JP2009163263A - Method for producing magnetic toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a magnetic toner whose performance is maintained even if being left under a severe environment, and which stably gives a high definition image over a long period even if being used under the severe environment as it is. <P>SOLUTION: The method is for producing a magnetic toner in which the surface of a magnetic toner particle at least including a binding resin, a mold releasing agent and a magnetic substance is provided with inorganic fine powder. The magnetic toner particle is produced in a water base medium; the magnetic substance is composed of magnetic iron oxide; the magnetic iron oxide is produced by oxidizing ferrous hydroxide in water, and also is the one obtained by being subjected to surface treatment with a silane coupling agent or a titanium coupling agent without being subjected to a drying stage after the oxidation reaction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a toner for developing an electrostatic latent image and an image forming method using electrophotography, electrostatic recording, magnetic recording, toner jet recording, and the like.

  Conventionally, a number of methods are known as electrophotographic methods. In general, an electric latent image is formed on an image carrier (hereinafter also referred to as a “photosensitive member”) using a photoconductive substance by various means. Then, the latent image is developed with toner to form a visible image. If necessary, the toner image is transferred to a transfer material such as paper, and then the toner image is fixed on the transfer material by heat or pressure. To obtain a copy.

  As a method for visualizing an electric latent image with toner, a cascade development method, a magnetic brush development method, a pressure development method, a magnetic brush development method using a two-component toner composed of a carrier and a toner, a toner carrier is an image carrier. Non-contact one-component development method in which the toner is allowed to fly from the toner carrier to the image carrier in a non-contact manner, a contact one-component development method in which the toner carrier is pressed against the image carrier and the toner is transferred by an electric field, and magnetic toner A so-called jumping method is also used in which a rotating sleeve having a magnetic pole at the center is used to fly between the photosensitive member and the sleeve by an electric field.

  As a jumping method, for example, in Japanese Patent Application Laid-Open No. 54-43027, an insulating magnetic developer is thinly applied on a toner carrier, and this is triboelectrically charged. A method is disclosed in which the image is developed in close proximity to the image and facing without contact. According to this method, the insulating magnetic developer is thinly coated on the toner carrier to allow sufficient frictional charging of the developer, and without contacting the electrostatic latent image while supporting the developer by magnetic force. Since the development is performed, transfer of the developer to the non-image portion, so-called fogging, is suppressed, and a high-definition image can be obtained.

  Such a one-component development method does not require carrier particles such as glass beads or iron powder as in the two-component method, and therefore the development device itself can be reduced in size and weight. Furthermore, since the two-component development method needs to keep the toner concentration in the developer constant, a device for detecting the toner concentration and supplying a necessary amount of toner is necessary. Therefore, the developing device is also large and heavy here. Since such a device is not necessary in the one-component development method, it is preferable because it can be made small and light.

Also, LED and LBP printers are the mainstream in the recent market as printer devices, and the direction of technology is higher resolution, that is, what was conventionally 240, 300 dpi is 400, 600, 800 dpi. Accordingly, the development method is also required to have higher definition. In addition, copying machines are becoming more sophisticated, and therefore are moving toward digitalization. In this direction, the method of forming an electrostatic latent image with a laser is the main method, so it is also proceeding in the direction of high resolution. Here, as with printers, a high-resolution and high-definition development method has been required. Yes. As one means for satisfying this requirement, the toner particle size has been reduced, and Japanese Patent Laid-Open Nos. 1-112253, 1-191156, 2-214156, and 2-284158 are disclosed. Japanese Patent Laid-Open Nos. 3-181952 and 4-162048 propose toners having a specific particle size distribution and a small particle size.

On the other hand, the toner image formed on the photoconductor in the development process is transferred to the transfer material in the transfer process, but the transfer residual toner in the image area and the fog toner in the non-image area remaining on the photoconductor are cleaned in the cleaning process. And stored in a waste toner container. For this cleaning process, conventional blade cleaning, fur brush cleaning, roller cleaning, and the like are used. From the standpoint of the apparatus, the apparatus becomes inevitably large in order to have such a cleaning apparatus, which is a bottleneck when aiming to make the apparatus compact. Furthermore, from the viewpoint of ecology, a system with little waste toner is desired in the sense of effective use of toner, and a toner having high transfer efficiency and low fog has been demanded.

  The developer used in such an image forming process is mainly composed of a binder resin and a colorant, and in addition, additives such as a charge control agent and a release agent are added to bring out the necessary characteristics as a toner. It is common to contain. As a colorant for a magnetic toner, a magnetic material is used as it is, or carbon black or a nonmagnetic inorganic compound, an organic pigment, a dye or the like is used together with a magnetic material. A material that is hardly compatible with the binder resin such as molecular weight polypropylene is used.

  The purpose of using the release agent is to prevent the toner having good fixability on the transfer target material from adhering to the surface of the fixing member. In recent years, printer devices have been increased in speed, and accordingly, further low-temperature fixing of toner has been demanded. Along with this, great efforts have been made to improve adhesion of toner to the surface of a fixing member, so-called offset. Has been paid. For example, Japanese Patent Publication No. 52-3304, Japanese Patent Publication No. 52-3305, Japanese Patent Laid-Open No. 57-52574, and the like have disclosed a technique for incorporating a wax as a releasing agent in the toner.

  Also, JP-A-3-50559, JP-A-2-79860, JP-A-1-109359, JP-A-62-1166, JP-A-61-227354, JP-A-61-94062. JP-A-61-138259, JP-A-60-252361, JP-A-60-252360, JP-A-60-217366, etc. disclose techniques for containing waxes. Yes.

  However, as described above, since the release agent is generally not compatible with the binder resin, it is relatively difficult to uniformly disperse the toner in the toner. The amount is not uniform, and it is not easy to achieve high image quality and high durability without fogging of non-image areas such as fog. In addition, the toner fluidity is deteriorated, the toner charge amount becomes more non-uniform, and when the toner is exposed to a high temperature for a long time, the wax migrates to the toner surface and the developability and transferability are further deteriorated. To do.

  On the other hand, the developing method using the insulating magnetic toner has an unstable element related to the insulating magnetic toner to be used. One of them is that a considerable amount of fine powdery magnetic material is mixed and dispersed in the insulating magnetic toner, and a part of the magnetic material is exposed on the surface of the toner particles. In addition, it affects the triboelectric chargeability, and as a result, causes fluctuation or deterioration of various characteristics required for the magnetic toner such as development characteristics, transferability, and durability of the magnetic toner.

  When the magnetic toner containing the conventional magnetic body is used, the above-mentioned problem occurs because the magnetic body is exposed on the surface of the magnetic toner. That is, by exposing magnetic fine particles having a relatively low resistance compared to the resin constituting the toner to the surface of the magnetic toner, the toner charging performance is lowered, the toner fluidity is lowered, and a long-term In use, the deterioration of the toner such as a decrease in image density due to the separation of the magnetic material due to the rubbing between the toners or the toner layer thickness regulating member, or the occurrence of shading unevenness called sleeve ghost is caused. Such a problem appears particularly conspicuously under high humidity where the triboelectric charge amount tends to decrease.

Yet another unstable factor is the dispersibility of the magnetic material. That is, ideally, it is desirable that the content of the magnetic substance of each toner particle and the dispersion state inside the particle are uniform, but generally, the toner is a binder resin for toner, a release agent, and an inorganic substance. It is not familiar with magnetic materials, and due to specific gravity difference and magnetic aggregation, it is practically impossible to completely disperse magnetic materials. If the magnetic material is not well dispersed inside the toner particles, the state of dispersion of the release agent is also non-uniform.

  As described above, as a recent technology direction, there has been a demand for a higher resolution and higher definition development method, and in order to respond to such a demand, progress has been made in the direction of reducing the particle size of the toner. However, as the toner particle size becomes smaller in this way, uniform dispersion of the material becomes an important technique. That is, unless fine individual toner particles contain a uniform amount of a magnetic material and a release agent in a uniform state, the deterioration of image characteristics and its stability tend to be more noticeable. This is because the toner particle size is simply reduced, and the adhesion force (mirror image force, van der Waals force, etc.) of the toner particles to the photoreceptor is larger than the Coulomb force applied to the toner particles in the transfer process. As a result, in addition to the increase in the residual toner after transfer, the decrease in the toner diameter is inevitably accompanied by an increase in charge amount and deterioration in fluidity, so that a difference in dispersibility tends to appear as a large difference in physical properties. This is because the ratio of fog and toner with poor transferability increases.

  Conventionally, proposals have been made regarding magnetic iron oxide as a magnetic substance contained in a magnetic toner, but there are still points to be improved. For example, JP-A-62-279352 proposes a magnetic toner containing magnetic iron oxide containing silicon element. Such magnetic iron oxide intentionally has silicon element present inside the magnetic iron oxide, but still has a point to be improved in the fluidity of the magnetic toner containing the magnetic iron oxide.

  In Japanese Patent Publication No. 3-9045, there is a proposal to control the shape of magnetic iron oxide to be spherical by adding silicate. The magnetic iron oxide obtained by this method uses silicate to control the particle shape, so that a large amount of silicon element is distributed inside the magnetic iron oxide, and the amount of silicon element present on the magnetic iron oxide surface is small. Since the smoothness of the magnetic iron oxide is high, the fluidity of the magnetic toner is improved to some extent, but the adhesion between the binder resin constituting the magnetic toner and the magnetic iron oxide is insufficient.

  Japanese Patent Application Laid-Open No. 61-34070 proposes a method for producing iron tetroxide by adding a hydrosilosilicate solution during the oxidation reaction to iron tetroxide. Although the iron tetroxide by this method has Si element near the surface, the Si element exists in a layer near the iron tetroxide surface, and the surface is weak against mechanical impact such as friction. Has a point.

  On the other hand, the toner is manufactured as a toner having a desired particle size by melting and mixing a binder resin, a colorant, and the like, uniformly dispersing, pulverizing with a fine pulverizer, and classifying with a classifier (pulverization method). However, there is a limit to the material selection range for the toner particle size reduction. For example, the resin colorant dispersion must be sufficiently brittle and capable of being finely pulverized by an economically usable production apparatus. From this requirement, in order to make the resin colorant dispersion brittle, when the resin colorant dispersion is actually finely pulverized at a high speed, particles having a wide particle size range are easily formed, and in particular, a relatively large proportion of fine particles ( There arises a problem that excessively pulverized particles) are included therein. Further, such highly brittle materials are often further pulverized or powdered when used as developing toners in copying machines and the like.

In addition, in the pulverization method, it is difficult to completely disperse solid fine particles such as a magnetic substance or a colorant or a release agent having low compatibility into a resin, and depending on the degree of dispersion, an increase in fog, It causes a decrease in image density. Furthermore, the pulverization method inherently exposes the magnetic substance and the release agent on the surface of the toner, so that problems still remain in the charging stability under the harsh environment such as the fluidity and high humidity of the toner. That is, in the pulverization method, there is a limit to the finer toner particles required for high definition and high image quality, and accordingly, the powder characteristics, particularly the uniform chargeability and fluidity of the toner are remarkably attenuated.

  In order to overcome the problems of the toner by the pulverization method as described above, and further to satisfy the above-described requirements, a toner production method by a suspension polymerization method has been proposed.

  The toner by suspension polymerization (hereinafter referred to as polymerized toner) can easily make the toner fine particles, and further, since the shape of the obtained toner is spherical, it has excellent fluidity and is advantageous for high image quality.

  In this suspension polymerization method, droplets of the monomer composition are generated in a dispersion medium having a large polarity such as water. Therefore, the component having a polar group contained in the monomer composition is an interface with the aqueous phase. Therefore, it is possible to form a so-called core / shell structure in which a nonpolar component is not easily present in the surface layer portion. In other words, the toner produced by the polymerization method generally contains the release agent component having a low polarity, and the influence of the wax on the toner surface is completely suppressed while maintaining the low temperature fixing property and the high temperature offset resistance inside the toner. Enables ideal toner design. However, when the polymer toner contains a magnetic substance and a release agent at the same time, its fluidity and charging characteristics are significantly lowered. This is because, in part, magnetic particles are generally hydrophilic and are likely to be present on the surface of the toner. Another is that magnetic particles are present inside the toner particles due to a difference in specific gravity or magnetic aggregation. This is because it tends to exist unevenly and the release agent is also unevenly distributed. In an extreme case, the magnetic substance may be present on one half of the toner particles and the release agent may be separated on the other half. Also, if the magnetic material is unevenly distributed in the center of the toner particles, the release agent is driven to the outside of the particles and exposed to the toner surface, and as described above, the fluidity is reduced and the image characteristics and durability at high temperatures are decreased. It leads to sexual deterioration. Furthermore, if a release agent having a low melting point is used for the purpose of low-temperature fixing, the blocking resistance, that is, the toner cohesiveness upon standing is also deteriorated.

  In order to solve this problem and to exhibit the advantages of the polymerized toner, two points are important: improvement of the surface properties of the magnetic material and improvement of physical properties such as compatibility with organic matter. Many proposals have been made regarding surface modification for improving the dispersibility of a magnetic substance in a polymerized toner. For example, various silane coupling agent treatment techniques for magnetic materials are disclosed in Japanese Patent Application Laid-Open Nos. 59-200254, 59-2000025, 59-200277, and 59-224102. Japanese Laid-Open Patent Publication Nos. 63-250660 and 10-239897 disclose techniques for treating silicon element-containing magnetic particles with a silane coupling agent.

  However, although the dispersibility in the toner is improved to some extent by these treatments, there is a problem that it is difficult to uniformly hydrophobize the surface of the magnetic material. The generation of non-magnetic particles cannot be avoided, and this is insufficient to improve the dispersibility in the toner to a good level. In addition, when a release agent is used at the same time, the dispersibility of the release agent is adversely affected as described above.

  Further, as an example of using hydrophobic magnetic iron oxide, Japanese Patent Publication No. 60-3181 proposes a toner containing magnetic iron oxide treated with alkyltrialkoxysilane. Although the addition of this magnetic iron oxide has certainly improved the electrophotographic properties of the toner, the surface activity of the magnetic iron oxide is inherently small, and coalesced particles are formed at the processing stage, and the hydrophobicity is not uniform. It is not always satisfactory.

  As described above, in the conventional surface-treated magnetic material, compatibility between hydrophobicity and material dispersibility is not necessarily achieved for use in a polymerized toner containing a release agent. It is difficult to obtain a toner having excellent performance even if it is manufactured.

  On the other hand, apart from these toner manufacturing methods or material dispersion methods, a method of adding inorganic fine particles as external additives to toner base particles has been proposed and widely used for the purpose of improving toner flow characteristics, charging characteristics and the like. Yes.

  For example, inorganic fine particles that have been hydrophobized in JP-A Nos. 5-66608 and 4-9860, or inorganic fine particles that have been hydrophobized and then treated with silicone oil or the like are added. No. 249059, JP-A-4-264453, and JP-A-5-346682 disclose a method of adding hydrophobized inorganic fine particles and silicone oil-treated inorganic fine particles in combination.

  Many methods for adding conductive fine particles as external additives have also been proposed. For example, carbon black as conductive fine particles is used to attach or adhere to the toner surface for the purpose of imparting conductivity to the toner, or for the purpose of suppressing excessive charging of the toner and making the tribo distribution uniform. It is widely known to use as an external additive. In JP-A-57-151952, JP-A-59-168458, and JP-A-60-69660, conductive fine particles of tin oxide, zinc oxide, and titanium oxide are respectively added to the high-resistance magnetic toner. The addition is disclosed. Japanese Patent Application Laid-Open No. 56-142540 discloses that conductive magnetic particles such as iron oxide, iron powder, and ferrite are added to a high-resistance magnetic toner to promote charge induction to the magnetic toner. Toners that have both developability and transferability have been proposed. Further, in JP-A-61-275864, JP-A-62-258472, JP-A-61-141452, and JP-A-2-120865, the toner is graphite, magnetite, polypyrrole conductive particles, polyaniline. In addition to the disclosure of adding conductive particles, it is known to add a wide variety of conductive fine particles to the toner.

  However, these improvement means are not sufficiently effective for toners having poor material dispersibility.

  From the viewpoint of making the apparatus compact or ecological as described above, a technique called simultaneous development cleaning or cleanerless has recently been proposed as a system without waste toner.

  However, the conventional technology related to simultaneous cleaning or cleanerless mainly focuses on positive memory, negative memory, etc. due to the influence of residual toner on the image as disclosed in JP-A-5-2287. there were. However, as the use of electrophotography is progressing, it is necessary to transfer toner images to various recording media. In this sense, it is not satisfactory for various recording media.

  JP-A-59-133573, JP-A-62-203182, JP-A-63-133179, JP-A-64-20587 are disclosed in which technologies related to cleanerless are disclosed. There are JP-A-2-302277, JP-A-5-2289, JP-A-5-53482, JP-A-5-61383, etc., but a desirable image forming method is not described, and the toner configuration Is not mentioned.

As a development method preferably applied to simultaneous development cleaning or cleanerless, conventionally, in the simultaneous development cleaning that essentially does not have a cleaning device, a configuration in which the surface of the image carrier is rubbed with toner and a toner carrier has been essential. Many contact development methods in which toner or toner contacts an image carrier have been studied. This is because it is considered that a configuration in which the toner or toner contacts and rubs the image carrier in order to collect the transfer residual toner in the developing unit is advantageous. However, the simultaneous development cleaning or cleaner-less process using the contact development method causes toner deterioration, toner carrier surface deterioration, photoreceptor surface deterioration or wear, etc. due to long-term use, and sufficient durability is solved. Not. Therefore, a development simultaneous cleaning method by a non-contact development method has been desired.

  In addition, in image forming methods used for electrophotographic devices and electrostatic recording devices, various methods are known for forming latent images on image bearing members such as electrophotographic photosensitive members and electrostatic recording dielectrics. ing.

  For example, in electrophotography, an electric latent image is formed by performing image pattern exposure after uniformly charging a photoconductor using a photoconductive material as an image carrier to the required polarity and potential. The method to do is common.

  Conventionally, a corona charger (corona discharger) has often been used as a charging device that uniformly charges (including static elimination processing) an image carrier to a required polarity and potential. The corona charger is a non-contact type charging device, and includes a discharge electrode such as a wire electrode and a shield electrode surrounding the discharge electrode, and is disposed in a non-contact manner with the discharge opening facing the image carrier that is a charged body. The image carrier surface is charged to a predetermined level by exposing the image carrier surface to a discharge current (corona shower) generated by applying a high voltage to the discharge electrode and the shield electrode.

  In recent years, as a charging device for an object to be charged such as an image carrier, a contact charging device has been proposed and put into practical use because it has advantages such as low ozone and low power as compared with a corona charger.

  The contact charging device contacts a charged member such as an image bearing member with a conductive charging member (contact charging member / contact charger) such as a roller type (charging roller), a fur brush type, a magnetic brush type, or a blade type. Then, a predetermined charging bias is applied to the contact charging member to charge the charged body surface to a predetermined polarity and potential.

There are two types of contact charging mechanism (i) discharge charging mechanism and ii) direct injection charging mechanism in the contact charging mechanism (charging mechanism, charging principle), and each characteristic depends on which is dominant. Appears.
i) Discharge Charging Mechanism This is a mechanism for charging the surface of the member to be charged by a discharge phenomenon that occurs in a minute gap between the contact charging member and the member to be charged. Since the discharge charging mechanism has a constant discharge threshold value for the contact charging member and the member to be charged, it is necessary to apply a voltage larger than the charging potential to the contact charging member. Further, although the generation amount is remarkably smaller than that of the corona charger, it is unavoidable that a discharge product is generated in principle, and thus harmful effects due to active ions such as ozone are unavoidable.
ii) Direct injection charging mechanism In this system, the surface of the charged body is charged by directly injecting the charge from the contact charging member to the charged body. It is also called direct charging, injection charging, or charge injection charging. More specifically, a medium-resistance contact charging member comes into contact with the surface of the member to be charged, and charge is directly injected into the surface of the member to be charged without going through a discharge phenomenon, that is, basically using no discharge. Therefore, even if the applied voltage to the contact charging member is an applied voltage that is equal to or lower than the discharge threshold, the object to be charged can be charged to a potential corresponding to the applied voltage. Since this charging system is not accompanied by the generation of ions, there is no adverse effect caused by the discharge products. However, since direct injection charging is used, the contact property of the contact charging member to the member to be charged greatly affects the charging property. Therefore, in order to take a configuration that comes into contact with the charged body at a higher frequency, a configuration in which the contact charging member has a denser contact point and a large speed difference from the charged body is required.

  In the contact charging device, a roller charging method using a conductive roller (charging roller) as a contact charging member is preferable in terms of charging stability and is widely used.

  As for the charging mechanism in the conventional roller charging, the discharge charging mechanism of i) is dominant. The charging roller is made of a conductive or medium resistance rubber material or foam. In addition, there are those obtained by laminating these to obtain desired characteristics.

  The charging roller has elasticity in order to obtain a certain contact state with the member to be charged, but has a large frictional resistance, and is often driven by the member to be charged or with a slight speed difference. Therefore, even if direct injection charging is attempted, a decrease in absolute charging ability, lack of contactability, contact unevenness due to the roller shape, and charging unevenness due to deposits on the object to be charged cannot be avoided.

  FIG. 2 is a graph showing an example of charging efficiency of contact charging in electrophotography. The horizontal axis represents the bias applied to the contact charging member, and the vertical axis represents the charged potential (hereinafter referred to as a photoreceptor) obtained at that time. The charging characteristic in the case of roller charging is represented by A. That is, charging starts after the discharge threshold of about −500V. Therefore, when charging to -500 V, apply a DC voltage of -1000 V, or in addition to a charging voltage of -500 V DC, apply an AC voltage with a peak-to-peak voltage of 1200 V so as to always have a potential difference greater than the discharge threshold. Thus, a method of converging the photoreceptor potential to the charging potential is common. More specifically, when the charging roller is brought into pressure contact with an OPC photoconductor having a thickness of 25 μm, the surface potential of the photoconductor starts to rise when a voltage of about 640 V or more is applied. Thereafter, the photosensitive member surface potential increases linearly with a slope of 1 with respect to the applied voltage. This threshold voltage is defined as the discharge start voltage Vth.

  That is, in order to obtain the photoreceptor surface potential Vd required for electrophotography, the charging roller requires a DC voltage higher than that required, that is, Vd + Vth. A method of charging by applying only the DC voltage to the contact charging member in this way is referred to as a “DC charging method”.

  However, in DC charging, the resistance value of the contact charging member fluctuates due to environmental fluctuations, etc., and Vth fluctuates when the film thickness changes due to the photoconductor being scraped, so that the potential of the photoconductor is set to a desired value. It is difficult.

  Therefore, an AC component having a peak-to-peak voltage of 2 × Vth or more is added to a DC voltage corresponding to a desired Vd, as disclosed in Japanese Patent Laid-Open No. 63-149669, in order to further uniform charge. An “AC charging method” is used in which the superimposed voltage is applied to the contact charging member. This is for the purpose of smoothing the potential due to AC, and the potential of the charged body converges to Vd, which is the center of the peak of the AC voltage, and is not affected by disturbances such as the environment.

  However, even in such a contact charging device, the essential charging mechanism uses a discharge phenomenon from the contact charging member to the photosensitive member, so that the voltage applied to the contact charging member is photosensitive as described above. A value higher than the body surface potential is required, and a trace amount of ozone is generated.

