JP4695531B2 - Carrier, developer, image forming method and process cartridge - Google Patents

Description

  The present invention relates to a carrier, a developer, an image forming method, and a process cartridge.

  In image forming methods such as electrophotography and electrostatic photography, a developer is used to develop the electrostatic latent image formed on the latent image carrier. The developer needs to be a suitably charged mixture, and a two-component developer obtained by mixing a toner and a carrier and a one-component developer not containing a carrier are known. Since the two-component developer uses a carrier, the frictional charging area with respect to the toner is large, and the charging characteristics are stable compared to the one-component developer, so that high image quality can be maintained over a long period of time. . Further, since it has a high ability to supply toner to the development area, it is often used especially for high-speed machines. In addition, two-component developers are widely used in digital electrophotographic systems in which an electrostatic latent image is formed on a photosensitive member with a laser beam or the like and the electrostatic latent image is visualized. It has been adopted.

  The carrier used in such a two-component developer is to prevent toner spent on the carrier surface, to form a uniform carrier surface, to prevent oxidation of the carrier surface, to prevent a decrease in moisture sensitivity, to extend the life of the developer, In order to protect the photoconductor from scratches and abrasion by the carrier, control the charge polarity, adjust the charge amount, etc., studies have been made to increase durability by coating with an appropriate resin material. . For example, those coated with a specific resin material, those obtained by adding various additives to the coating layer, and those obtained by attaching additives to the carrier surface are known.

  Patent Document 1 discloses that a carrier coating material is composed of a guanamine resin and a thermosetting resin that can be cross-linked with the guanamine resin. Patent Document 2 discloses a cross-linked product of a melamine resin and an acrylic resin as a carrier coating material. It is disclosed to use.

  In order to further enhance durability, Patent Document 3 discloses a resin component containing a resin component obtained by crosslinking a thermoplastic resin and a guanamine resin and a charge control agent. This makes it possible to obtain a resin layer having elasticity that can absorb the friction between the carrier and the toner generated during agitation for frictionally charging the developer and the friction between the carriers, and the toner to the carrier. It is possible to suppress the spent. However, the demand for high durability in the market is still high, and it is particularly important to suppress the destabilization of the charge amount and the decrease in resistance caused by spent toner on the carrier surface.

  Since the resin-coated carrier is insulated along with the resin coating and does not function as a developing electrode, there is a problem that an edge effect is likely to occur particularly in a solid image portion. In addition, since the counter charge at the time of toner removal becomes excessive, carrier adhesion to non-image portions due to electrostatic development is likely to occur.

  In order to solve this problem, for example, Patent Document 4 discloses a resin-coated carrier in which conductive carbon is dispersed as a conductive agent in a coating layer of the carrier. However, such a carrier, when used as a developer, between the carriers and between the carrier and the toner, due to friction, collision, etc., the carbon or the resin piece containing carbon is detached from the carrier coating layer, adhere to the toner, It is developed. This phenomenon does not pose a major problem when forming a copy image such as black characters using black toner. However, in the case of a developer combined with color toner, particularly yellow toner, color turbidity (color stain) is caused. It appears prominently as a problem.

  In particular, in the case of a carrier using core material particles with less unevenness on the surface, the problem of color stains appears remarkably. This is because, when core particles with many irregularities are used, the conductive fine particles enter into the concave portions on the surface of the core material particles, so that the surface of the coating resin tends to be relatively smooth, whereas there are few irregularities. When the core material particles are used, it is considered that the conductive fine particles are likely to appear on the surface of the coating resin because there is no space for the conductive fine particles to enter on the surface of the core material particles. When such a carrier is stressed, the conductive fine particles are liable to be detached from the surface of the carrier, which is likely to cause color stains.

Patent Documents 5 to 7 disclose carriers having a coating layer containing a conductive filler. In these carriers, it is possible to use conductive fillers as conductive fine particles without being limited to carbon. Therefore, in order to reduce the influence of colored substances released from the carrier on the toner, It is possible to select few materials. However, the purpose is to improve the image quality due to the electrical stability of the conductive filler, and the problem of color stains has not been solved.
JP-A-8-6307 Japanese Patent No. 2683624 JP 2001-117287 A JP-A-56-75659 JP-A-4-360156 JP-A-5-303238 JP-A-11-174740

  An object of the present invention is to provide a carrier capable of reducing development torque and suppressing occurrence of color stains, background stains, and carrier adhesion, in view of the above-described problems of the prior art. It is another object of the present invention to provide a developer, an image forming method, and a process cartridge using the carrier.

The invention according to claim 1, in carrier core material particles having magnetism are coated with a layer containing a binder resin, the core material particles have a weight average particle diameter Dw is Ri der than 32μm below 22μm , number average particle diameter is 1.20 or less the ratio Dw / Dp of weight average particle diameter Dw is 1.00 or more with respect to Dp, the content of the particle diameter is 20μm or less is 0 wt% or more 7 wt% or less And the content of particles having a particle size of 36 μm or less is 90 wt% or more and 100 wt% or less , the BET specific surface area is 300 cm ² / g or more and 900 cm ² / g or less, and contains the binder resin The layer further contains white conductive particles, and the white conductive particles are characterized in that the base particles are covered with a conductive coating layer containing tin dioxide and indium oxide . As a result, it is possible to provide a carrier that can reduce development torque and suppress the occurrence of color stains, background stains, and carrier adhesion.

According to a second aspect of the present invention, in the carrier according to the first aspect, in the white conductive particles, a layer containing tin dioxide is formed between the base particles and the conductive coating layer . It is characterized by. Thereby, the electroconductivity provision effect equivalent to carbon black can be expressed.

According to a third aspect of the present invention, in the carrier according to the first or second aspect, the substrate particles are aluminum oxide particles . Thereby, the white electroconductive particle which has a favorable color tone can be obtained.

The invention according to claim 4 is the carrier according to any one of claims 1 to 3, wherein the volume resistivity is 1 × 10 ¹¹ Ω · cm or more and 1 × 10 ¹⁶ Ω · cm or less. And Thereby, an image having a good image density can be formed.

According to a fifth aspect of the present invention, in the carrier according to any one of the first to fourth aspects, the layer containing the binder resin further contains hard particles. Thereby, the intensity | strength of the layer containing binder resin can be improved.

According to a sixth aspect of the present invention, in the carrier according to the fifth aspect, a ratio of a total weight of the hard particles and the white conductive particles to a weight of the layer containing the binder resin is 5% or more and 70% or less. It is characterized by being. Thereby, the abrasion resistance of the layer containing the binder resin can be improved.

The invention according to claim 7 is the carrier according to claim 5 or 6, wherein the hard particles are at least one of silica particles , titanium oxide particles, and alumina particles . Thereby, the strength of the layer containing the binder resin can be further improved.

According to an eighth aspect of the present invention, in the carrier according to any one of the fifth to seventh aspects, the hard particles and the base particles contain the same metal oxide particles . Thereby, the uniformity of the layer containing the binder resin can be improved.

The invention according to claim 9 is the carrier according to any one of claims 1 to 8, wherein the layer containing the binder resin further contains an aminosilane coupling agent. Thereby, the intensity | strength of the layer containing binder resin can be improved.

Invention according to claim 10, in the carrier according to any one of claims 1 to 9, wherein the binder resins are crosslinked product of thermoplastic resin and guanamine resin and crosslinking the thermoplastic resin and melamine resin It is characterized by being at least one of the objects. Thereby, the elasticity of the layer containing the binder resin can be improved.

According to an eleventh aspect of the present invention, in the carrier according to the tenth aspect, the thermoplastic resin is an acrylic resin. Thereby, the elasticity of the layer containing the binder resin can be further improved.

  According to a twelfth aspect of the present invention, in the carrier according to any one of the first to eleventh aspects, the core material particles have a magnetization of 50 emu / g or more and 150 emu / g or less when a magnetic field of 1 kOe is applied. It is characterized by being. Thereby, generation | occurrence | production of carrier adhesion can be suppressed.

The invention according to claim 13 is the carrier according to any one of claims 1 to 12, wherein the core material particles are Mn-Mg-Sr ferrite particles , Mn ferrite particles, or magnetite particles. It is characterized by. Thereby, generation | occurrence | production of carrier adhesion can be suppressed.

The invention according to claim 14 is the carrier according to any one of claims 1 to 13, wherein the core particles have a bulk density of 2.1 g / cm ³ or more and 2.6 g / cm ³ or less. It is characterized by that. Thereby, generation | occurrence | production of carrier adhesion can be suppressed.

According to a fifteenth aspect of the present invention, the developer includes the carrier and the toner according to any one of the first to fourteenth aspects. As a result, it is possible to provide a developer capable of reducing the development torque and suppressing the occurrence of color stains, background stains and carrier adhesion.

The invention of claim 16 is the image forming method, a latent image formed on the photosensitive member, characterized by having a step of developing by using a developer according to claim 15. Accordingly, it is possible to provide an image forming method capable of reducing the development torque and suppressing the occurrence of color stains, background stains, and carrier adhesion.

The invention of claim 17 is the image forming method according to claim 16, such that the distance between the photosensitive member with the opposing developing sleeve carrying the developer to the photosensitive member becomes 0.4mm or less The latent image formed on the photosensitive member is developed by applying at least one of a DC voltage and an AC voltage as a developing bias to the developing sleeve. Thereby, generation | occurrence | production of carrier adhesion can be suppressed.

