JP2006276062A - Electrophotographic two-component developer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic two-component developer that can keep developing property for a long period, prevent contamination in a machine by a slight cloud of the developer, and form a stable image with high picture quality. <P>SOLUTION: The electrophotographic two-component developer comprises a carrier and a toner including color particles which contain at least a binder resin and a colorant, and an external additive. The developer is characterized in that: the volume average particle size of the external additive ranges 20 to 200 nm; the surface coating rate of the toner by the external additive ranges 50 to 100%; and the adhesive force between the toner and the carrier measured by an apparatus for measuring adhesive force between fine particles ranges 200 to 1,000 nN under the condition of the pushing pressure of 100 to 1,000 nN on the toner before measurement. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a two-component developer for electrophotography used for developing an electrostatic latent image in electrophotography, electrostatic recording method and the like.

In the electrophotographic method, an electrostatic latent image formed on a latent image carrier (photoconductor) is developed with toner containing a colorant, and the resulting toner image is transferred onto a transfer member, which is then heated. The latent image carrier is cleaned to form an electrostatic latent image again. The dry developer used in such an electrophotographic method includes a one-component developer that uses a toner in which a colorant and the like are blended in a binder resin, and a two-component developer in which a carrier is mixed with the toner. Broadly divided. In a one-component developer, magnetic powder is used, and the magnetic one component is transported to the developer carrier by magnetic force and developed, and the developer is transported to the developer carrier by charging such as a charging roll without using magnetic powder and developed. It can be classified into one magnetic component. Since the latter half of the 1980s, the market for electrophotography has been strongly demanded for miniaturization and high functionality with the key to digitization, and in particular, high-quality prints close to high-quality printing and silver halide photography are desired for full color image quality.
Digitization processing is indispensable as a means for achieving high image quality, and the effect of digitization related to such image quality is that complex image processing can be performed at high speed. This makes it possible to control characters and photographic images separately, and the reproducibility of both qualities is greatly improved compared to analog technology. In particular, for photographic images, gradation correction and color correction are possible, and this is advantageous over analog in terms of gradation characteristics, definition, sharpness, color reproduction, and graininess. However, on the other hand, it is necessary to faithfully form a latent image produced by an optical system as an image output, and as a toner, an activity aimed at faithful reproduction is accelerated as the particle diameter is further reduced. However, it is difficult to obtain high image quality stably by simply reducing the particle size of the toner. In addition to improving the basic characteristics in development, transfer, fixing, and cleaning characteristics, the secondary process in these basic electrophotographic processes Improve disability is even more important.

  In particular, in a color image, three or four color toners are superimposed to form an image. Therefore, if any one of these toners exhibits different characteristics from the initial stage in terms of chargeability, developability, transferability, secondary contamination such as in-machine contamination in the development process, or performance different from other colors, color reproduction is reduced. Or, it may cause deterioration of graininess, image quality deterioration of uneven color, etc., or induce in-flight contamination. Recently, high-quality image quality is desired for full-color images, and it is difficult to obtain stable image quality when such changes in toner characteristics occur. In addition, improvement in stability of characteristics is becoming more important. In particular, in the development process, the developer charge distribution is aimed at narrowing to improve and stabilize developability, but toner and carrier having a particle size distribution can only improve to a certain degree of charge distribution, and the charge amount per toner particle is In general, there are fewer small diameter toners, and such toners do not have a sufficient mirror image force with the carrier. Therefore, the adhesion between the toner and the carrier is weak, and it becomes a cloud and causes internal contamination.

In addition, in order to improve fluidity, chargeability, and transferability, it has been proposed that the shape of the toner be close to a sphere (see, for example, Patent Document 1). In addition, the volume average particle diameter and average circularity of the spherical toner, and the atypical circularity content rate are prescribed to improve the cleaning performance by the cleaning blade, and further, the toner particle size and particle size distribution, the average circularity of the toner, By defining the circularity distribution, a developer that comprehensively considers transfer efficiency has been proposed (see, for example, Patent Documents 2 and 3).
Although these proposals are inventions in which the transfer efficiency is improved by making the average toner shape / shape distribution close to a sphere, the following problems are likely to occur when the toner is made close to a sphere.
In other words, the developer unit is provided with a transport amount control plate for controlling the developer transport amount to be constant, and the developer transport amount can be controlled by changing the interval between the developing roll and the transport amount control plate. Become. However, when a spherical toner is used, the fluidity as a developer is improved, and at the same time, it is hardened and the bulk density is increased. As a result, there is a phenomenon in which developer accumulation occurs in the conveyance regulation region, and the conveyance amount becomes unstable. By controlling the surface roughness on the developing roll and reducing the distance between the control plate and the developing roll, it is possible to improve the transport amount, but the packing property due to the developer pool becomes stronger and the stress applied to the toner accordingly. Also become stronger. As a result, the microstructure change of the toner surface, in particular, the external additive is buried or peeled off easily, and the external additive detached from the toner surface adheres to the carrier surface and the like. Toner that weakens the adhesion force more and more and does not have sufficient adhesion force is easily peeled off from the surface of the carrier by the centrifugal force associated with the rotation of the developing roll, becomes a cloud and causes contamination in the machine.

On the other hand, a method for controlling the toner charge amount has been proposed to improve the contamination inside the apparatus (for example, see Patent Document 4). In this proposal, the toner particle size distribution and the toner charge amount are specified, and the toner that satisfies the in-machine contamination is invented. However, although it can be satisfied with the conventional copying machine and printer, it has become smaller and lower in cost in recent years. Many devices that are equipped with LED arrays as exposure means, and such exposure means are installed near the photoconductor. There is a risk of inviting.
JP 62-184469 A Japanese Patent Laid-Open No. 11-344829 JP-A-11-295931 Japanese Patent Laid-Open No. 2002-189309

  The present invention has been made in view of the above-described conventional problems, and is intended for electrophotography that maintains developability over a long period of time, prevents in-machine contamination due to a light toner cloud, and can form a stable high-quality image. An object is to provide a two-component developer.

  As a result of intensive research, the present inventors have found that in-machine contamination due to extremely light cloud is related to the adhesion between the toner and the carrier, and controls the adhesion between the toner and the carrier. As a result, the inventors have found that the above object can be achieved and have completed the present invention. That is, the present invention

  <1> A two-component developer for electrophotography comprising a toner having colored particles containing at least a binder resin and a colorant and an external additive, and a carrier, wherein the volume average particle diameter of the external additive Is 20 to 200 nm, the surface coverage of the toner by the external additive is 50 to 100%, and the adhesion force between the toner and the carrier measured by the fine particle adhesion measuring device is the toner. It is a two-component developer for electrophotography that is 200 to 1000 nN when the pressing pressure before measurement is 100 to 1000 nN.

  <2> The binder resin for electrophotography according to <1>, wherein the binder resin is a crystalline resin having a durometer hardness of 40 to 70.

The action of the two-component developer for electrophotography of the present invention (hereinafter sometimes referred to as “the developer of the present invention” as appropriate) is not clear, but is presumed as follows.
In order to prevent in-machine contamination due to an extremely light cloud over a long period of time, the conventional chargeability and particle size distribution control alone are insufficient, and it is necessary to control the adhesion between the toner and the carrier. Between the toner and the carrier, electrostatic adhesion force (mirror image force) and non-electrostatic adhesion force (Van der Waals force, liquid crosslinking force) work.
Generally, in order to improve developability and transferability in a two-component developer for electrophotography, or to avoid secondary obstacles such as cloud, it is sufficient in the past to control electrostatic adhesion between toner and carrier. Met. However, it is difficult for a device in which the exposure unit is installed near the developing machine to obtain a stable high image quality with a conventional cloud amount. This is because even if the amount of cloud has not been a problem in the past, the toner slightly clouded adheres to the exposure means in the vicinity of the developing device, so that image density unevenness corresponding to the density of dirt due to the toner tends to occur. Because.

In particular, when the developer is used for a long time, the cloud level tends to gradually deteriorate due to the deterioration of the developer, and the image density unevenness is more likely to occur. Clouds are likely to occur with toners that have a particularly weak electrostatic adhesion between the carrier and the toner. Initially, even if it is very small, the charge exchange with the added toner does not go smoothly. This occurs remarkably when the charge distribution is wide. In particular, in the toner on the low charge side in the charge distribution, if the mirror image force with the carrier is smaller than the centrifugal force due to the rotation of the developing roll, clouding is likely to occur, and in-machine contamination is likely to be induced.
In the developer of the present invention, the external additive is fixed to the toner surface at a specified coverage, so that the developer has a stable developability and the adhesion with the carrier is controlled to be used for development. Except for the toner, the toner is not released from the carrier surface, prevents in-flight contamination by the cloud, and maintains a stable high image quality. The reason is that even if the electrostatic adhesive force is temporarily weakened, the loss of electrostatic adhesive force can be covered by sufficiently increasing the non-electrostatic adhesive force between the toner and the carrier. ing.

  According to the present invention, it is possible to provide a two-component developer for electrophotography capable of maintaining developability over a long period of time, preventing in-machine contamination due to a light cloud of toner, and forming a stable high-quality image.

Hereinafter, the two-component developer for electrophotography of the present invention will be described in detail.
The two-component developer for electrophotography of the present invention contains a toner having colored particles containing at least a binder resin and a colorant and an external additive, and a carrier, and the volume average particle size of the external additive is 20 to 200 nm, the surface coverage of the toner by the external additive is 50 to 100%, and the adhesion force between the toner and the carrier measured by the microparticle adhesion force measuring device is relative to the toner. When the pressing pressure before measurement is 100 to 1000 nN, 200 to 1000 nN is indicated.

In the present invention, the adhesion force is an adhesion force between one toner particle and one carrier particle. A larger value indicates stronger adhesion force, and a smaller value indicates smaller adhesion force.
The measurement of the adhesive force was carried out with a fine particle adhesion force measuring device PAF300 manufactured by Okada Seiko Co., Ltd. This apparatus is an apparatus that can directly measure the adhesion force of one toner on the surface of one carrier adhered on a substrate.
In the present invention, the measurement was repeated over 100 toners, and the average was taken as the toner adhesion.