  Further, when AC charging is performed for uniform charging, further generation of ozone, generation of vibration noise (AC charging sound) between the contact charging member and the photosensitive member due to an AC voltage electric field, and surface of the photosensitive member due to discharge As a result, the deterioration and the like became remarkable, which was a new problem. Fur brush charging uses a member (fur brush charger) having a conductive fiber brush portion as a contact charging member, and the conductive fiber brush portion is brought into contact with a photosensitive member as a member to be charged, and a predetermined charging is performed. A bias is applied to charge the photoreceptor surface to a predetermined polarity and potential. The charging mechanism of the fur brush charging is dominated by the discharge charging mechanism i).

Fur brush chargers are available in fixed and roll types. A fixed type is a medium-resistance fiber folded into a base fabric and bonded to an electrode. The roll type is formed by winding a pile around a metal core. A fiber density of about 100 fibers / mm ² can be obtained relatively easily. However, the contact property is still insufficient for sufficiently uniform charging by direct injection charging, and sufficiently uniform charging by direct injection charging. In order to perform the above, it is necessary to give the photoreceptor a speed difference that is difficult as a mechanical configuration, which is not practical.

  The charging characteristics of the fur brush charged when a DC voltage is applied take the characteristics shown in FIG. Accordingly, in the case of fur brush charging, both the fixed type and the roll type are charged using a discharge phenomenon by applying a high charging bias.

  On the other hand, the magnetic brush charging uses a member (magnetic brush charger) having a magnetic brush portion formed in a brush shape by magnetically restraining conductive magnetic particles with a magnet roll or the like as a contact charging member. Is brought into contact with a photosensitive member as a member to be charged, and a predetermined charging bias is applied to charge the surface of the photosensitive member to a predetermined polarity and potential.

  In the case of this magnetic brush charging, the direct injection charging mechanism of ii) is dominant as the charging mechanism. By using conductive magnetic particles constituting the magnetic brush portion having a particle diameter of 5 to 50 μm and providing a sufficient speed difference from the photoreceptor, uniform direct injection charging is possible. As indicated by C in the charging characteristic graph of FIG. 2, it is possible to obtain a charging potential substantially proportional to the applied bias. However, there are also disadvantages such as a complicated device configuration and conductive magnetic particles constituting the magnetic brush portion falling off and adhering to the photoreceptor.

  Here, consider the case where these contact charging methods are applied to a simultaneous development cleaning method and a cleanerless image forming method.

  In the development simultaneous cleaning method and the cleanerless image forming method, since there is no cleaning member, residual transfer toner remaining on the photoreceptor (including fog toner remaining untransferred due to the reverse polarity to the transfer bias) is included. Then, it contacts the contact charging member as it is and adheres or mixes. Further, in the case of a charging method in which the discharge charging mechanism is dominant, adhesion to the charging member is also deteriorated due to toner deterioration due to discharge energy. When commonly used insulating toner adheres to or mixes with the contact charging member, the chargeability is lowered.

  In the case of a charging method in which the discharge charging mechanism is dominant, the charging property of the member to be charged suddenly occurs when the toner layer attached to the surface of the contact charging member becomes a resistance that inhibits the discharge voltage. On the other hand, in the case of a charging method in which the direct injection charging mechanism is dominant, the transfer residual toner adhered or mixed reduces the contact probability between the surface of the contact charging member and the object to be charged, thereby charging the object to be charged. Sexuality decreases.

This reduction in the uniform chargeability of the object to be charged reduces the contrast and uniformity of the electrostatic latent image after image exposure, thereby reducing the image density or increasing the fog. In the simultaneous development cleaning method and the cleanerless image forming method, the charge polarity and charge amount of the transfer residual toner on the photoconductor are controlled, and the toner on the photoconductor is stably recovered in the development process, and the recovered toner is developed. The point is not to deteriorate the characteristics, and the charging polarity and the charge amount of the transfer residual toner are controlled by the charging member. This will be specifically described using a general laser printer as an example. In the case of reversal development using a charging member to which a negative polarity voltage is applied, a negatively chargeable photoreceptor and a negatively charged toner, the image visualized by the positive polarity transfer member is transferred to a recording medium in the transfer process. However, depending on the relationship between the type of recording medium (difference in thickness, resistance, dielectric constant, etc.) and the image area, the charging polarity of the residual toner varies from positive to negative. Further, fog toner having a reverse polarity generated due to non-uniformity of the toner charge amount is developed in the non-image portion. However, due to the negative polarity charging member when charging the negatively chargeable photoconductor, even if the toner remaining on the transfer along with the surface of the photoconductor is shifted to the positive polarity in the transfer process, it is originally a fog toner of reverse polarity. Even in this case, it is possible to make the charging polarity uniform to the negative side. Therefore, when reversal development is used as the developing method, the toner in the bright portion where the toner is to be developed is left with a negatively charged transfer residual toner, and the toner is developed in the dark portion where the toner is not to be developed. Due to the electric field, the toner is attracted toward the toner carrying member, and the toner is collected without remaining on the photosensitive member having the dark portion potential. That is, by controlling the charging polarity of the toner on the photosensitive member simultaneously with the charging of the photosensitive member by the charging member, the simultaneous development cleaning and the cleanerless image forming method are established.

  However, if the transfer residual toner adheres to or mixes with the contact charging member more than the toner charging polarity control capability of the contact charging member, the toner charging polarity cannot be made uniform, and the toner is collected by the developing member. It becomes difficult. Even when the toner is collected on the toner carrier, if the collected toner is not uniformly charged, the chargeability of the toner on the toner carrier is adversely affected and the development characteristics are deteriorated. Furthermore, when a toner with poor material dispersibility is used, poor toner accumulates in the developing unit with long-term use, leading to a significant deterioration in image characteristics.

  That is, in the simultaneous development cleaning and the cleanerless image forming method, the uniform dispersion of the magnetic substance and the release agent in the toner particles, the toner performance such as the developability and transferability, and the charging of the transfer residual toner. Charging control characteristics when passing through the member and adhesion / mixing characteristics to the charging member are closely linked to image characteristics and durability characteristics.

  Japanese Patent Publication No. 7-99442 also discloses a configuration in which powder is applied to a contact surface of a contact charging member with a surface to be charged in order to prevent charging unevenness and perform stable uniform charging. However, the contact charging member (charging roller) is driven and rotated (without speed difference driving) by the member to be charged (photosensitive member), and generation of ozone products is remarkably reduced as compared with a corona charger such as Scorotron. However, the charging principle is mainly based on the discharge charging mechanism as in the case of the roller charging described above. In particular, in order to obtain more stable charging uniformity, a voltage obtained by superimposing an AC voltage on a DC voltage is applied, and therefore, more ozone products are generated due to discharge. Therefore, when the apparatus is used for a long time, adverse effects such as image flow due to ozone products tend to appear. Furthermore, when applied to a cleanerless image forming apparatus, it becomes difficult for the applied powder to uniformly adhere to the charging member due to the mixing of the transfer residual toner, and the effect of uniform charging is diminished.

  Japanese Patent Laid-Open No. 5-150539 discloses that in an image forming method using contact charging, toner particles and silica fine particles that could not be blade-cleaned after repeated image formation for a long time adhere to and accumulate on the surface of the charging means. In order to prevent charging from being inhibited, it is disclosed that the toner contains at least visible particles and conductive fine particles having an average particle size smaller than the visible particles. However, the contact charging or proximity charging used here is based on the discharge charging mechanism, and has the above-described problems due to the discharge charging, not the direct injection charging mechanism. Further, when applied to a cleaner-less image forming apparatus, compared to the case where the cleaning mechanism is provided, a large amount of conductive fine particles and transfer residual toner have an influence on the charging property due to passing through the charging process. No consideration is given to the recoverability of the conductive fine particles and the transfer residual toner in the development process, and the influence of the collected conductive fine particles and the collected toner on the development characteristics of the toner. Further, when the direct injection charging mechanism is applied to the contact charging, a necessary amount of conductive fine particles is not supplied to the contact charging member, and charging failure occurs due to the influence of the transfer residual toner.

  Also, with proximity charging, it is difficult to uniformly charge the photoconductor with a large amount of conductive fine particles and transfer residual toner, and the effect of leveling the pattern of residual transfer toner cannot be obtained. A pattern ghost for shading is generated. Further, when the power supply is interrupted or a paper jam occurs during image formation, the contamination inside the apparatus with toner becomes significant.

Japanese Patent Laid-Open No. 11-15206 discloses that the simultaneous development cleaning image forming method improves the simultaneous development cleaning performance by improving the charge control characteristics when the transfer residual toner passes through the charging member. An image forming method using a toner having toner particles containing carbon black and a specific azo-based iron compound and an inorganic fine powder has been proposed. Further, in the simultaneous development cleaning image forming method, it has also been proposed to improve the simultaneous development cleaning performance by reducing the amount of residual transfer toner with a toner having excellent transfer efficiency that defines the shape factor of the toner. However, the contact charging used here is also due to the discharge charging mechanism, and not the direct injection charging mechanism, but has the above-mentioned problems due to discharge charging. Furthermore, even though these proposals have the effect of suppressing the chargeability deterioration due to the transfer residual toner of the contact charging member, the effect of positively increasing the chargeability cannot be expected.

  Further, among commercially available electrophotographic printers, a roller member that contacts the photoreceptor between the transfer process and the charging process, and a simultaneous development image forming apparatus that assists or controls the transfer residual toner recoverability in development. There is also. Such an image forming apparatus exhibits good simultaneous development cleaning ability and can greatly reduce the amount of waste toner, but the cost is increased and the advantage of simultaneous development cleaning is impaired in terms of miniaturization.

  On the other hand, in Japanese Patent Application Laid-Open No. 10-307456, simultaneous development cleaning using a direct injection charging mechanism for toner containing toner particles and electrically conductive charge accelerating particles having a particle size of ½ or less of the toner particle size is disclosed. An image forming apparatus applied to an image forming method is disclosed. According to this proposal, it is possible to obtain a developing simultaneous cleaning image forming apparatus that can greatly reduce the amount of waste toner without generating a discharge product, and is advantageous for downsizing at low cost. Alternatively, a good image that does not cause diffusion can be obtained.

  In Japanese Patent Laid-Open No. 10-307421, a toner containing conductive particles having a particle size of 1/50 to 1/2 of the toner particle size is applied to a simultaneous development image forming method using a direct injection charging mechanism. An image forming apparatus in which conductive particles have a transfer promoting effect is disclosed.

  Furthermore, in Japanese Patent Application Laid-Open No. 10-307455, the particle size of the conductive fine powder is set to 10 nm in order to make the particle size of the conductive fine powder smaller than the size of one pixel of the constituent pixels and to obtain better charging uniformity. It is described that it is set to ˜50 μm.

  In Japanese Patent Application Laid-Open No. 10-307457, in order to make it difficult to visually recognize the influence of a poorly charged portion on an image in consideration of human visual characteristics, the conductive particles are about 5 μm or less, preferably 20 nm to 5 μm. It is described that.

  Further, according to Japanese Patent Laid-Open No. 10-307458, the particle size of the conductive fine powder is set to be equal to or smaller than the toner particle size, so that the development of the toner is inhibited during development, or the development bias is passed through the conductive fine powder. By preventing leakage and eliminating image defects, and by setting the particle size of the conductive fine powder to be larger than 0.1 μm, the conductive fine powder is embedded in the image carrier to block exposure light. A developing simultaneous cleaning image forming method using a direct injection charging mechanism that solves the adverse effects and realizes excellent image recording is described.

  According to Japanese Patent Laid-Open No. 10-307456, a conductive fine powder is externally added to the toner, and the conductive fine powder contained in the toner is at least at the contact portion between the flexible contact charging member and the image carrier. However, it adheres to the image carrier in the development step and remains on the image carrier after the transfer step and is carried and intervened, so that a good image that does not cause poor charging and light shielding of image exposure can be obtained. A development simultaneous cleaning image forming apparatus is disclosed.

However, these proposals also have room for further improvement in the performance when using toner particles having a smaller particle diameter in order to improve stable performance and resolution in long-term repeated use. Moreover, these effects are limited without the performance of the toner particles themselves.

  An object of the present invention is to provide a toner and an image forming method that solve the above-mentioned problems of the prior art. That is, an object of the present invention is to provide a toner having stable charging performance and image characteristics regardless of the environment.

  Another object of the present invention is to provide a toner and an image forming method having stable image characteristics even when used for a long time in a high temperature environment.

  Furthermore, an object of the present invention is to provide a toner and an image forming method that enable good simultaneous development and cleaning image formation.

  An object of the present invention is to enable simultaneous development cleaning image formation that is advantageous for downsizing at low cost, which can significantly reduce the amount of waste toner without generating discharge products, and can be used repeatedly over a long period of time. Another object of the present invention is to provide a developing simultaneous cleaning image forming method capable of stably obtaining a good image without causing a charging failure and a toner used therefor.

  Another object of the present invention is to provide a toner and an image forming method that enable cleaner-less image formation in which good chargeability can be stably obtained.

  Another object of the present invention is to provide a toner and an image forming method capable of forming an image at the same time as a development simultaneous cleaning with excellent transferability and excellent recovery of transfer residual toner.

  An object of the present invention is to provide a developing simultaneous cleaning image forming method capable of stably obtaining a good image even when toner particles having a smaller particle diameter are used in order to improve resolution, and a toner used therefor. is there.

  As described above, the dispersion state of the magnetic substance and the release agent inside the toner particles greatly affects the toner performance, and can be said to be an important technique that affects the performance particularly in the case of a small particle size toner. Furthermore, if the toner transferability and fogging characteristics can be further improved, long-term maintenance of high image quality can be easily achieved in a contact charging method with less environmentally preferred ozone generation, and even in a cleanerless image forming method.

  Therefore, as a result of various studies on the physical properties and materials of the magnetic toner by the present inventors, the magnetic substance containing a good dispersion state in a hexane solution is contained, and the magnetic substance is not substantially exposed on the surface. The magnetic toner having an average circularity of 0.970 or more has a very uniform dispersion state of the magnetic substance and the release agent inside the toner, and as a result, has excellent blocking resistance, high transferability, and good quality. It has been found that it has fog characteristics and excellent developability. Furthermore, developability is good and high image density is high even at high temperatures where the developability deteriorates, transfer residual toner increases, or durability tends to decrease due to the influence of the release agent exposed on the toner surface. It was possible to obtain image quality images over the long term. Furthermore, it has been found that by using this type of magnetic toner, long-term maintenance of a high-quality image can be achieved even in an environmentally favorable contact charging method, and further in a cleanerless image forming method. It came to be completed.

  That is, the present invention is as follows.

  The present invention is a method for producing a magnetic toner having an inorganic fine powder on the surface of a magnetic toner particle containing at least a binder resin, a release agent and a magnetic substance, wherein the magnetic toner particle is produced in an aqueous medium, The magnetic body is made of magnetic iron oxide, and the magnetic iron oxide is produced by oxidizing ferrous hydroxide in water, and after the oxidation reaction, without undergoing a drying step, a silane coupling agent Alternatively, the present invention is a method for producing a magnetic toner, wherein the surface is treated with a titanium coupling agent.

  The present invention is also a method for producing a magnetic toner, wherein the toner particles are produced by a suspension polymerization method.

  The present invention is also the method for producing a magnetic toner, wherein the magnetic material has a volume average particle diameter of 0.05 to 0.3 μm.

  According to the present invention, it contains a minute magnetic material and a release material having special physical properties and improved dispersibility, and the magnetic material is not substantially exposed on the surface, and has a special surface shape and particle size. With the magnetic toner having the above, good toner performance is maintained even if it is left in a harsh environment, and a high-definition image can be stably provided for a long time even if it is used as it is in a harsh environment.

  Further, in the image forming method comprising the contact charging method and the magnetic one-component developing method using the magnetic toner of the present invention, and the image forming apparatus of the contact charging method, the contact transfer method, and the toner recycling process, the toner performance is deteriorated. Therefore, a good image can be stably obtained for a long time in repeated use over a long period of time after being left in a harsh environment.

  In addition, it is possible to use a simple member as the contact charging member, which can provide uniform chargeability, and has a simple structure and low-cost image formation free from obstructions caused by ozone products, obstructions due to poor charging, etc. Devices and process cartridges can be obtained.

1 is a schematic configuration diagram of an image forming apparatus for carrying out the method of the present invention. The charging characteristic graph of a contact charging member is shown. FIG. 2 is a schematic configuration diagram of an image carrier for carrying out the method of the present invention. The schematic block diagram of the contact transfer member for enforcing the method of this invention is shown. The schematic block diagram of the image forming apparatus in Examples 22-26 is shown. FIG. 2 shows a schematic diagram of a layer structure of an image carrier for carrying out the method of the present invention.

<1> Magnetic toner of the present invention The magnetic toner of the present invention is a toner having inorganic fine powder on the surface of magnetic toner particles having at least a binder resin, a release agent and a magnetic material.

  Examples of the binder resin used in the magnetic toner of the present invention include the following when the magnetic toner is produced by a pulverization method.

As the binder resin when the toner of the present invention is produced by a pulverization method, styrene such as polystyrene and polyvinyltoluene, and a homopolymer of a substituted product thereof; styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene -Vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate Copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-dimethylaminoethyl methacrylate copolymer, styrene-vinyl methyl ether Copolymer, styrene-vinyl ethyl acetate Styrene copolymers such as styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer Combined; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin, polyacrylic acid resin, rosin, modified rosin, temper resin, phenol resin, fat Aromatic or alicyclic hydrocarbon resins, aromatic petroleum resins, paraffin wax, carnauba wax and the like can be used alone or in combination. In particular, a styrene copolymer and a polyester resin are preferable in terms of development characteristics, fixing properties, and the like.

  When the toner of the present invention is produced by the suspension polymerization method, examples of the polymerizable monomer constituting the polymerizable monomer system to be used include the following.

  Examples of the polymerizable monomer include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-ethylstyrene, methyl acrylate, ethyl acrylate, Acrylic esters such as n-butyl acrylate, isobutyl acrylate, n-propyl acrylate, n-octyl acrylate, dodecyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, etc. , Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, Methacrylic acid dimethyl aminoethyl methacrylate esters such as diethylaminoethyl methacrylate and other acrylonitrile-methacrylonitrile-monomer acrylamide. These monomers can be used alone or in combination. Among the above monomers, styrene or a styrene derivative is preferably used alone or mixed with other monomers from the viewpoint of the developing characteristics and durability of the toner.

  The magnetic toner particles of the present invention have a release agent. Wax is used as a release agent. Examples of waxes that can be used in the magnetic toner of the present invention include petroleum waxes such as paraffin wax, microcrystalline wax, and petrolactam and derivatives thereof, montan wax and derivatives thereof, and Fischer-Tropsch method. Hydrocarbon waxes and derivatives thereof, polyolefin waxes and their derivatives typified by polyethylene, natural waxes and derivatives such as carnauba wax, candelilla wax, etc., which are oxides or block copolymers with vinyl monomers And graft modified products. Furthermore, fatty acids such as higher aliphatic alcohols, stearic acid and palmitic acid, or compounds thereof, acid amide waxes, ester waxes, ketones, hydrogenated castor oil and derivatives thereof, plant waxes, animal waxes and the like can also be used.

  The magnetic toner of the present invention contains a release agent, and the amount used is preferably 0.5 to 50 parts by mass with respect to 100 parts by mass of the binder resin. If the content is less than 0.5 parts by mass, the effect of suppressing offset is poor, and if it exceeds 50 parts by mass, the long-term storage stability is inevitably deteriorated and the dispersed state inside the toner becomes non-uniform, and the toner surface is not uniformly dispersed. Since it is difficult to suppress exposure, it is not preferable because it leads to deterioration of toner fluidity and image characteristics and durability.

Among the wax components, in the DSC curve measured with a differential differential calorimeter, those having a maximum endothermic peak in the region of 40 to 110 ° C. at the time of temperature rise are preferred, and those having in the region of 45 to 90 ° C. are more preferable. preferable. By having the maximum endothermic peak in the above temperature range, the mold releasability is effectively expressed while greatly contributing to low-temperature fixing. When the maximum endothermic peak is less than 40 ° C., the self-cohesive force of the wax component becomes weak, and as a result, the high temperature offset resistance tends to deteriorate. On the other hand, if the maximum endothermic peak exceeds 110 ° C., the fixing temperature becomes high and low temperature offset is likely to occur, which is not preferable. Furthermore, when granulation / polymerization is carried out in an aqueous medium and a toner is obtained directly by the polymerization method, if the maximum endothermic peak temperature is high, problems such as precipitation of a wax component mainly during granulation are undesirable. .

  The maximum endothermic peak temperature of the wax component is measured according to “ASTM D 3418-8”. For the measurement, for example, DSC-7 manufactured by PerkinElmer is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of heat uses the heat of fusion of indium. An aluminum pan is used as a measurement sample, an empty pan is set as a control, and measurement is performed at a heating rate of 10 ° C./min.

  Also, using the toner as a measurement sample, the endothermic peak area attributed to the wax, that is, the endothermic amount of the wax in the toner is obtained, and the wax content in the sample toner is compared with a sample in which the wax content is known. Can be requested.

  The magnetic material used in the magnetic toner of the present invention is mainly composed of magnetic iron oxide. More specifically, in a dispersion state in a hexane solution, when the absorbance at 500 nm after 5 minutes after dispersion is a-5 and the absorbance at 500 nm after 30 minutes after dispersion is a-30, a- 5, Use a magnetic material in which a-30 satisfies the following formula (1).

さらには、ヘキサン溶液中に分散後６０分経過した後の５００ｎｍにおける吸光度をａ−６０とした時、ａ−５、ａ−６０が下記式（２）を満たす磁性体であることが一層好ましい。

Further, it is more preferable that a-5 and a-60 are magnetic materials satisfying the following formula (2) when the absorbance at 500 nm after 60 minutes has passed after dispersion in the hexane solution is defined as a-60.

（ａ−３０）／（ａ−５）≦０．８である磁性体の場合、即ちヘキサン溶液中に分散させた際に沈降速度の速い磁性体の場合、トナー粒子内部での均一分散が難しく、離型剤の分散状態にも偏りを生じさせることがある。

In the case of a magnetic material satisfying (a-30) / (a-5) ≦ 0.8, that is, in the case of a magnetic material having a fast sedimentation speed when dispersed in a hexane solution, it is difficult to uniformly disperse inside the toner particles. In some cases, the dispersion state of the release agent may be biased.

As a magnetic material satisfying the above formula (1), magnetic iron oxides such as triiron tetroxide and γ-iron oxide, which may contain elements such as cobalt, nickel, copper, magnesium, manganese and aluminum, are the main components. The toner is obtained by subjecting the toner to a uniform surface treatment, and the toner is used alone or in combination of two or more thereof.

  As a more preferable physical property of the magnetic material, the absorption constant at 500 nm after 30 minutes after dispersion in the hexane solution is preferably 1000 or more, and the absorption constant at 500 nm after 60 minutes after dispersion is 1000 or more. More preferably it is. If the absorption constant at 500 nm after 30 minutes after dispersion in the hexane solution is less than 1000, it means that the dispersibility in organic matter is not so good, and it is difficult to obtain a toner with higher coloring power. It is not preferable.

  In the present invention, the absorbance and extinction constant in a dispersed state of a magnetic substance in a hexane solution can be measured as follows.

