JP5169408B2 - Image forming method, image forming apparatus, and process cartridge - Google Patents

Description

  The present invention relates to an electrophotographic image forming method, an image forming apparatus for implementing the image forming method, and a process cartridge.

  In an electrophotographic image forming apparatus such as a copying machine or a printer, the surface of an image carrier such as a uniformly charged photoconductor is exposed to form an electrostatic latent image, the electrostatic latent image is developed, and toner is developed. After forming the image, the toner image is transferred to a transfer material such as recording paper. The transfer material carrying the toner image passes through the fixing device, and the toner particles are fixed on the transfer material by heat or pressure to form an image.

  In the image forming apparatus, the developing device that develops the electrostatic latent image on the image carrier includes a one-component developing type that develops using toner particles containing a magnetic material, and toner particles and carrier particles. There is a two-component development type in which development is performed using a developer. 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 particles and the carrier particles are agitated in the developing apparatus, and the toner particles are given a charge from the carrier particles by friction. The toner particles are electrostatically attached to the outer surface of the carrier particles, and the carrier particles carrying the toner particles are conveyed to the development area. Under the condition that the developing bias is applied, the toner particles are separated from the carrier particles, and electrostatically adhere to the latent image portion of the image carrier to form a toner image. In the two-component development system, in order to provide an image that is highly durable and satisfies high stability, it is important that a stable charge amount is imparted from the carrier particles to the toner particles during stirring. For that purpose, it is important that the charge imparting ability of the carrier particles is stable even before and after long-time use.

  However, in the developing device in the normal two-component development system, the toner particles are consumed by the developing operation, while the carrier particles are not consumed but remain in the developing tank. For this reason, the carrier particles stirred together with the toner particles in the developing tank deteriorate as the stirring frequency increases. Specifically, a situation such as peeling of the resin coat on the surface of the carrier particles and adhesion of toner particles to the surface of the carrier particles occurs, and as a result, the resistance value of the carrier particles and the chargeability of the developer are gradually reduced. The developability of the developer is excessively increased, and problems such as an increase in image density and occurrence of fogging are induced.

  As a solution to the above problem, for example, in Patent Document 1, carrier particles are added together with toner particles consumed by development, and the carrier particles in the developing device are replaced little by little to suppress a change in charge amount. A developing device that stabilizes image density, that is, a so-called trickle developing type developing device is disclosed. However, even in the developing device disclosed in Patent Document 1, the proportion of deteriorated carrier particles 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. Met.

  Patent Document 2 discloses a developer containing carrier particles having a higher resistance value together with toner particles, as a developer to be replenished appropriately in the developing device, as compared with carrier particles previously stored in the developing device. It has been disclosed that, by using it, maintaining chargeability and suppressing deterioration in image quality.

  Furthermore, Patent Document 3 uses a developer containing carrier particles that impart a higher charge amount to toner particles together with the toner particles as a replenishment developer, thereby maintaining chargeability and suppressing deterioration in image quality. Is disclosed. However, since the amount of carrier particles 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 of the developer in the developing device or There was a problem in that the amount of charge was changed and the image density was likely to fluctuate.

  Further, in Patent Document 4, there is a method of replenishing each developer sequentially using a plurality of types of replenishment developer containing carrier particles having different physical properties from the carrier particles housed in the developing device in advance together with toner particles. It is disclosed. However, in practice, the specific gravity of the carrier particles and the toner particles is extremely different. Therefore, as disclosed in Patent Document 4, one of a plurality of carrier particles having different physical properties is contained in one toner particle supply container. In addition, it is very difficult to sequentially replenish the replenishment developer contained together with the toner particles into the developing device so as not to mix with each other, and the amount of toner with respect to the carrier particles in the developer is large. Particle deterioration tends to occur, and a stable image cannot be obtained over a long period of time.

  Further, as described in Patent Document 4, in order to increase the resistance value of the carrier particles for replenishment, the resistance value increases when the coating amount of the silicon coat layer coated on the carrier particle core material is simply increased. On the other hand, there is a problem that the charge amount of the carrier particles is lowered, and as a result, the image reproducibility of the developed image is lowered and the background portion is stained.

  For this reason, even in the trickle development method, in order to obtain more stable development characteristics, it is important that the carrier particles can maintain stable physical properties during long-term use.

  In addition, carrier particles used in the two-component development system prevent toner spent on the carrier particle surface, form a uniform surface of carrier particles, prevent surface oxidation, prevent moisture sensitivity deterioration, extend the life of the developer, For the purpose of protecting the body from scratches or wear by carrier particles, controlling the charge polarity or adjusting the charge amount, etc., studies have been made to increase durability by coating with an appropriate resin material. . For example, those coated with a specific resin material (Patent Document 5), those in which various additives are added to the coating layer (Patent Documents 6 to 12), and those in which additives are attached to the surface of carrier particles (Patent document 13) etc. which use is disclosed. Patent Document 14 discloses that a carrier particle coating material is formed of a guanamine resin and a thermosetting resin that can be crosslinked with the guanamine resin, and Patent Document 15 discloses a crosslinked product of a melamine resin and an acrylic resin as carrier particles. It is disclosed to be used as a coating material.

  Furthermore, in order to further increase durability, Patent Document 16 discloses a resin layer containing a resin component obtained by crosslinking a thermoplastic resin and a guanamine resin and a charge control agent. As a result, a resin layer having an elasticity sufficient to absorb a strong impact on the coating resin due to friction with toner particles generated during agitation to frictionally charge the developer or friction between carrier particles is obtained. The toner spent on the carrier particles can be suppressed to some extent.

  However, there is still a high demand for further life extension in the market. However, in order to achieve a longer life than the current state, it is already difficult to improve the carrier particles alone.

  In a developer used in the two-component development method, a resistance adjusting agent is included in the binder resin layer of carrier particles in order to obtain stable charging characteristics. Currently, carbon black is often used as the resistance adjuster. However, in the image forming apparatus for forming a color image, when carrier particles containing carbon black are used, carbon black, or carbon black from the binder resin layer on the surface of the carrier particles due to friction or collision between carrier particles or toner particles, A resin piece containing carbon black may be detached, and carbon black may be transferred into a color image, resulting in color stains.

  Various methods have been proposed so far to suppress such a phenomenon. For example, Patent Document 17 proposes carrier particles in which a conductive material (carbon black) is present on the surface of the core material and no conductive material is present in the coating layer. Patent Document 18 discloses that the coating layer has a carbon black concentration gradient in the thickness direction, and the coating layer has a lower carbon black concentration toward the surface, and carbon black is present on the surface of the coating layer. Non-existent carrier particles have been proposed. Patent Document 19 discloses a two-layer coated carrier in which an inner coating layer containing conductive carbon is provided on the surface of core material particles, and a surface coating layer containing a white conductive material is further provided thereon. Particles have been proposed.

  However, in recent years, in response to requests from consumers, the above-described electrophotographic image forming apparatus has a remarkable tendency to increase the speed, and accordingly, the stress received by the developer has increased dramatically. For this reason, even in the proposals of Patent Documents 17 to 19, it is difficult to completely prevent color contamination caused by the transfer of carbon black into an image.

  Patent Documents 20 to 22 show carrier particles in which a conductive filler is contained in a carrier particle coating layer. In these carrier particles, since it is possible to use conductive fillers as conductive fine particles without being limited to carbon, coloring is performed in order to reduce the influence of colored substances detached from carrier particles on toner particles. It is possible to select a material with a small amount. However, these proposals are aimed at improving the image quality due to the electrical stability of the conductive filler, and there is no mention of the color of the conductive filler. As incomplete.

  Accordingly, there is a need for a resistance adjusting agent that is less desorbed from the surface of the carrier particles and that does not cause color stains even if it is desorbed, and that exhibits electrical conductivity efficiently. There is a need for an electrophotographic image forming method using carrier particles using an agent.

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 JP 54-1555048 A JP 57-40267 A JP 58-108549 A JP 59-166968 A Japanese Patent Publication No. 1-19584 Japanese Examined Patent Publication No. 3-628 JP-A-6-202381 JP-A-5-273789 JP-A-8-6307 Japanese Patent No. 2683624 JP 2001-117287 A Japanese Unexamined Patent Publication No. 7-140723 JP-A-8-179570 JP-A-8-286429 JP-A-4-360156 JP-A-5-303238 JP-A-11-174740

  The present invention has been made in view of the above prior art. That is, in the image forming method of the two-component development system, the physical properties of the carrier particles in the developing device are kept stable, and the electric resistance of the carrier particles is reduced while suppressing the occurrence of carrier particle adhesion in the solid image portion during long-term use. An electrophotographic image forming method that can be adjusted in a downward direction and does not risk the occurrence of color stains on a color image even if the resistance adjusting agent is detached from the surface of the carrier particle, and image formation for carrying out this image forming method It is an object to provide an apparatus and a process cartridge.

  In particular, in the trickle developing method, the replenishing toner particles and the carrier particles may be stored for a long time in contact with each other, and the risk that the color of the conductive material on the surface of the carrier particles is transferred to the toner particles becomes high. Therefore, carrier particles that do not cause color stains are strongly desired.

  The present invention has been made in consideration of the above circumstances, and provides an electrophotographic image forming method capable of improving the above problems, and an image forming apparatus and a process cartridge for carrying out this image forming method. With the goal.