  In the present invention, the volume average particle size of the external additive is 20 to 200 nm, and the toner surface coverage by the external additive is required to be 50 to 100%. By setting within this range, it is possible to strengthen the adhesion of the external additive to the toner surface and not to affect the developability. If the external additive is less than 20 nm, the external additive is buried in the unevenness of the toner surface, making it difficult to exhibit the function as the external additive. On the other hand, if it exceeds 200 nm, the external additive is stably added to the toner surface. It becomes difficult to fix the agent.

  Clouding occurs when F (developing roll centrifugal force)> F (adhesion between toner carriers). Therefore, in order to suppress the cloud, the developing roll centrifugal force may be reduced (slowing the rotation speed) or controlled so as to increase the adhesion between the toner carriers. This is unrealistic because it reduces print productivity. Therefore, it is more effective to increase the adhesion between the toner carriers.

  In the present invention, the adhesion force between the toner and the carrier needs to be 200 to 1000 nN. Due to the adhesive force falling within this range, there is no significant change in the adhesive force from the initial stage even during long-term use, and stable image quality can be obtained. That is, even in the case of a toner having a charge distribution, the toner on the low charging side has a weak electrostatic adhesive force, but the weak adhesive force can be compensated by setting the adhesive force to 200 nN or more. it can. When the adhesive force is greater than 1000 nN, even if the electrostatic adhesive force is weak, the non-electrostatic adhesive force acts too strongly, causing the developability to deteriorate. The adhesion force between the toner and the carrier is preferably 300 to 800 nN, more preferably 400 to 700 nN.

The number average particle diameter of the toner in the present invention is preferably in the range of 5.0 to 7.0 μm, and more preferably in the range of 5.5 to 6.5 μm. If the thickness is less than 5.0 μm, the surface area of the toner is large, so that the non-electrostatic adhesion becomes too strong and the developability is lowered. On the other hand, if it is larger than 7.0 μm, the toner is likely to be scattered due to centrifugal force, and clouding is likely to occur. In the specified range, the balance between the action of the centrifugal force and the adhesive force can be achieved, and the generation of cloud can be suppressed.
In addition, it is preferable that the number average particle diameter is in the above range from the viewpoint of excellent color reproducibility in full-color image formation.

The colored particles used in the present invention are not particularly limited by the production method and the like as long as they contain at least a binder resin and a colorant, and known methods can be used.
The colored particles used in the present invention can be produced by a known kneading / pulverizing method, a chemical method such as emulsion polymerization or suspension polymerization, or the like. From the viewpoint of yield and environmental burden, it is preferable to produce toner by an emulsion polymerization method. Here, the production method using the emulsion polymerization method will be described in detail.

  In the emulsion polymerization method, a binder resin dispersion using an ionic surfactant and a colorant dispersed in an ionic surfactant of opposite polarity are mixed to form heteroaggregation to form aggregated particles having a toner diameter. (Aggregating step) After that, the toner is heated by heating above the glass transition point of the resin so that the aggregated particles are fused and integrated (fused step), washed and dried to produce a toner.

  In this method, the toner shape can be controlled from an indeterminate shape to a spherical shape by selecting a heating temperature condition or the like. Even if the polarities of the colorant particles and the binder resin particles are the same, the same aggregated particles can be generated by adding a surfactant having the opposite polarity. Further, before the aggregated particle dispersion is heated to fuse the aggregated particles, another particle (adhesive particle) dispersion is added and mixed to adhere the particles to the surface of the original aggregated particles, and then the resin. It is also possible to control the layer structure from the surface to the inside of the toner by adopting a method of fusing by heating above the glass transition point. Furthermore, this method makes it possible to coat the toner surface with a binder resin, coat with a charge control agent, and dispose a release agent and colorant particles near the toner surface.

  At this time, what is important in controlling the particle size distribution and shape distribution is to uniformly and steadily adhere particles (adhesion particles) of a particle dispersion added and mixed later to the surface of the aggregated particles. If the particles to be attached exist in a free state, or once attached particles are released again, the particle size distribution and shape distribution are easily widened. When the particle size distribution is widened, particularly when the toner is fine powder, it strongly adheres to the photoreceptor during development and causes black spots, and two-component developers tend to cause carrier contamination and shorten the developer life. To do. In the case of a one-component developer, it adheres to a developing roll, a charging roll, a trimming roll or a blade and contaminates it, causing deterioration in image quality. Furthermore, there is a problem of the particle size distribution in the toner as a major factor related to the deterioration of image quality and reliability.

  Further, when the toner is produced by the emulsion polymerization method, it is important to control the stirring conditions for the particle size distribution and the shape distribution. Since the viscosity of the dispersion rises during the formation of aggregated particles that are the base material and after the addition of adhering particles, if the dispersion is stirred at a high shear rate using an inclined paddle type stirring blade for the purpose of uniform mixing, the reaction vessel wall Further, since the adhesion of the aggregated particles to the stirring blade increases, the uniform particle size is hindered. In order to perform uniform stirring at a low shear rate, it is effective to use a stirring blade having a wide blade shape (flat plate blade) in the liquid depth direction.

  Further, it is also effective to remove coarse powder by filtering using a filter bag having an opening of 10 μm after forming aggregated particles. It is also effective to perform multistage or repeated processing as necessary. The influence of the particle size distribution or shape distribution on the image quality becomes larger as the volume average particle size of the toner is smaller or the toner shape is closer to a sphere.

  Usually, this agglomeration and fusion process mixes and agglomerates all together, so that the agglomerated particles can be fused in a uniform mixed state, and the toner composition becomes uniform from the surface to the inside. When the release agent is contained by the above method, the release agent is also present on the surface after the fusion, and external additives for generating filming and imparting fluidity are buried in the toner. This phenomenon is likely to occur.

  Therefore, in the aggregation step, the balance of the amount of the ionic surfactant of each initial polarity is shifted in advance to form and stabilize the first-stage base aggregated particles below the glass transition point, and then the second stage. A particle (adherent particle) dispersion treated with a surfactant having a polarity and quantity so as to compensate for the balance deviation can be added. Further, if necessary, after being slightly heated below the glass transition point of the resin contained in the matrix aggregated particles or additional particles to be stabilized, and then heated above the glass transition point, it was added in the second stage. It is possible to fuse the particles while adhering to the surface of the base aggregated particles. These agglomeration operations can be repeated several times stepwise. As a result, the composition and physical properties can be changed stepwise from the surface to the inside of the colored particles, and the toner structure is extremely controlled. It becomes easy.

  For example, in the case of a color toner used for multi-color development, after the mother aggregated particles are made up of binder resin particles and colorant particles in the first stage, another binder resin particle dispersion is added to the toner surface. By forming only the resin layer, the influence of the colorant particles on the charging behavior can be minimized. As a result, a difference in charging characteristics due to the type of colorant can be suppressed. Further, if the glass transition point of the binder resin added in the second step is set high, the toner can be coated in a capsule shape, and both heat storage stability and fixing property can be achieved.

Furthermore, if a release agent particle dispersion such as wax is added in the second stage, and a shell is formed on the outermost surface using a dispersion of resin having high hardness in the third stage, the wax is exposed to the toner surface. It is also possible to prevent the wax from acting as a release agent during fixing.
Further, after the release agent particles are included in the base aggregated particles, a shell may be formed on the outermost surface in the second stage to prevent the wax from being exposed. When the exposure of the wax is prevented, not only filming on the photoreceptor is suppressed, but also the powder fluidity of the toner can be improved.

  In this way, in the method in which particles (binder resin particles, release agent particles, etc.) are gradually attached to the surface of the aggregated particles and heated and fused, the maintenance of the particle size distribution and shape distribution, the volume average In addition to suppressing fluctuations in particle size and circularity, it is unnecessary to add a stabilizer such as a surfactant, base, or acid to increase the stability of the aggregated particles, or the addition amount thereof is minimized. It can be suppressed to the limit.

The dispersion diameter of the dispersed particles is preferably 1 μm or less when used as the base aggregated particles and when used as additional particles. Within the above range, the particle size distribution of the finally produced toner is narrow, free particles are not generated, and the toner performance and reliability are improved.
The amount of the particle dispersion to be added depends on the volume fraction of the base aggregate particles contained, and the amount of the additional particles is preferably adjusted to be within 50% (volume conversion) of the finally generated aggregate particles. When it is within 50%, it adheres to the base aggregated particles and does not generate separate new aggregated particles, which is preferable. In addition, the composition distribution and the particle size distribution can be narrowed, and desired performance can be obtained.

  In addition, the addition of particle dispersion is divided and performed stepwise or gradually, which is effective in suppressing the generation of new fine aggregate particles and sharpening the particle size distribution and shape distribution. It is. Further, when the particle dispersion is added, it is released by heating at a temperature not higher than the glass transition temperature of the base aggregated particles or the resin of the additional particles, preferably in the range of 40 ° C. lower than the glass transition temperature to the glass transition temperature. Generation of particles can be suppressed.

  The thermoplastic binder resin used as the binder resin in the toner of the present invention is styrene such as styrene, parachlorostyrene, α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, n-acrylate. (Meth) acrylic esters such as butyl, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate; acrylonitrile, methacrylonitrile Ethylenically unsaturated nitriles such as vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone; Polyethylene such as ethylene, propylene and butadiene Polymers such as monomers such as olefins, copolymers obtained by combining two or more of these, or a mixture thereof, as well as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins And non-vinyl condensation resins, mixtures of these with the vinyl resins, and graft polymers obtained by polymerizing vinyl monomers in the presence of these. These resins may be used alone or in combination of two or more.

  Among these, when an ethylenically unsaturated monomer is used, a resin particle dispersion can be prepared by carrying out emulsion polymerization or seed polymerization using an ionic surfactant or the like. As another method for preparing a resin particle dispersion, when using an oil-soluble resin, the resin is dissolved in a solvent that is oily and has relatively low solubility in water, and an ionic surfactant or polymer electrolyte is allowed to coexist in water. And a method of dispersing the particles in water with a disperser such as a homogenizer and then evaporating the solvent by heating or decompressing.

  Said thermoplastic binder resin can stabilize the particle | grains obtained by emulsion polymerization etc. by mix | blending a dissociable ethylenically unsaturated monomer. Examples of dissociating ethylenically unsaturated monomers include acrylic acid, methacrylic acid, maleic acid, cinnamic acid, fumaric acid, vinyl sulfonic acid, ethylene imine, vinyl pyridine, vinyl amine and other polymeric acids and polymeric bases Any of the ethylenically unsaturated monomers used as raw materials for the above can be used, but ethylenically unsaturated acids are preferred from the standpoint of ease of polymer formation reaction, and further, acrylic acid, methacrylic acid, malein Dissociable ethylenically unsaturated monomers having a carboxyl group such as acid, cinnamic acid, and fumaric acid are particularly effective for controlling the degree of polymerization and the glass transition point.