  In the present invention, measurement is performed using a Shimadzu spectrophotometer, UV-2200 (manufactured by Shimadzu Corporation) (the same applies to the examples described later).

  A magnetic material as a measurement sample is weighed. The mass at this time is A1 kg. Place the weighed sample in a sealable container. A hexane solution weighed in volume is added thereto and sealed. Let the volume of the hexane solution at this time be B1. The sample concentration at this time is preferably about 0.0002 kg of magnetic material per liter of hexane solution. The container is shaken lightly by hand and then subjected to a dispersion treatment with ultrasonic waves for 10 seconds.

  The obtained sample dispersion solution is placed in a quartz cell having a light transmission distance of 1 cm and quickly set in an apparatus, and the absorbance at a wavelength of 500 nm is measured 5 minutes after setting the cell. The absorbance at this time is defined as a-5 of the magnetic material.

  The cell is left in the apparatus as it is, and the absorbance at a wavelength of 500 nm is measured 30 minutes after setting the cell. The absorbance at this time is defined as a-30 of the magnetic material. Similarly, the absorbance at a wavelength of 500 nm is measured 60 minutes after setting the cell, and the absorbance at this time is defined as a-60 of the magnetic substance.

  Next, the sample concentration A1 / B1 (kg / L) was calculated, and (a-30) / (A1 / B1) was defined as the absorption constant at 500 nm after 30 minutes had passed after dispersion, and (a-60) / ( A1 / B1) is defined as an absorption constant at 500 nm after 60 minutes have passed since dispersion.

  In addition, as a volume average particle diameter of a magnetic body, 0.05-0.3 micrometer is preferable and 0.06-0.25 micrometer is still more preferable. When the volume average particle size is less than 0.05 μm, the blackness is remarkably lowered, the coloring power is insufficient as a colorant for black and white toner, and the cohesion between magnetic particles becomes strong. The tendency to worsen may be unavoidable. On the other hand, if the average particle diameter exceeds 0.3 μm, the mass per magnetic substance particle becomes heavy, and it tends to settle in the hexane solution, so that the dispersion state inside the toner particles becomes uneven. In addition, it is stochastically difficult to disperse the same number of magnetic materials in individual toner particles, and the dispersibility tends to deteriorate.

  In addition, the volume average particle diameter (Dm) of a magnetic body can be measured using a transmission electron microscope. Specifically, a powder sample of the toner to be measured is observed with a transmission electron microscope at a magnification of 40,000 times, and the particle diameter of 100 magnetic particles of 0.01 μm or more is measured in the field of view to determine the average particle diameter. Ask. The presence of magnetic particles of less than 0.01 μm hardly affects the dispersion state of the release agent, and even if it is slightly exposed on the toner surface, it does not adversely affect the triboelectric charge. In, you can basically ignore the effect.

  The particle shape of the magnetic material is preferably a hexahedron, octahedron, or tetrahedron polyhedron. Compared to the spherical case, the bulk of the magnetic material is increased and the cohesiveness is lowered, so that the dispersibility during toner production is further improved. The shape of such a magnetic material can be confirmed by SEM (scanning electron microscope) or the like. That is, the shape of the magnetic particles is observed by SEM, and the shape having the largest number ratio of particles is used as the powder shape of the sample.

In addition, the magnetic material used in the magnetic toner of the present invention is also preferably subjected to a surface treatment with a coupling agent in an aqueous medium. When hydrophobizing the surface, it is very preferable to use a method in which the surface treatment is performed while hydrolyzing the coupling agent while dispersing the magnetic particles so as to have a primary particle size in an aqueous medium. This hydrophobic treatment method is less likely to cause coalescence between the magnetic particles than the treatment in the gas phase, and the repulsive action between the magnetic particles due to the hydrophobic treatment works, so that the magnetic material is almost in the state of primary particles. Surface treated.

  The method of treating the surface of the magnetic material while hydrolyzing the coupling agent in an aqueous medium does not require the use of a coupling agent that generates a gas, such as chlorosilanes and silazanes, and further, In the phase, magnetic particles can be easily combined with each other, and a highly viscous coupling agent that has been difficult to be processed can be used, so that the hydrophobizing effect is great.

  Examples of the coupling agent that can be used in the surface treatment of the magnetic material according to the present invention include a silane coupling agent and a titanium coupling agent. More preferably used is a silane coupling agent, which is represented by the general formula (I).

［式中、Ｒはアルコオキシ基を示し、ｍは１〜３の整数を示し、Ｙはアルキル基、ビニル基、グリシドキシ基、メタクリル基の如き炭化水素基を示し、ｎは１〜３の整数を示す。ただし、ｍ＋ｎ＝４である。］
一般式（Ｉ）で示されるシランカップリング剤としては、例えばビニルトリメトキシシラン、ビニルトリエトキシシラン、γ−メタクリルオキシプロピルトリメトキシシラン、ビニルトリアセトキシシラン、メチルトリメトキシシラン、メチルトリエトキシシラン、イソブチルトリメトキシシラン、ジメチルジメトキシシラン、ジメチルジエトキシシラン、トリメチルメトキシシラン、ヒドロキシプロピリトリメトキシシラン、フェニルトリメトキシシラン、ｎ−ヘキサデシルトリメトキシシラン、ｎ−オクタデシルトリメトキシシラン等を挙げることができる。

[Wherein, R represents an alkoxy group, m represents an integer of 1 to 3, Y represents a hydrocarbon group such as an alkyl group, a vinyl group, a glycidoxy group, or a methacryl group, and n represents an integer of 1 to 3. Show. However, m + n = 4. ]
Examples of the silane coupling agent represented by the general formula (I) include vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, methyltriethoxysilane, Examples include isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-hexadecyltrimethoxysilane, and n-octadecyltrimethoxysilane.

  In particular, the magnetic substance is preferably hydrophobized in an aqueous medium using an alkyltrialkoxysilane coupling agent represented by the general formula (II).

［式中、ｐは２〜２０の整数を示し、ｑは１〜３の整数を示す。］
上記式におけるｐが２より小さいと疎水化処理は容易となるが、疎水性を十分に付与することが困難であり、トナー粒子からの磁性体の露出を抑制するのが難しくなる。またｐが２０より大きいと疎水性は十分になるが、磁性体粒子同士の合一が多くなり、トナー中へ磁性体粒子を均一に分散性させることが困難になり、カブリや転写性さらには選択現像性が悪化傾向となる。

[In formula, p shows the integer of 2-20, q shows the integer of 1-3. ]
When p in the above formula is smaller than 2, the hydrophobization treatment is easy, but it is difficult to sufficiently impart hydrophobicity, and it becomes difficult to suppress the exposure of the magnetic material from the toner particles. If p is larger than 20, the hydrophobicity is sufficient, but the coalescence between the magnetic particles increases, making it difficult to uniformly disperse the magnetic particles in the toner, fogging, transferability, and the like. Selective developability tends to deteriorate.

  On the other hand, when q is larger than 3, the reactivity of the silane coupling agent is lowered and the hydrophobicity is not sufficiently performed. In particular, p in the formula represents an integer of 2 to 20 (more preferably an integer of 3 to 15), and q represents an integer of 1 to 3 (more preferably an integer of 1 or 2). A coupling agent should be used.

  The treatment amount is 0.05 to 20 parts by mass, preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the magnetic material.

Here, the aqueous medium is a medium containing water as a main component. Specifically, water itself, water added with a small amount of a surfactant, water added with a pH adjusting agent, water added with an organic solvent can be raised as an aqueous medium. As the surfactant, a nonionic surfactant such as polyvinyl alcohol is preferable. The surfactant is preferably added in an amount of 0.1 to 5% by mass with respect to water. Examples of the pH adjuster include inorganic acids such as hydrochloric acid. Examples of the organic solvent include methanol. The organic solvent is preferably added in an amount of 0 to 500 mass% with respect to water.

  In order to treat the surface of the magnetic material with a coupling agent in an aqueous medium, a method of stirring an appropriate amount of the magnetic substance and the coupling agent in the aqueous medium can be mentioned. Stirring is sufficiently performed, for example, with a mixer having a stirring blade (specifically, a high shear force mixing device such as an attritor or a TK homomixer) so that the magnetic particles become primary particles in the aqueous medium. Is good.

  The surface-treated magnetic material thus obtained has no aggregation of particles and the surface of each particle is uniformly hydrophobized. Therefore, when used as a material for polymerized toner, the dispersibility in the toner particles is extremely high. At the same time, the dispersibility of the release agent is dramatically improved. In addition, there is no exposure of the magnetic substance and the release agent from the surface of the toner particles, and a substantially spherical polymerized toner is obtained.

As magnetic properties of the magnetic material, those having a magnetic field of 79.6 kA / m, a saturation magnetization of 10 to 200 Am ² / kg, a residual magnetization of 1 to 100 Am ² / kg, and a coercive force of 1 to 30 kA / m are preferably used. It is done. The magnetic properties of the magnetic material can be measured using a vibration type magnetometer (VSM-3S-15 manufactured by Toei Industry Co., Ltd.).

  By using such a magnetic material, it is possible to obtain the magnetic toner of the present invention having an average circularity of 0.970 or more and having substantially no magnetic material or release agent exposed on the surface. A toner having a sharp particle size distribution such that D4 / D1 is less than 1.4 can be easily obtained. Furthermore, when this toner is used in the image forming method of the present invention, high image quality stabilization can be achieved even under high temperature or high humidity environment.

  The magnetic material used in the toner of the present invention preferably uses 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin. More preferably, 20 to 180 parts by mass are used. If it is less than 10 parts by mass, the coloring power of the toner is poor, and it is difficult to suppress fogging. On the other hand, if the amount exceeds 200 parts by mass, the holding force due to the magnetic force on the toner carrier is increased and the developability is lowered, and it is difficult not only to uniformly disperse the magnetic material to individual toner particles, but also the fixability is lowered. There is a tendency to end up.

  For example, in the case of magnetite, the magnetic material used in the magnetic toner of the present invention is produced by the following method.

  A water-soluble phosphorus compound is added to an aqueous ferrous salt solution by adding an alkali such as sodium hydroxide in an amount equivalent to or greater than the iron component to a concentration of 0.05 to 5.0% by mass of the phosphorus element with respect to the iron element. (For example, phosphates such as sodium hexametaphosphate and primary ammonium phosphate, phosphates such as normal phosphate and phosphite) Aqueous solution, optionally 0 to 5.0 mass% silicon with respect to iron element An aqueous solution containing ferrous hydroxide is prepared by adding an aqueous solution of a water-soluble silicon compound (for example, water glass, sodium silicate, potassium silicate) so as to be an element. Air is blown in while maintaining the pH of the prepared aqueous solution at pH 7 or higher (preferably pH 7 to 10), and ferrous hydroxide is oxidized while heating the aqueous solution to 70 ° C. or higher to generate magnetic particles. .

Adjust the pH of the liquid at the end of the oxidation reaction, stir well so that the magnetic iron oxide becomes primary particles, add the coupling agent, stir well, stir, filter, dry, and lightly crush after stirring By doing so, a surface-treated magnetic material can be obtained. Alternatively, after the oxidation reaction is completed, the iron oxide particles obtained by washing and filtering are redispersed in another aqueous medium without drying, and then the pH of the redispersion is adjusted and the silane is stirred well. A coupling agent may be added to perform the coupling treatment. In any case, it is important to perform the surface treatment after the oxidation reaction without passing through the drying step, which is an important point for obtaining the magnetic toner of the present invention.

  As the ferrous salt, iron sulfate generally produced as a by-product in the production of sulfuric acid titanium, iron sulfate produced as a by-product with the surface cleaning of the steel sheet can be used, and iron chloride or the like can be used.

  In the method for producing magnetic iron oxide by the aqueous solution method, an iron concentration of 0.5 to 2 mol / l is generally used from the viewpoint of preventing the viscosity from increasing during the reaction and the solubility of iron sulfate. Generally, the lower the iron sulfate concentration, the finer the particle size of the product. Further, in the reaction, the larger the amount of air and the lower the reaction temperature, the easier the atomization. By using the surface-treated magnetic powder thus produced, the excellent magnetic toner of the present invention can be obtained, and by using such a magnetic toner for the image forming method of the present invention, it can be left in a harsh environment. It is possible to achieve high image quality under toner deterioration and high humidity.

  The magnetic toner of the present invention has an inorganic fine powder on the surface of the magnetic toner particles having the binder resin, the release agent, and the magnetic material.

  In the toner of the present invention, it is also a very preferable usage form that an inorganic fine powder having a number average primary particle size of 4 to 80 nm is added as a fluidizing agent in an amount of 0.1 to 4% by mass with respect to the whole toner. Inorganic fine powder is added to improve the fluidity of the toner and to make the toner base particles evenly charged. However, the inorganic chargeable powder is treated to make it hydrophobic and adjust the toner charge amount and improve the environmental stability. It is also preferable to provide such functions.

  When the number average primary particle size of the inorganic fine powder is larger than 80 nm, good toner fluidity cannot be obtained, and charging to the toner particles is likely to be non-uniform, and in addition to the deterioration of developability, There is a tendency that problems such as an increase in fog, a decrease in image density, and toner scattering cannot be avoided. When the average primary particle size of the inorganic fine powder is smaller than 4 nm, the cohesiveness between the inorganic fine powders becomes stronger, and the aggregate is not a primary particle but has a strong cohesiveness that is difficult to break even by crushing treatment and has a wide particle size distribution. And image defects caused by damaging the image carrier or toner carrier due to the aggregates. In order to make the charge distribution of the toner particles more uniform, the number average primary particle size of the inorganic fine powder is more preferably 6 to 35 nm.

  Further, when the amount of the inorganic fine powder added is less than 0.1% by mass with respect to the whole toner, the effect of improving the fluidity of the toner becomes small, and when it exceeds 4% by mass, the fixability of the toner tends to deteriorate. is there.

  The number average primary particle size of the inorganic fine powder is a photograph of the toner magnified by a scanning electron microscope, and is further mapped by the element contained in the inorganic fine powder by an elemental analysis means such as XMA attached to the scanning electron microscope. It can be measured by measuring 100 or more primary particles of inorganic fine powder adhering to or releasing from the toner surface and obtaining the number average primary particle size while contrasting the photograph of the toner.

  The content of the inorganic fine powder can be quantified using a calibration curve prepared from a standard sample using fluorescent X-ray analysis.

As the inorganic fine powder added to the toner of the present invention, silica, alumina, titania and the like can be used. For example, as silica, both a so-called dry method produced by vapor phase oxidation of silicon halide or a dry silica called fumed silica, and a so-called wet silica produced from water glass or the like can be used. Dry silica is preferred because there are few silanol groups on the surface and inside the silica fine powder, and there are few production residues such as Na ₂ O, SO ₃ ²⁻ . In dry silica, it is also possible to obtain composite fine powders of silica and other metal oxides by using other metal halogen compounds such as aluminum chloride and titanium chloride together with silicon halogen compounds in the production process. Is also included.

  The inorganic fine powder is preferably a hydrophobized product from the viewpoint of improving characteristics particularly in a high humidity environment. When the inorganic fine powder added to the toner absorbs moisture, the charge amount as the toner is remarkably lowered, and the developability and transferability are liable to deteriorate.

  Hydrophobing treatment agents for hydrophobizing inorganic fine powder include silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, silane coupling agents, other organic silicon compounds, and organic titanium compounds. And may be processed alone or in combination.

  Among these, it is preferable to treat with silicone oil, and more preferably, the inorganic fine powder is treated with silicone oil at the same time or after the hydrophobic treatment. The use of the inorganic fine powder hydrophobized in such a manner is sufficient to maintain a high charge amount of toner particles even in a high humidity environment and to reduce selective developability.

  The treatment conditions for such inorganic fine powder include, for example, a silylation reaction with a silane compound or the like as a first stage reaction to eliminate active hydrogen groups on the surface by chemical bonding, and then a surface with silicone oil as a second stage reaction. A hydrophobic thin film can be formed. As a usage-amount of a silylating agent, 5-50 mass% is preferable with respect to inorganic fine powder. If it is less than 5% by mass, it is not sufficient to eliminate the active hydrogen groups on the surface of the inorganic fine powder, and if it exceeds 50% by mass, the siloxane compound produced by the reaction between the excess silylating agents serves as a paste to serve as an inorganic fine powder. Aggregation of powders occurs and image defects are likely to occur.

The silicone oil preferably has a viscosity at 25 ° C. of 10 to 200,000 mm ² / s, more preferably 3,000 to 80,000 mm ² / s. If it is less than 10 mm ² / s, the inorganic fine powder is not stable, and the image quality tends to deteriorate due to heat and mechanical stress. If it exceeds 200,000 mm ² / s, uniform processing tends to be difficult.

  As a method for treating silicone oil, for example, inorganic fine powder silylated with a silane compound and silicone oil may be directly mixed using a mixer such as a Henschel mixer, or silicone oil may be mixed with inorganic fine powder. A spraying method may be used. Alternatively, after dissolving or dispersing silicone oil in an appropriate solvent, inorganic fine powder may be added and mixed to remove the solvent. A method using a sprayer is more preferable in that the formation of aggregates of inorganic fine powder is relatively small.

  The treatment amount of silicone oil is 1 to 23 parts by mass, preferably 5 to 20 parts by mass with respect to 100 parts by mass of the inorganic fine powder. If the amount of the silicone oil is too small, good hydrophobicity cannot be obtained, and if it is too large, the inorganic fine powder tends to aggregate.

  In addition to the above inorganic fine powder, the magnetic toner of the present invention can be used by adding a conductive fine powder having a volume average particle size smaller than the volume average particle size of the toner. And it is preferable from showing durability.

The reason for the addition effect is considered to be derived from the function of sharpening the triboelectric charge amount distribution of the toner. Since the toner of the present invention has substantially no magnetic substance exposed on the surface, it cannot be said that the charge transfer is fast. Therefore, some toner particles have a low charge amount, and it cannot be denied that the toner particles are slightly disadvantageous from the viewpoint of transferability and fogging developability. When conductive fine powder is added to a toner having such a configuration, it is considered that a uniform charge-enhancement reaction of entropy such as charge transfer from a toner having a high charge amount to a toner having a low charge amount is likely to occur.

The content of the conductive fine powder with respect to the entire toner is preferably 0.2 to 10% by mass. If the content of the conductive fine powder with respect to the whole toner is less than 0.2% by mass, the charge rate homogenization reaction rate under low humidity may not be sufficient. On the other hand, if it exceeds 10% by mass, it becomes difficult to maintain a sufficient charge amount under high humidity, and fog and transferability tend to be lowered, and durability tends to be deteriorated. 0.5-5 mass% is preferable, and the preferable resistance of the conductive fine powder is 1 × 10 ⁹ Ω · cm or less. When the resistance of the conductive fine powder is larger than 1 × 10 ⁹ Ω · cm, the homogenization reaction rate tends to be insufficient. Furthermore, if it is 1 × 10 ⁶ Ω · cm or less, the distribution of the charge amount is sharpened even under low humidity.

  The volume average particle diameter of the conductive fine powder is preferably 0.1 to 5 μm. When the volume average particle diameter is less than 0.1 μm, the effect of promoting the homogenization reaction rate is low. It is presumed that this is because charge transfer from a toner with a high charge amount to a toner with a low charge amount is not promoted so much because the probability that the conductive fine powder exists in the contact portion between the toner particles is reduced.

  Further, if the volume average particle size of the conductive fine powder is larger than 5 μm, the van der Waals force with the toner particles is reduced, and it is easily detached from the toner particles and adheres to the toner carrier, thereby inhibiting the frictional charging of the toner. Tend. From these viewpoints, the volume average particle size of the conductive fine powder is preferably 0.15 μm or more, more preferably 0.2 μm or more and 4 μm or less, and a non-magnetic material for suppressing adhesion to the toner carrier. It is preferable that

  The conductive fine powder is preferably a transparent, white or light-colored conductive fine powder because the conductive fine powder transferred onto the transfer material is not noticeable as fog. The conductive fine powder is preferably a transparent, white or light-colored conductive fine powder in the sense that it does not hinder the exposure light in the latent image forming step, and more preferably, the transmittance of the conductive fine powder to the exposure light is 30. % Or better.

  In the present invention, the light transmittance of particles can be measured by the following procedure. The transmittance is measured in a state where the conductive fine powder of a transparent film having an adhesive layer on one side is fixed for one layer. The light is irradiated from the vertical direction of the sheet, and the light transmitted through the back of the film is collected and the amount of light is measured. The transmittance of the particles is calculated as a net light amount from the light amount when only the film and the conductive fine powder are adhered. Specifically, it can be measured using a 310T transmission densitometer manufactured by X-Rite.

  The conductive fine powder in the present invention is preferably non-magnetic, for example, carbon fine powder such as carbon black and graphite; metal fine powder such as copper, gold, silver, aluminum and nickel; zinc oxide, titanium oxide, Metal oxides such as tin oxide, aluminum oxide, indium oxide, silicon oxide, magnesium oxide, barium oxide, molybdenum oxide, iron oxide, tungsten oxide; metal compounds such as molybdenum sulfide, cadmium sulfide, potassium titanate, or a composite thereof An oxide etc. are mentioned, It can use by adjusting a particle size and a particle size distribution as needed. Among these, inorganic oxide fine particles such as zinc oxide, tin oxide, and titanium oxide are particularly preferable.

Further, for the purpose of controlling the resistance value of the conductive inorganic oxide, a metal oxide doped with an element such as antimony or aluminum, or a fine particle having a conductive material on its surface can be used.
For example, titanium oxide fine particles surface-treated with tin oxide / antimony, stannic oxide fine particles doped with antimony, or stannic oxide fine particles.

  Commercially available tin oxide / antimony-treated conductive titanium oxide fine particles include, for example, EC-300 (Titanium Industry Co., Ltd.), ET-300, HJ-1, HI-2 (above, Ishihara Sangyo Co., Ltd.), W- P (Mitsubishi Materials Corporation).

  Examples of commercially available antimony-doped conductive tin oxide include T-1 (Mitsubishi Materials Corporation) and SN-100P (Ishihara Sangyo Co., Ltd.), and examples of commercially available stannic oxide include SH-S (Japan). Chemical Industry Co., Ltd.).

  The average particle size and particle size distribution of the electroconductive fine powder in the present invention are measured by measuring the liquid particle size distribution measuring apparatus in the 0.04 to 2000 μm range with a LS-230 type laser diffraction particle size distribution measuring device manufactured by Coulter. Can be implemented. As a measuring method, a trace amount of surfactant is added to 10 ml of pure water, 10 mg of a conductive fine powder sample is added thereto, and the mixture is dispersed for 10 minutes with an ultrasonic disperser (ultrasonic homogenizer). The method of measuring by 1 second and the frequency | count of a measurement is mentioned.

  In the present invention, as a method for adjusting the particle size and particle size distribution of the conductive fine powder, a method for setting the production method and production conditions so that the primary particle of the conductive fine powder can obtain a desired particle size and particle size distribution at the time of production. In addition, a method of agglomerating small particles of primary particles, a method of pulverizing particles of large primary particles, or a method by classification, etc. are possible. A method of attaching or fixing the above-mentioned conductive particles to a part or all of the surface, a method of using conductive fine particles having a form in which a conductive component is dispersed in particles having a desired particle size and particle size distribution are also possible. It is also possible to adjust the particle size and particle size distribution of the conductive fine powder by combining these methods.

