the colorant particles include a method in which a surface modifier is added to the dispersion of the colorant particles and this system is heated to react. The surface-modified colorant particles are collected by filtration, washed with the same solvent and filtered, and then dried.

《Internal additive》
The colored particles constituting the toner of the present invention may contain an internal additive other than the release agent such as a charge control agent. Examples of the charge control agent contained in the colored particles include nigrosine dyes, naphthenic acid or higher fatty acid metal salts, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, salicylic acid metal salts, or metal complexes thereof. Is mentioned.

(Toner particle shape factor)
The shape factor of the toner particles of the present invention will be described. The shape factor of the toner particles of the present invention is represented by the following formula and indicates the degree of roundness of the toner particles.

Shape factor = ((maximum diameter / 2) ² × π) / projection area Here, the maximum diameter is the maximum distance between the parallel lines when the projected image of toner particles on a plane is sandwiched between two parallel lines. The width of the particles. The projected area refers to the area of the projected image of the toner particles on the plane. This shape factor is obtained by taking a photograph in which toner particles are magnified 2000 times with a scanning electron microscope, and then analyzing the photographic image using “SCANNING IMAGE ANALYZER” (manufactured by JEOL Ltd.) based on this photograph. Was measured. At this time, the shape factor was measured by the above formula using 100 toner particles.

  In the toner particles constituting the toner for developing an electrostatic image, the toner particles having a shape factor in the range of 1.0 to 1.6 are preferably 65% by number or more, more preferably 70% by number or more. is there. More preferably, the number of toner particles having a shape factor in the range of 1.2 to 1.6 is 65% by number or more, and more preferably 70% by number or more.

  When the number of toner particles having a shape factor in the range of 1.0 to 1.6 is 65% by number or more, the triboelectric chargeability on the developer conveying member and the like becomes more uniform, and excessively charged toner is accumulated. In addition, since it becomes easier to replace the toner from the surface of the developer conveying member, problems such as development ghost are less likely to occur. Further, secondary effects such as the toner particles are less likely to be crushed, the contamination of the charging member is reduced, and the chargeability of the toner is stabilized are further exhibited.

  The method for controlling the shape factor is not particularly limited. For example, a method in which toner particles are sprayed into a hot air stream, a method in which toner particles are repeatedly applied with mechanical energy due to impact force in a gas phase, or a method in which toner particles are added in a solvent that does not dissolve toner and a swirling flow is applied. The toner having a shape factor of 1.0 to 1.6 or 1.2 to 1.6 is prepared by adding the toner into a normal toner so as to be within the range of the present invention. There is a way. In addition, the overall shape is controlled at the stage of adjusting the so-called polymerization method toner, and the toner whose shape factor is adjusted to 1.0 to 1.6 or 1.2 to 1.6 is similarly added to the normal toner. There is a way to adjust.

(Variation coefficient of toner particle shape factor)
The variation coefficient of the shape factor of the toner particles according to the present invention is calculated from the following equation.

Coefficient of variation (%) = (S ₁ / K) × 100
In the formula, S ₁ represents the standard deviation of the shape factor of 100 toner particles, and K represents the average value of the shape factor.

  In the toner particles constituting the toner of the present invention, the variation coefficient of the shape factor is preferably 16% or less, more preferably 14% or less. When the variation coefficient of the shape factor is 16% or less, the charge amount distribution becomes sharper and the image quality can be improved.

  In order to control the shape factor of the toner particles and the coefficient of variation of the shape factor uniformly without variation of lots, the resin particles (polymer particles) constituting the toner of the present invention were prepared (polymerized), and the resin particles were In the process of fusing and shape control, an appropriate process end time may be determined while monitoring the characteristics of the toner particles (colored particles) being formed. Monitoring means that a measuring device is incorporated in-line, and process conditions are controlled based on the measurement result. That is, for example, in a polymerization toner formed by incorporating shape measurements in-line, for example, by associating or fusing resin particles in an aqueous medium, the shape and particles are sequentially sampled during the fusing process. The diameter is measured and the reaction is stopped when the desired shape is achieved. Although it does not specifically limit as a monitoring method, The flow type particle image analyzer FPIA-2000 (made by Toa Medical Electronics Co., Ltd.) can be used.

  This apparatus is suitable because the shape can be monitored by performing image processing in real time while passing the sample liquid. That is, a pump or the like is used from the reaction field, and the shape is measured continuously, and the reaction is stopped when the desired shape is obtained.

(Toner number variation coefficient)
The number particle size distribution and the number variation coefficient of the toner of the present invention are measured by a Coulter Counter TA-II or a Coulter Multisizer (manufactured by Coulter Beckman).

  In the present invention, a Coulter multisizer is used, and an interface (manufactured by Nikkaki Co., Ltd.) that outputs a particle size distribution and a personal computer are connected. The aperture used in the Coulter Multisizer was 100 μm, and the volume and number of toners of 2 μm or more were measured to calculate the particle size distribution and average particle size. The number particle size distribution represents the relative frequency of the toner particles with respect to the particle size, and the number average particle size represents the median diameter in the number particle size distribution. The “number variation coefficient in the number particle size distribution” of the toner is calculated from the following equation.

Number variation coefficient (%) = (S ₂ / D _n ) × 100
In the formula, S ₂ represents a standard deviation in the number particle size distribution, and D _n represents a number average particle size (μm).

  The number variation coefficient of the toner particles constituting the toner for developing an electrostatic charge image of the present invention is preferably 27% or less, more preferably 25% or less.

  The reason why the number variation coefficient is adjusted to 27% or less is that, like the variation coefficient of the shape factor of the toner particles, the charge amount distribution becomes sharp, the transfer efficiency is increased, and the image quality is improved.