The invention according to claim 18, in the process cartridge, a photosensitive member, a latent image formed on the photosensitive member, is supported on one body developing means to development using a developer according to claim 15 The image forming apparatus main body is detachable. As a result, it is possible to provide a process cartridge capable of reducing development torque and suppressing occurrence of color stains, background stains, and carrier adhesion.

  According to the present invention, it is possible to provide a carrier that can reduce development torque and suppress the occurrence of color stains, background stains, and carrier adhesion. Furthermore, a developer, an image forming method, and a process cartridge using the carrier can be provided.

  Next, the best mode for carrying out the present invention will be described with reference to the drawings.

The present inventors have intensively studied to solve the above problems. As a result, the weight average particle diameter Dw is 22 to 32 μm, the ratio Dw / Dp of the number average particle diameter Dp to the weight average particle diameter Dw is 1.00 to 1.20, and the content of particles having a particle diameter of 20 μm or less is included. When the BET specific surface area of the core particles having a particle size of 0 to 7% by weight and a particle size of 36 μm or less is 90 to 100% by weight is set to 300 to 900 cm ² / g, the surface property is high, and development is performed. It has been found that a carrier capable of reducing torque can be obtained. Furthermore, the white conductive particles contained in the binder resin layer that coats the core particles have a conductive coating layer made of tin dioxide and indium oxide on the surface. A new technology concept has been devised so that even if it is detached from the carrier surface, it will not cause color stains.

  One method for improving the durability of the carrier is to reduce the torque in the developing section (hereinafter referred to as developing torque). By reducing the development torque, the stress applied to the developer can be reduced, and there is an effect of suppressing toner spent on the carrier surface and scraping of the binder resin layer. Moreover, since it leads also to the energy saving of the whole system, it is preferable also from a viewpoint of environmental protection.

  In the present invention, the development torque can be reduced by narrowing the particle size distribution of the core particles and reducing the BET specific surface area. As a result, the irregularities on the surface of the core material particles are reduced, the shape of the core material particles is close to a sphere, and the fluidity is improved, so that the development torque can be reduced.

  Specifically, in the carrier of the present invention, the weight average particle diameter Dw of the core material particles is 22 to 32 μm, and preferably 23 to 30 μm. At this time, when the particle diameter of the core material particle is large to some extent, if the particle diameter of the core material particle is small, the frictional force between the carriers is increased and the fluidity of the carrier is decreased, so that the development torque is increased. However, when the particle diameter of the core material particles is small as in the present invention, the weight average particle diameter Dw of the core material particles does not significantly affect the development torque.

  Note that when the weight average particle diameter Dw of the core material particles is larger than 32 μm, the toner is not developed faithfully with respect to the latent image, the variation in the dot diameter increases, and the graininess decreases. Further, when the concentration of the toner in the developer is high, background stains are likely to occur. When the weight average particle diameter Dw of the core material particles is smaller than 22 μm, since the magnetization is small, the magnetic binding force for holding the carrier on the developing sleeve becomes weak, and carrier adhesion is likely to occur.

  Carrier adhesion means a phenomenon in which a carrier adheres to an image portion or background portion of an electrostatic latent image. In general, the stronger the electric field is, the more easily carrier adhesion occurs. However, since the electric field is weakened by developing the toner using toner, the carrier adhesion is less likely to occur compared to the background portion. Note that the occurrence of carrier adhesion is not preferable because it causes inconveniences such as damage to the photosensitive drum and the fixing roller. At this time, if the Dw / Dp of the core material particles is larger than 1.20, the ratio of the fine particles becomes large, and carrier adhesion tends to occur.

  Content of the particle | grains which have a particle size of 20 micrometers or less in core material particle | grains is 0 to 7 weight%, 0 to 5 weight% is preferable and 0 to 3 weight% is more preferable. Further, the content of particles having a particle size of 36 μm or less in the core material particles is 90 to 100% by weight, and preferably 92 to 100% by weight. Furthermore, the content of particles having a particle size of 44 μm or less in the core particles is preferably 98 to 100% by weight. Thereby, the particle size distribution of the core material particles becomes narrow, and the occurrence of carrier adhesion can be suppressed. Even if the average particle diameter and the BET specific surface area of the core material particles are defined, the surface of the core material particles is not always smooth if the particle size distribution is wide. Furthermore, if the content of particles having a particle size of 20 μm or less in the core material particles is more than 7% by weight, the particle size distribution becomes wider, and particles with small magnetization are present throughout the magnetic brush. , Carrier adhesion tends to occur.

  The content of particles having a particle size of 20 μm or less in the core material particles is preferably 0.5% by weight or more. Thereby, it becomes possible to reduce the manufacturing cost of core particle.

In the present invention, BET specific surface area of the core particle is a ^{300~900cm 2 / g, 400~800cm 2 /} g are preferred. By setting the BET specific surface area of the core particles satisfying the above-mentioned weight average particle diameter Dw and particle size distribution Dw / Dp within the above range, the irregularities on the surface of the core particles are reduced and the shape becomes close to a sphere. For this reason, the fluidity | liquidity of a carrier becomes favorable, a torque becomes small, and high durability and energy saving can be achieved. If the BET specific surface area of the core particles is smaller than 300 cm ² / g, mesh clogging is very likely to occur in the classification process during production, and the yield is lowered, resulting in a very high production cost. Further, if the BET specific surface area of the core particles is larger than 900 cm ² / g, the torque of the developing sleeve increases, which is not preferable from the viewpoint of carrier durability and energy saving.

In the present invention, the weight average particle diameter Dw of the carrier, the core material particles, and the toner is calculated based on the particle diameter distribution (relationship between the number frequency and the particle diameter) of the particles measured on the basis of the number. The weight average particle diameter Dw in this case is given by the formula Dw = {Σ (nD ⁴ )} / {Σ (nD ³ )}
It is represented by Here, D is a representative particle size (μm) of particles present in each channel, and n is the total number of particles present in each channel. In addition, a channel shows the length for dividing | segmenting the particle size range in a particle size distribution figure into equal parts. Further, as the representative particle size of the particles existing in each channel, the lower limit value of the particle size stored in each channel was adopted.

In the present invention, the number average particle diameter Dp of the carrier and core material particles is calculated based on the particle diameter distribution of the particles measured on the basis of the number. The number average particle diameter Dp in this case is given by the formula Dp = {Σ (nD)} / (Σn)
It is represented by Here, D and n are the same as described above.

  In the present invention, a microtrack particle size analyzer model HRA9320-X100 (manufactured by Honeywell) can be used as a particle size analyzer for measuring the particle size distribution. The measurement conditions were a particle size range of 8 to 100 μm, a channel length (channel width) of 2 μm, a channel number of 46, and a refractive index of 2.42.

  The BET specific surface area of the core particles can be determined based on the BET equation by measuring the adsorption of nitrogen by the sample and the pressure change generated at that time. This measurement can be performed using a Micromeritics specific surface area automatic measuring device (TriStar 3000 / Surface Area and Porosity Analyzer).

  The carrier of the present invention has a conductive coating layer composed of tin dioxide and indium oxide on the surface in order not to cause color stains even when used in combination with the core particles satisfying the aforementioned weight average particle size, particle size distribution, and BET specific surface area. White conductive particles having the following are used.

  As described above, by reducing the BET specific surface area of the core material particles, it is possible to reduce the development torque, to achieve high carrier durability and energy saving of the entire system. However, when core particles having a small BET specific surface area are used, the problem of color stains due to conductive particles is likely to occur as described above. As a result of intensive research under the technical concept that the present inventors have no problem as long as the color of the conductive particles has a small influence on the color of the toner even when the conductive particles are easily detached in this way. It was concluded that the white conductive particles can reduce the influence on the color of the toner even if they are detached from the binder resin layer of the carrier. Specifically, the L value of the white conductive particles is preferably 70 or more, more preferably 80 or more, and particularly preferably 85 or more. The b value is preferably −10 or more and 10 or less, more preferably −5 or more and 5 or less, and particularly preferably −1 or more and 3 or less. If the L value of the white conductive particles is less than 70, the whiteness is not sufficient, which may adversely affect the color development of the toner. Further, when the b value of the white conductive particles is less than −10 or greater than 10, the saturation becomes high, and color stains may occur when the white conductive particles are fixed together with the toner.

  In the present invention, the method for measuring the color difference of the white conductive particles is as follows. First, 6 g of white conductive particles are measured with an upper pan balance. A white paper is laid on the forming die, and a stainless steel ring having an inner diameter of 40 mm and a height of 18 mm is placed thereon, and weighed white conductive particles are placed in the stainless steel ring, and a pressing metal fitting is placed thereon. Next, the L value and the b value are read with a colorimeter that is pressed using a small automatic press and is standardly adjusted with a standard plate. As the colorimeter, Z-10018P (manufactured by Nippon Denshoku Industries Co., Ltd.) or a measuring instrument having equivalent or better performance can be used.

  In the present invention, the conductive conductive layer made of tin dioxide and indium oxide is formed on the base particles in the white conductive particles, but the layer made of tin dioxide and the tin dioxide and indium oxide are formed on the surface of the base particles. By sequentially laminating the resulting conductive coating layers, the same conductivity imparting effect as that of carbon black can be exhibited. At this time, even if a conductive coating layer made of tin dioxide and indium oxide is formed on the surface of the substrate particles, the electrical influence of the substrate particles is great, and good conductivity may not be obtained. Further, when the surface of the base particles is coated with a mixed solution of tin dioxide hydrate and indium oxide hydrate, it is difficult to coat uniformly.

