JP5151440B2 - Electrophotographic developer carrier, developer, image forming method, image forming apparatus, and process cartridge - Google Patents

Description

  The present invention relates to an electrophotographic developer carrier, a developer, an image forming method using a two-component developer, an image forming apparatus, a developer supply apparatus, and a process cartridge.

In an electrophotographic image forming apparatus such as a copying machine or a printer, a uniformly charged image carrier surface is exposed to form a latent image, and the latent image is developed into a toner image. Transferred onto a transfer material such as recording paper. The transfer material carrying the toner image passes through the fixing device and fixes the toner on the transfer material by heat or pressure.
In the image forming apparatus, the developing device that develops the latent image on the image carrier includes a one-component developing type that develops using toner containing a magnetic material, and a developer composed of toner and carrier. There are two-component development systems that perform development.
Among them, the two-component developing type developing device is excellent in developability, and is currently the mainstream of image forming apparatuses. In particular, in recent years, it has been widely used in color image forming apparatuses that form full-color and multi-color images, and the demand for two-component developing type developing apparatuses is further increasing.

  In the two-component developing type image forming apparatus, the toner and the carrier are agitated in the developing device, and the toner is given a charge from the carrier by friction. The toner is electrostatically attached to the outer surface of the carrier, and the carrier carrying the toner is conveyed to the development area. Under the condition that the development bias is applied, the toner is separated from the carrier, and electrostatically adheres to the latent image portion of the image carrier to form a toner image. In the two-component development method, in order to provide a highly durable image satisfying high stability, it is important that a stable charge amount is imparted to the toner from the carrier during stirring. It is important that the charge imparting ability of the carrier is stable before and after long-time use.

  However, in the developing device in the normal two-component developing system, the toner is consumed by the developing operation, while the carrier is not consumed and remains in the developing tank. Therefore, the carrier stirred together with the toner in the developing tank deteriorates as the stirring frequency increases. Specifically, a situation such as peeling of the resin coat on the carrier surface or adhesion of toner to the carrier surface (toner spent) occurs, and as a result, the carrier resistance value and the chargeability of the developer gradually decrease, and development The developability of the agent is excessively increased, causing problems such as an increase in image density and fogging.

As a solution to the above problem, for example, in Patent Document 1, a carrier is added together with toner consumed by development, and the carrier in the developing device is replaced little by little, thereby suppressing a change in charge amount and image density. Has been disclosed, a so-called trickle developing type developing device.
However, even in the developing device disclosed in Patent Document 1, the ratio of deteriorated carriers gradually increases in the developing tank as it is used for a long time, and it is difficult to suppress problems such as an increase in image density. there were.

Further, in Patent Document 2, as a developer to be replenished appropriately in the developing device, a developer including a carrier having a higher resistance value than that of a carrier previously stored in the developing device together with the toner is used. In other words, it is disclosed to maintain chargeability and suppress deterioration of image quality.
Further, in Patent Document 3, as a replenishment developer, a developer containing a carrier that imparts a higher charge amount to the toner together with the toner is used to maintain the chargeability and suppress the deterioration of the image quality. It is disclosed.

  However, since the amount of carrier exchanged in the developing device differs at each time point due to the difference in toner consumption, in the method disclosed in Patent Document 2 or 3, the resistance value or charging of the developer in the developing device. There was a problem in that the amount of change changed and the image density was likely to fluctuate.

Further, Patent Document 4 discloses a method of sequentially replenishing each developer by using a plurality of replenishment developers containing a carrier having different physical properties from the carrier previously stored in the developing device together with the toner. Yes.
However, since the specific gravity of the carrier and the toner is extremely different in practice, as disclosed in Patent Document 4, one of a plurality of carriers having different physical properties is contained together with the toner in one toner supply container. It is very difficult to sequentially replenish the replenished developer in the developing device so as not to mix with each other, and since the amount of toner with respect to the carrier in the developer is large, the carrier is likely to deteriorate, A stable image cannot be obtained for a long time.

Further, as described in Patent Document 4, in order to increase the resistance value of the carrier for replenishment, the resistance value can be increased when the coating amount of the silicone coat layer coated on the carrier core material is simply increased. As a result, the charge amount of the carrier is lowered, and as a result, the image reproducibility of the developed image is lowered and the background portion is stained.
For this reason, in order to obtain more stable development characteristics in the trickle development method, it is important that the carrier can maintain a stable charge imparting ability even in long-term use.

  Further, in the trickle developing method, not only the toner but also the amount of carrier is fluctuated, so that it is difficult to control the ratio of the toner and the carrier in the developer. In particular, at the timing when toner or carrier is added to the developing device, a portion where the concentration of toner or carrier is locally high in the developer tends to occur. When adding toner or carrier to the developing device, if the toner and carrier for the additional amount are mixed in advance and supplied as a developer, such a local density increase can be mitigated. Since the developer supply amount depends on the toner consumption amount, the carrier supply amount may not be optimal. As described above, when the ratio between the toner and the carrier of the developer in the developing device is significantly changed, the charge amount is changed, so that the image density is easily changed.

  The granular carrier used in the two-component development system is for preventing toner filming on the carrier surface, forming a uniform carrier surface, preventing surface oxidation, preventing moisture sensitivity deterioration, extending the life of the developer, and the carrier of the photoreceptor. For the purpose of protecting from scratches or abrasion due to rust, controlling the charge polarity or adjusting the charge amount, it is usually coated with an appropriate resin material (see, for example, Patent Document 5), and various coatings are applied to the coating layer. A method of adding an additive (for example, see Patent Documents 6 to 8) has been performed.

Further, Patent Document 9 proposes an additive added to the carrier surface, and Patent Document 10 proposes a coating layer containing conductive particles larger than the coating layer thickness. ing.
Patent Document 11 proposes to use a carrier coating material mainly composed of a benzoguanamine-n-butyl alcohol-formaldehyde copolymer, and Patent Document 12 discloses a melamine resin and an acrylic resin. It has been proposed to use a crosslinked product as a carrier coating material.
However, there are still problems with durability or heat resistance, and there are problems of spent toner on the carrier surface, resulting in unstable charge amount, and occurrence of toner fog and the like. Furthermore, it is necessary to improve the environmental resistance.

  In recent years, there has been an increasing demand for further stabilization and higher image quality of electrophotographic images. In particular, attempts have been made to minimize and increase the density of the minimum latent image unit (1 dot) for the purpose of improving the image quality. To that end, it is important to faithfully develop the minimized latent image. It has become. Further, for stable image quality, it is an important issue to reduce variation in the charge amount distribution of the developer.

In order to faithfully develop a latent image, it is considered effective to reduce the particle size of the carrier, and the use of various small particle size carriers has been proposed.
Patent Document 13 proposes a magnetic carrier having an average particle size of less than 30 μm, which is composed of ferrite particles having a spinel structure. However, this is a carrier that is not resin-coated, and is used under a low development electric field, has poor development ability, and has no life because it is not resin-coated.

Further, in Patent Document 14, in an electrophotographic carrier having carrier particles, the carrier has a 50% average particle diameter (D50) of 15 to 45 μm, and the carrier contains 1 to 20 carrier particles smaller than 22 μm. Containing 3% or less of carrier particles smaller than 16 μm, 2 to 15% of carrier particles of 62 μm or more, and 2% or less of carrier particles of 88 μm or more, The carrier has a specific surface area S _{1 of the} carrier measured by an air permeation method and a specific surface area S _{2 of the} carrier calculated by the following formula 1 satisfying the condition of the following formula 2. Carriers are listed.
Formula 1 S ₂ = (6 / ρ · D ₅₀ ) × 10 ⁴ (ρ is the specific gravity of the carrier)
Formula 2 1.2 ≦ S ₁ / S ₂ ≦ 2.0

The following advantages can be obtained when this small particle size carrier is used.
[1] Since the surface area per unit volume is wide, sufficient triboelectric charging can be given to each toner. For this reason, the occurrence of low charge amount toner and reverse charge amount toner is small, and background stains are less likely to occur. In addition, the toner around the dots is free from dust and bleeding, and the dot reproducibility is good.
[2] Since the surface area per unit volume is large and scumming is less likely to occur, the average charge amount of the toner can be reduced and a sufficient image density can be obtained.
[3] Since the carrier has a small particle diameter, a dense magnetic brush can be formed. Further, since the fluidity of the ears is good, the traces of the ears hardly occur in the image.

  Furthermore, in Patent Document 15, the weight average particle diameter Dw is 22 to 32 μm, and the number average particle diameter Dp and the weight average particle diameter Dw are composed of magnetic core material particles and a resin layer covering the particle surface. A carrier for an electrophotographic developer having a ratio Dw / Dp of 1 <Dw / Dp <1.20, wherein the content of particles having a particle size of less than 20 μm is 0 to 7% by weight, and the content of particles of less than 36 μm An electrophotographic developer carrier characterized in that the amount is 90-100% by weight and the content of particles smaller than 44 μm is 98-100% by weight, which reduces fines and narrows the particle size distribution. This suppresses carrier adhesion caused by the reduction in particle size.

  Further, when the conventional carrier is made to have a small particle size, the irregularities on the surface of the core material are shrunk, and when viewed macroscopically, the surface property is improved and becomes close to a smooth state. The carrier with a smooth core material surface can uniformly disperse the stress on the carrier particles in the two-component developer. Tend to improve.

  However, even if the stress is evenly distributed, the carrier coating layer is scraped. When the surface properties of the carrier core material are increased, the stress can be evenly distributed to slow down the film scraping, but if used over a long period of time, the entire surface of the particle will be scraped, resulting in a residual film. It becomes almost no particles. Particles with no coating remaining are extremely weak in the ability to impart charge to the toner and do not function as a carrier. In addition, since the electrical resistance is low in the portion where the core surface is exposed due to the coating scraping, carrier adhesion due to injection charging is likely to occur, but the particle front where the coating does not remain has low resistance. Therefore, the probability that charges are injected is high, and as a result, carrier adhesion tends to occur.

Japanese Patent Publication No. 2-21591 Japanese Patent Laid-Open No. 3-145678 Japanese Patent Laid-Open No. 11-223960 JP-A-8-234550 JP 58-108548 A Japanese Patent Publication No. 1-19584 Japanese Examined Patent Publication No. 3-628 JP-A-6-202381 JP-A-5-273789 JP-A-9-160304 JP-A-8-6307 Japanese Patent No. 2683624 JP 58-144839 A Japanese Patent No. 3029180 Japanese Patent Laid-Open No. 2005-250424

  The present invention has been made in view of the above-described problems of the prior art, and in a two-component development type image forming apparatus, the charging property in the developing apparatus is kept stable, and the carrier adhesion of the solid image portion in long-term use is achieved. Providing a carrier for an electrophotographic developer that has good image density and granularity (roughness) while suppressing generation, and has little image density fluctuation caused by change in charge amount due to toner density fluctuation, impact caused by contact between carriers Providing a carrier that can suppress film scraping of the binder resin even during long-term use, and retains the effect of scraping off the toner spent component due to frictional contact between carriers, and a developer using the carrier, An object is to provide an image forming method, an image forming apparatus, and a process cartridge.

The present inventors have intensively studied to solve the above problems. The present invention has been made based on this.
The said subject is solved by (1)-(16) of this invention.

(1) A carrier for an electrophotographic developer comprising core particles and a coating layer covering the particles, and the toner and carrier are replenished to the developing device containing the toner and the carrier. In addition, the weight of the carrier used in the image forming apparatus that performs development while discharging the excess developer in the developing device, and / or the carrier accommodated in the developing device. The average particle diameter Dw is 22 μm or more and 32 μm or less, the ratio Dw / Dp of the number average particle diameter Dp to the weight average particle diameter Dw is 1.00 ≦ Dw / Dp ≦ 1.20, and the particle diameter x [μm] is 0 <x The content of particles having a range of <20 is 7% by weight or less, and the content of particles having a particle size y [μm] of 0 <y <36 is 90% by weight or more and 100% by weight or less. A carrier for an electrophotographic developer.

(2) The coating layer covering the core particles of the carrier contains a binder resin and at least one hard particle, and the particle diameter D1 (μm) of the hard particle and the average thickness h of the resin portion in the coating layer (Μm) satisfies the relationship of 1 <(D1 / h) <10. The carrier for an electrophotographic developer according to the above (1).
(3) The carrier for an electrophotographic developer according to (2), wherein the hard particles are alumina particles or particles based on alumina.

(4) The coating layer covering the core particles of the carrier contains second hard particles in addition to the hard particles, and the particle diameter D1 of the hard particles and the particle diameter D2 of the second hard particles satisfy D2 <D1. And satisfying the relationship 0.001 <(D2 / h) <1 between the particle diameter D2 (μm) of the second hard particles and the average thickness h (μm) of the resin portion in the coating layer. The carrier for an electrophotographic developer according to (2) or (3), which is characterized in that
(5) The carrier for an electrophotographic developer according to (4), wherein the second hard particles are titanium oxide particles or surface-treated titanium oxide particles.

(6) The average thickness T (μm) from the surface of the core material particle to the surface of the coating layer covering the core material particle is in the range of 0.1 ≦ T ≦ 3.0. The carrier for an electrophotographic developer according to any one of 1) to (5).
(7) The electrophotographic developer according to any one of (1) to (6), wherein the binder resin contains at least either a reaction product of an acrylic resin and an amino resin or a silicone resin. For carrier.
(8) The electron according to any one of (1) to (7), wherein magnetization when a magnetic field of 1000 Oersted is applied to the carrier is 50 emu / g or more and 100 emu / g or less. Carrier for photographic developer.

(9) The carrier for an electrophotographic developer according to any one of (1) to (8), wherein the core material particles are Mn—Mg—Sr ferrite, Mn ferrite, or magnetite. .
(10) An electrophotographic developer comprising the carrier for an electrophotographic developer according to any one of (1) to (9) and a toner.
(11) The electrophotographic developer as described in (10) above, wherein the weight ratio of the carrier in the replenishment developer is 3 wt% or more and less than 30 wt%.
(12) The electrophotographic developer as described in (10) or (11) above, wherein the weight ratio of the carrier in the developer contained in the developing device is 85 wt% or more and less than 98 wt%.