  Although the method for controlling the number variation coefficient in the toner of the present invention is not particularly limited, for example, a method of classifying toner particles by wind force can be used, but classification in liquid is effective for reducing the number variation coefficient. Is. As a method of classifying in this liquid, there is a method of separating and collecting toner particles according to a difference in sedimentation speed caused by a difference in toner particle diameter by using a centrifuge and controlling the rotation speed.

  In particular, when a toner is produced by a suspension polymerization method, a classification operation is indispensable in order to make the number variation coefficient in the number particle size distribution 27% or less. In the suspension polymerization method, it is necessary to disperse a polymerizable monomer in an oil droplet having a desired size as a toner in an aqueous medium before polymerization. That is, mechanical shearing by a homomixer or a homogenizer is repeated for large oil droplets of a polymerizable monomer, and the oil droplets are reduced to the size of toner particles. In the shearing method, the number particle size distribution of the obtained oil droplets is wide, and therefore the particle size distribution of the toner obtained by polymerizing the oil droplets is also wide. For this reason, classification operation is essential.

(Particle size distribution of toner particles)
As the toner particles constituting the toner of the present invention, when the particle diameter of the toner particles is D (μm), the natural logarithm lnD is taken on the horizontal axis, and the horizontal axis is divided into a plurality of classes at intervals of 0.23. In the histogram showing the reference particle size distribution, the sum of the relative frequency (m1) of the toner particles included in the most frequent class and the relative frequency (m2) of the toner particles included in the most frequent class after the most frequent class. A toner having (M) of 70% or more is preferable.

  When the sum (M) of the relative frequency (m1) and the relative frequency (m2) is 70% or more, the dispersion of the particle size distribution of the toner particles becomes narrow. Therefore, selective development can be performed by using the toner in the image forming process. Can be reliably suppressed.

  In the present invention, the histogram showing the particle size distribution based on the number is a natural logarithm lnD (D: particle size of individual toner particles) having a plurality of classes (0 to 0.23: 0.23) at intervals of 0.23. 0.46: 0.46-0.69: 0.69-0.92: 0.92-1.15: 1.15-1.38: 1.38-1.61: 1.61-1. 84: 1.84 to 2.07: 2.07 to 2.30: 2.30 to 2.53: 2.53 to 2.76, and so on). This histogram is created by a particle size distribution analysis program in which the particle size data of a sample measured by a Coulter Multisizer is transferred to a computer via an I / O unit according to the following conditions. is there.

"Measurement condition"
(1) Aperture: 100 μm
(2) Sample preparation method: Electrolyte [ISOTON R-11 (manufactured by Coulter Scientific Japan)] 50-100 ml, an appropriate amount of a surfactant (neutral detergent) is added and stirred, and 10-20 mg of a measurement sample is added thereto. Add This system is prepared by dispersing for 1 minute with an ultrasonic disperser.

(Toner particle size distribution)
The particle size distribution of the toner particles according to the present invention will be described.

  First, the toner used in the present invention is preferably monodispersed or close to the particle size distribution, and has a ratio (Dv50 / Dp50) of 50% volume particle size (Dv50) to 50% number particle size (Dp50). It is preferably 1.0 to 1.15, more preferably 1.0 to 1.13.

  That is, in the present invention, the latent image formed on the photoconductor is developed with a developer containing toner having the above particle size distribution characteristics on the surface of the photoconductor, and the visualized toner image is transferred to the intermediate transfer body. Furthermore, the image obtained by transferring the toner image from the intermediate transfer member to the recording material and fixing the toner image thereafter has improved image defects such as voids and character dust. Further, the photoconductor and the intermediate transfer member can be cleaned. Can be improved.

<Developer>
The developer used in the present invention will be described.

  The toner of the present invention may be used as a one-component developer or a two-component developer. When used as a one-component developer, a non-magnetic one-component developer or a magnetic one-component developer containing about 0.1 to 0.5 μm of magnetic particles in the toner can be used. be able to.

  Further, it can be mixed with a carrier and used as a two-component developer. In this case, conventionally known materials such as metals such as iron, ferrite and magnetite, and alloys of these metals with metals such as aluminum and lead can be used as the magnetic particles of the carrier. Ferrite particles are particularly preferable. The magnetic particles preferably have a volume average particle size of 15 to 100 μm, more preferably 25 to 80 μm. The volume average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited, and for example, olefin resin, styrene resin, styrene-acrylic resin, silicone resin, ester resin, or fluorine-containing polymer resin is used. In addition, the resin for constituting the resin-dispersed carrier is not particularly limited, and a known resin can be used. For example, a styrene-acrylic resin, a polyester resin, a fluorine resin, a phenol resin, or the like is used. be able to.

<Photoconductor>
Next, the photoconductor used in the present invention will be described.

  The photoconductor used in the present invention is an electrophotographic photoconductor used for electrophotographic image formation, and the effect of the present invention is remarkably exhibited when an organic electrophotographic photoconductor (organic photoconductor) is used. An organic photoconductor means an electrophotographic photoconductor formed by providing an organic compound with at least one of a charge generation function and a charge transport function essential for the construction of an electrophotographic photoconductor. It contains all known organic electrophotographic photoreceptors such as a photoreceptor composed of a substance or an organic charge transport material, a photoreceptor composed of a polymer complex with a charge generation function and a charge transport function.

  The constitution of the organic photoreceptor used in the present invention is described below.

<Conductive support>
The conductive support used for the photoreceptor may be either a sheet or a cylinder, but a cylindrical conductive support is preferred for designing an image forming apparatus in a compact manner. Cylindrical conductive support means a cylindrical support necessary for forming an endless image by rotating. Conductivity is within a range of 0.1 mm or less in straightness and 0.1 mm or less in deflection. A support is preferred. Exceeding the roundness and shake range makes it difficult to form a good image. As the conductive material, a metal drum such as aluminum or nickel, a plastic drum deposited with aluminum, tin oxide, indium oxide or the like, or a paper / plastic drum coated with a conductive substance can be used. The conductive support preferably has a specific resistance of 10 ³ Ωcm or less at room temperature.