  After forming a lower layer using commonly used coating materials such as aluminum oxide, zinc oxide, and zirconium oxide on the surface of the substrate particles, mixing of hydrates of tin dioxide and indium oxide When the liquid is coated, a uniform conductive coating layer can be formed. However, even if these coating materials are used, good conductivity may not be obtained due to the electrical influence of the lower layer. Therefore, by forming a layer made of tin dioxide in the lower layer, the conductive coating layer can be fixed uniformly and firmly, and the electrical influence from the lower layer can be reduced and good conductivity can be achieved. Can be obtained. Note that the lower layer may contain indium oxide as long as the conductivity is not impaired.

  Examples of the base particles include aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide, barium sulfate, zirconium oxide and the like, and they can be used alone or in combination of two or more. As a result, good conductivity can be obtained. This is considered to be because the compatibility between the base particles and the conductive treatment is good and the effect of the conductive treatment is exhibited well. Among these, aluminum oxide and titanium dioxide are preferable, and aluminum oxide is more preferable. This makes it easier to satisfy the above-described color difference condition. When titanium dioxide is used, it may be a rutile type, anatase type, or other structure.

  In the present invention, the following production method is exemplified as a production method of the white conductive particles. As a method for forming the lower layer of tin dioxide hydrate film, for example, after adding a tin salt or a stannate solution to an aqueous suspension of a white inorganic pigment, an alkali or an acid is added, and then the coating is performed. And a method of adding and coating a tin salt or a stannate and an alkali or an acid separately in parallel. In order to uniformly coat the surface of white inorganic pigment particles with tin dioxide hydrate, the latter parallel addition is more suitable. At this time, the aqueous suspension is kept warm at 50 to 100 ° C. It is preferable. Moreover, pH at the time of adding a tin salt or a stannate, and an alkali or an acid in parallel is usually 2-9. Since the isoelectric point of tin dioxide hydrate is 5.5, the pH is preferably 2 to 5 or 6 to 9, whereby the hydrolysis product of tin is converted to the surface of white inorganic pigment particles. Can be uniformly deposited.

  As the tin salt, for example, tin chloride, tin sulfate, tin nitrate or the like can be used. Moreover, as a stannate, sodium stannate, potassium stannate, etc. can be used, for example.

  Examples of the alkali include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, ammonia water, and ammonia gas. Examples of the acid include hydrochloric acid, sulfuric acid, nitric acid, acetic acid, and the like. .

The coating amount of the hydrate of tin dioxide is usually 0.5 to 50% by weight, preferably 1.5 to 40% by weight as SnO _{2 with} respect to the base particles. When the coating amount is less than 0.5% by weight, the coating state of the conductive coating layer becomes non-uniform, and the volume resistivity of the white conductive particles may increase due to the influence of the base particles. If the coating amount is more than 50% by weight, the amount of tin oxide hydrate that is not in close contact with the surface of the substrate particles increases, and the conductive coating layer may become non-uniform.

  Next, as a method for forming a conductive coating layer, a mixed solution of tin salt and indium salt and an alkali are added separately in parallel in order not to dissolve the previously coated tin dioxide hydrate film. It is preferable to use a method of forming a film. At this time, it is preferable to warm the aqueous suspension to 50 to 100 ° C. Moreover, pH at the time of adding a mixed solution and an alkali in parallel is 2-9 normally, and 2-5 or 6-9 is preferable. Thereby, the hydrolysis reaction product of tin and indium can be deposited uniformly.

  As the tin salt, for example, tin chloride, tin sulfate, tin nitrate or the like can be used. As the indium salt, for example, indium chloride, indium sulfate, or the like can be used.

The addition amount of tin dioxide is usually 0.1 to 20% by weight, preferably 2.5 to 15% by weight, as SnO _{2 with} respect to In ₂ O ₃ . When the amount of tin dioxide added is less than 0.1% by weight or more than 20% by weight, the conductivity may be lowered.

The coating amount of indium oxide is usually 0.05 to 2 and preferably 0.08 to 1.5 as the weight ratio of In ₂ O _{3 to} the base particles. If the weight ratio is less than 0.05, the conductivity may be reduced, and if it is more than 2, the conductivity may not be improved.

  In the present invention, the conductive particles mean particles having a volume resistivity of 1 to 500 Ω · cm. As will be shown in the examples described later, according to the present invention, white conductive particles having excellent electrical conductivity of 100 Ω · cm or less, and in some cases, 10 Ω · cm or less, which are comparable to those of antimony-containing products, can be obtained. it can.

  When performing the heat treatment of the white conductive particles, it is preferably performed in a non-oxidizing atmosphere, and the volume resistivity can be reduced by 2 to 3 orders of magnitude compared to those subjected to the heat treatment in air.

  In order to obtain a non-oxidizing atmosphere, an inert gas can be used. As the inert gas, for example, nitrogen, helium, argon, carbon dioxide gas or the like can be used. Industrially, heat treatment while blowing nitrogen gas is advantageous in terms of cost, and a product with stable characteristics can be obtained.

  The heat treatment temperature is usually 350 to 750 ° C, preferably 400 to 700 ° C. When the heat treatment temperature is lower than 350 ° C. or higher than 750 ° C., the conductivity may be lowered. Moreover, heat processing time is 15 minutes-4 hours normally, and 1-2 hours are preferable. When the heat treatment time is shorter than 15 minutes, the conductivity may decrease, and even when the heat treatment time is longer than 4 hours, the conductivity is not improved.

  When the volume resistivity of the white conductive particles exceeds 200 Ω · cm, the effect of reducing the resistance due to the white conductive particles is reduced, and it is necessary to increase the amount of white conductive particles added. At this time, the proportion of the white conductive particles is excessive compared to the proportion of the binder resin on the carrier surface. Therefore, the proportion of the binder resin that is a charging generation point is insufficient, and the charging ability is insufficient. It may become. Furthermore, since there are too many white conductive particles compared with the binder resin, the white conductive particles are likely to be detached, and the amount of change in charge amount, resistance, and the like may increase.

  Further, the content of white conductive particles (ratio of the weight of the conductive particles to the total weight of the conductive particles and the binder resin) is preferably 10% by weight or more and 70% by weight or less. Thereby, the effect which improves electroconductivity becomes remarkable. When the content of white conductive particles is less than 10% by weight, the ratio of the white conductive particles to the carrier surface is small compared with the ratio of the white conductive particles to the carrier surface. The effect of mitigating the accompanying contact is reduced, and durability may be reduced. On the other hand, when the content of white conductive particles is more than 70% by weight, the proportion of white conductive particles is excessive compared with the proportion of the binder resin on the carrier surface. A proportion of a certain binder resin may be insufficient, and charging ability may be insufficient. Furthermore, since there are too many white conductive particles compared with the binder resin, the white conductive particles are likely to be detached, and the amount of change in charge amount, resistance, and the like may increase.

  Furthermore, the oil absorption amount of the conductive particles is preferably 10 ml / 100 g or more and 300 ml / 100 g or less. Thereby, since the dispersibility with respect to the binder resin of electroconductive particle improves, the effect which adjusts resistance over a long term can be maintained.

The volume resistivity of the carrier of the present invention is preferably 1 × 10 ¹¹ to 1 × 10 ¹⁶ Ω · cm, more preferably 1 × 10 ¹² to 1 × 10 ¹⁴ Ω · cm. As a result, a sufficient image density can be obtained when the toner is used under an appropriate toner charge amount condition. When the volume resistivity of the carrier is smaller than 1 × 10 ¹¹ Ω · cm, when the developing gap (the closest distance between the photosensitive member and the developing sleeve) becomes small, charge is induced in the carrier and the carrier adheres. May occur. The same tendency may be seen when the linear velocity of the photosensitive member and the linear velocity of the developing sleeve are large. Furthermore, this tendency may become prominent when an AC bias is applied. In developing a color toner, a carrier having a low volume resistivity is generally used in order to obtain a sufficient toner adhesion amount. On the other hand, if the volume resistivity of the carrier is larger than 1 × 10 ¹⁶ Ω · cm, charges having a polarity opposite to that of the toner easily accumulate on the carrier, and carrier adhesion may occur.

  The volume resistivity of the carrier can be measured using the resistance measurement cell shown in FIG. Here, the surface areas of the electrodes 12a and 12b are 2 × 4 cm, and the distance between the electrodes 12a and 12b is 2 mm. In addition, after filling the cell 11 in which the electrodes 12a and 12b are accommodated in the fluororesin container with the carrier 13, a DC voltage of 100V is applied between the electrodes 12a and 12b, and the high resistance meter 4329A (4329A + LJK 5HVLVWDQFH OHWHU The volume resistivity of the carrier 13 can be measured by measuring the DC resistance using Yokogawa Hewlett-Packard Co.). At this time, the carrier 13 is inserted into the cell 11 until it overflows, and then the cell 11 is tapped 20 times, and the upper surface of the cell 11 is operated by one operation along the upper end of the cell using a nonmagnetic horizontal spatula. It can be filled by scraping flat. In addition, when filling, pressurization is unnecessary.

  The volume resistivity of the carrier can be adjusted by controlling the amount of conductive particles added, the thickness of the binder resin layer, and the like.

  In the present invention, in order to reinforce the binder resin layer and strengthen the coating strength, the binder resin layer preferably contains hard particles (hard non-conductive particles). Among these, particles of metal oxides and inorganic oxides are particularly preferable because they can increase the uniformity of the particle size and the affinity with the binder resin. Thereby, the reinforcement effect of a film can be enlarged. Examples of the hard particles include alumina, titanium oxide, zinc oxide, and iron oxide, and silica, titanium oxide, and alumina are particularly preferable. In addition, a hard particle can be used individually or in mixture of 2 or more types.

