JP2009186769A - Carrier, developer, developing device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier which hardly liberates conductive particles serving as a resistance-adjusting agent even when receiving a stress due to high-speed transport and does not cause color contamination on an image even when the conductive particles are liberated, and to provide a developer, a developing device, a process cartridge and an image forming apparatus containing the carrier. <P>SOLUTION: The carrier, which is mixed with toner and is used as a developer, is prepared by covering a core material particle 66 having magnetism with a binder resin layer 67. The binder resin layer 67 contains white conductive particles G3, and each of the conductive particles G3 is made to be a needle-like or rod-like fine particle having an aspect ratio of 3 to 200 which is prepared by forming a conductive covering layer G3b on the surface of a substrate particle G3a, while the conductive covering layer G3b is composed of an SnO<SB>2</SB>layer as a lower layer and a layer of In<SB>2</SB>O<SB>3</SB>containing SnO<SB>2</SB>as an upper layer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a carrier used for a developer for electrophotography, a developer including the carrier, a developing device, a process cartridge, and an image forming apparatus.

Conventionally, as a developing device using a two-component developer composed of a toner and a magnetic carrier, one having a structure shown in FIG. 8 is known. The developing device (4) shown in FIG. 8 is provided with a conveying path for supplying the developer to the developing roller (5), which is a developer carrying member, and a conveying path for stirring the developer. The developer is circulated by conveying the developer in opposite directions in the path.
In the developing device (4) shown in FIG. 8, the conveying path for supplying the developer to the developing roller (5) and the conveying path for collecting the developer supplied to the developing roller (5) and passing through the developing region are common. is there. Therefore, there is a problem that the toner concentration of the developer supplied to the developing roller (5) decreases toward the downstream side in the conveying direction of the conveying path supplied to the developing roller (5). When the toner density supplied to the developing roller (5) decreases, the image density during development also decreases.
As a solution to this problem, in the developing apparatuses described in Patent Document 1 and Patent Document 2, the developer auger for supplying the developer to the developing roller and the developer auger for collecting the developed developer are set in different developer transport paths. It is shown to be provided. Hereinafter, the configurations of the developing devices described in Patent Document 1 and Patent Document 2 will be described.

First, a developing device described in Patent Document 1 is shown in FIG.
In the developing device (4) shown in FIG. 9, a developer supply transport path (9) for supplying the developer to the developing roller (5), a developer recovery transport path (7) for recovering the developer that has passed through the development area, and Are provided separately.
In the developing device (4), since the developer that has passed through the developing region is sent to the developer recovery transport path (7), it does not enter the developer supply transport path (9). Accordingly, the toner concentration of the developer supplied to the developing roller (5) is constant without changing the toner concentration of the developer in the developer supply / conveyance path (9).
However, since the developer sent to the developer collecting / conveying path (7) is immediately supplied to the developer supply / conveying path (9), even if the toner is replenished and the toner concentration is properly maintained, the stirring is performed. There is a problem that image density becomes ununiform and density decreases during development. Such a problem becomes more conspicuous as an image having a high printing rate in which the toner concentration of the collected developer is lowered.

Next, a developing device described in Patent Document 2 is shown in FIG.
In the developing device (4) shown in FIG. 10, a developer supply transport path (9) for supplying the developer to the developing roller (5), a developer recovery transport path (7) for recovering the developer that has passed through the development area, and Are provided separately. Further, the developer supply and transport is performed while stirring the developer transported to the most downstream side of the developer supply transport path (9) and the recovered developer transported to the most downstream side of the developer recovery transport path (7). A developer stirring and conveying path (10) is provided to convey the developer in the direction opposite to the path (9).
In the developing device (4), since the developed developer is sent to the developer collecting / conveying path (7), the developed developer is not mixed into the developer supply / conveying path (9). Accordingly, the toner concentration of the developer supplied to the developing roller (5) is constant without changing the toner concentration of the developer in the developer supply / conveyance path (9).
Further, the developing device (4) does not immediately supply the recovered developer to the developer supply / conveyance path (9), but agitates the developer in the developer stirring / conveyance path (10) and then the developer supply / conveyance path (9). ) In the state where the developer that has passed through the developer supply transport path (9) without being developed and the recovered developer are agitated, are again supplied to the developer supply transport path (9). Supplied. As a result, a technique for preventing non-uniform image density and lowering of image density during development, which was a problem of the developing device (4) described in FIG.

  However, when this developing device (4) is used, the developer does not return from the development area to the developer supply / conveyance path (9), so that the developer can be stably supplied to the inner side of the developer supply / conveyance path (9). In order to supply the developer, it is necessary to increase the developer conveyance speed in the developer supply conveyance path (9) with respect to the developer supply speed to the development region. As a result, when the developer is supplied stably, the stress applied to the developer increases. When the stress applied to the developer is increased, the deterioration of the carrier is accelerated, which causes a decrease in durability.

Carriers used in the two-component development system prevent toner spent on the carrier surface, form a uniform carrier surface, prevent surface oxidation, prevent moisture sensitivity deterioration, extend the life of the developer, and damage the photoconductor carrier. Alternatively, for the purpose of protection from wear, control of charge polarity, adjustment of charge amount, etc., studies have been made to increase durability by coating with an appropriate resin material. For example, one coated with a specific resin material (Patent Document 3), one in which various additives are added to the coating layer (Patent Documents 4 to 10), and one having an additive attached to the carrier surface (Patent document 11) etc. which use is disclosed. Patent Document 12 discloses that a carrier coating material is composed of a guanamine resin and a thermosetting resin that can be crosslinked with the guanamine resin. Patent Document 13 discloses a cross-linked product of a melamine resin and an acrylic resin as a core of a carrier. It is disclosed to coat the material.
In order to further increase durability, Patent Document 14 discloses a resin layer containing a resin component obtained by crosslinking a thermoplastic resin and a guanamine resin and a charge control agent. This makes it possible to obtain a resin layer having sufficient elasticity to absorb a strong impact on the coating resin due to friction with toner or friction between carriers generated during stirring for frictionally charging the developer. . As a result, toner spent on the carrier can be suppressed to some extent.
However, the demand for higher durability in the market is still high. In particular, when the developer is transported at a high speed as in the above-described developing device, the stress applied to the developer is increased, and thus further improvement in durability is required.

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

Various methods have been proposed so far to suppress this phenomenon.
For example, Patent Document 15 proposes a carrier in which a conductive material (carbon black) is present on the surface of the core particle and the conductive material is not present in the coating layer.
Patent Document 16 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. A non-existent carrier has been proposed.
Patent Document 17 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. Has been proposed.
However, in recent years, in response to requests from consumers, the above-described electrophotographic image forming apparatus has a 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 15 to 17, it is difficult to completely prevent color stains caused by the transfer of carbon black into an image.

  Patent Documents 18 to 20 disclose carriers in which a conductive filler is contained in a carrier coating layer. In these carriers, it is possible to use conductive fillers as conductive particles without being limited to carbon. Therefore, the amount of coloring is small in order to reduce the influence of colored substances detached from the carrier on the toner. It is possible to select the material. However, this proposal aims to improve the image quality due to the electrical stability of the conductive filler, and since no mention is made of the color of the conductive filler, as a means to solve the above-mentioned problem of color contamination. Is incomplete.

  Therefore, even when subjected to high stress such as high-speed conveyance, there is little detachment from the carrier surface, and even if it is detached, a resistance adjuster that does not generate color stains and exhibits conductivity efficiently Therefore, there is a demand for the formation of an electrophotographic image with a carrier using such a resistance adjusting agent.

Japanese Patent No. 3127594 Japanese Patent Laid-Open No. 11-167260 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

Therefore, the present invention has been made in view of the above-mentioned problems, and the problem is that the conductive particles serving as the resistance adjusting agent are hardly detached even when subjected to stress due to high-speed conveyance, and the conductive particles are detached. Another object of the present invention is to provide a carrier that does not cause color stains on an image, and a developer, a developing device, a process cartridge, and an image forming apparatus including the carrier.
Also, desorption of the resistance regulator

The features of the present invention, which is a means for solving the above problems, are listed below.
The carrier of the present invention is used as a developer mixed with a toner, and the binder resin layer is coated with magnetic binder material particles, and the binder resin layer contains white conductive particles. The conductive particles are needle-shaped or rod-shaped fine particles having an aspect ratio of 3 to 200 formed by forming a conductive coating layer on the surface of the substrate particles, and the lower layer of the conductive coating layer is SnO _2. The upper layer and the upper layer are formed of an In ₂ O ₃ layer containing SnO ₂ .

The carrier of the present invention is further characterized in that the amount of SnO ₂ in the upper layer of the conductive coating layer is 0.1 to 20% by weight with respect to In ₂ O ₃ .
Further, in the carrier of the present invention, the binder resin layer further includes first hard particles, the particle diameter D1 of the first hard particles, and the average thickness h of only the resin portion in the binder resin layer. (D1 / h) satisfies the relationship 1 <(D1 / h) <10.
Further, in the carrier of the present invention, the binder resin layer further contains second hard particles, the particle diameter D2 of the second hard particles, and the average thickness h of only the resin portion in the binder resin layer. (D2 / h) satisfies the relationship of 0.001 <(D2 / h) <1.

In the carrier of the present invention, at least one selected from aluminum oxide, titanium oxide, zinc oxide, silicon dioxide, barium sulfate, and zirconium oxide is further used as the base particle of the conductive particles. It is characterized by that.
The carrier of the present invention is further characterized in that at least one selected from alumina, silica, titania, and zinc oxide is used as the first hard particles.
The carrier of the present invention is further selected from titanium oxide, zinc oxide, tin oxide, surface-treated titanium oxide, surface-treated zinc oxide, and surface-treated tin oxide as the second hard particles. At least one of the above is used.

The carrier of the present invention is further characterized in that all or part of the first hard particles are used as the white conductive particles.
The carrier of the present invention is further characterized in that all or part of the second hard particles are used as the white conductive particles.
In the carrier of the present invention, the average thickness from the surface of the core material particle to the surface of the binder resin layer covering the core material particle is in the range of 0.1 to 3.0 μm. And
The carrier of the present invention is further characterized in that the binder resin layer contains a reaction product of an acrylic resin and an amino resin and / or a silicone resin.