《Middle layer》
In the present invention, an intermediate layer having an improved adhesion to the photosensitive layer and an electrical barrier function may be provided between the conductive support and the photosensitive layer. The film thickness of the intermediate layer using the curable metal resin is preferably in the range of 0.1 μm to 5 μm.

<Photosensitive layer>
The photosensitive layer structure of the photoreceptor may be a single layer structure in which a charge generation function and a charge transport function are provided on one layer on the intermediate layer. More preferably, the function of the photosensitive layer is the charge generation layer ( CGL) and charge transport layer (CTL) are preferably separated. By adopting a configuration in which the functions are separated, an increase in the residual potential due to repeated use can be controlled to be small, and other electrophotographic characteristics can be easily controlled according to the purpose. In the negatively charged photoconductor, it is preferable that a charge generation layer (CGL) is formed on the intermediate layer and a charge transport layer (CTL) is formed thereon. In the positively charged photoconductor, the order of the layer configuration is the reverse of that in the negatively charged photoconductor. The most preferred photosensitive layer structure of the present invention is a negatively charged photoreceptor structure having the function separation structure.

  The structure of the photosensitive layer of the function-separated negatively charged photoreceptor will be described below.

<Charge generation layer>
The charge generation layer contains a charge generation material (CGM). As other substances, a binder resin and other additives may be contained as necessary.

  A known charge generation material (CGM) can be used as the charge generation material (CGM). For example, a phthalocyanine pigment, an azo pigment, a perylene pigment, an azulenium pigment, or the like can be used. Among these, the CGM that can minimize the increase in residual potential due to repeated use has a three-dimensional and potential structure that can form a stable aggregate structure among a plurality of molecules. Specifically, a phthalocyanine having a specific crystal structure. CGM of pigments and perylene pigments.

  For example, CGM such as titanyl phthalocyanine with a Bragg angle 2θ with respect to Cu-Kα ray having a maximum peak at 27.2 ° and benzimidazole perylene with the same peak with 2θ 22.4 has little deterioration due to repeated use. The increase in residual potential can be reduced.

  When a binder is used as the CGM dispersion medium in the charge generation layer, a known resin can be used as the binder, but the most preferred resins include formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Can be mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 600 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential associated with repeated use can be minimized. The thickness of the charge generation layer is preferably from 0.01 to 2 μm.

<Charge transport layer>
The charge transport layer contains a charge transport material (CTM) and a binder resin that disperses and forms a CTM. Other substances may contain additives such as antioxidants as necessary. A known charge transport material (CTM) can be used as the charge transport material (CTM). For example, a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, a butadiene compound, or the like can be used. These charge transport materials are usually dissolved in a suitable binder resin to form a layer. Among these, the CTM capable of minimizing the increase in residual potential due to repeated use has a high mobility and an ionization potential difference from the combined CGM of 0.5 (eV) or less, preferably 0 .25 (eV) or less. The ionization potential of CGM and CTM is measured with a surface analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.).

  Examples of the resin used for the charge transport layer (CTL) include polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, Polycarbonate resins, silicone resins, melamine resins, and copolymer resins containing two or more of these resin repeating units. In addition to these insulating resins, high molecular organic semiconductors such as poly-N-vinylcarbazole can be used. Most preferred as a binder for these CTLs is a polycarbonate resin. The thickness of the charge transport layer is preferably 10 to 40 μm.

  The average thickness of the charge transport layer is 5 to 15 μm from the viewpoint of reducing the difference in dielectric constant on the photoreceptor to stabilize the developability and transferability of the toner, and preferably obtaining the effects described in the present invention. The thickness is preferably adjusted to 6 to 13 μm. Here, the film thickness of the charge transport layer can be measured using an eddy current film thickness measuring device EDDY560C (manufactured by HELMUT FISCHER GMBTE CO). As the charge transport layer thickness, the thickness of the photosensitive layer is measured at 10 random locations, and the average value obtained from the measurement is adopted as the thickness value. Further, as the fluctuation range of the film thickness of the photoreceptor, it is preferable that the difference between the maximum film thickness and the minimum film thickness is 2 μm or less.

《Protective layer》
Various resin layers can be provided as a protective layer of the photoreceptor. In particular, an organic photoreceptor having high mechanical strength can be obtained by providing a crosslinked resin layer.

<Image forming method>
The image forming method of the present invention will be described.

  Image formation using toners of four colors yellow, magenta, cyan and black according to the present invention forms an electrostatic latent image on a photosensitive member having a photosensitive layer on a conductive support, and the electrostatic latent image is formed. The image is developed with a developer having the four color toners, a toner image is formed, the toner image is transferred to a transfer material (paper), and then the color toner is applied onto the transfer material (paper) with a heat roller fixing device. It is preferable to use an image forming apparatus equipped with a fixing method.

  FIG. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an aspect of an image forming method for forming a full color image using yellow, magenta, cyan and black toners according to the present invention.

  In FIG. 2, reference numeral 100 denotes a photosensitive drum (photosensitive member) which is an image forming member, which is a photosensitive member in which an organic photosensitive layer is coated on a drum (conductive support) and a resin layer is coated thereon, and is grounded. And rotated clockwise. Reference numeral 120 denotes a scorotron charger, which uniformly charges the circumferential surface of the photosensitive drum 100 by corona discharge. Prior to charging by the scorotron charger 120, the peripheral surface of the photosensitive member may be discharged by performing exposure by the exposure unit 110 using a light emitting diode or the like in order to eliminate the history of the photosensitive member in the previous image formation.