  In the present invention, non-conductive particles mean particles that exceed the volume resistivity of conductive particles, that is, particles that exceed 500 Ω · cm, and are different from the general definition of non-conductive particles.

  Since the conductive particles can reinforce the coating similarly to the hard particles, the shape, electrical resistance, strength, etc. of the binder resin layer can be controlled by using the conductive particles and the hard particles in a well-balanced manner. Is possible.

  In the present invention, the content of the conductive particles and hard particles in the binder resin layer is preferably 5 to 70% by weight, and more preferably 2 to 40% by weight. Here, the ratio of the conductive particles to the hard particles may be 100: 0. The content of the conductive particles and the hard particles is appropriately selected depending on the particle diameter and specific surface area of the particles to be used, but if it is less than 5% by weight, it may be difficult to develop the wear resistance effect of the coating, and 70% by weight. If it exceeds 50%, the particles may be easily detached, and the stability may be lowered.

  In order to make the binder resin layer uniform, it is preferable to use the same hard particles as the materials used for the base particles of the conductive particles. When hard particles different from the base particles of the conductive particles are used, there may be a deviation in the locations where the conductive particles and the hard particles exist due to the difference in specific gravity.

  In the present invention, the binder resin layer preferably contains an aminosilane coupling agent. Thereby, the intensity | strength of a binder resin layer can be improved.

  Examples of the aminosilane coupling agent include the following.

H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃
H ₂ N (CH ₂ ) ₃ Si (OC ₂ H ₅ ) _{3
H 2 N (CH 2) 3} Si (CH 3) 2 (OC 2 H 5)
_{H 2 N (CH 2) 3} Si (CH 3) (OC 2 H 5) 2
H ₂ N (CH ₂ ) ₂ NHCH ₂ Si (OCH ₃ ) _{3
H 2 N (CH 2) 2} NH (CH 2) 3 Si (CH 3) (OCH 3) 2
H ₂ N (CH ₂ ) ₂ NH (CH ₂ ) ₃ Si (OCH ₃ ) ₃
(CH ₃ ) ₂ N (CH ₂ ) ₃ Si (CH ₃ ) (OC ₂ H ₅ ) ₂
(C ₄ H ₉ ) ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃
The content of the aminosilane coupling agent in the binder resin layer is preferably 0.001 to 30% by weight. The binder resin layer preferably contains a silicone resin because it has high charge imparting performance.

  In the present invention, the binder resin layer preferably contains at least one of a crosslinked resin obtained by crosslinking a thermoplastic resin and a guanamine resin and a crosslinked resin obtained by crosslinking a thermoplastic resin and a melamine resin. . Thereby, moderate elasticity can be given to the binder resin layer. As a result, it is possible to absorb the impact on the binder resin layer due to the friction between the carriers or the toner generated when stirring to frictionally charge the developer, and the toner spent on the carrier and film scraping are suppressed. can do.

  The weight ratio of the crosslinked resin to the binder resin is preferably 20 to 50%. Thereby, the elasticity of the binder resin layer can be optimized. If the weight ratio is less than 20%, the crosslinking reaction may be insufficient, and the effect of improving wear resistance may be reduced. On the other hand, if the weight ratio exceeds 50%, the binder resin layer may be excessively cured due to an excessive crosslinking reaction. As a result, the ability to absorb impacts cannot be fully exhibited.

  A silicone resin or the like can be used as the thermoplastic resin, but an acrylic resin is particularly preferable. Although an acrylic resin is not specifically limited, Usually, a glass transition temperature is 20-100 degreeC, and 25-80 degreeC is preferable. When the glass transition temperature is lower than 20 ° C., blocking occurs at room temperature, and the storage stability may be lowered. On the other hand, when the glass transition temperature is higher than 100 ° C., the binder resin layer becomes hard and the elasticity may be lowered. For this reason, it becomes impossible to absorb the impact sufficiently.

  The binder coating layer preferably contains a charge control agent in order to set the charge amount of the developer to an optimum value. The charge control agent is not particularly limited, but it is preferable to use either aromatic sulfonic acid or phosphoric acid. Thereby, reaction with a guanamine resin will be in a preferable state, and the effect which adjusts electrification can be enlarged. As another charge control agent, for example, Catalyst 4040 (manufactured by Mitsui Cytec Co., Ltd.) can be used.

  In the present invention, the core particles preferably have a magnetization of 50 to 150 emu / g, more preferably 70 to 150 emu / g, when a magnetic field of 1 kOe is applied. Thereby, generation | occurrence | production of carrier adhesion can be suppressed.

  Magnetization can be measured as follows. First, a BH tracer BHU-60 (manufactured by Riken Denshi Co., Ltd.) is used, and 1.0 g of core material particles are packed in a cylindrical cell and set in an apparatus. Next, the magnetic field to be applied is gradually increased to 3 kOe, gradually decreased to 0 kOe, and the opposite magnetic field is gradually increased to 3 kOe. Further, after gradually reducing the magnetic field to 0 kOe, the magnetic field is applied in the same direction as the first. From the BH curve thus obtained, the magnetization when a 1 kOe magnetic field is applied is calculated.

  Examples of the core particles having a magnetization of 50 to 150 emu / g when a magnetic field of 1 kOe is applied include, for example, ferromagnetic materials such as iron and cobalt, magnetite, hematite, Li ferrite, Mn—Zn ferrite, Cu— Examples thereof include Zn-based ferrite, Ni-Zn-based ferrite, Ba-based ferrite, and Mn-based ferrite.

  Ferrite is a sintered body generally represented by the following formula.

(MO) _x (NO) _y (Fe ₂ O ₃ ) _z
Here, x, y, and z are composition ratios, and M and N are each independently a metal such as Ni, Cu, Zn, Li ₂ , Mg, Mn, Sr, or Ca, and a divalent metal It consists of a complete mixture of oxide and trivalent iron oxide.

  Examples of the core material particles having a magnetization of 70 to 150 emu / g when a 1 kOe magnetic field is applied include magnetite, Mn—Mg—Sr ferrite, and Mn ferrite.

The core particles of the present invention have a weight average particle diameter Dw of 22 to 32 μm and a BET specific surface area of 300 to 900 cm ² / g. It can be obtained by firing conditions, post-treatment with heat, adjustment of composition, etc. in the production process of the core particles. In addition, by combining these methods, core material particles having higher surface smoothness and close to true spheres can be obtained. Further, for example, as described in US2003 / 0209820A1, the surface of core particles can be smoothed and spheroidized by exposing the pulverized amorphous ferrite particles or raw materials for ferritization reaction to plasma. It is possible to

  In a feeder using vibration, core particles having good fluidity are conveyed quickly. Since core particles with little surface irregularity and close to a spherical shape have good fluidity, for example, when using an electromagnetic feeder, it is possible to select core particles having different fluidity depending on the difference in the conveyance speed. is there. For this reason, the core particle | grains with few surface unevenness | corrugations and near spherical shape can be obtained by making an electromagnetic feeder pass repeatedly.

In the present invention, the bulk density of the core material particles is usually at 2.1 g / cm ³ or more, preferably 2.1~2.6g / cm ^3, more preferably 2.35~2.60g / cm ³ Particularly preferred is 2.35 to 2.50 g / cm ³ . Thereby, generation | occurrence | production of carrier adhesion can be suppressed. When the bulk density of the core particles is smaller than 2.1 g / cm ³ , the porosity or surface irregularities may be increased. Further, even when the magnetization [emu / g] when a magnetic field of 1 kOe is applied is large, the substantial magnetization [emu / cm ³ ] per particle is small, so that carrier adhesion is likely to occur. .

It is possible to increase the bulk density of the core particles by increasing the firing temperature. However, if the bulk density of the core particles is greater than 2.6 g / cm ³ , the core particles are likely to be fused together. And may be difficult to disintegrate.

The bulk density of the core particles can be measured as follows according to a metal powder-apparent density test method (JIS-Z-2504). The core particles are allowed to flow naturally through an orifice having a diameter of 2.5 mm, and the core particles are poured into a 25 cm ³ stainless steel cylindrical container placed directly under the orifice, and then the upper surface of the container is made of non-magnetic material. Using a horizontal spatula, scrape flat along the top of the container in one operation. If the core particle is difficult to flow out with an orifice having a diameter of 2.5 mm, the core material particle may be flowed out from the orifice having a diameter of 5 mm. By this operation, the weight of the core particles per cm ³ can be obtained by dividing the weight of the core particles flowing into the container by the volume of the container 25 cm ³ . This is defined as the bulk density of the core particles.

  The carrier of the present invention can be produced by pulverizing or pulverizing a magnetic material and then classifying the magnetic material so as to obtain a predetermined particle size, and forming a binder resin layer on the surface of the obtained core material particles. it can.

  Examples of classification include wind classification and sieve classification (sieving). It is preferable to use a vibration sieving machine for classification of the core particles. However, in a commonly used vibrating screen, there is a problem that when trying to classify the core particles having a small particle size, the mesh of the screen (wire mesh) is clogged immediately, so classification workability is low. Very low. In particular, there is a problem that the yield is greatly reduced to about 30% when fine powder is classified. This is because the product portion is mixed in the particles removed by the classification process, and as a result, there is a problem that the cost becomes several times higher.