(13) The electrostatic latent image formed on the image carrier is replenished with toner and carrier to the developing device containing the toner and carrier, and the surplus in the developing device An image forming method in which development is performed while discharging the developed developer to form a visible image, wherein the carrier for electrophotographic developer according to any one of (1) to (9) is used as the carrier. An image forming method.
(14) An image carrier on which an electrostatic latent image is formed, a developing device that converts the electrostatic latent image into a visible image using a developer containing toner and a carrier, and development that supplies toner and carrier to the developing device. An electrophotographic developer according to any one of (1) to (9), comprising: a developer replenishing device; and a developer discharging device that discharges an excess developer in the developing device. An image forming apparatus using a carrier.

(15) In the image forming apparatus according to (14), the developer replenishing device for replenishing toner and carrier includes a housing container in which a shape for housing the replenishing developer is easily deformed, An image forming apparatus comprising a suction pump that sucks replenishment developer and supplies the developer to a developing device.

(16) An image carrier and a developing device that makes at least an electrostatic latent image formed on the image carrier a visible image with a developer including toner and a carrier are integrally supported, and the image forming device main body A process cartridge detachably provided; means for supplying toner and carrier to the developing device on the image forming apparatus main body side; and developer discharging means for discharging excess developer in the developing device; And a carrier for the electrophotographic developer according to any one of (1) to (9) is used as the carrier.

The present invention is described in further detail below.
The present inventors have intensively studied to solve the above problems. As a result, for the developing device in which toner and carrier are accommodated, the toner and carrier are replenished to the developing device, and development is performed while discharging the excess developer in the developing device. Occurs when the specific surface area of the carrier is increased by reducing the particle size of the carrier while suppressing the change in the charge amount due to the deterioration of the carrier, and the toner and the carrier are supplied into the developing device by the above developing method. It has been found that fluctuations in charge amount due to easy toner density fluctuations can be reduced. However, if the carrier particle size is reduced in order to obtain the above advantages, the magnetic binding force per particle is weakened, so that the carrier adhesion resistance is deteriorated. In order to overcome the above-mentioned disadvantages that are in a trade-off relationship while obtaining the above-mentioned advantages, the present inventors are most effective to reduce the fine powder component of the carrier and to have a narrow particle size distribution. It was found that the above problem can be solved by applying a carrier having an optimum particle size distribution to the above developing method.

  In addition, by providing convex portions made of hard particles on the surface of the carrier used in the above developing method, for the binder resin of the carrier coating layer, the impact due to contact between the carriers is reduced, and even in long-term use. The binder resin film scraping can be suppressed, and for the toner spent component on the carrier surface, the convex portion by the hard particles exerts the effect of cleaning the spent component (cleaning effect), and the toner spent It was found that it can be prevented.

When the charge amount varies, the image density varies. Therefore, it is desirable that the charge amount is always constant.
The charge amount correlates with the ratio of toner and carrier in the developer. Generally, the charge amount decreases as the toner concentration increases. This is because the coverage of the toner on the surface of the carrier particles changes. When the coverage increases, the amount of toner per unit surface area of the carrier particles increases, and the charging action is dispersed. The amount is lower.
Therefore, in order to stabilize the charge amount, it is preferable that the variation in the coverage with respect to the change in toner density is small (sensitivity is low).

The inventors of the present invention supply toner and carrier to the developing device, and with respect to toner concentration fluctuations that occur in the developing method performed while discharging the excess developer in the developing device, As a result of intensive studies on a method of suppressing the fluctuation, it has been concluded that it is effective to reduce the fluctuation of the toner coverage with respect to the carrier surface area as described above.
The toner coverage with respect to the carrier surface area can be calculated by the following equation.
Coverage [%] = (W _t / W _c ) × (ρ _c / ρ _t ) × (D _c / D _t ) × (1/4) × 100
In the formula, D _c is the weight average particle diameter [μm] of the carrier, Dt is the weight average particle diameter of the toner [μm], W _t is the weight of the toner [g], W _c is the weight of the carrier [g], ρ _t Represents the true toner density [g / cm ³ ], and ρ _c represents the true carrier density [g / cm ³ ]. From this equation, the coverage is a function of particle diameter D _c of the carrier, that the variations in coverage when more particle size D _c of the carrier is small toner concentration (W _t / W _c) is changed is reduced Recognize. Therefore, variations in the charge amount when the toner density as the particle diameter D _c of the carrier is small is changed less, the charge amount can be stabilized.

  In the carrier of the present invention, the weight average particle diameter Dw is 22 to 32 μm, preferably 23 μm to 30 μm. When the weight average particle diameter Dw is smaller than 22 μm, the magnetic binding force applied to the particles becomes weak, so that it is difficult to prevent carrier adhesion even if the particle size distribution is sharp. When the weight average particle diameter Dw is larger than 32 μm, the carrier adhesion is less likely to occur, but the toner is not developed faithfully with respect to the latent image, so that the variation in the dot diameter increases and the graininess decreases.

  The carrier adhesion indicates a phenomenon in which a carrier adheres to an image portion or a background portion of an electrostatic latent image. Carrier adhesion is not preferable because it causes inconveniences such as damage to the photosensitive drum and the fixing roller. On the other hand, when the ratio Dw / Dp of the number average particle diameter Dp and the weight average particle diameter Dw is larger than 1.20, the ratio of the fine particles increases and the carrier adhesion resistance deteriorates.

The content of particles having a particle size of less than 20 μm in the carrier is preferably 7% by weight or less, more preferably 5% by weight or less, more preferably 3% by weight or less.
When the particles smaller than 20 μm are larger than 7% by weight, the particle size distribution is widened, and particles with small magnetization are present everywhere in the magnetic brush, and the carrier adhesion is rapidly deteriorated.
The content ratio of carrier particles having a particle size smaller than 20 μm is preferably 0.5% by weight or more. If it is 0.5% by weight or more, a desired value can be obtained without cost.
Further, in the carrier particles having a weight average particle diameter Dw of 22 to 32 μm, a carrier having a sharp particle size distribution in which particles smaller than 36 μm are 90% by weight or more, more preferably 92% by weight or more is magnetic for each carrier particle. The variation in binding force is reduced, and carrier adhesion resistance can be greatly improved.

In the present invention, the weight average particle diameter Dw referred to for the carrier, the carrier core material 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 represented by the following formula.
D _w = {1 / Σ (nD ³ )} × {Σ (nD ⁴ )} (1)
In the formula (1), D represents a representative particle size (μm) of particles present in each channel, and n represents the total number of particles present in each channel. The channel indicates a length for equally dividing the particle size range in the particle size distribution diagram. In the present invention, a length of 2 μm is adopted.

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 the carrier 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 represented by the following formula.
D _p = (1 / ΣN) × (ΣnD) (2)
In formula (2), N represents the total number of particles measured, n represents the total number of particles present in each channel, and D represents the lower limit value of the particle size present in each channel (2 μm).

As a particle size analyzer for measuring the particle size distribution in the present invention, a Microtrac particle size analyzer (model HRA9320-X100: manufactured by Honeywell) was used.
The measurement conditions are as follows.
[1] Particle size range: 100-8 μm
[2] Channel length (channel width): 2 μm
[3] Number of channels: 46
[4] Refractive index: 2.42

  In the image forming apparatus of the two-component development system, the image density and graininess (roughness) are good while maintaining the charging property in the developing apparatus stably and suppressing the occurrence of carrier adhesion of the solid image part in long-term use. It is possible to provide a carrier for an electrophotographic developer with little image density fluctuation caused by a change in charge amount accompanying toner density fluctuation.

FIG. 1 is an explanatory diagram showing a carrier coating layer used in an embodiment of the present invention. As shown in FIG. 1, the carrier used in the present invention includes a core material 26 and a coating layer 27 that covers the core material 26. The coating layer 27 includes a binder resin and hard particles. (Hereinafter, referred to as the first particle G1), the particle diameter D1 (μm) of the first particle G1 is expressed by the following formula 1 <(D1 / h) It is preferable to satisfy <10.
As a layer covering the core material 26, it is possible to have other layers in addition to the covering layer 27. Furthermore, the coating layer 27 can contain other components as needed in addition to the binder resin, the first particles G1, and the second particles G2.

The average thickness h of the resin portion in the coating layer 27 represents the thickness of the film that exists in the direction perpendicular to the surface of the core material 26. In the thickness from the surface of the core material 26 to the surface of the coating layer 27, the particle portion The average thickness of the removed resin portion is shown.
As the thickness of the resin portion in the coating layer 27, the thickness ha of the resin portion existing between the surface of the core material 26 and the particles, the thickness hb of the resin portion existing between the particles, and the resin portion existing on the particles Thickness hc and the thickness hd of the resin portion existing on the core material 26.

  The average thickness h of the resin part in the coating layer 27 can be measured by observing the cross section of the carrier using, for example, a transmission electron microscope (TEM). Specifically, along the carrier surface, the thickness of the resin part in the coating layer 27 at intervals of 0.2 μm (the thickness ha of the resin part existing between the core material surface and the particles, the resin part existing between the particles) The thickness hb, the thickness hc of the resin part on the particles, and the thickness hd of the resin part on the core material) were measured using a transmission electron microscope (TEM), and 50 measurement values were obtained. Is the average thickness h of the resin portion in the coating layer 27.

As a specific calculation method, the value of the average thickness h of the resin portion in the coating layer 27 is a value obtained by summing up the respective measured values obtained by the above-described method and dividing the obtained value by the number of measured values. It is. The number of measured values is as follows: the thickness ha of the resin part existing between the surface of the core material 26 and the particles, the thickness hb of the resin part existing between the particles, the thickness hc of the resin part on the particles, and the core material 26 The thickness hd of each resin part is regarded as one and counted.
For example, at the measurement point A shown in FIG. 1, since the hb and the hc exist, the number of measurement values at the measurement point A is two.
Further, in the measurement method described above, a plurality of measurement values (for example, ha and hc) are obtained as measurement values of the thickness of the resin portion in the coating layer 27 at the last measured position among the 50 measurement values. In this case, a value obtained by dividing the total value of the measured values by the value of “49+ (number of measured values at the last measured point)” that is the number of measured values is the average thickness of the resin portion in the coating layer 27. Let h be the value.

The particle diameter D1 (μm) of hard particles (hereinafter referred to as first particles G1) contained in the coating layer 27 is 1 <(D1 / h) with respect to the average thickness h (μm) of the resin portion in the coating layer 27. ) <10, more preferably 1 <(D1 / h) <5.
When the particle diameter D1 of the first particle G1 and the average thickness h of the resin portion in the coating layer 27 satisfy the above relational expression, the first particle G1 is more convex than the carrier coating layer 27. This convex portion can alleviate the strong impact applied to the binder resin of the carrier coating layer 27 due to the frictional contact between the toner and the carrier or between the carriers when agitation is performed to frictionally charge the developer. Thereby, it can suppress that the film | membrane scraping of the binder resin of the carrier coating layer 27 which is a charging generation location generate | occur | produces.

Further, when the carriers are in frictional contact with each other, the particles that are convex with respect to the surface of the coating layer 27 scrape off the spent component of the toner adhering to the surface of the carrier, thereby obtaining a cleaning effect. . Thereby, it is possible to effectively prevent the phenomenon of toner spent.
When (D / h) is 1 or less, the first particles may be buried in the binder resin, and the effects of the first particles G1 added to the coating layer 27 may not be sufficiently obtained. Further, when (D / h) is 10 or more, the contact area between the first particles G1 and the binder resin becomes small, and sufficient binding force of the first particles G1 to the carrier particles cannot be obtained, so that the first particles G1 may be easily detached from the carrier particle surface.

The coating layer 27 preferably contains second hard fine particles (hereinafter referred to as second particles G2) in order to give the coating layer an appropriate moderate strength on average. The particle diameter D2 (μm) of the second particle G2 is in a relationship of D2 <D1 with the particle diameter D1 of the first particle G1, and 0.001 <with respect to the average thickness h (μm) of the resin portion in the coating layer 27. Those satisfying (D2 / h) <1 are preferable, and those satisfying 0.01 <(D2 / h) <0.5 are more preferable.
By making the particle diameter D2 of the second particles G2 smaller than the average thickness of the coating layer 27, the second particles G2 can be included while being dispersed in the coating layer 27. Therefore, the strength of the coating layer can be improved on average.

The volume resistivity value of the second particle G2 is preferably 1.0 × 10 ¹² Ω · cm or less, more preferably 1.0 × 10 ¹⁰ Ω · cm or less, and further preferably 1.0 × 10 ⁸ Ω · cm. It is as follows. By setting the volume resistivity of the second particle G2 to a low resistance of 1.0 × 10 ¹² Ω · cm or less, the charge imparting ability of the coating layer 27 is controlled to an appropriate low, and finally obtained. The image density can be increased.
The first particles G1 may be fine particles having high conductivity. The conductivity may be adjusted by blending particles that have been subjected to a treatment for enhancing conductivity and particles that have not been subjected to the treatment. The conductivity of the conductive fine particles themselves may be adjusted by adjusting the degree of treatment for increasing the conductivity.

A method for imparting conductivity to the fine particles is not particularly limited. For example, there is a method of forming a conductive coating layer on the surface of the substrate particles. In particular, by providing a structure in which a tin dioxide layer and a conductive coating layer made of tin dioxide and indium oxide provided on the tin dioxide layer are provided on the surface of the substrate particles, the same level of conductivity as carbon black is exhibited. Can be made.
However, even if a conductive coating layer made of tin dioxide and indium oxide is formed directly on the surface of the substrate, the electrical influence of the substrate particles is great, and good conductivity may not be obtained. In addition, even if a mixed solution of tin dioxide hydrate and indium oxide hydrate is directly coated on the substrate, it is difficult to uniformly coat the substrate surface, which causes problems in terms of quality. There is.