  After uniform charging of the photoreceptor, image exposure based on the image signal is performed by the image exposure unit 130. The image exposure unit 130 in this figure uses a laser diode (not shown) as an exposure light source. Scanning on the photosensitive drum is performed by light whose optical path is bent by the reflection mirror 132 through the rotating polygon mirror 131, the fθ lens, and the like, and an electrostatic latent image is formed.

  The electrostatic latent image is then developed by the developing device 140. On the periphery of the photosensitive drum 100, a developing device 140 is provided. The developing device 140 includes a flat toner such as yellow (Y), magenta (M), cyan (C), and black (K) and a developer having a carrier. The development of the first color is performed by a developing sleeve 141 that contains a magnet and rotates while holding the developer. The developer is regulated to a layer thickness of 100 μm to 600 μm on the developing sleeve 141 by a layer thickness forming means (not shown), and is conveyed to the developing region for development.

  At this time, the development is usually performed by applying a DC and / or AC bias voltage between the photosensitive drum 100 and the developing sleeve 141.

  In the full-color image forming method, after the visualization of the first color is completed, the second color image forming process is started, uniform charging is performed again by the scorotron charger 120, and the latent image of the second color is formed by the image exposure unit 130. Is done. For the third and fourth colors, an image forming process similar to that for the second color is performed, and a four-color visible image is formed on the circumferential surface of the photosensitive drum 100.

  After the image is formed, the transfer material (paper) P is fed to the transfer area by the rotation operation of the paper feed roller 170 when the transfer timing is ready. In the transfer area, a transfer roller (transfer device) 18 is pressed against the peripheral surface of the photosensitive drum 100 in synchronism with the transfer timing, and a multi-color image is batched by sandwiching a supplied transfer material (paper) P. And transferred.

  Next, the transfer material (paper) P is neutralized by a separation brush (separator) 19 brought into a pressure contact state almost simultaneously with the transfer roller, separated by the peripheral surface of the photosensitive drum 100, and conveyed to the fixing device 200, and heated roller After the color toner is welded by heating and pressurizing the pressure roller 201 and the pressure roller 202, the toner is discharged to the outside of the apparatus via the paper discharge roller 210. The transfer roller 18 and the separation brush 19 are separated from the peripheral surface of the photosensitive drum 100 after the transfer material (paper) P has passed to prepare for the next toner image formation.

  On the other hand, after the transfer material (paper) P is separated, the photosensitive drum 100 removes and cleans residual toner by the pressure contact of the blade 221 of the cleaning device 220, and receives the charge removal by the exposure unit 110 and the charging by the charger 120 again. The next image forming process is entered. When a color image is formed on the photosensitive member in an overlapping manner, the blade 221 moves immediately after cleaning the photosensitive member surface and retracts from the peripheral surface of the photosensitive drum 100.

  Reference numeral 30 denotes a detachable process cartridge in which a photoconductor, a charger, a transfer device, a separator, and a cleaning device are integrated.

  As an electrophotographic image forming apparatus, the above-described photosensitive member and components such as a developing device and a cleaning device are integrally coupled as a process cartridge, and this unit may be configured to be detachable from the apparatus main body. good. Further, at least one of a charging device, an image exposure device, a developing device, a transfer or separation device, and a cleaning device is integrally supported together with a photosensitive member to form a process cartridge, and a single unit that is detachable from the apparatus main body. It is good also as a structure which can be attached or detached using guide means, such as a rail of a main body.

  In the present invention, separately from the image forming apparatus shown in FIG. 1, a toner image is formed on an image forming body, and the toner images are sequentially transferred onto a transfer body (paper or an intermediate transfer body) and overlapped to form a color toner. An image forming apparatus that forms an image can also be used. One mode of such an image forming apparatus will be described with reference to FIG.

  FIG. 2 is a cross-sectional view showing an example of the image forming apparatus of the present invention using an intermediate transfer member (transfer belt). The image forming apparatus shown in FIG. 2 is also called a tandem full-color image forming apparatus.

  A tandem color copier is an image forming system (photosensitive drum, developing device, transfer device, etc.) provided independently for each developing color and arranged in parallel along the paper path. is there. In such a copying machine, each image forming system can simultaneously form toner images of each development color, and these toner images can be successively transferred onto a sheet during a series of sheet passing operations. For this reason, the image forming process can be speeded up as compared with a color copying machine in which toner images of each development color are sequentially formed on one photoconductor.

  The image forming apparatus shown in FIG. 2 includes an image reader unit IR that reads an original image roughly and a print unit PR that prints and reproduces the read image on a recording sheet. The image reader unit IR reads light information obtained by separating the original image into three primary colors of red (R), green (G), and blue (B) with a CCD sensor, and performs arithmetic processing on the image data. Is to do. In addition, the printer unit PR includes a transport unit 2 that transports the recording paper, and cyan (C), magenta (M), yellow (Y), and black (K) (hereinafter referred to as cyan, magenta, and yellow) as reproduction colors on the recording paper. , The color code “C, M, Y, K” is appropriately added to the number of the portion related to each reproduction color of black.) The four image forming units 3C, 3M, 3Y and 3K.

  The transport unit 2 is configured around an endless transport belt 27 stretched through a driving roller 24, a driven roller 25, and a tension roller 26, and transports recording paper on the transport belt 27 at a constant speed. It is like that. On the upstream side (feeding side) of the conveying belt 27, a sheet feeding cassette 21 for loading and storing recording paper of a predetermined size, a sheet feeding roller 22 for feeding recording sheets from the sheet feeding cassette 21 one by one, and the sheet feeding roller 21 are fed out. A timing roller 23 for feeding the recording paper onto the conveying belt 27 at a predetermined timing is provided. On the other hand, on the downstream side of the conveying belt 27, a fixing roller 28 for fixing the toner transferred to the recording paper and a paper discharge tray 29 for stacking and storing the recording paper after completion of copying are disposed. In addition, sensors are provided on the upstream side and the downstream side of the conveyor belt 27, respectively, so as to detect paper feed timing, paper jam, and the like.