  The present invention for solving the above problems includes the following technical features (1) to (12).
(1): Photosensitive toner particles from a developing device containing a developer obtained by mixing carrier particles composed of magnetic core material particles and a resin coating layer covering the surface of the core material particles with toner particles. In an image forming method for supplying an electrostatic latent image formed on a body surface and developing the electrostatic latent image, the resin coating layer includes white conductive fine particles, at least one hard particle, Second hard particles other than the hard particles, and the conductive fine particles are formed by laminating at least a lower layer containing tin dioxide and an upper layer containing tin dioxide and indium oxide on the surface of the particles serving as the base material. , Needle-like or rod-like fine particles having an aspect ratio of 3 to 200, and the particle diameter D of the hard particles ₁ The ratio (D) of (μm) and the average thickness h (μm) of the resin part in the resin coating layer ₁ / H) is 1 <(D ₁ / H) satisfying the relationship of <10, the particle diameter D of the second hard particles ₂ The ratio (D) between (μm) and the average thickness h (μm) of the resin part of the binder resin in the coating layer ₂ / H) is 0.001 <(D ₂ / H) <1 is satisfied, and the development is performed while supplying the developer to the developing device and discharging the excess developer in the developing device to the outside of the developing device. And
(2): In the image forming method described in (1) above, the base particles of the conductive fine particles are made of titanium oxide.
(3): In the image forming method described in (1) or (2) above, the hard particles are alumina particles or particles based on alumina.
(4): The image forming method according to any one of (1) to (3), wherein the second hard particles are titanium oxide particles or surface-treated titanium oxide particles.
(5): In the image forming method according to any one of (1) to (4), a part or all of the hard particles and / or the second hard particles contained in the resin coating layer are It is characterized by being white conductive fine particles.
(6) In the image forming method described in any one of (1) to (5) above, an average thickness T (μm) from the surface of the core material particle to the surface of the resin coating layer is 0.1. ≦ T ≦ 3.0.
(7): In the image forming method according to any one of (1) to (6), the resin contained in the resin coating layer is at least a reaction product of an acrylic resin and an amino resin or a silicone resin. It is characterized by including.
(8): In the image forming method according to any one of (1) to (7), the weight ratio of carrier particles in the developer supplied to the developing device is 3 wt% or more and 30 wt% or less. It is characterized by that.
(9): In the image forming method according to any one of (1) to (8), the weight ratio of carrier particles in the developer contained in the developing device is 85 wt% or more and 98 wt% or less. It is characterized by being.
(10) In the image forming method according to any one of (1) to (9), the replenishment is performed by sucking the developer for replenishment filled in a storage container whose shape is easily deformed. And is supplied to a developing device.
(11): An image is formed by using the image forming method described in any one of (1) to (10) above.
(12): Development that forms an image using the image forming method described in any one of (1) to (10) above, in the process cartridge in which at least the photosensitive member and the developing device are integrally formed. It is a device.

  According to the present invention, the resin coating layer includes white conductive fine particles, and the conductive fine particles include a lower layer containing tin dioxide and an upper layer containing tin dioxide and indium oxide on the surface of the particles serving as the base material. It is acicular or rod-shaped fine particles having an aspect ratio of 3 to 200 formed by laminating at least, and the development supplies the developer to the developing device and supplies the excess developer in the developing device. By discharging while out of the developing device, the physical properties of the carrier particles in the developing device are kept stable, and the carrier particle adhesion in the solid image portion is suppressed during long-term use, and the electrical resistance of the carrier particles is lowered. An electrophotographic image forming method that can be adjusted in the direction and has no risk of causing color stains on the color image even if the resistance adjusting agent is detached from the surface of the carrier particles. It is possible to provide an image forming apparatus and a process cartridge for carrying out the forming process.

  The present invention is described in further detail below.

  The present inventor has intensively studied to solve the above problems. As a result, in order to prevent the occurrence of defective images due to the deteriorated developer, the toner particles and carrier particles are transferred to the developing device containing the developer in which toner particles and carrier particles are mixed. In addition, the developer is developed while discharging the excess developer in the developing device, and in the binder resin layer on the surface of the carrier particles to be used, the binder resin layer has a needle-like or rod-like shape, and the lower layer is made of carbon dioxide. By including conductive fine particles having a conductive coating layer composed of a layer containing tin and a layer containing tin dioxide and indium oxide as an upper layer, good conductivity resulting from the structure of tin dioxide and indium oxide can be obtained. The function is stably exhibited over a long period of time due to the difficulty of detachment due to the shape, and the conductive fine particles can be made white in this configuration. One, even if the conductive particles from the carrier particles the resin layer is desorbed, or peeling each carrier particle resin layer, that does not generate color stain problem for image devised a technology initiative.

  In particular, the reserve replenishment developer has different storage periods and storage conditions depending on the usage conditions of the user, and may be stored for a long time in a poor environment. As described above, the developer in the developing system that replenishes / discharges the developer is stored in a state where the toner particles and the carrier particles are in contact with each other. Therefore, although there is a high risk that the resin layer of the carrier particles and the components thereof are transferred to the toner particles, the conductive fine particles according to the present invention are not easily detached, and the toner particles are white, so even if they are detached from the surface of the carrier particles, the toner particles Therefore, it can be said that this is a very suitable combination.

  Even if the resistance control agent with a small amount of coloring is used to suppress the problem of color stains, the higher the resistance control agent, the greater the influence on the resistance of the carrier particles when desorbing from the carrier particle surface. Therefore, the resistance control agent is preferably selected in the order in which color stains are not generated even in the unlikely event that the emphasis is placed on the difficulty of desorption.

  The shape of the conductive fine particles in the present invention is needle-shaped or rod-shaped. By making the shape of the conductive fine particles into a needle shape or a rod shape, the side surfaces of the conductive fine particles are easily exposed on the surface of the carrier particles when the conductive fine particles are dispersed in the resin coating layer. Moreover, it becomes easy to arrange | position in a mesh shape in parallel with respect to the carrier particle surface. As a result, the efficiency of the function of reducing the resistance of the carrier particles is improved. In addition, there is an effect that the conductive fine particles enter the recesses on the surface of the core material of the carrier particles and the conductive effect is not exhibited, and the conductive fine particles can be formed into a needle shape or a rod shape. It is very effective for efficiently expressing the functions of.

  The needle shape / bar shape in the present invention means that the aspect ratio is 3 to 200, preferably 3 to 100, more preferably 3 to 50. When the aspect ratio is less than 3, the above-mentioned bar / needle shape effect is hardly exhibited. When the aspect ratio is larger than 200, the moment is large with respect to the strength of the particles, so that the conductive fine particles are easily broken when applied to the surface of the core material of the carrier particles together with the binder resin. The shape effect is less likely to be exhibited.

  The aspect ratio of the conductive fine particles can be obtained, for example, by photographing a portion of the conductive fine particles in the resin coating layer on the cut surface of the conductive fine particles or carrier particles using a scanning electron microscope and a transmission electron microscope. In a two-dimensional field image, find the average value with the longest part of the conductive fine particles arbitrarily selected 50 as the longest diameter and the longest part on the axis perpendicular to the longest diameter as the shortest diameter, and remove them Can be calculated.

  In order to change the shape of the conductive fine particles to a needle shape or a rod shape, the shape of the substrate particles may be a needle shape or a rod shape. It is preferable to use titanium oxide as a raw material because it is easy to obtain needle-like or rod-like particles. In particular, when a rutile crystal structure is provided, a more preferable shape is easily obtained. Paying attention to electrical conductivity, the conductive fine particle base material is made of aluminum oxide, titanium oxide, zinc oxide, silicon dioxide, barium sulfate, or zirconium oxide. Becomes prominent. 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 the present invention, “titanium oxide” includes “titanium dioxide”.

  Even if the conductive fine particles or the resin coating layer containing the conductive fine particles is detached from the carrier particles, there is no problem with color smearing unless the conductive fine particles have a bad influence on the color development of the toner particles. As a result of intensive studies, the inventors have come to the conclusion that if the conductive fine particles are white, even if the conductive fine particles are detached from the resin coating layer of the carrier particles, the color development of the toner particles is not adversely affected. It was. Specifically, the powder color tone of the conductive fine particles has an L value of 70 or more, more preferably 80 or more, particularly preferably 85 or more, and a b value of −10 or more and 10 or less, more preferably −5 or more and 5 or less. Particularly preferably, it can be used without adversely affecting the color development of the toner particles as long as it is −1 or more and 3 or less.

  When the L value of the powder color tone is 70 or less, the whiteness is not sufficient, which adversely affects the color development of the toner particles. When the b value is -10 or less or greater than 10, the saturation becomes high, and color stains are generated when the toner is fixed together with the toner particles.

  Incidentally, the measurement method of the powder color tone in the present invention is as follows.

  First, weigh 6 g with an upper pan balance. Place a blank sheet on the molding die, place the following stainless steel ring, put the weighed sample there, and place the presser fitting. The L value and b value are read with the following color difference meter, which is pressed using a small automatic press and is standardly adjusted with a standard version.

Colorimeter (Nippon Denshoku Co., Ltd. Z-10018P or a measuring instrument with equivalent or better performance)
Stainless steel ring (inner diameter 40mmφ, height 18mm)

  In order to impart conductivity to the particles, a conductive coating layer may be formed 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 conductivity imparting effect equivalent to that of carbon black can be obtained. It can be demonstrated. However, even if a conductive coating layer made of tin dioxide and indium oxide is directly formed on the surface of the base material, good electrical conductivity may not be obtained due to the electrical influence of the base material particles. Also, even if a mixture of tin dioxide hydrate and indium oxide hydrate is coated directly on the substrate particles, it is difficult to uniformly coat the surface of the substrate particles, which is a problem in terms of quality. May occur.

  Mixing the hydrates of tin dioxide and indium oxide after coating the surface of the substrate particles with materials commonly used as coating materials such as aluminum oxide, titanium oxide, zinc oxide and zirconium oxide When the substrate particles are coated with the liquid, 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 containing tin dioxide and indium oxide can be fixed uniformly and firmly, and electrical adverse effects from the lower layer can be prevented. Good electrical conductivity could be obtained without receiving. 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.

Paying attention to the color tone, aluminum oxide and titanium oxide tend to satisfy the above-mentioned color tone conditions.
For these reasons, titanium oxide is preferable as the base particle of the conductive fine particles according to the present invention, and rutile type titanium oxide is particularly preferable. However, in the present invention, in addition to titanium oxide, those that exhibit good effects can be used as a base material for conductive fine particles.