  In the present invention, as a method capable of efficiently and sharply classifying core particles having a small particle diameter, a method of applying ultrasonic vibration to a wire mesh when classifying core particles using a vibration sieve Is mentioned. Thereby, core material particles having a particle size of less than 20 μm can be efficiently and sharply cut.

  The ultrasonic vibration can be obtained by supplying a high-frequency current to the converter and converting it into ultrasonic vibration. A PZT vibrator can be used as the converter. Specifically, the wire mesh can be vibrated by transmitting the ultrasonic vibration generated by the converter to a resonance member fixed to the wire mesh. The resonance member to which the ultrasonic vibration is transmitted resonates by the ultrasonic vibration and vibrates the wire mesh fixed to the resonance member. The frequency for vibrating the wire mesh is usually 20 to 50 kHz, preferably 30 to 40 kHz.

  The shape of the resonance member is not particularly limited as long as it is a shape suitable for vibrating the wire mesh, but is usually a ring shape. The vibration direction for vibrating the wire mesh is preferably a vertical direction.

  FIG. 2 shows an example of a vibration sieving machine. The vibration sieving machine 1 includes a cylindrical container 2, a spring 3, a base 4 (support), a wire mesh 5, a resonance ring 6, a high-frequency current cable 7, a converter 8, and a ring-shaped frame 9.

  In order to operate the vibration sieve machine 1 (circular sieve machine), a high-frequency current is supplied to the converter 8 via the cable 7. The high frequency current supplied to the converter 8 is converted into ultrasonic vibration. The ultrasonic vibration generated by the converter 8 vibrates in the vertical direction the resonance ring 6 to which the converter 8 is fixed and the ring-shaped frame 9 provided in series with the resonance ring 6. Due to the vibration of the resonance ring 6, the metal mesh 5 fixed to the resonance ring 6 and the ring-shaped frame 9 vibrates in the vertical direction.

  In the present invention, the core material particles can be obtained by classifying the pulverized product of the magnetic material. However, in the case of core material particles such as ferrite and magnetite, the primary granulated product before firing is prepared. The core material particles can be obtained by classification, further firing and classification. Moreover, after forming the binder resin layer on the surface of the core material particles, the core material particles covered with the binder resin layer may be classified. Such classification of the core particles is preferably performed using the vibration sieve shown in FIG.

  The developer of the present invention can be produced by using the carrier of the present invention and a toner. In particular, when a toner having a weight average particle diameter of 5 μm or less is used, the graininess is improved and a higher image quality is achieved.

  The toner used in the present invention contains a colorant, fine particles, a charge control agent, a release agent, and the like in a binder resin containing a thermoplastic resin as a main component. Various conventionally known toners can be used. . Such a toner can be manufactured by various toner manufacturing methods such as a polymerization method and a granulation method, and may be either an amorphous toner or a spherical toner. Either magnetic toner or non-magnetic toner can be used.

  As the binder resin for the toner, the following resins may be used alone or in combination of two or more. Styrene binder resins include homopolymers of styrene and its derivatives such as polystyrene and polyvinyltoluene, styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-acrylic. Acid methyl copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer , Styrene-α-chloromethacrylic acid methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer Polymer, styrene-mer Ynoic acid copolymer, styrene - styrene copolymer and maleic acid ester copolymer. Examples of the acrylic binder resin include polymethyl methacrylate and polybutyl methacrylate. Other binder resins include polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or aliphatic Examples thereof include hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, and paraffin waxes.

  Polyester can further lower the melt viscosity while ensuring the stability during storage of the toner, as compared with styrene resin and acrylic resin. In addition, polyester can be obtained by the polycondensation reaction of alcohol and carboxylic acid, for example.

  Examples of the alcohol include diols such as polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-propylene glycol, neopentyl glycol, 1,4-butenediol, , 4-bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A, and the like, and these are saturated or unsaturated having 3 to 22 carbon atoms Dihydric alcohol substituted with a hydrocarbon group, other dihydric alcohols, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, Tripen Esitol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylol Examples thereof include trivalent or higher alcohols such as propane and 1,3,5-trihydroxymethylbenzene.

  The carboxylic acids include monocarboxylic acids such as palmitic acid, stearic acid, oleic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malon Acids, divalent carboxylic acids in which they are substituted with saturated or unsaturated hydrocarbon groups having 3 to 22 carbon atoms, anhydrides of these acids, reaction products of lower alkyl esters and linolenic 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-methylenecarboxypropane, tetra (methylene Carboxyl) methane, 1,2,7,8-octane tetracarboxylic acid Enboru trimer acids, trivalent or higher polyvalent carboxylic acid anhydrides of these acids.

  As the epoxy resin, a polycondensate of bisphenol A and epochrohydrin can be used. For example, Epomic R362, R364, R365, R366, R367, R369 (Mitsui Petrochemical Co., Ltd.), Epotot Commercial products such as YD-011, YD-012, YD-014, YD-904, YD-017 (above, manufactured by Tohto Kasei Co., Ltd.), Epcot 1002, 1004, 1007 (above, manufactured by Shell Chemical Co., Ltd.) It is done.

  Examples of toner colorants include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, Hansa Yellow G, rhodamine 6G lake, calco oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, Dye pigments such as triallylmethane dyes, monoazo dyes, disazo dyes, and dyes can be used alone or in admixture of two or more.

  Examples of the magnetic material contained in the magnetic toner include ferromagnetic materials such as iron and cobalt, magnetite, hematite, Li-based ferrite, Mn-Zn-based ferrite, Cu-Zn-based ferrite, Ni-Zn ferrite, and Ba ferrite. Particles can be used.

  Examples of charge control agents that control the triboelectric chargeability of the toner include metal complex salts of monoazo dyes, nitrohumic acid and its salts, salicylic acid, naphthoic salts, metal complexes of dicarboxylic acids such as Co, Cr, Fe, amino compounds, quaternary Examples thereof include ammonium salt compounds and organic dyes.

  Examples of the toner release agent include low molecular weight polypropylene, low molecular weight polyethylene, carnauba wax, microcrystalline wax, jojoba wax, rice wax, and montanic acid wax, which can be used alone or in combination. .

  Further, an external additive can be added to the toner. In order to obtain a good image, it is preferable to impart sufficient fluidity to the toner.

As the external additive, in addition to the inorganic particles, general hydrophobic treated inorganic particles can be used in combination, but the average particle size of the hydrophobic treated inorganic particles (primary particles) is 1 to 100 nm. It is preferable that it is 5-70 nm. Moreover, it is preferable that the specific surface area by BET method of the inorganic particle (primary particle) hydrophobized is 20-500 m < ² > / g.

  Examples of the external additive include particles of silica, hydrophobic silica, fatty acid metal salts (such as zinc stearate and aluminum stearate), metal oxides (such as titania, alumina, tin oxide, and antimony oxide), and fluoropolymers. . Among these, hydrophobic silica particles, titania particles, titanium oxide particles, and alumina particles are preferable.

  As the hydrophobic silica particles, HDK H 2000, HDK H 2000/4, HDK H 2050EP, HVK21, HDK H 1303 (manufactured by Clariant Japan), R972, R974, RX200, RY200, R202, R805, R812 (and above) Manufactured by Nippon Aerosil Co., Ltd.).

  As titania particles, P-25 (manufactured by Nippon Aerosil Co., Ltd.), STT-30, STT-65C-S (above, manufactured by Titanium Industry Co., Ltd.), TAF-140 (manufactured by Fuji Titanium Industry Co., Ltd.), MT-150W, Examples include MT-500B, MT-600B, MT-150A (manufactured by Teica). Examples of the hydrophobized titanium oxide particles include T-805 (manufactured by Nippon Aerosil Co., Ltd.), STT-30A, STT-65S-S (manufactured by Titanium Industry Co., Ltd.), TAF-500T, TAF-1500T (manufactured by Fuji Titanium Industry Co., Ltd.), MT-100S, MT-100T (above, Teika Co., Ltd.) and IT-S (Ishihara Sangyo Co., Ltd.).

  As a method of hydrophobizing inorganic particles such as silica particles, titania particles, and alumina particles, hydrophilic inorganic particles are treated with a silane coupling agent such as methyltrimethoxysilane, methyltriethoxysilane, or octyltrimethoxysilane. A method is mentioned.

  The weight average particle diameter of the toner is preferably 3.0 to 9.0 μm, and more preferably 3.5 to 7.5 μm. The particle size of the toner can be measured using a Coulter counter (manufactured by Coulter Counter).

  In the developer of the present invention, the weight ratio of the toner to the carrier is preferably 2 to 25% by weight, and more preferably 3 to 20% by weight.

  The image forming method of the present invention forms an image by developing the latent image formed on the surface of the photoreceptor using the developer of the present invention. At this time, the image density can be improved by applying an AC voltage obtained by superimposing an AC voltage on a DC voltage as a developing bias applied from the outside. In particular, the granularity of highlights is improved.

  In the image forming method of the present invention, a toner having a weight average particle diameter of 3.5 to 7.5 μm is used, and when the carrier coverage with the toner is 50%, the charge amount of the toner is −10 to −50 μC / g. In addition, the developing sleeve faces the photosensitive member, and the distance from the photosensitive member is 0.4 mm or less. By applying an alternating voltage as a developing bias, high image quality with less carrier adhesion can be obtained. . In addition, when a DC voltage is applied instead of an AC voltage as the developing bias, carrier adhesion and edge effects are greatly improved, and the margin for dirt is increased, so that the toner coverage on the carrier can be increased. In addition, the toner charge amount and the developing bias can be lowered, and the image density can be improved.