  After the surface of the base particle is coated with a material generally used as a coating material such as aluminum oxide, zinc oxide or zirconium oxide, a mixed solution of tin dioxide hydrate and indium oxide hydrate is added to the base particle. When coated, a uniform conductive coating layer can be formed. However, even when these coating materials are used for the lower layer, good electrical conductivity cannot often be obtained due to the electrical influence of the coating material. Therefore, when tin dioxide is used as the coating material for forming the lower layer, the upper conductive coating layer can be fixed uniformly and firmly, and good electrical conductivity can be obtained without being adversely affected by electrical effects from the lower layer. I was able to get sex. Note that there is no problem even if a small amount of indium oxide component is mixed in the lower layer as long as the effect of the particles is not impaired.

  The substrate of the conductive fine particles has a remarkable improvement effect by using any one of aluminum oxide, titanium dioxide, zinc oxide, silicon dioxide, barium sulfate and zirconium oxide alone or in combination. This is considered to be because the compatibility with the conductive treatment of the particle surface is good and the conductive treatment effect is exhibited well. In particular, aluminum oxide and titanium dioxide are easy to satisfy the above-mentioned color tone conditions, and aluminum oxide is particularly easy to obtain a preferable color tone. However, the present invention is not limited to the above-mentioned particles, and those other than those that exhibit good effects can be used. In the case of titanium dioxide, it may be a rutile type, anatase type, or other structure.

The following aspects are mentioned as a more detailed manufacturing method of the electroconductive fine particles suitable for this invention. However, this is an example of a production method, and the production method of the conductive fine particles of the present invention is not limited to this method.
There are various methods for forming the lower layer of tin dioxide hydrate. For example, after adding a tin salt or a stannate solution to an aqueous suspension of a white inorganic pigment, Alternatively, there are a method of adding an acid, a method of adding a tin salt or tin hydrochloric acid and an alkali or an acid separately in parallel and performing a coating treatment. In order to uniformly coat the surface of the white inorganic pigment particles with the hydrated tin oxide, the latter parallel addition method is more suitable. At this time, the aqueous suspension should be kept warm at 50 to 100 ° C. Is more preferable. Moreover, pH at the time of adding tin salt or a stannate, an alkali, or an acid in parallel is set to 2-9. Since the isoelectric point of tin dioxide hydrate is pH = 5.5, it is important to maintain pH = 2-5 or pH 6-9, whereby the hydrolysis product of tin is converted into a white inorganic pigment. It can be uniformly deposited on the particle surface.

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 0.5 to 50% by weight, preferably 1.5 to 40% by weight as SnO _{2 with} respect to the base particles. If it is less than 0.5% by weight, the coating state of the hydrate of indium oxide containing tin oxide coated thereon becomes non-uniform, and the volume resistivity of the powder increases due to the influence of the base particles. . If it exceeds 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 coating tends to be non-uniform.

  Next, there are various methods of forming a coating of indium oxide hydrate containing tin dioxide as an upper layer. However, since the coating of the previously coated tin dioxide hydrate is not dissolved, a tin salt and an indium salt are used. A method in which a mixed solution and an alkali are separately added in parallel to form a film is more preferable. At this time, it is more preferable to heat the aqueous suspension to 50 to 100 ° C. In addition, it is important that the pH when the mixed solution and the alkali are added in parallel is 2 to 9, and preferably maintained at pH 2 to 5 or pH 6 to 9, so that the hydrolysis reaction product of tin and indium is uniform. Can be deposited.

As a raw material of tin, for example, tin chloride, tin sulfate, tin nitrate or the like can be used. As the indium raw material, for example, indium chloride, indium sulfate, or the like can be used.
The amount of tin dioxide added is 0.1 to 20% by weight, preferably 2.5 to 15% by weight as SnO _{2 with} respect to In ₂ O ₃ , and the desired conductivity is too small or too large. Cannot be obtained.
The amount of indium oxide to be treated is 5 to 200% by weight, preferably 8 to 150% by weight, as In ₂ O _{3 with} respect to the inorganic pigment of the substrate. However, the conductivity is hardly improved, and it is expensive and not preferable from the viewpoint of cost.

  In the present specification, “conductive” powder means a powder having a volume resistivity value of 1 to 500 Ω · cm. As will be shown in the examples described later, according to the present invention, a white conductive powder having excellent electrical conductivity of 100 Ω · cm or less, and in some cases 10 Ω · cm or less, comparable to that of an antimony-containing product can be obtained. .

When the heat treatment is performed, it is preferably performed in a non-oxidizing atmosphere at 350 to 750 ° C., and the volume resistivity of the powder can be lowered by 2 to 3 orders of magnitude as compared with the heat treatment in air. .
An inert gas can be used to create a non-oxidizing atmosphere. As the inert gas, for example, nitrogen, helium, argon, carbon dioxide gas or the like can be used. Industrially, it is advantageous in terms of cost to perform heat treatment while blowing nitrogen gas, and a product with stable characteristics can be obtained.
The temperature at the time of heating is 350 to 750 ° C., preferably 400 to 700 ° C., and it is difficult to obtain desired conductivity even when the temperature is lower or higher than this range. In addition, the heating time is not effective when the heating time is too short, and if the heating time is too long, no further effect can be expected, so about 15 minutes to 4 hours is appropriate, preferably about 1 to 2 hours. It is.

  Furthermore, when the powder specific resistance of the conductive fine particles exceeds 200 (Ω · cm), the resistance reducing ability of the conductive fine particles is low, and in order to set the carrier resistance to an appropriate value, A large amount of conductive fine particles is required. At this time, since the proportion of the particles is excessive as compared with the proportion of the binder resin on the surface of the carrier, the proportion of the binder resin that is a charging generation point is insufficient, and sufficient charging ability cannot be exhibited. In addition, since the amount of particles is too much compared to the amount of binder resin, the ability to hold particles by the binder resin becomes insufficient, and the particles are likely to be detached. It is not preferable because the properties cannot be obtained.

The volume resistivity of the conductive fine particles, the first particles G1, and the second particles G2 in the present invention can be measured, for example, as follows.
A sample is put in a cylindrical vinyl chloride tube having an inner diameter of 1 inch, and the upper and lower sides are sandwiched between electrodes. A pressure of 15 kg / cm ² is applied to these electrodes with a press machine for 1 minute. Subsequently, measurement with an LCR meter is performed in this pressurized state to obtain resistance (r). The volume resistivity can be obtained by calculating the obtained resistance value according to the following Equation 1.
Volume resistivity (Ω · cm) = (2.54 / 2) ² × (π / H × r) (1)
(In the formula (1), H is a value representing the thickness of the sample, and r is a value representing the resistance value of the sample.)
When the value of (D2 / h) is 1 or more, the second particle G2 is too large with respect to the thickness of the coating layer 27, so that the effect of dispersing and improving the strength of the coating layer on average is hardly exhibited. Become. Moreover, since the particle size of the 2nd particle | grains G2 is too small with respect to the coating layer 27 thickness as (D2 / h) is 0.001 or less, an effect becomes difficult to be acquired.

The average thickness T (μm) from the surface of the core material 26 to the surface of the coating layer 27 is preferably 0.1 ≦ T ≦ 3.0, and more preferably 0.1 ≦ T ≦ 2.0.
If the average thickness T from the surface of the core material 26 to the surface of the coating layer 27 is less than 0.1 μm, the total thickness of the coating layer 27 as a film covering the carrier core material 26 is too thin. As a result, the carrier core material 26 is likely to be exposed and the carrier durability is lowered.
On the other hand, if the average thickness T from the core material 26 to the surface of the coating layer 27 exceeds 3.0 μm, the film thickness formed on the surface of the core material 26 is too thick, so that the magnetization of the carrier tends to decrease and carrier adhesion occurs. There are things to do.
The average thickness h (μm) of the resin portion in the coating layer 27 is preferably 0.04 to 2 μm, and more preferably 0.04 to 1 μm.

The volume average particle diameter D1 of the first particles G1 is preferably 0.05 to 3 μm, and more preferably 0.05 to 1 μm.
The particle diameter D2 of the second particles G2 is preferably 0.005 to 1 μm, and more preferably 0.01 to 0.2 μm.
As shown in FIG. 1, the thickness T from the surface of the core material 26 to the surface of the coating layer 27 represents a thickness different from the average thickness h of the resin portion in the coating layer 27 described above. The thickness from the surface of the core material 26 to the surface of the coating layer 27 is shown.
As shown in FIG. 1, when the particle size of the particles added to the coating layer 27 is larger than the thickness of the resin portion in the coating layer 27, the particle size of the particles is changed from the surface of the core material 26 to the coating layer. The value corresponds to the thickness T up to 27 surfaces.
The average thickness T from the surface of the core material 26 to the surface of the coating layer 27 is obtained by, for example, observing the cross section of the carrier using a transmission electron microscope (TEM) and calculating the thickness from the surface of the core material 26 to the surface of the coating layer 27. Is a value obtained by measuring 50 points at intervals of 0.2 μm and averaging these measured values.

Examples of the first particles G1 include alumina particles, silica particles, titania particles, and zinc oxide particles. Among these, the alumina particles have good compatibility with a binder resin used for a carrier coating material, Not only is it excellent in terms of dispersibility and adhesiveness, but also has a very high hardness, so it is difficult for abrasion and cracking to occur in response to stress in the developing device 10, and the protective effect of the coating layer and scratching of the spent material over a long period of time. This is particularly preferable because it can exert a taking effect.
As the alumina particles, alumina particles having a particle size of 5 μm or less are preferable, and any particles that have not been surface-treated or those that have been surface-treated such as a hydrophobic treatment can be used.
As the silica, those used for toner and those other than that can be used, and those not subjected to surface treatment, those subjected to surface treatment such as hydrophobic treatment, and the like can be used. Further, the conductive fine particles may be used as the first particles G1.

The content of the first particles G1 contained in the coating layer 27 is preferably 10 to 80 wt%, and more preferably 20 to 60 wt%.
When the content of the first particles G1 in the coating layer 27 is less than 10 wt%, the proportion of the first particles G1 is too small compared to the proportion of the binder resin on the surface of the carrier particles. Since the effect of relieving contact with a strong impact is small, sufficient durability may not be obtained.
On the other hand, if it exceeds 80 wt%, the proportion of the first resin G1 is too large compared to the proportion of the binder resin on the carrier surface, and therefore the proportion of the binder resin that is the charge generation location becomes insufficient, which is sufficient. May not be able to demonstrate proper charging ability. Furthermore, since the amount of the first particles G1 is too large compared to the amount of the binder resin, the holding ability of the first particles G1 by the binder resin is insufficient, the first particles G1 are easily detached, and the charge amount and resistance are increased. In some cases, the amount of variation such as the above increases and sufficient durability cannot be obtained.
Here, content in the coating layer 27 of the 1st particle | grains G1 is represented by following formula (2).
Content of first particle G1 (wt%) = [content of first particle G1 / total amount of material contained in coating layer 27 (first particle G1 + second particle G2 + binding resin + other components)] × 100 ... (2)
As the second particle G2, at least one kind of particle selected from titanium oxide, zinc oxide, tin oxide, surface-treated titanium oxide, surface-treated zinc oxide, and surface-treated tin oxide is preferably used. It is done.

These particles have an appropriate hardness, have good compatibility with the resin used for the carrier coating material, and are excellent in dispersibility and adhesiveness. In particular, titanium oxide and surface-treated titanium oxide Is preferable as the second particle G2.
Further, even when a particle matrix other than the above is used, it is possible to improve the dispersibility by subjecting the particle surface to a surface treatment such as a hydrophobizing treatment, If the volume resistivity is within the above range, good effects can be obtained for the same reason as described above.

The content of the second particles G2 contained in the coating layer 27 is preferably 2 to 50 wt%, and more preferably 2 to 30 wt%.
The greater the content of the second particles G2 in the coating layer 27, the greater the effect of increasing the strength. However, when the content of the second particles G2 exceeds 50 wt%, the dispersion state of the second particles G2 inside the coating layer 27 is increased. Deteriorates significantly. When the dispersed state of the particles is deteriorated, the second particles G2 are partially aggregated inside the coating layer 27, so that the effect of the second particles G2 is hardly exhibited on average.
On the other hand, when the content of the second particles G2 in the coating layer 27 is less than 2 wt%, the content is too small, and thus the effect of adding the second particles G2 cannot be sufficiently obtained.
Content in the coating layer 27 of the 2nd particle | grains G2 is represented by following formula (3).
Content of second particle G2 (wt%) = [content of second particle G2 / total amount of material contained in coating layer 27 (first particle G1 + second particle G2 + binder resin + other components)] × 100 ... (3)

As the binder resin used for the carrier particle coating layer 27, a reaction product of an acrylic resin and an amino resin, or a silicone resin can be suitably exemplified.
There is no restriction | limiting in particular as a reaction material of an acrylic resin and an amino resin, Although it can select suitably according to the objective, The crosslinking reaction material of an acrylic resin and an amino resin is suitable.
There is no restriction | limiting in particular as an acrylic resin, Although it can select suitably according to the objective from all the acrylic resins, 20-100 degreeC is preferable among these, Glass transition temperature (Tg) is preferable, 25-80 ° C is more preferred. When the glass transition temperature (Tg) of the acrylic resin is within this range, the acrylic resin has appropriate elasticity, and the friction between the toner and the carrier or between the carriers in the stirring for frictionally charging the developer. Friction can absorb the impact when contacting the binder resin with a strong impact, and the coating layer can be maintained without being damaged.
When the glass transition temperature (Tg) is less than 20 ° C., the binder resin blocks even at room temperature, so that the storage stability is poor and it may not be practically used. On the other hand, when the glass transition temperature (Tg) exceeds 100 ° C., the binder resin is too hard and brittle, and cannot absorb the impact, and the binder resin is scraped from the brittleness and retains the particles. May not be able to be performed and may be easily detached.

