JP4095516B2 - Developer - Google Patents

Description

  The present invention relates to an electrophotographic image forming method for developing an electrostatic image and a developer used in a toner jet.

  Conventionally, as an image forming method, many methods such as an electrostatic recording method, a magnetic recording method, and a toner jet method are known. For example, electrophotography generally forms an electrical latent image on an image carrier such as a photoconductor using a photoconductive material by various means, and then develops the latent image with toner. A visible toner image is formed, and the toner image is transferred to a recording medium such as paper as necessary, and then the toner image is fixed on the recording medium by heat, pressure, or the like to obtain an image.

  In general, in such a method, after the transfer, the toner remaining without being transferred onto the recording medium on the image carrier is cleaned by various methods and stored in a waste toner container as waste toner. Repeated image forming methods have been used.

  On the other hand, as a system without waste toner, a technique called simultaneous development cleaning or cleanerless has been proposed. Patent Documents 1 to 8 and the like disclose technologies related to this cleanerless, but no detailed and specific configuration of the entire system is mentioned.

  In the simultaneous development cleaning that essentially does not have a cleaning device, it has become essential to rub the surface of the image carrier with toner and the toner carrier. Therefore, as a preferred development method, toner or toner is applied to the image carrier. Many contact development methods that come into contact 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 the cleaner-less process using the contact development method causes toner deterioration, toner carrier surface deterioration, image carrier surface deterioration or wear, etc. due to long-term use, and is a sufficient solution to durability characteristics. Not done.

  On the other hand, a direct injection charging mechanism has been proposed as a new environment-friendly new technique that enables simultaneous development cleaning not only in a contact development system but also in a non-contact development system and does not generate active ions such as ozone.

  This direct injection charging mechanism will be briefly described.

  The direct injection charging mechanism is a mechanism in which the surface of the charged body is charged by directly injecting charges 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 it is direct injection charging, the number of contact points and the contact area of the contact charging member to the member to be charged greatly affect the charging property. Therefore, in order to take a configuration in which the charged body is contacted more frequently, a configuration is required in which the contact charging member has a denser contact point, and the contact time with the charged body is maintained longer.

  Among them, as a method for increasing the density of the contact points between the charging member and the charged body, there is a high efficiency by providing conductive charge-promoting particles at the contact portion between the charging member and the charged body, so-called image carrier. A method for ensuring a good injection chargeability has been proposed.

  For example, in Patent Document 9, a developer containing toner particles and electrically conductive charge accelerating particles having a particle size equal to or smaller than ½ of the toner particle size is applied to a developing and cleaning image forming method using a direct injection charging mechanism. An image forming apparatus is disclosed. According to this proposal, it is possible to obtain a developing and cleaning image forming apparatus which 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.

  Further, according to Patent Document 10, conductive fine particles are externally added to the toner, and the conductive fine particles contained in the toner are developed at least at the contact portion between the flexible contact charging member and the image carrier. Development and cleaning that provides a good image that does not cause poor charging and shading of image exposure by adhering to the image carrier in the process and remaining on the image carrier after the transfer process. An image forming apparatus is disclosed.

  In Patent Document 11, a developer containing conductive fine particles having a particle size of 1/50 to 1/2 of the toner particle size is applied to a developing and cleaning image forming method using a direct injection charging mechanism. An image forming apparatus in which fine particles have a transfer promoting effect is disclosed.

  Furthermore, in Patent Document 12, the particle diameter of the conductive fine powder is set to 10 nm to 50 μm in order to make the particle diameter of the conductive fine particles equal to or smaller than the size of one constituent pixel and to obtain better charging uniformity. It is described to do.

  In Patent Document 13, in consideration of human visual characteristics, the conductive fine particles may be about 5 μm or less, preferably 20 nm to 5 μm, in order to make it difficult to visually recognize the influence of the poorly charged portion on the image. Are listed.

  Further, according to Patent Document 14, by setting the particle size of the conductive fine particles to be equal to or smaller than the toner particle size, the development of the toner is inhibited during development, or the development bias is prevented from leaking through the conductive fine particles. By eliminating the defects in the image and setting the particle size of the conductive fine particles to be larger than 0.1 μm, the adverse effect of shielding the exposure light by embedding the conductive fine particles in the image bearing member can be solved. A developing and cleaning image forming method using a direct injection charging mechanism for realizing recording is described.

  Patent Document 15 discloses a technique for improving the image characteristics as well as the direct injection charging property by strictly controlling the particle size distribution of the developer containing the conductive fine powder.

  On the other hand, many methods for adding conductive fine powder as an external additive have been proposed. For example, carbon black as a conductive fine powder adheres to or adheres to the toner surface for the purpose of imparting conductivity to the toner, or for suppressing excessive charging of the toner and making the tribo distribution uniform. It is widely used as an external additive. Further, Patent Documents 16 to 18 disclose that conductive fine powders of tin oxide, zinc oxide, and titanium oxide are externally added to the high-resistance magnetic toner, respectively. In Patent Document 19, conductive property powder such as iron oxide, iron powder, and ferrite is added to high resistance magnetic toner, and charge induction to the magnetic toner is promoted in the conductive magnetic powder so that developability and transferability are achieved. Toners that satisfy both requirements have been proposed. Furthermore, Patent Documents 20 to 23 disclose that graphite, magnetite, polypyrrole conductive powder, and polyaniline conductive powder are added to the toner, and it is known that a wide variety of conductive fine powders are added to the toner. It has been.

  On the other hand, many techniques for adding two types of external additives are also disclosed. Patent Documents 24 to 26 propose a technique for improving the durability stability and fluidity of a toner by adding two types of external additives having different particle diameters. However, in the simultaneous development cleaning or cleanerless process using the contact development method, sufficient solutions have been made to durability characteristics such as toner deterioration, toner carrier surface degradation, image carrier surface degradation or wear due to long-term use. However, there is room for improvement.

  Furthermore, in Patent Documents 27 to 31, although the preferred particle size of the conductive fine powder is described to some extent, the particle size distribution or constituent elements are not described. There is room for improvement.

  Also in Patent Document 32, sufficient performance is not always obtained, and it is necessary to view the material on a different scale from the past, and there is still room for improvement.

  In addition, these proposals are described on the assumption that the surface of the charging member is not contaminated, and the charging member is contaminated due to various pattern printing or the main body stop due to sudden abnormality. Considering that this is an unavoidable reality, it is necessary to promptly propose a direct injection charging mechanism that can withstand a certain amount of contamination of the charging member.

  On the other hand, in Patent Document 33, an AC voltage is applied to the charging member that is contaminated by the transfer residual toner during image recording, thereby eliminating the contaminated toner on the surface of the photoconductor, thereby providing good chargeability. An image recording apparatus for maintaining is proposed.

  However, this technique is also based on the idea of keeping the charging member surface contamination level with the transfer residual toner low and maintaining good chargeability. When the charging member surface is contaminated in an unusual use situation. The image quality is greatly impaired, and in some cases, the printer main body may be damaged.

  In addition, when conductive fine particles are added as an external additive to the toner to improve the image characteristics, the additive is often selected mainly focusing on the average particle diameter. However, considering the interaction between the toner particles and these conductive fine particles, the density of the contact points between them is actually significant and, like the direct injection charging mechanism, has a great influence on the image characteristics. However, there are few examples that have been examined in detail in this regard.

JP 59-133573 A JP-A-62-203182 JP-A-63-133179 JP-A 64-20587 Japanese Patent Laid-Open No. 2-302772 JP-A-5-2289 Japanese Patent Laid-Open No. 5-53482 JP-A-5-61383 JP-A-10-307456 JP-A-10-307456 Japanese Patent Laid-Open No. 10-307421 JP-A-10-307455 Japanese Patent Laid-Open No. 10-307457 JP-A-10-307458 JP 2001-235891 A JP 57-151952 A JP 59-168458 A JP 60-69660 A JP-A-56-142540 JP-A 61-275864 JP-A-62-258472 Japanese Patent Laid-Open No. 61-141452 Japanese Patent Laid-Open No. 02-120865 JP-A-2-45188 Japanese Patent No. 2893147 Japanese Patent No. 2754618 JP-A-10-307456 Japanese Patent Laid-Open No. 10-307421 JP-A-10-307455 Japanese Patent Laid-Open No. 10-307457 JP-A-10-307458 JP 2001-235891 A JP-A-11-149205

  An object of the present invention is to provide a developer capable of obtaining a good image without causing poor charging even when the developer is repeatedly used over a long period of time. In addition, when used in an image forming method including a contact charging step, a direct injection charging mechanism is used that substantially does not generate discharge products such as ozone and that can uniformly charge an image carrier with a low applied voltage. It is an object of the present invention to provide a developer that can uniformly perform uniform charging with a simple structure.

  In order to solve the above-mentioned problems, the present inventor has the following constitution of the developer.

That is, the present invention relates to a developer having at least toner particles containing a binder resin and a colorant, an inorganic fine powder, and a conductive fine powder.
When the wettability of the developer to a methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 80% is in the range of 35 to 80% by volume,
The inorganic fine powder contains at least silica treated with silicone oil,
The volume average particle diameter Da of the conductive fine powder and the number average particle diameter Db of the primary particles of the inorganic fine powder satisfy the following formula (1):
Da ≧ 10 Db (1)
The present invention relates to a developer characterized in that the release rate a of the conductive fine powder is 50 % to 95% and the release rate b of the inorganic fine powder is 0.1% to 3 %.

  In the present invention, when the wettability of the developer to a methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 10% is within the range of 40 to 85% by volume. It is preferable that

  Further, in the present invention, when the wettability of the developer to a methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 80% is C80, and the transmittance is 10 When the methanol concentration at% is C10, it is preferably within the range of the following formula (2).

      0 <C10-C80 ≦ 10 (2)

  In the present invention, it is preferable that the conductive fine powder is present as an aggregate and the volume average particle diameter thereof is 0.1 to 4 μm.

  In the present invention, the surface of the conductive fine powder is hydrophobized with at least one hydrophobic treatment agent selected from silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, and silane coupling agents. Preferably it has been treated.

  In the present invention, the content of the conductive fine powder is preferably 0.1 to 5.0% by mass of the whole developer.

In the present invention, the resistance of the conductive fine powder is preferably 10 ⁹ Ω · cm or less.

In the present invention, the resistance of the conductive fine powder is preferably 10 ⁶ Ω · cm or less.

  In the present invention, the conductive fine powder preferably contains at least one oxide selected from zinc oxide, tin oxide, and titanium oxide.

  In the present invention, the content of the inorganic fine powder is preferably 0.1 to 3.0% by mass of the whole developer.

  In the present invention, the inorganic fine powder is preferably treated with at least a silane compound and silicone oil.

  In the present invention, the number average particle diameter Db of the primary particles of the inorganic fine powder is preferably 4 to 80 nm.

  In the present invention, the developer preferably has a weight average particle diameter of 3 μm or more and 12 μm or less.

  Further, the developer of the present invention is preferably produced by adding and mixing inorganic fine powder and then adding conductive fine powder.

  According to the present invention, when used in an image forming method including a contact charging process, there is substantially no generation of discharge products such as ozone, and direct injection charging that can obtain uniform image carrier charging at a low applied voltage. Uniform charging using the mechanism can be performed uniformly with a simple structure, and even when the developer is used repeatedly over a long period of time, a good image can be obtained without causing charging failure.

  In the developer having at least toner particles containing a binder resin and a colorant, an inorganic fine powder, and a conductive fine powder, the present inventors have developed an inorganic fine powder and a conductive material having a specific relationship in particle size. By controlling the release rate of the conductive fine powder from the developer, when used in an image forming method including a contact charging step, there is substantially no generation of discharge products such as ozone, and uniform at a low applied voltage. Uniform charging using a direct injection charging mechanism that can charge the image bearing member can be performed uniformly with a simple configuration, and even when the developer is used repeatedly over a long period of time, a good image can be obtained without causing charging failure. It was found that it was obtained.

  Further, by using the developer of the present invention in the above image forming method, toner particles adhering to or mixing in the contact charging member as transfer residue or fog are reduced, and the supply of the conductive fine powder to the contact charging member is promoted. Therefore, it is possible to improve the uniform chargeability and to achieve an image forming method by high-quality contact charging that can be reproduced finely up to a halftone of a graphic image.

  In addition, the developer of the present invention, when used in an image forming method including a development and cleaning process, does not cause poor transfer residual toner collection or image defects due to uniform charging or inhibition of latent image formation, and reduces the amount of waste toner. A developing and cleaning image forming method that can be greatly reduced and is advantageous for downsizing at low cost is possible. Furthermore, the developer of the present invention enables a developing and cleaning image forming method having reduced durability and excellent durability.

  The developer of the present invention is characterized in that the release rate a of the conductive fine powder is 40% to 95%, and the release rate b of the inorganic fine powder is 0.1% to 5%.

  The developer having the above characteristics will be briefly described below together with the behavior during image formation.

  The developer of the present invention is a developer having at least toner particles containing a binder resin and a colorant, an inorganic fine powder, and a conductive fine powder. The characteristic fine powder has a specific release rate. When the electrostatic latent image formed on the image carrier is developed, an appropriate amount of the conductive fine powder contained in the developer is transferred from the developer carrier to the image carrier. The toner image formed on the image carrier by developing the electrostatic latent image is transferred to a transfer material such as paper in the transfer process. At this time, a part of the conductive fine powder on the image carrier also adheres to the transfer material, but the rest remains attached and held on the image carrier.

  When image formation is repeatedly performed on the image carrier, a well-known cleaning process performed between the transfer process and the charging process, that is, the developer component adhered and held on the image carrier is left on the image carrier. In the image forming method that does not include the step of removing from the toner, the toner particles remaining on the surface of the image carrier after transfer (hereinafter referred to as “transfer residual toner particles”) and the remaining conductive fine powder are contained in the image carrier. As the image carrying surface (hereinafter referred to as “image carrying surface”) moves, it is carried to the charging unit.

  When a contact charging member is used for charging the image carrier, the conductive fine powder is carried to a charging part, which is a nip formed by contact between the image carrier and the contact charging member, and is attached to the contact charging member. Mixed. Therefore, contact charging of the image carrier is performed with the conductive fine powder interposed in the nip portion.

  The conductive charging powder adheres to and mixes with the contact charging member, and the contact charging member is contaminated due to the adhesion and mixing of residual toner particles due to the conductive fine powder intervening in the charging portion. Since the resistance of the member can be maintained, the image carrier can be favorably charged by the contact charging member. If a sufficient amount of conductive fine powder is not present in the charged portion of the contact charging member, the charge of the image carrier easily decreases due to adhesion and mixing of the transfer residual toner particles to the contact charging member, resulting in image smearing. It is easy to produce.

  Further, by carrying the conductive fine powder positively in the nip formed by the contact between the image carrier and the contact charging member, it is possible to maintain close contact and contact resistance of the contact charging member to the image carrier. Therefore, direct injection charging of the image carrier by the contact charging member can be performed satisfactorily.

  The transfer residual toner particles pass through the charging portion or are gradually discharged from the contact charging member onto the image carrier, and reach the developing portion as the image carrying surface moves. Here, in the image forming method including the development and cleaning process, the development and cleaning, that is, the collection of the transfer residual toner particles is performed in the development process. Further, the conductive fine powder that remains adhered and held on the image carrier after the transfer step also reaches the developing portion along with the movement of the image carrying surface, like the transfer residual toner particles.