  The process cartridge of the present invention at least integrally supports a developing unit that develops a latent image formed on the surface of the photoreceptor using the photoreceptor and the developer of the present invention, and is detachable from the main body of the image forming apparatus. . Specific examples include a photoconductor, a charging brush that charges the surface of the photoconductor, a developing unit that develops a latent image formed on the surface of the photoconductor using a developer, and the photoconductor remaining on the surface of the photoconductor. And a process cartridge including a blade for wiping off the developer.

  Next, examples of the image forming method and the image forming apparatus of the present invention will be described in detail. However, these examples are for explaining the present invention and are not intended to limit the present invention.

  FIG. 3 shows an example of a developing device used in the image forming method of the present invention. It should be noted that modifications as will be described later belong to the category of the present invention.

  The developing device 40 is disposed to face the drum-shaped photoconductor 20 as a latent image carrier, and includes a developing sleeve 41 as a developer carrier, a developer accommodating member 42, a doctor blade 43 as a regulating member, and a support. The case 44 is mainly configured.

  A toner hopper 45 serving as a toner accommodating portion for accommodating the toner 21 is joined to a support case 44 having an opening on the photosensitive member 20 side. A developer agitating unit 46 that agitates the toner 21 and the carrier 23 and imparts a friction / release charge to the toner 21 is adjoined to the toner hopper 45 and accommodates the developer composed of the toner 21 and the carrier 23. A mechanism 47 is provided.

  Inside the toner hopper 45, a toner agitator 48 and a toner replenishing mechanism 49 are disposed as toner supplying means rotated by driving means (not shown). The toner agitator 48 and the toner replenishing mechanism 49 send out the toner 21 in the toner hopper 45 toward the developer accommodating portion 46 while stirring.

  A developing sleeve 41 is disposed in a space between the photoconductor 20 and the toner hopper 45. The developing sleeve 41, which is rotationally driven by a driving means (not shown) in the direction of the arrow in the figure, is a magnetic field disposed inside the developing device 40 so as not to change its position relative to the developing device 40 in order to form a magnetic brush by the carrier 23. It has a magnet (not shown) as a generating means.

  A doctor blade 43 is integrally attached to the developer accommodating member 42 on the side facing the side attached to the support case 44. In this example, the doctor blade 43 is disposed in a state where a certain gap is maintained between the tip and the outer peripheral surface of the developing sleeve 41.

  Using the developing device 40 in a non-limiting manner, the image forming method of the present invention is performed as follows. The toner 21 delivered from the inside of the toner hopper 45 by the toner agitator 48 and the toner replenishing mechanism 49 is conveyed to the developer accommodating portion 46 and agitated by the developer agitating mechanism 47, so that a desired friction / separation charge is obtained. Is granted. Further, the toner 21 is carried on the developing sleeve 41 as a developer together with the carrier 23 and is transported to a position facing the outer peripheral surface of the photoconductor 20, and the electrostatic latent image formed on the photoconductor 20 is electrostatically charged. As a result, a toner image is formed on the photoconductor 20.

  FIG. 4 shows an example of an image forming apparatus used in the image forming method of the present invention. Around the drum-shaped photoconductor 20, a charging member 32, an image exposure system 33, a developing device 40, a transfer device 50, a cleaning device 60, and a static elimination light source 70 are disposed. In this example, the surface of the charging member 32 Is in a non-contact state with respect to the surface of the photoreceptor 20 with a distance of 0.2 mm. When the photosensitive member 20 is charged using the charging member 32, the photosensitive member 20 is charged using an electric field in which an alternating current component is superimposed on a direct current component applied to the charging member 32 by a voltage applying unit (not shown). By doing so, it is possible to reduce charging unevenness.

  A negative-positive process will be described as an example of a series of image forming processes. A photoconductor 20 such as a photoconductor (OPC) having an organic photoconductive layer is neutralized by a static elimination light source 70, and is uniformly negatively charged by a charging member 32 such as a charging charger or a charging roller, and image exposure such as a laser optical system. A latent image is formed by light such as laser light emitted from the system 33 (in this example, the absolute value of the exposed portion potential is lower than the absolute value of the non-exposed portion potential).

  Laser light is emitted from a semiconductor laser and scans the surface of the photoconductor 20 in the direction of the rotation axis of the photoconductor 20 by a polygonal polygonal mirror (polygon) that rotates at high speed. The latent image formed in this way is developed with a developer composed of toner and carrier supplied on the developing sleeve 41 of the developing device 40 to form a toner image. At the time of developing the latent image, a predetermined DC voltage or a developing bias obtained by superimposing an AC voltage is applied between the developing sleeve 41 and the exposed portion and the non-exposed portion of the photoreceptor 20 from a voltage application mechanism (not shown). The

  On the other hand, a transfer medium 80 (for example, paper) is fed from a paper feed mechanism (not shown), and is synchronized between the photoconductor 20 and the transfer device 50 in synchronization with the leading edge of the image by a pair of upper and lower registration rollers (not shown). The toner image is transferred. At this time, it is preferable that a potential having a polarity opposite to that of toner charging is applied to the transfer device 50 as a transfer bias. Thereafter, the transfer medium 80 is separated from the photoreceptor 20, and a transfer image is obtained.

  Further, the toner remaining on the photoconductor 20 is collected in a toner collecting chamber 62 in the cleaning device 60 by a cleaning blade 61 as a cleaning member.

  The collected toner may be transported to a developing unit and / or a toner replenishing unit by a toner recycling unit (not shown) and reused.

  The image forming apparatus may be a device in which a plurality of developing devices 40 are arranged and the toner images are sequentially transferred onto the transfer medium 80 and then sent to the fixing mechanism to fix the toner by heat or the like. Alternatively, a plurality of toner images may be transferred to the transfer medium 80 and transferred to the transfer medium 80 at a time, and then the same fixing may be performed.

  FIG. 5 shows another example of an image forming apparatus used in the image forming method of the present invention. The photosensitive member 20 is provided with at least a photosensitive layer on a conductive support, and is driven by driving rollers 24a and 24b. The photosensitive member 20 is charged by a charging member 32, image exposure by an image exposure system 33, development by a developing device 40, and transfer. The transfer by the apparatus 50, the pre-cleaning exposure by the pre-cleaning exposure light source 26, the cleaning by the brush-like cleaning means 64 and the cleaning blade 61, and the static elimination by the static elimination light source 70 are repeated. In FIG. 5, the photoconductor 20 is irradiated with light before exposure from the support side. In this case, the support is translucent.

  FIG. 6 shows an example of the process cartridge of the present invention. The process cartridge integrally supports the photosensitive member 20, the proximity brush-shaped charging member 32, the developing device 40 containing the developer, and the cleaning blade 61, and is detachable from the image forming apparatus main body such as a copying machine or a printer. It is.

Hereinafter, the present invention will be described with reference to examples and comparative examples. In addition, this invention is not limited to the Example illustrated here. Moreover, below, a part represents a weight part.
(Example of toner production)
100 parts of a polyester resin, 3.5 parts of a quinacridone-based magenta pigment and 3.5 parts of a fluorinated quaternary ammonium salt were thoroughly mixed using a blender, melt-kneaded with a twin-screw extruder, allowed to cool, Coarsely pulverized with a cutter mill. Next, the mixture was finely pulverized with a jet airflow fine pulverizer and further classified with an air classifier to obtain toner base particles having a weight average average particle size of 6.8 μm and a true specific gravity of 1.22 g / cm ³ . Further, 0.8 parts of hydrophobic silica fine particles R972 (manufactured by Nippon Aerosil Co., Ltd.) were added to 100 parts of the toner base particles, and mixed with a Henschel mixer to obtain a toner.
(Conductive particle production example 1)
As a base particle, 100 g of rutile titanium dioxide having an average primary particle size of 0.35 μm was dispersed in 1 L of water to prepare a suspension. The suspension was kept warm at 70 ° C. Separately prepared solution of 36.7 g of indium chloride (InCl ₃ ) and 5.4 g of stannic chloride (SnCl ₄ .5H ₂ O) in 450 mL of 2N hydrochloric acid and 12 wt% aqueous ammonia were added to the pH of the suspension. Was simultaneously added dropwise over about 1 hour so as to maintain the temperature of 7-8. After completion of the dropwise addition, the treated suspension was filtered and washed, and the resulting treated pigment cake was dried at 110 ° C. Next, the obtained dry powder was heat-treated at 500 ° C. for 1 hour in a nitrogen gas stream (1 L / min) to obtain white conductive particles a.
(Conductive particle production example 2)
Carbon black ketjen black EC600JD (manufactured by Lion Akzo) was used as the conductive particles b.
(Conductive particle production example 3)
A suspension was prepared by dispersing 100 g of rutile titanium dioxide having an average primary particle size of 0.35 μm in 1 L of water. The suspension was kept warm at 70 ° C. A solution prepared by dissolving 11.6 g of separately prepared stannic chloride (SnCl ₄ .5H ₂ O) in 100 mL of 2N hydrochloric acid and 12% by weight aqueous ammonia so that the pH of the suspension is maintained at 7-8. , Simultaneously added over about 40 minutes. Subsequently, a solution prepared by dissolving 36.7 g of separately prepared indium chloride (InCl ₃ ) and 5.4 g of stannic chloride (SnCl ₄ .5H ₂ O) in 450 mL of 2N hydrochloric acid and 12 wt% aqueous ammonia were suspended. So as to maintain the pH of 7 to 8 at the same time over about 1 hour. After completion of the dropwise addition, the treated suspension was filtered and washed, and the resulting treated pigment cake was dried at 110 ° C. Next, the obtained dry powder was heat-treated in a nitrogen gas stream (1 L / min) at 500 ° C. for 1 hour to obtain white conductive particles c.
(Conductive particle production example 4)
White conductive particles d were obtained in the same manner as in the conductive particle production example 3 except that aluminum oxide having an average primary particle size of 0.35 μm was used as the base particles.