The amino resin is not particularly limited and can be appropriately selected from conventionally known amino resins according to the purpose. For example, by using guanamine or melamine, the charge imparting ability is remarkably increased. Can be improved.
There is no restriction | limiting in particular as a silicone resin, According to the objective from the silicone resin generally known, it can select suitably according to the objective, For example, straight silicone resin which consists only of organosilosan bonds, alkyd resin, polyester Examples thereof include silicone resins modified with resins, epoxy resins, acrylic resins, urethane resins, and the like.
Commercially available products can be used as the silicone resin. Examples of the straight silicone resin include KR271, KR255, and KR152 manufactured by Shin-Etsu Chemical Co., Ltd .; SR2400, SR2406, and SR2410 manufactured by Toray Dow Corning Silicone. .
Examples of the modified silicone resin include KR206 (alkyd modified), KR5208 (acrylic modified), ES1001N (epoxy modified), KR305 (urethane modified) manufactured by Shin-Etsu Chemical Co., Ltd .; SR2115 manufactured by Toray Dow Corning Silicone Co., Ltd. Epoxy modified), SR2110 (alkyd modified), and the like.
It is possible to use the silicone resin alone, but it is also possible to simultaneously use a component that undergoes a crosslinking reaction, a charge amount adjusting component, and the like.

  As the binder resin used for the carrier particle coating layer 27, in addition to the above-mentioned resins, those generally used as carrier coating resins can be used as necessary. Resin, polystyrene resin, halogenated olefin resin, polyester resin, polycarbonate resin, polyethylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, polytrifluoroethylene resin, polyhexafluoropropylene resin, vinylidene fluoride Examples thereof include copolymers with vinyl fluoride, and fluoroterpolymers such as terpolymers of tetrafluoroethylene, vinylidene fluoride and non-fluorinated monomers. These may be used individually by 1 type and may use 2 or more types together.

For example, the coating layer 27 is prepared by dissolving the first particles G1, the second particles G2, the binder resin, and the like in a solvent to prepare a coating solution, and then uniformly coating the coating solution on the surface of the core material 26 by a known coating method. It can be formed by applying and drying, followed by baking. Examples of the coating method include a dipping method, a rolling fluidized bed method, and a spray method.
There is no restriction | limiting in particular as said solvent, Although it can select suitably according to the objective, For example, toluene, xylene, methyl ethyl ketone, methyl isobutyl ketone, cersol butyl acetate, butyl cellosolve etc. are mentioned.
The baking is not particularly limited, and may be an external heating method or an internal heating method. For example, a stationary electric furnace, a fluid electric furnace, a rotary electric furnace, a burner furnace, etc. The method of using, the method of using a microwave, etc. are mentioned.

  There is no restriction | limiting in particular as the core material 26, According to the objective, it can select suitably from what is known as a two-component carrier for electrophotography, For example, a ferrite, magnetite, iron, nickel is mentioned suitably. Considering the environmental impact that has been remarkably advanced in recent years, if it is ferrite, for example, Mn ferrite, Mn—Mg ferrite, Mn—Mg—Sr ferrite, etc. are used instead of conventional copper-zinc ferrite. Is preferred. In addition, Mn—Mg—Sr ferrite, Mn ferrite, and magnetite are effective materials for suppressing carrier adhesion because they have high magnetization, as will be described in detail later.

The conventional small particle size carrier has a very big problem that the carrier easily adheres to it, and it has been a cause of generation of scratches on the photoreceptor and flaws on the fixing roller.
In particular, when the carrier has an average particle size of less than 32 μm, the roughness is greatly improved and the image quality is improved, but the carrier adhesion is very likely to occur and the problem is great. As a result of extensive studies by the present inventors on this issue, the following has been found.

Carrier adhesion to the background portion of the image or the image portion is caused by adhesion in the form of carrier particles or a cut magnetic brush when Fm <Fc. (Fm: magnetic binding force, Fc: force causing carrier adhesion)
The force Fc causing carrier adhesion is related to the development potential, background potential, centrifugal force applied to the carrier, carrier resistance, and developer charge amount. Therefore, in order to prevent carrier adhesion, it is effective to set each parameter so as to reduce Fc. However, since it is closely related to developing ability, background stain, toner scattering, etc., it should be changed greatly. Is currently difficult.

On the other hand, regarding the magnetic binding force Fm,
It is represented by Where K is the mass of the carrier,
M is the magnetization per unit mass. Also,
Is the gradient of the magnetic field strength (H) at the position where the carrier exists.
Since the magnetic binding force (Fm) on the carrier is proportional to the third power of the carrier radius (r), as the carrier becomes smaller in particle size, it rapidly decreases at the third power of the particle size, and the carrier adheres very much. It is easy to get up.

Therefore, the present inventors have made a prototype of a sample in which the magnetization of the carrier is shaken and studied, and the magnetization when a magnetic field of 1000 oersted (Oe) is applied is 50 emu / g or more, more preferably 70 emu / g or more. It has been found that carrier adhesion is improved. From the viewpoint of carrier adhesion, there is no particular limitation on the upper limit value. Usually, the upper limit is about 150 emu / g, but too strong magnetization may impair the smoothness of the magnetic brush. It is preferable that it is 100 emu / g or less.
When carrier adhesion occurs, it may cause damage to the photosensitive drum and the fixing roller, resulting in a decrease in image quality. If the magnetization of the carrier core particles is smaller than the above range, a sufficiently strong magnetic binding force Fm cannot be obtained, and carrier adhesion tends to occur, which is not preferable in practice.

The magnetization can be measured as follows.
A BH tracer (BHU-60 / manufactured by Riken Denshi Co., Ltd.) is used, and 1.0 g of carrier core particles are packed in a cylindrical cell and set in an apparatus. The magnetic field is gradually increased and changed to 3000 oersted, then gradually reduced to zero, and then the opposite magnetic field is gradually increased to 3000 oersted. Further, after gradually reducing the magnetic field to zero, a magnetic field is applied in the same direction as the first. In this way, the BH curve is shown, and the 1000 oersted magnetization is calculated from the figure.

Examples of the core particles used in the carrier of the present invention, which are 50 emu / g or more when a 1000 oersted magnetic field is applied, include, for example, iron, cobalt and other ferromagnetic materials, magnetite, hematite, Li-based ferrite, Mn- Examples thereof include Zn-based ferrite, Cu-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
However, x + y + z = 100 mol%, and M and N are Ni, Cu, Zn, Li, Mg, Mn, Sr, Ca, etc., respectively, and the divalent metal oxide and the trivalent iron oxide Consists of a complete mixture.

As the material of the core material particles constituting the carrier of the present invention, various conventionally known magnetic materials are used, but more preferable core material particles having a magnetization of 70 emu / g or more when a 1000 oersted magnetic field is applied. As mentioned above, for example, magnetite, Mn—Mg—Sr ferrite, Mn ferrite and the like can be mentioned.
In the present invention, the carrier resistivity is not limited, but is preferably 1 × 10 ¹¹ to 1 × 10 ¹⁶ [Ω · cm], more preferably 1 × 10 ¹² to 1 × 10 ¹⁴ [Ω · cm].
When the resistivity of the carrier is lower than 1 × 10 ¹¹ [Ω · cm], when the developing gap (the closest distance between the photosensitive member and the developing sleeve) becomes narrow, charge is induced in the carrier and the carrier adheres. It becomes easy to do. When the linear velocity of the photosensitive member and the linear velocity of the developing sleeve are large, a tendency of deterioration is observed. In addition, it is remarkable when an AC bias is applied. Usually, a color toner developing carrier is generally used having a low resistance in order to obtain a sufficient toner adhesion amount.
By using the carrier having the above resistance range under an appropriate toner charge amount, a sufficient image density can be obtained.
On the other hand, if it is larger than 1 × 10 ¹⁶ [Ω · cm], charges having a polarity opposite to that of the toner are likely to be accumulated, and the carrier is easily charged to cause carrier adhesion.

The carrier resistivity can be measured by the following method.
As shown in FIG. 2, a cell (21) made of a fluororesin container containing electrodes (22a) and (22b) having a distance between electrodes of 2 mm and a surface area of 2 × 4 cm is filled with a carrier (23), A DC voltage of 100 V is applied, and the DC resistance is measured with a high resistance meter 4329A (4329A + LJK 5HVLVWDQFH OHWHU; manufactured by Yokogawa Hewlett-Packard Co., Ltd.).
When filling the carrier resistance, fill the cell until it overflows, and after tapping the entire cell 20 times, use a non-magnetic horizontal spatula on the top surface of the cell along the top edge of the cell. Scrape flatly in one operation. No pressure is required during filling.
The carrier resistivity can be adjusted by controlling the amount of conductive fine particles, the film thickness of the resin coating layer, or the like.

In the embodiment of the present invention, the developer container 230 (see FIG. 4) includes the first particles G1 and the second particles G2 in the coating layer 27 that covers the surface of the core material 26. The carrier (see FIG. 1) is accommodated. In the image forming apparatus 100 (see FIG. 3), the replenishment developer including the carrier is supplied from the inside of the developer container 230 (see FIG. 4) into the developer container 14 (see FIG. 4).
In FIG. 4, the toner and the carrier replenished in the developer accommodating portion 14 are mixed together with the toner and the carrier accommodated from the beginning by the conveying screws 11a and 11b. Since the toner and the carrier, or the carriers are in strong contact with each other, the carrier surface is particularly likely to be scraped by friction at this portion.

However, in the carrier contained in the developer according to the present invention, a part of the first particles G1 are convex with respect to the coating layer 27. For this reason, as described above, even if the toner or other carrier particles come into contact with the coating layer 27 during the stirring and mixing, the impact is mitigated by the convex portions on the surface of the coating layer 27. For this reason, the rate at which film scraping on the carrier surface occurs can be greatly suppressed.
Further, since the spent component of the toner adhering to the carrier surface during stirring is scraped off by the first particles present as the projections, the occurrence of toner spent is prevented. Furthermore, the strength of the coating layer is increased by the second particles G2, and the film shaving itself hardly occurs. Therefore, the developer in the developer container 14 can maintain a more stable charge control effect for a long time.

  In the developing device 10, most of the deteriorated carrier is discharged by the developer discharging device 330. However, the possibility that part of the deteriorated carrier remains in the developer accommodating portion 14 for a long time is not zero, and in the image forming apparatus 100, when the toner consumption is small, the developer accommodating portion The carrier exchange amount at 14 is small, and the period during which the carrier stays in the developer accommodating portion 14 may become long.

  In the present embodiment, the carrier used for the replenishment developer is also applied to the developer in the developing device accommodated in the developer accommodating portion 14 before the replenishment developer in the developer container 230 is replenished. The same carrier is used. For this reason, even when the developer replacement amount is low, or when a part of the carrier accommodated from the beginning remains without being discharged from the developer accommodating portion 14, the same mechanism as described above is used for developing. The deterioration of the carrier in the agent container 14 is suppressed, and the developer can be kept in a stable state even after long-term use.

FIG. 3 is a diagram showing a schematic configuration of the image forming apparatus according to the embodiment of the present invention.
In the image forming apparatus main body 100, image forming units 2A, 2B, 2C, and 2D, which are process cartridges having the photoreceptor 1 as four image carriers, are detachably mounted on the image forming apparatus 100, respectively. ing. A transfer device in which the transfer belt 8 is mounted between a plurality of rollers so as to be rotatable in the direction of arrow A is disposed in the approximate center of the image forming apparatus 100.
The photosensitive member 1 provided in each of the image forming units 2A, 2B, 2C, and 2D is disposed so as to contact the lower surface of the transfer belt 8. In correspondence with the image forming units 2A, 2B, 2C, and 2D, developing devices 10A, 10B, 10C, and 10D having different toner colors are arranged.

The image forming units 2A, 2B, 2C, and 2D are units having the same configuration, the image forming unit 2A forms an image corresponding to magenta, and the image forming unit 2B forms an image corresponding to cyan. The image forming unit 2C forms an image corresponding to the yellow color, and the image forming unit 2D forms an image corresponding to the black color.
In each of the developing devices 10A, 10B, 10C, and 10D disposed in the image forming units 2A, 2B, 2C, and 2D, a two-component developer including toner and a carrier is used, and a developer replenishing device 200 described later is used. (See FIG. 5), toner is replenished in accordance with the output of a toner density sensor (not shown) provided in the developer container 14, and the carrier is also replenished to discharge the old developer and replace the developer. The development method that can be used is adopted.

Developer replenishing devices 200A, 200B, 200C, and 200D are disposed above the image forming units 2A, 2B, 2C, and 2D. The developer replenishing device 200 has a configuration for replenishing the developing device 10 with a new toner and a new carrier different from the toner to be supplied to the photosensitive drum 1, and the configuration is shown in FIG. Has been.
An exposure device 6 as a writing unit is disposed below the image forming units 2A, 2B, 2C, and 2D.

The exposure device 6 is arranged in four laser diode (LD) light sources prepared for each color, a set of polygon scanners composed of six polygon mirrors and a polygon motor, and the optical path of each light source. It is composed of a lens such as an fθ lens or a long cylindrical lens, or a mirror. Laser light emitted from the laser diode is deflected and scanned by a polygon scanner and irradiated onto the photosensitive member 5.
Between the transfer belt 8 and the developer supply device 200, there is provided a fixing device 9 for fixing the image on the transfer paper onto which the image has been transferred. A discharge path 51 is formed on the downstream side of the fixing device 9 in the conveyance direction of the transfer sheet, and the transfer sheet conveyed there can be discharged onto a discharge tray 53 by a discharge roller pair 52.
A paper feed cassette 7 that can store transfer paper is disposed below the image forming apparatus 100.