  The image forming units 3C, 3M, 3Y, and 3K form an image by an electrostatic copying method, and the photosensitive drums 4C and 4M are arranged above the transport belt 27 in parallel along the transport direction of the recording paper. 4Y and 4K. Around the photosensitive drums 4C, 4M, 4Y, and 4K, developing devices 5C, 5M, 5Y, and 5K that develop the electrostatic latent images formed on the photosensitive drums 4C, 4M, 4Y, and 4K, photosensitive Chargers 6C, 6M, 6Y, 6K for uniformly charging the surfaces of the photoconductive drums 4C, 4M, 4Y, 4K, and a cleaner 7C for removing the developer remaining on the photoconductive drums 4C, 4M, 4Y, 4K after development. , 7M, 7Y, 7K, etc. are arranged. Further, a transfer charger for transferring a toner image visualized on the photosensitive drums 4C, 4M, 4Y, and 4K onto the recording paper via the conveyance belt 27 directly below the photosensitive drums 4C, 4M, 4Y, and 4K. 8C, 8M, 8Y, and 8K are arranged.

  Next, the operation of the copying machine 1 configured as described above will be described. First, based on the intensity level of the optical information of the image for each color component of red (R), green (G), and blue (B) obtained by the image reader unit IR, the control unit of the copier 1 performs shading. Image calculation processing such as correction, density conversion, and edge enhancement is performed. Then, it is converted into written image data of each reproduction color of cyan (C), magenta (M), yellow (Y), and black (K), and these cyan (C), magenta (M), yellow (Y), The black (K) image data is temporarily stored in the control unit.

  Thereafter, based on the image data stored in the control unit, the exposure scanning units 9C, 9M, 9Y, and 9K emit modulated laser beams corresponding to the respective reproduction colors. On the other hand, the photosensitive drums 4C, 4M, 4Y, and 4K rotate in the direction of the arrow in FIG. 2, and after the surfaces are uniformly charged by the charging chargers 6C, 6M, 6Y, and 6K, the laser beams are used. Exposure scanning is performed. By such exposure, the electrostatic latent images corresponding to the reproduction colors formed on the photosensitive drums 4C, 4M, 4Y, and 4K are developed into the developing devices 5C, 5M, 5Y, and 5K that incorporate the developers of the reproduction colors. Are developed into toner images of respective colors. These toner images are recorded on the recording paper fed from the paper cassette 21 by the transfer chargers 8C, 8M, 8Y, and 8K at the opposing portions of the photosensitive drums 4C, 4M, 4Y, and 4K and the conveyor belt 27. Are sequentially transferred to each other. Thereafter, the recording paper onto which the four color toner images have been transferred is conveyed to the fixing roller 28. Then, the toner image of each color is melted to be a full color image by being heated by the fixing roller 28 and is fixed on the recording paper. After the image is fixed, the recording paper is discharged to a paper discharge tray 29. By the above operation, one sheet is copied.

  Next, the developing device 5C of the image forming apparatus shown in FIG. 2 will be described with reference to FIG.

  FIG. 3 is a configuration diagram showing an example of a developing unit used in the image forming apparatus of the present invention using an intermediate transfer member (transfer belt). Here, the developing unit 5C, which is one of the developing units, is described in more detail. Explained. The other developing devices 5M, 5Y, and 5K have the same configuration as the developing device 5C, and thus illustration and description thereof are omitted.

  Although not clearly shown in FIG. 3, the developing device 5 </ b> C is provided with three screws of a stirring screw 12, a supply screw 14, and a recovery screw 16 in parallel with each other in a developer storage tank 10 that stores the developer. Is. Each of them is provided with a large number of screw blades obliquely on a rotatable shaft, and each shaft is connected by a gear outside the developer storage tank 10 and is driven to rotate by a driving device such as a motor. It is like that. The rotation of the screw generates a transport force and transports the developer.

  And these three screws are arrange | positioned in the vertical direction, as shown in FIG. That is, the stirring screw 12 is located in the upper stage, the recovery screw 16 is located in the lower stage, and the supply screw 14 is located in the middle stage. Further, a developing roller 18 is provided at a height position between the supply screw 14 and the recovery screw 16 in a state in which a part thereof protrudes from the developer storage tank 10. By arranging the developing roller 18 in this way, the width dimension in the direction perpendicular to the axial direction of the developing device 5C is made compact. The developing roller 18 is positioned in the vicinity of the photosensitive drum 4C of the image forming unit 3C, and applies toner to the electrostatic latent image formed on the photosensitive drum 4C to develop it.

  A take-in portion 11 and a regulating blade 13 are provided on the upper outer peripheral surface of the developing roller 18. The take-in part 11 is for taking in the developer supplied from the supply screw 14 onto the developing roller 18, and the end 11 a opposite to the regulating blade 13 is upstream in the rotational direction from the position directly above the developing roller 18. It is arranged to be located on the side. The regulating blade 13 regulates the developer cutting-off in order to make the thickness of the developer thin layer formed on the developing roller 18 uniform, and is downstream of the developing roller 18 in the rotation direction. Arranged on the side. By arranging the take-in part 11 and the regulating blade 13 in this way, a space is created above the developing roller 18, so that the upper stirring screw 12 has a larger diameter than the conventional one. Is possible.

  That is, the capacity of the developing device 5C is increased without increasing the width dimension in the direction perpendicular to the axial direction. In FIG. 3, the take-in portion 11 is configured integrally with the developer storage tank 10, but can of course be configured separately.

  Next, the operation of the developing device 5C will be described. When a driving device such as a motor is rotated by control from the copying machine 1, each screw is rotated. If it does so, the conveyance force with respect to the developer in the developer storage tank 10 will arise.