  The following aspects are mentioned as a detailed manufacturing method of the electroconductive coating layer 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 tin dioxide hydrate in the lower layer is 0.5 to 50% by weight, preferably 1.5 to 40% by weight as SnO _{2 with} respect to the base particles. If the amount is too small, 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 the amount is too large, 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 for forming a coating of indium oxide hydrate containing tin dioxide as an upper layer. However, since the coating of hydrated tin dioxide previously coated does not dissolve, tin salt and indium A method in which a mixed solution of salt 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 coating amount of tin dioxide hydrate in the upper layer is 0.1 to 20% by weight, preferably 2.5 to 15% by weight as SnO _{2 with} respect to In ₂ O ₃ . If it is too long, desired conductivity cannot be obtained. The coating amount of the indium oxide hydrate is 5 to 200% by weight, preferably 8 to 150% by weight, as In ₂ O _{3 with} respect to the base particles, and if it is too small, the desired conductivity cannot be obtained, If the amount is too large, 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 reduced by 2 to 3 orders of magnitude compared with that heat-treated 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 resistance value of the carrier particles to an appropriate value, A large amount of fine particles is required. At this time, since the proportion of the binder resin on the surface of the carrier particles is excessive, 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 conductive fine particles is too large compared to the amount of binder resin, the ability to hold particles by the binder resin becomes insufficient, and the conductive fine particles are easily detached. This is not preferable because sufficient durability cannot be obtained.

  FIG. 1 schematically shows an embodiment of carrier particles according to the invention. The carrier particles shown in FIG. 1 include magnetic core material particles 26 and a resin coating layer 27 that covers the core material particles 26. The resin coating layer 27 is contained in a binder resin 28. It contains at least white conductive fine particles G3, and may contain first and second hard particles G1 and G2 and other components as necessary.

  Further, as shown in FIG. 2, the conductive fine particle G3 is formed by forming a conductive coating layer G3b on the surface of the base particle G3a. As shown in FIG. 3, the conductive fine particles G3 are formed by laminating a lower layer G3b1 containing tin dioxide on the surface of the base particle G3a and an upper layer G3b2 containing tin dioxide and indium oxide thereon. .

  In addition, conductive fine particles G3 may be used instead of all or part of the first hard particles G1. Further, the conductive fine particles G3 may be used in place of all or part of the second hard particles G2. Of course, the object of the present invention can be achieved even when the first and second hard particles G1 and G2 are absent and only the conductive fine particles G3 are present.

FIG. 4 is an explanatory view showing a resin coating layer of carrier particles used in the present embodiment.
As shown in FIG. 4, the carrier particles used in the present invention have a particle diameter D ₁ (μm) of the first particles G1 with respect to the average thickness h (μm) of the resin portion in the resin coating layer 27 as follows: Those satisfying the relationship of 1 <(D ₁ / h) <10 are preferable, and those satisfying the relationship of 1 <(D ₁ / h) <5 are more preferable. The resin coating layer 27 includes white conductive fine particles (needle-like or rod-like fine particles having an aspect ratio of 3 to 200 formed by laminating at least a lower layer containing tin dioxide and an upper layer containing tin dioxide and indium oxide). However, this is omitted in FIG.

  The average thickness h of the resin portion in the resin 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 resin coating layer 27, particles The average thickness of the resin part excluding the part is shown.

  As shown in FIG. 4, the thickness of the resin part in the resin coating layer 27 includes the thickness ha of the resin part existing between the surface of the core material 26 and the particles, and the thickness hb of the resin part existing between the particles. There are a thickness hc of the resin part existing on the particles and a thickness hd of the resin part existing on the core material 26.

  The average thickness h of the resin portion in the resin coating layer 27 can be measured by observing the cross section of the carrier particles using, for example, a transmission electron microscope (TEM). Specifically, the thickness of the resin portion in the resin coating layer 27 at intervals of 0.2 μm along the carrier particle surface (the thickness ha of the resin portion existing between the core material surface and the particle, the resin existing between the particles) The thickness hb of the part, 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) to obtain 50 measurement values. A value obtained by averaging the measured values is defined as an average thickness h of the resin portion in the resin coating layer 27.

  As a specific calculation method, the value of the average thickness h of the resin portion in the resin coating layer 27 was obtained by adding the respective measured values obtained by the above-described method and dividing the obtained value by the number of measured values. Value. 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. 4, since the hb and the hc exist, the number of measurement values at the measurement point A is two. Moreover, in the measurement method described above, a plurality of measurement values (for example, ha and hc) are measured as measurement values of the thickness of the resin portion in the resin coating layer 27 at the last measured location among the 50 measurement values. When obtained, the 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)”, which is the number of measured values, of the resin portion in the resin coating layer 27 is obtained. It is set as the value of average thickness h.

An average thickness h of the resin portion in the particle size D ₁ and the covering layer 27 of the first particle G1 is, satisfies the above relation, a direction of first particle G1 is convex with respect to the resin coating layer 27 of the carrier particles Become. By this convex portion, when stirring for triboelectrically charging the developer is performed, the strong impact applied to the binder resin of the carrier particle coating layer 27 due to the frictional contact between the toner particles and the carrier particles or between the carrier particles is alleviated. be able to. Thereby, it can suppress that the film | membrane scraping of the binder resin of the carrier particle coating layer 27 which is an electric charge generation location generate | occur | produces.

  Further, when the carrier particles are in frictional contact with each other, the particles that are convex with respect to the surface of the resin coating layer 27 scrape off the spent component of the toner particles adhering to the surface of the carrier particles. Can be obtained. Thereby, it is possible to effectively prevent the phenomenon of toner spent.

When the value of (D ₁ / h) is 1 or less, the first particles are buried in the binder resin, and the effect of the first particles G1 added in the resin coating layer 27 cannot be sufficiently obtained. Sometimes. Further, if the value of (D ₁ / h) is 10 or more, the contact area between the first particles G1 and the binder resin is reduced, and sufficient binding force of the first particles G1 to the carrier particles cannot be obtained. The first particles G1 may be easily detached from the carrier particle surfaces.

The resin coating layer 27 preferably contains second hard fine particles (hereinafter referred to as second particles G2) in order to give the resin coating layer 27 an appropriate moderate strength on average. The particle diameter D ₂ (μm) preferably satisfies 0.001 <(D ₂ / h) <1 with respect to the average thickness h (μm) of the resin portion in the resin coating layer 27, and 0.01 <(D _{2 /} h) <0.5 is more preferable. The particle size D ₂ of the second particle G2, is made smaller than the average thickness of the resin coating layer 27 may be included while dispersing a second particle G2 in the coating layer 27. Therefore, the strength of the resin coating layer 27 can be improved on average. When the value of (D ₂ / h) is 1 or more, since the second particles G2 are too large with respect to the thickness of the resin coating layer 27, the effect of dispersing and improving the strength of the resin coating layer 27 on average. Becomes difficult to be demonstrated. Also, if _(D 2 / h) is 0.001 or less, the particle size of the second particle G2 the resin coating layer 27 thickness is too small, it effect is obtained hardly.

Incidentally, the particle diameter D ₁ of the first hard fine particle G1, the particle diameter D ₂ of the second hard fine particle G2, and the particle diameter of the conductive fine particle G3 are volumetric using an automatic particle size distribution measuring apparatus CAPA-700 (manufactured by Horiba, Ltd.). The average particle size is measured. As a pretreatment for the measurement, 300 ml of a toluene solution is added to 30 ml of aminosilane (SH6020: manufactured by Toray Dow Corning Silicone) in a juicer mixer. To this solution, 6.0 g of a sample to be measured is added, the mixer rotation speed is set to a low speed, and the mixture is dispersed for 3 minutes to prepare a dispersion. An appropriate amount of the above dispersion is added to 500 ml of a toluene solution prepared in advance in a 1000 ml beaker and diluted. The diluting solution is continuously stirred with a homogenizer. This diluted solution is measured by the ultracentrifugal automatic particle size distribution analyzer CAPA-700 under the following measurement conditions.

Measurement condition rotational speed: 2000 rpm
Maximum particle size: 2.0 μm
Minimum particle size: 0.1 μm
Particle size interval: 0.1 μm
Dispersion medium viscosity: 0.59 mPa · s
Dispersion medium density: 0.87 g / cm ³

The volume resistivity value of the second particles 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. -It is cm or less. 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 resin coating layer 27 is controlled to an appropriate low level, and finally obtained. The density of image enhancement can be increased.

  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 obtained resistivity can be calculated by the following mathematical formula (1) to determine the volume resistivity.

Volume resistivity (Ω · cm) = (2.54 / 2) ² × (π / H) × r (1)
(However, in Formula (1), H is a value representing the thickness of the sample, and r is a value representing the resistance value of the sample.)

  The average thickness T (μm) from the surface of the core material 26 to the surface of the resin coating layer 27 is preferably 0.1 ≦ T ≦ 3.0, and more preferably 0.1 ≦ T ≦ 2.0. . When the average thickness T from the surface of the core material 26 to the surface of the resin coating layer 27 is 0.1 μm or less, the total thickness of the resin coating layer 27 as a film covering the carrier particle core material 26 is too thin. The phenomenon that the resin coating layer 27 is scraped and the carrier particle core material 26 is exposed easily occurs, and the durability of the carrier particles decreases. On the other hand, if the average thickness T from the core material 26 to the surface of the resin 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 particles tends to decrease, and the carrier particles May cause adhesion.

Further, the average thickness h (μm) of the resin portion in the resin 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. Particle size _{D 2} of the second particle G2 is preferably 0.005 to 1 [mu] m, 0.01 to 0.2 [mu] m is more preferable.

  As shown in FIG. 4, the thickness T from the surface of the core material 26 to the surface of the resin coating layer 27 represents a thickness different from the average thickness h of the resin portion in the resin coating layer 27 described above. The thickness from the surface of the core material 26 to the surface of the resin coating layer 27 at each point on the surface is shown. As shown in FIG. 1, when the particle diameter of the particles added to the resin coating layer 27 is larger than the thickness of the resin portion in the resin coating layer 27, the particle diameter of the particles is from the surface of the core material 26. The value corresponds to the thickness T up to the surface of the resin coating layer 27.