  That is, the conductive fine powder is present on the image carrier together with the transfer residual toner particles, and the transfer residual toner particles are collected in the development process. When the transfer residual toner particles are collected using a development bias electric field in the development process, the transfer residual toner particles are collected by the development bias electric field, whereas the conductive fine powder on the image carrier is It is difficult to be recovered because it is conductive. For this reason, a part of the conductive fine powder is recovered, but the rest remains attached to the image carrier.

  According to the study by the present inventors, the presence of the conductive fine powder that is difficult to be collected in the development step on the image carrier as described above is effective in improving the recoverability of the transfer residual toner particles on the image carrier. Was found to be obtained. In other words, the conductive fine powder on the image carrier acts as an auxiliary agent for collecting the residual toner particles on the image carrier, further ensuring the recovery of the residual toner particles in the development process, and collecting the residual toner particles. Image defects such as positive ghosts and fogging due to defects can be effectively prevented.

  Conventionally, most of the purpose of externally adding conductive fine powder to the developer is to control the triboelectric chargeability of the toner particles by attaching the conductive fine powder to the surface of the toner particles. The detached conductive fine powder has been treated as an adverse effect that causes a change or deterioration in developer characteristics or deterioration of the image carrier.

  In contrast, in the developer of the present invention, by controlling the particle size of the conductive fine powder and the inorganic fine powder, the conductive fine powder is actively released from the toner particle surface without releasing the inorganic fine powder. The above-described effects can be obtained by supplying the toner onto the image carrier, and at least the residual toner particles on the image carrier after the transfer process are few, and the conductive material that is free from the toner particles and remains on the image carrier. This is different from external addition of conductive fine powder to a developer, which has been studied in the past, in that the above-mentioned effects can be obtained more favorably because of the large amount of fine powder. That is, the developer of the present invention has an excellent effect in an image forming method including a contact charging step, an image forming method including a developing and cleaning step, or an image forming method including both of these steps.

  In the developer of the present invention, the conductive fine powder is easily released from the surface of the toner particles, and the conductive fine powder is formed on the image carrier after the transfer with the image carrier and the contact charging member in contact with each other. By carrying and interposing it in the charging portion, which is a nip portion, the chargeability of the image carrier is improved, charging failure is prevented, and stable and uniform charging is possible. Further, since the conductive fine powder is present on the image carrier in the development process, the conductive fine powder serves as a recovery aid for the transfer residual toner particles on the image carrier, and the recovery of the transfer residual toner particles in the development process. Therefore, image defects such as positive ghosts and fogging due to poor collection of residual toner particles can be effectively prevented.

  In the present invention, the conductive fine powder that adheres to the toner particle surface and behaves together with the toner particle (that is, the conductive fine powder that does not release from the toner particle surface) is an image bearing member in which the developer of the present invention is effective. It does not contribute to the promotion of chargeability and the improvement of development and cleaning performance. For this reason, toner particles having conductive fine powder strongly adhered to the surface have reduced triboelectric chargeability, resulting in lower developability, lower transferable toner particle recoverability during development and cleaning, and lower transferability due to lower transferability. Increasing the amount of toner may cause uniform charging or obstructing latent image formation.

According to the inventors' investigation on the effect of promoting the chargeability of the image carrier and the development and cleaning properties, the conductive fine powder and the inorganic fine powder are separated from the toner particles, that is, the conductive fine powder. The liberation rate a of the inorganic fine powder and the liberation rate b of the inorganic fine powder are: liberation rate b <release rate a (more preferably 20b <a)
It is better to control so as to satisfy In this way, by controlling the free state of the conductive fine powder and inorganic fine powder on the surface of the toner particles, the conductive fine powder passes through the transferred image carrier, and the image carrier and the contact charging member are connected. It is carried to the charging part, which is a nip part formed by contact, and by interposing the conductive fine powder, the charging property of the image carrier is improved, the occurrence of charging failure is prevented, and a stable and uniform one is obtained. Enables electrification. Further, if the conductive fine powder is present on the image carrier in the development step and the inorganic fine powder is appropriately adhered on the surface of the toner particles, the conductive fine powder is transferred to the toner remaining on the image carrier. It acts as a particle recovery aid, and the rising speed of recharged residual toner particles during recharging is faster, which ensures more reliable recovery of the residual toner particles in the development process, resulting in poor recovery of residual toner particles. Image defects such as positive ghost and fog can be effectively prevented.

  Even if image formation is repeated over a long period of time, the conductive fine powder newly moves to the image carrying surface in the development process, and together with the conductive fine powder remaining on the image carrying surface, the transfer process along with the movement of the image carrying surface. Then, it is carried to the charging unit and continuously supplied to the charging unit. In addition, since the liberated amount of the inorganic fine powder in the toner particles is controlled, the developer is hardly deteriorated even in long-term image formation. Therefore, even if the conductive fine powder is reduced by dropping off in the charging part or the uniform charge promoting ability of the conductive fine powder is deteriorated, the conductive fine powder continues to be supplied to the charging part. Even when used repeatedly, the chargeability of the image bearing member is prevented, and good uniform charging is stably maintained, and image defects such as positive ghosts and fogging due to poor collection of residual toner particles are effectively prevented. Can be prevented.

  As described above, the uniform chargeability is improved by promoting the supply of the conductive fine powder to the contact charging member by controlling the free state of the conductive fine powder and inorganic fine powder on the toner particle surface, and In addition, since the transfer residual toner can be effectively collected, an image forming method by high-quality contact charging capable of finely reproducing the halftone of the graphic image becomes possible.

Free state of conductive fine powder and inorganic fine powder from toner particles, that is, free rate a of conductive fine powder and free rate b of inorganic fine powder are free rate b ≧ free rate a
Is satisfied, the conductive fine powder tends to adhere firmly to the surface of the toner particles as compared with the inorganic fine powder, indicating that the inorganic fine powder is in a state of a large amount of release from the toner particles. Therefore, the conductive fine powder cannot be sufficiently supplied to the image bearing surface in the development process, and the conductive fine powder is hardly released from the toner particle surface in the transfer process. Further, since a large amount of inorganic fine powder is liberated from the developer, the rising of the charge of the developer is delayed, and toner particles remaining after transfer increase.

  For this reason, it is difficult to positively leave the conductive fine powder on the image carrier after transfer, and to actively supply the conductive fine powder to the charged portion, and many toner particles remain in the charged portion. As a result, the chargeability of the image carrier is lowered and image defects are likely to occur. Also, in the development and cleaning process, the conductive fine powder cannot be sufficiently supplied onto the image carrier, and the rising of the charge of the transfer residual toner is slow. On the contrary, since the transfer residual toner to be recovered increases, image defects such as positive ghost and fog due to poor recovery of transfer residual toner particles are likely to occur.

  Further, the release rate a of the conductive fine powder from the toner particles in the developer of the present invention is 40 to 95%, more preferably 50 to 95%. When the liberation rate a is lower than 40%, the conductive fine powder cannot be sufficiently supplied to the image bearing surface in the development process, and the conductive fine powder is hardly released from the toner particle surface in the transfer process. For this reason, the conductive fine powder remains positively on the image carrier after the transfer, and it becomes difficult to positively supply the conductive fine powder to the charging portion. Image defects are likely to occur. Also, in the development and cleaning process, the conductive fine powder cannot be sufficiently supplied onto the image carrier, and the effect of improving the recoverability of the transfer residual toner cannot be obtained. Image defects such as positive ghost and fog due to poor collection are likely to occur. Further, when the liberation rate a is higher than 95%, the conductive fine powder is almost free from the toner particles. Therefore, the conductive fine powder can be supplied to the image bearing surface in the development process, but the image can be obtained over a long period of time. As the formation is repeated, the concentration of the conductive fine powder in the developer decreases, and in the latter half of the endurance, it becomes difficult to positively supply the conductive fine powder to the charging portion, and the toner is charged to the charging portion. Since many particles remain, the chargeability of the image carrier is lowered and image defects are likely to occur. Also in the developing and cleaning process, the conductive fine powder cannot be sufficiently supplied onto the image carrier, and conversely, the amount of residual toner to be recovered increases. Image defects such as positive ghost and fog due to defects are likely to occur.

  Further, the liberation rate b of the inorganic fine powder from the toner particles in the developer of the present invention is 0.1 to 5%, more preferably 0.1 to 3%. When the liberation rate b is higher than 5%, a large amount of inorganic fine powder is liberated from the developer, so that the rising of the charge of the developer is delayed, and toner particles remaining after transfer increase.

  For this reason, a large amount of toner particles remain in the charging portion, and the chargeability of the image carrier is lowered and image defects are likely to occur. Also, in the development and cleaning process, since the rise of the charge of the transfer residual toner is slow, the effect of improving the recovery of the transfer residual toner cannot be obtained, and conversely the transfer residual toner to be recovered increases. Image defects such as positive ghosts and fogging due to poor collection of residual toner particles are likely to occur.

  When the liberation rate b is lower than 0.1%, it is indicated that almost no inorganic fine powder is liberated from the toner particles. In such a state, the degree of embedding of the inorganic fine powder in the toner particles is usually large. This is likely to happen. In such a case, not only the rising of charging is delayed, but also it becomes difficult to maintain the charge amount, so that it is difficult to obtain good developability.

  The release rate of the conductive fine powder and the inorganic fine powder from the toner particles in the present invention was measured by a particle analyzer (PT1000: manufactured by Yokogawa Electric Corporation), and the particle analyzer is 65 in the paper of Japan Hardcopy 97. Measurement is performed according to the principle described on page 68. Specifically, the apparatus is an apparatus in which fine particles such as toner are introduced into the plasma one by one, and the element of the luminescent material, the number of particles, and the particle size of the particles can be known from the emission spectrum of the fine particles. For example, consider the case where toner particles, in which silica is used as an inorganic fine powder and tin oxide is added as a conductive fine powder, are introduced into the plasma. The emission of carbon and the emission of Si atoms and Sn atoms are observed. That is, since one light emission is obtained for each toner particle, the number of toner particles can be obtained from the number of times of light emission. At that time, the Si and Sn atoms emitted within 2.6 msec from the emission of carbon atoms were simultaneously emitted, and the subsequent emission of Si and Sn atoms was only the Si and Sn atoms. In the toner of the present invention, simultaneous emission of carbon atoms, Si, and Sn atoms means that silica and tin oxide are attached to the toner particle surface, respectively, and emission of only Si and Sn atoms is It can be said that silica and tin oxide are liberated from the toner particles. As a specific method, a toner sample conditioned by being left overnight in an environment of a temperature of 23 ° C. and a humidity of 60% is measured using helium gas containing 0.1% oxygen in the environment. That is, carbon atoms (measurement wavelength 247.86 nm) are measured in channel 1, tin atoms (measurement wavelength 326.23 nm) are measured in channel 2, silica atoms (measurement wavelength 288.16 nm) are measured in channel 3, and carbon is measured in one scan. Sampling is performed so that the number of light emission of atoms is 1000 to 1400, and scanning is repeated until the total number of light emission of carbon atoms reaches 10,000 or more, and the number of light emission is integrated. Then, by counting the number of light emission of only Si and Sn atoms at that time, the number of free silica and tin oxide is obtained. At this time, the noise cut level is 1.50V.

  Further, the developer of the present invention is characterized in that the volume average particle diameter Da of the conductive fine powder and the number average particle diameter Db of the primary particles of the inorganic fine powder are Da ≧ 10 Db (preferably Da ≧ 20 Db). . According to the study by the present inventors, the adhesion / release state of the conductive fine powder and the inorganic fine powder on the surface of the developer prevents the occurrence of charging failure and enables stable and uniform charging. It has become clear that it is important to ensure the recovery of transfer residual toner particles in the development process and to effectively prevent image defects such as positive ghosts and fogging due to poor recovery of transfer residual toner particles. . In order to easily control the state of the developer surface, the particle sizes of the conductive fine powder and the inorganic fine powder are very important. That is, when the volume average particle diameter Da of the conductive fine powder and the number average particle diameter Db of the primary particles of the inorganic fine powder are Da <10 Db, the difference in the particle diameter between the conductive fine powder and the inorganic fine powder is small. In such a case, not only the conductive fine powder but also the amount of inorganic fine powder released from the toner particles tends to be large. Therefore, the conductive fine powder alone cannot be supplied to the image bearing surface in the development process. Further, since a large amount of inorganic fine powder is liberated from the developer, the rising of the charge of the developer is delayed, and toner particles remaining after transfer increase.

  For this reason, it is difficult to positively leave only the conductive fine powder on the image carrier after transfer, and to actively supply the conductive fine powder to the charging portion, and there are many toner particles in the charging portion. As a result, the chargeability of the image carrier is lowered and image defects are likely to occur. Also, in the development and cleaning process, since the rising of the charge of the transfer residual toner is slow, the effect of improving the recovery of the transfer residual toner cannot be obtained, and conversely the transfer residual toner to be recovered increases. Image defects such as positive ghosts and fogging due to poor collection of residual toner particles are likely to occur.

  As a manufacturing method for achieving the above liberation rate, there are cases where the addition timing of the inorganic fine powder and conductive fine powder added to the toner and the processing conditions (mixing time, etc.) of the mixing apparatus used at the time of addition are changed. Among these, the two-stage treatment condition in which the toner particles and the inorganic fine powder are first added and mixed in the mixing device and then the conductive fine powder is added is the separation of the adhesion state of the inorganic fine powder and the conductive fine powder to the toner particles. It is particularly preferable for controlling the rate.

  For example, Henschel mixer (manufactured by Mitsui Mining); Super mixer (manufactured by Kawata); Ribocon (manufactured by Okawara Seisakusho); A spiral pin mixer (manufactured by Taiheiyo Kiko Co., Ltd.) and a Ladige mixer (manufactured by Matsubo Co., Ltd.).

  Further, the developer of the present invention has a methanol concentration in the methanol / water mixed solvent at a specific concentration region when the wettability with respect to the methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm. Preferably it belongs.

  FIG. 1 shows a graph of the methanol concentration with respect to the transmittance of light having a wavelength of 780 nm of the developer of Example 1 described later. A region where the transmittance exceeds 80% indicates that the developer is hardly wetted with methanol, and a region where the transmittance is lower than 10% indicates that the developer is almost completely wetted.

  The wettability of the developer with respect to the methanol / water mixed solvent is greatly affected by the adhesion state of the inorganic fine powder to the toner particle surface.

  In the image forming method including the contact charging step, toner particles adhering to or mixed in the contact charging member as a transfer residue or fog are reduced even when the developer is used repeatedly over a long period of time, and the conductive fine powder on the contact charging member is reduced. It is particularly required to promote the supply and improve the uniform chargeability. As a result, an image forming method that does not cause charging failure due to contact charging is possible, and a good image that can be reproduced finely up to halftone of a high-quality graphic image can be obtained, but the magnetic toner is charged unevenly and charged. If the distribution of the amount varies, the developer charged on the developing sleeve and the charge amount of the developer on the sleeve vary greatly during repeated use of the developer over a long period of time. As a result, the charging failure occurs due to adhesion or mixing with the contact charging member. Further, toner spikes may be non-uniform on the sleeve and an image with many scattering may be generated.

  That is, in the present invention, when the wettability of the developer to a methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 80% is 35 to 80% by volume (preferably It is preferable that it is in the range of 45 to 75% by volume. Furthermore, in the present invention, when the wettability of the developer to a methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 10% is 40 to 85% by volume (preferably 50%). It is good that it is in the range of ˜80% by volume.