  Next, the operation of the image forming apparatus 100 in image formation will be described. When the image forming operation is started, each photoconductor 1 rotates in the clockwise direction in FIG. Then, the surface of each photoconductor 1 is uniformly charged by the charging roller 301 of the charging unit 3. Then, laser light corresponding to a magenta image by the exposure device 6 is applied to the photoreceptor 1a of the image forming unit 2A, and laser light corresponding to a cyan image is applied to the photoreceptor 1b of the image forming unit 2B. The 2C photoconductor 1c is irradiated with a laser beam corresponding to a yellow image, and the photoconductor 1d of the image forming unit 2D is irradiated with a laser beam corresponding to a black image, and a latent image corresponding to image data of each color. Are formed respectively. Each latent image reaches the position of the developing devices 10A, 10B, 10C, and 10D by the rotation of the photosensitive member 1, and is developed there by toners of magenta, cyan, yellow, and black. Become.

  On the other hand, the transfer paper is fed from the paper feed cassette 7 by the separation paper feed unit, and the toner image formed on each photoconductor 1 by the registration roller pair 55 provided immediately before the transfer belt 8. It is conveyed at the same timing. The transfer paper is charged to a positive polarity by a paper suction roller 54 disposed near the entrance of the transfer belt 8, and thereby electrostatically attracted to the surface of the transfer belt 8. The transfer paper is conveyed while being adsorbed to the transfer belt 8, and magenta, cyan, yellow, and black toner images are sequentially transferred to form a four-color superimposed full-color toner image. . The transfer paper is heated and pressed by the fixing device 9 to melt and fix the toner image, and then passes through a paper discharge system and is discharged onto a paper discharge tray 53 at the top of the image forming apparatus 1.

Next, the configuration around the developing device will be described. FIG. 4 is a schematic cross-sectional view showing the developing device provided in the image forming apparatus of the present invention and the surrounding structure. In FIG. 4, a developer replenishing device 200 (see FIG. 5) for replenishing a developer composed of new toner and carrier is provided in the developing device 10 above the developing device 10, and below the developing device 10. Is provided with a developer discharging device 300 for discharging the developer that has become excessive in the developing device 10.
The developing device 10 includes a housing 15 (see FIG. 5) having a developer accommodating portion 14 for accommodating a two-component developer composed of toner and a carrier, and a photoreceptor 1 as an image carrier on the opening side of the housing 15. The developer roll 12 as a developer carrying member disposed so as to rotate in a state close to the developer, and two transports as developer agitating and conveying members disposed so as to rotate within the developer container 14. The screws 11a and 11b and the layer thickness regulating member 13 disposed in pressure contact with or close to the surface of the developing roller 12 constitute the main part.

  Among these, the developing roller 12 is a cylindrical sleeve 121 that rotates and includes a magnet roll 120 fixed inside. Further, the developer accommodating portion 14 is divided into two by a central partition 14c, and is composed of accommodating spaces 14a and 14b that are communicated by communicating portions on both ends, and a conveying screw 11a that rotates in the accommodating spaces 14a and 14b. The developer is circulated and conveyed between the storage spaces 14a and 14b while being agitated by 11b. The layer thickness regulating member 13 has a double structure of a nonmagnetic member and a magnetic member, and is arranged so that the tip thereof faces a predetermined magnetic pole of the magnet roll 120.

The developer supply device 200 includes a developer container 230 that stores a two-component developer for supply, and a developer replenisher that sends the two-component developer in the developer container 230 to the developer storage unit 14 for supply. 220 (see FIG. 5). The developer replenisher 220 is provided between the developer container 230 and the developing device 10 so as to be connected to each other.
A detailed configuration of the developer supply device 200 will be described later with reference to FIG.

The developer discharging device 300 sends a recovery container 330 that recovers the two-component developer that has become excessive in the developer container 14 and the developer that overflows and overflows from the developer container 14 to the recovery container 330. It comprises a discharge pipe 331 as developer discharge means. The discharge pipe 331 is disposed such that the upper opening 331a is positioned at a predetermined height in the developer accommodating portion 14, and discharges the developer over the upper opening 331a at the predetermined height. It has become.
The developer discharge device of the present invention is not limited to the above-described configuration. For example, a developer discharge port is opened at a predetermined position of the housing 15 and a developer discharge port is provided instead of the discharge pipe 331. A conveyance member such as a discharge screw as a developer discharge unit may be installed in the vicinity, and the developer discharged from the developer discharge port may be transferred to the collection container 330.
Moreover, it is also possible to provide this discharge screw at the end or inside of the discharge pipe 331 of this embodiment.

Next, the developing operation of the developing device will be described with reference to FIG.
First, the developer in the developing device previously stored in the developer container 14 is stirred and sufficiently mixed by the conveying screws 11a and 11b and is frictionally charged, and then supplied to the developing roller 12. It adheres to the surface of the sleeve 121 in layers.
The layered developer adhering to the developing roller 12 is regulated to a predetermined thickness by the layer thickness regulating member 13 to be a uniform layer, and then the developing area that faces the photoreceptor 1 as the sleeve 121 rotates. It is conveyed to D. In this development area D, the toner of the two-component developer is electrostatically adsorbed to the latent image formed on the photoreceptor 1 in accordance with the image of the original on the image forming apparatus main body 100 (see FIG. 3). Development is performed, and a toner image is formed on the photoreceptor 1.
The toner image formed on the photoreceptor 1 is transferred onto the recording paper on the image forming apparatus main body 100 side, and is fixed on the recording paper by the fixing unit.

  By repeating this developing operation, the toner contained in the developer in the developing device in the developer accommodating portion 14 is consumed and gradually decreases. When this toner reduction is detected by the above-described toner density sensor. Then, the developer supply device 220 of the developer supply device 200 is driven. As a result, a replenishment developer containing a carrier and toner, which will be described in detail below, housed in the developer housing member 231 of the developer housing 230 is replenished. The new two-component developer replenished in the developer accommodating portion 14 is stirred by the conveying screws 11a and 11b in the developer accommodating portion 14 and sufficiently mixed with the developer in the developing device accommodated before replenishment. Is done.

  In the developer accommodating portion 14, the supply of the developer for replenishment from the developer replenishing device 200 causes the carrier and the toner to be replenished at a predetermined ratio, so that the amount of developer in the developer accommodating portion 14 gradually increases. It becomes. The two-component developer that becomes excessive in the developer accommodating portion 14 overflows beyond the regulated height of the accommodating portion 14 and is accommodated in the collection container 330 through the discharge pipe 331 of the developer discharging device 300.

The replenishment developer of the present invention is a material containing at least a toner and a carrier. As the toner for the replenishment developer stored in the developer container 230, the toner described later can be used, and the carrier has predetermined particles in the core material 26 as shown in FIG. A magnetic carrier on which the covering layer 27 is formed can be used.
Further, as the toner of the developer in the developing device, the same toner as that stored in the developer container 230 or a different toner can be used, and the carrier is also stored in the developer container 230. It can be used with the same carrier or different carriers.

  The weight ratio of the carrier in the developer accommodated in the developing device is desirably 85 wt% or more and less than 98 wt%. If the weight ratio of the carrier is less than 85 wt%, the toner ratio is too high, so that the toner cannot be sufficiently charged. In addition, toner scattering occurs, causing internal contamination. If the carrier weight ratio is 98 wt% or more, the carrier ratio is too high, so that the probability of collision between carriers in the developing device increases, which is disadvantageous for durability. Further, since the charge amount becomes too high, it is difficult to obtain an appropriate image density.

As shown in FIG. 5, the image forming apparatus 100 of the present embodiment fills a developer storage member 231 whose shape is easily deformed with suction, and sucks the supply developer with a screw pump 223. A developer replenishing device 200 that supplies the developing device 10 is provided.
Hereinafter, the configuration of the developer supply device 200 will be described in detail with reference to FIGS.
FIG. 5 is a schematic configuration diagram of a developer supply device 200 used in the present invention. Inside the developer container 230 provided in the developer supply device 200, a developer storage member 231 as a bag-shaped member capable of volume reduction is provided. A new replenishment developer to be replenished to the developer accommodating portion 14 of the developing device 10 is accommodated in the developer accommodating member 231. The developer accommodating member 231 is reduced in volume as the internal pressure decreases due to the developer being supplied to the developer accommodating portion 14.

The developer replenisher 220 includes a screw pump 223 that is connected to the upper end of a replenishing port 15 a provided at a predetermined location of the housing 15, a nozzle 240 that is connected to the screw pump 223, and a nozzle 240. And an air supply means 260 that is connected and is driven according to a detection signal from a toner concentration sensor (not shown) installed in the developer accommodating portion 14 to accommodate an appropriate amount of developer. The developer 230 is supplied from the container 230.
Between the screw pump 223 and the nozzle 240, there is a transport tube 221 as a developer transport passage communicating with the screw pump 223. The transport tube 221 is preferably made of a rubber material such as polyurethane, nitrile, and EPDM that is flexible and excellent in toner resistance.
The developer supply device 200 has a container holder 222 for supporting a developer container 230 as a developer container. The container holder 222 is made of a material having high rigidity such as resin. Yes.

The developer container 230 includes a developer storage member 231 as a bag-like member formed of a flexible sheet material, and a base portion 232 as a discharge port forming member that forms a developer discharge port.
There is no restriction | limiting in particular as a material of the developer accommodating member 231, A thing with good dimensional accuracy is used suitably. For example, a resin such as a polyester resin, a polyethylene resin, a polypropylene resin, a polystyrene resin, a polyvinyl chloride resin, a polyacrylic acid, a polycarbonate resin, an ABS resin, or a polyacetal resin is preferably exemplified.
Further, the base part 232 is provided with a sealing material 233 formed of sponge, rubber or the like, and the sealing material 233 is provided with a cross-shaped cut. Then, by passing the nozzle 240 of the developer replenisher 220 through this notch, the developer container 230 and the developer replenisher 220 are connected and fixed.

In the present embodiment, the base portion 232 is provided below the developer container 230. Here, the state where the base part 232 is provided below means that the base part 232 faces downward in the developer container 230 in a state where the developer container 230 is disposed in the developer supply device 200. It shows that it is provided at a position including a vertical component.
The position at which the base 232 is provided in the developer container body is not limited to this, and the developer container in a state where the developer container 230 is disposed in the developer supply device 200. 230 may be provided in the horizontal direction of the main body, or may be provided in an oblique direction.

The developer container is sequentially replaced with a new one as the toner is consumed. However, the developer container 230 according to this embodiment can be easily attached and detached by having the above-described configuration. In addition, it is possible to prevent toner leakage at the time of replacement or use.
The developer accommodating member 231 is not particularly limited in size, shape, structure, material, and the like, and can be appropriately selected according to the purpose.

As the shape of the developer accommodating member 231, for example, the above-described cylindrical shape can be preferably used, and it is preferable that spiral irregularities are formed on the inner peripheral surface thereof. By forming such irregularities, the toner stored in the storage member 231 can be smoothly transferred to the discharge port side by rotating the developer container 230. Furthermore, it is particularly preferable that a part or all of the spiral part has a bellows function.
The developer container 230 of the present invention can be easily attached to and detached from the developer replenishing device 200 of the image forming apparatus 100, is suitable for storage and conveyance, and has excellent handling properties.

  6A is an external view showing a schematic configuration of a nozzle 240 provided in the developer replenisher 220, FIG. 6B is an axial sectional view, and FIG. FIG. 6B is a cross-sectional view taken along line AA in FIG. As shown in FIG. 6B, the nozzle 240 has a double tube structure including an inner tube 241 and an outer tube 242 that accommodates the inner tube 241 therein. The inside of the inner tube 241 serves as a developer flow path 241a as a developer transport path for discharging the developer in the developer container 230. The toner in the developer container 230 is sucked by the suction force of the screw pump 223 and is drawn into the screw pump 223 through the developer flow path 241a.

  FIG. 7 is a cross-sectional view showing a schematic configuration of the screw pump 223. The screw pump 223 is called a uniaxial eccentric screw pump and includes a rotor 224 and a stator 225 therein. The rotor 224 has a shape in which a circular cross section is twisted in a spiral shape, is formed of a hard material, and is fitted inside the stator 225. On the other hand, the stator 225 is formed of a rubber-like flexible material, and has a hole whose elliptical cross section is spirally twisted, and the rotor 224 is fitted into this hole. Further, the helical pitch of the stator 225 is formed to be twice as long as the helical pitch of the rotor 224. The rotor 224 is connected to a drive motor 226 for rotating the rotor 224 via a universal joint 227 and a bearing 228.

In this configuration, the toner and carrier transported from the developer container 230 through the developer flow path 241 a of the nozzle 240 and the transport tube 221 enter the inside from the toner suction port 223 a of the screw pump 223. Then, it enters the space formed between the rotor 224 and the stator 225 and is sucked and conveyed in the right direction in FIG. 5 as the rotor 224 rotates. The toner that has passed through the space between the rotor 224 and the stator 225 falls downward from the toner dropping port 223 b and is supplied into the developing device 10 through the developer supply port 14 of the developing device 10.
Further, as shown in FIG. 5, the developer replenisher 220 used in this embodiment includes an air supply unit 260 (260 a and 260 b) that supplies air into the developer container 230.

As shown in FIG. 5, each air flow path 244a, 244b is connected to air pumps 260a, 260b as separate gas delivery devices via air supply paths 261a, 261b as gas supply paths, respectively.
As shown in FIG. 6B, the air flow path 244 is provided as an air supply passage between the inner tube 241 and the outer tube 242 of the nozzle 240 of the developer replenisher 220. As shown in FIG. 6C, the air flow path 44 includes two flow paths 244a and 244b that are independent of each other and have a semicircular cross section.

As the air pumps 260a and 260b, a normal diaphragm type air pump can be used. The air sent out from these air pumps 260a and 260b is supplied into the toner container 230 from air supply ports 246a and 246b as gas supply ports of the respective air channels through the air channels 244a and 244b, respectively. Each air supply port 246a, 246b is located below the toner outlet 247 as a developer outlet of the toner channel 241a in the figure. As a result, the air supplied from the air supply ports 246a and 246b is supplied to the toner in the vicinity of the toner outlet 247, and is left unused for a long period of time and the toner outlet 247 is clogged. Even in such a state, the toner blocking the toner outlet 247 can be destroyed.
The air supply passages 261a and 261b are provided with on-off valves 262a and 262b as closing means that are opened and closed by a control signal from a control unit as gas delivery control means (not shown). The on-off valves 262a and 262b operate to open the valve when the ON signal is received from the control unit and allow air to pass therethrough, and when the OFF signal is received from the control unit to close the valve and prevent the passage of air.