  Then, the developer conveyed by the stirring screw 12 to the left end falls and moves to the supply screw 14 and the recovery screw 16 below. On the other hand, the developer conveyed to the right end by the supply screw 14 and the recovery screw 16 overflows upward and moves to the stirring screw 12. Thus, the developer circulates counterclockwise in the developer storage tank 10.

  Along with the circulation of the developer, a part of the developer of the supply screw 14 is conveyed to the end 11 a of the take-in part 11, and the take-in part 11 takes in the developer onto the developing roller 18. Here, the end portion 11 a of the take-in portion 11 is positioned upstream of the developing roller 18 in the rotational direction, that is, in the vicinity of the supply screw 14. As a result, even if the developer conveyed from the supply screw 14 is accompanied by a pressure fluctuation, the pressure fluctuation is alleviated by the take-in portion 11, so that a constant amount of developer is stably supplied to the developing roller 18. Is done. Thereafter, the developer is subjected to ear cutting restriction by the restriction blade 13 and is made into a thin layer on the developing roller 18. At the time of this ear cutting restriction, a constant amount of developer is supplied to the restriction blade 13 at a substantially constant pressure, and an excessive pressure is not applied to the developer. The developer thin layer formed on the developing roller 18 applies toner to the electrostatic latent image on the photosensitive drum and develops it. Further, the excess developer on the developing roller 18 is collected by the collecting screw 16.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these embodiments.

Example 1
(Preparation of latex)
(Preparation of latex 1HML)
(1) Preparation of latex (1H) (nuclear particle formation: first stage polymerization)
In a 5000 ml separable flask equipped with a stirrer, temperature sensor, condenser, and nitrogen introducing device, 4 g of anionic surfactant (C ₁₀ H ₂₁ (OCH ₂ CH ₂ ) ₂ OSO ₃ Na) was added to 3040 g of ion-exchanged water. The dissolved surfactant solution (aqueous medium) was charged, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream. To this surfactant solution, an initiator solution in which 10 g of a polymerization initiator (potassium persulfate: KPS) was dissolved in 400 g of ion-exchanged water was added, the temperature was adjusted to 75 ° C., 528 g of styrene, and 204 g of n-butyl acrylate. A monomer mixture consisting of 68 g of methacrylic acid and 24.4 g of n-octyl-3-mercaptopropionate was added dropwise over 1 hour, and the system was polymerized by heating and stirring at 75 ° C. for 2 hours. (First stage polymerization) was performed to prepare a latex. This is referred to as “latex (1H)”.

(2) Preparation of latex (1HM) (formation of intermediate layer: second stage polymerization)
In a flask equipped with a stirrer, in a monomer mixture composed of 95 g of styrene, 36 g of n-butyl acrylate, 9 g of methacrylic acid, and 0.59 g of n-octyl-3-mercaptopropionic acid ester, 77 g of Exemplified Compound (19) ”was added, and the mixture was heated to 90 ° C. and dissolved to prepare a monomer solution. On the other hand, a surfactant solution obtained by dissolving 1 g of the above anionic surfactant in 1560 ml of ion exchange water is heated to 98 ° C., and latex (1H), which is a dispersion of core particles, is added to the surfactant solution as a solid content. After adding 28 g in terms of conversion, the monomer solution of the exemplified compound (19) was mixed and dispersed for 8 hours by a mechanical disperser “CLEARMIX” (manufactured by M Technique Co., Ltd.) having a circulation path. A dispersion (emulsion) containing emulsion particles (oil droplets) having a dispersed particle size (284 nm) was prepared. Next, an initiator solution in which 5 g of a polymerization initiator (KPS) is dissolved in 200 ml of ion-exchanged water is added to this dispersion (emulsion), and the system is polymerized by heating and stirring at 98 ° C. for 12 hours. (Second-stage polymerization) was performed to obtain a latex. This is referred to as “latex (1HM)”.

(3) Preparation of latex (1HML) (formation of outer layer: third stage polymerization)
To the latex (1HM) obtained as described above, an initiator solution prepared by dissolving 6.8 g of a polymerization initiator (KPS) in 265 ml of ion-exchanged water was added, and 249 g of styrene under a temperature condition of 80 ° C. A monomer mixed solution consisting of 88.2 g of n-butyl acrylate, 2 g of methacrylic acid, and 7.45 g of n-octyl-3-mercaptopropionic ester was added dropwise over 1 hour. After completion of the dropping, the mixture was heated and stirred for 2 hours to perform polymerization (third stage polymerization), and then cooled to 28 ° C. to obtain a latex. This latex is referred to as “latex (1HML)”. The composite resin particles constituting the latex (1HML) had a weight average particle size of 122 nm.

(Preparation of latex 2L (shell agent))
An initiator solution in which 14.8 g of a polymerization initiator (KPS) was dissolved in 400 ml of ion exchange water was charged into a flask equipped with a stirrer, and under a temperature condition of 80 ° C., 600 g of styrene, 190 g of n-butyl acrylate, A monomer mixture composed of 10.0 g of methacrylic acid and 20.8 g of n-octyl-3-mercaptopropionic acid ester was added dropwise over 1 hour. After completion of the dropwise addition, polymerization was carried out by heating and stirring for 2 hours, followed by cooling to 27 ° C. to obtain a latex (a dispersion of resin particles made of a low molecular weight resin). This latex is referred to as “latex (2 L)”. The resin particles constituting the latex (2L) had a peak molecular weight of 11,000, and the weight average particle diameter of the resin particles was 128 nm.

[Preparation of colored particles]
As described below, colored particles Bk1 to Bk5 (black), Y1 to Y5 (yellow), M1 to M5 (magenta), and C1 to C5 (cyan) were prepared.