The developer of the present invention is characterized by having any of the carriers described above and a toner.
The developing device of the present invention has the developer described above.
The developing device of the present invention is further provided in a developing roller and a developer supplying / conveying path formed along the axial direction of the developing roller, and supplies the developer to the developing roller while conveying the developer. And a developer supply / conveying member, and a developer collecting / conveying path formed along the axial direction of the developing roller, and supplying the developer collected from the developing roller after developing the photosensitive member Provided in a developer collecting and conveying member that conveys in the same direction as the conveying member, and a developer agitating and conveying path formed along the axial direction of the developing roller, and is not used for development and is most downstream in the developer supply and conveying path The developer transport direction by the developer supply transport member while stirring the surplus developer transported to the side and the recovered developer recovered from the developing roller and transported to the most downstream side of the developer recovery transport path; Opposite direction Characterized in that it comprises a developer stirring and conveying member for conveying the excess developer and the collected developer, the.
Further, in the developing device of the present invention, the developer recovery circuit, the developer supply transport path, and the developer agitation transport path are partitioned by a partition member, and the developer agitation transport path, the developer recovery transport path, Are in positions that conflict with each other in the height direction, and the developer supply conveyance path is provided at a position higher than the developer recovery circuit and the developer agitation conveyance path.

A process cartridge according to the present invention includes the developing device described above and a photosensitive member.
An image forming apparatus according to the present invention includes the developing device described above.

  In the carrier, the developer, the developing device, the process cartridge, and the image forming apparatus as the means for solving the above, the conductive particles as the resistance adjusting agent are difficult to be detached even under stress due to high-speed conveyance, and the conductive particles are detached. However, it does not cause color stains on the image.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

The present inventors have intensively studied to solve the above problems. As a result, in the two-component development system, the developing device is provided with a developer supply conveyance path, a developer recovery conveyance path, and a developer agitation conveyance path, thereby making it difficult for image density unevenness and density reduction during development to occur. It was. Moreover, white electroconductive particle was contained in the binder resin layer of the carrier surface to be used. The conductive particles, those obtained by forming a needle-like or conductive coating layer on the surface of the rod-shaped base material particles, the conductive coating layer, an In ₂ underlayer SnO ₂ layers, the upper layer comprising SnO ₂ It was composed of an O ₃ layer.
The developer having such a configuration exhibits good conductivity due to the configuration of SnO ₂ and In ₂ O ₃ , and is less likely to be detached due to the shape of the conductive particles. Even if the developer is subjected to high stress during conveyance, the function of the developer is stably exhibited over a long period of time. In addition, since the conductive particles can be white in this configuration, even if the conductive particles are detached from the carrier resin layer or peeled off together with the carrier resin layer, there is a problem of color stains on the image. Does not occur.
The inventor has conceived the technical idea as described above.
In other words, in image formation using a developing device including a developer supply transport path, a developer recovery transport path, and a developer agitation transport path, the combination of the developing apparatus and the above conductive particles causes stress on the developer. The present inventors have found that this is a very suitable combination that covers the disadvantage of the developing device that becomes large. Of course, the effect of the present invention can be obtained even in a developing device in which a path different from such a path is formed.

Even if the problem of color stains is suppressed by using conductive particles as a resistance control agent with a small amount of coloring, the higher the efficiency of conductive particles, the greater the effect on carrier resistance when detached from the carrier surface. . For this reason, it is preferable to select the conductive particles in the order that color stains are not generated even if they are detached, with emphasis placed on the fact that they are not easily detached.
The shape of the conductive particles in the present invention is a needle shape or a rod shape. By making the shape of the conductive particles into a needle shape or a rod shape, when the conductive particles are dispersed in the resin coating layer, it becomes difficult for the conductive particles to be detached from the resin coating layer. Side surfaces are easily exposed on the carrier surface. Moreover, it becomes easy to arrange | position in mesh shape in parallel with respect to the carrier surface. As a result, the efficiency of the function of reducing the carrier resistance is improved. Furthermore, there is also an effect that the conductive particles enter the recesses on the surface of the core particles of the carrier and the conductive effect is not exhibited, and it is possible to form the conductive particles in the shape of needles or rods. 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 smaller than 3, the above-described bar-like or needle-like effect is hardly exhibited. When the aspect ratio is greater than 200, the applied moment is large with respect to the strength of the particles, so that the conductive particles are easily broken when applied to the surface of the core particles of the carrier together with the resin. Becomes difficult to be demonstrated.
The aspect ratio of the conductive particle is, for example, a two-dimensional field image obtained by photographing the conductive particle portion in the coating layer of the conductive particle or the carrier split section using a scanning electron microscope and a transmission electron microscope. In the above, the longest portion of the 50 conductive particles selected arbitrarily is defined as the longest diameter, and the average value with the longest portion on the axis orthogonal to the longest diameter as the shortest diameter is calculated and calculated by dividing them. be able to.

In order to change the shape of the conductive 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, a more preferable shape is easily obtained when a rutile crystal structure is provided.
Paying attention to the conductivity, the base particles of the conductive particles are made of aluminum oxide, titanium oxide, zinc oxide, silicon dioxide, barium sulfate, or zirconium oxide. The effect becomes remarkable. This is considered to be because the compatibility with the conductive treatment on the particle surface is good and the conductive treatment effect is exhibited well. In the present invention, “titanium oxide” includes “titanium dioxide”. The particles of aluminum oxide, titanium oxide, zinc oxide, silicon dioxide, barium sulfate, and zirconium oxide are white powder.

Even if the conductive particles or the coating layer containing the conductive particles is detached from the carrier core particles, there is no problem with color smearing unless the conductive particles have a color that adversely affects the color of the toner. . As a result of intensive studies, the inventors have come to the conclusion that if the conductive particles are white, even if the conductive particles are detached from the resin coating layer of the carrier, the color development of the toner is not adversely affected. Specifically, the powder color tone of the conductive 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, -1 or more and 3 or less can be used without adversely affecting the color development of the toner.
When the L value of the powder color tone is less than 70, the whiteness is not sufficient, which adversely affects the color development of the toner. When the b value is less than −10 or greater than 10, the saturation becomes high, and color smear occurs when the toner is fixed together with the toner.

An example of the powder color tone measurement method in the present embodiment is as follows.
First, weigh 6 g with an upper pan balance. Place a blank sheet on the forming die, place a stainless steel ring, place a weighed sample on it, and place a holding metal fitting. The L value and b value are read with a color difference meter that has been pressed using a small automatic press and standardly adjusted with a standard version.
As the colorimeter, Z-10018P manufactured by Nippon Denshoku Industries Co., Ltd. or a measuring instrument having equivalent or better performance is used. The stainless steel ring having an inner diameter of 40 mm and a height of 18 mm is used.

In order to impart conductivity to the needle-shaped or rod-shaped substrate particles, a conductive coating layer may be formed on the surface of the substrate particles. In particular, by employing the structure in which a conductive coating layer made of SnO ₂ and In ₂ O ₃ provided on the SnO ₂ layer and the SnO ₂ layer on a conductive carbon black comparable level applied to the base particle surface The effect can be demonstrated.
However, even if a conductive coating layer made of SnO ₂ and In ₂ O ₃ is directly formed on the surface of the base material particles, the electrical influence of the base material particles is large, and good conductivity may not be obtained. . In addition, even if a mixed solution of SnO ₂ hydrate and In ₂ O ₃ hydrate is directly coated on the substrate particles, it is difficult to uniformly coat the surface of the substrate particles. May cause problems.

After coating the base particle surface with a material generally used as a coating material such as aluminum oxide, titanium oxide, zinc oxide, and zirconium oxide, SnO ₂ hydrate and In ₂ O ₃ water A uniform conductive coating layer can be formed by coating the substrate particles with a mixed solution with a Japanese product. 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 SnO ₂ is used as the coating material for forming the lower layer, the upper conductive coating layer can be fixed uniformly and firmly, and good conductivity without being adversely affected by electrical effects from the lower layer. I was able to get sex. Note that there is no problem even if a small amount of In ₂ O ₃ 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, it is preferable to use titanium oxide as the material of the base particles of the conductive particles of the present invention, and it is particularly preferable to use rutile type titanium oxide. However, the present invention can be used as base particles of conductive particles for those that exhibit good effects other than titanium oxide.

The following aspects are mentioned as a detailed manufacturing method of the electroconductive coating layer of the electroconductive particle suitable for this invention. However, this is an example of a production method, and the production method of conductive particles suitable for the present invention is not limited to this method.
There are various methods for forming a SnO ₂ hydrate film as a lower layer. 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 coating a tin salt or tin hydrochloric acid and an alkali or an acid separately in parallel. 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 SnO ₂ hydrate is pH = 5.5, it is important to maintain preferably pH 2-5 or pH 6-9. Can be uniformly deposited.

As the tin salt, for example, tin chloride, tin sulfate, or tin nitrate can be used. Moreover, as a stannate, for example, sodium stannate or potassium stannate can be used.
As the alkali, for example, sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, ammonia water or ammonia gas, and as the acid, for example, hydrochloric acid, sulfuric acid, nitric acid or acetic acid can be used.
The coating amount of the SnO ₂ hydrate 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 In ₂ O ₃ hydrate 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.

There are various methods of forming a coating of In ₂ O ₃ hydrate containing SnO ₂ in the upper layer, but since the coating of SnO ₂ hydrate coated earlier is not dissolved, tin salt and indium salt A method in which a mixed solution and an alkali are separately added in parallel to form a film is more preferable. At this time, it is more preferable to heat the aqueous suspension to 50 to 100 ° C. In addition, it is important that the pH when the mixed solution and the alkali are added in parallel is 2 to 9, and preferably maintained at pH 2 to 5 or pH 6 to 9, so that the hydrolysis reaction product of tin and indium can be made uniform. Can be deposited.
As a raw material of tin, for example, tin chloride, tin sulfate, or tin nitrate can be used. For example, indium chloride or indium sulfate can be used as the indium raw material.

SnO ₂ additive amount is 0.1 to 20 wt% as SnO ₂ with respect to _{an In} 2 _{O 3,} preferably a 2.5 to 15 wt%, it is too small, even if too much desired conductivity Cannot be obtained.
Processing amount of In ₂ O ₃ with respect to the inorganic pigment of the base particles, 5 to 200 wt% as _In 2 _{O 3,} preferably 8-150% by weight, not too little and the desired conductivity is 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, white conductivity having a very excellent conductivity of 100 (Ω · cm) or less, and in some cases 10 (Ω · cm) or less, comparable to that of an antimony-containing product. A powder 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, or carbon dioxide gas 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 350-750 degreeC, Preferably it is 400-700 degreeC, and when it is lower than this range and it is high, it is difficult to obtain desired electroconductivity. Moreover, since the heating time does not have a heating effect when it is too short, and a further effect cannot be expected even if it is too long, it is suitably about 15 minutes to 4 hours, preferably about 1 to 2 hours. is there.