Next, the operation of the developer supply device 220 in this embodiment will be described with reference to FIG.
The control unit receives the signal indicating that the toner density is insufficient from the developing device 10 and starts the developer supply operation. In this developer replenishment operation, first, the air pumps 260a and 260b are driven to supply air into the developer container 230, and the drive motor 226 of the screw pump 223 is driven to suck and convey the developer. .
When air is sent out from the air pumps 260a and 260b, the air enters the air flow paths 244a and 244b of the nozzle 240 from the air supply paths 261a and 261b, and is supplied into the developer container 230 from the air supply ports 246a and 246b. The By this air, the developer in the developer container 230 is agitated and becomes a state in which a large amount of air is contained, and fluidization is promoted.

Further, when air is supplied into the developer container 230, the internal pressure in the developer container 230 increases. Therefore, a pressure difference is generated between the internal pressure and the external pressure (atmospheric pressure) of the developer container 230, and a force that moves in the direction in which the pressure is applied acts on the fluidized developer. As a result, the developer in the developer container 230 flows out from the direction in which pressure is applied, that is, from the developer outlet 247.
In the present embodiment, the suction force by the screw pump 223 also acts, and the developer in the developer container 230 flows out from the developer outlet 247.

  As described above, the developer that has flowed out of the developer container 230 moves from the developer outlet 247 through the developer channel 241 a of the nozzle 240 into the screw pump 223 via the transport tube 221. Then, after moving in the screw pump 223, it falls downward from the developer dropping port 223 b and the developer is supplied into the developing device 10 from the developer supply port 14. When a certain amount of developer supply is completed, the control unit stops driving the air pumps 260a and 260b and the drive motor 226, closes the on-off valves 262a and 262b, and ends the toner supply operation. Thus, by closing the on-off valves 262a and 262b at the end of the toner supply operation, the toner in the toner container 230 is prevented from flowing back to the air pumps 260a and 260b through the air supply passages 244a and 244b of the nozzle 240. doing.

  The supply amount of air supplied from the air pumps 260 a and 260 b is set to be smaller than the suction amount of toner and air by the screw pump 223. Therefore, as the toner is consumed, the internal pressure of the developer container 230 decreases. Here, since the developer accommodating member 231 of the developer accommodating unit 230 in this embodiment is formed of a flexible sheet material, the volume is reduced as the internal pressure decreases.

FIG. 8 is a perspective view of the developer containing member 231 filled with the developer.
FIG. 9 is a front view showing a state in which the developer inside the developer containing member 231 is discharged and reduced in volume (squeezed). Here, it is desirable that the developer containing member 231 has a volume reduced by 60% or more.
In the developer container 231 of the developer container 230 shown in FIG. 8, a replenishment developer composed of a carrier and toner for replenishing the developing device 10 is accommodated as described above.
The supply developer preferably has a carrier weight ratio of 3 wt% or more and less than 30 wt% in the supply developer.
If the weight ratio of the carrier in the developer for replenishment in the developer container 230 is less than 3 wt%, the amount of the carrier to be replenished is very small, so that the replenishment effect cannot be obtained sufficiently. On the other hand, if it exceeds 30 wt%, stable supply of the replenishment developer to the developer accommodating portion cannot be obtained.

The toner contained in the developer for replenishment and the developer in the developing device includes at least a binder resin and a colorant, and further includes a release agent, a charge control agent, and other agents as necessary. Comprising ingredients.
The method for producing the toner is not particularly limited to one, and can be appropriately selected according to the purpose. Examples thereof include a pulverization method, a suspension polymerization method, an emulsion polymerization method, and a polymer suspension method in which an oil phase is emulsified, suspended or aggregated in an aqueous medium to form toner base particles.

  The binder resin for the toner used in the present invention is not particularly limited, and can be appropriately selected from known ones according to the purpose. For example, styrene such as polystyrene, poly-p-styrene, polyvinyltoluene, and the like Substituted homopolymer, styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, Styrene-methacrylic acid copolymer unit, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer Polymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer Styrene copolymers such as styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isopropyl copolymer, styrene-maleic acid ester copolymer, polythyme methacrylate resin, polybutyl methacrylate resin , Polyvinyl chloride resin, polyvinyl acetate resin, polyethylene resin, polyester resin, polyurethane resin, epoxy resin, polyvinyl butyral resin, polyacrylic acid resin, rosin resin, modified rosin resin, terpene resin, phenol resin, aliphatic or aromatic Hydrocarbon resins and aromatic petroleum resins can be used alone or in combination.

The colorant is not particularly limited and may be appropriately selected from known dyes and pigments according to the purpose. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G , G), cadmium yellow, yellow iron oxide, ocher, yellow lead, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR, A, RN, R), pigment yellow L, benzidine yellow (G, GR ), Permanent Yellow (NCG), Vulcan Fast Yellow (5G, R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Lead Red, Lead Red, Cadmium Red, Cadmium Mummer Curry Red, Antimony Zhu, Permanent Red 4R, Parare , Phi Sae Red, Parachlor Ortho Nitroaniline Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Risor Rubin GX, Permanent Red F5R, Brilliant Carmine 6B, Pogment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Light, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thioindigo Red B, Thioindigo Maroon, Oil Quinacridone red, pyrazolone red, polyazo red, chrome vermilion, benzidine orange, perinone orange, oil orange, cobalt blue, cerulean blue, alkaline blue rake, peacock blue rake, Victoria blue rake, metal-free phthalocyanine blue, phthalocyanine blue , Fast Sky Blue, Indanthrene Blue (RS, BC), Indigo, Ultramarine Blue, Bitumen, Anthraquinone Blue, Fast Violet B, Methyl Violet Lake, Cobalt Purple, Manganese Purple, Dioxane Violet, Anthraquinone Violet, Chrome Green, Zinc Green, Chrome oxide, pyridian, emerald green, pigment green B, naphthol green B, green gold, acid Examples include lean lake, malachite green lake, phthalocyanine green, anthraquinone green, titanium oxide, zinc white, and lithobon.
These may be used individually by 1 type and may use 2 or more types together.
The content of the colorant in the toner is preferably 1 to 15% by weight, and more preferably 3 to 10% by weight.

  The colorant may be used as a master batch combined with a resin. The resin is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, styrene or a substituted polymer thereof, styrene copolymer, polymethyl methacrylate resin, polybutyl Methacrylate resin, polyvinyl chloride resin, polyvinyl acetate resin, polyethylene resin, polypropylene resin, polyester resin, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, fat Aromatic hydrocarbon resin, alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin and the like. These may be used individually by 1 type and may use 2 or more types together.

There is no restriction | limiting in particular as a mold release agent, According to the objective, it can select suitably from well-known things, For example, waxes etc. are mentioned suitably.
Examples of waxes include carbonyl group-containing waxes, polyolefin waxes, long chain hydrocarbons, and the like. These may be used individually by 1 type and may use 2 or more types together. Among these, a carbonyl group-containing wax is preferable.
Examples of the carbonyl group-containing wax include polyalkanoic acid esters, polyalkanol esters, polyalkanoic acid amides, polyalkylamides, dialkyl ketones, and the like. Examples of the polyalkanoic acid ester include carnauba wax, montan wax, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecane. Examples thereof include diol distearate. Examples of polyalkanol esters include tristearyl trimellitic acid and distearyl maleate. Examples of the polyalkanoic acid amide include dibehenyl amide. Examples of the polyalkylamide include trimellitic acid tristearylamide. Examples of the dialkyl ketone include distearyl ketone. Of these carbonyl group-containing waxes, polyalkanoic acid esters are particularly preferred.
Examples of the polyolefin wax include polyethylene wax and polypropylene wax.
Examples of the long chain hydrocarbon include paraffin wax and sazol wax.

There is no restriction | limiting in particular as melting | fusing point of a mold release agent, Although it can select suitably according to the objective, 40-160 degreeC is preferable, 50-120 degreeC is more preferable, 60-90 degreeC is especially preferable.
When the melting point is less than 40 ° C., the wax may adversely affect the heat resistant storage stability, and when it exceeds 160 ° C., a cold offset may easily occur during fixing at a low temperature.
The melt viscosity of the release agent is preferably 5 to 1,000 cps, more preferably 10 to 100 cps, as a measured value at a temperature 20 ° C. higher than the melting point of the wax. When the melt viscosity is less than 5 cps, the releasability may be lowered, and when it exceeds 1,000 cps, the effect of improving hot offset resistance and low-temperature fixability may not be obtained.

There is no restriction | limiting in particular as content in the said toner of a mold release agent, Although it can select suitably according to the objective, 1 to 40 weight% is preferable and 3 to 30 weight% is more preferable.
When the content exceeds 40% by weight, the fluidity of the toner may be deteriorated.

The charge control agent is not particularly limited, and a positive or negative charge control agent can be appropriately selected and used depending on whether the charge charged on the photoconductor is positive or negative.
As the negative charge control agent, for example, a resin or compound having an electron donating functional group, an azo dye, a metal complex of an organic acid, or the like can be used. Specifically, Bontron (product numbers: S-31, S-32, S-34, S-36, S-37, S-39, S-40, S-44, E-81, E-82, E -84, E-86, E-88, A, 1-A, 2-A, 3-A) (above, manufactured by Orient Chemical Industry Co., Ltd.), Kaya Charge (part numbers: N-1, N-2), Kaya Set black (product number: T-2, 004) (above, Nippon Kayaku Co., Ltd.)), Eisenspiron black (T-37, T-77, T-95, TRH, TNS-2) (above, Hodogaya Chemical Industry Co., Ltd.), FCA-1001-N, FCA-1001-NB, FCA-1001-NZ, and the like (manufactured by Fujikura Kasei Co., Ltd.).

As the positive charge control agent, for example, basic compounds such as nigrosine dyes, cationic compounds such as quaternary ammonium salts, metal salts of higher fatty acids, and the like can be used. Specifically, Bontron (part numbers: N-01, N-02, N-03, N-04, N-05, N-07, N-09, N-10, N-11, N-13, P -51, P-52, AFP-B) (above, manufactured by Orient Chemical Co., Ltd.), TP-302, TP-415, TP-4040 (above, manufactured by Hodogaya Chemical Co., Ltd.), Copy Blue PR, Copy Charge ( Product number: PX-VP-435, NX-VP-434) (manufactured by Hoechst), FCA (product number: 201, 201-B-1, 201-B-2, 201-B-3, 201-PB, 201-PZ, 301) (manufactured by Fujikura Kasei Co., Ltd.), PLZ (product numbers: 1001, 2001, 6001, 7001) (manufactured by Shikoku Kasei Kogyo Co., Ltd.), and the like.
These may be used individually by 1 type and may use 2 or more types together.

  The addition amount of the charge control agent is determined by the toner production method including the type of the binder resin and the dispersion method, and is not uniquely limited, but is not limited to 0.1 parts by weight with respect to 100 parts by weight of the binder resin. 1-10 weight part is preferable and 0.2-5 weight part is more preferable. When the added amount exceeds 10 parts by weight, the chargeability of the toner is too high, the effect of the charge control agent is reduced, the electrostatic attraction with the developing roller is increased, the developer fluidity is reduced, and the image density is increased. If the amount is less than 0.1 part by weight, the charge rising property and the charge amount are not sufficient, and the toner image may be easily affected.

  In addition to binder resin, release agent, colorant, and charge control agent, inorganic fine particles, fluidity improver, cleaning improver, magnetic material, metal soap, etc. are added to the toner material as necessary. can do.

  As the inorganic fine particles, for example, silica, titania, alumina, cerium oxide, strontium titanate, calcium carbonate, magnesium carbonate, calcium phosphate, etc. can be used, and silica fine particles hydrophobized with silicone oil, hexamethyldisilazane, etc. It is more preferable to use titanium oxide that has been subjected to a specific surface treatment.

Examples of the silica fine particles include, for example, Aerosil (product numbers: 130, 200 V, 200 CF, 300, 300 CF, 380, OX50, TT600, MOX80, MOX170, COK84, RX200, RY200, R972, R974, R976, R805, R811, R812, T805, R202, VT222, RX170, RXC, RA200, RA200H, RA200HS, RM50, RY200, REA200 (above, manufactured by Nippon Aerosil Co., Ltd.), HDK (part number: H20, H2000, H3004, H2000 / 4, H2050EP, H2015EP, H3050EP) , KHD50), HVK2150 (above, manufactured by Wacker Chemical Co., Ltd.), Cabozil (Part No .: L-90, LM-130, LM-150, M-5, PTG, MS-55, -5, HS-5, EH-5, LM-150D, M-7D, MS-75D, TS-720, TS-610, TS-530) (or, can be used Cabot Corp.).
The addition amount of the inorganic fine particles is preferably 0.1 to 5.0 parts by weight, more preferably 0.5 to 3.2 parts by weight with respect to 100 parts by weight of the toner base particles.

The method for producing the toner in the present invention is not particularly limited as described above, but examples of the method for producing the pulverization method include the following.
The toner materials are mixed, and the mixture is charged into a melt kneader and melt kneaded. As the melt kneader, for example, a uniaxial or biaxial continuous kneader or a batch kneader using a roll mill can be used. For example, KTK type twin screw extruder manufactured by Kobe Steel, TEM type extruder manufactured by Toshiba Machine Co., Ltd., twin screw extruder manufactured by Casey Kay, PCM type twin screw extruder manufactured by Ikegai Iron Works Co., Ltd. Preferably used. This melt-kneading is preferably performed under appropriate conditions so as not to cause the molecular chains of the binder resin to be broken. Specifically, the melt kneading temperature is performed with reference to the softening point of the binder resin. If the temperature is higher than the softening point, cutting is severe, and if the temperature is too low, dispersion may not proceed.