<< Preparation of Colored Particles Bk1 >>: Black (1) Preparation of Colorant Dispersion 1 90 g of anionic surfactant (C ₁₀ H ₂₁ (OCH ₂ CH ₂ ) ₂ OSO ₃ Na) was stirred into 1600 ml of ion-exchanged water, Dissolved. While stirring this solution, 400.0 g of carbon black (Regal 330R: manufactured by Cabot Corp.) was gradually added, and then dispersed using a stirring device “CLEARMIX” (manufactured by M Technique Co., Ltd.). A colorant dispersion (hereinafter referred to as “colorant dispersion 1”) was prepared. The particle diameter of the colorant particles in this colorant dispersion 1 was 110 nm as measured using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.).

(2) (Aggregation / Fusion) Preparation of associated particles Latex 1 HML 420.7 g (in terms of solid content), 900 g of ion-exchanged water and 200 g of “colorant dispersion 1”, a temperature sensor, a cooling pipe, a nitrogen introducing device, It stirred in the reaction container (four necked flask) which attached the stirring apparatus. After adjusting the temperature in the container to 30 ° C., 5 mol / liter sodium hydroxide aqueous solution was added to this solution to adjust the pH to 8 to 11.0. Next, an aqueous solution in which 2 g of magnesium chloride hexahydrate was dissolved in 1000 ml of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, the temperature increase was started and the system was heated to 90 ° C. over 60 minutes. In this state, the particle size of the associated particles was measured with “Coulter Counter TA-II”. When the number average particle size reached 4 to 7 μm, an aqueous solution in which 40.2 g of sodium chloride was dissolved in 1000 ml of ion-exchanged water. Was added to stop the particle growth, and as a ripening treatment, fusion was continued by heating and stirring at a liquid temperature of 98 ° C. for 6 hours.

(3) Shelling operation Further, 96 g of latex 2L (resin particle dispersion) was added, and heating and stirring were continued for 3 hours to fuse the latex 2L to the surface of the aggregated particles of latex (1HML). Here, 40.2 g of sodium chloride was added, the mixture was cooled to 30 ° C. at 8 ° C./min, hydrochloric acid was added to adjust the pH to 2.0, and stirring was stopped. The produced salting-out, agglomeration and fusion particles were filtered, washed repeatedly with ion exchange water at 45 ° C., and then dried with hot air at 40 ° C. to obtain colored particles Bk1. In the preparation of colored particles, the dispersion state of the colorant is controlled by controlling the pH of the agglomeration step, the addition timing of latex 2L, and the stirring intensity, and the coefficient of variation of the particle size and particle size distribution is further determined by classification in the liquid. Etc. can be adjusted arbitrarily.

<< Preparation of Colored Particles Bk2 to Bk5 >>: Black Colored particles Bk2 to Bk5 having a controlled particle diameter were prepared according to the addition timing of sodium chloride as an aggregation terminator in the preparation of the colored particles Bk1.

<< Preparation of Colored Particles Y1 to Y5 >>: Yellow In the preparation of the colored particles Bk1, C.I. is used instead of carbon black (Regal 330R: manufactured by Cabot Corporation). I. Pigment Yellow 74 was used to produce colored particles Y1 to Y5 having a controlled particle size according to the timing of addition of sodium chloride as an aggregation stopper.

<< Preparation of Colored Particles M1 to M5 >>: Magenta In preparation of the colored particles Bk1, C.I. is used instead of carbon black (Regal 330R: manufactured by Cabot Corporation). I. Pigment Red122 was used to produce colored particles M1 to M5 having a controlled particle size depending on the timing of addition of sodium chloride as an aggregation terminator.

<< Preparation of Colored Particles C1 to C5 >>: Cyan In the preparation of the color particles Bk1, C.I. is used instead of carbon black (Regal 330R: manufactured by Cabot Corporation). I. Pigment Blue 15: 3 was used, and colored particles C1 to C5 having a controlled particle diameter were prepared according to the timing of addition of sodium chloride as an aggregation stopper.

[Production of toner]
<< Production of Black Toners Bk1 to Bk5 >>
1% by mass of hydrophobic silica (number average primary particle size = 12 nm, degree of hydrophobicity = 68) and hydrophobic titanium oxide (number average primary particle size = 20 nm, hydrophobized) to the colored particles Bk1 to Bk5 obtained above. The black toners Bk1 to Bk5 were prepared by adding 1.2 mass% of the degree = 63) and mixing with a Henschel mixer.

<< Preparation of Yellow Toners Y1 to Y5 >>
1% by mass of hydrophobic silica (number average primary particle size = 12 nm, degree of hydrophobicity = 68) and hydrophobic titanium oxide (number average primary particle size = 20 nm, hydrophobicized) are obtained in the colored particles Y1 to Y5 obtained above. The yellow toners Y1 to Y5 were prepared by adding 1.2 mass% of the degree = 63) and mixing with a Henschel mixer.

<< Production of Magenta Toners M1 to M5 >>
1% by mass of hydrophobic silica (number average primary particle size = 12 nm, degree of hydrophobicity = 68) and hydrophobic titanium oxide (number average primary particle size = 20 nm, hydrophobized) to the colored particles M1 to M5 obtained above. Degree = 63) was added in an amount of 1.2 mass% and mixed with a Henschel mixer to prepare magenta toners M1 to M5.

<< Production of Cyan Toners C1 to C5 >>
1% by mass of hydrophobic silica (number average primary particle size = 12 nm, hydrophobization degree = 68) and hydrophobic titanium oxide (number average primary particle size = 20 nm, hydrophobized) to the colored particles C1 to C5 obtained above. Degree = 63) was added in an amount of 1.2 mass% and mixed with a Henschel mixer to prepare cyan toners C1 to C5.