  The volume average particle size of the binder resin particles is desirably 1 μm or less, and more desirably in the range of 0.01 to 1 μm. When the volume average particle size of the binder resin particles is within the above range, it is advantageous in that uneven distribution among the toners is reduced, dispersion in the toners is improved, and variations in performance and reliability are reduced. The volume average particle diameter of the binder resin particles can be measured using, for example, a microtrack.

  Examples of the release agent in the present invention include low molecular weight polyolefins such as polyethylene, polypropylene and polybutene; silicones having a softening point by heating; fatty acids such as oleic acid amide, erucic acid amide, ricinoleic acid amide and stearic acid amide Amides; plant waxes such as ester wax, carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil, etc .; animal waxes such as beeswax; montan wax, ozokerite, ceresin, paraffin wax, microcrystalline Minerals such as waxes, Fischer-Tropsch waxes, petroleum-based waxes, and modified products thereof can be used. These waxes are dispersed in water together with ionic surfactants, polymer electrolytes such as polymer acids and polymer bases, and heated with a homogenizer or pressure discharge type disperser that can be heated above the melting point and impart strong shear. And a dispersion of particles of 1 μm or less can be prepared.

  The volume average particle size of the release agent particles is desirably 1 μm or less, and more desirably in the range of 0.01 to 1 μm. When the volume average particle size of the resin particles is within the above range, the uneven distribution between the toners is reduced, the dispersion in the toners is improved, and the variation in performance and reliability is advantageously reduced. The volume average particle diameter can be measured using, for example, a microtrack.

  Examples of the colorant in the present invention include carbon black, chrome yellow, hansa yellow, benzidine yellow, sren yellow, quinoline yellow, permanent orange GTR, pyrazolone orange, vulcan orange, watch young red, permanent red, brillianthamine 3B, and brillianthamine 6B. , DuPont oil red, pyrazolone red, risor red, rhodamine B rake, lake red C, rose bengal, aniline blue, ultramarine blue, calco oil blue, methylene blue chloride, phthalocyanine blue, phthalocyanine green, malachite green oxalate Pigment or acridine, xanthene, azo, benzoquinone, azine, anthraquinone, thi Indico, dioxazine, thiazine, azomethine, indico, phthalocyanine, aniline black, polymethine, triphenylmethane, diphenylmethane, thiazole, etc. can do.

  The volume average particle diameter of the colorant particles in the present invention is desirably 0.8 μm or less, and more desirably in the range of 0.05 to 0.5 μm. When the volume average particle size of the colorant particles is in the above range, the particle size distribution and shape distribution of the finally obtained toner are in an appropriate range, and free toner generation is unlikely to occur and toner composition is not unevenly distributed. In addition, it is preferable because reliability is improved. Further, the colorability in the toner and the shape controllability that is one of the characteristics of the emulsion aggregation method are good, and a toner having a shape close to a true sphere is easily obtained, which is preferable.

  Moreover, a charge control agent can be used as needed. Examples of the charge control agent include dyes composed of complexes of quaternary ammonium salts, nigrosine compounds, aluminum, iron, chromium, and various commonly used charge control agents such as triphenylmethane pigments. Among these, a charge control agent that is difficult to dissolve in water is preferable in order to control ionic strength that affects the stability during aggregation and fusion integration and to reduce wastewater contamination.

  Surfactants used for emulsion polymerization, seed polymerization, colorant dispersion, binder resin particles, release agent dispersion, aggregation, or stabilization thereof include sulfate ester, sulfonate, phosphate ester, Anionic surfactants such as soaps; Cationic surfactants such as amine salts and quaternary ammonium salts; Nonionic surfactants such as polyethylene glycols, alkylphenol ethylene oxide adducts, and polyhydric alcohols The agent can be exemplified, and it is also effective to use different kinds of surfactants in combination. As the dispersing means, a general dispersing machine such as a rotary shear type homogenizer, a ball mill having a media, a sand mill, or a dyno mill can be used.

  When using a composite composed of a binder resin and a colorant, the binder resin and the colorant are dissolved and dispersed in a solvent, then dispersed in water together with the appropriate dispersant, and then heated and decompressed. A method obtained by removing the solvent, a method in which a colorant is immobilized on a latex surface produced by emulsion polymerization or seed polymerization by mechanical shearing or electroadsorption can be employed. These methods are effective in suppressing the liberation of the colorant as additional particles and improving the chargeable colorant dependency.

Examples of the dispersion medium in the dispersion obtained by dispersing the binder resin particle dispersion, the colorant dispersion, the release agent dispersion, and the like include an aqueous medium.
Examples of the aqueous medium include water such as distilled water and ion exchange water, and alcohols. These may be used individually by 1 type and may use 2 or more types together.

  The binder resin particle dispersion, the colorant dispersion, the release agent dispersion, and the like are mixed and heated in a range of room temperature to the glass transition temperature of the binder resin, thereby binding resin particles, a colorant, and a release agent. Are aggregated to form aggregated particles. The number average particle diameter of the aggregated particles is preferably in the range of 3 to 10 μm.

  The content of the binder resin in the aggregated particles may be 40% by mass or less, and is preferably in the range of 2 to 20% by mass. Moreover, as content of the said coloring agent, it should just be 50 mass% or less, and it is preferable that it is about the range of 2-40 mass%. Furthermore, the content of the other components may be a level that does not hinder the object of the present invention, and is generally very small, specifically in the range of 0.01 to 5% by mass. Yes, about 0.5 to 2% by mass is preferable.

  Next, after passing through the adhering step, if necessary, the mixed liquid containing aggregated particles is heat-treated at a temperature equal to or higher than the softening point of the resin, generally in the range of 70 to 120 ° C. to fuse the aggregated particles and coloring A particle-containing liquid can be obtained. The smoothness of the toner can be controlled by the conditions of the heat treatment. When the heat treatment temperature is increased, the toner surface becomes smooth. Conversely, by lowering the heat treatment temperature, irregularities on the toner surface can be increased.

  The obtained colored particle dispersion is separated by centrifugal separation or suction filtration to separate the colored particles, washed 1 to 3 times with ion exchange water, and dried to obtain the colored particles used in the present invention. Can do.

As the binder resin used in the present invention, a crystalline resin having a durometer hardness of 40 to 70 is preferable.
When the crystalline resin having a durometer hardness of 40 to 70 is a binder resin, the toner surface is softer than an amorphous resin, so that external additives are likely to adhere. When the toner surface coverage of the external additive is high as in the present invention, if the resin of the toner is hard, the external additive tends to be peeled off, and the peeled off external additive may cause contamination of the photoreceptor and the charging member. .
In the present invention, “crystalline resin” refers to a resin having a clear endothermic peak rather than a stepwise endothermic amount change in differential scanning calorimetry (DSC). In the case of a polymer obtained by copolymerizing another component with the main chain of the crystalline resin, if the other component is 50% by mass or less, this copolymer is also called a crystalline resin.

  As the binder resin of the toner used in the present invention, those containing a crystalline resin as a main component are preferably used. Here, the “main component” refers to the main component of the components constituting the binder resin. Specifically, the component which comprises 50 mass% or more of the said binder resin is pointed out. However, in the present invention, among the binder resins, the crystalline resin is preferably 70% by mass or more, more preferably 90% by mass or more, and particularly preferably all are crystalline resins.

  Specific examples of the crystalline resin include long-chain alkyl dicarboxylic acids such as adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tridecanedioic acid, and butanediol, pentanediol, hexanediol. , Polyester resins using long-chain alkyl and alkenyl diols such as heptanediol, octanediol, nonanediol, decanediol, batyl alcohol; amyl (meth) acrylate, hexyl (meth) acrylate, (meth) acrylic acid Heptyl, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, tridecyl (meth) acrylate, myristyl (meth) acrylate, cetyl (meth) acrylate , (Meth) acrylic acid steer , Vinyl resins using long-chain alkyls such as (meth) acrylic acid oleyl and (meth) acrylic acid behenyl, alkenyl (meth) acrylic acid esters; From the viewpoint of chargeability and adjustment of the melting point within a preferable range, a polyester resin-based crystalline resin is preferable. An aliphatic crystalline polyester resin having an appropriate melting point is preferred.

  The crystalline polyester resin is synthesized from an acid (dicarboxylic acid) component and an alcohol (diol) component. In the following description, in the polyester resin, the component that was an acid component before the synthesis of the polyester resin is referred to as “acid-derived component”, and the component that was the alcohol component before the synthesis of the polyester resin is referred to as “alcohol. "Derived component".

-Acid-derived components-
Examples of the acid for forming the acid-derived constituent component include various dicarboxylic acids, and aromatic dicarboxylic acids and aliphatic dicarboxylic acids are preferable. Among them, aliphatic dicarboxylic acids are preferable, and linear carboxylic acids are particularly preferable. desirable.

  Examples of the aliphatic dicarboxylic acid include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelic acid, sebacic acid, 1,9-nonanedicarboxylic acid, and 1,10-decanedicarboxylic acid. 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, Or lower alkyl esters and acid anhydrides thereof, but are not limited thereto.

  Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, etc. Among them, terephthalic acid is an easily available, low melting point polymer. It is preferable in terms of easy formation.

  As the acid-derived constituent component, in addition to the aforementioned aliphatic dicarboxylic acid-derived constituent component and aromatic dicarboxylic acid-derived constituent component, a dicarboxylic acid-derived constituent component having a double bond, a dicarboxylic acid-derived constituent component having a sulfonic acid group, etc. Are preferably included.

  The component derived from a dicarboxylic acid having a double bond is derived from a lower alkyl ester or acid anhydride of a dicarboxylic acid having a double bond, in addition to a component derived from a dicarboxylic acid having a double bond. Components are also included. The dicarboxylic acid-derived component having a sulfonic acid group is derived from a lower alkyl ester or acid anhydride of a dicarboxylic acid having a sulfonic acid group, in addition to a component derived from a dicarboxylic acid having a sulfonic acid group. Components are also included.