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

FIG. 1 schematically shows an embodiment of the carrier of the present invention. The carrier shown in the figure has magnetic core particles (66) and a binder resin layer (67) covering the core particles (66). The binder resin layer (67) The binder resin contains white conductive particles (G3) and first and second hard particles (G1, G2).
The conductive particles (G3) are formed by forming a conductive coating layer (G3b) on the surface of the substrate particles (G3a).
In addition to the binder resin, the first hard particles (G1), the second hard particles (G2), and the conductive particles (G3), the binder resin layer (67) includes other components as necessary. Can also be included.
Further, all or a part of the first hard particles (G1) may be used as the conductive particles (G3). Further, all or a part of the second hard particles (G2) may be used as the conductive particles (G3). Of course, the object of the present invention can be achieved even when the first and second hard particles (G1, G2) are absent and only the conductive particles (G3) are present.

The average thickness h of the resin portion in the binder resin layer (67) shown in FIG. 2 represents the thickness of the film existing in the direction perpendicular to the surface of the core particle (66). ) In the thickness from the surface to the binder resin layer (67) surface, the average thickness of the resin portion excluding the particle portion is shown.
As the thickness of the resin portion in the binder resin layer (67), the thickness ha of the resin portion existing between the surface of the core particle (66) and the particles, the thickness hb of the resin portion existing between the particles, There is a thickness hc of the resin part existing on the particle and a thickness hd of the resin part existing on the core particle (66).
The average thickness h of the resin portion in the binder resin layer (67) can be measured by, for example, observing the cross section of the carrier using a transmission electron microscope (TEM). Specifically, along the surface of the carrier, the thickness of the resin portion in the binder resin layer (67) at intervals of 0.2 μm (the thickness ha of the resin portion existing between the core particle surface and the hard particles, hard The thickness hb of the resin part existing between the particles, the thickness hc of the resin part on the hard particles, and the thickness (hd) of the resin part on the core material particles (66) are measured using a transmission electron microscope (TEM). Then, 50 measurement values were obtained, and the average value of the measurement values was taken as the average thickness h of the resin portion in the binder resin layer (67).

As a specific calculation method, the value of the average thickness h of the resin portion in the binder resin layer (67) is the sum of the measured values obtained by the above-described method, and the obtained value is the number of measured values. The value divided by. The number of measurement values is as follows: the thickness ha of the resin part existing between the surface of the core particle (66) and the particle, the thickness hb of the resin part existing between the particles, the thickness hc of the resin part on the particle, and the core The thickness hd of the resin part on the material particles (66) is counted as one each.
For example, at the measurement point A shown in FIG. 2, since the hb and the hc exist, the number of measurement values at the measurement point A is two.
In the measurement method described above, a plurality of measurement values (for example, the ha and the above) are measured as the measurement values of the thickness of the resin portion in the binder resin layer (67) at the last measured position among the 50 measurement values. When hc) is obtained, a value obtained by dividing the total value of the measured values by the value of “49+ (number of measured values at the last measured point)”, which is the number of measured values, is the binder resin layer ( It is set as the value of the average thickness h of the resin part in 67).

The particle diameter D1 of the first hard particles (G1) contained in the binder resin layer (67) is 1 <(D1 / h) <10 with respect to the average thickness h of the resin portion in the binder resin layer (67). Satisfying the above relationship is preferable, and more preferably satisfying the relationship of 1 <(D1 / h) <5.
When the particle diameter D1 of the first hard particles (G1) and the average thickness h of the resin portion in the binder resin layer (67) satisfy the above relational expression, the carrier binder resin layer (67) is satisfied. The first hard particles (G1) are convex. This convex portion alleviates the strong impact given to the binder resin of the carrier binder resin layer (67) due to the frictional contact between the toner and the carrier or between the carriers when the developer is stirred to frictionally charge the developer. can do. Thereby, it can suppress that the film | membrane scraping of the binder resin of a carrier binder resin layer (67) which is a charging generation location generate | occur | produces.
Further, when the carriers are in frictional contact with each other, the particles that are convex with respect to the surface of the binder resin layer (67) scrape off the spent component of the toner adhering to the surface of the carrier. Can be obtained. Thereby, it is possible to effectively prevent the phenomenon of toner spent.
When the (D / h) is 1 or less, the first hard particles (G1) are buried in the binder resin and the first hard particles (G1) added in the binder resin layer (67). It may not be possible to obtain sufficient effects. In addition, when (D / h) is 10 or more, the contact area between the first hard particles (G1) and the binder resin is reduced, and sufficient binding force of the first hard particles (G1) to the carrier is obtained. In some cases, the first hard particles (G1) are easily detached from the carrier surface.

In order to give the binder resin layer (67) an appropriate average strength, the binder resin layer (67) preferably contains the second hard particles (G2), and the second hard particles ( The particle diameter D2 of G2) is preferably such that 0.001 <(D2 / h) <1 with respect to the average thickness h of the resin portion in the binder resin layer (67), more preferably 0.01 <( D2 / h) <0.5 is preferred.
The second hard particles (G2) are dispersed in the binder resin layer (67) by making the particle diameter D2 of the second hard particles (G2) smaller than the average thickness of the binder resin layer (67). Can be included. Therefore, the strength of the coating layer can be improved on average.

  As a measuring method of the particle diameter D1 of the first hard particles (G1) and the particle diameter D2 of the second hard particles (G2), a volume average particle diameter is measured with an automatic particle size distribution analyzer CAPA-700 (manufactured by Horiba). Measure. 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. Add 6.0 g of sample, set the mixer rotation speed to low and disperse for 3 minutes. An appropriate amount of the 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 with an ultracentrifugal automatic particle size distribution analyzer CAPA-700.

Measurement conditions Rotational speed: 2000rpm
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

Further, the volume resistivity value of the second hard 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 0.0 × 10 8 (Ω · cm) or less. By making the volume resistivity of the second hard particles (G2) as low as 1.0 × 10 12 (Ω · cm) or less, the charge imparting ability of the binder resin layer (67) is appropriately reduced. It is possible to increase the concentration of the image enhancement finally obtained.
The volume resistivity of the first hard particles (G1) and the second hard particles (G2) in the present embodiment can be measured, for example, as follows.
A sample is put in a cylindrical vinyl chloride tube having an inner diameter of 1 inch, and the upper and lower sides are sandwiched between electrodes. A pressure of 15 (kg / cm ² ) is applied to these electrodes with a press machine for 1 minute. Subsequently, measurement with an LCR meter is performed in this pressurized state to obtain resistance (r). The volume resistivity can be obtained by calculating the obtained resistance value by the following formula 1.
Volume resistivity (Ω · cm) = (2.54 / 2) 2 × (π / H × r) (1)
(In the formula (1), H is a value representing the thickness of the sample, and r is a value representing the resistance value of the sample.)

When the value of (D2 / h) is 1 or more, the second hard particles (G2) are too large with respect to the thickness of the binder resin layer (67). The effect of improving becomes difficult to be exhibited. Further, when (D2 / h) is 0.001 or less, the particle diameter of the second hard particles (G2) is too small with respect to the thickness of the binder resin layer (67), so that it is difficult to obtain the effect.
The average thickness T from the surface of the core particle (66) to the surface of the binder resin layer (67) is preferably 0.1 to 3.0 [mu] m, and more preferably 0.1 to 2.0 [mu] m.
When the average thickness T from the surface of the core particle (66) to the surface of the binder resin layer (67) is less than 0.1 μm, the binder resin layer (67) as a film covering the carrier core particle (66). Since the total thickness is too thin, the binder resin layer (67) is scraped and the carrier core particles (66) are likely to be exposed during running, and the durability of the carrier is lowered.
If the average thickness T from the core particle (66) to the surface of the binder resin layer (67) exceeds 3.0 μm, the film thickness formed on the surface of the core particle (66) is too thick. Magnetization tends to decrease and carrier adhesion may occur.

The average thickness h of the resin portion in the binder resin layer (67) is preferably 0.04 to 2 μm, and more preferably 0.04 to 1 μm.
The volume average particle diameter D1 of the first hard particles (G1) is preferably 0.05 to 3 μm, and more preferably 0.05 to 1 μm.
The volume average particle diameter D2 of the second hard particles (G2) is preferably 0.005 to 1 μm, and more preferably 0.01 to 0.2 μm.

As shown in FIG. 2, the thickness T from the surface of the core particle (66) to the surface of the binder resin layer (67) is different from the above-described average thickness h of the resin portion in the binder resin layer (67). The thickness from the surface of the core particle (66) to the surface of the binder resin layer (67) at each point on the carrier surface is shown.
As shown in FIG. 2, when the particle diameter of the particles added in the binder resin layer (67) is larger than the thickness of the resin portion in the binder resin layer (67), the particle diameter of the particles is The value corresponds to the thickness T from the surface of the core particle (66) to the surface of the binder resin layer (67).
The average thickness T from the surface of the core particle (66) to the surface of the binder resin layer (67) is observed, for example, by observing the cross section of the carrier using a transmission electron microscope (TEM) and binding from the surface of the core particle (66). The thickness up to the surface of the resin-resin layer (67) is a value obtained by measuring 50 points along the carrier surface at intervals of 0.2 μm and averaging these measured values.

Examples of the first hard particles (G1) include alumina particles, silica particles, titania particles, and zinc oxide particles. Among these, the alumina particles are compatible with a binder resin used for a carrier coating material. In addition to being excellent in terms of dispersibility and adhesiveness, the hardness is extremely high, so it is difficult to cause wear and cracking against stress in the developing device, and the protective effect of the coating layer over a long period of time In particular, it is preferable because it can exhibit the effect of scraping spent.
As the alumina particles, alumina particles having a particle size of 5 μm or less are preferable, and any particles that have not been surface-treated or those that have been surface-treated such as a hydrophobic treatment can be used.
As the silica, those used for toner and those other than that can be used, and those not subjected to surface treatment, those subjected to surface treatment such as hydrophobic treatment, and the like can be used.