  The higher the amount of inorganic fine powder attached to the surface of the developer, or the smaller the degree of embedding of the inorganic fine powder on the surface, that is, the higher the proportion of the toner particle surface covered by the inorganic fine powder, the higher the methanol. The developer gets wet with the density.

  As the amount of the inorganic fine powder adhering to the toner particle surface is larger or the embedding degree is smaller, the chargeability of the developer is improved and higher developability can be obtained. That is, when the transmittance is 80%, the methanol concentration is in the range of 35 to 80% by volume, and when the transmittance is 10%, the methanol concentration is 40 to 85% by volume. Stabilizes and exhibits excellent developability even under various environments such as low temperature and low humidity and high temperature and high humidity.

  However, when the methanol concentration when the transmittance is 80% exceeds 80% by volume or the methanol concentration when the transmittance is 10% exceeds 85% by volume, this is too much adhesion of the inorganic fine powder. Or it shows that the degree of embedding is too small, and the developer cannot obtain proper charging performance, which is not preferable. When the methanol concentration when the transmittance is 80% is lower than 35% by volume or when the transmittance is 10%, the methanol concentration is lower than 40% by volume. This indicates that the amount of powder attached is small or the degree of embedding is large. In such a case, it is difficult to maintain the charge amount and it is difficult to obtain good developability.

Further, the charge amount distribution of the developer is greatly influenced by the adhesion state of the inorganic fine powder to the toner particle surface, and the charge amount distribution becomes uniform as the uniformity of the inorganic fine powder adhesion state increases. The state of adhesion of the inorganic fine powder to the toner particle surface can be determined by measuring the wettability behavior of the developer with respect to the methanol / water mixed solvent. The more uniformly the inorganic fine powder adheres to the surface, the smaller the difference in methanol concentration from when the developer starts to wet with the methanol / water mixed solvent until it ends. In the present invention, when the wettability of the magnetic toner with respect to the methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 80% is C80, and the transmittance is 10%. When the methanol concentration of C10 is C10, the following formula (2)
0 <C10-C80 ≦ 10 (2)
Preferably, 0 <C10−C80 ≦ 8
Is within the range, the difference between the methanol concentration when the transmittance is 80% and the methanol concentration when the transmittance is 10% is reduced, that is, the charge amount distribution of the developer becomes uniform, It is also preferable in the sense that uniform and high chargeability can be quickly imparted.

  When C10-C80 is larger than 10%, the magnetic toner is non-uniformly charged, the distribution of the charge amount varies, and the developer charged on the developing sleeve and the sleeve when the developer is repeatedly used over a long period of time. The variation in the charge amount of the upper developer becomes large, and the toner particles adhere to or mix in the contact charging member as a transfer residue or fog, resulting in poor charging. Further, toner spikes may be non-uniform on the sleeve and an image with many scattering may be generated.

  Also, the presence of non-uniformly charged magnetic toner particles degrades image quality such as uniformity of image density and dot reproducibility.

  In the present invention, the relationship between the transmittance and the methanol concentration, that is, the wettability of the developer, that is, the hydrophobic property of the developer is measured using a methanol dropping transmittance curve. Specifically, as the measuring device, for example, a powder wettability tester WET-100P manufactured by Reska Co., Ltd. may be mentioned, and specific measuring operations may include the methods exemplified below.

  First, a method for the case where the initial methanol concentration is 40% by volume will be described. The initial methanol concentration is 30% by volume and 40% by volume, so that the concentration at the beginning of wetting of the developer and the concentration at the end of wetting can be measured. , 70 volume% 3 levels were properly used for measurement. 70 ml of a hydrated methanol solution composed of 40% by volume of methanol and 60% by volume of water is placed in a container, and dispersed for 5 minutes with an ultrasonic disperser in order to remove bubbles and the like in the measurement sample. In this, 0.5 g of a developer as a specimen is precisely weighed and added to prepare a sample solution for measuring the hydrophobic characteristics of the developer.

Next, while stirring the sample solution for measurement at a speed of 6.67 s ⁻¹ , methanol was added at 1.3 ml / min. Are continuously added at a dropping rate of, and the transmittance is measured with light having a wavelength of 780 nm to prepare a methanol dropping transmittance curve as shown in FIG. In this case, methanol is used as the titration solvent because various toner materials such as dyes, pigments, and charge control agents contained in the developer are less likely to elute and the surface state of the developer can be observed more accurately. It is. In this measurement, a glass flask having a diameter of 5 cm and a thickness of 1.75 mm was used as the flask, and a magnetic stirrer having a spindle shape of 25 mm in length and a maximum diameter of 8 mm and coated with fluororesin. What was done was used.

  In addition, the volume average particle size of the conductive fine powder of the present invention is preferably 0.1 μm to 4.0 μm (more preferably 0.1 μm to 2.0 μm).

  Those smaller than 0.1 μm tend to adhere firmly to the toner particle surface, and the conductive fine powder cannot be sufficiently supplied to the image bearing surface in the development process. Fine powder is not easily released.

  For this reason, it is difficult to positively leave the conductive fine powder on the image carrier after transfer, and to actively supply the conductive fine powder to the charging portion, thereby reducing the chargeability of the image carrier. Image defects are likely to occur. Also, in the developing and cleaning process, the conductive fine powder cannot be sufficiently supplied onto the image carrier, and the particle diameter is too small even if the conductive fine powder is supplied onto the image carrier. The effect of improving the transferability of the transfer residual toner is not obtained, and on the contrary, the transfer residual toner to be recovered increases, and thus image defects such as positive ghosts and fogging are likely to occur due to poor transfer residual toner particle recovery. .

  Further, among the conductive fine powders, those having a particle diameter exceeding 4 μm cannot promote the charging property of the image bearing member uniformly even when supplied to the charging portion, and thus the conductive fine powder cannot be promoted. It becomes easy to drop off from the charging member, and it becomes difficult to stably keep the conductive fine powder having a sufficient number of particles in the charging portion.

  Furthermore, since the number of particles of the conductive fine powder per unit mass is reduced, the conductive fine powder having a number of particles sufficient to obtain a uniform charge promoting effect of the image carrier is interposed in the charged portion. The amount of fine powder added to the developer must be increased.

  However, if the amount of conductive fine powder added is too large, the triboelectric chargeability and developability of the developer as a whole are lowered, and the image density and toner scattering are likely to occur. Further, since the conductive fine powder has a large particle size, the effect as a recovery aid for the residual toner particles in the development and cleaning process cannot be sufficiently obtained. Further, if the amount of the conductive fine powder on the image carrier is increased too much in order to enhance the recovery of the transfer residual toner particles, the image is formed by blocking the image exposure for forming the latent image due to the large particle size. Prone to defects.

  The particle diameter of the conductive fine powder can be measured as follows. That is, a photograph of the developer magnified by a scanning electron microscope was mapped with the elements contained in the conductive fine powder by an element analysis means such as an X-ray microanalyzer (XMA) attached to the scanning electron microscope. The photograph of the developer is contrasted, and the conductive fine powder existing on the surface of the toner particles is identified. It was introduced from a photograph of the developer magnified by a scanning electron microscope (for example, a photograph photographed with a field of view of 3000 to 5000 times by FE-SEMS-800 manufactured by Hitachi, Ltd.) or from a scanning electron microscope via an interface ( From the image information (magnified 3000 to 5000 times), an image of the specified conductive fine powder is introduced into an image processing device (for example, image analysis device Luzex III manufactured by Nireco Corporation), and analyzed to determine the particle size of the conductive fine powder. Desired.

  As described above, by controlling the wettability of the developer to a specific solvent and controlling the release rate of toner fine particles and conductive fine powder having a specific relationship with the particle size from the toner particles, It is possible to reduce toner particles adhering to or mixing in the contact charging member as residual or fogging, and to promote the supply of conductive fine powder to the contact charging member, improving the uniform charging property, and the halftone of the graphic image An image forming method by high-quality contact charging that can be reproduced finely and finely becomes possible.

  In the present invention, the metal oxide fine particles selected from silicon oxide, aluminum oxide and titanium oxide covering the surface of the conductive fine powder are silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, and silane cups. It is preferable that the surface is hydrophobized with at least one hydrophobizing agent selected from ring agents. By treating the metal oxide fine particles covering the surface of the conductive fine powder, environmental stability, in particular, charging stability under high temperature and high humidity and fluidity maintenance are improved.

  In the developer of the present invention, the content of the conductive fine powder is preferably 0.1 to 5.0% by mass (more preferably 0.1 to 2.0% by mass) of the entire developer. By setting the content of the conductive fine powder within the above range, an appropriate amount of the conductive fine powder for accelerating the charging of the image carrier can be supplied to the charging unit, and the transfer residual toner particles can be collected in the development and cleaning. The amount of conductive fine powder necessary for enhancing the properties can be supplied onto the image carrier.

  When the content of the conductive fine powder in the developer is too smaller than the above range, the amount of the conductive fine powder supplied to the charging portion is likely to be insufficient, and it is difficult to obtain a stable charge promoting effect of the image carrier. Even in image formation using development and cleaning, the amount of the conductive fine powder existing on the image carrier together with the transfer residual toner particles tends to be insufficient, and the effect of improving the recovery of the transfer residual toner particles is difficult to obtain. In addition, when the content of the conductive fine powder in the developer is too larger than the above range, excessive conductive fine powder is easily supplied to the charging portion, and a large amount of conductive fine powder cannot be held in the charging portion. In addition, exposure failure due to being discharged onto the image carrier is likely to occur. Further, the triboelectric charging property of the toner particles may be reduced or disturbed, which may cause a decrease in image density and an increase in fog. From such a viewpoint, the content of the conductive fine powder of the developer is preferably within the above range.

Further, the resistance of the conductive fine powder is preferably 10 ⁹ Ω · cm or less in order to impart to the developer the effect of promoting charging of the image carrier and the effect of improving transfer residual toner recovery. When the resistance of the conductive fine powder is too larger than the above range, the conductive fine powder is interposed in the nip portion between the charging member and the image carrier or in the vicinity of the charging region, and the conductive fine powder of the contact charging member is removed. Even if the close contact property to the image carrier is maintained, the charge promoting effect for obtaining good chargeability of the image carrier is reduced. Even during development and cleaning, the conductive fine powder tends to be charged with the same polarity as the transfer residual toner particles, so that it is easy to be recovered together with the transfer residual toner particles, and the conductive fine powder is difficult to recover as a recovery aid. In some cases, the improvement in the recoverability of the transfer residual toner due to the presence on the body may be significantly reduced.

  In order to sufficiently obtain the effect of promoting the charging of the image carrier by the conductive fine powder and to stably obtain a good uniform charging property of the image carrier, the resistance of the conductive fine powder is determined by the surface portion of the contact charging member. Alternatively, it is preferably smaller than the resistance of the contact portion with the image carrier, and more preferably 1/100 or less of the resistance of the contact charging member.

Furthermore, if the resistance of the conductive fine powder is 10 ⁶ Ω · cm or less, the charging of the image bearing member can be more satisfactorily overcome the inhibition of charging to the contact charging member due to the adhesion / mixing of insulating transfer residual toner particles. It is preferable that the process is carried out and that the effect of improving the recoverability of the transfer residual toner in the development and cleaning is obtained more stably. The resistance of the conductive fine powder is more preferably 100 to 10 ⁵ Ω · cm. Contact charging realizes good charging of the image bearing member, and development and cleaning are more effective in stabilizing the effect of improving toner recovery.

In the present invention, the resistance of the conductive fine powder can be determined by measuring and normalizing by the tablet method. That is, about 0.5 g of a powder sample is put in a cylinder with a bottom area of 2.26 cm ² and a voltage of 100 V is applied at the same time as a weight of 147 N (15 kg) is applied between the upper and lower electrodes arranged above and below the powder sample. Apply and measure the resistance, then normalize to calculate the specific resistance.

  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 order to prevent the exposure light from being hindered in the latent image forming step. Further, the conductive fine powder preferably has a transmittance of 30% or more for image exposure light forming this electrostatic latent image. The transmittance is more preferably 35% or more.

  Hereinafter, an example of a method for measuring the light transmittance of the conductive fine powder in the present invention will be described. The transmittance is measured in a state where the conductive fine powder is fixed one layer on the adhesive layer of a transparent film having an adhesive layer on one side. Light is irradiated from the vertical direction of the sheet, and the light transmitted to the back of the film is collected and the amount of light is measured. The light transmittance as the net light amount is calculated based on the difference in light amount between the case of the film alone and the case where the conductive fine powder is adhered. Actually, it can be measured using a 310T transmission densitometer manufactured by X-Rite.

  The conductive fine powder is preferably nonmagnetic. By making the conductive fine powder non-magnetic, transparent, white or light-colored conductive fine powder can be easily obtained. On the other hand, it is difficult for a conductive material having magnetism to be transparent, white, or light-colored by having magnetism. In the image forming method in which the developer is conveyed and held by the magnetic force, the conductive fine powder having magnetism becomes difficult to be developed, and the supply of the conductive fine powder onto the image carrier is insufficient or the developer. Conductive fine powder accumulates on the surface of the carrier and tends to cause adverse effects such as preventing development of toner particles. Further, when magnetic conductive fine powder is added to the magnetic toner particles, the conductive fine powder tends to be difficult to be separated from the toner particles due to magnetic cohesive force. Supplyability to the product tends to decrease.

  Examples of the conductive fine powder in the present invention include metal fine powders such as copper, gold, silver, aluminum, and nickel; zinc oxide, titanium oxide, tin oxide, aluminum oxide, indium oxide, silicon oxide, magnesium oxide, barium oxide, Metal oxides such as molybdenum oxide, iron oxide and tungsten oxide; among metal compounds such as molybdenum sulfide, cadmium sulfide and potassium titanate, or composite oxides thereof, the number average particle size of primary particles is 50 to 500 nm. The conductive fine powder having an aggregate of primary particles can be used, and those having the above preferable characteristics (resistance, transmittance, etc.) are preferably used. It is also preferable to use conductive fine powder having an adjusted particle size distribution in order to adjust the particle size and particle size distribution as a developer.

  Among these, the conductive fine powder contains at least one oxide selected from zinc oxide, tin oxide and titanium oxide, and the resistance of the conductive fine powder can be set low. Is preferable. Further, it is non-magnetic, white or light-colored, and is preferable in that the conductive fine powder transferred onto the transfer material is not noticeable as fog.

  In addition, for the purpose of controlling the resistance value of the conductive fine powder, metal oxide fine particles containing elements such as antimony and aluminum, and fine particles having a conductive material on the surface can also be used as the conductive fine powder. . For example, zinc oxide fine particles containing an aluminum element, tin oxide fine particles containing an antimony element, and the like.

  Furthermore, it is particularly preferable to use zinc oxide containing an aluminum element as the conductive fine powder because a conductive fine powder having high whiteness and a stable and low resistance can be obtained. The method for incorporating aluminum element into zinc oxide is not particularly limited, but it is particularly preferable to use a method for producing conductive zinc oxide as disclosed in JP-A-1-126228.

  The volume average particle diameter of the conductive fine powder may be measured by a diffraction method. The measurement method by a diffraction method is illustrated. A small 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). Using an LS-230 type laser diffraction particle size distribution measuring apparatus, the particle diameter is measured in the range of 0.04 to 2000 μm, and the measurement is performed with a measurement time of 90 seconds and a measurement count of once.

  In the present invention, when the conductive fine powder behaves mainly as an aggregate, the particle size of the conductive fine powder is defined not as the primary particle size but as the particle size as the aggregate.

  In the present invention, the developer also needs to have an inorganic fine powder having a primary particle number average particle diameter Db of 4 to 80 nm.