  The average thickness T from the surface of the core material 26 to the surface of the resin coating layer 27 is observed, for example, by observing a cross section of the carrier particle using a transmission electron microscope (TEM), and the thickness from the surface of the core material 26 to the surface of the resin coating layer 27. Is a value obtained by measuring 50 points along the surface of the carrier particles 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 the binder resin used for the coating material of the carrier particles. In addition to being excellent in terms of dispersibility and adhesiveness, the hardness is very high, so that wear and cracks are less likely to occur due to stress in the developing device 10, and the protective effect of the resin coating layer can be increased over a long period of time. This is particularly preferable because it can exert a scraping 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 particles 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 resin 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 resin coating layer 27 is 10 wt% or less, the proportion of the first particles G1 is too small compared to the proportion of the binder resin on the surface of the carrier particle particles. Sufficient durability may not be obtained because the effect of relieving contact with a strong impact on the surface is small. On the other hand, if it exceeds 80 wt%, since the proportion of the first particles G1 is too much compared to the proportion of the binder resin on the surface of the carrier particles, the proportion of the binder resin that is a charging occurrence point becomes insufficient, In some cases, sufficient charging ability cannot be exhibited. 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 resin 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 resin coating layer 27 (conductive fine particle G3 + first particle G1 + second particle G2 + binder resin + others) Ingredient)] × 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 as the carrier particle coating material, and are excellent in dispersibility and adhesiveness. In particular, titanium oxide or oxidized surface treated Titanium is preferred 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. Further, the conductive fine particles may be used as the second particles G2.

  The content of the second particles G2 contained in the resin 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 resin coating layer 27, the greater the effect of increasing the strength. However, if the content of the second particles G2 exceeds 50 wt%, the dispersion of the second particles G2 inside the resin coating layer 27 The condition gets much worse. If the dispersed state of the particles deteriorates, the second particles G2 partially aggregate together inside the resin 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 particle G2 in the resin coating layer 27 is 2 wt% or less, the content is too small, and thus the effect of adding the second particle G2 cannot be sufficiently obtained.

Content in the resin 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 resin coating layer 27 (conductive fine particle G3 + first particle G1 + second particle G2 + binder resin + others) Ingredient)] × 100 (3)

  As the binder resin used for the resin coating layer 27 of carrier particles, any of a reaction product of an acrylic resin and an amino resin, and a silicone resin can be preferably cited. 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 particles and the carrier particles or the carrier in the stirring for frictionally charging the developer. The friction between the particles allows the impact to be absorbed 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 20 ° C. or lower, the binder resin blocks even at room temperature, so that the storage stability is poor and may not be used practically. 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 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 particle coating resins can be used as required. Resin, polystyrene resin, halogenated olefin resin, polyester resin, polycarbonate resin, polyethylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, polytrifluoroethylene resin, polyhexafluoropropylene resin, vinylidene fluoride And fluorinated terpolymers 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 resin coating layer 27 is prepared by dissolving or dispersing the first particles G1, the second particles G2, the conductive fine particles G3, the binder resin, and the like in a solvent to prepare a coating solution, and then applying the coating solution to the core material 26. It can be formed by uniformly applying to the surface by a known coating method, drying, and 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.

  The volume average particle size of the carrier particle core material 26 used in the present embodiment is not particularly limited, but from the viewpoint of carrier particle adhesion to the image carrier 1 and prevention of carrier particle scattering, the volume average particle size. Is preferably 20 μm or more, and from the viewpoint of preventing the occurrence of abnormal images such as carrier particle streaks and preventing the deterioration of image quality, those having a thickness of 100 μm or less are preferable, and those having a diameter of 20 to 60 μm are particularly used. Therefore, it is possible to more appropriately meet the recent improvement in image quality.

The core material particle 26 is not particularly limited, and can be appropriately selected from those known as two-component carrier particles for electrophotography according to the purpose. For example, ferrite, magnetite, iron, nickel are preferable. It is done. 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.
Specifically, MFL-35S, MFL-35HS (manufactured by Powder Tech), DFC-400M, DFC-410M, and SM-350NV (manufactured by DOWA Electronics) are mentioned as suitable examples.

In the carrier particles of the present invention, the resistivity 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 particle is lower than 1 × 10 ¹¹ [Ω · cm], when the development gap (the closest distance between the photoconductor and the development sleeve) is narrowed, charge is induced in the carrier particle and the carrier Particle adhesion tends to occur. 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. In general, color toner developing carrier particles are generally used with low resistance in order to obtain a sufficient toner adhesion amount. By using carrier particles in the above resistivity range under an appropriate toner charge amount, a sufficient image density can be obtained. On the other hand, if the resistivity is greater than 1 × 10 ¹⁶ [Ω · cm], the charge having the opposite polarity to the toner particles tends to be accumulated, and the carrier particles are charged and the carrier particles are liable to adhere.

The resistivity of the carrier particles can be measured by the following method.
As shown in FIG. 5, a cell 11 made of a fluororesin container containing electrodes 12a and 12b having a distance between electrodes of 2 mm and a surface area of 2 × 4 cm is filled with carrier particles 13 and a DC voltage of 100 V is applied between both electrodes. , DC resistance is measured with a high resistance meter 4329A (4329A + LJK 5HLVLVWDQFH OHWHU; manufactured by Yokogawa Hewlett-Packard Co., Ltd.). The degree of filling at the time of measuring the resistance of the carrier particles is determined by using a horizontal spatula made of a non-magnetic upper surface of the cell 11 after the carrier particles 13 are put into the cell 11 and then the entire cell is tapped 20 times. Scrape flat along the top edge of the cell 11 in a single operation. No pressure is required during filling. The resistivity of the carrier particles 13 can be adjusted by controlling the amount of conductive fine particles and the thickness of the resin coating layer.

  The developer according to the present invention can be prepared by using the above-described carrier particles according to the present invention and toner particles.

  The toner particles used in the present invention include at least a binder resin and a colorant, and further include a release agent, a charge control agent, and other components as necessary. A method for producing toner particles will be described below, but the method for producing toner particles is not particularly limited to one, and can be appropriately selected according to the purpose. Examples include a pulverization method, a suspension polymerization method, an emulsion polymerization method, a polymer suspension method in which an oil phase is emulsified, suspended or aggregated in an aqueous medium to form toner particle base particles.

  The binder resin for the toner particles 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 The substituted homopolymer, styrene-p-chlorostyrene copolymer, styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer Styrene-methacrylic acid copolymer, 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 polymers, styrene-vinyl methyl ketone copolymers, styrene-butadiene copolymers, styrene-isopropyl copolymers, styrene-maleic acid ester copolymers, polythymethacrylate resins, 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 Aromatic hydrocarbon resins, aromatic petroleum resins and the like 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, Pigment 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 particles 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 40 ° C. or lower, 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. If the melt viscosity is 5 cps or less, the releasability may be lowered, and if 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 particle 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 particles 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 (Part No .: T-2, 004) (Nippon Kayaku Co., Ltd.), Eisenspiron Black (T-37, T-77, T-95, TRH, TNS-2) FCA-1001-N, FCA-1001-NB, FCA-1001-NZ (manufactured by Fujikura Kasei Co., Ltd.), and the like.

  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 particle production method including the type of the binder resin and the dispersion method, and is not uniquely limited, but is 0 for 100 parts by weight of the binder resin. 0.1 to 10 parts by weight is preferable, and 0.2 to 5 parts by weight is more preferable. When the added amount exceeds 10 parts by weight, the chargeability of the toner particles is too high, the effect of the charge control agent is reduced, the electrostatic attractive force with the developing roller is increased, the flowability of the developer is reduced, and the image The density may be lowered, and if it is 0.1 part by weight or less, the charge start-up property and the charge amount are not sufficient, and the toner image may be easily affected.

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

  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 toner particles 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 particle 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 current by centrifugal force or the like to produce toner particles having a predetermined particle size.

  In order to improve the fluidity, storage stability, developability, and transferability of the toner particles, 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, toner particles can be obtained by passing through a sieve for the purpose of removing coarse particles and aggregated particles.

  In the present invention, the weight ratio of the carrier particles in the developer contained in the developing device that converts the electrostatic latent image formed on the surface of the photoreceptor into a toner image is preferably 85 wt% or more and 98 wt% or less. . If it is 85 wt% or less, scattering of toner particles from the developing device is likely to occur, causing a defective image. If it is 98 wt% or more, the charge amount of the toner particles excessively increases or the supply amount of the toner particles is insufficient, so that the image density is lowered and a defective image is caused.

  In the present invention, as will be described later, a developer container containing a replenishing developer is connected to the developing device by a pipe or the like so that new carrier particles and toner particles can be replenished in the developing device. Then, in the developer container, in the resin coating layer 27 that covers the surface of the core material particle 26, the needle-like or rod-like base particle G3a having an aspect ratio of 3 to 200 is used as a base material, The carrier particles described above, comprising the binder resin layer 27 containing conductive fine particles G3 provided with a conductive coating layer G3b formed by laminating a lower layer containing tin dioxide and an upper layer containing tin dioxide and indium oxide. (Refer to FIGS. 1 to 3) and a replenishment developer composed of toner particles are accommodated.

  As will be described later, the toner particles and the carrier particle particles replenished in the developer accommodating portion in the developing device are mixed together with the toner particles and the carrier particles accommodated from the beginning by a conveying screw. Since the toner particles and the carrier particles, or the carrier particles are in strong contact with each other, the release of the raw materials contained in the resin coating layer on the surface of the carrier particles or the resin coating layer itself is particularly likely to occur at this portion.

  The developer container containing the replenishment developer can also be used as a detachable replenishment developer cartridge, in which case the toner particles and the carrier particles are stored in contact with each other. . When the toner particles and the carrier particles are in contact with each other for a long period of time, the risk that the raw materials contained in the resin coating layer on the surface of the carrier particles or the resin coating layer itself will move to the toner particles.