  The dicarboxylic acid having a double bond can be suitably used to prevent hot offset at the time of fixing since the entire resin can be crosslinked using the double bond. Examples of such dicarboxylic acids include, but are not limited to, fumaric acid, maleic acid, 3-hexenedioic acid, and 3-octenedioic acid. Moreover, these lower alkyl esters, acid anhydrides, etc. are also mentioned. Among these, fumaric acid, maleic acid and the like are preferable in terms of cost.

  The dicarboxylic acid having a sulfonic acid group is effective in that it can favorably disperse a coloring material such as a pigment. Further, when particles are prepared by emulsifying or suspending the entire resin in water, if the sulfonic acid group is present, the resin can be emulsified or suspended without using a surfactant. Examples of such a dicarboxylic acid having a sulfone group include, but are not limited to, 2-sulfoterephthalic acid sodium salt, 5-sulfoisophthalic acid sodium salt, and sulfosuccinic acid sodium salt. Moreover, these lower alkyl esters, acid anhydrides, etc. are also mentioned. Among these, 5-sulfoisophthalic acid sodium salt is preferable in terms of cost.

  All of these acid-derived components other than aliphatic dicarboxylic acid-derived components and aromatic dicarboxylic acid-derived components (dicarboxylic acid-derived components having double bonds and dicarboxylic acid-derived components having sulfonic acid groups) As content in an acid origin structural component, 1-20 structural mol% is preferable and 2-10 structural mol% is more preferable.

  When the content is less than 1 component mol%, pigment dispersion is not good, the emulsion particle size becomes large, and adjustment of the toner diameter by aggregation may be difficult, whereas it exceeds 20 component mol%. In some cases, the crystallinity of the polyester resin is lowered, the melting point is lowered, the storability of the image is deteriorated, or the emulsified particle diameter is too small to be dissolved in water, thereby causing no latex. In the present specification, “constituent mol%” refers to a percentage when each constituent component (acid-derived constituent component or alcohol-derived constituent component) in the polyester resin is defined as one unit (mol).

-Alcohol-derived components-
As the alcohol to be an alcohol-derived constituent component, an aliphatic diol is preferable. Specifically, for example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1, 6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13 -Tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, 1,20-eicosanediol, and the like, but are not limited thereto.

  The alcohol-derived constituent component has an aliphatic diol-derived constituent component content of 80 constituent mol% or more, and includes other components as necessary. As the alcohol-derived constituent component, the content of the aliphatic diol-derived constituent component is preferably 90 constituent mol% or more.

  When the content of the aliphatic diol-derived constituent component is less than 80 mol%, the crystallinity of the polyester resin is lowered and the melting point is lowered, so that toner blocking resistance, image storage stability, and low-temperature fixability deteriorate. May end up. Other components included as necessary include diol-derived components having double bonds and diol-derived components having sulfonic acid groups.

  Examples of the diol having a double bond include 2-butene-1,4-diol, 3-butene-1,6-diol, 4-butene-1,8-diol, and the like. Examples of the diol having a sulfonic acid group include 1,4-dihydroxy-2-sulfonic acid benzene sodium salt, 1,3-dihydroxymethyl-5-sulfonic acid benzene sodium salt, and 2-sulfo-1,4-butanediol sodium. Examples include salts.

  When adding these alcohol-derived components other than aliphatic diol-derived components (diol-derived component having a double bond and diol-derived component having a sulfonic acid group), the content in these alcohol-derived components Is preferably 1 to 20 mol%, more preferably 2 to 10 mol%.

  When the content of the alcohol-derived constituent component other than the aliphatic diol-derived constituent component is less than 1 constituent mol%, the pigment dispersion is not good, the emulsified particle size is large, and it is difficult to adjust the toner diameter by aggregation. On the other hand, if it exceeds 20 component mol%, the crystallinity of the polyester resin may be lowered, the image storage stability may be deteriorated, or the emulsified particles may be dissolved in water, and latex may not be produced.

  The durometer hardness of the binder resin of the toner preferably used in the present invention is 40 to 70, preferably 50 to 60. When the durometer hardness is lower than 40, the storage stability of the toner and the burying of the external additive become problems. On the other hand, if it is higher than 70, the external additive is easily peeled off, and a secondary failure is likely to occur in the actual machine.

  In the present invention, the durometer hardness of the crystalline resin was measured by the method of JIS K7215 (HAD).

  The method for producing the polyester resin is not particularly limited, and can be produced by a general polyester polymerization method in which an acid component and an alcohol component are reacted. For example, direct polycondensation, transesterification method, etc. Produced separately for different types. The molar ratio (acid component / alcohol component) when the acid component reacts with the alcohol component varies depending on the reaction conditions and the like, and cannot be generally stated, but is usually about 1/1.

  The production of the polyester resin can be carried out at a polymerization temperature of 180 to 230 ° C., and the reaction system is reacted under reduced pressure as necessary to remove water and alcohol generated during condensation. When the monomer is not dissolved or compatible at the reaction temperature, a solvent having a high boiling point may be added as a solubilizer and dissolved. In the polycondensation reaction, the dissolution auxiliary solvent is distilled off. If there is a monomer with poor compatibility in the copolymerization reaction, it is advisable to condense the monomer with poor compatibility with the monomer and the acid or alcohol to be polycondensed in advance before polycondensing with the main component. .

  Catalysts that can be used in the production of the polyester resin include alkali metal compounds such as sodium and lithium, alkaline earth metal compounds such as magnesium and calcium, and metal compounds such as zinc, manganese, antimony, titanium, tin, zirconium, and germanium. , Phosphorous acid compounds, phosphoric acid compounds, and amine compounds. Specific examples include the following compounds.

  For example, sodium acetate, sodium carbonate, lithium acetate, lithium carbonate, calcium acetate, calcium stearate, magnesium acetate, zinc acetate, zinc stearate, zinc naphthenate, zinc chloride, manganese acetate, manganese naphthenate, titanium tetraethoxide, titanium Tetrapropoxide, titanium tetraisopropoxide, titanium tetrabutoxide, antimony trioxide, triphenylantimony, tributylantimony, tin formate, tin oxalate, tetraphenyltin, dibutyltin dichloride, dibutyltin oxide, diphenyltin oxide, zirconium tetrabutoxide, naphthene Zirconate, zirconyl carbonate, zirconyl acetate, zirconyl stearate, zirconyl octylate, germanium oxide, triphenyl Phosphite, tris (2,4-di -t- butyl-phenyl) phosphite, ethyltriphenylphosphonium bromide, triethylamine, compounds such as triphenyl amine.

Next, the external additive used in the present invention will be described.
In the toner of the present invention, it is necessary to use an external additive having a volume average particle size of 20 nm to 200 nm.
As the external additive having a volume average particle diameter of 20 nm to 200 nm, an inorganic compound can be used, and a known one can be used. Examples thereof include silica, alumina, titania, calcium carbonate, magnesium carbonate, calcium phosphate, cerium oxide and the like. Depending on the purpose, the surface of these inorganic particles may be subjected to a known surface treatment.
In particular, TiO (OH) ₂ metatitanate has no effect on transparency, and has excellent chargeability, environmental stability, fluidity, caking resistance, stable negative chargeability, and stable image quality maintenance. Developers can be provided. In addition, the hydrophobized compound of metatitanic acid has an electric resistance of 10 ¹⁰ Ω · cm or more, which is effective for having good charging characteristics as a developer when processed into colored particles and used as a toner. It is.

Monodispersed spherical silica and monodispersed spherical organic particles are also preferably used as external additives. In the present invention, monodispersed spherical silica is more preferable.
Monodispersed spherical silica can be obtained by a sol-gel method that is a wet method. The particle size of the monodispersed spherical silica can be freely controlled by the weight ratio of alkoxysilane, ammonia, alcohol, water, reaction temperature, stirring rate, and supply rate in the sol-gel method hydrolysis and condensation polymerization step. Monodisperse and spherical shapes can also be achieved by making this method.
Specifically, tetramethoxysilane is dropped and stirred while applying temperature using ammonia water as a catalyst in the presence of water and alcohol. Next, the silica sol suspension obtained by the reaction is centrifuged to separate it into wet silica gel, alcohol and aqueous ammonia. A solvent is added to wet silica gel to form a silica sol again, and a hydrophobizing agent is added to hydrophobize the silica surface. A general silane compound can be used as the hydrophobizing agent. Next, the target monodispersed spherical silica can be obtained by removing the solvent from the hydrophobized silica sol, drying, and sieve. In addition, the silica thus obtained may be treated again. The production method of monodispersed spherical silica in the present invention is not limited to the production method described above.

As said silane compound, a water-soluble thing can be used. Examples of such a silane compound include chemical structural formula R _a SiX _4-a (wherein a is an integer of 0 to 3, R represents an organic group such as a hydrogen atom, an alkyl group, and an alkenyl group; Represents a hydrolyzable group such as a chlorine atom, a methoxy group, and an ethoxy group.), And any type of chlorosilane, alkoxysilane, silazane, and a special silylating agent is used. It is also possible.

  Specifically, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, tetraethoxysilane, Methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, hexamethyldisilazane, N, O- (bistrimethylsilyl) acetamide, N, N-bis (Trimethylsilyl) urea, tert-butyldimethylchlorosilane, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxy Silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-mercapto Representative examples include propyltrimethoxysilane and γ-chloropropyltrimethoxysilane. Particularly preferred examples of the hydrophobizing agent in the present invention include dimethyldimethoxysilane, hexamethyldisilazane, methyltrimethoxysilane, isobutyltrimethoxysilane, and decyltrimethoxysilane.

  The inorganic compound of the external additive is required to have a volume average particle size of 20 to 200 nm, and more preferably 50 nm to 100 nm in order to uniformly coat the toner surface. If it is less than 20 nm, even if the coverage of the toner surface is increased, it is buried in fine irregularities on the toner surface, and uniform coating becomes difficult.

  When the particle diameter of the external additive exceeds 200 nm, it is difficult to stably adhere to the toner surface, and it is easy to be detached by a slight impact, and the adhesion cannot be maintained during long-term use.

  In the present invention, the surface coverage by the external additive of the toner is 50% to 100%, preferably 70% to 80%.

  Here, the surface coverage of the toner by the external additive can be obtained by image analysis of a photograph of the toner. Specifically, it refers to the value obtained by the method described in the examples below.