  The particle diameter in the case where the conductive fine powder particles are formed as an aggregate is defined as the volume average particle diameter of the aggregate. There is no problem that the conductive fine powder exists not only in the state of primary particles but also in the state of aggregation of secondary particles. In any aggregation state, the form is not limited as long as the function of promoting the homogenization reaction of the charge amount can be realized.

In the present invention, the resistance of the conductive fine powder can be determined by measuring and normalizing by the tablet method. That is, a conductive fine powder sample of about 0.5 g is put in a cylinder with a bottom area of 2.26 cm ² , 15 kg of pressure is applied to the upper and lower electrodes, a voltage of 100 V is applied at the same time, a resistance value is measured, and then normalized. The specific resistance is calculated.

The magnetic toner of the present invention, for the purpose of improving the cleaning property, a primary particle diameter exceeding 30 nm (preferably less than 50m a specific surface area 2 / ^g), more preferably a primary particle diameter of 50nm or more (preferably a specific surface area 50m It is one of preferable modes to further add inorganic or organic fine particles close to spherical shape (less than ² / g). For example, spherical silica particles, spherical polymethylsilsesquioxane particles, spherical resin particles and the like are preferably used.

The magnetic toner of the present invention may contain a charge control agent in order to stabilize the charge characteristics. As the charge control agent, a known one can be used, and a charge control agent that has a high charging speed and can stably maintain a constant charge amount is particularly preferable. Further, when the toner is produced using a direct polymerization method, a charge control agent having a low polymerization inhibitory property and substantially free from a solubilized product in an aqueous dispersion medium is particularly preferable. Specific compounds include, as negative charge control agents, metal compounds of aromatic carboxylic acids such as salicylic acid, alkylsalicylic acid, dialkylsalicylic acid, naphthoic acid and dicarboxylic acid, metal salts or metal complexes of azo dyes or azo pigments, sulfones Examples thereof include a polymer compound having an acid or carboxylic acid group in the side chain, a boron compound, a urea compound, a silicon compound, and a calixarene. Examples of the positive charge control agent include a quaternary ammonium salt, a polymer compound having the quaternary ammonium salt in the side chain, a guanidine compound, a nigrosine compound, and an imidazole compound. The charge control agent is preferably used in an amount of 0.5 to 10 parts by mass with respect to 100 parts by mass of the binder resin. However, in the magnetic toner of the present invention, it is not essential to add a charge control agent, and the charge control agent is not necessarily contained in the toner by actively utilizing frictional charging with the toner layer thickness regulating member or the toner carrier. It is not necessary to include.

  The magnetic toner of the present invention can also contain a colorant. As the colorant, only the above-mentioned magnetic material may be used as the colorant, but magnetic or nonmagnetic inorganic compounds, known dyes and pigments, etc. May be used in combination. Specifically, for example, ferromagnetic metal particles such as cobalt and nickel, or alloys obtained by adding chromium, manganese, copper, zinc, aluminum and rare earth elements to these, particles such as hematite, titanium black, nigrosine dye / pigment , Carbon black, phthalocyanine and the like. These may also be used after treating the surface.

  The magnetic toner used in the present invention may further contain other additives such as a Teflon (registered trademark) powder, a zinc stearate powder, a lubricant powder such as polyvinylidene fluoride powder, or an oxidizing agent within a range that does not have a substantial adverse effect. Abrasives such as cerium powder, silicon carbide powder, and strontium titanate powder, or fluidity-imparting agents such as titanium oxide powder and aluminum oxide powder, anti-caking agent, and organic fine particles and inorganic fine particles of opposite polarity are developable. A small amount can be used as an improver. These additives can also be used after hydrophobizing the surface.

<2> Characteristics of Magnetic Toner of the Present Invention The average circularity of the magnetic toner of the present invention is 0.970 or more. A magnetic toner having an average circularity of 0.970 or more has excellent fog characteristics and transferability. The reason for this is that since the degree of circularity is very high, the magnetic toner forms thin spikes in the developing part, and the charging of individual toner particles becomes uniform, so there is little variation in the amount of charge that causes fogging, It is conceivable that the contact area between the particles and the photoconductor is small, and the adhesion force of the toner particles to the photoconductor due to the image force, van der Waals force, etc. is reduced, so that the transfer is easy.

  At this time, the mode circularity is more preferably 0.99 or more in the circularity distribution of the toner. When the mode circularity is 0.99 or more, it means that most of the toner particles have a shape close to a true sphere, and the above action becomes more remarkable, and the fog characteristic and transferability are further improved.

  The average circularity in the present invention is used as an index for quantitatively expressing the shape of the particles. In the present invention, the flow type particle image analyzer “FPIA-1000” manufactured by Toa Medical Electronics is used for measurement, The circularity (ai) of each particle measured for a particle group having a circle-equivalent diameter of 3 μm or more is obtained by the following equation (3), and the total circularity of all particles measured as shown by the following equation (4) Is divided by the total number of particles (m) and defined as the average circularity (am).

（式中、 Ｌ_０は磁性トナー粒子像と同じ投影面積をもつ円の周囲長を示し、Ｌは磁性ト
ナー粒子の投影像の周囲長を示す。）

(In the formula, L ₀ represents the perimeter of a circle having the same projected area as the magnetic toner particle image, and L represents the perimeter of the projected image of magnetic toner particles.)

また、モード円形度とは、円形度を０．４０から１．００まで０．０１毎に６１分割し、測定した各粒子の円形度をそれぞれ各分割範囲に割り振り、円形度頻度分布において頻度値が最大となるピークの円形度である。

Further, the mode circularity means that the circularity is divided into 61 parts every 0.01 from 0.40 to 1.00, and the measured circularity of each particle is assigned to each divided range, and the frequency value in the circularity frequency distribution. Is the maximum circularity of the peak.

  In addition, “FPIA-1000”, which is a measuring apparatus used in the present invention, calculates the circularity of each particle, and then calculates the average circularity and the mode circularity. A calculation method is used in which 40 to 1.00 are divided into 61 classes, and the average circularity and mode circularity are calculated using the center value and frequency of the dividing points. However, an error between each value of the average circularity and the mode circularity calculated by this calculation method and each value of the average circularity and the mode circularity calculated by the calculation formula that directly uses the circularity of each particle described above. Is very small and practically negligible.In the present invention, for the reasons of data handling such as shortening the calculation time and simplifying the calculation formula, Such a calculation method that is partially changed by using the concept of a calculation formula that directly uses the circularity may be used.

  The measurement procedure is as follows.

  A dispersion is prepared by dispersing about 5 mg of a magnetic toner in 10 ml of water in which about 0.1 mg of a surfactant is dissolved, and ultrasonic waves (20 KHz, 50 W) are irradiated to the dispersion for 5 minutes to adjust the concentration of the dispersion. Measurement is performed with the above apparatus at 5000 to 20,000 / μl, and the average circularity and mode circularity of a particle group having a circle-equivalent diameter of 3 μm or more are obtained.

  The average circularity in the present invention is an index of the degree of unevenness of the magnetic toner, and is 1.000 when the magnetic toner is perfectly spherical, and the average circularity becomes smaller as the surface shape of the magnetic toner becomes more complicated. Become.

  In this measurement, the reason why the circularity is measured only for the particle group having a circle equivalent diameter of 3 μm or more is that the particle group of the external additive existing independently of the toner particles in the particle group having a circle equivalent diameter of less than 3 μm. This is because the circularity of the toner particle group cannot be accurately estimated due to the influence of such a large amount.

  Further, the magnetic toner of the present invention is also characterized in that the magnetic material is not substantially exposed on the toner surface. Therefore, unlike the normal toner obtained by the pulverization method, the charge amount of the toner is difficult to leak. It is possible to obtain a good image with high image density under humidity.

  As described above, when the spherical toner is reduced in size and a release agent is further contained to achieve higher resolution while maintaining good fixability, control of the dispersion state of the release agent is also important. Technology.

  However, as described above, the simultaneous use of the magnetic substance and the release agent tends to cause a bias in the material dispersion inside the toner particles, and it is difficult to suppress the exposure of the release agent to the toner surface. Bad effects occur. In particular, the smaller the toner particle size, the more serious the adverse effect.

Therefore, the magnetic toner of the present invention is greatly characterized by using the above-described magnetic material that is well dispersed in a hexane solution. A magnetic substance that is uniformly dispersed in a hexane solution and has a slow sedimentation rate has a good dispersion state in the binder resin, and does not cause aggregation or the like during toner production. Since such a magnetic material can be uniformly dispersed without being biased inside the toner particles, the release agent present at the same time can be uniformly present inside the toner particles and is difficult to be exposed on the toner surface. Therefore, the small particle size magnetic toner of the present invention having a very good balance between fixability and blocking resistance, excellent transferability and developability even at high temperatures, and excellent developability can be obtained.

Magnetic properties of the magnetic toner for the additional inclusion of these magnetic bodies, the intensity of magnetization in a magnetic field 79.6 kA / m (1000 oersted) is ^{10~50Am 2 / kg (emu / g} ). If it is less than 10 Am ² / kg (emu / g), it is difficult to sufficiently improve the fog characteristic even if the triboelectric charge characteristic can be improved by the toner shape, and it may not be sufficient as a magnetic toner utilizing magnetic force. . On the other hand, if it exceeds 50 Am ² / kg (emu / g), the developability tends to decrease.

  The magnetic properties of the magnetic toner can be measured using a vibration magnetometer (VSM-3S-15 manufactured by Toei Kogyo Co., Ltd.), as with the magnetic material.

  According to the study by the present inventors, when a small particle size magnetic toner having a weight average particle size of 3 to 10 μm is manufactured using the magnetic material as described above, finer latent image dots can be faithfully developed. Therefore, the effect of improving the image characteristics is remarkable. When the weight average diameter of the toner is less than 3 μm, it is difficult to avoid a decrease in transfer efficiency even if the above-described magnetic material is used, and it becomes difficult to uniformly charge individual toner particles, thereby suppressing fog deterioration. Tend to be difficult. On the other hand, when the weight average diameter of the toner exceeds 10 μm, the characters and line images are likely to be scattered and it is difficult to obtain high resolution. A more preferred weight average particle size of the magnetic toner is 4 to 9 μm.

  In this case, the ratio D4 / D1 of the weight average particle diameter (D4) and the number average particle diameter (D1) of the toner is set to less than 1.4 to reduce the toner resolution, transfer efficiency, and fog suppression. It is more preferable for the balance of the improvement effect. Even if the weight average diameter of the toner is 3 μm or more, if the ratio of D4 / D1 is 1.4 or more, the ratio of toner particles having a small particle diameter in the particle size distribution is large. Is difficult.

Here, the average particle diameter of the toner can be measured by various methods such as Coulter Counter TA-II type or Coulter Multisizer (manufactured by Coulter Inc.). In the present invention, Coulter Multisizer (manufactured by Coulter Inc.) is used. An interface (manufactured by Nikka) and a PC9801 personal computer (manufactured by NEC) that output a number distribution and a volume distribution are connected, and a 1% NaCl aqueous solution is prepared using first-grade sodium chloride as the electrolyte. For example, ISOTON R-II (manufactured by Coulter Scientific Japan) can be used.
As a measurement method, 0.1 to 5 ml of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of the above electrolytic aqueous solution, and a measurement sample (toner) is further added.
2 to 20 mg. The electrolyte solution in which the sample is suspended is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and the volume distribution is measured by measuring the volume and number of toner particles of 2 μm or more using the 100 μm aperture as the aperture by the Coulter Multisizer. And the number distribution.

  Then, the volume-based weight average particle diameter (D4) obtained from the volume distribution of the present invention and the number-average length average particle diameter obtained from the volume average particle diameter (D) and the number distribution, that is, the number average particle. The diameter (D1) can be determined.

The magnetic toner of the present invention is also preferably characterized in that the magnetic material is not substantially exposed on the surface of the toner. Specifically, the carbon element present on the surface of the magnetic toner measured by X-ray photoelectron spectroscopy analysis The ratio (B / A) of the iron element content (B) to the iron content (A) is preferably less than 0.001, and more preferably less than 0.0005. This
There is no exposed magnetic material on the surface as a charge leakage site, and toner particles can have a high charge even under high humidity. For example, image printing with low fog and low transferability. Is possible for a long time, and the image quality and durability stability are greatly improved. This effect is more remarkable in an image forming method that combines a contact transfer process and a cleanerless process.

  The method of measuring the ratio (B / A) of the content (B) of the iron element to the content (A) of the carbon element present on the toner surface is as follows.

The ratio (B / A) of the content of iron element (B) to the content of carbon element (A) present on the toner particle surface according to the present invention (B / A) is determined by ESCA (X-ray photoelectron spectroscopy). And calculate. In the present invention, the ESCA apparatus and measurement conditions are as follows.
Equipment used: PHI 1600S type X-ray photoelectron spectrometer Measurement conditions: X-ray source MgKα (400 W)
Spectroscopic region 800μMφ
In the present invention, the surface atomic concentration is calculated from the measured peak intensity of each element using a relative sensitivity factor provided by PHI. This measurement is preferably performed by ultrasonically washing the toner, removing the external additive adhering to the surface of the toner particles, separating by magnetic force, and drying.

  A special toner in which the magnetic particles are not exposed on the surface of the toner particles is already disclosed in Japanese Patent Application Laid-Open No. 7-209904. However, Japanese Patent Laid-Open No. 7-209904 does not mention the circularity of the disclosed toner. In the image forming method of the present invention, the use of a toner having a specific average circularity is an essential element, and a developer as disclosed in JP-A-7-209904 is used in the form of use as in the present invention. It is unclear whether similar effects will be produced even if they are used. Japanese Patent Laid-Open No. 7-209904 does not describe the state of dispersion of the release agent. JP-A-7-209904 discloses an example in which polyethylene is used as a toner material, but if magnetic particles are present in the center of the toner particles, the polyethylene is present on the surface of the particles. It is difficult to avoid exposure from the toner surface. As a result, there is a concern about deterioration of toner physical properties and image characteristics.

  Furthermore, to summarize the toner configuration disclosed in Japanese Patent Application Laid-Open No. 7-209904, the toner layer has a structure in which a resin layer having no magnetic particles is formed with a certain thickness or more in the vicinity of the toner particle surface. Yes, this means that there is a considerable proportion of the toner surface layer where no magnetic particles are present. However, in other words, when the average particle diameter is as small as 10 μm, for example, the volume in which the magnetic particles can be present is small, so that it is difficult to enclose a sufficient amount of the magnetic particles. Moreover, in such a toner, in the toner particle size distribution, the ratio of the surface resin layer in which no magnetic particles are present differs between toner particles having a large particle size and small particles, and accordingly, the content of the magnetic material contained is also different. The developability and transferability also vary depending on the particle size of the toner, and selective developability depending on the particle size is likely to be seen. Therefore, when printing with such a magnetic toner for a long period of time, particles that contain a large amount of magnetic material and are difficult to develop, that is, toner particles having a large particle size are likely to remain, and the image density and image quality are deteriorated. It also leads to.

  As is derived from the above description, the preferable magnetic material dispersion state in the toner particles is a state in which the magnetic particles are present uniformly throughout the toner particles as much as possible without aggregation, and this is also the image forming of the present invention. It forms the basis of the characteristics of the magnetic toner related to the method. That is, when the volume average particle diameter of the toner is C, and the tomographic surface observation of the magnetic toner using a transmission electron microscope (TEM) is D, the minimum value of the distance between the magnetic material and the toner particle surface is D / C. The use of magnetic toner satisfying ≦ 0.02 is also one of the features of the present invention.

  In the present invention, the number of toner particles satisfying the relationship of D / C ≦ 0.02 is preferably 50% or more, more preferably 65% or more, and further preferably 75% or more. The reason is as follows.

When D / C ≦ 0.02 is not satisfied, no magnetic particles exist at least outside the boundary line of D / C = 0.02 in the toner particles. Assuming that the above-described particles are spherical, when one toner particle is the entire space, at least 11.5% of the space in which no magnetic material exists is present on the surface of the toner particle. Actually, the magnetic particles do not exist so as to be uniformly aligned at the closest position so as to form an inner wall inside the toner particles, so that it is clear that it becomes 12% or more. If there are no magnetic particles in this space per particle,
i) The magnetic substance is biased inside the toner particles, and the possibility of aggregation of the magnetic substance is extremely increased. As a result, the coloring power is reduced.
ii) Although the specific gravity of the toner particles increases according to the content of the magnetic material, the binder resin and the wax component are unevenly distributed on the surface of the toner particles. For this reason, even if a surface layer is provided on the surface of the toner particles by some means, if the toner particles or stress is applied to the toner particles during the manufacture of the toner, fusion or deformation is likely to occur. However, there is a high possibility that the toner will have a distribution in the powder characteristics resulting from deformation, which will adversely affect the electrophotographic characteristics, and that the blocking property during storage of the toner will deteriorate.
iii) In the particle structure in which the toner particle surface is only the binder resin and the wax and the magnetic particles are unevenly distributed inside, the toner particle outside is soft and the inside is hard, so that external additives are very easily embedded. In addition, the durability of the toner deteriorates. The risk of causing such harmful effects increases.

  If the number of toner particles satisfying D / C ≦ 0.02 is less than 50%, the above-mentioned adverse effects such as a decrease in coloring power, a deterioration in blocking property, and a deterioration in durability tend to become remarkable.

  Therefore, in the present invention, the number of toner particles satisfying D / C ≦ 0.02 is preferably 50% or more.

  As a specific observation method by TEM, a cured product obtained by sufficiently dispersing particles to be observed in a room temperature curable epoxy resin and then curing in an atmosphere at a temperature of 40 ° C. as it is, or A method of observing as a flaky sample with a microtome having frozen and diamond teeth is preferred.

  A specific method for determining the ratio of the number of corresponding particles is as follows.

  Particles for determining D / C by TEM are obtained by calculating the equivalent circle diameter from the cross-sectional area in the micrograph, and the value included in the width of ± 10% of the number average particle diameter is the relevant particle. / C is calculated. The ratio of particles having a D / C value calculated in this way of 0.02 or less is defined as being determined by the following formula. In this case, a magnification of 10,000 to 20,000 times is suitable for the microphotograph to perform measurement with high accuracy. In the present invention, a transmission microscope (H-600 model manufactured by Hitachi) is used as an apparatus, and observation is performed at an accelerating voltage of 100 kV, and observation and measurement are performed using a micrograph having an enlargement magnification of 10,000 times.

該磁性トナーの数平均粒径は後述するコールターカウンターにて決定するのが良い。

The number average particle diameter of the magnetic toner is preferably determined by a Coulter counter described later.

<3> Method for Producing Magnetic Toner of the Present Invention When the toner of the present invention is produced by a pulverization method, a known method is used. For example, the binder resin, magnetic material, release agent, charge control agent described above are used. In some cases, necessary components such as colorants and other additives and other additives are mixed thoroughly by a mixer such as a Henschel mixer or a ball mill, and then melt-kneaded using a heat kneader such as a heating roll, kneader or extruder. In addition, other toner materials such as a magnetic material are further dispersed or dissolved as necessary, and after cooling and solidification, pulverization, classification, and surface treatment as necessary. The toner of the present invention can be obtained by obtaining particles and, if necessary, adding and mixing inorganic fine powder and the like. Either the classification or the surface treatment may be performed first. In the classification step, it is preferable to use a multi-division classifier in terms of production efficiency.

  The pulverization step can be performed by a method using a known pulverizer such as a mechanical impact type or a jet type. In order to obtain a toner having a specific degree of circularity according to the present invention, it is preferable to further heat and pulverize or to add a mechanical impact as an auxiliary. Further, a hot water bath method in which finely pulverized (classified as necessary) toner particles are dispersed in hot water, a method of passing in a hot air stream, or the like may be used.

  Examples of means for applying mechanical impact force include a method using a mechanical impact type pulverizer such as a kryptron system manufactured by Kawasaki Heavy Industries, Ltd. There is a method of applying a mechanical impact force to the toner by a force such as a compressive force or a frictional force by pressing the toner against the inside of the casing by a centrifugal force with a blade rotating at high speed, as in a device such as a hybridization system manufactured by the manufacturer.

  In the case of using the mechanical impact method, a thermomechanical impact in which the processing temperature is a temperature in the vicinity of the glass transition point Tg (Tg ± 30 ° C.) of the toner is preferable from the viewpoint of preventing aggregation and productivity. More preferably, performing at a temperature in the range of the glass transition point (Tg ± 20 ° C.) of the toner is particularly effective for improving the transfer efficiency.

  Furthermore, the toner of the present invention is a method for obtaining a spherical toner by atomizing a molten mixture into air using a disk or a multi-fluid nozzle described in JP-B-56-13945, etc. An emulsion polymerization method typified by a dispersion polymerization method for directly producing a toner using an aqueous organic solvent in which the resulting polymer is insoluble or a soap-free polymerization method for producing a toner by directly polymerizing in the presence of a water-soluble polar polymerization initiator, etc. The toner can also be manufactured by a method of manufacturing the toner used.

  The toner according to the present invention can also be produced by a pulverization method, but the toner particles obtained by this pulverization method are generally amorphous, and the average circularity, which is an essential requirement of the toner according to the present invention, is required. In order to achieve a physical property of 0.970 or higher and a mode circularity of 0.99, it is necessary to perform mechanical / thermal or some special treatment. Further, in the pulverization method, since the magnetic substance is essentially exposed on the surface of the toner particles, it is difficult to satisfy the toner constituent requirement essential to the present invention that the magnetic substance is not substantially exposed on the surface of the magnetic toner. Therefore, the problem of improvement in image characteristics and durability under high humidity may not be solved.

Therefore, in order to solve the above-mentioned problems, it is preferable in the present invention that the toner is produced by a suspension polymerization method. In this suspension polymerization method, a polymerizable monomer, a colorant such as a magnetic material, and a release agent (further, if necessary, a polymerization initiator, a crosslinking agent, a charge control agent, and other additives) are uniformly dissolved or After dispersing to form a monomer composition, the monomer composition is dispersed in a continuous layer containing a dispersion stabilizer (for example, an aqueous phase) using a suitable stirrer and simultaneously subjected to a polymerization reaction. A toner having a desired particle size is obtained. The toner obtained by this suspension polymerization method (hereinafter, polymerized toner) has an average circularity of 0.00 because the individual toner particle shapes are almost spherical.
It is easy to obtain a toner satisfying the physical property requirement essential for the present invention of 970 or more, and such toner has a high transferability because the distribution of charge amount is relatively uniform.

  However, even if a normal magnetic substance is contained in the polymerized toner, it is difficult to suppress the exposure of the magnetic substance from the particle surface. Furthermore, not only the fluidity and charging characteristics of the toner particles are remarkably lowered, but also the toner having an average circularity of 0.970 or more is obtained due to the strong interaction between the magnetic substance and water during the production of the suspension polymerization toner. It's hard to be done.