  Table 1 shows the average values of the volume average particle diameter (Dv50) and the circularity of each toner of black, yellow, magenta, and cyan.

  For the obtained toner, a toner set shown in Table 2 was produced. The set number was similarly assigned to the developer.

(Development of developer)
As shown in the toner set shown in Table 2, a ferrite carrier having a volume average particle diameter of 60 μm coated with a silicone resin is mixed with each toner particle, and a developer having a toner concentration of 6% (black developer Bk1 To Bk5, yellow developers Y1 to Y5, magenta developers M1 to M5, and cyan developers C1 to C5) were prepared.

《Live-action evaluation》
The developer sets 1 to 3 and 6 (invention) obtained above and the developer sets 4 and 5 for comparison, and the developer sets 1 to 5 are developed using the image forming apparatus shown in FIG. With respect to the agent sets 4 to 6, full-color image formation was performed using the image forming apparatus of FIG. 1, and the color gamut and secondary color reproducibility were evaluated for each developer set. The results are shown in Tables 3 and 4.

(Color gamut)
The fixing temperature of each image forming apparatus is set to 140 ° C., and each primary color of magenta (M), cyan (C), and yellow (Y) and each primary color are superposed in a 1: 1 ratio. , Blue (B) and green (G) were output. Art paper (Mitsubishi Paper Co., Ltd., Tokishi Art) and Fuji Xerox Office Supply Co., Ltd. C2r (smoothness 28) were used as the paper. Japan Color (Japan Color) was selected as a standard color in Japan by the Japan National Committee of the International Organization for Standardization Printing Technology Committee (ISO / TC130). The selection is made by collecting one piece each of the most common sheet-fed lithographic process inks from eight representative ink manufacturers in Japan, and measuring the color values of each color developed under the same conditions. The selected Japan Color (Japan Color) was submitted to the International Organization for Standardization (ISO) in 1990 and is now the color standard in Japan. Standard color swatches are supplied by the Japan National Committee of the International Organization for Standardization Printing Technology Committee (ISO / TC130) and are readily available.

A: Color gamut equivalent to that of Japan Color was exhibited. O: Color reproducibility close to that of Japan Color was possible, but strictly, it did not reach the color gamut of Japan Color. X: The color gamut was significantly narrower than that of Japan Color. It is had.

(Secondary color reproducibility (color difference))
The color of the solid image portion of the secondary color (red, blue, green) in each of the first formed image and the 10,000th hair image was measured by “Macbeth Color-Eye 7000” and CMC (2: 1 ) The color difference was calculated using the color difference formula. If the color difference obtained by the CMC (2: 1) color difference formula is 5 or less, the color change of the formed image is acceptable.

◎: R, G, B color difference is less than 2 ○: R, G, B color difference is 2 or more and less than 3.5 △: R, G, B color difference is 3.5 or more color difference 5 Less than x: The color difference of any of R, G, and B is 5 or more.

  From Tables 3 and 4, it can be seen that the development set according to the present invention is clearly superior to the comparison in any evaluation of color gamut and secondary color reproducibility.

1 is a cross-sectional view illustrating an example of an image forming apparatus according to the present invention. 1 is a cross-sectional view illustrating an example of an image forming apparatus according to the present invention that uses an intermediate transfer member (transfer belt). FIG. 2 is a configuration diagram illustrating an example of a developing unit that uses an intermediate transfer member (transfer belt) and is used in the image forming apparatus of the present invention. It is a schematic diagram at the time of transferring in the order of Y, M, C, Bk with the same particle diameter. It is a schematic diagram at the time of transferring in the order of Bk, M, C, Y with the same particle diameter. FIG. 6 is a schematic diagram when the Bk toner is minimized and transferred in the order of Y, M, C, and Bk. FIG. 6 is a schematic diagram when Y toner is minimized and transferred in the order of Bk, M, C, and Y.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Copier 4C, 4M, 4Y, 4K Photosensitive drum 5C, 5M, 5Y, 5K Developer 10 Developer storage tank 11 Taking-in part 11a End part 12 Stirring screw 13 Regulation blade 14 Supply screw 16 Collecting screw 18 Developing roller 40 Toner supply port

Claims (4)

In an image forming method for forming a full-color toner image by superposing toners for developing electrostatic images of four colors of yellow, magenta, cyan and black on a transfer material, the toner for developing electrostatic images of four colors has a low volume average The particle size is set in three stages: particle size (Dv50L) toner, medium volume average particle size (Dv50M) toner, and high volume average particle size (Dv50H) toner, and the low volume average particle size toner is 3.5 μm or more and 7.5 μm. Less than, medium volume average particle size toner is 4.3 μm or more and less than 8.3 μm, high volume average particle size toner is in the range of 5.4 μm or more and less than 8.8 μm, and high volume average particle size toner and low volume average particle An image forming method, wherein the difference from the diameter toner is between 0.7 μm and 1.4 μm. The low volume average particle size (Dv50L) toner is black toner, the high volume average particle size (Dv50H) toner is yellow toner, the medium volume average particle size (Dv50M) toner is magenta and cyan toner, and the toner. 2. The image forming method according to claim 1, wherein the image is transferred from the photosensitive member to an intermediate transfer member, superposed on the intermediate transfer member, transferred onto a transfer material, and heat-fixed. The low volume average particle diameter (Dv50L) toner is yellow toner, the high volume average particle diameter (Dv50H) toner is black toner, the medium volume average particle diameter (Dv50M) toner is magenta and cyan toner, and the toner. 2. The image according to claim 1, wherein the image is superposed on the photoconductor and then transferred onto a transfer material, or the toner of each color is sequentially superposed and transferred from the photoconductor onto the transfer material, and heat fixing. The image forming method described. 4. The image forming method according to claim 1, wherein an average value of circularity of the four color electrostatic image developing toners is 0.94 to 0.99. 5.

Images