In the present invention, the external additive is added to the colored particles and mixed. The mixing is performed by a known mixer such as a V-type blender, a Henschel mixer, a Redige mixer, a Q-type mixer, or a hybridization system. It can be carried out.
At this time, various additives may be added as necessary. Examples of the additive include other fluidizing agents, cleaning aids such as polystyrene particles, polymethyl methacrylate particles, and polyvinylidene fluoride particles, or transfer aids. Moreover, you may pass a sieving process after external addition mixing.

  In the present invention, the factor that affects the adhesion between toner carriers is the adhesion strength of the external additive to the toner surface. If the external additive is loosely adhered to the toner surface, when the developing machine is subjected to agitation stress, the external additive moves on the toner surface and the non-electrostatic adhesion force with the carrier becomes weak. Therefore, it is preferable that the external additive is firmly fixed to the toner surface when it is added and mixed.

In the production method using the mixer, it is preferable that the product of the external addition share rate γ defined by the following formula (A) and the external addition mixing time is mixed under a condition satisfying the following formula (B).
γ = V / D (A)
(V: blade tip peripheral speed in the mixer (m / s), D: clearance between the blade tip and the mixer inner wall (m))
1000000 ≦ γ × T ≦ 2000000 (B)
(T: mixing time of external additive (second))

As described above, in the addition and mixing of the toner and the external additive in the dry method, the external additive can be fixed to the toner surface by giving the shear under the above conditions. Outside this range, it is difficult to control the adhesion between the toner carriers within a specified range, and it may be impossible to achieve both cloud prevention and developability.
Moreover, you may pass a sieving process after external addition mixing.
The toner of the present invention can be suitably produced by the production methods as described above, but is not limited to these production methods.

Next, the carrier used in the present invention will be described.
The carrier according to the present invention preferably has a median arithmetic mean height distribution of 0.2 μm to 0.4 μm in order to increase the adhesion with the toner. Here, the arithmetic average height Ra is a value obtained by extracting the reference length in the direction of the average line from the roughness curve of the carrier surface, and summing and averaging the absolute values of deviations from the average line of the extracted portion to the measurement curve. When the value is small, the surface is smooth. When the value is large, the surface is clear.
If the median of the arithmetic average height distribution of the carrier is less than 0.20 μm, the contact area with the toner cannot be secured, so that the carrier and toner slip easily, clouding from the developing roll occurs, and the inside of the machine Contamination will occur. In addition, if the median of the arithmetic average height distribution of the carrier is larger than 0.40 μm, the flowability of the developer is lowered and the magnetic brush on the developing roll becomes hard, so that the toner developed on the latent image carrier Image defects and roughness occur when the image is disturbed by the two-component developer adhering to the developing roll.
The arithmetic average height of the carrier was measured with an ultra-depth color 3D shape measuring microscope VK-9500 manufactured by Keyence Corporation. In this apparatus, a sample is irradiated with a laser to perform three-dimensional scanning. The laser reflected light at each position is monitored with a CCD camera to obtain three-dimensional surface information of the sample. The obtained surface information is statistically processed to obtain an index related to the surface roughness.

In the carrier according to the present invention, it is preferable to form a coating layer on the surface of the core particle from the viewpoint of controlling the volume resistance of the carrier and preventing toner adhesion to the carrier surface. In the case of a carrier having such a configuration, the surface properties (arithmetic average height) of the carrier can be controlled by the surface roughness of the core particles themselves and the coating state of the coating layer.
As a method for controlling the surface properties of the core particles, for example, in the case of ferrite powder, it can be obtained by appropriately selecting production conditions such as composition, calcination conditions, pulverization conditions, and sintering temperature. Specifically, the surface property can be smoothed by increasing the sintering temperature or extending the sintering time, and the surface irregularities are increased by increasing the sintering temperature or shortening the sintering time. Can be made. In particular, it is preferable to carry out with strict sintering temperature control.

Next, the core particle which is a component of the carrier will be described.
Examples of the core particles include those in which magnetic powder is used alone as core particles, and those in which magnetic powder is made into particles and dispersed in a resin (magnetic particle-dispersed resin core particles). The magnetic powder can be made into particles and dispersed in the resin by kneading and pulverizing the resin and magnetic powder, melting and spray-drying the resin and magnetic powder, or using a polymerization method to add the magnetic powder-containing resin in the solution. Examples include a polymerization method.
Examples of the magnetic material (magnetic powder) when magnetic powder is used alone for the core particles include magnetic metals such as iron, nickel and cobalt, and magnetic oxides such as ferrite and magnetite. The volume average particle size of the core particles is preferably 25 to 50 μm, more preferably 30 to 45 μm. When the volume average particle diameter is less than 25 μm, cavities adhere to the image part or the non-image part, and image defects such as white spots occur in the image part and black spots occur in the non-image part. The graininess is inferior, and white spots and image formation occur at the gradation boundary.
As magnetic characteristics of the core particle, the saturation magnetization at 3000 oersted is preferably 50 emu / g or more, and more preferably in the range of 55 to 90 emu / g. When the saturation magnetization is smaller than 50 emu / g, the carrier is developed and defects such as white spots occur.
As the core particles, it is possible to use all commonly used ferromagnetic particles, and specific examples thereof include triiron tetroxide, δ-iron sesquioxide, various ferrite powders, and magnetite granulated powders. . Among these, ferrite powder is preferable from the viewpoint of relatively low specific gravity and excellent transportability.

  As a method for producing magnetic particle-dispersed resin core particles, there is a method in which a monomer and magnetic particles are mixed and the monomers are polymerized to obtain carrier core particles. As the resin used for the polymerization, vinyl, epoxy, phenol, or the like is used. For example, as a method for producing a magnetic particle-dispersed resin core particle using a phenol resin, a magnetic particle-dispersed type is obtained by polymerizing phenols and aldehydes in the presence of a basic catalyst in an aqueous medium to which magnetic particles are added. Resin core particles are obtained.

  In the carrier according to the present invention, the surface property can be controlled even when the coating layer is applied. That is, when the surface property of the core particle is smooth, the surface property of the present invention can be obtained by adding particles having a large particle size to the resin to be coated and uniformly forming a composite film of the particle and the resin on the surface. it can. In the case of a carrier having a large surface unevenness, a carrier having a smooth surface property can be created by filling the unevenness of the core particle with the resin by increasing the amount of the resin to be coated.

The carrier coating layer according to the present invention will be described.
Examples of the resin that coats the magnetic particles include polyolefin resins such as polyethylene and polypropylene; polyvinyl and polyvinylidene resins such as styrenes such as styrene, chlorostyrene and vinylstyrene, acrylic resins, polyacrylonitrile, polyvinyl acetate, Polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole; vinyl chloride-vinyl acetate copolymer; styrene-acrylic acid copolymer, styrene / alkyl acrylate copolymer, styrene / alkyl methacrylate copolymer, styrene / acrylonitrile copolymer Polymer, styrene / butadiene copolymer, styrene / maleic anhydride copolymer; silicone resin; fluorine-containing resin; fluorine resin; polyester; polyurethane; Amino resins, epoxy resins and the like. In addition, a resin containing fluorine is preferably used in terms of carrier contamination. For example, fluoropolymers such as copolymers of vinylidene fluoride and acrylic monomers, copolymers of vinylidene fluoride and vinyl fluoride, terpolymers of tetrafluoroethylene, vinylidene fluoride and non-fluorinated monomers. Examples include terpolymers, fluorinated alkyl acrylates, fluorinated alkyl methacrylates, fluorinated epoxy resins, fluorinated polyester resins, and fluorinated silicon resins. Furthermore, what disperse | distributed electroconductive powder and crosslinked resin particles, such as carbon black, in fluorine-containing resin is preferable. By controlling the resistance value of the coating layer with a conductive powder such as carbon black, the carrier electrical resistance value can be controlled, and by dispersing the carbon black and the crosslinked resin particles in the fluorine-containing resin, a fluorine-containing resin can be obtained. Can be reinforced and peeling of the resin coating layer can be suppressed. Further, the surface property of the carrier according to the present invention can be achieved by selecting the size of the cross-linked resin particles corresponding to the surface property level of the magnetic particles. Furthermore, since basic carbon black and basic crosslinked resin particles are uniformly dispersed in the fluorine-containing resin, it is more preferable to use them.
Other examples include vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylic Α-methylene aliphatic monocarboxylic acid esters such as dodecyl acid, octyl (meth) acrylate and phenyl (meth) acrylate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; vinyl methyl ketone and vinyl hexyl Homopolymers or copolymers such as ketones and vinyl ketones such as vinyl isopropenyl ketone are listed. Furthermore, polyester, polyurethane, polyamide, modified rosin, paraffin, waxes and the like can be used.
The said coating resin may be used individually by 1 type, and may be used together 2 or more types.
The conductive powder preferably has a specific resistance of 10 ¹⁰ Ω · cm or less, and an average primary particle size of 0.02 to 0.2 μm, more preferably 0.02 to 0. .1 μm. The conductive powder is preferably added in an amount of 1 to 25% by mass, more preferably 3 to 15% by mass in the coating layer. The conductive powder is used for the purpose of controlling the volume resistance of the carrier. However, if the addition amount is too large, the charge leakage may be large and the charge level may be too low. On the other hand, if the addition amount is too small, the volume resistance is There are cases where almost no effect is exhibited.
The conductive powder is preferably present so as to be exposed on the surface of the carrier coating layer while having contact with the core particles coated with an insulating resin by a single conductive powder. As a result, most of the conductive powder can act as a conductive path in the coating layer.

Examples of the crosslinked particles used in the coating layer include benzoguanamine resin particles, melamine resin particles, and nitrogen-containing particles. The average primary particle size of these particles is preferably 0.1 to 1 μm, more preferably 0.2 to 0.8 μm. The addition amount of the crosslinked particles is preferably 1 to 50% by mass in the coating layer, and more preferably 10 to 30% by mass.
The coating amount of the coating layer varies depending on the surface properties of the core particles, and also the combination of the kind and amount of conductive powder and crosslinked particles, but is generally 0.2 to 5.0% by mass with respect to the core particles. Preferably, it is 1.0 to 3.5 mass%. It is possible to control the surface property of the carrier by adjusting the coating amount.
As a method for forming the coating layer, an immersion method in which the core particles are immersed in a coating layer forming solution containing the matrix resin, a conductive material, and a solvent, and a spray method in which the coating layer forming solution is sprayed on the surface of the core particles. There are a fluidized bed method in which the coating layer forming solution is sprayed in a state where the core particles are suspended by flowing air, and a kneader coater method in which the core particles and the coating layer forming solution are mixed in a kneader coater to remove the solvent.