The content of the first hard particles (G1) contained in the binder resin layer (67) is preferably 10 to 80% by weight, and more preferably 20 to 60% by weight.
When the content of the first hard particles (G1) in the binder resin layer (67) is less than 10% by weight, the ratio of the first hard particles (G1) to the proportion of the binder resin on the carrier surface is Since the occupying ratio is too small, the effect of relieving contact with a strong impact on the binder resin is small, so that sufficient durability may not be obtained.
On the other hand, if it exceeds 80% by weight, since the proportion of the first hard particles (G1) is too much compared to the proportion of the binder resin on the carrier surface, the proportion of the binder resin that is the charging occurrence site is Insufficient charging performance may not be achieved. Furthermore, since the amount of the first hard particles (G1) is too large compared to the amount of the binder resin, the holding ability of the first hard particles (G1) by the binder resin becomes insufficient, and the first hard particles ( G1) is likely to be detached, and the amount of fluctuation such as charge amount and resistance increases, so that sufficient durability may not be obtained.
Here, the content of the first hard particles (G1) in the binder resin layer (67) is represented by the following formula (2).
Content of first hard particles (G1) (% by weight) = [content of first hard particles (G1) / total amount of materials contained in the binder resin layer (67) (first hard particles (G1 ) + Second hard particles (G2) + conductive particles (G3) + binder resin + other components)] × 100 (2)

As the second hard particles (G2), at least one kind of particles selected from titanium oxide, zinc oxide, tin oxide, surface-treated titanium oxide, surface-treated zinc oxide, and surface-treated tin oxide. Are preferably used.
These particles have an appropriate hardness, are compatible with the resin used for the carrier coating material, and are excellent in dispersibility and adhesion. In particular, titanium oxide and titanium oxide with surface treatment Is preferable as the second hard particles (G2).
Further, even when a particle matrix other than the above is used, it is possible to improve the dispersibility by subjecting the particle surface to a surface treatment such as a hydrophobizing treatment, If the volume resistivity is within the above range, good effects can be obtained for the same reason as described above. The conductive particles may be used as the second hard particles (G2).

The content of the second hard particles (G2) contained in the binder resin layer (67) is preferably 2 to 50% by weight, and more preferably 2 to 30% by weight.
The greater the content of the second hard particles (G2) in the binder resin layer (67), the greater the effect of increasing the strength, but when the content of the second hard particles (G2) exceeds 50% by weight, The dispersion state of the second hard particles (G2) inside the binder resin layer (67) is greatly deteriorated. When the dispersion state of the particles is deteriorated, the second hard particles (G2) partially aggregate in the binder resin layer (67), so that the effect of the second hard particles (G2) is exhibited on average. It becomes difficult to be done.
On the other hand, when the content of the second hard particles (G2) in the binder resin layer (67) is less than 2% by weight, the content is too small, and thus the effect of adding the second hard particles (G2). Can't get enough.
The content of the second hard particles (G2) in the binder resin layer (67) is represented by the following formula (3).
Content (weight%) of second hard particles (G2) = [content of second hard particles (G2) / total amount of materials contained in the binder resin layer (67) (first hard particles (G1 ) + Second hard particles (G2) + conductive particles (G3) + binder resin + other components)] × 100 (3)

Preferable examples of the binder resin used for the binder resin layer (67) of the carrier include a reaction product of an acrylic resin and an amino resin, and a silicone resin.
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, Glass transition temperature Tg is preferable 20-100 degreeC among these, 25-80 degreeC is preferable. More preferred. When the glass transition temperature Tg of the acrylic resin is within this range, the acrylic resin has an appropriate elasticity, and the friction between the toner and the carrier or the friction between the carriers in the stirring for frictionally charging the developer. In contact with a strong impact to the binder resin, the impact can be absorbed and the coating layer can be maintained without being damaged.

When the glass transition temperature Tg is less than 20 ° C., the binder resin blocks even at room temperature, so that the storage stability is poor and it may not be practically used. On the other hand, when the glass transition temperature Tg exceeds 100 ° C., the binder resin is too hard and brittle, and cannot absorb the impact, and the binder resin is scraped from the brittleness and holds the particles. May not be possible 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) and SR2110 (alkyd modified).
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 binder resin layer (67), in addition to the above-mentioned resins, those commonly used as carrier coating resins can be used as necessary. , Polyvinyl resin, polystyrene resin, halogenated olefin resin, polyester resin, polycarbonate resin, polyethylene resin, polyvinyl fluoride resin, polyvinylidene fluoride resin, polytrifluoroethylene resin, polyhexafluoropropylene resin, fluorine resin And fluoroterpolymers such as copolymers of vinylidene fluoride and vinyl fluoride, and 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.

The binder resin layer (67) is prepared by, for example, preparing a coating solution by dissolving the first hard particles (G1), the second hard particles (G2), and the binder resin in a solvent. It can be formed by uniformly coating the surface of the core material particles (66) 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, and butyl cellosolve are mentioned.
The baking is not particularly limited, and may be an external heating method or an internal heating method, such as a fixed electric furnace, a fluid electric furnace, a rotary electric furnace, or a burner furnace. Examples of the method used include a method using a microwave.

The volume average particle diameter of the carrier core particles (66) used in the present embodiment is not particularly limited, but the volume average particle diameter is 20 μm from the viewpoint of carrier adhesion to the image carrier and prevention of carrier scattering. From the viewpoint of preventing the occurrence of abnormal images such as carrier streaks and preventing deterioration in image quality, those having a thickness of 100 μm or less are preferable, and in particular, those having a diameter of 20 to 60 μm are used. It is possible to more appropriately meet the demand for higher image quality.
The core material particles (66) are not particularly limited, and can be appropriately selected from those known as two-component carriers for electrophotography according to the purpose. For example, ferrite, magnetite, iron and 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-based ferrite, Mn-Mg-based ferrite, or Mn-Mg-Sr ferrite is used instead of the conventional copper-zinc based 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 preferable examples.

In the carrier 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 is lower than 1 × 10 ¹¹ (Ω · cm), when the developing gap (the closest distance between the photosensitive member and the developing sleeve) becomes narrow, charge is induced in the carrier and the carrier adheres. It becomes easy to do. When the linear velocity of the photosensitive member and the linear velocity of the developing sleeve are large, a tendency of deterioration is observed. In addition, it is remarkable when an AC bias is applied. Usually, a color toner developing carrier is generally used having a low resistance in order to obtain a sufficient toner adhesion amount.
By using the carrier having the above resistance range under an appropriate toner charge amount, a sufficient image density can be obtained.
On the other hand, if it is larger than 1 × 10 ¹⁶ (Ω · cm), the charge having the opposite polarity to the toner tends to be accumulated, and the carrier is charged and the carrier is likely to adhere.
The carrier resistivity can be measured by the following method.

As shown in FIG. 3, a cell (71) made of a fluororesin container containing electrodes (72a) and (72b) having a distance between electrodes of 2 mm and a surface area of 2 × 4 cm is filled with a carrier (73), A DC voltage of 100 V is applied, and the DC resistance is measured with a high resistance meter 4329A (4329A + LJK 5HVLVWDQFH OHWHU; manufactured by Yokogawa / Hewlett Packard).
When filling the carrier resistance, fill the cell until it overflows into the cell, tapping the entire cell 20 times, and then using a non-magnetic horizontal spatula along the top edge of the cell. Scrape flatly in one operation. No pressure is required during filling.
The carrier resistivity can be adjusted by controlling the amount of conductive particles and the thickness of the resin coating layer.

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

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

The colorant is not particularly limited and may be appropriately selected from known dyes and pigments according to the purpose. For example, carbon black, nigrosine dye, iron black, naphthol yellow S, Hansa yellow (10G, 5G , G), cadmium yellow, yellow iron oxide, ocher, yellow lead, titanium yellow, polyazo yellow, oil yellow, Hansa yellow (GR, A, RN, R), pigment yellow L, benzidine yellow (G, GR ), Permanent Yellow (NCG), Vulcan Fast Yellow (5G, R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Isoindolinone Yellow, Bengala, Lead Red, Lead Red, Cadmium Red, Cadmium Mummer Curry Red, Antimony Zhu, Permanent Red 4R, Parare , Phi Sae Red, Parachlor Ortho Nitroaniline Red, Resol Fast Scarlet G, Brilliant Fast Scarlet, Brilliant Carmine BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Risor Rubin GX, Permanent Red F5R, Brilliant Carmine 6B, 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 litbon.
These may be used individually by 1 type and may use 2 or more types together.
The content of the colorant in the toner is preferably 1 to 15% by weight, and more preferably 3 to 10% by weight.

  The colorant may be used as a master batch combined with a resin. The resin is not particularly limited and may be appropriately selected from known ones according to the purpose. For example, styrene or a substituted polymer thereof, styrene copolymer, polymethyl methacrylate resin, polybutyl Methacrylate resin, polyvinyl chloride resin, polyvinyl acetate resin, polyethylene resin, polypropylene resin, polyester resin, epoxy resin, epoxy polyol resin, polyurethane, polyamide, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, fat Aromatic hydrocarbon resins, alicyclic hydrocarbon resins, aromatic petroleum resins, chlorinated paraffins, and paraffins. 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 are mentioned suitably.
Examples of waxes include carbonyl group-containing waxes, polyolefin waxes, and long-chain hydrocarbons. 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, and dialkyl ketones. Examples of the polyalkanoic acid ester include carnauba wax, montan wax, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, and 1,18- Octadecanediol distearate is mentioned. Examples of the polyalkanol ester 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. Among these carbonyl group-containing waxes, polyalkanoic acid esters are particularly preferable.
Examples of the polyolefin wax include polyethylene wax and polypropylene wax.

Examples of the long chain hydrocarbon include paraffin wax and sazol wax.
There is no restriction | limiting in particular as melting | fusing point of a mold release agent, Although it can select suitably according to the objective, 40-160 degreeC is preferable, 50-120 degreeC is more preferable, 60-90 degreeC is especially preferable.
When the melting point is less than 40 ° C., the wax may adversely affect the heat resistant storage stability, and when it exceeds 160 ° C., cold offset may easily occur during fixing at a low temperature.
The melt viscosity of the release agent is preferably 5 to 1000 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 less than 5 cps, the releasability may be lowered, and if it exceeds 1000 cps, the effect of improving hot offset resistance and low-temperature fixability may not be obtained.

There is no restriction | limiting in particular as content in the said toner of a mold release agent, Although it can select suitably according to the objective, 1 to 40 weight% is preferable and 3 to 30 weight% is more preferable.
When the content exceeds 40% by weight, the fluidity of the toner may be deteriorated.
The charge control agent is not particularly limited, and a positive or negative charge control agent can be appropriately selected and used depending on whether the charge charged on the photoconductor is positive or negative.
As the negative charge control agent, for example, a resin or compound having an electron donating functional group, an azo dye, or a metal complex of an organic acid 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, a basic compound such as a nigrosine dye, a cationic compound such as a quaternary ammonium salt, or a metal salt of a higher fatty acid can be used. Specifically, Bontron (part numbers: N-01, N-02, N-03, N-04, N-05, N-07, N-09, N-10, N-11, N-13, P -51, P-52, AFP-B) (above, manufactured by Orient Chemical Co., Ltd.), TP-302, TP-415, TP-4040 (above, manufactured by Hodogaya Chemical Co., Ltd.), Copy Blue PR, Copy Charge ( Product number: PX-VP-435, NX-VP-434) (manufactured by Hoechst), FCA (product number: 201, 201-B-1, 201-B-2, 201-B-3, 201-PB, 201-PZ, 301) (manufactured by Fujikura Kasei Co., Ltd.), PLZ (product numbers: 1001, 2001, 6001, 7001) (manufactured by Shikoku Kasei Kogyo Co., Ltd.), and the like.
These may be used individually by 1 type and may use 2 or more types together.