  In addition, when the resin coating layer 27 is detached from the core agent particle 26, it is the conductive fine particles G3 that are most likely to cause color stains. Further, the detachment of the conductive fine particles G3 from the resin coating layer 27 has a great adverse effect on the electric resistance of the carrier particles. However, the carrier particles contained in the developer according to the present invention are those that are very difficult to be detached from the resin coating layer 27 by making the shape of the conductive fine particles G3 into needles or rods having an aspect ratio of 3 to 200. It becomes possible to.

  Further, even when the resin coating layer 27 is released, the occurrence of color stains can be suppressed because the white conductive fine particles G3 are used as the resistance control agent.

Furthermore, as described above as a preferable example, when D ₁ satisfies 1 <(D ₁ / h) <10, or when D ₂ further satisfies the relationship of 0.001 <(D ₂ / h) <1, Since some of the first particles G1 are convex with respect to the resin coating layer 27, as described above, toner particles and other carrier particles are added to the resin coating layer 27 during the stirring and mixing. Even if they come into contact, the impact is mitigated by the convex portions on the surface of the resin coating layer 27. For this reason, the rate at which film abrasion on the surface of the carrier particles occurs can be greatly suppressed.

  Further, since the spent component of the toner particles adhering to the surface of the carrier particles at the time of stirring is scraped off by the first particles that are convex, 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 other words, the present inventor has intensively studied paying attention to the problem of color stains peculiar to the developing method as described above, and as a result, the shape of the conductive fine particles is changed to a needle shape or a rod shape having an aspect ratio of 3 to 200. This makes it very difficult to separate from the resin coating layer, and even when the resin coating layer is released, the white conductive fine particles are used as a resistance control agent, so Therefore, the occurrence of color stains can be suppressed even in a developing method in which toner particles and carrier particles are replenished to the developing device and the developer remaining in the developing device is discharged. In addition, for providing conductivity, by using conductive fine particles provided with a conductive coating layer composed of a layer of tin dioxide in the lower layer and an indium oxide layer containing tin dioxide in the upper layer, the color and conductivity can be obtained. It was confirmed that both are possible.

The content of the conductive fine particles (G3) contained in the resin coating layer is 2 to 80% by weight, preferably 10 to 50% by weight. If it is less than 2% by weight, the conductivity becomes insufficient and resistance control becomes difficult, and if it exceeds 80% by weight, the conductive fine particles (G3) occupy the proportion of the binder resin on the surface of the carrier particles. Since the ratio is too large, the ratio occupied by the binder resin that is the location where the charge is generated becomes insufficient, and the charging ability may not be sufficiently exhibited. Further, as described above, the carrier resistivity is preferably in the range of 1 × 10 ¹¹ to 1 × 10 ¹⁶ [Ω · cm], more preferably 1 × 10 ¹² to 1 × 10 ¹⁴ [Ω · cm]. . Since the content of the conductive fine particles changes the resistivity of the carrier, the prescription amount is preferably set so that the resistivity of the carrier can be adjusted within the above range. In addition, content of electroconductive fine particles (G3) contained in a resin coating layer is represented by following formula (4).
Content of conductive fine particles G3 (wt%) = [content of conductive fine particles G3 / total amount of materials contained in coating layer 27 (conductive fine particles G3 + first particles G1 + second particles G2 + binder resin + other components) )] X 100 (4)

  In the developing device according to the present invention, most of the deteriorated carrier particles are discharged by the developer discharging device. However, some of the deteriorated carrier particles may not remain in the developer container in the developing device over a long period of time, and the amount of toner particles consumed is small when the image forming apparatus is operated. In some cases, the amount of carrier particles exchanged in the developer container in the developing device is small, and the period during which the carrier particles stay in the developer container may be long. In the embodiment according to the present invention, the developer in the developing device accommodated in the developer accommodating portion in the developing device is also replenished before the replenishing developer in the developer accommodating device outside the developing device is replenished. The same carrier particles as the carrier particles used in the developer are used. For this reason, even when the amount of developer exchange is low, or when some of the carrier particles accommodated from the beginning remain without being discharged from the developer accommodating portion, the same mechanism as described above is used for developing. Deterioration of carrier particles in the agent container is suppressed, and the developer can be kept in a stable state even after long-term use.

  Next, the case where an image is formed using a developer in which carrier particles and toner according to the present invention are mixed will be described. FIG. 6 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

  In the image forming apparatus main body 100 according to the present embodiment, image forming units 2M, 2C, 2Y, and 2K, which are process cartridges including the photoreceptors 1M, 1C, 1Y, and 1K, which are four image carriers, are formed. Removably attached to the device 100. A transfer device 8 in which an endless transfer belt 15 is rotatably mounted in a direction indicated by an arrow A between a plurality of rollers is disposed at substantially the center of the image forming apparatus 100.

  The drum-shaped photoconductors 1M, 1C, 1Y, and 1K provided in the image forming units 2M, 2C, 2Y, and 2K, respectively, are disposed on the lower surface of the transfer belt 15 so as to contact with each other. In correspondence with the image forming units 2M, 2C, 2Y, and 2K, developing devices 10M, 10C, 10Y, and 10K having different toner particle colors are arranged. The image forming units 2M, 2C, 2Y, and 2K are units having the same configuration, the image forming unit 2M forms an image corresponding to magenta, and the image forming unit 2C forms an image corresponding to cyan. The image forming unit 2Y forms an image corresponding to the yellow color, and the image forming unit 2K forms an image corresponding to the black color.

  In the developing devices 10M, 10C, 10Y, and 10K respectively disposed in the image forming units 2M, 2C, 2Y, and 2K, a two-component developer including toner particles and carrier particles is used, and magenta, cyan, and yellow are used. The developer of each color mixed with black toner particles and carrier particles is omitted from the developer replenishing devices 200M, 200C, 200Y, and 200K and provided in the developing devices 10M, 10C, 10Y, and 10K. A developing method is employed in which toner is replenished according to the output of the toner density sensor, carrier particles are also replenished, old developer is discharged, and the developer can be replaced.

  The developer replenishing devices 200M, 200C, 200Y, and 200K disposed in the space above the image forming units 2M, 2C, 2Y, and 2K are different from the toner particles that are to be supplied to the photoreceptors 1M, 1C, 1Y, and 1K. This is a configuration for supplying new toner particles and new carrier particles to the developing devices 10M, 10C, 10Y, and 10K, which will be described later.

  An exposure device 6 as a writing unit is disposed below the image forming units 2M, 2C, 2Y, and 2K. 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 route 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 is irradiated onto each of the photoconductors 1M, 1C, 1Y, and 1K corresponding to magenta, cyan, yellow, and black color images.

  Between the transfer belt 15 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 transport direction of the transfer paper P, and the transfer paper P transported there can be discharged onto a discharge tray 53 by a pair of discharge rollers 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, the photosensitive members 1M, 1C, 1Y, and 1K rotate in the clockwise direction in FIG. The surfaces of the photoreceptors 1M, 1C, 1Y, and 1K are uniformly charged by the charging roller 301 of each charging unit 3. Then, laser light corresponding to a magenta image by the exposure device 6 is applied to the photoreceptor 1M of the image forming unit 2M, and laser light corresponding to a cyan image is applied to the photoreceptor 1C of the image forming unit 2C. The 2Y photoconductor 1Y is irradiated with laser light corresponding to a yellow image, and the photoconductor 1K of the image forming unit 2K is irradiated with laser light corresponding to a black image. Each latent image is formed. Each latent image reaches the position of the developing devices 10M, 10C, 10Y, and 10K by rotating the photoreceptors 1M, 1C, 1Y, and 1K, and is developed by the toner particles of magenta, cyan, yellow, and black there. A four-color toner particle image is obtained. As described above, the toner images of the respective colors formed on the photoconductors 1M, 1C, 1Y, and 1K receive the bias voltages from the respective primary transfer rollers 4 and are sequentially superimposed and transferred on the transfer belt 15. The

  On the other hand, the transfer paper P is fed from the paper feed cassette 7 by the separation paper feed unit, and the transfer paper P is placed on each of the photoreceptors 1M, 1C, 1Y, and 1K by the registration roller pair 55 provided immediately before the transfer belt 15. The toner image is conveyed at the same timing as the formed toner image. A bias voltage is applied to the transfer paper P by a secondary transfer roller 54 disposed near the entrance of the transfer belt 15, and a four-color superimposed full-color toner image transferred to the surface of the transfer belt 15 is obtained. Transcribed. The transfer paper P is heated and pressed by the fixing device 9 to melt and fix the toner image, and then passes through the paper discharge system and is discharged onto the paper discharge tray 53 at the top of the image forming apparatus 1. The

  Next, the configuration around the developing device 10 according to the embodiment of the present invention will be described. FIG. 7 is a schematic cross-sectional view showing the developing device of one embodiment provided in the image forming apparatus of the present invention and the structure around it. In FIG. 7, a developer replenishing device 200 for replenishing a developer composed of new toner particles and carrier particles is provided in the developer accommodating portion 14a of the developing device 10 above the developing device 10. Below 10, a developer discharge device 300 that discharges the excess developer in the developing device 10 is provided.

  The developing device 10 includes a housing 10a having a developer accommodating portion 14 for accommodating a two-component developer S composed of toner particles and carrier particles, and the photosensitive member 1 as an image carrier on the opening side of the housing 10a. The developer roll 16 as a developer carrying member disposed so as to rotate in a state in which it is rotated, and two conveying screws 17a as developer agitating and conveying members disposed so as to rotate within the developer container 14. 17b and a layer thickness regulating member 18 disposed in pressure contact with or close to the surface of the developing roller 16 constitute the main part.

  Among these, the developing roller 16 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 communicated by communicating portions on both ends. A conveying screw 17a that rotates in the accommodating spaces 14a and 14b, The developer S is circulated and conveyed between the storage spaces 14a and 14b while being agitated by the developer 17b. The layer thickness regulating member 18 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 S1 for supply, and a developer that sends the two-component developer S1 in the developer container 230 to the developer container 14 for supply. And a replenisher 220. The developer replenisher 220 is provided between the developer container 230 and the developing device 10 so as to be connected to each other. The detailed configuration of the developer supply device 200 will be described later with reference to FIGS.