  The solvent used in the coating layer forming solution is not particularly limited as long as it dissolves the matrix resin. For example, aromatic hydrocarbons such as toluene and xylene, and ketones such as acetone and methyl ethyl ketone. And ethers such as tetrahydrofuran and dioxane can be used. Further, the film thickness of the resin coating layer is usually in the range of 0.1 to 10 μm, but in the present invention, in order to develop a stable carrier volume resistivity over time, in the range of 0.5 to 5 μm. Preferably there is.

  In the two-component developer for electrophotography of the present invention, the toner is preferably mixed and adjusted in the range of 3 to 15 parts by mass with respect to 100 parts by mass of the carrier, and more preferably in the range of 5 to 10 parts by mass.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” and “%” represent mass standards unless otherwise specified.
Various measurements used in each example were performed by the following methods.

(Volume average particle size of external additive)
For the measurement, a laser diffraction / scattering particle size distribution analyzer (HORIBA LA-920) was used.

(Surface coverage)
The surface coverage by the external additive of the toner was determined by the following method.
(1) A measurement sample is prepared by dispersing toner in a two-component mixed epoxy resin and allowing it to stand for one day to solidify.
(2) A section having a thickness of 100 nm is cut out from the measurement sample with a microtome.
(3) The slice is placed on a copper mesh, set in a high resolution electron microscope JEM-2010 (JEOL Ltd.), and photographed at 500,000 times with an applied voltage of 200 kV.
(4) The negative is stretched from 3 times to 10 times and printed.
(5) The surface of the toner having a diameter of 80 to 120% of the volume average particle diameter of the toner is observed by printing according to the procedures of (1) to (4), and the surface covering state on the entire surface of the toner is evaluated. The coverage is obtained from the following formula.
Coverage ratio = (first layer coating length + second layer coating length / toner outer circumference length) × 100 (%)
Here, the first layer coating length refers to the length of the external additive layer in direct contact with the surface of the colored particles. The second layer coating length refers to the length of the external additive layer that overlaps and adheres to the upper part of the external additive layer (first layer) that is in direct contact with the surface of the colored particles.
In the present invention, the average coverage of 10 toners is defined as the surface coverage. The volume average particle diameter of the toner was measured using a Coulter Multisizer II manufactured by Beckman Coulter.

(Adhesion measurement)
The measurement of the adhesive force was performed with a fine particle adhesion force measuring device PAF300 manufactured by Okada Seiko Co., Ltd. A method for measuring the adhesive force will be described with reference to FIG. FIG. 1 is an enlarged view of a main part of an apparatus for measuring adhesion between fine particles.
(1) A developer (carrier 2, toner 3) in which 3 parts of toner are mixed with 100 parts of carrier is attached to glass substrate 1 with an adhesive.
(2) The contact needle 4 is pressed against the toner 3 on the carrier 2 adhered on the glass substrate 1 in the direction of the glass substrate 1 at a pressing speed of 10 μm / s and a pressure of 100 nN to 1000 nN.
(3) The glass substrate 1 is moved away from the contact needle 4 at a speed of 10 μm / s, and the displacement amount of the contact needle 4 is measured.
(4) When the pressure applied to the contact needle 4 exceeds the adhesion force between the toner 3 and the carrier 2, the toner 3 and the carrier 2 are separated. The displacement amount 4 at this time shows the maximum value, and the displacement is converted into an adhesion force by computer processing and evaluated.

(Preparation of colored particles)
-Adjustment of colorant dispersion-
Cyan pigment (manufactured by Dainichi Seika Co., Ltd., copper phthalocyanine B15: 3) 50 parts nonionic surfactant (manufactured by Sanyo Kasei Co., Ltd., Nonipol 400) 5 parts 200 parts of ion-exchanged water (Manufactured by Ultra Turrax) for 10 minutes to obtain a colorant dispersion containing pigment particles having a center diameter of 168 nm.

-Adjustment of release agent dispersion-
Paraffin wax (Nippon Seiwa Co., Ltd., HNP0190, melting point 85 ° C.) 50 parts Cationic surfactant (Kao Corporation, Sanizol B50) 5 parts Ion-exchanged water 200 parts The above ingredients are heated to 95 ° C. and homogenizer (IKA). After sufficiently dispersing with Ultra Turrax T50), a dispersion with a pressure discharge homogenizer was performed to obtain a release agent dispersion containing release agent particles having a center diameter of 180 nm.

-Preparation of resin particle dispersion 1-
Styrene 330 parts n Butyl acrylate 70 parts Acrylic acid 6 parts Dodecanethiol 5 parts Carbon tetrabromide 4 parts First, a solution is prepared by mixing and dissolving the above components (415 parts in total), while a nonionic surfactant ( 6 parts manufactured by Kao Corporation, Nonipol 400) and 10 parts of an anionic surfactant (Daiichi Kogyo Seiyaku Co., Ltd., Neogen SC) are dissolved in 550 parts of ion-exchanged water, and the above solution is added and dispersed in a flask to emulsify. Then, 50 parts of ion-exchanged water in which 4 parts of ammonium persulfate was dissolved was added while slowly stirring and mixing for 10 minutes. Next, after sufficiently replacing the system with nitrogen, the flask was heated to 70 ° C. in an oil bath while stirring, and emulsion polymerization was continued for 5 hours as it was, with a center diameter of 171 nm, a glass transition point of 54 ° C., and a weight average molecular weight. An anionic resin particle dispersion 1 containing (Mw) 34,300 resin particles was obtained.

-Adjustment of colored particles 1-
Resin particle dispersion 1 200 parts Colorant dispersion (19.6% as solid content in dispersion) 40 parts Release agent dispersion (19.6% as solid content in dispersion) 50 parts Polyaluminum chloride 1 .23 parts After thoroughly mixing and dispersing the above components in a round stainless steel flask with a homogenizer (manufactured by IKE, Ultra Turrax T50), heat the agglomeration temperature to 52 ° C. while stirring the flask in an oil bath for heating. did. Then, after maintaining at 52 ° C. for 60 minutes, 60 parts of the resin particle dispersion 1 was further added and gently stirred.

  Thereafter, the pH of the system was adjusted to 6.0 with a 0.5 mol / L sodium hydroxide aqueous solution, and then the stainless steel flask was sealed and heated to 97 ° C. while continuing stirring using a magnetic seal, and thereafter The pH in the system was adjusted to 4.0 and held for 6 hours. After completion of the reaction, the mixture was cooled, filtered, sufficiently washed with ion exchange water, and then subjected to solid-liquid separation by Nutsche suction filtration. Further, it was dispersed again in 3 L of ion exchange water at 40 ° C., and stirred and washed at 300 rpm for 15 minutes. After repeating this washing operation five times, solid-liquid separation was performed using No5A filter paper by Nutsche suction filtration. Next, vacuum drying was continued for 12 hours to obtain colored particles 1. When the volume average particle diameter of the obtained colored particles 1 was measured using a Coulter Multisizer II type (aperture diameter: 50 μm, manufactured by Coulter, Inc.), the volume average particle diameter was 5.4 μm.

-Synthesis of crystalline polyester resin 1-
10-decanediol 17.4 parts 5-sodium dimethylsulfoisophthalate 2.2 parts dimethyl sulfoxide 10 parts dibutyltin oxide 0.03 part The catalyst was placed in a heat-dried three-necked flask and then subjected to reduced pressure. The inside air was replaced with nitrogen gas to create an inert atmosphere, and stirring was performed at 180 ° C. for 3 hours by mechanical stirring. Dimethyl sulfoxide was distilled off under reduced pressure, 26.5 parts of dimethyl dodecanedioic acid was added under a nitrogen stream, and the mixture was stirred at 180 ° C. for 1 hour.

Thereafter, the temperature was gradually raised to 220 ° C. under reduced pressure, and the mixture was stirred for 1 hour. When it became a viscous state, it was air-cooled, the reaction was stopped, and 36 parts of crystalline polyester resin 1 was synthesized. The weight average molecular weight (M _W ) of the obtained crystalline polyester resin 1 was 20000 and the number average molecular weight (Mn) was 17,000 as determined by gel permeation chromatography.

-Synthesis of crystalline polyester resin 2-
Ethylene glycol 124 parts 5-sodium sulfosulfophthalate dimethyl 22.2 parts dimethyl sebacate 213 parts Dibutyltin oxide 0.3 part as a catalyst After putting the above components in a heat-dried three-necked flask, the pressure in the container is reduced by a vacuum operation. Was replaced with nitrogen gas to create an inert atmosphere, followed by mechanical stirring at 180 ° C. for 5 hours.

Thereafter, the temperature was gradually raised to 220 ° C. under reduced pressure, and the mixture was stirred for 2 hours. When it became viscous, it was air-cooled, the reaction was stopped, and 220 parts of crystalline polyester resin 2 was synthesized. The weight average molecular weight (M _W ) of the obtained crystalline polyester resin 2 was 23000 and the number average molecular weight (Mn) was 11,000 as determined by molecular weight measurement (polystyrene conversion) by gel permeation chromatography.

-Synthesis of crystalline polyester resin 3-
20-eicosanediol 18.9 parts 5-sodium dimethylsulfoisophthalate 1.3 parts dimethyl sulfoxide 10 parts dibutyltin oxide 0.03 parts The catalyst was placed in a heat-dried three-necked flask and then reduced in pressure. The air in the container was replaced with nitrogen gas to create an inert atmosphere, and stirring was performed at 180 ° C. for 3 hours by mechanical stirring. Dimethyl sulfoxide was distilled off under reduced pressure, 15.9 parts of dimethyl dodecanedioic acid was added under a nitrogen stream, and the mixture was stirred at 180 ° C. for 1 hour.

Thereafter, the temperature was gradually raised to 220 ° C. under reduced pressure, and the mixture was stirred for 1 hour. When it became viscous, it was air-cooled to stop the reaction, and 33 parts of crystalline polyester resin 3 was synthesized. As a result of molecular weight measurement (polystyrene conversion) by gel permeation chromatography, the crystalline polyester resin 3 obtained had a weight average molecular weight (M _W ) of 21,000 and a number average molecular weight (Mn) of 17,000.