  In pulverization, the kneaded product obtained by the kneading is pulverized. In this pulverization, it is preferable that the kneaded material is first coarsely pulverized and then finely pulverized. At this time, a method of pulverizing by colliding with a collision plate in a jet stream, pulverizing particles by colliding with each other in a jet stream, or pulverizing with a narrow gap between a mechanically rotating rotor and a stator is preferably used.

In the classification, the pulverized product obtained by the pulverization is classified and adjusted to particles having a predetermined particle diameter. The classification can be performed, for example, by removing the fine particle portion by a cyclone, a decanter, centrifugation, or the like.
After the pulverization and classification are completed, the pulverized product is classified into an air stream by centrifugal force or the like to produce a toner having a predetermined particle size.

  Further, in order to improve the fluidity, storage stability, developability and transferability of the toner, inorganic fine particles such as hydrophobic silica fine powder may be further added to and mixed with the toner base particles produced as described above. For mixing the additives, a general powder mixer is used, but it is preferable to equip a jacket or the like to adjust the internal temperature. In order to change the load history applied to the additive, the additive may be added midway or gradually. In this case, you may change the rotation speed, rolling speed, time, temperature, etc. of a mixer. Alternatively, a strong load may be applied first, then a relatively weak load, or vice versa. Examples of the mixing equipment that can be used include a V-type mixer, a rocking mixer, a Ladige mixer, a Nauter mixer, and a Henschel mixer. Next, the toner can be obtained by passing through a sieve for the purpose of removing coarse particles and aggregated particles.

In this embodiment, the developer including the carrier and the toner described above is used as a replenishment developer and a developer for developing device in the image forming apparatus shown in FIG. Later, film removal on the carrier surface and generation of toner spent on the carrier surface are prevented, and a decrease in the charge amount of the developer in the developer container 14 and a decrease in the electrical resistance value of the carrier can be suppressed. Development characteristics can be obtained.
The carrier used in this embodiment is effective in preventing color stains and reducing resistance by using particles provided with a conductive coating layer made of tin dioxide and indium oxide as conductive particles. It is possible to achieve both control, and as a result, it is possible to adjust the resistance value without the need to contain carbon black that causes color smearing, and color image formation while maintaining stable chargeability Even when used in the apparatus, a high-quality color image with high color reproducibility and fineness can be provided without causing color stains on the image.
The configuration of the image forming apparatus used in the present invention is not limited to the above-described configuration described in the present embodiment, and other configurations may be used as long as they have similar functions. It is also possible to use an image forming apparatus having the same.

Hereinafter, the present invention will be described with reference to Examples , Reference Examples and Comparative Examples. In addition, this invention is not limited to the Example illustrated here. In the following, “parts” represents parts by weight, and “%” represents% by weight.
[Production of toner]
(Binder Resin Synthesis Example 1)
724 parts of bisphenol A ethylene oxide 2-mole adduct, 276 parts of isophthalic acid and 2 parts of dibutyltin oxide were placed in a reaction vessel equipped with a cooling pipe, a stirrer and a nitrogen introduction pipe, and reacted at 230 ° C. for 8 hours under normal pressure. The reaction was further carried out at a reduced pressure of 10 to 15 mmHg for 5 hours, followed by cooling to 160 ° C., 32 parts of phthalic anhydride was added thereto and reacted for 2 hours. Subsequently, it cooled to 80 degreeC and reacted with 188 parts of isophorone diisocyanate in ethyl acetate for 2 hours, and the isocyanate containing prepolymer (P1) was obtained.
Next, 267 parts of the prepolymer (P1) and 14 parts of isophoronediamine were reacted at 50 ° C. for 2 hours to obtain a urea-modified polyester (U1) having a weight average molecular weight of 64,000.
In the same manner as above, 724 parts of bisphenol A ethylene oxide 2-mole adduct and 276 parts of terephthalic acid were polycondensed at 230 ° C. for 8 hours under normal pressure, and then reacted for 5 hours at a reduced pressure of 10 to 15 mmHg. An unfinished polyester (E1) was obtained.
200 parts of urea-modified polyester (U1) and 800 parts of unmodified polyester (E1) are dissolved and mixed in 2000 parts of an ethyl acetate / MEK (1/1) mixed solvent, and the binder resin (B1) ethyl acetate / MEK is mixed. A solution was obtained.
A part was dried under reduced pressure, and the binder resin (B1) was isolated. Tg was 62 ° C.

(Polyester resin synthesis example A)
Terephthalic acid: 60 parts Dodecenyl succinic anhydride: 25 parts Trimellitic anhydride: 15 parts Bisphenol A (2,2) propylene oxide: 70 parts Bisphenol A (2, 2) ethylene oxide: 50 parts Place the flask in a 1 L four-necked round bottom flask equipped with a stirrer, condenser and nitrogen gas introduction tube, set the flask in a mantle heater, and introduce nitrogen gas from the nitrogen gas introduction tube. The temperature was raised while maintaining the active atmosphere, and 0.05 g of dibutyltin oxide was then added and reacted at a temperature of 200 ° C. to obtain polyester A. This polyester A had a peak molecular weight of 4200 and a glass transition point of 59.4 ° C.

(Master batch creation example 1)
Pigment: C.I. I. Pigment Yellow 155: 40 parts Binder resin: Polyester resin A: 60 parts Water: 30 parts The above raw materials were mixed in a Henschel mixer to obtain a mixture in which water was soaked into the pigment aggregate. This was kneaded for 45 minutes with two rolls set at a roll surface temperature of 130 ° C., and pulverized to a size of 1 mmφ with a pulverizer to obtain a master batch (M1).

(Toner Production Example A)
In a beaker, 240 parts of the binder resin (B1) in ethyl acetate / MEK solution, 20 parts of pentaerythritol tetrabehenate (melting point: 81 ° C., melt viscosity: 25 cps), and 8 parts of master batch (M1) were placed at 60 ° C. And a TK homomixer at 12000 rpm to uniformly dissolve and disperse the toner material solution.
In a beaker, 706 parts of ion-exchanged water, 294 parts of hydroxyapatite 10% suspension (Superite 10 manufactured by Nippon Chemical Industry Co., Ltd.) and 0.2 part of sodium dodecylbenzenesulfonate were uniformly dissolved.
Next, the temperature was raised to 60 ° C., and the toner material solution was added and stirred for 10 minutes while stirring at 12000 rpm with a TK homomixer.
The mixture was then transferred to a Kolben equipped with a stirrer and a thermometer, heated to 98 ° C. to remove the solvent, filtered, washed and dried, and then air classified to obtain toner particles.
Subsequently, 100 parts of the toner particles were mixed with 1.0 part of hydrophobic silica and 1.0 part of hydrophobic titanium oxide using a Henschel mixer to obtain “Toner A”.

An ultrathin section of this “toner A” was prepared, and a cross-sectional photograph (magnification × 100,000) of the toner was taken using a transmission electron microscope (H-9000H manufactured by Hitachi, Ltd.), and randomly selected from the photograph. The average value was determined from the dispersion diameter of 100 colorant portions. Here, the dispersion diameter of one particle is the average of the longest diameter and the shortest diameter, and the aggregate itself is one particle in the aggregated state.
The average dispersed particle diameter of the colorant was 0.40 μm. The colorant having a dispersed particle diameter of 0.7 μm or more was 4.5%.
Next, the particle size of “Toner A” was measured with a particle size measuring device “Coulter Counter TA2” manufactured by Coulter Electronics Co., Ltd., with an aperture diameter of 100 μm. As a result, volume average particle size (Dv) = 6.2 μm, number average particle size The diameter (Dn) was 5.1 μm.
Subsequently, the circularity of “toner A” was measured as an average circularity by a flow type particle image analyzer FPIA-1000 (manufactured by Toa Medical Electronics Co., Ltd.). In the measurement, 0.1 to 0.5 ml of a surfactant (alkylbenzene sulfonate) as a dispersant is added to 100 to 150 ml of water from which impure solids have been removed in advance, and a measurement sample is further added to 0.1 to 0.5 ml. About 0.5 g was added, the dispersion treatment was performed for about 1 to 3 minutes with an ultrasonic disperser, and the measurement liquid adjusted to a dispersion concentration of 3000 to 10,000 / μl was set. The resulting “Toner A” had a circularity of 0.96.

(Example of carrier production)
(Production Example 1)
-Acrylic resin solution (solid content concentration: 50 wt%) 2130 parts by weight-Aminosilane (solid content concentration: 100 wt%) 4 parts by weight-Silica fine particles (volume average particle size 0.07 μm) 1500 parts by weight-Toluene 6000 parts by weight Each of the above materials was dispersed with a homomixer for 10 minutes to prepare a resin layer forming solution. Using the core material a shown in Table 1 as the carrier core material, the resin solution is 30 g / min in an atmosphere of 55 ° C. in an atmosphere of 55 ° C. using a Spira coater (manufactured by Okada Seiko Co., Ltd.) so that the thickness h is 0.15 μm on the surface of the core material. It was applied in proportion and dried. The layer thickness was adjusted depending on the liquid amount. The obtained carrier was baked by standing 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 Carrier I. The average thickness T was 0.20 μm.

The volume average particle diameter of the core material was measured using a Microtrac Particle Size Analyzer (Nikkiso Co., Ltd.) SRA type with a range setting of 0.7 μm or more and 125 μm or less.
The average thickness h (μm) of the resin portion in the coating layer is obtained by observing the cross section of the carrier using a transmission electron microscope (TEM), and the thickness ha of the resin portion existing between the core material surface and the particles, The thickness hb of the resin part existing between the particles and the thickness hc of the resin part on the core material and the particle are measured at 50 points along the carrier surface at intervals of 0.2 μm, and the obtained measurement values are averaged. Asked.
The thickness T (μm) from the core material surface to the coating layer surface is observed with a transmission electron microscope (TEM), and the thickness T from the core material surface to the coating layer surface is determined by observing the carrier cross section. Were measured at intervals of 0.2 μm, and the obtained measured values were averaged.

(Production Example 2)
A carrier II shown in Table 2 was obtained in the same manner as in Production Example 1 except that the core material b shown in Table 1 was used as the carrier core material. The average thickness T was 0.20 μm.
(Production Example 3)
-Acrylic resin solution (solid content concentration: 50 wt%) 1500 parts by weight-Silicone resin solution (solid content 20 wt%) 1575 parts by weight-Aminosilane (solid content concentration: 100 wt%) 4 parts by weight-Silica fine particles (volume average) (Particle size 0.07 μm) 1500 parts by weight Toluene 6000 parts by weight Carrier III was obtained in the same manner as in Production Example 1 except that the material of the resin layer forming liquid was changed to the above. The average thickness T was 0.20 μm.

(Production Example 4)
・ Acrylic resin solution (solid content concentration: 50 wt%) 1500 parts by weight ・ Guanamine solution (solid content 70 wt%) 450 parts by weight ・ Aminosilane (solid content concentration: 100 wt%) 4 parts by weight ・ Silica fine particles (volume average particle) Diameter 0.07 μm) 1500 parts by weight Toluene 6000 parts by weight Carrier IV was obtained in the same manner as in Production Example 1 except that the material of the resin layer forming liquid was changed to the above. The average thickness T was 0.20 μm.
(Production Example 5)
A carrier V shown in Table 2 was obtained in the same manner as in Production Example 4 except that the core material c shown in Table 1 was used as the carrier core material. The average thickness T was 0.20 μm.

(Production Example 6)
A carrier VI shown in Table 2 was obtained in the same manner as in Production Example 4 except that the core material d shown in Table 1 was used as the carrier core material. The average thickness T was 0.20 μm.
(Production Example 7)
A carrier VIII in Table 2 was obtained in exactly the same manner as in Production Example 4 except that the core material e in Table 1 was used as the carrier core material. The average thickness T was 0.20 μm.
(Production Example 8)
A carrier VIII in Table 2 was obtained in exactly the same manner as in Production Example 4 except that the core material f in Table 1 was used as the carrier core material. The average thickness T was 0.20 μm.
(Production Example 9)
A carrier IX shown in Table 2 was obtained in the same manner as in Production Example 4 except that the core g shown in Table 1 was used as the carrier core material. The average thickness T was 0.20 μm.

(Production Example 10)
A carrier X shown in Table 2 was obtained in the same manner as in Production Example 4 except that the core material h shown in Table 1 was used as the carrier core material. The average thickness T was 0.20 μm.
(Production Example 11)
A carrier XI shown in Table 2 was obtained in the same manner as in Production Example 4 except that the core material i shown in Table 1 was used as the carrier core material. The average thickness T was 0.20 μm.
(Production Example 12)
A carrier XII shown in Table 2 was obtained in the same manner as in Production Example 4 except that the core material j shown in Table 1 was used as the carrier core material. The average thickness T was 0.20 μm.
(Production Example 13)
A carrier XIII shown in Table 2 was obtained in the same manner as in Production Example 4 except that the core material k shown in Table 1 was used as the carrier core material. The average thickness T was 0.20 μm.

(Production Example 14)
A carrier XIV shown in Table 2 was obtained in the same manner as in Production Example 4 except that the core material 1 shown in Table 1 was used as the carrier core material. The average thickness T was 0.20 μm.
(Production Example 15)
A carrier XV shown in Table 2 was obtained in the same manner as in Production Example 4 except that the core material m shown in Table 1 was used as the carrier core material. The average thickness T was 0.20 μm.
(Production Example 16)
Acrylic resin solution (solid content concentration: 50% by weight) 2130 parts by weight Aminosilane (solid content concentration: 100% by weight) 4 parts by weight Silica fine particles (volume average particle size 0.35 μm) 1500 parts by weight Carrier XVI was obtained in the same manner as in Production Example 15 except that the material of the resin layer forming liquid was changed to the above. The average thickness T was 0.40 μm.