（実施例１）
固形分２０重量％のシリコーン樹脂溶液ＳＲ２４１１（東レ・ダウコーニング社製）８０部、固形分５０重量％のアクリル樹脂溶液ヒタロイド３００１（日立化成社製）１０、１０部の導電性粒子ａ、トルエン１００部及びブチルセロソルブ１００部を、ホモミキサーを用いて、１０分間分散させ、結着樹脂層形成液を調製した。結着樹脂層形成液を芯材粒子Ａ（表２参照）の表面に層厚が０．１５μｍとなるように、スピラコーター（岡田精工社製）を用いて、５５℃の雰囲気下で３０ｇ／分で塗布し、乾燥した。なお、層厚の調整は、液量によって行った。さらに、１５０℃の電気炉で１時間焼成し、冷却後に目開き１００μｍの篩を用いて解砕して、キャリアを得た。

Example 1
80 parts of a silicone resin solution SR2411 having a solid content of 20% by weight (manufactured by Dow Corning Toray), 10 parts of acrylic resin solution Hitaloid 3001 having a solid content of 50% by weight (manufactured by Hitachi Chemical Co., Ltd.), 10 parts of conductive particles a, 100 of toluene Part and 100 parts of butyl cellosolve were dispersed for 10 minutes using a homomixer to prepare a binder resin layer forming solution. Using a spira coater (manufactured by Okada Seiko Co., Ltd.) so that the layer thickness is 0.15 μm on the surface of the core particle A (see Table 2), the binder resin layer forming liquid is 30 g / 55 ° C. in an atmosphere of 55 ° C. Apply in minutes and dry. The layer thickness was adjusted depending on the liquid amount. Further, it was baked in an electric furnace at 150 ° C. for 1 hour, and after cooling, it was crushed using a sieve having an opening of 100 μm to obtain a carrier.

なお、表２中、磁化は、１ｋＯｅの磁場を印加したときの磁化を意味する。
（比較例１）
導電性粒子として、導電性粒子ｂを用いたこと以外は、実施例１と同様にして、キャリアを得た。
（実施例２）
導電性粒子として、導電性粒子ｃを用いたこと以外は、実施例１と同様にして、キャリアを得た。
（実施例３）
導電性粒子として、導電性粒子ｄを用いたこと以外は、実施例１と同様にして、キャリアを得た。
（比較例２）
芯材粒子として、芯材粒子Ｂを用いたこと以外は、実施例３と同様にして、キャリアを得た。
（比較例３）
芯材粒子として、芯材粒子Ｃを用いたこと以外は、実施例３と同様にして、キャリアを得た。
（比較例４）
芯材粒子として、芯材粒子Ｄを用いたこと以外は、実施例３と同様にして、キャリアを得た。
（比較例５）
芯材粒子として、芯材粒子Ｅを用いたこと以外は、実施例３と同様にして、キャリアを得た。
（比較例６）
芯材粒子として、芯材粒子Ｆを用いたこと以外は、実施例３と同様にして、キャリアを得た。
（実施例４）
導電性粒子ａの添加量を２０部に増量したこと以外は、実施例１と同様にして、キャリアを得た。
（実施例５）
固形分２０重量％のシリコーン樹脂溶液ＳＲ２４１１（東レ・ダウコーニング社製）８０部、固形分５０重量％のアクリル樹脂溶液ヒタロイド３００１（日立化成社製）１０部、７部の導電性粒子ｄ、硬質粒子として、一次粒子の平均粒径が０．３４μｍの酸化亜鉛粒子３部、トルエン１００部及びブチルセロソルブ１００部を、ホモミキサーを用いて、１０分間分散させ、結着樹脂層形成液を調製した。

In Table 2, magnetization means magnetization when a magnetic field of 1 kOe is applied.
(Comparative Example 1)
A carrier was obtained in the same manner as in Example 1 except that the conductive particles b were used as the conductive particles.
(Example 2)
A carrier was obtained in the same manner as in Example 1 except that the conductive particles c were used as the conductive particles.
(Example 3)
A carrier was obtained in the same manner as in Example 1 except that the conductive particles d were used as the conductive particles.
(Comparative Example 2)
A carrier was obtained in the same manner as in Example 3 except that the core material particle B was used as the core material particle.
(Comparative Example 3)
A carrier was obtained in the same manner as in Example 3 except that the core material particle C was used as the core material particle.
(Comparative Example 4)
A carrier was obtained in the same manner as in Example 3 except that the core particle D was used as the core particle.
(Comparative Example 5)
A carrier was obtained in the same manner as in Example 3 except that the core material particle E was used as the core material particle.
(Comparative Example 6)
A carrier was obtained in the same manner as in Example 3 except that the core material particle F was used as the core material particle.
Example 4
A carrier was obtained in the same manner as in Example 1 except that the amount of the conductive particles a added was increased to 20 parts.
(Example 5)
80 parts of a silicone resin solution SR2411 having a solid content of 20% by weight (manufactured by Dow Corning Toray), 10 parts of acrylic resin solution Hitaloid 3001 having a solid content of 50% by weight (manufactured by Hitachi Chemical Co., Ltd.), 7 parts of conductive particles d, hard As particles, 3 parts of zinc oxide particles having an average primary particle diameter of 0.34 μm, 100 parts of toluene and 100 parts of butyl cellosolve were dispersed for 10 minutes using a homomixer to prepare a binder resin layer forming liquid.

A carrier was obtained in the same manner as in Example 1 except that the binder resin layer forming liquid was used.
(Example 6)
A carrier was obtained in the same manner as in Example 5 except that titanium oxide particles having an average primary particle size of 0.34 μm were used as the hard particles.
(Example 7)
A carrier was obtained in the same manner as in Example 5 except that aluminum oxide particles having an average primary particle size of 0.34 μm were used as the hard particles.
(Example 8)
A carrier was obtained in the same manner as in Example 3 except that the amount of the conductive particles d added was reduced to 3 parts.
Example 9
A carrier was obtained in the same manner as in Example 7 except that the addition amount of the conductive particles d was changed to 10 parts and the addition amount of the aluminum oxide particles was changed to 65 parts.
(Example 10)
80 parts of a silicone resin solution SR2411 having a solid content of 20% by weight (manufactured by Dow Corning Toray), 10 parts of acrylic resin solution Hitaloid 3001 having a solid content of 50% by weight (manufactured by Hitachi Chemical Co., Ltd.), 7 parts of conductive particles d, primary 3 parts of zinc oxide particles having an average particle diameter of 0.34 μm, chemical structural formula H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃
The binder resin layer forming solution was prepared by dispersing 1.5 parts of the aminosilane coupling agent represented by the formula: 100 parts of toluene and 100 parts of butyl cellosolve for 10 minutes using a homomixer.

A carrier was obtained in the same manner as in Example 7 except that the binder resin layer forming liquid was used.
(Example 11)
80 parts by weight of a silicone resin solution SR2411 with a solid content of 20% by weight (manufactured by Dow Corning Toray), 6.5 parts by weight of a guanamine resin solution Mycoat 106 with a solid content of 77% by weight (manufactured by Mitsui Cytec), 7 parts of conductive particles d, 3 parts of zinc oxide particles having an average primary particle size of 0.34 μm, chemical structural formula H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃
The binder resin layer forming solution was prepared by dispersing 1.5 parts of the aminosilane coupling agent represented by the formula: 100 parts of toluene and 100 parts of butyl cellosolve for 10 minutes using a homomixer.

A carrier was obtained in the same manner as in Example 7 except that the binder resin layer forming liquid was used.
(Example 12)
80 parts of a silicone resin solution SR2411 (made by Toray Dow Corning) having a solid content of 20% by weight, 5 parts of a melamine resin Cymel 303 (made by Mitsui Sydec Co., Ltd.) having a volatile content of 0% by weight, 7 parts of conductive particles d, primary particles 3 parts of zinc oxide particles having an average particle size of 0.34 μm, chemical structural formula H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃
The binder resin layer forming solution was prepared by dispersing 1.5 parts of the aminosilane coupling agent represented by the formula: 100 parts of toluene and 100 parts of butyl cellosolve for 10 minutes using a homomixer.

A carrier was obtained in the same manner as in Example 7 except that the binder resin layer forming liquid was used.
(Example 13)
55 parts by weight of a silicone resin solution SR2411 with a solid content of 20% by weight (manufactured by Dow Corning Toray), 6.5 parts of a guanamine resin solution Mycoat 106 with a solid content of 77% by weight (manufactured by Mitsui Cytec), and 50% by weight of a solid content Acrylic resin solution Hitaroid 3001 (manufactured by Hitachi Chemical Co., Ltd.) 5 parts, 7 parts of conductive particles d, 3 parts of zinc oxide particles having an average primary particle size of 0.34 μm, chemical structural formula H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃
The binder resin layer forming solution was prepared by dispersing 1.5 parts of the aminosilane coupling agent represented by the formula: 100 parts of toluene and 100 parts of butyl cellosolve for 10 minutes using a homomixer.