  This is because i) the magnetic substance is generally hydrophilic, and therefore tends to be present on the toner surface, and ii) the magnetic substance moves randomly when the aqueous solvent is stirred, and the surface of the suspended particles composed of the monomer is dragged. This is thought to be due to the fact that the shape is distorted and is not easily circular. In order to solve these problems, it is necessary to use a magnetic material having a good dispersion state in a hexane solution as described above, and for this purpose, a coupling agent in which the surface properties of the magnetic material are modified. It is preferable to use a magnetic material that has been surface-treated with. When the magnetic material is used as a material for the polymerized toner, the dispersibility in the toner particles becomes very good, and a magnetic toner having a nearly spherical shape can be obtained without exposing the magnetic material to the surface of the toner particles. . That is, the inclusion of iron element with respect to the content (A) of carbon element present on the surface of the magnetic toner having an average circularity of 0.970 or more and a mode circularity of 0.99 or more and measured by X-ray photoelectron spectroscopy. A magnetic toner having an amount (B) ratio (B / A) of less than 0.001 can be obtained.

  In order to make the number of toner particles satisfying the relationship of D / C ≦ 0.02 to be 50% or more, for example, when magnetic toner particles are produced by suspension polymerization, a surface layer of toner particles is formed. Therefore, it can be produced by adjusting the amount of the resin having a polar functional group added to the polymerizable monomer composition or adjusting the degree of hydrophobicity of the magnetic substance.

  Further, in order for the D4 / D1 ratio of the toner to be less than 1.4 and the weight average particle diameter of the toner to be 3 to 10 μm, it is necessary to appropriately select the stirring conditions for the polymerization and the dispersion stabilizer to be used. Can be achieved. Specifically, when the stirring is increased, the particle size is decreased, and when the stirring is decreased, the particle size is increased.

  Next, a method for producing the magnetic toner of the present invention by suspension polymerization will be described.

  As the polymerizable monomer constituting the polymerizable monomer system used in the polymerized toner according to the present invention, those described above can be used.

  In the production of the polymerized toner according to the present invention, a resin may be added to the monomer system for polymerization. For example, it contains hydrophilic functional groups such as amino groups, carboxylic acid groups, hydroxyl groups, sulfonic acid groups, glycidyl groups, and nitrile groups that cannot be used because monomers are water-soluble and dissolve in aqueous suspension to cause emulsion polymerization. When it is desired to introduce the monomer component into the toner, a random copolymer of these with a vinyl compound such as styrene or ethylene, a block copolymer, a graft copolymer, or the like, or a polyester It can be used in the form of a polycondensate such as polyamide, or a polyaddition polymer such as polyether or polyimine. When such a polymer containing a polar functional group coexists in the toner, the surface-treated magnetic substance and the wax component described above are phase-separated, resulting in stronger encapsulation, offset resistance, blocking resistance, and low-temperature fixability. Good toner can be obtained. When using such a high molecular polymer containing a polar functional group, the average molecular weight is preferably 5,000 or more. If it is 5,000 or less, particularly 4,000 or less, the present polymer is likely to concentrate near the surface, and this tends to adversely affect developability, blocking resistance, etc., which is not preferred.

In addition, resins other than those described above may be added to the monomer system for the purpose of improving the dispersibility and fixing properties of the material or image characteristics. Examples of the resin used include styrene such as polystyrene and polyvinyltoluene. And styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, Styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-dimethylaminoethyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene -Butyl methacrylate copolymer, styrene-dimethyl methacrylate Copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-maleic acid Styrene copolymers such as copolymers, styrene-maleic acid ester copolymers; polymethyl methacrylate, polybutyl methacrylate, polyvinyl acetate, polyethylene, polypropylene, polyvinyl butyral, silicone resin, polyester resin, polyamide resin, epoxy resin Polyacrylic acid resin, rosin, modified rosin, temper resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin and the like can be used alone or in combination.

  As addition amount of these resin, 1-20 mass parts is preferable with respect to 100 mass parts of monomers. If it is less than 1 part by mass, the effect of addition is small, while if it is added in an amount of 20 parts by mass or more, it becomes difficult to design various physical properties of the polymerized toner.

  Furthermore, if a polymer having a molecular weight different from the molecular weight range of the toner obtained by polymerizing the monomer is dissolved in the monomer and polymerized, a toner having a wide molecular weight distribution and high offset resistance can be obtained. I can do it.

  The polymerization initiator used in the production of the polymerized toner according to the present invention has a half-life of 0.5 to 30 hours during the polymerization reaction, and 0.5 to 20 parts by mass with respect to the polymerizable monomer. When the polymerization reaction is carried out in an amount, a polymer having a maximum between 10,000 and 100,000 in molecular weight can be obtained, and the toner can be provided with desirable strength and suitable melting characteristics. Examples of polymerization initiators include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis (cyclohexane-1-carbonitrile) Azo or diazo polymerization initiators such as 2,2′-azobis-4-methoxy-2,4-dimethylvaleronitrile, azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, Examples thereof include peroxide polymerization initiators such as cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide, and lauroyl peroxide.

  When the polymerized toner according to the present invention is produced, a crosslinking agent may be added, and a preferable addition amount is 0.001 to 15% by weight.

In the method for producing a polymerized toner according to the present invention, it is generally necessary as a toner such as the above-described toner composition, that is, a polymerizable monomer, a magnetic material, a release agent, a plasticizer, a charge control agent, a cross-linking agent, and optionally a colorant. Components and other additives such as organic solvents, polymer polymers, dispersants, etc., which are added to reduce the viscosity of the polymer produced by the polymerization reaction, are added as appropriate, homogenizer, ball mill, colloid mill, ultrasonic dispersion The monomer system uniformly dissolved or dispersed by a dispersing machine such as a machine is suspended in an aqueous medium containing a dispersion stabilizer. At this time, the particle size of the obtained toner particles becomes sharper by using a high-speed disperser such as a high-speed stirrer or an ultrasonic disperser to obtain a desired toner particle size at a stretch. The polymerization initiator may be added at the same time when other additives are added to the polymerizable monomer, or may be mixed immediately before being suspended in the aqueous medium. Further, a polymerization initiator dissolved in a polymerizable monomer or a solvent can be added immediately after granulation and before starting the polymerization reaction.

  After granulation, stirring may be performed using a normal stirrer to such an extent that the particle state is maintained and particle floating and sedimentation are prevented.

  When the polymerized toner according to the present invention is produced, a known surfactant or organic / inorganic dispersant can be used as a dispersion stabilizer. Among them, inorganic dispersants are unlikely to produce harmful ultrafine powders, and because of their steric hindrance, dispersion stability is obtained, so even if the reaction temperature is changed, stability is not easily lost, and cleaning is easy and does not adversely affect the toner. Can be preferably used. Examples of such inorganic dispersants include polyvalent metal phosphates such as calcium phosphate, magnesium phosphate, aluminum phosphate and zinc phosphate, carbonates such as calcium carbonate and magnesium carbonate, calcium metasuccinate, calcium sulfate and barium sulfate. Inorganic oxides such as inorganic salts, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, silica, bentonite and alumina can be mentioned.

  These inorganic dispersants may be used alone in an amount of 0.2 to 20 parts by mass with respect to 100 parts by mass of the polymerizable monomer, and when producing toner particles having a weight average particle diameter of 5 μm or less. 0.001 to 0.1 parts by mass of a surfactant may be used in combination.

  Examples of the surfactant include sodium dodecylbenzene sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, sodium oleate, sodium laurate, sodium stearate, potassium stearate and the like.

  When these inorganic dispersants are used, they may be used as they are, but in order to obtain finer particles, the inorganic dispersant particles can be generated in an aqueous medium. For example, in the case of calcium phosphate, a sodium phosphate aqueous solution and a calcium chloride aqueous solution can be mixed with high-speed stirring to produce water-insoluble calcium phosphate, which enables more uniform and fine dispersion. At the same time, a water-soluble sodium chloride salt is produced as a by-product. However, if a water-soluble salt is present in the aqueous medium, dissolution of the polymerizable monomer in water is suppressed, and an ultrafine toner based on emulsion polymerization is produced. Since it becomes difficult to generate | occur | produce, it is more convenient. Since it becomes an obstacle when removing the remaining polymerizable monomer at the end of the polymerization reaction, it is better to replace the aqueous medium or desalinate with an ion exchange resin. The inorganic dispersant can be almost completely removed by dissolving with an acid or alkali after completion of the polymerization.

  In the polymerization step, the polymerization is performed at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. When the polymerization is carried out in this temperature range, the release agent and wax to be sealed inside are precipitated by phase separation, and the encapsulation is more complete. In order to consume the remaining polymerizable monomer, it is possible to raise the reaction temperature to 90 to 150 ° C. at the end of the polymerization reaction.

  The polymerized toner particles are filtered, washed, and dried by a known method after the polymerization is completed, and the toner can be obtained by mixing the inorganic fine powder and adhering it to the surface. Moreover, it is one of the desirable forms of this invention to put a classification process in a manufacturing process and to cut coarse powder and fine powder.

  Examples of the magnetic toner particles of the present invention include those produced entirely by suspension polymerization as described above, but may be magnetic toner particles partially produced by suspension polymerization. Examples of toner particles partially produced by suspension polymerization include those obtained by mixing a charge control agent with toner particles. This method also makes it possible to control the optimum charge amount according to the developing system, and in the image forming method of the present invention, it is possible to further stabilize the balance between the toner particle size distribution and the triboelectric charge amount. .

  Since the magnetic toner of the present invention has not only good selective developability but also less fog and high transferability, it is suitably used for an image forming method using a contact charging process, and further a cleanerless image forming method. These uses are also part of the present invention. In the image forming method composed of the contact charging process, the key technology is to reduce the toner that is transferred to the charging process without being transferred, that is, the residual transfer toner and fog toner. The image forming method of the present invention is achieved by using toner.

  Further, in the cleanerless image forming method, the transfer residual toner passes through the charging process and is collected in the developing device in the developing process. However, such toner is often inferior in chargeability due to the dispersibility of the material. Therefore, it is accumulated in the developing unit with durability, and image characteristics are likely to deteriorate. However, since the magnetic toner of the present invention has uniform and good image characteristics for all toner particles, it can be used for a long time even in a cleanerless image forming method at a high temperature that is susceptible to the dispersion state of the release agent. Since the high image quality can be stably maintained, the image forming method of the present invention is achieved by using this magnetic toner.

<4> Image Forming Method of the Present Invention In the image forming method of the present invention, a voltage is applied to a charging member to charge the image carrier, and an electrostatic latent image is formed on the charged image carrier. An electrostatic latent image forming step, the image carrier, and a toner carrier for carrying magnetic toner on the surface are arranged at a predetermined interval, and the magnetic toner is placed on the surface of the toner carrier more than the interval. A developing step in which the toner is developed by transferring the magnetic toner to the electrostatic latent image in a developing portion to which a thin thickness is applied and an AC voltage is applied; and a toner image formed on the image carrier. And a transfer step for electrostatic transfer to a transfer material. In the image formation method, the toner on the toner carrier in the development step is the magnetic toner of the present invention.

  Next, embodiments of the image forming method of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

In FIG. 1, a primary charging roller 117, which is a contact charging member, a developing device 140, a transfer roller 114, a cleaner 116, a register roller 124, and the like are provided around a photosensitive drum 100 as an image carrier. The photosensitive drum 100 is charged to −700 V by the primary charging roller 117. (The applied voltage is AC voltage −2.0 kVpp (Vpp: peak-to-peak potential), DC voltage −700 Vdc), and exposure is performed by irradiating the photosensitive drum 100 with the laser beam 123 by the laser beam scanner 121. The electrostatic latent image on the photosensitive drum 100 is developed with a one-component magnetic toner by the developing device 140 and is transferred onto the transfer material by the transfer roller 114 in contact with the photosensitive drum via the transfer material. The transfer material on which the toner image is placed is conveyed to the fixing device 126 by the conveyance belt 125 or the like and fixed on the transfer material. In addition, toner partially remaining on the photosensitive drum is cleaned by the cleaner 116. The developing device 140 is provided with a cylindrical toner carrier 102 (hereinafter also referred to as “developing sleeve”) made of a nonmagnetic metal such as aluminum or stainless steel in the vicinity of the photosensitive drum 100. The gap with the developing sleeve 102 is maintained at about 300 μm by a sleeve / photosensitive drum gap holding member (not shown) or the like. This gap can be changed if necessary. Although not shown, a magnet roller is fixed and disposed concentrically with the developing sleeve 102 in the developing sleeve 102. However, the developing sleeve 102 is rotatable. The magnet roller is provided with a plurality of magnetic poles, S1 is developing, N1 is toner coating amount regulation, S2 is toner intake / conveyance, and N2 is toner blowout prevention. An elastic blade 103 is provided as a toner layer thickness regulating member that regulates the amount of magnetic toner that adheres to the developing sleeve 102 and is conveyed, and the toner conveyed to the developing region by the contact pressure of the elastic blade 103 against the developing sleeve 102 The amount is controlled. In the developing area, a developing bias having a DC voltage and an AC voltage is applied between the photosensitive drum 100 and the developing sleeve 102, and the toner on the developing sleeve 102 flies onto the photosensitive drum 100 in accordance with the electrostatic latent image and is visible. It becomes.

  In the image forming method of the present invention, the charging member is preferably in contact with the image carrier. This is because ozone is not generated and is a preferred form of environmental conservation.

  As a preferable process condition when the charging roller is used as shown in FIG. 1, the charging roller is in contact with the photosensitive drum while forming a contact portion, and the contact pressure against the photosensitive drum is 4.9 to 490 N / m. (5 to 500 g / cm) and DC voltage or DC voltage superimposed with AC voltage is used. In the case of using a DC voltage superimposed with an AC voltage, AC voltage = 0.5 to 5 kVpp, AC frequency = 50 to 5 kHz, and DC voltage = ± 0.2 to ± 5 kV are preferable.

  The charging bias applied to the contact charging member can obtain good chargeability only with a DC voltage, but an AC voltage (alternating voltage) may be superimposed on the DC voltage as in the above-described apparatus shown in FIG.

  The alternating voltage at this time preferably has a peak voltage of less than 2 × Vth (Vth: discharge start voltage when a DC voltage is applied) (V).

  If the peak voltage of the AC voltage applied to the DC voltage is not less than 2 × Vth, the potential on the image carrier may become unstable. The AC voltage when applying a bias in which an AC voltage is superimposed on the DC voltage is more preferably a peak voltage less than Vth. As a result, the image carrier can be charged without a substantial discharge phenomenon.

  As a waveform of the AC voltage, a sine wave, a rectangular wave, a triangular wave or the like can be used as appropriate. Further, it may be a pulse wave formed by periodically turning on / off a DC power source. In this way, a bias that periodically changes the voltage value can be used as the waveform of the AC voltage.

  In the present invention, the charging member preferably has elasticity in providing a contact portion for interposing a conductive fine powder between the charging member and the image carrier, and a voltage is applied to the charging member. In order to charge the image bearing member, it is preferable to be conductive. Therefore, the charging member includes a conductive elastic roller, a conductive elastic blade, a magnetic brush portion in which magnetic particles are magnetically constrained, and a magnetic brush contact charging member or conductive fiber in which the magnetic brush portion is brought into contact with the photosensitive member. It is preferable that the brush is constructed.

  Moreover, you may provide a releasable film on those surfaces. As the releasable coating, nylon resin, PVdF (polyvinylidene fluoride), PVdC (polyvinylidene chloride), fluorine acrylic resin, or the like can be applied.

  In the image forming method of the present invention, the developing step is an image forming method having a simultaneous development cleaning step or a cleaner-less step that also serves as a cleaning step of collecting toner remaining on the photoreceptor after the toner image is transferred onto the transfer material. Even preferred.

Further, in the development simultaneous cleaning image forming method or the cleanerless image forming method, the developing step is a step of developing the electrostatic latent image on the image carrier with toner, and the charging step forms a contact portion with the image carrier. In the magnetic toner of the present invention, the image bearing member is charged by applying a voltage to the charging member in contact with the charging member, and at least in the contact portion between the charging member and the image bearing member and / or in the vicinity thereof. The image forming method is preferably such that the conductive fine powder adhered to the image carrier in the development process and remains on the image carrier after the transfer process and is carried and interposed.

  First, the behavior of the toner particles and the conductive fine powder during the image forming process when the conductive fine powder is externally added to the magnetic toner particles in the simultaneous development image forming method will be described.

  An appropriate amount of the conductive fine powder contained in the toner is transferred to the electrostatic latent image on the image carrier in the development process together with the toner particles toward the image carrier.

  The toner image on the image carrier is transferred to the transfer material side in the transfer process. Part of the conductive fine powder on the image carrier also adheres to the transfer material side, but the rest remains attached to the image carrier. When a transfer bias having a polarity opposite to that of the toner is applied, the toner is attracted to the transfer material side and actively transferred, but the conductive fine powder on the image carrier is conductive. The toner does not actively transfer to the transfer material side, and a part of the toner adheres to the transfer material side, but the rest remains attached and held on the image carrier.

  In an image forming method that does not use a cleaner, the residual toner remaining on the surface of the image carrier after transfer and the above-mentioned residual conductive fine powder are transferred to the surface of the image carrier on the charging portion that is the contact portion between the image carrier and the contact charging member. It is carried as it is and adheres to and mixes with the contact charging member. Accordingly, contact charging of the image carrier is performed in a state where the conductive fine powder is interposed in the contact portion between the image carrier and the contact charging member.

  Due to the presence of the conductive fine powder, the contact charging member can be kept in close contact with the image bearing member and contact resistance regardless of contamination due to adhesion or mixing of the transfer residual toner to the contact charging member. The image bearing member can be favorably charged by the charging member. Further, the transfer residual toner adhering to and mixed in the contact charging member is uniformly charged with the same polarity as the charging bias by the charging bias applied from the charging member to the image carrier, and gradually moves from the contact charging member onto the image carrier. As the image carrier surface moves, it reaches the developing section and is simultaneously cleaned (collected) in the development process.

  Further, as the image formation is repeated, the conductive fine powder contained in the toner moves to the surface of the image carrier at the developing unit, and is moved to the charging unit through the transfer unit by the movement of the image carrying surface and charged. Since the conductive fine powder is continuously supplied to the part, even if the conductive fine powder decreases or deteriorates due to dropping or the like in the charging part, the charging property is prevented from lowering and good charging is prevented. Sex is stably maintained.

  If the amount of the conductive fine powder intervened at the contact portion between the image carrier and the contact charging member is too small, the lubricating effect of the conductive fine powder cannot be sufficiently obtained, and the contact between the image carrier and the contact charging member. It is difficult to rotationally drive the contact charging member to the image carrier with a speed difference due to the large friction. That is, the driving torque becomes excessive, and the surface of the contact charging member or the image carrier is scraped if it is forcibly rotated. Further, the effect of increasing the contact opportunity due to the conductive fine powder may not be obtained, and sufficient charging performance cannot be obtained. On the other hand, if the amount of intervening is too large, dropping of the conductive fine powder from the contact charging member is remarkably increased, which may adversely affect image formation.

From the above, the amount of conductive fine powder intervening at the contact portion between the image carrier and the contact charging member is preferably 1 × 10 ³ pieces / mm ² or more, more preferably 1 × 10 ^{4 to} 5 × 10 ^5. Pieces / mm ² are good. If it is lower than 1 × 10 ³ pieces / mm ² , a sufficient lubricating effect and an effect of increasing the contact opportunity cannot be obtained, and the charging performance may be lowered. If it is lower than 1 × 10 ⁴ pieces / mm ² , the charging performance may be lowered when there is a large amount of residual toner.

  The coating density range of the conductive fine powder is also determined by the density of the conductive fine powder applied to the image carrier to obtain the effect of uniform charging.

  Needless to say, at the time of charging, contact charging more uniform than at least the recording resolution (resolution of the electrostatic latent image) is necessary.

  In addition, the upper limit of the coating amount of the conductive fine powder is until the conductive fine powder is uniformly coated on the image carrier, and the effect is not improved even if it is further coated. This causes the harmful effect of blocking or scattering the exposure source.

  Since the upper limit of the coating density varies depending on the particle size of the conductive fine powder, it cannot be generally described. However, if it is described forcibly, the conductive fine powder is uniformly coated on the image carrier. The amount is the upper limit.

When the amount of the conductive fine powder exceeds 5 × 10 ⁵ pieces / mm ² , the dropping of the conductive fine powder to the image carrier increases remarkably, and the image carrier regardless of the light transmittance of the fine powder itself. Insufficient exposure to. When the particle size is 5 × 10 ⁵ particles / mm ² or less, the amount of particles falling off can be kept low, and the inhibition of exposure can be improved. The abundance of the powder dropped on the image carrier in the intervening amount range was 1 × 10 ² to 1 × 10 ⁵ pieces / mm ² , and therefore, the abundance that is not harmful in image formation is 1 An intervening amount of × 10 ^{4 to} 5 × 10 ⁵ pieces / mm ² is preferable.

  A method for measuring the amount of conductive fine powder present at the charging contact portion and the amount of conductive fine powder present on the image carrier in the electrostatic latent image forming step will be described. The amount of conductive fine powder intervening is preferably measured directly on the contact surface between the contact charging member and the image carrier, but there is a speed difference between the surface of the contact charging member forming the contact portion and the surface of the image carrier. In the present invention, since most of the powder existing on the image carrier before contacting the contact charging member is peeled off by the contact charging member while moving in the opposite direction, in the present invention, the powder reaches the contact surface portion. The amount of powder immediately before the surface of the contact charging member is defined as the amount of interposition.

  Specifically, the rotation of the image carrier and the conductive elastic roller is stopped in a state where no charging bias is applied, and the surface of the image carrier and the conductive elastic roller is displayed on a video microscope (OLYMPUS OVM1000N) and a digital still recorder ( Taken with DELTA IS SR-3100). With respect to the conductive elastic roller, the conductive elastic roller contacts the slide glass under the same conditions as the contact of the image bearing member, and the contact surface of the slide glass from the rear surface of the slide glass is 10 positions with a 1000 × objective lens. Shoot above. In order to separate individual particles from the obtained digital image, binarization processing is performed with a certain threshold value, and the number of regions where powder is present is measured using desired image processing software. Also, the abundance on the image carrier is measured by photographing the image carrier with the same video microscope and performing the same processing.

  In the present invention, it is preferable that the conductive elastic roller member used as the contact charging member has an Asker C hardness of 50 degrees or less. If the hardness is too low, the shape will not be stable and the contact with the charged body will be poor, and the roller member surface layer will be scraped by interposing conductive fine particles in the contact portion between the charging member and the image carrier. Damaged and stable chargeability cannot be obtained. On the other hand, if the hardness is too high, a charging contact portion cannot be secured between the charged body and the micro contact property to the charged body surface is deteriorated. Furthermore, 25-50 degree | times is a preferable range by Asker C hardness.

It is important that the roller member functions as an electrode having a sufficiently low resistance to charge the moving charged object while at the same time obtaining a sufficient contact state with the charged object by giving elasticity. On the other hand, it is necessary to prevent voltage leakage in the case where a defect site such as a pinhole exists in the member to be charged. When an electrophotographic photosensitive member is used as the member to be charged, the volume resistance value is 10 ³ to 10 ⁸ Ω · cm, more preferably 10 ⁴ to 10 ⁷ Ω · cm, in order to obtain sufficient chargeability and leakage resistance. Good resistance.

  The volume resistance value of the roller member is measured by applying 100 V between the core metal and the aluminum drum in a state where the roller is pressed against a cylindrical aluminum drum of φ30 mm so that the total pressure of 1 kg is applied to the core metal of the roller. Can be measured.