  If the number average particle size of the primary particles of the inorganic fine powder is too larger than the above range, or if the number average particle size of the primary particles is not added, the conductive fine powder is developed. It is difficult to uniformly disperse the toner particles in the agent, and it is difficult to supply the conductive fine powder uniformly on the image carrier. The conductive fine powder surface-treated with the lubricant used in the present invention tends to be easily released from the toner particles and tends to be difficult to uniformly disperse in the developer. For this reason, it is possible to disperse the conductive fine powder uniformly in the developer by using an inorganic fine powder having higher fluidity to the developer and smaller primary particle number average particle size. It turned out to be.

  When the conductive fine powder is not uniformly dispersed in the developer, it is easy to cause uneven supply of the conductive fine powder in the longitudinal direction on the image carrier, and when uneven supply to the contact charging member occurs. Causes poor charging of the image carrier corresponding to uneven supply of the conductive fine powder, and during development and cleaning, the recovery of the residual toner particles in correspondence with the reduced amount of the conductive fine powder on the image carrier This results in poor collection due to a drop in the image quality and appears as a streak-like image defect. In addition, when the transfer residual toner particles adhere to the charging member, the toner particles are easily fixed to the charging member, and it becomes difficult to stably obtain good charging characteristics of the image carrier. In addition, good developer fluidity cannot be obtained, and charging to toner particles tends to be uneven, and problems such as increased fog, decreased image density, and toner scattering cannot be avoided.

  When the number average particle size of the primary particles of the inorganic fine powder is smaller than 4 nm, the cohesiveness of the inorganic fine powder is strengthened, and the particle size distribution has a strong cohesive property that is difficult to break even by crushing treatment instead of the primary particles. It tends to behave as a wide aggregate and easily causes image defects due to development of the aggregate of inorganic fine powder, and image defects due to damage to the image carrier, development carrier or contact charging member. From these viewpoints, the number average particle diameter of the primary particles of the inorganic fine powder is preferably 6 to 50 nm.

  That is, in the present invention, the inorganic fine powder is not only added to improve the fluidity of the developer by adhering to the surface of the toner particles and to uniformly charge the toner particles, but also to develop the conductive fine powder. It also has the effect of uniformly dispersing the toner particles in the agent and supplying the conductive fine powder uniformly on the image carrier.

  In the present invention, the number average particle diameter of the primary particles of the inorganic fine powder can be measured as follows. That is, a photograph of the developer magnified with a scanning electron microscope, and further development developed with elements contained in the inorganic fine powder by an elemental analysis means such as an X-ray microanalyzer (XMA) attached to the scanning electron microscope By contrasting the photograph of the agent, 100 or more primary particles of the inorganic fine powder present on the surface of the toner particles adhering or liberating can be measured to determine the number average particle diameter.

In the present invention, the inorganic fine powder preferably contains at least one selected from silica, titania (titanium oxide) and alumina having a primary particle number average particle size of 4 to 80 nm. For example, as the silica fine powder, both a so-called dry method produced by vapor phase oxidation of silicon halide or dry silica called fumed silica, and so-called wet silica produced from water glass or the like can be used. but less silanol groups on the inner surface and the silica fine powder, also Na ₂ O, SO ₃ ^- it is preferable less dry silica of manufacturing residue such. 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.

  In the present invention, the inorganic fine powder is preferably hydrophobized. By hydrophobizing the inorganic fine powder, the chargeability of the inorganic fine powder in the high-humidity environment is prevented from decreasing, and the environmental stability of the triboelectric charge amount of the toner particles adhered to the surface is improved. Further, the environmental stability of development characteristics such as image density and fog as a developer can be further enhanced. Suppressing fluctuations in the chargeability of the inorganic fine powder and the charge amount of the toner particles with the inorganic fine powder attached to the surface due to the environment can prevent fluctuations in the ease of release of the conductive fine powder from the toner particles. Thus, the supply amount of the conductive fine powder on the image carrier depending on the environment can be stabilized, and the environmental stability of the image carrier chargeability and transfer residual toner particle recoverability can be improved.

  As treatment agents for hydrophobization treatment, treatment agents such as 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 may be used alone or in combination. And may be processed. Among these, the inorganic fine powder is particularly preferably treated with at least silicone oil. The treatment can be performed according to a known method.

  Examples of the silane compound used for the hydrophobizing treatment include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, and benzyl. Dimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilane mercaptan, trimethylsilyl mercaptan, triorganosilyl acrylate, vinyldimethylacetoxysilane, dimethylethoxy Silane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, 1,3-divinyltetramethyl Examples include tildisiloxane and 1,3-diphenyltetramethyldisiloxane.

The silicone oil preferably has a viscosity at 25 ° C. of 10 to 200,000 mm ² / s, and more preferably 3,000 to 80,000 mm ² / s. If the viscosity of the silicone oil is too smaller than the above range, the processing of the inorganic fine powder is not stable, and the processed silicone oil is detached, transferred or deteriorated by heat and mechanical stress, resulting in deterioration of image quality. Tend to. Moreover, when a viscosity is larger than the said range, there exists a tendency for the uniform process of an inorganic fine powder to become difficult.

  As the silicone oil used, for example, dimethyl silicone oil, methylphenyl silicone oil, α-methylstyrene modified silicone oil, chlorophenyl silicone oil, fluorine modified silicone oil and the like are particularly preferable.

  As a method for treating the silicone oil, for example, the inorganic fine powder treated with the silane compound and the silicone oil may be directly mixed using a mixer such as a Henschel mixer, or the silicone oil is sprayed onto the inorganic fine powder. A method may be used. Alternatively, after dissolving or dispersing silicone oil in a suitable solvent, silica 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 smaller than the above range, good hydrophobicity cannot be obtained, and if it is too large, problems such as fogging may occur.

  In the present invention, the inorganic fine powder is preferably treated with silicone oil at the same time as or after treatment with the silane compound. It is particularly preferable to use a silane compound for the treatment of the inorganic fine powder in order to increase the adhesion of the silicone oil to the inorganic fine powder and to make the hydrophobicity and chargeability of the inorganic fine powder uniform.

  As the treatment conditions for the inorganic fine powder, for example, a silylation reaction is performed as a first-stage reaction and silanol groups are eliminated by chemical bonds, and then a hydrophobic thin film is formed on the surface with silicone oil as a second-stage reaction. Can be mentioned.

  Moreover, it is preferable that content of an inorganic fine powder is 0.1-3.0 mass% of the whole developer in the developer of this invention. If the content of the inorganic fine powder is less than the above range, the effect of adding the inorganic fine powder cannot be sufficiently obtained, and if it is more than the above range, the inorganic fine powder is excessively inorganic with respect to the toner particles. The fine powder coats the conductive fine powder, and the behavior becomes the same as when the conductive fine powder has a high resistance. There is a tendency that the effects of the present invention, such as a reduction in charging effect on the body and a reduction in the recovery of transfer residual toner, are impaired. The content of the inorganic fine powder is more preferably 0.3 to 2.0% by mass, and further preferably 0.5 to 1.5% by mass with respect to the whole developer.

The inorganic fine powder having a primary particle number average particle size of 4 to 80 nm used in the present invention preferably has a specific surface area of 40 to 300 m ² / g by nitrogen adsorption measured by the BET method, preferably 60 to 250 m. More preferred is ² / g. The specific surface area can be calculated using the BET multipoint method by adsorbing nitrogen gas to the sample surface using a specific surface area measuring device Autosorb 1 (manufactured by Yuasa Ionics Co., Ltd.) according to the BET method.

  The toner of the present invention will be further described.

  From the viewpoint of storage stability, the resin composition according to the toner of the present invention has a glass transition temperature (Tg) of 45 to 80 ° C., preferably 50 to 70 ° C. When Tg is lower than 45 ° C., This may cause toner deterioration and offset during fixing. On the other hand, when Tg exceeds 80 ° C., fixability tends to decrease.

  As a method for measuring the glass transition temperature of the resin of the present invention, a differential thermal analysis measurement device (DSC measurement device), DSC-7 (manufactured by Perkin Elmer), EXSTAR6000, SSC / 5200 (manufactured by Seiko Instruments Inc.), DSC2920MDSC ( TA Instruments, etc.) can be used under the following conditions.

<Method for measuring glass transition temperature of resin>
Sample: 0.5-2 mg, preferably 1 mg
Temperature curve: Temperature increase I (20 ° C. to 180 ° C., temperature increase rate 10 ° C./min)
Temperature drop I (180 ° C. to 10 ° C., temperature drop rate 10 ° C./min)
Temperature increase II (10 ° C to 180 ° C, temperature increase rate 10 ° C / min)
Measurement method: Place the sample in an aluminum pan, and use an empty aluminum pan as a reference. The point of intersection between the line of the midpoint of the base line before and after the endothermic peak and the differential heat curve was defined as the glass transition point Tg.

  The binder resin component used in the present invention has a Mn (number average molecular weight) of 3000 to 20000 and a Mw (weight average molecular weight) of 50,000 to 500,000 in the molecular weight measured by GPC of the THF soluble component. It is preferable that it is the range of these. Within this range, the balance between fixability and durability is very good.

  These binder resin components can be mixed and dispersed in advance in the production of the magnetic toner. By mixing the wax component in advance, phase separation in the micro region is relaxed, and a good dispersion state is obtained.

  In the present invention, the molecular weight distribution of the toner or binder resin by GPC using THF (tetrahydrofuran) as a solvent is measured under the following conditions.

The column is stabilized in a 40 ° C. heat chamber, and THF as a solvent is allowed to flow through the column at this temperature at a flow rate of 1 ml per minute, and about 100 μl of a sample THF solution is injected and measured. In measuring the molecular weight of a sample, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the number of counts. As a standard polystyrene sample for preparing a calibration curve, for example, a product having a molecular weight of about 10 ² to 10 ⁷ manufactured by Tosoh Corporation or Showa Denko is used, and at least about 10 standard polystyrene samples are suitably used. . An RI (refractive index) detector is used as the detector. As the column, it is preferable to combine a plurality of commercially available polystyrene gel columns. For example, Shodex GPC KF-801, 802, 803, 804, 805, 806, 807, 800P manufactured by Showa Denko KK, TSKgel G1000H (HXL), G2000H (HXL), G3000H (HXL), G4000H (Tosoh Corporation) HXL), G5000H (HXL), G6000H (HHXL), G7000H (HXL), and a combination of TSK guard column.

  The sample is prepared as follows.

  Put the sample in THF, leave it for several hours, then shake well and mix well with THF (until the sample is no longer united) and let stand for more than 12 hours. At this time, the sample is left in THF for 24 hours or longer. Thereafter, a sample processing filter (pore size 0.45 to 0.5 μm, for example, available from Mysori Disc H-25-5 manufactured by Tosoh Corp., Excro Disc 25CR Gelman Science Japan Co., Ltd., etc.) can be used. This is a measurement sample. The sample concentration is adjusted so that the resin component is 0.5 to 5 mg / ml.

  As the kind of the binder resin in the present invention, styrene resin, styrene copolymer resin, polyester resin, polyol resin, polyvinyl chloride resin, phenol resin, natural modified phenol resin, natural resin modified maleic resin, acrylic resin, Examples include methacrylic resin, polyvinyl acetate, silicone resin, polyurethane resin, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumarone indene resin, and petroleum resin.

  As a comonomer for the styrene monomer of the styrene copolymer, styrene derivatives such as vinyltoluene, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, acrylic Acrylic acid ester such as phenyl acid; Methacrylic acid ester such as methacrylic acid, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate; Maleic acid; Double such as butyl maleate, methyl maleate, dimethyl maleate Dicarboxylic acid ester having a bond; acrylamide, acrylonitrile, methacrylonitrile, butadiene; vinyl chloride; vinyl ester such as vinyl acetate and vinyl benzoate; ethylene, propylene, butylene Such ethylenic olefins, vinyl methyl ketone, such as vinyl vinyl hexyl ketone, vinyl methyl ether, vinyl ethyl ether, vinyl propionate ether. These vinyl monomers are used alone or in combination of two or more.

  The binder resin in the present invention preferably has an acid value in the range of 1 to 100 mgKOH / g. Particularly preferred is a resin having an acid value of 1 to 70 mgKOH / g. If it exceeds 100 mgKOH / g, the triboelectric charge amount under high humidity is insufficient, and if it is less than 1 mgKOH / g, the triboelectric charging rate under low humidity becomes slow.

  Examples of the monomer for adjusting the acid value of the binder resin include acrylic acid such as acrylic acid, methacrylic acid, α-ethylacrylic acid, crotonic acid, cinnamic acid, vinyl acetic acid, isocrotonic acid, and angelic acid, and α- β-alkyl derivatives, fumaric acid, maleic acid, citraconic acid, alkenyl succinic acid, itaconic acid, mesaconic acid, dimethyl maleic acid, dimethyl fumaric acid and other unsaturated dicarboxylic acids and monoester derivatives or anhydrides thereof, etc. Such a monomer can be made alone or mixed and copolymerized with other monomers to produce a desired polymer. Among these, it is particularly preferable to use a monoester derivative of an unsaturated dicarboxylic acid in order to control the acid value.

  More specifically, for example, monomethyl maleate, monoethyl maleate, monobutyl maleate, monooctyl maleate, monoallyl maleate, monophenyl maleate, monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, monophenyl fumarate Monoesters of α, β-unsaturated dicarboxylic acids such as: monobutyl n-butenyl succinate, monomethyl n-octenyl succinate, monoethyl n-butenylmalonate, monomethyl n-dodecenyl glutarate, monobutyl n-butenyl adipate And monoesters of alkenyldicarboxylic acid such as

  The carboxyl group-containing monomer as described above may be added in an amount of 0.1 to 20 parts by mass, preferably 0.2 to 15 parts by mass, with respect to 100 parts by mass of all monomers constituting the binder resin.

  Examples of a polymerization method that can be used in the present invention as a method for synthesizing the binder resin of the present invention include a solution polymerization method, an emulsion polymerization method, and a suspension polymerization method.

  Among them, the emulsion polymerization method is a method in which a monomer (monomer) almost insoluble in water is dispersed as small particles in an aqueous phase with an emulsifier, and polymerization is performed using a water-soluble polymerization initiator. In this method, the reaction heat can be easily adjusted, and the termination reaction rate is low because the phase in which the polymerization is carried out (the oil phase consisting of the polymer and the monomer) and the aqueous phase are separate, resulting in a high polymerization rate. A product having a high degree of polymerization is obtained. Furthermore, the reason is that the polymerization process is relatively simple, and that the polymerization product is fine particles, so that it can be easily mixed with colorants, charge control agents and other additives in the production of toner. Therefore, there is an advantage as a method for producing a binder resin for toner.

  However, the added polymer is likely to be impure due to the added emulsifier, and an operation such as salting out is necessary to take out the polymer. Suspension polymerization is convenient to avoid this inconvenience.

  In suspension polymerization, it is good to carry out by 100 mass parts or less (preferably 10-90 mass parts) of monomers with respect to 100 mass parts of aqueous solvents. Examples of the dispersant that can be used include polyvinyl alcohol, partially saponified polyvinyl alcohol, calcium phosphate, and the like, and generally 0.05 to 1 part by mass with respect to 100 parts by mass of the aqueous solvent. The polymerization temperature is suitably 50 to 95 ° C., but is appropriately selected depending on the initiator used and the target polymer.

  The binder resin used in the present invention is preferably produced by using a polyfunctional polymerization initiator alone or in combination with a monofunctional polymerization initiator as exemplified below.