A carrier was obtained in the same manner as in Example 7 except that the binder resin layer forming liquid was used.
(Example 14)
A carrier was obtained in the same manner as in Example 10 except that the core particle G was used as the core particle.
(Example 15)
A carrier was obtained in the same manner as in Example 10 except that the core particle H was used as the core particle.
(Example 16)
A carrier was obtained in the same manner as in Example 10 except that the core material particle I was used as the core material particle.
(Example 17)
A carrier was obtained in the same manner as in Example 10 except that the core particle J was used as the core particle.
(Example 18)
A carrier was obtained in the same manner as in Example 10 except that the core material particle K was used as the core material particle.
(Example 19)
Example 13 except that melamine resin Cymel 303 (manufactured by Mitsui Sydec) having a volatile content of 0% by weight was used in place of 77% by weight of guanamine resin solution Mycoat 106 (manufactured by Mitsui Cytec). And got a career.
(Example 20)
A carrier was obtained in the same manner as in Example 5 except that silica particles having an average primary particle size of 0.31 μm were used as the hard particles.

（現像剤の製造及び評価）
トナー製造例で得たトナー１０部と、実施例及び比較例で得られたキャリア１００部を、ミキサーを用いて１０分攪拌して現像剤を作製した。

(Manufacture and evaluation of developer)
A developer was prepared by stirring 10 parts of the toner obtained in the toner production example and 100 parts of the carrier obtained in Examples and Comparative Examples for 10 minutes using a mixer.

  An image was formed using the obtained developer, and tests were conducted on development torque, color stain, image quality (background stain, granularity), carrier adhesion, and background stain after 50k run.

  When forming an image, a digital color copier / printer combined machine Imagio Color 4000 (manufactured by Ricoh) was used, and the development conditions were as follows.

Development gap (closest distance between photoreceptor and development sleeve): 0.35 mm
Doctor gap (closest distance between developing sleeve and doctor): 0.65 mm
Photoconductor linear velocity: 200 mm / sec (Developing sleeve linear velocity) / (Photoconductor linear velocity) = 1.80
Writing density: 600 dpi
Charging potential (Vd): -600V
Potential after exposure of the portion corresponding to the image portion (solid document) (V1): -150V
Development bias: DC component: -500 V / AC bias component: 2 kHz, -100 V to -900 V, 50% duty
Table 4 shows the evaluation results.

評価において採用した試験方法は、以下の通りである。
（１）現像トルク
現像装置に現像剤を７００ｇ入れた時の現像部のトルクを測定し、値が非常に大きいものを×とした。
（２）色汚れ
ベタ画像を出力して色差を測定した。具体的には、現像剤をセットした直後の画像をＸ−Ｒｉｔｅ ９３８ Ｄ５０（アムテック社製）により測定した値Ｅと、現像ユニット単独で１時間空攪拌した後に出力した画像をＸ−Ｒｉｔｅにより測定した値Ｅ’から、次式によりΔＥを求め、以下のようにランク付けした。

The test methods employed in the evaluation are as follows.
(1) Development torque The torque of the developing part when 700 g of the developer was put in the developing device was measured, and the value with a very large value was marked as x.
(2) Color stain A solid image was output and the color difference was measured. Specifically, the value E measured by X-Rite 938 D50 (manufactured by Amtec Co., Ltd.) was measured immediately after the developer was set, and the image output after stirring for 1 hour with the developing unit alone was measured by X-Rite. From the obtained value E ′, ΔE was obtained by the following equation and ranked as follows.

ΔE = EE
E = {(L ^* ) ² + (a ^* ) ² + (b ^* ) ² } ^1/2
(Read the value when Yellow ID is 1.4)
A: ΔE ≦ 2
○: 2 <ΔE ≦ 5
×: 5 <ΔE
At this time, ◎ and ○ were accepted and x was rejected.
(3) Background stain The stain on the background on the image was visually evaluated. At this time, very good ones were marked with ◎, good ones with ○, usable ones with Δ, and poor (unacceptable level) with x.
(4) Granularity Granularity (brightness range: 50 to 80) defined by the following formula was measured on transfer paper.

Granularity = exp (aL + b) ∫ (WS (f)) ^1/2 VTF (f) df
L: Average brightness f: Spatial frequency (cycle / mm)
WS (f): Power spectrum of brightness fluctuation VTF (f): Visual spatial frequency characteristics a, b: ◎ (very good) when coefficient granularity is 0 or more and less than 0.1, 0.1 or more and 0.0. A value of less than 2 was evaluated as ◯ (good), a value of 0.2 or more and less than 0.3 as Δ (usable), and a value of 0.3 or more as x (defective (unacceptable level)).
(5) Carrier adhesion Even if carrier adhesion occurs, it is a part of the carrier that is transferred to the paper.

An image pattern of 2 dot lines (100 lpi / inch) is created in the sub-scanning direction, developed by applying −400 V as a DC bias component, and the number of carriers attached between the 2 dot line lines (area 100 cm ² ). Were visually observed for evaluation. At this time, very good ones were marked with ◎, good ones with ○, usable ones with Δ, and poor (unacceptable level) with x.
(6) Background stain after 50k run 50,000 running evaluations were performed using a character image chart with an image area ratio of 6% while replenishing the toner used for initial image printing. The stain on the background portion under the above development conditions was evaluated in the same manner as (3).

It is a perspective view which shows an example of a resistance measurement cell. It is a perspective view which shows an example of a vibration sieve machine. It is sectional drawing which shows an example of the image development apparatus used with the image forming method of this invention. It is sectional drawing which shows an example of the image forming apparatus used with the image forming method of this invention. It is sectional drawing which shows the other example of the image forming apparatus used with the image forming method of this invention. It is sectional drawing which shows an example of the process cartridge of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vibrating screen machine 2 Cylindrical container 3 Spring 4 Base 5 Wire mesh 6 Resonant ring 7 High frequency current cable 8 Converter 9 Ring frame 11 Cell 12a, 12b Electrode 13 Carrier 20 Photoconductor 21 Toner 23 Carrier 24a, 24b Drive roller 26 Pre-cleaning exposure Light source 32 Charging member 33 Image exposure system 40 Developing device 41 Developing sleeve 42 Developer accommodating member 43 Doctor blade 44 Support case 45 Toner hopper 46 Developer accommodating portion 47 Developer agitating mechanism 48 Toner agitator 49 Toner replenishing mechanism 50 Transfer device 60 Cleaning Device 61 Cleaning blade 62 Toner recovery chamber 64 Brush-like cleaning means 70 Static elimination light source 80 Transfer medium

Claims (18)

In carrier core material particles having magnetism are coated with a layer containing a binder resin,
The core material particles state, and are less weight average particle diameter Dw at least 22 .mu.m 32 [mu] m, the ratio Dw / Dp of weight average particle diameter Dw to the number average particle size Dp is not less 1.00 to 1.20, the particle size There is less 7 wt% content of 0 wt% or more of the particles is 20μm or less, the particle size is not more than 100 wt% content of 90 wt% or more of the particles is less than 36 .mu.m, B ET specific surface area of 300cm ² / g or more and 900 cm ² / g or less,
Layer containing a binder resin may further contain a white Iroshirube conductive particles,
The carrier, wherein the white conductive particles are coated with a conductive coating layer containing tin dioxide and indium oxide . The carrier according to claim 1, wherein the white conductive particles have a layer containing tin dioxide formed between the base particles and the conductive coating layer . The carrier according to claim 1, wherein the substrate particles are aluminum oxide particles . 4. The carrier according to claim 1, wherein the volume resistivity is 1 × 10 ¹¹ Ω · cm or more and 1 × 10 ¹⁶ Ω · cm or less. The carrier according to any one of claims 1 to 4, wherein the layer containing the binder resin further contains hard particles. The carrier according to claim 5, wherein a ratio of a total weight of the hard particles and the white conductive particles to a weight of the layer containing the binder resin is 5% or more and 70% or less. The carrier according to claim 5 or 6, wherein the hard particles are at least one of silica particles , titanium oxide particles, and alumina particles . The carrier according to any one of claims 5 to 7, wherein the hard particles and the base particles contain the same metal oxide particles . The carrier according to any one of claims 1 to 8, wherein the layer containing the binder resin further contains an aminosilane coupling agent. The binder resins, the carrier according to any one of claims 1 to 9, characterized in that at least one of thermoplastic resin and a crosslinked product of guanamine resin and a crosslinked product of thermoplastic resin and melamine resin .   The carrier according to claim 10, wherein the thermoplastic resin is an acrylic resin.   The carrier according to any one of claims 1 to 11, wherein the core particles have a magnetization of 50 emu / g or more and 150 emu / g or less when a magnetic field of 1 kOe is applied. The carrier according to any one of claims 1 to 12, wherein the core particles are Mn-Mg-Sr ferrite particles , Mn ferrite particles, or magnetite particles . 14. The carrier according to claim 1 , wherein the core particles have a bulk density of 2.1 g / cm ³ or more and 2.6 g / cm ³ or less. A developer comprising the carrier and the toner according to claim 1. An image forming method comprising a step of developing a latent image formed on a photoreceptor using the developer according to claim 15. It provided a developing sleeve for carrying the developer so that the distance between the photosensitive member while facing the photosensitive member is 0.4mm or less,
The image forming method according to claim 16 , wherein the latent image formed on the photoconductor is developed by applying at least one of a DC voltage and an AC voltage as a developing bias to the developing sleeve. Wherein a photosensitive member, a latent image formed on the photosensitive body, that is supported on one body developing means to development using a developer according to claim 15, which is detachably attached to the image forming apparatus main body Process cartridge.

Images