  The roller member in the present invention can be produced, for example, by forming a middle resistance layer of rubber or foam as a flexible member on a cored bar. The middle resistance layer is formulated with a resin (for example, urethane), conductive particles (for example, carbon black), a sulfurizing agent, a foaming agent, and the like, and is formed in a roller shape on the core metal. Thereafter, if necessary, the roller member can be prepared by cutting and polishing the surface to adjust the shape. The surface of the roller member preferably has minute cells or irregularities in order to interpose conductive fine particles.

  This cell has dents having an average cell diameter in a spherical form of 5 to 300 μm, and the porosity of the surface of the roller member using the dent as a gap is preferably 15 to 90%.

  The material of the roller member is not limited to the elastic foam, but as the material of the elastic body, ethylene-propylene-diene polyethylene (EPDM), urethane, butadiene acrylonitrile rubber (NBR), silicone rubber, isoprene rubber, etc. In order to adjust the resistance, a rubber material in which a conductive material such as carbon black or a metal oxide is dispersed, or a foamed material thereof can be used. It is also possible to adjust the resistance using an ion conductive material without dispersing the conductive substance or in combination with the conductive substance.

  Examples of the core bar used for the roller member include aluminum and SUS.

  The roller member is disposed in pressure contact with the object to be charged as the image carrier with a predetermined pressing force against elasticity to form a charging contact portion that is a contact portion between the roller member and the image carrier. Let The width of the charging contact portion is not particularly limited, but is preferably 1 mm or more, more preferably 2 mm or more in order to obtain a stable and close adhesion between the roller member and the image carrier.

  Examples of the brush member as the contact charging member include a charging brush in which resistance is adjusted by dispersing a conductive material in commonly used fibers. As the fiber, generally known fiber can be used, and examples thereof include nylon, acrylic, rayon, polycarbonate, polyester and the like. As the conductive material, generally known conductive materials can be used. For example, conductive metal such as nickel, iron, aluminum, gold, silver or iron oxide, zinc oxide, tin oxide, antimony oxide, titanium oxide, etc. The conductive metal oxides, and further conductive powders such as carbon black. These conductive materials may be subjected to surface treatment for the purpose of hydrophobization and resistance adjustment as necessary. In use, it is selected in consideration of dispersibility with fibers and productivity.

When a charging brush is used as the contact charging member, there are a fixed type and a rotatable roll type. As the roll-shaped charging brush, for example, a roll brush can be obtained by winding a tape in which conductive fibers are piled around a metal core bar in a spiral shape. The conductive fiber has a fiber thickness of 1 to 20 denier (fiber diameter of about 10 to 500 μm), a brush fiber length of 1 to 15 mm, and a brush density of 10,000 to 300,000 per square inch (1 square meter) (About 1.5 × 10 ^{7 to} 4.5 × 10 ⁸ ) are preferably used.

It is preferable to use a charging brush having a brush density as high as possible, and it is also preferable to make one fiber from several to several hundreds of fine fibers. For example, it is possible to bundle 50 fine fibers of 300 denier, such as 300 denier / 50 filament, and plant the fibers as one fiber. However, in the present invention, the charging point for direct injection charging is determined mainly depending on the charging contact portion between the charging member and the image carrier and the density of conductive fine particles in the vicinity thereof. Therefore, the range of selection of the charging member is widened.

  Examples of the core bar used for the charging brush include the same ones used for the charging roller member.

The volume resistance value of the charging brush is preferably 10 ³ to 10 ⁸ Ω · cm in order to obtain sufficient chargeability and leakage resistance as in the case of the roller member.

  As materials for the charging brush, conductive rayon fibers REC-B, REC-C, REC-M1, and REC-M10 manufactured by Unitika Ltd., SA-7 manufactured by Toray Industries, Inc., manufactured by Nippon Kashige Co., Ltd. Sanderlon, Kanebo Beltron, Kuraray Co., Ltd. Kurabobo, Rayon carbon dispersed, Mitsubishi Rayon Co., Ltd. global, REC-B, REC- in terms of environmental stability Particularly preferred are C, REC-M1, and REC-M10.

  In addition, the flexibility of the contact charging member increases the chance of the conductive fine particles coming into contact with the image carrier at the contact portion between the contact charging member and the image carrier, thereby obtaining a high contact property. This is preferable from the viewpoint of improving direct injection chargeability. That is, the contact charging member comes into close contact with the image carrier via the conductive fine particles, and the conductive fine particles present at the contact portion between the contact charging member and the image carrier rub the surface of the image carrier without any gap. Therefore, the charging of the image carrier by the contact charging member is dominated by stable and safe direct injection charging without using the discharge phenomenon due to the presence of the charge accelerating particles, and high charging efficiency that cannot be obtained by conventional roller charging is obtained. Thus, a potential substantially equal to the voltage applied to the contact charging member can be applied to the image carrier.

  Further, by providing a relative speed difference between the moving speed of the surface of the charging member forming the contact portion and the moving speed of the surface of the image carrier, the conductive fineness is reduced at the contact portion between the contact charging member and the image carrier. It is preferable from the viewpoint that the opportunity for the powder to contact the image carrier is remarkably increased, higher contactability can be obtained, and direct injection charging property is improved.

  By interposing conductive fine particles at the contact portion between the contact charging member and the image carrier, a significant torque is generated between the contact charging member and the image carrier due to the lubricating effect (friction reduction effect) of the conductive fine powder. Thus, it is possible to provide a speed difference without increasing the contact speed and notably scraping the surface of the contact charging member and the image carrier.

  In order to temporarily collect and level the transfer residual toner on the image carrier carried by the charging unit on the contact charging member, the contact charging member and the image carrier may be moved in the opposite directions at the contact unit. Preferably good. For example, it is desirable that the contact charging member is driven to rotate, and the rotation direction of the contact charging member is rotated in the direction opposite to the moving direction of the image carrier surface at the contact portion. That is, it is possible to preferentially perform direct injection charging by once separating the transfer residual toner on the image carrier by reverse rotation and performing charging.

  Although it is possible to move the charging member in the same direction as the moving direction of the image carrier surface to give a speed difference, the charging property of direct injection charging is the ratio of the peripheral speed of the image carrier to the peripheral speed of the charging member. Therefore, in order to obtain the same peripheral speed ratio as in the reverse direction, the rotation speed of the charging member is larger in the forward direction than in the reverse direction. Therefore, it is advantageous in terms of the rotation speed to move the charging member in the reverse direction. It is.

  As a configuration for providing the speed difference, the contact charging member can be rotationally driven to provide a speed difference between the image carrier and the contact charging member. The peripheral speed ratio described here can be expressed by the following expression (5) (the charging member peripheral speed is a positive value when the surface of the charging member moves in the same direction as the surface of the image carrier at the contact portion).

相対速度差を示す指標としては、下式（６）で表される相対移動速度比がある。

As an index indicating the relative speed difference, there is a relative movement speed ratio represented by the following expression (6).

（式中、Ｖｃは帯電部材表面の移動速度、Ｖｐは像担持体表面の移動速度であり、Ｖｃは、当接部において帯電部材表面が像担持体表面と同じ方向に移動するとき、Ｖｐと同符号の値とする。）
相対移動速度比は、通常には１０〜５００％である。

(Where Vc is the moving speed of the surface of the charging member, Vp is the moving speed of the surface of the image carrier, and Vc is Vp when the surface of the charging member moves in the same direction as the surface of the image carrier at the contact portion. (It shall be the value of the same sign.)
The relative movement speed ratio is usually 10 to 500%.

  In order to temporarily collect the transfer residual toner on the image bearing member and carry conductive fine particles to perform direct injection charging, the conductive elastic material which is a flexible member as described above as a contact charging member is used. It is preferable to use a roller member or a rotatable charging brush roll.

Next, the image carrier will be described. In the image forming method of the present invention, the volume resistance value of the outermost surface layer of the image carrier (hereinafter also referred to as “photoreceptor”) is preferably 1 × 10 ⁹ or more and less than 1 × 10 ¹⁵ Ω · cm. . It is preferable that the outermost surface layer of the photoreceptor has a volume resistance value in the above range, which can give better chargeability. In the charging method by direct injection of charges, charges can be exchanged more efficiently by lowering the resistance on the photosensitive member side to be charged. To this end, it is good preferably as a volume resistivity of the outermost surface layer is less than 1 × 10 ¹⁵ Ω · cm. On the other hand, in order to hold an electrostatic latent image as an image carrier for a certain period of time, the volume resistance value of the outermost surface layer is preferably 1 × 10 ⁹ Ω · cm or more.

  In the present invention, the volume resistance value of the outermost surface layer of the image bearing member is a layer having the same composition as the outermost surface layer of the image bearing member on a polyethylene terephthalate (PET) film having gold deposited on the surface. And measuring this by applying a voltage of 100 V in an environment of 23 ° C. and 65% with a volume resistance measuring device (4140BpAMER manufactured by Hewlett-Packard Company).

The photoreceptor of the present invention is preferably a photosensitive drum or a photosensitive belt having a photoconductive material such as amorphous selenium, amorphous silicon, CdS, ZnO ₂ or an organic photosensitive material.

In the present invention, the contact angle with respect to water on the surface of the photoreceptor is preferably 85 ° or more. For such a photoreceptor, a polymer binder whose surface is an organic photosensitive layer is mainly used. Furthermore, what is comprised by providing mold release property can be used. For example, when a surface layer mainly composed of a resin is provided on an inorganic photoreceptor such as selenium or amorphous silicon, or when a surface layer composed of a charge transport material and a resin is used as a charge transport layer of a function separation type photoreceptor, Furthermore, there are cases where a surface layer as described above is provided thereon. Examples of means for imparting releasability to such a surface layer include the following.
(1) A resin having a low surface energy is used as the resin itself constituting the film.
(2) Add additives that impart water repellency and lipophilicity.
(3) A material having high releasability is powdered and dispersed in the resin.

  As an example of (1), it is achieved by introducing a fluorine-containing group, a silicone-containing group or the like into the resin structure. As (2), a surfactant or the like may be used as an additive. Examples of the material having releasability (3) include one or more lubricating fine particles selected from a fluororesin, a silicone resin, a polyolefin resin, and the like. Among them, a compound containing a fluorine atom, that is, polytetrafluoroethylene, Examples thereof include polyvinylidene fluoride and carbon fluoride.

  By these means, the contact angle with respect to water on the surface of the photoreceptor can be set to 85 degrees or more, and toner transferability and durability of the photoreceptor can be further improved. 90 degrees or more is preferable. Of these, polytetrafluoroethylene is particularly preferred. In the present invention, the means (3) for dispersing the releasable powder such as fluorine-containing resin in the outermost surface layer is suitable. In this case, the contact angle with water can be increased by increasing the amount of the lubricating fine particles added to the resin of the surface layer.

  The measurement of the contact angle is defined by the angle between the liquid surface and the surface of the photoconductor (the angle inside the liquid) where the free surface of water is in contact with the photoconductor using a drop type contact angle meter.

  In addition, the said measurement shall be performed at room temperature (about 21-25 degreeC).

  In order to contain these lubricating fine particles on the surface of the photosensitive member, a layer in which the lubricating fine particles are dispersed in the resin used for the surface layer is provided on the outermost surface of the photosensitive member, or originally composed mainly of the resin. In the case of the organic photoreceptor, a lubricating fine particle may be dispersed in the outermost surface layer without providing a new surface layer. The addition amount is preferably 1 to 60% by mass, and more preferably 2 to 50% by mass with respect to the total weight of the surface layer. If the amount is less than 1% by mass, the effect of improving the transferability of the toner and the durability of the photoreceptor is insufficient. If the amount exceeds 60% by mass, the strength of the film is reduced, or the amount of incident light on the photoreceptor is significantly reduced. Therefore, it is not preferable.

  The image forming method of the present invention is a direct charging method in which the charging step makes the charging member contact with the photosensitive member so as to form a contact portion, and the photosensitive member is charged by applying a voltage. However, since the load on the surface of the photoconductor is larger than the method using corona discharge in which the charging means does not come into contact with the photoconductor, the above configuration has a remarkable improvement effect in terms of the photoconductor life. This is one of preferred application forms.

  One preferred embodiment of the photoreceptor used in the present invention will be described below. The photoreceptor has an organic photosensitive layer on a conductive substrate.

  As the organic photosensitive layer, a photosensitive layer may be used which may be a single layer type in which the charge generating material and the charge transporting material are the same, or a functionally separated type photosensitive layer having a charge transporting layer and a charge generating layer. . That is, an organic photosensitive layer is provided on a conductive substrate, and a protective layer is provided on the surface. A laminated photosensitive layer having a structure in which a charge generation layer and then a charge transport layer are laminated in this order on a conductive substrate is one preferred example.

  Examples of the conductive substrate include metals such as aluminum and stainless steel, plastics having a coating layer made of aluminum alloy, indium oxide-tin oxide alloy, paper / plastic impregnated with conductive particles, plastics having a conductive polymer, etc. Cylindrical cylinders and films are used. On these conductive substrates, the purpose is to improve the adhesion of the photosensitive layer, improve coating properties, protect the substrate, cover defects on the substrate, improve charge injection from the substrate, and protect against electrical breakdown of the photosensitive layer. An undercoat layer may be provided.

  Undercoat layer is polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenol resin, casein, polyamide, copolymer nylon, glue, gelatin, polyurethane -It is made of a material such as aluminum oxide. The membrane pressure is usually about 0.1 to 10 μm, preferably about 0.1 to 3 μm.

  The charge generation layer is made of azo pigments, phthalocyanine pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethane dyes, selenium, amorphous silicon, etc. It is formed by dispersing a charge generating substance such as an inorganic substance in an appropriate binder and coating or vapor deposition. The binder can be selected from a wide range of binder resins, such as polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacrylic resin, phenol resin, silicon resin, epoxy resin, vinyl acetate resin, etc. Is mentioned. The amount of the binder contained in the charge generation layer is selected to be 80% by mass or less, preferably 0 to 40% by mass. Further, the film pressure of the charge generation layer is preferably 5 μm or less, particularly preferably 0.05 to 2 μm.

  The charge transport layer has a function of receiving charge carriers from the charge generation layer in the presence of an electric field and transporting them. The charge transport layer is formed by dissolving a charge transport material in a solvent together with a binder as required, and coating, and the film pressure is generally 5 to 40 μm. Examples of charge transport materials include polycyclic aromatic compounds having structures such as biphenylene, anthracene, pyrene, phenanthrene in the main chain or side chain, nitrogen-containing cyclic compounds such as indole, carbazole, oxadiazole, pyrazoline, hydrazone compounds, Examples include styryl compounds, selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide.

  In addition, binders for dispersing these charge transport materials include resins such as polycarbonate resin, polyester resin, polymethacrylic acid ester, polystyrene resin, acrylic resin, polyamide resin, and organic such as poly-N-vinylcarbazole and polyvinylanthracene. A photoconductive polymer etc. are mentioned.

  Moreover, you may provide a protective layer as a surface layer. As the resin for the protective layer, polyester, polycarbonate, acrylic resin, epoxy resin, phenol resin, or a curing agent for these resins may be used alone or in combination of two or more.

  Moreover, you may disperse | distribute electroconductive fine particles in resin of a protective layer. Examples of the conductive fine particles include metals and metal oxides, preferably zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin oxide coated titanium oxide, tin coated indium oxide, There are ultrafine particles such as antimony-coated tin oxide and zirconium oxide. These may be used alone or in combination of two or more.

  In general, when particles are dispersed in a protective layer, it is necessary that the particle diameter of the particles is smaller than the wavelength of incident light in order to prevent scattering of incident light by the dispersed particles, and the particles are dispersed in the protective layer in the present invention. The particle diameter of the conductive fine particles and insulating lubricating fine particles is preferably 0.5 μm or less. Moreover, 2-90 mass% is preferable with respect to the protective layer total weight, and, as for content in a protective layer, 5-80 mass% is more preferable. The thickness of the protective layer is preferably from 0.1 to 10 μm, more preferably from 1 to 7 μm.

  The surface layer can be applied by spray coating, beam coating or penetration (dipping) coating of the resin dispersion.

  Next, the contact transfer process preferably applied in the image forming method of the present invention will be specifically described. In the present invention, the recording medium that receives the transfer of the toner image from the image carrier may be an intermediate transfer member such as a transfer drum. When the recording medium is an intermediate transfer member, a toner image can be obtained by transferring again from the intermediate transfer member to a transfer material such as paper.

  In the contact transfer process, the developed image is electrostatically transferred to the transfer material while contacting the transfer means via the photosensitive member and the transfer material. The contact pressure of the transfer means is a linear pressure of 2.9 N / m. It is preferably (3 g / cm) or more, more preferably 19.6 N / m (20 g / cm) or more. If the linear pressure as the contact pressure is less than 2.9 N / m (3 g / cm), it is not preferable because transfer of the transfer material and transfer failure are likely to occur.

Further, as a transfer means in the contact transfer process, an apparatus having a transfer roller or a transfer belt is used. FIG. 4 shows an example of the configuration of the transfer roller. The transfer roller 34 comprises at least a core metal 34a and a conductive elastic layer 34b, the conductive elastic layer such as urethane or EPDM dispersed a conductive material such as carbon, the volume resistivity ^{1 × 10 6 ~1 × 10 10} Ω · The transfer bias is applied by a transfer bias power source 35.

  The image forming method of the present invention is particularly effective when the contact transfer method is used in an image forming apparatus in which the surface of the photoreceptor is an organic compound. In other words, when the organic compound forms the surface layer of the photoconductor, the adhesion to the binder resin contained in the toner particles is stronger than other photoconductors using inorganic materials, and the transferability is further reduced. This is because they tend to.

  Further, when the contact transfer method is applied to the image forming method of the present invention, the photoconductor used is not particularly limited, and examples thereof include those described above.

  In addition, the image forming method of the present invention to which the contact transfer method is applied is particularly effective for an image forming apparatus having a small-diameter photoreceptor having a diameter of 50 mm or less. That is, in the case of a small-diameter photoconductor, the curvature with respect to the same linear pressure is large, and pressure concentration tends to occur at the contact portion. Although the belt photoreceptor is considered to have the same phenomenon, the present invention is also effective for an image forming apparatus having a radius of curvature of 25 mm or less at the transfer portion.

  Further, in the image forming method of the present invention, in order to obtain a high image quality without fogging, a magnetic toner having a layer thickness smaller than the closest distance (between S and D) between the toner carrier and the photoreceptor is formed on the toner carrier. It is developed in a development step of applying and developing by applying an AC voltage. That is, the toner layer thickness regulating member that regulates the magnetic toner on the toner carrying member is used by setting the closest gap between the photosensitive member and the toner carrying member to be wider than the toner layer thickness on the toner carrying member. The toner layer thickness regulating member that regulates the magnetic toner on the carrier is regulated by an elastic member that is in contact with the toner carrier via the toner. This is particularly preferable from the viewpoint of obtaining a uniform charge which is less likely to occur.

  In the present invention, it is preferable that the toner carrying member is disposed facing the photosensitive member with a separation distance of 100 to 1000 μm. If the separation distance of the toner carrier from the photosensitive member is less than 100 μm, the change in the development characteristics of the toner with respect to the fluctuation of the separation distance becomes large, so that it is difficult to mass-produce an image forming apparatus that satisfies stable image quality. Sometimes. When the separation distance of the toner carrying member from the photosensitive member is larger than 1000 μm, the followability of the toner to the latent image on the photosensitive member is lowered, so that the image quality is lowered such as a lower resolution and a lower image density. Preferably 120-500 micrometers is good.

In the present invention, it is preferable to form an electrostatic latent image by forming a toner layer of 5 to 50 g / m ² on the toner carrier and transferring the toner from the toner layer onto the photoreceptor. When the toner amount on the toner carrier is smaller than 5 g / m ^2, it is difficult to obtain a sufficient image density, and unevenness of the toner layer is caused due to excessive charging of the toner. When the amount of toner on the toner carrier exceeds 50 g / m ² , toner scattering tends to occur.

  In the present invention, development is preferably performed in a developing process in which an alternating electric field is applied to the toner carrier and development is performed, and the applied developing bias may superimpose an alternating voltage (AC voltage) on a DC voltage.

  As a waveform of the AC voltage used for the developing bias, a sine wave, a rectangular wave, a triangular wave, or the like can be used as appropriate. Further, it may be a pulse wave formed by periodically turning on / off a DC power source. In this way, a bias that changes the voltage value periodically can be used as the waveform of the alternating voltage.

An alternating electric field of at least a peak-to-peak electric field strength of 1 × 10 ⁶ to 1 × 10 ⁷ V / m and a frequency of 100 to 5000 Hz is applied as a developing bias between the toner carrier that carries toner and the image carrier. It is preferable to do.

  The toner carrier used in the present invention is preferably a conductive cylinder (developing roller) formed of a metal such as aluminum or stainless steel or an alloy. In addition, a conductive cylinder may be formed of a resin composition having sufficient mechanical strength and conductivity, or a conductive rubber roller may be used. Furthermore, it is not limited to the cylindrical shape as described above, and may be an endless belt that is rotationally driven.

  The surface roughness of the toner carrier used in the present invention is preferably in the range of 0.2 to 3.5 μm in terms of JIS centerline average roughness (Ra).

  If Ra is less than 0.2 μm, the charge amount on the toner carrying member becomes high, and the developability becomes insufficient. When Ra exceeds 3.5 μm, unevenness occurs in the toner coat layer on the toner carrier, resulting in uneven density on the image. More preferably, it is in the range of 0.5 to 3.0 μm.

In the present invention, the surface roughness Ra of the toner carrier is determined according to the JIS surface roughness “JISB 060”.
1 "corresponds to the centerline average roughness measured using a surface roughness measuring instrument (Surfcoder SE-30H, manufactured by Kosaka Laboratory Ltd.). Specifically, a 2.5 mm portion as the measurement length a is extracted from the roughness curve in the direction of the center line, the center line of this extraction portion is the X axis, the direction of the vertical magnification is the Y axis, and the roughness curve is When expressed by y = f (x), the value obtained by the following formula (7) is expressed in micrometers (μm).

さらに、本発明の磁性トナーは高い帯電能力を有するために、現像に際してはトナーの総帯電量をコントロールすることが望ましく、本発明に係わるトナー担持体の表面は導電性微粒子及び／又は滑剤を分散した樹脂層で被覆されていることが好ましい。

Further, since the magnetic toner of the present invention has a high charging ability, it is desirable to control the total charge amount of the toner during development, and the surface of the toner carrier according to the present invention is dispersed with conductive fine particles and / or lubricant. It is preferable that the resin layer is covered.

In the coating layer of the toner carrier, the conductive fine particles contained in the resin material preferably have a resistance value of 0.5 Ω · cm or less after being pressed at 11.7 Mpa (120 kg / cm ² ).

  The conductive fine particles used for the toner carrier are preferably carbon fine particles, a mixture of carbon fine particles and crystalline graphite, or crystalline graphite. The conductive fine particles preferably have a particle size of 0.005 to 10 μm.

  Examples of the resin material include thermoplastic resins such as styrene resin, vinyl resin, polyethersulfone resin, polycarbonate resin, polyphenylene oxide resin, polyamide resin, fluororesin, fiber resin, and acrylic resin; epoxy resin, polyester A thermosetting resin or a photocurable resin such as a resin, an alkyd resin, a phenol resin, a melamine resin, a polyurethane resin, a urea resin, a silicone resin, or a polyimide resin can be used.