  Specific examples of the polyfunctional polymerization initiator having a polyfunctional structure include 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,3-bis- (t-butylperoxy Isopropyl) benzene, 2,5-dimethyl-2,5- (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di- (t-butylperoxy) hexane, tris- (t-butyl) Peroxy) triazine, 1,1-di-t-butylperoxycyclohexane, 2,2-di-t-butylperoxybutane, 4,4-di-t-butylperoxyvaleric acid-n-butyl ester , Di-t-butylperoxyhexahydroterephthalate, di-t-butylperoxyazelate, di-t-butylperoxytrimethyladipate, 2,2-bis- ( , 4-di-t-butylperoxycyclohexyl) propane, 2,2-t-butylperoxyoctane and various polymer oxides, etc., a functional group having a polymerization initiating function such as two or more peroxide groups in one molecule. And a polyfunctional polymerization initiator having a peroxide group in one molecule such as diallyl peroxydicarbonate, t-butylperoxymaleic acid, t-butylperoxyallylcarbonate and t-butylperoxyisopropyl fumarate And a polyfunctional polymerization initiator having both a functional group having a polymerization initiating function and a polymerizable unsaturated group.

  Of these, more preferred are 1,1-di-t-butylperoxy-3,3,5-trimethylcyclohexane, 1,1-di-t-butylperoxycyclohexane, di-t-butylperoxy. Hexahydroterephthalate, di-t-butylperoxyazelate and 2,2-bis- (4,4-di-t-butylperoxycyclohexyl) propane, and t-butylperoxyallyl carbonate.

  These polyfunctional polymerization initiators are preferably used in combination with a monofunctional polymerization initiator in order to satisfy various performances required as a binder for toner. In particular, it is preferable to use in combination with a polymerization initiator having a decomposition temperature of a half-life of 10 hours which is lower than the decomposition temperature for obtaining a half-life of 10 hours of the polyfunctional polymerization initiator.

  Specifically, benzoyl peroxide, 1,1-di (t-butylperoxy) -3,3,5-trimethylcyclohexane, n-butyl-4,4-di (t-butylperoxy) valerate, dichroic Organic peroxides such as milperoxide, α, α'-bis (t-butylperoxydiisopropyl) benzene, t-butylperoxycumene, di-t-butylperoxide, azobisisobutyronitrile, diazoamino Examples include azo and diazo compounds such as azobenzene.

  These monofunctional polymerization initiators may be added to the monomer at the same time as the polyfunctional polymerization initiator, but in order to keep the efficiency of the polyfunctional polymerization initiator appropriate, in the polymerization step, It is preferably added after the half-life indicated by the polyfunctional polymerization initiator has elapsed.

  These initiators are preferably used in an amount of 0.05 to 2 parts by mass with respect to 100 parts by mass of the monomer from the viewpoint of efficiency.

  It is also preferable that the binder resin is crosslinked with a crosslinking monomer.

  As the crosslinkable monomer, a monomer having two or more polymerizable double bonds is mainly used. Specific examples include aromatic divinyl compounds (eg, divinylbenzene, divinylnaphthalene, etc.); diacrylate compounds linked by alkyl chains (eg, ethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4 -Butanediol diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, and acrylates of the above compounds replaced with methacrylate); alkyl chain containing an ether bond Diacrylate compounds (eg, diethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycol # 400 diacrylate, Ethylene glycol # 600 diacrylate, dipropylene glycol diacrylate, and acrylates of the above compounds in place of methacrylate); diacrylate compounds linked by a chain containing an aromatic group and an ether bond (eg, polyoxyethylene) (2) -2,2-bis (4-hydroxyphenyl) propane diacrylate, polyoxyethylene (4) -2,2-bis (4-hydroxyphenyl) propane diacrylate, and methacrylates of the above compounds Furthermore, polyester-type diacrylate compounds (for example, trade name MANDA (Nippon Kayaku)) are mentioned. As polyfunctional crosslinking agents, pentaerythritol acrylate, trimethylol ethane triacrylate, trimethylol propane triacrylate, tetramethylol propane triacrylate, tetramethylol methane tetraacrylate, oligoester acrylate, and acrylates of the above compounds are replaced with methacrylate. Triallyl cyanurate, triallyl trimellitate; and the like.

  These crosslinking agents are preferably used in the range of 0.00001 to 1 part by mass, preferably 0.001 to 0.05 part by mass, with respect to 100 parts by mass of the other monomer components.

  Among these crosslinkable monomers, aromatic divinyl compounds (especially divinylbenzene), diethers linked by a chain containing an aromatic group and an ether bond are preferably used from the viewpoint of toner fixing properties and offset resistance. Examples include acrylate compounds.

  As other synthesis methods, a bulk polymerization method and a solution polymerization method can be used. However, in the bulk polymerization method, a polymer having a low molecular weight can be obtained by polymerizing at a high temperature to increase the termination reaction rate, but there is a problem that the reaction is difficult to control. In that respect, the solution polymerization method can easily obtain a polymer with a desired molecular weight under mild conditions by utilizing the difference in chain transfer of radicals by a solvent and adjusting the amount of initiator and reaction temperature. Is preferable. In particular, a solution polymerization method under a pressurized condition is also preferable in that the amount of the initiator used is minimized and the influence of the remaining initiator is minimized.

  The composition of the polyester resin used in the present invention is as follows.

  Examples of the divalent alcohol component include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1, 6-hexanediol, neopentyl glycol, 2-ethyl-1,3-hexanediol, hydrogenated bisphenol A, and bisphenol represented by the formula (E) and derivatives thereof;

(In the formula, R is an ethylene or propylene group, x and y are each an integer of 0 or more, and the average value of x + y is 0 to 10.)
And diols represented by the formula (F);

  Examples of the divalent acid component include benzene dicarboxylic acids such as phthalic acid, terephthalic acid, isophthalic acid, and phthalic anhydride or anhydrides thereof, lower alkyl esters; alkyl dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, and azelaic acid. Acids or anhydrides thereof, lower alkyl esters; alkenyl succinic acids or alkyl succinic acids such as n-dodecenyl succinic acid and n-dodecyl succinic acid, or anhydrides, lower alkyl esters thereof; fumaric acid, maleic acid, citraconic acid, itaconic acid Dicarboxylic acids such as unsaturated dicarboxylic acids or anhydrides thereof, lower alkyl esters;

  Moreover, it is preferable to use together the trihydric or more alcohol component and trivalent or more acid component which work as a crosslinking component.

  Examples of the trihydric or higher polyhydric alcohol component include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butane. Triol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxybenzene, etc. Is mentioned.

  Examples of the trivalent or higher polycarboxylic acid component in the present invention include trimellitic acid, pyromellitic acid, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5, 7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylene Carboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid, empole trimer acid, and their anhydrides, lower alkyl esters;

(Wherein X is an alkylene group or alkenylene group having 5 to 30 carbon atoms having one or more side chains having 3 or more carbon atoms)
And polycarboxylic acids such as anhydrides and lower alkyl esters thereof and derivatives thereof.

  The alcohol component used in the present invention is 40 to 60 mol%, preferably 45 to 55 mol%, and the acid component is 60 to 40 mol%, preferably 55 to 45 mol%. Moreover, it is preferable that the polyvalent component more than trivalence is 5-60 mol% in all the components.

  The polyester resin can also be obtained by a generally known condensation polymerization.

  The waxes used in the present invention include the following. For example, low molecular weight polyethylene, low molecular weight polypropylene, polyolefin copolymer, polyolefin wax, microcrystalline wax, paraffin wax, aliphatic hydrocarbon wax such as Fischer-Tropsch wax; oxide of aliphatic hydrocarbon wax such as oxidized polyethylene wax Or block copolymers thereof; plant waxes such as candelilla wax, carnauba wax, waxy wax, jojoba wax; animal waxes such as beeswax, lanolin, spermaceti; mineral systems such as ozokerite, ceresin, petrolactam; Waxes; waxes mainly composed of aliphatic esters such as montanic acid ester wax and castor wax; those obtained by partially or fully deoxidizing aliphatic esters such as deoxidized carnauba wax . Further, saturated linear fatty acids such as palmitic acid, stearic acid, montanic acid, or long-chain alkyl carboxylic acids having a long-chain alkyl group; unsaturated fatty acids such as brassic acid, eleostearic acid, and valinal acid; stearyl alcohol Saturated alcohol such as eicosyl alcohol, behenyl alcohol, cannavir alcohol, seryl alcohol, melyl alcohol, or alkyl alcohol having a long chain alkyl group; polyhydric alcohol such as sorbitol; linoleic acid amide, oleic acid amide, lauric acid Aliphatic amides such as acid amides; saturated aliphatic bisamides such as methylene bisstearic acid amide, ethylene biscapric acid amides, ethylene bislauric acid amides, hexamethylene bisstearic acid amides; Unsaturated fatty acid amides such as inamide, hexamethylenebisoleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide; m-xylene bisstearic acid amide, N, Aromatic bisamides such as N'-distearylisophthalamide; aliphatic metal salts such as calcium stearate, calcium laurate, zinc stearate and magnesium stearate (commonly referred to as metal soap); aliphatic hydrocarbons Wax grafted with a vinyl monomer such as styrene or acrylic acid; Partial esterified product of fatty acid and polyhydric alcohol such as behenic acid monoglyceride; Hydroxyl group obtained by hydrogenating vegetable oil Methyl ester compounds It is.

  In addition, these waxes have a sharp molecular weight distribution using a press sweating method, a solvent method, a recrystallization method, a vacuum distillation method, a supercritical gas extraction method or a melt liquid crystal deposition method, a low molecular weight solid fatty acid, a low molecular weight A solid alcohol, a low molecular weight solid compound, and other impurities are preferably used.

  Magnetic iron oxide may be used as the colorant of the present invention, in which case it can be used as a magnetic toner. As the magnetic iron oxide, iron oxides such as magnetite, maghemite, and ferrite are used, and the surface of the magnetic iron oxide is used. Or what contains a nonferrous element inside is preferable.

  When the present invention is applied as a magnetic toner, the magnetic iron oxide used therein preferably contains 0.05 to 10% by mass of a different element on the basis of the iron element. Especially preferably, it is 0.1-5 mass%.

  Moreover, it is preferable that these magnetic iron oxides contain 20-200 mass parts with respect to 100 mass parts of binder resin. More preferably, 50 to 120 parts by mass are contained.

  The different element is preferably an element selected from magnesium, aluminum, silicon, phosphorus, and sulfur. The following lithium, beryllium, boron, germanium, titanium, zirconium, tin, lead, zinc, calcium, barium, scandium, vanadium, chromium, manganese, cobalt, copper, nickel, gallium, cadmium, indium, silver element, Examples of the metal include palladium, gold, mercury, platinum, tungsten, molybdenum, niobium, osmium, strontium, yttrium, and technetium.

These magnetic iron oxides preferably have a number average particle diameter of 0.05 to 1.0 μm, more preferably 0.1 to 0.5 μm. Magnetic iron oxide having a BET specific surface area of ² to 40 m ² / g (more preferably 4 to ²⁰ m ² / g) is preferably used. There is no restriction | limiting in particular in a shape, The thing of arbitrary shapes is used. As magnetic characteristics, under a magnetic field of 795.8 kA / m, the saturation magnetization is 10 to 200 Am ² / kg (more preferably 70 to 100 Am ² / kg), and the residual magnetization is 1 to 100 Am ² / kg (more preferably 2 ˜20 Am ² / kg) and those having a coercive force of 1 to 30 kA / m (more preferably 2 to 15 kA / m) are preferably used.

Further, when a magnetic toner is used as the toner of the present invention, the density of the magnetic toner is desirably 1.3 to 2.2 g / cm ³ . Furthermore, it is preferable that it is the range of 1.5-2.0 g / cm < ³ >. The mass (density) of the magnetic toner correlates with the magnetic force, electrostatic force, and gravity acting on the magnetic toner particles. When the density of the magnetic toner is within this range, the action of magnetic iron oxide is appropriate. The balance between magnetic force and magnetic force is good, and excellent developing power can be exhibited.

On the other hand, when the density of the magnetic toner is less than 1.3 g / cm ³ , the magnetic force is low because the action of magnetic iron oxide on the magnetic toner is weak. For this reason, the electrostatic force for flying to the photosensitive drum at the time of development is superior, resulting in an excessive development state, leading to fogging and an increase in consumption. On the other hand, when the magnetic toner density is over 2.2 g / cm ³ , the action of magnetic iron oxide on the magnetic toner becomes stronger and the magnetic force becomes stronger than the electrostatic force, and the strong magnetic force action is large and the specific gravity is also heavy. Therefore, it is difficult to fly from the sleeve at the time of development, resulting in a state of insufficient development, leading to low image density and image deterioration.

  In some cases, the magnetic iron oxide used in the magnetic toner of the present invention may be treated with a silane coupling agent, a titanium coupling agent, titanate, aminosilane, or the like.

  The toner of the present invention preferably contains a charge control agent.

  Examples of the toner that controls the negative charge include the following compounds.

  Organic metal complexes and chelate compounds are effective, and examples include monoazo metal complexes, acetylacetone metal complexes, aromatic hydroxycarboxylic acids, and aromatic dicarboxylic acid metal complexes. Others include aromatic hydroxycarboxylic acids, aromatic mono- and polycarboxylic acids and their metal salts, anhydrides, esters, and phenol derivatives of bisphenol.

  Among these, an azo metal complex represented by the following formula (I) is preferable.

[In the formula, M represents a coordination center metal, and examples thereof include Sc, Ti, V, Cr, Co, Ni, Mn, and Fe. Ar is an aryl group, which is an aryl group such as a phenyl group or a naphthyl group, and may have a substituent. In this case, examples of the substituent include a nitro group, a halogen group, a carboxyl group, an anilide group, an alkyl group having 1 to 18 carbon atoms, and an alkoxy group having 1 to 18 carbon atoms. X, X ', Y and Y' are -O-, -CO-, -NH-, -NR- (R is an alkyl group having 1 to 4 carbon atoms). C + represents a counter ion, and represents hydrogen, sodium, potassium, ammonium, aliphatic ammonium, or a mixed ion thereof. ]

  In particular, Fe or Cr is preferred as the central metal, halogen, alkyl group or anilide group is preferred as the substituent, and hydrogen, alkali metal, ammonium or aliphatic ammonium is preferred as the counter ion. A mixture of complex salts having different counter ions is also preferably used.

  The following compounds are used to control the toner to be positively charged.

  Nigrosine modified products such as nigrosine and fatty acid metal salts; quaternary ammonium salts such as tributylbenzylammonium-1-hydroxy-4-naphthosulfonate, tetrabutylammonium tetrafluoroborate, and analogs such as phosphonium salts Onium salts and lake pigments thereof; triphenylmethane dyes and lake pigments thereof (as rake agents, phosphotungstic acid, phosphomolybdic acid, phosphotungsten molybdic acid, tannic acid, lauric acid, gallic acid, ferricyanide, Ferrocyanide, etc.); metal salt of higher fatty acid; diorganotin oxide such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide; dibutyltin borate, dioctyltin borate, di Black hexyl scan such diorgano tin borate such tin borate; guanidine compounds; imidazole compounds. These can be used alone or in combination of two or more. Among these, triphenylmethane compounds and quaternary ammonium salts whose counter ions are not halogen are preferably used. The following formula (II)

[Wherein R ₁ represents H or CH ₃ , and R ₂ and R ₃ represent a substituted or unsubstituted alkyl group (preferably C1 to C4). ]
A copolymer with a polymerizable monomer such as styrene, acrylic acid ester or methacrylic acid ester described above can be used as a positive charge control agent. In this case, the homopolymer and copolymer have a function as a charge control agent and a function as a binder resin (all or a part thereof).