The addition amount of the charge control agent is determined by the toner production method including the type of the binder resin and the dispersion method, and is not uniquely limited, but is not limited to 0.1 parts by weight with respect to 100 parts by weight of the binder resin. 1-10 weight part is preferable and 0.2-5 weight part is more preferable. When the added amount exceeds 10 parts by weight, the chargeability of the toner is too large, the effect of the charge control agent is reduced, the electrostatic attraction with the developing roller is increased, the developer fluidity is reduced, and the image density If the amount is less than 0.1 part by weight, the charge rising property and the charge amount are not sufficient, and the toner image may be easily affected.
In addition to binder resin, release agent, colorant, and charge control agent, inorganic fine particles, fluidity improver, cleaning improver, magnetic material, metal soap, etc. are added to the toner material as necessary. can do.

As inorganic fine particles, for example, silica, titania, alumina, cerium oxide, strontium titanate, calcium carbonate, magnesium carbonate, or calcium phosphate can be used, and silica fine particles hydrophobized with silicone oil, hexamethyldisilazane, or the like. 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 numbers: 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) (manufactured by Cabot Corporation) can be used.
The addition amount of the inorganic fine particles is preferably 0.1 to 5.0 parts by weight, more preferably 0.5 to 3.2 parts by weight with respect to 100 parts by weight of the toner base particles.

The method for producing the toner in the present embodiment is not particularly limited as described above, but examples of the method for producing the pulverization method include the following.
The toner materials are mixed, and the mixture is charged into a melt kneader and melt kneaded. As the melt kneader, for example, a uniaxial or biaxial continuous kneader or a batch kneader using a roll mill can be used. For example, KTK type twin screw extruder manufactured by Kobe Steel, TEM type extruder manufactured by Toshiba Machine Co., Ltd., twin screw extruder manufactured by Casey Kay Co., Ltd., PCM type twin screw extruder manufactured by Ikekai Tekko Co., Ltd. Preferably used. This melt-kneading is preferably performed under appropriate conditions that do not cause the molecular chain 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. In this case, 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 by removing the fine particle portion by, for example, a cyclone, a decanter, or centrifugation.
After the pulverization and classification are completed, the pulverized product is classified into an air stream by centrifugal force or the like to produce a toner having a predetermined particle size.

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

  In this embodiment, the weight ratio of the carrier in the developer is preferably 85% by weight or more and less than 98% by weight. If it is less than 85% by weight, toner scattering from the developing device tends to occur, which causes a defective image. If it is 98% by weight or more, the charge amount of the toner is excessively increased or the supply amount of the toner is insufficient, so that the image density is lowered and a defective image is caused.

As an image forming apparatus to which the present invention is applied, an embodiment of a tandem type color laser copying machine (hereinafter simply referred to as “copying machine”) in which a plurality of photoconductors are arranged in parallel will be described.
FIG. 4 is a schematic configuration diagram of an example of a copying machine according to the present embodiment. The copier includes a printer unit (100), a paper feeding device (200) on which the printer unit (100) is placed, a scanner (300) fixed on the printer unit (100), and the like. An automatic document feeder (400) fixed on the scanner (300) is also provided.
The printer unit (100) includes four process cartridges (18Y, M, C, K) for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K). An image forming unit (20). (Y, M, C, K) attached to the numbers of the respective symbols indicate members for yellow, cyan, magenta, and black. In addition to the process cartridges (18Y, M, C, K), an optical writing unit (21), an intermediate transfer unit (17), a secondary transfer device (22), a registration roller pair (49), a belt fixing type A fixing device (25) and the like are provided.
The optical writing unit (21) has a light source (not shown), a polygon mirror, an f-θ lens, a reflecting mirror, and the like, and irradiates the surface of a photoreceptor to be described later with laser light based on image data. The process cartridge (18Y, M, C, K) includes a drum-shaped photoreceptor (1Y, M, C, K), a charger, a developing device (4Y, M, C, K), a drum cleaning device, a static eliminator, etc. have.

The yellow process cartridge (18) will be described below.
The upper surface of the photoreceptor (1Y) is uniformly charged by a charger as a charging means. The surface of the photoreceptor (1Y) that has been subjected to the charging process is irradiated with laser light that has been modulated and deflected by the optical writing unit (21). Then, the potential of the irradiation part (exposure part) is attenuated. By this attenuation, an electrostatic latent image for Y is formed on the surface of the photoreceptor (1Y). The formed electrostatic latent image for Y is developed by a developing device (4Y) as developing means to become a Y toner image.
The Y toner image formed on the Y photoconductor (1Y) is primarily transferred to an intermediate transfer belt (110) described later. The surface of the photoconductor (1Y) after the primary transfer is cleaned of residual toner by a drum cleaning device.
In the Y process cartridge (18Y), the photoconductor (1Y) cleaned by the drum cleaning device is discharged by the charge eliminator. Then, it is uniformly charged by the charger and returns to the initial state. The series of processes as described above is the same for the other process cartridges (18M, C, K).

Next, the intermediate transfer unit (17) will be described.
The intermediate transfer unit (17) includes an intermediate transfer belt (110) and a belt cleaning device (90). Further, it also has a tension roller (14), a drive roller (15), a secondary transfer backup roller (16), four primary transfer bias rollers (62Y, M, C, K) and the like.
The intermediate transfer belt (110) is tensioned by a plurality of rollers including a tension roller (14). Then, it is endlessly moved clockwise in the drawing by the rotation of the drive roller (15) driven by a belt drive motor (not shown).
The four primary transfer bias rollers (62Y, M, C, K) are disposed so as to contact the inner peripheral surface side of the intermediate transfer belt (110), respectively, and receive primary transfer bias from a power source (not shown). Further, the intermediate transfer belt (110) is pressed from the inner peripheral surface thereof toward the photoconductors (1Y, M, C, K) to form primary transfer nips, respectively. In each primary transfer nip, a primary transfer electric field is formed between the photoreceptor (1) and the primary transfer bias roller (62) due to the influence of the primary transfer bias.

The above-described Y toner image formed on the Y photoconductor (1Y) is primarily transferred onto the intermediate transfer belt (110) due to the influence of the primary transfer electric field and nip pressure. On this Y toner image, the M, C, K toner images formed on the M, C, K photoconductors (1M, C, K) are sequentially superimposed and primarily transferred. By the primary transfer of the superposition, a four-color superposed toner image (hereinafter referred to as a four-color toner image) that is a multiple toner image is formed on the intermediate transfer belt (110).
The four-color toner image superimposed and transferred on the intermediate transfer belt (110) is secondarily transferred to a transfer sheet as a recording sheet (not shown) at a secondary transfer nip described later. Transfer residual toner remaining on the surface of the intermediate transfer belt (110) after passing through the secondary transfer nip is cleaned by a belt cleaning device (90) that sandwiches the belt with the driving roller (15) on the left side in the drawing.

Next, the secondary transfer device (22) will be described.
Below the intermediate transfer unit (17) in the figure, a secondary transfer device (22) is provided in which a paper conveying belt (24) is stretched by two stretching rollers (23). The paper conveying belt (24) is moved endlessly in the counterclockwise direction in the drawing in accordance with the rotational drive of at least one of the stretching rollers (23). Of the two stretching rollers (23), one roller disposed on the right side in the drawing is between the intermediate transfer belt (110) and the secondary transfer backup roller (16) of the intermediate transfer unit (17). ) And the paper conveying belt (24). By this sandwiching, a secondary transfer nip is formed in which the intermediate transfer belt (110) of the intermediate transfer unit (17) and the paper transport belt (24) of the secondary transfer device (22) are in contact with each other. Then, a secondary transfer bias having a polarity opposite to that of the toner is applied to the one stretching roller (23) by a power source (not shown). By applying this secondary transfer bias, the four-color toner image on the intermediate transfer belt (110) of the intermediate transfer unit (17) is directed from the belt side to the one stretching roller (23) side in the secondary transfer nip. Thus, a secondary transfer electric field for electrostatic movement is formed. The transfer paper fed into the secondary transfer nip in synchronization with the four-color toner image on the intermediate transfer belt (110) by the registration roller pair (49) was affected by the secondary transfer electric field and nip pressure. A four-color toner image is secondarily transferred. Instead of the secondary transfer method in which the secondary transfer bias is applied to one of the tension rollers (23), a charger for charging the transfer paper in a non-contact manner may be provided.

In the paper feeding device (200) provided at the lower part of the copying machine main body, a plurality of paper feeding cassettes (44) capable of accommodating a plurality of transfer papers stacked in a bundle of paper are stacked in the vertical direction. It is arranged like this. Each paper feed cassette (44) presses the paper feed roller (42) against the uppermost transfer paper of the paper bundle. Then, by rotating the paper feed roller (42), the uppermost transfer paper is sent out toward the paper feed path (46).
A paper feed path (46) for receiving transfer paper fed from the paper feed cassette (44) includes a plurality of transport roller pairs (47) and a pair of registration rollers (49) provided near the ends in the path. Have. Then, the transfer paper is conveyed toward the registration roller pair (49). The transfer paper conveyed toward the registration roller pair (49) is sandwiched between the rollers of the registration roller pair (49). On the other hand, in the intermediate transfer unit (17), the four-color toner image formed on the intermediate transfer belt (110) enters the secondary transfer nip as the belt moves endlessly. The registration roller pair (49) feeds the transfer paper sandwiched between the rollers at a timing at which it can be brought into close contact with the four-color toner image at the secondary transfer nip. As a result, in the secondary transfer nip, the four-color toner image on the intermediate transfer belt (110) is in close contact with the transfer paper. Then, it is secondarily transferred onto the transfer paper and becomes a full color image on the white transfer paper. The transfer paper on which the full-color image is formed in this manner exits the secondary transfer nip as the paper transport belt (24) moves endlessly, and then is sent from the paper transport belt (24) to the fixing device (25). It is done.