  The developer discharge device 300 collects, in the collection container 330, a collection container 330 that collects the two-component developer that has become excessive in the developer storage unit 4, and the developer S that overflows from the developer storage unit 14. It comprises a discharge pipe 331 as a developer discharge means to be sent. 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 location of the housing 10a, and the developer discharge port is replaced with a 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 S in the developing device previously stored in the developer storage unit 14 is stirred and sufficiently mixed by the conveying screws 17a and 17b and is frictionally charged, and then supplied to the developing roller 16. , And adheres to the surface of the sleeve 121 in layers. The layered developer S adhering to the developing roller 16 is regulated to a predetermined thickness by the layer thickness regulating member 18 to be a uniform layer, and then developed to face the photoreceptor 1 as the sleeve 121 rotates. It is conveyed to region D. In the developing region D, the toner particles of the two-component developer S are statically applied to the electrostatic 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. 6). Development is performed by electroadsorption, and a toner image is formed on the photoreceptor 1. The toner image formed on the photoreceptor 1 is transferred onto the transfer paper P on the image forming apparatus main body 100 side, and is fixed on the transfer paper P by the fixing device 9.

  By repeating this developing operation, the toner particles contained in the developer S in the developing device 14 in the developer accommodating portion 14 are consumed and gradually decreased. This decrease in the toner particles is detected by the toner concentration sensor. Then, the developer supply unit 223 of the developer supply device 200 is driven. As a result, the replenishment developer S1 containing carrier particles and toner particles, 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 S1 replenished in the developer accommodating portion 14 is stirred by the conveying screws 17a and 17b in the developer accommodating portion 14 and sufficiently with the developer S in the developing device accommodated before replenishment. To be mixed.

  In the developer accommodating portion 14, the carrier particles are replenished at a predetermined ratio together with the toner particles by replenishing the replenishing developer S <b> 1 from the developer replenishing device 200, so that the amount of developer in the developer accommodating portion 14 is increased. Gradually becomes excessive. The two-component developer S that has become 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 S1 of the present invention is a material containing at least toner particles and carrier particles. As the toner particles of the replenishment developer stored in the developer container 230, toner particles described later can be used. As the carrier particles, predetermined particles are formed on the core member 26 as shown in FIG. Magnetic carrier particles in which the coating layer 27 having the above is formed can be used.

  Further, as the toner particles of the developer S in the developing device, the same toner particles as those stored in the developer container 230 or different toner particles can be used, and the developer particles can also be used as carrier particles. The same carrier particles as those contained in the container 230 or different carrier particles can be used.

  In the image forming apparatus 100 of the present embodiment, the developer storage member 231 whose shape is easily deformed is filled with the replenishment developer S1, and the replenishment developer is sucked by the screw pump 223 and supplied to the development device 10. A developer supply device 200 is provided.

Hereinafter, the configuration of the developer supply device 200 will be described in detail with reference to FIGS.
FIG. 8 is a schematic configuration diagram of a developer supply device 200 according to an embodiment 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 S <b> 1 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 accordance with a decrease in internal pressure due to the developer S1 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 the replenishing port 10 b that is opened at a predetermined location of the housing 10 a, 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 230 is sequentially replaced with a new one as the toner particles are consumed. However, the developer container 230 of the present 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 particles 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 embodiment can be easily attached to and detached from the developer supply device 200 of the image forming apparatus 100, is suitable for storage and conveyance, and has excellent handleability.

  9A is an external view showing a schematic configuration of a nozzle 240 provided in the developer replenisher 220, FIG. 9B is an axial sectional view thereof, and FIG. 9C is a diagram of FIG. It is sectional drawing of code | symbol AA in 9 (b). As shown in FIG. 9B, 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 particles in the developer container 230 are sucked by the suction force by the screw pump 223, and are drawn into the screw pump 223 through the developer flow path 241a.

  FIG. 10 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, toner particles and carrier particles conveyed from the developer container 230 through the developer flow path 241 a of the nozzle 240 and the conveyance 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. 10 as the rotor 224 rotates. The toner particles that have passed through the space between the rotor 224 and the stator 225 fall downward from the toner dropping port 223b, and pass through the developer replenishing port 10b of the developing device 10 so that the developer accommodating portion 14 of the developing device 10 can be used. Supplied in.

  The developer replenisher 220 used in this embodiment includes an air supply unit 260 that supplies air into the developer container 230. As shown in FIG. 8, the air flow paths 244a and 244b are connected to air pumps 260a and 260b as separate air supply means via air supply paths 261a and 261b as gas supply paths, respectively. As shown in FIG. 9B, the air flow paths 244a and 244b are provided as air supply passages between the inner tube 241 and the outer tube 242 of the nozzle 240 of the developer replenisher 220. As shown in FIG. 9C, the air flow paths 244a and 244b are composed of two flow paths 244a and 244b having a semicircular cross section that are independent of each other.

  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 particles near the toner outlet 247, and is left unused for a long period of time, leaving the toner particles at the toner outlet 247. Even if the toner becomes clogged, the toner particles blocking the toner outlet 247 can be broken down.

  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 through the screw pump 223, the developer falls downward from the developer dropping port 223b, and the developer is replenished into the developing device 10 from the developer replenishing port 10b. 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 replenishment operation, the toner particles in the toner container 230 flow back to the air pumps 260a and 260b through the air supply passages 244a and 244b of the nozzle 240. It is preventing.

  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 particles and air by the screw pump 223. Therefore, as the toner particles are 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. 11 is a perspective view of a state in which the developer accommodating member 231 is filled with the developer. FIG. 12 is a front view showing a state where the developer in the developer containing member 231 has been 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. 11, the replenishment developer S1 composed of carrier particles and toner particles for replenishing the developing device 10 is housed as described above. . In the replenishment developer S1, the weight ratio of carrier particles in the replenishment developer S1 is preferably 3 wt% or more and 30 wt% or less. When the weight ratio of the carrier particles in the replenishment developer S1 in the developer container 230 is 3 wt% or less, the amount of carrier particles to be replenished is very small, so that the replenishment effect cannot be sufficiently obtained. . On the other hand, if it exceeds 30 wt%, stable supply of the replenishment developer to the developer accommodating portion cannot be obtained.

  Next, the carrier particles according to the present invention and the developer in which the carrier particles and the toner particles are mixed will be described with reference to examples and comparative examples according to the present invention. In addition, this invention is not limited to the Example illustrated here. In the following, “parts” represents parts by weight, and “%” represents% by weight.

  Next, the carrier particles according to the present invention and the developer in which the carrier particles and the toner particles are mixed will be described with reference to examples and comparative examples according to the present invention. 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 particles]
(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

  The above composition was placed in a 1 L four-necked round bottom flask equipped with a thermometer, stirrer, condenser and nitrogen gas introduction tube, this flask was set in a mantle heater, and nitrogen gas was introduced from the nitrogen gas introduction tube. Then, the temperature was raised while maintaining the inside of the flask under an inert 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: Polyester resin A: 60 parts Water: 30 parts

  The raw materials were mixed with 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 particle 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 particle 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 particle material solution was added and stirred for 10 minutes while stirring at 12000 rpm with a TK homomixer. Next, this mixed solution was transferred to a Kolben equipped with a stir bar and a thermometer, heated to 98 ° C. to remove the solvent, filtered, washed, dried, and then classified by air to obtain toner particles.

  Next, 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 particles A”. An ultrathin section of this “toner particle A” was prepared, and a cross-sectional photograph (magnification × 100,000) of the toner particle was taken using a transmission electron microscope (H-9000H, manufactured by Hitachi, Ltd.). The average value was determined from the dispersion diameter of the selected 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 particle 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. The volume average particle diameter (Dv) = 6.2 μm, the number The average particle size (Dn) was 5.1 μm. Subsequently, the circularity of the “toner particles 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 particle A” had a circularity of 0.96.

(Production example of conductive fine particles)
(Production Example 1)
100 g of aluminum oxide (average primary particle size 0.05 μm, aspect ratio: 197) was dispersed in 1 liter of water to obtain a water suspension. This suspension was kept warm at 70 ° C. A solution prepared by dissolving 11.6 g of separately prepared stannic chloride (SnCl ₄ .5H ₂ O) in 100 ml of 2N hydrochloric acid and 12 wt% aqueous ammonia so that the pH of the suspension is maintained at 7-8. Simultaneous addition over about 40 minutes. Subsequently, a solution prepared by dissolving 36.7 g of indium chloride (InCl ₃ ) and 5.4 g of stannic chloride (SnCl ₄ .5H ₂ O) separately prepared in 450 ml of 2N hydrochloric acid and 12 wt% aqueous ammonia was prepared. It was dripped simultaneously over about 1 hour so that pH might be kept at 7-8. After completion of the dropwise addition, the treated suspension was filtered and washed, and the resulting treated pigment cake was dried at 110 ° C. Subsequently, the obtained dry powder was heat-treated at 500 ° C. for 1 hour in a nitrogen gas stream (1 liter / min) to obtain white conductive fine particles A. The average primary particle size was 0.05 μm and the aspect ratio was 197.

(Production Example 2)
White conductive fine particles B were obtained in the same manner as in Production Example 1 except that the base material was changed to aluminum oxide (average primary particle size: 0.07 μm, aspect ratio: 3.2). The average primary particle size was 0.07 μm and the aspect ratio was 3.2.

(Production Example 3)
100 g of aluminum oxide (average primary particle size 0.08 μm, aspect ratio: 32) was dispersed in 1 liter of water to obtain a water suspension. This suspension was kept warm at 70 ° C. Separately prepared solution of 36.7 g of indium chloride (InCl ₃ ) and 5.4 g of stannic chloride (SnCl ₄ .5H ₂ O) in 450 ml of 2N hydrochloric acid and 12 wt% aqueous ammonia was added to the pH of the suspension. Were simultaneously added dropwise over about 1 hour so as to maintain 7 to 8. After completion of the dropwise addition, the treated suspension was filtered and washed, and the resulting treated pigment cake was dried at 110 ° C. Subsequently, the obtained dry powder was heat-treated at 500 ° C. for 1 hour in a nitrogen gas stream (1 liter / min) to obtain white conductive fine particles C. The average primary particle size was 0.08 μm and the aspect ratio was 32.