  As a method of incorporating a charge control agent into the toner, there are a method of adding it inside the toner particles and a method of adding it externally. The amount of these charge control agents used is determined by the toner production method including the type of binder resin, the presence or absence of other additives, and the dispersion method, and is not uniquely limited. Preferably, it is used in the range of 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the binder resin.

  As a method for producing the toner of the present invention, the above-described toner constituent materials are sufficiently mixed by a ball mill or other mixer, and then kneaded well using a heat kneader such as a hot roll kneader or an extruder, and then solidified by cooling. Thereafter, a method of obtaining toner by mechanically pulverizing and classifying the pulverized powder is preferable. In addition, a polymerization method in which a predetermined material is mixed with a monomer that constitutes the binder resin to obtain an emulsion suspension, followed by polymerization to obtain a toner; a so-called microcapsule toner comprising a core material and a shell material In which a predetermined material is contained in the core material, the shell material, or both of them; and a method of obtaining the toner by dispersing the constituent materials in the binder resin solution and then spray-drying. Furthermore, the developer of the present invention can be produced by sufficiently mixing the desired additive and toner particles with a mixer using the various methods described above as required.

  For example, as a mixer, Henschel mixer (made by Mitsui Mining); Super mixer (made by Kawata); Ribocorn (made by Okawara Seisakusho); Nauter mixer, turbulizer, cyclomix (made by Hosokawa Micron); Spiral pin mixer (Manufactured by Taiheiyo Kiko Co., Ltd.); Ladige mixer (manufactured by Matsubo Co., Ltd.), and kneaders: KRC kneader (manufactured by Kurimoto Iron Works Co.); bus co kneader (manufactured by Buss); TEM type extruder (Manufactured by Toshiba Machine Co., Ltd.); TEX twin-screw kneader (manufactured by Nippon Steel Works); PCM kneader (manufactured by Ikegai Iron Works Co., Ltd.); three roll mill, mixing roll mill, kneader (manufactured by Inoue Seisakusho Co., Ltd.); Mining company); MS pressure kneader, Nider Ruder (Moriyama Seisakusho); Banbury mixer (Kobe Steel) As a pulverizer, a counter jet mill, a micron jet, an inomizer (manufactured by Hosokawa Micron); an IDS type mill, a PJM jet pulverizer (manufactured by Nippon Pneumatic Industry); a cross jet mill (manufactured by Kurimoto Iron Works); URMAX (manufactured by Nisso Engineering Co., Ltd.); SK Jet O Mill (manufactured by Seishin Enterprise Co., Ltd.); Kryptron (manufactured by Kawasaki Heavy Industries, Ltd.); Turbo Mill (manufactured by Turbo Industry Co., Ltd.); , Micron Classifier, Spedick Classifier (manufactured by Seishin Enterprise Co., Ltd.); Turbo Classifier (Nisshin Engineering Co., Ltd.); Micron Separator, Turboplex (ATP), TSP Separator (manufactured by Hosokawa Micron Co.); Elbow Jet (Nittetsu Mining) Dispurge) Separator (manufactured by Nippon Pneumatic Kogyo Co., Ltd.); YM Microcut (manufactured by Yaskawa Shoji Co., Ltd.), and as a sieving device used for sieving coarse particles, Ultrasonic (manufactured by Koei Sangyo Co., Ltd.); Resona sieve , Gyroshifter (manufactured by Tokusu Kosakusha); Vibrasonic system (manufactured by Dalton); Soniclean (manufactured by Shinto Kogyo); Turbo screener (manufactured by Turbo Kogyo); Micro shifter (manufactured by Hadano Sangyo); Circular A vibration sieve etc. are mentioned.

  One embodiment of the configuration of the image forming apparatus of the present invention will be described with reference to FIG. This image forming apparatus is a laser printer (recording apparatus) of a development and 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, a magnetic one-component developer is used as a developer, and the developer layer on the developer carrier and the image carrier are not in contact with each other. 2 is an example of an image forming apparatus for non-contact development arranged to be.

  Reference numeral 1 denotes a rotating drum type OPC photoconductor as an image carrier, which is rotationally driven at a peripheral speed (process speed) of 120 mm / sec in the clockwise direction (in the direction of the arrow).

  Reference numeral 2 denotes a charging roller as a contact charging member. The charging roller 2 is disposed in pressure contact with the photoreceptor 1 with a predetermined pressing force against elasticity. Reference numeral n denotes a charging contact portion that is a contact portion between the photosensitive member 1 and the charging roller 2. In this aspect, the charging roller 2 is rotationally driven at a peripheral speed of 120 mm / sec in the facing direction (opposite to the moving direction of the photosensitive member surface) at the contact portion n with the photosensitive member 1. That is, the surface of the charging roller 2 as a contact charging member has a relative speed difference of 200% relative to the surface of the photoreceptor 1.

  The relative movement speed ratio indicating the relative speed difference described here can be expressed by the following equation.

Relative moving speed ratio (%) = | (Vc−Vp) / Vp | × 100
(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.)

  In the present invention, the ratio of the moving speed of the surface of the image carrier to the relative moving speed of the surface of the charging member facing it is preferably 10 to 500%, more preferably 20 to 400%. When the relative movement speed ratio is less than 10%, the contact probability between the contact charging member and the image carrier cannot be increased sufficiently, and the chargeability of the image carrier by direct injection charging is maintained. Is difficult. In addition, the charging amount of the image carrier is suppressed by limiting the total amount of the developer component interposed in the contact portion between the image carrier and the contact charging member by sliding between the contact charging member and the image carrier. And the effect of leveling the pattern of residual toner particles and improving the recoverability of the developer during development and cleaning cannot be sufficiently obtained. When the relative moving speed ratio is larger than 500%, the moving speed of the charging member surface is remarkably increased. Therefore, the developer component carried to the contact portion between the image carrier and the contact charging member is used. As a result, the image carrier and the contact charging member are likely to be worn out or scratches are easily generated, resulting in a shortened life.

  Further, when the moving speed of the charging member is 0 (in a state where the charging member is stationary), the contact point of the charging member with the image carrier becomes a fixed point. This is not preferable because the effect of suppressing the charging inhibition of the image carrier and the effect of leveling the pattern of the residual toner particles and improving the recoverability of the developer in the simultaneous development cleaning are liable to decrease.

  In addition, conductive fine powder is applied to the surface of the charging roller 2 so that the coating amount is uniform in one layer.

  A DC voltage of -700 V is applied as a charging bias to the cored bar 2a of the charging roller 2 from the charging bias application power source S1. In this embodiment, the surface of the photoreceptor 1 is uniformly charged by a direct injection charging method to a potential (−680 V) substantially equal to the voltage applied to the charging roller 2.

  Reference numeral 3 denotes a laser beam scanner (exposure device) including a laser diode and a polygon mirror. This laser beam scanner outputs laser light whose intensity is modulated in accordance with time-series electric digital pixel signals of target image information, and scans and exposes the uniformly charged surface of the photoreceptor 1 with the laser light. By this scanning exposure, an electrostatic latent image corresponding to target image information is formed on the rotary photoconductor 1.

  Reference numeral 4 denotes a developing device. The electrostatic latent image on the surface of the photoreceptor 1 is developed as a toner image by the developing device. The developing device 4 of this embodiment is a non-contact type reversal developing device using a negatively chargeable magnetic one-component insulating developer as a developer. The developer 4d contains toner particles (t) and conductive fine powder (m).

  Reference numeral 4a denotes a non-magnetic developing sleeve having a diameter of 16 mm that includes a magnet roll 4b as a developer carrying member. The developing sleeve 4a is disposed to face the photosensitive member with a separation distance of 320 μm, and the developing portion (developing region portion) a which is a portion facing the photosensitive member 1 has a moving direction of the surface of the photosensitive member 1. The developing sleeve 4a is rotated at a peripheral speed ratio of 110% of the peripheral speed of the photosensitive member 1 so that the moving direction of the surface of the developing sleeve 4a is a forward direction.

  A thin layer of developer 4d is coated on the developing sleeve 4a by an elastic blade 4c. The developer 4d is given a charge while the layer thickness on the developing sleeve 4a is regulated by the elastic blade 4c.

  The developer 4d coated on the developing sleeve 4a is transported to the developing portion a which is a facing portion between the photosensitive member 1 and the developing sleeve 4a as the developing sleeve 4a rotates.

A developing bias voltage is applied to the developing sleeve 4a from a developing bias applying power source S2. The developing bias voltage is a superposition of a DC voltage of −420 V and a rectangular AC voltage having a frequency of 1500 Hz and a peak-to-peak voltage of 1600 V (electric field strength of 5 × 10 ⁶ V / m). One-component jumping development is performed between.

  Reference numeral 5 denotes a medium-resistance transfer roller as a contact transfer means, which forms a transfer nip b by contacting the photosensitive member 1 with a linear pressure of 98 N per meter of contact length in the longitudinal direction. 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 5 from a transfer bias application power source S3. As a result, the toner image on the photosensitive member 1 side is sequentially transferred onto the surface of the transfer material P fed to the transfer nip portion b.

In this embodiment, the transfer roller-5 having a resistance of 5 × 10 ⁸ Ωcm is used, and transfer is performed by applying a DC voltage of + 2000V. That is, the transfer material P introduced into the transfer nip portion b is nipped and conveyed by the transfer nip portion b, and the toner images formed and supported on the surface of the photosensitive member 1 on the surface side are successively subjected to electrostatic force and pressing force. Will be transcribed.

  Reference numeral 6 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 1 side is separated from the surface of the photoconductor 1 and introduced into the fixing device 6 to receive the fixing of the toner image. It is discharged out of the apparatus as an image formed product (print, copy).

  The image forming apparatus according to this embodiment has the cleaning unit removed, and the developer remaining on the surface of the photoreceptor 1 after the transfer of the toner image onto the transfer material P (transfer residual toner particles) is removed with a cleaner. Rather, as the photosensitive member 1 rotates, it reaches the developing portion a via the charging contact portion n and is developed and cleaned (collected) in the developing device 4.

  In the image forming apparatus of this aspect, the three process devices of the photoconductor 1, the charging roller 2, and the developing device 4 are collectively configured as a process cartridge that is detachable from the image forming apparatus main body. The combination of process devices to be processed into a process cartridge is not limited to the above, and is arbitrary.

  An appropriate amount of the conductive fine powder m mixed in the developer 4d of the developing device 4 is transferred to the photosensitive member 1 side together with the toner particles t when the electrostatic latent image on the photosensitive member 1 is developed by the developing device 4.

  The toner image on the photoreceptor 1, that is, the toner particle t, is attracted to the transfer material P, which is a recording medium, and actively transfers at the transfer portion b due to the influence of the transfer bias. However, since the conductive fine powder m on the photosensitive member 1 is conductive, it does not actively transfer to the transfer material P side, and remains substantially adhered and held on the photosensitive member 1.

  In the present invention, since the image forming apparatus does not have a cleaning process, the transfer residual toner particles t and the conductive fine powder m remaining on the surface of the photoconductor 1 after transfer are exposed to light as the photoconductor 1 rotates. It is carried to a charging contact portion n that is a contact portion between the body 1 and a charging roller 2 that is a contact charging member, and adheres to or mixes with the charging roller 2. Therefore, direct injection charging of the photosensitive member 1 is performed in a state where the conductive fine powder m exists in the charging contact portion n.

  Due to the presence of the conductive fine powder m, even when the toner particles t adhere to and mix in the charging roller 2, the charging roller 2 can maintain a precise contact property and contact resistance with the photosensitive member 1. Thus, direct injection charging of the photosensitive member 1 can be performed.

  That is, the charging roller 2 is in close contact with the photosensitive member 1 through the conductive fine powder m, and the conductive fine powder m rubs the surface of the photosensitive member 1 without a gap. As a result, in the charging of the photoreceptor 1 by the charging roller 2, stable and safe direct injection charging without using a discharge phenomenon is dominant, and high charging efficiency that cannot be obtained by conventional roller charging or the like is obtained. Therefore, a potential substantially equal to the voltage applied to the charging roller 2 can be applied to the photoreceptor 1. Further, the transfer residual toner particles t adhering to or mixed in the charging roller 2 are gradually discharged from the charging roller 2 onto the photosensitive member 1 and reach the developing unit a as the surface of the photosensitive member 1 moves, and are developed in the developing device 4. It is also cleaned (collected).

  In the development and cleaning, the toner particles remaining on the photosensitive member 1 after the transfer are developed at the next and subsequent developments in the image forming process (after development, again at the development of the latent image through the charging process and the exposure process). This is recovered by the fog removal bias of the developing device (fogging removal potential difference Vback which is a potential difference between the DC voltage applied to the developing device and the surface potential of the photoreceptor). In the case of reversal development as in the image forming apparatus in this embodiment, this development and cleaning is performed by the electric field for collecting toner particles 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 for attaching (developing) toner particles.

  Further, when the image forming apparatus is operated, the conductive fine powder m contained in the developer of the developing device 4 is transferred to the surface of the photosensitive member 1 at the developing portion a, and transferred along with the movement of the surface of the photosensitive member 1. Since the conductive fine powder m continues to be sequentially supplied to the charging portion n by being carried to the charging contact portion n through the portion b, the conductive fine powder m decreases in the charging portion n due to dropping or the like. Even if the conductive fine powder m of the charging portion n is deteriorated, a decrease in charging property is prevented and good charging property is stably maintained.

  Thus, in an image forming apparatus using a contact charging method, a transfer method, or a toner recycling process, a uniform charging property can be provided with a low applied voltage by using the simple charging roller 2 as a contact charging member. In addition, although the charging roller 2 is contaminated with the transfer residual toner particles, ozone-less direct injection charging can be stably maintained over a long period of time, and uniform chargeability can be provided. Therefore, it is possible to obtain an image forming apparatus with a simple configuration and low cost, which is free from troubles caused by ozone products, troubles caused by defective charging, and the like.

Further, as described above, the conductive fine powder m needs to have a resistance value of 1 × 10 ⁹ Ω · cm or less in order not to impair the chargeability, but the developer is directly applied to the photoreceptor 1 in the developing portion a. In the case of using a contact developing device that makes contact, if the resistance value of the conductive fine powder m is too small, charge is injected into the photoreceptor 1 by the developing bias through the conductive fine powder m in the developed image agent, and image fogging occurs. Will occur.

  However, in this embodiment, since the developing device is a non-contact type developing device, a developing bias is not injected into the photoreceptor 1 and a good image can be obtained. Further, since no charge is injected into the photosensitive member 1 in the developing portion a, it is possible to give a high potential difference between the developing sleeve 4a and the photosensitive member 1 such as an AC bias. As a result, the conductive fine powder m can be easily developed uniformly, so that the conductive fine powder m can be uniformly applied to the surface of the photoreceptor 1 and uniform contact can be made at the charging portion to obtain good chargeability. Therefore, a good image can be obtained.