  Among them, those having releasability such as silicone resin and fluororesin, and those having excellent mechanical properties such as polyethersulfone, polycarbonate, polyphenylene oxide, polyamide, phenol resin, polyester, polyurethane, styrene resin are more. preferable. In particular, a phenol resin is preferable.

  The conductive fine particles used for the toner carrier are preferably used in an amount of 3 to 20 parts by mass per 10 parts by mass of the resin component of the coating layer.

  When carbon fine particles and graphite particles are used in combination, it is preferable to use 1 to 50 parts by mass of carbon fine particles per 10 parts by mass of graphite.

The volume resistivity of the resin coating layer of the toner carrier in which conductive fine particles are dispersed is preferably 1 × 10 ⁻⁶ to 1 × 10 ⁶ Ω · cm.

  In the present invention, the surface of the toner carrier that carries the toner may move in the same direction as the moving direction of the image carrier surface, or may move in the opposite direction. When the moving direction is the same direction, the ratio is preferably 100% or more with respect to the moving speed of the image carrier. If it is less than 100%, the image quality is poor. The higher the moving speed ratio, the more toner is supplied to the development site, the more frequently the toner is desorbed from the latent image, and the unnecessary parts are scraped off and applied to the necessary parts. Thus, an image faithful to the latent image can be obtained. Specifically, the moving speed of the toner carrier surface is preferably 1.05 to 3.0 times the moving speed of the image carrier surface.

<5> Process Cartridge of the Present Invention The process cartridge of the present invention is configured to be detachable from the image forming apparatus used in the image forming method of the present invention, and is at least selected from the group consisting of an image carrier and charging means. One means is supported integrally with the developing means.

  Examples of the developing means used in the process cartridge of the present invention include a normal developing device having toner, a toner container for storing the toner, a toner carrier, and the like.

  The toner used in the process cartridge of the present invention is preferably the above-described magnetic toner of the present invention.

  Since the developing means is a detachable process cartridge as in the above configuration, even if the toner life ends, it can be realized as an image forming apparatus simply by changing each means and member, and used without waste. can do.

  Hereinafter, the present invention will be specifically described with reference to production examples and examples, but this does not limit the present invention in any way. In addition, all the parts in the following mixing | blending are a mass part. In addition, the toner and other physical property measuring methods of the present invention can be measured by the methods described in the above detailed description.

<1> Manufacture of magnetic body The surface treatment magnetic bodies 1-8 and the magnetic body 1 were obtained as follows.

<Manufacture of surface-treated magnetic body 1>
In ferrous sulfate aqueous solution, l. An aqueous solution containing ferrous hydroxide was prepared by mixing 0 to 1.1 equivalents of caustic soda solution.
While maintaining the pH of the aqueous solution at around 9, air was blown and an oxidation reaction was performed at 80 to 90 ° C. to obtain a slurry solution of magnetic particles. After washing and filtering, this hydrous slurry liquid was once taken out. At this time, a small amount of water-containing sample was collected and the water content was measured. Next, this water-containing sample was re-dispersed in another aqueous medium without drying, and then the pH of the re-dispersed liquid was adjusted to about 6, and the silane coupling agent (n-C ₁₀ H _{21 was} thoroughly stirred. 0.2 parts by mass of Si (OCH ₃ ) ₃ ) was added to the magnetic iron oxide (the amount of magnetic particles was calculated as a value obtained by subtracting the water content from the water-containing sample), and a coupling treatment was performed. The produced hydrophobic magnetic material was washed, filtered and dried by a conventional method, and the resulting particles were sufficiently crushed. Next, the hydrophobic magnetic material thus obtained was subjected to a hydrophobic treatment again with 0.3 parts by mass of a silane coupling agent (n-C ₁₀ H ₂₁ Si (OCH ₃ ) ₃ ) by a dry method, and the surface-treated magnetic material 1 was obtained. Table 1 shows the physical properties of the obtained surface-treated magnetic material.

<Manufacture of magnetic body 1>
The oxidation reaction proceeded in the same manner as in the production of the surface-treated magnetic body 1, the magnetic iron oxide particles produced after the oxidation reaction were washed, filtered and dried, and the aggregated particles were crushed to obtain the magnetic body 1.

<Manufacture of surface-treated magnetic body 2>
After re-dispersing the magnetic material 1 in another aqueous medium, the pH of the re-dispersed liquid is adjusted to about 6, and a silane coupling agent (n-C ₁₀ H ₂₁ Si (OCH ₃ ) is stirred with sufficient stirring. ₃ ) was added in an amount of 0.5 parts by mass to the surface-treated magnetic body 1, and a coupling treatment was performed. The obtained magnetic particle slurry was washed, filtered and dried by a conventional method, and then the agglomerated particles were crushed to obtain a surface-treated magnetic body 2. Table 1 shows the physical properties of the obtained surface-treated magnetic body 2.

<Manufacture of surface-treated magnetic body 3>
In the production of surface-treated magnetic material 2, and 0.5 parts by mass with respect to the magnetic body 1 the amount of silane coupling agent _{(n-C 10 H 21 Si} (OCH 3) 3) was surface treated with gas phase Otherwise, the surface-treated magnetic body 3 was obtained in the same manner as in the production of the surface-treated magnetic body 2. Table 1 shows the physical properties of the obtained magnetic substance.

<Manufacture of surface-treated magnetic body 4>
The production of the surface-treated magnetic body 1 except that (n-C ₆ H ₁₃ Si (OCH ₃ ) ₃ ) was used instead of (n-C ₁₀ H ₂₁ Si (OCH ₃ ) ₃ ) as the silane coupling agent. A surface-treated magnetic body 4 was obtained by the same method. Table 1 shows the physical properties of the obtained magnetic substance.

<Manufacture of surface-treated magnetic body 5>
Production of surface-treated magnetic body 1 except that (n-C ₁₈ H ₃₇ Si (OCH ₃ ) ₃ ) was used in place of (n-C ₁₀ H ₂₁ Si (OCH ₃ ) ₃ ) as a silane coupling agent A surface-treated magnetic body 5 was obtained by the same method. Table 1 shows the physical properties of the obtained magnetic substance.

<Manufacture of surface-treated magnetic bodies 6-8>
In the production of the surface-treated magnetic body 1, the surface-treated magnetic bodies 6 to 8 are obtained by appropriately changing the production conditions (pH, stirring speed, oxidation reaction speed, air blowing amount, etc.) and the amount of the hydrophobizing agent. It was. Table 1 shows the physical properties of the obtained magnetic substance.

<2> Production of conductive fine powder Conductive fine powders 1 to 5 were obtained as follows.

<Conductive fine powder 1>
Fine particle zinc oxide with a volume average particle size of 3.7 μm, particle size distribution of 0.5 μm or less is 6.6% by volume, and 5 μm or more is 8% by number (resistance 80 Ω · cm, primary particle size 0.1 to 0.3 μm of oxidation) The obtained product obtained by granulating zinc primary particles by pressure (white) is defined as conductive fine powder 1. When the conductive fine powder 1 was observed with a scanning electron microscope at 3000 times and 30,000 times, it was composed of 0.1 to 0.3 μm primary particles of zinc oxide and 1 to 10 μm aggregates.
In accordance with the exposure light wavelength 740 nm of the laser beam scanner used for image exposure in the image forming apparatus of Example 1 to be described later, a light source with a wavelength of 740 nm is used, and the transmittance in this wavelength region is 310T transmission type manufactured by X-Rite. When measured using a densitometer, the transmittance of the conductive fine powder 1 was about 35%.

<Conductive fine powder 2>
Finely divided zinc oxide (resistance: 440Ω · resistance) obtained by air classification of the conductive fine powder powder 1 and having a volume average particle size of 2.4 μm, 0.5 μm or less in the particle size distribution is 4.1% by volume, and 5 μm or more is 1% by number. cm, transmittance 35%) is defined as conductive fine powder 2. When the conductive fine powder 2 was observed with a scanning electron microscope, it was composed of zinc oxide primary particles of 0.1 to 0.3 μm and aggregates of 1 to 5 μm, but compared with the conductive fine powder 1. Then, the primary particles were decreased.

<Conductive fine powder 3>
Finely divided zinc oxide (resistance 1500 Ω · cm, with a volume average particle size of 1.5 μm, 0.5 μm or less in the particle size distribution of 35% by volume, and 5 μm or more 0% by weight obtained by air classification of the conductive fine particles 1 Conductivity fine powder 3 is defined as a transmittance of 35%). When this conductive fine powder 3 was observed with a scanning electron microscope, it was composed of 0.1 to 0.3 μm zinc oxide primary particles and 1 to 4 μm aggregates. Then, the primary particles increased.

<Conductive fine powder 4>
Fine particle zinc oxide having a volume average particle size of 0.3 μm, 0.5 μm or less in the particle size distribution is 80% by volume, and 5 μm or more is 0% by number (resistance 100 Ω · cm, primary particle size 0.1 to 0.3 μm, white, transmission The rate is 35% and the purity is 99% or more). When the conductive fine powder 4 was observed with a scanning electron microscope, it was composed of 0.1 to 0.3 μm zinc oxide primary particles with few aggregates.

<Conductive fine powder 5>
After removing coarse particles of aluminum borate with a volume average particle size of 2.8 μm surface-treated with tin oxide / antimony by air classification, fine particles are removed by repeating filtration after being dispersed in an aqueous system. Grayish white conductive particles having a diameter of 3.2 μm and a particle size distribution of 0.5 μm or less of 0.4% by volume and 5 μm or more of 1% by number were obtained. This is designated as conductive fine powder 5.
Table 2 shows typical physical property values of the conductive fine powders 1 to 5.

<3> Manufacture of magnetic toner (a) Manufacture of magnetic toner particles <Manufacture of magnetic toner particles 1>
After adding 451 g of 0.1M Na ₃ PO ₄ aqueous solution to 709 g of ion-exchanged water and heating to 60 ° C., 67.7 g of 1.0M CaCl ₂ aqueous solution was gradually added, and hydrochloric acid was added to adjust the pH of the solution. Was adjusted to about 8.5 to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .
・ Styrene 80 parts ・ n-butyl acrylate 20 parts ・ unsaturated polyester resin 5 parts ・ negative charge control agent (monoazo dye-based Fe compound)
(Compound represented by the following general formula (III)) 1 part / surface-treated magnetic material 1 90 parts

上記処方をアトライター（三井三池化工機（株））を用いて均一に分散混合した。なお、以下の磁性トナーに用いられる負電荷性制御剤も上記一般式（ＩＩＩ）で表されるものである。

The above formulation was uniformly dispersed and mixed using an attritor (Mitsui Miike Chemical Co., Ltd.). The negative charge control agent used in the following magnetic toner is also represented by the above general formula (III).

This monomer composition was heated to 60 ° C., and 20 parts of ester wax mainly composed of behenyl behenate (maximum endothermic peak 72 ° C. in DSC) was added and mixed therewith. 7 ′ of 2′-azobis (2,4-dimethylvaleronitrile) [t1 / 2 = 140 minutes, at 60 ° C.] and dimethyl-2,2′-azobisisobutyrate [t1 / 2 = 270 minutes, 60 ° C. Under conditions; t1 / 2 = 80 minutes, at 80 ° C.] 2 g was dissolved.
The polymerizable monomer system was put into the aqueous medium, and the mixture was granulated by stirring at 10,000 rpm for 15 minutes with a TK homomixer (Special Machine Industries Co., Ltd.) in an N ₂ atmosphere at 60 ° C. . Thereafter, the mixture was reacted at 60 ° C. for 7 hours while stirring with a paddle stirring blade. Thereafter, the liquid temperature was raised to 80 ° C., and stirring was further continued for 3 hours. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve Ca ₃ (PO ₄ ) ₂ , filtered, washed with water, and dried to obtain magnetic toner particles 1 having a weight average particle diameter of 6.6 μm.
The physical properties of the obtained magnetic toner particles 1 are shown in Table 3 together with those of the magnetic toner particles obtained in the production of the following magnetic toner particles.

<Production of magnetic toner particles 2 to 8>
Magnetic toner particles 2 to 8 were obtained in the same manner except that surface-treated magnetic materials 2 to 8 were used in place of surface-treated magnetic material 1 in the production of magnetic toner particles 1.

<Manufacture of magnetic toner particles 9>
Magnetic toner particles 9 were obtained by the same method except that the magnetic material 1 was used instead of the surface-treated magnetic material 1 in the production of the magnetic toner particles 1.

<Manufacture of magnetic toner particles 10>
In the production of the magnetic toner particles 1, the amount of Na ₃ PO ₄ aqueous solution added and the amount of CaCl ₂ aqueous solution added were adjusted to change the amount of Ca ₃ (PO ₄ ) ₂ in the aqueous medium, and sodium dodecylbenzenesulfonate was further added. As a result, magnetic toner particles 10 having a weight average particle diameter of 2.9 μm were obtained.

<Manufacture of magnetic toner particles 11 and 12>
Magnetic toner particles 11 and 12 were obtained by the same method except that the prescription amount of the surface-treated magnetic material 1 was changed to 9 parts and 202 parts in the production of the magnetic toner particles 1, respectively.

<Manufacture of magnetic toner particles 13 and 14>
Magnetic toner particles 13 and 14 were obtained in the same manner as in the production of the magnetic toner particles 1 except that the prescription amount of the ester wax was changed to 0.47 parts and 50.6 parts, respectively.

<Manufacture of magnetic toner particles 15>
Magnetic toner particles 15 were obtained in the same manner as in the production of magnetic toner particles 1 except that wax mainly composed of polyethylene (maximum value of endothermic peak in DSC 115 ° C.) was used instead of ester wax.

<Manufacture of magnetic toner particles 16>
After adding 451 g of 0.1M Na ₃ PO ₄ aqueous solution to 709 g of ion-exchanged water and heating to 60 ° C., 67.7 g of 1.0M CaCl ₂ aqueous solution was gradually added, and hydrochloric acid was added to adjust the pH of the solution. Was adjusted to about 8.5 to obtain an aqueous medium containing Ca ₃ (PO ₄ ) ₂ .
・ Styrene 80 parts ・ n-butyl acrylate 20 parts ・ unsaturated polyester resin 5 parts ・ negative charge control agent (monoazo dye-based Fe compound) 1.2 parts ・ surface-treated magnetic substance 1 108 parts The mixture was uniformly dispersed and mixed using Mitsui Miike Kako Co., Ltd.). This monomer composition was heated to 60 ° C., and 24 parts of ester wax used in the production of the magnetic toner particles 1 was added and mixed therewith, and the polymerization initiator 2,2′-azobis (2,4- Dimethylvaleronitrile) [t1 / 2 = 140 minutes, 60 ° C.] 7.2 parts and dimethyl-2,2′-azobisisobutyrate [t1 / 2 = 270 minutes, 60 ° C .; t1 / 2 = 80 minutes, 80 ° C.] 2 parts were dissolved.

The polymerizable monomer system was charged into the aqueous medium and granulated by stirring at 10,000 rpm for 15 minutes in a TK homomixer (Special Machine Industries Co., Ltd.) at 60 ° C. in an N ₂ atmosphere. . Thereafter, the mixture was reacted at 60 ° C. for 3 hours while stirring with a paddle stirring blade. Thereafter, the liquid temperature was raised to 80 ° C., and stirring was continued for another hour. Next, in this aqueous suspension, 16 parts of styrene, 4 parts of n-butyl acrylate, 0.4 part of 2,2′-azobis (2,4-dimethylvaleronitrile), 0.1 part of sodium behenate, A mixture of 20 parts of water was added, and the liquid temperature was changed to 80 ° C. and stirring was continued for 6 hours. After completion of the reaction, the suspension was cooled, hydrochloric acid was added to dissolve Ca ₃ (PO ₄ ) ₂ , filtered, washed with water, and dried to obtain magnetic toner particles 16 having a weight average particle diameter of 7.5 μm.

<Manufacture of magnetic toner particles 17>
Styrene / n-butyl acrylate copolymer (weight ratio 80/20) 100 parts Unsaturated polyester resin 5 parts Negative charge control agent (monoazo dye-based Fe compound) 1 part Surface treatment magnetic material 90 parts 10 parts of ester wax used in the production of magnetic toner particles 1 The above materials are mixed in a blender, melt kneaded with a biaxial extruder heated to 110 ° C., and the cooled kneaded product is coarsely pulverized with a hammer mill. The pulverized product was finely pulverized by a turbo mill (manufactured by Turbo Kogyo Co., Ltd.), and the obtained finely pulverized product was classified by wind to obtain black powder 17 having a weight average particle diameter of 7.5 μm.

<Manufacture of magnetic toner particles 18>
Magnetic toner particles 18 were obtained by subjecting the magnetic toner particles 17 to spheronization using an impact surface treatment device (treatment temperature 55 ° C., rotary treatment blade peripheral speed 90 m / sec.).

(B) Manufacture of magnetic toner <Manufacture of magnetic toner 1>
100 parts of magnetic toner particles 1 are treated with hexamethyldisilazane on silica having a number average primary particle size of 12 nm and then treated with silicone oil, and 1 part of hydrophobic silica fine powder having a BET value of 140 m ² / g after treatment. Were mixed with a Henschel mixer (Mitsui Miike Chemical Co., Ltd.) to prepare magnetic toner 1. The formulation of magnetic toner 1 is shown in Table 4 together with the following production examples of magnetic toners 2 to 21 and comparative magnetic toners 1 ′ to 5 ′.

<Manufacture of magnetic toner 2>
Magnetic toner 2 was prepared by mixing 0.6 part of hydrophobic silica fine powder used in the production of magnetic toner 1 with 100 parts of magnetic toner particles 2.
<Manufacture of magnetic toners 3-6>
Magnetic toners 3-6 were prepared by mixing 100 parts of magnetic toner particles 4-7 with 1 part of hydrophobic silica fine powder used in the production of magnetic toner 1.
<Manufacture of magnetic toners 7 and 8>
Magnetic toners 7 and 8 were prepared by mixing 100 parts of magnetic toner particles 8 and 12 with 0.6 part of hydrophobic silica fine powder used in the production of magnetic toner 1.
<Manufacture of magnetic toners 9 and 10>
Magnetic toners 9 and 10 were prepared by mixing 100 parts of magnetic toner particles 13 and 14 with 1 part of hydrophobic silica fine powder used in the production of magnetic toner 1.
<Manufacture of magnetic toner 11>
Magnetic toner 11 was prepared by mixing 0.6 part of hydrophobic silica fine powder used in the production of magnetic toner 1 with 100 parts of magnetic toner particles 15.
<Manufacture of magnetic toner 12>
Magnetic toner 12 was prepared by mixing 100 parts of magnetic toner particles 16 with 1 part of hydrophobic silica fine powder used in the production of magnetic toner 1.
<Manufacture of magnetic toner 13>
Magnetic toner 13 was prepared by mixing 100 parts of magnetic toner particles 18 with 1.0 part of hydrophobic silica fine powder used in the production of magnetic toner 1.
<Manufacture of magnetic toners 14 to 16>
100 parts of magnetic toner particles 1 are treated with hexamethyldisilazane and the surface is treated with 1 part of fine hydrophobic silica powder having a BET value of 200 m ² / g after treatment and iso-butyltrimethoxysilane. 1 part of hydrophobic titanium oxide fine powder with a BET value of 100 m ²² g afterwards or 1 part of hydrophobic alumina fine powder with a BET value of 150 m ² g after treatment with iso-butyltrimethoxysilane Thus, magnetic toners 14 to 16 were prepared.
<Manufacture of magnetic toner 17>
Magnetic toner 17 was prepared by mixing 100 parts of magnetic toner particles 1 with 1 part of hydrophobic silica fine powder used in the production of magnetic toner 1 and 2 parts of conductive fine powder 1.
<Manufacture of magnetic toners 18 to 21>
100 parts of magnetic toner particles 1 are mixed with 1 part of hydrophobic silica fine powder used in the production of magnetic toner 1 and 2 parts of each of conductive fine powders 2 to 5, and magnetic toners 18 to 21 are mixed. Was prepared.

<Manufacture of magnetic toner 1 '>
Magnetic toner 1 ′ was prepared by mixing 100 parts of magnetic toner particles 3 with 0.6 part of hydrophobic silica fine powder used in the production of magnetic toner 1.
<Manufacture of magnetic toner 2 '>
Magnetic toner 2 ′ was prepared by mixing 100 parts of magnetic toner particles 9 with 0.6 part of hydrophobic silica fine powder used in the production of magnetic toner 1.
<Manufacture of magnetic toner 3 '>
Magnetic toner 3 ′ was prepared by mixing 100 parts of magnetic toner particles 10 with 2.0 parts of hydrophobic silica fine powder used in the production of magnetic toner 1.
<Manufacture of magnetic toner 4 '>
Magnetic toner 4 ′ was prepared by mixing 100 parts of magnetic toner particles 11 with 0.6 part of hydrophobic silica fine powder used in the production of magnetic toner 1.
<Manufacture of magnetic toner 5 '>
Magnetic toner 5 'was prepared by mixing 100 parts of magnetic toner particles 17 with 1.0 part of hydrophobic silica fine powder used in the production of magnetic toner 1.

<Example 1>
As an image forming apparatus, LBP-1760 was remodeled, and the same one as shown in FIG. 1 as shown in the above embodiment was used.
First, the following photoreceptor 1 was manufactured as an image carrier used in the examples of the present invention.

<Manufacture of photoreceptor 1>
As a photoreceptor, an aluminum cylinder having a diameter of 30 mm was used as a base. The photosensitive member 1 was prepared by sequentially laminating layers having the structure as shown in FIG.
(1) Conductive coating layer: Mainly composed of a powder of tin oxide and titanium oxide dispersed in a phenolic resin. Film thickness 15 μm.
(2) Undercoat layer: Mainly composed of modified nylon and copolymer nylon. Film thickness 0.6 μm.
(3) Charge generation layer: Mainly composed of an azo pigment having absorption in a long wavelength region dispersed in a butyral resin. Film thickness 0.6 μm.
(4) Charge transport layer: Mainly composed of a hole-transporting triphenylamine compound dissolved in a polycarbonate resin (molecular weight of 20,000 by the Ostwald viscosity method) at a mass ratio of 8:10, and polytetrafluoroethylene powder ( 10% by mass of the average particle size of 0.2 μm) was added to the total solid content and dispersed uniformly. Film thickness 25 μm. The contact angle with water was 95 degrees. The contact angle was measured using pure water, and the device used was Kyowa Interface Science Co., Ltd., contact angle meter CA-X type.

  As the image carrier, the organic photoreceptor (OPC) drum of the photoreceptor 1 obtained above was used. A rubber roller charger in which conductive carbon is dispersed as a primary charging member and coated with nylon resin is brought into contact with this photoreceptor (contact pressure 60 g / cm), and a bias in which an AC voltage of 2.0 kVpp is superimposed on a DC voltage of −700 Vdc. To uniformly charge the surface of the photoconductor. Subsequent to primary charging, an electrostatic latent image is formed by exposing the image portion with laser light. At this time, the dark portion potential Vd = −700 V and the light portion potential VL = −150 V.