  The fixing device (25) includes a belt unit that moves the fixing belt (26) endlessly while being stretched by two rollers, and a pressure roller (27) that is pressed toward one roller of the belt unit. I have. The fixing belt (26) and the pressure roller (27) are in contact with each other to form a fixing nip, and the transfer paper received from the paper conveying belt (24) is sandwiched between them. Of the two rollers in the belt unit, the roller that is pressed from the pressure roller (27) has a heat source (not shown) inside, and pressurizes the fixing belt (26) by the generated heat. The pressed fixing belt (26) heats the transfer paper sandwiched in the fixing nip. The full color image is fixed on the transfer paper by the influence of the heating and the nip pressure.

The transfer paper subjected to the fixing process in the fixing device (25) is stacked on the stack portion (57) protruding from the left side plate in the drawing of the printer housing, or the toner is also applied to the other surface. Return to the secondary transfer nip described above to form an image.
When copying a document (not shown), for example, a bundle of sheet documents is set on the document table (30) of the automatic document feeder (400). However, when the original is a single-sided original that is closed in a main form, it is set on the contact glass (32). Prior to this setting, the automatic document feeder (400) is opened with respect to the copying machine main body, and the contact glass (32) of the scanner (300) is exposed. Thereafter, the single-bound document is pressed by the closed automatic document feeder (400).
When a copy start switch (not shown) is pressed after the document is set in this way, the document reading operation by the scanner (300) starts. However, when a sheet document is set on the automatic document feeder (400), the automatic document feeder (400) automatically moves the sheet document to the contact glass (32) prior to the document reading operation. In the document reading operation, first, the first traveling body (33) and the second traveling body (34) start traveling together, and light is emitted from a light source provided in the first traveling body (33). Then, the reflected light from the document surface is reflected by a mirror provided in the second traveling body (34), passes through the imaging lens (35), and then enters the reading sensor (36). The reading sensor (36) constructs image information based on the incident light.

In parallel with the document reading operation, each device in each process cartridge (18Y, M, C, K), intermediate transfer unit (17), secondary transfer device (22), and fixing device (25) are provided. Start driving each one. Then, based on the image information constructed by the reading sensor (36), the optical writing unit (21) is driven and controlled, and Y, M, C on each photoconductor (1Y, M, C, K). , K toner images are formed. These toner images are four-color toner images that are superimposed and transferred onto the intermediate transfer belt (110).
Further, almost simultaneously with the start of the document reading operation, the paper feeding operation is started in the paper feeding device (200). In this paper feed operation, one of the paper feed rollers (42) is selectively rotated, and the transfer paper is sent out from one of the paper feed cassettes (44) accommodated in multiple stages in the paper bank (43). The fed transfer paper is separated one by one by the separation roller (45), enters the paper feed path (46), and is then conveyed toward the secondary transfer nip by the conveyance roller pair (47). In some cases, paper is fed from the manual feed tray (51) instead of such paper feeding from the paper feeding cassette (44). In this case, after the manual feed roller (50) is selectively rotated and the transfer paper on the manual feed tray (51) is sent out, the separation roller (52) separates the transfer paper one by one and the printer unit (100). Paper is fed to the manual paper feed path (53).

In the case of forming another color image composed of toner of two or more colors, the copying machine stretches the intermediate transfer belt (110) in a posture in which the upper stretched surface is substantially horizontal, and the upper stretched surface. All the photoreceptors (1Y, M, C, K) are brought into contact with each other. On the other hand, when forming a monochrome image consisting only of K toner, the intermediate transfer belt (110) is tilted to the lower left in the drawing by a mechanism (not shown), and the upper stretched surface is set to Y, M. , C away from the photoconductors (1Y, M, C). Of the four photoconductors (1Y, M, C, K), only the K photoconductor (1K) is rotated counterclockwise in the drawing to form only the K toner image. At this time, for Y, M, and C, not only the photosensitive member (1) but also the developing device (4) is stopped to prevent unnecessary consumption of the photosensitive member (1) and the developer.
The copying machine includes a control unit (not shown) configured by a CPU or the like that controls the following devices in the copying machine, and an operation display unit (not shown) configured by a liquid crystal display, various key buttons, and the like. The operator sends a command to the control unit by a key input operation on the operation display unit, so that one of the three modes is selected from the three-sided print mode, which is a mode for forming an image only on one side of the transfer paper. You can choose one. The three single-sided printing modes include a direct discharge mode, a reverse discharge mode, and a reverse decal discharge mode.

  FIG. 5 is an enlarged configuration diagram showing the developing device (4) and the photosensitive member (1) included in one of the four process cartridges (18Y, M, C, K). As shown in FIG. 5, the surface of the photosensitive member (1) is charged by a charging device (not shown) while rotating in the direction of arrow G in the drawing. The surface of the charged photoconductor (1) is supplied with toner from the developing device (4) to the latent image on which an electrostatic latent image is formed by laser light emitted from an exposure device (not shown) to form a toner image. .

The developing device (4) has a developing roller (5) as a developer carrying member for supplying a developer to the latent image on the surface of the photoreceptor (1) while moving the surface in the direction of arrow I in the drawing. ing. Further, a supply screw (8) is provided as a developer supply / conveying member that conveys the developer in the depth direction of FIG. 5 while supplying the developer to the developing roller (5).
A developing doctor (12) for regulating the developer supplied to the developing roller (5) to a thickness suitable for development, on the downstream side in the surface movement direction from the portion facing the supply screw (8) of the developing roller (5). It has.
The developed developer that has passed through the developing unit is collected downstream from the developing unit, which is the part of the developing roller (5) facing the photoconductor (1), and the collected developer that has been collected is supplied to the supply screw. A recovery screw (6) is provided as a developer recovery transport member that transports in the same direction as (8). A developer supply transport path (9), which is a developer supply transport path provided with a supply screw (8), is provided in the lateral direction of the developing roller (5), and a developer recovery transport path (7) provided with a recovery screw (6). Are arranged below the developing roller (5).

The developing device (4) is provided with a developer agitation transport path (10) in parallel with the developer recovery transport path (7) below the developer supply transport path (9). The developer agitating / conveying path (10) includes an agitating screw (11) as a developer agitating / conveying member that conveys the developer to the near side in the figure, which is in the opposite direction to the supply screw (8) while agitating the developer. .
The developer supply transport path (9) and the developer agitation transport path (10) are partitioned by a first partition wall (133) as a partition member. In the first partition wall (133), the developer supply / conveyance path (9) and the developer agitation / conveyance path (10) are partitioned at both ends of the front side and the back side in the drawing, and the developer The supply conveyance path (9) and the developer agitation conveyance path (10) communicate with each other.

The developer supply transport path (9) and the developer recovery transport path (7) are both partitioned by the first partition wall (133), but the developer supply transport path (9) of the first partition wall (133). No opening is provided at a location separating the developer recovery transport path (7).
In addition, the two conveying paths of the developer stirring and conveying path (10) and the developer collecting and conveying path (7) are separated by a second partition wall (134) as a partition member. The second partition wall (134) has an opening on the front side in the figure, and the developer agitation transport path (10) and the developer recovery transport path (7) communicate with each other.
The supply screw (8), the recovery screw (6) and the stirring screw (11) are made of resin screws. For example, each screw diameter is φ18 mm, screw pitch is 25 mm, and rotation speed is about 600 rpm. Is mentioned.

The developer thinned by the developing doctor (12) made of stainless steel on the developing roller (5) is transported to a developing area which is a portion facing the photosensitive member (1) for development. The surface of the developing roller (5) is V-groove or sandblasted. As an example of the configuration, an Al (aluminum) tube having a diameter of 25 mm is used, and the gap between the developing doctor (12) and the photoreceptor (1) is 0. .3 mm or so.
The developer after development is collected in the developer collection conveyance path (7), conveyed to the front side of the cross section in FIG. 5, and at the opening of the first partition wall (133) provided in the non-image area. The developer is transferred to the developer stirring and conveying path (10). The developer is supplied from a toner replenishing port provided on the upper side of the developer stirring and conveying path (10) in the vicinity of the opening of the first partition wall (133) on the upstream side in the developer conveying direction in the developer stirring and conveying path (10). Toner is supplied to the agitating and conveying path (10).

Next, the circulation of the developer in the three developer conveyance paths will be described.
FIG. 6 is a perspective sectional view of the developing device (4) for explaining the flow of the developer in the developer conveying path. Each arrow in the figure indicates the moving direction of the developer.
FIG. 7 is a schematic diagram of the flow of the developer in the developing device (4). Like FIG. 6, each arrow in the drawing indicates the moving direction of the developer.
In the developer supply / conveyance path (9) that receives the developer supplied from the developer stirring / conveyance path (10), the developer is supplied to the developing roller (5), while the supply screw (8) is on the downstream side in the conveyance direction. Transport developer. Then, the excess developer that is supplied to the developing roller (5) and is not used for development and is transported to the downstream end in the transport direction of the developer supply transport path (9) is stirred by the developer from the opening of the first partition wall (133). It is supplied to the conveyance path (10) (arrow E in FIG. 7).

The recovered developer fed from the developing roller (5) to the developer recovery transport path (7) and transported to the downstream end in the transport direction of the developer recovery transport path (7) by the recovery screw (6) is second partition wall ( 134) is supplied to the developer stirring and conveying path (10) (arrow F in FIG. 7).
The developer agitating and conveying path (10) agitates the supplied excess developer and the recovered developer, and is downstream in the conveying direction of the agitating screw (11) and upstream in the conveying direction of the supplying screw (8). And is supplied from the opening of the first partition wall (133) to the developer supply transport path (9) (arrow D in FIG. 7).
In the developer stirring / conveying path (10), the collected developer, surplus developer, and toner replenished as necessary by the transfer unit by the stirring screw (11) are supplied to the developer collecting / conveying path (7) and the developer supply / conveyance. The developer is stirred and conveyed in the direction opposite to the developer in the path (9). Then, the agitated developer is transferred to the upstream side in the transport direction of the developer supply transport path (9) communicating with the downstream side in the transport direction. A toner concentration sensor (not shown) is provided below the developer stirring and conveying path (10), and a toner supply control device (not shown) is operated by the sensor output to supply toner from a toner storage unit (not shown). ing.

  The developing device (4) shown in FIG. 5 includes a developer supply transport path (9) and a developer recovery transport path (7), and the developer supply and recovery are performed in different developer transport paths. Spent developer is not mixed into the developer supply / conveyance path (9). Therefore, it is possible to prevent the toner concentration of the developer supplied to the developing roller (5) from decreasing toward the downstream side in the transport direction of the developer supply transport path (9). In addition, since the developer recovery conveyance path (7) and the developer agitation conveyance path (10) are provided, and the developer recovery and agitation are performed in different developer conveyance paths, the developed developer is in the middle of agitation. It wo n’t fall. Therefore, since the sufficiently stirred developer is supplied to the developer supply transport path (9), the developer supplied to the developer supply transport path (9) is prevented from being insufficiently stirred. Can do. In this way, it is possible to prevent the toner density of the developer in the developer supply / conveyance path (9) from being lowered and to prevent the developer in the developer supply / conveyance path (9) from being insufficiently stirred. Therefore, the image density during development can be made constant.