  A speed difference is easily and effectively provided between the charging roller 2 and the photosensitive member 1 by the lubricating effect (friction reduction effect) of the conductive fine powder m on the contact surface n between the charging roller 2 and the photosensitive member 1. Is possible. By this lubricating effect, friction between the charging roller 2 and the photosensitive drum 1 is reduced, driving torque is reduced, and scraping or scratches on the surface of the charging roller 2 or the photosensitive drum 1 can be prevented. Also, by providing this speed difference, the chance of the conductive fine powder m contacting the photoconductor 1 at the mutual contact surface portion (contact portion) n between the charging roller 2 and the photoconductor 1 is remarkably increased, and high contactability is achieved. Can be obtained. Therefore, good direct injection charging can be obtained, and a good image can be stably obtained.

  In this embodiment, the charging roller 2 is driven to rotate, and the rotation direction of the charging roller 2 rotates in the direction opposite to the moving direction of the surface of the photosensitive member 1, so that the charging roller n is carried on the photosensitive member 1. The transfer residual toner particles are temporarily collected on the charging roller 2 to obtain an effect of leveling the amount of the transfer residual toner particles present in the charging portion n. For this reason, occurrence of charging failure due to uneven distribution of the transfer residual toner particles at the charging contact portion is prevented, and more stable charging property can be obtained.

  Furthermore, by rotating the charging roller 2 in the reverse direction, the transfer residual toner particles on the photoconductor 1 are once separated from the photoconductor 1 and charged, whereby direct injection charging can be performed predominantly. Further, the effect of reducing the falling off of the conductive fine powder m from the charging roller 2 is obtained, and the chargeability of the image carrier due to excessive dropping off of the conductive fine powder m from the charging roller 2 is not caused.

  Also, a mode (contact charging member cleaning) in which the transfer residual toner adhering to and mixed in the contact charging member, which is a charging inhibiting factor, is efficiently excluded from the contact charging member during non-image recording such as between papers. If the toner according to the present invention is used in an image forming method in which the level of contamination of the contact charging member due to residual toner on the contact charging member is normally kept low, a further excellent charging property and image characteristics can be obtained over a long period of time. It can be maintained stably.

  That is, a contact charging member cleaning mode is provided to apply a DC + AC voltage to the contact charging member, and the contact charging member is loaded with conductive fine powder, so that the transfer residual toner contaminating the contact charging member is efficiently removed. High charging performance can also be achieved with respect to charging characteristics after image formation with high discharge and image ratio.

  Conventionally, the contact charging member and the toner are firmly adhered. However, the conductive charging powder and the toner are interposed between the conductive charging powder and the AC bias of 5 to 1000 Hz is applied between the contact charging member and the toner. The contact charging member can be quickly cleaned by reducing the adhesion force and generating an appropriate potential difference between the contact charging member and the image carrier. That is, the charging method by direct injection is a method in which a charging potential approximately equal to the applied voltage can be obtained, and therefore it is difficult to generate a potential difference between the contact charging member and the image carrier, and the conductive fine powder according to the present invention is used. However, it is difficult to completely clean the members. Therefore, a frequency of 5 to 1000 Hz where a difference in bias is likely to occur before and after the charging unit is a desirable condition for discharging the toner.

  When the frequency is less than 5 Hz, potential unevenness occurs on the photosensitive member corresponding to the frequency, and image density unevenness is likely to occur correspondingly. On the other hand, if the frequency exceeds 1000 Hz, the movement of the toner cannot follow, the cleaning effect is reduced, and the chargeability is liable to deteriorate.

  When the toner according to the present invention is used in a cleaner-less system including a direct injection charging process, the photoreceptor used has at least a photosensitive layer and a charge injection layer on a conductive support, and the charge injection layer The relationship between the elastic deformation rate We (OCL) (%) measured on the charge injection layer and the elastic deformation rate We (CTL) (%) measured on the photosensitive layer when the film thickness is d (μm) is as follows. When the approximate expression (3) is satisfied, the image has good performance on fog and chargeability on the image.

−0.71 × d + We (CTL) ≦ We (OCL)
≦ 0.03 × d ³ −0.89 × d ² + 8.43 × d + We (CTL) Equation (3)
However, We% = We / (We + Wr) × 100
We: Work of elastic deformation (nJ), Wr: Work of plastic deformation (nJ)
(The measurement environment is 23 ° C./55% RH.)

  If the elastic deformation rate on the surface of the photoconductor is controlled within the above range, setting it to the right side or less prevents embedding of the conductive fine powder and suppresses fogging, while setting it to the left side or more prevents the photoconductor surface from being scraped. Can maintain high chargeability.

  When forming the charge injection layer, it is preferable to use conductive particles. Examples of the conductive particles used include metals, metal oxides, and carbon black. These may be used alone or in combination of two or more. It can also be used in combination. When two or more types are used in combination, they may be simply mixed, or may be in the form of a solid solution or fusion.

  The average particle size of the conductive particles used in the present invention is preferably 0.3 μm or less, and particularly preferably 0.1 μm or less, from the viewpoint of the transparency of the charge injection layer.

  Among these conductive particles, it is preferable to use a metal oxide from the viewpoint of transparency. As described above, particularly when the conductive particles are composed of the same metal element as the conductive fine powder added to the toner, Becomes better.

  Here, when various physical properties of the conductive fine powder contained in the toner are measured, the toner container 4 is removed after the printing of a large number of sheets in a cleanerless system without the cleaning mode. A clean cleaner is attached, and then the printer is operated in the normal cleaning mode to collect the conductive fine powder in the cleaner container, and the measurement is repeated until a sufficient amount is collected.

  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 mass parts.

[Production Example of Conductive Fine Powder A-1]
The acidic tin chloride aqueous solution was controlled at 60 to 80 ° C., and an aqueous ammonia solution was added thereto to generate a precipitate, followed by filtration and washing to obtain a slurry of conductive fine particles. The obtained slurry was dried and crushed, and then calcined at 500 ° C. for 2 hours in a nitrogen atmosphere and further at 500 ° C. for 1 hour in a nitrogen / hydrogen mixed gas atmosphere, and crushed again to obtain metal compound fine particles. . The obtained metal compound fine particles were subjected to a surface treatment with 3.5 parts by mass of methyl hydrogen silicone oil. As a surface treatment method, 100 parts by mass of metal compound fine particles and 3.5 parts by mass of methyl hydrogen silicone oil diluted with toluene were added to a heating type mixer, and the solvent was removed while stirring and mixing at 80 ° C. Thereafter, heat treatment was performed at 120 ° C. for 30 minutes while continuing mixing. After returning to room temperature, crushing treatment was performed. The physical properties of the obtained conductive fine powder A-1 were volume resistance 8 × 10 ² Ωcm and Da = 1.3 μm.

[Production Example of Conductive Fine Powder A-2]
In Production Example 1 of metal compound fine particles, metal compound fine particles were produced by appropriately adjusting the tin chloride concentration, the addition rate of the aqueous ammonia solution, the firing temperature and the firing time. In a heating mixer, 100 parts by weight of the metal compound fine particles were produced. On the other hand, while spraying a solution obtained by adding 2 parts by mass of iso-butyltrimethoxysilane to 100 parts by mass of ethanol, the mixture was stirred and mixed at 80 ° C., and after the spraying was completed, the temperature was further increased to 120 ° C. and a heat treatment was performed for 30 minutes. . After taking out, it cooled to room temperature, crushed, and obtained electroconductive fine powder A-2 which performed surface treatment. Table 1 shows the physical properties of the obtained fine particles.

[Production Example of Conductive Fine Powder A-3]
A hydrochloric acid aqueous solution having a pH of about 1 in which tin chloride and antimony chloride are mixed and dissolved so that the molar ratio of tin and antimony is 100: 7 is brought to 80 ° C., and an aqueous sodium hydroxide solution is added thereto to form a coprecipitate. Then, filtration and washing were performed to obtain a slurry of conductive fine particles. The obtained slurry was dried and crushed, then calcined at 500 ° C. for 3 hours, and crushed again to obtain metal compound fine particles. Thereafter, in a heating mixer, 100 parts by mass of metal compound fine particles were stirred and mixed at 80 ° C. while spraying a solution obtained by adding 1.5 parts by mass of trimethylethoxysilane to 100 parts by mass of ethanol. The temperature was raised to 120 ° C. and a heat treatment for 30 minutes was performed. After taking out, it cooled to room temperature, crushed, and obtained the electroconductive fine powder A-3 which gave the surface treatment. Table 1 shows the physical properties of the obtained fine powder.

[Production Example of Conductive Fine Powder A-4, 7]
In the production example of the metal compound fine particles A-3, after adjusting the tin chloride concentration, the molar ratio of tin and antimony, the addition rate of the sodium hydroxide aqueous solution, the firing temperature and the firing time as appropriate, the surface treatment is applied to make the conductive fine powder. A-7 was obtained without A-4 and surface treatment. Table 1 shows the physical properties of the obtained fine powder.

[Production Example of Conductive Fine Powder A-5, 6]
An aqueous ammonium carbonate solution and an aqueous aluminum sulfate solution were mixed, put into an aqueous solution in which zinc oxide was dispersed, stirred at 60 ° C. for 1 hour, filtered and washed with water to obtain a slurry. This slurry was dispersed in ion-exchanged water, and carbon dioxide gas was blown in for 4 hours while maintaining the temperature at 30 ° C. After standing for a while, the supernatant was discarded, and the remaining slurry was spray-dried with a spray dryer to obtain a dry powder. This powder was thermally decomposed at 250 ° C. for 5 hours to obtain conductive zinc oxide fine powders A-5 and 6. Table 1 shows the physical properties of the obtained fine powder.

[Developer Production Example 1]
Material composition / Binder resin 100 parts by mass (styrene-acrylic resin (glass transition temperature Tg by DSC measurement is 58 ° C., acid value 23.0 mgKOH / g, MPC by GPC (number average molecular weight) 7000, Mw (weight average molecular weight) 400000, monomer ratio: 72.5 parts by mass of styrene, 20 parts by mass of n-butyl acrylate, 7 parts by mass of mono-n-butyl malate, 0.5 parts by mass of divinylbenzene)
・ 95 parts by mass of magnetic iron oxide (average particle size: 0.20 μm, BET specific surface area: 8.0 m ² / g, coercive force: 3.7 kA / m, saturation magnetization: 82.3 Am ² / kg, residual magnetization: 4 .0 Am ² / kg)
Polyethylene wax (melting point: 110 ° C.) 4 parts by mass Iron azo complex (T-77 manufactured by Hodogaya Chemical Co., Ltd.) 2 parts by mass The above compound was melt-kneaded with a biaxial extruder heated to 130 ° C., and cooled. Was roughly crushed with a hammer mill. The pulverization was performed by mechanical pulverization using a turbo mill (manufactured by Turbo Kogyo Co., Ltd.). The resulting finely pulverized product was subjected to strict classification and removal of ultrafine powder and coarse powder with a multi-division classifier (Elbow Jet Classifier manufactured by Nittetsu Mining Co., Ltd.) using the Coanda effect to obtain toner particles 1. The obtained toner particles 1 had a weight average diameter of 8.0 μm.

next,
100 parts by mass of toner particles 1 1.0 parts by mass of hydrophobic silica B-1 having a primary particle diameter of 12 nm (BET 115 m ² / g hydrophobized with dimethyl silicone oil and hexamethyldisilazane)
-Conductive fine powder A-1 0.4 part by mass First, inorganic fine powder B-1 is mixed for 2 minutes at 70 s ^-1 in Henschel mixer FM10C / l (Mitsui Mining Co., Ltd.), and then conductive. Developer ¹ was further added and mixed at 33 s ^-1 for 1 minute to obtain Developer 1. FIG. 1 shows a graph of methanol concentration with respect to the transmittance of the developer 1 having a wavelength of 780 nm. C80 was 62% and C10 was 64%. The release rate a of the inorganic fine powder was 1.3%, and the release rate b of the conductive fine powder was 88%. Table 3 shows the toner formulation and physical properties.

[Developer Production Examples 2 to 4, 7, 9 to 12]
In the same manner as in Production Example 1, toner particles 1 are used, and the conductive fine powders shown in Table 1 and the inorganic fine powders shown in Table 2 are used. 2-4, 7, 9-12 were obtained. Table 3 shows the wettability and release rate properties of the obtained developer.

[Developer Production Examples 5 and 6]
Material composition / Binder resin 100 parts by mass (polyester resin (glass transition temperature Tg by DSC measurement 57 ° C., acid value 32.0 mg KOH / g, Mw / Mn by GPC = 16.9, monomer ratio: BPA-PO: 70 mol) BPA-EO: 30 mol, TPA: 90 mol, TMA: 40 mol))
・ 95 parts by mass of magnetic iron oxide (average particle size: 0.20 μm, BET specific surface area: 8.0 m ² / g, coercive force: 3.7 kA / m, saturation magnetization: 82.3 Am ² / kg, residual magnetization: 4 .0 Am ² / kg)
-Polyethylene wax (melting point 110 ° C) 4 parts by mass-Iron azo complex (T-77 manufactured by Hodogaya Chemical) 2 parts by mass

  The above compound was melt-kneaded with a biaxial extruder heated to 130 ° C., and the cooled kneaded product was coarsely pulverized with a hammer mill. The pulverization process is pulverized with a fine pulverizer using impingement airflow pulverization, and the resulting fine pulverized product is divided into ultrafine powder and coarse particles using a multi-division classifier (Nittetsu Mining Co., Ltd. elbow jet classifier) using the Coanda effect. Toner particles 5 were obtained by strictly classifying and removing the powder. The resulting toner particles 5 had a weight average diameter of 8.0 μm.

  In the same manner as in Production Example 1, toner particles 5 are used, and the conductive fine powders shown in Table 1 and the inorganic fine powders shown in Table 2 are used. 5 and 6 were obtained.

[Developer Production Example 8]
The toner particles 1 were used to instantaneously pass through hot air at 300 ° C. to obtain toner particles 8.

  In the same manner as in Production Example 1, toner particles 8 are used, and the conductive fine powders shown in Table 1 and the inorganic fine powders shown in Table 2 are used. 8 was obtained.

[Photoconductor Production Example 1]
A 30 mm × 260.5 mm aluminum cylinder was used as a support, and a methanol solution of polyamide resin was applied thereon by a dipping method to provide an undercoat layer having a thickness of 0.5 μm.

  4 parts by mass of oxytitanium phthalocyanine pigment, 2 parts by mass of polyvinyl butyral resin, and 80 parts by mass of cyclohexanone were dispersed in a sand mill apparatus for about 4 hours. This dispersion was applied onto the undercoat layer to form a 0.2 μm charge generation layer.

  Next, 10 parts by mass of the triphenylamine compound and 10 parts by mass of the polycarbonate resin were dissolved in 100 parts by mass of monochlorobenzene. This solution was applied onto the charge generation layer and dried with hot air to form a charge transport layer having a thickness of 20 μm.

  Next, as a charge injection layer, 50 parts by mass of antimony-doped tin oxide fine particles surface-treated with silicone oil were dispersed in 150 parts by mass of ethanol, and further 20 parts by mass of polytetrafluoroethylene fine particles were added and dispersed. Thereafter, 150 parts by mass of a resol-type thermosetting phenol resin as a resin component was dissolved to obtain a preparation liquid.

Using this prepared solution, a film was formed on the previous charge transport layer by a dip coating method, followed by drying with hot air to form a charge injection layer, whereby a photoreceptor 1 was obtained. At this time, the film thickness of the charge injection layer of the photosensitive member 1 is measured using an instantaneous multi-photometry system MCPD-2000 (manufactured by Otsuka Electronics Co., Ltd.) due to light interference because of the thin film, and the film thickness is 2 μm. there were. As another method for measuring the film thickness, the cross section of the film of the photoreceptor can be directly observed and measured with an SEM or the like.