-Synthesis of crystalline polyester resin 4-
4-Butanediol 90.1 parts 5-Dimethyldimethylsulfoisophthalate 22.2 parts Dimethyl adipate 161.1 parts Dibutyltin oxide 0.3 part as a catalyst By operation, the air in the container was replaced with nitrogen gas to create an inert atmosphere, and stirring was performed at 180 ° C. for 5 hours by mechanical stirring.

Thereafter, the temperature was gradually raised to 220 ° C. under reduced pressure, and the mixture was stirred for 30 minutes. When it became viscous, it was cooled with air, the reaction was stopped, and 220 parts of crystalline polyester resin 4 was synthesized. The weight average molecular weight (M _W ) of the obtained crystalline polyester resin 4 was 7200 and the number average molecular weight (Mn) was 2600, as determined by molecular weight measurement (polystyrene conversion) by gel permeation chromatography.

-Preparation of resin particle dispersion 2-
150 parts of the obtained crystalline polyester resin 1 was put in 850 parts of distilled water, and mixed and stirred with a homogenizer (manufactured by IKA Japan: Ultra Tarax) while heating to 85 ° C. Obtained.

-Adjustment of colored particles 2-
<Adjustment of aggregated particles>
2400 parts of the resin particle dispersion 2, 100 parts of the colorant dispersion, 63 parts of the release agent dispersion, 10 parts of lauroyl peroxide, 5 parts of aluminum sulfate (manufactured by Wako Pure Chemical Industries), and ion-exchanged water 100 parts in a round stainless steel flask, adjusted to pH 2.0, dispersed using a homogenizer (manufactured by IKA: Ultra Turrax T50), and then heated to 72 ° C. in an oil bath for heating. Heated with stirring. After maintaining at 72 ° C. for 3 hours, observation with an optical microscope confirmed that aggregated particles having a volume average particle diameter of about 5.0 μm were formed. After further heating and stirring at 72 ° C. for 1 hour, observation with an optical microscope confirmed that aggregated particles having a volume average particle diameter of about 5.5 μm were formed.

<Fusion process>
The pH of this aggregated particle dispersion was 2.4. Therefore, an aqueous solution obtained by diluting sodium carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) to 0.5% was gently added to adjust the pH to 5.0, and then heated to 83 ° C. while stirring was continued for 3 hours. .

  Thereafter, the reaction product was filtered, sufficiently washed with ion-exchanged water, and then dried using a vacuum dryer to obtain colored particles 2. When the volume average particle diameter of the obtained colored particles 2 was measured using a Coulter Multisizer II type (aperture diameter: 50 μm, manufactured by Coulter, Inc.), the volume average particle diameter was 5.5 μm.

-Preparation of resin particle dispersion 3-
150 parts of the obtained crystalline polyester resin 2 was put in 850 parts of distilled water, and mixed and stirred with a homogenizer (manufactured by IKA Japan: Ultra Tarax) while heating to 80 ° C. to obtain a resin particle dispersion 3 Obtained.

-Adjustment of colored particles 3-
<Preparation of aggregated particles>
2400 parts of the resin particle dispersion 3, 100 parts of the colorant dispersion, 63 parts of the release agent dispersion, 10 parts of lauroyl peroxide, 5 parts of aluminum sulfate (manufactured by Wako Pure Chemical Industries), and ion-exchanged water 100 parts in a round stainless steel flask, adjusted to pH 2.0, dispersed using a homogenizer (manufactured by IKA: Ultra Turrax T50), and then heated to 63 ° C. in an oil bath for heating. Heated with stirring. After maintaining at 63 ° C. for 3 hours, observation with an optical microscope confirmed that aggregated particles having a volume average particle diameter of about 4.8 μm were formed. After maintaining heating and stirring at 63 ° C. for an additional hour, observation with an optical microscope confirmed that aggregated particles having a volume average particle diameter of about 5.3 μm were formed.

<Fusion process>
The pH of this aggregated particle dispersion was 2.4. Accordingly, an aqueous solution obtained by diluting sodium carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) to 0.5% was gently added to adjust the pH to 5.0, and then the mixture was heated to 75 ° C. while maintaining stirring and maintained for 3 hours. .

  Thereafter, the reaction product was filtered, sufficiently washed with ion-exchanged water, and then dried using a vacuum dryer to obtain colored particles 3. When the volume average particle diameter of the obtained colored particles 3 was measured using a Coulter Multisizer II type (aperture diameter: 50 μm, manufactured by Coulter, Inc.), the volume average particle diameter was 5.3 μm.

-Preparation of resin particle dispersion 4-
150 parts of the obtained crystalline polyester resin 3 was put in 850 parts of distilled water, and mixed and stirred with a homogenizer (IKA Japan: Ultra Tarax) while heating to 99 ° C. Obtained.

-Adjustment of colored particles 4-
<Preparation of aggregated particles>
2400 parts of resin particle dispersion 4, 100 parts of colorant dispersion, 63 parts of release agent dispersion, 10 parts of lauroyl peroxide, 5 parts of aluminum sulfate (manufactured by Wako Pure Chemical Industries), and ion-exchanged water 100 parts in a round stainless steel flask, adjusted to pH 2.0, dispersed using a homogenizer (manufactured by IKA: Ultra Turrax T50), and then heated to 88 ° C. in an oil bath for heating. Heated with stirring. After maintaining at 88 ° C. for 3 hours, observation with an optical microscope confirmed that aggregated particles having a volume average particle diameter of about 4.2 μm were formed. After maintaining heating and stirring at 88 ° C. for another hour, observation with an optical microscope confirmed that aggregated particles having a volume average particle diameter of about 5.2 μm were formed.

<Fusion process>
The pH of this aggregated particle dispersion was 2.4. Therefore, an aqueous solution obtained by diluting sodium carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) to 0.5% was gently added to adjust the pH to 5.0, and then heated to 97 ° C. and kept for 3 hours while continuing stirring. .

  Thereafter, the reaction product was filtered, sufficiently washed with ion-exchanged water, and then dried using a vacuum dryer to obtain colored particles 4. The volume average particle diameter of the colored particles 4 obtained was measured using a Coulter Multisizer II type (aperture diameter: 50 μm, manufactured by Coulter Inc.), and the volume average particle diameter was 5.4 μm.

-Preparation of resin particle dispersion 5-
150 parts of the obtained crystalline polyester resin 4 was put in 850 parts of distilled water, and mixed and stirred with a homogenizer (manufactured by IKA Japan: Ultra Tarax) while heating to 70 ° C. to obtain resin particle dispersion 5 Obtained.

-Adjustment of colored particles 5-
<Preparation of aggregated particles>
2400 parts of the resin particle dispersion 5, 100 parts of the colorant dispersion, 63 parts of the release agent dispersion, 10 parts of lauroyl peroxide, 5 parts of aluminum sulfate (manufactured by Wako Pure Chemical Industries), and ion-exchanged water 100 parts in a round stainless steel flask, adjusted to pH 2.0, dispersed using a homogenizer (manufactured by IKA: Ultra Turrax T50), and then heated to 50 ° C. in an oil bath for heating. Heated with stirring. After maintaining at 50 ° C. for 3 hours, observation with an optical microscope confirmed that aggregated particles having a volume average particle diameter of about 4.8 μm were formed. After further heating and stirring at 50 ° C. for 1 hour, observation with an optical microscope confirmed that aggregated particles having a volume average particle diameter of about 5.4 μm were formed.

<Fusion process>
The pH of this aggregated particle dispersion was 2.4. Accordingly, an aqueous solution obtained by diluting sodium carbonate (manufactured by Wako Pure Chemical Industries, Ltd.) to 0.5% was gently added to adjust the pH to 5.0, and then the mixture was heated to 65 ° C. and kept for 3 hours while continuing stirring. .

  Thereafter, the reaction product was filtered, sufficiently washed with ion-exchanged water, and then dried using a vacuum dryer, whereby colored particles 5 were obtained. When the volume average particle diameter of the obtained colored particles 5 was measured using a Coulter Multisizer II type (aperture diameter: 50 μm, manufactured by Coulter, Inc.), the volume average particle diameter was 5.6 μm.

[Manufacture of carrier A]
Mn-Mg-Sr ferrite particle finely pulverized product A (manufactured by Powdertech Co., Ltd.) was put into a mechanomill, and the surface irregularities were reduced mechanically and classified to obtain ferrite classified core particles A.
Ferrite-classified core particles A (volume average particle size 40 μm) 1000 parts ・ Toluene 150 parts ・ Styrene / methyl methacrylate / vinyl pyrrolidone copolymer (copolymerization ratio: 25/70/5, weight average molecular weight: 50,000) 10 parts・ Carbon black (volume average particle size 50 nm) 4 parts ・ Melamine resin particles (volume average particle size 300 nm) 3 parts Addition of carbon black and melamine resin particles after dissolving coating resin in a solvent in advance, glass beads 2 mm and roll mill The mixture was dispersed for 30 minutes and the glass beads were removed, and then the solvent was removed by drying under reduced pressure while stirring and mixing in the reduced pressure kneader together with the ferrite classified core particles A (the degree of vacuum at this time is substantially the drying time) The vacuum degree is -600 mmH so that the tanning time after drying is 10 minutes and the total tanning time after drying is 40 minutes. The temperature during drying control to 80 ° C.), and sieved to obtain a carrier A of the resin coating type a sieve subsequent mesh opening 75 [mu] m.

[Manufacture of carrier B]
Mn-Mg-Sr ferrite particle finely pulverized product B (manufactured by Powdertech Co., Ltd.) was put into a mechanomill, and the surface irregularities were reduced mechanically and classified to obtain ferrite classified core particles B.
Ferrite-classified core particle B (volume average particle size 30 μm) 1000 parts, toluene 150 parts, styrene, methyl methacrylate, vinylpyrrolidone copolymer (copolymerization ratio: 25/70/5, weight average molecular weight: 100,000) 30 Part · carbon black (volume average particle diameter 50 nm) 5 parts · melamine resin particles (volume average particle diameter 300 nm) 4 parts In advance, the coating resin is dissolved in a solvent, and then carbon black and melamine resin particles are added, and glass beads 2 mm After mixing and dispersing in a roll mill for 30 minutes and removing the glass beads, the solvent is removed by drying under reduced pressure while stirring and mixing in the reduced pressure kneader together with the ferrite classified core particles A (the degree of vacuum at this time is substantially dry) The vacuum level is -600m so that the total tanning time after drying is 10 minutes and the tanning time after drying is 30 minutes. Hg, dry temperature control to 80 ° C.) of sieved to obtain a carrier B of the resin coating type a sieve subsequent mesh opening 75 [mu] m.