(Production Example 4)
White electroconductive fine particles D were obtained in the same manner as in Production Example 1 except that the base material was changed to aluminum oxide (average primary particle size: 0.05 μm, aspect ratio: 205). The average primary particle size was 0.05 μm and the aspect ratio was 205.

(Production Example 5)
White conductive fine particles E were obtained in the same manner as in Production Example 1 except that the base material was changed to aluminum oxide (average primary particle size: 0.07 μm, aspect ratio: 2.4). The average primary particle size was 0.07 μm and the aspect ratio was 2.4.

(Production Example 6)
Carbon black (manufactured by Lion Akzo, Ketjen Black EC600JD) was used as conductive fine particles F as they were.

(Production Example 7)
White conductive fine particles G were obtained in the same manner as in Production Example 1 except that the base material was changed to titanium oxide (average primary particle size: 0.08 μm, aspect ratio: 32, rutile type). The average primary particle size was 0.08 μm and the aspect ratio was 32.

(Production Example 8)
White conductive fine particles H were obtained in the same manner as in Production Example 1 except that the base material was changed to titanium oxide (average primary particle size: 0.37 μm, aspect ratio: 27, rutile type). The average primary particle size was 0.37 μm and the aspect ratio was 27.

(Example of carrier particle production)
(Production Example 1)
-Acrylic resin solution (Hitaroid 3001: manufactured by Hitachi Chemical Co., Ltd.) 2130 parts [solid content concentration: 50% by weight]
Aminosilane (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ) 4 parts [solid content concentration: 100% by weight]
・ Conductive fine particles A 1500 parts ・ Toluene 6000 parts

  Each of the above materials was dispersed with a homomixer for 10 minutes to prepare a resin layer forming solution. DFC-400M (manufactured by DOWA Electronics Co., Ltd., volume average particle size 35 μm, ferrite particles) is used as a carrier particle core material, and a Spira coater (Okada Seiko Co., Ltd.) is used so that the resin solution has a thickness h of 0.15 μm on the core material surface. Applied at a rate of 30 g / min in an atmosphere of 55 ° C. and dried. The layer thickness was adjusted depending on the liquid amount. The obtained carrier particles were left standing in an electric furnace at 150 ° C. for 1 hour and fired. After cooling, the carrier particles were pulverized using a sieve having an opening of 100 μm to obtain carrier particles A. The average thickness T was 0.20 μm.

  The volume average particle size of the core material was measured using a SRA type of a Microtrac particle size analyzer (manufactured by Nikkiso Co., Ltd.) with a range setting from 0.7 μm to 125 μm.

  The average thickness h (μm) of the resin portion in the coating layer is determined by observing a cross section of the carrier particle using a transmission electron microscope (TEM), and the thickness ha of the resin portion existing between the core material surface and the particle. Then, the thickness hb of the resin part existing between the particles and the thickness hc of the resin part on the core material or the particle are measured at 50 points along the carrier particle surface at intervals of 0.2 μm, and the obtained measurement values are obtained. Obtained on average.

  The thickness T (μm) from the core material surface to the coating layer surface is determined by observing the cross section of the carrier particles using a transmission electron microscope (TEM), and the thickness T from the core material surface to the coating layer surface is determined by the carrier. 50 points were measured along the particle surface at intervals of 0.2 μm, and the measured values obtained were averaged.

(Production Example 2)
A carrier particle B was obtained in the same manner as in Production Example 1 except that MFL-35HS (Powder Tech Co., volume average particle size 35 μm, ferrite particle) was used as the carrier particle core material. The average thickness T was 0.20 μm.

(Production Example 3)
SM-350NV as carrier particles core (DOWA Electronics Co., volume average particle diameter of 50 [mu] m, magnetite particles) using a weight loss specific surface area ratio calculated from the particle size of the core material coated material amount ⁽³⁵ 2/50 ² times The carrier particles C were obtained in the same manner as in Production Example 1, except that The average thickness T was 0.21 μm.

(Production Example 4)
A carrier particle D was obtained in the same manner as in Production Example 1 except that the conductive fine particle B was used as the conductive fine particle. The average thickness T was 0.20 μm.

(Production Example 5)
A carrier particle E was obtained in the same manner as in Production Example 1 except that the conductive fine particle C was used as the conductive fine particle. The average thickness T was 0.20 μm.

(Production Example 6)
A carrier particle F was obtained in the same manner as in Production Example 1 except that the conductive fine particle D was used as the conductive fine particle. The average thickness T was 0.20 μm.

(Production Example 7)
A carrier particle G was obtained in the same manner as in Production Example 1 except that the conductive fine particle E was used as the conductive fine particle. The average thickness T was 0.20 μm.

(Production Example 8)
A carrier particle H was obtained in the same manner as in Production Example 1 except that the conductive fine particle F was used as the conductive fine particle. The average thickness T was 0.20 μm.

(Production Example 9)
A carrier particle I was obtained in the same manner as in Production Example 1 except that the conductive fine particle G was used as the conductive fine particle. The average thickness T was 0.20 μm.

(Production Example 10)
-Acrylic resin solution (Hitaroid 3001: manufactured by Hitachi Chemical Co., Ltd.) 2130 parts [solid content concentration: 50% by weight]
Aminosilane (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ) 4 parts [solid content concentration: 100% by weight]
Conductive fine particles G 750 parts Alumina particles A (volume average particle size 0.35 μm) 750 parts Toluene 6000 parts

  Carrier particles J were 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 0.40 μm.

(Production Example 11)
-Acrylic resin solution (Hitaroid 3001: manufactured by Hitachi Chemical Co., Ltd.) 2130 parts [solid content concentration: 50% by weight]
Aminosilane (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ) 4 parts [solid content concentration: 100% by weight]
-Conductive fine particles G 750 parts-Alumina particles A (volume average particle size 0.35 µm) 750 parts-Titanium oxide particles A (volume average particle size 0.015 µm) 500 parts-Toluene 6000 parts

  Carrier particles K were 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 0.42 μm.

(Production Example 12)
-Acrylic resin solution (Hitaroid 3001: manufactured by Hitachi Chemical Co., Ltd.) 1500 parts [solid content concentration: 50% by weight]
Silicone resin solution (SR2410: manufactured by Toray Dow Corning) 1575 parts [solid content concentration: 20% by weight]
Aminosilane (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ) 4 parts [solid content concentration: 100% by weight]
-Conductive fine particles G 750 parts-Alumina particles A (volume average particle size 0.35 µm) 750 parts-Titanium oxide particles A (volume average particle size 0.015 µm) 500 parts-Toluene 6000 parts

  Carrier particles L were 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 0.42 μm.

(Production Example 13)
-Acrylic resin solution (Hitaroid 3001: manufactured by Hitachi Chemical Co., Ltd.) 1500 parts [solid content concentration: 50% by weight]
-450 parts of guanamine solution (My Coat 106: manufactured by Mitsui Cytec Co., Ltd.) [solid content concentration: 70% by weight]
Aminosilane (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ) 4 parts [solid content concentration: 100% by weight]
-Conductive fine particles G 750 parts-Alumina particles A (volume average particle size 0.35 µm) 750 parts-Titanium oxide particles A (volume average particle size 0.015 µm) 500 parts-Toluene 6000 parts

  Carrier particles M were 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 0.42 μm.

(Production Example 14)
-Acrylic resin solution (Hitaroid 3001: manufactured by Hitachi Chemical Co., Ltd.) 1500 parts [solid content concentration: 50% by weight]
-450 parts of guanamine solution (My Coat 106: manufactured by Mitsui Cytec Co., Ltd.) [solid content concentration: 70% by weight]
Aminosilane (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ) 4 parts [solid content concentration: 100% by weight]
Conductive fine particles H 1500 parts Titanium oxide particles A (volume average particle size 0.015 μm) 500 parts Toluene 6000 parts

  Carrier particles N were 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 0.42 μm.

(Production Example 15)
Carrier particles O were obtained in the same manner as in Production Example 11 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 0.08 μm.

(Production Example 16)
Carrier particles P were obtained in the same manner as in Production Example 11 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 3.02 μm.

[Example 1]
Using 7 parts of the toner particles A obtained in the toner particle production example and 93 parts of the carrier particles A obtained in the carrier particle 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 of the toner particles A obtained in the toner particle production example and 20 parts of the carrier particles A obtained in the carrier particle production example 1 were stirred for 10 minutes with a mixer to prepare a replenishment developer S1. .

(Image definition)
Using a modified machine equipped with a developing device shown in FIG. 7 in a commercially available digital full-color printer (Ricoh Co., Ltd., image Neo Neo C600), the developer S in the developing machine and the developer S1 for replenishment are set, and the image area is 5%. A character chart (the size of one character is about 2 mm × 2 mm) was output, 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 charge and the amount of change in carrier particle resistance before and after the running test.

  The amount of charge reduction was measured by the following method. First, a sample that was mixed and frictionally charged at a ratio of 7% by weight of toner particles to 93% by weight of initial carrier particles was measured by a general blow-off method (TB-200, manufactured by Toshiba Chemical Corporation). The value is the initial charge amount. Next, toner particles are removed from the developer after running by the blow-off device, and the toner particles are newly mixed at a ratio of 7% by weight with respect to 93% by weight of the obtained carrier particles. The charge amount of the sample triboelectrically charged is measured in the same manner as the initial carrier particles, and the difference from the initial charge amount is defined as the charge reduction amount. The target value of the charge reduction amount is within 10.0 μC / g. Since the cause of the decrease in the charge amount is the toner spent on the surface of the carrier particles, the decrease in the charge amount can be suppressed by reducing the toner spent.