The gap between the photosensitive drum and the developing sleeve is 300 μm, and the toner carrier has a resin layer with a layer thickness of about 7 μm and a JIS centerline average roughness (Ra) of 1.0 μm as described below. Using a developing sleeve formed on a cylinder, a developing magnetic pole of 85 mT (850 gauss), a toner regulating member having a thickness of 1.0 mm and a free length of 1.0 mm of a silicone rubber blade of 29.4 N / m (30 g / cm) The contact was made with linear pressure.
-Phenol resin 100 parts-Graphite (average particle diameter of about 7 µm) 90 parts-Carbon black 10 parts Next, a developing bias in which a DC voltage of -500 V, a frequency of 2000 Hz, and an AC voltage of 1600 V between peaks was superimposed was used. The peripheral speed of the developing sleeve was 110% (103 mm / sec) in the forward direction with respect to the peripheral speed of the photosensitive member (94 mm / sec).

Further, a transfer roller as shown in FIG. 4 (made of ethylene-propylene rubber in which conductive carbon is dispersed, the volume resistance value of the conductive elastic layer is 10 ⁸ Ω · cm, the surface rubber hardness is 24 °, the diameter is 20 mm, the contact pressure is 59 N / m (60 g / cm)) was set at a constant speed with respect to the peripheral speed (94 mm / sec) of the photosensitive member in the direction A in FIG. 4, and the transfer bias was set at 1.5 kV DC.
As a fixing method, there was used a fixing device of LBP-1760 which does not have an oil application function and which is fixed by heating and pressing with a heater through a film. At this time, a pressure roller having a fluororesin surface layer was used, and the diameter of the roller was 30 mm. The fixing temperature was set to 180 ° C. and the nip width was set to 7 mm.

First, magnetic toner 1 was used as the magnetic toner. First, it was left to stand at a temperature of 50 ° C. for 3 days. Thereafter, an image printing test was performed with the magnetic toner in an environment of 30 ° C. and 80% RH. As the transfer material, 90 g / m ² paper was used. As a result, the magnetic toner 1 exhibited high transferability in the initial stage, no characters or lines were not transferred out, and a good image without fogging on the non-image area was obtained.
Next, durability was evaluated with an image pattern having a printing rate of 4%. Image evaluation was performed as follows.

  The transfer efficiency is determined by tapering the transfer residual toner on the photoconductor after the solid black image is transferred with a Mylar tape and pasting it on the paper. When the Macbeth concentration of the tape affixed was d, and the Macbeth concentration of the Mylar tape affixed on unused paper was e, the following equation (8) was calculated approximately.

転写効率は９０％以上であれば問題の無い画像である。

If the transfer efficiency is 90% or more, the image has no problem.

Further, the resolving power at the initial stage of durability was evaluated based on the reproducibility of a small-diameter isolated single dot at 600 dpi, which is easy to close due to the latent image electric field and difficult to reproduce.
◎ Very good: Less than 5 defects in 100 ○ Good: 6-10 defects in 100 △ Practical use: 11-20 defects in 100 x Impractical use: Defect in 100 20 or more The fog of the non-image portion was measured using REFECTECTOMER MODEL TC-6DS manufactured by Tokyo Denshoku. A green filter was used as the filter, and the calculation was performed according to the following formula (9). The smaller the value, the less fog.

カブリは、２．０％以下であれば良好な画像である。画像濃度はマクベス濃度計ＲＤ９１８（マクベス社製）で測定した。初期画像濃度は画出し２０枚目の濃度とした。定着オフセット性は、初期から耐久１００枚までの画像サンプルの裏側に発生する汚れを観察し、発生枚数を数えた。

If the fog is 2.0% or less, a good image is obtained. The image density was measured with a Macbeth densitometer RD918 (manufactured by Macbeth). The initial image density was the density on the 20th image. The fixing offset property was determined by observing dirt generated on the back side of the image sample from the initial stage to 100 durability sheets and counting the number of generated sheets.

  The determination of the state of dispersion of the release agent inside the toner particles was made by evaluating the image characteristics and durability after standing at 50 ° C. for 3 days. When the state of dispersion of the release agent is not good, a part of the release agent is exposed to the toner surface by this standing, and the toner performance is deteriorated. The results obtained are shown in Table 5. As can be seen from Table 5, the magnetic toner 1 showed good results up to 2000 printed sheets even in the durability evaluation after standing at 50 ° C. for 3 days.

<Reference Examples 2 and 13 and Examples 3-12 and 14-21>
As the magnetic toner, magnetic toners 2 to 21 were used, and an image printing test and durability evaluation were performed under the same conditions as in Example 1. As a result, there were no problems in the initial image characteristics, and no problem was obtained in any of the 2000 prints. The results are shown in Table 5.

<Comparative Examples 1-5>
The magnetic toners 1 ′ to 5 ′ were used as the magnetic toner, and an image formation test and durability evaluation were performed by the same image forming method as in Example 1. As a result, there was a problem with the image characteristics immediately after being left, and it deteriorated further with the durability test. This is considered to reflect the non-uniform dispersion state of the release agent inside the toner particles. The results are shown in Table 5.

<Example 22>
The toner of the present invention is also applicable to a cleanerless image forming method or a simultaneous development image forming method. First, the following photoreceptor 2 was manufactured as an image carrier used in the examples of the present invention.

<Manufacture of Photoconductor 2>
The photoreceptor is a photoreceptor using an organic photoconductive material for negative charging (hereinafter referred to as an OPC photoreceptor), and an aluminum cylinder having a diameter of 30 mm was used as a base. A layer having a structure as shown in FIG. 6 was sequentially laminated thereon by dip coating to prepare a photoreceptor.
(1) Conductive layer: a conductive particle-dispersed resin layer (tin oxide and titanium oxide) having a thickness of about 20 μm provided to smooth out defects of aluminum cylinders and prevent the occurrence of moire due to reflection of laser exposure. And a powder obtained by dispersing the powder in a phenol resin).
(2) Positive charge injection preventing layer (undercoat layer): Plays a role to prevent the positive charge injected from the aluminum substrate from canceling the negative charge charged on the surface of the photoreceptor, and 10 ⁶ by methoxymethylated nylon. This is a medium resistance layer having a thickness of about 1 μm, the resistance of which is adjusted to about Ω · cm.
(3) Charge generation layer: a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a butyral resin, and generates positive and negative charge pairs upon receiving laser exposure.
(4) Charge transport layer: a layer having a thickness of about 25 μm in which a hydrazone compound is dispersed in a polycarbonate resin, and is a P-type semiconductor. Accordingly, negative charges charged on the surface of the photoreceptor cannot move through this layer, and only positive charges generated in the charge generation layer can be transported to the surface of the photoreceptor.
(5) Charge injection layer: photocurable acrylic resin, conductive tin oxide ultrafine particles and particle size of about 0.2
5 μm tetrafluoroethylene resin particles are dispersed. Specifically, tin oxide particles having a particle size of about 0.03 μm, doped with antimony and having a low resistance, are 100% by mass with respect to the resin, 20% by mass of polytetrafluoroethylene resin particles, and 1. 2% by mass dispersed. The coating solution thus prepared was applied to a thickness of about 2.5 μm by spray coating, and cured by light irradiation to form a charge injection layer.
The surface resistance of the obtained photoreceptor was 5 × 10 ¹² Ω · cm, and the contact angle of the photoreceptor surface with water was 102 °.

Next, a manufacturing example of the charging member used in the embodiment of the present invention will be described.
<Manufacture of charging member 1>
A SUS roller having a diameter of 6 mm and a length of 264 mm is used as a core, and a medium-resistance foamed urethane layer is formed on the core as a roller. Further, the shape and surface properties were adjusted by cutting and polishing to prepare a charging roller having a diameter of 12 mm and a length of 234 mm as a flexible member. The obtained charging roller had a resistance of 10 ⁵ Ω · cm and a hardness of 30 degrees in Asker C hardness. When the surface of the charging roller was observed with a scanning electron microscope, the average cell diameter was about 90 μm and the porosity was 55%.

FIG. 5 is a schematic structural model diagram of an example of an image forming apparatus according to the present invention.
The image forming apparatus of this example is a laser printer (recording apparatus) of a development simultaneous cleaning process (cleanerless system) using a transfer type electrophotographic process. It has a process cartridge from which a cleaning unit having a cleaning member such as a cleaning blade is removed, uses magnetic toner as a developer, and is arranged so that the toner layer on the toner carrier and the image carrier are not in contact with each other. It is an example of non-contact development.
(1) Overall schematic configuration of the printer of the present example The rotating drum type OPC photosensitive member 21 of the photosensitive member 2 obtained above as an image carrier is a peripheral speed (process speed) of 94 mm / sec in the X direction of the arrow. ).
The charging roller 22 serving as the charging member 1 as a contact charging member is disposed in pressure contact with the photoreceptor 21 with a predetermined pressing force against elasticity. Reference numeral n denotes a charging contact portion that is a contact portion between the photosensitive member 21 and the charging roller 22. In this example, the charging roller 22 is rotationally driven at a peripheral speed of 100% in a facing direction (a direction opposite to the moving direction of the photosensitive member surface = an arrow Y direction) at a charging contact portion n that is a contact surface with the photosensitive member 21. ing. That is, the surface of the charging roller 22 as a contact charging member has a speed difference with respect to the surface of the photoreceptor 21. Further, the conductive fine powder 1 was applied to the surface of the charging roller 22 so that the amount applied was uniform at about 1 × 10 ⁴ pieces / mm ² .
Further, a DC voltage of -700 V was applied as a charging bias to the cored bar 22a of the charging roller 22 from a charging bias application power source. In this example, the surface of the photosensitive member 21 is uniformly charged by a direct injection charging method at a potential (−680 V) substantially equal to the voltage applied to the charging roller 22. This will be described later.

A laser beam scanner (exposure device) 23 including a laser diode, a polygon mirror, etc. as exposure means outputs a laser beam whose intensity is modulated in accordance with a time-series electric digital pixel signal of target image information. Then, the uniformly charged surface of the photosensitive member 21 is scanned and exposed. By this scanning exposure, an electrostatic latent image corresponding to target image information is formed on the surface of the rotating photosensitive member 21.
The electrostatic latent image on the surface of the photoreceptor 21 is developed as a toner image by the developing device 24.
The developing device 24 of this example is a non-contact type reversal developing device using the magnetic toner 17 used in Example 17 as a developer. As described above, the conductive fine powder 1 is externally added to the magnetic toner 17.

The gap between the photosensitive drum 21 and the developing sleeve 24a as the toner carrier is 310 μm, and the developing sleeve 24a has a layer thickness of about 7 μm and a JIS centerline average roughness (Ra
) Using a developing sleeve in which a 1.0 μm resin layer is formed on an aluminum cylinder having a diameter of 16 mm with a blasted surface, a magnet roll having a developing magnetic pole of 90 mT (900 gauss) is included, and a thickness 1 as a toner layer thickness regulating member An elastic blade 24c made of urethane having a length of 0.0 mm and a free length of 1.5 mm was brought into contact with a linear pressure of 29.4 N / m (30 g / cm).
・ Phenolic resin 100 parts ・ Graphite (average particle size of about 7 μm) 90 parts ・ Carbon black 10 parts Also, in the developing part a (developing area part) opposite to the photosensitive member 21, the rotating direction of the photosensitive member 21 and the order In the direction (arrow W direction), the photosensitive member 21 is rotated at a peripheral speed of 120% of the peripheral speed.

The developing sleeve 24a is coated with a thin layer of toner by an elastic blade 24c. The layer thickness of the toner with respect to the developing sleeve 24a is regulated by the elastic blade 24c, and an electric charge is applied. At this time, the amount of toner coated on the developing sleeve 24a was 16 g / m ² .
The toner coated on the developing sleeve 24a is conveyed to the developing portion a, which is a facing portion between the photosensitive member 21 and the developing sleeve 24a, by the rotation of the sleeve 24a.
A developing bias voltage is applied to the developing sleeve 24a from a developing bias applying power source. The development bias voltage is obtained by superimposing a DC voltage of −420 V and a rectangular AC voltage having a frequency of 1600 Hz and a peak-to-peak voltage of 1500 V (electric field strength of 5 × 10 ⁶ V / m) between the developing sleeve 24 a and the photosensitive member 21. A one-component jumping development was performed at a.

  A medium-resistance transfer roller 25 as a contact transfer unit is brought into pressure contact with the photosensitive member 21 with a linear pressure of 98 N / m (100 g / cm) to form a transfer nip portion b. A transfer material P as a recording medium is fed to the transfer nip b from a paper feed unit (not shown) at a predetermined timing, and a predetermined transfer bias voltage is applied to the transfer roller 25 from a transfer bias application power source. Then, the toner image on the photosensitive member 21 side is sequentially transferred onto the surface of the transfer material P fed to the transfer nip portion b.

In this example, a roller resistance value of 5 × 10 ⁸ Ω · cm was used, and transfer was performed by applying a DC voltage of + 3000V. That is, the transfer material P introduced into the transfer nip part b is nipped and conveyed by the transfer nip part b, and the toner image formed and supported on the surface of the photosensitive member 21 on the surface side is successively subjected to electrostatic force and pressing force. Will be transcribed.
Reference numeral 26 denotes a fixing device such as a heat fixing method. The transfer material P that has been fed to the transfer nip portion b and has received the transfer of the toner image on the photoconductor 21 side is separated from the surface of the photoconductor 21 and introduced into the fixing device 26, and the toner image is fixed and the image is received. It is discharged out of the apparatus as a formed product (print, copy).

  In the printer of this example, the cleaning unit is removed, and the residual toner remaining on the surface of the photoconductor 21 after the transfer of the toner image onto the transfer material P is not removed by the cleaner, and is charged as the photoconductor 21 rotates. The developing unit a is reached via the contact part n and is simultaneously cleaned (collected) in the developing device 24.

  In the printer of this example, the three process devices including the photosensitive member 21, the charging roller 22, and the developing device 24 are collectively configured as an image forming apparatus and a process cartridge 27 that are detachable from the printer main body. The combination of the image forming apparatus and the process equipment to be a process cartridge is not limited to the above, and is arbitrary. Reference numeral 28 denotes an attachment / detachment guide / holding member for the process cartridge.

(2) Behavior of conductive fine powder in this embodiment The conductive fine powder mixed in the magnetic toner in the developing device 24 is used together with the toner when the electrostatic latent image on the photosensitive member 21 side is developed by the developing device 24. An appropriate amount shifts to the photoconductor 21 side.
The toner image on the photosensitive member 21 is attracted to the transfer material P, which is a recording medium, under the influence of the transfer bias at the transfer nip portion b and actively transfers. However, the conductive fine powder on the photosensitive member 21 is conductive. As a result, it does not actively transfer to the transfer material P side, and remains substantially adhered and held on the photoreceptor 21.

  In the present invention, since the image forming apparatus does not have a cleaning step, the residual transfer toner remaining on the surface of the photoconductor 21 after transfer and the above-described residual conductive fine powder are charged by the photoconductor 21 and a contact charging member. It is carried as it is by the movement of the surface of the photosensitive member 21 to the charging contact portion n which is the contact portion of the roller 22, and adheres to or mixes with the charging roller 22. Therefore, direct injection charging of the photosensitive member 21 is performed in a state where the conductive fine powder exists in the charging contact portion n between the photosensitive member 21 and the charging roller 22.

  Due to the presence of the conductive fine powder, even when the toner adheres to and mixes with the charging roller 22, the contact property and contact resistance of the charging roller 22 to the photosensitive member 21 can be maintained. 21 direct injection charging can be performed. That is, the charging roller 22 comes into close contact with the photosensitive member 21 through the conductive fine powder, and the conductive fine powder existing on the mutual contact surface between the charging roller 22 and the photosensitive member 21 slides on the surface of the photosensitive member 21 without a gap. By rubbing, the charging of the photosensitive member 21 by the charging roller 22 is dominated by stable and safe direct injection charging without using the discharge phenomenon due to the presence of the conductive fine powder, which is not obtained by conventional roller charging or the like. Charging efficiency is obtained, and a potential almost equal to the voltage applied to the charging roller 22 can be applied to the photoconductor 21.

  Further, the transfer residual toner adhering to or mixed in the charging roller 22 is gradually discharged from the charging roller 22 onto the photosensitive member 21, reaches the developing unit along with the movement of the surface of the photosensitive member 21, and is simultaneously cleaned (collected) by the developing unit. .

  In the simultaneous development cleaning, the toner remaining on the photosensitive member 21 after the transfer is developed in the subsequent image forming process, that is, the photosensitive member is continuously charged and exposed to form a latent image, and the latent image is developed. It is recovered by the fog removal bias Vde of the developing device, that is, the potential difference between the DC voltage applied to the developing device and the surface potential of the photosensitive member. In the case of reversal development as in the printer in this embodiment, this simultaneous development cleaning is performed by using an electric field for collecting toner from the dark portion potential of the photosensitive member to the developing sleeve by the developing bias and from the developing sleeve to the bright portion potential of the photosensitive member. This is done by the action of an electric field that adheres.

  Further, when the image forming apparatus is operated, the conductive fine powder mixed in the toner of the developing device 24 is transferred to the surface of the photosensitive member 21 at the developing portion a, and the transfer nip portion b is moved by the movement of the image carrying surface. Then, the particles are carried to the charging contact portion n and new particles are continuously supplied to the charging contact portion n, so that the conductive fine powder is reduced or dropped in the charging contact portion n. Even when the deterioration of the charging property is prevented, the charging property is prevented from being lowered, and good charging property is stably maintained.

  Thus, in the image forming apparatus of the contact charging method, the transfer method, and the toner recycling process, the simple charging roller 22 is used as the contact charging member, and the applied roller 22 can be applied at a low applied voltage regardless of contamination of the transfer roller with the transfer residual toner. Ozone-less direct injection charging can be maintained stably over a long period of time, uniform chargeability can be imparted, and there is no obstruction caused by ozone products, no obstruction due to poor charging, etc., simple configuration, low-cost image formation A device can be obtained.

Further, as described above, the conductive fine powder needs to have an electric resistance value of 1 × 10 ⁹ Ω · cm or less in order not to impair the chargeability. Therefore, when using a contact developing device in which the toner directly contacts the photosensitive member 21 in the developing section a, through the conductive fine powder in the toner,
Charges are injected into the photosensitive member 21 by the developing bias, and image fogging occurs.
However, in this example, since the developing device is a non-contact type developing device, a developing bias is not injected into the photosensitive member 21, and a good image can be obtained. Further, since no charge is injected into the photosensitive member 21 in the developing portion a, it is possible to give a high potential difference between the developing sleeve 24a and the photosensitive member 21, such as an alternating bias, and the conductive fine powder is uniformly developed. Therefore, the conductive fine powder is uniformly applied to the surface of the photosensitive member 21 and is uniformly contacted at the charging portion, so that good chargeability can be obtained and a good image can be obtained.
By interposing the conductive fine powder in the charging contact portion n between the charging roller 22 and the photosensitive member 21, the lubricating effect (friction reduction effect) of the conductive fine powder is provided between the charging roller 22 and the photosensitive member 21. It is possible to easily and effectively provide a speed difference.

  By providing a speed difference between the charging roller 22 and the photosensitive member 21, the chance of the conductive fine powder contacting the photosensitive member 21 at the charging contact portion n of the charging roller 22 and the photosensitive member 21 is significantly increased. High contactability can be obtained and good direct injection charging is possible. In this embodiment, the charging roller 22 is driven to rotate, and the rotation direction of the charging roller 22 rotates in the direction opposite to the moving direction of the surface of the photosensitive member 21, so that the photosensitive member 21 is carried to the charging contact portion n. The upper transfer residual toner is temporarily collected by the charging roller 22 to obtain an effect of leveling. That is, it is possible to preferentially perform direct injection charging by once separating the transfer residual toner on the photosensitive member 21 by reverse rotation and performing charging.

  Further, in this embodiment, due to the lubrication effect of the fine powder by interposing an appropriate amount of the conductive fine powder in the charging contact portion n between the photosensitive drum 21 as the image carrier and the charging roller 22 as the contact charging member. It is easy to reduce the friction between the charging roller 22 and the photosensitive drum 21 and to rotate the charging roller 22 with respect to the photosensitive drum 21 with a speed difference. That is, the driving torque is reduced, and the charging roller 22 and the photosensitive drum 21 can be prevented from being scraped or scratched. Furthermore, sufficient charging performance can be obtained by increasing the contact opportunity with the particles. Further, there is no adverse effect on the image formation due to the removal of the conductive fine powder from the charging roller 22.

(3) Evaluation In this example, the toner cartridge was filled with 200 g of the magnetic toner 17 that was allowed to stand at 50 ° C. for 3 days, and an image formation test was performed in an environment of 30 ° C. and 80% RH. As the photoreceptor, a photoreceptor having a volume resistance of 5 × 10 ¹² Ω · cm of the outermost surface layer of the photoreceptor 2 was used, and 90 g / m ² of paper was used as the transfer material. In the initial image characteristics, fog due to poor charging was not observed, and a good image density with high resolution was obtained. At this time, the photoreceptor potential after direct injection charging was -670 V with respect to the applied charging bias of -690 V. Next, durability was evaluated with an image pattern having a printing rate of 4%. As a result, image defects caused by charging failure did not occur until after 2000 intermittent printings, and good direct injection charging properties were obtained. The photoreceptor potential after direct injection charging after intermittent printing of 2,000 sheets is -655 V with respect to the applied charging bias of -690 V, and the chargeability deterioration from the initial stage is as small as 15 V. There was no decline. The results obtained are shown in Table 6. As can be seen from Table 6, when the magnetic toner 17 was used, even in the cleanerless image forming method of the present invention, the selective developability was small, and good durability was exhibited up to 2000 sheets.

<Examples 23 to 26>
Durability was evaluated under the same conditions as in Example 22 using magnetic toners 18-21. The results obtained are shown in Table 6. As can be seen from Table 6, there was little selective developability in any of the cleanerless image forming methods, and good durability was exhibited up to 2000 durability sheets.

100: Photosensitive drum (image carrier)
102: Development sleeve (toner carrier)
103: Elastic blade 114: Transfer roller 116: Cleaner 117: Primary charging roller 121: Laser beam scanner 124: Register roller 125: Conveying belt 126: Fixing device 140: Developer 141: Stirring member P: Transfer material 34: Transfer roller 34a: cored bar 34b: conductive elastic layer 21: photoconductor 22: charging roller 22a: cored bar 23: laser beam scanner 24: developing device 24a: developing sleeve 24b: stirring member 24c: elastic blade (toner layer regulating member)
25: transfer roller 26: fixing device 26a: heater 26b: fixing film 26c: pressure roller 27: process cartridge 28: cartridge holding member 11: aluminum substrate 12: conductive layer 13: injection preventing layer 14: charge generation layer 15: charge Transport layer 16: Charge injection layer 16a: Conductive particles (conductive filler)

Claims (3)

A method for producing a magnetic toner having an inorganic fine powder on the surface of a magnetic toner particle containing at least a binder resin, a release agent and a magnetic substance,
The magnetic toner particles are produced in an aqueous medium,
The magnetic body is made of magnetic iron oxide, and the magnetic iron oxide is produced by oxidizing ferrous hydroxide in water, and after the oxidation reaction, without undergoing a drying step, a silane coupling agent Alternatively, a method for producing a magnetic toner, wherein the surface is treated with a titanium coupling agent.   The method of manufacturing a magnetic toner according to claim 1, wherein the toner particles are manufactured by a suspension polymerization method.   The method for producing a magnetic toner according to claim 1, wherein the magnetic material has a volume average particle diameter of 0.05 to 0.3 μm.

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