In the developer stirring and conveying path (10), the toner and the carrier are mixed together by the stirring screw (11). In particular, in the developing device in this embodiment, the developer and the carrier or the carriers are in strong contact with each other because the developer is conveyed at a relatively high speed in order to stably supply the developer to the back side of the supply conveyance path. The film on the carrier surface is likely to be scraped. If the colored substance is detached from the carrier surface due to film scraping, it causes color stains.
However, in the carrier contained in the developer in the present embodiment, since the conductive particles are needle-shaped or rod-shaped, the conductive particles having a function as a resistance adjusting agent are difficult to be detached and hardly cause a color stain. . Further, since the conductive particles are not easily detached, the carrier resistance is unlikely to decrease. Further, even if the conductive particles are detached, the conductive particles are white, so that no color smear occurs.
The configuration of the image forming apparatus used in the present embodiment is not limited to the above-described configuration, and an image forming apparatus having another configuration may be used as long as it has a similar function. Is possible.

Hereinafter, the present invention will be described with reference to examples and comparative examples. However, the present invention is not limited to the examples illustrated here. In the following, “parts” represents parts by weight, and “%” represents% by weight.
[Production of toner]
(Binder Resin Synthesis Example 1)
724 parts of bisphenol A ethylene oxide 2-mole adduct, 276 parts of isophthalic acid and 2 parts of dibutyltin oxide were placed in a reaction vessel equipped with a cooling pipe, a stirrer and a nitrogen introduction pipe, and reacted at 230 ° C. for 8 hours under normal pressure. Furthermore, after reacting for 5 hours at a reduced pressure of 10 to 15 mmHg, the mixture was cooled 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 to obtain an ethyl acetate / MEK solution of a binder resin. It was.
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 product is placed in a 1-liter four-necked round bottom flask equipped with a thermometer, stirrer, condenser and nitrogen gas inlet tube, this flask is set in a mantle heater, and nitrogen gas is introduced from the nitrogen gas inlet tube. Then, the temperature was raised in a state where the inside of the flask was maintained in an inert atmosphere, and 0.05 g of dibutyltin oxide was then added to react 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 (CI Pigment Yellow 155): 40 parts-Binder resin: Polyester resin A: 60 parts-Water: 30 parts The above raw materials are mixed in a Henschel mixer, and the mixture in which water is soaked in the pigment aggregate is obtained. Obtained. This was kneaded for 45 minutes with two rolls set at a roll surface temperature of 130 ° C. and pulverized to a size of φ1 mm with a pulverizer to obtain a master batch (M1).

(Toner Production Example A)
In a beaker, 240 parts of the binder resin (B1) in ethyl acetate / MEK solution, 20 parts of pentaerythritol tetrabehenate (melting point: 81 ° C., melt viscosity: 25 cps), and 8 parts of master batch (M1) were placed at 60 ° C. And a TK homomixer at 12000 rpm to uniformly dissolve and disperse the toner material solution.
In a beaker, 706 parts of ion-exchanged water, 294 parts of hydroxyapatite 10% suspension (Superite 10 manufactured by Nippon Chemical Industry Co., Ltd.) and 0.2 part of sodium dodecylbenzenesulfonate were dissolved uniformly.

Next, the temperature was raised to 60 ° C., and the toner material solution was added and stirred for 10 minutes while stirring at 12000 rpm with a TK homomixer.
Next, this mixed solution was transferred to a Kolben equipped with a stirrer 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 A”.
An ultrathin section of this “toner A” was prepared, and a cross-sectional photograph (magnification × 100,000) of the toner was taken using a transmission electron microscope (H-9000H, manufactured by Hitachi, Ltd.). 100 points randomly selected from the photograph The average value was determined from the dispersion diameter of the colorant portion. Here, the dispersion diameter of one particle is the average of the longest diameter and the shortest diameter, and the aggregate itself is one particle in the aggregated state.
The average dispersed particle diameter of the colorant was 0.40 μm. The colorant having a dispersed particle diameter of 0.7 μm or more was 4.5%.

Next, the particle size of “Toner A” was measured with a particle size measuring device “Coulter Counter TA2” manufactured by Coulter Electronics Co., Ltd., with an aperture diameter of 100 μm. The diameter (Dn) was 5.1 μm.
Subsequently, the circularity of “Toner A” was measured as an average circularity by a flow type particle image analyzer FPIA-1000 (manufactured by Toa Medical Electronics Co., Ltd.). In the measurement, 0.1 to 0.5 ml of a surfactant (alkylbenzene sulfonate) as a dispersant is added to 100 to 150 ml of water from which impure solids have been removed in advance, and a measurement sample is added to 0.1 to 0.5 ml. About 0.5 g was added, and dispersion treatment was performed for about 1 to 3 minutes with an ultrasonic disperser, and a measurement liquid with the dispersion concentration adjusted to 3000 to 10000 / μl was set. The resulting “Toner A” had a circularity of 0.96.

Hereinafter, this will be described with reference to Table 1.
(Production example of conductive particles)
(Production Examples 1 to 3)
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 were added so that the pH of the suspension was maintained at 7-8. Simultaneous addition over 40 minutes. Subsequently, 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.
Next, 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 particles A. The average primary particle size was 0.05 μm and the aspect ratio was 197.

(Production Example 4)
White conductive particles B were obtained in the same manner as in Production Example 1 except that the material of the base particles 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 5)
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 were adjusted to pH of the suspension. It dripped simultaneously over about 1 hour so that it might hold | maintain 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. Next, 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 particles C. The average primary particle size was 0.08 μm and the aspect ratio was 32.

(Production Example 6)
White conductive particles D were obtained in the same manner as in Production Example 1 except that the material of the base particles 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 7)
White conductive particles E were obtained in the same manner as in Production Example 1 except that the material of the base particles 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 8)
Carbon black (manufactured by Lion Akzo, Ketjen Black EC600JD) was used as conductive particles F as it was.

(Production Examples 9-13, 15, 16)
White conductive particles G were obtained in the same manner as in Production Example 1 except that the material of 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 14)
White conductive particles H were obtained in the same manner as in Production Example 1 except that the material of the base particles 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 production)
(Production Example 1)
Acrylic resin solution (Hitaroid 3001: manufactured by Hitachi Chemical Co., Ltd.): 2130 parts by weight [solid content concentration: 50% by weight]
Aminosilane (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ )
: 4 parts by weight [solid content concentration: 100% by weight]
-Conductive particles A: 1500 parts by weight-Toluene: 6000 parts by weight

  Each of the above materials was dispersed with a homomixer for 10 minutes to prepare a resin layer forming solution. DFC-400M (manufactured by DOWA Electronics Co., Ltd., volume average particle size 35 μm, ferrite particles) is used as the carrier core material, and the above-mentioned resin solution is spiracoater (Okada Seiko Co., Ltd.) so that the thickness h is 0.15 μm on the core particle surface. Made 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 was baked by standing in an electric furnace at 150 ° C. for 1 hour, and after cooling, it was crushed using a sieve having an opening of 100 μm to obtain Carrier I. The average thickness T was 0.20 μm.

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

(Production Example 2)
A carrier II 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 particles) was used as the carrier core material. The average thickness T was 0.20 μm.

(Production Example 3)
SM-350NV (manufactured by DOWA Electronics, volume average particle size 50 μm, magnetite particles) is used as the carrier core material, and the amount of the coating material is reduced (352/502 times) by the specific surface area ratio calculated from the particle size of the core material particles. A carrier III was 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 IV was obtained in the same manner as in Production Example 1 except that the conductive particles B were used as the conductive particles. The average thickness T was 0.20 μm.

(Production Example 5)
A carrier V was produced in the same manner as in Production Example 1 except that the conductive particles C were used as the conductive particles. The average thickness T was 0.20 μm.

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

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

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

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

(Production Example 10)
Acrylic resin solution (Hitaroid 3001: manufactured by Hitachi Chemical Co., Ltd.): 2130 parts by weight [solid content concentration: 50% by weight]
Aminosilane (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ): 4 parts by weight [solid content concentration: 100% by weight]
-Conductive particles G: 750 parts by weight-Alumina particles A (volume average particle size 0.35 [mu] m): 750 parts by weight-Toluene: 6000 parts by weight A production example except that the material of the resin layer forming liquid is changed to the above. In the same manner as in Example 1, Carrier X was obtained. The average thickness T was 0.40 μm.

(Production Example 11)
Acrylic resin solution (Hitaroid 3001: manufactured by Hitachi Chemical Co., Ltd.): 2130 parts by weight [solid content concentration: 50% by weight]
Aminosilane (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ ): 4 parts by weight [solid content concentration: 100% by weight]
Conductive particles G: 750 parts by weight Alumina particles A (volume average particle size 0.35 μm): 750 parts by weight Titanium oxide particles A (volume average particle size 0.015 μm): 500 parts by weight Toluene: 6000 parts by weight Carrier XI was obtained in the same manner as in Production Example 1 except that the material of the resin layer forming liquid was changed to the above. The average thickness T was 0.42 μm.

(Production Example 12)
Acrylic resin solution (Hitaroid 3001: manufactured by Hitachi Chemical Co., Ltd.): 1500 parts by weight [solid content concentration: 50% by weight]
Silicone resin solution (SR2410: manufactured by Toray Dow Corning): 1575 parts by weight [solid content concentration: 20% by weight]
Aminosilane (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ )
: 4 parts by weight [solid content concentration: 100% by weight]
Conductive particles G: 750 parts by weight Alumina particles A (volume average particle size 0.35 μm): 750 parts by weight Titanium oxide particles A (volume average particle size 0.015 μm): 500 parts by weight Toluene: 6000 parts by weight Carrier XII was obtained in the same manner as in Production Example 1 except that the material of the resin layer forming liquid was changed to the above. The average thickness T was 0.42 μm.

(Production Example 13)
Acrylic resin solution (Hitaroid 3001: manufactured by Hitachi Chemical Co., Ltd.): 1500 parts by weight [solid content concentration: 50% by weight]
・ Guanamine solution (My Coat 106: manufactured by Mitsui Cytec Co., Ltd.): 450 parts by weight [solid content concentration: 70% by weight]
Aminosilane (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ )
: 4 parts by weight [solid content concentration: 100% by weight]
Conductive particles G: 750 parts by weight Alumina particles A (volume average particle size 0.35 μm): 750 parts by weight Titanium oxide particles A (volume average particle size 0.015 μm): 500 parts by weight Toluene: 6000 parts by weight Carrier XIII was obtained in the same manner as in Production Example 1 except that the material of the resin layer forming liquid was changed to the above. The average thickness T was 0.42 μm.