(Production Example 17)
Acrylic resin solution (solid content concentration: 50% by weight) 2130 parts by weight Aminosilane (solid content concentration: 100% by weight) 4 parts by weight Alumina fine particles (volume average particle size 0.37 μm) 1500 parts by weight Toluene 6000 parts by weight Carrier XVII was obtained in the same manner as in Production Example 15 except that the material of the resin layer forming liquid was changed to the above. The average thickness T was 0.41 μm.
(Production Example 18)
Acrylic resin solution (solid content concentration: 50% by weight) 2130 parts by weight Aminosilane (solid content concentration: 100% by weight) 4 parts by weight Alumina fine particles (volume average particle size 0.37 μm) 1500 parts by weight Zinc oxide particles ( Volume average particle size 0.020 μm) 500 parts by weight Toluene 6000 parts by weight Carrier XVIII was obtained in the same manner as in Production Example 15 except that the material of the resin layer forming liquid was changed to the above. The average thickness T was 0.41 μm.

(Production Example 19)
Acrylic resin solution (solid content concentration: 50% by weight) 2130 parts by weight Aminosilane (solid content concentration: 100% by weight) 4 parts by weight Alumina fine particles (volume average particle size 0.37 μm) 1500 parts by weight Titanium oxide particles ( Volume average particle size 0.015 μm) 500 parts by weight Toluene 6000 parts by weight Carrier XIX was obtained in the same manner as in Production Example 15 except that the material of the resin layer forming liquid was changed to the above. The average thickness T was 0.41 μm.
(Production Example 20)
Carrier XX was obtained in the same manner as in Production Example 15 except that the coating amount of the resin solution was changed so that the thickness h was 0.05 μm. The average thickness T was 0.09 μm.

(Production Example 21)
Carrier XXI was obtained in the same manner as in Production Example 19 except that the coating amount of the resin solution was changed so that the thickness h was 2.40 μm. The average thickness T was 3.03 μm.
( Reference Example 1)
Using 7 parts by weight of toner A obtained in the toner production example and 93 parts by weight of carrier I obtained in carrier production example 1, the mixture was stirred for 10 minutes with a mixer to prepare a developer to be accommodated in the developing machine. Further, 80 parts by weight of the toner A obtained in the toner production example and 20 parts by weight of the carrier I obtained in the carrier production example 1 were stirred for 10 minutes with a mixer to prepare a replenishment developer.
(Image definition)
A developer in which a developing device shown in FIG. 4 is mounted on a commercially available digital full color printer (manufactured by Ricoh Co., Ltd., imagio Neo C600) is set with a developer in the developing machine and a developer for replenishment. The size of one character was about 2 mm × 2 mm), and the fineness of the image was evaluated from the character reproducibility. The ranking of evaluation was performed as follows.
◎: Very good, ○: Good, △: Acceptable, ×: Unusable level for practical use

(durability)
100k images were output for the above-mentioned image definition evaluation and used as a running test for durability evaluation. Durability was evaluated by the amount of decrease in chargeability of the carrier and the amount of change in resistance before and after the running test.
The amount of decrease in chargeability of the carrier was measured by the following method.
First, a sample that was mixed and frictionally charged at a ratio of 7% by weight of toner to 93% by weight of the initial carrier was measured by a general blow-off method (Toshiba Chemical Co., Ltd., TB-200). The initial charge amount. Next, the toner is removed from the developer after running by the blow-off device, and the toner is newly mixed at a ratio of 7% by weight with respect to 93% by weight of the obtained carrier, and is triboelectrically charged in the same manner as the initial carrier. The sample is measured for the charge amount in the same manner as the initial carrier, and the difference from the initial charge amount is defined as the charge capacity reduction amount. The target value of the charging capacity reduction amount is within 10.0 μC / g. The main cause of the decrease in charging ability is considered to be the toner spent on the carrier surface, and the reduction in charging ability can be suppressed by reducing the toner spent.

The amount of change in the carrier resistance value was measured by the following method.
The carrier was put between the electrodes of the resistance measurement parallel electrode (gap 2 mm), DC 1,000 V was applied, and the resistance value after 30 sec was measured with a high resist meter. A value obtained by converting the obtained value into a volume resistivity is defined as an initial resistance value. Next, the toner in the developer after running is removed by the blow-off device, and resistance measurement is performed on the obtained carrier by the same method as the resistance measurement method, and the obtained value is converted into volume resistivity. The difference from the initial resistance value is defined as the carrier resistance value change amount. The target value of the carrier resistance value variation is within 3.0 [Log (Ω · cm)] in absolute value. The cause of the resistance change is scraping of the carrier coating layer, spent toner component, large particle detachment in the carrier coating layer, and the like, and by reducing these, the change in carrier resistance can be suppressed.

(Charge stability against toner density change)
A sample obtained by mixing 10% by weight of toner with respect to 90% by weight of the initial carrier and frictionally charging the sample was measured for the charge amount in the same manner as the initial charge amount measurement in the durability test. The difference from the initial charge amount (change in charge amount) was used as an index of charge stability against changes in toner density. The target value of the change in charge amount is within 4.0 [μC / g] in absolute value.
(Skin carrier adhesion)
The developer in the developing machine and the developer for replenishment are set in a remodeled machine equipped with a developing device shown in FIG. 4 in a commercially available digital full color printer (manufactured by Ricoh Co., Ltd., imagio Neo C600), and the background potential is fixed at 150V. An A3 character chart with an image area of 1% (the size of one character is about 2 mm × 2 mm) was output, and the evaluation was performed based on the number of carrier deposits on the background portion. The ranking of evaluation was performed as follows.
◎: 0, ○: 2 or more and 5 or less, △: 6 or more and 10 or less, ×: 11 or more

(Comparative Example 1)
The evaluation device is not modified (the development device shown in FIG. 4 is not installed), and the system is changed to a system that replenishes only the toner without supplying / recovering the developer without using the developer Neo C600. Except that, the evaluation was performed in the same manner as in Reference Example 1.
(Comparative Examples 2 to 6, Reference Examples 2 to 11 and 15, and Examples 12 to 14 and 16 )
Evaluation was performed in the same manner as in Reference Example 1 except that the carriers used for the developer in the developing machine and the replenishment developer were used in the combinations shown in Table 2 using the carriers prepared in Production Examples 2 to 21.

(Example 17)
Evaluation was performed in the same manner as in Reference Example 1 except that a replenishment developer was prepared using 98 parts by weight of toner A obtained in the toner production example and 2 parts by weight of carrier XIX obtained in carrier production example 19. It was.
(Example 18)
Evaluation was performed in the same manner as in Reference Example 1, except that 69 parts by weight of toner A obtained in the toner production example and 31 parts by weight of carrier XIX obtained in carrier production example 19 were used to prepare a replenishment developer. It was.
(Example 19)
Evaluation was performed in the same manner as in Reference Example 1 except that the developer in toner was prepared using 16 parts by weight of toner A obtained in the toner production example and 84 parts by weight of carrier XIX obtained in carrier production example 19. It was.
(Example 20)
Evaluation was performed in the same manner as in Reference Example 1 except that the developer in the developing machine was prepared using 1 part by weight of toner A obtained in the toner production example and 99 parts by weight of carrier XIX obtained in carrier production example 19. It was.

Table 1 shows carrier core materials used in the production examples, Table 2 shows carriers prepared in the production examples, combinations of the above Reference Examples 1 to 11 and 15, Examples 12 to 14 and 16 to 20, and Comparative Examples 1 to 6 Table 3 shows the evaluation results.

FIG. 1 is an explanatory view showing a coating layer of an electrophotographic carrier of the present invention. FIG. 2 is a perspective view of a resistance measurement cell used for measuring the resistivity of the carrier. FIG. 3 is a schematic diagram showing the configuration of the image forming apparatus according to the present invention. FIG. 4 is a diagram showing a schematic configuration showing the structure around the developing unit of the developing device according to the embodiment of the present invention. FIG. 5 is a schematic configuration diagram of a developer replenishing unit used in the present invention. 6A is an external view showing a schematic configuration of a nozzle provided in the developer replenishing device, FIG. 6B is an axial sectional view thereof, and FIG. 6C is a reference numeral in FIG. It is sectional drawing of AA. FIG. 7 is a sectional view showing a schematic configuration of the screw pump. FIG. 8 is a perspective view of a state in which the developer is filled in the developer accommodating member. FIG. 9 is a front view showing a state in which the developer inside the developer containing member is discharged and reduced in volume.

Explanation of symbols

21 Cell 22a Electrode 22b Electrode 23 Carrier 100 Apparatus Main Body 1 Photoconductor 2A, 2B, 2C, 2D Image Forming Unit 3 Charging Unit 301 Charging Roller 6 Exposure Device 7 Paper Feed Cassette 8 Transfer Belt 9 Fixing Device 10A, 10B, 10C, 10D Developing device 10a Partition member 10b Toner concentration sensor 11a, 11b Conveying screw 12 Developing roller 13 Layer thickness regulating member 14 Developer accommodating portion 15 Housing 15a Supply port

200A, 200B, 200C, 200D Developer supply device 220 Developer supply device 221 Conveying tube 222 Container holder 223 Screw pump 224 Rotor 225 Stator 226 Drive motor 227 Universal joint

230 Developer container 231 Developer container 232 Base part 233 Sealing material 240 Nozzle 241 Inner tube 241a Developer channel 242 Outer tube 244 Air channel 246a, 46b Air supply port 247 Developer outlet

260 Air supply means 260a, 260b Air pump 261a, 261b Air supply path 262a, 262b On-off valve 300 Developer discharge device 330 Collection container 331 Discharge pipe

51 Paper discharge path 52 Paper discharge roller pair 53 Paper discharge tray 54 Paper adsorption roller 55 Registration roller pair 26 Core material 27 Cover layer ha, hb, hc Cover layer thickness T Average thickness from core material surface to cover layer surface G1 1st 1 particle G2 2nd particle

Claims (14)

A carrier for an electrophotographic developer comprising a core material particle and a coating layer covering the particle, the toner and carrier being replenished to the developing device with respect to the developing device containing the toner and the carrier, Weight average particle diameter of a carrier used in an image forming apparatus that performs development while discharging the excess developer in the developing apparatus, and / or a carrier accommodated in the developing apparatus. Dw is 22 μm or more and 32 μm or less, the ratio Dw / Dp of the number average particle diameter Dp to the weight average particle diameter Dw is 1.00 ≦ Dw / Dp ≦ 1.20, and the particle diameter x [μm] is 0 <x <20 range 7 wt% content of the particles is less, Ri particle size y [[mu] m] is 0 <y <36 der content of less 100% by weight to 90% by weight of the particles is in the range of,
The coating layer covering the core particles of the carrier contains a binder resin and at least one kind of hard particles, and the particle diameter D1 (μm) of the hard particles and the average thickness h (μm) of the resin portion in the coating layer Satisfies the relationship 1 <(D1 / h) <10,
The coating layer covering the core particles of the carrier includes second hard particles in addition to the hard particles, and the particle diameter D1 of the hard particles and the particle diameter D2 of the second hard particles satisfy a relationship of D2 <D1. In addition, the particle diameter D2 (μm) of the second hard particles and the average thickness h (μm) of the resin portion in the coating layer satisfy a relationship of 0.001 <(D2 / h) <1. Carrier for electrophotographic developer. The carrier for an electrophotographic developer according to claim 1, wherein the hard particles are alumina particles or particles based on alumina. The carrier for an electrophotographic developer according to claim 1, wherein the second hard particles are titanium oxide particles or surface-treated titanium oxide particles. 4. The average thickness T (μm) from the surface of the core material particle to the surface of the coating layer covering the core material particle is in the range of 0.1 ≦ T ≦ 3.0. The carrier for an electrophotographic developer according to any one of the above. 5. The electrophotographic developer according to claim 1, wherein the binder resin contains at least either a reaction product of an acrylic resin and an amino resin or a silicone resin.
Career. 6. The carrier for an electrophotographic developer according to claim 1, wherein magnetization when a magnetic field of 1000 oersted is applied to the carrier is 50 emu / g or more and 100 emu / g or less. The carrier for an electrophotographic developer according to claim 1, wherein the core material particles are Mn—Mg—Sr ferrite, Mn ferrite, or magnetite. An electrophotographic developer comprising the carrier for an electrophotographic developer according to any one of claims 1 to 7 and a toner . The electrophotographic developer as a replenishing developer filled in the developer accommodating portion, wherein the weight ratio of the carrier in the electrophotographic developer is 3 wt% or more and less than 30 wt%. The electrophotographic developer according to 8. The electrostatic latent image formed on the image carrier is supplied to the developing device with respect to the developing device in which the toner and the carrier are accommodated. An image forming method in which development is performed while discharging the agent to form a visible image, wherein the carrier for electrophotographic developer according to any one of claims 1 to 7 is used as the carrier. Method. The toner and carrier are stored in the developing device by supplying toner and carrier to the developing device and discharging the excess developer in the developing device. The image forming method according to claim 10, wherein the weight ratio of the carrier in the developer is 85 wt% or more and less than 98 wt%. An image carrier on which an electrostatic latent image is formed, a developing device that converts the electrostatic latent image into a visible image using a developer containing toner and carrier, and a developer supply device that supplies toner and carrier to the developing device And a developer discharging device that discharges the excess developer in the developing device, and the carrier for an electrophotographic developer according to any one of claims 1 to 7 is used as the carrier. An image forming apparatus. 13. The image forming apparatus according to claim 12, wherein the developer replenishing device for replenishing toner and carrier includes a storage container in which a shape for storing the replenishment developer is easily deformed, and a replenishment developer in the storage container. An image forming apparatus having a suction pump that sucks and supplies the toner to a developing device. An image carrier and a developing device that at least forms an electrostatic latent image formed on the image carrier into a visible image using a developer including toner and a carrier are integrally supported and detachable from the image forming apparatus main body. A process cartridge provided on the image forming apparatus main body side, comprising: means for replenishing toner and carrier to the developing device; and developer discharging means for discharging the excess developer in the developing device; A process cartridge using the carrier for an electrophotographic developer according to any one of claims 1 to 7 as the carrier.