[Manufacture of Carrier C]
Polyethylene (weight average molecular weight 90000, softening point 145 ° C.) 20 parts spherical magnetite (volume average particle size 1.0 μm) 80 parts The above composition is melt-mixed while maintaining a high temperature of 170 ° C. with a heating attritor, and then a disk type nozzle Spraying cooling was performed using a spraying device having the above, and classification was further performed to obtain classified core particles C.
・ Classified core particle C (volume average particle diameter 45 μm) 1000 parts ・ Toluene 150 parts ・ Styrene, methyl methacrylate, vinylpyrrolidone copolymer (copolymerization ratio: 25/70/5, weight average molecular weight: 200,000) 45 parts Carbon black (volume average particle size 50 nm) 3 parts, melamine resin particles (volume average particle size 300 nm) 5 parts In advance, the coating resin is dissolved in a solvent, and then carbon black and melamine resin particles are added. After mixing and dispersing for 30 minutes and removing the glass beads, the solvent is removed by drying under reduced pressure while stirring and mixing in the reduced pressure kneader together with the classified core particles C (the degree of vacuum at this time is that the actual drying time is 20 minutes). Min., So that the tanning time after drying is 40 minutes and the total tanning time is 60 minutes. 0 ℃ to control), and sieved to obtain a carrier C of the resin coating type a sieve subsequent mesh opening 75 [mu] m.

Example 1
Add 5.9 parts of spherical silica (volume average particle size 100 nm, sol-gel method, hexamethyldisilazane (HMDS) treatment) to 100 parts of colored particles 1, and blend at a peripheral speed of 55 m / S × 15 minutes with a 20 L Henschel mixer. Thereafter, coarse powder was removed using a sieve having an opening of 45 μm to obtain a toner. At this time, the surface coverage was 80%. Further, 100 parts of carrier A and 5 parts of this toner were stirred with a V blender at 40 rpm × 20 minutes and sieved with a sieve having an opening of 212 μm to obtain a developer.

(Example 2)
After adding 5.8 parts of spherical silica (volume average particle diameter 100 nm, sol-gel method, HMDS treatment) to 100 parts of the colored particles 2, blending was performed at a peripheral speed of 55 m / S × 15 minutes with a 20 L Henschel mixer, and then 45 μm Coarse powder was removed using an open sieve, and a toner was obtained. At this time, the surface coverage was 80%. Further, 100 parts of carrier A and 5 parts of this toner were stirred with a V blender at 40 rpm × 20 minutes and sieved with a sieve having an opening of 212 μm to obtain a developer.

(Example 3)
After adding 8.9 parts of metatitanic acid (volume average particle diameter 50 nm, i-butyltrimethoxysilane treatment) to 100 parts of the colored particles 3 and blending with a 20 L Henschel mixer at a peripheral speed of 55 m / S × 15 minutes, Coarse powder was removed using a sieve having an opening of 45 μm to obtain a toner. At this time, the surface coverage was 98%. Further, 100 parts of carrier B and 5 parts of this toner were stirred with a V blender at 40 rpm × 20 minutes and sieved with a sieve having an opening of 212 μm to obtain a developer.

Example 4
After adding 6.3 parts of resin particles (manufactured by Soken Chemical Co., Ltd., volume average particle size 195 nm) to 100 parts of the colored particles 1, blending at a peripheral speed of 60 m / S × 19 minutes with a 20 L Henschel mixer, Coarse powder was removed using an open sieve to obtain a toner. At this time, the surface coverage was 53%. Further, 100 parts of carrier C and 5 parts of this toner were stirred with a V blender at 40 rpm × 20 minutes, and sieved with a sieve having an opening of 212 μm to obtain a developer.

(Example 5)
After adding 3.8 parts of rutile-type titanium oxide (volume average particle diameter 25 nm, decylsilane treatment) to 100 parts of the colored particles 3 and blending with a 20 L Henschel mixer at a peripheral speed of 40 m / S × 15 minutes, Coarse powder was removed using an open sieve to obtain a toner. At this time, the surface coverage was 65%. Further, 100 parts of carrier B and 5 parts of this toner were stirred with a V blender at 40 rpm × 20 minutes and sieved with a sieve having an opening of 212 μm to obtain a developer.

(Comparative Example 1)
After adding 6.5 parts of spherical silica (volume average particle size 130 nm, sol-gel method, HMDS treatment) to 100 parts of the colored particles 2 and blending with a 20 L Henschel mixer at a peripheral speed of 35 m / S × 15 minutes, 45 μm Coarse powder was removed using an open sieve, and a toner was obtained. At this time, the surface coverage was 98%. Further, 100 parts of carrier B and 5 parts of this toner were stirred with a V blender at 40 rpm × 20 minutes and sieved with a sieve having an opening of 212 μm to obtain a developer.

(Comparative Example 2)
After adding 1.9 parts of gas phase method silica particles (volume average particle diameter 22 nm, HMDS treatment) to 100 parts of colored particles 2 and blending with a 20 L Henschel mixer at a peripheral speed of 40 m / S × 15 minutes, Coarse powder was removed using an open sieve to obtain a toner. At this time, the surface coverage was 70%. Further, 100 parts of carrier A and 5 parts of this toner were stirred with a V blender at 40 rpm × 20 minutes and sieved with a sieve having an opening of 212 μm to obtain a developer.

(Comparative Example 3)
After adding 22.57 parts of sol-gel silica (volume average particle size 210 nm, HMDS treatment) to 100 parts of colored particles 1 and blending with a 20 L Henschel mixer at a peripheral speed of 55 m / S × 15 minutes, a sieve having an opening of 45 μm Was used to remove coarse powder to obtain a toner. At this time, the surface coverage was 80%. Further, 100 parts of carrier C and 5 parts of this toner were stirred with a V blender at 40 rpm × 20 minutes, and sieved with a sieve having an opening of 212 μm to obtain a developer.

(Comparative Example 4)
After adding 1.8 parts of vapor phase method silica particles (volume average particle size 18 nm, HMDS treatment) to 100 parts of the colored particles 3 and blending with a 20 L Henschel mixer at a peripheral speed of 40 m / S × 15 minutes, 45 μm Coarse powder was removed using an open sieve, and a toner was obtained. At this time, the surface coverage was 68%. Further, 100 parts of carrier B and 5 parts of this toner were stirred with a V blender at 40 rpm × 20 minutes and sieved with a sieve having an opening of 212 μm to obtain a developer.

(Comparative Example 5)
After adding metatitanic acid (volume average particle size 50 nm, i-butyltrimethoxysilane treatment) 4.2 parts to 100 parts of the colored particles 5 and blending with a 20 L Henschel mixer at a peripheral speed of 60 m / S × 19 minutes, Coarse powder was removed using a sieve having an opening of 45 μm to obtain a toner. At this time, the surface coverage was 48%. Further, 100 parts of carrier C and 5 parts of this toner were stirred with a V blender at 40 rpm × 20 minutes, and sieved with a sieve having an opening of 212 μm to obtain a developer.

(Comparative Example 6)
After adding 7.7 parts of sol-gel silica (volume average particle size 120 nm, i-butyltrimethoxysilane treatment) to 100 parts of the colored particles 5 and blending with a 20 L Henschel mixer at a peripheral speed of 35 m / S × 15 minutes, Coarse powder was removed using a sieve having an opening of 45 μm to obtain a toner. At this time, the surface coverage was 115%. Further, 100 parts of carrier A and 5 parts of this toner were stirred with a V blender at 40 rpm × 20 minutes and sieved with a sieve having an opening of 212 μm to obtain a developer.

(Evaluation)
The developers shown in Examples and Comparative Examples were evaluated as follows. The evaluation results are shown in Table 1. Table 1 also shows the surface coverage, adhesion, and durometer hardness of the binder resin.

(Evaluation of developability)
Development performance and in-machine contamination were evaluated using Docu Center Color 400 manufactured by Fuji Xerox. As an evaluation, initial development performance after 50,000 sheets printing and in-machine contamination were evaluated.
First, each developer having a toner concentration of 5% was accommodated in the developing device of the image forming apparatus and left in an environment of a temperature of 20 ° C. and a humidity of 50% RH for 24 hours. Thereafter, the toner charge amount in the developing machine is adjusted to 30 μc / g at the time of evaluation, and development is performed depending on whether or not the toner development amount on the surface of the photosensitive member at that time can be maintained in the range of 35 to 55 g / m ^2. Sex was evaluated.
The target optimum development amount is 45 to 50 g / m ² , and the evaluation was made according to the following criteria.
・ 45-50g / m ²・ ・ ・ ・ ・ ・ ・ ・ ◎
・ 35 to 44 g / m ² or 51 to 55 g / m ^2.
・ 30-34g / m ² or 56-60g / m ²・ ・ ・ ・ △
・ Less than 30 g / m ² or 61 g / m ² or more

In-machine contamination was evaluated by visually observing the periphery of the developing machine in the actual machine according to the following criteria. Note that the allowable range is up to Δ.
-Almost no in-flight contamination is seen ...
・ Slight contamination is seen in the aircraft
・ In-flight contamination is seen △ △
・ In-flight contamination is noticeable ... ×

  From Table 1, it can be seen that by using the developer of the present invention, good developability over a long period of time and in-machine contamination due to the cloud can be prevented, and high image quality can be stably obtained.

It is a principal part enlarged view of the adhesive force measuring apparatus between microparticles.

Explanation of symbols

1 Glass substrate 2 Carrier 3 Toner 4 Contact needle

Claims (1)

A two-component developer for electrophotography comprising a toner having colored particles containing at least a binder resin and a colorant and an external additive, and a carrier,
The volume average particle diameter of the external additive is 20 to 200 nm, the surface coverage of the toner by the external additive is 50 to 100%, and the toner measured by an adhesion measuring apparatus between fine particles and the toner An electrophotographic two-component developer having an adhesion force with a carrier of 200 to 1000 nN when the pre-measurement pressing pressure on the toner is 100 to 1000 nN.

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