(Production Example 14)
Acrylic resin solution (Hitaroid 3001: manufactured by Hitachi Chemical Co., Ltd.): 1500 parts by weight [solid content concentration: 50% by weight]
・ Guanamine solution (My Coat 106: manufactured by Mitsui Cytec Co., Ltd.): 450 parts by weight [solid content concentration: 70% by weight]
Aminosilane (H ₂ N (CH ₂ ) ₃ Si (OCH ₃ ) ₃ )
: 4 parts by weight [solid content concentration: 100% by weight]
Conductive particles H: 1500 parts by weight Titanium oxide particles A (volume average particle size 0.015 μm): 500 parts by weight Toluene: 6000 parts by weight Manufacture except that the material of the resin layer forming liquid is changed to the above. In the same manner as in Example 1, Carrier XIV was obtained. The average thickness T was 0.42 μm.

(Production Example 15)
A carrier XV was 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)
A carrier XVI was 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)
[Example 1]
Using 7 parts by weight of toner A obtained in the toner production example and 93 parts by weight of carrier I obtained in carrier production example 1, the developer was prepared by stirring for 10 minutes with a mixer. Hereinafter, this will be described with reference to Table 2.

(Image definition)
A developer is set in a remodeling machine equipped with a developing device shown in FIG. 5 in a commercially available digital full-color printer (Ricoh Co., Ltd., imgio MP C4500), and a character chart with an image area of 5% (the size of one character is 2 mm × About 2 mm), and the fineness of the image was evaluated from the character reproducibility. The ranking of evaluation was performed as follows.
◎: Very good, ○: Good, △: Acceptable, ×: Unusable level for practical use

(durability)
100,000 images were output for the above-mentioned image definition evaluation, and a running test for durability evaluation was performed. Durability was evaluated by the amount of decrease in charge and the amount of change in carrier 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 to 93% by weight of the initial carrier was measured by a general blow-off method (TB-200, manufactured by Toshiba Chemical Corporation). Charge amount. Next, the toner is removed from the running developer by the blow-off device, and the toner is newly mixed at a ratio of 7% by weight with respect to 93% by weight of the obtained carrier, and is triboelectrically charged in the same manner as the initial carrier. The sample is measured for the charge amount in the same manner as the initial carrier, and the difference from the initial charge amount is defined as the charge 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 carrier surface, the decrease in the charge amount can be suppressed by reducing the toner spent.

The amount of change in the carrier resistance value was measured by the following method.
The carrier was put between the electrodes of the resistance measurement parallel electrode (gap 2 mm), DC 1000 V was applied, and the resistance value 30 seconds later was measured with a high resist meter. A value obtained by converting the obtained value into a volume resistivity is defined as an initial resistance value. Next, the toner in the developer after running is removed by the blow-off device, and the obtained carrier is subjected to resistance measurement by the same method as the resistance measurement method, and the obtained value is converted into volume resistivity. The difference from the initial resistance value is defined as the carrier resistance value change amount. The target value of the change amount of the carrier resistance value is 3.0 [Log (Ω · cm)] in absolute value.

(Skin carrier adhesion)
A developer is set in a remodeling machine equipped with the developing device shown in FIG. 5 on a commercially available digital full-color printer (Ricoh Co., Ltd., imgio MP C4500), the background potential is fixed at 150 V, and an A3 character chart with an image area of 1% (The size of one character is about 2 mm × 2 mm) was output, and the evaluation was performed based on the number of carrier adhesion occurrences in 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 is output after stirring for 1 hour with the developing unit alone. And the value (E ') which measured the image by X-Rite, (DELTA) E was calculated | required by following Formula, and it ranked as follows.
ΔE = EE
(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

(Image density unevenness)
A solid image was output after 100,000 images were output for the above-mentioned image definition evaluation, and rank evaluation was performed visually for unevenness in image density.
A: State in which there is no unevenness on the image ○: State in which density unevenness is slightly observed but does not cause a problem ×: State in which density unevenness is very conspicuous outside the allowable range

[Comparative Example 1]
The same as in Example 1 except that the evaluation apparatus is an imagio MP C4500 that is not modified to mount the developing device shown in FIG. And evaluated.

[Comparative Examples 2-5, Examples 2-12]
Evaluation was performed in the same manner as in Example 1 except that the carrier used in the developer was the carrier prepared in Production Examples 2 to 16.

FIG. 1 is an explanatory view showing an embodiment of the carrier of the present invention. FIG. 2 is an explanatory diagram showing a carrier coating layer according to an embodiment of the developer of the present invention. FIG. 3 is a perspective view of a resistance measurement cell used for measuring the resistivity of the carrier. FIG. 4 is a schematic configuration diagram of the copying machine according to the present embodiment. FIG. 5 is a schematic configuration diagram of the developing device and the photoreceptor. FIG. 6 is a perspective sectional view of the developing device for explaining the flow of the developer. FIG. 7 is a schematic diagram of the developer flow in the developing device. FIG. 8 is a schematic configuration diagram of a conventional developing device. FIG. 9 is a schematic configuration diagram of the developing device described in Patent Document 1. In FIG. FIG. 10 is a schematic configuration diagram of a developing device described in Patent Document 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 4 Developing device 5 Developing roller 6 Collection screw 7 Developer collection conveyance path 8 Supply screw 9 Developer supply conveyance path 10 Developer stirring conveyance path 11 Stirring screw 14 Stretching roller 15 Driving roller 16 Secondary transfer backup roller 17 Intermediate transfer unit 18 Process cartridge 20 Image forming unit 21 Optical writing unit 22 Secondary transfer device 23 Tension roller 24 Paper transport belt 25 Fixing device 26 Fixing belt 27 Pressure roller 30 Document table 32 Contact glass 33 First traveling body 34 Second traveling body 35 Imaging lens 36 Reading sensor 42 Paper feed roller 43 Paper bank 44 Paper feed cassette 45 Separation roller 46 Paper feed path 47 Transport roller pair 49 Registration roller pair 50 Manual feed roller 51 Manual tray 52 Separation roller 53 Manual feed Paper feed 57 Stack unit 62 Primary transfer bias roller 66 Core particle 67 Binder resin layer 71 Cell 72a, 72b Electrode 73 Carrier 90 Belt cleaning device 100 Printer unit 110 Intermediate transfer belt 133 First partition wall 134 Second partition wall 200 Paper feed device 300 Scanner 400 Automatic Document Feeder GX White Charged Particle G1 First Hard Particle G2 Second Hard Particle G3 Conductive Coating Layer G3a Base Material Particle G3b Conductive Coating Layer

Claims (17)

In a carrier mixed with toner and used as a developer and having a binder resin layer coated on magnetic core particles,
The binder resin layer contains white conductive particles;
The conductive particles are needle-shaped or rod-shaped fine particles having an aspect ratio of 3 to 200 formed by forming a conductive coating layer on the surface of the substrate particles,
The carrier is characterized in that the conductive coating layer is composed of a SnO ₂ layer as a lower layer and an In ₂ O ₃ layer containing SnO ₂ as an upper layer. The carrier according to claim 1,
The amount of SnO ₂ in the upper layer of the conductive coating layer is 0.1 to 20% by weight with respect to In ₂ O ₃ . In the carrier according to claim 1 or 2,
The binder resin layer contains the first hard particles, and the ratio (D1 / h) between the particle diameter D1 of the first hard particles and the average thickness h of only the resin portion in the binder resin layer, A carrier characterized by satisfying a relationship of 1 <(D1 / h) <10. The carrier according to claim 3,
The binder resin layer contains second hard particles, and the ratio (D2 / h) between the particle diameter D2 of the second hard particles and the average thickness h of only the resin portion in the binder resin layer, A carrier characterized by satisfying a relationship of 0.001 <(D2 / h) <1. The carrier according to claim 1,
A carrier characterized in that at least one selected from aluminum oxide, titanium oxide, zinc oxide, silicon dioxide, barium sulfate, and zirconium oxide is used as the base particles of the conductive particles. The carrier according to claim 3,
The carrier characterized in that at least one selected from alumina, silica, titania, and zinc oxide is used as the first hard particles. The carrier according to claim 4,
As the second hard particles, at least one selected from titanium oxide, zinc oxide, tin oxide, surface-treated titanium oxide, surface-treated zinc oxide, and surface-treated tin oxide is used. A career characterized by that. The carrier according to claim 3,
The carrier according to claim 1, wherein all or part of the first hard particles are used as the white conductive particles. The carrier according to claim 4,
All or part of said 2nd hard particle is used as said white electroconductive particle. The carrier characterized by the above-mentioned. The carrier according to any one of claims 1 to 9,
The average thickness from the surface of the said core material particle to the surface of the binder resin layer which coat | covers this core material particle exists in the range of 0.1-3.0 micrometers. The carrier characterized by the above-mentioned. The carrier according to any one of claims 1 to 10,
The carrier, wherein the binder resin layer contains a reaction product of an acrylic resin and an amino resin and / or a silicone resin. A developer comprising the carrier according to any one of claims 1 to 11 and a toner. A developing device comprising the developer according to claim 12. The developing device according to claim 13,
A developing roller;
A developer supplying / conveying member provided in a developer supplying / conveying path formed along the axial direction of the developing roller, for supplying the developer to the developing roller while conveying the developer;
Development that is provided in a developer collecting and conveying path formed along the axial direction of the developing roller, and that conveys the developer collected from the developing roller after developing the photosensitive member in the same direction as the developer supplying and conveying member. An agent collecting and conveying member;
Excess developer that is provided in the developer stirring and conveying path formed along the axial direction of the developing roller and is transported to the most downstream side of the developer supply and conveying path without being used for development, and collected from the developing roller. Developer that transports surplus developer and recovered developer in a direction opposite to the developer transport direction by the developer supply transport member while stirring the recovered developer transported to the most downstream side of the developer recovery transport path An agitating and conveying member;
A developing device comprising: The developing device according to claim 14, wherein the developer recovery circuit, the developer supply transport path, and the developer stirring transport path are partitioned by a partition member,
The developer agitation transport path and the developer recovery transport path are in a position where they conflict with each other in the height direction,
The developer supply transport path is provided at a position higher than the developer recovery circuit and the developer agitation transport path. 16. A process cartridge comprising the developing device according to claim 14 and a photoconductor. An image forming apparatus comprising the developing device according to claim 14.

Images