  The amount of change in the carrier particle resistance value was measured by the following method. Carrier particles were introduced 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, toner particles in the developer after running are removed by the blow-off device, and resistance measurement is performed on the obtained carrier particles by the same method as the resistance measurement method. The difference from the initial resistance value is defined as the change amount of the carrier particle particle resistance value. The target value of the carrier particle resistance value change amount is within 3.0 [Log (Ω · cm)] in absolute value. The cause of the resistance change is scraping of the carrier particle coating layer, spent toner component, large particle detachment in the carrier particle coating layer, etc., and reducing these can suppress the change in carrier particle resistance. .

(Skin carrier particle adhesion)
The developer S and replenishment developer S1 are set in a modified machine equipped with a developing device shown in FIG. 7 on a commercially available digital full-color printer (Ricoh Co., Ltd., imgio Neo C600), and the background potential is fixed at 150V. Then, an A3 character chart (the size of one character is about 2 mm × 2 mm) with an image area of 1% was output, and the evaluation was performed based on the number of carrier particles attached to 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

(Color stains)
A solid image was output and measured by X-Rite. Specifically, the developer is set, and the image immediately after the setting is measured by X-Rite (X-Rite 938 D50, manufactured by Amtec Co., Ltd.) and the image after stirring for 1 hour with the developing unit alone. A value (E ′) obtained by measuring the image by X-Rite and ΔE by the following equation was obtained and ranked as follows.

ΔE = EE
E = (L ² + a * ² + b * ² ) ^1/2
(Read the value at Yellow ID = 1.4)
E = initial agent E value E ′ = after air stirring for 1 hour ◎: ΔE ≦ 2
○: 2 <ΔE ≦ 5
×: 5 <ΔE

[Comparative Example 1]
Evaluation was performed in the same manner as in Example 1 except that imago Neo C600, which had not been modified, was used as an evaluation apparatus, and the system was changed to a system in which only the toner particles were replenished to the developing machine without supplying / recovering the developer. went.

[Comparative Examples 2-5, Examples 2-12]
Evaluation was performed in the same manner as in Example 1 except that the carrier particles used in the developer S in the developing device and the replenishment developer S1 were the carrier particles prepared in Production Examples 2 to 16.

Example 13
Evaluation was performed in the same manner as in Example 1 except that 98 parts of the toner particles A obtained in the toner particle production example and 2 parts of the carrier particles M obtained in the carrier particle production example 13 were used to prepare a replenishment developer. Went.

Example 14
Evaluation was made in the same manner as in Example 1 except that 69 parts of toner particles A obtained in the toner particle production example and 31 parts of carrier particles M obtained in carrier particle production example 13 were used to prepare a replenishment developer. Went.

Example 15
Evaluation was conducted in the same manner as in Example 1 except that 16 parts of toner particles A obtained in the toner particle production example and 84 parts of carrier particles M obtained in carrier particle production example 13 were used to create a developer in the developing machine. Went.

Example 16
Evaluation was carried out in the same manner as in Example 1 except that 1 part of toner particles A obtained in the toner particle production example and 99 parts of carrier particles M obtained in carrier particle production example 13 were used to create a developer in the developing machine. Went.

  An outline of the carrier particles produced above is shown in FIG. The carrier particles used in Examples 1 to 16 and Comparative Examples 1 to 5 and the evaluation results are shown in FIG.

  As is apparent from the evaluation results shown in FIG. 14, when the developing device shown in Comparative Example 1 that does not replenish and recover the developer is used, the charge reduction amount is 12.7 μc / g, which is the target of 10.0 μc. / G is exceeded and toner spent is generated. Further, when only the indium oxide layer containing tin dioxide is formed as the conductive coating layer of the conductive fine particles contained in the carrier particle coating layer shown in Comparative Example 2, the fineness of the image is poor and it is practically usable. Absent. Furthermore, as shown in Comparative Examples 3 and 4, when the aspect ratio of the conductive fine particles deviates from the range of 205 and 2.4 and 3 to 200, the resistance change amount is the target value of 3.0 log (Ω · cm ), And the carrier particle coating layer is scraped off and spent toner components are generated. Furthermore, when carbon black is used as the conductive material shown in Comparative Example 5, color stains are generated.

  On the other hand, in each of the examples according to the present invention, the developing device for supplying and collecting the developer is used, and white conductive fine particles having an aspect ratio of 3 to 200 are used. It is clear that it is possible to form a good image while exhibiting a finer image fineness than that of the image and suppressing the background carrier adhesion and color stains.

  In particular, when the first hard particles and the second hard particles such as aluminum oxide and titanium oxide shown in Examples 6 to 16 are contained in the coating layer, the amount of charge reduction and resistance change are suppressed. It is clear that this is possible and shows good results.

It is sectional drawing which shows schematic structure of the carrier for electrophotography of one Embodiment by this invention. It is an expanded sectional view of the X section of FIG. It is an expanded sectional view of the electroconductive fine particle of the Y part of FIG. It is a schematic sectional drawing for demonstrating the binder resin thickness in the coating layer of the electrophotographic carrier of one Embodiment by this invention. It is a perspective view of the resistance measurement cell used for the measurement of the resistivity of the carrier by this invention. 1 is a schematic cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view showing a schematic configuration showing a structure around a developing unit of a developing device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a schematic configuration of a developer supply unit according to an embodiment of the present invention. (A) is an external view which shows schematic structure of the nozzle provided in a developer supply apparatus, (b) is the axial sectional drawing, (c) is on the AA line in (b). It is sectional drawing cut | disconnected. It is sectional drawing which shows schematic structure of the screw pump shown in FIG. FIG. 3 is a perspective view of a state in which a developer is filled in a developer accommodating member according to an embodiment of the present invention. FIG. 12 is a front view showing a state in which the developer inside the developer accommodating member shown in FIG. 11 is discharged and reduced in volume. It is a table | surface figure which shows the characteristic of the carrier used by this invention and a comparative example. It is a table | surface figure which shows the evaluation result of the Example by this invention, and a comparative example.

Explanation of symbols

1, 1M, 1C, 1Y, 1K Photoconductor 2M, 2C, 2Y, 2K Image forming unit 3 Charging unit 4 Primary transfer roller 5 Cleaning device 6 Exposure device 9 Fixing device 10, 10M, 10C, 10Y, 10K Developing device 10a Housing 10b replenishment port 14 developer accommodating portion 15 transfer belt 16 developing rolls 17a and 17b conveying screw 18 layer thickness regulating member 26 core material 27 covering layer 28 binder resin 200A, 200B, 200C, 200D developer replenishing device 220 developer replenisher 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 233 Sealing material 240 Nozzle 241 Inner tube 241a Developer channel 242 Outer tube 24 Air flow path 246a, 46b Air supply port 247 Developer outlet 260 Air supply means 260a, 260b Air pump 261a, 261b Air supply path 262a, 262b Open / close valve 300 Developer discharge device 330 Collection container 331 Discharge pipe ha, hb, hc Cover Layer thickness T Average thickness G1 from core material surface to coating layer surface First particle G2 Second particle G3 White conductive fine particles G3a Base particle G3b Conductive coating layer S Developer S1 Replenishment developer

Claims (12)

The toner particles are formed on the surface of the photoreceptor from a developing device containing a developer formed by mixing carrier particles composed of magnetic core material particles and a resin coating layer covering the surface of the core material particles with toner particles. In an image forming method for supplying to a developed electrostatic latent image and developing the electrostatic latent image,
The resin coating layer includes white conductive fine particles , at least one hard particle, and second hard particles other than the hard particles ,
The conductive fine particles are needle-like or rod-like fine particles having an aspect ratio of 3 to 200 formed by laminating at least a lower layer containing tin dioxide and an upper layer containing tin dioxide and indium oxide on the surface of particles serving as a base material. Yes,
The ratio (D ₁ / h) of the particle diameter D ₁ (μm) of the hard particles to the average thickness h (μm) of the resin portion in the resin coating layer satisfies the relationship of 1 <(D ₁ / h) <10. ,
The ratio (D ₂ / h) between the particle diameter D ₂ (μm) of the second hard particles and the average thickness h (μm) of the resin portion of the binder resin in the coating layer is 0.001 <(D ₂ / H) satisfies the relationship <1
The image forming method, wherein the developing is performed while supplying the developer to the developing device and discharging the excess developer in the developing device to the outside of the developing device. The image forming method according to claim 1.
An image forming method, wherein the conductive fine particles are made of titanium oxide. The image forming method according to claim 1 or 2 ,
An image forming method, wherein the hard particles are alumina particles or particles based on alumina. The image forming method according to any one of claims 1 to 3 ,
The image forming method, wherein the second hard particles are titanium oxide particles or surface-treated titanium oxide particles. The image forming method according to any one of claims 1 to 4 ,
An image forming method, wherein a part or all of the hard particles and / or the second hard particles contained in the resin coating layer is the white conductive fine particles. The image forming method according to any one of claims 1 to 5 ,
An image forming method, wherein an average thickness T (μm) from the surface of the core particle to the surface of the resin coating layer is in a range of 0.1 ≦ T ≦ 3.0. The image forming method according to any one of claims 1 to 6 ,
The image forming method, wherein the resin contained in the resin coating layer contains at least either a reaction product of an acrylic resin and an amino resin or a silicone resin. The image forming method according to claim 1 ,
An image forming method, wherein a weight ratio of carrier particles in the developer supplied to the developing device is 3 wt% or more and 30 wt% or less. The image forming method according to any one of claims 1 to 8 ,
An image forming method, wherein a weight ratio of carrier particles in the developer contained in the developing device is 85 wt% or more and 98 wt% or less. The image forming method according to any one of claims 1 to 9 ,
In the replenishment, the replenishing developer filled in a storage container whose shape is easily deformed is sucked by a suction pump and supplied to a developing device. An image forming apparatus that forms an image by using the image forming method according to claim 1 . In a process cartridge in which at least the photosensitive member and the developing device are integrally formed,
A process cartridge, wherein the developing device is a developing device that forms an image using the image forming method according to claim 1 .

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