  The elastic deformation rate We% was measured using the above-described Fisher hardness meter (H100VP-HCU). The elastic deformation rate We% is read by detecting the indentation depth in a state where the load is applied by pushing the film into the film to be measured by applying a load with a diamond indenter with a square pyramid at a tip angle of 136 ° and pushing the load to 1 μm. . As described above, the elastic deformation rate We% is obtained from the elastic deformation work We (nJ) and the plastic deformation work Wr (nJ) using the above formula. The measurement was performed 10 times by changing the measurement position on the same sample, and the average was obtained from 8 points excluding the maximum value and the minimum value.

  The elastic deformation rate {We (OCL)} from the charge injection layer is measured directly from the charge injection layer of the electrophotographic photosensitive member, and the elastic deformation rate {We (CTL)} from the charge transport layer is measured. Was measured on the photosensitive layer after the charge injection layer was removed. The method for removing the charge injection layer was performed using a lapping tape (C2000: manufactured by Fuji Photo Film Co., Ltd.) with a drum polishing apparatus manufactured by Canon Inc., but is not limited thereto. However, the hardness of the photosensitive layer is measured at the point where the charge injection layer is completely removed while sequentially measuring the film thickness and observing the surface so that the charge injection layer is polished as much as possible so as not to polish the photosensitive layer. However, when the remaining film thickness of the photosensitive layer is 10 μm or more, it has been confirmed that almost the same value is obtained, and even when the photosensitive layer is excessively polished, when the remaining film thickness of the photosensitive layer is 10 μm or more, Nearly the same value is obtained. However, it is more preferable to measure in a state where the charge injection layer is eliminated as much as possible and the photosensitive layer is not polished as much as possible.

  The elastic deformation ratio We (CTL) of the photoreceptor 1 was 42, the lower limit (left side) of Formula (3) was 40.6, and the upper limit (right side) of Formula (3) was 55.5. On the other hand, We (OCL) was 55.5%.

[Production Example 1 of Charging Member]
A SUS roller with a diameter of 6 mm and a length of 264 mm is used as a core, and a medium-resistance urethane foam layer is formed in the shape of a roller on the core with urethane resin, carbon black as a conductive material, sulfiding agent, foaming agent, etc. Further, the charging member 1 having a diameter of 12 mm and a length of 234 mm was prepared as a flexible member by cutting and polishing to adjust the shape and surface properties.

The obtained charging member 1 had a resistance value of 10 ⁵ Ωcm and a hardness of 30 degrees in Asker C hardness.

<Example 1>
FIG. 2 shows an overall schematic configuration of the image forming apparatus of this example. FIG. 2 shows a laser printer (recording apparatus) of a development simultaneous cleaning process (cleanerless system) using a transfer type electrophotographic process. A process carts ridge removing the cleaning unit having a cleaning member such as cleaning blade, a toner using the toner 1, is arranged to the toner layer and the image carrier on the toner carrying member is in a non-contact A non-contact development method is used.

  A photoconductor 1 as an image carrier is the photoconductor obtained in Production Example 1, and is driven to rotate at a peripheral speed (process speed) of 94 mm / sec in the X direction of an arrow.

As the contact charging member, the charging member 1 obtained in the charging member manufacturing example 1 is used as the charging roller 2, and the charging roller 2 has a predetermined resistance against the photoreceptor 1 against elasticity as shown in the figure. It is disposed in pressure contact with the pressing force. Reference numeral n denotes a charging contact portion that is a contact portion between the photosensitive member 1 and the charging roller 2. In this example, the charging roller 2 is rotationally driven at a peripheral speed of 100% in the facing direction (arrow Y direction) at a charging contact portion n that is a contact surface with the photoreceptor 1. The surface of the charging roller 2 has a relative speed difference of 200% relative to the surface of the photoreceptor 1. Further, the conductive fine powder A-1 is applied to the surface of the charging roller 2 so that the application amount is uniform at about 1 × 10 ⁴ pieces / mm ² .

  Further, a DC voltage of -650 V was applied as a charging bias to the cored bar 2a of the charging roller 2 from the charging bias application power source S1. In this example, the surface of the photoreceptor 1 is uniformly charged by a direct injection charging method at a potential (−630 V) substantially equal to the voltage applied to the charging roller 2.

  A laser beam scanner (exposure device) 3 including a laser diode, a polygon mirror, or the like, which is an 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 photoreceptor 1 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 1. The electrostatic latent image on the surface of the photoreceptor 1 is developed as a toner image by the developing device 4 as a developing unit.

  The developing device 4 of this example is a non-contact type reversal developing device using the toner 1 as the toner.

As a toner carrier, a developing sleeve 4a in which a resin layer having a layer thickness of about 7 μm and a JIS centerline average roughness (Ra) of 1.0 μm having the following configuration is formed on an aluminum cylinder having a diameter of 16 mm blasted on the surface is used. A magnetic roll of 90 mT (900 gauss) of development magnetic pole is included, and an elastic blade 4c made of urethane having a thickness of 1.0 mm and a free length of 1.5 mm as a toner layer thickness regulating member is 29.4 N / m (30 g / cm). The contact was made with linear pressure. The gap between the photoreceptor 1 and the developing sleeve 4a was 290 μm.
・ Phenolic resin 100 parts by mass ・ Graphite (volume average particle size of about 7 μm) 90 parts by mass ・ Carbon black 10 parts by mass Further, the developing sleeve 4a is provided in the developing part a (developing area part) which is the part facing the photoreceptor 1. Thus, the photosensitive member 1 is rotated in the forward direction (arrow W direction) at a peripheral speed of 120% of the peripheral speed of the photosensitive member 1.

The developing sleeve 4a 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 4a is regulated by the elastic blade 4c, and an electric charge is applied. At this time, the amount of toner coated on the developing sleeve 4a was 16 g / m ² .

The toner coated on the developing sleeve 4a is transported to the developing portion a which is a facing portion between the photosensitive member 1 and the developing sleeve 4a by the rotation of the developing sleeve 4a. A developing bias voltage is applied to the sleeve 4a from a developing bias applying power source S2. The development bias voltage is a superposition of a DC voltage of −440 V and a rectangular AC voltage with a frequency of 1600 Hz and a peak-to-peak voltage of 1500 V (electric field strength of 5 × 10 ⁶ V / m). In the meantime, one-component jumping development was performed in the developing section a.

  The transfer roller 5 having a medium resistance as a contact transfer unit is brought into pressure contact with the photosensitive member 1 with a linear pressure of 98 N / m (100 g / cm) to form a transfer contact portion b. The transfer contact portion b is fed with a transfer material P at a predetermined timing from a paper supply unit (not shown), and a predetermined transfer bias voltage is applied to the transfer roller 5 from a transfer bias application power source S3. The toner image on the body 1 side is sequentially transferred onto the surface of the transfer material P fed to the transfer contact portion b.

In this example, the transfer roller 5 has a volume resistance value of 5 × 10 ⁸ Ωcm, and transfer was performed by applying a DC voltage of + 2000V. That is, the transfer material P introduced into the transfer contact portion b is nipped and conveyed by the transfer contact portion b, and the toner image formed and supported on the surface of the photosensitive member 1 on the surface side is successively subjected to electrostatic force. It is transferred by pressing force. The transfer material P that has been fed to the transfer contact portion b and has received the transfer of the toner image on the photosensitive member 1 side is separated from the surface of the photosensitive member, and is introduced into a fixing device 6 such as a heat fixing method as a fixing means. The toner image is fixed and discharged as an image formed product (print, copy) to the outside of the apparatus.

  In the image forming apparatus of this example, the cleaning means is removed, and residual toner remaining on the surface of the photoconductor 1 after the transfer of the toner image onto the transfer material P is not removed by the cleaner, and the photoconductor 1 is rotated. At the same time, it reaches the developing portion a via the charging contact portion n and is simultaneously cleaned (collected) by the developing device 4.

  Conventionally, since the toner is an insulator, the mixing of the untransferred toner into the charging contact portion n is a factor that causes a charging failure in charging the photosensitive member. However, even in this case, since the conductive fine powder A-1 having a large BET value is present in the charging contact portion n between the photosensitive member 1 and the charging roller 2, the contact property of the charging roller 2 to the photosensitive member 1 is high. Therefore, the ozone-less direct charging can be stably maintained over a long period of time at a low applied voltage regardless of the contamination of the charging roller 2 due to the transfer residual toner, and a uniform charging property can be provided. .

Further, in this embodiment, the charging roller 2 is switched between the DC bias voltage and the AC voltage in series by switching the switch of the charging bias application power source by the sequence control circuit at the time of paper non-image recording. DC voltage to the core metal 2a: -650V
AC voltage: A rectangular wave superimposed voltage having a peak-to-peak voltage of 200 V and a frequency of 500 Hz is applied.

In addition, during the interval between the sheets, the developing sleeve 4a of the developing device 4 is similar to that at the time of image recording.
DC voltage: -440V
AC voltage: A peak-to-peak voltage of 1500 V, a frequency of 1.6 kHz, and a rectangular wave superimposed voltage were applied.

  By maintaining these bias relationships, the toner that is negatively frictionally charged on the charging roller 2 is developed on the photosensitive member 1 (the toner on the charging roller 2 is discharged to the photosensitive member 1 side), and the toner is further developed. Can be recovered by the back contrast of the developing device 4.

In this embodiment, 320 g of toner 1 is filled in the image forming apparatus, and the toner is used until the amount of toner in the toner cartridge decreases due to an image pattern including only horizontal lines with a printing area ratio of 2%. 75g / m ² A4 copy paper is used as the transfer material, in a high temperature and high humidity environment (30 ° C, 80% RH), in a normal temperature and humidity environment (23.5 ° C, 60% RH), and in a low temperature and humidity environment. 5000 sheets were printed intermittently at 15 ° C. and 10% RH, and the following evaluations were performed for the initial durability period, the durability period of 5000 sheets, and the standing time for one day. The results are shown in Tables 4-6.

[Evaluation]
The transfer efficiency is determined by tapering the transfer residual toner on the photoconductor after the solid black image transfer with a Mylar tape and pasting it on the paper. The Macbeth density value is C, and the Mylar is applied on the paper with the toner after the fixing before the transfer. When the Macbeth concentration of the tape was affixed to D and the Macbeth concentration of the Mylar tape affixed on unused paper was assumed to be E, it was approximately calculated by the following formula. If the transfer efficiency is 80% or more, the image has no practical problem.

      Transfer efficiency (%) = (DC / DE) × 100

The dot reproducibility was evaluated by the reproducibility of one small-diameter isolated dot at 600 dpi, which is easy to close due to the electrostatic latent image electric field and difficult to reproduce.
◎: Very good, 5 or less defects in 100 ○: Good, 6 to 10 defects in 100 Δ: Practical, 11 to 20 defects in 100 ×: Impractical, 100 More than 20 defects

  The fog on the paper was measured using a REFECTMETER MODEL TC-6DS manufactured by Tokyo Denshoku. A green filter was used as the filter. The fog value was calculated from the following formula using a solid white image. If the fog on paper is 2.0% or less, a good image is obtained.

  Fog (reflectance) (%) = reflectance on standard paper (%) − reflectance of sample non-image area (%)

  The image density was measured with a Macbeth densitometer RD918 (manufactured by Macbeth).

The charging property is a mixed image of a solid image and a non-image at the upper end (3 cm from the image front end), and a uniform halftone image after 3 cm from the image front end, that is, a ghost image in which charging ghost is likely to occur. It was evaluated by. In the halftone part, the image density of the non-image corresponding part and the image density of the solid image corresponding part developed darker due to poor chargeability were measured, and the difference between them was obtained.
◎: Very good, difference between both is less than 0.05 ○: Good, difference between both is 0.05 or more and less than 0.1 Δ: Practical use, difference between both is 0.1 or more and less than 0.2 ×: Practical No, the difference between them is 0.2 or more

  With regard to the toner recoverability, five sheets of solid black with the largest transfer residue are continuously fed and then solid white is continuously fed. At this time, if a large amount of transfer residue cannot be collected, fogging occurs on the paper. The toner recoverability was evaluated based on the fog value at this time. In this case as well, a good image can be said if it is 2% or less.

<Example 2 , Reference Examples 1-6 , Comparative Examples 1-4>
Evaluations were made in the same manner as in Example 1 except that the toner formulation and physical properties shown in Table 3 were used. The results were as shown in Tables 4-6.

It is the graph which showed the transmittance | permeability with respect to methanol concentration of the developer 1 of Example 1 of this invention. 1 is a schematic view of an example of an image forming apparatus used in the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 2a Charging roller core 2b Flexible layer 3 Exposure device 4 Developing device 4a Developing sleeve 4b Magnet roll 4c Elastic blade 4d Toner 5 Transfer roller 6 Fixing device S1 Power supply for charging member S2 Power source for development S3 Transfer Power supply

Claims (14)

In a developer having at least toner particles containing a binder resin and a colorant, an inorganic fine powder, and a conductive fine powder,
When the wettability of the developer to a methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 80% is in the range of 35 to 80% by volume,
The inorganic fine powder contains at least silica treated with silicone oil,
The volume average particle diameter Da of the conductive fine powder and the number average particle diameter Db of the primary particles of the inorganic fine powder satisfy the following formula (1):
Da ≧ 10 Db (1)
A developer, wherein the release rate a of the conductive fine powder is 50 % to 95%, and the release rate b of the inorganic fine powder is 0.1% to 3 %. When the wettability of the developer to a methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 10% is in the range of 40 to 85% by volume. The developer according to claim 1 . When the wettability of the developer to a methanol / water mixed solvent is measured by the transmittance of light having a wavelength of 780 nm, the methanol concentration when the transmittance is 80% is C80, and the methanol concentration when the transmittance is 10%. when was the C10, developer according to claim 1 or 2, characterized by satisfying the following formula (2).
0 <C10-C80 ≦ 10 (2) The developer according to any one of claims 1 to 3 , wherein the conductive fine powder exists as an aggregate and has a volume average particle diameter Da of 0.1 to 4 µm. The surface of the conductive fine powder is hydrophobized with at least one hydrophobizing agent selected from silicone varnish, various modified silicone varnishes, silicone oil, various modified silicone oils, silane compounds, and silane coupling agents. The developer according to any one of claims 1 to 4 , wherein Developer according to any one of claims 1 to 5 content of the conductive fine powder is characterized in that from 0.1 to 5.0% by weight of the total developer. Developer according to any one of claims 1 to 6 wherein the electrically conductive powder, the resistance is equal to or less than 10 ⁹ Ω · cm. Developer according to any one of claims 1 to 6 wherein the electrically conductive powder, the resistance is equal to or less than 10 ⁶ Ω · cm. The conductive fine powder, zinc oxide, developer according to any one of claims 1 to 8, characterized by containing tin oxide, an oxide of at least one selected from titanium oxide. The developer according to any one of claims 1 to 9 , wherein the content of the inorganic fine powder is 0.1 to 3.0% by mass of the whole developer. The silica developer according to any one of claims 1 to 10, characterized in that treated with at least a silane compound and silicone oil. The developer according to any one of claims 1 to 11 , wherein the number average particle diameter Db of primary particles of the inorganic fine powder is 4 to 80 nm. Developer according to any one of claims 1 to 12 weight average particle diameter of the developer is equal to or is 3μm or 12μm or less. Developer, after adding and mixing inorganic fine powder, the developer according to any one of claims 1 to 13, characterized in that it is manufactured by adding a conductive fine powder.

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